Extensible cable structure

BACKGROUND OF THE INVENTION

This invention pertains to extensible conductors of electricity, light or fluid between relatively linearly movable pieces of $ equipment.

Measuring and control instruments are commonly mounted in racks permitting the instrument to be removed from the front of the rack for replacement, repair, adjustment, etc. The back of the rack is frequently substantially inaccessible. Per- ¹⁰manent power, control and sensor connections are usually provided at the back of the rack so that they will be protected and not interfere with removal of the instruments. The completion of these connections to the instruments presents . _san annoying problem. ¹³

Some installations have employed rigid plug-in arrangements, which are often unsatisfactory because of misalignment, corrosion, interference by foreign matter, etc. Flexible connections are generally more satisfactory. The connecting 20 flexible conductors are most frequently bundled together to limit relative movement and in lengths sufficient to allow for necessary movement, the slack being allowed to sag. The sagging bundle may interfere with movement of the connected or other instrument and may become abraded by projections. 25 Various schemes for supporting the bundle at intermediate points have been used, including springs, arms and lazy tongs. Flat cables have been sharply bent in zigzag fashion and may be either self-supported or otherwise stiffened between the bends. Most of these alternatives have a disadvantage in occu- 30 pying a considerable space behind the instrument.

SUMMARY OF THE INVENTION

The present invention provides support for the conductor, avoids sharp bends, controls and limits flexure, protects against abrasion, provides additional electrical insulation, and provides storage in a limited space. The position of each conductor is fixed with respect to other conductors, controlling electrical interference. The structure is rugged, simple and inexpensive to manufacture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an extensible cable structure according to a preferred embodiment of this invention, showing how it is used with the cable structure extended.

FIG. 2 is a side view of the cable structure in use in retracted position.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment shown in the drawings comprises a fixed piece of equipment 1, a linearly movable piece of equipment 2, and an extensible cable structure 3 in accordance with this invention connecting the pieces of equipment. The equipment 1 comprises a permanently mounted terminal board 4 having a plurality of terminals, such as screw terminals 5 and pin type solder terminals 6, mounted thereon and permanently connected to power supplies, sensors and controls (not shown). The equipment 2 (shown in part) comprises a measuring or control instrument (not shown) mounted on a chassis 7, movable linearly toward and away from the terminal board as shown by the double headed arrow. On the chassis are terminals, as in a terminal block 8, for joining with separable terminals on free ends 9', 10', 11' of connecting wires 9, 10, 11, twisted together in a cable 12 to reduce noise, to the instrument. The other free ends 9, 10, 11 of wires 9, 10, 11 are soldered to respective control terminals 6 on the terminal board 4.

The extensible cable structure 3 comprises a self-reliant support 13 of normally plane flexible insulating material such as nylon sheet. The support 13 is slit from one end to form a central strip 14 to be fixedly mounted at a disjoined mountable end 15 upon the terminal board 14 as by screws 16. The remaining portions are slit from the other end 17 to form strips

18, 19, 20, 21 parallel to strip 14. Stripe 19, 20 are joined at the other end 17 to strip 14, and are joined to respective strips 18,21 at opposite ends 22,23 respectively to provide a pair of mirror image serpentine paths in the support. The disjoined ends of the outer strips 18, 21 are shown attached to a bar 24 mountable on the chassis 7 as by screws 25. A smooth circular or rounded hole 26 at the closed end of each slit relieves stress at such points to prevent tearing. The cable 12, following a serpentine bath from terminal board 4 to terminal block 8 along strips 14,19,18 (or 14,20,21), is affixed as by straps 27 to that normally plane surface 28 of support 13 which is remote from the terminal board 4 to further insulate and protect the wires 9,10,11 from terminals 5,6. The straps may be retained in place by notches 29 in one or both edges of strips 14,18,19, 20, 21 or by the holes 26. A shielded power cable 30, comprising wires 31, 32,33 having free ends 31', 32', 33' and 31, 32, 33 respectively connecting screw terminals 5 to power terminals (not shown) on the instrument 2, is also affixed the support 13 as by straps 27. Any conductors, such as cables 12 and 30, affixed to the support 13 are arranged in a single layer to conserve space, avoid abrasion, and control electrical interference.

The support 13 is initially attached rigidly to the terminal board 4 by screws 16 through the disjoined mountable end 15, and the free ends 9 ,10, 11, 31', 32', 33' are connected to respective terminals 6, 5. With the instrument 2 positioned away from the terminal board 4, the bar 24 is drawn forward and fastened to chassis 7 by screws 25, causing the strips 14, 18,19,20,21 of support 13 to assume a zigzag configuration, as shown in FIG. 1. The free ends 9', 10', 11' are plugged into the terminal block 8, and free ends 31, 32, 33 are connected to power terminals (not shown). The instrument 2 is then moved to its installed position close to the terminal board 4, as shown in HG. 2. The extensible cable structure 3 then occupies little space, flat against the terminal board 4 with the support 13 providing protection for the wires and cables 12, 30 from the terminals 5 (not shown), 6. There are no sharp bends in the wires and cables at any time and flexure is limited, providing small likelihood of wire breakage.

While this embodiment has the mounted ends 15 and 24 in mutually perpendicular orientation, it will be obvious that mounted end 24 could lie in the same plane as, or in a plane parallel to, mounted end 15. Other flexible conductors, such 45 as light conducting filaments and fluid conducting tubes, may be substituted for electric wires. The various types of flexible conductors affixed to the support 13 may be considered as a flat cable and are so referred to in the term, extensible cable structure,” used to describe this invention. The scope of the 50 invention is defined by the claims and is not limited to the preferred embodiment described and shown herein.