US3555215A

US3555215A - Modular limit switch

Info

Publication number: US3555215A
Application number: US831018A
Authority: US
Inventors: William F Dehn
Original assignee: Allen Bradley Co LLC
Current assignee: Allen Bradley Co LLC
Priority date: 1969-06-06
Filing date: 1969-06-06
Publication date: 1971-01-12
Anticipated expiration: 1988-01-12

Abstract

A limit switch includes tiered contact modules, each comprising a case made up of a base and a removable cover with a movable contact carrier therein. A headed retaining pin extends through the cover, base and contact carrier, and a retaining clip at the other end of the pin acts with the head to hold the elements of the module together. The pin is rotatable and has a tool socket in the head and has a threaded portion beyond the retaining clip which is used to mount the module in the housing of the switch. The upper contact carrier is fitted with an extension engageable with the carrier of the lower module. The extension is threaded to be axially adjustable and has a noncircular cross section. An adjustment wheel has a mating noncircular opening which receives the extension to provide a keyed connection so that rotation of the wheel causes adjustment of the extension. The switch housing is vertically split and a gasket is interposed between the two parts, the gasket comprising a central web which seals off the two sections from one another and skirts which extend into respective housing sections to provide electrical isolation.

Description

United States Patent [72] Inventor William F. Dehn Milwaukee, Wis. [21] Appl. No. 831,018 [22] Filed June 6, 1969 [45] Patented Jan. 12,1971 [73] Assignee Allen-Bradley Company Milwaukee, Wis. a corporation of Wisconsin [54] MODULAR LIMIT SWITCH 5 Claims, 14 Drawing Figs.

[52] US. Cl 200/47, 200/166 [51] lnt.Cl ..H0lh 21/28 [50] Field of Search ZOO/16683, l53.l9,47, 167A 56] References Cited UNITED STATES PATENTS 2,921.166 1/1960 Few et al. 200/166X 3,275,764 9/1966 Klessling et al 200/47 3,287,516 11/1966 Nielsen 200/47 Primary Examiner-Robert K. Schaefer Assistant Examiner-H. J. Hohauser Attorneys-Allan W. Lieser and Arthur H. Seide ABSTRACT: A limit switch includes tiered contact modules, each comprising a case made up of a base and a removable cover with a movable contact carrier therein. A headed retaining pin extends through the cover, base and contact carrie'r, and a retaining clip at the other end of the pin acts with the head to hold the elements of the module together. The pin is rotatable and has a tool socket in the head and has a threaded portion beyond the retaining clip which is used to mount the module in the housing of the switch. The upper contact carrier is fitted with an extension engageable with the carrier of the lower module. The extension is threaded to be axially adjustable and has a noncircular cross section. An adjustment wheel has a mating noncircular opening which receives the extension to provide a keyed connection so that rotation of the wheel causes adjustment of the extension. The switch housing is vertically split and a gasket is interposed between the two parts, the gasket comprising a central web which seals off the twd sections from one another and skirts which extend into respective housing sections to provide electrical isolation.

PATENTEUJANIZIBYI 8555215 sum 1 or 3 INVENTOR WILLIAM F. DEHN ATTORNEY PATENTEUJ-ANIZIB?! 3555215 SHEET 3 [IF 3 INVENTOR WILLIAM F'. DEHN ATTORNEY MODULAR LIMIT SWITCH BACKGROUND OF THE INVENTION This invention relates to electrical limit switches, and particularly to a modular, double pole switch particularly suitable for oiltight or watertight applications.

Many types of limit switches have been proposed and used, but there are certain problems in manufacturing effective switches, particularly in the case of double pole switches for use in situations where the switch must be oiltight and/or watertight. For one thing, it is difficult to provide the necessary two switching mechanisms in the housing in such a manner as to give desirable flexibility while maintaining simplicity and low cost. Further, where there are two switches in the housing it is difficult to synchronize their operation so that they operate simultaneously or in a selected sequence. Still further, it is difficult with a switch of minimum size to provide the necessary sealing for oiltight or watertight applications in conjunction with electrical isolation for the switch components.

SUMMARY OF THE INVENTION It is the object of this invention p to provide a limit switch which includes tiered contact modules of a unique, simple and highly effective design.

It is another object of the invention to provide extension operating means between the two modules which is adjustable to establish a desired operation.

Still another object is to provide a limit switch incorporating a unique preformed gasket which serves not only to provide for necessary sealing but also gives electrical isolation.

