US2254699A - Lift - Google Patents

Description

| F. JAsEPH 2,25%@9 LIFT A Filed Sept. 23, 1940 2 Sheets-Sheet 2 ,e0 A u 72O O Patented Sept. 2, 1941 LIFT Lawrence F. Jaseph, Memphis, Tenn., assignor to Rotary Lift Company, Memphis, Tenn., a corporation of Delaware Application September 23, 1940, Serial No. 357,849

4 Claims.

This invention relates to lifts.

It will be explained as embodied in a lift particularly adapted for the elevation of automobiles for underbody servicing.

In lifts of the type frequently referred to as air-hydraulic or semi-hydraulic, the plunger as well as the cylinder serves as a reservoir for oil. To raise the lift, air pressure is applied to the interior of the plunger above the oil level and as the plunger. rises, oil ows therefrom through 'a restricted passage into the chamber formed between the stationary cylinder and the movable plunger. To lower the lift, the air pressure is released from the interior of the plunger and. under the influence of the weight of the descending plunger and its load, the oil is forced back from the cylinder through the restricted passage into the plunger. In such lifts an air pocket tends to form in the space between the plunger and the cylinder between the upper level of the oil and the packing at the top of the cylinder. Because of seepage of air into this pocket during operations of the lift, the pocket tends to become larger with the result that unsatisfactory operation and loss of oil may result.

In orderl to overcome this diiilculty, it has been common practice to provide an external manually operated vent for the air pocket, the vent being normally closed by suitable means, such as a plug. Frequently, however, installers and cperators neglect to vent the air pocket with the result that unsatisfactory operation of the lift, as well as loss of oil therefrom may take place, as mentioned heretofore.

The object of my invention is to provide an automatic air bleeder which will prevent the formation of objectionable air pockets in lifts.

A further object is to provide an automatic air bleeder, integral with the mechanism, which will allow the unwanted air in the lift to escape each time the lift is operated.

A further object is to provide a bleeder which will automatically exhaust the air in the lift both at the time of the initial operation of the lift, and at all times thereafter.

Another object is to provide an automatic air bleeder which may be used with a combination air and hydraulic lift.

A further object is to provide a lift which will operate accurately, smoothly, safely, and economically with a minimum amount of attention on the part of the operator.

Another object is to provide an automatic bleeder for lifts which is simple in construction and operation and whichis economical to manufacture.

Other objects, advantages, and capabilities of the invention will appear from the following description of preferred embodiments thereof, taken in conjunction with the accompanying drawings, in which similar numerals refer to similar parts.

In the drawings: 4

Fig. 1 is a vertical section of a lift showing one arrangement of a bleeder pipe to vent automatically the air pocket below the packing, and

Fig. 2 is a vertical section of a modified arrangement for accomplishing this end.

Referring first to Fig. 1, the lift includes a cylinder or outside casing 5 sealed at the lower end and open at the top. Usually, as indicated, the cylinder is embedded in the ground with its upper open end slightly below the level of thev ground or garage floor. Slidably arranged within the cylinder is a hollow piston or plunger 6, which carries the automobile supporting superstructure. In order to maintain an air-tight seal between the plunger and the open end of the cylinder, conventional packing 'l and an adjustable gland 8 are employed. By reference to the drawings it may be seen that the plunger-is tightly sealed at its upper end by means of a piston head I2 which is drilled and tapped to receive a threaded air-tight fill-plug I3.

An air line I6, open at its upper end, enters the cylinder by means of an air-tight elbow I1, and extends loosely through an orice I5 in the lower head Ill of the plunger, to a point somewhat below the upper plunger head I2 when the plunger is in its lowermost position, as shown by the dotted lines. Preferably the orice I5 is larger than the air line I6 by an amount which will produce a safe and proper lowering speed with the air pressure released by restricting the ow of oil-or other liquid-from the cylinder to the plunger during descent of the plunger. If desired, a differential valve may be employed to vary the size of the eiective liquid passage between cylinder and plunger when the plunger is elevated and when it descends, such, for example, as set forth in United States Patent No. 1,689,145 to Lunati.

