GB2138598A - Electrical Circuitry for Setting the Position of an Appliance - Google Patents
Electrical Circuitry for Setting the Position of an Appliance Download PDFInfo
- Publication number
- GB2138598A GB2138598A GB08410082A GB8410082A GB2138598A GB 2138598 A GB2138598 A GB 2138598A GB 08410082 A GB08410082 A GB 08410082A GB 8410082 A GB8410082 A GB 8410082A GB 2138598 A GB2138598 A GB 2138598A
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- United Kingdom
- Prior art keywords
- value
- measured voltage
- bridge
- electrical circuitry
- potentials
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Classifications
-
- E—FIXED CONSTRUCTIONS
- E06—DOORS, WINDOWS, SHUTTERS, OR ROLLER BLINDS IN GENERAL; LADDERS
- E06C—LADDERS
- E06C5/00—Ladders characterised by being mounted on undercarriages or vehicles Securing ladders on vehicles
- E06C5/32—Accessories, e.g. brakes on ladders
- E06C5/34—Indicating devices
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D3/00—Control of position or direction
- G05D3/12—Control of position or direction using feedback
- G05D3/14—Control of position or direction using feedback using an analogue comparing device
- G05D3/1472—Control of position or direction using feedback using an analogue comparing device with potentiometer
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Automation & Control Theory (AREA)
- Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)
Abstract
To position an appliance such as a rescue cage of a turntable ladder, circuitry is used which comprises desired-value and actual-value elements (13 and 14) which are connected in a measuring bridge (10), the desired-value element (13) being connected to the other parts of the circuitry by a lead (11) in a cable (5) also containing leads (1, 2, 3, and 4) which carry potentials other than the measured voltage potential of the desired-value element (13), and means are provided to obviate faulty operation of the control system in the event of cable defects. One way of doing this (Figure 1) consists in restricting the potentials of the supply voltage to the measuring bridge (10) so as to make the extreme value of the measured voltage smaller than the difference between any of the extreme potentials of the measured voltage and any of the other potentials, and in providing a safety cut-off (30) if the value of the measured voltage is greater than its extreme value. A second method (Figure 2) involves isolating the measuring bridge (10) from the other potentials completely, by eliminating direct electrical contact between them. <IMAGE>
Description
SPECIFICATION
Electrical Circuitry for Setting the Position of an Appliance
This invention relates to electrical circuitry for use in setting the position of an appliance which can be moved by a drive unit, especially but not exclusively for use in setting the position of a rescue cage of a turntable ladder, comprising a desired-value element and an actual-value element, which are parts of a measuring bridge and which are in the form of variable resistors, potentiometers, or other electrical devices so that a measured voltage taken across the bridge diagonals represents the deviation of the actual from the desired value, a control circuit which responds to the measured voltage and delivers a control signal for controlling the drive unit so as to reduce the measured voltage to substantially zero, the desired-value element being connected to the actual-value element by a cable which contains additional leads for applying a power voltage to equipment situated adjacent to the desired-value element.
German Patent Specification 22 07 894 describes, for the purpose of setting the position of an appliance, the use of a desired-value element to determine the desired position of the appliance and of an actual-value element to indicate the real position at any time, these elements being arranged in the form of a bridge, in such a way that the voltage measured across the bridge diagonals represents the deviation of the desired value from the actual value. This arrangement, which is designed primarily for the remote control of the drive unit of a rotatable aerial, embodies a control circuit which responds to the measured voltage, and emits a control signal to control the drive unit in the direction required to reduce the measured voltage to zero.
In many applications of a servo or overrun control of this construction, the operating station contains the desired-value element, and is located in a position distant from that of the actual-value element and the control circuit. Also, the two positions move relative to each other whenever the position of the movable appliance is altered.
This is the case, for example, if the moveable appliance is the rescue cage of a turntable ladder, which can be manoeuvred by the people in it For this purpose, the rescue cage is fitted with a control desk which accommodates, among other things, the desired-value element for the overrun control of the swivelling base or the extending mechanism of the turntable ladder. It is usual in such cases to connect the desired-value element to the actual-value element and to the control circuit which, together with the drive unit, are located at the base of the turntable ladder, via the same cable, which also contains the leads employed to carry the power supply to other equipment required in the rescue cage. These other items of equipment may be, for instance, floodlights and electrical appliances used in rescue operations.
