Abstract: In lieu of a pair of bevel gears which mesh to rotate about axes inclined to one another, each gear is carried on a cylindrical base having a boss extending from one end and co-axial with the base. Each tooth is integral with both the base and the boss and the adjacent walls of adjacent teeth are parallel for portion of their respective lengths such that the teeth are bulbous. Point engagement exists between the teeth. For a given pair of gears the angle between the axis of rotation can be widely varied.

Abstract: An apparatus for imparting torsion to a tubular member, including a body member, an arm member, a saddle member, and a loop means such as a chain. Torsion is imparted to the tubular member by inducing tension into the chain entrained around the tubular member so that the tubular member is brought to bear against the body member or dies in the body member. A variety of configurations of the apparatus are possible, permitting adjustment to accept different diameter tubular members and assuring maximum positive load reaction.

Abstract: A cut-off tool or deep grooving tool and support therefor for use on a turning lathe, in which a cut-off tool is secured in a tool holder on a cross slide, the support being inserted between the protruding cutting end of the cut-off tool and an extending portion of the slide bed that carries the tool holder on the cross slide of the lathe. The support is longitudinally adjustable between the cut-off tool and the cross slide and has its upper end formed as a spade of narrower width than the cutting edge of the cut-off tool, and transfers the cutting forces on the cutting edge directly to the cross slide bed. The lower edge of the cut-off tool and the upper surface of the spade portion of the support are supplied with co-operating male and female profiles to ensure constant centering of the spade formed end of the support relative to the cut-off tool.

Abstract: The invention relates to a method for cutting continuous reinforcing material in a sheet molding compound comprising passing the sheet molding compound into contact with a plurality of blades projecting from the exterior surface of a rotating roll. The blades pierce the sheet molding compound to sever the continuous reinforcing material located therein as the sheet molding compound is advanced past the roll.

Abstract: Apparatus for producing all over pin hole perforations in the plies for multiwall bags except at the tops and bottoms in the area of interply pasting.

Abstract: The cutter ring finds especial utility in the trimming of printed circuit boards, the cutter ring being provided with a beveled cutting edge having a number of nonuniformly or unevenly spaced notches formed therein.

Abstract: A neck for a stringed instrument which is adjustable to counteract warping by tensioning a strap of substantially inextensible material positioned within the neck. In one embodiment, the strap is positioned inside a conduit inside the neck which can be bowed to counteract the warping. The strap is positioned in the conduit in the shape of an arc with the ends of the strap closer to the finger board or the strings than the central region of the strap by a plurality of rod members fixedly secured to the conduit. One end of the strap is fixedly secured to one end of the conduit and the other end can be moved to tension the strap and bow the conduit and neck to counteract warping. In another embodiment, the strap is shaped as an arc inside the conduit by an elongated filler element having an arcuate bottom surface which progressively increases in depth from the ends of the filler element toward the central region of it.

Abstract: A compact, double-acting piston-type fluid activated device having an axially reciprocable piston for controlled, predetermined deceleration of the piston as it approaches the limit at each end of its travel within a cylindrical bore. The cylindrical bore is sealed at each end by end walls removably retained in the bore. Each end wall is provided with a central counterbore in its inner surface which in cooperation with the piston provides a cushioning chamber. The area of the counterbore central surface is critically related to the circular cross-sectional area of the cylindrical bore in which the end wall is to be secured, being in the range from about 60% to about 85% thereof. A vent passage places the cushioning chamber in preselectedly restricted flow communication with porting means in the wall of the device, each port being located intermediate the end walls. A method is provided for removably circumferentially locking each end wall in the operating cylinder with a wire snap ring having a hooked end.

Abstract: A fluid control unit comprising a drive piston having first and second faces and a drive rod. The drive piston has first and second fluid responsive faces exposable to fluid under pressure. The fluid under pressure acting on the first face urges the drive piston in a first direction and the fluid under pressure acting on the second face urges the drive piston in a second direction. First and second overridable detents drivingly couple the drive piston and the drive rod for movement in first and second directions, respectively. The coupling force provided by the first detent varies with the pressure of the fluid to which the first face of the drive piston is exposed, and the coupling force provided by the second detent varies with the pressure of the fluid to which the second face of the drive piston is exposed.

