US3210722A

US3210722A - Helical spring type connector

Info

Publication number: US3210722A
Application number: US233729A
Authority: US
Inventors: Robert H Johns
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-10-29
Filing date: 1962-10-29
Publication date: 1965-10-05
Anticipated expiration: 1982-10-05

Description

Oct. 5, 1965 R. H. JOHNS HELICAL SPRING TYPE CONNECTOR Filed 001:. 29, 1962 lNVENTR United States Patent 3,219,722 HELKCAL SPRING TYPE CUNNECTOR Robert H. Johns, 815 Fetters Mill Road, Bryn Athyn, Pa. Filed Get. 29, 1962, bier. No. 233,729 7 Claims. ((31. 339256) This invention relates to what the name implies, a helically coiled spring of the type that has long been serving as a quickly attachable and detachable solderless electrical connector. An object is to provide a device of this sort which is capable of more firmly holding a wire inserted and moved transversely between the convultions of such a coil and less likely to be accidentally ejected. Another object is to provide Simultaneously with the foregoing, a coil which may be easily grasped, with less danger of the fingers slipping. Still another object is to provide a support for such a coil, by means of which it may be conveniently mounted in an upright position in a perforated board, especially when the perforations are not of precisely the same diameter.

A helix of spring metal is said to be an early type of solderless electrical connector. During its long existence it has not been satisfactory because of a tendency for the clamping portions of the convolutions to function as inclined planes with a component of the clamping pressure tending to expel an inserted wire extending transversely of the axis of the helix. Now this tendency has been eliminated and the inserted wire is now held in position as soon as the transverse conductor has been moved past the axis of the helix with no tendency to be expelled as was the case before.

According to this invention each convolution of the spring helix has straight sides and approximates a polygon, preferably with four sides. An inserted wire may now be pushed transversely into the new coil to abut one of the sides of a quadrilateral convolution as a stop. As long as the inserted wire is pushed into the coil to a position beyond the longitudinal axis of the coil, there will be no tendency for it to be expelled.

Referring to the drawing,

FIG. 1 is a side view through one embodiment of this invention inserted in a perforated plate.

FIG. 2 is a top plan view of a coil of FIG. 1 type without a supporting plate.

FIG. 3 illustrates a wire inserted in the upper convolutions of a coil of FIG. 1 type before it has been moved past the coil axis.

FIG. 4 shows the wire fully inserted into the convolutions of FIG. 3.

FIG. 5 is a top plan view of the inserted wire and coil of FIG. 4 turned 90.

The coil in FIG. 1 comprises an upper portion of approximately polygonal convolutions and a lower portion 11 formed of circular convolutions of decreasing diameters, inserted in a perforation 12 in a plate or foundation 13. A timed steel music wire has been found suitable for the portions 1% and 11. To obtain the bends having a permanent set for the upper polygonal convolutions, the angles are formed by winding the wire tightly on a mandrel whose cross-section is an equilateral triangle.

The lower portion 11 in FIG. 1 is tapered to facilitate this lower portion expansively clamping the coil within a circular recess 12. To effect such clamping the coil is pushed and turned or twisted into the hole 12 in a direction tending to reduce the diameters of the tapered circular convolutions. Friction between the recess 12 and the lower portion of the spring tends to wind the tapered convolutions tighter and reduce their diameters, permitting the lower portion 11 to penetrate deeper into the hole 12. Then on cessation of the torque the tapered layers expand against the walls of the perforation to hold the entire coil in its upstanding position normal to the plane of the plate 13. To employ a clockwise twist for inserting the connector into a perforation, the spring coil is wound such that the direction of the spiral is the same as that of a left hand thread. A connector is removed from a perforation in plate 13 by imparting a torque in the same direction as that used in inserting it, which also tends to reduce the diameter of the lower tapered portion and free it from the perforation.

By virtue of the length of contact between the convolutions of the lower portion of the spring and the walls of the perforation, and the uniform expansive force between them, the tapered lower portion of the spring affords a secure mounting device for the electrical connector upper portion.

The relative diameters for the wire size and for the inserted or clamped Wire in FIGS. 3 to 5 are only examples.

