GB1586552A

GB1586552A - Method of and an apparatus for weighing

Info

Publication number: GB1586552A
Application number: GB480978A
Authority: GB
Original assignee: Soehnle Waagen GmbH and Co KG
Current assignee: Soehnle Waagen GmbH and Co KG
Priority date: 1977-02-15
Filing date: 1978-02-07
Publication date: 1981-03-18
Also published as: DE2706231A1; FR2380540A1

Description

(54) A METHOD OF AND AN APPARATUS FOR WEIGHING (71) We, SOEHNLE-WAAGEN GMBH CO., of 7157 Murrhardt, Wurttemberg, Federal Republic of Germany, a Kommanditgesellschaft organised under the laws of the Federal Republic of 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:- This invention relates to a method of weighing and an apparatus used for effecting the method.

The method is of the kind in which a load is placed on a movable weighing surface of a weighing mechanism and electronic circuitry in combination with the mechanism is employed to produce an indication in the form of an analog or digital visual display and/or print-out of the weight of the load.

Theapparatus is of the type comprising in combination a weighing mechanism and electronic circuitry, the weighing mechanism including a movable weighing surface and a disc which rotates as the weighing surface moves up upon being unloaded, the said disc being provided with incremental graduations, the said circuitry including scanning means for scanning the said graduations, and indicator means for producing indications in the form of analog or digital visual displays and/or print-outs of the weights of loads placed on and removed from the weighing surface.

With some methods of the kind referred to it is not possible to weigh living beings satisfactorily because the said indication of the weight fluctuates due to the slightest movements and jolting of the load on the weighing surface and thus the weight indication constantly varies. The invention is therefore intended to provide improvements in a method of the kind referred to and in an apparatus of the type referred to, suitable for weighing persons or living animals.

According to the invention a method of weighing of the kind referred to is characterised by the steps of preventing the said circuitry from producing the said indication during dynamic operations, that is whilst the weighing surface is moving due to the load thereon, setting a counting device in the said circuitry to zero, that is in readiness for operation, when the loaded weighing surface has been substantially at rest for not less than a predetermined period, removing the load from the weighing surface for the counting device to operate during the return of the weighing mechanism from its loaded position to its unloaded position, and using signals from the counting device to produce the said indication.

With the - weighing method of the invention it is possible to avoid fluctuations of the weight indications, whereas in known digital-display personal balances when the display stands just at the limit of a digit step such fluctuations are caused by somewhat unsteady standing, or even merely by the heartbeat which causes a dynamic force component in the vertical direction of about 2 newtons. With the weighing method of the invention it is possible for a weight display device to remain dark during the dynamic operations and for the weight to be displayed statically without any fluctuations only after the unloading of the weighing mechanism.

The method of the invention also avoids the necessity of setting the unloaded weighing mechanism to a zero point, because when the weighing surface is loaded and substantially at rest the apparatus is at a zero point from which the weighing operation proceeds, and influences deriving from different surfaces on which the apparatus is placed are largely eliminated.

It is advantageous if the said predetermined period is about 0.5 seconds.

The magnitude of the permissible movements of the weighing surface during the said predetermined period can advantageously be adjustable or proportional to the weight of a load on the weighing surface so that smaller weights can be ascertained with adequate accuracy.

If the said predetermined period is determined with regard to a mean time lapse following the weight loading of the weighing surface, even lively animals can be weighed with satisfactory accuracy.

According to the invention a weighing apparatus of the type referred to is characterised in that the said scanning means comprises two light-emitting diodes or other light sources and two respective photo-transistors relatively offset in phase by substantially 90" with respect to the said graduations and connected to a forwardbackward logic with a pulse-counter, there being a flip-flop and a mono-flop through which the pulse-counter is set to zero, that is in readiness for operation, as soon as the loaded weighing surface has been substantially at rest for a predetermined period, the circuitry being arranged so that the pulse-counter counts the pulses from the photo-transistors as the disc rotates during the rising of the weighing surface due to removal of the load, and upon the conclusion of the pulse counting by the pulse counter the pulse counter value is fed to the indicator means which thereupon accordingly produces the said indications.

It is advantageous if the two light sources and two photo-transistors are arranged relatively offset in phase 90 , the distance between them being a multiple of one of the spaces between the disc graduation marks plus or minus an amount equal to one quarter of one of the spaces between the disc graduation marks.

