US2558143A - Medical practice chair - Google Patents

Description

June 26, 1951 N. E. LAUTERBACH MEDICAL PRACTICE CHAIR l6 Sheets-Sheet 1 Filed July 2, 1946 m mm 9 N ,z 6 E H V r m 0 57, n H W H N N 4.

June 1951 N. E. LAUTERBACH 2,558,143

MEDICAL PRACTICE CHAIR Filed July 2, 1946 16 Sheets-Sheet 2 v JNVENTOR. Norman 5 Z3215 eracfz BY, I ,4 1-

June 26, 1951 Q LAUTERBACH 2,558,143

MEDICAL PRACTICE CHAIR Filed July 2, 1946 16 Sheets-Sheet 5 IN VEN TOR. ./Vorman Lauzerbach #25 A! for/1e June 26, 1951 N. E. LAUTERBACH 2,558,143

MEDICAL PRACTICE CHAIR Filed July 2, 1946 16 Sheets-Sheet 4 Fig 4 Norma/4 E. Lauzmfiach BYa LQ I f/zs Attomg/ J1me 1951 NE. LAUTERBACH 2,558,143

' MEDICAL PRACTICE CHAIR Filed July 2, 1946 l6 Sheets-Sheet 5 l N VEN TOR. v Norma/2 5 Zaz/ferbach N. E. LAUTERBACH MEDICAL PRACTICE CHAIR June 26, 1951 16 Sheets-Sheet 6 Filed July 2, 1946 QQN Q \m NH]. @Q D g as wmw \L @k INVENTOR.

. Norma/7 E. Ldzzzerba ch June 26, 1951 N. E. LAUTERBACH 2,558,143

MEDICAL PRACTICE CHAIR Filed July 2, 1946 l6 Sheets-Sheet 7 K9 0 1\ (Q Q N Q o r no N n INVENTOR.

Norma/2 EL-auzzrbach His AZZor/zey June 26, 1951 N. E. LAUTERBACH MEDICAL PRACTICE CHAIR l6 Sheets-Sheet 8 Filed July 2, 1946 INVENTOR. 1 /1: Avior/1e y m m. E w l E. N

June 26, 1951 Filed July 2, 1946 N. E. LAUTERBACH MEDICAL PRACTICE CHAIR 16 Sheets-Sheet 9 Hz's Aztomey June 26, 1951 N. E. LAUTERBACH MEDICAL PRACTICE CHAIR 1e Shets-Sheet 10 Filed July 2, 1946 Fig /4 x I Ar/171799 72 ww o IN VEN TOR. Norman E Lauzerbach #23 Attorney June 26, 1951 N. E. LAUTERBACH MEDICAL PRACTICE CHAIR 7 Filed July 2, 1946 16 Sheets-Sheet 11 June 26, 1951 N. E. LAUTERBACH 2,558,143

' MEDICAL PRACTICE CHAIR Filed July 2, 1946 1e Sheets-Sheet 12 #15 Altar/ray June 26, 1951 LAUTERBACH 2,558,143

' MEDICAL PRACTICE CHAIR Filed July 2, 1946 16 Sheets$heer. 15

Q s L A t\ m Q R; R g Kfi r l a h b 8; J s

k g I L J INVENTORY N0 7/773/7 Aaz/zerbac/z BY H25 Azwmey June 26, 1951 N, E, LAUTERBACH 2,558,143

MEDICAL PRACTICE CHAIR Filed July 2, 1946 Y 16 Sheets-Sheet 14 INVENTOR.

- //z's Atzomey Norman E, [.gzerbach I June 26, 1951 N. E. LAUTERBACH MEDICAL PRACTICE CHAIR l6 Sheets-Sheet 15 Filed July 2, 1946 NNN h R mm w m m m m 5 m w 54 Z W H NY B June 26, 1951 N. E. LAUTERBACH MEDICAL PRACTICE CHAIR l6 Sheets-Sheet 16 Filed July 2, 1946 I INVENTOR. Norma/1 E. Lauzerbaciz Patented June 26, 1951 MEDICAL PRACTICE CHAIR Norman E. Lauterbagch, Newark, N. Y., assignor to Ritter Company, Inc., Rochester, N. Y., a

corporation of Delaware Application J uly 2, 1946, Serial No. 680,983

Claims. 1

This. invention relates to chairs of the variety adapted for use by the medical profession during examinations, treatments, and minor opera-, tions, one object of the invention being. to provide' an improved. chair of such character having a more adjustable, convenient, and efficient construction.

