Air Lift Jack

Abstract

A lift jack is powered by compressed air and is sealed against the admission of dirt and water into the air cylinder. The air cylinder is provided with a bottom wall or base having a normally convex curvature that becomes concave, in an "oil can" effect, when the jack is placed under load and compressed air applied to the piston within the air cylinder. Convex curvature of the bottom wall allows the relatively heavy lift jack to be moved along on a floor plane more easily and with less effort, and with no damage to the floor surface. An extensible member, adapted to be pin-connected to the main lift cylinder, is also provided to increase the lift height of the jack. The upper surface of the air cylinder is arranged with radial corrugations, to provide great strength and rigidity and to eliminate material deflection of the lift cylinder in load lifting operation. A lift handle is fixedly secured to the main cylinder of the jack for easier portability and in such attitude that the entire unit is carried in a more balanced manner, without injury to the person carrying the jack or damage to the jack.

Description

The invention involves an air-operated piston in a cylinder having an "oil can" type bottom plate, a radially corrugated top plate cover member, formed as a casting and having a hub section extending into and secured to the main air cylinder, a piston having an outer perimeter slightly spaced from the inner wall surface of the air cylinder and provided with a medial annular seal of substantial thickness so that at 180 psi, the air jack is capable of lifting at least 13,500 pounds of load. An axial lift cylinder is secured to the piston, with a removable lift pad at its distal end. The bottom of the piston is provided with a spacing pad of such height that when the piston is at rest on the bottom plate, a space is provided for admission of compressed air under the piston, the fitting connecting the air supply conduit to the air cylinder being secured adjacent the bottom edge of the air cylinder at the bottom plate.

A significant and critical factor, in addition to the features described above, is an upper cover for the air cylinder, in which the over-all height of the lift cylinder bearing, which is integrally formed with the cover member in a casting, includes an outer peripheral hub section adapted to be secured within and to the upper end of the air cylinder, a flange extending outwardly from the hub section to overlie the edge of the air cylinder, a radially corrugated top plate cover portion providing great strength against distortion to the cover member, and a central axial hub section or bearing having a seal within its bore to exclude dirt, water and other deleterious matter that may find itself upon the outer surface of the lift cylinder which rides within the bore of the cover member. The radially corrugated cover surface tapers upwardly from the peripheral flange to substantially increase the over-all height of the bearing and provide maximum support of the lift cylinder against deflection and pivoting.

The air cylinder is also provided with a tapering coiled spring adapted to bear at its base upon one side of the piston and at its other end against the inner surface of the radially corrugated upper end wall adjacent the lift cylinder, to bias the piston to seated position upon the bottom plate when air is released and discharged from the air cylinder.

The air lift jack of this invention is adapted to be supplied with compressed air furnished by any suitable source through a conduit having a manually-operable control valve therein. A supplementary telescoping height-increasing lift cylinder is also provided and is adapted to receive the lift pad removably supported upon the main lift cylinder in the distal end of the supplementary lift cylinder.

The handle of the lift jack is a substantially semi-circular ring having its ends fixedly secured to the outer wall of the air cylinder so that when the jack is lifted thereby, the person carrying it will not ordinarily bump into it and either sustain an injury or damage the jack. The handle is so disposed that the jack pivots from the handle at an angle less than 90.degree. to the floor plane.

It is an object of the invention to provide an air operated lift jack for substantially heavy loads having the features generally described above and more specifically described below in the specification. A further object is to provide an air lift jack of relatively simple and economical construction, of substantially high efficiency, and which is adapted to be portable or readily moved on a floor surface. Still another object is to provide an air lift jack that is extremely sturdy of construction, of substantially high lift capacity, safe and simple to operate, sealed against the entry of dirt and moisture, and having an upper end cover for the air cylinder which is capable of handling and accepting large lateral loads. Yet another object is the provision of a supplementary telescoping lift cylinder adapted to substantially increase the lifting height of the air jack. A further object is to provide an air lift jack having a normally convexly curved bottom plate whereby the jack can be moved into position under the load with relative ease and very little effort.

