EP2365502A1

EP2365502A1 - Power tools and switching apparatus therefor

Info

Publication number: EP2365502A1
Application number: EP10155766A
Authority: EP
Inventors: Endre Zador
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2010-03-08
Filing date: 2010-03-08
Publication date: 2011-09-14
Anticipated expiration: 2030-03-08
Also published as: CN102189533A; EP2365502B1; CN102189533B

Abstract

The present invention relates to power tools and switching apparatus therefor. In particular, it relates to switching apparatus for apparatus, such as power tools, particularly hedgecutters, which require two actuators to be gripped, one by each hand, usually for safety reasons, in order to provide power to the prime mover of the apparatus, such as an electric motor. We describe an apparatus for activating an electrical switch (30) for energising an electric motor. The switch has a switch actuator (30a, 30b) actuatable in an actuation direction by means of an actuation assembly. The actuation assembly comprises first and second operator-actuatable actuation members (11, 12, 33, 35, 44, 45) and is characterised in that the first and second actuation members (11, 12, 33, 35, 44, 45) each comprises a respective arm (20, 21, 42, 50), at least one of which arms (20, 21, 42, 50) includes a switch actuator bearing surface (27). The arms (20, 21, 42, 50) of the first and second actuation members are arranged such that the first and second actuator members (11, 12, 33, 35, 44, 45) are movable between a first configuration in which the switch actuator bearing surface (27) is spaced from the switch actuator (30a, 30b) in the actuation direction and in a direction orthogonal to the actuation direction; and a second configuration in which the switch actuator bearing surface contacts and depresses the switch actuator (30a, 30b). In moving between the first and second configurations, that arm on which the switch actuator bearing surface (27) is formed is adapted to move in a linear motion to align the bearing surface with the switch actuator and the other arm is adapted to move in an arcuate motion to draw the switch actuator bearing surface into operative engagement with the switch actuator (30a, 30b).

Description

The present invention relates to power tools and switching apparatus therefor. In particular, it relates to switching apparatus for apparatus, such as power tools, which require two actuators to be gripped, one by each hand, usually for safety reasons, in order to provide power to the prime mover of the apparatus, such as an electric motor.
Hedgecutters and chainsaws are two such tools, the two-handed switching arrangement ensures that the hands of the operator are kept well away from the moving components of the tool in use.
EP0214455 describes one arrangement, in a hedgecutter, in which each of the actuators is associated with a separate electrical switch such that the electrical circuit to the motor is only completed when both switches are operated.
EP0750837 , an earlier application of the present applicant, also describes a two-handed switching arrangement for a hedge cutter. This arrangement avoids the need for two separated switches. The arrangement comprises two pivotable actuators each of which actuators includes a rack each of which acts, when the actuators are pivoted, upon a common gear to lift a rod into actuating engagement with a microswitch.
The present invention seeks to provide a switching apparatus which avoids the need for two separated electrical switches and also avoids the need for a gear arrangement, with consequential reduced complexity and cost of construction.
Accordingly, in its broadest sense, the present invention comprises a power tool comprising an electrical motor adapted to be energised by means of an electrical switch including a switch actuator actuatable in an actuation direction by means of an actuation assembly; wherein the actuation assembly comprises first and second operator-actuatable actuation members; characterised in that at least one of the first and second actuation members comprises an arm comprising a switch actuator bearing surface; wherein the at least one arm of the first and second actuation members is arranged such that the first and second actuator members are movable between a first configuration in which the switch actuator bearing surface is spaced from the switch actuator in the actuation direction and in a direction orthogonal to the actuation direction; and a second configuration in which the switch actuator bearing surface contacts and depresses the switch actuator.
Preferably, each of the first and second actuation members comprises an arm and both arms are arranged to cooperate to cause the switch actuator bearing surface to contact and depress the switch actuator in the second configuration.
Preferably, in moving between the first and second configurations, that arm on which the switch actuator bearing surface is formed is adapted to move in a linear motion to align the bearing surface with the switch actuator and the other arm is adapted to move in a generally arcuate motion to draw the switch actuator bearing surface into operative engagement with the switch actuator.
In one embodiment, the first operator-actuatable actuation member has a generally L-shaped form formed by the arm and an elongate member, wherein the arm defines an angle with the elongate member which is variable in use.
In certain embodiments, the second operator-actuation member has a generally L-shaped form formed by the arm and an elongate member, wherein the arm defines an angle with the elongate member of the second actuation member which is variable in use.
The arm of at least one of the actuation members is advantageously mounted pivotally on the elongate member or is formed, suitably by moulding, as a unitary component which is flexible in the area of a junction between the arm and the elongate member.
In certain preferred embodiments, the switch actuator bearing surface is formed on a surface of the arm of the first actuation member; and the second actuation member is mounted for a pivotal movement at a point adjacent a junction between the arm and the elongate member.
In alternative embodiments, the switch actuator bearing surface is formed on a surface of the arm of the second actuation member and the second actuation member is mounted for pivotal movement at a point remote a junction between the arm and the elongate member and wherein the arm of the first actuation member further comprises a ramped surface adapted to bear, in use, against a corresponding surface to cause the arm to move towards the switch actuator.
The first actuation member is suitably mounted for pivotal movement at a point substantially intermediate the elongate member.
Alternatively, the first actuation member is an elongate member moveable between the first and second positions by means of a linear motion.
The above and other aspects of the present invention will now be described in further detail with reference, by way of example only, to the accompanying drawings, in which:

