US2947840A - Electric switch - Google Patents

Description

Aug. 2, 1960 R. F. PARK ET AL ELECTRIC swncn Filed April 25, 1958 United States Patent ELECTRIC swrrcn Rodney F. Park, Elm Grove, and Robert D. Thomas, Fox Point, Wis., assiguors to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Filed Apr. 25, 1958, Ser. No. 730,833

17 Claims. (Cl. 200--160) This invention relates to electric switches' and more particularly to switch operating mechanisms provided with an emergency release mechanism for releasing the switch from its operating position.

While not limited thereto, the invention is especially applicable to trigger operated electric switches incorporated in the handles of portable electric power tools and the like.

A general object of the invention is to provide improved means for translating interrupted angular motion into reciprocatory motion.

A more specific object of the invention is to provide a trigger operated electric switch with an improved emergency release mechanism.

Another specific object of the invention is to provide such emergency release mechanism which is operated in response to the normal reflex action of the operator under abnormal conditions.

Another specific object of the invention is to provide an improved electric switch of the trigger operated type wherein the switch is actuated to its operating position when the trigger is-pressed a given amount to its first stopping position and is automatically tripped to its normal position when the trigger is pressed further, the trigger being returned to its normal position and reset when released.

Another specific object of the invention is to providesuch automatically tripping switch wherein return of the trigger to its normal position and resetting thereof requires an additional manual operation on the part of the operator.

Another object of the invention is to provide an improved electric switch for accomplishing the aforementioned objects which is simple in construction and reliable in operation, and may be economically manufactured primarily from stamped sheet metal parts and readily assembled.

Other objects and advantages of the invention will hereinafter appear.

While the apparatus hereinafter described is eflectively adapted to fulfill the objects stated, it is to be understood that I do not intend to confine my invention to the particular preferred embodiment of electric switch disclosed inasmuch as it is susceptible of various modifications without departing from the scope of the appended claims.

The invention will now be described with reference to the accompanying drawings wherein:

Figure 1 is a partly sectional front elevation view of an electric switch constructed in accordance with the invention;

Fig. 2 is a left end elevation view of the switch of Fig. 1;

Fig. 3 is a perspective view of the guide link detail of the switch of Fig. 1;

Fig. 4 is a front elevation view of the switch actuating mechanism in its operating position and, in broken lines,

in its emergency release position; and

Fig. 5 is a fragmentary view of a modification of the invention. 7

' Referring to Figs. 1 and 2, the switch is provided with a substantially inverted U-shaped frame 2 the left-hand portion of which is provided with a rising inverted U- shaped enlargement from approximately its mid-point 2a. The legs of the U-shaped frame at its right-hand portion are provided with outwardly extending portions 2b as seen in Fig. 2 to provide a seating surface for an insulating switch contact supporting housing 4. Housing 4 is secured by screws 6a and 6b or the like to frame 2 in abutting relation to outwardly extending portions 2b. Screws 6a and 6bare shown riveted over frame 2 at .their threaded ends to prevent loosening'of housing 4.

Housing 4 may be provided in a well-known manner with stationary contacts electrically connected to external wiring terminals (not shown) and a movable contact operable for bridging the stationary contacts as hereinafter described.

An elongated, generally inverted U-shaped contact actuating member or guide link 8, more clearly shown in Fig. 3. is slidably accommodated within the U-shaped frame and extends from the left-hand end of frame 2 into overlapping relation with housing 4. Link 8 is provided with an elongated slot 8a for receiving screw 6a and to permit longitudinal reciprocation of link 8 relative thereto. Link 8 is also provided at its right-hand end as seen in Fig. 1 with a perpendicular actuator pin 8b rigidly secured to the bottom of the U and extending into housing 4 for actuating the movable contact therein and a semispherical nib on its upper surface which may be lubricated for sliding enegagement with the inner'surface of the U- shaped frame. Link 8 is further provided with a combined return spring retaining and guide link releasing element 10 rigidly secured thereto as by spot welding or the like. Element 10 is provided with a return spring retaming portion 10a extending upwardly substantially perpendicular to guide link 8 for receiving one end hook of a return spring 12. The left-hand enlarged portion of frame 2 is provided with an elongated slot 20 for accommodating spring 12 and an aperture 2d adjacent the right-hand end of slot 20 for receiving the other end hook of spring 12, the latter being normally under tension to bias guide link 8 in theright-hand direction against screw 6b. Element 10 is also provided with laterally extending portions 10b for providing an emergency release structure as hereinafter described.

