US3844360A

US3844360A - Hand held power tool with duplex handle

Info

Publication number: US3844360A
Application number: US00315846A
Authority: US
Inventors: R Green; A Anderson; A Guarino
Original assignee: Textron Inc
Current assignee: Textron Inc
Priority date: 1972-12-18
Filing date: 1972-12-18
Publication date: 1974-10-29
Anticipated expiration: 1991-10-29
Also published as: FR2210487B1; GB1418528A; IT1002277B; JPS4989300A; FR2210487A1; CA986819A; JPS5824303U; DE2362012A1

Abstract

A hand held power tool, for example a chain saw is provided with a transversely extending front handle and with a second handle which extends over the top of the power unit of the tool in a fore-and-aft direction. The fore-and-aft handle is provided with a forward hand grip portion located approximately above the center of gravity of the power tool and a rearward hand grip portion located at the rear of the power unit. An independently operable trigger member controlling the engine throttle is provided for each hand grip portion so that the engine can be controlled by an operator gripping either hand grip portion of the fore-and-aft handle. Moreover, a choke valve operating member is provided adjacent the forward hand grip portion while an onoff switch is located below a median portion of the fore-and-aft handle in position to be operated by an operator holding the tool by either hand grip portion.

Description

United States Patent [191 Green et a1.

1451 Oct. 29, 1974 Primary Examiner-Frank L. Abbott Assistant Examiner-William F. Pate, Ill Attorney, Agent, or FirmRobert 1E. Burns; Emmanuel J. Lobato; Bruce L. Adams 5 7 ABSTRACT A hand held power tool, for example a chain saw is provided with a transversely extending front handle and with a second handle which extends over the top of the power unit of the tool in a fore-and-aft direction. The fore-and-aft handle is provided with a forward hand grip portion located approximately above the center of gravity of the power tool and a rearward hand grip portion located at the rear of the power unit. An independently operable trigger member controlling the engine throttle is provided for each hand grip portion so that the engine can be controlled by an operator gripping either hand grip portion of the foreand-aft handle. Moreover, a choke valve operating member is provided adjacent the forward hand grip portion while an on-off switch is located below a median portion of the fore-and-aft handle in position to be operated by an operator holding the tool by either hand grip portion.

18 Claims, 12 Drawing Figures HAND HELD POWER TOOL WITH DUPLEX HANDLE FIELD OF INVENTION The present invention relates to hand held power tools and is especially applicable to chain saws. In particular it relates to novel means for holding and controlling such power tools in a convenient and safe manner.

BACKGROUND OF INVENTION Heretofore, a hand held power tool such as a chain saw has customarily been provided with a front handle located at the forward part of the power unit and extending transversely of the fore-aft axis of the unit and a rear handle located at the rear of the power unit and usually of a pistol grip" configuration. The power tool is held and manipulated by gripping the front handle with one hand and the rear handle with the other. The,

desirable to have one hand in position to operate the throttle trigger as soon as the engine starts. However, it is not convenient to hold the power unit down by the rear handle since the location of the rear handle makes it difficult to counteract the pull of the starter cord. If the unit is held by the front handle or by some other part of the power unit, it is not possible immediately to operate the throttle trigger when the engine starts. Moreover, since the front handle is customarily located approximately over the center of gravity of the power tool, the hand holding the front handle must take almost all of the weight of the tool. In some circumstances however. it is desirable for the two hands of the operator to share the weight of the power tool so that one does not become overly tired. This cannot be done with the prior construction.

