US 3783955 A
A portable power tool having two work implements, such as a drill bit and a screwdriver bit, located at opposite ends of the body of the tool and facing in opposite directions with the body being mounted on a handle so that it can be turned through 180 DEG relative to the handle to bring one or the other of the implements into a working position. The body is provided with guard means so that whichever implement is not working is covered by the guard means. An air motor for driving the work implements may be mounted in the body of the tool or in the handle and driving the work implements through suitable gearing.
Description (OCR text may contain errors)
o United States Patent 1 1 [111 3,783,955 Gill 1 Jan. 8, 1974 POWER TOOL 2,229,951 1/1941 West et a1 173/48 x 1751 1mm Peter o Wolverhampton, 3232332 12/1323 "11351 3 England 3,034,550 5/1962 Dahl 7/15 x  Assignee: G.K.N. Screws & Fasteners Limited,
wofley, England Primary ExaminerErnest R. Purser 22 i 21 1972 Att0rneyJOhn W. Malley et al.
App]. No.2 246,271
Lebus 51/128 X  ABSTRACT A portable power tool having two work implements, such as a drill bit and a screwdriver bit, located at upposite ends of the body of the tool and facing in opposite directions with the body being mounted on a handle so that it can be turned through l80relative to the handle to bring one or the other of the implements into a working position. The body is provided with guard means so that whichever implement is not working is covered by the guard means. An air motor for driving the work implements may be mounted in the body of the tool or in the handle and driving the work implements through suitable gearing.
14 Claims, 8 Drawing Figures SHEET 1 OF 4 :EEEEzzEz:
PATENTEI] JAN 81974 PATENTEDJAN 8 m4 SHEET [1F 5 8 N0 5 mm vs no mm mm mm mm EON 3 R3 cm R R 1 POWER TOOL FIELD OF THE INVENTION This invention relates to portable power tools (such as for example, drills, screwdrivers, rivet applicators).
BACKGROUND OF THE INVENTION The broad object of the invention is to provide a new or improved power tool having a pair of holders for different types or sizes of work implement whereby a selected implement can be used as desired followed by change over to another type or size of implement without having to remove one implement and replace it in its holder with another one as is the case with the generally known conventional forms of power tools which have only one holder for the working implement. For example, with a conventional electric drill when it is desired to perform a drilling operation followed by a countersinking operation the working implement, namely the drill bit, has to be changed for a different type of Working implement namely the countersinking bit after the hole has been drilled. In other cases it is sometimes preferred to use two separate tools such as for example in the inserting of self tapping screws where one tool is used to drill the hole and another tool is used to insert the screw.
SUMMARY OF THE INVENTION According to the invention there is provided a power tool comprising a body, two holders for work implements mounted in or on said body in opposed relationship so that the implement in one holder is presented in a direction directly opposite to the direction in which the implement in the other holder is presented, power means in or on the body for supplying the motive power to each of the holders, guard means on the body for effectively guarding the implement not in use when the other implement is being used and means for moving the holders relatively to the guard means to bring one of the holders into its operating position while the other holder is in a position where its implement is within the region of protection of the guard means.
For a portable hand tool a preferred form of power means is a generally known form of air motor which is driven from a source of compressed air and which can be easily housed within the body of the tool or within a handle projecting from the body.
Using such an air motor, in one form of tool in accordance with the invention the body is of generally cylindrical configuration and has a handle projecting transversely frome one side thereof, the handle also being of a generally cylindrical form and providing a housing for the accommodation of the air motor and its associated gearing. The output shaft from the air motor may project into the body of the tool and the work implement holders may be mounted on either side of said power output shaft so as to be directly aligned within the body and each holder may have a rotary shaft for supplying the motive power to its work implement and conveniently the two shafts may be arranged in axial alignment and may both be driven directly by suitable gearing from the output shaft of the air motor.
