WO2004003956A1

WO2004003956A1 - Positioning device for a funnel for a cathode ray tube

Info

Publication number: WO2004003956A1
Application number: PCT/IB2003/002397
Authority: WO
Inventors: Pieter Scholten; Peter A. J. Jacobs
Original assignee: Koninklijke Philips Electronics N.V.; KUNNEN, Henricus, Josephus
Priority date: 2002-06-27
Filing date: 2003-06-12
Publication date: 2004-01-08
Also published as: AU2003233137A1

Abstract

The invention relates to a positioning device for positioning a funnel for a cathode ray tube. The positioning device comprises two fixed x-discs (27, 28) being positioned on top of a receiving block and two movable y-discs (43, 44) being accommodated in a frame. At one side, the frame is tiltable about a tilting axis, whereas at another side, the frame is connected to the receiving block by means of a helical spring (39). During insertion of a funnel (5) into the positioning device, the funnel abuts against the movable y-discs first and subsequently abuts against the fixed x-discs. In this way, abutment and support of the funnel by both the x-discs and the y-discs is assured, whereby positioning of the funnel is performed in an accurate way.

Description

Positioning device for a funnel for a cathode ray tube

The present invention relates to a positioning device for positioning an article, especially a funnel for a cathode ray tube.

Cathode ray tubes are well known, and generally comprise from front to back a rectangular panel, a cone and a cylindrical neck. The combination of the cone and the neck is referred to as funnel.

In a cathode ray tube, the neck accommodates an electrode system having three electron guns for generating three electron beams. In order to deflect the electron beams on their way to the screen, deflection coils are coaxially arranged about a longitudinal axis of the cathode ray tube, at a back portion of the cone. Originally, this back cone portion used to have a circular cross-section.

As there is a tendency towards shallower cathode ray tubes having larger panels, the deflection of the electron beams requires more and more power. At the same time, there is a tendency towards reducing the power consumption of cathode ray tubes. In order to bring the power consumption of cathode ray tubes to an acceptable level, the design of several cathode ray tubes has been changed, as a result of which a major part of the back cone portion has a substantially rectangular cross-section. In this way, the deflection coils can be positioned closer to the electron beams, and less power is required to deflect these electron beams.

For several processing steps in the manufacture of a cathode ray tube, it is required that the funnel is positioned in a predetermined way, according to a certain reference system. By "reference system" is meant an imaginary system comprising well-defined points in space, which points constitute reference points which are referred to in determining the exact position of the funnel. For positioning the funnel and for defining a reference system, a positioning device being suitable for receiving and holding the funnel is utilized. A known positioning device is suitable for positioning a funnel comprising a back cone portion having a circular cross-section, and comprises a set of three discs, with rotary shafts of the discs being positioned in one and the same plane and being evenly distributed over a circle, a centre point of which determines a point of a longitudinal axis of the funnel. When a funnel is placed in such a positioning device, the three discs abut against the back cone portion, such that the weight of the funnel is more or less evenly distributed over the discs. The cone is held by the positioning device in a predetermined, centred way, such that x-positions and y- positions in a plane perpendicular to the longitudinal axis of the funnel can be accurately determined starting from the centre point of the circle over which the rotary shafts of the discs are distributed, and z-positions along the longitudinal axis of the funnel can be accurately determined starting from the plane in which the rotary shafts of the discs are positioned. It will be understood that the known positioning device comprising three discs is not suitable for positioning funnels comprising a back cone portion of which the major part has a substantially rectangular cross-section.

It is an object of the present invention to provide a positioning device which is suitable for positioning articles in a predetermined and sufficiently accurate way, which in particular can be designed so as to be suitable for positioning funnels comprising a back cone portion of which the major part has a substantially rectangular cross-section.

