Piston pump of the type having at least three pumping chambers

Abstract

A piston pump (1,1′,1″) is described, of the type having at least three pumping chambers (20) comprising: a plurality of pistons (45), a head (10) in which a plurality of through holes (15) are made, in each of which a respective piston is slidably housed and in each of which a respective pumping chamber is at least partially contained, a cover (155,155′,155″) removably fixed to the head and provided with a first face (165) in contact with the head and an opposite second face (160), and a delivery channel (175,185,185′,185″,190) formed in the cover (155,155′,155″).

Description

TECHNICAL FIELD

[0001] The present invention relates to a pump, in particular a pump provided with a plurality of pumping chambers and suitable for high pressures.PRIOR ART

[0002] Piston pumps provided with several pumping chambers, commonly known as multi-cylinder pumps, generally comprise a head in which a plurality of holes are made, e.g. arranged with longitudinal axes parallel to each other, and each of which comprises or at least partially defines a respective pumping chamber whose volume is cyclically varied by a piston sliding in the hole. In order to collect and channel the fluid that has been pressurised in the pumping chambers, said pumps comprise a delivery channel with multiple delivery conduits, each of which is made in the head as a transverse through hole and intersecting a respective hole that makes a pumping chamber available. Said delivery channels are connected to collection conduits (one or more connection conduits that are also part of the delivery channel), also made in the head, which connect all the delivery conduits with an outlet mouth for the pumped fluid, to which a pipe is usually attached, through which the pumped fluid is conveyed.

[0003] As the number of pumping chambers increases, it is possible to reduce the flow fluctuations at the delivery, but at the same time it becomes more difficult to make a compact pump with small delivery channels.

[0004] An object of the present invention is to make available a pump with a plurality of pumping chambers that is compact, all within the framework of a rational and cost-effective solution. Such object is achieved by the features of the invention indicated in the independent claim. The dependent claims outline preferred and / or particularly advantageous aspects of the invention.DISCLOSURE OF THE INVENTION

[0005] In particular, the invention makes available a piston pump of the type having at least three pumping chambers (in parallel with each other with respect to suction and delivery) comprising:

[0006] a plurality of pistons, (the movement of which changes the volume of the pumping chambers in order to pump a fluid),

[0007] a head in which a plurality of through holes are made, in each of which a respective piston is slidably accommodated and in each of which a respective pumping chamber is at least partially contained,

[0008] a cover removably attached to the head and having a first face in contact with the head and an opposite second face, and

[0009] a delivery channel made in the cover,

[0010] This solution makes the pump particularly compact.

[0011] A particularly important, therefore required, feature is to make delivery channels of reduced dimensions in order to reduce the pump surface areas subject to other pressures, thus reducing the portions of the pump that must be made of material that can withstand the stresses of the pressurised fluid, in this regard the delivery channel can comprise:

[0012] a plurality of blind cavities made in the cover, each having an opening made in the first face at a respective opening made in the head by a corresponding through hole of the plurality of through holes,

[0013] a plurality of connection channels made in the cover, each of which extends from one blind cavity to another adjacent blind cavity, connecting all the blind cavities together in a loop path,

[0014] an outlet mouth made in the cover and connected (by means of a conduit, e.g. very short) to at least one between a blind cavity and a connection conduit.

[0015] Thanks to this solution an axial piston pump with reduced flow rate fluctuations at the delivery is made available which is robust and compact and particularly efficient in fluid-dynamic terms. In particular, these characteristics make it possible in a pump with more than two cylinders, to minimize the size of the delivery channel, which, as is well known, is stressed by the cyclic loads that generate the pressure pulsations due to the pumping of the liquid. The minimization of volumes and surfaces subject to such pulsations makes it possible to reduce the dimensions of the pump and / or, with the same pump dimensions, allows the use of less valuable materials, i.e. less resistant to pulsations.

[0016] In a first embodiment of the connection conduits, the cover may comprise a first face in contact with the head and an opposite second face, and the connection conduits may each comprise:

[0017] a first pair of side walls, opposed to each other and each having a respective curved surface having a single axis of curvature transverse with respect to the first face and to the second face, and

[0018] a second pair of side walls, flat and opposed to each other, each extending from one side wall to the opposite side wall and transverse to the axes of curvature of the first pair of side walls

[0019] Thanks to this solution, the branch conduits are simpler and cheaper to make compared to the prior art.

[0020] The invention also makes available a method for implementing a connection conduit in a piston pump according to the first embodiment of the connection conduits. Said method comprising the steps of:

[0021] providing a disc milling cutter,

[0022] inserting the disc milling cutter into a first blind cavity of the plurality of blind cavities, through the opening of said blind cavity, and

[0023] moving the disc milling cutter, along a direction transverse to a central axis of the opening of the first blind cavity, towards a second blind cavity of the plurality of blind cavities adjacent to the first blind cavity, until the disc milling cutter intersects said second adjacent blind cavity or intersects a portion of a connection conduit previously made by inserting the disc milling cutter into the second blind cavity through the opening of the second blind cavity and moving the disc milling cutter for a predetermined length towards the first blind cavity, along a direction transverse to a central axis of the opening of the first blind cavity, thereby making the connection conduit

[0024] In this way the connection conduits are faster and cheaper to make.

[0025] In a second embodiment of the connection channels, the cover may comprise a first face in contact with the head and an opposite second face, and the connection conduits may each comprise:

[0026] a first curved side wall extending from one blind cavity to another blind cavity, joined by the connection conduit, and having concavity facing a central area of the cover,

[0027] a second curved side wall extending from one blind cavity to another blind cavity, joined by the connection conduit, which is radially closer to said central zone than the first side wall and which also has concavity facing the central area, and

[0028] a third side wall and a fourth side wall, opposing each other and connecting the first wall and the second wall on opposite sides.

[0029] This makes the channels fluid-dynamically optimal and particularly compact, i.e. the surface areas that are in contact with the pressurised fluid are particularly small.

[0030] In a third embodiment of the connection conduits, the connection conduits can be made as rectilinear through holes entirely contained in the cover and each running from a blind cavity to another high proximal blind cavity.

[0031] This solution also makes it possible to quickly and easily make the connection conduits.

[0032] For example, the invention may provide that said through holes are inclined with respect to a central axis of the blind cavity opening.

[0033] In addition to or as an alternative to the foregoing peculiar delivery channel configurations, in order to improve the aspect of reducing the size of the delivery channel and making the pump more resistant, still taking care to make sure it is compact and light, the invention may provide that the cover may be made of a metal material and the head be made of a polymer material.

[0034] Thus, for the same operating pressures, the pump is cheaper to produce and lighter than a conventional pump in which the head is made of metal. This configuration is enabled by the fact that the delivery channels are made in the cover, so the surfaces that have to withstand high pressures are in a metal body.

[0035] To improve on this aspect of the invention, the invention may provide that each through hole may be at least partially lined with a respective tubular liner made of metal material.

[0036] This allows the operating pressure to be increased compared to the case where the through hole is not lined.

[0037] According to an aspect of the invention, the tubular liner extends away from the cover until it contacts an annular (high-pressure) sealing gasket housed in the pump and adapted to embrace a piston sliding in the tubular liner.

[0038] According to an aspect of the invention, an annular (high-pressure) sealing gasket can be inserted into a portion of the tubular liner distal from the cover.

[0039] This means that when the tubular liner is removed, the high-pressure gasket is also removed, making assembly and maintenance operations quicker and easier.

[0040] According to an aspect of the invention, the pump may comprise a delivery valve for each hole, said delivery valve being housed in the hole or in the blind cavity of the respective hole or partly in the hole and partly in the blind cavity, and each tubular liner extending directly from a valve body of each delivery valve, said valve body being made of a metal material (a connection between the valve body and the tubular liner is fluid-tight, so that no fluid can flow into the connection area).

[0041] According to another aspect of the invention, the delivery valve may comprise a tubular spacer contained in the tubular liner directly interposed between a surface of the valve body at the portion from which the tubular liner extends and the sealing gasket.

[0042] This prevents the piston in its movement from driving the sealing gasket out of position.

[0043] According to yet another aspect of the invention, the delivery valve may comprise a further annular sealing gasket, e.g. a low-pressure one, (also adapted to sealingly embrace the piston sliding in the tubular liner), which is inserted into the tubular liner and which is at least partially contained in the internal volume, wherein the further gasket is further away from the valve body than the gasket.

[0044] This means that when the pressure valve is removed, the high-pressure gasket and the low-pressure gasket are also removed, making assembly and maintenance even quicker and easier.

[0045] According to a further aspect of the invention, the tubular liner may comprise a portion distal from the valve body and through which the gasket may be inserted into the internal volume, and wherein the delivery valve may comprise a retaining body removably attached to the tubular liner and adapted to prevent the gasket and / or further gasket from exiting the internal cavity through the opening of the tubular liner (the retaining body partially obstructing the portion through which the gasket may be inserted).

[0046] The invention may also provide that the tubular liner may be made in one piece at least with a portion of the valve body of the delivery valve from which it extends.

[0047] Irrespective of the presence or absence of the tubular liner, when the connection conduits form the loop, the invention may provide that the pump may comprise a suction channel, which is provided with an inlet mouth formed in the cover, from which a blind hole is derived crossing both the cover and the head, and from which a plurality of connection conduits branch off (preferably crossing only the head) which reach the respective holes, wherein an assembly formed by the blind cavities and the connection conduits of the delivery channel surrounds said blind hole (in other words, the loop of the connection conduits surrounds the blind hole).

[0048] Again, irrespective of the presence of the tubular liner, a pump according to claim 2 may comprise a delivery valve for each pumping chamber. In this case, the connection conduits can be located entirely downstream of the delivery valves from the direction of fluid flow through the pump.

[0049] According to another aspect of the invention, each blind cavity can be selectively placed in fluid communication with a respective pumping chamber by the delivery valve.

[0050] According to yet another aspect of the invention, each blind cavity and the respective opening are at least partially occupied by a respective delivery valve of the plurality of delivery valves.

[0051] The pump of the invention may comprise a crankcase in which a piston drive mechanism is housed and to which the cylinder head is removably attached, and a plurality of threaded connecting parts which pass through the head and clamp the head between the cover and the crankcase.

[0052] Preferably, the pump can be an axial piston pump of the inclined plate type (preferably fixed plate inclination).BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Further features and advantages of the invention will be more apparent after reading the following description provided by way of non-limiting example, with the aid of the accompanying drawings.

[0054] FIG. 1 is an axonometric view of a first embodiment of a pump according to the invention, said first embodiment also containing elements in common with the other embodiments, as will become clearer below.

[0055] FIG. 2 is a top view of the pump of FIG. 1.

[0056] FIG. 3 is a sectional view of a first embodiment of the pump according to plane III-III of FIG. 2.

[0057] FIG. 4 is an enlargement of a detail IV of FIG. 3.

[0058] FIG. 5 is a side view of a valve assembly according to the invention with which all the embodiments of the pump according to the invention are equipped.

[0059] FIG. 6 is a bottom view of the valve assembly of FIG. 5.

[0060] FIG. 7 is a sectional view of the valve assembly of FIGS. 5 and 6 according to the section plane VII-VII.

[0061] FIG. 8 is a sectional view of the valve assembly of FIGS. 5 and 6 according to the section plane VIII-VIII.

[0062] FIG. 9 is a sectional view of the first embodiment of the pump, but valid for both embodiments of the pump, according to section plane IX-IX.

[0063] FIG. 10 is a sectional view of the first embodiment of the pump, according to the section plane X-X.

[0064] FIG. 11 is a top view of second embodiment of a pump according to the invention.

[0065] FIG. 12 is a sectional view of the pump of FIG. 11 according to the section plane XII-XII.

[0066] FIG. 13 is an enlargement of a detail XIII of FIG. 12.

[0067] FIG. 14 is a sectional view of the pump of FIG. 12 according to the section plane XIV-XIV.

[0068] FIG. 15 is an axonometric view of a first portion of a cover of the pump of FIGS. 11-14.

[0069] FIG. 16 is an axonometric view of a second portion of the cover of the pump of FIGS. 11-14.

[0070] FIG. 17 is a top view of third embodiment of a pump according to the invention.

[0071] FIG. 18 is a sectional view of the pump of FIG. 17 according to the section plane XVIII-XVIII.

[0072] FIG. 19 is an enlargement of a detail XIX of FIG. 18.

[0073] FIG. 20 is a sectional view of the pump of FIG. 17 according to the section plane XX-XX.

[0074] FIG. 21 is a top view of a first portion of a cover of the pump of FIGS. 17-20.

[0075] FIG. 22 is a sectional view of the first portion of the cover of FIG. 21 according to the section plane XXII-XXII.

