US2037993A - Heater and circulator for thermostatic baths - Google Patents

Description

LNE 2? (11%@ Q., Haw-mma@ Er AL HEATER AND CIRCULAOR FOR THERMOSTATIC BATHS Filed April 27, 1935 In Ver? "Ofw i Mw.

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Patented Apr. 21, 1936 uNlrgn stares PATZNT OFFICE HEATER AND CRCULATOR FOR THERMSTATEC BATES Application April 27, 1935, Serial No. 18,699

4 Claims.

This invention relates to thermal baths such as are used by biologists, chemists and physicists for maintaining objects immersed in the liquid at some definite temperature.

The objects of the invention are to provide a heater and circulator of unitary self-supporting form suitable for use in an open vessel without having brackets or the like extending to the walls of the vessel or to outside supports; and to provide improvements in the construction and arrangement of a turbine circulator and heater for efficiently controlling the temperature of the bath.

A specific embodiment of the invention is illustrated in the drawing, wherein:

Figure 1 shows the operating unit in side elevation in combination with a thermal bath receptacle which is shown in section.

Fig. 2 is an enlarged vertical sectional detail of the heater and circulator.

Fig. 3 is a diagram showing electric circuit connections for the heating coil.

'I'he heating and circulating unit is made so that it will stand in operating position on the floor of a receptacle and unattached to the side walls thereof, and comprises a supporting frame structure having mounted therein a central penstock tube through which the bath liquid circulates upwardly under the action of an impeller iitted within the tube.

At the top of the tube is a head structure serving as a support for the motor, a thermometer, and a thermostat for regulating the delivery of heat to the bath liquid. The heat is applied from a coil Wound upon the tube and surrounded by a spaced and insulated cylindrical housing which separates it from the bath liquid and assures that the heating effect is concentrated upon the liquid within the tube. The function of the thermostat is to control heat delivery by the coil.

The drawing shows a bath receptacle I having inlet and overflow connections 2 and 3 for the circulating medium, usually water, and which serves to maintain at some xed point the temperature of an object immersed in the bath.

The circulating and heating unit comprises a supporting base li having a central opening 5 in line with a tube extending upwardly from the base and terminating at its upper end in a motor support or head l. Motor 8 is bolted to the support 'I and the shaft 9 of the motor carries a rotor IIJ tting the bore of tube 6. The rotor I E) has a spiral channel II in its cylindrical surface and through which the bath liquid is driven up- Wardly when the motor is in operation. The

(Cl. 21S-39) openings I2 at the upper end of the tube 6 provide uniformly spaced radial outlets for the bath liquid.

The liquid is heated as it passes upwardly through the tube by means of a heating coil I3 which consists of suitable resistance wire wound upon the tube and having a plurality of connections ifi, Fig. 3, with a rheostat I5 whereby more or less of the coil is rendered effective for heating purposes when a thermostatically op- 10 erated relay l5 permits the closing of contacts El. Those contacts are normally held closed as by a spring I8 except when the relay is energized through the closing of a local circuit I 9 by a mercury contactor represented by the bulb 15 2l, and described in detail in our copending application for patent, Serial No. 18,698, filed April 27, 1935 on Thermo-regulators. This contactor is carried by a bracket on the head 'I.

The coil d3 is housed within the cylindrical casing 2| which separates it from the bath liquid and has a cap 22 at its upper end extending therefrom to the tube 6.

A thermometer for ascertaining the temperature of the bath liquid is indicated at 23 and is 25 supported by a bracket on the frame structure l.

The electrical connections to the motor heater and regulator are housed in an outlet box 24 mounted on top of the motor and connected to a source of current and other control devices not 30 shown in Fig. 1 by the cable 25. For simplicity of illustration, the relay is shown as actuated by current from a battery although in actual practice we use a more complicated circuit for obtaining the desired minute relay current from 35 the line circuit to the motor as described in our copending application Serial No. 20,058, led May 6, 1935.

In operation of the heating and circulating unit the motor is in constant operation and the heat is supplied at a rate to exactly compensate for losses to the atmosphere and surrounding objects. The rate of the heat delivery by the coil is roughly regulated by the setting of multistage switch i5, and the temperature of the bath is 45 then automatically controlled by the intermittent operation oi circuit opener I 6 under control of the temperature responsive element 29.

The temperature responsive element may be set to close the local circuit I5 at some precise tem- 50 perature to a fraction of a degree. Thus heat is supplied as needed but the temperature of the bath water cannot exceed the temperature predetermined by the setting of the thermostatic regulator Z. This closing of the regulator circuit Cil actuates the relay to open the normally closed heater circuit and the constant circulation of the bath maintains a constant temperature over the period of operation.

Although but one specic embodiment of this invention is herein shown and described, it is to be understood that details as set forth may be altered or omitted without departing from the spirit of the invention as defined by the following claims.

We claim:

1. A thermal bath comprising a reservoir for a bath of liquid heating medium, a vertically disposed tube within said reservoir having inlet and outlet openings respectively located adjacent the bottom and top of said reservoir,v an impeller within said tube for driving the heating medium through said tube, an electric heating coil surrounding said tube, and a heat insulating jacket housing said coil and positioned to prevent direct heating of the bath outside the penstock.

2. In a thermal bath, a heating and circulating unit comprising a vertical penstock tube having openings at the bottom and top thereof for circulating the contents of said bath, an impeller in said tube having an upwardly extending shaft, a motor carried on said tube for driving said shaft, an electric heating element surrounding said penstock tube, a jacket cooperating with said tube to house said heating element, and a base frame carrying said unit.

3. A heating and circulating unit of the class described comprising a supporting base having concentric upwardly extending tubes the inner tube being longer than the outer tube, and having radial outlet perforations above the outer tube, a cap for the outer tube closing the space between both tubes, a heating coil between the tubes, a motor supported on the upper end of the inner tube and having a shaft extending therein and carrying an impeller for circulating a bath liquid through said inner tube.

4. A heating and circulating unit of the class described comprising a supporting base having concentric upwardly extending tubes the inner tube being longer than the outer tube, and having radial outlet perforations above the outer tube, a cap for the outer tube closing the space between both tubes, a heating coil between the tubes, a motor supported on the upper end of the inner tube and having a shaft extending therein and carrying an impeller for circulating a bath liquid through said inner tube, a bracket carried by said inner tube and having means for holding a thermo-regulator in said bath at one side of said unit.

CHARLES H. MILLER. PAUL SHERRICK.

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