Where such a cable connection is employed between the desired-value element and the control circuit, there is a danger of cable defects giving rise to distorted readings of the measured voltage. Any distortion of the measured voltage caused by a cable defect, may bring the control circuit into undesired operation, resulting in uncontrolled movement of the appliance. The provision of an emergency switch, controlled by the operator, for shutting off the drive unit as a safety measure does not resolve this problem satisfactorily, as the reaction time of the operator may be too long to ensure a switch-off within the required time. The same drawback is found also with the so-called dead-man function of the oil pressure switch, which has been used hitherto, since this switch needs, in the initial control phase when faults occur, an operator-dependent reaction time.In both cases, the critical point is that the safety switch-off occurs only after the uncontrolled movement has begun.
An aim of the present invention is to improve the inherent safety of electrical circuitry of the construction set out in the opening paragraph of the present specification. Accordingly, the present invention is directed to such electrical circuitry in which the voltages applied to the measuring bridge are applied in such a manner that the measured voltage potentials cannot be confused with the power supply potentils.
The principle of the invention consists thereunder in ensuring, by means of a separate voltage supply to the bridge, that the potentials of the measured voltage cannot be confused with the potentials of the power supply. Thus, if a fault occurs in the cable linking the desired-value element and the control circuit, which produces a short circuit between the lead carrying the measured voltage and either of the power supply lines, the potential then appearing on the measured voltage lead can, because of the fact that, in accordance with the invention, the potentials cannot be confused, be distinguished from the interference-free potential of the measured voltage, so that the danger of an uncontrolled movement can be avoided.The elimination, through the use of a separate voltage supply for the bridge, of confusion between potentials can be achieved in two ways:
According to one way of doing this, the potentials of the voltage supply to the bridge are limited in such a way that the extreme value of the measured voltage is less than the difference between any of the extreme potentials of the measured voltage and any of the power supply potentials. A safety circuit is also provided which receives the measured voltage and switches off the drive unit if the value of the measured voltage exceeds the extreme value. In a manner which will be explained later with reference to an example, this embodiment can be arranged so as to ensure that the drive unit is switched off in the event of any possible combination of short circuits in the cable, and also in the event of any kind of break in the cable.
According to a second method, there is no direct electrical contact whatsoever between the bridge and the supply voltage. The consequence is that, if a shortcircuit arises between any of the leads connected to the bridge and one of the power supply lines in the cable, no distortion of the measured voltage can occur.
Thus, with the first method of implementation referred to above, a safety switch-off is effected if the measured voltage is distorted as a result of cable faults. In the case of the second method of implementation on the other hand, care is taken to ensure, from the outset, that a short-circuit in the cable between any of the leads connected to the bridge and a power supply line does not affect the measured voltage.
Examples of electrical circuitry in accordance with the present invention are illustrated in the accompanying drawings, in which Figures 1 and 2 are circuit diagrams of respective such examples.
In the Figure 1 arrangement there is a bridge 10 which contains a potentiometer 1 3 in a first arm and a potentiometer 1 4 in a second arm, the potentiometers 13 and 14 being in parallel. The sliders 1 5 and 1 6 of the two potentiometers 1 3 and 14 form the diagonals of the bridge, and the measured voltage is the voltage drop across these sliders. The inputs to the bridge 10 are at the junction 17 between the upper ends of the potentiometers 13 and 14, and at the junction 18 between the lower ends of the two potentiometers. Input 17 is connected through a resistor 6 to one line 1 of a power supply, which receives a positive supply voltage from a source of power (not shown).Input 1 8 is connected through a resistor 7 to the other power supply line 2, which carries the negative pole or supply voltage of the power source.
The bridge constitutes a measuring circuit of electrical circuitry for setting the position of an appliance, which can be moved by means of a motor 50. This appliance may be, for example, a rescue cage (not depicted) of a turntable ladder, at the base of which the motor 50 is located, in order to alter the position of the ladder so as to move the rescue cage upwards (by forward running of the motor) or downwards (by reverse running of the motor). At the same time, through a mechanical coupling indicated by the broken line 51, the motor 50 moves the slider 16 of the potentiometer 14 to accord with the movement of the rescue cage. The potential take off this slider therefore indicates the position of the rescue cage, so that the potentiometer 14 constitutes a measured-value element.
