Indicia-coded electrical cable

Abstract

An electrical cable includes a sheath that envelops at least two internal conductors, and an indicia visible on the sheath is representative of the internal conductor.

Description

This invention relates to indicia-marked electrical cable.

BACKGROUND

As shown in FIG. 1, an armored electrical cable 10 used, for example, to wire buildings has insulated wires 12 encased in a helically wound steel sheath 14. To install the cable, the wires at each end of the sheath are stripped of insulation 16, and the exposed conductors 18 are connected to terminals or other wires inside of a junction box, switch box or other enclosure.

The installer knows which connections to make at each end of the cable because the wire insulations are color-coded. For example, a ground wire may have one color, and wires carrying different phases of AC power could have other colors. The insulation colors are often dictated by industry practice. A cable used for a particular purpose, such as to wire three-phase 277-volt power, typically has several (e.g., four) internal wires and a particular combination of color-coded insulations on the wires. The insulation colors may comply, for example, with the B-O-Y (brown, orange, yellow) convention, in which brown, brown and orange, or brown, orange and yellow, are used depending on the number of internal wires that need to be marked in the cable. In addition, common and ground wires in the cable may have gray and green insulations. The installer (or someone who maintains the cable after installation) can easily identify the purpose of a given cable (e.g., that it is a 277-volt cable) by the predefined combination of insulation colors that are associated with that purpose.

As shown in FIG. 2, once the installation is done, the sheath 14 and the junction boxes 20 at both ends of the cable hide the internal wires from view.

The sheath of a cable can be marked to indicate the function of the cable as described in U.S. Pat. No. 5,350,885, incorporated by reference. The markings can include color-coded coatings and patterns.

SUMMARY

In general, in one aspect the invention features an electrical cable including a sheath that envelops at least two internal conductors, and an indicia visible on the sheath and representative of the internal conductor.

One of the advantages of the invention is that someone who is familiar with the combination of indicia used on the conductors to imply a particular function for the cable can identify the function by looking only at the sheath.

Implementations of the invention may include one or more of the following features. Conductor indicia may be visible on the internal conductors. There may be at least two different conductor indicia that are visible on the internal conductors, and at least two different sheath indicia that are visible on the sheath, the sheath indicia being representative of the combination of internal conductors. The sheath indicia may be indicative of the conductor indicia on the conductors. The internal conductors may include electrical wires. The conductor indicia may include the colors of insulation on the conductors. The conductor indicia may be visible at multiple locations along the length of the conductors. The indicia may be visible at multiple locations along the length of the sheath. The sheath indicia may be the same as least one of the conductor indicia. The sheath may include a helically wound metal strip bearing the sheath indicia. The sheath indicia may include a stripe of ink around the circumference of the sheath. The indicia may be representative of a function of the cable. There may be electrical connections between ends of the conductors and terminals or other conductors, junction boxes may contain the electrical connections, and the conductor indicia may be hidden by the sheath and the junction boxes.

In general, in another aspect, the invention features a method of forming a cable by applying a sheath indicia along the length of a surface of a strip of material, wrapping the strip of material to form the sheath, and using the sheath to envelop internal conductors on which conductor indicia are visible, the sheath indicia being representative of the internal conductors.

In general, in another aspect, the invention features an electrical cable including a sheath that envelops an internal conductor, and an indicia visible on the sheath and symbolizing a gauge of the internal conductor.

Other advantages and features will become apparent from the following description and from the claims.

FIG. 1 is a side view of a cable.

FIG. 2 is a perspective view of a junction box and cables.

FIG. 3 is a side view of an indicia-coded cable.

FIG. 4 is a schematic view of a coating machine.

In an example implementation of the invention shown in FIG. 3, an MC or AC type 277-volt flexible armored cable 40 includes several internal wires, e.g., wires 52, 54 having insulations 56, 58 that are colored, e.g., brown and orange.

As shown in FIG. 3, to indicate that the cable is of the particular type, stripes of color 42, 44, and 46, are marked as stripes around the circumference of the outer surface of the sheath 48. In one example, the colors 42 and 44 are selected to match the colors of the insulations of two of the internal wires. The color 46 is selected to indicate the type of the cable, e.g., MC or AC.

A person who installs or maintains the cable can quickly and intuitively recognize the colors of the stripes 42 and 44 as the ones used for the two insulations in the particular type of cable, even though he may not be able to see the insulation on the internal wires. He can also recognize the cable as being of type MC or AC based on the color of stripe 46. Knowing the type or function of a given cable without seeing the insulations on the internal wires can save time and reduce hazards.

In FIG. 3, the stripes 42, 44, 46 are shown as three different patterns that represent respectively three solid colors: brown and orange, the colors of two of insulations on two of the internal wires, and blue, to indicate that the cable is type MC.

The sequence of three stripes is repeated all along the length of the cable, with each of the two stripes 42, 44 in each set being relatively shorter, for example two inches each, and the stripe 46 being relatively longer, e.g., twenty inches.

