US2914647A

US2914647A - Radiant heater

Info

Publication number: US2914647A
Application number: US677479A
Authority: US
Inventors: Kingston E Ganske; Albert G Bill
Original assignee: Arvin Industries Inc
Current assignee: Meritor Inc
Priority date: 1957-08-12
Filing date: 1957-08-12
Publication date: 1959-11-24
Anticipated expiration: 1976-11-24

Description

NOV- 24, 1959 K. E. GANsKE ErAL 2,914,647

RADIANT HEATER Filed Aug. l2, 1957 INVENTORS KINGSTON E GAA/SKF ALBERT G. B/L L United States Patent O 2,914,647 RADIANT HEATER Kingston E. Ganske and Albert G. Bill, Columbus, Ind., assignors to Arvin Industries, Inc., Columbus, Ind., a corporation of Indiana Application August 12, 1957, Serial No. 677,479

11 Claims. (Cl. 219-34) SOuI'CC.

It is the general object of our invention to provide a radiant heater which will overcome the difiiculties and disadvantages described above by providing safety with increased radiant heat output. More specifically, it is the .object of our invention to provide a radiant heater whose radiant heat output will be controlled in response to variations in radiant heat reflected back to said heater.

In carrying out our invention in the preferred form, there is provided a housing having an open forwardly presented face. A radiant heat source is mounted within `the housing and provided with a suitable retlector adapted to reflect and direct the radiant heat outwardly from the heater through the open face of the housing. Conveniently, the heater output is controlled by a thermostat operable for opening and closing the electric circuit to the heat source. The thermostat is mounted at the front of the heater and insulated therefrom, with its forwardly presented face of relatively large extent sensing variations in the amount of radiant energy reflected back tovward the heater. Thus, when an object placed in front of the heater reflects a predetermined amount of radiant energy back to the thermostat, the thermostat will be actuated to open the circuit to the heat source to reduce the heat output and prevent burning the object.

The accompanying drawings illustrate our invention. In such drawings: i

Fig. 1 is a front view of a radiant heater embodying our invention;

Fig. 2 is a vertical section taken on the line 2-2 of Fig. 1;

Fig. 3 is an enlarged horizontal section of the thermostat shown in Figs. 1 and 2;

Fig. 4 is a fragmental vertical section of a modified form of our invention;

Fig. 5 is a fragmental vertical section of another modiiied form of our invention; and

Fig. 6 is a Wiring diagram of a heater employing the heat responsive control means shown in Fig. 5.

As illustrated in the drawings, our heater may be mounted in any suitable housing 10 having an open forwardly presented face provided with a protective grill 12. For purposes of convenience, the housing 10 is tiltably supported at each of its ends on floor-engaging legs 14, and is provided with a handle for carrying the heater from one location to another.

Disposed within the housing 10 is a pair of reflectors 16 extending the length of the housing and having a generally parabolic cross-section. Desirably, the reflectors ICC 16 are formed from sheets of highly reiiective metal for reflecting and directing radiant heat outwardly from the heater through the open face of the housing 10. The reflectors may be mounted in the housing 10 in any convement manner.

Any suitable source of radiant heat, such as a Calrod heating element, a resistance winding on a ceramic core, or the like, may be employed in our heater. As shown, we employ a pair of radiant heating elements 23 formed from coils of nichrome wire enclosed in glass tubes. Each of the heating elements 23 extends the length of one of the reflectors 16 and is mounted adjacent the focus thereof through blocks 19 of heat and electrical insulating material.

The outputof the heating elements 23 is controlled by a radiant heat-responsive thermostat 30 desirably cen-` tered in the forwardly presented face of the heater. The thermostat 30 is mounted on a reflective cover 32 extending rearwardly over the adjacent forward edges of the reflectors 16 toward the heating elements 23. The cover 32, which is conveniently formed from the same reflective material as the reflectors 16, diverges outwardly from the heating elements 23 to shield the thermostat 30 from the direct and reflected radiation of the elements 23. A face plate 34 is mounted on the cover 32 by a roll seam 35 which bindingly retains the plate 34 on the cover 32.

The thermostat 30 is mounted on the face plate 34 by bolts 36 received in a thermostat housing 38 and retained` in the plate 34. Preferably, a heat insulating spacer 41 is received on each of the bolts 36 to dispose the thermostat out of contact with the plate 34 and the cover 32 and thereby insulate the thermostat from any heat that may be conducted away from the cover 32 and plate 34. Any suitable type of thermostat actuated by reflected radiant heat may be used in our heater. One type of such a thermostat is shown in Fig. 3, and comprises an outer metal housing 38 having a generally cylindrical configuration with an inwardly directed lip 42 provided at one of its ends. A radially extending flange 44 is disposed at the opposite end of the housing 38 which receives the bolts 36 retaining the thermostat on the cover plate 34. Press fit within the housing 38 is a base 46 formed of a heat resistant phenolic material and having an end plate 47 disposed substantially coplanar with the housing flange 44. A pair of inwardly directed arms 48 are formed integrally with the side walls of the base 46 for supporting a pair of contacts 50 connected in the electrical circuit of the heating elements 23 by wires 52. Fixedly mounted on one end of a plunger 54 movable within the base between the ends of the arms 48 is a metal bridge 56 normally disposed against the contacts 50 for closing the electrical circuit to the heating elements 23. The plunger 54 is urged in this vnormally closed-circuit position by a leaf spring 57 secured to the bridge 56 and bearing against the base end plate 47.

