US3744372A

US3744372A - Semi-hydraulic lift and improved valve therefor

Info

Publication number: US3744372A
Application number: US00239020A
Authority: US
Inventors: J Davis
Original assignee: Dresser Industries Inc
Current assignee: Dresser Industries Inc
Priority date: 1972-03-29
Filing date: 1972-03-29
Publication date: 1973-07-10
Anticipated expiration: 1990-07-10
Also published as: AU5372673A; AR195600A1; CA958403A; BR7302243D0

Abstract

A low oil safety valve for use in semi-hydraulic lifts or hoists is disclosed herein. The improved valve includes a buoyant member that floats the valve in the lift hydraulic oil to hold the valve inoperative until the oil level in the lift drops below a predetermined, safe level. Attached to the lower end of the buoyant member is a seal member that includes an outer seal portion and an inner seal portion. The outer seal portion is engageable with the bottom plate of the lift plunger to prevent air and oil, when the oil level is below the predetermined safe level, from being discharged into the lift cylinder and thus causing erratic movement of the plunger. The inner seal portion encircles and sealingly engages an air line extending into the plunger to completely close the opening through the bottom plate of the hoist. The air line seal and the bottom plate seal are carried by the buoyant member, thus, both seals can be quickly and easily replaced without the necessity of removing the plunger from the cylinder as is usually necessary to replace the air line seal which is most often found in the bottom plate.

Description

United States Patent 1 Davis 1 SEMI-HYDRAULIC LIFT AND IMPROVED VALVE THEREFOR [75] Inventor:

[52] US. Cl 91/4 A [51] Int. Cl FlSb 21/04 {58] Field of Search 91/4 A [56] References Cited UNITED STATES PATENTS 2,637,302 5/1953 Harrison et al. 91/4 A 2,970,577 2/1961 Sinclair 91/4 A 3,140,641 7/1964 Clark et al. 91/4 A 3,237,523 3/1966 Wallace 91/4 A 3,363,511 1/1968 Hott et al.... 91/4 A 3,435,731 4/1969 Browne 91/4 A Primary ExaminerPaul E. Maslousky Attorney- Robert W. Mayer, Roy L. VanWinkle et al.

[111 3,744,372 [451 July 10, 1973 [57} ABSTRACT A low oil safety valve for use in semi-hydraulic lifts or hoists is disclosed herein. The improved valve includes a buoyant member that floats the valve in the lift hydraulic oil to hold the valve inoperative until the oil level in the lift drops below a predetermined, safe level. Attached to the lower end of the buoyant member is a seal member that includes an outer seal portion and an inner seal portion. The outer seal portion is engageable with the bottom plate of the lift plunger to prevent air and oil, when the oil level is below the predetermined safe level, from being discharged into the lift cylinder and thus causing erratic movement of the plunger. The inner seal portion encircles and sealingly engages an air line extending into the plunger to completely close the opening through the bottom plate of the hoist. The air line seal and the bottom plate seal are carried by the buoyant member, thus, both seals can be quickly and easily replaced without the necessity of removing the plunger from the cylinder as is usually necessary to replace the air line seal which is most often found in the bottom plate.

7 Claims, 4 Drawing Figures PATENIE JUL 1 @1915 FIG. 3

PICS. 2

FIG.

SEMI-HYDRAULIC LIFT AND IMPROVED VALVE THEREFOR BACKGROUND OF THE INVENTION This invention relates generally to semi-hydraulic lifts or hoists. More particularly, but not by way of limitation, this invention relates to semi-hydraulic lifts for automotive vehicles that incorporate an improved low oil level safety valve.

The improved valve and hoist described hereinafter is an improvement over the valves and hoists shown and described in US. Pat. No. 3,140,641 issued July 14, 1964 to J. E. Clarke, et al, U. S. Pat. No. 3,237,523, issued Mar. 1, 1961 to G. A. Wallace, and U. S. Pat. No. 3,453,731 issued Apr. 1, 1969 to A. T. Browne.

Each of the aforesaid patents illustrates a hoist structure having appropriate seals to provide both an outer seal for closing the opening through the bottom plate of the plunger and an inner seal that seals against the air line. The problems encountered with such hoists have primarily involved the inner seal.

