Hydraulic pump comprising a piston adapted for a reciprocating movement and a removable sleeve

Abstract

The invention relates to a hydraulic pump provided with a pump body comprising a duct intended for a flow of pressurized liquid, from the inlet of the pump to the outlet of said pump, wherein the pump is equipped with a piston adapted to perform a reciprocating movement inside a chamber, which is itself present inside said pump body, said movement being possible by virtue of the pressure exerted on the piston by said flow of liquid and a mechanism adapted to modify the direction of the pressure on said piston, the chamber having an inner wall adapted to cooperate with the circumference of the piston.

Description

[0001] DESCRIPTION

[0002] TITLE: HYDRAULIC PUMP COMPRISING A PISTON ADAPTED FOR RECIPROCATING MOVEMENT AND A REMOVABLE SLEEVE

[0003] Field of invention

[0004] The invention relates to a hydraulic pump provided with a pump body comprising a chamber for guiding a flow of pressurized liquid from the inlet of the hydraulic pump to the outlet of said hydraulic pump, said hydraulic pump being equipped with a piston adapted to perform a reciprocating movement inside said chamber thanks to the pressure exerted on said piston by said flow of liquid.

[0005] In addition, the hydraulic pump is provided with a mechanism adapted to modify the direction of the pressure exerted on the piston, in which the chamber present inside the pump body comprises an inner wall adapted to cooperate with the circumference of said piston. The piston, adapted to carry out a reciprocating movement, is connected to a suction element in the form of a rod adapted to continue the movement of the piston and suck a determined quantity of fluid inside the pump thanks to the reciprocating movement of the piston. Thus, a determined quantity of fluid can mix with the flow of liquid inside said pump. The piston of the hydraulic pump according to the invention is formed as a differential piston comprising a first part having a first diameter and a second part having a second diameter, different from the first diameter.The inner wall of the hydraulic pump chamber comprises a first part, with a first diameter, adapted to cooperate with the first part of the piston, and a second part, with a second diameter, different from said first diameter, adapted to cooperate with the second part of the piston.

[0006] State of the art

[0007] A hydraulic pump according to the above introduction is known in the state of the art. The basic principle for the operation of a hydraulic pump according to the invention is described in French patent applications FR2896281 and FR3042235. Said documents FR2896281 and FR3042235 describe a device for injecting an additive product into a liquid, said injection device being provided with a differential piston positioned so as to slide in an enclosure having two cylinders whose sections correspond to those of the two elements of said piston. The piston of said injection device is adapted to execute an alternating movement according to which the movement of said piston is controlled by a pressurized liquid progressing from the inlet of the injection device towards the outlet of said injection device.A hydraulic motor provided with a differential piston is described in more detail in French patent applications FR2896281 and FR3042235, relating to a hydraulic machine, more particularly a hydraulic motor, comprising a casing and a piston adapted to slide inside said casing. The piston according to patent application FR2896281 is adapted to slide in the casing, said piston separating two chambers, the hydraulic machine comprising hydraulic switching means allowing the supply of liquid and the evacuation of the chambers separated by said piston. Said means are adapted to modify the pressure exerted on the piston in order to ensure its reciprocating movement.

[0008] Hydraulic pumps known from the prior art are provided with a piston exerting a reciprocating movement inside a pump body, said movement generating wear of the various parts making up said hydraulic pumps. The outer surface of the piston sliding relative to the inner surface of the hydraulic pump, said surfaces are exposed to wear during use.

[0009] For optimal operation of a hydraulic pump, as described below, it is necessary to ensure a perfect seal between the inner wall of said hydraulic pump and the outer wall of the piston.

[0010] Typically, the piston is fitted with sealing elements such as soft lips which, if defective, can be replaced during a hydraulic pump maintenance step. However, if the inside of the hydraulic pump is too worn, replacing the lips is not enough to ensure optimal sealing and operation of the hydraulic pump. When the inside of the hydraulic pump is damaged by excessive use and can no longer be repaired, the entire hydraulic pump must be replaced.

