Power tool having interchangeable tool head

Abstract: A power tool (10) includes a motor (22) mounted there within. The motor has an output (20) for engagement with an input of an attachment member (32) presented thereto. The coupling between the motor output (20) and the attachment member (32) is by means of a snap-fit coupling achieved by way of resiliently biased arms (56) within the tool engaging with an annular recess (54) formed on the attachment member (32).

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. Even with such a proposed solution problems still exist, however. It has been found that the user perceives as either problematic or irritating the fact that interchanging such discrete attachments can take some time. Very often the user needs to ensure accurate mating of the connecting parts and this may also entail manually connecting the individual component parts by, for example, a nut and bolt connection. It is thus an object of the present invention to at least alleviate the aforementioned shortcomings by provision of a power tool whereby discrete attachments may be readily and easily coupled and decoupled from the body of the tool without the need for a separate manual connection operation, such as the one described above, by the user of the tool. According to the present invention there is provided a power tool comprising a body portion having a housing defining a handle and a motor mounted within the housing, which motor is arranged to drive an axially extending 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; and within which opening of the body portion is a first engagement means for selective engagement with co-operable second engagement means formed on or from one of the plurality of attachment members; the tool characterised in that the first engagement means is moveable between a first position to couple with the second engagement means and a second position uncoupled from the second engagement means; and wherein the second engagement means comprises a spigot projecting from an attachment member, which spigot defines an annular recess electively co-operable with the first engagement means thereby to restrain the attachment member from axial displacement relative to the body portion. Power tools according to the preamble of claim 1 are known from DE 1 902 315 U or BE 643 674A. Preferably the first engagement means is biased so as to be urged into engagement with the co-operable second engagement means in its rest position. This provides that once the co-operable second engagement means is in position, it will remain there and be restrained by the first engagement means. In a preferred embodiment the first engagement means is spring biased into its rest position. Additionally it is possible that the first engagement means comprises a plurality of arms. Advantageously the co-operable second engagement means, when presented to the first engagement means is held in rigid engagement with the body portion by the first engagement means. This means that the power tool is then automatically in a state of readiness to be used. Advantageously when the co-operable second engagement means is presented to the first engagement means the spigot of the second engagement means acts against the biasing of the first engagement means thereby to enable coupling of the co-operable second engagement means with the first engagement means. Preferably the coupling between the co-operable second engagement means and the first engagement means is a snap-fit coupling. This ensures that the body portion and the attachment member are definitely in correct engagement in order for the user to be able to start to use the tool. Preferably the spigot is arranged as a tapered leading edge of the co-operable second engagement means. Advantageously the first engagement means includes a manually operable release member to release the selective engagement between the first engagement means and the co-operable second engagement means. This allows the user to readily separate the attachment member portion from the body. Preferably the release member acts against the biasing of the first engagement means. It is also desirable that the release member acts to cause the arms to move. 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, and; Figures 6(a) and 6(b) show respectively a view of an attachment member in accordance with the present invention which has been laterally sectioned from above and then also from above, but with the member having been turned upside down. 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-operatively engage 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 shaped so as to provide the user with easy access to an actuating switch means (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 means (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 means (12) in conventional manner. On activation of the switch means (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 (labeled 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, 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 Figure 4 in addition to 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 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 fit snugly within the opening and mate with the outer periphery of the body portion (4). As the drill/driver mechanism (32) is brought into position an angled edge (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 means (12) permanently open. This provides a form of safety release mechanism which prevents accidental actuation of the switch means (12) until such times as the attachment member, or, as in this example, the drill/driver mechanism (32) is in position. The drill/driver mechanism (32) has a drive 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 (22). It will be appreciated that when the male and female cogs of the output spindle (20) and the drive spindle (40) mate together, then actuation of the motor (22) will cause simultaneous rotation of the output spindle (20) and the drive 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) is free to 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 drive 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 drive spindle (40). By referring then also to Figures 6(a) and 6(b) the method of attachment of the drill/driver mechanism (32) to the body portion (4) will now be described. Those skilled in the art will appreciate that whilst in this example a drill/driver mechanism (32) is described as an attachment member, any suitable power tool means may be employed as an alternative. For example, instead of a drill/driver mechanism (32) a sander or a jigsaw could form the attachment member. As, however the choice of attachment purpose is not relevant to the present invention no further reference thereto will be made herein. As can be seen from Figure 6(a) the drill/driver mechanism (32) includes a main member (46) which has there within the functional mechanism for taking the rotary output of the spindle (20) and turning that into a geared rotary output for the drill/driver mechanism. It is the right hand end of the drill/driver mechanism (32) as viewed from Figure 6 which is presented to the opening (18) of the body portion (4). The drill/driver mechanism (32) has at this end a co-operable second engagement means which in this example is a spigot (48). This spigot (48) is formed so as to have two tapered annular rings (50,52) at the foremost portion thereof. The purpose of these tapered annular rings (50,52) will be described here below. The co-operable second engagement means also defines an annular recess (54) for co-operation with a first engagement means which is formed from the body portion (4) within the opening (18). In this example the first engagement means comprises a plurality of biased arms (56) which are shown more clearly in Figures 2,3 and 4. The biased arms are, in this example, spring biased by means of their shape into a rest position which is at least no wider than the maximum diameter of the annular recess (54). When the user wishes to insert the drill/driver mechanism (32) into the opening (18) and thereby to engage it with the body portion (4) so that the rotation of spindle (20) will cause simultaneous rotation of the female member (42) of the drill/driver mechanism (32) the following procedure is carried out: The user presents the spigot (48) into the opening (18) such that in addition to the operation described above with reference to the tapered edge (34) and pivotal release mechanism (36), the tapered annular rings (50,52) will force apart the arms (56) because as can be seen, particularly from Figure 6(a) given that the separation of the arms (56) is no greater than the diameter of the annular recess (54) then clearly the tapered edges will splay or force apart the arms (56). Continued insertion of the mechanism (32) into the opening (18) will cause the arms (56) to snap-fit into place within the recess (54) when aligned therewith due to their spring biasing. In this manner therefore the user will hear a "click" when the snap-fit connection is in place and will therefore know that the entire tool is now ready for use. Furthermore, if for any reason the user attempts to pull the drill/driver mechanism (32) from the body portion (4) this will not be possible due to the engagement between the arms (56) and the annular recess (54). When the user wishes to remove or change the drill/driver mechanism (32) the operation requires depressing of a manually operable release member, in this example a button (58), whose depression causes the arms (56) to splay apart. The user must ensure that sufficient force is applied to depress the button (58) by sufficient amount to enable splaying of the arms (56) apart by an amount sufficient to clear the annular recess (54) and also the annular ring upon which particularly the tapered ring (52) is formed. Once this has occurred the user may simply then pull or withdraw the drill/driver mechanism (32) from the opening (18). Thus by the above operation the user is able to selectively engage the body portion (4) with the drill/driver mechanism (32). Although in the Figures 6(a) and 6(b) the chuck mechanism itself is not described in any detail it would be apparent to those skilled in the art that the chuck head (44) will form part of this mechanism but has not been shown for the reasons of clarity. 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). Those skilled in the art will appreciate that whilst in the above example a battery powered tool has been described there is no necessity for this to be the case. The advantages of the present invention are equally efficacious with corded or so called mains powered tools as well as battery operated.

