Note: Descriptions are shown in the official language in which they were submitted.
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SWIVELLING WHEEL ASSEMBLY FOR A CART
Background of the Invention
This invention relates to the wheel assembly for a
cart or other mobile mechanism, of the type which contains a
wheel which swivels around a vertical axle, and may be
locked or unlocked by the rotation of the latter in one
direction or the other. Such wheel assemblies include a
thrust bearing with at least one circular housing fixed by
its central portion to the lower end of a vertical swivel
axle, a fork joint with at least two lateral extensions
whose lower ends support the wheel's horizontal axle, and
one upper circular cover connected to the upper ends of the
lateral extensions. The cover cooperates with bearings
placed around the lower end of the vertical axle so that the
fork joint can rotate around the latter. Prior art wheel
assemblies are known to contain devices for locking the fork
joint in relation to the vertical swivel axle. Such devices
are disclosed, for example, in U.S. Patent No. 4,494,272.
In the device disclosed in the '272 patent, part of the
fork joint's locking device is accessible from the outside
and may be damaged. Because of this, the proper operation
of the device cannot be assured on an ongoing basis.
Moreover, the known wheel assembly of this patent requires a
major modification to the fork joint, particularly in the
area of the wheel axle, which must be capable of moving in
the oblong openings made in the fork joint. Another problem
with this known swivelling wheel is the fact that
controlling the unlocking of the fork joint entails abruptly
stopping the wheel for an instant. In addition, the locking
devices for the known swivelling wheel assembly have a large
number of unprotected individual parts, and are therefore,
subject to rapid wear and deterioration.
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Summary of the Invention
The purpose of the present invention is to eliminate
such problems and to provide a swivelling wheel which is
simple in design, protected against external damage, and has
a reduced number of individual parts.
Within the framework of a swivelling wheel assembly of
the type referred to above, the assembly of the present
- invention includes a double control lever which is pivotally
mounted in the space between the external housing of the
fork joint and the wheel's tread in the area of the fork
joint's lateral extensions. The lever is in the form of a
curved lever whose two arms encompass an angle of between
90 and 160. The lower arm moves between two outermost
positions located in proximity to a radial plane running
through the pivot axis of the lever and the wheel's axis of
rotation. The lower lever arm has at its lower end a
friction device which is resiliently urged into engagement
with the wheel's tread. The upper lever arm is housed in
the space enclosed by the fork joint above the wheel's
tread, and includes, as a locking means a tip which extends
perpendicularly to the lever's pivot axle, and in the
direction toward the periphery of the fork joint. A second
locking means consists of a locking slot for receiving the
- locking tip without any significant lateral play. The slot
is constructed in the lower end of the vertical swivel axle
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or a component which is an integral part of the latter. One
of the two stops for limiting the pivoting movement of the
control lever is placed in the space located about the wheel
and between the lateral extensions of the fork joint. This
stop works in conjunction with a first lower portion of the
control lever. The second stop consists of either the
bottom of the locking slot, or the lower bottom edge of the
component containing the locking slot, and works in
conjunction with the upper lever arm's locking tip.
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A circular cover of the fork joint contains a tracking
groove extending along the center plane of the fork joint
and perpendicular to both the wheel axle and the control
lever's pivot axle. The tracking groove operates to guide,
without significant lateral play, a portion of the upper
lever arm or the locking tip along its entire path between
the two outermost positions of the lever.
With the construction of the present invention, the
locking device is completely protected, contains a reduced
number of individual parts, and is continually operational,
despite possible wear on the part of the wheel's tread.
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Brief Description of the Drawings
Fig. 1 is a side elevation, partly in cross-section, of
a first embodiment of the swivelling wheel assembly of the
present invention;
Fig. 2 is a perspective view of one part of the locking
device of the present invention;
Fig. 3 is an exploded perspective view of the several
components which make up the second part of the locking
device;
Fig. 4 is a side elevation, partly in cross-section, of
a second embodiment of the swivelling wheel assembly of the
present invention;
Fig. 5 is a side elevation, partly in cross-section, of
a third embodiment of the swivelling wheel assembly of the
present invention; and
Fig. 6 is a side elevation, partly in cross-section, of
a fourth embodiment of the present invention.
