`
`
`(19)
`Federal Republic of Germany
`German Patent and Trademark Office
`
`
`
`
`
` (11) DE 39 30 479 A1
`
`(12)
`
`Utility Model Patent Text
`
`
`
`(21) File designator: P 39 30 479.5 (51) International classification5:
`B 60 C 23/04
`B 60 C 29/00
`G 08 C 17/00
`G 01 L 17/00
`F 16 L 27/08
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`(22) Application date: September 12, 1989
`(43) Publication date: March 14, 1991
`
`
`(71) Applicantr:
`Rainer Achterholt, Durach 8968, Germany
`
`(74) representative:
`W. Kern, registered engineer; H. Briem, registered
`chemist, holder of doctorate, Patent Attorneys,
`Munich 8000, Germany
`
`(72) Inventor: same as applicant
`
`
`
`
`An application for examination has been made in accordance with § 44 of the Patent Act
`
`
`(54) Valve with a signal-generating device for
`
`vehicle tires
`
` A
`
` valve (1) for vehicle tires is equipped with a
`device for generating a pressure reduction
`signal able to be transmitted wirelessly. On the
`valve (1) there is situated a valve base (10),
`from which a valve shaft (2) projects. The signal-
`generating device exhibits a reference chamber
`(44) able to be impinged on by a target
`pressure, which is bordered in part by a
`membrane (40) which is impinged on by the tire
`pressure to be monitored. Additionally belonging
`to the signal-generating device is a transmitter, a
`power supply device (26) and a mechanical
`switching circuit (41, 42) that normally is open,
`which is closed when the membrane is
`deflected, whereupon the transmitter is
`activated. This signal-generating device is
`attached on the side of the valve base (10)
`facing away from the valve shaft (2). The
`transmitter exhibits a sequential control, which,
`after a short-term signal transmission, interrupts
`this signal transmission and again places the
`transmitter into a state of readiness.
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`FEDERAL PRINTING OFFICE JANUARY 1991
`108 011/364 12/60
`
`108 011/364
`
`SCHRADER
`EXH. 1013
`Page 1013-1
`
`

`

`
`
`Specification
`
`The invention relates to a valve with a device for
`generating a pressure reduction display signal, able to
`be transmitted wirelessly, for vehicle tires. This valve
`is especially meant for tires of passenger cars and
`trucks. The valve can be used with tires having tubes
`and for tubeless tires.
` More particularly, the invention relates to a valve
`with a device for generating a pressure reduction
`display signal able to be transmitted wirelessly for
`vehicle tires, with a base from which a valve shaft
`projects. The signal-generating device exhibits a
`membrane impinged on by the tire pressure to be
`monitored, which is able to be deflected when the tire
`pressure becomes abnormal. Additionally, the signal
`generating device exhibits a transmitter, a power
`supply device and a mechanical switching circuit that
`normally is open, which is closed when the membrane
`is deflected, whereupon the transmitter is activated.
` A valve of this type is known from the German
`patent disclosure text 36 05 661. The signal-
`generating device is attached to the side of the shaft of
`the known valve. Its presence can impair the visual
`appearance and make it hard to attach other wheel
`accessories like ornamental covers and the like. The
`membrane of the known device is pretensioned by a
`spring. Such arrangements are designed for only a
`narrowly limited pressure range dependent on the
`elastic force of the spring. The membrane must be
`able to withstand the tire pressure, which reduces the
`sensitivity of the arrangement. Additionally, even the
`permissible tire pressure oscillations that occur with
`typical tire usage can cause the membrane to be
`deflected, thus triggering false alarms. The
`membrane, pretensioned by the spring, should
`activate a switch when tire pressure is excessively high
`or low, whereupon the transmitter is activated. For as
`long as the impermissible tire pressure prevails, the
`transmitter remains activated and draws energy from
`the power source. Doubts exists as to whether this
`known proposal can be implemented or has already
`been implemented.
