DE9306773U1 - Fastening device made of plastic, in particular for circuit boards - Google Patents

Description

Plastic fastening device, especially for circuit boards

The invention relates to a fastening device made of plastic, in particular for circuit boards.

Fastening systems with which circuit boards are fastened in housings and with which several circuit boards are connected to one another, arranged one above the other and kept at a distance, are generally known. The fastening system used is spacer bolts with a hole with an internal thread on one axial end and with a pin with an external thread on the other axial end. The spacer bolts are either round or have an external hexagon. The spacer bolts are made of either plastic or metal or a ceramic material. The board to be fastened has through holes through which the external thread pins of the spacer bolts are inserted. Either screw-

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•; · · * **. ** fea*Öppenheimjr.&Cle..Köln(BLZ37030200)Kto.Nr. 10760 '. j · ·**; ·* ·* Deutsche BankAG. Köln (BLZ37070060) Kto. Nr. 1165018 ·* *··* *··* · ! PÖertglro Köln (BLZ 37O1005O) Kto. Nr. 654-500

nuts or additional spacer bolts are screwed on. When the screw nut or spacer bolts are tightened, the board is held clamped between two spacer bolts or a spacer bolt and the corresponding screw nut. The known fastening system therefore requires several parts to be screwed together; however, the screwing takes a relatively long time, which is why the assembly effort is comparatively high.

For fastening circuit boards, in particular for connecting two circuit boards, spacer bolts are also known which are inserted into holes in the circuit boards in a locking manner. The locking connection is sometimes not sufficiently strong, so that the circuit boards can still move against each other despite being connected via the spacer bolts.

Finally, connection techniques are known that have a dowel-like holder with a collar that is inserted into the aligned holes of two parts to be connected. A pin is then inserted into the dowel-like holder, which widens the holder so that it is secured against being accidentally pulled out of the holes and the two parts to be connected are firmly connected to one another.

The invention is based on the object of creating a plastic fastening system, in particular for circuit boards, in which the elements fixing the part to be fastened are plugged together, the elements of the fastening device being connected to one another by clamping.

To solve this problem, the invention proposes a fastening device made of plastic, in particular for circuit boards, which has:

- a receiving element provided with at least one receiving recess,

- at least one clamping sleeve for frictionally engaging insertion into the at least one receiving recess of the receiving element, wherein the receiving element encloses the at least one clamping sleeve over its entire insertion length immersed in the at least one receiving recess, and

- at least one clamping pin for frictional insertion into the ^ at least one clamping sleeve, wherein

- the at least one clamping sleeve is held in a clamping manner in the at least one receiving recess of the receiving element when the clamping pin is in the clamping sleeve.

The plastic fastening device according to the invention has a receiving element that can be designed as a separate part or can be connected to an object to which a part to be fastened is to be fixed using the plastic fastening device according to the invention. The receiving element is preferably a sleeve that is open on at least one side. The receiving element has at least one receiving recess that can accommodate at least one clamping sleeve. The clamping sleeve can be inserted into the receiving recess of the receiving element with friction; the depth of the receiving recess is dimensioned such that the clamping sleeve is completely enclosed by the receiving element when it

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&khgr;&eegr; the at least one receiving recess is inserted. The fit between the clamping sleeve and the receiving recess can be a press fit; advantageously, however, the outside diameter of the clamping sleeve is equal to the inside diameter of the receiving recess. More generally, the cross section of the clamping sleeve is equal to the cross section of the receiving recess. Furthermore, the fastening device according to the invention also includes at least one clamping pin which can be inserted into the at least one clamping sleeve with frictional engagement. When the clamping pin is received by the clamping sleeve and the clamping sleeve is in the receiving recess, the clamping sleeve is held against the receiving recess from the inside, i.e. is clamped in the receiving recess. The clamping pin exerts a radially outward clamping tension on the clamping sleeve, which is why the clamping sleeve is held securely in the receiving recess.

The plastic fastening device according to the invention is a plug-in system, whereby the fastening is brought about by generating clamping forces. The fastening system according to the invention is designed in particular for printed circuit boards. These printed circuit boards have through holes at their corners and possibly also at their edges, through which clamping sleeves are inserted. The diameter of the through holes in the board is larger than the outer diameter of the clamping sleeves.

The clamping sleeves extending through the through holes of the boards are inserted into the receiving recesses of the receiving elements. Clamping pins are then inserted into the clamping sleeves inserted into the receiving recesses.

press the clamping sleeves from the inside against the boundary walls of the receiving recesses. In order to secure the circuit board to the receiving element, either the clamping pins have heads or the clamping sleeves have collars on one of their axial elements; while the receiving elements are arranged on one side (for example the bottom) of the circuit board, the collars of the clamping sleeves or the heads of the clamping pins are on the other side of the circuit board (top). Both the receiving elements and the collars or heads rest on the edges of the circuit board through-holes.

