US3011161A - Pushbutton supervised fire detection system - Google Patents

Description

Nov. 28, 1961 E. J. FREUNDT 3,011,161

PUSHBUTTON SUPERVISED FIRE DETECTION SYSTEM Filed March 3, 1959 ARMATURE OF V/BRATOR I 7'0 CLEAN CONTACTS /4 AND /5 RELAY TA IVSFOAMEA 5 s coAmAky 22 -/z I I NoRMAuY m I l1 CLOSZ-D 2 [5 SWITCH ,9 TfMPl-RATURE amen/v5 3 DEV/C58 (NORMALLY CLOSED) l6 Sol/N0 TRANSFORMER Zf SECONDARY DEV/cf My a m INVENTOR.

United States Patent O 3,011,161 PUSHBUTTON SUPERVISED FIRE DETECTION SYSTEM 'Edmund John Freundt, Indianapolis, Ind.,

I assignor to Gladys E. Freundt Filed Mar. 3, 1959, Ser. No. 796,888 2 Claims. (Cl. 340-214) Few residences have been provided with fire detection systems, partly because householders are reluctant to accept the associated burden of supervision, testing, or inspection of such a system.

Thesimple series fire detection circuit, once it is installed in the average home, generally receives no supervision from the householder. With this type of circuit, vital signal wires may become defective, or fuses may blow; and the householder may not know about it unless a test switch, if installed, is periodically used. The unsupervised series fire detection circuit possesses only limited responsive power to act. 'Said action may occur only when the fire detection circuit loses energy at a time when the signal-producing circuit is fully operative.

There are numerous vital elements of a simple series fire detection circuit, other than those in the fire detection circuit itself, wherein failure may occur without causing the signal producing circuit to become responsive. These elements are: availability of voltage from the supply transformer; goodness of the transformer windings; goodness of primary fuses or thermal elements in the system; goodness of the two supply lines to the relay circuit; goodness of the two contacts of the relay; goodness of the relay armature pivots or bearings; goodness ofthe contacts of the audible device when self-contact controlled; goodness of the coil of the audible device; goodness of the supply lines from the relay to the typical,- remote sound device. Even the relay coil and associated fire detection circuit are vulnerable to failure without detection, if such failure occurs in conjunction with a failure of any of the vital elements just described.

The foregoing summary indicates the flimsy reliability characteristics of the unsupervised series fire detection circuit. Such an unsupervised circuit has no inherent attributes of reliability. There has long been recognition of this fact, which emphasizes the need for some form of automatic supervision over the goodness of the circuit mentioned; and particularly so, when installed in the average residence.

However, conventional types of supervised, closed circuit fire detection systems generally require double circuits and elaborate equipment. Such systems are prohibitive in cost for the average householder; and are completely unsuited for residential use, where the necessary skilled maintenance for such a system is difiicult to obtain.

This invention contributes to the limited technology in this specific field by a novel circuitry, including an improved sound device. Said combination obtains complete supervison over a normally closed fire detection circuit of the residential type noted. This supervision is achieved through suitable interconnection of the unsupervised, closed circuit fire detection system with an open circuit door-signal system, such as the doorbell or chime circuit which exists in almost all residences.

The basic functioning of this system is such that the door-signal system functions in the usual manner from pushbutton operation, and failure of any vital element in the fire detection system, or the door-signal system, renders the door-signal system inoperative. This system provides thorough supervision over all of the numerous elements in the fire detection system. v

The system achieves this result at the very modest cost of merchandising the additional equipment to add to an existing door-signal system. Such equipment generally 3,011,161 Patented Nov. 28,1961

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consists of a universal package containing the additional door-signal transformer, an inexpensive sounddevice of an improved type, and the equivalent of a relay. The

package is suitable for connection to any standard doorbell or chime circuit.

