US 3902159 A
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United States Patent 1191 Parolin 1 Aug. 26, 1975 1 1 VEHICLE WARNING SIGNAL SWITCHING APPARATUS INCLUDING CIRCUIT MOMENTARILY INTERRUPTED ONLY IN RESPONSE TO MOVEMENT IN ONE OR AN OPPOSED PAIR OF DIRECTIONS  Inventor: John J. Parolin, Boston, Mass.
 Assignee: Cole-Hersee Company, South Boston, Mass.
22 Filed: Feb. 26, 1973 21 Appl. No.: 335,779
Primary Examiner-Marshall M. Curtis Attorney, Agent, or Firm-Charles Hieken; Jerry Cohen AMBER SCHOOL BUS l 5 7 ABSTRACT A vehicle warning-signal arrangement, particularly useful for the selective disabling and self-restoration of automatic sequential light flashings aboard school buses, involves a door-actuated multi-circuit electrical switch, one circuit of which is momentarily interrupted in but the door-closing half of a switching cycle, together with an operator-latched solenoid switch and an automatic flasher, the switch interconnections allowing warning lights to be turned on by the operator and stop lights to be turned on automatically when a door is then opened, but also insuring that door closure will in turn restore a circuit condition permitting a door-opening without attendant improper flashing of the stop lights; the multi-circuit switch is operated by a plunger which momentarily disconnects one set of contacts only during its inward or door-closing travel as the result of unique coaction between a shaped enlargement on the plunger, an elastomeric O-ring closely surrounding and rideable over the enlargement of the plunger, and an apertured springbiased polecarrying plate through which the plunger but not the O-ring will pass.
7 Claims, 7 Drawing Figures AMBER RED RED STOP LIGHT mmmmszsms 3802,1593
SHEET 1 [IF 3 AMBER 7 RED RED STOP LIGHT SCHOOL BUS l\ ls FLASHER 2d PATENTEU wrsz m 3 902,159
III a l VEHICLE WARNING SIGNAL SWITCHING APPARATUS INCLUDING CIRCUIT I MOMENTARILY INTERRUPTED ONLY IN RESPONSE TO MOVEMENT IN ONE OR AN OPPOSED PAIR OF DIRECTIONS BACKGROUND OF THE INVENTION The present invention relates to improvements in electrical switching apparatus such as is used in controlling Warning lights aboard school buses and the like, and, in one particular aspect, to novel and improved switching arrangements for operator-selected control over certain automatic door-actuated excitations of warning lights, as well as to unique momentaryinterrupting switch constructions which are especially suited to the requirements of such switching arrangement's.
A conventional attention-commanding safety warning-light system for school buses involves the flashing of amber warning lights as the vehicle approaches a stop, and then the flashing of red stop lights so long as the door or doors are open to permit the boarding or discharge of passengers. Preferably, such a system is under control of adoor-operated switch which will insure that the stop lights must operate without fail during' those hazardous times when passengers may be alighting or entering. However, it is also mandatory that the same vehicle not display flashing stop lights when at rest for other purposes, such as a temporary halt with door open as required by law at a railroad crossing. These conflicting requirements can be satisfied in part by way of a simple type of operatoractuated switching which-would disable the warning system, but this introduces another control and device to which an already busy operator must give attention, and there is no assurance that thewarning system will always be reset to function when needed. More complex networks, involving additional door-operated switches, for example, tend to introduce significantly higher costs, both as to system components and installation.
According to the invention, there is warning signal means, such as flashing warning lights on a school bus, responsive to energization with electrical energy for providing a warning signal. First manually actuated switching means, such asa relay with a holding winding and contacts delivers electrical energy to the warning signal means when in the closed condition, such as when the contacts are closed, has holding means, such as the holding winding, responsive to interruption of a holding energy for returning the first switching means to the open condition, such as when the contacts are open, and is responsive to 'manual actuation for assuming the closed condition. There is a source of the holding energy. Second switching means has an armature movable in first and second opposed directions and includes means responsive to movement of the armature in the first direction for coupling the holding energy to the holding means and means responsive to movement of the armature in the second direction for interrupting the coupling of the holding energy to the holding means to thereby restore the first switching means to the open condition.
