GB1586920A - Rotary motion pulse generator - Google Patents

Description

(54) ROTARY MOTION PULSE GENERATOR (71) We, KIENZLE APPARATE GMBH, a German Body Corporate of Villingen-Schwenningen, Germany do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a pulse generator serving to resolve a rotational movement into individual pulses having an optoelectronic light barrier comprising a slotted blind rotating in the path of radiation between a light source and a light receiving element.

In rotary motion pulse generators of the above described kind as a light source very often a modulated source of radiation is used. As a light source Ga-AS-luminescent diodes are being used to a very large extent.

The modulation is produced mechanically in a most simple manner by a blind having slots or holes. The pulses are produced in that slotted blind mounted on a rotatable shaft interrupts and clears the path between the radiation source and a correspondingly arranged light receiver. The number of pulses per revolution depends on the number of teeth arranged on the circumference of the blind.

On the receiver side there are photoelectric elements. which are selected in dependence on their application with a view to the required sensitivity and dimensions. Siphototransistors are in widely extended use which are combined with two or more other transistors to a so-called photo-Darlington.

Bv this circuitry the photocurrent is amplified, thereby improving the sensitivitv of the phototransistor, however. also increasing the pickup time.

Light source and light receiver together are arranged at an optimal distance of each other in a cast plastic carrier so that the two parts together form a fork-shaped part between the prongs of which the slotted disk or the hole disk rotates as a modulator. The cast plastic carrier is provided at its periphery with a projection or a recess by means of which a definite position of the light barrier with respect to the modulator is predetermined.

The individual parts such as the light emitter and/or the light receiver may not be of equal technical quality so that depending on the tolerances of the parts there are unavoidable differences in the switching characteristics. Only for predetermined testing conditions the tolerances of the range of signal generation may be determined for a multiplicity of measurements the switching range being determined in the form of data sheets for each light barrier module.

If and when rotary motion pulse generators are for instance used in corinection with measuring volumes and calculating prices in sales apparatus, such as for instance when issuing petrol by means of petrol pumps, where the pulses generated are proportional to the volume and price and serve to be treated in a counting and calculating device, a high security of switching performance for the pulse generator must be demanded also due to the corresponding regulations of the authorities. For an application of this kind it should also be observed that in the start-stop-operation of the liquid flow the pulse generator which is directly coupled to the volume meter should not produce any erroneous pulses which might be introduced into the calculation and indication of the measured values. Pulses which result from backward rotations of the slotted blind may be avoided by mounting on the shaft thereof a return stop in the form of a roller clutch. But also a roller clutch may not be made without a certain amount of play so that this measure is only of limited efficiency with respect to avoid erroneous pulses.

It is therefore amongst the objects of the invention to design a device in pulse generators of the above described kind by means of which it is possible to avoid immanent switching mistakes at such light barriers which may result for instance from tolerances in the position of the light barrier, but also from the switching times of the electronic elements, or from the hysteresis of the light barrier with respect to the return stop etc.

According to the invention we provide a pulse generator serving to resolve a rotary motion into individual pulses comprising an opto-electronic light barrier consisting of a slotted blind rotating between a light source and a light receiving element, wherein the slotted blind consists of two coaxially arranged slotted disks of similar configuration, which are rotatably adjustable with respect to each other to a desired tooth and slot proportion, the teeth and slots gradually tapering from the periphery of the disks towards the interior of the disk, and each tooth and slot having its centre line inclined both to the respective radius passing through the function of the periphery and centre line and to the tangent to said radius at substantially the same angle.

By means of the above solution it is possible to create a combined slotted blind consisting of similar slotted disks wherein starting from a light-dark-effect at a proportion of 1 : 1 every other desired proportion in sensing the widths of teeth and slots may be adjusted. Since the widths of the teeth and slots taper from the periphery to the centre of the disks despite of the tolerances in production and despite of varying radial engagement of the path of radiation of the light barrier there is always an equal proportion between the teeth and slots. The combined slotted blind also allows for varying tolerances in the electronic parts to be compensated especially as for the effective switching point which almost exclusively depends on the radiation intensity. Due to the inclination of the flanges of the teeth and slots which deviates from the usual radial arrangement of teeth and slots in the modulating zone the electronic switching hysteresis of the light barrier may be enlarged to cover a bigger angle. That means tolerances inherent in the return stop of a roller ratchet can be absorbed by the switching hysteresis resulting from an enlarged switching angle so that it becomes ineffective with respect to producing erroneous pulses.