Another object is to provide a chair of the above character having head,.back, arm, and foot rests adjustable-to. and frompositions lying substantially in the plane of the chair seat, for converting the chair into a substantially'fiat,v tablelike support,

Another object is to provide such a chair having a compensated, anatomically correct hinge movement of the back. and head; rest sections relative to the seat, as required for the comfort of the patient.

Another object is to supply a chair of the nature described having connections, such as armrest structures, between the back rest and foot. rest sections for adjusting the foot rest section by the adj ustmentof theback rest.

Another object is to afford a chair having a construction such as described above. in which leg and foot rest sections are releasably connected with a back rest section for movement withor independently of the latter,

Another object is to provide a chair of the character described in which the foot rest section is maintainedin a horizontal position throughoutits angular range of adjustment relative to the chair seat, as well as provisions for locating the foot rest at different levels to suit different patients in kneeling on the foot rests for certain examination work.

Another object is the provision of a leg rest pad adapted to support the patients legs when the chair is adjusted to ahorizontal position, to be used as a cover for the foot-support when the latter isretracted to folded position and to be positioned on and used as a pad for the foot rest in the different elevated positions thereof.

Another object isthe provision of a chair having a head rest adapted to be selectively positioned to afford either the usual head pads, or substantially flat rigid surfaces for supporting the head and neck of a patient against sagging during administration of an anaesthetic. A further and more specific object is to provide a head rest having. means for automatically locking the flat head supporting surfaces in position for use. A further object is to supply such a chair provided with stirrups for supporting. the feet of a. patient in suitable position for certain examinationsand so constructed as to be readily ex tended for use or compactly retracted to positionat the sides of the chair.

A further object is to provide a chair having stirrups of the above character so supportedas to be conveniently adjustable to different posi tions of use to suit difierent patients.

To these and other ends the inventionresides in certain improvements and combinations of parts, all as will be hereinafter more fully described,' the novel features being pointed out in the claims at the'end of the specification In the drawings:

, Fig. 1 is a side elevation of a chair embodying the present invention and arranged to support a patient in upright sitting position;

Fig. 2 is a front elevation thereof;

Fig. 3 is a rear elevationthereof Fig. 4. is a top-plan view of the chair arranged horizontall with portions of the seat broken away to disclose parts of the mechanism;

Fig. 5 is a side elevation of the chair in the same general arrangement with parts of the sea broken'away;

Fig. 6 is an enlarged fragmentary detail View of a latching means shown in Fig. 5;

Fig. 7 is a side elevation with theback rest and head rest lying substantially inthe plane of the seat and with the leg rest so arranged that the patient may kneel on it;

Fig. 8 is a side elevation with the backrest and head rest-in the plane of the seat,thefoot rest being folded under the leg rest and the-stirrups extended and elevated;

Fig. 9" is an enlarged top planview of the seat frame and associated mechanism;

Fig. 10 is an enlarged fragmentary view of certain details of themecha'r'iism shown in Figa 9 Fig. 11 isa fragmentary sideelevation of the seat frame, partly brokenaway to show a" locking means;

Fig. 12 is a sectional view on Fig. 11;

Fig. 12 is a perspective view of the base portion on the backrest and of themea'ns for'lbcking it in position;

Fig. 13 is an enlarged sectional elevation of portions of 'the' seat frame and backrest showing the back rest lockingmeans;

Fig. 14 is a fragmentary view partly broken away and'partly in-section substantially as seen from the line I 4-I 4 in-Fig. 13;

7 Fig; 15 isan enlarged side elevation-ofthe seat frame andthe: frame for supporting the leg and the line 12-42 in 3 foot rests and associated mechanism, partly broken away and partly in section;

Fig. 16 is an enlarged top plan view of the foot rest with the foot supporting section in raised position;

Fig. 17 is a front elevation of the same;

Fig. 18 is an enlarged side elevation of the head rest detached, with its flat surfaces in one head supporting position;

Fig. 19 is a rear view of the same with its flat surfaces in a different supporting position;

Fig. 20 is a top plan view of the head rest with its fiat surfaces locked in supporting position;

Fig. 21 is a similar view with the head pads in supporting position;

Fig. 22 is an enlarged sectional elevation substantially on the line 22-22 in Fig. 21;

