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Publication numberUS3772545 A
Publication typeGrant
Publication dateNov 13, 1973
Filing dateDec 22, 1972
Priority dateDec 22, 1972
Publication numberUS 3772545 A, US 3772545A, US-A-3772545, US3772545 A, US3772545A
InventorsHatschek R
Original AssigneeVibro Meter Ag
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Cable connector assembly
US 3772545 A
Abstract
A cable connector assembly for minerally insulated electric cables and comprising a cable plug disposed at the cable end and a socket adapted to receive the cable plug. The cable plug is composed of contact members and of insulators disposed in consecutive aligned relationship and being of cylindrical shape, the outside diameter thereof corresponding in size to the cable diameter. The socket comprises contact elements separated by insulating discs provided with a common passage extending therethrough which is adapted to receive the cable plug.
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United States Patent Hatschek et al.

[ Nov. 13, 1973 CABLE CONNECTOR ASSEMBLY Inventor: Rudolf A. Hatschek, F ribourg,

Switzerland Vibro-Meter AG, Fribourg, Switzerland Filed: Dec. 22, 1972 Appl. No.: 317,550

Related US. Application Data Continuation of Ser. No. 193,607, Oct. 28, 1971, abandoned.

Assignee:

US. Cl ..310/7l,310/8.4,339/182 R, 339/182 RS, 183

Int. Cl. ..I-10lr 17/18 Field of Search 310/71, 8.3; 339/182 R, 339/182 RS, 183

References Cited UNITED STATES PATENTS Wilson 339/183 X 779,098 l/1905 Raymond 339/183 X 3,234,500 2/1966 Buckland 339/182 R 3,289,149 11/1966 Pawloski 1 339/183 3,291,926 12/1966 Nelson 339/182 RS Primgg' Examiner-J. D. Miller AssistantExaminer-Mark O. Budd AttorneyGeorge J. Netter [5 7] ABSTRACT A cable connector assembly for minerally insulated electric cables and comprising a cable plug disposed at the cable end and a socket adapted to receive the cable plug. The cableplug is composed of contact members and of insulators disposed in consecutive aligned relationship and being of cylindrical shape, the outside diameter thereof corresponding in size to the cable diameter. The socket comprises contact elements separated by insulating discs provided with a common passage extending therethrough which is adapted to receive the cable plug.

8 Claims, 3 Drawing Figures PATENTED NOV 1 3 I973 SHEET 10F 2 W Hk CABLE CONNECTOR ASSEMBLY This is a continuation of US. Pat. application Ser. No. 193,607, filed Oct. 28, 1971, now abandoned.

The invention relates to a cable connector assembly adapted to be used for connecting to equipment or interco'nnecting minerally insulated electric cables having two conductors which are embedded in an inorganic insulating material and which are surrounded by a metal tube, more particularly for measuring and control systems comprising thermocouples, piezoelectric signal generators or pick-ups or the like. The cable connector assembly comprising a cable plug disposed at the cable end and'a socket adapted to receive the cable plug.

A frequent requirement in the electric measuring and control art is to transmit signals from pick-ups or signal generators which are mounted in relatively hot zones or through high-temperature areas. Minerally insulated cables have accordingly been devised in which the steel conductors are embedded in an inorganic insulating material, generally magnesium oxide, enclosed by a steel tube. Cables of this kind tolerate temperatures up to above 1,000 C. One important job for which such cables are used is to supervise aircraft engines, in particular they are used in the vibration monitoring systems of rotating engine parts by means of piezoelectric accelerometers and for temperature supervision by means of thermocouples in a fire alarm system or for function checks. The pick-ups not just the thermocouples but the vibration pick-ups too are required to be placed inside the engine very near the parts to be supervised, so that detailed information from any disturbances which may occur is available and diagnosis is greatly simplified, since it is immediately apparent which particular engine component is causing abnormal vibrations, or the exact place where there is overheating. 7 i

A main difficulty in assembling pick-ups or signal generators inside an engine is the laying of the cable. The places where the pick-ups are actually disposed are usually not very hot since bearings, gearboxes and so on are oil lubricated and thus cooled. However, the cables usually have to extend through zones inside. the engine where there is spraying oil; also, they often have to pass through stationary engine parts on their way to the outside surface of the engine. This is why minerally insulated cables are preferred, for they can withstand high temperatures, have good mechanical strength and are of relatively small diameter something like 1.6 to 3.5 mm. For example, thin minerally insulated cables must be used where a signal line, as is usually the case, inside a stator blade leads to the outside of the engine, since stator blades are fairly thin and so any passages in them for cables must be relatively narrow.

