Piston pump

Abstract

A piston pump (1) for pumping a liquid is described. The piston pump (1) comprises a head (10), a piston (45), a first annular sealing gasket (60), a second annular sealing gasket (80) and an annular body (100). A cylinder (15) is obtained in the head (10). The piston (45) is slidably inserted in the cylinder. The first annular sealing gasket (60) is in circumferential sealing contact with the piston (45). The second annular sealing gasket (80) is in circumferential sealing contact with the piston. The annular body (100) circumferentially surrounds the piston (45) and is at least partially housed in a housing seat (110) obtained in the head in a portion of the cylinder (15). The annular body (100) comprises a first housing seat (150), a second housing seat (155) and a third housing seat (185). The first annular sealing gasket (60) is housed in the first housing seat (150). The second annular sealing gasket (80) is housed in the second housing seat (155). A third annular sealing gasket (190) is housed in the third housing seat (185), the third annular sealing gasket (190) being interposed between the annular body (100) and the housing seat (110) of the annular body.

Description

Technical Field

[0001] This invention relates to a piston pump, and more particularly to a piston pump for high pressure and suitable for low viscosity fluids. Background Technology

[0002] A piston pump typically includes a head, in which at least a cylinder is present, at least partially forming a pumping chamber, wherein a piston slides for pumping liquid.

[0003] At least one pair of annular sealing gaskets surrounding and contacting the piston are inserted between the cylinder and the piston and are adapted to eliminate or at least significantly reduce pressure fluid leakage that would otherwise occur through the gap between the cylinder and the piston.

[0004] Typically, the gaskets are stacked on top of each other in the (annular) seat obtained in the cylinder, with anti-pinch annular elements possibly inserted between the gaskets, in a direction parallel to the sliding axis of the piston relative to the cylinder.

[0005] The problem with this solution is that the gaskets must be manually inserted and stacked one by one by the operator into the seats obtained in the cylinder, which is a labor-intensive operation, especially since the diameter of the piston in most pumps on the market is less than 5 cm, which prevents the operator from easily accessing the receiving seats.

[0006] Furthermore, regardless of piston size, and therefore pump size, the gaskets may move as the piston inserts into the cylinder. Even when they do not move, they are not particularly effective guides for piston insertion because they are deformable.

[0007] Therefore, known solutions can affect pump production time.

[0008] The object of this invention is to overcome the limitations of the prior art with a reasonable and economical solution. The dependent claims summarize the preferred and / or particularly advantageous aspects of the invention. Summary of the Invention

[0009] In particular, the present invention provides a piston pump for pumping liquids, comprising:

[0010] The head, in which at least the cylinder block is obtained;

[0011] Piston, which can be slidably inserted into the cylinder;

[0012] The first annular sealing gasket circumferentially seals the contact piston (i.e., a part of the piston);

[0013] The second annular sealing gasket circumferentially seals the contact piston (i.e., a portion of the piston); and

[0014] An annular body that circumferentially surrounds the piston (i.e., a portion of the piston) and is at least partially housed in a receiving seat obtained in the head within a portion of the cylinder.

[0015] The ring-shaped body includes:

[0016] A first receiving seat, wherein a first annular sealing gasket is received;

[0017] A second receiving seat, wherein a second annular sealing gasket is received; and

[0018] The third receiving seat contains a third annular sealing gasket, which is positioned between the annular body and the receiving seat of the annular body.

[0019] Since placing the gasket into the annular body and then placing the annular body into the cylinder is simpler (and therefore faster) than placing the gasket directly into the cylinder as in prior art equipment, the annular body according to the invention allows for faster assembly operations during pump machining and maintenance.

[0020] According to one aspect of the invention, the pump may include a crankcase fixed to a head, the crankcase being provided with a piston annular guide surface and another receiving seat for an annular body, the other receiving seat for receiving a portion of the annular body extending from the head.

[0021] Therefore, gasket alignment can be achieved by precisely machining the crankcase, where the portion of the crankcase housing in the annular body must be machined to form the annular guide surface of the piston, without the need for precise machining of the cylinder block portion of the head. Since it is not necessary to precisely manufacture two housings for the annular body in the crankcase and head to achieve proper gasket alignment, gasket alignment is accelerated and production time is shortened. In particular, due to this solution, the housing of the annular body in the head can be formed with a lower precision than that of the housing formed in the crankcase, and therefore also lower than the precision required for machining the guide surface (where precision refers to a combination of dimensional tolerances, coaxiality tolerances, and positional tolerances relative to a fixed reference point on the pump, e.g., defined by screws securing the head to the crankcase).

[0022] The alignment of this type of pad is important for the following reasons:

[0023] The clearance between the piston and the cylinder extends to the pump crankcase, which houses the mechanism for driving the piston, configured to move the piston within the cylinder by reciprocating motion to pump liquid. For reciprocating piston pumps, this mechanism is the crankshaft; for rotary axial pumps, it is the rotary plate.

[0024] When the pumped liquid is, for example, water, and there is lubricating oil or grease in the crankcase used to lubricate the drive mechanism, the damage from leakage is greater because the pumped liquid contaminates the lubricant and reduces its effectiveness.