In the fastening system according to the invention, the main thing is that the individual parts are in frictional clamping engagement with one another, thus preventing the individual parts from becoming unintentionally loose. The object to be fastened is held on the receiving element by either the clamping sleeve extending through a through hole or similar recess in the part to be held or the clamping pin having a widened end that projects beyond the edge of the through hole or recess in the part to be fastened.

In an advantageous development of the invention, the receiving element is designed as a sleeve that is open on both sides, the inner cavity of which forms two receiving recesses at its axial ends. With such a receiving element, two circuit boards can be connected to one another while maintaining the distance determined by the axial length of the sleeve receiving element. Clamping sleeves are inserted into the two ends of the receiving element, which are connected by through holes in the

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The circuit boards are pushed through. The clamping pins are then inserted.

It is advantageous if the clamping sleeve has a collar at one end and the clamping pin is provided with a head that protrudes radially beyond the collar of the clamping sleeve. When the fastening system is inserted into one another, the head of the clamping pin is then spaced apart from the part to be secured (circuit board) by the thickness (axial extension) of the collar of the clamping sleeve. To release the fastening device, for example, a screwdriver or similar can be used to grasp under the head of the clamping pin and the clamping pin can be moved out of the clamping sleeve in an axial direction. In this way, the fastening device can be released in a simple manner; in particular, this allows the individual parts and the entire fastening device to be reused.

A further development of the invention has already been discussed, in which the receiving element has the function of a spacer element. It is also advantageous if the receiving element itself has at least one clamping pin in addition to its at least one receiving recess, with which the receiving element can be inserted frictionally into a clamping sleeve, which in turn is inserted into the receiving recess of another receiving element. Each receiving element has a receiving end (namely the end provided with the receiving recess) and an insertion end (namely the end provided with the clamping pin). With such receiving elements, several circuit boards can be connected and fastened to one another in parallel and one above the other, whereby

the distance between adjacent circuit boards is determined by the length of the receiving elements between their receiving recesses and their clamping pins.

Advantageously, the receiving element is provided with a recess which is arranged around the clamping pin of the receiving element to receive the collar of a clamping sleeve.

Two embodiments of the plastic fastening device according to the invention for printed circuit boards are explained in more detail below using the figures. In detail:

Fig. 1 is a perspective view of a

Housing with the help of the fastening device fixed circuit board, whereby the housing is shown partially broken open,

Fig. 2 is a section along the line H-II of Fig.

1 with an exploded view of the fastening device according to Fig. 1,

Fig. 3 is a section along the line IH-III of Fig. 1 with the fastening elements inserted into one another.

contraption,

Fig. 4 the extension of the fastening device according to Fig. 1 for connecting several printed circuit boards arranged one above the other and their

fastening in, for example, a housing and

Fig. 5 a second embodiment of the fastening device for connecting two circuit boards.

Fig. 1 is a perspective view of a housing 10, only partially shown, to which a circuit board 12 is fixed using the fastening device 14 according to the invention. The fastening device 14 includes a receiving element 16, which in this embodiment of the invention is connected in one piece to the housing 10. The receiving element 16 is designed as a sleeve or socket that is open at the top and has an axial and cylindrical receiving recess 18. The receiving recess 18 is open towards the upper end of the receiving element 16. The circuit board 12 rests on the receiving element 16. The circuit board 12 has a through hole 20 for each receiving element 16, which is aligned with the receiving recess 18 of the receiving element 16. A clamping sleeve 22 is pushed through the through hole 20 from above, which has a sleeve section 24 and a collar 26 projecting radially from it at one axial end. When the clamping sleeve 22 is received by the through hole 20 and the rest by the receiving recess 18, the collar 26 is located on the top 28 of the circuit board 12, while the upper end of the receiving element 16 rests against the bottom 30 of the circuit board 12. The clamping sleeve 22 is traversed over its entire axial length by a cylindrical cavity 32, which is designed to receive the axial section 34 of a clamping pin 36. The clamping pin 36 is provided with a lens head 38, which is connected to the axial section 34 of the clamping pin 36.

