US3766348A

US3766348A - Two part casing for trigger switch with one part mounting all switch contact members

Info

Publication number: US3766348A
Authority: US
Inventors: D Johnson
Original assignee: Arrow Hart Inc
Current assignee: Cooper Industries LLC; Arrow Hart Inc
Priority date: 1972-04-24
Filing date: 1972-04-24
Publication date: 1973-10-16
Anticipated expiration: 1990-10-16

Abstract

The parts of an electric switch are contained within a two-part insulating casing in which a trigger member slides and operates an over-center mechanism to impart a snap action movement to a yoke which causes a movable contact carrier to operate bridging contacts. Sets of fixed contacts are engaged and disengaged by different bridging contacts with one bridging contact always remaining in contact with one fixed contact of its set. The fixed contacts are stamped from sheet metal and are mounted edgewise in separate slots in the casing. All of said fixed and bridging contact members are mounted in one of said casing parts.

Description

United States Patent 1191 Johnson Oct. 16, 1973 [54] TWO PART CASING FOR TRIGGER 3,673,365 6/1972 Schadow 200/16 D x SWITCH WITH N T MOUNTING ALL 3,548,276 12/1970 Gross 318/380 X SWITCH CONTACT MEMBERS 3,588,411 6/1971 Milcoy 200/ 157 [75] Inventor: David W. Johnson, Newington,

Conn Primary Examiner-Robert K. Schaefer w Assistant ExaminerRbcrt A. Vanderhye [73] Asslgnee: Arrow-hart, Inc., Hartford, Conn. Atmmey winiam E Sonnekalb, In [22] Filed: Apr. 24, 1972 [21] App]. No.: 246,951 [57] ABSTRACT The parts of an electric switch are contained within a U-S. D, two-part insulating casing in which a trigger member 200/166 CT slides and operates an over-center mechanism to imf Clm H0111 13/08, H0111 1/58, H0111 13/30 part a snap action movement to a yoke which causes a Fleld of Search 76, C, movable ontact carrier to operate contacts 200/16 D, 166 BH, 166 CT Sets of fixed contacts are engaged and disengaged by different bridging contacts with one bridging contact References Cited always remaining in contact with one fixed contact of UNITED STATES PATENTS its set. The fixed contacts are stamped from sheet 2,776,348 1 1957 Korry 200/76 metal and are mounted edgewise in Separate Slots in 3,290,463 12/1966 Johnson 200/76 x the g- All o i fi and bn'dging Contact members are mounted in one of said casing parts.

7 Claims, 9 Drawing Figures 1 a 3/ li i i I l i 'Q' /33 f 2/ a e 49 D-i l I 1 TWO PART CASING FOR TRIGGER SWITCH WITH ONE PART MOUNTING ALL SWITCH CONTACT MEMBERS This invention relates to electric switches for controlling the operation of portable electric power-operated hand tools and more particularly relates to a snap action electric switch having a trigger as an operating member for movable contacts and having fixed contacts which are engaged and. disengaged by movement of the trigger member and movable contacts to cause encircuiting connections to an electric :motor for operating it at full power or dynamically braking the motor immediately upon disconnecting it from the power lines.

BACKGROUND OF THE INVENTION The patent of T.A.O. Gross U.S. Pat. No. 3,548,276 issued Dec. 15, 1970, discloses a circuit suitable for use in connection with electric power operated portable hand tools for dynamically'braking the motor when the circuit to it from the source of power is broken. This circuit contemplates use of a conventional double pole double throw switch to connect a universal or a series wound motor directly in series circuit with the power lines in the on position of the switch and to brake the connection of the motor to the power lines in off position, while concomitantly connecting the motor winding with the dynamic braking circuitry.

BRIEF DESCRIPTION OF THE INVENTION According to the invention, the parts of the switch are mounted within a two-part insulating casing containing two sets of contacts which are connectable to an electric motor and the power line by movement of a movable contact in in one position of the switch. In another position of the switch, the contacts are connected to electronic circuit components including diodes and a small size capacitor which are also contained within the insulating casing and to the motor to cause dynamicbraking of the motor. An insulating movable contact carrier carries two bridging contacts each of which bridges either a common and one or the i'olhfil of two other contacts of the set as a slidable trigger is moved in and outwardly of the casing and operates a snap action over-center yoke which causes movement of the movable contact carrier.

It is an object of the invention to provide a novel compact trigger-operated switch for use in a portable electric power operated tool utilizing the circuit of said patent or of any other suitable dynamic braking circuit.

Other objects and advantages of the invention will appear as it is described in connection with the accompanying drawing.

