Abstract: A hot melt pumping and dispensing apparatus for heating and pumping a heat liquefiable product from a barrel includes a platen movable into the barrel and having a plurality non-perforated, sector-shaped cast heater segments, each provided with an electric heater, arranged in a circle on the lower face of the platen and having inner ends defining a central space at a common apex thereof. The segments are spaced from each other to define narrow radial passageways between adjacent segments opening into the central space for delivery of liquefied product thereinto. A cartridge-type pump carried by the platen communicates with the central space. The lower face of each heater segment is provided with depending heat conducting cylindrical projections which extend in advance of the segments into the product in the barrel to preheat and soften the product.

Abstract: A heater is disclosed having a PTC thermistor heating element rigidly wedged in an intermediate space of the member to be heated by use of at least one wedge-shaped member. The wedge-shaped member has a surface which is at least the size of the heating elment so an optimum heat transmission is guaranteed.

Abstract: A heater module adapted to be used in an apparatus for melting and dispensing thermoplastic material, with other like modules for forming a pre-melt and/or a melting stage for heating the thermoplastic material. Each module is of uniform construction and includes an elongated core having a plurality of longitudinally spaced first fins projecting from one side of the core and second fins projecting from the other side of the core, but longitudinally and uniformly staggered from the first fins, so that a plurality of parallel modules adjacent to each other will have the recesses between adjacent fins closed by the opposite fins to form longitudinally staggered vertical holes for the fluid passage of the melted thermoplastic material.

Abstract: A built-in well type food warmer includes a heating element assembly which is separably engaged with the underside of a food well by adjustable hanger members. The heating element assembly includes an upper heat distribution plate which is nestable within a recess formed in the bottom of the food well. The heating element assembly is enclosed by a tray member which is resiliently mounted within an enclosure. Brackets extending outwardly from the enclosure are attached to the lower ends of baffle hangers which extend downwardly from an upper rim of the food well. The hangers are formed of two separable members, adjustably connected together for selectively adjusting the length of the hanger. As the hangers are shortened, the heating element assembly is resiliently biased into contact with the bottom surface of the food well within a recessed portion thereof.

Abstract: A heating assembly adapted to be releasably mounted externally of an instrument for the transfer of heat to the instrument by conduction to maintain the instrument at a desired temperature.

Abstract: An adjustable temperature warming plate for an electric coffee maker in which a fixedly positioned metal hot plate has an electric heating element disposed beneath and adjacent the hot plate with the supporting means for the electric heating element permitting the heating element to pivot about a contact point near the edge of the hot plate for varying the thermal coupling of the heating element to the hot plate by changing the spacing between the heating element and the hot plate. A pressure element is provided to urge the heater toward the contact point and a setting element is provided to adjust the spacing between the heating element and the hot plate. This provides a simple and reliable means for varying the thermal coupling of the heating element to the hot plate and consequently the temperature of the warming plate. The heating element includes a tube unitary therewith forming a continuous flow water heating tube for the coffee maker.

Abstract: This invention pertains to the forming of a laminated plastic such as Formica (trademark of Formica Corporation) having a decorative facing layer. A controlled heating cylindrical column of metal is provided. This cylindrical column is secured to a base which may be secured to a workbench or the like. A control apparatus is also provided which includes an "on-off" switch, a temperature indicator, a variable voltage or current control and an indicator light for determining when the apparatus is in operation.

Abstract: The invention provides a heating panel which is made up of a plurality of heat conducting elongated plates. The plates are profiled in cross-section so as to be of Z-shape and they are pushed together so as to lie lengthwise parallel. The web portions abut for the current submission of heat between the plates, and there is a heating pipe passing through apertures in the plates and which is in heat conducting engagement with said plates.

Abstract: Improved heat roller fixing apparatus comprising an inner cylinder having a heater therein, an outer cylinder, and a vacuum chamber which is formed between the inner cylinder and the outer cylinder and which contains a liquid heat transfer medium at low pressure is described. In particular, improvements obviating excessive heating of the inner cylinder are made by placing the heat transfer medium in the chamber so as to be in contact with the lower portion of the inner cylinder at least when said outer cylinder is stationary, or by mounting on the inner cylinder a member which serves to stir or pour the heating medium on the inner cylinder and also to transfer heat indirectly from the inner cylinder to the outer cylinder through the heating medium so that speedy evaporation of the heating medium and safe and stable fixing of images are accomplished.

