U.S. patent number 3,924,330 [Application Number 05/484,552] was granted by the patent office on 1975-12-09 for hydraulically operated working machine.
This patent grant is currently assigned to Nitto Kohki Co., Ltd.. Invention is credited to Kyoichi Hirokawa, Minoru Kaneko, Yasuo Kazama, Masunari Kowada, Shigeru Mitsuhashi, Noboru Saito, Michihiro Shoji.
United States Patent |
3,924,330 |
Mitsuhashi , et al. |
December 9, 1975 |
Hydraulically operated working machine
Abstract
Hydraulically operated working machine such as a puncher
provided with a piston retracting mechanism including a high power
piston retracting element or elements such as an urethane body or
bodies or a washer spring or springs and disposed outside the
machine main parts confining a piston chamber, all the auxiliary
elements such as a piston shifting mechanism being incorporated
within the machine main parts for convenience in use and
transportation of the machine.
Inventors: |
Mitsuhashi; Shigeru (Tokyo,
JA), Hirokawa; Kyoichi (Tokyo, JA), Saito;
Noboru (Tokyo, JA), Kaneko; Minoru (Tokyo,
JA), Shoji; Michihiro (Tokyo, JA), Kowada;
Masunari (Tokyo, JA), Kazama; Yasuo (Tokyo,
JA) |
Assignee: |
Nitto Kohki Co., Ltd. (Tokyo,
JA)
|
Family
ID: |
14032849 |
Appl.
No.: |
05/484,552 |
Filed: |
July 1, 1974 |
Foreign Application Priority Data
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Aug 4, 1973 [JA] |
|
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48-91668 |
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Current U.S.
Class: |
30/362;
30/358 |
Current CPC
Class: |
B26F
1/34 (20130101); B21D 28/002 (20130101); B65H
3/0883 (20130101) |
Current International
Class: |
B65H
3/08 (20060101); B21D 28/00 (20060101); B26F
001/02 (); B26F 001/34 () |
Field of
Search: |
;30/358,362,361,180,228 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Smith; Al Lawrence
Assistant Examiner: Zatarga; J. T.
Attorney, Agent or Firm: Ostrolenk, Faber, Gerb &
Soffen
Claims
What is claimed is:
1. A hydraulically operated working machine usable for punching and
cutting operations and the like comprising, in combination:
a main frame having an interior piston chamber reducing to a narrow
opening suited for guiding piston reciprocation;
a cap mounted upon the side of said main frame opposite said
opening and arranged so as to close one end of said piston
chamber;
a main operating handle joined to said main frame and aligned
transverse to the longitudinal axis of the piston chamber, said
handle being provided with an internal conduit for connecting said
piston chamber to a supply source of pressured fluid for moving the
piston assembly in a first direction;
a piston mechanism comprising a piston member mounted for
reciprocal movement within said piston chamber and provided on one
side with a first extension which extends in said first direction
through said main frame and into said opening;
a work head mounted at the free end of said first extension for
reciprocating engagement with the workpiece adjacent said opening,
said piston member being further provided with a second extension
which extends in a second direction opposite said first direction
through said piston chamber and said cap;
a holding member mounted upon the free end of said second
extension; and
resilient piston retracting means arranged on the exterior side of
said cap and positioned between said holding member and said cap
for urging said piston mechanism in said second direction.
2. Hydraulically operated working machine as claimed in claim 1
further comprising a piston shifting mechanism incorporated within
said main frame and main handle and having a detection terminal
partially extending into said piston chamber in an arrangement to
be depressed by said piston mechanism when moving in said first
direction.
3. Hydraulically operated working machine as claimed in claim 2
further comprising a cavity formed in said main frame; said piston
shifting mechanism further including a shifting switch positioned
within said cavity and having a movable contact operated by said
detection terminal; means for resiliently biasing said detection
terminal in said second direction; a socket positioned at the free
end of said handle; means extending through said main frame and
said handle for electrically connecting said shifting switch to
said socket; and a pair of control switches arranged on said handle
near said frame and being connected in electrical series with said
shifting switch and said socket.
