US 2876326 A
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Description (OCR text may contain errors)
United This invention relates to improvements in electrically heated roadways and particularly to an improved electrical system for melting ice or snow formation on the roadway or preventing the accumulation of ice and snow thereon by preheating.
An object of the invention is to provide the panels of a roadway with heating elements, the heating elements of one panel being interconnected with the heating elements of the next panel by a specially designed jumper which is arranged to permit expansion and contraction due to the temperature differentials in the concrete panels of the roadway without stressing any parts of the system which would be subjected to fracture or other failure due to the application of stress.
Another object of the invention is to provide a heating system for roadways regardless of the roadway used, that is as a highway, a private driveway and others, the heating system for the roadway consisting of heating elements which function as reinforcing7 rods for the concrete panels and also function to emit heat, these elements being operatively connected together from panel to panel by means of a jumper, the jumper in each instance including a exible wire whose ends are connected to the confronting but spaced heating elements of adjacent panels by means of connections which are capable of yielding when the panels expand and contract at their expansion joints.
A further object of the invention is to provide a jumper as described above wherein the jumper includes a conductive wire fastened at its ends to adjacent heating elements in adjacent panels and passing through yielding sleeves embedded in the concrete of the panels whereby when the wire is flexed-due to expansion and contraction of the adjacent concrete panels, no stress will'be transmitted to the joining parts of the wire with the heating elements inasmuch as the wire will be flexed in the space provided for such llexure.
, Another object of the invention is to provide an improved heated roadway of the electrical operative type where there are heating elements in the separate concrete panels, these heating elements being controlled thermostatically in accordance with preset requirements.
These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:
Figure 1 is a plan view of a fragmentary part of a roadway which has the roadway heated system incorporated therewith;
Figure 2 is an enlarged fragmentary sectional view showing the novel jumper between the heating elements of adjacent panels;
Figure 3 is a transverse sectional view taken along the line 3-3 of Figure 1;
Figure 4 is a fragmentary perspective view of one of the heating elements and a portion of one of the jumpers of a compressible material on the top of which tar or` some other sealing material is placed.
The heating system applied to the typical roadway 10 takes advantage of the fortunate coincidence that concrete and steel have practical identical coefficients of expansion. Accordingly, the heating elements for the roadway 10 are made of steel rods. In the fragmentary part of a roadway 10 there are rods 28, 21, 22, 23, 24,
and 25 together with rods 26, 27, 28, 29, 30 and 31. Rods 20, 25, 26 and 31 are in panel 16; rods 21, 24, 27 and 30 are in panel 14, and rods 22, 23, 28 and 29 are located in panel 12. Each of the rods is embedded in the concrete a safe distance below the upper surface thereof, for example in an 8 inch concrete roadway the rods may be located approximately 2%. inches below the top surface thereof. In that way they will function to reinforce the concrete in tension near the upper surface thereof, as is required, to strengthen the concrete for typical road and highway use. Additionally, each of the rods terminates a distance from the ends of the rods and are not exposed to the atmospheric air and moisture. In keeping these rods embedded completely in the concrete and preventing the air and moisture from reaching them the rods will not rust. Moreover', electrolytic action is materially reduced.
In Figure l panels 14 and 16 are fragmentarily shown in order to illustrate that an indenite number of panels` may be interconnected to form a single system. The electrical demands and limitations will determine the number of panels which can be interconnected by the heating system for the roadway.
The rods 20, 21, 22, 23, 24 and 25 are along one side ofthe roadway, while the remainder of the rods are along the other side of the roadway. The first mentioned group of rods extend through the successive panels 16, 14- and 12 and the rods 22 and 23 are connected by a conductive bar 38 at their outer ends. A similar conductive bar 39 connects the bars 28 and 29 in order to form a branch separate from the branch connected by -bar 38. The confronting ends of adjacent bars in adjacent panels are operatively connected together for electrical conduction by means of a jumper, a typical jumper 42 being shown in Figure 2 and in Figure 4. It consists of a wire 44 that is preferably of bendable copper and in an insulating sheath 46. This wire extendsv through an aperture 47 formed in the expansion joint and is embedded in the concrete of the panels 12 and 14. One end portion of the wire and its sheath 46 passes through a yielding conduit 48, as rubber hose, the latter being sufficiently large in diameter to have the curved end portion of the jumper wire passed loosely therethrough. Clamp 50 connects the copper conductive wire 46 to the heating element rod 29. The opposite end of the copper wire 44 is secured to the heating elementrod 30 (Figure 2) by means of a clamp 52. The clamps are conductive and very rmly fasten the wire 44 to the adjacent ends of the heating element rods 29 and 30. Conduit 54 which is identical to conduit 48 is embedded in the concrete of panel 14 and has the curved end portion of the jumper wire passed loosely therethrough. The loose :tit between the wire and the conduits 48 and 54 is to allow the expansion and contraction of the concrete panels to take place without stressing the hea 'ng element rods, the wire 44 or the clamps 50 and S2. Moreover, the wire 44 is capable of sliding in its sheath 46 to further assure that stresses will not be transmitted to the clamps and the heating element rods.
