US3590177A

US3590177A - Limit switch

Info

Publication number: US3590177A
Application number: US833018A
Authority: US
Inventors: Martin D Ustin; Edward W Baumgartner
Original assignee: Buchanan Electrical Products Corp
Current assignee: Buchanan Electrical Products Corp
Priority date: 1969-06-13
Filing date: 1969-06-13
Publication date: 1971-06-29
Anticipated expiration: 1988-06-29
Also published as: AU1632070A; GB1312667A; BE751986A; FR2052550A5; DE2029110A1

Abstract

A limit switch in which an actuating head is mounted on the housing. Electrical switches are mounted in the housing, without fasteners, by means of a removable support structure. Eccentric adjustment members are provided for adjusting the amount of pretravel of the switch actuating mechanism. A terminal block is provided which both aids in supporting the switches and provides means for making external connection to them.

Description

United States Patent [72] Inventors Martin D. Ustin Union; Edward W; Baumgartner, lrvington, both of, NJ.

[21] Appl. No. 833,018

[22] Filed June 13, 1969 [45] Patented June 29, 1971 [73] Assignee Buchanan Electrical Products Corporation Union, NJ.

[54] LIMIT SWITCH 24 Claims, 8 Drawing Figs.

[51] lnt.Cl ...H0lh 21/28 [50] Field of Search 200/47, 166 CT, 6 B, 6 A

[56] References Cited UNITED STATES PATENTS 3,097,271 7/1963 Denison .1200/166 x ITCS 3,257,856 6/1966 Parns, Jr 200/47 X 3,275,764 9/1966 Kiessling et a1. 200/47 3,287,516 11/1966 Nielsen 200/47 3,303,298 2/1967 Dobes 200/47 3,306,997 2/1967 Jacobs... 200/47 3.317.687 5/1967 Dehn 200/47 Primary Examiner-Robert K. Schaefer Assistant Examiner-H. J. l-lohauser Attorney-Curtis, Morris and Safford ABSTRACT: A limit switch in which an actuating head is mounted on the housing. Electrical switches are mounted in the housing, without fasteners, by means of a removable support structure. Eccentric adjustment members are provided for adjusting the amount of pretravel of the switch actuating mechanism. A terminal block is provided which both aids in supporting the switches and provides means for making external connection to them.

LIMIT SWITCH This invention relates to electrical switches, and particularly to electrical limit switches.

A limit switch typically is used to stop a mechanical movement by turning off the energization to a drive motor which is causing the movement. For example, the switch often is positioned near a machine to limit the movement of a cutting tool. The limit switch usually has an actuating arm or plunger with a roller on it. When a machine component contacts the roller and depresses the plunger or rotates the arm, this mechanical movement opens or closes an electrical switch so as to stop or limit the movement of the machine component.

One problem with prior limit switches is that often it is difficult and slow to change the electrical switch which is mounted in the housing of the limit switch device. Furthermore, in certain prior art limit switches, the electrical switch is mounted on the same portion of the limit switch structure as is the head which carries the actuating arm. As a result, in order to obtain a fair degree of speed in changing the electrical switch, it has been customary to change the entire portion of the device which includes both the electrical switch and the actuating head. The disadvantage of this procedure is that the new head probably will not be set to the position of the old head so that the new head must be adjusted before it can be used. Thus, the switch-changing process is slowed even further.

Another problem with prior limit switchs is that it often is difficult and time-consuming to change the amount of pretravel of the switch; that is, the distance which the plunger or actuating arm must move before the electrical switch is actuated.

Still another problem with prior limit switches is that it often is difficult to secure external wires to the wiring terminals in the switching device. Also, it often is complicated to connect the electrical switches to the wiring terminals.

In accordance with the foregoing, it is an object of the present invention to provide a limit switch device in which the electrical switches can be changed relatively rapidly and easily. It is a further object of the present invention to provide such a device in which the amount of pretravel of the actuating mechanism can be adjusted rapidly and easily. It is another object of the present invention to provide such a device which is easy to wire and to which it is easy to connect and mount an electrical switch.

