US3351724A

US3351724A - Road treadle switch

Info

Publication number: US3351724A
Application number: US563756A
Authority: US
Inventors: William C Goble
Original assignee: Raybestos Manhattan Inc
Current assignee: Raymark Industries Inc
Priority date: 1966-07-08
Filing date: 1966-07-08
Publication date: 1967-11-07
Anticipated expiration: 1984-11-07

Description

NOV. 7, 1967 W C. GOBLE ROAD TREADLE SWITCH A:2 sheets-shewL 1 Filed July a, 1966 E/ E PM M HM 2/ 05/ ,Z s/V/A 4.1.. Z/ l W f ATTORNEY w. c. GOBLE 3,351,724

ROAD TREADLE SWITCH Nov. 7, 1967 Filed July 8, 1966 2 Sheets-Sheec 2 INVENTOR W/c/HM 6'. 60am.:

United States Patent() 3,351,724 ROAD TREADLE SWITCH William C. Goble. East Paterson, NJ., assignor to Raybestos-Manhattan, Inc., Passaic, NJ., a corporation of New Jersey Filed .lilly 8, 1966, Ser. No. 563,756 8 Claims. (Cl. 200-86) This invention relates to -a road treadle switch.

The prime object of the present-invention isdirected to a road treadle switch of the type in which an envelope of elastomeric material encases switch members operated by treadle depression of a passing vehicle Iapplied to and acting on the top wall of the envelope, the treadle switch embodying means for improving the wear resistance and thus the life expectancy thereof while still providing and retaining the flexibility necessary for proper treadle switch operation.

Road treadle switches have been manufactured with envelopes or shells m-ade of an elastomeric material so as to provide flexibility required for transmitting pressure applied thereto tothe encased switch contacts. The envelopes are usually constructed to embody some modifying or added means for enhancing to a predetermined desired degree the flexibility of the top wall thereof in the areas that are subject to treadle depression. The elastomeric top wall of the treadle switch, subjected to repeated depressing and scufing action of the wheels of a vehicle stopping at and starting from a toll station normally wear relatively fast, and in the'course of time render the treadle inoperative, requiring frequent replacements. The means employed to enhance the flexibility of the treadle top is such that it undesirably acts to increase the wear and thus more rapidly reduce the useful life of the treadle, particularly in those parts thereof which are in the path of the Vehicle wheels.

In carrying out the prime object of the present invention, the road treadle m-ade of an elastomeric material possessing an inherent resilience and abrasive resistance, and an inherent as Well as an added enhanced flexibility is combined with wear improving means incorporated into surface areas of the top wall of the elastomeric envelope between and spaced by .adjoining flexibility areas thereof, said means comprising wear pads having abrasive resistance greater than the inherent resistance of said adjoining flexibility areas, with the result that the wear resistancev of the switch treadle and hence the life expectancy thereof is improved while the necessary and predetermined flexibility is provided and retained.

To the accomplishment of the foregoing objects and such other objects as may hereinafter appear, my invention relates to the road treadle switch as defined in the n appended claims taken together with the following specification thereof and the accompanying drawings, in

which:

FIG. l is a top plan view of a first form of a road treadle switch embodying the principles of the present invention;

FIG. 2 is a view thereof shown on lan enlarged scale and taken in cross-section inthe plane of the line 2-2 of FIG. 1;

FIG. 3 is a fragmentary view thereof shown on the same scale as FIG. 2 and taken in cross-section in the plane of the line 3--3 of FIG. 1; Y

3,351,724 Patented Nov. 7, 1967 FIG. 4 is a top plan view of a second form of a road treadle switch of the invention;

FIG. 5 is a view ofthe latter shown on an enlarged scale and taken in cross-section in the plane of the line S-S of FIG. 4;

FIG. 6 is a fragmentary view thereof shown on the same scale as FIG. 5 and taken in cross-section in the plane of the line 6-6 of FIG. 4; v

FIG. 7 is a plan view of a modification of the second form of the roadvtreadle switch of the invention;

FIG. 8 is a view of the latter shown on an enlarged scale and taken in cross-section in the plane of the line 8-8 of FIG. 7; and

FIG. 9 is a fragmentary view thereof shown on the same scale as FIG. 8 and taken in cross-section in the plane of the line 9-9 of FIG. 7.