During the operation of lifts and hoists, and particularly when the oil level is low, a very low hydrostatic head exists on the safety valve even when the lower or outer seal portion is in sealing engagement with the bottom plate of the plunger. Also, and even though some differential in pressure is created due to the flow of air and liquid between the air line and the inner seal, the formation of a fluid-tight seal with the air line is very difficult due, at least in part, to the very low forces available.

As will be appreciated by those skilled in the art, the attempt to form a fluid-tight seal between a smaller diameter member and a seal having a larger diameter than the diameter of the member results in the seal wrinkling or buckling as the seal collapses inwardly. A seal may be attained over the major portion of the surface area, but there are usually portions thereof wherein leakage occurs.

It is also necessary that the valve be free to float along the air line as the liquid level changes in the plunger. Accordingly, the inner seal that closely encircles the air line, must have a sufficiently large inside diameter to permit such freedom of movement and, yet, must be capable of collapsing inwardly into tight sealing engaement with the air line.

It will be noted in the Browne patent, cited above, that the seal for the air line is located in the bottom plate of the plunger and the safety valve does not have to form a seal with the air line. With the seal located in this position, a fluid-tight seal can be attained and maintained at all times. However, the telescoping action of the plunger with respect to the air line exposes the seal to constant wear which severely reduces the life of the seal. The seal must be replaced fairly often and, since the seal is located at the bottom of the plunger, it is necessary to remove the entire plunger from the 'liftcylinder in order to accomplish the replacement. The expense and difficulties involved in replacing a seal located in the bottom plate of the plunger are apparent.

Accordingly, it is one object of this invention to provide an improved semi-hydraulic lift that incorporates a buoyant low oil safety valve that seals against the air line and bottom plate when the liquid level is below a predetermined valve.

A further object of the invention is to provide an improved low oil safety valve that effectively closes the opening extending through the bottom plate of the plunger and seals against the air line.

Still another object of the invention is to provide an improved low oil safety valve for hydraulic lifts that is easy and inexpensive to manufacture, requires little or no maintenance, and that can be quickly and easily replaced when necessary.

SUMMARY OF THE INVENTION This invention contemplates an improved semihydraulic lift including a cylinder, an air line extending longitudinally within the cylinder and a plunger located within the cylinder encircling the air line. The plunger is moveable telescopically with respect to the air line and cylinder. A bottom plate on the plunger is normally immersed in a liquid and has an opening extending therethrough to receive the air line. An improved low level control valve is slidingly disposed on the air line within the plunger and includes: a buoyant body encircling the air line and forming an annular space with the air line; a resilient valve body attached to the buoyant body and having an outer seal portion projecting relatively toward the bottom plate and an inner seal portion projecting lengthwise into the annular space. The inner seal portion encircles the air line and has a thin, flexible cross-section and spaced notches in the end disposed in the annular space to permit the inner seal portion to sealingly engage the air line independently of the outer seal portion.

The foregoing and additional objects and advanages of the invention will become more apparent as the following detailed description is read in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a cross-sectional view of an improved hoist constructed in accordance with the invention.

FIG. 2 is a cross-sectional view of the hoist of FIG. 1, but illustrating the hoist in a difierent operating position.

FIG. 3 is an enlarged cross-sectional view of a portion of the hoist of FIG. 1 showing the low oil safety valve in detail.

FIG. 4 is a view similar to FIG. 3, but illustrating the valve of FIG. 3 in another operating position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing and to FIG. 1 in particular, shown therein and generally designated by the reference character 10 is a semi-hydraulic lift or hoist that is constructed in accordance with the invention. The hoist 10 includes a cylinder 12 that is normally located in a pit (not shown) and disposed in a substantially vertical position as illustrated.

The cylinder 12 has a closed lower end 14. An air line 16 is connected to the lower end 14 of the cylinder 12 and extends therethrough into a plenum 18 mounted on the lower end 14 of the cylinder 12. The plenum 18 is connected to a source of compressed air (not shown) by an air line 20.