` Additionally, from German patent text 35 46 338, a
`valve cap for air-filled tires is known, that conveys an
`optically detectable pressure reduction display. The
`inner area of the known valve cap is divided by a
`membrane into a pressure chamber impinged on by
`the tire pressure to be monitored, as well as a
`reference chamber, which is impinged on by a target
`pressure when the valve cap is screwed onto a tire
`valve. This reference chamber is in part bordered by a
`see-through housing section. If the pressure to be
`monitored drops below the target pressure, then the
`preferably colored membrane is deflected in the
`direction of the see-through housing section, and the
`fact that this membrane becomes visible serves to
`display that pressure has dropped. It is not possible
`for signals to be transmitted wirelessly with this
`known valve cap.
` The task of the present invention consists in making
`available a tire valve of the type mentioned initially,
`
`
`
`which does not differ in terms of its visual appearance
`and handling capability from known tire valves, the
`signal-generating device of which has both high
`sensitivity and applicability over a wide range of
`differing tire pressures, is not disturbed by normal,
`permissible tire pressure oscillations, and the
`transmitter of which is designed to be maintenance-
`free for many years of use, and if necessary for
`numerous alarm impulses, which can safely be
`distinguished from outside signals.
` Based on a valve with a device for generating a
`pressure-reduction display signal for vehicle tires,
`able to be transmitted wirelessly, according to the
`generic type indicated above, the invention-specific
`solution of this problem is characterized in that the
`signal-generating device is attached on the side of the
`base facing away from the valve shaft. The transmitter
`exhibits a sequential control, which, after a short-term
`signal transmission, interrupts this signal
`transmission and again places the transmitter into a
`state of readiness. The signal-generating device
`exhibits a reference chamber, which is able to be
`impinged on by a target pressure when the tire valve
`is opened, and is closed in pressure-tight fashion
`when the valve is closed. This reference chamber is
`bordered in part by the membrane, which assumes a
`deflected setting away from the reference chamber,
`thus allowing the control circuit to be closed, if the
`tire pressure to be monitored is smaller than the
`target pressure.
` This combination of features yields a valve for air-
`filled tires, equipped with a signal-generating device,
`that can be manipulated like a customary tire valve.
`The signal-generating device attached to the valve
`base is in the interior of the tire and cannot impair the
`visual appearance of the valve, nor can it keep other
`tire components such as ornamental caps from being
`attached. The components of the signal-generating
`device are protected from unauthorized removal of
`the tire valve. Together with the reference chamber,
`the electrical and/or electronic components of the
`transmitter and a battery, the signal-generating device
`constitutes a single component which is easily
`installed, is of small dimensions, and is low in weight.
`For example, such a signal generating device could be
`implemented in the form of a cylindrical component
`which exhibits an outer diameter of about 18 mm, a
`length of about 7 mm and – including the battery – a
`weight of less than 10 g. No substantial contribution
`to the out-of-balance condition of the tire by the tire
`valve is made by the presence of this signal-generating
`device. Because the switching of the transmitter to a
`signal transmission indicating tire pressure too low is
`then interrupted automatically after a brief time, an
`alarm pulse does not consume much energy. The
`power supply device of the signal-generating device
`can for example be a lithium battery that delivers 3 V
`and a capacity of about 40 mAh. With such a battery,
`the signal-generating device of the invention-specific
`valve can trigger at least 500 to 1000 alarm impulses.
