Door Jamb Switch

The present invention relates to the art of mechanically actuated switches, and more particularly relates to an improved switch and electrical contact mounting therefore, to be used on a door jamb.

U.S. Pat. Nos. 3,249,727 and 3,251,971 are incorporated by reference herein as background information on self-adjusting door jamb switches of the general type to which the present invention is particularly applicable.

In motor vehicles, it is common practice to employ one or more door jamb switches to activate electrical circuits in response to the opening and/or closing of a door. In general practice, these switches include an element that is shifted between a first and second condition when the vehicle door is opened and closed. A spring loaded plunger extends outwardly under spring tension when the door is opened, and is depressed when the door is closed. Due to dimensional variations in the design, manufacture and assembly of motor vehicles, the distance between the inner face of a door and its matching door jamb may be different from door to door. To compensate for this condition, self-adjusting door jamb switches as shown generally in U.S. Pat. Nos. 3,249,727 and 3,251,971 have been commonly employed by the automotive industry. Also of note is U. S. patent application Ser. No. 331,123 entitled "Improved Door Jamb Switch", filed Dec. 15, 1981, now U.S. Pat. No. 4,406,935 and assigned to the assignee of the present invention. These switches have a collapsible plunger or other arrangement which self-adjusts upon the initial closing of the door against the jamb after the switch has been installed. Thereafter, the switch operates in accordance with this initial adjustment. Generally, in these self-adjusting door jamb switches the plunger is adapted to reciprocate longitudinally in a mounting sleeve fixed onto the door jamb. The switch has a first contact assembly mounted to the sleeve, and a second contact assembly mounted to the reciprocating plunger. In the typical case, when the plunger is in its extended, door opened, position, electrical contacts on the two contact assemblies close, and when the plunger is in its depressed, door closed, position, the electrical contacts open.

Although self-adjusting door jamb switches have been known in the past, the self-adjusting aspect of the switch has been in the longitudinal adjustment of the plunger movement or extension within the sleeve. This adjustment, however, does not assure that the electrical contact surfaces of the switch are in good alignment. In the past, fairly close tolerances were required for individual parts of the switch in order to obtain good contact alignment. This added to the time and cost required to produce and inspect the individual parts and the switch assembly itself. Even then, contact alignment was not always adequate. In such cases, where contact alignment was less than optimum, the switches might fail prematurely due to wear and/or arcing due to poor surface contact. Also, as is known in the art of electrical switches, the current carrying capacity or rating of a switch can be adversely affected by poor alignment of the contact surface. Ultimately, without close tolerances on individual parts of the prior art switches, they might never function properly at all in some cases.

In accordance with the present invention then, there is provided an improvement in electrical switches by which the foregoing contact alignment problem is minimized or overcome. In the preferred embodiment the switch is of the type having a housing adapted to be fixedly secured onto a door jamb, a first electrical contact mounted on a plunger supported in the housing for reciprocation along an operating axis relative thereto and a second electrical contact which is supported on the housing to engage and disengage the first contact in response to displacement of the plunger in opposite directions between first and second actuated or operative positions by a door. In accordance with the invention, one or both of the first and second contacts are resiliently mounted with respect to either the plunger or housing respectively, so that one or both can move or "float" and self-align with the other upon interengagement. In accordance with one aspect of the invention, the resilient mounting allows axial, lateral and angular spring loaded contact movement relative to the operating axis of the plunger.

In accordance with another aspect of the invention, one or both of the contacts are mounted so as to provide rotational movement thereof with respect to the operating axis of the switch.

The "floating" contact assembly can comprise a contact block or terminal block onto which a contact is mounted. The contact can consist of the contact itself, or can comprise a contact or electrically conductive contact surface mounted onto a holder, with the holder being resiliently mounted onto the block. The "floating" electrical contact can be mounted in a cavity of the contact block, the cavity being cylindrical in cross-section with its axis being parallel to the operating axis of the switch. A resilient washer is located in the bottom of the cavity. The outward surface of the contact is contoured to have a radial dimension which increases along the operating axis of the switch in a direction toward the base of the cavity. This outer surface dimension radially increases to a ridge or enlarged portion as it approaches the bottom of the cavity and thereafter decreases as it approaches a base portion of the contact which abuts the resilient washer. The contact movably fits within said cavity, the outer diameter at the ridge or enlarged portion being less than the diameter of the cavity so as to allow free movement of the contact therein. The contact is retained in said cavity by means of an inward circumferential flange on the interior surface of the cavity, the diameter of the opening through the flange being somewhat smaller than the diameter of the contact at the ridge or enlarged portion.