[0025] The aforementioned sealing gaskets are typically lip-shaped, and they wear down due to friction between the sealing gasket and the piston (i.e., friction with the lateral cylindrical surface of the piston).

[0026] A high degree of coaxiality is required between the gasket and the piston to avoid wear concentration areas that could lead to premature gasket failure and to obtain proper pressure distribution applied to the piston by the gasket, otherwise even a new gasket may cause leakage.

[0027] To achieve this high degree of coaxiality, in particular, to align the bores of the cylinder block with respect to the positions of the cylinder block and crankcase, and / or to form a receiving seat for obtaining a gasket in the cylinder block, in prior art pumps, precise machining (and therefore expensive and time-consuming) is required to form the bores of the cylinder block.

[0028] This problem is exacerbated in multi-cylinder pumps. Due to the increased number of cylinders, in addition to the tolerance of each cylinder, the positional tolerance of each cylinder relative to other cylinders must also be considered. Therefore, ensuring the coaxiality of the gaskets in all cylinders is more labor-intensive.

[0029] According to one aspect of the invention, since alignment can be achieved by machining the crankcase (which in any case must be machined to obtain the piston guide surface) and using an annular body (which in any case must be machined to obtain the gasket housing), forming a housing for the annular body in the crankcase allows the avoidance of the aforementioned costly and labor-intensive head machining in order to obtain coaxiality between the first and second sealing gaskets and the piston.

[0030] According to another aspect of the invention, the head portion having the cylinder and the annular seat can be made of a polymer material.

[0031] Therefore, lighter, cheaper, and faster-manufacturing heads and pumps than those made of metal in existing technologies can be obtained. Thanks to the alignment of the gasket achieved through the housing obtained in the annular body and crankcase, the advantages offered by the use of polymer materials can be maximized. This is because the tolerance accuracy values ​​of the cylinder block and housing obtained in the head through head molding do not require any material removal operations to improve accuracy, which is impossible in metal heads, where material removal is necessary after molding or die-casting operations anyway.

[0032] To emphasize the advantages described above, the present invention allows for the creation of crankcases with more precise tolerances than the head, thus being faster and cheaper than prior art pumps. The annular body can be accommodated in a housing obtained in the head with a clearance value greater than the clearance value of another housing manufactured in the crankcase for the annular body to be inserted.

[0033] The invention may also provide that the first receiving seat extends in a direction parallel to the sliding axis of the piston in the cylinder than the first annular sealing gasket extends in the same direction.

[0034] Therefore, in this direction, the entire first liner is housed within the seat and can maintain proper alignment during operation. Furthermore, contact between the liner and the receiving seat is prevented.

[0035] Alternatively, the present invention may provide a piston having a first end that is always housed in a cylinder, a first receiving seat having an opening toward the first end, and a pump that may include a preload ring inserted into the opening, the preload ring contacting a first annular sealing gasket, and the preload ring extending axially from the annular body through the opening.

[0036] Therefore, the first liner can be preloaded.

[0037] Specifically, the first liner (referred to as the high-pressure liner) is made of a more rigid material than the second liner, and the first liner can be preloaded even without pressurized fluid due to the preload ring.

[0038] According to another aspect, the pump can be of the axial piston and rotary tilting plate type, with an automatic suction valve and an automatic discharge valve, the pump being provided with multiple cylinders parallel to each other, wherein the corresponding pistons slide for pumping liquid. Attached Figure Description

[0039] Further features and advantages of the invention will become clear from the following description provided by way of non-limiting example, with the aid of the accompanying drawings.

[0040] Figure 1 This is an isometric view of the pump according to the present invention.

[0041] Figure 2 yes Figure 1 A front view of the pump.

[0042] Figure 3 It is based on Figure 2 A sectional view of plane III-III.

[0043] Figure 4 yes Figure 3 A magnified view of details IV.

[0044] Figure 5This is a view of the annular body according to the invention, the annular body being as follows Figure 3 and Figure 4 A cross-sectional view is shown, and it is isolated from the rest of the pump components. Detailed Implementation

[0045] Referring specifically to these figures, 1 generally represents a high-pressure piston pump, preferably suitable for pumping liquids with low viscosity (e.g., water). The pump shown is a multi-cylinder axial piston pump; however, the concept of the invention can be applied to single-cylinder pumps and / or reciprocating pumps. The concept of the invention is more significant for multi-cylinder pumps because they are more difficult to manufacture and assemble. For example, multi-cylinder pumps (especially axially inclined plate type pumps with more than three cylinders) require the assembly of a large number of parts, thus saving more time, and due to the presence of various cylinders, they require more precise machining to enable all moving parts and corresponding housings and gaskets.

[0046] In particular, as will be described in more detail below, the pump 1 shown is a pump of the type with a fixed tilt angle rotary plate and has an automatic valve for adjusting the pumping flow rate.

[0047] Pump 1 includes a head 10 (i.e., a cylinder head), the head 10 having at least a cylinder 15, the cylinder 15 at least partially defining the volume of the liquid pumping chamber 20.

[0048] In the illustrated embodiment, the head 10 includes a plurality of cylinders 15 (i.e., circular straight holes), for example, more than three, each cylinder 15 at least partially defining the volume of a corresponding liquid pumping chamber 20. As will be described in detail below, the pumping chambers 20 are independent of each other.