In accordance with the present invention, the foregoing objects are met by the provision of a limit switch in which the actuating head is secured to the housing. Electrical switches are mounted in the housing, without fasteners, by means of a removable support structure. Eccentric adjustment members which are accessible from a front opening in the housing are provided for adjusting the amount of pretravel of the switch actuating mechanism. A wiring and terminal block is provided for mounting the switches and for easily connecting wires thereto. 7

Further objects and advantages of the invention will be either pointed out in or apparent from the following description and drawings. In the drawings:

FIG. 1 is an exploded perspective view of one embodiment of the present invention;

FIG. 2 is a partially schematic cross-sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a partially cross-sectional view of a component of the switching device shown in FIGS. I and 2;

FIG. 4 is a partially cross-sectional view of a component of a device shown in FIGS. I through 3;

FIGS. 5, 6 and 7 are cross-sectional views of the actuating heads of three further embodiments of the present invention; and

FIG. 8 is a cross-sectional view of a component of one embodiment of the invention.

GENERAL DESCRIPTION Referring first to FIG. I, the limit switch device 10 includes a housing 12, a turret or actuating head 14 rotatably mounted on the housing 12, and an arm 18 with a roller 20 at one end. The arm 18 is secured to a shaft 16 which is rotatably mounted in the turret I4. Rotation of the shaft 16 by means of the arm 18 causes a plunger 50 (FIG. 2) to be depressed.

Two

electrical switches

22 and 24 are mounted in the housing 12 and are positioned (See FIG. 2) so that when the plunger 50 is depressed downwardly, it depresses a switch-actuating member 36 which in turn depresses switch buttons 25 on the

switches

22 and 24, thus actuating the switches. Wires 34 enter the bottom of the housing through a conduit 35 and are connected to a terminal block 26 which is mounted in the housing 12. Each switch has four blade-shaped electrical contacts 23 which fit into receptacles in the terminal block 26 and thus are connected to the wires 34, and thence to a control circuit (not shown) to limit the motion of the object which hits the arm 18, or to perform other control functions.

THE TURRET The turret 14 is made in two

halves

60 and 62 which are fastened together by means of a pair of screws 65 (see FIG. 1 As is shown in FIG. 2, the turret 14 can be rotated to any position within a full circle by means of a worm 58 which meshes with gear teeth 59 cut into the lower edge of the generally cylindrically shaped turret 14. By turning the worm 58 with a screwdriver, the rotary position of the turret 14 can be adjusted as desired so as to accommodate the limit switch to actuation in a multitude of different positions.

The actuating mechanism can be adjusted to operate in three different modes; only with clockwise motion of the arm 18, or only with counterclockwise motion, or with both clockwise and counterclockwise motion of the arm 18. Adjustment to one or the other of these modes is effected by first lifting a flexible protective covering 44, and then depressing a spring-loaded plunger 46 (with a screwdriver or the like) so as to disengage a latch member 47 from one of three notches 48 which normally holds the shaft 16 in a particular longitudinal position. Then, the shaft 16 is either pulled or pushed longitudinally to a new position, the plunger 46 is released, and the spring return for the latch member 47 engages it in a different notch 48.

Two mirror-

image cams

40 and 42 are attached to the shaft 16. A roller 52 is attached to the upper end of plunger 50. The

cams

40 and 42 are shaped so that when the shaft 16 is in its rest position, neither cam depresses the roller. However, when the latch member 47 is in the middle one of the three notches 48, rotation of the arm 18 in either the clockwise or counterclockwise direction will cause one of the

cams

40 or 42 to engage the roller 52, thus causing depression of the plunger 50 and actuation of the

switches

22 and 24.

