US3281579A - Conductive rubber heating mantle - Google Patents

Description

1965 M. GLICKSMAN CONDUCTIVE RUBBER HEATING MANTLE Filed April 21, 1964 United States Patent York Filed Apr. 21, 1964, Ser. No. 361,393 1 Claim. (Cl. 219-535) This invention relates generally to the field of conduc tive rubber like heating elements, and more particularly to an improved form thereof which may be made at very low cost, for use in conjunction with a large number of different applications.

In many laboratory processes, it is desirable to heat open flasks in the absence of an open flame. This is particularly desirable where volatile, highly inflammable solvents and the like are being evaporated, and in other procedures wherein even distribution of heat about the flask is essential. In the prior art, there have been provided electrically powered heating mantles, which comprise broadly a wire mesh heating element about which insulative covers are sewn. To provide maximum heat distribution, the mantles are shaped to correspond to the outer configuration of the flask to be heated, and in some instances the mantle is made in two parts which are interconnected by slide fastener or similar interconnecting means, to permit the body portion of the flask to be completely surrounded. While devices of this type are reasonably sufiicient and effective, and are readily flexed to enable the flask to be positioned therein, because of the presence of wire heating elements, the breakage of which renders the device inoperative, the expendability of devices of this type has long been accepted. Despite this fact, the mantles have been relatively costly, so that the extensive replacement of such devices over a relatively short period of useful life has been a serious disadvantage.

It is among the principal objects of the present inven tion to provide an improved form of heating mantle, in which the relatively frangible current conducting wires of the prior art have been eliminated, to be replaced by a rubber like conducting medium which may be conveniently flexed as required, and which is substantially indestructible in normal use.

Another object of the invention lies in the provision of an improved heating mantle of the class described in which the cost of fabrication may be far less than that of the existing prior art devices, with consequent wide sale, distribution and use.

Yet another object of the invention lies in the provision of an improved rubber like heating mantle capable of continued operation over sustained relatively high degree temperatures without deleterious effect.

A further object of the invention lies in the provision of a heating mantle of the class described in which all of the elements are formed in mutually fused relation, thereby eliminating a large number of hand operations during the manufacturing procedure, and avoiding points of potential mechanical weakness.

A feature of the invention lies in the wide variety of shapes and configurations possible in the formation of individual heating mantles embodying the invention.

Another feature of the invention lies in the provision of integrally molded thermostatic means for controlling the operating temperature of the disclosed embodiments.

These objects and features, as well as other incidental ends and advantages, will more fully appear in the progress of the following disclosure, and be pointed out in the appended claim.

In the drawing, to which reference will be made in the specification, similar reference characters have been employed to designate corresponding parts throughout the several views.

3,281,579 Patented ()ct. 25, 1966 FIGURE 1 is a view in elevation showing a first embodiment of the invention.

FIGURE 2 is a vertical central sectional view of the first embodiment.

FIGURE 3 is an enlarged fragmentary vertical sectional view showing the details of integrally molded thermostatic means.

FIGURE 4 is a vertical central sectional view corresponding to that seen in FIGURE 2, but showing a second embodiment of the invention.

FIGURE 5 is a horizontal sectional view of an alternate form of the second embodiment.

In accordance with the first embodiment of the invention, the device, generally indicated by reference character 10, comprises broadly a base element 11, a lower heating element 12, and an upper heating element 13.

The base element 11 is preferably formed from a rubber-like material, and is of suflicient thickness to have both mechanical supporting ability, and electrical and heat insulative properties. While the base element 11 may be formed from natural rubber, where high operation temperatures are involved, it is preferable that the same be formed from a synthetic resinous material capable of withstanding such temperatures, such as silicone rubber. As best seen in FIGURES 1 and 2, the base element 11 includes a flanged base member 15 bounded by a lower surface 16, an upper surface 17 and a peripheral surface 18. Extending upwardly from the base member 15 is a vertical support member 19 bounded by a cylindrical outer surface 20 and defining a quasihemispherical recess 21.

The lower heating element 12 is formed from electrically resistive rubber-like material, and may also be of silicone rubber to which there has been admixed a sufficient quantity of powdered electrically conductive graphite to obtain the desired degree of limited conductivity. This technique is well known in the conductive rubber art, and need not be further elaborated herein. The element 12 is bonded to the surface of the recess 21 in the base element 11, and is bounded by an outer surface 24, and an inner surface 25. A peripheral flange 26 on the base element 11 which forms a reinforcing means as well as a means for selectively interconnecting with the upper heating element 13. Bonded to the inner surface 25 is an inner electrically insulative layer 27, which is preferably formed by brush or a spray coating a room temperature vulcanizing silicone rubber of a type which will withstand the normal operating temperature of the device without deteriorating. As best seen in FIGURE 2, this layer is preferably extended to meet with the base element 11, so that the heating element 12 is completely enclosed.