[0049] Therefore, the cylinder block 15 has at least a channel characterized by the cylindrical inner surface 16.

[0050] For example, there exists at least one cylinder head that can be formed as a single body, i.e., it can be obtained by processing a single body, which is obtained by solidifying a single melt or by injecting material into a mold.

[0051] In a preferred embodiment, this single body is made of a polymer material, making the pump lightweight, economical, and capable of rapid manufacturing.

[0052] However, it is not excluded that, in embodiments not shown, there may be cylinder heads formed by multiple single components fixed to each other, which are made of polymer material.

[0053] The number of cylinders in the multiple cylinder blocks is greater than three (i.e. at least four), preferably five, and the corresponding central axes of the cylinder blocks are arranged parallel to each other.

[0054] For example, the cylinder blocks are arranged radially along a common axis, and the central axes of individual cylinder blocks are parallel to this common axis. Furthermore, the cylinder blocks are arranged at equal distances from each other and at the same distance from the common axis. In other words, the cylinder blocks (i.e., the central axes of the cylinder blocks) are arranged at equidistant angles along an imaginary circle centered on the common axis and located in a plane perpendicular to the common axis.

[0055] In the illustrated embodiment with five cylinders, the central axis of these cylinders passes through the vertices of an imaginary regular pentagon located on a plane perpendicular to the central axis of these cylinders themselves.

[0056] The head may include a first surface 25 (the first surface 25 is, for example, flat) transverse to the cylinder axis, and an opposite second surface 30 transverse to the cylinder axis.

[0057] For example, in the molding step of polymer materials, the cylinder is manufactured as a hole, and each cylinder is provided with an opening 35 formed on the first surface 25.

[0058] In particular, in the illustrated embodiment, the cylinder body is formed as a through hole extending from the first surface 25 to the second surface 30, with a first opening 35 formed in the first surface 25 and a second opening 40 formed in the second surface 30.

[0059] It is not excluded that, in alternative embodiments, the cylinder block may be formed as a blind hole, and has an opening only on the first face 25 (i.e., the first opening).

[0060] Pump 1 includes a piston 45 that is slidably inserted into a cylinder 15 and at least partially inserted into the cylinder (e.g., only partially inserted into the cylinder). In other words, pump 1 includes a plurality of pistons 45, each piston being slidably and partially inserted into a corresponding cylinder 15 of a plurality of cylinders.

[0061] In the illustrated embodiment, the piston 45 (i.e., each piston 45) has a first axial end 50 facing the pumping chamber 20 (e.g., the first axial end 50 also partially defines the pumping chamber 20) and an opposing second axial end 55 extending from the cylinder body 15 out of the head through the opening 35.

[0062] Pump 1 includes a plurality of annular gaskets adapted to circumferentially seal around piston 45 (i.e., each piston 45) to prevent pumped liquid from leaking from the pumping chamber into the opening 35 in the first face 25.

[0063] Specifically, the pump 1 includes a first annular sealing gasket 60, commonly referred to as a high-pressure gasket, which circumferentially seals a portion of the piston 45 (therefore, the first annular sealing gasket circumferentially contacts and surrounds the piston and is coaxial with the piston), namely a portion of the skirt of the piston 45.

[0064] The first annular sealing gasket is elastic (i.e., resilient), for example, made of a polymer material.

[0065] It must be noted that, in this specification, the term elastic / resilient means that it is capable of undergoing significant elastic deformation under normal working loads to achieve its intended function. In this embodiment, the gasket elastically deforms to adhere to the relevant surface in order to create a possible watertight seal.

[0066] Preferably, the first annular sealing gasket 60 is lip-shaped.

[0067] For details, please refer to the following: Figure 5 The first annular gasket includes an inner annular lip 65 and an outer annular lip 70. The inner annular lip 65 circumferentially seals the portion of the contact piston 45, and the outer annular lip 70, for example, substantially forms a V-shaped cross-section with the inner annular lip.

[0068] The inner annular lip 65 and the outer annular lip 70 diverge from the same side of the ring 75, for example having a generally rectangular cross-section.

[0069] Pump 1 also includes a second annular sealing gasket 80, commonly referred to as a low-pressure gasket, which circumferentially seals a portion of the piston 45 (thus surrounding and coaxial with the piston), namely a portion of the skirt of the piston 45 (which partially (almost completely) overlaps with the portion acted upon by the first gasket).

[0070] For example, the two gaskets are aligned with each other in a direction parallel to the cylinder axis, with the first annular sealing gasket 60 being closer to the first axial end 50 of the piston than the second annular sealing gasket, i.e., closer to the pumping chamber 20.

[0071] The second annular sealing gasket is also elastic (i.e., resilient), for example, made of polymer materials.

[0072] Furthermore, preferably, the second annular sealing gasket 80 is also lip-shaped.

[0073] Like the first gasket, the second gasket includes an inner annular lip 85 and an outer annular lip 90, the inner annular lip 85 being in circumferential sealing contact with the aforementioned portion of the piston 45, and the outer annular lip 90 forming, for example, substantially a V-shaped cross-section with the inner annular lip.

