Abstract: An otterboard and a method of manufacturing an otterboard are disclosed wherein the otterboard is comprised of a plate member, a shoe member and a sole plate. The shoe member is formed of a tough wear resistant material and attached to a bottom side of the plate member. The sole plate is made of a hardenable steel and has a bottom side with grooves formed therein for receiving inserts of a hard wear resistant material. The method of manufacturing the otterboard includes the step of electro-discharge machining the shoe member so that the sole plate may be connected to the shoe member.

Abstract: An automatic hooksetting fishing rod holder including a mounting member formed of a strap including a stake section; a pivot carried by the mounting member; a holder arm member pivotably connected to the pivot and including a forward portion extending on one side of the mounting member for engaging a fishing rod handle; a spring interconnected between the mounting member and the holder arm member to urge the forward portion of the holder arm upwardly; and a latch including a pawl pivotably attached to one of the members and a pawl engaging seat on the other of the members for restraining upward motion of the forward portion of the holder arm member until a downward force on the forward portion disengages the pawl and seat.

Abstract: A play set comprising a three-dimensional doll figure and a variety of flexible, resilient clip-on pieces representing clothing for the doll to wear, vehicles and animals for the doll to ride in and/or on, etc. The doll has an original appearance, i.e. original clothes, pose, etc. The clip-on pieces may cover over portions of the original appearance and replace them in addition to adding to them. For example, original arm positions and a shirt may be replaced by different arm positions and a coat. Similarly, legs of a standing figure may be replaced by a motorcycle and legs positioned astride the motorcycle. In preferred form, the figure is bias-relief, having a flat rear surface defining a peripheral shoulder and the clip-on pieces each conform generally to the front of the bias-relief figure and have retaining lips that engage the peripheral shoulder.

Abstract: An improved method of applying a chemical treatment agent to a wood structure characterized by the conventional steps of forming a hole in a wood object, and inserting a container enclosing the treatment agent into the hole. The improvement comprises sealing the container with a suitable closure means fabricated out of a material which undergoes an interaction with the chemical treatment agent or its vapors. When the sealed container carrying the chemical treatment agent is inserted within the prepared hole, and when the hole is thereafter plugged such that the sealed container is substantially confined within the wood structure, the treatment agent and/or its vapors degrade or dissolve the closure means thereby providing an opening through which the chemical agent and its vapors are released into the internal structure of the wood object.

Abstract: To provide water to a plant in a standard pot, a removable, preassembled plastic separator disc fits within the walls of the pot near its bottom to form a soil compartment above it for the roots of the plant and a water reservoir beneath it. Water is supplied to the soil for the plant by a porous plug that extends through the center of the plastic divider into the water compartment below it. Water is added to the water compartment through a first plastic tube and air is displaced through a second plastic tube both of which extend through the disc and soil. The separator disc is preassembled into a kit with porous plug and tubes to fit standard tapered pots.

Abstract: A garage door operation control apparatus comprises a disc rotatable in interlocked relation with a door driving system, which disc actuates an upper limit switch and a lower limit switch at the door upper and lower limit positions respectively. The interlocked relation of the driving system and the disc may be cancelled thereby to adjust the responsive position of the limit switches.

Abstract: A door edge and hinge guard in the form of a U-shaped member is secured to a door frame longitudinally thereof to protect the edge of an open door and its hinge therein by resiliently deflecting objects such as shopping carts and the like away from contact with the edge of the door and the hinge.

Abstract: A metal door or window frame comprises mobile and fixed frameworks each formed by a sub-frame including a substantially tubular section effective to be positioned on the side thereof facing the room interior and a cover section effective to be positioned on the side thereof facing outwards, between the sub-frames and the cover sections insulating material elements being provided for defining an uninterrupted heat insulating barrier therebetween.

Abstract: A sash adapted to be received in an opening in a window or the like having channels constituting tracks for the sash at opposite sides of the opening. The sash comprises a pair of side members, a pair of cross members, and fasteners for securing the side and cross members together at corner joints of the sash. The fasteners at the ends of a cross member comprise a pair of screws each having a threaded shank and a head. The shank of each screw extends through a hole in one of the side members and is received in threaded engagement in an opening in the end of the cross member. The head of each screw projects out from the respective side member, has an inner face in engagement with the side member and is adapted to be received in one of the tracks in sliding engagement for enabling sliding movement of the sash in the tracks.