Fig. 23 is a sectional plan View substantially.

on the line 2323 in Fig. 22;

Fig. 24 is a side elevation partly broken away and partly in section showing an arm rest and stirrup supporting means;

Fig. 25 is an enlarged sectional elevation on the line 25-25 in Fig. 24;

Fig. 26 is a front elevation of the parts shown in Fig. 24;

Fig. 2'7 is a side elevation of a stirrup and part of the supporting means therefor detached;

Fig. 28 is an enlarged side elevation, partly in section, showing the stirrup supporting means, and

Fig. 29 is an enlarged view, partly in section, of parts of the arm rest shown in Fig. 24.

The preferred embodiment of the invention herein disclosed, by way of illustration, comprises a chair having a circular base 40, Fig. 1, supporting an electric motor 4! and a housing 42 for hydraulic mechanism for raising and lowering a chair supporting column 43 which is mounted for rotation also in the housing, as well understood in the art. At 44 is a foot lever controlling the rotation of the chair and at 45 are foot levers for raising and lowering the chair. These parts for moving the chair column may have any known or suitable construction and form no part of the present invention. The chair column carries at its top a generally circular supporting head 46 formed with bearings 41, Figs. 4 and 9, for trunnions 48 by which a seat frame 49 is supported for tilting movement on the chair base. Means are pro vided, as hereafter described, for releasably locking the seat frame in adjustably tilted position. The seat frame 49 is a generally rectangular, hollow frame, as shown, on which the back rest, arm rests, and leg and foot rests are supported in connected relation for movement together simultaneously to diiferent adjusted positions. The back rest and its adjustable association with the seat frame will be first described.

The rear of the seat frame is formed with an integral, hollow, box-like portion indicated generally at 50, Figs. 9, and 11 to 13, inclusive, with which the back rest is pivotally connected. This portion 50 comprises spaced, rearwardly extending walls 5! the front and lower sides of which are curved substantially in a semi-circle, as shown. Walls 5| are formed with bearings for a spindle 52, Fig. 13, pivotally supporting an irregularly shaped member 53 forming the base portion of the back rest, and carrying means for locking the back rest in different pivotally adjusted positions, as hereafter described. Fixed on and extending upwardly from member 53 is a post 54, Fig. 1, slidably received in a bearing in a member 55 having in its rear face an undercut or dove-tail vertical groove (not shown) slidably receiving a similarly shaped tongue on'a member 56. Member 58 is provided with a clamp (not shown) operated by a handle 51 for locking its tongue in vertically adjusted position in the groove of member 55. Member 56 is provided at its upper end with lugs 58 between which is pivotally supported a depending arm 59 secured to the rear side of a substantially rectangular, padded back rest 60 shaped to conform comfortably to the patients back. Member 56 is also formed on its rear wall with an undercut or dove-tail vertical groove slidably receiving a tongue on a member 6! provided with clamping means (not shown) operated by a handle 62 for looking it in vertically adjusted position on member 56. Member 6] is the lower supporting part of a head rest constructed as hereafter described. Such back and head rest parts 56 to 62, inclusive, may have any known or suitable construction, being well understood in the art and forming no part of the present invention.

The means for locking the back rest in adjustably tilted relation to the chair seat frame 49 comprises a part 63 (Figs. 13 and 14) projecting downwardly from the base portion 53 of the back rest and having a wedging block 64 set into its lower edge and secured by a screw, as indicated at 65. Block 64 has its opposite ends tapered forwardly and inwardly as at 66 for cooperation with cylindrical rollers 61 rolling between the tapered ends of the block and hardened metal wear strips 68 of arcuate shape secured to the spaced walls 51 as by means of screws 69. Leaf springs 19 fixed to portion 63 of the back rest, as by means of screws II, have their free ends bearing against the rollers 61, respectively, so as to normally press the same into wedging engagement between the ends of the block 64 and the wear strips 68, thus normally locking the back rest against rearward tilting movement. A bar [2 is secured at its ends, as by means of screws 13, to the flanges 5|, respectively, and carries, intermediate its ends, a pair of lugs 14 positioned to be struck by the part 64 of the base of the back rest, so as to form stops limiting the downward tilting movement of the back rest assembly.