Referring now more in detail to the drawings and having reference first to the form of the invention shown in FIGS. 1 to 3 thereof, the road treadle of the present invention comprises an envelope or shell E defined by a ytop wall 10, a bottom wall 12,

opposite side walls

14 and 16 and

opposite end walls

18 and 20 and the switch members S, S encased thereby, two of which are shown in the drawings. Each of the switch members S comprises normally open contact elements movable to switch closing condition by the treadle depression of the top wall 10 of the envelope E, the said contact elements for each switch member comprising a metal base plate 22 as the lower contact element (serving for both switch members) and a spring steel plate 24 as the upper contact element, the

upper contact elements

24, 24 being supportingly spaced from the lower contact element 22 by an encircling mount 26.

The shell or envelope E is m-ade or fashioned from an elastomeric material possessing inherent resilience, flexibility and abrasive resistance. Such an elastomeric mate rial is either a synthetic rubber such las neoprene or G.R.S. rubber as illustrated in the drawings or may be a polyurethane as hereinafter described. Such an elastomeric material provides flexibility required for transmitting pressure applied to the top wall of the envelope E to operate the encased switches S, S. In the kform of the invention shown in FIGS. l to 3 the structure of the switch elements and particularly the provision of

cavities

28, 28 between the contact elements of the switches define means for enhancing to a desired degree the ilexibility of the top wall of the envelope in the areas that are subject to treadle depression.

In carrying out the principles of the present'invention in all of the constructional forms shown in the drawings,

the envelope E comprising the elastomeric material in.

itself possessing resilience, flexibility, and abrasive resistance, is combined with wear improving means incorporated into surface areas of the top wall of the elastomeric envelope between and spaced by adjoining flexibility areas thereof, said means comprising wear pads having abrasive resistance greater than the inherent abrasive resistance of said adjoining iiexibility areas.

Reverting now to the form of the invention shown in FIGS. 1 to 3, the wear improving pads arey located in and confined to the normal path areas of the wheels of a passing vehicle. To this end the top wall 10 of the envelope is subdivided at its surface into the spaced ilexibility areas designated F, F and wear pad areas into which are incorporated wear pads W, W, the wear pads bei-ng arranged in the normal path of the wheels of a vehicle and between and spaced by the adjoining flexibility areas F, F.

Where the elastomeric material of the envelope E comprises a synthetic rubber, the wear pads W, W are made of a polyurethane material. Polyurethanes comprise a group of synthetics with end products characterized as flexible and elastomeric rubber-like products of superior strength, good elasticity, extremely good abrasion resistance and hardness, and resistance to greases, oils, and solvents. Basically they are reaction products of polyols and isocyanates, the major contributing variable being the polymers or polyfunctional resins which can be alkyd, polyesters or polyethers. These resins are of a class based `on polyhydric alcohols and organic or polybasic acids. Adipic acid and glycols of various types are the prime source of polyols used in the manufacture of polyurethanes. The polyurethane elastomer selected for the wear pads W, W is preferably a liquid polyurethane produced by the E. I. du Pont Company and sold as their Adiprene L liquid urethane elastomer', the preferred Adiprene product for use in the making of the treadle wear pad of the present invention being Du Ponts Adiprene L-lOO which yields a solidified product having a durometer hardness of 88-90 and Adiprene L-420 which yields a solidilied product having a durometer hardness of 80.

While such polyurethane pads also have an inherent flexibility and resilience, they possess an abrasive resistance substantially greater than the inherent abrasive resistance of the rubber elastomer of the flexibility areas F, F of the envelope E.

For mounting the wear pads W, W into the spaces provided therefor in the top wall of the envelope E, the surface of the neoprene or G.R.S. rubber which is first produced in molded cured form, is first cleaned of oils and grease by the use of a solvent such as methyl ethyl ketone. The cleaned surface then receives a coat of a suitable cement. This is allowed to air dry. The liquid polyurethane is then poured onto the prepared surface and is then subjected to a heat treatment of 212 F. for a period of three hours.