[0011] As a general rule, the pump bodies of the hydraulic pump, as described below, are made of plastic. In order to ensure the strength imposed by the operation of such pumps, the walls of said pump bodies are relatively thick in order to withstand the pressure exerted on said walls. This means that the hydraulic pump according to the invention has a relatively high weight. In order to control the dimensions of the interior of the hydraulic pump optimally, and to correspond to the external dimensions of the piston, the dimensions of the pump bodies must be perfectly controlled during the production of said hydraulic pump, said control having an influence on its production cost.

[0012] For the reasons set out above, there is a need to propose certain improvements to the hydraulic pumps known from the prior art by offering the possibility of repairing certain parts of said pumps, thus avoiding changing the entire pump in the event of wear. Furthermore, and generally speaking, it would be preferable to reduce the number of parts constituting a hydraulic pump and having to meet defined dimensions, said parts being necessary to ensure a perfect seal between the interior of the hydraulic pump and the exterior of the piston.

[0013] Subject of the invention

[0014] The subject of the present invention relates to a hydraulic pump provided with a pump body comprising a chamber intended for a flow of pressurized liquid, from the inlet of the pump towards the outlet of said pump, the pump being equipped with a piston adapted to carry out a reciprocating movement inside said chamber thanks to the pressure exerted on the piston by said flow of liquid and thanks to a mechanism adapted to modify the direction of the pressure on said piston, the chamber having an inner wall adapted to cooperate with the circumference of the piston, said piston being connected to a suction element in the form of a rod, said rod being adapted to continue the reciprocating movement of the piston and also being adapted to suck a determined quantity of fluid inside the pump, thanks to said reciprocating movement, thus allowing said determined quantity of fluid to mix with the flow of liquid through the pump,said piston being formed as a differential piston comprising a first part having a first diameter and a second part having a second diameter, different from the first diameter, the inner wall of said chamber comprises a first part with a first diameter adapted to cooperate with the first part of the piston and a second part with a second diameter, different from the first diameter, adapted to cooperate with the second part of the piston, the inner wall of the chamber being produced by means of a sleeve, said sleeve being removably fixed inside the pump body.,

[0015] According to one embodiment of the invention, the piston separates the chamber into a first part and a second part, and the mechanism is adapted to modify the direction of the pressure on the piston, said piston comprising hydraulic switching means to allow the supply and evacuation of the parts of the chamber, separated by the piston, said hydraulic switching means being controlled by the movement of the piston.

[0016] According to one embodiment of the invention, the sleeve is provided with a radically extending fixing element adapted to cooperate with a fixing element located in the pump body in order to fix said sleeve inside the pump body.

[0017] According to one embodiment of the invention, the sleeve securing element is in the form of a lip or pin and the pump body securing element is in the form of a radically extending slot or groove, the sleeve securing element and the pump body securing element being adapted to secure said sleeve by pivoting it about its lateral axis, thereby allowing the lip or pin of the sleeve to penetrate inside the slot or groove of the pump body.

[0018] According to one embodiment of the invention, the sleeve is provided with an external thread and the pump body is provided with an internal thread adapted to cooperate with said external thread of the sleeve, to fix the sleeve in the pump body using said thread.

[0019] According to one embodiment of the invention, the sleeve comprises a first part in the form of a tube having a first diameter and a second part in the form of a tube having a second diameter, different from the first diameter, said first and said second tubes being connected by a determined number of separate fixing elements.

[0020] According to one embodiment of the invention, the first and second parts of the sleeve are arranged in such a way that at least a part of the first part of said sleeve extends around at least a part of the second part of the sleeve.

[0021] According to one embodiment of the invention, the hydraulic pump comprises a first body member and a second body member, said first and second body members being removably positioned on each other to allow opening and closing of the pump body, said pump further comprises a fastening element for providing a loose connection between the first body member and the second body member, said fastening element being adapted to be fixed on the outside of the first and second body members of the pump.

[0022] According to one embodiment of the invention, a first of the first and second body members comprises a protruding element for contacting the interior of a fixing ring, the interior of said fixing ring and the exterior of the second body member of the first and second body members comprising a thread for fixing the fixing ring to the exterior of the pump body by means of said thread.