The frequency of such supervision is determined by the frequency of operation of the associated'door-signal sys''.

door-signal system, by virtue of its associated nuisance problem when inoperative, is a matter of considerable importance to most housewives, and to householders in general. Thus, it is only in rare cases that any 'malfunc-.

tion in this system remains undetected for any length of time. rected in order to eliminate the attendant household nuisance. Said system is thus an ideal medium for super-' vising'the goodness of an associated fire detectionsystem. I

This system of supervision is designed for commercial distribution as a packaged fire detection system for installation in the average residence. signal transformer, pushbutton, 'door signal device, and associated wiring are utilized without any major alteration. The additional circuitry consists of the' installation of the closed circuit type of fire detectors, which are also furnished with the package; and connection of this circuit to the door-signal system and the additional equipment already noted. x

During the history of door-signal circuit utilization'and development of the simple, unsupervised series circuit for fire detection purposes, no composition has been offered to interconnect both circuits for supervisory purposes. There is no evidence of associating the inherent supervisory attributes of the ordinary doorbell pushbutton' with supervision of a fire detectionsystem.

The principal reasons for the total absence of a useful composition in this field will now be summarized. The purpose of this summary is to itemize each obstacle to the effectuation of the object of thisinvention, with attendant specification of the novel composition required-to overcome each obstacle, so that the original manner in which this invention satisfies each specification may readi ly become apparent.

j operation of the pushbuttonl 'The limitations which heretofore have prevented the development of any useful composition in this specific field are now listed, being given suitable reference num: bers, so that the novel achievements of this invention may conveniently be ascertained by suitable comparison of the following numbered sections with those sections appearing later, which describe the detailed operation of said invention. These limitations are:

(1) Characteristics of the common door-signal pushbutt0n.--This device is the simplest switching device known, consisting of a single .fixed contact, and a single movable contact. It has only one realizable function, which is to close a circuit. To utilize said device .to achieve the opening. of a relay circuit, as is required to effectuate the functioning of this system, requires novel use of circuits to obtain the desired degree of circuit control without using the only. known alternative. Said alternative is the use of a ballast resistor in series with the relay coil, and the shunting of the relay coil by the Such a method imposes additional burden on the associated supply transformer; and, because of extremely stringent transformer output limitations, thismethodis not practical. 7 Y

(2) The characteristics ofstandard door-signal dvices. -Typi'cal residential-type;- door-signal devices. may

Malfunctions, once detected, are promptly c0r-' The existing door-J be classified as low-current, self-contact-controlled, vibrating; high-current, self-contact-controlled, vibrating; or high current, non-vibrating, chime. Most residential doorsignal devices are of the inexpensive, high-current, vibrating type, when associated with a doorbell system. Most chimes are of the high current type, and are capable of the equivalent of single-stroke action, being incapable of producing a continuous signal. The self-contact controlled type of sound device will not operate properly when connected in series with another device of the same type. A low current device will not operate properly when connected in parallel with a high current device, since their performance is determined by the peculiar characteristics of the standard door-signal transformer. Normally, door-signal transformers are de signed to supply only one sound device. Also, a low current, contactless type of vibrator, or a low current chime, will not operate properly when connected in series with a high current chime. In general, the joint use of door-signal devices requires a careful appraisal of the associated impedance characteristics of the devices involved, and of the transformer regulation characteristics.

Since a supervisory system of the type presented by this invention requires utilization of an additional sound device that must function jointly with some existing sound device having incompatible operating characteristics, said additional sound device should have some novel characteristic to effectuate the required joint operation.

(3) Characteristics of the available relay.The relay available for a low cost interconnection of this type is necessarily inexpensive, since the cost of a high grade, hermetically sealed relay would result in a prohibitive rice level for the package. The low cost relay requires considerable contact maintenance because of its construction, but primarily because of the lack of use of its contacts. It is a fell established fact that the inherent tendency toward contact failure in the low cost relay has been a significant deterrent in the development of a reliable, low cost, closed circuit type of fire detection system for the average residence.