In accordance with certain aspects of the present teachings, the creation of a relatively simple and inex pensive warning-light system for school buses, involving only a single door-operated switch unit, which will reliably condition itself for single-cycle automatic sequencing of'both flashing warning and stop lights upon actuation by the operator, is linked to the concept of having the door switch momentarily interrupt one of its switching circuits only when the door is being closed after having been opened. That momentary interruption is effective to reset a self-holding solenoid switch by which the operator had initiated one cycle of sequencing of the flashing lights, and, thereafter, the operator may intentionally omit the sequencing by refraining from actuation of the solenoid switch when the bus is to stop for some purpose other than admitting or discharging passengers. Once the system has been operator-conditioned to follow the desired sequencing, however, it will be strictly observed in accordance with door opening and closure, without further operator attention.
The momentary-interrupt switching entailed in the foregoing is unusual in that a single door-actuated plunger must be capable of simply shifting electrical excitation from warning to stop lights during a movement in one direction associated with the opening of the door, and, during its movement in the opposite direction, associated with closing of the door, it must momentarily break another circuit which is nevertheless not'interrupted by the other movement.
SUMMARY OF THE INVENTION By way ofa summary statement concerning one practice of this invention, a school-bus signalling system, involving sets of different-color warning-and stop-lights which are to be flashed in sequence as the bus is stopped and its door opened to permit boarding or discharge of passengers, includes a conventional motordriven flasher switch in association with an operatoractuated self-holding solenoid switch and a single triple-circuit door-actuated switch. When the usual stop is about to be made for passengers, the operator actuated the relay switch, and the latter energizes itself to sustained closure through the then-closed contacts of a momentary-interrupt relay circuit of the door switch of the thenclosed door. At the same time, the operator-actuated relay switch connects electrical excitation to the motor-driven flasher, and the latter commences periodic pulsing of current to alternate ones of amber warningsignal lamps, through different closed lampcircuit contacts of the door switch associated with the then-closed door. Once the door is opened upon stopping of the vehicle, the plunger-armature of the door switch is spring-biased to a new position at which it opens the previously-closed lamp-circuit contacts associated with the amber warning lights and transfers the contact closures to those associated with red stop lights. Importantly, the momentary-interrupt relay circuit contacts of the door switch have remained closed, and the stop lights are thus flashed so long as the door is open. Upon closure of the door, the door-switch plunger is moved back to its initial position, and, in the course of that particular motion only, the doorswitch contacts associated with the momentary-interrupt relay circuit are transiently separated and the holding coil of the relay switch becomes tie-energized. As a result, the
relay switch cuts off all power to the warning system,
In achieving the desired momentary interruption of one set of contacts of the door-responsive switch only during an inward plunger travel associated with closing of the door, the plunger is shaped to exhibit a shoulder just smaller than the surrounding mated opening through a plate of a contact carrier which cooperates with those particular contacts. Further, a stretchable O-ring is disposed around the plunger, its inner diameter being less than the outer diameter of the shoulder, and its middle diameter being greater than the diameter of the plate opening. In its outwardly-extended position, the plunger traps the O-ring between its shoulder and the plate, and, as the plunger is moved inwardly during a door-closing movement, the O-ring necessarily pushes the plate inwardly and separates its shorting contact from the stationary contacts of the interrupt circuit under consideration. That separation is only momentary, however, because continued inward travel of the plunger causes the contact plate to strike mechanical stops and the plunger shoulder is then forced to push its way through the O-ring. At that time, the O- ring stretches annularly and rides over the plunger shoulder, whereupon the contact-carrier plate then becomes freed of plunger restraint and is quickly springactuated back to its intitial position where it again closes with the stationary contacts. When the plunger is later extended outwardly once more, during a dooropening cycle of its movements, the O-ring is rolled back over the plunger shoulder, the latter having a gradual taper promoting that action, and into a readied position between the shoulder and plate once again; there is no interruption of contact connections during the last-described movement of the plunger, because the contact-carrier plate is not disturbed by the rollback interaction between the plunger shoulder and O- ring.
