US3003018A - Retractile cords - Google Patents

Description

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RETRACTILE CORDS Filed Aug. 24, 1959 2 Sheets-Sheet 1 :T yg T-- "M u /6 .g J4 f7 f3 f1? (fe/z for.'

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RETRACTILE CORDS Filed Aug. 24, 1959 2 Sheets-Sheet 2 United States Patent "ice p 3,003,018 RETRACTILE CORDS John Brown Cook, North Haven, Conn., nsslg'nor to The Whitney Blake Company, Hamden, Conn., a corporation of Connecticut Y Filed Aug. 24, 1959, Ser. No. 835,769 3 Claims. (Cl. 174-69) This invention relates to retractile cords suitable for use in various appliances, such as telephones, coffee pots and the like in which the appliance ismoved from time to time, and in which the retractile cord is designed to take up the slack and avoid the unsightly appearance incident to the use of ordinary cords or iacketed conductors. t

The term cord refers to one or more conductors, such as one or morelengths of llexiblecopper wire, which are enclosed within a jacket formed of suitable insulating material, to provide what is often referred to as a jacketed conductor. A retractile cord is a cord of helical shape andelastic,: to'the end that the helical cord will return to its original position after extension. f

It is an object of the present invention to provide a retractile cord of greater compactness, that is, one in which the helix, when retracted, is shorter with respect to its extended length than in the casefof the usual retractile cord.

According to this invention, the conductors of the retractile cord are arranged side by side in a plane which is generally perpendicular to the axis ofthe helix, thus providing a jacketed conductor which is ribbon-like or flat in appearance. In the usual multi-conductor type of each other thus providing a cord of improved appearance. r'

Still another object is to provide a retractile cord of improved retractile properties.

Accordingto the present invention, .the inner portion of the jacketed conductor is crimped in a sinusoidal manner so that the alternate ridges and depressions will nest in the corresponding ridges and depressions of adjacent convolutions. Furthermore, this crimping substantially increases the extensibility over a fiat retractile cord which'is not crimped, and at the same time improves the retractile properties of the cord.

In the ordinary retractile cord wherein the jacket is in circular cross section, the retractile properties are, generally speaking, a function of the diameter of the helix with respect to the diameter of the jacketed conductor,

the lower the diameter ratio, the greater being the resilience of the helix. As a result, the ratio of extensibility is generally of the order of 4 or 5 to l.

By making an uncrimped at retractile cord structure having an increased diameter ratio, the ratio of Yextensibility can be increased substantially since,in theory, the extended length would be the uncoiled length of the innermost element, which is to say, the product ofthe inner diameter, the number of convolutions, and pi. Actually however, this result cannot be obtained since the uncrimped flat configuration prevents the convolution'y from unwinding with the result that the ratio` of extensibility is more of the order ofk 10 or 12 to l.

However, I have found that by crimping the inner portion of each convolution, that the extensibility can be very considerably increased; as a matter of fact, in certain n 3,003,018 lPatented Oct. 3, 1961 diameter ratios, or proportions of helix diameter to jacket i width, the cord is extensible to a length in excess of the theoretical but unattainable maximum indicated above, which is the function of the inner diameter of the helix, and that this increased extensibility kis attained without introducing additional winding stresses in the cord.,

A further object of my invention is to provide` vfor a portable appliance orthe like an improved storage ar rangement so that the'appliance and the cord will prt?r sent a neat and self-contained appearance; a A

Other objects, features and advantages will become apparent as the description. proceeds.

With reference nowy to the drawings in which like reference numerals represent like parts:

FIG. 1 is a side elevation of an appliance `which ine corporates a `preferred embodiment of my invention;

FIG. 2 isa plan view of FIG. 1; I 1 j FIG.\3 is an elevation of the retractile cord of FIG. l in its retracted position; ,y

FIG. 4k is aplan view'of FIG. 3;

FIG. 5 is a section taken along line 5-5 of FIG. 4'; AFIG. 6 is an elevation `of the retractile cord in its extended position; and i FIG. 7 is a section showing a modification. j

In FIGS. l and 2 an-appliance such ras a telephone instrument 10 is shown which comprises a basell and a hand set 12 which is removably received by a cradle 13. The hand set is electrically connected to the base 11 by a retractile cord 14 having an upper end portion 15, a lower end portion 16 andan intermediate portion17 in the form of a helix. Although the end portions 15 and 16 may also be of the helical form to be described here inafter, it is preferable lto so manufacture the cord that these arestraight anduncrimpcd as shown in FIGS. l and 2.

