Safety switch for power tools

Information

  • Patent Grant
  • 6575285
  • Patent Number
    6,575,285
  • Date Filed
    Wednesday, November 14, 2001
    23 years ago
  • Date Issued
    Tuesday, June 10, 2003
    21 years ago
Abstract
A clutch safety switch of a power chainsaw includes a safety member slidably connected to the casing and a trigger which is not able to be squeezed when the safety member is not slid away. A gear connected to the power source has engaging recesses and a clutch device member is rotatably mounted to an output shaft which is independent from the gear. A link is connected between the safety member and a plate connected to the clutch member which is rotated to engage the output shaft with the gear by sliding the safety member. A lever is connected to the plate which is pivoted by pushing the lever to allow the link to move in a horizontal portion of an L-shaped slot in the plate to make the safety member be pushed back to disengage the clutch device from the gear to release the connection.
Description




FIELD OF THE INVENTION




The present invention relates to a switch for a chainsaw wherein the power cannot be engaged with the chainsaw by pushing a lever to a remote position.




BACKGROUND OF THE INVENTION




A conventional switch device for a power tool generally includes a trigger which is engaged with a trigger assembly. When pulling the trigger, the circuit of the power tool is activated and the tool is operated. However, most of the triggers have no safety device to avoid the user to touch the trigger unintentionally so that it is possible that the trigger is pulled unintentionally and the chainsaw for example is running. This is extremely dangerous so that there is a need to develop a safety device to prevent the situation from happening.




SUMMARY OF THE INVENTION




In accordance with one aspect of the present invention, there is provided a clutch safety switch for a power tool and the clutch safety switch comprises a casing having a slot for a safety member slidably engaged therewith. A lug extends from an underside of the safety member and a trigger is pivotally located in the casing and has a protrusion which is interfered by the lug of the safety member. A link has an end thereof connected to the safety member. A gear is received in the casing and connected to a power source. The gear is independently mounted to an output shaft and a plurality of engaging recesses are defined in the gear. A plurality of guide rods and guide members respectively extend from an inside of the casing. A clutch member is mounted to the output shaft and has a plurality of blades each of which has a guide slot in which respective one of the a plurality of guide rods extends. Each blade has a tapered extension extending therefrom which is able to be movable along the guide member. An engaging member is movably mounted to the output shaft and has bosses extending from a side thereof. A cover is fixed on the clutch member and the engaging member is retained in a central hole in the clutch member by the cover. A link is connected between the safety member and a plate connected to one of the blades of the clutch member. The plate has an L-shaped slot so as to receive an end of the link. A spring has one end thereof connected to the plate and the other end of the spring is fixed to a rod in the casing. A lever is pivotally connected to the casing and an extension is connected to the lever. The extension has a first elongate slot and a second elongate slot. Two pins in the casing are located in the first elongate slot and a position rod extending from the plate is movably engaged with the second elongate slot.




The primary object of the present invention is to provide a clutch safety switch for a power tool wherein the clutch device disengage the power from the output shaft by pushing a lever on the casing.




The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention.




BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is an exploded view to show a clutch safety device of a power chainsaw of the present invention;





FIG. 2

is a side view to show the clutch safety device of the present invention;





FIG. 3

is a side view to show the clutch safety device of the present invention wherein the clutch member is rotated by sliding the safety member;





FIG. 4A

shows that the engaging member is not yet moved to engage with the clutch member of the clutch safety device of the present invention;





FIG. 4B

shows that the engaging member is moved to engage with the clutch member of the clutch safety device of the present invention, and





FIG. 5

shows that the link is located in a horizontal of the L-shaped slot in the plate when pushing the lever.











