Vacuum-operated Lift Plate Rim

Abstract

A vacuum-operated lift plate assembly including a curved main plate, an elongate resilient rim extending in a continuous course around the main plate defining a mouth for the lift plate assembly, a shear pad secured to the main plate and a contact-operated valve mounted on the main plate. The rim comprises an outer platform having a resilient facing, adapted to contact an object to be lifted, and a continuous mounting flange connected to the platform by an outwardly inclined wall. A plurality of supporting ribs, spaced at regular intervals on the outside of the rim, interconnect the outer platform, the inclined wall, and the mounting flange. The mounting flange is sealingly retained to the main plate by elongate segments located between the ribs. The segments are secured in position by bolts extending through holes in the segments and the main plate.

Description

BACKGROUND OF THE INVENTION

The present invention relates to an improvement in a vacuum-operated lift plate assembly. More particularly, the invention concerns an improved rim structure for a vacuum-operated lift plate adapted to lift and hold objects, such as paper rolls, without the use of pallets.

Vacuum-operated load grabs are widely used in industry for handling loads without the use of pallets. In particular, the handling of such articles as paper rolls is facilitated by the use of vacuum-operated attachments for lift trucks, which contact the outer surface of the roll. Use of such attachments is desirable since the likelihood of damaging the roll is reduced and the use of cumbersome, time-consuming connectors is not required.

In general, a vacuum-operated load grab includes one or more lift plates each of which contacts the side of the load and defines a closed space between the load and the lift plate. The load grab further includes vacuum supply means for evacuating the closed spaces whereby atmospheric pressure forces the load grab and the load together. The friction or shear force between the load and the contacting surfaces of the load grab, established by the atmospheric pressure, enables upward force to be transmitted to the load from the load grab. The shear force is of sufficient magnitude to permit an upward force sufficient to lift and transport the object.

Various lift plate designs have been suggested in the prior art for contacting or attaching to a load. In some instances, the means forming the mouth of the lift plate comprises a flexible rim of relatively soft, yieldable rubber or other elastomer. The flexibility of the rim is provided so that the rim easily conforms to the shape of the object to be handled and forms a seal therewith. One disadvantage of this type of construction is that a rim that is too soft tends to fold or curl over on itself during the initial contact with the load object, particularly when the first contact is from a lateral direction. Such curling prevents an effective seal between the rim and the load.

If the rim is made of stiff material to obviate this problem, the rim is less easily conformable to the surface of the load. Consequently, formation of a suitable seal may not be possible, or the lift plate may be limited to use with objects of a narrow range of sizes.

Another type of rim for a vacuum-operated lift plate is illustrated in U.S. Pat. No. 3,326,593 to Farmer et al. The lift plate described therein includes a rim having an outer casing, comprising a pair of laterally spaced sidewalls of flexible material, and an inner material filling the casing to support the sidewalls. A platform of resilient material is mounted across the sidewalls, adapted to contact the load and provide the necessary friction or shear force. The rim functions satisfactorily to lift loads of a wide variety of sizes. However, it has been found that repeated flexing of the sidewalls, which occurs at the corners of the lift plate upon each compression of the rim, results in undue wear at the corners. Consequently, the rim is not sufficiently durable for satisfactory use.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide a novel rim structure for a vacuum-operated lift plate which includes means for forming a seal with a load.

It is another object of the invention to provide improved rim means, forming a mouth for a vacuum-operated lift plate, which is extremely durable and not subject to excessive wear at the corners of the mouth.

It is yet a further object of the invention to provide an improved rim structure for a vacuum-operated lift plate, which can be molded as an integral structure and easily installed on lift plates of different contour.

It is yet a further object of the invention to provide an improved rim for a lift plate, having a continuous base portion and a continuous platform portion connected by an inclined sidewall, and wherein said platform is supported by a plurality of ribs connected at intervals between the platform and the base portion.

These and other objects of the invention are attained by a rim design which includes an elongate flexible wall extending in a continuous course around the outer edge of a main plate to define a mouth for the lift plate. A contact-operated vacuum regulating valve is mounted on the main plate.

The rim structurally comprises an outer platform having a resilient facing thereon adapted to contact and conform to the surface of the load. A continuous rim mounting flange is connected to the main plate. The outer platform is supported above the mounting flange by an outwardly inclined wall. A plurality of supporting ribs, spaced at intervals on the outside of the rim, interconnect the platform, the inclined wall, and the mounting flange. The mounting flange is secured to the main plate by a plurality of elongate segments or washers located between the ribs. The washers are retained in position by suitable fastening means such as bolts extending through holes in the washers and in the main plate.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent from the following detailed description of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a front elevation view of a lift plate assembly in a material-handling apparatus, with each lift plate in the assembly being provided with a rim designed in accordance with the invention;

FIG. 2 is a cross-sectional view taken along lines 2--2 in FIG. 1;

FIG. 3 is a cross-sectional view taken along the lines 3--3 in FIG. 1; and

FIG. 4 is a perspective view of a section of the lift plate rim showing the rib structure and the washers securing the rim to the main plate.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, one preferred embodiment of the invention is illustrated comprising a vacuum-operated roll grab 10 for lifting and carrying large rolls of paper. The roll grab arrangement generally comprises six lift plates 12 mounted on a common equalizer plate 11. The equalizer plate is adapted to be mounted on a lifting and carrying device such as a lift carriage 13 forming part of a lift truck, not shown. To accommodate the circular conformation of cylindrical objects such as paper rolls, the lift plates and the equalizer plate are curved so that the rims of the lift plates will closely fit the curvature of the paper rolls when standing on end.

