US 2654869 A
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Oct. 6, 1953 Filed April 1'7, 1950 R. L. MUDD, JR
ELECTRICSWIVEIL PLUG 2 Sheets-Sheet 1 INVENTOR. 694/ 1. Mann J22, BY
rfrromvsY Patented Oct. 6, 1953 UNITED STATES PATENT OFFICE 2,654,869 ELECTRIC SWIVEL FLU'G Ralph I1. Mudd, Jr., Maplewood Park, Ill. Application April 17, 1956, Serial No. 156,341
My invention relates to improvements in electric swivel plugs and similar devices.
My invention relates more particularly to an improved construction of swivel plug whereby an electrical connection is maintained between the source of electricity and an extension cord attached to the plug by means of a rotatable center piece which may turn with the cord.
In many industries where electric hand power tools are employed the tools are frequently used in such manner that the extension cord between the tool and the plug becomes turned and twisted with the result that the plug is disengaged from the socket and thus the tool is disconnected and its operation stops. This not only results in loss of time and annoyance to the user but also in gradually tearing the connection between the cord and the plug. All this can be avoided by the provision and use of a swivel plug of the type to which this application refers.
The principal object of the present invention is to provide an improved swivel plug oi the type described which is capable of long and hard usage without becoming broken or out of order.
A further object of the invention is to provide a swivel plug of the type described having a revolvable centerpiece secured in an outer shell against removal.
A- further object of the invention is to provide effective means for rotatably fastening the extension cord to the revolvable center piece.
A further object of the invention is to provide a ball bearing mounting for the center piece within the outer shell whereby ease of operation is efiected.
Other objects and advantages will be more apparent from the following description wherein reference is had to the accompanying drawings, upon which Fig. 1 is a side elevational view of an extension cord having a swivel plug of the type to which this invention relates;
Fig. 2 is a top view thereof;
Fig. 3 is an enlarged vertical section therethrough taken on the line 33 of Fig. 2;
Fig. 4 is a cross-sectional view showing the clamp member for fastening the cord or conduit to the center piece of the swivel plug and is taken on the line 4-4 of Fig. 3;
Fig. 5 is a cross-sectional view taken on the line 55 of Fig. 3;
Fig. 6 is a horizontal sectional view taken on the line 6-6 of Fig. 3;
Fig. 7 is a similar view except thatit is looking in the opposite direction; and
Fig. 8 is a side elevational view of the rotat able center piece.
In the embodiment of the inventio which I have chosen to illustrate and describe the same, in Fig. 1 I have shown an extension cord to which may have one end entering the I2 in the outer housing member 14 or the swivel plug, the clamp [6 being positioned adjacent for a purpose which will be presently apparent.
The socket engaging prongs l8 which eiitei-id outwardly from the forward end of the housing member [4 may befastened therein by suitable screw members which engage in suitable tapped openings 22 in the endor the housing member [4. A pair of lead wires 24 and 26 extend from the prongs [8, the lead wire 24 extending to a circular well 21 fastened in the upper face 28 of a cylindrical chamber 30 formed in the housing l4, and the wire 26' extending to and being con nected to a shallow metallic ring 32 shaped to form a groove and positioned in the surface 28 of the chamber 39. i
The chamber 30 and outlet H are adapted to receive a rotatable center piece member 34 which has a cylindrical body portion 36 adapted to fit in the chamber 33 and a reduced stein 38 extend ing downwardly in the bore l2. F61 providing a frictionless rotation of the center piece 3'4 m the housing L4,- 1 provide complementary grooves 40 in one wall or the chamber 3|! and grooves 42 in the bottom shoulder or the member 36 adapted to receive the ballbearings mountedm-asuit able raceway 44. It will be understood that the outer shell is molded in two halves so that it will receive the rotatable center piece and its connections.