The other potentiometer of the bridge 10 forms a desired-value element for the positioning of the rescue cage. If the position of the slider 1 5 of this potentiometer is altered, then the slider potential changes accordingly. The voltage across the potentiometers 1 5 and 1 6 is the required measured voltage, which in size and polarity shows the extent and direction of any deviation between the actual and the desired position of the appliance.
The measured voltage is applied in a control circuit 20 across the inputs of a first differential amplifier 21 and, with reversed polarity, across the inputs of a second differential amplifier 22. If the desired value and the actual value are equal to each other there exists no potential difference between the potentiometer sliders 1 5 and 1 6.
The measured voltage is thus zero, so that neither of the differential amplifiers delivers any output signal. In that case, the motor 50 is not energized.
If the slider 15 of the desired-value potentiometer 13 is shifted in, for example, a positive direction (upwards in Figure 1), its potential will become more positive than the potential of the slider 1 6, causing the differential amplifier 21 to respond and apply through its output lead 23 a signal to the "forwards" input of the motor control circuit 60. This brings the motor 50 into forward drive, which moves the rescue cage upwards and, at the same time, shifts the slider 1 6 of the'actual-value potentiometer 14 upwards, thereby making the potential of the slider 1 6 more positive. When the potential of the slider 1 6 reaches the desiredvalue potential to which the slider 1 5 has been set, the measured voltage is again zero, so that the control signal from the output of the amplifier ceases, and the motor stops.The rescue cage has then attained the desired position set on the potentiometer 13.
If the position of the slider 1 5 of the desiredvalue potentiometer 1 3 is moved in a negative direction (downwards), the differential amplifier 22 comes into operation, so as to apply a control signal appearing on its output lead 24 to the "reverse" input of the motor supply circuit, which causes the motor 50 to run in reverse, until the measured voltage is again zero.
The part of the bridge 10 which contains the desired-value potentiometer 1 3 is connected, in the case shown, by a cable to the control circuit 20 (and also with the actual-value potentiometer 14). Such a cable connection is necessary when the desired-value potentiometer 13 is located in an operating position at a distance from the control circuit and the motor. Should the operating position, as in the example described here, be situated in the moveable rescue cage of a turntable ladder, this cable link may be subjected to severe tension and bending stresses, which means that there is a risk of cable faults. As well as breaks in the cable, short-circuits may occur between the leads connected to the bridge and other leads carrying external voltages.
In the circuitry shown in Figure 1, the cable link between the location of the control circuit 20 and the location of the desired-value potentiometer 13 contains a total of five conductors or leads: (1) the measurement lead 11 between the slider 1 5 of the desired-value potentiometer 1.3 and the control circuit 20; (2) the connecting lead 3 connecting respective ends of the bridge potentiometers 1 3 and 14; (3) the connecting lead 4 connecting the other ends of the bridge potentiometers 13 and 14, the leads 3 and 4 applying the supply voltage to the bridge; (4) the power supply lead 1, and (5) the power supply lead 2, the leads 1 and 2 carrying the potentials of the power supply.These power supply leads 1 and 2 are also required in order to provide power for other equipment in the rescue cage, as was mentioned earlier. A description is given below of how it is possible, by specially limiting the supply voltage to the bridge, and by employing a safety circuit 30, to ensure that cable faults which distort the potential on the measurement lead 1 t can not produce any undesired or uncontrolled excitation of the motor 50.
The potentials of the voltage supply to the inputs 17 and 18 of the bridge, and thus on the supply leads 3 and 4, are limited compared to the potentials of the power supply voltage on leads 1 and 2 in such a way that the extreme value of the measured voltage reading is less than the difference between any extreme value of the measured voltage potentials, and any of the power supply potentials. The term "extreme value" stands for the value at the end of the range of possible values of the parameter concerned, 'when the system is in proper working order. The potentials measured at the sliders 1 5 and 1 6 have their extreme values when each slider is positioned at the end of the adjustable range of each potentiometer.The measured voltage attains its extreme value with one polarity when the slider 1 5 is in its furthest positive position and the slider 1 6 in its furthest negative position, and its extreme value with the opposite polarity when the slider 1 5 is in its furthest negative position and the slider 1 6 in its furthest positive position.
