CN2371566Y - Door type metal detector - Google Patents

Abstract

The utility model provides a door type metal detector, which is mainly composed of an oscillator, an amplifier, a detector head, a wave detecting low-level gate circuit and a follow-up circuit. The utility model is characterized in that the detector head is unshielded separated type, and a transmitter coil and the receiving coil of a balancing unit are respectively arranged on both sides of a detecting channel. The physical distribution is subjected to the examination when passing the detecting region, and the utility model generates alarm signals to the objects mixed with the metal objects. The metal detector has the advantages of high sensitivity, high resolution, high anti-interference capability, no screen, material saving, low cost, high performance-price ratio, simple structure, convenient installation and operation, etc., and is highly suitable for being used in safety detecting departments of customs, airports, stations and wharves.

Description

A kind of door type metal detector

The utility model relates to detecting instrument, a kind of door type metal detector of more specifically saying so.

Door type metal detector mainly is to be used for checking the instrument that whether is mixed with metallics among logistics in the operation passage, the stream of people.Be widely used in that the non-conducting material logistics detects in the safety check department of customs, airport, station, harbour and the plant produced line.Existing door type metal detector mainly constitutes (referring to Fig. 1) by detecting head and control circuit, and it comprises high frequency oscillator, detecting head, tuned amplifier, wave detector, low-frequency amplifier, monostalbe trigger, power supply and topworks (referring to Fig. 2); Three coils around the logistics corridor coiling are arranged in the probe, wherein transmitting coil is placed in the middle, two reverse connections of receiving coil are arranged on the transmitting coil both sides symmetrically, and the travelling belt that transports material therefrom passes, and whole detecting head periphery is by electromagnetism conductor shielding (referring to Fig. 3).Its principle of work is: transmitting coil is under the oscillator high-frequency current drives, in the notch of logistics corridor, form the high frequency alternating electromagnetic field, under the ideal conditions that no metal object exists in notch, two groups of technical parameters are identical, oppositely the induction electromotive force of the receiving coil that connects is cancelled each other, no signal output.When being mixed with metallic impurity in the detected logistics when entering the detecting head notch, just destroyed the symmetry of transmitting coil both sides alternating electromagnetic fields, occur uneven, at this moment receiving coil just produces a high-frequency am signal output (referring to Fig. 4), and wherein, the oscillation frequency of oscillator is that carrier wave, metal signal are modulating wave, this mixes ripple through frequency-selecting amplification, detection, take out metal signal, deliver to low-frequency amplifier and amplify, in order to promote monostalbe trigger control warning, indication and topworks's action.

The problem that this detector exists is: destroy accuracy and the sensitivity that detects in order to prevent undesired signal, must be with the metallic conductor housing parcel shielding of will popping one's head in, to isolate the influence of detection channels notch external electromagnetic field, get rid of the interference of non-detecting area metal signal and other signal.But, to import and export and can not seal again, this contradiction just occurred, and in this case, wanting to obtain fully, shielding is very difficult.In order to obtain shield effectiveness preferably, generally be to adopt the method that strengthens shield ranges.Simultaneously, in view of the magnetic line of force has the characteristic that trend concentrates on magnetic conductor, just must make between coil and the screen layer enough distances will be arranged, avoid causing the unevenness that the notch internal magnetic field distributes and cause surveying the phenomenon that the detection sensitivity of each point on the cross section had big-difference, when serious even the blind area may occur! Like this, the size of mask frame certainly will be quite big.In addition,, just require shielding construction to have enough intensity, therefore increase the thickness of screen layer again for the undesired signal that prevents that screen layer from causing because of external carbuncles such as vibrations.As a result, this huge and heavy metallic shield frame is placed on the periphery of detecting head reach, and not only having taken up an area of takes up space but also waste starting material increases cost.Also can cause the problem that makes new advances simultaneously.The framework microdeformation that is caused by mechanical vibration or temperature variation all can produce very important undesired signal, and the signal that the so big metallic object of volume produces is far longer than the signal that metallic impurity produced in the logistics certainly.Principle of work by the balanced type metal detector, the receiving coil balance that the signal of metallic shield frame is placed by symmetry offsets, and then remove to detect the signal of newly-increased metallic impurity, this just removes the material of the weighing milligram order of magnitude as the balance that uses several tons of mass balances, its sensitivity is very low.On the other hand, the transmitting coil and the receiving coil of this frame metal detector are structure as a whole, and travelling belt needs to pass from coil, also makes troubles to installation.In a word, it is conspicuous using the way isolation undesired signal of shielding and the drawback that itself brought, and how overcoming this defective is the problem of pendulum in face of engineering technical personnel.