[0076] FIG. 23 is an axonometric view of the first portion of the cover of FIG. 21 and 22.BEST MODE OF THE INVENTION

[0077] With particular reference to these figures, a pump, in particular of the piston type, for high pressures (i.e. pressures of at least 50 bar), preferably suitable for pumping low-viscosity liquids, such as water or water-containing solutions, has been comprehensively indicated by 1,1′,1″. Further, with particular reference to the enlargements, the pump is preferably of the type provided with a plurality of pumping chambers 20 (i.e. pumping the liquid in parallel with each other), in particular at least three pumping chambers 20, e.g. five pumping chambers 20 and e.g. with automatic valves for regulating the pumping flow.

[0078] The pump illustrated is a multi-cylinder axial piston pump of the inclined-plate type, however, the concepts of the invention are applicable to different pump types, such as a single-cylinder pump and / or a reciprocating pump.

[0079] In particular, the pump 1,1′,1″ shown is of the type provided with a fixed-inclination rotating plate, as will be hereinafter better disclosed, and with automatic valves for adjusting the pumping flow.

[0080] The pump 1,1′,1″ comprises a head 10 in which there is at least one (straight) hole 15, e.g. a cylindrical or circular hole (formed by one or more cylindrical or circular sections coaxial to each other), which contains within it at least partially a pumping chamber 20. In other words, at least part of a total volume of a pumping chamber 20 is contained within a volume defined by a respective hole 15.

[0081] It is not excluded that in an alternative embodiment, the holes may have a different cross-section from the circular one, e.g. they may have a polygonal cross-section, such as square or octagonal.

[0082] In the embodiment illustrated, the head 10 comprises a plurality of holes 15, e.g. equal in number to the number of pumping chambers, each containing within it at least partially a volume of a respective pumping chamber 20 of the liquid. The pumping chambers 20 are independent of each other, each being delimited by respective automatic delivery and suction valves, as will become clear below.

[0083] For example, at least the head portion in which the hole is obtained, i.e. In which the holes are obtained, may be made as a single-piece body, i.e. may be obtained by processing a single body obtained by the solidification of a single melt or injection of material in a mould.

[0084] In the preferred embodiment, such single-piece portion is made of a polymer material, such to make the pump light, economic and quick to be manufactured. Even more preferably, the entire head is made of polymer material (and is monolithic).

[0085] However, it cannot be ruled out that in an embodiment not shown, the portion of the head in which the hole 15 is made, i.e. the holes 15, consists of several parts made of polymer material, each monolithic and attached to each other (either removably or non-removably, e.g. welded).

[0086] The hole 15, i.e. each hole 15, extends substantially coaxially around its own central axis (with respect to which the hole is symmetrical), and, for example, the holes 15 are arranged in the head with their respective central axes parallel to each other.

[0087] For example, in the case of the inclined plate pump with fixed inclination shown in the figures, the holes are arranged radially around a common axis, with respect to which the central axes of the individual holes are parallel. Furthermore, the holes are placed at an equal distance from each other and at the same distance in relation to the common axis. In other words, the holes, i.e. the central axes of the holes, are arranged at equidistant angles to each other along an imaginary circumference centred on the common axis and lying on a plane perpendicular to the common axis.

[0088] Still in the illustrated embodiment, in which there are five holes, the central axes of the holes pass through the vertices of an imaginary regular pentagon lying on a perpendicular plane to the central axes of the cylinders themselves.

[0089] In the case of a reciprocating pump, however, the holes 15 would be aligned with each other along a direction perpendicular to the central axis.

[0090] The head 10 may comprise a first face 25, which is transverse (perpendicular) to the central axis of the hole, i.e., to the axes of all the holes, and is, for example, flat, and an opposing second face 30, which is also transverse (perpendicular) to the central axis of the hole, i.e., to the axes of all the holes.

[0091] The hole 15, i.e. each hole 15, is made, e.g. during the moulding of the polymer material, as a hole with an opening 35 made in the first face 25.

[0092] With particular reference to the enlargements of figures in the illustrated embodiment, the hole, i.e. each hole, is made, e.g. in the moulding of the polymer material, as a through hole extending from the first face 25 to the second face 30, making a first opening 35 (circular) in the first face 25 and a second opening 40 (circular) in the second face 30.

[0093] Going from the second opening 40 towards the first opening 35, the hole 15, i.e. each hole 15, has a narrow portion (with respect to at least the second opening 40) that makes available a shoulder surface 18, which is transverse to the central axis of the hole, in particular perpendicular to it, and faces towards the second opening 40.

[0094] For example, also going from the first opening 35 to the second opening 40, the hole 15, i.e. each hole 15, has a narrow portion (compared to at least the first opening 35) that makes available an additional shoulder surface, which is transverse to the central axis of the hole and faces in the opposite direction to the shoulder surface 18 and towards the first opening 35.

[0095] Going into more detail about the conformation of the hole 15, i.e. each hole 15, it comprises at least one internal (cylindrical) tubular surface 16 (coaxial to the central axis of the hole itself) extending directly from the first opening 35 towards the second face 30 of the head 10.

[0096] The hole 15, i.e. each hole 15 also includes an additional inner (cylindrical) tubular surface 17 coaxial to the inner tubular surface 16 and extending from the second opening 40 towards the first face of the head itself. Between the surface 16 and the surface 17 an inner tubular (cylindrical) surface 19 is interposed having a cross-sectional area (with respect to the central axis) smaller than a cross-sectional area of the surface 16 and the surface 17.

[0097] The surface 19 is (directly) contiguous to the surface 17 and is connected to it (directly) by the shoulder surface 18.

[0098] Similarly, 19 is (directly) contiguous to the surface 16 and is connected to it (directly) by the further shoulder surface.

[0099] In the case illustrated where the surfaces 19 and 17 are circular, i.e. cylindrical, the surface 18 is a circular crown, or loop, lying on a surface perpendicular to the central axis of the hole 15.

[0100] The number of tubular and shoulder surfaces obviously varies depending on the type of automatic valves inserted in the hole and the method of centring them and the gaskets in the head, as will become clearer later on.

[0101] Therefore, a possible third tubular surface should not be ruled out, perhaps even one with a larger diameter than the tubular surface 16 and which allows the centring of the crankcase in relation to the head. Or it is not excluded that the surface 18 faces the first face.

[0102] The pump 1,1′,1″ comprises a piston 45 sliding in the hole 15 along a sliding axis and partially contained therein. That is, the pump comprises a plurality of pistons 45, each sliding in a respective hole 15 of the plurality of holes along a respective sliding axis, and partially inserted therein. Preferably, the sliding axis coincides with the central axis of the hole.

[0103] In the embodiment illustrated, the piston 45, i.e. each piston 45, has a first axial end 50 contained (always) in the hole and an opposing second axial end 55 extending from the cylinder 15 externally to the head through the opening 35.

[0104] The pump 1 comprises a plurality of annular gaskets adapted to circumferentially sealingly enclose the piston 45, i.e. each piston 45, to avoid pumping liquid leakages from the pumping chamber towards the opening 35 in the first face 25.

[0105] In particular, the pump 1,1′,1″ comprises a first annular sealing gasket 60, commonly known as a high pressure gasket, which circumferentially sealingly contacts a portion of the piston 45, i.e., circumferentially contacts a portion of a casing of the piston 45, wherein casing means the side surface of the piston extending coaxially to the sliding axis from one axial end of the piston to the other. Said gasket can additionally be said to circumferentially embrace the piston in contact and is coaxial to the piston, i.e. coaxial to the sliding axis of the piston.

[0106] The first annular sealing gasket is elastic, i.e. resilient, for instance made of a polymer material.

[0107] The first annular sealing gasket 60 is preferably lipped.

[0108] Referring in particular to FIG. 5, the first annular sealing gasket comprises an inner annular lip 65, which sealingly circumferentially contacts said portion of the piston 45, and for example an outer annular lip 70, preferably substantially forming a cross-section V with the inner annular lip.

[0109] The inner annular lip 65 and the outer annular lip 70 branch out from a same side of a ring 75, for instance having a cross section with a substantially rectangular shape.

[0110] The pump 1,1′,1″ also comprises a second annular sealing gasket 80, commonly known as low-pressure gasket, which sealingly circumferentially contacts a portion of the piston 45 (thus it embraces and is coaxial with the piston), i.e. a portion of the casing of the piston 45 (such portion partially overlaps, almost entirely, the portion on which the first gasket acts).

[0111] For instance, the two gaskets are aligned between each other along a direction parallel to the direction of the cylinder axis, with the first annular sealing gasket 60 closer to the first axial end 50 of the piston, i.e. to the pumping chamber 20, than the second annular sealing gasket.

[0112] Also the second annular sealing gasket is elastic, i.e. resilient, for instance made of a polymer material.

[0113] Furthermore, also the second annular sealing gasket 80 is preferably of the lipped type.

[0114] Like the first gasket, the second gasket comprises an inner annular lip 85, which sealingly circumferentially contacts said portion of piston 45, and for example an outer annular lip 90, preferably substantially forming a cross-section V with the inner annular lip.

[0115] The inner annular lip 85 and the outer annular lip 90 branch out from a same side of a ring 95, for instance having a cross section with a substantially rectangular shape.

[0116] In the illustrated embodiment, the pump comprises a first annular sealing gasket 60 and a second annular sealing gasket 80 for each piston 45.

[0117] The pump 1,1′,1″ may comprise a crankcase 100, to which the head 10 is rigidly fixed (i.e. with no residual degrees of freedom), preferably in a removable manner (e.g. by means of a plurality of threaded connection members clamping the head between the crankcase and a portion (head) of the threaded connection member itself. The head, for example, contacts the crankcase at its first face 25. In particular, the crankcase 100 comprises a flat face placed directly in contact with the first face 25 of the head 10.

[0118] The crankcase 100 contains within it a drive mechanism configured to set the piston 45, or pistons 45, in motion in order to pump liquid into the pumping chamber, or chambers. In the illustrated embodiment, the driving mechanism comprises a rotating inclined plate 105, adapted to receive a rotatable motion from a driving shaft outside the pump and having a fixed inclination.

[0119] The inclined plate 105 is housed in the crankcase 100, is rotatably associated with it with respect to an axis of rotation A (e.g. coaxial to the common axis of the cylinders), and for example comprises a flat annular surface lying on a plane inclined with respect to the axis of rotation A (the inclination of which is not variable). Specifically, the inclined plate is rotatably associated via a bearing with a flange 115, which is bolted to the crankcase 100, and through which the crankcase can be attached to a motor or frame (thanks to holes made in the flange) with respect to which the external drive shaft is rotatably associated. In particular, following the rotation of the inclined plate 105, the piston, or pistons, are slid along the sliding axis between a top dead position, in which the volume of the pumping chamber is minimal, and a bottom dead position, in which the volume of the pumping chamber is maximum.

[0120] In detail, the second axial end of the piston, i.e. of each piston, is kept in contact, by the force exerted by a respective elastic element 106, of an annular guide 107 lying on the annular plane surface of the inclined plate 105, for instance by interposing a roller axial bearing.

[0121] Each elastic element, for example in the form of a compression coil spring 106 coaxial to the piston, has a first end connected to the crankcase 100 and a second end connected to the piston 45, for example near the second end 55.

[0122] The second axial end 55 may be rounded and convex in shape and the annular guide 107 may have a plane annular surface parallel to the plane annular surface of the plate. In addition, the crankcase may comprise an annular guide surface (i.e. essentially an internal cylindrical surface) 120, e.g. cylindrical, adapted to guide the piston (with very little or no clearance) 45 as it slides in the hole. That is, the piston is sliding associated with said annular guide surface, which defines the sliding axis X of the piston itself. Such sliding axis may not be perfectly coaxial with the central axis of the hole 15 due to (dimensional and geometrical) production tolerances. In other words, the sliding axis X corresponds to the centre axis of the hole 15 net of the tolerances due to the production and assembly of the components, in particular the production tolerances of the head with its holes, the crankcase with its annular guide surfaces, and the assembly of the head with the crankcase.

[0123] In the illustrated embodiment, a guide annular surface 120 for each piston is present in the crankcase.

[0124] The guide annular surface 120 is made available by a (cylindrical) guide bushing 125, for instance made of metal, preferably steel, inserted in a housing hole made in the crankcase.

[0125] In the illustrated embodiment, the crankcase comprises a plurality of guide bushings 125 each one adapted to guide a respective piston 45 sliding along the corresponding cylinder.

[0126] The guide surface 120 is located between a volume of the crankcase in which the piston drive mechanism is housed and a respective hole 15.

[0127] In particular, the elastic element 106 that pushes the piston towards the inclined plate is interposed between a portion of the crankcase that makes said guide surface available, in particular a portion that supports the guide bushing, and the portion of the piston near the second end 55.

[0128] Such guide bushing 125, i.e. each guide bushing 125, is in communication with the opening 35 made in the first face of the first head 10, i.e. with the respective opening made in the first face.

[0129] In particular, the crankcase includes at the opening 35, i.e. at each opening 35 a through hole 130, which has a larger diameter than the annular guide surface and which makes a corresponding opening at a (flat) face of the crankcase in contact with the first face 25. This through hole 130 is crossed by the piston and connects the guide bushing to the cylinder head.

