US3060900A - Vehicle lifting mechanism - Google Patents

Description

Oct. 30, 1962 .1. J. PELoUcH 3,050,900

VEHICLE LIFTING MEGHANISM Filed Nov. 9, 1960 5 Sheelzs-Sheei'I 1 INVENTOR. JAMES J. PELGUCH BY fm1;

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'ATTORNEYS Oct. 30, 1962 Filed Nov. 9, 1960 J. J. PELOUCH lvial-HOLE LIFTING MECHANISM 5 Sheets-Sheet 2 ATTORNEYS Oct. 30, 1962 J. J. PELoUcH VEHICLE LIFTING MECHANISM 5 Sheets-Sheet 3 Filed Nov. 9. 1960 .H Dof,... Tu No ma MP lm s E M A J l 4 4 ,wz

ATTORNEYS Oct 30, 1962 .1.J. PELoucl-l VEHICLE LIFTING MECHANISM Filed NOV. 9. 1960 INVENTOR.

JAMES PELOUCH Oct. 30, 1962 J. J. PELoUcH VEHICLE LIFTING MECHANISM 5 Sheets-Sheet 5 Filed Nov. 9, 1960 INVENTOR.

JAMES J. PELOUCH r 'g t (n, 1 ii The invention relates in general to lifting devices and more particularly to vehicle lifts.

An object of the invention is to provide a lift having a piston and cylinder arrangement with valve means for controlling gas pressure between the piston and hydraulic liquid which is contained in the cylinder and in the specific embodiment also in the piston which includes a hollow construction.

Another object of the invention is to provide a lift which includes a cylinder with a piston therein which is movable between upper and lower positions by the action of gas pressure acting between the piston and hydraulic liquid in the piston, with valve means for allowing and preventing gas pressure buildup depending on the hydraulic liquid level.

Another object of the invention is to provide a vehicle lift with a safety valve for controlling the operation of the cylinder and piston depending on the liquid level of the lift,

Another object of the invention is to provide a vehicle lift with a safety control valve which may be removed from the lift if necessary without the necessity of having to completely remove the lift piston from the cylinder which is a comparatively large job.

Another object of the invention is to provide a vehicle lift with means for preventing dangerous operation which means, instead of preventing flow of hydraulic liquid between a hollow piston and a cylinder when the liquid level is too low, prevents the build up of gas pressure between the piston and the hydraulic liquid.

Another object of the invention is to provide a vehicle lift having a vertical cylinder with a hollow piston movable between upper and lower positions therein and hydraulic liquid in the piston and cylinder and transferrable therebetween Vby passageway means in the lower portion of the piston, with valve means controlled by the hydraulic liquid level whereby if the liquid level is too low the valve prevents gas pressure buildup and subsequent raising of the piston. Provision is also made whereby the valve is positively kept closed when the piston is raised thus insuring gas pressure buildup when desired in the raised condition of the piston.

Another object of the invention is to provide a control apparatus for controlling the ow of a fluid from an enclosure which ow is caused by the action of a gas under pressure.

Another object of the invention is to provide a control apparatus for a full hydraulic lift which prevents operation with insufcient hydraulic uid and permits operation with sufficient hydraulic huid and also insures operation of the lift after the same has been raised.

Another object of the invention is to provide a lifting mechanism with a control which insures that the mechanisrn will not operate at dangerously low hydraulic fluid levels.

Another object of the invention is to provide a valve for a conduit which is controlled by a normal liquid level before operation and after operation a means is provided whereby the valve is maintained closed regardless of the liquid level.

Another object of the invention is to provide a full hydraulic lift which includes a hydraulic reservoir or tank and which is actuated with gas under pressure with a valve for the tank which prevents gas actuation if the 3,06%,960 Patented Oct. 30, 1962 hydraulic level is too low and which permits gas actuation if the hydraulic level is proper and with the valve having means which keeps the valve in a predetermined position so that after actuation it remains in such position regardless of the hydraulic level.

Other objects and a fuller understanding of this invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings, in which:

FIGURE l is a side elevational View in section of the lifting mechanism of the present invention in its lower position;

FIGURE 2 is a side elevational view similar to FIGURE l but showing the lifting mechanism in raised position;

FIGURE 3 is a fragmentary side elevational view in section of the upper portion of the lift piston corresponding to that shown in FIGURE 1 but showing the hydraulic oil or liquid at a proper level;

`FIGURE 4 is a plan view of the upper end of the piston shown in FIGURE 3;

FIGURE 5 is a side elevational view showing a full hydraulic lift incorporating the teachings of the present invention;

FIGURE 6 is an enlarged fragmentary side elevational view of a portion of the apparatus shown in FIGURE 5;

FIGURE 7 is a view similar to FIGURE 6 but showing the valve in open position; and

FIGURE 8 is a view similar to FIGURE 5 but showing the lift in the up position.

