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Патент USA US3090414

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R. L. ROBY
UBE FOR
3,090,404
IC INDICATOR
F'i llllllllllll 61
INVENTOR.
ROBERT L. ROBY
Y
.
.
United States
atcnt
Free
1
3,090,404
PRESSURE TUBE FOR TRAFFIC INDICATOR
Robert L. Roby, San Marcos, Calif., assignor to Accurate
Products Company Inc., Paci?c Beach, Calif.
Filed July 24, 1961, Ser. No. 126,276
4 Claims. (Cl. 138—11§)
3,090,404
Patented May 21, 1963
2
ing materials such as fabrics; but these did not correct the
shortcoming.
At the present time, pressure hoses are good for about
half a million cycles; but this is too short a life for heavily
travelled roads.
Objects and Drawings
This invention relates to pressure tubes, and more par
It is therefore the principal object of my invention to
provide an improved tripper.
ticularly to tubes of this type that are used to activate
devices that count tra?ic, switch signals, open or close 10
It is another object of my invention to provide a tripper
doors, or perform some similar work.
that is sensitive to small weights.
It is a further object of my invention to provide a trip
BACKGROUND
per that has a long life.
As is well known, tra?ic signals are frequently arranged
The attainment of these objects and others will be
to favor a busy street; but a device in the side street trips 15 realized from the following speci?cation, taken in con
the signal when a vehicle passes over the device. These
junction with the drawings, of which
trippers are frequently buried in the roadway, and are thus
FIGURE 1 is a diagrammatic representation of how
subject to drippage of rain water, dirt, and the like.
my pressure tube is used;
Another use of these trippers is to count vehicles pass
FIGURE 2 is a cross sectional View of my pressure tube
ing a given spot. This information aids tra?ic authorities
under normal uncollapsed conditions; and
in planning roads and highways, establishing patterns for
FIGURE 3 is a cross sectional view of my pressure tube
turns and signal lights, determining the type of pavement
and repairs that would be most satisfactory, and helps them
under collapsed conditions.
Brief Description of the Invention
ground type, that type of installation would be advanta
provides many desirable characteristics.
Detailed Description of the Invention
in many other ways.
It is also desirable to alert the operator of service sta 25
Broadly stated, my invention contemplates a pressure
tions when a car drives in. Another, but similar situa
tube whose base is slightly concave, and has ribs to pre
tion, requires that a door be opened or closed when a
vent movement of the pressure tube when run over by the
person or vehicle passes a given location. Other situa
wheels of vehicles. My pressure tube also has a convex
tions of this general type will be familiar to the reader.
top portion, and contains an oval longitudinal air cham
It is apparent that if the trippers can be of the above 30 ber. This combination of tube-shape and chamber-shape
geous.
The most widely used tripper is a strip of material that
is stretched across the road, path, or corridor, so that the
weight of a passing vehicle or person can be used to ob~
tain the desired vresult.
One form of tripper has two vertically-spaced-apart
metallic strips therein, and the weight of the passing ob
jects caused the metallic strips to touch and thus com
As may be seen from FIGURE 1, in obtaining tra?ic
information, my pressure tube 10‘ is placed across a road
“ way 12. As previously indicated, it may be used in other
locations; ‘but for ease of explanation, its use will be dis
cussed in terms of a road and vehicles.
The distal end 16 of pressure tube 10' is sealed. This
plete an electric circuit. Not only is this form of tripper 40 result may be accomplished by doubling back the end of
expensive, but the metallic strips soon corrode and destroy
the tube, by insertin a plug into it, or in any other suit
able manner.
‘
the usefulness of the tripper.
Another form of tripper is a sealed pressure tube that
contains a given volume of air. The weight of a passing
The proximal end of pressure tube 10 is attached to
a utilization device 18, which may be a counter, a switch
object collapses a portion of the tube, thus causing an
that controls signal lights or an alarm, a mechanism that
increased air pressure that activates associated equipment. 45 opens or closes doors, or any other piece of apparatus.
This system is satisfactory but it was found however, that
While various arrangements may be used, the one shown
the available pressure tubes had a limited life.
in FIGURE 1 provides information on tra?ic moving in
Prior-art pressure tubes took the form of hoses that had
a given direction; and places the utilization device on the
round cross sections. These had several disadvantages.
50 shoulder of the roadway, where it may be checked, re
'Firstly, when struck by the tire of a vehicle, the round
paired, studied, etc. without danger from passing vehicles.
hose tended to roll away. This continued movement put
a strain on the attachment to the utilization device.
In FIGURE 2, there is shown a cross sectional view
of my pressure tube 10' in its normal uncollapsed state.