As indicated heretofore, the body of the envelope E may also be made of a polyurethane material, in which event the wear pads W, W are made either of a higher wear resistant polyethylene or of a wear resistance rigid material such as steel. In this case the envelope E is first produced as follows: The metal base plate 22 is suitably prepared and placed in a forming receptacle (not shown) whose dimensions conform to the desired final size of the treadle being manufactured. The treadle of FIGS. 1 to 3 is generally made having a length of from 8 feet to 10 feet and a width of 4 inches to 14 inches (nominally 10% inches) and a height of l inch. The upper

spring contact plates

24, 24 are mounted spacedly from the lower metal contact plate 22 by means of the mounts 26 which encircle the

cavities

28, 28, the upper contact spring plates being framed in the mounts 26, which latter are made of rubber or a like material designed to seal the

enclosure cavities

28, 28. With these parts of the switch members S, S assembled and with suitable fixtures or plugs being also set up in the receptacle for forming the

road mounting orifices

39, 30, the liquid polyurethane is then poured into the forming receptacle, the liquid polyurethane flowing about and encasing the switch members S, S. In the assembling step of the switch members the proper conducting lead wires 32, 32 (see FIG. l) are connected to the `

contact elements

24, 24 of the switch members. The next operation is the curing of the thus completed assembly in a dry heat at a temperature of about 180 F. for the period of about one hour. Where the wear pads W, W now comprise a polyurethane material having a higher abrasion resistance than the polyurethane material of the envelope E, the wear pads are incorporated into the top wall of the envelope as follows: The surface of the cured polyurethane is washed with xylene, and the uncured polyurethane used to form the wear pads is then poured onto the prepared surface. The assembly is then subjected to a dry heat of 212 F. for a period of an hour. Where the wear pads W, W are made to comprise a rigid high abrasive material such as steel, the surface of the steel is irst prepared by shot blasting or chemical etching; and in either case the steel is treated such as in a vapor degreaser to remove oils and grease. The surface of the steel is then coated with a cement; and a tack coat of a suitable cement is then applied to the surface of the seat for the pads W, W and allowed to dry. The wear pads are then applied; and under a high pressure and temperature the assembly is cured.

In each of the described structures in the form of the invention shown in FIGS. 1 to 3, there are thus wear improving pads W, W incorporated into surface areas of the top wall of the elastomeric envelope E between and spaced by adjoining flexibility areas F, F thereof, said wear improving pads having abrasive resistance greater than the inherent resistance of said adjoining flexibility areas, with the result that the Wear resistance of the switch treadle and hence the life expectancy thereof is improved while the necessary and predetermined ilexibility is provided and retained. In the form of the invention depicted in FIGS. 1 to 3 the life expectancy of the treadle switch is extended also by confining the wear improving pads to the areas defined by the normal path of the wheels of a passing vehicle.

In FIGS. 4 to 6 of the drawings is shown a second form of the invention wherein features of treadle flexibility and resilience are obtained in another way customarily employed with rubber treadles. In this form of the invention the treadle envelope E comprises a shell having a top wall 10', a bottom wall 12', side walls 14 and 16' and end walls 18 and 20' encasing switch members S, S', the contact elements of which (not independently shown) are indicated by the mark X. As before the envelope E' is made of a rubber elastomeric material possessing an inherent resilience, abrasive resistance and flexibility. In this form a road treadle the flexibility of the road treadle is enhanced by the provision of flex grooves in the top wall of the road treadle as Well as open spaces in the body of the vtreadle as will be presently described. This form of road treadle is made by assembling with an uncured body of rubber a steel supporting plate 33 functioning to rigidify the structure and a number of bars (four in number) enveloped by a rubber impregnated cloth, these bars serving to produce the

cavities

34, 34 and a number of bars (three in number) serving to form the

additional spaces

36, 36. This assembly is placed into a mold shaped to the form shown in cross-section in FIG. 5, the form being such as to provide or produce flexing grooves 38, 38l in the top wall of the envelope and seats 39, 39 for the subsequent incorporation therein of wear pads W', W. After the molding of this assembly, the bars which form the cavities 34 are withdrawn leaving in the cavities the rubber impregnated cloth 40 which now defines the walls of the

cavities

34, 34, the withdrawing of the remaining bars leaving or producing the

cavities

36, 36, which latter function, as a supplement to the flexing

grooves

38, 38 for enhancing the flexibility of the treadle structure to the required degree.

In this form of construction there is also produced at the bar withdrawing end of the treadle shell, integral socalled boots 42., 42 of the rubber elastomer through which previously attached lead wires 44 extend, the bars being withdrawn through these extending boots, after which sealing means are inserted to seal the lead wires at this end of the treadle. l

In this form of the treadle structure wear pads W', W' are incorporate-d into the top wall of the treadle envelope E' by being mounted in the seats 39 provided therefor,

the wear pads W', W being thus incorporated into the surface areas of the top wall of the envelope between and spaced by the adjoining flexibility areas vprovided by the flexing

grooves

38, 38, the flexibility in this case being further supplemented by the similarly spaced provision of the

cavities

36, 36. y

In this form ofthe structure the flexing

grooves

38, 38 comprise a plurality of grooves arranged longitudinally of the envelope E and spaced transversely of the top wall of the envelope, the wear pads W', W also extending longitudinally of the envelope E and being located between and in alternatingy relation with the

longitudinal flexing grooves

38, 38.

