US3832851A

US3832851A - Hydraulic actuator

Info

Publication number: US3832851A
Application number: US00303308A
Authority: US
Inventors: H Kiernan
Original assignee: Hydro Stack Manufacturing Corp
Current assignee: Oilgear Co
Priority date: 1972-11-03
Filing date: 1972-11-03
Publication date: 1974-09-03
Anticipated expiration: 1991-09-03

Abstract

An hydraulic actuator capable of intensifying and multiplying force applications in relation to the available hydraulic pressure includes a cylinder having a closure sealing off its rear end and a piston bearing at its forward end. A piston in the forward part of the cylinder is provided with a forwardly projecting rod extending through the opening in the bearing. This rod is adapted to apply the intensified force to the selected load. An intensifying unit within the cylinder rearwardly of the forward piston includes a stationary piston barrel within the cylinder adapted to receive the hollow tube extension of a central piston. A valve forming part of the central piston is adapted to open to permit the available hydraulic pressure to pass through the passages of the central piston and its tube for application to the forward piston. When the valve is closed, the central piston is adapted to move forwardly thereby moving the piston tube within its barrel to intensify the hydraulic pressure acting against the forward piston and proportionately increase the force applied to the load. A valve opening means in the form of a forwardly projecting pin on a spring biased piston located rearwardly of the central piston facilitates opening of the valve to permit retraction of the central piston and consequently the reduction of the applied intensified force and eventual retraction of the forward piston rod.

Description

United States Patent 1 Kiernan HYDRAULIC ACTUATOR [75] Inventor: Henry E. Kiernan, Huntington Station, NY.

[73] Assignee: Hydro-StackMfgCorp Huntington Station, NY. I

22 Filed: Nov. 3,1972

[21] Appl. No.: 303,308

[52] US. Cl. 60/563, 60/575 [51] Int, Cl n F 15b 3/00 [58] Field ofSearch 60/54.5 HA, 54.6 HA, 60/54.5 A, 54.6 A, 563, 575

[56] References Cited 7 v UNITED STATES PATENTS 1,970,999 8/1934 Ferris et al...'... .[60/545 HA 2,372,015 3/1945 Rockwell 60/54.5 A 2,633,001 3/1953 Porter 60/54.5 A 3,473,328 10/1969 Mayhew 60/54.5 A FOREIGN PATENTS OR APPLICATIONS 560,678 4/1944 Great Britain 60/54.5 HA 178,613 3/1962 Sweden.; 60/54.5 HA

Primary ExaminerEdgar W. Geoghegan Assistant Examiner-A. M. Zupcic Attorney, Agent, or Firm-Kane, Dalsimer, Kane, Sullivan and Kurucz 57 i 9 ABSTRACT An hydraulic actuator capable of intensifying and mul-' tiplying force applications in relation to the available hydraulic pressure includes a-cylinder having a closure sealing off its rear end and a piston bearing at its forward end. A piston in the forward part of the cylinder is provided with a forwardly projecting rod extending through the opening in the bearing. This rod is adapted toapply the intensified force to the selected load. An intensifying unit within the cylinder rearwardly of the forward piston includes a stationary pisthe forward piston and proportionately increase the force applied to the load. A valve opening means in the form of a forwardly projecting pin on a spring biased piston located rearwardly of the central piston facilitates opening of the valve to permit retraction of the central piston and consequently the reduction of the applied intensified force and eventual retraction of the forward piston rod. 1

11 Clainis, 3 Drawing Figures PAIENIEDSEPB m4 3.882.851

sage: 10$ 2 SHEET 20$ 2 PATENIEnsm I914 2 A 4 JQ showing the manner in 1 HYDRAULIC ACTUATOR BACKGROUND OF THE INVENTION I-Ieretofore in' designing machinery, it would become necessary to provide or incorporate an hydraulic cylinder with a relatively high clamping force in pounds thrust and very frequently with a long piston travel in order to clear adjacent equipment. Inasmuch as the formula for Force (F) in pounds is:

. F Sq. Area of the piston X Pressure (P.S.I.), the

machine designer had three design methods from be from 300 to 1,000 psi. Under these circumstances, the designer must install:

a. a high pressure pump to handle the clamping requirements andth'en reduce the balance of the flow to the lower pressure. This requires more expensive equipment with higher operating costs because more horsepower is required thus the attendant oil heat-up problems; or

. b. aseparate small high pressure pump for only handling the clamping operation; or

c. expensive and bulkymechanical. linkage.

