US3588776A

US3588776A - Safety cable

Info

Publication number: US3588776A
Application number: US790784A
Authority: US
Inventors: Elwood R Horwinski
Original assignee: Lewis Engineering Co
Current assignee: Lewis Engineering Co
Priority date: 1969-01-13
Filing date: 1969-01-13
Publication date: 1971-06-28
Anticipated expiration: 1988-06-28

Abstract

A CABLE HAVING A SAFETY FEATURE WHEREBY IT IS ADAPTED TO MONITOR AND SIGNAL CONDITIONS OF HEAT, COLD, ABRASION, FIRE, EXPLOSION, ETC. COMPRISING A BUNDLE OF CORE WIRES ABOUT WHICH THERE IS SPIRALLY WRAPPED A FLEXIBLE PAPER-THIN PLASTIC RIBBON IN OR ON WHICH CONDUCTING MEANS COMPRISING ONE OR MORE LONGITUDINALLY EXTENDING INSULATED CONDUCTORS ARE CARRIED. THE CONDUCTOR MEANS MAY HAVE A VERY LOW FUSING POINT, OR THEY MAY BE ADAPTED TO CONSTITUTE THE B ULB ELEMENT OF A RESISTANCE THERMOMETER BRIDGE OR BOTH. THE LOW FUSING POINT CONDUCTOR MEANS ARE CONNECTED WITH AN INDICATOR DEVICE AT A SIGNALLING STATION ADJACENT ONE END OF THE CABLE. THE INDICATOR SIGNALS WHEN THE CIRCUIT IS BROKEN AS BY MELTING DUE TO EXCESSIVE HEAT. AT THIS SIGNALLING STATION A RESISTANCE THERMOMETER OR EQUIVALENT DEVICE IS CONNECTED TO THE CONDUCTOR MEANS CONSTITUTING THE BULB, WHEREBY A CONTINUOUS CHECK IS HAD ON TEMPERATURE CONDITIONS OF THE CABLE.

Description

United States Patent 3,588,776 [72] Inventor Elwood R. Horwinski 2.7749 0 12/1956 ZrccardrJr 337/415 Chesire, Conn. 2,670.419 211954 Kliever et a1 337/415 [21] Appl.No. 790,784 2.998.840 9/1961 Davis. 338/211(UX) [22] Filed Jan. 13,1969 "1.297.846 1/1967 Peltier 337/416 [45] Patented [73] Assignee June 28, 197] Lewis Engineering Company Naugatuck, Conn.

[54] SAFETY CABLE 5 Claims, 11 Drawing Figs.

511 mu .G08b2l/00, HOlb7/32,H01h37/76 so FieldofSearch 337/416.

415, 397, 231; 338/21'l,212; 219/438,499; 174/1 1, 1 15, 117; 340/227 (C), 276 (cursory) 6/1897 Arnold Primary Examiner-Bernard A. Gilheany Assistant E.raminer Dewitt M Morgan Anorney-H. Gibner Lehmann ABSTRACT: A cable having a safety feature whereby it is adapted to monitor and signal conditions of heat, cold, abrasion, fire, explosion, etc. comprising a bundle of core wires about which there is spirally wrapped a flexible paper-thin plastic ribbon in or on which conducting means comprising one or more longitudinally extending insulated conductors are carried. The conductor means may have a very low fusing point, or they may be adapted to constitute the bulb element of a resistance thermometer bridge or both. The low fusing point conductor means are connected with an indicator device at a signalling station adjacent one end of the cable..The indicator signals when the circuit is broken as by melting due to excessive heat. At this signalling station a resistance thermometer or equivalent device is connected to the conductor means constituting the bulb, whereby a continuous check is had on temperature conditions ofthe cable.

atented June 28, 1971 3,588,776

*REGULATED g a POWER 4 SUPPLY INVENTOR.

