BACKGROUND OF THE INVENTION

1• Field of the Invention

The present invention is directed to an apparatus for lifting a first member relative to a second member, and in particular to a device for raising and lowering a roller apparatus. 2. Description of the Prior Art

Roller apparatuses which may be used with various pieces of equipment for selectively engaging the ground for rolling the equipment are well-known. Such a device includes one or more rollers or casters which may be mounted singly or along a mounting bar and may be lowered and raised between an engaging and non-engaging position. The rollers are moved between a raised position wherein the supported device has its legs on the floor and cannot be rolled and lowered position wherein the legs are lifted from the floor and the rollers support the equipment.

Prior roller apparatuses have required workers to bend over and reach under the stage for actuating, lifting or lowering the rollers by pushing or pulling on a handle near the ground. Other attempts to ease actuation have utilized an extended handle which is raised somewhat so that an operator need not bend over as far. However, these devices still require reaching under a stage or other device to its support structure and actuating the handle by hand, which may require a great deal of strength. This may cause strain to the worker and is inconvenient as well as difficult.

It can be seen then that a roller apparatus would have increased utility if it did not require bending over to actuate. It can be seen that if such a mechanism could be operated by foot rather than by hand, it would provide easier operation. The present invention addresses these and other problems associated with raisable roller assemblies.

SUMMARY OF THE INVENTION

The present invention relates to a roller assembly lift mechanism as may be used with mobile equipment, such as a stage, having rollers which can be moved between a raised and lowered position. The lift mechanism moves the roller assembly up and down so that the supporting legs of the equipment may be raised from the ground and the stage may be rolled.

The roller assembly is pivotally connected to a frame member of the mobile equipment. The roller assembly and the frame are mounted by a number of links for pivoting the frame about the roller assembly. A foot operated pedal provides mechanical advantage to pivot the links up and down for raising and lowering the frame relative. A first pedal is used to pivot the frame up and down and a second pedal is used to engage or disengage a stop member for limiting motion of the frame. The stop is selectively engageable so that it may be engaged to lift the stage from the ground and disengaged to lower the stage. In a preferred embodiment, both pedals are located near the floor and may be operated at the same time with one foot.

These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein like reference letters and numerals indicate corresponding elements throughout the several views: Figure 1 shows a perspective view of a mobile folding stage having a roller assembly and a lift mechanism according to the principles of the present invention;

Figure 2 shows a side elevational view of the lift mechanism for the stage shown in Figure 1 with the stage in a raised position;

Figure 3 shows a side elevational view of the lift mechanism shown in Figure 2 with the actuator pedal depressed to lift an end pivot link off a stop; Figure 4 shows a side elevational view of the lift mechanism shown in Figure 2 with the actuator pedal depressed and a stop release pedal depressed and the stop retracted;

Figure 5 shows a side elevational view of the lift mechanism shown in Figure 2 with the stage in an intermediate position between fully raised and fully lowered;

Figure 6 shows a side elevational view of the lift mechanism shown in Figure 2 with the stage fully lowered;

Figure 7 shows a top plan view of the lift mechanism shown in Figure 2;

Figure 8 shows a side elevational view of a second embodiment of a lift mechanism with the stage fully raised;

Figure 9 shows a side elevational view of the lift mechanism shown in Figure 8 with the actuator pedal depressed and the retaining hook disengaged;

Figure 10 shows a side elevational view of the lift mechanism shown in Figure 8 with the actuator pedal depressed and the release pedal depressed; and,

Figure 11 shows a side elevational view of the lift mechanism shown in Figure 8 with the stage fully lowered.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the several views, and referring in particular to Fig. 1, there is shown a mobile stage, generally designated 20. Although a stage is shown, other large mobile structures, such as tables or bleachers, could also be utilized with the present invention. The stage 20 includes stage panels 24 mounted over a frame 22. The frame 22 includes support legs 26 at each corner. Frame cross members 28 extend between each of the two pairs of legs 26. In order to be mobile, the stage 20 includes a pair of roller assemblies 40. The roller assemblies 40 include a mounting bar 44 having rollers or casters 42 mounted thereon. The mounting bar 44 pivotally mounts to the frame cross member 28 on pivot links 52, as explained hereinafter.

The roller assembly 40 is adjustable between a raised and lowered position. With the roller assembly 40 in the raised position, the legs 26 engage the floor and support the stage 20 so that the stage 20 is firmly set and will not move. With the roller assembly 40 in the lowered position, the legs 26 are raised from the floor and the stage 20 is supported by rollers 42 and is free to roll.

In order to facilitate raising and lowering of the roller assembly 40, a lift mechanism 50 is utilized, as shown in Fig. 2. The lift mechanism 50 includes pivot links 52 connecting the roller assembly mounting bar 44 to the frame cross member 28. The pivot links 52 each include outside side members 66 extending on either

side of the roller mounting bar 44 and frame cross member 28, as also shown in Fig. 7. The side members 66 are connected by an upper cross member 68 and a lower cross member 70. The upper cross member 68 is welded or otherwise connected to the frame cross member 28 while the lower cross member 70 is connected to the roller mounting bar 44. A center member 72 extends between the upper and lower cross members 68 and 70 intermediate the roller mounting bar 44 and frame cross member 28. An actuator pedal 80 extends outward beyond the leg 26 and is connected to the bottom cross member 70. In addition, the lift mechanism 50 includes a spring 54 within a spring housing 56. The spring 54 connects to a rod 58 extending from a stop 64 to a release pedal 60. Release pedal 60 pivotally connects to the rod 58 at pivot point 62. The release pedal 60 pushes against the cross member 76 extending from the roller mounting bar 44 to move the rod 58 forward and back. Mounted at the end of the rod 58 is a sliding stop 64 which is utilized for allowing or preventing the pivot link 52 at the lift mechanism 50 to either raise or lower. On top of the housing 56 is a stop 74 which also engages the cross member 68 of the pivot link 52 at the end of its range of motion. At the position shown in Fig. 2, the stage 20 is elevated so that the legs 26 are lifted from the ground. At this position, the stage 20 is supported on the rollers 42 and may be easily moved. At this position, the block 64 supports the upper cross member 68 of the end pivot link 52. This prevents the frame cross member 28 from lowering and maintains the legs 26 elevated off the floor. To lower the stage 20, the actuator pedal 80 is depressed slightly. This actuation pivots the end link 52 upward and moves the upper cross member 68 off the stop 64 and into engagement with the upper stop 74 on top of the spring housing 56. It can be appreciated that depressing the actuator pedal 80

