US3693500A

US3693500A - Fluid pressure controlled power unit

Info

Publication number: US3693500A
Application number: US41857A
Authority: US
Inventors: Stanley C Crandall; David B Puryear
Original assignee: Gilbert and Barker Manufacturing Co Inc
Current assignee: Gilbarco Inc
Priority date: 1970-06-01
Filing date: 1970-06-01
Publication date: 1972-09-26
Anticipated expiration: 1989-09-26

Abstract

An air powered, oil controlled power unit including a cylinder having a plunger and control valve mounted for reciprocation therein. Air from a supply source pressurizes a liquid within the plunger for displacement thereof, upon opening of a control valve by air pressure, by permitting the oil to flow from within the plunger into the cylinder. Closing of the valve immediately stops plunger displacement. The unit is provided with a displaceable, automatically controlled safety latch and a leg member to prevent rotation of the plunger relative to the cylinder. A float assembly cooperates with the valve to prevent elevation of the plunger when the oil level within the unit drops below a predetermined point.

Description

United States Patent Crandall et al.

[4 1 Sept. 26, 1972 [54] FLUID PRESSURE CONTROLLED POWER UNIT [72] Inventors: Stanley C. Crandall, Greensboro,

NC. 27408 David B. Puryear, Summerfield, NC. 27358 [73] Assignee: Gilbert 7 8r Barker Minfic'hirifig" Company, New York, N.Y.

[22] Filed: June 1, 1970 [21] Appl. No.: 41,857

[52] US. Cl. ..91/4 A, 92/24 [51] Int. Cl. ..FlSb 21/04, FlSb 15/26 [58] Field of Search ..91/4 R, 4 A; 92/24 [56] Reierences Cited UNITED STATES PATENTS 2,471,989 5/1949 Weaver ..91/4 2,637,302 5/1953 Harrison et al. ..91/4 2,638,075 5/1953 Towler ..91/4 3,001,512 9/1961 Cohin ..91/4 3,060,900 10/1962 Pelouch ..91/4 3,447,421 6/1969 Pelouch ..91/4

FOREIGN PATENTS OR APPLICATIONS 107,350 5/1939 Australia ..91/4

Primary ExaminerPaul E. Maslousky Attorney-David Rabin [5 7] ABSTRACT An air powered, oil controlled power unit including a cylinder having a plunger and control valve mounted for reciprocation therein. Air from a supply source pressurizes a liquid within the plunger for displacement thereof, upon opening of a control valve by air pressure, by permitting the oil to flow from within the plunger into the cylinder. Closing of the valve immediately stops plunger displacement. The unit is provided with a displaceable, automatically controlled safety latch and a leg member to prevent rotation of the plunger relative to the cylinder. A float assembly cooperates with the valve to prevent elevation of the plunger when the oil level within the unit drops below a predetermined point.

2 Claims, 4 Drawing Figures FLUID PRESSURE CONTROLLED POWER UNIT BACKGROUND, BRIEF SUMMARY AND OBJECTS OF THE INVENTION This invention relates to a fluid controlled power unit for supporting heavy loads, and of the type comprising a cylinder and plunger assembly, partially filled with hydraulic fluid, and compressed air control means for regulating the flow of hydraulic fluid between the interior of the cylinder and the interior of the plunger.

The power unit is particularly adapted for lifting and lowering automobiles for servicing them by securing a super structure to the upper end of the power unit.

Present automotive lifts are generally of two basic types, semi-hydraulic lifts which use air pressure for lifting power, and full hydraulic lifts which use air pressure to pressurize oil. The present full hydraulic lifts utilize large tanks either buried under the ground or set in a remote location for pressurizing the oil. However, the installation of such lifts is expensive due to the external tank. The present semi-hydraulic lifts normally have fluid piped through a flanged portion at the bottom of the casing of the power unit. Such units are difficult and expensive to remove and install due to the external piping. In addition, the semi-hydraulic lifts do not have the ability to stop at intermediate heights with any accuracy due to the air inside the lift which, when the valve is closed, must be expanded before the lift can be stopped.