The means for releasing the back rest locking means comprises an arm 15 extending rearwardly from base portion 53 of the back rest and recessed at 16 for the reception of the lower end ll of a lever 18 extending upwardly in rear of the back rest so as to be in convenient reach of the operator. Lever I8 is pivotally supported on a spindle l9 journaled at its ends in the opposite walls formed by recess 16 in arm 15. The lower end Tl of the lever is extended laterally as at 80, Fig. 14, and formed with a slot 81 extending upwardly therein through its lower edge, for the reception of a plate-like member 82. Studs 83 are threadedly engaged in holes in the lateral extensions of the lever, so as to bear at their their lower ends against the upper edge of plate 82, these studs being locked in adjusted position by means of nuts 84.

Plate 82 is received at its lower edge within an upwardly turned flange 85 in a housing or shell 86 having forwardly extending opposite side walls 81 pivotally mounted on the back rest spindle 52. Each wall 81 has a forwardly extending arm 88, the end of which is reversely bent upon itself, as at 89, to provide a thickened terminal portion. These arms are positioned to extend between the wedge-shaped ends66 of bar 64 and the arcuate plates 68- onthe seat frame, for engagementwith the wedging rollers 61, and it isevident-from this construction that forward movement of lever l-8-presses downward- 1y onplate 82, soas to swing shell 86 counterclockwise, Fig. 13, and thus engage and free the rollers 61 to release the back for lowering ad-'- justment.

To normally maintain the backrest locked inposition for sustaining the weight of the patient, the lower end 1-! of lever 18 has a finger 99, Fig. 13; arranged to bear downwardly on a downwardly extending pointed end 91- of ashort lever 92 located in a slot in the end of lever I8 and pivoted on its spindle 19-. This end oflever 92 is arranged to bear againsta-leafspring 93 fixed by a screw 94 to the portion 63 of the back rest, these parts being so arranged that the spring normally presses theshort lever 92' in a counterclockwise direction (Fig. 13), soas to maintain lever IB-in a rearward'position from which it may be moved forwardly, as described above, to release the back rest looking or wedging means. The upper end 95- of the short lever 92 is so arranged that at the lower limit of itsmovement, with lever 'I 8- released, it snaps behind a shoulder 95- formed on the-bottom wall of the portionfio of the seat frame, thus locking the back rest against raising movement also until the upper end of the lever 92 is lifted by pressing lever it toward the back rest. The-back rest will thus be locked against movement in either direction when lowered to the position in which it lies substantially inthe plane of the chair seat; It will be noted that the controlling lever I8 moves with and maintains a uniform relation to the rear side of the back rest, so asto be readily located and grasped by the operator and that only a slight pressure of the lever toward the back rest is required to release itfor movement to the desired position. The above back rest locking means is claimed in my divisional patent application, Serial No. 119,093, filed October 1, 1 949.

The tilting or pivotal movement of the back rest about the spindle 52 located in rear of the seat and of the back of the patient, is compensated by means for automatically sliding the associated back rest portions on post 54', toward the chair seat, as the back rest is lowered from the vertical position shown in Fig. 1. Such means preferably comprises an advantageous construction and association of the arm rests by which they effect such sliding movement of the back rest in relation to a secondpivotalaxis locatedintermediate the front and back of the seat.

To this end, each arm rest comprises a metal frame 91-, Figs. 1, 24, and 25, on which is mounted an arm receiving portion 98 having a generally broad and substantially flat upper surface which may be made of plastic or other known material suitable for the purpose. The arm rest frame has its upper rear end 9-9 pivotally connected at I90 with arms Ill-I extending forwardly from the part 55 of the back rest which slides on the pivoted post 5 1. At its opposite end each armrest has fixed thereto a trunnion I92 pivotally' supported in a bearing in the side'of the seat frame. The trunnion extends through beyond the face of the inner side ofthe frame for connection with mechanism hereafter described. Strong coiled springs I03 connected to the seat frame at IM and to the arm rest trunnions', serve to counteract the weight of the patient against the back rest and to assist in: lifting the. back rest and patient to a sitting posiion.

It is evident from this construction that as the back rest is lowered pivotally about spindle: 52,- the' arm rests slide the backrest downwardly on: post-54 toward the seat,-thus controlling its-movements with reference also to the axis of the: pivotal connection of the arm rests withthe seat frame, intermediate the front and rear. of the: seat. Such movement of the back rest is thuscontrolled with reference to pivots located inrear and infront of the back'of the patient, so accomplish an anatomically correctcompensating hinge movement of the back and head rest sections of the chair. Furthermore, the arrangement and connection of the arm rests is suchthat while functioning. efficiently inthe upright position of the back rest, as-shown in-Fig. 1, they may belowered with the back rest so as to lie substantially in the plane of the seat, as shown in Fig. 5, thus extending in lateral directions the substantially flat, table-like support provided: by the chair as a whole, and serving as arm'support's throughout the entire angular range of adjust ment of the chair.

