AU767441B2 - A portable air driven belt planing machine - Google Patents

Description

A PORTABLE AIR DRIVEN BELT PLANING MACHINE FIELD OF THE INVENTION This invention is directed to a portable air driven belt planing machine which finds particular use to remove surface rubber from the spliced area when joining conveyor belting used in the underground coal mining industry. The invention is however not limited to this particular use.

BACKGROUND ART Conveyor belting used to carry coal becomes damaged and requires repair. The repair usually requires the worn or damaged area to be cut away and a new segment to be spliced into position. The spliced belt creates raised joins of rubber that need to be machined away to provide a smooth belt surface.

Portable air driven belt planing machines are known which are used to remove surface rubber however these machines suffer from a number of disadvantages.

These known machines are powered by compressed air and are handheld. The machine has an air motor that has an inlet that is coupled to the compressed airline and an outlet for exhaust air. A belt cutting rotor is provided which is not dissimilar to a rotor on a wood planer and typically comprises a horizontally mounted elongate rotating rotor. The rotor rotates at high speed and the swarf that is cut from the belt passes into a waste chamber that is positioned above and slightly behind the cutting rotor. The chamber has an outlet through which the swarf passes. The rotor is rotated by a drive pulley arrangement that consists of a primary pulley attached to the motor shaft, a small secondary pulley attached to the cutting rotor and a drive belt extending between the two pulleys.

Because these machines are used underground, they must be very reliable in use and must not be subject to frequent breakdowns and maintenance requirements.

One disadvantage with the existing belt planing machine is that the drive belt often does not last one full days operation. Therefore, if the drive belt snaps or looses its tensile strength this causes early failure of the 2 drive belt and the operator must stop operations to change the broken belt.

There would be an advantage if it were possible to reduce the failure rate of the drive belt design.

Another disadvantage with these existing machines is that the waste chamber often gets clogged with the swarf especially during heavy cutting and the operator is required to stop the machine and to physically clear the waste port. The existing machine uses the exhaust air from the air motor to blow the swart through the outlet, but the design of the conventional machine is such that the air flow through the waste chamber is of fairly low velocity and therefore the chamber and particularly the outlet can still be clogged. In the conventional machine, the exhaust air from the air motor is ducted through the drive belt housing and into the waste chamber. However, the drive belt housing has a relatively large volume and this slows down the velocity of the air passing into the waste chamber. Using the drive belt housing as an air passageway also requires the drive belt housing to be tightly sealed and this can make opening of the housing to repair the drive belt a more difficult and time consuming step.

In existing machines, the cutting rotor is mounted for rotation by a pair of spindle bearings. The end face of the cutting rotor is spaced away from the spindle bearing and the bearing seals have no protection from the swarf. It is found that the swarf will erode the seals and the bearings will fail.

Indeed, the bearings can fail in one day's operation and this requires the operator to dismantle the cutting head and to change the spindle bearings.

It is important in this type of machine to have a depth adjustment design that is reliable such that the depth does not vary inadvertently. Any undesirable variation in the depth cutting can damage the conveyor belt.

Existing machines also have an expensive moulded plastic throttle control hand piece design which is difficult and expensive to repair and there would be an advantage if this could be improved upon.

OBJECT OF INVENTION It is an object of the invention to provide a portable air driven belt planing machine which may at least partially overcome the abovementioned disadvantages or provide the public with useful or commercial choice.

In one form the invention resides in a portable air driven belt planing machine comprising an air motor which has an inlet for incoming compressed air an outlet for exhaust air, a belt cutting rotor, a waste chamber associated with the cutting rotor and which has an inlet and an outlet and into which the swarf from the rotor passes, a drive belt housing, characterised in that the machine has an air duct extending between the outlet of the motor and the waste chamber to blow pressurised air through the waste chamber, the air duct bypassing the drive belt housing.

It is found that by having a separate duct (for instances a air pipe) extending between the exhaust air outlet of the motor and the waste chamber and bypassing the drive belt housing, air passes through the waste chamber at a much higher velocity and the incident of swarf clogging the outlet of the waste chamber is reduced or even eliminated.

It is also found that by bypassing the drive belt housing, deterioration of the drive belt is remarkably reduced. While not wishing to be bound by theory, it appears that the compressed air contains contaminates such as oil and this oil contaminates the drive belt material and causes the drive belt to loose its tensile strength causing early failure of the belt. By having the compressed air (which can be contaminated with oil) bypassing the drive belt housing, the drive belt retains its tensile strength and has a much longer working life.

Suitably, the air duct comprises a pipe or tube which has a diameter that is substantially constant along its length such that the velocity of the air is not slowed by expansion of the internal volume of the duct. It is envisaged that the air duct can be throttled to increase the velocity of the air passing through the waste chamber. Suitably, the air duct will have a diameter that maximises the velocity of the air but does not significantly retard operation of the air motor.

The air duct preferably passes pressurised air into one end of the waste chamber that is remote from the outlet of the waste chamber to facilitate blowing swarf through the outlet.

