DESC:TECHNICAL FIELD
[0001] The present disclosure relates generally to stacked printed circuit boards, and more specifically, relates to a means to provide orientation guidance for insertion and removal of printed circuit boards.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present disclosure. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed disclosure, or that any publication specifically or implicitly referenced is prior art.
[0003] Many electronic devices include one or more circuit boards such as printed circuit boards (PCB'S), which are positioned in or with respect to a chassis or box. Examples from among the numerous types of electronic devices which have circuit boards provided in a chassis or a box, include computers such as personal computers, work stations, laptop computers, personal digital assistants, communication devices such as network routers, switches, bridges and the like, telephones, telefax machines, entertainment devices such as audio or video equipment and the like.
[0004] Printed circuit boards (PCBs) are typically positioned within a housing or cage for computer applications and communication applications such as local area network applications. The PCB is normally retained in the housing. The retaining of the PCB is often by fasteners which are fixed to the housing or cage or are otherwise connected to the housing or card cage. Preferably, such a connection allows the PCB to be securely fixed in position but also allows for a removal of the PCB, if replacement is necessary
[0005] Printed circuit boards (PCBs) are provided with card ejectors typically coupled/mounted on either side of the PCBs for removal and insertion of cards in chassis of electronic device. Card ejectors are widely used for engaging and disengaging printed circuit boards into sub-racks or card frames. However, there is difficulty in removal and insertion of cards in chassis of electronic devices when multiple printed circuit boards are stacked or sandwiched with each other.
[0006] Therefore, there is a need for a means to provide a simple and efficient solution to ensure easy insertion and extraction of the stacked PCBs.

OBJECTS OF THE INVENTION
[0007] An object of the present invention relates generally to guiding mechanism to provide orientation guidance to printed circuit boards, and more specifically relates to an apparatus and method of guiding arrangements for insertion and removal of printed circuit boards.
[0008] Another object of the present invention is to provide an apparatus to ensure simultaneous engagement and disengagement between mating connectors of multiple stacked cards and base board.
[0009] Yet another object of the present invention is to provide an apparatus that can provide simple and efficient solution which can grasp the stacked PCBs and ensure equal insertion and extraction force at contact point of connectors.

SUMMARY
[0010] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in Detailed Description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
[0011] The present disclosure relates generally to stacked printed circuit boards, and more specifically, relates to a means to provide orientation guidance for insertion and removal of printed circuit boards.
[0012] In an aspect, the present disclosure relates to an apparatus for stacking printed circuit boards, said apparatus comprising: a stack comprising a housing having a width and adapted to hold one or more printed circuit boards; a horizontal base comprising one or more base connecters , each of the base connectors adapted to receive and couple with a card connector of corresponding one or more printed circuit boards; a vertical frame coupled with the base, said frame adapted to receive the stacked PCBs and comprising one or more guides, wherein the one or more guides are aligned with the base so as to facilitate the card connectors of the one or more printed circuit boards to couple with the corresponding one or more base connectors; and at least two tab element pivotable configured to top of the stacked PCBs at any of the two ends of the stacked PCBs along width of the housing, said at least two tab element adapted to move between a first position and a second position.
[0013] In an embodiment, the present disclosure relates to an apparatus, wherein said vertical frame comprises one or more guides adapted to receive the corresponding printed circuit boards.
[0014] In another embodiment, the at least two tab element have a cam profile and is adapted to engage with the vertical frame as the at least two tab element moves between the first position and the second position.
[0015] In another embodiment, movement of the at least two tab element to the first position provides a uniform downward force to act on the one or more printed circuit boards to facilitate the one or more card connectors to couple with the corresponding one or more base connectors.
[0016] In another embodiment, movement of the at least two tab element to the second position creates a lifting movement to provide a uniform puling force to act on the one or more printed circuit boards to facilitate the one or more card connectors to de-couple with the corresponding one or more base connectors.
[0017] In another embodiment, at the second position, the tab element is away from the one or more guides.
[0018] In another embodiment, at the first position, the at least two tab element is adapted to cover at least a part of the width of the frame while being level with top of the frame.
[0019] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The following drawings form part of the present specification and are included to further illustrate aspects of the present disclosure. The disclosure may be better understood by reference to the drawings in combination with the detailed description of the specific embodiments presented herein.
[0021] FIG. 1 illustrates isometric view of stacked cards.
[0022] FIG. 2 illustrates front view of stacked cards.
[0023] FIG. 3 illustrates an assembly setup for the cards.
[0024] FIG. 4 illustrates misaligned engagement of stacked cards.