Where, as indicated, the material of the envelope E is an elastomer such as neoprene or G.R.S. rubber, the material of the pads W', W is a polyurethane of the class heretofore mentioned, namely a cured polyurethane obtained from a liquid polyurethane such as the Adiprene L-l or the Adiprene L-420 liquid urethane elastomer (produced and sold by the E. I. du Pont Company), the former yielding a solidified product having a durometer hardness of 88-90 and the latter yielding a solidified produ-ct having a durometer hardness of 80. Such wear pads are incorporated into the top w-all of the envelope E in the s-ame way as heretofore described in connection with the making of the envelope E, where the parts of the latter are formed `with the similar materials.

The road treadle of FIGS. 4 to 6 may also be produced by making the envelope E of a polyurethane material such as the one having a lower durometer hardness and by then making the pads W', W thereof either of a polyurethane m-aterial having a greater durometer hardness or by making the same of a metal such as a steel plate or bar. In this event the envelope E is made by pouring the liquid polyurethane into a forming receptacle in which are assembled the steel supporting plate 33, the four bars enveloped by the rubber impregnated cloth serving to produce the

cavities

34, 34 and the three bars serving to form the

additional spaces

36, 36, this assembly being arranged in the forming receptacle reversely to that shown in FIG. 5 of the drawings, suitable members being set in the bottom of the receptacle for forming-the

flex grooves

38, 38

yand the seats 39, 39V in the top wall of the treadle.

With these parts thus assembled the liquid polyurethane is poured into the forming receptacle producing, after the heating step (curing is at a dry'heat at a ternperature of about 180 F. for the period of about one hour), the cast treadle portrayed in the drawings. After these operations the -bars forming the

cavities

34, 34 and the

spaces

36, 36 are withdrawn in the manner previously described and switch members S', S are then inserted into the

cavities

34, 34 and the treadle thereupon sealed. The pads W', W are then mounted and Secured to the

seats

39, 39 provided therefor. These wear pads made either of a polyureth-ane having a greater abrasion resistance lthan the polyurethane of the envelope E or made of a metal such as a steel bar or plate are secured in their seats in the same Ways as heretofore described for these respective materials.

Again here as in the first form of the invention the wear improving pads are incorporated into surface areas of the top wall of the elastomeric envelope between and spaced by adjoining flexibility areas thereof, and the wear improvingpads introduce an abrasive resistance greater than the inherent abrasive resistance of the flexibility areas of the treadle which adjoin the location of the Wear pads.

The road treadle depicted in FIGS. 7 to 9 of the drawings embodies the same structure as the road treadle depicted in FIGS. 4 to 6 of the drawings with the exception that in the treadle of FIGS. 7 to 9, in addition yto the plurality of longitudinal flexing grooves, Ithere are provided a series of flexing grooves arranged betweenk said longitudinal flexingA grooves and spaced longitudinally of the top wall of the envelope, with wear pads located and -arranged in the spaces provided between said plurality and said series `of flexing grooves. In this form of treadle structure the parts similar to Ithe parts which are the same as the treadle structure of FIGS. 4 to 6 are designated by the same reference characters. The additional series of flexing grooves which are arranged -between the

longitudinal grooves

38, 38 and which are spa-ced longitudinally of the top wall of the envelope are designated by the

reference characters

382, 382. The wear pads which are then loc-ated and arranged in all of the spaces provided by the plurality of flexing

grooves

38, 38 and the series of flexing

grooves

382, 382 are designated by the reference .character W2. With this construction flexibility of the treadle structure as a whole is produced both longitudinally and transversely of the treadle structure to a maximum degree.

In all of the forms of the road treadle switch disclosed, a high wear resistant material in the form of the wear resistant pads or strips is placed in the areas that have been subjected to extreme wear. The required flexibility for the satisfactory operation of the treadle switches is provided by the juncture of flexible elastomer inbetween the pads or strips of the wear resistant material. In all of these forms of the invention the elastomer is depressed in the areas or grooves that receive practically :little or no abrasive wear. As a result a longer life road treadle switch is provi-ded with increased efficient operation thereof at toll installations of turnpikes, bridges, etc.