Abstract: A replacement door which accommodates a wide variety of existing hinge spacings on a door jamb. The door includes a frame with at least one continuous hinge channel member. The channel member includes a plurality of offset sections spaced along its length. The offset sections are substantially longer than the length of commonly used hinges to thereby span the range of normally encountered hinge locations. Front and rear skins are connected to the frame with the edges of the skins being supported by the major surface of the hinge channel. Segments of the skins in an alignment with existing hinge locations may be removed to expose selected portions of the offset sections for flush mounting of the hinges. The elongated offset sections permit the use of the door structure as a common replacement for doors having a wide variety of hinge spacings.

Abstract: Window structure including a thermal break window frame and a sash coupler for selectively coupling movable window sash in inner and outer windows for movement together. The window frame includes an inner and outer frame portion and an insulating member which are constructed and arranged so that the insulating member is positioned between the inner and outer window frame portions with surface to surface contact therewith over a substantial area extending transversely of the plane of the window structure. The insulating member may be snapped, staked or crimped into assembly with the inner and outer frame portions and rigidly secures the inner and outer window frame portions together. The thickness of the insulating member may vary and it may be solid or hollow in accordance with rigidity and insulating requirements. The sash coupler is secured to a movable sash of the inner window and is formed to selectively engage a projection on a movable sash on the outer window.

Abstract: A device for mounting a door in a door opening defined by at least one wall dge, e.g. for a desk, cabinet or building structure, comprises a door frame member in the form of a U-profile which straddles this edge and is affixed thereto. According to the invention, on the edge turned toward the opening, the wall is provided with a mounting element having a rib projecting in the direction of the opening which is clamped against a retaining profile received within the frame member by the movement of a wedge by a screw which is inserted through a hole in the frame member and has its head located within a rabbet for the door set into the frame member. The retainer also has a flange which cooperates with a clamping member actuated by another screw located at the rabbet to engage a shank of a hinge pin or like element.

Abstract: The pin holder has at least one vertical projection which fits in mating relationship against the flat front faces of the lateral lugs of the rocker arm. Shims are inserted between the projection and the lateral lugs. Fastening means extending through said projection into said lugs in a direction perpendicular to the axis defined by the pins held by the pin holder, maintains the alignment of said pins in the horizontal plane which includes the axis of oscillation of the polishing lap.

Abstract: The invention provides a novel and efficient apparatus for shaping wafer materials of exact dimensions from a single crystal rod. Different from the conventional procedure, the single crystal rod is first ground to have a cross section larger than the desired wafer by a margin to grind and then sliced into margined wafers and the margined wafer is subjected to contour grinding tracing a prototype of the desired wafer. The invention also provides an apparatus for the above process, with which the margined wafer can be not only ground to the exact diameter and outer shape but also chamfered at the peripheral edges successively by a single mounting on the apparatus.

Abstract: An improved skylight having high structural strength and improved insulation capabilities. A sheet of polycarbonate plastic is formed into an outer dome having an extended flange around the perimeter of the dome. The extended flange has first and second steps formed therein adjacent to the perimeter of the dome. A second dome having its narrow flange around its perimeter forms a middle dome having its narrow flange fitting into the first of the steps in the flange of the outer dome and having its dome spaced a short distance from the outer dome to provide a narrow dead air space having good insulation properties. A third dome having a narrow flange around its perimeter forms an inner dome in which its flange will overlap the flange of the middle dome and fit into the second step in the outer dome flange and having the inner dome spaced a short distance from the middle dome providing a second insulating dead air space to minimize heat flow through the three domes.

Abstract: A building construction comprising spaced parallel structural members, such as rolled steel beams and girders, forming a plurality of horizontally disposed structural bays in which the compression flanges of the girders are restrained against lateral displacement or buckling under compressive loads by concrete joists having notched end portions, especially during construction and prior to hardening of concrete poured thereover to form floor slabs. The joists are supported by, and extend transversely between, the girders. Adjacent end portions of the joists are connected to each other to form continuous lines of tension or compression ties at selected intervals along the girders. In a preferred embodiment, the continuous ties terminate at horizontal trusses formed at the end of a row of bays by at least one diagonally disposed truss member, such as a cable.

Abstract: A wood log of substantial thickness and having flat top and bottom surfaces interrupted by complementary tongues and grooves along the length thereof. One or more slots open from at least one of the surfaces with the total slot depth extending over all but a small portion of the top to bottom thickness of the log. The slots are filled with an insulating material.