This object is achieved by a positioning device comprising at least three stops for abutting against the article and supporting the article, wherein at least one stop is movable according to a predetermined path so as to be able to temporarily move along with the article when the article and the positioning device are moved relative to each other for the purpose of insertion into the positioning device, in a direction substantially equal to a direction in which the article is relatively moved. Due to the fact that the positioning device according to the invention comprises at least one movable stop being movable in a direction substantially equal to the direction in which the article is relatively moved during insertion into the positioning device, it is possible to assure abutment of all stops of the positioning device against an inserted article. In other words, a situation where an inserted article is not supported by all stops due to deviations in size can be avoided. In this way, an accurate and reproducible positioning of the article is obtained.

In a possible embodiment, the positioning device comprises four stops, wherein two stops are fixedly arranged at a predetermined mutual distance, and two stops are movably arranged at a fixed predetermined mutual distance. In this embodiment, the positioning device is especially suitable for positioning funnels comprising a back cone portion of which the major part has a substantially rectangular cross-section.

In said possible embodiment, the fixed distance between the two fixed stops on the one hand and the fixed distance between the two movable stops on the other hand define two pitch measures of the funnel to be received.

The position of the fixed stops can be chosen so as to accurately define an x-position and a z-position of the funnel. The movable stops are solely movable in the z-direction, and can be chosen so as to accurately define a y-position of the funnel. An initial position of the movable stops can be chosen such that during insertion of the funnel, the funnel contacts the movable stops first. The z-position of the movable stops is then automatically adjusted by a further movement of the funnel, until the point where the funnel contacts the fixed stops as well. In this way, it is assured that both the fixed stops and the movable stops abut against an inserted funnel. Such a funnel is then properly held by the positioning device. Utilizing this embodiment of the positioning device according to the invention, any funnel of a certain design can be accurately positioned, in spite of small deviations in size which inevitably appear in actual practice.

It will be understood that the positions of the fixed stops and the movable stops have to be chosen very carefully. It is not only required that they are accurately arranged at their respective mutual distances, but also that the fixed stops and the movable stops are accurately arranged at proper positions with respect to each other, which positions are determined by the design of the article to be received by the positioning device.

The invention will now be explained in greater detail with reference to the Figures, in which similar parts are indicated by the same reference signs, and in which: Fig. 1 is a partial longitudinal sectional view of a cathode ray tube; Fig. 2 is a top view of a positioning device according to the invention, wherein a cross-sectional view of a portion of a funnel being placed in the positioning device is shown; and Fig. 3 is a longitudinal sectional view taken on the line A- A of Fig. 2, wherein in comparison with Fig. 2 a larger portion of the funnel is shown. Fig. 1 is a longitudinal sectional view of a cathode ray tube 1 comprising a glass envelope having a panel 2, a cone 3 and a neck 4. The combination of cone 3 and neck 4 is referred to as funnel 5. The panel 2 comprises a substantially rectangular display window 6 and an upright edge 7. The neck 4 is substantially cylindrical, a neck wall 8 being substantially parallel with regard to a longitudinal axis 9 of the cathode ray tube 1.

The neck 4 accommodates an electrode system 10 having three electron guns for generating three electron beams 11, 12, 13. The electron beams 11, 12, 13 are directed towards a rectangular display screen 14 which is provided on the inside of the display window 6 and which comprises a large number of red, green and blue luminescing phosphor elements being laid down in narrow bands. On their way to the display screen 14, the electron beams 11, 12, 13 are deflected by deflection coils 15 which are coaxially arranged about the longitudinal axis 9 of the cathode ray tube 1.

The cone 3 comprises a front cone portion 16 and a back cone portion 17. A back end 18 of the back cone portion 17 is joined to a front end 19 of the neck 4, for example by means of melting. The periphery of the back end 18 of the back cone portion 17 is adapted to the periphery of the front end 19 of the neck 4 by being circular. A front end 20 of the front cone portion 16 is joined to the upright edge 7 of the panel 2, for example by means of fritting. The periphery of the front end 20 of the front cone portion 16 is adapted to the periphery of the upright edge 7 by being substantially rectangular. During several steps in the production process of the cathode ray tube 1 , after the cone 3 and the neck 4 are joined together, the cone 3 and the funnel 5 need to be accurately positioned, according to a certain reference system. An example of such a step is the step of applying frit on the front end 20 of the front cone portion 16.