In Fig. 3, the fastening device 14 is shown in its assembled state, in which the circuit board 12 is held on the housing 10. The clamping pin 36 has a slightly

larger diameter than the inner diameter of the cavity 32 in the clamping sleeve 22. The outer diameter of the clamping sleeve 22 in its sleeve section 24 is equal to the inner diameter of the receiving recess 18 of the receiving element 16. The clamping pin 36 exerts a radially outward-acting tension on the clamping sleeve 22, which ensures that the clamping sleeve 22 is pressed from the inside against the boundary 40 of the receiving recess 18. As a result, the individual parts of the receiving element 16, clamping sleeve 22 and clamping pin 36 are connected to one another in such a firmly frictional manner that unintentional loosening is prevented.

As can be seen in particular in Fig. 3, the head 38 of the clamping pin 36 projects radially beyond the collar 26 of the clamping sleeve 22. By inserting a pointed object, for example a screwdriver, between the top 28 of the circuit board 12 and the head 38 of the clamping pin 36, the latter can be moved in the axial direction and the fastening device 14 can be released.

Fig. 4 shows an extension of the fastening device 14 of Figs. 1 to 3 for arranging and connecting several printed circuit boards 12 one above the other and kept at a distance from one another. As in Figs. 1 to 3, the housing 10 is provided with receiving elements 16, which have receiving recesses 18. These receiving recesses 18 enclose the clamping sleeves 22 over their entire insertion length, i.e. over the length of their sleeve section 24 which is inserted into the receiving recess 18. In contrast to the fastening device 14 according to Figs. 1 to 3, in the extension according to Fig. 4, instead of a clamping pin 36

with head 38, a spacer element 42 is provided, which is designed as a cylindrical part and has an axial clamping pin 44 at one axial end. This clamping pin 44 is suitable for being inserted into a clamping sleeve 22. At the other axial end, the spacer element 42 has a receiving recess 46 for receiving a clamping sleeve 22. The spacer element 42 therefore takes on the function of both a clamping pin and the function of a receiving element and also serves as a spacer between two adjacent boards 12. The first spacer element 42, whose clamping pin 44 is inserted into the clamping sleeve 22 received by the receiving element 16, in turn also receives a clamping sleeve 22, which is inserted into the receiving recess 46. This clamping sleeve 22 is passed through the through hole 20 of the second circuit board 12 resting on the spacer element 42 and inserted into the receiving recess 46. A next spacer element 42 is then inserted into this clamping sleeve 22 with its clamping pin 44. As indicated in Fig. 4, a large number of circuit boards 12 can be arranged one above the other and connected to one another at a distance determined by the length of the spacer elements 42, with the entire stack of circuit boards being carried by the housing 10. As also shown in Fig. 4, the spacer elements 42 have ring recesses 48 at their ends carrying the clamping pins 44, which are arranged around the clamping pins 44 and are surrounded by edges 50 of the spacer elements 42. These ring recesses 48 accommodate the collars 26 of the clamping sleeves 22 into which the clamping pins 44 of the spacer elements 42 are inserted. The topmost board 12 of the board stack according to

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Fig. 4 is held in accordance with Figs. 1 to 3 on the uppermost spacer element 42 by means of a clamping pin 36 with head 38 inserted into the associated clamping sleeve 22.
5

Fig. 5 shows a fastening device in which the receiving element is a sleeve body 52, the two axial ends of which are open and form receiving recesses 54 for receiving clamping sleeves 22.

Fig. 5 shows this fastening device in an exploded view. A printed circuit board 12 is arranged at both axial ends of the sleeve body 52, whereby the through holes 20 of the boards 12 are connected to the cylindrical inner cavity of the sleeve body 52, i.e.

are aligned with its receiving recesses 54. As with the fastening devices according to Figs. 1 to 4, the clamping sleeves 22 are inserted through the through holes 20 of the boards 12 and, as far as possible, are inserted into the receiving recesses 54 at the axial ends of the sleeve body 52. The clamping pins 36 are then inserted into the clamping sleeves 22.

As far as the dimensions of the individual parts of the fastening device are concerned, the following dimensions have proven to be appropriate. The axial section 34 of a clamping pin 36 is 8 mm long. The clamping pin has a diameter of 2 mm in its axial section 34. The head 38 of the clamping pin 36 is 6 mm in diameter. Including the head 38, the clamping pin 36 has an axial extension of 9 mm. The clamping sleeve 22 has a total length of 7 mm, with the sleeve section 24 being 6 mm long and the axial extension of the collar 26 being 1 mm. The outer diameter of the sleeve section 24 is 3 mm and that

