Abstract: A spindle brake for a spinning or twisting machine has a pair of arms whose jaws are engageable with the whorl of a spinning or twisting spindle. One of these arms carries a belt-lifting roller adapted to lift the belt away from the whorl when the brake is actuated thereby preventing friction between the belt and the immobilized whorl.

Abstract: A tendon for use in posttensioning prestressed concrete comprising a multi-wire strand wherein individual peripheral abutting wires define an overall somewhat regular geometric cross-sectional strand configuration. The strand has both internal and external interstices wherein said external interstices are substantially fully filled with a dielectric plastic material such as a high molecular polyolefin material such as high density polyethylene. The plastic material forms a casement which completely surrounds the strand and forms a smooth outer surface having a circular cross-sectional configuration. A friction reducing grease-like material is coated on the outside of the casement and the entire structure thereafter enclosed in a plastic jacket. The above structure is formed by progressively extrusion coating the wire strand with the dielectric plastic, the thus coated strand with the grease-like material and the thus coated composite with plastic to form the jacket.

Abstract: Apparatus to cause a running length of yarn to vibrate at its harmonic frequency and to electronically measure the harmonic frequency thereof to provide a signal which can be employed to maintain and/or correct the parameters of the system to maintain a desired tension in the yarn being run.

Abstract: An apparatus for the conjoint gripping of bobbins by means of pins or spigots formed of a rigid material, mounted at a support or carrier, and insertable into the bobbins. An expansible hose or tube member extends lengthwise of the support, this hose member when subjected to an increased internal pressure serving to press the bobbins against the pins or pin members inserted therein. This known apparatus has the advantage that there does not occur damage to the entering pin members, nor does there arise permanent deformation or destruction thereof. Yet, such apparatus possesses the shortcomings that the seized bobbins, when pressed against the pin members, are not positioned with sufficient accuracy in a direction parallel to the longitudinal direction of the support.

Abstract: A manually operated spinning machine which is readily collapsible for transportation or storage. The spinning machine consists of a compartment which has an open front and a lid, the lid being movable between a closed position and an open position. A wheel is housed within the compartment for rotation in a vertical plane parallel to the front. A spinning head is mountable on the inside of the lid so that, when the lid is in the open position, the spinning head can be positioned with its pulley aligned with the wheel. A belt is provided for coupling the wheel and the pulley. Treadle means are connectable to the wheel through a crank for effecting rotation of the wheel.

Abstract: Installation for generating superheated steam from raw water containing salt using preheaters for heating the raw water. The last preheater, as seen in the flow direction of the raw water, is followed via a control valve by a decompression cylinder. Part of the raw water evaporates and the vapor is withdrawn from the dome of the decomposition cylinder by a compressor which compresses and heats it and discharges it as superheated steam.

Abstract: An internal combustion engine misfire detection system is described which counts the transitions in the output of an oxygen sensor in a closed loop air/fuel ratio controller over a predetermined time period and compares the transition count with a limit count determined to be the number which would occur at the engine speed during a misfire condition. When the number of transitions exceeds the limit count, a warning lamp is energized and secondary air to an oxidizing converter is diverted to the atmosphere.

Abstract: This engine is designed to be operated by diversity of methods. It comprises a master cylinder which has the shape of the capital letter "T". Oil is compressed in this cylinder from its vertical line. The two opposite sides of this master cylinder have conical channels in them. Next to each side of the master cylinder and outside it, there is a rotating disc with poaches or pockets in it. Deep in each poach there is a draining duct which opens in the thickness of that rotating disc. The two rotating discs are attached together by an axle crossing the master cylinder from one side to another. As the assembly is tight, and if an amount of oil is compressed in the master cylinder through its vertical or pumping line, then the oil will have no passage out of it except through the conical channels of the cylinder's sides.And as oil gushes under pressure from the sides it encounters the rotating disc with the poaches, and thus forces it to spin to be able to get out from it.

Abstract: In variable fill-type fluid couplings, a driving impeller and a driven runner are coupled for joint rotation by means of a liquid medium in an active liquid chamber formed by the rotating members. The active liquid chamber is continuously bled at a selected constant rate and continuously fed at a rate that can be changed to control the volume of fill of the liquid therein. Charging liquid is fed from a source to enter a mouth of the active liquid chamber. To insure that all of the charging liquid enters the active liquid chamber, the mouth is provided with a charging liquid collector that forces charging liquid past the mouth and into the active liquid chamber. The liquid collector can comprise an outer ring, an inner ring, and a plurality of pitched blades between the two rings. The collector rotates with the driving impeller, thereby forcing charging liquid past the mouth and into the active liquid chamber.

