Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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C~IAI~! SA~I SAFETY ~UAPD
2 FIELD OF THE IrlVENTIO~I
3 This invention relates to protective devices for chain
4 saws, and more particularly to chain saw guards oF the type
which reduce the possibility of injury when a chain saw is
6 used.
7 BACKGROU~ID OF THE INVENTION
8 The increasing use of chain saws has resulted in an
9 increasing number of chain saw accidents, many of which are
extremely serious. One of the primary causes of accidents
11 involving chain saws is the problem of chain saw kickback.
12 ~ickback usually occurs when the chain first enyages the
13 object to be cut and can cause the saw to fly out of
14 control, often rotating in the air and striking the user
while the blade is still in motion.
Many chain saws now include safety devices such as
17 chain brakes which are intended to operate when kickback
18 occurs. However, the operating mechanisms for such devices
19 often become clogged with saw dust preventing proper
operation and the brake mechanisms involved may not be
21 properly serviced thereby resulting in operational failures
22 in use. Certainly, the increasing incidence of chain saw
23 accidents would seem to indicate that such mechanisms have
24 not been entirely effective.
Other forms of safety devices have also been proposed
26 over the years including that shown in United States Patent
27 ~o. 4335513 Owens. This patent describes a bar which is
28 pivotted to the handle of the chain saw to overlie the top
29 run o-f the chain at a fixed spacing therefrom to avoid
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contact between the chain and the bar. While the
concept behind the safety bar described in this Patent
is commendable, the device has never been commercial-
ized and suffers from a number of disadvantages.
Firstly, the device is only suitable for "in line"
chain saw handles, that is, where the handle is
situated in alignment with the cutter bar of the saw,
and such chain saws are quite rare. Secondly, the
mounting of the safety bar on the handle of the chain
saw prevents the use of the device with chain saws
having chain brakes or anti-vibration devices fitted
thereto, since such devices occupy the space in which
the safety bar is intended to be positioned. Thirdly,
the mounting of the safety bar on the handle of an
existing chain saw would severely weaken the strength
of the handle so that the device is really only
suitable for use with a handle which has been specifi-
cally manufactured with a mounting fitting adapted to
accept the pivot mechanism for the safety bar.
Fourthly, the device must be manually pivo-ted to
enable boring or undercut operations to be performed,
and since this reduces the control which the operator
has over the saw, such an operation is regarded as
being potentially dangerous. FR-A-2585615, Bec,
discloses a protecting device for a chain saw includ-
ing chain bar mounting nuts, comprising mounting
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bracket means, pivot means carried by said bracket
means, an elongate protecting bar attached to said
pivot means, means for biasing said bar towards a rest
position in which the bar extends parallel to the
chain of said chain saw.
SUMMARY OF THE INVENTION AND OBJECTS
I-t is an object of the present invention to
provide an improved protective device for a chain saw
which is capable of being securely fitted to an
existing chain saw and which at least reduces the
difficulties associated with the other shortcomings
described above.
According to the present invention, there is
provided a protective device for a chain saw, compris-
ing mounting bracket means, pivot means carried by
said bracket means, an elongate protecting bar
attached to said pivot means, and means for biasing
sald bar towards a rest position in which the bar
extends in use generally parallel to the chain of said
chain saw, characterized in that said mounting bracket
means includes a member having a top portion and
depending side portions which in use are positioned on
either side of the chain bar of the chain saw, said
pivot means being carried by said bracket means, and
said protecting bar being positioned so that a portion
thereof engages said top portion to maintain said bar
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in its rest position and to prevent con-tact wi-th sa,id
chain saw, said bracket means having means formed in
or attached to at least one of said side portions for
attachment of said bracket means to the chain saw.
In one form, the present invention provides
a
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1 protecting device for a chain saw inc1uding chain ~ar
2 mounting nutsl comprising mounting bracket means, pivot
3 means carried by said bracket means, and elongate protecting
4 bar attached to said pivot means, means for biasing said bar
towards a rest position in which the bar extends in use
generally parallel to the chain of said chain saw, said
7 bracket means including provision for attachment of said
8 bracket means to the body of the chain saw by means of the
9 chain bar mounting nuts thereof.
