EP0218056B1 - Pyrodetector for the detection of a body intruding its detection field - Google Patents

Abstract

A pyrodetector having a concave mirror containing a sensor element arranged in a focus thereof. The sensor element is on a film and is distinguished by a compact structure. The concave mirror is formed of a body having a rectangular cross-section, of a reflector part, and of sidewalls positioned perpendicularly relative to one another. An opening is provided in a reflector portion through which a retaining part provided with plug pins is inserted. The concave mirror, an evaluation means arranged outside of the concave mirror behind the reflector portion, and a honeycomb lattice and a covering are accommodated as an overall arrangement in a housing.

Description

The invention relates to a pyrodetector for the detection of a body entering its detection area, which has a temperature deviating from its surroundings, containing a concave mirror for focusing the heat radiation emanating from this body, a first sensor element attached in the focus of the concave mirror, and at least one further sensor element for compensation environmental influences, a film made of one and the same electrically non-conductive material, in particular polyvinylidene difluoride, with the same permanent orientation polarization and electrodes located thereon for the first and the further sensor elements, and this arrangement is fastened in a holder, also containing one for the incident radiation-permeable cover of the mirror cavity and an electronic evaluation device, the film with the sensor elements being arranged in the concave mirror so that the i In the concave mirror, reflected radiation is present on both surface sides of the film, the concave mirror being a parabolic mirror that is dimensioned such that its focus lies in the inner half of the concave mirror, the film with the sensor elements also lying in the optical axis of the concave mirror, so that the first sensor element is essentially only hit by such radiation from the body to be detected which is at a greater distance, which has been reflected in the concave mirror, and wherein a thin film made of polyethylene is used as a cover, which acts as a support in front the honeycomb grid arranged in the mirror cavity is stretched.

A pyrodetector with these features is described in detail in EP-A-0 023 354 with regard to its structural design and in particular its mode of operation. The European patent mentioned corresponds to DE-A-2 930 632 together with DE-A-3 028 252 and US-A-4 404 468.

A preferred embodiment for the thin film made of polyethylene serving as a cover is described in the same priority European patent application EP-A-0 218 057.

A particularly preferred constructive design for the arrangement of the sensor elements in a holding frame and a method for their production is described in the priority European patent application EP-A-0 216 136.

The present invention has for its object to provide an embodiment for the pyrodetector of the type specified, which is particularly space-saving due to a compact design and construction and can therefore have particularly small external dimensions.

• a) der Hohlspiegel besteht aus einem Körper mit rechteckigem Querschnitt mit einer großen Achse und einer kleinen Achse, und enthält einen Reflektorteil, der zu zwei Ebenen eine gewölbte Fläche bildend gekrümmt ist, und senkrecht aufeinanderstehende Seitenwände,
• b) die Folie mit den Sensorelementen ist parallel zur kleinen Achse angeordnet und zusammen mit einem die Folie tragenden Halterahmen durch eine Öffnung im Reflektorteil des Hohlspiegels eingesetzt,
• c) von der Öffnung verlaufen parallel zueinander zwei U-förmige Teile einer Halterung für den Halterahmen der Folie mit den Sensorelementen in den Hohlraum des Hohlspiegels,
• d) außerhalb des Hohlspiegels und hinter seinem Reflektorteil ist eine elektronische, aus einer Platine mit gedruckten Leiterbahnen, aktiven und passiven elektrischen Bauelementen bestehende Auswerteeinrichtung angeordnet, an die über Steckerstifte des Halterahmens die Sensorelemente angeschlossen sind,
• e) die elektronische Auswerteeinrichtung wird von mit Widerhaken versehenen federnden Klammern gehalten, die an der Außenseite des Hohlspiegels befestigt sind,
• f) die gesamte Anordnung aus Hohlspiegel mit den Sensorelementen, der elektronischen Auswerteeinrichtung und dem mit der Abdeckfolie versehehenen Wabengitter ist in einem Störeinflüsse abschirmenden Gehäuse untergebracht.