4. Hydraulically operated working machine as claimed in claim 1 in
which said piston retracting mechanism comprises at least one high
power piston retracting elements placed on said cap and surrounding
said second extension, said holding member comprising a
flange-shaped member fixed to the free end of said second extension
in such an arrangement as to compress and retracting element
between said holding member and said cap upon movement of said
piston mechanism in said first direction.
5. Hydraulically operated working machine as claimed in claim 4 in
which said high power retracting element comprises a cylindrical
shaped urethane body.
6. Hydraulically operated working machine as claimed in claim 4 in
which said high power piston retracting element comprises washer
springs superimposed upon each other.
7. Hydraulically operated working machine as claimed in claim 6 in
which said piston retracting mechanism further comprises a guide
cylinder placed on said cap and surrounding said second extension
and having at least two upwardly extending projections which are in
meshing engagement with peripheral cut-outs formed in said
flange-shaped member, said washer springs being inserted over said
guide cylinder and its upper projections.
Description
The present invention relates to a hydraulically operated working
machine, and more particularly relates to an improvement in the
structure of an hydraulically operated working machine of a
single-acting piston type such as a puncher or the like.
In the case of conventional hydraulically operated working machines
of a single-acting piston type such as punchers, the forward stroke
of the piston mechanism is in general actuated by oil pressure
while the return stroke of same is actuated by repulsion of a
spring element or elements disposed within the machine main parts.
In other words, the piston retracting mechanism is in general
incorporated within the machine main parts which confine a piston
chamber.
Due to this incorporation of the piston retracting mechanism within
the machine main parts, demand for a strong piston retracting force
naturally requires enlarged repulsion of the piston retracting
mechanism. This inevitably results in a correspondingly increased
oil pressure exerted on the piston mechanism and enlarged size of
the spring element or elements. Therefore, in order to obtain a
strong piston retracting force, it is necessary to provide the
working machine with a large, stalwart and stout structure.
However, this need for the stalwart machine structure does not meet
the recently growing general demand for compact working machines
for convenience in use and transportation of same. Especially in
the case of such working machines as punchers, handy and compact
machine structures are preferred by their users.
Employment of a spring element or elements of rather small size,
i.e. small repulsion, as the piston retracting element in a
puncher, for example, forces the users to provide relatively large
clearances between the puncher and the hole to be punched. It is
experienced generally that such large clearance between the punch
and the hole causes production of sharp irritating noises at the
time of the punching operation and low quality surface condition of
the hole wall after the punching. In addition, spring elements of
the relatively small size will fatigue very easily and can hardly
withstand long use.
Therefore, in order to enhance the utility of the hydraulically
operated working machine of a single-acting piston type it is
strongly required to provide the machine with a high power piston
retracting mechanism on one hand and a relatively handy, compact
and light structure on the other hand.
Even aside from the viewpoint of the machine size, incorporation of
the piston retracting mechanism within the machine main parts makes
maintenance and component replacement operations very troublesome
and difficult. As already mentioned, the piston retracting
mechanism endures repeated compression under severe conditions and
is liable to fatigue which leads to destruction and hence loss of
its expected function. So, it is preferable that the piston
retracting mechanism should be so combined with the machine
structure that the same can be very easily disassembled for
replacement from the machine structure.
It is further desired by the users that auxiliary elements of the
machine, e.g. the mechanism for admission and discharge of
pressured fluid into and out of the piston chamber and electric
arrangement for shifting of the piston strokes, should not be
exposed on the outer side of the machine so that the machine can be
easily used and transported.
The primary object of the present invention is to provide an
improved hydraulically operated working machine such as a puncher
provided with highly enhanced piston retracting force together with
a relatively handy, compact and light structure.