All of the foregoing objects are attained in a switch which is highly effective and durable while being relatively simple and inexpensive.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view in elevation of an electrical limit switch constituting a preferred embodiment of the invention;

FIG. 2 is a front view in elevation of the rear section of the housing of the switch of FIG. 1;

FIG. 3 is a view in cross section through the plane 3-3 shown in FIG. 2;

FIG. 4 is a rear view in elevation of the front section of the housing of the switch of FIG. I, with a sealing gasket in place;

FIG. 5 is an enlarged rear view similar to FIG. 4, but with the sealing gasket removed and one contact module omitted and other parts broken away;

FIG. 6 is a view in cross section through the plane 66 shown in FIG. 5, but showing both contact modules;

FIG. 7 is a view in cross section through the plane 7-7 shown in FIG. 6;

FIG. 8 is a top plan view of one of the contact modules of the switch of FIG. 1;

FIG. 9 is a rear view in elevation of the contact module of FIG. 8;

FIG. 10 is a bottom plan view of the contact module of FIG.

FIG. 11 is an exploded view in perspective of the contact module of FIG. 8;

FIG. 12 is a side view in elevation of the sealing gasket of the switch of FIG. 1;

FIG. 13 is a front view in perspective of the sealing gasket of FIG. 12; and

FIG. 14 is a rear view in perspective of the sealing gasket of FIG. 12.

DESCRIPTION OF THE PREFERRED EMBODIMENT The limit switch shown in the drawings includes a metal housing designated generally by the reference numeral 1, an operating head 2 atop the housing 1, and an actuating arm 3 connected to the operatinghead 2. An operating plunger 4 leads from the operating head 2 downwardly into the housing 1. The operating mechanism is conventional, and various types of such mechanism are well known to those skilled in the art so that the mechanism has not been shown nor will it be described in detail. As is conventional, pivotal movement of the actuating arm 3 will operate to cause extension or retraction of the plunger 4 which will in turn result in actuation of the contact modules to be described.

The housing 1 is vertically split to define a front section 5 and a rear section 6, the split preferably being on a diagonal as shown to provide for a housing 1 of reduced overall height. Screws 7 connect the

housing sections sections

5 and 6 together, and a sealing gasket 8 which will be described in detail below is interposed between the two sections. As can best be seen in FIGS. 2 and 3, the rear housing portion 6 is provided with opposite corner mounting holes 9 which are adapted to receive screws (not shown) for mounting the switch on a wall or panel.

Mounted within the rear housing section 6 is an exterior terminal assembly designated generally by the reference numeral 10. The assembly 10 includes a base portion 11 formed of a suitable insulating material which is attached to the rear of the housing portion 6 by means of screws 12. Attached to the base 11 are screw-type electrical terminals 13 which include forwardly extending legs 14 that are engageable by bayonet prongs extending from the contact modules of the switch as will be described. External circuit wires (not shown) are connected to the terminals 13 and led outwardly through an opening 15 at the lower end of the housing portion 6.

The exterior terminal base 11 includes an upstanding wall 16 which extends substantially continuously about its periphery and is inwardly spaced from the associated walls of the housing section 6. The base 11 also includes spaced sets of transverse walls 17 which divide it into two vertically spaced sets of four terminals 13, and transverse walls 18 which extend between the members of the respective sets of terminals 13 to divide each set into two vertically spaced pairs.

Within the front housing portion 5 are mounted two identical contact modules, each designated by the reference numeral 20, the two modules 20 together constituting switch means and being tiered or mounted vertically above one another in the housing portion 5. In FIG. 5, the lower module 20 is shown only in dotted outline for the sake of simplicity and to illustrate more clearly the construction of the housing. The modules 20 are of generally rectangular configuration, and each comprises a case made up of a base portion 21 which defines a rear wall 22, sidewalls 23, and upper wall 24 and a lower wall 25. A removable cover. 26 completes the case and defines a front wall facing the rear wall 22. A retaining pin designated generally by the reference numeral 27 has an enlarged head 28 which bears against the outside of the cover 26; and the pin 27 extends through the rear wall 22 to terminate in a threaded end 29 which is screwed into the housing portion 5 to mount the module 20 thereon. The outside of the rear wall 22 is provided with a pair of locating bosses 30 which are received in mating sockets in the wall of the housing 5 to properly locate the module 20.