Elwooa R. Hor'wLnsk'L Y A a SAFETY CABLE CROSS REFERENCES TO RELATED APPLICATIONS l. Copending application of Elwood R. Horwinski, Ser. No. 755,203, filed Aug. 26, 1968, entitled Tamperproof Cable and Detection System," and having common ownership with the present application.

2. Copending application of Elwood R. l-lorwinski, Ser. No. 761,725 filed Sept. 23, 1968, entitled Area Security Apparatus and having common ownership with the present application.

3. Copending application of Conrad S. Ham and Elwood R. Horwinski, Ser. No. 780,931 filed Oct. 28, 1968, entitled Printed-Circuit Type Security Apparatus for Protecting Areas, and having common ownership with the present application.

4. Copending application of Elwood R. I-lorwinski, Ser. No. 777,397 filed Nov. 20, 1968, entitled Area Security System Comprising Strain and Heat-Responsive Network, and having common ownership with the present application.

BACKGROUND This invention relates to safety cables, such as those wherein means are provided to indicate abnormal conditions like excessive heat or cold, abrasion, fire, explosion and the like. l-leretofore, various types of electrical alarm or indicator systems have been employed in security or other areas to monitor conditions of heat, cold, abnormal pressures and the like. These devices have been in the nature of fire alarms, smoke alarms, pressure-sensitive alarms etc., each intended specifically to monitor one particular condition for which purpose a special installation was made. The alarms or indicators generally were not associated with cables carrying wires for other purposes, as for example the transmission of intelligence, signals and the like. Instead, special installations were employed, comprising the sensing means ofthe alarm systems. This, together with the additional space and accommodations required, constituted a distinct drawback. Also, these special installations involved additional cost since the sensing devices had to be oriented and specially mounted in the areas which were to be protected. Special wiring was needed to connect them with the signalling or indicating equipment, as well. All of this involved considerable installation time and expense.

SUMMARY The above drawbacks and disadvantages of prior sensing, signalling and alarm equipment are obviated by the present invention, one object being to provide a novel and improved sensing and signalling means incorporated in cables intended to carry unrelated data such as communications, control, signalling and like information, to the end that separate or special installation and wiring of sensing devices is eliminated. Another object of the invention is to provide a novel and improved safety cable adapted to carry messages, signals or other information, which cable has incorporated in it novel sensing means responsive to conditions of heat, cold, abrasion, etc., enabling these to be continuously monitored and instantly detected when excessive limits are reached.

The foregoing is accomplished by the provision of a novel spiral wrap placed around the signal-carrying bundle of wires of the cable, said wrap comprising a substantially paper-thin flexible plastic ribbon which carries one or more conductors, having special characteristics such as a low melting point and a resistance response adapted for use with a resistance thermometer. The conductors of the spiral wrap may be variously interconnected at one end of the cable. At the other cable end they are brought to a signal or alarm station where they are joined to bridges, relays or similar equipment to provide the desired indications.

Other features and objects of the invention reside in the provision of an improved safety cable construction as above set forth, which is especially simple to manufacture, economical, reliable and foolproof in its operation, saving of space, and which has a wide variety of uses.

Other features and advantages will hereinafter appear.

In the drawings illustrating several embodiments of the invention: I

FIG. 1 is a fragmentary detail of a safety cable made in accordance with the invention, illustrating one type of spiral wrap comprising a plastic ribbon having a plurality of spacedapart ribbonlike conductors.

FIG. 2 is a schematic circuit diagram illustrating connections made to the cable of FIG. 1 for purposes of monitoring temperatures, indicating conditions of excessive heat, etc.

FIG. 3 is a transverse section through the spiral wrap ofFlG. 1, taken on the line 3-3 thereof.

FIG. 4 is a fragmentary detail of a spiral wrap cable made in accordance with the invention, wherein the core wires are enclosed in two spiral wraps of plastic ribbon, each having sensing conductors. The spiral wrap ribbons of FIG. 4 show conductor configurations which are different from that of FIG. 1.

