GB2403686A

GB2403686A - Tensioning device for chain saws

Info

Publication number: GB2403686A
Application number: GB0413942A
Authority: GB
Inventors: Andrea Possamai
Original assignee: GGP Italy SpA
Current assignee: GGP Italy SpA
Priority date: 2003-07-08
Filing date: 2004-06-22
Publication date: 2005-01-12
Also published as: FR2857286B3; GB0413942D0; ITVE20030013U1; DE202004010205U1; ES1057944Y; FR2857286A3; ES1057944U

Abstract

A tensioning device for electric chain saws comprising a casing 2 provided with a closure cover 3 and housing a bar 16 along which the chain 12 is guided, said bar 16 being provided with a slotted aperture engaged by a threaded pin (16, fig 1) rigid at one end with the casing and engagable at the other end by a tightening knob (20, fig 1) said bar 16 being provided with a lug (24, fig 1) engagable in a spiroidal groove (26, fig 3) provided in a ring (28,fig 3) interposed between the tightening knob (20, fig 1) and the bar 16, said ring (28, fig 3) and said cover being provided with mutually engagable elastic means 32, (34, fig 3).

Description

The present invention relates to a tensioning device for electric chain

saws or power chain saws.

Electric chain saws are known comprising a casing fitted with a handgrip and housing an electric motor, the shaft of which rigidly carries a sprocket engaging a chain provided with cutters and guided in its rotation by a tensioning bar.

These electric chain saws present however the drawback that with ongoing use, the chain tends to lose its degree of tensioning with consequent slackening. This slackening on the one hand constitutes a danger for the operator as the chain can escape from its seat provided in the bar, and on the other hand generates vibration annoying to the operator and causing difficulties during the work.

An object of the invention is to provide a tensioning device for electric chain saws which enables the degree of tensioning to be adjusted easily and comfortably.

This and further objects which will be apparent from the ensuing description are attained according to the invention by a tensioning device for electric chain saws comprising a casing provided with a closure cover and housing a bar along which the chain is guided, said bar being provided with a slotted aperture engaged by a threaded pin rigid at one end with the casing and engagable at the other end by a tightening knob, said bar being provided with a lug engagable in a spiroidal groove provided in a ring interposed between the tightening knob and the bar, said ring and said cover being provided with mutually engagable elastic means. e À À

À e À À e. À cc À e. À

The present invention is further clarified hereinafter with reference to the accompanying drawings, in which: Figure 1 is a longitudinal section through an electric chain saw according to the invention, Figure 2 shows it in side view, and Figure 3 shows the ring in two frontal views.

As can be seen from the figures, the electric chain saw according to the invention comprises substantially a casing 2 with cover 4 housing a motor (not shown in the drawings), the shaft 6 of which rigidly carries a sprocket 8 which engages the links 10 of a chain 12 provided with cutters 14.

The chain 12is guided and returned along a guide bar 15 having one end housed in the casing 2.

In that end of the bar housed in the casing there is inserted a threaded pin 16 engagable by a nut 18 rigid with a closure knob 20.

An L-shaped appendix 22 is press-fitted to the bar 15 and has its lug 24 inserted into a spiroidal groove 26 provided in a ring 28 interposed between the knob 20 and the casing 2 housing the bar.

The tensioning device of the invention operates in the following manner.

After slackening the closure knob 20 the operator rotates the ring 28 so that the engagement between the lug 24 and the spiroidal groove 26 causes the bar 16 to move axially, so tensioning the chain. This configuration is maintained stable by the elastic engagement between a ! era ::e: . he::: À À ... ....

Àe:. À: Àe: finger 32 present on the inner surface of the cover 4 of the casing 2 and a toothed portion 34 provided on the ring 28.

When the required degree of tension has been reached, the knob 20 is again rotated in the direction which clamps the bar 16 between the nut 18 and the casing of the chain saw. To prevent accidental withdrawal of the ring 28 from the knob 20, the lateral surface of this latter presents an annular portion 36 which engages teeth 38 provided on the inner surface of the ring.

In the same manner, to prevent withdrawal of the ring from the casing the lateral surface of the ring is provided with an annular portion 40 which engages the casing.

From the aforegoing it is apparent that the tensioning device of the invention enables the degree of tensioning to be adjusted in a simple and comfortable manner, with only a small number of components in play.

Claims

c # c c c À - 4 CLAIMS

1. A tensioning device for electric chain saws comprising a casing provided with a closure cover and housing a bar along which the chain is guided, said bar being provided with a slotted aperture engaged by a threaded pin rigid at one end with the casing and engageable at the other end by a tightening knob, said bar being provided with a lug engageable in a spiroidal groove provided in a ring interposed between the tightening knob and the bar, said ring and said cover being provided with mutually engageable elastic means.

2. A tensioning device as claimed in claim 1, characterized in that the ring is provided with a toothed portion with which an elastic appendix provided on the cover engages.

3. A device as claimed in claim 1, characterized in that the lateral surface of the knob presents an annular portion which engages teeth provided on the inner surface of the ring.

4. A tensioning device for electric chain saws substantially as described herein and with reference to the accompanying Figures 1, 2 and 3.