Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to an improved differ-
ential pressure hydraulic power convertor. More specifically,
the present invention relates to an improved differential
pressure hydraulic power convertor having interchangeable piston
assemblies and sleeves to easily vary the ratio of the output
fluid pressure to the input fluid pressure of the convertor.
The prior art discloses hydraulic pressure convertors
employing differential pistons which, on the power stroke,
operate a pump which delivers fluid under pressure at a higher
pressure than the line pressure supplied from a pressurized
source. In these prior art devices, valve means connect the
power cylinder at both sides continuously to the fluid pressure
source and alternately connect the cylinder at opposite sides
of the piston to each other. Such prior art devices are exem-
plified in U~ S. Patent ~os. 2,749,886 and 3,589,839. Typically,
in these devices, the piston is driven on its power stroke by
the differential in total pressure on its opposite sides and is
driven on its return stroke by full line pressure applied to
one side while the other side is vented to exhaust pressure.
However, these prior art devices do not use the
potential of the line pressure to the best advantage, do not
operate to effect as rapid a return as desirable of the differ-
ential piston after completion of its power stroke, do not
provide a re~enerative circuit for the transfer of fluid
pressure from the power side of the differential piston to the
opposite side of the piston during the return stroke, and can-
not be easily converted from one ratio to another desired ratio
of output fluid pressure to the input fluid pressure.
Another type prior art differential pressure hydraulic
power convertor eliminates many of the undesirable features in
the prior art devices discussed above by operating under full
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line pressure on its power stroke by fluid being applied to
its cylinder at one side of the differential piston while the
cylinder at the opposite side of the piston is vented to atmos-
pheric pressure. In this prior art device, the system is re-
generative on the return stroke, and the shift from advance to
return of the piston is substantially instantaneous due to a
specialized control valve. Such a prior art device is dis-
cussed in U. S. Patent No. 3,737,254.
However, although the prior art device disclosed in
U. S. Patent No. 3,737,254 eliminates many of the problems of
previous prior art devices, the convertor cannot be easily
converted from one ratio to another desired ratio of output
fluid pressure to input fluid pressure.
In contrast to the prior devices, the present inven-
tion comprises an improved differential pressure hydraulic power
convertor which utilizes full line pressure on its power stroke
by fluid being applied to its cylinder at one sidë of the differ-
ential piston while the cylinder at the opposite side of the
piston is vented to atmospheric pressure, which is regenerative
on the return stroke of the piston, which shifts from advance
to return of the piston substantially instantaneously, and
which can be easily converted from one ratio to another desired
ratio of output fluid pressure to input fluid pressure. The
present invention comprises a differential pressure hydraulic
power convertor constructed such that interchangeable piston
assemblies and sleeves can be used to easily vary the ratio of
the output fluid pressure to the input fluid pressure of the
convertor.
In one aspect of the present invention, there is
provided a hydraulic pressure convertor including a valve
housing, a pump housing and a power cylinder therebetween
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having a differential piston located therein, wherein the :~
improvement comprises: said pump housing including a cylindri-
cal bore therethrough having seal means located therein, and
a piston assembly detachably secured to the differential piston
of said power cylinder.
In a further aspect of the present invention, there
is provided a hydraulic pressure convertor including a valve
housing, a pump housing and a power cylinder therebetween
having a differential piston located therein, wherein the
improvement comprises: said pump housing including a cylindri-
cal bore therethrough, and a piston assembly detachably secured
to the differential piston o~ said power cylinder and in slid-
: able engagement with the cylindrical bore of said pump housing.