In order tohold rigidly the plunger 6 as it rises and falls within the cylinder 5, there is provided a bearing cage I8 which is securely fastened to the interior of the cylinder by means of an annular collar I9, as well as by means of bolts 20 at the upper flange of the bearing cage. The upward movement of the plunger is limited by a stop-ring 2l which is adapted to engage a bearing 21 at the lower extremity of the bearing ca e.

in automatic bleeder pipe 22, disposed vertically within the plunger 3, passes through the wall of the plunger at a point below the pack-` ing,preferably immediately below an upper bearing 28 in the lbearing cage I8 when the plunger is ln a fully or nearly fully raised position. The lower` end of the bleeder pipe 22 is open, and extends to a pointl slightly above the lower plunger head Il of the plunger 5.

To make certain that the air in the space between the plunger 6 and the cylinder 5 will be entirely exhausted by the action of the bleeder pipe 22, a plurality of holes 23 are drilled throughout the circumference of the 4bearing cage I8 to permit the level of the oil to equalize inside and outside the bearing cage.

'Ihe initial installation and operation of the lift is as follows: After the parts have been assembled the plunger 6 will be at rest upon the blocks 24 at the bottom of the cylinder, as is shown by the dotted lines. The lift is then filled with oil up to the point somewhat below the open end of the inside air line I 6, and the ull-plug I3 is screwed into place. Air pressure is supplied by a compressor or other suitable source connected to an exterior air line 25 by means of an elbow 26. As the plunger 3 rises, impelled by the increased pressure within it. the oil will flow through the orice l into the outer cylinder 5. Naturally, the air pressure within the plunger will be exerted equally in all directions, so that the same force which is exerted against the interior of the plunger to force it upward is likewise exerted against the surface of the oil. As the plunger rises, the pressure of the air upon the surface of the oil within the plunger will cause the oil in the cylinder to rise into the space or "pocket between the plunger 6 and the cylinder 5 between the packing 1 and the lower bearing ring 21, compressing any air trapped therein. The pressure within this pocket will be somewhat lower than the pressure required within the plunger to raise the plunger and its load.

When the plunger reaches its fully raised position, as shown by the heavy lines in Fig. 1, the upper opening of the bleeder pipe 22 is above the oil level, while the lower opening of the bleeder pipe extends below the surface of the oil.

The bleeding operation of this embodiment is accomplished as follows: When the air pressure within the plunger is released and the plunger descends. a differential between the pressure within the plunger and within the cylinder outside of the plunger exists-the pressure on the outside of the plunger being greater than that within the plunger. 'I'his differential in pressure causes air, if any be present in the space or pocket" between the plunger 6 and cylinder 5 above the lower bearing ring 21, to flow through the bleeder pipe 22 into the plunger. Air flow through the bleeder pipe 22 continues during lowering of the plunger and, because of the slight viscosity and density of air, a considerable volume of air will pass through the bleeder pipe 22 in a short time.A And as the air passes through the bleeder pipe into the plunger, oil rises to take its place in the pocket. The first time the lift is operated after being filled with oil, the oil level will drop equal to the volume required to fill the air pocket between the plunger 6 and the cylinder 5 between the packing 1 and the lower bearing ring 21. It may be desirable, therefore,

to add oil after the first few operations in order to establish the proper operating level.

Referring now to Fig. 2, it will be observed that another embodiment of the invention is illustrated, wherein a bleeder pipe 3| is used in conjunction with a valve 30 to accomplish the automatic bleeding operation. This valve consists of a housing 32, a valve seat 33, a movable ball 34, and a retaining pin 35. The bleeder pipe is arranged within the plunger S and passes through the wall of the plunger at a point which will be below the packing-preferably immediately below the upper bearing 28 in the bearing cage i8 when the plunger is in a fully or nearly fully raised position.