As'explained above,-the seatframeis supported for tilting movement on the top 46 of the elevatingcolumn 43' and the arm rest structure is utilized in part for controlling means for locking the seat frame in adj ustably tilted position on the column; Such means preferably comprises a sleeve I05 keyed on the inner end of thetrunm'on I92 of one of the arm rests (Fig. 1 0'). Fixed in this sleeve: are one or more radially extending pins I06 received in inclined slots II'I'I in acap- I98 rotatably and slidably mounted on the sleeve so as to be controlled for movement both concentrically and axially of the sleeve. The cap. I08 has a strap- 199 clamped thereto and formingpart of the end ofan angular lever IIlLFigs. 9, 10, and 15, extending rearwardly and upwardly along the under side of the adjacent arm rest. Set concentrically in the cap is a threaded plug II I- of hardened steel having thereina socket I I2'for thereception ofthe rounded and hardened end I E3 of a thrust element or rod H4. This end of the rod is thus supported concentrically with the trunnion of the arm rest, so as to be undisturbed by its tilting movement on the seat frame, and it will be seen that the swinging of lever III] rotates cap I08 whose inclined slots I91 move the cap axially of l the sleeve to press its plug I II againstrod H4 to thrust it longitudinally. It will also be noted that lever H9 is mounted on and follows the movements of the arm rests, so as to be conveniently and easily located for actuation by the operator of the chair. Rod I-I4 thrusts at its opposite end against the resistance of spring actuated meansfor operating the locking means controlling the tilting movement of the seat frame on the elevated column of the chair base, as hereafter described. Thrust rod H4 has its other end II5, Fig. 9, rounded and hardened and seated in a socket I I6 in a lever III pivoted at II8 on a lug II9 on the head of the elevating column, The rod socket H6 is located concentrically with the axis of the seat frame trunnions 48, so that the rod is unaffected. by tilting movement of the seat frame on the column. At I29 is a coiled compression spring having one end seated in-a recess in lever Ill and the other end seated in a recess in an extended portion I2 I' of the adjacent column bearing 41.

The means for releasably locking the seatframe in its adjustable tilted positions on the base comprises, preferably, a block In (Figs. 9, 1.1, and 12) pivotally supported by trunnions 123- having bearings in lug H9 and a. cooperating. lug IN spaced therefrom on thehead of the column. This pivoted block I22 is formed with a bearing opening which slidably receives a spindle I25 connected with the chair frame, as hereafter described. Block I22 has a slot I26 extending inwardly to its bearing to provide for compressive clamping of the block around the spindle to lock itthereto. Such locking compression of the block is preferably accomplished by means of a rod I21 sliding longitudinally in a bore in lug HQ, with one end bearing against lever II! and the other against the adjacent side of the block. The opposite side of the block is supported by a short stop rod I28 fixed in lug I24.

Locking rod I25 is carried by a head I29 formed on or otherwise secured to the top of the rod and pivoted on a spindle I30 carried in lugs I3I projecting inwardly from an abutment I32 on the seat frame. A coiled compression spring I32a, carried by an adjusted screw I32b, on the rod head I28, in position to strike block I22, serves to cushion the return of the seat frame to horizontal position, and a Washer I320, on the lower end of 'the rod, limits its movement in the opposite direction.

It will be evident from this construction that the pressure of spring I20 against lever III normally thrusts rod I21 longitudinally to compress block I22 into locking engagement with the spindle carried by the seat frame so as to lock the latter in adjusted position. Lever IIO may be rotated through a slight angle, however, to cam cap I08 axially of sleeve I05, as previously explained, and thereby thrust rod II4 against lever Ill and thus release block I22 to relieve its locking action on the seat frame rod I25, thus freeing the seat frame for tilting movement as long as lever H is held in such position. During such tilting movement of the seat frame, the thrust rod II4 is turned bodily about its end concentric with the tilting axis of the frame, so as not to affect the operation of the frame looking means, notwithstanding the location of the other end of the thrust rod in eccentric relation to such pivotal axis. The adjustable seat frame and locking means therefor are claimed in my divisional application, Serial No. 119,094, filed October 1, 1949.