In a further aspect of the present invention, therei9 provided an improved hydraulic pressure convertor including
a body having an inlet and an outlet, a motor assemblage carried
by the body and including a power cylinder and a differential
driving piston reciprocable therein, a pumping assemblage, means ~--
connecting the differential driving piston to the pumping assem-
blage, a first conduit in continuous communication at one endwith the inlet and with the power cylinder at the side of the
differential driving piston to which fluid pressure is to be
applied for driving the differential driving piston on its
~ power stroke, a second conduit continuously in communication at
one end with the power cylinder at the opposite side of the
differential driving piston, each of said conduits having a
valving port spaced from its said one end, a valve operative in
a first operating position in which it blocks the valving port
of the first conduit and concurrently connects the valving port
of the second conduit with the outlet and operative in a second
operating position in which it effects communication of said
ports with each other and concurrently stops communication of
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the second port with the outlet, lost motion connecting means
connecting the valve to the differential piston so as to effect
actuation of the valve toward said first operating position past
a predetermined center position as the differential piston is
moved a predetermined distance on its power stroke and to effect
actuation of the valve toward said second operating position
past said center position as the differential piston is moved
a predetermined distance on its return stroke, and over-center
spring means connected to the valve and operative when the valve
is actuated past said center position in directions toward said
first and second operating positions, respectively, to drive
the valve with a snap action to the one of the said first and
second operating positions toward which the valve was being
actuated as it passed said center position, wherein the improve-
ment comprises: said hydraulic pressure convertor having a
variable ratio of the pressure of the outlet fluid from said
pumping assemblage to the pressure of the inlet fluid to said
motor assemblage by varying the size of a detachable piston
assembly attached to said differential driving piston in said
power cylinder and varying the size of a pumping assemblage
means operatively associated with said detachable piston assem-
bly, wherein said differential driving piston comprises a driv-
ing piston having stem means operably associated with said motor
assemblage, having differential piston connected to the stem
; portion, thereby separating said motor assemblage and said
pumping assemblage, and having stub connecting shaft means
connected to said differential driving piston and extending
into said power cylinder, the stub connecting shaft means having
a transverse bore therethrough; said pumping assemblage having
a housing being fonmed having a substantially cylindrical bore
therethrough and having a seal means located in an annular
cavity therein; and said detachable piston assembly comprising:
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piston means, sleeve means secured to the piston means, the
sleeve means having a bore therein receiving the stub connect-
ing shaft means of said differential driving piston therein
and having a transverse bore therein which aligns with the
transverse bore in the stub connecting shaft means of said
differential driving piston when the sleeve means is assembled
thereto; and resilient pin means securing the sleeve means to
the stub connecting shaft means of said differential driving
piston by engaging the transverse bore in the sleeve means and
the transverse bore in the stub connecting shaft means.
The foregoing advantages and the preferred embodi-
ments of the invention will be better understood from the
following specification taken in conjunction with the accompany-
ing drawings.
The invention is illustrated by way of example in
the accompanying drawings wherein:
FIGURE 1 is a view of a prior art differential
pressure hydraulic power convertor.
FIGURE 2 is a cross-sectional view along line 2-2 of
the prior art differential pressure hydraulic power convertor
shown in FIGURE 1.
FIGURE 2a is a view of a check valve arrangement for
controlling fluid flow in the inlet and outlet of the differen-
tial pressure hydraulic convertor as shown in FIGURES 1 and 2.
FIGURE 3 is a cross-sectional view along line 3-3 of
the prior art differential pressure hydraulic power convertor
shown in FIGURE 2.
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FIGURE 4 is a cross-sectional view along line x-x of
FTGURE 3 of a first embodiment of the present invention with
the mounting bracket and fasteners shown in full view. -
FIGURE 5 is a cross-sectional view along line x-x
of FIGURE 3 of a second embodiment of the present invention with
the mounting bracket and fasteners shown in full view.
FIGURE 6 iS a cross-sectional view along line x-x of
FIGURE 3 of a third embodiment of the present invention with the
mounting bracket and fasteners shown in full view.
Referring to FIGURE 1 of the drawings, a typicalprior
art differential pressure hydraulic convertor is shown. The con-
vertor comprise~ a body 1 compo3ed of a valve houoing 2, a pump
housing 3, and a power cylinder 4 therebetween and communicat-
ing therewith. The vaIve housing 2 may be formed of a main
body portion 5 closed at its outer end by a cover 6 in sealed
relation thereto.