The controlled air lift of the present invention is basically a semi hydraulic lift including an air actuated hydraulic valve for controlling the ascent and descent of the lift. Air supply lines pass between the cylinder and plunger walls for pressurizing oil in the plunger and for actuating the valve which is mounted on the plunger. With the valve opened, hydraulic fluid flows between the plunger and cylinder for displacing the plunger upwardly or for permitting the plunger to lower depending upon the pressure within the plunger and cylinder. When the plunger has reached the prescribed height, the air actuated hydraulic valve is closed stopping the lift immediately. A safety latch, associated with the air supply line controlling the air actuated valve, is retracted automatically during displacement of power unit is provided with an internal anti-rotationdevice, and a float assembly for preventing hydraulic fluid flow through the air actuated hydraulic valve when hydraulic fluid within the power unit falls below a predetermined level. In addition, a plug is located within the top plate of the plunger so that compressed air within the plunger can be tapped and supplied to drive air actuated tools.

One of the primary objects of the invention is the provision of a power unit for lifting heavy loads in which compressed air or other similar elastic fluids are utilized in conjunction with oil or similar inelastic fluids to positively and accurately control the plunger of the power unit.

Another object of the invention is the provision of an air-powered, oil-controlled power unit wherein fluid is piped into the top of the power unit cylinder eliminating external piping to the lower portion of the power unit thereby facilitating installation and removal of the unit.

A further object of the invention is the provision of a novel safety device for preventing actuation of the power unit plunger when the level of the liquid therein falls below a predetermined level.

An important feature of the invention is the provi-v sion of a power unit having an automatically controlled safety latch located internally of the unit to lock the plunger in prescribed positions.

Another feature of the invention is a power unit provided with an elastic fluid actuated, hydraulic valve mounted interally thereof for positively trapping the hydraulic fluid to hold the plunger at rest in an elevated position.

Still another feature of the invention is an airpowered, oil-controlled power unit that is safe in opera-.

tion, readily installed or removed, and maintained with minimum expense.

Other objects and advantages of the invention will become apparent during the course of the following description.

BRIEF DESCRIPTION OF THE FIGURES DETAILED DESCRIPTION OF THE INVENTION I Referring to the drawing, the improved power unit 10 comprises, in general, a cylinder 12 having a lower end closure 14 and an upper casing head 16; a piston or plunger 18 recriprocable within the cylinder 12 and protruding through the upper casing head 16; and compressed air conduits for pressurizing a body of hydraulic fluid A confined within the plunger and the cylinder and for actuating a valve 20 for controlling the flow of hydraulic fluid A between the plunger 18 and the cylinder 12.

The cylinder or casing 12, preferably formed of black iron pipe or equivalent materials, has the lower closure 14 secured therein by welding while the upper end of the cylinder 12 receives a casing head 16. The casing head 16 includes a bearing 24, an outer ring member 26 welded to cylinder 12 and a wiper retaining member 22 secured to bearing 24 by fasteners 23. The bearing 24 is positioned atop the cylinder 12 and sealed by an O-ring 28. The outer ring member 26 is provided with a recess 25 for receiving a retaining ring 27 which is snapped in position for trapping the bearing 24. The wiper retaining member 22 and bearing 24 have wiper members 30 and. 34 supported therein for slidably engaging the outer wall of plunger 18 to prevent foreign material from contacting seal 32. Bearing 24 has seal 32 supported therein for slidably engaging the outer wall of plunger 18 to prevent leakage of hydraulic fluid during reciprocation thereof. In addition, seal 33 is located intermediate the outer ring member 26 and wiper retaining member 22.

To prevent rotation of the plunger 18 relative to cylinder 12, a channel or U-shaped anti-rotation leg 36 is secured within the cylinder 12 for cooperation with the lower bearing 38 of the plunger. The anti-rotation leg 36 extends vertically to a point approximately one foot below the top of the cylinder 12 for slidably guiding the notched bearing 38 which is secured to the plunger 18 for slidably engaging the cylinder inner walls.

