EP0394714A2

EP0394714A2 - Identification device with inductive antenna coupling

Info

Publication number: EP0394714A2
Application number: EP90106406A
Authority: EP
Inventors: Bruno G. Viereck; Josef Schuermann
Original assignee: Texas Instruments Deutschland GmbH
Current assignee: Texas Instruments Deutschland GmbH
Priority date: 1989-04-12
Filing date: 1990-04-04
Publication date: 1990-10-31
Anticipated expiration: 2010-04-04
Also published as: EP0394714A3; EP0394714B1; ATE155288T1; DE69031008T2; DE3912034C1; DE69031008D1

Abstract

The invention relates to an identification device (10) consisting of a transmitter and receiver section (12) and an antenna connected thereto via an antenna coupling (16). Known identification devices are awkward to handle and trouble-prone in particular under rough use conditions. The new identification device is to be suitable in particular for mobile use and remain functionable even under rough ambient conditions. For this purpose in the antenna coupling (16) a dividable transformer (18) is arranged, a first transformer half having a core (20) and a winding (21) being accommodated in the transmitter and receiver section (12) and a second transformer half having a core (22) and a winding (23) being accommodated in the antenna (14). The two windings (21, 23) are inductively coupled in the connected state of the transmitter and receiver section (12) and the antenna (14).

Description

The invention relates to an identification device consisting of a transmitter and receiver section and an antenna connected thereto via an antenna coupling.
Identification devices of the type according to the preamble can be used for sending interrogation pulses to transponders carried for example by animals and receiving data transmitted by the transponders as reaction to the interrogation pulses. Since the range of the signals transmitted by the transponders is not very large the antenna of the identification device is so constructed that it can easily be brought into the vicinity of a transponder to be interrogated. However, this makes the antenna bulky and long, so that the identification device cannot easily be transported. In particular in mobile use, for example by veterinary surgeons or government inspectors, this would however be desirable.
It is already known to connect an antenna with the corresponding transmitter and receiver section detachably via an antenna coupling. Known antenna couplings are trouble-prone from both the electrical and the mechanical point of view.
In particular in use under unfavourable ambient conditions, for example in stables, stalls or on fields, the antenna coupling systems available fail due to soiling. Usually, the known antenna couplings have a galvanic connection and the plug-type connections used are easily soiled. In addition, with plug-type connections under rough use conditions bending of the connection contacts can easily occur so that the entire identification device then no longer functions.
It is therefore desirable to equip an identification device with a contactless antenna coupling. This can be implemented basically with an antenna coupling with inductive coupling. However, the particular problem is encountered here of making the inductively coupled antenna coupling mechanically stable and electrically functionable even under rough ambient conditions.
The problem thus arises of further developing an identification device according to the preamble in such a manner that it is suitable for mobile use and remains functionable even under rough ambient conditions.
The solution of this problem is provided by the features of claim 1. This gives an identification device in which the transmitter and receiver section and the antenna are connected together via an inductively coupled antenna coupling. The transformer forming the core piece of the inductive coupling is divided into two parts, a first transformer half being accommodated in the transmitter and receiver section and a second transformer half in the antenna.
Advantageously, the cores can each be formed by a pot core half. This gives a great reduction in stray fields.
In another preferred further development instead of the pot core halves of a pot core transformer E cores may also be employed for the cores.
An advantageous constructional further development of the invention is represented by the features of claim 3. The antenna coupling is accordingly formed substantially from an antenna mounting flange mounted on the transmitter and receiver section, an antenna-side antenna tube support and a coupling ring for screwing the antenna tube support to the antenna mounting flange. An antenna coupling made in this way is simple to manipulate and permits in simple manner a water-tight connection of the antenna to the housing of the transmitter and receiver section so that the identification device is suitable for use in moist and chemically aggressive surroundings. Due to the simple construction this configuration represents an economic alternative to the comparatively very expensive water-tight connectors.
The aforementioned embodiment can be further developed by a stop ring on the antenna tube support corresponding to the features of claim 4. The coupling ring thus remains ready to grip even on the antenna detached from the transmitter and receiver section. In addition, the edge of the coupling ring covers the end of the antenna tube member so that the diaphragm closing the antenna tube member is advantageously protected from damage.
The features of claim 5 give another advantageous embodiment of the invention. In this case on the antenna side an insert member of rectangular cross-section is formed which is adapted to be inserted into a correspondingly formed insert region within the transmitter and receiver section. This further development first has the advantage that the antenna is always automatically mounted in a position correctly aligned with respect to the transmitter and receiver section. According to the further developments of this embodiment according to claims 6 to 8 an antenna coupler is obtained which is largely insensitive to soiling. If for example in the disassembled state dirt particles should get into the insert region of the transmitter and receiver section on assembly they are engaged by the front end of the insert member and conveyed into the hollow chamber formed between the insert member and insert region. This makes it possible to prevent dirt particles getting between the diaphragms covering the transformer halves. A penetration of dirt particles during the engaged state is prevented in advantageous manner by the hood provided on the antenna side.
A further advantageously developed antenna coupling is set forth in claims 9 to 11. The particular advantage of this embodiment resides in that by the specific configuration of the bayonet fastener with few parts a robust and easily manipulatable connection is provided.
The embodiment according to claim 12 utilizes the previously mentioned advantageous bayonet fastener. In this case the diaphragm covering the antenna-side transformer half is protected particularly effectively from mechanical damage by the projecting edge of the antenna tube support.
Claims 13 and 14 relate to specific further developments of the antenna belonging to the identification device. By a single operation the antenna can accordingly be dismantled or reassembled and in the assembled state at its bending point it has substantially the same stability with respect to bending stresses as an antenna made in one part.
Further details, features and advantages of the invention will be apparent from the following description of the examples of embodiment illustrated in the drawings, wherein:

