Powered hand-tool

Abstract

 A powered hand-tool comprising a housing containing a motor and a shaft rotatably driven by the motor, the shaft extending, at least in use, to the exterior of the housing, the motor and shaft being movable with respect to the housing against resilient means also contained in the housing, such that pressing the shaft in a first direction directly or indirectly against a workpiece via the housing with a force sufficient to overcome a return force provided by the resilient means causes the shaft and the motor to move with respect to the housing in an opposite direction, such movement causing, in use, actuation of the motor, and hence rotation of the shaft.

Description

[0001] The present invention relates to powered hand-tools, for example electrical screwdrivers, drills, sanders and the like.

[0002] Push-to-start screwdrivers, which are actuated by pressing the head of the screwdriver against a screw which is abutted against a workpiece are known from US Patent Nos. 4,442,738, 5,044234 and 5,557,990. However the screwdriver disclosed in US 4,442,738 is fluid-operated (rather than electrically operated) and the screwdrivers disclosed in all of these US patents have extremely complex actuation mechanisms.

[0003] The present invention seeks to provide a push-to-start powered hand-tool, which has a simple construction and which is therefore simple to manufacture and operate. The invention is preferably a screwdriver and it will be described primarily with reference to screwdrivers, but the invention may comprise a drill, a sander or substantially any hand-tool which operates by rotation of a shaft and which may benefit from a push-to-start system.

[0004] Accordingly, the present invention provides a powered hand-tool comprising a housing containing a motor and a shaft rotably driven by the motor, the shaft extending, at least in use, to the exterior of the housing, the motor and shaft being movable with respect to the housing against resilient means also contained in the housing, such that pressing the shaft in a first direction directly or indirectly against a workpiece via the housing with a force sufficient to overcome a return force provided by the resilient means causes the shaft and the motor to move with respect to the housing in an opposite direction, such movement causing, in use, actuation of the motor, and hence rotation of the shaft.

[0005] The invention has the advantage that because the motor and the shaft are movable with respect to the housing, and because it is this movement which causes actuation of the motor and hence rotation of the shaft, the construction of the hand-tool may be simpler than that of the screwdrivers disclosed in the above mentioned US patents. In particular, because the motors of those prior art screwdrivers do not move with respect to their housings, their actuation mechanisms and the manner in which their screwdriver heads are rotably driven by their motors, are of necessity more complex than in the present invention. Such complexity causes considerable weight, size, and manufacturing time and cost disadvantages, as well as providing significant risk of mechanical failure. The relative simplicity of the present invention enables such disadvantages to be avoided.

[0006] In preferred embodiments of the invention, the actuation of the motor is caused by the movement of the motor and shaft with respect to the housing causing an electrical connection between the motor and an electrical power source forming part of, or external to, the hand-tool.

[0007] Advantageously, the actuation of the motor may be caused by the movement of the motor and shaft with respect to the housing bringing the motor into electrical connection with electrical contacts in the housing, the electrical contacts being connected, in use, to an electrical power source. Preferably the electrical power source is contained, in use, in the housing. Most preferably, the power source comprises a battery, especially a rechargeable battery. In a particularly preferred embodiment of the invention, the battery is situated generally adjacent to the motor.

[0008] The shaft which is rotatably driven by the motor is preferably elongate. However, the term "shaft" as used herein is intended to encompass substantially any drive means which is capable of transmitting torque supplied by the motor to the exterior of the housing to carry out the work of the powered hand-tool (whether it be screwing or unscrewing a screw fastener into or out of a workpiece, drilling a hole in a workpiece, sanding a workpiece, or any other suitable function). By "workpiece" is meant anything worked on by the tool.

[0009] Preferably, the shaft extends to the exterior of the housing through a front end thereof, and preferably the movement of the motor and the shaft that causes actuation of the motor is in a direction generally towards a rear end of the housing.

[0010] It is generally preferred for the resilient means to be situated between a rear surface of the motor (on the opposite side of the motor to the front end of the housing), and the rear end of the housing.

[0011] More preferably, the resilient means is situated between the rear surface of the motor and an abutment surface in the housing to the rear of the motor.