As shown in FIG. 4, one way to mark the sheath of FIG. 3 with the colored stripes is to coat successive sections of a steel strip 62 with colored ink as it comes from a feed roll 60 and just before the strip enters a forming machine 64 where it is convoluted. One good way to apply the ink is by spraying, but the ink could also be applied using wipe, drip, brush, transfer wheel, or transfer roll devices. Multiple coating machines can be provided in sequence along the production line to coat successive ones of the stripes. Or a single coating machine 66 capable of coating different ink colors can apply the colors in succession.

In the case of a single coating machine that applies the ink “on-the-fly” to the steel strip just before it enters the forming (convoluting) machine, the coating machine must be able to switch coating colors quickly and to apply and cure the ink in a short time between when the strip arrives at the coating machine and when it is delivered into the forming machine.

One way to achieve the color switching is to provide reservoirs of liquid ink 68, 70, 72 from which ink can be withdrawn to the coating station 69, and a delivery mechanism 71 that allows rapid switching among the different ink reservoirs 68, 70, 72. The delivery mechanism includes pumping equipment and valving that is controlled by an electronic controller 73 to accomplish the switching in accordance with a predetermined sequence of colors to be applied.

In addition, the composition and characteristics of the ink and the manner in which the ink is maintained in the machine should be arranged so that the cured ink imparts an easily visible marking to the sheath of the cable. The solids in the ink can be made to remain evenly suspended in the liquid carrier until the ink is applied to the sheath, by continuous mixing.

A variety of inks can be used. The inks could be water-based, acetone-based, or uv-cured. Epoxy coatings, powder coatings, paints, tapes, or films could also be used. An example is a water-based ink comprising a mixture of water, polymers, pigments, 2-butoxyethanol (<0.003), 1-methyl-2-pyrrolidinone (2.5), 2-butanone (<0.5), and N,N-diethylethanamine (<0.5) and available from Performance Coatings Corporation of Levittown, Pa. (The numbers in parentheses represent percentages by weight.)

Other embodiments are within the scope of the following claims.

Although the colors of the markings on the sheath may be identical to the colors on the insulations of the corresponding internal wires, the colors may also differ, for example, by any one or a combination of measures of color, such as hue, saturation, luminance, or intensity. It is useful to choose the combination of sheath colors so that they may be recognized intuitively by a person who is familiar with the color combination of the internal wires that are associated with a particular type of cable. The sheath colors could be different from but indicative of the internal colors. For example, if the internal colors are pink, plum, and brown, the external colors could be red, purple, and black.

As in the example given above, it may not be necessary to include all of the internal colors on the sheath because a subset of the colors may suffice to indicate the type of cable. For example, if the internal colors are red, white, green, brown, and black, it may be sufficient to show red, white, and brown on the sheath. On the other hand, all of the colors of the internal colors may be shown on the sheath. In the case when fewer than all of the colors are shown on the sheath, the ones that are not shown can be ones that identify internal wires in a way that is not unique to the type of cable being marked. For example, cables commonly use internal wire insulation that is gray, green, or white to indicate common conductors or equipment grounds. Those colors might not be included in the colors on the sheath because they do not convey as much information to the observer as the other internal wire insulation colors do.

The patterns in which the internal wire insulation colors are marked on the sheath need not be circumferential stripes of equal length along the sheath. The stripes could be of different lengths for different colors and the boundaries of the stripes could be at different angles to the length of the cable rather than perpendicular as in FIG. 3.

Rather than being circumferential stripes that intersect the longitudinal axis of the cable, the colors could be provided continuously along the length of the cable, for example as continuous longitudinal stripes. The longitudinal stripes could be repeated around the circumference of the cable so that the orientation of the installed cable about its longitudinal axis would not affect an observer's ability to see the combination of colors. Longitudinal stripes would not have to be continuous but could be interrupted periodically along the length of the cable. The longitudinal stripes could be coated on the sheath after the strip has been convoluted. A wide variety of patterns other than stripes could also be used, for example, spots or symbols.

The sections of cable that are not marked to indicate the colors of the internal wires could be left plain, for example, the plain steel of a typical helically wound armored cable. Or those sections could be colored in a manner that did not relate directly to the colors on any of the internal wires, as in FIG. 1 where color 46 indicates the type of the cable (MC or AC for example).

The combination of markings need not all be colors nor need any of them be colors. One or more of the markings could be in the form of patterns of a single color, or markings other than colors, for example, embossing or engraving on the sheath. Such patterns may be more durable and easier and cheaper to apply than colors.

Instead of colors, the internal wires could be identified by patterns or other markings and those patterns or markings could be indicated or implied by the sheath markings.

The sheath need not be helically wound, but could be any other kind of metal sheath, such as round or box conduit, solid flexible sheathing that has been formed with helical or other bendable features, or other continuous sheathing.

The sheath need not be metal but could be other materials such as plastic or cloth.

The cable could be designed for purposes other than power distribution.