`Therefore, it is possible to accommodate the signal-
`generating device in the interior of the tire in
`maintenance-free fashion. Because, according to the
`
`SCHRADER
`EXH. 1013
`Page 1013-2
`
`

`

`invention, the pressure is detected with the aid of a
`reference chamber, the membrane is merely subjected
`to the slight difference between the pressure to be
`monitored and the target pressure. The membrane
`can be designed to be thin and highly sensitive. A
`single embodiment form of a signal-generating device
`can be employed at a great variety of tire pressures,
`because only the difference between the tire pressure
`to be monitored and the target pressure stored in the
`reference chamber is detected. Such a reference
`chamber yields optimal results in connection with a
`mechanically operable, electrical switching circuit,
`because a comparatively small displacement of the
`membrane suffices to close the switching circuit
`which is normally open. Neither appreciable weight,
`or any elastic forces need to be overcome to displace
`the membrane. A high sensitivity is achieved, which is
`nonetheless not affected by the permissible tire
`pressure oscillations that occur with normal tire use,
`because these tire pressure oscillations for the most
`part are tire pressure increases that do not cause
`membrane deflection. Preferably the transmitter
`generates two signal frequencies with a differing
`frequency, which are emitted alternately with a preset
`pulse sequence. By this means, a close and
`characteristic coupling can be achieved with an
`assigned receiver, which in practice cannot be
`jammed by outside signal sources. To each
`transmitter or each tire valve, a correspondingly
`tuned receiver is assigned, with the maximum
`distance between transmitter and receiver preferably
`being less than 1000 mm. They are assigned to a
`specific wheel via the assigned receiver, which is
`linked directly with a display device on the dashboard
`of the vehicle or the like. A single embodiment form of
`the invention-specific valve is suited for all the wheels
`of a vehicle. Surprisingly, the presence of steel belts in
`a vehicle wheel also does not hamper propagation at
`the signal frequencies and reliable receipt of them by
`the receiver. Under these conditions, a false alarm as a
`result of permissible tire pressure oscillations or as a
`result of outside-source transmissions, as well as
`disturbance to other receivers, can be virtually
`precluded.
` Advantageous embodiments and further
`developments of the invention are obtained from the
`subordinate claims.
` As already stated, the signal-generating device
`exhibits a reference chamber, which, when the tire
`valve is open, can be impinged on by a target pressure,
`and when the tire valve is closed, is closed in pressure-
`tight fashion. With a typical tire valve, the valve shaft
`is bordered by a valve borehole, on which a valve seat
`is configured, which can adjoin a valve body, to close
`the tire valve. According to one viewpoint of the
`invention, provision can be made to have a channel
`terminate in this valve seat, via which the reference
`chamber is able to be impinged on by a pressurized
`medium. If this valve body is loosened from its valve
`seat by a displacement of a valve tappet, such as in
`order to get to the desired pressure via the valve of an
`air-filled tire, then the pressured medium can be
`exchanged between the reference chamber and valve
`
`
`
`borehole via this now open channel, whereby the
`reference chamber is impinged on by a desired target
`pressure. If the valve body thereupon is again applied
`to the valve seat, to close the tire valve, the channel is
`also closed, and the reference chamber is and remains
`closed in pressure-tight fashion.
` According to another alternative, within the valve
`borehole a tube section can be situated, which adjoins
`a channel or a channel section, via which the reference
`chamber can be impinged on with a pressurized
`medium. Into this tube section, an additional auxiliary
`valve is inserted, which is jointly opened or closed
`with the tire valve. For example, this auxiliary valve
`can be a check valve, also situated within the valve
`borehole, which normally assumes its closed setting.
`If the valve tappet is pressed down to open the tire
`valve, then an extension of this valve tappet acts on
`the check valve and opens it. After the tire valve
`closes, the check valve again assumes its closed setting
`under the action of a spring or the like.
` The signal-generating device exhibits a reference
`chamber in which a target pressure can permanently
`be stored. The reference chamber is configured within
`a flat container, which in essence consists of a
`container base and a one-piece circumferential
`container wall, which for its part exhibits a front
`surface. The container opening is closed by the
`membrane, which is placed on the inner side of the
`circumferential container wall. A cylindrical section of
`the circumferential container wall projects over the
`membrane.
` Within the circumferential container wall, an
`opening is made, which starts at the front surface of
`the circumferential container wall, ends in the inner
`container space or in the reference chamber, and is
`attached to the channel in the valve base or in the
`valve shaft. Via this channel and the opening, the
`reference chamber can be impinged on by a
`pressurized medium that exhibits the target pressure.
` On the section of the circumferential container wall
`that projects out over the membrane, at opposite
`locations a guide section is attached that is, for
`example, in the shape of a metallic handle. The guide
`section is situated parallel to the membrane and at a
`small distance from its at-rest position. The guide
`section is connected in electrically conducting fashion
`with the circuit of the transmitter and forms a fixed
`contact of the switching circuit.