[0012] Preferably the resilient means comprises a spring, e.g. a compression spring. The preferred form of spring is a helical spring, but other forms of spring and/or other resilient means may be used.

[0013] In preferred embodiments of the invention, the electrical contacts extend generally forwardly towards the motor in a direction generally away from the rear end of the housing. More preferably, the electrical contacts extend generally forwardly and outwardly. Most preferably, the actuation of the motor is caused, in use, by electrical conductors attached to the motor touching the electrical contacts when the motor and shaft are moved with respect to the housing against the return force of the resilient means. A particularly convenient arrangement is one in which the resilient means is situated between the electrical contacts.

[0014] A particularly advantageous preferred feature of the invention is that the direction of rotation of the shaft when driven by actuation of the motor may be determined by the polarity of electrical connections between the motor and the power source. For example, the direction of rotation of the shaft may be reversed by rotating the motor with respect to the electrical contacts such that the polarity of electrical connections between the electrical conductors of the motor and the electrical contacts is reversed.

[0015] To this end, at least part of the motor may be retained in a front portion of the housing which is rotatable with respect to the remainder of the housing, rotation of the front portion of the housing causing the rotation of the motor.

[0016] Alternatively, the hand-tool may include a member which is movable with respect to the housing thereby to determine the polarity of the electrical connections between the motor and the power source. Preferably, when the movable member is in a first position the shaft rotates clockwise when actuated, and when the movable member is in a second position the shaft rotates anticlockwise when actuated. Advantageously, when the movable member is in its first position the movement of the motor and the shaft causes a first electrical connection (between the motor and the power source) to be made, and when the movable member is in its second position the movement of the motor and the shaft causes a second electrical connection (between the motor and the power source) to be made. Preferably, when the movable member is in a third position, the motor cannot be actuated.

[0017] The invention will now be described, by way of example, with reference to the accompanying drawings, of which:

Figure 1 is a perspective drawing of an embodiment of a screwdriver according to the invention;

Figure 2 is a perspective drawing showing the interior of the screwdriver shown in Figure 1;

Figure 3 is another perspective view showing the interior of the screwdriver shown in Figures 1 and 2;

Figure 4 is a simplified perspective cross-sectional view of the screwdriver shown in Figures 1 to 3;

Figure 5 (views (a) and (b)) shows details of another embodiment of a screwdriver according to the invention; and

Figure 6 shows a view of the interior of the screwdriver embodiment shown in Figure 5.

[0018] Figure 1 shows an embodiment of a hand-tool according to the invention, in the form of a powered screwdriver 1. The drawing shows a housing 3 of the screwdriver, the screwdriver having a front end 5 and a rear end 7. A shaft 9, containing a recess 11 into which replaceable screwdriver heads (not shown) may be inserted, extends from the interior to the exterior of the housing 3 through a front portion 13 of the housing.

[0019] Figures 2 and 3 show the screwdriver 1 with half of the main portion of the housing 3 removed so that the internal components of the screwdriver are visible. The housing 3 contains an electric motor 15 to which the shaft 9 is connected such that it may be rotatably driven by the motor. The motor 15 and shaft 9 are movable with respect to the housing 3 against a helical wire compression spring (not shown, for clarity) located in a cylindrical recess 17 between a rear surface 19 (see Figure 3) of the motor 15 and an abutment surface 21 in the housing behind the motor. In use, if the screwdriver is held by the housing 3 and the shaft 9 is pressed (directly or indirectly) against a workpiece via the housing in the first direction (as indicated by arrow A in Figure 2), with a force sufficient to overcome a return force provided by the helical spring located in recess 17, the shaft 9 and motor 15 will move with respect to the housing 3 in an opposite direction (as indicated by arrow B in Figure 2). The rear surface 19 of the motor 15 has electrical conductors 23 protruding from it (the electrical conductors being electrically connected to the motor). The rearward movement of the shaft 9 and motor 15 brings the conductors 23 into contact with forwardly and outwardly extending electrical contacts 25 located behind the motor 15. The electrical contacts 25 are electrically connected to the terminals (not shown) of a battery 27 located within the housing 3 generally adjacent to the motor 15. Consequently, the rearward movement of the motor 15 brings it into electrical contact with the terminals of the battery 27, thereby actuating the motor and rotating the shaft 9.