To achieve this object, the pyrodetector of the type specified at the outset is characterized according to the invention by the features:

• a) the concave mirror consists of a body with a rectangular cross section with a large axis and a small axis, and contains a reflector part which is curved to form a curved surface to form two planes, and side walls which are perpendicular to one another,
• b) the film with the sensor elements is arranged parallel to the small axis and inserted together with a holding frame carrying the film through an opening in the reflector part of the concave mirror,
• c) two U-shaped parts of a holder for the holding frame of the film with the sensor elements run parallel to one another from the opening into the cavity of the concave mirror,
• d) outside the concave mirror and behind its reflector part there is an electronic evaluation device consisting of a circuit board with printed conductor tracks, active and passive electrical components, to which the sensor elements are connected via plug pins of the holding frame,
• e) the electronic evaluation device is held by barbed spring clips which are attached to the outside of the concave mirror,
• f) the entire arrangement of concave mirror with the sensor elements, the electronic evaluation device and the honeycomb grid provided with the cover film is accommodated in a housing shielding against interference.

The ratio between the small axis and the large axis of the body of the concave mirror is preferably in the range from 1: 1.3 to 1: 1.7.

Preferred dimensions for the minor axis are 24.0 mm and for the major axis 36.0 mm or for the minor axis 13.6 mm and for the major axis 18 mm. In the first case, the length of the pyrodetector is 36 mm, measured from the front front given by the honeycomb grid to the outside of the housing base, while in the second case this length is 52 mm, because here the evaluation device can be arranged differently.

The curved surface of the reflector part of the concave mirror is preferably rotationally symmetrical, the curvature of this surface following a parabolic function, for example the function y2 = f (x) = 22 x.

The two parts of the holder preferably protrude into the cavity of the concave mirror or they are integrated in the two side walls of the concave mirror, which are parallel to the major axis of the body of the concave mirror.

The circuit board of the electronic evaluation device is preferably perpendicular to the optical axis of the concave mirror, and the connector pins of the holding frame are fastened in holes in the circuit board. These holes and thus the connector pins are electrical over the printed Lei railways connected with the overall economy.

On the other hand, it is advantageous if the circuit board of the electronic evaluation device is arranged in the direction of the optical axis and parallel to the major axis of the concave mirror, and if the connector pins are mechanically connected to the circuit board and to the overall circuit via the printed conductor tracks.

For better use of space and in the event that it cannot be made extremely small, the circuit board can preferably be arranged perpendicular to the plane of the film with the sensor elements.

The body of the concave mirror is preferably made of plastic and is mirrored at least on the surface of its cavity by a metal coating forming the reflector part.

In this case it is advantageous to connect the resilient clamps in one piece to the body of the concave mirror, i.e. that the body and the brackets in one operation, e.g. B. by centrifugal casting or in the pressing process.

In order to ensure adequate shielding against external interference, at least the housing consists of electrically conductive plastic, but the body of the concave mirror can also consist of electrically conductive plastic.

On the other hand, the housing can be made of metal.

In the latter two cases, the shielding against external interference is completed if the honeycomb grille itself contains a metal coating or is also made of conductive plastic or metal. This is explained in detail in the European patent mentioned at the beginning.

The invention ensures a particularly space-saving possibility of constructing a pyrodetector since external dimensions can be achieved which are at least five to ten times smaller than previously known pyrodetectors.

The invention is explained below with reference to the accompanying figures.

