WO2000043672A1

WO2000043672A1 - Hydraulic pump

Info

Publication number: WO2000043672A1
Application number: PCT/KR1999/000286
Authority: WO
Inventors: Young-Sun Ryuh; Jong-Cheol Park
Original assignee: Samjoo Machinery Co Ltd
Current assignee: Samjoo Machinery Co Ltd
Priority date: 1999-01-21
Filing date: 1999-06-10
Publication date: 2000-07-27
Anticipated expiration: 2001-07-21
Also published as: JP2002535552A; AU4170999A; JP3375332B2; CN1286742A; JP2003155973A; KR200169204Y1; CN1136388C; KR19990021863U

Abstract

A hydraulic pump includes a case (12) having a plurality of fluid paths (8, 10) and a cylindrical shaped groove (6) with a shaft-bearing hole. A shaft (2) is inserted into the shaft-bearing hole (4)of the groove (6) such that it can be rotated. A plurality of cylinder members (14) are disposed in the groove (6) of the case (12) each with a cylinder hole (16) such that they can be rotated upon receipt of a rotational power of the shaft (2). A piston member (32) is positioned in each of the cylinder members (14) and reciprocates within the cylinder hole (16) with the rotation of the cylinder member (14). A wobble plate member (26) having an inclined side is combined with the case (12) such that it covers an opening portion of the groove (6). Each of the cylinder members (14) has a bottom side in a direction of the opening portion of the groove (6). A shoe (24) having a waist is fixed to the piston member (32) via a connecting member (30) and contacts the inclined side of the wobble plate member (26). The cylinder member (14) is provided with a barrel (20) shaped portion at its bottom side and the shoe with a stepped portion at its waist. An elastic shoe holder (36) is inserted onto the stepped portion of the shoe (24). The elastic shoe holder (36) has a rounded center hole (28), and a plurality of elastic bodies (40) combined with each other in a body and inwardly bent around the center hole (38). The insertion of the elastic shoe holder (36) is performed through the rounded center hole (38). When the elastic shoe holder (36) is inserted onto the stepped portion of the shoe (24), the elastic bodies (40) contact the barrel shaped portion. The bent portions (44) of the elastic bodies (40) are formed each with a curved shape.

Description

HYDRAULIC PUMP

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a hydraulic pump and, more particularly,

to a hydraulic pump which can perform the function of holding a shoe only with

one member in an appropriate manner.

(b) Description of the Related Art

Generally, when a hydraulic pump is employed for the high-pressure

pumping purpose, it is usually provided with a wobble plate member having an

inclined side and a piston member having a shoe. In this structure, since the

shoe of the piston member should tightly contact the inclined side of the wobble

plate member to properly induce high-pressure pumping operation of the overall

device, a sue holding mechanism is usually employed for that purpose.

Fig. 4 is a sectional view illustrating a wobble plate based hydraulic

pump. The hydraulic pump includes a case 58 having a plurality of fluid paths

52 and 54 and a cylindrical shaped groove 56 with a shaft-bearing hole 57, and

a shaft 50 inserted into the shaft-bearing hole 57 of the groove 56 to be rotated.

A plurality of cylinder members 60 are disposed in the groove 56 of the case 58

each with a cylinder hole 62 such that they can be rotated upon receipt of

rotational power of the shaft 50. Further, each of the cylinder member 60 has a

passing hole 76 for allowing passage of a fluid between the cylinder hole 62 and

each of the fluid paths 52 and 54. A piston member 64 is positioned in each of the cylinder members 60 and reciprocates within the cylinder hole 62. A

wobble plate member 68 is combined with the case 58 such that it covers an

opening portion of the groove 56. The wobble plate member 68 has a

protruded portion 65 forming a top side 66 inclined by a predetermined angle.

The piston member 64 includes a piston 70 reciprocating within the

cylinder hole 62, and a shoe 72 fixed to the piston 70 via a connecting member

74 and moving along the inclined side 66 of the wobble plate 68 with the

rotation of the cylinder member 60. The connecting member 74 is formed with

a ball joint such that the shoe 72 can freely move along the inclined side of the

wobble plate 68.

A shoe holder 78 is placed around the shoe 72 to stick it to the wobble

plate 68. A pair of collars 80 is positioned within the cylinder member 60 with a

predetermined distance and an elastic member 82 is tensioned between the

collars 80. A barrel member 86 is inserted between the shaft 50 and the shoe

holder 78 to support the shoe holder 78 against the shoe 72. A pin member 84

sticks in between the barrel member 86 and the neighboring collar 80.

In the aforementioned hydraulic pump, upon receipt of elastic force from

the elastic member 82, the pin member 84 transmits it to the barrel member 86

which in turn compresses the shoe holder 78 onto the inclined side 66 of the

wobble plate member 68.

