US2656449A

US2656449A - Electric radiant heat drier

Info

Publication number: US2656449A
Application number: US284746A
Authority: US
Inventors: Everett C Elgar
Original assignee: General Electric Canada Co
Current assignee: General Electric Canada Co
Priority date: 1951-05-01
Filing date: 1952-04-28
Publication date: 1953-10-20
Anticipated expiration: 1970-10-20

Description

Oct. 20, 1953 E. c. ELGAR ELECTRIC RADIANT HEAT DRIER Filed April 28, 1952 Inventor": Everett Gil-gar,

ls Attor'ne Patented Oct. 20, 1953 UNITED STATES PATENT OFFICE ELECTRIC RADIANT HEAT DRIER Everett C. Elgar, Toronto, Ontario, Canada, 'assignor to Canadian General Electric Company, Limited, Toronto, Ontario, Canada, a comma tion of Canada Application April'28, 1952, Serial No. 284,746 In Canada May 1, 1951 4 Claims. 1

My invention relates to an electric heater used for drying purposes. More particularly, it relatesto a heater so constructed to supply infrared 'heat to material travelling past the heat source on a conveyor.

In a number of manufacturing processes it is necessary to dry materials such as paperor textiles which are unwound from one roll and subjected to an intense heat suflicient to dry the material without danger of damaging the material and which are then rewound on a second roll. In order to prevent the paper or other material from scorching or burning it is necessary thatit passthe heat source at a sufficient speed. Consequently, a heat source of considerable intensity .is-required. In the past gas fires or infra-red lamps have been used for such purposes. A glowing electric resistance element emanating infra-red rays has been found most satisfactory from the standpoint of the amount of heat emitted.

The heater of my invention has particular applicability to the drying of printed sheets which pass the heating element on a conveyor while the printing ink is still wet. It isnecessary that these printedsheets. be dried quickly so that the sheets may be stacked one on top of the other.

It has been the custom to use gas flames in drying the printed sheets. However there is considerable danger of scorching or burning the paper when this type of a heat source is used. In addition such a system isnot adapted to a simple control for cutting off the heat .in the event ofa stoppage of the conveyor. Both infrared lamps and glowing electrical resistance elements have also beentried. In the case of the lamps sufiicient heat is not'obtained, but it has been found that a resistance element of the'type known as a sheathed wire element comprising a coiled electrical resistance wireembedded in a refractory material such as magnesium, oxide and enclosed by a metallic sheath capable or attaining a very high temperature, providesmore satisfactory results.

However in the use of such a high intensity source of heat radiation it isnecessary to provide a rapid means for preventing heat radiation from reaching the paper in the event of a work stoppage. Suchmeans usually consist of acomplicated mechanism for rotating the heating element away from the paper in addition to switching off the supply of electrical energy. It is, therefore, my intention to provide a heat drying unit of the type employing an electrical sheathed wire resistance element in conjunction with 'a simplified means of preventing heat radiation in the event of a work stoppage. In addition I intend to provide a heat drying unit of the'above type which will take full advantage of the heat radiated by the electric element.

I It is an object therefore-of the present-invn tion to provide a simple drying unit for newly printed sheets of paper or like material while they are in motion past the heat source.

It is a further object to provide an efficient compact heater equipped with an electric infra-f red emitting element of such intensity that printed sheets may be dried on passing the element at a sufficient rate so thatthe paper is not scorched. I I v A still further object is to provide an electric heater for drying printed sheets so adapted that should a stoppage of the conveyor carrying the printed sheets past the heater occur, the intense radiated heat from the heating element can be immediately deflected from the paper.

Other objects will become apparent from a consideration of the following description and the drawing in which Fig. 1 is a perspective view of the heater with a printed'sheet travelling'on the conveyor through the heater. Fig. 2 is a view taken along a line AA (Fig. 1) in the direction of the arrows and is on an enlarged scale with the reflector rotated through from its position shown in Fig. 1 and Fig. 3 is a section through line BB of Fig. 2 on an enlarged scale.

