TRIGGER MECHANISM FOR HAND-OPERATED POWER DEVICE INCLUDING INDEPENDENTLY OPERABLE LOCKING DEVICES PROVIDING AUTOMATIC LOCK OFF AND MANUAL LOCK-ON OPERATION
United States Patent 3873796
A trigger mechanism for a hand-operated power tool includes a manually operable trigger movable between inoperative and operative positions, a first manually operable locking device which automatically locks the trigger in its inoperative position and permits the trigger to be manually unlocked for movement between its operative and inoperative positions, and a second manually operable locking device which permits the trigger to be locked in its operative position. The locking devices require distinct, intentional actions for operation and thus provide a safeguard against accidental operation of the power tool.
US Patent References:
Motor driven tool switch
Wappat - October 1933 - 1929662
Trigger switch with automatic kick-off
Johnson - October 1957 - 2810051
Electrical switch assembly
Wolkov - November 1957 - 2812405
Trigger locking means for hand-portable power-operated device
Filander - July 1965 - 3194084
Trigger locking means for portable electric device
Elligson - November 1965 - 3217559
Motor driven tool switch
Wappat - October 1933 - 1929662
Trigger switch with automatic kick-off
Johnson - October 1957 - 2810051
Electrical switch assembly
Wolkov - November 1957 - 2812405
Trigger locking means for hand-portable power-operated device
Filander - July 1965 - 3194084
Trigger locking means for portable electric device
Elligson - November 1965 - 3217559
Application Number:
05/478655
Publication Date:
03/25/1975
Filing Date:
06/12/1974
View Patent Images:
Export Citation:
Assignee:
The Black and Decker Manufacturing Company (Towson, MD)
Primary Class:
Other Classes:
200/43.170, 200/320
International Classes:
H01H3/20; H01H9/06; H01H3/02; H01H9/02; H01H3/20
Field of Search:
200/157,321,322,328,319,320,60,318
US Patent References:
Primary Examiner:
Schaefer, Robert K.
Assistant Examiner:
Smith, William J.
Attorney, Agent or Firm:
Slotnik, Joseph Bloom Leonard Murphy Edward R. D.
Parent Case Data:
This is a continuation of application Ser. No. 377,041, filed July 6, 1973 now abandoned.
Claims:
What is claimed is
1. A trigger mechanism for a hand-operated power device including a motor and a control operatively associated with the motor, comprising:
2. A trigger mechanism for a hand-operated power device including a motor and a control operatively associated with the motor, comprising:
3. A trigger mechanism for a hand-operated power tool including an electric motor and a switch operatively associated with the motor, comprising:
4. A trigger mechanism for a hand-operated power tool including an electric motor and a handle which supports a switch operatively associated with the motor, comprising:
5. A trigger mechanism for a hand-operated power tool including an electric motor and a handle which supports an on-off switch operatively associated with the motor, comprising:
6. A trigger mechanism for a hand-operated power tool including an electric motor and a hollow handle which support an on-off switch operatively associated with the motor, comprising:
7. A trigger mechanism for a hand-operated power tool including an electric motor and a hollow handle which supports a switch operatively associated with the motor, comprising:
8. A trigger mechanism for a hand-operated power tool including an electric motor and a hollow handle which supports an on-off switch operatively associated with the motor, comprising:
9. A trigger mechanism for a hand-operated power tool including an electric motor and a hollow handle which supports an on-off switch operatively associated with the motor and provided with a movable actuator to control its operation, comprising:
1. A trigger mechanism for a hand-operated power device including a motor and a control operatively associated with the motor, comprising:
2. A trigger mechanism for a hand-operated power device including a motor and a control operatively associated with the motor, comprising:
3. A trigger mechanism for a hand-operated power tool including an electric motor and a switch operatively associated with the motor, comprising:
4. A trigger mechanism for a hand-operated power tool including an electric motor and a handle which supports a switch operatively associated with the motor, comprising:
5. A trigger mechanism for a hand-operated power tool including an electric motor and a handle which supports an on-off switch operatively associated with the motor, comprising:
6. A trigger mechanism for a hand-operated power tool including an electric motor and a hollow handle which support an on-off switch operatively associated with the motor, comprising:
7. A trigger mechanism for a hand-operated power tool including an electric motor and a hollow handle which supports a switch operatively associated with the motor, comprising:
8. A trigger mechanism for a hand-operated power tool including an electric motor and a hollow handle which supports an on-off switch operatively associated with the motor, comprising:
9. A trigger mechanism for a hand-operated power tool including an electric motor and a hollow handle which supports an on-off switch operatively associated with the motor and provided with a movable actuator to control its operation, comprising:
Description:
The present invention relates to a trigger mechanism for a hand-operated power device and, more particularly, to a trigger mechanism for a portable, hand-operated power tool driven by an electric motor which is automatically locked off when the trigger mechanism is inoperative and which permits the tool to be temporarily locked on for continuous operation.