• Fig. 1 einen Pyrodetektor im Schnitt längs der Linie I - in Fig. 2;
• Fig. 2 . den Pyrodetektor nach Fig. 1 im Schnitt längs der Linie 11 - 11;
• Fig. 3 eine Draufsicht auf den Pyrodetektor gemäß Fig. 1 entsprechend Pfeil A;
• Fig. 4 einen Pyrodetektor gemäß Fig. 2 im Schnitt längs der Linie IV - IV;
• Fig. 5 eine Draufsicht auf die Frontpartie des Pyrodetektors gemäß Pfeil B in Fig. 1;
• Fig. 6 einen Schnitt durch den Pyrodetektor gemäß Fig. 1 längs der Linie VI - Vl;
• Fig. 7 den Pyrodetektor gemäß Fig. 1 läng der Linie VII - Vll;
• Fig. 8 eine andere Ausführungsform des Pyrodetektors im Schnitt längs der Linie VIII - VIII in Fig. 9;
• Fig. 9 den Pyrodetektor gemäß Fig. 8 im Schnitt längs der Linie IX - IX in Fig. 8;
• Fig. 10 eine Seitenansicht des Pyrodetektors gemäß den, Fig. 8 und 9 in Richtung des Pfeiles C in Fig. 8.

Show it:

• 1 shows a pyrodetector in section along the line I - in Fig. 2.
• Fig. 2. the pyrodetector of Figure 1 in section along the line 11-11.
• 3 shows a plan view of the pyrodetector according to FIG. 1 according to arrow A;
• 4 shows a pyrodetector according to FIG. 2 in section along the line IV-IV;
• 5 shows a plan view of the front part of the pyrodetector according to arrow B in FIG. 1;
• 6 shows a section through the pyrodetector according to FIG. 1 along the line VI-VI;
• 7 shows the pyrodetector according to FIG. 1 along the line VII - VIII;
• 8 shows another embodiment of the pyrodetector in section along the line VIII-VIII in FIG. 9;
• FIG. 9 shows the pyrodetector according to FIG. 8 in section along the line IX-IX in FIG. 8;
• 10 is a side view of the pyrodetector according to FIGS. 8 and 9 in the direction of arrow C in FIG. 8.

Corresponding parts of the drawings are provided with the same reference numerals.

1 to 4 show that the concave mirror 1 consists of a body 25 which has a rectangular cross section with a large axis 16 and a small axis 17. The concave mirror 1 contains a reflector part 26 which is curved to form a curved surface 18 in two planes. The hollow spine 1 also contains perpendicular side walls 27 and 28, the side walls 27 being arranged parallel to the minor axis 17 and the side walls 28 being arranged parallel to the major axis 16.

The concave mirror 1 contains barbs 8 on its front part (left in FIG. 1), behind which the honeycomb grid 7 is fastened by barbs 9. A cover 5 made of a polyethylene film is stretched over the honeycomb grid 7.

The concave mirror 1 has an opening 15 in the optical axis 6 - 6, from which the two parts of the holder 12 protrude into the cavity of the concave mirror 1. These two parts are U-shaped. A holding frame 14 is inserted through the opening 15 and carries the film 13 with the sensor elements 2, 3 and 4.

These sensor elements 2, 3 and 4 are formed by electrodes, as described in detail, for example, in the aforementioned European patent specification or also in the aforementioned priority German patent application. The two electrodes are separated from one another by a quasi-meandering metal-free strip 30. The sensor element arrangement is connected to the evaluation device 11 via lines which merge into plug pins 22 of the holding frame 14.

The electronic evaluation device 11, which, as is known per se in the other context, is preferably provided with a layer of, for example, polyimide, polyethylene terephthalate or zappon lacquer for protection against environmental influences, is held by resilient clamps 24 which are provided with barbs 23. in the event that the circuit board 19 does not lie directly on the reflector part 26, there are spacers 31 which are preferably also integrally connected to the body 25 of the concave mirror 1, as are the resilient clamps 24. In the present exemplary embodiment, the spacers 31 effectively represent an extension of the side walls 28 of the body 25. The length of the spacers 31 is dimensioned such that active and passive electrical components located on the circuit board 19, which are not shown here for reasons of clarity, between the board 19 and the reflector part 26 ha sufficient space ben if the printed conductor tracks are present on the side of the board 19 facing away from the reflector part 26.