There are therefore special difficulties in connecting cables to signal pick-ups and in interconnecting cable conductors. Since conventional cable plugs are usually of much greater diameter than the cable, the plugs can be fitted to the cable ends only after the laying of the cable. However, the cable ends of minerally insulated cables must be hermetically sealed since the inorganic insulant is hygroscopic and its dielectric coefficient would drop undesirably if it absorbed mositure, yet it is virtually impossible to thoroughly heat, evacuate and hermetically seal cables already assembled in an engine.

It is an object of this invention to obviate these diffculties by the provision of an adequately heat-resistant cable connector assembly for minerally insulated cables, which assembly comprises a cable plug providing a hermetic closure of the cable end and which can be fitted thereto before the cable is assembled in the engine without making cable assembly more difficult.

According to the invention the cable plug comprises two substantially cylindrical ceramic insulators and two tubular contact members whose outside diameters correspond at least substantially to the metal tube size of the minerally insulated cable, the two tubular contact members being disposed in consecutive aligned relationship so that the first insulator follows the metal tube of the cable, the first contact member engages like a sleeve or nipple or the like over the two insulators and the second contact member is engaged like a cap on the outside end of the second insulator, the insulators being metallized on their surfaces in contact with the metal tube and with the contact members and being hermetically secured thereto by brazing. The socket for receiving the plug element according to the invention comprises at least two consecutive contact elements which are separated from one another by insulating discs and through which at least one common passage extends. Spring liners or the like are inserted into the contact elements and cooperate with the contact members of the cable plug which is adapted to be plugged into the common passage and ensure satisfactory electrical contact.

Pin-like plug elements of relatively small diameter are used in radio and telecommunications, in the form of a contact pin which is connected to an electrical conductor and which has a widened head, a sleeve made of an insulant, as a rule plastics, being drawn on to the pin shank and bearing a sleeve-like contact element connected on its outside. to the second conductor. A plug casing whose dimensions greatly exceed cable diameter is needed to provide a strong connection between the plug element and the cable sheath or covering. Also, a conventional plug element of this kind cannot provide hermetic sealing of the cable end, nor is its ability to withstand heat sufficient for use in conditions of severe thermal stressing.

The cable plug according to the invention, on the other hand, forms a hermetically tight cable end piece whose diameter is little, if at all, greater than cable diameter and which is in a strong mechanical connection with the metal covering of the cable. Cable assembly is therefore facilitated even though the passages for the cable are narrow. Since a hermetic closure can be provided by the cable plug according to the invention before assembling the cable in the engine, there is no need to dry out and evacuate the cable in the place of assembly. Also, although of simple construction, the ability of the cable plug according to the invention to withstand high temperatures is the same as that of minerally insulated cable. The socket of the cable connector assembly according to the invention is of simple design and advantageously adapted to receive the cable plug. With three contact elements disposed one after another in this fashion, not only do the cable conductors have provision for electrical connection but the metal covering or sheath of the minerally insulated cable has provision for connection as screening. A socket of this kind can be disposed on or in the casing of the associated signal generator; it is particularly suitable for providing a conductive connection between two pieces of cable, e.g. between a minerally insulated cable disposed in an engine to be monitored and a conventional cable extending from the outside of the engine.

