Abstract: A channel culture device for agricultural is disclosed. A plurality of elongated reservoir channels are provided adjacent growing channels. The reservoir channels which may be above or within the soil, provide metered amounts of water and nutrients to the growing channels through their walls. An exterior channel is provided which forms the perimeter of a soil bed. The exterior channel includes an inner flexible wall which absorbs the lateral pressure of the soil bed acting on it to prevent buckling of the exterior channel.

Abstract: There is disclosed a motion control and locking apparatus for the passenger entry and exit doors of a mass transit vehicle, which passenger entry and exit doors are desired to be locked when the vehicle is moving between stations and are desired to be unlocked only when the vehicle has stopped at the desired location for passenger entry and exit within a station.

Abstract: What follows is a description of a three track mechanism assembly for a vehicle door, and in particular for a light rail vehicle door. Each track mechanism includes a guide rail for guiding the door in its opening and closing movement relative to the vehicle body. Two of the track mechanisms include actuators for producing the opening and closing movement of the door. One of these actuators produces the desired longitudinal displacement of the door relative to the vehicle body, while the other actuator produces the desired transverse displacement of the door relative to the vehicle body. In addition, an extraction device can be included with the track mechanism having the actuator producing the desired longitudinal displacement for assisting the other actuator in producing the desired transverse displacement of the door relative to the vehicle body.

Abstract: A safety roller assembly in a plug door for a railway car is disclosed which includes a safety roller traveling in a retaining guide with a recess being formed in the lower support surface of the retaining guide to receive a safety crank connected to the safety roller when the plug door is closed. A safety shoe is provided beneath the safety roller to prevent it from ever falling through the recess in the lower support surface.

Abstract: A catch basin grate and receiving frame locking assembly is installed on a catch basin grate and interfitted with a receiving frame, in turn imbedded in a pavement, thereby preventing the removal of the catch basin grate only by a designated workman having a special pivotal lever tool. On one side of the catch basin grate a depending structure is either made integrally with the grate or bolted to it, and it supports a horizontal projecting portion which interfits with the receiving frame. On the opposite side of the catch basin grate, two depending structures are either made integrally with the grate or bolted to it and they support a horizontal movable locking member.

Abstract: A thread grinding machine comprising a headstock movable to-and-fro upon a machine frame. This to-and-fro movement is generated by a threaded rod driven by a spindle and transmission means and a rod member pivotably mounted at one end in a fixed adjustment arm of the headstock and at the other end guided to be axially and pivotably movable at the threaded rod. The rod member is also guided to be axially displaceable in a guide element pivotably mounted in a bearing block adjustably connected with the machine frame. A control device reverses the direction of rotation of the driven spindle.

Abstract: A blade sharpening or grinding device comprises an abrasive surface for acting on a blade edge, a second surface to receive a flat face of the blade to define the angle of the edge ground onto the blade, and a third surface to be abutted by the blade edge to limit the extent to which the blade is advanced into the abrasive surface. The second surface may be adjustable to vary the grinding angle and the second surface and/or the third surface may be adjustable to control the extent to which grinding takes place. Preferably the abrasive surface is provided on a belt driven over two pulleys by an electric motor.

Abstract: A drill grinding fixture for drills of between about 1/16 to 1/2 inch diameter, including an inclined trough member for receiving the drill to project from the forward end of the trough member toward the vertical face of a grinding wheel. The trough member is rotatable on a vertical pin of which the axis is offset 1/8 inch to the left of the bottom of the V-shaped trough, the pin being located between about 1/2 and 3/4 of an inch in front of the wheel face. The trough member is provided with a recess to receive a drill holder which is rockable about the axis of the drill to present one and the other cutting lip of the drill for grinding.

Abstract: A generating method and apparatus for grinding cylindrical gears by means of two substantially plate-shaped or dished grinding wheels which machine a right tooth flank and a left tooth flank by means of practically point-shaped contact zones disposed at their related lateral edge. Between the gear and both grinding wheels there is accomplishd a to-and-fro generating motion in relation to the base circle or cylinder of the gear. The connection line between the contact zones of the grinding wheels is maintained at such a spacing from the base circle that in each end or terminal position of the generating motion one grinding wheel machines a tooth tip and at the same time the other grinding wheel machines a tooth root.