[0023] According to one embodiment of the invention, the first and second body members are adapted to be moved to a position allowing them to be fixed to each other by means of said fixing ring by a lateral movement. According to one embodiment of the invention, one of the first and second body members is provided with a lock, said lock being adapted to block the rotation of the sleeve inside the pump body, as soon as the first and second pump body members are assembled.

[0024] Brief description of the drawings

[0025] The aim, object and characteristics of the invention will appear more clearly on reading the following description given with reference to the figures in which:

[0026] [Fig. 1] shows a sectional and perspective view of an embodiment of a hydraulic pump according to the invention,

[0027] [Fig. 2] represents an exploded view of the main parts of the hydraulic pump according to the invention during their assembly,

[0028] [Fig. 3] illustrates a detailed view of the sleeve of the hydraulic pump according to the invention as well as its fixing inside said hydraulic pump,

[0029] [Fig. 4] shows the use of a lock to prevent rotation of the sleeve of the hydraulic pump according to the invention and thus allowing its fixing inside said hydraulic pump,

[0030] [Fig. 5] represents a schematic view of the flow of water circulating inside the hydraulic pump allowing the piston to be moved in a first direction, and

[0031] [Fig. 6] illustrates the flow of water circulating inside the hydraulic pump allowing the piston to move in a second direction, and

[0032] [Fig. 7] represents a perspective and sectional view of a part of the hydraulic pump according to the invention,

[0033] [Fig. 8] shows a sectional and perspective view of a second embodiment of a hydraulic pump according to the invention, and

[0034] [Fig. 9] shows a sectional and perspective view of a third embodiment of a hydraulic pump according to the invention. The present description refers to hydraulic pumps. In the context of said description, the term "hydraulic pump" refers to any hydraulic machine, more particularly to hydraulic motors, comprising an outer body, creating a casing, and a piston capable of sliding, in a back-and-forth movement, inside said casing.

[0035] Within the present description, the term "hydraulic pump" refers more particularly to a pump adapted to mix a primary flow, such as a flow of water, and a secondary flow, such as an additive, which additive is added to this primary flow using the reciprocating movement exerted by the piston and generated inside the hydraulic pump.

[0036] Within this description, the term "translational movement" is also used. The term "translational movement" refers to a movement in which an element, or body, performs a translation but no other movement such as rotation or the like. The term "translational movement" distinguishes from a rotation of a first element relative to a second element.

[0037] Figure 1 shows a sectional and perspective view of a hydraulic pump 100 according to the invention. The hydraulic pump 100 comprises a first body member 10 and a second body member 20, positioned one on top of the other in order to together form the pump body of the hydraulic pump 100. The first body member 10 is fixed on the second body member 20 using a fixing ring 30 positioned outside the body members 10, 20.

[0038] The body members 10, 20 are adapted to be positioned against each other by performing a translational movement. This means that, unlike hydraulic pumps known from the prior art, the two body members 10, 20 of the hydraulic pump according to the invention are not fixed to each other by means of rotation, said rotation being able to be achieved, for example, via a thread. The advantage of these measures lies in the fact that the positioning of the first body member 10 relative to the body member 20 is not determined by the degree of screwing of said body members 10, 20 onto each other but is determined by the respective shape of said body members 10, 20.

[0039] To enable the use of a fixing ring 30, serving to fix the body members 10, 20 to each other, the first body member 10 is provided with a protrusion 11 on which the fixing ring 30 can exert a certain pressure. The outside of the second body member 20 is provided with a thread 24 (as shown in Figure 2) on which the thread inside the fixing ring 30 can be fixed. Thus, the two body members 10, 20 and the fixing ring form a unit as soon as said fixing ring has been completely screwed onto said body members 10, 20.

[0040] Figure 1 shows the second body member 20 provided with a water inlet 21 and a water outlet 22. The path of the water, from the inlet 21 to the outlet 22, is schematically illustrated in Figures 5 and 6 which will be described below.