It should be apparent that the equalizer plate can be formed of any desired curvature and dimensions to fit objects of a particular size. Furthermore, the load grab is not limited to use with lift trucks nor for lifting cylindrical objects. Thus, for grasping flat-sided objects, a flat equalizer plate and/or flat lift plates can be provided.

In a load grab embodying a plurality of lift plates, it is desirable that a contact-operated vacuum control valve be provided for each lift plate to control the supply of vacuum thereto. A plurality of such valves 20 are shown in FIG. 1 for the lift plates 12. Each lift plate otherwise comprises a curved main plate 21 having a backing plate 22 secured on one side thereof by welds 23. The main plate and backing plate are formed with aligned circular openings 24 therein adapted to receive a valve 20 described in detail hereinafter. The main plate is provided with a resilient outer rim 25 depending therefrom along a continuous course to form a mouth for the lift plate. The rim face 26 is adapted to contact a curved surface of a load object such as a paper roll, to be lifted and to form a pressure seal therewith. The structural details of the rim 25 are described hereinafter. One or more shear pads 14 of conventional design are secured to the main plate, adapted to contact the load. Use of these pads is not essential but facilitates the handling of heavy loads.

The main plate and backing plate are pivotally secured to the equalizer plate by a mounting bracket 31 on the backing plate and corresponding brackets 34 provided on the equalizer plate and arranged to extend adjacent to brackets 31. Aligned cylindrical bores 35 are formed in brackets 31, 34 adapted to receive pins 36. Washers 38 are provided over the outer ends of the pins to retain the latter in position, and cap screws 39, extending through corresponding threaded holes in brackets 34 secure the washers.

A leaf spring 40 is secured to the back of the lift plate assembly adapted to engage the equalizer plate and maintain the lift plate at a desired angle with respect to the equalizer plate. A pad 41 is provided at the outer edge of the equalizer plate to cushion any impact between the back of the lift plate and the equalizer plate.

Referring particularly to FIG. 3, the structure of a valve 20 is illustrated in detail, generally comprising a base member 51 having a semispherical ball 52 reciprocally retained therein. The base is generally cup-shaped, having a flange 54 formed about the outer periphery thereof. The flange is adapted to fit within an annular groove 56 defined between backing plate 22 and bracket 31. A sealing ring 58 is provided between the flange and the backing plate, adapted to form a pressure seal therebetween when cap screws 55 are tightly secured, forcing the members together. The base further includes circular outer walls 60 that define a cylindrical inner bore closed at one end by a base wall 61 having an elevated portion 62. A circular opening 65 is formed in the elevated portion defining a valve seat 63 which communicates with an inner chamber 64 formed between the base wall and bracket 31.

A source of vacuum, not shown, communicates with chamber 64 via a length of tubing 66 threadably secured within a hole 67 in bracket 31. The source of vacuum is adapted to evacuate the space between the lift plate and the load when valve 50 is open.

Ball 52 of the valve includes a hollow semispherical portion 70 having straight walls 71 depending therefrom, and an elongate center post 73 attached to the inner periphery of portion 70. The ball is fabricated of nylon or some other material having a low coefficient of friction and is mounted for reciprocal movement within the bore in base 51, with walls 71 adapted to fit loosely within walls 60. The center post 73 extends through opening 65 and receives a rubber valve 76 secures at the end of the post by a screw 78 engaging threaded hole 79.

A normally compressed coil spring 80 is provided between base 51 and 52, adapted to hold the valve in a normally closed position. Any other suitable resilient means can be used as well as the coil spring. The force of the spring can be overcome by contact between the ball of the valve and the surface of the load. As the ball is moved inwardly, valve 76 is unseated permitting air to be evacuated through the valve by the vacuum supply. Sufficient clearance exists between walls 71 and walls 60 to permit ample air flow during such evacuation. However, holes can be provided through the ball if desired to facilitate airflow. Release of the lift plate form the load is accomplished by a main valve, not shown, under the control of the operator of the lift truck. The main valve momentarily shuts off the vacuum supply and admits atmospheric pressure into line 66.

Referring now to FIGS. 2-4, the structural details of the lift plate rim are described in detail. The lift plate rim is preferably a continuous, integral element formed of molded rubber or other suitable elastomeric material. Formation of the rim by molding is an economic manufacturing technique and the use of an integral molded rim of the type described permits the rim to be installed directly upon lift plates of different contour. However, it should be apparent that the use of a rim having several sections is possible without departing from the invention. Also, the rim can be fabricated by any other suitable technique.

