US 2244933 A
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Description (OCR text may contain errors)
June l0, 1941. R, R- ARMSTRONG `2,244,933
y VEHICULAR TRAFFIC SWITCH Filed April l1, 1938 FIB-E /4 /5 55 56 /0 57 5l 57 /0 57 541 /O /7 542 /6 /0 56 55 /5 /4Z E "A d /Zy E,
. INVENTOR. Palo/7 rms/rong ATTORNEY.
Patented June 10, 1941 UNITED STATES PATENT OFFICE VEHICULAR TRAFFIC SWITCH Ralph R. Armstrong, San Francisco, Calif.
Application April 11, 1938, Serial No. 201,319
This invention relates generally to electrical switches of the type adapted to be installed in a roadway, for operation by the wheels of vehicular traffic. Such devices nd useful application in various electrical systems, as for example systems for counting vehicular traflic, various electrical signalling systems, or other systems or arrangements where its is desired to control an electrical circuit responsive to the passing of a vehicle along a given path.
It is an object of the invention to provide a switch of the above character which will be simple in construction, and which will be suiciently rugged to withstand the severe vehicular traffic of present-day highways.
A further object of the invention is to afford a switch structure having a novel form of contactor assembly, which can be readily removed as a unit for replacement or repair.
Another object of the invention is to provide an improved form of a vehicular switch which can be assembled in multiples for consecutive operation, with provision for removing or replacing separate switch structures or contactor units.
Additional objects of the invention will appear from the following description in which the preferred embodiment of the invention has been set forth in detail in conjunction with the accompanying drawing.
Referring to the drawing:
Fig. 1 is a plan view, illustrating a switch structure in accordance with the present invention, disposed within a roadway.
Fig. 2` is a cross-sectional detail on an enlarged scale, taken along the line 2-2 of Fig. 1.
Fig. 3 is a cross-sectional detail showing one of the units incorporated in the installation of Figs 1 and 2, together with the parts serving to mount the same in a roadway.
The complete tread structure illustrated in Figs. 1 and 2, consists generally of a plurality of duplicate switches Ill, carried by a common mounting means I-I. The length of the tread structure may vary in different instances. For example in instances where it is desired to operate the switches by wheels on one side of a single line of motor traffic, the complete tread structure may be say two to five feet in length. Where the wheels on both sides of a single line of vehicular trailic are to pass over the tread structure, the length may be from seven to ten feet. Longer lengths can be used if desired, as for example a length sufcient to extend entirely across a multi-lane roadway.
The mounting means II may vary as to structural details, but as illustrated it consists of a bottom plate I2, together with the side and end angles I3. Thus a shallow pan or retainer is provided, which can be mounted within a roadway, with its upper edge substantially flush with the roadway surface I4.
The construction of the individual switches Ill can be best understood by reference to Fig. 3. Each switch consists of an elongated body I6, extending substantially the entire length of the mounting II, together with an inner contactor assembly Il. Body I6 is preferably made entirely of resilient rubber, and is formed to afford a longitudinally extending passageway I8, to receive the contactor assembly II. Extending over the passageway I8 there is a top Wall I9, the upper surface 2| of which is convex to engage the wheels of vehicles. The lower or base portion 22 of the body I6 is preferably formed to afford laterally extending flanges 22a, which facilitate proper retention of the switch Within the mounting means II, Base portion 22 is integrally connected with the top wall I9, by the upright side walls 23.
Since the top and side Walls I9 and 23 are formed of resilient material, the weight of a vehicle wheel upon the top Wall I9 causes this wall to be depressed, and the vertical dimensioning of the passageway I8 to be decreased. It is such decrease in the vertical dimensioning of the passageway I8, which causes operation of the contacts of the contactor assembly Il.
The contactor assembly I1 in its preferred form, consists of a strip or core 24 of resilient material, like resilient vulcanized rubber, together with a pair of contactor strips 26. Strips 26 are formed of spring sheet metal, and preferably the sheet metal is bent to afford a substantially C-shaped cross-sectional contour. In other words these strips are generally channel-shaped, with the side flanges of the channels provided with inturned portions 21. It is portions 21 of the strips 26 which are normally in opposed spaced relationship, and which are brought into electrical contact by depressing the top wall I9. The resilient strip 24 is generally square or rectangular in cross-sectional contour, and in order to afford portions for detachable engagement with the strips 26, Ithe sides of the strip 24 are provided with longitudinally extending grooves 28. 'I'hus upper and lower portions 29 are provided, which are embraced by the strips 26, and which afford suilicient retention whereby the metal strips retain themselves in engagement with the rubber strip 24, as an assembly unit. Since portions 23 are readily deformable it is apparent that one may readily detach one or both of the strips 26 from the rubber strip 2d, 0r re-assemble these strips together, merely by applied manual force.
The metal strips 25 extend substantially the full width of the longitudinal passageway I8. The rubber strip 24 is of considerable less width than the width of passageway I3, but suflicient width is provided to avoid any buckling when it is compressed to bring portions 2l' in direct contact. In general it may be said that the width of the rubber strip 24 should be greater than onehalf its vertical dimensioning. Such proportioning of the strip 24 together with the provision of grooves 28, avoids possible pinching o'l rubber-of the strip between the contacting portions 2l, which if permitted would defeat the desired electrical engagement.