[0130] An annular seal 135 is housed in the through hole 130, which embraces a portion of the piston 45 and is configured to prevent the entry into the respective hole 15 of oil contained in the crankcase for lubrication of the cylinder drive mechanism and lubrication of the guide surfaces.

[0131] Irrespective of the gasket 135, the through hole 130 has a variable cross-section and makes available an annular shoulder surface 140 facing the first face of the head.

[0132] For example, the annular shoulder surface 140 is located closer to the head than the guide surface 120.

[0133] The crankcase, like the head, can be made of polymer material (with the metal guide bushings inserted during or after the moulding of the polymer material).

[0134] In that case in the crankcase there are metal inserts 150 provided with a female thread which allow to tighten a threaded connection member, such as a screw 145, which is fitted through the head by a through hole 151 made in the head itself.

[0135] Preferably the pump comprises a plurality of threaded connection members 145, for instance the same number as the number of cylinders, configured to fix the head 20 to the crankcase 5 and that are inserted in an equal number of through holes 151 obtained in the head 20.

[0136] For example, the pump may comprise a (rigid) cover 155, 155′, 155″, e.g. made of a metal material, preferably stainless steel or aluminium or brass, removably attached to the head.

[0137] For example, the threaded connection members, i.e. the screws, allow the head to be clamped between the crankcase and said cover. In particular, the cover and head are clamped between a head of the threaded connection members, i.e. screws, and the crankcase. The through holes 151 also extend through the cover.

[0138] The cover, in the illustrated embodiment, comprises a first face 160 in (direct) contact with the second face 30 of the head 10, an opposing second face 165 (substantially parallel to the first face 160) and a blind cavity 175, e.g. in the form of a blind (cylindrical) hole, provided with an opening 176 (circular) made in the first face 160 and which is aligned with the second opening 40.

[0139] So that the hole 15 and the blind cavity 175 together essentially form a blind hole, of which the blind cavity 175 includes a bottom surface 180 that delimits the blind cavity itself (in the direction away from the first face of the cover; further it is said bottom surface 180 that makes the cavity blind).

[0140] The bottom surface 180 is spaced by a non-zero amount from the second face of the head and facing towards it and the piston 45 sliding in that hole 15.

[0141] The opening 176 has a smaller passage section, i.e. diameter, than the passage section, i.e. diameter, of the second opening 40 with which it communicates. In this way, the first face 160 of the cover makes available an abutment surface 177 that extends substantially from a perimeter of the opening 176 to a perimeter of the second opening 40 and, for example, is (flat and) perpendicular to a central axis of a corresponding hole 15.

[0142] The blind cavity 175 comprises a tubular side surface 178 extending from the bottom surface 180 to the opening 176 (thus up to the abutment surface 177) and is for example a cylindrical surface (coaxial to the central axis of the hole 15).

[0143] The invention provides a blind cavity as described above for each hole 15.

[0144] Since the blind cavities are aligned with the respective holes along the axes of the holes themselves, the blind cavities are therefore circumferentially arranged, in the case of the pump being an axial pump with an inclined plate, around the axis of rotation of the plate in the same way as the holes are arranged, therefore angularly equidistant along the imaginary circumference having its centre on the axis of rotation of the plate and eccentric to said axis.

[0145] The cover 155,155′,155″ also comprises a delivery channel, e.g. made entirely in the cover, (located downstream of the pumping chamber with respect to a direction of a pumping fluid through the pump).

[0146] With particular reference to FIGS. 1 and 10, the delivery channel comprises the blind cavity 175, i.e., the blind cavities 175, and a plurality of connection channels 185,185′, 185″ made (entirely) in the cover and each of which runs from one blind cavity to another proximal or adjacent blind cavity, said plurality thus connecting all the blind cavities together in a (closed) loop path. It can also be said that two cavities that are proximal to each other are joined by a single connection channel of the plurality of connection channels and that each connection channel only extends from one blind cavity to a closer cavity. In total, the number of connection conduits is equal to the number of blind cavities (therefore holes 15, therefore pumping chambers).

[0147] It should be noted that as they are made entirely in the cover it also means that they do not intersect the first face or the second face of the cover itself, for example they always have a non-zero distance from the first face and from the second face of the cover.

[0148] For example, the pump may comprise at least three pumping chambers, thus three holes 15, consequently the plurality of blind cavities may comprise a first blind cavity 175, a second blind cavity 175 and a third blind cavity 175. In this case, the plurality of connection channels comprises a first connection channel 185,185′, 185″ connecting (only) the first blind cavity to the second blind cavity, a second connection channel 185, 185′, 185″ connecting (only) the second blind cavity to the third blind cavity, and a third connection channel 185,185′,185″ connecting (only) the third blind cavity to the first blind cavity.

[0149] In the embodiment illustrated, in which there are five pumping chambers, thus five holes, thus five blind cavities, the plurality of blind cavities comprises a first blind cavity 175, a second blind cavity 175, a third blind cavity 175, a fourth blind cavity 175 and a fifth blind cavity 175. In such a case, the plurality of connection channels comprises a first connection channel 185,185′, 185″ connecting (only) the first blind cavity to the second blind cavity, a second connection channel 185, 185′, 185″ connecting (only) the second blind cavity to the third blind cavity, a third connection channel 185,185′, 185″ connecting (only) the third blind cavity to the fourth blind cavity, a fourth connection channel 185, 185′, 185″ connecting (only) the fourth blind cavity to the fifth blind cavity, and a fifth connection channel 185,185′, 185″ connecting (only) the fifth blind cavity to the first blind cavity.

[0150] At least one between a blind cavity and a connection channel is directly connected by means of an outlet channel to an outlet mouth 190 (made in the cover) at which there are means to connect a pipe to the outlet mouth itself, for example in the form of a threaded element coaxial to the outlet mouth. In the illustrated embodiments of the pumps, the outlet mouth generally extends from a blind cavity of the plurality of blind cavities.

[0151] Each connection channel 185,185′,185″ connects only two adjacent blind cavities 175 (proximal to each other) or may connect only two blind cavities (proximal to each other) and the outlet mouth.

[0152] Regardless of the exact conformation of the connection conduits, the head alone, or the head with the cover attached to it, make available a plurality of blind holes 15, 175 (straight and e.g. also cylindrical overall) with a bottom wall 180 facing the pump crankcase and delimiting the hole itself.

[0153] The pump according to the invention can have different types of connection channels and covers, a detailed description of which will be given later.

[0154] The pump 1,1′,1″ also comprises a suction channel, which is provided with an inlet mouth 195, also made in the cover, from which at least one suction conduit in fluid communication with a hole 15 or a blind cavity 175 is derived, or from which a plurality of suction conduits in fluid communication with a respective hole or blind cavity is derived.

[0155] In particular, the intake conduit directly intersects the (respective) hole 15 (or the blind cavity in an embodiment not shown).

[0156] For example, the plurality of inlet conduits comprises a blind hole passing through both the cover (in which it makes the inlet mouth 195) and the head, and a plurality of connection channels 199 (radial with respect to the axis of rotation A) reaching the respective holes 15, thus one for each respective hole.

[0157] Regardless of whether there is an initial common blind hole, the plurality of suction conduits comprises (only) a first (common) section 197 deriving from the inlet mouth 195 and made only in the cover, and a second (common) section 198 subsequent to the first section and made in the head (said second section comprises, for example, a bottom wall opposite the inlet mouth 195). From this second section, connection channels 199 branch off.

[0158] The blind hole is, for example, coaxial to the axis A, and is preferably substantially cylindrical or truncated cone shaped.

[0159] The connection channels of the delivery channel and the blind cavities are arranged around the blind hole 197,198, in particular the first section 197 made in the cover, surrounding it without intersecting it, i.e. essentially forming a (closed) loop path around it (thus radially outward from the blind hole with respect to the axis A).

[0160] To prevent leakage of liquid at the interface between the cover and the head, there is an annular sealing gasket coaxial and external to said through hole of the channel and which is housed in an annular groove made in the first face of the cover.

[0161] This blind hole is for example coaxial to the axis of rotation of the inclined plate.

[0162] As mentioned above, the pump includes automatic valves to control the pumped fluid, including an automatic one-way delivery valve and an automatic one-way suction valve for each pumping chamber.

[0163] Said delivery valve and the suction valve (of an individual pumping chamber, i.e. of each pumping chamber) are intended as means of automatically regulating the inlet and outlet of fluid from the pumping chamber based respectively on a pressure difference between the suction channel and the pumping chamber and on a pressure difference between the pumping chamber and the delivery channel.

[0164] Operation based on the pressure difference is essentially that of one-way hydraulic valves, of which the suction valve is configured and oriented to open only when the pressure in the pumping chamber is lower than the pressure in the suction channel, while the delivery valve is configured and oriented to open only when the pressure in the pumping chamber is higher than the pressure in the delivery channel.

[0165] For example, such means can be made available by a single delivery and suction valve assembly 200 (one for each pumping chamber) removably insertable into the pump, in particular (entirely) removably insertable (and with reduced clearance or to size) into the hole 15, and for example also removably insertable into a pump blind cavity 175, or (entirely) removably insertable into a pump blind hole (15,175) which contains within it a volume of a pumping chamber (and in which a piston slides). It is specified that ‘entirely’ means that the unit with all its components fits into the pump in a removable manner. For example, the entire valve assembly can be removed from the pump as a single body for maintenance.

[0166] Further, the valve assembly 200 is not secured by threaded connection members or other means to the pump (and does not include threaded portions for attachment to the pump), but is retained therein only by clamping (all or part of it) between two abutment or shoulder surfaces, which, for example, are made available by the cover and the head (it is not excluded that the valve assembly in alternative embodiments may be clamped in a vice between the head and the crankcase alone, e.g. between the head and a spacer which insists on a shoulder surface of the crankcase).

[0167] Since it is not retained other than by the pump assembly, in particular by the attachment of the cover to the head, i.e. to the crankcase, it is not necessary to unscrew it from the hole in which it is inserted in order to remove the valve assembly.

[0168] In the following, the pressure and suction valve assembly 200 will be abbreviated as valve assembly 200.

[0169] Overall, the valve assembly 200 is configured to selectively put the suction channel in fluid communication with the pumping chamber and to selectively put the pumping chamber in fluid communication with the delivery channel.

[0170] The valve assembly 200 comprises a (rigid) valve body 205, e.g. monolithic, preferably also made (entirely) of metal material, e.g. brass or stainless steel or aluminium.

[0171] In the illustrated embodiment, the valve body 205 can be inserted to size (with reduced clearance) into the blind hole of the pump containing the volume of the pumping, which in the illustrated embodiment is made available by the hole 15, and for example also by the blind cavity 175. The valve body 205 then slides to size (in contact) along surface 17, the surface 19 on the head side 10 and along the side surface 178 on the blind cavity side 175.

[0172] Additionally, the hole 15 and cover 155, 155′, 155″ can be conformed to clamp the valve body 205, or a portion of the valve body 205, between them when the cover is attached to the head (i.e. to the crankcase). In the embodiment illustrated, this task is performed by the surface 17 and by the abutment surface 177, which contact (directly) the valve body 205, i.e. clamp a portion of the valve body 205, in a vice grip, i.e. they clamp said portion in a vice grip, with each other when the cover is fastened to the head (i.e. to the crankcase).

[0173] The valve body 205 comprises a first (longitudinal) end 210 and an opposing second (longitudinal) end 215, which longitudinal ends are aligned with each other along a central axis of the valve body itself (these longitudinal ends are intersected by said central axis). When the valve assembly 200 is inserted into the pump, the central axis of the valve body 205 is substantially coaxial to the central axis of the hole 15, i.e. of the respective hole 15.

[0174] When placed in the pump, the first end 210 is distal from the crankcase, i.e. from the piston 45, and the second end 215 is proximal to the crankcase, i.e. to the piston 45. In other words, the first end 210 is proximal to the bottom surface 180 and the second end 215 is distal from the bottom wall 180.

[0175] Additionally, when placed in the pump, the first end 210 is inside the blind cavity 175 and the rest of the valve body is in the hole 15.

[0176] The first end 210 makes available a first face, e.g. circular, transverse (perpendicular) to the central axis of the valve body and directed (facing) in the opposite direction to the crankcase, i.e. directed (facing) towards the bottom surface 180.

[0177] Similarly, the second end 215 makes available a second face, e.g. circular, transverse (perpendicular) to the central axis of the valve body and directed (facing) towards the crankcase, i.e. directed (facing) in the opposite direction to the bottom surface 180.

[0178] The first face and second face are connected by a tubular (and circular, e.g. cylindrical or formed by several cylindrical sections) side surface that extends from one end of the valve body to the other.

[0179] The valve body 205 comprises a first abutment surface 220 that contacts (directly) the cover 155,155′, 155″, i.e. it contacts a portion of the first face 160 of the cover, in particular it contacts the (entire) abutment surface 177.