An embodiment of the invention is described in the following and has been shown in the drawings.

Figure I shows the whole pulse generator with the housing lid taken off on one side, Figllre 2 is a section through the pulse generator, Figure 3 is the slotted disk blind comprising two similar slotted disks, Figure 4 is a section of the arrangement and shape of the tooth and slot zone.

In the representation according to Figure 1 within the housing 1 there is shown a complete pulse generator system comprising two separate light barrier units 2 and 3. The light barriers 2 and 3 are the usual optoelectronic light barriers with for instance Ga-As-diodes as emitters and in each case one photo transistor as a receiver. For amplifying the photocurrent on the receiving side there is a second transistor which according to the known Darlington circuit is combined with a photo transistor to a complete circuit arrangement delivering a high photocurrent at its output. The diode as a light source and the photo transistor as a receiver are arranged at a certain distance of each other. For instance they are fixedly arranged in a cast plastic carrier 8 so that the light from the light source essentially only reaches the detector of the receiver. Between the light source and the detector there is an air gap 4 within which an object may be moved within the radiation path.

This means that the intensity of the light reaching the detector is modified thereby producing a signal at the output of the Darlington circuit which is treated in desired manner. Since the authorities require that the security be twofold for the pulse generation the pulse generator in accordance with Figure 1 contains two light barriers 2 and 3 the output signals of which are compared in the electronic circuitry for checking purposes. This means also that erroneous pulses are more easily recognized. Since the two light barriers 2 and 3 for this purpose cooperate with the same modulating element 5 they must be arranged at a certain distance of each other and must also be in a predetermined local arrangement to the moving modulator zone 6. To this end the light barriers 2 and 3 are soldered to a circuit plate and cast by plastics to form a carrier 8.

As a guiding element for positioning the light barriers 2 and 3 within the housing 1 and with respect to a housing lid 9 there are lugs 10, ll, 12 and 13 arranged at the circuit plate protruding above the carrier 8. The lugs are taken up by recesses 14 in the internal wall of the housing. A cable 15 having several leads leaves the carrier 8 and passes on the signals to the calculating unit.

Within the same housing parts 1 and 9 with the carrier 8 for the light barriers 2 and 3 there are bores 16 and 17 for mounting a shaft 18 (Figure 2) which carries the modulator element 5. In the enlarged part of bore 16 there is unrotatably mounted a return stop clutch 19 which serves to avoid any reverse rotation of shaft 18, in accord ance with the embodiment of Figure 1 in counterclockwise direction. As may also be seen from Figure 1 to 3 the modulator element 5 consists of two similar slotted discs 20 and 21, the disc 21 being riveted to the bushing 22. The bushing 22 is unrotatably and axially secured by means of a pin 36 to the shaft 18. The slotted disc 20 is coaxially mounted and slightly rotatable on bushing 22 and has diametrically arranged arc-shaped holes 23, 24. At the same distance of the center in corresponding radial position the slotted disk 21 has bores 25, 26.

By means of screws 27 the rotatable disk 20 may be adjusted to a definite angular position with respect to slotted disk 21. The defined angular position of the two slotted disks 20 and 21 is essential for the pulse generation since due to this adjustable angular position the modulator zone 6 may be adjusted to any desired proportion of the light-dark-change in the radiation path.

Within the limitations of the production tolerances a highly exact position of the modulator zone 6 with respect to the radiation path between the light barriers 2 and 3 is ensured since the shaft 18 is mounted in the fixed and equal housing part 1 and 9 in the bores 16 and 18 and also since simultaneously the carrier 8 for the light barriers is mounted between lugs 10, 11, 12, 13 and recesses 14 in the same two housing parts 1 and 9. The position of the housing parts 1 and 9 to each other is defined by a cast-on pin 28 at lid 9 and a correspondingly arranged bore 29 in housing 1, the two housing parts being secured by several screw connection 30.

