GB2204485A

GB2204485A - Locking device for castor wheels

Info

Publication number: GB2204485A
Application number: GB08810621A
Authority: GB
Inventors: Dieter Mellwig
Original assignee: SCHULTE SOEHNE KG A
Current assignee: SCHULTE SOEHNE KG A
Priority date: 1987-05-06
Filing date: 1988-05-05
Publication date: 1988-11-16
Anticipated expiration: 2008-05-05
Also published as: IT8821145V0; IT8820343A0; DE8706475U1; GB8810621D0; IT1217208B; FR2614845B1; GB2204485B; FR2614845A1

Abstract

A castor wheel 10 of a container 44 includes a locking device for preventing pivoting movement of the wheel fork 11, and rotational movement of the wheel, the device comprising a rotatable cam 26 having recess 28, said cam 26 being acted upon by a positioning pin 24 which passes centrally through the bearing head and which is biased upwardly in the releasing direction by a resilient brake member (38, fig 1). The rotational movement of the cam is limited by abutment faces 31,32 on a housing. The cam is rotated into the locked position shown by a lever 41 connected to abort 42 engageable in a scoring lock 43. On releasing the lock 43, the cam is rotated in an anti-clockwise direction by the upwardly urged pin 24 until the pin engages in the recess 28. <IMAGE>

Description

tOCKING DEVICE FOR CASTOR WHEELS This invention relates to a locking device for castor wheels, particularly, but not exclusively, castor wheels provided on refuse containers, for preventing the pivoting movement of the wheel fork which is mounted via a bearing head, and preventing the rotational movement of the wheel, and to a castor wheel provided with such a locking device.

In the case of a prior locking device of the aforementioned type, a positioning shaft consists of a tubular casing which projects beyond a positioning pin and which has portions in the region of the positioning pin which are shaped to form a cam, i.e. the tubular casing is provided with a longitudinally extending depression. In the region of the positioning pin, this depression forms a bead disposed at a distance from the rotational centre of the positioning shaft, so that upon a corresponding pivoting of the positioning shaft via a lever, the bead provides for total locking, i.e. both braking of the wheel and also locking of the pivoting movement of the wheel fork. The locked position can be maintained because the switching lever is engaged by a bolt of a security lock until such time as the security lock is released.Consequently, manipulation of the lever is prevented so that even on an inclined surface, the parked refuse container will stand reliably fast. By virtue of the eccentric disposition of the cam formed by a bead on the positioning shaft, the resilient brake pull rod ought, when the securing lock is undone, to pivot the positioning shaft, via the positioning pin and together with its lever, into a released position automatically, due to the spring force of the brake pull rod. However, in the case of this prior solution, by virtue of the friction resistances in conjuction with the curved form of the cam achieved by the depression, this function cannot be reliably achieved unless the spring force is increased by strengthening the brake pull rod or the distance between the centres of rotation of that cam portion which is formed by a bead is enlarged.Increasing the spring force of the brake pull rod will however make actuation of the locking device more difficult when it has to be locked, while increasing the distance between the bead and the centre of rotation of the positioning shaft will so increase the amount of space needed for the locking device that fitting such a device on the existing refuse containers becomes a problem.

In the case of another locking device which is disclosed in DE-OS 36 04 551, the cam which co-operates with the positioning pin and which is rotationally rigidly connected to a positioning shaft comprises a trough-like cam portion for the released position of the positioning pin while the locking position of the positioning pin is maintained by a non-rising switching curve on the cam. In order to achieve automatic return in the event of the security lock being undone, then in the case of this prior solution, the cam has a peripheral projection which is acted upon by the push member of a spring arranged to return in the releasing direction. This restoring spring which acts on the cam is an accessory to the leaf spring which biases the positioning pin in the releasing direction and which is fixed on the back of the wheel fork.