Figs. 2 and 3 show a positioning device 21 according to the invention, which is suitable for receiving and holding a funnel 5, especially a funnel 5 in which a major part of the back cone portion 17 has a substantially rectangular cross-section. More in particular, the positioning device 21 is suitable for centring a funnel 5 and for placing the funnel 5 in a predetermined position in the direction of its longitudinal axis 22 (which corresponds to the longitudinal axis 9 of the cathode ray tube 1 as shown in Fig. 1). In the following, a z-direction is defined as the direction in which the longitudinal axis 22 of the funnel 5 extends. An x-direction and a y-direction which is perpendicular to the x-direction are defined as directions in a plane perpendicular to the z- direction. The x-direction corresponds to a direction in which two opposite long sides of the display screen 14 on the display window 6 extend, whereas the y-direction corresponds to a direction in which two other opposite short sides of the display screen 14 extend, the latter direction corresponding to the direction in which the luminescing phosphor elements on the display screen 14 extend. In the following description of the positioning device 21, definitions of an x-direction, a y-direction and a z-direction relate to the way in which the funnel 5 is to be placed in the positioning device 21.

The positioning device 21 comprises a receiving block 23 having a cylindrical receiving space 24 for receiving the neck 4 and part of the back cone portion 17. The shape of the receiving block 23 is not important. The same is true for the shape of the receiving space 24, as long as this space 24 offers enough room for allowing free insertion of the neck 4 and part of the back cone portion 17. At a top surface 25 of the receiving block 23, at a circumference 26 of the receiving space 24, which in Fig. 2 is partly depicted by means of a dotted line, two circular x-discs 27, 28 are provided on rotary shafts 29, 30, which rotary shafts 29, 30 extend in the y-direction. The x-discs 27, 28 comprise curved surfaces 31, 32 which are destined to abut against the back cone portion 17. The diameter of the x-discs 27, 28 is typically 16 mm, but of course other values for the diameter can be chosen within the scope of the present invention. In the shown example, the x-discs 27, 28 are at the same y- position, the distance between the x-discs 27, 28 being determined by a pitch measure of the funnel 5 in the x-direction at a certain z-position.

At the top surface 25 of the receiving block 23, a frame 33 is arranged. Preferably, the frame 33 is mirror symmetrical about an axis of symmetry 34 extending in the x-direction, which in Fig. 2 is depicted by means of a dotted line. Near a fixed side 35, the frame 33 is tiltable about a tilting axis 36 extending in the y-direction. Preferably, the tilting axis 36 is constituted by a linear narrowed portion 37 of the frame 33, whereby a resilient joint is obtained, which is resilient in the z-direction and rigid in the x-direction and the y- direction.

Near a free side 38, which is opposite the fixed side 35, the frame 33 is connected to the receiving block 23 by means of a helical spring 39 extending in the z- direction. Preferably, the spring 39 is positioned on the axis of symmetry 34 of the frame 33. A holder 40 is provided to engage the free side 38 of the frame 33, in order to keep the frame 33 in an initial position in which the frame 33 is slightly tilted with respect to the top surface 25 of the receiving block 23, as indicated by dotted lines in Fig. 3.

