Conveyor trolley wheel assembly

An improved wheel configuration for use in a conveying system includes a solid wheel body (11) produced from a high temperature resistant hard wearing polymer material, the wheel body being carried rotatably on a shaft member (13, 28, 39, 46) which in turn is mounted from a support member (16) adapted to carry some desired object over a path defined by the conveying system, the shaft member (13, 28, 39, 46) and a retaining element (14,45) forming a connection which defines a predetermined length of said shaft member on which the wheel body is carried without axial pressure being applied to said wheel body (11) such that rotation of said wheel body (11) would be impaired.

BACKGROUND OF THE INVENTION 
The present invention relates to improvements in rollers for use in 
conveying equipment, particularly of the type adapted to convey 
manufactured parts through a series of manufacturing stages. 
Commonly conveying equipment of this type is often used to convey parts 
into and out of ovens where paint or the like might be dried or cured. 
Thus the conveying equipment must also be capable of withstanding the 
environmental conditions through which such parts are moved. In one 
configuration, rollers of the aforementioned kind consist of a metal wheel 
adapted to rotate and roll on a suitable guide track with a hanger element 
depending therefrom which carries the part to be transported. Commonly two 
such wheels might be located oppositely disposed with their respective 
hangers commonly joined and carrying the part to be transported. There are 
numerous other forms of similar conveyors where there is some form of 
wheel assembly or combination arranged in use to roll in, on, over or 
around a metal guide track of a desired formation. For example there are 
known arrangements comprising pairs of wheels journaled on a support 
structure with adjacent support structures interconnected by universal 
pivoting joints. The pairs of wheels may in some situations be arranged 
such that adjacent pairs have their axes of rotation generally at right 
angles to one another. These assemblies are often used when lighter loads 
are to be carried and perhaps tighter curves in the desired track are 
required. In such arrangements heavier loads can be accommodated by adding 
wheel pairs to the assembly. Commonly conveying arrangements as aforesaid, 
whatever, the combination or configuration, have traditionally used metal 
wheels with some form of bearing that required lubrication. The 
lubrication normally being supplied periodically by application of a 
grease gun to a grease nipple provided for the purpose. When such roller 
wheels pass into and out of ovens operating at temperatures often in 
excess of 400.degree. F., there is considerable strain placed on the 
lubricating performance of the grease. In addition, in some conveying 
systems, the supporting wheel combinations may be required to travel 
through refrigeration areas or the like where very cold temperatures can 
be experienced which provide a further factor affecting wheel and 
lubricant performance. As a result very expensive greases must be used. 
Despite this, even the greases available for use in hot temperature zones 
have temperature capabilities just above the usual oven operating 
temperatures and can fail in unusual conditions, i.e. being stalled in the 
oven zone for a longer than usual time. Of course there are also 
situations where conveyor systems operate in ambient or near ambient 
temperature conditions. Often one or more people can be continuously 
employed to supply grease to the rollers or wheels as they pass a certain 
point in the conveying system so that grease is used in such cases at a 
reasonably high rate. The operators can, however, occasionally overfill 
the roller wheels with grease and this can lead to seizure of the wheels. 
Finally, metal wheels rolling on metal guide tracks have the disadvantage 
of creating substantial and unwanted noise. There are, therefore, a 
substantial number of problems with these existing wheels. 
The objective of the present invention is, therefore, to provide a wheel 
assembly for conveyor systems of the aforementioned kind which will avoid 
the need of lubrication such as grease and thereby overcome or 
substantially minimise some if not all of the foregoing difficulties with 
presently used metal wheel systems. 
SUMMARY OF THE INVENTION 
According to one aspect of the present invention there is provided a wheel 
configuration for use in a conveying system comprising a guide track in or 
on which the wheel configuration for use in a conveying system comprising 
a guide track in or on which the wheel configuration is adapted to roll, 
said wheel configuration being adapted to be mounted from support means 
which in turn is intended to carry a load along said guide track, said 
wheel configuration including shaft member means adapted to be connected 
to said support means, a wheel body formed of polymer materials having an 
outer peripheral surface adapted to roll along said guide track, dry 
bearing means axially extending between said shaft member means and said 
wheel body, said bearing means having an inherent dry coefficient of 
friction adapted to permit rotation of said dry bearing means on said 
shaft member means whereby said wheel body rotates during rolling along 
said guide track, first retainer means being provided at an outboard end 
(relative to said support means) of said shaft member means radially 
extending therefrom to retain said wheel body on said shaft member means, 
and connection means cooperating with said shaft member means positively 
preventing axial pressure being applied to radial faces of said wheel body 
beyond a predetermined limit permitting operational rotation of said wheel 
body when assembled. 