Referring to FIGURE 2, mounted within the cylinder 4
~or reciprocation axially thereof is a differential piston 8
having a stem 9 at the end adjacent the pump housing 3 and
having a stem 10 at its opposite end. The valve housing 2
has an internal bore 11 coaxial with, and connected at its
inner end to the adjacent end of, the cylinder 4. At the
opposite end of the bore 11 and in communication therewith is
a valving cavity 12 in which valve means, later to be described,
are provided for controlling reciprocation of the piston 8 and
regenerative circuitry. At the opposite end of the cylinder 4
from the valve housing 2, the body is provided with a bore 14,
coaxial with the cylinder 4, in which the stem 9 is received.
The stem 10 fits the bore 11 with the normal operat-
ing clearance sufficient to guide the piston 8 in an axialpath. The stem 10 is provided with a circumferential groove
.
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15 in which an 0-ring 16 is disposed for effecting a seal to ~ :
prevent the escape of pressuri~ed fluid from the cylinder 4
into the cavity 12.
The valve housing 2 of the body has an inlet 18 and
an outlet 19.
As illustrated, the convertor utilizes a pumping
assemblage driven by the differential piston 8. The pumping
piston 22, in effect, is a continuation of the outer end of
stem 9.
The pump housing 3 has a cavity 23 in which is dis-
posed a pump cylinder 24 having a bore 25 generally coaxial
with the cylinder 4 and with the bore 11. The pump cylinder .
24 is retained within cavity 23 between a resilient seal means
26 and the mounting bracket 27.
The fluid is supplied to the pump cylinder 24 by
means of inlet port 28, fluid passages (not shown), through a
suitable check valve assembly (not shown) and into cylinder 24 :`
through cavity 23 and ports 33 and 34.
Pressurized fluid is exhausted from the pump cylinder
24 via ports 33 and 34 therein by means of fluid passageways ~ -
(not shown~, through a suitable check valve assembly (not
shown), and through the outlet port 38.
The inlet 18 of the valve housing 2 i9 connected by
a duct 44 to the cylinder 4 at the left hand side of the piston
8. The duct 44 provides continuous communication between the
inlet 18 and the cylinder 4 independently of the operating
positlons of the valving means. The outlet 20 of the housing 2
is connected by a duct 45 to the cavity 12 continuously.
The stem 10 is provided with a first duct 46 which is
continuously connected by a lateral duct 47 with the clyinder 4
at the left or power side of the piston 8. The opposite end of
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the duct 46 is sealed~ The duct 46 has a valving surface,
spaced from the piston 8, and an annular port 48 opening through
its outer circumferential surface at the valving surface. The
stem 10 has a second duct 50 which extends endwise of the stem
entirely through the stem and through the piston 8 and opens at
its inner end into the cylinder 4 through the face or side of
the piston 8 opposite from the stem 10. The duct 50 is sealed
at its opposite end. Intermediate its ends, the duct 50 has an
annular valving port 51 which opens through the valving surface
of the stem from the port 48. The valving surface is ground and
polished.
Mounted within the cavity 12 and in concentric relation
to the stem 10 is a valving sleeve 55 which is polished on the
interior thereof to precisely fit the valving surface of the
stem 10, As shown, the sleeve 55 closes the port 48 and permits
the flow from port 51 into cavity 12, from which it is vented
through outlet 20, The sleeve 55 has an internal groove 56
which, when the sleeve is translated to the right, disconnects
the port 51 from the cavity 12 and connects it to the port 48
thereby interconnecting the duct 46 and the duct 50 such that
the cylinder 4 at the inlet side of the piston 8 communicates
with the outlet side of piston 8 so that the piston is moved
to the left on a return stroke from the power stroke. When
this occurs, the pressurized fluid in the cylinder 4 at the
inlet side of the piston 8 is transferred to the cylinder 4
at the opposite side of the piston 8.