In accordance with another aspect of the invention, one contact is conical in shape, having a conical contact surface, and also having spiralling flutes thereon. The second contact has multiple contact pegs wherein, when the first and second contacts are moved to the first, closed position the pegs come into surface contact with the flutes of the conical surface and cause the conical contact member to rotate.

In another aspect of the invention, the contacting surfaces of respective contacts have complimentary mating surface configurations to each other so as to increase the contact area between the surfaces.

The primary object of the present invention is the provision of an improved door jamb switch, having improved alignment characteristics of the electrical contact surfaces.

Another object of the invention is the provision of an improved door jamb switch with an improved current carrying characteristic but without corresponding closer dimensional tolerances for the individual parts of the switch.

A further object of various aspects of the invention is an improved switch which has a reduced tendency to wear prematurely or to arc due to contact misalignment.

A further object of various aspects of this invention is to provide an improved switch of the type described with a reduced requirement for time and cost for manufacture, assembly and inspection.

These and other objects and advantages will become apparent from the following description of a preferred embodiment of the invention taken together with the accompanying drawings in which:

FIG. 1 is a pictorial view illustrating the preferred embodiment of the invention;

FIG. 2 is a cross-sectional view of the preferred embodiment of the invention in a first, plunger extended, actuated position;

FIG. 3 is a cross-sectional view of the preferred embodiment of the invention in a second, plunger depressed, actuated position;

FIG. 4 is a cross-sectional view taken generally along line 4--4 of FIG. 2 and showing one contact;

FIG. 5 is an enlarged cross-sectional view of the contact portion of the switch as depicted in FIG. 2;

FIG. 6 is an elevation view showing an alternate embodiment of the surface configuration of one of the contacts;

FIG. 7 is an elevation view depicting another alternate embodiment of the surface configuration of one of the contacts;

FIG. 8 is a cross-sectional view taken generally along line 8--8 in FIG. 7 and depicting a part of the surface configuration of the contact depicted in FIG. 7; and,

FIG. 9 is a cross-sectional view of an alternate embodiment of the contact portion of the switch of FIGS. 1-5 wherein both contacts are resiliently mounted.

Referring now to the drawing FIGS. 1-5, wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting it, a door jamb switch A is fastened by means of a mounting nut 1 onto a standard jamb B and includes a housing assembly 2 which supports a fixed first contact assembly 14 and a reciprocable plunger assembly 3 to be described hereinafter. The plunger assembly 3 includes plunger 4 at one end thereof with an outwardly extending knob 5 adapted to be engaged by a vehicle door D in accordance with standard practice, an operating shaft 9, and as will become more apparent hereinafter, a second contact assembly 15 located at the opposite end of the plunger assembly 3 for reciprocation therewith along a longitudinal operating axis X of the switch A between a door opened position, as shown in FIG. 2, and a door closed position, as shown in FIG. 3.

The mounting nut 1 includes a hex head 6 and a threaded shank 8 adapted to be threaded into an aperture on the door jamb B to secure the switch A in place thereon. In the embodiment shown, the housing assembly 2 includes a sleeve member 10, and the nut 1 is provided with a bore 11 to fixedly receive the sleeve 10 as by a tight friction fit therebetween. The sleeve 10 is generally cylindrical in shape and is formed from an electrically conductive material such as brass. The sleeve 10 has an inner cavity 12 to receive and movably support the plunger assembly 3 for reciprocation longitudinally along the operating axis X. The inner end of sleeve 10 is provided with a radially outward extending circumferential ridge 13, and the fixed first contact assembly 14 is mounted on this inner end of the sleeve 10 and retained thereon by the ridge B.