In one preferred arrangement, a second retainer means is provided at an 
inboard end of said shaft member whereby the wheel body is retained 
between the two retainer members. Alternatively, the support means itself 
may form a retainer on the inboard side of the wheel body. 
In a further preferred arrangement, the shaft member may include a plain 
bearing in tubular form located between an inner shaft part and the inner 
peripheral surface of said wheel body. Preferably the plain bearing is 
produced from a material having an inherent low dry coefficient of 
friction adapted to permit relative movement between appropriate surfaces 
to allow rotation of the wheel body without the use of any liquid or 
semi-liquid lubricant materials. A suitable solid material of this type 
might be a PTFE (polytetrafluoroethylene) based plastics material, the 
constituents being selected dependant upon the end use of the wheel 
configuration. In a particularly preferred arrangement, for either high or 
low temperature operation, the aforesaid plain bearing may further include 
radial flanges adapted to be positioned between substantially stationary 
radial surfaces on either side of the wheel body and the wheel body 
itself. These stationary radial surfaces may be formed by inner surfaces 
of the retainer means or perhaps on the support means. Conveniently, a 
plain bearing of the aforesaid configuration will be split along its 
length, preferably at its mid point such that each half is identical. 
According to a second aspect, the present invention provides a wheel 
assembly comprising a wheel body, a metal shaft and a solid bearing 
located between said shaft and said wheel body. Conveniently, the wheel 
body is a high temperature resistant, hard wearing plastics material. The 
wheel body may for example be made from a composite material based on a 
high temperature resin bound and reinforced with fibre or fibre laminates. 
The resin may be high temperature epoxy or phenolic resin and the fibres 
may be aramid fibres or fibre laminates. 
Preferably the solid bearing is produced from a blend of PTFE 
(polytetrafluoroethylene) and minerals which are selected for high 
temperature bearing use. The solid bearing may conveniently comprise an 
annular section having radially extending end regions located at either 
end, the end regions being engaged by radially extending flanges of the 
metal shaft. The solid bearing thereby is provided with axially extending 
and radially extending bearing surfaces between the metal shaft and its 
end flanges and the bearing material. 
In a particularly preferred embodiment the bearing is formed by a pair of 
bearing half parts of substantially the same shape each having one of the 
radially extending regions. In this manner the bearing half parts might in 
use be swapped about to accommodate possible uneven wear and thereby 
extend the operational life of the assembly. Moreover, if one part becomes 
damaged, the part might be readily replaced without having to replace the 
whole bearing. 
In a further preferred embodiment, the bearing means may be formed by 
filaments or filament web material in a plurality of layers bound by a 
thermosetting plastics resin material, the filament or filament web 
material being formed at least partially by a material having an inherent 
dry coefficient of friction whereby said wheel body, in use, rotates on 
said shaft member means. 
Conveniently, the layers in the bearing zone are a synthetic low friction 
self lubricating polymer, blended, woven, or formed into a matrix with a 
high strength natural fibre or a polyester or aramid fibre. The filament 
material is at least partly formed by a polytetrafluoroethylene (PTFE) (or 
its substitutes) based material. Preferably part of the filament material 
or filament web material is formed from a reinforcing material of 
sufficient strength such as aramid fibres. The filament material or 
filament web material is preferably wound in a continuous or substantially 
continuous length, however, layered discrete lengths could also be used 
but would be more difficult to handle in production. The depth of the 
bearing zone should be at least sufficient to ensure that the dry low 
coefficient of material is not worn away during normal use. 
According to a second aspect, the present invention provides a method of 
producing a wheel configuration for use in a conveying system comprising a 
guide track in or on which the wheel configuration is adapted to roll, 
said wheel configuration being adapted to be mounted for rotation on a 
shaft member of support means which, in turn, is intended to carry a load 
along said guide track, said method comprising providing fibre laminates 
or filaments which are at least partially formed from or contain a 
material having an inherently low dry coefficient of friction, winding 
said fibre laminates or filaments onto a mandrel to form a plurality of 
layers, bonding said layers with a thermosetting resin material to thereby 
form a bearing zone, and forming a wheel body of a plastics material on an 
outer surface of said bearing zone, said wheel body having an outer 
peripheral surface adapted to roll on said guide track. 
Conveniently, the fibre laminates or filaments may be continuous (or 
semi-continuous) or may be in discrete lengths. The fibre laminate may be 
in the form of a woven web having filaments of the low dry coefficient of 
friction material extending either lengthwise or crosswise or in both 
directions. Preferably, the material having a low dry coefficient of 
friction is polytetrafluoroethylene (PTFE) based or is based on any of 
known substitutes for PTFE. The bonding thermosetting resin material is 
conveniently a high temperature resistant epoxy or phenolic resin. 