• Fig. 3 zeigt den Pyrodetektor gemäß Fig. 1 mit Blick gemäß Pfeil A als Draufsicht, und zwar etwa im Maßstab 1,5 : 1 zur tatsächlichen Größe des Pyrodetektors.
• Fig. 4 läßt erkennen, daß in den beiden U-förmigen Teilen der Halterung 12 der Halterahmen 14 mit der die Sensorelemente tragenden Folie 13 eingesetzt ist. Fig. 4 zeigt ferner, daß die Dicke des Gehäuses 10 relativ gering ist, so daß die für die Achsen 16 und 17 angegebenen Abmessungen beim fertigen Pyrodetektor nur geringfügig überschritten sind.
• Fig. 5 zeigt eine Draufsicht auf die Vorderfront des Pyrodetektors gemäß Pfeil 8 in Fig. 1. Man erkennt die Anordnung des Wabengitters 7, die beiden Teile der Halterung 12 und die Widerhaken 8, die am Hohlspiegel 1 angebracht sind. Ferner befindet sich in Blickrichtung hinter dem Wabengitter die Abdeckfolie 5.
• Fig. 6, die einen Schnitt längs der Linie VI - VI in Fig. 1 darstellt, läßt die Öffnung 15 im Reflektorteil 26, die Seitenwände 27 und 28, die federnden Klammern 24 und die Abstandhalter 31 deutlich hinsichtlich ihrer Lage und Anordnung erkennen.
• Fig. 7, die einen Schnitt längs der Linie VII - VII in Fig. 1 darstellt, zeigt die Seite der Platine 19, auf der die gedruckten Leiterbahnen 20 der Auswerteeinrichtung enthalten sind. Durch die Löcher 29 ragen die hier nicht gezeigten Steckerstifte 22 des Halterahmens 14 hindurch und sind beispielsweise durch Tauchlötung mit den gedruckten Leiterbahnen 20 verbunden. Die Widerhaken 23, die sich an den federnden Klammern 24 befinden, übergreifen die Platine 19, wofür in diesen Randbereichen Ausnehmungen gezeigt sind. Auf diese Weise wird die Platine 19 und damit die gesamte Auswerteeinrichtung 11, gegebenenfalls im Zusammenwirken mit den Abstandhaltern 31, sehr sicher an der Rückseite des Hohlspiegels 1 festgehalten.

The entire arrangement of the pyrodetector made of concave mirror 1 with the sensor elements 2, 3, 4, the electronic evaluation device 11 and the honeycomb grid 7 provided with the cover film 5 is accommodated in a housing 10 shielding against interference. This housing 10 can consist of metal or of plastic coated with metal or preferably of electrically conductive plastic, wherein an electrically conductive injection-molded plastic based on polyamide can advantageously be used as the plastic, e.g. B. EP Grilamid W 5941, a polyamide 12 from Ems-Chemie AG.

• FIG. 3 shows the pyrodetector according to FIG. 1 with a view according to arrow A as a top view, namely on a scale of 1.5: 1 to the actual size of the pyrodetector.
• Fig. 4 shows that in the two U-shaped parts of the bracket 12, the holding frame 14 is inserted with the film 13 carrying the sensor elements. Fig. 4 also shows that the thickness of the housing 10 is relatively small, so that the dimensions specified for the axes 16 and 17 are only slightly exceeded in the finished pyrodetector.
• 5 shows a plan view of the front of the pyrodetector according to arrow 8 in FIG. 1. The arrangement of the honeycomb grating 7, the two parts of the holder 12 and the barbs 8 which are attached to the concave mirror 1 can be seen. Furthermore, the cover film 5 is located behind the honeycomb grid in the viewing direction.
• Fig. 6, which shows a section along the line VI - VI in Fig. 1, shows the opening 15 in the reflector part 26, the side walls 27 and 28, the resilient brackets 24 and the spacers 31 clearly in terms of their location and arrangement.
• FIG. 7, which shows a section along the line VII-VII in FIG. 1, shows the side of the circuit board 19 on which the printed conductor tracks 20 of the evaluation device are contained. The plug pins 22, not shown here, of the holding frame 14 protrude through the holes 29 and are connected to the printed conductor tracks 20, for example by dip soldering. The barbs 23, which are located on the resilient clamps 24, overlap the circuit board 19, for which recesses are shown in these edge regions. In this way, the circuit board 19 and thus the entire evaluation device 11, possibly in cooperation with the spacers 31, is held very securely on the back of the concave mirror 1.

