Note: Descriptions are shown in the official language in which they were submitted.
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EXTRACTING DEVICE FOR PLUG
This invention relates to an extracting device for a
plug which may be plugged into a socket, and which is
carried by an electric appliance, machine or similar
5 devices, such as electric engine heaters in motor
vehicles, battery chargers for electric vehicles and
the like.
If one forgets to extract a plug which has been plugged
into a socket, for example by the use of an engine
heater, this may lead to a powerful jerk being applied
to the electric cable holding the plug. Thus the plug,
cable and/or socket may be damaged.
In NO patent No. 165 088 a device is disclosed, which
is arranged to effect an automatic withdrawing of a
plug being part of an electric heating device for motor
vehicles. The withdrawing device of this heating device
is very bulky, meant to be mounted in a garage, and
arranged to pull the coupling up to a position at a
higher level, out of the reach of children. For this
purpose the known device has a weight-loaded, upward
sloping, pull-biased wire for moving said electrically
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established coupling up to the top of a column, where
the coupling no longer represents a hazard.
A wire connected to the plug is subjected to an upward
sloping pull to said higher coupling parking level, by
means of a weight attached to the other end of the
wire, and the wire is placed over a pulley at the top
of the column. The device requires a column of a
certain minimum height, which provides a plug-pulling
device too bulky for diverse application.
lo The object of the present invention was to eliminate or
substantially alleviate the imperfections, drawbacks
and restrictions on application of the state of the
art, as represented by the above NO patent.
The aim has essentially been achieved by means of an
automatic, remotely controlled, plug-extracting device
of the initially mentioned kind, having the features
stated in the characterizing part of claim 1.
Advantageous subordinate features, describing preferred
embodiments, have been made the objects of subsequent,
dependent, subordinate claims.
In a plug-extracting device according to the invention
is included at least one central, axially directed
piston in the plug, which piston has two main positions
along the longitudinal axis of the piston, namely a
first, withdrawn, idle position, in which the front
attacking end of the piston towards the fixed socket
does not apply any push force when the contact pins of
the plug are fully engaged in the insertion holes of
the socket with the aim of intentionally establishing
an electric connection between a plug at the end of an
electric cable belonging to an electric appliance etc.
and the socket fixed to the wall, or the loose
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extension socket; and a working position, displaced
axially forwards, in which the piston through its
attacking end exerts such a considerable push force
against the adjacent, outward central portion of the
5 socket that the contact pins of the plug are not able
to resist the push force, but are extracted from the
socket.
The piston has an idle position and an activated state.
The piston may be activated directly or indirectly. In
one embodiment in which the object of the invention is
used in an engine heater in a motor vehicle, around the
piston, which consists of ferro-magnetic metal and
forms a core, is wound an electric line wire for the
formation of a concentric induction coil with a wire
connection to earth and to the starting motor of the
vehicle. In the established electric circuit may be
connected a condenser arranged to accelerate the coil.
When the starting motor is activated on starting the
car motor, the coil about the piston receives elec-
tricity from the storage battery of the vehicle. Onactivation, i.e. when the coil is made current
carrying, the piston is subjected to a powerful axially
directed displacement in the direction of the socket,
whereby the plug is forced out.
In another embodiment the piston is not influenced
directly by the current in the coil, but indirectly, as
a compression spring retains the piston in an idle
stand-by position, in which the spring is kept in an
idle, tensioned state by means of a transverse,
elongate blocking or locking device, preferably of
ferro-magnetic metal, about which is wound a
corresponding line wire for the formation of a coil of
the same kind as the coil around the piston according
to the first embodiment. The blocking or locking means
of this embodiment is spring-biased towards the
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blocking position. In this embodiment the piston may
consist of any suitable material.
The second embodiment is primarily meant to be
connected to portable electrically driven appliances
and tools, such as vacuum cleaners, electric lawn
mowers, electric hand-held tools and similar.
Such electric appliances and tools are usually plugged,
by a plug at the end of a cable, into a socket in a
wall, or into a socket-shaped connecting part at the
end of an extension cord. When the work is finished,
the user must walk to the end of, for example, the
cable of the vacuum cleaner and pull the plug out.
When, for example, the plug of the cable of the vacuum
cleaner is plugged into said socket, the piston is
displaced against the force of the spring in a
direction away from the socket, while the spring is
being axially compressed. The compression spring, in
the form of a helical spring, is positioned in a
concentric sleeve which has a bottom at its end nearest
to the socket. In the opposite end of the plug is a
retaining/abutment means for the adjacent end of the
compression spring, and in which retaining/abutment
means is formed a guiding hole for the piston. Said
blocking or locking means will, when the piston is
withdrawn and the compression spring is tensioned
between said sleeve bottom and retaining or abutment
means, under the influence of the spring adopt a
pushed-out, effective blocking position, in which the
blocking or locking means with its outer end portion
engages behind the bottom of the sleeve, thus
preventing the compression spring of the piston from
expanding.
.... . . . . ..