` The invention-specific valve is equipped with a
`power supply source to supply the electrical and/or
`electronic components of the transmitter with current
`or voltage. Here this can be a lithium battery, which
`possesses a capacity of at least 40 mAh and delivers a
`voltage of 3 V. Such a battery can be configured as a
`round cell, and is integrated into the housing of the
`signal-generating device. The circuit of the
`transmitter as a rule is in a readiness state, in which
`virtually no energy is drawn from the battery. The
`transmitter switches from a readiness state to an
`activated state, in which the transmitter emits signal
`frequencies, by closing of a switching circuit.
`Preferably a part of this switching circuit is a guide
`section, which is placed parallel to and at a small
`
`SCHRADER
`EXH. 1013
`Page 1013-3
`
`

`

`distance to the at-rest position of the membrane. The
`counter-piece forms a small metal plate which is
`situated in the center of the membrane and touches
`the guide section when the membrane is deflected,
`thus closing an electrical circuit or the switching
`circuit. Hereupon the circuit is activated and the
`transmitter emits signal frequencies. This switching
`circuit operates in reliable, sensitive and rapid
`fashion, because no substantial counterforces need to
`be overcome. A membrane deflection of a few tenths
`of a millimeter is sufficient to close the switching
`circuit.
` After the switching circuit is closed, a signal is
`emitted once, for a limited time duration. Preferably
`the signal transmission is limited to about 1 to 3
`seconds. Preferably, such a signal transmission can
`consists of alternating, periodic emission of differing
`signal frequencies. This can, for example, be
`implemented with a transmitter provided according to
`the invention, which in essence consists of a digital
`circuit and an oscillating circuit, the coil of which is
`configured as a transmitting antenna. According to
`one essential viewpoint of the present invention, a
`sequential control of the digital circuit is provided,
`which after a short-duration signal transmission,
`again interrupts this signal transmission, and shifts
`the transmitter back into a readiness state.
` For this, the digital circuit can exhibit, as essential
`functional groups, preferably an RC generator, a
`starter device (trigger), a modulation circuit, a multi-
`stage frequency divider and a power amplifier able to
`be switched on and off. The RC generator (oscillator)
`delivers various signal frequencies, the particular
`frequency of which is determined by the components
`of resistor (R) and condenser (C). The circuit is
`designed so that, via various feedbacks of frequency
`dividers, the corresponding functional groups of the
`digital circuit are guided so that, by closing the
`switching circuit, the circuit is triggered and a
`complete signal transmission is carried out. When this
`is done, then the power amplifier and the RC
`oscillator are switched off, thus resulting in a very
`substantial reduction of the power drawn from the
`battery. By this means, the circuit is again switched
`back to readiness, and is ready to emit a new signal,
`even if the switching circuit continues to be closed. A
`signal is only emitted after the membrane is reset and
`the switching circuit has been opened, and again
`closed when a tire pressure drop has again been
`detected.
` The transmitter signal is preferably emitted at
`relatively long-wavelength frequencies in the kHz
`range. In this range, interference by outside signal
`sources cannot be expected. Nonetheless, the
`transmitter signal can be passed without interference
`to receiver(s) preferably at a distance of no more than
`1000 mm in the wheel area of the vehicle.
` To increase recognition between the transmitter
`and receiver, and to preclude that outside signals will
`trigger false alarms, the transmitter signal preferably
`consists of two different frequencies (for example 9.6
`kHz and 10.4 kHz), which are generated over a time
`span of 10 to 20 milliseconds. The overall duration of
`
`
`
`a transmitter signal preferably consists of only a few
`seconds, for example 1 to 3 seconds, and especially
`preferred 1.6 seconds. Under these conditions, the
`capacity of the above-mentioned lithium battery
`suffices for at least 5oo to 1000 alarm impulses, i.e.
`for the entire expected service life of the valve.
`Therefore, the signal-generating device, including its
`battery, can be accommodated at a location inside the
`tire that is not easily accessible.