Another object of the present invention is to provide an improved
hydraulically operated working machine such as a puncher whose
piston retracting mechanism can be replaced very easily by reduced
trouble in the maintenance work.
Another object of the present invention is to provide an improved
hydraulically operated working machine such as a puncher having an
outer design conveniently suited for handling and transportation of
same.
A further object of the present invention is to provide an improved
hydraulically operated working machine such as a puncher, which,
when used as a puncher, is capable of forming holes through work
pieces with minimized clearance, enhancing the accuracy in hole
formation, advantageously limiting the production of irritating,
sharp noises at the time of the punching operation and providing
the punched holes with smooth and fine wall surfaces.
In order to attain the above-described objects of the present
invention, the hydraulically operated working machine of the
present invention comprises a piston retracting mechanism attached
to the machine at a position outside the machine main parts
confining a piston chamber, in engagement with an extension of the
piston mechanism, the piston retracting mechanism including as its
major part, one or more high power retracting elements such as
urethane bodies or superimposed washer springs and auxiliary
mechanisms, e.g. a mechanism for admission and discharge of the
pressured operating fluid into and out of the piston chamber, are
all incorporated within the machine main parts. The machine is
preferably provided with a further mechanism for automatically
shifting the piston strokes.
Further features and advantages of the present invention will be
made clearer from the following description, reference being made
to the embodiments shown in the accompanying drawings in which;
FIG. 1 is a top plan view of the hydraulically operated working
machine according to one aspect of the present invention,
FIG. 2 is a side plan view of the hydraulically operated working
machine shown in FIG. 1,
FIG. 3 is a side plan view, partly in section, of the first
embodiment of the hydraulically operated working machine shown in
FIG. 2,
FIG. 4 is a sectional plan view taken along the line IV -- IV in
FIG. 3,
FIG. 5 is a sectional plan view taken along the line V -- V in FIG.
3,
FIG. 6 is a fragmentary sectional plan view of the piston shifting
mechanism and its related parts used in the hydraulically operated
working machine shown in FIG. 3,
FIG. 7 is a fragmentary sectional plan view of the main handle
possessed by the hydraulically operated working machine shown in
FIG. 3,
FIG. 8 is a circuit diagram usable for the hydraulically operated
working machine according to one aspect of the present
invention,
FIG. 9 is a fragmentary sectional plan view of a modification of
the hydraulically operated working machine shown in FIG. 3,
FIG. 10 is a side plan view, partly in section, of the second
embodiment of the hydraulically operated working machine shown in
FIG. 2,
FIG. 11 is a perspective plan view of a guide cylinder usable for
the hydraulically operated working machine shown in FIG. 10,
FIG. 12 is a sectional plan view taken along the line XII -- XII in
FIG. 13, and
FIG. 13 is a side plan view, partly in section, of the
hydraulically operated working machine shown in FIG. 10 with the
piston retracting mechanism in a compressed disposition.
The first embodiment of the present invention is shown in FIGS. 1
through 3, in which the hydraulically operated working machine of
the present invention includes a C-shaped main frame 1, a cap 2
disposed to the upperside of the main frame 1 and accommodating an
interior mounted piston mechanism which will be later explained in
detail, a piston retracting mechanism 3 mounted to the upperside of
the cap 2, a main handle 4 disposed sideways to the main frame 1,
an auxiliary handle 6 disposed also sideways to the main frame 1, a
piston mechanism 7 accommodated within the main frame 1, the cap 2
providing for an axial reciprocation, and a work part 8 disposed to
the lower end of the piston mechanism 7.