In FIG. 3 the conductor 14 is clamped between the

convolutions

15 and 16. A side 17 of the polygonal co-nvolution opposite the place of entrance of the wire 14 into the helical coil serves as an abutment wall limiting further movement of the conductor transversely of the helix. An essential feature of the polygonal convolution is that it permits the entry of an inserted wire all the way to the polygon side 17, with the resulting tilt of the longitudinal axis of the connector. This tilt provides the cramping force that retains the inserted wire in stable equilibrium in the spring. A wire inserted into a conventional spiral spring cannot penetrate to such a depth without permanently deforming the spring, since the length of the spring element to which a torsional stress of the spring is chiefly confined becomes shorter as the inserted wire is pushed farther into the helix. The stress of any spiral or helical spring is applied to an element of the spring or are of a convolution as a torsional stress. As an inserted trans verse wire passes the longitudinal axis of a helical spring of circular cross-section and advances farther into the spiral, it must twist the spring open wider, yet at the same time, the length of arc of a circular convolution to which this greater torsional stress is applied decreases. This increasing torison on a decreasing length of arc will twist the spring material past its elastic limit in torsion if an inserted wire is pressed transversely through the spiral spring against the opposite side. In the present invention each convolution of the spring is a polygon. The torsional stress exerted on the spring when a wire is inserted transversely into the spring is distributed throughout the entire length of the polygon side 17. This allows. the inserted wire to be pushed to a position against side 17 as an abutment without building up prohibitively large torsional stresses in the spring material. A gripping tendency of the polygonal convolutions upon an inserted wire is produced by the torsion of polygonal side 17, illustrated in FIGS. 3 and 4. The vertical motion of side 17 also imparts a tilt to the

convolutions

15 and 16 below and above the inserted wire, bringing

vertices

18 and 19 in FIG. 5 into the gap in the spring as barriers opposing the transverse motion of the inserted wire.

The angle of the vertices between polygon sides is preferably more than 60 and less than 90 or about This angle is what causes the vertices of the several convolutions to be not aligned longitudinally of the spring. The reason for these angles being substantially uniform and of the approximate value stated is believed to be due to the 60 bends on the winding fonn or mandrel, causing a permanent set to occur in the Wire being wound after it is removed from the form which has a cross section of an equilateral triangle. The aforementioned wire known as music wire or piano wire will give the results described. Other types of spring wire will give results with the vertices having some other value more than 60 and less than 90 but nevertheless capable of causing the several vertices to be out of alignment longitudinally.

FIGS. 3 to 5 do not show the tapered lower portion for the sake of simplicity.

Perhaps a chief advantage of the present invention is the provision of a spring type electrical connector that affords a secure clamp on the conductors attached to it. A second new result is the provision of a tapered few circular convolutions constituting a firm support for the electrical connector above a circular perforation. A third new result is the formation of the several vertices in nonalignment longitudinally of the spring, providing a better finger and thumb grip on the upper coil portion 10. While the convolutions are generally of four sides as illustrated, the terms polygon and quadrilateral are be lieved appropriate although the four sides of a convolution are not strictly closed nor coplanar. A feature is believed to be the localization of torisional stresses to the side functioning as an abutment, an adjacent side at one end being bent upward while that at the opposite end is bent downward by the inserted wire, resulting in a torsional clamp by the abutment side and its adjacent convolutions.

I claim:

1. The combination with a helical metal spring type connector having each of a plurality of its convolutions of polygonal shape and having more than three sides for a substantial portion of its axial length, of an electrical conductor extending through said helical connector generally normal to the axis of said helical connector and contiguous to one of said polygon sides of said connector on an inner side thereof between such side and the axis of said connector, whereby on insertion of said conductor between connector convolutions and on relative lateral movement between said conductor and connector across and beyond the axis of the connector, the conductor is held more securely within the connector than would be the case were the connector convolutions of circular shape or were the conductor not moved laterally well past said axis of said helical connector.

