Abstract: In a high-pressure cleaning apparatus comprising an electric motor, a high-pressure pump driven by the electric motor, and an automatic switching-off means for the electric motor including a switch actuatable by an actuating element moveable in dependence upon the pressure or the flow of the liquid being conveyed by the high-pressure pump, in order to reduce the switching expenditure it is proposed that a switching-off element which is manually actuatable on the high-pressure cleaning apparatus be associated with the same switch so that in one position of the switching-off element, the switch cuts off the power supply to the electric motor independently of the pressure or the flow of the liquid being conveyed, whereas in the other position the switch is actuatable by the actuating element.

Abstract: The invention relates to a pressure switching device of the type used in motor vehicles and includes a pressure sensor 21 arranged in a housing 3, which generates an electrical signal U according to the pressure p of a pressure medium or monitored fluid transmitted through a supply opening 15 of housing 3. The pressure switching devices includes an interpretation and switching unit 55 adapted to received the electrical sensor signal U and is further adapted to compare the sensor signal with at least one switching threshold value to trigger a switching function or a sequence of switching functions upon the electrical sensor signal exceeding and/or falling short of the switching threshold value.

Abstract: A tap-resistant security circuit. In the preferred embodiment, the apparatus includes a conduit including an electrically conductive wire surrounded by a gas-filled, gas impermeable sheath. At one end of the conduit is a pressure switch which is normally open but is maintained closed by the pressure in the gas-filled conduit. The other end of the conduit is sealed. If the gas-filled conduit is disturbed, for example, if an attempt is made to cut the wire, the gas within the conduit escapes, the pressure holding the switch closed drops and the circuit is opened. As a result, any attempt to by-pass or "tap" the wire results in the current through the wire being interrupted.

Abstract: A coupling and switch system for subsea electrical power distribution employs fluid-filled contact housings. The coupling and switch system includes two mutually spaced contact housings mounted along a common centerline. A space between the contact housing has therein a coupling housing or middle piece having contact elements. The middle piece when or after mounting between the contact housings is anchored in a fluid-tight manner thereto by axial movement of one or both contact housings. The contact elements of the middle piece can be moved into respective contact housings with the middle piece in the mounted position.

Abstract: Systems and apparatus for integrating an air switch and a power cord into an electric motor, and methods for assembling an electric motor including an integral air switch and an integral power cord, are described. In one embodiment, an air switch and a power cord are incorporated into an electric motor. No additional removable cover is required for the switch and cord. To eliminate the motor centrifugal switch, an air switch is provided to control energization and de-energization of the motor windings. The air switch includes a snap action switch to cut-out the start winding used for ensuring that the rotor has sufficient starting torque.

Abstract: A remote switch includes a fluid-containing tube connected to a fluid-sensing switch. A hot wire sensor detects changes in flow through the conduit tube and is electrically connected to breaker switch circuitry. Because the switch is responsive to flow, rather than pressure, the operation of the switch will continue, even if the conduit becomes punctured, cut or damaged. The device is particularly useful as a means for actuating a safety switch to interrupt the electrical power in an emergency.

Abstract: This invention provides a valveless method and apparatus for high speed switching of liquid flow between intersecting microchannels. Liquid flow is controlled by manipulating external driving pressures. The switch comprises three intersecting microchannels, each having a liquid reservoir at its nonintersecting end for liquid inlet and outlet. It further includes applying a driving pressure to each reservoir switching the driving pressures. The microswitch of this invention operates to establish a liquid flow from a first channel to a second channel by applying a pressure differential between the first and second reservoirs, while simultaneously preventing flow into the third channel by applying a pressure to the third reservoir which equals the pressure at the junction of the three channels. By switching one or more driving pressures, the flow to the second channel can be stopped and the liquid flow redirected to the third channel.

Abstract: A device for control and monitoring of pressure in a system combines a conventional three pole pressure switch with the following additional features: (1) a lock mechanism with three influencing input factors and a single resulting output contact action, (2) a three pole thermal release device as one of the input factors, and (3) a remote control tripping device as another input factor, all integrated into a single, compact, modular unit. The thermal release device comprises a plurality of bimetals which sense electrical flow passing through the device, and which are mechanically connected to a locking mechanism to shut off current if the electrical flow reaches a predetermined maximum. If any of the three inputs activates the locking mechanism, the device must be reset by an operator.