Since the stem 9 is of smaller diameter than stem 10
with the total area of the piston 8 exposed to the pressurized
fluid in the cylinder 4 being greater than at the face of the
piston adjacent stem 9, the piston will be translated to the
left when the fluid in the cylinder 4 is vented to the piston
which contains stem 9,
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When the piston 8 is fully returned and the valve
sleeve 55 is moved to its extreme left hand position, the
pressurized fluid admitted through the inlet 18 is directed
to the left side of piston 8 and the fluid at the right side
of piston 8 is vented through the duct 50, port 51, cavity 12
and duct 45 to the outlet 20.
To connect outlet ports 48 and 51 in their proper
relationship the valve slcove 55 must be moved from one operat-
ing position to the other on each stroke of the piston 8. To
support the valve sleeve 55 a plurality of circumferentially
spaced springs 57 are used. The circumferential spacing of the
springs 57 relative to the valve sleeve 55 is such that the
forces of the springs 57 are balanced to hold the sleeve float-
ingly in coaxial relation with the stem 10.
To move the valve sleeve 55 endwise in opposite
directions past the over-center positions of the springs 57,
the sleeve is provided with diametrically opposed openings 66
in which pin 67 on the stem 10 is accommodated for movement
endwise with the stem relative to the valve sleeve. The open-
ing 66 is of sufficient size relative to the pin 67 to providea lost motion connection between the stem 10 and valve sleeve 55.
As shown, the valve sleeve 55 is at its extreme left
position, and the pin 67 rests in the right hand portion of the
opening 66. Accordingly, as the stem 10 moves to the right,
the valve sleeve 55 i5 driven immediately thereby to the right,
the springs 57 being compressed and rocking to the right. This
continues until the valve sleeve passesthe over-center position,
whereupon the springs 57 drive the valve sleeve 55 to its extreme
right hand position with a snap action which is permitted by the
lost motion provided by the opening 66 and the pin 67~ The valve ~ -
sleeve 55 remains in the extreme right hand position with the
pin 67 now in the lefthand portion of the opeing 66, or
.
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close thereto, such that as the piston 8 returns and the stem 10
moves to the left, the valve sleeve 55 is moved therewith until
it again reaches the over-center position, whereupon it is moved
to its extreme left position by the spring 57.
Referring to FIGURE 2a, a suitable check valve assembly
through which fluid flows into and out cylinder 24 in the prior
art differential pressure hydraulic convertor is shown.
Referring to the prior art differential pressure
hydraulic convertor of FIGURE 3, the relationship between the
check valves 31 and 37 and their respective inlet port 28 and
outlet port 38 is shown. As illustrated, the check valves 31
and 37 are located approximately 90 from their respective
inlet port 28 and outlet port 38. The inlet port 28 is connected
to the check valve 31 by fluid passage 29 while check valve 37
is connected to outlet port 38 by fluid passage 35. Typically,
four fasteners 36 are used to secure the pump housing 3 to the
valve housing 2, although any suitable number may be used.
Referring to FIGURE 4, an embodiment of the present
invention is shown. FIGURE 4 is a typical cross-sectional view
of the present invention such as would be taken along line x-x
of FIGURE 3.
The present invention is an improved prior art differ-
ential pressure hydraulic convertor comprising a valve housing
102, cylinder 104 and pump housing 103. The present invention
contemplates the use of a prior art valve housing 2, differential
piston 8, and sleeve 55 as describéd hereinbefore, except the
stem 9 of differential piston 8 is modified so as to provide a
stub connecting shaft rather than a pumping piston.