As is clearly seen from FIG. 2, the main frame 1 has a C-shaped
side view profile and is composed of an upper jaw 11, a lower jaw
12 and a connecting arm 13 for integrally connecting the two jaws
11 and 12. The upper half of the upper jaw 11 is internally
threaded and the lower half of the same is provided with a through
hole 14 for accommodating the work part 8. The lower jaw 12 is
provided with a seat for a die 16 and a vertical through hole 17 in
communication to with the center hole of the die 16. The through
hole 14 of the upper jaw 11, the die 16 and the through hole 17 of
the lower jaw 12 are in a coaxial alignment. In the case of the
illustrated embodiment, the die 16 held by the lower jaw 12 is
suited for the punching operation and, therefore, the through hole
17 of the lower jaw 12 is used for discharging punched pieces of
work pieces to be operated upon.
The cap 2 is composed of an upper flange part 21 and a piston
cylinder 22 formed downwards integrally of the upper flange part
21, the upper flange part 21 defining the upper end of a piston
chamber 23. The piston cylinder 22 of the cap 2 is externally
threaded for a threaded engagement with the internally threaded
upper part of the main frame upper jaw 11. In communication with
the piston chamber 23, a pressure fluid passage 24 is formed in the
upper flange part 21 of cap 2. A center through-hole is formed
vertically in the upper flange part 21 of cap 2 in order to allow
for reciprocal sliding of the later described piston rod of the
piston mechanism 7.
The piston retracting mechanism 3 forms the main part of the
present invention and is mounted to the upperside of the cap upper
flange part 21. In other words, the piston retracting mechanism 3
is located quite outside the main body of the working machine in
the present invention. This piston retracting mechanism 3 is
comprised of a hollow cover 31 fixed to the cap upper flange part
21 and a retracting element 32 made of urethane rubber and encased
within the cover 31. In the case of the illustrated embodiment,
this retracting element 32 is divided into two pieces by a later
described separator plate. The retracting element 32 is placed on
the upper face of the cap upper flange part 21 in an idle
engagement with the later described piston mechanism 7.
The piston mechanism 7 includes a piston plunger 73 slidably
accommodated within the piston chamber 23, an upper piston rod 72
and a lower piston rod 74, the three parts being formed integrally
of each other. The upper piston rod 72 extends upwardly into the
cover 31 through the center through hole of the cap upper flange
part 21 and the urethane rubber retracting element 32. A flange 71
is fixed to the top end of the upper piston rod 72 via a set bolt
76 with its underface in direct contact with the upper face of the
retracting element 32. In the case of the illustrated embodiment, a
horizontal separator plate 77 is fixed substantially at a midway
point of the upper piston rod 72 in order to divide the retracting
element 32 into two pieces. The lower piston rod 74 is suited for
holding the later described work part 8.
In the case of the illustrated embodiment, the work part 8 is
designed so as to be suitable for punching operations and is
provided with a punch 82 which coacts with the die 16 held by the
main frame lower jaw 12. An externally threaded fixer ring 83 is in
threaded engagement with the internally threaded bottom hollow
portion of the lower piston rod 74 in order to secure the punch 82
to the bottom end of the lower piston rod 74. In order to slidably
guide the reciprocation of the lower piston rod 74, a guide sleeve
81 is fixedly fitted into the through hole 14 of the main frame
upper jaw 11. At a position slightly below the guide sleeve 81, a
stripper 84 is threaded at its upper portion to threadedly engage
the internally threaded lower portion of the through hole 14 while
spacedly embracing the exposed portion of the punch 82. The inner
periphery of this stripper 84 is so dimensioned that the lower
piston rod 74 is axially slidable through the stripper 84. The
piston plunger 73, the lower piston rod 74, the punch 82 and the
die 16 are arranged in coaxial alignment.