[0025] FIG. 5 illustrates slanted engagement of the cards in lateral direction.
[0026] FIG. 6 illustrates misaligned extraction of stacked cards.
[0027] FIG. 7 illustrates slanted extraction in lateral direction.
[0028] FIG. 8 illustrates an isometric view of the card ejector with card connector, according to an embodiment of the present disclosure.
[0029] FIG. 9 illustrates a perspective view of card cage assembly, according to an embodiment of the present disclosure.
[0030] FIG. 10 illustrates the tab element of card ejector, according to an embodiment of the present disclosure.
[0031] FIG. 11 illustrates line diagram showing coupling effect, according to an embodiment of the present disclosure.
[0032] FIG. 12 illustrates the sectional view of card ejector, according to an embodiment of the present disclosure.
[0033] FIG. 13 illustrates multiple stacked cards in the card ejector, according to an embodiment of the present disclosure.
[0034] FIG. 14 illustrates stacked cards assembly in card frame, according to an embodiment of the present disclosure.
[0035] FIGs. 15A-15B illustrate engagement process (also referred to as first position), according to an embodiment of the present disclosure.
[0036] FIGs. 16A-16B illustrate disengagement process (also referred to as second position), according to an embodiment of the present disclosure.
[0037] FIG. 17 illustrates line of action of force, according to an embodiment of the present disclosure.
[0038] FIG. 18 illustrates strain plot of the card ejector, according to an embodiment of the present disclosure.
[0039] FIG.19 illustrates stress plot of the card ejector, according to an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0040] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0041] If the specification states a component or feature “may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.
[0042] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0043] The use of any and all examples, or exemplary language (e.g., “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non – claimed element essential to the practice of the invention.
[0044] FIG. 1 illustrates isometric view of stacked cards.
[0045] FIG. 2 illustrates front view of stacked cards.
[0046] Referring to FIG. 1 and FIG. 2, the apparatus includes chassis that can accommodate multiple cards PC1, PC2 stacked with each other by three pairs of connectors C5, C6, C7. Multiple cards can include printed circuit boards (PCBs), also known as printed wiring boards, that can be used to interconnect and assemble electronic circuits. The operating temperature, mechanical strength, and other characteristics of a PCB may vary according to the application in which the PCB is used. PCBs provide electrical conductor paths between the circuits disposed upon them.
[0047] Many electronic devices include one or more circuit boards such as printed circuit boards (PCB'S), which are positioned in or with respect to a chassis or box. Examples from among the numerous types of electronic devices which have circuit boards provided in a chassis or a box, include computers such as personal computers, work stations, laptop computers, personal digital assistants, communication devices such as network routers, switches, bridges and the like, telephones, telefax machines, entertainment devices such as audio or video equipment and the like.
[0048] Printed circuit boards (PCBs) are typically positioned within a housing or cage for computer applications and communication applications such as local area network applications. The PCB is normally retained in the housing. The retaining of the PCB is often by fasteners which are fixed to the housing or cage or are otherwise connected to the housing or card cage. Preferably, such a connection allows the PCB to be securely fixed in position but also allows for a removal of the PCB if replacement is necessary.
[0049] In an embodiment, chassis or stacked card assembly can include a base board and mating connectors (C1-C4). Connector C1 and C2 are mounted on 1st and 4th card of stacked card assembly whereas connector C3 and C4 are mounted on base of a cut-out or opening in the board.
[0050] In another embodiment, chassis can accommodate multiple cards stacked with each other by three pairs of connectors C5, C6, C7. Chassis can be configured with first and second pin blocks a plurality of pin sockets receiving pins extending outward from the edges of the circuit board. In FIG. 1, circuit boards are inserted into the chassis by aligning side edges. The edges are slid between the surfaces to bring the pins into the vicinity of the pin blocks. However, when the pins are relatively delicate, such as small diameter pins, e.g. of the type that may be provided on boards having 1000 pins or more, the relatively more delicate pins may be damaged or bent by forces imparted to the pins during attempts to bring the pins into alignment with the pin sockets.
[0051] Insertion of boards into a chassis or a box may be performed in a number of situations including during initial fabrication of an electrical device, during testing, repair or replacement of the electrical device or components thereof, during ordinary maintenance, upgrading or modification of an electrical device (which may, in many cases, be performed by a substantially untrained end user).