Abstract: A scouring and cleaning cloth having a coating of a solid binding agent on at least a portion of each surface in an open pattern applied by a printing process, said pattern comprising superelevated bars, the bars in at least one surface having embedded therein at least one of an abrasive and a soap additive.

Abstract: A building construction comprising a self-supporting skeletal frame formed of light gauge metal structural members of a generally channel configuration which are used singly or welded back-to-back to form H assemblies for particular applications such as for intermediate wall studs, roof rafters and roof purlins. Corner wall studs are formed of a pair of welded back-to-back channels with a third channel welded along one pair of side flanges thereof. Wall sections are disposed between each adjacent pair of wall studs within the confines defined by opposed channel openings of each pair, and roof sheeting is applied atop the roof rafters and purlins. Standard ceiling tiles are supported between the roof rafters and purlins on the lower flanges thereof within the confines of the opposed channel openings.

Abstract: An improved grouted earth anchor having a modified end configuration that reduces undesirable tensile stress in the grout ball. The reduction in tensile stress is accomplished by locating the enlarged end section of the end configuration of the anchor rod away from the bottom of the grout ball, and by shaping the enlarged end section in a predetermined manner in order to make the compressive stress trajectories between the surface of the enlarged end section and the surface of the grout ball as straight as possible.

Abstract: Resin is sprayed onto the inside of a mold. Fiberglass is then applied to the resin to form a shell having a bottom, side walls and an upper, outwardly turned lip. The fiberglass forms a somewhat roughened surface on the inner side of the completed shell, thereby eliminating the cracking and chipping of the inner surface which has heretofore occured when the fiberglass was on the outer side of the shell and the inner surface of the shell was smooth resin.After the required plumbing is mounted on the shell, the shell can be installed at the desired location, usually in the ground and frequently near a swimming pool.A hole is formed in the ground somewhat larger than the shell and at least three stakes of appropriate length are driven into the bottom of the hole, adjacent the periphery thereof, to a depth such that the upper ends of the stakes coincide with the desired height of the lip of the shell. The shell is then lowered into the hole so that the lip rests on the stakes for support of the shell.

Abstract: A wall unit having a vapor-proof evacuatable envelope and a supporting core in the envelope. Wall shells form the outer sides of the element, and screw means extend through and rigidly interconnect the wall shells and thus the element, the screw means having flanges which can be adjusted toward or away from each other to adjust the pressure applied to the wall element by the screw means. Horizontal and vertical reinforcement means are pre-stressed and cast in the outer wall shell.

Abstract: A wall-base joint for a concrete tank is constructed by providing in a base a groove larger than the width of a tank wall, placing the wall in the groove to leave a groove portion on each side of the wall, prestressing the wall with a first compressive force, filling the inner (with respect (with respect to the center line of the base) groove portion with concrete and curing it to form a first plug therein, prestressing the wall further with a second compressive force to counteract a fraction of the bending moments produced by the liquid in the tank when it is full, and filling the outer groove portion with concrete and curing it to form a second plug to lock the inner plug into permanent compression.

Abstract: A standard construction unit is provided by a monolithic precast reinforced concrete panel which has a generally rectangular peripheral configuration. A pair of flanges project from and extend longitudinally along the opposite sides of one face thereof to provide the unit with a shallow U-shaped cross-section. Connector elements are embedded within the other face of the panel adjacent its sides to permit connection of it to adjacent like panels. Door or window openings may be provided in the web portion.A building structure is supported on a footing and has walls, a roof and, optionally, a floor formed from the standard panels. The walls are formed by a plurality of the panels disposed vertically in side-by-side relationship and connected to each other by side fastener means bridging the panels and engaged with the connector elements and, at their lowermost ends, to the footing.

Abstract: A construction for insuring that the edges of panels used in elevated floor systems do not become loose with handling. The construction comprises serrated surfaces on the tops and bottoms of the panel flanges, which interfit with corresponding complementary serrations on the inner facing surfaces of the channel edge strip. The serrations on the flange also extend under the outer portion of the wear surface covering layer to inhibit loosening.

Abstract: Structural members, especially components of a modular building, are joined at longitudinally extending and abutting surfaces by a correspondingly elongate connector having a cross-shaped transverse section. Each such member surface is formed with a pair of intersecting saw-cut slots that extend lengthwise of the surface and have a V-shaped transverse section in which the apex of the V lies substantially at the surface and in which the legs of the V diverge inwardly into the member. The members are arranged with the apexes of their respective pairs of slots in mutually opposed registry to define a composite, transverse slot configuration that is the complement of the cross-shaped connector and the connector is inserted endwise into the slots with opposed pairs of connector legs interlocking with the opposed pairs of V-shaped slots, respectively, and is driven longitudinally into the joint.