Abstract: There is disclosed a throttle control means connected to the throttle which in response to operator input puts the throttle in one of two positions, the first fully open and the second an idle position, a transmission control system including desired speed input means responsive to operator input producing a signal indicative of the drive wheel speed desired by the operator, actual speed means connected to the drive wheels for generating a signal proportional to the road speed of the vehicle, comparing means connected to the desired speed and actual speed means and to the transmission for comparing the desired speed means and the actual speed means and, responsive to results from such comparing, generating a control signal changing the output-to-input speed ratio of the transmission.

Abstract: A short master cylinder uses solenoids to control the master cylinder compensating and bypass functions. The pressurizing pistons each use only one seal. There is a unitary primary piston and booster output push rod. The booster power piston return spring returns the primary piston and, through a lost motion interconnection, the secondary piston, omitting the secondary piston spring. Brake pedal travel and pressure sensors control the solenoid valves, reducing lost brake pedal travel.

Abstract: A low-pressure casing for a brake booster for automotive vehicles comprises two casing shells which are sealingly interconnected and include a reinforcement plate at the inner surface of the casing end wall of each casing shell. The reinforcement plate is fastened to the master brake cylinder or to the automotive vehicle by means of fastening bolts. The section of the casing end wall which lies radially outside the reinforcement plate is of truncated-cone-shaped construction and merges into a cylindrical section of the casing. Inserted in the inner of the casing at the transition from the truncated-cone-shaped section into the cylindrical section is a prop ring which is via webs formed integrally with the reinforcement plate.

Abstract: High-pressure hydraulic hoses are employed in hydrostatic drive systems to interconnect the transmission and motors thereof. It is imperative that fluid leakage be held to a minimum, or preferably eliminated, particularly where a vehicle employing the drive system is operated in a high-temperature environment, such as a foundry. The hose assembly (13) of this invention provides a high degree of system reliability, relative to hydraulic leaks, and shields a high-pressure hose thereof (14) against damage and heat conduction to hydraulic fluid therein. The hose assembly (13) comprises a flexible high-pressure hose (14), an impervious flexible jacket (17) surrounding the hose in out-of-contact relationship therewith to define a fluid chamber (18) therebetween, and a mounting assembly (22) for mounting the hose (14) and the jacket (17) on a support member (23) to maintain them in out-of-contact relationship relative to each other.

Abstract: A master cylinder assembly has a low pressure, high volume displacement quick take-up chamber and a high pressure, low volume displacement pressurizing chamber formed by a stepped bore and a stepped piston. A compensation control and blow-off valve unit has a peripheral lip seal type valve providing compensation flow on brake release but preventing flow from the quick take-up chamber during brake apply. A normally closed check valve can open to provide communication between the quick take-up pressurizing chamber and the fluid reservoir. When the pressurizing cup for the high pressure chamber closes its compensation port, the check valve is subjected to the pressure in the quick take-up pressurizing chamber. Initial fluid flow is obtained from the quick take-up chamber past the pressurizing cup into the high pressure chamber.

Abstract: A master cylinder assembly has a low pressure, high volume displacement quick take-up chamber and a high pressure, low volume displacement pressurizing chamber formed by a stepped bore and a stepped piston. A compensation control and blow-off valve unit has a peripheral lip seal type valve providing compensation flow on brake release but preventing flow from the quick take-up chamber during brake apply. A valve body is integrally molded as a part of the reservoir. A normally closed check valve can open to provide communication between the quick take-up pressurizing chamber and the fluid reservoir. When the pressurizing cup for the high pressure chamber closes its compensation port, the check valve is subjected to the pressure in the quick take-up pressurizing chamber. Initial fluid flow is obtained from the quick take-up chamber past the pressurizing cup into the high pressure chamber.

Abstract: A short master cylinder assembly having a transversely disposed compensation and bypass port controlled by a check valve. The check valve is cammed to the open position by a pressurizing piston, and is closed by spring action upon movement of the pressurizing piston in the pressure actuating direction.