According to the present invention there is provided a locking device for a castor wheel for preventing pivoting movement of the wheel fork and hence of the wheel, the fork being rotatably mounted via a bearing head, said device comprising a cam connected to a rotatable shaft and acting on a positioning pin that passes through the centre of the bearing head and is biased in the releasing direction by a resilient brake member, said cam having a recess engaged by said positioning pin in the released position and a locking cam portion that rises towards said recess in the locking direction of rotation, the rotational movement of the cam being limited by abutment faces on the housing side.

The portion of the locking cam which rises in the locking direction ensures that the cam is always subject to the action of a force component aimed in the releasing direction. By reason of the abutment faces on the housing side, the cam is unable to turn too far either in the locking direction or in the releasing direction. In this case, the locked position can be maintained in known manner by the security lock, while in the event of the securing lock being released, the locked position which prevents wheel movement and pivoting movement is automatically cancelled out by the inherent elasticity of the brake member.

In order to keep the positioning shaft free from constraining forces, the positioning pin is preferably contained in a guide housing fixed on the bearing head and in which the cam is supported to be pivotally movable on a portion of its outer periphery. As a result, the reaction forces exerted by the positioning pin and acting on the cam are transmitted to the positioning shaft only in the direction of a releasing movement, while the thrust forces are initiated via the guide housing into the bearing head of the castor wheel itself.

For a definite cam position both in the released position and also in the locked position of the cam, the said cam, according to a further feature of the invention, has a circular peripheral portion of 1800 plus its pivoting angle between the locked position and the released position, the said periphery merging on both sides into tangential faces between which is disposed the control cam formed by the ratchet recess and the rising portion of the locking cam.

A simple mounting of the locking device can be achieved in that the guide housing fixed on the bearing head consists of two half shells engaged in a tubular casing connected rigidly to the bearing head. In this respect, the said half shells advantageously have in their space for receiving the cam mutually supplementing side walls which form the respective abutment faces for the cam.

An embodiment of the invention will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a castor wheel provided with a locking device according to the invention taken along the line I-I indicated in Figure 2, and Figure 2 shows a front elevation of the castor wheel shown in Figure 1, which is partly in section in the region of the cam of the locking device.

The wheel 10 shown in dash-dotted lines in Figure 1 is rotatably mounted on a spindle 13 between the side plates of a wheel fork 11 interconnected by a transverse member 12. Rigidly connected to the transverse member 12 is a cup-shaped member 14 of a bearing head 15. The bottom of the cup-shaped member 14 is arranged as a race for two ball bearing rings and the bottom of the member 14 is located between a connection plate 17 having a central bore 16 and a bearing ring 18 which is centrally connected to the plate 17. Both the connecting plate 17 and the bearing ring 18 have a matching race for the ball bearing rings which are supported on the cup-shaped member 14. Located centrally in relation to the bore 16, there is provided on the connecting plate 17 of the bearing head 15 a tubular casing 19, secured to the plate 17 by welding for example.A guide casing 20 consisting of two half shells 21 and 22 are form-lockingly disposed inside the tubular casing 19. This guide casing 20 has at the bottom thereof a bore to accommodate the square shank 24 of a positioning pin 23, the top of which pin 23 has a spherical member 25 bearing on the cam surface 27 of a cam 26. This cam surface 27 consists of a ratchet recess 28 and a locking curve portion 29 rising in relation to the locking movement.

The cam 26 has an arcuate outer periphery 30 bearing on a semi-circular guide path provided in a space defined by the half shells 21 and 22, the arcuate periphery 30 of the cam 26 extending on the side opposite the cam surface 27 through an angle of 1800 plus the pivoting angle between the locked position and the released position, this arcuate periphery 30 merging on either side into tangential faces 31 and 32 between which the cam surface 27 is disposed. In the centre of the cam 26 there is a non-circular bore 33 which is engaged with a non-circular portion of a shaft 34. The space housing the cam 26 in the half shells 21 and 22 is semi-circular at the top and has parallel and perpendicularly extending mutually opposed side walls which form abutment faces 35 and 36 for the tangential faces 31 and 32 of the cam 26.

