DE2002844A1 - Switching device with control by measuring sensor - Google Patents

Description

DR.-ING. RICHARD GLAWE

MONKS

7002844

PATENT LAWYERS

DIPL-ING. KLAUS DELFS DIPL.-PHyS. DR. WALTER MOLL

HAMBURG MUNICH

8000 Munich 22 · Liebherr «tro8e20 · Tel. (OSIl) 2265 43 2000 Hamburg 52 Walzstrasse 12 Tel. (0411) 892255

YOUR MESSAGE FROM

OUR SIGN

A 95

MONKS

THE HORSTMANM GEAR COMPANY LIMITED

■ Newbridge Works , Bath, Somerset, England

Switching device controlled by a sensor.

The invention relates to a sensor controlled Switching device with a two-position switch that switches automatically depending on the electrical resistance of a is controlled by an environmental variable influenced sensor, the resistance changing according to changes in the Ambient size changes, so that one controlled by the two-position switch Load is switched on or off when the

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Ambient size in one direction or / in the opposite direction runs through a certain setpoint.

A typical example of such a system is the combination of a photocell in series with a current-sensitive element of a two-position switch for switching street lights on at dawn and switching them off at dusk. The current-sensitive element can be the heating element of a thermal bimetal switch, the actual switch being designed in the manner of a microswitch, which is preloaded into one switch position and can be moved into the other switch position by bending a heated bimetal element accordingly. The micro-switch usually i'st not the actual load switch, but also controls the load switch with a relay or to another intermediate element, as for example in the patent application P 22 I9 53o.O described.

For the sake of simplicity , the invention is described below with reference to such a switching system controlled by a photocell.

Among other things because of the difference in the forces that are used on the one hand to switch on and on the other hand to switch off need to be exercised, it is practically impossible for this to happen

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■ both "processes with exactly the same state of the photocell or another sensor.

If, for example, the lighting is switched on at dusk, when the intensity of daylight has dropped to a certain value and the resistance of the photocell has increased accordingly, then at dawn the lighting will not be at the same daylight intensity, i.e. with the same resistance of the photocell switched on. . * The reason for this lies in the fact that the current controlling the switch in the photocell circuit, in which the controlled switch switches in one direction, differs from the current required for switching in the opposite direction, while on the other hand the current for a given one .The resistance value of the photocell has the same value, regardless of whether the resistance of the photocell is rising or falling. Therefore, depending on the type of circuit used, the lighting can be too long or too short. . m be switched on.

The invention is therefore particularly aimed at creating a sensor-controlled switching system, where the difference between the two values of the Ambient size in which the two-position switch is on

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or is turned off, is much less than this is the case with known switching systems.

According to the invention, a switching device controlled by a sensor with a two-position switch, which is automatically controllable as a function of the rise and fall of the electrical resistance of a sensor when there is a change in an environmental variable and thereby alternately changes its switching position, characterized by a compensation resistor and further switching means, the W automatically add the compensation resistor to the resistance of the sensor when the two-position switch has been switched in one direction, and then remove the compensation resistor again after the two-position switch has been switched in the opposite direction.

The compensation resistor can be continuously in series with be switched to the sensor, with the other switching

• Means consist of a short-circuit switch that leads to the Compensation resistor is connected in parallel, so that the compensation resistor by opening the switch Resistance of the probe added and then removed again by closing the switch.

Instead, two optionally switchable current loops can be assigned to the sensor, one of which

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the 'contains the compensation resistor, the further switching means consist of a changeover switch, which in one switch position the sensor with one current loop and in the other switch position the probe with the. other current loop connects.

The further switching means are preferably also controllable by coupling with the two-position switch.

According to a preferred embodiment is a delay device provided, whereby each of the alternating switching operations of the further switching means takes place, " after the two-position switch has changed its switching position. -.