The insulating members of the cable plug according to the invention can, with advantage, be identical; preferably, the insulators are formed with axial passages through which the conductors extend, one conductor being secured to a place on the inside surface of the contact member between the two insulators, the other conductor extending through a central passage of the cap-like end contact member and being hermetically secured to the outside thereof by brazing or welding. In this construction it is a fairly simple job to beat out the cable end and to evacuate through the axial passages in the insulating members and through the central passage of the cap-like contact member before the second conductor is welded to the outside of the cap-like contact member to close the central passage hermetically. Also, the insulators can be reduced on those of their surfaces withwhich they contact the metal covering of the cable and the contact members, so that the contact members can be wholly or partly recessed in the insulating members and the cable plug has a relatively smooth outside surface.

Conveniently, if the cable plug according to the invention is to be used for thermocouple lines, the contact members are made of the same material as the cable conductors, to obviate the formation of extra thermocouples at the contact zones. 1

The common passage provided in the contact elements of the socket may extend through the insulating discs separating the contact elements. If the common passage in the insulating discs is smaller than the outside diameter of the spring means preferably formed by radially resilient contact sleeves inserted into the common passage, the sleeves are reliably anchored in the passages of the contact elements.

In a preferred embodiment of the invention advantageously suitable for connecting a minerally insulated cable to piezoelectric signal generators, in particular to piezoelectric accelerometers, the socket adapted to receive the cable plug is formed by the piezoelectric signal generator itself having piezoelectric crystal discs separated by electrodes. In this embodiment, the electrodes of the signal generator are used as the contact elements of the socket, the crystal discs forming the insulating discs. With this construction, the minerally insulated cable can be connected to the signal generator, just by means of a single central passage in the piezoelement itself, thus rendering the provision of a separate socket unnecessary.

The invention is explained in more detail below with reference to the accompanying drawings, in which:

FIG. 1 shows, by way of example, a view in axial section of a cable plug according to the invention connected to a cable end;

FIG. 2 shows a view in longitudinal section of a socket or box for interconnecting two cables, and

preferably steel, covering or sheath 5 which also forms the electrical screening of cable 1. Sheath 5 is followed by a cylindrical insulating member 6 of a ceramic material, for example aluminum-oxide ceramic, and a second and identical insulating member 7 is disposed in alignment with member 6. Between the two members 6 and 7 is a first contact member 8 which is tubular and which acts as a connecting nipple between the two insulating members 6, 7. A cap-like second contact member 9 is disposed on the outwards end of the insulating member 7. The two insulating members 6, 7 have axil passages 10, 11 through which the conductors 2, 3 extend. Between the two insulating members 6, 7 the conductor 2 is secured to a place, 12 of the inside surface of contact member 8 by brazing or welding, but conductor 3 extends through axial passage 11 in insulating member 7 and terminates in a central passage 13 of contact member 9. A weld connection 14 secures conductor 3 to the outside of member 9 and closes passage 13 hermetically.

The outside diameter of all the integers 6-9 is no greater than the outside diameter of cable sheath 5. The cable plug is therefore no thicker than cable 1 and therefore does not cause any difficulties in cable assembly. In the embodiment shown theinsulating members 6,7 are reduced or stepped at their ends to receive the components following them, so that the cable plug has a substantially smooth outside surface. The cable plug components and the integers 6-9 are hermetically sealed together by brazing, as is the insulating member 6 to sheath 5. An adhesive metal layer is applied to boundary surfaces 15 in FlG. l to metallise the insulating members 6,7. One possible way of providing the metallising is to sinter molybdenum at a high temperature on the surface of the members 6,7, whereafter the sintered layer is consolidated by electro-nickel-plating. The resulting brazed bond is mechanically strong and sealing-tight and can withstand temperatures of more than 800 C.

The weld 14 on the outside of the contact member 9 is the last item to be formed when the cable plug is assembled. Before welding, the cable 1 and the inside of the otherwise finished cable plug is first thoroughly heated to remove moisture, then evacuated via the central passage 13 in contact member 9, then filled with an inert gas, for example helium or a helium-nitrogen mixture. After the gas filling the conductor 3 is welded to contact member 9 by means of the weld 14, the cable plug and therefore the cable end being sealed hermetically. The cable plug can then be tested for hermeticity in a mass spectrometer, conveniently with the helium serving as indicator.

