Power Tool

This invention relates to a power tool 1 of the kind having a driven member 15 adapted to releasably hold at least one working element 46. The power tool 1 can operate in either a working mode in which the driven member 15 is driven to enable the working element 46 to perform work, or an adjustment mode, in which the driven member 15 is adjusted to grip or release the working element 46. The power tool 1 includes a selector 17 operable to cause the power tool 1 to operate in either the working or adjustment mode. A power drill 1 is one form of power tool to which the invention is applicable.

This invention relates to power tools of the kind having a driven member adapted to releasably hold at least one working element. The invention is applicable to all types of power tools, including powered garden tools. It is applicable to tools in which the working element is a drill bit, a saw blade, a cutting wheel, a grinding wheel, or any other element used to cut, shape, or otherwise treat a workpiece (for example), or is a driving element such as a screwdriver blade, or a socket spanner for example.

A power drill is one form of power tool to which the invention is applicable. In that example application of the invention, the driven member is a chuck, and the working element is a drill bit. It will be convenient to hereinafter describe the invention with particular reference to power drills, but it is to be understood that the invention has broader application. It will also be convenient to hereinafter describe the invention with particular reference to portable power tools, whereas the invention is applicable to power tools of a non-portable nature.

Conventional power drills typically have a three jaw chuck for gripping a drill bit. The chuck jaws are adjustable to suit drill bits of various sizes, and in some cases such adjustment is carried out by use of a key. In other cases it is carried out by manually twisting the outer sleeve of the chuck or alternatively the user grips the outer sleeve and power is applied to the chuck, whereby the user provides a resistance force. In either case, the process of securing or releasing a drill bit can be laborious and time consuming. When the user provides the resistance force, the user's hand can be damaged if the user fails to release the sleeve when the chuck has tightened. Other forms of power tools utilize a key or hand operated driven member and suffer the same inconvenience when removal or replacement of the working element is required.

It is an object of the present invention to provide a power tool that is convenient and safe to use. It is a further object of the invention to provide a power tool having means for driving the gripping jaws of the driven member towards an open or closed condition. It is a still further object of the invention to provide such a power tool in which the jaws are motor driven.

According to the present invention, there is provided a power tool including a driven member that is operable to grip and drive at least one working element, power drive means connected to the driven member the power tool being operable in either a working mode in which the driven member is driven to enable the working element to perform work, or an adjustment mode in which the driven member is adjusted to grip or release the working element, and selector means operable to cause the power tool to operate in one or the other of said modes. It is to be appreciated that the motor could be hydraulically or pneumatically driven, and that the working element could be any device adapted to perform work when driven so as to undergo rotary movement, linear movement, or any other type of movement.

In a preferred embodiment the driven member includes a body part and an adjustment part that when in an adjustment mode are movable relative to one another, to grip or release said working element, and said parts move together when in the working mode. The power drive means is preferably connected to the body part so as to thereby drive the driven member.

The power tool preferably includes locking means operable to engage said adjustment part and thereby enable the two said parts to move relative to one another, and said selector means is operable to cause said locking means to engage with or disengage from said adjustment part. It is preferred that the power tool is in the working mode when said locking means is disengaged from said adjustment part, and is in said adjustment mode when said locking means is engaged with the adjustment part. It is preferred that relative movement occurs in response to operation of the power drive means while the locking means engages the adjustment part.

It is preferred that the power drive means includes a motor and a gear assembly through which said motor is connected to said driven member. It is further preferred that the power drive means is operable to drive said body part at either a slow speed or a relatively fast speed, and is caused by said selector means to drive said body part at said slow speed when in said adjustment mode.

In a preferred embodiment the driven member is a chuck adapted to grip and drive a working element in the form of a drill bit, and said power drive means operates to rotate said chuck during said working mode. It is preferred that the body part is a chuck head and said adjustment part is an adjusting nut, when in adjustment mode the locking means engages the adjusting nut to stop it rotating with the chuck head. It is further preferred that rotation of the chuck head relative to the adjustment nut moves two or more jaws to grip or release the dill bit.