Figure 1 is a perspective view of the key components of a first embodiment of a switching apparatus in accordance with the present invention in a non-operative configuration;
Figure 2 is a part view of the apparatus in Figure 1 in another direction;
Figure 3 is a side view of the arrangements of Figure 1;
Figure 4 is an exploded view of the principal components of the embodiment of Figure 1;
Figures 5 and 6 are views corresponding to those of Figures 1 and 3 in a first intermediate configuration in which the rear actuator only has been moved to an operative position;
Figures 7 and 8 are views corresponding to those of Figures 1 and 3 in a second intermediate configuration in which the front actuator only has been moved to an operative position;
Figures 9 and 10 are views corresponding to those of Figures 1 and 3 in an operative configuration in which both the rear and front actuators have been moved to operative positions;
Figure 11 is a perspective view of a half-shell of a housing for a hedge cutter including the switching apparatus of Figures 1 to 10.
Figure 12 is a side view of a second embodiment of a switching apparatus in accordance with the present invention;
Figure 13 is a side view of a third embodiment of a switching apparatus in accordance with the present invention;
Figure 14 is a side view of a modification of the embodiment of Figures 1 to 11;
Figure 15 is a side view of a fourth embodiment of a switching apparatus in accordance with the present invention;
Figure 16 is a perspective view of the principle components of the embodiment of Figure 15; and
Figures 17 to 19 are side views of the embodiment of Figure 13 respectively in a first intermediate position, a second intermediate position and in an operative position.