The minerally insulated cable 1 can have a cable plug according to the invention at both its ends and thus be hermetically sealed. It is a simple matter to assemble such a cable, one of its ends being connected to a signal pick-up such as a piezoelectric accelerometer or a thermocouple while its other end is connected to an appropriate socket or box of a signal line which is connected for example outside the engine to be monitored. Alternatively the minerally insulated cable can have one end permanently connected to signal generator or thermocouple, in which event a cable plug according to the invention is required only for its other end. When such a system is assembled, for example inside an engine, signal generator or thermocouple is fitted first, whereafter the cable is led through the various passages to the outside. The job of laying the cable in this way is facilitated by the narrowness of the cable plug according to the invention and the factthat the same is firmly connected to the cable sheath, the plug element'not being connected in this case to the signal generator or thermocouple.

FIGS. 2 and 3 show two different ways of connecting the cable plug of FIG. 1. The embodiment shown in FIG. 2 is of a connecting socket or box which can be disposed for example on the outside of an engine casing. The socket or box comprises two metal contact elements 16,17 which are secured in casing 19 of the socket by a metal screw 18 serving as contact member for the steel covering or sheath 5 of cable 1. One insulating disc 20 each, conveniently of ceramic, is disposed between the contact elements 16,17 and the screw 18, and at the end of contact element 16 is another insulating disc 21 which bears via a plate spring 22 on an end wall of casing 19. The spring 22 serves to compensate for any inequalities in heat expansion between the components of the box or socket and to ensure that the contact elements 16,17 fit without clearance inside the casing 19.

A common passage 23 extends through all the integers 1620 and is adapted to receive a cable plug secured to the end of cable 1. A resilient sleeve 24 is disposed in each contact member 16,17 and in the screw 18. The members 24 provide electrical contact between the contact members l6,l7 and the contact members 8,9 of the cable plug and between screw 18 and cable sheath 5. Socket apertures 25 are provided laterally on the two contact elements 16,17 and receive spring liners or sleeves or the like 26, to receive plug pins 27 disposed at the-end of a conventional cable 28 screwed by means of a locknut 29 to a cylindrical plug extension 30 secured to casing 19.

Screw 18 has on its outside an O-ring 31 which serves to seal the box or socket and, if necessary, to secure the cable.

A minerally insulated cable could be connected at this place to the box or socket instead of the conventional cable 28, in which event the requisite contact elements for receiving a cable plug according to the invention in the plug extension 30 could be disposed in very much the same way as in the casing 19. Alternatively, the contact elements can be disposed in consecutive and aligned relationship to one another so that the ends of two cables can be interconnected coaxially. Another advantageous possibility is for the same contact elements to have two passages disposed in parallel adjacent relationship to one another and to have the requisite spring sleeves or liners or the like, in which event two pieces of cable can be inserted into the two passages either parallel and beside one another in the same direction or in opposite directions and thus be joined together.

In the construction shown in FIG. 3, a minerally insulated cable 1 having at its end a cable plug of the kind shown in FIG. 1 is plugged directly into a piezoelectric accelerometer comprising a casing 32 in which a baseplate 33 having a prestressing sleeve 34 is secured, a seismic weight 35 and a piezoelement 36 being disposed in sleeve 34. Piezoelement 36 comprises three crystal discs 37 with electrodes 38,39 therebetween. A central passage 23 extends through the integers 33 and 37-39 and is adapted to receive the cable plug. in just the same way as in the embodiment shown in FIG. 2,

spring sleeves 24 or the like are inserted in passage 23 and provide direct electrical contact between the cable contact members 8,9 and the electrodes 38,39 and between the cable sheath 5 and the baseplate 33, which serves as an earthing connection. Sealing-tightness and, where applicable, location of cable 1 is provided by an O-ring 31. In this embodiment, therefore, the cable plug is inserted directly in the pick-up i.e., the piezoelement 36 -'and so no separate connecting socket or box is required.