Abstract: A coffee brewer, and, in particular, a single cup coffee brewer includes separate first and second members. The first member seats on a cup or similar receptacle and has a ground coffee receiving chamber formed therein. The second member is used to regulate the flow of hot water of similar fluid into the chamber. An aperture formed in the first member allows brewed coffee to flow from the chamber into the receptacle and regulates, by its size, the flow time of brewed coffee into the receptacle. A seal between the two members prevents the ground coffee from soaking in the brewing fluid.

Abstract: Thin potato slices are fried to chips in a two-stage operation. In the first stage the slices are fried in oil to a moisture content of 3-10% by weight. This product is removed from the oil and the moisture content is reduced to 1.5-2.5% by weight in a second stage by the supply of heat. To reduce the moisture content in the second stage at least a portion of the frying vapors substantially without false air and having a temperature of at least 120.degree. C., is guided from the space above the oil of the first stage to the slices removed from the oil.

Abstract: An improved breaker head is disclosed for use on automatic egg breaking machines. These machines receive whole eggs from a conveyor or other egg feeder and crack, open and drain the eggs. This improved head has a cracking knife arrangement which engages the inner side portions of the egg shells. This facilitates egg drainage by permitting a more complete and a more rapid draining of the egg white, facilitates the yolk removal, and adjusts knife penetration in accordance with the egg size to protect yolks from knife damage in smaller eggs.

Abstract: A delay primer unit for detonating an explosive material in a borehole with a detonating cord down line extending into the borehole wherein the unit comprises an explosive element capable of detonating the explosive material upon being detonated, means for preventing direct detonation of the explosive element by the down line and an elongated, flexible time delay detonation element having a first end slidably connected to the down line and a second end connected in detonation relationship with the explosive element and generally movable with respect to the first end. The delay element is used to mount the explosive element on the down line.

Abstract: A projectile contains a load to be ejected therefrom during a flight and includes a one-piece casing having a streamlined outer surface and having a portion containing the load. The casing has a reduced wall thickness at a section of such portion, and a metallic liner is cast onto the inner wall of the casing at such section, the liner having an inner diameter substantially equal to the inner diameter of the remainder of the casing at such portion. An external guide ring on the casing is located on the greater wall thickness thereof, and projections on the inner wall of the casing at such section engage grooves provided in the liner.

Abstract: A percussive tool, such as a tamping tool used with railroad bed tamping apparatus, has a replaceable work bit, such as a tamping foot. The removable tamping foot is secured to a shank by a tapered force fit. A repulsive force is generated between the shank and the tamping foot when it is desired to remove the tamping foot from the shank. Production of the repulsive force is achieved by pumping a fluid into an expandable chamber between the shank and the tamping foot. Preferably, a hand-operated grease gun drives grease into the expandable chamber to produce the repulsive force.

Abstract: An improved rail car moving vehicle adapted for travel alternately in one mode on rail wheels on a railway track and in an off-track mode on ground wheels, with weight transfer capabilities from a coupled railway car when in the on-rail mode, and characterized by improvements, including: a tricycle configuration of ground wheels provided by a pair of non-steerable, closely-spaced rear road wheels adapted to have frictional driving engagement with the driven axle of a rail wheel set and relatively widely-spaced steerable front ground wheels; a frame design that provides ample strength with respect to a bending or vertical load while having torsional rigidity not sufficient to normally cause one of the rail wheels to lift off from the track more than the radial dimension of its flange; a rear coupler assembly including a coupler carrier independently hinged to the vehicle frame for supporting a laterally swinging coupler independently pivoted to the frame at the inner end of the coupler arm; a pair of steerable

Abstract: A rail vehicle having a driving bogie frame and a vehicle frame, in which these frames are interconnected by means of supporting springs and at least one of the end faces of said frames are interconnected by air springs. The air springs communicate with a source of compressed air through a conduit system having two branch lines respectively connected to the interior of the air springs while adjustable pressure control valves are respectively arranged in these branch lines. The two branch lines are interconnected by a conduit having an adjustable throttle valve interposed therein. Depending on the respective driving direction of the vehicle by adjusting the valves in the branch lines a differential pressure is established between the air pressures in the air springs connected to the branch lines so that the respective end of the bogie frame is pulled up or pressed down so that the wheel set relief is compensated for.