More particularly, the first contact assembly 14 includes a support comprising a contact block or terminal block 16 which can, for example, be molded around the inner end of the sleeve 10 and ridge 13. The contact block 16 has a cavity 17 surrounding the operating shaft 9. The cavity 17 has a generally cylindrical radially inward surface with its axis parallel to and coinciding with the operating axis X. The cavity 17 has an outer end 18 and an inner end or base portion 19, and the inward surface of the cavity 17 has a circumferentially radially inwardly projecting flange 20 at a point intermediate the outer and inner ends 18 and 19. A resilient annular member or washer 21 which can be made from rubber, or other suitable springy resilient material, is seated in the cavity 17 at the base 19 thereof. The washer 21 can have a snut fit into the cavity 17 and its thickness is selected as a function of its spring rate, as will be more readily appreciated when the operation of the device is discussed below. The washer 21 and the inner end 19 of the cavity 17 both include passages 22 and 23 respectively, through which the shaft 9 and a projecting portion 31 of the second contact assembly 15 can freely pass.

Also in the cavity 17, between the washer 21 and the flange 20, is a shorting contact 25 made from an electrically conductive material. This contact 25 is thin walled and surrounds, and is generally symmetric with respect to, the axis of the shaft 9, and has an electrically conductive continuous and smooth conical-frustom or frusto-conical contact surface portion 27 having a smaller diametrical portion 28 and a large diametral portion 29, and its axis parallel to the operating axis. The smaller diametral portion 28 of the contact surface 27 is oriented toward the second contact assembly 15, discussed below, and is provided with a central opening 30 for the shaft 9 and the projecting portion 31 of the second contact assembly 15. The frusto-conical contact surface portion of the shorting contact is symmetrical about and extends outward of the operating axis X and the shaft 9, and away from the second terminal block 24 to a maximum diameter or ridge portion 32, and thereafter symmetrically tapers back toward the axis X to a base portion 34. The shorting contact 25 has an outer surface which is circular in cross-section in any plane perpendicular to the operating axis X. The diameter of the outer surface of shorting contact 25 at the ridge portion 32 is somewhat less than the diameter of the cavity 17 so that the shorting contact 25 can readily move or "float" therein against the resilient washer 21, but larger in diameter than the radially inward surface diameter of the flange 20 so that the shorting contact 25 is held and resiliently supported in the cavity 17 by the flange 20 after being pressed or "snapped" past the flange 20 during assembly. Although the shorting contact 25 in the preferred embodiment is a single piece made from conductive material, it could be comprised of multiple contacts and could be mounted on a supporting base or holder wherein the holder would engage the resilient washer 21.

Referring now more particularly to the plunger assembly 3, it includes a plunger 4 with a plastic molded body 36 mounted for reciprocation within the cavity 12 of the sleeve 10 and has, at its outer end, the knob 5. This knob has an inwardly facing abutment or surface 37 which is used in the longitudinal self-adjusting feature of the switch. Details of the longitudinal self-adjusting characteristics of the switch are known in the art, and are not therefore described in detail herein.

The metal shaft 9 which has an end extending into a recess 38 in the body 36 of the plunger 4 is held thereon and secured against rotation and translation by a knurled portion 39. The shaft 9 can be assembled into the body 36, or the body 36 can be molded around the knurled end 39 of the shaft 9. This shaft 9 slidably extends along the operating axis X through the cavity 12 of the sleeve 10, through a clearance opening 40 in the inner end thereof, through the passages 22 and 23 in the resilient washer 21 and the cavity 17 of the first contact block 16 respectively, and through the central opening 30 in the shorting contacts 25. The shaft 9 is surrounded in the sleeve 10 by a biasing spring 42 that forces the plunger 4 and knob 5 to the outermost position, as shown in FIG. 2. The second contact assembly 15 is mounted to the innermost end of of the shaft 9 and includes a support member which comprises a second contact block or terminal block 24 molded from an insulating material such as plastic. The second terminal block 24 is secured onto the innermost end of the shaft 9 by a knurled portion 43 of the shaft 9 and received in a recess therefore in the block 24 so as to be movable longitudinally with respect to the first contact assembly 14 along the operating axis X in conjunction with the reciprocation of the shaft 9. Appropriate wires 44 extend outwardly from the block 24 for connecting the switch A to a desired electrical circuit. The second terminal block 24 includes a hollow cylindrical projecting portion 31 which surrounds the inner end of the shaft 9 and has a length such that the end of the projecting portion 31 extends into the first terminal block 16 even when the switch A is opened as shown in FIG. 3.