With this arrangement the body may comprise an outer casing which at its ends includes guard means for the work implements and an inner casing within which inner casing the aforesaid holders are mounted, the arrangement being that the outer casing is slidable upon the inner casing so that when relative sliding movement takes place between the outer and inner casings in one direction one of the work implements is projected beyond its associated guard means and the other work implement is withdrawn within its associated guard means.
Conveniently, the handle which houses the air motor is also of cylindrical form and is arranged so as to project at right angles from thebody and rack and pinion form of gearing may be provided between the outer housing of the handle and the outer casing of the body whereby rotation of the outer casing of the body relative to the outer housing of the handle causes an axial displacement of the outer casing of the body relatively to the inner casing thereof thus causing movement of the respective guard means in relation to the work implements guarded thereby.
In another embodiment according to the invention an air motor for driving the shafts of both work holders may be mounted within a generally cylindrical body which itself is mounted for rotation upon a handle about an axis at right angles to the axis of the cylindrical body and the handle may have fixed thereon a projecting guard means, the arrangement being that the body may be swung through so as to bring one work implement out of the region and protection of the guard means into an operating position whilst moving the other work implement back into the region of'protection of the guard means.
In a further embodiment according to the invention the body may be of generally cylindrical form, housing a motor and gearing for driving the holder arranged in axial alignment, the body being mounted for rotation upon a handle about an axis at right angles to the axis of the cylindrical body and there being provided at each end of the body a two-part guard comprising a first sleeve fixed to the body and a second sleeve telescopically engaged with the first sleeve so as to be movable between a fully extended position in which it guards its associated work implement and a retracted position in which it exposes the implement.
BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated in the accompanying drawings wherein:
FIG. 1 is a view in section in side elevation of one form of tool,
FIG. 2 is a section on the line 2--2 of FIG. 1,
FIG. 3 is a section on the line 33 of FIG. 1,
FIG. 4 is a view to a smaller scale of the complete tool in side elevation,
FIG. 5 is a view in side elevation of another form of tool,
FIG. 6 is a scrap plan view of the one end of the tool,
FIG. 7 is a sectional view in side elevation of another form of tool, and
FIG. 8 is a scrap plan view of one end of the tool.
DESCRIPTION OF PREFERRED EMBODIMENTS The form of tool shown in FIGS. l-to 4 of the drawings is one suitable for accommodating two rotary work implements such as, for example, a drill for drilling a hole in metal sheet and a screwdriver bit for driving a self-tapping screw into such drilled hole.
The body of the tool comprises the outer casing 10 which at each end has screwed thereon the guard means indicating at 11 and 12. The outer casing is of generally cylindrical form with the outer end portions of the guards members 11 and 12 being tapered to generally frusto-conical form and each having an open end through which the associated w'ork implement can project. The body further comprises a cylindrical inner casing 13 and the arrangement is such that the outer casing can slide freely in the axial direction upon the inner casing 13.
Projecting at right angles to the axis of the body at one side thereof is a handle generally indicated at 14 and comprising an outer cylindrical housing 15 within which is housed a known form of air motor with its associated gearing indicated at 16. The output shaft 17 from the air motor 16 projects through an opening into the space within the inner casing 13 and has fixed thereon a first bevel gear 18 and a second bevel gear 19.
The body comprising outer casing 10 and inner casing 13 can rotate relative to the handle about the central axis of outer housing 15. Fixed to the outer housing 15 of the handle is a gear wheel 20 and this meshes with a toothed rack 21 which is fixed to the outer casing 10 of the body.
Two work implement holders 22 and 23 are mounted fixedly within the inner casing 13 and each has rotatably mounted therein its appropriate driving shaft for providing the rotary motion required to operate its associated work element and in the particular example shown the holder 22 is the type adapted to take a drill bit 24 whilst the holder 23 is the type adapted to take a screwdriver bit 25, the screwdriver bit being spring loaded axially in known manner so that it is not con nected to its rotary drive shaft until axial pressure has been applied to engage the screwdriver bit with a screw whereupon the screwdriver bit moves axially against the spring pressure and the drive is connected from its drive shaft.
