US3678440A

US3678440A - Yieldable electrical plug

Info

Publication number: US3678440A
Application number: US77994A
Authority: US
Inventors: Richard C Gilsdorf
Original assignee: Bell and Howell Co
Current assignee: Bell and Howell Co
Priority date: 1970-10-05
Filing date: 1970-10-05
Publication date: 1972-07-18
Anticipated expiration: 1989-07-18

Abstract

An electrical plug has a hollow-cylindrical shell contact member and a center contact member carried by a spring wire which extends through the shell contact member. An electrically insulating resilient sleeve for the spring wire fills the space between the spring wire and the shell contact member and projects from the shell contact member to avoid contact between the shell and center contact members during flexing of the spring wire.

Description

United States Patent Gilsdorf 1451 July 18,1972

[54] YIELDABLE ELECTRICAL PLUG [72] Inventor: Richard C. Gllsdorf, Duarte, Calif. [73] Assignee: I Bell & Howell Company, Chicago, Ill. [22] Filed: Oct. 5, 1970 21 Appl. 110.; 77,994

52 us. c1. ..339/61 R, 339/183, 339/252 P 511 1111 c1. 11011 13/08 [58] Field of Search ..339/s9 61, 64, 339/182, 183,252; 179/1 PC, 175

[56] References Cited UNITED STATES PATENTS 2,249,153 7/1941 Martin ..339/l83 3,242,456 3/1966 Duncan ..339/64 am, ,5 1e 1 FOREIGN PATENTS OR APPLICATIONS 536,665 5/1941 Great Britain ..339/252 P Primary Examiner-Joseph l-l. McGlynn Attorney-Luc P. Benoit ABSTRACT An electrical plug has a hollow-cylindrical shell contact member and a center contact member carried by a spring wire which extends through the shell contact member. An electrically insulating resilient sleeve for the spring wire fills the space between the spring wire and the shell contact member and projects from the shell contact member to avoid contact between the shell and center contact members during flexing of the spring wire.

2 Clalns, 3 Drawing Figures YIELDABLE ELECTRICAL PLUG BACKGROUND OF THE INVENTION There exist electrical receptacle devices which perform aswitching function in that they interrupt an electrical circuit upon insertion of an electrical plug into the receptacle device. Devices of this type have been employed for many years in telephone equipment and have, accordingly, become known I as telephone jacks.

A more recent example of such receptacle devices is embodied in the earphone outlet of transistor radios and small tape recorders. In that type of equipment, a receptacle is frequently provided which has the function of connecting an internal sound amplifier to an external earphone for private listening, while at the same time disconnecting the internal loudspeaker from the sound amplifier.

With time,-a need has come to exist for an electrical plug that would be insertable for electrical contact into the receptacle device without effecting by its insertion an interruption of the electrical circuit of which the receptacle device forms a part. The proposal has, accordingly, been made to substitute a coil spring for the rigid center contact member normally provided in the type of plug'under consideration. This coil spring has the shape of a typical center contact member and is laterally yieldable so as to engage an electrical contact member in the receptacle without interrupting the electrical circuit that extends through the receptacle.

The latter coil spring solution has, however, failed to operate properly with smaller jacks of the typetypically employed, for instance, in small portable transistor radios and tape recorders.

SUMMARY OF THE INVENTION The subject invention overcomes the above mentioned disadvantages and resides in an electrical plug having a shell contact member and a center contact member and being constructed for insertion into a receptacledevice having a receptacle member for receiving the shell contact member, having a relatively movable contact member engageable by the center contact member, and having electrical circuit means operatively associated with the movable contact member and having first and second switching states and being switched from the first to the second switching state upon movement of the relatively movable contact member substantially by a predetermined amount of movement.

The subject invention more specifically resides in the improvement comprising, in combination with the above mentioned center contact member of the electrical plug, elongate resilient mounting means extending substantially through the shell contact member and connected to the center contact member and resiliently mounting the center contact member for movement relative to the movable contact member of the receptacle device upon insertion of the plug into the receptacle device and while the center member engages the movable contact member of thereceptacle device. In accordance with a further feature of the subject invention, the resiliency of said center contact mounting means is so dimensioned that the above mentioned electrical circuit means remain in the first switching state despite engagement of the relatively movable contact member of the receptacle device by the center contact member of the electrical plug.

Also in accordance with the subject invention, the resilient mounting means include a spring wire extending through the shell contact member and carrying the center contact member and an electrically insulating resilient sleeve for the spring wire. This resilient sleeve fills the space between the shell contact member and the spring wire. Furthermore, the resilient sleeve projects from the shell contact member toward the center contact member to avoid electrical contact between the center contact member and the shell contact member during flexing of the spring wire.