Various further and more specific objects, features and advantages of the invention will appear from the description given below, taken in connection with the accompanying drawings, illustrating by way of example a preferred form of the invention. Reference is here made to the drawings annexed hereto and forming an integral part of this specification, in which

FIG. 1 is a side elevational view of the air lift jack of this invention positioned in lifting attitude under the load, on a very substantially reduced scale.

FIG. 2 is an elevational view, partially in section, of the air lift jack of this invention.

FIG. 3 is a top plan view of the jack illustrated in FIG. 2.

FIG. 4 is a fragmentary vertical sectional view taken substantially on the line 4--4 of FIG. 3.

FIG. 5 is a fragmentary elevational view, illustrating the telescoping arrangement of the supplementary lift cylinder and the main lift cylinder of the air jack.

The air lift jack 10 of this invention comprises the air cylinder 12, bottom plate 14, the radially corrugated top cover member 16, piston 18, piston return spring 20, main lift cylinder 22, lift pad 24 removably disposed at and upon the distal end of the lift cylinder, handle 26 affixed to the air cylinder body, and the air conduit fitting 28 to and with which the air conduit 30 and manual valve 32 are removably secured and connected.

The body 34 of air cylinder 12 is preferably made of steel tubing. At its lower end, the edge of the cylinder body is disposed upon and weldingly secured and sealed to the bottom plate 14 so that a peripheral flange 36 extends outwardly beyond the wall of the air cylinder. The bottom plate 14 is also made of steel and is provided with a convexly formed or pre-stressed curved bottom crown portion 38 of relatively slight curvature but of sufficient height so that the axial central portion of the plate pivots upon a flat floor plane, allowing the air lift jack to rotate, pivot or ride upon the curved central portion 38 and permitting facile sliding of the jack into position under a load L to be raised. The diameter of the convexly curved portion 38 is substantially less than the diameter of the air cylinder body. The air lift jack can thus be moved more easily or drawn more freely and with less effort upon the ground floor plane A (FIG. 2), than would be possible with a perfectly flat planar bottom plate. When the air lift jack is under load upon the ground plane line A' (FIG. 2), the curved bottom crown portion 38 buckles or "oil cans" into the upper concave attitude substantially represented by the broken line 40, allowing the air cylinder body to bear fully and directly upon the outer peripheral flange 36 of the bottom plate and the annular portion 41 next thereto adjacent and inwardly thereof. When the load is released by depleting the air supply, the force of the spring 20 on top of the piston causes the piston to go down and forces the bottom crown portion 38, intermediate the cylindrical wall 34, into its original convex posture.

The upper air cylinder cover member 16 is made as an integral steel casting and comprises the lower hub portion 42 secured within and to the upper end of the air cylinder 12 by screws 44, the hub flange 46 overlying the edge of the air cylinder, and the corrugated cover portion 48 having the radial corrugations 50 extending from the crown hub end 52 to the cover flange 46. The radially extending corrugations 50 give very substantial strength and support to the lift cylinder 22 against cocking as it rises and extends upwardly above the distal edge of the crown end 52. A central bearing 54, integrally formed in the cover member, extends from the crown hub end 52 to a plane passing substantially through the distal edge of the hub portion 42 (FIG. 4). The hub end 52 is provided with a counterbore 55 seating a rubber-type metal shrouded seal 57 pressed thereinto.

The piston 18 comprises a body 56 having a substantially medial annular groove 58 in its outer edge filled with a ring seal 60 making pressure bearing sealing contact with the inner wall surface of the cylinder body 34. The piston body 56 is also provided with a bottom seating pad 62 and a lift cylinder support hub 64 axially disposed on the other side of the piston body and upon which the lift cylinder 22 is fixedly mounted, by welding the lower end of the lift cylinder to the upper surface of the piston body 56. The pad 62 and hub 64 are preferably integrally formed with the piston body 56 as a steel casting.