Accordingly, it is one of the objects of the present invention to provide novel and improved vehicle warning-signal switching apparatus of low-cost and uncomplicated construction which responds to operator actuation by automatically imposing a sequencing of light flashings until a vehicle door has been both opened and reclosed.
Another object is to provide unique and advantageous switching for school-bus light-flashing wherein a prescribed sequencing of warning-and stop-light connections is assured by the cooperative relationships of an operator-actuated self-holding switch and a dooractuated switch which develops a momentary interrupt only during a door-closing operation.
A yet further object is to provide a plunger-operated switch wherein an expandable O-ring, an aperturcd contact-carrying plate, and a shaped shoulder on the plunger cooperate to produce a transient separation of certain switching contacts only during travel of the plunger in one of its two directions of reciprocal motion.
BRIEF DESCRIPTION OF THE DRAWINGS Although the features of this invention which are considered to be novel are expressed in the appended claims, further details as to preferred embodiments, as well as to further objects and advantages, may be most readily comprehended through reference to the following description taken in connection with the accompanying drawings, wherein:
FIG. 1 illustrates an improved SChOOI-bUS lightflashing switching arrangement, in partly schematic and pictorial conventions;
FIG. 2 is a partly erosssectioned plan view ofa plungeractuated multiple-circuit switch, useful in the arrangement of FIG. 1, which includes unique momentary-interrupt provisions for one of its circuits;
FIG. 3 provides a sectioned side view of the switch of FIG. 2;
FIG. 4 is plan view like that of FIG. 1, with the switch plunger shown fully depressed;
FIG. 5 represents a sectioned side view of the switch of FIG. 4;
FIG. 6 provides a detail enlargement of a portion of the switch of FIGS. 2-5, in a sectioned side view; and
FIG. 7 depicts a self-holding operator-actuated solenoid switch useful in the arrangement of FIG. 1, with portions broken away and sectioned to expose constructional details.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, wherein like reference characters are used for corresponding parts throughout the several views, the improved switching arrangement is represented in association with school-bus warning and stop lights, in FIG. 1. There, an upper rear portion 8 of a school bus is shown to include the customary pairs of amber warning lights, 9,, and 9,,, and red stop lights, 10,, and 10,,, and a further stop light 11 for a side warning flag is also depicted. Both the pairs of warning and stop lights are intended to be flashed alternately, and respectively in succession first as the vehicle decelerates toward a stop for boarding or discharging passengers and then as a door is opened. For these purposes, a conventional motorized flasher, 12, including a battery-powered motor 12,, and commutator-type switch 12,,, is employed to distribute power to the warning and stop lights, and the arrangement further includes an operatoractuated self-holding relay switch 13, and a multiple-circuit door-actuated switch 14. When a side warning flag is used, a further single-pole singlethrow momentary switch 15 serves to make an electrical connection to a vacuum relay.
