Contact foil and carrier device with a contact foil and a method for its production

Abstract

Contact foil for establishing electrical connections between contacts (11, 39) of a first and a second contact field (6, 10) arranged opposite one another at a short distance, the contact foil (3) having a plurality of contact elements (5) enclosed by a flexible carrier web (26) made of plastic, and each contact element (5) having a contact surface (8, 9) accessible for contacting on each of the two flat sides of the contact foil (3), characterized in that the carrier web (26) is connected to a protective foil (27, 28) on at least one of the two flat sides of the contact foil (3), that the protective foil (27, 28) has a smooth and stable surface, and that the protective foil (27, 28) has holes (29, 30) through which the contact elements (5) with contact surfaces (8, 9) protrude.

Description

[0001] The invention relates to a contact foil according to the preamble of claim 1 and to a carrier device with an inkjet cartridge according to the preamble of claim 9. Furthermore, the invention relates to a method for producing a contact foil according to the independent method claim.

[0002] Flexible printed circuit boards are known that can be designed as flat contact strips, with conductor tracks embedded in a flat plastic carrier material. The conductor tracks can be freely accessible, for example, in the edge area of ​​such a flexible printed circuit board to enable electrical contact to the exposed conductor tracks.

[0003] To contact a contact pad provided on an inkjet cartridge, exposed conductor tracks can be formed with curved contact surfaces, allowing the curved contact surfaces to contact the contacts of an inkjet cartridge located in one plane. Such a contact is known from US Pat. No. 5,598,194 A. Since inkjet cartridges must be changed relatively frequently, contact problems can arise with the curved contact surfaces after frequent changes. Particularly in printer applications with high ink consumption and thus frequent cartridge changes, wear and tear can occur on the curved contact surfaces, leading to contact problems.

[0004] Furthermore, contact foils are known from US 2003 / 0178221 A1 and from US 3 680 037 A, which have several contact elements enclosed by a plastic carrier material.

[0005] The invention is based on the object of creating a contact foil with which the best possible electrical contact is possible between the individual contacts of a first contact field and a second contact field.

[0006] This problem is solved by the features specified in claim 1. The contact foil has a plurality of contact elements enclosed by a flexible plastic carrier strip, each of which has an accessible contact surface for contacting on each of the two flat sides of the contact foil. To increase the mechanical stability of the contact foil, the carrier strip is connected on at least one of the two flat sides to a protective foil. This protective foil has holes through which the contact elements with contact surfaces protrude. The side of the carrier strip on which the protective foil is located can thus form a very smooth and stable surface for the contact foil, which can withstand even greater mechanical stress.The contact foil can thus be used to create a secure electrical connection between opposing contacts of two contact pads. The flexibility of the contact foil means that the individual contact surfaces of the contact foil can be securely applied to the contacts of the opposing contact pads, even if certain dimensional tolerances exist. Pressing the contact surfaces of the contact foil onto the opposing contact pads is particularly optimal when one of the two contact pads is also located on a flexible or at least bendable carrier material. This is the case, for example, when the first contact pad is part of a flexible printed circuit board, so that the second contact pad can then be part of an inkjet cartridge with an integrated print head.

[0007] The contact elements of the contact foil can advantageously be designed as metallic spheres, which can also be surface-coated. Excellent contact properties are achieved by a gold-plated sphere surface.

[0008] According to a further development of the invention, the outer surface of the contact elements is more than 80% enclosed by the carrier track. This ensures that the contact elements are securely embedded in the plastic material of the carrier track, with contact elements designed as balls being held in a form-fitting and thus very securely in the plastic material of the carrier track.

[0009] The size of the contact elements can vary depending on the application. For contacting the contacts of an inkjet cartridge's contact pad, very good results were achieved in tests using a contact foil whose contact elements were gold-plated metal balls with a diameter of 0.8 to 1.2 mm. With such a contact foil, the carrier web can preferably have a layer thickness of 0.5 to 1.1 mm to ensure secure fixation of the metal balls in the contact foil. A greater layer thickness of the carrier web also results in a greater enclosure and thus more secure fixation of the metal balls in the carrier web. With a stronger enclosure, only smaller contact surfaces of the metal balls protrude on both sides of the carrier web.