The air line 16 is disposed coaxially in the cylinder 12 and extends upwardly to approximately the upper end 22 of the cylinder 12. The upper end 22 of the cylinder 12 includes appropriate bearings and seals 24 for operably supporting a plunger 26 that is telescopically disposed within the cylinder 12.

The plunger 26 includes a top end closure 28 which may be removable or at least include a removable inspection opening for access to the interior of the plunger 26. Also extending through the top closure 28 is an oil level gauge 30 which provides an indicia for assisting in maintaining the oil level in the hoist at a predetermined level for safely operating the hoist.

A bottom plate 32 on the plunger 26 has an opening 34 extending therethrough to receive the air line 16 and also to receive a deflector member 36 which also encircles the air line 16. As may be seen more clearly in FIG. 3, the opening 34 is sufficiently large to permit fluid flow therethrough even though both the deflector member 36 and the air line 16 are disposed therein.

To stabilize the plunger 26 in the cylinder 12, an annular bearing 38 encircles the lower end of the plunger 26 and is disposed in sliding engagement with the interior wall of the cylinder 12. It should be pointed out that the plunger 26 will also carry, at its upper end, a superstructure (not shown) that is appropriately arranged and constructed to engage and lift a vehicle or to perform other services that may be required of the hoist 10.

As previously mentioned, the air line 16 extends upwardly within the plunger 26 terminating in an abutment member 40 which provides a stop or upper limit for a low oil safety valve 42 that is slidingly disposed on the air line 16.

As shown in FIG. 3, the deflector member 36 is located in the opening 34 and has a diameter slightly smaller than the diameter of the opening 34 to provide an annular space therethrough through which oil can flow as the plunger 26 moves in the cylinder 12. The upper end of the deflector member 36 is formed into a flange 44 that extends outwardly to a diameter larger than the diameter of the opening 34. Fluid flowing through the opening 34 is deflected to prevent the formation of bubbles which may cuase erratic operation of the hoist 10.

The low oil safety valve 42 includes a buoyant body 46 that encircles the air line 16 and forms an annular space 48 therewith. The buoyant body 46 is to be constructed from a material that provides sufficient buoyancy so that the valve 42 will float at or near the surface of the oil in the hoist 10.

A valve member 50 is attached to the lower end of the buoyant member 46 and is constructed from a resilient material which is compatible with the oil in the hoist. The valve member 50 includes a downwardly projecting, annular outer seal portion 52 that is arranged to sealingly engage the bottom plate 32. The outer seal portion 52 has a diameter sufficiently large to encircle the flange 44 of the deflector member 36 and thus form a continuous seal with the surface of the bottom plate 32 to close the opening 34. A radially extending flange portion 54 of the valve member 50 connects the outer seal portion 52 with an inner seal portion 56 that projects upwardly into the annular spac 48 in the buoyant body 46.

It will be noted that the inner seal portion 56 is of relatively thin cross-section and has an inner diameter somewhat larger than the outer diameter of the air line 16 so that the valve 42 is free to move relative to the air line 16 as the oil level changes in the hoist 10. The upper end of the inner seal portion 56 is provided with a plurality of spaced notches 58 to increase the flexibility of the inner seal portion 56 and to make it more responsive to the relatively small fluid head that will be remaining in the annular space 48 when the oil level is low. Also, the inner seal portion 56 must be sufficiently flexible to move in response to the relatively small differential in pressure that exists as oil passes downwardly through the space between the inner seal portion 56 and the air line 16.

As mentioned earlier, one of the difficulties in forming a seal with a smaller diameter member, such as the air line 16, has been the tendency of the seal member which is larger in diameter, to buckle and thus form an imperfect seal. The notches 58 are provided so that as the seal portion 56 collapses inwardly, the inner surface thereof will continuously engage the exterior of the air line 16 and form a fluid-tight seal therewith.

As an example of the structure and dimensions of the inner seal portion 56, it has been found that with a cross-sectional thickness of 0.031 of an inch and a heighth of 0.500 of an inch, notches 58 cut approximately 0.375 of an inch deep and having a base dimen sion of 0.047 of an inch will provide sufficient flexibility and permit sufficient collapse to provide an effective seal between the inner seal portion 56 and the air line 16. It should, of course, be understood that these dimensions are given by way of example only and that reasonable variations therefrom should work equally well and are contemplated by the invention. The size and shape of the notches 58 will also vary with the hardness of the material utilized in forming the valve member 50.