As the operator approaches a stop for the boarding or discharge of passengers, the shaft 13,, of switch 13 is depressed, thereby establishing electrical continuity between the positive supply of the vehicle battery 16 and an output switch terminal 13,,. From the latter connection, excitation is delivered to terminal 12,. of the flasher combination 12, causing motor 12,, to rotate and commutate the battery power alternately to flasher terminals 12,, and 12,. At the same time switch shaft 13,, is depressed against internal spring biasing, an internal self-holding coil within it, 13,. in FIG. 7, becomes energized by way of its connections with output terminal 13,, and a further terminal, 13,,, which is grounded through lead 17 and the normally-closed momentaryinterrupt pair of switch contacts 14,, and 14,, of door switch 14, the contact 14,, being grounded. Coil 13,. thereby maintains the shaft 13,, in the depressed condition wherein its associated contacts establish continuity of electrical supply to the flasher combination 12. Because of this arrangement, even a transient interruption of the connection between normally-closed doorswitch contacts 14,, and 14,, will cause the self-holding relay 13 to spring open and cease excitation of the flasher and lights until shaft 13,, is once again depressed by the operator.
In the aforementioned sequencing wherein the operator has initially actuated relay shaft 13,, and thereby started the motor-flasher commutation, the flasher terminals 12,, and 12,. alternately excite the amber warning-signal lights 9,, and 9,, through leads 18 and 19, switch contacts 14,. and 14,,, switch contacts 14,, and 14,, and leads 20 and 21. The necessary individual closures between contacts 14,. and 14,,, and between 14,, and 14,, are established by shorting contact bars carried at the inner end of plunger 14,, of that switch, when it is fully depressed by closure of a vehicle main door. Subsequently, opening of the door, after the bus has stopped, allows the plunger 14,, to be sprung to an outwardly-extended position, and the shorting contacts then also move forward and thereby establish new connections between contact 14,. and 14,, and between 14,, and 14,. Leads 22 and 23, joined with the pair of contacts 14,, and 14,, respectively, then convey the excitations from commutation terminals 12,, and 12,. to the red stop lights 10,, and 10,,, such that they flash in alternation so long as the bus remains stopped with its main door open.
Importantly, all of the signalling is to be terminated only upon reclosureof the door, subject to wholly automatic recycling only if the operator once'again intentionally depresses plunger 13,, of the self-holding switch 13. In that connection, the continuity between contacts 14,, and 14,, of door-switch 14 becomes critical, inasmuch as depression of the plunger 14,, by a closing door must at least momentarily interrupt that continuity while, in subsequent return movement of that plunger upon opening of the door, there must be no such interruption. A preferred construction of a suitable multicircuit switch, operated by the door, and including unique provisions for the aforesaid one-way momentary interruption of one of the circuits, appears in FIG. 2-6.
In certain instances when the same vehicle is to be stopped and the main door opened for reasons other than permitting passengers to enter or leave, the abovedescribed sequencing of light flashings must be avoided. The operator then need only omit actuation of the relay switch 13, and only the usual brake-operated stop lights will then respond. Stops at railroad crossings, as required by law, can therefore be made without violating statutes prohibiting the flashings of amber and red lights except in connection with school-bus stops serving passengers,
As is represented in FIGS. 1-6, the door-operated switch 14 includes a generally rectangular form of metal housing, 25, capped by an insulating cover, 25,,, from which the terminals for switch contacts 14,,-14, and 14, and 14, extend outwardly for purposes of connection in the switching circuits which have been described. Door-actuated plunger 14,, is urged toward its outwardly-extended condition, shown in FIGS. 2 and 3, by a coiled spring 26 trapped between that plunger and its surrounding guide-bushing 27 mounted at the front end of the switch. The innermost end of plunger 14,, is secured to a longitudinally-slidable saddle 28 on which two side-by-side contact bars. 29 and 30, of conductive material are supported in insulated relationship by a contact carrier member 31. When the switch plunger is fully extended (FIGS. 2, 3 and 6), as allowed by an open-door condition, the attached saddle 28 is likewise in a forward position, where the contact bars 29 and 30 respectively engage the left set of contacts 14,. and 14,, and the right set of contacts 14,, and 14,. Full depression of plunger 14,,, upon closure of the door with which the switch is associated, causes the saddle 28 to slide to a rearmost position (FIGS. 4 and 5) at which the contact bars 29 and 30 respectively engage the left set of contacts 14, and 14, and the right set of contacts 14,, and 14,. Carrier member 31 is biased upwardly, by action of entrapped spring 32, such that good electrical contacting can be realized while at the same time allowing the contact bars to be slid between the forward and rear switching positions. Locations of the aforesaid sets of top-mounted contacts are designated by dashed linework and related reference characters having distinguishing single-prime accents in FIGS. 2 and 4, where cover 25,, is removed to expose internal features of construction.