SUMMARY OF THE INVENTION The principal object of the present invention is to provide a hydraulic cylinder having the following ad'- vantages, attributes and characteristics:

a. relatively small bore cylinder b. proportionately high output force c. relatively low input hydraulic'pressure d. any length of low force pretravel of piston rod before a load is encountered v e. standard manufacturing equipment and techniques may be employed in manufacturing the cylinder and its BRIEF DESCRIPTION or THE FIGURES ln the drawing: 1

FIG. 1 is a longitudinal sectional view of the hydraulic cylinder of this invention prior to actuation by the available hydraulicpressure; I

FIG. 2*is ,a cross-section view taken along the line 22of FIG. .l; and

FIG. 3'is a longitudinal sectional view of the cylinder which theforce applied to the load is intensified.

DETAILED DESCRIPTION In the drawing, a cylinder 10 includesa forward end l2.and a rearend 14. The rear end 14 is closed by a blindend-cap 16 fixed in place by a retaining ring 18..

The juncture. between the cap 16 and associated internal surfaces of the cylinder end 14 is sealed by means of the interposed O-ring 20. At the forward end is an internal position rod bearing 22 which is fixed in place by means of the retaining ring 24. The interposed O- ring 26 cooperates in sealing the juncture between the bearing 22 and adjacent surfaces of cylinder forward end 12. Within the forward part of the cylinder 10 is a forward piston 28 with O-ring 30 sealing the juncture between piston and the cylinder walls. A forwardly pro.- jecting rod 32 extends from the piston 28 through the coaxial bore 34 of the bearing 22. The rod 32 is sealed within the bearing 22 by the O-ring'36. The interposed spring 38 biases piston 28 away from the bearing 22. A force intensifying or multiplying mechanism is disposed rearwardly of the piston 28'within the cylinder 10 and includes a piston barrel 40 in which travels the piston tube 42 which projects forwardly from the central piston 44. The barrel 40 is retained within the cylinder 10 and in sealing relationship with the internal cylinder walls by the retaining ring 46 and O-ring 48 respectively. The central bore 50 of the barrel 40 advantageously receives the piston 42 and is in sealed relationship therewith by the O-r'ing 52. The central piston .44 is in sealing engagement with the intern'al walls of the cylinder 10 by means of the interposed O-ring 54.

The piston 44 includes a coaxial bore 56 which extends into the bore of the piston tube 42. A barrel associated with the piston 44 includes a ball 58 and a valve seat 60. A spring 62 urges the ball 58 towards the'valve seat 60. The spring 64 disposed about the tube 42 urges the maturely because ordinarily the rod 42 should not move until the load is encountered. A'swill be appreciated when the hydraulic pressure is equal on both sides of the ball 58, the spring 62 will force the ball against theseat 60 to thereby close the valve at which time the available hydraulic pressure will act 'upon the piston 44 to drive the piston tube 42 forwardly into the bore 50 to intensify the pressure upon'the forward piston 28. Consequently, the force is applied to the load by the 'r0d32. a f

A valve opening mechanism is present within the rear part of the cylinder 10 to unseat the ball 58 when itis desired to retract the rod 32 and the force upon the loadfllhis mechanism includes a rearward piston 66 in sealed relationship with the internal cylinder walls by means of the interposed O-ring 68. A forwardly-projecting pin 70'is adapted to unseat the ball 58 during the retraction of rod 32 from the load. Spring 72 between the rearward piston 66 and the plug l6bias'es' the piston 66 forwardly. A'stop ring 74 limits the extent of forward travel of the piston 66 under the influence of this spring 72. Spring 72 as well as spring 38 are only required for single acting spring return operation. This spring is generally strong enough to open the check valve ball 58 by overcoming the spring 62.