Conveniently, the fibre laminates or filaments are passed through a bath 
of the thermosetting resin material before being wound on the mandrel. 
Preferably the wheel body is formed by winding fibre laminates or 
filaments onto the outer surface of the bearing zone to form a plurality 
of layers bonded with a thermosetting plastics material thereon. 
Conveniently, the thermosetting plastics material is the same material as 
used in the bearing zone. Preferably the fibre laminates or filaments in 
the wheel body zone are formed from aramids. 
In a preferred method of construction, a wide bearing zone and wheel body 
is formed from a mandrel as aforesaid and after curing, is machined to 
divide same up into a plurality of individual wheels of desired shape and 
configuration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
With regard to FIGS. 1 and 2, the wheel assembly and hanger combination 
comprises a wheel assembly 10 including a wheel body 11, a solid bearing 
12, metal shaft 13, a fastening screw or bolt element 14 and a hanger 15. 
The hanger 15 includes a depending section 16 which operates with another 
similarly constructed assembly to carry a part through a series of 
manufacturing steps. In use the pair of wheel bodies roll on an 
appropriate guide track (not shown) to achieve this desired transport of 
the part. 
The wheel assembly comprises a solid wheel body made of a high temperature 
hard wearing plastics material which will have the effect of achieving the 
required wear characteristics while limiting the amount of noise generated 
during use of the assembly. The plastics material may be a high 
temperature resistant epoxy or phenolic based resin bound and reinforced 
with aramid fibre laminates. The wheel body 11 has a central bore 17 to 
accommodate the bearing 12 and the mounting shaft 13. The bearing 12 is 
conveniently formed in two parts of substantially the same shape and 
dimensions each having an axial section 18 and a radially extending flange 
19 which is accommodated in an annular recess 20 in the wheel body 11. The 
mounting shaft 13 is also preferably constructed in two parts 21, 22 each 
having a radially extending flange 23 of similar dimensions to the flanges 
19 of the bearing. The shaft part 21 includes an axial section 24 of a 
length equivalent to twice the axial length of one bearing part so that 
the two bearing parts are effectively retained between the flanges 23 of 
the mounting shaft 13. In this manner axial and radial bearing surfaces 
are provided. The shaft mounting part 22 includes an axial extending 
trunnion 25 which is received within a bore 26 within the shaft part 21. 
Finally a single screw or bolt 14 may be used to pass through the hanger 
15 and the shaft parts 21, 22 to be screwed into a bore 27 in the shaft 
part 22 to hold the complete assembly together. If desired, a spring 
washer may also be used to prevent loosening of the bolt during use. 
FIGS. 3 and 4 illustrate an embodiment similar to FIGS. 1 and 2 except that 
in this case, the trunnion of shaft part 22 includes a coaxially extending 
shaft portion 47 with an outward thread formation 48 that is adapted to 
pass through the shaft part 21 and the hanger 16 to be engaged by a 
castellated nut 46. The end of the shaft portion 47 may include a slot 49 
enabling engagement with a screw driver to allow the element 22 to be held 
stationary while tightening the nut thereon. 
If desired, a spring washer 50 or some other washer designed to inhibit 
loosening of the nut 46 might be used. Finally a split pin 51, can be 
employed engaging within a transverse hole 52 in the shaft portion 47 and 
the nut 46 to positively prevent loosening of the nut 46. 
In the foregoing manner, the provision of a wheel and hanger assembly is 
achieved without the need to use any separate lubrication system and which 
can be safely used in high, low or ambient temperature situations. 
FIGS. 5 to 11 illustrate further differing preferred wheel constructions 
within the scope of the present invention. FIG. 5 illustrates a wheel body 
11 mounted on a shaft member 28. The shaft member 28 may be produced from 
a metal such as steel and is formed of two sections 29, 30. The section 29 
includes an outboard retaining flange 31 and an inner shaft part 32 
received within a bore 33 of a shaft part 34 of the second section 30. The 
second section 30 may also include a radially extending retainer flange 
35. The length of the shaft part 34 is selected to be no less than the 
width of the wheel body 11 so that when a connecting means 14 such as a 
bolt is tightened, substantially no axial pressure is applied against the 
radial faces 36, 37 of the wheel body 11. 
FIG. 6 illustrates a configuration where the shaft member 39 is formed in 
one part with a face 40 of the support member 16 acting as the inboard 
retaining element for the wheel body 11. In this case, the length of the 
shaft section 41 of the member 39 is no less than the width of the wheel 
body 11 so that no axial pressure is applied against the faces 36, 37 of 
the wheel body when the bolt 14 is tightened. 
