Hand tools abstract
A device in power driven hand tools, preferably chain saws having
a grip handle, and a bow handle mounted on top of the tool body.
The grip handle is mounted for rotational movement about its support
shaft. The bow handle is arranged to be pivoted around the tool
Hand tools claims
What I claim is:
1. An improved power driven hand tool having a body containing
a driving motor and a tool driven by said driving motor, a handle
arrangement to hold and control said hand tool during operation
thereof, the improvement comprising said handle arrangement comprising
a first grip handle in the form of a bow handle, said bow handle
projecting from the hand tool and arranged to be pivoted about an
exterior face of said hand tool body about a first pivot axis, and
a second grip handle, said second grip handle being mounted on said
hand tool for rotational movement about a longitudinal handle axis
for the purpose of allowing the grip on said second grip handle
to be retained irrespective of the angular position of said hand
tool body relative to said first grip handle.
2. An improved power driven hand tool as claimed in claim 1 wherein
said hand tool is a power driven chain saw, said chain saw comprising
a saw bar projecting from the tool body, a saw chain travelling
around said saw bar, the second grip handle comprising an elongate
grip handle mounted at the end of said tool body opposite said saw
bar and extending essentially in the lengthwise direction of said
saw bar, and the bow handle projecting above said hand tool body
transversely relative to the lengthwise direction of said hand tool,
the improvement comprising said bow handle arranged for pivotal
movement around at least one of the sides of said tool body, a shaft
extending essentially in the lengthwise direction of said tool body,
said second grip handle being mounted on said shaft for rotation
between the attachment points of said shaft to said tool body, the
rotational axis of said second grip handle not coinciding with the
axis of pitvotement of said bow handle.
3. An improved power driven hand tool as claimed in claim 2 said
bow handle is arranged for pivotal movement relative to said hand
tool body under frictional resistance allowing continuous angular
setting of said bow handle relative to said tool body.
4. An improved power driven hand tool as claimed in claim 2 wherein
said rotational axis of said second grip handle extends at an angle
relative to the pivot axis of said bow handle.
5. An improved power driven hand tool as claimed in claim 4 wherein
said angle is less than 90.degree..
6. An improved power driven hand tool as set forth in claim 1 wherein
a control for the drive motor is carried by the second grip handle
and is rotatable with said second grip handle.
7. An improved power driven hand tool as set forth in claim 2 wherein
a control for the drive motor is carried by the second grip handle
and is rotatable with said second grip handle.
Hand tools description
BACKGROUND OF THE INVENTION
The subject invention concerns a device for use in power-driven
hand tools to hold and control the hand tool during operation thereof.
One example of a hand tool which is contemplated to be fitted with
the device in accordance with the subject invention is the power
saw or chain saw which is used in forest management e.g. for felling
and for lopping off branches. In lopping operations which involve
sawing off branches from felled, recumbent tree trunks it is necessary
to direct the guide bar of the chain saw in such a manner that its
plane is parallel with or extends along the trunk of the tree to
ensure that minimum amounts of the knots or branches remain after
the cutting operation. To ensure this guide bar position at all
times the operator need either to shift his grip on the handles
or twist his hands and/or arms in such a manner that he obtains
the desired angle with respect to each individual knot or branch.
If the operator choses the first possibility to work with the chain
saw, he must perform a complicated manoeuvre which, if it is to
be performed safely, requires that the operator puts down the saw
on a support before he shifts his grip thereon. To alter the angle
of hands and arms, the solution most commonly adopted for reasons
of convenience, is extremely unsuitable because it prevents the
operator from exercising adequate muscular strength and therefore
lessens his ability to control the saw. This could have serious
consequences, such as bodily injuries, in case the saw jams or jerks.
From an ergonometrical viewpoint it is also unsuitable to work with
the chain saw if the operator has to hold his hands and/or arms
in abnormal positions, which in addition to giving the disadvantages
mentioned above results in uncomfortable and tiring working positions
which in turn may lead to work injuries, such as backaches and worn-out
A chain shaw construction intended to make it possible to operate
the chain saw without having to assume the hitherto necessary uncomfortable
and unsuitable work positions is suggested in the Swedish Patent
Application No. 8001841-9 (corresponding to DE-OS-No. 2 909 777).
This publication describes a chain saw the front bow handle of which
is pivotably mounted for movement about the longitudinal axis of
the saw body and which comprises a mechanism by means of which the
handle may be blocked in a number of different angular position.
The rear grip handle together with the throttle control is, however,
fixedly mounted to the body of the saw.