The legs of U-shaped guide'link 8 at the extreme lefthand end thereof as seen in Fig. l are provided with aligned apertures 8d, more clearly seen in Fig. 3, for receiving a rotatable pin 14 hereinafter described. The

upper left-hand end of the enlarged portion of U-shaped frame 2 is provided with aligned apertures 2e. A generally inverted U-shaped trigger member 16 straddles the left-hand enlarged portion of frame 2 and is provided with correspondingly aligned apertures 16a for receiving a pivot pin 18 therethrough and through apertures 2e. Pin 18 may be a pivot or the like for pivoting trigger member 16 on frame 2. Trigger member 16 is provided with a depressed portion 16b having an aperture therein for receiving one end hook of a tension spring 20. The other end hook of spring 20 is retained in an annular groove 14a in the mid-portion of pin 14, the shank portion of the hook being received in a notch Se in the end of guide link 8 to prevent pin 14 from longitudinal displacement. Notch Se is more clearly shown inFig. 3.

Each of the depending leg portions of U-shaped trigger member 16 is provided with a'semi-circular notch or catch 22 for receivingthe end portions of pin 14, the opposite end portions of pin 14 extending laterally of the switch mechanism beyond the leg portions of trigger member 16. As will be apparent, tension spring 20 retains pin 14 in catch 22. Also, the connection of spring 3 20 to trigger member 16 being displaced outwardly from a line running through pin 14 and pivot pin 18, spring 20 biases trigger member '16 in its normal released position as shown in Fig. 1.

The depending leg portions of trigger member 16 are also provided with operating edges 24 for engagement with laterally extending portions b. Edges 24 terminate in substantially perpendicular extensions 26 for guiding the trigger member into the tool handle when the latter is pressed. One leg of U-shaped frame 2 is provided with a rectangular notch 28 shown in Fig. 1 and the other "leg thereof is provided with a downwardly depending portion 30 having a rectangular aperture 32 (Fig. 4) aligned with notch 28 for receiving laterally extending portions 10b and permitting reciprocal movement of the latter therewithin. Portion 30 is also provided with a pair of apertures 34 or the like for securing the switch to a portable tool.

Each depending leg portion of trigger member 16 is further provided between catch 22 and operating edge 24 with an operating edge aifording free travel of rotatable pin 14 thercalong with a minimum of perpendicular force being applied thereby to the guide link when the emergency release mechanism is actuated, and for facilitating resetting of pin 14 within catch 22 when the trigger is released. To this end, the edge 24a of each depending leg portion extending from operating edge 24 toward the catch is substantially parallel to the axis of the guide link when the trigger member is in its operating position shown in solid lines in Fig. 4, and terminates at the catch in an upwardly angled camming edge 24b.

Trigger member 16 is provided with a curved surface 36 graduated from a rounded surface at its ends to a flat surface at its mid-portion for receiving the finger of the operator. A pair of inwardly extending pressformed stops 37 for abutment against the upper corners of frame 2 are provided in member 16 as shown in dotted lines in Fig. 4 to limit clockwise pivoting of trigger member 16 when the latter is pressed to release the switch. A puslrbutton 38 which may be set following pressing of trigger member 16 is provided for maintaining the switch in its operating position. Pushbutton 38 is provided with a pin 40 slidably extending through .4 from the stationary contacts. Thus, the external circuit which may lead to a portable tool motor or the like is interrupted.