Secondly, when the prior-art pressure hose had been
Tube 10 is made of a resilient rubber-like or plastic-like
material.
moved as far as it could go by a ?rst wheel or a ?rst set
of aligned Wheels, the succeeding wheel or set of aligned 55 As may be seen, it has an air channel 19‘, and the bot
wheels to hit the tube stretched the tube, so that when
tom 20' of the pressure tube 10 is concave, so that the
the succeeding wheel or set of aligned wheels had passed,
pressure tube normally sits on its longitudinal edges 22.
the pressure hose snapped back toward its original posi
As soon as a wheel 24 of a vehicle strikes pressure tube
tion. This continued movement and snapping~back caused
10, the longitudinal edges 22 are pressed tightly against
60
a great deal of abrasion, and severely shortened the life of
roadway
12, so that the pressure tube cannot skid, bounce,
the pressure hose.
or ‘be moved from its original position. 1Further move
Thirdly, if the walls of the prior-art pressure hose were
ment of Wheel 24 ?attens out the concave bottom 20 of
made thin enough to collapse under the Weight of the
my pressure tube, and further deters movement of my
pressure tube.
vehicle, this collapsing produced a great deal of stress on
the walls, and they soon failed. If, on the other hand, 65
It will be seen that the above road-holding action keeps
the walls of prior-art pressure hoses were made thick
the pressure tube at substantially the same location at all
times; and thus overcomes some of the shortcomings of
enough to withstand the constant collapsing, they would
prior-art pressure hoses.
not collapse under the weight of motorcycles or sports
In FIGURE 3, a cross sectional view of the pressure
cars; and thus would not provide the desired results.
70
tube 10‘ is shown in its collapsed state. As previously
In an attempt to overcome the latter shortcoming, prior
explained, the resiliency of the material has permitted
art pressure hoses used walls that incorporated strengthen
the ‘bottom portion 20‘ to be ?attened so that it, longitudi
3,090,404,
nal edges 22, and longitudinal ribs 26- are all in intimate
contact with roadway 12.
that the speci?cation and drawing are to be considered as
merely illustrative rather than limiting.
The weightrof the wheel (not shown) has also col
I claim:
lapsed the pressure tube so that air duct 19 has also been
v
1. A pressure tube comprising a length of resilient ma
terial having a cross section that approximates a semi
oval, said tube having a bottom wall, side walls and a top
collapsed. Depending upon the weight of the vehicle, the
side portions 28 of the air duct 19 may be still partially
‘open, so that the pressure is equalized throughout the
pressure tube.
£5.
parture from the spirit and scope of the invention, and
wall de?ning a longitudinal passage substantially centrally
therethrough, said passage being substantially oblong in
-
It will be noted from FIGURE 3 that the thick side
cross section having a major axis of substantial length
walls 30 of the pressure tube 10 support the weight of 10 -which has a minimum length of approximately one-third
the vehicle, due to the substantially greater mass of the
the width of the tube, the longitudinal axis of the passage
material that form side walls 30, the relatively thin upper
being parallel to the longitudinal axis of the tube and
wall 32 of air duct 19 collapsing easily without excess
the short ends of the oblong being rounded, the outer
deformation. I also believe that the oblong shape of the
surface of said side walls and top wall joining to form a
air duct directs lines of stress downward and outward to
smoothly convex surface extending from substantially
the greater body of rubber, which is better able to absorb
the ‘bottom of one side wall to substantially the ‘bottom
them. This means that my structure overcomes'the wall
of the other side wall, the outer surface of said bottom
tlexing characteristic of prior-art pressure hoses; and
wall being slightly concave transversely of the tube so
that said tube normally rests on its longitudinal edges,
obviates the failures due thereto.
I
Once the wheel of the vehicle has passed over my pres 20 said top wall being of such thickness and material that
sure tube, the resiliency of the material causes it to spring
it is readily collapsed by the weight of an overriding ob
back to its normal uncollapsed condition.
ject, of substantial weight.
'
At the present time, a sample of my pressure tube has
2. The tube for a tra?ic indicator as set forth in claim
undergone over two million cycles; and shows no appreci
1 wherein said tube has a plurality of transversely spaced
able sign of deterioration. Estimates of experienced tra?ic 25 longitudinal ribs on the outer surface of the bottom wall.
analysts are that it should be able to withstand many
more cycles before having to be replaced.
Advantages
outline.
It will be obvious that my pressure tube has many ad- “
vantages over prior-art devices. It is a simple extrusion,
and is therefore readily available in any desired length.
It tends to remain in the same location, thus easing the
strain on the utilization device.
It does not crawl or
snap-back, thus minimizing the abrading thereof._ ,It is
an on-the-surface installation, and may be easily installed
or replaced when and where desired. It is extremely long
lived, and very low in cost.
3. The tube for the tra?ic indicator as set forth in
claim 2 wherein the vertices of the ribs'de?ne a concave
7
It is understood that minor variation from the form of 40
the invention disclosed herein may be made without de
4. The tube for a traf?c indicator as set forth in claim 2
wherein the ribs are of triangular cross section and have
their apexes disposed downwardly.
References Cited in the ?le of this patent
UNITED STATES PATENTS
1,915,167
2,107,350
2,440,533
2,750,232
Salsbury ____________ _- June 20,
Stubbins _____________ __ Feb. 8,
Antonson ___________ __ Apr. 27,
Szantay et al. ________ __ June 12,
1933
1938
1948
1956
2,922,613
Beachan et a1. ________ __ Jan. 26, 1960
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