FIG. 7 illustrates a still further configuration similar to FIG. 6 but in 
this case including a plain tubular bearing 42 of a low coefficient of 
friction material such as PTFE based materials. It will of course be 
appreciated that, depending on the application, such a plain tubular 
bearing might be included in the embodiments of FIGS. 5 and 6. Moreover a 
bearing arrangement as disclosed in FIGS. 2 and 4 might also be used. 
FIG. 8 illustrates a still further possible embodiment. In this case the 
shaft section 41 has an outboard flange 31 and a section of reduced 
diameter 43 which passes through a bore 44 in the support member 16. The 
reduced diameter section 43 may be threaded along its length or plain 
through the member 16 but at least its end is threaded to allow a nut 45 
and washer or lock washer to secure the assembly together as illustrated. 
Naturally any of the previously described bearing arrangements could also 
be used in this embodiment. 
A still further preferred embodiment is illustrated in FIG. 9 where the 
shaft section 46 is integrally formed with the support member 16. A 
tubular bearing 42 may be used if desired and the wheel body 11 is 
retained on the shaft section 40 and bearing 42 by swaging or mechanically 
deforming the end of the shaft section radially outwardly as illustrated 
to create a retaining flange 47. 
Yet other embodiments are illustrated in FIGS. 10 and 11 which are similar 
to the embodiment of FIG. 8. In FIG. 10, a washer 53 is provided between 
the radial face 37 of the wheel body 11 and the adjacent face of the 
support member 16. If desired the washer may be formed from a low friction 
material such as a plastics material based on PTFE but it could also be 
formed from standard metal materials or the like. In FIG. 11, a bearing 
sleeve 54 is combined with radial flange 55 located between the face 37 
and the support member 16. In this embodiment, both an axial bearing and a 
rotational bearing is provided. 
The wheel body 11 may itself be produced from a number of differing 
thermosetting plastics materials. The wheel body 11 may be based on 
thermosetting reinforced resins with reinforcing materials being synthetic 
or natural minerals in nature. The wheel body may be formed of synthetic 
fibre reinforced resin, either filament wound or laminated depending upon 
the application of the product. Wheel construction can also be in the form 
of molded, reinforced resins with the reinforcement being mineral based 
products, i.e. glass fibre, glass bead, carbon, coke, graphite or other 
natural occurring minerals. Reinforcing materials can also be polymeric in 
nature, i.e. other thermoplastic and/or thermoset resins blended with the 
base resin to reinforce construction of the wheel body. All resin 
components used in the wheel body construction should have required 
strength, wear resistance, corrosion resistance and environment 
compatibility for the intended purpose of the unit. 
Bearings used in the wheel assembly should have a low dry coefficient of 
friction and therefore require no lubrication. Desirably any bearing 
materials used should have long life and low maintenance characteristics. 
Bearings used in the wheel assembly may be thermoplastic and/or thermoset 
in nature with the primary purpose being as a self-lubricating, long life, 
low maintenance component. Basic construction of the bearings can be in 
the form of molded and machined bearings utilising Polytetrafluoroethylene 
(PTFE) with natural, mineral or synthetic reinforcements to give strength, 
improved wear characteristics, environmental compatibility and low 
frictional coefficients. Construction of the bearings can also be in the 
form of extruded and machined, injection molded or automatically molded 
resin products and reinforcing materials including but not limited to PTFE 
based materials. 
The axial or shaft assemblies may be in the form of plated steel, stainless 
steel or other material compatible with the wheel body and bearing 
components and the environmental conditions of the end application. The 
design of the split axle allows the user to safely assemble the various 
components without over torquing the wheel/bearing assembly thus causing 
excessive loading on the assembly. Straight axles can also be utilised in 
applications where wheel assembly is to retrofit existing hardware and a 
split axle design is inappropriate. 
Components are designed to be used in conjunction with the operating 
conditions of the end user. Combinations of materials and production 
processing are predicated on actual applications. All materials are 
designed to function in the broadest possible environmental and operating 
conditions including but not limited to cryogenic temperatures, high 
temperatures up to 350.degree. C., corrosive environments, water, steam, 
under loads in excess of 1000 kg, and at speeds up to 120 meters per 
minute, all without the use of liquid or semi-liquid lubrication. 