When trigger member 16 is pressed toward its operating position shown in solid lines in Fig. 4, it pivots on pin 18 in the clockwise direction. maintains the end portions of pin 14 within catches 22 so that the pivotal movement of the trigger member eflects longitudinal sliding movement of guide link 8 in the left-hand direction. The movable contact may be provided in a well-known manner with an over-center compression spring so that the movable contact snaps to its closed position when movei over its center position in the left-hand direction and snaps to its open position when moved over its center position in the right-hand direction. Thus, when the trigger member approaches its operating position wherein edges 24 thereof abut lateral extensions 10b, actuator pin 8b moves the movable contact over its center position to snap the movable contact to its closed position and provides a definite feel' for the operator. In this position the movable contact bridges the stationary contacts to close the external circuit.

When it is desired to stop the operation of the portable power tool, the trigger member may be released. As a result, return spring 12 moves guide link 8 in the righthand direction against stop screw 6b to interrupt the contacts and spring 20 pivots trigger member 16 to its normal position.

When an abnormal condition occurs in the operation of the tool, the normal reflex action of the operator is to grip the handle and consequently the trigger member more tightly rather than to release the same. This is especially true in the operation of portable power drills and the like where a twisting or binding action requires a tighter hand grip on the part of the operator to prevent injury to the workpiece, the tool or the operator.

An essential feature of the invention is to provide an emergency release mechanism operative in response to further pressing of the trigger member beyond its operating position for interrupting the contacts. Thus, .the normal reflex action of the operator efiects stopping of the portable power tool. To this end, when the trigger member is further pressed from its operating position aligned apertures in the g portions of frame 2 and 6 shown in solid lines in Fig. 4 to its dotted line position,

having an enlarged end portion 42 to-prevent removal of the pin through the apertures. The area surrounding the aperture in frame 2 next to enlarged end portion 42 may be pressed inwardly so that the latter clears the trigger member when the pushbutton is retracted. A helical compression spring 44 surrounds pin 40 between the pushbutton and the leg portion of frame 2 for retracting pin 40 when the trigger member is manipulated. The depending leg portion of trigger member 16 on the pushbutton side is provided with an enlarged opening '46 as shown in Fig. 4 sufliciently large to clear wring 44 when the trigger member is operated. The other depending leg portion of trigger member 16 is provided with a more restricted opening 48 as shown in Fig. 4 in concentric alignment with pin 40 when trigger member 16 is pressed to its operating position. Opening 48 is sufliciently large to receive enlarged end 42 freely therethrough when the trigger member is pressed to its operating position and to maintain the same in such position as shown in Fig. 4. v

The operation of the switch will now be described. Let it be assumed that trigger member 16 is in its normal released position as shown in Fig. '1.\ The trigger member is biased in this counterclockwise position on pivot pin 18 by tension spring 20 which also biases pin 14 into semi-circular catches 22. Return spring 12 biases guiderlink 8 in its extreme right-hand direction against screw 6b which forms a stop therefor. In this condition, it may be assumed for exemplary purposes that actuator pin 8b maintains the movable contact separated 15 turn spring 12 maintains the contacts open.

operating edges 24 of trigger member 16 bear against lateral extensions 10b to pivot guide link 8 downwardly through a small angle in the counterclockwise direction. This counterclockwise movement of guide link 8, which effects substantially downward movement of the lefthand end of the guide link, in conjunction with the clockwise pivotal movement of the trigger member forces pin 14 to roll out of semi-circular catches 22. As a result, return spring 12 overpowers tension spring 20 to snap guide 8 quickly in the right-hand direction against stop screw 6b. The result is to interrupt the contacts and stop the power tool. Stops 37 abut against the upper corners of frame 2 to limit the movement of the trigger member. Stops 37 are provided to prevent imposition of shear forces on extension 1% between operating edge 24 and the lower edge of aperture 32. Pin 14 is arranged to rotate to reduce wear thereon. It will be apparent that when pin 14 is thus forced out of catcher 22, pin 14 rolls along edges 24!: and 240, the latter edge being substantially parallel to the line of travel of pin 14 to atford free movement of the latter and consequently the guide link to its normal position. The small downward movement applied to pin 14 by camming edge 24b is not suflicient to significantly impede movement of the guide link under the force of spring 12.