The coiled tapered spring 20 has its base end at rest upon the upper surface of the piston body 56 and its smaller end compressively bearing upon the inner surface of the radially corrugated portion 48 of the cover 16, adjacent the lift cylinder 22. The spring 20 biases the piston to its bottoming position, with the seating pad 62 bearing upon the inner surface of the curved central portion 38 of the bottom plate 14, when air is released and discharged from the air cylinder 12 through operation of the manual control valve 32. Although a coiled tapering spring is illustrated and described above, it will be understood by persons skilled in the art that equivalent means for biasing the piston to its return bottom position may also be utilized in the combination of this air lift jack.

The lift cylinder 22 is preferably made of steel tubing and comprises a body 68 of cylindrical form, the proximal end of which is mounted and supported upon the hub section 64 of the piston body 56 and is weldingly secured to the face of the piston body, as described above and illustrated particularly in FIG. 2. The distal end of the lift cylinder has an internal chamfer 69 and extends through and beyond the cover member 16, which supports it axially of the air cylinder, and is provided with the readily removable lift pad 24 adapted to engage and contact the load L to be raised. The lift cylinder body 68 is also provided with transverse openings 70,70 through which a headed pin 72 can be placed for securing the lift cylinder and pad in elevated position upon the cover hub end 52, upon release of air from the air cylinder 12, and also for securing the auxiliary lift cylinder 74 as will be more fully described below.

The load-engaging lift pad 24 is of steel and provided with upwardly directed edge flanges 78,78, and a hub portion 79 adapted to closely seat within the distal end of the lift cylinder body 68. The top surface configuration of the lift pad can of course be varied in design for the load or loads to which the lift jack of this invention is more frequently or regularly applied.

The handle 26 is of steel in a generally semi-circular ring form extending laterally from the air cylinder body 34 and secured to its outer surface in a fixed substantially horizontal posture, preferably by welding.

The air line fitting 28 is generally in the form of a fitting or nipple, the segment of a solid member, either rectilinear (as shown) or circular in cross-section, with a portion cut in a plane oblique to its top surface so that the outer plane of the member 28 is at an angle oblique to the base plane of the bottom plate 14 and is weldingly secured to the air cylinder body 34 closely adjacent the bottom plate flange 36. When fitting 28 has been affixed to the air cylinder body or wall 34, the fitting having a threaded bore 80 therethrough to threadedly receive and engage a suitable fitting 81 at the distal end of the air line conduit 30, an air passage or opening 82 is drilled through the air cylinder wall 34 closely adjacent the bottom wall 14 and communicating with the threaded bore 80 of fitting 28. Thus, when air is discharged into the air cylinder, it will be directed into the space under the piston body 56 in the area of the seating pad 62 which raises the piston body above and from the inner surface of the bottom plate 14.

A clip 88 for storing the pin 72 is secured by one of the screws 44 to the exterior of the air cylinder body 34.

The auxiliary lift cylinder 74 (FIG. 5) is provided with a cylindrical body 90 adapted to telescope and closely fit and slide within the cylindrical body 68 of the main lift cylinder 22. A plurality of transverse openings 92,92 are disposed through the walls of the auxiliary lift body 90 to receive the pin 72 when a pair of openings 92,92 are in register with openings 70,70 of the main lift body 68. The distal end of the auxiliary lift body 90 is provided with a coupling member 94 securely affixed thereto by welding or any other suitable means, the coupling member extending substantially beyond the distal end of the body to provide a support for the removable lift pad 24 which has its hub portion 79 seated therewithin. The auxiliary lift cylinder 74 is of such length that when the pin 72 is engaged in both lift members 22 and 74, a substantial bearing portion 96 of auxiliary cylinder 74 extends through the cover member 16 and into the area of the air cylinder 12 to provide firm support against cocking as the lift pad 24 is raised and elevated by piston 18.