The air motor of conventional belt planing machines is a large slow revving air motor that rotates at approximately 3,300 rpm. The cutting rotor typically has a rotating speed of approximately 15,000 rpm and therefore the pulley design requires a relatively large primary pulley and a relatively small secondary pulley. It is found that the small secondary pulley can be a major contributing factor to early belt failure because only a few of the belt teeth (typically about 4) are in contact with the pulley at any one time. This is due to the secondary pulley having a small diameter.

Therefore, it is preferred that the air motor of the present invention is a higher speed air motor and typically rotates at approximately 5,000-15,000 rpm and preferably rotates at about 9,000 rpm. By having the higher rotating air motor, the secondary pulley can have a larger diameter and can typically contact about 8 teeth in the drive belt reducing the drive belt load and the heat in the pulley. It is anticipated that the belt life will increase approximately 4 times compared to conventional machines.

The machine according to the invention may comprise an improvement to the cutting rotor to reduce erosion of the bearing seals. It is preferred that spacers or slingers are positioned between the bearings and the cutting rotor to reduce swarf from entering into the bearing seal area.

A further improvement to the belt planing machine according to the invention is in the depth adjustor design. In conventional models, depth adjustment cannot be secured to maintain the setting. In one aspect of the present invention, an improvement is obtained by incorporating a spring loaded cam collar arrangement that does not allow the depth gage to alter with vibration but still allows easy adjustment.

Another improvement to the belt planing machine according to one aspect of the invention is in the throttle control valve design.

Conventional machines have a plastic throttle control handpiece that is expensive to repair and replace and contains threaded inserts that become loose and causes excessive leakage of compressed air. Excessive leakage of compressed air reduces the performance of the air motor and also the ability for the exhaust air to properly blow the waste chamber clean of swarf.

In an embodiment of the present invention, the throttle control valve design has been improved. The improvement can include a standard metal ball valve and a linkage device to control the valve. This reduces the replacement or repair costs of the valve and the handpiece.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention will be described with reference to the following figures: Figure 1 illustrates the machine from one side and clearly shows the drive belt housing.

Figure 2 illustrates the machine from the other side and clearly shows the outlet of the waste chamber.

Figure 3 illustrates an improvement to the depth adjustor design.

Figure 4 illustrates a conventional spindle bearing design.

Figure 5 illustrates an improvement according to an embodiment of the invention and containing spacers between the cutting rotor and the spindle bearings.

Figure 6 illustrates an improvement to the throttle control of the machine.

BEST MODE Referring to the drawings and initially to figures 1 and 2 there is illustrated an air driven belt planing machine 10. Machine 10 is manufactured from steel, brass and plastic to make it particularly suitable in the underground coal mining industry. Electric power tools made from aluminium cannot be used underground. The machine is handheld and contains a front handgrip 11 and a rear handgrip 12. Machine 10 contains an air motor 13. Air motor 13 is a small high speed air motor having a rotation speed of approximately 9,000 rpm making it rotate much faster than the conventional machines having an air motor which rotates at 3,300 rpm. Air motor 13 has an inlet 14 and an outlet 15. Inlet 14 is associated with a throttle arrangement that will be described in greater detail below. Grip 12 is hollow and the free end of grip 12 couples to a high-pressure compressed air hose (not illustrated) which means that compressed air passes through grip 12, through inlet 14 to rotate air motor Machine 10 contains a drive belt housing 16 that is best illustrated in figure 1. Housing 16 is a closed metallic housing. Inside housing 16 is a primary pulley that connects to the shaft of air motor 13. This pulley is of smaller diameter than the pulley used in conventional motors.

In a forward part of the machine is a belt-cutting rotor (see figure The rotor is positioned just behind a forward wheel 19, and the positioning of the belt cutter rotor is already known in the art. The rotor is mounted for rotation about an axle 20 and one end of axle 20 is illustrated in figure 2. The other end of axle 20 is mounted to a small secondary pulley (not illustrated) which is positioned within housing 16 and which has a diameter that is larger than the diameter of the secondary pulley of a conventional machine. In the embodiment, the ratio between the primary and the secondary pulley is 1%:1 (as opposed to 41/:1 in relation to existing machines). This allows the smaller secondary pulley to contact 8 teeth in the drive belt (as opposed to about 4 teeth in conventional machines) which reduces the belt load and the heat in the pulley. The belt cutting rotor rotates at approximately 15,000 rpm.

The belt cutting rotor sits below a waste chamber 20. Waste chamber 22 has a lower elongate inlet such that the swarf (cuttings) from the rotating cutting rotor is flung into the waste chamber. Waste chamber 22 has an outlet 23 that is illustrated in figure 2 and through which the swarf passes.

On the other side of waste chamber 22 is an inlet 24 (see figure 1).

With the present machine, the motor outlet 15 and the waste chamber inlet 24 are directly connected via an air duct 25. Air duct comprises a pipe having a relatively constant diameter. The diameter of the pipe being approximately the diameter of the inside of grip 12 which means that that air motor 15 is not unduly subject to back pressure. Air duct completely bypasses housing 16 which means that no part of the exhaust air passes through housing 16. Air duct 25 allows the high-pressure exhaust to pass directly into the inlet 24 of the waste chamber 22 which provides a source of high-pressure air to blow all the swarf out through outlet 23. This is in contrast to existing machines where the exhaust air passes through housing 16 which slows down the exhaust air and therefore makes it much less suitable for blowing waste chamber 22 clean. Moreover, the oily compressed air does not contact the drive belt and it is found that oil will cause the drive belt to loose its tensile strength causing early failure. With the arrangement according to the embodiment of the invention, no oily compressed air will contact the drive belt that is within housing 16.

