US2883641A - Automatic wire gripping terminal - Google Patents

Description

April 21, 1959 v. R. DESPARD 2,883,64L

AUTOMATIC WIRE GRIPPING TERMINAL Filed July 2, 1956 INVENTOR VICTOR R. DESPARD ATTORNEYS United States Patent AUTOMATIC WIRE GRIPPING TERMINAL Victor R. Despard, Syracuse, N.Y., assignor to Pass & @zymour, Inc., Syracuse, N.Y., a corporation of New ork Application July 2, 1956, Serial No. 595,405

8 Claims. (Cl. 339-216) This invention relates to electric wiring devices and more particularly to automatic conductor gripping terminals for use with such devices.

It is a general object of the present invention .to provide a novel and simple but effective automatic conductor gripping terminal for electric wiring devices.

ing with a single folded wire spring whereby circuits may be easily forwarded.

Still another important 'object of the invention con- .sists in the provision of a dual spring wire releasing device of extreme simplicity.

A further important object of the invention consists in the total absence of fastening means for the parts of the conductor gripping terminals other than thecover for the general area in which they are mounted.

A'still further object of the invention consists in the arrangement of the wire spring releasing means to prevent destructive bending of either spring of a dual unit if excess tension is placed on a connected conductor in an endeavor to withdraw it without releasing the spring.

Other and further objects and features of the invention will be more readily understood upon a consideration of the accompanying drawing and following specification wherein is disclosed a single exemplary embodiment of the invention, with the understanding that such modifications thereof and substitutions of equivalents may be .made therein as fall within the scope of the appended claims without departing from the spirit of the invention.

In said drawings: Fig. 1 is a .rear elevation of a moulded, box-mounting .type of lamp holder fitted with automaticconductor gripping terminals constructed in accordance with the present invention;

Fig. 2 is a fragmentary section on :an enlarged scale through the lamp holder body and one of the terminals taken on the plane of line 2-2 of Fig. 1;

Fig. 3 is a top plan view of one of the terminals apart from the lamp holder base and showing the three parts thereof in assembled relationship;

.Fig. 4 is a perspective View of the assembled parts of a terminal showing two conductors gripped thereby;

Fig. 5 is a sectional view similar to Fig. 2 illustrating the manner in which the conductor wire gripping is ef- .fected;

Fig. 6 is a view similar to Fig. 5 but showing the wire releasing mechanism in operation; and

lCe

wiring and the wiring devices forming the terminals thereof has emphasized the need for some means for attaching the wire ends to wiring devices other than the well known screw type terminals, where the end of the wire after being bared of its insulation was formed into an open loop and clamped beneath the head of a binding screw. The time consumed in this operation is considerable, even if all goes well, but if the screw is inadvertently withdrawn too far and dropped in the litter of a new construction operation, if the proper size screw driver is not at hand nor the proper tool for forming the open eye in the end of the wire, then considerable additional time may be expended.

All of the above and other considerations warrant the expenditure of a small additional percentage in the cost of a wiring device which is more than recovered in the saving in labor if the wire can be automatically gripped and connected by the mere operation of poking its bared end through a hole or opening in the housing of the Wiring device.

Various forms of automatic wire gripping devices have already appeared, but to some degree they all suffer either from excessive cost of manufacture and assembly, in that they necessitate the use of expensive materials capable of both conducting electricity readily and having good spring characteristics, or they occupy too much space for some uses. About the only suitable material for the dual purpose of conductivity and springiness is .some form of Phosphor bronze which is relativelyexpensive compared with other materials used ,in the construction of terminal devices.

In accordance with the present invention such costly materials are eliminated by using an open sided, conductorend receiving channel of conducting material which can be brass, copper or ordinary bronze, in which the end of the conductor wire lies, and is held therein and pressed against the bottom of the channel by means of a simple steel wire spring bent into a simple folded shape to be most effective in the performance of this duty.

The invention is illustrated in connection with a moulded, box-mounting ,type of lamp holder, commonly referred to as a box cover socket, but obviously this is merely by way of illustration for the terminal device is capable of use in many other positions where suflicient housing depth is available to accommodate it.

