FR2680625A1 - DEVICE FOR DETECTION OF FOREIGN BODIES FOR HARVESTER. - Google Patents

Abstract

The invention relates to a device for detecting foreign bodies. The device for detecting foreign bodies in a harvested product stream 20, conveyed by a transport roller 21 and a preliminary pressing roller 22, between which a passage slit is formed, is equipped with an electromagnetic metal detector 1, which scans the passage slot and whose signal is used to stop the transport roller 21 when it exceeds a predefined threshold value, the signal derived from a speed signalizer 3, 30 acting on an amplification of the signal from the metal detector . The invention is applicable to harvesters.

Description

The invention relates to a device for detecting foreign bodies in one

  harvested product stream, conveyed by a transport roll and a roll of

  preliminary pressing, between which a slot of

  sage is formed, whose width is adapted to the flow

  harvested product, this device being equipped with a

  Electromagnetic metal detector, which explores the passage slot and whose signal is led to a threshold value switch, whose output signal acts on a switch, which stops the roller when the signal of the metal detector exceeds a value

predefined threshold.

  By DD 247 117 A 3, we already know such a dis-posi-

  detection of foreign bodies, in which a

  transport roller is combined with a roller of

  preliminary wise, a metal detector being provided, whose signal is constantly measured and compared with a predefined threshold value, during the surpassing of which a stop signal is sent to the transport device.

  Preliminary pressing is measured constantly

  cultively to the sense of transport of the crop and the measured value is driven to the value comparator

  threshold, parallel to the acceleration signal.

  This device for detecting foreign bodies is

  proprio motive for near-constant flow harvesters

  so much and conveying the harvest at a speed pretty much

  equals A certain discontinuity in the flow of the re-

  colte, due to the presence of a foreign body,

  the acceleration of the pressure roller by

  port to product speed, response sensitivity

  is relatively low at low speeds.

  In addition, the disturbance signals, which the detection

  metal collector seizes from the pre-press roll

  because of vibrations and lack of magnetic homogeneity, are all the higher

  the cross section of the product stream, i.e.

  the interval between the preliminary pressing roll and the metal detector is lower and the speed of transport of the product, ie the rotation of the roll, is fast, so that the threshold value, respectively predefined, is set above the amplitude level of the disturbance signal under the conditions mentioned and that, in other cases, only a relatively low response sensitivity

is obtained.

  The object of the invention is to improve the foreign body detection device, described above, so that its sensitivity of response is as much as possible independent of the current of the

  conveyed product, as well as the speed of it.

  The solution to the problem lies in the fact that the preliminary press roll and / or the transport roll is equipped with a synchrotransmitter, the signal of which a speed signal is constantly derived and that the signal of the metal detector is reinforced by a signal amplifier upstream of the

  switch threshold value, so that this amplifier

  tion, controlled by the speed signal, either

  all the weaker as the latter is higher.

  Advantageous design types are provided,

  In addition, the position signal is exploited further

  to control the signal response sensitivity of the metal detector so that when the product passage slot formed between the transport roller and the preliminary press roll is narrow, so when the metal detector is subjected to a high disturbing influence, the response threshold -3-

be reduced and vice versa.

  In a particularly advantageous embodiment

  of the invention, the signal from the metal detector is filtered, upstream of the

  switch threshold value, by a frequency filter

  these, letting a range of signal frequencies pass

  useful, the frequency filter being controlled adequately-

  as regards its filtering frequencies, with the

speed signal.

  The speed of advance of the harvested product is advantageously derived, directly from the transport roller or the preliminary pressing roll, by a speed sensor, in the known manner. The speed signal thus obtained is straightened and filtered, if necessary, and then used. by a position signal of a position indicator of the preliminary press roll, for the purpose of controlling the sensitivity of response to the signals of the metal detector and, in addition, if appropriate, an acceleration signal of this In this way, it is possible to set the threshold value, respectively adapted to the speed and above which a disconnection signal is launched, slightly above the disturbance signal level, which makes it possible to obtain a sensitivity.

  high response in the entire field of work.

  In addition, the signals of the metal detector and the acceleration signal of the position signaler are advantageously evaluated separately and the eventual disconnection signals are combined into an OR function, a specific adaptation to the two levels of the respective disturbance signals. metal detector and the acceleration signal taking place and a high response sensitivity thus obtained in

  the whole area of work for both signals.

  The response sensitivity to the useful signals of the metal detector and / or the position signaler is increased by a bandpass filter, in which the frequencies are modified with the measured transport speed, preferably in proportion to this, of so that a filtering of the wanted signal takes place according to the spectrum of the disturbance signal and the useful signal and that a good Storabstand gleichbleibend is obtained when the discrimination of the value of

  amplitude threshold followed, as expected.