As a result, the shoe 72 of the piston member 64 sticks to the inclined

side 66 of the wobble plate member 68 and moves along the inclined side 66

with the rotation of the cylinder member 60. At this time, the piston 70 of the ^> piston member 64 reciprocates within the cylinder hole 62 of the cylinder

member 60. In this operation, when the shoe 72 of the piston member 64

moves downward on the inclined side 66, a fluid is introduced into the cylinder

hole 62 through the fluid-input path 52 via the passing hole 76. In contrast,

when the shoe 72 moves upward on the inclined side 66, the fluid introduced

into the cylinder hole 62 is discharged through the fluid-output path 54 via the

passing hole 76. In this way, the desired hydraulic pressure can be obtained in

the hydraulic pump.

However, in the aforementioned shoe holding mechanism, the plurality

of shoe holding components including the collar members 80, the elastic

members 82, the pin member 84, the barrel member 86 and the shoe holder 78

may cause complicated structure, retarded manufacturing time and increased

manufacturing cost, resulting in bad production efficiency. For it can be

conceived that some of the shoe holding components are not indispensable in

such a shoe holding mechanism.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a hydraulic pump which

can effectively perform the function of holding a shoe only with one member.

This and other objects may be achieved by a hydraulic pump with an

elastic shoe holder. The hydraulic pump includes a case having a plurality of

fluid paths and a cylindrical shaped groove with a shaft-bearing hole. A shaft is

inserted into the shaft-bearing hole of the groove such that it can be rotated. A

plurality of cylinder members are disposed in the groove of the case each with a cylinder hole such that they can be rotated upon receipt of a rotational power of

the shaft. A piston member is positioned in each of the cylinder members

and reciprocates within the cylinder hole with the rotation of the cylinder

member. A wobble plate member having an inclined side is combined with the

case such that it covers an opening portion of the groove. Each of the cylinder

members has a bottom side in a direction of the opening portion of the groove.

A shoe having a waist is fixed to the piston member via a connecting member

and contacts the inclined side of the wobble plate member.

The cylinder member is provided with a barrel shaped portion at its

bottom side and the shoe with a stepped portion at its waist. An elastic shoe

holder is inserted onto the stepped portion of the shoe. The elastic shoe

holder has a rounded center hole, and a plurality of elastic bodies combined

with each other in a body and inwardly bent around the center hole. The

insertion of the elastic shoe holder is performed through the rounded center

hole. When the elastic shoe holder is inserted onto the stepped portion of the

shoe, the elastic bodies contact the barrel shaped portion. The bent portions

of the elastic bodies are formed each with a curved shape for effecting a good

elasticity.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention, and many of the

attendant advantages thereof, will be readily apparent as the same becomes

better understood by reference to the following detailed description when

considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or the similar components, wherein:

Fig. 1 is a sectional view of a hydraulic pump with an elastic shoe

holder according to a first preferred embodiment of the present invention;

Fig. 2A is a perspective view of the elastic shoe holder shown in Fig. 1 ;

Fig. 2B is a front view of the elastic shoe holder shown in Fig. 1 ;

Fig. 2C is a plan view of the elastic shoe holder shown in Fig. 1 ;

Fig. 3A is a perspective view of an elastic shoe holder for a hydraulic

pump according to a second preferred embodiment of the present invention;

Fig. 3B is a plan view of the elastic shoe holder shown in Fig. 3A;

Fig. 3C is a front view of the elastic shoe holder shown in Fig. 3A; and

Fig. 4 is a sectional view of a hydraulic pump according to a prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of this invention will be explained with reference

to the accompanying drawings.

Fig. 1 is a sectional view illustrating a hydraulic pump with an elastic

shoe holder according to a first preferred embodiment of the present invention,

and Figs. 2A to 2C are views illustrating the elastic shoe holder.

As shown in Fig. 1 , the hydraulic pump includes a case 12 having a

plurality of fluid paths 8 and 10 and a cylindrical shaped groove 6 with a shaft-

bearing hole 4, and a shaft 2 inserted into the shaft-bearing hole 4 of the groove

6 such that it can be rotated. A plurality of cylinder members 14 are disposed

in the groove 6 of the case 12 each with a cylinder hole 16 such that they can

be rotated upon receipt of rotational power of the shaft 2. Further, each of the cylinder members 14 has a passing hole 18 for allowing passage of a fluid

between the cylinder hole 16 and each of the fluid paths 8 and 10. A barrel

shaped portion is protruded from a bottom side of the cylinder member 14 in a

body. The barrel shaped portion has a rounded side facing the shoe 24

5 hereinafter referred to simply as a barrel 20. The barrel 20 is to perform the

same function as that of the barrel member employed in the conventional

hydraulic pump. A piston member 32 is positioned in each of the cylinder

members 14 and reciprocates within the cylinder hole 16 of the cylinder member

14.

10 A wobble plate member 26 is combined with the case 12 such that it

covers an opening portion of the groove 6. The wobble plate member 26 has a

top portion forming an inclined side 28.

The piston member 14 includes a piston 32 reciprocating within the

cylinder hole 16, and a shoe 24 fixed to the piston 22 via a connecting member

15 30 such that it can move along the inclined side 28 of the wobble plate member

26 with the rotation of the cylinder member 14. The connecting member 30 is

formed with a ball joint to ensure smooth moving of the shoe 24 along the

inclined side 28.

