SCIE A CHAINE

CHAIN SAW

Abrégé français

La tronçonneuse à chaîne selon l'invention est dotée d'un moteur (2), d'une bride de chaîne (6), d'un dispositif de blocage de la bride de la chaîne (5), et d'une roue dentée d'entraînement (4) montée sur l'axe du moteur par verrouillage (12) et engrènement de la chaîne (6). La roue dentée d'entraînement (4) est considérablement plus large dans le sens de l'axe par rapport à la largeur de la chaîne (6) et présente en son centre une arête (7), plus large que les dents (8) fabriquée dans le même plan et divisant ladite roue dentée d'entraînement (4) en deux parties, une partie dentée ouverte (4.1, 4.2) dont une est utilisée et l'autre est en réserve, étant prévue des deux cotés de cette dernière.

Abrégé anglais

The chain saw includes a motor (2), a chain flange (3), a chain (6), a chain
flange lock (5), and a drive toothwheel (4) on the motor
axle secured to it by key locking (12) and driving the chain (6). The drive
toothwheel (4) is noticeably wide in the direction of the axle in
comparison to the width of the chain (6) and it has a ridge (7) in die centre
higher than the teeth (8) manufactured from the same blank
and dividing the drive toothwheel (4) into two, with an open tooth section
(4.1, 4.2) at both sides, one of which is in use and the other in
reserve.

Revendications

5
Claims
1. A chain saw, which includes a motor, a chain
flange, a chain, a chain flange lock, and a drive toothwheel on
the motor axle secured to it by key locking and driving the
chain, characterized in that the drive toothwheel is wider in
the direction of the axle than the width of the chain and that
it has a ridge in the centre higher than the teeth manufactured
from the same blank and dividing the drive toothwheel into two,
with an open tooth section at both sides, one of which is in use
and the other in reserve.
2. A chain saw in accordance with claim 1,
characterized in that the ridge of the drive toothwheel has a
slope on both sides in order to protect the cutting tooth of the
chain.
3. A chain saw in accordance with either one of claims
1 or 2, characterized in that the ridge of the drive toothwheel
extends on top of the chain flange.
4. A chain saw in accordance with any one of claims
1 to 3, characterized in that there is a roller 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.
5. A chain saw in accordance with any one of claims
1 to 4, characterized 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 aforementioned ridge
and the flange driver.

Description

WO 94127795 ,~ ~ PCT/FI94/00226
1
CHAIN SAW
The object of the invention is a chain saw, which includes a
motor, a chain flange, a chain, a chain flange lock, and a drive
toothwheel on the motor axle secured to it by key locking and
driving the chain.
Chain saws are used a great deal in 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. Parti-
cularly 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, i.e.
that in which the outer surface of the drive toothwheel is
smooth, with only depressions made in the surface of the wheel
for the drive links. This kind of drive toothwheel controls and
keeps the chain in the right position. But branches and other
small 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 damaged. Further, for
reasons of manufacture it is not worth making wheels of this
kind wide in the direction of the axle. Therefore the drive
toothwheel 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 intention of the invention is to create a new kind of chain
saw, by means of which the aforementioned faults in known chain
saws are avoided. The characteristic features of the invention
are presented in the accompanying Patent Claims. When the

WO 94/27795 ~ ~ ~ ~ PCT/FI94/00226
2
toothing is made open on both sides in accordance with the
invention, chains of varying width will fit the drive tooth-
wheel. 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, theteeth of which are strengthened. ''
For this reason it is easy the carry out heat-treatment. Other
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.
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 can be seen in
Figures 1 and 2. The flange 3 is pushed in a known manner over
bolts 5 and 3 up to the drive toothwheel 4 and is tightened on
the counter-member 5.2 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. Roller 13 is attached to the end of the
axle by bolt 14 and preventing drive toothwheel 4 from detaching
itself. In accordance with Figure 1 the teeth 8 of the drive
toothwheel 4 drive the counter-teeth 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 6.2, in order to protect ;A
which the ridge is sloped, as shown later. In accordance with
Figure 2 there are two tooth parts 4.1 and 4.2 in drive tooth-
wheel 4 and between them a ridge 7 formed from the same blank.
The chain thus settles on the drive toothwheel 4.1 between the
ridge 7 and the flange driver 10.

WO 94127795 PCT/FI94/00226
3
Roller 13 that retains the drive toothwheel forms itself a chain
retainer, if the chain breaks. This roller 13, which is essen-
tially smaller than the drive toothwheel, is very wide in
relation to the width of the chain and includes a cylindrical
component 13.1 and flanges 13.2.
J
In accordance with Figures 3 and 4 the drive toothwheel 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 milling machine in such a way that
teeth 8 are formed on both sides. In accordance with Figure 4
the upper part of the ridge 7 includes a slope 9, which protects
the cutting blade 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,~precise during
felling, because during felling the flange places itself below
the chain. The ridge effectively 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 com-
ponents 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.
5

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