Abstract: An internal combustion engine is equipped with a supercharger which includes an intake port, an intake passage communicated with the intake port and a compressor interposed in the intake passage and compressing the intake air flowing through the intake passage. A unidirectional valve such as a reed valve is disposed inside the intake passage in series with the compressor in order to prevent backflow of the supercharged air inside the intake passage and thus to prevent a drop in the engine output when a throttle valve inside the intake passage is abruptly closed.

Abstract: An internal combustion engine, especially of the two stroke cycle diesel type, has a turbocharger with a supplemental mechanical drive for maintaining a minimum speed ratio relative to engine speed, when exhaust energy is insufficient to provide a higher speed, so as to maintain adequate charging air for engine operation throughout the engine speed range. In order to provide more efficient operation during engine operation at idle and in a lower portion of the operating range where a reduced amount of charging air is adequate, a secondary lower speed ratio is provided by the mechanical drive system. A speed responsive clutch is included to disconnect the higher speed primary drive during engine operation in the lower speed range and permit operation at the more efficient secondary speed ratio.

Abstract: An improved swirler assembly prevents flow separation in the diffuser secn. An annular swirling layer of air surrounds a linear jet with mixing occurring between these air flows prior to the diffuser section. A center tube through the swirler section provides the linear jet which mixes with the swirler flow in a mixing area prior to the diffuser section.

Abstract: A flameholder arrangement for a gas turbine combustor or the like includes a primary flameholder such as an elongated V-gutter extending across a main flow stream of gaseous components within the combustor. Vortices are shed by the trailing edges of the primary V-gutter flameholder and circulate in essentially two-dimension flow fields in planes normal to the elongated V-gutter to produce a downstream wake. In addition, a plurality of winglets are carried by the primary flameholder and are configured so as to shed vortices rotating about axes generally parallel to the main flow stream. More particularly, the winglets are carried by the outer surfaces of the V-gutter elongated walls, and lie in planes normal to the V-gutter walls and angled with respect to the flow stream. The resultant flow in the wake downstream of the V-gutter is three-dimensional for enhanced mixing of the gaseous components.

Abstract: A dilution cycle control system for an absorption refrigeration system is disclosed. The control system includes a time delay relay for sensing shutdown of the absorption refrigeration system and for generating a control signal only after expiration of a preselected time period measured from the sensed shutdown of the absorption refrigeration system, during which the absorption refrigeration system is not restarted. A dilution cycle for the absorption refrigeration system is initiated in response to generation of a control signal by the time delay relay. This control system is particularly suitable for use with an absorption refrigeration system which is frequently cycled on and off since the time delay provided by the control system prevents needless dilution of the absorption refrigeration system when the system is turned off for only a short period of time and then is turned back on.

Abstract: An automatic switching system for car cooler is disclosed.In consideration of the fact that the maximum load is imposed on an engine in acceleration period and the vacuum pressure is introduced to a diaphragm room and a diaphragm enforced by a spring member is in response to the vacuum pressure and the switching member is connected perpendicular to the center of the diaphragm is moved to make/break the contact of car cooler.By these provisions, the load on the engine in acceleration can be reduced and fuel consumption can be saved.

Abstract: An air cycle refrigeration system (10) pressurizes and cools flight compartment (115) and cabin (120) by the provision of chilled air thereto. Trim valves (180) and (205) set by a common actuator (195) control the mixture of uncooled system inlet air with the chilled air for individual regulation of the temperatures of the cabin and flight compartment.

Abstract: A heat pump system comprising a compressor and two heat exchangers connected in a refrigerating circuit is provided with refrigerant flow restricting means between the heat exchangers which imparts relatively high restriction to the flow of refrigerant between the heat exchangers in one direction and a relatively lower restriction to the flow of refrigerant between the heat exchangers in the opposite direction.

Abstract: A reversible, hermetically-sealed rotary compressor driven by a reversible electric motor for use in a refrigeration system comprising a compressor cylinder, a rotor eccentrically rotatable in the cylinder and a vane dividing the cylinder into interchangeable high and low pressure sides. A switch-over member automatically directs refrigerant into one or the other fluid passageways leading to the refrigeration system as an incident of motor rotation.

Abstract: The present invention relates to a process for making mesh tights or panty-hose, with seam and elastic belt incorporated therein, and to tights obtained thereby. Over the height of the elastic belt, in a strip of about 2 cm width on either side of the slit made for joining two hose elements by a seam, an elastic yarn is knitted with one needle out of two, on the needles of the strip with the exception of the central needle, then the basic yarn is knitted on all the needles of the circular machine used, the hose elements are slit along the wale of the central needle and are joined by a seam.

