US 2396901 A
Description (OCR text may contain errors)
F. E. TIFFANY '-DETACH ABLE PLUG Fil ed Jan. 2, 1
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1 a m a March 19 1946.
YINI/ENTOR v FRANK E.T1FFANY Patented Mar. 19, 1946 DETACHABLE PLUG Frank E. Tiffany, Claremont, Callfl, assignor, by mesne assignments, to Lockheed Aircraft Corporatioma corporation oiCaliiornia I Application January 2, 1943, Serial 'No. 471,201 4 Claims. (01. 173-361) This invention relates to, a new and improved device for connecting leads of electrical devices such as, for instance, as are used in operating portable electrical devices, and has special reference to detachable two or more terminals as in so-called high'cycle or multi-phase connectors, which may also carry a ground connection.
In the use of commercially available connector plugs for port-able electrical tools and equipment, considerable trouble has beenexperienced both due to the extended contacts and to ignorant or careless insertion and removal of such plugs from their complementary extension couplings, convenience outlets, receptacles, etc. The extending prongs or contact blades become damaged from lying around on the floor or being dropped thereon, and inexperienced employees may further damage the plugs by attempting to straighten the blades, force the plugs into the receptacles in improper alignment, or to pry the blades out of their receptacles when disconnecting the same.
It is an object of this invention to provide novel means for protecting the binding posts of such plugs when the device is not in use.
Another object of the invention' is to provide novel means of recessing a plug into a socket to prevent the harmful and hazardous insertion of a screwdriver, or similar object, between the plug and socket to pry the two apart. r
A further object of the invention is to provide a simple effective electrical plug having a contact blade cover which retracts when the plug is inserted into a socket, and which automatically advances over the cont-act blades of the plug when the plug is removed from the socket.
Other and further important objects of this invention will be apparent from the disclosures in the specification and the accompanying drawing.
This invention in its preferred form isillustrated in the drawing and hereinafter more fully described.
In the drawing:
Figure I is a side elevation showing one embodiment of my invention as'applied to a heavyduty or multi-phase connector.
Figure II is a sectional elevation thereof with the contact blade cover in its extended position wherein it envelops'and protects the blades.
Figure III is a sectional elevation of a plug and socket with the contact blade cover in its retracted position.
Figure IV is a bottom Figure I.
As shown in the drawing:
I have chosen to illustrate an embodiment of my invention designed to interchange with comview of the plug of mercially available plugs such as are in common use for heavy duty services in industrial establlshments where portable electric tools are in electrical connectors having 5 use. The particular type and arrangement of terminals or contact blades illustrated correspond to a so-called "twist-lock is pushed straight in and then slightly turned to lock it in place.
The present invention relates particularly to devices adapted for making detachable electrical connections, such, for example, as are used for connecting electric motors and other portable electrical devices to sources of current supply, such as wall or floor or other convenience outlets in garages and factories, and includes a plug cap generally designated Ill, a socket which may be in the form of a conventional wall or portable receptacle or mating plug, shown without details and generally designated as l I, and an insulating contact blade cover l2. The plug cap l0 consists of a suitable shell or casing l3 having a cord aperture in its nearly closed top. An annular insulating and supporting member I5, is arranged in the upper portion of the shell I3 and has an inwardly extending portion l6 which supports legs I! of inwardly and then outwardly extending complementary members l8 which are adapted to be clamped together to hold the lead in cord in place. A, support member 2| having its top side against the lower face of member l5 is removably mounted inside of the shell l3 and supports a series of contact blades 23, arranged to form a circular pattern having unequal radii from the center of blade cover l2. As shown, three of these live terminals may be used and a similar fourth or ground terminal blade 24 may be oiiset relative to the others the corresponding receptacle, mating coupling, or convenience outlet. For readyidentiflcation of the ofiset terminal, it may be made slightly larger and/or longer than the a portion 25 protrudes beyond the lower surface of blade cover I2. Contact blades 23 and 24 each have a lateral portion 26 extending sideways therefrom in a clockwise direction.
At the uppermost end of contact blades 23 and 5 24, I providefour binding posts 21, which may be of the conventional type to form attachments for electrical wire lead-ins.
A peripheral shoulder 29 is formed on the lower portion of support member 2| and adjacent the 0 shell l3. A similar shoulder 30 is provided on the upper portion of blade cover l2 adjacent shell i3, and the two shoulders leave a recess to accommodate a compression spring 3|. Screws 32 attached to blade cover l2 are adapted to travel upward and downward with the blade .cover l2 in slots 33 out vertically in the lower portion of shell l3. The screws 32 are engageable with the ends of the slots to limit the travel of the cover l2.
On the upper face of socket II, I provide a raised portion 34 having an inside radius slightly plug where the plug to properly locate the live terminals relative tov live terminals 23 so that larger than that of the plug I and extending above the lower surface of plug cap II) and blade cover I2 to provide a recess into which plug cap I0 seats when the connection is completed.
