GB1579281A

GB1579281A - Swivel castor

Info

Publication number: GB1579281A
Application number: GB327477A
Authority: GB
Original assignee: PROGRESSUS ROLLEN AG
Current assignee: PROGRESSUS ROLLEN AG
Priority date: 1976-02-25
Filing date: 1977-02-25
Publication date: 1980-11-19
Also published as: DE2702211A1; CH610247A5; NL7701493A

Abstract

The castor contains a wheel (1) which is mounted in a fork (2), and a holder (7) which is intended for insertion in the mobile hospital bed, a counterpressure ring (4) being inserted in the web (3) of the fork (2). A longitudinally displaceable vertical bolt (14) is inserted in the holder (7), which vertical bolt (14) extends into the counterpressure ring (4). In addition, a notched disc (23) is provided which is connected in a positively engaging fashion with the vertical bolt (14). The end of the vertical bolt (14) which is near to the wheel (1) is designed as a brake (27, 29) for the wheel. Such a castor is not only simpler than previously known castors of the same type but is also more reliable in operation. <IMAGE>

Description

(54) SWIVEL CASTOR (71) We, PROGRESSUS ROLLEN AG, a Swiss Company of Industriestrasse, Dielsdorf, Switzerland, do hereby declare the invention for which we pray that a Patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement:- This invention relates to a swivel castor for a moveable object, for example for a hospital bed, of the kind comprising a wheel rotatably mounted in a fork, and a holder fitting to be secured to the moveable object, the holder fitting comprising a fork-receiving socket portion in which a thrust ring of the fork is rotatably mounted.

Castors of the kind set forth are well-known and they are commonly arranged so as to be adjustable to any one of three different operative arrangements as required. For example, in a first arrangement the' wheel may be free to roll over the floor and the fork also be free to rotate in the fork-receiving socket. The castor wheel, or wheels, can be used in this arrangement for moving the object to be displaced around corners and curves. However, if the object is to be moved in a straight line only, the castor can be adjusted so as to assume a second arrangement, in which the wheel is rotatable but the fork is locked against rotation relative to the holder fitting. Finally, when it is desired for the object to remain stationary, the castor can be adjusted to assume a third arrangement in which both the wheel and the fork are locked and the object is immobilised.

Although conventional castors of the kind set forth are of fairly complicated construction, it has been found that such castors may not work with the required degree of reliablity.

The invention provides a swivel castor of the kind set forth comprising a locking member mounted between said thrust ring and said holder fitting, the locking member being prevented from rotation relative to one of said ring and said fitting and being resiliently urged towards the other of said ring and said fitting to engage therewith to prevent relative rotation between said ring and said fitting, the castor comprising a control pin which extends from said fitting to said locking member and comprises means arranged to engage the locking member so that by a movement of the pin in the direction of its length the pin can move the locking member out of engagement with said other of said ring and said fitting to permit relative rotation between said ring and said fitting.

In a construction in which the locking member is prevented from rotation relative to the holder fitting, and is resiliently urged towards the thrust ring, to prevent the locking member from rotation relative to the holder fitting the control pin can be non-rotatably mounted in the holder fitting and the locking member non-rotatably mounted on the control pin. The locking member may be slidably mounted on the control pin, the pin comprising a shoulder arranged to engage the locking member to enable the pin to move the locking member out of engagement with the ring. First spring means may be arranged to urge the control pin away from the ring, and second spring means can be arranged to urge the locking member towards the ring and the shoulder.

Alternatively the locking member can be prevented from rotation relative to the ring and resiliently urged towards the holder fitting.

In this construction the locking member can be non-rotatably mounted on the ring, and be rotatable relative to a control pin which is non-rotatable in the holder fitting.

In either of the constructions referred t'o, the locking member may comprise an annular disc portion and lug portions which project radially outwards from the disc portion. The lug portions can be arranged to engage in recesses in said other of the ring and the fitting to prevent relative rotation between the locking member and said other of the ring and the fitting.

When the control pin is non-rotatably mounted in the holder fitting, it may comprise an externally toothed portion which can be moved into engagement with an internally toothed portion of the thrust ring to prevent relative rotation between the fitting and the ring. The arrangement may be such that the teeth are interengaged at the same time as the locking member is also acting to prevent rotation, but alternatively they may each act to prevent rotation at different times (i.e. with different positions of adjustment of the control pin).

There now follow detailed descriptions, to be read with reference to the accompanying drawings, of two embodiments which illustrate the invention by way of example.

In the accompanying drawings: Figure 1 shows, partly in longitudinal section, a first embodiment; Figure 2 is a view in section on line II-II of Figure 1; Figure 3 is a view in side elevation of the second embodiment; Figure 4 is a front view of the castor of Figure 3, with the castor in a first position of adjustment; Figure 5 is a partial front view of the castor ot Figure 3, showing the castor in a second position of adjustment; and Figure 6 is a partial front view of the castor of Figure 3, the castor being in a third position of adjustment.