For effective charging of the forward/backward logic there may be two Schmitt triggers by which square-wave signals are formed, one between each of the photo-transistors and the forward/backward logic.

For the complete current interruption after the use of the apparatus, there may be a further mono-flop with a setting time to control a relay switching off the current supply after a time delay; this further monoflop may have a setting time of about 3 sec.

and itself be set in action through a switch controlled by the weighing mechanism, when the weighing surface is practically unloaded.

The circuitry preferably includes two AND-gates, a NAND-gate, and an OR-gate.

How the invention may be put into practice is explained in greater detail hereinafter, with reference to the accompanying schematic drawings, wherein: Figure 1 is an oblique view of parts of a weighing mechanism without its weighing surface, Figure 2 is a circuit diagram, and Figure 3 is a modified circuit diagram of the weighing apparatus.

As partially illustrated in Figure 1, a weighing mechanism 3 comprises weighing levers 2 mounted on a base plate 1 to support a movable weighing surface (not shown). Through a lever (not shown) of the weighing mechanism 3 a rack 4 moves to rotate a disc 5 with incremental graduations 6 in proportion to the weight of any load on the weighing surface. The graduations 6 include marks to interrupt the passage of the light from light-emitting diodes 7 and 7' to respective photo-transistors 8 and 8'.

Thus on rotation of the disc 5, current pulses are delivered by the photo-transistors 8 and 8'.

The two light-emitting diodes 7 and 7' are arranged under the disc 5, and the two photo-transistors 8 and 8' are arranged above the disc 5. The light-emitting diode 7 and the photo-transistor 8 are spaced by a distance equal to a multiple of one disc graduation plus or minus one quarter of one disc graduation in relation to the lightemitting diode 7' and the photo-transistor 8'. This causes a 900 phase shift of the current pulses delivered by the phototransistors 8 and 8' as they are passed by the graduation lines when the disc 5 rotates.

The two laterally displaced pulse trains thus generated render possible evaluation by a forward/backward logic 9 (Figures 2 and 3).

For the achievement of square-wave pulses, two Schmitt triggers 10 and 10' are arranged one between each photo-transistor 8 and 8' and the two inputs of the forward-backward logic 9.

Figure 2 shows an UP-output 11 and a DOWN-output 12 from the logic 9 connected each to a respective input of a counter block 13, to which three further counter blocks 14 to 16 are connected. The counter blocks 13 to 16 form a counting device in the form of a pulse counter 17.

The counter blocks 13 to 16 are in communication each with a respective digit position of a digital indicator means 18 by which an indication in the form of an analog or digital visual display and/or print-out of the weight of the load is produced in accordance with the number of the counted pulses to be displayed when the display inputs 19 carry a signal. The counter blocks 13 to 16 can be set to zero by a signal on a line 20 (Figures 2 and 3) to a re-setting device.

Figure 3 shows the outputs 11 and 12 from the forward-backward logic 9 connected firstly through an OR-gate 32 to the input of the counter block 13, and additionally through a flip-flop 33 to the inputs of the counter blocks 13 to 16. The up/down recognition is here obtained through the additional flip-flop 33, and is fed to the counter blocks 13 to 16, the counting pulses being passed through the OR-gate 32 to the first counter block 13.

Both Figures 2 and 3 show that the outputs 11 and 12 of the forward-backward logic 9 are further connected with an RSflip-flop 21 which, through a mono-flop 22 is set to about 0.5 seconds setting time, can set the pulse counter 17 in action if no further pulse sequences arrive during the setting time of about 0.5 seconds, which is a predetermined period. As long as pulses are still arriving the pulse counter 17 is repeatedly re-set to zero by the re-setting device by the signals delivered through the line 20 from the mono-flop 22.

A further mono-flop 25 is connected through an AND-gate 23 and a NAND-gate 24 with the mono-flop 22. The mono-flop 25, with a setting time of about 3 seconds, controls a relay 26 by which a battery 27 can be disconnected from the entire electronic system when a period of about 3 seconds has elapsed after the completion of a weighing operation. In parallel with the relay 26 is a switch 28 which closes on loading of the weighing surface (not shown) and opens on unloading. The closing of the switch 28 sets the further mono-flop 25 and the pulse counter 17 in action.

