Smoke/Fire Detector

This is related to patent application Ser. No. 08/511,019, filed Aug. 3, 1995, now is patented as U.S. Pat. No. 5,710,541, inventors Lawrence G. Stanley and Wayne A. Nelson, assigned to the same assignee as the present invention.

This invention relates generally to smoke/fire detectors and more particularly to smoke/fire detectors having a base section and removable sensor section.

As is known in the art, one type of smoke/fire detector is made up of a base section and a removable sensor section. The base section is adapted for mounting to a ceiling, wall or other building structural member and includes electrical terminals for enabling electrical connection to the building wiring to provide electrical power to the detector and smoke/fire detection signals to a remotely located station, for example.

The sensor section includes the smoke/fire detection element, such as an ionization, photo-optical or heat sensor. The sensor section is removable from the base in order to replace one type of sensor with another type, or to replace the sensor when it becomes defective. Thus, each sensor section/base section pair must be constructed to provide for both mechanical and electrical removable/attachable interconnection. Further, in some countries, each electrical interconnection is required to use a bifurcated contact; that is, when one electrical contact is to engage, or mate with another electrical contact, one of the contacts must make physical contact with at least two points of the other, mating electrical contact. Thus, each base section electrical contact, for example, must make physical contact with two points on each corresponding sensor section electrical contact. While the two contact points may be on one surface of the mating contact, improved mechanical stability results when the two contact points are on opposing surfaces of the mating contact.

In one base section/detector section arrangement, the base section includes a pair of separate electrical contacts for engagement with points on opposite surfaces of a corresponding sensor section electrical contact. Each one of the pair of electrical contacts of the base section is a stamped, single piece having a relatively large mounting portion which terminates into an elongated, cantilevered finger-like contact. The mounting portions of the pair of contacts are encapsulated into the plastic, generally disk shaped, base section and are electrically connected to a common screw fixture also encapsulated into the base section. A screw, threaded into the screw fixture, provides an electrical terminal for securing an electrical wire which provides power to, or receives sensor signals from, the sensor section. The sensor section electrical contact is adapted to mate, and contact, with the pair of base electrical contacts and has opposing surfaces which are disposed in planes parallel to the base. The distal ends of the finger-like contacts of the pair of base electrical contacts extend in opposing, vertically spaced directions parallel to the surface of the base section and are configured to engage the opposing surfaces of the corresponding sensor section electrical contact when the sensor electrical contact is inserted into the space between the corresponding pair of finger-like base section electrical contacts. The engagement provides electrical connection between the base section pair of contacts and the sensor section contact, and also provides a mechanical inter-lock between the base section and the sensor section.

In accordance with the present invention, a structure is provided for an electrical contact. A recessed pocket is formed in the structure. The pocket has a pair of opposing sidewalls, a platform, and a resilient tongue-like member protruding into a region between the opposing sidewalls. Upper surfaces of the platform and the tongue-like member are disposed in a common plane spaced from the bottom portions of the sidewalls to provide a channel therebetween. When engaged by an electrical contact, the tongue-like member is adapted to be depressed downward enabling side edge portions of the electrical contact to slide within the channel. The tongue-like member is configured and arranged to urge the contact upward against the bottom portions of the sidewalls with the tongue-like member snapping behind a projection from a bottom of the electrical contact producing an audible click and securely locking the electrical contact into place in the channel.

In a preferred embodiment, the electrical contact has a hole formed therein. The hole has a rim disposed about a peripheral portion of the hole to provide the projection. An edge portion of the tongue-like member is adapted to engage a portion of the rim to secure the electrical contact in the channel.