The foregoing requirement with regard to the supply voltage potentials to the bridge as against the power supply potentials is met when the supply voltage between the leads 3 and 4 amounts to less than one third of the power supply voltage between leads 1 and 2 and is, in addition, less than the potential difference between the leads 1 and 3 and the potential difference between the leads 2 and 4. This is achieved by means of resistors 6 and 7 which each have a resistance value which is greater than the total resistance of the two parallel arms of the bridge.
The consequence of limiting the supply voltage to the bridge 10 is that, in the case of a shortcircuit between the measurement lead 11 and either of the power supply leads 1 and 2 within the cable length represented by the broken line frame 5, the measured value assumes in every instance (i.e. in every possible position of the potentiometer sliders 1 5 and 16) a value which is greater than the maximum value possible (the extreme value) in proper operation. This means that the overstepping of this extreme value can be taken to indicate the existence of a fault and used to switch off the motor 50 as a safety measure.
For this purpose, a safety circuit 30 is provided which receives the measured voltage and-delivers a signal that switches off the motor, if the value of the measured voltage is greater than the extreme value.
The safety circuit 30 contains two contact
assemblies 31 and 32, which take the form of
differential amplifiers with response threshold.
The differential amplifiers 31 and 32 in the safety
circuit 30 are arranged in the same way and
receive the measured voltage in a similar manner
to the differential amplifiers 21 and 22 in the
control circuit 20.
The safety circuit 30 differs from the control
circuit 20 in that the differential amplifiers 31 and
32 deliver an output signal to the lead 33 only
when the measured voltage exceeds a
predetermined threshold value. This threshold
value is selected to be a little higher than the
extreme value of the measured voltage. The
output from the safety circuit to the lead 33 is
coupled to the motor supply circuit 40, in order to
switch off the motor 50.
In order to guarantee that the safety circuit 30
will also be brought into action if a short-circuit
occurs with the cable 5, between the
measurement lead 11 and either of the bridge
supply leads 3 and 4, a favourable arrangement
provides for the desired-value and actual-value
potentiometers, with respect to the range over
which they can be adjusted, to be proportioned
and arranged in the bridge in such a way that the
extreme value of the measured voltage is also
smaller than the difference between any of the
extreme potentials of the measured voltage and
any potential of the power supply. This is
achieved by having, between each end of the
adjustable range of the potentiometer concerned
and the respective nearest input to the bridge, a
resistor which has, in each case, a higher value
than the resistance between one end and the
other of the adjustable range.This is illustrated in
detail in Figure 1 for the desired-value
potentiometer 1 3. There, the potentiometer
resistance 13 is divided by broken lines into three
sections, namely a centre section 13a, which
represents the adjustable range of the
potentiometer, and the two end sections 1 3b and
13c. The resistance value of each of the sections 1 3b and 1 3c is greater than the resistance of the
section 13a. The same division exists in the actual-value arm of the bridge with respect to the
adjustable range of the potentiometer 1 4. If, with
this arrangement, a break occurs in the supply
lead 3 inside the cable 5, then the slider 1 6 of the
actual-value potentiometer 1 4 will attain the
potential of the other supply lead 4. The value of
the measured voltage then exceeds its extreme
value, which brings the safety circuit 30 into
operation. A similar situation applies in the case
of a break in the bridge supply lead 4. The slider
1 6 then acquires the potential of the supply lead
3, so that the measured voltage likewise becomes
larger than its extreme value. Equally, a short
circuit between the measured voltage lead 11 and
either of the bridge supply leads 3 and 4 inside
the cable 5 causes the safety circuit to respond,
because the measured voltage then becomes in a
similar way greater than its extreme value.
Another favourable arrangement provides for
the input to the safety circuit 30, which receives
the measured voltage potential coming from the
desired-value element 13, to be connected
through at least one decoupling resistor to one of
the power supply poles. In the case of Figure 1,
this connection is made, for instance, via the
resistor 36, which lies between the input to the
differential amplifier, which is connected to the
measured voltage lead 11, and the power supply
lead 2.The result of this connection is that, in the
event of a break occurring in the measured
voltage lead 11 inside the cable 5, the input to the
safety circuit 30 which is connected to this
measurement lead assumes the negative
potential of the lead 2, so that the potential
difference sensed by the safety circuit 30
becomes greater than the extreme value of the
measured voltage, and the safety circuit responds,
switching off the motor 50.