With the latch member 47 in the left one of the three notches 48, the roller 52 will engage only the cam 40, and the plunger 50 will be depressed only by rotation of the shaft 16 in one direction. When the latch member 47 is in the right one of the three notches, only the cam 42 will engage the roller 52 and the plunger 50 will be depressed upon rotation of the shaft only in the other of the two directions.

A member 54 with a flat lower surface bears against a flat cutout portion in the shaft 16 under the pressure of a pair of coil springs 56. This provides means for returning the arm 18 to its initial rest position. Each of the actuating buttons 25 of the

switches

22 and 24 is spring-loaded, and this spring loading returns the plunger 50 to its uppermost position when the switch actuation movement is completed. Further details regarding the operation of this mechanism are given in application Ser. No. 567,172 filed on July 22, 1966, and assigned to the same assignee as this patent application. The disclosure of that patent application hereby is incorporated herein by reference.

3 TI-IE ADJUSTABLE SWITCH ACTUATING MEMBER slotted head and can. be driven by a screwdriver to rotate it to a new position. Each projection thus is positioned either relatively closer to or farther away from one of the switch buttons 25 so as to'provide means for adjustment of the amount of pretr'aver' of theactu ating mechanism.

The surfaces of the body 36 which bear against the mating edges of the

projections

37 and 39 are serrated as shown-at 43 in FIG. 3. The

projections

37 and 39 have two teeth which engage the serrations in order to provide means for'holding the

projection

37 or 39 in a position to which it is moved. The body of member 36 preferably is made out of an insulating plastic material such as nylon, and the

projections

37 and 39 advantageously are made out of another insulating material suchas that sold under the trademark -Delrin."

TERMINAL COVER AND SWITCH MOUNTING MEANS Referring again to FIG. 1, an insulating cover 28 fits into the housing to cover the terminal block and to assist in supporting the

switches

22 and 24 in the housing 12. A cover 30 and a gasket 32 are secured to the housing by means of screws 31 to provide an oiltight cover for the housing.

In accordance with another feature of the present invention, the terminal cover 28 is used to assist in supporting the

electrical switches

22 and 24, as well asto cover the terminal block ridge 69 around the edges of the locations of the switches helps to insulate the switches.

.T he innermost end of the blades 23 of the

switches

22 and 24 extend into and are held by the terminal block 26 (See FIG.

4). This assists in holding the switches in place..

THE TERMINAL BLOCK As in shown in FIG. 4, the terminal block 26 includes a body 73 made of nonconductive material such as plastic in which are mounted several short tubes 74 having a rectangular crosssectional shape. These tubes are made out of a conductive metal such as copper. Fitted into one sidewall of each tube 74 is a screw 76. Screw 76 has an enlarged inner end 80 which bears against the bare end of one of the wires 34 so as to hold the wire in place and in contact with the metal tube 74. A conductive spring metal clip 82 engages the outside of each tube 74. Each member 82 has a curved portion 75 which acts to hold one of the blades 23 in contact with one of the tubes 74.

Thus, when one of the blades is inserted through the holes 72 in the terminal block cover 28, the switch is supported at two points; at the point where it contacts the material of the cover plate 28, and also at the point where the blade makes contact with the clip 82 and one of the metal tubes 74. Thus, mounting means on the housing 12 or cover 30 are not required.

The foregoing arrangement is particularly simple to use and convenient in that the wires 34 can be connected to the terminal block simply by inserting their ends in the tubes 74 and tightening the screws 76. The spring ,clips 82 provide an easy and simple means of simultaneously supporting the switches and making electricalcontact between the wires 34 and the switch blades 23.

Another advantage of the present invention is that the amount of pretravel of the switch easily can be adjusted by simply removing the cover 30, inserting a screwdriver into the slots in the heads of the

projections

37 and 39, and then turnthem with other switches. No tools are necessary. Screws and bolts are not needed to hold the switches in place.

