Electronic drainage system

Claim 2

An electronic drainage system for monitoring the air and liquids flowing in a suction conduit from an inaccessible body cavity and for controlling the suction in the suction conduit, said system comprising: suction control means for controlling the suction in the conduit for the purpose of regulating the air and liquid flow from the cavity, said suction control means maintaining a suction in the conduit; suction transducer means for monitoring the air pressure in the suction conduit and for generating an actual suction signal whose value is reflective of the actual suction in the conduit; and adjusting means for automatically adjusting said suction control means in increments varying in proportion to deviations in the value of said actual suction signal from a predetermined suction value.

Claim 3

The invention according to claim 1 wherein said suction control means comprises air admission means for admitting atmospheric air into the conduit, and said adjusting means comprises means for adjusting said air admission means to control the amount of air admitted into the conduit to regulate the suction in the conduit.

Claim 4

The invention according to claim 2 wherein said adjusting means further comprises: suction selection means for generating a predetermined suction value signal whose value corresponds to the predetermined suction value; differential integrating means electrically connected to said suction transducer means and to said suction selection means for receiving said actual suction signal and said predetermined suction value signal and for generating a differential integrated signal corresponding to the integral of the difference between said actual suction signal and said predetermined suction value signal; and motor means electrically connected to said differential integrating means and to said air admission means, said motor means adjusting said air admission means according to the value of said differential integrated signal to establish said predetermined suction value in the conduit.

Claim 5

The invention according to claim 3 wherein said suction control means comprises variable orifice means including relatively movable members defining a variable orifice in the conduit; and said motor means is operatively connected to at least one of said members to move said members relative to each other to establish an orifice of the size necessary for admitting atmospheric air into the conduit to establish the predetermined suction value in the conduit.

Claim 6

The invention according to claim 4 wherein said variable orifice means comprises: a first member having a first orifice for admitting atmospheric air into the conduit; and a second member movable relative to said first member and having a second orifice, said second member being movable between a position wherein said first and seocnd orifices are substantially out of alignment for substantially blocking the flow of air into the conduit, and a position wherein said first and second orifices are substantially in full alignement for admitting a large amount of air into the conduit, said first and second orifices cooperating to define said variable orifice; said motor means being connected to said second member for moving said second member relative to said first member according to the value of said differential integrated signal.

Claim 7

The invention according to claim 5 wherein said first member further includes a supplemental orifice alignable with said first orifice for venting air from the conduit; and said adjusting means further includes comparison means electrically connected to an electrical source, said source transmitting to said comparison means a positive pressure signal whose value corresponds to a predetermined positive value, to said suction transducer means and to said motor means; said comparison means generating positive pressure vent signal for adjusting said motor means to move said second member to align said supplemental orifice with said first orifice to vent air from the conduit when said actual suction signal exceeds said positive pressure signal.

Claim 8

The invention according to claim 1 and further comprising: patient air flow transducer means for generating an air flow signal whose value is reflective of the rate of flow of air from the body cavity in the conduit.

Claim 9

The invention according to claim 7 wherein said patient air flow transducer means comprises: flap valve means mounted across the conduit between a closed position for blocking the conduit to air flow and a wide open position for enabling a maximum air flow; and an electrical air flow circuit operatively connected to said flap valve means for generating a patient air flow signal corresponding to the amount of movement of said flap valve means.

Claim 10

The invention according to claim 8 and further including means for moving said flap valve means to the closed position when the pressure in the conduit exceeds atmospheric pressure.

Claim 11

The invention according to claim 7 and further including patient air flow filtering means for filtering from the signal generated by said air flow transducer means signal components reflective of pressure variations in the conduit caused by normal activity in the body cavity.

Claim 12

The invention according to claim 1 and further comprising: positive pressure vent means for venting air from the conduit when the air pressure in the conduit exceeds a predetermined value, to prevent fluid in the conduit from flowing into the body cavity.

Claim 13

The invention according to claim 1 and further comprising: negativity transducer means for generating an electrical actual negativity signal reflective of the negativity pressure in the body cavity.

Claim 14

The invention according to claim 12 and further comprising: negativity air admission means electrically connected to said negativity transducer means and being actuable for admitting atmospheric air into the conduit when said negativity signal exceeds a predetermined suction value.