[0010] The carrier web can advantageously be made of polyurethane, which provides high flexibility for the contact foil. According to a further development of the invention, the carrier web can also be designed as a silicone foil.

[0011] It is also possible for the contact elements to be soldered to conductor tracks or contacts of a flexible circuit board on one side of the contact foil. This firmly connects the flexible circuit board to the contacts of the contact foil on one side, while the entire arrangement still retains a high degree of flexibility, allowing the contact elements to be pressed against the contacts of a contact pad, for example, the contact pad of an inkjet cartridge.

[0012] The invention is further based on the object of creating a carrier device for receiving and contacting an inkjet cartridge equipped with a print head.

[0013] The solution to this problem is achieved with the features of claim 9. In the carrier device, a contact foil according to the invention is arranged between a first and a second contact field, which contact foil enables reliable contact due to its flexibility and due to the stability of the individual contact elements, in particular even after frequent changing of the inkjet cartridge used.

[0014] It is particularly advantageous to press the contact foil against the contact elements of a contact field on the inkjet cartridge using an elastic pressure pad. The elastic pressure pad can be pressed against the back of a flexible circuit board, so that the flexible circuit board is pressed against the contact foil on one side, so that the contact foil is pressed against the contact field of the inkjet cartridge with its other side. Since the flexible circuit board, the contact foil, and also the elastic pressure pad possess a certain degree of flexibility, optimal contact with the contact elements of the contact field of the inkjet cartridge is ensured, even if there are slight manufacturing tolerances in the area of ​​the contact elements.

[0015] The printing pad can be advantageously manufactured as a rectangular single- or multi-layer plate, with a thickness ranging, for example, from 1 mm to 5 mm. The printing pad can be made of foam rubber, with one side of the printing pad additionally being provided with a slightly firmer rubber layer. However, other suitable plastic materials can also be used.

[0016] To apply the elastic pressure pad to the back of the circuit board with the appropriate pressure, a pressure plate made of metal or another dimensionally stable material can be placed against the pressure pad. The pressure plate can be pressed against the pressure pad using spring force or a suitable screw connection.

[0017] The alignment of the print pad can automatically adjust to the alignment of the contact pad on the inkjet cartridge if the print pad is mounted so that it can pivot. This also compensates for an inaccurate alignment of the inkjet cartridge's contact pad with respect to the flexible circuit board.

[0018] According to a further development of the invention, the flexible circuit board can protrude from a circuit board of an electrical print head control device attached to the support device. This allows the support device to accommodate not only the inkjet cartridge but also the electrical control device, thereby achieving a very compact overall arrangement for a print head with a control device.

[0019] The carrier device is ideally suited for use in printers for labeling goods. Due to its compactness and robustness, the carrier device is also particularly suitable for use in egg printers, which print quality and origin data on chicken eggs.

[0020] The invention is further based on the object of specifying a method for producing a contact foil which can be used as an electrical contact element between the contacts of a first and a second contact field.

[0021] This problem is solved by the features specified in claim 15. The individual contact elements are first fixed in position so that they can then be embedded in a plastic compound. After a curing period, the contact foil with the embedded contact elements can be used as a finished contact foil. A potting compound can be used as the plastic compound, which encloses the contact elements in such a way that the contact surfaces of the contact elements remain free on both sides of the finished contact foil. The contact elements can be fixed electromagnetically or by means of a suction device in combination with a perforated positioning plate.

[0022] The contact elements are inserted between two perforated protective films, whereby the plastic compound is then injected into the space between the two protective films so that after curing a flexible carrier compound and thus a flexible contact film is obtained.

[0023] The invention is explained in more detail below with reference to embodiments shown in the drawing.

[0024] They show: Fig. 1 a carrier device with a contact foil according to the invention, Fig. 2 which in Fig. 1 used contact foil, Fig. 3 a partial side view of the contact foil of Fig. 2, Fig. 4 a simplified representation of an inkjet cartridge with a contact field, Fig. 5 a horizontal sectional view AA according to the Fig. 1 marked cutting line, Fig. 6 an enlarged section of a sectional view of the contact foil of Fig. 1, Fig. 2 and Fig. 5, Fig. 7 a partial section of a contact foil with protective film applied on one side, Fig. 8 a partial section of a contact foil without protective film, Fig. 9 a partial section of a contact foil with an adjacent flexible circuit board, Fig. 10 a flexible printed circuit board protruding from a circuit board of a control device and Fig. 11 a pressure plate pressed against a pressure pad by means of a compression spring.