An embodiment of the invention is described below explained in more detail with reference to the drawing, which schematically shows the circuit diagram of a controlled by a photocell Switching device for switching the street lights on and off shows. "-, ..'._..-

The circuit comprises a photocell 1 with, variable. Barem resistance and the heating element 2 of a bimetal switch provided with changeover contacts 3 j 5 · photocell 1 and heating coil 2 are connected in series via intermediate switching elements, consisting of a first exchange

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switch l8, 2o and a compensation resistor 21, and lie between the terminals L, W of a voltage source. The bimetal switch has two fixed side contacts 3 * 5 and a movable contact 4, the is carried by the free end of a pear alarm 4a. When the heating coil 2 is de-energized and consequently cold, the bimetal switch is in the on position, the movable contact 4 rests against the one side contact 3, as shown in the drawing; if in the Heating winding 2, a current flows that is not less than a predetermined minimum value, is heated as a result Bime.tallarrn 4a bent so that the movable contact 4 separated from the one side contact 3 and on the other side contact 4 is brought to the plant, whereby this switch from the on to the off position is brought. The bimetal switch is thus biased into the one-position.

As will be explained, the on position is that Switch position in which a consumer circuit 24, which contains street lamps, is switched on and energized will. The off position is the switching division at which the consumer circuit is switched off.

The first changeover switch 18, 19, 2o contains one pivotable Kontakbartn 18, which is constantly with one side

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a photocell 1, the other side of which is connected to the supply terminal L. The contact arm 18 is movable between two rare contacts 19-2o, one of which (19) is connected directly to the heating winding 2 and the other (2o) is connected to the heating winding 2 via the compensation resistor 21. As shown, the first changeover switch is in the on position, in which the compensation resistor ^f 21 is not "between the photocell '1 and the heating winding 2. This is the state in which the first changeover switch automatically moves after the consumer circuit 24 has been switched on, as will be explained. In the other or off position, in which the first changeover switch moves after the consumer circuit has been switched off, the contact arm ^ comes to rest on the other side contact 2ο and connects the compensation resistor 21 in series with the photocell 1 and the heating coil 2.

The system shown comprises an electric synchronous motor I5, the winding 15 of which is connected between the one supply terminal L and the movable contact arm of a second changeover switch, preferably a microswitch, the rare contacts 6, J of which are connected to the fixed contacts ^, 4 of the bimetal switch establish an optional connection between these switches. In the drawing is the

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second changeover switch in the on position, in which he is automatically brought after the consumer group

has been switched on. The synchronous motor I5 drives one rotation
disc Kj clockwise via a reduction gear 15a. The turntable 16 carries four drivers lo which are arranged at equal intervals and are used for switching actuation, two drivers 11 alternating for switching on with two drivers 12 for switching off. The turntable carries a stop plate Io between every two drivers. A main switching device 17 * is switched on and off by actuating the consumer 24, has in addition to the turntable 16 a switch-on lever 14 and a switch-off thebel 13, with which the on-driver 11 and the off-driver 12 cooperate to the switching device 17 to operate. The stop plates Io can act on a switching element 9, which is connected to the contact arm '

8 of the second changeover switch is coupled via a known mechanism 23, which is therefore shown more schematically in the drawing, in such a way that the switching state of the second changeover switch changes each time a stop plate Io comes to a stop on the changeover element 9. The contact arms 8, 18 of the two changeover switches are mechanically coupled (22) so that the interaction of a stop plate Io with the switching device

9 the switch positions of the two changeover switches can be changed at the same time.

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The circuit shown in the drawing is an inventive modification of the circuit described in the earlier application mentioned above. If, in the circuit shown, the first changeover switch 18, 2o, the compensation resistor 21, the parallel connections between the side contacts 19, 2o and the heating winding 2 together with the mechanical coupling 22 are omitted and replaced by a direct connection between the photocell 1 and the heating winding 2 , the result is the circuit described in the earlier application. The so resulting ■ gj circuit with a direct connection between the photocell 1 and the heating coil 2 would work like this;

Assume that. Night is, 'so that the non-illuminated photocell 1 has a high resistance and practically no current flows in the heating winding 2, so that the bimetal switch is in the cold EIn-S division, as shown, and the consumer circuit 24 for "the streets lighting is switched on because the main switch 17 was actuated by a one-driver 11. After the main switch I7 was actuated by a one-driver 11, the switching device 9 was actuated by a stop disk Io, so that the changeover switch 8 in the on position , brought: is in which the supply circuit for the motor 15; is interrupted, since the contact arm 8 from the side

. tenkorjtalct 6 is separated, If in the morning the Tagelloht-in-.