In the prior art, portable, hand-operated power tools, e.g., electrically powered hedge or shrub trimmers, grass shears and power saws, have included trigger mechanisms incorporating automatic lock-off and manual lock-on features. These features have been provided by a locking device movable between lock-off and lock-on positions to control the operation of a trigger. The automatic lock-off feature has protected an operator against accidential operation of the power tool, and the lock-on feature has enabled the operator to continuously operate the power tool without the necessity of exerting continuous manual pressure on the trigger.
The prior art trigger mechanisms have been capable of operation by a simple activity to operate the power tool between its lock-off and lock-on states. For example, it has been possible for an operator, by continuous movement of the locking device in a single direction, to unlock the trigger mechanism from its lock-off state and to operate the trigger mechanism to its lock-on state. Since only a simple activity has been required to operate the prior art trigger mechanisms from lock-off to lock-on states, the possibility of accidental lock-on operation of the power tool has been enhanced along with the attendant risk of injury to the operator.
To avoid the disadvantages of the prior art, it is desirable to provide a trigger mechanism having automatic lock-off and manual lock-on features for a portable, hand-operated power tool which requires a positive, intentional action, distinct from the activity required to unlock the trigger mechanism, to operate the trigger mechanism into its lock-on state. The requirement of a positive, intentional action minimizes the possibility of inadvertent lock-on operation of the tool.
It is an object of the present invention to provide a trigger mechanism for a hand-operated power tool which provides automatic lock-off and manual lock-on operation and requires an operator to consciously perform a complex activity to operate the trigger mechanism from its lock-off state to its lock-on state to minimize the possibility of inadvertent operation of the tool.
It is an additional object of the present invention to provide a trigger mechanism for a hand-operated power tool incorporating a first locking device which automatically locks the trigger in an inoperative position and permits the trigger to be unlocked for manual operation and a second locking device which permits the trigger to be locked in an operative position, wherein the locking devices require distinct, intentional actions by an operator to unlock the trigger and to lock the trigger in its operative position.
In accordance with the invention, a trigger mechanism for a hand-operated power device including a motor and a control operatively associated with the motor comprises a trigger manually movable from an inoperative position to an operative position to actuate the control and operate the motor; first locking means for normally locking the trigger in its inoperative position, the first locking means being movable from a first, lock-off position, cooperatively engageable with the trigger to prevent movement of the trigger from its inoperative position to its operative position, toward a second, unlock position wherein the trigger is manually movable to its operative position to actuate the control, and second locking means operable independently of the first locking means for locking the trigger in its operative position, the second locking means being movable from a first, unlock position out of the path of movement of the trigger to a second, lock-on position cooperatively engageable with the trigger to lock the trigger in its operative position to continuously actuate the control and operate the motor. Preferably, the trigger is normally biased toward its inoperative position, the first locking means is normally biased toward its lock-off position, and the second locking means is normally biased toward its first, unlock position. The first and second locking means are independently operable and require distinct actions by an operator to unlock the trigger for movement from its inoperative position to its operative position and to lock the trigger in its operative position.
In a preferred embodiment of the trigger mechanism, for use in a hand-operated power tool including an electric motor and a handle which supports a switch operatively associated with the motor, the first and second locking means comprises manually operable locking levers pivotally mounted adjacent to a finger engageable body of the trigger. The first locking lever is normally biased to a lock-off position in registration with a lock-off surface on the trigger body to prevent movement of the trigger body from its inoperative position to its operative position, and it is pivotable to an unlock position out of registration with the lock-off surface to permit the trigger body to be moved to its operative position. The second locking lever is normally biased to an unlock position out of the path of movement of the trigger body and is pivotable to a lock-on position wherein it is cooperatively engageable with a lock-on member on the trigger body to lock the trigger body in its operative position. In the operation of the trigger mechanism, an operator is required to perform distinct actions to pivot the first locking lever to unlock the trigger body for manual movement to its operative position and to pivot the second locking lever to lock the trigger body in its operative position.
The automatic lock-off and manual lock-on features of the trigger mechanism of the present invention preclude inadvertent operation of the power tool. The automatic lock-off feature requires an operator to perform an unlock activity prior to the actuation of the trigger to operate the tool. In addition, the manual lock-on feature requires the operator to perform a separate action, which is distinct from the unlock activity, to achieve lock-on operation of the power tool. These safety features of the trigger mechanism prevent an inexperienced operator from accidentally turning on the power tool and locking the tool on for continuous operation.