OPERATION OF THE PREFERRED EMBODIMENT With the hoist 10 in the condition illustrated in FIG. 1, air is introduced through the air line 20 into the plenum 18 from which it passes into the air line 16 and outwardly of the upper end thereof. Oil contained within the plunger 26 is then forced downwardly through the opening 34 into the interior of the cylinder 12.

As the oil is displaced out of the plunger 26, the plunger 26 begins to rise as is illustrated in FIG. 2. The valve 42 floats near the surface of the oil and will continue to do so as the plunger 26 rises in the cylinder 12. In the event that there is not sufficient oil in the plunger 26 to permit the full extension of the plunger 26 relative to the cylinder 12, the low oil safety valve 42 will move relatively downwardly along the air line 16 with the oil level until the outer seal portion 52 thereon engages the bottom plate 32 as shown in FIG. 4. When this occurs, oil is prevented from passing the outer seal 52 through the opening 34 and an increase in flow ve locity occurs between the inner seal portion 56 and the air line 16.

A force is exerted on the inner seal portion 56 both by the differential in pressure due to the flow and also due to the slight head of fluid existing in the annular space 48. The flexibility of the inner seal portion 56 and the notches 58 permit the inner seal portion 56 to move into sealing engagement with the air line 16 thereby preventing the flow of oil and air into the cylinder 12 and thus stopping the upward movement of the plunger 26 relative to the cylinder 12. It should also be noted that the configuration of the valve member 50 affords complete independence of the inner and outer seal portions. That is, deformation or movement of the outer seal portion 52 is not necessary to permit the inner seal portion 56 to sealingly engage the air line 16. The fluid-tight seals prevent erratic movement of the plunger 26 which can occur if air is expelled from the plunger 26 into the cylinder 12 instead of oil.

To lower the plunger 26, air pressure is released from the line which permits air to flow from the interior of the plunger 26 and outwardly through the air line 16. The valve 42 lifts off the bottom plate 32 permitting oil to return from the cylinder 12 into the interior of the plunger 26 and the plunger 26 returns to the position illustrated in FIG. 1.

One highly desirable feature of the invention is that the seal between the air line 16 and the valve 42 is carried by the valve 42 and thus will be accessible from the upper end of the plunger 26. This arrangement avoids the necessity of removing the plunger 26 in the event that wear does occur on the seal portion 56. Since the seal portion 56 is normally out of engagement with the air line 16, it is not contemplated that the valve 42 will need to be replaced with any degree of frequency.

It will be understood that the foregoing detailed description is but an example of the invention and that many modifications and variations can be made therein without departing from the spirit and scope of the invention.

The invention is defined as follows:

1. in an improved semi-hydraulic lift, including a cylinder, an air line extending longitudinally within the cylinder and a plunger located within the cylinder encircling the air line and moveable telescopically with respect to the air line and cylinder, the plunger having a bottom plate immersed in a liquid and an opening through the bottom plate to receive the air line, and including an improved low level control valve, comprising:

a buoyant body encircling the air line within the plunger and forming an annular space with the air line; and,

a resilient valve body attached to said buoyant body and slidingly disposed on the air line, said valve body including an outer seal portion projecting relatively toward the bottom plate and an inner seal portion projecting lengthwise into said annular space, said inner seal portion being disposed adjacent to the air line and having a thin flexible crosssection and spaced notches in the end disposed in said annular space to permit movement of said inner seal portion into sealing engagement with the air line independently of said outer seal portion.

2. The improved semi-hydraulic lift of claim 1 wherein the notches in said inner seal portion are triangular in configuration and have a base dimension slightly greater than the thickness of said end crosssection and have a height about three-fourths of the length of said inner seal portion.

3. The improved semi-hydraulic lift of claim 1 wherein said inner seal portion is spaced from said buoyant body, whereby the liquid in said annular space exerts a force on said inner seal portion when said outer seal portion is in engagement with the bottom plate, in a direction to move said inner seal portion toward the air line.