With reference to Figures 1 to 4, the key components of a switching apparatus in accordance with the present invention include an electrical microswitch 10 associated with an electrical circuit providing electrical power to a motor (not shown) to provide motion appropriate to the apparatus, such as the blades of a hedgecutter (not shown); and first and second elongate pivotable actuator members 11, 12. In the specific arrangement shown, first actuator member 11 is intended to be actuated, in use, by the rearmost-placed hand of the operator and second actuator member 12 is indented to be actuated by the front most-placed hand. For clarity, in describing the embodiment shown, we will use the terms front and rear actuator members.
Front actuator member 12 is pivotable about a point substantially centrally along its length, carried on a front pin 13. Rear actuator member 11 is pivotable about a point towards the front thereof and carried on a rear pin 14. Pins 13, 14 are typically projections moulded integrally with a housing for the apparatus.
The switching apparatus also includes a first end stop 15, 16 respectively associated with the front and rear actuator members 12, 11 to provide a positive surface against which the user can depress the actuator members in use. In preferred embodiments, biasing means (not shown) are included to bias both actuators into the 'Off' configuration illustrated in Figures 1 to 3. A spring is a suitable biaising means, particularly a compression spring. The apparatus suitably also includes a second end stop 17, 18 associated with each actuator against which the actuators are biased by the biasing means in the 'Off' configuration.
The actuator members 11, 12 of this embodiment will now be described in further detail. The front actuator member 12 includes front actuator member arm 20 at the rear end thereof and the rear actuator member 11 includes rear member actuator arm 21 at the front end thereof. The arms 20,21 generally form an L-shape with the body or beam of the respective actuator member. Front actuator member arm 20 includes an elongate aperture 22 (Fig. 4) through which rear actuator member arm 21 can be inserted such that a rearward-facing distal surface portion 23 of rear actuator member 11 can contact a forward-facing distal surface portion 24 of front actuator member 12. In the preferred embodiment shown, the forward-facing surface of front actuator member arm 20 includes a longitudinal rib 25 at each side to act as a guide for rear actuator 21.
Aperture 22 also serves to provide that arm 20 has a degree of flexibility with respect to the main body of front actuator member 12. In the embodiment shown, aperture 22 extends into a portion of the main body of front actuator member 12 to enhance flexibility.
The distal portion of arm 20 of front actuator member 12 includes a bearing surface 27 on the rearward-facing surfaces thereof. Bearing surface bears, in use, against an actuator 30 of switch 10 to cause energising of the motor. In the embodiment shown, microswitch 10 includes two switch elements, each with a separate actuator 30a, 30b, such that both switching elements must be depressed to energise the motor. The two switch elements in the embodiment shown are associated with a construction of product in which the motor also supplies a regenerative braking function to stop the cutter blades quickly when either switch element is released. To achieve this one of the switches disconnects the motor from the mains supply and reconfigures its internal windings as a generator while the second switch then provides a short circuit across it to dissipate the system energy. With such an arrangement it is prudent to arrange for a momentary time delay between the switching points. This is achieved in the current design by small differences in the positions of the two parts of ramp 26 and in the heights of the two parts of bearing surface 27 so that both microswitch actuators are actuated by these features but with a slight delay.
The effect of the pivoting arrangement described above is that when the front actuator member 12 is operated, front arm 20 is caused to move downwardly by virtue of being centrally pivoted. Rear arm 21 of rear actuator member 11 is caused to move in an arc, drawing its distal end towards microswitch 10.
The operation of the switching apparatus will now be described in further detail. Figures 1 to 3 show the apparatus in the 'Off' configuration. Ramp 26 and bearing surface 27 of front actuator member arm 20 do not contact switch actuator 30. Figures 5 and 6 show the assembly in a first intermediate configuration in which the rear actuator member 11 has been moved into its operative position. As can be seen, pivoting of rear actuator member 11 about the pivot axis defined by rear pin 14 causes arm 21 to move in an arcuate manner to bear against arm 20 of front actuator member 12 causing it to be flexed towards switch actuator 30. However, ramp 26 and bearing surface 27 are at a position vertically spaced from switch actuator 30 and so do not make contact therewith. The electrical switch is not activated.
Figures 7 and 8 show the switching apparatus in a second intermediate configuration. In this configuration, front actuator member 11 has been moved into its operative position by pivoting about the pivot axis of front pin 13. This causes ramps 25 of arm 20 of front actuator 11 into an opposed orientation with switch actuator 30. However, bearing surface 27 is insufficiently close to switch actuator 30 to cause it to move into its motor- energising position. The electrical switch remains inactivated.
Figures 9 and 10 show the switching apparatus in the operative configuration in which both front and rear actuator members 11, 12 have been moved into their operative configurations. As will be appreciated, pivoting of front actuator member 12 has caused ramp 26 into an opposed orientation with respect to switch actuator 30 and pivoting of rear actuator 11 has pulled flexible arm 20 such that ramp 26 slides upwardly until bearing surface 27 pushes against switch actuator 30 thereby causing activation of the switch and energising of the motor. If either front or rear actuator is released, operative contact between bearing surface 27 and switch actuator 30 is removed, deactivating the electrical supply to the motor.
