Abstract:
A support frame assembly including at least one pair of generally vertical spaced uprights joined together by transversely extending structural members and having caster wheel support members for supporting a rotatably mounted caster wheel mounted axle and a pedal actuatable lever engaging the axle to allow selective movement of the caster wheel mounted axle between &#34;mobile&#34; and &#34;use&#34; mode conditions--the invention further including a joined second pair of generally vertical spaced uprights each having a caster wheel support member for yieldably supporting a caster wheel arrangement for selective movement between &#34;mobile&#34; and &#34;use&#34; modes.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to support frame assemblies and more particularly to a unique arrangement for readily adjusting various types of support frame assemblies between &#34;mobile&#34; and &#34;use&#34; modes--particularly step ladder and platform assemblies. 
     Mobile support frame structures incorporating various mechanical assemblies for adjusting such support frame structures between &#34;mobile&#34; and &#34;use&#34; modes are generally well known in support frame art. In this regard, attention is directed to U.S. Pat. No. 5,653,306, issued to R. B. Bendickson et al on Aug. 5, 1997 and to U.S. Pat. No. 5,791,434, issued on August 11 to Paul R. Swiderski and to the several patent references cited therein. These aforementioned patents recognized and resolved many of the comparatively complex constructions, assemblies, uses, and maintenance problems of previous assemblies as does the unique structural arrangement of the present invention described herein, the present invention further providing a mobile ladder and platform structural arrangement which further simplifies and minimizes the required operational pressures to adjust various types of structural support frames between alternative &#34;mobile&#34; and &#34;use&#34; modes. The present invention accomplishes its unique arrangement in a straightforward and economical manner, requiring a minimum of parts and a minimum of manufacturing, assembling, operating and maintenance steps to accomplish the desired adjusted positions for various types of support frame members and particularly for step ladder structural frame assemblies. 
     Various other features of the present invention will become obvious to one skilled in the art upon reading the disclosure set forth herein. 
     BRIEF SUMMARY OF THE INVENTION 
     More particularly the present invention provides a support frame structure which can be utilized in various structural support assemblies including single and extensible ladder frames, step ladders and platform support frames, the support frame structure including at least one pair of generally vertically extending spaced uprights connected by transversely extending cross-beam members and further including a structural assembly for selectively adjusting the support frame between a stationary &#34;use&#34; mode condition and a movable &#34;mobile&#34; mode condition comprising: caster wheel support means connected to the lower portion of the support frame; axle mean pivotally mounted on the structural support means and including caster wheel means mounted thereon; leverage means pivotally mounted on the structural support means with a portion thereof in cooperative engagement with the pivotal axle mean; and, actuating means cooperative with the leverage and axle means to provide for movement of the axle means and the caster wheel means mounted thereon between the support frame &#34;use&#34; mode and the support frame &#34;mobile&#34; mode conditions. In addition, the present invention provides a novel support frame structural assembly which does not require the actuated leverage and axle arrangement aforedescribed, the novel structural assembly including a pair of aligned spaced uprights joined by transversely extending beams with caster wheel support means fixed to the lower portion of the transversely extending beams for the spaced uprights; and, caster wheel means yieldingly supported by the upright joining beans to adjustably and yieldably extend below the lower extremities of the pair of spaced uprights when the support frame is free of user-added weight in a &#34;mobile&#34; mode and to extend above the lower extremities of the spaced uprights when the support frame is in a user-added weight &#34;use&#34; mode. The present invention further provides unique arrangements for the caster wheel means to be held for movement in a preselected aligned position or to be rotatable in accordance with elected movement of the support frame. 
