Abstract: A method for monitoring efficiency of an exhaust gas aftertreatment device is presented. The efficiency is inferred from the amount of fuel required to perform purge of the device after it has been saturated with exhaust gas components such as NOx and oxygen to a predetermined level. The level of saturation is determined from the amount of tailpipe emissions as indicated by the tailpipe exhaust gas sensor. This method improves precision in determining device efficiency and therefore eliminates unnecessary sulfur purges and improves fuel economy. Also, better emission control is achieved since the tailpipe exhaust gas sensor allows closed loop monitoring of NOx emissions and prevents the device from overfilling.

Abstract: A method for determining the efficiency of a three-way catalyst is presented. It is shown that more accurate results are achieved if the efficiency estimates are performed when the engine is at idle or during low load operating conditions. The efficiency is inferred from the amount of fuel required to purge the device after it has been fully saturated with oxidants due to lean operation. Due to improved accuracy and reduced reductant waste, this method allows for improved emission control and fuel efficiency.

Abstract: An apparatus for reliably and quickly detecting a fault in an exhaust system of an internal combustion engine, based on an output of an air/fuel ratio sensor mounted in the exhaust system. The apparatus includes: a control unit which provides a rich air/fuel ratio forcefully and continuously when detecting the presence or absence of a fault in the exhaust system; and a determining unit which determines that there is a fault in the exhaust system when the sensor mounted in the exhaust system does not produce an output that corresponds to the rich air/fuel ratio being provided under control of the control unit. The detection accuracy of the apparatus is enhanced by making provisions to perform the exhaust system fault detection when the engine is in an idling state in which the fluctuation in pressure is large and the effect of exhaust pipe leakage is most pronounced.

Abstract: Achieved is an air/fuel ratio control apparatus for an internal combustion engine where the purification ability of a three-way catalyst is brought back to an optimal state immediately after a fuel cut by expelling oxygen absorbed by the three-way catalyst due to the fuel cut without being affected by the oxygen absorption amount of the three-way catalyst before the fuel cut.

Abstract: A method and apparatus for controlling the operation of a “lean-burn” internal combustion engine in cooperation with an exhaust gas purification system having an emissions control device capable of alternatively storing and releasing NOx when exposed to exhaust gases that are lean and rich of stoichiometry, respectively, optimizes vehicle fuel economy while complying with emissions standards by prohibiting lean engine operation only when tailpipe emissions, calculated in terms of grams of an exhaust gas constituent per vehicle mile traveled, exceeds a permissible threshold value. The threshold value is preferably itself periodically determined based upon a detected or determined level of vehicle activity, such that vehicle activity characterized by greater transient engine operation prescribes a relatively lower level of permissible vehicle emissions.

Abstract: A method for regenerating a diesel particulate filter (10) in the exhaust gas system of a diesel engine (5) is disclosed in which particulate matter is burned by increasing the temperature in the diesel particulate filter (10).

Abstract: An exhaust purifying method and apparatus of an internal combustion engine are provided with an exhaust switch valve for switching a flow of exhaust gas flowing into an exhaust filter. By switching the exhaust switch valve, the exhaust gas is fed from one side and the other side of the filter, thereby stirring the soot (particulates) in the exhaust gas deposited on the filter having a NOx absorbent and an active-oxygen discharging agent supported thereon. Thus, the soot in the exhaust gas is continuously burned. Moreover, the switching of the exhaust switch valve and the rich spike are inhibited from being conducted simultaneously. In the case where the rich spike is conducted in order to discharge and reduce NOx absorbed in the NOx absorbent, the exhaust gas containing a large amount of HC and CO can be prevented from being discharged into the atmosphere without being purified.

Abstract: In a rotary servo valve (1) provided with at least two kinds of pump port (33, 39) for high and low pressures, a spool (11) that is free to rotate and free to reciprocate linearly is installed into a spool guide hole (7) of the valve main body (9), a servo motor (15) that rotates and drives the spool and a linear type actuator (13) that reciprocatedly travels are disposed, and the pump ports are selectively changed over by the reciprocation of the spool, and cylinder ports are selectively changed over by the rotation and at the same time the flow rate is controlled.

