US2032417A - Constant temperature device - Google Patents

Description

March 3,A 1936. J, JACOBS 2,032,417

CONSTANT TEMPERATURE DEVI CE Filed Aug. 28, 1930 t i v 'ful Patented Mar. 3 1936 UNITED STATES PATENT OFFICE CONSTANT TEMPERATURE DEVICE Application August 28,

Germany February 27, 1930 12 Claims.

In order to maintain constant wave-length in transmitting apparatus controlled by quartz elements, it is necessary to take care that the piezoelectrical crystal is protected vagainst variations of temperature. This fact becomes evident if it is considered that a change of temperature of the quartz of 1 degree centigrade at a 300 metres wave will cause a change of frequency of about 50 cycles. Therefore itis necessary to obtain a constancy in temperature up to say l/ 100 degree centigrade. I

It has been suggested to place the quartz crystal into an ice-water mixture, however, the use of this method offers some difficulties in many d instances, since the necessary ice is not always available. For that reason another way is resorted to in practice and the piezo-crystal is introduced into a chamber, having as emcient a heat insulation as possible. By means of a device arranged within the chamber and dependent on the temperature, the interior of the chamber is always heated up again, if its temperature drops below a definite value. In order to avoid a drop in temperature, the heat insulation is carried out as efficiently as possible. A drawback of these arrangements however, is that in consequence of the eflicient heat insulation a rise of temperature will occur close to the quartz crystal, changing thereby the wave-length slowly but gradually.

If great pretensions are made on the constancy of the frequency, as such is necessary for instance, in common wave broadcasting with local synchronizing at the individual transmitting stations, those known devices will fail. According to the invention the chamber possessing a fine heat insulation is dispensed with and a chamber is used, consisting of a highly heat conducting body, in which is arranged the device (quartz crystal) to be maintained at a constant temperature, while the temperature of the highly heat conducting body is kept at a higher degree than its surroundings. It is obvious that a device of this type may be employed to advantage for a good many purposes, for instance a tuning fork may be provided therein.

An embodiment of the arrangement according to this invention is illustrated by way of example in the accompanying drawing.

Referring to the drawing a hollow space Q is provided within a highly heat conducting body, which space is adapted to receive the quartz crystal. The mounting of the latter is not shown in the drawing, since it is immaterial for the construction and design of the thermostat device 1930, Serial N0. 478,348

(Cl. 21S-19) proper. The connection with the quartz crystal is effected by means of the two leads Z1 and Zz. The efficient heat conductor is formed of a copper cylinder K1, whose outer peripheral surface is provided with a. plurality of small grooves H in which is placed a heating coil.

By means of such embedding of the heating coil in the mass of copper proper, with the provision of course of the necessary electrical insulation, easy conduction of the heat from the said heating coil to the copper cylinder is ensured. The copper cylinder K1 is provided at its top with an opening for introducing the quartz crystal, which opening is locked by means of the closing element V, which fits tightly. 'I'he hollow space 15 Q containing the quartz crystal can be illled with hydrogen or some other gas or it may be evacuated respectively. Into a boring located close to the heating coil there is arranged a mercury thermometer T having contacts t1 and tz. By 20 means of these contacts t1, tz the heating coil ls controlled by the interposition of the customary source of voltage or a relay respectively. The distance between the thermometer contacts is preferably so chosen, that variations of tempera- 25 ture of 116 degree centgrade are considered. Upon the cylinder K1 referred to above, another cylinder K2 likewise consisting of highly heat conducting material, is placed, so that as a whole a well conducting body is obtained, in which is embedded the heating coil, so that a uniform and good conduction of the heat from the heating coil to the surrounding parts is obtained.

In many instances it is of advantage to provvide the external cylinder with cooling ribs or fins R. The whole arrangement is covered at the top and bottom with layers of felt F and insulating material J, so that a loss of heat in that direction is avoided.

The mode of operation of the arrangement is 40 as follows:

If the heating coil is connected, the contact thermometer T will interrupt the heating element after the desired temperature is reached. If now, for instance, the temperature will drop by ,15 degree centigrade, the heating element is again connected. With the aid of the arrangement of the outer cylinder K2 of copper referred to above, a rapid succession of heating and cooling periods is obtained dependent on the surrounding temperature, since the heat-wave radiating in an outward direction will be subjected to a rapid cooling action causing a rapid cooling of the surrounding parts of the heating wire or the thermometer arranged near the latter respectively, through the radiation of the heat. Thus, the whole arrangement remains at a higher temperature than the surrounding atmosphere. Conditions are so chosen, that connecting and disconnecting of the heating element that is,J the average frequency of the heating and cooling periods, will occur so rapidly that no rise of temperature of the internal copper cylinder will take place due to the heat penetrating into the interior of the device. I

In order to accelerate the adjustment of the condition of equilibrium it is preferable to heatl the highly heat conducting body in the first place with an increased intensity of current and allow the arrangement to work on lesser intensity of current'later on.

It must be pointed out yet, that the quantity of heat set free by the oscillating quartz crystal as compared with that required for the heating up of the copper cylinder, is so small and the heat conductivity of the copper so high, that through the heat set free by the quartz crystal in the space provided for the latter, no rise in temperature will occur. i With a testing arrangement it was possible to fully maintain the heavy conditions referred to above as regards the constancy of the frequency.

