US3858140A

US3858140A - Time-delay relay and method of assembling same

Info

Publication number: US3858140A
Application number: US00383946A
Authority: US
Inventors: J Hancock
Original assignee: Texas Instruments Inc
Current assignee: Texas Instruments Inc
Priority date: 1973-07-30
Filing date: 1973-07-30
Publication date: 1974-12-31
Anticipated expiration: 1991-12-31
Also published as: IT1018750B; DE7425172U; DE2435517B2; JPS5043453A; FR2239753B1; GB1455600A; DE2435517A1; FR2239753A1; JPS5848976B2

Abstract

A time-delay relay comprising a housing having a chamber in which are mounted a thermostatic switch assembly and an electric heater in heat transfer relation with the thermostatic switch assembly for heating the latter to effect actuation of the contacts thereof. A pair of heater terminals are positioned in terminal-receiving slots in the housing, and have portions in conductive electrical contact with the heater. A cover overlies the thermostatic switch assembly and has means engageable with the terminals thereby to retain the terminals within the housing. A retainer is provided which is snapped into a position spanning the mouth of the chamber thereby to hold the terminals, heater, thermostatic switch assembly, and the cover in their assembled position. Also disclosed is a method of assembling a time-delay relay in which the various components are inserted into respective openings in a chamber of a housing and in which the various components are secured relative to one another and relative to the housing by means of a retainer.

Description

United States Patent [1 1 Hancock TIME-DELAY RELAY AND METHOD OF ASSEMBLING SAME [75] Inventor: John T. Hancock, Garland, Tex.

[73] Assignee: Texas Instruments Incorporated,

Dallas, Tex.

[22] Filed: July 30, 1973 [21] Appl. No.: 383,946

Primary Examiner-J. D. Miller Assistant Examiner-Fred E. Bell Attorney, Agent, or Firm-John A. Haug; James P. McAndrews; Edward J. Connors [4 1 Dec. 31, 1974 5 7] ABSTRACT A time-delay relay comprising a housing having a chamber in which are mounted a thermostatic switch assembly and an electric heater in heat transfer relation with the thermostatic switch assembly for heating the latter to effect actuation of the contacts thereof. A pair of heater terminals are positioned in terminalreceiving slots in the housing, and have portions in conductive electrical contact with the heater. A cover overlies the thermostatic switch assembly and has means engageable with the terminals thereby to retain the terminals within the housing. A retainer is provided which is snapped into a position spanning the mouth of the chamber thereby to hold the terminals, heater, thermostatic switch assembly, and the cover in their assembled position. Also disclosed is a method of assembling a time-delay relay in which the various components are inserted into respective openings in a chamber of a housing and in which the various components are secured relative to one another and relative to the housing by means of a retainer.

11 Claims, 6 Drawing Figures TIME-DELAY RELAY AND METHOD OF ASSEMBLING SAME BACKGROUND OF THE INVENTION This invention relates to thermostatic electrical switches and is particularly concerned with a timedelay relat (TDR) utilizing a thermostatic switch assembly for opening and closing an electrical circuit.

More particularly, this invention is concerned with a TDR in which certain electrical terminals and a thermostatic switch assembly are held in position relative to one another and relative to a housing by means of a retainer adapted to be snapped into position in a chamber in the housing. In prior art TDRs the thermostatic switch assembly was adhesive-bonded or riveted to a housing and electrical terminals were riveted to the housing. The adhesive bonding procedure required that the adhesive be cured, and this curing cycle increased the assembly time of the unit. Both the application of the adhesive and the installation of the rivets for the terminals involved separate manufacturing steps which increased production time and costs. Known prior art assembly procedures have required the TDR components to be brought together along different axes or planes (e.g., both vertical and horizontal) thereby necessitating that the unit be turned during assembly thus resulting in increased production time and requiring complicated production machines.

SUMMARY OF THE INVENTION Among the several objects of this invention may be noted the provision of a TDR which may be assembled without the use of adhesive or rivets; the provision of such a TDR in which all parts may be brought together along one axis or plane (e.g., a vertical one) thereby to simplify assembly; the provision of such a TDR in which terminals may readily be installed in the housing without the use of rivets; the provision of such a TDR which, once assembled, substantially precludes tampering; the provision of such a TDR in which many of the components thereof perform multiple functions; the provision of a method of assembling a TDR unit which simplifies the assembly procedure of TDRs and which results in increased production at lower cost; and the provision of such a TDR which is of rugged contruction and is reliable in operation. Other objects and features of this invention will be in part apparent and in part pointed out hereinafter.