` Ther retractile cord 14 rests on a platform 28 which projects outwardly from the base 11, and a suitable piu 19 may project upwardlyfrom the base through the helix 17 in order to facilitate the stacking of the core by its own resilience when the hand set 12 is returned to its cradle 13.

As shown in FIG. 5, the retractile cord .14 comprises a plurality of metallic conductors which are arranged side by side in ar common plane,'four conductors 20, 21, 22 and 23 being shown for the purpose of illustration. The conductors are maintained in their side b'y side position and insulated from each other .by ra jacket 24 which provides a cord of ribbon like appearance which could be described as flat, except for the crimps 26. The conductors 20 to 23 may each be provided with lindividual jackets, not shown, in the customary manner,

ing the rdesired retractile .or resilient properties. Ani

example of a suitable .jacket composition is vsetforth in co-pending application of Edgar L. Love, Serial No.

659,698, tiled VMay 16,' 1957,'together withy the curingk characteristics thereof. Where individual jackets 'are `also provided these may be of a suitable resin or rubbery like composition, or even of fabric, according to the usual practice in the jacketed conductor art.

The cord is extruded in straight or uncoiled form so that for a given section the length of all of the metallic conductors r20 to 23 is the same. Therefore, when the cord'is wound into a helix wherein the general plane of the conductors of each convolution is substantially perpendicular to thel axis of the helix, the inner cords 20, 21 and 22 will tend to buckle.

According to my invention, the inner portion 25 of the cord` is providedwith crimps 26 which take up the excess length ofthe inner cordsy in the jacket, the crimps providing both improved retractile properties and facilitating the stacking of the cord.

n VT he crimps are of similar shape and are equidistantly epaced from each other so'that when in contracted form the crimps of one convolution will nest with the crimps of adjacent convolutions. The crimps are applied both to the metallic conductors Ztl to 23 and to the jacket 24 so that the insulation thickness will be substantially uniform. The crimping is done after the cord has been extruded and as it is being placed on a suitable mandrel for curing. The mandrel preferably is a grooved mandrel the inner portions of the grooves being also crimped so as to insure that the crimps in the jacket will be maintained during curing, to the end that the jacket is given a set both in the helical form and in the crimped form.

By virtue of the fact that the uncrimped length of the inner conductors is equal to the length of the outer conductor 23 the ratio of extensibility is considerably increased over that of an uncrirnped flat cord which is extruded in helical form. In the latter instance, of course, the maximum theoretical extension length is the uncoiled length of the innermost conductor. However, as pointed out above, this degree of extensibility cannot be attained because the innermost filament of the helix tends `to maintain the same radius of curvature with the result that the extensibility is limited to that which arises from the torsional flexure of the jacketed cord.

However, when the flat cord is crimped, as in the present invention, additional extension is provided by the fact that the crimped inner filament permits an un- Winding or an increase in the radius of curvature.

As an example, the helix of FIGS. 3 and 4 may have an outer diameter of 2% inches, an inner diameter of "1% inches, and a convolution thickness of approximately .'15 inch. A coil comprising 51/6 convolutions can be extended to 341/2 inches which is to be compared with a theoretical extension of 28 inches in an uncrimped iiat coil, as determined by the inner diameter, and with a theoretical'maxirnum of 381/2 inches if the outer filament is taken as controlling, or 361/2 inches if the length of the outer conductor 23 is taken as controlling.

The 341/2 inches of extension is about double the extension that can be attained without the crimping, where the extension is limited to the torsional deformation of the cross section of the cord. In other words, the additional unwinding action that is permitted by the crimping adds about 100% to the extension.