The accompanying drawings illustrate a preferred embodiment of the invention and, together with the description, serve to explain the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation, partially cutaway, of a portable, hand-operated power tool, e.g., a shrub or hedge trimmer, including a handle which supports a trigger mechanism comprising a manually movable trigger and first and second locking devices constructed in accordance with the principles of the present invention, a motor and a cutting blade assembly;
FIG. 2 is a plan view of the portable power tool of FIG. 1 illustrating the construction of the handle in two sections;
FIGS. 3 is an enlarged side view, taken along line 3--3 of FIG. 2, of the handle of the portable power tool, with one handle section removed, illustrating the trigger in its inoperative position, the first locking device in its lock-off position to lock the trigger in its inoperative position, and the second locking device in its inoperative position out of engagement with the trigger;
FIG. 4 is an enlarged side view, partially in section, of a portion of the handle of the portable power tool of FIG. 1 illustrating the first locking device operated from its lock-off position to its unlock position;
FIG. 5 is an enlarged side view, partially in section, of the same portion of the power tool handle illustrating the trigger raised from its inoperative position to its operative position; and
FIG. 6 is an enlarged side view, partially in section, of the same portion of the power tool handle illustrating the second locking device moved to its lock-on position to lock the trigger in its operative position.
DETAILED DESCRIPTION
FIG. 1 illustrates a portable, hand-operated power tool, e.g., a shrub or hedge trimmer, which incorporates a trigger mechanism constructed according to the principles of this invention. The power tool includes an elongated, hollow handle, generally 20, consisting of two (2) half sections 22 and 24 (FIG. 2). The half-sections of handle 20 are essentially mirror images of each other and are held together by a plurality of screws or bolts 26, 28, 30 and 32 (FIG. 1).
Referring to FIGS. 1 and 2, handle 20 includes a rearward portion which is relatively narrow and elongated to provide a convenient shape to be gripped by the hand of an operator. The handle also includes an enlarged forward portion to support a housing 36 for a motor 34 which drives the power tool. A hand grip 38 is secured at the top of the housinng to allow the operator to grip the tool with both hands.
As shown in FIG. 1, a cutting blade assembly, generally 40, extends forward from the front end of handle 20. The cutting blade assembly is standard in construction and, thus, only a portion of the assembly is illustrated.
Cutting blade assembly 40 includes a lower, stationary blade 42, an upper, reciprocating blade 44, and an elongated support member 46 which extends forward from the front end of the handle above reciprocating blade 44. Lower, stationary cutting blade 42 is secured to support member 46 by a plurality of nuts and bolts 48 (one shown in FIG. 1) spaced along the cutting blade assembly. Upper, reciprocating blade 44 includes a plurality of elongated slots 50 extending longitudinally along the blade for receiving bolts 48 to permit blade 44 to be reciprocated relative to stationary blade 42 and support member 46. A drive mechanism (not shown) is provided to convert the rotary output of motor 34 to reciprocating motion of blade 44.
In the present embodiment, the rear end of handle 20 is provided with a power cord receptacle 52 for receiving a detachable power cord (not shown) to connect the tool to an electrical power source. The power cord receptacle receives a specially shaped power cord connector (not shown) of the detachable power cord to enable the tool to be connected to the power source. It is understood that the detachable power cord and receptacle do not constitute any part of the present invention and that other power cord arrangements, e.g., a permanently attached power cord, can be used to supply electric power to the tool.
Referring to FIG. 3, the tool includes a plug 54 located within the interior of handle 20 with a pair of plug blades 56 (one shown in FIG. 3) extending rearwardly into power cord receptacle 52. A generally rectangular support 58 extends inwardly from the interior of handle section 22 for supporting plug 54 in a fixed position relative to the handle. The connector of the detachable power cord (not shown) received in power cord receptacle 52 is adapted to make electrical contact with plug blades 56 to connect the tool to a source of electrical power. rectangular support 58 includes a first, cylindrical projection 60 extending inwardly from the interior of handle section 22 including a central opening for receiving screw 26 in the assembly of the handle.
As shown in FIG. 3, the power tool handle supports a control in the form of an on-off switch 62 operatively associated with motor 34. Switch 62 includes an actuator 64 normally biased downward to an off position and movable upward to an on position to operate the motor. A first pair of conductors 66 (only one shown) connects plug 54 to switch 62. In addition, a second pair of conductors 68 (only one shown) connects switch 62 to motor 34.
Handle section 22 includes additional cylindrical projections 70 and 72 for receiving screws 28 and 30 (FIG. 1), respectively, in the assembly of the handle. A similar cylindrical projection (not shown) is provided on the interior of handle section 22 for receiving screw 32.
The power tool handle supports a trigger mechanism for actuating switch 62 to control on-off operation of motor 34. The trigger mechanism provides automatic lock-off, manual unlock, and manual lock-on operations for control of the motor. The manual unlock and lock-on operations require intentional, distinct actions by the operator to unlock the trigger mechanism for manual operation and to achieve continuous operation of the power tool.