It is also a well established fact that the typical low cost doorbell has an astonishingly reliable contact life, and seldom fails because of the accumulation of chemical and organic films that persistently cause the failure of relay contacts. The basic reason for the reliable performance of the ordinary vibrating doorbell resides in the fact that the self-contact controlled vibrator has associated with its frequent use an automatic contact cleaning function. Said function is eifectuated by virtue of the vibratory forces acting on the contacts.

Since a supervisory system of the type presented by this invention requires utilization of a relay, said device should not only be capable of functioning as a switching device, but should provide some form of automatic contact cleaning associated with complete utilization of all features promoting circuit reliability which reside in the inherent qualities of the normally open door-signal system.

(4) T he. peculiar characteristics of the standard doorsignal transfrmer.-The standard door-signal transformer is designed for use with the usual doorbell installation, or its equivalent, where secondary fuse protection is not feasible. Such transformers are'designed' to give safe Operation under such conditions, in that adequate protection against secondary short circuit current is provided by the internal construction of the transformer. Such transformers are limited by regulatory bodies to a maximum secondary short circuit current of six amperes. The practical effect of this ruling is to limit the volt-ampere capacity of any one transformer, in the voltage ranges commonly used with doorbells or chimes, to volt-amperes.

Also, because of this limitation, door-signal trans: formers necessarily have very high impedances. Voltage regulation is extremely poor. For example, a typical doorbell transformer, rated at 10 volts open circuit, 5 volt-amperes, delivers 1.2 amperes to a low cost doorbell with a transformer terminal pressure of only 3 volts.

The wide variation between no-load voltage and fullload voltage of such transformers imposes prohibitive limitations on the use of a door-signal transformer for operation of a control relay. Such a relay coil, unless operated from an independant transformer, must be operated in conjunction with additional load, which, if controlled by said relay contacts, would reduce relay coil voltage from a nominal value of about of the opencircuit voltage of its transformer, to about 40% of such voltage when the relay contacts applied additional, full load to the transformer. Under such condition, the relay coil circuit, when closed to cause disconnection of the load, would obviously 'be incapable of functioning.

For the reasons just described, a supervisory type of system of the type presented by this invention requires novel use of a relay coil circuit to insure reliable operation of the relay under all possible conditions of load applied by the relay contacts to the system.

(5) Characteristics of door-signal transformers with respect to capacity and with respect to parallel operati0n.The total load applied to a. system of this type would be the existing sound device, which'would continue to be supplied with voltage from the existing transformer, a relay coil, and an additional sound device. The relay coil would represent a burden of 4 volt-amperes; the additional sound device would represent a burden of 10 volt-amperes.

Using conventional connection schemes, the total system load would require a total of three transformers; one for the relay coil, one for the existing sound device, and one for the additional sound device. The only manner in which such transformers could be utilized is through parallel operation of all transformers, or allocation of individual load to individual transformers.

Parallel operation of such transformers would pose the immediate problems of how to deenergize the relay coil without the use of a ballast resistor; the necessary addition of secondary protective devices to limit the secondary wiring short circuit current to the value permitted for one transformer; and the problem of how to operate devices having widely divergent impedance characteristics from said transformers. In general, such problems have no practical answer; parallel operation of transformers being impossible under the conditions limiting switching and impedance matching in this interconnection.

Individual operation of transformers would require means to disconnect the individual transformers from their associated load. This would impose an impossible condition on the only available switching device, which is a simple, double-contact pushbutton.

Study of the limitations just described indicates that the only practical manner in which successful operation of an interconnected system of the type noted may be efiectuated is through the use of a novel circuit arrangement, using only two transformers, one being the existing transformer; said circuit permitting the utilization of the additional transformer for energizing the relay coil alone; or for energizing the relay-contact switched load when the relay coil is not energized; or for energizing both the relay coil and the additional load during the transient time interval required for the relay contacts to separate in response to the application of voltage to the relay coil. Said circuit would thus be required to insure proper operating voltage for the relay coil under all conditions of system operation, with no imposition of fixed losses in control resistors. In addition, such circuit control would be required that the door-signal circuit could not be operative unless all vital functions of the fire detection circuit were operative.