Only the end portion 29 of the pin 27 is threaded, and the body of the pin which extends through the base 21 and cover 26 is free to rotate with respect thereto without axial movement. A C-shaped retaining clip 32 is removably attached to the pin 27 just outside the rear wall 22, the pin 27 being provided with a suitable groove to receive the retaining clip'32, and the rear wall 22 is provided with a shallow recess 33 for the clip 32. The clip 32 acts with the head 28 to hold the cover 26 on the base 21 while allowing the pin 27 to rotate. The head 28 is provided with a hexagonal tool socket 34, and a hexagonal wrench can be used torotate the pin 27 to mount and dismount the module 20 in the housing portion 5, the pin 27 thus serving both as both a mounting and assembly means for the module 20. In the preferred embodiment shown, the pin 27 is of a two-part construction with the major portion including the head 28 being formed of an insulating plastic material and the threaded end 29 being formed as a separate metal insert. Obviously, however, the pin 27 could be of onepiece construction, and a screw slot or other tool socket could be substituted for the socket 334.

The module base 21 is provided with internal walls which define a vertical slide track 35, and a molded movable contact carrier- 36 formed of an insulating material is vertically reciprocally slidable in the track 35. The track 35 opens through the

walls

24 and 25 so that the upper end of the carrier 36 is accessible through the top wall 24 and the lower end of the carrier 36 isaccessible through the lower wall 25. The lower end of the carrier 36, which is designated by the reference numeral 37, is of reduced size, and a return spring 38 surrounds the end 37 and operates between the bottom end of the body of the carrier 36 and the lower casing wall 25 to urge the carrier 36 upwardly. The carrier 36 is provided with an opening 39 therethrough that is transverse to the front wall 26 and rear wall 22 and that is in alignment with and elongated in the direction of the track 35. The pin 27 is received through the opening 39, and the elongation thereof allows and establishes the limits of vertical movement of the carrier 36.

The carrier 36 carries a movable contact blade 42 provided at its opposite ends with upper and lower movable contacts 43. The blade 42 is shaped to define central toggle spring portions 44 which are effectively interposed between the cam'cr 36 and the body of the blade 42 and operate in conventional fashion to give it a toggle or snap-over type of action. Upper and lower stationary contact terminals 45 are mounted in the cover 26 and extend inwardly into the base 21 to present upper and lower stationary contacts 46, the members of facing pairs of stationary contacts 46 preferably preferably being slightly convergent to accommodate for bowing of the contact blade 42 in response to the toggle springs 44. The terminals 45 extend outwardly through the cover 26 to terminate a in bayonet prongs 47 which are engageable with respective exterior terminal portions 14 to complete a connection into an exterior circuit.

As shown in the drawings, the contact modules are both in a normal or unactuated position in which the return springs 38 have moved the movable contact carriers 36 upwardly, the main operating plunger 4 being retracted in this position. In normal position, the movable contacts 43 are in engagement with the lower stationary contacts 46, and the toggle springs 44 are operating to urge the carrier 36 upwardly and the movable contacts 43 downwardly. Movement of the carriers 36 downwardly will, however, cause the springs 44 to move over center resulting in a snap-over action in which the movable contacts 43 move upwardly to be against the upper stationary contacts 46, all in relatively conventional fashion.

A metal extension member 50 is threaded into the lower end 37 of the contact carrier 36 of the upper module 20 and butts against the upper end of the contact carrier 36 of the lower module 20. The extension 50 thus serves as a rigid extension of the upper carrier 36 and serves to transmit downward motion of the plunger 4 from the upper carrier 36 to the lower carrier 36 so that both will be moved in response to extension of the plunger 4. By virtue of its threaded connection with the upper carrier 36, the extension Sill is axially adjustable, and it will be apparent that such axial adjustment will vary the relative timing of the operation of the two modules 20. That is, the further the extension 50 is extended the sooner the lower module Zll will operate. As a result, it is possible by adjusting the extension 56 to establish simultaneous or sequential operation of the two modules 2% as desired.

Adjustment of the extension 50 is accomplished by means of an adjustment wheel 51 which lies flat between the two modules 20 with its periphery accessible from the front as the elements are seen in H6. 5. As can be seen in FlGS. 6 and 7, the body of the extension 56) has a hexagonal cross section (although any noncircular cross section could be used) and the wheel Si is provided with a central opening 52 of mating configuration which slidably receives the extension 50. This establishes a keyed micrometer type of connection so that as the wheel 51 is rotated the extension 50 will be rotated and because of its threaded connection with the upper carrier 36 will also be moved axially. The periphery of the wheel 51 is preferably slotted or knurled to allow for easier turning with a screwdriver or other tool.