Abstract: A presser member, into which the container is loaded, is manually depressable against the action of its return spring into pressure-contact engagement of the container with an electric heating plate containing a PTC heating resistor. The depression stroke produces closure of a switch to energize both the PTC resistor and an electromagnet keeping the presser member in its depressed condition. A timer circuit opens the switch at the elapse of a prealably experimentally determined heating time during which the liquid reaches its consumption temperature, whereby heating is terminated and the return spring lifts the pressure member with the container to unloading position.

Abstract: A thermostatically controlled pre-weld heater is described in which a temperature sensor is mounted, intermediate the legs of a pre-weld heater, in a position to sense accurately, and then thereby to control, the temperature of the workpiece so as to accurately control the temperature of the area to be welded by opening and closing the circuit to the electrical current supplied to the heater coil in the legs of the pre-weld heater.

Abstract: A device for heating a drink in a thermoplastics container sealed by a metal cover, in which the container is placed in a support upside-down and depressed to bring its cover into contact with an electrical heater, the depression of the container support operating a microswitch which energizes the heater and a support-retaining electromagnet to heat the container for a timed interval. The resistance of the heater is measured during heating by a Wheatstone bridge and utilized to regulate the temperature reached by the heater.

Abstract: Heat is transferred from a hot reservoir to an intermittent user such as a domestic appliance through an intermediate heat exchanger. Heat storing material maintains a substantially constant temperature at its phase transition point. When the intermittent user is operating, a heat exchange fluid such as NaK transfers heat from the heat storing material to a thermally degradable organic thermal exchange fluid through the intermediate heat exchanger to the intermittent user at substantially the temperature of the heat storing material. When the intermittent user is not operating, circulation of the fluids stops which allows the thermal exchange fluid to cool thereby reducing its thermal degradation. The heat storing material is selected for a high latent heat of phase transition, the heat exchange fluid is selected for thermal stability, and the thermal exchange fluid is selected for intermittent user needs such as mobility in a liquid phase at hot and cold temperatures.

Abstract: An aquarium heater having a heat resistant plastic housing. A heat producing electric resistance wire is positioned in the plastic housing in an aluminum foil container. In one embodiment, the container is an aluminum foil pouch which encloses the heat producing electric resistance wiring. The aluminum foil pouch is filled with sand. In another embodiment, the aluminum container is an annular pan and the electrical resistance wire is coiled in the pan.

Abstract: A dual mode heat pipe includes roadways, bridges, etc., includes an auxiliary evaporator formed concentrically with the upper end of a vertically disposed primary evaporator portion. The auxiliary evaporator portion comprises an annular sleeve disposed about the upper end of the primary evaporator portion and arranged between the primary evaporator portion and the condenser portion of the heat pipe such that all of the condensed working fluid returning to the primary evaporator portion must enter and overflow the auxiliary evaporator portion prior to return to the primary evaporator portion. The auxiliary evaporator portion is provided with heat input means whereby the auxiliary evaporator may function even in the absence of heat pipe function by the primary evaporator.

Abstract: The roller comprises a core and a shell secured to said core. The shell is made up of two coaxial pipes, i.e. an inner pipe secured to the core in the middle and an outer pipe fastened to the inner pipe in the middle and at the ends. This allows the shell to be made of small-diameter thin-walled pipes thus reducing the roller deflection and decreasing considerably the weight both of the roller proper and of the equipment utilizing said roller.

Abstract: A cooking utensil that includes the combination of a heat transmitting metal bottom wall, preferably stainless steel with a heat generating source including a high heat-conductive metal body, preferably aluminum, the bottom wall having a substantially planar lower surface and said high heat-conductive metal body presenting a flat surface to the lower surface of the bottom wall, a plurality of releasable clamping devices carried by the bottom wall and projecting therebelow generally peripherally of the high heat-conductive metal body at spaced intervals therearound each clamping device including a threaded post and nut threadably engageable therewith and including a resilient washer for engaging and urging the metal body upwardly into full resilient abutment with the lower surface of the bottom wall and a releasable rigid support formation carried by the margins of the bottom wall to embrace and engage the metal body from below to bear upwardly thereagainst over the range of applied temperatures to thereby con

Abstract: A heater element is formed by disposing a pair of heater wires and a pair of thermocouple wires and a powdered mineral material in a metal sheath which is subjected to repeated drawing and annealing operations and is then cut to a desired length after which at one end, the heater wires are welded together and the thermocouple wires are welded to the sheath and the sheath is welded to form a closed end wall. At the opposite end, the heater and thermocouple wires are connected to suitable connection wires. The sheath is formed into a helical coil structure and installed in a runnerless bushing of a plastic molding machine.

