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Патент USA US2107651

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Feb. 8, 1938.
Filed Jan. 25, 1935
2 Sheets-Sheet l
Feb. 8, 1938._
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\ Filed Jan. 25, 1935
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Patented Feb. 8, 1938
Sidney Reynell Smith, Liverpool, England, as
signor, by mesne assignments, to Automatic
Telephone & Electric Company Limited, Lon
don, England
Application January 25, 1935, Serial No. 3,371
In Great Britain February 15, 1934
2 Claims.
The present invention relates to electric
switches and is more particularly concerned with
pressure-operated switches of the type inserted
in the road surface to act as vehicle detectors in
Vehicle-actuated traffic control systems. In well
known prior constructions of this type, the weight
or” vehicles traversing the detector flexes a re
silient conductor sheet into contact with another
conductor sheet to complete an electrical circuit.
l i)
In such prior arrangements the springiness of
the resilient conductor sheet is primarily relied
upon to separate the electrical contacts when the
vehicle had passed off it.
In the construction according to the present
invention, the resilient conductor sheet is re
tained but its resiliency plays little or no part
in bringing about the separation of the contact
sheets since it is now supported by other resilient
means which may be subjected to great strain
without the possibility of its taking on a per
manent set.
According to another feature of the invention,
the resilient conductor sheet may be readily re
moved for examination or replacement without
disturbing the complete detector assembly or elec
trical wiring.
The invention will be better understood from
the following description of one way of carrying
it into effect, which will be explained in connec
tion with the accompanying drawings.
Figure 1 shows a plan View of the vehicle de
tecting unit.
Figure 2 is a section view along the line 2-2 of
Figure l.
Figure 3 is a section view' along the line 3-~3
of Figure 1.
Figure 4 is a section View along the line 4-4
of Figures 2 and 5, and
Figure 5 is a section view along they line 5_5
of Fig. l.
Referring to Figure 5, it will be appreciated
that the unit comprises a substantial tread mem
ber El of moulded rubber which seats between two
shoulders 22, welded on a metal bed plate 23 and
45 is clamped into position by metal strips of L
section 24 which run the full length of the de
tector and register with moulded grooves in the
tread member. The purpose of these grooves is to
prevent the tread being stroked out of position
by the continuous impact of heavy vehicles. The
resilient conductor sheet 25 is shown accommo
dated in slots in the tread member into which it
may be inserted lengthways but it could also be
moulded and if necessary provided with suitable
55 projections or ears to ensure that it should main
(Cl. 200-86)
tain its position. The eiïect in either case is that
the sheet 25 is suspended over a pair of contact
bars 21, 28 lying side by side on a hard rubber bed
29. Two contact members 21, 28 are provided to
adapt the unit to detect traine passing in one
direction only, and the manner in which this
may be effected follows:
When a Vehicle passes over the unit the rubber
tread is depressed and carries with it the resilient
conductor sheet 25 which ñrst comes into en 10
gagement with the contact bar lying nearer the
point of application of the pressure and as the
traffic passes over the detector the resilient sheet
then bridges both Contact bars. The movement>
produced is of a rolling type and when the vehicle 15
leaves the detector the rubber tread 2l resumes
its normal position and lifts the resilient sheet 25
clear of both contact bars 21, 28.
The `contact bars 21, 28 are securely fastened
to the hard rubber bed plate 29 by a number of
screws 3û, in the manner shown in Figures 1, 4,
and 5, and the mounting is suniciently robust to
support the traffic passing over them. Alter
natively, if unidirectional detection is not re
quired, the two bars 21, 28 could be connected
together so as to have the same eiîect or be
replaced by one bar of double width. Rubber
studs 32 are provided at intervals along the tread
member on both sides of the cavity carrying the
resilient strip 25 and their function is to ensure
that the strip shall not come into contact with
the bars in case the tread should become dis
torted after long use.