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In the second embodiment the blocking/locking means
consists of ferro-magnetic material, and its coil has a
line connection to the current carrying cables through
a signal decoder. The signal decoder/receiver picks up
current to the coil, and is arranged to receive a
signal, which is to make it respond and axially
withdraw the blocking/locking means for the release of
the sleeve surrounding the compression spring, which
thereby presses the piston forwards towards the socket,
whereby the same course of events as by the first
embodiment is repeated.
The signal to the signal decoder/receiver comes from a
transmitter which may be attached to the electric
appliance or tool, to which the plug belongs, for
example a vacuum cleaner or an electric saw.
Practically, it is conceivable, in the second
embodiment, that when the user of a vacuum cleaner
operates a button which activates a reel for retracting
and winding the cable of the vacuum cleaner, an output
signal is simultaneously given from a signal
transmitter in the vacuum cleaner to the signal
decoder/signal receiver in the plug, to activate the
blocking/locking means in order to release the piston
and effect the forcing out of the contact pins of the
plug from the socket.
The invention will be explained in detail in the
following, with reference to the exemplary embodiments
illustrated in the accompanying drawings. Reference is
made to the drawings, in which
Figs. 1 and 2 show, in axial section, a first
embodiment;
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Fig. 1 showing a plug-extracting device comprising a
rod-shaped piston centrically arranged in a plug, which
by its contact pins is positioned for immediate
plugging into a socket, which may be fixed to the wall,
or be at the end of an extension cord;
Fig. 2, corresponding to fig. 1, but showing the plug
plugged into the socket, whereby the centric piston of
the plug has been pushed axially backwards to an idle
stand-by position;
Figs. 3 and 4 show, in axial section, a second
embodiment;
Fig. 3 showing the plug in the position for immediate
plugging into a socket, corresponding to fig. l;
Fig. 4 showing the plug in its plugged-in position,
corresponding to fig. 2;
Fig. 5 shows, in axial section, a plug-extracting
device according to a third embodiment, the plug being
in the extracted position;
Figs. 6 and 7 show, in axial section, a plug-extracting
device according to a fourth embodiment;
Fig. 6 showing the plug positioned for immediate
plugging into a socket, corresponding to fig. l;
Fig. 7 showing the plug in the plugged-in position,
corresponding to fig. 2.
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Referring first to figs. 1 and 2; a plug 10 has axially
flush guiding holes 12, 12' in its opposite end walls
10', 10'' for a centrically arranged, linearly formed
rod-piston 14 with an outer attacking head 14', which
in the withdrawn, idle stand-by position of the piston
14, fig. 2, may have been retracted into a recess in
the end wall surface 10'' of the socket 10, nearest to
the socket 16. In fig. 2, conventional contact pins 18,
18' of the plug 10 are plugged into corresponding bores
20, 20' having inner contact sleeves 22, 22', in which
the friction between the pins 18, 18' and the walls of
the bores ensures the engagement as long as the piston
14 is not activated, fig. 2.
An embodiment of the plug-extracting device as shown in
figs. 1 and 2, may, for example, be used in engine
heaters in private cars and lorries, buses and when
charging storage batteries for electric cars, wheel
chairs etc.
In the embodiment according to figs. 1 and 2 the
centric piston 14 has got a wound-on line wire for the
formation of an induction coil 24, as the piston
consists of ferro-magnetic metal. The coil 24 is,
through two electric wires 26, 26', via a condenser 28
which is arranged to enable acceleration of the coil
24, but which may optionally be omitted, connected to
earth and to the starting motor (not shown) of the
motor vehicle.
When the plug 10 is left, unintentionally, in its
plugged-in position in the socket, in accordance with
fig. 2, and starting of the motor vehicle through the
starting motor is initiated, the latter will supply
power to the coil 24, which has a direction of windings
which thereby causes an axial displacement of the
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ferro-magnetic core/piston 14 in the direction towards
the socket 16. Thus, the device is arranged so, that
the piston 14 exerts an axial push force against the
socket 16 greater than the longitudinal component of
force of the frictional force between the contact pins
of the plug lO and the complementary bores of the
socket 16. Thereby the plug is pushed out of the socket
until the two are fully separated, fig. 1. When the
motor of the motor vehicle starts, the current to the
starting motor is interrupted and the coil 24 is dead.
A second embodiment is shown in figs. 3 and 4, in which
parts corresponding or functionally equivalent to parts
according to figs. 1 and 2 are designated by the same
reference numerals.
Thus, the plug 10 according to figs. 3 and 4 has a
piston 14 arranged thereto, which piston 14 has an
attacking head 14' and is guided by a hole 12' in the
front end wall 10'' of the plug 10 and by a hole 12 in
the rear end wall lO'. The socket 16 has, thereby, a
configuration which is almost identical to that shown
in figs. 1 and 2. The contact pins 18, 18' and their by
friction determined engagement and retention in the
bores 20, 20' of the socket 16, are exactly as in the
embodiment according to figs. 1 and 2, and will
consequently not be described in detail.