Three electrically conductive elongated contacts, or contact pegs, 46, 47 and 48 extend out of the second terminal block 24. These contacts 46, 47 and 48 can be molded into the second terminal block 24, and are intended to extend out of the block 24 by equal amounts, all parallel to the operating axis X of the switch A, although in actual manufacture and assembly there will be differences between them with respect to both alignment and amount of extension. As can be more readily seen in FIG. 4, the contacts 46, 47 and 48 are equally spaced both angularly about and radially from the shaft 9, and about the operating axis X. In the preferred embodiment, the contacts 46, 47 and 48 have rounded, protruding contact ends. The wires 44 referred to above are each connected to one of the contacts for eventual further connection to the intended electrical circuits to be switched.

In operation of the embodiment illustrated in FIGS. 1-5, when the plunger assembly 3 is depressed as by closing the door D, the second contact assembly 15 and thus the second terminal block 24 and contact pegs 46, 47 and 48 are displaced into a first operative position with respect to the first contact assembly 14, such that the contact pegs 46, 47 and 48 are out of engagement with the shorting contact 25. When the door D is opened, the spring 42 in the sleeve 10 biases the plunger 4 to an extended position and hence the contact pegs 46, 47 and 48 are moved longitudinally along the operating axis X with respect to the first contact assembly 14 to a second operative position in which the contact pegs 46, 47 and 48 are in biased engagement at distributed points around the operating axis X with the contact surface 27 of the shorting contact 25 to complete appropriate circuits. If there is any misalignment due, for example, to a difference in the lengths of the individual contacts 46, 47 or 48 or their position in the terminal block 24, the "floating" shorting contact 25 can move longitudinally, angularly, and/or even radially with respect to the operating axis to compensate for the misalignment. More particularly in this respect, as shown in FIG. 5, if one contact peg 46 is longer than the other two contact pegs or is radially closer to the operating axis X than the other two pegs, this one peg 46 will engage the shorting contact 25 before the other two but the resilience of the washer 21 will allow the shorting contact 25 to be displaced in relation to the operating axis X so that uniform electrical contact is established between all of the contact pegs 46, 47 and 48 and the shorting contact 25.

In the preferred embodiment, the shape and dimensions of base portion of the shorting contact are selected to give symmetrical response about the operating axis X of the switch, and the spring rate and thickness of the washer are selected to provide a desired amount of contact force between the pegs 46, 47 and 48 and the shorting contact 25, and a desired amount of travel or movement of the shorting contact 25. Determination of these factors can be made empirically for each different design.

FIG. 6 is an elevation view of a first alternate shorting contact 50 which can be substituted for the shorting contact 25 depicted in FIGS. 1-5. It is generally a view as would be seen looking at the shorting contact as mounted in the direction of the arrows designated 6--6 in FIG. 5. The shorting contact 50 has the same basic frusto-conical outer contact surface shape, but in the embodiment of FIG. 6, the contact surface has radially outward spiralling flutes 51 as opposed to being smooth. With combined reference to FIGS. 5 and 6, it can be appreciated that in operation, when the shaft 9 is moved to its extended (door open) position, as the contact pegs 46, 47 and 48 begin to engage the shorting contact 50, the individual pegs 46, 47 and 48 will engage the fluted surface of the shorting contact 50. Upon this initial engagement, the resilient washer 21 will be compressed, thus allowing additional travel of the pegs 46, 47 and 48 toward the shorting contact 50 but now in surface contact therewith. During the additional travel, the pegs 46, 47 and 48 will have a tendency to follow the flutes 51 creating a rotational force on the shorting contact 50. This rotational force, because the shorting contact is "floating" and not fixed, will cause the shorting contact to rotate slightly. Thus, each time the switch is actuated, the shorting contact 50 rotates slightly and brings a new contact area into position for the next operation. This assists in distributing the wear from repeated operation over the entire surface of the shorting contact 50.