As previously indicated, the gasket 8 is interposed between the

housing portions

5 and 6. It is preferably formed of .an elastomeric, moldable insulating material such as nylon or rubber, and includes a central web 55 which extends across the facing portions of the

housing sections

5 and 6 to seal them off from one another, the periphery of the web 55 being clamped between the facing edges of the

housing portions

5 and 6 to effect a tight seal. The central portion of the web 55 is dished to accommodate the elements inside the housing 1, and

onet prongs 47 are received with a relatively tight fit. Thus,

moisture which might collect in the rear housing portion 6 is effectively held out of the front housing portion 5.

In addition to the central web 55, the gasket 8 comprises a forwardly extending skirt 57 which extends into the front housing portion 5 and surrounds the switch means the two modules 20, the modules 20 being sufiiciently spaced from the walls of the housing section 5 to receive the skirt 57 therebetween. The upper wall of the skirt 57 is cut out to receive the plunger 4, and the skirt 57 includes a central portion 57' which extends between the two modules 20 and is cut out to receive the wheel 51. A second, rear skirt 58 extends into the rear housing section 6, being received in the space around the wall 16 to surround the terminal means 1-0. The skirt 58 includes a central portion 58' which extends between the walls 17 and, with the lower wall of the skirt S8, is cut out to receive the exterior wiring (not shown). Being of insulating material, the

skirts

57 and 58 provide electrical isolation for the switch and terminal elements in the front and

rear housing portions

5 and 6 by establishing an elongated arc path. Thus, the gasket 8 serves not only to provide an effective seal between the

sections

5 and 6, but also provides for effective electrical isolation, all with a single unit that is easily moldable and readily inserted and removed.

As indicated, the limit switch shown has several important advantages. First, the contact modules 20 are highly effective while being relatively simple and inexpensive. A particular feature is the use of the single pin 27 to hold the components of the modules 20 together and also to mount the modules 20 in the housing portion 5. ln addition to the module construction, the extension 50 and wheel 5i. provide a simple but highly effective means to establish a desired mode of operation for the two modules 20. Further, the unique preformed gasket 3 serves the two important functions of providing an effective seal and also providing electrical isolation. Although a preferred embodiment of the invention has been shown and described herein to attain these advantages, it will be obvious that various modifications in both structure and use would be possible without departure from the true spirit of the invention. The modules 20 might, for example, be used singly or in groups of more than two. Gaskets like the gasket 8 might be used in either single or multiple constructions. In view of these and many other possible modifications, the invention is not intended to be limited by the showing of herein or in any other manner except as may specifically be required.

lclaim:

l. A contact module for a limit switch or the like, said module comprising: a case having opposite upper and lower walls and a base portion defining a rear wall and a removable cover defining a front wall facing the rear wall, the case further defining a vertical slide track opening through the upper wall; stationary contact means in the case; a movable contact carrier in the case that is reciprocally movable along the track with an upper end of the carrier being accessible through the open upper end of the track, the carrier being provided with an opening therethrough that is transverse to the front and rear walls and elongated in the direction of the track; movable contact means carried by the carrier to be selectively engageable with the stationary contact means; and

a retaining pin that rotatably extends through the front and rear walls of the case and the carrier opening, the pin having a head that engages the outside of the cover and is provided with a tool socket, the pin also having a head that engages the outside of the cover and is provided with a tool socket, the pin also having a thread d end extending beyond the rear wall; and a retainer clip removably attached to the pin inwardly of the threaded end, the clip engaging the outside of the rear wall to cooperate with the head to hold the base and cover together while allowing the pin to rotate freely so that the threaded end can be used to attach the module to a support.

2. In a limit switch or the like including a housing and a pair of contact modules mounted in the housing one above the other, the improvement wherein the modules include vertically reciprocally movable contact carriers that are aligned with the lower end of the upper carrier facing the upper end of the lower carrier; an extension threadedly fitted to one of said facing ends of the carriers to be axially adjustable with respect thereto and to be engageable with the other carrier, said extension having a portion of noncircular cross section; and an adjustment wheel with a mating noncircular opening through which the extension passes to provide a keyed connection between the wheel and extension as a result of which rotation of the wheel causes rotation and resulting axial adjustment of the extension.

3. A limit switch according to claim 2 wherein each of the modules comprises: a case having opposite upper and lower walls and a base portion defining a rear wall and a removable cover defining a front wall facing the rear wall, the case further defining a vertical slide track opening through the upper and lower walls, the movable contact carrier being reciprocally movable along the track with the ends of the carrier being accessible through the open ends of the track, the carrier being provided with an opening therethrough that is transverse to the front and rear walls and elongated in the direction of the track; stationary contact means in the case; movable contact means carried by the carrier to be selectively engageable with the stationary contact means; and a retaining pin that rotatably extends through the front and rear walls of the case and the carrier opening, the pin having a head that engages the outside of the cover and is provided with a tool socket, the pin also having a threaded end extending beyond the rear wall that is received in the housing to mount the module thereon; and a retainer clip removably attached to the pin inwardly of the threaded end, the clip engaging the outside of the rear wall to cooperate with the head to hold the base and cover together while allowing the pin to rotate freely.