The cables for extending the electrical connec
tions to the contact bars and flexible plate ter
minate in a separate chamber 40. Referring now
to Figures 1, 2, and 3, it will be noted that this
chamber or splice box 40 is located at the side of
the detector, rather than at its end, so as to avoid
introducing a dead spot, or region in the detector
not sensitive to pressure actuations. The actual
connections to the contact bars and ilexible steel
plate element are effected by means of springy
strips of metal, 4|, 42, 43, and as shown in Figure
2 the left hand contact bar 21 has riveted to its
underside a U-shaped springy connecting link 42
which is accommodated in a slot 45 in the hard
rubber bed plate 29 and is held in position by two
bolts 46 which pass through the main bed plate
23 and are threaded into a brass bar 48 provided
with a terminal 49 at its end. Insulating bush
ings 54, and pads 5U, 5| are provided to prevent
contact with the metal bed plate 23 which is at
earth potential. Connection with the right hand
contact bar 28 is effected by another piece of 55
springy material 43, which is accommodated in
a further cavity 55 in the hard rubber bed plate
29 and is of angular shape as indicated in Fig
ures 1 and 4, the free end rising to connect with
the underside of the bar 28.
Connection with the resilient contact strip 25
is effected in the manner shown more clearly in
Figure 3. The sides of the cavity in the tread
2l supporting the strip: 25 are cut away for an
inch or so, so that the strip projects for this
distance unsupported and establishes rubbing
contact with the U-shaped spring member 4l
shown. A metal block 51 is provided under
neath the free end of the spring 4l about the
area where it contacts with the resilent conduc
tor 25, to form a stop for limiting the move~
ments of the spring and to prevent it from be
coming distorted in the event of heavy traffic
passing over this particular point in the detector.
20 In this case also, external connection from the
spiing is made through the fastening bolts 56
and, as shown in Figure l, the three terminal
members 48, 58, 68, are supported by the bridge
pieces 52, 53 at the point Where they enter the
splicing chamber 4U to withstand the strain of
the connecting cable. As will be appreciated
from Figures 2 and 3, the splice box 40 is welded
to the bed plate 23 of the detector unit and is
provided with inlet conduit 3l and outlet con
duit 35 for accommodating the connecting ca
bles to the control equipment.
The complete assembly described is arranged
to be embedded in a concrete foundation in the
road and will preferably be provided with bars
or ñns (not shown), around which the concrete
sets to anchor the unit ñrmly to the road surface.
It will be appreciated that if it is desired to gain
access to the contacts 25, 21, 28, after the de
tector has been installed it is only necessary to
remove the screws 3l holding the clamping mem
bers 24 and lift out the rubber tread member 2l.
out above, and others, are achieved.
It is to be
understood that various modifications in the
structural details or arrangement of the parts,
or changes in the designs herein exemplified may
be made Without departing from the spirit of
the invention as deñned by the claims.
Having described my invention what I claim
as new and desire to secure by Letters Patent of
the United States is:
1. In a vehicle operated switch, the combina
tion of a relatively long and narrow receptacle
adapted to be imbedded substantially horizon
tally in the roadway for operation by vehicles
passing thereover, a stationary contact bar ex
tending longitudinally in Said receptacle, a re
silient insulating cover mounted in said recep
tacle, said cover having projecting portions ex
tending downward and longitudinally thereun
der and formed with slotted recesses extending
longitudinally and horizontally in said project 20
ing portions with the open edges of said recesses
spaced laterally in opposed relation to each
other, and a contact strip slideably mounted in
said recesses so as to be resiliently supported by
said cover for engagement with said stationary
contact bar only under pressure by vehicles on
said cover.
2. In a traffic operated circuit closer, a sub
stantially rigid and relatively long and narrow
receptacle, a contact bar mounted therein, a re
contact bar and providing slotted recesses ex
tending horizontally and longitudinally along
its inner walls with the open edges of the recesses
spaced laterally opposite each other, and a flex
ible contact strip detachably mounted in said
slotted recesses so as to be normally supported
out of engagement with said bar and for engag
ing said bar upon pressure applied to the outer
tread member may be substituted without dis
surface of said cover and upon release of presn
sure being restored by resilience of the cover to
turbing the electrical connections.
normal position.
rI'his may subsequently be replaced or a new
Thus the several objects speciñcally brought
silient insulating cover removably mounted in
said receptacle and forming a cavity over said
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