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of the collar 26 is 5 mm. The inner diameter of the clamping sleeve is 2 mm and is therefore the same size as the diameter of the clamping pin 36. The receiving recess 18 of a receiving element 16 has an inner diameter of 2.9 mm and is therefore 0.1 mm smaller than the clamping sleeve 22 in terms of its outer diameter. This means that there is a press fit between the receiving recess 18 and the clamping sleeve 22. The depth of a receiving recess is at least 5 mm, so that with a 1 to 2 mm thick circuit board, the entire part of the sleeve section 24 that protrudes beyond the circuit board is received by the receiving recess 18. The spacer elements 42 have a length of between 10 mm and a maximum of 35 mm, depending on requirements, whereby this is the dimension between the two axial ends of the spacer elements 42, i.e. without the length of the clamping pins 44 of the spacer elements 42. The length of these clamping pins 44 is 7 mm, whereby the ring recesses 48 surrounding the clamping pins 44 are 1.1 mm deep and have an inner diameter of 2 mm and an outer diameter of 5.1 mm. The receiving recesses 46 of the spacer elements 42 have a diameter of 2.9 mm. The depth of these recesses 46 is 7 mm. The spacer elements 42 themselves have an outer diameter of 6 mm. The sleeve bodies 52 according to Fig. 5 have an axial length in the range between 10 and 35 mm and are 6 mm thick in the outer diameter, while the inner diameter is 2.9 mm.

As has also been found, it is also expedient if the axial sections 34 of the clamping pins 36 have a length of only 5 mm. Accordingly, the length of the sleeve sections 24 of the clamping sleeves 22 is then only 4 mm, while the sleeve bodies 52 have an axial length of only 5 mm.

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The spacer elements 42 are then only 4.9 mm long (between the two axial ends without the clamping pin 44). The length of the clamping pin section that protrudes beyond the axial end is 5.1 mm. As far as the other dimensions are concerned, these are the same as the lengths previously specified.

Claims (8)

EXPECTATIONS 1. Fastening device made of plastic, in particular for circuit boards, with - a receiving element (16; 42; 52) which has at least one receiving recess (18; 46; 54), - at least one clamping sleeve (22) for frictionally engaging insertion into the at least one receiving recess (18; 46; 54) of the receiving element (16; 42; 52), wherein the receiving element (16; 42; 52) encloses the at least one clamping sleeve (22) over its entire insertion length immersed in the at least one receiving recess (18; 46; 54), and - at least one clamping pin (36; 44) for frictionally engaging into the at least one clamping sleeve (22), wherein - the at least one clamping sleeve (22) is held in a clamping manner in the at least one receiving recess (18; 46; 54) of the receiving element (16; 42; 52) when the clamping pin (36; 44) is located in the clamping sleeve (22). 2. Fastening device according to claim 1, characterized in that the at least one clamping sleeve (22) has a collar (26) at one of its axial ends. 3. Fastening device according to claim 2, characterized in that the at least one clamping sleeve (22) is designed to be inserted through a through hole (20) of the part to be fastened (printed circuit board 12) - 15 - is provided, wherein the collar (26) of the clamping sleeve (22) and the receiving element (16; 42; 52) are arranged on different sides (28, 30) of the part to be fastened (printed circuit board 12) facing away from one another when the at least one clamping sleeve (22) is inserted into the at least one receiving recess (18; 46; 54) of the receiving element (16; 42; 52). 4. Fastening device according to one of claims 1 to 3, characterized in that the at least one receiving recess (18; 46; 54) of the receiving element (16; 42; 52) is cylindrical, the inner diameter of the at least one receiving recess (18; 46; 54) of the receiving element (16; 42; 52) being substantially equal to the outer diameter of the at least one clamping sleeve (22), and that the inner diameter of the at least one clamping sleeve (22) is smaller than the diameter of the at least one clamping pin (36; 44), the at least one clamping sleeve (22) and the at least one clamping pin (36; 44) forming a press fit with one another. 5. Fastening device according to one of claims 1 to 4, characterized in that the receiving element (16) is a sleeve which is open on at least one side and which is connected to an object (housing 10) to which a part (printed circuit board 12) is to be fastened. 6. Fastening device according to one of claims 1 to 4, characterized in that the receiving element (52) is a sleeve open on both sides, whose inner cavity forms two receiving recesses (54) at the axial ends. 7. Fastening device according to one of claims 1 to 6, characterized in that at least one receiving element (42) is provided which has at least one receiving recess (46) for receiving a clamping sleeve (22) and at least one clamping pin (44) for frictionally engaging insertion into a clamping sleeve (22). 8. Fastening device according to one of claims 2 to 6 and 7, characterized in that the receiving element (42) has around the clamping pin (44) a recess (48) for receiving the collar (26) of the clamping sleeve (22), into which the clamping pin (44) of the receiving element (42) can be inserted.