In accordance with the invention, the trigger mechanism includes a trigger manually movable from a first, inoperative position to a second, operative position to actuate the control and operate the motor. In a preferred embodiment of the trigger mechanism, means is provided for normally biasing the trigger toward its first, inoperative position. The preferred embodiment of the trigger mechanism shown in FIG. 3 includes a trigger, generally 80, mounted within the interior of handle 30 which includes a finger engageable body 82 protruding downwardly through a trigger opening defined by adjacent slots provided in the bottom of handle sections 22 and 24. Trigger 80 also includes a lever 84 extending rearwardly from its finger engageable body 82. Lever 84 is pivotally mounted at its rear end on a pivot pin 86 extending inwardly from the interior of handle section 22.
In addition, the rear end of lever 84 is provided with an inclined slot 88 for receiving a leaf spring 90. In an alternative embodiment, leaf spring 90 can be integral with arm 84 of the trigger. The leaf spring extends upwardly into engagement with the top of handle 20 to normally bias trigger body 82 in a downward, inoperative position (FIG. 3). The upper surface of trigger body 82 includes a front ledge or actuating surface 92 for engaging actuator 64 of switch 62 upon upward movement of the trigger to its operative position. The upper surface of trigger body 82 also includes a rear ledge or lock-off surface 94. An opening 96 extends downwardly into the trigger body between front ledge 92 and rear ledge 94. Further, the front surface of trigger body 82 includes a notch which provides a downwardly extending lip or lock-on member 98.
In accordance with the invention, the trigger mechanism includes first locking means for normally locking the trigger in its inoperative position. The first locking means is movable from a normal, lock-off position wherein the locking means is cooperatively engageable with the trigger to prevent movement of the trigger from its first, inoperative position to its second, operative position, toward a second, unlock position wherein the trigger is manually movable to its operative position to actuate the motor control.
Referring to FIG. 3, in the preferred embodiment of the trigger mechanism, the first locking means is embodied as a manually operable locking device or lever, generally 100, pivotally mounted on the power tool handle. Locking device 100 includes a cylindrical body 102 mounted on a pivot pin 104 extending inwardly from the interior of handle section 22. A stem 106 extends upwardly from cylindrical body 102 through an opening provided in the top of the handle. A manually engageable button 108 is provided at the top of stem 106 to enable the operator to pivot locking device 100 about pivot pin 104. A locking arm 110 extends downwardly from cylindrical body 102 toward trigger body 82 terminates in a flat, bottom surface 112. An integral leaf spring 114 projects from cylindrical body 102 and is received in a notch 116 provided at the top of handle section 22.
In addition, the trigger mechanism includes second locking means operable independently of the first locking means for locking the trigger in its operative position. The second locking means is movable from a first, unlock position out of the path of movement of the trigger to a second, lock-on position cooperatively engageable with the trigger to lock the trigger in its operative position to continuously actuate the control and operate the motor.
Referring to FIG. 3, in the preferred embodiment of the trigger mechanism, the second locking means is embodied as a manually operable locking device or lever, generally 120, pivotally mounted on the power tool handle. Locking device 120 comprises a cylindrical body 122 mounted on a pivot pin 124 extending inwardly from the interior of handle section 22 adjacent to the front surface of trigger body 82. A finger engageable portion 126 extends downwardly from cylindrical body 122 through another opening provided in the bottom of the handle to enable the operator to pivot locking device 120 about pivot pin 124. A lock-on finger 128 extends upwardly from cylindrical body 122. In addition, an integral leaf spring 130 projects from cylindrical body 122. A pin 132 is provided on the interior of handle section 22 adjacent to its bottom surface. The free end of leaf spring 130 is received between pin 132 and the bottom surface of handle section 22 to normally bias lock-on finger 128 to an unlock position out of the path of movement of trigger body 82.
If, with locking device 100 in its normal, lock-off position (FIG. 3), the operator attempts to raise trigger body 82 from its inoperative position, bottom surface 112 of locking arm 110 engages rear ledge or lock-off surface 94 of the trigger body to prevent upward movement of the trigger to its operative position. When it is desired to unlock the trigger mechanism, the operator engages and moves button 108 rearwardly to pivot locking device 100 in a clockwise direction, as indicated by arrow 134 (FIG. 4), against the bias of its leaf spring 114. The locking device is thus moved to an unlock position wherein locking arm 110 is out of the path of movement of lock-off surface 94 of the trigger body and in registration with opening 96.
As shown in FIG. 5, using his index finger in the normal fashion, the operator can then move trigger body 82 upward to is operative position to move actuator 64 upward to actuate switch 62. Upon upward movement of the trigger body, locking arm 110 is received in opening 96. If, with trigger body 82 in its operative position, the operator releases button 108 to allow integral leaf spring 114 to return locking device 100 toward its initial lock-off position, locking arm 110 is urged into engagement with the rear edge of opening 96 to prevent the locking device from completely returning to its lock-off position. If, however, the trigger body 82 is completely released by the operator, locking device 100 is automatically returned to its lock-off position (FIG. 3) by its integral leaf spring 114.