Abstract: Cryogenic insulation seal for a concrete container, having an inner cryogenic liquid tank, comprising a concrete floor slab, a vertical concrete wall moveably supported on the concrete floor, and insulation positioned within the container adjacent the horizontal floor slab and the vertical concrete wall, and including a metal, e.g. steel, liner positioned around the inner surface of the container, adjacent the inner surfaces of the floor slab and the concrete wall and supporting the insulation, and forming an inner seal around the container. The steel liner is inclined from the vertical at a corner above the floor slab and is attached to the vertical concrete wall at a predetermined height above the floor slab, forming a gap between the liner and the concrete vertical wall at the corner, and permitting inward lateral motion of said vertical wall with respect to the floor slab at such corner, while permitting the steel liner and the insulation supported by the liner to flex and maintain a seal at the corner.

Abstract: This invention relates to energy conserving structural elements, commonly called window or door frames with outer framing being adapted to be installed in building wall rough openings, said framing has a strip of compressible expandable thermal insulation fastened in a recess in said framing and an enveloping means maintains said thermal insulation in a compressed state until said structural element is installed in said building wall, said enveloping means is of tearable material that can be rendered inoperative allowing said thermal insulation to expand and fill said air gap, reducing heat transfer either direction through said air gap.This invention relates to all objects constructed to be inserted into other objects creating an air gap that should be sealed and thermally insulated.

Abstract: A collapsible structure comprises a separating structure of poor wet strength sandwiched between two sheets of material, at least one of which is of such a nature as to allow the passage of moisture. The invention also includes a method of building using such a structure.

Abstract: An apparatus and method for joining panel members into walls or dividers is provided which allow thermal expansion of the panel members to be absorbed by the joints. The panel construction includes turned down edges having grooves on the inside faces of the edges. Each edge is sized to fit side-by-side in a channel with the edge of an adjoining panel and with their grooves over ridges on the inner walls of the sides of the channel. An insert member having protrusions on its sides is wedged between the side-by-side edges for maintaining the grooves over the ridges while allowing pivotal movement of the edges around the ridges.

Abstract: Apparatus for slitting an elongated bag enclosing an article. The apparatus includes a bag support and a mechanism for engaging a portion of the bag wall adjacent the middle of the bag and pulling the engaged wall portion in a direction transverse to the axis of the bag so that the engaged wall portion extends in such transverse direction away from the article enclosed in the bag. The apparatus includes a pair of blades and mechanism for forcing the blades through the wall of the bag between the engaged wall portion and the article to puncture the bag. The blade movement mechanism is arranged to move the blades in opposite directions towards the end of the bag after the blades have so punctured the bag wall to slit the wall of the bag longitudinally.

Abstract: Pouching apparatus for increasing the volume of material packed into a pouch. The apparatus includes a filler wheel assembly, means for rotating said assembly, a vacuum transfer wheel mounted below said filler wheel assembly and rotatable therewith, a plurality of vertical lands circumferentially spaced around said transfer wheel to receive a web of pouches, means for applying vacuum to said lands, a plurality of tuck fingers movably mounted on the transfer wheel between said lands, a stationary, circumferential cam mounted adjacent said transfer wheel to raise said tuck fingers to form an upward tuck in the bottom of each pouch of said web thereby increasing its capacity. The apparatus also includes clips to hold the web on the lands of the transfer wheel. The apparatus also includes a feed roll which feeds said web onto said transfer wheel at a preselected speed somewhat greater than the speed of said transfer wheel to force pouches into the space between said lands.

Abstract: There is provided an apparatus and method of packaging commodities in a flexible wrapper. The apparatus includes first and second stations with a wrapper engaging assembly moving between the first and second stations, wrapper cutting and sealing means which severs a bag length from a continuous roll of flexible material, a component for opening the open leading end of the wrapper at the second station, a funnel which is preferably expandable and which engages the open mouth of the wrapper so as to permit loading of the commodity into the wrapper, and a further assembly which seals the open mouth of the bag length, preferably under vacuum, by having a component preferably in the form of a pair of fingers which engages the mouth of the bag to place it under tension whereafter a sealing assembly seals the mouth of the bag to form an improved weld across the mouth of the bag.