Abstract: An electrical kitchen appliance, such as a garbage disposal unit, is operated by providing a pneumatically actuated switch which prevents the user from being shocked due to the presence of water in the area. The pneumatic switch can be moved between an on and an off position so that electrical current is supplied or cut off from the appliance. A non-electrically conductive air conduit is connected to the switch and leads to a remote location from the appliance. A bellows is supplied at the remote location and forces air through the conduit to the pneumatic switch, switching the appliance on or off. Because the bellows is not electrically connected to the switch and is located at remote distance, electrical shock due to the presence of water is eliminated.

Abstract: A pressure switch has a housing with a mounting bracket and a flexible diaphragm defining a wall of the pressure sensing cavity in the housing. Movement of the diaphragm operates an electric switch. The diaphragm is spring biased and an adjustment arm is frictionally mounted in a pair of guide surfaces on the mounting bracket. The arm contacts a cap on one end of the bias spring and is movable in the guide surfaces for adjusting the position of the spring cap for calibration. The mounting bracket is mounted to the housing by inserting a lug on the bracket in a recess in the housing and crimping a folded tab on the bracket to engage another recess in the housing. In another embodiment using a housing of all molded plastic, the adjustment arm frictionally engages a slot molded in the housing and is moved in the slot for calibration.

Abstract: A sliding type adjustment mechanism for changing settings of a diaphragm type pressure switch adjusted by moving an external lever to move a plunger for changing the preload on the diaphragm. An external metal mounting bracket has a pair of spaced parallel slots which serve as ways. A plastic slider with a cam surface engaging the lever has a pair of lugs, each of which engages one of the slots for guiding the slider on the bracket. The slider has an integrally formed spring tab providing friction against the bracket to hold the slider in a selected position. A recess in the bracket relieves the tab friction at the limit of the slider travel to allow the lever to bias a steep-ramp portion of the cam surface to move the slider to an initial position.

Abstract: In accordance with illustrative embodiments of the present invention, a safety bypass switch for use with explosive well tools includes a hollow conductive body having a copper conductor rod extending axially therethrough, a spring-loaded contact element movable transversely in the body between a first position where a surface of the element engages the rod to provide a solid short between the rod and the body, and a second position where such surface is out of engagement with the rod, and a diaphragm or piston for operating the contact element in a manner such that a predetermined hydrostatic pressure in the well bore will shift the contact element to the second position. The springs which bias the element toward the first position are mounted internally and externally of the body. In another embodiment of the invention a manually operated grounding switch is used in combination with the hydrostatic pressure operated switch to provide redundant assurance against accidental firing.

Abstract: The invention concerns a simple, inexpensive and small detector, particularly for use in the medical pumps, for detecting over-pressure in a pipe (1) and setting off an alarm when an over-pressure is detected. The detector for detecting over-pressure in the pipe (1) along which a fluid (3) flows may comprise a T junction (5) for deriving a fraction of the flowing fluid (3) from the pipe (1); at least one tube (7) wherein there is fitted at least one obturating member (9); and an assembly for detecting the displacement of the obturating member (9) in the tube (7) and for generating a signal in response to detecting displacement of the obturating member (9).

Abstract: A switch actuator for use with an electrical switch sensitive to changes in air pressure includes a bellows formed of a flexible material. The bellows is attached to a nipple having a passageway for operatively connecting the actuator to the electrical switch. A sleeve is shrink fitted over the outer surface of the nipple, causing the bellows to be lodged between the sleeve and the nipple. The sleeve includes a tubular sidewall with an inwardly-extending flange defining a central opening. A button is slidable relative to the sleeve and includes a projection extending through the central opening to engage the bellows. Pressing the button deforms the bellows, thereby decreasing the volume of a cavity formed between the bellows and the nipple.

Abstract: The stored-spring-energy actuator mechanism (210) for the high-voltage circuit breaker (218) has a spiral spring (216) which can be loaded by means of the loading device (212). The high-voltage circuit breaker (218) can be switched on once and off once with the energy stored in the loaded spiral spring (216). The energy stored in the fluid-pressure accumulator (258) is sufficiently great to charge the spiral spring (216) at least once. The working-stroke movement of the piston rod (242) in arrow direction (A) is transformed via the gear segment (236) into a rotation through 360.degree. of the gear (232) meshing with this gear segment (236). The spiral spring (216) is thereby loaded via the loading lever (230).