The drive shaft of holder 22 has a bevel gear 26 fixed at its inner end and in mesh with the bevel gear 19 on the output shaft 17 from the air motor and the drive shaft of holder 23 has a bevel gear 27 at its inner end and in mesh with the other bevel gear 18 on the output shaft from the air motor.
The arrangement of the gearing is such that the gearing 19, 26, provides a high speed drive to the drill bit whereas the gearing 18, 27 provides a reduced speed drive to the screwdriver bit.
The position of the tool as shown in FIG. 1 is for the operation of the drill bit with the gear 20 along at the left hand end of the rack 21, as seen in the drawing, with the result that the outer casing 10 has been slidden to the right, as seen in the drawing, so as to bring the guard 11 back and clear of the drill bit 24 which is projecting from the open end of the guard. Conversely, with the gear 20 at the extreme right hand end of the rack 21 the guard 12 would be drawn back and the screwdriver bit would be projecting from the open end of the guard 12 (as shown in FIG. 4.).
In practice, therefore, by holding the outer housing 15 of the handle stationary and by turning the outer casing of the body through 180 about the vertical axis of the handle, the rack and pinion gearing 20, 21 causes relative movement between the inner and outer casings of the body and thus a movement of the outer casing 10 between the limits imposed by the length of the rack 21 to expose one or the other of the work implements of the tool.
Trigger means for operating the tool and also providing a form of safety lock are shown in FIGS. 1 to 4 and hereinafter described.
By means of a suitable adapter 8 an air hose can be connected to the lower end of the handle 14 and within the end portion 28 of the air motor there is provided a valve mechanism for controlling the supply of compressed air to the motor. (see FIG. 3).
A trigger for operating the tool is mounted upon the handle 14 at a position approximately just below midway between the ends of the handle, the trigger being in the form of a bar 29 which is pivotally mounted about an axis 30 which is at right angles to the axis of the handle and the bar extending substantially from top to bottom of the handle.
At its lower end this bar 29 engages with a U" shaped yoke 31 which slides in the generally horizontal plane (assuming the handle to be held vertically), between spaced apart flanges 32 on the portion 28 of the air motor and one side or the other side of this U" yoke, (depending on whether the tool is set for drilling or screwdriving), is used to operate plunger mechanism 33 for opening and closing the air inlet valve 34 to the motor.
The rack 21 (see FIG. 2) is for-med upon one face of an elongated aperture in a plate 35 which is secured to the underside of the outer casing 10 of the body. The gear 20 can travel along this aperture during movement from one end of the rackto the other. At each end the plate 35 has a slot 36 extending in the axial direction of the body.
At its upper end the bar 29 forming the trigger has a projecting nose 37 which is adapted to engage within one or the other of the aforesaid end slots 36 and the bar 29 forming the trigger is acted upon above and below its pivotal axis by springs 38 and 39 which are arranged to normally hold the bar in a position in which the nose 37 at its upper end is engaging within the entrance of one of the aforesaid slots 36 and the yoke 31 at the lower end is in a position in which the valve mechanism 33, 34 controlling the inlet of air to the motor is in the closed position. (This position of nose 37 is shown in full lines in FIG. 2.). Thus, in this condition the tool is in a safe position with the air to the motor cut off and the outer casing of the body 10 locked in relation to the handle 14 so that it cannot be turned from one position to the other. In this position, if the trigger is now pressed at its upper end, that is the end nearest the body, then the lower end moves away from the handle and this outwards movement of the yoke 31 operates the valve mechanism to admit air to the air motor and thus drive whichever implement is projecting from the end of the body. When the trigger bar is released it moves back into the position in which the air supply is cut off and in which the nose at the top of the trigger bar is still engaging within the slot 36 so as to prevent any movement of the body in relation to the handle. During the operation of the work implement this nose is engaged to the full extent within such slot preventing any possibility of movement between the body and the handle. (The position of nose 37 shown in dotted lines on the right in FIG. 2.).