The center piece 34 is provided with a central well 46 within which an upwardly projecting wiper member 48 is positioned, the wiper member being provided with a dome-shaped head 50 adapted to engage in the well 21 in the housing member [4. A pair of spring contact members 52 and 54 are securely fastened to a ring-shaped member 56 positioned in a suitable groove in theupper surface of the rotatable center piece 34. A wire lead 58 may extend from the ring 56 down to a socket 60 positioned in the lower end of the stem 34, and a similar lead 62 may extend downwardly from the contact member 48 to a similar socket 64. The wires 66 and 68 of the conduit 10 are adapted to be fastened to the two members 60 and 64 to eilect an electrical connection between the conduit 10 through the wires 58 and 62, the spring contact fingers, the wires 24 and 26, to the prong members It.
A means for mechanically connecting together the rotatable center piece 34 and the conduit I will now be described. This may include the clamp member l6 previously mentioned which rigidly fastens to a pair of pin members 79 and 12 that extend upwardly through the end of the stem 38 into suitable sockets therein to rigidly engage the same. The clamp member [8, as shown, is provided with a screw member 83 for rigidly fastening the same about the conduit l3 so that when the wires 66 and 68 are connected to the posts 60 and 64 and the pins 18 and '12 are engaged in the end of the stem 38, both an electrical and a rigid mechanical connection are made between the conduit I0 and the rotatable center piece 34.
With the construction shown it can be seen [i the use of such a swivel plug prevents the breaking of these wires, it being well known that normal twisting causes them to break and sets up resistance in the wire because the unbroken wires must carry the additional load. Thus it can be seen that the swivel plug acts as a safety device in that it prevents to a large degree the shortcircuiting of circuits which are now normally caused by frayed or broken wires due to twisting of the same during use.
casing having rigid prongs extending forwardly that when the 'cord [0 is rotated it will carry the center piece 34 with it, the center piece being free to rotate upon the ball bearing members B,
the spring wiper fingers 48, 52 and 54 frictionally engaging the members 2'! and 32 in the station- :ary outer housing so that a gocd electrical connection is completed between the cord and the prong members I8.
From the above and foregoing description it will be apparent to those skilled in the art that I have provided a comparatively simple yet highly eflicient electric swivel plug which has a revolving center piece turning with the cord, yet at all times completing an electrical connection between the cord and the source of electricity.
The only moving member, the center piece, is V mounted for rotation upon ball bearing members which reduce the friction therein to a minimum,
the contact being at all times held through spring fingers which yieldingly wipe upon metal rings or well members in the stationary or body member of the plug. 7 Due to their location and resiliency, the spring fingers also have a tendency to balance the device in use.
While I have illustrated and described the swivel plug and its adaptation for use with power tools and other appliances, it is of course understood that the uses to which it may be put are not limited thereby. Its use in connection with telephoneswhere an object is to prevent twisting of the cord when the instrument is frequently used is also contemplated. In addition the plug has a safety factor in that where it is used with r telephones where the wires are very fine and there is a multiplicity of them in each lead-in,
from the front thereof, said casing having a cylindrical chamber therein, a reduced bore from said chamber to the back end of said plug, a center piece rotatablyv mounted in said chamber and having a reduced portion extending outwardly through said bore, an electric cord connected thereto, a clamp on said cord, a pair of pin members connected to said clamp and engaging in' openings in the end of the reduced portion of said center piece to operatively connect said cord and center piece together for rotary movement, and means for making an electric circuit between said prongs and said cord, said means including a rotary track in said chamber, a spring pressed pivot on said center piece and a wiper engaging said track, said wiper connected to one wire in said cord and said pivot connected to the other, a cup connected by a wire embedded in said casing to one of said prongs, said pivot rotatable therein and said rotary track connected by another wire embedded in said casing to the other of said prongs;
RALPH L. MUDD, JR.
References Cited in the file or this patent UNITED STATES PATENTS Number Name Date 1,450,172 Dewald Apr. 3, 1923 1,821,132 Baker Sept. 1, 1931 1,981,854 Comiskey u Nov. 27, 1934 2,181,145 .Mose Nov. 28, 1939 2,459,032 Korth Jan. 11, 1949 2,486,167 Jurasevich 'Oct. 25,1949