Abstract: Hydraulic driving device with a hydraulic motor and a bearing arrangement in which the output shaft of the hydraulic motor is supported. Typically, the bearing arrangement is axially supported on the output shaft between a shoulder of the output shaft and a nut screwed onto the output shaft. To reduce overall length, the invention provides that the shoulder is located on the side of the bearing arrangement opposite from the end of the output side of the output shaft, and a friction-disc pack directly bears on the bearing arrangement. The motor has a braking device, including the friction-disc pack and at least one braking cylinder with a spring chamber and a release chamber. A braking valve in the braking position supplies the spring chamber with the load pressure and the release chamber with the tank pressure, and in the release position supplies the spring chamber with the tank pressure and the release chamber with the load pressure.

Abstract: Micromechanical actuation apparatus includes a substrate with an actuator mounted on the substrate and a micro-transmission mounted on the substrate coupled to the electrothermal actuator. The actuator, such as an electrothermal actuator, is responsive to electrical power to drive two output beams inwardly or outwardly in opposite directions. The micro-transmission couples the force from the two output beams and transmits the displacement of the output beams to an output node of the micro-transmission. The amplification of the micro-transmission provides a much larger displacement of a beam connected to the output node than the displacement of the output beams of the actuator.

Abstract: A turbocharged internal combustion engine is provided with a diverter valve arranged to divert part of the exhaust gas flow along a conduit for introduction into a turbine region. Exhaust gases flow from the conduit, through appropriate galleries in the turbocharger casing, into internal passages formed in at least some of the stator blades. From the internal passages, the exhaust gas passes through holes positioned near the downstream ends of the convex surfaces of the stator blades. In this manner, the diverted gas is introduced into the comparatively lower pressure of the turbine region thereby enabling the diverted exhaust gas to rejoin the mainstream exhaust gas and to do useful work in driving the rotor blades while, at the same time, avoiding choking the stator blades.

Abstract: The present invention is directed to a system and method for controlling an engine braking system having an engine with at least one intake and exhaust valve, intake and exhaust manifolds, a turbocharger connected to the intake and exhaust manifolds, and at least one pressure regulation valve. The method may comprise the steps of measuring a value of an engine parameter; adjusting the pressure of the exhaust manifold responsive to the measured engine parameter value; actuating the at least one exhaust valve; and adjusting a pressure gradient across the turbocharger.

Abstract: A method and apparatus for efficiently generating mechanical or electrical energy. The method includes the steps of heating a vaporizable, first liquid heat transfer medium to generate a high pressure vapor; utilizing the high pressure vapor to provide mechanical energy and thereafter condensing the vapor to a liquid; and recycling the condensed liquid to the heating step for re-use as the first liquid heat transfer medium. The apparatus includes a closed loop heat transfer medium system having a first heat exchanger for heating a vaporizable, first liquid heat transfer medium to generate a high pressure vapor; a mechanical device which utilizes the high pressure vapor to provide mechanical energy; a condenser for condensing the vapor to a liquid; and piping for fluidly connecting the first heat exchanger, mechanical device and condenser, and for recycling the condensed liquid to the first heat exchanger for re-use.

Abstract: A system of combining balanced, independent, self-starting and initially separated internal combustion engines, wherein engines not immediately required for power can be shut down. Shut down engines are disconnected from the running engine or engines, and drive train. This system will dramatically reduce fuel consumption and the amount of exhaust gases. A microprocessor determines vehicle power requirements from engine sensors. Hydraulic pistons under control of the microprocessor bring the individual engine units into and out of engagement with each other. Friction plates and locking pins are provided for coupling the crankshafts at predetermined relative angular positions.

Abstract: A combustor can simultaneously reduce the amount of NOx exhaust and combustion oscillation. The combustor has an internal cylinder which accommodates a premixing nozzle and an external cylinder which accommodates the internal cylinder, and includes an air flow passage which supplies air from a compressor to the premixing nozzle. The air flow passage is provided with a punched metal plate near the maximum velocity fluctuation position whereat the velocity fluctuation of the air flow increases to a maximum.

Abstract: An assembly method in which a brazing metal is initially filled into radial wells pierced in an annular injection piece having first injection orifices for discharging a primary fuel, and in a cylindrical endpiece surrounding the annular injection piece and having secondary injection orifices for discharging a secondary fuel; thereafter the annular injection piece is fitted inside the cylindrical endpiece and these pieces are together fitted on a first tube for feeding primary fuel and a second tube for feeding secondary fuel and surrounding the first tube, and also to an outer wall of the injector; finally, the end portion of the injector as assembled in this way is placed in an enclosure where it is heated so as to melt the brazing metal to unite the parts.