To change from one implement to another the trigger bar is now grasped at its lower end and pivoted so that its lower end moves in towards the handle and its upper end outwardly so that the nose on the upper end is disengaged from the aforesaid slot 36, (see dotted line position of nose 37 on left side in .FIG. 2.), and then the outer casing can be rotated through 180 to cause relative traverse between the gear 20 and rack 21 to bring the other work implement into the operative condition in which it is projecting beyond its guard. Having reached this position release of the trigger bar causes it to return to its neutral position in which the nose at the top of the trigger bar again engages in the entrance of the other slot 36 and locks the body from movement in relation to the handle.
The aforesaid end slots are such that one side of the slot is longer than the other, (see FIG. 2), the longer side thus forming a stop against which the nose 37 at the top of the trigger bar engages after there has been movement through 180 so thatthe two positionsof the body in relation to the handle are determined by the longer sides of the aforesaid slots.
It will be appreciated that although the example above has been described in relation to two work implements having a rotary action, itis possible for appropriate mechanism to be incorporated within either or both of the holders 24, 25 to give a reciprocating or hammering motion to a work implement or a combined rotary and hammering effect can be'obtained with generally known mechanisms.
The necessity for providing effective guard members will be appreciated when it is understood that in operating the one implement, for example the screwdriver bit, the operator would have the tool positioned with the other implement, namely the drill, pointing directly at his body and would be applying axial pressure in the direction towards the screwdriver bit so that in the event of any slip the projecting end of the drill, if not otherwise guarded, could cause serious injury to the operator particularly as with the arrangement shown such drill would be rotating by virtue of its connection through the gearing to the drivefrom the air motor.
Reference is now made to FIGS. 5 and 6 which show a further embodiment of the invention, being a somewhat simpler form of tool.
ln FIGS. 5 and 6 the body 40 of the tool is of generally cylindrical form with the air motor (not shown) for providing the drive mounted within such body substantially at the mid position thereof and having an extension of its shaft at both ends so that one end can provide a drive to one tool holder 41 and the other end can provide a drive to the other tool holder 42 with the tool holders being mounted at opposite ends of the cylindrical body 40.
A pistol grip type of handle generally indicated at 43 is provided, connected to the intermediate portion 44 of the body and the body is mounted on the handle so that it can be swivelled through 180 about an axis which is normal to its own axis upon a suitable bearing pedestal 45 provided between the pistol grip handle 43 and the body portion 44.
In this embodiment a single guardmember 46 is provided which extends from the handle 43 near the position of mounting between the handle and the body and which has a part 47 which extends rearwardly of the handle for a sufficient distance to enable its outer end to be curved upwardly into the form of a cup 48 in which position it provides a guard for the projecting end of the work implement which is not being used.
The air supply to the motor is taken up through the pistol grip handle and through a generally known form of control valve and a press-button trigger mechanism 49 is provided on the front edge of the pistol grip handle to control operation in the normal way. A locking mechanism between the trigger mechanism and the body (similar to that shown in FIG. 2) is provided so that when one work implement is in the operative position and is in use there is no possibility of any movement taking place between the body and the handle. A nose 50 on the trigger mechanism is used to engage in one or the other of two slots 51 on the underside of the body.
Reference is now made to FIGS. 7 and 8 which shows another embodiment of the invention.
The main part of the body shown at 60 is of generally cylindrical form and housesan air motor 61 and at one end the body 60 has screwed thereon an extension 62 in which is housed a high ratio reversing gear box 63 driven from the driving shaft of the air motor and driving an adjustable multiplate friction clutch 64, to which is drivingly connected the holder 65 for a screwdriver bit 66.
The other end of the shaft of theair motor drives a low ratio non-reversing gear box 67, the output shaft of which drives the chuck 68 into which is fitted a drill bit 69. The parts so far described are components of generally known construction and the arrangement pro vides for a high speed drive from the air motor to the chuck 68 for drilling and a low speed drive to the holder 65 for using the bit 66 for inserting screws.
