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Патент USA US2130500

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Sept. 20, 1938.
E. D. LAWSON
-
AUTOMATIC SAFETY SWITCH FOR VEHICLES
Filed Aug. 10, 1935
2,130,500
2,130,500
V Patented Sept'ZO, 1938
' -' UNITED .STATES PATENT 0FFlC_E=_
AUTOMATIC SAFETY SWITCH FOB
'
.
VEHICLES
Edward D._ Lawson, Park Ridge, Ill.
Application August 10, >1935, Serial No. 35,648
6 Claims. (Cl. 200-42)
'This invention relates to safety switches, but is
particularly concerned with switches, adapted for
use in the electrical circuit of an automotive ve
hicle, of such construction that the circuit shall
5 automatically break if the vehicle on which the
switch is used should turn over in any way be
yond some predetermined angle, the purpose of
the switch being to cause the circuit to become
dead, thus stopping the engine and eliminating
the danger of ?re from electrical origin.
A switch of this kind intended for use on auto—
motive vehicles and particularly motor cars, is
subjected to tremendous jars and shocks. Where
the switch contains a ?uid, it is quite a problem
to prevent undesired movement or surging of the
?uid without introducing features ‘of construction
which complicate the switch and increase its cost.
One 01’ the objects of the present invention is
to provide a ?uid type safety switch such for ex
ample as a mercury type switch which shall be
simple and inexpensive in construction and in
which means shall be provided to prevent unde- -
sired surging of the ?uid during the normal oper
ation of the motor vehiclereven though‘ it be op
25' erating over extremely rough roads or other
ground.
‘
'
I
It is another object of the invention to provide
a switch of this type having means which shall
cooperate withcertain ‘natural forces tending to
30 maintain the body of the ?uid in a certain pre
7 determined position and shape until the abnor
posed of a' number of materials, but is preferably
made of a molded substance which is a good elec
trical insulator. As here shown, it is of substan
tially rectangular shape and is of suilicient depth
to provide a recess for the accommodation'of two
switch tubes, later to be described, in superposed
relation.
Formed in the body of the casing 5 is a cross
like depression comprising the aligned portions
6-45’ and 1—‘i'.
Centrally, the‘ depression is en
larged and shaped to receive and hold snugly two
superposed blocks 8 and 8' of cushion material
to be described in detail later.
‘
In the cross-like depression before described,
there are two mercury switch tube elements 9 and
I0 of similar construction. The tube element 9 is
arranged at the bottom of the recess and extends
diagonally across the casing. The tube element
i0 is spaced above the tube element 9 and like
wise is positioned diagonally but substantially at 20
right angles to the ?rst mentioned tube. V
In Fig. 4 there is illustrated the two cushion
blocks 8 and 8' in superposed condition and in
the relation which they occupy when in the eas
ing 5. These blocks are preferably composed of
rubber of a fairly ?rm texture and yet having
su?icient resilience to permit being pressed into
position in the opening provided therefor'in the
casing 5, a slight compression of the block hold
ing it ?rmly in position.
,
mal forces developed by the vehicle turning over trally arranged hole I | of a size substantially the
or tilting beyond a predetermined angle shall be same as the external diameter of the switch tube
element intended to be positioned therein. By
sumcient to breakdown or alter this status.
making a snug ?t it is possible to press the tube
The
invention
consists
in
certain
features
of
35
construction and in the combination and arrange ' element into the opening H and have the block
?rmly holding the same. It will be understood
ment of the several parts which will be herein
that block 8 receives-tube designated in in Fig. l
after fully described. The preferred embodi
ment is illustrated in the accompanying drawing. and that block 8' receives the tube marked 9 in
In the drawing:—
40
the same view.
>
Fig. l is a perspective‘ view of the switch with
the face plate removed in order to expose the in
terior construction.
'
'
'
Fig. 2 is a longitudinal‘sectional view of one
45 of the switch tubes removed from the casing
' and from its cushioning holder.
Fig. 3 is a cross-sectional view through one of
' the tubes just above the top level of the mercury
and illustrating a suppressor plate carried by one
50
of the electrodes, and
'
30
Each block is provided with a cylindrical cen
'
Fig. 4 is a perspective view of a pair of cushion
blocks for holding the tube element in position
in the switch housing.
The switch casing or housing as a whole is
65 designated by the reference 5. It may be com‘.