As shown on the attached drawings, a cart or other
mobile platform, which is not shown, contains a wheel 2
which is capable of swivelling around the vertical swivel
axle 3 and of being locked or unlocked by the rotation of
the wheel 2 in one direction or the other. The wheel 2
contains a horizontal rotating axle 4 whose ends are
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supported by at least two lateral extensions or forks 5 of a
fork joint 6. The upper end of the fork joint, which is in
the form of a circular cover 7, is fastened by means of a
thrust bearing 8 to the lower end of the vertical swivel
axle 3. It may be noted that the vertical swivel axle is
laterally offset in relation to the vertical plane passing
through the horizontal axle 4 of the wheel 2.
As can be seen on Figs. l and 4, the thrust bearing 8
includes a first circular housing 9 and a second circular
housing lO fixedly mounted, like the first, on the lower end
of the vertical axle 3. The two housings 9 and lO are open
at the bottom. The first housing 9 is an external housing
and is located above the second lower housing lO and has an
external rounded extension 9a and a circular downwardly
turned base portion 9b which, in the area of the internal
opening, rests on the circular base lOa of the lower housing
lO. The two housings 9, lO are mounted on the vertical axle
3 and their inner edges are enclosed by two ring-shaped
: collars 3a, 3b of the vertical axle 3.
At its lower end, the lower housing lO has an outer
circular edge lOb whose upper surface serves as the rolling
path for a first series of roller bearings or similar
- devices ll which support the circular cover 7 of the fork
joint 6. In the area of the circular junction between the
rounded extension 9a and the circular base portion 9b, the
upper housing 9 defines a rolling path in the form of a
groove 12 which houses a second series of roller bearings 13
resting on the upper side of the circular cover 7.
- As shown in Figs. l and 4, the external housing 9
covers and surrounds, particularly on its lower side, the
circular cover 7 and the lower housing lO. The lower
housing lO is, in turn, enclosed by the cover 7.
- It is possible to use an upper housing 9 whose
extension 9a is curved upwards from the outer edge of the
groove 12. In such a construction, which is shown in Fig.
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6, the housing 9 is open toward the bottom in order to have
a circular external groove 14 adjacent to the groove 12.
The groove 14 is open toward the top and is slightly deeper
than the groove 12. The groove 14 is bounded by a
horizontal flange 15 which is slightly raised and can be
used, for example, to fasten the bearing 8 to the connecting
receptacle of a cart which is not shown.
In the embodiment shown in Fig. 5, the thrust bearing 8
carries two roller flanges 8a, 8b. The second roller flange
8b encloses the first flange 8a and is fixed to the circular
cover 7 for the fork joint 6. The first flange 8a is, in
turn, fixedly mounted on the vertical axle 3 and the
external housing 9.
The swivelling wheel 1 also contains a locking device
16 for the fork joint 6. The locking device includes two
parts. One part is mounted on the fork joint while the
~- other part is fixed relative to the vertical axle 3. The
part of the locking device on the fork joint includes a
; pivot mechanism 17 in the form of a double curved control
- lever which has an upper lever arm 17a and a lower lever arm
17b, which encompass an angle of between 90 and 160. This
double curved control lever 17 is housed in the space
between the thrust bearing 8, the lateral extensions 5 of
the fork lift 6 and the wheel 2. In the examples shown in
- Figs. 1, 4 and 5, the lever is located vertically between
the upper or external housing 9 of the bearing 8 and the
tread 2a of the wheel 2, and laterally between the lateral
extensions 5 of the fork joint 6. The joining piece between
the two lever arms 17a, 17b is connected to the lateral
extensions 5 of the fork joint 6 using a single horizontal
axle 18 or two coaxial pivot axles 18 riveted onto the
extensions 5. The pivot axle 18 of the lever 17 is located
on the side of the fork joint 6 on which the vertical
distance between the locking device 16 and the tread 2a of
the wheel 2 is the greatest.
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The locking device 16 also includes a friction device
19 installed on the lower end of the lower lever arm 17b and
permanently and resiliently applied to the tread 2a of the
wheel 2. This friction device is capable of causing the
double control lever 17 to pivot toward one of two outermost
positions a~out the pivot axle 18. In one such position,
the supporting fork joint is immobilized in relation to the
vertical axle 3; and in the other, the fork joint 6 is free
to rotate in relation to the vertical axle 3.
The friction device l9 consists of a tubular piston l9a
which is guided so that it can slide axially in a housing 20
with an appropriate section, for example, a circular
; section, constructed coaxially in the lower lever arm 17b in
such a manner as to be open at the bottom. The lower end
i l9b of the tubular piston projects from the housing 20 in
the lower lever arm 17b, and is shaped as a spherical cap.