[0052] As designs of electronic devices have evolved, circuit boards have been developed having a relatively larger number of pins, such as over 1,000, and in some cases over 1,400 pins, in such a fashion that the spatial density of the pins in at least some parts of the board, require pins of relatively smaller diameter, in particular, of diameters such that the pins are relatively delicate and may be unable to withstand the forces resulting from a somewhat misaligned board insertion process without bending, breaking or other undesirable deformation or damage to one or more pins. Accordingly, it would be useful to provide an apparatus which can reduce misalignment between a board and a pin block, or otherwise reduce misalignment between pins and pin sockets (or other electrical connectors) so as to reduce or avoid pin damage.
[0053] FIG. 3 shows stacked card assembly having edge connector C1 and C2 which can mate with connector C3 and C4 respectively present on the base board. The connector details are as follows:
[0054] C1 and C2: SEAF-RA200 pin board edge connector (samtec) and C3 and C4: SEAM 200 PIN connector (samtec). With reference to samtec document, Mated height of 200 pin SEAM and SEAF-RA connector= 11.75 mm, Mating force of connectors=23.33 lbs, Unmating force of connectors= 13.11 lbs. However, these are just exemplary values, and that the actual values can be a wide range, and the values included here are just for illustrative purposes other values and integer multiples are possible as well.
[0055] In an implementation, the process of engaging and disengaging the mating connectors C1 with C3 and C2 with C4 becomes difficult because of the following reasons. Referring to FIG. 4 and FIG.5, engaging process of mating connectors C1 with C3 and C2 with C4 can be explained. During mating of stacked PCBs with base board, the engagement of connectors C1 with C3 and C2 with C4 requires application of equal insertion force to overcome the frictional resistance at contact point for their concurrent mating. Application of unequal insertion force can lead to two types of misalignment as illustrated in FIG. 4 and FIG.5.This misaligned assembly may lead to wear of mating connectors.
[0056] During extraction of stacked cards as illustrated in FIG. 6 and FIG. 7, the stacked cards assembly is preferable to be ejected perpendicularly with respect to base board for simultaneous disengagement of connectors C1 and C2 with C3 and C4, respectively. Perpendicular aligned extraction can be achieved only if the extraction force F1 and F2 applied on card 1 and card2 are equal. Due to frictional resistance at contact point of mating connectors, the perfect vertical or perpendicular ejection cannot be achieved by manual ejection. Further, any misaligned ejection can lead to wear of mating connectors (C1, C2, C3 and C4).
[0057] Thus, a card ejector for stacked PCBs is needed which can overcome the above mentioned drawbacks, and readily grasp the stacked PCBs and ensure equal insertion and extraction force at contact point of mating connectors.
[0058] The present disclosure relates generally to stacked printed circuit boards, and more specifically, relates to a means to provide orientation guidance for insertion and removal of printed circuit boards.
[0059] In an aspect, the present disclosure relates to an apparatus for stacking printed circuit boards, said apparatus comprising: a stack comprising a housing having a width and adapted to hold one or more printed circuit boards; a horizontal base comprising one or more base connecters , each of the base connectors adapted to receive and couple with a card connector of corresponding one or more printed circuit boards; a vertical frame coupled with the base, said frame adapted to receive the stacked PCBs and comprising one or more guides, wherein the one or more guides are aligned with the base so as to facilitate the card connectors of the one or more printed circuit boards to couple with the corresponding one or more base connectors; and at least two tab element pivotable configured to top of the stacked PCBs at any of the two ends of the stacked PCBs along width of the housing, said at least two tab element adapted to move between a first position and a second position.
[0060] In an embodiment, the present disclosure relates to an apparatus, wherein said vertical frame comprises one or more guides adapted to receive the corresponding printed circuit boards.
[0061] In another embodiment, the at least two tab element have a cam profile and is adapted to engage with the vertical frame as the at least two tab element moves between the first position and the second position.
[0062] In another embodiment, movement of the at least two tab element to the first position provides a uniform downward force to act on the one or more printed circuit boards to facilitate the one or more card connectors to couple with the corresponding one or more base connectors.
[0063] In another embodiment, movement of the at least two tab element to the second position creates a lifting movement to provide a uniform puling force to act on the one or more printed circuit boards to facilitate the one or more card connectors to de-couple with the corresponding one or more base connectors.
[0064] In another embodiment, at the second position, the tab element is away from the one or more guides.
[0065] In another embodiment, at the first position, the at least two tab element is adapted to cover at least a part of the width of the frame while being level with top of the frame.
[0066] FIG. 8 illustrates an isometric view of the card ejector with card connector, according to an embodiment of the present disclosure.