` The entire transmitter with all of the electrical
`and/or electronic components is preferably designed
`as a module. The components, including two chips, an
`RC generator and number of condensers and
`resistors, are situated on a circuit board, which forms
`a printed circuit. In one practical embodiment form, a
`round circuit board with a diameter of about 17 mm
`suffices to admit all the components. This circuit
`board with the components is protected within a
`plastic housing, on the outer circumference of which –
`in a groove – the transmitter coil is accommodated,
`designed as a wire winding. The entire signal-
`generating device including a reference chamber with
`a switching circuit, transmitter and battery, can form
`a single, integrated component with a diameter of
`about 18 mm and a length of about 7 mm. Apart from
`being accessed for the tire pressure to be monitored,
`the component can be designed to be encased, to
`avoid damage by component parts of the pressurized
`medium within the tire. The entire integrated
`component weighs less than 10 g and thus does not
`substantially increase the weight of a traditional metal
`valve.
` A separate receiver is assigned to each tire valve
`with its transmitter. Typically belonging to each
`receiver is a ferrite rod with a receiver antenna and a
`known receiver circuit. The receiver circuit is supplied
`with power from the power supply source of the
`vehicle. The outputs of the receiver circuit are
`connected via connection cables with a display device
`on the dashboard or the like of the vehicle. Parts of
`the display device include an electronic assessment
`device, which assigns the impulse deriving from a
`specific transmitter and receiver to the pertinent
`wheel display. Additionally, the display device
`generates an optically and/or acoustically detectable
`warning signal to the impulse obtained from the
`receiver, which remains also after signal frequencies
`stop being transmitted, until the driver of the vehicle
`has deleted or reset the warning display.
` After the issuance of an alarm impulse, the signal-
`generating device is again ready to emit a new alarm
`impulse, after the membrane has gone back to its at-
`rest position. This can occur especially after the valve
`tappet has been pressed down, because then the
`access to the reference chamber has been opened and
`pressure has been equalized or the target pressure has
`been reset.
` In what follows, the invention is explained in more
`detail using a preferred embodiment form with
`reference to the drawings; shown in the latter are:
` Figure 1, using a schematic section depiction, an
`invention-specific valve with a signal-generating
`device
`
`SCHRADER
`EXH. 1013
`Page 1013-4
`
`

`

` Figure 2, an altered embodiment form of the valve
`according to figure 1 with another alternative for
`impinging onto the reference chamber with a target
`pressure.
` The embodiment form of an invention-specific valve
`depicted in figure 1 consists in essence of the valve 1
`and a signal-generating device. The valve 1 exhibits a
`valve shaft 2, which borders a valve borehole 3. On the
`inner circumference of valve borehole 3, a valve seat 4
`is configured. On this valve seat 4, a valve body 5 can
`adjoin, which is pressed on by a spring 7 against valve
`seat 4, and closes valve 1. With valve body 5, a valve
`tappet 6 is connected in one-piece fashion, through
`the shifting of which the valve body 5 can be removed
`from valve seat 4, so that a pressurized medium can
`pass through valve borehole 3. The outer
`circumference of valve shaft 2 can be equipped with a
`stepped outer threading 8 and 9. A valve base 10 is
`shaped onto valve shaft 2 in one-piece fashion.
` In a typical application, this valve 1 is guided
`through a valve hole in a rim, so that – at an
`intermediate position of a seal not depicted – the
`valve seat 10 comes to adjoin the inner wall of the rim.
`Then a union nut is screwed onto outer threading 9
`and the valve 1 is secured to the rim. In this case the
`valve 1 is meant for a tubeless vehicle tire. The entire
`valve 1 typically consists of metal, such as a zinc-
`copper alloy or an aluminum alloy.
` According to one viewpoint of the present invention,
`within valve shaft 2 a channel 12 is made, which
`empties on one side on valve seat 4 and on the other
`side on a front surface 11 of valve base 10. When valve
`body 5 comes to rest on valve seat 4, this channel 12
`also is closed. When valve body 5 is removed from
`valve seat 4, a pressurized medium can pass through
`channel 12.
` On the side of valve body 10 facing away from valve
`shaft 2, a signal generating device is situated, such
`that a flow connection remains between valve
`borehole 3 and the inner tire space.
