Expansible chamber devices – Relatively movable working members – Interconnected with common rotatable shaft
Reexamination Certificate
1999-11-16
2002-03-05
Ryznic, John E. (Department: 3745)
Expansible chamber devices
Relatively movable working members
Interconnected with common rotatable shaft
C092S129000
Reexamination Certificate
active
06352017
ABSTRACT:
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 shoes only with one shoe-holding 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 provided with a swash plate having an inclined side, and a plurality of piston each having a shoe. In order to induce high-pressure pumping operation of such a swash plate-based hydraulic pump in an appropriate manner, the shoe of the piston should tightly contact the inclined side of the swash plate. A sue holding mechanism is usually employed for that purpose.
FIG. 7
is a cross sectional view illustrating a swash plate-based hydraulic pump. The hydraulic pump includes a case
58
having a plurality of fluid paths
52
and
54
and a cylinder-shaped groove
56
with a shaft-bearing hole
57
, and a shaft
50
inserted into the shaft-bearing hole
57
of the groove
56
such that it can be rotated. A cylinder block
60
is disposed in the groove
56
of the case
58
such that it can be rotated upon receipt of rotational power of the shaft
50
. The cylinder block
60
has a plurality of cylinders
62
each with a passing hole
76
for allowing passage of a fluid between the cylinder
62
and each of the fluid paths
52
and
54
. A piston
64
is inserted into the cylinder
62
such that it can reciprocate. A swash plate
68
is combined with the case
58
such that it covers an opening portion of the groove
56
. The swash plate
68
has a protruded portion
65
with a top side
66
inclined by a predetermined angle.
A shoe
72
is fixed to the piston
64
via a connecting member
74
and moving along the inclined side
66
of the swash plate
68
with the rotation of the cylinder block
60
. The connecting member
74
is formed with a ball joint so that the shoe
72
can freely move along the inclined side of the swash plate
68
.
A shoe holder
78
is placed around the shoe
72
to stick it to the swash plate
68
. A pair of collars
80
are provided within the cylinder block
60
with a predetermined distance, and an elastic member
82
is tensioned between the collars
80
. In order to compress the shoe holder
78
against the shoe
72
, a barrel member
86
is disposed between the shaft
50
and the shoe holder
78
, and a pin member
84
in turn sticks in between the barrel member
86
and the collar
80
close to the barrel member
86
.
In the aforementioned hydraulic pump, the pin member
84
receives elastic force from the elastic member
82
and transmits it to the barrel member
86
. The barrel member
86
in turn compresses the shoe holder
78
against the inclined side
66
of the swash plate
68
. In this way, the shoe
72
sticks to the inclined side
66
of the swash plate
68
and moves along the inclined side
66
with the rotation of the cylinder block
60
. At this time, the piston
64
reciprocates within the cylinder
62
of the cylinder block
60
.
In this operation, when the shoe
72
moves downward on the inclined side
66
, a fluid is introduced into the cylinder
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
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 collars
80
, the elastic member
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 for holding the shoes.
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 shoe-holding 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 cylinder-shaped groove with a shaft-bearing hole. A shaft is inserted into the shaft-bearing hole of the groove such that the shaft is rotated. A cylinder block is disposed in the groove of the case with a plurality of cylinders such that the cylinder block is rotated upon receipt of a rotational power of the shaft. The cylinder block has a barrel-shaped bottom portion surrounding the shaft. A piston is inserted into each of the cylinders such that the piston reciprocates. A swash plate is combined with the case such that the swash plate covers an opening portion of the groove. The swash plate has an inclined side facing the cylinder block. A shoe has a top side, a bottom side and a stepped middle portion. The top side of the shoe is connected to the piston via a connecting member. The bottom side of the shoe contacts the inclined side of the swash plate. The elastic shoe holder is held between the barrel-shaped bottom portion of the cylinder block and the stepped middle portion of the shoe to compress the shoe against the inclined side of the swash plate.
The elastic shoe holder includes a base with a center hole and a rounded inner edge defining the center hole. The barrel-shaped bottom portion of the cylinder block surrounding the shaft is partially inserted into the center hole of the base. The rounded inner edge of the base contacts the barrel-shaped bottom portion of the cylinder block. A plurality of shoe-holding parts are branched from the base while spacing apart from each other with a predetermined distance. Each shoe-holding part has upper and lower flat portions arranged parallel to each other and a bent portion interconnecting the upper and lower flat portions. The upper flat portion of the shoe-holding part is extended from the base to the bent portion, and the lower flat portion of the shoe-holding part is extended from the bent portion toward the base. The upper and lower flat portions of the shoe-holding part have holes one by one with a common central axis. The shoe-holding part is inserted onto the stepped middle portion of the shoe through the holes of the upper and lower flat portions.
REFERENCES:
patent: 4620475 (1986-11-01), Watts
patent: 5046403 (1991-09-01), Riedhammer
patent: 5249507 (1993-10-01), Kawahara et al.
patent: 5520088 (1996-05-01), Dixen
patent: 5647266 (1997-07-01), Claas
patent: 5730042 (1998-03-01), Engel
patent: 5862704 (1999-01-01), Seljestad
patent: 5950520 (1999-09-01), Kurosawa
patent: 1498938 (1989-08-01), None
Park Jong-Cheol
Ryuh Young-Sun
Baker & Botts LLP
Samjoo Machinery Co., Ltd.
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