[0180] This first abutment surface 220 is transverse (perpendicular) to the central axis of the valve body, in other words it is coplanar to the abutment surface 177.

[0181] For example, the first stop surface 220 is shaped like a circular crown (consequently it contacts the cover along a circumference).

[0182] The valve body 205 also includes a second abutment surface 225 that contacts (directly) the head 10, i.e. it contacts (directly) the (entire) shoulder surface 18.

[0183] This second abutment surface 225 is transverse (perpendicular) to the central axis of the valve body, in other words, it is coplanar to the shoulder surface 18.

[0184] For example, the second abutment surface 225 is shaped like a circular crown (consequently contacting the head along a circumference).

[0185] When the valve assembly is inserted into the pump and the cover is attached to the head (i.e. the crankcase), the valve body is clamped in a vice grip between the abutment surface 117 and the shoulder surface 18, which hold the valve body in contact with the first abutment surface 220 and the second abutment surface 225 respectively.

[0186] It can also be said that when the valve assembly is inserted into the pump and the cover is attached to the head (i.e. the crankcase), a portion of the valve body comprised between the first abutment surface 220 and the second abutment surface 225 is clamped between the cover and the head.

[0187] The valve body 205 may, for example, be conformed like a revolution body obtained by a revolution about said central axis, e.g. said body being composed of a plurality of cylindrical sections adjacent to one other.

[0188] In the embodiment illustrated, the valve body 205 comprises a side surface (substantially coaxial to the central axis) extending from the first face to the second face of the valve body itself.

[0189] The side surface comprises a first section 230, e.g. cylindrical (outer cylindrical surface), which extends from the first face of the valve body to the first abutment surface 220.

[0190] The first section 230 is inserted (entirely) in the blind cavity 175, in particular it is inserted to size (with reduced clearance) in the side surface 178.

[0191] The side surface then comprises a second section 235, e.g. cylindrical (cylindrical outer surface), which extends from a perimeter of the first abutment surface 220 distal from the first section 230, to the second abutment surface 225.

[0192] The second section 235 is inserted (entirely) into the hole 15, in particular it is inserted to size (with reduced clearance) in the surface 17.

[0193] The side surface then comprises a third section 240, e.g. cylindrical (cylindrical outer surface), which extends from a perimeter of the second abutment surface 225 distal from the second section 235, to the second face of the valve body.

[0194] The third section 240 is inserted (entirely) into the hole 15, in particular it is inserted to size (with reduced clearance) in the surface 19.

[0195] The valve assembly 205 comprises a first conduit 245 adapted to be selectively connected, as will become clearer later, with the delivery channel. In particular, the first conduit, or a plurality of first conduits as will be described below, is the only passage of the valve assembly (and the entire pump) through which the fluid pumped into the (respective) pumping chamber can (selectively) reach the delivery channel.

[0196] The first conduit 245 is made (entirely) in the valve body 205, e.g. in at least one metal portion of the valve body (by removal of material), and extends (solely) from a first (single) (circular) opening 250 made in the first end 210, in particular in the first face of the valve body 205, extending to a second opening 255 made in the second end 215. In particular, it is the second opening, i.e. a section of the first conduit proximal to the first opening that can be selectively connected, as will become clearer later, with the supply channel.

[0197] For example, the first opening 250 is made in a central portion of the first end 210, i.e. of the first face, of the valve body, e.g. in a central position with respect to the side surface of the valve body.

[0198] Further, the first opening 250 lies on a plane substantially perpendicular to the central axis of the valve body.

[0199] The second opening 255, when the valve assembly is inserted into the pump, is always in direct fluid communication with the pumping chamber. In particular, there is no means of regulating the flow through the second opening, neither in the valve assembly nor in the pump, that would prevent the fluid pumped into the first conduit from entering.

[0200] More specifically, there is no shutter capable of occluding, even partially, the second opening 255.

[0201] At the first opening 250, the valve body 205 makes available a first annular sealing seat, which comprises, i.e. consists of, an annular surface 260 surrounding the opening 250, which is coaxial thereto (coaxial to a central axis of symmetry of the opening), and e.g. which runs (extends) from a perimeter (and circular) edge of the first opening 250 (or consists of said perimeter edge).

[0202] For example, the annular surface 260 faces in the opposite direction with respect to the second end of the valve body.

[0203] The annular surface 260 of the first annular sealing seat may be an annular perimeter edge, preferably chamfered / rounded, of the opening 250 or a convex annular surface (e.g., a ball sector) or, as in the illustrated embodiment, a flared, i.e., truncated-conical surface, arranged so that its cross-sectional area increases going from the first opening 250 in the direction away from it (i.e., in the direction of radial departure from the central axis of the hole) and from the second end of the valve body along the central axis.

[0204] In further detail, the first opening 250, i.e. the first annular sealing seat, is always in fluid communication with the second opening 255. In particular, there is no means of regulating the flow through the first conduit between the first opening 250 and the second opening 255, neither in the valve assembly nor in the pump, which would prevent the fluid from flowing between the first and second openings.

[0205] For example, the first opening 250 is coaxial and centred to the central axis of the hole 15.

[0206] The second opening 255 is, for example, made in the second face of the valve body 205 at an eccentric position with respect to the central axis of the hole (and which does not intersect it), e.g. as a circular opening.

[0207] In further detail, the first conduit 245 comprises a first section 261 that extends from the first opening as a blind hole (coaxial to the central axis of the valve body, i.e. coaxial to the central axis of the hole 15) and from which a second section extends to the second opening 255.

[0208] The second section of the first conduit 245 comprises a first portion 265, which extends from the second opening 255 as a blind hole parallel to and eccentric to a central axis of the valve body 205, and a second portion 266 which is made as a through hole intersecting the first section 261, i.e. its blind hole, and the second portion 266. This second portion 266 is inclined with respect to a central section of the valve body.

[0209] In the illustrated embodiment, there is a plurality of (four) first conduits 245, which from the first opening 250 extend to a corresponding plurality of second openings 255 made in the second end, i.e. in the second face, independent of each other and all arranged eccentrically with respect to the central axis of the valve body 205, e.g. also angularly equidistant from the central axis of the valve body (so that the second openings lie with their respective centres on an imaginary circumference having its centre on the central axis and lying on a plane perpendicular thereto).

[0210] In further detail, the first conduits all extend from the common section 260 to the second openings 255, and the first portions of the second sections of each first conduit are arranged eccentrically with respect to the central axis of the valve body, angularly equidistant from the central axis of the valve body.

[0211] When, as in the embodiment illustrated, the valve assembly is both supply and suction, i.e. not only supply, it also comprises a second conduit 270 that is adapted to always be in fluid connection with the suction channel, i.e. with a respective suction conduit. In addition, the second conduit 270 is adapted to be selectively connected, as will become clearer later, with the pumping chamber. In particular, the second conduit, i.e. a plurality of second conduits as will be described below, is the only passage of the valve assembly (and the entire pump) through which the fluid pumped in the delivery channel can (selectively) reach the (respective) pumping chamber.

[0212] The second conduit 270 is built (entirely) into valve body 205 and does not intersect (at any point) the first conduit 245, i.e. the first conduits 245.

[0213] The second conduit is provided with a first opening 275, made in the tubular side surface of the valve body 205 comprised between the first end and the second end; in particular, it is made, when the valve assembly is inserted into the pump, at a section of said side surface proximal to an intersection area between the hole 15 and the suction conduit, so as to always be in direct fluid communication with the suction conduit. In particular, the first opening 275 is made in the second section 235 and is (always) in direct fluid communication with the intersection area between the hole 15 and the suction conduit.

[0214] Additionally, there is no means of regulating the flow through the first opening, neither in the valve assembly nor in the pump, which would prevent the fluid pumped into the second conduit from entering the suction conduit.

[0215] In the illustrated embodiment, the second conduit 270 comprises a plurality of (four) first openings 275 all made in the side surface of the valve body, in particular in the second section 235, and e.g. angularly equidistant from each other around the central axis of the valve body (axis of revolution), i.e. the central axis of the hole 15.

[0216] The second conduit 270 extends from the first opening 275 to a (single) second opening 280 made in the second end 215 of the valve body 205, in particular in the second face of the valve body 205, i.e. centrally located with respect to the second opening 255 of the first conduit 245 (and centrally located with respect to the side surface of the valve body). Preferably the second opening 280 is coaxial with the first opening 250.

[0217] At the second opening 280, the valve body 205 makes available a second annular sealing seat, which comprises, i.e. consists of, an annular surface 285 surrounding the opening 280, which is coaxial thereto (coaxial to a central axis of symmetry of the opening), and e.g. which runs (extends) from a perimeter (and circular) edge of the second opening 280 (or consists of said perimeter edge).

[0218] For example, the annular surface 285 faces in the opposite direction with respect to the first end of the valve body.

[0219] The annular surface 285 of the second annular sealing seat may be an annular perimeter edge, preferably chamfered / rounded, of the opening 280 or a (circular) convex annular surface (e.g., a ball sector) or, as in the illustrated embodiment, a flared, i.e., truncated-conical surface, arranged so that its cross-sectional area increases going from the second opening 280 in the direction away from it (i.e., in the direction of radial departure from the central axis of the hole) and from the first end of the valve body along the central axis.

[0220] In further detail, the second opening 280, i.e. the second annular sealing seat, is always in fluid communication with the first opening 255. In particular, there is no means of regulating the flow through the second conduit between the first opening 275 and the second opening 280, neither in the valve assembly nor in the pump, which would prevent the fluid from flowing between the first and second openings.

[0221] The second conduit is substantially L-shaped, in particular comprising a first section 290 which is derived as a hole from the first opening 275 of the second conduit itself towards a central area of the valve body, i.e. towards the central axis of the valve body or towards the central axis of the hole 15, (perpendicularly to the central axis) and a second section 295 which is derived from the second opening 280 of the second conduit 270 as a blind hole transverse to the first section 290 and intersecting said first section 290.

[0222] In the illustrated embodiment, the second conduit 270 comprises a plurality of first openings 275 from each of which a corresponding first section 290 of the second conduit 270 is derived, which first sections flow into a common second section 295 which is derived from the second opening 280 of the second conduit 270. Therefore, it can also be said that the valve body comprises a plurality of second conduits.

[0223] The second sections of the first conduits 245 pass through portions of the valve body located between two adjacent first sections of the second conduits and the tubular side surface of the valve body itself.

[0224] The valve assembly comprises a first (rigid) shutter 300 movable between a closed position, in which it hermetically obstructs the (only) first opening 250 of the first conduit 245, and an open position, in which it is spaced apart from the first opening of the first conduit and allows flow through the first opening.

[0225] In particular, when the valve assembly is inserted into the pump, in the closed position the first conduit is isolated from the delivery conduit, i.e. the pumping chamber is isolated from the delivery conduit, while in the open position the pumped fluid can flow from the pumping chamber to the delivery conduit through the first opening 250.

[0226] Between the open position and the closed position, the shutter moves along a sliding axis which is substantially straight and coaxial to the central axis of the first opening 250, i.e. coaxial to the central axis of the (respective) hole 15.

[0227] Additionally, in the open position, the first shutter is at a greater distance from the second end than when in the closed position.

[0228] With particular reference to FIGS. 7,8, the first shutter 300 comprises a contact surface 305 adapted to generate a (hermetic) seal with the first annular sealing seat of the first opening 250 when it is in the closed position (under the action of a force that keeps it pressed against said seat). The contact surface is coaxial to the central axis of the first opening 250, i.e. coaxial to the central axis X of the (respective) hole 15.

[0229] Such a contact surface 305 contacts (directly), (only) in said closed position, at least partially the first annular sealing seat along at least one closed annular path, for example said path being a circumference.

[0230] The contact surface comprises, i.e. is made up of, an annular surface (which makes a closed ring path, hence a complete ring) that can be either convex (spherical sector) or truncated cone shaped.

[0231] The valve assembly comprises an elastic element, e.g. in the form of a compression helical spring 310, which generates a force on the first shutter in the direction of keeping the shutter in the closed position. When the force generated on the first shutter (first face) by the pressurised fluid in the first conduit exceeds the sum of the force generated by the elastic element on the shutter (second face) and the force generated on the shutter by the pressurised fluid present downstream (with respect to the direction of flow along the pump from suction and delivery) of the first opening, the first shutter moves to the open position and the fluid can go to the delivery channel.

[0232] The elastic element is held in position by means of a fixed (socket) cage 315, for example removably, to the valve body 205, so that the elastic element is substantially interposed between a portion of said cage and the first shutter. Said cage includes passage holes for the liquid.

[0233] The valve assembly comprises a second (rigid) shutter 320 movable between a closed position, in which it hermetically obstructs the (only) second opening 280 of the second conduit 270, and an open position, in which it is spaced from the second opening of the second conduit and allows flow through the second opening itself.