In accordance with another feature of the invention, a smoke/fire detector assembly is provided. The detector assembly includes a base section having a plurality of electrical contacts and a removable/attachable sensor section having a corresponding plurality of electrical contacts. Each one of the sensor section electrical contacts is adapted to electrically contact a corresponding one of the base section electrical contacts. Each one of the base section electrical contacts has a hole formed therein. The hole has a projecting rim disposed about its periphery for receiving an electrical contact screw. The base section has a plurality of recessed pockets formed therein. Each one of the pockets has disposed therein a corresponding one of the plurality of base section electrical contacts. Each one of the pockets has a pair of opposing sidewalls, a platform, and a resilient tongue-like member protruding into a region between the opposing sidewalls. Upper surfaces of the platform and the tongue-like member are disposed in a common plane spaced from the bottom portions of the sidewalls to provide a channel therebetween. When engaged by a corresponding one of the base section electrical contacts, the tongue-like member is configured to depressed downward enabling side edge portions of the electrical contact slide within the channel. The tongue-like member is configured and arranged to urge the electrical contact upward against the bottom portions of the sidewalls. The tongue-like member is configured to snap behind the rim with an audible click and securely lock the electrical contact into place in the channel.

FIGS. 1 and 2 are perspective, exploded views of a smoke/fire detector, FIG. 1 showing the detector from one perspective and FIG. 2 showing the detector from an opposite perspective;

FIGS. 3, 4, 5 and 6 are views of an exemplary one of a plurality of electrical contacts included in a base section of the detector of FIGS. 1 and 2; FIG. 3 being a side elevation view; FIG. 4 being a top view; FIG. 5 being a front elevation view; and, FIG. 6 being a perspective view;

FIG. 7 is a plan view showing the relationship between electrical contacts of a sensor section of the detector of FIGS. 1 and 2 and the electrical contacts of the base section prior to such contacts becoming electrically connected;

FIG. 8 is a elevation view showing the relationship between electrical contacts of the sensor section of the detector of FIGS. 1 and 2 and the electrical contacts of the base section prior to such contacts becoming electrically connected;

FIGS. 9, 10, 11, and 12 are views of an additional electrical contact included in a base section of the detector of FIGS. 1 and 2; FIG. 9 being a side elevation view; FIG. 10 being a top view; FIG. 11 being a front elevation view; and, FIG. 12 being a perspective view;

FIG. 13 is a plan view showing the relationship between electrical contacts of a sensor section of the detector of FIGS. 1 and 2 and the electrical contacts of the base section after such contacts become electrically connected;

FIG. 14 is a elevation view showing the relationship between electrical contacts of the sensor section of the detector of FIGS. 1 and 2 and the electrical contacts of the base section after such contacts become electrically connected; and, FIG. 14a is a elevation view of the portion of FIG. 14 enclosed by a circle labelled 14a.

FIGS. 15, 16, 17 and 18 are views of an exemplary one of a plurality of electrical contacts according to the invention; FIG. 15 being a side elevation view; FIG. 16 being a top view; FIG. 17 being a front elevation view; and, FIG. 18 being a perspective view;

FIGS. 19-21 are partially broken away views of a mounting plate according to the invention, such mounting plate having a recessed pocket formed therein adapted to have snapped therein the electrical contact of FIGS. 15-18; FIG. 19 being a cross sectional elevation view of the pocket; FIG. 20 being a top plan view of the pocket, the cross section of FIG. 19 being along line 19--19 in FIG. 20; and FIG. 21 is a bottom plan view of the pocket;

FIGS. 22, 23, 24, and 25 are views of an additional electrical contact according to the invention; FIG. 22 being a side elevation view; FIG. 23 being a top view; FIG. 24 being a front elevation view; and, FIG. 25 being a perspective view;

FIGS. 26, 27 and 28 are partially broken away views of the mounting plate of FIGS. 19-21 with the contact of FIGS. 15-16 partially inserted into the pocket; FIG. 26 being a cross sectional elevation view; FIG. 27 being a top plan view, the cross section of FIG. 26 being along line 26--26 in FIG. 27; and FIG. 28 being a bottom view;

FIGS. 29, 30, and 31 are partially broken away views of the mounting plate of FIGS. 19-21 with the contact of FIGS. 15-16 being fully inserted into the pocket; FIG. 29 being a cross sectional elevation view; and FIG. 30 being a top plan view, the cross section of FIG. 29 being along line 29--29 in FIG. 30; and FIG. 31 being a bottom view.

