GB2240877A - Hand tool with lock-on/lock-off mechanism - Google Patents

Abstract

A lock-on/lock-off mechanism for a hand tool comprises a trigger 17 which is movable between a motor-on position and a motor-off position and a latching mechanism 19 which has to be moved to a first position from a lock-off position to allow the trigger 17 to be moved to the motor-on position. If it is desired to latch the trigger 17 in the motor-on position, the latching mechanism 19 must be moved in a different direction from the direction it must be moved to release the trigger from its motor-off position. When the trigger 17 is squeezed with the latching mechanism 19 in its lock-on position, spring means causes the latching mechanism 19 to move to its lock-off position and allows the trigger 17 to move back to its motor-off position. The latching mechanism 19 may include a slider 47 moveable in opposite directions or a slidable actuator moveable in opposite directions by two lateral buttons and a front button. A fixed catch 57 is provided on a casing 21 of the tool with which the trigger 17 cooperates in the lock-on and lock-off positions, under the control of the moveable slider or actuator. <IMAGE>

Description

HAND TOOL WITH LOCK-ON/LOCK-OFF MECHANISM This invention relates to a lock-on/lock-off mechanism for a hand tool and to a hand tool provided with such a mechanism.

Hand operated power tools, whether they be air powered, mains electric operated or battery operated or of the rechargeable battery variety (i.e. a cordless tool), are normally operated by means of a trigger and with such tools there is now a demand to be able to lock the operating trigger in a motor-on mode so as to enable the user to concentrate on the task being performed with the hand tool and to enable him to obtain maximum control of the tool with his hands. Furthermore, for safety reasons, there is also a requirement that the hand tool should not be inadvertently switched to a motor-on mode, e.g. by accidentally moving the trigger to a motor-on position when the tool is first picked up. This is particularly important with cordless hand tools.There is therefore a demand for the tool to have a mechanism for locking the trigger in a motor-off position so that the trigger can only be moved to its motor-on position when required.

Various proposals for such lock-on/lock-off mechanisms have been put forward in the past; for example, in DE-A2315841.0, a lock-on/lock-off mechanism is disclosed wherein a trigger is controlled by a latch arrangement which, in a first position, prevents trigger operation, (lock-off). The latch can then be slid forwards to allow the trigger to be operated, and once in operation, the trigger can be lockedon by sliding the latch further forwards. This mechanism can be accidentally locked-on, because the latch has to be moved in the same direction as it moves when it is displaced from its lock-off mode.

In US-A-4280026, two lock-on/lock-off mechamisms are disclosed. In the first, there is a latch which has a first lock-off position in which a trigger slidable at right angles to the direction of movement of the latch cannot be moved. When the latch is depressed to a second position, the trigger can be slid forward to a tool operating position, and when it is desired to lock the trigger in this position, the latch is depressed further, thus preventing the trigger sliding back to an off position.This mechanism has the same disadvantages as that of DE-A-2315841.0. In the second mechanism disclosed in US-A-4280026, a pivotable latch is provided which controls a sliding trigger, the latch being pivoted anti-clockwise from a first lock off position to allow sliding of the trigger to a motor-on mode, and being pivoted further anti-clockwise to a lock-on position to lock the trigger in a motor on mode. Again, this mechanism suffers from the disadvantage mentioned above.

According to the present invention, we provide a hand tool having a lock-on/lock-off mechanism for controlling the operation of the hand tool, said mechanism comprising an on/off trigger for switching a motor of the tool on and off, said trigger being mounted in a housing, for movement between a motor-off position and a motor-on position, and a latching mechanism also mounted in the housing for movement in one direction from a lock off position in which said trigger cannot be moved from its motor off position to a first position in which said trigger can be moved to its motor-on position, said latching mechanism then being movable in a different direction to a lock-on position in which said trigger is maintained in its motor-on position, and wherein the trigger and latching mechanism are so constructed that when said trigger is squeezed when the latching mechanism is in its lock-on position, spring means will cause the latching mechanism to move to its lock-off position and allow the trigger automatically to move back to its motor-off position.