The main handle 4 has a longitudinal through-hole 41 which merges
into an enlarged chamber 41a near the junction between the main
handle 4 and the main frame 1 as is clearly shown in FIG. 4. A pipe
42 is inserted into the through-hole 41 while occupying the upper
half of the latter. At the inner end portion the pipe 42 is
externally threaded for threadedly engaging the upper flange part
21 of the cap 2, the center hole 44 of the pipe 42 communicates
with the pressure fluid passage 24 formed in the upper flange part
21 of cap 2 and two sets of set screws 43 are provided in order to
securely fix the main handle 4 to the shoulder of the upper jaw 11
of the main frame 1. The outer end portion of pipe 42 is so shaped
as to fit a connection or coupling of a suitable pressure fluid
source not shown in the drawing. As shown in more detail in FIG. 7,
the outer end of the through hole 41 of the main handle 4 diverges
outwardly and a fixing nut 46 is screwed over the outer end portion
of the pipe 42 so that its converging side abuts snugly against the
outwardly diverging end of the through-hole 41.
At the time of assembly of main handle 4 and its related parts,
pipe 42 is inserted into the through-hole 41 of the main handle
with its inner-end portion being screwed into the upper flange part
21 of cap 2 and the fixing nut 46 is fastened. Next, set screws 43
are fastened so that the main handle 4 is firmly fixed to main
frame 1. In the way above described, the three members, i.e. main
handle 4, main frame 1 and cap 2 are firmly combined to each other
via pipe 42.
A cavity 18 is formed within upper jaw 11 of main frame 1 as shown
in FIGS. 5 and 6 and a piston shifting mechanism 9 is incorporated
within the cavity 18, which is closed from the outside by a cover
93. The piston shifting mechanism 9 includes a shifting switch 91
encased within the cavity 18 being carried by the cover 93 (see
FIG. 5) and a detection terminal 92 which is partly exposed into
the piston chamber 23, while confronting the undersurface of the
piston plunger 73, being urged by a compression spring 94
accompanying the same. The bottom end of the detection terminal 92
confronts contact 95 of the shifting switch 91. When the piston
plunger 73 approaches the lower end of the piston chamber 23 during
its downward stroke, the detection terminal 92 is depressed and its
bottom end accordingly pushes down the contact 95 of the shifting
switch 91. Upon cancellation of the depression on the detection
terminal 92 by the upward movement of the piston plunger 73, the
detection terminal 92 is again partly exposed into the piston
chamber 23 due to the repulsion by the compression spring 94 and
the contact 95 of the shifting switch 91 resumes its free
disposition.
A hole 13 is formed through the upper jaw 11 of main frame 1 and
main handle 4 in order to connect cavity 18 for the piston shifting
mechanism 9 to the enlarged chamber 41a in the main handle 4.
Electric connections 96 run from the shifting switch 91 to a socket
97 disposed at the free end of the main handle 4 through the
above-described hole 19 in the main frame 1 and the lower half of
the through hole 41 in the main handle 4. The socket 97 is suited
for connection to a suitable electric source (not shown). In
combination with the electric connections 96 between the shifting
switch 91 and the socket 97, a pair of control switches 47 are
arranged near the inner end of the main handle 4 as clearly shown
in FIGS. 3 and 4. As shown in FIG. 8, the control switches 47, the
shifting switch 91 and the electric connections 96 form a series
electric circuit and one of the control switches 47, which is for
switching on the machine, is accompanied with a self-maintaining
relay.
The hydraulically operated working machine, that is the punching
machine in the case of the above-described first embodiment,
according to one aspect of the present invention having the
above-described structure operates in the following manner.
In order to start the running of the pressured fluid source, one of
the control switches 47 is depressed by the operator's hand
gripping the main handle 4. Upon starting of the running of the
pressured fluid source, the pressured fluid, say pressured oil, is
admitted into the piston chamber 23 through the center hole 44 of
the pipe 42 and the pressured fluid passage 24 of the main frame 1.
This admission of the pressured fluid causes a corresponding
downward stroke of the piston plunger 73. Because the upper flange
71 cooperatively forms one body with the piston plunger 73 via the
upper piston rod 72, the flange 71 moves downwardly following the
downward stroke of the piston plunger 73 and the highly elastic
retracting element 32 is compressed in between the flange 71 and
the upper flange part 21 of the cap 2. The piston plunger 73
undergoes further movement and approaches the lower end of the
piston stroke while overcoming the repulsion by the retracting
element 32. With this downward stroke of the piston mechanism 7 the
punch 82 of the work part advances downwards and, in cooperation
with the die 16 held by the lower jaw 12 of the main frame 1,
punches a hole in a workpiece placed on the die 16.