The body part 60 is mounted on the upper end of a swivel tube 70 which extends downwardly through an axial passage in a pistol grip handle 71 and which swivel tube assembly contains a generally known form of air valve mechanism generally indicated at 72. The whole of the assembly of swivel tube'and valve mechanism 70 and 72 is rotatably mounted in the pistol grip handle 71 so that the body 60 being connected to the upper end of the swivel tube 70 can be turned relative to the handle 71 about the axis of the tube 70. At the forward side of the handle 71 there is a press-button trigger 73 controlling a valve rod 74 for the opening and closing of the air valve to allow admission of air to the air motor 61, the air supply being connected to the bottom end of the handle 71. v
The guard for surrounding each work implement comprises a fixed outer sleeve and a movable tele- 'scopicinner sleeve and in the position shown in FIG.
outer sleeve 75 is fixed at its inner end to the body 60 v and the inner sleeve is in two parts and comprises a cylindrical part 76 and connected thereto a forward frusto-conical part 77 and as shown the forward edge of the cylindrical part 76 projects beyond the rear end of the frusto-conical part 77. A ring 78 is secured to the interior of the assembly of the inner sleeve and a coil spring 79 acts between this ring and the inner end of the outer sleeve 75 at the position where it is fixed to the body 60 so that the spring 79 is urging the inner sleeve assembly in the outward direction into the position in which it would cover and act as a guard for the drill bit 69.
shown in FIG. 7 by the engagement of the forward edge of the sleeve 76 with a nose 82 which is carried at one end of a spring metal strip 83 the other end of which is fixed to a U-shaped bracket 84 secured to the forward face of the pistol grip handle 71. The nose 82 has an inclined forward edge so that as the inner sleeve assembly of the guard is pulled into the retracted position by the finger piece 81 its innermost edge when engaging the forward inclined edge of the nose 82 will deflect the nose 82 radially outwardly until the inner sleeve has moved to its fully retracted position whereupon the nose 82 can snap back into position and engage with the forward edge of the sleeve 76 to prevent the sleeve from moving outwardly during the operation of the tool using the drill bit 69. On its underside the outer sleeve 75 is provided with a rectangular slot 85 to permit, the movement of the nose 82 into and out of engagement with the inner sleeve assembly of the guard and as will be seen from FIG. 8 the circumferential width of the slot 85 is substantially greater than the width of the nose 82 for the purpose hereinafter described.
In FIG. 8 there is shown in full lines the position of the guard when the drill bit is being operated and the inner sleeve assembly of the guard withdrawn wholly within the outer sleeve 75. The outer sleeve 75 is also shown in dotted lines in a position in which the body 60 has been turned relative to the handle 71 through a small angle to a position in which the forward edge of the sleeve 76 has just moved out of engagement with the nose 82 so that the straint is removed from the inner sleeve assembly of the guard and it has been urged outwardly by the spring 79 the frusto-conical part 77 of the inner guard assembly being shown in the extended position in chain dotted lines in FIG. 8. Hence the act of commencing to turn the body of the tool relative to the handle 71 to'change from one working position to another automatically ensures that the inner sleeve assembly of the telescopic guard moves into its outer operative position in which it protects the drill bit 69 and the drill bit cannot be exposed again until a deliberate action is taken to retract the inner sleeve assembly of the guard by moving the finger piece 81 rearwardly.
In the righthand side of FIG. 7 there is shown a similar form of telescopic guard for the driver bit 66, the guard here being shown in its operative guarding position and also there is shown means whereby the inner sleeve of the telescopic guard is prevented from being moved into its retracted position whilst the driver bit is in this inoperative or out of work position. Thus, whilst the drill bit is being used, should the operator apply any pressure to the extended inner sleeve of the telescopic guard it cannot move inwardly and thus there is no danger of the screwdriver bit becoming exposed and creating a hazard.