Considering the language just quoted, it will be understood that the invention is applicable to receptacles which are designed to interrupt an electrical circuit upon insertion of a standard plug, as well as to receptacles which are designed to close an electrical circuit upon insertion of a standard plug.

The elongate resilient contact mounting means according to the subject invention have proved effective and faultlessly operative in situations in which the above mentioned prior-art coil spring solution has failed. The spring wire according to the subject invention is not to be confused with the above mentioned prior-art coil spring. That coil spring was provided and designed to constitute the center contact member itself. The spring wire just defined, on the other hand,'is not the contact member, but is rather a mounting means for the center contact member.

Of course, if one wishes to form the center contact member out of a coil spring he may do so without stepping beyond the scope of the subject invention, provided he also employs elongate resilient mounting means of the above mentioned type for mounting his coil-spring type center contact member. The use of a rigid center contact member on the elongate resilient mounting means is, however, preferred from the point of view of economy, durability and operational stability.

The subject invention also resides in an electrical plug which comprises, in combination, handle means, a substantially hollow-cylindrical shell contact member mounted on and projecting from the handle means, a center contact member projecting substantially coaxially relative to the shell contact member, and elongate resilient mounting means connected to the center contact member and extending substantially through the shell contact member and resiliently mounting the center contact member for lateral movement of the center contact member relative to the shell contact member.

The resilient mounting means include a spring wire extending through the shell contact member and carrying the center contact member and an electrically insulating resilient sleeve for the spring wire. The resilient sleeve fills the space between the shell contact member and the spring wire. Also, the resilient sleeve projects from the shell contact member toward the center contact member to avoid electrical contact between the center contact member and the shell contact member during flexing of the spring wire.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will become more readily apparent from the following detailed description of a preferred embodiment thereof, illustrated by way of example in the accompanying drawings, in which:

FIG. 1 is an illustration, partially in section, of essential parts of a jack-type receptacle device;

FIG. 2 is a longitudinal section through an electrical plug in accordance with a preferred embodiment of the subject invention, with part of its handle being shown broken off for improved illustration; and

FIG. 3 shows the plug of FIG. 2 inserted in the receptacle of FIG. I, and illustrates also electrical circuits that may be em ployed in connection with the depicted devices.

DESCRIPTION OF PREFERRED EMBODIMENTS The contact member 13, which is in the form of a resilient blade, has a bent end portion adapted for engagement by part of an electrical plug that is inserted into the receptacle 10 through the receptacle member 12. The contact member 14, which is also in the form of a contact blade, carries a conventional contact tip 22. In their quiescent state, the

contact members

13 and 14 are biased toward each other so that the contact tip 22 of the member 14 is in engagement with the contact member 13.

To illustrate the standard operation of the receptacle 10, a conventional electrical plug 23, illustrated in dotted outline, is shown inserted in FIG. 1 into the receptacle 10. The plug 23 has a handle 24, part of which is shown broken off. A shell contact member 25 of the plug 23 is mounted on the handle 24. The shell contact member 25 of the plug 23 is in electrical engagement with the receptacle member 12 when the plug 23 is inserted into the receptacle 10.

The electrical plug 23 further includes a center contact member 27 which is electrically insulated from the shell contact member 25. In accordance with conventional practice, the lateral dimensions of the center contact member 27 are such that the contact member 13 is lifted away from the contact tip of the contact member 14 when the electrical plug 23 is inserted into the receptacle 10. In this manner, it is not only possible to connect an external device to an internal component, but also to interrupt at the same time an internal circuit of the apparatus with which the receptacle device 10 is associated.

By way of familiar example, it is possible for the receptacle 10 to disconnect an internal loudspeaker from the internal amplifier output, while an external earphone is connected to the internal amplifier output by way of the standard plug 23.

As has been explained in the corresponding patent application, Ser. No. 47,689, Sound Reproduction Methods and Apparatus, filed June 19, 1970, by Leonard A. Farrari, and assigned to the subject assignee, there are situations in which it is desirable to connect an external device to the apparatus associated with the receptacle without altering by virtue of such connection the electrical circuit that extends through the receptacle.

The electrical plug 30 shown in FIG. 2 provides the latter function and thus satisfies a widespread need. This plug 30 has an electrically insulating handle 31, only part of which is shown in FIG. 2. The plug 30 further includes a substantially hollow-cylindrical shell contact member 32 which projects from the handle 31 and which is removably mounted on the handle 31 by means of a threaded connection 33.

A stepped substantially cylindrical mounting member 35 is partially inserted into the end of the shell contact member adjacent the handle 31. The mounting member 35 is of an electrically insulated material, such as a phenolic resin, and is held in the shell contact member by means of a press fit. The mounting member 35 presses a connecting device 36 into electrically conducting engagement with the shell contact member 30. The shell contact member 30 has a lateral detent 38 to assure an uninterrupted electrical contact between the receptacle member 12 and the contact device 36 when the plug is inserted into the receptacle 10.

