CA1274955A

CA1274955A - Castor brake mechanism

Info

Publication number: CA1274955A
Application number: CA000520000A
Authority: CA
Inventors: Stafford T. Screen
Original assignee: Colson Castors Europe Ltd
Current assignee: Colson Castors Europe Ltd
Priority date: 1985-10-07
Filing date: 1986-10-07
Publication date: 1990-10-09
Anticipated expiration: 2007-10-09
Also published as: DE3633845A1; GB8623958D0; GB8524668D0; GB2181343A; GB2181343B

Abstract

ABSTRACT
CASTOR BRAKE NECHANISM
A castor has a tubular mounting member (1) rotatably carrying at its lower end a castor bodly (2) having a fork portion journalling a wheel (4). A brake pedal (5) pivots on the member (1)) about a horizontal axis to move a dis-shaped brake element (40) downwardly against the wheel by means of a cam mechanism (21 ,31). The brake pedal (5) is thus positioned independently of the angular position of the body (2). The brake element (40) engages the wheel (4) as a position spaced from the rotational axis fo the body (2) so as to hold this 2 against rotation.

Description

~ ~7~*95~.~

CA~TOR B~AKE MEC~IANIS~
DESCRIPTION
The description relates to a castor incorporating a brake mechanism.
The present invention provides a castor comprising a castor body, a mounting head, means journalling the castor body on the rnounting head for rotation about a substantially vertical swivel axis 7 wheel means, wheel mounting means journalling wheel means on the castor body for rotation about a wheel axis spaced from the swivel axis, a brake element, and means mounting the brake element for selective movement into and out of braking engagement with the wheel means, the wheel mounting means comprising means selectively adjustable to alter the position of the wheel axis on the body to thereby alter the position of the wheel relative to the brake element.
The wear of the wheel rim and/or the brake element due to braking can thus be accommodated by adjustment - of the means mounting the castor wheel or wheels on the body. The or each wheel can thus be journalled on a shaCt received in eccentric bushings which can be rotated and secured in a position corresponding to a desired spatial relation between the wheel and the brake element.
The castor body conveniently mounts the wheel or wheels between spaced side arms. It is advantageously formed of plastics material, which is however subject to deformation.
The invention accordingly provides a castor comprising a castor body having two spaced side arms of plastics material, a castor wheel received between the side arms, and mounting means rotatably mounting the ., wheel to the side arms, the mounting means compri~ing bushes each received in an aperture through a respective one of the side arms, a bolt extelldlng through the bushes, a fastener received on the bolt for tightening on the bushes, and a metal spindle carrying the wheel on the bolt for rotation about the wheel axis, whereby engagement of the bushes with the spindle on tightening of the fastener prevents deformation by "cold flow" of the side arms.
The brake element can move generally verticallv, conveniently along the substantially vertical axis about which the castor body rotates on the mounting head and can be operated by a cam member which can be configured so as to facilitate assembly of the castor.
The invention accordingly provides a castor comprising a body, a mounting head, means mounting the body on the mounting head for rotation about an upright swivel axis, wheel means, means journalling the wheel means on the body for rotation about a wheel axis spaced from the swivel axis, an elongate brake element having an upper portion, means guiding the brake element on the mounting head for lengthwise movement between braking and release positions, a cam member journalled by the mounting head for rotation about an axis transverse to the direction of movement of the brake element, the cam member comprising a cam and enlarged end portions having the cam between them, a spring acting between the mounting head and the brake element to urge the upper end portion thereof into engagement with the cam, whereby the cam member is retained against axial displacement thereof by reception of the upper end portion between the enlarged cam membex end portions, the cam being so shaped that rotation of the cam member effects movement of the brake element between the braking and the release position thereof.

3~S

The invention is further described below, hy way of illustration, with reference to the accompanying drawings, in which:
Figure 1 is a rear view of a castor embodying the invention;
Figure 2 is a fragmentary view of a cam mechanism included in the castor;
Figure 3 is a partial side view of the castor with parts shown in section; and Figure 4 is a plan view of the castor~
The illustrated castor comprises a mounting head 1, by which the castor is secured to an article of furniture which it is to support, and a body 2. The body 2 is carried at the lower end of the mounting head for rotation about an axis which is substantially vertical in use and incudes a fork portion journalling a wheel 4 for rotation about an axis which is a generally horizontal and spaced from the vertical axis.
The castor includes an operating or control member 5 by 7~3 ~