[0074] The inner annular lip 85 and the outer annular lip 90 diverge from the same side of the ring 95, for example having a generally rectangular cross-section.

[0075] In the illustrated embodiment, the pump includes a first annular sealing gasket 60 and a second annular sealing gasket 80 for each of the plurality of cylinders 15.

[0076] The pump also includes an annular body 100, i.e., a plurality of annular bodies 100, one for each piston, the annular body 100 circumferentially surrounding a portion of the piston, i.e., the annular body 100 having a central through-hole 105 into which a portion of the piston 45 is inserted (see...). Figure 5 (where the piston is not shown), the annular body 100 is shaped to serve as a housing for receiving the first and second annular sealing gaskets, and the annular body 100 is at least partially received in the head (particularly in the cylinder portion of the head, see...). Figure 4 (See the enlarged view) in the housing 110. A more detailed description is provided for the cylinder section near the opening 35.

[0077] The receiving seat 110 is shaped as an annular recess (i.e., an annular groove) formed in the cylinder and entering the first surface. In particular, the opening 35 is defined by this recess.

[0078] For details, please refer to the following: Figure 4 The housing 110 includes an annular support surface 115 which is transverse to the central axis of the cylinder and extends from the cylindrical inner surface 16 of the cylinder 15 in a direction away from the central axis of the cylinder.

[0079] The annular support surface 115 faces the second axial end 55 of the piston (i.e., towards the opening 35 in the head).

[0080] Preferably, the annular support surface 115 is planar. However, it is not excluded that, in alternative embodiments, the annular support surface 115 may be tapered.

[0081] In the illustrated embodiment, the receiving seat 110 further includes an annular side surface 120 that extends from the outer periphery of the annular support surface 115 (i.e., the far side of the central axis of the cylinder) to the first surface 25 (e.g., forming a first opening) along the axial direction of the cylinder body (e.g., parallel to the central axis of the cylinder body). Thus, the annular surface is coaxial with the central axis of the cylinder body and the cylindrical inner surface of the cylinder body.

[0082] In the illustrated embodiment, the annular side 120 includes at least a cylindrical portion. Since the annular body is shaped as a cylinder with a through hole 105 coaxial with the piston (at least in the portion of the insertion receiving seat 110), the annular body is provided with an outer annular side 125 opposite to the inner annular side defining the through hole, which has a cylindrical portion.

[0083] Specifically, in the illustrated embodiment, the annular side 120 includes two cylindrical portions, one of which extends from the annular support surface 115, and the second cylindrical portion is coaxial with the first cylindrical portion and has a diameter greater than that of the first cylindrical portion. The second cylindrical portion begins at an enlarged portion that is directly inserted between the first and second cylindrical portions and extends directly into the opening.

[0084] Therefore, the outer annular portion 125 of the annular body also has two cylindrical portions with different diameters to match the annular side 120.

[0085] In an embodiment not shown, where the annular body is designed as a prism with a cylindrical through-hole for piston sliding, the annular side may have a polygonal cross-section (based on the cross-section perpendicular to the cylinder axis).

[0086] The ring-shaped main body is formed into a single main body.

[0087] The annular body essentially includes a first annular surface 130 (e.g., planar) facing the annular support surface 115 (preferably transverse to the cylindrical axis), and an opposing second annular surface 135 (e.g., planar) facing the direction opposite to the annular support surface 115 (preferably transverse to the cylindrical axis).

[0088] The annular body also includes an inner annular cylindrical surface 140 that substantially defines the through hole, and an outer annular side surface 125 facing in a direction opposite to the inner annular cylindrical surface 140 (towards the side of the receiving seat). These surfaces extend substantially between the two surfaces of the annular body.

[0089] The outer annular side 125 is inserted into the annular side 120 of the receiving seat 110 with a small gap.

[0090] In fact, this annular surface is defined by its thickness in the radial direction relative to the central axis of the cylinder body.

[0091] The annular body is generally shaped as a (cylindrical) tubular body, wherein the first annular surface 130 and the second annular surface 135 define the axial end of the tubular body, the outer annular side surface 125 defines the outer side wall of the (cylindrical) tubular body, and wherein the cylindrical through hole 105 is formed coaxially with the cylindrical annular side surface (i.e. its cylindrical portion).

[0092] As described above, the annular body 100 is shaped to serve as a housing for the first and second annular sealing gaskets. In particular, the annular body 100 is shaped such that the first and second annular sealing gaskets do not contact the head 10.

[0093] Specifically, the annular body 100 includes a first receiving seat 150 and a second receiving seat 155. The first receiving seat 150 receives a first annular sealing gasket 60, and the second receiving seat 155 receives a second annular sealing gasket. These receiving seats are shaped such that the gaskets contact the piston.

[0094] Specifically, the first receiving seat 150 and the second receiving seat 155 are shaped into an annular groove formed in the inner cylindrical surface 140 of the annular body.

[0095] Specifically, the first receiving seat 150 also has an annular opening 160 facing the first axial end 50 of the piston 45 (i.e., towards the pumping chamber 20) or facing the annular support surface 115, and the opening 160 passes through the first annular surface 130. In particular, this opening 160 extends to the piston.