when the trigger member is released, tension spring 20 pivots the same in the counterclockwise direction to its normal released position wherein pin 14 enters catches 22 to automatically reset the operating mechanism while time- As e Tension spring 20 through. Release of the trigger member while the pushbutton is being pressed hooks enlarged end portion 42 around the edge of aperture 48 to prevent spring 44 from retracting pin 40. Thus, pin '40 maintains the trigger member in its operating position and the contacts closed. To reopen the contacts, the operator need press the trigger member only an amount suflicient to permit the edge of aperture 48 to clear enlarged portion 42 and to release the trigger member. .Spring 44 retracts pin 40 and springs 20 and 12 return the trigger member to its normal position and move guide link 8 in the right-hand direction to reopen the contacts.

The modification shown in Fig. 5 is similar to Figs. 1

through 4 except that a small notch 24d having a leading edge thereto from operating edge 24a is provided on each depending leg portion of the trigger member at the junction of edges 24a and 24b. This notch provides an additional safety feature in that it prevents automatic return of the trigger member to its normal position and resetting of the mechanism when the trigger member is released after emergency release of the switch. When the trigger is released after pressing thereof to its dotted line position shown in Fig. 4, pin 14 will roll along edge 24a and stop in notch 24d. As a result, repressing of the trigger member will not reclose the switch contacts. To reset the operating mechanism, it is necessary for the operator to manually pull the trigger member so that pin 14 rolls out of notch 24d and into catch 22. This additional manual operation alerts the operator to a locked motor or other abnormal condition and prevents rapid repeated operation of the switch following emergency release thereof. As will be apparent, notch 24d provides an additional safety feature to protect the operator, the tool and the work piece under certain abnormal conditions.

We claim: I

1. In an electric switch, in combination, a depressible trigger member, means for normally maintaining the switch in its normal position when said trigger member is in its normal undepressed position, means comprising a switch actuator responsive to depressive movement of said trigger member to an intermediate stopping position for actuating the switch to its operating position, and separable latch means comprising cooperating portions on said switch actuator and saidtrigger member responsive to further depressive movement of trigger member beyond said stopping position for permittingreturn of the switch from said operating position to said normal position. i

2. The invention defined in claim 1, together with means responsive to release of said trigger member for returning the same to its normal undepressed position without actuating the switch. I

3. The invention defined in claim 2, together with means responsive to the last mentioned means for resetting said latch means whereby the switch is again rendered operable lijn response to a depressive movement of said trigger mem- 4. In an electric switch, in combination, a depressible trigger member, means for normally maintaining the switch in its normal position when said trigger member is in its normal undepressed position, means responsive to depressive movement of said trigger member to an intermediate stopping position for actuating the switch to its operating position, means comprising a rotatable coupling member responsive to further depressive move- 5. In an operating mechanism'for translating interrupted I angular motion into reciprocatory motion, in combination, a pivotal driving member operable through a predetermined angle, a reciprocatory driven member biased in a first direction, said members comprising substantially frictionless means for coupling the same to one another for movement of said reciprocatory member in a second direction under the driving force of said pivotal member when said pivotal member is moved to an intermediate stopping point on its operating angle, and means responsive to movement of said pivotal member beyond said intermedi ate point for disengaging said coupling means to permit movement of said reciprocatory member in said first direction.

6. The invention defined in claim 5, wherein said coupling means comprises a cylindrical roller carried by said reciprocatory member, a complementary catch on said pivotal member, and means for biasing said roller in said catch whereby said reciprocatory member is driven by said pivotal member to said stopping point.