Fig. 1 is a schematic side view of the identification device according to the invention;
Fig. 2 is a longitudinal section through an embodiment of the antenna coupling;
Figs. 3a and 3b each show schematical longitudinal sections (from the front and side) of a second embodiment of the antenna coupling;
Fig. 4a is a schematic longitudinal section from the front of a third embodiment of the antenna coupling;
Fig. 4b is a sketch to clarify the antenna coupling fastener according to the embodiment shown in Fig. 4a;
Fig. 5 is a schematic longitudinal section from the front through a fourth embodiment of the antenna coupling; and
Fig. 6 is a detail view of a preferred embodiment of the antenna.

An identification device 10 consists according to the schematic representation in Fig. 1 substantially of a transmitter and receiver section 12 and an antenna 14. The transmitter and receiver section 12 and the antenna 14 are detachably connected to each other via an antenna coupling 16. The antenna 14 is bent at its free end and is preferably connected via the antenna coupling 16 to the transmitter and receiver section 12 in such a manner that the bent portion of the antenna 14 points obliquely downwardly when the identification device 10 is in a horizontal position. The entire identification device 10 may be held at a grip 17.
The antenna coupling 16 illustrated in Fig. 2 is an inductive coupling which connects the antenna 14 to the transmitter and receiver section 12 without using galvanic contacts. The central part of the antenna coupling 16 is a two-part transformer 18 which in the example of embodiment illustrated in Fig. 2 is a pot core transformer. A first pot core half 20 is disposed with its winding 21 in the transmitter and receiver section 12 whilst a second pot core half 22 is disposed with its winding 23 in the antenna 14.
In the ready-to-operate state of the identification device 10 in which the transmitter and receiver section 12 and the antenna 14 are connected together via the antenna coupling 16 the two pot core halves 20, 22 are associated with each other in such a manner that the windings 21, 23 are inductively coupled, a gap 24 being present between the pot core halves 20, 22.
The pot core half 22 is disposed centrally in an antenna mounting flange 30. The latter is sealed towards the antenna 14 by a diaphragm 26. Preferably both the antenna mounting flange 30 and the diaphragm 26 are made integrally from plastic. The antenna mounting flange 30 is screwed to the housing 31 of the transmitter and receiver 12 using a seal. The pot core 20 in the interior of the antenna mounting flange 30 is centered by a pot core holder 40 and pressed by the latter via a rubber spring 41 against the diaphragm 26. The pot core holder 40 itself is screwed to a transmitter mounting plate 42 in the transmitting and receiving section 12. The rubber spring 41 consists preferably of sponge rubber adhesive on both sides.
The antenna 14 is held with one end in an antenna support 32. The end of the antenna support 32 facing the antenna mounting flange 30 is sealed with a diaphragm 28 which is preferably adhesively attached. The second pot core half 22 is pressed by a pot core holder 43 bearing on the antenna support 32 via a rubber spring 44 against the diaphragm 28. The pot core holder 43 serves not only as abuttment for pressing the pot core 22 against the diaphragm 28 but also as holding means for a printed circuit board 45 on which an antenna damping circuit is disposed.
Arranged on the antenna support 32 is a coupling ring 34 by means of which the antenna support 32 can be screwed to the antenna mounting flange 30. The two diaphragms 26 and 28 are pressed against each other so that between the two pot core halves 20 and 22 a gap is formed corresponding substantially to the thickness of the two diaphragms 26 and 28.
Cut into the surface of the antenna support 32 is a groove 36 in which a stop ring 38 lies, for example an O ring. Said stop ring 38 serves to prevent the coupling ring 34 slipping off the antenna support 32 in the released state. Preferably, the groove 36 with the stop ring 38 is arranged an axial distance from the diaphragm 28 which is smaller than the length of the outer surface of the coupling ring 34 so that the latter protectively surrounds the diaphragm 28 even in the disassembled state of the antenna 14.
