Automatic delivery and suction valve assembly and pump provided with said valve assembly

Abstract

An automatic suction and delivery valve assembly (200, 200', 200''), which may be removably inserted in high pressure pumps (1,1'), is described, said valve assembly comprising: a valve body (205) provided with a first end (210) and an opposite second end (215), a first duct (245) developing from a first opening (250) made in the first end of the valve body to a second opening (255) made in the valve body, a second duct (270) made in the valve body and not intersecting the first duct, provided with a first opening (275) made in the valve body and a second opening (280) made in the second end of the valve body, a first shutter (300) movable at least between a closed position in which it tightly obstructs the first opening (250) of the first duct, and an open position, in which it is spaced from the first opening (250) of the first duct and allows the passage of a flow through the first opening itself, and a second shutter (320) movable at least between a closed position, in which it tightly obstructs the second opening (280) of the second duct, and an open position, in which it is spaced from the second opening (280) of the second duct and allows the passage of a flow through the second opening. Where the valve body (205) at the first opening of the first duct and the second opening of the second duct makes available an annular sealing seat (260) of the first shutter and an annular sealing seat (285) of the second shutter, respectively. In addition, the first and second shutters each comprise a corresponding contact surface (305, 325) which at least partially contacts, when the shutter is in the closed position, the respective annular seat along at least one closed annular path, which contact surfaces (305, 325) each comprise either a respective convex annular surface or a truncated-cone surface.

Description

[0001] AUTOMATIC DELIVERY AND SUCTION VALVE ASSEMBLY AND PUMP PROVIDED WITH SAID VALVE ASSEMBLY

[0002] TECHNICAL FIELD

[0003] The present invention relates to a valve, in particular an automatic delivery and suction valve assembly for pumps, e.g. high pressure pumps, and a pump provided with said valve, preferably an axial piston pump.

[0004] PRIOR ART

[0005] They are known automatic delivery and suction valve assemblies which, if connected to the pumping chamber of a pump, to a delivery duct and to a suction duct, automatically allow, based on pressure differences, to suck the liquid to be pumped through the suction duct towards the pumping chamber and to send the fluid pumped from the pumping cham- ber to the delivery duct.

[0006] A known embodiment of said automatic valve assemblies comprises a single valve body in which a central duct is made which passes through it from one side to the other defining a first opening at a first axial end and a second opening at a second axial end of the valve body. Such central duct is configured to place in fluid communication the pumping cham- ber with the delivery duct.

[0007] The valve assembly then comprises a plurality of peripheral ducts eccentric to the central duct and each provided with a first opening made in a side surface of the valve body placed between the first end and the second end, and a second opening made in the second end of the valve body. Each peripheral duct is configured to place the suction duct in fluid communication with the pumping chamber.

[0008] The valve assembly also comprises a first shutter, to tightly close the first opening of the central duct under the thrust of a first elastic element, and a second shutter to tightly close all the second openings of the peripheral duct under the thrust of a second elastic ele- ment.

[0009] In particular, the valve assembly is shaped such that when the volume of the pumping chamber increases, a depression is generated therein which overcomes the force of the second elastic element releasing the second openings of the peripheral ducts from the second shutter. When the volume of the pumping chamber is reduced, an over-pressure is generated in the pumping chamber itself which overcomes the force of the first elastic element, releasing the first opening of the central duct from the first shutter. A drawback of the prior art is that in order to close the second openings of the peripheral ducts, which are positioned eccentrically around the second opening of the central duct, it is required to use a shutter provided with a plane circular crown contact surface, which in the closed position perfectly lies on a plane circular crown surface made in the valve body and in which the second openings of the peripheral ducts are made. This solution is expensive because in order to create the plane surface of the circular crown of the contact surface and the plane surface of the circular crown in the valve body, it is required to carry out precise and expensive machining in order for the two surfaces to be perfectly plane and parallel, so as to be entirely in contact with each other when the shutter is in the closed position. In case this parallelism was not observed, it would not be possible to ensure perfect valve sealing, with the consequent risk of fluid pressure passing into the suction lines during pumping.

[0010] An object of the present invention is to overcome the limits of the prior art in the context of a rational and cost-effective solution. The dependent claims outline preferred and / or particularly advantageous aspects of the invention.

[0011] DISCLOSURE OF THE INVENTION

[0012] In particular, the invention makes available an automatic suction and delivery valve as- sembly, which may be removably inserted in high-pressure pumps, said valve assembly comprising: - a valve body provided with a first end and an opposite second end,

[0013] - a first duct developing from a first opening made in the first end of the valve body to a second opening made in the valve body,

[0014] - a second duct made in the valve body and which does not intersect the first duct, provided with a first opening made in the valve body and a second opening made in the second end of the valve body,

[0015] - a first shutter movable at least between a closed position, in which it tightly ob- structs the first opening of the central duct, and an open position, in which it is spaced from the first opening of the central duct and allows the passage of a flow through the first opening, - a second shutter movable at least between a closed position, in which it tightly obstructs the second opening of the peripheral duct, and an open position, in which it is spaced from the second opening of the peripheral duct and allows the passage of flow through the second opening, and wherein the valve body at the first opening of the first duct and the second opening of the second duct makes available an annular sealing seat for the first shutter and a sealing annular for the second shutter, respectively, wherein the first and second shutters each comprise a corresponding contact surface which at least partially contacts, when the shutter is in the closed position, the respective annular seat along at least one closed annular path, which contact surfaces each com- prise a respective convex annular surface or a truncated-cone surface.

[0016] Thanks to this valve assembly architecture, which does not employ plane shutters, i.e., whose contact surfaces are not a plane circular crown of the prior art, the valve is more resistant to dirt and fouling, as any accumulating dirt does not compromise the sealing as in the case of flat shutters, and it is also cheaper to manufacture, as the shutters of the invention and the associated sealing seats require less precise and less expensive pro- cessing than that required to manufacture a flat shutter and its perfectly parallel flat seat. The shutters according to the invention are more resistant to dirt than flat shutters be- cause any dirt or fouling that may settle between the abutment surface of the shutter and the shutter itself would tend to lift a portion of the shutter (cause the shutter to tilt) and consequently a fluid could pass uncontrolled between the shutter and the abutment sur- face thereof.

[0017] According to one aspect of the invention, the convex annular surface may be a revolution surface obtained by the revolution of a curved segment around an axis of revolution.

[0018] According to another aspect of the invention, the contact surface may be a sphere sector. According to yet another aspect of the invention, the first opening of the first duct may be made in a central portion of the first end and the second opening of the second duct may be made in a central portion of the second end.

[0019] According to a further aspect of the invention, the first opening of the first duct and the second opening of the second duct may be coaxial.

[0020] The invention may further provide that the second duct may comprise a first tract which originates from the first opening of the second duct towards a central area of the valve body and a second tract which originates from the second opening of the second duct as a blind hole transverse to the first tract and intersecting said first tract. In the embodiment shown, the valve assembly comprises a plurality of first ducts all de- veloping from the first opening made in the first end of the valve body to a plurality of respective second openings made in the second end of the valve body, and wherein the second opening of the second duct is made in the second end of the valve body in a central position relative to the plurality of second openings of the first ducts.

[0021] According to an aspect of the invention, the first ducts may comprise a common first tract developing from the first opening as a blind hole and a plurality of second tracts develop- ing from the first tract, each independent of the other second tracts, as blind holes which create a respective second opening of the plurality of second openings at the second end of the valve body.

[0022] According to another aspect of the invention, the second tracts of the first ducts may be eccentric to the second tract of the second duct and are each provided with at least one portion parallel to the second tract of the second duct.

[0023] According to another aspect of the invention, the valve assembly may comprise a tubular (cylindrical) jacket developing (without interruption) from the second end, around the sec- ond opening of the first duct and, for example, also around the second opening of the second duct, in a direction moving away from the first end (wherein said tubular jacket comprises an inner tubular surface radially more external than the second opening of the first duct). According to a further aspect of the invention, in a portion of the tubular jacket distal from the second end of the valve body, a sealing gasket may be inserted (in a seat either by interference or elastic deformation) adapted to enclose a piston slidably accommodated therein.

[0024] The invention also makes available a pump provided with the valve assembly of claim 1 in direct fluid communication with a pumping chamber of the pump itself.

[0025] BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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 accom- panying drawings. Figure 1 is an axonometric view of a first embodiment and a second embodiment of a pump according to the invention.

