Spring connector for electrically connecting tracks of a display screen with an electrical circuit

[0002] This application is based on French Patent Application No. 00 12 509 filed Oct. 2, 2000, the disclosure of which is hereby incorporated by reference thereto in its entirety, and the priority of which is hereby claimed under 35 U.S.C. §119.

[0003] 1. Field of the Invention

[0004] The invention relates to a spring connector for electrically connecting at least one track of a display screen with an electrical circuit. It also relates to a display system including the spring connector and a terminal including the display.

[0005] 2. Description of the Prior Art

[0006] The document WO-99/00877 discloses a metal spring connector for electrically connecting tracks of a liquid crystal display (LCD) screen to tracks of a printed circuit. The connector also holds the display screen in position.

[0007] Liquid crystal displays are covered with a material, such as indium tin oxide (ITO), that is fragile and therefore easily scratched by a metal connector of the type previously cited.

[0008] Another prior art solution interleaves a flexible connector between the tracks of the LCD and the tracks of the printed circuit. The connector is then compressed between the screen and the circuit. This kind of assembly is not simple and in the event of poor fixing the connection may be unreliable. Also, the force applied to the circuit is too high and the travel of the connector is too small to provide a reliable connection. An object of the invention is thus to alleviate the drawbacks of the prior art. It therefore proposes a connector not only for connecting a display to a printed circuit in a reliable and efficient manner, with no possibility of scratching the material covering the display screen, but also for holding the display in position. The connector is also easy to fit and remove.

[0009] The invention provides a spring connector for connecting at least one electrical track of a display screen with an electrical circuit, the connector including holding means for holding the display screen in position, a flexible metal foil forming a spring, and a plastics material film which includes at least one electrical track, has substantially the same shape as the metal foil, and is fixed to one face of the metal foil, wherein at least one of the tracks of the plastics material film is adapted to connect tracks of the display screen with the electrical circuit.

[0010] The spring connector is substantially S-shaped with a top part forming the means for holding the display screen in position.

[0011] The invention also provides a display system including a display screen, which includes at least one electrical track, an electrical circuit for controlling the display screen, and a spring connector of the type previously cited, wherein the display screen and the electrical circuit are disposed substantially facing each other.

[0012] The invention finally provides a terminal including the above display system and further including support means for supporting the display screen and the electrical circuit and spacer means for maintaining the spacing between the display screen and the electrical circuit.

[0013] The invention will become clearer in the light of the following description, which is given with reference to the accompanying drawings.

[0014] FIG. 1 is a diagrammatic view in cross section of a display system according to the invention.

[0015] FIG. 2 is a diagrammatic partial view of the display system shown in FIG. 1, as seen in the direction of the arrow II.

[0016] FIG. 3 is a view of the spring connector according to the invention in cross section.

[0017] FIGS. 4aand 4bare respectively top and bottom perspective views of the plastics material film of the spring connector when it is bent to shape.

[0018] FIGS. 5aand 5bare respectively top and bottom perspective views of the metal foil of the spring connector when it is bent to shape.

[0019] FIG. 6 is a top perspective view of the spring connector including the assembled film and metal foil.

[0020] FIG. 7 is a plan view of the plastics material film before it is bent to shape, showing its tracks.

[0021] FIGS. 8aand 8bare respectively bottom and top perspective views of the display screen, the spring connector and the printed circuit when disassembled.

[0022] FIG. 9 is a view similar to FIG. 8bof the display screen and the spring connector when assembled.

[0023] Finally, FIG. 10 is a bottom perspective view of the display screen connected to the printed circuit by means of the spring connector.

[0024] Referring to FIG. 1, the display system 1 includes a display screen 2 substantially parallel to, facing and spaced from a printed circuit 3.

[0025] The display screen 2 is a liquid crystal display (LCD) screen and in this embodiment comprises first and second glass plates 5, 5′ with the liquid crystal contained between them.

[0026] The first glass plate 5 is of generally parallelepiped shape, defining substantially rectangular top and bottom main faces 5a, 5b. The bottom main face 5bfaces the printed circuit 3.

[0027] The free edges of respective shorter sides of two main faces 5a, 5bform a fixing edge 5cand a connecting edge 5dof the display screen 2.

[0028] At least the bottom main face 5bincludes electrical tracks 5i(FIG. 8a) connecting components of the display screen 2 to a control device 4 for the screen, usually called the “driver”. The electrical tracks 5iextend from the connection edge 5d.