Claim 15

The invention according to claim 13 and further comprising: negativity comparison means electrically connected to an electrical source transmitting an electrical signal to said negativity comparison means corresponding to said predetermined suction value, and to said negativity transducer means, for generating a negativity signal to actuate said negativity air admission means when said actual negativity signal exceeds said predetermined suction value.

Claim 16

The invention according to claim 14 wherein said negativity air admission means comprises: valve means for opening and closing a port in the conduit to the atmosphere; solenoid rod means for moving said valve means between the opening and closing positions; and solenoid coil means energizable for moving said rod to open said valve means in response to the generation of said negativity signal.

Claim 17

The invention according to claim 12 and further comprising: maximum negativity holding means operatively connected to said negativity transducer means for storing the maximum actual negative signal generated by said negativity transducer means over a period of time.

Claim 18

The invention according to claim 38 wherein said maximum negativity holding means includes: storage means for storing the maximum actual negativity signal generated by said negativity transducer means, and means for replacing any such stored signal with a yet greater actual negativity signal subsequently generated by said negativity transducer means.

Claim 19

The invention according to claim 12 and further comprising: excessive negativity means electrically connected to said negativity transducer means for opening the conduit to the atmosphere when said actual negativity signal exceeds a predetermined value.

Claim 20

The invention according to claim 1 and further comprising: liquid collection means for receiving liquids drained from the body cavity; and liquid collection transducer means for generating signals reflective of the amount of liquid collected by said liquid collection means.

Claim 21

The invention according to claim 19 wherein said liquid collection means comprises a chamber, and the invention further comprises: dead space limiter means for blocking to air flow from the conduit a portion of said chamber not filled with liquid to expedite air and liquid flow from the body cavity.

Claim 22

The invention according to claim 20 wherein said dead space limiter means comprises a receptacle for receiving predetermined quantities of liquid drained from the body cavity, and emptying means actuable for discharging liquid from said receptacle into said chamber when said receptacle has received said predetermined quantity of liquid.

Claim 23

The invention according to claim 21 wherein said emptying means comprises: electrical emptying circuit means having contacts operatively associated with said receptacle, the impedance between said contacts being low when said receptacle has received said predetermined volume of liquid and said impedance being otherwise high; said emptying means being actuable for discharging liquid from said receptacle when the impedance between said contacts is low.

Claim 24

The invention according to claim 22 wherein said contacts are disposed to contact liquid collected in said receptacle only when said receptacle has received said predetermined volume of liquid in said receptacle to assume between them a low resistance, and said contacts assuming between them a high resistance when said receptacle has not received said predetermined volume of liquid, and wherein said electrical emptying circuit means comprises: resistance means having a resistance value intermediate said high and low resistances between said contacts; and electrical source means for impressing a voltage across said resistance means and across said contacts; and switch means for closing said circuit means to actuate said emptying means when the resistance between said contacts is low.

Claim 25

The invention according to claim 23 wherein said switch means comprises: inverter means electrically connected to said contacts, to said resistance means, and to said emptying means; said inverter means having a low state wherein it does not transmit a signal to actuate said emptying means when the resistance between said contacts is high, and said inverter means having a high state wherein it transmits an energizing signal to actuate said emptying means when the resistance between said contacts is low.

Claim 26

The invention according to claim 24 wherein said emptying means comprises: door means actuable for opening said receptacle to discharge the liquid contents of said receptacle; and solenoid means connected to said door means for actuating said door means in response to energization of said solenoid means, said solenoid means being electrically connected to said inverter means and being energized in response to the transmission of said energizing signal by said inverter means.

Claim 27

The invention according to claim 24 wherein said switch means further comprises: transistor means for transmitting an actuating signal to said emptying means in response to the transmission of an energizing signal by said inverter means.

Claim 28

The invention according to claim 24 and further comprising: door means actuable for opening said receptacle to discharge the liquid contents of said receptacle; solenoid means connected to said door means for actuating said door means in response to energization of said solenoid means; biassing means for closing said door means when said solenoid is de-energized; transistor means for transmitting an actuating signal to said solenoid means to energize said solenoid means in response to the transmission of an energizing signal by said inverter means; and delay means for maintaining the energization of said solenoid means to maintain said door means open for emptying said receptacle.

Claim 29

The invention according to claim 19 wherein said liquid collection transducer means comprises volume transducer means for generating volume signals reflective of the volume of liquid collected in said liquid collection means.