[0027] Figure 2 is a top view of the pump of Figure 1 . Figure 3 is a section view of a first embodiment of the pump according to the plane Ill-Ill in Figure 2.

[0028] Figure 4 is an enlargement of a detail IV of Figure 3.

[0029] Figure 5 is a side view of a valve assembly according to the invention which the first embodiment of the pump is provided with.

[0030] Figure 6 is a view from below of the valve assembly of Figure 5.

[0031] Figure 7 is a section view of the valve assembly of Figure 5 and 6 according to the section plane VII-VII.

[0032] Figure 8 is a section view of the valve assembly of Figure 5 and 6 according to the section plane VIII-VIII.

[0033] Figure 9 is a section view of the first embodiment of the pump, but valid for both embod- iments of the pump, according to the section plane IX- IX.

[0034] Figure 10 is a section view of the first embodiment of the pump, but valid for both embod- iments of the pump, according to the section plane X-X . Figure 11 is a section view of a first embodiment of the pump according to the plane XI- XI in Figure 2.

[0035] Figure 12 is an enlargement of a detail XII of Figure 11.

[0036] Figure 13 is a side view of another embodiment of a valve assembly according to the invention, which the second embodiment of the pump is equipped with. Figure 14 is a view from below of the valve assembly of Figure 13.

[0037] Figure 15 is a section view of the valve assembly of Figure 13 and 14 according to the section plane XV-XV.

[0038] Figure 16 is a section view of the valve assembly of Figure 13 and 14 according to the section plane XVI-XVI. Figure 17 is a section view of a third embodiment of the valve assembly according to the invention.

[0039] BEST MODE TO IMPLEMENT THE INVENTION

[0040] With particular reference to these figures, a pump, in particular of the piston type, for high pressures (i.e. pressures of at least 50 bars), preferably suitable for pumping low-viscosity liquids, such as water or water-containing solutions, has been globally referred to as 1 ,

[0041] 1'. Furthermore, with particular reference to the enlargements in Figure 4 and Figure 12, the pump is preferably of the type provided with a plurality of pumping chambers 20 (par- allel with each other, i.e. pumping the liquid in parallel with each other), in particular at least three pumping chambers 20, such as five pumping chambers 20 and, for instance, with automatic valves for adjusting the pumping flow. The pump shown is a multi-cylinder axial piston pump of the inclined-plate type, however, the concepts of the invention may be applied to different types of pumps, such as a single- cylinder pump and / or an alternative pump.

[0042] In particular, the pump 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.

[0043] The pump 1 ,1 ’ comprises a head 10 wherein at least one (straight) hole 15, e.g. a cylin- drical or circular hole (formed by one or more cylindrical or circular tracts coaxial to each other) is made, which at least partially contains a pumping chamber 20 therein. In other words, at least a part of a total volume of a pumping chamber 20 is contained within a volume defined by a respective hole 15.

[0044] It is not excluded that in an alternative embodiment, the holes may have a cross-section other than the circular one, e.g. they may have a polygonal cross-section, such as square or octagonal

[0045] In the embodiment shown, the head 10 comprises a plurality of holes 15, e.g. equal in number to the number of pumping chambers, each one at least partially containing therein 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 hereinafter.

[0046] For example, at least the head portion wherein the hole is made, i.e. wherein the holes are made, may be formed in 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.

[0047] In the preferred embodiment, such single-piece portion is made of a polymeric material, such as to make the pump light, cheap and quick to be manufactured. Even more prefer- ably, the entire head is made of a polymeric material (and is made in a single piece).

[0048] However, it cannot be excluded that in an embodiment not shown, the head portion wherein the hole 15, i.e. holes 15, are made, consists of several polymeric parts, each of them made in a single piece, fixed to each other (either removably or also non-removably, e.g. welded).

[0049] The hole 15, i.e. each hole 15, develops substantially coaxially around its own central axis (in relation 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.

[0050] For example, in the case of the inclined plate pump with fixed inclination of 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 an equal distance in relation to the common axis. In other words, the holes, i.e. the central axes of the holes, are arranged angularly equally-spaced from each other along an imaginary circumference centred on the common axis and lying on a plane perpendicular to the common axis.

[0051] Still in the embodiment shown, wherein there are five holes, the central axes of the holes pass through the vertices of an imaginary regular pentagon lying on a plane perpendicular to the central axes of the cylinders.

[0052] In the case of an alternative pump, however, the holes 15 would be aligned with each other along a direction perpendicular to the central axis.

[0053] 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 holes, and is, for example, plane, and an opposite second face 30, which is also transverse (perpendicular) to the central axis of the hole, i.e. to the axes of all the holes.

[0054] The hole 15, i.e. each hole 15, is created for example during the step of moulding the polymeric material, as a hole provided with an opening 35 made in the first face 25.

[0055] With particular reference to the enlargements of Figures 4 and 12, in the embodiment shown, the hole, i.e. each hole, is made, e.g. in the step of moulding the polymeric mate- rial, as a through-hole extending from the first face 25 to the second face 30, obtaining a first (circular) opening 35 in the first face 25 and a second (circular) opening 40 in the second face 30.

[0056] Going from the second opening 40 towards the opening 35, the hole 15, i.e. each hole 15, has a narrow portion (compared to at least the second opening 40) that makes avail- able a shoulder surface 18, which is transverse to the central axis of the hole, in particular perpendicular thereto, and is directed towards the second opening 40. For example, even going from the first opening 35 to the second opening 40, the hole 15, i.e. each hole 15, has a narrow portion (in relation to at least the first opening 35) which makes available a further shoulder opening, which is transverse to the central axis of the hole and is directed towards a direction opposite the shoulder surface 18 and towards the first opening 35.

[0057] Talking in greater detail about the shape of the hole 15, i.e. of each hole 15, it comprises at least one inner (cylindrical) tubular surface 16 (coaxial to the central axis of the hole itself) developing directly from the first opening 35 towards the second face 30 of the head 10. The hole 15, i.e. each hole 15 also comprises an additional inner (cylindrical) tubular surface 17 coaxial to the inner tubular surface 16 and developing from the second open- ing 40 towards the first face of the head itself. Between the surface 16 and the surface 17, an inner tubular (cylindrical) surface 19 having a cross-section (relative to the central axis) smaller than a cross-sectional area of the surface 16 and surface 17 is interposed . The surface 19 is (directly) contiguous to the surface 17 and is (directly) connected thereto by the abutment surface 18.

[0058] Similarly, the surface 19 is (directly) contiguous to the surface 16 and is (directly) con- nected thereto by the additional abutment surface.

[0059] In the case shown wherein the surfaces 19 and 17 are circular, i.e. cylindrical, the surface 18 is a circular crown, or ring, lying in particular on a surface perpendicular to the central axis of the hole 15.

[0060] In the embodiment of the pump shown in Figure 12, the surface 16 is not present as the surface 19 extends up to the first opening 35.

[0061] The number of tubular and shoulder surfaces obviously varies depending on the type of automatic valves inserted in the hole and on the method of centring them and the gaskets in the head, as will become clearer hereinafter.

[0062] Therefore, a possible third tubular surface should not be excluded, perhaps even one with a larger diameter than the tubular surface 16 and which allows centring the crankcase in relation to the head. Or it may not even be excluded a condition in which the surface 18 is directed towards the first face.

[0063] The pump 1 ,1 ’ comprises a piston 45 sliding into the hole 15 along a sliding axis and partially contained therein. That is, the pump comprises a plurality of pistons 45, each sliding into 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.

[0064] In the embodiment shown, the piston 45, i.e. each piston 45, has a first axial end 50 contained (always) in the hole and an opposite second axial end 55 protruding from the cylinder 15 out of the head through the opening 35.

[0065] The pump 1 ,1 ’ comprises a plurality of annular gaskets adapted to circumferentially seal- ingly 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. In particular, the pump 1 ,1 ’ comprises a first sealing annular gasket 60, commonly known as a high pressure seal, which circumferentially sealingly contacts a portion of the piston 45, i.e., it circumferentially contacts a portion of a piston skirt 45, where skirt refers to the side surface of the piston extending coaxially to the sliding axis from one axial end of the piston to the other. It may additionally be said that said gasket circumferentially encloses the piston with contact, i.e. it is coaxial to the sliding axis of the piston.