Briefly, a time-delay relay unit of this invention comprises a housing having a chamber and terminalreceiving slots therein. A thermally responsive switch assembly adapted to make and break an electrical circuit is mounted within the chamber. This switch assembly has contacts and a thermostatic switch element therewithin, the contacts being movable into and out of engagement with one another in response to actuation of the thermostatic element when the latter is subjected to predetermined temperature conditions. A heater energized by a second circuit is positioned in a heattransfer relation with the switch assembly for heating the thermostatic element. A pair of terminals adapted for electrical contact with the heater is provided in the housing, these terminals constituting a portion of the second circuit. The heater and the switch assembly are mounted within the chamber, and the terminals are received by the terminal-receiving slots in the housing. A

cover overlies the chamber and has means engageable with the terminals thereby to retain the terminals within the housing. A retainer engageable with the housing is forced into position at the mouth of the chamber thereby to hold the cover, the switch assembly, the heater and the terminals in an assembled relation relative to one another within the housing.

The method of this invention of assembling a timedelay relay unit comprises first inserting the terminal members into the openings in the housing with portions of the terminals extending into the chamber. Then, the heater and the switch assembly are inserted into the chamber with the heater in electrical contact with the above-mentioned portions of the terminals and in heattransfer relation with the switch assembly. A cover is then installed in the chamber to overlie the switch assembly and the heater, the cover being engageable with the terminal members, and then a retainer is applied across the mouth of the chamber, the retainer being engageable with the housing at the sides of the chamber thereby to positively secure the terminal members, the heater, the switch assembly and the cover in an assembled position relative to the housing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a time-delay relay (TDR) of this invention;

FIG. 2 is an enlarged plan view of the TDR;

FIG. 3 is a vertical section taken on line 3-3 of FIG. 2 with parts broken away to show some interior details;

FIG. 4 is an enlarged partial plan view of a portion of the TDR housing prior to installation of the terminals and switch assembly; and

FIGS. 5 and 6 are front views of the two heater terminals.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawings, a time-delay relay unit (TDR) of this invention, indicated in its entirety at l, is shown to comprise a housing 3 of nonconductive material (e.g., a molded synthetic resin) having a chamber 5 and a pair of terminal-receiving slots 7a, 7b molded therein. An enclosed unitary thermostatic switch assembly 9 is mounted within chamber 5. This switch assembly includes a case 11 adapted for reception in chamber 5 and a pair of contacts 13a, 13b mounted within the case.

As shown in FIG. 3, contact is mounted on a bracket 15 and contact 13b is secured to the free end of a contact arm 17 resiliently cantilevered from one side of the switch casing and being movable therewithin to bring contact 13b into and out of mating engagement with contact 130. Contacts 13a, 13b are normally biased closed by the arm 17.

A thermostatic element 19 such as a snap-acting bimetallic disk of the type disclosed, for example, in US. Pat. No. l,448,240, is mounted within case 11. Because of its nondevelopable or dished shape element 19 will snap from one curvature position to an opposite one in response to change of temperature so as to provide mechanical power to actuate the contact arm l7 of switch assembly 9. Disk 19 is mounted at the bottom of case 11 within a cup-shaped end closure 21 thereof which is formed from a material such as copper having good electrical and thermal conductivity. The periphery of disk 19 is supported by an internal shoulder 23 of cup 21. A pill-shaped heater 25 is bonded in heat-transfer relation to the undersurface of cup 21, this heater constituting means for heating disk 19. This heater may be formed of a material with a resistivity-temperature curve having a steep-sloped positive temperature coefficient (referred to as PTC) such as is described and illustrated in US. Pat. No. 3,489,976. At temperatures below a predetermined elevated temperature, the bimetallic disk is dish-shaped with its upper face concave (see FIG. 3). Upon being heated, the disk snaps over center so that its upper face is convex. An actuator or transfer pin 26 is axially slidable within a central bore of a cylindrical pin guide 27 so that when disk 19 snaps into its convex upward curvature it will be moved upwardly to engage a lobe 28 intermediate the ends of contact arm 17 thereby to lift arm 17 to open contacts 13a, 13b.