The reciprocable plunger 18, also preferably constructed of black iron pipe, has a ring 40 recessed within one end of the plunger a distance sufficient to permit nylon air supply hoses to be positioned beneath it when the plunger is in a lowered position. The ring 40 is secured to the inner wall of plunger 18 by a weld 42. A bottom plunger plate 44 is secured by bolts 46 or other suitable fasteners beneath the ring 40 as shown by FIG. 1. The bottom plate 44 which is sealed to the ring 40 within an O-ring 48 can be removed easily to facilitate repair of various components. An upper plunger'ring 50 is recessed slightly within plunger 18 and welded thereto for receiving the top plunger plate 52 fastened thereto by bolts 54. A sealing ring 56 is located between the ring 50 and plate 52. The top plunger plate 52 has an opening 58 provided therein in a pipe coupling 60 welded thereto. A plug 62, threaded into coupling 60 may be removed to check the level of hydraulic fluid within the plunger, or the plug may be removed and a conduit secured to coupling 60 so that pressurized air in the plunger above the hydraulic fluid level could be tapped to provide a source of pressurized air to drive various pneumatically operated tools.

Although not clearly shown in FIG. 3, the bearing 38, welded to the outside of the plunger, is provided with diametrically opposed notches or slots. One slot engages the anti-rotation leg 36 to keep the plunger from rotating, while the other slot allows

air inlet pipes

64, 66 to pass between the inner wall of cylinder 12 and the outer wall of plunger 18. A stop ring 68, also slotted in the same areas the bearing 38 is slotted, is welded to the exterior of the plunger 18 for engaging the cylinder head 16 to limit the upward travel of the plunger.

The valve for controlling the flow of hydraulic fluid A between the interior of the plunger 18 and the cylinder 12 is mounted above the plunger bottom plate 44 for reciprocation therewith. The plate 44 has a ring 70 welded thereto and a plurality of small holes 72 therethrough located inside the ring 70. The valve 20 is held to the ring 70 with a snap ring 74 and sealed with an O-ring 76. The valve body 78, having the upper end sealed by a plug 82, houses a piston 80 having a portion 84 which seats with the lower end of the valve body. A spring 86 normally holds the valve in the closed position, however, when air enters through plug 82 and into chamber 88, the piston head 90 pushes the portion 84 downwardly permitting hydraulic fluid to flow through openings 92 in the valve body. Preferably the valve body is made from an acetal resin and the valve piston from stainless steel in order to provide a hard piston in a softer valve seat area not susceptible to corrosion.

In the event the hydraulic fluid A within the plunger 18 falls below a predetermined level, a safety mechanism cooperates with the valve 20 to prevent displacement of the plunger 18 within the cylinder 12. The safety mechanism includes a metallic sleeve 94 and float member 96 which are secured together and placed around the body 78 of valve 20. When the level of the hydraulic fluid A within the plunger 18 becomes low, the float, which is made of a foam material, will drop down covering the openings 92 of the valve body shutting off fluid flow between the plunger and cylinder even when the valve is opened thus stopping displacemerit of the plunger. A ring member 98 fixed to valve body 78 limits upward displacement of the float member 96 when the plunger is sufficiently filled with hydraulic fluid.

Air under pressure is utilized for controlling the operation of valve 20 and for pressing upon the hydraulic fluid A for forcing the hydraulic fluid from within the plunger 18 into the cylinder 12 when the valve 20 is open.

Compressed air is supplied from an external source, not shown, through valve 100, into conduit 104, through air supply junction block 105, through conduit 64 which passes between the cylinder and plunger walls, through junction block 107 and through coiled, flexible nylon hose 110. From nylon hose 110 the air under pressure passes through an opening in plunger plate 44 and upwardly through air pipe 112. The air pipe 112 which extends to a height above the level of hydraulic fluid A has its lower end secured to plate 44 while the upper open end is attached to the plunger upper ring 50 by a clamp member 114. The valve 100 is v a conventional three position, three way valve that can be locked in any one of the neutral, pressure and exhaust positions. The air supply through pipe 112 to the upper part of plunger 18 can be left on for serving as a source of compressed air for operating various tools attached to coupling 60.

For actuating the control valve 20 which is located internally of plunger 18, air is supplied from an external source through valve 102, conduit 106, junction block 105, conduit 66, coiled nylon hose 108, safety device 116, and air line 118 into the valve body 78. Control valve 102 is a conventional two position valve that is spring loaded to return to the exhaust position thereby providing a dead man operation for the control of the plunger 18. When the valve 102 is opened, air forces the valve piston downwardly compressing spring 86 and permitting hydraulic fluid A to flow through opening 72 and the lower plate 44 of plunger 18 thereby displacing the plunger. Whenever the valve is released, it will exhaust air from the internal control valve 20 thereby closing the valve 20 and stopping displacement of the plunger 18.

