GB2239063A

GB2239063A - Variable speed drive comprising a pulley with radially movable parts

Info

Publication number: GB2239063A
Application number: GB8927701A
Authority: GB
Inventors: Fraser Milne
Original assignee: National Research Development Corp UK
Current assignee: National Research Development Corp UK
Priority date: 1989-12-07
Filing date: 1989-12-07
Publication date: 1991-06-19
Also published as: GB8927701D0

Abstract

A variable diameter pulley 10 comprises a plurality of pulley components 12-15 which can be moved radially by an axially displaceable adjustment member 21 to after the effective diameter of the pulley. The pulley components (12-15) are externally arcuate and are preferably mounted on radial spokes (17) which are acted on by the axially displaceable adjustment member (21) which is conical. There may be one variable and one fixed diameter pulley or two variable diameter pulleys with a tensioning wheel in a bolt drive system. <IMAGE>

Description

VARIABLE SPEED DRIVE The present invention relates to variable speed drives.

According to the present invention, a variable diameter pulley for use in such a drive comprises a plurality of pulley components with belt-contacting externally arcuate surfaces and adjustment means for varying the distance of said arcuate surfaces from the rotation axis of the pulley.

Conveniently, the pulley components are supported on radially-extending support parts adapted to make sliding contact with the sloping surfaces of an axially disposed adjustment member.

Conveniently, in this last case, the adjustment member comprises a conical part mounted for sliding engagement with correspondingly profiled mating surfaces of the support parts.

The invention also includes a variable speed belt drive incorporating at least one pulley in accordance with the present invention.

Preferably, two such pulleys are provided so as to give a wide range of possible drive ratios.

If desired, a belt-tensioning idler pulley may be included to compensate for any changes in belt tension that would otherwise be introduced by a change in effective pulley diameter.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying somewhat diagrammatic drawings in which: Figures 1 and 2 are a longitudinal section and an end view of a variable diameter pulley in accordance with the present invention; and Figures 3 and 4 are diagrammatic side views of two variable speed belt drives including the pulleys of Figures 1 and 2.

Thus referring first to Figures 1 and 2, the variable diameter pulley 10 illustrated comprises four belt-contacting members 12,13,14,15 each of externally arcuate form.

The members 12-15 are mounted on radial spokes 17, the inner ends of which are profiled to mate with the conical end 19 of an adjustment member 21.

The radial spokes 17 and the adjustment member 21 are all supported by a hub member 23 having an axial bore 25 for mounting on an external axle (not shown).

An annular rib portion 27 on the hub member 23 provides guide surfaces for the radial spokes 17 while an annular plate portion 29 provides axial support for the belt-contacting members 12-15 over the whole range of their radial setting. As can be seen from Figure 1, belt-contacting surfaces of the members 12-15 are profiled to engage with a so-called poly-V belt.

The barrel portion 31 of the adjustment member 21 is externally threaded to engage with a threaded bore 33 of the hub member end face 35. Clearly, rotation of the adjustment member will vary the axial position of the conical end 19 to vary the radial position of the belt-contacting members 12-15 and hence the effective diameter of the pulley 10.

Turning now to Figures 3 and 4, these show variable speed belt drives including respectively one and two variable diameter pulleys 10 as above described.

In these Figures, reference numeral 37 indicates a poly-V belt in each case and numeral 39 indicates a belt-tensioning idler which is optional in the Figure 4 arrangement provided the effective diameters of the two pulleys are carefully adjusted to keep their aggregate diameter substantially constant.

In Figure 3, reference numeral 41 indicates a conventional fixed-diameter poly-V belt pulley.

It will be appreciated that although in the illustrated embodiment, the pulley 10 comprises four separate pulley components 12-15, this number is in no way critical and other embodiments (not shown) of the invention are substantially identical to that illustrated except that they comprise a different number of components e.g. two, three, five, six etc.

Claims

1. A variable diameter pulley comprising a plurality of pulley components with belt-contacting externally arcuate surfaces and adjustment means for varying the distance of said arcuate surfaces from the rotation axis of the pulley.

2. A pulley as claimed in Claim 1 in which the pulley components are supported on radially-extending support parts adapted to make sliding contact with the sloping surfaces of an axially disposed adjustment member.

3. A pulley as claimed in Claim 2 in which the adjustment member comprises a conical part mounted for sliding engagement with correspondingly profiled mating surfaces of the suppport parts.

4. A variable speed belt drive incorporating at least one pulley as claimed in any preceding claim.

5. A variable speed belt drive as claimed in Claim 4 in which there are two said pulleys.

6. A variable speed pulley or belt drive substantially as hereinbefore described with reference to, and/or as illustrated in, the accompanying drawings.