Abstract: An apparatus is provided for wet processing, preferably jet dyeing, textile material in endless rope form in an enclosed compact vessel by circulating the rope of material through a rope transport tube under the influence of a Venturi-induced jet of processing liquid and then collecting the material in the bottom of the vessel in an accumulator section at least partially submerged in the treatment liquid for recirculation through the transport tube by the jet of processing liquid. The apparatus is characterized by an accumulator section having a length at least one-half of the inside peripheral cross-sectional dimension of the vessel about a horizontal axis and a rope transport tube having a length of at least two-thirds of the inside peripheral cross-section dimension of the vessel about the horizontal axis and preferably positioned in the lower portion of the vessel to extend at least around the outside of the accumulator section and between the accumulator section and an inside wall of the vessel.

Abstract: A padlock is provided with bidirectional locking pins so that a key can be turned in either direction to operate the padlock. The padlock has a circular slot in the bottom portion to allow the insertion of a cylindrical key which has teeth and recesses corresponding with the lock pins. A locking ball holds a U-shaped lock bar in place. When the key is turned the ball moves inwardly to release the lock bar and to unlock the padlock. Turning the key in the opposite operation will lock the padlock.

Abstract: A cylinder type combination lock which is capable of being set in any desired combination of numbers and the like or changed from the once set specific combination to any other combination without using any tool.

Abstract: A hydraulically inflatable roll for flat rolled products is formed with a constant cross section internal fluid channel spaced uniformly from its working surface and extending spirally from end to end of the roll. The channel is connected through an end of the roll to a source of hydraulic fluid under pressure and also to a pressure transducer which in turn is connected to a display device. A proximity trigger is associated with an end of the roll so as to signal the start and the end of the circumferential travel of the channel past the contact line between roll and work when the roll is rotated, and the pressure exerted on that moving area in that interval is continuously measured and transmitted to the display device. Means are also disclosed for using that signal to control gauge and shape of the rolled product.

Abstract: There is disclosed a method for hot lubricated metal extrusion in which a billet is extruded into a solid or tubular form by means of a die and/or a mandrel with an organic lubricant interposed within a container, the method comprising feeding a combustion improver or a mixture of a combustion improver and water into an extruded product thereby burning off the carbide of the lubricant deposited on the surfaces of the extruded product.

Abstract: A fluidized bed die container holding a lubricant compound receives material which is to be reduced in a die. Pressurized air entering the bed beneath the lubricant agitates the particles to fluidize them so that contact is continually assured between the lubricant and the material, and the pressurized air is used to help cool the die.

Abstract: A rim forming apparatus, substantially comprising a frame having two superimposed drivable and substantially vertically slidable spindles for applying thereon rim forming tools or rolls, the lower spindle being movable by means of a hydraulic cylinder relative to the upper spindle, while the upper spindle is tiltable in the plane through the two spindles for compensating the deflection of the two spindles during the rim forming process, wherein the spindles carrying the rim forming rolls are each received in the one end of a swivelling arm the other end of which is mounted in the frame.

Abstract: An apparatus and method for manufacturing helically wound coils is disclosed which is capable of constantly producing dimensionally accurate edge-wound stator cores for dynamoelectric machines. The device uses a rotating ring of pins to pull a prepunched continuous strip of material between two components which operate cooperatively to deform the strip by thinning one of its edges. The deforming force is held constant to avoid aberrational deformations due to variations in strip thickness. A braking means provides tension on the strip as it progresses through its deformation and a suitable dereeler provides a continuous supply of straight, pre-punched strip material. The apparatus provides for either two power driven deforming members or one power driven member and one idler.

Abstract: The present invention relates to a cold pilger rolling mill and a method and means for manufacturing tubes with externally and/or internally thickened portions by reducing the tubes over a mandrel by means of grooved rolls which are mounted in a reciprocating roll stand. The invention provides several different varying diameter grooves on the rolls, which grooves can be brought into play one after the other by rotation of the rolls through an adjustment of the toothed racks on which the rolls are mounted. Consequently, at least one groove is provided for the rolling out of the required cross-section of most of the tube and a second groove is provided for the rolling of a thickened portion of the tube. It is essential that a smoothing zone is associated with each groove, and a zone for rotating and advancing the tube is associated with at least one of the grooves.