The available hydraulic pressure is introduced into the cylinder through port76. In addition, exhaust ports 78, .and 82 are provided. Of course, these will assume 'a different role during the retraction of rod 32 from the load. 1

In operation and assuming the initial disposition of parts illustrated in FIG. 1, low pressure hydraulic fluid or oil will flow through port 76 ordinarily from a directional control valve (not shown). This fluid will flow into the Chamber provided rearwardly of the rear face of the central piston 44 and forwardlyof the front face of the rear piston 66. This fluid under the available hydraulic pressure flows past the open ball check valve 58 through the interconnected passageways of the piston 44 and the piston tube 42 through the bore 50 and eventually into the chamber provided rearwardly of the forward piston 28. At the same time, the hydraulic fluid entering the port 76 acts upon the forward face of the rearward piston 66 causing it to retract against the bias of the spring 72. When the piston rod 32 meets resistance from the load, pressure will eventually equal out on both sides of the ball 58 and by now the pin 70 will have retracted sufficiently to permit the spring 62 to force the ball 70 rearwardly onto its seat 60 thereby closing the valve. When this occurs, the piston 44 will. move forwardly to cause the piston tube 42 to move forwardly within the bore 50. This intensifies the pressure within the chamber rearwardly of the piston 28 by a value related to the ratio between the internal diameter of the cylinder and the bore 50. Thus, the force applied to the load through the rod 32 is multiplied by a corresponding amount. The hydraulic fluid is forced to pass through the

ports

78, 80 and 82 and ordinarily would be directed to a tank through the directional control valve (not shown), In the illustrated embodiment the length of the displacement of rod 32 will be approximately equal 'to the cubic inch volume of the bore 50, with relation to the volume of part 10.

When it is desired to relieve the force on the loadas applied through .the rod 32 and eventually retract this rod, the directional control valve (not shown) is reversed now' sending oil or the selected hydraulic fluid from the cylinder port 76 to the tank and the fluid under pressure into

cylinder ports

78, 80 and 82. The fluid entering port 82 causes the piston 66 to move forwardly. In the meantime the hydraulic fluid entering port 78 causes the piston 28 to retract. The piston 44 will also be retracted and eventually the pin 70 will unseat the ball-58. The entrapped fluid will pass through the opened check valve ball 58 and exit through port 76. The hydraulic cylinder is now ready to initiate and complete another force applying cycle.

In a specificand somewhat successful embodiment of the invention the cylinder had an'internal bore diame ter of 2 inches while bore 50 had adiameter of 0.5 inches- With this ratio, there was a consequent 16- "to one pressure increase in the chamber immediately behind the forward piston 28 during the forward thrust of the rod 32 against the load. This had the result of 5,026 pounds of force exerted against the load bypiston rod 32 whenul00 psi hydraulic pressure was present at port 76.'Thu's, the several aforenoted objects and advantages are most effectively attained. In this connection, there is no requirement for external valving nor derstood that this invention is in no sense limited thereby and its scope is to be determinedby that of the appended claims.

I claim:

1. An hydraulic actuator for hydraulic systems for intensifying force applications in relation to' the available hydraulic pressure of the system comprising: a tubular shell of essentially uniform internal diameter throughout and having a forward end and a rearward end, closure means for sealing off the rearward end, a coaxial piston bearing at the forward end having a coaxial piston rod receiving opening therethrough, a forward coaxial piston in the shell near the forward end, the forward piston having a diameter essentially the same as that of the interior of the shell and being in sealing relationship therewith, a coaxial piston rod coupled with the forward piston and extending forwardly through the opening in the piston bearing: intensifying means for permitting the rod to encounter a resistance offered by a load while the forward piston is exposed to the available hydraulic pressure and thereafter automatically intensifying thepressure on the forward pistonto increase the force transmitted through the rod to the load, the intensifying means including a coaxial stationary piston barrel having a hollow piston tube receiving opening and being within the tubular shell and rearwardly of the forward piston, that part of said barrel within said shell having a'diameter essentially the same as that of the interior of the shell and being in sealing relationship therewith, acoaxial central piston with a passage therethrough in the tubular shell rearwardly of the barrel, the said central piston having a diameter essentiallythe same as that of the interior of the shell and being in sealing relationship therewith, a coaxial hollow piston tube having a passage and coupled with the central piston, the tube extending forwardly'into the opening of the barrel, the passage of the central piston being in communication with the passage of the piston tube, valve means associated with the central piston for opening to permit the passages to transmit the available hydraulic pressure to the forward piston whereupon the rod is adapted to encounter the resistance offeredby the load and for closing to permit the central piston to move forwardly under the influence of the available hydraulic pressure and to move the piston tube forwardly to intensify the hydraulic pressure against the forward piston and proportionately intensify the force applied to the load.

