US 3806702 A
A weatherproof electrically insulative mat having an electrical heat producing conductor therein and adapted for placement on an exterior surface to prevent accumulation of snow on such surface. A control system for supplying current to the conductor including a precipitation sensor, a temperature sensor and a control unit responsive to the sensors so that power is supplied to the conductor in the mat only when there is precipitation and the temperature is below 35 DEG . An improved mat structure that is approximately symmetrical of the central plane thereof so that when one side of the mat wears the mat can be reversed.
Claims available in
Description (OCR text may contain errors)
United States Patent [191 Spencer 1111 3,806,702 1 1 Apr. 23, 1974 1 1 APPARATUS FOR PREVENTING SNOW ACCUMULATION  US. Cl 219/528, ZOO/61.04, 219/201,
219/284, 219/345, 239/75, 340/234  Int. Cl. H05b 3/34  Field of Search 219/201, 202, 213,217,
 References Cited UNITED STATES PATENTS 2,745,942 5/1956 Cohen 219/528 2,844,696 7/1958 Custer 10/1964 Barbour et a1 338/214 3,164,820 1/1965 Hulett ZOO/61.04 X
3,440,396 4/1969 Greene, .11. 219/201 FOREIGN PATENTS OR APPLICATlONS 727,020 3/1955 Great Britain 219/522 Primary Examiner-volodymyr Y. Mayewsky Attorney, Agent, or Firm-Robert Charles Hill [5 7] ABSTRACT A weatherproof electrically insulative mat having an electrical heat producing conductor therein and adapted for placement on an exterior surface to prevent accumulation of snow on such surface. A control system for supplying current to the conductor including a precipitation sensor, a temperature sensor and a control unit responsive to the sensors so that power is supplied to the conductor in the mat only when there is precipitation and the temperature is below 35. An improved mat structure that is approximately symmet- -3,540,6S5 1 H1970 Hinrichs 239/75 rical of the central plane thereof so that when one side 2,503,457 4/1950 spell et a1..... 219/528 of the mat wears the mat can be reversed. 2,712,591 7/1955 Rogell 219/528 X 2,834,862 5/1958 Me ers 219/345 1 Claim,'3 Drawing Figures 20 ZZT aa/ fiectptzafmrz r --1/ 52m 220v 1 l 1 0/4/67 I 1 Zl/Z ZCfi 9Z\ 1 l f Z6 20 I 7Zl77flcl'd/ul't I jem'ar' L- M PATEMTED APR 2 31914 wn w I w FIG. 2.
APPARATUS FOR PREVENTING SNOW ACCUMULATION BACKGROUND OF THE INVENTION This invention relates to a heat producing mat for placement on an exterior surface so as to prevent accumulation of snow on such surface. More particularly the invention relates to a system for activating the mat in response to weather conditions in the environment 4 in which the mat is installed.
Solutions to the problems solved by the present invention have been attempted by prior art workers. By way of example, there is an electric heating mat, disclosed in U. S. Pat. No. 3,281,578, that is adapted for placement on sidewalks and the like and it has electrical conductors embedded therein for preventing accumulation of snow. Such device is of an extremely complex configuration and does not afford reversal to achieve wear distribution as does the present invention. Another example of an attempted solution of the prob lem is embodied in a snow melting mat, disclosed in U. S. Pat. No. 2,844,696 which has the disadvantages referred to above in that the mat is not symmetrical about its central plane and therefore cannot be reversed to distribute wear thereon. As far as is known, the provision of an automatic control system for a mat so that the mat is operated only when needed is not disclosed in the prior art.
SUMMARY OF THE INVENTION The invention provides a mat having an exterior formed of two substantially identical laminations of rubber or like weather-proof electrically insulative material. Between the two laminations is an electrical conductor adapted to generate heat in response to current flow therethrough. The two sheets are laminated together so that the conductor is completely encased and protected from wear and abrasion. For activating the heat producing conductor the present invention provides a control system 7 that employs a precipitation sensor arrd a temperature sensor. The two sensors are connected to a controller which acts to supply current to the heat producing conductor in the mat only when there coexists precipitation and a temperature less than about 35 F.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of an installation of the present invention on an exterior porch or deck.
FIG. 2 is a fragmentary view and enlarged scale taken along line 2-2 of FIG. 1.