FIG. 5 is a transverse section through one plastic ribbon of FIG. 4, taken on the line 5-5 thereof.

FIG. 6 is a detail of a safety cable having a spiral wrap plastic ribbon, illustrating another form of conductor configuration carried thereby.

FIG. 7 is a fragmentary detail of a spiral wrap safety cable showing a plastic ribbon having still another configuration of conductors.

FIG. 8 is a fragmentary detail of a cable showing a spiral wrap ribbon having yet another configuration of conductors.

FIG. 9 is a detail ofa cable showing spiral wrap ribbons one of which has yet another conductor configuration.

FIG. 10 is a transverse section through the spiral wrap ribbon of FIG. 9, taken on the line 10-10 thereof.

FIG. I! is a detail of a cable having a spiral wrap ribbon showing still another conductor configuration thereon.

Referring first to FIGS. ll-3, the safety cable designated 18 therein comprises a bundle of wires 20 constituting a core, and an outer extruded plastic jacket 22 which comprises the protective covering. In accordance with the present invention, between the core bundle 20 and the outer jacket 22 there is provided a novel spiral wrap constituted of a substantially paperlike flexible plastic ribbon 24 having tenuous longitudinal edge portions, said ribbon carrying a plurality of conductors extending along the length thereof in spaced, insulated relation to each other and to the core bundle. The'ribbon 24 comprises a thin plastic strip 26 to one surface of which there have been applied thin metallic conducting ribbons 28 30, 32 and 34. The

conductors

28, 30, 32 and 34 may be adhered to the plastic strip 26 by the use of a suitable adhesive. Or, the plastic strip 26 may be of the pressure-sensitive type sold commercially as adhesive tape or pressure-sensitive tape.

As shown, the

ribbons

28 and 32 are of greater width than the

ribbons

30, 34 and are constituted ofa metallic substance or alloy of relatively low melting point with respect tometals generally. Such alloy may be of lead and tin composition, or may have another suitable formulation. The

metal ribbons

30, 34 are advantageously like thin foil, constituted of nickel. The composite spiral wrap ribbon 24- overlaps at its edge portions, as will be understood, and the insulation between the

metallic ribbons

28, 30, 32 and 34 is effected by the plastic strip 26 itself, at the overlapping edge portions thereof.

Referring to FIG. 2 at one end of the cable 18 the

metal ribbons

30, 34 are joined, as indicated at 36. Also, the

metal ribbons

28, 32 are joined, as indicated at 38. The other end of the cable I8 is brought to an alarm or signalling station, which is indicated by the broken line rectangle designated 40.

The station 40 may comprise a relay 42 whose coil 54 is connected through a battery 44 with terminals G and H to which the

metal ribbons

28, 32 are connected.

A continuous current thus flows through the

metal ribbons

28, 32 having the low fusing point since such ribbons at the station 40 present a continuous sensing circuit of definite resistance, such current maintaining the armature 46 of the relay separated from its cooperable stationary contact 48. A signal bell 50 is connected through a battery 52 with the armature 46 and cooperable contact 48, as shown. As long as the relay coil 54 remains energized, the signal bell 50 will be silent. However, if due to a condition of heat, one of the

ribbons

28, 32 of low melting point should be melted, this would break the circuit through the relay coil, releasing the armature 46 and effecting a sounding of the signalbell 50 which then indicates the condition of excessive heat or other circumstance causing the break.

The

metal ribbons

30,34 are brought to a temperaturemeasuring bridge circuit 56 located at the station 40, being connected to terminals M and N of such bridge. The bridge 56 comprises three other legs beside that constituted by the

nickel ribbons

30, 34, such three other

legs containing resistors

58, 60 and 62. A galvanometer or indicating instrument 64 is connected to sliders ofpotentiometer devices 66, 68 constituting two opposite corners" of the bridge circuit. The remaining two opposite corners are represented by junctions A and XY. A potential is applied to such remaining junctions from a regulated power supply 70 having one terminal connected to the junction A and having two other terminals connected to a potentiometer 72 whose slider is connected to the terminal Y. The terminal X is connected to a rheostat 74 which in turn is connected to one end of the potentiometer resistor element of the potentiometer 72.