FIG. 1of the drawings shows one form of portable power drill to which the invention is applicable, but as previously stated the invention is applicable to other types of power tools, including non-portable power tools. The drill1shown inFIG. 1incorporates an example embodiment of the invention. The drill1may be battery operated, or it may be operated by connection to an AC power supply through a DC transformer. The drill1as shown byFIG. 1includes a body2having a pistol grip3at the back end, and closed loop handle4adjacent the front end. It is preferred that the loop handle4is connected to a front part5of the body2that is rotatable about the longitudinal axis6(FIG. 2) of the body2so that the disposition of the handle4can be changed. By way of example, the disposition of the handle4may be adjustable relative to the pistol grip3so that the handle4can be located beneath the body2as shown byFIG. 1, or at either side of the body2, or above the body2, according to requirements.

It is preferred that handle locking means (not shown) is operable to releasably lock the handle4in a selected disposition. A manually engageable button (not shown) or locking nut may be operable to release the locking means so as to permit adjustment of the disposition of the handle4.

FIG. 2is a diagrammatic illustration of one particular arrangement of the drill1. In that arrangement, a replaceable battery8is located within the pistol grip3, or within another convenient part of the drill1, and is connected to the motor9through a suitable switch10. The switch10may be opened and closed through operation of a finger engageable trigger11, and a lock button (not shown) may be operable to releasably hold the trigger11in the switch-closed position. Such trigger locks are well known and do not require further description in this specification. Access to the battery8may be made possible by operating a lock release button12and thereby enabling a rear part13to be separated from the remainder of the body2.

If desired, the motor9may be operated by direct connection to an AC power source14through the intermediary of a DC transformer (not shown). Alternatively the motor9may be operated from a battery8supplied for an AC power source14.

In the particular arrangement shown, the drill1includes a three jaw chuck15located within the body part5and being connectable with the motor9through a gear assembly16. It is preferred that a mode selector17is operable to enable the drill1to operate in any one of three modes. In one of those modes (the adjustment mode) the motor9is operable to adjust the position of the chuck jaws18relative to the body part or chuck head. The jaw adjustment connection is illustrated diagrammatically inFIG. 2by the broken line20. In each of the other two modes (the drive modes) the gear assembly16connects the motor9to the chuck15in a manner such that the chuck15can be driven (rotated) to perform a drilling operation. In one of the drive modes the chuck15is rotated at a relatively low speed, and it is rotated at a relatively high speed in the other drive mode. The chuck drive connection is illustrated diagrammatically inFIG. 2by the broken line21.

FIG. 3is a diagrammatic illustration of one form of gear assembly16suitable for use in the drill1. The assembly16includes three gear systems, a first input system22, a second input system23, and an output system24. Each of the input systems22and23is connected to the input shaft25through which the motor9is connected to the gear assembly16. The output system24is connected to the output shaft26, which forms part of the connection between the input shaft25and the chuck15.

The first input system22includes a ring gear27fixed to a body28of the gear assembly16, which is in turn connected to the drill body2(not shown inFIG. 3). The input system22also includes sun gear29that is rotatable with the input shaft25, and three planet gears30, each of which meshes with both the ring gear27and the sun gear29. Each planet gear30is rotatably mounted on a respective spindle31arranged parallel to the axis6, and each spindle31is connected to a flange32of a first transfer member33. The transfer member33is mounted for rotation about the axis6, and forms part of a connection between the input systems22and23. It will be apparent that other means could be adopted to connect the systems22and23. The relationship between the gears27,29and30is indicated byFIG. 4.

The second input system23includes a first ring gear34fixed to the body28, a second ring gear35that is moveable relative to the body28in the direction of the axis6, three planet gears36, and a sun gear37fixed to the member33. As best shown byFIG. 5, each planet gear36meshes with the sun gear37and the inner teeth38of the ring gear35, and outer teeth39of the ring gear35mesh with the fixed ring gear34in the mode of operation as shown byFIG. 3. Each planet gear36is connected to the flange40of a second transfer member41through a spindle42on which the planet gear36is rotatably mounted (FIG. 3). The member41is mounted for rotation about the axis6. The input system23is thereby connected to the output system24, but other arrangements could be used for that purpose.