[0096] For details, please refer to the following: Figure 5 The first receiving seat 150 therefore includes a lateral cylindrical surface 165 (or is composed of lateral cylindrical surfaces 165). The lateral cylindrical surface 165 extends from the inner circumference of the first annular surface 130 (which is substantially defined by the intersection of the opening 160 and the first annular surface 130) toward the interior of the annular body (along the central axis of the cylinder) to a planar annular surface 170 of the first receiving seat, the planar annular surface 170 being transverse (perpendicular) to the central axis of the cylinder and extending to the inner cylindrical surface 140.

[0097] In practice, the first receiving seat 150 is shaped as a cylindrical hole with a diameter larger than that of the inner cylindrical surface 140. The cylindrical hole passes through the first annular surface 130 and enters only a predetermined portion of the annular body.

[0098] The first receiving seat extends in a direction parallel to the central axis of the cylinder body, which is greater than the first annular sealing gasket extends in the same direction. In other words, the distance between the planar annular surface 165 and the first annular surface 130 is greater than the extension of the first annular sealing gasket in the direction of the central axis of the cylinder body.

[0099] Or, in other words, the extension along the direction of the lateral cylindrical surface 165 is greater than the extension along the direction of the first annular sealing gasket 60.

[0100] It must be noted that, in this specification, the planar annular surface is essentially shaped as a circular ring located on a plane.

[0101] The second receiving seat 155 is formed as a (complete) groove with a cylindrical bottom surface 175 facing the piston 45 (e.g., coaxial with the lateral cylindrical surface 165 of the first receiving seat 150), from which two opposing annular surfaces 180 extend, the two annular surfaces 180 being transverse (perpendicular) to the central axis of the cylinder (e.g., a plane) and reaching the cylindrical inner surface 16.

[0102] The first receiving seat 150 and the second receiving seat 155 are spaced apart from each other by an annular wall of the annular body. For example, such a wall is defined by a cylindrical inner surface 16, a lateral cylindrical surface 165 and an annular surface 180 adjacent to the first receiving seat 150.

[0103] Once inserted into the first receiving seat, the first annular sealing gasket 60 contacts the lateral cylindrical surface 165 at least by means of the outer annular lip 70, for example by means of the ring 75 contacting the planar annular surface 170.

[0104] When the second annular sealing gasket 80 is inserted into the second receiving seat 155, the second annular sealing gasket contacts the cylindrical bottom surface 175 with its outer annular lip, for example, by contacting the annular surface 180 away from the first receiving seat 150 with its ring 95.

[0105] The annular body 100 also includes a third receiving seat 185 facing the receiving seat 110 (particularly facing the annular side 120 of the receiving seat 110). The third receiving seat 185 includes a third annular gasket 190, which is placed directly between the annular body and the receiving seat 110 (i.e., between the annular body and the annular side 120 of the receiving seat 110) to obtain a watertight seal between the annular body and the receiving seat 110.

[0106] Specifically, the third receiving seat 185 is shaped as an annular groove formed in the outer annular side 125 and facing the annular side 120.

[0107] For details, please refer to the following: Figure 5 The third housing includes a cylindrical bottom surface 195 facing the annular side 120 (e.g., coaxial with the lateral cylindrical surface 165 of the first housing 150), from which two opposing annular surfaces 200 extend, the annular surfaces 200 being transverse (perpendicular) to the central axis of the cylinder (e.g., also a plane) and reaching the outer annular surface 125.

[0108] The distance between the third receiving seat and the first annular surface 130 is not zero, that is, there is a non-zero thick wall (defined by the annular body) between the first annular surface and the annular surface 200 adjacent to the first annular surface 130.

[0109] The third annular gasket 190 is, for example, an O-ring, i.e., having an annular cross-section.

[0110] The third annular gasket 190 contacts only the annular side 120 of the third receiving seat and the receiving seat 110.

[0111] The annular body 100 may further include a fourth receiving seat 205 facing the receiving seat 110 (particularly facing the annular side 120 of the receiving seat 110 in the head). The fourth receiving seat 205 includes a fourth annular gasket 210, which is placed directly between the annular body and the receiving seat 110 (i.e., between the annular body and the annular side 120 of the receiving seat 110) to obtain a watertight seal between the annular body and the receiving seat 110.

[0112] Specifically, the fourth receiving seat 205 is shaped as an annular groove formed in the outer annular side 125 and facing the annular side 120.

[0113] In the illustrated embodiment, the fourth housing includes a cylindrical bottom surface facing the annular side 120 (e.g., coaxial with the lateral cylindrical surface 165 of the first housing), from which two opposing annular surfaces extend, the annular surfaces being transverse (perpendicular) to the central axis of the cylinder (e.g., also planar) and reaching the outer annular surface 125.

[0114] The distance between the fourth receiving seat and the first annular surface 130 is greater than the distance between the third receiving seat and the first annular surface 130. In addition, the distance between the fourth receiving seat and the receiving seats is not zero, that is, there is a non-zero thick wall between the two receiving seats (defined by the annular body).

[0115] The fourth annular gasket 210 is, for example, an O-ring, i.e., having an annular cross-section.