The swivel castor shown in Figure 1 comprises a wheel 1 which is rotatably mounted in a fork assembly 2. A web portion 3 of the fork assembly 2 is formed with an opening in which is fitted a thrust ring 4 of the fork assembly.

The thrust ring is externally threaded, and a clamping ring 5 and a nut 6 are screwed onto the threaded thrust ring 4 and clamp the web portion 3 between them securely.

The castor shown in Figure 1 also comprises a holder fitting 7 which comprises a housing portion 8 and a cup-shaped fork-receiving socket portion 9. The housing portion 8 and the socket portion 9 are formed integrally from a single piece of material. The housing portion 8 is adapted to be secured to a movable object (For example a hospital bed, not shown).

The thrust ring 4 is rotatably mounted in the socket portion 9 of the holder fitting 7. A radially inwardly facing groove 10 is provided in the socket portion. A radially outwardly facing groove is provided at the thrust ring 4, between a flange portion 12 of the ring 4 and the clamping ring 5. Bearing balls (Figure 1) are located in the groove 10, radially between the holder fitting and the thrust ring, so that the fork assembly 2 is rotatably mounted on the holder fitting 7. A seal 13 is provided to exclude dirt, water and the like from the bearing balls.

A control pin of the swivel castor comprises a bolt 14 which extends through the holder fitting 7 and the thrust ring 4. The bolt is slidable in the direction of its length, but nonrotatably mounted, in the housing portion 8 of the holder fitting 7. A cylindrical pin 15 passes through the bolt 14 and through the housing portion 8, the ends of the pin 15 being guided in elongate slots 16 (seen, in respect of the second embodiment, in Figure 3); sliding displacement of the bolt 14 with respect to the housing portion 8 is limited by the ends of the slots 16. An upper end portion of the bolt 14 is provided with a thread for engagement with a first nut 17 followed by a cap nut 18.A bush 19 on the bolt 14 is biassed by a compression spring 20 into abutment with the first nut 17, the other end of the spring being supported by a shoulder of the housing portion 8 to urge the control pin in a direction away from the thrust ring 4. Suitable means for adjusting the castor, by adjustment of the position of the control pin, are provided on the object to which the castor is secured; these means are not specifically described herein because suitable actuating devices for this purpose are well-known. The adjusting means is arranged to act on the cap nut 18 to displace the bolt 14 downwards as required, the spring 20 acting to return the bolt upwards.

The castor comprises a locking member 23 mounted between the thrust ring 4 and the bottom of the socket portion 9 of the holder fitting 7. As seen in Figure 2, the locking member 23 comprises an annular disc portion and diametrically opposed lug portions 26 which project radially outwards from the disc portion. The locking member is non-rotatably mounted on the bolt 14, being slidably mounted on a barrel-shaped portion of the bolt (see Figure 2). Since the bolt 14 is non-rotatably mounted in the housing portion 8, the locking member is thus prevented from rotation relative to the holder fitting.Compression springs 24, mounted in axially extending recesses in the housing portion 8, resiliently urge the locking member towards the thrust ring 4; in a first position of adjustment of the castor, as shown in Figure 1, the locking member 23 is held by the springs 24 against a shoulder of the control pin, provided by an end face of a pinion 21 secured to the bolt 14. In this first position of adjustment, the wheel 1 can rotate and the fork assembly 2 is free to swivel on the holder fitting 7, so that an object on which the castor is mounted can be steered. In an annular end face of the thrust ring 4 there are provided diametrically opposed recesses 25 adapted to receive the lug portions 26 of the locking member 23 when the control pin is lowered to a second position of adjustment.

Upon engagement of the lug portions 26 in the recesses 25, relative rotation between the thrust ring 4 and the locking member, and so between the ring and the holder fitting 7, is prevented but the wheel 1 can still rotate.

By a subsequent return movement of the bolt 14 in the direction of its length upwards, the locking member 23 can be moved out of engagement with the thrust ring 4, owing to engagement of the end face of the pinion 21 with the locking member, to once again permit relative rotation between the thrust ring and the holder fitting.

The pinion 21 is secured to the bolt 14 by means of a pin 22. Pinion 21 provides an ex ternally toothed portion of the control pin which, by movement of the bolt 14 along its length downwards to a third position of adjustment, can be moved into engagement with an internally toothed portion 28 of the thrust ring 4; such engagement prevents relative rotation between the control pin and the thrust ring.

A lower end portion of the bolt 14 is threaded and a lock nut 27 is screwed onto this thread.

In the third position of adjustment of the control pin, the nut 27 engages the periphery of the wheel 1 to act as a brake on the wheel.