Another object is to provide a novel construction of a snap action double-pole double throw, triggeroperated switch, which may be economically assembled from economically manufactured parts, and including electronic circuit components within a com? pact casing, for use in a dynamic braking circuit.

In the drawing, FIG. 1 is a side elevation view of a switch embodying the invention.

FIG. 2 is a side elevation view with the cover removed and viewed from the opposite side from FIG. 1.

FIG. 3 is an end elevation view.

FIG. 4 is a perspective view partly broken away of the contact carrier and one movable contact used in the invention.

FIG. 5 is a section view along line 5-5 of FIG. 4.

FIG. 6 is an exploded perspective view of the upper contact and terminal members.

FIG. 7 is an exploded perspective view of the lower contacts and terminal members.

FIG. 8 is a detailed view showing in side elevation the end terminal member.

FIG. 9 is a schematic view of the switch contacts and terminals when used in a dynamic braking circuit.

Referring to the drawing, two

mating casing halves

10 and 20 are molded of insulating material into convenient elongated tapered rectangular shape with hollowed-out and recessed interiors to accommodate the parts of the switch mechanism when the halves are put together. 7

At one end of the casing guideways 21 are provided for a rectilinearly slidable trigger member 30 which has a finger engaging portion 30a of common shape exterior to the casing, and a portion 30b extending into the casing and slidable in the guideways of the casing halves.

A coiled compressed biasing spring 21 seats at one end in a recess in the finger portion 30 of the trigger while its opposite end presses against the casing to bias the trigger to off position.

To operate the movable parts of the switch an overcenter coiled compression spring 33 engages at one end with a nub 30c on the inner end of the trigger and seats at its other end on the transverse portion of a U-shaped sheet metal yoke 31. The yoke is pivotally mounted by outwardly extending trunnions seated in aligned bearing recesses in the casing halves. The transverse portion of the yoke engages a longitudinally slidable contact carrier 35 made of molded insulating material which is T-shaped in cross-section and extends parallel to the travel of the trigger and adjacent the inner portion 30b of the trigger. The contact carrier 35 is guided in its sliding movement by engagement with the casing and the fixed contacts hereinafter described.

The contact carrier has a guide part 35a and a contact carrying part 35c perpendicular to the guide part, the carrier part 350 having oppositely facing parallel surfaces facing the cover part 10 and the base part 20 of the casing. Seated on each of these surfaces is a stamped metal

movable bridging contact

37, 39, respectively, of flattened dumbbell shape having

domed contact buttons

37c, 390 at each end. The contact buttons are adapted to engage different fixed contacts (as hereinafter described) as the carrier 35 is moved by the yoke 31 as the yoke swings between off and on positions when the trigger is finger pressed in and returns outwardly when released. In order that the movable contacts may resiliently engage the various fixed contacts and be biased toward them, two coiled compression springs 38 are provided in two spaced cylindrical bores 35b or recesses beneath the contact buttons 35c.

The fixed contacts for engagement and disengagement by the movable bridging contacts are mounted in the base half 20 of the casing in spaced positions as will now be described.

The fixed contacts are located in two levels in parallel planes. Only for convenience in reference, the contacts in these levels will be referred to as upper and lower contacts simply to identify them, it being obvious that the invention is not limited to higher or lower location of the contacts with respect to each other or to the casing parts.

The

contact members

40, 50, 60, 70, 80 and 90 are all stamped from sheet metal into the various shapes illustrated in FIGS. 6 and 7 and are mounted edgewise in separate slots molded in the base half of the casing. The contour of each slot is complementary to the edgewise contour of the member which it receives. Some of the members have flat terminal extensions which project through apertures in the flat floor of the base half 20 as described below.

Viewing FIG. 2, the second, fourth and

sixth members

40, 50 and 60 each have flat central body portions as may be seen in detail in FIG. 7. From each, a finger extends towards the movable contact carrier 35 thus providing

upper contacts

43, 53, 63 which have flat under edge surfaces lying in the same plane and adapted to be engaged by the bridging contact 37 as it is slid to and fro by movement of the carrier 35 uncler influence of the yoke 30. 7

.

Members

40 and 50 on the edges opposite the contact fingers each have a terminal lug, 41 and 56 respectively, extending from its inner edge through apertures in the base half 20.

The first, third and

fifth members

70, 80 and 90, each have flat central body portions as may be seen in detail in FIG. 6. From each, a finger extends toward the movable contact carrier thus providing

lower contacts

72,82 and 92, which have flat upper edge surfaces lying in the same plane and adapted to be engaged by the bridging contact 39 as it is slid to and fro by movement of the carrier 35 under the influence of yoke 30.