DETAILED DESCRIPTION OF THE INVENTION




Referring to

FIGS. 1 and 2

, the clutch switch device of the present invention comprises a casing


1


, a trigger assembly


2


and a clutch device


3


. The casing


1


includes a handle


11


of the power chainsaw and a pin


12


for pivotally connecting the trigger assembly


2


extends from an inside of the casing


1


. An activation switch frame


13


is connected above the trigger assembly


2


. A rod


16


is located in the casing


1


and a spring


17


has one end thereof connected to the rod


16


. The trigger assembly


2


includes an activation switch


21


which is received in the activation switch frame


13


and a trigger


22


which has a protrusion


221


and is pivotally mounted to the pin


12


. A slot


14


is defined through the casing


1


so that a safety member


23


is slidably engaged with the slot


14


and a stop member


15


located at a closed end of the slot


14


. A thumb portion


231


extends from the safety member


23


and through the slot


14


, a lug


232


extending from an underside of the safety member


23


so that when the protrusion


221


contacts the lug


232


, the trigger


22


cannot be squeezed. The safety member


23


has a head


233


and a link


25


is connected to the head


233


. A spring


24


has one end connected to the head


233


and the other end of the spring


24


is connected to the stop member


15


. The clutch device


3


includes a first gear


32


which is connected to a power source such as a motor (not shown) and a clutch device casing


31


for an output shaft


34


extending therefrom. A second gear


33


is located in the clutch device casing


31


and engaging recesses


331


is defined in a central portion of the second gear


33


. The second gear


33


and the output shaft


34


are two independent members which are not connected with each other. A clutch member


35


has three blades


351


extending radially outward therefrom at equal intervals and the output shaft


34


extends through a central hole of the clutch member


35


. A guide slot


352


is defined in a remote end of each of the blades


351


and a tapered extension


353


extends from each of the blades


351


. Three guide rods


311


and three guide members


312


extend from the clutch device casing


31


. The guide rods


311


are received in the guide slots and the guide members


312


are shaped to cooperate with the tapered extensions


353


. A spring


355


has one end connected to a hole


354


defined in one of the three blades


351


and the other end of the spring


355


is connected to a guide rod


311


in one of the guide slots


352


. A pushing portion


357


is connected a remote end of one of the blades


351


and has a hole


356


for being connected to the other end of the spring


17


. A plate


36


is connected to the pushing portion


357


and has an L-shaped slot


361


for receiving the other end of the link


25


. The link


25


is engaged with a vertical portion of the L-shaped slot


361


. A support plate


362


is connected to the plate


36


so as to prevent the link


25


from dropping from the L-shaped slot


361


. An engaging member


37


has bosses


371


on a side and is movably mounted to the output shaft


34


. A cover


38


is mounted to the output shaft


34


and fixed to the clutch member


35


so that the engaging member


37


is retained in the central hole of the clutch member


35


. When the bosses


371


are engaging with the engaging recesses


331


in a central portion of the second gear


33


, the output shaft


34


is driven by the second gear


33


. A plurality of rollers are embedded in the engaging member


37


so as to reduce the frictional wear between the cover


38


and the engaging member


37


.




A lever


19


is pivotally connected to the casing


1


and an extension


26


is connected to the lever


19


. The extension


26


has a first elongate slot


261


and a second elongate slot


262


. Two pins


27


,


28


extending from the inside of the casing


1


are located in the first elongate slot


261


so as to guide the direction of movement of the extension


26


when the lever


19


is pushing away from the handle


18


on the top of the casing


1


. A position rod


363


extends from the plate


36


and is movably engaged with the second elongate slot


262


. A frame


29


is located in the casing


1


and below the extension


26


and has a tip portion extending therefrom. A plurality of notches are defined in an underside of the extension


26


and the tip portion is engaged with one of the notches.




As shown in

FIGS. 2 and 4A

, when the safety member


23


is not slid toward the chainsaw, the protrusion


221


contacts the lug


232


so that the trigger


22


cannot be squeezed.




As shown in

FIGS. 3 and 4B

, the lever


19


is positioned at the position where the tip portion is engaged with the notch on the right end of the frame


29


, and the safety member


23


is pushed to remove the lug


232


, the trigger


22


can be squeezed to activate the activation switch


21


to operate the chainsaw. In the meanwhile, the spring


24


is compressed when the safety member


23


is pushed and the link


25


pushes the plate


36


so as to let the clutch member


35


rotate clockwise. The rotation of the clutch member


35


and its blades


351


make the tapered extensions


353


to move along the guide members


312


to let the bosses


371


move and engage with the engaging recesses


331


as shown in FIG.