Instead of the rod-shaped antenna used in the previously described example of embodiment a ring antenna may also be employed, the construction of the antenna coupling 16 in the manner described being retained.
In Figs. 3a and 3b a second embodiment of the antenna coupling 16 is shown. In this example of embodiment in the transmitter and receiver section 12 an insert region 50 is disposed into which an antenna-side insert member 52 can be inserted. The insert region 50 has a rectangular cross-section, the cross-sectional area being substantially in two stages. In the outer portion of the insert region the cross-sectional area is broader than in the inner portion of the insert region 50, as can be seen in Fig 3b The insert member 52 is fixed in the insert region 50 by a snap means consisting of projections 56 which are arranged in the insert region 50 and which can enter detent engagement with recesses 58 correspondingly provided in the insert member 52.
The first pot core half 20 is disposed in a side wall 54 of the insert region 50 behind the diaphragm 26. The second pot core half 22 is arranged in the insert member 52 in such a manner that in the engaged state of the insert member 52 it lies opposite the first pot core half 20. A projection 64 is formed on the side of the insert member 52 lying opposite the second pot core half 22. Said projection bears in the engaged state on a side wall of the insert region 50, the cross sectional area of which as described above is small compared with that of the outer insert region. The purpose of reducing the cross-sectional area is for the insert member 52 to be easily insertable in the outer insert region without resistance whilst in the inner insert region it must be fixed in a position in which a defined gap is set between the two pot core halves 20 and 22. This is ensured by bearing of the projection 64 on the wall portion of the insert region 50 corresponding thereto. In this embodiment as well a gap 24 is formed between the two pot core halves and corresponds substantially to the thickness of the two diaphragms 26 and 28.
The embodiment shown in Figs. 3a and 3b is distinguished in particular by its robustness; it withstands mechanical stresses particularly well. This embodiment in particular is made insensitive by a simple constructional form also to soiling which in the region of the antenna coupling 16 can otherwise easily lead to functional disturbance. A protection against soiling is first formed by an antenna-side hood 62 which in the engaged state covers the opening of the insert region 50. In addition, in the engaged state between the insert member 52 and the insert region 50 a cavity 60 is formed. The latter serves to receive any dirt particles possibly present in the insert region 50 prior to insertion of the insert member 52, said particles being pushed along the insert region 50 by the inserted insert member 52 into the cavity 60.
In the example of embodiment illustrated in Fig. 3a as transformer a pot core transformer is used. Instead of the pot core transformer an E core transformer may also be employed.
The example of embodiment of the antenna coupling 15 illustrated in Fig. 4a contains similarly to the previously described example of embodiment an insert region 70 which is arranged in the transmitter and receiver section 12 and an antenna-side insert member 72 insertable into said region 70. The insert region 70 and the insert member 72 in this case however have a circular cross-section and the two pot core halves 20, 22 after engagement of the insert member 72 in the insert region 70 lie opposite each other centrally at the bottom 74. The insert member 72 consists essentially of a core portion 79 and a sleeve 80 which is adhered thereto and which is sealed with a diaphragm 28 at its end face 76. The second pot core half 22 is pressed against the diaphragm 28 by means of a spring 81 bearing against the core portion 79. The insert member 52 is detachably anchored in the insert region 50 by a bayonet fastener 78. The two studs 82 of the bayonet fastener 78 are integrally formed on the sleeve 80. The studs may be inserted into the stud guide 83 and locked by rotating the entire insert member 72.