[0116] The fourth annular gasket 210 contacts only the annular side 120 of the fourth receiving seat and the receiving seat 110.

[0117] The annular body does not include the pad seat obtained in the first annular surface 130 or the second annular surface 135.

[0118] The ring-shaped body is, for example, rigid and preferably made of metal (e.g., brass).

[0119] The term "rigid" refers to the fact that it does not deform significantly under normal working loads.

[0120] The annular body 100 may also include a discharge channel 215 (e.g., a plurality of discharge channels) having a first passage and a second passage, the first passage being obtained in a portion of the outer annular side 125 of the annular body included between a third and a fourth receiving seat, and the second passage being formed in a portion of the inner cylindrical portion 140 of the annular body included between the first and second receiving seats.

[0121] Pump 1 may include a crankcase 220, which is rigidly fixed (i.e., with no remaining degrees of freedom) to head 10 and, for example, contacts head 10 on a first surface 25. In particular, crankcase 220 includes a plane that directly contacts the first surface 25 of head 10.

[0122] The crankcase 220 contains a drive mechanism configured to initiate the movement of the piston within the cylinder to pump fluid.

[0123] In the illustrated embodiment, the drive mechanism includes a rotating tilting plate 225 adapted to receive rotatable motion via a drive shaft outside the pump.

[0124] A swashplate 225 is housed in a crankcase 220 and rotatably associated with the crankcase 220 relative to an axis of rotation A (e.g., coaxial with the common axis of the cylinder block), and includes a planar annular surface 230 located on an inclined plane relative to the axis of rotation A. Specifically, the swashplate is rotatably associated by a bearing and a flange 235 bolted to the crankcase 220, which allows the crankcase to be secured to a motor or frame rotatably associated with an external motor shaft.

[0125] Specifically, as the tilt plate 225 rotates, the piston slides along the sliding axis between the top dead center of the pumping chamber 20, where the volume is smallest, and the bottom dead center, where the volume is largest.

[0126] Furthermore, the crankcase may include an annular guide surface 240 (e.g., cylindrical) adapted to guide the piston 45 to slide within the cylinder block (i.e., the piston is slidably associated with the annular guide surface 240) and define the piston's sliding axis X. Due to manufacturing tolerances (dimensional and geometric), this sliding axis may not be perfectly coaxial with the cylinder block's central axis.

[0127] In the illustrated embodiment, an annular guide surface 240 for each piston is present in the crankcase.

[0128] The annular guide surface 240 can be achieved, for example, by a guide bushing 245 inserted into a receiving hole in the crankcase, the guide bushing 245 being made of, for example, metal (preferably steel).

[0129] In the illustrated embodiment, the crankcase includes a plurality of guide bushings 245, each guide bushing 245 being adapted to guide a corresponding piston 45 to slide along a corresponding cylinder block.

[0130] This guide bushing 245 (i.e., each guide bushing 245) communicates with an opening 35 formed in the first surface of the first head 10 (i.e., a corresponding opening formed in the first surface).

[0131] Pump 1 may include an axially hollow spacer 250, in which a piston can slide. The spacer contacts an annular body 100 at its axial end and an annular abutment surface transverse to the central axis of the cylinder at its opposite axial end, is coaxial with the piston, and is positioned between a guide bushing and the annular body. For example, the spacer may also include a gasket acting on the piston.

[0132] The second axial end of the piston (i.e., each piston) is kept in contact with the annular guide 260 located on the annular plane of the inclined plate 225 by a force applied by the corresponding elastic element 255 (e.g., by an inserted roller axial bearing).

[0133] Each elastic element has a first end connected to the crankcase 220 and a second end connected to the piston 45 (e.g., near the second end 55).

[0134] The shape of the second axial end 55 can be an outwardly convex circle, and the annular guide 260 can have a planar annular surface parallel to the plate.

[0135] In a preferred embodiment, the crankcase includes another receiving seat 270 of the annular body 100, which receives a portion of the annular body 100 extending from the head 10 (i.e., extending from the head through the opening 35). The crankcase can thus be precisely machined to achieve gasket alignment, and the portion of the crankcase in the receiving seat of the annular body must be manufactured to obtain the piston guide surface.

[0136] Specifically, the annular body (i.e., each annular body) is accommodated in the receiving seat 110 obtained in the head 10 with a gap value that is greater than the gap value in another receiving seat 270 formed when the annular body is inserted into the crankcase.

[0137] Furthermore, the piston 45 (i.e., each piston) is slidably inserted into the annular guide surface 240 with a gap value that is at least equal to (preferably less than) the gap value of the annular body inserted into another receiving seat.

[0138] In the illustrated embodiment, the crankcase includes a through-hole (i.e., a hole through each cylinder block), in which an annular guide surface 240 is obtained (i.e., in which a guide bushing is received), and the piston passes through from one end of the through-hole to the other.

[0139] Another receiving seat 270 is formed at the through hole and is located in the crankcase surface that contacts the first surface 25 of the head.

[0140] Another receiving seat 270 is shaped to form an annular recess (i.e., an annular groove) in the through hole, thereby causing the crankcase surface to contact the head.