The valve 20 is designed so that fluid pressure inside the power unit at any point will close the valve regardless of whether or not the spring 86 is functioning properly. If the plunger 18 is in an elevated position and the air pressure in the top of the plunger, above the level of hydraulic fluid A, is evacuated, the fluid pressure on the bottom of the valve piston portion 84 is great enough to close the valve. If the plunger 18 is pressurized with air, the area on the upper part 88 of the valve piston is greater than the area of the lower piston portion 84, insuring closure of the valve. The spring 86 is not necessary for normal operation of the valve. However, if the plunger 18 is operated in an unloaded condition, the fluid pressure inside the power unit may not be great enough to operate the valve satisfactorily. Therefore, the spring is added to insure closure of the valve 20 at low operating pressures. The speed of the plunger 18 is controlled by the small opening 72 within plunger plate 44.

The power unit is provided with an automatic bleed tube 120 as shown by FIG. 1. The tube 120 has its lower end 122 secured by a clamp 124 on plate 44 adjacent a low pressure area within the cylinder adjacent opening 72. They tube passes through a slot in the plunger and extends vertically between the plunger and cylinder walls, similar to

conduits

64, 66 to a point adjacent the stop ring 68 where it is secured by suitable means to the exterior of plunger 18.

The power unit 10 incorporates an internal safety latch mechanism 116 thereby eliminating conventional external safety legs. The tamper proof, safety latch mechanism 116 is automatically controlled upon actuation of valve 20. The latch 116, mounted under the bottom plunger plate 44 for displacement therewith, includes a lock member 126 mounted for reciprocation within a U-shaped bracket 128 and through an opening 130 in the wall of plunger 18 where it normally slides along anti-rotation leg 36. When the plunger 18 is toward the upper limit of travel the lock member 126 will extend out over the top portion 132 of leg 36, due to the action of coil spring 134, and due to the fluid pressure within the cylinder 12 acting upon the outer surface 137 of piston 138 thereby trapping the plunger 18 in a raised position. A connecting rod 136 fastens the lock member 126 to piston 138 located within a block member 140 secured to plate 44. The spring 134 acts between the block 140 and lock member 126 and normally forces the lock member 126 to an extended position. The control air passing from the nylon hose 108 to air line 118 and valve passes through a chamber 142 within the latch block 140 for withdrawing the lock member 26 during displacement of the plunger 18. The air pressure in line 108, which has one end connected to block 140, pushes the piston 138 to the right, as shown in FIG. 1, and pulls the lock member 126 to an unlatched position. This happens each time the valve 102 is opened in order to displace plunger 18. When the control air pressure is removed from valve 20, thereby stopping and locking the plunger, the air is also evacuated from the chamber 142 of the latch block 140. The spring 134 between the block 140 and lock member 126 and pressure of fluid A on piston surface 137 return the latch to the extended position and, if above the anti-rotation leg 36, locks the plunger 18 into position.

The safety mechanism 144 is provided to disengage the safety latch assembly 116 in the event a control air signal through

conduits

108, 118 cannot be provided to unlatch the lock member 126. The safety mechanism includes a release rod 146 having the upper end 148 mounted for rotation within bearing 24 and having a tab 150 secured to the lower end. The rod and tab are normally biased against the cylinder inner wall by a spring 152. However, when the rod 146 and tab 150 are rotated 90 degrees against the bias of spring 152, the tab 150 pushes the safety latch member 126 to a disengaged position. In order to rotate the rod 146, the bleed screw 154 and ball 156 must be removed from the ring 22. At this time, a socket head screw wrench can be placed in the socket head screw 158 secured to the top of release rod 146 for rotating the rod The manual bleed screw normally is threaded into ring 22 and seats sealing ball 156 to close an opening 160 in bearing 24. Bleed screw 154 has openings 162 provided therein for permitting air to pass therethrough when the screw is rotated slightly and released from engagement with ball 156.