B~IEF DESCRIPTION OF THE DRAWI~!GS
11 Two presently preferred embodiments of the invention
12 will now b~e described with reference to the accompanying
13 drawings in which:-
14 Fig. 1 is a fragmentary side elevation of a protected15 device embodying the invention showing one manner of fitting
16 to a chain saw;
17 Fig. 2 is a sectional end elevation of the device shown
13 in Fig, 1 taken along the line 2-2 of Fig. l;
19 Fig, 3 is a sectional end elevational of the protectlon
bar taken along the line 3-3 in Fig, 1,
21 fig, 4 is a perspective view of the mounting plates
22 associated with the mounting bracket for the protective
23 device shown in Fig, l;
24 Fig, 5 shows schematically how the protactive device
operates to allow the chain saw to be used effectively, and
26 Fig, 6 is a fragmentary elevation of a modification
27 showing the use of upper and lower protection bars, and
28 Fig, 7 is a detailed view of a modified end fitting ~or
29 the protectiny bar,
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2 DESCRIPTIO~I OF PREFERRED E~lBODIMENTS.
3 Referring firstly to Figs 1-4 of the drawings, the
4 chain saw protective device embodying the invention will be
seen to comprise a mounting bracket l of rectangular U-
shaped configuration in end elevation ~see Fig, 2) having a
7 top member 2 from which depend side members 3 and 4, each
8 of which is provided with forwardly projecting portions 5
9 which are shaped to define saw dogs 7. The forwardl~
projecting portions 5 of side portions 3 and 4 support a
11 pivot bolt 8 which is positioned forwardly of and parallel
12 to the top member 2, as well as a bolt 9 carrying a
13 rotatable sleeve which is positioned adjacent the free end
14 of the side members 3 and 4 to rigidly space the side
members 3 and 4 and to provide a rotatable contact which
16 prevents significant damage in the event that the chain
17 contacts the sleeve 10.
18 The pivot bolt 8 carries a short support bar ll o~
l9 rectangular channel-shaped configuration which in turn
carries an elongate protection bar 12 which is detachably
21 secured to the support bar 11. A torsion spring 13
22 surrounds the pivot bolt and engages the support bar 11 and
23 the top member 2 of the bracket 1 to bias the support bar 11
24 towards engagement with the top member 2 to maintain the
protection bar 12 parallel to the top run of the chain in
26 use.
27 The mounting bracket 1 carries a first mounting plate
28 14 which is secured thereto by bolts 15 and 16. The bolts
29 15 and 16 are received in cross-slotted holes 14a and 14b
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1 formed in the plate 14 to allow for the plate 14 to be
2 adjustably postioned Y/ith respect to the bracket 1. The
3 mounting plate 14 is formed with a central shallow channel
4 portion 17 which receives one end of a second mounting plate
18 having a pair of elongate openings 19 and l9a by means of
6 which the plate 18 may be bolted to the body of the chain
7 saw using the chain bar securing bolt(s) 20. The end
8 portion of the second mounting plate 18 has its edges formed
9 with serrations 13a and the sides of the channel portion 17
are correspondingly serrated at 17a so that the second
11 mounting plate 18 may be rigidly but adjustably engaged in
12 the channel 17.
13 The plate 18 is preferably formed with an offset
14 portion 18b to allow the plate to be used for attachment to
different types of chain saw. By inverting the plate 18
16 that portion of the plate 18 having the opening l9a may be
17 laterally repositioned to allow for different positioning of
18 chain bar mounting bolts. The offset 18b further allo~s for
19 the plates 14 and 18 to be mounted on either s;de of the
mounting bracket 1, and to be mounted with the offset
21 position in or out, thereby effectively laturally
22 repositioning the bracket 1 and the ~ar 12 to suit various
23 saws.
24 While the first and second mounting plates 14 and 18
may be manufactured as a single piece to suit a particular
26 make of chain saw or range of chain saws, the above
27 described connection between the plates 14 and 18 is
28 preferred since it allows the mounting bracket 1 to be
29 secured to the widest range of different types of chain
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1 saws. In some instances it may be necessary to position
2 packing washers between the body of the chain saw and the
3 plate 18 to facilitate rigid connection of the plate by
4 means of the chain bar bolts. Similarly, the structure of
the mounting bracket l may be modified to enable its direct
6 attachment to the chain bar mounting bolt(s) or to a
7 specifically provided mounting point on the body of the
8 chain saw. Of course, different components may be orovided
9 to enable the device to be connected to chain saws having
widely varying types of chain bar mounting bolts and in this
ll regard the above described combination of plates 14 and l~
12 may be found to be most convenient.