Furthermore, since this additional extension results in a iiattening of the crimps, which represents either an elongation of the inner filament of the jacketed material or a flexural deformation of the cross section, the crimping in itself introduces an element of Velasticity resulting in improved retractile properties.

Therefore, the present invention provides not only increased ratio of extensibility, but also an improvement in retractile properties. Furthermore, as pointed out above, the crimps provide a means of nesting the convolutions with respect to each other so as to provide a -helix or stack which will retain its right cylindrical configuration of uniform diameter, thus providing a much neater appearance than if the crimps were not present.

The advantages of the present invention can be obtained with either'a greater orlesser number of metallic conductors. However, the retractile properties of the cord are primarily a function of the size, shape and proportions of the jacket material and of the helix, with the result that the location of the one or more conductors within the jacket cross section does not affect the results obtained. In other words, where only two conductors are necessary, these two conductors could be conductors 22 and 23 or 20 and 21, or any other combination of the four conductors shown, the other two being eliminated. This is not to say that the width or the proportions of the jacket may not be varied according to the number of conductors provided in the jacket, but, as a general pro position, I have found that a flat crimped cord provides a very definite advantage over the cord of circular cross section of the prior art. Where more than one conductor is required, the desired jacket cross section is best obtained by disposing the conductors in side by side relationship.

Although my improved retractile cord is of utility and various applications, as indicated above, it is of particular utility in connection with an appliance such as a telephone, coffee pot, clock, and the like in which the selfstacking characteristics of the cord may be utilized by providing a definite location for the cord when retracted, or for that portion Vof the cord which is retracted. in the application illustrated, the base of the telephone provides a platform for the Yreception of the cor-d. In the case of certain other appliances, however, as shown in FIG. 7, a bell-shaped base 3d, of a lamp, for instance, is provided Which provides -a cavity 3i for the reception of a tlwo conductor appliance cord 32 which is manufactured in accordancewith the principles of this invention, the plug end 33 of the cord extending outwardly through a slot 34 in the base, and the unused portion of the cord resting on the table 35 or other surface on which thev appliance itself is supported, the helix 32 being concealed by the bell-shaped base. ln such an arrangement, the free or plug end of the cord can be either at the top or the bottom of the helix.

' Although only a preferred embodiment of my invention has been shown and disclosed herein it will be understood that various modifications and changes can be made without departing from the scope of the invention as pointed outby the appended claims.

I claim:

l. A retractile cord comprising a plurality of parallel conductors valigned side by side, a jacket surrounding same to provide a flat, jacketed cord, said cord being arranged in a helix the axis of which isperpendicular to the general plane of the cord, and the inner edges of the convolutions being crimped toprovide indentations which register with the indentations of adjoining convolutions so that said .convolutions will nest within each other.

2. A retractile cord comprising a metallic conductor covered by a jacket formed of a cured elastomer, said cord being arranged in helical shape, and being at in cross section, with the iiatness of the cord being in a plane substantially perpendicular to the axis of the helix, the inner portionsof said cord being crimped lto permit a partial unwinding of the helix in vorder to provide in creased extensibility.

3. A retractile cord comprising a plurality of metal conductors of uniform length aligned side by side in parallel relationship, a jacket formed of a cured elastomer surrounding same to provide a flat jacketed cord, said cord being arranged in a helical shape With the plane of said conductors approximately perpendicular to the axis of the helix, the innermost one of said conductors and that portion of the jacket which surrounds the same being crimped so as to permit elongation of said innermost conductor and its surrounding jacket when said helix is extended, the crimping of said jacket imparting resilience to said retractile cord when extended.

References Cited in the le of this patent UNITED STATES PATENTS 1,865,069 Allen June 28, 1932 2,609,417 Cox et al. Sept. 2, 1952 2,678,779 Bellmer May i8, 1954 2,704,782 Ames Mar. 22, 19,55

y FOREIGN PATENTS 762,343 Great Britain Nov. 28, 1956 1,155,793Y France Dec. 2, 1957

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