It will be ,seen from the foregoing description
that, with any possible cable fault which gives a
distortion of the measured voltage,-the measured
voltage automatically assumes a value which is
greater than its maximum possible value during
normal operation. This causes the safety circuit
30 to switch off the motor 50. In the case of other
possible cable faults, such as a break in the power
supply lines 1 and 2, a short-circuit between the power lines and a short-circuit between the
bridge leads 3 and 4, no final measured voltage
will be produced at all, so that the motor stops.
Besides the resistor 36 already mentioned, a
further resistor 35 is provided at the relevant
input connection to the differential amplifier 31 of
the safety circuit 30 between this input point and
the measurement lead 11. The two resistors
together form a voltage divider for determining
the input and output of the differential amplifier.
For reasons of symmetry, the other differential
amplifier 32 in the safety circuit 30, as well as the
two differential amplifiers 21 and 22 in the
control circuit 20, have similar voltage dividers
connected to their inputs. The values of the
resistors 35 and 36 have to be taken into account
when adjusting the actual response threshold of
the differential amplifier 31.
It may also be mentioned that the resistors 6
and 7, which determine the supply voltage
potentials to the bridge 10, do not necessarily
have to be on the same side of the cable 5 as the
desired-value potentiometer 1 3. They can equally
well be positioned on the other side of the cable,
where the actual-value potentiometer 14 and the
control circuit are situated.
In a second embodiment of the invention, an
example of which is represented in Figure 2, the
impossibility of confusing the supply potentials to
the bridge with the power lead potentials is
brought about by eliminating direct contact
between the supply to the bridge and the power
supply leads. In Figure 2, those parts which
perform the same functions as corresponding
parts in Figure 1 have been given the same
reference numbers. For the sake of clarity, the motor and the motor supply circuit are not shown in Figure 2.
The arrangement of Figure 2 is different from that of Figure 1 in that the resistors 6 and 7 are absent, the bridge supply voltage being obtained instead from a bridge supply circuit 80, which has no direct electrical connection with the power supply leads 1 and 2. A further difference is that, in Figure 2, a safety circuit is not present and an isolating transfer circuit 60, 70 is connected to the output circuit of the control circuit 20, in order to transmit to the motor supply circuit (not shown) control signals V and R for forward and reverse running of the motor.
The bridge supply circuit comprises a vibrator 81 , which breaks the power supply voltage received from the power supply leads 1 and 2, into pulses which are fed through an isolating transformer 82 to a rectifier 83, in order to apply direct current voltage potentials, at points which have no direct electrical contact with the power supply leads 1 and 2, to the inputs 1 7 and 18 of the bridge 1 0. In a similar manner, each transfer circuit 60, 70 contains a vibrator 61,71 for each of the control signals V and R, which breaks up the output signal from the relevant differential amplifier 21 or 22 into pulses, and feeds these via an isolating transformer 62 or 72 to a rectifier 63 or 73, from the direct current output of which the control signals are taken for triggering the motor supply circuit.This transfer unit 60, 70, ensures that there is no direct electrical contact between the bridge 10 and the power supply leads 1 and 2 via the motor supply circuit. This indirect coupling must be connected as shown, after the differential amplifiers 21 and 22, because these differential amplifiers are supplied, in the case shown, from the supply voltage of the bridge. If, instead, the supply voltage for the differential amplifiers 21 and 22 is taken from the power supply leads 1 and 2, isolating couplers would have to be fitted to the input instead of the output circuits of the differential amplifiers.
The consequence of isolating circuits from direct electrical contact as just described is that a short-circuit between any of the leads 3, 4 and 11 connected to the bridge 10 and either of the power supply leads 1 and 22 inside the cable 5 does not affect the measured voltage sensed at the inputs to the differential amplifiers 21 and 22.
Such a short-circuit is not therefore capable of putting the motor control into an uncontrolled state.
In an alternative construction, the bridge supply circuit 80 can even be replaced by a battery. It is likewise possible to fit, in place of transformer-based transfer circuits 60 and 70, other coupling devices not involving direct electrical contact, such as optical couplers, each consisting of a light-emitting diode, to which the output signal from the respective differential amplifier 21 or 22 is fed, and a phototransistor to receive the light from this light-emitting diode.