,~,., mo~?ement of which the castor can b* selecti~ely ~,ra`~ecl against \;heel rotation and swivelling.
The mo~nting llead 1 comprises a tubular member 11, for exa'ple of steel, for reception in a recess of the furniture article, for e~ample into the lower end o~ a hollow m2tal bed leg 12 of a hospital bed. The member 11 and th2 leg 12 are non-rotatably secured together by suitable fastener means extending through diametrically op?osed aligned apertures 14 in the member and t;~e leg.
At its lower end, the tubular member 11 externally carries the inner race 15 of a ball bearing and has an internal annular flange 16 which guides for axial mo~ement therein a cam follower 20 having a head pGrtion 21 from which a stem portion 22 of srnaller aiameter downwardly extends. The cam follower 20 is urged upwaLdl~? by a l-eturn spring 24 recei~ed betweerl the ~per erid of the flange 16 and the annular surfac~
beneath tne cam follower head portion 21.
The l~wer end of the leg 12 abuts against an external annular step formed by a lower portion of the !u},ular nember 11 of greater external diameler 3bou~
which is carried aplasticscasing 30. Diametrically aligned apcrtures extend thrGugh ',~e plastics c,,sin~ ,9 and the member 11 and journalled th~rein are end portiGns 30 oE circular cross-section of a shaft having betw-_en the end portions a cam portion 31 of seglr,ental cross-secticn.
The portion 31 is of smaller diameter than ~he E,ortions 30 and the shaft is r-~tained againc-t axial displacelent by r2ccr-,ion of ,he head portion 21 betweel-l the,~ lar~er diameter portions.
'~'he shatt is part of the control m~-ber S and c~rries at one end, externally of the casing 29, a _wo-dllll"d lever o whicn t}le two limbs 32 ha~7e ;n angie of about 1('5 between them. The two limbs 32 extend 3~ radiaily of the shaft and expose fiat upper su~-faces con~?enient for foot operation and wilich ma~ bear ~ ~7~ 35 aF,propl:ia~ markinc3s as apE)ears from Figure 4.
In the position shown, the arcuate surLaCe o~ th~
cam port.ion 31 engages tne cam Eollower heacl portion 21 which is accordingly held down against the return spring ~. B-~ turnlng the control member 5 about the cam portion axis -through about 75, the flat of the ca~
portion 31 overlies the head portion, allowing the cam follower 20 to be moved by the return spring into an upper position.
Thc bo_y 2 comprises an annular portion 35 which surrounds the lower end of the tubular member 11 and f~oln the unoer side of which two spaced walls 36 extend downwardly to form a fork in which the wheel 4 is journalled. The portion 35 has an internal groo~e in which is received the outer race 37 of the ball bearing. The body 2 is advantag-ously an integrally moulded plastics member, the outer race 37 being ~ecureu wilnin it during the mouiding operation.
The lower end of the cam follower 20 projects beyond the lower end of the ~ember 11 and has non-rc,t-itio;-ially seculed to it a headed pin 39 on the shank of which is retained a braking element in the furm o~ a uisc ~îû the lower side of which includes an approxi.mately frusto-conlcal braking surface which is also curved in radial cross-section to correspond at least aopro~imately to the outer periphery of the wheel 4, which is preferably constituted by a tyre for example of rubber. ~h- bra~ing surface can be radially ridg.-d ~o elll~lcii~ae frictional engasement with the Iyre.
In the position s~,own, with the cam follower depL-SSed, Lhe brake disc 4û is engaged with the wheel 4 ayainst the force of the return spring 24. This braking ensasc~,cnt is ef,~ecti;;e re-ga-,-dlcss of the anyular position oI the body 2 r and thus of the wheel 4, about the -vertical s~ivel a~;is, because wllatever the angular position, a part of the non-rotatable brake disc will be engai~ed with the whcel. The wheel 4 is brakil-~gly engaged at a position spaced from the swivel axis, so the application of the brake not only opposes rotation of the wheel, but also swivelling of the body 2 on ~he ~iounting head 1.
~ hen it is desired to release the brake ~lechanism, the control member 5 is turned, about the axis of the cam ~ortion 31, conveniently by the action of the operator's foot on one of the limbs 32 in the anti-clockwise direction from the position shown in FigurP 2to engage 'he flat of the cam portion 31 ~ith the cam :tollower ~0. The return spring 24 lifts the cam follower 20, conveniently by some 1.5 mm., so the brake disc 40 rises clear of the wheel which can urn freelyr as can the body 2 on the mounting head 1.
To accor~iodate wear of the hrake disc 0 -~nd of ~:h~
wheel lyre, .he wheel 4 is adjus.ably mount_d on the side walls ~6 oi the body. As appears from Pigures 1 and 3, the side walls 36 have aligned arertures receiving bushes 41 provided with diametrically opposed axiall-y *,Y~ e ::din~, ridges 42 receivable in upper and lo~er a-oo~es 44 extending axially in the side wall apertures.
~ e b;shes 41 carl cor.sequen-tly be received in eitiier of two ~ositions angularly sp~ce~ 18,0 apart. Th2 whePl 4 is journa]led on a metal bush 45 on the shank of a bolt 46, held in place by a nut 47, and extel1dinq Ihrough bor~s in the bushes 41 which are offset fro~l the cor~lon axes of the bushes. Consequently, the whe2l axis mai- hav2 an upper or a lower posltion, deper!dirlg on the orientation chosen for the bushes 41. Ini~ially, the wh el axis will be in its lower position, at i~s fur hest sr,acing from the brake disc 40. To adjust lor wear, -tne retaining nut 47 is xemoved from the bolt 46 ~o enable the two bushes -o be turned through 1 sn~ / after wh-ch the nut is restored and tightened. The wheel axis can be raised thereby by, for example, about 3~i 1 . 5 mm. to acconunodate wear. The enyayernent of the bushes 41 with the bush 45 se.rves to prevent "cold flow"
of th~ material oE the side walls 36 when these are formed of plastics material, under tightenirlg of the 5 nut 47 on the bolt 46.
As will be evident, the invention can be ernbodied in a v ariety o ways other than as speciEically described and shown.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A castor comprising a castor body, a mounting head, means journalling the castor body on the mounting head for rotation about a substantially vertical swivel axis, wheel means, wheel mounting means journalling wheel means on the castor body for rotation about a wheel axis spaced from the swivel axis, a brake element, and means mounting the brake element for selective movement into and out of braking engagement with the wheel means, the wheel mounting means comprising means selectively adjustable to alter the position of the wheel axis on the body to thereby alter the position of the wheel means relative to the brake element.