A pair of terminals 29a, 29b is inserted in their respective receiving slots 7a, 7b in housing 3 (one terminal in each slot). Each terminal 29a, 29b has a contact portion 31a, 31b, respectively which extends into chamber so that the contact portion 31a of terminal 29a engages and electrically contacts the central undersurface of heater 25 and contact portion 31b of terminal 29b engages and electrically contacts cup 21, which constitutes the other terminal of heater pill 25. Thus, terminals 29a, 29b and heater 25 form a heater circuit to which electrical power is supplied for heater energization.

Switch assembly 9 includes a pair of terminals 33a, 33b, each connected to a respective contact 13a, 13b, these terminals and contacts constituting an electrical circuit which is opened in delayed response to energization of the heater circuit by disk 19 snapping overcenter and opening contacts 13a, 13b. It is to be understood that the arrangement of the disk and contacts may be such that the contacts will be opened or closed on a rise in temperature.

Terminals 29a, 29b are substantially identical in structure in their upper portions, both including a shank portion 35a, 35b, a quick-connect

portion

37a, 37b with

shoulders

39a, 3% between the shank and quickconnect external

terminal portions

37a, 37b and with

shoulders

41a, 41b at the lower ends of the shank portion. Each terminal has a tab 43a, 43b struck from the shank portion with its free upper end extending outwardly from the shank portion and inwardly toward chamber 5 when the terminal is received in its respective terminal-receiving slot 7a, 7b. As shown in FIG. 3, contact portion 31a of terminal 29a is an elongate arm extending into chamber 5 for firm electrical contact with the undersurface of heater 25. And contact portion 31b of terminal 33b has its relatively short contact finger 31b struck from its shank 35b so as to extend into the chamber for electrical contact with the periphery of cup 21, and thus conductive electrical contact with the top surface of heater 25. Terminals 29a, 29b are preferably made of a resilient electrical conductor material, such as a good cooper electrical alloy. The contact portions 31a, 31b are formed so as to be biased into resilient firm engagement with heater 25 and with cup 21, respectively, thereby to maintain excellent electrical contact therewith.

Terminal-receiving slots 7a, 7b in housing 3 are identical, and thus only one slot need be described in detail. Each slot includes a thin, blind slot 45 (see FIG. 4) in the housing generally parallel to the axis of chamber 5 for reception of the shank portions 31a, 31b of a re spective terminal 29a, 29b inserted therein, and a connecting slot 47 extending heightwise of the chamber along the length of the shank slot providing an opening between the chamber and-the shank slot thus enabling the contact portions 31a, 31b of the terminals to extend from the shank-receiving slot into the chamber. Within each shank-receiving slot 45 are stops 49(see FIG. 3) engageable with

shoulders

41a, 41b at the bottom of the shank of each terminal 29a, 29b thereby to properly position each terminal in the housing upon being inserted into its respective slot 7a, 7b. As indicated at 51, stops are provided in housing 3 on the walls of chamber 5, these stops being engageable by the periphery of cup 21 of switch assembly 9 thereby to position the case 11 when it is seated in the chamber in an assembled position in which heater 25 and cup 21 are properly located within the housing for electrical contact with contact portions 31a, 31b of terminals 29a, 29b.

As best seen in FIGS. 2 and 4, chamber 5 is a blind hole of generally circular cross section and has a mouth 53 of generally rectangular cross section. A cover of insulating material, generally indicated at 55, fits within the mouth of the chamber, to engage the upper surface of case 11 of the unitary thermostatic switch assembly 9 and to hold the latter in its installed seated position in the chamber. Cover 55 is of generally rectangular shape in plan and has a close fit (but not a tight fit) within the mouth of the chamber. The cover has lugs 57 extending from opposite ends of the cover into slots 47 which engage the inner faces of shank portions 35a, 35b and the upper free ends of tabs 43a, 43b of terminals 29a, 29b, thereby preventing movement of the terminals and retaining them in their installed position in the housing. As indicated at 59, cover 55 has a plurality of gripping ledges on its undersurface for engagement with the upper portion of switch body 11 of switch assembly 9 thereby to hold the latter in its installed position.