The manually controlled air valve 32 is provided with a quick disconnect fitting 96 for an air supply conduit 98 connected to a source of compressed air serving the air cylinder 12.

In operation, the air lift jack 10 functions and performs as follows. Air under pressure is admitted from the air supply source through the manually controlled valve 32, conduit 30, fitting 28 and opening 82 into the air space under the piston body 56 provided by the seating pad 62 which rests upon the bottom plate 14 in its convexly curved portion 38 on the ground line A (FIG. 2). As air under pressure charges into this air cylinder space, piston 18 is raised against the biasing force of compression spring 20 to lift the cylinder 22 and pad 24 against the load L, raising the same. When the load has been raised to its desired height, the manual control valve 32 is released by the operator, causing the piston supported load to rest upon the air cushion within the air cylinder 12 under the piston. The applied load causes the convexly curved portion 38 of the bottom plate 14 to "oil can" inwardly to the posture represented generally by the line 40 (FIG. 2), the peripheral flange 36 and annular portion 41 of the bottom plate resting fully upon the ground line A'. The flange 36 and bottom plate portion 41 provide a substantially enlarged support area for the air lift jack under the load being carried by the lift pad, lift cylinder and piston.

Since the transverse openings 70,70 can be disposed in any position longitudinally of the lift cylinder body 68, the pin 72 can be inserted either as a support or as a safety fitting against a drop of the lift cylinder upon the cushion of air supporting the piston 18. When the pin is so engaged, the lift cylinder can only fall or recede to the line where the pin 72 meets the upper cover element 52.

The auxiliary lift cylinder 74 is attached to the main lift cylinder 22 by telescoping the bearing portion 96 within the body 68 of the main lift cylinder until a pair of transverse openings 92,92 is aligned and in register with openings 70,70. The pin 72 is then passed through both pairs of openings to lock the auxiliary lift cylinder and the main lift cylinder in fixed posture. The lift pad 24 is then transferred to coupling 94, the lift pad hub portion 79 being seated securely in the bore at the distal end of the coupling.

As illustrated and described above, the spring 20 is of substantially heavy spring steel construction to more readily retract the piston to a bottom position upon release of air pressure from the air cylinder 12. The cover member 16 has a substantially long bearing surface to more adequately support the lift cylinder 22 and prevent its cocking under the heavy loads carried thereby. Handle 26 is so located that a better balance of the jack is achieved as it is manually carried. Handle or rod means, for sliding the air lift jack 10 under the load to a position more remote than is shown in FIG. 1, can also be either removably or fixedly secured to the air lift jack structure above disclosed. The air jack can be manufactured in various lift heights, depending upon the load applications to which the jack will be put, yet the size of the air jack permits easy storage in a minimum amount of space.

Additionally, the internal chamfer 69 at the distal end of the lift cylinder 22 removes any burrs at that edge which might cause the supplementary or auxiliary lift cylinder 74 to stick or wedge in the main lift cylinder, and allows the auxiliary lift cylinder to seat more fully and release more readily.

The upper seal 57 in cover 16 is also significantly desirable when the lift jack 10 is used under farm tractors. Many tractor tires are loaded with liquid chloride and when repairs are necessary for these tires, often the chloride spills from the tires upon the jack. Therefore, protection of the lift cylinders against corrosive attack is necessary. The seal 57 provides a large amount of this protection.

To assure a broader base of support in the lifting operation, the wider base provided by the flanged bottom plate 14 helps to keep the lift jack from being pressed deeply into the ground when raising a farm tractor in the field.

Although a particular preferred embodiment of the invention has been disclosed herein for purposes of explanation, further modifications or variations thereof, after study of this specification, will or may become apparent to those skilled in the art to which the invention pertains. Reference should be had to the appended claims in determining the scope of the invention.