If it is desired to lock trigger 80 in its operative position, the operator engages finger engageable portion 126 of locking device 120 with the side of his index finger which is on the switch body 82 and moves the locking device 120 in a clockwise direction, as indicated by arrow 136 (FIG. 6), against the bias of leaf spring 130. Locking device 120 is thus moved to a lock-on position with finger 128 located below lip 98 of trigger body 82. The operator then releases the trigger body 82 to allow leaf spring 90 to bias the trigger body slightly downwardly to move lip 98 into engagement with finger 128. Leaf spring 90 exerts a sufficient downward bias force on trigger body 82 to maintain locking device 120 in its lock-on position against the bias of its integral leaf spring 130. With the trigger mechanism in its lock-on configuration (FIG. 6), the operator can release both trigger body 82 and finger engageable portion 126 of locking device 120 without terminating operation of the power tool motor.
When it is desired to terminate the lock-on operation of the trigger mechanism, the operator raises trigger body 82 slightly to disengage its locking member or lip 98 from finger 128 of locking device 120. Upon disengagement of lip 98 and finger 128, leaf spring 130 pivots locking device 120 in a counter clockwise direction to return finger 128 to its unlock position out of the path of movement of lip 98 of the trigger. The operator then releases trigger body 82 to allow leaf spring 90 to return the trigger body to its downward, inoperative position. As the trigger returns to its inoperative position, locking arm 110 of locking device 100 moves out of opening 96 in trigger body 82 to permit leaf spring 90 to return the locking device to its lock-off position (FIG. 3). Locking arm 110 moves into registration with rear ledge or lock-off surface 94 of the trigger body to prevent upward movement of the trigger body to its operative position. The trigger is thus automatically locked in its inoperative position to prevent inadvertent operation of the power tool.
The preferred embodiment provides a trigger mechanism having automatic lock-off and manual lock-on features. The trigger mechanism requires distinct actions, i.e., pivotal movement of two (2) independently operable locking levers to unlock the trigger for manual control of the power tool and to lock the trigger in its operative position for continuous operation of the tool. The requirement of distinct, intentional actions precludes inadvertent operation of the trigger mechanism.
The invention, in its broader aspects, is not limited to the specific details shown and described, and modifications may be made in the details of the trigger mechanism without departing from the principles of the present invention.
In the prior art, portable, hand-operated power tools, e.g., electrically powered hedge or shrub trimmers, grass shears and power saws, have included trigger mechanisms incorporating automatic lock-off and manual lock-on features. These features have been provided by a locking device movable between lock-off and lock-on positions to control the operation of a trigger. The automatic lock-off feature has protected an operator against accidential operation of the power tool, and the lock-on feature has enabled the operator to continuously operate the power tool without the necessity of exerting continuous manual pressure on the trigger.
The prior art trigger mechanisms have been capable of operation by a simple activity to operate the power tool between its lock-off and lock-on states. For example, it has been possible for an operator, by continuous movement of the locking device in a single direction, to unlock the trigger mechanism from its lock-off state and to operate the trigger mechanism to its lock-on state. Since only a simple activity has been required to operate the prior art trigger mechanisms from lock-off to lock-on states, the possibility of accidental lock-on operation of the power tool has been enhanced along with the attendant risk of injury to the operator.
To avoid the disadvantages of the prior art, it is desirable to provide a trigger mechanism having automatic lock-off and manual lock-on features for a portable, hand-operated power tool which requires a positive, intentional action, distinct from the activity required to unlock the trigger mechanism, to operate the trigger mechanism into its lock-on state. The requirement of a positive, intentional action minimizes the possibility of inadvertent lock-on operation of the tool.
It is an object of the present invention to provide a trigger mechanism for a hand-operated power tool which provides automatic lock-off and manual lock-on operation and requires an operator to consciously perform a complex activity to operate the trigger mechanism from its lock-off state to its lock-on state to minimize the possibility of inadvertent operation of the tool.
It is an additional object of the present invention to provide a trigger mechanism for a hand-operated power tool incorporating a first locking device which automatically locks the trigger in an inoperative position and permits the trigger to be unlocked for manual operation and a second locking device which permits the trigger to be locked in an operative position, wherein the locking devices require distinct, intentional actions by an operator to unlock the trigger and to lock the trigger in its operative position.