The frame 33 has an opening 41 to allow passage of the funnel 5 and to prevent the frame 33 from abutting against the x-discs 27, 28. At a circumference 42 of the opening 41, two circular y-discs 43, 44 are provided on rotary shafts 45, 46, which rotary shafts 45, 46 extend in the x-direction. The y-discs 43, 44 comprise curved surfaces 47, 48 which are destined to abut against the back cone portion 17. The diameter of the y-discs 43, 44 is typically 16 mm, but of course other values for the diameter can be chosen within the scope of the present invention. In the shown example, the y-discs 43, 44 are at the same x- position, the distance between the x-discs 43, 44 being determined by a pitch measure of the funnel 5 in the y-direction at a certain z-position. It will be understood that the positions of the y-discs 43, 44 are related to the positions of the x-discs 27, 28, the nature of the relation being determined by the design of the back cone portion 17.

In the shown example, the x-position of the y-discs 43, 44 is chosen such that the y-discs 43, 44 are positioned exactly in a centre plane extending between the x-discs 27, 28, at identical distances from a plane in which the x-discs 27, 28 are positioned. In this arrangement, the line along which this centre plane and a centre plane extending between the y-discs 43, 44 intersect, constitutes a reference line for the longitudinal axis 22 of the funnel 5. The x-position of the y-discs 43, 44 is approximately halfway between the tilting axis 36 of the frame 33 and the free side 38 of the frame 33. In the initial position of the frame 33, the z- position of the y-discs 43, 44 is somewhat different from the z-position of the x-discs 27, 28. Once a funnel 5 is supported by the x-discs 27, 28 and the y-discs 43, 44, the z-position of the y-discs 43, 44 more or less corresponds to the z-position of the x-discs 27, 28. Although the above-described relation between the positions of the x-discs 27, 28 and the y-discs 43, 44 yields a very accurate positioning device 21, and also offers an excellent basis for defining a reference system, this relation can be chosen differently within the scope of the present invention.

The positioning device 21 further comprises a set of three rotatable circular discs 49, which is arranged inside the receiving space 24. Only two of the three discs 49 are shown in the longitudinal sectional view of Fig. 3. In the shown example, the discs 49 extend in an x,y-plane and are destined to abut against the neck 4 of the funnel 5. Preferably, the discs 49 are evenly distributed over a circle having a centre point which is positioned at the longitudinal axis 9 of the funnel 5.

In the following, the process of placing a funnel 5 in the positioning device 21 is described.

Initially, the frame 33 is in the initial position in which the free side 38 of the frame 33 is biased against the holder 40 by the spring 39. When the funnel 5 is moved in the z-direction and is inserted into the positioning device, the following events subsequently take place: 1) the neck 4 contacts the set of discs 49;

2) the back cone portion 17 contacts the y-discs 43, 44;

3) the frame 33 and the y-discs 43, 44 are moved in the z-direction towards the receiving block 23 under the influence of the weight of the funnel 5; until 4) the back cone portion 17 contacts the x-discs 27, 28.

When these events have taken place, the funnel 5 is positioned in a predetermined manner, such that the funnel 5 is centred as a result of the longitudinal axis 9 of the funnel 5 being brought into a predetermined x,y-position, and the funnel 5 being held at a predetermined z-position. Both the x-position and the z-position of the funnel 5 are determined by the x-discs 27, 28, whereas the y-position of the funnel 5 is determined by the y-discs 43, 44. Additionally, the discs 49 prohibit rotation of the funnel 5 in any z-plane.

It will be noted that in the shown positioning device 21, the y-discs 43, 44 do not move exactly in the z-direction during insertion of a funnel 5. Instead, the y-discs 43, 44 move with the frame 33 according to a circular path about the tilting axis 36. Still, in actual practice, positioning of the funnel 5 can be performed in a sufficiently accurate way. The ratio between the distance in the x-direction between the y-discs 43, 44 and the tilting axis 36 on the one hand and the distance in the z-direction between the holder 40 and the top surface 25 of the receiving block 23 on the other hand can be chosen such that the allowed movement of the y-discs 43, 44 is actually only in the z-direction. For the purpose of accurately processing funnels 5 during certain production steps, a reference system can be related to the positioning device 21, as all funnels 5 of a certain design which are placed in the positioning device 21 are accurately centred and brought into a predetermined z-position. In such a reference system, centre points of the x- discs 27, 28 serve as reference points for the x-direction and the z-direction, whereas centre points of the y-discs 43, 44 serve as reference points for the y-direction.