Each of the two slotted disks 20 and 21 is provided with teeth 32 and slots 33 having the same shape and surface. By angularly adjusting the two discs a slotted blind 31 results which in combination with the light barriers 2 and 3 allow, starting from a tooth-to-slot-proportion of I . 1, also any other light-dark-proportion to be adjusted.

Due to the light-dark-proportion being adjustable the light intensity may be varied by choosing a corresponding width of the teeth.

This means that any unavoidable tolerances in the switching qualities of the electronic parts may be eliminated by this device.

The shape of the teeth 32 and the slots 33 (see the section A according to Figure 4) is such that it tapers gradually from the periphery to the centre of the disks. If a certain light-dark-proportioll has once been set at the slotted disk blind 3 tit is ensured that over the whole range of the modulator zone 6 that means in radial direction of the whole hight of the teeth there is always the same light-darkproportion. 'this means that the position of the light barrier 2, 3 is independent of radial arrailgement of the radiation path within the modulator zone 6.

The uniform reduction in the widths of the teeth and slots 32, 33 is achieved by equally dividing the outside circle 37 and the root circle 38 of the teeth 32 and the slots 33.

As may also be seen from an embodiment shown in Figure 4 the position of the teeth 32 and the slots 33 with respect to the circular slotted disks 20, 21 is characterized by an arrangement which is inclined to the radius and also tangentially. By the inclined arrangement of the teeth 32 and slots 33 an electronic hysteresis of the light barrier is achieved over a wider angular range a.

Assuming that as shown in the example according to Figure 4 the radiation path 39 of the light barrier 2 or 3 has a certain for instance circular shaped cross-section, then the radiation path 39 is limited to an angle P for a normal radially extending flange of the slots.

In the arrangement according to Figure 4, however, due to the inclined shape of the teeth the range which the tooth and the slot covers is extended to the angle a on the circle 40 of the radiation path 39 this angle being much bigger than it would be for tooth shapes in which the teeth and slots have radially extending flanges. As may be seen from Figure 4 the angle which is covered by a slotted disc of the known kind as compared to the angle covered by a slotted disc 20, 21 with the inclined arrangement of the teeth 32 and slots 33 is enlarged at the proportion of : a = 3 : 5. The angle which is covered by the slotted disk from the first moment when the radiation path 39 is partially cleared until it is partially covered or correspondingly until it is completely covered may therefore be enlarged by one unit for each flange of the slot as compared with three angular units for the actual width of the slot. This means that any tolerances in the return stop of the clutch 19 may be more easily compensated. Erroneous pulses from the light barrier which result from two high tolerances in the return stop of the mechanical clutch 19 can therefor be eliminated.

This means that when the angle at which the radiation path is effective is enlarged also the electronic hysteresis is essentially increased. When the effective angular range with respect to the slotted disk blind 31 which corresponds to the electronic hysteresis of the light barrier is bigger than the tolerances in the return stop a production of erroneous pulses by a possible reverse rotation of the slotted disk blind 31 is absolutely avoided.

WHAT WE CLAIM IS: 1. A pulse generator serving to resolve a rotary motion into individual pulses comprising an opto-electronic light barrier consisting of a slotted blind rotating between a light source and a light receiving element, wherein the slotted blind consists of two