The dimension of the machine parts are so designed that the
undersurface of the piston plunger 73 depresses the detection
terminal 92 of the piston shifting mechanism 9 at the very moment
that the punching operation is completed. By this depression, the
electric circuit shown in FIG. 8 is opened and this causes shifting
of the operation of the pressured fluid source. In other words, the
pressured fluid in the piston chamber 23 is discharged therefrom
and the repulsion of the compressed retracting element 32 forces
the piston plunger 73 to move upwardly. This upward movement of the
piston plunger 73 automatically cancels the depression on the
detection terminal 92 of the piston shifting mechanism 9 and the
detection terminal 92 resumes its initial disposition being urged
by the compression spring 94. With a prescribed time delay, i.e.
when the piston plunger 73 comes to the end of its upward stroke,
the shifting switch 91, now free of the depression by the detection
terminal 12, is closed and the electric circuit in FIG. 8 is closed
thereby. This closing of the electric circuit induces restarting of
the running of the pressured fluid source, the pressured fluid is
admitted into the piston chamber 23 and the piston mechanism 9
repeats its reciprocal upward and downward strokes in order to
carry out the successive punching operations.
In the case of the above-described embodiment, the urethane
retracting element 32 is divided into two pieces by the separator
plate 77 disposed to the middle portion of the upper piston rod 72.
However, the retracting element 32 can also be in the form of a
single piece such as shown in FIG. 9.
The second embodiment of the present invention is shown in FIGS. 10
through 13, in which parts substantially similar to those of the
first embodiment in their structures and functions are designated
with common reference numerals. In the case of this embodiment, the
structures of the main frame 1, the cap 2, the main handle 4, the
auxiliary handle 6, the piston mechanism 7, the work part 8 and the
piston shifting mechanism 9 are substantially similar to those of
the first embodiment. That is, this second embodiment is different
from the first embodiment in the structure of the piston retracting
mechanism 3.
Similar to the case in the first embodiment, the piston retracting
mechanism 3 is confined within the hollow cover 31 fixed on the
upper side of the cap 2 and an upper piston rod 72, which is
upwardly integral of the piston plunger 73, and extends into the
hollow of the cover 31. A guide cylinder 130 is placed on the
uppersurface of the cap 2 being concentrically and freely inserted
over the upper piston rod 72. As shown in FIG. 11, this guide
cylinder 130 is provided with a plurality of upper projections 131
extending from its upper edge and the projections 131 define
cut-outs 132 between them. The guide cylinder 130 is further
provided with a bottom flange 133 of a somewhat larger diameter. In
actual use, the guide 130 is preferably provided with six sets of
upper projections 131 in order to adequately maintain the coaxial
alignment of the later described washer springs.
A member 134 is fixed to the top of the upper piston rod 72 by a
fixing nut 135 while being received within a space defined by the
upper projections 131 of the guide cylinder 130 and its upper end
flange 136 has a diameter larger than the outer diameter of the
guide cylinder 130, more exactly larger than the outer diameter of
the circle defined by the outer peripheries of the upper
projections 131 of the guide cylinder 130. This upper end flange
136 of member 134 is provided, on its peripheral edge, with a
plurality of cut-outs 137. The number of cut-outs 137 of the upper
end flange 136 corresponds to that of the upper projections 131 of
the guide cylinder 130 and, in the assembled disposition, the upper
projections 131 are in a slidable engagement with the peripheral
cut-outs 137 as shown in FIG. 12.
