U.S. patent number 3,609,635 [Application Number 04/754,188] was granted by the patent office on 1971-09-28 for self-ejecting electric plug.
This patent grant is currently assigned to Product Design & Manufacturing Corp.. Invention is credited to Lee M. Harris.
United States Patent |
3,609,635 |
Harris |
September 28, 1971 |
SELF-EJECTING ELECTRIC PLUG
Abstract
The plug includes a plunger normally spring retracted between
the prongs and a chamber containing thermally expansible material
and an electric heater which is the plug cord circuit, a remote
switch closure energizing the heater to expand the material against
the plunger to drive it outwardly and eject the plug from the
receptacle.
Inventors: |
Harris; Lee M. (Dayton,
OH) |
Assignee: |
Product Design & Manufacturing
Corp. (Willoughby, OH)
|
Family
ID: |
27384166 |
Appl.
No.: |
04/754,188 |
Filed: |
August 21, 1968 |
Current U.S.
Class: |
60/520; 60/516;
439/159; 60/531 |
Current CPC
Class: |
F03G
7/06 (20130101); H01R 13/637 (20130101); H01R
13/7132 (20130101); H05B 3/00 (20130101); H01R
2103/00 (20130101); H01R 24/28 (20130101) |
Current International
Class: |
F03G
7/06 (20060101); H01R 13/633 (20060101); H01R
13/637 (20060101); H05B 3/00 (20060101); H01R
13/70 (20060101); H01R 13/713 (20060101); H01r
013/62 () |
Field of
Search: |
;339/45 ;60/25,98,98RD
;52/1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Moore; Richard E.
Claims
I, therefore, particularly point out and distinctly claim as my
invention:
1. A thermally actuated device for converting electrical energy
rapidly to mechanical energy by volume and pressure increase due to
a liquid to gas phase change of a working fluid, comprising body
means, a distensible member in sealed engagement with said body
means forming a fluid chamber therewith, said distensible member
including an annular fold therein projecting into said fluid
chamber and adapted for unfolding upon an increase of pressure in
said fluid chamber, said distensible member having a central
portion supported by said annular fold adapted for substantially
linear movement away from and toward said body means, an inert
dielectric fluorinated hydrocarbon liquid filling said fluid
chamber when said distensible member is in a folded condition,
electrical resistance heating means supported in said body means,
being disposed in said fluid chamber and completely submerged in
said liquid for heating that portion of said liquid in contact
therewith to vaporization temperature, thereby to raise the
pressure in said fluid chamber and cause movement of said
distensible member and further comprising means for confining said
distensible member for such substantially linear movement, said
confining means being exterior of said body means and rigidly
connected thereto.
2. A thermally actuated device as set forth in claim 1 further
comprising a plunger supported for linear movement in said
confining means, said plunger being in abutment with said central
portion of said distensible member, and a spring in engagement with
said plunger for urging same against said distensible member.
3. A thermally actuated device as set forth in claim 2 wherein said
distensible member is a rubber diaphragm adapted for distension
without stretching, by rolling along said annular fold therein,
thereby providing substantially no resistance to movement of said
central portion.
4. A thermally actuated device as set forth in claim 3 wherein said
body means comprises a rigid cup and said diaphragm is secured at
the mouth of said cup, said annular fold being fully received
within said cup and adapted for unfolding exteriorly thereof to
provide linear movement of said central portion greater than the
depth of said cup.
5. A thermally actuated device as set forth in claim 4 wherein said
confining means comprises a cylindrical member rigidly secured to
said cup and adapted for support of said plunger and said spring.
Description
This invention relates to an electric plug which can eject itself
from a receptacle for self-disconnect action.
The copending application of John T. Venaleck, Ser. No. 689,663,
filed Dec. 11, 1967 and now Pat No. 3,475,715 issued Oct. 28, 1969,
discloses a plug assembly on this order in which the ejection is
under the control of a solenoid included in the circuit which is
energized by connection of the plug in the receptacle. More
particularly, this assembly comprises a plunger between the contact
prongs which is normally biased outwardly by a spring and
mechanically latched within the plug when pushed in by the
insertion of the plug in the receptacle. The solenoid, when its
circuit is completed by closure of a switch, withdraws the latch,
thereby freeing the plunger for outward drive by its spring and
hence the ejection of the plug from the receptacle.
One primary area of interest for this plug has been in electric
cords for portable appliances used in the home, with the vacuum
cleaner being a prime example, and it has been found that the
variation in receptacles, especially throughout older homes, is
even greater than was expected, with the result that the plug for
this application required a fairly heavy spring force for reliable
ejection. Increasing the spring force of course requires
proportionately more pressure by the housewife in the insertion of
the plug in the receptacle, with the latch necessarily stronger,
the solenoid larger, and the overall size increased.
It is a principal object of the present invention to provide such a
plug with an improved ejector mechanism having appreciably greater
capacity without the noted shortcomings of the solenoid plug
form.
Another object is to provide an improved self-ejecting plug which
is inexpensive to produce and relatively trouble free by virtue of
simplicity of its design and operating mode.
Other objects and advantages of the present invention will become
apparent as the following description proceeds.
