US 3611247 A
Description (OCR text may contain errors)
United States Patent Inventors James S. Adams;
John W. Heidacher; Ralph C. Blaken, all of Batesville, Ind. Appl. No. 849,102 Filed Aug. 1 l, 1969 Patented Oct. 5, 1971 Assignee Hill Rom Company, Inc.
SAFETY ELECTRlCAL PLUG 3 Claims, 6 Drawing Figs.
US. Cl. 339/ 14 P, 339/196 R, 339/206 R rm. (3 H0lr 3/06, l-lOlr 33/04 Field of Search 339/ 14,
Primary ExaminerStephen .l. Novosad Assistant ExaminerRobert A. Hafer Attorneys-George H. Simmons and Robert V. J ambor ABSTRACT: A safety plug, for connecting an electrical appliance to a source of power, having a plurality of chambers each individual to one of the three terminals of the plug and having a transparent cover for said chambers to permit visual inspection of the connections therein without disassembling the plug.
SAFETY ELECTRICAL PLUG PRIOR ART condition. This is particularly true in hospitals with the various apparatuses used in connection with patients in the various rooms and wards of the hospital as well as in other instances where proper grounding of a piece of apparatus is essential from a safety standpoint.
In certain instances of which we are aware plugs adapted for use in connection with hospital appliances are said to be capable of ready inspection to insure that the connections therein are in proper condition. Since this inspection involves disassembling, the danger of damage to these connections upon reassembly thereof is increased.
THIS INVENTION The present invention provides as its main object a safety plug in each of which of the three terminals thereof is disposed in-a chamber individual to that terminal and each of these chambers is closed by a transparent cover which permits inspection of the conditions of the terminals in the plug without any disassembly of the plug. The plug also provides means for clamping the cord in the plug in such manner that strains upon the cord are not extended to the terminals therein and the chances of damage to these terminals is greatly reduced if not entirely eliminated.
BRIIEF DESCRIPTION OF THE DRAWING This invention will be best understood by reference to the accompanying drawing in which a preferred embodiment of the invention is shown by way of example and in which:
FIG. I is a side elevational view of a completely assembled P F 16. 2 is a top side plan view of the plug shown in FIG. 1;
. FIG. 3 is a cross-sectional view taken substantially along the line 3-3 of FIG. 1 looking in the direction of the arrows;
FIG. 4 is a cross-sectional view taken along the line 4-4 of FIG. 1 looking in the direction of the arrows;
FIG. 5 is a bottom side plan view of the cap of the plug; and
FIG. 6 is a top side plan view of the base of the plug.
Referring now to the drawing in more detail, the plug consists of a base 10 in which power terminals 11 and 12 and a grounding terminal I3 are fixed. Preferably the base 10 is formed of a plastic of high dielectric strength and the terminals are fixed therein during molding of the base.
Rising out of the upper surface of the base is a Y-shaped wall 14, one arm of which is disposed between terminals 11 and 12, a second arm disposed between terminals 11 and 13, and a third arm disposed between terminals 12 and 13. As will be seen best in FIG. 3, the wall 14 extends out of a raised central section 15, which is generally circular in shape, and has a tapered outer edge.
The cover of the plug extends over the terminals and has sidewalls 21 which extend downwardly to the upper surface of the base 10 of the plug. The cover is held on the base by screws 22, which are threaded into bosses 23 within the cover.
In the example shown, a Y-shaped wall 24 depends from the under surface of the top of the cover 20, and as will be seen in FIG. 3, terminates in close proximity to the wall 14 on the base with which wall 24 is aligned.
The cover 20 contains an end extension 26, which is equipped with bosses 27 at its opposite sides. These bosses contain perforations for receiving screws, as will presently appear. Extending between bosses 27 are an end wall 28 and an inner wall 29, and from FIG. 4, it will be seen that each of these walls has a centrally located indentation somewhat elliptical in shape.
Registered with the extension 26 is a clamp bar 30, which has end walls 31 and 32 which register with walls 28 and 29 of the extension 26. Walls 31 and 32 have an indentation shaped similar to, and registered with, the indentation in walls 28 and 29. The cord 34 is positioned in this pair of indentations, and as the screws 33 are tightened to clamp the clamp bar on the extension, the cord is clamped to the plug in such manner that stress placed on the cord is not transmitted to theconductors therein. I
As will be seen in FIG. 6, the wall 14 terminates short of the outer edge of the raised portion 15 of the base 10. Conductor 36 of the cord extends past the end of the portion of wall 14, between terminals 12 and 13, and is connected to terminal 12 by clamping. Ground conductor 37 is extended to the ground plug 13 and attached thereto by clamping, and conductor 38 extends around the end of wall 14 disposed between tenninals 11 and 13, and is connected to tenninal 11 by clamping.
As will be seen in FIG. 5, the Y-shaped wall 24 of the cover extends to the sidewall 21, and to the bosses 23 within the cover. Thus, wall 24 extends over that portion of the conductors which is disposed at the ends of the wall 14. Through this arrangement, a chamber within the plug and cover is fonned for each of the three terminals of the plug, and should the connection between one of the conductors and its associated terminal become disengaged, there is no danger of that loose conductor coming into contact with one of the other terminals or conductors.
In the embodiment shown by way of example, the upper edge of wall 14 is disposed in substantial alignment with the tops of the terminals, and wall 24 extends into close proximity to wall 14. Preferably, wall 24 will engage wall 14. However, because of tolerances required in molding, this is not feasible in commercial production. The dimensions are maintained so that the registered surfaces of the two walls lie as close together as possible.
In the embodiment shown by way of example, a wall 14 terminates approximately in line with the upper ends of the terminals, and it is contemplated that in certain instances it may be advantageous to continue the wall 14 upwardly into close proximity to the top portion of the cover. In such instances, wall 24 would be eliminated from the cover.
Preferably, the base 10 and the cover 20 are both molded from a plastic material such as methylmethacrylate orits equivalent. If desired, suitable dyes may be added to the material in the base to give it a distinctive color. Preferably, however, the cover 20 is transparent so that these conditions of the conductors and connections to the terminals can be observed without disassembling the plug in any manner.
SUMMARY OF THE INVENTION From the foregoing, it will be apparent that this invention provides a high-quality three-prong plug for appliances, tools, and the like, which plug includes means for preventing a wire loosened from the terminal to which it is supposed to be attached from coming into contact with other terminals, and the production of a short circuit in the plug is prevented. By making the cover out of a transparent material, the condition of the plug can be visually ascertained in a convenient manner, which renders the plug especially advantageous in installations where such inspections are frequently made in a routine manner.
What we claim is:
1. A safety plug for removably connecting an electrical appliance to a source of electrical power, comprising:
a. a base member;
b. two power contacts and a grounding contact fixed in said base and projecting from one side thereof and having terminals located on the other side of the base;
g. a Y-shaped wall depending from said cover, aligned with the wall on the base, extending to the sidewall of the cover and engaging the conductor to hold it in position.
2. A safety plug as specified in claim 1 in which said wall means prevents a conductor that has loosened from its terminal from coming into contact with another terminal.
3. A safety plug as specified in claim 1 in which the base, the cover and the clamp bar are molded from a rigid plastic material having high dielectric strength.