[0025] The Fig. The carrier device 1 shown in Figure 1 essentially consists of a support frame 2, to the rear of which a contact foil 3 is attached, and behind this a flexible printed circuit board 4. The flexible printed circuit board 4 is designed here as a plastic strip with embedded conductor tracks 44. In the area of ​​the contact foil 3, contact surfaces of the conductor tracks 44 of the flexible printed circuit board 4 are exposed, so that contact elements 5 partially embedded in the contact foil 3 can establish electrical contact with the conductor tracks 44 located in the flexible printed circuit board 4. The plurality of contact elements 5 thus contact a first contact field 6, not visible here, of the flexible printed circuit board 4.

[0026] In the Fig. 2 and Fig. 3, the contact foil 3 with the contact elements 5 embedded therein is shown separately. The contact elements 5 are embedded in a transparent carrier strip made of a plastic material, in such a way that Fig. 2 visible front side as well as on the back side, projecting contact surfaces of the contact elements 5 remain free. In Fig. 3, which shows an enlarged partial side view of the contact foil 3, it can be seen how the contact elements 5 designed as metal balls 7 protrude slightly on both sides of the contact foil 3, so that contact surfaces 8, 9 on the metal balls 7 remain free on both sides.

[0027] In Fig. Figure 4 shows a simplified illustration of a commercially available inkjet cartridge with a contact field 10 comprising a plurality of individual contacts 11. The illustrated inkjet cartridge 12 has a print head 13 on its underside (not visible here), which is controlled via the contacts 11 by a control device located outside the inkjet cartridge 12.

[0028] The inkjet cartridge 12 can be inserted into the Fig. 1, so that an edge 14 projecting downwards at the front of the inkjet cartridge 12 is positioned behind two retaining webs 15, 16 ( Fig. 1). An upper locking edge 17 on the inkjet cartridge 12 can engage with a locking element 18 of the carrier device 1 of Fig. 1, so that the inkjet cartridge 12 is held releasably yet securely in the carrier device 1. The inkjet cartridge 12 inserted into the carrier device 1 in this way contacts the contacts 5 of the contact foil 3 with its contacts 11, which in turn are in contact connection with contacts of the flexible printed circuit board 4 on their rear side.

[0029] The first contact field 6, which is located on the flexible circuit board 4 behind the contact foil 3 in Fig. 1 is thus electrically connected to the second contact field 10, which comprises the contacts 11 of the inkjet cartridge 12, via the contact elements 5 of the contact foil 3. In order to achieve a secure contact, it is particularly advantageous if the flexible circuit board 4 of Fig. 1 is pressed against the contact field 10 of the inkjet cartridge 12 by means of a pressing device in the area of ​​the contact foil 3 on the non-visible back side. In an enlarged detailed view of Fig. 5 this is explained in more detail below.

[0030] In the sectional view of Fig. 5 shows that a pressure pad 19, which can be made as an elastic plate made of foam rubber, is pressed against the back 21 of the flexible circuit board 4 by means of a pressure plate 20. This presses the contact elements 5 of the contact foil 3 against the contacts 11 of the inkjet cartridge 12 via the flexible circuit board 4. The effective pressure and counterpressure are indicated by the two arrows 22, 23. The strength of this pressure depends, among other things, on how the screw connection is adjusted using the screw connections 24, 25. The screw connections 24, 25 act between the support frame 2 and the pressure plate 20.

[0031] In Fig. 5, the contact elements 5 are designed as metal balls that are embedded in a flexible carrier strip 26 made of an elastic plastic material. Polyurethane, for example, is very suitable as a plastic material, although a silicone material can also be used as a carrier strip. It is essential that the carrier strip has sufficient flexibility so that distance tolerances between the flexible circuit board 4 and the contact field 10 of the inkjet cartridge 12 can be compensated. The flexibility of the carrier strip 26 and thus of the contact foil 3 is also essential for the inkjet cartridge 12 with its contacts 11 to be held in its Fig. 5 shown mounting position with pressure on all contact elements 5.