[0066] The first sealing annular gasket is elastic, i.e. resilient, for instance made of a polymeric material.

[0067] The first sealing annular gasket 60 is preferably lipped.

[0068] Referring in particular to Figure 5, the first sealing annular gasket comprises an inner annular lip 65, which sealingly circumferentially contacts said portion of the piston 45, and for instance an outer annular lip 70, preferably substantially forming a cross-section V with the inner annular lip.

[0069] The inner annular lip 65 and the outer annular lip 70 originate from a same side of a ring 75, for instance having a cross-section with a substantially rectangular shape. The pump 1 also comprises a second sealing annular gasket 80, commonly known as low-pressure gasket, which sealingly circumferentially contacts a portion of the piston 45 (thus it encloses and is coaxial with the piston), i.e. a portion of the skirt of the piston 45 (such portion partially overlaps, almost entirely, the portion on which the first gasket acts). For instance, the two gaskets are aligned between each other along a direction parallel to the direction of the cylinder axis, with the first sealing annular gasket 60 closer to the first axial end 50 of the piston, i.e. to the pumping chamber 20, than the second sealing annular gasket. Also the second sealing annular gasket is elastic, i.e. resilient, for instance made of a polymeric material.

[0070] Furthermore, also the second sealing annular gasket 80 is preferably of the lipped type.

[0071] Similarly to the first gasket, the second gasket comprises an inner annular lip 85, which sealingly circumferentially contacts said portion of the piston 45, and, for instance, an outer annular lip 90, preferably substantially forming a cross-section V with the inner an- nular lip.

[0072] The inner annular lip 85 and the outer annular lip 90 originate from a same side of a ring 95, for instance having a cross-section with a substantially rectangular shape. In the embodiment shown, the pump comprises one first sealing annular gasket 60 and one second sealing annular gasket 80 for each cylinder 45.

[0073] The pump 1 may comprise a crankcase 100, to which the head 10 is rigidly fixed (i.e. without residual degrees of freedom), preferably in a removable manner (e.g. by means of a plurality of threaded connecting pieces clamping the head between the crankcase and a portion (head) of the threaded connecting member itself. The head, for example, contacts the crankcase at its first face 25. In particular, the crankcase 100 comprises a plane face placed directly in contact with the first face 25 of the head 10.

[0074] The crankcase 100 contains therein a drive mechanism configured to set the piston 45, i.e. the pistons 45, in motion in order to pump liquid into the pumping chamber, or cham- bers.

[0075] In the embodiment shown, the drive mechanism comprises a rotating inclined plate 105, adapted to receive a rotatable motion by a driving shaft outside the pump and having a fixed inclination.

[0076] The inclined plate 105 is housed in the crankcase 100, is rotatably associated with it in relation to a rotation axis A (e.g. coaxial to the common axis of the cylinders), and for example comprises a plane annular surface lying on a plane inclined in relation to the rotation axis A (the inclination of which is not variable). Specifically, the inclined plate is rotatably associated, by means of a bearing, to a flange 115, which is bolted to the crank- case 100, and through which the crankcase may be fixed to a motor or frame (by means of holes drilled in the flange) against which the outer drive shaft is rotatably associated.

[0077] In particular, following the rotation of the inclined plate 105, the piston, each piston, is slid along the sliding axis between a top dead centre position, wherein the volume of the pumping chamber is minimal, and a bottom dead centre position, wherein the volume of the pumping chamber is maximum.

[0078] 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.

[0079] Each elastic element, which is 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. 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. substantially an inner cylindrical surface) 120, e.g. cylindrical, adapted to guide the piston (with a small or no clearance) 45 as it slides into the hole. That is, the piston is slidably associated with said annular guide surface, which defines the sliding axis X of the piston itself. Such slid- ing axis may not be perfectly coaxial with the central axis of the hole 15 due to (dimen- sional and geometrical) productive tolerances. In other words, the sliding axis X corre- sponds to the central axis of the hole 15 net of the tolerances due to the production and assembly of the components, in particular the manufacturing tolerances of the head with its holes, the crankcase with the relative annular guide surfaces, and the assembly of the head with the crankcase.

[0080] In the embodiment shown, a guide annular surface 120 for each piston is present in the crankcase.

[0081] The guide annular surface 120 is made available for instance by a (cylindrical) guide bushing 125, for instance made of metal, preferably steel, inserted into a housing hole made in the crankcase.

[0082] In the embodiment shown, the crankcase comprises a plurality of guide bushings 125 each one adapted to guide a respective piston 45 sliding along the corresponding cylin- der. The guide surface 120 is interposed between a volume of the crankcase wherein the piston drive mechanism and a respective hole 15 are housed.

[0083] 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.

[0084] Such guide bushing 125, i.e. each guide bushing 125, is in communication with the open- ing 35 made in the first face of the first head 10, i.e. with the respective opening made in the first face.

[0085] In particular, the crankcase comprises at the opening 35, i.e. at each opening 35, a through-hole 130, having a larger diameter than the annular guide surface and which creates a corresponding opening at a (plane) face of the crankcase in contact with the first face 25. Such through-hole 130 is passed through by the piston and connects the guide bushing to the head.

[0086] In the through-hole 130, an annular sealing gasket 135 is housed which encompasses a portion of the piston 45 and is configured to prevent an oil, contained in the crankcase for lubricating the cylinder drive mechanism and lubricating the guide surfaces, from entering into the respective hole 15.

[0087] Irrespective of the gasket 135, the through-hole 130 has a variable section and makes available an annular shoulder surface 140 directed towards the first face of the head.

[0088] For example, such an annular shoulder surface 140 is located closer to the head than the guide surface 120. The crankcase, like the head, may be made of a polymeric material (with the metal guide bushings inserted during or after the moulding of the polymeric material).

[0089] In such a case, in the crankcase they are present inserts 150 provided with a female thread which allow to tighten a threaded connecting member, such as a screw 145, which is fitted through the head by a through hole 151 made in the head. Preferably the pump comprises a plurality of threaded connecting members 145, for in- stance in the same amount as the cylinders, configured to fix the head 20 to the crankcase 5 and that are inserted in the same amount as the through holes 151 obtained in the head 20.

[0090] For example, the pump may comprise a (rigid) cover 155, e.g. made of a metal such as stainless steel or aluminium, and the threaded connecting members, i.e. the screws, allow the head to be clamped between the crankcase and said cover. In particular, the cover and the head are clamped between a head of the threaded connecting members, i.e. screws, and the crankcase. The through holes 151 also extend through the cover.

[0091] The cover, in the embodiment shown, comprises a first face 160 in (direct) contact with the second face 30 of the head 10, an opposite 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 a (circular) opening 176 made in the first face 160 and which is aligned with the second opening 40.

[0092] So that the hole 15 and the blind cavity 175 together substantially form a blind hole, the blind cavity 175 of which comprises a bottom surface 180 delimiting the blind cavity itself (in the direction moving away from the first face of the cover; furthermore it is said bottom surface 180 which makes the cavity as blind).

[0093] The bottom surface 180 is spaced, by a non-zero amount, from the second face of the head and is directed towards it and towards the piston 45 sliding in that hole 15.

[0094] The opening 176 has a passage section, i.e. a diameter, smaller than the second passage section, i.e. a diameter of the second opening 40 with which it communicates. The first face 160 of the cover thus makes available an abutment surface 177 extending substan- tially from a perimeter of the opening 176 to a perimeter of the second opening 40 and, for example, is (plane and) perpendicular to a central axis of a corresponding hole 15.

[0095] 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 instance a cylindrical surface (coaxial to the central axis of the hole 15).

[0096] The invention provides the presence of a blind cavity as described above for each hole 15.

[0097] The cover 155 also comprises a delivery channel, e.g. entirely obtained in the cover, (located downstream of the pumping chamber in relation to a fluid pumping direction through the pump).

[0098] Referring in particular to Figures 1 and 10, the delivery channel comprises the blind cavity 175, i.e. the blind cavities 175, and at least one connecting, or delivery, channel 185 connecting the blind cavity 175, i.e. all the blind cavities 175, to an outlet port 190 (made in the cover) at which means, adapted to connect a pipe to the outlet port itself, are pro- vided, for example in the form of a threaded element coaxial to the outlet port.

[0099] It is not however excluded that, in embodiments not shown, the cover may not comprise the cavities and, for example, only serve to close the holes 15, in which case the bottom surfaces would consist of portions of the first face of the cover closing the second open- ings of the holes 15.

