GB2179907A - Pulling device for a shaft - Google Patents

Abstract

A pulling device for a shaft, particularly a roller blind shaft, is in the form of a housing (1) in which a cord pulley (2) is rotatably mounted, the cord pulley carrying a cord (5), arms (8, 9) of which extend out of the housing (1) through openings (7) at the bottom of the housing. The openings are symmetrically disposed on opposite sides of a vertical plane extending centrally through the housing and containing the axis of rotation of the cord pulley. The openings are mutually divergent, being directed downwardly and outwardly from said plane. If the cord pulley starts to rotate other than by pulling the cord, for example by the weight of the pulley itself, the cord which would normally be fed out of one of said openings is carried past said opening to double- back on itself and prevent further rotation of the cord pulley. A cord stop is provided to enhance the locking of the cord. <IMAGE>

Description

SPECIFICATION Pulling device for a shaft This invention relates to a pulling device for a shaft, and in particular for a roll shaft around which material is wound and unwound, such as in a roller blind.

The object of the invention is to provide such a pulling device in a convenient and effective form.

According to the invention a pulling device for a shaft comprises a cord pulley supported in a housing for rotation about an axis and having a part thereof for connection with the shaft, in use, the housing having a pair of spaced cord openings, a cord wound about said cord pulley and having parts thereof passing through said openings respectively, the openings being mutually divergent and each opening being at an angle to a plane whicn contains said axis and extends vertically through the housing when the device is in use.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which; Figure 1 is a front view of a housing of a pulling device of the invention, Figure 2 is a cross-sectional view on the line 2-2 of Figure 1, Figure 3 is a front view of a cord pulley of the pulling device, Figure 4 is a side view of the cord pulley, Figure 5 is a rear view of a cover of the pulling device, the cover snap-fittingly engaging with the housing, Figure 6 is a cross-sectional view on the line 6-6 of Figure 5, Figure 7 is a schematic perspective view of the pulling device, with its cover removed, and showing the run of tne cord under normal operation, Figure 7a is a schematic view of the cord configuration in Figure 7, Figure 8 is a schematic view similar to Figure 7, but showing the way in which the cord locks back on itself if the cord pulley rotates other than by a pulling of the cord, and Figure 8a is a schematic view, like Figure 7a, showing the cord configuration in Figure 8.

The pulling device of the invention comprises a generally shell-shaped nousing 1 of plastics material, in which is rotatably supported a cord pulley 2, the housing having a plastics material cover 12 which snapfittingly engages with the housing to retain the pulley therein. The housing has a flat rear face 13 containing a slot 14, from which a flat pin, not shown, extends for retention in a complementary slot in a conventional roller blind bracket affixed to a wall or other surface, in use. Around the periphery of the rear face of the device is an upstanding, generally circular side wall 3, having however its lower end thickened.

Surrounded by the side wall 3, the interior surface 15 of the housing is of flat, circular form. At its centre is a rectangular projection 16 through which the slot 14 in the rear face 13 extends. The centre of the slot 14 forms the axis of rotation for the cord pulley 2 which is rotatably mounted on an annular projection 17 centred on said axis and which surrounds and is spaced from said projection.

The projections 16 and 17 are the same height as the side wall 3. The side wall 3 has a pair of slots 18 therein extending inwardly from the rear face 13, the slots 18 breaking through the side wall to form openings. The slots are equi-angularly spaced on opposite sides of the vertical centre line of the housing about which it is symmetrical. A further slot 18 is provided in the rear of its lower thickened part.

The cord pulley 2 has a cylindrical centre portion 4 around the periphery of which a cord 5 is wound, the cord substantially filling the annular space between the portion 4 and the interior surface of the side wall 3, but allowing smooth rotation of the pulley by means of the cord, the pulley having a circular recess in its rear face which rotatably fits over the projection 17. At each of its sides the cord is held to the pulley by two sets of mutually staggered, spaced lugs 6 extending radially from a rear part of the portion 4. The lugs 6, whose inward faces are sloped downwardly, thus define a channel in which the cord is held. Knife edges 19 are provided to grip the cord more securely.

