GB2500119A

GB2500119A - Hand held device incorporating printed circuit board

Info

Publication number: GB2500119A
Application number: GB1305245.1A
Authority: GB
Inventors: Paul Stewart Overy Brown
Original assignee: Premier Diagnostics Ltd
Current assignee: Premier Diagnostics Ltd
Priority date: 2013-03-22
Filing date: 2013-03-22
Publication date: 2013-09-11
Anticipated expiration: 2033-03-22
Also published as: GB2500119B; GB201305245D0

Abstract

A hand held enclosure comprising a PCB 31 sandwiched between top 11 and bottom 12 parts of a casing. The PCB is loosely retained by pedestals 21, 23 on the casing. The printed circuit board has a socket 33 mounted thereon for receiving a plug. The PCB also has gaskets 22 to receive the said pedestals. The enclosure further comprises resilient pads 37 between the PCB and casing to resist movement of the PCB in a direction perpendicular to plug attachment direction but to allow positional adjustment in the attachment direction. This arrangement allows an external plug to be inserted into the socket on the PCB and also reduces the damage caused by vibration or shock passing from the plug to the socket, i.e. during handling of the device.

Description

Held Held Device Incorporating Printed Circuit Board

This invention relates to a hand held device incorporating a printed circuit board (pcb), and in particular to a device having a socket mounted on the pcb.

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Hand held devices containing a pcb are well-known. One typical device comprises a two-part plastic moulding defining a hand held enclosure within which is located a pcb and other components. In use the pcb is mounted by sandwiching it between the two parts of the enclosure. In one embodiment, a hand held diagnostic device of this 10 kind includes a socket to receive a data lead/plug, whereby electronic information is provided for processing in the device. Such a device may be used for diagnosis, display and like purposes in relation to an electrical system of a vehicle, and the data lead/plug may be linked to a standard on-board diagnostic (OBD) module of the vehicle.

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Several difficulties arise in relation to design of such devices, in particular providing adequate robustness at an acceptable cost. For example, a typical hand held device must be designed to cope with rough handling and shock loading in addition to repeated plugging and unplugging of the plug/socket connection.

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Within the device, robustness is particularly required in relation to the pcb, in order to avoid premature failure of the components mounted thereon.

If a socket is mounted on the pcb, the pcb must itself be relatively rigidly mounted 25 within the enclosure so as to resist pushing and pulling due to connection and disconnection of the plug with the socket. On the other hand, a relatively rigid mounting tends to transmit vibration and shock loading directly from the enclosure to the pcb. Rattling of the pcb within the enclosure is particularly undesirable.

30 An additional desirable feature is a means of temporarily maintaining the pcb in the correct relative position prior to closing the enclosure. Such means should ideally be very inexpensive since they become redundant as soon as the enclosure is closed to retain the pcb.

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The present invention provides an inexpensive solution to these difficulties.

According to the invention there is provided a hand held enclosure comprising a base and a lid, the enclosure having a planar printed circuit board therein sandwiched 5 between pedestals of the base and lid, the printed circuit board being loosely retained by said pedestals against movement within said enclosure, said printed circuit board having a socket mounted thereon for receiving a plug in an attachment direction in the plane of said printed circuit board, and a compliant gasket being provided for one or more of said pedestals to take-up clearance perpendicular to the plane of said printed 10 circuit board, wherein opposite resilient pads at the edge of said printed circuit board respectively engage opposite internal surfaces of said enclosure so as to resist movement of the printed circuit board in the plane thereof and perpendicular to the attachment direction, but to allow positional adjustment in the attachment direction.

15 In such an arrangement the printed circuit board is loosely located by the pedestals. This in turn avoids tight tolerancing which would increase manufacturing expense and could place the printed circuit board under stress in the event of deformation of the enclosure. Generally speaking the printed circuit board is loosely located in a mid-plane of the enclosure (typically a rectangular box-like plastic moulding) so as to 20 permit location of components on both sides thereof.

The gaskets, which may be resilient, take up any clearance between the relatively rigid printed circuit board and relatively rigid enclosure in the direction orthogonal to the plane of the circuit board.

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The pads, which may also be resilient, take up lateral clearance so as to prevent movement (rattling) in the plane of the circuit board and perpendicular to the attachment direction. In one embodiment the pads are suitably compliant and or resilient, and may be an elastomer. In one embodiment resilient buffers having a 'U' 30 section fit on opposite edges of the printed circuit board.

Corresponding pads are not provided in the attachment direction, so as to ensure that end loads on the printed circuit board, due to connection and disconnection of the

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plug, are taken through the suitable abutments of the printed circuit board and enclosure. Such abutments are positioned so as to relieve components of the printed circuit board from stress, and in one embodiment are the pedestals. Thus easy assembly, due to loose tolerancing, is assured, whilst subsequent engagement of the 5 abutment surfaces is permitted.