Referring to figures 4 and 5, there is illustrated the cutting rotor 18 having an axle 20 (one end of the axle being illustrated in figure 2) which is mounted for rotation to spindle bearings 26, 27. It can be seen that a gap 28, 29 is present between each end face of cutting rotor 18 and the respective spindle bearing 26, 27.

Figure 5 illustrates an embodiment of the invention where gaps 28, 29 are closed off using spacers or slingers 30 that are fastened to the rotor spindle. The rotating slingers 30 prevent any unwanted matter from entering the bearing seal area. It is found that the slingers reduce erosion of the seals and therefore failure of the bearings. The slingers are fixed to the rotor and just clear the outer race of the spindle bearing. Waste material is repelled from the seal areas.

The machine has a depth adjusting mechanism. The depth adjusting mechanism is illustrated in figure 1 and figure 2 and uses wheel 19 that is rotatably mounted to a frame 31 and the frame (and therefore wheel 19) can be lowered or raised by rotation of knob 32. Knob 32 rotates a threaded rod 33 into and out of a threaded collar 34 to raise or lower wheel 19 thereby adjusting the depth cutting of the belt cutting rotor.

Referring to figure 3 there is illustrated this part of the machine in greater detail. In particular, a helical spring 35 is positioned between knob 32 and collar 34 to maintain the required depth adjustment and to prevent the depth gage from altering with vibration.

The flow of compressed air can be regulating by a valve. The valve forms parts of a handpiece 36. With the present machine, handpiece 36 is made entirely of metal and uses a brass ball valve and a linkage device to control the valve. This arrangement is illustrated in figure 6 and shows the incoming air pipe (forming part of grip 12), a ball valve 37, a ball valve control arm 38, a link piece 39, and a trigger 40. Depressing of trigger 40 allows more or less compressed air to pass into motor 13.

The machine according to an embodiment uses a polished stainless steel base plate that allows for easy sliding of the planar over the belting material. The machine has a weight reduction of between 10 to with respect to conventional machines. A silencer can be incorporated into the exhaust port of the air motor reducing the high noise levels of existing machines and thus reducing operator stress. The position of grips 11, 12 are lower to the base of the machine to provide easier operator control.

The machine according to the invention overcomes deterioration of the drive belt by diverting exhaust air from motor 13 away from housing 16.

The belt cutting rotor has a longer life by virtue of the slingers 30 being positioned to reduce waste from eroding the bearing seals. The waste chamber has a continuous flow of high pressure air to clean swarf from the waste chamber, the high pressure air coming directly from the exhaust outlet of the motor and not via the drive belt housing. The depth adjustor design has been modified to prevent adjustment occurring with machine vibration. The throttle control handpiece has been improved to prevent excess leakage of compressed air.

It should be appreciated that various other changes and modifications can be made to the embodiment described without departing from the spirit and scope of the invention.

Claims (9)

1. A portable air driven belt planing machine comprising an air motor which has an inlet for incoming compressed air and outlet for exhaust air, a belt cutting rotor, a waste chamber associated with the cutting rotor and which has an inlet and an outlet and into which the swarf from the rotor passes, a drive belt housing, characterised in that the machine has an air duct extending between the outlet of the motor and the waste chamber to blow pressurised air through the waste chamber, the air duct bypassing the drive belt housing.

2. The machine of claim 1, wherein the air duct is a pipe.

3. The machine as claimed in any one of the preceding claims, wherein the waste chamber has an opening which is remote from the outlet and the air duct is connected to the opening to blow swarf through the chamber and through the outlet.

4. The machine as claimed in any one of the preceding claims, wherein the air motor rotates at between 5,000-15,000 rpm.

The machine of claim 4, wherein the air motor rotates at about 9,000 rpm.

6. The machine as claimed in any one of the preceding claims, wherein the cutting rotor is mounted for rotation via bearing seals, at least one slinger being position between the rotor and the bearing seals to reduce erosion of the bearing seals.

7. The machine of claim 6, wherein the slingers are fixed to the rotor.

8. The machine as claimed in any one of the preceding claims, comprising a depth adjusting mechanism which has a wheel which is rotatably mounted to a frame which can be raised and lowered by rotation of a knob which rotates a threaded rod into and out of a threaded collar to raise or lower the wheel, a helical spring being positioned between the knob and the collar to maintain the required depth adjustment and to prevent the depth gage from altering with vibration.

9. The machine as claimed in any one of the preceding claims comprising a throttle control that has a metal ball valve and a linkage device to control the valve. A machine substantially as hereinbefore described with reference to figures 1-3 and 5-6. Dated this 11th day of April 2002 John MclLVENNA and Alison Ruth MclLVENNA By their Patent Attorneys CULLEN CO.