In an alternative embodiment (not shown) a pin and slot or other equivalent arrangement is provided between the distal portion of arm 20 in the region of either ramp 26 or bearing surface 27 and the adjacent contacting surface of rear actuator member 11 such that rearward facing distal surface portion 23 of rear actuator member 11 and forward facing distal surface portion 24 of front actuator member 12 are held in contact with but permitted to slide against one another. By this means release of the rear actuator will mechanically remove bearing surface 27 from contact with the switch actuators rather than this being achieved only by the natural resilience of arm 21 or the spring return of the switch actuators.
Figure 11 shows the arrangement described above in position in a housing half-shell of a hedge cutter. The motor, gearbox, blades and electrical connections are omitted for clarity.
A first alternative arrangement is illustrated in Figure 12. In the embodiment of Figures 1 to 11, the front actuator member 12 is moved into its operative position by means of an upward motion, by gripping the proximal end of the actuator with the fingers. In the embodiment shown in Figure 12, the front actuator member 31 is moved by means of a pushing movement applied to a proximal hand trigger 32. Front actuator member 31 of this embodiment thereby pivots in the rotationally opposite direction to that of Figures 1 to 11. Accordingly, the ramp on the distal portion of the arm of front actuator member is reversed in its direction, directly upwardly with respect to switch actuator 30 rather than downwardly.
A further alternative embodiment is shown in Figure 13. In this embodiment, a front actuator member 33, rather than being pivotable, is mounted for a simple sliding motion within the housing. The actuator can then be operated conveniently by the thumb or palm of the users hand.
Figure 14 shows a variation on the embodiment of Figures 1 to 11. Rather than arm 20 being formed integrally but flexibly with the main body of the front actuator member, the arm 34 is formed as a separate component hingedly mounted upon the main body 35 of the front actuator member. The operation of the apparatus is otherwise the same as for that of the first embodiment.
In the embodiments described above, the front and rear actuator members are interlinked and the switch actuating bearing surface is provided on a rearward facing surface of the front actuator member. The front actuator member is flexible or includes a hinged arm to allow the rear actuator member to pull it into engagement with the switch actuator 30. An alternative embodiment is shown in Figures 15 to 19. In this arrangement, front actuator member 40 comprises an elongate main body 41 a distal arm 42 flexibly formed with main beam 41 and a proximally formed trigger handle 43. As with the first embodiment, front actuator is pivotably mounted on a pin 44 at a point substantially centrally along the main beam 41.
Rear actuator member 45 is pivotally mounted at the rear thereof, again upon a pin 46 suitably formed as an element of the apparatus housing. Rear actuator member 45 includes a rear actuator member arm 50 generally as described above. However, the arms 42, 50 of the front and rear actuators are not interlinked. Arm 50 is, in this embodiment, flexibly formed with the elongate main body of the rear actuator. The ramp and bearing surface which act to engage and depress the microswitch actuator are, in this embodiment, formed on the rearward-facing surface of arm 50 of the rear actuator member. Vertical alignment of the bearing surface with the switch actuator 30 is accordingly provided by movement of the rear actuator member, rather than the front actuator member. Horizontal alignment is correspondingly provided by movement of the front actuator member 40. Distal arm 42 of front actuator member 40 includes, towards its distal end, a rearward-facing flat surface 50 which slides, in use, against a corresponding forward-facing surface 51 on the rear actuator member. The forward-facing surface of distal arm 42 includes a wedge-shaped portion 53 which bears against a guide pin 54 provided in the housing opposite switch actuator 30 as the front actuator member 40 is moved from its non-operative or 'Off' position as shown in Figure 13 to its operative position as shown in Figures 17 and 18.
Figure 15 shows both front and rear actuator member 40, 45 in their non-operative or rest positions. Fig. 17 shows the effect of operation of the rear actuator member 45. As rear actuator member 45 is pulled by the user, it pivots about its rear-positioned pivot axis 55 until it bears against end stop 16. At this point, switch actuating bearing surface 27 becomes positioned opposite switch actuator 30 of the microswitch 10. In Figure 18, the rear actuator member remains it its non-operative position and the front actuator member 40 has been moved into its operative position, pivoting about a generally central pivot axis at pin 44 until it contacts end stop 15. Wedge shaped portion 53 has been guided by guide pin 54 into closer proximity with switch actuator 30, distal arm 42 flexing with respect to the main body 41 of front actuator 40. In flexing, arm 42 of front actuator member 40 pushes against arm 50 of rear actuator 45. However, wedge-shaped portion 53 of arm 50 is not raised to become positioned opposite the switch actuator 30. Accordingly, the electrical switch 10 remains in the `Off position.
Figure 19 shows the 'On' configuration in which both front and rear actuator members are in their operative positions. Wedge-shaped portion 53 has been elevated to oppose switch actuator 30 and ramp 26 has been depressed and flexed into a bearing position against arm 50 of the rear actuator to push wedge-shaped portion 53 against switch actuator 30. It will be appreciated that the thickness of arm 50 at the position of the bearing surface 27 combined with that of wedge-shaped portion 53 is selected to exceed the rest separation between switch actuator 30 and guide pin 54 by an amount sufficient to cause electrical actuation of switch 10.
In an alternative embodiment (not shown) a pin and slot or other equivalent arrangement is provided between the distal portion of arm 50 in the region of either ramp 26 or bearing surface 27 and the adjacent contacting surface of front actuator member 40 such that rearward facing flat surface 50 and forward facing surface 51 are held in contact with but permitted to slide against one another. Additionally pin and slot or other equivalent arrangements are provided to retain wedge portion 53 in contact with guide pin 54 while permitting it to slide as required. By this means release of either actuator will mechanically remove bearing surface 27 from contact with the switch actuators rather than this being achieved only by the natural resilience of arms 50, 42 or the spring return of the switch actuators.