4. An improved semi-hydraulic lift comprising:

a normally, vertically oriented cylinder at least partially filled with a liquid;

a hollow plunger located in said cylinder for telescoping movement, said plunger having a bottom plate with an opening extending therethrough;

an air line connected to said cylinder and projecting through the opening into said plunger; and,

valve means slidingly located on said air line within said plunger, said valve means including a buoyant body encircling and forming an annular space with said air line, and resilient valve body attached to said buoyant body, said valve body having an outer seal portion projecting toward said bottom plate and being engageable therewith to close said opening and an inner seal portion projecting into said annular space, said inner seal portion being disposed adjacent to said air line and having a thin, flexible cross-section and spaced notches in the end disposed in said annular space to permit movement of said inner seal portion into sealing engagement with said air line independently of said outer seal portion when said outer seal portion is in sealing engagement with said bottom plate.

5. The improved lift of claim 4 wherein said outer seal portion is annular in configuration;

said inner seal portion is annular in configuration, spaced from said outer seal portion and of smaller diameter than said outer seal portion; and,

a radially extending flange portion extending between the lower end of said inner seal portion and the upper end of said outer seal portion retaining said seal portions in spaced relationship.

6. The improved lift of claim 5 and also including a deflector member located in said opening and having a radially extending flange disposed within said plunger, said flange having an outer diameter sized to fit within said outer seal portion.

7. The improved semi-hydraulic lift of claim 6 wherein the notches in said inner seal portion are triangular in configuration and have a base dimension slightly greater than the thickness of said end crosssection and have a height about three-fourths of the length of said inner seal portion.

Claims

1. In an improved semi-hydraulic lift, including a cylinder, an air line extending longitudinally within the cylinder and a plunger located within the cylinder encircling the air line and moveable telescopically with respect to the air line and cylinder, the plunger having a bottom plate immersed in a liquid and an opening through the bottom plate to receive the air line, and including an improved low level control valve, comprising: a buoyant body encircling the air line within the plunger and forming an annular space with the air line; and, a resilient valve body attached to said buoyant body and slidingly disposed on the air line, said valve body including an outer seal portion projecting relatively toward the bottom plate and an inner seal portion projecting lengthwise into said annular space, said inner seal portion being disposed adjacent to the air line and having a thin flexible cross-section and spaced notches in the end disposed in said annular space to permit movement of said inner seal portion into sealing engagement with the air line independently of said outer seal portion.

2. The improved semi-hydraulic lift of claim 1 wherein the notches in said inner seal portion are triangular in configuration and have a base dimension slightly greater than the thickness of said end cross-section and have a height about three-fourths of the length of said inner seal portion.

4. An improved semi-hydraulic lift comprising: a normally, vertically oriented cylinder at least partially filled with a liquid; a hollow plunger located in said cylinder for telescoping movement, said plunger having a bottom plate with an opening extending therethrough; an air line connected to said cylinder and projecting through the opening into said plunger; and, valve means slidingly located on said air line within said plunger, said valve means including a buoyant body encircling and forming an annular space with said air line, and a resilient valve body attached to said buoyant body, said valve body having an outer seal portion projecting toward said bottom plate and being engageable therewith to close said opening and an inner seal portion projecting into said annular space, said inner seal portion being disposed adjacent to said air line and having a thin, flexible cross-section and spaced notches in the end disposed in said annular space to permit movement of said inner seal portion into sealing engagement with said air line independently of said outer seal portion when said outer seal portion is in sealing engagement with said bottom plate.

5. The improved lift of claim 4 wherein said outer seal portion is annular in configuration; said inner seal portion is annular in configuration, spaced from said outer seal portion and of smaller diameter than said outer seal portion; and, a radially extending flange portion extending between the lower end of said inner seal portion and the upper end of said outer seal portion retaining said seal portions in spaced relationship.

7. The improved semi-hydraulic lift of claim 6 wherein the notches in said inner seal portion are triangular in configuration and have a base dimension slightly greater than the thickness of said end cross-section and have a height about three-fourths of the length of said inner seal portion.