CA1049902A - Power saw chain - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
The present invention provides a power saw chain comprising driving links, side links and cutting links joined together in a guidable manner, which cutting are provided with cutting edges and shoulder attachments, said cutting links having a pivot located in front of the cutting edge in the direction of motion of the chain, the underside of the rear end of the cutting links being provided with play in respect of the guide plate supporting the saw chain.

Description

The present invention relates to a saw chain of a type ; which is used in power saws, in particular in devibrated power saws.
The present invention will be illustrated by way of the accompanying drawings in which:
Fig. 1 is a detail of a conventional chain saw chain, Fig. 2 is a detail of a chain saw chain according to ~ one embodiment of the invention, and ; Fig. 3 is a detail of a chain saw chain according to another embodiment of the invention.
It has become more and more customary to equip power saws with vibration-dampening elements by means of which the motor in the saw is insulated, with respect to vibration, from the two handles of the saw. Thus the motor is no longer the major problem for a vibration-free power saw. After the motor i~ comes the saw chain as a source of vibrations, and to avoid vibrations fro~ this source it is necessary that this chain operates without thrusts and jerks. A usual cause for the chains used hitherto to have a high vibration level is presumably 20 that the cutting links are subjected to very different loads when -~cutting through a log. One or two links at a time may, for example, have a considerably greater cutting depth than others ~
which then, more or less, idle. When such a cutting link under ~ .
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high load meets a knot or passes the work onto another link, a jerk occurs in the chain which is felt as vibration. Since this ~
type of vibration is very pronounced when working, for example, I
~, in hard-textured wood, it is desirable to find some type of saw ~ chain where jerks of this type are substantially diminished and ~
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consequently the vibration level is lower, i.e. a saw chain with -- 30 a smoother mode of operation than that of conventional chains, ~` which in principle have links of an appearance according to Figure 1. When this conventional saw chain moves in a cut, ., ~ .
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a cutting force F acts upon ~he cutting edge 1 of a cutting link

2 which tries to swivel round a point 3. Since this lies behind (after) the cutting edge, the cutting edge tends, during the application of the force F, to lift off the guide plate 4.
Consequently the cutting depth will increase and the force F will likewise increase. In practice the swivel movement upwardly of the cutting link is limited by a shoulder attachment 5, but since a high cutting speed of the chain is aimed at, this shoulder is located considerably below the cutting edge. As an example it can be said that if the cutting effect is distributed evenly over each cutting link, the cutting depth per link during the greater part of its path through the cut would be less than 0.1 mm. The maximum cutting depth per link, as determined by the difference in height between the cutting edge and the shoulder attachment, is in the present case 0.7 mm. It is evident from this therefore that the predominant part of the cutting effect can be concentrated on one or two cutting links in the cut.
The present invention solves the problem of changing the geometry of the cutting link so that an application of a force F on the cutting edge, the same may give way in the direction towards the guide plate of the saw. As a result of this the chain is given a smoother mode of operation, as a result of which the stresses in the chain are reduced. Beside a reduction in the vibrations the risk of chain rupture and the hazard of accident associated therewith is diminished.
According to the present invention there is provided a power saw chain comprising driving links, side links and cutting links joined together in a guidable manner, which cutting are provided with cutting edges and shoulder attachments, said cutting links having a pivot located in front of the cutting edge in the direction of motion of the chain, the underside of the rear end of the cutting links being provided with play in respect .

of the guide plate supporting the saw chain.
Thus in accordance with the present invention there is provided a saw chain having cutting links which have a pivot located in the front of the cutting edge in the direction of motion of the chain so that the underside of the rear end of the cutting links is provided with play in respect of the guide plate supporting the chain.
Referring once more to the drawings and particularly .~
Fig. 1 for the driving of a saw chain 6 around a saw guide plate periphery, all driving links 7 are provided with projections 8 which at the inner end of the guide plate mesh with teeth on a chain sprocket wheel and are intended to be guided in the guiding track between longitudinal side plates of the saw guide plate.
Between each pair of driving links in the chain is a side link 0 which has points of support 11 against the edges of the ;' said side plates. The driving links in one and the same pair are formed by means of cutting links 2 which in the exmaple in Figure 1 also have supports against the said edges. The cutting links 2 are thus fixed downwardly against the guide plate, so ~- 20 that the links have a tendency, under the effect oftheforce F -on their edge 1, to be swivelled around the point 3. This causes the aforesaid problem in conventional chains.
In Figure 2 one of the points of support on the , cutting links 12 has been removed by the levelling of the ,~ underside of the rear end of the link. The link has thus been set free of the guide plate at this end, which means that the .'; ::.
link now can swivel around a front point of support 13 when a .!
force F is applied to its edge. The chain can nevertheless still :
operate, because when the link swivels around the front point of support, a moment arises, owing to the tractive force of the chain, on thelink which will swivel the same backwards. The link ~ will then be held in a state of equilibrium by the forces which .,,,, .
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- 3 -~0~9902 act upon the same during the work. For example, the cutting edge .~ l may give way when passing a hard knot in the wood, instead of giving off an impulse of force as was the case in saw chains according to Fig; l.
In Figure 3 the points of support on the cutting - links 14 have been removed by the levelling of the undersides of ,-~
the links, so that the cutting links have been set free of the ~, saw guide plate. The side links lO, however, continue to have two points of support 11 each on the edges of the side plates, which means that the cutting link can now swivel a~out the rear rivet 15 in the side link. The tractive force in the chain, however, maintains the cutting link raised off the guide plate . as can be seen in Figure 3.
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Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A power saw chain comprising driving links, side links and cutting links joined together in a guidable manner, which cutting are provided with cutting edges and shoulder attachments, said cutting links having a pivot located in front of the cutting edge in the direction of motion of the chain, the underside of the rear end of the cutting links being provided with play in respect of the guide plate supporting the saw chain.

2. A chain in accordance with claim 1, in which the pivot is the point of support against the guide plate of the front end of the cutting link.

3. A power saw chain in accordance with claim 1, in which the play is effected by the levelling of the underside of the rear end of the cutting link.