FR2692008A1 - Hydraulic pump with inlet valves incorporated into pistons - Google Patents

Abstract

Hydraulic fluid enters the pump body at the aperture (8) and floods the space (7). The swashplate (17) rotates on the slanted face (6) of the driven shaft (6), with pressure lubrication through the passage (30). The triangular section rods (24) have spherical heads (23) locked into the swash plate.As the rods (24) move in the direction (F1), they pull the pistons and open the gap (r) allowing fluid to flow through the pistons into the space (9). Moving in the direction (F2), they seat in the end of the pistons and the hydraulic lock forces fluid through the non return valve (11) to the delivery passage (13).

Description

Improvement to hydraulic piston pumps fitted with suction valves.

 In patent application No. 92.02334 filed on February 28, 1992 by the applicant, an improvement has been described in hydraulic piston pumps according to which each piston is provided with a non-return valve arranged so that the discharge pressure is permanently re-injected inside the sliding stud by which said piston bears on its cam.

 In said patent application, four embodiments of this invention have been described and claimed.

 The present application relates to a fifth embodiment shown in the appended figure which is a view in longitudinal couple of this fifth embodiment.

 As described in patent application No. 92.02334 mentioned above, the hydraulic pump shown is in two parts 1 and 2, part 1 carrying the motor shaft 3 by means of bearings 4 and 5, said shaft 3 carrying the bias plate 6, which struggles in the supply chamber 7 connected to the supply orifice 8. The part 2 comprises a plurality of cylindrical bores 9, parallel to the axis of the shaft 3 and arranged all around each bore 9 having at its bottom a pipe 10 which, through a discharge non-return valve 11 communicates with a pipe 12 which opens into the outlet orifice 13. In each bore 9 is placed a piston 14 which is in bearing against the oblique face 6a of the bias plate 6 by means of a sliding pad called pad 17. Each piston 14 is linked in traction with its pad 17, which is kept in sliding contact against the face 6a of the bias plate 6 by a retaining plate 19, fixed to plate 6 by a bolt 21 comprising a shim 18 of thickness in order to avoid any blocking of the studs by the retaining plate 19.

 Each piston 14 has a spherical head 37, which rests in a housing 22 formed in the stud 17.

 Analogously to what was described in application No. 92.02334, the spherical head 37 has a circular flat formed at a large circle perpendicular to the axis of the piston, so that it is possible to penetrate the spherical head 37 in its housing 22 when the axes of the head and of the housing coincide and it is no longer possible to remove it when these axes no longer coincide: thus, the head 37 of the piston 14 is integral in pulling the stud 17.

 The piston 14 is a hollow piston provided with a spherical head 37 which is traversed right through by a pipe 43. This pipe 43 opens on one side into the bore 4a of the hollow piston 14 and on the other hand into the hollow volume located inside the stud 17 and constituted by the spherical housing 22 and the bore 29.

 At the end of the internal bore 14a which is situated on the opposite side from its end 15 is disposed a cylindrical ring 45 whose internal wall 14a is conical. This ring 45 moves between a position in which it bears against the bottom of the bore 14a, where the pipe 43 opens out and a second position in which it is retained by a circlip 46.

 The hollow piston 14 comprises, at its end opposite its end 15 of a plurality of holes 48, which open into the part 47 of the bore 14a of said piston 14 in which the ring 45 can move.

 When the ring 45 is in abutment against the circlip 46, it allows communication between the supply chamber 7 and the bore 14a; when this ring bears against the bottom 14b of said bore 14a, it closes the passages 48.

 It can therefore be seen that in the suction phase (movement along F1) the hydraulic fluid located in the chamber 7 penetrates inside the hollow piston 14 and that in the delivery phase (movement according to F2) the hydraulic liquid cannot no longer return to the chamber 7 is discharged by the piercing 10 through the discharge valve 11, the pipe 12 and the outlet orifice 13.

Claims (5)

Claims  1. Hydraulic pump with pistons reciprocating back and forth by pressing, via a stud, against a cam carried by a motor shaft, characterized in that a device making a non-return valve feed is incorporated into each piston (14); while the discharge pressure is constantly re-injected inside the stud (17) by which said piston (14) is supported on said cam (6).  2. Hydraulic pump according to claim 1, wherein the supply device forming a non-return valve is arranged inside the piston (14) which is hollow.  3. Hydraulic pump according to claim 2, in which the stud (14) comprises a bore (14a) and a spherical head (37) which rest in a spherical housing (22) formed in a sliding stud (17) to which it is secured in traction, said spherical head being traversed by a pipe (43) which brings the discharge pressure inside the sliding stud (17).  4. Pump according to claim 3, wherein the piston is provided, at the bottom of its bore (14a) with holes (48) which allow said bore (4a) to communicate with the supply chamber (7) in which is debate the swash plate (6).  5. Pump according to claim 4, wherein said communication orifices (48) are open or closed by a valve constituted by a ring (45) which moves between a position where it abuts against the bottom (14b) of the 'bore (14a) and another it rests against a circlip (46).