SUMMARY OF INVENTION It is an object of the present invention to provide means for holding, manipulating and controlling hand held power tools in a manner which is more convenient and safer than with power tools of prior construction. In accordance with the invention an elongate handle which extends over the power unit in a fore-and-aft direction and is located approximately in the median vertical plane of the unit when in normal upright position is provided with a forward hand grip portion which lies approximately over the center of gravity of the power tool and a rearward hand grip portion located at the rear ofthe power unit. Moreover, each of the hand grip portions is provided with individually operable engine control means, for example a throttle operating trigger. Hence, the engine can be controlled when the handle is held by the forward hand grip portion and can likewise be controlled when the handle is held by the rearward hand grip portion. The power unit is also provided with a transversely extending handle located near the front end of the power unit. The front handle is preferably of the wrap-around'type extending across the top and along at least one side of the power unit. The power tool is normally held with one hand gripping the front handle and the other hand gripping either the front hand grip portion or the rear hand grip portion of the handle that extends in a fore-and-aft direction over the power unit. When the engine is being started, the power tool is conveniently held with one hand gripping the forward hand grip portion of the fore-and-aft handle while the starter cord is being pulled with the other hand. The engine is preferably provided with a choke valve operable by a member located adjacent the forward hand grip portion so that an operator holding the power tool by the forward hand grip portion has accessible to him both the choke control and throttle control of the engine. The engine is preferably also provided with an on-off switch which is located on top of the easing below a median portion of the fore-aft handle so that it can be actuated from either hand grip portion. This provides the safety feature that the engine can be turned off quickly by the operator regardless of whether he is holding the power tool by the forward hand grip portion or by the rearward hand grip portion.

BRIEF DESCRIPTION OF DRAWINGS Further characteristics, objects and advantages of the invention will appear from the following description of a preferred embodiment shown by way of example in the accompanying drawings in which:

FIG. 1 is a side view partially in longitudinal section of a chain saw embodying the invention;

FIG. 2 is a side view of a portion of the fore-aft handle of the chain saw;

FIG. 3 is a plan view of the power unit of the chain saw with portions broken away to show internal construction;

FIG. 4 is a front view of the power unit with portions broken away;

FIGS. 5, 6, 7, 8 and 9 are cross sections through the fore-aft handle taken respectively on the lines 5--5, 6--6, 7-7, 8-8 and 9-9 in FIG. 1;

FIG. 10 is a perspective view of a lever forming a part of the connections between the engine and engine control means on the fore-aft handle; and

FIGS. 11 and 12 are perspective views of motor control trigger members located respectively at the forward hand grip portion and rearward hand grip portion of the fore-aft handle.

DESCRIPTION OF PREFERRED EMBODIMENT In the drawings there is shown byway of example a chain saw havinga power unit 1 comprising an internal combustion engine housed in a casing 2. The casing is shown as being formed of two moldings or

castings

2a and 2b which are preferably formed of magnesium or aluminum and are secured together by a plurality of bolts 3. At one side of the power unit there is provided a sprocket 4 which is driven by the engine and drives a cutting chain running on a guide'bar or cutter bar 5 which projects forwardly from the power unit. The driving sprocket 4 is shown protected by a guard 6. At

the opposite side of the power unit there is a fan and starter assembly 7 comprising a fan which is mounted on the engine crank shaft and draws air in through an annular grill 8 to cool the engine and a rewind starter having a cord provided with a handle 9 which is pulled to turn the engine over to start it. In addition to housing the engine and its accessories, the casing 2 contains reservoirs for fuel and for oil for lubricating the guide bar and chain. These reservoirs are filled through openings closed by removable caps 11 and 12. At the front of the casing there are provided one or more spikes 13 which are engageable with the trunk of a tree or a log that is being cut by the chain saw to assist in feeding the cutter. bar through the work. i

To provide for hand holding and manipulating the chain saw, the power unit is provided with two

handles

15 and 20. The first handle 15 is located near the forward end of the power unit and is disposed at least generally in a transverse plane perpendicular to the foreaft axis of the power unit and located approximately at or somewhat in front of the center of gravity of the saw including the power unit, cutter bar and chain. It is shown as comprising a piece of tubing which is bent to form an upper approximately horizontal portion 15a disposed above the forward portion of the power unit, an approximately vertical portion 15b which is spaced from one side of the power unit and an inturned lower portion 150 which fits over a projection 16 of the casing and is secured by a screw 17. The upper end of the handle l5.fits over a projection 18 on the side of a forward portion of the handle 20 and is secured by a screw 19.

