The present invention relates to an apparatus for removing teeth of a trench digging apparatus.

A trench digging apparatus, of the type described in the specification of the applicant's copending application entitled "A Trench Digging Apparatus" and filed concurrently with this application, comprises a plurality of cutting teeth which are used to excavate a trench. The teeth are mounted on respective plates which are disposed on an endless digging chain. A cutting tooth 10 mounted on one of the plates 11 is illustrated in Figure 1. A tooth holder 12 is attached to the plate 11 and is adapted to receive and hold therein the tooth 10. The tooth 10 is inserted into the holder 12 so that

its conical cutting tip 14 remains exposed and is held within the holder 12 by a split ring (not shown) . During an excavation operation the tooth 10 engages soil to be excavated with considerable force which causes the tooth 10 to be difficult to remove upon the completion of the excavation.

Normally a tooth 10 is removed, as shown in Figure 1, from the holder 12 using an appropriate steel plate 16. The plate 16 has one end 18 which is bent downwards normal to the plate 16 and is adapted to engage the tooth 10 about an annular recess 20 of the tooth 10. The opposite end 22 of the plate 16 is also bent downwards normal to the plate 16. Once positioned on the tooth 10, as shown in Figure 1, the plate 16 is used to remove the tooth 10 by striking a surface of the opposite end 22 so as to cause the first end 18 to pull the tooth 10 from the holder 12. This, however, is a cumbersome, time-consuming and labour intensive method of removing the tooth 10 from the holder 12.

Accordingly, an object of the present invention is to provide an apparatus which overcomes, at least in part, the disadvantages associated with using the plate described above.

In accordance with the present invention there is provided an apparatus for removing teeth of a trench digging apparatus, comprising means for engaging a tooth disposed in a holder, means for engaging said holder, and means for moving said tooth engaging means with respect to said holder engaging means and away from said holder.

Preferably said tooth engaging means is disposed within said holder engaging means.

Preferably said moving means comprises a hyraulic cylinder. Preferably the piston of the cylinder is coupled to the tooth engaging means.

Preferably the holder engaging means comprises a tube. Preferably the tube is affixed to the cylinder.

Preferably the tooth engaging means comprises jaws adapted to engage an annular recess of the tooth.

A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings wherein:

Figure 1 is a side viewof a previously known apparatus for removing teeth attached to a tooth in a holder;

Figure 2 is a partial cross-sectional view of an apparatus according to the present invention attached to a tooth in a holder; and

Figure 3 is a cross-sectional view A-A of the apparatus of Figure 2 as attached to a tooth.

An apparatus 30 for removing teeth of a trench digging apparatus, as shown in Figures 2 and 3, comprises a hydraulic cylinder 32, a tube, or barrel, 34 and a tooyh engaging part 36. The tooth engaging part 36 includes a plurality of jaws 38

which are adapted to fit over the conical end 40 of the tooth 10 and engage the annular recess 20 of the tooth 10. The ends 42 of the jaws 38 are resiliently biased, to a limited extent, in towards one another and include inward protrusions 44 which snap-fit within the recess 20 once the ends 42 have been forced over the conical end 40 of the tooth 10. The jaws 38 are joined at a base portion 46 of the tooth engaging part 36 and this base portion 46 is affixed to the piston 48 of the cylinder 32.

The tube 34 is attached to the cylinder 32, by means of an O-ring 50 and is configured so that the piston and the tooth engaging part 36 are able to move within the tube 34. The end 52 of the tube 34, opposite the cylinder 32, is adapted to engage the holder 12 when the jaws 38 of the tooth engaging part 36 engage the tooth 10. The end 52 of the tube 34 abuts the surface 54 of the holder 12 into which the tooth 10 is inserted.

The tooth engaging part 36 is held in position within the tube 34 by means of an O-ring 56 disposed within the base 46 and an O-ring 58 disposed in the ends 42 of the jaws 38. The O-ring 58 is used to resiliently bias the ends 42 so that when they are passed over the conical portion 40 of the tooth 10 the protrusions 44 fit within the recess 20 of the tooth 10.

Once the apparatus 30 has been used to engage the tooth 10 and abut the holder 12, as shown in Figure 2, the tooth 10 may be removed from the holder by activating the cylinder 32 so as to drive

the piston 48 away from the holder 12 in the direction of the arrow 60. When the piston 48 is fully retracted in the cylinder 32 the tooth 10 is no longer disposed in the holder 12 and is held by the tooth engaging part 36.

Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention as hereinbefore described with reference to the accompanying drawings.