This construction does not constitute a significant improvement
in safety since the saw operator still needs either to change his
grip on the rear saw handle or else bend his wrist into an abnormal
position. This prior-art construction also increases the load on
the wrist since it is necessary, when pivoting the bow handle downwards,
both to counteract the movement of the saw and to carry most of
the weight of the saw by the hand holding the rear handle. Instead
of reducing the risks of work injuries this constructions tends
to increase the possible hazards. This is confirmed in research
investigations carried out by the Swedish National Board of Industrial
Safety. This research shows that the right hand, i.e. precisely
the hand which normally manipulates the rear saw handle, is the
one most frequently injured. This is essentially due to the very
considerable number of bending movements of the load-carrying wrist
that the right hand has to perform. The number of such bending movements
evidently is increased considerably when using a chain saw constructed
as taught in the Swedish Patent Application No. 8001841-9 referred
to above, and consequently this teaching cannot be regarded to offer
a satisfactory solution to the problems involved.
The purpose of the subject invention is to provide a power-driven
hand tool in which the problems outlined in the aforegoing have
SUMMARY OF THE INVENTION
More precisely, these problems are solved in accordance with the
teachings of the invention therein that the hand tool is equipped
with a first grip handle in the form of a bow handle projecting
from the hand tool, which first grip handle is arranged to be pivoted
along at least one of the side faces of the hand tool, and with
a second grip handle which is mounted on the hand tool for rotational
movement about the longitudinal handle axis for the purpose of allowing
the grip on this grip handle, once effected, to be retained irrespective
of the angular position of the hand tool.
Further characteristics and developments of the inventive object
will appear from the following description and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in closer detail in the following
with reference to the accopanying drawings, wherein a power operated
chain saw has been chosen to exemplify the teachings of the invention.
In the drawings,
FIG. 1 is a perspective view of a part of a power-operated chain
saw provided with handles in accordance with the invention.
FIG. 2 is a view of the same chain saw as in FIG. 1 but shows the
saw in a different angular position,
FIG. 3 is an exploded view of the body of a chain saw incorporating
handles in accordance with the invention.
FIG. 4 shows one example of a position that the operator may assume
when working with the chain saw in accordance with the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
The hand tool in accordance with the invention is equipped with
a grip handle 20 which is rotationally mounted on a shaft 22 for
rotational movements about the latter between the handle attachement
points 26 28 and with a bow handle 18 which is pivotally mounted
for pivotal movements relative to the body 12 of the chain saw 10
perpendicularly to the longitudinal direction of the saw body.
The grip handle 20 is equipped with a throttle control 24 which
is connected to the motor 30 of the chain saw. The throttle control
24 should at all times assume such a position that independently
of the rotational angle of the saw 10 the operator is able to regulate
the speed of the motor 30. For this purpose the grip handle 20 in
accordance with the invention is rotationally mounted in the manner
described in the aforegoing.
The bow handle 18 has an annular extension forming a loop which
encircles the body 10 of the saw. This loop comprises two sections
as appears from FIG. 3 in which figure are illustrated the bow handle
18 and its lower part 18a, the latter being attached to the handle
part 18 by means of screws 32. A groove extends around the saw body
12 in which the annular extension of the bow handle 18 is received
The desired stability of the construction is achieved by mounting
the bow handle 18 with friction in such a manner that a predetermined
minimum force is required to turn the handle 18 in relation to the
saw body 12. Mounting the handle in this way has the advantage that
all positions in which the bow handle 18 is set is felt by the operator
as being stable.
FIG. 4 illustrates a chain saw operator involved in lopping off
branches from a tree trunk with the aid of a power saw equipped
with handles in accordance with the invention. The drawing figure
illustrates clearly the advantage afforded by the pivotable bow
handle 18 and the rotatable grip handle 20. When using a power saw
10 of conventional construction in the working position illustrated
in FIG. 4 the operator would have had e.g. to twist the hand gripping
the grip handle 20 in order to reach the throttle control 24 which
would have resulted in an ergonometrically disadvantageous body
position and impaired control over the comparatively dangerous work
tool. By using a power saw 10 incorporating handles 18 20 in accordance
with the invention the saw may be turned freely during the performance
of the job because of the absence of blocking means and the operator
need not risk to let go of his grip about any one of the two handles
18 20. Owing to this arrangement the operator is therefore allowed
rapidly and at the same time comfortably to move the saw into the
position which is correct for sawing off each individual branch
without exposing himself to any unnecessary risks of injuring himself
or of other hazards.
The embodiment of the invention described in the aforegoing is
to be regarded as an example only and a number of other modifications
and embodiments are possible within the scope of the appended claims.
For instance, with the same advantages the invention is applicable
not only to chain saws but also to hedge cutters, cutting machines,
angle grinders machines and the like.