[0041] Furthermore, the second body member 20 is provided with a cylindrical-shaped element 23 adapted to cooperate with a fluid injector. As shown in FIG. 1 , a sleeve 40 is positioned inside the body members 10, 20. A perspective view of said sleeve 40 is shown in FIG. 2. The sleeve 40 comprises a first part 41 , essentially in the form of a tube, forming an inner wall of the hydraulic pump 100, having a first diameter. A second part 42, also essentially in the form of a tube, is connected to said first part 41. As illustrated in FIG. 1 , the second part 42 has a diameter smaller than the diameter of the part 41 of the sleeve 40. As can be seen in FIG. 1 , the lower part of the first part 41 of the sleeve 40 at least partially envelops the upper part of the second part 42 of said sleeve 40.The first part 41 and the second part 42 are connected to each other by means of a determined quantity of connection elements 43. Said connection elements 43 have the initial function of ensuring the alignment of the first part 41 and the second part 42 of the sleeve 40. The spacing between the connection elements 43 allows the passage of water from the inlet 21 of the hydraulic pump to the outside of the second part 42 to the inside of the part 41 of the sleeve 40, thus allowing optimal operation of the hydraulic pump. As illustrated in Figure 1, the sleeve 40 includes a flange 44 secured between, respectively, the first body member 10 and the second body member 20 during assembly of said body members 10, 20. A more detailed representation of the exact securing of the sleeve 40 between these two body members 10, 20 is seen in Figures 3 and 4.

[0042] The hydraulic pump 100 is provided with a piston 50 adapted to perform a reciprocating movement inside the sleeve 40. For reasons of clarity, said piston is not shown in FIG. 1. For the particular operation and shape of the piston 50, reference is made more particularly to documents FR2896281 and FR3042235.

[0043] In Figure 1, the cylindrical element 23 is connected to a liquid metering device adapted to suck a certain quantity of liquid inside the hydraulic pump, thus allowing said quantity of liquid to mix with the flow of water moving from the inlet 21 to the outlet 22 of the hydraulic pump 100. The metering device is not described in detail within the present description and, for its operation, reference is made to the documents FR2896281 and FR3042235.

[0044] Figure 2 represents an exploded and perspective view of the different elements forming the body of the hydraulic pump and allowing the piston 50 to move correctly inside the hydraulic pump 100. The hydraulic pump 100 comprises, as explained with reference to Figure 1, a first body member 10, a second body member 20 whose interior is adapted to receive a sleeve 40. The two body members 10, 20 can be connected to each other by means of a fixing ring 30 which cooperates on the one hand with the protuberance 11 of the first body member 10 and, on the other hand, with the thread 24 present on the outside of the second body member 20. Figure 2 also represents the inlet 21 and the outlet 22 of the second body member 20 of the hydraulic pump 100.

[0045] In order to ensure optimum sealing between the outside of the sleeve 40 and the inside of the second body member 20 of the hydraulic pump 100, the sleeve 40 is provided with a first sealing lip 45, fixed using a fixing ring 46, and a second sealing lip 47. These two sealing lips 45, 47 are made of a flexible material such as rubber or any other similar material.

[0046] Figure 2 also shows that the body member 10 of the hydraulic pump 100 is provided, at its lower end, with a sealing element 15, which is adapted to provide a seal between the body members 10, 20 during their assembly.

[0047] Figure 3 shows a detailed view of the sleeve 40 located inside the second body member 20 of the hydraulic pump 100. The rim 44 of the sleeve 40 is provided with a lip or pin 48. Furthermore, the interior of the second body member 20 of the hydraulic pump 100 is provided with a fastening element 25 adapted to cooperate with said lip or pin 48 of the sleeve 40. The fastening element 25 defines a radially extending slot or groove. When the sleeve 40 is positioned inside the second body member 20 of the hydraulic pump 100, said sleeve 40 can pivot so that the lip or pin 48 is positioned inside said slot or groove and thereby fixed using the fastening element 25 forming part of the second body member 20.