In the present invention the pump housing 103 com-
prises a prior art pump housing 3 as described hereinbefore,except that the housing 103 has a cylindrical kore 124 having
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a seal cavity 127 and seal means 128 therein and having a
chamfered edge 126 at one end thereof. Contained within pump
housing 103 is a sleeve 125 having an outwardly flared end 1~9
which mates with chamfered edge 126 of pump housing 103 being
r~etained in engagement therewith by mounting bracket 127. me
sl^cve 125 also is formed having an annular seal cavity 131
having a sealing means 132 therein to sealingly engage bore
125, annular recess 130 which communicates with the fluid
passages (not shown) leading to the fluid check valves (not
: 10 shown), first cylindrical bore 133 having a plurality of
apertures 134 therein to communicate with annular recess 130
and second cylindrical bore 135 to receive piston 122 therein.
Any suitable type seal means 128 and 132 may be used, although
a "T" type elastomeric seal means having a fiber back-up ring
is preferred.
The piston assembly comprises a piston 122 having an
annular seal cavity 137 containing a sealing means 138 therein,
the piston being secured by means of an interference fit to
piston sleeve 123 which, in turn, is secured to stub connect-
ing shaft 109 by a resilient pin 136. The resilient pin 136 is
- inserted through aperture (not shown) in sleeve 123 and en-
gages aperture 137 in stub connecting shaft 109. To allow fluid
communication to the rear of piston 122 and the face of connect-
ing stub shaft 109, aperture 138 is provided in the piston -~
sleeve 123. Although the piston 122 is secured to the piston
sleeve 123 by means of an interference fit, any suitable
fastening means may be used. Similarly, any suitable type
seal means 138 may be used, although "T" type elastomeric seals
having fiber back-up rings are preferred.
Referring to FIGURE 5, another embodiment of the pre-
sent invention is shown. FIGURE 5 is a typical cross-sectional
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view of the present invention such as would be taken along
line x-x of FIGURE 3,
As before, the embodiment of the present invention as
illustrated in FIGURE 5 is an improved prior art differential
pressure hydraulic convertor comprising a valve housing 102,
cylinder 104 and pump housing 103.
However, the embodiment of the present invention as
illustrated in FIGURE 5 utilizes a plug 140 having an outwardly
flared end 141 thereon which mates with chamfered edge 126 of
pump housing 103 being retained in engagement therewith by
mounting bracket 127, and having an annular seal cavity 142
having a seal means 143 therein. The seal means 143 may be
of any suitable type, although a "T" type elastomeric seal
means having fiber back-up rings is preferred.
The embodiment of the present invention as illustrated
in FIGURE 5 also utilizes a piston assembly comprising a piston
144 which reciprocates in bore 124 of pump housing 103 and is
sealingly engaged by seal means 128. The piston 144 is secured
by means of an interference fit to piston sleeve 145 which, in
turn, is secured to connecting stub shaft 109 by a resilient pin
136. m e resilient pin 136 is inserted through aperture (not
shown) in sleeve 145 and engages aperture 137 in stub connecting
shaft 109. To allow fluid communication to the rear of piston
144 and the face of connecting stub shaft 109, aperture 138 is
provided in the piston sleeve 123. Similar to the piston
assembly of FIGURE 4, although the piston 144 is secured to
piston sleeve 145 by means of an interference fit, any suitable
fastening means may be used.
Referring to FIGURE 6, yet another embodiment of the
present invention is shown. m e embodiment of the present inven-
tion as illustrated in FIGURE 6 is an improved prior art differ-
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ential pressure hydraulic convertor comprising a valve housing
102, cylinder 104 and pump housing 103.
However, in contrast to the embodiment shown in FIGURE
4 and FIGURE 5, the embodiment as illustrated in FIGURE 6
ut:ilizes a two-piece sleeve 150 within which piston 170 is
received. The sleeve 150 comprises a first portion 151 and a
second portion 152.
