Pulley assemblies

For use primarily in a conveyor system wherein articles are required to be propelled along a predetermined path by driven belt means, the invention provides a pulley assembly having a rim member movable into and out of contact with the belt means responsive to a cam which is actuated by the propelled articles. The pulley assembly may itself directly drive the belt means or it may contact and thus drive the propelled articles or it may contact rollers in said predetermined path and upon which said articles rest.

This invention concerns pulley assemblies and relates more especially to 
pulley assemblies for use with powered conveyors of the type wherein 
articles to be conveyed rest on rolling elements such as wheels or rollers 
and drive to those articles is supplied by a driving belt which either is 
applied directly to the said articles or alternatively is applied to some 
or to all of the rolling elements on which the articles may rest. 
Situations often arise in the operation of conveyors which require numbers 
of articles, such as boxes or parcels, to be allowed to remain stationary 
and to accumulate at some point along the conveyor path. When this 
happens, the drive to the belt must be kept going and must initially be 
continued to be applied from the belt to the conveyed articles in order 
that subsequent articles may be fed to the rear of the queue. However, 
continued application of the drive to the queued articles produces 
pressure on the articles which accumulates along the length of the queue 
and can both damage the articles and overload the drive. 
It has already been proposed to avoid dangerous pressure accumulation by 
arranging that the first article to reach a point where further progress 
is to be prevented can be arrested either by imposing a barrier against 
which the action of the conveyor continually urges the article or where 
the drive can be disconnected from the region of the conveyor occupied by 
the article for the latter purpose, the presence of the article in that 
conveyor region operates a sensor means effective to disconnect drive from 
the immediately upstream area of the conveyor and successive sensor means 
are arranged in successive upstream areas of the conveyor and are operable 
responsive to the arrival of succeeding articles in those areas to cause 
or initiate the removal of the drive applied to those succeeding articles. 
Such sensor means may employ the energy available in the driving belt to 
achieve the removal of drive from the conveyed articles or they may 
control the operation of separate energy sources but the former is usually 
preferred. 
When circumstances arise, as a result of which the leading article is 
released, it is usual to restore drive to the next succeeding article and 
then to continue that restoration successively along the queue as the 
articles move along the conveyor. 
In one widely used arrangement, drive is supplied to the conveyed articles 
or to the rolling elements, as the case may be, by applying the driving 
belt to the same, usually by engaging the top run of the belt against them 
and conversely, drive is removed by disengaging the belt. In sections of 
the conveyor path where such belt engagement and disengagement is 
required, this is often accomplished by supporting the upper run of the 
belt on a roller carried on a spindle mounted at each end on a bell crank 
lever or other eccentric member which is actuated responsive to the 
aforementioned sensor means, thereby to lift the upper arm of the belt 
towards or to lower it from the conveyor path and thus to cause the belt 
to drive or not to drive the conveyed articles, according to prevailing 
conditions. Whilst such an arrangement is quite satisfactory for many 
applications, however, it will be appreciated that it does require the 
availability of not inconsiderable amounts of energy for its operation and 
that such energy ultimately represents a demand on the driving power 
available from the driving belt. For example, the sensor means is often a 
mechanically displaceable member constituting the input to a mechanical 
linkage by which the mounting spindle of the belt supporting roller is 
lifted or lowered, displacement of the said member taking place as a 
conveyed article comes into contact or releases contact with it. However, 
the operation of such a mechanical linkage not only draws significant 
energy from the driving belt but is dependent upon the force applied to 
the sensor means and therefore essentially upon the weight of the conveyed 
article. Thus, it cannot be adjusted to respond to relatively light 
articles, for example, to empty boxes and yet control full boxes, and for 
similar reasons, it may not be entirely consistent and reliable in 
operation and it may impede the passage of articles. This is particularly 
the case where, as is usual, the belt supporting roller is biased towards 
a lifted position and the mechanical linkage is required, where drive is 
to be removed from the conveyed articles, to overcome that bias and 
maintain said roller in a lowered position. 
Other arrangements previously used make use of a cam-shaped roller to 
support the driving belt. The rotation of the cam-shaped rollers can be 
arrested with the cams in a position so that the belt dragging over the 
stationary cams passes clear of the articles or their support rollers. 
This action wastes energy from the main drive. 
The invention seeks to avoid the problems described immediately above by 
providing a belt supporting roller assembly which is less dependent for 
its operation upon the weight of the conveyed articles and which avoids 
waste of energy from the driving belt. 
The present invention accordingly provides a pulley assembly comprising a 
cylindrical rim which, intermediate its axial ends, has a radially 
inwardly directed and axially apertured flange, a hub member having an 
intermediate portion passing with substantial radial clearance through the 
axial aperture of the flange, means adjoining said intermediate portion 
for constraining axial movement of the flange with respect to the hub 
member, and retractable spoke means displaceable between a normal position 
wherein the pulley rim is supported by said means in coaxial relation to 
the hub member and a retracted position wherein that support is removed 
and said rim undergoes a radial displacement causing its flange to engage 
directly on the hub member. 
By virtue of the radial displacement available to the pulley rim, a belt 
supported on it is enabled to be moved between driving and non-driving 
positions. 
Preferably the spoke means are capable of being angularly displaced or 
tilted relative to the hub member and they may for this purpose take the 
form of arcuate segments which are circularly distributed around the hub 
member and which, in addition to spoke portions engageable between the 
pulley rim and the hub member, have axially directed cam follower elements 
accessible to a cam or the like by which the desired tilting motion is 
effected consequent upon pulley rotation. 
The aforementioned constraining means may include a radial flange adjoining 
the intermediate portion of the hub member and rotationally fixed on or 
integral with the latter and the arcuate spoke segments may be arranged 
between said flange and an axially spaced fulcrum similarly carried by the 
hub member. 
Conveniently, a centering spring is interposed between the hub member and 
the pulley rim, both to restore the latter into its coaxial relation with 
the hub member when the arcuate spoke segments are released into their 
normal, rim-supporting condition, and also to drivingly connect the rim 
and the hub member for maintaining the spoke segments in rotation with the 
remainder of the pulley assembly. In this latter connection, the hub 
member flange may be keyed to ensure positive transmission of the rotary 
motion to the spoke segments.