2. The invention in accordance with claim 1 wherein the tubular shell includes an inlet port for receiving hydraulic fluid under pressure and transmitting it to the passages and to the central piston. i i

3. The invention in accordancewith claim 1 wherein valve opening means are provided in the shell rearwardly of the central piston for cooperating in opening the valve means to expose the available hydraulic pressure to the forward piston and for permitting the valve means'to close-to thereby cooperate in intensifying the pressure against the forward piston, and for opening the valve means when the forces 'on the load; are to be removed. 7 p e 4. The invention in accordance with claim 3 wherein the valve opening means comprises a rearward piston in the shell rearwardly of the central piston, a pin projecting forwardly from the rearward piston for engaging and opening the valve means when the rearward piston is in a forward position, stop means for determining the forward position of the. rearward piston, spring means interposed between the rearward piston and the closure means at the rearward end of the tubular shell for biasing the rearward piston forwardly against the stop means, and the rearward piston adapted to move rearwardly under the available hydraulic pressure against the bias of the spring means for permitting the valve means to close.

5. The invention in accordance with claim 1 wherein the valve means includes a spring biased ball in the passage of the central piston and a valve seat in the rearward part of the central piston for receiving the ball.

6. The invention in accordance with claim 1 wherein a spring is interposed between the central piston about the piston tube and the stationary barrel, and the spring has a greater value than force required to move the forward piston in the absence of said load.

7. The invention in accordance with claim 1 wherein means are provided between the shell and the barrel for fixing the barrel in a stationary position within the shell.

8. The invention in accordance with claim 1 wherein a spring is interposed between the bearing and the forward piston biasing the forward piston in a rearward direction.

9. The invention in accordance with claim 4 wherein the shell includes outlet ports between the bearing and the forward piston, between the barrel and the centralpiston and the rear closure and the rearward piston and an inlet port for receiving hydraulic fluid under pressure and transmitting it to the passages and the central piston. 1

10. An hydraulic actuator for hydraulic systems for intensifying force application in relation to the available hydraulic pressure of the system comprising: a cylinder having an essentially uniform internal diameter therewith, a coaxial piston rod coupled with the forward piston and extending forwardly through the opening in the piston bearing; intensifying means for automatically intensifying the pressure on the forward piston to increase the force transmitted through the rod to a' load, the intensifying means includes a coaxial 'stationary piston barrel having a hollow piston tube receiving opening and being within the cylinder and rearwardly of' the forward piston, that part of said barrel within the shell having a diameter essentially the same as that of the interior of the shell and being in sealing relationship therewith, a central coaxial piston with a passage therethrough in the cylinder rearwardly of the barrel,- the said central piston having a diameter essentially the same as that of the interior of the shell and being in sealing relationship therewith, a coaxial hollow piston tube having a passage and coupled with the central piston, the tube extending forwardly into the opening of the barrel, the passage of the central piston being in communication with the passage of the piston tube, valve means for opening to transmit the available hydraulic pressure through the passages to the forward piston and thereafter closing whereupon the central piston is adapted to move forwardly underthe influence of the available hydraulic pressure and to move the piston tube forwardly to intensify the hydraulic pressure against the forward piston and proportionately intensify the force applied to the load.