40
As is clearly illustrated in Fig. 1, the depres
sions 6-6’, '|-—'!' in the housing I are slightly
greater in size than the ‘tube, thus providing a
clearance space around the tubes in order to pre
vent any possible contact of the tube with the ad
jacent wall of the housing 5. In other words,the
two tube elements, by means of the blocks 8-8’
are ?rmly held. and positioned against movement
in any direction and with the clear space separati
ing the tubes from the various parts of the hous 50
ing and from each other.
' In‘ Fig. 2 I have illustrated one of the switch
tubes independently of the cushion holding block
and removed from the switch housing 5. Inas
much as the two tubes are of like construction, a
2
2,130,500
description‘ of one will suffice for both. It is
composed of a glass tube ii’ of substantially cy~
lindrical shape, closed at one end I 3 bythe sub
over or reaches some predetermined angle then
the forces mentioned are overcome and the mer
cury flows to the other end of the tube, thus
stantially dome-shaped portion. At the lower
end, the glass walls are pressed together, provid
breaking the electrical circuit, thereby causing
the engine to stop and making all parts electri
ing the solid portion ll through which the elec
trodes l5 and I6 pass from the exterior to the
interior of the tube. Inthe lower end of the tube
I have provided a body of mercury I1. I prefer
cally dead.
I prefer also, so to form, position and arrange
the plate 20 that it will act as a positive me
chanical valve. To this end, .the plate is eccen—
trically disposed within the tube as best shown'
mercury for reasons which will later appear.
The upper part i8 of the tube is preferably ?lled - in Fig. 3 so that there is a- very small space 2|
with an inert gas. It is known that the molecules
at the surface of a liquid are subjected to a force
tending to draw them inward.
This force, in
15 eiiect, is like pressing the surface toward the in
22 diametrically opposite. The space 22, there
fore, becomes the “gate” through which the mer
side as though by a tough elastic sheet stretched
over the surface. The final result is to shape the
liquid so that it shall tend to have the least pos
sible surface, 1. e. that of a sphere. This result
does not entirely obtain in all instances, but there
is usually considerable curvature to the top sur—
face of the liquid. This contracting force is usu
ally termed surface tension. In the case of mer
cury, the molecular force is relatively great so
that the surface tension is likewise considerable
and hence results in a very pronounced curvature
at the top surface. This, I have indicated in Fig.
2 at H. The pull seems to be the greatest ad
jacent the wall of the tube so that the liquid
surface assumes a curve of smaller radius at that
It is believed, from the foregoing, that the op
eration of the switch will be understood. How—
ever, referring brie?y to Fig. 1, it will be seen that
one electrode of one tube is electrically connected 20
to one electrode of the other tube by a conductor
23. The other electrode of tube 9 is connected
to the binding post 24 by the conductor 25 and
the other electrode of tube I0 is connected to the ‘
binding post 26 by conductor 21. The conductors
29 and 30 respectively connected to the binding
posts 2!; and 26, it will be understood, form a
part of the electrical system of the vehicle to
which the switch is a?ixed.
It will be observed that each. mercury tube ele-.
ment is a very simple construction so that it
As an aid in checking the tendency of the mer
cury to surge when the vehicle is subjected to
lends itself to rapid and practically automatic
manufacture and hence can be produced at low
cost. The two mercury tubes, in turn, are very
quickly and easily assembled in the casing 5
and there held in place by cushion blocks 8-8’
in which the tubes have been placed prior to
positioning in the casing 5.
In practice a face plate, not shown, is fastened
to the casing 5 so as to prevent tampering with
the switch. The face plate also aids in holding
the blocks 8 against undesired movement later
ally of the casing.
It will also be understood that the switch is
intended to occupy a vertical position, i. 'e. the
tubes are positioned in vertical planes. Conven
20 at the end of one of the electrodes of the tube.
The disc or plate 20 as shown, is positioned so
that it contacts the upper surface of the mercury
when the tube is in normal operating position.
It thus may be said to act as a surge suppressor
because it assists the molecular forces in holding
the mercury in position.
I I also prefer to provide a supplementary elec
trode portion 20“ of arcuate form. As shown it
is a?ilxed to the electrode that carries the plate
45 20. The portion 208‘ aids in preventing surging
because the mercury is confined at the top by
the plate 20 and more or less anchored by the
arcuate electrode portion 20“. This construction
also provides intermediate of the electrodes, por-,
50 tions relatively close together , and which are
bridged by the mercury even though a consider
able portion may have ?owed away from the bot
tom of the tube. It will thus be obvious that there
are several restraining influences which prevent
55 undesired surging of the mercury. There is force
of gravity which is considerable due to the density
of mercury. Furthermore, since the air has been
exhausted and replaced with an inert gas, there
is no air that'c'an be trapped under the mercury.