In the drawings, a pulley rim 10 has, intermediate its axial ends, a radial 
flange 12 formed with an axial aperture 14. A hollow hub member 16, which 
when in use is mountable on a spindle 18, passes with substantial radial 
clearance through the aperture 14 and is formed with an integral flange 20 
preventing axial movement of the pulley rim 10 in one direction relative 
to the hub member. Similar movement of the rim 10 in the opposite axial 
direction is prevented by an annular shoulder 22 on the hub member and by 
a flat spiral spring 24 connected between the shoulder 22 and the inner 
peripheral surface of the rim 10, the spring 24 serving to locate a washer 
26 against the flange 12 and also acting to centre the rim coaxially 
relative to the hub member. 
Axially outwardly of its integral flange 20, the hub member 16 is also 
integrally formed with a flucrum member 28 comprising a pair of 
frusto-conical portions in back-to-back relation and defining a pivotal 
edge 30. Between the fulcrum member 28 and the flange 20, three circularly 
spaced, arcuate spoke members 32 are seated on the hub member with their 
outer peripheral edges engaged in an annular rebate 34 of the flange 12. 
The radially inner periphery of each arcuate segment 32 is axially 
thickened to present an axially outer edge 36 pivotally engaging the 
junction between the hub member 16 and fulcrum member 28 and from this 
axially thickened periphery extends an axially directed arm 38 terminating 
in a cam follower end 40. A garter spring 42 embracing the inner 
peripheral ends of the spoke members 32 maintains them seated on the hub 
member 16 and supporting the rim 10. 
In operation, for example when the pulley assembly is used to support a 
moving belt 44 the belt rotates the pulley rim 10, which is supported 
coaxially on the hub member 16 through the spoke members 32, and the rim 
10, through the spring 24, rotates the hub member 16 on the spindle 18. 
When it is desired to disengage the belt 44, for example from rollers of a 
conveyor or from roller-supported articles on a roller conveyor, an 
arcuate cam 46 (FIG. 4) is displaced to intercept the rotational path of 
the cam followers 40 of the arcuate spokes 32, the latter thus being 
tilted out of their normal positions into the retracted positions shown in 
FIG. 4, where they are disengaged from the rebate 34. The driving tension 
and the weight of the belt 44 then urge the pulley rim 10 radially 
downwards until the flange 12 seats on the hub member 16 and the pulley 
continues rotating on that seat but with the belt 44 at a lower position 
than its normal position, again as shown in FIG. 4. Keys 48 are provided 
on the hub member flange 20 to ensure that rotary motion is at all times 
transmitted to the arcuate segmental spokes. 
As will be noted from the drawings, the cam 46 is positioned to actuate 
each segmental spoke 32 as the spoke traverses its lowermost position and, 
therefore, when it is most lightly loaded. As a result, the effort needed 
to place the cam 46 in its illustrated operative position and to maintain 
it in that position against the reaction of the actuated cam follower 40 
is also very low and can be applied, in a conveyor assembly for example, 
by a mechanical linkage (not shown) of which the input member may 
accordingly sense the passage not only of relatively heavy articles but 
also of quite light articles. On release of the cam 46 from the position 
wherein it intercepts the cam followers 40, the garter spring 42 urges the 
spokes 32 back towards their normal positions and, as rotation of the rim 
10, driven by the belt, continues, the spokes 32 successively re-seat 
themselves in the annular rebate 34 of the rim. Positive re-seating 
results from the freedom of the leading spoke 32 (at the instant the cam 
46 is released) to enter the segmental area 35 of the rebate 34 which is 
defined at the lowest part of the latter when the hub member 16 and spokes 
32 are eccentric to the rim 10. Once the leading spoke has re-engaged in 
the recess, then during subsequent rotation of the assembly it acts as a 
rotating wedge between the hub member 16 and the pulley rim 10, lifting 
the rim 10 to the concentric position, which is thereafter stabilised as 
the next following spokes 32 enter the rebate 34. A radius (not shown) may 
conveniently be formed on the leading edge of each spoke 32 to assist this 
action.