A retainer 61, adapted to be forced or snapped into a locking position in chamber mouth 53, positively holds and locks the cover in position in the housing. With the cover lugs 57 in engagement with tabs 43a, 43b terminals 29a, 29b and with cover ledges 59 in engagement with switch body 11 of switch assembly 9, all the components of the time-delay unit are securely held relative to one another and relative to housing 3 in an assembled position by means of retainer 61. MOre particularly, retainer 61 is preferably made of a stiff, resilient material, such as spring steel. The retainer is generally of rectangular shape in plan and has tabs 63 extending endwise therefrom. Tabs 63 are bent up from the plane of the main section of the retainer and the length of the retainer from one tab to another is slightly greater than the interior dimensions of chamber mouth 53 whereby, upon installation of the retainer, the retainer must be forced into the chamber mouth. With the retainer properly installed, it is contiguous to the upper surface of cover 55 and securely holds the latter in position relative to the housing. Preferably, cover 55 is made of an electrically insulative material, such as a thermosetting synthetic resin, thereby to electrically insulate the switch assembly from retainer 61. It will be further noted that, upon installation of retainer 61 in chamber mouth 53, retainer tabs 63 are deformed or sprung so as to have an interference fit or engagement with opposing surfaces of the housing at the mouth of the chamber as the retainer is pushed into the chamber mouth. With tabs 63 being bent up away from the main section of the retainer, any attempt to remove an installed retainer from the chamber mouth will cause the ends of the tabs to dig into the side walls of the chamber mouth and thus effectively prevent removal of this retainer. This self-tightening or self-locking feature of the retainer prevents tampering with the time-delay relay unit after assembly.

In accordance with this invention, a simpler, more rapid and less costly method of assembly is accomplished by first inserting terminal members 29a, 29b into their respective terminal-receiving slots 7a, 7b in housing 3. Case 11 enclosing unitary thermostatic switch assembly 9, along with heater 25 secured to the bottom thereor, is then inserted into its installed position in chamber 5 with the contact portions 31a, 31b of terminals 29a, 29b in electrical contact with the heater and with cup 19 respectively and with the heater in heat transfer station with the cup. Cover 55 is then placed in chamber mouth 53 with lugs 57 extending into contact-receiving slots 47 for engagement with tabs 41 on terminals 29a, 29b and with ledges 59 in engagement with switch body 11. Retainer 61 is then snapped into position in chamber mouth 51 above cover 55 thereby positively to secure terminals 29a, 29b, switch assembly 9 and cover 55 in their respective assembled positions (see FIG. 3) relative to housing 3. The method of assembling a time-delay relay unit of this invention eliminates the need for adhesive bonding the switch assembly to the housing, permits all parts to be brought together during assembly along a common vertical axis or plane, eliminates the need to rivet heater terminals 29 a, 29 b to the housing, and provides an assembled unit which is of small over-all size and which effectively eliminates tampering with the unit after assembly.

n view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made inthe above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A time-delay relay comprising:

a housing having a chamber and terminal receiving slots therein;

a thermally responsive switch assembly mounted within said chamber and having contacts and a thermostatic element, said contacts being movable into and out of engagement with one another in response to actuation of the thermostatic element when the latter is subjected to predetermined temperature conditions thereby to make and break a first circuit;

a heater in heat-transfer relation with said switch assembly for heating said thermostatic element, said heater being energized by a second circuit;

a pair of terminals adapted for conductive electrical contact with said heater, said terminals constituting a portion of said second circuit, said heater and said switch assembly being mounted within said chamber and said terminals being received by said terminal receiving slots in said housing; a cover overlying said chamber and having means engageable with said terminals thereby to retain the terminals within said housing; and

a retainer engageable with said housing adapted to be forced into position at the mouth of the chamber thereby to hold the cover, switch assembly, heater and terminals in assembled relation within said housing.

2. A time-delay relay as set forth in claim 1 wherein said chamber is a blind hole in one face of the housing, this one face of the housing constituting the top of the housing, said terminal-receiving slots being adjacent said chamber and extending generally parallel to the chamber, each said slot having a portion thereof opening into said chamber substantially along the length of said slot.

