US2180706A - Temperature control device - Google Patents

Description

Nov. 21, 1939. H. E. GOLDSTINE TEMPERATURE CONTROL DEVICE Filed 001:. 50, 1936 INVENTOR HALLAN E. GOLDSTINE BY/KZ ATTORNEY Patented Nov. 21, 1939 PATENT OFFICE TEMPERATURE CONTROL DEVICE Hallan Eugene Goldstine, Rocky Point, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application October 30, 1936, Serial No. 108,434

3 Claims.

This invention relates to a new and novel piezoelectric crystal oven and holder.

An object of this invention is to improve the temperature regulation within a crystal oven of a piezo-electric crystal.

Another object of this crystal unit is to keep the oven wall temperature the same on all sides of the crystal box and thus prevent large differences in temperature within the crystal unit.

Still another object of this invention is to provide a temperature regulator for a piezo-electrio crystal holder in which the holder is arranged with cooling members to maintain constant temperature on the crystal.

A feature of this invention is the arrangement of the cooling members within the oven so as to smooth out the variations in the temperature.

Another feature of this invention is the arrangement of cooling members located on the electrode of the crystal holder to smooth out variations in temperature.

Although piezo-electric crystal holders and ovens for maintaining the wall at constant-temperature are old in the art, I have found that in the construction of the crystal oven it is necessary to either keep the crystal holder itself at a predetermined temperature by insulating it from the ambient temperature so that changes in the ambient temperature would have little effect on the change of the crystal holder, or to hold the temperature of the oven wall at a constant temperature by supplying a thermostatic element for controlling the temperature, which element may be in the form of a bimetallic strip.

'When a bimetallic strip type of thermostat is used, it is found desirable to distribute the heat more evenly within the oven, so that the temperature within theoven will be uniform. However, when using such a bimetallic strip type of thermostat, it is generally diflicult to get good' thermal conductivity between the thermostat and the wall. By this invention, the temperature near thermostat element is maintained substantially constant by placing it within a thin metallic tube which is connected to the wall of the container forthe piezo-electric crystal. Also, when desired, the crystal holder itself is arranged with a number of metallic fins for radiating the heat developed within the crystal.

The crystal holder is so constructed that the heat developed by the crystal may be dissipated to the air in the box by means of copper radiating fins, and also the crystal if placed in the box cold will reach the box temperature faster than normal due to the better heat conductivity from the box air temperature to the crystal. This will reduce the frequency change due to the crystal heating when oscillating, because the crystal will not get as hot and it will not take as long to reach an equilibrium with the box temperature.

The crystal container may also have enclosed part of the apparatus of the crystal circuit, such as a coil and condenser whereby they are also held at a fixed temperature.

This invention will be more completely understood by referring to the accompanying drawing, in which:

Fig. 1 is a front view partly in section through the crystal oven;

Fig. 2 is a side view partly in section taken on lines A-A of Fig. 1; a r

Fig. 3 is a plan view of the crystal holder; while Fig. 4 is a section of Fig. 3.

Referring now in detail to the drawing, the oven I is composed of a fiber box 2 having an insulating space 3 which is filled with any suitable insulation material, such as felt. The felt is covered with a mica sheet 4 on which is located the heating element or winding 5. Outside of the winding there is a mica sheet between the heater .and wall or shield 6, preferably made of heavy copper. A thermostat l, which may be of the type having a bimetallic strip or thermostat, is supported within a metallic tubular container 8, preferably of copper. One end of container 8 is provided with an insulating bushing 9 which is composed preferably of a' phenol condensation product, to electrically insulate one side of the thermostat from shield 6. However, if the thermostat is to be operated so that there is no Potential difference between it and the metallic tubular sleeve 8, there would be no need of using the insulating bushing 9. The outer portion of tube 8 has located thereon a plurality of metallic fins or heat conducting members ill which are equally spaced. The purpose of fins l is to provide a plurality of heat conducting vanes to maintain metallic tube 8 at substantially the same temperature as the inner walls 6 of box 2 so that the tl :rmostat I responds more promptly to the wall temperature than if a solid metallic memfive sides of the box, all except the front. They may be located in the front also, if connections are provided to disconnect the heater when the front is removed. The heater is then electrically insulated from the copper wall of the crystal box by means of a thin sheet of mica. This gives good thermal contact from the heater to the copper wall.

A piezo-electric crystal holder is shown in Figs. 3 and 4 and consists of an upper electrode l2 and a lower electrode E3, the electrodes being placed apart from each other by a metallic ring M and an insulating member I5. A connection is taken from the upper electrode M by a terminal member l6 and from the lower electrode l3 by a terminal member H, the crystal l8 being located substantially central within the space between electrodes I2 and i3. The lower electrode I3 is provided with a plurality of radiating fins i9, which are preferably composed of any good heat conducting material, such as copper.

The piezo-electric crystal holder is located within the container by two insulating supports 2! firmly secured to the copper shield 6. Knurled nuts 22 are provided to clamp the piezoelectric crystal holder to the insulating supports 2|.

While only one modification of this invention is shown, it is distinctly understood that this invention is not to be limited to the one shown, but is capable of taking other forms, and therefore said walls substantially the same, means to make said thermostat immediately respond to changes in temperature within said casing, said means comprising a hollow metallic member surrounding said thermostat and located parallel to one of the walls of said casing and closely adjacent thereto, and a plurality of heat conducting vanes mounted outside of said metallic member and secured to the wall by a metallic plate.

2. A temperature control device comprising a casing having inner walls of high thermal con ductivity metal, a heating element within the walls of said casing, a thermostat *to control said heating element to maintain the temperature of said walls substantially the same, means to make said thermostat immediately respond to changes in temperature within said casing, said means comprising a tubular metallic member located parallel to and closely adjacent to one of the walls of said casing, said tubular member enclosing said thermostat, and a plurality of heat said wall and connected thereto. a

3. A temperature control device comprising a casing having inner walls of high thermal conductivity metal, a heating element within at least five walls of said casing, a thermostat to control said heating element to maintain the temperature of said walls substantially the same, means to make said thermostat immediately respond to changes in temperature within said casing, said means comprising a tubular metallic member located parallel to and closely adjacent to one of, the walls of said casing, said tubular member enclosing said thermostat, and a plurality of heat conducting vanes mounted outside of said metallic member and in a plane at right angles to said wall and connected thereto.

HALLAN EUGENE GOLDSTINE.

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