Referring particularly to Fig. 1 my drier resembles a box-like structure 2 of sheet metal consisting of end plates 3 joined by sidewalls 4 and a base plate 5. The side walls 4 terminate short of the base plate 5 forming a slot '6 extending the entire length of the box 2 and having as boundaries the lower edge of the side walls 4, base plate '5 and end plates 3.

The box 2 is adapted to be mounted by means of bolts through the end plates 3 to the frame of a printing press. Tapes 1 of a continuous conveyor carrying the printed sheets 8 and is carry freshly printed sheets 8 through the drier. The box 2 is ofsufiicient length to bridge the conveyor carrying theprinted sheets 8 and is shown in Fig. 1 with a section removed in order to illustrate the drier on a convenient scale.

A heating element 9 of the type previously described as a sheathed wire element extends the length of the box and is mounted centrally of the side walls 4, and extends through openings in the end plates 3. The end walls carry connection boxes [0 and H in which connections and controls for energizing the heating element are contained; When the heating element is energized it emits infra-red rays which are used to dry the ink on the printed sheets 8 passing through the drier.

A reflector I2 is mounted over the heater ele ment 9 in a manner for rotation about the element from a position above the element as shown in Fig. 2 where it reflects heat from the element to the paper 8, through 180 to a second position as shown in Fig. 1 where it is interposed between the heater and the paper. Since there is an intense heat emitted by the element 9 it is apparent that if the conveyor is brought to a stop, the paper passing through the drier will be scorched or burnt. Even though the power is promptly cut off, the residual heat from the heating element which is of high heat capacity would be suflicient to damage the paper.

My invention, therefore, provides a drier of the above character which incorporates a re flector so mounted that the printing press operator may interpose the reflector between the heating element and the paper within a moments notice.

The reflector I2 is preferably of sheet metal and may be provided with a separate reflector material l3 as shown in Fig. 2 fastened to the inner surface of the reflector I2. The peak of the reflector material is preferably indented as shown in Fig. 2 at Ho 50 that the maximum radiation to the paper is obtained since the emitted rays will not be reflected back to the heating element 9.

In addition to reflector l2, side reflectors I4 are attached to the side walls 4 of the box 2 as shown in Fig. 2. These reflectors are bent to cooperate with the rotatable reflector i2 irt forming a nearly continuous reflecting surface around the top and sides of the heating element 9 in order to utilize the maximum radiation. Electrical connections between the connection boxes I and Il may be made through the space I5 defined between the side walls 4 and the side reflectors [4. For example if connection box I6 is used as a junction box for connection of the heating element 9 with the outside electrical supply and connection box I I is used to house a switch mechanism, the return conductors between the switch box H and the junction box 10 may be carried through the space IS.

The mounting of the reflector I2 is more clearly shown in Figs. 2 and 3. The reflector [2 comprises a reflecting trough portion to which the reflecting material I3 is fastened and a pair of segmental end plates 16. Apertures ll, are provided centrally in the reflector end plates I6. A bushing I8 is inserted through the external face of the reflector end plate 16 into the aperture IT. The bushing 58 is provided with a bearing surface IS, a threaded portion 26 and a head 2| and is held in position by means of a lock nut 22 engaging the threaded portion and bearing against a metal plate 23. The head 2| on the bushing bears against the opposite side of the plate 23.

A circular toothed gear 24 provided with an internal bushing in its hub is fltted over the bearing surface 19 of the bushing I 8 and is secured to the reflector end plate [6. Reflector end plate i5 is shown partially broken away in Fig. 2 to reveal the gear 24. The metal plate 23 which is also used for dissipating excess heat carries a segmental gear pivotally mounted on a stud 21 and carrying a handle 25 which projects beyond the drier structure for easy access. The

teeth of the segment 25 mesh with the gear 24 in such a manner that when the handle 26 is in a position shown in Fig. l, the reflector I2 is between the heater 9 and the conveyor tapes 1 and when the handle is moved to the position shown in Fig. 2 rotating the gear segment 25 through about it causes the reflector to be rotated to its normal operating position for reflecting heat rays on the paper sheets 8.

