GB2223443A

GB2223443A - Portable wood sawing apparatus

Info

Publication number: GB2223443A
Application number: GB8820303A
Authority: GB
Inventors: Norman Crossett
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-08-26
Filing date: 1988-08-26
Publication date: 1990-04-11
Also published as: GB8820303D0

Abstract

A wood saw has a chassis which is portable and can be positioned at a workstation and powered from the power take- off of a tractor. The saw-blade 4 is movable between a retracted safety position and a forward cutting position. A linkage system requires the operator's foot to depress a pedal 15 so as to simultaneously clamp the wood in a guide channel 13 and release a lock 18 on the forward movement of the saw-blade. The operator must use his foot to clamp the wood and release the blade, his hand to bring the blade mechanism forward, and his other hand to rest on a handle on the chassis to steady himself. With both hands in use, and the blade re-locking after the cut, the system is intrinsically safe in unskilled operation. <IMAGE>

Description

PORTABLE SAFETY WOOD SAW This invention relates to a portable power saw, for logs and heavy timber, with built-in features which render it intrinsically safe for use on the farm by unskilled workers.

Circular saws of all types are inherently dangerous and those portable ones, which are presently in use, are composed of a mass of machine guards and trip switches.

The latter are only effective in electric powered machines and are of little use under normal working circumstances because of the energy already stored in the blade at the time of power cut-off and the mere instant of time which is only required to inflict lacerations on the operator's hands.

From a Health and Safety at Work point of view it is important that the large saw blade be only near the operator when sawing is in progress and that the workpiece be not handled during the ripping operation.

This specification would require that the work piece be clamped, rather than be hand held or guided, and that the saw-blade be pivoted so that it can be advanced, or withdrawn, from the wood. Intrinsic safety would eventually require the two operations to be interlinked and synchronised so that the workpiece is just clamped before the saw blade reaches the surface of the work. A portable saw with these safety features is the subject of the invention herein described. According to the present invention there is provided a portable safety wood saw comprising a frame or chassis, which can be wheeled, a means of introducing rotatory power from the take-off shaft of a tractor and means of advancing, or retracting, the saw blade simultaneously with the clamping, or release, of the workpiece.

A specific embodiment of the invention will now be decribed by way of example with reference to the accompanying drawing in which: FIGURE 1 shows a front side view of the saw on its chassis.

FIGURE 2 shows a rear side view of the saw on its chassis.

FIGURE 3 shows power drive mechanism.

FIGURE 4 shows the safety catch mechanism.

Referring to the drawing the portable safety wood saw comprises a chassis, or frame, 1 which houses a bearing, 2 which is directly connected to an input shaft, 3 which is connected to the power output of the tractor when the saw is in use. Power transmission to the saw blade 4 is by means of triple belts 5 in tension on pulleys 6 and 7 by means of a belt adjuster 8.

When the circular blade 4 is being driven it can rotate in a number of positions from idling, in the retracted mode, to fully forward in the cutting mode; these options being selected by movement of the operator's handle 9 which is connected to the shank 10 which carried top bearing 11 and joins it radially to the main drive bearing 2. At the end of each cutting operation the high speed blade must return smoothly and safely to the retracted position and this is accomplished by the use of a simple damper in the form of a piston shock absorber 12. The log or heavy timber is presented to the saw by means of a guide channel 13 but as already stated in terms of safety it is essential that the workpiece be mechanically clamped in its guide channel before the saw blade reaches the surface of the log or timber.

This is accomplished by means of clamp 14 which is activated and held down on the workpiece by the use of a foot loaded pedal 15 which has two linkages; a rod 16 which applies the foot effort to the clamp 14 and a further rod 17 which activates a safety catch 18 which, when in the down position, ensures that there is no way that the saw blade can be advanced towards the operator unless the pedal 15 is purposely depressed. The return action on these rods is accomplished by means of the spring link system 19.

In use the blade normally resides as shown in Figure 1, with the housing clad in steel safety mesh in a frame 20, but when required for ripping purposes the blade is clamped by depressing the foot pedal 15 and bringing the blade forward to the already clamped workpiece by the forward action of the handle 9. At this point the operator will have his left foot on the pedal 15, his left hand on the handle 9 and it is now found that if a hold or rest handle is screwed to the near top of the frame, or chassis, at about 21 all his risk members, as far as mechanical saving operations are concerned, are designed well away from the blade circumference and the entire operation is "fail safe".

Claims

1. A portable safety wood saw comprising a chassis which can be wheeled and stationed and operated from the power take-off from a tractor and which has means of advancing or retracting the rotating saw blade in its carriage simultaneously with the clamping or releasing of the workpiece.

2. A portable safety wood saw as in Claim 1 wherein the clamping of the workpiece by foot pedal action within a linkage system also simultaneously releases a locking mechanism in the saw-blade carriage.

3. A portable safety wood saw as in Claim 2 wherein the saw-blade in its carriage can be advanced to the workpiece by means of an operator's carriage handle after it has been unlocked by foot action on a workpiece clamp.

4. A portable safety wood saw as in Claim 2 wherein the release of the foot pedal workpiece clamp allows the saw-blade carriage to be returned to the retracted position under the damping action of a piston type shock absorber.

5. A portable safety wood saw as in Claim 3 wherein the chassis is provided with an operator's grasp or rest handle which provides a point for stabilising the body when applying the efforts to both the foot pedal and saw carriage handle.

O. A portable safety wood saw as in any of the above Claims in which the operation of the machine involves the use of the foot and both hands thereby rendering the operation intrinsically safe.