Abstract: An elongated wall mounted electric space heater is constructed of an elongated trough-like wall box having junction boxes at both ends thereof, and a single subassembly including a finned straight resistance heater element, a housing surrounding the heater element, the housing being elongated and generally rectangular in cross-section and including a U-shaped front cover section secured at the ends of its U-arms to a rear member supporting the heater element, and thermal cutout means mounted on the rear member of the housing and connected in circuit with the heater element. The housing includes apertured upper and lower generally horizontal walls to facilitate the flow of air between the fins of the heater element. Low resistance conductor loops extend into the respective junction boxes and connect opposite ends of the heater element to opposite ends of the thermal contact means.

Abstract: A percolator is provided with a preassembled partition plate heater assembly wherein a one-piece non-corrosive metal partition plate has a centrally located pump well. An annular heat distribution plate surrounds the well and is fixedly connected to a bottom surface of said plate. A main heater coil surrounds said well and is mechanically coupled to said heat distribution plate. An auxiliary heater coil is radially outwardly from said main heater coil and is mechanically coupled to said heat distribution plate. A thermostat is in direct contact with a bottom surface of said partition plate and is releasably supported by said heat distribution plate.

Abstract: An electric resistance heater engageable with work to be heated including a work-engaging heater structure of minor thermal mass per unit area and including an elongate primary heating element arranged to establish high watt density throughout said heater structure, a power supply, a temperature control means between and connected with the primary heating element and the power supply; said temperature control means including a work engaging body of greater thermal mass per unit area than the heater structure and carried by said heater structure in spaced relationship with the primary heating element, a normally closed thermal responsive switching device within the body and operable to open when the temperature of the body is heated by heat conducted from the work to a predetermined operating temperature, an elongate secondary heating element arranged in the body to delivery sufficient heat into the body to normally maintain the temperature thereof at a temperature slightly below said operating temperature whe

Abstract: A space heater comprises a heater plate made of a metal sheet provided with vertical corrugations, the corrugations in the bottom portion of the sheet being compressed to a flat strip of a thickness not less than three times the thickness of the sheet. The corrugations are so dimensioned that the unfolded length of the metal sheet is three times the length of the corrugated length of the heater body. One, two or more electric flat heating elements are laid along the compressed bottom edge and pressed against it by a U-shaped retaining channel. When serving as a room air-heater, the heater plate is covered on one or both sides by protective panels to prevent people from touching the hot plate and to increase convective air current flow.

Abstract: The heating apparatus for applying heat to the interior of a chamber includes a modular, removable, electrical, heat-producing unit and a heat pipe mountable in a wall of the chamber with one end of the pipe arranged to receive heat from the electrical heat producing unit exterior of the housing and with another end of the pipe constructed and arranged to apply heat to the medium within the chamber. The heat pipe has high conductivity with a low temperature differential between the ends thereof and the heat producing unit includes an electric coil positioned about and removably secured to the one end of the heat pipe. The electric coil is embedded in a high thermal conductivity, low electrical conductivity filler material which is surrounded by a low thermal conductivity insulating jacket and which is received around a metal core member which is removably secured to the one end of the heat pipe.

Abstract: An improved electrical heater using a vacuum surrounding the heating element instead of the usual gaseous or liquid medium for transfer of the heat to external means of dissipation. The heating element, enclosed and sealed in a surrounding encasement which has been evacuated after being sealed, transmits its heat across the vacuum by radiation to the encasement and thence to a series of fins as the means of external dissipation. The heater thereby improves the efficiency of the utilization of the electrical energy used to supply the heat source. The heat dissipating fins are provided with integral spacer lips and are secured on the surrounding encasement by end plates which are formed with downwardly extending portions forming feet on which to stand the heater.

