Information
-
Patent Grant
-
6812425
-
Patent Number
6,812,425
-
Date Filed
Monday, November 24, 200320 years ago
-
Date Issued
Tuesday, November 2, 200419 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Leydig, Voit & Mayer, Ltd.
-
CPC
-
US Classifications
Field of Search
US
- 200 522
- 200 318
- 200 321
- 200 322
- 200 3322
- 200 334
-
International Classifications
-
Abstract
A trigger mechanism for a power tool, comprises a chassis, a trigger mounted movably to the chassis, and an electrical switch mounted to the chassis and activated by movement of the trigger between ON and OFF positions to close and open an electrical circuit. A locking mechanism attached to the chassis is user-activated to unlock the trigger in the OFF position and trigger-activated to release the trigger in the ON position. The mechanism includes a single, spring-loaded locking pin arranged to lock the trigger in both the ON and the OFF positions.
Description
The present invention relates to an electric trigger switch of the type intended for use in a hand-held power tool such as an electric drill or rotary drive tool for example.
BACKGROUND OF THE INVENTION
More particularly, although not exclusively, the invention relates to an electric trigger switch with a locking mechanism enabling the trigger to be locked in ON and OFF positions.
It is known to provide locking mechanisms for power tool trigger switches. These mechanisms typically include a pushbutton enabling the trigger to be locked down in the ON position, so that there is no need for a user to keep pulling the trigger. Inadvertent depression of the trigger from the OFF position to the ON position presents a safety risk.
It is an object of the present invention to overcome or substantially ameliorate the above problem and/or more generally to provide an improved locking trigger switch for a power tool.
SUMMARY OF THE INVENTION
According to the invention, there is provided a trigger mechanism for a power tool, comprising a chassis, a trigger mounted to the chassis for movement between ON and OFF position, and an electrical switch mounted to the chassis for activation by movement of the trigger between the ON and OFF positions to close and open an electrical circuit. A locking mechanism attached to the chassis is included, that being user-activated to unlock the trigger in the OFF position and trigger-activated to release the trigger in the ON position.
Preferably, the trigger is mounted pivotally to the chassis.
More preferably, the trigger mechanism includes an activating rod extending from the trigger to the electrical switch.
In a preferred embodiment, the locking mechanism comprises a single locking member arranged to lock the trigger in both the ON and the OFF positions.
More preferably, the locking member comprises a locking pin extending through the trigger and the chassis.
Further more preferably, the locking mechanism includes a locking plate fixed to the trigger and having a slot through which the locking pin passes.
Yet further more preferably, the locking pin has a narrow shank portion and a wide shank portion, and the slot of the locking plate has a width through which the narrow shank portion can pass to permit movement of the trigger and a widening at one end through which the wide shank portion is engageable to lock the trigger in the OFF position.
It is preferred that the locking mechanism further includes a pushbutton secured to the locking pin and a spring co-acting between the pushbutton and the locking plate to bias the locking pin to lock the trigger in the OFF position and to release the trigger in the ON position.
It is further preferred that the locking pin has an end remote from the pushbutton, and the trigger has an aperture into which the head is engageable to lock the trigger in the ON position.
In a preferred embodiment, the locking mechanism includes a spring biassing the locking member to lock the trigger in the OFF position and to release the trigger in the ON position.
More preferably, the locking member comprises a locking pin extending through the trigger and the chassis, the trigger including a pair of opposed side walls embracing the chassis and through which a shank of the locking pin extends, the shank having an end engageable with one trigger wall to lock the trigger in the OFF position and an opposite end engageable with the other trigger wall to lock the trigger in the ON position.
In a specific construction, the electrical switch includes two pairs of terminals, each pair being for an individual electrical circuit that are openable and closable upon movement of the trigger.
BRIEF DESCRIPTION OF DRAWINGS
The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which:
FIG. 1
is an exposed top and left side perspective view of an embodiment of a trigger mechanism in accordance with the invention;
FIG. 2
is a top and left side perspective view of the trigger mechanism of
FIG. 1
in the assembled condition;
FIG. 3
is a front view of the trigger mechanism of
FIG. 1
, shown lying on the left side;
FIG. 4
is a left side view of the trigger mechanism of
FIG. 3
;
FIG. 5
is a top plan view the trigger mechanism of
FIG. 3
;
FIG. 6
is a rear view of the trigger mechanism of
FIG. 3
;
FIG. 7
is a schematic circuit diagram of the trigger mechanism and an associated switchbox of
FIG. 6
;
FIG. 8
, including
FIGS. 8A-8D
, is a series of right side views that illustrate sequentially pulling of a trigger of the trigger mechanism of
FIG. 1
at different stages; and
FIG. 9
is a right side view of the trigger of FIG.
8
.
DETAIL DESCRIPTION OF PREFERRED EMBODIMENT
Referring to the drawings, there is shown a trigger mechanism
10
embodying the invention for a hand-held power tool such as an electric drill, grinder, sander, saw, grinder, rotary driving tool or any other power tool or electrical device of the type that includes a finger-activated pull trigger for switching on and off the tool or device.