Abstract: A pressure responsive switch apparatus comprising a housing including a wall defining a passageway having an end adapted to communicate with a source of fluid under pressure, a switch supported by the housing, an actuator which is movably supported by the housing and which includes an end extending into the passageway, an actuator for actuating the switch in response to movement of the actuator, and a cup-shaped member detached from the actuator and located within the passageway and between the actuator and the end of the passageway for sealingly engaging the wall and moving the actuator away from the end of the passageway in response to pressure from the fluid source.

Abstract: The invention concerns an electrical reversing switch, which is especially suited for switching of high-frequency electrodes. This switch has an over mounted pneumatic cylinder, which moves on pistons arranged on both sides, and thus produces electric contacts.

Abstract: In a stored-spring-energy type actuator mechanism for a high-voltage circuit breaker, energy is stored in a spiral spring in order to switch on the circuit breaker and also to load a switch-off spring of the circuit breaker. To store sufficient energy for more than one switch-on operation, a fluid-pressure accumulator is provided in which sufficient energy is stored to wind up the spiral ring at least one additional time through a fluid-pressure motor. Between the pressure accumulator and the motor is a control valve which opens when the spiral spring is partly unloaded, causing the hydraulic motor to rewind the spring.

Abstract: A remote controlled door lock apparatus is provided for use in connection with a conventional door lock. The apparatus includes a solenoid operated element for mounting on the door and for connection to the door lock, and a remote control element for connection to the solenoid element for remotely locking and unlocking the door lock.

Abstract: A resilient element such as a thin flat plate or disc spring, commonly known as a "Belleville" spring, which is capable of deflection along an axis normal to its surface is modified to include an amplifying segment disposed in a central aperture in the form of an approximately "W" shaped strip connected at its ends to opposite positions on the inner margin of the central opening. The central portion of the "W" forms an inverted "U" which is subjected, after positioning within the central aperture, to torquing stress in the plane of the material to bring the ends of the open end of the "U" slightly closer together than the inner edges of the "U" nearest its closed end. One of a pair of Switch contacts is mounted on the closed end of the "U" shaped portion of the device opposite another contact carried on the switch base.

Abstract: A pressure switch wherein electrode plates are provided on both sides of a pressure conductive rubber plate. The pressure switch is interposed between a body and a receiving block slidably fitted to the body so that both electrodes may be connected with each other by connecting the rubber plate into conductive state to obtain an electric signal across the electrodes. The pressure applied to the rubber plate is regulated by a variable spring.

Abstract: A pressure receiving member which has a diaphragm held in a pressure receiving case is manufactured independently of a main sensor body member, which has a switch accommodated in a switch case. The pressure receiving member and the main sensor body member are then assembled to provide a pressure sensor.According to the present invention, since the pressure receiving portion and the main sensor body are manufactured individually, a diaphragm inversion movement test can be carried out individually of the testing of switch turning on and off, and hence only satisfactory pressure receiving portion and main sensor body which passed the respective tests will be utilized in the operation of assembling pressure sensors.

Abstract: A fluid responsive switching mechanism is located on a brake actuator in a vehicle to signal impending brake actuation as quickly as possible to reduce the risk of accidents such as rear end collisions. Direct contact with the brake actuator by the driver to initiate brake actuation causes the fluid responsive switching mechanism to immediately energize brake indicators upon such contact. In one example of the invention, an electric switch is located inside a fluid filled chamber located on a brake pedal in the vehicle. In a second example of the invention, an electric switch is located outside such fluid filled chamber.

Abstract: A switch is responsive to fluid flow within a conduit. It is highly sensitive to variations in flow and forms an effective seal between the fluid and atmosphere. It includes a plastic pivot ball in a spherical seat. A blade extends from the pivot ball into the conduit where it can be displaced by fluid flow to rotate the ball. A lever is eccentrically connected to the pivot ball and extends upwardly within a closed, non-magnetic, housing. The upper end of the lever carries a magnet which actuates a switch outside the housing. An adjustable spring between the top of the lever and the housing permits adjustment of the sensitivity of the response.