Abstract: A head assembly for a cotton harvesting machine which provides many combinations of row widths and various row harvesting capacities. The head assembly includes a main cross auger frame with row unit support structure which slidably receives a plurality of vertically adjustable row units. The support structure permits simultaneous transverse adjustment of each individual row unit and its associated hydraulic lift cylinder. An extension frame is provided for adding extra row units for increased capacity or accommodating widely spaced rows of cotton. Row units and lift cylinders are freely slidable between the main frame and the extension, and the extension is removable to lessen machine width during transport. The main cross auger frame includes a pair of transversely spaced bearings which journal opposite ends of a main cross auger. An auger extension is attached to a shaft which extends through the extension end bearing to eliminate need for relocating the bearing or providing a telescoping auger.

Abstract: A cotton module builder comprising an open-top frame. At the rear end of the frame is a rear door mounted for pivotal movement. When seed cotton has been compressed into a module, it is removed from the open-top frame, while the rear door is opened. While the seed cotton is being compressed by the cotton module builder, the rear door is closed. Secured to the rear end of the frame is a cradle that supports extractor apparatus for removing foreign matter from seed cotton before the seed cotton is deposited into the open-top frame for compression. Pivotally supported by the cradle is a basket and lifting conveyor. Means are provided for raising and lowering the basket and lifting conveyor. Before the rear door of the module builder is opened for the removal of a cotton module from the open-top frame, the basket and the lifting conveyor are raised out of the path of movement of the rear door and the compressed cotton module advancing therethrough.

Abstract: A turf scarifier and raker includes a housing with an elongated upright handle and having suitably positioned wheels designed to permit traversing movements over turf while the operator is in a standing position. The housing has an electric motor positioned in essentially the same plane as a tine assembly driven by the electric motor. The tine assembly has a plurality of tines which extend through an opening at the bottom of the housing. The tines result from a plurality of torsion coil springs having radially extending active ends that are serially threaded on rods arcuately and radially located about a central axle of the tine assembly. The active ends come into contact with the turf when the device is operated. At the same time, the other ends of the springs are inhibited from turning torque, preferably by lying in abutment against the central axle.

Abstract: A grass collection bag which can be removably supported on a lawn mower comprises a main body portion having a first access opening which can be connected to the grass discharge outlet of the lawn mower and a second access opening which serves as an outlet through which accumulated grass clippings can be dumped from the bag. Foldable first and second end panels are joined along one edge to each other and attached to the main body portion of the bag adjacent to the second access opening. A cord member is connected to each of the end panels. The cord members are joined to effect simultaneous folding of each end panel upon itself and back along the main body portion of the bag to bring the junction of the end panels into a position overlying and closing the second access opening.

Abstract: Mushroom harvesting machine provided with rotary knives which are positioned in stepped formation sequentially one below the other and with an upright conveyor belt provided with carriers and wherein the rotary knives are positioned at an angle of inclination .alpha..

Abstract: A grain pickup for use with combines in harvesting windrowed crops is formed of a cylinder with a plurality of cylindrical, interlocking tooth modules located thereon, each of the modules having a plurality of pickup teeth extending radially outwardly therefrom.

Abstract: Method for connecting an upper thread to a lower thread, which includes inserting the threads into a longitudinal groove formed in a chamber for connecting the threads with a thread feeder being movable from a thread receiving position to a thread delivery position, splicing the threads together in the chamber using compressed air acting on the threads from the side, securely holding the threads up to the application of the compressed air when the threads are inserted into the chamber uncrossed, and securely holding the threads which are inserted into the chamber during the splicing in the immediate vicinity of the chamber when the threads are crossed during movement of the thread feeder, and a device for carrying out the method.

Abstract: A wire rope formed of a plurality of strands of wire rope elements wound around a core, and incorporating a lubricant which comprises a microporous polymeric lubricating medium.

Abstract: An improved hollow string comprising a hollow core containing gelatinous oil and a wrapping thread, which is used for rackets for ball games, such as tennis, squash, badminton, etc., and into the hollow cavity of which there is charged gelatinous oil of high viscosity which is in a state of gel at normal temperature and has a melting point of 30.degree. C. or higher and fluidity at a temperature of 50.degree. C. or higher.

Abstract: A combustor of a gas turbine including fuel distributing and supplying means including a plurality of sets of fuel nozzles arranged circularly on the head of the combustor and each fuel nozzle being provided with a combustion primary air swirler, and a plurality of fuel supply systems each connected to one fuel nozzle or a plurality of fuel nozzles. One set of fuel nozzles is located inside another set of fuel nozzles and projects further inwardly into the interior of the combustor. The number of the fuel supply systems handling a supply of fuel can be increased or reduced depending on the volume of fuel.