The trigger mechanism
10
has a moulded plastics chassis
18
including a chassis mounting plate
19
having a pair of fixing apertures by which the chassis
18
is mounted internally of a power tool body nearby its handle. A switchbox
20
extends from the mounting plate
19
and is received within the handle of the power tool body. The mechanism
10
includes a spring-loaded plastics trigger
11
mounted pivotally to the chassis
18
by means of a metal pivot pin
12
that passes through small holes
13
and
30
in the trigger
11
and chassis
18
.
The trigger
11
has a pair of opposed side walls embracing the chassis
18
, to each of which there is formed a pinhole
23
for receiving an activating rod pin
22
that also passes through a middle pinhole
25
at one end of an activating rod
21
. The rod
21
depends from the pin
22
into the switchbox
20
. Upon pivoting of the trigger
11
about the pivot pin
12
, the other pin
22
moves up and down to cause generally vertical longitudinal sliding movement of the activating rod
21
that in turn operates the switch within the switchbox
20
. A locking mechanism is provided to prevent accidental depression or pulling of the trigger
11
.
The locking mechanism comprises a locking pin
16
that extends laterally through the trigger
11
and through the chassis
18
and a metal locking plate
17
secured inside the trigger
11
. One side wall of the trigger
11
has a curved aperture
25
that is superimposed upon a curved slot
31
of the locking plate
17
. The curved slot
31
has a widening
29
at it upper end.
The locking pin
16
has a wide shank portion
27
and a narrow shank portion
32
. The narrow shank portion
32
is sized to pass and passes freely through the slot
31
of the locking plate
17
, whereas the wide shank portion
27
can only pass through the widening
29
of the metal slot
31
.
The locking pin
16
includes a barbed end
33
that extends co-axially from the narrow shank portion
32
and is secured within an external plastics lock button
14
. Also included is a wide flat head
28
at the outer end of the wide shank portion
27
, which is sized to fit within an aperture
26
in the other side wall of the trigger
11
but be retained by the chassis
18
at a position behind the aperture
26
.
Disposed around the narrow shank portion
32
is a compression coil spring
15
that co-acts between the lock button
14
and the locking plate
17
, thereby biassing the locking pin
16
lengthwise outwards in the direction of the button
14
. In the outermost position of the locking pin
16
, the wide shank portion
27
has its inner end engaging within the widening
29
of metal slot
31
, whereby the trigger mechanism
10
is locked normally in the OFF position (FIGS.
8
A and
9
).
In operation, the trigger
11
cannot be depressed by a user unless the lock button
14
is first pressed against the force of spring
15
to push the wide shank portion
27
out of the metal slot widening
29
. Once the wide shank portion
27
is released from the locking plate
17
, the trigger
11
can be pulled with both slots
25
and
31
passing over the narrow shank portion
32
until the trigger
11
is fully depressed (FIG.
8
B).
Not until the trigger
11
is fully depressed, its wall aperture
26
comes into alignment with the locking pin head
28
. At this condition, upon further pressing of the lock button
14
, the head
28
fits into and through the aperture
26
to thereby lock the trigger
11
in the ON position (FIG.
8
C).
There is a spring (not shown) inside the trigger
11
and bearing against the chassis
18
to bias the trigger
11
towards the OFF position. The force exerted by this spring maintains contact between the head
28
and aperture
26
, overcoming the force exerted by the spring
15
on the locking pin
16
. As a result, the trigger
11
is held in the ON position until such time as the trigger
11
is pressed momentarily inwards slightly. When the trigger
11
so moves, the force exerted by the coil spring
15
on the locking pin
16
retracts the head
28
from the aperture
26
, thereby allowing the trigger
11
to self return to the OFF position.
As depicted in
FIG. 7
, the switchbox
20
includes two pairs of electrical terminals
1
and
2
. Each pair of these terminals defines an electrical switch that is operable by movement of the trigger
11
between the ON and OFF positions for closing and opening an individual electrical circuit. One such circuit includes an electric motor for driving the power tool, whilst the other circuit may be employed for an auxiliary electrical element such as a power-on indicator lamp.
The subject locking mechanism utilizes a single locking member or pin
16
that serves two functions, i.e. for locking the trigger
11
in both the ON and the OFF positions, making use of opposite ends of a portion of the locking pin
16
. That is, one end of the wide shank portion
27
(adjoining the narrow shank portion
32
) is engageable with one wall of the trigger
11
to lock it in the OFF position, whilst the opposite end (adjoining the head
28
) is engageable with the other trigger wall to lock the trigger
11
in the ON position.
The invention has been given by way of example only, and various modifications and/or variations to the described embodiment may be made by persons skilled in the art without departing from the scope of the invention as specified in the accompanying claims. For example, the trigger might slide linearly, rather than pivot upon a pivot pin, in which case the curved slots could be replaced with linear slots and the activating rod might extend in the direction of movement of the trigger.