To operate the plunger, air supply valve is opened allowing air to flow through

conduit

104 and 64, coiled hose 110, up through air pipe 112 and into the plunger 18 above the hydraulic fluid A therein. This pressurizes the hydraulic fluid A in the plunger 18. However, the lift will not move since the valve 20, which is the only opening between the plunger 18 and cylinder 12, is normally closed. When valve 102 is opened, air will flow through

conduit

106 and 64, coiled hose 108, through chamber 142 of safety latch mechanism 116, through air line 118 and into valve 20. The valve 20 then will open allowing hydraulic fluid A to flow from the plunger through openings 92 and 72 into the cylinder 12 thus acting upon plate 44 and forcing plunger 18 upwardly. When the plunger has been displaced upwardly a desired distance, the control valve 102 is switched to the exhaust position thus evacuating chamber 88 of valve 20 and permitting the valve to close stopping the plunger at once. Therefore, the plunger 18, when displaced upwardly to any position, is supported by a column of hydraulic fluid A below plate 44, rather than air. The plunger 18 will rise no further, even if the air supply valve 100 is in the open position. The valve 100 now can be either left on, moved to a neutral position so that air cannot flow in either direction, or turned to exhaust. The ability of the plunger to remain in a fixed position'is dependent only upon the internal valve 20, not on the air supply into the plunger. Also it is to noted that once pressurized air enters the various conduits and hose leading to valve 20, the lock member 126 is automatically retracted from opening 130 due to air pressure in chamber 142. When such air pressure is exhausted, spring 134 forces the lock member back through opening 130. If the plunger is in an elevated position the member 126 will protrude over the upper portion 132 of leg 36 serving as a safety lock. During upward displacement of the plunger, the coiled nylon hoses 108, are extended. Also, the anti-rotation device prevents the bottom bearing 38 from crushing the air supply tubes running down the inside of the cylinder.

To lower the plunger 18, air supply valve 100 is turned to exhaust air from within plunger 18 and then the control valve 102 is operated to supply air to internal valve 20. The valve opens permitting fluid to flow from within the cylinder 12 into plunger through openings 72 and 92. Again, when the plunger has been lowered to a selected position due to a load acting thereon, the control valve 102 is turned to exhaust and the valve 20 will close, stopping the plunger. Each time the valve 20'is opened, the safety latch mechanism 116 will disengage and allow the lift to be raised or lowered.

We claim:

1. In a fluid pressure actuated power unit for lifting and lowering heavy loads; a cylinder, a plunger mounted for reciprocation within said cylinder, means on the upper end of said plunger for mounting a support member thereon, said cylinder and said plunger containing an inelastic fluid therein, means for introducing fluid pressure into said plunger above the level of inelastic fluid contained therein, elastic fluid operated means, positioned within the confines of said cylinder, regulating inelastic fluid flow between said plunger and said cylinder for accurately controlling the position of said plunger relative to said cylinder, said elastic fluid operated means including a fluid actuated valve, and means for directing fluid flow to and from said valve, and a safety latch means for trapping said plunger in a raised position, said means for directing elastic fluid flow to and from said valve cooperating with said latch means for automatically retracting said latch means during displacement of said plunger and for permitting displacement of said latch means to a locking position after displacement of said plunger to a prescribed location.

2. In a fluid pressure actuated power unit for lifting and lowering heavy loads; a cylinder, a plunger mounted for reciprocation within said cylinder, means on the upper end of said plunger for mounting a support member thereon, said cylinder and said plunger containing an inelastic fluid therein, means for introducing fluid pressure into said plunger above the level of inelastic fluid contained therein, an elastic fluid operated means, positioned within the confines of said cylinder, regulating inelastic fluid flow between said plunger and said cylinder for accurately controlling the position of said plunger relative to said cylinder, said elastic fluid operated means including a fluid actuated valve, and means for directing fluid flow to and from said valve, said means for introducing fluid pressure into said plunger above the inelastic fluid level and said means for directing elastic fluid flow to and from said valve includes a plurality of discrete conduit means positioned intermediate said cylinder wall and said plunger wall and a plurality of coiled, flexible hoses located within said cylinder.

* III II l