3. A time-delay relay as set forth in claim 2 wherein each terminal has a shank portion adapted to be received by said slot upon insertion of its lower end into the slot from above, a contact portion extending from the shank portion through said slot portion and into the chamber for conductive electrical contact with said heater.

4. A time-delay relay as set forth in claim 3 wherein each terminal has a tab struck from its shank portion, said tab angling away from said shank portion and inwardly and upwardly toward said chamber, said tab being received within said portion of said slot and being engageable by said means on said cover thereby to retain the terminals within the housing.

5. A time-delay relay as set forth in claim 4 wherein each said slot has a stop therewithin engageable by a respective terminal inserted therein for positioning the terminal in a desired installed position within the slot relative to the housing in which said contact portion is in position for conductive electrical contact with said heater.

6. A time-delay relay as set forth in claim 2 wherein said means on said cover engageable with said terminal comprises a pair of lugs, one for each terminal, each lug extending into said portion of said terminal-receiving slot and being engageable with a respective terminal.

7. A time-delay relay as set forth in claim 6 wherein said cover is engageable with said thermally responsive switch assembly thereby to hold the switch in position within said housing.

8. A time-delay relay as set forth in claim 7 in which said thermally responsive switch assembly is an enclosed unitary assembly and said heater is secured to the undersurface thereof.

9. A time-delay relay as set forth in claim 1 wherein said retainer is made of a relatively stiff, resilient material and is of a length somewhat longer than the distance from one side to the other of the mouth of said chamber, portions of said retainer adjacent the sides of the chamber being forced into engagement with opposing surfaces of the housing at the mouth of the chamber, said portions of the retainer preventing removal of the retainer from the housing once it has been forced into position.

10. A time-delay relay as set forth in claim 9 wherein the mouth of said chamber is rectangular in cross section and said retainer is generally in the shape of a rectangle having a plurality of tabs extending endwise therfrom, said tabs being bent up from the plane of said retainer and being engageable with opposite sides of the mouth of the chamber thereby to lock the retainer relative to the housing upon inserting the retainer into the mouth of the chamber.

11. A method of assembling a time-delay relay, said relay comprising a housing with a chamber and with openings for the reception of terminal members, a thermostatic switch assembly, a heater for heating said switch assembly, and a pair of terminal members for supplying electrical power to the heater, said method comprising the steps of:

inserting said terminal members into said openings in the housing, portions of said terminals extending into said chamber;

inserting said heater and said switch assembly into said chamber with the heater in conductive electrical contact with said portions of the terminals and in heat-transfer relation with the switch assembly;

position relative to the housing.

Claims

1. A time-delay relay comprising: a housing having a chamber and terminal receiving slots therein; a thermally responsive switch assembly mounted within said chamber and having contacts and a thermostatic element, said contacts being movable into and out of engagement with one another in response to actuation of the thermostatic element when the latter is subjected to predetermined temperature conditions thereby to make and break a first circuit; a heater in heat-transfer relation with said switch assembly for heating said thermostatic element, said heater being energized by a second circuit; a pair of terminals adapted for conductive electrical contact with said heater, said terminals constituting a portion of said second circuit, said heater and said switch assembly being mounted within said chamber and said terminals being received by said terminal receiving slots in said housing; a cover overlying said chamber and having means engageable with said terminals thereby to retain the terminals within said housing; and a retainer engageable with said housing adapted to be forced into position at the mouth of the chamber thereby to hold the cover, switch assembly, heater and terminals in assembled relation within said housing.

11. A method of assembling a time-delay relay, said relay comprising a housing with a chamber and with openings for the reception of terminal members, a thermostatic switch assembly, a heater for heating said switch assembly, and a pair of terminal members for supplying electrical power to the heater, said method comprising the steps of: inserting said terminal members into said openings in the housing, portions of said terminals extending into said chamber; inserting said heater and said switch assembly into said chamber with the heater in conductive electrical contact with said portions of the terminals and in heat-transfer relation with the switch assembly; installing a cover in said chamber to overlie the switch assembly and heater, said cover being engageable with said terminal members; and applying a retainer across the mouth of the chamber to span the cover and engage the housing at the sides of the mouth of the chamber thereby positively securing the terminal members, the heater, the switch assembly and the cover in an assembled position relative to the housing.