Abstract: A maintenance-free anodized aluminum post having longitudinal grooves therein for mating with complementary brackets. The post is hollow and has a constant wall thickness. Each groove has a curved portion and a flat portion. The brackets may be moved in the grooves adjustably, and may be locked to the post without causing any deformation of the post or bracket.

Abstract: A method of providing a moisture proof or moisture resistant foundation insulation for buildings involves digging a narrow ditch around the building, providing an insulating foil in the ditch, providing drainage material in the bottom of the ditch and refilling the ditch. Preferred foils are of plastics material with an expanded layer on at least one side.

Abstract: A cup packaging device for seriately receiving, counting and loosely nesting into a group on a first conveyor segment a preset number of cups, nesting the cups into a more tightly nested stack on a subsequent conveyor segment, conveying the tightly nested group of cups at an accelerated speed past a verifying device to determine if the number of cups in the group matches the previously counted number, laterally offloading to a holding tray a stack of cups in response to a count mismatch signal or a downstream component malfunction signal, advancing an acceptable stack into a bagging device, conveying the bagged stack longitudinally out of the bagging device and then transferring the stack laterally into a collection bin. The conveyor system comprises separately driven conveyor segments which are operated at speeds that vary from one another and are also changed during each cycle.

Abstract: Bags having side panels and front and back panels -- such as laminated paper bags in which produce such as biscuits and cookies are sold -- may have closures attached to them so that the bag is closed and sealed with product inside for wholesale and retail sales, and may be opened and re-closed by the end purchaser. Where the closures comprise a pre-formed plastic closure having at least one open jaw into which the top of the bag, when shut, is inserted, and which are applied to a portion of the front panel of the bag. Apparatus is provided for applying the closure to the bag, which apparatus comprises means for applying the closure to the folded top of the bag which is intended to be inserted in the closure when in use, means for applying adhesive to the closure, and means for maintaining the closure and surface of the bag in contact one with the other while the adhesive between them becomes effective.

Abstract: In an apparatus for mounting electrical components having connecting wires extending outwardly from opposite ends thereof in a belt by locating each such wire between a respective pair of superimposed bands, the toothed, transport wheels and rollers to which the bands are fed and at which such bands are combined with the wires interposed therebetween are axially adjustable to provide for the ready use of the apparatus in the context of components of a range of dimensions, the tape-feed arrangements similarly being adjustable to maintain their alignment with a respective roller.

Abstract: The present invention relates to a speed control unit associated with a peanut combine for driving and controlling the peripheral speed of a forwardly disposed crop engaging pick-up reel rotatively mounted transversely about the front of the peanut combine. The speed control unit basically includes a dual input drive system including a first drive operatively connected to at least one ground engaging wheel of the combine for providing an input drive corresponding to the ground speed of the peanut combine. A second generally constant input drive is provided from a power take-off source associated with the peanut combine. These two drives simultaneously drive a centrifugal clutch which includes an output drive member that is driven at a speed corresponding to the faster of the two input drives.

Abstract: A mower with two pairs of counterrotating cutting disks has a frame on which two yokes are mounted for independent swinging about a horizontal axis transverse to the direction of travel, each yoke carrying a pair of coacting horizontal conditioning rollers which in a working position lie in the wake of a respective disk pair to gather and press the mown crop coming from these disks. The conditioning rollers are driven from a pair of ancillary shafts on the machine frame, operatively linked with the disk drive, through extensible and universally jointed transmission shafts enabling each yoke to be separately swung into a retracted position.

Abstract: In a tobacco combine having a pair of contra-rotating defoliation blade members, upper and lower guides are provided for assuring proper positioning of the tobacco leaves for defoliation without impeding the speed of defoliation such as by gripping engagements of the stalk. The upper guide has diverged forward ends which converge toward one another (in a direction toward the rear) and project downwardly (in a direction forward of the defoliating blade members), intermediate portions which converge gradually rearwardly with downwardly sloping parallel portions which, in turn, are connected by curved portions to rear suspension brackets.