  As the particular disturbing frequencies

  strong, manifesting itself in the signals of the de-

  tector, come from the ribs of the trans-

  port and preliminary pressing roll, the filter

  of the detector present, in a pre-arranged embodiment

  of the invention, two sectors for eliminating

  nation of disturbing frequencies, which are each controlled, in their absorption frequency ranges, by a rotation signalator, on

each of the two rollers.

  Another advantageous embodiment of the invention is

  the fact that the threshold value of

  is obtained, automatically, from the disturbing level of the detector signals, this threshold value being formed proportionately or

  a predefined interval with respect to the disturbance level

straightened and equalized.

  Advantageous designs of the device are

presented in figs 1 and 2.

  Figure 1 shows a cross-section of a

  positive transport with signal transmitters; -

  Figure 2 shows a block diagram of the device.

  Fig. 1 shows a cross-section of the harvested product transport device (20), hay, for example, which is driven by means of a transporting conveyor (21) driven from a preliminary pressing roll (22) and other rollers, at a chopper (23), from which the chopped product (20 A) is discharged The preliminary pressing roller (22) is pressed by spring force (F), approximately perpendicular to the direction of transport to the transport roller (21), and is mounted displaceable or pivotable in the direction of the spring force (F).

  foreign bodies serves, on the one hand, to protect the chopper

  especially the blades and the bar and, on the other hand, to keep all metal parts

  the difference of the chopped product For this reason the

  A coupling disconnection device and a transport roller brake circuit are designed with respect to the drive unit for rapid reaction such that undesirable foreign bodies are detected as the rollers pass. (21, 22)

  do not reach the chopper (23) and may be

  after a brief reversal of the product.

  the transport roller (21) The transport speeds of a modern harvester being of the order of 1 to 4 m / sec, we only have a fraction of a second to put the transport device reliably

off.

  As a metal detector (1), a device is

  provided in the transport roller (21), which

  is composed of permanent magnets and coils of

  field, whose common sensing characteristic

  roughly corresponds to the division of the field into two

  lobes, represented by lines of the same sensitivity.

  6 - The detector characteristic passes through the slot, located between the rollers (21, 22), the width (W) of which can vary in a wide range, for example from

  at 150 mm It follows that, for a large slot,

  of width, especially in the farthest slit area, the sensitivity of the detector is more

  weak It is obvious that the veins of the two rou-

  even if helical, they cause magnetic field disturbances, the result of which are dominant disturbance frequencies, caused in dependence on the speed and number of

  ribs In addition, also the modifications of the

  slot, when fitting the rollers, that

  the local differences in the material of the rolls

  sporadic disturbance signals and

at lower frequencies.

  The transport roller (21) is equipped with a magnetic speed sensor (3) whose frequency and signal amplitude corresponds to the speed of rotation. A speed sensor (30) can also be provided. pre-roll (22), which is advantageous in the case of a relatively high slip difference between the

  transport roll and the preliminary pressing roll

  seminar. The preliminary pressing roller (22) is provided with a position signaling sensor (4), which preferably consists of a potentiometer. The angular position of this potentiometer makes it possible to constantly measure the width (W) of the slot.

  used to control the response sensitivity.

  Signals signals (1, 3, 30, 4) are driven on the input side to a control device (ST), which controls, on the output side, the switching on and off.

  coupling circuit of the transport roller (21).

  The figure represents a block diagram of the device

  (ST) with input keys (8, 9), signaling

  (2, 3, 30, 4), adjusting and indicating components

  Connectors (6, 7, 11, 5, 14) connected The function groups, represented in the control device (ST), may consist of hardware or software,

  therefore in switching circuits or parts of

  control signal (STP), the analogue signals of the pre-amplified and filtered alarms (1, 4) being received by the control processor (STP), using a multiplexer and a analog-to-digital converter and then processed according to

other functions.

  The control of the signal processing in the control device (ST) is done, primarily, in dependence on a forward speed signal (GS, TS) This is obtained, in principle, from a part of a metal detector (MS) signal disturbance signal generated by the lamellae of one of the

  In the device shown, a transmission

  rotational speed (3) is however provided,

  whose frequency and / or signal amplitude is pro-

  proportional to the speed of rotation of the transport roller The signal of the rotation speed sensor (3) is transformed into a speed signal (GS) by a

  frequency-voltage converter (F / U) or a rectifier.

