US3820190A - Steerable assembly for wheelchairs and the like - Google Patents

Abstract

A STEERABLE ASSEMBLY FOR WHEELCHAIRS, MOVABLE BEDS AND LIKE DEVICES ADAPTED TO BE MOVED ACROSS THE GROUND OR FLOOR ON ROLLERS. THE ASSEMBLY HAS A PAIR OF UPRIGHT TRANSVERSELY INTERCONNECTED TUBULAR POSTS AT THE BOTTOM OF WHICH ARE PROVIDED CASTER ROLLERS IN RESPECTIVE BIFURCATED CASTER SUPPORTS OR FORKS. WITHIN THE LATTER, BIFURCATED SPRINGS CAN BE DEFLECTED IN OPPOSITE DIRECTIONS TO ENGAGE THE POST AND THE ROLLER PERIPHERY TO IMMOBILIZE THE SUPPORT AND THE ROLLER WHEN AN ACTUATING MEMBER IS SWUNG FROM POSITION TO ANOTHER. THE ACTUATING MEMBER FORMS A TOGGLE WITH A CROSSBAR MEMBER AS IT IS DISPLACED THROUGH A DEAD-CENTER POSITION AND HAS A PAIR OF PINS AT ITS ENDS WHICH ENGAGE, THROUGH SLOTS IN THE POSTS, RESPECTIVE SLIDES CONTROLLING THE SHAFTS WHICH OPERATE THE BIFURCATED SPRINGS.

Description

[ 1 June 28, 1974 STEERABLE ASSEMBLY FOR WHEELCHAIRS AND THE LIKE [75] Inventor: Friedhelm Miiller,Tonisheide,

Germany i [73] Assignee: Firma Happe & Co., Tonisheide,

Wulfrather Str., Germany 221 Filed: May22, 1972 21 Appl. No.: 255,448

[30] Foreign Application Priority Data Germany 16/35 1,564,850 3/1969 France 16/35 Primary ExaminerBobby R. Gay Assistant Examiner-Doris L. Troutman Attorney, Agent, or Firm-Karl F. Ross; Herbert Dubno 5 7 ABSTRACT A steerable assembly for wheelchairs, movable beds and like devices adapted to be moved across the ground or floor on rollers. The assembly has a pair of upright transversely interconnected tubular posts at the bottom of which are provided caster rollers in respective bifurcated caster supports or forks. Within the latter, bifurcated springs can be deflected in opposite directions to engage the post and the roller periphery to immobilize the support and the roller when an actuating member is swung from one position to another. The actuating member forms a toggle with a crossbar member as it is displaced through a deadcenter position and has a pair of pins at its ends which engage, through slots in the posts, respective slides controlling the shafts which operate the bifurcated springs.

14 Claims, 12 Drawing Figures ?ATENTEBJM28 W4 1820, 1 90 SHEET 5 OF 5 iii .7

STEERABLE ASSEMBLY FOR WHEELCHAIRS AND THE LIKE FIELD OF THE INVENTION My present invention relates to steerable assemblies for wheelchairs, hospital beds, walking frames, convalescent, prosthetic and like appliances or apparatus in which a pair of swivelable or steerable wheels rest upon the floor. More particularly, the invention relates to improvements in a manually actuated mechanism for arresting the steerable wheels in such devices.

BACKGROUND OF THE INVENTION In wheelchairs, movable beds such as hospital beds and convalescent beds, walking frames and like medical appliances and other apparatus or devices adapted to roll along the ground, it is customary to provide at least two steerable casters whose rollers engage the ground and support the assembly. Such additional assemblies of this type may be provided and a single assembly of two casters may be used with other propel-.

ling means. The term steerable is used herein to refer to a roller arrangement which can be displaced angularly about an upright axis when the assembly movement suffers a direction change. It is not necessary within this definition to provide means for, individually swinging each roller about the upright axis and the steering movement may be a result of entrainment of the assembly by the remainder of the structure in a wheelchair or the like in which the main wheels may be operated manually or automatically and steering accomplished by varying the rates and/or sense of rotation of the main wheels.