` Belonging to this signal-generating device is a
`sheath 20, on the outer circumference of which a
`groove 21 is made, and on the inner circumference of
`which a projection 22 is shaped. On this projection 22
`a circuit board 23 is braced, on which are located the
`electrical and/or electronic components 24, 24’, 24’’
`and 24’’’ of a transmitter. Also part of this transmitter
`is a transmitter coil 25 configured as a wire winding,
`which is accommodated within the groove 21 on the
`outer circumference of the sheath 30. Further, in the
`inner space of the sheath 20, a round cell battery 26 is
`accommodated and secured. From the attachment
`clamps 27 and 28 of round cell battery 26, wires lead
`to circuit board 23.
` Additionally the signal-generating device exhibits a
`container 30, which essentially consists of a container
`floor 31 and a circumferential container wall 32,
`which in turn exhibits a front surface 35. On the inner
`circumference of circumferential container wall 32 a
`membrane 40 is clamped, in the center of which a
`small metal plate 41 is attached. A reference chamber
`44 is provided, which is bordered by the membrane
`40, the container floor 31 and the circumferential
`
`
`
`container wall 32. In the circumferential container
`wall, an opening 36 is made, which starts at the front
`surface 35 of the circumferential container wall 32,
`and ends in the reference chamber 44. This opening
`36 extends to a section of the channel 12 in the valve
`base 10, so that with the aid of the channel 12 and of
`the opening 36, a flow connection results from valve
`seat 4 to reference chamber 44.
` One section of the circumferential container wall 32
`projects out over the membrane 40. A guide section
`42 is placed at a small distance to membrane 40 and
`parallel to same, and attached at opposing places of
`this section of the circumferential container wall 32
`that project out over membrane 40. The small metal
`plate 41 attached in the center of membrane 40 and
`the guide section 42 together form a mechanical
`switching circuit that as a rule is open. Both the metal
`plate 41 and the guidance section 42 are attached via a
`wire to printed circuit 23. If a membrane is deflected,
`the metal plate 41 contacts the fixed guidance section
`42, and a circuit is closed, which activates the digital
`circuit of the transmitter in a readiness state,
`whereupon a signal is emitted.
` As depicted in the drawing, the sheath 20 and the
`container 30 with their particular components are
`connected to each other and together form an
`integrated component. This component can be
`embedded in cast resin or encapsulated in some other
`way, to ensure protection from components of the
`pressurized medium in the tire. Adjoining valve base
`10, this component can exhibit a cover plate 37, which
`protects against direct contact of the compressed
`medium with the membrane 40. In this cover plate 37,
`an opening 38 is made, through which the tire
`pressure to be monitored impinges constantly on
`membrane 40.
` Figure 2 shows an alternative embodiment form of
`the invention-specific valve, the signal-generating
`device of which is designed in the same way as
`explained above in reference to figure 1. What differs
`is that the valve 1 within valve borehole 3 exhibits a
`standard valve insert 13. Flush with this valve insert
`13, within the valve borehole 3 there is a tube section
`14, in which an auxiliary valve 15 is inserted. This
`auxiliary valve 15 can be designed as a check valve, the
`valve body 17 of which is compressed by a spring 18
`against a valve seat 19. This pipe section adjoins the
`channel 12 of valve 1. On valve insert 13, a rod 14
`projecting out over its support is attached. When the
`valve tappet 6 is activated, this rod 14 touches valve
`body 17 of auxiliary valve 15 and moves it away from
`its valve seat 19. The pressurized medium can enter
`into tube section 15, flow through channel 12 and get
`through opening 36 into reference chamber 44. After
`valve tappet 6, acted upon by the spring on valve
`insert 13, has returned to its initial position, the rod 14
`also has gotten free from valve body 18 of auxiliary
`valve 15 and its spring 17 compresses valve body 18
`against its valve seat 19 and closes auxiliary valve 15.
`The reference chamber 44 is closed and a target
`pressure is permanently stored therein.