Claim 30

The invention according to claim 19 wherein said liquid collection transducer means comprises weight transducer means for generating weight signals reflective of the weight of liquid collected in said liquid collection means.

Claim 31

The invention according to claim 1 and further comprising: temperature transducer means for generating signals reflective of the temperature of fluids in the body cavity.

Claim 32

The invention according to claim 1 wherein said adjusting means comprises: set point selection means for establishing a reference signal reflective of said predetermined suction value; and error signal generating means electrically connected to said set point selection means, to said suction transducer means, and to said suction controlling means, for generating adjusting signals to said suction controlling means to adjust said suction controlling means to bring the actual suction signal within a predetermined limit from the predetermined suction value.

Claim 33

The invention according to claim 1 wherein said suction control means comprises: variable orifice means for controlling the suction in the conduit by admitting atmospheric air into the conduit, said variable orifice means including relatively movable members defining a variable orifice in the conduit; and wherein said adjusting means comprises: means for moving at least one of said members to establish an orifice of the size necessary for admitting atmospheric air into the conduit to establish the predetermined value of suction in the conduit.

Claim 34

The invention according to claim 32 wherein said suction control means further comprises: suction air flow measuring means for measuring the rate of atmospheric air flow through said variable orifice into the conduit.

Claim 35

The invnetion according to claim 33 wherein said suction air flow measuring means comprises: flap valve means movably mounted across said variable orifice, said flap valve means being movable by an amount reflective of the air flow rate through said orifice, and electrical circuit means for generating a suction air flow signal corresponding to the amount of movement of said flap valve means.

Claim 36

The invention according to claim 34 wherein said suction control means comprises: a first member having a first orifice for admitting atmospheric air into the conduit, said flap valve means being mounted for movement between a position closing said first orifice and a position opening said first orifice corresponding to a maximum flow of air through said first orifice; and a second member movable relative to said first member and having a second orifice, said second member being movable between a position wherein said first and second orifices are substantially out of alignment for substantially blocking the flow of air into the conduit, and a position wherein said first and second orifices are substantially in full alignment for admitting a large amount of air into the conduit, said first and second orifices cooperating to define said variable orifice according to the extent said first and second orifices overlap; said adjusting means being operatively connected to said second member for moving said second member relative to said first member according to deviation of said actual suction signal from the predetermined suction value.

Claim 37

The invention according to claim 35 wherein said first member further comprises a supplemental orifice, said second member being movable to align said second orifice with said supplemental orifice for venting gas from the conduit when the air pressure in the conduit exceeds atmospheric pressure by a predetermined amount.

Claim 38

The invention according to claim 1 wherein said adjusting means comprises: suction selection means for generating a suction signal whose value corresponds to the predetermined suction value; differential integrating means electrically connected to said suction transducer means and to said suction selection means for receiving said actual suction signal and said suction signal, and for generating a differential integrated signal corresponding to the integral of the difference between said suction selection signal and said actual suction signal; and motor means operatively connected to said suction control means and to said differential integrating means for adjusting said suction control means according to the value of said differential integrated signal to establish said predetermined suction value in the conduit.

Claim 39

The invention according to claim 37 and further including positive pressure vent means for venting air from the conduit when the air pressure in the conduit exceeds a predetermined positive value to prevent air in the conduit from flowing into the body cavity, said positive pressure vent means comprising: comparison means electrically connected to an electrical source, said source transmitting to said comparison means a positive pressure signal whose value corresponds to said predetermined positive value, to said suction transducer means, and to said suction regulator means; said comparison means generating a positive pressure vent signal for adjusting said suction control means to vent air from the conduit when said actual suction signal exceeds said positive pressure vent signal.

Claim 40

The invention according to claim 1 and further including suction flow filtering means for filtering from the signal generated by said suction transducer means signal components reflective of short term pressure variations.

Claim 41

The invention according to claim 1, 2, 12, 19, 30, 32, 34, 37 or 3, and further comprising display means electrically connected to the respective transducer means for displaying the signals generated by the respective transducer means and the signal corresponding to said predetermined suction value.