11. An hydraulic actuator for hydraulic systems for intensifying force applications in relation to the available hydraulic pressure of the system comprising: a tubular shell of essentially uniform diameter throughout and having a forward end, a coaxial piston bearing at the forward end having a coaxial piston rod receiving opening therethrough, a forward coaxial piston in the shell near the forward end, a coaxial piston rod coupled with the forward piston and extending forwardly through the opening in the piston bearing: intensifying means for permitting the rod to encounter a resistance offered by a load while the forward piston is exposed to the available hydraulic pressure and thereafter automatically intensifying the pressure. on the forward piston to increase the force transmitted through the rod to the load, the intensifying means including a coaxial stationary piston barrel having a hollow piston tube receiving opening and being within the tubular shell and rearwardly of the forward piston, a coaxial central piston with a passage therethrough in the tubular shell rearwardly of the barrel, a coaxial hollow piston tube having a passage and coupled with the central piston, the tube extending forwardly into the opening of the barrel, the passage of the central piston being in communication with thepassage of thepiston tube, valve means associated with the central piston for opening to permit the passages to transmit the available. hydraulic pressure to the forward piston whereupon the rod is adapted to encounter the resistance offered by the load and for closing to permit the central piston to move forwardly under the influence of the available hydraulic pressure and to move the piston tube forwardly to intensify the hydraulic pressure against the forward piston and proportionately intensify the force applied to the load, the valve opening means comprising a rearward piston in the shell rearwardly of the central piston, a pin projecting forwardly from the rearward piston for engaging and opening the valve means when the tubular shell for'biasing the rearwardly piston for-' wardly against the stop means, and the rearward piston adapted to move rearwardly underthe available hydraulic pressureagainst the bias of the springmeans for permitting the valve means to close.

Claims

1. An hydraulic actuator for hydraulic systems for intensifying force applications in relation to the available hydraulic pressure of the system comprising: a tubular shell of essentially uniform internal diameter throughout and having a forward end and a rearward end, closure means for sealing off the rearward end, a coaxial piston bearing at the forward end having a coaxial piston rod receiving opening therethrough, a forward coaxial piston in the shell near the forward end, the forward piston having a diameter essentially the same as that of the interior of the shell and being in sealing relationship therewith, a coaxial piston rod coupled with the forward piston and extending forwardly through the opening in the piston bearing: intensifying means for permitting the rod to encounter a resistance offered by a load while the forward piston is exposed to the available hydraulic pressure and thereafter automatically intensifying the pressure on the forward piston to increase the force transmitted through the rod to the load, the intensifying means including a coaxial stationary piston barrel having a hollow piston tube receiving opening and being within the tubular shell and rearwardly of the forward piston, that part of said barrel within said shell having a diameter essentially the same as that of the interior of the shell and being in sealing relationship therewith, a coaxial central piston with a passage therethrough in the tubular shell rearwardly of the barrel, the said central piston having a diameter essentially the same as that of the interior of the shell and being in sealing relationship therewith, a coaxial hollow piston tube having a passage and coupled with the central piston, the tube extending forwardly into the opening of the barrel, the passage of the central piston being in communication with the passage of the piston tube, valve means associated with the central piston for opening to permit the passages to transmit the available hydraulic pressure to the forward piston whereupon the rod is adapted to encounter the resistance offered by the load and for closing to permit the central piston to move forwardly under the influence of the available hydraulic pressure and to move the piston tube forwardly to intensify the hydraulic pressure against the forward piston and proportionately intensify the force applied to the load.

2. The invention in accordance with claim 1 wherein the tubular shell includes an inlet port for receiving hydraulic fluid under pressure and transmitting it to the passages and to the central piston.

3. The invention in accordance with claim 1 wherein valve opening means are provided in the shell rearwardly of the central piston for cooperating in opening the valve means to expose the available hydraulic pressure to the forward piston and for permitting the valve means to close to thereby cooperate in intensifying the pressure against the forward piston, and for opening the valve means when the forces on the load are to be removed.