It is also a common practice, especially in wheelchairs and like appliances, to provide means for arresting the casters so as to retain the assembly in place. Since each caster arrangement is swingable about an upright axis and ,carries a roller which is journaled about a generally horizontal axis, the arresting means should immobilize both the caster support and the roller.

Where wheelchairs and like structures with frames are provided, the casters may be disposed at the feet of respective posts or legs which areinterconnected by a crossbar arrangement. A conventional actuating system for an appliance of this type makes use of a handle controlling the arresting means and operating a member extending through the crossbar. This system has the disadvantage that additional means must be provided to retain the handle in its locking and unlocking position. Also mounting the crossbar and the actuating system contained therein is difficult and expensive and the system has been found to fail frequently in practice as a result of jamming within the crossbar. Finally, the arrangement of the actuating mechanism at least in part within the crossbar interconnecting the two posts results in excessive wear of the moving parts.

It should be noted also that conventional systems using actuating mechanisms within a crossbar have customarily employed cable devices for force transmission between the actuating and actuated elements of the arresting mechanism. Such cable arrangements are prone to wear, difficult to repair and frequently unreliable.

OBJECTS OF THE INVENTION It is the principal object of the present invention to provide an improved assembly with steerable wheels or rollers which avoids the aforementioned disadvantages.

provide an improved low-cost arresting mechanism for a steerable assembly of the class described.

SUMMARY OF THE INVENTION These objects and others which will become apparent hereinafter are attained, in accordance with the present invention which provides a steerable assembly comprising a pair of transversely interconnected tubular posts, each of which comprises a respective vertically shiftable shaft operating an arresting mechanism within the caster support to lock the latter against rotation about the respective upright axis and to lock the associated roller against rotation. According to an important feature of the invention, a crossbar interconnects the posts and cooperates with the actuating member which also transversely bridges them but is located externally of the crossbar. The posts are provided with respective vertically extending slots through which pins of the actuating member may pass to act upon the respective shafts, the latter being biased by springs within the posts such that the srpings also act to hold the actuating member against the crossbar in a toggle joint when the actuating member is shifted past a dead-center position to displace the pins.

More generally, where the crossbar member and the actuating member lie parallel to one another and are usually horizontal, the actuating member is angularly displaceable about an axis transverse to the upright axes of the posts between two positions with different spacings of the transverse axis from the crossbar member. One of the members, generally the actuating member or a part thereof is displaceable relative to the other member (usually the crossbar member) along the posts to actuate the pins, shafts and arresting devices as described. The actuating member in all cases, however, operates toggle-fashion for self-locking or movement into a position in which the spring acts against selfdisplacement of the actuating member in one position of the arresting mechanism. The toggle arrangement may make use of a bent-lever construction of the actuating member.

The resulting arresting mechanism for the steerable assembly is particularly suitable for use with the steerable wheels of a wheelchair since it allows handles on the actuating member to extend from either end thereof, i.e. on opposite sides of the wheelchair. The assembly is light, requires little room and can be exposed to considerable stress without damage. Since the toggle system uses the interfltting or interengaging relationship of a fixed crossbar with a swingable actuating bar, no complicated indexing arrangement is required and operation of the device is particularly simple. Furv 3 v thermore, since the actuating member or a part thereof cradles the crossbar member in the locked position and a displacement along the post is necessary to bring the actuating member through the dead-center position to release it, there is'no danger that the arresting mechanism will be inadvertently released.