SIDE-ACTUATED SWITCH FIG. 5 shows the actuating head or turret of another limit switch constructed in accordance with the present inven tion. The remainder of this limit switch is the same as is shown in FIGS. 1 through 4 andis not shown in FIG. 5 for the sake of simplicity in the drawings.

The turret 100 is formed of two

halves

101 and 103, and has a shaft 102 slidably mounted in the turret and extending in a direction perpendicular to the axis of the plunger 50. The shaft 102 has a groove 104 into which is fitted a retaining ring 108. Shaft 102 has a section 109 with two flats cut on it, and a cylindrical right end portion 111 of a diameter smaller than that of the left end. A spring retainer cup with a rectangular external shape fits onto the flats of section 109, and a coil spring 112 fits into the cup and thrusts the cup against the retaining ring 108. The ring 108 abuts a ridge 106 to stop its movement towards the left.

The cup 110 has a beveled edge 116 which abuts the beveled edge of a cam 118 fastened to the upper end of plunger 50. When the shaft 102 is pressed inwardly, it slides in

bearings

105 and 114, and the beveled edge 116 forces the cam 118 and slides plunger 50 downwardly in bearing 120 to operate the switches. Two of the edges of the cup are beveled as shown at 1 16 in order to facilitate the use of a roller on the end of shaft 102. As in the embodiment shown in FIGS;11 through 4, the turret 100 is rotatable so that it can be actuated from many different directions. The internal shape of the turret is such that it engages the rectangularly-shaped outside of cup member 110 to keep it from rotating in the turret.

TOP ACTUATED SWITCH FIG. 6 shows the turret of another embodiment of the invention. Again, as in FIG. '5, the remainder of the limit switch is not shown in order to simplify the drawings.

The turret 130 has two

halves

132 and 134, and has a depressable actuating button 136 extending vertically from its top. The lower portion of button 136 is secured to a spring retainer cup 138, which is functionally similar to the cup 110 shown in FIG. 5. A coil spring 140 fits into the cup 138. The external shape of the cup is such that it will not rotate in the housing. The plunger 50 has a reduced cross section with

spring retainer cups

146 and 148 and a small coil spring 150 surrounding the reduced portion of the plunger. The top portion of the plunger fits into a hole 144 in the bottom portion of the button 136. v

When the button 136 is depressed, the spring 140 is compressed and the plunger 50 is depressed until the switches have been actuated. Shortly thereafter, the bottom retainer 148 for the small spring hits the inside bottom wall of the housing 134. From then on, further depression of the button 136 does notdepress the plunger 50 any further; instead, the spring 150 compresses and the top 145 of plunger 50 moves up into the hole 144. Thus, the motion of the plunger 50 is limited to that necessary to actuate the switches.

UNIVERSALLY ACTUATED SWITCH FIG. 7 shows the turret of another switch embodiment of the present invention. Its operation is the same as that of the switch shown in FIG. 6, except that a universal" actuating lever 166 replaces the button 136.

Lever 166 is secured to a hemispherical member 168 which is movably mounted in a bearing structure 170. A cover 172 made of rubber, flexible plastic or other. suitable flexible material is fitted around the ball joint and the lever 166. When the lever 166 is pushed from the side, it pivots about the ball joint and the lower edge of the hemisphere 168 depresses a ring 169 which depresses the cup 138 to push the plunger 50 downwardly and actuate the switches in the housing, as in the FIG. 6 embodiment. The lever 166 can be actuated from almost any direction. Two of the positions to which it can be shifted are shown in dashed outline in FIG. 7.

, ROLLERS Another advantageous feature of the invention is shown in FIG. 1. The roller 20 is fastened to the arm 18 by means of a self-tapping screw 21. Thus, the user of the'limit switch can select among a number of different roller sizes and types and can attach the roller himself.

