Railway Ballast Broom Element Clamp Plate, Broom Element and Extrusion Process for Manufacturing Broom Element and Associated Apparatus Field of the Invention The following invention relates to a broom clamp, a broom element and a process of extruding a broom element. These components are typically adapted for use in railway track maintenance. A ballast broom comprises a rotating ballast broom reel having a number of broom elements extending radially therefrom. The broom reel is mounted upon a railroad car known as a ballast regulator and is driven to rotate as the car moves along the railway tracks such that the distal portions and tips of the broom elements engage with and shift ballast from the railway sleepers or ties. The ballast broom reel generally extends transversely of the railway tracks and has a length which is substantially equal to that of the sleepers or ties. The ballast broom reel would generally include many rows of broom elements, with each row typically having four or five radially extending elements.

It is known to connect the broom elements to the rotating broom reel by means of a clamp. As shown in Fig. 1, a rotatably driven ballast broom reel 8 comprises a number of clamp brackets 7 extending radially therefrom. A rubber broom element 11 is secured to each clamping bracket 7 by means of a clamp plate. Fig. 1 shows a known ballast broom reel 8 having a prior art clamp plate 2 affixed thereto in one location for illustration purposes only. A bolt 5 passes through clamp plate 2 and through a hole 9 in the clamp bracket 7. A nut 4 is engaged upon the exposed thread 6 of the bolt 5 and is tightened to compress the proximal end of broom element 11 and retain the same in position. Each clamp 11 typically retains a pair of parallel co- extensive broom elements 11. Unfortunately, flying railway ballast and other debris can strike and damage the exposed thread 6 making it very difficult to remove the nut 4 to replace the broom elements 11 when they wear down.

Known ballast broom elements are formed from extruded rubber with the transverse cross-section of the element being constant throughout the length of the element. As the ballast broom reel 8 rotates, the distal tip of each broom element 11 contacts the ballast to sweep the same away. The linear velocity of the contact tip is greatest prior to the commencement of tip wear, whereupon the length of the broom element diminishes and the linear contact velocity between the broom tip decreases as a result of the reduced tip radius. That is, maximum wear occurs with a new broom element immediately after replacement.

Another problem associated with known broom elements is that the cross- sectional shape at the proximal end is constant, requiring a substantial clamping force

for retention of the broom element 11 to counteract centrifugal forces as the broom reel 8 rotates.

Object of the Invention It is the object of the present invention to overcome or substantially ameliorate at least one of the above disadvantages and/or more generally to provide an improved ballast broom clamp plate, an improved broom element and a process of extruding an element such as a broom element so as to provide a non-constant transverse cross- section.

Disclosure of the Invention There is disclosed herein a clamp plate for use in fixing a broom element to a clamp bracket of a rotary ballast broom reel of a railway ballast sweeping apparatus, the clamp bracket having: a pair of arms, each adapted to bear against a respective broom element, and a depending leg situated between said pair of arms and having an internal bore, wherein said internal bore comprises internal thread adapted to engage with a bolt passing through the clamp bracket.

Preferably, the clamp plate further having a bulbous protrusion into which said bore extends.

Preferably, said clamp plate is formed as a casting.

Preferably, said clamp plate is formed from metal.

There is further disclosed herein a ballast broom element formed of hard wearing, resilient material having a substantially constant cross-sectional area throughout at least a portion of its overall length and a portion of variable cross- sectional area at an end region thereof.

Preferably, said ballast broom element further comprises a tab at the end opposite to the end of variable cross-sectional area, said tab serving to assist in retaining the broom element to a broom clamp.

Preferably, the ballast broom element is formed as an extrusion or a moulding.

Preferably, said portion having a variable cross-sectional area tapers from a position wherein the cross-sectional area is approximately twice that of the substantially constant cross-sectional area portion and diminishes toward that portion.

Preferably, the cross-sectional shape of the substantially constant area portion is circular.

Preferably, the cross-section of the variable cross-sectional area portion is oval shaped.