8, 9 and 10 show another embodiment of the pyrodetector, in which the circuit board 19 of the evaluation device 11 is arranged in the direction of the optical axis 6 - 6 and parallel to the major axis 16. Active and passive electrical components are shown on the side of the circuit board 19 that is visible in plan view, which ensure the functioning of the evaluation device 11 by means of appropriate circuitry, namely in that a corresponding signal is generated from the respective detection situation, which signal is then sent to a switch to be actuated, for example is passed on via the connection contacts 32.

9 that the two U-shaped parts of the holder 12 are integrated into the side walls 28, which are parallel to the major axis 16 of the body 25 of the concave mirror 1. The opening 15 has a corresponding width which almost - except for the wall thicknesses - extends to the side walls 28.

This makes it possible to use in this pyrodetector a holding frame 14 with the sensor film 2 carrying the sensor elements 2, 3 and 4, the dimensions of which practically correspond to the dimensions of a holding frame which fits into the embodiment according to FIGS. 1 and 2.

The plane of the board 19 of the evaluation device 11 is perpendicular to the plane of the film 13, so that it is necessary to deform the connector pins 22 accordingly.

FIG. 10 shows the housing 10 with the honeycomb grating 7 mounted in front thereof and a dashed side view of the pyrodetector according to arrow C in FIG. 8.

Reference symbol list

• 1 concave mirror
• 2 first sensor element
• 3 further sensor element
• 4 further sensor element
• 5 radiation-permeable cover
• 6 optical axis
• 7 honeycomb grids
• 8 barbs on the concave mirror
• 9 barbs on the honeycomb grid
• 10 housing
• 11 electronic evaluation device
• 12 Bracket for the sensor elements
• 13 foil (sensor element foil)
• 14 holding frame
• 15 Opening in concave mirror 1
• 16 major axis of the concave mirror 1
• 17 small axis of the concave mirror 1
• 18 curved surface
• 19 PCB of the electronic evaluation device
• 20 printed conductor tracks on the board 19 21 active and passive electrical components
• on the patina 19
• 22 connector pins of the holding frame 14
• 23 barbs on the spring clips 24 24 spring clips
• 25 Body of the concave mirror 1
• 26 reflector part
• 27 side walls of the concave mirror 1
• 28 side walls of the concave mirror 1
• 29 holes in the board 19 for the connector pins 22
• 30 metal-free strips
• 31 spacers
• 32 connection contacts

Claims (12)

1. Pyrodetector for detection of a body entering into a detection area of the pyrodetector, said body having a temperature deviating from its environment, containing a concave mirror (1) for focussing the heat radiation emanating from this body, a first sensor element (2) positioned at the focus of the concave mirror (1), at least one further sensor element (3, 4) for the compensation of environmental influences, a film (13) of uniform electrically non-conductive material, especially of polyvinylidene difluoride (PVDF), having an iso- directional, permanent orientation polarization and with electrodes situated thereon, being provided for the first and further sensor elements (2, 3, 4), and this arrangement being secured in a mounting (12), containing furthermore a covering (5) of the cavity of the mirror which is permeable to incident radiation and an electronic evaluation means (11), the film (13) with the sensor elements (2, 3, 4) being arranged in the concave mirror (1) such that radiation reflected by the concave mirror (1) is incident on both surface sides of the film (13), the concave mirror (1) being a parabolic mirror dimensioned such that its focus lies in the inner half of the concave mirror (1), the film (13) with the sensor elements (2, 3, 4) furthermore lying in the optical axis (6 - 6) of the concave mirror (1) so that the first sensor element (2) is essentially impinged only by a radiation of the body to be detected, situated at a great distance, which has been reflected in the concave mirror (1), and a thin film of polyethylene being used as covering (5), which is stretched over a honeycomb lattice (7) acting as a support and which is arranged in front of the cavity of the mirror, characterized by the features:

a) the concave mirror (1) is formed of a body (25) having a rectangular cross-section with a major axis (16) and a minor axis (17), contains a reflector part (26) curved in two planes to form an arced surface (18), and mutually perpendicular side walls (27, 28),

b) the film (13) with the sensor elements (2, 3, 4) is arranged parallel to the minor axis (17) and is inserted, together with a retaining frame (14) carrying the film (13), through an opening (15) in the reflector part (26) of the concave mirror (1),

c) extending parallel to one another from the opening (15) are two U-shaped parts of a mounting (12) for the retaining frame (14) of the film (13) with the sensor elements (2, 3, 4) into the cavity of the concave mirror (1),

d) an electronic evaluation means (11) comprising a circuit board (19) with printed interconnects (20), and active and passive electrical components (21) is arranged outside the concave mirror (1) and behind the reflector part (26) thereof, the sensor elements (2, 3, 4) being connected to said evaluation means via plug pins (22) of the retaining frame (14),

e) the electronic evaluation means (11) is held by resilient clamps (24) provided with barbs (23), said clamps being secured to the outside of the concave mirror (1),

f) the entire arrangement of concave mirror (1) with the sensor elements (2, 3, 4), the electronic evaluation means (11) and the honeycomb lattice (7) provided with the cover film (5) is accommodated in a housing (10) which provides shielding against disturbing influences.

2. Pyrodetector according to Claim 1, characterized in that the ratio between minor axis (17) and major axis (16) of the body (25) lies in a range from 1 :1.3 to 1 : 1.7.

3. Pyrodetector according to Claim 1, characterized in that the arced surface (18) of the reflector part (26) of the concave mirror (1) is rotatio- nalfty symmetric and the curvature of said surface follows a parabolic function.

4. Pyrodetector according to Claim 1, characterized in that both parts of the mounting (12) project into the cavity of the concave mirror (1 ).

5. Pyrodetector according to Claim 1, characterized in that both parts of the mounting (12) are integrated in the two side walls (28) of the concave mirror (1) which lie parallel to the major axis (16) of the body (25) of the concave mirror (1).

6. Pyrodetector according to Claim 1, characterized in that the circuit board (19) of the electronic evaluation means (11) is arranged perpendicular to the optical axis (6 - 6) of the concave mirror (1), and the plug pins (22) of the retaining frame (14) are secured in holes (29) of the circuit board (19).

7. Pyrodetector according to Claim 1, characterized in that the circuit board (19) of the electronic evaluation means (11) is arranged in the direction of the optical axis (6 - 6) and parallel to one of the two axes (16 or 17) of the concave mirror (1), and the plug pins (22) are connected to the circuit board (19).

8. Pyrodetector according to Claim 7, characterized in that the circuit board (19) is arranged perpendicularto the plane of the film (13) with the sensor elements (2, 3, 4).

9. Pyrodetector according to Claim 1, characterized in that the body (25) of the concave mirror (1) is formed of plastic and is made reflective at least on the surface of its cavity by a metal coat forming the reflector part (26).

10. Pyrodetector according to Claim 9, characterized in that the resilient clamps (24) are connected as one piece to the body (25) of the concave mirror (1).

11. Pyrodetector according to Claim 1, characterized in that at least the housing (10) is formed of electrically conductive plastic.

12. Pyrodetector according to Claim 1, characterized in that the housing (10) is formed of metal.

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