The cable could be marked in a variety of ways other than coating with ink. For example, the markings could be painted, silk-screened, sprayed, enameled, printed, embossed, anodized, engraved, or cut, or applied using powdered metals. The markings need not be applied to the strip prior to helical winding but could be applied to the sheathing or the material from which the sheathing is made either before the sheathing is formed, before the internal wires are encased in the sheathing, or after they have been encased.

If the strip is coated prior to convolution, the coating need not be done in-line as described above but could be done off-line and then reloaded onto a take-up reel for later use.

When the marking is done by coating ink stripes along the length of a metal strip, the stripes need not be the full width of the strip. The stripe could be narrow and positioned at any place across the width of the strip. It is useful to position the stripe in the middle of the strip so that when the strip is convoluted the coloring appears on the ridges of the sheath rather than on the troughs. It is also useful to make the stripes narrower than the whole width of the strip so that the continuity of the ground formed by the successful convolutions along the length of the finished sheath are not interrupted by the ink at the edges of the strip. Or conductive ink can be used if the stripe is to span the whole width of the strip.

When different types of cable are to bear combinations of markings, the markings on respective cables may bear a relationship to one another to indicate common features of the cables as by using blue to indicate MC cables. Or, by way of another example, various 120-volt power cables could all bear purple stripes in addition to any stripes needed to represent the colors on the internal wires.

Other features of the internal wires can be represented by the markings on the sheath, for example the gauge of the wires, the type of insulation and the type of wires. 12-gauge wire covered with brown insulation, for example, could be indicated by printing a repeated series of brown numbers 12 along the strip instead of a continuous stripe, or by adding an additional colored stripe (e.g., white) around the circumference of the sheath.

In a specific example, a high voltage 12-gauge four-wire MC cable in which two of the wire insulations are brown and orange could be marked by a repeated set of stripes in which one stripe is formed of brown 12s, one stripe is formed of orange 12s, and one longer stripe is a continuous blue.

Claims

1. A 3-phase, 277-volt armored power cable, comprising: a first electrical conductor have brown colored insulation;a second electrical conductor having orange colored insulation; anda helically wound metal strip enveloping the electrical conductors and bearing brown and orange colored indicia.

2. The cable of claim 1 wherein the helically wound metal strip further bears a third indicia indicating MC or AC type cable.

3. The cable of claim 1 wherein the colors on the helically wound metal strip differ in hue, saturation, luminance, or intensity from the corresponding colors on the conductor insulations.

4. The cable of claim 1 wherein the indicia comprise circumferential stripes.

5. The cable of claim 1 wherein the indicia comprise longitudinal stripes.

6. The cable of claim 1 wherein the indicia comprise brown colored numbers corresponding to a gauge of the first electrical conductor and orange colored numbers corresponding to a gauge of the second electrical conductor.

7. An armored cable, comprising: a plurality of electrical conductors, said plurality of electrical conductors comprising at least first and second electrical conductors;the first electrical conductor having a first colored indicia on an insulation material surrounding said conductor;the second electrical conductor having a second colored indicia on an insulation material surrounding said conductor; anda sheath surrounding the insulated electrical conductors and bearing third, fourth and fifth indicia, said third and fourth indicia being the same as said first and second colored indicia, said third and fourth indicia representative of a function or gauge of at least one of the plurality of electrical conductors, said fifth indicia representative of a type of said armored cable.

8. The armored cable of claim 7, wherein the third and fourth indicia comprise third and fourth colors that are the same as the colors of the first and second colored indicia.

9. The armored cable of claim 7, at least one of the third and fourth indicia is representative of a gauge of one of the first and second electrical conductors.

10. The armored cable of claim 7, wherein the sheath is plastic.

11. The armored cable of claim 7, wherein the third indicia further comprises text.

12. The armored cable of claim 7, wherein the sheath comprises a helically wound metal strip.

13. The armored cable of claim 7, wherein the type of said armored cable is selected from the list consisting of AC cable and MC cable.

14. An armored cable, comprising: a plurality of electrical conductors including at least first and second electrical conductors;the first electrical conductor having a first colored indicia on an insulation material surrounding said conductor;the second electrical conductor having a second colored indicia on an insulation material surrounding said conductor; anda sheath surrounding the insulated electrical conductors and bearing third, fourth and fifth indicia, said third and fourth indicia comprising colors that are the same as, and representative of, the first colored indicia and the second colored indicia, said fifth indicia representative of a type of said armored cable.

15. The armored cable of claim 14, wherein at least one of the third and fourth indicia is representative of a function of at least one of the first and second electrical conductors.

16. The armored cable of claim 14, at least one of the third and fourth indicia is representative of a gauge of one of the first and second electrical conductors.

17. The armored cable of claim 14, wherein the sheath is plastic.

18. The armored cable of claim 14, wherein the third indicia further comprises text.

19. The armored cable of claim 14, wherein the sheath comprises a helically wound metal strip.

20. The armored cable of claim 14, wherein the type of said armored cable is selected from the list consisting of AC cable and MC cable.