Preferably, the trigger is mounted in the housing for sliding movement and the latching mechanism includes a slider which is also mounted in the housing for sliding movement, but in a plane at right angles to the plane of movement of the trigger.

Preferably, the latching mechanism is biassed to its lock-off position and pressure must be maintained thereon to maintain it in its first position and the trigger is biassed by a spring to its motor-off position and pressure must be maintained thereon to hold it in its motor-on position except when said latching mechanism is in its lock-on position.

Preferably, the latching mechanism includes a fixed catch within the housing, which co-operates with means on the trigger to hold the trigger in both its motor-on and its motor-off positions.

When it is desired to move the trigger from its motoron position to turn off power to the motor, pressure is applied to the trigger to cause it to move upwardly which will cause the means thereon to move out of co-operation with the fixed catch, release of pressure on the trigger will then allow the trigger to move under the bias of its spring to its motor-off position, thus causing a switch to disconnect the power from the motor and allowing biassing means associated with the latching mechanism to move the latter back to its lock-off position in which the trigger is locked in its motor off position.

Preferably, the trigger has a pair of resiliently deformable laterally spaced pillars upstanding therefrom interconnected by a crossbar and each end of the crossbar is provided with a lateral extension which is of inverted generally equi-lateral triangular construction but with an upstanding rib at a rear end of its upper face and said extensions providing the means on the trigger which cooperate with the fixed catch, said slider having a rearwardly extending tail which may be bifurcated and which terminates in a depending flange having a downwardly opening centrally located slot therein in which the crossbar is located, whereupon fore and aft sliding movement of the slider will cause said pillars to be deflected from their upright position, the fixed catch secured to the housing of the hand tool having spaced locking jaws with which the lateral extensions are arranged to co-operate.

Preferably, the locking jaws each have a downwardly opening recess in which the upwardly extending rib on the top face of the triangular extensions can engage when the latching mechanism is in its lock-off position, and an upwardly extending recess located rearwardly of the downwardly facing recess in which the lower apex of the triangular extensions engage when the latching mechanism is in its lock-on position.

Preferably, the slider is slidable horizontally forwardly from a lock-off position to a first position which moves the crossbar and its lateral projections with it from beneath the locking jaws thus enabling the trigger to be depressed and moved from its motor-off position to a motoron position by raising the trigger against the bias of its spring, whereupon the lateral extensions will move upwardly within the slot from a lower end thereof to an upper end thereof, such upward movement also causing a leading end of a forwardly projecting arm on the trigger to move a switch actuator for a motor for the tool from a motor-off to a motor-on position.

With the trigger in its motor-on position and the latching mechanism is maintained in its first position, it is possible to turn the tool on and off by depressing and releasing the trigger as desired, since release of the trigger will result in the trigger moving back to its motoroff position by virtue of the spring bias acting on the trigger and a similar spring bias acting on the switch actuator. However, if the latching mechanism, i.e. the slider, is released from its first position, it will automatically return to its lock-off position, due to the resiliency of the upstanding pillars.

However, if it is desired to lock the trigger in a motor-on position, the latching mechanism must be moved from its first position to its lock-on position and this means that the slider must be slid rearwardly while the trigger is fully depressed and this will result in the crossbar and its lateral extensions being moved rearwardly by virtue of the engagement of the crossbar in the slot, such a rearward movement being permitted by rearward flexing of the pillars supporting the crossbar, the arrangement being such that when the latching mechanism is in its lock-on position, with the slider slid rearwardly, the lower apex of each lateral crossbar extension will be located above the upwardly facing recess in the locking lugs of the fixed catch on the housing.If the pressure on the trigger is then subsequently released, said apexes will move into locking engagement with said upwardly extending recesses and latch the trigger in its motor-on position. The switch actuator is not affected because of the resiliency of the forwardly projecting arm on the trigger.When it is desired to release the trigger from its latched motor-on position, it is merely necessary to squeeze the trigger so as to move it upwardly slightly, thereby moving the apexes of the lateral extensions out of the upwardly facing recesses in the locking jaws, whereupon the natural resiliency of the pillars will cause the crossbar and lateral extensions to move forwardly in front of the locking jaws, whereupon the spring bias acting on the trigger can move the latter back to a motor-off condition, the lateral extensions moving past the locking jaws with a camming action as the trigger moves downwardly under its spring bias and then springing back so that the upstanding ribs on the upper face of the lateral projections will be located beneath the downwardly facing recesses on the locking jaws, thus locking the trigger in a motor-off condition.

