GB2166004A

GB2166004A - Printed circuit board mounting apparatus

Info

Publication number: GB2166004A
Application number: GB08525721A
Authority: GB
Inventors: Adrian Q Lindley; Roger Bellamy
Original assignee: CAMLOC IND FIXING
Current assignee: CAMLOC IND FIXING
Priority date: 1984-10-19
Filing date: 1985-10-18
Publication date: 1986-04-23
Also published as: GB8426477D0; GB2166004B; FR2572240A1; FR2572240B1; GB8525721D0; DE8529634U1

Abstract

Apparatus for mounting and retrieving printed circuit boards in a rack comprises a base provided with a fixed portion 5 forming opposed wedging surfaces. A bore extends through the fixed portion from one wedging surface to the other and receives an screw 8 on which are mounted movable wedging portions 7 having respective right and left hand threaded portions whereby rotation of the screw threaded member causes the movable wedging portions to ride up or down the opposed wedging surfaces. The bore through the fixed portion is shaped to permit movement of the screw threaded member in a direction transverse to its axial direction and leaf spring 9 is located in the bore to bias the wedging portions to their lower, inoperative positions. Additional wedging portions can be provided between the fixed and movable wedging portions. <IMAGE>

Description

SPECIFICATION Printed circuit board mounting apparatus The present invention relates to apparatus for mounting and fastening printed circuit boards or cards within a rack or chassis.

Apparatus for mounting and fastening printed circuit boards has already been proposed and it is already known to use a wedging arrangement for locking a printed circuit board to a rack. However, the construction of the wedging arrangement is such that the wedging arrangement tends to stick in a wedging position which means that some mechanical force has to be applied to the board even after the wedging arrangement has been theoretically released in order to release the board from the rack.

The present invention has been designed in order to provide a wedging arrangement which will overcome the above difficulty.

The present invention provides a wedging arrangement for locking a printed circuit board into a rack wherein co-operating stationary and movable wedges are arranged to be moved relative to each other in order to clamp a printed circuit board in a rack, biasing means being provided for biasing the movable wedges to an inoperative position.

Preferably, the wedging arrangement comprises a central wedging member fixedly attached to a printed circuit board and associated with co-operating movable wedging members at either end thereof. A screw extends from one movable wedging member through a channel in the central wedging member to the other movable wedging member such that when the screw is rotated in one direction the movable wedging members, together with the screw, are caused to move relative to the central wedging member in such a manner that there is a component of movement transverse to the axis of the screw. The central wedging member prefera bly is provided with a spring which is located between the screw and a spring seat on the central wedging member for biasing the screw and the two movable wedging members to an inoperative position.

The spring biasing means may be a simple leaf spring or else a more complicated spring arrangement in order to ensure the application of distributed spring forces along the length of the screw in order to prevent any tendency for one of the wedging members to stick.

Features and advantages of the present in vention will become more apparent from the following description of embodiments thereof given by way of example when taken in conjunction with the accompanying drawings, in which: Figure 1 shows a side view of a printed circuit board provided with a wedging arrange ment according to the present invention; Figure 2 shows an end view of the arrangement shown in Fig. 1 when located in a rack for printed circuit boards; and Figure 3 shows a side of another printed circuit board provided with a further embodiment of the wedging arrangement according to the present invention.

Referring firstly to Figs. 1 and 2, a printed circuit board 1 is retained in a rack 2 by means of a wedging arrangement generally indicated by the reference numeral 3.

The rack 2 has at least one wall provided with slots 4 for the retention of printed circuit boards and the slots are of a substantially greater width than the thickness of the printed circuit board so as to receive both the edge of a printed circuit board and a wedging arrangement 3.

In Fig. 1, the wedging arrangement comprises a first portion 5 which is arranged to be fixed by means of screws 6 to an edge of a printed circuit board. An elongate channel extends through the whole length of the portion 5 and a co-operating, movable wedge portion 7 is provided at each end of the portion 5. The portions 7 are joined together by means of a screw 8 which extends through the portion 5 in the channel provided in the portion 5.The arrangement is such that when the screw member is rotated in a direction to tend to bring the wedging portions 7 together by virtue of the mating wedging surfaces between the portion 5 and the movable portion 7, the portions 7 move in a direction transverse to the axis of the screw member and move from the position shown in Fig. 1 to a position where upper surfaces 7a of the movable wedging members extend above the level of the board 1 by a greater height than the upper surface 5a of the central portion.

When this operation is carried out with the printed circuit board 1 and wedging arrangement 3 in position in a slot 4 of a rack 2, the effect is to lock the edge of the printed circuit board in the slot 4.

Movement of the wedge portions 7 is achieved by one of the portions 7 having a right hand screw thread and the other of the portions having a left hand screw thread with the screw 8 having correspondingly threaded portions so that on rotation of the screw 8 in one direction the portions move towards each other and on rotation of the screw 8 in the opposite direction, the portions move away from each other.