At said thickened lower end of the side wall 3, a pair of generally straight openings 7 are provided therethrough to allow passage of the two arms 8, 9 of the cord 5 which hang vertically down from the pulling device in use.

These arms 8, 9 are unconnected, if the cord has two free ends, but would be connected if the cord was in the form of a loop. In either case the two arms should hang down far enough to enable either one to be pulled to rotate the pulley in one direction or the other as required. Some form of weight can be provided at the lower part of the cord.

Each opening 7 extends from the interior cylindrical surface of the side wall 3 to the exterior of the wall 3. The openings 7 are mutually divergent and symmetrically disposed on opposite sides of said axis of symmetry of the housing. Each opening is spaced from and directed outwardly from a diametral plane passing vertically through the device in its intended position of use, this plane containing the axis of symmetry. At the side of each opening furthest from said plane, the junction with the cylindrical interior surface of the wall 3 is cut away to form a semi-cylindrical surface 20 at the bottom of which, in the surface 15, is a circular recess 21 which continues the surface 20 around half its periphery. A cylindrical steel peg 10 is fitted in each recess 21 with half its remaining surface against the surface 20, and its other half engaged by the cord 5.On the opposite side of each opening there is a step forming a groove 11 acting as a cord stop at 900 to the surface 15. The action of this stop will be described. Apart from the rounded part of the peg 10, and the groove 11, each side of the slot is substantially straight as can be seen from Figure 1.

Instead of a separate peg, the cord engaging rounded surface could be part of the housing.

The peg is preferred however because of wear considerations.

From a front surface of the portion 4 of the pulley there projects a cylindrical spindle 4a with four, equi-angularly spaced, tapering axial ribs 4b extending along its length. The spindle and ribs fit, in use, into a tube at one end of the roller blind. The other end of the roller blind is retained in a conventional manner by means of a round pin inserted in a plug for the end of the roller blind tube, the pin being rotatably received in a roller blind bracket fixed to a wall or other surface. The plug can be of the same form as the spindle 4a and ribs 4b, these projecting from a circular flange from the rear of which the round pin projects.

The cover 12 shown in detail in Figures 5 and 6 has the same general shape as the housing and is in the form of a flat plate 22 from the periphery of which three ears 23 extend rearwardly, the relative positions of the ears on the symmetrical cover matching the positions of the slots 18 so that, in use, respective cam ramps 24 on the inner surfaces of the ears can snap-fittingly engage with the slots 18 to secure the cover to the housing.

The cover has a circular hole 25 therein which has its centre as the rotational axis of the cord pulley, when the cover is fitted to the housing, the diameter of the hole 25 being slightly larger than the diameter of the pulley portion 4 so that the front part of the portion 4 is received in said hole 25, in use, with the lugs and cord being retained behind said cover in the housing. The rear of the cover has a pair of circular recesses 26 to receive the upper ends of the pegs 10 respectively.

Figure 7 shows how the cord is disposed under normal operation. The cord 5 is wound around the majority of the cylindrical periphery of the rear part of the portion 4 of the pulley, but at the lower part of the space between the portion 4 and the interior surface of the side wall, the arms 8, 9 of the cord respectively pass through the pair of openings 7. As shown, each cord arm passes around the outwardly facing semi-cylindrical surface of the pin 10 and through the opening to hang vertically down in a plane displaced outwardly with respect to a vertical plane at the entry of the cord into the opening. If required the lower part of the side of the opening containing the groove 11 may be slightly rounded, as shown, to assist with a smooth passage of the cord when either arm 8 or 9 is pulled to rotate the pulley and thus to wind the blind up or down.