In a modified version of the invention, the slider is replaced by a slidable actuator which is controlled by left and right hand latch actuating buttons and a front latch actuating button and a hinge plate, the slidable actuator which may be bifurcated being provided with an upstanding flange with an upwardly opening slot therein which replaces the depending flange on the slider, and in which slot the cross bar joins the upper ends of pillars on the trigger is located.

Preferably, the slidable actuator has a central slot therein, with which one end of the hinge plate engages, the other end being pivotally connected to the housing of the tool, and lateral cam surfaces each engageable by an inner end face of respective ones of the left and right hand latch actuating buttons, the front button having a pair of projecting plates on its inner face with slots at their inner ends which engage with a transverse pin located in the hinge plate to transfer axial movement of the front button into pivotal movement of the hinge plate to move the plate and hence the slidable actuator to a lock-on position when the front button is depressed after the trigger has moved the switch actuator into the motor-on position.

The transverse pin is positioned so as to reduce the distance moved by the front button and to increase the force required to move the latching mechanism to a lock-on mode.

Two embodiments of lock-on/lock-off mechanism according to the present invention are now described by way of example with reference to the accompanying drawings, in which: - FIGURE 1 is a longitudinal section through a tool incorporating the lock-on/lock-off mechanism of the invention and showing the trigger locked in its motor-off position; FIGURE 2 is a scrap view of the tool of Figure 1 and showing the mechanism in an alternative position allowing the trigger to be moved to a motor-on position; FIGURE 3 is a view similar to Figure 2 but showing the trigger in its motor-on position; FIGURE 4 is a view similar to Figure 3 but showing the latching mechanism in an alternative lock-on position with the motor on; FIGURE 5 is a side view of the trigger shown in Figures 1-4; FIGURE 6 is an end view of the trigger shown in Figure 5;; FIGURE 7 is a plan view of the trigger; FIGURE 8 is a perspective view of the trigger; FIGURE 9 is a side view of a slider forming part of the latching mechanism for the trigger; FIGURE 10 is an end view of the slider; FIGURE 11 is a plan view of the slider; FIGURE 12 is an underneath view of the slider; FIGURE 13 is a longitudinal section through part of an alternative embodiment of tool, showing a modified embodiment of lock-on/lock-off mechanism with a trigger in a latched in position; FIGURE 13a is a schematic plan view of part of the latching mechanism; FIGURE 14 is a view similar to Figure 13 but showing the latching mechanism in a first position showing the trigger locked in its motor-off position;; FIGURE 14a is a view similar to Figure 13a showing the position occupied by part of the latching mechanism in Figure 14, which would allow the trigger to be moved to a motor-on position; FIGURE 15 is a view similar to Figure 14 but showing the trigger in a motor-on position; FIGURE 16 is a view similar to Figure 15 but showing the trigger in a motor-on position and showing the latching mechanism in full lines in its lock-on position and in broken lines in a release position; FIGURE 16a is a schematic plan view showing the position occupied by part of the latching mechanism when the tool is in a lock-on mode as shown in Figure 16.

Referring to the first embodiment of the invention shown in Figures 1-12, the tool shown in Figures 1-4 is of largely standard construction with a handle 1 at its rear end (which could define a hollow casing for batteries or a power pack), a motor 3 located in a central region thereof beneath which is a drive mechanism indicated generally at 5 which will convert rotary movement of an output shaft of the motor 3 into reciprocating movement of a drive shaft 7, the front end of the drive shaft being supported in a pivot bearing 9 and terminating in a blade supporting housing 11 so that when a blade is housed therein it will project from a front end 13 of the tool and be caused to reciprocate at high speed when the motor is switched on. A switch actuator for the motor is indicated generally at 15.

