Note: Descriptions are shown in the official language in which they were submitted.
~ ~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
8--
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.