Another advantageous roller construction is shown in FIG. 8. The roller 200 is composed of an inner core 206 made of a plastic such as Nylon, and an outer metal ring 204 tightly fitted onto the core. The core 206 is rotatably mounted on a hub 202 extending from the actuating arm 18. A screw 208 is threaded intoa hole in the hub 202 to hold the roller 200 in place. The nylon core can be used alone as a roller, or, if a harder surface or a larger diameter is required, the user can add the ring 204 to the core 206. The composite roller 200 is lighter than would be a solid metal roller of the same size.

The above description of the invention is intended to be illustrative and not limiting. Various changes or modifications in the embodiments described may occur to those skilled in the art and these can be made without departing from the spirit or scope of the invention.

We claim:

1. An electrical limit switch device comprising a housing adapted to be mounted on a support structure, a removable cover for said housing, an electrical switch having contact projections, an actuating member in said housing for actuating said switch in response to being driven by an actuating motion, wiring terminal means in said housing, and switch support means for selectively insulating said switch from said terminal means for supporting said switch with its contact projections engaging said terminal means with said switch in position to be actuated by movement of said actuating member, said support means being removable from said housing and separate from said cover.

2. Apparatus as in claim 1 in which said switch support means includes an insulating plate with apertures through which said projections extend and a ledge for supporting said switch against the force of said actuating member, and resilient gripping means in said terminal means.

3. Apparatus as in claim 2 in which said resilient gripping means forms a conductive receptacle for connecting a wire to one of said switch contact projections.

4. An electrical limit switch device comprising a housing adapted to be mounted on a support structure, an electrical switch in said housing, an actuating member in said housing for actuating said switch in response to being driven by an actuating motion, means for adjusting the length of travel of said actuating member before it actuates said switch, said means including a rotatable spacer member on said actuating member, said spacer member being assymetiic about its axis of rotation to provide different amounts of spacing in different ones of its rotational positions.

5. Apparatus as in claim 4 including a removable coverfor said housing, said rotatable spacer member having a head shaped to receive a rotary driving tool, said spacer member being positioned to be drivable by such a tool when the latter is inserted through the opening in said housing which is left when said cover is removed.

6. Apparatus as in claim 4 in which said spacer member is positioned and mounted to be movable in a direction transverse to said axis of rotation in order to actuate said switch.

7. An electrical limit switch device comprising a housing adapted to be mounted on a support structure, an electrical switch having contact projections, wiring terminal means in said housing, said wiring terminal means having a plurality of conductive tubular members, a clamping member extending into each such tube through a sidewall of said tube to grip a wire therein, a conductive spring clip around the outside of each such tubular member, with said contact projections of said switches being clamped between said clips and said tubular members.

8. Apparatus as in claim 7 in which each of said tubular members has a rectangular cross-sectional shape.

9. Apparatus as in claim 7 including a removable cover for said housing, and in which said clamping member comprises a threaded screw, and driving tool-engaging means in the head of said screw, with said screw head facing towards said cover.

10. Apparatus as in claim 1 including an arm secured to a shaft, a turret rotatably mounted on said housing, with said shaft rotatably mounted in said turret, and means drivably coupling said shaft to said actuating member.

11. An electrical limit switch device comprising a housing, a turret rotatably mounted on said housing, a worm and mating gear engaged together to rotate said turret with respect to said housing, an electrical switch in said housing, an actuating member in said housing for actuating said switch in response to being driven by an actuating motion, a push member extending out from said turret and depressable to move said actuating member, and spring return means for said push member.

12. Apparatus as in claim 11 in which said push member is mounted to move in the same direction as said actuating member.

13. Apparatus as in claim 11 in which said push member is mounted to move in a direction perpendicular to the direction of motion of said actuating member, and including cam means for drivably coupling said push member to said actuating member.

14. Apparatus as in claim 11 including additional spring means for limiting the movement of said actuating member to a predetermined distance without so limiting the movement of said plunger.