Abstract: There is disclosed herein a buckle support system for use with a curtain-style lading-restraining device of the type which is suspended from an overhead support and includes a plurality of vertically-spaced and laterally-extending restraining belts, each of which includes a buckle for tightening the belt. A cable system is provided which is secured at its uppermost end to the overhead support and which connects to each buckle. Stop sleeves are secured or crimped to the cable at positions to engage and support each buckle so that the weight of the buckle is carried by the overhead support through the cable system. This system, in addition to supporting the weight of the buckles, deters buckle theft or removal, since in order to obtain the buckle, the belts and the cable must be severed.

Abstract: A cantilevered shelf assembly having a shelf with a rectangular mortised opening therein, the opening containing a generally C-shaped clamp member having the free end thereof adjacent the outer perimeter of the opening. A second C-shaped clamp member is secured to a wall or the like with the free ends thereof generally perpendicular to the wall surface for fitting within the opening in overlapping relation with the free ends of the C-shaped member within the opening. The shelf and C-shaped members when assembled have aligned openings for passage therethrough of a pin member for supporting the shelf. For longer shelves, a second similar assembly can be provided.

Abstract: The combustion chamber of the oven is bounded at the top by a lid which can be swung open and at the bottom by a grating. The grating has one or more sections which pivot about an axis to dump slag. A hollow interior of the grating forms a section of the exhaust gas system. The lid includes a channel for air supply, the air passing through a perforated plate in the bottom of the lid into the combustion chamber. A perforated tube extending vertically along the axis of the combustion chamber opens into the channel in the lid and supplies air down into combustible materials filled into the combustion chamber. The depth to which the air is supplied can be regulated by a piston which can be adjusted vertically within the tube to extend the air flow to the depth desired. The incinerator is filled from above in layers.

Abstract: A floating semi-submersible platform is heave stabilized by velocity damping of platform motion. Vertical velocity of the platform is sensed and a force is applied to the platform as a function of and in opposition to the sensed heave velocity. The system may be passive, as by provision of velocity damping in tethering cables. It may be actively hydrostatic by employing variable ballast tanks and water pumps or air pressure for displacement of water, or it may be actively hydrodynamic by employing propellers or rotor blades for thrust generation. By applying a heave opposing force that is proportional to heave velocity, the platform response to waves at the platform resonant period is greatly reduced with exertion of relatively small magnitude opposing forces, whereby the platform may be designed with a considerably smaller resonant period for a given set of expected conditions.

Abstract: A semi-submersible floating apparatus for operating at sea and a method of assembling the same are disclosed. The apparatus comprises two or more submerged or bottom hulls supporting, by pillars, one or more working platforms or top hulls all of which are elongate floating bodies adapted to be individually constructed. The top hull is arranged transversely of the bottom hulls and is affixed by lateral connections adjacent the tops of the pillars. In assembling the apparatus, the bottom hulls are interconnected and fitted with the pillars and then ballasted until the bottom hulls are submerged. The top hull is floated until centered transversely of the bottom hulls and raised to a position for the lateral connection thereof. Alternately, the top hull is connected to the pillars and the bottom hulls are deballasted to raise the top hull above the level of the sea.

Abstract: An acoustic alarm arrangement associatable with a pneumatic tire for generating a signal indicating that pressure of gas in the tire decreases from a predetermined magnitude, has a housing arranged to be connected with a tire and bounding an inner chamber, a signal element associated with the housing and actuated under the action of a strike, and a striking element movable in the inner chamber between an inoperative position in which it is spaced from the signal element and an operative position in which it approaches and strikes the latter. The striking element subdivides the inner chamber into a first compartment communicating with the interior of the tire, and a second compartment.

Abstract: Coating apparatus wherein a pretreated sheet metal ribbon passes from a supply coil successively through entry rolls, coating rolls, a curing oven, cooling apparatus, and tension rolls to a recoiler. The ribbon extends through the coating rolls and the curing oven as a long-span catenary. No looping facility is required. The apparatus incorporates novel leading end gripper means and trailing end gripper means for establishing and terminating the catenary in a manner which minimizes the unusable length of ribbon, that is, the uncoated leading end and uncoated trailing end of the processed ribbon. A method of initiating, maintaining, and terminating the catenary is disclosed.