The telescopic guard for the screwdriver bit comprises an outer sleeve 86 and an inner sleeve assembly 87 which has a forward part 88 of reduced diameter so as to provide an internal shoulder and a coil spring 89 acts between this internal shoulder and the position where the outer sleeve 86 is connected to the body 60 so as to normally urge the inner sleeve assembly into the forward protective position, as shown in FIG. 7. The inner sleeve assembly is provided with a finger piece 90 working in a slot 91 on the upper side of the outer sleeve 86 so that the inner sleeve assembly can be withdrawn into its retracted position by hand against the pressure of spring 89.
On its underside the outer sleeve 86 has a rectangular slot 92 the same as the slot 85 in the upper guard and when the screwdriver bit is in use in the operative position the nose 82 operates through this slot 92 to engage the outer face of the shoulder 93 btween the two parts 87 and 88 of the inner sleeve assembly so as to hold the inner sleeve assembly in its retracted position against the pressure of the spring 89.
The means for preventing inwards movement of the inner sleeve assembly 87, 88 when it is in the position shown in FIG. 7 comprises an arm 94 fixed to the upper end of the handle 71 and extending rearwardly thereof and having at its outer end an upwardly projecting lug 95 which lies within the slot 92 when the parts are in the position shown in FIG. 5 and which provides an abutment engaged by the inner edge of inner sleeve 87 thus preventing any inwards movement of inner sleeve 87 so long as the parts are in the position shown in FIG. 7. Thus, whilst the one worked implement is in use the inner sleeve assembly of the guard of the other implement not in use cannot be inadvertently pushed inwardly to expose the implement and create a hazard.
It will be appreciated that when the tool-is in the reverse position to that shown in FIG. 7 the lug 95 will operate in the same way to prevent any inwards movement of the inner sleeve 76 of the other guard by similar engagement with the inner edge of this inner sleeve.
To prevent any movement of the body relative to the handle when one or the other of the implements is actually in use there is provided a locking action between the trigger 73 and two slots 96 and 97 formed on the underside of the body, such slots being diametrically opposed and each slot having a longer side and a shorter side.
The longer sides of the slots 96 and 97 are shown in the drawing and in the position shown the trigger 73 being in the inoperative position is just outside the mouth of the slot 97 (i.e., it is clear of the shorter side of the slot). When the trigger 73 is pressed inwardly to operate the air motor its upper portion enters within the slot 97 tothe full depth and in this position positively prevents any turning movement of the body 16 relative to the handle 71. The same action takes place when the tool is in the other position using the screwdriver bit 66 when the trigger co-operates with the slot 96.
The upper part of the trigger also provides a locating stop when the body 16 is swung from one position through l80 to the other when the longer side of either slot 96 or 97 comes into engagement with the upper part of the trigger at the end of the arc of movement, thus setting the body of the tool in the correct position relative to the handle for whichever implement is to be used.
1. A power tool including an elongate body; power means; two implement holders directed in opposite directions and disposed at or adjacent opposed end por- 9 tions of the tool body and powered by said power means; a handle extending generally at right angles to the axis of elongation of the body and having trigger means for selectively operating said power means; and guard means arranged to guard one implement which is not in use while the other implement is being used, the guard means being operatively associated with the handle, the handle being rotatable on its own axis relative to the body of the tool between extreme positions in which the trigger means face towards each end portion and hence each implement respectively and the guard means being arranged so that, when the trigger means on the handle are directed towards one implement whereby that implement is in an operative condition in which it is capable of being used, the guard means is effective to guard the other implement from external contact and when the handle is rotated from said position prior to operating the other implement, the guard means is automatically moved thereby into a position where it is effective to guard said one implement from external contact.
2. A power tool according to claim 1 wherein the body is of generally cylindrical form and has a handle projecting transversely from one side thereof said handle being of generally cylindrical form and providing housing for an air motor and gearing, the output shaft from the air motor projecting into the body of the tool and the work implement holders being mounted in axial alignment on either side of said output shaft and each holder having a rotary shaft for supplying power to its work implement driven by gearing from the output shaft of the air motor.