Task of the present utility model provides a kind of door type metal detector without mask frame, and it can eliminate metal undesired signal and other undesired signal that non-detecting area comes effectively, and itself can not produce interference; Highly sensitive, resolution is high.

In order to finish above-mentioned task, the technical scheme that the utility model is taked is: this door type metal detector comprises high frequency oscillator and radiating circuit, trigger, indicator, alarm and topworks, it is characterized in that it also comprises:

---the split type detecting head of a secondary unshielded frame, constitute by transmitting coil L and balance receiving element coil L1, L2, transmitting coil and receiving coil branch are arranged, their coaxial relatively respectively both sides that are installed in sense channel, L is connected with the radiating circuit of high frequency oscillator GF, L1, L2 are flute profile, the cube that a height h equals depth D is formed in involutory back, be connected the two ends of resistance R with opposite polarity, their another common port is an earth terminal, the end that R is connected with L1 is output terminal e1, and that end that R is connected with L2 is output terminal e2;

---the amplifier N1 and the N2 of two symmetries, the input end IN1 of its N1 is connected with the output terminal e1 of described L1, and the input end IN2 of N2 is connected with the output terminal e2 of described L2, and the output terminal of N1 is OUT1, and the output terminal of N2 is OUT2;

---a detection-low level gating circuit, constitute by linear detector and low level gate, the input end V2 of linear detector is connected with the output terminal OUT2 of N2, its output terminal V2 ' is connected with an input end D of low level gate, another input end V1 of low level gate is connected with the output terminal 0UT1 of N1, the output terminal V1 ' of low level gate is connected with the input end usr of described trigger, and the output terminal of trigger connects the input end of described indicator, alarm and topworks respectively.

The transmitting coil L of split type detecting head and balance receiving element coil L1, L2 are plate structure, are supported by supporting base.

Balance receiving element coil L1, L2 can be unit, also can be two balancing units that above brick pattern is installed, or recombiner unit, and its mode of connection can be both-end output, also can be connected into single-ended output.

The utility model has the advantages that: 1. can effectively eliminate non-search coverage metal undesired signal; 2. highly sensitive, resolution is high, working stability is reliable; 3. need not shielding, to take up an area of duty few, can save material, and can reduce cost the cost performance height; 4. simple in structure, install and use all very convenient.

Fig. 1 is the profile organigram of prior art frame metal detector.

Fig. 2 is the principle of work block diagram of prior art metal detector.

Fig. 3 is the wiring diagram that transmits and receives coil of prior art detecting head.

Fig. 4 is the section of prior art detecting head and the signal graph of the interior metal object of passage notch.

Fig. 5 is the contour structures synoptic diagram of the split type probe of door type metal detector of the present utility model.

Fig. 6 is inner structure and the transmitting coil Distribution of Magnetic Field figure of Fig. 5.

Fig. 7 is receiving coil L1 and the geometric configuration of L2 and the wiring diagram of coil among Fig. 6.

Fig. 8 is the structure of a balance receiving element and the distribution plan of secondary magnetic field.

Fig. 9 is two balance receiving element brick pattern mounting structure figure.

Figure 10 is the structural drawing of plural equilibrium receiving element.

Figure 11 is the circuit diagram of detection-low level gating circuit.

Below in conjunction with accompanying drawing the utility model is done to describe in further detail.