A plurality of washer springs 138 are inserted over the guide
cylinder 130 and its upper projections 131 with the lowermost one
in abutment with the shoulder of the bottom flange 133 of the guide
cylinder 130 and the uppermost one in abutment with the underside
shoulder of the upper end flange 136 of member 134.
The hydraulically operated working machine of the above-described
second embodiment of the present invention operates in the
following manner, operations similar to those described in
connection with the foregoing first embodiment being omitted in the
explanation.
Following the downward movement of the piston plunger 73 in the
piston chamber 23, the member 134, which is connected in one body
to the piston plunger 73 via the fixing nut 135 and the upper
piston rod 72, moves downwardly and compresses the washer springs
138. When the piston plunger 73 completes its downward stroke, the
piston retracting mechanism 3 of the present embodiment assumes the
disposition shown in FIG. 13, in which the washer springs 138 are
compressed into an almost flat disposition.
During this compression, the internal surface contact of the washer
springs 138 with the external periphery of the upper projections
131 of the guide cylinder 130 prevents infavourable diametrical
slip between the superimposed washer springs 138. In addition,
axial turning of the upper piston rod 72 and the piston plunger 73
is effectively prevented by the meshing engagement between the
upper projections 131 of the guide cylinder 130 and the peripheral
cut-outs 137 of member 134.
After completion of the punching operation, the pressured fluid in
the piston chamber 23 is discharged therefrom and the repulsion of
the washer springs 138 forces the piston plunger 73 to move
upwardly via member 134 and the upper piston rod 72. When the
piston plunger 73 completes its upward stroke, the work part
retracting mechanism 3 of the present embodiment resumes the
disposition shown in FIG. 10.
As is clearly understood from the foregoing explanation, a number
of advantages can be resulted from employment of the present
invention.
The hydraulically operated working machine of the present invention
is firstly characterized by the fact that the piston retracting
mechanism is located outside the machine parts confining the piston
chamber for the piston plunger. Thanks to these structural
characteristics, maintenance work for replacement of the work part
retracting mechanism can be considerably simplified. In addition,
dimension of the piston retracting mechanism can be designed quite
freely without regard to that of the machine parts confining the
piston chamber. Further, as there is no need to give a large
durable structure to the machine parts confining the piston
chamber, the working machine as a whole can be of a remarkably
light weight and manufacturing accuracy of the machine can be
excellently enhanced.
The hydraulically operated working machine of the present invention
is secondly characterized by the fact that the piston retracting
mechanism is capable of providing a very large repulsion force in
spite of its relatively short stroke. Thanks to such a very large
repulsion force, holes can be punched through workpieces while
leaving minimized clearances and this leads to the remarkably
improved accuracy of the punched hole sizes and the considerably
lowered sharp uncomfortable noises during the punching operation.
Further, shortness in the necessary stroke enables the piston
retracting mechanism to be structured very compactly. The strong
and durable repulsion of the retracting element, i.e. the urethane
piece(s) in the first embodiment and the washer springs in the
second embodiment, can withstand long use even under severe
operational conditions.
The hydraulically operated working machine of the present invention
is thirdly characterized by the fact that the mechanism for
admission and discharge of the pressured fluid into and out of the
piston chamber is completely incorporated within the cap and the
main handle. This makes the handling and transportation of the
machine very simple and convenient. Absence of connecting tubes or
like members outside the main body of the machine simplifies and
improves the design of the machine.
The hydraulically operated working machine of the present invention
is further characterized by the fact that all the elements
composing the electric circuit are incorporated within the main
frame and the main handle and the control switches are located near
the root end of the main handle. This gives simplicity and
convenience in the handling and transportation of the machine in
the actual use. Operation of the machine can be very easily
controlled by using fingers of the operator's hand gripping the
main handle. In addition, as the relatively fragile piston shifting
mechanism is placed within the main frame being attached to the
inside face of the cover, the same is well be protected from
external shock and the replacement of same can be carried out very
simply.
* * * * *