Before proceeding to the detailed description of the interconnected systems, an understanding of the improved sound device and relay noted under (2) and (3) is neces sary.

In accordance with the specifications noted, this invention achieves an improved sound device which operates properly as a sound device with any of the standard doorsignal devices commonly encountered in this interconnection. In addition, the improved sound device has the necessary characteristics of a simple relay. The improved sound device achieves circuit simplicity and reliability heretofore not possible by reducing the four contacts previously associated with relay control of a self-contact-controlled vibrating sound device to one relay contact and one sound device contact.

Still another improvement resides in the derivation of the important function of automatic contact cleaning.

The specifications for the improved sound device are simple. A sound device is used that has the necessary attributes to act as a contactless vibrator, or as a selfcontact-controlled vibrator. The fixed contact of said vibrator is replaced by the relay contact which is attached to the movable armature of a conventional relay.

The improved sound device has two possible contact arrangements. The first location is at the free end of the armature. In this case, the device operates as a conventional, self-contact-controlled vibrator, Whose energy supply is also under the control of the associated, integral relay combination.

The second location for the contact arrangement is near the fixed end of the armature. In this case, the device is designated as a contact cleaning vibrator.

When used as a contact cleaning vibrator, the contacts, in their deenergized position, mate with normal contact pressure, and produce the minimum voltage drop associated with their inherent contact resistance characteristics. However, when the device is energized, the contacts receive vigorous vibrations from the armature of the sound device. The contacts are subjected to rapid acceleration and deceleration through the small but finite amplitude of sound device armature travel. The contacts are hammered with numerous minute blows. A field of uniform sparking verifies the condition of minute contact separation, but said separation has no appreciable effect upon the proper operation of the sound device.

In the first contact arrangement, the contacts are subjected to additional forces from the incidence of greater amplitude of armature vibration, and the presence of contact arcing, with attendant heat and pitting of contacts. However, for both contact arrangements, the basic result is a form of automatic contact cleaning. The rapid acceleration and deceleration of the contacts through their amplitude of travel, the mechanical blows, and the faceto-face rubbing action are equivalent to high-grade maintenance activity in maintaining clean contacts, in that each of the numerous operations of the improved sound device results in the removal of loose films of chemical or of organic matter from the contact faces. While such films, considered alone, are usually not detrimental to contact conductivity, and are easily removed by any simple v1- bratory process, said film, if not periodically removed, rapidly builds up to the point where contact failure is assured. Imaddition to the removal of the foreign matter noted, the incidence of frequent, vigorous vibrations from said device effectively discourages insect nesting, and its attendant toll of contact interference. Also, such vibration is a major force in preventing the accumulation of larger particles of foreign matter; such particles generally being subjected to disintegrating forces before moisture and chemical actions solidify them into armaturetravel blocking particles, or the like.

One of the preferred embodiments of this invention is now described. Reference is made to the accompanying drawing, which applies to a doorbell interconnection, but which also applies to a chime interconnection, with due consideration of the exception which is described later.

The various circuit elements are listed as follows: 5, 6,

7, 8, 9, 13, 16, 18, 19, 2t), and 21 are connecting wires; 1, 2, 3, and 4 are the terminals of transformer secondaries; 23 is the additional transformer, 24 is the existing transformer; pushbutton 22 is the control device formerly controlling the original sound device 17 relay coil 12 controls the mating of its contact 15 with contact 14; contact 15 is mounted on the movable armature of the relay; contact 14 is attached to the fixed end of the armature of contact cleaning vibrator 11, hereafter referred to as device 11; the functions of device 11 are to-produce an audible signal as a contactless vibrator, and to maintain vibration cleansing of contacts 14 and 15; normally closed temperature sensitive element 10, wires 6, 9, and 21, plus relay coil 12, are the only elements included in any reference to the fire detection circuit.