There are diodes 34, 35 and 36 to prevent undesired feedback in some branches of the circuit. Each of the illustrated circuit arrangements functions as follows:- On loading of the weighing surface the disc 5 rotates, and also the switch 28 is closed, and thus the circuit is connected to the battery 27. At the same time a red lightemitting diode 29 lights up and the contacts of the relay 26 open up, the output Q of the mono-flop 25 lying at H-level. The lightemitting diodes 7 and 7' and the phototransistors 8 and 8' scan the rotating disc 5, and the marks of its graduations 6 successively or progressively interrupt the two light ray paths whilst the weighing surface rises due to unloading.The phototransistors 8 and 8' are thus constantly switched on and off during the rotation of the disc, and the square-wave signals from the Schmitt triggers 10 and 10' pass to the forward-backward logic 9, and there deliver short pulses which correspondingly are added or subtracted in the series-connected counter blocks 13 to 16. At the same time all the output pulses from the forwardbackward logic 9 pass to a gate and the RSflip-flop 21 connected as a frequency divider. The falling flanks of the output signal from the RS-flip-flop 21 trigger the connected mono-flop 22, that is to say every alternate pulse arrival from the forwardbackward logic 9 causes the mono-flop 22, set to about 0.5 seconds, to start afresh, the re-starting occurring repeatedly.Thus the output Q of the mono-flop 22 lies at low level as long as re-starting pulses arrive at the input of the mono-flop 22 at intervals of less than about 0.5 seconds.

When the said intervals exceed the predetermined period of about 0.5 seconds the output Q goes to H-level, whereby the AND-gate 23 switches and is held by feedback. The exceeding of the intervals of about 0.5 seconds signifies that the loaded weighing surface and the disc 5 have been substantially stationary for about 0.5 seconds. A single pulse from only one photo-transistor 8 or 8' is not effective to inhibit the above-mentioned re-starting.

When current flows through the ANDgate 23 a signal lamp 30, for example a green light-emitting diode which illuminates the "kg" sign, lights up, and furthermore a positive flank of a pulse sets the pulse counter 17 to zero, and the mono-flop 25 sets for the indicator means 18 to be prepared by an AND-gate 31.

After the lighting up of the green signal lamp 30 the load is removed from the weighing surface, and the disc 5 rotates, and the switch 28 opens. The forward-backward logic 9 recognises this as "forward" and feeds the counting pulses to the corresponding input of the counter block 13 and now all further pulses are counted.

When the disc 5 comes to a halt, the output Q of the mono-flop 22 passes to H-level, whereby the AND-gate 31 switches and thus allows the pulse counter 17 to feed signals to the indicator means 18.

With the relieving of the weighing surface, the mono-flop 25 is at the same time also set in action for the contacts of the relay 26 to open after the set delay time of about 3 seconds and thus the entire circuit arrangement is separated from the battery 27.

The entire electronic circuit arrangement is preferably executed in CMOS technique, and can be accommodated in a housing together with the indicator means 18, and this housing can be detachably mounted on a housing accommodating the mechanism 3 and can be removed for convenient reading and secured for example to a wall or a stand or other support.

WHAT WE CLAIM IS:- 1. A method of weighing, of the kind in which a load is placed on a movable weighing surface of a weighing mechanism (3), and electronic circuitry in combination with the mechanism (3) is employed to produce an indication in the form of an analog or digital visual display and/or printout of the weight of the load, characterised