The second handle 20 extends in a generally foreand-aft direction over the engine. It is shown as comprising a portion 20a which extends upwardly and rearwardly from a lower rear portion of the casing 2 and a portion 20b which is curved and extends forwardly to the front portion of the power unit. As seen in FIGS. 3 and 4, the handle 20 is located approximately midway between the opposite sides of the power unit and is thus disposed generally in the median vertical fore-aft plane of the unit. The portion 20b of the handle extending over the power unit is contoured to provide a forward hand grip portion 21 occupying approximately the forward half of the handle portion 20b and a rearward hand grip portion 22 occupying approximately the rearward half. As seen in the drawings, the cross sectional shape and dimensions of the handle are varied so as to define the two hand grip portions in such manner than an operator naturally grips the handle by one or the other hand grip portion and can tell by the feel of the handle that his hand is in the desired position. Moreover, a downward protuberance 23 at the back of the forward hand grip portion 21 and a downward curve 24 ofthe handle at the rear of the rearward hand grip portion assists an operator in properly positioning his hand by feel.

The fore-aft handle 20 is hollow and is shown in the drawings as comprising in cross section a lower portion 25 which is of upwardly opening channel cross section and a removable cover 26 which is of downwardly opening channel cross section. The lower portion 25 of the handle is integral with the casing 2, being formed as a portion of the same molding or casting that forms the casing part 2a. The upper portion or cover 26 is removable and is conveniently formed as a plastic molding. The cover 26 and lower channel portion 25 fit together as shown in the cross sectional FIGS. 5 to 9. The cover 26 is removably held in place by integral downwardly extending hook portions 26a of the cover which fit under a portion 27 at the forward portion of the easing and an integral downwardly extending hook portion 26b at the rear of the cover which fits under a portion 28 at the rear of the handle. An opening 29 at the rear of the handle provides access for insertion of a tool to engage the hook portion 26b to disengage it from the portion 28 and thereby release the cover 26 for removal. The material from which the cover is made is sufficiently resilient to permit flexing to engage the hook portion 2612 with, and to disengage it from, the portion 28 of the handle.

Each of the hand grip portions of the fore-aft handle 20 is provided with means for controlling the engine of the power unit. The power unit is illustrated as comprising a two cycle internal combustion engine having a carburetor 30. The carburetor has a throttle valve controlled by an arm 31. The engine throttle is controllable by a trigger member 32 in the forward hand grip portion 21 and is independently controllable by a trigger member 33 in the rearward hand grip portion 22. The connections between the trigger members and the throttle comprise a lever 34 which is pivotally mounted in the forward portion of the handle 20 and has an arm connected with the throttle lever 31 by a link 35. The trigger member 32 of the forward hand grip portion 21 is slidably guided for upward movement in the handle and has a lateral projection 32a which is engageable with an arm on the lever 34 to rotate the lever in a counterclockwise direction when the trigger member 32 is moved upwardly. This movement of the lever 34, transmitted through the link 35, moves the throttle lever 31 in a direction to open the throttle. The trigger member 33 of the rearward hand grip portion 22 is pivotally mounted for rotary movement in a counterclockwise direction from the rest position shown in FIG. 2 and has an arm engageable with an abutment on a connecting rod 36 having a forward end portion engageable with an arm of the lever 34. When the trigger 33 is moved in a counterclockwise direction, the connecting rod 36 moves forwardly and presses on an arm of the lever 34 to swing the lever in a counterclockwise direction and thereby move the throttle toward open position. The throttle member 32 of the forward hand grip portion is normally held in the rest position shown in FIG. 1 by gravity and by the return spring (not shown) of the throttle acting through the connecting link 35 and lever 34. The throttle member 33 of the rearward hand grip portion 22 is normally held in rest position by gravity and by a spring 37, one end of which bears on a support 38 in the handle while the other end acts on the trigger 33 to move it in a clockwise direction. With the arrangement shown, the engine throttle can be actuated independently either by the trigger member 32 of the forward hand grip portion 21 or the trigger member 33 of the hand grip portion 22 while the other trigger remains in rest position.