Claim 42

An electronic drainage system for monitoring and controlling the flow of fluid in a suction conduit for an inaccesible body cavity, said system comprising; adjusting means for generating signals whose values are reflective of a predetermined suction value; suction transducer means for generating actual suction signals whose values are reflective of the suction in the conduit; suction control means operatively connected to said adjusting means and to said suction transducer means for admitting atmospheric air into the conduit to regulate the suction in the conduit according to the value of said adjusting means signals and of said actual suction signals while maintaining air suction in the conduit and suction air flow transducer means for generating suction air flow signals whose values are reflective of the air flow into the conduit; patient air flow transducer means associated with said suction control means for generating patient air flow signals whose values are reflective of the rate of patient air flow in the conduit; negativity transducer means associated with said patient air flow transducer means for generating actual negativity signals whose values are reflective of the negativity pressure in the body cavity; liquid collection means for collecting liquid drain from the body cavity, and liquid collection transducer means for generating liquid collection signals whose values are reflective of the amount of liquid collected by said liquid collection means; and temperature transducer means for generating temperature signals whose values are reflective of the temperature of fluid in the body cavity; multiplexer means electrically connected to said at least two signal generating means for alternatively transmitting signals from said at least two signal generating means; display means for displaying in intelligible form symbols in response to signals transmitted to said display means; and signal processing means electrically connected to said multiplexer means for processing signals transmitted by and received from said multiplexer means into signals readable by said display means, and for transmitting processed signals to said display means.

Claim 43

An electronic drainage system for monitoring and controlling the flow of fluid in a suction conduit for an inaccesible body cavity, said system comprising; adjusting means for generating signals whose values are reflective of a predetermined suction value; suction transducer means for generating actual suction signals whose values are reflective of the suction in the conduit; suction control means operatively connected to said adjusting means and to said suction transducer means for admitting atmospheric air into the conduit to regulate the suction in the conduit according to the value of said adjusting means signals and of said actual suction signals while maintaining air suction in the conduit and suction air flow transducer means for generating suction air flow signals whose values are reflective of the air flow into the conduit; patient air flow transducer means associated with said suction control means for generating patient air flow signals whose values are reflective of the rate of patient air flow in the conduit; negativity transducer means associated with said patient air flow transducer means for generating actual negativity signals whose values are reflective of the negativity pressure in the body cavity; liquid collection means for collecting liquid drain from the body cavity, and liquid collection transducer means for generating liquid collection signals whose values are reflective of the amount of liquid collected by said liquid collection means; and temperature transducer means for generating temperature signals whose values are reflective of the temperature of fluid in the body cavity; multiplexer means electrically connected to said at least two signal generating means for alternatively transmitting signals from said at least two signal generating means; display means for displaying in intelligible form symbols in response to signals transmitted to said display means; and signal processing means electrically connected to said multiplexer means for processing signals transmitted by and received from said multiplexer means into signals readable by said display means, and for transmitting processed signals to said display means.

Claim 44

The invention according to claim 41 wherein said signal generating means each generate analog signals, said display means comprises digital display means for displaying said signals in response to digital signals transmitted to said digital display means, and said signal processing means comprises analog-to-digital converter means for converting analog signals received from said signal generating means into digital signals readable by said digital display means.

Claim 45

The invention according to claim 41 and further comprising: parameter locking means electrically connected to said multiplexer means for locking said multiplexer means to transmit signals from only a selected one of said signal generating means to said signal processing means.

Claim 46

The invention according to claim 43 and further comprising: parameter indicating means electrically connected to said parameter locking means for indicating the selected one of said signal generating means locked by said multiplexer means.

Claim 47

The invention according to claim 44 wherein said display means comprises a numerical display for displaying a number to which said selected signal corresponds.

Claim 48

The invention according to claim 41 wherein said displays means comprises a plurality of numerical display electrically connected to said signal generating means respectively, for displaying a number to which the signal generated by said respective signal means corresponds.

Claim 49

The invention according to claim 41 wherein said signal processing means comprises an amplifier for amplifying the respective signals transmitted to said amplifier by said multiplexer means.

Claim 50

The invention according to claim 41 wherein said liquid collection transducer means includes weight transducer means for generating weight signals whose values are reflective of the weight of the liquid collected by said liquid collection means.