Referring now to FIGS. 1 and 2, a smoke/fire detector assembly 10 is shown. The assembly 10 includes a base section 12 and a removable/attachable sensor section 14.

The sensor section 14 includes a sensor head 14H and a removable/attachable sensor base 14B, both of dielectric material, here plastic. The sensor head 14H is of conventional design to encloses a smoke/fire detection element, not shown, such as an ionization, photo-optical or heat sensor. The smoke/fire detection element, not shown, and other electronic components, not shown, are electrically interconnected and mounted, in a conventional manner, by a printed circuit board 15 (FIG. 2). The printed circuit board 15, with its mounted smoke/fire detection element, not shown, and other electrical components, not shown, is mounted to the sensor head 14H in a conventional manner. The sensor head 14H is attachable/removable from the sensor base 14B in any conventional manner in order enable replacement of one type of smoke/fire detection element with another type, or to enable replacement of the sensor head 14H when it becomes defective.

The sensor base 14B is removable from, and reattachable to, the base section 12. Here, the sensor base 14B has three spade shaped male electrical contacts 18a, 18b, 18c, respectively, as indicated. The male electrical contacts 18a, 18b, 18c are a stamped, single piece of electrically conductive material, here phosphor bronze. More particularly, the three spade shaped male electrical contacts 18a, 18b, 18c are inserted through slots 16a, 16b, 16c, respectively, as indicated. Ends 20a, 20b, 20c of the electrical contacts 18a, 18b, 18c, respectively, protrude from surface 22 (FIG. 1) of sensor base 14B, pass through holes 24a, 24b, 24c (FIG. 2) respectively, formed in the printed circuit board 15, and plug into female electrical receptacles, not shown, mounted to the printed circuit board 15 for electrical connection to the smoke/fire detection element, not shown. The other ends 26a, 26b, 26c of electrical contacts 18a, 18b, 18c, respectively, protrude from surface 28 (FIG. 2) and are adapted to plug into base section 12 female electrical contacts 30a, 30b, 30c, respectively, in a manner to be described below. The mid-portion of electrical contacts 18a, 18b, 18c, are provided with detents 31a, 31b, 31c, respectively, which project outwardly from the surfaces of the electrical contacts 18a, 18b, 18c, as shown more clearly in FIG. 14a for detent 31c. These detents 31a, 31b, 31c are inserted into slots 35 formed in the sensor base 14B. Thus, each one of the electrical contacts 18a, 18b, 18c is disposed in the sensor base 14B of the sensor section 14 and projects longitudinally from such sensor section 14, here vertically from the sensor section 14, as shown.

Base section 12 includes: a dielectric, here plastic, mounting plate 34 adapted for mounting, in a conventional manner, to a ceiling, wall or other building structural member, not shown; the plurality of electrical contacts 30a, 30b, 30c which correspond, and electrically interconnect with, electrical contacts 18a, 18b, 18c, respectively; an additional electrical contact 30d; and screws 32a, 32b, 32c, 32d, respectively, and washers 36a, 36b, 36c, 36d, respectively, as shown, for affixing to electrical wires, not shown. Thus, screws 32a, 32b, 32c provide electrical terminal for the assembly 10. The electrical contacts 30a, 30b, 30c, 30d snap onto the bottom of conductors the electrical contacts 30a, 30b, 30c, 30d, respectively, to the bottom surface 48 (FIG. 2) of the base 12 by retaining snaps 31 which engage opposite surfaces of each one of the contacts 30a, 30b, 30c, 30d, as indicated in FIG. 2.