A typical electrical system is shown in Figure 5 wherey the wires 57 and 58 are secured respectively to the buses 60 and 61, whereon there is, for example, 200 volts A. C. Wires 57 and 58 connect to the terminals of a stepdown transformer 62 in whose primary there is thermostatie switch 64 in order to control the energization of the transformer. Thermostat 64 may be located at any convenient position. As shown in Figure 5 the branch 66 is serially connected with the branch dS, all of the heating element rods and jumpers entering into a single circuit including the secondary of the stepdown transformer In use when the thermostatic switch 64 demands, the branches 66 and d8 embedded in the concrete panels are heated. ln such operation the panels of the roadway would be preheated in order to prevent the accumulation of snow and ice thereon. As the panels expand and contract due to temperature differentials caused by heating the panels either by the heating elements therein or by seasonal changes in temperature, the jumpers permit such expansion without unduly stressing the connections between the rods of the heating elements. 1t is understood that the thermostatic switch 64 may he removed in favor of an ordinary switch or other types of controls may be used as deemed necessary or desirable for the particular installation involved. In addition, the number of panels may be increased or decreased and the number of branches in a single panel may be varied.
The foregoing is considered as illustrative only of the principles of the invention. Further, since numero-us modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.
What is claimed as new is as follows:
l. A heated roadway comprising at least two roadway panels, an expansion joint between said panels, heating elements in said panels, means passed through said expansion joints and partially embedded in said panels for interconnecting adjacent heating elements of adjacent panels, said means including for each pair of adjacent heating elements a jumper wire and means connecting the ends of said jumper wire to said pair of heating element, and a yielding conduit embedded in said panels adjacent tosaid pair of heating elements, said wire passed through and loosely tted in said yielding conduits so that said wire is free to move within said yielding conduits in response to expansion and contraction of the adjacent panels.
2. In a heated roadway which includes two panels of concrete adjacent to each other and an expansion joint between said panels together with heating elements which terminate in said panels adjacent to but spaced from said expansion joint, the improvement comprising a jumper interconnecting said heating elements, said jumper including a conductive wire, means at the ends of said wires securing said ends to the ends of said heating elements, and yielding means through which portions of said wire pass to provide freedom vforrmovement of said wire when said panels expand and contract.
3. In a heated roadway which includes two panels of concrete adjacent to each other and an expansion joint between said panels together with heating elements which terminate in said panels adjacent to but spaced from said expansion joint, the improvement comprising a jumper interconnecting said heating elements, said jumper including a conductive wire, means at the ends of said wires securing said ends to the ends of said heating elements, and yielding means through which portions of said wire pass to provide freedom for movement of said wire when said panels expand and contract, said yielding means including a conduit of yielding material through which a curved portion of said wire passes and is loosely dis posed.
4. In a roadway which includes a pair of concrete panels which are superposed, an expansion joint between said panels, a heating system for said panels comprising two branches of heating elements embedded in said panels and spaced from each other, electrically conductive means connecting said branches in series, a stepdown transformer arranged to energize branches, means operatively connecte-d with said stepdown transformer for controlling the energization of the latter, at least one of said branches including separate heating elements located in said concrete panels, an expansible jumper assembly interconnecting said separate heating elements, said jumper assembly comprising a conductive element attached at its ends to said heating elements, and means embedded in said panels through which said conductive element passes loosely so that when said panels expand and contract said conductive element yields and has clearance to move therein.
5. The construction of claim 4 wherein said conductive element comprises a wire on which an insulated sheath is disposed, said heating elements being spaced from.the confronting ends of said panels so that said wire with its sheath passes into and is embedded in portions of the concrete panels and said sheath having said Wire movable therein in response to relative motion of one panel with respect to the other.
6. In `a heating system for concrete panels that are separated by an expansion joint, a heating element in each panel and spaced from the ends thereof, a jumper embedded in said panels and including a conductor secured at its ends to said heating elements at a position remote from the confronting end surfaces thereof, said conductor passed through said expansion joint, and means operatively connected with said conductor and located in one of said panels for providing an expansion chamber in which said conductor may move in response to expansion of said concrete panels.
References Citedin the tile of this patent UNITED STATES PATENTS 1,349,136 Lillard Aug. 10, 1920 1,788,107 Hynes Jan. 6, 1931 2,190,225 Vollmer Feb. 13, 1940 2,203,078 Carter June 4, 1940 2,327,231 Westcott Aug. 17, 1943 2,503,600 Tice Apr. 11, 1950 2,533,409 Tice Dec. 12, 1950 2,606,989 Gomersall Aug. 12, 1952 FOiitElGN PATENTS 113,192 Australia May 27, 1941 419,843 Great Britain Nov. 20, 1934 552,910 Great Britain ...Apr 29, 1943