As already mentioned in the above, the positioning device 21 is especially suitable for receiving and holding a funnel 5 of which the major part of the back cone portion 17 has a substantially rectangular cross-section. In Fig. 2, such a substantially rectangular cross-section is depicted. In the shown example, the x-discs abut against opposite sides 50, 51 of the back cone portion 17, which extend in the y-direction, exactly in the centre of these sides 50, 51. The y-discs abut against opposite sides 52, 53 of the back cone portion 17, which extend in the x-direction, exactly in the centre of these sides 52, 53. In this way, accurate centring of the funnel 5 is performed. As the frame 33 which accommodates the y-discs 43, 44 tilts about the tilting axis 36 in a resilient manner, and as the spring 39 is also resilient, the funnel 5 is received in a resilient manner. This is an important advantage of the shown example of the positioning device 21 according to the present invention. Possible peaks in the contact forces which build up under the influence of the weight of the funnel 5 as soon as contact between the funnel 5 and the y-discs 43, 44 is established are absorbed by the resilient joint and the spring 39. This effect leads to a reduction of the risk of damage to or even breakage of the glass from which the funnel 5 is made.

A funnel 5 which is placed in the positioning device 21 is entirely supported by the x-discs 27, 28 and the y-discs 43, 44. Preferably, the tension of the spring 39 is adjustable, so that a more or less equal distribution of the weight of the funnel 5 over the x- discs 27, 28 and the y-discs 43, 44 can be obtained. The tension of the spring 39 should then be adjusted to half of the weight of the funnel 5. This also contributes to a reduction of the risk of damage to or even breakage of the glass from which the funnel 5 is made, as in this way it is assured that Hertzian stresses in the glass will be kept below a critical level. Further, this contributes to an accurate positioning of the funnel 5, as in this way it is assured that during insertion of the funnel 5 into the positioning device 21, the funnel 5 is able to move the y-discs 43, 44 until it contacts the x-discs 27, 28. It will be understood that should the tension of the spring 39 be too high, the funnel 5 will only be supported by the y-discs 43, 44, which is undesirable.

It will be clear to a person skilled in the art that the scope of the present invention is not limited to the examples discussed in the foregoing, but that several amendments and modifications thereof are possible without deviating from the scope of the invention as defined in the attached claims. The positioning device 21 can be utilized for receiving different types of funnels 5, as long as their back cone portions 17 are of the same design.

Although the shown positioning device 21 is especially suitable for receiving and holding a funnel 5 comprising a back cone portion 17 of which the major part has a substantially rectangular cross-section, the positioning device 21 according to the invention can be utilized for positioning many types of articles. More in particular, the positioning device 21 according to the invention can be utilized for positioning funnel-shaped articles comprising a first portion having a relatively small diameter, which can be inserted into the receiving space 24, and a second portion having a relatively large diameter, which can not pass the x-discs 27, 28 and y-discs 42, 43. For example, the positioning device 21 can also be used for receiving and holding a funnel 5 comprising a back cone portion 17 having a circular cross-section. In order to make the positioning device 21 suitable for receiving a particular type of article, all that is needed is choosing proper positions for the x-discs 27, 28 and the y- discs 43, 44 and also for the discs 49, the positions being derived from the design of the article. The positions of the x-discs 27, 28 and the y-discs 43, 44 with respect to each other should be chosen such that abutment of both the x-discs 27, 28 and the y-discs 43, 44 against an article which is placed in the positioning device 21 is assured.