The base section 12 electrical contacts 30a, 30b, 30c which correspond, and electrically connect, to sensor section 14 electrical contacts 18a, 18b, 18c (FIGS. 1 and 2), are identical in construction. Here, each of the electrical contacts 30a, 30b, 30c is a stamped, single piece of electrically conductive material, here phosphor bronze. An exemplary one thereof, here electrical contact 30a, is shown in detail in FIGS. 3, 4, 5 and 6. Thus, each one of the electrical contacts 30a, 30b, 30c, has a first section 40a, 40b, 40c, respectively, with a surface 42a, 42b, 42c adapted for mounting to the mounting plate 34. More particularly, the first sections 40a, 40b, 40c, respectively, snap onto the mounting plate 34 by snaps 31(FIG. 2) which snap onto opposing surface porions of the electrical contacts. More particularly, the surfaces 42a, 42b, 42c contact ledges of recessed pockets 45a, 45b, 45c (FIG. 2) formed, along with the snaps 31, into mounting plate 34. Further, the first sections 40a, 40b, 40c, each has a threaded hole 44a, 44b, 44c, respectively, to receive screws 32a, 32b, 32c, 32d. As noted above, the screws 32a, 32b, 32c provide an electrical terminal for connecting to the building wiring, not shown, to provide electrical power to the detector assembly 10 and smoke/fire detection signals from the detector element, not shown, to a remotely located monitoring station, not shown.

Each one of the base section 12 electrical contacts 30a, 30b, 30c also has a second section 52a, 52b, 52c, respectively. The first sections 40a, 40b, 40c and the second section 52a, 52b, 52c have a common edge 56a, 56b, 56c, respectively, as shown. Each of the electrical contacts 30a, 30b, 30c has a surface 58a, 58b, 58c, respectively, extending perpendicular to surface 42a, 42b, 42c, respectively, as shown, and a pair of finger-like members, 60'a, 60"; 60'b, 60"b; 60'c, 60"c, respectively, extending from a second edge 62a, 62b, 62c, respectively, of the second section 52a, 52b, 52c, respectively, as shown. The second edge 62a, 62b, 62c, of the second section 52a, 52b, 52c, respectively, is perpendicular to the common edge 56a, 56b, 56c, of the first and second sections 40a, 52a, 40b, 52b, 40c, 52c, respectively. The finger-like members 60'a, 60"a; 60'b, 60"b; 60'c, 60"c are laterally spaced along, and cantilevered from, the second edge 62a, 62b, 62c, of the second section 52a, 52b, 52c, respectively. The finger-like members 60'a, 60"a; 60'b, 60"b; 60'c, 60"c extend along a common direction 64a, 64b, and 64c, respectively, as shown. Distal ends 66'a, 66"; 66'b, 66"b; 66'c, 66"c of the finger-like members 60'a, 60"a; 60'b, 60"b; 60'c, 60"c, respectively, are spaced from each other laterally in a direction 68a, 68b, 68c, respectively, as shown, perpendicular to the common direction common direction 64a, 64b, 64c, respectively, as shown, to receive, in spaces 70a, 70b, 70c, and contact opposing surfaces of the first end 26a, 26b, 26c, of electrical contact 18a, 18b, 18c, respectively, as shown in FIGS. 7 and 8. Thus, each electrical interconnection is made by a bifurcated contact. That is, each base section electrical contact 30a, 30b, 30c makes physical contact with two points on opposing surfaces of the mating sensor section 14 electrical contact 18a, 18b, 18c, respectively, improving mechanical stability compared with an arrangement making contact with only two points on the same surface of a mating electrical contact.

The additional base section 12 electrical contact 30d, shown in detail in FIGS. 9, 10, 11 and 12, is provided to engage, together with one of plurality of base section 12 electrical contacts, here sensor section 12 electrical contact 20a, a common one of the sensor section 14 electrical contacts, here sensor section 14 electrical contact 18a, as shown. Thus, sensor section 14 electrical contact 18a is contacted by two base section electrical contacts, here electrical contact 30a and electrical contact 30d.

