Power tool having interchangeable tool head

Abstract: A power tool (2) includes a motor (22) pivotally mounted within the housing of the tool. The tool is able to accept any one of a plurality of attachment members (32). The motor (22) is adapted to pivot in order that accurate axial alignment with any one of the attachment members presented to the motor occurs.

Description: The present invention relates to a power tool and has particular although not exclusive, relevance to battery powered tools. It is conventional for power tools to be designed and built for a dedicated purpose, such as a drill, a jigsaw or a sander. If the user needs to undertake a sanding operation he will use a dedicated sander. If then he needs to drill a hole in a workpiece he will swap the sander for a dedicated drill, and so on. Whilst such swapping over of dedicated tools is not inconvenient, it does mean that, particularly for the person who needs to use power tools relatively infrequently, considerable expense is incurred in acquiring a broad range of these dedicated power tools. Furthermore, in the case of so-called "cordless" or battery-powered tools, the user will either need to change the battery pack when changing dedicated tools, or have several ready-charged batteries available for use. These alternative options are cumbersome or expensive respectively. Solutions to the above problems have been proposed in the past and one such solution entails providing a power tool including a motorised drive which is capable of accepting any one of a plurality of discrete attachments which achieve a dedicated purpose. This means that rather than purchasing a dedicated entire power tool for each job, the user only has to purchase a dedicated attachment (which is cheaper than a dedicated entire tool) and just swap these over as and when necessary. There still exist certain problems with such solutions, however. In a system such as the discreet attachments described above, it is important to achieve a high degree of alignment between the body of the tool providing the drive and the attachment which receives the drive. In the case of a rotational drive such as a drive shaft, a high degree of axial alignment between the driving and driven shafts is imperative in order to achieve an efficient transfer of energy between the two and also to avoid creating unnecessary mechanical wearing at the interface between the shafts. In US-3,772,542 there is shown a tool with an outer plastics shell which deforms under pressure, to avoid this shell deformation causing stress or misalignment between the motor and the tool output spindle, two dimentially opposed resilient mounting blocks are applied between the stator of the motor and the inner surface of the shell. It is an object of the present invention to at least alleviate the aforementioned shortcomings by providing a power tool including a body portion defining a handle and a motor mounted within the body portion, which motor is arranged to drive an output spindle of the tool; the body portion further defining an opening around the output spindle, which opening accepts any one of a plurality of attachment members presented thereto, the power tool characterised in that the motor is mounted within the housing by a plurality of supports spaced along the axial length of the motor and wherein at least one of the supports of the plurality does not rigidly contact the motor, thereby to permit the motor to move within its mounting. Thus, by enabling the motor of the body portion of the tool to move, a high degree of axial and positional alignment between the output spindle of the motor and the rotational drive of the attachment may be achieved because this degree of movement permits of automatic co-axial alignment between the two parts. Preferably at one end of the axial length of the motor a plurality of supports make rigid contact therewith and at the other end of the axial length of the motor at least one of the supports of the plurality do not rigidly contact the motor thereby allowing the motor to pivot about the point at which it is in rigid contact with the said supports. By provision of pivoting movement of the motor, the amount of movement, or "play" exhibited by the motor may be limited and have any unnecessary movement avoided. Additionally or alternatively the motor, at either end of its axial length, is formed in circular cross-section and the supports of the plurality are found therearound. This shape permits a method of construction of the power tool which is relatively easy to assemble. In a preferred embodiment the plurality of supports is formed from, or integrally with, the body portion itself. Also the body portion may be formed in two halves which two halves come together and thereby encapsulate the motor therewithin. The present invention will now be described, by way of example only and with reference to the accompanying drawings, of which:- Figure 1 shows a front perspective view of a body portion of a power tool in accordance with the present invention; Figure 2 shows a part cut-away view of the body portion of Figure 1; Figure 3 shows a side part-sectioned view of the body portion of Figure 1 without an attachment member presented thereto; Figure 4 shows a side part-sectioned view of the body portion of Figure 1 with an attachment member presented thereto; Figure 5 shows an end-on part cut-away view of Figure 4; Figure 6 shows a side view of one of the plurality of attachment members to be presented to the body portion. This is a drill/driver mechanism for a drill; Figure 7 shows an alternative attachment to Figure 6, this being a jigsaw attachment, and; Figure 8 shows yet another