US2796488A

US2796488A - Treadle and treadle process

Info

Publication number: US2796488A
Application number: US395474A
Authority: US
Inventors: Cooper Benjamin
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-12-01
Filing date: 1953-12-01
Publication date: 1957-06-18
Anticipated expiration: 1974-06-18

Description

June 18, 1957 COOPER 2,796,488

TREADLE AND TREADLE PROCESS 7 Filed Dec. 1, 1953 2 Sheats-Sheet 1 W W \W Y INVENTOR.

MAM/ml 600P2 ATTOEA/EX June 18, 1957 COOPER 2,796,488

TREADLE AND TREADLE PROCESS Filed Dec. 1. 1953 Z'SheetS-Sheet 2 INVENTOR. 42 BfM/AM/N sm te JTTOEIVEY United States Patent'Of TREADLE AND TREADLE PROCESS Benjamin Cooper, Brooklyn, N. Y.

Application December 1, 1953, Serial No. 395,474

11 Claims. (Cl. 200-86) This invention relates to a process for making treadles having electrical contacts therein and to the treasdle made by such process.

T-readles generally comprise one or more pairs of normally open contacts that are mounted Within a sealed resilient envelope that is adapted to be embedded in a roadway whereby vehicles traversing the roadway will roll over the resilient envelope thereby effecting a closure of the normally open switches therein. Heretofore extraneous means have been utilized to maintain the spacing between the contact strips during manufacture and since these contacts could be effected by moisture a rubber resilient envelope is molded therearound. Previously, difficulty has been experienced in securing contacts to the rubber envelope and to the spacing of each related pair of contacts. Treadles generally are made by assembly of the contact strips with uncured rubber in a mold which is subsequently heated under pressure to a point where the uncuredrubber fuses into a homogeneous mass.

In assembling the contact strips, prior to the molding thereof in the envelope, complex means were utilized to secure the strips in spaced relationship to the resilient envelope.

The present invention provides a simple and inexpensive process for attaching contalct strips to a resilient envelope and for spacing said strips one from the other.

Therefore, one of the principal objects of the invention resides in the provision of a process for attaching metallic contact strips to a rubber envelope during the molding of said envelope.

Still another object of the invention is to provide a highly improved method [for spacing the contact strips one a trea'dle, a canvas cover for each of the respective canvas strips, folding the edges of the cover over and under the respective strips whereby metallic surfaces of each contact strip are exposed in a complemental manner one to the other and placing the covered contact strips in a mold with uncured rubber, applying heat and pressure to the mold whereupon the impregnated canvas covering is effectively fused with the rubber to seal the contact strips in the envelope thereby preventing viscous uncured rubber from getting in between the contact strips during the molding process.

Still another object of the invention is to provide a treadle having improved contact mounting means therein.

Other ancillary objects will be, in part, hereinafter apparent and will be, in part, hereinafter pointed out.

, In the drawings:

Figure 1 is a plan view of a treadle embodying the invention;

Figure 2 is a cross-section taken along line 2-2 of Figure 1, illustrating the relationship of the contact strips in the envelope;

2,796,488 Patented June 18, 1957 ice Figure 3 is a cross-sectional view illustrating a single contact treadle;

Figure 4 is an end view of a treadle before a plug has been inserted to seal the envelope;

Figure 5 is an enlarged fragmentary view of a single contact illustrating the method of mounting said contact relative to the treadle ground plate;

Figure 6 is a fragmentary plan view of a contact strip illustrating the method of attaching a conductor thereto;

Figure 7 is a cross-sectional view of a treadle embodying av two contact assembly insulated from the treadle ground plate and illustrating the method of covering the contact strips when a pair of strips is utilized;

Figure 8 is a cross-sectional view taken along line 88 of Figure 7, particularly illustrating the withdrawal of the core employed to maintain the spacing between contact strips during the molding process;

Figure 9 is an enlarged fragmentary cross-sectional view of the two contact assembly and the method of preparing said assembly with the rubber impregnated canvas;

Figure 10 is an end elevation partially cut away to illustrate a further embodiment of a treaxile wherein a pair of two contact strips is utilized;

Figure 11 is an isometric projection of a single contact strip having thereon the impregnated canvas cover illustrating the fold of canvas flaps;

Figure 12 is an isometric projection of the rubber plug that is inserted in the hole that is left in the end of the envelope after the spacer core has been withdrawn.