[0029] In the embodiment shown, the control device 4 is fixed rigidly to the bottom main face 5b, near the connecting edge 5d.

[0030] The second glass plate 5′ is rigidly fixed to the bottom main face 5bof the first glass plate 5. It extends from the fixing edge 5csubstantially as far as the control device 4.

[0031] In a different embodiment, the control device 4 could be fixed to the second glass plate 5′.

[0032] The printed circuit 3 is in the conventional form of a printed circuit card, one face 3aof which carries components necessary in particular for transmitting information to be displayed on the display screen 2. The face 3afaces the bottom main face 5b.

[0033] The display system 1 includes a support device 6 for supporting the display screen 2 and a spacer device 7 for holding the display screen 1 at the required distance from the printed circuit 3.

[0034] In the embodiment shown, the support device 6 is formed of two substantially perpendicular walls 6a, 6bjoined together at one edge. As shown in FIG. 1, the support device 6 has a substantially L-shaped cross section.

[0035] The wall 6ais substantially parallel to and extends along the bottom main face 5′bof the second glass plate 5′. The wall 6bis near the fixing edge 5cand extends away from the printed circuit 3.

[0036] The wall 6bhas a first abutment 6′ near its free end 6cand on the same side as the display screen 2. The abutment is located relative to the wall 6aso that the fixing edge 2cof the display screen 2 and the associated part of the light guide 5 are held between the first abutment 6′ and the wall 6a.

[0037] The wall 6bhas a second abutment 6″ near its free end 6cand on the opposite side to the display screen 2.

[0038] The spacer device 7 includes a wall 7asubstantially parallel to the wall 6bof the support device 6, on the opposite side to the display screen 2.

[0039] In the embodiment shown, the spacer device 7 is an integral part of the housing B of the terminal incorporating the display system 1. Accordingly, as shown in FIG. 1, the housing B includes a glass screen V substantially parallel to and extending along the top main face 5aof the display screen 2. The glass screen V adjoins the wall 7aso that their combination has a substantially L-shaped cross section.

[0040] The wall 6bhas a first abutment 6′ near its free end 6cand on the same side as the display screen 2. The abutment is located relative to the wall 6aso that the fixing edge 5cof the display screen 2 and the associated part of the light guide 5 are held between the first abutment 6′ and the wall 6a.

[0041] The wall 7ahas on its inside face 7b, which faces the support device 6, a lug 7dadapted to abut against the second abutment 6″. The lug 7dis at a distance from the free edge 7csuch that, when it is abutted against the second abutment 6″, the display screen 2 is held away from the printed circuit 3. In this embodiment, it is approximately one millimeter away when the screen 2 is substantially parallel to the printed circuit 3.

[0042] In a different embodiment, the screen 2 could be inclined to the printed circuit 3. In this case, the connecting edge 5dwould remain spaced from the printed circuit 3 at a substantially similar distance and the fixing edge 5cwould be raised so that the display screen 2 and the printed circuit 3 would be at an angle less than or equal to 45° to each other. The spring connector 9 is described next with reference to FIGS. 3 and 6.

[0043] The connector 9 is formed of a flexible metal foil 10, constituting a spring, and a plastics material film 11. The metal foil 10 and the plastics material film 11 have substantially identical rectangular general shapes before the connector is bent to shape.

[0044] The plastics material film 11 is fixed to one face of the metal foil 10, namely its outside face 10a. In the embodiment shown, the plastics material film 11 is glued rigidly edge-to-edge to the metal foil 10.

[0045] When it is formed by bending the metal foil 10 and the plastics material film 11 to shape, the connector 9 has a substantially S-shaped cross section.

[0046] The top part 9aof the S-shape is intended to hold the display screen 2 in position, forming a clamp fitting over the connecting edge 5d, as explained later. The bottom part 9bof the S-shape is intended to be in contact with the electrical circuit 3.

[0047] The S-shape of the metal foil 10 is described in more detail next with reference to FIGS. 5aand 5b.

[0048] The top part 9aof the S-shape is formed of a top flange 12 and a middle flange 13 joined together by a supporting core 14.

[0049] The top flange 12 and the middle flange 13 face each other and are substantially parallel to each other in a plane P. They have substantially the same width I measured in a direction D. They have substantially the same length L measured in a direction D′ perpendicular to the direction D.