The lifting mechanism of the present invention is peculiarly adapted for use as -a vehicle lift and the forthcoming description taken along with the drawings has been directed to this type of device. The vehicle lift illustrated is for the purpose of raising a vehicle from the door or ground level which has been indicated generally by the reference numeral 10. The lift includes a cylinder 12 positioned in substantially a vertical position bel-ow ground level. A piston i3 is positioned within the cylinder and is Iadapted for movement between upper and lower positions in the cylinder. FIGURE 1 shows the piston in its lowermost position in the cylinder and FIGURE 2 shows the piston in its uppermost or raised position within the cylinder. It will be noted from FIGURES l and 2 that the piston comprises a hollow construction which includes a cylindrical body 15 which is closed at its lower end by an end wall 16 and at its upper end by first and second end plates 17 and 18, lrespectively, which are welded in position. An air or gas supply tube or pipe 20 extends from the exterior of the lift axially into the hollow piston construction, through the lower or first end portions or the piston and cylinder to the upper or the second end portion of the piston when it is in its lower position (FIGURE l). The end wall 16 of the piston 13 is provided with an opening or passageway means 23 which is for the purpose of providing fluid communication between the hollow piston construction and the cylinder. An angle iron 24 is suitably secured in position adjacent the passageway means Z3 and is for the purpose of smoothing out liquid flow therethrough. An oil or hydraulic liquid conduit 27 is provided and communicates with the cylinder 12 for providing the desired amount of hydraulic liquid or liuid to the hollow piston and cylinder arrangement. The upper end of the conduit 27 is covered by means of a threaded cap 2S and a dip stick 29 is located in the upper end of the conduit 27 so that an operator may determine the liquid level at any time desired. The air tube 2@ extends to a suitable air supply such as a compressor and interposed in the tube is a suitable valving arrangement which has not been shown which may be operated by hand or by other means for either supplying air under pressure to the piston and cylinder arrangement or exhausting pressurized air therefrom.

A superstructure 31 is secured to the upper end of the piston 13 by means of a plurality of bolts 32 extending therethrough `and into the end plate 18. The superstructure carries the mechanism for engaging a vehicle to raise the same from lloor or ground level a suicient vertical distance upwardly to enable one to gain access to the underside of the vehicle. Secured to the superstructure by suitable means is a safety leg 34 which travels with the superstructure and piston and is guided in this travel by means of an annular guide member 35 which is suitably recessed in the floor or ground adjacent the cylinder 12. The safety leg is provided with a notch or recess 37 (FIGURE 2) intermediate its upper and lower ends and into this recess a pivoted latch 38 is adapted to reside. 'I'he purpose of this construction is to insure that once the lift has been raised to its upper position that it will not accidentally be lowered thereby damaging persons and property.

Wall means 40 (FIGURES 3 and 4) are provided in the upper end of the hollow piston construction 13 and more specically -in the end plates 17 and 18 and an air Valve assembly 42 is mounted at this opening. The air valve assembly 42 includes a closure member 45 secured in the opening 40 by means of screws 46 extending into the end plate 17. `Passageway means 48 are provided through the closure member for providing communication between the hollow piston construction and the exterior of the lift mechanism or -in other words to the atmosphere. The closure member 45 is provided with a valve seat 50. A valve 52 is adapted to move between open and closed positions with the valve seat 50 to either allow or prevent iluid passage through the passageway means 48. 'I'he valve is controlled by means of a iloat member 54 and is connected thereto by means of a rod 55. TheV float resides within a guide tube 56 which is iixedly secured to the end plate 17 which closes the upper end of the hollow piston construction. The upper end of the guide tube 56 is provided with openings 58 which provide for the passage of fluid to the passageway means 48. The valve 52 is guided and supported by means of a bracket which includes an apertured plate 60 secured to the closure member by means of rods 61. A stop in the form of a cotter pin 63 is provided in the end of the guide tube 56 to limit the travel of the float 54. The rod 55 is provided with a ilange or shoulder 65 `and a valve control weight 67 is pivotally connected to the guide tube '6 between irst and second end portions thereof 68 and 69, respectively. The rst end portion 68 of the valve control weight 67 engages the air supply tube 20 in the lower position of the piston and this keeps the second end portion 69 from engaging the ilange 65 on the rod 55. In the raised position of the piston the second end portion of the valve control weight 67 engages the flange 65 because of its unsymmetrical mounting (FIGURE 2) and this insures that the valve 52 remains on the seat 50 when the piston is in a raised condition.