Abstract: A discharge boot is connected to the clipping discharge chute of a rider-type mower with a flexible conduit extending from the boot to the blower input of a yard-type vacuum cleaner towed behind the mower. The boot includes a hollow rigid housing with a flexible rubber-like wall which can be cut to conform to the contour of the clipping discharge chute so that the chute can be positioned within the boot and maintained in position by a bracket connecting boot and the chute.

Abstract: An apparatus for applying in continuous manner about a flexible hose a plurality of reinforcing wraps. The apparatus comprises generally a first yarn treating head including a first bobbin table and a second yarn treating head including a second bobbin table. The first and second bobbin tables rotate in opposite directions. Each bobbin table has mounted thereon a plurality of yarn carrying bobbins on each side of the table, for example, four bobbins per side. The apparatus can then accommodate a total of 16 bobbins, eight of which are located at each head, to wind reinforcing wraps of any desired number of yarns from two to 16 by utilizing all or only some of the bobbins.

Abstract: A marine rigging apparatus for splicing new wire cable of the type having twisted wire strands to a portion of worn wire cable taken from a rotatable drum on a fishing vessel docked or moored adjacent a dock, said apparatus including a motor vehicle having a base mounted thereon, at least one bearing mounted on the base, at least one drum rotatably supported by the bearing, a hydraulic motor operatively connected to the drum for rotating the drum to wind the worn cable onto the drum, a rigger's vise mounted on the base for clamping portions of cables to be spliced with the cables being restrained against rotation about the axes of the cables, and a twister device mounted on the base for rotating one of the cables in a direction opposed its natural twist to relieve the tension in the strands of the cable at a desired location on the cable to permit an efficient and quick splicing of the other cable to the twisted cable.

Abstract: Apparatus and method for directly obtaining a spun yarn from slivers. The apparatus comprises a drafting device for the sliver, a first fluid turning nozzle, a false twisting device rotating in a direction opposite to the turning direction of the fluid turning nozzle and a take-up means.

Abstract: Self-twist plural yarn strands are produced by a system wherein at least two singles yarn strands are individually twisted to form twisted strands each having longitudinally spaced nodes. The strands are separately conveyed around a yarn wheel and brought together in a parallel relationship with the nodes of one strand substantially aligned with the nodes of each other strand. The corresponding nodes from one strand are fastened to those of each other strand by heating with an electric arc and the strands are removed from the wheel and allowed to ply. The node fastening means comprises a pair of electrodes and a circuit for supplying arc-producing voltage across the electrodes. One electrode is mounted on the wheel and extends diagonally across and under the node location. The other electrode is fixed adjacent the wheel so that the arc traverses the yarn as it passes from one end of the diagonal electrode to the other.

Abstract: An open-end spinning apparatus having a fiber conveying path between a fibrous material feed device and a spinning compartment. A trash separating device which includes an aperture and a dividing edge is provided for removing trash from the fibrous material as it is conveyed along the conveying path extending around an opening roller. A collection chamber is provided for receiving the trash from the trash separating device. Interposed between the trash separating device and collection chamber is an auxiliary chamber. A first aperture extends through a wall of the auxiliary chamber through which a stream of air flows for being introduced into the fiber conveying path. A second aperture is provided in an opposed wall of the auxiliary chamber through which a smaller stream of air is removed from the auxiliary chamber along with small particles of fly and trash.

Abstract: A free-floating ring is disposed in an annular chamber between a fixed outer ring based on the ring rail and an inner ring which is adjustable up and down axially in relation to the outer ring. The outer ring has circumferentially spaced camming slots in its side wall slidably receiving radial cam pins fixed to the inner adjustable ring. One such cam pin on each inner ring is extended to engage slidably within a slot in an actuating bracket secured to a shifter rod extending longitudinally of the ring rail and guided within bearings on the ring rail. Movement of the shifter rod longitudinally of the ring rail in one direction or the other produces raising or lowering of the gang of inner rings to vary the yarn tension. An opening for yarn threading is provided in the annular side wall of each outer ring.

Abstract: A yarn ending unit, applied to an open-end spinning machine, which performs ending by means of the ending unit running in front of said spinning machine. The ending unit includes a friction roller for driving a package unit and a friction roller for driving a feed roller, both fitted to said ending unit. The two friction on rollers are driven by a variable speed electric motor, the number of revolutions of which can be controlled in response to the number of revolutions of a rotor fitted to said spinning machine. A hook is provided for each spinning machine, to hold one end of a yarn, and said hook is designed to be operable by a solenoid, energized by output from the control means.

