GB2162463A

GB2162463A - Power tool

Info

Publication number: GB2162463A
Application number: GB08519368A
Authority: GB
Inventors: John Ernest Thomas
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-08-04
Filing date: 1985-08-01
Publication date: 1986-02-05
Also published as: GB2162463B; GB8519368D0; GB8419954D0

Abstract

A chain saw comprises a cutting chain (36) which is entrained around a planar, elongate guide (16). The guide (16) passes through a sole plate (14) which is longer, in the direction parallel to the plane of the guide, than the length of the guide. A handle (10) encloses an electric motor and is arranged substantially parallel to, and spaced apart from, the sole plate (14). The handle is longer than the guide (16), thus providing a chain saw which is easily controllable with one hand. The saw may be used to make plunge cuts and to cut shapes in materials. <IMAGE>

Description

SPECIFICATION Power tool The invention relates to a power tool, and in particular, but not exclusively, to a chain saw.

There are basically three types of power saw, a chain saw in which a looped chain is driven around a guide bar, a circular saw in which a serrated cutting disc is rotated rapidly, and a "jig-saw" in which a cutting blade is reciprocated rapidly. Conventional chain saws are used mainly for cutting timber and are employed when great accuracy is not required, since they are relatively difficult to control and not very manoeuvrable. A circular saw is used for more accurate work and can be used to make plunge cuts, but because of the nature of the cutting disc it can not be used to make intricate cuts, and its use is often restricted to cutting straight. Moreover, if a plunge cut is made with a circular saw, the diameter of the cutting disc necessary is more than twice the depth of the cut, and so a circular saw is often bulky.A "jig-saw" can be used to make intricate cuts, but can not be used on very thick or strong material and can not be used to make plunge cuts.

In accordance with a first aspect of the invention, there is provided a power tool comprising a cutting chain, an elongate, laminar guide around which the said chain is entrained, a sole plate having a substantially flat planar portion, through which plate the said guide and chain project, and a motor whose axis of rotation is substantially parallel to the plane of the guide and to the plane of the flat planar portion of the sole plate, the axis of rotation of the motor and the plane of the flat planar portion of the sole plate being substantially perpendicular to the longitudinal axis of the guide.

Preferably the motor is at least partially housed within an elongate handle, and preferably the axis of rotation of the motor is substantially parallel to the longitudinal axis of the handle.

In accordance with a second aspect of the present invention, there is provided a power tool comprising a cutting chain, an elongate, laminar guide around which the said chain is entrained, a sole plate through whch the said guide and chain project, and an elongate handle whose longitudinal axis is arranged substantially parallel to the plane of the said guide and whose length is greater than or equal to the length of the said guide.

Preferably, the handle contains a prime mover, e.g. an electric motor.

In accordance with a third aspect of the present invention, there is provided a power tool comprising a cutting chain movable by driving means, an elongate, laminar guide around which the said chain is entrained, a sole plate having a substantially flat planar portion, which portion is arranged substantially perpendicularly to the longitudinal axis of the guide, through which plate the said guide and chain project, the length of the substantially flat, planar portion of the sole plate being greater than or equal to the length of the portion of the guide which projects through the sole plate on the opposite side of the sole plate to the driving means.

Preferably, the ratio of the length of the sole plate in the said direction and the length of the guide which projects through the sole plate is from one to four.

The above power tools can provide a chain saw which can be used to make plunge cuts, may be used to cut limited curves, can cut relatively thick materials and can be operated with one hand.

By way of example only, specific embodiments of the present invention will now be described, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a first embodiment of power saw according to the invention; Figure 2 is a side elevation of the power saw of Fig. 1; Figure 3 is a section along line Ill-Ill in Fig.

1; Figure 4 is a section along line IV-IV in Fig.

1; and Figure 5 is a side view, in part section, of a second embodiment of power saw according to the invention.

A power saw comprises an electric motor 10, a gear housing 12, a sole plate 1 4 and a chain guide plate 1 6 passing through a gap 1 8 in the sole plate 14. The motor 10 has a generally cylindrical casing 20 which is also used as a handle, and a drive shaft 22 (Fig.

3) from the motor, which shaft projects into the gear housing 12, the drive shaft being provided with a small bevel gear 24. An air inlet 26 at the end of the motor housing 20 allows air to be drawin in by a fan (not illustrated) inside the housing, which fan rotates with the motor, and expelled through a cowling 28 in the opposite end of the housing, thus providing cooling for the motor.

Referring to Figs. 3 and 4, a large driven bevel gear 30 is mounted in bearing 32 in the gear housing 1 2 with its axis of rotation perpendicular to the axis of the drive shaft 22. Attached to, and rotatable with, the bevel gear 30 is a drive sprocket 34 which is used to drive a cutting chain 36. The amount of slack in the chain is variable by altering the position of the guide plate 18, using two Allen bolts 37. An oil reservoir 38 is provided on one side of the gear housing 1 2. This supplies oil to the chain via a bore 40 leading from the base of the reservoir to lubricate and cool the chain.The flow of oil may be turned on or off by means of a tap 42 which is rotatable between two positions, controllable by a detent mechanism 44, and which, in the illustrated position, aligns the bore 40 in the plug of the tap with the outlet of the reservoir, allowing oil to flow by gravity.