In the prior art of Fig. 1～Fig. 4,1 of Fig. 1 is a probe, the 2nd, and electric control box, the 3rd, notch, the 4th, travelling belt.The L0 of Fig. 3 is a transmitting coil, and L10, L20 are receiving coils, and E is a screen layer, and GF is and the link of high frequency oscillator that e10, e20 are the output terminals of receiving coil, are connected with the input end of signal processing circuit.The rf of Fig. 4 is a high frequency balanced signal waveform, and am is the modulated wave signal waveform of metal signal, and af is that direction shown in the arrow is the logistics direction through sound signal (the being metal signal) waveform that draws behind the phase-shift detection.

Fig. 5～Figure 11 provides embodiment of the present utility model.

Fig. 5 is the contour structures synoptic diagram of the split type probe of door type metal detector of the present utility model.Among the figure, the 5th, the transmitting coil plate, the 6th, receiving coil plate, arrow are sense channel.From scheming as seen, it and existing detecting head are different (referring to Fig. 1, Fig. 3), and transmitting coil and receiving coil are divided into two independent parts and are placed in the plate of cement structures, and configuration is installed relatively, the middle sense channel that forms, the no conductor shielding of periphery.

Fig. 6 is inner structure and the transmitting coil Distribution of Magnetic Field figure of Fig. 5.Among the figure, L is that transmitting coil, L1 and L2 are receiving coils.Shape and the technical parameter of L1 and L2 are identical, staggered relatively, form a cube that highly equals the degree of depth jointly, are called the balance receiving element.Eight angle A, B of balance receiving element, C, D, E, F, G, H form 6 planes.Front surface A BCD is parallel with transmitting coil L, and it is with forming detecting area between the transmitting coil L, analyte from detecting area by being subjected to an examination.Remaining 5 face, ABFE is a left surface, CDHG is a right flank; ADHE is an end face, and BCGF is the bottom surface, and EFGH is the back side.

Fig. 7 is the geometric configuration figure of receiving coil L1 and L2 among Fig. 6.Two coils are flute profile, and the cube that a height h equals depth D is formed in involutory back, as arrow indication among the figure.L1 exports and single-ended output dual mode with the both-end that is connected with of L2: what both-end was exported is connected as the A among the figure, with opposite polarity receive the two ends of resistance R on L2 L1, their other end is the common ground end, an end of getting ready is an end of the same name, at two signal e1 of the two ends of R output and e2; Disturb lessly in environment for use, and the less demanding occasion of detection accuracy also can be connected into single-ended output, as the B among the figure, with L1 and L2 oppositely and connect, and an end ground connection, other end output single-ended signal e is connected with circuit (see figure 2) accordingly.

Fig. 8 is the structural drawing of a balance receiving element.If: detecting area has a metal object M (left figure) when occurring, this M produces secondary field under the effect at launching site, L2 is passed in side, end face and bottom surface left, L1 is passed in side, end face and bottom surface to the right, cut L2 and L1 respectively in the opposite direction, therefore can obtain two signal that polarity is identical outputs at the output terminal of two coils.

Non-detecting area outside search coverage for example has a metal object M ' (right figure) when occurring, so in the outside, left side of receiving coil:

1. magnetic flux a passes L1 and L2 simultaneously in the same way, because L1 and L2 oppositely connect, the induction electromotive force of Chan Shenging has just been cancelled each other on the contrary because of direction thereon;

2. magnetic flux b passes end face, and only passes L1, and magnetic flux C passes the bottom surface, also only passes L1;

3. magnetic flux d passes the front, only passes L2, and magnetic flux e passes the back and also only passes L2.

With regard to 2, with regard to 3 two kind of situation, be a cube that highly equals the degree of depth because L1 and L2 constitute, top, two sides, the end equate that with the surface area on two sides, front and back if with the flattening of two coils, can see: magnetic flux b, c pass L1 in the same way; D, e pass L2 in the same way, article 4, (the actual magnetic line of force is a lot of to the magnetic line of force, say something for example, here only draw representational 4) direction of passing two coils all is consistent, like this, with the magnetic line of force of same density and with same direction, two the coil L1 and the L2 that pass equal area, mutually reversal connection will produce two equal and opposite in directions, opposite polarity signal, two signals offset mutually, from non-detecting area metal M ' undesired signal that produced just has been eliminated.The receiving coil that L1, L2 are combined into this structure is referred to as the balance receiving element.In actual applications, in order to satisfy the different requirements of surveying height, can be as the case may be with several balancing units with the installation that superposes of cordwood mode.