In accordance with the invention, a trigger mechanism for a hand-operated power device including a motor and a control operatively associated with the motor comprises a trigger manually movable from an inoperative position to an operative position to actuate the control and operate the motor; first locking means for normally locking the trigger in its inoperative position, the first locking means being movable from a first, lock-off position, cooperatively engageable with the trigger to prevent movement of the trigger from its inoperative position to its operative position, toward a second, unlock position wherein the trigger is manually movable to its operative position to actuate the control, and second locking means operable independently of the first locking means for locking the trigger in its operative position, the second locking means being movable from a first, unlock position out of the path of movement of the trigger to a second, lock-on position cooperatively engageable with the trigger to lock the trigger in its operative position to continuously actuate the control and operate the motor. Preferably, the trigger is normally biased toward its inoperative position, the first locking means is normally biased toward its lock-off position, and the second locking means is normally biased toward its first, unlock position. The first and second locking means are independently operable and require distinct actions by an operator to unlock the trigger for movement from its inoperative position to its operative position and to lock the trigger in its operative position.
In a preferred embodiment of the trigger mechanism, for use in a hand-operated power tool including an electric motor and a handle which supports a switch operatively associated with the motor, the first and second locking means comprises manually operable locking levers pivotally mounted adjacent to a finger engageable body of the trigger. The first locking lever is normally biased to a lock-off position in registration with a lock-off surface on the trigger body to prevent movement of the trigger body from its inoperative position to its operative position, and it is pivotable to an unlock position out of registration with the lock-off surface to permit the trigger body to be moved to its operative position. The second locking lever is normally biased to an unlock position out of the path of movement of the trigger body and is pivotable to a lock-on position wherein it is cooperatively engageable with a lock-on member on the trigger body to lock the trigger body in its operative position. In the operation of the trigger mechanism, an operator is required to perform distinct actions to pivot the first locking lever to unlock the trigger body for manual movement to its operative position and to pivot the second locking lever to lock the trigger body in its operative position.
The automatic lock-off and manual lock-on features of the trigger mechanism of the present invention preclude inadvertent operation of the power tool. The automatic lock-off feature requires an operator to perform an unlock activity prior to the actuation of the trigger to operate the tool. In addition, the manual lock-on feature requires the operator to perform a separate action, which is distinct from the unlock activity, to achieve lock-on operation of the power tool. These safety features of the trigger mechanism prevent an inexperienced operator from accidentally turning on the power tool and locking the tool on for continuous operation.
The accompanying drawings illustrate a preferred embodiment of the invention and, together with the description, serve to explain the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation, partially cutaway, of a portable, hand-operated power tool, e.g., a shrub or hedge trimmer, including a handle which supports a trigger mechanism comprising a manually movable trigger and first and second locking devices constructed in accordance with the principles of the present invention, a motor and a cutting blade assembly;
FIG. 2 is a plan view of the portable power tool of FIG. 1 illustrating the construction of the handle in two sections;
FIGS. 3 is an enlarged side view, taken along line 3--3 of FIG. 2, of the handle of the portable power tool, with one handle section removed, illustrating the trigger in its inoperative position, the first locking device in its lock-off position to lock the trigger in its inoperative position, and the second locking device in its inoperative position out of engagement with the trigger;
FIG. 4 is an enlarged side view, partially in section, of a portion of the handle of the portable power tool of FIG. 1 illustrating the first locking device operated from its lock-off position to its unlock position;
FIG. 5 is an enlarged side view, partially in section, of the same portion of the power tool handle illustrating the trigger raised from its inoperative position to its operative position; and
FIG. 6 is an enlarged side view, partially in section, of the same portion of the power tool handle illustrating the second locking device moved to its lock-on position to lock the trigger in its operative position.
DETAILED DESCRIPTION
FIG. 1 illustrates a portable, hand-operated power tool, e.g., a shrub or hedge trimmer, which incorporates a trigger mechanism constructed according to the principles of this invention. The power tool includes an elongated, hollow handle, generally 20, consisting of two (2) half sections 22 and 24 (FIG. 2). The half-sections of handle 20 are essentially mirror images of each other and are held together by a plurality of screws or bolts 26, 28, 30 and 32 (FIG. 1).
Referring to FIGS. 1 and 2, handle 20 includes a rearward portion which is relatively narrow and elongated to provide a convenient shape to be gripped by the hand of an operator. The handle also includes an enlarged forward portion to support a housing 36 for a motor 34 which drives the power tool. A hand grip 38 is secured at the top of the housinng to allow the operator to grip the tool with both hands.
As shown in FIG. 1, a cutting blade assembly, generally 40, extends forward from the front end of handle 20. The cutting blade assembly is standard in construction and, thus, only a portion of the assembly is illustrated.
Cutting blade assembly 40 includes a lower, stationary blade 42, an upper, reciprocating blade 44, and an elongated support member 46 which extends forward from the front end of the handle above reciprocating blade 44. Lower, stationary cutting blade 42 is secured to support member 46 by a plurality of nuts and bolts 48 (one shown in FIG. 1) spaced along the cutting blade assembly. Upper, reciprocating blade 44 includes a plurality of elongated slots 50 extending longitudinally along the blade for receiving bolts 48 to permit blade 44 to be reciprocated relative to stationary blade 42 and support member 46. A drive mechanism (not shown) is provided to convert the rotary output of motor 34 to reciprocating motion of blade 44.