Referring to the drawings in detail, 10 generally designates a trea'd'le comprising a rubber envelope 12 that is afiixed to a ground plate 14 provided with mounting holes 16 and having embedded therein a contact strip 18 covered-by a rubber impregnated canvas duck 20. Attached to the contact strip 18, by riveting or the like, is a connector 22 and afiixed to the connector is a conductor 24. The conductor may be connected to extraneous equipment, not shown, and not forming a part of this invention. The trea'dle 10 is embedded in a roadway whereby the upper surface thereof is substantially disposed in the plane of the roadway with a central raised portion designated as 26 being disposed slightly above the plane of the roadway whereby the wheels of vehicles rolling over the treadle will compress center portion 26 and effect a contacting of the exposed portion 18a of strip 18 with a not shown.

Referring to Figure 2, there is shown a treadle 10 disposed in a mold 30, which comprises an upper shell 32 and a lower shell 34. In making the present invention, the conventional method of providing a rubber envelope is utilized, e., layers of uncured rubber are assembled to provide substantially the dimension of the treardle. The layers of uncured rubber are positioned on top of the treadle contact strips. The assembled structure then is placed within a mold and the mold mounted in pressure means, not shown. A pressure of approximately 50,000 pounds is applied to the respective halves of mold 30 while the mold is heated to approximately 300 degrees for a predetermined period of time.

The uncured layers of rubber that have been manually assembled in the shell are cured by the heating pressure to form a homogeneous mass having the shape of the mold. This process is conventional and widely used in the making of treadles. The present invention appertains to the steps of the process for making a treadle arsasss wherein the contact strips are especially prepared with a covering that effectively bonds the strips to the homogeneous mass and further insulates one strip from the other as hereinafter appearing.

The embodiment of the invention illustrated in Figures 1 through 6 comprises the making of a single contact-grounded treadle. This embodiment consists in applying a rubber impregnated piece of duck 40, of substantially greater width than the Width of the contact strip, and folding the margins thereof under the contact strip 18. As shown in Figure 3, the folds 42 of the impregnated duck 40 extend under the contact strip 18 for a relatively small distance compared to the overall width of the strip 18.

V The strip ,18, together with the enfolded duck, is manually placed on the steel ground plate 14 in proper relationship. The folds 42 of the impregnated duck are placed on a coating of ty-ply which is a commercial well known rubber'bonding agent previously applied to the steel plate 14 except for that portion of the plate which will be contacted by the underside of the contact strip 18. The layers of uncured rubber are positioned on top of this assembly and the curing process as hereinbefore 'set forth is performed. The curing process eifectively bonds the uncured rubber to the impregnated canvas duck, the canvas duck to the covered portions of the contact strip 18, and the folds 42 to the ty-ply bonding agent and subsequently to the steel ground plate 14. To prevent collapse of the spaced contact strip 18 during the curing process, a removable strip 44 is inserted under strip 18 between said strip and the ground plate. Strip 44 merely reinforces the strip 18 during the curing process wherein the extremely high pressures exert force on strip 18. The strip 44 is withdrawn through a hole 46 that is formed in one end of the treadle during the curing process. The hole 46 results from the presence of a mold plug, not shown, but which effectively forms the desired hole during the curing process. The provision of such :a hole 46 is well known to those skilled in the art. After the cured treadle is removed from the mold, a plug 48 of rubber such as shown in Figure 12, is inserted in the hole 46, of course, after the removal of the spacer strip 44 and then the plug 48 is vulcanized to eifectively seal the contact strip within envelope 12.

The bonding qualities of the rubber impregnated duck and the folds 42, while permitting an effective homogeneous assembling, prevents the flowing of the uncured rubber between the cont-act strip 18 and the ground plate 14. Heretofore special extraneous means have been necessary to seal out the cured rubber during the pressurized curing operation. 7

The contact strip 18 is now bonded over a maximum surface to the remaining elements of the treadle and the folds 42 provide an accurate spacer for maintaining the desired spacing between the insulated contact strip 18 and the grounded plate 14. The application of pressure on the top of the envelope 12 compresses the contact strip 18 and effects the engagement thereof with ground plate 14, thereby completing an electrical circuit through said contact strip and ground plate 14. Obviously, suitable conductors connected respectively to the contact strip 18 and ground plate 14, connegt the treadle switch to the external counting apparatus, not shown.