Claim 51

The invention according to claim 41 wherein said liquid collection transducer means includes volume transducer means for generating volume signals whose values are reflective of the volume of liquid collected by said liquid collection means

Claim 52

An electronic drainage system for monitoring gases and liquids flowing in a suction conduit from a pleural cavity and for controlling the suction in the suction conduit, said system comprising: suction control means for controlling the suction in the conduit for the purpose of regulating the flow of gas and liquid from the pleural cavity, said suction control means including air admission means for admitting atmospheric air into the conduit while maintaining a suction in the conduit; suction transducer means for monitoring the pressure in the suction conduit and for generating actual suction signals whose values are reflective of the suction in the conduit; positive pressure vent means for venting gas from the conduit when the gas pressure in the conduit exceeds atmospheric pressure by a predetermined amount; patient air flow transducer means for generating air flow signals whose values are reflective of the rate of air flow from the pleural cavity in the conduit; patient negativity transducer means for generating actual negativity signals whose values are reflective of the negativity pressure in the pleural cavity; excessive negativity means for admitting atmospheric air into the conduit when the actual negativity is less than a predetermined value; liquid collection means for collecting liquid drained from the pleural cavity; multiplexer means electrically connected to said suction transducer means, said patient air flow transducer means and to said patient negativity transducer means, for alternatively transmitting the signals generated by said respective transducer means; signal processor means electrically connected to said multiplexer means for processing signals transmitted by said multiplexer means; and display means electrically connected to said signal processor means for displaying in intelligible form signals corresponding to the signals transmitted by signal processor means.

Claim 53

An electronic drainage system for monitoring gases and liquids flowing in a suction conduit from a pleural cavity and for controlling the suction in the suction conduit, said system comprising: suction control means for controlling the suction in the conduit for the purpose of regulating the flow of gas and liquid from the pleural cavity, said suction control means including air admission means for admitting atmospheric air into the conduit while maintaining a suction in the conduit; suction transducer means for monitoring the pressure in the suction conduit and for generating actual suction signals whose values are reflective of the suction in the conduit; positive pressure vent means for venting gas from the conduit when the gas pressure in the conduit exceeds atmospheric pressure by a predetermined amount; patient air flow transducer means for generating air flow signals whose values are reflective of the rate of air flow from the pleural cavity in the conduit; patient negativity transducer means for generating actual negativity signals whose values are reflective of the negativity pressure in the pleural cavity; excessive negativity means for admitting atmospheric air into the conduit when the actual negativity is less than a predetermined value; liquid collection means for collecting liquid drained from the pleural cavity; multiplexer means electrically connected to said suction transducer means, said patient air flow transducer means and to said patient negativity transducer means, for alternatively transmitting the signals generated by said respective transducer means; signal processor means electrically connected to said multiplexer means for processing signals transmitted by said multiplexer means; and display means electrically connected to said signal processor means for displaying in intelligible form signals corresponding to the signals transmitted by signal processor means.

Claim 54

The invention according to claim 50 and further comprising: maximum negativity holding means electrically connected to said signal processor means for receiving and retaining actual negativity signals generated by said negativity transducer means whose value exceeds that of previously generated actual negativity signals.

Claim 55

The invention according to claim 51 wherein said maximum negativity holding means comprises latching means for storing maximum negativity signals; and wherein said system further comprises comparison means electrically connected to said multiplexer means and to said latching means for comparing actual suction signals transmitted by said multiplexer means with the maximum negativity signal stored in said latching means, and for generating a new maximum negativity signal when an actual suction signal exceeds the stored maximum negativity signal, said latching means storing the actual suction signal in response to the generation of a new maximum negativity signal.

Claim 56

The invention according to claim 52 and further comprising: AND gate means having high and low states; and said AND gate means having an output connected to said latching means, and first, second and third inputs; decoder means having a maximum negativity gate connected to the first input of said AND gate means, said maximum negativity gate transmitting a decoder signal to the first input of said AND gate means in response to maximum negativity timing signals; oscillator means for periodically transmitting maximum negativity timing signals to said decoder means; and counter control means electrically connected to the second input of said AND gate means for periodically generating store signals; and wherein said comparison means has an output port electrically connected to the third input of said AND gate means; said AND gate means assuming its high state in response to the transmission of a decoder signal, a store signal and a new maximum negativity signal to its respective first, second and third inputs; and said latching means replacing a stored maximum actual negativity signal with the new maximum negativity signal in response to said AND gate assuming its high state.

Claim 57

The invention according to claim 51 for arbitrarily resetting said maximum negativity holding means to a predetermined value.

Claim 58

The invention according to claim 51 wherein said maximum negativity means is further electrically connected to said multiplexer means for periodically receiving signals generated by said negativity transducer means.