The structures, operation and uses as well Ias theadvantages secured by road treadle switches of the present invention will thus be apparent from the above detailed description thereof. It will be further apparent that many changes may be made therein without departing yfrom the spirit of the invention defined in the following claims.

I cl-aim:

1. A road treadle switch comprising an envelope defined by a top wall, a bottom wall, opposite side walls, and opposite end walls, and switch members encased by said envelope, the said switch members comprising normally open contact elements movable to switch closing condition by treadle depression of a passing vehicle acting on the top Wall of said envelope, characterized by the said envelope comprising an elastomeric material possessing inherent resilience, flexibility and abrasive resistance, said elastomeric material providing in the top wallr ofV said envelope spaced areas lpossessing said inherent resilience, flexibility and abrasive resistance, combined with wear improving means incorporated into surface areas of the top wall of said elastomeric envelope between land spaced by said flexibility areas thereof, said means comprising wear pads having abrasive resistance greater than the inherent abrasive resistance of said 'adjoining flexibility areas.

2. The road treadle switch of claim 1 in which the wear improving pads are located in andconfined -to the normal path area of the vehicle.

3. The' road treadle switch of claim 1 in which the elastomeric envelope embodies means for enhancing the inherent flexibility of the top wall thereof in the areas that are subject to treadle depression, and the said Wear pads are located in spaced relation to said last mentioned areas.

4. The road treadle switch of claim 3 in which the means for enhancing the inherent flexibility of the top wall of the envelope comprise a plurality of longitudinal flexing grooves arranged in said flexibility areas of the top wall of the envelope and spaced transversely of the top wall of the envelope, and the rear pads are located and arranged between said flexing grooves.

5. The road treadle switch of claim 1 in which the elastomeric material of the envelope is selected from the group consisting of rubber and polyurethane, and the material of the wearV pads is selected from the group consisting of a polyurethane or a metal, the polyurethane of v the wear pads having a higher abrasion resistance than elastomeric material of the envelope is selected from the group consisting of rubber and polyurethane, and the material of the wear pads is selected from the group consisting of a polyurethane or a metal, the polyurethane of the wear pads having a higher abrasion resistance than the rubber and polyurethane of the envelope.

7. The road tre-adle switch of claim 3 in which the material of the envelope is rubber .and the material of the wear pad is selected from the group consisting of a polyurethane and steel.

8. The road treadle switch of claim 3 in which the means for enhancing the inherent flexibility of the top wall of the envelope comprise a plurality of longitudin-al flexing grooves spaced transversely of the top wall of the envelope land a series of leXing grooves arranged between Asaid longitudinal grooves and spaced longitudinally of the top wall of the envelope, and the wear pads are located and arnanged in the spaces between said plurality and series of ilexing grooves.

No references cited.

BERNARD A. GILH-EANY, Primary Examiner.

H. LEWITTER Assistant Examiner.

Claims

1. A ROAD TREADLE SWITCH COMPRISING AN ENVELOPE DEFINED BY A STOP WALL, A BOTTOM WALL, OPPOSITE SIDE WALLS, AND OPPOSITE END WALLS, AND SWITCH MEMBERS ENCASED BY SAID ENVELOPE, THE SAID SWITCH MEMBERS COMPRISING NORNALLY OPEN CONTACT ELEMENTS MOVABLE TO SWITCH CLOSING CONDITION BY TREADLE DEPRESSION OF A PASSSING VEHICLE ACTING ON THE TOP WALL OF SAID ENVELOPE, CHARACTERIZED BY THE SAID ENVELOPAE COMPRISING AN ELASTOMERIC MATERIAL POSSESSING INHERENT RESILIENT, FLEXIBILITY AND ABRASIVE RESISTANCE, SAID ELASTOMERIC MATERIAL PROVIDING IN THE TOP WALL OF SAID ENVELOPE SPACED AREAS POSSESSING SAID INHERENT RESILIENCE, FLEXIBILITY AND ABRASIVE RESISTANCE, COMBINED WITH WEAR IMPROVING MEANS INCORPORATED INTO SURFACE AREAS OF THE TOP WALL OF SAID ELASTOMERIC ENVELOPE BETWEEN AND SPACED BY SAID FLEXIBILITY AREAS THEREOF, SAID MEANS COMPRISING WEAR PADS HAVING ABRASIVE RESISTANCE GREATER THAN THE INHERENT ABRASIVE RESISTANCE OF SAID ADJOINING FLEXIBILITY AREAS.