Preferably, said ballast broom element is formed from a material selected from the group consisting of rubber, fillers and anti-degradants.

There is further disclosed herein a method of extruding an element having variable cross-section, the method having forcing an extrudate in an extrusion direction through a pair of dies including a fixed die and a moving die adapted to move in a direction transverse to the extrusion direction, the moving die being moved so as to result in an extrusion having a variable cross-sectional area.

There is further disclosed herein an apparatus for extruding an element having a variable cross-section, the apparatus having: a fixed die having an aperture therein and through which an extrudate can pass in an extrusion direction, and a moving die adapted to move in a direction substantially transverse to the extrusion direction and having an aperture therein.

Preferably, the apparatus further comprises a support block and wherein bearings are situated between the moving die and the support block.

Preferably, the aperture in the fixed die and the aperture in the moving die comprise respective profiles such that in selective alignment of the dies, a circular extrusion can result and in other alignments, an oval shaped extrusion can result.

There is further disclosed herein an extruder for extruding an element having a variable cross-section, the extruder having a head to which there is affixed a fixed die having an aperture therein and through which an extrudate can pass in an extrusion direction, and a moving die contained within the head and adapted to move in a direction substantially transverse to the extrusion direction and having an aperture therein.

Preferably, the moving die is connected to a double acting hydraulic cylinder located on the head.

Brief Description of the Drawings Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings, wherein: Fig. 1 is a schematic end elevational view of a rotary ballast broom reel showing only two of four clamp brackets upon one of which is shown a prior art clamp plate 2 and upon another of which is shown a new clamp plate 12.

Fig. 2 is a schematic end elevational view of the new clamp plate, Fig. 3 is a schematic side elevational view of the new clamp plate of Fig. 2, Fig. 4 is a schematic plan view of the new clamp plate of Figs. 2 and 3, Fig. 5 is a schematic cross-sectional illustration of the clamp plate of Figs. 2,3 and 4, taken at V-V of Fig. 4, Fig. 6 is a schematic elevational view of a broom element 11,

Figs. 7,8 and 9 are schematic cross-sectional views of the broom element of Fig. 6, taken at VII-VII, VIII-VIII and IX-IX respectively, Fig. 10 is a schematic elevational view of another broom element, Fig. 11 is a schematic elevational view of a fixed die for use in an extrusion process, Fig. 12 is a schematic elevational view of a movable die for use in association with the fixed die of Fig. 11, Fig. 13 is a schematic side elevational view of an extruding die arrangement having the dies of Figs. 11 and 12 in a first position, Fig. 14 is a schematic side elevational view of an extruding die arrangement having the dies of Figs. 11 and 12 in a second position, Fig. 15 is a front elevational view of an alternative extrusion die apparatus in a first configuration, Fig. 16 is a schematic front elevational view of the apparatus of Fig. 15 in a second configuration, Fig. 17 is a schematic cross-sectional side elevational view of the apparatus of Figs. 15 and 16, and Fig. 18 is a schematic plan view of the apparatus of Figs. 15,16 and 17.

Description of the Preferred Embodiments In Figs. 2 to 5 there is schematically depicted a clamping plate 12 for attachment to a clamp bracket 7 of a rotary ballast broom reel 8 as shown in Fig. 1.

Drum 8 is adapted to rotate such that the distal end of the broom elements 11 rotate in the direction indicated by arrow A.

Clamp plate 12 is typically formed as a metal casting and comprises a pair of opposed arms 19, each adapted to partially surround a proximal end portion of a broom element. Located between the arms 19 is a depending leg 16 having an internal bore 17 therein. To enable a relatively long bore 17 to accommodate a long bolt, a bulbous protrusion 13 is provided at the upper surface of the clamp plate 12 between the respective arms 19. The protrusion 13 serves to protect the thread of the bolt 14.

Internal thread 18 is provided in the bore 17.

At the leading edge of each arm 19 there is provided a lip 15 with a curved undersurface adapted to reduce localised pressure applied by the plate 12 to the broom element 11 upon tightening of a bolt 14 (Fig. 1) passing upwardly through the clamp bracket 7 and into threaded engagement with internal thread 18 of plate 12.