4


B. Therefore, the power can be transferred from the second gear


33


to the output shaft


34


to drive the chainsaw.




When releasing the trigger


22


, the activation switch


21


is released and the safety member


23


is moved back by the spring


24


. The springs


17


and


355


pull the clutch member


35


to rotate counter clockwise and the bosses


371


are disengaged from the engaging recesses


331


. The power is then not transferred to the output shaft


34


and the chainsaw stops.




As shown in

FIG. 5

, when pushing the lever


19


to a remote position to let the tip portion engage with the notch on the left end of the frame


29


, the distal end of the extension


26


lifts the plate


36


upward to let the link


25


be located in the horizontal portion of the L-shaped slot


361


. In other words, the link


25


can be freely moved within the horizontal portion of the L-shaped slot


361


. Therefore, the safety member


23


can not be positioned as the position shown in FIG.


3


and the safety member


23


will be pushed back to its original position by the spring


24


. The trigger


22


is not able to be squeezed to operate the chainsaw. This lever


19


ensures that the chainsaw will not be operated unintentionally even if the safety member


23


is unintentionally slid.




While we have shown and described the embodiment in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.



Claims
  • 1. A safety switch for a power tool, comprising:a casing having a slot defined therethrough and a safety member slidably engaged with said slot, a lug extending from an underside of said safety member, a trigger pivotally located in said casing and having a protrusion which is interfered by said lug of said safety member, a spring having one end thereof connected to said safety member and the other end of said spring connected to a stop member in said casing, a link having an end thereof connected to said safety member; a gear received in said casing and adapted connected to a power source, said gear independently mounted to an output shaft and a plurality of engaging recess defined in said gear, a plurality of guide rods and guide members respectively extending from an inside of said casing; a clutch member mounted to said output shaft and having a plurality of blades each of which has a guide slot in which respective one of said a plurality of guide rods extends, each blade having a tapered extension extending therefrom which is able to be movable along said guide member, an engaging member movably mounted to said output shaft and having bosses extending from a side thereof, a cover fixed on said clutch member and said engaging member being retained in a central hole in said clutch member by said cover; one of said blades having a plate connected thereto and said plate having an L-shaped slot, the other end of said link engaged with said L-shaped slot in said plate, another spring having one end thereof connected to said plate and the other end of said another spring fixed to one of said plurality of guide rods in said casing, and a lever pivotally connected to said casing and an extension connected to said lever, said extension having a first elongate slot and a second elongate slot, two pins extending from said inside of said casing and located in said first elongate slot, a position rod extending from said plate and movably engaged with said second elongate slot.
  • 2. The safety switch as claimed in claim 1, wherein a frame located in said casing and has a tip portion extending therefrom, a plurality of notches defined in an underside of said extension and said tip portion engaged with one of said notches.
  • 3. The safety switch as claimed in claim 1, wherein a spring has one end thereof connected to one of said blades and the other end of said spring is connected to one of said guide rods in said guide slot of one of the rest of said blades.
  • 4. The safety switch as claimed in claim 1, wherein a plurality of rollers are embedded in said engaging member and said cover contacts said rollers.
  • 5. The safety switch as claimed in claim 1, wherein a thumb portion extends from said safety member and through said slot.
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Number Name Date Kind
4152833 Phillips May 1979 A
4335514 Overy et al. Jun 1982 A
4432139 Kohler et al. Feb 1984 A
4594780 Schliemann et al. Jun 1986 A
4680862 Wieland et al. Jul 1987 A
4753012 Schurr Jun 1988 A
5065476 Dohse et al. Nov 1991 A
5243764 Wieland Sep 1993 A
5709032 Mizutani et al. Jan 1998 A
5724737 Stones Mar 1998 A