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. counter blocks 13 to 16. The up/down recognition is here obtained through the additional flip-flop 33, and is fed to the counter blocks 13 to 16, the counting pulses being passed through the OR-gate 32 to the first counter block 13. Both Figures 2 and 3 show that the outputs 11 and 12 of the forward-backward logic 9 are further connected with an RSflip-flop 21 which, through a mono-flop 22 is set to about 0.5 seconds setting time, can set the pulse counter 17 in action if no further pulse sequences arrive during the setting time of about 0.5 seconds, which is a predetermined period. As long as pulses are still arriving the pulse counter 17 is repeatedly re-set to zero by the re-setting device by the signals delivered through the line 20 from the mono-flop 22. A further mono-flop 25 is connected through an AND-gate 23 and a NAND-gate 24 with the mono-flop 22. The mono-flop 25, with a setting time of about 3 seconds, controls a relay 26 by which a battery 27 can be disconnected from the entire electronic system when a period of about 3 seconds has elapsed after the completion of a weighing operation. In parallel with the relay 26 is a switch 28 which closes on loading of the weighing surface (not shown) and opens on unloading. The closing of the switch 28 sets the further mono-flop 25 and the pulse counter 17 in action. There are diodes 34, 35 and 36 to prevent undesired feedback in some branches of the circuit. Each of the illustrated circuit arrangements functions as follows:- On loading of the weighing surface the disc 5 rotates, and also the switch 28 is closed, and thus the circuit is connected to the battery 27. At the same time a red lightemitting diode 29 lights up and the contacts of the relay 26 open up, the output Q of the mono-flop 25 lying at H-level. The lightemitting diodes 7 and 7' and the phototransistors 8 and 8' scan the rotating disc 5, and the marks of its graduations 6 successively or progressively interrupt the two light ray paths whilst the weighing surface rises due to unloading.The phototransistors 8 and 8' are thus constantly switched on and off during the rotation of the disc, and the square-wave signals from the Schmitt triggers 10 and 10' pass to the forward-backward logic 9, and there deliver short pulses which correspondingly are added or subtracted in the series-connected counter blocks 13 to 16. At the same time all the output pulses from the forwardbackward logic 9 pass to a gate and the RSflip-flop 21 connected as a frequency divider. The falling flanks of the output signal from the RS-flip-flop 21 trigger the connected mono-flop 22, that is to say every alternate pulse arrival from the forwardbackward logic 9 causes the mono-flop 22, set to about 0.5 seconds, to start afresh, the re-starting occurring repeatedly.Thus the output Q of the mono-flop 22 lies at low level as long as re-starting pulses arrive at the input of the mono-flop 22 at intervals of less than about 0.5 seconds. When the said intervals exceed the predetermined period of about 0.5 seconds the output Q goes to H-level, whereby the AND-gate 23 switches and is held by feedback. The exceeding of the intervals of about 0.5 seconds signifies that the loaded weighing surface and the disc 5 have been substantially stationary for about 0.5 seconds. A single pulse from only one photo-transistor 8 or 8' is not effective to inhibit the above-mentioned re-starting. When current flows through the ANDgate 23 a signal lamp 30, for example a green light-emitting diode which illuminates the "kg" sign, lights up, and furthermore a positive flank of a pulse sets the pulse counter 17 to zero, and the mono-flop 25 sets for the indicator means 18 to be prepared by an AND-gate 31. After the lighting up of the green signal lamp 30 the load is removed from the weighing surface, and the disc 5 rotates, and the switch 28 opens. The forward-backward logic 9 recognises this as "forward" and feeds the counting pulses to the corresponding input of the counter block 13 and now all further pulses are counted. When the disc 5 comes to a halt, the output Q of the mono-flop 22 passes to H-level, whereby the AND-gate 31 switches and thus allows the pulse counter 17 to feed signals to the indicator means 18. With the relieving of the weighing surface, the mono-flop 25 is at the same time also set in action for the contacts of the relay 26 to open after the set delay time of about 3 seconds and thus the entire circuit arrangement is separated from the battery 27. The entire electronic circuit arrangement is preferably executed in CMOS technique, and can be accommodated in a housing together with the indicator means 18, and this housing can be detachably mounted on a housing accommodating the mechanism 3 and can be removed for convenient reading and secured for example to a wall or a stand or other support. WHAT WE CLAIM IS:-

1. A method of weighing, of the kind in which a load is placed on a movable weighing surface of a weighing mechanism (3), and electronic circuitry in combination with the mechanism (3) is employed to produce an indication in the form of an analog or digital visual display and/or printout of the weight of the load, characterised

by the steps of preventing the said circuitry from producing the said indication during dynamic operations, that is whilst the weighing surface is moving due to the load thereon, setting a counting device (17) in the said circuitry to zero, that is in readiness for operation, when the loaded weighing surface has been substantially at rest for not less than a predetermined period, removing the load from the weighing surface for the counting device (17) to operate during the return of the weighing mechanism (3) from its loaded position to its unloaded position, and using signals from the counting device (17) to produce the said indication.

2. A method according to Claim 1, wherein the said predetermined period is substantially 0.5 seconds.

3. A method according to Claim 1 or 2, wherein movements of the weighing surface due to weight variations which are less than the minimum unit of weight in the said indication remain neglected in determining whether the weighing surface is substantially at rest.