[0100] Furthermore, it is not excluded that in an alternative embodiment the holes 15 are blind holes that each make a bottom surface available (in which case the cover is not even present, or if it is present, it does not have the function of closing the holes 15).

[0101] In cases wherein the pump has no cavity in the cover, or no cover at all is present, the abutment surface 177 is made available by a portion of the head (as well as the side surface 178). Furthermore, in such case the shoulder surface 18 is not present and its function will have to be performed by a spacer. Therefore, irrespective of the exact shape, the head alone or the head with the cover fixed thereto make available a plurality of blind holes 15, 175 (straight and also overall cylindri- cal) provided with a bottom wall 180 directed towards the pump crankcase and delimiting the hole itself. In cases wherein the cover does not have the blind cavity, the delivery channel is made in the head. The pump also comprises a suction channel, which is provided with an inlet port 195, also made in the cover or head, from which at least one suction duct 196 in fluid communica- tion with a hole 15 or blind cavity 175 originates, i.e. from which a plurality of suction ducts in fluid communication with a respective hole or blind cavity originate.

[0102] In particular, the suction duct directly intersects the (respective) hole 15 (or the blind cavity in an embodiment not shown).

[0103] For example, the suction duct comprises a blind hole that passes through the cover (in which it makes the inlet port 196) as well as the head, and from which suction channels reaching respective holes originate. To prevent leakage of liquid at the interface between the cover and the head, a sealing annular 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, is present.

[0104] As mentioned above, the pump comprises 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. Said delivery valve and the suction valve (of an individual pumping chamber, i.e. of each pumping chamber) are intended as means which automatically adjust the inlet and outlet of the fluid from the pumping chamber based respectively on a pressure difference be- tween the suction channel and the pumping chamber and at a pressure difference be- tween the pumping chamber and the delivery channel.

[0105] The operation based on the pressure difference is substantially similar to the one-way hydraulic valves, the suction valve of which is configured and oriented such as to open only when the pressure in the pumping chamber is lower than the pressure in the suction channel, while the discharge valve is configured and oriented to open only when the pres- sure in the pumping chamber is higher than the pressure in the delivery channel.

[0106] According to the invention, such means are made available by a single delivery and suc- tion valve assembly 200, 200’, 200” (one for each pumping chamber) which may be re- movably inserted in the pump, in particular which may be (entirely) removably inserted (and with a small clearance or to measure) in the hole 15, and for example also in the blind cavity 175, i.e. which may be (entirely) removably inserted in a pump blind hole (15, 175) which contains therein a volume of a pumping chamber (and wherein a piston slides). It must be specified that “entirely” means that the assembly with all its components wholly fits into the pump in a removable manner. For example, the entire valve assembly may be removed from the pump as a single body in case of maintenance.

[0107] Furthermore, the valve assembly 200, 200’, 200” is not fixed to the pump by means of threaded connecting members or other means (and does not comprise threaded portions for fixing to the pump), but is only retained therein by clamping it (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 between the head and the crankcase only, e.g. between the head and a spacer which insists on a shoulder surface of the crankcase). In order to remove the valve assembly, it is not required to unscrew it from the hole wherein it is inserted, as it is not retained but for the assembly of the pump, in particular of the cover to the head, i.e. to the crankcase.

[0108] Hereinafter, the delivery and suction valve assembly 200, 200’, 200” will be abbreviated as valve assembly 200, 200’, 200”. Overall, the valve assembly 200, 200’, 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. The valve assembly 200, 200’, 200” comprises a (rigid) valve body 205, e.g. made in a single piece, preferably also made of metal, e.g. brass or stainless steel.

[0109] In the embodiment shown, the valve body 205 may be inserted to measure (with a small clearance) into the blind hole of the pump containing the volume of the pumping chamber, which in the embodiment shown is made available by the hole 15, and for example also by the blind cavity 175. The valve body 205 then slides to measure (in contact) along the surface 17, the surface 19 on the head side 10 and along the side surface 178 on the blind cavity side 175.

[0110] Furthermore, the hole 15 and the cover 155 may be shaped so as to clamp the valve body 205, i.e. a portion of the valve body 205, between them when the cover is fixed to the head (i.e. to the crankcase). In the embodiment shown, such a task is performed by the surface 17 and the abutment surface 177, which contact (directly) the valve body 205, i.e. a portion of the valve body 205, clamping it, i.e. they clamp said portion, between each other when the cover is fixed to the head (i.e. to the crankcase). The valve body 205 comprises a first (longitudinal) end 210 and an opposite second (lon- gitudinal) end 215, the longitudinal ends of which are aligned with each other along a central axis of the valve body itself (such longitudinal ends are intersected by said central axis).

[0111] 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

[0112] 15.

[0113] 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.

[0114] Furthermore, 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.

[0115] The first end 210 makes available a first face, e.g. circular, transverse (perpendicular) to the central axis of the valve body and directed to (facing) the direction opposite the crank- case, i.e. directed towards (facing) the bottom surface 180.

[0116] 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 towards (facing) the base, i.e. directed to (facing) the direction opposite to the bottom surface 180.

[0117] The first face and second face are connected by a tubular (and circular, e.g. cylindrical or formed by several cylindrical tracts) side surface extending from one end of the valve body to the other. The valve body 205 comprises a first abutment surface 220 which contacts (directly) the cover 155, i.e. contacts a portion of the first face 160 of the cover, specifically contacts the (entire) abutment surface 177.

[0118] 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. For example, the first abutment surface 220 is shaped like a circular crown (consequently it contacts the cover along a circumference).

[0119] The valve body 205 also comprises a second abutment surface 225 that contacts (di- rectly) the head 10, i.e. contacts (directly) the (entire) shoulder surface 18.

[0120] Such second abutment surface 225 is transverse (perpendicular) to the central axis of the valve body, in other words, it is coplanar to the shoulder surfacel 8.

[0121] For example, the second abutment surface 225 is shaped like a circular crown (it conse- quently contacts the head along a circumference).

[0122] When the valve assembly is inserted into the pump and the cover is fixed to the cylinder head (i.e. the crankcase), the valve body is clamped 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.

[0123] It may also be said that when the valve assembly is inserted into the pump and the cover is fixed to the head (i.e. to the crankcase), a portion of the valve body between the first abutment surface 220 and the second abutment surface 225 is clamped between the cover and the head.

[0124] The valve body 205 may, for example, be shaped as a body of revolution obtained by a revolution around said central axis, for example said body being composed of a plurality of cylindrical tracts adjacent to each other.

[0125] In the embodiment shown, 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.

[0126] The side surface comprises a first tract 230, e.g. cylindrical (outer cylindrical surface), which develops from the first face of the valve body to the first abutment surface 220.

[0127] The first tract 230 is inserted (entirely) in the blind cavity 175, in particular it is inserted to measure (with a small clearance) in the side surface 178.

[0128] The side surface then comprises a second tract 235, e.g. cylindrical (outer cylindrical surface), which develops from a perimeter of the first abutment surface 220 distal from the first tract 230, to the second abutment surface 225.

[0129] The second tract 235 is (entirely) inserted in the hole 15, in particular it is inserted to measure (with a small clearance) in the surface 17.

[0130] The side surface then comprises a third tract 240, e.g. cylindrical (outer cylindrical sur- face), which develops from a perimeter of the second abutment surface 225 distal from the second tract 235, to the second face of the valve body.

[0131] The third tract 240 is (entirely) inserted in the hole 15, in particular it is inserted to measure (with a small clearance) in the surface 19.

[0132] The valve assembly 205 comprises a first duct 245 adapted to be selectively connected, as will become clearer hereinafter, with the delivery channel. In particular, the first duct, i.e. a plurality of first ducts as will be described hereinafter, is the only passage of the valve assembly (and of the entire pump) through which the fluid pumped into the (respec- tive) pumping chamber may (selectively) reach the delivery channel.

[0133] The first duct 245 is (entirely) made in the valve body 205 and extends (solely) from a first (single) opening 250 (circular) made in the first end 210, specifically in the first face of the valve body 205, developing to a second opening 255 made in the second end 215. In particular, it is the second opening, i.e. a tract of the first duct proximal to the first opening that can be selectively connected, as will become clearer hereinafter, with the delivery channel. 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 position central to the side surface of the valve body.