A lower, outer, edge of the nut 17 is chamferred at such an angle that the resultant chamfer face extends substantially tangentially to the wheel when it engages the wheel periphery.

The arrangement of the castor is such that when the control pin is fully depressed, so that the nut 27 on the end of the bolt 14 engages the periphery of the wheel 1, the locking member 23 is engaged in the recesses 25 in the thrust ring 4 and the teeth of the pinion 21 are engaged with the teeth of the toothed portion 28 of the thrust ring 4. The castor is thus locked against both rotation of the wheel 1 and swivelling of the fork assembly 2 in the holder fitting 7. A hospital bed may be subject to maximum service load when stationary, and the provision of the pinion 21 is addition to the locking member 23 gives the locking mechanism substantial strength.Upon release of pressure on the cap nut 18, the spring 20 moves the bolt 14 upwards to its first position of adjustment, the nut 27 is disengaged from the toothed portion 28 of the thrust ring 4, and the locking member 23 is lifted out of engagement with the thrust ring 4, to once again permit rotation of the wheel 1 and swivelling of the fork assembly 2 in the holder fitting 7.

Figures 3 to 6 show a second construction of swivel castor. This second castor is of very similar construction to the first castor except that the locking member 23 is non-rotatably mounted on the thrust ring 4, instead of on the bolt 14, and is resiliently urged towards the holder fitting 7, by springs (not shown) mounted in the thrust ring 4, for engagement of the lug portions 26 in recesses 25 in the holder fitting 7. The locking member 23 can rotate wtih the thrust ring 4 relative to the bolt 14.

As shown in Figures 4, 5 and 6, the lug portions 26 of the locking member 23 are, in all positions of adjustment of the control pin, engaged in diametrically opposed recesses in the thrust ring 4, and in one position of adjustment of the castor they are engaged also in the recesses 25 in the holder fitting 7.

When the castor is in the adjusted position shown in Figure 4, with the locking member engaged in the recesses 25, the wheel 1 is free to rotate but the fork assembly 2 is locked against swivelling on the holder fitting 7, since the locking member 23 prevents rotation of the thrust ring 4 relative to the holder fitting.

In the position of adjustment shown in Figure 5, the bolt 14 has been slightly depressed so that the locking member 23 is disengaged from the recesses 25, so that the wheel is free to rotate and the fork assembly 2 can swivel on the holder fitting 7. In the position of adjustment shown in Figure 6, a brake shoe 29 mounted at the lower end of the bolt 14 engages the periphery of the wheel 1 to prevent rotation of the wheel, and also the pinion 21 meshes with the toothed portion 28 of the thrust ring 4. Thus in the second embodiment a non-steerable condition of the castor is achieved with the topmost position of the control pin, a fully free condition of the castor is achieved with a middle position of the control pin, and a fully locked condition is achieved with the control pin fully depressed.In the fully locked condition the locking member 23 is not engaged with the holder fitting 7, but the pinion 21, being meshed with the toothed portion 28 of the thrust ring, prevents swivelling of the fork assembly 2.

WHAT WE CLAIM IS: 1. A swivel castor of the kind set forth comprising a locking member mounted between said thrust ring and said holder fitting, the locking member being prevented from rotation relative to one of said ring and said fitting and being resiliently urged towards the other of said ring and said fitting to engage therewith to prevent relative rotation between said ring and said fitting, the castor comprising a control pin which extends from said fitting to said locking member and comprises means arranged to engage the locking member so that by a movement of the pin in the direction of its length the pin can move the locking member out of engagement with said other of said ring and said fitting to permit relative rotation between said ring and said fitting.

2. A castor according to claim 1 in which the locking member is prevented from rotation relative to said fitting and is resiliently urged towards said ring to engage therewith.

3. A castor according to claim 2 in which said control pin is non-rotatably mounted in said fitting and said locking member is nonrotatably mounted on said control pin.

4. A castor according to claim 3 in which said locking member is slidably mounted on said control pin, said pin comprising a shoulder arranged to engage said locking member to enable said pin to move said locking member out of engagement with said ring.

5. A castor according to claim 4 comprising first spring means arranged to urge said control pin away from said ring, and second spring means arranged to urge said locking member towards said ring and said shoulder.