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. ance with the embodiment of Figure 1 in counterclockwise direction. As may also be seen from Figure 1 to 3 the modulator element 5 consists of two similar slotted discs 20 and 21, the disc 21 being riveted to the bushing 22. The bushing 22 is unrotatably and axially secured by means of a pin 36 to the shaft 18. The slotted disc 20 is coaxially mounted and slightly rotatable on bushing 22 and has diametrically arranged arc-shaped holes 23, 24. At the same distance of the center in corresponding radial position the slotted disk 21 has bores 25, 26. By means of screws 27 the rotatable disk 20 may be adjusted to a definite angular position with respect to slotted disk 21. The defined angular position of the two slotted disks 20 and 21 is essential for the pulse generation since due to this adjustable angular position the modulator zone 6 may be adjusted to any desired proportion of the light-dark-change in the radiation path. Within the limitations of the production tolerances a highly exact position of the modulator zone 6 with respect to the radiation path between the light barriers 2 and 3 is ensured since the shaft 18 is mounted in the fixed and equal housing part 1 and 9 in the bores 16 and 18 and also since simultaneously the carrier 8 for the light barriers is mounted between lugs 10, 11, 12, 13 and recesses 14 in the same two housing parts 1 and 9. The position of the housing parts 1 and 9 to each other is defined by a cast-on pin 28 at lid 9 and a correspondingly arranged bore 29 in housing 1, the two housing parts being secured by several screw connection 30. Each of the two slotted disks 20 and 21 is provided with teeth 32 and slots 33 having the same shape and surface. By angularly adjusting the two discs a slotted blind 31 results which in combination with the light barriers 2 and 3 allow, starting from a tooth-to-slot-proportion of I . 1, also any other light-dark-proportion to be adjusted. Due to the light-dark-proportion being adjustable the light intensity may be varied by choosing a corresponding width of the teeth. This means that any unavoidable tolerances in the switching qualities of the electronic parts may be eliminated by this device. The shape of the teeth 32 and the slots 33 (see the section A according to Figure 4) is such that it tapers gradually from the periphery to the centre of the disks. If a certain light-dark-proportioll has once been set at the slotted disk blind 3 tit is ensured that over the whole range of the modulator zone 6 that means in radial direction of the whole hight of the teeth there is always the same light-darkproportion. 'this means that the position of the light barrier 2, 3 is independent of radial arrailgement of the radiation path within the modulator zone 6. The uniform reduction in the widths of the teeth and slots 32, 33 is achieved by equally dividing the outside circle 37 and the root circle 38 of the teeth 32 and the slots 33. As may also be seen from an embodiment shown in Figure 4 the position of the teeth 32 and the slots 33 with respect to the circular slotted disks 20, 21 is characterized by an arrangement which is inclined to the radius and also tangentially. By the inclined arrangement of the teeth 32 and slots 33 an electronic hysteresis of the light barrier is achieved over a wider angular range a. Assuming that as shown in the example according to Figure 4 the radiation path 39 of the light barrier 2 or 3 has a certain for instance circular shaped cross-section, then the radiation path 39 is limited to an angle P for a normal radially extending flange of the slots. In the arrangement according to Figure 4, however, due to the inclined shape of the teeth the range which the tooth and the slot covers is extended to the angle a on the circle 40 of the radiation path 39 this angle being much bigger than it would be for tooth shapes in which the teeth and slots have radially extending flanges. As may be seen from Figure 4 the angle which is covered by a slotted disc of the known kind as compared to the angle covered by a slotted disc 20, 21 with the inclined arrangement of the teeth 32 and slots 33 is enlarged at the proportion of ss: a = 3 : 5. The angle which is covered by the slotted disk from the first moment when the radiation path 39 is partially cleared until it is partially covered or correspondingly until it is completely covered may therefore be enlarged by one unit for each flange of the slot as compared with three angular units for the actual width of the slot. This means that any tolerances in the return stop of the clutch 19 may be more easily compensated. Erroneous pulses from the light barrier which result from two high tolerances in the return stop of the mechanical clutch 19 can therefor be eliminated. This means that when the angle at which the radiation path is effective is enlarged also the electronic hysteresis is essentially increased. When the effective angular range with respect to the slotted disk blind 31 which corresponds to the electronic hysteresis of the light barrier is bigger than the tolerances in the return stop a production of erroneous pulses by a possible reverse rotation of the slotted disk blind 31 is absolutely avoided. WHAT WE CLAIM IS:

1. A pulse generator serving to resolve a rotary motion into individual pulses comprising an opto-electronic light barrier consisting of a slotted blind rotating between a light source and a light receiving element, wherein the slotted blind consists of two

coåxially arranged slotted disks of similar configuration, which are rotatably adjustable with respect to each other to a desired tooth and slot proportion, the teeth and slots gradually tapering from the periphery of the disks towards the interior of the disk, and each tooth and slot having its centre line inclined both to the respective radius passing through the junction of the periphery and centre line and to the tangent to said radius at substantially the same angle.

2. A pulse generator substantially as described herein with reference to and as iliustrated by the accompanying drawings.

3. A pulse generator as claimed in claim 1, substantially as hereinbefore described.