The system functions as follows: Transformers 23 and I 24 are connected in cumulative series. Operation of pushbutton 22 shunts relay coil 12; device 11 is energized from transformer 23; contacts 14 and 15 are closed, and vibrate through a very small amplitude in accordance with the vibrations of device 11, said vibration of contacts having no effect on the vibration frequently ofdevice 11, yet insuring vibration cleaning of contacts 14 and 15; sound device -17 receives full voltage from transformer 24.

The supervisory function of this circuit is accomplished, since sound device 17 cannot operate unless every element in the entire system is operative. The goodness of the entire system is indicated by appropriate signals from device 11 and sound device 17; both signals being required, since device 11 must be audibly operative for the contact cleaning function to be operative; this function being considered of great importance for its maintenance activity.

The worst possible type of failure is completely supervised by this system. For example, the loss of secondary voltage from either transformer is supervised. The loss of secondary voltage from transformer 24 is noted by the loss of response from sound device .17. The loss of voltage from the secondary of transformer 23 transforms the relay into a vibrating buzzer; also device 11 is then inoperative.

During the condition of a fire, or equivalent interruption of the fire detection circuit, the relay coil loses energy, and relay contact 15 mates with contact 14. Both sound device 17 and device 11 are now in series with the total voltage of the two transformers. In spite of the fact that sound device 17 is almost always a selfcontact controlled vibrator, not adapted for series operation with any other similar device, excellent performance is obtained from said device in its series operation with device 11, since device 11, designed to operate as a contactless vibrator, will operate properly with any type of sound device. The excellent operation of sound device 17 during the emergency condition noted is due to the unusual qualities of the circuit. The circuit is more fully described in the following paragraph.

In the doorbell system, the existing sound device is the major source of signal during a fire. The contact cleaning vibrator in the doorbell system is designed to operate under pushbutton control to maintain the contact cleaning activity, and to give audible evidence of the presence of-such activity. During the emergency condition, the contact cleaning vibrator functions as a current regulating impedance; and the production of a fire detection signal, while evident, is of minor consequence.

Under emergency conditions, the disadvantages of unfavorable impedance ratios between the sound devices, fully controlled as they are. in this invention for relay voltage control purposes, become distinct advantages. During this condition, practically all commonly used sound devices Which may be connected to this system receive substantial overvoltage, resulting in the production of a vigorous signal which is Well suited for emergency' application.

The favorable distribution of voltages, during the em ergency condition in the doorbell system is achieved through novel use of the ratio between the voltages of the two transformers; and the ratio between the impedance of the contact cleaning vibrator and the impedance range commonly encountered with standard door-signal devices.

The impedance of the contact cleaning vibrator is established as a function of the maximum and minimum impedances of the devices to be matched. The transformer ratio is fixed, since in the doorbell system the standard, existing transformer for the average installation is rated at volts, 5 volt-amperes. The additional transformer is rated at 16 volts, 1O volt-amperes. Novel use is made of this voltage distribution to enable the relay to receive adequate pull-in voltage during the Worst phases of operation of the system; which is when the relay circuit, having been opened for emergency purposes, or deenergized by loss of voltage to the entire system, or some fault in its wiring, is closed. At such time, the transformers are fully loaded by the two sound devices, and such load cannot be removed until the relay coil receives sufiicient voltage to operate its contact. The relay coil circuit is such that the relay coil receives voltage from the equivalent of a floating neutral con nection, whose natural tendency is to maintain a voltage range which assures reliable operation of the relay under a wide range of operating conditions.

For the chime system, sound device 17 is replaced by device 11. Device 11 in this system provides the emergency signal during a fire, since the chime is incapable of producing a continuous signal. The chime is connected to replace device 11.

A summary of the improvements incorporated in this invention now indicates complete agreement with the basic specifications noted under ('1), (2), (3), (4), and (5). The major improvements advancing the art in this area are:

(or) Use of a simple, normally open, double contact pushbutton to control energy supply to a relay coil Without the use of resistors, or the addition of any fixed power loss, or the use of an additional relay.