Disposed within the body of the lower element 12 is a recess 29 into which there is fitted a thermostatic switch 30 of well known type, the outer surface of which forms a contact for electrical communication with the body of the material forming the element 12. The core of the switch 30 communicates with a first conductor 31, in turn connected to a source of electrical potential. A second contact 32, which may, if desired, include a second thermostatic switch is positioned within an oppositely disposed area of the element 12, and is connected to a second conductor 33, the conductor 33 completing the electrical circuit with the source of electrical potential (not shown).

The upper heating element 13 is constructed in a manner similar to the lower heating element 12,, and a seen in FIGURES l and 2 is generally of quasi-hemispherical shape. An electrical and heat insulative layer 35 is bonded to an outer surface 36, while the inner surface 37 is provided with an electrically insulative layer 43 which corresponds to the layer 27 of the element 12. To permit egress of the opening of the flask to be heated, there is preferably formed an axially disposed opening 38, while a peripheral flange 39 is provided with a recess 40 selectively interconnectable with the peripheral flange 26 on the element 12. The element 13 is provided with current carrying wires 44 and 45 as well as a thermostatic switch 46 and power cord 50'.

During operation, the upper and lower heating elements 12 and 13, respectively are separated to permit insertion of the flask 47 therebetween. When the cylindrical neck 48 of the flask is extended through the opening 38, the elements 12 and 13 may be interconnected to completely enclose the spherical body portion 49 of the flask, whereby even heat distribution and minimum heat loss are obtained during operation. Either half of the device may be selectively powered as required.

Turning now to the second embodiment of the invention, there is illustrated in FIGURE 4 a device 50 suitable for use in conjunction in heating a flat-bottomed flask 51. The base element 52, conductive layer 53- and upper electrically insulative layer 54 are all of generally planar configuration, and this embodiment is of such configuration that may also be used for heating almost any type of container, such as cofifee percolators, sauce pans and the like. As is the case in the first embodiment, the layer 54 is preferably indirect contact Wit-h the base element 52, to completely enclose the conductive layer 54.

The alternate form 60 of the second embodiment is generally similar but is of irregular peripheral configuration to permit the even heating of an irregularly-shaped object (not shown). Parts corresponding to the principal form of the second embodiment have been designated by corresponding reference characters with the additional suffix a.

I wish it to be understood that I do not consider the invention limited to the precise details of structure shown and set forth in this specification, for obvious modifications will occur to those skilled in the art to which the invention pertains.

I claim:

As a new article of manufacture, an electrically powered heating mantle comprising: a first heating element including a base member of solid relatively rigid rubberlike material of sufficient thickness to have substantial electrical and heat insulative properties, an electrically conductive member of rubber-like material having one surface thereof bonded to a surface of said base member, and an electrically insulative, heat conductive member bonded to an oppositely disposed surface of said conductive member; said conductive member being of generally spherical configuration, and having a recess therein for the reception of an article to be heated; and a second generally spherically shaped element, including a base member of rubber-like material having substantial electrical and heat insulative properties, an electrically conductive member of rubber-like material having one surface bonded to a surface of said base member, and an electrically insulative heat conductive member bonded to an oppositely disposed surface of said conductive member; said first and second elements having mutually interconnecting means.

References Cited by the Examiner UNITED STATES PATENTS 2,052,644 9/1936 Murphy 219528 2,231,506 2/1941 Morey 219535 2,404,736 7/1946 Marick 219-535 X 2,406,367 8/1946 Griflith et al. 244-134 2,482,665 9/1949 Geyer 219-528 X 2,572,695 10/1951 Briscoe et al. 219-535 2,607,876 8/1952 Bergen et al. 219-535 X 2,688,070 8/1954 Freedlander 219528 2,739,083 3/1956 Brown et a1. 117211 2,799,764 7/ 1957 Chandler 117345 FOREIGN PATENTS 713,742 8/1954 Great Britain.

RICHARD M. WOOD, Primary Examiner.

V. Y. MAYEWSKY, Assistant Examiner.

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