Abstract: An automatic spraying apparatus comprising storage tanks each storing therein each one of at least two liquid components which are mixed to produce hard urethane foam, a pump for feeding said each liquid component under pressure, a spray gun for mixing said liquid components fed from said pumps and spraying the mixture, a mechanism for displacing said spray gun in a plane spaced apart from and substantially in parallel with a surface to be sprayed, and a control unit for controlling the displacement of said spray gun so as to follow a predetermined path.

Abstract: The specification discloses apparatus for allowing movement of a live animal between spaced apart play areas. An endless track extends between a plurality of spaced apart animal play areas. A vehicle is movable along the track to allow access to the play areas. Structure is responsive to the presence of an animal within the vehicle in order to cause the vehicle to move the animal from one of the play areas to another of the play areas. Structure is provided to terminate movement of the vehicle in the vicinity of the play areas in order to allow the animal to exit the vehicle. When the animal again enters the vehicle, the animal is transported to the next play area.

Abstract: A method and apparatus for improving the feed conversion of poultry confined within a poultry raising house. A guide rail having a moveable carriage attached thereto is provided within the house and a baffle positioned adjacent the floor of the house is attached to the carriage. The carriage is periodically caused to move along the guide rail whereby the baffle is moved over substantially the entire floor area of the house so that poultry within the house are disturbed and forced to move to a feeding location.

Abstract: An improved animal feeder particularly suitable for hogs, cattle and the like which is characterized by an improved feed control construction which includes a novel threaded drive construction cooperating with an inclined plane connection to a movably mounted feed gate to save time and effort in adjusting the flow of feed to the feeder troughs when required.

Abstract: The bottom hinged stanchion posts of an animal headgate are displaced from a closed position to an open position by an actuator lever after one of a pair of oppositely engaging one-way locking elements is manually released from engagement with a common lock rod connected to one of the gate posts. An opening pressure applied to the posts in the open position releases the engaged locking element to permit the gate to close under a spring bias applied through the actuator lever.

Abstract: An animal leash including an elongated leather strip on which there is sewn a transparent polyvinyl chloride strip having a prism design on one surface thereof and an opaque polyvinyl chloride strip secured to the one surface of the transparent strip. The combined polyvinyl chloride strips are sewn to the leather strip resulting in a leash having a light reflective surface. The areas around the stitching are crimped thereby increasing the reflecting angle of the polyvinyl chloride.

Abstract: The air-supply system for a fluidized-bed furnace includes two air conduits for the same combustion zone. The conduits feed separate sets of holes in a distributor plate through which fluidizing air flows to reach the bed. During normal operation, only one conduit and set of holes is used, but the second conduit and set of holes is employed during start-up.

Abstract: Fuel injection apparatus comprising a fuel injector and a surface which can be vibrated, the apparatus being such that in operation the injector is vibrated to inject atomized fuel towards the surface which is also vibrated so that any particles of insufficiently atomized fuel can hit the vibrating surface and be further atomized.

Abstract: A liquid cooling system for an internal combustion engine includes a conventional radiator and circulating system and pressure cap, the latter having pressure and vacuum relief valve components for limiting the maximum operating pressure of the system and for limiting negative pressures to avoid damage during cooling after engine shutdown. A second, temperature responsive, pressure relief valve provides a lower system relief pressure as long as the temperature of the coolant in the radiator top tank remains below a certain level. When that level is exceeded, a thermally actuated valve excludes the second pressure relief valve from the system and maximum operating pressure is then limited, at a higher level by the valving of the pressure cap. In an alternative embodiment, an infinitely variable pressure relief valve responsive to and controlled by changes in coolant temperature replaces the fixed second pressure relief valve and its thermal actuator.

Abstract: A two cycle loop scavenging engine of the crankcase precompression type having a pair of equally dimensioned scavenging passages 14, 16 disposed in a cylinder block 10 behind an apertured cylinder line 12. The passages are symmetrically positioned on opposite sides of a vertical plane A including the cylinder axis and oriented at an angle .theta. to a plane normal to the crankshaft 17. Recessed notches 22, 23 in the lower periphery of the piston skirt 20a mate with notches 12e, 12f, respectively, in the bottom of the cylinder liner at the entrances to scavenging passages 14, 16 at the bottom of each piston stroke. The notches 22, 23 have unequal cross-sectional areas to compensate for unequal fuel mixture pressures at the scavenging passage entrances caused by the rotation of the crankweb 17a, thereby producing a more uniform fuel mixture distribution in the cylinder.