To the accomplishment of the foregoing and related ends the
invention, then, comprises the features hereinafter fully described
and particularly pointed out in the claims, the following
description and the annexed drawing setting forth in detail a
certain illustrative embodiment of the invention, this being
indicative, however, of but one of the various ways in which the
principle of the invention may be employed.
In said annexed drawing:
FIG. 1 is a perspective view of a new self-ejecting electric plug
in accordance with the present improvements;
FIG. 2 is a longitudinal sectional view of the plug as indicated by
the line 2--2 in FIG. 1; and
FIG. 3 is an electrical schematic of a plug and appliance
combination.
Referring now to the drawing in detail, the plug comprises first
and second body parts 10 and 11, which are preferably made of rigid
plastic. The part 10 is generally annular, thereby defining a bore
12, with a radial stop flange 13 at the outer end of the bore and
an annular relief 14 in the inner end face for purposes to be
described.
The part 11 is in the nature of an end cap having a cylindrical
recess 15 on the same axis as the bore 12, with a slightly larger
inside diameter as shown. The outer or open end of the part 11
abuts the inner end of the part 10, with the two having the same
outside diameter, and the end face of the former has a groove 16
opposed to the annular relief 14 in the end face of the latter.
An elastic diaphragm 17, made for example of rubber, is arranged as
a wall separating the recess 15 from the adjoining bore 12 and
sealing the joint between the parts 10 and 11 by having a
peripheral bead 18 sealingly gripped in the groove 16 and relief
14. The diaphragm preferably has a fold 19 which it normally
assumes and which permits ready distension of the diaphragm
outwardly into the bore 12.
The recess contains a quantity of thermally expansible and
contractable material 20 and a schematically shown electric heating
coil H operative when energized to expand such material and thereby
exert an outward force at the diaphragm 17.
Such force is applied through the diaphragm to a plunger 21 in the
bore 12, also made of a rigid plastic, having a flange 22 at its
inner end. A return spring 23 extends from this plunger flange to
the stop flange 13 at the outer end of the bore 12 and serves
normally to hold the plunger in the relatively retracted condition
shown. Two metal prongs 24, 25 are attached to the outer face of
the body part 10 by bolts 26, 27 which extend completely through
this part and also through the part 11 at the rear of which they
receive electric wire terminals 28, 29 and nuts 30, 31.
Accordingly, the bolts serve also to unite the body parts 10 and 11
and electrically connect the prongs 24, 25 respectively to the
terminals 28, 29. The plunger is between the prongs, and two wires
32, 33 extend from the terminals 28, 29. As shown in the schematic
of FIG. 3, one end of the heating coil H is connected to wire 32,
while the other continues as a third wire 34. The plug assembly is
encased within an insulative cover 35, for example, of rubber
molded thereabout, and the wires 32, 33 and 34 extend through an
insulative cord body 36 to the appliance or other device served by
the cord.
In the FIG. 3 schematic, the circle 37 represents an electric
appliance and dashed line 38 the division between the plug circuit,
above the line, and the cord and appliance circuit. The latter
includes an on-off switch 39 and additionally a pushbutton switch
40 connected between wires 33 and 34, so that the heating coil in
the plug can selectively be energized by closure of the pushbutton
conveniently at the appliance.
When a housewife operating the appliance wishes to disconnect the
plug from the circuit, she need only close the heater switch 40,
with the resulting heating of the thermally expansive material 20
in the plug almost immediately effective to force the plunger 21
outwardly against the return spring force for automatic ejection of
the plug from the receptacle. Such material is selected to provide
quick response within substantially normal plug size and it has
been found that Freon, a halogenated hydrocarbon containing a
fluorine atom, is very satisfactory in this respect and also in
recycling. This inert, dielectric liquid will vaporize at about
200.degree. F., and that part of the liquid contacted by and
proximate to the heater in the plug can be almost immediately
heated to this temperature sufficiently to develop ejection force
with a relatively small resistance element at normal energization.
For example, a plunger force well over the 15 lbs. which appears
reliable for ejection from household sockets, has been developed in
less than 1 second with a heater of about 470 watts at 115
volts.
When the plug is ejected, the circuit for the heater in the same is
also automatically disabled along with the appliance or other cord
connected device, the expansion material as quickly contracts and
the return spring retracts the plunger to its normal nonobstructive
position. The power output is substantial and more than adequate
readily to effect disconnection of even a tightly held plug.
It will also be apparent that the number and character of the
components permit economic manufacture with high efficiency and
reliability. While the heating coil has been shown schematically
for convenience of illustration, it can in fact be a simple wire
coil of sufficient heating capacity relative to the fluid or
material used to perform with the desired quick response.
While the plug part of the plug-receptacle combination is
preferably the actuated part in the described application, it will
be appreciated generally that such an automatic disconnect can also
be realized comparably by incorporating the ejecting assembly in
the receptacle, with the plunger in this case normally retracted
between the socket contacts and driven outwardly against the plug
to eject the latter.
Other modes of applying the principle of the invention may be
employed, change being made as regards the details described,
provided the features stated in any of the following claims or the
equivalent of such be employed.
* * * * *