US2835288A - Cutting tools incorporating safety devices - Google Patents

Description

May 20, 1958 R. J. JONES CUTTING TOOLS INCORPORATING SAFETY DEVICES Filed Aug. 50, 1956 v //VVN70/? Robert John Jones ATTORNEY United States Patent'Ofiiice l atented May 20, 1958 2,835,288 CUTTING TOOLS IN CORPORATING SAFETY DEVICES Robert John Jones, Upper Norwood, London, England,

assignor to The Distillers Company Limited, Edinburgh, Scotland, 21 British company Application August 30, 1956, Serial No. 607,065 Claims priority, application Great Britain October 29, 1955 7 Claims. (Cl. 143-459) The present invention relates to safety devices for machine-driven saws and knives and more pertieuarly to a modified form of table for use with band saws, circular saws, band knives and reciprocating saws hereinafter refer-red to as cutting tools.

Y The use of safety devices in one term or another in cennectienwitn numerous dilferent types of cutting tools is well known. Saw blades, for example, are normally uarded ever unused sections of their length or periphery in order to reduce chances of accidental contact of the operators hands with the saw blade. A considerable ortion of the cutting blade, however, is usually left unguarded, so constituting a danger to the operator whose hands may approach the blade while pushing the workpiece forward towards the cutting edge. Even if the workpiece is moved forward mechanically, it is'difl'lcultto ensure that the operator cannot reach the blade with his hands.

It is an object of the present invention to provide a cutting tool incorporating an improved safety dev'iee.

According to the present invention, a cutting tool can prises a movable table adapted to support the workpiece to be cut and bearing a slot to accommodate the cutting blade of the tool, a retractable guard partly surrounding thecutting blade when the table is in its home position, a locking device preventing the table being moved towards the blade and having a releasing mechanism, means for activating the releasing mechanism which can only be operated by both hands of the operator whereby the table can be moved to bring the workpiece against the cutting blade, an inner portion of the surface ofthe table being movable only in a linear manner between the operator and the plane of the cutting blade and being coplanar with and accommodated within an outer portion of the surface of the table so that the outer portion of the surface can be turned with respect to the inner portion of the surface in the plane of the table surface.

The locking device and releasing mechanism are preferably in the form of a pawl and ratchet device which enables the table to be pulled towards the operator freely but only pushed towards the blade when the pawl and ratchet are disengaged by means such as a hand operated lever or a spring-loaded twist grip. In order that the table may be released only by the use of both the operators hands, such a ratchet mechanism may be duplicated, there being one on either side of the table, Alternatively, two hand operated levers or hand operated spring-loaded twist grips may be adapted to retract the same pawl, one, for instance, operating as a safety catch while the other engages the pawl to move it away from the ratchet. Inustead of a ratchet mechanism, a braking mechanism may be substituted, the hand-operated levers being used to retract one or more spring-loaded friction pads. If desired, however, the table may be released by means of, an electrical device or of a eompressedair devlee operated by the use of two press-action switches.

The releasing mechanism used is such that the connection between the means fpr actuating t he releasing mechani sm and the locking device is suificiently flexible to enable the accommodating portion of the table to be used. The guards may,

table is to be moved manually,

moved both in a linear and in a rotary manner when the table is being pushed towards the cutting blade.

As an additional safety measure, the table is preferably fitted with means to return it to its original home" position after it has been pushed forward to conduct a cutting operation. If the table is fitted with an unidirectional locking device such as a ratchet mechanism described above, this may conveniently take the form of a counterweight which is raised when the table is pushed forwards and will serve to return the table to its home position. It is an essential feature of the invention that the cutting tool comprises a guard partly surrounding the cutting blade which is removed from the blade as the table supporting the workpiece to be cut is pushed towards the blade. Conversely, as the table is returned to its home position the guard also returns to its position around the blade. While in a preferred embodiment: of the invention the guards are rigidly attached to the table so that the guard is retracted and the blade exposed only when the table is moved forward, other types of guard may be for instance, be pivotally attached to some fixed point above the table, the latter serving to lock them in position while the action of moving the table forwards releases the guards, which may then hinge backwards under the action of the workpiece, as the blade moves through the latter; in. this case the table may be fitted with a device such as a stud, whereby the guards are kept in position over the blade when the machine is not in use. Alternatively, the guards may be arranged to be retracted vertically when the table is moved towards the blade.

Theouter and inner portions of the table may conveniently be arranged to form a complete, level table the inner non-rotatable portion being a circular disc set in a coplanar and contiguous position within the remainder of the table. Preferably the cutting blade when in position in the unretracted guard is arranged to be with in the rear half of the inner portion of the table. The ratios between the diameter of the circular portion of this table and the total length and width of the table, which give a relationship between the rotatable and non-rotatable areas of the table, should preferably be such as to allow a suthciently large rotatable area on to which may be fixed a number of clamps or other holding devices whereby the workpiece can be firmly attached to the rotatable portion of the table. The two sides of the rotatable portion of the table may be connected behind the guard, relative to the operator, by means of a removable plate, or alternatively, the two sides may be so designed as to form a continuous portion of the table permanently connected behind the guard.

The table is suitably arranged to move by being mounted on a system of rollers, slides or wheels running on rails, slides or guides; or on ballor roller-bearings.

Such a system by means of which the outer and rotatable portion of the table can be turned through a circle or through any are of a circle is imposed on to a second system allowing the whole table to be moved forwards and backwards in a linear direction relative to the operator. Suitable means for effecting such a combination of linear and rotary movements can be provided, for example, by having a linear track beneath tl e table on which can run flanged wheels supporting a circular track; along this circular track can run flanged wheels fixed to and supporting the table. movement of the whole table and the speed of rotation of the non-stationary portion of the table, very many different types of curved cut can be made in the workpiece.