The additional electrical contact 30d is a stamped, single piece of electrically conductive material, here phosphor bronze, and includes a first section 40d with a surface 42d adapted for mounting to the mounting plate 34 (FIGS. 1 and 2). More particularly, the first section 40d has a threaded hole 44d to receive, and thereby become secured to the base section 12, screws 32d (FIGS. 1 and 2). More particularly, the surface 42d contacts ledge of recessed pocket 45d (FIG. 2) formed in surface 48 mounting plate 34 and are affixed in place with screw 32d and washers 36d from the opposite surface 50 (FIG. 1) of the mounting plate 34. The screw 32d is are also used to provide an electrical terminal for connecting to the building wiring, not shown.

Electrical contact 30d also has a second section 52d. The first section 40d and the second section 52d have a common edge 56d, as shown. The electrical contact 30d has a surface 58d extending perpendicular to surface 42d, as shown, and a finger-like member 60d extending from a second edge 62d of the second section 52d, as shown. The second edge 62d of the second section 52d is perpendicular to the common edge 56d of the first and second sections 40d, 52d. The finger-like member 60d is cantilevered from the second edge 62d of the second section 52d. The finger-like member 60d extends is a direction opposite to direction 64a of contact 30a. The distal end of the finger-like member 60d of the additional base section 12 electrical contact 30d is bifurcated to provide two distal ends 66'd, 66"d, to make contact with two points on the same surface of the sensor section 14 electrical contact 18a, the opposite surface of such sensor section 14 electrical contact 18a being contacted by the pair of finger-like members 60'a, 60"a of base section 12 electrical contact 30a.

As noted above, the sensor base 14B is attachable to/removable from the base section 12. More particularly, and referring again to FIGS. 1 and 2, the sensor base 14B is formed with three tabs 15a, 15b, 15c, adapted to be inserted into slots 17a, 17b, 17c formed in the mounting plate 34. Further, as noted above in connection with FIGS. 3-6, distal ends 60'a, 60"a are laterally displaced along surface 58a. Thus, a shown in FIG. 13, distal end 60d of contact 30d and distal end 62'a of contact 30a are in a vertical, overlaying relationship, while distal end 60"a of contact 30a and distal end 60d of contact 30d are disposed in a lateral relationship, as shown. When inserted into slots 17a, 17b, 17c, the base electrical contacts 18a, 18b, 18c become positioned to slide into the space 70a, 70b, 70c between distal ends 66'a, 66"a, 66'b, 66"b, 66'c, 66"c, respectively, as indicated in FIGS. 13 and 14. Once inserted, the sensor base 14B is rotated in the direction indicated by arrow 19 so that the tabs 15a, 15b, 15c, slide into receiving pockets 21, in an inter-locking arrangement, to thereby lock the sensor base 14B to lock the base section 12. Further, when rotated, the contact 18a, 18b, 18c slide into the spaces 70a, 70b, 70c, respectively of contacts 30a, 30b, 30c, respectively. More particularly, when rotated, the leading edge of contacts 18a, 18b, 18c engage the distal ends 66'a, 66"a, 66'b, 66"b, 66'c, 66"c, respectively, urging them further apart by camming action while maintaining physical contact with the opposing surfaces of the contacts 18a, 18b, 18c, respectively, because of the resiliency of the cantilevered finger-like contacts 30a, 30b, 30c, 30d. Thus, distal ends 66"a, 66'a contact upper and lower portions, respectively, as shown in FIG. 8, of opposing surfaces, here right and left sides. respectively, of contact 18a and distal ends 66'd, 66"d of contact 30d contact two adjacent portions of the left upper surface of contact 18a, as shown. Distal ends 66"c, 66'c contact opposing surfaces of contact 18c, and, likewise distal ends 66"b, 66'b contact opposing surfaces of contact 18b, as shown 8. Reversing the rotation process enables the sensor base 14B to be removed from the mounting plate 34.