The lever 34 is shown in more detail in FIG. 10. The lever is pivotally mounted in the handle by means of integral trunnion portions 34a which project from opposite sides of the lever and are received in socket portions 40 provided in the lower part 25 of the fore-aft handle. The trunnion portions 34a of the lever 34 are held in the socket portions 40 by portions 41 which project downwardly from the handle cover 26. Hence the lever 34 can be assembled merely by dropping it into the lower portion of the handle so that the trunnions 34a rest in the sockets 34 and then securing the cover 26 in place. The lever 34 has an arm 34b which is provided at its end with a hole 340 for receiving the link 35 which is preferably formed of a suitably bent wire. An upwardly projecting second arm 34d is provided with a socket (FIG. 1) flanked by web portions 342 to receive the forward end of the connecting rod 36. A rearward projection 34f constituting in effect a third arm of the lever is engageable by the projection 32a of the trigger 32 so as to turn the lever 34 in a counterclockwise direction when the trigger is moved upwardly.

The trigger 32 of the forward hand grip portion 21 is shown in more detail in FIG. 11. It will be seen to be generally rectangular in shape with a concave lower end portion 32b for engagement by a finger of the operators hand to move the trigger upwardly. The above mentioned projection 32a extends approximately perpendicularly from the forward side edge of the trigger member in position to be engageable with the arm 34f of the lever 34. The upper portion of the trigger member is bifurcated by a slot 320 extending in a fore-andaft direction to straddle the connecting rod 36. The trigger 32 extends down through a slot in the lower handle portion and its downward movement is limited by engagement of laterally enlarged portions 32d with the bottom part 25 of the handle on opposite sides of the slot. The trigger 32 is guided by an upstanding portion 42 in the lower part of the handle and is assembled merely by dropping it into place before the connecting rod 36 is installed.

The connecting rod 36 is a straight length of wire or rod which is received in slots in the

upstanding portions

38 and 42 of the lower part 25 of the handle. It is re tained by downwardly projecting

portions

43 and 44 of the cover 26, the lower portions of which are bifurcated to receive the rod. Hence, the rod can be assembled merely by dropping it into the lower portion of the handle so as to be received in the slots of

portions

38 and 42 and then securing the cover 26 in place. The connecting rod 36 is provided near its rear end with an abutment which is shown as being provided by a washer 36a which is secured to the rod, for example by welding or brazing.

The trigger member 33 of the rearward hand grip portion 22 is shown in more detail in FIG. 12. It is provided at opposite sides with laterally projecting integral trunnions 33a which are received in sockets 45 in the lower part 25 of the handle (FIG. 5). The trunnions 33a of the trigger member 33 are retained in the sockets 45 by downwardly projecting portions 46 of the cover. Hence the trigger can be assembled merely by dropping it into place and then applying the cover 26. An upwardly projecting arm 33!) is bifurcated to straddle the rear end portion of the connecting rod 36 and engage the washer 36a secured on the rod. The rear end of the spring 37 bears on the washer 36a and hence acts through the washer to bias the trigger in a clockwise direction. Rotation in a clockwise direction is limited by a projection 330 which is engageable with the bottom of the handle. In rest position, a portion of the trigger extends down through a slot in the handle in position to be engaged by a finger of the operators hand when gripping the rearward hand grip portion 22.

In assembling the parts in the handle, the

trigger members

32 and 33 and the lever 34 are positioned in the lower part 25 ofthe handle as described above. The connecting rod 36 with the spring 37 thereon is then placed in position and the cover 26 is then secured in place, thereby likewise securing the trigger members, lever and connecting rod. The assembly of the parts is thereby made extremely simple and inexpensive.

The throttle is also provided with a customary choke valve operable by an arm 50 which extends through an opening in the top of the casing and is located in the vicinity of the forward hand grip portion 21. Hence, an operator hodlding the chain saw by the forward hand grip portion can easily and conveniently actuate both the trigger 32 controlling the throttle and the arm 50 controlling the choke valve of the carburetor.

The engine is also shown provided with an on-off switch 51 in the ignition circuit. The switch must be in on position in order for the engine to be started and run. Hence, the engine can be quickly stopped by moving the switch to off" position. The switch 51 is mounted on the top of the casing below and slightly to one side of the handle 20 at a position about the middle of the handle and hence approximately between the forward and rearward hand grip portions. It can hence be operated by a finger of the operators hand when gripping either the forward or the rearward hand grip portion of the handle. Hence, in case of need, the engine can be stopped quickly regardless of which hand grip portion is being used by the operator.