Fig. 9 is the structural drawing that two balance receiving element brick patterns are installed.Being a balancing unit above the left side among the figure, is a balancing unit below, for tandem is installed, its wiring is as the right, and L1 connects with L1 ', and L2 connects with L2 ', be connected on the resistance R two ends with opposite polarity then, the other end is a common end grounding, and e1, e2 are output terminals.

Figure 10 is the structural drawing of plural equilibrium receiving element.Among the figure, L1, L1 ' and around together, L2, L2 ' and around together, the technical parameter of four coils all is identical with shape, then they are closed up, as the figure of arrow points, just constituted the balance receiving element of combined type, this structure is actually two balance receiving elements that L1, L2 and L1 ', L2 ' constituted and is placed on same cubical each bar rib, and each corresponding coil L1, L2 are on the identical geometric position with L1 ', L2 '.Its mode of connection is as figure the right, and L2 ' links with L1 end of the same name, and L1 ' links with another end of the same name of L2, and e1, e2 are output terminals.This structure is except having metal undesired signal to non-detecting area the effect that averages out on the field flux distribution in space, because two coils of each unit are oppositely to connect back output, played the effect of balance again, so be called the plural equilibrium structure.

In sum, since transmitting coil and receiving coil be split separately independently, form detection channels in the middle of the configuration back relatively, therefore, need not to disconnect travelling belt during installation, extremely easy to use, and also the width of passage can be regulated arbitrarily, in the detecting area of passage, the intensity of signal can not have very big-difference because of the metal object position is different basically.Because if metal object is nearer apart from transmitting coil, then far away apart from receiving coil relatively, otherwise, nearer apart from receiving coil, then far away apart from transmitting coil, so the power of signal is consistent basically, can not change because of the metal object present position is different.The size of test surface by the width decision of coil, can narrow down to it sufficient size, thereby can determine the position of metal object more accurately basically, and sensitivity and resolution all greatly improve.

Yet, take above-mentioned measure after, problem solves fully.Speak of above, the prerequisite of eliminating non-detecting area metal undesired signal is: the magnetic flux that equates, pass two bucking coils of equal areas with identical direction.This is a condition in the ideal case, in fact, make top, bottom surface, area preceding, the back side accurately equates, does not accomplish on the technology, simultaneously, the distribution of magnetic flux also can not be fully uniformly, position and reciprocal influence thereof that metal object occurs more can cause the distortion in magnetic field, so the metal object undesired signal of non-detecting area just can not offset fully.In addition, we also see, if when metal object appears at the receiving coil back side, the secondary field that its produces to the effect of receiving coil except flow direction on the contrary, its character metal object interior with being in detecting area is the same.So, only rely on the balance receiving element also to be not enough to eliminate the metal undesired signal that non-detecting area comes completely, also must manage from circuit, to be improved.From the analysis of front as can be known, metal object only is in the detecting area, and two coils that oppositely connect just can obtain the signal of identical polar.Therefore, adopt following detection-low level gating circuit, just can take out the signal of these two identical polars, the metal undesired signal that the non-detecting area of filtering comes, promptly opposite polarity signal.