Abstract: An electric heater, particularly adapted for supplying heat to hazardous areas where the atmosphere in the area contains particles or fumes that are readily ignited. The heater includes one or more heat radiating members, each cast about a sheathed electric heating element. The terminal ends of the heating element extend into a sealed explosion-proof terminal box. The heat radiating members are serially disposed in a tubular casing, and a motor-operated fan blows air through the casing and over the members, the air being heated as it flows over the heat radiating members.Each member is in the form of an annular hub having integral, heat-dissipating fins extending radially thereof. The outer surface of the hub is formed with a contour that is angled or curved in the direction of the air flow, and such contour is constructed and arranged to provide a Venturi effect to draw air from the inner portion of the hub to the outer periphery and thus prevent build-up of excessive heat at the inner portion.

Abstract: A plurality of receptacles are provided each having pockets for receiving a bottle containing a shampoo or hair conditioner to be warmed. Each receptacle includes a U-shaped water conduit having a pair of legs extending beyond one side wall thereof. The bight portion of each conduit is closed by a spring loaded flap valve extending parallel to the bight. An opening is provided behind each flap valve which is in line with the legs of the U-shaped conduit. A first receptacle is connected to a pair of openings in a master heating unit containing a thermostat, a heating coil, and a pump for pumping water from a source past the heating coil through one of the openings in the U-shaped conduit of the first receptacle and back to the other side of the pump through the other leg of the U-shaped conduit in the first receptacle, warming the contents of the bottles supported within the first receptacle.

Abstract: A heating device for applying heat to the interior of a closed container containing a liquid therein to be heated includes an elongate cartridge-type electric heating unit and at least one heat pipe having a heat absorbing end and a heat transmitting end. The electric heating unit is attached to the heat absorbing end of each heat pipes and the heating device is secured in an aperture in the wall of the container by means of a mounting flange. The electric heating unit is mounted in an aperture in the mounting flange and the heating unit and at least one heat pipe attached thereto extend into the interior of the chamber to apply heat to the liquid in the container.

Abstract: Radial projections are formed at opposed ends of a double walled hollow cylinder which form a vapor condensation chamber such that the radially outer wall is heated by means of vapors condensing thereon. Heating elements are mounted at the annular compartments and a steel wool packing is carried within each compartment and extends in a continuous annular manner throughout each compartment to distribute vaporizable liquid by the steel wool packing for effective vaporization as a result of energization of the heating elements.

Abstract: Apparatus for defrosting a heat exchanger, comprises a plurality of spaced parallel heat exchanger fins having sets of circular, collared, axially aligned apertures. The collars of each set coacting to define an essentially continuous tube. Refrigerant tubes pass through the essentially continuous tubes defined by a majority of the sets of apertures and are sized for engagement by the collars of the apertures in intimate heat conductive relation. Axially replaceable electrical heating elements traverse the essentially continuous tubes defined by a minority of sets of apertures instead of refrigerant tubes and the heating elements are sized to fit loosely in the apertures so the heat is transmitted from the element to the collars both by radiation and by conduction and so that axial relative movement between the elements and the collars is enabled.

Abstract: Contact heater station mechanism for use in a thermoforming machine for particularly forming thermoplastic synthetic plastic and superplastic metal alloy sheets into shapes, such machines having a sheet transfer station, a heating station, and a forming station with relatively movable mold parts, and providing a circuit for sheet carrying carriages which index individually clamped sheets from one station to another cyclically in a path of travel. The mechanism includes platens mounted on the machine frame at the heating station to move toward and away from the path of travel of the carriages and sheets. A heater carrrier for elongate electrical resistance heaters carries a contactor plate, and is rigidly mounted to each platen in a manner to permit universal thermal expansion of the carrier and plate with respect to the platen.

Abstract: A heat treating appliance coilable about steel piping for heating it before or relieving stresses in it after welding comprises an elongate reticulate sleeve of interlaced heat and oxidation wire having lengths of electrical heating cable each doubled back along itself and fixed inside and along the sleeve so as to form cable legs spaced apart in the sleeve and having terminal portions extending outside it, from respective openings near one end thereof, for connection with a current source. The sleeve has end portions extending beyond the cables therein, and each bent back upon itself into a loop, for securing the appliance in place on the structure to be heat treated.