Claims: A power tool (10) comprising a body portion (4) having a housing defining a handle and a motor (22) mounted within the housing, which motor (22) is arranged to drive an axially extending 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 (32) presented thereto; and within which opening of the body portion is a first engagement (56) means for selective engagement with co-operable second engagement (48) means formed on or from one of the plurality of attachment members; the tool characterised in that the first engagement means is moveable between a first position to couple with the second engagement means and a second position uncoupled from the second engagement means; and wherein the second engagement means comprises a spigot (48) projecting from an attachment member, which spigot defines an annular recess (54) selectively co-operable with the first engagement means to thereby restrain the attachment member from axial displacement relative to the body portion. A power tool according to Claim 1 wherein the first engagement means defines a rest position and is biased so as to be urged into engagement with the second co-operable engagement means (48) in this rest position. A power tool according to Claim 2 wherein the first engagement means (56) is spring biased into its rest position. A power tool according to any one of Claims 1-3 wherein the first engagement means (56) comprises a plurality of arms (56). A power tool according to any one of the preceding claims wherein the co-operable second engagement means (48) when presented to the first engagement means is held in rigid engagement with the body portion (4) by the first engagement means. A power tool according to Claim 5 when appendant to Claim 2 wherein when the co-operable second engagement means is presented to the first engagement means the spigot (48) of the second engagement means acts against the biasing of the first engagement means thereby to enable coupling of the co-operable second engagement means with the first engagement means. A power tool according to Claim 6 wherein the coupling between the co-operable second engagement means and the first engagement means is a snap-fit coupling. A power tool according to either Claim 6 or Claim 7 wherein the spigot (48) is arranged as a tapered leading edge (50) of the co-operable second engagement means. A power tool according to any one of the preceding claims wherein the first engagement means includes a manually operable release member to release the selective engagement between the first engagement means and the co-operable second engagement means. A power tool according to Claim 9 when appendant to Claim 2 wherein the release member acts against the biasing of the first engagement means. A power tool according to Claim 10 when appendant to Claim 4 wherein the release member acts to cause the arms (56) to move.

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