The output system24includes a ring gear43fixed to the body28, three planet gears44, and a sun gear45that forms part of or is connected to the transfer member41. Each planet gear44meshes both with the ring gear43and the sun gear45. The output system24can be connected to the output shaft26in any appropriate manner. In the particular arrangement shown, each planet gear44of the output system24is connected to the output shaft26so as to transmit drive to that shaft. For that purpose, each planet gear44may be rotatably mounted on a respective spindle46, each of which is connected to a flange47secured to the shaft26. Other drive arrangements could be adopted.

Drive can be transmitted from the output shaft26to the chuck15in any appropriate manner, and the chuck15can be of any suitable construction. In the particular arrangement shown, the chuck15includes a head portion48that is connected to the shaft26and carries three jaws18. Each jaw18has a gripping face49adapted to clamp against the shank of a drill bit50(FIG. 1), and adjustment means is provided to enable the jaws18to be moved as required according to the diameter of the drill bit50to be engaged.

In the particular arrangement shown, each jaw18is slidably mounted on the head portion48so as to be moveable relative to the head portion48along a path arranged angularly relative to the axis6. The adjustment means includes an adjusting nut51rotatably mounted on the head portion48and meshing with each jaw18through a thread or worm connection. The arrangement is such that rotation of the nut51relative to the head portion48moves the gripping face49of each jaw18either towards or away from the axis6, as shown byFIGS. 6 and 7.

It is preferred that the chuck15can be driven at either a high speed of rotation or a low speed of rotation. For that purpose, the mode selector17may be operable to select either the high speed mode or the low speed mode.

FIG. 3illustrates the condition of the gear assembly16when the low speed mode has been selected. In that mode, the input shaft25drives the first input gear system22through rotation of the sun gear29. In the particular arrangement shown, the planetary gear system22functions as a speed reduction mechanism. That is, because the planet gears30mesh with a fixed gear27and a rotating sun gear29, the speed of rotation of the system22at the axis of each planet gear30is less than the speed of rotation of the sun gear29. The transfer member33rotates at the same relatively low speed because of its connection with the system22through the spindles31.

The second input system23, when arranged as shown byFIG. 3, provides a further speed reduction because it is a planetary gear system similar to the system22. In that regard, it is relevant that the second ring gear35meshes with the fixed ring gear34, and is thereby held against rotation relative to the body28. The planet gears36therefore mesh with a fixed ring gear35and a rotating sun gear37, and as a consequence the speed of rotation of the system23at the axis of each planet gear36is less than the speed of rotation of the sun gear37. The transfer member41rotates through the drive connection formed by the spindles42, and therefore rotates at a speed less than that of the transfer member33.

Further speed reduction occurs between the transfer member41and the output shaft26because those two components are connected through a planetary gear system24which functions in the same manner as the gear system22. The speed reduction influence of the gear system24may be the same as or different to the speed reduction influence of either of the input gear systems22and23, according to requirements. It will be appreciated that in some circumstances, there may not be a need for a third speed reduction, in which event the planetary gear system24could be omitted.

FIG. 8shows the change in the gear assembly16that arises when the mode selector17has been operated to select the high speed mode. When that selection is made, the ring gear35is caused to move axially to the left so as to mesh with a pinion gear52and separate from the fixed ring gear34. The pinion gear52forms part of or is fixed to the transfer member33so as to rotate with that member. As shown byFIG. 8, the ring gear35remains in engagement with the planet gears36and thereby locks those gears against rotation relative to both the sun gear37and the ring gear35. The speed reduction influence of the second input system23is thereby removed, and in the particular arrangement shown the speed of rotation at the axis of each planet gear36is the same as the speed of rotation of the transfer member33. It follows that the transfer member41is rotated at the same speed which is a higher speed than occurs in the arrangement as shown byFIG. 3. The gear system24retains its speed reduction influence, but the speed of rotation of the output shaft26is nevertheless higher than in theFIG. 3arrangement.