Abstract: A food serving system for delivering prepared meals to locations remote from the point of preparation, such as to patients in hospitals and nursing homes, which includes a mobile cart having its own low voltage rechargeable power pack that may be utilized to make the cart self powered. The cart has a tier of racks for carrying removable, generally flat, individual, food serving trays. The trays may be disposable or reusable. Each tray is provided with one or more thermally isolated heat transfer devices which may be energized when the tray is placed on a rack in the cart. The trays are constructed to carry conventionally styled, removable dishes, bowls, cups, etc., that may be either disposable or reusable, and the dishes and bowls containing foods to be maintained at a reduced or elevated temperature are placed on the heat transfer devices.

Abstract: Improved heat transfer is obtained between a solid and a fluid by using polycrystalline metal whiskers attached to the solid member which comes in contact with the fluid.

Abstract: During the construction of display gas panels front and back panels are connected together by means of a seal which forms a chamber for receiving a display gas. A hole is provided in the back plate which is outside the display viewing area and a glass tube is fitted into this hole and sealed to the assembly. The tube is used to first evacuate and then admit display gas into the chamber. An electric tip-off oven is used to collapse the tube stem to form a permanent seal. A cast protective heat sink and a reflective foil wafer are used to protect the gas panel and the tube-to-gas panel interface from damage by the oven.

Abstract: The apparatus comprises a turntable carrying, in a circular array centered on a central rotational axis of the turntable, a plurality of vials extending below the underside of the turntable. A stepper motor imparts stepwise rotational motion to the turntable so that during dwell periods of the turntable, specimens in the vials can be investigated optically.Air in a space below the turntable and bounded laterally and at the bottom by an enclosure is circulated by a rotating vane, and a thermistor, responsive to the temperature in the region of the vials, controls a heater in the space below the turntable so as to maintain the temperature of the vials substantially at a predetermined value.

Abstract: A room air heater which includes a vertically disposed tubular housing or casing mounted on a mobile supporting structure for ease of movement to a desired location and including a heat exchange coiled tube communicating with a tank having an electric resistance heating element disposed therein. The tank and heating coil are filled with a heat exchange medium in the form of compressed air which circulates through the coil and tank due to the heat imparted to the air by the heating element. A circulating fan is provided in the upper end of the housing for forcing room air downwardly therein in heat exchange relation to the coil with the housing having openings at the bottom thereof for discharge of heated air. Manually adjustable thermostatic controls and a pressure gauge are provided for enabling safe operation of the heater.

Abstract: The underside of the bottom wall of an electric cooker contains a sheathed electric heater element intermittently staked and keyed to the sides and base of a receiving channel to control and confine growth and resist twisting movement of the element therein during heating.

Abstract: A golf ball warmer adapted to warm and store at the desired temperature the golf balls and a heat retaining carrying case for the warmed balls.

Abstract: Apparatus for controlling the surface temperature of a fusing roller of the type having a heat-insulative, release surface over a thermally conductive core, by (1) internally heating the core, (2) sensing the temperature of the core rather than of the external release surface, (3) providing different temperature control settings for the core sensor and (4) selectively switching the internal heating means into operative relation with a predetermined control setting in anticipation of changes in heat loss from the external surface. The core of the fusing roll is thereby controlled toward the different temperature control settings, one at the "copy run" condition, another at the "idle" condition, and in some instances the same control setting is used for the "copy run" and the "idle" condition.

Abstract: An electric hotplate with a thermostat includes a heating plate which is joined to the surrounding cold zones by means of a bridge of relatively thin sheet metal. The actuating device for a thermostatic switch is operated by the vertical movement of the heating plate. This movement arises as a consequence of the horizontal expansions and contractions of the heating plate due to changes in temperature, such movements being converted, by means of the bridge, which acts as a hinge, to vertical movements.

Abstract: A protective for a stove plate of an electric range comprises a heat-resistant aluminum foil into which bulges have been embossed corresponding to the heating units. The embossing is carried out by hand by laying a piece of foil on the stove plate and pressing the foil on and around the heating units. Stripes of a temperature-indicating salt, such as NH.sub.4 MnP.sub.2 O.sub.7, which change color at a predetermined temperature are preferably applied to the foil to give visual indication of over-heating.

Abstract: The apparatus comprises a turntable carrying, in a circular array centered on a central rotational axis of the turntable, a plurality of vials extending below the underside of the turntable. A stepper motor imparts stepwise rotational motion to the turntable so that during dwell periods of the turntable, specimens in the vials can be investigated optically.Air in a space below the turntable and bounded laterally and at the bottom by an enclosure is circulated by a rotating vane, and a thermistor, responsive to the temperature in the region of the vials, controls a heater in the space below the turntable so as to maintain the temperature of the vials at a predetermined value.