attachment, this being a sander. By referring firstly to Figure 1, a power tool shown generally as (2) includes a body portion (4) formed from two halves of a plastics clamshell. The two halves (6,8) co-operate together to encapsulate the internal mechanisms of the power tool, which will be described here below. The body portion (4) defines a handle (10) which in use of the tool (2) is grasped by the user. The handle (10) is so shaped to provide the user with easy access to an actuating trigger (12) in the form of a pistol grip, which is conventional in the art of power tools. The body portion (4) is formed from the two halves of clamshell (6,8) also to define an opening shown generally as (14), through which batteries (16) for powering the tool may pass. Those skilled in the art will appreciate that the choice of batteries for powering the tool (2) depends upon the work which the tool is required to undertake. The batteries per se form no part of the present invention and so will not be described in any more detail herein. At the opposite end of the body portion (4) from the battery opening (14) the two halves of the clamshell (6,8) define an opening (18) through which an output spindle (20) of a motor (22) housed within the body portion (4) (and shown in more detail in Figure 2) is mounted. By referring now also to Figures 2 and 3, the internal mechanism of the tool (2) will be described in more detail. In Figure 2 it will be understood that the half clamshell (6) has been removed for clarity. It can be seen that through the battery opening (14) a pair of batteries (16) have been passed and are electrically coupled via terminals (24) and switch (12) to the motor (22). The batteries (16) are retained within their opening (14) by a detent mechanism (26) which can be manually operated in order to allow the removal of the batteries (16) from the body portion (4). The motor (22) is selectively coupled to the batteries (16) via the switch (12) in conventional manner. On activation of the switch (12) the user selectively couples the motor (22) to the battery (16) thereby energising the motor (22) which in turn provides a rotational force upon the output spindle (20). In example shown the output spindle (20) has connected thereto a cog for reasons which will become apparent hereinafter. As is conventional in the art of power tools the motor (22) is provided with a forward/reverse switch (28) the operation of which determines the sense of rotation of the output spindle (20). Whilst remembering of course that the half clamshell (6) is not shown in Figure 2, although the motor (22) is mounted within the body portion (4), a plurality of ribs (30) actually provide support to the motor (22) within the body portion (4). The ribs (30) can be seen more clearly from Figures 2 and 3. It is important to note that in the example shown in these figures, the foremost rib (labelled 30(a)) does not actually contact the motor (22) itself, but stops slightly short thereof. It will be apparent that due to the foremost rib (30(a)) not directly contacting the motor (22) itself, that therefore the motor (22) has a slight degree of movement within its mounting position provided by the plurality of ribs (30). It will also be apparent to those skilled in the art that any one or ones of the combination of the plurality of ribs (30) may stop short of directly contacting the motor (22). The direct contact between the ribs (30) and the motor (22), when it does occur, needs to be rigid thereby to provide a good degree of support to prevent the motor (22) moving at this point of contact. Where the rib (30(a)) is deliberately designed to stop short of and therefore not form any direct or rigid contact with the motor (22), then this permits for movement of the motor (22) relative to the rib (30). Because in the example shown the foremost rib (30 (a)) allows a small degree of movement of the motor (22) adjacent thereto, it will be apparent that the output spindle (20) will thus have a slight degree of movement or "play". This degree of "play" occurs in a plane defined by an orthogonal set of axis (conventionally termed x-y). The x-y axis within which the spindle (20) is free to have a limited degree of movement is shown more clearly in Figure 5. Referring now particularly to Figures 4 and 6 in addition to all other Figures 1 to 3 and 5, it can be seen that a power tool (2) has had presented thereto an attachment member (32), in this example a drill/driver mechanism (32) for driving a drill bit. It can be seen that the drill/driver mechanism (32) is presented to the body portion (4) at the opening (18) for the output spindle (20). The outer periphery of the drill/driver mechanism (32) is shaped so as to co-operate within the opening and mate with the outer periphery of the body portion (4). A plate member (100) defining a circular hole is formed from the body portion (4) within the opening (18). The plate member (100) is arranged to have a diameter substantially the same as the diameter of the outer periphery of the foremost tapered annular flange (102) formed on the drill/driver mechanism (32). Due to the substantial matching of these diameters, on presentation of the drill/driver mechanism (32) to the opening (18), the insertion of annular flange (102) into plate member (100) the former will be accurately located within the latter. The taper on the front face of flange (102) serves to aid the accurate location necessary. As the drill/driver mechanism (32) is brought into position a tapered protrusion (34) thereof abuts against a pivotally moveable release mechanism (36). When this occurs the right-hand side of the pivotal release mechanism (36) moves down as