Abstract: A fuel control having an electrically operated metering valve and a manually operated metering valve through which fuel is independently scheduled to an engine. During normal operation, the electrically operated metering valve controls the flow of fuel to the engine in response to an operator input signal. However, should an electrical failure occur, the manually operated metering valve is activated to schedule fuel to the engine. The manually operated metering valve has a pressure responsive member that receives an input signal representative of the discharge pressure of a compressor in the engine to prevent surging during acceleration.

Abstract: A fan engine having a core engine and a fan duct has bleed ports positioned circumferentially around the compressor housing of the core engine to bleed flow into the fan duct. A strap covers the circumferential line of holes and it is moved between an open and closed position by a U-shaped flexure element which biases the bleed port seal strap to an open position while an actuator moves the seal strap to a position to close the bleed ports. The ends of said U-shaped flexure elements are connected to the ends of the seal strap and are connected to links which insure that the ends of the strap are moved in a predetermined path.

Abstract: An auxiliary steering flow control device having known features of a rotatable steering spindle which initially effects axial shift of a valve sleeve through a torsional stressing device acting on a pair of compressibly arched leaf springs longitudinally disposed on the axis of the steering spindle and carried in a holder within the steering spindle. The leaf springs have contiguous contacting arched surfaces on the steering spindle axis and the arched configuration effects a back to back pretensing that augments the potential energy that can be stored in the springs, particularly in arched surface contiguity with each other.

Abstract: A control valve for a hydraulic booster steering system provides gradual control of inlet flow to the system pump to complete cut off of output, or by throttling of inlet flow to effect a pilot stream through the pressure pump. This occurs in the neutral position of the control valve during straight ahead steering. Where flow through the pump intake feed means is thus impeded, the pump simply cavitates in a known manner and to be of a type which is suction regulated, having a check valve means at the pressure outlet side. The advantage of cutting off inlet flow to the pump during straight ahead steering, or at least throttling of such inlet flow by a constantly open throttle passage, is to save energy otherwise wasted in heating the fluid.

Abstract: A signal bleed-down valve in a load responsive system which is positioned in the sensing line between the pump compensator and control valve. The valve in the absence of sufficient pilot pressure opens the pump compensator to drain. Otherwise, the valve is controlled by pilot flow across a fixed orifice in the spool which creates a pressure drop acting against a spring, and moves the valve spool to a position metering the pilot flow so as to maintain a constant flow level across the valve spool regardless of the pressure level.

Abstract: An energy convertor machine generally includes an elongated member and at least two sets of one or more elastomeric bag members, each elastomeric bag member having a liquid with a low vaporization temperature disposed therein, wherein heating means and a cooling means are provided, wherein one set of elastomeric bag members is being heated while the other set is being cooled thereby causing one set of elastomeric bag members to be expanded while the other set of elastomeric bag members are contracting. A means for rotating the elongated member is provided, wherein the rotating means is activated by the alternate expansion and contraction of the two sets of elastomeric bag members.

Abstract: A hydraulic circuit (32), for example, remotely controls a work element (14) and contains first apparatus (34), such as a master cylinder (42), which passes a fluid pressure signal through a fluid pathway (38, 40) in response to an input signal. Second apparatus (36), such as a slave cylinder (44), correspondingly delivers an output signal for controlling the work element (14). Temperature variation can cause fluid volume changes which disrupt synchronized operation of the master and slave cylinders (42, 44). Third apparatus (74) positions the fluid pathways (38, 40) in fluid communication with a tank (28) in the absence of the fluid signal. If the signal passes through one pathway (38, 40), that pathway (38, 40) is automatically blocked from communication with the tank (28). Thus, when the fluid signal is absent from the fluid pathways (38, 40), volume compensation occurs because of dilution of the fluid in the circuit (32) with the tank fluid.

Abstract: An internal combustion engine in which a rotor or turbine is driven by the exhaust gases of a pair of interconnected double-acting pistons. The double-acting pistons are interconnected by a pinion gear and are internally constructed to have an inner piston slidably reciprocating within a chamber defined within an outer piston. The purpose of the inner piston is to feed additional fuel into the main combustion chamber in a controlled manner. Exhaust gases are collected and washed before being exhausted to the atmosphere or recycled within the engine.