[0032] In Fig. Figure 6 shows a contact foil 3, partially in section, with a protective foil 27, 28 on each side. Both protective foils 27, 28 are provided with corresponding holes 29, from which contact surfaces 8, 9 of the contact elements 5, designed as metal balls, protrude on both sides. The plastic material sandwiched between the protective foils 27, 28 can be injected between the protective foils 27, 28. However, it is also possible for the three layers of the contact foil to be glued together one after the other, and for each of the layers, namely the protective foils 27, 28 and also the carrier web 26, to be provided with corresponding holes to accommodate the spherical contact elements 5.

[0033] In Fig. 7, a protective film 28 is provided only on the underside of the carrier web 26, while in Fig. 8 no protective films are present. The carrier web 26 can be a polyurethane casting compound, which has the desired flexibility after curing. In the manufacture of the Fig. The contact elements 5, designed as metal balls 7, can be positioned and held in depressions 30 or holes 31 of a positioning plate 32 using the contact foil 3 partially shown in Figure 8. A potting compound 33 is then applied, which surrounds the contact elements 5 in the manner shown and, after curing, forms a flexible carrier track 26. The metal balls 7, which preferably have a gold-plated surface and can be made of a magnetic metal, are largely enclosed by the carrier track 26 and are thus securely held in a form-fitting manner by the carrier track.

[0034] When applying the casting compound 33, the metal balls 7 can be held in position electromagnetically or by a negative pressure acting on holes 31. The electromagnetic fixation is in Fig. 8 by an electromagnet 34. In addition, the directional arrow 35 indicates that the metal cap 7 is sucked against the positioning plate 32 by means of negative pressure at the hole 31 and is thereby fixed in its position. Fig. Figure 8 shows both possible fixation variants, which are typically used alternatively in a manufacturing process. However, it is also possible to use electromagnetic fixation and fixation using negative pressure in combination.

[0035] Fig. Figure 9 shows a section of a contact foil 3 whose contact elements are soldered to contact points 36, 37. In such a design, the contact elements 5 are already fixed by soldering, so that the potting compound 33 can be easily applied to the flexible printed circuit board 4 to surround the contact elements 5 in the manner shown and thus embed them in the carrier track 26.

[0036] In Fig. 10 shows a circuit board 40 of a control device 41, from which a flexible printed circuit board 4 with a first contact field 6 with a plurality of contacts 39 protrudes downwards. The dimensions of the circuit board 40 with flexible printed circuit board 4 are essentially based on the Fig. 1 shown support device 1 or adapted to its support frame 2, so that the entire Fig. 10 can be attached to the carrier frame 2. The contact foil 3 is then placed on the first contact field 6, which then establishes contact between the first contact field 6 and the second contact field 10 of an inkjet cartridge 12 inserted into the carrier device 1.

[0037] In Fig. 11 is a modification of the representation of Fig. 5, not only is a pressure plate 20 arranged behind the pressure pad 19, but an additional pressure plate 42 is provided, which presses the pressure plate 20 against the pressure pad 19 via compression springs 43. The pressure plate 20 is mounted with play so that the pressure plate 20 can pivot relative to the additional pressure plate 42. This is advantageous when there is no exact parallel alignment between the pressure system, consisting of the pressure pad 19, pressure plate 20, and additional pressure plate 42, and the alignment of the contact field 11 of the inkjet cartridge 12.

[0038] The pressure pad 19 is designed in two layers and consists of an elastic layer 46 made of foam rubber and an additional rubber layer 45. In principle, suitable elastic plastics can also be used as materials for the two layers 45, 46.

[0039] The contact foil according to the invention enables secure contact between contact pads arranged at a short distance from one another, as is the case with the contacting of inkjet cartridges with an integrated print head. However, the contact foil can also be used for other applications. The metal balls used as contact elements 5 in the exemplary embodiments can also be replaced by other contact body shapes. The spherical contact surfaces on the contact elements 5 are advantageous when sliding a contact pad laterally on, since the spherical surfaces have good sliding properties with respect to the contacts applied to them.