Abstract: An auxiliary charge of air, fuel mixture, and/or recycled exhaust gas is injected into the combustion chambers of an engine through directional ports adjacent the spark plug gaps to enhance combustion, reduce noxious emissions, scavenge exhaust gases, etc. The injection timing is controlled by cam driven valves, and the magnitude thereof is regulated in accordance with both engine temperature and throttle valve opening or engine load, the latter being sensed by vacuum passages adjacent the throttle in the carburetor throat or by a direct coupling to the throttle valve.

Abstract: An automotive emission control system includes a servo connected between the carburetor and the distributor and between an engine driven air pump and the distributor to advance the ignition timing as a function of changes in carburetor spark port vacuum and/or air pump pressure to provide various degrees of timing advance and retard; the servo includes a pair of diaphragms that are interconnected so that movement of one advances the timing by a first amount, the second advancing the timing independently of the other and being additive or the only advance.

Abstract: A sensor which determines an operational variable of a system, for example an oxygen sensor of an internal combustion engine, generates a usable output voltage only at the proper elevated temperature. In order to uncouple the control loop from an improperly operating sensor, i.e., a cold sensor, the internal resistance of the sensor is monitored by passing through it a test current and by comparing the resulting voltage drop to a set-point value. Whenever the internal resistance is too high, indicating non-readiness, the control loop is opened and a substitute average output value is supplied to the fuel injection system or to the system driven by the control loop. During normal operation, the sensor is tested periodically with short test pulses to continuously monitor the operational readiness, but the main test current is normally shut off, thereby preventing falsification of the output signal.

Abstract: Crankcase ventilation valve for internal combustion engines with a valve casing which is divided into a first and a second chamber by a displaceable wall sealingly attached at the periphery, wherein the first chamber is in communication with the atmosphere and the second chamber is in communication on the one hand through an inlet tube with the crankcase and on the other hand through an outlet tube with the suction device by way of a cylindrical tubular member disposed in the second chamber, the displaceable wall and the tubular member being constructed as a non-return valve and the valve seat being surrounded by a concentric ring space which is connected to the inlet tube.

Abstract: A self-regulating, fast-response fuel vaporizer is disclosed which is cape of promoting increased efficiency of combustion of the fuel supplied to a spark ignition engine throughout the entire working range of the engine. The vaporizer comprises an inlet conduit through which fuel-air mixture is admissible to the engine, the mixture being directly heated within the conduit by an exhaust conduit which intersects with the inlet conduit. Use is made in the design of the respective heat transfer surfaces, of an inherent effect that flow pulsations have upon heat transference between a gas flowing in a tube and the walls of that tube, to provide a selected inverse relationship between heat transfer coefficient and engine speed whereby automatic regulation may be achieved of the heat supplied to the fuel-air mixture for all engine speeds.

Abstract: An arrangement for inducting auxiliary heated air into the intake manifold of a carbureted internal combustion engine in an efficient, optimal manner, which achieves substantially complete vaporization of the fuel with a relatively low volume of auxiliary air. The arrangement includes an air induction tube receiving filtered air, which tube is connected to a heater tube disposed within the interior of the exhaust system or to a hot water heat exchanger to heat the auxiliary air, which is then inducted into the engine intake manifold via an insulated double wall tube and a metering block which produces a controlled flow of the heated air into a pair of distributor tubes extending from the metering block into branch cavities of the engine intake manifold.

Abstract: An internal combustion engine with applied ignition, preferably with a warm-up controller for a continuously operating fuel injection, in which the control pressure of the fuel injection is discontinuously controllable in dependence on different parameters with one or several jumps in the characteristic curve.

Abstract: A fuel injection apparatus for an internal combustion engine comprises a fuel feeding device for feeding intermittently a high pressure fuel to a fuel injection valve apparatus for injecting fuel to the engine. The fuel injection valve apparatus comprises a valve housing formed with a fuel chamber and an injection orifice, and a needle valve element slidably disposed within the valve housing for opening and closing the injection nozzle orifice. The injection orifice is opened by the high pressure fuel supplied from the fuel feeding apparatus, and is closed by a biasing means such as a spring in association with a hydraulic thrusting means which accumulates the high pressure fuel to thrust the needle valve element toward the injection orifice closing position thereby to accomplish a rapid termination of the fuel injection. The fuel feeding apparatus comprises a cylinder and a plunger. The cylinder has a feed hole , while the plunger has a notch having a straight leading edge.