4. The invention in accordance with claim 3 wherein the valve opening means comprises a rearward piston in the shell rearwardly of the central piston, a pin projecting forwardly from the rearward piston for engaging and opening the valve means when the rearward piston is in a forward position, stop means for determining the forward position of the rearward piston, spring means interposed between the rearward piston and the closure means at the rearward end of the tubular shell for biasing the rearward piston forwardly against the stop means, and the rearward piston adapted to move rearwardly under the available hydraulic pressure against the bias of the spring means for permitting the valve means to close.

9. The invention in accordance with claim 4 wherein the shell includes outlet ports between the bearing and the forward piston, between the barrel and the central piston and the rear closure and the rearward piston and an inlet port for receiving hydraulic fluid under pressure and transmitting it to the passages and the central piston.

10. An hydraulic actuator for hydraulic systems for intensifying force application in relation to the available hydraulic pressure of the system comprising: a cylinder having an essentially uniform internal diameter throughout having a forward end and a rearward end, closure means for sealing off the rearward end, a coaxial piston bearing at the forward end having a piston rod receiving opening therethrough, a forward coaxial piston in the cylinder near the forward end, the forward piston having a diameter essentially the same as that of the interior of the shell and being in sealing relationship therewith, a coaxial piston rod coupled with the forward piston and extending forwardly through the opening in the piston bearing; intensifying means for automatically intensifying the pressure on the forward piston to increase the force transmitted through the rod to a load, the intensifying means includes a coaxial stationary piston barrel having a hollow piston tube receiving opening and being within the cylinder and rearwardly of the forward piston, that part of said barrel within the shell having a diameter essentially the same as that of the interior of the shell and being in sealing relationship therewith, a central coaxial piston with a passage therethrough in the cylinder rearwardly of the barrel, the said central piston having a diameter essentially the same as that of the interior of the shell and being in sealing relationship therewith, a coaxial hollow piston tube having a passage and coupled with the central piston, the tube extending forwardly into the opening of the barrel, the passage of the central piston being in communication with the passage of the piston tube, valve means for opening to transmit the available hydraulic pressure through the passages to the forward piston and thereafter closing whereupon the central piston is adapted to move forwardly under the influence of the available hydraulic pressure and to move the piston tube forwardly to intensify the hydraulic pressure against the forward piston and proportionately intensify the force applied to the load.

11. An hydraulic actuator for hydraulic systems for intensifying force applications in relation to the available hydraulic pressure of the system comprising: a tubular shell of essentially uniform diameter throughout and having a forward end, a coaxial piston bearing at the forward end having a coaxial piston rod receiving opening therethrough, a forward coaxial piston in the shell near the forward end, a coaxial piston rod coupled with the forward piston and extending forwardly through the opening in the piston bearing: intensifying means for permitting the rod to encounter a resistance offered by a load while the forward piston is exposed to the available hydraulic pressure and thereafter automatically intensifying the pressure on the forward piston to increase the force transmitted through the rod to the load, the intensifying means including a coaxial stationary piston barrel haviNg a hollow piston tube receiving opening and being within the tubular shell and rearwardly of the forward piston, a coaxial central piston with a passage therethrough in the tubular shell rearwardly of the barrel, a coaxial hollow piston tube having a passage and coupled with the central piston, the tube extending forwardly into the opening of the barrel, the passage of the central piston being in communication with the passage of the piston tube, valve means associated with the central piston for opening to permit the passages to transmit the available hydraulic pressure to the forward piston whereupon the rod is adapted to encounter the resistance offered by the load and for closing to permit the central piston to move forwardly under the influence of the available hydraulic pressure and to move the piston tube forwardly to intensify the hydraulic pressure against the forward piston and proportionately intensify the force applied to the load, the valve opening means comprising a rearward piston in the shell rearwardly of the central piston, a pin projecting forwardly from the rearward piston for engaging and opening the valve means when the rearward piston is in a forward position, stop means for determining the forward position of the rearward piston, spring means interposed between the rearward piston and the closure means at the rearward end of the tubular shell for biasing the rearwardly piston forwardly against the stop means, and the rearward piston adapted to move rearwardly under the available hydraulic pressure against the bias of the spring means for permitting the valve means to close.