Abstract: A method of utilizing a methane-containing gas by feeding the methane-containing gas to a gas engine of a gas engine/generator assembly generating electricity comprises the step of passing combustion air containing an inert gas through a membrane separating installation to reduce the content of the inert gas before feeding the combustion air to the gas engine.

Abstract: A combustion chamber according to the invention has a number b0 of annularly arranged burners, of which a number k of modulatable burners have means for modulating a fuel mass flow, k being k<b0, and the modulatable burners being arranged in such a way that between every pair of adjacent modulatable burners are arranged in each case a1, a2, . . . ak nonmodulatable burners, and that the values a1+1, a2+1, . . . , ak+1 are not integral divisors of b0. In a preferred embodiment of the invention, a highest value of LCM(b0, a1+1), LCM(b0, a2+1), . . . LCM(b0, ak+1) is maximum, LCM designating the lowest common multiple. It thereby becomes possible to damp a maximum number of azimuthal vibration modes of the combustion chamber by means of a minimum number of modulatable burners. Each pair of modulatable burners gives rise to at least one undesirable vibration or instability which, however, is damped by the other modulatable burner or burners arranged according to the invention.

Abstract: Methods and apparatus for control of NOx in catalytic combustion systems, and more particularly to control of thermal or/and prompt NOx produced during combustion of liquid or gaseous fuels in the combustor sections of catalytic combustor-type gas turbines, by controlled injection of water in liquid or vapor form at selected locations, orientations, amounts, rates, temperatures, phases, forms and manners in the compressor and combustor sections of gas turbines. The ratio of thermal NOx ppm reduction to water addition, in weight %, is on the order of 4-20, with % NOx reduction on the order of up to about 50-80% and NOx of below 2 ppm. Liquid water, steam or superheated steam can be used to reduce NOx in combustion systems operating at reaction zone temperatures above 900° C., preferably 1400° C. to 1700° C. The amount of water added is sufficient to provide a concentration of water in the range of from about 0.

Abstract: Apparatus and methods for performing switching of heat flow in magnetic refrigeration systems are provided. In one embodiment, microelectromechanical (MEM) switches are provided for switching from a heat absorption phase and a heat rejection phase of a magnetic refrigeration cycle. In other embodiments, these MEM switches are replaced by thermoelectric switches. The thermoelectric switches operate such that an “on” state is defined as heat flow being allowed by virtue of the thermal conductivity of the thermoelectric switch. An “off” state is defined as a net zero heat flow through the thermoelectric switch obtained by providing a current that is just sufficient to offset the heat flow through the thermoelectric switch due to its thermal conductivity. In some embodiments, the thermoelectric switches are “directly coupled” thermoelectric switches, meaning that they are energized by a direct electrical coupling to a current source.

Abstract: A method and apparatus for measuring the cooling efficacy of air comprising coupling a resistive element to a temperature sensing element, applying a voltage across the resistive element, adjusting the voltage across the resistive element so that the temperature indicated by the temperature sensing element is nearly proportional to the temperature of a locally disposed heat sensitive component for a change in environmental parameters, and coupling the output of the temperature sensing element to a control circuit wherein the control circuit controls a space cooling element.

Abstract: The present invention discloses a miniature thermodynamic device that can be constructed using standard micro-fabrication techniques. The device can be used to provide cooling, generate power, compress gases, pump fluids and reduce pressure below ambient (operate as a vacuum pump). Embodiments of the invention relating to the production of a cooling effect and the generation of electrical power, change the thermodynamic state of the system by extracting energy from a pressurized fluid. Energy extraction is attained using an expansion process, which is as nearly isentropic as possible for the appropriately chosen fluid. An isentropic expansion occurs when a compressed gas does work to expand, and in the disclosed embodiments, the gas does work by overcoming either an electrostatic or a magnetic force.

Abstract: A Stirling refrigerating machine, comprising a regenerator provided in a flow path for a working medium reciprocating between an expansion space and a compression space formed in a cylinder, wherein a flow strengthener making uniform the flow of the working medium passing through the regenerator is provided on one or both of the expansion and compression space sides of the regenerator, whereby, because the nonuniformity of the flow of the working medium passing through the regenerator is improved, a regenerated heat exchanging efficiency can be increased, and thus the performance of the refrigerating machine can be increased.