According to the present invention, therefore, an arscribed provides a connecting member externally of the crossbar interconnecting the posts and havinga pair of slide bodies therewithin which are actuated by pins extending through slots of the posts, the slots running in the vertical direction or parallel to the vertical axes of the posts. As the actuating member is swung about an axis, which may correspond to the. axis of the crossbar ormay be spaced therefrom, portions at the ends of the actuating bar, eccentrically carrying the pins, shift the latter axially of the posts to operate the arresting members. The actuating member thus constitutes amechanism for translating angular displacement about a generally horizontalaxis into vertical displacement of the slide bodies along the vertical axis of the post,

,The actuating member is shaped as a bent lever or toggle having at least a portion cradling the crossbar in the position of the actuating member in which it is to be retained. The actuating bar may be provided with a pair of laterally projected handle portions which can be manipulated by a patient in the wheel chair on either side with ease. Furthermore, the: handle portion may constitute the part of the actuating assembly forming the cradle with the actuating bar or may be separate from the cradle member when the latterconstitutes a toggle link of generally circular segmental configuration. Since the actuating bar connecting the two handle portions lies externally of the crossbar 'b etween'both legs of the wheelchair, i.e. between both: legs of the wheel chair, i.e. between both tubular posts, the cross-7 bar, the actuating bar and thelegs can be substantially flush (without protruding members) except for the lat erally projecting handles. The toggle, bent-lever oreccentric construction allows the actuating memberrto rest against the crossbar so that the former is retained Of course, the crank may also be located below the crossbar whereupon the actuating member draws the slide against the force of the spring when: the actuating member shifted through the dead center position. in the orientation of the crank above the crossbantof course, the springmay' simply be relieved topermit it i to operate the braking element. resting mechanism for an assembly of the character dec According to a further feature of the invention, the. handle portions may be interconnected by a bar located externallyof the crossbar as previously noted while the handle portions are rotatable about the axis of the crossbar thereon and carryinglink elements op erating the pins. The link elements, in this case; form the toggle arrangement. According to yet another fea ture of the invention, the connectingbar-between the handle portions constitutes a sleeve coaxially surrounding the crossbar and rotatable thereon, the connecting bar being indirectly tied' to links as noted.

DESCRIPTION or THE DRAWING The above and other objects, features and advan tages of thepresent invention will become more readily FIG; 4 isa cross-section taken along the line lV IV V r of FIG. 2;

FIGLS is a vertical section through an assembly according to another embodiment of the invention with the parts in their braking position;

FIG. 6' is a sectionof the assembly of FIG. 5 with the 7 parts in their released position;

FIG. 7 is a section taken along the line VlI Vllof FIG. 5; I

in placein a selfretaining manner without any addi-t V tional indexing means.

According to a more specific feature of the il'lVEfltion, the actuating bar bridging the two postsis formed as a simple crank with offset end portions, the latter being constituted as side plates or linked the crank-- and carrying the pins'The slide body within eachpost pre'ferably'forms a seatfor'acompression-typecoil;

spring which acts throughtthe pins andiside'platesor, cheeks of the crank. to retain the latter sin fitsgselfii locking position against thecrossbar afterthe'crank has been shiftedthrougha dead-center position'i Toaone side, of this dead-center'position, correspondingfto a,

first actuating position of the slide body andptheishaft upon which it acts, the spring functions' to;urge the,

braking member into engagementawith the post andlor the roller tolock the caster against movementlathe other position, eg the positioncin, which the actuating member is selfretain'ed against the crossbar, the spring is stressed and the locking elements are relieved. The spring thus acts as a so-called braking spring to hold the brake in an engaged condition. The crank or actuating member can then be located above the crossbar which may have a collar rotatably engaged by the actuating member to facilitate movement of the crank thereover.

Fit). 8 is a vertical section through the posts or legs of a wheelchair according to anotherembodiment of V the invention;

FIG. 9 is a detail view of a portion of the latter assembly in the braking position of the parts,

FIG; 10 is a cross-sectional view taken along the line X X of FIG. 8;

FIG. 11 is a ,fragmental sectionof theactuating LY mechanism according to yet another embodimentof thev invention; and I FlGull is a section taken- "alongthe line: X111} X]! M ems. 11.2

srsc ricnss mmo a 7 in FIG. '1 of the drawing; 1; milestones softener I a; wheel chairgwhich is; provided wit'hthe caster assent bly: according; to; the invention. The wheel chair'com priseslfourlegs orpostsrformingatubularflank onlythe two from posts of which; have been jnusnatedat -1. and 1 the pins by semicircular journaled. The assembly, according to the present invention, is designed to lock the caster arrangements 4.