The passageway means 48 is provided with a flapper valve 71 which is for the purpose of insuring that foreign matter does not enter the passageway means 48, however the passage of gas from the interior of the piston is not obstructed by the flapper valve. A first guide bushing 73 is xedly secured in the interi-or of the hollow piston construction by means of a bar which is welded at opposed ends to opposite walls of the piston. This bar is of a narrow width and does not obstruct lluid llow. A second guide bushing 74 is secured within the hollow piston construction and is connected to the guide tube 56 of the air valve assembly. These two bushings 73 and 74 are for the purpose of maintaining the position of the air supply tube with respect to the piston during raising and lowering movements of the piston.

Packing I88 is provided between the cylinder 12 and piston 13 to prevent the escape of hydraulic liquid on movement of the piston. A plurality of stops 79 are positioned circumferentially around the walls of the cylinder 12 and are held in position by bolts 80. The stops are adapted to be engaged by a plurality of lugs 81 circumferentially spaced around the lower end Vof the piston 13 to limit upward movement of the piston. In originally assembling the piston 13 and cylinder 12 it is necessary to tur-n the piston so the lugs 81 are out of alignment with the stops 79 and then the piston can be put into position. The piston is then again turned to align the lugs and stops and the safety leg is attached.

As mentioned in the objects, one of the primary advantages of the lift of the present invention is that if the oil or hydraulic liquid is at an unsafe level, the lift will not function at all rather than functioning under a dangerous condition. The dangerous condition results when the oil drops to such a level that if the piston were raised, the oil level would be below the end wall 16 of the piston. This would result in air acting upon the end wall 16 tending to urge the piston upwardly and air being compressible could build up an extremely high pressure and if the piston stuck in the cylinder for some reason and then if loosened would urge the piston upwardly at eX- cess speeds resulting in possible damage. Under normal operation with the air under pressure being contained within the hollow piston construction, the speed at which the piston is permitted to travel upwardly and downwardly within the cylinder is determined -by the metering of hydraulic liquid through the passageway or opening 23. FIGURE 3 illustrates the relative positions of the piston and the air intake tube when the piston is in the lower position. 'Ihis ligure also shows the hydraulic liquid or oil at a proper level in the piston and cylinder arrangement. It will be noted that in this position the float 54 maintains the valve 52 in closed position. FIGURE l illustrates the hydraulic oil or liquid level as being dangerously low and in this condition it will be noted that the iloat member 54 maintains the valve 52 in open position. The proper liquid level shown in FIGURE 3 has been indicated by the reference numeral 76 and the dangerously low liquid level of FIGURE l has been indicated by the reference numeral 77.

In operation, assume that the hydraulic liquid level is proper (FIGURE 3) and it is desired to raise the superstructure 31 from the ground or iloor level. To accomplish this end, air is introduced into the upper end of the hollow piston construction and this air under pressure exerts a force between the liquid level 76 and the end place 17 of the piston. With the valve 52 closed this pressure causes the piston to move upwardly to the position shown in FIGURE 2. As the piston moves upwardly, the rst end 68 of the valve control weight `67 disengages the air supply tube 20 and the second end p0rtion of the control weight engages -the flange on the connecting rod 55. This insures that the valve 52 is prevented from opening when it is desired to lower the lift and air pressure is removed from the hollow piston by way of the air supply tube 20. It will be appreciated -that this is necessary since if the valve were not maintained in the closed position it would be impossible to again pressurize the interior of the piston without having completely lowered the superstructure. An example of this would be if the operator had neglected to release the latch y38 which cooperates with the recess 37 on the safety leg and the superstructure has been lowered to this position. It would be necessary to raise the piston and the superstructure again in order to disengage the latch. With this accomplished the pressure could be removed from the piston 13. The liquid level 78 shown in FIGURE 2 is in effect the liquid level 76 but lthis level is lower upon raising of the piston because of the displacement of the lower portion of the piston in the hydraulic liquid.

Let it be assumed now that the hydraulic liquid level is dangerously low as indicated in FIGURE l and an attendant or operator is desirous of raising the superstructure. With the oil at the level 77, the float member 54 causes the valve 52 to be opened or unseated, because there is not enough oil to Ibuoy up the float member 54 and gravity causes the valve to assume the position shown in FIGURE l. Upon the introduction of air under pressure into the upper end of the hollow piston construction the `air immediately passes through passageway 4S past the ilapper valve 71 and out to the atmosphere thereby preventing any pressure buildup. Without pressure buildup the lift cannot be raised at all and this along with the escape of air will readily bring it to the attention of an operator of the device. In order to enable the mechanism to operate, it is necessary that he remove the cap 28 from the hydraulic liquid supply conduit 27 and fill the piston cylinder arrangement with hydraulic liquid to a proper level as indicated by the dip stick 29. It will also be noted that when the piston is lowered to its lowermost position, the valve control weight 67 is rendered inoperative and the only thing controlling the valve 52 upon an operator being desirous of raising the lift is the iloat which is in turn dependent upon the liquid level in the hollow piston construction.