Plunger movement for opening and closing the circuit to elements 23 is accomplished by a slightly convex bimetal disc 60 comprising a forwardly presented sheet of metal 62 having a relatively low coefficient of expansion and a rearwardly disposed sheet of metal 64 having a relatively high coefficient of expansion. The disc 60 is held in the thermostat 30 by having its margins bindingly received between the forward end of the base 46 and the housing lip 42, thereby permitting the central portion of the disc to flex with a snap-action, or oil can eiect, in response to temperature variations in the disc. Preferably, the thermostat is disposed at the front of the heater in a position so that the wires forming the grill 12 do not shield or block the disc 60 from the heat reflected back toward the heater and thereby reduce its sensitivity. The sensitivity of the disc may be further increased by roughening and darkening the forwardly presented face of the disc metal sheet 62 to render it more absorptive to reected radiant heat.

In operation, the thermostat 30 is actuated to open the electrical circuit to the heating elements 23 by radiant heat reflected back toward the heater from an object or objects disposed in front of the heater. When the amount of reected heat is sufcient to actuate the thermostat, the metal 64 comprising the rearwardly presented face of the disc 60 expands, flexing the disc to snap its center portion rearwardly and moving the plunger 54 in a like direction. As the plunger moves rearwardly, the bridge 56 is displaced away from the contacts 50 opening the electrical circuit to the heating elements 23 and reducing their output. When the radiant heat reflected back to the disc 60 has been reduced because of the reduced output of the heating elements 23 or by the removal of the reflecting object, the metal sheet 64 cools and contracts to its normally convex position, and the plunger 54 under the influence of the spring 57 moves forwardly with the brid-ge 56 engaging the contacts 50 to close the electrical circuit to the heating elements 23.

A modified form of our invention is shown in Fig. 4. In this modification, the heat responsive means comprises an elongated metal plate 68 extending longitudinally across the open forwardly presented face of the heater for sensing variations in the amount of heat reflected back to the heater by an object or objects disposed in front of the heater. Desirably, the plate 68 is formed from a metal strip having a high coefficient of thermoconductivity with its forwardly presented face darkened to absorb radiant heat reflected back toward the heater. The plate 68 is secured by bolts 69 to a face plate 70 of a shielding cover 72 mounted on the adjacent faces of a pair of reflectors 16 and extending the length of the heater to shield the plate 68 from the heating elements 23 disposed in front of the apeXes of the rellectors 16. An insulating spacer sleeve 78 is disposed on each of the bolts 69 for displacing the plate 68 away from the plate 70 to insulate the plate 68 from the cover and plate 72 and 7 0 respectively.

Desirably centered on the back face of the plate 68 is a heat responsive switch including a contact 79 and a switch arm 80 having a contact point 81 at one of its ends normally engaging said contact for closing a circuit through wires 82 to the heating elements 23. The arm 80 is secured to the plate 68 by a heat conductive mounting block 84 adapted to conduct heat away from the plate 68 to the arm 80 for actuating said arm to open and close the contacts 79 and 81. Conveniently, the arm 80 is a bimetallic strip comprising a metal strip 85 with a relatively low coecient of expansion disposed against the mounting block 84, and a metal strip 86 with a relatively high coetiicient of expansion which carries the contact point 81 in normally circuit-closed position against the contact 79. Thus, when the heater is in operation and a heat reflecting object is placed in front of the heater, the object will reflect radiant heat back toward the heater to raise the temperature of the plate 68. This increase in temperature will be transmitted to the arm 80 through the mounting block 84 causing the strip 86 to expand and bend the arm toward the plate 68 opening the contacts 79 and 81 to open the circuit to the heating elements 23. When the radiant heat reected to the plate 68 has been reduced because of the reduced output of the heating elements 23 or by removing the reflecting object, both the plate 68 and the arm 80 cool, causing the strip 86 to contract and dispose the contact point 81 in its normally closed position against the contact 79.