Members

70 and 80 on the opposite contact fingers each have terminal lugs, 73 and 84 respectively, extending from its inner edge through apertures in the base half 20. t

The members'60 and 90 may have terminal portions but do not require them in the usage for which the disclosed embodiment is intended.

The

movable contact members

37 and 39 are of such length that their dome-shaped contact portions 37c and 39c, respectively, are spaced-apart a distance equal to the spacing of the contact fingers. Specifically and for example, the upper movable contact 37 has its contact buttons spaced apart the same distance as the upper

fixed contacts

43 and 53; and this distance is the same as the distance between the contact fingers53 and 63. Thus, when the switch is in the off position as illustrated in FIG. 2, contact 37 bridges the

upper contact fingers

63 and 53. When the switch is moved into the on position, the movable contacts will slide into position where it will engage and bridge the

contact fingers

43 and 53.

Likewise, the lower contact 39 in the off position of FIG. 2 will bridge the

lower contact fingers

92 and 82; and when moved into the on position the lower contact 39 will bridge the

lower contact fingers

82 and 72.

From the foregoing, it will be clear that the switch can occupy only two positions even though the trigger may be in transit between its fully depressed or fully released positions. Movement of the trigger will not become effective to change the'position of the

movable contact members

37,39 unitl the over-center spring 33 is moved through an over-center position in respect to the yoke 31 as the trigger is actuated. As the overcenter position is passed through, the yoke will move the contact carrier and bridging-contacts with a snap action. 1

As will now be described, the

fixed contacts

53, 63 and 82, 92 have circuit connections to electronic circuit components for dynamic braking of a motor which may be connected to the switch terminals, whilst the

fixed contacts

72, 73 are connected respectively to one power line and to one side of the motor A armature. In the off position contact 72 is not engaged by the bridging contact 39, in consequence of which the power to the motor is cut off and only the braking circuitry is connected operatively. On the other hand, while the braking circuitry is connected operatively (in the off position) it is ineffective after the motor armature has stopped turning.

One use of the invention is in connection with the circuit of the above mentioned Gross U.S. Pat. No. 3,548,276. When so used, a capacitor C is mounted within the casing near the lower end and is connected at its negative end to a terminal 100 made of stamped sheet metal and mounted in the end of the base 20 of the casing in a slot similarly to the other terminal and contact members. The terminal member 100 has a terminal lug 101 extending through an aperture in the casing wall for external connection thereto of an external resistor (not shown) in accordance with said U.S. Pat. No. 3,548,276.

Also connected to the terminal 100 isthe anode of a diode D-l whose cathode is connected to the cathode of another diode D-2 and to the positive side of the capacitor C and to the contact member 60 by wires which are soldered intoa notch 62 formed in the upper edge of the member 60.

The anode of the diode D-2 is connected to the contact 80. To the terminal 84 of the contact is also connected one end of the field or stator winding S of the motor, while the other end of that winding is connected to terminal 56 of the contact 50.

A shunt connection 49 consisting of flexible highly conductive bowed metallic strips positioned face to face with their ends in notches in the contacts 40 and connects those contacts electrically.

From the foregoing, it will be observed that by the edgewise mounting of the contact and terminal members in slots in base portion 20 of the casing, a considerable number of contact and'terminal members can be compactly arranged in insulated relation. Also by-having the contact fingers in two levels a single bridging I contact carrier can be conveniently positioned with bridging contacts mounted thereon in the different planes in which each contact member must move to bridge its set of fixed contacts. In addition to the foregoing, the compact arrangements of the fixed and movable contact members permits the use of an over-center type of action in a unit. It is particularly important, when the invention is applied to a circuit such as that of U.S. Pat. No. 3,548,276, that the movable contacts disconnect the power line from the. motor prior to the encircuiting of the braking circuitry and also that the switch and its contained components be small enough to be readily and conveniently mounted within the handle of a portable power-operated tool such as a saw.

Many modifications within the scope of the invention will occur to those skilled in the art. Therefore, the invention is not limited to the precise form herein'described.

I claim:

1. An electric switch comprising an insulating casing made of two cooperating parts recessed to cooperatively receive and position conductive switch and circuit elements, a trigger member slidable in a cavity at one end of said casing, a yoke member pivotally mounted in said casing and operable between two positions, an over-center spring connecting said trigger member and said yoke imparting snap action movement to said yoke incident to movement of said trigger member, a movable contact carrier operated to and fro by said yoke member in the same direction as said trigger member, a plurality of bridging contact members mounted on said carrier in insulated relation, a plurality of sets of fixed contacts engageable and disengageable by different bridging contact members, all said fixed and bridging contact members being mounted in one of said casing parts, said fixed contacts being stamped from sheet metal and mounted edgewise in separate slots in said casing in generally parallel relationship to one another and in a direction transverse to the direction of movement of said movable contact members, said bridging contact members each remaining in engagement with one of the fixed contacts of its set in both positions of said yoke.