The vertical downwardly pulling force applied to the cord arm 8 or 9 pulls the cord off the pulley at the entry to one of the openings 7 as the pulley rotates, whilst simultaneously at the other opening the cord is being rewound onto the pulley. In each case passage of the cord in the openings 7 is being guided by the pegs 10. Figure 7a illustrates this arrangement.

Once the blind has been so adjusted to a desired position, it is important that it is maintained in that position and that the pulley does not substantially rotate under a force created by the weight of the blind.

With the device of the invention such rotation is prevented, due to the geometric arrangement of the openings, namely that the angling of the openings causes the cord initially to be carried past the plane in which it is disposed on leaving the opening. Figure 8 shows how this occurs, in use.

Figure 8 illustrates what occurs if the weight of the blind causes the pulley to begin to rotate in the direction of arrow A. Initially there would be some slight rotation of the pulley. However, without a vertical pulling force on either of the arms 8, 9, the cord adjacent the right hand peg 10 (as viewed in Figure 8) would be carried around with the pulley past the peg 10 to double back on itself, as best shown in Figure 8a. The cord also engages in the groove 11 thus to lock the pulley against any further movement under the weight of the blind. This locking action limits the doubling back of the cord and prevents interference with the cord passing around the other pin 10.

In the example shown and described the openings are at approximately 450 to the vertical but other suitable alternative angles could of course be used. The pulling device can be used at either or both ends of a roller blind.

The housing is preferably moulded and has been designed for ease of moulding so that no sliding cores are required.

The pulley device is particularly advantageous in being effective, in use, whilst comprising a minimum number of moving parts, in particular not requiring any separate (moveable) wedging or clamping element(s) to prevent rotation due to the weight of the blind.

Claims (14)

1. A pulling device for a shaft comprising a cord pulley rotatably supported in a housing for rotation about an axis and having a part thereof for connection with the shaft, in use, the housing having a pair of spaced cord openings, a cord wound about said cord pulley and having parts thereof passing through said openings respectively, the openings being mutually divergent and each opening being at an angle to a plane which contains said axis and extends vertically through the housing when the device is in use.

2. A pulling device as claimed in claim 1, wherein at its junction with the interior of the housing each cord opening has a cord stop, the arrangement being such that if the cord pulley starts to rotate other than by the action of the cord, the cord, which would normally be fed out of the housing through one of the openings if such rotation of the cord pulley was by way of the cord, is carried past the entrance to said one of the openings into engagement with an associated cord stop, thereby to prevent further rotation of the cord pulley.

3. A pulling device as claimed in claim 2, wherein each cord stop is a groove at the side of the junction nearer said plane.

4. A pulling device as claimed in claim 3, wherein for each opening the lowermost part of the side containing the groove is rounded.

5. A pulling device as claimed in any one of the preceding claims, wherein the side of each opening at its junction with the interior of the housing which is further from said plane is rounded, the cord normally running over said rounded part, in use.

6. A pulling device as claimed in claim 5, wherein each rounded part is provided by a cylindrical peg fitted in a location in the housing at said junction.

7. A pulling device as claimed in any one of the preceding claims, wherein said cord openings are substantially straight.

8. A pulling device as claimed in claim 7, wherein said openings diverge at 450 to said plane.

9. A pulley device as claimed in any one of the preceding claims wherein said part of the cord pulley for connection with the shaft is an externally ribbed spindle.

10. A pulley device as claimed in any one of the preceding claims, wherein the cord pulley has a plurality of radially extending lugs extending around respective axially spaced peripheral portions to locate the cord around the pulley.

11. A pulley device as claimed in claim 10, wherein a cord channel is defined between said peripheral portions, the channel being provided with knife edges to grip said cord.

12. A pulley device as claimed in any one of preceding claims, wherein the housing has a detachable cover.

13. A pulling device as claimed in any one of the preceding claims, wherein the openings are symmetrical about said plane.

14. A pulling device for a shaft substantially as hereinbefore described, with reference to, and as shown in the accompanying drawings.