I claim:

1. A constant temperature apparatus comprising a solid metallic body closely surrounding a device to be maintained at constant temperature, `an electric heater winding arranged on the outside surface of said body, a closely fitting shell of high heat conducting material of substantially lesser thickness than and surrounding said body, cooling fins carried by said shell, a thermostatic device controlling said heater winding and mounted closely to said heater winding, said thermostatic device having operating contacts adjusted for upper and lower temperature limits for controlling said heater winding to maintain said i'lrst body at a temperature higher than the surrounding temperature.

2. A constant temperature apparatus, comprising a solid metallic body enclosing an inner space including a device to be maintained at constant temperature; an electric heater winding arranged \in a spiral groove on the outside surface of said body; a second hollow metallic body closely fitting to and surrounding said first body; a thermostatic device controlling said heater winding and mounted in a-recess of said first body close to said heater winding; and operating contacts of said thermostatic device adjusted for upper and lower temperature limits for controlling said heater winding to maintain said rst lbody at a temperature higher tha'n that of the surrounding atmosphere.

3. A constant temperature apparatus, as described in claim 2, in which said first body has a recess and a removable cover member tightly fitted in the opening of said recess to provide .a hollow closed space for mounting a piezo crystal, and insulated connecting leads for said crystal passing through-said first body.

4. A constant temperature apparatus comprising a solid hollow body of high heat conducting material closely enclosing a chamber to be maintained at constant temperature thereby forming a continuous high heat conducting path from said chamber to the outside atmosphere subjected to temperature variations, means for applying periodic heat waves to said body at a frequency dependent on the surrounding temperature to maintain said body at a temperature higher than the surrounding temperature, said means comprising a unit embedded within. said body at a closer distance to the outer surface than to the inner surface of said body for dissipating the applied heatmore rapidly away than towards the interior of said body, the average frequency of said heat waves being furthermore such as to substantially prevent heat penetration into the interior of said body during the intervals between successive heat waves.

5. A constant temperature apparatus comprising a cylindrical metallic hollow body closely surrounding a device to be maintained at constant temperature, an insulated electric heater winding embedded in said body at a place farther removed from its inner than from its outer cylindrical surface, a thermostatic device controlling said heater winding arranged close to said heater .Winding to maintain said body at a higher temperature than the surrounding temperature, radiating f'lns carried by said body to further facilitate heat dissipation in the outward direction and heat insulating means for preventing heat radiation in the axial direction of said body.

6. A constant temperature apparatus comprisrounded solely by high heat conducting material;

a thermostatic device controlling said heater winding and mounted close to said heater winding, said thermostatic device having contacts adjusted for upper and lower temperature limits for controlling said heater winding to maintain the temperature thereof higher than the surrounding temperature; and means for preventing heat radiation in the longitudinal direction of said-body.

7. A constant temperature apparatus comprising a solid cylindrical metallic body enclosing a chamber to be maintained at constant temperature; an electric heater winding arranged in a spiral groove on the outside surface of said body; a hollow metal cylinder closely fitting to and surrounding said first body; a thermostatic device mounted close to said heater winding;

means including radiating fins mounted on the outside of said second body for dissipating heat applied by said winding more rapidly in the outward direction than towards said chamber; operating contacts of said thermostatic device adjusted for upper and lower temperature limits tainer at a distance closer to its outer than to its inner surface, a shell closely fitting said container to thereby form a continuous high heat conducting path from the interior of said container to the outside atmosphere subjected to temperature variations, thermostatic means connected with and disposed close to said heating means, and means controlled by said thermostatic means for controlling said heating means Cil to maintain said container at a temperature higher than the surrounding temperature.

9. A constant temperature apparatus comprising a heavy walled container of high heat conductingmaterial enclosing a chamber housing a device subject to both internal and external heat influence thereby forming a continuous high heat conducting path from the interior of said container to the outside atmosphere subjected to temperature variations, electric heating means mounted on the outside of said container, a hollow body of high heat conducting material closely tting and surrounding said container and allowing better heat radiation towards the outside than towards the inside of said container,

thermostatic means connected to and located close to said electric heating means, and means controlled by said thermostatic means for controlling said heating means to maintain said container at a temperature higher than the surrounding temperature.

10. A constant temperature apparatus comprising a heavy walled metallic cylindrical container enclosing a chamber adapted to house an electromechanical vibratile element, an electric heater winding mounted on the outside cylindrical surface of said container, a metallic shell closely tting and surrounding the outside cylindrical surface of said container thereby forming a continuous high heat conducting path from the interior of said container to the outside atmosphere subjected to temperature variations, thermostatic means mounted close to said heater winding having contacts adjusted for predetermined upper and lower temperature limits, said contacts controlling said heater winding to maintain the temperature of said container higher than the surrounding temperature, and heat insulating means for preventing heat dissipation in the axial direction of said container.

11. A constant temperature apparatus comprising a heavy walled metallic container enclosing a space to be maintained at constant temperature thereby forming a continuous heat conducting path from said chamber to the outside atmosphere subject to temperature variations, an electric heater winding embedded in said container at a place closer to its outer than to its inner surface, and a thermostatic device controlling said heater winding and arranged close to said heater winding.

12. A constant temperature apparatus comprising a heavy walled metallic housing enclosing a space to be maintained at constant temperature thereby forming a continuous heat conducting path from said chamber to the outside atmosphere subject to temperature variations, an insulated electric heater winding embedded -in said housing at a place to cause more rapid heat transfer in the direction towards the outside than towards the inside of said housing, and a thermostatic device controlling said heater winding and arranged close to said heater winding.

JOHANNES JACOBS.

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