The plug 30 of FIG. 2 further includes a center contact member 40 which is closely similar to the center contact member 27 of the plug 23 shown in FIG. 1. The center contact member 40 of the plug 30 is mounted on elongate resilient mounting means 42. The elongate resilient mounting means 42 extend substantially through the shell contact member 32. This is an important feature of the illustrated preferred embodiment, since it improves the attainable lateral resiliency of the mounting means 42. The mounting means 42 include a substantially straight elongate spring wire 43. One end of the spring wire 43 carries the center contact member 40 which is crimped to the wire 43 at 45. The other end of the spring wire 43 extends through a central bore 47 in the mounting member 35 and is bent at 48. This bent portion extends through and retains a connecting device 49 which is crimped to the bent portion 48.

The resilient mounting means 42 further include an electrically insulating resilient sleeve 50 for the spring wire 43. The resilient sleeve 50 is substantially located in the shell contact member 32 so as to fill the space between the shell contact member 32 and the spring wire 43. In this manner, the mounting means 42 form a resilient core of the plug 30. The sleeve 50 projects somewhat from the shell contact member 32 as shown at 52, so as to avoid an electrical contact between the center contact member 40 and the shell contact member 32 when the spring wire 43 is flexed during the operation of the plug 30.

In our prototypes, we used rubber for the sleeve 50 and 0.015 Diameter beryllium wire for the spring wire 43. Other materials may be employed, but it is important that the resiliency of the center contact mounting means 42 be so dimensioned that the contact member 13 remain in electrical contact with the contact tip 22 of the contact member 14 when the plug 30 is inserted into the receptacle device 10. Such an insertion is shown in FIG. 3 in which like reference numerals as among FIGS. 1,2 and 3 designate like parts.

Comparing FIGS. 1 and 3, it is seen that the insertion of the plug 30 of FIG. 2 is not capable of displacing the contact member 13 into the position shown in FIG. 1 by a dotted outline 54 and indicating the switching state in which the contact between the member 13 and tip 22 is broken. Rather, the presence of the elongate resilient center contact mounting means 42 according to the subject invention enables the contact member 13 of the receptacle 10 to laterally displace the center contact 40 by action through the bent end of the contact member 13.

This does not mean that no lateral displacement at all of the member 13 is tolerable when the center contact member 40 of the plug 30 engages the contact member end portion 20. Since the

contact members

13 and 14 are biased toward one another, a limited lateral travel of the contact member 13 may occur without an interruption of the electrically conducting engagement of the contact tip 22 of the contact member 14 with the contact member 13.

Since the contact between the

members

13 and 14 is not broken by the plug 30, a different function is attainable with the plug 30 according to the subject invention than with the prior-art plug 23. To illustrate this fact by way of example, rather than by way of limitation, certain circuit components have been shown in FIG. 3.

More specifically, an output 56 of an electronic amplifier 57 is shown connected to the contact member 13. The electronic amplifier 57 may be an internal sound amplifier of a transistor radio or portable tape recorder. Accordingly, an electrical sound signal may be applied to the input 58 of the amplifier 57. An internal loudspeaker 60 is shown connected between the contact member 14 and ground. When the contact member 13 is in the solidly illustrated position, an electrical circuit exists between the amplifier 56 and the loudspeaker 60 by way of the contact member 13, the contact tip 22 and the contact member 14. In this manner, the internal loudspeaker 60 will aurally reproduce the amplified sound signals provided by the internal amplifier 57.

Owing to the nature and presence of the resilient center contact mounting means 42, the circuit between the internal loudspeaker 60 and amplifier 57 will not be interrupted by the insertion of the plug 30 into the receptacle device 10. This is so despite of the fact that the center contact member 40 makes electrical contact with the contact member 13 through the bent portion 20 of the latter.

A second electrical circuit is thereby established which extends from the amplifier output 56 through the contact member 14, bent end portion 20, center contact member 40, spring wire 43, and connecting device 49. Upon insertion of the plug 30 into the receptacle device 10, a third electrical contact is established between the connecting device 36 and ground through the shell contact member 32 and the receptacle member 12.

Accordingly, an external amplifier 63 has its input leads 62 respectively connected to the devices 36 and 43 so that the input of the external amplifier 63 is connected in parallel to the internal loudspeaker 60 through the above mentioned second and third electrical circuits which come into being upon insertion of the electrical plug 30 into the receptacle device 10. In consequence, the external amplifier 63 is enabled to drive an external loudspeaker 65 upon insertion of the plug 30 into the receptacle device 10.