'By employing the thermostatic control mechanism illustrated in Fig. 4 it is possible to sense variations in the amount of heat retiected back toward the heater which can not be sensed by the control mechanism shown in Fig. 1. The elongated sensing strip 68 extending transversely across the face of the heater can sense the heat reflected from a small object disposed in front of the heater near one end of the emitted heat beam which would not be reflected back to, and sensed by, the centrally positioned thermostat 30 embodied in the heater illustrated in Fig. 5

Still another modification of our invention is shown in Figs. 5 and 6. In this modification a plurality of small thermostats 88 are mounted in the forwardly presented face of the heater and are insulated from a radiant heat source 90 by means of any suitable shielding 92. Desirably, each of the thermostats 88 is provided with a face plate 94 adapted for absorbing and transmitting to said thermostat heat that is reflected back toward the heater from an object disposed in front of said heater. The several thermostats 88 and their respective contacts 95 are connected in series by wires 96 to a relay 98 operable for actuating a switch to open and close the circuit to the radiant heat source 90. Thus, if a heat reflecting object is positioned in front of the heater to reflect heat back to any one of the thermostats 88, said thermostat will be actuated to disengage its contact for actuating the relay 98 to open the switch 160, thereby opening the circuit to the heat source 90 to reduce the output of the heater and prevent igniting of the rellecting object.

We claim as our invention:

l. In a radiant heater, a housing for said heater having an open forwardly presented face, a radiant heat source disposed within said housing, reflectors mounted rearwardly of said heat source for directing heat outwardly `from Said heater through its open face, heat responsive means mounted in said housing forwardly of said reectors and radiant heat source and operable for controlling the output of said heat source, and an insulating shield mounted on said reflectors for supporting said heat responsive means in a position insulated from heat directed away from said heater and disposing said heat responsive means in the forwardly presented face of said housing for actuation by heat directed back toward said heater.

2. In a radiant heater, a housing for `said heater having an open forwardly presented face, a pair of spaced radiant heating elements disposed within said housing, a reflector mounted behind each of said pair of heating elements and extending forwardly therefrom for directing heat outwardly from said heater through its open face, and heat-responsive means mounted on the forward edge of the reflectors in the forwardly presented heater face forwardly of and between said pair of heating elements, said heat-responsive means being insulated from said pair of heating elements for selective actuation by heat reflected back to said heater to control the output of said pair of heating elements.

3. ln a radiant heater, a housing for said heater having an open forwardly presented face, a radiant heat source disposed within said housing, a reflector mounted rearwardly of said heat source for directing heat outwardly from said heater through its open face, and heat responsive means supported on the reflector forwardly of said radiant-heat source at the open forwardly presented heater face for controlling the output of `said heat source, said heat responsive means being insulated from said radiant-heat source for selective actuation by heat reflected back toward the heater.

4. A radiant heater as set forth in claim 3 in which said heat responsive means comprises a heat absorbent disc adapted to be actuated by heat reflected back toward said heater for operating a switch to open and close the circuit to said radiant-heat source.

5. A radiant heater as set forth in claim 3 in 'which said heat responsive means comprises a bimetallic disc substantially centered in the open face of said heater, said disc being flexed by heat reected back toward the heater to operate a switch for opening and closing the circuit to said radiant-heat source.

6. A radiant heater as set forth in claim 3 in which said heat responsive means comprises a plate of heatconductive metal adapted to absorb radiant heat reflected back to the heater for actuating a bimetallic strip mounted thereon to open and close the circuit to said heating elements.

7. A radiant heater as lset forth in claim 3 in which said heat responsive means comprises an elongated heat conductive plate extending across the open face of said heater, and a bimetallic strip connected to the rearward face of said plate, said strip being movable in response to temperature variations of said plate for opening and closing the circuit to said heating elements.

8. A radiant heater as set forth in c1airn'3 in which said heat responsive means comprises an elongated heat conductive plate extending transversely across the open face of said heater, and a bimetallic strip connected to the rearward -face of said plate at substantially the center thereof, said Istrip being movable in response to temperature variations of said plate for opening and closing the circuit to said heating elements.

9. A radiant heater as set forth in claim 3 in which said heat responsive means comprises a Isensing element responsive to heat reflected hack to the heater for actuating a relay controlling a switch to open and close the circuit to said heating elements.

10. A radiant heater as set forth in claim 3 in which said heat responsive means comprises a plurality of sensing elements responsive to heat reilected back to the heater for actuating a relay for controlling a switch to open and close the circuit to said heating elements.

11. A radiant heater as set forth in claim 3 in which said heat responsive means comprises a plurality of sensing elements responsive to heat reflected back to the heater for actuating a relay for controlling a switch to open and close the circuit to said heating elements, `said sensing elements being connected in series to said relay for actuating said relay in response to actuation of any of said sensing elements.

References Cited in the le of this patent UNITED STATES PATENTS 1,652,686 Schoenfeld Dec. 13, 1927 1,704,479 Kercher et al Mar. 5, 1929 2,459,169 Koei Ian. 18, 1949 2,459,170 Koci Ian. 18, 1949 2,534,097 Akeley Dec. 12, 1950 2,590,328 Koci Mar. 25, 1952 2,662,963 Wessel Dec. 15, 1953 2,667,828 Koci Feb. 2, 1954 2,714,644 Harrison Aug, 2, 1955 2,753,421 Mertler July 3, 1956 2,806,421 Huck Sept. 17, 1957 FOREIGN PATENTS 440,839 Great Britain Jan. 7, 1936