Claims
- 1. A trigger mechanism for a power tool, comprising:a chassis; a trigger mounted to the chassis for movement between an ON and an OFF position, wherein the trigger is mounted pivotally to the chassis; an electrical switch mounted to the chassis for activation by movement of the trigger between the ON and OFF positions to close and open an electrical circuit; and a locking mechanism attached to the chassis, the locking mechanism being user-activated to unlock the trigger in the OFF position and trigger-activated to release the trigger in the ON position.
- 2. The trigger mechanism as claimed in claim 1, including an activating rod extending from the trigger to the electrical switch.
- 3. The trigger mechanism as claimed in claim 1, wherein the locking mechanism comprises a single locking member arranged to lock the trigger in both the ON and the OFF positions.
- 4. The trigger mechanism as claimed in claim 3, wherein the locking member comprises a locking pin extending through the trigger and the chassis.
- 5. The trigger mechanism as claimed in claim 4, wherein the locking mechanism includes a locking plate fixed to the trigger and having a slot through which the locking pin passes.
- 6. The trigger mechanism as claimed in claim 5, wherein the locking pin has a narrow shank portion and a wide shank portion, and the slot of the locking plate has a width through which the narrow shank portion can pass to permit movement of the trigger and a widening at one end through which the wide shank portion is engageable to lock the trigger in the OFF position.
- 7. The trigger mechanism as claimed in claim 5, wherein the locking mechanism further includes a pushbutton secured to the locking pin and a spring co-acting between the pushbutton and the locking plate to bias the locking pin to lock the trigger in the OFF position and to release the trigger in the ON position.
- 8. The trigger mechanism as claimed in claim 7, wherein has an end remote from the pushbutton, and the trigger has an aperture into which the head is engageable to lock the trigger in the ON position.
- 9. The trigger mechanism as claimed in claim 3, wherein the locking mechanism includes a spring biassing the locking member to lock the trigger in the OFF position and to release the trigger in the ON position.
- 10. The trigger mechanism as claimed in claim 9, wherein the locking member comprises a locking pin extending through the trigger and the chassis, the trigger including a pair of opposed side walls embracing the chassis and through which a shank of the locking pin extends, the shank having an end engageable with one trigger wall to lock the trigger in the OFF position and an opposite end engageable with the other trigger wall to lock the trigger in the ON position.
- 11. The trigger mechanism as claimed in claim 1, wherein the electrical switch includes two pairs of terminals, each pair being for an individual electrical circuit that are openable and closable upon movement of the trigger.
- 12. A trigger mechanism for a power tool, comprising:a chassis; a trigger mounted to the chassis for movement between an ON and an OFF position; an electrical switch mounted to the chassis for activation by movement of the trigger between the ON and OFF positions to close and open an electrical circuit; and a locking mechanism attached to the chassis, the locking mechanism being user-activated to unlock the trigger in the OFF position and trigger-activated to release the trigger in the ON position; wherein the locking mechanism comprises: a single locking member arranged to lock the trigger in both the ON and the OFF positions, wherein the locking member comprises a locking pin extending through the trigger and the chassis, the trigger including a pair of opposed side walls embracing the chassis and through which a shank of the locking pin extends, the shank having an end engageable with one trigger wall to lock the trigger in the OFF position and an opposite end engageable with the other trigger wall to lock the trigger in the ON position; and a spring biassing the locking member to lock the trigger in the OFF position and to release the trigger in the ON position.
- 13. A trigger mechanism for a power tool, comprising:a chassis; a trigger mounted to the chassis for movement between an ON and an OFF position; an electrical switch mounted to the chassis for activation by movement of the trigger between the ON and OFF positions to close and open an electrical circuit; and a locking mechanism attached to the chassis, the locking mechanism being user-activated to unlock the trigger in the OFF position and trigger-activated to release the trigger in the ON position; wherein the locking mechanism comprises: a single locking member arranged to lock the trigger in both the ON and the OFF positions, wherein the locking member comprises a locking pin extending through the trigger and the chassis; and a locking plate fixed to the trigger and having a slot through which the locking pin passes, wherein the locking pin has a narrow shank portion and a wide shank portion, and the slot of the locking plate has a width through which the narrow shank portion can pass to permit movement of the trigger and a widening at one end through which the wide shank portion is engageable to lock the trigger in the OFF position.
- 14. A trigger mechanism for a power tool, comprising:a chassis; a trigger mounted to the chassis for movement between an ON and an OFF position; an electrical switch mounted to the chassis for activation by movement of the trigger between the ON and OFF positions to close and open an electrical circuit; and a locking mechanism attached to the chassis, the locking mechanism being user-activated to unlock the trigger in the OFF position and trigger-activated to release the trigger in the ON position; wherein the locking mechanism comprises: a single locking member arranged to lock the trigger in both the ON and the OFF positions, wherein the licking member comprises a locking pin extending through the trigger and the chassis; a locking plate fixed to the trigger and having a slot through which the locking pin passes; and a pushbutton secured to the locking pin and a spring co-acting between the pushbutton and the locking plate to bias the locking pin to lock the trigger in the OFF position and to release the trigger in the ON position.
US Referenced Citations (8)