  If foreseen, adequate switching is

  set behind the second rotational speed sensor (30), speed signals (G 51, TSI) being especially generated for controlling a

  filter sector which eliminates disturbances in

  the progress of the preliminary press roll.

  8 - The position indicator (4) is connected to the control device (ST) so that its signal of

  position (PS) corresponds approximately to the

  slot position between the two transport rollers This position signal (PS) sets the processing of the metal detection signal (MS) of the metal detector (2) on the one hand, and is post-processed for detecting non-metallic foreign bodies, the two differentiators (D1, D2), connected one behind the other, forming an acceleration signal (BS) from the position signal (PS ). The acceleration signal (BS) and the signal of

  detection of metals (MS) are treated similarly

  they are driven, respectively, one after

  the other, an amplifier (1 V, 4 V) adjustable, coordinated

  given, and a controllable frequency filter (1 F, 4 F), then to a threshold value switching (1 S, 4 S) The output signals of the threshold value switching (1 S, 45) are collected via an OR (Gi) logic circuit intersector and thus, on the input side, conducts to the control processor (STP), which then drives the switch-off magnet (11), which stops the

  carrier For the control of the interrup-

  preferentially, a switch to

fast reaction known.

  The control of the signal amplifiers (l V, 4 V) is carried out so that their amplification is even lower as the transport speed, therefore the speed signal (GS), is higher technically, this is done as follows: the speed signal is fed to a feedback amplifier (RV) whose feedback signal (RS) acts on a controlled voltage divider (R, RT) composed of a resistor (R) and a a MOS-FET transistor (RT), so that the generated 9-voltage division signal corresponds to a fixed reference voltage (UR). The feedback signal (RS) thus obtained is driven, as a control signal, signal amplifiers (1 V, 4 V), as well as to a suitably designed voltage divider (R 1, RT 1; R 4, RT 4), whose output signal is then amplified. The control of the frequency filters (1 F, 4 F) takes place, depending on the kind of filter, directly with the speed signal (GS) and / or with the prescribed feedback signal (RS), resulting, so that the limit frequencies and the bandwidth of the filter

  are proportional to the magnitude of the speed signal.

  especially in case of RC circuit with

controllable resistors.

  Alternatively, switched capacity filters are advantageously provided. These (shown in indents) are controlled directly by the speed synchronization signals (TS, T 51) obtained from the signals of the rotational speed sensors (3, 30). ) With a rectifier and an amplifier (SV) In this way, all the filter parameters are always proportional to the synchronization signals and thus adjusted to the transport speed of the harvested product, the height of the disturbing frequencies and the slope of the signal useful, caused by a foreign body,

  being also proportional to it.

  In addition, it is advantageously provided, independently of the position signal (PS) to raise

  respectively the amplification factor of the amplifier

  signal detector (1 V) of the metal detector signal

  (MS) to compensate for the loss of sensitivity

  metal detector (1) when increasing the width of the slot The position signal (PS) -

  is simply conducted through a division

  voltage, on a MOS-FET (MT) transistor, in a counter-coupled voltage divider (RG, MT), so that the counter-coupling is reduced

  when the position signal (PS) increases.

  In another advantageous embodiment, provision is made not to constantly predetermine the threshold value (SW) of the threshold value switch (15) of the metal detection signal (MS), but to form this signal (MS). automatically, from the signal level of disturbance To do this, the signal, amplified in the signal amplifier (1 V) and unfiltered is rectified with a spike rectifier (SG) and filtered, and the output voltage of the signal rectifier thus obtained is amplified by a predefinable factor and driven, as threshold value (SW), to the threshold value switch (1 S) of the signal of the metal detector (MS). The amplification factor can be simply formed using a resistor

adjustable (EP).

  A corresponding or similar automatic threshold value generation switching can also be used for a threshold value preset of the second switch (4 S), in case of a level of

  higher disturbance of the acceleration signal (BS).

  When the preliminary pressing roll is relatively wide, it is appropriate to have, on each side, a position indicator, whose signals are chained together, preferably added. The favorable design of the metal detector with double-lobed characteristic gives, respectively, in the presence of metal parts, twice a point of il -

  positive voltage and a negative voltage peak.

  For this reason, it is advantageously planned to subject the amplified and filtered detection signal to a bi-plate rectification in a rectifier coupling (1 G), before driving it to the threshold value switch.

(l S).

  The introduction keys (8, 9) are used for signaling a start of the transport device and signaling a reversal when encountering an obstacle. The processor then appropriately excites the control magnets. (6, 7) In addition, when a foreign object is detected, the control processor (STP) turns on a signal lamp (14) until the reversal indicated by the second lamp signaling

(5) took place.