The invention further comprises a frame pivotally connected with the front end of the seat frame for supporting adjustable leg and foot receiving rests, this frame being arranged for movement either conjointly with or independently of the back and arm rests, as may be found desirable. To this end a shaft I33, Figs. 9 and 15, is mounted for rocking movement at its opposite ends in bearings in the sides of the seat frame. Mounted to rock independently on the shaft is a sleeve I34 to the opposite ends of which are fixed a pair of spaced arms I35 having upper ends of goose neck shape to avoid interference with the front end of the seat frame. Arms I35 are rigidly connected with each other, as by means ofa cross bar I36, Fig. 15, and form a hinged frame of rigid construction for supporting the leg and foot rests, as hereafter described. Arms I35 are formed with outwardly projecting shoulders I31 adapted to strike the bottoms of the sides of the seat frame and stop the foot rest frame in its lowermost position, as shown in Fig. 15. The means for pivotally elevating this frame by the pivotal lowering of the back rest of the chair will now described.

Keyed to the ends of shaft I33, beyond the ends of sleeve I34, are a pair of cross arms I38 each having one end pivotally connected at I with a link I40 pivoted at its opposite end I4I to the outer end of an arm I42 keyed on the trunnions, I02, of the arm rests, so that the tilting movement of the back rest, imparted to the arm rests, as described above, is transmitted by the arm rests as a rocking movement of shaft I33, the arm rests serving in this arrangement as an actuatin connection between the back rest and the foot rest frame.

The opposite or lower end of one arm I38 is pointed as at I43, Fig. 6, for engagement with the suitably shaped end I44 of a plunger I45 sliding longitudinally in a hole I46 in the ad: jacent arm I35 of the foot rest frame. Plunger I45 has its other end reduced in diameter to provide a chamber housing a coiled compression spring i4? tending to project the plunger into the path of movement of the actuating arm I38. Pivoted at I48 to the reduced end of the plunger is a lever I43 having opposing surfaces I50 and I5I. Pivot I48 is located nearer the surface I50 so that when the lever is turned to present that surface to the frame, plunger I45 is released for movement by its spring into the path of the actuating arm I38. Lever I49 may be turned, however, to present its other surface I5I to the frame arm I35, thereby withdrawing the plunger into its bearing out of the path of the actuating arm I38, so as to disconnect the foot rest frame and leave it unaffected by tilting movement of the back and arm rests.

For supportin the foot rest, arms I35 are connected at their lower ends by a shaft I52, Figs. 15 to 17, inclusive, on which are pivotally carried a pair of spaced arms I53 extending rearwardly from the main supporting frame 54 of a sectional foot rest indicated generally at I55. Means are provided, comprising a parallel motion linkage, for controlling the pivotal movement of the foot rest on its frame, so as to maintain it substantially horizontal, or parallel with the chair seat, in any tilted position to which the foot rest frame may be moved with the back rest, as may be seen by comparison of Figs. 1 and 5.

For this purpose the foot rest frame I54 has spaced rearwardly extending arms I56 carrying a shaft, or trunnions I51, arranged to be engaged in open notches I58 in the lower ends of a pair of spaced links I59 pivoted at their upper ends on trunnions I60 on lugs I6I on the seat frame. For maintaining the links I59 in position for engagement with the foot rest, a metal strap I62 has its ends fixed to the rear side of a cover plate I63 having ears I64 fixed by screws to the arms I35. The intermediate portion of strap I62 is deflected to pass behind a rod I connecting the links I59 so as to hold the links in position for engaging the foot rest. Means are provided for releasably securing the links to the foot rest comprising a latch I66 pivoted at IE! to one of the links, and havin a stop flange I68 at one end, and hooks I59 at the other for engagement with the shaft I57, to hold it in the end notches of links I59, the latches being urged to engaging positionby a ravity arrangement or by springs, as desired. The ends of the latches beyond their hook portions are preferably so shaped, as at I58, as to be cammed back to clear notches I58a, by the engagement therewith of shaft I 51, so that the foot rest may be latched to the links I50 without manual operation of the latches. The latch may be manually operated to release the foot rest for foldin pivotally upwardly against the frame, as hereafter referred to.

Images