Figure 11 is the circuit diagram of detection-low level gating circuit.For clarity, the prime in the frame of broken lines and the annexation of subsequent conditioning circuit have been provided.Among the figure, GF is a high frequency oscillator, L is a transmitting coil, L1 and L2 are two symmetries, the receiving coil that technical parameter is identical, and they oppositely dock by resistance R, N1～N4 is a low maladjustment voltage type operational amplifier, model is OP-07, and V is junction type N channel field-effect pipe (G is that grid, S are that source electrode, D are drain electrodes), pinch-off voltage Up is-4V about.E1 is the output terminal of L1, and e2 is the output terminal of L2.N1, N2 make the amplifier usefulness of two symmetries, and the input end of N1 is IN1, and output terminal is OUT1, and the input end of N2 is IN2, and output terminal is OUT2.N3 and V and peripheral cell stabilivolt VD1, VD2, resistance R 1, R3, R5 form the low level gate, and wherein R5 is the resistance of V, and the voltage stabilizing value of stabilivolt is 5.1V.N4 and peripheral cell semiconductor diode VD3, VD4, resistance R 2, R4 form linear detector.In the circuit, R1=R2=R3=R4, V1 are input ends of gate, V2 is the input end of wave detector, and V2 ' is the output terminal of wave detector, and D is another input end of gate, V1 ' is the output terminal of gate, is connected with the input end usr of subsequent conditioning circuit trigger.They have constituted detection-low level gating circuit together.

Circuit can be designed to the gating positive signal, also can be designed as the signal of gating negative polarity.This circuit design is a gating negative polarity signal, if change the gating positive signal into, as long as VD1～VD4 is connect conversely, corresponding field effect transistor is used P ditch deferent instead, and resistance R5 reconfiguration+6V just.

In this circuit, when the signal that two input end V1 that detection-low level gating is meant at circuit and V2 have two negative polarity simultaneously arrives, only select a less output of signal level." level " refers to absolute value here.Two signals that this gate occurs two input end V1 and V2, if be zero simultaneously, perhaps simultaneously for just or one positive one negative, output terminal V1 ' export zero, in a word, in two signals if any one 〉=0, export be zero.Have only when two signals of V1 and V2 appearance are negative polarity simultaneously, circuit is just selected that lower signal output of level.

Be example with gating negative polarity signal now, by the transmission of signal, variation relation illustrates its principle of work.

1.V1, V2 end is at 0 o'clock, promptly the prime no signal is sent here,

2.V1, V2 end is timing (for example there is the caused undesired signal of metal object in the balance receiving element back side, sort signal just with detecting area in metal signal anti-phase), because V1 is for just, stabilivolt VD1 forward conduction, voltage on the Vp point is forward voltage drop-0.7V of VD1, G point current potential is-0.7-5.1=-5.8V that field effect transistor is ended.Because V2 for just, is output as 0 after detection, so V1 '=0.

3.V1, V2 is one positive one when negative, promptly there is the caused undesired signal of metal object in balance receiving element both sides, in the case:

4.V1, V2 end is when negative, i.e. the metal signal that metal object causes in the detecting area, at this moment circuit just compares the level of V1 and V2 automatically, selects more low level signal to export:

(because R2=R4, the V2 ' that exports after the V2 detection is identical with the V2 level, and in fact V1 and V2's relatively is exactly the comparison of V1 and V2 '.)

When the level of V1 is lower than the level of V2 ', N3 exports positive voltage, stabilivolt VD2 punctures, the controlled conducting of field effect transistor, V2 ' is fed to output terminal V1 ' by field effect transistor, and at this moment field effect transistor is equivalent to a thyrite, and it is subjected to the output voltage control of amplifier N3, when the level of output terminal V1 ' equated with the level of input end V1, circuit reaches balance, and (the circuit balancing condition was

Because R1=R3, so V1=-V1 ').Satisfy above-mentioned condition, the level of V2 ' must only in this way could guarantee that V2 ' is by still equaling the level of V1 after the field effect transistor pressure drop greater than the level of V1.This shows that when the level of V1 during less than the level of V2, circuit is selected low level signal V1 output.When the level of V1 was higher than the level of V2 ', circuit still repeated said process, but because the level of V2 ' is lower than the level of V1, and the level that V2 ' is fed to V1 ' end by field effect transistor also is lower than the level of V1 certainly.Under this situation, circuit can not reach above-mentioned equilibrium condition (being V1=-V1 '), thereby the amplifier N3 voltage breakdown (5.1V) of having exported VD1 punctures VD1 and forms feedback channel.The output of N3 has also punctured stabilivolt VD2 simultaneously, and the voltage that makes field effect transistor V grid is 0 volt, the abundant conducting of field effect transistor, and its conducting resistance is reduced to hundreds of ohms, and the voltage of V2 ' does not almost have pressure drop and arrives output point V1 ' by field effect transistor V.That is to say that when the level of V1 was higher than the level of V2 ', circuit was selected the lower signal V2 ' output of level.