The lock-on/lock-off mechanism of the invention is located at the front end of the handle 1 immediately adjacent the switch actuator 15 and the motor 3 and comprises a trigger shown generally at 17 and a latching mechanism shown generally at 19. The trigger is mounted for sliding movement within a casing 21 of the tool in a plane extending generally normal to the longitudinal axis of the handle 1 and hereinafter called the vertical plane, whereas the latching mechanism 19 has a slider 20 which is mounted for sliding movement within the casing 21 in a plane normal to said vertical plane and hence parallel to the longitudinal axis of the handle 1. It will thus be appreciated that the slider 20 can be moved forwardly towards the front end 13 or rearwardly towards the handle 1 of the pad saw, whereas the trigger 17 can be moved upwards or downwards in said vertical plane.

The trigger 17 is shown in detail in Figures 5-8 and has a main body portion 23 with a lower curved finger engaging face 25 and two upstanding pillars 27 projecting upwardly from the body portion 23. The upper ends of the pillars 27 are interconnected by a crossbar 29 and on each end of the crossbar, a lateral extension 31 is provided which is of inverted generally equi-angular triangular cross section.

An upstanding rib 33 is provided at the rear end of the upper face of each extension 31. The trigger is formed of a resiliently deformable material, such as a semi-rigid plastics material, which means that the pillars 27 can flex to and fro. The trigger 17 has further upstanding projections 35 which are used to mount it within the casing 21 and a forwardly projecting arm 37 for operating the switch actuator 15. A further spring locating projection 39 upstands from a central region of the trigger and the trigger 17 is biassed to its motor-off position by a spring 41.

The slider 20, which is shown in detail in Figures 912, has a portion 42 which is slidably supported for fore and aft movement in the casing 21 in a slideway 43 and is biassed to a lock-off position shown in Figure 1 by a spring force provided by the resilient nature of the pillars 27, due to the cross bar 29 connecting their upper ends being engaged with the tail end of the slider as described below.

The slider has a main body 45 with an actuating knob 47 on the top thereof, a front end 49 of the actuator being located beneath a part of the housing 21 in which the motor 3 is located. The tail end of the slider 20 is bifurcated, and connected to the main body at 51, the bifurcated parts supporting the portion 42, and terminating in depending flanges 53 having downwardly opening centrally located slots 55 therein, in which the crossbar 29 is located. Hence, sliding movement of the slider 20 in fore and aft directions will cause similar movement of the crossbar 29.

A fixed catch 57 is mounted on the casing 21, the catch providing two spaced locking jaws with which the respective lateral extensions 31 of the crossbar co-operate to maintain the mechanism either in a locked-off or locked on mode. Each jaw is shaped to provide a downwardly facing recess 59 for co-operation with a rib 33 on the respective extension 31 to hold the trigger in a lock-off mode, and an upwardly facing recess 61 with which the lower apices of the extensions 31 engage when the trigger is to be held in a lock-on mode.

It will thus be appreciated that when the mechanism is in its position shown in Figure 1 with the slider 20 in its position of rest and the trigger 17 in its motor-off position, the two downwardly facing recesses 59 of the catch 57 will overlie the ribs 31 and thus prevent the trigger being moved from its motor-off position, i.e. the trigger will be locked or latched in its motor-off position as it will be unable to be actuated, i.e. moved upwardly.

When it is desired to operate the hand tool, the latching mechanism 19 must first be actuated by moving the slider 20 forwardly from its position shown in Figure 1 (the lock-off position) (against the bias provided by the pillars 27) to a first position shown in Figure 2. This will cause the crossbar 29 by virtue of its engagement with the slots 55, to move forwards, against the natural resiliency (spring bias) of the pillars 27, thus moving the extensions 31 in front of the recesses 59.