[0067] Referring to FIG. 8, the housing having a width and can be adapted to hold one or more printed circuit boards. The housing includes a horizontal base 4, a vertical frame 7 coupled with the base 4, and tab element 2. The horizontal base 4 can include one or more base connecters 5, 6. The frame 7 can include one or more guides 3. The guides 3 can be aligned with the base 4 so as to facilitate the card connectors 8, 9 of the one or more printed circuit boards to couple with the corresponding one or more base connectors 5, 6. The two tab element 2 can be pivotable configured to top of the stacked PCBs at any of the two ends of the stacked PCBs along width of the housing and can be adapted to move between a first position and a second position.
[0068] In an embodiment, card ejector can be used in conjunction with a card frame 7 having card guiding slot. The card ejector can be mounted on two adjacent corners of stacked PCBs as shown in FIG. 8. The card frame 7 having card guiding arrangement 3 shown in FIG. 9. During insertion, the stacked cards can freely be guided in individual card guide slots of card frame until stacked card’s connector 8, 9 initially confronts the receiving connector 5, 6 (also referred to as base connectors (5,6)) present on base board 4. At this point, tab element 2 of corresponding card ejectors are pressed, which in turn exerts equal insertion force at contact point of mating connectors leading to simultaneous mating of connectors.
[0069] In an embodiment, when it is desired to remove the stacked cards, the tab element 2 of the ejectors mounted on either side of the stacked PCBs can be simultaneously rotated about 90 degree causing the ejector to impart an upward ejection force as the lever of ejector bear against the chassis, ensuring equal ejection force on both pairs of mating connector. The tab element shown in FIG. 10. This leads to simultaneous disengagement of connectors.
[0070] In an embodiment, the tab element 2 of the ejectors can move between the first position and the second position, wherein, at the second position, the at least two tab element is away from the one or more guides, and at the first position, the at least two tab element is adapted to cover at least a part of the width of the frame while being level with top of the frame.
[0071] In another embodiment, the tab element 2 of the ejectors has a cam profile and can be adapted to engage with the vertical frame as the at least two tab element 2 can move between the first position and the second position, wherein movement of the at least two tab element 2 to the first position provides a uniform downward force to act on the one or more printed circuit boards; and wherein movement of the at least two tab element 2 to the second position can create a lifting movement to provide a uniform puling force to act on the one or more printed circuit boards. The coupling effect of the tab element can be shown in FIG. 11.
[0072] In another embodiment, card ejector module for multiple stacked PCBs is used to ensure simultaneous engagement and disengagement between mating connectors of multiple stacked cards and base board 4. FIG. 12 shows dimensional details of the card ejector for multiple stacked cards. The distance between the holding slots can be varied based on the pitch of the mating connectors and distance between the stacked cards.
[0073] In an embodiment, card ejector having application as inserting and ejecting dual stacked PCB with base board 4. Card ejector can be used to mount the stacked PCBs in any orientation either vertical or horizontal. PCBs with all the available thickness can be used in card ejector. Card ejector can be manufactured from metal like aluminium and non-metal like acrylonitrile butadiene styrene (ABS) and nylon.
[0074] FIG. 13 shows assembly of four cards stacked with each other using three-pairs of connectors C5, C6, C7. The connector 8 can be mounted on the first card and the connector 9 can be mounted on the fourth card in row.
[0075] FIG. 14 shows the base board having pair of connectors 5,6, which can mate with the connectors 8, 9 of the stacked printed circuit cards, respectively. It also shows card frame having card guiding slot. The components include face against which the ejector recess bear against the chassis 1, card ejector module 2 for multiple stacked cards, card guide slot 3, base board 4, connectors 5, 6, 8, 9 and card frame 7.
[0076] In an embodiment, the ejector can include a tab element 2 or a handle, the rotatable nature of the coupling permits the ejector to be rotated between a fasten position with the tab substantially parallel to an axis of the PCB and a unfasten position with the tab about 90 degrees.
[0077] FIG. 15A and FIG. 15B illustrate the engagement process (also referred to as first position, herein) of printed circuit cards. During insertion process, the stacked cards can freely be guided in card guide slot without restriction until stacked card’s connectors 8, 9 encounter the base connector 5, 6. At this point, tab element 2 of corresponding card ejectors can be pressed, which in turn exerts equal insertion force at contact point of mating connectors leading to simultaneous mating.
[0078] FIG. 16A and FIG. 16B illustrate the disengagement process (also referred to as second position, herein) of printed circuit cards. When it is desired to remove the card, the tabs of the two card ejectors are simultaneously rotated through an angle of 90 degrees about pivot point, causing the card ejector to impart an upward ejection force as the edges of ejector bear against the chassis. This results in application of same extraction force on both the pairs of mating connectors which leads to smooth disengagement of the mating connectors.