Claims

[1] Contact foil for establishing electrical connections between contacts (11, 39) of a first and a second contact field (6, 10) arranged opposite one another at a short distance from one another, wherein the contact foil (3) has a plurality of contact elements (5) enclosed by a flexible carrier strip (26) made of plastic, and each contact element (5) has a contact surface (8, 9) accessible for contacting on each of the two flat sides of the contact foil (3), characterized by that the carrier web (26) is connected to a protective film (27, 28) on at least one of the two flat sides of the contact film (3), that the protective film (27, 28) has a smooth and stable surface, and that the protective film (27, 28) has holes (29, 30) through which the contact elements (5) with contact surfaces (8, 9) protrude. [2] Contact foil according to claim 1, characterized by that the contact elements (5) are metal balls (7). [3] Contact foil according to one of claims 1 or 2, characterized by that the outer surface of the contact elements (5) is enclosed by more than 80% of the carrier track (26). [4] Contact foil according to one of the preceding claims, characterized by that the contact elements (5) are gold-plated metal balls (7). [5] Contact foil according to one of the preceding claims, characterized by that the contact elements (5) are metal balls (7) with a diameter of 0.8 mm to 1.2 mm, and that the carrier track (26) has a layer thickness of 0.6 mm to 1.1 mm. [6] Contact foil according to one of the preceding claims, characterized by that the carrier web (26) is made of polyurethane. [7] Contact foil according to one of claims 1 to 5, characterized by that the carrier web (26) is designed as a silicone film. [8] Contact foil according to one of the preceding claims, characterized bythat the contact elements (5) on a flat side of the contact foil (3) are soldered to contacts (39) formed on conductor tracks (44) of a flexible printed circuit board (4). [9] Support device with an inkjet cartridge (12) equipped with a print head (13) and detachably inserted into the support device, in which a contact field (10) located on the inkjet cartridge (12) is connected via a contact field (6) located on a flexible printed circuit board (4), characterized bythat a contact foil (3) for establishing electrical connections between contacts (11, 39) of the contact fields (6, 10) arranged opposite one another at a short distance is arranged between the two contact fields (6, 10), wherein the contact foil (3) has a plurality of contact elements (5) enclosed by a flexible carrier strip (26) made of plastic and each contact element (5) has a contact surface (8, 9) accessible for contacting on each of the two flat sides of the contact foil (3). [10] Carrier device according to claim 9, characterized by that an elastic pressure pad (19) is applied with pressure to the rear side of the flexible circuit board (4) facing away from the inkjet cartridge (12), which presses the flexible circuit board (4) against the contact elements (5) of the contact film (3) and thus the contact elements (5) also against the contact field (10) on the inkjet cartridge (12). [11] Carrier device according to claim 9, characterized bythat an elastic pressure pad (19) is integrated into the flexible circuit board (4), which presses the flexible circuit board (4) against the contact elements (5) of the contact foil (3) and thus the contact elements (5) also against the contact field (10) on the inkjet cartridge (12) with mechanical pressure. [12] Support device according to one of claims 10 or 11, characterized by that the pressure pad (19) consists of at least one elastic layer of foam rubber (46), rubber (45) or a suitable plastic material. [13] Carrier device according to one of claims 10 to 12, characterized by that a pressure plate (20) rests on the pressure pad (19) on its rear side facing away from the flexible printed circuit board (4), and that the pressure plate (20) is clamped against a support frame (2) of the carrier device (1) and against the inkjet cartridge (12) inserted in the carrier device (1). [14] Carrier device according to one of claims 10 to 13, characterized by that the alignment of the print pad (19) automatically adapts to the alignment of the contact field (10) arranged on the inkjet cartridge (12). [15] Method for producing a contact foil (3) for producing electrical connections between contacts (11, 39) of a first and a second contact field (6, 10) arranged opposite one another at a short distance, wherein the contact foil (3) has a plurality of contact elements (5) enclosed by a flexible carrier web (26) made of plastic, and each contact element (5) has a contact surface (8, 9) accessible for contacting on each of the two flat sides of the contact foil (3) characterized bythat the contact elements (5) are inserted and fixed in a predetermined position between two perforated protective films (27, 28) in a first production step, and that a plastic mass is then injected into the space between the two protective films (27, 28), which, after curing, results in a flexible carrier web (26) to which the flexible protective films (27, 28) adhere on both flat sides. [16] Method according to claim 15, characterized by that the contact balls (7) are fixed in positioning holes (31) by means of negative pressure and / or electromagnetically.

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