[0050] The top flange 12 is delimited by a front free edge 12aopposite a connecting edge 12bfrom which the supporting core 14 extends. The front edge 12aand the connecting edge 12bare joined at each end by two lateral edges 12c, 12d. The two lateral edges 12c, 12dare parallel to each other in the direction D.

[0051] The top flange 12 has three adjoining portions 15a, 15b, 15c. The three portions 15a, 15b, 15cextend over the whole of the length L from the front edge 12ato the connecting edge 12b.

[0052] The first portion 15aextends from the front edge 12aover a width I′ measured in the direction D which is of the order of one quarter the width I. It has a substantially V-shaped cross section over the whole of the length L. The first portion 15ahas a bevel function.

[0053] Thus the first portion 15ais formed of:

[0054] a first branch 15idelimited by the front edge 12aand extending in a first direction d inclined to the plane P, and

[0055] a second branch 15iiadjoining the first branch 15iand the second portion 15band extending in a second direction d′ inclined to the plane P.

[0056] In the example shown, the angle α between the two branches 15iand 15iiis of the order of 150°.

[0057] The first portion 15aadjoins a second portion 15bextending over a width I″ measured in the direction D of the order of one eighth the width I. The second portion 15bis inclined to the plane P in substantially the direction d. Its function is to reinforce the top flange 12.

[0058] Finally, the second portion 15bis followed by a plane third portion 15csubstantially parallel to the plane P. The third portion 15cis aligned with the line of intersection 15iiibetween the branches 15iand 15ii.

[0059] The third portion 15cincludes at least one guide wall 16 substantially perpendicular to the plane P and extending toward the middle flange 13. The guide wall 16 adjoins a lateral edge 12c, 12d. It has a height h (FIG. 6) measured perpendicularly to the plane P that is less than or equal to the distance between the top flange 12 and the middle flange 13.

[0060] In this embodiment, the third portion 15chas two parallel guide walls 16 each extending from a respective lateral edge 12c, 12d.

[0061] The supporting core 14 is substantially perpendicular to the top and middle flanges 12 and 13. It has two substantially parallel longitudinal edges 14a, 14b. One longitudinal edge 14aadjoins the connecting edge 12band the other longitudinal edge 14badjoins the middle flange 13.

[0062] The supporting core 14 has a substantially C-shaped cross section with the concave side facing toward the inside of the top part 9a. This shape increases the elasticity of the connector 9.

[0063] Referring to FIG. 5b, the middle flange 13 has two substantially identical end parts 17, 18 and a blade part 19. The three parts 17 to 19 adjoin the longitudinal edge 14b.

[0064] The end parts 17, 18 are substantially plane and each has a length L′ measured in the direction D′ of the order of one fifth the length L. They lie in a common plane parallel to the plane P.

[0065] Each end part 17, 18 has two parallel opposite free lateral edges 17a, 17a′ and 18a, 18a′, respectively. The lateral edges 17aand 18aface the respective lateral edges 12cand 12dof the top flange 12. Also, the lateral edges 17a′ and 18a′ face each other and are separated by a gap E, part of which is occupied by the blade part 19.

[0066] Each end part 17, 18 further includes, substantially perpendicular to the lateral edges 17a, 17a′ and 18a, 18a′, respectively:

[0067] an edge 17b, 18badjoining the supporting core 14, and

[0068] a delimiter edge 17c, 18cdelimiting the top part 9a.

[0069] The blade part 19 is disposed between the end parts 17, 18 and spaced from the lateral edges 17a′ and 18a′. It has a substantially inverted V-shaped cross section over the whole of its length. Its concave side faces away from the top 9aof the connector 9. Also, the blade part 19 has a width I_mmeasured in the direction D of the order of one quarter the width of the end parts 17, 18 measured in the same direction.

[0070] The bottom part 9bof the S-shape is formed by the middle flange 13 and a bottom flange 20 connected together by a connecting core 21.

[0071] The bottom flange 20 and the middle flange 13 face each other. They have substantially the same width I measured in the direction D.

[0072] The bottom flange 20 is formed by two spaced, separate and generally plane contact parts 22, 23 in the same plane P′. The plane P′ is inclined relative to the plane P so that the height of the bottom part 9boccupies the free space between the display screen 2 and the printed circuit 3. The angle of inclination β of the bottom flange is of the order of 5° (FIG. 3).