Each of the caster arrangements 4, as also will be apparent from FIG. 1, comprises a bifurcated caster support or fork 7, the arms 7a and 7b of which receive the rubber-tire wheel 6 between them. The wheel 6, also referred as a roller, is journaled on an axle 6 between the arms 7a and 7b of the fork as is customarily the case.

From FIGS. 1 through 4 it will also be apparent that the individual caster arrangements 4 comprise two sets of ball bearings 8 and 9 flanking and inwardly extending flange 7c of the fork and disposed on top and on the bottom of the latter. The upper bearing cage 11a is carried by a guide sleeve 11. The lower cage 11b forms an apron on this sleeve and is also formed along its outwardly turned underside with a series of teeth or recesses 20.

A nonrotatable and axially fixed guide sleeve 11 is provided in each of the posts 1 and 2 and is formed with a boss 110 having a shoulder lld upon which the tubular hollow post rests. A screw 10 inserted through the wall of the post locks the respective sleeves in place. The screw 10 thus limits the angular displacement of the sleeve 11 with respect to the post and prevents the post from being lifted from the sleeve in the axial direction.

The central bore 12 of each sleeve receives an actuating shaft l3 forming part of the actuating element for the arresting mechanism. At its lower end the shaft or pin 13 engages one arm of a Z-shaped bent plate 14 whose other arm or shank I4 is received between the free end of a bifurcated leaf spring l5, l6 anchored to the fork 7 between the arms of the latter by a pin 19 via a pair of substantially U-shaped arms of a bent member 18, the latter holding the leaf spring and the plate 14 against lateral movement. The leaf spring comprises an upper leaf 16 whose upwardly bent plank 16' engages the teeth to prevent rotation of the fork 7 relative to the sleeve 11 and thus with respect to the post. The lower leaf 17 has a shoe portion l7 adapted to frictionally engage the periphery of the wheel or roller 6 thus, as the plate 14 is swung in the counter-clockwise sense on the pin 19, it spreads the leaves of the leaf spring apart to arrest the fork and the roller. The leaves of the leaf spring are riveted at their other end 15. The assembly l4, 18, 19 is located below the downwardly concave plate 21 forming the member 11b.

According to the invention, the shaft 13 is vertically shiftable in the post and, as represented in FIG. 4, is connected to a piston-like slide body 22 urged downwardly by a coil spring 23 seated against this slide. At its upper end, the spring 23 is seated upon a plate 24 anchored in the post by inwardly bent rib 1a. The slide 22 is provided with a transverse bore 22' receiving the crank pin 25 traversing a vertically extending slot 26 above the crossbar 3.

From FIGS. 1 through 4, moreover, it will be apparent that the pins 25 are carried by the side plates or cheeks 27 of an actuating means represented generally at 29 and forming a crank. The side plates 27 are joined together-by a tubular connecting bar 28 bridging the posts 1 and 2 and located wholly externally of the crossbar 3. It will be evident also that two such plates 27 and pins 25 are provided for the simultaneous actuation of the arresting mechanism of both casters.

The connecting bar 28 is provided at its opposite end with a pair of handles 29 which, as shown in FIG. I, lead forwardly and laterally outwardly for easy manipulation by the patient. The bar 28 rides a pair of lowfriction rings 30, e.g. of polytetrafluoroethylene, which may be'rotatable or fixed on the crossbar 3 at the ends thereof.

As can be seen from FIG. 4, each of the posts is formed with a horizontal stub 3" onto which the tube 3 is pressfitted, the latter carrying the rings 30. The handles 29' extend radially from the crossbar 28 which actuates the rings 30 so that in one operating position the bar 28 and the handle 29 engage rings 30 at locations A and B located on an opposite side of a plane P extending through the axis of the pins 25 and the rings 30. As a consequence member 28 forms a simple crank with a 'deadcenter position defined by the plane P through which the axis of the bar 28 may be swung. In that position, the actuating assemblies 28, 29 cradle the ring 30 at each end of the crossbar 3 and the clutch formed by the handle portions. In this case, the axis of angular displacement of the actuating member coincides with the axis of the pins. Since the spring 23 urges the pin 25 downwardly, the actuating member is held in place against self or accidental displacement.