[0234] In particular, when the valve assembly is inserted into the pump, in the closed position the second conduit is isolated from the pumping chamber, i.e. the pumping chamber is isolated from the suction channel, while in the open position the pumped fluid can flow from the suction channel to the pumping chamber through the second opening 280.

[0235] Between the open position and the closed position, the shutter moves along a sliding axis which is substantially straight and coaxial to the central axis of the second opening 280, i.e. coaxial to the central axis of the (respective) hole 15.

[0236] Additionally, in the open position, the second shutter is at a greater distance from the first end than when in the closed position.

[0237] The first shutter and the second shutter are external to the valve body.

[0238] The second shutter 320 comprises a respective contact surface 325 adapted to generate a (hermetic) seal with the second annular sealing seat of the second opening 280 when it is in the closed position (under the action of a force that keeps it pressed against said seat). The contact surface is coaxial to the central axis of the second opening 280, i.e. coaxial to the central axis X of the (respective) hole 15.

[0239] Such a contact surface of the second shutter contacts (directly), (only) in said closed position, at least partially the second annular sealing seat along at least one closed annular path, for example said path being a circumference.

[0240] As in the case of the contact surface of the first shutter, the contact surface of the second shutter comprises, i.e. consists of, an annular surface (which makes a closed-loop path, hence a complete loop) that can be either convex or truncated cone shaped.

[0241] The valve assembly comprises an elastic element, e.g. in the form of a compression helical spring 330, which generates a force on the second shutter 320 in the direction of keeping the shutter in the closed position. When the force generated on the second shutter (first face) by the pressurised fluid in the second conduit exceeds the sum of the force generated by the elastic element on the second shutter (second face) and the force generated on the second shutter by the pressurised fluid present downstream (with respect to the direction of flow along the pump from suction and delivery) of the second opening of the second conduit, the second shutter moves to the open position and the fluid can flow from the delivery channel to the suction chamber.

[0242] The elastic element is held in position by means of a fixed (socket) cage 335, for example removably, to the valve body 205, so that the elastic element is substantially interposed between a portion of said cage and the second shutter. Said cage includes passage holes for the liquid.

[0243] For both shutters, where the annular sealing seat is truncated cone shaped, the contact surface is preferably convex and not truncated cone shaped. If the annular sealing seat is convex or a rounded edge, the contact surface can be either convex or truncated cone shaped.

[0244] In order to prevent the fluid to be pumped or already pumped from entering between the valve body 205 and the hole 15 and / or the blind cavity 175, the valve assembly comprises a plurality of annular (static) seals housed in respective annular grooves in the side surface of the valve body 205 and insisting on the hole 15 and / or the blind cavity 175.

[0245] In particular, the valve assembly 200 comprises a first annular sealing gasket 340 housed in an annular groove and contacting the blind cavity, in particular the side surface 178, providing a hermetic seal between the first section 230 of the side surface of the valve body and the blind cavity, namely the side surface 178.

[0246] The valve assembly also includes a second annular sealing gasket 345 housed in an annular groove and contacting the respective hole 15, in particular the surface 17. In further detail, the annular groove that accommodates the second annular sealing gasket 345 is made in a portion of the side surface of the valve body that is located between the first opening of the second conduit, i.e. the first openings of the second conduit and the abutment surface 220. In this way, the pumped fluid cannot leak into the gap between the valve body and the hole, and thus cannot infiltrate between the cover and the face of the head in contact with the cover.

[0247] Furthermore, in combination with a third annular 350 gasket, the second gasket prevents pressurised fluid from entering from the pumping chamber into the second conduit and thus into the suction channel.

[0248] The third annular gasket 350 contacts the respective hole 15, in particular the surface 17. In particular, the annular groove that accommodates the third annular sealing gasket is made in a portion of the side surface of the valve body that is located between the first opening of the second conduit, i.e. the first openings of the second conduit, and the abutment surface 225.

[0249] The valve assembly may comprise a tubular liner 360 (rectilinear, e.g. cylindrical) extending seamlessly from the second end of the valve body, i.e. from an outer perimeter edge (proximal to the side surface of the valve body) of the second face of the second end, around the opening of the conduit, i.e. around the second opening 255 of the first conduit 245, in the direction away from the first end. The tubular liner 360 can also be said to extend from the second end, in particular from the second face, as a continuation of the side surface of the valve body, for example as a continuation of the third section 240 of said side surface.

[0250] The purpose of the tubular liner is to protect the head, particularly the head made of polymer material, from the pressures generated in the pumping chamber, so it is made of a metal, preferably a metal such as brass or stainless steel or aluminium. Although the example was made with the pump having a head made of a polymer material, the same considerations can be made in the case where the head is made of a metal having such an elastic modulus and fatigue strength that the pump's integrity cannot be guaranteed at the operating pressures for which it is designed. Additionally, if there is a cover, as in the embodiment illustrated, and said cover accommodates part of the valve assembly and at least part of the delivery channel, the cover must be made of metal, or the delivery channel must be lined on the inside with a metal liner.

[0251] Aside from these considerations, it is specified that it is not strictly necessary to apply the tubular liner only in the case of heads made of polymer material or any other material that is not sufficiently resistant to the pressures involved, but it can also be applied to heads made of a material that is not sufficiently resistant to the working pressures, in order to protect said head and increase its life over time, also in consideration of the lower cost of replacing the valve assemblies compared to the entire head.

[0252] In the illustrated embodiment the tubular liner 360 is a monolithic body with the (entire) valve body 205, however, it is not excluded that in an alternative embodiment not illustrated the tubular liner could be welded to the valve body, in particular to its second face, or it could be attached to the valve body (at the second end) in a removable manner, for example by means of threaded connection members. In particular, in the case of threaded connection members, the liner could comprise a threaded surface adapted to be screwed onto a corresponding threaded surface made at the second opening and could comprise a housing for a static sealing gasket.

[0253] The tubular liner 360 comprises a (single) first end, which is the end derived directly from the second end of the valve body 205, and an opposite (single) second end, wherein the first end and the second end are spaced along the central axis of the valve body, i.e. along the central axis of the second opening 255 (which is then the central axis of the hole 15 when the valve assembly is inserted into the pump). In addition, the tubular liner extends around an axis that is coaxial to at least one of the central axes listed above, and the first end and second end are spaced along that axis.

[0254] The tubular liner 360 has a constant cross-section (with respect to the central axis) from the first end to the second end.

[0255] The tubular liner, for example, is conformed as a rectilinear body having a constant cross-sectional area (with respect to the central axis) along its extension from its first end to the second end.

[0256] When the valve assembly 200 is inserted into the pump, the tubular liner is, for example, entirely contained within the volume of the hole 15. However, if, as will become clearer in the following, if the high-pressure gasket 60 is located in the crankcase or the low-pressure gasket was is housed in the tubular body, the tubular liner may extend into the crankcase. In principle, the tubular liner has an extension such that its second end is in close proximity, for example at, preferably in tight contact with the high-pressure gasket 60 preventing the liquid in the pumping chamber from coming into contact with the hole 15. In the embodiment illustrated, the tubular liner extends as far as the first face of the head (irrespective of whether the second end is in the head or protrudes into the crankcase). The tubular liner 360 comprises an inner tubular surface 365, e.g. cylindrical, and parallel to the central axis of the valve body, i.e. the central axis of the second opening 255, i.e. the central axis of the hole 15. Preferably the inner tubular surface is also coaxial to these axes when the valve assembly is inserted into the pump.

[0257] The surface 365 is radially (with respect to the central axes) outermost with respect to the second opening 255, i.e. it extends from a portion or edge of the second face that is around and outside the second opening. In this way, the internal volume of the tubular liner itself is in fluid communication with said second opening. In particular, the surface 365 is radially outermost with respect to all the second openings 255, i.e. it extends from a portion or edge of the second face that is around and outside a portion or surface of the second face in which all the second openings of the first conduit are made. In this way, the internal volume of the tubular liner itself is in fluid communication with all second openings.

[0258] The surface 365 is also radially outermost with respect to the second opening of the second conduit. It is also radially outermost than the cage that retains the second shutter, so that it is possible to insert such cage into the tubular body and secure it to the valve body during assembly and maintenance.

[0259] The tubular liner 360 also comprises an outer tubular surface 370, e.g. having the same shape as the hole 15, in particular the surface 19, and substantially the same size, so that the outer tubular surface 370 fits into the hole 15, or into the surface 19, with reduced clearance.

[0260] Thus, in the embodiment illustrated, the outer tubular surface is cylindrical and coaxial to the inner tubular surface 365.

[0261] The outer tubular surface 370 is substantially, in the embodiment illustrated, like a continuation of the side surface of the valve body, e.g. like a continuation of the third section 240 of said side surface, in the direction away from the first end of the valve body.

[0262] For example, the third section 240 and the outer tubular surface 370 have the same diameter.

[0263] The tubular liner 360 also comprises an annular surface 375, e.g., flat and transverse (perpendicular) to the inner tubular surface 365 and outer tubular surface 370, which joins said tubular surfaces and essentially defines the limit of the extension of the tubular liner in the direction away from the first end, thus essentially defining the second end of the tubular body.

[0264] The tubular liner 360, i.e. its internal tubular surface 365, defines an internal volume of the tubular liner itself in (direct, always direct) fluid communication with the opening, i.e. the second opening 255 of the first conduit 245. This internal volume comprises at least a portion of the volume of the pumping chamber.

[0265] The inner tubular surface 365 has a larger cross-sectional area, i.e. diameter, than a cross-sectional area, i.e. a diameter, of the piston 45.

[0266] In use, the piston 45 is at least partially contained, with (abundant) clearance, in the internal volume of the tubular liner 360. In practice, between the inner tubular surface 365 and the piston 45, there is an annular gap of non-zero thickness and length.

[0267] The distance between the surface 365 and the surface 370 defines the thickness of the tubular liner.

[0268] The tubular liner 360 extends from the second end away from the first, along the axis of the valve body or the axis of the second opening of the first conduit or the axis of the hole 15, to an annular sealing gasket which sealingly embraces a portion of the piston, which flows through this seal. In particular, the tubular liner extends up to (in direct contact with) the first annular sealing gasket 60 so that this gasket 60 seals the tubular liner, i.e. it seals the inner tubular surface 365, (so as to prevent fluid in the pumping chamber from contacting the hole 15).

[0269] In detail, this contact is made so that the internal volume of the tubular body is closed at one end by the fluidic seal formed by the contact between the first annular sealing gasket 60 and the contact between said gasket 60 and the piston 45.

[0270] For example, this is achieved with the gasket 60 sealed (by elastic deformation) into the inner cavity of the tubular body.

[0271] Preferably, said gasket 60 sealingly contacts the inner tubular surface 365 along a closed annular path transverse to the central axis.

[0272] Specifically, the gasket 60 is inserted into the internal volume of the tubular liner and is sealed on a portion of the inner tubular surface 365. For example, the outer annular lip 70 seals said portion of the inner tubular surface. Additionally, the annular lip 70 is accommodated in the annular gap formed in use between the inner tubular surface and the piston.

[0273] The configuration thus obtained allows the internal cavity to be isolated from the rest of the volume of the hole 15, e.g. it enables the pumping chamber to be isolated from the rest of the volume of the hole 15. In other words, the pumping chamber is thus delimited at least partially (or entirely) by the second end of the valve body, the tubular liner, gasket 60, the piston, the first conduit 245, the first shutter and the second shutter (when said shutters are in the closed position).

[0274] Although not illustrated, it is not excluded that in a non-illustrated embodiment, the tubular body may comprise an annular groove made in the inner tubular surface 365 adapted to serve as a partial housing seat for the gasket 60.

[0275] Between the gasket 60 and the second end, i.e. the second face, of the valve body, a (rigid) tubular spacer 400 is interposed to prevent the piston 45 in its stroke from displacing said gasket towards the second end of the valve body.

[0276] The tubular spacer 400 comprises a first (direct) longitudinal contact end of the second face of the valve body and an opposite second longitudinal contact end (e.g. by interposing a pusher ring 405) of the gasket 60.

[0277] The tubular spacer is entirely contained within the internal volume of the tubular liner and, for example, comprises a (cylindrical) inner tubular surface 410, and an opposite (cylindrical) outer tubular surface in contact with the inner tubular surface 365.

[0278] The inner tubular surface 410 of the tubular spacer is arranged radially, with respect to the central axis of the second opening, or of the valve body or of the hole, and, for example, more outwardly with respect to the second opening 280 of the second conduit, and more inwardly with respect to the second opening 255 of the first conduit, or to the plurality of second openings 255 of the first conduit.

[0279] When the surface 410 is also radially innermost with respect to the second opening 255, at least one groove or cut 415 is made in the tubular spacer which extends from the inner tubular surface towards the outer tubular surface, thus allowing fluid communication between the second opening 255 of the first conduit with the internal volume defined by the tubular spacer, thus allowing fluid communication between the second opening 255 and said internal volume, i.e. with the pumping chamber. This groove or cut 415 extends at least from an intermediate portion (between the first and second ends) of the tubular spacer, to the first end of the tubular spacer itself, making in said end an opening at the second opening 255.