[0141] In the illustrated embodiment, another receiving seat 270 has a transverse annular support surface 275 (e.g., perpendicular to the sliding axis of the piston), the transverse annular support surface 275 extending from the annular inner surface 280 of the through hole in a direction away from the sliding axis.

[0142] The annular support surface 275 faces the first axial end 50 of the piston, i.e., the opening 35 of the head, and the annular support surface 115 of the receiving seat 110.

[0143] Preferably, the annular support surface 275 is planar; however, it is not excluded that, in alternative embodiments, the annular support surface 115 may be conical, depending on the shape of the second face of the annular body.

[0144] In the illustrated embodiment, another receiving seat 270 further includes an annular side surface 285, which extends from the outer periphery of the annular support surface 275 (i.e., the distal side of the cylinder block central axis) to the crankcase surface of the contact head (e.g., forming an opening in the crankcase) in a direction parallel to the sliding axis. The annular side surface 285 is substantially coaxial with the annular guide surface 240. Furthermore, the annular side surface 285 is coaxial with the annular side surface of the receiving seat, taking into account manufacturing and assembly tolerances.

[0145] In the illustrated embodiment, the annular side 285 is cylindrical because, at least in the portion where the other receiving seat 270 is inserted, the annular body is cylindrical.

[0146] The annular body is fully accommodated in the accommodating seat 110 formed in the head 10 and another accommodating seat 270 formed in the crankcase 220 (i.e., accommodated in the volume defined by the respective surfaces).

[0147] The third and fourth annular sealing gaskets do not contact the other housing 270 formed in the crankcase.

[0148] As described above, the gap between the annular body and the receiving seat is greater than the gap between the annular body and another receiving seat. In particular, the gap between the outer surface 125 of the annular body and the annular side surface 120 of the receiving seat 110 is greater than the gap between the outer surface 125 of the annular body and the annular side surface 285 of another receiving seat 270.

[0149] In other words, the precision of the connection between the annular body and the annular body seat of the crankcase is greater than the precision of the connection between the annular body and the annular body seat in the cylinder block.

[0150] It should be noted that the gap value refers to the minimum possible thickness of the gap between two components with a gap connection (taking into account manufacturing and assembly tolerances).

[0151] For illustrative purposes only, and to emphasize that this structure allows for precise machining of the crankcase while retaining the head obtained by molding, the annular side 120 of the housing 110 may be formed with a displacement of H7 type nominal diameter (according to UNI6388 ISO R.286), and the annular side 285 of the other housing 270 may be formed with a displacement of H8 type nominal diameter.

[0152] The head is connected to the crankcase via a threaded connection device 295, which essentially clamps the annular body 100 in the corresponding receiving seat.

[0153] The crankcase (like the head) can be made of polymer materials.

[0154] In this case, there is an insert 300 with internal threads in the crankcase to allow tightening of a threaded connector (e.g., a screw) that passes through a hole formed in the head assembly.

[0155] Preferably, the pump includes a plurality of threaded connectors (e.g., the same number as the cylinder block) configured to secure the head 20 to the crankcase 5, the plurality of threaded connectors being inserted into an equal number of through holes obtained in the head 20.

[0156] For example, the pump may include a cover 305 made of metal, for example, with a threaded connection that allows the head to be clamped between the crankcase and the cover.

[0157] Preferably, the pump may include a preload ring 310, which is partially inserted into the first receiving seat 150 and extends from the annular body through an opening in the first receiving seat. In particular, the preload ring 310 extends through the opening from a first surface of the annular body (i.e., the plane in which the first surface extends).

[0158] The preload ring contacts the first annular sealing gasket and the housing such that when the head and crankcase are fixed together, the preload ring contacts the housing 110 (i.e., the annular support surface 115 of the housing) and compresses the first annular gasket to preload it, so that the first annular gasket can contact the piston even under low or zero pressure conditions.

[0159] When this preloaded ring 310 is present, there is a gap between the first surface of the annular body and the annular abutment surface of the receiving seat. Therefore, the two surfaces do not contact each other.

[0160] Therefore, the first annular sealing gasket only contacts the piston, the annular body (i.e., the surface of the corresponding first receiving seat), and the preload ring. The second annular sealing gasket only contacts the piston and the annular body (i.e., the surface of the corresponding second receiving seat).

[0161] The preloaded ring 310, for example, has a T-shaped cross-section.

[0162] Pump 1 may include an intake valve 315 and an output valve 320 for cylinder 15 (i.e., one for each cylinder 15), the valves of cylinder 15 being unidirectional and automatic and allowing flow to be limited from and to pumping chamber 20. Specifically, intake valve 315 allows only inflow into pumping chamber 20, and output valve 320 allows only outflow from pumping chamber 20.

[0163] It should be noted that an automatic valve is a valve configured to automatically open when the pressure difference between two environments separated by the valve reaches a predetermined value, thereby allowing fluid communication between the two environments to which the valve is inserted. Specifically, automatic valves do not utilize electromechanical operating mechanisms, but only pressure differences.

[0164] Each suction valve 315 includes an inlet and an outlet in fluid communication with the pumping chamber, and each output valve 320 includes an inlet and an outlet in fluid communication with the pumping chamber.