[0020] Therefore, in use, a screwdriver head is inserted into recess 11 of shaft 9, and the head is located against the head of a screw fastener which is itself abutted against a workpiece into which the screw fastener is to be screwed. The user holds the housing 3 of the screwdriver, and presses (in direction A) the shaft 9, screwdriver head and screw fastener against the workpiece via the housing 3 with a sufficient force to overcome the compression force of the helical spring located in recess 25 behind the motor 15. Consequently, the motor 15 and shaft 9 together move backwards within the housing 3 (in direction B) until the electrical conductors 23 touch the electrical contacts 25 and the motor is actuated by the battery 27, thereby rotating the shaft 9 and turning the screw via the screw-head located in recess 11.

[0021] Figure 4 shows a simplified diagram of the screwdriver with the battery excluded, for clarity, in cross-section, illustrating schematically that the shaft 9 and motor 15 comprise a single assembly which moves as a unit. The shaft 9 may be driven by the motor 15 via one or more gears or the like (not shown, for clarity).

[0022] The motor 15 and shaft 9 are located (as an assembly) in the front portion 13 of the housing 3 of the screwdriver. The motor 15 and shaft 9 are slidably retained in the front portion 13 so that they can slide in the forward and back directions A and B with respect to the front portion. However, the motor 15 and shaft 9 are prevented from rotating within front portion 13 by means of a longitudinal projecting ridge 29 of the motor 15 which is slidably located in a longitudinal channel 31 provided in an internal surface of the front portion 13 of the housing 3.

[0023] The front portion 13 of the housing is itself rotatable with respect to the remainder of the housing 3, about the main axis (shown in dashed lines in Figure 4) of the screwdriver 1. When the front portion 13 is rotated, the motor 15 and shaft 9 are rotated with it. This enables the direction in which the motor revolves and hence the direction of driven rotation of the shaft, to be reversed, since manually rotating the motor through 180° prior to actuation reverses the polarity that each of the electrical conductors 23 of the motor experiences when they contact the electrical contacts 25. The screwdriver may therefore be switched between clockwise and anticlockwise rotational modes by manually twisting the front portion 13 of the housing through 180° prior to actuation.

[0024] Figures 5(a) and 5(b) show details of the motor 15 and associated printed circuit board 33 of another embodiment of a screwdriver according to the invention. A view of the interior of this entire screwdriver embodiment is shown in Figure 6. In this embodiment, instead of the housing 3 including a rotatable front portion 13, a movable member 35 at the rear of the housing is used to determine the direction of rotation of the shaft 9 (as driven by the motor 15).

[0025] As shown in Figure 5(a), the printed circuit board (pcb) 33 attached to the rear surface 19 of the motor 15 includes flexible electrical contacts 25 and electrical conductors 23. As shown in Figure 5(b), the movable member 35 includes projections 37 which, when the movable member is in a first position (as drawn in Figure 5(b)) causes the two electrical contacts on the right hand side of the pcb 33 to form electrical connections with their respective electrical conductors 23 when the motor 15 is moved towards the rear of the housing. This causes rotation of the shaft in a first rotational direction. If the movable member is moved with respect to the housing in a direction perpendicular to the axis of the shaft to a second position, projections on the movable member will instead cause the electrical contacts on the left hand side of the pcb 33 to form electrical connections with their respective electrical conductors 23 when the motor is moved towards the rear of the housing. This causes rotation of the shaft in an opposite, second, rotational direction.

[0026] A part 39 attached to the pcb 33 and the motor 15, and interposed between the movable member 35 and the pcb, prevents the motor being pushed towards the rear of the housing when the movable member is in a third, central position (due to contact between the movable member and the part 39). The movable member 35 is movable from the exterior of the housing by means of buttons 41 situated on opposite sides of the exterior of the housing. The movable member 35 includes an aperture 43 to permit the compression spring 45 to extend between the rear of the housing and the part 39 (which is attached to the motor).