The illustrated arrangements are suitable, not only for controlling rescue cages of turntable
ladders, but can also improve the inherent safety
of any overrun control where a desired-value
element together with an actual-value element forms a measuring bridge, and where there is a
danger of extraneous voltages getting into the
bridge.
Claims (18)
1. Electrical circuitry for use in setting the
position of an appliance which can be moved by a
drive unit, especially but not exciusively for use in
setting the position of a rescue cage of a turntable -ladder, comprising a desired-value element and
an actual-value element, which are parts of a
measuring bridge and which are in the form of
variable resistors, potentiometers, or other
electrical devices so that a measured voltage
taken across the bridge diagonals represents the
deviation of the actual from the desired value, a
control circuit which responds to the measured
voltage and delivers a control signal for
controlling the drive unit so as to reduce the
measured voltage to substantially zero, the
desired-value element being connected to the
actual-value element by a cable which contains
additional leads for applying a power voltage to
equipment situated adjacent the desired-value
element, in which the voltages applied to the
measuring bridge are applied in such a manner
that the measured voltage potentials cannot be
confused with the power supply potentials.
2. Electrical circuitry according to claim 1, in
which the potentials of the supply voltage to the
bridge are limited as against the power supply
potentials in such a way that the extreme value of
the measured voltage is smaller than the
difference between any of the extreme potentials
of the measured voltage and any of the power
supply potentials, and in which a safety circuit is
provided which receives the measured voltage
and switches off the drive unit if the value of the
incoming measured voltage exceeds the extreme
value.
3. Electrical circuitry according to claim 2, in
which the desired-value and actual-value
elements are, as regards their adjustable range,
proportioned and arranged in the bridge in such a
way that the extreme value. of the measured
voltage is also less than the difference between
any of the extreme potentials of the measured
voltage and any potential coming from the supply
voltage.
4. Electrical circuitry according to claim 2 or
claim 3, in which the safety circuit is placed at the
end of the cable opposite that of the desired-value
element.
5. Electrical circuitry according to claim 1, in
which the bridge incorporates the desired-value
and actual-value elements each as a
potentiometer, which lie in parallel arms between
the input points of the bridge and the sliders of
which form the measured voltage points of the
bridge diagonals, and in which the cable
connects, through a first lead, one end of the bridge arm which contains the desired-value element to one end of the bridge arm which contains the actual-value element, through a second lead connects together the other ends of the two arms and, via a third lead, joins the slider of the desired-value potentiometer to the control circuit.
6. Electrical circuitry according to claim 2 or claim 5, in which the input to the bridge is effected by joining the first input point through a first resistor to one pole of the power supply voltage and the second input point through a second resistor to the other pole of the power supply, and in which each of these resistors has a larger value than the total resistance of the two parallel arms of the bridge.
7. Electrical circuitry according to claim 6, in which, between each end of the adjustable range of the desired-value potentiometer and the respective nearest input point of the bridge, there is in each case a resistance which is greater than the resistance between one end and the other of the adjustable range.
8. Electrical circuitry according to claim 6 or claim 7, in which the safety circuit incorporates two contact assemblies with a threshold response, which each receive at a positive and a negative input the two potentials of the measured voltage, in transposed polarity, and each of which delivers an output signal to switch off the drive unit if the potential difference in the polarity assigned to it between its inputs exceeds the extreme value of the measured voltage.
9. Electrical circuitry according to any preceding claim, in which the input to the safety circuit which receives the measured voltage potential coming from the desired-value element is connected to one of the poles of the power supply through at least one decoupling resistor.
10. Electrical circuitry according to claim 8 or 9, in which the contact assemblies contain differential amplifiers.
11. Electrical circuitry according to claim 1, in which the bridge has no direct electrical contact whatsoever with the power supply.
12. Electrical circuitry according to claim 11, in which the bridge is supplied from a battery.
13. Electrical circuitry according to claim 11, in which the input points of the bridge are joined to the direct current output of a rectifier, the alternating current input to which is coupled to the secondary winding of an isolating transformer whose primary winding is fed through a vibrator from the power supply.
14. Electrical circuitry according to any one of claims 11 to 13, in which the output signal from the control circuit is transmitted to the drive unit through a coupling which isolates from direct electrical contact.