It should be noted that the attachment of the base and sensor sections 12, 14 are, here preferably performed by robotics (i.e.; automation) type assembly equipment. It is noted that, using vertically extending electrical contacts for the sensor section 14 enables such sensor section 14 to be robotically inserted into a sensor section 14 test fixture, not shown. The tested sensor section 14 may be robotically removed from the test fixture, and then, if successfully tested, robotically attached to a corresponding base section 12.

Referring now to FIGS. 15-18, an exemplary one of the base section electrical contacts 30a, 30b, 30c (FIGS. 1 and 2), is shown modified in accordance with the invention. It should be understood that while only modified contact 30'a is shown, the other contacts 30b, and 30c would also be modified to that shown for contact 30'a (FIGS. 15-18). The electrical contact 30'a is here again a stamped, single piece of electrically conductive material, here phosphor bronze. The electrical contact 30'a has a first section 40'a with a surface 42'a adapted for snapping into recessed pocket 45'a of a mounting plate modified in accordance with the invention, here to mounting plate 34' shown, and to be described in detail, in connection with FIGS. 19-21.

More particularly, and referring again to FIGS. 15-18, the first section 40'a has a threaded hole 44a' hole formed therethrough to receive screw 32a, as described above in FIGS. 1 and 2. The hole 44'a is formed with a dimple 81a into the upper surface 42'a of first section 40'a. It is noted that the dimple 81a creates projection or rim 80a which projects from the bottom surface 82a of the first section 40'a. Further, the first section 42'a has a pair of opposing open-ended (or U-shaped) slots 84a, 85b formed in side edges of section 40'a, as shown. The remaining portion of the electrical contact 30'a is the same as electrical contact 30a described above in connection with FIGS. 3-6. Thus, the electrical contact 30'a has a second section 52'a. The first section 40'a and the second section 52'a have a common edge 56'a, as shown. The electrical contact 30'a has a surface 58'a extending perpendicular to surface 42'a, as shown, and a pair of finger-like members, 60'a, 60a" extending from a second edge 62'a of the second section 52'a, as shown. The second edge 62'a of the second section 52'a is perpendicular to the common edge 56'a of the first and second sections 40'a, 52'a. The finger-like members 60'a, 60"a are laterally spaced along, and cantilevered from, the second edge 62'a of the second section 52'a. The finger-like members 60'a, 60"a extend along a common direction 64'a, as shown. Distal ends 66'a, 66a" of the finger-like members 60'a, 60"a are spaced from each other laterally in a direction 68'a, as shown, perpendicular to the common direction common direction 64'a, as shown, to receive, in space 70'a and contact opposing surfaces of the first end 26a of electrical contact 18a (FIGS. 1 and 2).

The additional electrical contact 30'd shown in FIGS. 22-25 is again a stamped, single piece of electrically conductive material, here phosphor bronze, and includes a first section 40'd with a surface 42'd identical to the first section 40'a of the contact 30'a shown and described above in connection with FIGS. 15-18 and is adapted for mounting to the mounting plate 34' (FIGS. FIGS. 19-21). More particularly, the first section 40'd has a threaded hole 44'd formed with a dimple 81d into the upper surface 42'd of first section 40'd. It is noted that the dimple 81d creates projection, or rim 80d which projects from the bottom surface 82d of the first section 40'd. Further, the first section 42'd has a pair of opposing open-ended (or U-shaped) slots 84d, 85d formed in edges thereof, as shown. Thus, the first sections 40'a and 40'd are identical in construction and configuration. The remaining portion of the electrical contact 30'd is the same as electrical contact 30d described above in connection with FIGS. 3-6. Thus, the electrical contact 30'd has a second section 52'd. The first section 40'd and the second section 52'd have a common edge 56'd, as shown. The electrical contact 30'd has a surface 58'd extending perpendicular to surface 42'd, as shown, and a finger-like member 60'd extending from a second edge 62'd of the second section 52'd, as shown. The second edge 62'd of the second section 52'd is perpendicular to the common edge 56'd of the first and second sections 40'd, 52'd. The finger-like member 60d is cantilevered from the second edge 62'd of the second section 52'd. The finger-like member 60'd extends is a direction opposite to direction 64'a of contact 30'a. The distal end of the finger-like member 60'd is not however bifurcated.