The piston 14 has not a coil of its own arranged
thereto, but is, on the other hand, provided with a
compression spring in the form of a helical spring 30,
which is surrounded, in its compressed state, fig. 4,
by a sleeve 32, having an end wall 32', which is fixed
to the piston 14. The sleeve 32, 32' will enclose a
part of the length of the compression spring 30 when
this is ex~nded, fig. 3. The compression spring 30 is
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suspended between the front surface of the end wall 10'
and the sleeve bottom which is formed by the rear
surface of the end wall 32' of the sleeve. The task of
the compression spring 30 is to expand from the
compressed state in fig. 4 to the state according to
fig. 3, thereby pushing the plug 10 out of the socket
16 in the same way as described in connection w$th the
embodiment in figs. 1 and 2.
Before such a plug-extraction is to be actuated
automatically and by remote control, the compression
spring 30 must be kept in its compressed state, fig. 4.
This is done by means of a spring-loaded (34) blocking
means 36 extending and being displaceable in one
direction transverse to the longitudinal axis of the
~5 piston 14 and the spring 30. In the withdrawn, spring-
loaded, stand-by position of the extraction piston 14
and the corresponding position of the compression
spring 30, fig. 4, the compression spring 34 of the
blocking means 36 has moved its outer blocking end
portion 36' in behind the sleeve bottom constituted
by the end wall 32' of the sleeve 32. Thereby the
expansion of the spring 30 is prevented and the piston
14 is retained in its withdrawn, idle position.
In this embodiment it is the blocking means 36 of
preferably ferro-magnetic material which is surrounded
by a coil 38 of line wire, that has a signal
decoder/receiver 28 arranged thereto, and through which
it is connected to the current carrying conductors 50,
50' of the electric cable.
The embodiment according to figs. 3 and 4 may be used
with portable appliances and tools, such as vacuum
cleaners, electric lawn mowers and similar electric
tools.
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The signal decoder/receiver 28 picks up current to the
coil 38 and is arranged to receive a signal making it
respond. The signal comes from a transmitter (not
shown) which may be attached to, for example, a vacuum
5 cleaner. It is known within the art to use the current
carrying conductors 50, 50' as such signal carriers.
By a vacuum cleaner it is conceivable, practically,
that when the user operates a button activating a reel
for winding the cable of the vacuum cleaner, a signal
10 is sent by said transmitter through the conductors 50,
50' and 26, 26' to a signal decoder/signal receiver 28
arranged to the plug lO. The signal decoder 28 is thus
arranged to pull by the reel 38 the blocking means 36
against the spring 34. Thereby the sleeve 32 is
15 released and the spring 30 presses the piston 14
through the sleeve 32, 32' in towards the socket 16,
whereafter the push-out procedure of the plug 10
follows exactly as previously explained. Reference
numeral 40 designates a housing enclosing the signal
20 decoder/receiver 28 and the blocking means 36.
Fig. 5 shows a modification of the embodiment according
to figs. 1 and 2, and essentially shows another
positioning of the piston's 14a' rear portion,
surrounded by the coil, as it is connected to the
25 piston 14 through a flexible rod 14a. The flexible rod
14a and the conductors 50, 50', 26, 26' may be
positioned together with the flexible rod 14a within a
protective tube 51.
A somewhat elongate hollow body 42 has two end walls
30 transverse to the longitudinal axis of the adjacent
piston portion 14a', which end walls have one guiding
hole each for said piston portion 14a'.
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The embodiment according to fig. 5 leaves more freedom
of choice as to placing the coil/condenser 24, 28,
which does not have to be placed at the plug 10 itself.
The embodiment according to fig. 5 works in the same
way as the embodiment according to figs. 1 and 2, and
the way of working will not be explained again.
Figs. 6 and 7 show a further embodiment which
essentially corresponds to the embodiment of figs. 3
and 4, and identical parts in these figures are
lo designated by the same reference numerals. The
embodiment in figs. 6 and 7 differs from the other
embodiments by having, instead of a central rod-like
piston 14, 14a, an alternatingly moveable, spring-
loaded tube 14B with a central longitudinal axis. The
tube-shaped piston 14B has a graded portion 14B' of
larger diameter tboth internally and externally), but
in the example smaller wall-thickness than the
remaining part of the tubular piston 14B. Thereby is
formed a radially directed, annular abutment surface
14B'', which one end of the compression spring 30A
bears against. The second end of the spring 30A bears
supportingly against an end surface 52' in an annular
space 52, formed in the plug 10, for the spring 30A.
In the plugged-in position of the plug 10 in the socket
16, the blocking means 36 bears with its blocking end
against an annular radial surface 14B''', so that the
compression spring 30A is kept in compressed stand-by
position as shown in fig. 7. As in the embodiment in
figs. 3 and 4, the blocking means 36 consists of ferro-
magnetic material and is surrounded by a coil 38 ofline wire, which has a signal decoder/receiver 28
arranged thereto, and which communicates through the
latter with the current carrying conductors 50, 50' in
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the electric cable. For the rest, this further
embodiment is configured as previously described in
connection with figs. 3 and 4.