`
`
`
`Patent Claims
`
`
`
`SCHRADER
`EXH. 1013
`Page 1013-5
`
`

`

`1. A valve with a device for generating a pressure
`reduction display signal able to be transmitted
`wirelessly for vehicle tires, with a valve base (10),
`from which a valve shaft (2) projects, whereby the
`signal-generating device exhibits a membrane (40)
`impinged on by a tire pressure to be monitored ,
`which can be displaced when tire pressure is
`abnormal, this signal-generating device additionally
`exhibiting a transmitter (24, 24’, 24’’, 24’’’; 25) a
`power supply device (26) and a mechanical switching
`circuit (41, 42) that normally is open, which is closed
`by a membrane displacement, whereupon the
`transmitter is activated, characterized in that
`the signal-generating device is attached to the side of
`the valve base (10) facing away from the valve shaft
`(2);
`the transmitter (24, 24’, 24’’, 24’’’; 25) exhibits a
`sequential controller, which, after a brief signal
`transmission, interrupts this signal transmission and
`shifts the transmitter again into a readiness state;
`the signal-generating device exhibits a reference
`chamber (44), which, when the tire valve (1) is open,
`is able to be impinged on by a target pressure and
`when the tire valve (1) is closed, is closed in pressure-
`tight fashion; and
`this reference chamber (44) is bordered in part by the
`membrane (40), which assumes a setting displaced
`away from the reference chamber (44), and causes the
`switching circuit (41, 42) to be closed, when the tire
`pressure to be monitored is lower than the target
`pressure.
`
`2. Valve according to claim 1, wherein the valve shaft
`(2) adjoins a valve borehole (3), on which a valve seat
`(4) is configured, on which a valve body (5) may
`adjoin, to close the tire valve (1), characterized in that
`in this valve seat (4) a channel (12) empties, via which
`the reference chamber (44) is able to be impinged
`upon by a pressurized medium.
`
`3. Valve according to claim 1, characterized in that
`within the valve borehole (3) a tube section (14) is
`situated, which borders on a channel (12), via which
`the reference chamber (44) is able to be impinged
`upon by a pressurized medium; and
`into this tube section (14) an auxiliary valve (15) is
`inserted, which is jointly opened or closed with the
`tire valve (1).
`
`4. Valve according to claim 3, characterized in that the
`auxiliary valve (15) is designed as a check valve.
`
`5. Valve according to one of claims 1 to 4,
`characterized in that the signal-generating device
`exhibits a sheath (20), on the inner circumference of
`which a printed circuit (23) is supported, on which the
`electrical and/or electronic components (24, 24’ 24’’,
`24’’’) of the transmitter are attached.
`
`6. Valve according to claim 5, characterized in that as
`part of the transmitter there is a transmitter coil (25)
`configured as a wire winding, which is accommodated
`
`
`
`in a groove (21) on the outer circumference of the
`sheath (20).
`
`7. Valve according to claim 5 or 6, characterized in
`that in the inner space of the sheath (20) a battery
`(26) is accommodated and attached.
`
`8. Valve according to one of claims 1 to 7,
`characterized in that part of the signal-generating
`device is a flat container (30), which is essentially
`bordered by a container base (31) and a
`circumferential container wall (32), the container
`opening of which is closed by the membrane (40).
`
`9. Valve according to claim 8, characterized in that in
`the circumferential container wall (32) an opening
`(36) is made, which starts at a front surface (35) of the
`circumferential container wall (32), empties into the
`reference chamber (44) and is connected to the
`channel (12) in the valve base (10) or valve shaft (2).
`
`10. Valve according to one of claims 1 to 9,
`characterized in that the switching circuit consists of a
`small metal plate (41) attached in the center of the
`membrane (40) and a guide section (42), which is
`attached parallel to, and at a small distance from, the
`at-rest position of the membrane (40).
`
`11. Valve according to one of claims 1 to 10,
`characterized in that the transmitter is a digital switch
`and exhibits an oscillatory circuit, the coil (25) of
`which is configured as a transmitter antenna.
`
`12. Valve according to claim 11, characterized in that
`the digital switch exhibits an RC generator, a starter
`device (trigger), a modulator circuit, a multistage
`frequency divider and a power amplifier capable of
`being switched on and off.
`
`13. Valve according to one of claims 1 to 12,
`characterized in that the transmitter generates two
`different, relatively long-wavelength signal
`frequencies in the kHz range, which are emitted
`alternately.
`
`14. Valve according to claim 12 or 13, characterized in
`that a sequential control of the dig