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If the intensity rises to a predetermined value, the resistance of the photocell 11 decreases to a value which allows the passage of a current of sufficient strength through the heating coil 2, so that by bending of the bimetallic arm 4a changed the state of the bimetallic switch, the contacts 3, 4 separated and the contact 4 with the Side contact 5 is brought into contact, so that hereby the feed circuit for the motor 15 is closed. The turntable 16 is driven by the motor 15,

^ to switch off the lighting circuit 24 by means of the main switch 17 by an off driver 12 engages the switch-off lever 15 .. Then the turntable 16 is rotated further until a stop plate Io actuates the switching device 9 to vbn the contact arm 8 Separate side contact 7, so that the feed circuit for the motor is interrupted and the motor and thus the turntable 16 comes to a standstill. The contact arm 8 now rests against the other side contact 6, but the supply circuit for the motor is not closed because the moving

™ borrowed contact 4 of the bimetal switch is not on the side contact J5. The whole system is now in the off-switching state. _r

At dusk, the resistance of the photo cell 1 rises again to a higher value and the current in the heating winding falls below the operating value, the heating winding

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cools down, and as a result of the subsequent cooling of the bimetal arm 4a, the movable contact 4a becomes the side contact 5 separated and comes to the other rare contact 3 to System to start the engine 15 again. Of the Consumer circuit 24 is through the main switch IJ switched on by a one-driver 11 the engaging lever 14 actuated. Then a stop plate actuates the switching device 9 * to flip the contact arm 8, so that "the contact arm 8 is separated from the side contact 6 is, whereby the motor 15 stops, and comes ineffective on the side contact 7 to the plant. The system is now again in the on-state.

Although this system described earlier

Having significant merits, it tends to have a drawback to show which is common to all sensor controlled systems in which a load switch is connected to a relay or some other intermediate mechanism. The situation can be explained as follows:

The bimetal switch is preloaded in the on position and can be moved into the off position by heating the bimetal arm 4a and thus bending it against the preload . It is assumed that the main switch 17 is switched off and that the consumer 24 consisting of the lighting is to be switched on when the

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Daylight intensity influencing photocell 1 has fallen to 5 fc (5 foot candles) and the corresponding resistance of photocell is Rp. The heating coil 2 of the bimetal switch has an essentially constant resistance Rc and the voltage E of the voltage source is constant. The current intensity in the heating winding is E / (Rp + Rc) and corresponds to a cooling of the heating winding 2 to the state that allows the movement of the bimetallic arm 4a into the on position. The arrangement is such that a greater force is required to move the bimetallic switch into the off position in order to switch off the consumer 24 at dawn, so that the current in the heating winding 2 is greater than E / (Rp + Rc must be) and, consequently, the consumer 24 is not turned off before the effective light intensity is increased to a value which is greater than 5 fc This larger * light intensity a photocell resistance Rp ¹ must be equal to the lower than Rp, wherein the higher amperage E / (Rp ¹ + Rc) is sufficient to effect the UmsehaltVorgang α. If the current required for switching off is 50 # greater than the current at which it is switched on, and if the resistance of the photocell at a light intensity of 5 fc is twice as great as the resistance of the heating coil, i.e. Rp = 2 Rc, then it follows that for switching off the resistance of the photocell ^{must be reduced from Rp to Rp 1} «Rc, ie

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the resistance of the photocell is halved. In typical Cases this will lower the resistance of the photocell only achieved when the effective daylight intensity has risen to Io fc or even 15 fc. That difference between the switch-on and switch-off conditions of the system, based on the photocell resistance referred to as the on-off ratio and is in typical Cases 1: 2.

It is quite evident that a street lighting system operated by a photocell controlled monitor with an on-off ratio of. is controlled less than 1: 1 is disadvantageous because the street lights can remain switched on for too long, which means a considerable waste of energy, especially in the winter months.