Claims

A power tool comprising an electrical motor adapted to be energised by means of an electrical switch (30) including a switch actuator (30a, 30b) actuatable in an actuation direction by means of an actuation assembly; wherein the actuation assembly comprises first and second operator-actuatable actuation members (11, 12, 33, 35, 44, 45); characterised in that at least one of the first and second actuation members (11, 12, 33, 35, 44, 45) comprises an arm (20, 21, 42, 50), comprising a switch actuator bearing surface (27); wherein the at least one arm (20, 21, 42, 50) of the first and second actuation members is arranged such that the first and second actuator members (11, 12, 33, 35, 44, 45) are movable between a first configuration in which the switch actuator bearing surface (27) is spaced from the switch actuator (30a, 30b) in the actuation direction and in a direction orthogonal to the actuation direction; and a second configuration in which the switch actuator bearing surface contacts and depresses the switch actuator (30a, 30b).
A power tool as claimed in claim 1 wherein each of the first and second actuation members comprises an arm (20, 21, 42, 50) and both arms are arranged to cooperate to cause the switch actuator bearing surface to contact and depress the switch actuator in the second configuration.
A power tool as claimed in claim 1 or claim 2 wherein, in moving between the first and second configurations, that arm on which the switch actuator bearing surface (27) is formed is adapted to move in a linear motion to align the bearing surface with the switch actuator and the other arm is adapted to move in an arcuate motion to draw the switch actuator bearing surface into operative engagement with the switch actuator (30a, 30b).
A power tool as claimed in any one of claims 1 to 3 wherein the first operator-actuatable actuation member (11) has a generally L-shaped form formed by the arm and an elongate member, wherein the arm defines an angle with the elongate member which is variable in use.
A power tool as claimed in any one of claims 1 to 4 wherein the second operator-actuation member (12) has a generally L-shaped form formed by the arm and an elongate member, wherein the arm defines an angle with the elongate member of the second actuation member which is variable in use.
A power tool as claimed in claim 4 or claim 5 wherein the arm of at least one of the actuation members is pivotally mounted on the elongate member.
A power tool as claimed in claim 4 or claim 5 wherein at least one of the actuation members is formed as unitary component which is flexible in the area of a junction between the arm and the elongate member.
A power tool as claimed in any one of claims 4 to 7 wherein the switch actuator bearing surface is formed on a surface of the arm (20) of the first actuation member; and the second actuation member is mounted for a pivotal movement at a point adjacent a junction between the arm and the elongate member.
A power tool as claimed in any one of claims 4 to 7 wherein the switch actuator bearing surface is formed on a surface of the arm (50) of the second actuation member (45) and the second actuation member (45) is mounted for pivotal movement at a point remote a junction between the arm and the elongate member and wherein the arm (42) of the first actuation member (40) further comprises a ramped surface adapted to bear, in use, against a corresponding surface (54) to cause arm (42) to move towards switch actuator (30a, 30b).
A power tool as claimed in any preceding claim wherein the first actuation member is mounted for pivotal movement at a point substantially intermediate the elongate member.
A power tool as claimed in any one of claims 1 to 3 wherein the first actuation member is an elongate member moveable between the first and second positions by means of a linear motion.
A power tool as claimed in any preceding claim in the form of a vegetation cutting apparatus, preferably a hedge cutter.