The shoe 24 has a stepped portion at its waist, hereinafter referred to

0 simply as a stopper 34. An elastic shoe holder 36 having a predetermined

elasticity is inserted onto the stopper 34 of the shoe 24 and sticks thereto.

As shown in Figs. 2A to 2C, the elastic shoe holder 36 has a rounded

center hole 38 and a plurality of elastic bodies 40 combined with each other in a body and inwardly bent around the center hole 38. That is, each of the elastic

bodies 40 is double-sided in parallel toward the center hole 38 at its bent

portion 44. Further, each of the elastic bodies 40 has a hole 42 at its double-

sided portion. A free end formation side of the elastic body 40 adjacent to the

hole 42 contacts the barrel 20 to be in a stuck state while an opposite side of

the elastic body 40 sticks to the stopper 34 of the shoe 24.

Thanks to the elastic force of the elastic shoe holder 36 operated

between the barrel 20 and the shoe 24, it becomes possble that the shoe 24

tightly contacts the inclined side 28 of the wobble plate member 26 and moves

along the inclined side 28 with the rotation of the cylinder member 14 in a stable

manner.

The bent portion 44 of the elastic body 40 is formed with a curved shape

to produce an effective elastic force.

In operation, when the shaft 2 transmits a rotational force to the cylinder

member 14, the shoe 24 fixed to the piston 22 via the connecting member 30

moves along the inclined side 28 of the wobble plate member 26 so that the

piston 22 reciprocates within the cylinder hole 16 of the rotating cylinder

member 14. In case the shoe 24 moves downward on the inclined side 28, a

fluid is introduced into the cylinder hole 16 through the fluid-input path 8 via the

passing hole 18. In contrast, when the shoe 24 moves upward on the inclined

side 28, the fluid introduced into the cylinder hole 16 is discharged through the

fluid-output path 10 via the passing hole 18.

Figs. 3A to 3C are views illustrating an elastic shoe holder for a hydraulic pump according to a second preferred embodiment of the present

invention. In this preferred embodiment, the overall components of the

hydraulic pump except the elastic shoe holder are the same as those in the

first preferred embodiment.

As shown in Figs. 3A and 3B, the elastic shoe holder 49 has a rounded

center hole 45, a spherical portion 46 centered around the center hole 45, and a

plurality of plates 48 extended away from the spherical portion 46. The

spherical portion 46 has a predetermined curvature such that it contacts the

barrel 20 of the cylinder member 14. In this structure, since the upper and

lower diameters of the spherical portion 46 are naturally differentiated, a desired

elasticity can be obtained with the elastic shoe holder 49.

As described above, the inventive hydraulic pump can perform the

function of holding a shoe only with one member of the elastic shoe holder in an

appropriate manner. This results in reduced manufacturing time, economical

manufacturing cost and good production efficiency.

While the present invention has been described in detail with reference

to the preferred embodiments, those skilled in the art will appreciate that various

modifications and substitutions can be made thereto without departing from the

spirit and scope of the present invention as set forth in the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A hydraulic pump including a case having a plurality of fluid

paths and a cylindrical shaped groove with a shaft-bearing hole, a shaft

inserted into the shaft-bearing hole of the groove to be rotated, a plurality of

cylinder members disposed in the groove of the case each with a cylinder hole

such that the cylinder members can be rotated upon receipt of a rotational

power of the shaft, a piston member positioned in each of the cylinder members

to reciprocate within the cylinder hole of the cylinder member, a wobble plate

member having an inclined side, the wobble plate member being combined with

the case such that the wobble plate member covers an opening portion of the

groove, each of the cylinder member having a bottom side positioned in a

direction of the opening portion of the groove, and a shoe fixed to the piston

member via a connecting member and contacting the inclined side of the

wobble plate member, the shoe having a waist, the hydraulic pump comprising:

a barrel shaped portion protruded from the bottom side of the cylinder

member in a body;

a stepped portion formed at the waist of the shoe; and

an elastic shoe holder inserted onto the stepped portion of the shoe, the

elastic shoe holder having a side portion contacting the barrel shaped portion.

2. The hydraulic pump of claim 1 wherein the elastic shoe holder

comprises a rounded center hole, and a plurality of elastic bodies combined with

each other in a body and inwardly bent around the center hole, and wherein the

elastic shoe holder is inserted onto the stepped portion of the shoe through the rounded center hole and the side portion of the elastic shoe holder contacting

the barrel shaped portion corresponds to the elastic bodies.

3. The hydraulic pump of claim 2 wherein each of the bent

portions of the elastic bodies has a curved shape.

4. The hydraulic pump of claim 1 wherein the elastic shoe holder

comprises a rounded center hole, a spherical portion centered around the

rounded center hole, and a plurality of plates extended away from the spherical

portion, and wherein the elastic shoe holder is inserted onto the stepped portion

of the shoe through the rounded center hole and the side portion of the elastic

shoe holder contacting the barrel shaped portion corresponds to the spherical

portion.

5. The hydraulic pump of claim 4 wherein the spherical portion has

a predetermined curvature and, upper and lower diameters different from each

other.