A further saddle, 33, is disposed within the housing 25, between saddle 28 and the front end of the housing, and supports an insulating carrier 34 for a transverselyextending contact bar 35 associated with the contact pair 14,,-14,,. Unlike saddle 28, the further saddle 33 is not fixed with plunger 14,,, but is instead slidable in relation to it because of a slight enlargement of the openings through that saddle 33 in relation to external diametric dimensions of the internally-mated plunger. Springs such as springs 36 urge the contact carrier 34 and contact bar 35 upwardly, for engagement with the contact pair 14,,-14,,, and spring 37 between saddles 28 and 33 tends to maintain saddle 33 in the illustrated forward position where its contact bar 35 connects the contact pair 14,,14,,. For purposes of clarity in FIGS. 2 and 4, the contact bar 35, shown partly broken away, and the saddle 31 with its contact carrier and contact bars, are superimposed in full-line view over what would otherwise be cross-sectional parts of the switch. Normally, spring 37 between the two saddles tends to hold saddle 33 in the forward position irrespective of whether door-actuated plunger 14,, is in the fullyextended position (FIGS. 2 and 3) or fully-depressed position (FIGS. 4 and 5). And, once the plunger has been fully depressed (FIGS. 4 and 5), it may thereafter extend itself fully outwardly (FIGS. 2 and 3), upon opening of the associated door, without interference with the saddle 33 then in its forward position, because the accommodating front and rear saddle openings 36,, and 36,, (FIG. 6) through which the plunger passes are both of larger diameter than any mating parts of that plunger. However, as the plunger is gradually depressed from the forward position (FIGS. 2 and 3) toward the fully-depressed position (FIGS. 4 and 5), the saddle 33 is first pressed and moved rearwardly, along with the plunger, because of an interference which exists between it and anelastically-expandable O-ring 38 and a shaped enlargement 14, on a reduceddiameter portion 14,,. of the plunger.
The rear annular face of enlargement 14,- is substantially transverse to the axis of plunger 14,,. or may be only slightly inclined, whereas its forward surface (to the left in FIGS. 2-6) is preferably more tapered or frustro-eonical. O-ring 38 has an inner diameter, in place about reduced-diameter plunger portion 14,-. which is about the same as said reduced diameter. and has an outer diameter in excess of the diameter of the front opening 36,, through saddle 33. Further, the radial thickness of enlargement 14,- is preferably less than one-half the annular thickness of O-ring 38, and the diameter of saddle openings 36,, is preferably less than that of the circular middle of the O-ring in its position around reduced portion 14,. The latter relationships tend, to prevent jamming of the O-ring between the plunger enlargement and saddle, well as to prevent the O-ring from being squeezed through the saddle opening 36 A bushing 39, provides a front stop against which the O-ring may rest at times when it is in a stationary dwell condition.