2. A switch as claimed in claim 1 in which said sets of fixed contacts have the contact surfaces of the sets in spaced planes.

3. A switch as claimed in claim 2 in which said contact carrier has oppositely facing contact surfaces on which said bridging contact members are supported, spring means supported in said carrier resiliently supporting at least one of said-bridging contacts.

4. An electric switch adapted for dynamically braking an electric motor, comprising an insulating casing made of two cooperating parts recessed to cooperatively receive and position conductive switch and circuit elements, a trigger member slidable in a cavity at one end of said casing, a yoke member pivotally mounted in said casing and operable between two positions, an over-center spring connecting said trigger member and said yoke imparting snap action movement to said yoke incident to movement of said trigger member, a movable contact carrier operated to and fro by said yoke member in the same direction as said trigger member, a plurality of bridging contact members mounted on said carrier in insulated relation, a plurality of sets of fixed contacts engageable and disengageable by different bridging contact members, all said fixed and bridging contact members being mounted in one of said casing parts, said other casing part having recesses to guide the movement of said trigger member, said fixed contacts being stamped from sheet metal and mounted edgewise in separate slots in said casing in generally parallel relationship to one another and in a direction transverse to the direction of movement of said movable contact members, said bridging contact members each remaining in engagement with one of the fixed contacts of its set in both positions of said yoke, and a separate terminal member mounted in a separate slot in said casing and extending through a wall thereof, a capacitor in said casing connected to said separate terminal and to one of said contacts, and two diodes in said casing having opposite ends thereof connected to said one contact, one of said diodes being also-connected to said separate terminal, and the other diode being connected also to one of said contact and terminal members.

5. A switch as claimed in claim 4 in which said sets of fixed contacts have the contact surfaces of the sets in spaced planes.

6. An electric switch comprising an insulating casing made of two cooperating parts recessed to cooperatively receive and position conductive switch and circuit elements, a trigger member slidable in a cavity at one end of said casing, a yoke member pivotally mounted in said casing and operable between two positions, an over-center spring connecting said trigger member and said yoke imparting snap action movement to said yoke incident to movement of said trigger member, a movable contact carrier operated to and fro by said yoke member in the same direction as said trigger member, a plurality of bridging contact members mounted on said carrier in insulated relation, said contact carrier having oppositely facing contact surfaces on which said bridging contact members are supported, and spring means supported in said carrier resiliently supporting at least one of said bridging contacts, a plurality of sets of fixed contacts engageable and disengageable by different bridging contact members, all said fixed and bridging contact members being mounted in one of said casing part, said other casing part having recesses to guide the movement of said trigger member and said yoke member; said fixed contacts being stamped from sheet metal and mounted edgewise in separate slots in said one casing part in generally parallel relationship to one another and in a direction transverse to the direction of movement of said movable contact members, said bridging contact members each remaining in engagement with one of the fixed contacts of its set in both positions of said yoke.

7. A switch as claimed in claim 6 in which a plurality of said fixed contacts have terminal portions extending through apertures in the wall of said casing.

Claims

3. A switch as claimed in claim 2 in which said contact carrier has oppositely facing contact surfaces on which said bridging contact members are supported, spring means supported in said carrier resiliently supporting at least one of said bridging contacts.

4. An electric switch adapted for dynamically braking an electric motor, comprising an insulating casing made of two cooperating parts recessed to cooperatively receive and position conductive switch and circuit elements, a trigger member slidable in a cavity at one end of said casing, a yoke member pivotally mounted in said casing and operable between two positions, an over-center spring connecting said trigger member and said yoke imparting snap action movement to said yoke incident to movement of said trigger member, a movable contact carrier operated to and fro by said yoke member in the same direction as said trigger member, a plurality of bridging contact members mounted on said carrier in insulated relation, a plurality of sets of fixed contacts engageable and disengageable by different bridging contact members, all said fixed and bridging contact members being mounted in one of said casing parts, said other casing part having recesses to guide the movement of said trigger member, said fixed contacts being stamped from sheet metal and mounted edgewise in separate slots in said casing in generally parallel relationship to one another and in a direction transverse to the direction of movement of said movable contact members, said bridging contact members each remaining in engagement with one of the fixed contacts of its set in both positions of said yoke, and a separate terminal member mounted in a separate slot in said casing and extending through a wall thereof, a capacitor in said casing connected to said separate terminal and to one of said contacts, and two diodes in said casing having opposite ends thereof connected to said one contact, one of said diodes being also connected to said separate terminal, and the other diode being connected also to one of said contact and terminal members.