With the aid of Fig. 4b the detent mechanism of the bayonet fastener can again be clarified. Fig. 4b shows firstly the stud guide 83 in the insert region 70. Above the horizontally extending portion of the stud guide 83 in the insert region 70 a recess 84 is disposed so that between the horizontally extending portion of the stud guide 83 and the recess 84 only a narrow web 85 is left. Both the studs 82 and the two webs 85 have an elasticity due to their material properties. Because of this elasticity the stud 82 on starting the pivoting of the respective stud 82 into the horizontally extending portion of the stud guide 83 is deflected so that the stud 82 can be pushed beneath the web 85. Due to its deflection the stud 82 is under stress. As a result a pressure force originating from the stud 82 is exerted on the web 85. This pressure force generates in the resilient web 85 a trough-like deformation as illustrated in Fig. 4b. By this trough the stud 82 is fixed in the horizontally extending portion of the stud guide 83. Of course, the stud 82 can be turned out of this locking position again by appropriate rotation of the insert member 72.
The embodiment of the antenna coupling 16 shown in Fig. 5 comprises similarly to the embodiment according to Fig. 1 an antenna mounting flange 90 disposed on the transmitter and receiver section. On the antenna side an antenna support 92 is formed with an edge 94 having an internal diameter corresponding substantially to the external diameter of the antenna mounting flange 90 so that the antenna support 92 can be pushed in sleeve-like manner over the antenna mounting flange 90. The antenna mounting flange 90 and the antenna support 92 can be connected together via a bayonet fastener 98. The mode of operation of the bayonet fastener 98 corresponds substantially to that of the bayonet fastener 78 in the example of embodiment according to Fig. 4a.
The antenna mounting flange 90 is also sealed by a diaphragm 26. In this case as well the diaphragm 26 is immediately adjoined by the first pot core half 20. A bottom 96 is surrounded by the edge 94 in the antenna support 92. Said bottom is covered by the diaphragm 28, immediately behind which the second pot core half 22 is disposed. After fixing the antenna support 92 on the antenna mounting flange 90 by means of the bayonet fastener 98 the two pot core halves 20 and 22 are disposed directly opposite each other, being separated from each other only by the gap 24 which corresponds substantially to the thickness of the diaphragms 26 and 28.
In the examples of embodiment according to Figs. 3a and 3b, Fig. 4 and Fig. 5, due to the configuration of the respective antenna coupling 16 on assembly of the identification device 10 the antenna 14 can be automatically brought into the correct working position with respect to the transmitter and receiver section 12. In this working position, as shown in Fig. 1 and already explained in the description thereof, the inclined portion of the antenna 14 points obliquely downwardly when the identification device 10 is aligned horizontally.
In Fig. 6 an embodiment of the antenna 14 is shown which is advantageous in particular when the relatively long antenna must be folded into a handy form. For this purpose the antenna 14 is divided into two parts and can be folded together about a joint 100. In the interior of the antenna tube a tube member 102 is displaceably arranged in such a manner that in the collapsed antenna it is retracted into a tube member and in the assembled antenna 14 projects into the two antenna tube members so that the latter can no longer be pivoted about the joint 100. The tube member 102 is longitudinally displaceable in the antenna tube in the direction of the arrow a and oppositely to said direction via a stirrup member 104 projecting out of a slot provided in the antenna 14.