The guide plate is an elongate plate of metal about 1 2 cm long and 3 cm wide, with a rounded edge and which is provided with a groove 46 in its periphery The groove is used to accommodate extensions (not illustrated) on the teeth of the chain 36 and thus to guide the chain smoothly around the guide plate. A sprocket 48 is rotatably mounted at the end of the guide bar remote from the gear housing, to provide a smoother guiding of the chain and to reduce friction losses.

The sole plate 14 comprises a flat, substantially rectangular piece of metal 50 about 1 5 cm long and 10 cm wide, with the end 52 remote from the motor housing 20 inclined at an angle of 30 degrees to the plane of the rectangular piece 50. The plane of the rectangular piece is parallel to the longitudinal axis of the motor housing 20 and is spaced apart therefrom by about one inch (2.54 cm). The gap 18 is generally V-shaped, and allows an operator to see the material about to be cut by the chain. As best seen in Fig. 2, the length of the rectangular portion 50 of the sole plate, i.e. the portion which, in use, contacts a material to be cut, is longer than the guide plate.

Electrical power is supplied to the motor via a cable 54. In use, an operator grips the motor casing 20, which also functions as a handle, his fingers being positioned in the gap between the casing and the sole plate. The rectangular portion of the sole plate is placed on the material to be cut, and the chain 36 is aligned correctly. A thumb-operated switch 56 is depressed, turning on the motor. Operation of the motor causes the sprocket 34 to rotate and the cutting chain 36 is thus driven in an anti-clockwise manner as seen in Figs. 1 and 2.

A large proportion of the weight of the saw, i.e. the motor, is contained in the casing 20, which is also the handle. Since an operator will be holding on to the handle during use, the weight therein may be easily controlled, and one-handed operation of the device is possible, leaving the other hand free to steady a workpiece.

The relatively small width of the guide allows the cutting of limited curves, and the relatively low torque produced by the chain at the end of the guide allows the cutting chain to be held easily against a workpiece to cut directly into a workpiece in a direction of the elongate axis of the guide, to make a plunge cut.

A second embodiment of the invention is illustrated in Fig. 5. This is generally similar to the first embodiment, having a motor casing 20', a guide bar 16' and a chain 36', the chain being driven by a sprocket 34'. A drive shaft 22' extends from the casing 20' into a gear box 12' and the drive is transferred to the sprocket by means of bevel gears 24', 30'. The major difference is that the sole plate 50' extends beneath substantially the whole length of the motor casing 20', thus providing an extremely stable cutting position. Also, it is possible to pivot the motor about the axis of the bevel gear 30' to provide a handle at various angles. The operation of the saw is identical to the first embodiment.

Claims

-1. A power tool comprising a cutting chain, an elongate, laminar guide around which the said chain is entrained, a sole plate having a substantially flat planar portion, through which plate the said guide and chain project, and a motor whose axis of rotation is substantially parallel to the plane of the guide and to the plane of the flat pianar portion of the sole plate, the axis of rotation of the motor and the plane of the flat planar portion of the sole plate being substantially perpendicular to the longitudinal axis of the guide.
2. A power tool as claimed in claim 1, wherein the motor is at least partially housed within an elongate handle.
3. A power tool as claimed in claim 2, wherein the axis of rotation of the motor is substantially parallel to the longitudinal axis of the handle.
4. A power tool as claimed in claim 2 or claim 3, wherein the length of the handle is greater than or equal to the length of the guide.
5. A power tool as claimed in any of claims 2 to 4, wherein the handle is spaced apart from the flat, planar portion of the sole plate.
6. A power tool comprising a cutting chain, an elongate, laminar guide around which the said chain is entrained, a sole plate through which the said guide and chain project, and an elongate handle whose longitudinal axis is arranged substantially parallel to the plane of the said guide and whose length is greater than or equal to the length of the said guide.
7. A power tool as claimed in claim 6, wherein the handle contains a prime mover.
8. A power tool as claimed in claim 7, wherein the prime mover comprises an electric motor.
9. A power tool as claimed in any of claims 6 to 8, wherein the sole plate has a substantially flat planar portion, the longitudinal axis of the handle being substantially parallel to, and spaced apart from, the said portion.
10. A power tool comprising a cutting chain movable by driving means, an elongate, laminar guide around which the said chain is entrained, a sole plate having a substantially flat planar portion, which portion is arranged substantially perpendicularly to the longitudinal axis of the guide, through which plate the said guide and chain project, the length of the substantially flat, planar portion of the sole plate being greater than or equal to the length of the portion of the guide which projects through the sole plate on the opposite side of the sole plate to the driving means.
11. A power tool as claimed in claim 10, wherein the ratio of the length of the sole plate in the said direction and the length of the portion of the guide which projects through the sole plate is from one to four.
1 2. A power tool as claimed in claim 10 or claim 11, wherein the length of the guide is less than 1 5 cm.
1 3. A power tool as claimed in any of claims 10 to 12, wherein the width of the guide is less than 5 cm.
14. A power tool constructed and arranged substantially as herein described, with reference to, and as illustrated in, Figs. 1 to 4 or Fig. 5 of the accompanying drawings.