US3548573A

US3548573A - Cylinder with integral accumulator

Info

Publication number: US3548573A
Application number: US722016A
Authority: US
Inventors: Robert D Krehbiel
Original assignee: Cessna Aircraft Co
Current assignee: Cessna Aircraft Co
Priority date: 1968-04-17
Filing date: 1968-04-17
Publication date: 1970-12-22
Anticipated expiration: 1987-12-22

Description

Dec. 22, 1970 R. D. KREHBIEL CYLINDER WITH INTEGRAL ACCUMULATOR Filed April 17, 1968 IIILIHUIIII I I INVENTOR. ROBERT D. KREHBIEL United States Patent Oihce 3,548,573 CYLINDER WITH INTEGRAL ACCUMULATOR Robert D. Krehbiel, Hutchinson, Kans., assignor to The Cessna Aircraft Company, Wichita, Kans., a corporation of Kansas Filed Apr. 17, 1968, Ser. No. 722,016 Int. Cl. A01d 67/00 US. Cl. 56208 Claims ABSTRACT OF THE DISCLOSURE A linear hydraulic cylinder having a pressure charged accumulator integrally formed in the cylinder. The accumulator applies a continuous load moving force on the cylinder piston so that the hydraulic pressure necessary to actuate the piston under a heavy load is substantially reduced.

In many applications, hydraulic cylinders are required to continuously support or lift a very heavy load. Requirements of this type consume a large amount ofenergy in maintaining a constant high pressure in the cylinder to counterbalance the static load and even higher pressures to lift the load. The primary purpose of the present invention is to reduce the pressure requirements of such a system by the use of a pressurized accumulator which acts as a counterbalance to the weight of the load. With a substantial part of the static load counteracted by the accumulator, the system pressure necessary to raise and lower the cylinder is very slight. Another function of the integral accumulator is that of a shock absorber. When the cylinder is supporting a heavy load, on a moving vehicle for example, the jolts and bumps are absorbed by the compressible chamber of the accumulator rather than directly transmitted through an uncompressible fluid system.

While the present invention may be used in many other applications, it has particular utility as'a table cylinder for supporting and positioning the header unit on a selfpropelled combine. The massive header unit, which includes the harvesting mechanism, is pivotally mounted on the vehicle so that it can be raised and lowered with respect to the ground by said cylinder or a pair of cylinders.

Previous attempts to counterbalance the weight of the header with mechanical springs and separately mounted gas accumulators have met with very limited success in light of their cumbersome size, added equipment, and space requirements. The integral cylinder-accumulator of the present invention is completely interchangeable with any normal table cylinder without any additional space and equipment requirements.

It is therefore the principal object of the present invention to provide an improved linear hydraulic cylinder having a gas or liquid accumulator integrally formed therewith to counterbalance the load requirements of the cylinder.

Another object of the present invention is to provide an integral cylinder-accumulator which is readily interchangeable with a conventional table cylinder.

A further object of the invention is to provide a hydraulic cylinder with a shock absorbing compressible chamber integrally contained therein.

Further objects and advantages of the invention will be apparent when the following description is read in connection with the accompanying drawings in which:

FIG. 1 is an axial sectional view through the integral cylinder unit which incorporates the invention, with a conventional control system schematically illustrated;

3,548,573 Patented Dec. 22, 1970 FIG. 2 is an axial sectional view through a modified form of cylinder with an improved control system schematically illustrated; and

FIG. 3 is a symbolic side elevational view of a header unit on a combine.

Referring to FIG. 1 of the drawings for a detailed description of the invention, the integral cylinder-accumulator is generally identified by reference numeral 10. The cylinder 10 is made up of a cylinder barrel 12 closed at one end -by a fixed head 13. Slidably positioned in the cylinder bore 14 is a piston 15. Recessed in the circumference of bore 14 is a conventional O-ring seal 16 preventing leakage between the piston and the bore. Snap ring 17 limits the outer extension of piston 15 when it abuts shoulder 18 of a counter bore 21. Longitudinally disposed in piston 15 is an axial bore 19 containing a floating pin or plunger 20. The enlarged head of pin 20 separates the working chamber 21 of the cylinder 12 from a gas-charged accumulator chamber 22. Snap ring 28, recessed in the bore 19, contacts the enlarged head of pin 20 as piston 15 approaches the outer end of its stroke.