(b) The use of a total of two door-signal transformers.

(c) Development of an improved sound device for use as a combined sound device, contact-cleaning vibrator, and current regulating impedance.

(d) Development of an improved sound device for use as a combination sound device and relay, in which combination the minimum possible number of operative and control contacts are required to effectuate the operative function, and the relay control function.

(2) Development of a supervisory circuit wherein every vital function of the door-signal circuit and of the fire detection circuit must be operative before the doorsignal device may operate.

(f) Development of a circuit utilizing unequal vol ages, the equivalent of a floating neutral, and a current regulating impedance, to provide proper operating voltage to a control relay, and to insure proper current flow to sound devices having incompatible impedance characteristics.

(g) Development of a circuit which discriminates between pushbutton control, and the inauguration of an emergency condition, in its ability to provide over-voltage for the principal sound device utilized during the emergency condition.

There are various embodiments which may be devised for this invention. The numerous possible embodiments utilize the basic circuitry and equipment associated with the embodiments which are now described, or suitable modifications thereof. The principal features of various embodiments are noted as follows:

(a) In which the door-signal pushbutton shunts the secondary of a door-signal transformer, to which the fire detection circuit relay is also connected. Suitable circuits energize the sound devices from additional voltage sources.

([2) In which the system described by the accompanying drawing is modified by disconnecting wire 13 from wires 2% and 21; wire 19 is removed; and wire 13 is connected to terminal 3.

(c) In which the door-signal pushbutton shunts the contacts of the fire detection circuit relay, or shunts the suitably arranged contacts of associated, vibrating-type sound devices, or desired combinations of such relay and sound device contacts.

(d) In which two identical transformers are connected in differential series with two sound devices, one being the contact cleaning vibrator. The midpoint of the transformer connection is in series with the contact system of the contact cleaning vibrator; said contacts are also in series with the coil of the contact cleaning vibrator. The tire detection circuit is connected to another transformer, where the relay coil may be shunted by operation of the door-signal pushbutton.

What is claimed is:

1. A fire detection system consisting essentially of two interrelated electrical circuits, a fire-alarm circuit and an imperfection-detection circuit, said imperfectiondetection circuit being a doorbell system subjected to usage with reasonable frequency; a transformer having a tapped secondary providing a relatively low voltage alternating current for operation of the doorbell system, a voltage for the temperature responsive portion of the fire alarm system, and a summation voltage for actuating the bell as a fire alarm; a plurality of temperature sensitive devices which are normally closed but which open when subjected to excessive temperature; a pair of contact points adapted to be held open normally, to be closed whenever a temperature sensitive device is sulficiently overheated to electrically open the temperature sensitive device, and to be vibrated during the closing of the doorbell button; an electromagne-t in the temperature responsive portion of the fire alarm system said electromagnet normally being energized to urge the pair of contact points open; an electromagnet energized when the doorbell button is closed, said energized electromagnet vibrating the contact points.

2. A fire detection system comprising: a temperatureresponsive electrical circuit comprising a source of voltage, a plurality of temperature sensitive devices which are normally closed but-which open when subjected to a preselected elevated temperature, and a pair of contact points; a system for detecting imperfections in said electrical circuit opened by excessive temperature, said imperfection-detection system comprising an electrical circuit comprising a source of voltage, an electromagnetic bell, and a manually operated doorbell button, and an electromagnet positioned to vibrate said contact points of the temperature responsive circuit, the electromagnetic bell failing to ring during the depression of the doorbell button if there is any imperfection in the temperature responsive circuit, and the voltage sources of the temperature responsive circuit and the voltage source of the door bell circuit being connected in series to direct a higher than normal voltage to the electromagnetic bell in the event that the temperature responsive circuit detects such preselected elevated temperature.

References Cited in the file of this patent UNITED STATES PATENTS

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