US 2722597 A
Description (OCR text may contain errors)
1955 1.. E. STEINER ARTICULATED ELECTRIC HEATING MAT 2 Sheets-Sheet 1 Filed Jan. 19, 1955 IN VENTOR. L EON/QED 5 S TE/A/EE HTTOENE) 1955 E. STEINER 22,597
ARTICULATED ELECTRIC HEATING MAT Filed Jan. 19, 1955 2 Sheets-Sheet 2 United States Patent ARTICULATED ELECTRIC HEATING MAT Leonard E. Steiner, Westfield, N. J. Application January 19,1955, Serial No. 482,707
3 (Shims. (Cl. 219*) This invention is an articulated electric heating mat Of the g n ra cha a te desc be in my a nt 2,549,944, ed April 2 195 Thi ype. qfrna mprises a succession of elongated bars arranged in edge to edge sequence with their contiguous edges of interfitting p mentary rc e orm, to pe mit aid bars to articulate when the mat is wrapped about or unwrapped from the cylindrical body which it is desired to heat. Each bar is provided, with longitudinally spaced apart transverse holes extending from edge to edge and the respective holes of the several bars register With one another to form spaced apart parallel passages extending the full length of the mat. An electrical heating coil is passed back and forth through these passages in succession and is connected to terminals at one end of the mat. The heating coil is of resistance wire and when electric current is passed therethrough the mat is heated and serves to heat the cylindrical body or core about which it is wrapped.
In prior mats of this general character, such as the mat of my said patent, the bars of the mat were fabricated from refractory material. Such material tends to some extent to insulate the heating element from the core.
With the, foregoing considerations in mind, the primary object of the present invention is to provide a heating mat wherein the heating efficiency of the input current is very materially increased.
In the preferred form of the mat of the present invention, one set of alternate bars are made of highly conductive metal, such as aluminum, copper or bronze, while the intermediate bars are of refractory material, such as a ceramic. The refractory bars are preferably cylindrical in form, while the interposed metal bars have concave opposite edges formed on the same radius as the refractory bars, so that the successive bars are adapted to articulate into conformity with the core about which they are to be wrapped. Furthermore those faces of the metal bars which are to contact with the core are of concave arcuate form of a radius corresponding to the radius of the core, so as to contact throughout the entire transverse width of each bar with the surface of said core. The several bars are provided with registered transverse holes as heretofore, the holes in the metal bars being provided with insulating refractory bushings, so that the metal bars are insulated from the heating coil which passes therethrough.
When such a mat is wrapped about a cylindrical core, there will be a practically continuous contact between the metal bars of the mat and the surface of the core throughout the entire circumference of the latter, thus assuring a practically uninterrupted heat exchanging surface between the mat and the core, with resulting maxi mum rate of heat exchange. This higher rate of heat exchange allows a given number of thermal units to be exchanged at lower temperature differential than through poorer heat conducting ceramic material. This characteristic is beneficial to life of heating element.
In practice. I prefer to externally enclose the wrapped a in a ng. such as shown in aforesaid patent, with a body of asbestos or some other suitable heat nsulating material interpo ed be w n the mat and said o sing. The metal ars of. he t, when made of al minum, pper or bronz will h ve. a higher c efficient of expansi n than the cor whi h. is. commonly formed from iron or steel. To compensate for this, the housing, whichv is preferably of the split type with lugs at. t p i p e ra y held toge her in an elastic manner, so as to resiliently aintain the metal. surfaces of the mat at all times in contact with the surface of the core, irrespective of temperature changes or differ-- n s. in coefficients f. expansi n.
Features. of the invention, other than those adverted l b pp r n from the hereinafter detailed di 'pon. d ppended claims, when re d n co junction with the accompanying drawings.
The accompanying drawings illustrate one practical embodiment of the invention, but the construction therein shown is to. be understood as illustrative, only, and not as defining the limits of the invention.
Fig. 1 is a, fragmental perspective view of a mat embodying the present invention,
Fig. 2 shows the mat in section, wrapped about a cylindrical body.
Fig. 3 is a section on the line 3..3 of Fig. 4 showing one of the metal bars of the mat.
Fig. 4 is an end view of said metal bar.
Fig. 5 is a side elevation of the refractory bars.
Fig. 6 is an end view of one of said, refractory bars.
Fig. 7 is an end view of the mat wrapped about a core, shown in section and enclosed within a metal housing with intermediate insulating material.
Fig. 8 shows a section of a modified form of bar which may be used in lieu of the cylindrical bars shown in the other figures of the drawing,
In the embodiment of the invention of Figs. l-7 of the drawings, such metal bar 1 is made as shown in Figs.