With such arrangement of the bridge 56 and power supply 70, changes in the temperature of the cable 18 will cause changes in the resistance of the

nickel ribbons

30, 34 whereby an unbalance of the bridge 56 will be effected, resulting in a changed temperature reading at the galvanometer or instrument 64. Further details of the operation of the bridge 56 bridge regulated power supply are not given herein since they are explained fully in U.S. Pat. No. 2,761,052 issued to Knud J. Knudsen.

It will now be seen from the foregoing that temperature conditions of the cable 18 may be readily monitored and read at the station 40, and that breakage of any of the

conductors

28, 32 due to excessive heat which causes melting, or due to abrasion or other physical disrupting forces, will result in the alarm bell 50 being sounded. The cable 18 carrying the signal bundle or core wires 20 is seen to be constituted in a novel manner by use of the spiral wrap 24 whereby it has sensing elements which are utilized at the station 40 to provide the desired indications. The cable is of simple and economical construction, being readily fabricated by utilizing existing equipment and processes.

Another embodiment of the invention, illustrating a different form of safety cable is depicted in FIGS. 4 and 5. In these FIGS. the core wires 76 are enclosed by spiral-wrap conductor-carrying ribbons 78, 80 which are wound in opposite directions. An outer protective jacket 82 of extruded plastic surrounds the spiral wrapping. The ribbons 78, 80 may be identical, each comprising a paper-thin plastic strip 84, a metallic ribbon or foil 86 of an alloy having a low melting point, and a fine nickel wire 88 extending alongside of and spaced from the ribbon 86. The metal ribbon 86 and wire 88 may be secured to the strip 84 by suitable adhesive, or the strip 84 may be provided with a pressure-sensitive adhesive surface for this purpose.

The two metal ribbon conductors 86 will be joined to each other at one end of the cable 77, their other ends being connected to the terminals G and H of the station 40 shown in FIG. 2 in place of the

conductors

28, 32. The conductors 88 of the ribbons are also joined to each other at one end of the cable 77, and theirother ends are connected to the terminals M and N in the bridge of FIG. 2, in place of the

conductors

30, 34.

FIG. 6 shows acable 90 having a core bundle 92 of five wires, one wire 94 of which constitutes a return for a conductor of the spiral wrap ribbon 96. The wire 94 may be ofnickel, for example, constituting a return for the nickel conductor 98 of the ribbon 96, such

ribbon having conductors

100, 102 of low melting point alloy. At one end of the cable 90, the

conductors

100, 102 will be connected to each other, as will also the

conductors

94, 98. At the other end of the cable, the

conductors

94,98, 100 and 102 will be connected to a bridge like the-bridge 56 and an alarm such as shown in FIG. 2 comprising the relay 42 and associated signal bell.

Another embodiment of the invention is illustrated in FIG. 7, wherein the cable 104 has a spiral wrap 106 comprising a fusable conductor .108 and a nickel conductor 110, and wherein the core bundle 112 includes

return conductors

114, 116 respectively for the conductors 108, of the spiral wrap 106. With such construction, the wire 114 which is connected with the nickel wire 110 would constitute the resistance thermometer bulb, and the wire 116 which is connected to the fusible alloy ribbon 108 would be included in the circuit of the relay alarm.

Another embodiment of the invention is illustrated in FIG. 8, wherein a cable 117 has a spiral wrap ribbon 118 comprising two

nickel wires

120, 122 and a fusible ribbon 124, the core bundle 126 including a return circuit wire 128 which at one end of the cable is connected to the fusible-ribbon 124. The two

nickel wires

120, 122 are connected together at one cable end, as will be understood, and the connections at the other end of the cable are carried out in the manner already indicated above, to a resistance thermometer bridge and a relay indicator device.