Abstract: A rod mill guide tube has a channel member of U-shaped cross-sectional configuration to which a cover member of T-shaped cross-sectional configuration is fastened whereby no seam edge is presented which a rod passing therethrough may contact.

Abstract: A combined portable sheet bending brake and coil holder wherein the coil holder is mounted and removed from the brake without the use of tools. The brake comprises a frame having a fixed jaw and a movable jaw, an anvil member secured to the fixed jaw, the movable jaw having a clamping surface movable between workpiece clamping and non-clamping positions relative to the anvil member. A bending member is hinged to the fixed jaw. The coil holder supports a coil of sheet material. The frame of the brake and the coil holder have interengaging hooks whereby the coil holder may be mounted and removed from the frame. When the coil holder is in position, the coil is positioned such that the leading edge of the coil may be extended between the clamping surfaces and clamped to permit cut off of a desired length of sheet material.

Abstract: A pipe press having a main press section and at least one end press section aligned with the main section for movement with and independently of the main section. The press is designed to accommodate elongate heavy gauge steel pipe blanks having lengths varying between the length of the main section and the combined composite length of the main and end sections. Because of the independence of the end section relative to the main section, the main section is loaded uniformly, even though a blank may be of a length less than the combined composite length of the press. The end press section is free to move axially relative to the main press section to accommodate elongation of a blank during operation of the press. Actuating cylinders for the press are arranged in paired sets extending transversely of the press dies to provide increased load capacity, without resorting to the use of extraordinarily large cylinders.

Abstract: A portable swaging tool for affixing, onto the end of an electrical cable, a terminal of the type that fits on the terminal post of an electrical storage battery such as may be used to drive the starting motor of an internal combustion engine. A handle carrying one of a pair of cooperating jaws has pivoted to it a clamping member carrying the other cooperating jaw so as to be juxtaposed to the first jaw when the free end of the clamping member is swung to and against the handle. The handle also carries clamping screw means for forcing the clamping member against the handle to clamp a terminal pre-inserted between the jaws and to swage the terminal tightly onto the end of a battery cable pre-inserted into a bore in the terminal.

Abstract: A system and process for calibrating a computer-based combustion gas analyzer is disclosed. The process includes introducing a series of gas samples into the analyzer, each sample containing a known concentration of a particular gas. The output of the analyzer is recorded and compared with the known gas concentrations to compute calibration coefficients which are used to calibrate the analyzer.

Abstract: An ultrasonic technique for remotely inspecting a body is described. A transducer (14), capable of generating and detecting ultrasonic signals, is coupled to the body. An ultrasonic signal (A.sub.o) is launched by the transducer (14) into the body (e.g. 10, 11) and is reflected by any imperfection (e.g. 12) therein. The effects of variations of the transmission coefficient between the transducer and the body are substantially eliminated by intentionally cutting a predetermined calibration notch (22) into the body under test. The analysis of the reflected ultrasonic signals at the notch (22) and at any imperfection (e.g. 12) within the body gives an indication of the quality of the body independently of the transducer/body transmission coefficient.

Abstract: Apparatus and method for nondestructive detection of loose parts or faulty onds in sound transducers by measuring erratic second-order nonlinear difference-frequency responses of the test transducer to a pulsed high level dual-frequency sound field produced by a high power projector. Such field may be generated by combining a high frequency carrier signal at frequency f.sub.o with a low frequency tone burst signal at frequency f/2 in a double balanced modulator so as to produce the dual-frequency pulse at f.sub.o +f/2 and f.sub.o -f/2. The test transducer converts the dual-frequency pulse into a plurality of linear and nonlinear frequency components including the difference-frequency f.

Abstract: A soft contact lens is rested freely on a planar or convex (preferably spherical) surface immersed in a liquid. The liquid enclosed between the inner surface of lens and the planar or convex surface is sucked off and the volume of sucked off liquid is measured. A vessel with immersion liquid, having a plane or convex surface of its bottom is provided with a hole, which is connected with a measuring capillary tube through a broadened inlet chamber containing a mercury drop. The measuring capillary tube is furnished with a scale corresponding to its volume and is connected, at the outlet, with a drain or pressure reservoir through a broadened outlet chamber and a unit for pressure variation. The volume sucked off is determined by the shift in the mercury drop.