Abstract: A process is provided for the safe storage of sodium percarbonate in a bulk container that is substantially closed to the ambient atmosphere. A temperature is measured at at least one position inside the sodium percarbonate stored in bulk and, with an increase in temperature within the range of 0.5 to 10° C. per day, in particular 1 to 5° C. per day, dry air is passed periodically or continuously through the bulk material until the increase in temperature has fallen to a value of less than 1° C. per day in particular less than 0.5° C. per day.

Abstract: A method for providing refrigeration wherein a first multicomponent refrigerant is condensed to form a saturated liquid and vaporized against a condensing second multicomponent refrigerant which has a dew point less than the dew point and preferably the bubble point of the saturated liquid, and has a bubble point greater than that of the vaporizing first multicomponent refrigerant, and after providing refrigeration to a refrigeration load, may be superheated against the condensing first and second multicomponent refrigerants.

Abstract: This invention relates to an air-conditioning system for passenger aircraft for conditioning humidity-containing air under excess pressure for air-conditioning a passenger aircraft cabin, comprising at least one compressor and two expansion turbines, where in accordance with the invention a droplet coalescing device with succeeding water separator is disposed between the expansion turbines.

Abstract: An air conditioner having a compressor, refrigerant condenser coil and accumulator submerged in water in a water tank, wherein the water is cooled by evaporative cooling when air is drawn through water sprayed into an air inlet duct communicating with the water tank. The compressor is cooled by the water in the water tank which is cooled by evaporative cooling. The water level in the water tank is maintained by a float valve connected to a water line to replenish evaporating water.

Abstract: Described is a climate control system with an air conditioning or a heat pump and a method to provide desirable temperature and humidity of indoor air. In addition to a compressor, a condenser, an evaporator, and an expansion device, the air conditioner/heat pump includes an auxiliary coil, valve means, refrigerant communication means, and control means. In hot climate the system operates in two separate modes: a conventional cooling mode and a cooling mode with enhanced dehumidification. In the conventional cooling mode the valve means direct refrigerant leaving the condenser to the expansion device and then to the auxiliary coil to absorb heat from conditioning air by refrigerant in the auxiliary coil. In this mode an extra amount of liquid refrigerant is stored in the refrigerant communication means.

Abstract: A sound suppression system for suppressing the noise of an engine within an enclosure of an outdoor unit for a transport refrigeration system. A resonator is provided to suppress noise caused by the inflow of air to the air intake manifold of the engine, and a sound panel is provided in the bottom wall of the enclosure to suppress noise emanating from the engine. The resonator and the sound panel are co-located in the same plane and are preferably integrally formed of a molded plastic material.

Abstract: A cooling system for cooling one or more components that produce heat. The cooling system includes sprayers configured to spray cooling fluid toward the components. A detection system includes a radiation source and a radiation sensor that pass radiant energy in the vicinity of the component such that the radiant energy is affected by passing through the vaporizing spray coolant. A controller controls the flow rates of the sprayers in response to levels of radiant energy detected by the radiation sensor, allowing the controller to more accurately control the wall temperature and cooling regime achieved by the spray cooling. The source and sensor are aimable or otherwise configured for gathering information for different thermal zones of the component, providing the controller with information that is helpful in separately controlling the wall temperature and/or cooling regime in each zone.

Abstract: The air conditioning system 100 may include a compressor 101, a heating circuit 152, and a capacity controller 181. The compressor 101 has a suction port 116, a discharge port 120, a driving unit 130 provided within a driving chamber 110, a first passage 201 and a second passage 105. The driving unit 130 may decrease compressor output discharge capacity when the pressure within the driving chamber 110 increases. The first passage 201 may connect the discharge port 120 to the driving chamber 110 and the second passage 105 may connect the driving chamber 110 to the suction port 116. The capacity controller 181 may open the first passage 201 when the refrigerant discharge pressure results predetermined pressure. By opening the first passage 201, the high-pressure refrigerant may be released from the discharge port 120 to the driving chamber 110 through the first passage 201.

Abstract: A portable refrigerator kit for perishable pet products for keeping perishable pet products from spoiling while the user is out camping with one's pets.

Abstract: A system for shading an air conditioning unit from sunlight uses one or more sheets of solar screen material attached to a frame. The frame is coupled to the air conditioning unit using various bracketing arrangements. The system is easy to install, does not significantly restrict air flow, is adjustable, and is attached directly to the air conditioning unit.