.In line with what has been mentioned hereinabove, rearward movement of plunger 14,, upon closing of the associated door, causes enlargement 14, to press against O-ring 38, and the latter in turn presses against the front of saddle 33, such that the entire saddle 33 is forced rearwardly and its contact bar 35 thus momentarily separates itself from and interrupts continuity between 3circuit contacts 14,, and 14,. That interruption continues only until the rear of saddle 33 engages mechanical stops-in its rearward travel, such stops being shown in the form of shallow punched-metal tabs 40 projecting inwardly from the sides of the housing 25 (FIGS. 2, 4 and 5). These tabs are disposed far enough rearwardly of the forward position of saddle 33 to permit the latter to move rearwardly without obstruction until the contact bar 35 is positively disengaged from the associated contacts 14,, and 14, a typical rearmost orientation .of the rear of saddle 33 being shown in dashed linework 33 in FIGS. 4 and 5. Once these stop tabs are engaged by saddle 33, and rearward movement of the latter is halted, the continuing rearward thrust of the rear face of plunger enlargement 14,- against the inner portions of O-ring 38 cause the latter to be expanded diametrically and to ride forward over that enlargement. That ride-up expanding action is illustrated in its initial stage for O-ring 38 in FIG. 6, although it will of course be understood that the plunger and saddle would in fact be displaced more rearwardly (i.e., to the right) than actually shown in that enlargement which was aimed at clarification of constructional details. Radiallyoutward squeezing of the inner part, and consequent diametric expansion, of the O-ring 38, follows necessarily from the facts that is cannot pass through saddle opening 36 and that all squeezing is confined to the radially inner portions of the O-ring. Once the O-ring has been expanded in this fashion it ceases interfering with plunger movement and rolls forward over the frusto-conical front surface of enlarge ment 14,, allowing the plunger to advance to its rearmost position (FIGS. 4 and 5) and allowing the spring 37 to snap the saddle 33 forward to the position at which its contact bar 35 once again engages contacts 14,,and 14 as desired. During return of the plunger to a fully-extended position (FIGS. 2, 3 and 6) as the door is opened, the O-ring rests against bushing 39 while the frustoconical front of enlargement 14, is pulled through it by action of the plunger return spring 26, with the result that the O-ring expands, rides over the enlargement 14,, and once again locates itself between the enlargement and saddle 33 in readiness for a subsequent momentary-interrupt action when the closing door depresses plunger 14,,
Self-holding relay switch 13 may be of the general type illustrated in FIG. 7, and including a solenoid coil 13,. which holds the armature end 13,. of its plunger 13,, in a rear fully-depressed position once the plunger 13,, has been depressed by the operator and until the connection between the aforementioned switch contacts 14,, and 14,, has been momentarily interrupted during closure of a door. A plunger-return spring, not shown, then re-extends the plunger 13,, to ready it for a subsequent actuation by the operator. Forthe purposes which have been described hereinabove, the solenoid winding 13 is electrically connected between terminal 13,, and an internal side contact, opposite contact 13,, to which the positive side of battery source 16 also becomes connected whenever contact 13, is shorted with said contact (served by terminal 13) upon bridging of the two by a suitable armature contact 13,, movable with the plunger 13,,.
The warning system may include a momentaryinterrupt switch which is separate from a noninterrupting switch serving the flashing lights, inasmuch as it is not essential that all three circuits be controlled by one switch unit, although that is distinctly advantageous. In other modifications, the momentary interrupt may instead be changed to become a momentary connection, and the switch may be associated with actuations other than by a door. Although an O-ring has been specifically referred to, that element may be fashioned of material other than a rubber, and may have a cross-sectional configuration other than of the usual circular form; a split metal or plastic ring, expandable in response to the applied forces, may be substituted, for example.
Accordingly, modifications, substitutions and variations in relation to the specific embodiments selected for illustration and description will be evident to those skilled in the art, and it is therefore to be understood that these may be effected without departure from the spirit and scope of this invention in its broader aspects and as set forth in the appended claims.