3-5. It is. provided with longitudinal spaced apart holes,v 2', each of which is provided with a refractory bushing,
3 which may be made separately and thereafter introduced into the holes or molded directly in such holes. Each of the longitudinal edges of each bar 1 is of concave cross-section as shown at 4. The radius of the arc is the same as the radius of the adjacent refractory bars 5 which are cylindrical, as shown in Fig. 6. When the bars are assembled side by side, the holes in all of the bars register with one another and the holes 6 in the refractory bars are flared toward the surfaces of said bars 5 to permit registration of said holes 6 with the holes in the bushings 3 in adjacent metal bars 1 in all positions of articulation between the bars. An electrical resistance coil 7 is adapted to be threaded back and forth through the passages provided by said alined holes in the mat as described in my aforesaid patent.
Each end of the mat has a terminal bar 8 of refractory material, provided at one edge with a channel 9 to house those portions of the resistance coil 7 which pass from one series of alined holes to the next. One terminal bar is also provided with perforations 10 through which the resistance wire at the opposite ends of the coil may be led to electric terminals 11, as shown in Fig. 7. The terminals 11 are supported on one of the lugs 12 formed at one end of the split housing 13 which is preferably of metal, the terminal 11 being insulated from the lug 12 in any appropriate manner, as by insulating bushings and washers. The split housing 13 is provided at its other end with a companion lug 14 and both the lugs 12 and 14 are perforated for the passage of the bolt 15 with springs 16 interposed between the lugs and the head and nut of the bolt. The nut is screwed upon the bolt to maintain the springs 16 under tension so that these springs serve to compress a packing of asbestos or the like 17 (Fig. 7) interposed between the wrapped mat and the housing 13. The pressure thus exerted on the packing serves to maintain the inner surface of the metal bars at all times in contact with the circumference of the core C about which the mat is wrapped.
In practice the surfaces 1:: of the metal bars, which are contiguous to the core, are of concave arcuate form of the same radius as the circumference of the core and consequently there is direct contact between the entire width of each of the metal bars 1 and the core and this extensive metal to metal surface contact is maintained by the compressed springs 16, irrespective of differences in coefficients of expansion between the mat and the core.
It will be further noted from Figs. 2 and 7 that the adjacent edges of the metal bars are practically in contact, in fact they may be actually in contact with one another, when the mat is Wrapped about the core with the result that there is a practically uninterrupted heat exchanging engagement between the metal bars and the core. This insures a maximum heating efficiency with the mat of this invention.
In the foregoing detailed description the bars have been referred to as of refractory material such as a ceramic and this is the preferred construction. However, if desired, these parts may also be made of metal and the holes therethrough may be provided with refractory bushings without departing from this invention. There is, however, no advantage in having the cylindrical bars or" metal for the adjacent edges of the bars 1. come into substantial contact with one another so that the cylindrical bars 5 do not actually touch the surface of the core C.
In the event that I make the intermediate bars 5 of metal, I preferably depart from the cylindrical form shown in Figs. 1-7 of the drawings and make these bars with the cross section shown in Fig. 8. In this view the bars 5b which correspond to the cylindrical bars 5, are provided with an internal bushing 2a. The core contacting surface 5:; of each bar 5b is convex and is curved on the radius of the core with which a mat so constructed is adapted to cooperate, so that, when such a mat is wrapped about the core all of the bars of such mat will conform to and contact throughout with the surface of the core.
The foregoing detailed description sets forth the invention in its preferred practical form, but the invention is to be understood as fully commensurate with the appended claims.
Having thus fully described the invention, what I claim as new and desire to secure by Letters Patent is:
1. An electric heating mat comprising: a succession of bars arranged in parallel relation with contacting articulating surfaces to permit the mat to be Wrapped about a cylindrical core, at least alternate bars being of metal and having concave core contacting surfaces of a radius corresponding to that of the core, each of said bars being provided with longitudinally spaced apart holes which register with holes in adjacent bars, an electrical resistance coil threaded through the holes of the several bars in succession, the holes in the metal bars being bushed with insulating refractory material to insulate such bars from the coil, and resilient means for maintaining the concave surfaces of the metal bars in contact with the core at all times irrespective of differences in coefficients of expansion between the metal bars and the core.
2. An electric heating mat comprising: a succession of bars arranged in parallel relation with contacting articulating surfaces to permit the mat to be wrapped about a cylindrical core, at least alternate bars being solid metal bars having concave core contacting surfaces of a radius corresponding to that of the core, each of said bars being provided with longitudinally spaced apart holes which register with holes in adjacent bars, and an electrical resistance coil threaded through the holes of the several bars in succession, the holes in the metal bars being bushed with insulating refractory material to insulate such bars from the coil.
3. An electric heating mat according to claim 1, wherein alternate bars are of metal and intermediate bars are of non-metallic refractory material.
References Cited in the file of this patent UNITED STATES PATENTS 1,240,584 Laraway et al Sept. 18, 1917 1,855,092 Browne Apr. 19, 1932 2,022,466 Hess Nov. 26, 1935 2,231,251 Chaney Feb. 11, 1941 2,549,944 Steiner Apr. 24, 1951