It will be noted that the present application discloses a lift which includes a cylinder and piston which piston is movable between upper and lower positions by gas pressure action between the piston and hydraulic liquid in the piston with valve means for allowing and preventing gas pressure buildup depending on the hydraulic liquid level. The present invention also provides a construction in a semi-hydraulic lift for rendering the lift ineffective when the lift is in a dangerous condition. This stems from a control of the gas pressure which control is in turn geared to the hydraulic liquid level. The valve mechanism by which this is accomplished may be easily removed from the lift if necessary without the necessity of having to completely remove the lift piston from the cylinder. This is a comparatively expensive, and time consuming job. In the present construction all that is necessary if something should go wrong with the valve is to remove the assembly by means of the screws 46. Another advantage of the present invention is that when the hydraulic liquid drops to a dangerous level it simply will not function and when the liquid level is proper the valve remains lclosed at all times. This is a great advantage over some of the present day control mechanisms whereby when the liquid level reached a dangerous condition the valve will open and close for a period of time with a great deal of force and in many instances results in damage to the valve and valve seat. This problem is eliminated by use of the present mechanism.

FIGURES 5 8 incorporate the teachings of the Present invention; however, the teachings have been incorporated into what is commonly referred to as a full hydraulic lift. The vehicle lifting apparatus shown in yFIGURES 5-8 has been indicated generally by the reference numeral 81 yand includes in combination a cylinder 32 located below floor level S5 land in a generally vertical position. A piston 83 is positioned in the cylinder and is adapted to be raised and lowered between the positions shown in FIGURES 5 and 8. FIGURE 5 shows the piston in the fully lowered position and FIGURE 8 shows the piston in the fully raised position. Packing 84 is positioned in a recess in the upper portion of the cylinder 32 and acts between the cylinder walls and the piston to prevent loss of hydraulic lluid from therebetween. The piston is raised and lowered by the action of hydraulic uid which will be described in more detail hereinafter.

It will be noted that the top of the cylinder is substantially even with the floor level 8S in this construction in the down or lowered position. A vehicle engaging superstructure 88 is appropriately secured to the upper portion of the piston and is adapted to be raised and lowered in accordance with the movement of the piston. The superstructure 88 is adapted to engage the under portion of vehicles to raise the same in a manner which is well known to those skilled in the art. A safety leg 89 is secured to the superstructure 8S and is housed in a safety leg housing 90. The safety leg is for the purpose of providing a mechanical connection which insures that the lift cannot be lowered accidentally. The safety leg 89 also includes pin or obstruction means 91 which have been indicated only diagrammatically, the operation and purpose of which will be obvious from viewing FIG- URES 5 and 8.

A hydraulic fluid supply tank 94 is provided which has upper and lower portions 95 4and 96, respectively. This supply tank has been shown as positioned above the floor level 85; however, it will be appreciated that the supply tank may be located in many diiferent places. A hydraulic iluid conduit 99 leads from the lower portion of the supply tank 94 to the cylinder S2. A valve 14H) is interposed in the conduit 99 and permits ilow of hydraulic uid from the supply tank to the cylinder and prohibits ow of the same in the reverse direction unless the valve 100 is actuated by an operator of the apparatus. An air supply tube 103 extends from `a pressurized source of gas, not shown, such as air and extends through a hand operated valve 104 and into the upper portion of the supply tank 94. The valve 104 is such that it may provide flow therethrough to the tank or it may prevent ow therethrough and exhaust the tank to atmosphere. It will be noted in FIGURES 6 and 7 that a deector plate 195 is provided inside the supply tank and this is for the purpose of preventing pressurized gas, such as air from blowing directly down upon the surface of the hydraulic iluid which causes the hydraulic fluid to froth up or be entrained with air.