Abstract: An electronic timepiece having an A.M. and P.M. display function. The characters A or P are displayed during time setting or correction by one discretionary display element of a plurality of display elements normally used for displaying time.

Abstract: Control circuitry for an electronic timepiece that is capable of producing a signal representative of the timing rate of the electronic timepiece's time standard and the amount that the timing rate of the electronic timepiece is varied, is provided. Control circuitry is positioned intermediate divider circuitry capable of producing an adjusted low frequency time signal and a time display that displays time in response to the adjusted low frequency signal being applied thereto. The control circuitry is adapted to apply the adjusted low frequency time signal produced by the divider circuit to the display. The control circuit is further coupled to timing rate adjustment circuitry for adjusting the timing rate of low frequency time signal produced by the divider circuitry, in order to produce a signal representative of the timing rate of the time standard and of the amount of adjustment of the timing rate of the low frequency time signal affected by the timing rate adjustment circuitry.

Abstract: An electro-optical display timepiece provided with a display changeover switch circuit manually controlled by a single external push button so that various displays including an alarm function display, chronograph function display and timer function display as well as time display may be obtained in accordance with the length of a time period, for which the push button is being continuously depressed.

Abstract: A digital display timepiece being provided with electro-optical display devices in which when clock information corrected partition marks provided near respective units in a clock information indicator are adapted to flash whereby the numerical figure to be corrected in a display portion can be easily confirmed.

Abstract: A calendar watch movement with a double cam arrangement that drives the date-indicating wheel one step every 24 hours and locks the wheel between driving periods. The first cam has a hook that engages the toothed inner portion of the date-indicating wheel and advances the wheel by one tooth each 24 hours. The cam also has an arcuate peripheral portion that fits in between two successive teeth and locks the wheel when it is not being advanced. The first cam is integral with a co-axial star wheel which is driven by a second cam having both a hook and an adjacent shoulder that advance the star extensions. The second cam is driven by the hour wheel.

Abstract: An improved back-up control for use in an aircraft gas turbine engine is presented and includes a fuel control valve adapted to meter the flow of fluid to the gas turbine engine, first means for providing a mechanical position signal indicative of the magnitude of a desired fuel flow change to the engine and second means for limiting the rate at which a change in the signal is transmitted to the fuel control valve thereby limiting the rate of change in fuel flow to the engine. The second means may limit the transmission rate in response to inlet pressure. A variable geometry control valve is provided for varying the position of the variable elements of the gas turbine engine in response to said mechanical position signal and the second means limits the rate at which a change in the signal is received by the variable geometry control valve.

Abstract: A high bypass ratio gas turbofan engine provided with a hybrid mixer for mixing that portion of the bypass stream equivalent to a bypass ratio of substantially two with the core engine hot gas stream. The mixture is passed through a common exhaust nozzle.

Abstract: An exhaust double pipe used for interconnecting an exhaust manifold with a catalytic converter of an internal combustion engine, comprising an inner pipe and an outer pipe. The outer pipe comprises a first pipe and a second pipe. The outer end of the first pipe is welded to a flange together with one end of the inner pipe. The outer end of the second pipe is welded to another flange together with the other end of the inner pipe. The inner end of the first pipe is directly fitted into the inner end of the second pipe, or is indirectly connected to the inner end of the second pipe via a spacer so as to be able to slide relative to the second pipe.

Abstract: A fluid motor including a rotatable output shaft and a fluid inlet and a fluid outlet is provided for serial connection in a domestic water system supply pipe. A rotary electrical generator is also provided and the output shaft of the fluid motor is drivingly coupled to the generator. A bank of storage batteries is further provided and the generator includes a pair of electrical potential output conductors electrically connected to the bank of batteries through current regulating structure whereby the batteries may be recharged as a result of the fluid motor driving the generator. An auxiliary domestic electrical wiring system is provided and is electrically connected to the bank of storage batteries.