Claims

We claim:

1. An air operated lift jack comprising in combination

an air cylinder,

a piston operatively slidable in said air cylinder and having

a bottom seating pad on the bottom side thereof, and a lift cylinder support hub on the top side thereof,

a bottom base plate secured in air sealing relationship to the bottom edge of said air cylinder and having

a peripheral flange extending beyond the perimeter of the air cylinder,

a flexible central axial portion provided with a normally convexly curved bottom crown portion of relatively slight curvature but of sufficient height that said portion pivots upon a flat ground plane,

said central portion being adapted to flex upwardly and curve concavely within said air cylinder when said cylinder is charged with air and said jack is in load supporting and elevating posture,

an integrally formed cover member for and secured to the top edge of said air cylinder and having

a plurality of downwardly tapering radial corrugations extending from the upper crown end of said cover member to a peripheral flange adapted to overlie said air cylinder top edge,

a hub section of reduced diameter under said cover flange to which said air cylinder top edge is secured, and a lift cylinder bearing of substantial length axial and central of said cover,

a coiled piston return spring bearing upon said piston at one end and upon said cover at its other end to bias said piston to seated position upon said bottom plate,

a tubular main lift cylinder fixedly secured at one end to said piston and seated upon said support hub, disposed within said return spring, and extending through and beyond said cover bearing,

said main lift cylinder having a pair of aligned transverse pin receiving openings therein,

a pin adapted to be disposed in and through said main lift cylinder openings,

a load lift pad removably seated upon the distal end of said main lift cylinder and having a hub portion adapted to fit slidingly within said distal end,

an air conduit coupling fitting fixedly secured to said air cylinder at the lower end thereof adjacent said bottom plate peripheral flange and communicating with an air passageway through said air cylinder disposed in the plane of said piston bottom seating pad, so that air is admitted into said air cylinder between said piston bottom side and said bottom plate,

and an air conduit having a manually operable control valve therein communicating with a source of compressed air at one end and with said coupling fitting at its other end to provide an air supply to said air cylinder.

2. The lift jack structure defined in claim 1, wherein

said piston is formed as an integral unit with a body,

said bottom seating pad on one side and said lift cylinder support hub on the other side of said body,

said seating pad and support hub being substantially axial and central of said body.

3. The lift jack structure defined in claim 1, wherein

said cover lift cylinder bearing extends from a plane passing substantially through the distal edge of said hub section to the upper crown end of said cover member.

4. The lift jack structure defined in Claim 1, and including

a handle for manually carrying said lift jack secured to said air cylinder adjacent its upper edge and offset to one side thereof,

whereby when said lift jack is raised by said handle, the former pivots on said handle at an angle oblique to the ground plane.

5. The lift jack structure defined in claim 1, and including

a tubular auxiliary lift cylinder having

a cylindrical body adapted to telescopically fit and slide closely within said main lift cylinder,

and a tubular coupling member secured to and extending from the distal end of said cylindrical body adapted to receive said load lift pad hub portion therein.

6. The lift jack structure defined in claim 5, wherein

said auxiliary lift cylinder body is provided with at least one pair of aligned transverse pin receiving openings adapted to come into register with said pair of main lift cylinder openings,

whereby upon such registration said pin is seated through said openings to provide an extended lift cylinder for said lift jack.

7. The lift jack structure defined in Claim 5, wherein

said auxiliary lift cylinder body is provided with a plurality of pairs of aligned transverse pin receiving openings,

each of said latter pairs of openings adapted to come into register with said pair of main lift cylinder openings,

whereby upon any such registration said pin is seated through said openings to provide a lift cylinder of extended height for said lift jack.

8. The lift jack structure defined in claim 1, wherein

said piston is provided with an annular groove and a piston seal disposed in said groove for sealing said piston in sliding engagement with said air cylinder.

9. The lift jack structure defined in claim 1, and including

a pin storage ring secured to said air cylinder adjacent said cover member peripheral flange.

10. The lift jack structure defined in claim 1, and including

a seal about said main lift cylinder in said cover member at its upper crown end, to seal said air cylinder and piston against contamination.