[0079] FIG. 17 illustrates line of action of force. Calculation of force required to eject the stacked cards assembly:
With reference to samtec (OEM of connector C1, C2, C3 & C4) document,
Unmating force of 200 pin SEAM and SEAF connector= 13.11 lbs.
Thus, for a pair of 200 pin SEAM and SEAF connector, required unmating Force= 13.11x2 = 26.22 lbs.
So, Ejection force required on each card ejector = 26.22/2 = 13.11 lbs.
At pivot point of each ejector, the vertical force required to eject cards = 13.11lbs. (Refer FIG. 17).
Converting pounds to Newton, 13.11 lbs. = 58.26 Newton.
Moment of 58.26 N generated about x-x:
Moment1 = F x Normal Dist.
= 58.26x 0.01 N-m.
= 0.582 N-m.
The moment generated at axis x-x about axis z-z should be equal to moment generated at axis x-x about axis Y-Y,
F x (0.01+0.018) = 0.582 N-m
F = 0.582/ (0.01+0.018) = 20 Newton. Hence, the force required on each ejector for ejecting stacked cards is = 20 Newton. However, these are just exemplary values, and that the actual values can be a wide range, and the values included here are just for illustrative purposes other values and integer multiples are possible as well.
[0080] FIGs. 18 and 19 show the strain plot and stress concentration on various locations of the card ejector manufactured from ABS material. The yield strength of ABS is 3x107N/m2. The maximum developed stress for the given case is 1.24x107N/m2.
[0081] The present invention, in various embodiments, includes components, methods, processes, systems and/or apparatus substantially as depicted and described herein, including various embodiments, sub-combinations, and subsets thereof. Those of skill in the art will understand how to make and use the present invention after understanding the present disclosure. The present invention, in various embodiments, includes providing devices and processes in the absence of items not depicted and/or described herein or in various embodiments hereof, including in the absence of such items as may have been used in previous devices or processes, e.g. for improving performance, achieving ease and\or reducing cost of implementation.
[0082] It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refer to at least one of something selected from the group consisting of A, B, C … and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc. The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.
[0083] While various embodiments of the present disclosure have been illustrated and described herein, it will be clear that the disclosure is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art, without departing from the spirit and scope of the disclosure, as described in the claims.

ADVANTAGES OF THE PRESENT INVENTION
[0084] The present invention provides an apparatus to ensure equal insertion and extraction force at contact point of mating connectors.
[0085] The present invention provides an apparatus to ensure simultaneous engagement and disengagement between mating connectors of multiple stacked cards and base board.
[0086] The present invention provides an apparatus that can provide simple and efficient solution which can grasp the stacked PCBs and ensure equal insertion and extraction force at contact point of connectors.
[0087] The present invention provides an apparatus that can prevent a connector from being broken due to failure to draw out the mating connectors at proper alignment.
,CLAIMS:1. An apparatus for stacking printed circuit boards, said apparatus comprising:
a stack (1) comprising a housing having a width and adapted to hold one or more printed circuit boards;
a horizontal base (4) comprising one or more base connecters (5, 6), each of the base connectors adapted to receive and couple with a card connector (8, 9) of corresponding one or more printed circuit boards;
a vertical frame (7) coupled with the base, said frame adapted to receive the stacked PCBs and comprising one or more guides (3), wherein the one or more guides are aligned with the base so as to facilitate the card connectors (8, 9) of the one or more printed circuit boards to couple with the corresponding one or more base connectors (5, 6); and
at least two tab element (2) pivotably configured to top of the stacked PCBs at any of the two ends of the stacked PCBs along width of the housing, said at least two tab element (2) adapted to move between a first position and a second position.
2. The apparatus as claimed in claim 1, wherein said vertical frame comprises one or more guides adapted to receive the corresponding printed circuit boards.
3. The apparatus as claimed in claim 1, wherein the at least two tab element have a cam profile and is adapted to engage with the vertical frame as the at least two tab element moves between the first position and the second position.
4. The apparatus as claimed in claim 3, wherein movement of the at least two tab element to the first position provides a uniform downward force to act on the one or more printed circuit boards to facilitate the one or more card connectors to couple with the corresponding one or more base connectors.
5. The apparatus as claimed in claim 3, wherein movement of the at least two tab element to the second position creates a lifting movement to provide a uniform puling force to act on the one or more printed circuit boards to facilitate the one or more card connectors to de-couple with the corresponding one or more base connectors.
6. The apparatus as claimed in claim 1, wherein, at the second position, the tab element is away from the one or more guides.
7. The apparatus as claimed in claim 1, wherein, at the first position, the at least two tab element is adapted to cover at least a part of the width of the frame while being level with top of the frame.