Abstract: A glass or ceramic cooking vessel of the type commonly employed in slow cookers is provided with heating apparatus for heating the vessel in a substantially uniform manner. An electric heating element is supported in a position spaced from the vessel such that direct conduction of heat to the vessel is prevented, heat transfer means being provided to conduct heat from the heating element to the vessel over an extended portion of the vessel's outer surface.

Abstract: A cartridge heater and multiple thermocouple assembly comprising an elongate outer heavy walled structurally supportive metal sheath, an elongate thin walled, yieldable, orienting metal tube extending through the sheath and defining an annulus, a plurality of axially aligned pairs of thermocouple cables and spacer rods fixed to the tube in circumferential spaced parallel relationship and extending through the annulus in interfering engagement with the sheath, a resistance element extending through the tube, conductor terminals for the element accessible at one end of the tube and a filler of particulate dielectric material compacted in the tube about the element and in the annulus between the sheath, tube and adjacent pairs of cables and rods, said cables being of different lengths and having outer ends with conductors accessible at an end of the annulus and having inner ends with thermocouple junctions located at spaced points longitudinally of the sheath.

Abstract: A heating system including a heat pipe containing evaporable heat transporting material, a closed reservoir containing heat-accumulating material within said heat pipe, and a quantity of said evaporable material in said reservoir for maintaining the same pressure in said reservoir and in said heat pipe.

Abstract: Device for grilling and broiling food comprising an electrically heated lower plate member adjacent to one end of which is provided an upstanding turret element on which an upper plate member, also electrically heated, is pivotally and adjustably supported so as to perform the cooking operation without, as a consequence exerting any pressure on the food product. Further modified embodiments disclosed herein reveal various concepts for supporting the upper plate member in an adjustable manner.

Abstract: A yarn heater has an elongate, hollow metal yarn heating member with a substantially constant internal cross-section, an electric yarn heating element mounted externally of the heating member and a baffle located internally inside of the heating member extending longitudinally therein and dividing the inside space into two passageways. The heating member is filled with a heating fluid which when heated by the heating element consists of a liquid phase and a vapor phase. Located at the lower end of the baffle is an aperture for permitting automatic circulation of the heating fluid. A yarn heating surface located at the front of the heating member and extending along the length thereof is formed with a pair of longitudinal grooves for guiding the yarn.

Abstract: A hot well, especially for food, and a method of heating the well in which an electric heating element is supported beneath the bottom of the well while a heat sink in the form of a U-shaped member formed of a highly heat conductive metal, such as aluminum, is fitted over the well from below. The U-shaped member has a bottom part beneath the heating element and side parts which are parallel to and in intimate heat exchange relation with the sides of the well. Energization of the heating element directly heats the bottom of the well, principally by radiation directly from the heater and by radiation reflected from the bottom part of the U-shaped member. The bottom part of the U-shaped member also absorbs heat from the heating element and, by conduction upwardly along the side parts of the U-shaped member, heat is also supplied to the sides of the well.

Abstract: An improved heating device such as a heating pad comprising a fabric base and insulated resistance wire mounted in said pad, preferably in a backward and forward sinuous pattern, at least one thermostat connected in series with the resistance wire element at both ends by means of lead wires of a low resistance metal such as copper, each thermostat being positioned intimately with a span or straight portion forming part of a sinuous loop of resistance wire, a switch connected in series with the resistance wire, and a plurality of bars of a metal such as lead mounted in the pad. In an improved embodiment the insulation on the resistance wire is formed of a plastic material able to withstand the elevated temperatures attained by the resistance wire during operation.

Abstract: The apparatus comprises a turntable carrying, in a circular array centered n a central rotational axis of the turntable, a plurality of vials extending below the underside of the turntable. A stepper motor imparts stepwise rotational motion to the turntable so that during dwell periods of the turntable, specimens in the vials can be investigated optically.Air in a space below the turntable and bounded laterally and at the bottom by an enclosure is circulated by a rotating vane, and a thermistor, responsive to the temperature in the region of the vials, controls a heater in the space below the turntable so as to maintain the temperature of the vials substantially at a predetermined value.