With the pin 25 held in its upper position (FIG. 2), the spring 23 is compressed, the shaft 13 is also in its upper position and the plate 14 is canted in its clockwise sense. The leaf springs 16 and 17 are disengaged from the toothed rim 20 of plate 21 and from the periphery of the wheel 6 as described. When one or both handles 29 are lifted, the connecting bar 28 shifts in the counterclockwise direction (FIG. 2) to clear the rings 30 and the crossbar 3. With such release of the actuating member, the spring 23 urges the slide 22 downwardly, likewise carrying the pin in this direction and raising the handles into the position shown in FIG. 3. Simultaneously, the shaft 13 is urged downwardly, thereby canting the Z-shaped plate in the counterclockwise sense and twisting the shank 14 of this plate between the leaf springs 16 and 17. The leaf spring 16 is urged upwardly and engages the teeth 20 to prevent rotation of theforce 7 whereas the leaf spring 17 is urged against the periphery of the wheel 6 to prevent rotation of the latter.

To facilitate assembly of the actuating elements, an abutment bolt 31 is thread into the slide body 22 and extends between the spring seat 24 to have a head 31 at its free end. The bolt 31 is screwed into the slide body 22 to the extent necessary to maintain the transverse bar 22 always within the opening defined by the slot 26. This also limits the stroke of the spring 23 and prevents undue stress upon the leaf springs 16 and 17. The pins 25 can then be inserted into the bores 22' without difficulty and without requiring preassembly of the caster arrangement 4.

ln FIGS. 5 7, l have shown another embodiment of the invention wherein the spring 32 acts as a brakerelease spring, i.e. urges the shaft 113 upwardly. In this embodiment, the coil spring 32 is seated at its lower end against the guide sleeve 111 and bears, at its upper end, against the slide body 122. The shaft 113 is here threaded into the slide body 122 to limit the stroke of the spring 32 and maintain the transverse bore of the slide body in alignement with the slide 126.

The actuating bar 128 and its side plates 127 which carry the pins 125 can engage the underside of the .nience of theuser. I g I 7 FIGS. 8 l illustrate another embodiment of the incrossbar 103 and its rings 130 in the crotch from below in a kenematic reversal of the system shown in FIGS.

' 1 4. Inthis position, the shaft 113 is held downwardly mitted to approach the crossbar' l03to relieve th'ear-' resting mechanism.

From FIG. 6 it can be seen that the connecting bar 128 maybe provided with a furtherabutment29' handles of the ends thereof may be employed. It will be used equally well with a system in whichtlie spring opwhich may be an extension of the actuating'arm 129 and can engage the ring 130 from below at the location C..Thecontact with the bar 128 at location D and of i the abutment 29 at the location C, inthe form of a further cradle. retains the actuating armin its unlocked position as'illustrated in FlG. 6. As indicated in'broken '7 lines in FIG. 6, moreover, the handle 129 may be pro vided on the opposite side of the bar 128 for the convevention in which nondescribed portions. as in the case of FIGS. 7, correspond to those previously illuswhich operate the plate 14 etc. of the casters 204 are threaded into the slide body 222 while acoil spring'223 is provided between a spring seat 224 and the slide body above the latter. The connecting bar 228: of the actuating mechanism here bridges a pair of levers: 33 mounted on respective rings 30 at opposite ends of the crossbar 3. A hinge or articulation, 35 eccentrically connects each lever 33 to a link 34 of semicircular con figuration, the links 34 carrying the pins 225 which traverse the slots 226 and engage the slide 222 as previously described.Adead-center position is'defined by the plane P between the axis of the crossbar 3 and the axis of pins 225. The links 34 are semicircular segments adapted to rest against the crossbar 3 and cradle the latter as shown in broken lines in FIG. 8. Sincefthe force of spring 223 urges the pin 225 downwardly and the links 34 entrain the pivots 35 similarly, with the axis, E of the pins located to the letft of the plane R (dead center position), the actuating system is in a selfblocking condition. In this position,as in FIGQZ, the

shaft 223 relieves the locking arrangement and free movementof thecast is permitted. Note that the hanenabling the braketo be applied.