Claims

1. Identification device (10) consisting of a transmitter and receiver section (12) and an antenna (14) connected thereto via an antenna coupling (16), characterized in that in the antenna coupling (16) a dividable transformer (18) is arranged, a first transformer half having a core (20) and a winding (21) being received in the transmitter and receiver section (12) and a second transformer half having a core (22) and a winding (23) being received in the antenna (14), and that the two windings (21, 23) are inductively coupled in the connected state of the transmitter and receiver section (12) and the antenna (14).

2. Device according to claim 1, characterized in that the two cores (20, 22) are each formed by a pot core half.

3. Device according to claim 2, characterized in that the transmitter and receiver section (12) comprises an antenna mounting flange (30) which is sealed by a diaphragm (26), the first pot core half (20) being arranged immediately behind the diaphragm (26) centrally in the antenna mounting flange (30), that the antenna (14) is held at one side in an antenna support (32) which is likewise sealed with a diaphragm (28), the second pot core half (22) being disposed immediately behind the diaphragm (28) centrally in the antenna support (32), and that the antenna support (32) is connected by means of a coupling ring (34) to the antenna mounting flange (30) in such a manner that the two diaphragms (26, 28) lie closely against each other.

4. Device according to claim 3, characterized in that in a groove (36) encircling the antenna tube support (32) a stop ring (38) is received, the groove (36) having an axial distance from the diaphragm (28) which is smaller than the length of the outer surface of the coupling ring (34).

5. Device according to any one of claims 1 to 4, characterized in that in the transmitter and receiver section (12) an insert region (50) is cut which has a rectangular cross-section and into which a correspondingly shaped insert member (52) of the antenna (14) can be inserted, the first transformer half being disposed in a side wall (54) of the insert region (50) and the second transformer half being disposed in the insert member (52) in such a manner that in the connected state the two transformer halves lie opposite each other, and that the insert member (52) is adapted to be locked in the insert region (50).

6. Device according to claim 5, characterized in that in the detent position between the insert member (52) and the insert region (50) a cavity (60) is formed.

7. Device according to claim 5 or 6, characterized in that between the insert member (52) and antenna (14) a hood (62) is disposed.

8. Device according to any one of claims 5, 6 or 7, characterized in that at the wall of the insert member (52) lying opposite the second transformer half a projection (64) is formed in such a manner that in the detent position it defines an air gap (24).

9. Device according to any one of claims 1 to 3, characterized in that in the transmitter and receiver section (12) an insert region (70) of circular cross-section is formed into which a correspondingly formed insert member (72) of the antenna (14) can be inserted, the first transformer half being arranged centrally directly in the bottom (74) of the insert region (70) whilst the second transformer half is arranged centrally in the end wall (76) and that the insert member (72) can be locked in the insert region (70).

10. Device according to claim 9, characterized in that the insert member (72) can be locked in the insert region (70) by means of a bayonet fastener (78).

11. Device according to claim 9 or 10, characterized in that the second transformer half is spring-loaded within the insert member (72) to define an air gap (24) in the detent position.

12. Device according to claim 1 or 2, characterized in that the transmitter and receiver section (12) comprises an antenna mounting flange (90) which is sealed by a diaphragm (26), the first transformer half being disposed directly behind the diaphragm (26) centrally in the antenna mounting flange (90), that the antenna (14) is held on one side in an antenna support (92) which comprises a projecting edge (94) adapted to be placed onto the antenna mounting flange (90), and that the second transformer half is arranged in the bottom (96) surrounded by the edge (94) centrally directly behind a diaphragm (28).

13. Device according to any one of the preceding claims, characterized in that the antenna (14) is divided and can be bent and folded up about a joint (100).

14. Device according to claim 13, characterized in that the antenna (14) can be locked against bending by a tube member (102) internally displaceable in the region of the separation line thereof.

15. Device according to claim 1, characterized in that the two cores (20, 22) are each formed by an E core.