The first portion 151 comprises a cylindrical member
having an outwardly flared end 153 which mates with chamfered
edge 126 of pump housing 103 being retained in engagement there-
with by mounting bracket 127, having an annular seal cavity 154
containing seal means 155 therein, having a cylindrical bore 156
which receives piston 170 therein, having a plurality of apertures
157 which allow fluid communication between cylindrical bore 156
and the exterior of the cylindrical member, having a reduced
diameter portion 158 to allow fluid communication with the fluid
passages (not shown) leading to the fluid checX valves (not
shown) in pump housing 103, and having a threaded portion 159
at one end of the cylindrical member which mates with first
threaded bore 160 of the second portion 152.
The second portion 152 comprises a cylindrical member
having a first threaded bore 160, having a seal cavity 161 con-
taining a sealing means 162 therein, having a second bore 163
which receives piston 170 slidably therein, having an opening
164 and having an outer cylindrical surface:l65 which mates
with cylindrical bore 124 and engages seal means 128 of pump
housing 103. Any suitable seal means 128, 155 and 162 may be
used, although "T" type elastomeric seals having fiber back-up
rings are preferred.
The piston assembly comprises a piston 170 which is
secured by means of an interference fit to piston sleeve 171
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which, in turn, is secured to stub connecting shaft 109 by a
resilient pin 136. The resilient pin 136 is inserted through
apertures (not shown) in sleeve 171 and engages aperture 137 in
connecting stub shaft 109. To allow fluid communication to
the rear of piston 170 and the face of connecting stub shaft 109,
aperture 172 is provided in the piston sleeve 171.
Referring to FIGURE 4, FIGURE 5 and FIGURE 6 it can be
easily seen that the various embodiments of the present invention
utilize the same valve housing 102, cylinder 104, pump housing
103 and connecting stub shaft 109. Similarly, it can be easily
seen that to vary the ratio of the outlet fluid pressure to the
:~ inlet fluid pressure it is merely necessary to install either a
different piston assembly and plug, or piston assembly and
sleeve. By utilizing an easily relasable pin type connection,
the piston assembly can be easily released from the connecting
stub shaft 109, while utilizing a constant diameter bore in the
pump housing 103 allows the use of either the end of the
appropriate piston or the appropriate ~leeve, either of which
can be easily inserted into the pump housing 103.
It should be noted that when the piston of the present
invention as illustrated in FIGURE 4 is too small in diameter to
accommodate seal means 138 therein, a piston assembly and sleeve
arrangement should be used.
To convert a prior art differ0ntial pressure hydraulic
converter as shown in FIGURES 1, 2, 2a and 3 to the improved
model of differential pressure hydraulic convertor as shown in
FIGURES 4, 5 and 6, it is necessary to machine the prior art
stem 9 and piston 22 into a stub connecting shaft 109 having an
aperture therein, replace cylinder 4 with cylinder 104 which is
slightly longer than original cylinder 4 to compensate for the
increase in length of the piston assembly of the improved
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convertor, and bore out pump housing 3 to have a cylindrical
bore therethrough which has a seal cavity located therein and
has a chamfered edge 126 located at the end of the bore that
ahuts the mounting bracket of the convertor. After a suitable
seal means has been installed in the seal cavity 128 machined
into pump housing 3 any desired piston assembly and sleeve, if
necessary, can be installed in the convertor to easily vary the
ratio of outlet fluid pressure to inlet fluid pressure.
It should be noted that although a seal means 128 has
been provided in the pump housing 103 to sealingly engage either
the sleeves 125 or 151, or piston 144, an alternative sealing
.
arrangement (not illustrated) can be provided by deleting the
seal means 128 and cavity 127 in the pump housing 3 and install-
ing a suitable sealing means, such as an 0-ring type seal in
the outer periphery of one end of the sleeve 125 or 151, or
piston 144 to sealingly engage the pump housing 3,
Since the improved differential pressure hydraulic
convertor can be easily converted to any desired ratio of out-
put fluid pressure to inlet fluid pressure merely by installing
different piston assemblies and sleeves, if necessary, the
improved convertor is readily adaptable to a wide variety of
environments and uses.