In the present embodiment, the rear end of handle 20 is provided with a power cord receptacle 52 for receiving a detachable power cord (not shown) to connect the tool to an electrical power source. The power cord receptacle receives a specially shaped power cord connector (not shown) of the detachable power cord to enable the tool to be connected to the power source. It is understood that the detachable power cord and receptacle do not constitute any part of the present invention and that other power cord arrangements, e.g., a permanently attached power cord, can be used to supply electric power to the tool.
Referring to FIG. 3, the tool includes a plug 54 located within the interior of handle 20 with a pair of plug blades 56 (one shown in FIG. 3) extending rearwardly into power cord receptacle 52. A generally rectangular support 58 extends inwardly from the interior of handle section 22 for supporting plug 54 in a fixed position relative to the handle. The connector of the detachable power cord (not shown) received in power cord receptacle 52 is adapted to make electrical contact with plug blades 56 to connect the tool to a source of electrical power. rectangular support 58 includes a first, cylindrical projection 60 extending inwardly from the interior of handle section 22 including a central opening for receiving screw 26 in the assembly of the handle.
As shown in FIG. 3, the power tool handle supports a control in the form of an on-off switch 62 operatively associated with motor 34. Switch 62 includes an actuator 64 normally biased downward to an off position and movable upward to an on position to operate the motor. A first pair of conductors 66 (only one shown) connects plug 54 to switch 62. In addition, a second pair of conductors 68 (only one shown) connects switch 62 to motor 34.
Handle section 22 includes additional cylindrical projections 70 and 72 for receiving screws 28 and 30 (FIG. 1), respectively, in the assembly of the handle. A similar cylindrical projection (not shown) is provided on the interior of handle section 22 for receiving screw 32.
The power tool handle supports a trigger mechanism for actuating switch 62 to control on-off operation of motor 34. The trigger mechanism provides automatic lock-off, manual unlock, and manual lock-on operations for control of the motor. The manual unlock and lock-on operations require intentional, distinct actions by the operator to unlock the trigger mechanism for manual operation and to achieve continuous operation of the power tool.
In accordance with the invention, the trigger mechanism includes a trigger manually movable from a first, inoperative position to a second, operative position to actuate the control and operate the motor. In a preferred embodiment of the trigger mechanism, means is provided for normally biasing the trigger toward its first, inoperative position. The preferred embodiment of the trigger mechanism shown in FIG. 3 includes a trigger, generally 80, mounted within the interior of handle 30 which includes a finger engageable body 82 protruding downwardly through a trigger opening defined by adjacent slots provided in the bottom of handle sections 22 and 24. Trigger 80 also includes a lever 84 extending rearwardly from its finger engageable body 82. Lever 84 is pivotally mounted at its rear end on a pivot pin 86 extending inwardly from the interior of handle section 22.
In addition, the rear end of lever 84 is provided with an inclined slot 88 for receiving a leaf spring 90. In an alternative embodiment, leaf spring 90 can be integral with arm 84 of the trigger. The leaf spring extends upwardly into engagement with the top of handle 20 to normally bias trigger body 82 in a downward, inoperative position (FIG. 3). The upper surface of trigger body 82 includes a front ledge or actuating surface 92 for engaging actuator 64 of switch 62 upon upward movement of the trigger to its operative position. The upper surface of trigger body 82 also includes a rear ledge or lock-off surface 94. An opening 96 extends downwardly into the trigger body between front ledge 92 and rear ledge 94. Further, the front surface of trigger body 82 includes a notch which provides a downwardly extending lip or lock-on member 98.
In accordance with the invention, the trigger mechanism includes first locking means for normally locking the trigger in its inoperative position. The first locking means is movable from a normal, lock-off position wherein the locking means is cooperatively engageable with the trigger to prevent movement of the trigger from its first, inoperative position to its second, operative position, toward a second, unlock position wherein the trigger is manually movable to its operative position to actuate the motor control.
Referring to FIG. 3, in the preferred embodiment of the trigger mechanism, the first locking means is embodied as a manually operable locking device or lever, generally 100, pivotally mounted on the power tool handle. Locking device 100 includes a cylindrical body 102 mounted on a pivot pin 104 extending inwardly from the interior of handle section 22. A stem 106 extends upwardly from cylindrical body 102 through an opening provided in the top of the handle. A manually engageable button 108 is provided at the top of stem 106 to enable the operator to pivot locking device 100 about pivot pin 104. A locking arm 110 extends downwardly from cylindrical body 102 toward trigger body 82 terminates in a flat, bottom surface 112. An integral leaf spring 114 projects from cylindrical body 102 and is received in a notch 116 provided at the top of handle section 22.