It will be noted at this juncture that the plug 30 according to the illustrated preferred embodiment of the subject invention has an omnidirectional feature in that its function is not dependent upon the rotational position at which the plug 30 is inserted into the receptacle device with respect to a longitudinal axis'through the plug 30. This significantly increases the'ease of operation and certainty of function of the electrical plug.

'As has been explained in the above mentioned copending Ferrari application, the external loudspeaker 65 may be designed to reproduce a base range of the sound information processed by the internal amplifier 57, while the internal loudspeaker 60 need then only be capable of reproducing a higher tonal range.

The nature, construction and purpose of the electrical plug according to the subject invention having been disclosed in detail, various areas of utility thereof will become apparent or suggest themselves to those skilled in the electrical arts.

[claims 1. In an electrical plug having a shell contact member and a center contact member and being constructed for insertion into a receptacle device having a receptacle member for receiving said shell contact member, having a relatively movable contact member engageable by said center contact member, and having electrical circuit means operatively associated with said movable contact member and having first and second switching states and being switched from said first to said second switching state upon movement of said relatively movable contact member substantially by a predetermined amount of movement, the improvement comprising, in combination with said center contact member of said electrical lug: p elongate resilient mounting means extending substantially through said shell contact member and connected to said center contact member and resiliently mounting said center contact member for movement relative to said movable contact member of said receptacle device upon insertion of said plug into said receptacle device and while said center contact member engages said movable contact member of said receptacle device, the resiliency of said center contact mounting means being so dimensioned that said electrical circuit means remain in said first switching state despite engagement of said relatively movable contact member of said receptacle device by said center contact member of said electrical plug, said resilient mounting means including a spring wire extending through said shell contact memberand carrying said center contact member and an electrically insulating resilient sleeve for said spring wire, said resilient sleeve filling the space between said shell contact member and said spring wire, and said resilient sleeve projecting from said shell contact member toward said center contact member to avoid electrical contact between the center contact member and the shell contact member during flexing of said spring wire.

2. An electrical plug comprising in combination:

handle means;

a substantially hollow-cylindrical shell contact member mounted on and projecting from said handle means;

a center contact member projecting substantially coaxially relative to said shell contact member; and

elongate resilient mounting means connected to said center contact member and extending substantially through said shell contact member and resiliently mountin said center contact member for lateral movement of sai center contact member relative to said shell contact member, said resilient mounting means including a spring wire extending through said shell contact member and carrying said center contact member and an electrically insulating resilient sleeve for said spring wire, said resilient sleeve filling the space between said shell contact member and said spring wire, and said resilient sleeve projecting from said shell contact member toward said center contact member to avoid electrical contact between the center contact member and the shell contact member during flexing of said spring wire.

Claims

1. In an electrical plug having a shell contact member and a center contact member and being constructed for insertion into a receptacle device having a receptacle member for receiving said shell contact member, having a relatively movable contact member engageable by said center contact member, and having electrical circuit means operatively associated with said movable contact member and having first and second switching states and being switched from said first to said second switching state upon movement of said relatively movable contact member substantially by a predetermined amount of movement, the improvement comprising, in combination with said center contact member of said electrical plug: elongate resilient mounting means extending substantially through said shell contact member and connected to said center contact member and resiliently mounting said center contact member for movement relative to said movable contact member of said receptacle device upon insertion of said plug into said receptacle device and while said center contact member engages said movable contact member of said receptacle device, the resiliency of said center contact mounting means being so dimensioned that said electrical circuit means remain in said first switching staTe despite engagement of said relatively movable contact member of said receptacle device by said center contact member of said electrical plug, said resilient mounting means including a spring wire extending through said shell contact member and carrying said center contact member and an electrically insulating resilient sleeve for said spring wire, said resilient sleeve filling the space between said shell contact member and said spring wire, and said resilient sleeve projecting from said shell contact member toward said center contact member to avoid electrical contact between the center contact member and the shell contact member during flexing of said spring wire.

2. An electrical plug comprising in combination: handle means; a substantially hollow-cylindrical shell contact member mounted on and projecting from said handle means; a center contact member projecting substantially coaxially relative to said shell contact member; and elongate resilient mounting means connected to said center contact member and extending substantially through said shell contact member and resiliently mounting said center contact member for lateral movement of said center contact member relative to said shell contact member, said resilient mounting means including a spring wire extending through said shell contact member and carrying said center contact member and an electrically insulating resilient sleeve for said spring wire, said resilient sleeve filling the space between said shell contact member and said spring wire, and said resilient sleeve projecting from said shell contact member toward said center contact member to avoid electrical contact between the center contact member and the shell contact member during flexing of said spring wire.