In order to release the printed circuit board from the slot 4, it is necessary to rotate the screw in the opposition direction so as to tend to separate the movable portion 7. However, this does not necessarily ensure that the printed circuit board 1 will be completely re leased from the slot in view of the fact that one of the wedging portions 7 may stick. For this reason, the wedging portions 7 are biased to an inoperative position which is the posi tion shown in Fig. 1. This is preferably achieved by means of a spring member located in the channel in the portion 5 and arranged to act on the screw 8.

Depending on a number of factors including the length of the member 5, the spring may be of any one of a number of different types and/or shapes. As shown in Fig. 1, the spring 9 is seen to have two effective spring portions 9a and 9b disposed adjacent opposite ends of the portion 5. Were the portion 5 shorter, a simple leaf spring could be used to replace the spring 9.

Turning now to the embodiment shown in Fig. 3, this is basically the same as the embodiment shown in Fig. 1 but instead of having a wedging arrangement involving one fixed and two movable members, this arrangement comprises one fixed and four movable members.

In this embodiment, similar reference numerals are used to those used in Fig. 1 to represent similar parts and the detailed description thereof will consequently be abbreviated. The central portion 5 is similar to or identical to that shown in Fig. 1 and movable wedging members 10 which are operated on by the screw 8 are similar to the wedging members 7 in Fig. 1 with the exception that the slope of the wedging faces thereof is no longer such that they are arranged to engage with the sloping faces on the wedging portion 5.

Rather, additional intermediate movable wedging portions 11 are provided between the end movable wedging portions 10 and the middle portion 5.

The intermediate portions 11 are each provided with channels extending axially therethrough which receive the screw 8 and are dimensioned to permit the movement of the wedging portions 11 relative to the screw 8 in a direction transverse to the axis of the screw 8.

As before, the central portion 5 is provided with a biasing spring 9 but in this embodiment the intermediate wedging portions 11 are also each provided with biasing means 12 again located in order to biase the movable wedging portions towards the inoperative position which is shown in Fig. 3 by acting on the screw 8.

In operation and in order to retain a printed circuit board in a slot 4 of a rack 2, the screw 8 is rotated in order to draw the movable end wedging portions 10 together. This has the effect of raising surfaces 1 1a of the intermediate wedging portions 11 above the level of the surface 5a and thereby lock the printed circuit board in a slot.

It is to be noted that the wedging portions 10 and 11 and the screw 8 are capable of moving bodily away from the printed circuit board 1. This has the advantage that relatively long slots can be accommodated using this type of wedging arrangement but also a more even clamping of the circuit board can be achieved than in the Fig. 1 arrangement.

It will be noted that in Figs. 1 and 3 a simple screw driver slot is provided in one end of the screw 8 in order to enable rotation of the screw. This has been shown merely for convenience as the exact way in which the screw is rotated is not significant and in fact could with advantage be replaced by a hex recess drive arrangement as is known in the art.

For completeness, it is to be noted that the wedge portions are preferably made of a aluminium or an alloy thereof, the spring or springs are made of stainless steel and the screw is made of any suitable material which may be either stainless steel or alloy steel.

It is preferred to provide one or both ends of the screw 8 with an indicator so that the condition of the apparatus can be seen from the end.

Further, while the term "screw thread" has been used above, it will be understood that less than one complete turn of the screw 8 may be sufficient to move the apparatus from the clamping to the unclamped position and vice versa.

Claims

1. Wedging apparatus for locking a printed circuit board into a rack, comprising a base member provided with a fixed wedging portion, movable wedging portions arranged to co-operate with the fixed wedging portion, a screw threaded member rotation of which is arranged to cause movement of the fixed and movable wedging portions relative to each other from a first, inoperative condition to a second condition in order to clamp a printed circuit board in a rack, and biasing means for biasing the movable wedging portions to the first, inoperative condition.

2. Apparatus according to claim 1, wherein there are two movable wedging portions provided with respective right and left hand screw threaded portions, and wherein the screw threaded member extends through a bore in the fixed wedging portion, said bore permitting movement of the member in a direction transverse to the axial direction of the member.

3. Apparatus according to claim 2 and comprising two further movable wedging portions each arranged between one of the firstmentioned movable wedging portions and a wedging surface of the fixed wedging portion, the screw threaded member extending through bores in the two further movable wedging portions.

4. Apparatus according to claim 3, wherein the bores in the two further movable wedging portions are dimentioned to permit movement of the screw threaded member in a direction transverse of the axial direction of the member.

5. Apparatus according to claim 4, wherein the biasing means comprises spring means in the bores of the two further movable wedging portions.

6. Apparatus according to any one of the preceding claims, wherein the biasing means comprises a spring member in the bore of the fixed wedging portion.

7. Apparatus according to claim 6, wherein the spring member is a leaf spring.

8. Apparatus according to any one of the preceding claims, wherein one or both ends of the screw member is provided with an indica tor whereby the condition of the apparatus may be visually monitored.