FIGS. 7 and 8 show still another configuration for the shorting contact. FIG. 7 depicts an elevation view of a shorting contact 60 similarly as in FIG. 6, and FIG. 8 shows a cross-sectional view of the shorting contact 60 taken on the line designated 8--8 in FIG. 7. In this embodiment, the contact surface 61 of the shorting contact 60 has individual grooves 62 therein which extend in a generally straight line on the surface 61 radially outward from the operating axis X. The shape of these grooves is made to conform with and mate with individual ones of the contact pegs 46, 47 and 48 on the second terminal block 24. With this complimentary surface configuration for the shorting contact 60, there is a large actual contact surface area between the shorting contact 60 and the individual contact pegs 46, 47 and 48 of the second terminal block 24, thus increasing the current carrying capacity of the switch over a configuration having point contact between the surfaces.

In the embodiments described thus far, the shorting contact is resiliently mounted or "floating". Alternatively, the contacts corresponding to pegs 46, 47 and 48 on the second terminal block 24 can be similarly resiliently mounted or "floating", either alone or in combination with a "floating" shorting contact. FIG. 9 depicts such a configuration and with reference to FIG. 9, contacts 71, 72 and 73 corresponding to contact pegs 46, 47 and 48 described hereinbefore, are resiliently mounted in a contact block 75 similarly mounted in the switch as the contact block 24 in the embodiment depicted in FIGS. 1-5. The terminal block or contact block 75 has a protruding portion 76 which is centrally located and extending toward a shorting contact block 77, similar to the one depicted in FIGS. 2-5, along the operating axis X. The protruding portion 76 has a cavity 78 therein along the operating axis X to fixedly receive the operating shaft 9. An annular cavity 79 surrounds the protruding portion 76 and has a cylindrical radially inward surface with its axis generally parallel to and coinciding with the operating axis X of the switch A, and has an annular opening 80 at a first end of the cavity 79 facing the shorting contact 81, and an innermost base or bottom wall portion 82 at an opposite end. The cavity 79 also has a radially inward extending circumferential flange 83 on its inner surface at the opening 80. Clearance holes 84, one for each of the three contacts 71, 72 and 73, are provided through the bottom wall of the cavity 79 for wires 75 connected to the individual contacts 71, 72 or 73.

Seated against the bottom wall 82 of the cavity 79 is a resilient annular washer 90 having contact peg holes 87 therethrough, each being aligned with one of the holes 84 in the terminal block 75 for the wires 85.

The three contacts 71, 72 and 73 are molded into a common holder 88 such that they are in alignment with the corresponding holes 84 in the second terminal block 75. The outer surface of the holder 88 is generally circular in cross-section in a plane perpendicular to the operating axis X, being cylindrical in outer surface shape with its axis as assembled parallel and coinciding with the operating axis X of the switch A. The holder 88 includes a central clearance hole 87 therethrough for the shaft 9 and the protruding portion 76 of the second terminal block 75. A radially outward extending, axially convex, circumferential ridge 89 is provided on the outer surface of the holder 88. The ridge 89 is smaller in outside diameter than the inside diameter of the cavity 78, but is larger in diameter than the radially inward surface of the flange 83 so that the holder 86 can be pressed or "snapped" into the cavity of the terminal block 75 past the inward flange 83 thereof to be supported resiliently, or in a "floating" manner, therein between the flange 83 and the resilient washer 90.

In a manner similar to that described in connection with the embodiment depicted in FIGS. 2-5, when the shaft 9 is moved to its extended (door opened) actuated position, the contacts 71, 72 and 73 in the holder 88 can longitudinally, angularly and radially move upon engagement with the shorting contact 81 against the resilient washer 90 so as to provide a desired contact alignment and uniform interengaging contact force.

Although several particular embodiments and aspects of the invention have been described, many modifications readily apparent to those skilled in the art are possible. For example, although the shorting contact has been described as being made out of an electrically conductive material, only the contact area need be conductive. Further, the contact area may have discontinuities or individual contact surfaces to switch different circuits in an isolated manner. Further, while three contact pegs are preferred in the second terminal block, which are equally spaced radially and angularly about the operating axis, it will be appreciated that a fewer or greater number could be used, possibly with unequal spacing, without departing from various aspects of the invention. Still further, although in the configuration of FIG. 9 all three contact pegs are mounted in a common holder with the holder being mounted in the second terminal block, individual contacts could be separately mounted in the terminal blocks so that they can individually self-adjust.

Other modifications can be made without departing from the invention, and it is to be understood that the foregoing descriptive matter is to be interpreted only as an illustration of the invention and not as a limitation.