Claim 59

The invention according to claims 16 or 51 and further comprising means for arbitrarily resetting said maximum negativity holding means.

Claim 60

The invention according to claims 41, 50 or 55 and further comprising processor-printer means electrically connected to said multiplexer means for periodically receiving signals transmitted by said multiplexer means and for periodically printing values corresponding to the respective values of said received signals in intelligible form.

Claim 61

The invention according to claims 1, 41 or 50 and further comprising an electrical battery for energizing said system, and low battery voltage warning means connected to said battery for generating a warning signal when the voltage of said battery falls below a predetermined value.

Claim 62

The invention according to claims 41, or 50 and further comprising electrical battery means for energizing said system, low battery voltage warning means connected to said battery means and to said display means for transmitting a warning signal to said display means for indicating when the voltage of said battery means falls below a predetermined value.

Claim 63

The invention according to claim 50 wherein said signal processor means comprises amplifier means for amplifying signals generated by said respective transducer means and transmitted by said multiplexer means.

Claim 64

The invention according to claim 60 wherein said processor means further comprises: voltage-to-frequency converter means connected to said amplifier means for receiving signals amplified by said amplifier means; and first counter means electrically connected to said voltage-to-frequency means for generating count signals according to the frequency of said amplified signals; said display means being connected to said first counter means for generating in intelligible form, signals according to the count signals generated by said first counter means.

Claim 65

The invention according to claims 50 or 61 and further comprising system clock and timing function means electrically connected to said multiplexer means and to said signal processor means for generating timing signals to control the timing and sequencing of the operations of said multiplexer means and of said signal processor means.

Claim 66

The invention according to claim 61 and further comprising system clock and timing function means electrically connected to said multiplexer means and to said signal processor means for generating timing signals to control the timing and sequencing of the operations of said multiplexer means and of said signal processor means, said system clock and timing function means comprising: decoder means electrically connected to said multiplexer means for adjusting said multiplexer means to transmit actual signals from said suction transducer means, in response to the reception of timing signals by said decoder means; second counter means electrically connected to said decoder means for sending timing signals to said decoder means in response to timing pulses; and oscillator means for sending timing pulses to said second counter means to cause said second counter means both to actuate said decoder means and to cause said multiplexer means to transmit actual suction signals from said suction transducer means.

Claim 67

The invention according to claim 50 and further comprising: mode indicator means electrically connected to said display means for indicating the type of signal being displayed on said display means.

Claim 68

The invention according to claim 63 wherein said decoder means includes a plurality of gates corresponding to the respective transducer means, the respective gates having high states when said multiplexer means transmits signals from the transducer means to which the respective gates correspond, and said system comprising: mode indicator means electrically connected to the respective gates of said decoder means, said mode indicator means generating intelligible signals reflective of which of said gates is in its high state for indicating the transducer means from which said multiplexer means is transmitting signals to said display means.

Claim 69

The invention according to claim 64 or 65 wherein said mode indicator means comprises mode indicator lights and said intelligible signals comprises illumination of the respective lights.

Claim 70

The invention according to claim 63 and further comprising: counter control means electrically connected to said oscillator means and to said first counter means for controlling said first counter means, said counter control means generating store signals to said first counter means in response to timing pulses from said oscillator means to limit the number of count signals generated by said first counter means, and said counter control means generating reset signals in response to the termination of said store signals to reset said first counter means in preparation for the next signal to be transmitted by said multiplexer means.

Claim 71

The invention according to claim 50 or 51 and further comprising: locking means for locking said multiplexer means to transmit a particular one of its input signals for display on said display means, said locking means comprising: system clock and timing function means electrically connected to said multiplexer means and to said signal processor means for generating timing signals to control the timing and sequencing of said multiplexer means and of said signal processor means; voltage source means; parameter transmission means energizable for alternatively transmitting signals corresponding to signals transmitted by said multiplexer means; mode select means actuable for selectively connecting said parameter transmission means to said voltage source means to energize the selected parameter transmission means; and clock connection means connecting said parameter transmission means to said system clock and timing function means; said clock connection means being actuable in response to actuation of the respective mode selection means to increase the frequency of the generation of timing signals by said system clock and timing function means to decrease the time when said multiplexer means next transmits the signal to which said mode select means corresponds.

Claim 72

The invention according to claim 1, 41 or 50 wherein said suction control means maintains a fixed value of suction in the conduit.