Abstract: Improvement to electro-fluid relays useable to signal either the maximum or minimum limit of pressure in a fluid system, or the position of a movable part of a jack.The relay is constituted of a pipe fitting (1,2) attached directly onto an apparatus (5) or onto a pipe and including a body presenting a pneumatic control inlet (6) in communication with the said apparatus or the said piping, the said control inlet (6) being linked to a space situated on one side of an elastic membrane (16) submitted to the fluid pressure established in the control inlet (6), the said membrane (16) being linked by a transmission member (18) sliding in the body to a means of control (22) of an electric contactor (23).The invention is utilized for the control of a jack.

Abstract: A brake light switch and brake line connector assembly for a master cylinder, the assembly including a pressure actuated light switch having a threaded stem which is adapted to be connected to a threaded opening provided in the high pressure side of the master cylinder, the threaded stem including an inner passage and an annular groove around the outside connected to the passage by a port, and a Banjo connector assembly including a Banjo connector and a pair of soft metal washers, the Banjo connector being mounted on the annular groove in the threaded stem of the light switch and sealed thereon by the washers, to connect the master cylinder to the brake line.

Abstract: A water level control device and method of making the same are provided, the device comprising a frame provided with an elongated slot having a first portion, a movable cam follower carried by the frame for setting the desired water levels to be provided by the device, and a slide cam member having a projection extending through the slot to guide sliding movement thereof relative to the frame, the projection having an interlocking part interlocking with the frame while the projection is disposed in the first portion of the slot. The cam member has a cam surface engaging the cam follower to set the same in desired water level setting positions thereof when the projection is in the first portion of the slot. The slot has a second portion thereof for unlocking with the interlocking part when the projection of the cam member is disposed in the second portion whereby the cam member can be easily detached from or attached to the frame.

Abstract: A switch responsive to fluctuations in the level of a vacuum. A ball is contained in an upright chamber and is normally in contact with an actuating means in the chamber. The actuating means is normally biased to one position but is shifted by the weight of the ball to another position. The chamber is connected to the vacuum source so as to apply a lifting suction force to the ball. If the suction force exerted by the vacuum exceeds a predetermined level, the ball will be lifted from the actuating means thereby shifting the position of the actuating means and generating a signal indicative of the vacuum level. Means are provided to adjust the level of vacuum necessary to lift the ball from the actuating means.

Abstract: A pressure switch having a ball valve or contact mounted in an internal chamber to move in response to predetermined relatively high and relatively low fluid pressures in an inlet that opens into the chamber to make or break an electrical circuit through the switch and that incorporates a one-piece sealing element that is constantly exposed to the fluid pressure and is uniquely formed and cooperative with the ball contact and with the walls of the chamber to prevent leakage of the fluid from the chamber effectively without significantly interfering with free unobstructive movement of the ball contact in use.

Abstract: A pressure change sensor includes a flexible hollow body to receive pressure changes, an inner body in said flexible hollow body, the inner body being of a size less than and a shape different from the hollow of said hollow body to prevent total occlusion of the hollow body interior under pressure, and a fluid operated switch in fluid communication with the interior of the hollow body responsive to pressure changes applied to the hollow body.

Abstract: An adjustable pressure responsive switch assembly includes a unitary slide cam and button with projections extending outwardly from the slide cam. The support bracket mounted on the pressure switch includes an elongated slot having an enlarged opening at one end. The slide cam projections are adapted to be inserted in the enlarged opening and then be slidingly received in the elongated slot. The slide cam cannot be removed from the bracket unless it is moved all the way to one extreme so that the projections can be removed from the enlarged opening. This movement is prevented by stops formed as part of the cam.

Abstract: An electrical pressure switch that can be readily adapted for either normally open or normally closed operation and that has opposed annular seats, a movable contact and ball valve movable between and individually engageable with the seats, and an O-ring uniquely associated with the ball valve and a related sealing surface in seated, unseated and all intermediate positions of the valve to maintain an effective seal at all times against fluid pressure to which the switch is connected.

Abstract: The compressed-gas device for the life-saving services which can be activated by water, more especially the automatic separating coupling for parachutes, comprises a channel (9) and two detector chambers (10, 11) which, via openings (12, 13), are connected to the channel (9) and, via openings (14, 15), are connected to one respective opposite outer surface (16, 17) of the device. The cross-section of the outwardly directed openings (14, 15) is larger than that of the connection openings (12, 13) to the channel (9). Only when the measuring block (2) is completely immersed in water are three pairs of electrodes (18, 19; 20, 21; 22, 23) bridged by water so that a fuel-gas charge is ignited via an electric circuit (7) with the aid of an igniter (8) (FIG. 2).