The trigger 17 can now be depressed, i.e. moved upwardly, from the position shown in Figure 2 to the position shown in Figure 3 since the crossbar 29 can slide up the slots 55, thus causing the arm 37 to move the switch 15 to a motor-on position by virtue of pressure applied to its underside by the arm 37. This upward movement of the trigger 17 will result in the extensions 31 moving to a position in which their lower apices are above an upper face 63 of each locking jaw on the fixed catch 57 and will allow the slider to move back under its spring bias (provided by pillars 27) to its position of rest (see Figure 3). With the mechanism in this position, this allows the operator of the hand tool either to control the operation of the hand tool by manipulation of the trigger 17 or to lock the trigger into a motor-on position as required.

As can be seen from Figure 3, if the operator released pressure on the trigger 17 so as to allow the trigger to move downwardly under the bias of the spring 41, the trigger will move back to the position shown in Figure 1, because the extensions 31 will cam over leading edges 65 of the jaws 57, and then spring back due to the resiliency of pillars 27, to their locked-off position. It will thus be appreciated that if no pressure is maintained on the slider 20, e.g. by the operator's thumb of either hand, the slider 20 will then spring back under the bias of the pillars 27 to its first position shown in Figure 1, and when the trigger 17 is released, it will automatically return to its Figure 1 lock-off position.However, so long as pressure is maintained on the slider 20 to maintain it in its Figure 2 position (and its Figure 3 dotted line position) the trigger 17 can be moved up and down at will, thus turning the tool on and off.

Should the operator wish to lock the tool in a motoron position, he must maintain the trigger fully depressed, i.e. in its Figure 3 position, and move the slider 20 rearwardly by applying pressure to the knob 47 against the bias of the pillars 27 until the slider 20 is in the position which is shown in Figure 4. This results in the extensions 31 being moved to a position in which they overlie the upwardly facing recesses 61 of the locking jaws 29. Provided the slider 26 is maintained in its position shown in Figure 4 by continued rearward pressure on the knob 47, the trigger can be locked in its motor-on position merely by releasing pressure on the underface 25 of the trigger, thus allowing its biassing spring 41 to move the trigger downwardly a short distance, so that the lower apices of the extensions 31 will engage in the recesses 61.

The trigger cannot now move to a motor-off position, as is apparent from Figure 4, and the hand tool is now locked in a motor-on mode.

When the operator wishes to switch off the hand tool and move the trigger 17 to its motor-off position, all he needs to do is to allow the slider 20 to move to its Figure 1 position under the influence of the pillars 27 and to depress the trigger 17, i.e. move it upwardly as far as possible from the position shown in Figure 4 until the lower apices of the extensions 31 are no longer in the recesses 61. Then, the natural resiliency of the pillars 27 will move the extensions 31 and the slider 20 to the dotted line position shown in Figure 4, i.e. the full line position in Figure 3, whereupon, as previously described, the spring 41 will automatically move the latching mechanism and the trigger back to the position shown in Figure 1, i.e. the lock-off position, provided the operator has released the trigger 17. While this is happening, a spring associated with the switch actuator 15 will move the switch actuator downwardly automatically, so as to turn off the motor 3.

It will thus be appreciated that whenever the operator wishes to turn off the motor, the latching mechanism will automatically move to a trigger lock-off position.

Referring now to the modified construction shown in Figures 13-16, parts similar to those of Figures 1-12 have the same reference numerals.

In this embodiment, the latching mechanism has three operating buttons, a left hand button 71, a right hand button 73 and a front button 75, all of which co-operate with a slidable actuator 77, instead of the slider 20. The actuator 77 has, at its rear end (right end as viewed in the figures) and upstanding pair of flanges 79, in which slots 55 are formed, and in which the cross bar 29 engages, as in the previous embodiment. As in the previous embodiment, the trigger 17 has upstanding pillars 27 which support the crossbar 29, but because of the location of the switch for the hand tool, a rearwardly extending arm 38 is provided on the trigger 17, which engages a switch actuator 16.