[0165] Pump 1 includes a corresponding receiving seat for each suction valve 315, which is obtained directly in the head, for example, as a hollow cavity with an opening provided on the outer surface of the head, the opening of which flows out of the head and is closed by a suction cap 325 configured to hold the corresponding suction valve 315 in its receiving seat. In the illustrated embodiment, this opening of the valve seat corresponds to a second opening 40, and the suction valve cap is held in place by a cover 305.

[0166] Therefore, in the illustrated embodiment, the intake valve is substantially coaxial with the corresponding cylinder 15.

[0167] In the illustrated embodiment, the pump further includes a suction passage for delivering liquid to be pumped to the cylinder, the suction passage including a first channel 330 substantially coaxial with the common axis of the cylinder, and a conduit 335 branching from the first channel 330 to a suction valve seat.

[0168] The inhalation passage (particularly its first passage 330) is in fluid communication with the discharge passage 215 of the annular body 100 via a suitable conduit formed at the head.

[0169] Pump 1 includes a housing for each output valve 320, which is obtained directly in the head, for example, as a hollow cavity provided with an opening that flows out of the head and is closed by an output cap 340 configured to hold the respective output valve 320 in the proper position in the housing.

[0170] In particular, in order to secure the output cap 340 to the head made of the material, the head of the present invention is provided with a metal insert 345 provided with internal threads to allow the output cap to be tightened, so the output cap is provided with external threads.

[0171] In the illustrated embodiment, the receiver of the output valve is connected to the cylinder body directly or via a pipe.

[0172] Pump 1 also includes an output passage for collecting the pumped liquid, the output passage being in direct fluid communication with an output valve and positioned downstream of the valve relative to the fluid direction when the pump is in use. For example, the output passage is in direct fluid communication with the outlet of each output valve 320.

[0173] The pump according to the present invention operates as follows:

[0174] As the tilting rotating plate moves, the movement of the corresponding piston towards the bottom dead center in one or more cylinders creates a vacuum in the pumping chamber, causing the corresponding output valve to close and the corresponding suction valve to open. Liquid is then drawn in and passes through the corresponding suction valve to the corresponding pumping chamber 20. Upon reaching the bottom dead center, the piston rises to the top dead center due to the thrust of the rotating plate, creating overpressure in the pumping chamber, causing the suction valve to close and the output valve to open.

[0175] In this operation, the piston optimally (and therefore uniformly) rubs against the first and second sealing gaskets, thanks to the centering effect obtained through the annular body, which further allows for simpler and faster pump assembly.

[0176] Therefore, the present invention can be modified and varied in many ways, and all modifications and variations fall within the scope of the present invention.

[0177] Furthermore, all details can be replaced by other technically equivalent components.

[0178] In practice, the materials used, as well as the possible shapes and sizes, can be determined according to requirements without deviating from the scope of protection of the following claims.

Claims

1. A piston pump (1) for pumping liquid, said piston pump (1) comprising: - Head (10), wherein at least the cylinder (15) is obtained; - Piston (45), which is slidably inserted into the cylinder; - A first annular sealing gasket (60) circumferentially seals against the piston (45). - A second annular sealing gasket (80) circumferentially seals against the piston (45). as well as - An annular body (100) that circumferentially surrounds the piston (45) and is at least partially housed in a receiving seat (110) obtained in the head (10) within a portion of the cylinder (15); The annular body (100) includes: - First receiving seat (150), wherein the first annular sealing gasket (60) is received. - A second receiving seat (155) wherein the second annular sealing gasket (80) is received; and - A third receiving seat (185) is provided for receiving a third annular sealing gasket (190), the third annular sealing gasket (190) being disposed between the annular body (100) and the receiving seat (110) of the annular body; - A crankcase (220) fixed to the head (10), the crankcase (220) being provided with an annular guide surface (240) for the piston (45) and another receiving seat (270) for the annular body (100), the other receiving seat (270) receiving a portion of the annular body extending from the head, wherein the annular body (100) is received in the receiving seat (110) obtained in the head (10) with a gap value greater than the gap value of the annular body inserted into the other receiving seat (270) obtained in the crankcase (220).

2. The piston pump (1) according to claim 1, wherein, At least the head portion of the receiving seat (110) in which the cylinder (15) and the annular body (100) are obtained is made of polymer material.

3. The piston pump (1) according to claim 1, wherein, The first receiving seat (150) extends in a direction parallel to the sliding axis (X) of the piston (45) in the cylinder (15) more than the first annular sealing gasket (60) extends in the same direction.

4. The piston pump (1) according to claim 1, wherein, The piston (45) has a first end (50) that is always housed in the cylinder (15), the first housing (150) having an opening (160) facing the first end, and wherein the piston pump includes a preload ring (310) inserted into the opening, the preload ring (310) contacting the first annular sealing gasket (60), and the preload ring (310) extending through the opening (160) out of the annular body (100).

5. The piston pump (1) according to any one of claims 1 to 4, wherein, The piston pump is of the type with an axial piston and a rotating tilting plate, and has an automatic suction valve and an automatic discharge valve. The piston pump is provided with a plurality of parallel cylinders (15), wherein the corresponding pistons (45) slide for pumping liquid.

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