The inventive use of a Kompensationswiders tandes 2L and the same time with the second change switch 6, 8 actuatable first change charter 18, 2o, the optional adding of the resistance .21 to the series connection of photocell 1 and heating coil 2 controls, allows the system to work with one essential cheaper and more economical on-off ratio operated can be.

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For example, suppose that when the effective light intensity drops to 5 fc, the resistance of the photocell is 1 Io kg ohm and that the constant resistance the heating coil is also Io kg ohm. It is also assumed that when the current intensity of the heating coil 2 The bimetallic arm 4 has cooled down to E / j5o A and is bent that the bimetal switch changes from the setting to & Le Off position and thereby the Switching on the consumer 24 is effected by the main switch 17. While changing the bimetal switch from the on to the off position, the first changeover switch 18, 2o has that switch position in which the compensation resistor 21 is in series with the photocell 1 and ■ the heating winding 2, so that in the case of a compensation resistor from Io kg ohms the aforementioned total resistance (Rp + Rc'r + Rc) = 150 kg ohms, so that the current strength in the heating winding 2 has the amount of E / 3> o A.

It is further assumed that the current strength Wf in the heating coil 2, which causes the force of the bimetal arm 4a required for the transition of the bimetal switch to the off position to switch off the consumer 24, must be 50 # greater than the current strength which the switching on of the consumer 24 is permitted. Therefore, after switching on the consumer 24, when the second changeover switch 4, 6 for switching off the motor

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15 'is actuated, at the same time also the' first changeover switch 18, 2o operated via the clutch 22 to the Remove compensation resistor 21 from the series connection of the photocell and the heating coil. if now the effective daylight intensity increases to 5 fe, the resistance of the photocell 1 is back to Io kg ohms decreased so that the effective total resistance (Rp + Rc) has the value of 20 kg ohms. The amperage in the heating coil 2 has risen to I / 2o A, which is 1.5 times the heating current at which the consumer is switched on

became, and thus has exactly the value at which the τ

consumer is switched off.

Thus, the system improved according to the invention has the effect that the consumer 24, e.g. the same effective daylight intensity is switched on or off at dusk or dawn, which is what is required On-off ratio of 1: 1.

After the main switch 17 is in its off position (J.

has returned, the first changeover switch 18, 2o is automatically returned to the off position and thus into the standby position, which allows the consumer 24 to be switched on when the current in the heating winding 2 has fallen to the first-mentioned lower value.

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It can be seen without further ado that by a suitable choice of the value of the compensation resistor 24 in relation for the supply voltage E, the one required for switching the main switch 17 on the bimetal switch 4, 6 on and off Current intensities and the operating data of the photocell 1 not only set the on-off ratio to 1: 1, but can be set even further in the sense that switching off at daylight intensity takes place, which is less than the daylight intensity at which it is switched on.

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Claims (3)

Patent a η s ρ r u c He ly By sensor-controlled switching device with a two-position switch, which can be switched automatically to one and the other switching state depending on the rise and fall of the electrical resistance of a sensor when the ambient conditions change, geke η η ζ eic fr η et by a: compensation resistor . ; M stood (21) and further switching means («18» 2o), which automatically add the compensation resistor to the resistance of the sensor (1) when the two-position switch 0, 5) is switched to one switching state, and remove the compensation resistor again after the two-position switch has been switched to the opposite switching state. 2. Switching device according to claim l, characterized ra overall ^ characterizing t that the compensation resistor (21) (respectively 20,21, 2, 19, 2) in one of two optionally switchable current loops, and in that the further switching means comprise a changeover switch ( 18, 2o) exist, which connects the sensor (1) to one current loop (2o, 21, 2) in one switching position and to the other current loop (2o, 21, 2) in the other so-called loop. - - I ₇ ...
009884/1384 BATH ORIGINAL 3. Switching device according to claim 2, characterized in that the changeover switch (18, 2o) with the two-position switch 0 ₃ 5) via a delay mechanism (15, 16, 9, 6-8, 22) is coupled such that each switching movement of the changeover switch (18, 2o) only takes place after a change in the switching status of the two-position switch (3 to 5). - 18 - 009884/1384