Referring now to the drawings, and first to Figs. 1 and 2, it will be seen that the wiring device comprises a moulded, circular base or housing 10 suitably perforated at 11 and 12 to accept mounting ,or fastening screws which secure it down against a junction or fixture box of the circular or octagonal type for which it acts as a cover. The fragmentary section of Fig. 2 illustrates the socket sleeve 13 projecting integrally and centrally from the front face of the circular base shown in 'Fig. 1 and formed of suitable insulation material as porcelain or synthetic resin. The socket sleeve is internally threaded at 14 during the moulding operation to directly accommodate the threaded screw shell of an incandescent lamp for mechanically positioning in-the socket. An open channel or groove 15 longitudinally extended through the threaded portion accommodates a springy contact strap 16 which is sufficiently bowed to extend into the socket opening to engage the crests of the threads on the screw shell of the lamp and make contact therewith. Obviously there is also acentral lamp contact, not shown, and as illustrated in Fig. 1 the switch mechanism 18, of the pull chain type, serves to permit control of the flow of current to the lamp as desired.

Two of the automatic wiring terminals T are shown.- in the large rectangular recess 20' in the back of the device and each is of the dual type, whereby it may accommodate two conductor ends to facilitate circuit extension, where desired, without splicing. The recess 20 is only of slight depth, as shown at 21, Fig. 2, to accommodate "the insulating closure or cover plate 22, as shown in Fig. 7, which covers up the switch and most of the live portions of the terminals, and has a mechanical function as will appear as the description proceeds.

The area 23 at the bottom of the recess 20 is substantially flat and in it is the deep, irregularly shaped compartment 24 for receiving the switch mechanism and the oddly shaped identical chambers 25 of irregular depth, each for accommodating one of the dual, conductor-wiregripping terminal devices now to be described.

In Fig. 2 each single wiring terminal is shown to be accommodated in a notch-like chamber or compartment 27, forming an offshoot of chamber 25, as will later appear. Roughly this notch is of V configuration lengthwise as well as transversely, having the straight end wall 30 substantially normal to the surface 23 and the bottom wall 31 inclined to wall 30 at an angle of the order of 50. The wall 31 is also straight except for its outer end where it curves upwardly at 32 to meet the surface 23. The side walls 33 of notch 27 converge toward the bottom wall 31 but adjacent wall 30 are normal to the surface 23.

As seen in Fig. 1 the two walls 30 in each composite chamber 25 are laterally spaced by a deep vertical passage 34, which in the right chamber 25, which is depicted in Fig. 2, has an extension 35 in the nature of an opening from chamber 25 into the interior of socket 14, and in this is an extension of the screw shell engaging contact 16 which is integral with and extends centrally from the bottom of a terminal plate 37, which is common to both wire grippers in a chamber 25. In the other chamber 25 a short extension from plate 37 is riveted as shown at 37 to a switch contact.

Each terminal plate 37 has a fiat central section 38 bordered by bent or trough-like portions 39 forming grooves 40, one at either longitudinal edge thereof. The material of these grooves is first bent substantially at right angles to the plane of the flat portion 38, then bent in an arc, to a radius slightly larger than that of the largest conductor to be connected thereto, until it extends parallel to the first bent portion, and is then extended some distance beyond the inner face of the area 38, as shown at 41. At either side of the extension tang 36, and its equivalent on the other terminal plate, the lower plate edge is straight, as shown at 44 in Fig. 4, to rest against the wall 45 at the bottom of notch 27 adjacent flat wall 30, thus positioning the terminal plate against further movement into the compartment. The upper edge 46 of the terminal plate is also straight and arranged flush with the surface 23 to be engaged by the cover plate and prevented from longitudinal movement out of its chamber.

Projecting beyond the edge portion 46 of the terminal plate are the extensions 47 of grooves 39, but of considerably lesser depth, as seen at 48, Fig. 2. These are intended to project into and be flush with the outer face of the wire entrance holes 50 in cover plate 22, where they insure accurate alignment of these holes with the grooves, and present easy entrance apertures for longitudinally inserting the conductor wires.