Wall means 106 define an opening in the upper portion of the supply tank and an air valve assembly indicated generally by the reference numeral 107 is located in this opening. The air valve assembly includes a closure member 1129 secured in the opening by way of threads 110 and is provided with a valve seat 111. Passageway means 113 extend through the closure member 109 and provide for communication between the interior of the upper portion of the supply tank and the outside atmosphere. A support member 116 is secured by a screw 117 to the closure member 109 and extends generally vertically downwardly therefrom into the upper portion of the supply tank. A valve 119 is provided and is adapted to engage and disengage the valve seat 111 to open and close the passageway means 113. A rod 120 is flxedly secured at one end portion to the valve 119 and extends downwardly through spaced bearing members 121 :and 122 which are carried by support member 116. A oat member 124 is provided which has a cylindrical opening 125 extending therethrough and the oat member is located between the bearing members 121 and 122 with an intermediate portion of the rod member extending through the cylindrical opening 125. It will be noted that there is clearance between the rod and the cylindrical opening which enables the tloat member and rod to move vertically relative to each other. Abutment means 127 are provided on the rod above the float member 124- and the abutment means in this embodiment takes the form of a spring-like wire member wrapped tightly around the rod 120. Wall means 13) are provided on a lower portion of the support member 116 and deiine an inclined surface below the float member in line with the iloating vertical travel of the float member.

The operation of the lift mechanism shown in FIG- URES 5-8 will be described hereinafter. Assume the hydraulic fluid level is at a sate level indicated by reference numeral 133 in FIGURES 5 and 6, and the lift is in the lowered position as shown. All that is necessary is to actuate the valve 104 and pressurized air is introduced into the upper portion of the supply tank through tube 163. Since the hydraulic lluid is at a safe level 133i, the iloat member 124 is in engagement with the abutment means 127 which holds the valve 119 on the valve seat 111 (FIGURES and 6). The pressurized air then acts upon the surface of the hydraulic fluid forcing the same through the hydraulic iluid conduit 99 into the cylinder 82 thereby raising the lift to the position shown in FIGURE 8. When the lift has been raised, the safety leg S9 is set as shown in FIGURE 8 and the lift is mechanically prevented from lowering. It will be noted in FIGURE 8 that as the hydraulic fluid is forced out of the supply tank, the iioat member travels vertically downwardly and engages the inclined surface 130 wedging against the rod 1293. This, along with the action of the air pressure against the underface of the valve 119 keeps the valve in closed position. When it is desired to lower the lift, all that is necessary is to disengage the pin means 91 of the safety leg, depress valve 100, and let the air out of the upper portion of supply tank by means of the valve 104.

If the operator has inadvertently neglected to disengage the safety leg and the above procedure is gone through, it will be noted that the air will be exhausted from the upper portion of the supply tank and there will be no air acting on the valve 119, and under normal circumstances the valve would drop open. Since the oat member is engaged with the inclined surface, the wedging action between the Ifloat member and the rod prevents the valve from opening. As a result, the valve 103 can be reopened and air can be reintroduced into the upper portion of the supply tank to raise the lift again so the safety leg can be disengaged.

If it be assumed that the lift is in the down position as shown in FIGURE 5 and the hydraulic fluid level is at an unsafe level 136, indicated in FIGURE 7, then the oat is positioned downwardly of that shown in FIGURE 5 and as a result, the rod and valve member are also in the down position because there is no means to tend to hold the same up. As a result, when air under pressure is introduced through the tube 103, it immediately travels through the passageway means 113 and out to atmosphere. This serves as an automatic warning to an operator that the hydraulic -uid level is dangerously low in the supply tank.

It will therefore be seen that a lifting mechanism has been provided with a control which insures that the mechanism will not operate at dangerously low hydraulic fluid levels. The teachings incorporated into the structure of FIGURES 5 8 illustrate how the overall teachings of the basic invention can be incorporated into a full hydraulic lift as distinguished from the lift of FGURES 1 4. The teachings of the invention might be said to relate to a control apparatus for controlling the `flow of fluid from an enclosure which iiow is caused bythe action of a gas under pressure. The -full hydraulic lift which incorporates the teachings of the present invention includes -a hydraulic reservoir or tank which is actuated with a gas under pressure and the tank has a valve which prevents gas actuation if the hydraulic level is too low and which permits gas actuation if the hydraulic level is proper, and the valve is also provided with means which keeps it in a predetermined position so that after actuation, it remains in such position regardless of the hydraulic level.

This application is a continuation-impart of my application, Serial No. 790,009, filed January 29, 1959, for Vehicle Lifting Mechanism, now abandoned.

Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes inthe details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What is claimed is:

l. A vehicle lift for raising a vehicle from floor level including in combination a cylinder located below said oor level and in a vertical position, a piston positioned in said cylinder and comprising a hollow construction, said piston being movable between upper and lower positions in said cylinder, said piston and cylinder each having first and second end portions, an air supply tube extending axially into said piston through said first end portion of said piston and cylinder to said second end portion of said piston in its lower position, passageway means in said piston providing for fluid communication between said first end portion of said piston and said first end portion of said cylinder, an oil conduit communicating with said cylinder for supplying oil to said cylinder and to said piston through said passageway means, a superstructure, means securing said superstructure to said second end portion of said piston, a safety leg secured to said superstructure for preventing accidental lowering of said piston, wall means defining an opening in said second end portion of said piston, an air valve assembly mounted at said opening, said air Valve assembly including a closure member secured in said opening and having a seat valve, passageway means through saidV closure member providing Vfor fluid communication between said hollow piston construction and atmosphere, a oat member, a valve adapted to engage said valve seat, a rod xedly secured at one end portion to said float member and at the other end portion to said valve, a guide tube within which said float member resides, a flange on said rod, a valve control weight pivotally mounted on said guide tube and having first and second end portions, said first end portion engaging said air supply tube in the lower position of said piston and keeping said second end portion from engagement with said flange, and said second end portion engaging said flange in the upper position of said piston to insure that said valve remains on said valve seat.

2, A vehicle lift for raising a vehicle from -tloor level including in combination a cylinder located below said floor level and in a vertical position, a piston positioned in said cylinder and comprising a hollow construction, said piston being movable between upper and lower positions in said cylinder, said piston and cylinder each having first and second end portions, -a gas supply tube extending into said piston through said first end portion of said piston to said second end portion of said piston in its lower position, passageway means in said piston providing for fluid communication between said first end portion of said piston and said -rst end portion of said cylinder, a hydraulic liquid conduit communicating with said cylinder for supplying hydraulic liquid to said cylinder and to said piston through said passageway means, a safety leg secured to said lift for preventing accidental lowering of said piston, an air valve assembly mounted in said second end portion of said piston, said air valve assembly including a valve seat, passageway means through said piston providing for communication between said hollow piston construction and atmosphere, a float member, a valve adapted to engage said valve seat, a rod tixedly secured at one end portion to said float member and at the other end portion to said valve, a 4guide tube within which said float member resides, a flange means on said rod, a valve control weight having first and second end portions, said first end portion engaging inoperative means in the lower position of said piston to keep said second end portion lfrom engagement with said flange, and said second end portion engaging said flange in the upper position of said piston to insure that said valve remains on said valve seat.

3. A vehicle lift for raising a vehicle from floor level including in combination a cylinder llocated below said oor level and in a vertical position, a piston positioned in said cylinder and comprising a hollow construction, said piston being movable between upper and lower positions in said cylinder, said piston and cylinder each having first land second end portions, a gas supply tube extending into said piston through said first end portion of said piston to said second end portion of said piston in its lower position, passageway means in said piston providing for fluid communication between said rst end portion of said piston and said rst end portion of said cylinder, a hydraulic liquid conduit communicating with said cylinder for supplying hydraulic liquid to said cylinder and to said piston through said passageway means, an air valve assembly mounted in said second end portion of said piston, said -air valve assembly including a valve seat, passageway means through said piston providing for fluid communication between said hollow piston construction and atmosphere, a 4iioat member, a valve adapted to engage said valve seat, means connecting said iioat member and valve, a safety means engaging said valve in the upper position of said piston to insure that said valve remains on said valve seat and means for rendering said safety means inoperative in the lower position of said piston.

4. A lift mechanism including in combination ya cylinder, a piston movable between upper and lower positions in said cylinder, oil in the lower portion of said cylinder at a predetermined level, said oil and said piston defining an yair chamber, means for introducing air under pressure into said air chamber and for releasing the same, passageway means -in said piston providing communication between said air chamber and the atmosphere, valve means carried by said piston and movable between open and closed positions for allowing and prohibiting ow through said passageway means, a float member connected to said valve means and in said lower piston position and with suiiicient oil level maintaining said valve means in closed position, introduction of `air under pressure into said air chamber causing said piston to move to said upper position with said air under pressure maintaining said valve means in closed position, safety weight means engaging said valve means in the upper position of said piston to maintain said valve means in closed position even in the absence of air under pressure, and means for engaging said safety weight means in the lower position of said piston to render the same inoperative and the position of said valve means thereby being dependent upon said float member and said oil.

5. A lift mechanism -including in combination a cylinder, a piston movable between upper and lower positions in said cylinder, hydraulic liquid in the lower portion of said cylinder at a predetermined level, said hydraulic liquid and said piston defining a gas chamber, means for introducing gas under pressure into said gas chamber and for releasing the same, passageway means in said piston providing communication between said gas chamber and the atmosphere, valve means carried by said piston and movable between open and closed positions for allowing and prohibiting flow through said passageway means, a iioat member connected to said valve means and in said lower piston position and with suliicient hydraulic liquid level maintaining said valve means in closed position, introduction of gas under pressure into said gas chamber causing said piston to move to said upper position with said gas under pressure maintaining said valve means in closed position, safety means engaging said valve means in the upper position of said piston to maintain said valve means in closed position even in the yabsence of gas under pressure, and means for engaging said safety means in the lower position of said piston to render the Sme inoperative and the position of said valve means thereby being dependent upon said float member and said hydraulic liquid.

