AU680502B2 - Chain saw - Google Patents

Description

ClIAIN SAW The invention relates to a chain saw, which includes a motor, a chain flange, a chain, a chain flange lock, and a drive toothwheel oin tile motor axle secured to it by key locking and driving the chain.

Chain saws are used a great deal ill forestry. The power of chain saws in relation to size and weight is superior in comparison to e.g. circular saws, A problem, however, lies in the wear in the chains, cutting flanges, and drive toothwheels, and especially in timber harvesters, in the chain remaining in place. Particularly during felling, when the axle of the drive toothwheel is vertical, there is much to be desired in the ability of the chain to remain on the drive toothwheel.

At present, the so-called solid wheel is regarded as best, ie. that in which tile outer surface of the drive toothwheel is cylindrical interrupted only by recesses made in the surface of the wheel forming teeth engaging the drive links of a chain. This kind of drive toothwheel controls and keeps the chain in the right position. But branches and other sniall pieces of wood more than 5 mm in diameter are easily pulled in between the chain and the wheel. The chain then rises out of the depressions and is often also 20 damaged. Further, for reasons of ianufacture it is not worth making wheels of this kind wide in the direction of the axle. Therefore the drive tootlwheel wears the axle and key.

Previously so-called open tooth drive wheels were made wider in order to thus reduce the stress between the axle and the wheel, But it is difficult to direct a wide open tooth drive wheel laterally. In addition, here too pieces are easily drawn between the chain and the tooth, but these seldom damage the chain.

The present invention seeks to create a new kind of chain saw, by means of which the aforementioned faults in known chain saws are avoided, Thus, according to the present invention there is provided a chain saw, which includes a motor, a chain flange, a chain, a chain flange lock, and a drive toothwheel keyed by a keyway to an axle of the motor and driving the chain, characterised in that the drive toothwheel has all axial width more than twice the width of the chain, the too thwheel including a central ridge and two open tooth sections, one on either side of the ridge amid including teeth, the ridge and the tooth sections being integrally formed, the ridge being higher than the teeth and separating the open tooth sections on both sides, the toothwheol being reversible so that either tooth section may be used to drive the chain while the other remains in reserve.

Conveniently, the ridge of the drive toothwheel has a slope on both sides in order to protect cutting teeth formed on the chain.

Preferably, the ridge of the drive toothwhool extends on top of the chain flange.

In a preferred embodiment, there is a retaining wheool essentially smaller than the drive toothwheel and equipped with an end flange and forming a chain retainer, which also locks the drive toothwheel onto the axle.

Preferably, there is a chain flange driver in connection with the motor, against which the drive toothwheel is placed, when the chain remains between the ridge and the flange driver.

When the toothing is made open on both sides in accordance with the invention, chains of varying width will fit the drive toothwheel, The chain will, however, remain on top, because there is a ridge in the centre of the toothwheel that it higher than the toothing. The toothwheel ridge gives considerable additional support to the toothing, the teeth of which are 'strengthened. For this reason it is easy to carry out heat-treatment. Other 20 advantages and forms of application of the invention appear in connection with the following example of application.

In what follows, the invention is illustrated by reference to the accompanying Figures, which show one chain saw in accordance with the invention, and the drive toothwheel used in it.

25 Figure 1 shows the chain saw from in front, with the drive wheel in partial cross-section.

Figure 2 shows the chain driver and the flange driver without flange or chain.

Figures 3 and 4 show the drive toothwheel in detail.

The principal components of the chain saw are the motor 2, chain flange 3, chain 6, chain flange lock 5, and the drive toothwheel 4 driving the chain. The chain flange lock includes a mounting surface 5.1, a retainer or counter-member 5.2, bolts 5.3 and nuts 5.4. Elements of flange lock 5 can be seen in Figures 1 and 2. The flange 3 is pushed in a known manner over bolts 5.3 up to the drive toothwheel 4 and is tightened against surface 5.1 by the counter-member 5,2 retained by means of nuts 5.4 on the bolts 5.3, In Figure 4 the drive toothwheel 4 is attached to the motor axle by means of key locking. A retaining wheel 13 is attached to the end of the axle by bolt 14 and prevents drive toothwheel 4 from detaching itself. In accordance with Figure 1 the teeth 8 of the drive toothwheel 4 drive tlli counter-teeth 6.1 of the chain 6, which run in the groove in the flange in a manner that is, as such, known. The chain includes a cutting tooth 0.2. In accordance with Figure 2 there are two tooth parts 4.1 and 4.2 in drive toothwheel 4 and between them a ridge 7 integrally formed from the same solid blank. The chain is carried on the drive toothwhoel 4.1 between the ridge 7 and the flange driver Wheel 13 that retains the drive toothwhool acts as a chain retainer, if the chain breaks. The wheel is essentially smaller than the drive toothwheel, but is very wide in relation to the width of the chain and includes a cylindrical component 13.1 and flanges 13.2.

In accordance with Figures 3 and 4 the drive toothwlheel has a considerable width in comparison to the width of the chain, when the keyway 12 carries the rotating force with a smaller surface pressure than previously. Material is milled away from a blank of ridge height using an NC mmilling machine in such a way that teeth 8 are formed on both sides. In 20 accordance with Figure 4 the upper part of the ridge 7 includes a slope 9, o" which protects the cutting tooth 6.2, see Figure 1. The diameter of the ridge is advantageously about 10 mm higher than the toothing. The sloping ridge keeps the chain laterally in place and precise during felling, because during felling the flange is positioned below the chain. The ridge effectively 25 prevents pieces of wood from getting between the chain and the teeth.

Whereas known types of drive toothwheels intended for 8 9 mm wide chains are 12 mm wide, the drive toothwheel in accordance with the invention is 25 mm wide. It has two 10 mm wide components and a 5 mm wide ridge. The slope of the ridge gives slightly more space for the chain. A larger drive toothwheel is used for larger chains.

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Claims (6)

1. A chain saw, which includes a motor, a chain flange, a chain, a chain flange lock, and a drive toothwheel keyed by a keyway to an axle of the motor and driving the chain, characterised in that the drive touthwheel has an axial width more than twice the width of the chain the toothwheel including a central ridge and two open tooth sections, one on either side of the ridge and including teeth, the ridge and the tooth sections being integrally formed, the ridge being higher than the teeth and separating the open tooth sections on both sides, the toothwheel being reversible so that either tooth section may be used to drive the chain while the other remains in reserve.

2. A chain saw as claimed in Claim 1, characterised in that the ridge of the crive toothwheel has a slope on both sides in order to protect cutting teeth formed on the chain.

3. A chain saw as claimed in Claim 1 or Claim 2, characterised in that the ridge of the drive toothwheel extends on top of the chain flange.

4. A chain saw as claimed in any one of Claims 1 3, characterised in that there is a retaining wheel essentially smaller than the drive toothwheel and equipped with an end flange and forming a chain retainer, which also 20 locks the drive toothwheel onto the axle.

5. A chain saw as claimed in any one of Claims 1 4, characterised in that there is a chain flange driver in connection with the motor, against which the drive toothwheel is placed, when the chain remains between the ridge and the flange driver. 25

6. A chain saw as claimed in any preceding claim and substantially as hereinbefore described with reference to and/or as shown in the accompanying drawings, DATED this twenty-sixth day of May 1997 LAURI KALERVO KETONEN Patent Attorneys for the Applicant: F.13. RICE CO. S.,