[0048] Since the first body member 10 and the second body member 20 can be positioned against each other and fixed by means of a translational movement (in contrast to a rotational movement), the first body member 10 is therefore provided with a lock 13 as shown in Figure 4. When the first body member 10 and the second body member 20 are assembled, said lock 13 is adapted to fill the space located next to the lip or pin 48, thus avoiding a voluntary movement of the sleeve 40 during the use of the hydraulic pump 100. Thanks to the respective shapes of the body members 10, 20, the sleeve 40 is fixed and completely immobile inside the hydraulic pump 100 during the operation of said hydraulic pump 100.

[0049] The use of the sleeve 40, as described in Figures 1 to 4, has the advantage that the parts 41 and 42 of the sleeve 40 respectively form an inner wall for a first part and a second part of the piston with a first diameter and a second diameter. When the inner wall, formed by the sleeve, undergoes wear resulting from the use of the hydraulic pump 100, the user can repair said hydraulic pump 100 by replacing said sleeve 40. With reference to Figure 1, the user can open the hydraulic pump 100 by pivoting the fixing ring 30, thus releasing the first body member 10 and the second body member 20 and giving access to the interior of the hydraulic pump 100. The fixing ring 30 can be removed entirely in order to facilitate the replacement of the sleeve 40. After replacement of said sleeve 40, the sealing of the interior of said sleeve 40 and of the piston 50 is again optimal.

[0050] One of the advantages of using a removable sleeve is that if the hydraulic pump 100 wears out, it is not necessary to replace the entire hydraulic pump, but only the defective part, i.e. the sleeve.

[0051] The limited volume and weight of the sleeve 40, compared to the volume and weight of the pump body, provided with the first body member 10 and the second body member 20, represents another advantage linked to the use of said removable sleeve 40. This means that, during the production of the sleeve 40, the respective dimensions of said sleeve 40, and more particularly the diameter of its first part 41 and the diameter of its second part 42, are easier to control than the dimensions of the body member of the hydraulic pump according to the prior art. The optimized control of said dimensions allows optimal operation of the hydraulic pump 100 and lower production costs.

[0052] Figures 5 and 6 represent a schematic view of the path of a flow of liquid, such as water, from the inlet 21 of the hydraulic pump 100 to the outlet 22 of said hydraulic pump 100.

[0053] Figure 5 shows a simplified sectional view of the hydraulic pump 100 to illustrate the reciprocating movement of the piston 50 positioned inside the sleeve 40 located in the hydraulic pump 100.

[0054] Figure 5 shows the first body member 10 and the second body member 20, illustrated in their assembled position. The first body member 10 and the second body member 20 are assembled using the fixing ring 30 fixed on the outside of said body members 10, 20. As shown in Figure 5, the sleeve 40 is held between the body members 10, 20 using the flange 44 (as shown in Figure 1) of said sleeve 40 itself held between the ends of said body members 10, 20.

[0055] As explained with reference to Figures 3 and 4, after the assembly of the first body member 10 and the second body member 20, the sleeve 40 can no longer be moved inside the hydraulic pump 100. A piston 50 is present inside the sleeve 40. It should be understood that Figure 5 represents a schematic view of said piston 50. The piston 50 is provided with a first portion, schematically indicated using the reference number 51, providing a first diameter. Said first portion 51 is adapted to cooperate with the first portion of the sleeve 41. The contact between the outside of the first portion 51 of the piston 50 and the inside of the first portion 41 of the sleeve 40 is ensured in a sealed manner in order to avoid a flow of fluid between these respective ends. By means of an intermediate element 53, the first part 51 of the piston 50 is connected to a second part 52 of said piston 50 of a second diameter.The second diameter of the second part 52 of the piston 50 is smaller than the diameter of the first part 51 of the piston 50. The second part 52 of the piston 50 essentially has the shape of a disc whose circumference cooperates with the inner wall of the second part 42 of the sleeve 40 in order to ensure optimal sealing between these two elements during the back-and-forth movement of the piston 50 inside the hydraulic pump 100. The intermediate part 53 essentially has the shape of a tube and contains a mechanism for respectively opening and closing orifices present in the first part 51 and the second part 52 of the piston 50. Said mechanism, opening and closing said orifices, is not described in the present description but some of its embodiments are described in French patent applications FR2896281 and FR3042235.