Referring now again to FIGS. 19-21, the modified mounting plate 34' is again plastic, here however, formed with a pair of opposing bracket-shaped side walls 90a, 92a which project perpendicular to surface 94a, as shown in FIGS. 19 and 20. The recessed pocket 45'a is formed with a C-shaped platform 95a having a pair of opposing, spaced ledges 96a, 98a, terminating along inner lower edges of the side walls 90a, 92a, as shown, and a tongue-like member, or cantilevered protrusion 93a having a distal end 99a which projects into the opening 97a formed in the central region of the C-shaped platform 95a, as shown. It is noted that the platform 95a and protrusion 99a have upper surfaces disposed in a common plane and that such plane is spaced from, i.e., recessed below, the upper surface 94a of the mounting plate 34'. More particularly, it is noted that the sidewalls 90a, 92a have end walls 101, 103 with bottom portions 105, 107 terminating along surfaces which are parallel to the above-mentioned common plane but which are spaced above such common plane to provide a slot, or channel 108 between: (a) the upper surfaces of the platform 108 and protrusion 99a; and, (b) the bottom portions 105, 107 of the sidewalls 90a, 92a. The channel 108 has a terminating edge 112, as shown. For reasons to become apparent in connection with FIGS. 26-31, it should be noted that: (a) the bottom portions 105, 107 are tapped along a surface which faces away from edge 112, as shown; (b) the length, L, of the channel 108 is here longer than the length, L', of the contact 30'a; and, (c) the width, W, between the inner opposing surfaces of sidewalls 90a, 92a is substantially equal to, but slightly greater than, the width, W', of the contact 30'a.

It is also noted that L-shaped slots 120a, 122a (FIG. 21) are provided. The slots 120a, 122a, are formed by rectangular shaped openings formed through the platform 95a, as shown in FIG. 21, exposing the bottom portions 105 of the side walls 90a, 92a. Likewise, rectangular openings are formed in the platform to expose the bottom portions 107 of the sidewalls 90a, 92a. That is the bottoms are disposed over the openings, as shown in FIG. 21.

Referring now to FIGS. 26, 27 and 28, the initial engagement between one of the modified electrical contacts, here contact 30'a with the recessed pocket 45'a is shown. It is first noted that the U-shaped sidewalls 92a, 90b form a frame to enable the first section 42'a to sit on the tongue-like member or protrusion 93a and the C-shaped platform including the ledges 96a, 98a (FIG. 20). It is next noted that as the leading edge 110 of the first section 40'a slides into the channel 108, the projection or rim 80a depresses the resilient tongue-like, protrusion 93a downward, as shown, by camming action thereby enabling opposing side edge portions 103 of the first section 30'a to slip under the bottom portions of the sidewalls 90a, 90b, as indicated more clearly in FIG. 26.

Referring now to FIGS. 29, 30 and 31, the electrical contact 30'a is shown fully inserted into the channel 108 (FIG. 19) with the forward edge 110 against the end of the channel 108 and the section 58'a against the forward portion 109 of the bottom portion 107 of endwall 103, as shown. The resilient tongue-like protrusion 93a wedges the first section upwardly against the bottom portions of the sidewalls 90a, 92a and the edge portion 119 of the tongue-like protrusion 93a snaps back of (i.e., behind the portion 121 of) the projection or rim 80a with an audible click and now the electrical contact 30'a is securely locked in place in the channel 108. That is, as shown in FIGS. 29, 30 and 31, the electrical contact 30'a is now securely snapped and locked into the recessed pocket 45'a.

Other embodiments are within the spirit and scope of the appended claims.