6. A lift mechanism including in combination a cylinder, a piston in said cylinder movable between upper and lower positions, said cylinder adapted to contain a hydraulic liquid with the liquid and said piston defining a chamber, -means for supplying pressurized gas to said chamber, passageway means providing for communication from said chamber to the exterior of said lift mechanism, valve means carried by said piston and cooperating with said passageway means for closing `and opening the same depending upon the hydraulic liquid level in the lower position of said piston, means for engaging said valve means in the upper position of said piston for insuring that said valve means remain closed, and means for rendering said means for engaging said valve means inoperative in the lower position of said piston.

7. A vehicle lift for raising a vehicle including in combination a cylinder located in a substantially vertical position, a piston positioned in said cylinder :and comprising a generally hollow construction, said piston being movable between upper and lower positions in said cylinder, a gas supply tube extending into said piston through one end portion thereof `and extending to the other end portion of said piston, passageway means in said piston providing for fluid conmiunicating between said one end portion of said piston and the lower end portion of said cylinder, a hydraulic iiuid passage communicating with said cylinder for supplying hydraulic iluid to said cylinder and to said piston through said passageway means, conduit means providing for communication from the other end portion of said piston to the exterior thereof, valve means carried by said piston and cooperating with said conduit means for closing and opening the same depending upon the hydraulic fluid level in said piston while the same is in its lower position, means cooperating with said valve means in the upper position of said piston for insuring that said valve means remain closed regardless of the hydraulic uid level, and means for rendering said means which cooperate with said valve means inoperative in the lower position of said piston whereby the condition of said valve means -is dependent on the hydraulic fluid level.

8. Vehicle lifting apparatus including in combination a cylinder located below iloor level and in a generally vertical position, a piston positioned in said cylinder and adapted to be raised and lowered and having a vehicle engaging superstructure connected thereto to move in accordance with the movement of said piston, a hydraulic fluid supply tank having upper and lower portions, a hydraulic iiuid conduit leading from said lower portion of said supply tank to said cylinder, an air supply tube extending to said upper portion of `said supply tank, wall means deiining an opening in said upper portion of said supply tank, an air valve assembly mounted at said opening, said air valve assembly including a closure member secured in said opening and having a valve seat, passageway means through said closure member providing for communication between said upper portion of said supply tank and atmosphere, a float member having a cylindrical opening extending therethrough, a valve adapted t0 engage said valve seat, a rod iixedly secured at one end portion to said valve and extending 'through said cylindrical opening in said iioat member and the other end portion slidably residing in a bearing member, abutment means on said rod above said float member, wall means delining an inclined surface below said float member in line with the floating travel thereof, said iioat member with suliicient hydraulic fluid level in said supply tank in the down position of said piston engaging said abutment means to close said valve and with insuliicient hydraulic fluid level permitting said rod and valve to lower thus opening said passageway means, said float member in the up position of said piston lowering to engage said inclined surface to wedge said rod against said cylindrical opening in said float member to insure that said valve remains on said valve seat in the up position of said piston.

9. Vehicle lifting apparatus including in combination a cylinder with a piston positioned therein and adapted to be raised and lowered and having a vehicle engaging superstructure connected thereto to rnove in accordance to the movement of said piston, a iiuid supply tank having upper and lower portions, a -iiuid conduit leading from said lower portion of said supply tank to said cylinder, a gas supply tube extending to said upper portion of said supply tank, wall means defining an opening vin said upper portion of said supply tank, a valve assembly mounted at said opening, said valve assembly including a closure member secured in said opening and having a valve seat, passageway means through said closure member providing V.for communication between said upper portion of said supply tank and atmosphere, a float member having an opening extending therethrough, a valve vadapted to engage said valve seat, a rod secured at one end portion to said Valve and extending through said opening in said float member and the other end portion slidably residing in a bearing member, abutment means on said rod above said oat member, wall means defining an inclined surface below said oat member in line with the floating travel thereof, said liloat member with suicient fluid level in said supply tank in the down position of said piston engaging said abutment means to close said valve and with insuicient iluid level permitting said rod and valve to lower thus opening said passageway means, said oat mem-ber in the up position of said piston lowering to engage said inclined surface to wedge said rod against said opening in said float member to insure that said valve remains on said valve seat in the up position of said piston. yl0. Vehicle lifting apparatus including in combination a cylinder and a piston positioned therein and adapted to be raised and lowered, a uid supply tank, a fluid conduit leading from said supply tank to said cylinder, a gas supply tube extending to said supply tank, wall means defining an opening in a portion of said supply tank, a valve assembly mounted at said opening, said valve assembly including a closure member secured in said opening'and having a valve seat, passageways means through said closure member providing for communication between said supply tank and atmosphere, a oat member having an opening therethrough, a valve adapted to engage said valve seat, a rod secured at one end portion to said valve and extending through said opening in -said float member, abutment means on said rod above said float member, Wall means defining wedging surface means below said oat member in line with the floating travel thereof, said oat mem-ber with sufcient uid level in saidsupply tank in the down position of said piston engaging said abutment means to close said valve and with insufficient fluid level permitting said rod and valve to lower thus opening said passageway means, said float member in the up position of said piston lowering to engage said wedging surface means to Wedge Said rod against said opening in said float member to insure that said valve remains on said valve seat in the up position of said piston.