13 The protecting bar 12 is in the present embodiment made
14 from extruded PVC or the like and has a generally U-shaped
cross-section with downwardly depending legs l9 and 20
16 formed with ribs 21 positioned to engage groove(s) 21a
17 formed in the sides of the support bar 11. The bar 12 is
18 also formed with opposed grooves 22 within which edges of d
l9 protective steel or other strip 23 may be recelved to reduce
damage to the bar in the event that chain contact occurs.
21 The strip 23 is held in position by bending its ends in the
22 manner shown in Fig, 1 over the top of the bar 12.
23 The bar 12 also supports a shaped end fitting 24 of
24 moulded plastics material which extends from the end of the
bar and has a generally curved nose portion which promotes
26 outward deflection of the bar on engagement with an object
27 to be cut by the chain saw. It will be noted from Fig l of
28 the drawings that the end of the bar 12 and the end fitting
29 24 project beyond the end of the chain saw in use and an
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l overhang of the order of lOOmm has been found to be
2 satisfactory. This overhang allows the bar 12l to be
3 pivotted away from the chain saw by engagement with the
4 object to be cut to enable boring and undercut operations to
S be performed without the need to manually pivot the bar 12.
The different modes of operation of a chain saw fitted
7 with the protective device embodying the invention will be
8 clearly understood from the schematic representations
9 appearing in Fig. 5 of the drawings. It will be appreciated
that a normal top cut ~ill cause the bar 12 to be pivotted
11 against the action of the spring 13 as the bar engages the
12 top of the object being cut. Boring operations may be
13 performed by engaging the end fitting 24 against the object
14 to be bored to pivot the arm 12 sufficiently so that the end
of the chain saw may engage the object. As boring
16 progresses, the bar 12 is progressively pivotted by
17 engagement ~/ith the object in the manner shown in Fig. 5.
18 If desired, the protecting bar 12 may be held out of
l9 its operative position by means of a wire stay 26 engaging
holes 27 and 28 in the side member 3 and the support bar 11.
21 The stay 26 is preferably formed with an intermediate bend
22 such that in the event that kickback occurs during operation
23 of the chain saw in this mode, the stay 26 will collapse so
24 that the protecting bar 12 may reassume its operative
25 position.
26 Referring now to Fig. 5 of the drawings. a modification
27 in which an additional safety bar 12 and support bar 11 are
28 pivotally attached to the bolt 9 at the lower end of the(l~
29 to provide protection for the lower run of the chain. The
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1 bar12 at the lower end is preferably longer than the bar 12
2 at the upper end so that the lower bar may be first
3 displaced to enable normal top cut operations to be
4 performed.
To restrain the mounting bracket 1 against vibration
6 and to further render rigid the attachment of the bracket 1
7 to the chain saw, a short stabilizing link 30 may be
8 attached to the bolt 8 by means of a nut 31, with the
3 opposite end of the link 30 being attached to the body of
1~ the saw using the one of the attachment bolts used to attach
11 the saw dogs present on most chain saws. The stabilizing
12 link 30 is most useful where the chai~ bar is attached by
13 means of a single bolt or nut.
14 Referring now to Fig. 7, it wi11 be noted that the end
fitting 24 has been replaced by a rotatable wheel l,~, This
16 arrangement ensures that the bar 12 will move smoothly over
17 the object to be cut on initial contact
18 It will be appreciated from the above that the device
19 embodying the invention provides a simple yet effective
means of protecting the user against injury in the event of
21 kickback occurring or in the event of mishandling of the
22 chain saw. Of course, no device can offer complete
23 protection against a careless operator but the device
24 according to the invention will provide protection against
injuries due to kickback, In addition, the tunnel defined
26 by the U-shaped protecting bar 12 provides a passage for saw
27 dust which is carried by the chain to travel to the end of
28 the chain rather than spraying upwardly from the top of the
2g chain as normally occurs. This provides an additional
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1 safety feature and reduces the extent to which the user is
2 fouled by sawdust. The attachment of the device in a secure
3 manner to the body of the chain sa~.~, most preferably via the
4 chain bar securing bolt(s) provides a particu1arly secure
means of attachment to the chain saw. In the preferred form
6 described above, the use of interchangeable mounting plates
7 enables the device to be fitted to the widest possible range
8 of different makes and models of chain saw thereby enabling
9 wide spread use of the protective device.
The claims form part of the disclosure of this
11 specification.
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