Conventional seals

23 and 24 prevent the leakage of gas or fluid from the accumulator chamber 22 into the chamber 21. Passage 25 connects chamber 22 to a conventional charging valve 26. Sleeve 27, surrounding the valve, protects it against possible injury. Motive fluid is supplied to the cylinder working chamber 21 from a fluid pressure source 30 via a directional control valve 32 and fluid entry port 29. Fluid is returned from the cylinder to drain 36 when valve 32 is moved to the left. Both the head and rod end of the cylinder 10 are provided with

pivotal mounting lugs

33 and 34 respectively.

FIG. 3 symbolically illustrates the cylinder 10 operatively connected to header unit 11 of a self-propelled combine.

OPERATION OF FIG. 1 EMBODIMENT In operation, the cylinder 10 is pivotally attached to a vehicle (not shown) by lug 33, while the lug 34 on the rod end of the cylinder is attached to the header or whatever the movable load might be. Prior to actuating the cylinder 10, the gas accumulator chamber 22 is precharged to a relatively high pressure through valve 26. The charging pressure causes pin 20 to move to the left until it contacts the head 13 of the cylinder.

To actuate the cylinder 10, valve 32 is moved to the right allowing fluid from pressure source 30 to flow into the working chamber 21. The pressure necessary to actuate piston 15 is substantially reduced due to the pressure in accumulator chamber 22. For example, if the accumulator chamber is pre-charged with 1000 p.s.i. (area of 1 sq. in), the static weight of the header being 12.00 lbs. (effective area of piston 15 being 4 sq. in.), it would re-g quire a pressure in working chamber 21 of only 50 p.s.i. to actuate the cylinder and raise the header. In a conventional cylinder it would require a pressure of 240 p.s.i. to lift the same load. The charging pressure in the accumulator chamber 22 can, of course, be varied so that the efiective force exerted by pin 20 against head 13 does not exceed the static load on the cylinder. As piston 15 moves to the right from its FIG. 1 position, the accumulator pressure causes pin 20 to remain in contact with head 13. Once the header or other load is lifted to the desired position, valve 32 is moved to its middle position locking fluid in the cylinder working chamber 21. In operating position, with the piston 15 positioned approximately at its midstroke, the pin 20 acts as a shock absorber to the system when, as frequently happens, the header hits a high spot on the ground. With a conventional cylinder the damaging shock could not be absorbed, but with the present cylinder, pin 20 moves to compress the gas chamber 22 and absorb the shock.

FIG. 2

The integral cylinder-accumulator 40 shown in this figure has a modified form of fluid accumulator and is operated by an automatic header height control System42.

Cylinder 40 includes a barrel 43, head 44, with a piston 45 slidably positioned in bore 46 to define a working chamber 47. Recessed in the circumference of bore 46 is a conventional seal 48. Snap ring 49 limits the outer travel of piston 45 when it contacts shoulder 51. Longitudinally disposed in piston 45 is a bore 52 containing a floating pin 50. Pin 50 exerts a continuous force on head 44 due to the pressure in accumulator chamber 53. Chamber 53 is supplied with a source of fluid from an auxiliary pump 54, which is maintained at a constant pressure by a. relief valve 55, and a spring actuated accumulator 6.

The automatic header height control system includes a mechanical feeler 57 mounted on the header which senses the height of the header above the ground surface. Fluid pressure source 58 supplies a continuous flow through a variable restriction valve 60 via directional control valve 61 and reservoir 63. The cylinder working chamber 47 is subjected to the fluid pressure immediately upstream from restriction valve 60, via conduit 62. As valve 60 becomes more restrictive, the pressure increases in chamber 47.

The cylinder embodiments shown in both FIGS. 1 and 2 are most advantageously used when the cylinder is continuously supporting the static weight of the header, as in the automatic system of FIG. 2. In the conventional control system of FIG. 1, the counterbalancing advantage of the cylinder is mitigated because for a good part of the time the valve 32 is in the center lock-out position.

OPERATION OF FIG. 2 EMBODIMENT When valve 61 of the automatic header height control is moved to the left of the FIG. 2 position, fluid begins to continuously flow from source 58 to reservoir 63 across restriction valve 60. If the header is too high above the ground, feeler 57 pivots clockwise signaling valve 60 to decrease the restriction. The decrease in restriction decreases the pressure in cylinder working chamber 47 via conduit 62 causing piston 45 to retract and lower the header until feeler 57 comes in contact with the ground. When the header is too near the ground, the feeler 57 rotates in the opposite direction, causing the valve 60 to increase the restriction, thus causing pressure in the cylinder working chamber 47 to increase, extending the piston 45 and raising the header.