The pads tend to insulate the printed circuit board from loads transmitted through the wall of the enclosure, whilst providing sufficient friction to allow movement of the printed circuit board in the attachment direction without rattling. Slight endwise 10 movement of the printed circuit board may be allowed at each attachment and detachment of the plug.

A secondary advantage of the pads is that during assembly, the printed circuit board is retained in place in the base of the enclosure, and will not readily drop out if for 15 example a part-assembly is upturned before the lid is attached. This arrangement increases the possibilities for assembly.

Other features of the invention will be apparent from the following description of a preferred embodiment illustrated by way of example only in the accompanying 20 drawings in which:-

Fig. 1 is a plan view of an enclosure according to the invention;

Fig. 2 is an end elevation of an enclosure according to the invention;

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Fig. 3 is a plan view of the open enclosure showing a circuit board in position;

Fig. 4 is a view on line 4-4 of Fig. 3, showing the enclosure prior to closing thereof;

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Fig. 5 is an enlarged scrap section showing a mount for the circuit board;

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Fig. 6 is an enlarged scrap section showing an edge buffer for the circuit board; and

Fig. 7 is an enlarged plan view of a portion of the circuit board in relation to a 5 support pedestal.

With reference to Figs. 1 and 2, a somewhat rectangular box-like enclosure 10 comprises upper and lower clam shell mouldings (11, 12) of e.g. ABS. In this embodiment the mouldings are substantially identical and provide an enclosed space 10 for electronic equipment, in particular a printed circuit board and associated electrical components for use in vehicle diagnostics.

The mouldings may clip together and/or may have fixing screws as will be described below. The enclosure has an aperture (13) in one or both ends to permit attachment of 15 a cable via a connector of a plug/socket arrangement. The other end of the cable may attach to the OBD port of a vehicle electrical system, or to a computer or other electrical device.

The enclosure has a symmetrical waist (14) to permit it to be held comfortably in one 20 hand. The enclosure may also have apertures (not shown) adapted to reveal internal components such as warning lamps, switches, displays and the like, as required by design and circumstances of use.

Figs. 3 and 4 illustrate a typical internal configuration.

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The lower clam shell moulding 12 includes four upstanding pillars 21 which support a printed circuit board 31 in approximately the mid-plane of the enclosure 10. The circuit board has four corresponding holes 32 to receive a cylindrical spigot 22 of each pillar 21. The spigots 22 locate the circuit board laterally, in the X-Y plane, and are a 30 relatively loose fit so that some relative movement of the circuit board is possible. Whilst a precision sliding fit might be possible, the extra expense associated with tight tolerancing is not justified, and in any event might induce stresses to the circuit board on account of temperature variations of the enclosure, in use.

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The upper clam shell moulding also includes pillars 23 which engage over the corresponding spigots 22 to retain the circuit board in the Z direction. Fig. 4 illustrates that the mating edges of the clam shell mouldings 11, 12 may be 5 interengageable or somewhat serpentine to provide for resistance to entry of dust, moisture and the like.

As will be apparent from Fig. 4, the printed circuit board is a relatively loose fit in the Z direction, so as to avoid any risk of undue compressive pressure due to squeezing of 10 the circuit board between the pillars 21, 23; thus the height of the spigots 22 is slightly greater than the thickness of the circuit board 31, by e.g. 0.2 - 0.5mm.

A socket 33, 34 is mounted to each end of the circuit board for access through a corresponding aperture 13 in the enclosure. Within the socket, electrical connecting 15 pins are provided for mating within a corresponding plug. In use, in this embodiment, power and information is provided via a connection lead for the purposes of diagnosis of a vehicle electrical system. Another connection lead may connect the circuit board to a computer or the like, for example for conducting a vehicle emissions test. Alternatively a radio module 35 mounted on the circuit board may wirelessly provide 20 connection to such a computer.

Electrical components of the circuit board 31 are not illustrated but may extend above and below the board. A processor 36 may be provided, preferably at the opposite end with respect to a radio module 35 to minimize electrical interference.

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The clam shell mouldings may clip together and/or be secured conventionally by screws passing through clearance holes 24 in each one of a pair of the pillars, 21, 23 and engageable in suitably dimensioned attachment holes 25 of the other of the pillars 21, 23. The screws may be self-tapping in attachment holes 25.