3. A power tool according to claim 2 wherein the body comprises an outer casing which at its ends includes guard means for the work implements and an inner casing within which inner casing the aforesaid holders are mounted, the arrangement being that the outer casing is slidable upon the inner casing so that when relative sliding movement takes place between the outer and inner casings in one direction one of the work implements is projected beyond its associated guard means and the other work implement is withdrawn within its associated guard means.
4. A power tool according to claim 3 wherein the handle has an outer cylindrical housing arranged to project at right angles from the body and rack and pinion gearing is provided between the outer housing of the handle and the outer casing of the body whereby rotation of the outer casing of the body relative to the outer housing of the handle causes an axial displacement of the outer casing of the body relatively to the inner casing thereof thus causing movement of the respective guard means in relation to the work implements associated therewith.
5. A power tool according to claim 4 wherein a rack is fixed to the under side of the outer casing of the body and has meshing engagement with a pinion fixed to the outer housing of the handle.
6. A power tool according to claim 1 wherein the body is of generally cylindrical form and houses therein a motor for driving the shafts of both work holders the body being mounted upon a handle for rotation about an axis at right angles to the axis of the cylindrical body and the handle having fixed thereon a projecting guard means, the arrangement being that the body may be rotated through 180 so as to bring one implement out of the region of protection of the guard means into an operating position whilst moving the other implement back into the region of protection of the guard means.
7. A power tool according to claim 6 wherein the guard means comprises an arm fixed at one end to a handle adjacent where the body is mounted thereon said arm extending radially outwardly from the handle and having its outer end curved back to provide the guard for one or the other of the work implements.
8. A power tool according to claim 1 wherein the body is of generally cylindrical form and houses a motor and gearing for driving the holders arranged in axial alignment, the body being mounted for rotation upon a handle about an axis at right angles to the axis of the cylindrical body and there being provided at each end of the body a two-part guard comprising a first sleeve fixed to the-body and a second sleeve telescopically engaged with the first sleeve so as to be movable between a fully extended position in which it guards its associated work implement and the retracted position in which it exposes the implement.
9. A power tool according to claim 8 wherein each two-part guard has the second sleeve slidable telescopically within the first sleeve and spring urged in the direction outwardly of the first sleeve, there being fixed to the handle of the tool, at the front thereof, a resilient locking member which projects through the wall of the outer sleeve and engages part of the inner sleeve, of the guard which is in the front position for operation of its implement, so as to hold the inner sleeve in the retracted position.
10. A power tool according to claim 9 wherein the said locking member comprises a nose at the free end of a resilient arm the upper end of which is fixed to the handle, the nose projecting through a circumferential slot in the outer sleeve and such slot being wider in the direction transverse to the axis of the sleeve than the nose, whereby a small angular movement of the body from the operative position results in the said part of the inner sleeve moving out of engagement with the nose to permit the inner sleeve to be spring urged to its outer position.
11. A power tool according to claim 10 wherein, at its rear side, the handle has fixed thereto a locking lug which projects through the aforesaid slot of the guard, the implement of which is in the inoperative positon, and engages a part of the inner sleeve to prevent same from being moved inwardly in relation to the outer sleeve.
12. A power tool according to claim 11 wherein the inner sleeve of each guard has a finger piece on its wall projecting outwardly through an elongated slot in the outer sleeve whereby the inner sleeve can be moved manually from its extended position to its retracted position.
13. A power tool according to claim 1 wherein two similar slots are provided on the underside of the body of the tool and the trigger has a part arranged so as to engage in one or other of the slots when the trigger is pressed to operate the motor, whereby relative movement between the body and the handle when the motor is driven is prevented.
14. A power tool according to claim 13 wherein each said slot has one side edge longer than the other and an open mouth through which said part of the trigger engages when it is pressed to operate the motor, and said part of the trigger being engaged also by the longer edge of the slot when it is in the released position so as to act as a stop defining the operative position of the body whichever work implement is in use.
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