15. Electrical circuitry according to claim 14, in which the coupling which isolates from direct electrical contact comprises a vibrator, an isolating transformer connected after it and a following rectifier.
16. Electrical circuitry according to claim 14, in which the coupling which isolates from direct electrical contact consists of an optical coupler.
1 7. Electrical circuitry according to any preceding claim, in which the control circuit contains two differential amplifiers whose inputs receive the measured voltage in transposed polarity, and whose outputs control the direction of motion of the drive unit, according to the polarity of the measured voltage.
18. Electrical circuitry for use in setting the position of an appliance which can be moved by a drive unit, substantially as described herein with reference to Figure 1 or Figure 2 of the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19833314233 DE3314233A1 (en) | 1983-04-20 | 1983-04-20 | ARRANGEMENT FOR ADJUSTING THE POSITION OF A DEVICE, IN PARTICULAR THE RESCUE BASKET OF A TURNTABLE |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8410082D0 GB8410082D0 (en) | 1984-05-31 |
| GB2138598A true GB2138598A (en) | 1984-10-24 |
| GB2138598B GB2138598B (en) | 1987-08-05 |
Family
ID=6196828
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08410082A Expired GB2138598B (en) | 1983-04-20 | 1984-04-18 | Electrical circuitry for setting the position of an appliance |
Country Status (3)
| Country | Link |
|---|---|
| DE (1) | DE3314233A1 (en) |
| FR (1) | FR2547077B1 (en) |
| GB (1) | GB2138598B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10016137C2 (en) * | 2000-03-31 | 2003-08-21 | Iveco Magirus | Drehleiter |
| DE10016136C2 (en) * | 2000-03-31 | 2003-08-21 | Iveco Magirus | Turntable ladder control |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB747555A (en) * | 1952-12-05 | 1956-04-11 | Bristol Company | Remote positioning system |
| GB1149046A (en) * | 1966-10-17 | 1969-04-16 | Cochran And Company Annan Ltd | Electrical circuit |
| GB1157954A (en) * | 1965-04-07 | 1969-07-09 | Express Transformers & Control | Control System for a Ship |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1019741B (en) * | 1954-09-04 | 1957-11-21 | Siemens Ag | Follow-up control, especially for stage lighting systems |
| DE1588641A1 (en) * | 1967-03-04 | 1970-04-09 | Rexroth Gmbh G L | Device for controlling a servomotor, in particular a direct current shunt motor |
| US3714540A (en) * | 1970-11-10 | 1973-01-30 | Oxy Metal Finishing Corp | Isolation and transforming circuit |
| US3789283A (en) * | 1973-02-20 | 1974-01-29 | Honeywell Inc | Condition control reversible motor system |
| DE2836337C2 (en) * | 1978-08-19 | 1987-01-22 | Iveco Magirus AG, 7900 Ulm | Device for switching and monitoring the movements of a motor-driven turntable ladder or similar height-adjustable work equipment |
| DE2837842A1 (en) * | 1978-08-30 | 1980-03-13 | Anschuetz & Co Gmbh | ARRANGEMENT CONTROLLING ARRANGEMENT |
| US4250441A (en) * | 1979-03-09 | 1981-02-10 | Honeywell Inc. | Servo apparatus with electrical motion limiting |
-
1983
- 1983-04-20 DE DE19833314233 patent/DE3314233A1/en active Granted
-
1984
- 1984-03-27 FR FR8404787A patent/FR2547077B1/en not_active Expired
- 1984-04-18 GB GB08410082A patent/GB2138598B/en not_active Expired
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB747555A (en) * | 1952-12-05 | 1956-04-11 | Bristol Company | Remote positioning system |
| GB1157954A (en) * | 1965-04-07 | 1969-07-09 | Express Transformers & Control | Control System for a Ship |
| GB1149046A (en) * | 1966-10-17 | 1969-04-16 | Cochran And Company Annan Ltd | Electrical circuit |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2138598B (en) | 1987-08-05 |
| FR2547077B1 (en) | 1988-02-05 |
| DE3314233A1 (en) | 1984-10-25 |
| FR2547077A1 (en) | 1984-12-07 |
| GB8410082D0 (en) | 1984-05-31 |
| DE3314233C2 (en) | 1992-07-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20000418 |