Each compartment 27 of chamber 25 has sloping side walls 33 merging toward the bottom, as seen in Fig. l, and, where they meet the inclined bottom Wall 31, the width is substantially that of the wire 52 from which the conductor wire gripper springs are formed. This is a hard drawn steel wire in the nature of piano wire having extreme resilience. For each dual gripper device a single piece of this wire is used, bent into the form of dual grippers, as best seen in Figs. 1, 2 and 4. Such dual grippers include the common central cross bar 53, the right angled extensions 54 therefrom and lying in the same plane, and the straight terminal portions 56 each connected to an extension 54 by a short radius are 55. The length of extensions 54 is such as to reach in Fig. 2 from the bottom wall 45, in the area accommodating the terminal plate, to substantially the curve 32. The free ends 57 of the terminal portions of the springs substantially engage the material of the terminal plate each at the bottom of its respective channel, as best seen in Figs. 2 and 4.

The construction of the gripper spring unit is such that it may be dropped in position in chamber 25 and its extensions, following the positioning of the terminal plate therein and will automatically assume the arrangement shown in Figs. 1 and 2, with the cross bar 53 resting at 57 against the inner flat face of the terminal plate and the extensions 54 resting on the notch bottoms 31 with their curved elbow portions 55 just clearing the curve at 32. The portions 58 of the arcs 55 are just beneath the level of the surface 23.

The arms 56 form an angle of substantially included between them and the line of the bottom of the channel, this smaller included angle being presented outwardly so that as a bared wire conductor is pressed down into the channel from hole 50 it will engage near the free end of arm 56 and press it downwardly to the position shown, for instance, in Fig. 5, separating its tip sufliciently from the bottom wall of the channel to admit the wire at this end. Under these circumstances the spring arm 56 returns as far as it can, engages the conductor wire and forces it tightly against the wall of the channel bottom. The angular relationship is such that the conductor wire cannot be withdrawn, for on effort to pull it out the arm 56 is only lifted and more tightly presses its free end thereof against the conductor wire and the latter against the channel wall. The ends of arms 56 are cut oif cleanly at right angles to present a biting edge. The whole spring assembly is prevented from moving backwardly and hence releasing the conductor by engaging against the faces 32 at the back end of each of the portions 27 of the terminal recess. The cover 22 engages the spring at the points 58 should it attempt to move upwardly and prevents withdrawal and hence conductor release.

Release may be effected, however, of one or both conductor wires, in one terminal, simultaneously by means of a device now about to be described. This comprises a plate of relatively thick metal 60 of a width to just fit between the extended wings 41 of the channel edges, as seen in Fig. 3, with one of its faces resting against the surface 38 of the terminal plate. The opposite face of the release plate 60 bears against the surface 62 of the portion of the base forming the separator between the notches 27 of the terminal recess. This wall 62 stops at the height indicated by the reference character 63, Fig. 2, for a purpose later to be described. At 65, a distance below the upper face of the plate 60 determined by the positions of the spring arms 56, the plate is narrowed by cutting away the portions numbered 64 in Fig. 4, whereby a tongue 66 is formed which passes between the arms 56 while the surfaces 65 rest on them. The lower end of the tongue stops short of the cross bar 53 located at 57 in Fig. 2.

It will be seen that if pressure is applied downwardly on the top surface of release plate 60, the surfaces 65 will press down on the arms 56 and flex them out of contact with conductors, as in Fig. 6, which may be in the grooves, so that these may then be withdrawn readily.

The top surface of the release plate is normally held flush with the surface 23, as seen in Fig. 2, by the arms 56, but is prevented from moving upwardly from this position by engagement with the cover plate. This arrangement prevents destructive bending of any of the spring arms 56 by excessive withdrawal tension on any conductor held thereby. By properly adjusting the height of the wing portions of the release plates which overlie 5 the spring arms 56, the ends of the latter may be prevented from approaching any closer to the bottoms of their channels than desired and thus conductor wire cutofi on excessive withdrawal tension be prevented.

In order to permit access to the release plates, the cover plate above each of them is provided with an elongated slot 68 therethrough, one arranged between each pair of channel entrance holes 50, and having its long dimensions transverse to an axis connecting the pair of holes. Thus a screw driver with a relatively small blade may be pressed through the slot 68 and engage transversely across the upper edge of the release plate for pushing the latter downwardly for releasing conductors. This explains the cut-away area above the surface 63 on the central partition, for that provides room for inward movement of the screw driver blade. In order that the blade may also be not interfered with by the upper edge of the channeled terminal plate, this is provided with a central slot 70, clearly seen in Figs. 1, 3 and 4. To prevent excessive release movement which might damage the dual grippers, the screw driver blade is stopped by surface 63 and by the bottom of slot 70 to limit its penetration. Moreover the tongue 66 of the release blade bottoms on cross wire 57 as seen at Figure 6.