The arrangement of FIGS. 11 and l2is. of course. generally similarto that of FIGS. 8-'- 10except that the connecting bar 228 is replaced by a sleeve 328'which bridges the two handle portions 13.3,whoselinks 13 engage the pins 325 as previously described. The sleeve 328 is a pipe coaxial with the tube3. The pipe 328 is rigidwith respect to torsion stresses so that either of the tratedin. FIGS. 1 4.In this embodiment5theshafts'2l3' understood that the systems of FIGS. 8 12 can 'be erates to release the brake as described in connection with FIGS; 5 7. I V

I claim:

l. A steerable assembly comprisingiarpair of upright I transversely interconnected posts;

respective caster supports mounted on said posts for rotation about respective upright axes; V respective rollers journaled on said supports androllingly carrying the assembly;

axially shiftable locking elements respectively mounted on said posts and operatively engageable I with the respective-supports for releasably arresting said supports relativeto said posts and releasably arresting said rollers relative; to said supports to immobilize said assembly; I 7 H I a crossbar member interconnecting said posts;

an actuatingmember bridgingsaid posts externally of said crossbar member, said actuating member being pivotally connected to said element for angular displacement with respect to anaxis transverse g V to said upright axes between two positions with different spacings of said transverse axis from said crossbar member, said actuating member engaging I said crossbar membertoggle-fashion against self displacement in one of said positions, one of said members being shiftable along said posts generally in the direction of said upright axis; and

means connectingoneofsaidmembersw-i'thsaidelei ments for controlling same upon angular displace ment of said actuating member between said positions.

7 r 2. The assembly defined in claim l and forming part of a wheel chair or the like wherein said one of said members is said said actuating member and said crossbar memberis fixed to. said posts. said actuating: mem

' slots.

3. The assembly defined in claim 2 wherein said actuating member has the configuration of a crankshaft 'lyingbetween said posts andcomprises a'tran'sverse bar parallel to said crossbar member anda. pair of eccentric g links fixed to the ends of said transversebar and provided with said pins said transverse bar being -swingable between saidpositionsthrough adead-center position wherein the axis of said transverse bar, saidtrans f each of said posts, at least one brake element below eachsh'aft andengageable thereby for retaining the re-' spective support. and. roller against. mo ement, spring means in each post actingupon the respective shafts and urgingsaid actuating member into selfretaining engagement with said crossbar member in said one of said positions: r

v 5. The assembly defined in claim 4. wherein said actuating member is located above: said crossbar memben:

6. The assembly defined in claim 4 wherein said actuating member is located below said crossbar member.

7. The assembly defined in claim 1 wherein said actuating member comprises handle means rotatably mounted on said crossbar member, and link means articulated to said handle means and engageablewith said elements.

8. The assembly defined in claim 7 wherein said link means is articulated to said handle means along said transverse axis and is connected to said elements by a pair of pins defining a further axis, said handle means being swingable between said position through a deadcenter position wherein said further axis and said transverse axis are coplanar with said crossbar member.

9. The assembly defined in claim 8 wherein said crossbar member is provided with a pair of bearing links at opposite ends thereof rotatably supporting said handle means.

10. The assembly defined in claim 9 wherein said link means comprises a pair of generally segmental links at opposite ends of said crossbar member.

11. The assembly defined in claim 9 wherein said handle means includes a sleeve surrounding said crossbar member and rotatable thereon.