Claims

1. A powered hand-tool comprising a housing containing a motor and a shaft rotatably driven by the motor, the shaft extending, at least in use, to the exterior of the housing, the motor and shaft being movable with respect to the housing against resilient means also contained in the housing, such that pressing the shaft in a first direction directly or indirectly against a workpiece via the housing with a force sufficient to overcome a return force provided by the resilient means causes the shaft and the motor to move with respect to the housing in an opposite direction, such movement causing, in use, actuation of the motor, and hence rotation of the shaft.

2. A hand-tool according to Claim 1, in which the actuation of the motor is caused by the movement of the motor and shaft with respect to the housing causing an electrical connection to be made between the motor and an electrical power source forming part of, or external to, the hand-tool.

3. A hand-tool according to Claim 1 or Claim 2, in which the actuation of the motor is caused by the movement of the motor and shaft with respect to the housing bringing the motor into electrical connection with electrical contacts in the housing, the electrical contacts being connected, in use, to an electrical power source.

4. A hand-tool according to Claim 2 or Claim 3, in which the electrical power source is contained, in use, in the housing.

5. A hand-tool according to Claim 4, in which the power source comprises a battery, preferably a rechargeable battery.

6. A hand-tool according to Claim 5, in which the battery is situated generally adjacent to the motor.

7. A hand-tool according to any preceding claim, in which the shaft extends to the exterior of the housing through a front end thereof, and the movement of the motor and the shaft that causes actuation of the motor is in a direction generally towards a rear end of the housing.

8. A hand-tool according to Claim 7, in which the resilient means is situated between a rear surface of the motor on the opposite side of the motor to the front end of the housing, and the rear end of the housing.

9. A hand-tool according to Claim 8, in which the resilient means is situated between the rear surface of the motor and an abutment surface in the housing to the rear of the motor.

10. A hand-tool according to any one of claims 7 to 9, in which the resilient means comprises a spring.

11. A hand-tool according to Claim 7 when dependent upon Claim 3, in which the electrical contacts extend generally forwardly towards the motor in a direction generally away from the rear end of the housing.

12. A hand-tool according to Claim 11, in which the electrical contacts extend generally forwardly and outwardly.

13. A hand-tool according to Claim 11 or Claim 12, in which the actuation of the motor is caused, in use, by electrical conductors attached to the motor touching the electrical contacts when the motor and shaft are moved with respect to the housing against the return force of the resilient means.

14. A hand-tool according to any one of claims 11 to 13, in which the resilient means is situated between the electrical contacts.

15. A hand-tool according to Claim 2 or Claim 3, or any claim dependent thereon, in which the direction of rotation of the shaft when driven by actuation of the motor is determined by the polarity of electrical connections between the motor and the power source.

16. A hand-tool according to Claim 15 when dependent upon Claim 13, in which the direction of rotation of the shaft may be reversed by rotating the motor with respect to the electrical contacts such that the polarity of electrical connections between the electrical conductors of the motor and the electrical contacts is reversed.

17. A hand-tool according to Claim 16, in which at least part of the motor is retained in a front portion of the housing which is rotable with respect to the remainder of the housing, rotation of the front portion of the housing causing the rotation of the motor.

18. A hand-tool according to claim 15, further comprising a member which is movable with respect to the housing thereby to determine the polarity of the electrical connections between the motor and the power source.

19. A hand-tool according to claim 18, in which, when the movable member is in a first position the shaft rotates clockwise when actuated, and when the movable member is in a second position the other shaft rotates anticlockwise when actuated.

20. A hand-tool according to claim 19, in which, when the movable member is in its first position the movement of the motor and the shaft causes a first electrical connection (between the motor and the power source) to be made, and when the movable member is in its second position the movement of the motor and the shaft causes a second electrical connection (between the motor and the power source) to be made.

21. A hand-tool according to claim 19 or claim 20, in which, when the movable member is in a third position, the motor cannot be actuated.

22. A hand-tool according to any preceding claim, which comprises a screwdriver, a drill, a sander, or the like.

Drawing