7. In an operating mechanism for translating interrupted angular motion into reciprocatory motion, in combination, a pivotal member operable through a predetermined angle, a reciprocatory member biased in a first direction, said members comprising substantially frictionless means for coupling the same to one another for movement of said reciprocatory member in a second direction under the driving force of said pivotal member when said pivotal member is moved to an intermediate stopping point on its operating angle, said coupling means comprising a cylindrical roller carried by said reciprocatory mem ber, a complementary catch on said pivotal member, and means for biasing said roller in said catch; and means responsive to movement of said pivotal member beyond said intermediate point for disengaging said coupling means to permit movement of said reciprocatory member in said first direction, said disengaging means comprising lateral extensions on said reciprocatory member in the path of said pivotal member for forcing said roller out of said catch when said pivotal member is moved beyond said intermediate point.

8. The invention defined in claim 5, wherein said coupling means comprises a pin mounted on said reciprocatory member, a semi-circular catch on said pivotal member for receiving said pin, and means for maintaining said pin in said catch. while said pivotal member is moved to said intermediate point.

9. The invention defined in claim 5, wherein said disengaging means comprises lateral extensions on said reciprocatory member in the path of movement of said pivotal member for moving said reciprocatory member to effect disengagement of said coupling means when said pivotal member is moved beyond said intermediate point.

10. In an electric switch,-in combination, a supporting frame, a depressible trigger member pivoted on said frame, a switch actuating member slidably mounted in said frame for reciprocating axial movement therein, first spring means normally biasing said switch actuating member into a first axial position in said frame, second spring means connected between said trigger member and said switch actuating member for biasing said trigger member into its normal undepressed position and for coupling said switch actuating member to said trigger member for movement to a second axial position when said triggermember is 7 pressed a predetermined amount, and means responsive to further pressing'of said trigger member beyond said predetermined amount for uncoupling said switch actuating member therefrom to render said first spring means etfective to overpower said second spring means and to move said switch actuating member back into said first position.

11. The invention defined in claim 10, wherein said trigger member overlies said switch actuating member and said second spring means is rendered efiective responsive to release of said trigger member for pivoting the latter relative to said switch actuating member back to said normal position and for recoupling the latter thereto.

12. The invention defined in claim 10, wherein the last mentioned means comprises lateral projections on said switch actuating member for engagement with said trigger member when the latter is pressed said predetermined amount and further pressing of said trigger member ett'ecting movement of said switch actuating member substantially perpendicular to its axis to uncouple the latter from said trigger member.

13. The invention defined in claim 10, wherein said trigger member overlies said switch actuating member and said second spring means is rendered etIective responsive to release of said trigger member for pivoting the latter relative to said switch actuating member back toward said normal position, together with means on said trigger member for stopping the same short of its normal position, recoupling of said members requiring manual movement of said trigger member back to its normal position.

14. In an electric switch having a supporting frame, a depressible trigger member pivoted on said irame, a longitudinal switch actuating member slidably accommodated in said frame for reciprocating axial movement therein, and a first spring yieldably maintaining said switch actuating member in a first axial position when said trigger is in a released condition, the improvement comsesame prising spring means connected between a portion of said trigger member offset from its pivot and said switch actuating member for yieldably maintaining said trigger member in its normal undepressed position and for yieldably latching portions of said members ,to one another to efiect axial movement of said switch actuating member to a second position when said trigger member is pressed at predetermined amount, means effecting engagement of said trigger member and said switch actuating member at portions spaced from said latching portions in said second position, further pressing of said trigger member requiring application of greater force thereon to move the latched portion of said switch actuating member away from said trigger member against the force of said spring means to effect disengagement of said members, said disengagement rendering said-first spring operative to restore said switch actuating member to said first axial position against the force of said spring means, and said spring means restoring said trigger member to said normal undepressed position responsive to release thereof without further movement of said switch actuating member and relatching said members in such position.

15. The invention defined in claim 14, wherein one of said members is provided with a reduced friction rotary element for receipt in a cooperating catch in the other element under the force of said spring means.

16. The invention defined in claim 15, wherein said catch comprises a substantially semi-circular slot for receiving said rotary element.

17. The invention defined in claim 14, together with stop means for limiting said further pressing movement of said trigger member following disengagement of said members.

References Cited in the file of this patent UNITED STATES PATENTS 2,616,009 Roeser; 0ct.28, 1952

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