Abstract: A hydraulic system for supplying hydraulic fluid to a hydraulically operated device alternately at pressures of different values, said system comprising a first hydraulic circuit arranged to be supplied with hydraulic fluid at a low pressure by a pump and for supplying the hydraulic device with fluid at said low pressure through a pilot operated valve, a second hydraulic circuit provided with a pressure multiplier piston device which produces hydraulic fluid at a pressure greater than that of the low pressure fluid and having a first chamber connected to the first hydraulic circuit and a second chamber of smaller area than the first chamber connected to the second hydraulic circuit, the second hydraulic circuit being provided with a pressure accumulator for maintaining high pressure in the second hydraulic circuit and said second hydraulic circuit being provided with a second pilot operated valve for supplying the hydraulic device with fluid at said high pressure.

Abstract: A multiple speed hoisting system has a first fluid circuit, with a maximum effective cross-sectional area for hoisting heavy loads at low speed, and a second fluid circuit, with a smaller effective cross-sectional area for hoisting lighter loads at higher speed. These circuits are separately actuated by a valve that is responsive to a regulating means for selectively positioning the valve. A pressure operated control, that is in flow communication with the second fluid circuit, automatically cancels the influence of the valve regulating means, in response to a predetermined pressure level in the second fluid circuit, and allows the valve to revert to a position actuating the first fluid circuit. Undesirable oscillations within the system between the pressure operated control and the valve regulating means are avoided.

Abstract: A unitary plastic molded snap-on end cap for gutters constitutes a vertical end wall having a pair of flanges projecting outwardly normally about the periphery of the end wall from both sides thereof so that the same molded article may be used to cap either left-hand or right-hand open ends of gutters. Positive engagement of the gutter and the cap is provided by forming a groove in the cap having a rib which engages a projection formed on the gutter wall before the cap is applied thereto.

Abstract: A removable closure apparatus for tubular members of offshore platforms and the like utilizes a body inserted in the tubular member. A seal formed in an annulus between the inner surface of the tubular member and the outer surface of the body is bonded to each of the surfaces of the body and the tubular member. The seal is broken by use of a flexible tensile bearing inlay spirally embedded within the seal. The inlay is torn from the seal to destroy the structural integrity thereof and permit removal of the body. The inlay has one end affixed to the body and a second end extending upwardly through the member for manipulation from the upper end thereof. A force applied to the second end of the inlay causes it to tear the seal along a spiral path.

Abstract: In a vegetables and fruits-storing method of conventional controlled atmosphere storage including continuously feeding the air of a definite oxygen content such as, for example, 2 - 3% by volume and definite amount obtain by means of an adsorber into a refrigerator to obtain an atmosphere suitable for storage of the vegetables and fruits, an improved method wherein the improvement comprises in the first step feeding the open air and the atmosphere of the refrigerator to be recycled in such order or simultaneously into the adsorber packed with an adsorbent such as zeolite or the like which adsorbs more nitrogen than oxygen, adsorbing the nitrogen in the open air and the atmosphere and expelling the high oxygen content air of the adsorber having oxygen content lower than that of the open air but higher than that of desired atmosphere of the refrigerator, in the next step expelling a part of the remained high oxygen content air, and in the further next step, desorbing the nitrogen and the remained high oxygen co

Abstract: An automatic ice maker control circuit having an improved tolerance to sense the presence of stuck ice pieces in a predetermined pocket of an ice tray. A solid state temperature sensor and time delay circuit includes an operational amplifier controlled by a temperature sensor in one portion of a bridge network for sensing above or below freezing temperatures in the pocket, depending upon the presence of liquid or a stuck cube respectively, in said sensing pocket. The ice maker is conditioned for immediate harvest after the below freezing temperature is effected in the tray pocket when the sensor senses an above-freezing temperature. The time delay circuit conditions the ice maker for a delayed harvest until the predetermined temperature is effected in the tray sensing pocket if the sensor senses a below-freezing temperature.

Abstract: A method and apparatus for initiating the defrost of refrigeration equipment on demand. A defrost clock which normally controls the conventional refrigeration and defrost modes of a refrigeration system includes an auxiliary switch to cease operation of the clock motor a predetermined time prior to normal defrost initiation. The defrost clock thus remains in the refrigeration mode until the demand defrost sensor switch, or an optional demand switch, initiates a defrost cycle of the refrigeration equipment. The closure of the demand defrost switch or the optional switches causes the defrost clock motor to run for a predetermined short period of time. The defrost clock switch subsequently closes slightly prior to initiation of a defrost to guarantee that the clock runs throughout the defrost mode. Thereafter, the defrost clock controls the length of the defrost and will terminate defrost upon a signal from a thermostat, or by a time signal, or a pressure signal.