one views Figure 4, and the left-hand side moves up thereby allowing the projecting peg (38) to be removed from its previously biased position wherein it held the switch (12) permanently open. This provides a form of safety release mechanism which prevents accidental actuation of the switch (12) until such times as the attachment member, or, as in this example, the drill/driver mechanism (32) is in position. The attachment member (32) has a driven spindle (40) to which is coupled at its end a female cog member (42) which is designed to engage with the male cog on the output spindle (20) of the motor. It will be appreciated that when the male and female cogs of the output spindle (20) and the driven spindle (40) mate together, then actuation of the motor (22) will cause simultaneous rotation of the output spindle (20) and the driven spindle (40) thereby rotating the head (44) of the drill/driver mechanism (32). It is the presentation of the drill/driver mechanism (32) to the opening (18) of the body portion (4) which requires a more detailed description of the movement of the motor (22) within its plurality of mounted ribs (30). As the motor (22) axis is free to conically pivot slightly about its rear mounting portion defined by those of the plurality of ribs (30) which sit in rigid direct contact with the motor, this therefore allows an automatic alignment to occur between the axis of rotation of the motor spindle (20) and the axis of rotation of the driven spindle (40). If this were not the case, i.e. if the motor were not free to move slightly, then on presentation of the drill/driver mechanism (32) to the opening (18), there will be no guarantee of an accurate axial alignment of both the motor (22) and its output spindle (20) for the drill/driver mechanism (32) and its driven spindle (40). It will be apparent that the motor (22) is formed in circular cross-section this is chosen as being advantageous for allowing the ribs (30) of the plurality thereof to be shaped so as to accommodate the motor (22) more easily. There is no necessity for the motor (22) to have a circular cross-section or indeed the drill/driver mechanism (32) or their respective spindles (20,40). The ribs (30) of the plurality thereof have been formed from the plastics material of the clamshell halves (6,8). If desired the ribs (30) could be formed from separate members such as metal or other plastics members glued or otherwise stuck to the clamshell halves (6,8). Referring now briefly to Figures 6 to 8, different ones of the plurality of attachment members are shown. Figure 6 shows a drill attachment (46) for presenting to the body portion (4) and coupling thereto via the opening (18). Figure 7 shows a jigsaw attachment (48) and Figure 8 shows a sander attachment (50). Whilst those skilled in the art will appreciate that the internal mechanisms of each of the attachment members (46, 48 and 50) will be different and adapted to suit the purpose of each attachment member, this is not germane to the present invention and so will not be described herein. For the purposes of the present inventions, it is sufficient to appreciate that each of these attachment members (46, 48 and 50) must be presented and coupled to the body portion (4) as already herein described. It will be understood by those skilled in the art that the term "rigid" is intended to cover solid, rather than resilient contact. Thus it would be possible to form the ribs (30) of a resilient material which permanently contacted the motor (22), or indeed coat the motor in a resilient material, such as silicone rubber, whilst still remaining within the scope of the present invention.

Claims: A power tool including a body portion (4) defining a handle (10) and a motor (22) mounted within the body portion, which motor is arranged to drive an output spindle (20) of the tool; the body portion further defining an opening (18) around the output spindle, which opening accepts any one of a plurality of attachment members (46, 48, 50) presented thereto, the power tool characterised in that the motor is mounted within the housing by a plurality of supports (30), spaced along the axial length of the motor and wherein at least one of the supports (30a) of the plurality does not rigidly contact the motor, thereby to permit the motor to move within its mounting. A power tool according to Claim 1 wherein at one end of the axial length of the motor a plurality of supports (30) make rigid contact therewith and at the other end of the axial length of the motor at least one of the supports (30) of the plurality do not rigidly contact the motor thereby allowing the motor to pivot about the point at which it is in rigid contact with the said supports. A power tool according to Claim 2 wherein the other end of the axial length of the motor (22) is the output end of the motor. A power tool according to any one of the preceding claims wherein the motor (22), at either end of its axial length, is formed in circular cross-section and the supports of the plurality are found therearound. A power tool according to any one of the preceding claims wherein the plurality of supports (30) is formed from, or integrally with, the body portion (4) itself. A power tool according to any one of the preceding claims wherein the body portion (4) is formed in two halves, which two halves come together and thereby encapsulate the motor (22) therewithin. A power tool according to any one of the preceding claims wherein the motor (22) is connected to the output spindle (20).

Inventors: WADGE BRIAN, WADGE, BRIAN
Applicants: BLACK & DECKER INC, BLACK & DECKER INC.
Application year: 1998
Main classification: B25F3
IPC codes: B25F5, B25F3