FIGS. 9 and 10are exploded views of the gear assembly16as particularly described in the preceding passages of this specification.

Any suitable mechanism could be adopted to cause the ring gear35to move between the two positions as shown byFIGS. 3 and 8respectively. In the particular arrangement shown, that mechanism includes a lever53pivotally mounted on the gear assembly body28and arranged to be moved about the pivot mounting by operation of the selector17. The lever53can be connected to the ring gear35in any suitable manner, such as by means of a linkage54(FIGS. 3 and 8).

It is preferred that the motor9is of the reversible type, and any suitable means may be adopted to enable selection of forward or reverse rotation of the chuck15. A drive direction selector facility may be provided at a convenient location, such as at the back end of the drill body2.

The drill1may be provided with means whereby adjustment of the chuck jaws18can be effected through operation of the motor9. Such power adjustment of the chuck15can be achieved in any suitable manner, and one example arrangement will now be described by reference toFIGS. 3,6,7and8.

In the example arrangement, locking means is provided enabling the chuck adjusting nut51to be releasably locked against rotation with the chuck head48. When the nut51is in that locked position, forward or reverse rotation of the chuck head48results in coaction between the jaws18and the nut51such that the position of the jaws18is adjusted inward or outwards, according to the direction of the rotation of the motor9. Various releasable locking arrangements could be adopted for the foregoing purpose. One example arrangement is shown in the accompanying drawings and is described below.

In the particular arrangement shown, a locking sleeve56is mounted on the gear assembly body28at a location within the drill body2adjacent the chuck15. The sleeve56is mounted so as to be moveable relative to the chuck15in the direction of the axis6.FIGS. 3 and 8show the sleeve56in a chuck unlocked condition, andFIGS. 6 and 7show the sleeve56in a chuck locked position. Locking engagement between the sleeve56and the chuck15can be achieved in any suitable fashion. In the arrangement shown, the sleeve56is provided with an internal spline57that is cooperatively engageable with an external spline58formed on the adjustment nut51. The sleeve56may be held against rotation relative to the body28by cooperative engagement between the spline57and an external spline59of a member60fixed to or forming part of the body28. Other arrangements could be adopted to hold the sleeve56against rotation whilst permitting it to move in the direction of the axis6.

The position of the sleeve56may be adjusted directly by the user, or by means of the mode selector17. When using the mode selector17, by way of example, the sleeve56may be connected to the ring gear35so as to move with that gear. Any suitable means may be adopted for that purpose including linkage means61connected to the selector lever53. Such simultaneous20movement of the sleeve56and the ring gear35is illustrated byFIGS. 3 and 8. That is,FIG. 8shows the ring gear35moved to the left of the position shown byFIG. 3, and also shows the sleeve56moved in the same direction to substantially the same extent.

The locked condition of the chuck nut51is achieved by moving the sleeve56to the right beyond the position shown byFIG. 3so that theFIG. 6position is adopted. It is preferred that the corresponding movement of the ring gear35is such as to leave that gear in meshing engagement with both the fixed ring gear34and the sun gear36. Under those circumstances, adjustment of the chuck jaws18is effected while the chuck head48is rotating in the slow speed mode. Other arrangements could be adopted.

After completion of a chuck adjustment operation, the selector17can be operated to select either the low speed mode (FIG. 3) or the high speed mode (FIG. 8). As will be apparent fromFIGS. 3 and 8, the sleeve56is separated from the chuck nut47in both of those situations.

It will be apparent from the foregoing description that a power tool incorporating the invention is convenient to use. It is also safe to use because of the absence of a key for enabling operation of the tool gripping device. Such keys can cause serious injury if left on the tool when the tool is operated. Furthermore operation of the tool gripping device is achieved without the user supplying a resisting force, thereby reducing the likelihood of damaging the user's hand. Other features and advantages of a power tool incorporating the invention will be apparent from the foregoing detailed description of an example embodiment of the invention.

Finally it is to be understood that various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention as defined in the accompanying claims.