At the botom end of the positioning pin 23 there is a screw-threaded stud which carries a cap nut 37. This cap nut 37 is acted upon by an inherently resilient brake member 38 fixed to the transverse member 12 of the fork 11. Above the cap nut 37 there is rotatably mounted on the positioning pin 23 a star-shaped locking member 39 which is held against axial retaining discs of the positioning pin 23 by a thrust spring 40 which contacts the collar portion of the connecting plate 17. In the locked position shown in Figure 1, this star-shaped locking member 39 engages a corresponding internally toothed housing in the back member 12 of the fork.

Rotationally rigidly connected to the positioning shaft 34 is a lever 41 connected on the other side to a bolt 42 in rotatingly articulating fashion, the bolt 42 in turn engaging in known manner into a securing lock 43 of a refuse container 44. In per se known manner, this refuse container is rigidly connected by brackets to the connecting plate 17 of the bearing head 15.

In the locked position shown in the drawings, the switching lever 41 is depressed so that the portion 29 of the locking cam bears on the spherical member 25 of the positioning pin 23 which, in a correspondingly depressed position, presses the brake member 38 onto the periphery of the wheel 10, furthermore permitting of the locked position for the star-shaped locking member 39 which is biased by the thrust spring 40. The bolt 42 achieves thereby an engaged position in the securing lock 43 so that despite the action of the inherent resilience in the brake member 38, the positioning pin 23 cannot be moved upwardly.Only when, by release of the securing lock 43 by means of a key provided for the purpose, is the bolt 42 released does the spring force of the brake member 38 become effective so that by reason of the horizontal force component generated by the inclined portion 28 of the locking curve, pivot the cam 26 in anti-clockwise direction as viewed in Figure 2 so that the spherical member 25 of the positioning pin 23 can engage in the ratchet recess 28 in the cam so that on the one hand the brake member 38 is released from engagement with the wheel 10 while on the other hand the star-shaped locking member 39 is lifted so far above the back 12 of the fork 11 that no resistance is offered to pivoting of the wheel fork 11. Naturally, pivoting of the cam results in a pivoting of the lever 41 upwardly into a realeased position. To achieve a fresh locked position, the lever 41 is depressed into the position shown in Figure 2 so that also the cam 26 pivots back into the locked position shown in Figure 2, totally locking the castor wheel.

Claims

1. A locking device for a castor wheel for preventing pivoting movement of the wheel fork and hence of the wheel, the fork being rotatably mounted via a bearing head, said device comprising a cam connected to a rotatable shaft and acting on a positioning pin that passes through the centre of the bearing head and is biased in the releasing direction by a resilient brake member, said cam having a recess engaged by said positioning pin in the released position and a locking cam portion that rises towards said recess in the locking direction of rotation, the rotational movement of the cam being limited by abutment faces on the housing side.

2. A locking device as claimed in claim 1, in which the positioning pin is contained in a guide housing fixed on the bearing head and in which the cam is supported in the guide housing to be pivotally movable about a portion of its outer periphery.

3. A locking device as claimed in claim 1 or claim 2, in which the cam comprises a circular peripheral portion extending through 1800 plus its pivoting angle between the locked position and the released position, the said peripheral portion merging at both ends into tangential faces between which is disposed a control cam surface formed by the recess and the rising locking cam portion of the cam.

4. A locking device as claimed in claim 2 or claim 3 when dependent upon claim 2, in which the guide housing fixed on the bearing head consists of two half shells mounted in a tubular casing connected to the bearing head.

5. A locking device as claimed in claim 4, in which the half shells define a space in which the cam is received, said shells having side walls which form the respective abutment faces for the cam.

6. A locking device for a castor wheel, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

7. A castor wheel provided with a locking device as claimed in any preceding claim.