12 -

Claims (8)

claims:   1 Device for detecting foreign bodies in a harvested product stream (20), conveyed by a transport roll (21) and a preliminary pressing roll (22), between which a passage slot is formed, the width of which (W) is adapted to the flow of   harvested product, this device being equipped with a   electromagnetic metal detector (1), which explores the passage slot and whose signal is led to a threshold value switch (1 S), whose output signal acts on a switch (11), which stops the transport roller ( 21) when the signal (MS) of the metal detector exceeds a predefined threshold value (SW), characterized in that the preliminary pressing roller (22) and / or the transporting roller (21) is / are equipped with a speed signaling device (3, 30), the signal of which a speed signal (GS, TS, G 51, T Sl) is constantly derived and that the signal of the metal detector (MS) is amplified, in upstream of the threshold value switch (1 S), by a signal amplifier (l V), the amplification by the speed signal (GS, G 51)   being all the smaller as this one is bigger.   2 device for detecting foreign bodies according to claim 1, characterized in that the preliminary pressing roller (22) is equipped with at least one position indicator (4) arranged to start a position signal (PS). corresponding   approximately the width of the transmission slot   port, and that the position signal (PS) is led to the signal amplifier (l V) so that its amplification is as great as the signal of position (PS) is smaller.   13 - 3 Device for detecting foreign bodies according to claim 1 or 2, characterized in that the signal of the metal detector (MS) is filtered, upstream of the threshold value switch (i S), by a frequency filter (1 F, 4 F), passing a range of useful signal frequencies, and that the frequency filter (1 F) is suitably controlled, as to its frequencies, by the speed signal (GS, TS, GSI, T 51).   4 Device for detecting foreign bodies according to claim 3, characterized in that the signal of the filtered metal detector is led to a biplate (IG) rectifier switching, whose output signal is fed to the value switch threshold (15).   Device for detecting foreign bodies according to claim 2, characterized in that   that the position signal (PS) is driven, successively   two differentiators (D1, D2) and that an acceleration signal (BS) thus obtained is fed to a second threshold value switch (4 S), the output signal of which is driven, in a OR switching, with the output signal of the other threshold value switch (1 S), to the switch-off device (11) who stops the transport.   A device for detecting foreign bodies according to claim 5, characterized in that the acceleration signal (BS) is filtered with a frequency filter (4 F), upstream of the threshold value switch (4 S), which because of its characteristic 14 - band pass, lets pass the signal frequencies   useful for acceleration, the frequencies of passage,   sorption and characteristic limiting frequencies being proportional to the signal / signals (GS, TS, G 51, T 51).   7 Device for detecting foreign bodies according to claim 5 or 6, characterized in that the acceleration signal (BS) is amplified, upstream of the threshold value switch (4 S), by a second signal amplifier (4 V ), the amplification by the speed signal (GS) being all the more   weak that this one is higher.   8 device for detecting foreign bodies according to claim 7, characterized in that the second signal amplifier (4 V) is controlled in its amplification by the position signal (PS), so that its amplification is even greater   that the position signal (PS) is higher.   9 device for detecting foreign bodies according to claim 1 or 6, characterized in that the speed signal is at least one synchronization signal (TS, T 51), whose cycle frequency   is proportional to the signal frequency of the signal   rotation, and that the frequency filter   is composed of capacitor resistance components, com-   by the cycle signal (TS, T 51).   Device for detecting foreign bodies according to   one of the preceding claims,   characterized by the fact that the signal of the metal detector (MS), unfiltered, - amplified by the first signal amplifier (IV), is fed to a peak disturbance level (SG) rectifier, whose output signal , memorized with a time constant, relatively long with respect to a useful signal time behavior, and amplified, is conducted as a threshold value (SW) at the first threshold value switch (1 S) or at the second threshold value switch (45).   11 Apparatus for detecting foreign bodies according to claim 10, characterized in that the relation between threshold value (SW) and output signal of the disturbance level rectifier is adjustable. 12 Device for detecting foreign bodies according to   one of the preceding claims,   characterized in that the position signal (PS) and the speed signal (GS) are multiplied and temporally integrated and the result is output as the harvested product rate value. 13 Device for detecting foreign bodies according to   one of the preceding claims, characterized by the fact   that the position signal (PS), the signal of the signaling   rotation and the metal detector (MS) signal are conducted and digitized, to a program-controlled digital (ST) control device which filters the first and second filters (1 F, 4 F), the operation of the bi-plate rectifier (1G) and the peak value rectifier (SG), as well as the OR function of the OR (GI) logic circuit and excites   appropriately the dis-positive switch off (11).