Rim 25, structurally comprises a mounting flange 27, adapted to be secured to the main lift plate, and a platform section 26 adapted to contact and conform to the surface of the load. The platform section is spaced generally above the mounting flange and secured thereto by an inclined wall 28, which also serves to form the inner surface of the mouth of the lift plate. Wall 28 is preferably inclined at approximately a 45.degree. angle outwardly with respect to the mounting flange, as shown. The inclined wall serves to resist inward folding of the platform in the event the initial contact between the platform and the paper roll is from a lateral direction. However, the degree of incline necessary to achieve this result is minimized by the presence of ribs 29 provided along the outer periphery of the rim. The ribs are spaced at suitable intervals and secured between the platform and the mounting flange. Ribs 29 are also secured to the side of wall 28 and, therefore, tend to provide appreciable support to the platform.

The platform includes a facing strip 30 of soft resilient material such as sponge rubber or an elastomeric material, adapted to seal against the outer surface of the paper roll. This facing strip can be inset into the main platform, or the entire platform can be comprised of the resilient material. The mounting flange of the rim is secured to the main plate by fastening means including short segments or washers 16 spaced between the ribs. Bolts 17 capped by nuts 18 are used to secure the mounting flange firmly between segments 16 and the main plate. The use of a plurality of short segments enables the rim to be easily fitted to main plates having different contours. Accordingly, the rim described is much easier to install than a rim utilizing a integral fastening strip to retain the rim to the main plate.

In the embodiment described, the platform section of the rim is depressed upon contact with the load until the shear pads within the lift plates are contacted. The incline of the wall and the spacing of the ribs enables the platform to be easily depressed. However, the structure described provides sufficient resilience that the platform is brought into satisfactory engagement to form a seal between the rim and the load. Furthermore, with the structure described an appreciable amount of shear force is exerted upon the load by the rim platform. This was not heretofore possible with a rim design including a soft platform facing and an easily depressable rim surface.

The use of supporting ribs along with an inclined wall, between the rim platform and base section, serves to prevent the rim from folding over in to the center of the lift plate in the event of lateral contact with the load. The location of the rim platform above the base section, and outwardly from the center of the base section also contributes to this result. With the rim structure described it has been found that repeated use does not result in tearing or excessive wear at the corners of the mouth of the lift plate.

In using the lift plate assembly described and illustrated, the equalizer plate is maneuvered over an object to be lifted. When properly positioned, the equalizer plate is moved into contact with the object whereby the rim of one or more of the lift plates is engaged. The contacting lift plate rims will be depressed sufficiently that the load comes into contact with the shear pads and the base of vacuum control valve. Upon contact of the ball by the object, the valve is opened and the vacuum supply evacuates the space under the lift plate. This, in turn, creates force between the lift plate rim and the shear pad and the load, permitting the load to be lifted and transported by the lift truck.

If the object to be lifted is not sufficiently large to embrace all the lift plates, the valves which are not contacted remain closed and the vacuum supply to the actuated lift plates is not affected.

Claims

It is claimed and Desired to Secure by Letters Patent:

1. A vacuum-operated lift plate assembly including

a main plate,

a rim extending in a continuous course that defines a mouth of said lift plate assembly,

fastening means securing said rim to one side of said plate,

said rim comprising a mounting flange, a platform having one sealing side, a wall connecting said mounting flange and said platform with said platform being arranged substantially over said mounting flange on the same side of said wall as said mounting flange with said sealing side facing away from said main plate to contact load objects, a plurality of ribs spaced at intervals around the outside of said rim, each rib connected to the mounting flange and the platform to support the platform and deter inward folding thereof, and

means for evacuating the mouth of said lift plate assembly.

2. A lift plate assembly as described in claim 1, wherein said wall is outwardly inclined with respect to said main plate and said ribs are secured to said wall to support the platform against lateral movement into the mouth of said assembly.

3. An assembly as described in claim 2, wherein the mounting flange, the wall, and the platform are fabricated of a resilient material and wherein the surface of said platform includes a portion formed of soft resilient rubber.

4. An assembly as described in claim 1, wherein said fastening means comprise a plurality of elongate washers said washers being positioned adjacent said mounting flange between said ribs, and means for clamping said washers in fixed position with respect to said main plate.

5. A lift plate assembly including

a main plate forming the back of the assembly;

a resilient rim extending in a continuous course that defines a mouth of the lift plate assembly;

fastening means securing said rim to one side of said main plate;

said rim comprising a mounting flange, a platform having at least one sealing side with a strip of soft, resilient, elastomeric material secured thereto, a wall connecting said mounting flange and said platform, said wall being outwardly inclined with respect to said main plate;

said platform being arranged substantially over said mounting flange on the same side of said wall as said mounting flange with the strip facing away from the main plate, positioned to contact load objects;

a plurality of ribs arranged at intervals around the outside of said rim, said ribs being attached to the platform, the mounting flange, and the wall;

said fastening means comprising a plurality of washers, said washers being located adjacent said mounting flange between said ribs, and means for clamping said washers in fixed position with respect to said main plate; and

means for evacuating the mouth of said lift plate assembly.