[0280] In particular, there being a plurality of second openings 255 of the first conduit 245, the spacer comprises a plurality of grooves or cuts 415 each positioned at a respective second opening 255.

[0281] In order to align the tubular spacer with the valve body, i.e. to align the groove or cut 415 with the opening 255 (or to align the grooves or cuts 415 with the respective opening), the valve assembly comprises at least one reference element to allow for a single mechanical alignment between the valve body and the tubular spacer. In the embodiment shown, the reference element comprises a pin 500 that can be inserted into a hole made in the second end of the valve body and from which it protrudes so that it can also be inserted into a hole made in the first end of the tubular spacer.

[0282] The tubular spacer is shaped to be passable by the piston. In detail, the inner tubular surface has a cross-section such that piston 45 can slide with clearance within an internal volume defined by said inner tubular surface itself. Furthermore, this cross-sectional area is such that the second shutter is unobstructed, and is for example radially larger than the cage of the second elastic element.

[0283] The pump, i.e. the valve assembly, may comprise an annular body 420 (rigid and made / manufactured as a monolithic body distinct from the valve body and tubular liner) in which a through hole 421 is made in direct fluid communication with the internal volume of the tubular liner, i.e. with the pumping chamber. This through hole is therefore coaxial to the central axis of the valve body and is adapted to be crossed by the piston 45 (during its movement between top dead centre and bottom dead centre) A housing for the low-pressure seal 80 (located between the first face and second face) is made in the through hole 421. This housing is shaped like an annular groove in which the low-pressure gasket 80 is inserted and retained in order to prevent the gasket 80 from moving (along the central axis) dragged by the piston 45.

[0284] The low-pressure seal is arranged in such a way that the outer annular lip 90 makes a tight seal with one surface of the annular groove.

[0285] The annular body 420 comprises a drainage channel 424 adapted to place in fluid communication the suction channel with a volume comprised between the piston, the high-pressure gasket and the low-pressure gasket, so that any leakage of pressurised fluid from the high-pressure gasket can be discharged at suction pressure.

[0286] Additionally, in order to prevent leakage, the annular body 420 or a portion of the head at the annular body comprises a housing groove to accommodate a static sealing gasket 422.

[0287] The annular body 420 comprises a side surface 423 that fits snugly, i.e. with reduced clearance, into a portion of the through hole 130 that lies between the shoulder surface 140 and the face of the crankcase in contact with the head.

[0288] In the embodiment of the valve assembly 200, only the high-pressure gasket 60 is part of the valve assembly, i.e. it is removed from the head with the rest of the valve assembly, while the high-pressure gasket is not part of the valve assembly.

[0289] In that case, the annular body comprises a first face 425 (e.g., annular, planar and transverse, i.e., perpendicular, to the central axis of the valve body) on which the second end of the tubular liner rests and for example the gasket 60, i.e., the ring 75 of the gasket 60, (in this way the gasket 60 is held in place (clamped in a vice) between the tubular spacer and the annular body).

[0290] The annular body 420 also comprises a second face 430 (e.g., annular, planar and transverse, i.e., perpendicular, to the central axis of the valve body) that rests on the annular shoulder surface 140, e.g., so that when the cover is fixed to the crankcase, the valve body, tubular liner and annular body 420 are clamped between the cover and the crankcase, i.e., between the annular shoulder surface 140 and the surface 176.

[0291] In this embodiment 420, the seat of the gasket 422 is made in the annular body.

[0292] The tubular liner 360 is preferably a monolithic body, e.g. monolithic with the valve body 205, however, this does not exclude the possibility that it may be formed by several sections interlocked in series or screwed to one other, possibly where the seal between one section and the other is ensured by static-type annular sealing gaskets.

[0293] The first opening 250 (with the related annular sealing seat 260) of the first conduit, the first shutter and the first elastic element together essentially make a one-way delivery valve.

[0294] The second opening 280 (with the related annular sealing seat 285) of the second conduit, the second shutter and the second elastic element together essentially make a one-way delivery valve.

[0295] Although only one embodiment of the valve assembly with tubular liner is illustrated in the figures and comprises both the first and second conduits, it cannot be excluded that the valve assembly may include the tubular liner and not the second conduit. In that case the valve assembly would be a one-way delivery valve with a tubular liner. Also, the liner may not be present, in which case, although the presence of the liner would be preferred, the spacer should extend from the annular body 420 to the second end of the valve so as to keep the valve body in contact with the cover and clamp it between the spacer and the cover due to the fastening of the cover to the crankcase.

[0296] Therefore, the pump according to the invention comprises a delivery valve, to be understood either as a portion of the valve assembly performing the function of controlling the delivery from the pumping chamber, said portion thus comprising the valve body, the first conduit, the first shutter, the elastic element of the first shutter and the cage (the latter if necessary) or as a valve which performs only the function of controlling the delivery and is equipped with the valve body, the first conduit, the first shutter, the elastic element of the first shutter and the cage (the latter if necessary), thus not comprising the second conduit with the related second shutter and elastic element.

[0297] The delivery valve thus defined, of which there is one for each pumping chamber 20, is (directly) interposed between the respective pumping chamber and a corresponding section of the delivery channel (the delivery valve is thus immediately upstream of the delivery channel with respect to the direction of flow through the pump).

[0298] In particular, the delivery valve, i.e. all the delivery valves, are located (entirely) upstream of the connection conduits of the delivery channel.

[0299] In further detail, the first opening that is selectively occluded by the first shutter is located (entirely) upstream of the connection conduits of the delivery channel.

[0300] In addition or alternatively, it can also be said that between each pumping chamber and an internal volume of the respective blind cavity, said volume being defined by the side wall, the back wall and the first end of the valve body, a corresponding delivery valve is interposed, so that this volume can only be placed in fluid communication with the pumping chamber by means of the delivery valve, i.e. only when the first shutter is in the open position. The internal volume of the cavity is isolated from the pumping chamber in the first instance via the gasket 340 and the shutter when it is in the closed position.

[0301] This volume is therefore directly in fluid communication with the first opening of the first conduit when the first shutter is in the open position.In the Figures

[0302] FIGS. 1-10 illustrate a first embodiment of the connection channels 185, which corresponds to the embodiment 1 of the pump.

[0303] In such an embodiment, with particular reference to FIG. 10, the connection conduits 185 are each provided with at least one first pair of side walls 185a, which are opposed to each other, i.e. facing each other, and each comprise at least one curved surface having a respective single axis of curvature, which axis of curvature is transverse (perpendicular) with respect to the first and second faces of the cover, i.e. with respect to a plane perpendicular to the central axes X of the holes 15. In other words, this axis of curvature is parallel to the central X axes of the holes 15.

[0304] In the embodiment illustrated, there are two consecutive pairs of curved surfaces, where each of said pairs extends from a respective blind cavity, i.e. from the side wall in the blind cavity, to join the other pair of opposing curved surfaces, which extend from a proximal blind cavity, i.e. from the side wall in the proximal blind cavity, in an area at a substantially intermediate distance between the blind cavities that the connection conduit connects.

[0305] For example, the curved surfaces define respective concave portions of the side walls facing each other. In addition, the curved surfaces of the side walls of each connection conduit 185 are symmetrical with respect to an axis of symmetry containing the central axis X of the respective hole 15 (in particular, this axis of symmetry contains the central axes X of the holes 15 of the blind cavities that the connection conduit 185 connects).

[0306] Each connection conduit 185 also comprises a second pair of side walls 185b, preferably flat and opposed to each other. Each wall of the additional pair of side walls is configured to extend from a side wall 185a to the opposite side wall 185a.

[0307] For example, the side walls 185 of the pair of side walls 155 each lie on a transverse plane (perpendicular) to the axes of curvature of the curved surfaces of the first pair of side walls, i.e. they lie in transverse planes (perpendicular) to the central axes X of the holes 15.

[0308] The first pair of side walls 185a and the second pair of side walls 185b entirely form the respective connection conduit 185.

[0309] In order to form the connection conduits of the embodiment indicated by 185 the invention makes available the following method.

[0310] The method envisages the step of providing a disc milling cutter, that is a disc milling cutter equipped with a shaft, adapted to allow the connection to a device able to transmit a rotational motion to the shaft, and a disc-shaped body equipped with teeth to remove material and rotationally integral with the shaft (without residual degrees of freedom). In particular, the disc-shaped body is fixed to the shaft so that a central axis, that is an axis of symmetry, of the disc-shaped body is coaxial to a central axis of the shaft, in relation to which the shaft is placed in rotation.

[0311] The disc-shaped body is preferably of the three-cut type, that is it is able to remove material along a side cylindrical portion and along a pair of planar opposite faces which de-limit the top and bottom of the cylindrical side portion.

[0312] The disc-shaped body has a radius that is greater than its height (measured in the direction of the axis of rotation of the shaft to which it is attached), while the shaft is preferably shaped like a cylindrical body, in this case elongated, i.e. its height is greater than its radius.

[0313] For example, the disc-shaped body has a larger diameter than a diameter of the shaft, for example the diameter of the disc-shaped body is such that the disc-shaped body protrudes from the shaft along a radial direction, in particular greater than an amount greater than half the minimum distance between two proximal blind cavities.

[0314] Additionally, the diameter of the disc-shaped body is smaller than an average diameter of the blind cavity (measured transverse to the axis X) so that it can be easily inserted into the blind cavity. In particular, the insertion that must be allowed is along the axis X.

[0315] The method then involves inserting the disc milling cutter inside the blind cavity 175 translating it along the axis X 8 without removing material, i.e. along a central axis of the blind cavity that is coaxial to the central axis when the cover is mounted on the head.

[0316] Prior to this stage, the blind cavities 175 may have been previously made during casting or after casting by removing material from a block of material. For example, the method could involve the same disc milling cutter that makes the connection conduits having a diameter such that it forms the blind cavity, for example with a single translation.

[0317] Following the step of inserting the disc milling cutter into the blind cavity 175, the method includes the step of stopping the insertion of the disc milling cutter into the blind cavity when the entire disc-shaped body is inside the blind cavity and a minimum distance between the first face of the cover at the opening of the blind cavity and the disc-shaped body is non-zero. This step also envisages maintaining the milling cutter as it was inserted.

[0318] Next, the method comprises the step of moving the disc cutter, i.e. translating the disc milling cutter, along a path, e.g. straight, towards an adjacent (proximal) blind cavity, along a transverse direction, e.g. perpendicular, to the respective central axis (of the blind cavity i.e. of the hole 15, as explained above) so as to create at least one recess extending from the side surface of the cavity, for example said recess is provided with two opposing curved surfaces 185a each provided with an axis of curvature and two opposing planar surfaces 185b.

[0319] The transverse movement in the direction towards the other blind cavity occurs until the cutter shaft is almost in contact with the side wall of the blind cavity.

[0320] If the two proximal blind recesses were sufficiently close together, the previous step would result in not only a recess, but the entire connection conduit 185.

[0321] In the embodiment illustrated, however, the distance is large (i.e. it is greater than the difference between the disc-shaped body of the cutter and its shaft) and a further step is required to create the connection conduit 185, i.e. to remove the cutter from the recess and blind cavity, insert the milling cutter in the adjacent (proximal) blind cavity towards which the milling cutter was translated in the previous step, and basically repeat the above steps by translating the milling cutter after inserting it, as described above, until the milling cutter meets the previously formed recess and makes an opening there that puts the two adjacent (proximal) blind cavities in communication.

[0322] The connection conduit is of course made by rotating the shaft of the disc milling cutter in order to remove material from the cover.

[0323] For all the connection conduits, this method must be repeated as many times as there are blind cavities.

[0324] In this embodiment of FIGS. 1-10, the outlet mouth 190 is in direct fluid connection, in particular extending from, a blind cavity of the plurality of blind cavities, and for example exits into a side wall of the cover. In particular, there are two distinct outlet mouths 190, e.g. diametrically opposed with respect to the axis A, each running from a respective blind cavity, and for example exiting into a side wall of the cover that connects the first face and the second face of the cover itself.

[0325] FIGS. 11-16 illustrate a second embodiment of the connection conduits 185′, which corresponds to the embodiment 1′ of the pump.

[0326] In such an embodiment, the connection conduits each comprise a first curved side surface 185′ a extending from one blind cavity to the other blind cavity (i.e., from the respective adjacent (proximal) side surfaces 178), i.e., the blind cavities joined by a single connection conduit 185′, and having concavity facing a central area of the cover, i.e., towards the section 197, i.e., the axis A. For example, the first curved side surface 185′a has a single axis of curvature, preferably located at the central area of the cover, i.e. at the section 197, i.e. the axis A. In particular, the first curved side surface 185′a is, for example, a cylindrical side surface sector having an axis of curvature coaxial to the axis A.