Abstract: A fuel flow control system which, in response to the true mass of air entering the throttle body of an engine, provides a regulated flow of fuel to the throttle body, thereby delivering the optimum mass fuel-air ratio to the engine and maintaining idealized engine performance. The air flow rate drawn through the throttle body by the engine is monitored along with air temperature and pressure, and an electronic control circuit computes the true mass of air and the ideal fuel flow rate which will produce the optimum mass fuel-air ratio. The circuit generates a command signal to a novel fuel flow regulating assembly which adjusts the fuel flow in response to the command signal. The regulating assembly includes a control valve positionable in response to the command signal and a pressure differential mechanism movably responsive to the control valve position. A fuel flow metering valve in turn is positioned by the pressure differential mechanism.

Abstract: A transistorized ignition system is protected against interruption of power supply by, for example, turn-off of the main or ignition switch while the transistor is in conductive condition so that, upon sudden interruption, an ignition event could be triggered at a time unsuitable for the remainder of the engine. A turn-off protection circuit is provided which includes a coupling resistor connected to the junction of the primary of the ignition coil and the main ignition current supply transistor thereto. The coupling resistor is connected in a circuit which holds the main current supply transistor in conductive condition, supplied from the energy stored in the ignition coil even after the main, ignition switch has been opened. A closed circuit for current flow due to this stored energy is provided within the overall ignition circuit.

Abstract: To provide for extended true running of the distributor shaft and prevent wear on relatively movable mechanical components within the distributor, such as a shaft and bearings, a centrifugal spark advance/retard mechanism, or the like, the relatively movable parts are included in the lubricating circuit of the engine, for example by being connected to the pressure lubrication system of the engine or located to be exposed to oil mist in the engine compartment and arising upon operation of the engine, so that the relatively movable parts are constantly lubricated by the engine lubricating system.

Abstract: The lubrication of an engine crank shaft is monitored using a wheatstone resistance measuring bridge one of the arms of which includes lubricating oil ducts between the crank shaft and crank case of the engine, balanced against a reference resistance provided by a resistance measuring cell through which the engine lubricating oil flows. The resistance measuring cell may have an external heater for heating the oil in the cell to a temperature compatible with that of the oil in the engine bearings when the engine is running.

Abstract: A rotary internal combustion engine includes a housing having trochoidal inner periphery, a substantially triangular rotor having three arch-like peripheral faces and rotatably mounted within the housing, a recess of substantially spoon-like shape provided in each of the peripheral faces of the rotor, a fuel port provided in the housing in communication therewithin, and an elongated air intake port provided in the side wall of the housing so as to be opened and closed by a side face of the rotor according to the rotation thereof. The air intake port is inclined upwardly in the direction of rotation of rotor, and is disposed at such a relative position that it gradually moves towards the rear end portion of a combustion chamber defined by the inner periphery of the housing and each of the peripheral faces of the rotor. To the air intake port, may be connected means for adjusting the air flow in response to the operating mode of the engine.

Abstract: A method and apparatus for aligning the streets of a semiconductor wafer for sawing or scribing with a single motion control switch. One end of a street is first aligned with a reticle in the Y-direction with this motion control switch. The wafer is then moved in the X-direction while the operator with the same control switch, controls the rotation of the wafer so as to align the street with the reticle. Automatic Y-direction alignment is provided during this rotation by determining the Y-direction misalignment which occurs from the rotation, and by automatically moving the wafer saw blade assembly in the Y-direction to provide the necessary compensation.

Abstract: A self-extinguishing grill combination comprises an hibachi-type grill and a substantially air-tight pouch dimensioned to receive the grill with its charge of burning solid fuel. The pouch has an opening sized to pass the grill. The opening is provided with a substantially air-tight closure adjustable between open and closed positions. The grill with its charge of burning fuel is inserted into the pouch through the opening after which the opening is sealed with the closure, thereby sealing off the pouch interior and extinguishing the burning fuel.

Abstract: A combination stove-fireplace assembly for an open-top fire pit. A fire hood supported on legs above the pit is vertically movable between raised and lowered positions through a cable and pulley arrangement located below the top of the pit. The hood is vented by a unitary stack which moves vertically through a roof mount as the hood is raised and lowered.