The forward hand grip portion 21 is located approximately above the center of gravity of the chain saw so than an operator can support all or most of the weight of the chain saw with one hand gripping the forward hand grip portion of the fore-aft handle. Thus the saw can conveniently be carried with one hand. The length of the handle between the two triggers is sufficient that the saw can be held firmly by the forward hand grip portion without actuating either trigger. For some types of cutting, an operator can hold the forward hand grip portion 21 of the fore-aft handle with his right hand while gripping the transverse handle 15 with his left hand to assist in guiding and controlling the saw. Moreover, when starting the engine, it is convenient to hold the saw on the ground or other suitable support by grip ping the forward hand gripportion with the right hand while pulling the starter cord by means of the handle 9 with the left hand. With his right hand in this position, the operator can control the choke valve by means of the arm 50 and the throttle valve by means of the forward trigger member 32. He can also conveniently manipulate the on-off switch 51. For other types of cutting it is convenient to hold the saw with the right hand gripping the rearward hand grip portion 22 while the left hand grips the transverse handle 15. By having his right hand on the rear hand grip portion 22 at the rear of the power unit, an operator has more leverage to pivot the saw about the spikes 13 engaging a side of a log or tree to feed the cutter bar into the work. When the saw is held in this manner the weight of the saw is distributed between the transverse handle 15 located somewhat forwardly of the center of gravity of the saw and the rear hand grip portion 22 located at the rear of the power unit. The saw is controlled by the rear trigger member 33.

It will thus be seen that the construction in accordance with the present invention provides means for holding, manipulating and controlling a chain saw or other hand held power tool in a convenient and safe manner. The manner in which the power tool is held can be varied according to the wishes of the operator in order to hold the tool in the best manner for each particular operating condition. Moreover, changing the manner in which the tool is held from time to time is helpful in avoiding operator fatigue. Whether the tool is held by the forward hand grip portion or the rearward hand grip portion, the operator has full control of its operation and can, moreover, stop the engine quickly in the event'of an emergency.

While a preferred embodiment of the invention has been illustrated in the drawings and is herein particularly described, it will be understood that the invention is in no way limited to this embodiment and that many modifications and variations in construction can be made while retaining the overall configuration.

What we claim and desire to secure by Letters Patent is:

1. In a hand held power tool comprising a power unit having a front and a rear, said power unit comprising a casing and a motor in the casing and having speed control means, and a tool unit disposed at the front of the power unit and driven by said power unit, means for manually holding and controlling said power tool comprising a first handle disposed transversely at the front of the power unit and a second handle extending over the power unit from the rear toward the front thereof, said second handle having two separate hand grip portions arranged in tandem, namely a forward hand grip portion comprising a forward portion of said second handle and located approximately over the center of gravity of the power tool and a rearward hand grip portion comprising a separate rearward portion of said second handle and located wholly rearwardly of said forward hand grip portion and rearwardly of the center of gravity of the power tool, first motor control means at the forward end of the forward hand grip portion of said second handle in position to be digitally operated by an operator holding said forward hand grip portion, second motor control means forward of the rearward hand grip portion of said second handle in position to be digitally operated by an operator holding said rearward hand grip portion, said second motor control means being located between said forward hand grip portion and said rearward hand grip portion and means connecting said first and second motor control means with said second control means of the motor, whereby said motor can be controlled by an operator holding said second handle by either said forward hand grip portion or said rearward hand grip portion.

2. A power tool according to claim 1, wherein said second handle is contoured to define said forward and rearward hand grip portions so that an operator can properly position his hand on one or the other of said hand grip portions by feel.

3. A power tool according to claim 1, wherein said second handle extends rearwardly beyond the rear of the casing.

4. A power tool according to claim 1, wherein said second handle is hollow and said connecting means is disposed in part in said hollow handle.

5. A power tool according to claim 4, wherein said second handle comprises a lower portion which is integral with said casing and a cover removable secured on said lower portion.

6. A power tool according to claim 5, wherein said cover is molded plastic material and is provided at opposite ends with integral hooking portions which hook onto said lower portion to secure the cover.