Abstract: A two-stage exhaust-driven supercharger aggregate is disclosed which comprises a low-pressure supercharger and a high-pressure supercharger. Each of the two superchargers is provided with a compressor driven by a respective turbine. Each of these superchargers is arranged on a separate shaft. In order to provide sufficient space for auxiliary components such as supercharger-air coolers, a bypass system and the like, and to obtain one compact structural unit, the pressure ratio of the low-pressure compressor is made greater than the pressure ratio of the high-pressure compressor by at least 40%. In this way, the geometrical exterior dimensions of the high-pressure supercharger becomes substantially smaller than the dimensions of the low-pressure supercharger. The shaft of the high-pressure supercharger is arranged such that it is parallel to, and offset laterally relative to the shaft of the low-pressure supercharger.

Abstract: An improvement is provided in a process and apparatus for in-line slush making, for use in, for example, concrete cooling. The improvement comprises connecting the inlet used to convey liquid such as water to the manifold section of the lance so that its longitudinal axis forms an acute angle with respect to the longitudinal axis of the inlet for introducing a cryogen into the lance. This improvement substantially eliminates failure to properly make slush due to a build-up of ice within the means used to control the flow of cryogen to the system. Additional improvements to the apparatus comprise substantially aligning the sealed head of the manifold with the longitudinal axis of the inlet for conveying the liquid to the lance to eliminate and to prevent freeze-up of the liquid in the dead space found in the "T" lance design of the prior art.

Abstract: A cabinet cooler or freezer which efficiently utilizes cryogenic refrigeration either with or without mechanical refrigeration. The freezer intermittently freezes relatively large batches of food by efficiently utilizing the natural expansion effect of a liquid cryogen, in combination with mechanical circulation by blowers, to create an overall circulation that efficiently removes heat from the food. A secondary circulation effect is induced, in a manner similar to the operation of a jet pump, which amplifies the circulation and allows CO.sub.2 to be employed with modulating valve control to achieve uniformly low temperature throughout the cabinet without snow build-up on the cabinet bottom. Some cabinet versions create a cyclonic circulation pattern about a vertical axis that is particularly effective.

Abstract: A building is heated by means of a heat pump operated with a mixture of at least two working fluids, the proportion of the minor constituent being from 0.5 to 20% by mole and the difference between the critical temperatures of the two fluids being at least 20.degree. C. Heat is received from a fluid at a temperature between 0.degree. and 20.degree. C.

Abstract: An apparatus responsive to the amount of refrigerant flow in a refrigerant circulating system includes a sensing capacitor mounted in a refrigerant passage, the capacitance of the sensing capacitor being varied depending on a change in the dielectric constant of the refrigerant which in turn being dependent on the amount of the refrigerant. The sensing capacitor forms an element of a resistance-capacitance oscillatory circuit and it also forms a ring oscillator together with another capacitor and a plurality of inverters and resistors. The oscillation frequency of the ring oscillator is detected to determine the amount of the refrigerant flowing through the refrigerant passage.

Abstract: A demand defrost control system having a timing circuit operable after a duration of time to energize a defrost heater including temperature responsive means for automatically altering the duration of time between defrost cycles.

Abstract: A refrigeration apparatus having an ice making mechanism and structure for operating the mechanism to deliver ice therefrom at timed intervals. The apparatus includes means for defrosting the apparatus. Further structure is provided for causing the length of the timed ice making intervals to be increased to include the amount of time required to effect the defrosting of the apparatus plus a preselected amount of time. In the illustrated embodiment, a timer, including a timer motor, is provided for controlling operation of the ice making mechanism. An electrical circuit is provided for electrically interconnecting components of the apparatus whereby the timer motor is energized concurrently with the operation of the compressor of the refrigeration apparatus and is de-energized concurrently with the operation of the defrost heater of the apparatus.

Abstract: A two-stage refrigeration system including a primary cooling circuit which may be of the mechanical, vapor-compression type and a secondary closed system which is limited to an evaporator, located in the product storage area, a condenser and the necessary interconnecting conduits. The two circuits are operatively linked by a heat exchanger located outside the product storage area. The heat exchanger serves as the evaporator of the primary, caustic refrigerant system, and as the condenser of the secondary, relatively safe, volatile refrigerant system. Means are provided to prevent the refrigerant of the primary circuit from entering the secondary circuit in the event of heat exchange leakage. The heat exchanger design as well as the primary circuit control permits a rapid response to changes in temperature in the product storage area without requirement of controls on the secondary side of the system.