As previously pointed out in Fig. 1, the switch bodies I6 extend substantially the entire length of the mounting I I. The contacter assemblies I'I can be divided into a number of sections, it is simpler practice to afford a single assembly extending the entire length ,of the body I6. At one end of the mounting II a terminal box 3! can be provided, into which lead wires can extend from the metal strips of the several switches I3. A multiple conductor cable can lead from box 3|, for connection with other parts of .an electrical system.
Irrespective of the precise type of mounting employed for the switch, and irrespective of the number of switches used in a group, it is desirable to employ strips or anges which overlie the body anges 22a, and which carry the main thrust of vehicles. Thus in Figs. 1 and 2 metal clamps 33 and 34 are provided, which have anges 36 and 31 to overlie the flanges 22a of the switch bodies. Clamps 33 and 34 rest directly upon and are secured to the base plate I2, whereby the upper surfaces of these clamps form in eifect a continuation of the roadway surface, and sustain the downward pressure and thrust of vehicle wheels. Suiilcient clearance 38 is afforded between the outer surfaces of the switch body walls 23, and the adjacent flanges of the clamps, whereby the top wall I9 can be `depressed until its upper surface is co-extensive with the upper surfaces of clam-ps 33 and 34. Also the switches are so dimensioned, and the spacing between the clamps such that the tires of motor Vehicles will not depress the top wall I8 materially below the road surface. Some adjustment of the relationship between top wall I9, and the road surface, can be had by placing shims 4l -beneath the anges 36 and 31. Increasing the thickness of such shims will serve to effectively lower the upper switch surface 2I, with respect to the road surface, an-d conversely decreasing the thickness of the shims will serve to compensate for wearing away of the upper surface 2 I.
Operation of the switch described above can be briefly outlined as follows: Depression of a portion of the top wall I9 of the switch causes the resilient core 24 of the contacter unit, below the depressed area, to be compressed t0 cause portions 21 of the contacter strips 25 to be brought into direct electrical engagement. A certain amount of bending of strips 26 is necessarily involved but such bending is well within the elastic limits of materials like hard bronze, copper, or monel metal. While the wheel of a motor vehicle is in engagement with the top surface 2| of the switch, the downward pressure from the wheel tire is carried mainly by the adjacent clamps, and that part of the downward thrust carried by the switch itself is accommodated by the compressed side walls 23, and by the base portion 22 underlying the longitudinal passage I8. Immediately after the wheel has passed over the switch, the switch body returns to its original form, and the parts of the switch unit spring back to their normal positions as shown in Fig. 3.
In the event the switch unit I'I should become disabled through long usage, before the body I6 has reached the end of its useful life, the contactor assembly or unit can be slid longitudinally from the body, and the injured parts repaired or replaced, or a new assembly inserted.
1. In a trafhc switch, an elongated casing vformed to afford an inner longitudinally extending passageway, said casing being adapted to be installed in conjunction with a roadway whereby the tcp wall of the casing is adapted to be engaged and depressed by vehicular traffic, thereby decreasing the vertical dimensioning of said passageway, and contacting means disposed within said passageway and adapted to be operated by a decrease in the vertical dimensioning of said passageway, said contacting means comprising a strip of resilient material, and electrical contacting strips retained on the upper and lower portions of said strip of resilient material and adapted to be brought into electrical engagement by compressing said strip of resilient material in a vertical direction, the upper strip having depending side portions and the lower strip having upwardly extending side portions, said side portions loosely embracing the upper and lower portions of the resilient strip and forming oloctrical contact surfaces.
2. In a traic switch, an elongated casing formed to afford an inner longitudinally extending passageway, said casing being adapted to be installed in conjunction with a roadway whereby the top wall of the casing is adapted to be engaged and depressed by vehicular traffic, thereby decreasing the vertical dimensioning of said passageway, and a contacter assembly removably disposed within said longitudinal passageway, said assembly comprising a strip of resilient Inaterial, said strip having a width substantially less than the width of said passageway, and a pair of oppositely faced channel-shaped strips of sheet spring metal embracing the upper and lower lportions of said strip of resilient material, said metal strips having a width substantially equal to the width of said passageway and having opposed side portions adapted to be brought into direct physical engagement, upon compressing said strip of resilient material in a vertical direction responsive to downward movement of said top wall.
3. In a trailic switch, an elongated casing formed to afford an inner longitudinally extending passageway, said casing being adapted to be installed in conjunction with a roadway whereby the top wall of the casing is adapted to be engaged and depressed by vehicular trailic, thereby decreasing the vertical dimensioning of said passageway, and a contactor assembly adapted to be removably disposed within said longitudinal passageway, said assembly comprising a pair of conductor strips formed of sheet metal bent to have a cross-sectional contour substantially C-shaped, and a strip of resilient rubber having its upper and lower portions embraced by said conductors, whereby when said assembly is disposed within metal embracing the upper and lower portions of said strip of resilient material with the opposite inturned edge portions of the Ranges thereof extending into said grooves in interlocking relation, the strip of resilient material being compressible to permit electrical contact between the inturned edge portions of said metal strips.
RALPH R. ARMSTRONG.