Further describe the course of work of circuit below:

1. no metal object exists in the detection zone of start back.The front was said, L1, L2 are owing to be oppositely to connect, induction electromotive force is cancelled each other, no signal output, and promptly e1, e2 are equal to 0, the output voltage of N1, N2 is that the voltage of V1, V2 also equals 0, N3, N4 output voltage also equal 0, and field effect transistor is by pinch off, and V1 ' point exports 0, subsequent conditioning circuit is not all worked, and instrument can not respond.

2. there is metal object to occur in the detection zone.The front was said, metal object is subjected to the launching site in detection zone effect can produce secondary field reverse cut L1, L2, obtain two signals that polarity is identical respectively at its output terminal, because circuit is got the negative polarity gating, the first via is exported to the signal of V1 for negative after N1 amplifies.What the second road e2 exported to V2 after N2 amplifies also is negative, and detection-low level gating circuit selects the lower signal of level from the output of V1 ' point in V1 and two signals of V2, the indicator of triggering following, alarm and topworks's work.

3. the elimination of Gan Raoing.Usually, the appearance of undesired signal is to cause owing to there is the electromagnetic field in metal object existence or space the peripheral both sides of detection zone, because two receiving coil L1, L2 of balance receiving element oppositely connect, so this undesired signal can be exported one positive one negative signal at two output terminals of balance receiving element, signal after amplifier N1 and N2 amplify also is opposite polarity on V1, V2 end, and this one positive one negative signal is exported zeroly behind detection-low level gating circuit and by filtering.

What be worth mentioning at last is, adopt the benefit of low level gating can make the amplitude of output signal slowly be changed to maximum from zero, slowly change to zero from maximum again, make the people directly feel the process of metal object by popping one's head in, this from weak to strong again from being different from paroxysmal undesired signal fully to weak signal characteristic by force, be convenient to the operator and make right judgement.

Claims (3)

1. door type metal detector, it comprises high frequency oscillator and radiating circuit, trigger, indicator, alarm and topworks, it is characterized in that it also comprises:

---the split type detecting head of a secondary unshielded frame, constitute by transmitting coil L and balance receiving element coil L1, L2, transmitting coil and receiving coil branch are arranged, their coaxial relatively respectively both sides that are installed in sense channel, L is connected with the radiating circuit of high frequency oscillator GF, L1, L2 are flute profile, the cube that a height h equals depth D is formed in involutory back, be connected the two ends of resistance R with opposite polarity, their other end is a common end grounding, the end that R is connected with L1 is output terminal e1, and that end that R is connected with L2 is output terminal e2;

---the amplifier N1 and the N2 of two symmetries, the input end IN1 of its N1 links to each other with the output terminal e1 of described L1, and the input end IN2 of N2 is connected with the output terminal e2 of described L2, and the output terminal of N1 is OUT1, and the output terminal of N2 is OUT2;

---detection one a low level gating circuit, constitute by linear detector and low level gate, the input end V2 of linear detector is connected with the output terminal OUT2 of N2, its output terminal V2 ' is connected with an input end D of low level gate, another input end V1 of low level gate is connected with the output terminal OUT1 of N1, the output terminal V1 ' of low level gate is connected with the input end usr of described trigger, and the output terminal of trigger connects the input end of described indicator, alarm and topworks respectively.

2. door type metal detector according to claim 1 is characterized in that: the transmitting coil L of split type detecting head and balance receiving element coil L1, L2 are plate structure, are supported by supporting base.

3. door type metal detector according to claim 1 and 2, it is characterized in that: balance receiving element coil L1, L2 can be unit, also can be two balancing units that above brick pattern is installed, or recombiner unit, its mode of connection can be both-end output, also can be connected into single-ended output.

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