Abstract: A rain sensor for an automotive wiper control system detects rain conditions to produce a rain condition indicative signal. The rain sensor includes a vibrator, the outer surface of which is exposed to rain drops and which vibrates or oscillates at an amplitude and frequency corresponding to the energy applied by rain drops. The rain sensor is adapted to produce the rain condition indicative signals corresponding to the vibration amplitude of the vibrator. The vibrator is resiliently suspended within a sensor casing by means of a resilient member which is adapted to allow vibration of the vibrator as rain drops hit the outer surface and to absorb vibrational noises transmitted through the vehicle body. The resilent member simultaneously serves to waterproof the components within the sensor casing.

Abstract: A medical fluid injection system comprises a flexible conduit, a supply device, a movable element, and a blocking condition detection device. The supply device supplies a pressurized medical fluid through the flexible conduit. The movable element is moved for forcing the flexible conduit in a stressing direction to cause creep in the flexible conduit. The blocking condition detection device detects whether or not the flexible conduit is forced in an anti-stressing direction opposed to the stressing direction. In a specific form of the present invention, a monitor may be provided for monitoring whether the movable element is exactly moved or not.

Abstract: A mechanism for the instantaneous tripping of an electrical contact in response to a progressive variation in applied fluid pressure. Contact is made by a conductive element movable along its longitudinal axis between an open position and a closed position. The upper portion of the interior wall of the contact element comprises opposed first and second sloping sections of substantially triangular cross-section having a side in common at their connection. A throttle is defined by the connection between the sloping sections. A cage member partially positioned within the conductive element is movable therein in response to the applied fluid pressure. The cage member includes a head portion having a channel therethrough perpendicular to the longitudinal axis of the conductive element. At least one ball is housed in the channel and is movable along the longitudinal axis of the channel and up and down the sloping sections in response to the movement of the cage member within the conductive element.

Abstract: A safety device for discharging high voltage circuits operated in pressurized containers. The device is positioned within an elbow or other protrusion through which passes the high voltage feed-through electrode. In one embodiment the grounding contact is automatically forced against the high voltage contact by the expansion of a bellows upon decompression of the container while in an alternate embodiment, the grounding contact is manually threaded against the high voltage contact.

Abstract: A switch especially useful for interrupting high frequency induction heating currents is comprised of mating conical shaped contacts. The contact parts of the switch are water cooled by internal cooling channels which are not affected by making or breaking of the switch. The opposing contacts are mounted on separable pieces of the switch; when the clamp is released one side of the switch can be freely separated from the first part. Thus, inflexible high power electrical connections can be made and boken in a vacuum environment through physical movement of the coil and load.

Abstract: A fluid actuated switch including a fluid responsive vane pivotally mounted within a fluid directing channel is provided. The vane oscillates a movable electrical contact between two spaced stationary electrical contacts opening a first electrical circuit and enclosing a second electrical circuit as it moves from one stationary contact to the other. An adjustable holding assembly is associated with the vane for holding the movable switch contact into engagement with the stationary contacts such that a predetermined fluid force is required to move the vane opening one of the circuits and closing the other of the circuits.

Abstract: An optical device, such as the switch, for controlling the passage of a light beam into and out of an end face of a waveguide such as a glass fiber includes utilizing either a layer or drop of liquid material to control the light passage. The liquid material can be a layer, which has changeable optical properties, which can occur by applying a magnetic field, heat or electrical field or the material can be a layer of electrolyte material which will precipitate a reflective layer or electrochromic layer in response to an application of an electrical field. In another embodiment, the liquid material may be moved into and out of engagement with the end face to change the reflective nature of the end face and to cause decoupling of light from the end face or block the transmission of light.

Abstract: The conical tip of a load applying member (42) acts against one side (136) of a movable plate (120). A spring (84) urges the conical tip of a biasing member (88) against the other side (138). In response to a relatively small movement of member (42) against plate (120), plate (120) pivots about a first axis a.sub.1 to depress the operator (102) of a first snap-action switch (98). In response to a relatively large movement of member (42), plate (120) pivots away from contact with operator (102), first about auxiliary axis a.sub.4 and then about third axis a.sub.3. In response to an intermediate movement, plate (120) pivots to depress the operator (103) of a second snap-action switch (99), first about second axis a.sub.2 and then about auxiliary axis a.sub.4. Axis a.sub.4 is defined by first and second fulcrums (71, 134). Axis a.sub.2 is defined by second fulcrum (134 ) and operator (102); axis a.sub.3 is defined by first fulcrum (71) and operator (103). Axis a.sub.