6. A castor according to claim 1 in which the locking member is prevented from rotation relative to said ring and is resiliently urged

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. ternally toothed portion of the control pin which, by movement of the bolt 14 along its length downwards to a third position of adjustment, can be moved into engagement with an internally toothed portion 28 of the thrust ring 4; such engagement prevents relative rotation between the control pin and the thrust ring. A lower end portion of the bolt 14 is threaded and a lock nut 27 is screwed onto this thread. In the third position of adjustment of the control pin, the nut 27 engages the periphery of the wheel 1 to act as a brake on the wheel. A lower, outer, edge of the nut 17 is chamferred at such an angle that the resultant chamfer face extends substantially tangentially to the wheel when it engages the wheel periphery. The arrangement of the castor is such that when the control pin is fully depressed, so that the nut 27 on the end of the bolt 14 engages the periphery of the wheel 1, the locking member 23 is engaged in the recesses 25 in the thrust ring 4 and the teeth of the pinion 21 are engaged with the teeth of the toothed portion 28 of the thrust ring 4. The castor is thus locked against both rotation of the wheel 1 and swivelling of the fork assembly 2 in the holder fitting 7. A hospital bed may be subject to maximum service load when stationary, and the provision of the pinion 21 is addition to the locking member 23 gives the locking mechanism substantial strength.Upon release of pressure on the cap nut 18, the spring 20 moves the bolt 14 upwards to its first position of adjustment, the nut 27 is disengaged from the toothed portion 28 of the thrust ring 4, and the locking member 23 is lifted out of engagement with the thrust ring 4, to once again permit rotation of the wheel 1 and swivelling of the fork assembly 2 in the holder fitting 7. Figures 3 to 6 show a second construction of swivel castor. This second castor is of very similar construction to the first castor except that the locking member 23 is non-rotatably mounted on the thrust ring 4, instead of on the bolt 14, and is resiliently urged towards the holder fitting 7, by springs (not shown) mounted in the thrust ring 4, for engagement of the lug portions 26 in recesses 25 in the holder fitting 7. The locking member 23 can rotate wtih the thrust ring 4 relative to the bolt 14. As shown in Figures 4, 5 and 6, the lug portions 26 of the locking member 23 are, in all positions of adjustment of the control pin, engaged in diametrically opposed recesses in the thrust ring 4, and in one position of adjustment of the castor they are engaged also in the recesses 25 in the holder fitting 7. When the castor is in the adjusted position shown in Figure 4, with the locking member engaged in the recesses 25, the wheel 1 is free to rotate but the fork assembly 2 is locked against swivelling on the holder fitting 7, since the locking member 23 prevents rotation of the thrust ring 4 relative to the holder fitting. In the position of adjustment shown in Figure 5, the bolt 14 has been slightly depressed so that the locking member 23 is disengaged from the recesses 25, so that the wheel is free to rotate and the fork assembly 2 can swivel on the holder fitting 7. In the position of adjustment shown in Figure 6, a brake shoe 29 mounted at the lower end of the bolt 14 engages the periphery of the wheel 1 to prevent rotation of the wheel, and also the pinion 21 meshes with the toothed portion 28 of the thrust ring 4. Thus in the second embodiment a non-steerable condition of the castor is achieved with the topmost position of the control pin, a fully free condition of the castor is achieved with a middle position of the control pin, and a fully locked condition is achieved with the control pin fully depressed.In the fully locked condition the locking member 23 is not engaged with the holder fitting 7, but the pinion 21, being meshed with the toothed portion 28 of the thrust ring, prevents swivelling of the fork assembly 2. WHAT WE CLAIM IS:

1. A swivel castor of the kind set forth comprising a locking member mounted between said thrust ring and said holder fitting, the locking member being prevented from rotation relative to one of said ring and said fitting and being resiliently urged towards the other of said ring and said fitting to engage therewith to prevent relative rotation between said ring and said fitting, the castor comprising a control pin which extends from said fitting to said locking member and comprises means arranged to engage the locking member so that by a movement of the pin in the direction of its length the pin can move the locking member out of engagement with said other of said ring and said fitting to permit relative rotation between said ring and said fitting.

towards said fitting to engage therewith.

7. A castor according to claim 6 in which said locking member is non-rotatably mounted on said ring.

8. A castor according to any one of the preceding claims in which said locking member comprises an annular disc portion and lug portions which project radially outwards from said disc portion to engage in recesses in said other of said ring and said fitting to prevent relative rotation between the locking member and said other of said ring and said fitting.

9. A castor according to any one of the preceding claims in which said control pin is non-rotatably mounted in said fitting and comprises an externally toothed portion which can be moved into engagement with an internally toothed portion of said thrust ring to prevent relative rotation between said fitting and said ring.

10. A castor according to any one of the preceding claims in which said control pin can be moved in the direction of its length until an end portion thereof engages the periphery of said wheel to act as a brake on the wheel.

11. A castor according to any one of the preceding claims in which said thrust ring is rotatably mounted in said fork-receiving socket portion of the holder fitting by means of a plurality of bearing balls located radially between the ring and said fitting.

12. A swivel castor substantially as described with reference to Figure 1 and 2 of the accompanying drawings.

13. A swivel castor substantially as described with reference to Figures 3 to 6 of the accompanying drawings.