I claim:

1. A cable connector assembly adapted for use in completing connection to equipment or interconnecting electric cables having a'pair of conductors embedded in an inorganic insulating material enclosed by a metal tube, said assembly comprising:

cable plug means including,

a first cylindrical insulator of main body diameter less than that of the cable metal tube outer diameter and having one end of reduced diameter that is fittingly received within said cable metal tube with the cable conductors passing through longitudinally extending openings in said insulator,

a hollow cylindrical metal tube of outer diameter substantially identical to that of the cable tube fittingly received onto a reduced diameter end portion of said first insulator, one of said cable conductors being connected to said metal tube at an interior surface,

a second cylindrical insulator having an end of reduced diameter fittingly received within the hollow cylindrical metal tube and spaced from the first insulator end portion, said second insulator having a main body diameter not more than the outer diameter of said hollow cylindrical metal tube, said second insulator being provided with an opening extending longitudinally thereof through which the other cable conductor passes, and

a cylindrical metal cap of diameter substantially identical with that of the cable metal tube having an open end received onto a reduced diameter portion of the other end of said second insulator and a closed end wall with an axially extending opening through which the other cable conductor extends for securement to the metal cap on its outer surface,

said reduced diameter end portions of said first and second insulators being metallized and bodies of brazing means interconnecting said metallized end portions and the cable tube, hollow cylindrical metal tube and cylindrical metal cap, respectively, hermetically sealing the interior of said plug means; and

socket means for receiving therewithin said cable plug means and the end portion of the cable tube received onto said first insulator including,

individual contact means for the cable tube, hollow cylindrical metal tube and metal cap arranged in mutually spaced relation and having a common opening therethrough through which said plug means and cable tube passes,

insulating discs separating the contact means, and

individual spring means resiliently electrically interconnecting the cable tube, hollow cylindrical metal tube and metal cap to the respective contact means.

2. A cable connector assembly as in claim 1, wherein the common passage provided in the contact elements of the socket extends through the insulating discs and is smaller in diameter than the outside diameter of the spring means.

3. A cable connector assembly adapted for completing connection to equipment or interconnecting electric cables having a pair of conductors embedded in an inorganic insulating material enclosed by a cylindrical metal sheath, said assembly comprising:

cable plug means including,

a first cylindrical insulator of main body diameter less than that of the cable metal sheath outer diameter and having one end fittingly received within said cable sheath with the cable conductors passing through respective longitudinally extending openings in said insulator,

a hollow cylindrical metal tube of outer diameter substantially identical to that of the cable tube received onto the other end portion of said first insulator, one of said cable conductors being connected to said metal tube at an interior surface thereof,

a second cylindrical insulator having an end received within the hollow cylindrical metal tube and spaced from the first insulator end portion, said second insulator having a main body diameter not greater than the outer diameter of said hollow cylindrical metal tube and said second insulator being provided with an opening extending longitudinally thereof through which the other cable conductor passes, and

a cylindrical metal cap of diameter substantially identical and no greater than that of the cable metal sheath having an open end received onto the other end portion of said second insulator and a closed end wall with an axially extending.

opening through which the other cable conductor extends for securement to the metal cap,

said end portions of said first and second insulators being metallized and bodies of brazing means interconnecting said metallized end portions and the cable tube, hollow cylindrical metal tube and cylindrical metal cap, respectively, thereby hermetically sealing the interior of said plug means; and

socket means for receiving therewithin said cable plug means and the end portion of the cable sheath received onto said first insulator including,

individual contact means for the cable sheath, hollow cylindrical metal tube and metal cap arranged in mutually spaced relation and having a common opening through which said plug means and cable sheath passes,

insulating discs separating the contact means, and

individual spring means resiliently electrically interconnecting the cable sheath, hollow cylindrical metal tube and metal cap to the respective contact means.