The heat dissipating plate 23 is mounted on the end Wall 3 and shields the switch box I I from considerable heat. Switch box I l is mounted on the heat dissipating plate 23 and the end wall 3.

The base plate 5 of the drier is made of a heat absorbent refractory material, such as asbestos board. During the time elapsed between the passage of successive printed sheets 8 along the tapes 1, this heat absorbent material stores up reflected heat at its upper surface layer so that considerable stored-up heat may be given ofi to the succeeding printed sheet as it passes over this absorbent layer.

I have thus provided a drier that utilizes all the available radiated heat. The asbestos board is considerably more efiective in providing additional heat for drying than a reflective material placed in the same position. This is due to the fact that a heat conducting reflective surface tends to conduct the heat away from the upper surface where the heat rays are incident whereas the asbestos material tends to maintain a high temperature at the surface which is desirable in our application.

In the operation of the drier, the printed sheets 8 are carried along on tapes I of the conveyor past the heating element 9. Heat is transmitted to the paper by direct radiation from the element 9, reflected heat from the reflectors l2 and I3 and from the absorbent panel 5 beneath the moving paper. The supply of electrical energy may be controlled by the switch in switch box H.

In the event the moving conveyor is stopped, switching off the power will not have any immediate effect in decreasing substantially the amount of heat radiated. However, rotation. of the reflector I 2 by means of handle 26 attached to gear segment 25 places the reflector between the heating element and the paper. As a result very little heat is radiated to the paper during this period and it is possible that the heating element may remain switched into the circuit. This is a simple mechanism and does not require that the whole heating element assembly be rotated along with the reflector.

It will be evident therefore that I have provided a simple unit for drying printed sheets providing an intense source of heat radiation which eliminates the need for cumbersome mechanism to remove the source of heat a sub stantial distance from the paper in the event of a failure in the conveyor mechanism. This unit is compact and a number of similar units may very easily be mounted side by side on a press, depending on the amount of heat required. In such cases a coupling connection may be made between operating mechanism for rotating the reflector so that one control only need be actuated in order to rotate the reflectors in each unit.

' What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric radiant heat drier comprising an elongated housing structure having two end plates, a base plate and a pair of side walls terminating short of the base plate thereby providing a slot extending the length of the housing through which a travelling conveyor is adapted to pass carrying material to be dried, an electrical heating element mounted in the housing above the slot and coextensive therewith in a position to extend transversely of the conveyor and spaced in close proximity thereto, a trough-like reflector mounted in the housing and extending throughout the length of the heater element, means mounting said reflector in the housing for rotation about its axis in a manner such that it may be moved from a position wherein it reflects heat from the heater to the material to be dried to a second position where it is interposed between the heater and the material.

2. An electric radiant heat drier as claimed in claim 1 in which the base plate comprises a refractory material such as asbestos for storing reflected heat during periods between the passage of successive sheets of material to be dried.

3. An electric radiant heat drier as claimed in claim 1 in which reflector plates are provided on the side Walls of the housing shaped to form an extension of the sides of the rotatable reflector.

4. An electric radiant heat drier as claimed in claim 1 in which the means for rotating the reflector comprises a handle pivotally connected to the housing and carrying a segmental gear for cooperation with a gear fixed to an end wall of the reflector trough.

EVERETT C. ELGAR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 693,385 Faulds Feb. 18, 1902 1,450,022 Doyle Mar. 27, 1923 1,802,407 Danninger et a1. Apr. 28, 1931 2,127,956 Helmer Aug. 23, 1938 2,455,047 Doyle Nov. 30, 1948 2,479,913 Doyle Aug. 23, 1949 2,559,410 Doyle July 3, 1951 2,565,570 Messinger Aug. 28, 1951 2,599,029 Turner et a1. June 3, 1952 2,619,734 Geldhof et a1 Dec. 2, 1952 FOREIGN PATENTS Number Country Date 309,209 Canada Mar. 10, 1931 382,099 Germany Sept. 28, 1923