     It is to be understood that various changes can be made in one or more of the several parts of the inventive structural assembly arrangements described herein by one skilled in the art without departing from the scope or spirit of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring to the drawings, which disclosed embodiments of the present invention here employed with step ladder structure: 
     FIG. 1 is a broken view from inside the bottom of the lower portion of a step ladder looking outwardly, incorporating certain of the novel features of the present invention with the step ladder being shown in a &#34;mobile&#34; mode condition; 
     FIG. 2 is an enlarged cross-sectional side view of the front structure taken in a plane through line 2--2 of FIG. 1, the step ladder being shown in a &#34;mobile&#34; mode condition; 
     FIG. 3 is an enlarged cross-sectional side view similar to that of FIG. 1, taken in a plane through line 3--3 of FIG. 1, the step ladder being in a &#34;mobile&#34; mode condition; 
     FIGS. 2A and 3A are views similar to FIGS. 2 and 3, respectively, with the step ladder being shown in a &#34;use&#34; condition; 
     FIG. 4 is an isometric view of the caster frame assembly and caster wheel assembled therewith; 
     FIGS. 5 and 6 are broken, isometric views of structure similar to the structures of FIGS. 2 and 2A, respectively, disclosing such structures in &#34;mobile&#34; and &#34;use&#34; mode conditions, respectively; 
     FIGS. 7 and 8 are broken, isometric views of structures such as disclosed in FIGS. 5 and 6 in &#34;mobile&#34; and &#34;use&#34; mode conditions, respectively; 
     FIG. 9 is a broken rear view of the upper and lower portion of the ladder disclosing a still further novel concept of the invention independent of the actuating systems of FIGS. 1-3, 2A and 3A; 
     FIGS. 10 and 11 are enlarged cross-sectional side views of the rear support structure taken in a plane through line 10--10 of FIG. 9 with the structure in both views in weight removed &#34;mobile&#34; mode condition, the caster wheel stem of FIG. 10 having a multi-sided cross-section with a fixed stirrup so that the caster wheel moves in fast, preselected alignment and with the caster wheel stem of FIG. 11 having a circular cross-section and rotatable stirrup mounting so that the wheel rotates in response to support frame directional movement; and 
     FIG. 12 is an enlarged cross-sectional side view similar to the fixed stirrup view of FIG. 10 with the support frame structure in weight applied &#34;use&#34; mode condition. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings, it can be seen that the novel support fame assembly is here disclosed as part of a support frame structure in the form of a step ladder assembly 2 including aligned front (FIGS. 1-8) and rear pairs (FIGS. 9-12) of generally vertically extending spaced stringers 3 and 4, respectively. As known in the step ladder art, the stringer pairs 3 and 4 are collapsibly and extendably hinged together at their respective upper portions to include a support platform 10 (FIG. 9) with the first or front pair of stringers 3 having a plurality of suitably spaced horizontally extending steps 6. As is conventional, each step 6 is connected at the opposite ends thereof to the front stringers 3. As also is conventional, the aligned second or rear stringer pair 4 (FIG. 4) has transversely extending structural beams 7 (FIG. 9) connected at opposite ends to the spaced stringers. In this regard, and as will be more fully described hereinafter (FIGS. 9-12), at least one of the transversely extending and stringer connected beams is of cross-sectional U-shaped configuration to serve as part of one novel feature of the present invention. 
     Referring to FIGS. 1-8 of the drawings, the first or front pair of stringers 3 has a first spaced pair of caster wheel structural support member assemblies 8, 8&#39; fastened to the underface of the lowest of front steps 6, these caster wheel support member assemblies 8, 8&#39; are in spaced relation to each other and each extends downwardly in fastened two-piece, 8 and substantially normal thereto 8&#39; fashion, each assembly 8, 8&#39; being adjacent and parallel to one of the stringers of the front spaced stringer pair 3. It is to be understood that 8 and 8&#39; can be formed as one integral piece if so desired. Opposed and spaced, aligned rotary disk members 9 are rotatably mounted adjacent the distal end of each downwardly extending support member assembly 8, 8&#39; with the peripheral surface of each rotary disk members 9 incorporating a selectively contoured and correspondingly aligned notch 11 (FIGS. 2, 3 and 6). 
     Also, rotatably mounted on and between the spaced, downwardly extending support members are the opposite extremities of a longitudinally extending caster wheel support axle 12 (FIGS. 1 and 4). Axle 12 terminates at its opposite extremities in U-shaped configurations with the opposed distal legs 12&#39; of each extremity of axle 12 being rotatably mounted on an adjacent downwardly extending caster wheel support member 8&#39;. The rotatably longitudinally extending portion of axle 12 freely nests in the correspondingly aligned notches 11 of the rotatably mounted rotary disk 9 (FIGS. 5-8). It is to be noted that each of the aforedescribed U-shaped configurations at the opposite extremities of rotatable axle 12 includes a stem housing 15 incorporating a stem (not shown) connected to caster wheel saddle 14 which supports caster wheel 16. Stem housing 15, in turn, engages and is fixed in receiving loop 13, which is part of the rotatably mounted and supported distal legs 12&#39; of the U-shaped end extremities of rotatable axle 12. 