Abstract: An inspection device detects flooding in a hollow structural member such as the leg of an oil or gas rig so as to detect the presence of through wall cracks in the member. The device comprises an ultrasonic transducer for transmitting a pulsed beam of ultrasonic sound to pass through opposing faced walls or wall portions of the member and a visual indicator responsive to time spaced echoes of the ultrasonic beam reflected respectively from the opposing walls or wall portions and received by the transducer to indicate the presence or absence of flooding in the member. The transducer is located in the bridge plate of a jig and its beam passes through an aperture in a support frame of the jig. The support frame has a pair of spaced magnetic feet attached to a bracket on the frame and a further magnetic foot secured to the frame, the feet permitting the jig to be clamped onto a steel rig member so that the transducer can be optimally aligned with the member to optimize received echoes.

Abstract: Sources which emit tracer gas at a known constant rate are positioned throughout a building. Samples of air are collected in selected rooms with constant rate adsorbent samplers. Samplers are analyzed in a laboratory to determine the tracer gas concentration during the period sampled, which concentration is compared to the known volume of the building to determine air infiltration rates. The tracer gas emission rate is rendered independent of room temperature by allowing the gas to escape through specially designed orifices which automatically open and close in response to changes in temperature. In one design, an orifice is formed in a material which expands and contracts with variations in temperature surrounded by a second, less elastic material. In another design, the area of an orifice is changed by a needle valve imbedded in a material which expands and contracts with temperature variations to move the needle in and out of the orifice.

Abstract: A rotational viscometer or tapered bearing simulator for testing motor oils and other fluids has a stator, a matching rotor fitting into it, and a drive shaft extending axially from the rotor. The shaft is direct-driven by a multispeed synchronous AC motor mounted on a low-friction turntable free to rotate over a limited arc. Torque experienced by the turntable is measured by a strain gage. The turntable rests on a platform which is vertically adjustable by and cantilevered from a fine screw-equipped elevator bracket. For temperature control, the stator is embedded in thermally insulating material and surrounded by an electric heating coil and a passageway through which air may flow. The stator and rotor have closely matched parallel surfaces produced by fine grinding. The rotor may have flats modified with a small fillet to entrap any minute particles in the test fluid. A pre-load assembly including weights applies measured torque to the turntable to calibarate and help stabilize the instrument.

Abstract: A pressure differential gage and a method for detecting the presence of noncondensible gases in a refrigeration system. The pressure differential gage comprises a housing, a diaphragm, first and second tubes, a reference fluid, and indicator means. The diaphragm separates the housing into first and second chambers. The first tube has one end in fluid communication with the first chamber and a second end open to receive a sample vapor, which determines the pressure in the first chamber. The second tube has one end in fluid communication with the second chamber and a closed second end. The reference fluid is located in the second tube and determines the pressure in the second chamber. The indicator means is actuated by the diaphragm to indicate when the pressure in the first chamber differs from the pressure in the second chamber.

Abstract: A thermal contact resistance having a thermocouple whereby the contact resistance between a probe of the thermocouple and a test material is less dependant on the thermal conductivity of the test material and more dependent on its hardness.

Abstract: A air flow rate meter apparatus includes an air bypass line, which branches off from a filter housing on the air intake fitting of an internal combustion engine and discharges at a restriction of the air intake tube upstream of a throttle valve. An injection valve is disposed in the restricted section, ejecting fuel in the direction toward a throttle valve. The air bypass line extends vertically and has a first U-shaped section, the connecting portion of which is located at a lower level than its legs. A temperature-dependent resistor in the form of a hot wire or hot strip is disposed in the downstream leg of the first U-shaped section, so that during a burnoff procedure of the temperature-dependent resistor a flow is effected in the direction toward the mouth of the air bypass line, thus preventing the aspiration of a fuel-air mixture into the air bypass line and thus avoiding the danger of ignition with the possible destruction of the temperature-dependent resistor.

Abstract: To measure the mass air flow in the induction passage of an engine, a small venturi located centrally in the passage serves as an air sampling tube. A slotted aperture in the wall of the tube at the venturi throat allows a hot film sensor to extend into the venturi throat from a support such as a printed circuit board mounted outside the venturi. The film sensor is in the form of a loop supported only at its ends on the support. The loop comprises a substrate of flexible insulating film material coated with an electrical resistance layer forming the active element of the sensor. The loop has a major dimension extending arcuately and transversely of the air flow through the venturi and a minor dimension extending parallel to the air flow.