[0056] As illustrated in Figure 5, the first part 51 of the piston 50 is provided with a first orifice 511 and a second orifice 512. Depending on the position of the piston 50, illustrated in Figure 5, the orifices 511, 512 are visible in an open position. The second part 52 of the piston 50 is provided with two orifices 521, 522. Depending on the position of the piston 50 shown in Figure 5, the orifices 521, 522 are visible in a closed position. A succession of arrows, as shown in Figure 5, makes it possible to follow the path of a pressurized fluid, from the inlet 21 to the outlet 22 of the hydraulic pump 100. Said hydraulic pump 100 is, for example, adapted to receive a flow of pressurized water at the inlet 21. Said pressurized fluid penetrates inside the hydraulic pump 100 and abuts against the second part 52 of the piston 50. The two orifices 521, 522 being closed, the fluid cannot pass through the second part 52 of the piston 50.Under the influence of this pressure, the piston moves upwards from its position as shown in Figure 5. This is schematically indicated by the arrow 61. This movement is possible because the ports 511, 512 of the first part 51 of the piston 50 are open. The liquid present inside the hydraulic pump 100 can move with the help of the piston 50 and push said liquid, firstly within the space between the first part 41 of the sleeve 40 and the second part 42 of said sleeve 40, then towards the outlet 22.

[0057] In other words, the piston 50 delimits on the one hand, inside the hydraulic pump 100 a first space 71 located between the inlet 21 of said hydraulic pump 100 and the lower part of the piston 50, and, on the other hand, a second space 72 delimited from the second part 52 of the piston towards the upper part of the hydraulic pump 100. Finally, a third space 73 is delimited under the second part 51 of the piston 50 and extends between the two parts 41, 42 of the sleeve 40 towards the outlet 22. This means that, according to the example illustrated in FIG. 5, the space 71 is separated from the space 72 by the second part 52 of the piston 50. On the other hand, said space 72 is in communication with the third space 73.

[0058] Figure 6 illustrates the example in which the orifices 511, 512 of the first part 51 of the piston 50 are closed and the orifices 521, 522 of the second part 52 of the piston 50 are open. According to the position illustrated in Figure 6, the water which enters the inlet 21 of the hydraulic pump 100 flows through the first space 71 and, thanks to the opening of the orifices 521, 522 of the piston 50, continues its path to the space 72. The surface of the first part 51 of the piston 50 being wider than the surface of the second part 52 of said piston 50, as illustrated in Figure 6, the hydraulic pressure pushes said piston 50 downwards. This is schematically illustrated in Figure 6 using the arrow 62. In other words, according to the example illustrated in Figure 6, the first space 71 is in communication with the second space 72, which is not, however, in communication with the third space 73.

[0059] Referring to Figures 5 and 6, it can be seen that, thanks to the pressurized flow which enters through the inlet 21 of the hydraulic pump 100, a constant flow circulates within said hydraulic pump 100 and is expelled via the outlet 22 of said hydraulic pump 100. During the passage of the pressurized flow, the piston 50 performs a back-and-forth movement inside the sleeve 40, said back-and-forth movement being obtained thanks to the hydraulic pressure and does not require any other source of energy such as, for example, electrical energy. The back-and-forth movement of the piston 50 allows the operation of a mechanism for injecting a liquid, which mechanism is schematically indicated in a simplified manner with the reference number 80. The back-and-forth movement of the piston 50 imposes on the injection mechanism 80 a back-and-forth movement inside the element 23 of the hydraulic pump 100.The injection mechanism 80, as shown in Figure 6, is connected with a mechanism adapted to suck a determined quantity of liquid towards the interior of the hydraulic pump 100, allowing said quantity of liquid to mix with the pressurized flow present inside said hydraulic pump 100.

[0060] Examples of an injection mechanism of this type are not described in more detail within the present description but are known, for example, within the document FR2205361 and the document EP0255791.