FIG. 3 is a schematic diagram of the control system of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly to the drawing reference numeral .12 indicates a mat constructed according to the present invention in place upon an exterior surface 14. Exterior surface 14 is a porch or deck surface in the drawing but it is to be understood that the present invention can be used on walkways, stairways, sidewalks, and the like. As shown in more detail in FIG. 2, mat 12 includes substantially identical sheets or laminations 16 and 18. Laminations l6 and 18 are constructed of weatherproof electrically insulative material such as rubber, fabric reinforced rubber, neoprene, or the like.
Each lamination or sheet preferably has a thickness in the range of approximately three-sixteenths inch to ap proximately three-eighths inch so that the overall thickness of mat 12 is in the range of about three-eighths inch to about three-fourths inch.
Disposed intermediate lamination 16 and 18 is an electrically power heat producing conductor 20. As seen in FIG. 1, heat producing conductor 20 is disposed throughout mat 12 in a sinuous pattern. The conductor is retained in place between the laminations l6 and 18 because after the conductor is laid out the two laminations are fastened together by suitable adhesive or by volcanizing so that there is a weatherproof joint 22 therebetween which maintains the parts of the matin assembled condition and excludes entry of moisture to conductor 20.
Conductor 20 has one or more externally extending terminations 22 T. With reference to FIG. 3, there are two such terminations at one extremity of the mat to which the line terminals of a 220 volt AC supply are connected. One conductor designated by reference numeral 20 in FIG. 3 extends directly through the mat and the other conductor 20 after following a sinuous path exits the mat and is connected to a power switch 24 that has contacts of sufficient capacity to switch the which the sensor is fastened to the railing structure 34 surrounding the deck surface 14. The sensor has an upwardly exposed surface in which there are several concentric ring shape surfaces which when spanned by moisture on the surface transmit a signal to controller 26 that indicates such condition. Temperature sensor 32 provides a signal to the controller 26 when the temperature sensed in the environment in which the sensor is installed reaches a preselected magnitude. Although not shown in FIG. 1, temperature sensor 32 is likewise mounted in the environment of mat 12 so that it can sense the temperature adjacent the mat.
The invention operates as follows:
Before significant snowfall occurs, mat 12 is disposed on deck surface 14 with sensor 30 installed as shown in FIG. 1 and temperature sensor 32 installed in the environment of the mat. The temperature sensor 32 is preset to respond at a temperature in the range of about 32 35 F. Should precipitation occur at a temperature above the range of about 32 35 F, such precipitation will be rain and in such condition there is no necessity to supply power to conductor 20 in the mat. Be-
a temperature above about 32 35 F, power is no longer needed and controller 26 actuates power switch 24 to interrupt the power. Thus the present invention is active only when environmental conditions require it and is not active at other times.
In one system designed according to the present invention, the following elements were found to function properly. The identifying numbers set forth below are the trade designations of components furnished by Easy Heat Wirecraft Co.
Power switch 24 PS-22-2 Controller 26 AS-3C Precipitation Sensor 30 AS-3-S Temperature Sensor 32 RTT-90 In such exemplary system the overall thickness of mat 12 is about nine-sixteenths inch; the mat is extremely rugged and can be reversed when the upper surface thereof has been partially worn by foot traffic or the like.
Thus it will be seen that the present invention provides a system which functions to prevent accumulation of snow or ice on an exterior surface and which requires no attention in that it operates automatically. Moreover, electric power is conserved in that the system is active only when the environmental conditions require it. Finally, mat 12because of its symmetrical construction, is both inexpensive to produce and of long life because it can be reversed when one side thereof is partially worn.
Although one embodiment of the invention has been shown and described, it will be obvious that other adaptations and modifications can be made without departing from the true spirit and scope of the invention.
What is claimed is:
1. Apparatus for preventing snow accumulation on a surface disposed in an environment comprising a mat conformable to the surface, said mat including a weather impervious electrically insulative exterior member and an electrically operated heat producing element interiorly thereof, said electrically insulative member comprising first and second substantially identical sheets and said electrical heating element being disposed intermediate said sheets so that either side of said mat can be placed outward of the surface, means for supplying electric power to said electrical heating element, and means for controlling said power supplying means, said controlling means including means for sensing the presence of snow precipitation in the environment, means for sensingthe temperature in the environment, and means for operatively connecting said temperature sensing means to said precipitation sensing means so as to supply electric power to said electrical heating element only when the temperature in the environment is below about 32-35 F and snow precipitation is present in the environment.