4. A method according to Claim 3, wherein adjustments are made in respect of the size of the said weight variations.

5. A method according to any one of Claims 1 to 4, wherein the said predetermined period is determined with regard to a mean time lapse following the weight loading of the weighing surface.

6. A method according to Claim 5, wherein the mean time lapse is an average of the time intervals which occur before the loaded weighing surface is substantially at rest.

7. An apparatus when used in effecting a method according to any one of Claims 1 to 6, comprising in combination a weighing mechanism (3) and electronic circuitry, the weighing mechanism (3) including a movable weighing surface and a disc (5) which rotates as the weighing surface moves up upon being unloaded, the said disc (5) being provided with incremental graduations (6), the said circuitry including scanning means for scanning the said graduations (6), and indicator means (18) for producing indications in the form of analog or digital visual displays and/or print-outs of the weights of loads placed on and removed from the weighing surface characterised in that the said scanning means comprises two light-emitting diodes (7, 7') or other light sources and two respective phototransistors (8, 8') relatively offset in phase by substantially 900 with respect to the said graduations (6) and connected to a forwardbackward logic (9) with a pulse-counter (17), there being a flip-flop (21) and a monoflop (22) through which the pulse-counter (17) is set to zero, that is in readiness for operation, as soon as the loaded weighing surface has been substantially at rest for a predetermined period, the circuitry being arranged so that the pulse-counter (17) counts the pulses from the photo-transistors (8, 8') as the disc (5) rotates during the rising of the weighing surface due to removal of the load, and upon the conclusion of the pulse counting by the pulse counter (17) the pulse counter value is fed to the indicator means (18) which thereupon accordingly produces the said indications.

8. An apparatus according to Claim 7, comprising two Schmitt triggers (10, 10'), one between each of the photo-transistors (8, 8') and the forward-backward logic (9).

9. An apparatus according to Claim 7 or 8, wherein the said mono-flop (22) is timesettable.

10. An apparatus according to Claim 9, wherein the mono-flop (22) is set at substantially 0.5 seconds.

11. An apparatus according to Claim 7, 8, 9 or 10, comprising a further mono-flop (25) with setting time by means of which a relay (26) for switching the current supply is controlled with time delay.

12. An apparatus according to Claim 11, wherein the further mono-flop (25) has a setting time of substantially 3 seconds and is set in action through a contact (28) controlled by the weighing mechanism (3).

13. An apparatus according to any one of Claims 7 to 12, wherein the first-mentioned mono-flop (22) and an AND-gate (31) prepare the indicator means (18) after conclusion of the pulse counting.

14. An apparatus according to any one of Claims 7 to 13, comprising a signal light (30) controlled through the first-mentioned mono-flop (22).

15. An apparatus according to Claim 13, wherein the forward-backward logic (9) controls the flip-flop (21) with the connected mono-flop (22), the pulse counter (17) is fed with the pulses from the forward-backward logic (9), and through the flip-flop (21) with the first-mentioned monoflop (22) and the AND-gate (31), the pulse counter (17) is set in operation and is re-set through the output of the first-mentioned mono-flop (22).

16. An apparatus according to any one of Claims 7 to 15, wherein the indicator means (18) is accommodated in a housing which is removable from a housing accommodating the weighing mechanism (3) and can be secured to a wall or other support.

17. An apparatus according to Claim 16, wherein the housing accommodating the indicator means (18) is attached through connection means to the housing accommodating the weighing mechanism (3).

18. An apparatus according to any one of Claims 7 to 17, wherein the indicator means (18) includes a liquid crystal display with an illuminating system.

19. An apparatus according to any one of Claims 7 to 18, wherein the forwardbackward logic (9) has two outputs (11, 12) connected through an OR-gate (32) to a first counter block (13) in the pulse counter (17), the said two ouputs (11, 12) of the forwardbackward logic (9) being additionally connected through a further flip-flop (33) to the- inputs of the said counter block (13) and to the inputs of further counter blocks (1416) in the pulse counter (17).

20. An apparatus according to any one of Claims 7 to 19, comprising diodes (34, 35 and 36) to avoid feedback.

21. A method of weighing, substantially as hereinbefore described.

22. An apparatus for weighing, substantially as hereinbefore described with reference to and as illustrated diagrammatically in the accompanying drawings.