The bolt 14 passes through a hole 9 in clamp bracket 7. The thread of bolt 14 (not shown) is completely encased within the bore 17 and thus is not exposed to flying debris resulting from the action of the broom elements 11 on railway ballast.

In use, it is a relatively simple matter to remove the broom elements 11 for replacement. The bolt 14 is partly loosened by use of a spanner or socket for example, and the worn broom element removed.

An example of a broom element 11 is shown in Figs. 6 to 9. The broom element 11 is typically an extrusion of rubber, including fillers and anti-degradants, and comprises a main portion 60 of substantially constant circular cross-section as shown in Fig. 8. The distal end portion 61 of the broom element 11 tapers outwardly such that at position VII-VII the cross-section is approximately in the form of an elongate oval as shown in Fig. 7. The proximal end 62 of broom element 11 comprises a tab 63. The profile of the tab is shown in Fig. 9. Tab 63 serves to engage the back edge of clamp plate 12 so as to counteract centrifugal forces of the rotating broom element 11 upon rotation of ballast broom reel 8.

In Fig. 10 there is schematically depicted an alternative broom element 11 having a curved, bulbous profile at end portion 61. The distal tip 64 might be outwardly bowed due to the release of pressure within the extrudate when element 11 is cut just after an extrusion process. Similarly, the proximal end may comprise a concave recess 65. These are not design features, but features inherently resulting from the manufacturing process.

In Figs. 11 to 14, various components of an apparatus for producing a variable cross-section extrusion are shown. These components comprise a fixed die 100 (Fig.

11) having an oval shaped aperture 101 therethrough. A movable die 103 is shown in Fig. 12. Movable die 103 comprises an aperture 104 having an upper curve which corresponds to the shape of the upper curve of aperture 101 in fixed die 100.

The movable die 103 also comprises a pair of opposed bearing channels 105 which interengage with bearings 106 which ride along a support block 107.

As shown in Figs. 13 and 14, the movable die 103 is adapted to move in a direction transverse to extrusion direction B between a first position maximising the cross-sectional area as shown in Fig. 13, and a second position minimising the cross- sectional area as shown in Fig. 14. The position of movable die 103 as shown in Fig.

13 corresponds with the distal end of an extruded broom element as shown at Fig. 7, whereas the position of movable die 103 shown in Fig. 14 corresponds with the substantially constant minimal cross-sectional area of the broom element 11 as shown in Fig. 8. It is envisaged that the movable die will be controlled so as to move at a speed appropriate for the extrusion speed of the extrudate.

Once the appropriate length of broom element is extruded, a cutting blade will sever the element 11 from the remaining extrudate.

In Figs. 15 to 18 of the accompanying drawings, there is schematically depicted an alternative extruding die apparatus 150. The apparatus 150 includes an

extrusion head 158 within which there is situated a moving die 154. The moving die is adapted to be driven by means of a double acting hydraulic cylinder 151 mounted on the head 158. The double acting hydraulic cylinder 151 would be provided with an internal linear transducer. A ram 153 affixed to the moving die passes through a wall of the head to the hydraulic cylinder 151. Fitted into the end of the head 158 is a fixed oval die 155. Although not shown, a retaining nut or ring would be used to prevent the fixed die 155 from being pushed forward by the flow of extrudate in the direction indicated by arrow F.

Machined into the back face of the fixed die 155 is a channel indicated by reference numeral 152. It is within this channel that the moving die 154 slides by action of the double acting hydraulic cylinder 151.

An advantage of the embodiment of Figs. 15 to 18 is that by way of containment of the moving die wholly within the head of the extruder, the need for roller or ball bearings is eliminated by using pressurized semi-liquid rubber as a lubricant for the sliding of the die plates rather than an obstacle to sliding movement.

That is, leakage of rubber which extrudes laterally from the moving die plate is prevented. The only moving part penetrating the wall of the extruder head is the ram 153 of the double acting hydraulic cylinder 151.