[0061] As clearly visible in Figures 5 and 6, the reciprocating movement of the piston 50 within the hydraulic pump 100 may generate some wear as it is used. According to the present invention, the wear that may be observed relates only to parts constituting the sleeve 40 and the piston 50. It does not relate to elements such as the first body member 10 and the second body member 20. In case of necessity, for example wear, the hydraulic pump 100 can be repaired by changing only parts such as the sleeve 40 and / or elements constituting the piston 50.

[0062] Figure 7 shows a perspective and sectional view of a portion of the hydraulic pump 100 according to the invention. Figure 7 shows more particularly the presence of different sealing elements used for the hydraulic pump 100. Figure 7 firstly illustrates the presence of a sealing element 15 located between the respective ends of the first body member 10 and the second body member 20. Figure 7 then illustrates a sealing lip 45, which ensures sealing between the outside of the sleeve 40 and the inside of the second body member 20. Finally, Figure 7 illustrates the sealing lip 47, which ensures sealed contact between the lower end of the sleeve 40 and the inside wall of the second body member 20. The sealing lips 45, 47 are essentially in the form of a “V”. Said sealing lips 45, 47 are made of a flexible material such as rubber.It should be noted that when the sleeve 40 is fixed inside the hydraulic pump 100 according to the invention, no movement is possible between the sleeve and the inner walls of the first and second body members 10, 20 of said hydraulic pump 100. This means that the sealing lips 45, 47 are not exposed to friction resulting from movement of the surfaces relative to each other. In other words, the seal can be guaranteed static and not dynamic.

[0063] Furthermore, it should be noted that the sealing element 15, depending on its assembled position, is crushed between the respective ends of the first body member 10 and the second body member 20. During the assembly of the hydraulic pump 100 according to the invention, the first body member 10 and the second body member 20 are assembled by means of a translational movement. That is to say, no relative rotation between said first body member 10 and the second body member 20 is carried out. This means that the sealing element 15 is, during its assembly, exposed to compressive forces, respectively exerted by the first body member 10 and the second body member 20, and that no additional force, such as, for example, a torsional force, is exerted on said sealing element 15.

[0064] The use of a fixing ring 30 (shown in Figure 1) implies that the respective rotation between the body members 10, 20 can be avoided, thus respecting the integrity of the sealing element 15 during the assembly process. It should be noted that the fixing ring 30 used in the hydraulic pump 100 according to the invention has the advantage of being made using a different material than that used to make, respectively, the first body member 10 and the second body member 20 of said hydraulic pump 100. This means that said material, used for said first body member 10 and said second body member 20 can be selected according to the specific characteristics desired for this type of body members 10, 20. The material of the fixing ring 30 can, therefore, be selected exclusively in order to optimize the sealing function of the hydraulic pump 100 according to the invention.Figure 8 shows a perspective and sectional view of a part of a second embodiment of a hydraulic pump 200 according to the invention. Figure 8 shows more particularly the fixing of the sleeve 240 on the second body member 220.

[0065] As shown in Figure 8, the sleeve 240 is provided with an external thread 245 adapted to cooperate with an internal thread 205 on the second body member 220. Said thread 205, 245 is adapted to fix the sleeve on the second body 220 by means of a rotation of said sleeve 240 relative to the second body member 220.

[0066] The use of a thread 205, 245 to secure the sleeve 240 to the second body member 220 has the advantage that the two elements are secured together using a relatively large connection surface. Said connection surface is resistant to the relatively large forces exerted during use of the pump 200.

[0067] Figure 8 shows the presence of different sealing elements used to ensure the seal between the first body member 210, the second body member 220 and the sleeve 240. Figure 8 first illustrates the presence of a sealing element 215 located between the respective ends of the first body member 210 and the second body member 220. Figure 8 then illustrates a sealing lip 245, which ensures the seal between the exterior of the sleeve 240 and the interior of the second body member 220.