Midway between its ends, the actuator 77 is stepped at 79, and at its front it is provided with two wings 81, the trailing edges of which provide inclined cam surfaces 83 (see Figure 13a). Each of the buttons 73 and 75 is slidable laterally within an insert which locates in a casing 21 of the tool, and has on its inner end an inclined end face 85 a cam which cooperates with a respective cam surface 83.

Hence, when either of the buttons 73 is depressed, the actuator will be moved from its Figure 13a position to its Figure 14a position.

Between the two wings 81, an aperture 87 is provided in the actuator 77, in the centre of which is a connecting pin 89, and with which one end 93 of a hinge plate 91 engages, the end of the plate 91 being bifurcated for this purpose. The plate 91 is pivoted to the casing 21 at its opposite end 95, and carries a transversely extending pin 97 located just above the centre of the plate (e.g. one-third the way down). The front button 75 is located within an insert 99 in a front face of the casing 21, and has a stem projecting rearwardly through the insert 99, which terminates at its rear end in two spaced arms 101, in each of which a rearwardly extending slot is provided. The two ends of the pin 97 engage within respective ones of the slots 101, so that when the button 75 is depressed, the hinge plate 91 will be rotated anti-clockwise to the position shown in Figure 16.

Figures 13 and 13a show the tool with the trigger in a motor off mode, and the lock-on/lock-off mechanism in a lock-off position, because the extensions 31 are located beneath the downward facing recesses 59 of the fixed catch 57. To switch on the motor, the operator must first depress one of the buttons 71 or 73, thus causing the slidable actuator 77 to be cammed forwards by engagement of a surface 85 with a cam surface 83, as shown in Figure 14a. As in the previous embodiment, this will cause the crossbar 29 to be moved forwardly, thus moving extensions 31 out of the influence of the catch 57, and allowing the trigger to be depressed, as is apparent from Figure 14.Depression of the trigger 17 will move the lock-on/lock-off mechanism to the position shown in Figure 15, when the arm 38 will actuate the switch to turn on the motor, and if the button 73 is not held in a depressed state, will allow pillars 27 to move the extensions to the position shown in Figure 15. As in the previous embodiment, if the trigger is now released, then it will return to its Figure 13 position, and the latching mechanism will be allowed to return to a lock-off position.

If it is required to switch the tool on and off using the trigger 17, one of the buttons 73 must be kept depressed, so that the slidable actuator 77 is kept in the Figure 14 position.

When the operator wishes to operate the tool with the trigger 17 in a lock-on mode, he must depress the front button 75, and this will then cause the actuator 77 to be moved rearwardly as shown in Figures 16 and 16a, thus causing the extensions 31 to move above the upwardly facing recesses 61 in the catch 57, so that when the trigger is released, the mechanism will move to the lock on position as shown in Figure 16.

The mechanism is moved to a motor off mode, as in the previous embodiment, merely by squeezing the trigger 17 so as to lift the extensions 31 out of the recesses 61, whereupon the resiliency of the pillars 27 will move the extensions forwardly, thus allowing the trigger to return under its spring bias to its motor-off mode, and the mechanism automatically to return to a lock-off position as shown in Figure 13.

It will thus be appreciated that the present invention provides a safety device for hand tools which always re-sets itself to a lock-off position, which means the tool cannot accidentally be picked up and switched on at the same time.

The separate switch on function must be performed. The tool cannot be left in a lock-on mode, and furthermore, cannot be accidently moved to a lock-on mode because to lock-on the trigger, an actuator has to be moved in a different direction to the direction it has to be moved to 'switch' the tool from a lock-off mode.

It will be appreciated that various modifications can be made to the above described constructions without departing from the invention, which is defined in the claims appended hereto.

Claims (12)

1. A hand tool having a lock-on/lock-off mechanism for controlling the operation of the hand tool, said mechanism comprising an on/off trigger for switching a motor of the tool on and off, said trigger being mounted in a housing, for movement between a motor-off position and a motor-on position, and a latching mechanism also mounted in the housing for movement in one direction from a lock off position in which said trigger cannot be moved from its motor off position to a first position in which said trigger can be moved to its motor-on position, said latching mechanism then being moveable in a different direction to a lock-on position in which said trigger is maintained in its motor-on position, and wherein the trigger and latching mechanism are so constructed that when said trigger is squeezed when the latching mechanism is in its lock-on position, spring means will cause the latching mechanism to move to its lock-off position and allow the trigger automatically to move back to its motor-off position.