2. A castor as claimed in claim 1 wherein the wheel mounting means comprises bush means journalling the wheel means and carried by the body for rotation thereon about an axis spaced from the wheel axis whereby rotation of the bush means effects the adjustment of the position of the wheel axis.

3. A castor as claimed in claim 2 wherein the castor body comprises two spaced wheel supports having the wheel means therebetween, and wherein the rotatable bush means comprises two bushes each received in a respective one of the wheel supports, and means for securing the bushes in selected angular positions corresponding to a desired position of the wheel axis on the body.

4. A castor as claimed in claim 3 wherein the means for securing bushes comprise interfitting formations on the supports and the bushes.

5. A castor as claimed in claim 4 wherein the selected angular positions are 180° apart.

6. A castor as claimed in claim 3, 4 or 5 wherein the supports are of plastics material and wherein tightenable metal fastener means secure the wheel means between the supports, the bushes receiving the tightening stress of the fastener means, whereby deformation of the supports under this stress is avoided.

7. A castor as claimed in claim 1 wherein the brake element is mounted by the mounting means for movement into and out of the braking engagement along the swivel axis, and wherein the selectively adjustable mounting means is adapted to move the wheel axis position in a direction parallel to the swivel axis.

8. A castor as claimed in claim 7 having spring means biassing the brake element out of braking engagement, and cam means selectively operable to move the brake element into braking engagement against the bias of the spring means.

9. A castor comprising a castor body having two spaced side arms of plastics material, a castor wheel received between the side arms, and mounting means rotatably mounting the wheel to the side arms, the mounting means comprising bushes each received in an aperture through a respective one of the side arms, a bolt extending through the bushes, a fastener received on the bolt for tightening on the bushes, and a metal spindle carrying the wheel on the bolt for rotation about the wheel axis, whereby engagement of the bushes with the spindle on tightening of the fastener prevents deformation by "cold flow" of the side arms.

10. A castor as claimed in claim 9 having a brake member selectively movable into and out of braking engagement with the castor wheel and wherein the bushes are selectively rotatable in the side arm apertures about an axis spaced from the wheel axis to thereby adjust the position of the wheel axis relative to said brake member.

11. A castor as claimed in claim 10 further comprising means adapted to retain the bushes in a selected angular position thereof.

12. A castor as claimed in claim 10 wherein the bushes and the side arms have interengaging formations thereon permitting a first position of the bushes and a second position thereof angularly spaced from the first position by 180°.

13. A castor as claimed in claim 9, 10 or 11 wherein the body is carried by a mounting member for swivelling thereon about an upright swivel axis spaced from the wheel axis, and wherein the brake member is movable along the swivel axis.

14. A castor comprising a body, a mounting head, means mounting the body on the mounting head for rotation about an upright swivel axis, wheel means, means journalling the wheel means on the body for rotation about a wheel axis spaced from the swivel axis, an elongate brake element having an upper portion, means guiding the brake element on the mounting head for lengthwise movement between braking and release positions, a cam member journalled by the mounting head for rotation about an axis transverse to the direction of movement of the brake element, the cam member comprising a cam and enlarged end portions having the cam between them, a spring acting between the mounting head and the brake element to urge the upper end portion thereof into engagement with the cam, whereby the cam member is retained against axial displacement thereof by reception of the upper end portion between the enlarged cam member end portions, the cam being so shaped that rotation of the cam member effects movement of the brake element between the braking and the release position thereof.

15. A castor as claimed in claim 14 having a control lever secured to the cam member at one end thereof externally of the mounting head.

16. A castor as claimed in claim 15 wherein the control lever comprises two arms, and each of the arms extends generally radially from the axis of rotation of the cam member.

17. A castor as claimed in claim 14, 15 or 16 wherein the cam member is journalled in the mounting head by the enlarged end portions.