[0068] Figure 9 shows a sectional and perspective view of a third embodiment of a hydraulic pump 300 according to the invention. According to Figure 9, the sealing between respectively the first member of the body 310, the second member of the body 320 and the sleeve 340 is obtained using an assembly of a first sealing lip 315 and a second sealing lip 345, the two sealing lips 315, 345 being positioned on opposite sides of a rim 350 of the sleeve 340.

Claims

Claims 1. Hydraulic pump provided with a pump body comprising a chamber intended for a flow of pressurized liquid, from the inlet of the pump to the outlet of said pump, the pump being equipped with a piston adapted to carry out a reciprocating movement inside said chamber thanks to the pressure exerted on the piston by said flow of liquid and thanks to a mechanism adapted to modify the direction of the pressure on said piston, the chamber having an inner wall adapted to cooperate with the circumference of the piston, said piston being connected to a suction element in the form of a rod, said rod being adapted to continue the reciprocating movement of the piston and also being adapted to suck a determined quantity of fluid inside the pump, thanks to said reciprocating movement, thus allowing said determined quantity of fluid to mix with the flow of liquid through the pump,wherein said piston is formed as a differential piston comprising a first portion having a first diameter and a second portion having a second diameter, different from the first diameter and wherein the inner wall of said chamber comprises a first portion with a first diameter adapted to cooperate with the first portion of the piston and a second portion with a second diameter, different from the first diameter, adapted to cooperate with the second portion of the piston. characterized in that the inner wall of the chamber is made by means of a sleeve, said sleeve being removably fixed inside the pump body., 2. A hydraulic pump according to claim 1, wherein the piston separates the chamber into a first piece and a second piece, and wherein the mechanism, adapted to change the direction of pressure on the piston, comprises hydraulic switching means to allow the supply and discharge of the pieces of the chamber, separated by the piston, said hydraulic switching means being controlled by the movement of the piston.

3. A hydraulic pump according to claim 1 or 2, wherein the sleeve is provided with a radially extending fastening element adapted to cooperate with a fastening element located in the pump body in order to fix said sleeve inside the pump body.

4. A hydraulic pump according to claim 1, 2 or 3, wherein the sleeve securing member is in the form of a lip or pin and the pump body securing member is in the form of a radially extending slot or groove, the sleeve securing member and the pump body securing member being adapted to secure said sleeve by pivoting it about its lateral axis, thereby allowing the lip or pin of the sleeve to penetrate inside the slot or groove of the pump body.

5. Hydraulic pump according to claim 1 or 2, wherein the sleeve is provided with an external thread and the pump body is provided with an internal thread adapted to cooperate with said external thread of the sleeve, to fix the sleeve in the pump body using said thread.

6. Hydraulic pump, according to one of claims 1 to 5, in which the sleeve comprises a first part in the form of a tube having a first diameter and a second part in the form of a tube having a second diameter, different from the first diameter, in which the first and second tubes are connected by a determined number of separate fixing elements.

7. A hydraulic pump according to claim 6, wherein the first and second portions of the sleeve are arranged such that at least a portion of the first portion of said sleeve extends around at least a portion of the second portion of the sleeve.

8. A hydraulic pump according to any preceding claim, wherein said hydraulic pump comprises a first body member and a second body member, said first and second body members being removably positioned on top of each other to allow opening and closing of the pump body, wherein the hydraulic pump further comprises a fastening element for providing a lateral connection between the first body member and the second body member, said fastening element being adapted to be secured to the exterior of the first and second body members of the pump.

9. A hydraulic pump according to claim 8, wherein one of the first and second body members comprises a protruding element for contacting the interior of a securing ring, the interior of said securing ring and the exterior of the second body member of the first and second body members comprising a thread for securing the securing ring to the exterior of the pump body by means of said thread.

10. A hydraulic pump according to claim 8 or 9, wherein the first and second body members are adapted to be moved into a position enabling them to be secured to each other by means of said securing ring by a translational movement.

11. A hydraulic pump according to claim 9 or 10, when dependent on claim 3, wherein one of the first and second members of the body is provided with a lock, said lock being adapted to block rotation of the sleeve inside the pump body, once the first and second members of the pump body are assembled.

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