[0327] Each connection conduit 185′ further comprises a second curved side surface 185′b extending from one blind cavity to the other blind cavity (i.e. from the respective side surfaces 178) joined by the connection conduit, which is radially closer to said central area (to the axis A) than the first curved side surface 185′ a and which also has concavity facing the central area, i.e. towards the section 197, i.e. towards the axis A. The second surface is similar to the first and has a single axis of curvature, preferably located at the central zone of the cover, i.e. the axis A. In particular, the second curved side surface 185′b is also, for example, a sector of cylindrical side surface having an axis of curvature centred on the axis A, but in this case the second curved side surface is obtained from a cylinder having a smaller radius than the cylinder with which the first curved side surface is obtained (in other words, the axis of curvature of the first and the second is substantially the same and the first has a smaller radius of curvature than the second).

[0328] The first and second curved side surfaces are essentially parallel to the axis A.

[0329] Each connection channel 185′ further comprises a third side surface 185′c and a fourth side surface 185′d, which are opposed to each other and connect the first curved side surface and the second curved side surface on opposite sides of these first and second surfaces.

[0330] For example, these third and fourth curved side surfaces are planar and transverse (perpendicular) to the axis X.

[0331] Together, these four surfaces form a respective entire conduit 185′.

[0332] In order to define in even greater detail the conformation of the first and second walls, a profile obtained from the section of the first curved side surfaces of all the connection conduits 185′ can be identified with respect to a section plane perpendicular to the central axes X, which profile lies on a first circumference (substantially centred on the axis A), which circumference has a larger diameter than a second circumference (substantially centred on the axis A) on which the profiles obtained from the section of the second curved side surfaces of all the connection conduits 185′ lie with respect to a section plane perpendicular to the central axes X.

[0333] It can substantially be said that altogether the connection conduits 185′ form a plurality of sections of a circular loop, e.g. with opposing walls (the first and second) parallel to the axis A, essentially coaxial to the central axis A and intersecting all the blind cavities of the plurality of blind cavities. In addition, along such a loop the connection conduits have a constant cross-sectional area (with respect to a direction of fluid flow through the connection conduits) at each of their points.

[0334] In the illustrated embodiment, in order to achieve such a configuration of the connection conduits and to accommodate part of the valve assembly in the cavity, the cover 155′ is made in (at least) two portions, of which a first portion 155′a and a second portion 155′b can be removably connected to each other (although it is not excluded that in a embodiment not illustrated they can be welded to each other). This removable connection is made by means of the threaded connection members 145 that clamp the head between the crankcase and the cover.

[0335] The first portion 155′a, for example made as a disc-shaped body (such as a cylindrical disc-shaped body coaxial to the axis A), comprises a first face in contact with the second portion 155′b and an opposing second face which makes available at least part of the second face 165 of the cover. In the first portion 155′a, a first section of each blind cavity is made, said first section comprising the respective end wall 180 and a first portion 178′a of the side wall 178 which is derived directly from the end wall 180. The first sections are thus essentially formed like blind holes that make an opening in the first face of the first portion 155′a.

[0336] At its first face, the first portion 155′a comprises a planar (flat) surface 600 perforated by the first sections of each blind cavity and engraved by a plurality of grooves each connecting two adjacent (proximal) first sections of blind cavities to each other. Each of these grooves intersects the first portion 178′a of the side wall of said first sections of blind cavities adjacent (proximal) to each other.

[0337] These grooves follow a curved trajectory with concavity facing the central area of the cover, in particular said trajectory has radius of curvature centred on the axis A. In particular, each of said grooves makes available the first curved side surface 185′a, the second curved side surface 185′b and the third side surface 185′c of a respective connection conduit 185′ (wherein the third side surface 185′c substantially makes a bottom surface of said groove).

[0338] Overall, the grooves draw a loop, e.g. circular, preferably coaxial to the axis A, which intersects all the first sections of the blind cavity.

[0339] It is not ruled out that in an alternative embodiment not illustrated, the grooves could be rectilinear, so that the first wall and the second wall would be rectilinear.

[0340] The surface 600 of the first face is preferably transverse (perpendicular) to the axes X, in particular the axis A. As will become clearer later on, the important thing, however, is that this surface of the first portion is in direct contact, and along its entire extension, with a conjugate surface made in the second portion.

[0341] In the illustrated embodiment, the first curved side surface 185′a and the second curved side surface 185′b are made available entirely from the first portion 155′a, however, it is not excluded that in an embodiment not illustrated, in addition to the groove made in the first portion of the cover, there is a second groove made in the second portion of the cover and that the first and second side walls are made available partly from the first groove and partly from the second groove.

[0342] The first portion 155′a comprises a central through hole 605 that is surrounded (without intersection) by the first sections of the blind cavities and grooves and that crosses the first portion from the first face to the second face, e.g. this central through hole is coaxial to the axis A.

[0343] The first portion 155′a comprises the outlet mouth 190, in particular in the embodiment illustrated the outlet mouth 190 extends from a first section of the first plurality of blind cavities, e.g. by drilling through the respective bottom wall 180 (consequently the outlet mouth is created in the second face of the cover 155′).

[0344] The second portion 155′b comprises a disc-shaped body (e.g. a cylindrical disc-shaped body coaxial to the axis A), having a first face that makes available the (entire) first face 160 and an opposing second face in contact with (and complementary to) the first face of the first portion 155′a, i.e. of the surface 600.

[0345] In the disc-shaped body of the second portion 155′b there is a second section of each blind cavity, said second section comprising the respective opening 176 of the blind cavity, and a second portion 178′b of the side wall 178 which is derived directly from the opening 176. The second sections are therefore substantially through holes that pass through the disc-shaped body from its first face to its second face. Altogether, the first section and the second section each form a respective entire blind cavity.

[0346] In the embodiment illustrated, the second section of blind cavity made in the second portion 155′b has a conformation such that the first end of the valve body with the entire surface area 230 is inserted into said second section of blind cavity to size, i.e. the second portion 178′b has a diameter such that the surface area 230 is inserted into it to size. Furthermore, this second section has an extension in the direction of the axis X that is essentially equal to the extension of the surface 230 in the same direction.

[0347] Again in the embodiment illustrated, the first portion 178′a has a smaller diameter than the portion 178′b, i.e. than the surface 230, so that a portion of the first face of the first portion 155′a which is located around the first section of blind cavity forms an annular abutment surface on which a portion of the first end of the valve body rests.

[0348] At its second face, the second portion 155′b makes available a planar (flat) surface 610 perforated by the second sections of each blind cavity. For example, the planar surface 610 contacts the planar surface 600 along its entire extension, in particular the planar surface 610 is also transverse (perpendicular) to the central axes X, i.e. the axis A.

[0349] The second face of the disc-shaped body of the second portion, i.e. the planar surface 600, when in contact with the first face of the first portion 155′a, closes one side of the grooves (a side opposite the bottom surface of the grooves i.e. opposite the third side wall, thus closing a groove opening that the groove itself forms in the planar surface 600) forming together with the grooves the entire connection conduits 185′. In particular, the second face, i.e. the flat surface 610, makes available the fourth side surface 185′d of the connection conduits. For purely illustrative purposes, two sections of the flat surface 610 have been drawn in FIG. 16, making two corresponding fourth side surfaces 185′d available.

[0350] The second portion 155′b comprises a first (cylindrical) tubular body 625 extending from the second face of the second portion 155′b in a direction away from the first face of the second portion itself, which is surrounded (without intersections) by the second sections of the blind cavities and which makes available the first section 197 of the blind hole, in particular an inner tubular surface of the first tubular body makes available said first section 197.

[0351] The first tubular body 625 fits to size into the hole 610, in particular a (cylindrical) outer tubular surface 630 of the first tubular body 625 fits to size into the hole 605.

[0352] The first tubular body 625, at one end opposite the second face of the disc-shaped body of the second portion 155′b, makes the inlet mouth 195 available. In particular, the inner tubular surface of the first tubular body makes the inlet mouth 195 available.

[0353] The second portion 155′b also comprises a second (cylindrical) tubular body 635 extending from the second face of the second portion 155′b in a direction away from the first face of the second portion itself, which surrounds (without intersections) the second sections of the blind cavities and makes available the side surface of the cover connecting the first face 160 to the second face 165 of the cover itself.

[0354] The first portion 155′a is inserted to size on the second portion 155′b, e.g. it is inserted to size in a cavity between the first tubular body 625 and the second tubular body 635 and has the second face of the second disc-shaped body of the second portion as the bottom wall.

[0355] Specifically, the second tubular body comprises a (cylindrical) inner tubular surface 640 and the first portion 155′a comprises a (cylindrical) outer annular side surface 645. As a result, the annular side surface 645 is inserted to size on the inner tubular surface 640 while at the same time the outer tubular surface 630 of the first tubular body 625 is inserted to size in the hole 605.

[0356] In order to ensure a fluidic seal between the two portions of the cover and to prevent leakage of liquid in the interface area of the two portions, i.e. between the first face of the first portion and the second face of the second portion, there is at least one (static) annular sealing gasket 615 radially (with respect to the axis A) more external with respect to the blind cavities, and a radially more internal (static) annular sealing gasket 620. Of which both gaskets insist on an annular section of the first portion 155′a and an annular section of the second portion 155′b.

[0357] The annular sealing gasket 615 can be interposed in direct contact between the inner tubular surface 640 and the side surface 645, preferably in the side surface 645 a groove is made to accommodate the gasket 615.

[0358] With regard to the annular sealing gasket 620, it can, for example, be interposed in contact between the outer tubular surface 630 and the hole 605, preferably in the outer tubular surface 630 a groove is made to accommodate the gasket 620.

[0359] It cannot be ruled out that in an alternative embodiment, gaskets could insist on the surface 600 and on the surface 610, e.g. in one of the two, or in both, there could be annular grooves for housing the gaskets.

[0360] Furthermore, it is not excluded that in an alternative embodiment the first portion and the second portion of the cover 155′ could be two disc-shaped bodies stacked on top of each other, so the first tubular body and the second tubular body would not be present. In this case, the first portion and the second portion would each make available a section of the side surface of the cover connecting the second face 165 to the first face 160 and a section of the blind hole section 197.

[0361] The portions of the holes 151 made in the cover are divided into a first section made in the first portion 155′a and a second section made in the second portion 155′b.

[0362] In order to make the cover 155′, and thus to make the connection conduits 185′, the invention makes available a method comprising a first cylindrical disc-shaped body, provided with a through hole 605, to make the first portion 155′a, and a second cylindrical disc-shaped body, from which a first tubular body and a second tubular body rise, to make the second portion 155′b.

[0363] The method involves making a plurality of blind holes in the first disc-shaped body by removing material, so as to make the first sections of the blind cavities 175 (thus the first sections are angularly equidistant as blind cavities).

[0364] The method also involves making grooves in the first face of the first portion, e.g. by removing material, preferably using a disc milling cutter or a slot mill.

[0365] In addition, the method involves drilling through holes in the second disc-shaped body to form the second sections of the blind cavities, leaving the surface 610 seamless so that the grooves can be closed on one side when the two portions of the cover are assembled. Then, by removing material, all the other necessary holes and gasket sealing seats described above will be drilled in the two disc-shaped bodies.

[0366] FIGS. 17-23 illustrate a third embodiment of the connection conduits 185″, which corresponds to the embodiment 1″ of the pump.

[0367] In this embodiment, the connection channels 185″ are made as straight (and cylindrical) through holes entirely contained in the cover and each (only) extending from one blind cavity to an adjacent (proximal) blind cavity (i.e. from the respective side surfaces of said blind cavities). Specifically, these through holes create a first opening 185″a in a blind cavity, i.e. in the side surface of the blind cavity, and a second opening 185″b in the adjacent (proximal) blind cavity, i.e. in the side surface of the adjacent (proximal) blind cavity. These through holes do not pass through any other part of the cover than the parts comprised between two adjacent blind cavities. In other words, these through holes do not pass through either the first face, the second face or the side surface of the cover itself.

[0368] These through holes are inclined with respect to a central axis of the blind cavity opening. Consequently, one of the first opening and the second opening is closer to the first face or the second face of the cover than the other opening.

[0369] The inclination allows a drill or a slot mill to be used to make the through hole by inserting the tip of the tool into a blind cavity, resting the tip on the side wall from the blind cavity and pushing the tool through the blind cavity drilling the side wall.

[0370] In the illustrated embodiment, in order to achieve such a configuration of the connection conduits and to accommodate part of the valve assembly in the cavity, the cover 155″ is made in (at least) two portions, of which a first portion 155″a and a second portion 155″b can be removably connected to each other (although it is not excluded that in a embodiment not illustrated they can be welded to each other). This removable connection is made by means of the threaded connection members 145 that clamp the head between the crankcase and the cover.

[0371] The first portion 155″a, for example made as a disc-shaped body (such as a cylindrical disc-shaped body coaxial to the axis A), comprises a first face in contact with the second portion 155″b and an opposing second face which makes available at least part of the second face 165 of the cover. In the first portion 155″a, a first section of each blind cavity is made, said first section comprising the respective end wall 180 and a first portion 178″a of the side wall 178 which is derived directly from the end wall 180. The first sections are thus essentially formed like blind holes that make an opening in the first face of the first portion 155″a.