The device described is highly effective for holding conductor wires, permits them to be inserted by mere pushing, permits their release with the use of a tool common with all electricians, and provides a construction extremely simple and effective. No complicated parts are involved and none are fastened in position other than by the cover plate which receives fastening screws through the openings 75 and into the holes 76 in the material of the base. The assembly is extremely simple and cannot go wrong. The springs, which are of steel, do not conduct any current and hence their temper cannot be drawn.

I claim:

1. In a wiring device housing containing at least one contact member and means for automatically gripping and connecting a pair of conductor wires to said contact comprising a terminal plate electrically connected to said contact and having two parallel grooves therein with one end of each extending and exposed through a wall of said housing to slidably receive an end section of one of said conductor wires therein, a conductor wire gripping means for each groove comprising two straight arms of spring wire having an integral connecting elbow and diverging therefrom at an included angle of the order of 35, a recess in said housing having a wall supporting and positioning said terminal plate and pairs of converging walls forming narrow channels for said gripping means with one of the arms of each gripping means being the gripping arms and inclined at an angle of the order of 85 to the bottom of said groove and having its free end substantially in engagement with said bottom for directly gripping said wire, the junctions of the converging walls of each recess channel supporting the other arm of each gripping means substantially throughout its length at an angle of substantially 50 to said groove bottom and out of contact therewith, means connecting the other arms of said gripping means together at their remote ends whereby the pairs of divergent arms are selfmaintained in parallel planes, said connecting means engaging against said terminal plate between the said grooves, and a removable cover for said recess adapted to engage said elbows to maintain said gripping means in said recess.

2. The device of claim 1 in which the terminal plate has an intermediate raised flat portion between said spaced, parallel grooves, and a single conductive release device slidable over said fiat portion and engaging said gripping arms of said two gripping means for flexing them simultaneously out of contact with the groove bottoms.

3. An automatic conductor wire gripping terminal comprising an insulating base having a substantially fiat outer surface, dual, parallel, laterally spaced V-notches in said base terminating at their larger ends at said surface and with one wall common to each V extending to meet the other and being substantially normal to said surface, a terminal plate, having grooves formed along spaced parallel edges thereof, in said notches with the convex sides of said grooves against said common wall, a wire gripping means comprising straight, divergent arms of spring wire integrated by a sharp bend and arranged in each said notch with the free end of each outermost arm substantially engaging in the bottom of one of said grooves at a lower position below said outer surface than the bend between the arms of a pair, means connecting the inner ends of the other arms together and bearing on said terminal plate between said grooves, and a flat cover sheet for said notches bearing on said surface, having a conductor wire entrance opening in line with each said groove, and serving to retain said wire gripping means in said notches by engagement with said bends.

4. The device of claim 3 in which said terminal plate has a raised area between said grooves, a wall of said base being spaced from and parallel to said area, a release plate slidable between said area and last mentioned wall and having arms extending over and resting on the outermost arms of said gripping means, and an opening in said cover for the insertion of a tool for pressing said release plate down to flex the gripping arms away from the groove bottoms to release conductor wires gripped thereby.

5. The device of claim 4 in which the last mentioned cover opening is elongated to accept the blade of a screw driver and extends between the conductor wire entrance openings and transverse through an axis connecting them.

6. The device of claim 5 in which said terminal plate is notched in the upper edge of said raised area to clear a screw driver blade used to depress said releasable plate.

7. The device of claim 4 in which the outer groove walls extend beyond the plane of said raised area on the terminal plate in the direction of and to provide end guides for the release plate.

8. The device of claim 4 in which said release plate slides in a plane normal to the said cover, said plate being sized to engage the underside of said cover to limit the approach of the outermost arms of the wire gripping means to the bottoms of the respective grooves to prevent conductor wire cut-off on excessive withdrawal effort thereon.

References Cited in the file of this patent UNITED STATES PATENTS 2,705,785 Benander Apr. 5, 1955 2,705,787 Benander Apr. 5, 1955 2,738,482 Benander Mar. 13, 1956

Images