7. A power tool according to claim 5, wherein said second motor control means comprises a trigger having a pivot portion, and wherein said lower portion of the second handle has means for receiving said pivot portion to pivotally support said trigger and said cover has means for retaining said pivot portion in said receiving means whereby said trigger can be assembled merely by dropping it into the lower portion of said second handle and thereafter securing said cover in place.

8. A power tool according to claim 7, wherein said connecting means comprises a connecting rod extending forwardly in said second handle from said trigger, said lower portion and cover of said second handle having cooperating means for guiding said connecting rod, whereby said connecting rod can be assembled by dropping it into said lower portion and thereafter securing said cover in place.

9. A power tool according to claim 8, wherein said first motor control means comprises a movable trigger, and wherein said connecting means further comprises a pivoted lever having a portion engageable by said connecting rod, a portion engageable with said trigger of the forward hand grip portion and a portion connected with said speed control means of the motor, said lower portion of the second handle having means for guiding said last mentioned trigger and for pivotally supporting said lever, whereby said last mentioned trigger and lever can be assembled by dropping them into said lower portion of the second handle and thereafter securing said cover in place.

10. A power tool according to claim 4, wherein said first motor control means comprises a first trigger movably mounted in said second handle and having a rest position in which a portion thereof extends below said second handle at the forward end of said forward hand grip portion, and said second motor control means comprises a second trigger movably mounted in said second handle and having a rest position in which a portion thereof extends below said second handle at the forward end of said rearward hand grip portion.

11. A power tool according to claim 10, wherein said connecting means comprises means operably connecting both of said triggers to said motor speed control means for operation of said speed control means by either one of said triggers while the other of said triggers remains in its rest position.

12. A power tool according to claim 11, wherein said connecting means comprises a lever pivotally mounted at the front of said second handle, means connecting said lever with said motor speed control means, said lever having a portion engageable by said first trigger to pivot said lever in a direction to operate said speed control means and a connecting rod in said hollow handle and movable by said second trigger, said rod being engageable with a portion of said lever to pivot said lever in a direction to operate said speed control means.

13. A power tool according to claim 1, wherein said motor is an internal combustion engine and said speed control means comprises a carburetor having a throttle to which said connecting means is connected.

14. A power tool according to claim 13, wherein said carburetor has a choke valve and a choke valve operating member located adjacent said forward hand grip portion of said second handle in position to be digitally operated by an operator holding said forward handle portion.

15. A power tool according to claim 13, wherein said engine has an on-off switch located at the top of said casing below a median portion of said second handle in position where it can be actuated by an operator holdmg said second handle b i h id f rw d or aid dle is connected to a lower rear portion of said casing. rearward hand grip portion.

16. A power tool according to claim 1, wherein said 18. A power unit according to claim 1, wherein said first handle Comprises a tubular handle disposed generpower tool is a chain saw and has a cutter bar extending in a Plane perpefldicular to a f the forwardly from said power unit and spikes on the front power unit and having an approximately horizontal of Said casin g in position to be engageable with the upper portion above the forward portion of the power unit and an approximately vertical side portion at one work whereby Y' secqnd handle whgn held by id f h power unit rearward hand grip portion affords leverage to pivot 17 A power i according to claim 1 h i one said chain saw about said spikes in engagement with the end of said first handle is connected to second handle Work and thereby move Said Cutter bar into the Workat its forward end and the opposite end of said first han-

Claims

15. A power tool according to claim 13, wherein said engine has an on-off switch located at the top of said casing below a median portion of said second handle in position where it can be actuated by an operator holding said second handle by either said forward or said rearward hand grip portion.

16. A power tool according to claim 1, wherein said first handle comprises a tubular handle disposed generally in a plane perpendicular to a fore-aft axis of the power unit and having an approximately horizontal upper portion above the forward portion of the power unit and an approximately vertical side portion at one side of the power unit.

17. A power unit according to claim 16, wherein one end of said first handle is connected to second handle at its forward end and the opposite end of said first handle is connected to a lower rear portion of said casing.

18. A power unit according to claim 1, wherein said power tool is a chain saw and has a cutter bar extending forwardly from said power unit and spikes on the front of said casing in position to be engageable with the work, whereby said second handle when held by the rearward hand grip portion affords leverage to pivot said chain saw about said spikes in engagement with the work and thereby move said cutter bar into the work.