The table can be moved forward and turned manually, for example by the use of handles and levers. If the the systems providing a.

By varying the speed of linear.

means for linear motion and turning motion are preferably such as enable the operator to perform both types of movement of the table, successively or simultaneously,

without it being necessary for him to change the position of his hands. It is preferred to have the system of guides and rollers, or their equivalents, by which the two kinds of motion of the table can be made, such that a force applied to the table laterally can be so transmitted by the rollers on the guides allowing the rotary movement of the table that it is effectively applied to these guides and in turn to their rollers which allow the linear movement. The ratio of the distance between the two linear guides and the mean diameter of the circular guides is preferably so arranged that the stability and easy turning of the table is ensured.

In order to counteract the tendency of the inner portion of the table to turn when the outer portion of the table is rotated, the inner portion of the table is preferably arranged so that it can travel along a guiding track, subsidiary to and parallel with the main linear track by means of which the whole table can be moved forward in a linear direction relative to the operator.

As an alternative to manual operation, the table may he moved-mechanically; the linear motion and the turning motion may be imparted by separate means, or the two types of motion may be linked so that a predetermined cut is made into a workpiece. Linked movement to give such a cut in an automatic and reproducible manner would be of practical use in routine or repetitive work. A further locking device, such as a friction pad, may be employed so as to prevent accidental turning movement of the table when a linear cut is made. This device is preferably such that the table of the invention can be used as desired either for making linear cuts and curved cuts into the workpiece or for making linear cuts only.

A further safety device which may be fitted to the table comprises a. projecting button which can be depressed by the weight of a workpiece. The button is connected by suitable means to the locking and releasing mechanism and is so arranged that when there is no workpiece on the table to depress the button, it is impossible to move the.

table.

Additional safety features of known type, such as wire mesh guards around the cutting tool, may be provided if desired.

. In the accompanying drawings, which are for a particular embodiment of the invention, Figure 1 shows a side elevation of part of a band saw incorporating the safety device of the invention and Figures 2 and 3 show a plan view of the same apparatus.

In the figures, the saw table 1 is mounted on flanged wheels 2 which can travel along the circular rails 3. These rails are formed into a platform 4 mounted on flanged wheels 4A which can travel along the linear rails 5. The table bears a slot 6 to accommodate the saw blade 7. A guard 8 is mounted on the table which shields the blade when the table is in the home position as shown in the figures. The guard 8 is rigidly attached to the inner and nonrotatable portion 9 of the table which is set in a coplanar and contiguous position within the outer and rotatable portion 10 of the table. The inner portion of the table is suitably arranged so that it can also travel along the guiding rails 20, any tendency to turn when the outer portion of the table is rotated being thereby prevented. The table is fitted with handles 11, and levers 12 which operate by means of the flexible cables 22, the ratchets 13, of which only one is shown as revealed by the cut away portion of the table.

The workpiece 14 to be cut is mounted on the saw table in the position shown in Figure 1, being attached to the outer portion 10 of the table by the clamps 21 and extending over part of the inner portion 9 of the table. The weight of the workpiece serves to depress the button 15 which co-operates" with the ratchet mechanism, as

4 shown in Figure 3, so that the table cannot be moved unless the workpiece is mounted in position on the table.

When making a cut, table 1 and the workpiece 14 are pushed forward by pulling the levers 12 towards the handls 11, applying forward linear force, and also lateral force as required, to the handles 11 until the desired cut into the workpiece has been completed. The handles are then released, whereupon the counterweight 16, serves to return the saw table 1 and guard 8 to their home positions so that the saw blade 7 is within the guard 8 whether or not the ratchets 13 are in the released position.

In order to change the saw blade 7, the plate 17, which normally closes the slot 18, in the bracket 19 is removed, the plate being rebolted in position when a new blade has been fitted. This arrangement enables blade changing to be carried out without removing the saw table.

I claim:

1. A cutting tool comprising a base, work-supporting table having a slot and horizontally movable on said base between a work-loading and -unloading and a work-cutting position, a cutting element supported by the base and extending through the slot and movable through a plane at'substantially a right angle to the table for cutting action, a retractable guard movable on and with the table and partly surrounding the cutting element when the table is in the loading position, tracks on the base along which the table is movable towards and away from the cutting position, the guard retracting from the cutting element by the movement of the table towards the cutting position, locking means for preventing movement of the table along the tracks toward the cutting position, the locking means being provided with a releasing mechanism operable only by both hands of an operator and means for moving the table into the cutting position when the looking 'means are held released, the table having an inner part of the surface movable only in a linear manner between the operator and the plane of the cutting element and coplanar with and accommodated within an outer portion of the surface of the table so that the outer portion can be turned with respect to the inner portion in the plane of the table surface.

2. A cutting tool in accordance with claim 1, wherein the said guard is rigidly attached to said movable table.

3. A cutting tool in accordance with claim 1, wherein the locking means and releasing mechanism comprise a pawl and ratchet arranged to enable the table to be pulled freely toward the operator but moved toward the cutting element only when the pawl and ratchet are disengaged.

4. A cutting tool in accordance with claim 3, wherein hand operated levers are provided for disengaging the pawl and ratchet.

5. A cutting tool in accordance with claim 4, wherein the hand operated levers are disposed one on each side of the table.

6. A cutting tool in accordance with claim 1, wherein the movable table is provided with means for automatically returning it to its original home position when the operator ceases to operate the table moving means.

7. A cutting tool in accordance with claim 6, wherein the returning means comprises a counterweight which is raised during the movement of the table toward the cutting position.

References Cited in the file of this patent UNITED STATES PATENTS

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