The operation of this embodiment of the bleeder pipe is as follows: When the air pressure within the plunger 6 is released and the plunger is a1- lowed to descend, the pressure within the plunger will necessarily decrease more rapidly than the pressure in the air pocket for the reasons already stated. This difference in pressure causes air, if any be present in the space or pocket between the plunger 6 and the cylinder 5 above the lower bearing ring 21, to flow through the bleeder pipe 3|, to unseat the ball 3l, and to ilow into the plunger 6. The ball 3| is prevented from leaving the valve assembly entirely by means of the retaining pin 35.

On the other hand, when the pressure in the space between the plunger 6 and the cylinder 5 between the packing 1 and the lower bearing ring 2l is less than the pressure within the plunger I. as during upward travel of the plunger, the ball 34 will close against the valve seat 33 because of the greater pressure within the plunger. When the ball is in this position air from within the plunger cannot enter the space between the plunger and the cylinder, and thus the air pocket is prevented from re-forming after being eliminated. The bleeder pipe with the valve 30 works equally well whether it is above or below the level of the oil.

0f course, the action of both embodiments of the bleeder pipe is entirely automatic, so that every time the lift is operated, the air that would ordinarily accumulate will be disposed of. as described, simply by the raising and lowering of the plunger, and without any effort on the part of the operator.

Although this invention has been described in connection with certain specific embodiments, the principles involved are susceptible of numerous other applications that will readily occur to persons skilled in the art. 'I'he invention is, therefore, to be limited only by the scope of the appended claims.

Having thus described the various features of the invention, what I claim as new and desire to secure by United States Letters Patent is:

l. A lift of the type having a relatively movable cylinder and plunger with fluid-tight packing therebetween and wherein air pressure released within the plunger above the level of a liquid contained therein exerts upward pressure on the plunger and downward pressure on the liquid to elevate the plunger and force the liquid from the plunger through a restricted passage into the cylinder, characterized by an air bleeder pipe opening at one end through the wall of the plunger at a point below the packing when the plunger is fully elevated and opening at the other end within the plunger.

2. A lift of the type having a relatively movable cylinder and plunger with fluid-tight packing therebetween and wherein air pressure released within the plunger above the level of a. liquid cont tained therein exerts upward pressure on the plunger and downward pressure on the liquid to elevate the plunger and force the liquid from the plunger through a restricted passage in-to the cylinder, characterized by an air bleeder pipe opening at one end through the wall of the plunger at a point below the packing when the plunger is fully elevated and opening at the other end below the level of the liquid in the plunger.

3. In a lift, the combination of a cylinder open at one end and closed at the other end, a hollow plunger slidably mounted in the cylinder, the upper end of the plunger being closed and the lower end having a restricted passage into the cylinder, uid presure-tight packing between the cylinder and plunger, a liquid partly filling the cylinder and plunger, an air pressure inlet opening into the plunger above the oil level therein,

the air pressure acting upwardly on the upper closed plunger head and downwardly upon the liquid to elevate the plunger andforce liquid from the plunger through the restricted passage into the cylinder, and an air bleeder passage extending through the wall of the plunger at a point slightly below the packing when the plunger is fully elevated and extending to a point below the liquid level in the plunger to permit the escape of air trapped between the plunger and cylinder when air pressure is released from the plunger.

4. A lift of the type having a relatively movable cylinder and plunger with uid-tight packing therebetween and wherein air pressure released within the plunger above the level of a liquid contained therein exerts upward pressure on the plunger and downward pressure on the liquid to elevate the plunger and force the liquid from the plunger through a restricted passage into' the cylinder, characterized by a bleeder pipe within the plunger opening at one end through the wall of the plunger at a point below the packing when the plunger is fully elevated, and a check valve in said bleeder pipe for arresting the flow of iluid from the inside to the outside of the plunger, while permitting the ow of uid from the outside to the inside of the plunger.

LAWRENCE F. JASEPH.

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