In addition, the trigger mechanism includes second locking means operable independently of the first locking means for locking the trigger in its operative position. The second locking means is movable from a first, unlock position out of the path of movement of the trigger to a second, lock-on position cooperatively engageable with the trigger to lock the trigger in its operative position to continuously actuate the control and operate the motor.
Referring to FIG. 3, in the preferred embodiment of the trigger mechanism, the second locking means is embodied as a manually operable locking device or lever, generally 120, pivotally mounted on the power tool handle. Locking device 120 comprises a cylindrical body 122 mounted on a pivot pin 124 extending inwardly from the interior of handle section 22 adjacent to the front surface of trigger body 82. A finger engageable portion 126 extends downwardly from cylindrical body 122 through another opening provided in the bottom of the handle to enable the operator to pivot locking device 120 about pivot pin 124. A lock-on finger 128 extends upwardly from cylindrical body 122. In addition, an integral leaf spring 130 projects from cylindrical body 122. A pin 132 is provided on the interior of handle section 22 adjacent to its bottom surface. The free end of leaf spring 130 is received between pin 132 and the bottom surface of handle section 22 to normally bias lock-on finger 128 to an unlock position out of the path of movement of trigger body 82.
If, with locking device 100 in its normal, lock-off position (FIG. 3), the operator attempts to raise trigger body 82 from its inoperative position, bottom surface 112 of locking arm 110 engages rear ledge or lock-off surface 94 of the trigger body to prevent upward movement of the trigger to its operative position. When it is desired to unlock the trigger mechanism, the operator engages and moves button 108 rearwardly to pivot locking device 100 in a clockwise direction, as indicated by arrow 134 (FIG. 4), against the bias of its leaf spring 114. The locking device is thus moved to an unlock position wherein locking arm 110 is out of the path of movement of lock-off surface 94 of the trigger body and in registration with opening 96.
As shown in FIG. 5, using his index finger in the normal fashion, the operator can then move trigger body 82 upward to is operative position to move actuator 64 upward to actuate switch 62. Upon upward movement of the trigger body, locking arm 110 is received in opening 96. If, with trigger body 82 in its operative position, the operator releases button 108 to allow integral leaf spring 114 to return locking device 100 toward its initial lock-off position, locking arm 110 is urged into engagement with the rear edge of opening 96 to prevent the locking device from completely returning to its lock-off position. If, however, the trigger body 82 is completely released by the operator, locking device 100 is automatically returned to its lock-off position (FIG. 3) by its integral leaf spring 114.
If it is desired to lock trigger 80 in its operative position, the operator engages finger engageable portion 126 of locking device 120 with the side of his index finger which is on the switch body 82 and moves the locking device 120 in a clockwise direction, as indicated by arrow 136 (FIG. 6), against the bias of leaf spring 130. Locking device 120 is thus moved to a lock-on position with finger 128 located below lip 98 of trigger body 82. The operator then releases the trigger body 82 to allow leaf spring 90 to bias the trigger body slightly downwardly to move lip 98 into engagement with finger 128. Leaf spring 90 exerts a sufficient downward bias force on trigger body 82 to maintain locking device 120 in its lock-on position against the bias of its integral leaf spring 130. With the trigger mechanism in its lock-on configuration (FIG. 6), the operator can release both trigger body 82 and finger engageable portion 126 of locking device 120 without terminating operation of the power tool motor.
When it is desired to terminate the lock-on operation of the trigger mechanism, the operator raises trigger body 82 slightly to disengage its locking member or lip 98 from finger 128 of locking device 120. Upon disengagement of lip 98 and finger 128, leaf spring 130 pivots locking device 120 in a counter clockwise direction to return finger 128 to its unlock position out of the path of movement of lip 98 of the trigger. The operator then releases trigger body 82 to allow leaf spring 90 to return the trigger body to its downward, inoperative position. As the trigger returns to its inoperative position, locking arm 110 of locking device 100 moves out of opening 96 in trigger body 82 to permit leaf spring 90 to return the locking device to its lock-off position (FIG. 3). Locking arm 110 moves into registration with rear ledge or lock-off surface 94 of the trigger body to prevent upward movement of the trigger body to its operative position. The trigger is thus automatically locked in its inoperative position to prevent inadvertent operation of the power tool.
The preferred embodiment provides a trigger mechanism having automatic lock-off and manual lock-on features. The trigger mechanism requires distinct actions, i.e., pivotal movement of two (2) independently operable locking levers to unlock the trigger for manual control of the power tool and to lock the trigger in its operative position for continuous operation of the tool. The requirement of distinct, intentional actions precludes inadvertent operation of the trigger mechanism.
The invention, in its broader aspects, is not limited to the specific details shown and described, and modifications may be made in the details of the trigger mechanism without departing from the principles of the present invention.