In the shown example, the x-discs 27, 28 on the one hand and the y-discs 43, 44 on the other hand are at the same y-position and the same x-position, respectively. Although this is preferred, it does not constitute an essential feature of the present invention. For example, if the positioning device 21 is utilized for positioning funnels 5 comprising a back cone portion 17 of which the major part has a substantially rectangular cross-section, there are many possibilities for the positions of the x-discs 27, 28 and the y-discs 43, 44 along the sides 50, 51, 52, 53 of the back cone portion 17. However, with different positions of the x-discs 27, 28 and the y-discs 43, 44, it will be more difficult to define a reference system.

Preferably, as shown, the positioning device 21 comprises rotatable discs 27, 28, 43, 44, which function as stops for supporting the funnel 5. Within the scope of the present invention, it is possible to utilize many other types of stops, for example segments of circular discs, balls or segments of balls. Utilization of discs or balls is advantageous, as a well-defined contact line or contact point between each stop and the funnel 5 is obtained. In this respect, it is noted that a small diameter of the discs or balls is preferred over a large diameter, as the accuracy of the definition of the contact line or contact point increases with decreasing diameter. However, there is a limit to the decrease in diameter, as the Hertzian stresses in the glass of the funnel 5 are higher when the funnel contacts discs or balls having a small diameter than when the funnel 5 contacts discs or balls having a large diameter. A suitable value for the diameter is 16 mm, as already mentioned in the above.

Another advantage of the utilization of discs or balls as stops is that these can be mounted in a freely rotatable manner, in order to minimize friction between the stops and the funnel 5.

In the above, a preferred way of keeping the y-discs 43, 44 at a fixed distance during movement is disclosed: namely, by arranging the y-discs 43, 44 in a frame 33. However, there are other ways in which the y-discs 43, 44 may be arranged. For example, each y-disc 43, 44 may be arranged at the end of a rod being mounted on a helical spring and being guided so as to be movable only in the z-direction. In such an embodiment, it is important that the rods are mounted on springs having the same characteristic, and that the y- discs 43, 44 are loaded equally during insertion of the funnel 5 into the positioning device 21, in order to ensure that the y-discs 43, 44 remain at a fixed mutual distance. These preconditions cannot be fully met in practice, so that this embodiment is less accurate than the shown positioning device 21, and therefore far less preferred.

There are many ways of connecting the frame 33, near its free side 38, to the receiving block 23. In the shown positioning device 21, one helical spring 39 being positioned at the axis of symmetry 34 of the frame 33 is utilized. In a less preferred embodiment, two identical springs are utilized, which are placed at the same x-position, at identical distances in the y-direction from the axis of symmetry 34. Instead of a helical spring 39, any other suitable element can be utilized for biasing the y-discs 43, 44 in a direction opposite to the direction in which the funnel 5 is to be inserted into the positioning device 21, such an element preferably being resilient. The fact that in the above only a positioning device 21 comprising fixedly arranged x-discs 27, 28 and movably arranged y-discs is disclosed, does not imply that it is not possible to have the x-discs 27, 28 movably arranged and the y-discs 43, 44 fixedly arranged. However, the embodiment as shown is preferred for positioning devices 21 suitable for positioning funnels 5 for cathode ray tubes 1, as the positioning of a funnel 5 in the x- direction is more critical than in the y-direction. The reason for this is that the luminescent phosphor elements on the display screen 14 extend in the y-direction, so that the position of the funnel 5 would still relate to the same phosphor element in the pattern of phosphor elements in case of a slight deviation in the y-direction, whereas the position of the funnel 5 would relate to another phosphor element in the pattern of phosphor elements in case of a slight deviation in the x-direction.

In the above descriptions of how the positioning device 21 can be utilized for positioning a funnel 5, only a movement of the funnel 5 is mentioned. Within the scope of the invention, it is also possible that for inserting the funnel 5 into the positioning device 21 both the funnel 5 and the positioning device 21 move towards each other, or that only the positioning device 21 moves. The description of a movement of the funnel 5 is intended to be just a practical non-limiting example of a movement of the funnel 5 and the positioning device 21 with respect to each other.