placed on the lower contact strip 52 and a second piece of rubber impregnated duck 60 is wrapped around the bottom surface of strip 52 and folds 62 thereof are disposed over the margin of the covered strip 50. Thus, the strip 50 is spaced and insulated from the strip 52 by means of the folds 58. The assembled contact strips are positioned on the ground plate 54 after a. coating of ty-ply shown as 64 is applied over the entire surface thereof. The layers of uncured rubber are then positioned on the contact strip assembly and a curing process as hereinbefore set forth is performed. A spacer strip 66 is disposed between the

respective strips

50 and 52 to maintain said strips in their properly spaced relationship during the pressurized curing process. When cured, the duck surrounding the contact strips is effectively bonded thereto and to the homogeneous mass of cured rubber. The upper contact 50 is distorted by pressure of a vehicle rolling over the treadle to engage the lower contact strip 52 as shown in dotted line in Figure 7 and effectively closes the electrical circuit for actuating the external counting apparatus, not shown. The insulated contact strips 50 and 52 are so bonded through the medium of rubber impregnated duck that a sealed unit results. Fur thermore, this successful bonding cannot loosen by repe'titious actuation and accordingly provides a treadle having long lasting qualities.

A two-switch contact treadle is shown in Figure 10 wherein two sets of insulated strips are disposed in a single rubber envelope. In assembling this dual embodiment, a further step is provided wherein a rubber block 70 of cured rubber is interposed between the respective sets of contacts. In the curing operation, this rubber block 70 is integrally bonded to the rubber envelope while maintaining the correct spacing relationship between the respective sets of contacts.

While the process hereinbefore described appertains to single and a dual contact strip treadles, it will be understood that the process'is equally applicable to multipletype treadles.

It will be seen, therefore, that there is provided a process in which the several objects of this invention are achieved and which is adapted to meet the conditions of practical use. 1

The invention claimed is:

1. A process for making a treadle switch consisting in placing a rubber impregnated flexible strip over the top surface of an elongated metallic contact member, folding the margins of the strip over the margins of the contact member and partially under said contact member and leaving a portion of the underside of said contact member uncovered, placing the covered contact member with the uncovered portion facing downwardly on a ground plate wherein the contact member is spaced from the ground plate by the strip margins, placing uncured rubber over the covered contact member and beyond the A second embodiment of .a treadle utilizing the present novel process is shown in Figures 7, 8 and 9 wherein an insulated-contact type treadle is shown. ln this latter embodiment of the invention, a pair of steel contact strips 50 and 52 are assembled in a treadle wherein both strips are insulated from the ground plate 54. Here again, the same curing process is employed. However, the novel steps of coating the contact strips with the impregnated rubber duck differs from the steps hereinbefore described. The upper strip 50 is wrapped with the rubber impregnated duck 56 in a manner hereinbefore described wherein the margins 58 thereof are folded over and underthe contact strip; This covered strip is then margins of the contact member and on the ground plate to form a rubber envelope, and curing the uncured rubber by heat and pressure whereby the rubber impregnated strip is bonded to the rubber envelope.

2. A process for making treadle switches consisting in covering a metallic contact member with a cover of flexible rubber impregnated duck, folding the duck over the margins of the metallic member and partially under said metallic member adjacent to the margins thereof and leaving a portion of the underside of said contact member uncovered, applying a bonding agent to portions of one side of a metallic ground plate, placing the covered contact member on the ground plate wherein the uncovered portion of the contact member is disposed over the uncovered portion of the ground plate and the covered portionof the underside of the contact member is disposed on the bonding agent, placing uncured rubber over the covered contact and beyond the margins of the contact member and on the bonding agent on the ground plate to form a rubber envelope, and curing the uncured rubber by heat and pressure whereby the rubber impreg- WWW nated duck is bonded to the rubber envelope and to the bonding agent and the bonding agent is bonded to the ground plate.

3. A process for making a treadle switch consisting in placing a rubber impregnated flexible strip over the top surface of an elongated contact member, folding the margins of the strip over the margins of the contact member and partially under said contact member and leaving a portion of the underside of said contact member uncovered, placing the covered contact member with the uncovered portion facing downwardly on a second contact member, placing the first and second contact members on a second rubber impregnated flexible strip, folding the margins of the second strip up and over the first covered strip, coating a ground plate with a bonding agent, placing the covered first and second strips on the bonding agent on the ground plate, placing uncured rubber on the covered first and second strips and on the bonding agent to form a rubber envelope, and curing the uncured rubber by heat and pressure whereby the rubber impregnated strips are bonded one to the other and to the rubber envelope and said envelope and the portion of the strip on the bonding agent is bonded to the ground plate.

