CA1205360A

CA1205360A - Starter control for a chain saw motor

Info

Publication number: CA1205360A
Application number: CA000424572A
Authority: CA
Inventors: Rolf A.G . Johansson
Original assignee: Electrolux AB
Current assignee: Electrolux AB
Priority date: 1983-03-25
Filing date: 1983-03-25
Publication date: 1986-06-03

Abstract

ABSTRACT OF THE DISCLOSURE
At the start-up of a power chain saw, the throttle control is locked in a starting position by means of a throttle retaining member which may cause the saw chain to start to race and thereby cause injuries when the engine starts, if no arrangement is provided to keep the chain in a rest position. A connection is provided between the retaining member and the brake mechanism mounted in the saw whereby the chain is always braked when the throttle control is in the start position.

Description

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The present invention relates to a starting control o~ an i.nternal combustion engine provi.ded with an adjustment means for the start position of the tl~rottle control.
At the start-up of a power chai.n saw, the throttle control is locked in a starting positi.on by means of a retai.ni.ng member which causes the saw chain motor to race when the engine starts. This may involve a ri.sk of accident as the chain saw operator may have diffi.culty in controlling the operati.on of the saw. In order to decrease the ri.sk of accident the manufacturers recommend several procedures at the start, i..e., maintaining the saw between the legs of the operator, or agai.nst the ground. With regard to the fact. that the a~orementioned recommendati.ons are diffi-cuLt to use, or may be forgotten, it is consLdered important to make arrangements which eliminate the ri.sk of injuri.es at the start-up of the saw.
The present inventi.on consti.tutes an arrangement having a connection between a brake mechanism provided on the saw and the throttle retaini.ng member, so that the saw cha;.n i.s always braked when the throttle control, by said member, is adjustecl for start-up. ~s soon as said member is released, ancl the throttle is free, the brake must be disengagecl so that the chai.n can operate. The connection between said member and the brake thus consti.tutes an addi-tional trigger;.n~ device or the usually sprLng-actuated bralce hav;.ng some kind of a tri.gger whi.ch, when actuated, releases the spri.ng acti.on in the brake, which is then engagecl.

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An embodiment of such a starting control con-structed in accordance with the present invention is described hereinafter with reference to the accompanying drawings, in which:
FIG. 1 is a partial sectional and a parti.al eleva-tional view, of a power chain saw where the starting control and the brake are shown in running condition, and FIG. 2 is a partial sectional and a partial eleva-tional view showing the control of the brake in a starting posi.tion.
Referring to FIGS. 1 and 2 9 the power saw 10 as illustrated has a rear handle 11, a carrying handle 12 and a protection stirrup 13. In the rear handle 11 a finger grLp 14 ls shown mounted on a shaft 15, about which it may be rotated to control the throttle (not shown) by means of a rod 16. A portion of the grip i.s constituted of an arm 17 having two steps 18, 1~ which coact with a throttle-retaining member 20, pivoted on a shaft 21 so that an end 22 projecting above the handle can be rotated i.n a backward position. A bowden wire 23 is operatlvely extended from the arm, and in its forward end, is secured to a double armed lever 2~ havi.ng a p:i.vot 25. When the retaining member 22 is rotated backwards the lever will perorm a similar movement. Furthermore, when the retaining member is returned by means of a spring 26S the lever returns to its initial posi.t;.on.
The braking mechanism is shown in the forward end of the saw body and is usually operated by means of the stirrup 13. Thus, when the latter is rotated forwards around a pivot shat 27, for example, by the operator's ~2~`536~) hand, a braking force is exerted by a spring 28 which is extended between a fixed point (not shown) and a double armed lever 29. A brake band 30 wound around the centri-fugal clutch drum 31 of the saw is tensioned and thereby brakes the drum. The protection effect thereof will be to stop the rotation of the saw chain in the ev~nt of a kick-back, if the operator's hand hits the stirrup 13.
As stated hereinbefore, a rotating saw chain, aEter the start o~ the engine, involves a risk of accident.
The additional triggering device as mentioned is shown in FIGS. 1 and 2 and constitutes a Bowden wire 23, the lever 24, and a sear 32 on the stirrup 13 cooperating with the lever. ~s seen in FIG. 1 the lower end of the lever, in running order is provided with an angle piece 33 and is introduced in a slot 34 of the sear. The end thereof is then in a locking position against the double armed lever 29 so that the brake is retained in an off-position. As stated before, the lever 24 is rotated on i.ts pivot 25 when a pulLing occurs in the wire by rotation of the member 20 and the rotation makes the angle piece 23 slide up on the sloping edge 35 of the slot and thus forces the sear 32 to rotate upwards around a pivot constituted of the shaft 27 of the stirrup. The locking contact between the double armed lever 29 and the sear then ceases and a position according to FIG. 2 comes about, that i9, the spring 28 rotates the double armed lever and tensions the brake band 30 around the drum 31. In this position the saw chain is locked, simultaneously as the finger grip 14 is positioned for start according to FIG. 2. When the engine is started the operator presses the ~inger grip st;ll a bit inwards ~Z~)5360 and the contact between the lower end of the member 20 and the arm 17 ceases, the spr;ng 26 returns the member 20 and the lever 24 to the positions shown in FIG. 1. The brake is then disengaged by a short rotation backwards of the back into the position shown in FIG. 1.
The above-described embodiment is applied to a brake mechanism known per se, but the arrangement can be modified in order to be adaptable with other mechanisms.
The illustrated member 20 is a preferred embodiment of the invention in order to facilitate the description, but :it shall not be considered a standard for the invention, which can be modified with respect to other embodiments of a retaining member.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A starting control for a power chain saw which is adjustable to an active or non-active position so that in the active position it will act on a carburetor of an internal combustion engine for said chain saw while in a starting position, which chain saw is provided with a brake mechanism for braking a chain driving part of a centrifugal clutch between the engine shaft and the chain, characterized in that a connecting member to said brake mechanism is disposed in said starting control to engage the brake mechanism to brake a part of the clutch when the starting control is in the active position.

2. A starting control according to claim 1, characterized in that the control and the connecting member are reset from said active into said non-active position by an elastic member.

3. A starting control according to claim 1, characterized in that the connecting member is extended from the rear handle of the power saw to the brake mechanism at said part of the clutch, and is constituted of a traction member.

4. A starting control according to claim 3, characterized in that one end of the traction member is fastened to a retaining member of the control in the form of a lever and the other end is fixed to another lever which is meshed with a sear in the brake mechanism.