Claims

CLAIMS:

1. Positioning device for positioning an article, especially a funnel for a cathode ray tube, the positioning device comprising at least three stops for abutting against the article and supporting the article, wherein at least one stop is movable according to a predetermined path so as to be able to temporarily move along with the article when the article and the positioning device are moved relative to each other for the purpose of insertion into the positioning device, in a direction substantially equal to a direction in which the article is relatively moved.

2. Positioning device according to claim 1, comprising two fixed stops being arranged at a predetermined mutual distance, and two movable stops being arranged at a fixed predetermined mutual distance.

3. Positioning device according to claim 2, wherein centre planes extending between the two fixed stops on the one hand and the two movable stops on the other hand intersect in a direction substantially equal to the direction in which the article and the positioning device are to be moved relative to each other for the purpose of insertion into the positioning device.

4. Positioning device according to any of claims 1-3, further comprising biasing means for biasing the at least one movable stop in a direction opposite to the direction in which the article is to be relatively moved for the purpose of insertion into the positioning device.

5. Positioning device according to claim 4, wherein a biasing tension of the biasing means is adjustable.

6. Positioning device according to claim 4 or 5, wherein the biasing means comprise a helical spring.

7. Positioning device according to any of claims 2-6, further comprising coupling means for rigidly interconnecting the two movable stops.

8. Positioning device according to claim 7, insofar as dependent on any of claims 4-6, wherein the biasing means act directly on the coupling means.

9. Positioning device according to claim 7 or 8, wherein the two movable stops are accommodated in a frame being movable with respect to the two fixed stops.

10. Positioning device according to claim 9, wherein the frame is tiltable about a tilting axis.

11. Positioning device according to claim 10, wherein the frame comprises a linear narrowed portion acting as the tilting axis.

12. Positioning device according to any of claims 9-11, further comprising a holder for engaging a free side of the frame.

13. Positioning device according to any of claims 2-12, wherein the two movable stops are positioned in a centre plane extending between the two fixed stops.

14. Positioning device according to claim 13, wherein the two movable stops are arranged at identical distances from a plane in which the two fixed stops are positioned.

15. Positioning device according to any of claims 1-14, wherein the stops comprise at least partly circular discs, and wherein an at least partly curved surface of the discs is destined to abut against the article.

16. Positioning device according to claim 15, wherein the discs are rotatably arranged.

17. Positioning device according to claim 16, wherein rotary shafts of the discs extend in a direction substantially perpendicular to the direction in which the article is to be moved for the purpose of insertion into the positioning device.

18. Positioning device according to any of claims 1-17, further comprising a set of three circular discs for abutting against the article, the discs being arranged beyond the fixed stops and the movable stops, seen in the direction in which the article is to be relatively moved for the purpose of insertion into the positioning device.

19. Positioning device according to claim 18, wherein the discs are rotatably arranged.

20. Positioning device according to claim 18 or 19, wherein the discs extend in a plane substantially perpendicular to the direction in which the article and the positioning device are to be moved relative to each other for the purpose of insertion into the positioning device.

21. Positioning device according to any of claims 1-14, wherein the stops comprise balls.

22. Method for positioning an article, comprising the step of providing a positioning device by arranging at least three stops for abutting against the article and supporting the article, such that at least one stop is movable according to a predetermined path so as to be able to temporarily move along with the article, when the article and the positioning device are moved relative to each other for the purpose of insertion into the positioning device, in a direction substantially equal to a direction in which the article is relatively moved, and that at least one other stop is fixed.

23. Method according to claim 22, further comprising the steps of moving the article and the positioning device with respect to each other until the article contacts the at least one movable stop, and subsequently continuing moving the article and the positioning device with respect to each other until the article contacts the at least one fixed stop.