11. Vehicle lifting apparatus including in combination a cylinder and a piston positioned in said cylinder and adapted to be moved between rst and second position, a -uid supply tank, a uid conduit leading from said supply tank to said cylinder, a gas supply tube extending to said supply tank, wall means defining an opening in said supply tank, a gas Valve assembly mounted at said opening, said gas valve assembly including a closure member secured in said opening and having a valve seat, passageway means through said closure member providing for communication between said supply tank and atmosphere, a oat member having an opening extending therethrough, a valve adapted to engage said valve seat, a rod secured at one end portion to said valve and extending through said opening in said oat member `and the other end portion slidably residing in a bearing member, abutment means on said rod above said float member, and wall means defining an inclined surface below said oat member in line with the floating travel thereof.

12. A control apparatus for controlling the flow of a liquid from an enclosure formed by Wall means into which enclosure a gas under pressure is adapted to be introduced including in combination conduit means providing for communication from the enclosure to the exterior thereof, valve means carried by the Wall means which define the enclosure and cooperating with said conduit means for closing and opening the same depending on the liquid level in the enclosure while the liquid is at its inoperativelevel in the enclosure, means cooperating with said valve means when gas under pressure is in the enclosure and the liquid level is at its operative level for insuring that said Valve means remain closed regardless of the liquid level, and means for rendering said means which cooperate with said valve means inoperative while lthe liquid is at its inoperative level whereby the condition of said valve means is dependent on the liquid level.

13. A hydraulic lift including in combination wall means defining an enclosure for containing hydraulic uid, first conduit means communicating with said enclosure for the passage of hydraulic uid to and from said enclosure, second conduit means communicating with said enclosure for introducing gas under pressure into an upper portion of said enclosure to force the hydraulic iluid out said first conduit means, passageway means in said Wall means which define said upper portion of said enclosure to provide for the exit of gas from said enclosure, Valve means for opening and closing said passageway means to control the air pressure in the upper portion of said enclosure, said valve means being controlled by the hydraulic lluid level in said enclosure when there is substantially no gas pressure in the upper portion of said enclosure in the inoperative condition of said lift and in this situation said valve means being closed when the hydraulic uid level is at a determined safe level and being openV when the hydraulic fluid level is at a determined unsafe level, introduction of pressurized gas into said upper portion of said enclosure `through said second conduit means in the closed condition of said valve means causing at least a portion of said hydraulic fluid to travel through said rst conduit means from said enclosure to lower the hydraulic fluid level in an opera- `tive condition of said lift and means exclusive of the pressurized gas in said upper portion of said enclosure cooperating with said valve means when the hydraulic fluid level is lowered in the operative condition of said lift whereby said valve means remains closed regardless of the hydraulic uid level.

14. A liquid flow apparatus including in combination a tank having upper and lower portions, liquid conduit means for transmitting liquid to and from said lower portion of said tank to provide inoperative and operative liquid levels, gas conduit means for pressurizing said upper portion of said tank to force liquid through said liquid conduit means to provide the operative liquid level, and passageway means in said upper portion of said tank providing communication therefrom to atmosphere, valve means `at said passageway means for opening and closing same, said valve means at the inoperative liquid level being open or closed depending on the liquid level in the tank and means cooperating with said valve means at the operative liquid level for insuring that said valve means remains closed regardless of the liquid level in said tank.

References Cited in the le of this patent UNITED STATES PATENTS 1,841,900 Lunati s Ian. 19, 1932 1,868,935 Breneman luly 26, 1932 2,336,817 Thompson Dec. 14, 1943 2,550,882 Sturm et al May 1, 1951 2,705,502 Thompson Apr. 5, 1955

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