In one preferred construction for high or low temperature operation, the 
wheel body may be formed by winding fibre laminates or filaments onto a 
mandrel. The laminates may be in the form of sheets or a continuous web 
and preferably are aramids. The filament or laminate may be passed through 
a bath of resin prior to winding on the mandrel. Alternatively the 
reinforcing filament or laminate could be impregnated with resin after 
winding on the mandrel. Conveniently the resin is adapted to resist the 
intended temperatures and temperature gradients of end use but may be a 
high temperature epoxy or phenolic resin. After curing of the resin, the 
construction is removed from the mandrel and this construction can then be 
divided into wheel components and machined to the desired sizes and final 
shape. The advantage of this form of construction is that the reinforcing 
distributes the loads around the wheel rather than being located at a 
point as would be the case with a cast plastics material wheel. 
Referring now to FIG. 12, a wheel assembly 10 is shown secured to a 
conveyor support hanger 16 by a shaft member 60. The wheel assembly 10 has 
an outer wheel body 61 with a peripheral outer surface 62 adapted to roll 
in a guide track or the like 63. A bearing zone 64 of the wheel assembly 
10 is located inwardly of the wheel body 61 and includes a bore 65 having 
a sliding fit over a central cylindrical shaft portion 66 of the shaft 
member 60. An outer end of the central shaft portion 66 has an integrally 
formed radially extending retaining flange 67 which is received in a 
recess 68 in the wheel assembly 10 so that the outer face 69 of the flange 
67 is substantially flush with an outer face 70 of the wheel assembly 10. 
At the inner end of the central shaft portion 67 there is an abutment 
portion 71 having a diameter less than the central portion 67 which is 
adapted to abut against the adjacent face 72 of the hanger 16. A further 
end shaft portion 73 is threaded and engages with a threaded bore 74 in 
the hanger 16. The end shaft portion 73 is reduced in diameter relative to 
the abutment portion 71 so that when threading the end portion 73 into the 
bore 74, the abutment portion 73 engages the hanger face 72 to define a 
minimum distance between the flange 67 and the hanger face 72. If desired, 
a washer 75 may be provided over the abutment portion 71 and a recess 76 
is provided in the inner face 77 of the wheel to accommodate the washer. 
The distance between the inner faces of the two recesses 68 and 77 is such 
as to ensure no axial pressure is applied to these faces or between the 
inner wheel face 77 and the adjacent hanger face 72. The shaft member 60 
is conveniently prevented from disengagement with the hanger (i.e. 
rotating to disengage the threaded connection) by a circlip 78. Obviously, 
any other fastening means might be used such as a nut on a threaded shaft. 
Moreover, any style of shaft construction might be employed such as those 
disclosed in FIGS. 1 to 11 so long as axial pressure on the radial faces 
of the wheel is avoided. 
Reference will now be made to the construction of the bearing zone 65. This 
zone is formed by a plurality of layers 79 of filaments which are at least 
partially formed from a PTFE based material or a suitable substitute 
therefor. These may be single filaments or filaments made into webs as 
shown in FIG. 13. At least some of the filaments in the bearing zone 
should be reinforcing type fibres such as aramids to provide adequate 
strength to the bearing zone. For example, the filaments 80 in the 
longitudinal direction (horizontal in FIG. 13) may be aramid fibres 
whereas the filaments 81 in the transverse direction may be PTFE based 
fibres. The layers 79 may be bonded by a thermosetting resin such as a 
phenolic or epoxy based resin. Each layer 79 is required to extend to the 
radial faces of either the recesses 68, 77 or the radial faces 70, 77 of 
the wheel assembly 10 so as to ensure PTFE (or its equivalent) material is 
located at all stationary/rotating surface interfaces. The wheel body 61 
may be manufactured in a similar manner to the foregoing except that the 
filament of PTFE (or its equivalent) are replaced by reinforcing material 
filaments. For example, when a web such as that shown in FIG. 13 is used, 
both the filaments 80, 81 in the zone 61 are of reinforcing standard, e.g. 
an aramid. The thermosetting resin material in the zone 61 is also 
preferably a high temperature resistant resin material. Manufacturing 
techniques for the wheel assembly 10 may be as earlier described herein. 
In an alternative arrangement, the wheel body might be separately formed 
and fitted onto the bearing zone and suitably bonded thereto. 
By the arrangement discussed above with reference to FIGS. 12 and 13, it is 
possible to create a wheel body that can be used in extreme temperatures 
and temperature differentials without the need of liquid or semi-liquid 
lubricants but which also does not require the separate manufacturing 
steps required for the solid dry lubricant bearing member disclosed in 
FIGS. 1 to 11. 
Although the present invention has been described with reference to 
preferred embodiments, workers skilled in the art will recognize the 
changes may be made in the form and detail without departing from the 
spirit and scope of the invention.