15. An electrical limit switch device comprising a housing, a member extending out of said housing and engageable to actuate a switch in said housing, spring return means for returning said member to its disengaged position, a plunger drivable by said member to actuate said switch, and spring means for limiting the movement of said plunger to a predetermined distance without so limiting the movement of said member.

16. Apparatus as in claim 15 in which said member is a lever mounted on said housing by a ball joint, and means for translating pivotal movement of said lever into movement of said plunger.

17. Apparatus as in claim 15 in which said member is a pushbutton slidable in the direction of said plunger.

18. Apparatus as in claim 5 in which serrations are located between said contact member and said actuating member.

19. Apparatus as in claim 5 including a plurality of said switches, and a plurality of said contact members on said actuating member, there being one contact member per switch.

20. An electrical limit switch device comprising a housing adapted to be mounted on a support structure, a removable cover for said housing, an electrical switch having contact projections, an actuating member in said housing for actuating said switch in response to being driven by an actuating motion, wiring terminal means in said housing, switch support means removable from said housing and separate from said cover for supporting said switch with its contact projections engaging said terminal means with said switch in position to be actuated by movement of said actuating member, an arm secured to a shaft, a turret rotatably mounted on said housing, with said shaft rotatably mounted in said turret, means drivably coupling said shaft to said actuating member, a roller on said arm, said roller having a nonmetallic core fitted into a metallic ring, said ring forming the outer periphery of said roller.

I matching the internal contours of said housing, the external dimensions of said support member being smaller than the internal dimensions of said housing by a relatively small amount so that said support member fits into and supports itself in said housing, said support member having means for supporting said switch with'its contact projections engaging said terminal means with said-switch in position to be actuated by movement of said actuating member.

22. A limit switch as in claim 21 in which said support member comprises an insulating plate with apertures through which said projections extend and a ledge for supporting said switch against the force of said actuating member, and resilient gripping means in said terminal means.

23,. A limit switch as in claim 21 in which said support member includes a guide for guiding the movement of said actuating member.

24. A limit switch as in claim in which the movementlimiting spring means includes a compression spring extending around said plunger, a pair of abutments on said plunger for limiting the expansion of said compression spring, and means for normally holding one end of said compression spring against said member with the other end spaced from a stop structure by a predetermined distance, both ends of said compression spring being free to move on said plunger during compression of said spring.

Claims

4. An electrical limit switch devicE comprising a housing adapted to be mounted on a support structure, an electrical switch in said housing, an actuating member in said housing for actuating said switch in response to being driven by an actuating motion, means for adjusting the length of travel of said actuating member before it actuates said switch, said means including a rotatable spacer member on said actuating member, said spacer member being assymetric about its axis of rotation to provide different amounts of spacing in different ones of its rotational positions.

5. Apparatus as in claim 4 including a removable cover for said housing, said rotatable spacer member having a head shaped to receive a rotary driving tool, said spacer member being positioned to be drivable by such a tool when the latter is inserted through the opening in said housing which is left when said cover is removed.

21. An electrical limit switch device comprising a housing adapted to be mounted on a support structure, a removable cover for said housing, an electrical switch having contact projections, an actuating member in said housing for actuating said switch in response to being driven by an actuating motion, wiring terminal means secured to and within said housing, a switch support member having external contours generally matching the internal contours of said housing, the external dimensions of said support member being smaller than the internal dimensions of said housing by a relatively small amount so that said support member fits into and supports itself in said housing, said support member having means for supporting said switch with its contact projections engaging said terminal means with said switch in position to be actuated by movement of said actuating member.

23. A limit switch as in claim 21 in which said support member includes a guide for guiding the movement of said actuating member.

24. A limit switch as in claim 15 in which the movement-limiting spring means includes a compression spring extending around said plunger, a pair of abutments on said plunger for limiting the expansion of said compression spring, and means for normally holding one end of said compression spring against said member with the other end spaced from a stop structure by a predetermined distance, both ends of said compression spring being free to move on said plunger during compression of said spring.