Abstract: A refrigeration system includes an evaporator housing sealed to a first side of a circuit board containing a logic module, the evaporator housing including an evaporator block in thermal communication with the logic module. The evaporator housing further includes at least a humidity sensor for detecting a humidity within the evaporator housing. In another aspect of the invention, the refrigeration system includes a heater on a second side of the circuit board opposite the evaporator housing, the heater being in thermal communication with plated through-holes of the circuit board to maintain the circuit board above local ambient temperature. In another aspect of the invention, a source of dry pressurized air is provided into the sealed evaporator housing through a though-hole drilled directly under the logic module.

Abstract: The present invention relates to a mechanical means for defrosting plates used in cold storage. Frost reduces the transfer of heat to the plates and partially or totally obstructs the passage of air. Several methods are used to remove frost from plates: hot water, sprayed steam, hot gas, heating elements. In the present invention, scrapers sweep the surface of the plates to remove the frost. This method allows to remove the frost while the plates are being discharged, which improves the performance of the plates and does not affect the residual charge of the plates. The proposed defrosting system is made up of vertical scrapers located on either side of the plates. The upper and lower extremities of the scrapers are fastened to scraper supports. These supports move along tubular guide bars which are parallel to and located beneath and above the plates.

Abstract: An alternative powered evaporative cooler has a squirrel cage fan. A low voltage DC motor is provided to power the squirrel cage fan. A pulley system is coupled to the squirrel cage fan and the low voltage DC motor for transferring energy from the low voltage DC motor to rotate the squirrel cage fan. A low voltage DC power source is provided to power the low voltage DC motor.

Abstract: The present invention is directed to an ice cube catcher that is attachable to a refrigerator door to catch ice cubes dispensed from the outlet of the dispenser. Preferably, the ice cube catcher includes a body that has a lower integral portion and two end portions. The integral portion and ends contact the refrigerator once the catcher is mounted on the refrigerator door. The body may be a single piece construction or be constructed of two body members that are joined together in a telescopic fashion such that the length of the catch can be adjusted to accommodate different size ice cube dispensers. The ends of the body have flanges or protrusions upon which are secured magnets or other types of attachment fixtures for mounting the catcher onto the refrigerator.

Abstract: A computer system is described having a refrigeration cycle for a logic processor each utilizes first and second refrigeration cycles, each including a respective adsorber/desorber. Each adsorber/desorber is alternatingly cooled and heated. A liquid is adsorbed into the adsorber/desorber when being cooled and desorbed when the adsorber/desorber is heated. When the liquid is desorbed from the adsorber/desorber, and a checkvalve is closed, a pressure of the liquid increases. The adsorber/desorber together with the checkvalve act as a compressor in the respective refrigeration cycle. Heating and cooling is alternated so that one adsorber/desorber always adsorbs liquid while the other adsorber/desorber desorbes liquid. Thermal swings of the logic processor are thereby avoided.

Abstract: The present invention provides a structure of an evaporation region of an absorption diffusion type refrigerating circulation. The refrigerating circulation comprises a generator, a rectifier, a condenser, an evaporator, a concentrated ammonia aqueous solution tank, and an absorber. An ammonia liquid pipe and a hydrogen pipe are arranged in a pipeline of the evaporator. The evaporator at the evaporation region has a simple shape and structure, and can be processed easily, hence saving the space thereof. Because the ammonia liquid pipe and the hydrogen pipe are arranged in the evaporator, the effect of heat exchange thereof is better, and the refrigerating temperature is lower.

Abstract: Saturated or sub-cooled liquid is supplied to the expander of an expressor. Starting just prior to the end of the inlet process or just after the completion of the inlet process, high pressure vapor from the expressor compressor discharge is supplied to the cavity defining a trapped volume under going expansion.

Abstract: A jewelry piece to hold the ends of a plurality of parallel beaded jewelry strings has two interdigitated U shaped bodies. Each body has a slot along at least one edge in which to slide the end pieces of each bead string. This jewelry piece can be used as a coupling for a necklace or bracelet or for an earring with hanging beaded strings.

Abstract: A molten glass (8) is successively supplied from a nozzle (5) to a plurality of molding dies (7) and gradually cooled to form glass masses. Each glass mass is reheated in an air atmosphere to a temperature corresponding to a viscosity of 104-106 poises and press-molded by a mold to produce a press-molded product. The press-molded product is polished to form a final glass product.