Assuming that the various contacts of the devices each have a lead wire connected with them, when it is desired to connect the plug II! with the socket II, contact blade 24 is inserted into its slot'in the socket II to obtain alignment. By applying pressure to the top of shell I3, the blade cover is depressed, compressing spring 3|. By turning the plug cap III clockwise, the lateral portions 26 or the blades 23 and 24 are caused to look into suitable contacts in the socket II. Thus it can be. seen that when plug cap III is seated, it is recessed into socket II preventing the possible harmful and hazardous insertion of a screwdriver or similar article between cap I0 and socket I I to efiect their separation.
In removing the plug I0 from the socket I I, the plug I0 is slightly turned counterclockwise and lifted upward, whereupon the blade cover I2 is extended over the contact blades 23' and 24 by the compression spring 3|, preventing any injury to the contact blades 23 and 24 during the time the plug is disconnected from its socket.
It will thus be seen that 1 have invented an improved safety plug wherein the contact blades or terminals of the detached plug are against accidental injury while lying around under foot, and in which ignorant or careless operators cannot bend or distort the terminals in attempts at improper assembly and cannot injure themselves by trying to pry the plug out of the receptacles by inserting a tool between the plug and the receptacle.
Having thus described my invention and the present preferred embodiment thereof, I desire to emphasize the fact that many modifications may be resorted to in a manner limited only by a just interpretation of the following claims.
I claim as my invention:
1. An electrical multi-circuit connecting plug for removable engagement with convenience outlets or the like, comprising an enveloping shell having an end wall with an opening therein to receive a multiple lead cable, an insulated mounting block positioned within said shell adjacent said end wall thereof, a plurality of blade contacts carried by said mounting block and mounted in general parallel relation with the axis of said shell, said blade contacts extending out of and beyond the other end of said shell to, engage with said outlet,- one of said blade contacts being varied in length relative to the others to identify the same, and in its relative position with respect to the others to orient the plug relative to its outlet, a second insulating block having apertures therethrough through which said blade contacts extend, said second block being so constructed and arranged as to slide in and partially out of said shell whereby in its extended or outer position it substantially embraces and covers the projecting portions of said blade contacts, and a single spring arranged under compression between said blocks for yieldingly projecting said second block to its outer position upon disengagement of the plug from an outlet, said spring surrounding said plurality of blade contacts.
2. An electrical plug for removable engagement with an outlet, or the like, comprising a shell having an end wall provided with an opening for protected guard block slidable in the receiving a multiple lead cable, a block secured in the shell adjacent said end wall and having spaced apertures, a plurality of spaced contact blades attached to said block and extending through said apertures and continuing outwardly through the shell to project beyond the other end thereof for engagement with an outlet, the engagement of the blades in said block sustaining the blades against lateral displacement, a second block slidable in the shell and having spaced apertures slidably receiving the blades to guard the blades and to sustain the blades against lateral displacement, said second block being movable between an extended position where it substantially covers the' projecting portions of the blades and a retracted position where it is substantially entirely within the shell, and means for yieldingly urging said second block to its extended position comprising a helical spring in surrounding relation to the plurality of blades and engaged under compression between the first named block and said second block. p
3. An electrical plug for removable engagement with an outlet, or the like, comprising a shell having an opening in one end for receiving a multiple lead cable, a plurality of contact blades secured in the shell for connection with the cable leads and extending longitudinally through the shell to project beyond its other end for engagement with an outlet, one blade projecting beyond the shell a greater distance than the other blades, a
shell and having apertures slidably receiving the blades, the block being movable between an extended position where it projects from said other end of the shell to form a guard for the projecting portions of the blades and a retracted position within the shell, said one blade being the only blade that projects from the block when the block is in its extended position, and a single helical spring in the shell in surrounding relation to the plurality of blades and acting outwardly against the block for yieldingly urging the block to its extended position.
4. An electrical plug for removable engagement with an outlet, or the like, comprising a shell having an opening in one end for receiving a multiple lead cable, a block secured in the shell adjacent said end and having spaced apertures, contact blades attached to said block and extending through said apertures and continuing outwardly through the shell to project beyond the other end thereof for engagement with an outlet, the engagement of the blades in said block sustaining the blades against lateral displacement, 9. second block slidable in the shell and having spaced apertures slidably receiving the blades to guard the blades and to sustain the blades against lateral displacement, said second block being movable between an extended position where it substantially covers the projecting portions of the blades and a retracted position where it is substantially entirely within the shell,
and has its inner end contacting or adjacent the opposing end of the first named block, said ends of the blocks being formed and related to leave an annular space in the shell adjacent the side wall thereof when said second block is in its retracted position, and a spring in said space in spaced surrounding relation to the plurality 01 contact blades and under compression between the blocks for yieldingly urging said second block to its extended position.