A spring 21 is contained in the lower lever arm 17b and
pushes the friction device 19 against the tread 2a of the
wheel 2. This spring 21 is placed partially inside the
tubular piston l9a and partially outside the piston in the
housing 20 of the lower lever arm 17a. The upper end of the
spring engages against the pivot axle 18. Alternatively,
the upper end of the spring can engage against an internal
flange in the housing 20 or other internal structure of the
double control lever 17. At its other lower end the spring
engages against the friction device 19, and, more precisely
against the internal surface of the spherical cap l9b.
Ihe locking device 16 also includes a locking means 22
consisting of a tip which extends from and is an integral
part of the free end of the upper lever arm 17a. The
locking means 22 extends perpendicularly to the pivot axle
18 of the lever 17 in the direction toward the periphery of
the thrust bearing.
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The remaining part of the locking device 16 includes a
second locking means 23 which is located on a component of
the wheel assembly which remains stationary during rotation
of the fork joint 6 about the axle 3. The locking means 23
operates in conjunction with the locking means 22 to
immobilize the supporting fork joint 6 against rotation on
its vertical swivel axle 3. As shown in Figs. 1 and 6, the
locking means 23 is located in the inner, lower housing 10
of the thrust bearing 8. Alternatively, in the embodiments
of Figs. 4 and 5, the locXing means 23 is an integral part
of the external stationary housing 9 of the bearing 8.
The locking means 23 consists of a locking slot open in
the direction of the first locking means 22 and capable of
receiving, without any significant lateral play, the first
locking means, that is to say, the locking tip 22 which is
an integral part of the upper lever arm 17a. This slot 23
is located along a vertical center plane of the fork joint
6. This plane passes through the axis of the vertical axle
3 and is perpendicular to the horizontal axis 4 of the wheel
2 and to the horizontal pivot axle 18 of the double lever 17
when the cart on which the swivelling wheel assembly 1 is
mounted moves straight ahead. As can be seen in the
drawing, the pivot axle 18 of the double lever 17 is located
near the periphery of the circular cover 7 of the fork joint
6 and also near the locking slot 23.
Finally, the locking devices 16 include two stops 24,
25 which serve to limit the pivot angle of the double
control lever 17 between its two outermost positions. These
two stops form with the pivot axle 18 a relatively small
angle on the order of 3 to 15, and are located in
proximity to a radial plane of the wheel 2. The latter
plane passes through the lever's pivot axle 18 and the
wheel's axle 4 of rotation. In this manner, the lower lever
arm 17b shall not deviate overly from a position in which
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its axis extends vertically in relation to the tread 2a,
i.e., perpendicular to the surface of the tread where
engagement with the friction device 19 occurs.
The first stop 24 for the control lever 17 is placed in
the space located above the wheel 2 and between the lateral
extensions 5 of the fork joint 6 and works in conjunction
with a first portion, for example, the lower lever arm 17b
of the control lever 17, while the second stop consists of
; the downwardly facing bottom surface of the locXing slot 23
` and the downwardly facing bottom edge surface of the housing
10 9 or 10 which contains the slot 23. The stop 25 works in
conjunction with the locking tip 22 to limit the pivoting of
- the lever 17 in the counter-clockwise direction as viewed in
the drawings.
The circular cover 7 of the fork joint 6 contains a
tracking groove 26 along the center vertical plane of the
fork joint 6. This groove lies in a plane perpendicular to
the axle 4 of the wheel 2 and the pivot axle 1~ of the
; double lever 17; and, as with the locking device 16, is
located on the side of the fork joint 6 on which the
distance between the cover 7 and the tread 2a is the
greatest. The tracking groove 26 is open at the bottom and
aligned with the upper lever arm 17a and locking tip 22 so
as to guide, with no significant lateral play, these members ~-
in their pivoting path between the control lever's 17
outermost positions. Due to this construction, the locking
of the fork joint 6 is transmitted to the swivel axle 3
along the shortest distance between the swivelling fork
joint 6 and housing 9 and 10 which is fixedly mounted on the
vertical swivel axle 3.
The locking slot 23 may be placed radially outwardly of
the tracking groove 26 formed in the cover 7 as in the
construction of Figs. 4 and 5 where the slot 23 is located
on the external housing 9. The locking slot 23 may also be
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placed radially inwardly of the groove 26 as in the
construction shown in Figs. 1 and 6 where the slot is placed
on the internal housing 10.
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