60 If ‘air were present and became trapped under the
mercury, it would act like a. spring to agitate the
mercury, which would be objectionable‘.
}
Another restraining in?uence is the molecular
force which produces a surface tension that draws
65 the top surface of the mercury inwardly so that
said top surface tends to take on a dome shape.
However, because of the fixed position of the
plate 20 with respect to said top surface, said sur
face tension is resisted and the surface is flat
70 tencd out so that an upward thrust is produced
against the underside of the plate. This prevents
any incipient tendency of the mercury to surge
through inertia set up by the jolting of the ve
hicle, from becoming effective. of course, when
the vehicle containing the switch actually turns
15
cury ?ows when'the vehicle is tilted or turns over.
place as indicated at l9“. '
. heavy jolting or jarring, I provide a plate or disc
v
between the wall of the tube ‘and the edge of the
plate at one side and a substantially larger space
oi
iently the rear face 5' of the casing can be placed
against a vertical wall of the motor vehiclebody
and the casing held in place by suitable fastening
devices.
'
.
It will further‘ be obvious that-the switch may
be fully assembled at the factory and that no spe
cial operations are necessary to condition the
switch for use, except to see that the switch is
mounted in a vertical plane.
While inv describing the invention, I have re
ferred in detail to the arrangement and con
struction of the various parts, it will be under
stood that changes may be made provided such
changes come within the scope of the appended
claims.
I claim as my invention:
'
-
1. A switch of the kind described embodying
therein a pair of tubes oppositely inclined from
the perpendicular, the tubes being ‘arranged in
different vertical planes, means providing a cush
ion having openings therein through which said
tubes extend with a snugiit so as to ‘be supported
by said means, a quantity of mercury normally
disposed in the bottom end of each tube, and a
pair of electrodes associated with/each tube and
opening thereinto to engage in the mercury in the
respective tubes, the electrodes of both tubes
being adapted‘for connection in the circuit to be
controlled.
oi
2,180,500
4. A switch element embodying a tube, a
therein a pair of tubes oppositely inclined from
quantity of liquid, adapted to conduct electricity,
normally disposed in the bottom end of the tube,
the perpendicular, the'tubes being arranged in
di?’erent vertical planes and crossing each other
to present a substantially X form, cushion means
supporting said tubes at the point where they
cross each other, a quantity of mercury nor
mally disposed in the bottom end of each tube.
and a pair of electrodes associated with each
10 tube and opening thereinto to engage in the
mercury in the respective tubes, the electrodes
, for both tubes being adapted for connection in
'15
3
2. A switch of the kind described ‘embodying
the circuit to be controlled.
3. A switch oi’ the kind described embodying
therein a casing having an X shaped depression
therein formed by a pair of channels which inter
sect one another. said depression having an
enlargement at said intersection, a pair of tubes
oppositely inclined from the perpendicular, the
tubes being arranged in di?erent vertical planes
but crossing each other at said enlargement. a
quantity of mercury normally disposed in the
bottom end of each tube, a pair of electrodes asso
ciated with each tube and opening thereinto to
engage in the mercury in the respective tubes.
the electrodes for both tubes being adapted for
connection in the circuit to be controlled, and a
, cushion block disposed in said enlargement and
surrounding the central portion of each tube and
serving to hold the tube in place in said casing.
.
a pair of electrodes associated with the tube and
opening thereinto to engage in the said liquid, a
plate ?xed in said tube against movement and
substantially paralleling the top 01' the liquid
when the tube is in normal position, and a sup
plementary electrode portion carried by one of
the electrodes and spaced below the said plate. 10
5. A switch element embodying a tube, a quan
tity of liquid, adapted to conduct electricity, nor
mally disposed in the bottom end of the tube, a
pair of electrodes associated with the tube and
opening thereinto to engage in the said liquid, a 15
plate, iixed in said tube against movement and
substantially paralleling the top_ .01’ the liquid
when the tube is in normal position, and an
arcuate electrode portion carried by one of the
electrodes below said plate.
20
6. A switch element embodying a tube, a quan
tity oi’ liquid adapted to conduct electricity-nor
mally disposed in the bottom end oi the tube, a
pair or electrodes associated with the tube and
opening thereinto to engage in said liquid, a plate 25
carried by one of the electrodes and substantially
paralleling the top of the liquid when the tube is
in operable position, said plate being eccentrically
disposed within the tube.
V
EDWARD D. LAWSON.
30
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