Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
104990Z
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
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104990Z
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
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link now can swivel around a front point of support 13 when a
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force F is applied to its edge. The chain can nevertheless still
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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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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
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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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