requires very little effort as there is great mechanical advantage for lifting the relatively short pivot links 52. At this point of lowering the stage 20, the release foot pedal 60 is depressed to slide the stop 64 out of the path of motion of the upper cross member 68. The weight of the stage 20 then forces the frame cross member 28 down and the upper cross member 68 moves below the top of the stop 64. Once the upper cross member 68 has cleared the stop 64, the release foot pedal 60 may be released so that the stop 64 may slide back to its original position as biased by the spring 54, as shown in Fig. 5. The weight of the stage 20 continues to force the frame downward until the legs 26 engage the ground, as shown in Fig. 6. To raise the legs 26 off the ground so that the stage 20 may be rolled, the actuator pedal 80 must be depressed from its raised position shown in Fig. 6 to its depressed position, as shown in Fig. 4. In addition, as also shown in Fig. 4, the release pedal 60 must be depressed so that the stop 64 is retracted.

This allows the upper cross member 68 to clear the top of the stop 64. At the point of motion shown in Fig. 4 with the upper cross member 68 above the top of the stop 64, the release pedal 60 may be released. The spring 54 biases the stop 64 into the path of motion of the upper cross member 68, as shown in Fig. 3. At this point, the actuator pedal 80 may be released and the weight of the stage forces pivot link 64 downward so that the upper cross member 68 rests on top of the stop 64 with the legs 26 elevated.

It can be appreciated that raising and lowering can be conducted with one foot as both the release pedal 60 and actuator pedal 80 are sufficiently close that they may be depressed with the same foot, as shown most clearly in Fig. 7.

Referring now to Figs. 8-11, there is shown a second embodiment of a lift mechanism 100, generally designated 100. The lift mechanism 100 includes pivot links 102 connecting the frame cross member 28 to the roller mounting bar 44. Each pivot link 102 includes an upper cross member 116 connected to the frame cross member 28 and a lower cross member 118 connected to the roller mounting bar 44. A center link 120 connects the upper and lower cross members 116 and 118 and extends intermediate the roller mounting bar 44 and frame cross member 28. A stop pin 122 is mounted on the center member 120 and actuator pedal 124 connects to the pivot link 102 for pivoting back and forth for lifting and. lowering the stage 20. In addition, the lift mechanism 100 includes a release foot pedal 104 connected to the pivot link 102 by a linkage 106. The linkage 106 includes an end hook member 108 pivotally connected to a connecting member 112. The connecting member 112 pivots about the upper cross member 116 of the pivot link 102. The hook member 108 engages the end of roller mounting bar 44 and hooks about a rounded end portion 126.

Referring now to Fig. 8, lift mechanism 100 is shown engaged so that stage 20 is lifted off the floor. In this position, the hook member 108 of the linkage 106 engages the rounded end portion 126 of the roller mounting bar 44. This prevents any downward movement of the stage 20 or mechanism 100 about the pivot links 102.

To lower the stage 20 so that the legs 26 will engage the ground, the actuator pedal 124 must be depressed slightly, as shown in Fig. 9. This rotates the pivot link 102 upward. The linkage 106 is also moved by this motion so that the hook member 108 is pushed away from the end portion 126. At this point, the release pedal 104 is depressed, thereby lifting the hook member 108 up and over the rounded end portion 126, as shown in Fig. 10. The weight of the stage 20 will

naturally tend to push the pivot link 102 downward and pull the hook member 108 beyond the rounded end portion 126. It can be appreciated that the stage is lowered at this point by gradually allowing the actuator pedal 124 to be lifted upward. At the same time, the release pedal 104 must be depressed so that the hook member 108 remains raised above the rounded end portion 126. Once the hook member 108 has been pushed on top of the roller mounting bar 44 and past the end portion 126, the release pedal 104 may be released and the motion of the stage can be controlled with the actuator pedal 124. The weight of the stage 20 pushes the pivot links 102 downward and raises the actuator pedal 124 to the position shown in Fig. 11. As shown in Fig. 10, the downward motion of the actuator pedal is limited by the pin 122 engaging the frame cross member 28 so that the actuator pedal 124 cannot be pushed into the floor.

When the stage 20 is in the stationary position, the lift mechanism is in the position shown at Fig. 11. To elevate the legs 26, the actuator pedal 124 is depressed. This motion pivots the links 102 upward and raises the frame cross member 28 and the entire stage 20, as shown in Fig. 9. The pedal must be depressed far enough so that the hook member 108 extends down around the end portion 126. Once the hook 108 has been lowered to a point below the end portion 126, the actuator pedal 124 may be released. The weight of the stage will then pivot the link 102 downward pulling the linkage 106 away from the leg 26. This pulls the hook member 108 around the end portion 126. The hook 108 prevents the frame cross member 28 from moving downward any further and keeps the legs 26 raised off the floor. The stage is supported on the rollers 42 at this point and may be rolled freely in any direction. It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing

description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.