[0134] Furthermore, the first opening 250 lies on a plane substantially perpendicular to the cen- tral axis of the valve body. 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, no means for ad- justing the flow through the second opening is present, neither in the valve assembly nor in the pump, which is capable of preventing the fluid pumped into the first duct from en- tering.

[0135] More specifically, no shutter capable of occluding, even partially, the second opening 255 is present. 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 which for instance develops (extends) from a perimeter (and circular) edge of the first opening 250 (or consists of said perimeter edge). For example, the annular surface 260 is directed to the direction opposite to the second end of the valve body.

[0136] 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 sphere sector) or, as in the embodiment shown, a flared, i.e. truncated-cone sur- face, arranged so that its cross-section increases as it goes from the first opening 250 in the direction moving away from it (i.e. in the direction moving radially away from the cen- tral axis of the hole) and from the second end of the valve body along the central axis.

[0137] 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, no means for adjusting the flow through the first duct placed between the first opening 250 and the second opening 255 is present, neither in the valve assembly nor in the pump, which is capable of pre- venting the fluid pumped into the first duct from entering.

[0138] For example, the first opening 250 is coaxial and centred to the central axis of the hole 15. The second opening 255 is 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), such as a circular-shaped opening.

[0139] In greater detail, the first duct 245 comprises a first tract 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 tract develops reaching the second opening 255.

[0140] The second tract of the first duct 245 comprises a first portion 265, which develops from the second opening 255 as a blind hole parallel 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 tract 261 , i.e. its blind hole, and the second portion 266. Such second portion 266 is in- clined relative to a central tract of the valve body. In the embodiment shown, there is a plurality (four) of first ducts 245, which develop from the first opening 250 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 eccentri- cally with respect to the central axis of the valve body 205, e.g., also angularly equally- spaced from the central axis of the valve body (so that the second openings lie with their respective centre on an imaginary circumference having its centre on the central axis and lying on a plane perpendicular thereto).

[0141] In further detail, the first ducts all develop from the common tract 260 to the second open- ings 255, and the first portions of the second tracts of each first duct are arranged eccen- trically relative to the central axis of the valve body, angularly equally-spaced from the central axis of the valve body.

[0142] The valve assembly also comprises a second duct 270, adapted to be always in fluid connection with the suction channel, i.e. with a respective suction duct. In addition, the second duct 270 is adapted to be selectively connected, as will become clearer hereinaf- ter, with the pumping chamber. In particular, the second duct, i.e. a plurality of second ducts as will be described hereinafter, 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.

[0143] The second duct 270 is (entirely) obtained in the valve body 205 and does not intersect (at any point) with the first duct 245, i.e. the first ducts 245. The second duct is provided with a first opening 275, made in the tubular side surface of the valve body 205 between the first end and the second end; in particular, it is made, when the valve assembly is inserted in the pump, at a tract of said side surface proximal to an intersection zone between the hole 15 and the suction duct, so as to be always in direct fluid communication with the suction duct. In particular, the first opening 275 is made in the second tract 235 and is (always) in direct fluid communication with the inter- section zone between the hole 15 and the suction duct.

[0144] Furthermore, no means for adjusting the flow through the first opening is present, neither in the valve assembly nor in the pump, which is capable of preventing the fluid pumped into the second duct from entering the suction duct.

[0145] In the embodiment shown, the second duct 270 comprises a plurality (four) of first open- ings 275 all made in the side surface of the valve body, in particular in the second tract 235, and for example angularly equally-spaced from each other around the central axis of the valve body (axis of revolution), i.e. the central axis of the hole 15.

[0146] The second duct 270 extends from the first opening 275, or from the openings 275 to a (unique) second opening 280 made in the second end 215 of the valve body, in particular in the second face of the valve body 205, e.g. in a central position in relation to the second opening 255 of the first duct 245 (and central to the side surface of the valve body). Pref- erably the second opening 280 is coaxial with the first opening 250.

[0147] 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 which, for instance, develops (extends) from a perimeter (and circular) edge of the second opening 280 (or consists of said perimeter edge).

[0148] For example, the annular surface 285 is for instance directed opposite to the first end of the valve body.

[0149] The annular surface 285 of the second annular sealing seat may be an annular perimeter edge, preferably chamfered / rounded, of the opening 280 or an annular (circular) convex surface (e.g., a sphere sector) or, as in the embodiment shown, a flared, i.e. truncated- cone surface, arranged so that its cross-section increases as it goes from the second opening 280 in the direction moving away from it (i.e. in the direction moving radially away from the central axis of the hole) and from the first end of the valve body along the central axis.

[0150] 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, no means for adjusting the flow through the second duct placed between the first opening 275 and the second open- ing 280 is present, neither in the valve assembly nor in the pump, which is capable of preventing the fluid pumped into the first duct from entering.

[0151] The second duct is substantially L-shaped, in particular comprising a first tract 290 which originates as a hole from the first opening 275 of the second duct 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 tract 295 which originates from the second opening 280 of the second duct 270 as a blind hole transverse to the first tract 290 and intersecting said first tract 290. In the embodiment shown, the second duct 270 comprises a plurality of first openings 275 from each of which a corresponding first tract 290 of the second duct 270 originates, which first tracts flow into a common second tract295 which originates from the second opening 280 of the second duct 270. Therefore, it may also be said that the valve body comprises a plurality of second ducts. The second tracts of the first ducts 245 pass through portions of the valve body placed between two adjacent first tracts of the second ducts and the tubular side surface of the valve body itself.

[0152] The valve body 205 is a rigid (entirely rigid) body, preferably also made in a single piece, e.g. made of a metal material selected from the group between brass and stainless steel. The first duct, i.e. the first ducts, and the second duct are made of said single-piece body by removing material.

[0153] The valve assembly comprises a first (rigid) shutter 300 movable between a closed posi- tion, wherein it tightly obstructs the (only) first opening 250 of the first duct 245, and an open position, wherein it is spaced from the first opening of the first duct and allows the passage of a flow through the first opening.

[0154] In particular, when the valve assembly is inserted into the pump, in the closed position the first duct is isolated from the delivery channel, i.e. the pumping chamber is isolated from the delivery channel, while in the open position the pumped fluid can flow from the pumping chamber to the delivery duct through the first opening 250. 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.

[0155] Furthermore, in the open position, the first shutter is at a greater distance from the second end, greater than when it is in the closed position. Referring in particular to Figures 7, 8, 15-17, the first shutter 300 comprises a contact surface 305 adapted to generate a (tight) sealing 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.

[0156] Such a contact surface 305 (directly) contacts, at least partially, (only) in said closed po- sition, the first annular sealing seat along at least one closed annular path, for example said path being a circumference.

[0157] The contact surface comprises, i.e. consists of, an annular surface (which creates a closed loop path, hence a complete loop) that can be either convex or truncated-cone.

[0158] The convex surface may also be defined as a rounded surface without edges, which is in particular obtained by the revolution of a curved segment around an axis of revolution. Such an axis of revolution is coaxial to the central axis of the first opening 250, i.e. it is coaxial to the central axis X of the (respective) hole 15.

[0159] In particular, such curved segment comprises a first end closer to the second end of the valve body 205 than a second end of the segment itself. In addition, the second end is radially further away from the axis of revolution than the first end. Furthermore, the curved segment comprises a single concavity, i.e. it is defined by a single radius of curvature, the concavity of which is directed towards the axis of revolution.

[0160] In the embodiment shown, the convex surface, i.e. the contact surface, consists of a spherical sector.

[0161] Regarding the truncated-cone surface, it is specified that it is the outer side surface of a truncated cone interposed between the two bases of the truncated cone.

[0162] The first shutter comprises a first face directed towards the first opening and the first annular sealing seat, which makes the contact surface available, and an opposite second face, on which a housing seat for the end of an elastic element is obtained, preferably as an annular recess, as will be described hereinafter.

[0163] In the embodiment shown, the shutter is substantially shaped as a discoidal body, e.g. processed by plastic deformation, which makes available the first face and the second face, with the corresponding contact surface and housing seat of the elastic element. The valve assembly comprises an elastic element, such as in the form of a coil spring 310, which generates a force on the first shutter, e.g. by insisting with one end thereof on the second face of the shutter, in the direction of holding the shutter in the closed position. When the force generated on the first shutter (first face) by the pressurised fluid in the first duct exceeds the sum of the force generated by the elastic element on the shutter (second face) and the force generated on the shuter by the pressurised fluid present downstream (in relation to the flow direction 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. The elastic element is held in position by means of a (socket) cage 315 fixed, 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 comprises holes for the passage of the liquid.