     To move each of the caster wheel saddles 14 and the associated caster wheels 16, a longitudinally extending actuating member, here discloses as foot pedal 18 is longitudinally recessed along the bottom portion thereof (FIGS. 1 and 5-8) to rotatably receive in nesting engagement the longitudinally extending central portion of axle 12 which extends between the spaced, aligned notched rotary disks 9. Opposite ends of axle 12 are positioned to each engagingly be received in notch 11 of each rotary disk 9 (FIGS. 7 and 8) and slotted links 18&#39;, each link being connected at one of the two ends of foot pedal 18, and each being connected at an opposite end to a rotary disk 9. Helical coil springs 19, (FIGS. 2, 2A, 5 and 6) are provided to extend between each of the downwardly extending caster wheel structural support members 8&#39; and the notched rotatable disk members 9. It is to be understood that, if desired, foot pedal 18 may also be fixedly attached to rotary disk 9. 
     The opposed ends of each helical coil spring 19 are connected at preselected positions on each downwardly extending two-piece support assembly 8, 8&#39; and the rotary disk member 9, respectively, so that ready, light pressure responsive movement of notched rotary disk 9 by the notch engaged axle 12, which can be initiated when foot pedal 18 is actuated, causes caster wheels 16 to be moved to a &#34;mobile&#34; mode. Helical coil springs 19 further serve to yieldably restrain the caster wheels when the structural assembly is moved by imposed &#34;user&#34; weight to a &#34;use&#34; mode. Advantageously helical coil springs 19 can be so positioned to obtain ideal balanced conditions, when the longitudinal axis of the spring (FIGS. 1, 2 and 5) is caused to pass over the rotation center of rotary disk 9 when the foot pedal 18 is actuated to ladder &#34;mobile&#34; mode and when the caster wheels 14 are moved to restrained ladder &#34;use&#34; mode by imposed user weight on the structural assembly. Auxiliary secondary springs 20 (FIG. 2) are provided to extend in fastened relation between each rotary disk 9 and assembly 8, 8&#39;. These secondary spring 20 serve to further hold the caster wheel assembly when in &#34;use&#34; mode condition. 
     In accordance with still another feature of the present invention and as can be seen in FIGS. 9-12 of the drawings, the aforedescribed rear stringer pairs 4 disclosing the rear of support platform 10, can include at its lower portion a cross-sectionally U-shaped, horizontally and transversely extending support beam member 21 with the base leg portion 22 extending in a generally vertical plane and the spaced side legs 23 extending in generally horizontal planes. A set of caster wheels 24 are rotatably mounted on spaced, stemmed caster wheel frames 26 with the stems 27 thereof slidably projecting through aligned apertures in the horizontally extending spaced side legs 23. Each stem 27 is surrounded by a compressible helical coil spring 28 extending between spaced side legs 23. A stem mounted stop 29 is positioned at the lower extremity of each coil spring 28 so that spring 28 compresses when the ladder support frame is in a &#34;use&#34; condition above the lower extremities of the upright stringers (FIG. 12) and extends or expands when the ladder support frame is free of user imposed weight and the caster wheels 24 are urged below the lower extremities of the stringers to be in a &#34;mobile&#34; mode condition (FIGS. 10 and 11). As can be seen in FIGS. 10 and 12 of the drawings, each stem 27 is of multi-sided cross-section to engage with apertures in side legs 23 of similar multi-sided cross-section, allowing only fixed straight-line or &#34;tracking&#34; movement of rear casters 24. Alternatively, as can be seen in FIG. 11, each stem 27 can be of circular cross-section to engage with apertures in side legs 23 of similar circular cross-section with a bearing arrangement in caster frame 26, like the bearing arrangement of caster wheel housings 15, allowing free rotation of caster wheels 24. 
     In a typical operation of the inventive apparatus, to move a support platform, such as the step ladder disclosed, from a &#34;use&#34; mode condition to a &#34;mobile&#34; mode condition, it is only necessary that the &#34;use&#34; mode condition weight be removed and foot pedal 18 be lightly actuated. This causes slotted links 18&#39; connected to pedal 18, to move notches 11 of rotary disks 11, which disks are rotatably mounted on 8&#39;, into engagement with the ends of axle 11. The light pressure exerted on pedal 18 and thus on the central body portion of axle 12, as well as the pressure exerted at the extremities of axle 12 by notches 11 of rotary disks 9, causes the caster wheels 14 supported by axle 12 to move below the feet of rails 3 against the forces of helical coil springs 19 and secondary holding spring 20 to place the caster wheel assembly into &#34;mobile&#34; mode condition with the rear caster wheels 24 also being in a &#34;mobile&#34; mode condition by removal of the &#34;use&#34; condition weight, the support platform can be readily moved to another location where &#34;use&#34; mode weight along with springs 19, 20 and 28 cause the caster wheel assembly to be raised and held in support platform &#34;use&#34; mode condition.