[0073] Each contact part 22, 23 faces an end part 17, 18. It has a length L″ measured in the direction D′ substantially equal to the length L′ of each end part 17, 18.

[0074] As shown in FIG. 5b, each contact part 22, 23 is shaped like a comb. In this embodiment it has four teeth 22a, 23asubstantially parallel to each other, in the same plane and extending in the direction D.

[0075] It is to be noted that the comb-shape of the contact parts 22, 23 distributes forces over the bottom flange 20. This can be advantageous if the printed circuit 3 with which they come into contact is not perfectly flat. Of course, this particular shape is in no way exclusive, and other embodiments can be envisaged.

[0076] As can be seen in FIG. 3 in particular, the free edge 22b, 23bof each contact part 22, 23 is inclined toward the supporting core 14 at an angle γ relative to the plane P′ of the order of 30°. A contact point 24 is thus formed, on the side opposite the middle flange 13, at the intersection between the raised free edge 22b, 23band the main portion of the contact part 22, 23.

[0077] The connecting core 21 is formed of two substantially identical and coplanar core portions 21a, 21b. Like the supporting core 14, each core portion 21a, 21bis C-shaped with the concave side facing toward the inside of the bottom part 9b.

[0078] The longitudinal edges 21a′, 21b′ of each core portion 21a, 21badjoin the delimiter edge 17c, 18c. The other longitudinal edges 21a″, 21b″ of each core portion 21a, 21badjoin the edge 22c, 23copposite the raised free edge 22b, 23b.

[0079] As shown in FIGS. 4aand 4b, the plastics material film 11 is substantially the same shape as the metal foil 10 when they are bent into the S-shape. The same reference numbers are therefore used as for the metal foil 10, with the suffix′.

[0080] The only difference lies in the shape of the bottom flange 20′ of the plastics material film 11. This is formed of two continuous portions 22′, 23′ intended to cover the respective contact parts 22, 23 but having no teeth.

[0081] This shape covers the teeth 22a, 23acompletely to provide them with good protection. In a different embodiment, the portions 22′, 23′ could also be comb-shaped.

[0082] The shape of one portion 22′ is such that, when the plastics material film 11 covers one face of the metal foil 10, only one tooth 22aof the corresponding contact part 22 is not covered by the plastics material film 11 (FIGS. 4band 10). When the connector 9 is fitted, that tooth 22ahas a ground contact function. The metal connector is therefore connected to the ground of the circuit.

[0083] The plastics material film 11 also has at least one electrically conductive track 25 on one of its faces, referred to as the connection face 11a.

[0084] In the embodiment shown (FIG. 7), a plurality of tracks 25 extend from the free longitudinal edge 19a′ of the blade part 19′ to the raised free edges 22b′, 23b′ of each portion 22′, 23′. The tracks 25 are distributed so that they cover the whole of the surface of the plastics material film 11. They are also spaced from each other so that they overlie the teeth 22a, 23aof the bottom flange 20.

[0085] The face 11bof the plastics material film 11 without the tracks 25 is fixed to the outside face 10aof the metal foil 10.

[0086] The assembly of the display system 1 of the invention is described next with reference to FIGS. 8a, 8bto 10.

[0087] The top part 9aof the connector 9 is interengaged with the connecting edge 2dof the display screen so that the free end of the connecting edge 2dabuts against the supporting core 14. The arrow I in FIG. 8ashows the insertion direction. Insertion of the connection edge 2dinto the top part 9ais guided by the guide walls 16, among other things to ensure a good connection between the various tracks 5i, 25.

[0088] The longitudinal free edge 19aof the blade part 19 abuts against the control device 4 to make the connection between its contacts and the tracks 25 (see FIG. 10). Because of its shape, it also applies additional pressure to the display screen 2.

[0089] It is to be noted that the top flange 12 also protects the control device 4 from light and electrostatic discharges reaching the display screen 2.

[0090] In the embodiment shown in FIG. 10 the connecting core 21 is near the second glass plate 5′.

[0091] Finally, the contact point 24′ on the bottom flange 20′ of the plastics material film 11 comes into contact with the face 3aof the printed circuit 3 and applies a reaction force F to it (FIG. 2).

[0092] The display system 1 assembled in this way can easily be mounted inside a terminal, for example a telephone handset (not shown).

[0093] Of course, the invention is not limited to the embodiments that have just been described.