[0164] The valve assembly comprises a second (rigid) shutter 320 movable between a closed position, in which it tightly obstructs the (only) second opening 280 of the second duct 270, and an open position, in which it is spaced from the second opening of the first duct and allows the passage of a flow through the first opening.

[0165] The valve assembly does not comprise any shutters other than the first and second shut- ters. In particular, when the valve assembly is inserted into the pump, in the closed position the second duct is isolated from the pumping chamber, i.e. the pumping chamber is iso- lated from the suction channel, while in the open position the pumped fluid may flow from the suction channel to the pumping chamber through the second opening 280.

[0166] The shutter moves between the open position and the closed position 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.

[0167] Furthermore, in the open position, the second shutter is at a greater distance from the first end than when it is in the closed position.

[0168] The first and second shutters are external to the valve body. The second shutter 320 comprises a respective contact surface 325 adapted to generate a (tight) sealing 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. Such contact surface of the second shutter (directly) contacts, at least partially, (only) in said closed position, the first annular sealing seat along at least one closed annular path, for example said path being a circumference. 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 creates a closed-loop path, hence a complete loop) that can be either convex or truncated-cone.

[0169] The convex surface may also be defined as a rounded surface without edges, which is in particular obtained by the revolution of a curved segment around an axis of revolution.

[0170] This axis of revolution is coaxial to the central axis of the second opening 280, i.e. it is coaxial to the central axis X of the (respective) hole 15.

[0171] In particular, such curved segment comprises a first end closer to the first end of valve body 205 than a second end of the segment itself. In addition, the second end is radially further away from the axis of revolution than the first end. Furthermore, the curved seg- ment comprises a single concavity, i.e. it is defined by a single radius of curvature, the concavity of which is directed towards the axis of revolution.

[0172] In the embodiment shown, the convex surface, i.e. the contact surface, consists of a spherical sector. The second shutter comprises a first face directed towards the first opening and the first annular sealing seat, which makes the contact surface available, and an opposite second face, on which a housing seat for the end of an elastic element is made, preferably as an annular recess, as will be described hereinafter.

[0173] In the embodiment shown, the shutter is substantially shaped as a discoidal body, e.g. processed by plastic deformation, which makes available the first face and the second face, with the corresponding contact surface and housing seat of the elastic element.

[0174] The valve assembly comprises an elastic element, such as in the form of a coil spring 330, which generates a force on the second shutter 320, e.g. by insisting with one end thereof on the second face of the shutter, in the direction of holding the shutter in the closed position. When the force generated on the second shutter (first face) by the pres- surised fluid in the second duct 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 (in relation to the flow direction along the pump from suction and discharge) of the second opening of the second duct, the second shutter moves to the open position and the fluid can go from the delivery channel to the suction chamber.

[0175] The elastic element is held in position by means of a (socket) cage 335 fixed, 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 comprises holes for the passage of the liquid.

[0176] For both shutters, in case the respective annular sealing seat is truncated-cone, the con- tact surface is preferably convex and not truncated-cone. If the annular sealing seat is convex or a rounded edge, the contact surface may be either convex or truncated-cone. In order to prevent the fluid to be pumped or being pumped from entering between the valve body 205 and the hole 15 and, tor the blind cavity 175, the valve assembly comprises a plurality of annular (static) sealing gaskets 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.

[0177] In particular, the valve assembly 200, 200’ comprises a first sealing annular gasket 340 housed in an annular groove and contacting the blind cavity, in particular the side surface 178, creating a tight sealing between the first tract 230 of the side surface of the valve body and the blind cavity, i.e. the side surface 178.

[0178] The valve assembly also comprises a second sealing annular gasket 345 housed in an annular groove and contacting the respective hole 15, in particular the surface 17. In further detail, the annular groove housing the second sealing annular 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 duct, i.e. the first openings of the second duct, and the abutment surface 220. Hence, 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.

[0179] Furthermore, in combination with a third annular gasket 350, the second gasket prevents the pressurised fluid from entering from the pumping chamber into the second duct and thus into the suction channel.

[0180] The third annular gasket 350 contacts the respective hole 15, in particular the surface 17. In particular, the annular groove housing the third sealing annular gasket is made in a portion of the side surface of the valve body that is located between the first opening of the second duct, i.e. the first openings of the second duct and the abutment surface 225.

[0181] In contrast to the embodiment of the valve assembly 200” of Figure 17, in the embodi- ments of the valve assembly 200, 200’, said valve assembly comprises a tubular jacket 360, 360’ (straight, e.g. cylindrical) developing, in particular without interruption, from the second end of the valve body, i.e. from an outer peripheral edge (proximal to the side surface of the valve body) of the second face of the second end, around the duct opening, i.e. around the second opening 255 of the first duct 245, in the direction moving away from the first end. It may also be said that the tubular jacket 360, 360’ develops from the second end, in particular from the second face, as a continuation of the side surface of the valve body, e.g. as a continuation of the third tract 240 of said side surface.

[0182] The purpose of the tubular jacket is to protect the head, in particular the head made of a polymeric material, from the pressures generated in the pumping chamber, therefore it is made of a metal, preferably a metal such as brass or stainless steel. Although the exam- ple was carried out with the pump having a head made of a polymeric material, the same considerations may be made in case the head is made of a metal having such an elastic modulus and fatigue strength that the pump integrity cannot be guaranteed at the oper- ating pressures for which it is designed. Furthermore, if the cover is present, as in the embodiment shown, and said cover houses 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 inside with a jacket made of metal.

[0183] In addition to these considerations, it must be specified that the tubular jacket is not strictly required only in the case of heads made of polymeric material or any other material that is not resistant enough to the pressures involved, but it may also be applied to heads made of a material that is not resistant enough to the working pressures, in order to pro- tect said head and increase life thereof over time, also considering the lower cost of re- placing the valve assemblies compared to the entire head.

[0184] In the embodiment shown the tubular jacket 360, 360’ is made in a single piece with the (entire) valve body 205, however, it is not excluded that in an alternative embodiment not shown, the tubular jacket could be welded to the valve body, in particular to its second face, or it could be fixed to the valve body (at the second end) in a removable manner, for example by means of threaded connecting members. In particular, in the case of threaded connection members, the jacket may comprise a threaded surface adapted to be screwed onto a corresponding threaded surface made at the second opening.

[0185] The tubular jacket 360, 360’ comprises a (single) first end, which is the one which directly originates 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 the central axis of the hole 15 when the valve assembly is inserted into the pump). In addition, the tubular jacket develops 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.

[0186] The tubular jacket 360, 360’ has a constant cross-section (in relation to the central axis) from the first end to the second end.

[0187] For example, the tubular jacket 360, 360’ is shaped as a straight body having a constant cross-section (relative to the central axis) along its extension from its first end to the sec- ond end.

[0188] When the valve assembly 200, 200’ is inserted into the pump, the tubular jacket is, for example, entirely contained within the volume of the hole 15. However, if, as will become clearer hereinafter, the high-pressure gasket 60 was located in the crankcase or the low- pressure gasket was also housed in the tubular body, the tubular jacket could extend into the crankcase. As a principle, the tubular jacket has such an extension that its second end is close to, for instance at, preferably in sealing 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 shown, the tubular jacket extends as far as the first face of the head (irrespective of whether the second end is in the cylinder head or protrudes into the crankcase).

[0189] The tubular jacket 360, 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 said axes when the valve assembly is inserted into the pump. The surface 365 is radially (relative to the central axes) more external relative to the sec- ond opening 255, i.e. it develops from a portion or edge of the second face that is around and external to the second opening. The inner volume of the tubular jacket is thereby in fluid communication with said second opening. In particular, the surface 365 is radially more external relative to all the second openings 255, i.e. it develops from a portion or edge of the second face that is around and external to a portion or surface of the second face wherein all the second openings of the first duct are made. The inner volume of the tubular jacket itself is thereby in fluid communication with all the second openings. The surface 365 is even radially more external relative to the second opening of the sec- ond duct. It is also radially more external relative to the cage that holds the second shutter, so that such a cage may be inserted into the tubular body and secured to the valve body during the assembly and maintenance steps. The tubular jacket 360 also comprises an outer tubular surface 370, such as having the same shape as the hole 15, in particular of the surface 19, and substantially the same size, so that the outer tubular surface 370 fits to measure, or with a small clearance, into the hole 15, i.e. in the surface 19.