2. In a process for moving an elongated substantially straight electrical conductor transversely of itself between polygonal convolutions of a helical spring connector of electrically conductive metal wire of generally circular cross section, the combination therewith of the improvement for enhancing the clamping force of the convolutions contiguous said conductor on the conductor, said improvement comprising transversely moving said conductor past the axis of said connector and toward a side of said connector substantially opposite the place of entry of said conductor into said connector whereby the contiguous and other convolutions slope in a converging direction toward the place of entry of the conductor into the connector after said conductor has moved past said axis.

3. A process according to claim 2 which includes moving said conductor transversely between convolutions until said conductor substantially abuts a side of the connector polygon convolution opposite the approximate location at which the conductor entered said connector.

4. A helical spring type connector having a hollow axial portion across which an electrical conductor may be moved when inserted between adjacent coaxial convolutions of the helical spring, said spring connector containing the improvement for better holding at least one such conductor against coming out of the connector accidentally by movement of the conductor laterally, said improvement comprising at least three generally similar bends in each convolution whereby each such convolution is of polygonal shape and is adapted to have any one of its generally straight sides to constitute an abutment on its inner side for a conductor inserted laterally of itself and the connector and moved past the axis of said connector when said abutment side gets under a torsional stress due to one convolution side adjacent to the abutment side passing under and the other adjacent convolu tion side passing over said conductor.

5. A helical spring type connector according to claim 4 having convolutions of generally quadrilateral shape with the vertex angle between each pair of adjacent sides being of more than 60 and less than 6. A connector according to claim 4 in which said connector is secured to a generally flat plate with the helical connector axis upstanding and generally normal to said plate.

7. A helical connector according to claim d in which each convolution is of general quadrilateral shape except in an end portion of said connector having circular convolutions which are tapered about 5 to a projected axis of said connector whereby the tapered end portion may be inserted in a generally cylindrical perforation of a plate and rotated in a direction tending to reduce the diameter of at least one of the tapered circular convolutions when friction tends to wind the tapered convolutions tighter within the walls of said perforation.

References Cited by the Examiner UNITED STATES PATENTS 317,887 5/85 Thompson 339256 640,479 1/00 Mills 339--254 1,225,630 5/17 Hicks. 1,780,826 11/30 Kuhn 339112 1,946,889 2/34 Wessel. 2,124,461 7/38 Challet 33925 6 2,216,201 10/40 Keller 29155.55 2,473,570 6/49 Chirelstein 29155.55 2,957,218 10/60 Sponsel 24-66 FOREIGN PATENTS 111,126 11/17 Great Britain.

OTHER REFERENCES Unusual Uses for Helical Wire Springs, from Product Eng. Design Manual, 1959, pages 328 and 329 (page 329 only relied upon).

JOSEPH D. SEEKS, Primary Examiner.

Claims

4. A HELICAL SPRING TYPE CONNECTOR HAVING A HOLLOW AXIAL PORTION ACROSS WHICH AN ELECTRICAL CONDUCTOR MAY BE MOVED WHEN INSERTED BETWEEN ADJACENT COAXIAL CONVOLUTIONS OF THE HELICAL SPRING, SAID SPRING CONNECTOR CONTAINING THE IMPROVEMENT FOR BETTER HOLDING AT LEAST ONE SUCH CONDUCTOR AGAINST COMING OUT OF THE CONNECTOR ACCIDENTALLY BY MOVEMENT OF THE CONDUCTOR LATERALLY, SAID IMPROVEMENT COMPRISING AT LEAST THREE GENERALLY SIMILAR BENDS IN EACH CONVOLUTION WHEREBY EACH SUCH CONVOLUTION IS OF POLYGONAL SHAPE AND IS ADAPTED TO HAVE ANY ONE OF ITS GENERALLY STRAIGHT SIDES TO CONSTITUTE AN ABUTMENT ON ITS INNER SIDE FOR A CONDUCTOR INSERTED LATERALLY OF ITSELF AND THE CONNECTOR AND MOVED PAST THE AXIS OF SAID CONNECTOR WHEN SAID ABUTMENT SIDE GETS UNDER A TORSIONAL STRESS DUE TO ONE CONVOLUTION SIDE ADJACENT TO THE ABUTMENT SIDE PASSING UNDER AND THE OTHER ADJACENT CONVOLUTION SIDE PASSING OVER SAID CONDUCTOR.