2. A hand tool according to Claim 1 wherein the trigger is mounted in the housing for sliding movement and the latching mechanism includes a slider which is also mounted in the housing for sliding movement, but in a plane at right angles to the plane of movement of the trigger.

3. A hand tool according to Claim 1 or 2 wherein the latching mechanism is biassed to its lock-off position and pressure must be maintained thereon to maintain it in its first position and the trigger is biassed by a spring to its motor-off position and pressure must be maintained thereon to hold it in its motor-on position except when said latching mechanism is in its lock-on position.

4. A hand tool according to Claim 1, 2 or 3 wherein the latching mechanism includes a fixed catch within the housing, which co-operates with means on the trigger to hold the trigger in both its motor-on and its motor-off positions.

5. A hand tool according to Claim 4 wherein the trigger has a pair of resiliently deformable laterally spaced pillars upstanding therefrom interconnected by a crossbar and each end of the crossbar is provided with a lateral extension which is of inverted generally equi-lateral triangular construction but with an upstanding rib at a rear end of its upper face and said extensions providing the means on the trigger which co-operate with the fixed catch, said slider having a rearwardly extending tail which terminates in a depending flange having a downwardly opening centrally located slot therein in which the crossbar is located, whereupon fore and aft sliding movement of the slider will cause said pillars to be deflected from their upright position, the fixed catch secured to the housing of the hand tool having spaced locking jaws with which the lateral extensions are arranged to co-operate.

6. A hand tool according to Claim 5 wherein the locking jaws each have a downwardly opening recess in which the upwardly extending rib on the top face of the triangular extensions can engage'when the latching mechanism is in its lock-off position, and an upwardly extending recess located rearwardly of the downwardly facing recess in which the lower apex of the triangular extensions engage when the latching mechanism is in its lock-on position.

7. A hand tool according to Claim 6 wherein the slider is slidable horizontally forwardly from a lock-off position to a first position which moves the crossbar and its lateral projections with it from beneath downwardly opening recess in the locking jaws thus enabling the trigger to be depressed and moved from its motor-off position to a motoron position by raising the trigger against the bias of its spring, whereupon the lateral extensions will move upwardly within the slot from a lower end thereof to an upper end thereof, such upward movement also causing a leading end of a forwardly projecting arm on the trigger to move a switch actuator for a motor for the tool from a motor-off to a motor-on position.

8. A hand tool according to Claim 6 or 7 wherein the slider is movable rearwardly to a lock-on position when the trigger is held in a motor-on mode, whereupon the apices on the underside of the extensions will be moved into a position in which they will engage in the upwardly extending recess when the trigger is released to hold the trigger in a lock-on mode.

9. A hand tool according to any one of Claims 5-8 wherein the flange on the slider depends from its tail and the slot is downwardly opening.

10. A hand tool according to any one of claims 5-8 wherein the slider is in the form of a slidable actuator which is controlled by left and right hand latch actuating buttons and a front latch actuating button and a hinge plate, the flange on the slidable actuator being an upstanding flange with an upwardly opening slot therein.

11. A hand tool according to Claim 10 wherein the slidable actuator has a central slot therein, with which one end of the hinge plate engages, the other end being pivotally connected to the housing of the tool, and lateral cam surfaces each engageable by an inner end face of respective ones of the left and right hand latch actuating buttons, the front button having a pair of projecting plates on its inner face with slots at their inner ends which engage with a transverse pin located about one-third of the distance along the length of the hinge plate to transfer axial movement of the front button into pivotal movement of the hinge plate to move the plate and hence the slidable actuator to a lock-on position when the front button and the trigger are depressed.

12. A hand tool substantially as hereinbefore described with reference to the accompanying drawings.