4. A process for making a treadle switch consisting in covering a contact member with a flexible rubber impregnated cover having central portion on one side thereof cut away to expose the contact member, placing the covered contact member on a ground plate with the uncovered portion facing downwardly, coating the remainder of the ground plate with a bonding agent, placing uncured rubber over the contact strip and the ground plate to form a rubber envelope, and curing the assembled envelope to bond the rubber impregnated cover to the contact member and to the rubber envelope and bonding the remaining portion of the rubber envelope to the ground plate.

5. A process for making a sealed envelope with a pair of spaced electrical contacts therein consisting in covering a contact member with a rubber impregnated strip, folding the margins of the strip over the margins of the contact member and partially under said contact member, placing the covered contact member with the folds of the covered strip facing downwardly on the upper surface of a second contact member to space one con tact member from the other, placing the second contact member on a second rubber impregnated strip, folding the margins of the second rubber impregnated strip over the margins of the first covered strip, placing uncured rubber over the covered strips, and curing the uncured rubber by heat and pressure whereby the rubber impregnated strips and the uncured rubber form a homogeneous mass with the folds of the first rubber impregnated strip effectively spacing one strip from the other.

6. A process for making a mountable switch treadle consisting in placing a rubber impregnated flexible strip over the top surface of each of a plurality of contact members, folding the margins of the strips over the margins of the contact members and partially under said contact members and leaving a portion of the underside of said contact members uncovered, placing the covered contact members with the uncovered portions thereof facing downwardly on a metallic ground plate, placing strips of cured rubber between each adjacent contact member of said plurality of contact members, placing uncured rubber over the covered members and the cured rubber strips to form a rubber envelope, and curing the uncured rubber by heat and pressure whereby the plurality of contact members and the interposed strips are bonded to the rubber envelope.

7. A process for making a treadle switch consisting in placing a rubber impregnated flexible strip over the top surface of an elongated metallic contact member, folding the margins of the strip over the margins of the contact member and partially under said contact member and leaving a portion of the underside of said contact member uncovered, placing the covered contact member with the uncovered portion facing downwardly on a ground plate, inserting a spacer strip between the uncovered portion of the contact member and the ground plate, placing uncured rubber over the covered contact member and beyond the margins of the contact member and on the ground plate to form a rubber envelope, curing the uncured rubber by heat and pressure whereby the rubber impregnated strip is bonded to the rubber envelope, removing the spacing strip after the uncured rubber is cured and sealing the hole resulting in the envelope from the removal of the spacer strip with a plug.

8. A switch treadle comprising a ground plate, an elongated flat contact strip covered on one surface throughout its length by a flexible insulating rubber impregnated fabric, portions of said fabric overlapping the side margins of said contact strip and folded thereunder with the fabric terminal edges spaced one from the other to provide a linear uncovered portion throughout the length of the other surface on the underside of said contact member, said folded fabric portions further providing a predetermined parallel spaced relationship between the uncovered portion of the contact strip and the ground plate throughout the length of said contact strip, and a rubber envelope bonded to said fabric and covering said contact member on said ground plate.

9. A switch treadle comprising a ground plate, an elongated flat contact strip covered throughout its length by a flexible insulating rubber impregnated fabric, portions of said fabric overlapping the side margins of said contact strip and folded thereunder with terminal edges of the fabric spaced one from the other to provide a linear uncovered portion throughout the length of the underside of said contact member, said folded fabric portions further providing a predetermined parallel spaced relationship between uncovered portions of the contact strip and the ground plate throughout the length of said contact strip, a rubber envelope bonded to said fabric and covering said contact member on said ground plate, and conductor means connected to said contact member.

10. A switch treadle comprising a pair of flat elongated contact members, a flexible rubber impregnated cover on each of said contact members, portions of said cover overlapping the margins of each contact member and folded therearound with the cover terminal edges spaced apart equally throughout the length of each contact member and providing spaced adjacent uncovered portions of the pair of contact members, said folded cover portions of at least one cover being disposed between the pair of said contact members in aligned relation to space said parallel members equidistantly throughout their length one from the other, and a rubber envelope bonded to said rubber impregnated covers.

11. A switch treadle comprising a pair of flat elongated contact members, a flexible rubber impregnated cover on each of said contact members, folds of one of said covers disposed between said pair of contact members to space said members one from the other and providing adjacent uncovered portions of said contact members and said other cover being adapted to encompass both of said contact members, a rubber envelope bonded to said rubber impregnated covers, and a ground plate bonded to said envelope and electrically insulated from said contact members by said other cover.

References Cited in the file of this patent UNITED STATES PATENTS 2,138,549 La Bell Nov. 29, 1938 2,165,227 Cooper July 11, 1939 FOREIGN PATENTS 639,212 Great Britain June 21, 1950