[0372] At its first face, the first portion 155″a comprises a planar (flat) surface 700 perforated by the first sections of each blind cavity.

[0373] The first face, thus the surface 700, and the second face of the first portion are not intersected by the holes that make the connection conduits 185″.

[0374] The surface 700 of the first face is preferably transverse (perpendicular) to the axes X, in particular the axis A. As will become clearer later on, the important thing, however, is that this surface of the first portion is in direct contact, and along its entire extension, with a conjugate surface made in the second portion.

[0375] The first portion 155″a comprises the inlet mouth 195 and a central through hole 705 extending from said inlet mouth, which is surrounded (without intersection) by the first sections of the blind cavities and which crosses the first portion from the first face to the second face, for example said central through hole is coaxial to the axis A. Said central through hole 705 substantially represents an initial portion of the section 197 starting from the entrance mouth 195.

[0376] The first portion 155″a comprises the outlet mouth 190, in particular in the embodiment illustrated the outlet mouth 190 extends from a first section of the first plurality of blind cavities, e.g. by drilling through the respective bottom wall 180 (consequently the outlet mouth is created in the second face of the cover 155′).

[0377] The second portion 155″b comprises a disc-shaped body (e.g. a cylindrical disc-shaped body coaxial to the axis A), having a first face that makes available the (entire) first face 160 of the cover 155″ and an opposing second face in contact with (and complementary to) the first face of the first portion 155″a, i.e. of the surface 600.

[0378] In the disc-shaped body of the second portion 155″b there is a second section of each blind cavity, said second section comprising the respective opening 176 and a second portion of the side wall 178 which is derived directly from the opening 176. The second sections are therefore substantially through holes that pass through the disc-shaped body from its first face to its second face. Altogether, the first section and the second section each form a respective entire blind cavity. For example, the first sections and the second sections have the same diameter, however it is not excluded that they could have different diameters as in the case of the cover 155′.

[0379] At its second face, the second portion 155″b makes available a planar (flat) surface perforated by the second sections of each blind cavity. For example, the planar surface contacts the planar surface 700 along its entire extension, in particular the planar surface 710 is also transverse (perpendicular) to the central axes X, i.e. the axis A.

[0380] The second portion essentially acts as a spacer for the first portion in relation to the head. This allows for sufficiently long connection conduits. Otherwise, if the cover were a single body, the greater depth of the entire blind cavity compared to its first section alone would mean that the conduits would have to be inclined more in order to be able to be drilled easily with a tool, since the longer and narrower a socket body such as the blind cavity is, the more, with the same size drill bit or milling cutter, it would be necessary to incline the tool in order to be able to insert it into the cavity and drill a hole that is transverse to the side walls of the blind cavity itself. However, more inclined conduits would mean that the blind cavities would have to be either closer together or larger, which would worsen pump performance.

[0381] In the preferred embodiment, the through holes that make the connection conduits 185″ have an inclination with respect to the first face of the cover, i.e. the second face of the head, i.e. the surface 700, of an angle I comprised between 15° and 35°, preferably between 20° and 30°, in particular comprised between 23° and 27°. Likewise, these connection conduits form an acute angle comprised between 55° and 75°, preferably between 60° and 70°, particularly comprised between 63° and 67°, with the axis X of the respective blind cavity they intersect.

[0382] With particular reference to FIG. 19, In order to ensure a fluidic seal between the two portions of the cover and to prevent leakage of liquid in the interface area of the two portions, i.e. between the first face of the first portion and the second face of the second portion, there is at least one (static) annular sealing gasket 715 radially (with respect to the axis A) more external with respect to the blind cavities, and a radially more internal (static) annular sealing gasket 720. Of which both gaskets insist on an annular section of the first portion and an annular section of the second portion.

[0383] The gaskets, for example, insist in contact with the surface 700 and the surface 710, and are housed in respective annular gasket grooves in at least one of the two surfaces.

[0384] The first and second portions of the cover 155″ are two disc-shaped bodies stacked on top of each other and having the same diameter. In this case, the first portion and the second portion each make available a section of the side surface of the cover connecting the second face 165 to the first face 160 and a section of the blind hole section 197.

[0385] The portions of the holes 151 made in the cover are divided into a first section made in the first portion 155″a and a second section made in the second portion 155″b.

[0386] In order to make the cover 155″, and thus to make the connection conduits 185″, the invention makes available a method comprising a first cylindrical disc-shaped body, provided with a through hole 705, to make the first portion 155″a, and a second disc-shaped body to make the second portion 155″b.

[0387] The method involves making a plurality of blind holes in the first disc-shaped body by removing material, so as to make the first sections of the blind cavities 175 (thus the first sections are angularly equidistant as blind cavities).

[0388] The method also involves drilling, along a straight direction, with a tool such as a drill or a slot mill inclined to the axis X, the side wall of a first section of a blind cavity until the tip of the tool enters the first section of an adjacent blind cavity.

[0389] Then, by removing material, all the other necessary holes and gasket sealing seats described above will be drilled in the two disc-shaped bodies.

[0390] The operation of the pump according to the invention is as follows.

[0391] The piston 45, i.e. each piston 45, under the action of the drive mechanism contained in the crankcase moves along its sliding axis in the hole 15 between a lower dead centre position, where the volume of the pumping chamber is maximum, and an upper dead centre position, where the volume of the pumping chamber is minimum.

[0392] When the piston moves from top dead centre to bottom dead centre, a pressure drop occurs in the pumping chamber which causes the first shutter (delivery shutter) to close, and when the pressure becomes lower than the pressure in the suction channel, it causes the second shutter (suction shutter) to open, thus allowing fluid to be sucked from the delivery channel into the pumping chamber. Specifically, the fluid enters from the delivery channel into the first opening 275, i.e. into the first openings 275, passes through the first conduit and exits from it through the second opening 280.

[0393] Upon reaching bottom dead centre, the piston moves towards top dead centre, compressing the fluid and thus increasing the pressure in the pumping chamber. As a result of the increase in pressure, the second shutter moves to the closed position and the first shutter moves to the open position, allowing the pumped fluid to reach the delivery channel. Specifically, under the thrust of the piston, the fluid flows into the second opening of the first conduit, i.e. the second openings of the first conduit, and from there, passing through the first opening 250, it arrives in the delivery channel.

[0394] If the tubular liner is present, the fluid under the thrust of the piston passes through the grooves or cuts in the tubular spacer before reaching the second openings of the first conduit.

[0395] The tubular liner allows the pressurised fluid to be contained and directed, preventing it from coming into contact with the inner surfaces of the hole 15.

[0396] After passing through the first conduit opening, the pumped fluid enters the internal cavity immediately downstream from the direction of flow from suction to delivery and flows to the outlet mouth 190. Depending on the configuration of the delivery channel, and which blind cavity of the plurality it is, from the blind cavity the fluid may flow directly to the delivery mouth 190 if it is directly communicating with the blind cavity, or it may enter a connection conduit and from there flow to the outlet mouth 190, or it may enter a connection conduit and from there to a consecutive adjacent blind cavity until it enters the connection conduit or a connecting blind cavity from which it may flow directly to the outlet mouth 190.

[0397] When the pump needs to be serviced or assembled, the user simply unscrews the screws that secure the cover to the crankcase, removes the cover, and, thanks to the shape of the hole and the side surface of the valve body, simply pulls the valve assembly out of the hole, thus also removing the high-pressure seal.

[0398] It should be noted that in this discussion, rigid is understood to mean not noticeably deformable under normal working loads to which it is subjected. In other words, a rigid element does not perform its function for which it was designed also by means of its own deformation.

[0399] An elastic element is defined as a body that is shaped in such a way that it deforms (only) elastically under the working loads to which it is subjected and therefore also (or only) performs its function through its own elastic deformation. It is to be noted that the term elastic deformation is to be understood as opposed to plastic deformation.

[0400] In the present case a gasket is elastically deformed to adhere to certain surfaces in order to generate a possibly hermetic seal.

[0401] Further, it should be noted that a monolithic body is defined as a body obtained from the solidification of a single casting, or injection, of (a single) material in a mould and, if necessary, subsequent processing of this solidified body by removal of material.

[0402] When we talk about a ball sector, we specify that this geometric element is an annular surface that makes a closed loop and is defined as a portion of the spherical surface directly interposed between two planes parallel to each other and both intersecting the spherical surface.

[0403] The term to size and with reduced clearance is understood to mean that the elements with this coupling can slide in relation to each other without any particular effort and without tilting appreciably with respect to the sliding direction. If, on the other hand, there is abundant clearance, the elements may tilt appreciably in the direction of travel.

[0404] An axis of curvature is defined as an axis around which a curved surface extends and whose surface is maintained parallel to said axis. In particular, all planes tangent to the curved surface are parallel to said axis. For example, it may be the set of centres from which the radii of curvature of the section profiles of the curved surface itself sectioned with respect to planes parallel to one other (and perpendicular to the axis of curvature itself). When there is a single axis of curvature, it means that the curved surface is like a rectangular or square sheet folded by pushing two opposite sides towards each other. Examples of surfaces with a single axis of curvature are cylindrical surfaces, surfaces obtained from the translation along an axis of sections of a two-dimensional oval, surfaces obtained from the translation along an axis of sections of a two-dimensional parabolic curve, surfaces obtained from the translation along an axis of sections of a two-dimensional exponential curve, etc.

[0405] The invention thus conceived is susceptible to several modifications and variations, all falling within the scope of the inventive concept.

[0406] Moreover, all details can be replaced by other technically equivalent elements.

[0407] In practice, the materials used, as well as the contingent shapes and sizes, can be what-ever according to the requirements without for this reason departing from the scope of protection of the following claims.

Claims

1. A piston pump having at least three pumping chambers comprising:a plurality of pistons,a head in which a plurality of through holes are made, in each of which a respective piston is slidably accommodated and in each of which a respective pumping chamber is at least partially contained,a cover removably attached to the head and having a first face in contact with the head and an opposite second face, anda delivery channel made in the cover.

2. The pump according to claim 1, wherein said delivery channel comprises:a plurality of blind cavities made in the cover, each having an opening made in the first face at a respective opening made in the head by a corresponding through hole of the plurality of through holes,a plurality of connection channels made in the cover, each of which extends from one blind cavity to another adjacent blind cavity, connecting all the blind cavities together in a loop path,an outlet mouth made in the cover and connected to at least one from a blind cavity and a connection channel.

3. The pump according to claim 2, wherein the connection conduits each comprise:a first pair of side walls, opposed to each other and each having a respective curved surface having a single axis of curvature transverse with respect to the first face and to the second face of the cover, anda second pair of side walls flat and opposed to each other, each extending from one side wall to the opposite side wall of the first pair of side walls and trans-verse to the axes of curvature of the first pair of side walls.

4. The pump according to claim 2, wherein the connection conduits are made as rectilinear through holes entirely contained in the cover and each extending from a blind cavity to another adjacent blind cavity.

5. The pump according to claim 4 wherein said through holes are inclined with respect to a central axis (X) of the opening of the blind cavity.

6. The pump according to claim 2, wherein the connection conduits each comprise:a first curved side surface extending from one blind cavity to another ad-jacent blind cavity, joined by the connection conduit itself, and having concavity facing a central area of the cover,a second curved side surface extending from one blind cavity to another adjacent blind cavity, joined by the connection conduit itself, which is radially closer to said central zone than the first curved side surface and which also has concavity facing the central area, anda third side surface and a fourth side surface opposed each other and connecting the first curved side surface and the second curved side surface on opposite sides of said curved side surfaces.

7. The pump according to claim 1, comprising:a crankcase in which a piston drive mechanism is housed and to which the head is removably attached, anda plurality of threaded connection members that cross the head and clamp the head between the cover and the crankcase.

8. The pump according to claim 2, comprising a suction channel, which is provided with an inlet mouth, formed in the cover and from which a blind hole is derived, which passes through both the cover and the head and from which a plurality of connection channels (199) branch off to the respective holes, wherein an assembly formed by the blind cavities and the connection conduits of the delivery channel sur-rounds said blind hole.

9. The pump according to claim 1, wherein the cover is made of metal material and the head is made of polymer material.

10. The pump according to claim 9, wherein each through hole is at least partially lined with a tubular liner made of metal material.

11. The pump according to claim 2, comprising a delivery valve for each pumping chamber, wherein the connection channels are entirely downstream of the delivery valves with respect to the fluid flow direction through the pump.

12. The pump according to the claim 11, wherein each blind cavity is selectively placed in fluid communication with a respective pumping chamber by the delivery valve13. The pump according to 11, wherein the blind cavity and the respective opening are at least partially occupied by a respective delivery valve.

14. The pump according to claim 1, wherein the pump is an axial piston and inclined plate type pump.

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