What I claim as new and desire to secure by Letters Patent of the United States is:
1. Switching apparatus for controlling warning signals such as flashing lights on school buses and the like,
comprising a first operator-actuated switch including an electromagnet winding and a cooperating armature movable to close a first set of contacts in response to operator actuation thereof and maintaining closure of said contacts only so long as said winding is energized, a second switch including a second set of contacts and an armature for closing and opening said second set of contacts in response to movements of said armature in alternate directions, said second switch including means for changing the continuity condition of said second set of contacts between electrically closed and opened conditions transiently only during travel of said armature in one of said directions, means for moving said armature in said alternate directions in response to movements of a part of a vehicle such as a door or the like, warning-signal means, means energizing said warning-signal means from a source through said first set of contacts, and means responsive to the continuity condition between said second set of contacts for energizing said winding from said source and through said first set of contacts, whereby actuation of said first switch results in excitation of said warning signal means until said first switch is automatically opened upon occurrence of movement of said armature of said second switch in both of its alternate directions of movement.
2. Switching apparatus as set forth in claim 1 wherein said warning-signal means comprises lights periodically energized from said source through an electricallyoperated flasher switch, both said lights and said flasher switch being energized from said source through said first set of contacts, and wherein said armature of said second switch includes a spring-biased plunger extended and depressed in response to opening and closing of a vehicle door.
3. Switching apparatus as set forth in claim 2 wherein said lights include amber warning lights and red stop lights aboard a school bus. wherein said second switch includes a third set of contacts certain of which are associated exclusively with said warning lights and said stop lights, respectively, and contacting means fixed to and movable with said plunger between a first position wherein it establishes continuity between said flasher switch and the contacts associated with said warning lights when said door is closed and a second position wherein it establishes continuity between said flasher switch and contacts associated with said stop lights when said door is opened.
4. Switching apparatus as set forth in claim 3 wherein said means for changing the continuity condition of said second set of contacts only during travel of said armature in one of said directions electrically opens said second set of contacts during depression of said plunger upon closing of said door of a school bus.
5. Switching apparatus as set forth in claim 4 wherein said means for changing said continuity condition of said second set of contacts comprises a contact carrier slidable in axial directions in relation to said plunger, a switch housing within which said contact carrier is guided for sliding movement, said plunger being freely mated with said contact carrier within said housing by way of an opening through said carrier and having a door-actuated end projecting from said housing, spring means urging said plunger end to a forward outwardlyextending relationship with a front of said housing, said plunger having an enlargement along one portion thereof between adjoining portions of lesser crosssection, an expandable ring member coaxial with said plunger and having an inner periphery smaller than the outer periphery of said enlargement and smaller than said opening and having an outer periphery larger than the outer periphery of said enlargement and larger than said opening, said enlargement having a periphery smaller than said opening, both the periphery of said enlargement and the opening extending radially to positions which correspond to less than half the distance from the inner to outer peripheries of said ring member, said ring member being disposed between said carrier and a front part of said housing, said enlargement being movable axially with said plunger from a forward position ahead of said front part and ring member to a more rearward position, stop means limiting rearward sliding motion of said carrier in relation to said housing beyond a predetermined limited amount, said second set of contacts comprising a pair of contacts disposed for electrical closure by said carrier when said carrier is in a forward position and for electrical opening when said carrier is in a rearward position within said housing, and spring means urging said contact carrier in a forward direction within said housing.
6. Switching apparatus as set forth in claim 5 wherein said ring member comprises an expandable O-ring of elasticallydeformable material, wherein said opening, said enlargement, and said portions of lesser crosssection are substantially circular, and wherein said enlargement has a substantially blunt rear surface and a gradually-tapered front surface.
7. Switching apparatus for controlling warning signals comprising,
warning signal means responsive to energization with electrical energy for providing a warning signal, first manually actuated switching means for delivering electrical energy to said warning signal means when in the closed condition having holding means responsive to holding energy for staying in the closed condition and to interruption of said holding energy for returning said first switching means to the open condition and being responsive to manual actuation for assuming said closed condition, a source of said holding energy, second switching means having an armature movable in first and second opposed directions including means responsive to movement of said armature in said first direction for coupling said holding energy to said holding means and means responsive to movement of said armature in said second direction for interrupting the coupling of said holding energy to said holding means to thereby restore said first switching means to said open condition.
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