4. A limit according to claim 3 wherein: the housing is split into two facing sections, with one section containing the modules, said modules together constituting switch means, and the other section containing external terminal means, both the switch means and the terminal means being inwardly spaced from the side walls of the associated housing section about substantially their entire circumferences, one of said switch and terminal means having bayonet means projecting toward and engageable with the other when the housing sections are assembled; and there is a gasket of insulating material interposed between the housing sections, said gasket including a central web extending across the facing portions of the housing sections to seal off one housing section from the other, said central web having opening means therethrough through which the bayonet means are received with a close fit, the gasket including a first skirt on one side of the web that extends a substantial distance into one of the housing sections to substantially surround the switch means and a second skirt on the opposite side of the web that extends a substantial distance into the other housing section to substantially surround the terminal means.

5. In a limit switch or the like of the type comprising a housing split into two facing sections, with one section containing switch means and the other section containing external terminal means, one of said switch and terminal means having bagonet means projecting toward and engageable with the 0 er when the housing sections are assem led, the improvement wherein each of said switch and terminal means is inwardly spaced from the sidewalls of the associated housing section about substantially its entire circumference; and there is a gasket of insulating material interposed between the housing sections, said gasket including a central web extending across the facing portions of the housing sections to seal off one housing section frorn'the other, said central web having opening means therethrough through which the bayonet means are received with a close fit, the gasket including a first skirt on one side of the web that extends a substantial distance into one of the housing sections to substantially surround the switch means and a second skirt on the opposite side of the web that extends a substantial distance into the other housing section to substantially surround the external terminal means.

33 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 555,215 Dated January 12, 1971 Inven tor William F Dehn It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 24, delete "p Column 2, line 11, delete "sections" (second occurrence) Column 2, line 71, delete "both" (first occurrence) Column 3, line 31, delete "preferably" (second occurrence) Column 3, line 34, delete "a" Column 4, line 60, delete "of" Column 5, lines 4 through 6, delete head that engages the outside of the cover and is provided with a tool socket, the

pin also having a" Column 5, line 14, after "wherein" a colon (z) should appear Column 6, line 4, after "limit" insert switch Column 6, line 31, after "wherein" a colon (z) should appear Signed and sealed this 11th day of May 1971.

(SEAL) Attest:

EDWARD M.FI.EIGHER,JR. WILLIAM E. SGHUYLER, JR. fitesting O ficer Commissioner of Patents

Claims

1. A contact module for a limit switch or the like, said module comprising: a case having opposite upper and lower walls and a base portion defining a rear wall and a removable cover defining a front wall facing the rear wall, the case further defining a vertical slide track opening through the upper wall; stationary contact means in the case; a movable contact carrier in the case that is reciprocally movable along the track with an upper end of the carrier being accessible through the open upper end of the track, the carrier being provided with an opening therethrough that is transverse to the front and rear walls and elongated in the direction of the track; movable contact means carried by the carrier to be selectively engageable with the stationary contact means; and a retaining pin that rotatably extends through the front and rear walls of the case and the carrier opening, the pin having a head that engages the outside of the cover and is provided with a tool socket, the pin also having a head that engages the outside of the cover and is provided with a tool socket, the pin also having a threaded end extending beyond the rear wall; and a retainer clip removably attached to the pin inwardly of the threaded end, the clip engaging the outside of the rear wall to cooperate with the head to hold the base and cover together while allowing the pin to rotate freely so that the threaded end can be used to attach the module to a support.

5. In a limit switch or the like of the type comprising a housing split into two facing sections, with one section containing switch means and the other section containing external terminal means, one of said switch and terminal means having bayonet means projecting toward and engageable with the other when the housing sections are assembled, the improvement wherein each of said switch and terminal means is inwardly spaced from the sidewalls of the associated housing section about substantially its entire circumference; and there is a gasket of insulating material interposed between the housing sections, said gasket including a central web extending across the facing portions of the housing sections to seal off one housing section from the other, said central web having opening means therethrough through which the bayonet means are received with a close fit, the gasket including a first skirt on one side of the web that extends a substantial distance into one of the housing sections to substantially surround the switch means and a second skirt on the opposite side of the web that extends a substantial distance into the other housing section to substantially surround the external terminal means.