[0190] Thus, in the embodiment shown, the outer tubular surface is cylindrical and coaxial to the inner tubular surface 365.

[0191] The outer tubular surface 370, in the embodiment shown, is substantially a continuation of the side surface of the valve body, e.g. as a continuation of the third tract 240 of said side surface, in the direction moving away from the first end of the valve body.

[0192] For example, the third tract 240 and the outer tubular surface 370 have the same diame- ter.

[0193] The tubular jacket 360, 360’ also comprises an annular surface 375, e.g. plane and trans- verse (perpendicular) to the inner tubular surface 365 and to the outer tubular surface 370, which joins said tubular surfaces and substantially defines the limit of the extension of the tubular jacket in the direction moving away from the first end, thus substantially defining the second end of the tubular body.

[0194] The tubular jacket 360, 360’, i.e. its inner tubular surface 365, defines an inner volume of the tubular jacket in (direct, always direct) fluid communication with the opening, i.e. with the second opening 255 of the first duct 245. Such inner volume comprises at least a portion of the volume of the pumping chamber. The inner tubular surface 365 has a cross-section, i.e. a diameter, greater than a cross- section, i.e. a diameter, of the piston 45.

[0195] In use, the piston 45 is at least partially contained, with (plenty of) clearance, in the inner volume of the tubular jacket 360, 360’. In practice, between the inner tubular surface 365 and the piston 45, there is an annular gap with a non-zero thickness and length. The distance between the surface 365 and surface 370 defines the thickness of the tub- ular jacket.

[0196] The tubular jacket 360, 360’ extends from the second end moving away from the first one, along the axis of the valve body or the axis of the second opening of the first duct or the axis of the hole 15, to a sealing annular gasket that sealingly encloses a portion of the piston, which slides through this sealing. In particular, the tubular jacket extends up to (in direct contact with) the first sealing annular gasket 60 so that such gasket 60 sealingly contacts the tubular jacket, i.e. it sealingly contacts the inner tubular surface 365, (so as to prevent the fluid present in the pumping chamber from contacting the hole 15).

[0197] In detail, such contact is made in such a way that the inner volume of the tubular body is closed at one end thereof by the fluidic sealing formed by the contact between the first sealing annular gasket 60 and the contact between said gasket 60 and the piston 45. For example, this is obtained with the gasket 60 sealingly inserted (by means of elastic deformation) into the inner cavity of the tubular body.

[0198] Preferably, said gasket 60 sealingly contacts the inner tubular surface 365 along a closed annular path transverse to the central axis.

[0199] In particular, the gasket 60 is inserted into the inner volume of the tubular jacket and is sealingly fitted on a portion of the inner tubular surface 365. For example, the outer an- nular lip 70 sealingly contacts said portion of the inner tubular surface. Furthermore, the annular lip 70 is housed in the annular gap formed in use between the inner tubular sur- face and the piston.

[0200] The configuration thus obtained allows the inner cavity to be isolated from the rest of the volume of the hole 15, for instance it allows to isolate the pumping chamber 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 jacket, the gasket 60, the piston, the first duct 245, the first shutter and the second shutter (when said shutters are in the closed position). Although not shown, it is not excluded that in an embodiment not-shown, the tubular body may comprise an annular groove made in the inner tubular surface 365 to serve as a seat partially housing the gasket 60.

[0201] Between the gasket 60 and the second end, i.e. the second face, of the valve body, a tubular (rigid) spacer 400 is interposed, adapted to prevent the piston 45, in its stroke, from displacing said gasket towards the second end of the valve body.

[0202] The tubular spacer 400 comprises a first longitudinal end (directly) contacting the second face of the valve body and an opposite second longitudinal end contacting (e.g. by inter- posing a pusher ring 405) the gasket 60.

[0203] The tubular spacer is entirely contained within the inner volume of the tubular jacket and, for example, comprises a (cylindrical) inner tubular surface 410, and an opposite (cylin- drical) outer tubular surface contacting the inner tubular surface 365.

[0204] The inner tubular surface 410 of the tubular spacer is arranged radially, relative to the central axis of the second opening, or of the valve body or of the hole, and, for instance, more external relative to the second opening 280 of the second duct, and more internal to the second opening 255 of the first duct, i.e. to the plurality of second openings 255 of the first duct.

[0205] When the surface 410 is also radially more internal relative to the second opening 255, at least one groove or cut 415 is made in the tubular spacer which develops from the inner tubular surface towards the outer tubular surface, placing the second opening of the first duct 255 in fluid communication with the inner volume defined by the tubular spacer, thus allowing a fluid communication between the second opening 255 and said inner vol- ume, i.e. with the pumping chamber. Such 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, forming an opening in said end at the second opening 255.

[0206] In particular, as there is a plurality of second openings 255 of the first duct 245, the spacer comprises a plurality of grooves or cuts 415 each positioned at a respective second open- ing 255.

[0207] In order to align the tubular spacer to the valve body, i.e. to align the groove or cut 415 to the opening 255 (or to align the grooves or cuts 415 to the respective opening), the valve assembly comprises at least one reference element adapted to allow for a unique me- chanical alignment between the valve body and the tubular spacer. In the embodiment shown, the reference element comprises a pin 500 which may 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.

[0208] The tubular spacer is shaped in such a way that the piston may pass through. In detail, the inner tubular surface has a cross-section such that the piston 45 may slide with a clearance within an inner volume defined by said inner tubular surface. Furthermore, said cross-section is such that the second shutter is hindered, and is for example radially larger than the cage of the second elastic element.

[0209] The pump, i.e. the valve assembly, may comprise an annular body 420, 420’ (rigid and made / manufactured as a single-piece body distinct from the valve body and tubular jacket) in which a through-hole 421 is formed in direct fluid communication with the inner volume of the tubular jacket, 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 passed through by the piston 45 (during its movement between the top dead centre and bottom dead centre) A seat for housing the low-pressure gasket 80 (located between the first face and second face) is made in the through-hole 421. Such housing seat 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.

[0210] The low-pressure gasket is arranged in such a way that the outer annular lip 90 creates a tight sealing with one surface of the annular groove. The annular body 420, 420’ comprises a drainage channel 424 adapted to place the suc- tion channel with a volume between the piston, the high-pressure gasket and the low- pressure gasket, so that any pressurised fluid leakage from the high-pressure gasket can be discharged at the suction pressure.

[0211] Furthermore, in order to prevent leakages, the annular body 420, 420’ or a portion of the head at the annular body comprises a groove for housing a static sealing gasket 422.

[0212] The annular body 420, 420’ comprises a side surface 423 that fits to measure, i.e. with a small clearance, into a portion of the through-hole 130 that is located between the abut- ment surface 140 and the face of the crankcase contacting the head.

[0213] 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.

[0214] In such a 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 jacket rests and for instance, the gasket 60, i.e., the ring 75 of the gasket 60, (the gasket 60 is thereby held in place (clamped) between the tubular spacer and the annular body).

[0215] The annular body 420 also comprises a second face 430 (such as annular, planar and transverse, i.e. Perpendicular to the central axis of the valve body) that rests on the an- nular shoulder surface 140, so that when the cover is fixed to the crankcase, the valve body, tubular jacket and annular body 420 are clamped between the cover and the crank- case, i.e. between the annular shoulder surface 140 and the surface 176. In this embodiment 420, the seat of the gasket 422 is made in the annular body.

[0216] In the embodiment of the valve assembly 200’, of Figures 11 and 16, both the high-pres- sure gasket and the low-pressure gasket are part of the valve assembly and are therefore extracted from the head with the rest of the valve assembly.

[0217] In such a case, the annular body 420’ is shaped as a holding body fixed to the second end of the tubular jacket, e.g. in a removable manner, preferably screwed to the tubular jacket. In particular, in the embodiment shown, the tubular jacket comprises a threaded portion 435 (at the second end) onto which a corresponding threaded portion of the an- nular body 420’ is screwed.

[0218] In this embodiment 420’, the gasket seat 422 is preferably made in the portion of the head at the annular body 420’, e.g. in the surface 19.

