US3003659A

US3003659A - Collapsible reservoir

Info

Publication number: US3003659A
Authority: US
Inventors: Prentice M Miller
Original assignee: Clark Equipment Co
Current assignee: Doosan Bobcat North America Inc
Priority date: 1958-09-11
Filing date: 1958-09-11
Publication date: 1961-10-10
Anticipated expiration: 1978-10-10

Description

Oct. 10, 1961 P. M. MILLER 3,003,659

COLLAPSIBLE RESERVOIR Filed Sept. 11, 1958 FIG. I

INVENTOR.

PRENTICE M. MILLER United States Patent f 3,003,659 COLLAPSIBLE RESERVOIR Prentice M. Miller, Battle Creek, Mich., assignor to Clark Equipment Company, a corporation of Michigan Filed Sept. 11, 1958, Ser. No. 760,396 1 Claim. (Cl. 220-85) This invention relates to reservoirs and more especially to collapsible reservoirs particularly adapted for use in hydraulic systems.

Frequently, indoor industrial vehicles, such as industrial lift trucks, are required to operate in manufacturing areas wherein a corrosive, highly dust laden, or otherwise contaminated atmosphere is present. Heretofore, exended use of such vehicles in contaminated atmospheres has often resulted in damage to parts of the vhicles hydraulic system. Hydraulic systems for industrial lift trucks usually include in a closed circuit an oil reservoirs, one or more hydraulic pumps, and various hydraulic motors such as a piston and cylinder assembly for lifting a load on an upright mast located adjacent one end of the vehicle and others for tilting the mast. The oil reservoir of such a system has heretofore been vented to the atmosphere so that atmospheric pressure is maintained above the surface of the hydraulic oil in the reservoir irrespective of variations in the volume thereof which, of course, varies from a maximum to a minimum depending upon whether one or more hydraulic devices in the circuit are in operation. With such an arrangement air from the atmosphere is drawn into the reservoir as the volume of liquid therein decreases.

In an atmosphere which is contaminated by corrosive elements, eventual damage to the hydraulic devices through which the hydraulic fluid flows will usually be caused as a result of absorption of such elements by the hydraulic fluid.

I have devised a simple but extremely effective construction, by means of which such harmful result is avoided. According to this invention I provide an expansible and contractible bladder element which is sealinly connected with the reservoir of such an hydraulic system. The bladder element is located to communicate with the air space above the liquid contained in the reservoir so that the bladder automatically contracts and expands as the liquid level lowers and rises, respectively.

It is an important object of this invention to provide a collapsible container connected to a reservoir in an hydraulic system for the purpose of maintaining adequate gas pressure above the liquid level in the reservoir while sealing the reservoir from communication with the surrounding atmosphere.

It is another object of this invention to seal a liquid reservoir from communication with the surrounding atmosphere while providing means associated with the reservoir for minimizing variations in pressure in the air space of the reservoir with variations in the volume of liquid contained therein.

Referring now to the drawing, a liquid reservoir is represented by the numeral 10, the liquid therein by the numeral 12, and the air space thereof by the numeral 14. A pump 16 communicates with the liquid 12 through the suction pipe 18 and a filter 20 for pumping pressurized fluid to one or more hydraulic devices, not shown, connected between a pressure discharge conduit 22 and a low pressure return line 24. Line 24 is connected to a 3,003,659 Patented Oct. 10, 1961 conduit 26 which conducts low pressure return liquid back to the reservoir 10.

A frame or screen 28 extends upwardly from the reservoir and is connected to the upper surface thereof. Within the frame 28 is mounted a flexible bladder member 30, which may be of rubber or plastic, for example, the bladder having an open section 32 therein which is secured in sealed relation with a cylindrical wall 36 by means of a ring 34. The wall 36 forms an aperture 38 in the upper Wall of the reservoir 10, whereby the space internal of bladder member 30 is in continuous and free communication with air space 14. A valvular means 40 is connected to bladder 30, and may, for instance, be of the type used with the inner-tubular members of tires and the like. Valvular means 40 may be used to control the gas or air pressure internal of bladder 30 at any given ambient temperature and pressure con dition and when the liquid 12 fills the reservoir to a given level.

In operation the bladder 30 will collapse as the level of liquid 12 is lowered during operation of pump 16 and will expand as the liquid level is raised. Preferably, the bladder element should be capable of sufl'icient change in volume to maintain substantially constant the pressure in space 14 during a change in volume of the liquid in the reservoir between maximum and minimum.

Although the construction of my device is simple, which in itself is a virtue, it solves a long standing problem by aflording a reservoir for hydraulic systems which is sealed from communication with surrounding contaminated atmosphere and in which the air or gas space tends to remain at a relatively fixed pressure despite variations in the level of liquid therein.

'11: will also be readily apparent to persons skilled in the art that a second beneficial result may be realized by my construction if the bladder element is initially pressurized an amount which is substantially equal to or somewhat greater than the suction head of the pump 16. The result of such pressurization has the effect of neutralizing the suction head of the pump; i.e., allowing the suction side of the pump to operate at a zero or positive gage pressure rather than at a negative gage pressure, thus eflecting an increase in pump efl'iciency.

Although only one embodiment of the invention has been illustrated and described, various changes in the form and relative arrangement of the parts may be made to suit requirements.

I claim:

A hydraulic supply system for vehicles operating in contaminated atmosphere comprising a closed rigid reservoir containing sealed from the surrounding atmosphere and containing hydraulic fluid, a gaseous fluid contained in the space of the reservoir above the level of the hydraulic fluid, a flexible bladder-like reservoir containing such gaseous fluid and adapted to expand and contract its volume to minimize variations in pressure therein under certain conditions, a rigid passage connected to the rigid reservoir and extending into the flexible reservoir for continuously communicating the gaseous fluid in the flexible reservoir with the gaseous fluid in the rigid reservoir, said flexible reservoir having a flexible opening for receiving said rigid pasage, said opening being formed of an annular loop, a sealing ring received in said annular loop for sealing said flexible opening with respect to said rigid passage, variations in the level of hydraulic gaseous fluid pressure in the supply system is maintained while said system is sealed from contamination by the atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS Bessesen Oct. 16, 1923 Perry Dec. 13, 1927 Johnson Oct. 30, 1928 Kindl Mar. 28, 1939 Knauth July 21, 1942 Johnson Apr. 18, 1944 Shriro Aug. 13, 1946 Amidon Sept. 1, 1953 Fletcher Oct. 12, 1954 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No. 3,003,659 October 1O 1961 Prentice M. Mil 'ler It is h'ereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column l',fl.lines 18 and 19 for "reservoirs" read reservoir column 2, line 51, strike out "containing.,

Signed and sealed this 3rd day of April 1962.

(SEAL) Attest:

ERNEST W. SWIDER I DAVID L. LADD Attesting Officer Commissioner of Patents