4. A cable connector assembly adapted to be used for connecting to equipment or interconnecting minerally insulated electric cables having two conductors embedded in an inorganic insulating material enclosed by a metal tube, said assembly comprising:

a cable plug disposed at the cable end and a socket adapted to receive the cable plug;

the cable plug being composed of two tubular contact members connected to the cable conductors and of two substantially cylindrical insulators of ceramic material electrically insulating the contact members from one another, the outside diameters of the contact members and of the insulators corresponding at least substantially to the metal tube size of the cable, the two tubular contact members and the insulators being disposed in consecutive aligned relationship so that the first insulator follows the metal tube, the first contact member being disposed between and engaging at both ends thereof over the two insulators and the second contact member being engaged like a cap on the outside end of the second insulator, the insulators being metallized on their surfaces in contact with the metal tube and with the contact members and being hermetically secured thereto by brazing; and

the socket including at least two consecutive contact elements provided with at least one common passage extending therethrough and insulating discs separating the contact elements from one another, spring means being inserted into the contact elements and cooperating with the contact members of the cable plug which is adapted to be plugged into the common passage in the contact elements of the socket.

5. A cable connector assembly adapted to be used for connecting to equipment or interconnecting minerally insulated electric cables having two conductors embedded in an inorganic insulating material enclosed by a metal tube, said assembly comprising:

a cable plug disposed at the cable end and a socket adapted to receive the cable plug;

the cable plug being composed of two tubular contact members connected to the cable conductors and of two substantially cylindrical insulators of ceramic material electrically insulating the contact members from one another, the outside diameters v of the contact members and of the insulators corresponding at least substantially to the metal tube size of the cable, the two tubular contact members and the insulators being disposed in consecutive aligned relationship so that the first insulator follows the metal tube, the first contact member being disposed between and engaging at both ends thereof over the two insulators and the second contact member being engaged like a cap on the outside end of the second insulator, the insulators being metallized on their surfaces in contact with the metal tube and with the contact members and being hermetically secured thereto by brazing; and

the socket including at least two consecutive contact elements provided with at least one common passage extending therethrough and insulating discs separating the contact elements from one another, spring means being inserted into the contact elements and cooperating with the contact members of the cable plug which is adapted to be plugged into the common passage in the contact elements of the socket, said socket further including a piezoelectric signal generator having piezoelectric crystal discs separated by electrodes, the electrodes forming the contact elements and the crystal discs of the signal generator forming the insulating discs of the socket.

diameter below that of the surfaces with which they contact the metal tube of the cable and the contact members.

8. A cable connector assembly as claimed in claim 3, wherein the common passage provided in the contact elements of the socket extends through the insulating discs and is smaller in diameter than the outside diameter of the spring means inserted into the contact elements.

UNlTED STATES PATENT O'FFICE CERTIFICATE OF CORRECTION 3,772,545 Dated November 13, 1973 Rudolf A. Hat schek. I

"Patent No.

"I nv entor(s) I It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2 line 156; delete the period (J after "'outside". Column 4, line. 11, "axil" should read axial Column 9, lin 3 ,f'[thre'ugh"' should read through Signed 'ar ld sealed this 24th day of September 1974'.

(SEAL) Attest: McCOY M..'GIB'SON JR. 0. MARSHALL DANN V Attesting Officer v Commissioner of Patents uscoMM-oc scan- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,772 ,545 Dated November 13, 1973 Rudolf A. Hatschek Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 36, delete the period after "outside"; Column 4 line 11, "axil" should read axial Column 9, line 3,"?thrugh" should read through Signed; and sealed this 24th day of September 1974 (SEAL) Attest:

McCOY M. 361350: JR. I c. MARSHALL DANN. Attesting Officer Commissioner of Patents 7 FORM, po-ioso (10-69)

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3982059 *Oct 17, 1975Sep 21, 1976The Machlett Laboratories, IncorporatedFlexible cable termination
US4829235 *Apr 1, 1987May 9, 1989The United States Of America As Represented By The Administrator Of The National Aeronautics And Space AdministrationFour-terminal connector for measuring resistance of a pyrotechnic initiator
US6634896 *Aug 23, 1999Oct 21, 2003Patrick PotegaMethod and apparatus for transferring electrical signals among electrical devices
US8146867 *Jun 14, 2005Apr 3, 2012Aeroastro, Inc.Modular spacecraft design architecture
Classifications
U.S. Classification310/71, 310/346, 439/669, 310/329
International ClassificationH01R13/533
Cooperative ClassificationH01R13/533
European ClassificationH01R13/533