Abstract: The invention relates to a method and apparatus for supporting the middle section of a glass panel to be bent in a mold. During a preheating process of a glass panel, its middle section is supported by middle support elements carried along with a mold carriage. At the start of a bending process, the middle support is released by pushing bearing rods through the bottom of the mold carriage. The middle support for the glass panel is lowered upon the bearing rods gradually under the control of glass panel thermometry. A controlled hoisting and lowering of the bearing rods is performed by a hoisting and lowering mechanism present in a carriage elevator. The invention makes it possible to implement a middle support also in an automatically operating serial furnace.

Abstract: In a method of manufacturing a chemical reinforced glass substrate, consideration is previously made about a relationship between conditions of chemical reinforcement for a glass substrate and deformation caused by the chemical reinforcement at an edge portion of the glass substrate. The glass substrate is chemically reinforced on the basis of the relationship so that an edge profile is shaped into a desirable edge profile during the chemical reinforcement. The resultant chemical reinforced glass substrate is flat and smooth in a wide area and effective to improve a recording density and to avoid head crashes.

Abstract: The invention relates to a process for the production of internally-hardened glass tubes, in which in a tube-drawing process for the production of glass tubes that is known in the art, a coated drawing tool, for example in the process according to Danner a coated mandrel or in the process according to Vello or in A-drawing process a coated needle, is used, whose coating releases coating material upon contact with the inside surface of the tube that is produced and accumulates on the inside glass surface. The chemical resistance is increased by this internal hardening. The invention also relates to devices for implementing this process and uses of the tubes that are produced according to these processes.

Abstract: A device for producing optically homogeneous, streak-free quartz glass bodies having a large diameter including a furnace or melting device having an inner chamber with a pair of openings opposite one another. One or more movable burners are displaceable into one of the openings and the respective glass body to be produced is located in the other opening. Both the burner and glass body are movably positioned. In the course of the production of the quartz glass body, a relative movement is effected in the axial and radial directions between the burner and the quartz glass body such that the distance from the burner outlet opening pertaining to the quartz glass body decreases as the distance from the burner to the X-X axis of the quartz glass body increases.

Abstract: A retaining device is fitted into the end of the handlebar of a personal vehicle such as a bicycle or motorcycle. The device has a shackle, a cable, or a spring loaded lever which extends out of the distal end of the handlebar whereby it can be used to retain such items as a motorcycle helmet or a flotation vest. The retaining device may include a lock. A cable can be used, and a cap fitted over the retaining device attached to the distal end of the cable.

Abstract: A lock cylinder-free lock device is constructed to include a casing, a locating block fixedly covered on a top side of the casing, the locating block having a plurality of vertical pinholes, a locking block moved in the casing between the locking position and the unlocking position, the locking block having spring-supported pins respectively extended out of a stepped top sidewall thereof and adapted for engaging into the pinholes of the locating block when the locking block moved to the locking position, and a key adapted for unlocking the locking block, the key having bottom pins of different lengths adapted for inserting into the pinholes of the locating block to disengage the spring-supported pins the locating block.

Abstract: A leaf spring includes a plate having a hole into which a key cylinder is inserted, a notch into which a convex portion of the key cylinder is inserted, and spring tabs which can be bent elastically in the insertion direction of the key cylinder formed thereon. The top end of the spring tabs is inclined with respect to the bottom of the rectangular groove before bending, so that the top end is partially brought into contact with the back wall edge after bending. The key cylinder can be attached simply by inserting the key cylinder into the hole of an attachment unit. Freedom of the assembly order is therefore increased. Furthermore, the vibration of the key cylinder in the insertion direction of the key cylinder is reduced.

Abstract: An apparatus for celibrating rotary power assembly impulse tools comprises a variable rate simulated test joint in which a rotary shaft is braked by brake shoes in direct contact with the shaft under the control of a computer. The braking torque applied to the shaft by the brake shoes is gradually increased while the shaft is driven at free-running speed by the tool being calibrated, and the pulsed output of the impulse tool is monitored. The monitored pulsed output is initially erratic, but settles down to a regular stream of output pulses. The first pulse of that regular stream can be identified. The magnitude of the braking torque is then increased as a linear function of time with a predefined gradient representative of the torque rate of the joint being simulated, commencing with the identified first pulse. The apparatus is the first such apparatus to be able to provide thoroughly reliable and consistent torque calibration for impulse tools.