Abstract: A switch is disclosed having a plurality of conductors entering a chamber containing a movable contact element. Air pressure applied to the contact element moves it into contact with at least one of the conductors.

Abstract: An invention is disclosed wherein one portion of conductor is fastened to a housing and another portion is movable. Fluid pressure applied through a passage forces the movable portion into contact with electrical terminals.

Abstract: Input force transmitted from a monitored process variable is applied against a displaceable double beam mechanism being opposed by a dual spring bias presettable individually to the separate set points of the switch. Comprising the double beam mechanism is an equalizer beam underlying a pair of scissor beams such that displacement force incurred by the equalizer beam is conducted through the scissor beams and supported push rods to operate the switch actuators. In a hi/lo set point embodiment two switches are separately actuated in a predetermined sequence while in a deadband embodiment a single switch is independently settable for make and break.

Abstract: Apparatus and method are disclosed for actuating a desired device, such as a switch controlling a pump, in response to a predetermined pressure condition in a selected environment of varying pressure, such as closed vessel. A tube having a flattened segment of deformable material is disposed in fluid communication with the selected environment and a flattened segment of the tube is inserted between a tube support surface and a movable tube segment compression member. When the flattened tube segment expands in response to an increased pressure condition within the monitored environment, the tube segment compression member moves to actuate the device.The flattened tube segment unexpectedly improves the precision and consistency in actuating the device exactly at the predetermined pressure condition.

Abstract: The invention provides a flow sensor (10) for providing an electrical output indicating a no flow condition, an intermediate flow rate, and a high flow rate and is particularly suited for sensing the flow of lubricant to a two-cycle engine. The flow sensor (10) includes a metallic reed valve member (22) which contacts a valve seat (28) to provide a no flow signal or an adjustable contact member (31) to provide a high flow signal. The reed valve member (22) contacts neither the valve seat (28) nor the contact member (31) to indicate an intermediate flow rate.

Abstract: An air-operated switching device includes first and second spaced supports on which an armature is mounted. The armature includes a resilient blade fixedly mounted at a first end on the first support and for sliding movement with respect to the second support. A resilient contact finger extends from the slidably supported end of the armature and includes a free end having a contact thereon. A fixed contact is positioned in alignment with the contact of the finger. An air-operated actuator applies pressure to the blade causing it to flex with the one end of the blade moving slidably over the second support, thereby causing the finger contact to be moved into engagement with the fixed contact with a wiping motion.

Abstract: A hydraulic drive for an electrical switch is disclosed including magnetically operated control signal organs for initiating closing and opening of the electrical switch which is hydraulically driven by a drive with a differential piston moving in a drive cylinder. A switch-over control valve is employed for selectively pressurizing and depressurizing a larger end face of the piston. In order to prevent "pumping" of the switch by such a switch drive system according to the present invention, the control signal organ which is opened in connection with the initiation of the closing of the switch is manipulated hydraulically at approximately the same time as the pressurization by the switch-over control valve of the larger piston end face of the differential piston of the drive commences. The hydraulic manipulation shifts the control signal organ back into a closed position. This arrangement permits at most only one on-off switching cycle to occur, and thus "pumping" of the switch is prevented.

Abstract: Liquid flow sensing apparatus which in the illustrative embodiment is used to sense an occluded vein (cessation of blood flow). A flexible pressure pillow is connected in the blood flow line and is inserted into a housing in contact with a metallic leaf spring. The position of the leaf spring is adjusted relative to an eddy current proximity sensor so that the sensing apparatus is calibrated to a no-alarm position during proper blood flow. If blood flow ceases, the flexible pressure pillow contracts thereby moving the leaf spring away from the eddy current proximity sensor and an alarm condition is thereby detected.

Abstract: A flow detector including an orifice for forming a vena contracta to activate a connected pressure detector so as to trigger an alarm mechanism upon the occurrence of disconnect of the patient exhalation valve in a mechanical ventilator system. A configuration of the flow detector makes erroneous hookup of the ventilator and pressure detector hoses all but impossible.