In the embodiment of FIGS. 9 and 10 the cable 130 has a wire core bundle 132 including a return circuit wire 134 which at one end of the cable is connected with a nickel wire 136 extruded into a spiral-wrap plastic ribbon 138. The core bundle 132 has a wrapping of Mylar plastic tape or ribbon 140 over which the conductor-carrying ribbon 138 is wound. The cable of FIGS. 9 and 10 is intended to provide temperature measurements, without indications resulting from excessive heat since it does not have fusible elements in the spiral wrap.

In FIG. 11 there is illustrated a cable 142 having a bundle of core wires 144 which contains a return circuit wire 146 for connection with a fusible alloy ribbon 148 of a spiral-wrap tape 150. The cable 142 is adapted to indicate a condition of excessive heat, sufficient to melt the alloy ribbon 148, and has no temperature sensing elements of nickel wire or ribbon, as with embodiments of the invention described above.

It will now be understood from the foregoing that I have provided a novel and improved safety cable containing sensing elements in the form of spiral conductors carried by a spiral wrap plastic tape or ribbon, whereby the cable will serve as a sensing device in addition to its function of carrying information by means of a core bundle. The cable is seen to be simple in construction, and economical, providing a reliable means for indicating and signalling conditions of heat, cold, fire, abrasion, explosion and the like.

In place of a single cable, two cables may be employed in a self-balancing arrangement wherein the spiral wrap conductors of each cable constitute a different leg of a temperaturesensing bridge, for example. The cables may be strung 4 or 5 feet apart, for example, where conditions of heat or cold would warrant such arrangements.

Variations and modifications are possible, andportions of the improvement may be used without others.

Iclaim:

1. A safety cable comprising, in combination:

a. a flexible core of sufficient length to enable it to be extended between remote points,

b. paper-thin, flexible plastic spiral-wrap ribbon means wound about said flexible core, said ribbon means having tenuous longitudinal edge portions,

0. a conductor on the ribbon means and extending along the length thereof,

d. said conductor being spaced from longitudinal edges of the ribbon means and being disposed along a side surface thereof, and

e. means extending along said flexible core and at one end thereof permanently electrically connected to said conductor, providing a permanent return electrical circuit, said means and conductor at the other end of the core thereby presenting at all times a continuous sensing circuit of definite resistance,

. an additional conductor of melting point different from that of said first-mentioned conductor, carried by the ribbon means and extending along the length thereof and spaced from said first-mentioned conductor, and

. a second means extending along said flexible core and at one end thereof electrically connected to said additional conductor, providing a second return circuit, said second means and said additional conductor being electrically independent of'said first-mentioned conductor and firstmentioned means and presenting a second continuous sensing circuit which is electrically independent of said first-mentioned sensing circuit,

. one ofsaid conductors being oflow-melting point alloy,

. said other conductor having a temperature coefficient of resistance adapted for use with an electrical temperature measuring instrument.

2. A safety cable as in claim 1, wherein:

a. the said first-mentioned conductor is of metal of relatively low melting point with respect to metals which are not alloyed,

b. said second conductor extending generally in parallelism to and being uniformly spaced from said first-mentioned conductor and comprising fine nickel wire.

3. A safety cable as in claim 1, wherein:

a. said first-mentioned means providing the return circuit comprises a third conductor carried by the ribbon means and extending along the length thereof in spaced relation to said first-mentioned conductor.

4. A safety cable as in claim 1, wherein:

a. said first-mentioned conductor is of metal of low melting point with respect to metals which are not alloyed,

b. said other conductor having an electrical resistance making it suitable for insertion in a resistance thermometer circuit.

5. A cable as in claim 1, wherein:

a. the core is electrically conducting and insulated from the said two return-circuit means and from said two conductors.