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In use, as has been explained above, the circuit board 31 is retained loosely in the enclosure 10. Clearances in the X, Y and Z directions may be in the range 0.1 - 0.5 mm, and the circuit board may rattle in this condition. Whilst loose fitting ensures

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easy assembly and an unstressed circuit board, a rattling circuit board may place unnecessary loads on components of the circuit board and give a user an impression of a fault.

5 In order to take-up clearance in the Z direction, a compliant gasket or O-ring 26 may be placed over each spigot 22 prior to assembly of the circuit board 31 on the pillars 21, as illustrated in Fig. 5. The gasket or O-ring 26 should be sufficiently compliant to take-up the clearance in the Z direction without imposing a significant compressive load when the enclosure 10 is closed.

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Engaging and disengaging a plug with the socket will generally impose significant end loadings on the circuit board 31, which are reacted through the pillars 21 to the user's hand. It is desirable for the circuit board to be permitted to move in the Y direction so that the circuit board can abut directly the corresponding spigot 22 (Fig. 7). In this 15 condition the clearance of the holes 32 is taken up at one side. Forces in the X direction will generally exceed any clamping force exerted by the gasket 26 in the Z direction. The abutment illustrated in Fig. 7 ensures that compressive loads are taken via a known and predictable load path.

20 In order to provide controlled resistance to movement in the X direction, the circuit board 31 is provided with compliant pads 37 on either side in the region of the waist 14. These pads take up the clearance between the circuit board and the inner face of the enclosure, and allow for relative sliding of the circuit board 31 to take-up the clearance between the circuit board and the spigots 22. Friction holds the circuit 25 board in one or other end condition.

In one embodiment the pads 37 comprise short lengths of split elastomeric tubing, or a grooved cylinder of a resilient material, and are retained on the circuit board by the inherent resilience thereof. Other kinds of pad, for example silicone rubber deposits, 30 are also suitable.

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Connection and disconnection of a plug cause loads to be transferred from the circuit board 31 to the enclosure 10 in opposite directions, on the X axis. In use the pads 37 allow such movement to ensure corresponding abutment of the spigots 22.

It will be understood that the pads 37 are also effective in the Y direction, and give a more solid feel to the enclosure by resisting squeezing of the enclosure between fingers and thumb, notwithstanding that the wall thickness of the enclosure may be small.

Yet another advantage of the pads 37, is that the circuit board is retained in the lower clam shell moulding 12 during assembly, so that it may for example be upturned prior to attachment of the upper clam shell moulding 11. This feature allows different assembly possibilities having regard to routine attachment and positioning of components on or about the enclosure.

In one embodiment, the pads are short, in the region of necessary frictional resistance to movement, whilst resistant force when connecting the plug/socket.

15-25mm, so as to not presenting a achieve the significant

Claims

1. A hand held enclosure comprising a base and a lid, the enclosure having a planar printed circuit board therein sandwiched between pedestals of the base and lid, 5 the printed circuit board being loosely retained by said pedestals against movement within said enclosure, said printed circuit board having a socket mounted thereon for receiving a plug in an attachment direction in the plane of said printed circuit board, and a gasket being provided for one or more of said pedestals to take-up clearance perpendicular to the plane of said printed circuit board, wherein opposite resilient pads 10 at the edge of said printed circuit board respectively engage opposite internal surfaces of said enclosure so as to resist movement of the printed circuit board in the plane thereof and perpendicular to the attachment direction, but to allow positional adjustment in the attachment direction.

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2. An enclosure according to claim 1, and comprising a waisted, substantially rectangular box, said pads engaging said surfaces at the waist.

3. A enclosure according to claim 2, wherein said box is symmetrical.

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4. An enclosure according to any preceding claim, and having an end wall through which said socket protrudes.

5. An enclosure according to any preceding claim, and having oppositely directed sockets.

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6. An enclosure according to claim 5, wherein said sockets have a common connection/disconnection axis.

7. An enclosure according to any preceding claim, wherein a plurality of said 30 pedestals of one of the base and lid, engage corresponding apertures of said printed circuit board.

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8. An enclosure according to claim 7, wherein said plurality of pedestals each include a spigot at the free end thereof, said spigot passing through a corresponding aperture for engagement by a respective spigot of the other of the base and lid.

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9. An enclosure according to claim 8, wherein the base of each spigot defines a shoulder to support said printed circuit board at a pre-determined height in said enclosure.

10. An enclosure according to claim 8 or claim 9, wherein a said gasket is 10 provided over each spigot.

11. An enclosure according to claim 10, wherein each said gasket comprises a resilient O-ring.

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12. An enclosure according to any preceding claim, wherein said pads each comprise a 'U' section buffer adapted to resiliently engage the edge of said printed circuit board.

13. An enclosure substantially as described herein with reference to the 20 accompanying drawings.

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