When valve 61 is in the center position, as illustrated, the fluid is locked in the cylinder with the weight of the header cut-off from the pressure source 58. If valve 61 is moved to the right of the illustrated position, the entire fluid flow is directed into working chamber 47 as in the conventional FIG. 1 system.

The operation of the cylinder 40 is the same as described in connection with FIG. 1, with the floating pin 50 supporting a majority of the header weight, thereby requiring a very low pressure in working chamber 47 to actuate the cylinder.

As piston 45 is extended pin 50 continues to exert a lifting force against head 44 because of the fluid pressure in expanding accumulator chamber 53. Accumulator pump 54 and relief valve 55 maintain a constant pressure in chamber 53 as the pin 50 extends. Any shock loads on the cylinder, or rapid movement of piston 45, is compensated by the spring-loaded accumulator 56. While the FIG. 2 embodiment does not have the advantage of a selfcontained accumulator unit, it does have the advantage over FIG. 1 of a constant accumulator pressure at any position of the accumulator pin.

Having described the invention with suflicient clarity to enable those familiar with the art to construct and use it, I claim:

1. A combination hydraulic cylinder and accumulator com risin a cylinfier barrel defining a fluid working chamber closed at one end and having a reduced d1ameter piston rod aperture at the opposite end;

a fluid port in the cylinder barrel for supplying motive fluid to the working chamber;

a piston means positioned within the cylinder barrel for reciprocal movement, with a rod portion extending through said aperture in sealing relat1on;

a blind axial bore in said piston means closed at one end opening into the working chamber at the opposite end;

a floating pin slidably positioned in sealing relation within the axial bore, defining an expansible pressure chamber in said bore extending between said bore closed end and the inner end of the pin; and

means for introducing pressure through said rod mto said pressure chamber providing an accumulator for absorbing shock loads imposed on the cylmder and whereby said pin is urged against the closed end of the cylinder barrel and a resultant counterbalanclng force is imposed on the piston when the pressure in the accumulator exceeds that in the working chamber.

2. A combination cylinder and accumulator as set forth in claim 1 in which the means for introducing pressure into said pressure chamber includes a charging valve in the rod portion of the piston means, connected to the precharged pressure chamber.

3. A combination cylinder and accumulator as described in claim 1 in which the means for introducing pressure into said pressure chamber includes an inlet port through a wall of said piston means which is located out side the cylinder barrel when said piston means is at the innermost end of its stroke, said inlet port being in open communication with said pressure chamber.

4. The assembly described in claim 3 further including:

a source of fluid pressure in continuous communication with said inlet port to maintain a desired pressure in said expansible pressure chamber; and

means communicating with said expansible pressure chamber limiting pressure therein to a predetermined maximum.

5. In an automatic header height control system which includes a continuous source of fluid pressure ducted through a variable restriction valve and returned to the source, a mechanical height sensing feeler operatively connected to said variable restriction valve to vary the restriction as the feeler moves in response to the contour of the ground, a cylinder motive fluid line in fluid communication with the pressure source upstream of the restriction valve, subject to the varying back pressure created by the restriction valve, the improvement comprising:

a cylinder barrel defining a fluid working chamber having a fixed head at one end and a piston rod aperture at the opposite end;

a fluid port in the cylinder barrel connected to said motive fluid line for supplying fluid to the working chamber;

a piston means positioned wtihin the cylinder barrel for reciprocal movement, with the rod portion extending through said aperture in sealing relation;

a blind axial bore in said piston means extending longitudinally thereof, and opening into said working chamber;

a floating pin slidably positioned within the open end of said axial bore and extending into contact with the fixed head of the cylinder barrel, and defining an expansible accumulator pressure chamber at the enclosed end of the pin; and means for introducing pressure into the accumulator pressure chamber providing an accumulator for absorbing shock loads im- 5 posed on the cylinder and whereby said pin is urged 3,309,852 3/1967 Allen 56208 against the closed end of the cylinder barrel and a 2,186,266 1/1940 Onions 244-102 resultant counterbalancing force is imposed on the 2,679,827 6/1954 Perdue v 92--8 piston when the pressure in the accumulator exceeds 3 1 305 19 5 Lorimer 9 37 that in the Working chamber- 5 3,353,352 11/1967 Gardner 6051 References Cited UNITED STATES PATENTS 2,669,972 2/1954 Cross 91-207 3,088,264 5/1963 Sallee 56210 10 ANTONIO F. GUIDA, Primary Examiner