12. A steerable assembly for a wheelchair comprising a pair of upright transversely interconnected posts;

respective caster supports mounted on said posts for rotation about respective upright axes;

respective rollers journaled on said supports and rollingly carrying the assembly; axially shiftable locking elements respectively mounted on said posts and operatively engageable with the respective supports for releasably arresting said supports relative to said posts and releasably arresting said rollers relative to said supports to immobilize said assembly;

a crossbar member interconnecting said posts;

an actuating member bridging said posts externally of said crossbar member, said actuating member being angularly displaceable with respect to an axis transverse to said upright axes between two positions with different spacings of said transverse axis from said crossbar member, said actuating member engaging said crossbar member toggle-fashion against selfdisplacement in one of said positions, one of said members being shiftable along said posts generally in the direction of said upright axis; and

means connecting one of said members with said elements for controlling same upon angular displacement of said actuating member between said positions, said one of said members being said actuating member and said crossbar member is fixed to said posts. said actuating member being provided with at least one handle and forming therewith a bent lever, said posts being provided with respective slots parallel to the respective upright axes, said means connecting said one of said members with said elements including respective pins coupled with said actuating member and extending through said slots, said actuating member having the configuration of a crankshaft lying between said posts and comprising a transverse bar parallel to said crossbar member and a pair of eccentric links fixed to the ends of said transverse bar and provided with said pins, said transverse bar being swingable between said positions through a deadcenter position wherein the axis of said transverse bar, said transverse axis and said crossbar member are substantially coplanar, said posts being tubular, further comprising a guide sleeve mounted in each of the tubular posts and anchored therein against rotation, said shafts each extending slidably and nonrotatably through the respective sleeve, said spring means being formed as a coil compression spring, said shaft being provided with a slide block forming a seat for said coil compression spring, said pins extending through said slots and engaging said slide blocks, said supports each being provided with an inwardly extending flange connected rotatably to the respective sleeveby a ball-bearing arrangement, said supports being bifurcated and receiving the respective rollers between arms of the support being provided with a bifurcated leaf spring having a first portion deflectable into engagement with the respective sleeve and a second portion deflectable into engagement with the respective sleeve and a second portion deflectable into engagement with the periphery of the respective roller, and a Z-shaped member between the portions of the respective leaf spring and engageable by the respective shaft for deflection of said portions. 7

13. A steerable assembly comprising a pair of upright transversely interconnected posts;

respective caster supports mounted on said posts for rotation about respective upright axes;

respective rollers journaled on said supports and rollingly carrying the assembly;

axially shiftable locking elements respectively mounted on said posts and operatively engageable with the respective supports for releasably arresting said supports relative to said posts and releasably arresting said rollers relative to said supports to immobilize said assembly;

a crossbar member interconnecting said posts;

an actuating member bridging said posts externally of said crossbar member, said actuating member being'angularly displaceable with respect to an axis transverse to said upright axes between two positions with different spacings of said transverse axis from said crossbar member, said actuating member engaging said crossbar member toggle-fashion against selfdisplacement in one of said positions, one of said members being shiftable along said posts generally in the direction of said upright axis; and

means connecting one of said members with said elements for controlling same upon angular displacement of said actuating'member between said positions, said actuating member comprising handle means rotatably mounted on said crossbar member, and link means articulated to said handle means and engageable with said elements, said link means being articulated to said handle means along said transverse axis and being connected to said elements by a pair of pins defining a further axis, said handle means being swingable between said position through a dead-center position wherein said further axis and said transverse axis are coplanar with said crossbar member, said posts being tubular, and a guide sleeve mounted in each of the tubular posts and anchored therein against rotation,

' said shafts each extending slidably and nonrotata-' bly through the respective sleeve, said spring a seat for said coil compression spring, said pins exblocks, said supports each being provided with an inwardly extending flange connected rotatably to 7 means being formed'as a coil compressionspring, said shaft being provided with a slide block'forming,

7 tending. through esaidaslotsr and engagingisaideslide the respective sleeve by a ball-bearing arrangemenLsaidsjupports being bifurcated and xeceivifng; the' respective rollers between: armsiofth'esu pport, each support be-ingiprovided' with a bifurcated leaf;-

spring having a first portion vdeflectable into engagement with the respective sleeve and asecond f1 portion 'deflec'table into engagement with the pei riphery of the respective roller; and a Z-shaped member between the portions of the respective leaf 1 spring and engagea'ble' by the respective shaft-"for deflection of said portions. a

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