[0219] The annular body 420’ has a first face 425 (such as annular, planar and transverse, i.e. perpendicular, to the central axis of the valve body) on which the gasket 60, i.e. the ring 75 of the gasket 60, rests (the gasket 60 is thereby held in place (clamped) between the tubular spacer and the first face of the annular body 420’, i.e. clamped between the tub- ular spacer and the first face of the annular body 420’).

[0220] The annular body 420’ also comprises a second face 430 (such as annular, planar and transverse, i.e. perpendicular, to the central axis of the valve body) that rests on the an- nular shoulder surface 140.

[0221] Although shown only for the embodiment of the valve assembly 420’, in an embodiment not shown wherein only the gasket 60 and not the gasket 80 is present within the inner volume of the tubular jacket, there may still be the holding body, which, in such an em- bodiment directly contacts the gasket 60 so that it is held in place (clamped) between the holding body and the tubular spacer.

[0222] In all the embodiments of the valve assembly shown in Figures 1 -16, the tubular jacket 360 is preferably a single-piece body, e.g. integral with the valve body 205, however, this does not exclude that it may be formed of several tracts in series interlocked or screwed to each other, possibly where the sealing between one tract and the other is ensured by annular gaskets of the static type.

[0223] The first opening 250 (with its annular sealing seat 260) of the first duct, the first shutter and the first elastic element together substantially create a one-way delivery valve.

[0224] The second opening 280 (with the relative annular sealing seat 285) of the second duct, the second shutter and the second elastic element together substantially create a one- way delivery valve.

[0225] Although only one embodiment of the valve assembly with tubular jacket is shown in the figures and comprising both the first and second ducts, it cannot be excluded that the valve assembly comprises the tubular jacket and not the second duct. In such a case the valve assembly would be a one-way delivery valve with tubular jacket.

[0226] The operation of the pump according to the invention is as follows.

[0227] The piston 45, i.e. each piston 45, under the action of the drive mechanism contained in the crankcase moves in the hole 15 along its sliding axis between a lower dead centre position, wherein the volume of the pumping chamber is maximum, and a top dead centre position, wherein the volume of the pumping chamber is minimum.

[0228] When the piston moves from the top dead centre to the 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 the fluid to be sucked from the delivery channel into the pumping chamber. In particular, the fluid enters from the delivery channel into the first opening 275, i.e. into the first openings 275, it passes through the first duct and exits therefrom through the second opening 280

[0229] Upon reaching the bottom dead centre, the piston moves towards the 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. In particular, under the thrust of the piston, the fluid flows into the second open- ing of the first duct, i.e. the second openings of the first duct, and from there, passing through the first opening 250, it reaches the delivery channel. In case the tubular jacket 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 duct. The tubular jacket makes it possible to contain and channel the pressurised fluid, pre- venting it from coming into contact with the inner surfaces of the hole 15.

[0230] When the pump needs maintenance or needs to be assembled, the user simply has to unscrew the screws that secure the cover to the crankcase, remove the cover and, thanks to the shape of the hole and the side surface of the valve body, simply pull the valve assembly to extract it out of the hole, for instance in the embodiment of Figures 3-10, by doing so, the high-pressure gasket is extracted, and in the embodiment of Figures 11 -16 the high-pressure gasket and low-pressure gasket are also extracted.

[0231] It should be noted that in this disclosure, rigid means not noticeably deformable under the normal working loads which it is subjected to. In other words, a rigid element does not perform the function for which it was designed even by its own deformation.

[0232] An elastic element refers to a body that is shaped so as to deform, (only) elastically, under the working loads to which it is subjected and therefore also (or only) performs its function by its own elastic deformation. It must be specified that the definition elastic deformation is to be understood as opposed to plastic deformation.

[0233] In the present case a gasket is elastically deformed to adhere to determined surfaces in order to generate a possibly tight sealing.

[0234] Furthermore, it must be specified that single-piece body refers to a body obtained from the solidification of a single casting, or injection, of (a single) material into a mould and, possibly, by subsequent processing of said solidified body by removal of material.

[0235] When we speak of a sphere sector, it must be specified that such a geometric element is an annular surface that forms a closed loop and is defined as a portion of the spherical surface directly interposed between two planes parallel to each other and both intersect- ing the spherical surface. The terms to measure and with a small a clearance mean that the elements characterised by such a coupling can slide in relation to each other without any particular effort and without tilting appreciably relative to the sliding direction. If, on the other hand, there is a large clearance, the elements may tilt appreciably relative to the advancement direction. The invention thus conceived is susceptible to several modifications and variations, all falling within the scope of the inventive concept.

[0236] Moreover, all details may be replaced by other technically equivalent elements. 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

CLAIMS1. An automatic suction and delivery valve assembly (200, 200’, 200”), which may be removably inserted in high-pressure pumps (1 ,1 ’), said valve assembly comprising:- a valve body (205) provided with a first end (210) and an opposite second end (215),- a first duct (245) developing from a first opening (250) made in the first end of the valve body to a second opening (255) made in the valve body,- a second duct (270) made in the valve body and which does not intersect the first duct, provided with a first opening (275) made in the valve body and a second opening (280) made in the second end of the valve body,- a first shutter (300) movable at least between a closed position, wherein it tightly obstructs the first opening (250) of the first duct, and an open position, wherein it is spaced from the first opening (250) of the first duct and allows the passage of a flow through the first opening, - a second shutter (320) movable at least between a closed position, wherein it tightly obstructs the second opening (280) of the second duct, and an open posi- tion, wherein it is spaced from the second opening (280) of the second duct and allows the passage of a flow through the second opening, and wherein the valve body (205) at the first opening of the first duct and the second opening of the second duct makes available an annular sealing seat (260) of the first shutter and an annular sealing seat (285) of the second shutter, respectively, wherein the first shutter and second shutter each comprise a corresponding contact sur- face (305, 325) which at least partially contacts, when the shutter is in the closed position, the respective annular seat along at least one closed annular path, which contact surfaces (305, 325) each comprise a respective convex annular surface or a truncated-cone sur- face.

2. The valve assembly (200, 200’, 200”) according to claim 1 , wherein the convex an- nular surface is a revolution surface obtained by the revolution of a curved segment around an axis of revolution.

3. The valve assembly (200, 200’, 200”) according to claim 1 or 2, wherein the contact surface is a sphere sector.

4. The automatic valve assembly (200, 200’, 200”) according to any one of the pre- ceding claims, wherein the first opening (250) of the first duct is made in a central portion of the first end (210) and the second opening (280) of the second duct is made in a central portion of the second end (215).

5. The valve assembly (200, 200’, 200”) according to claim 4, wherein the first opening(250) of the first duct and the second opening (280) of the second duct are coaxial.

6. The valve assembly (200, 200’, 200”) according to any one of the preceding claims, wherein the second duct comprises a first tract (290) which originates from the first open- ing (275) of the second duct towards a central area of the valve body, and a second tract (295) which originates from the second opening (280) of the second duct as a blind hole transverse to the first tract and intersecting said first tract.

7. The valve assembly (200, 200’, 200”) according to any one of the preceding claims, comprising a plurality of first ducts (245) all developing from the first opening (250) made in the first end of the valve body to a plurality of respective second openings (255) made in the second end of the valve body, and wherein the second opening (280) of the second duct (270) is made in the second end of the valve body in a central position relative to the plurality of second openings (255) of the first ducts.

8. The valve assembly (200, 200’, 200”) according to the preceding claim, wherein the first ducts (245) comprise a first common tract (261 ) which develops from the first opening (250) as a blind hole and a plurality of second tracts which extend from the first tract, each independent of the other second tracts (265, 266), and each make in the second end of the valve body a respective second opening (255) of the plurality of second openings.

9. The valve assembly (200, 200’, 200”) according to the preceding claim, wherein the second tracts (265, 266) of the first ducts are eccentric to the second tract (295) of the second duct and are each provided with at least one portion (265) parallel to the second tract of the second duct.

10. The valve assembly (200, 200’, 200”) according to claim 1 , comprising a tubular jacket (360, 360’) developing from the second end (215), around the second opening (255) of the first duct, in a direction moving away from the first end (210).

11. The valve assembly (200, 200’, 200”) according to claim 10, wherein in a distal portion from the second end (215) of the valve body of the tubular jacket (360, 360’) a sealing gasket (60), adapted to sealingly enclose a piston (45), is inserted.

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