GB2122424A - Panel mounting electrical instrument casing assembly - Google Patents

Abstract

An instrument casing assembly has an outer casing 10 securable in an aperture in a panel 63 and an inner casing 11 which is a sliding fit through an aperture 26 in the front panel 19 of the outer casing. Plug and socket or edge connectors interconnect the inner casing and the outer casing between the rear panels of the casings. The outer casing 10 has only lateral side wall panels 12 and 13 and no upper and lower walls. The upper and lower panels 22 and 24 of the inner casing also form walls of the outer casing when the instrument is pushed right home. A lever 41 is a handle to withdraw the inner casing and pivots flush with the bezel 42 of the instrument front panel to lock the inner casing in position when fully inserted into the outer casing. A spring loaded latch 50 engages a protruding part 58 of the lever 41 to prevent accidental release. <IMAGE>

Description

SPECIFICATION Panel mounting electrical instrument casing assembly The present invention relates to a panel mounting electrical instrument casing assembly. Electrical instruments are commonly mounted behind panels in appropriate racking. There are various industry standard instrument casing sizes intended to fit corresponding standard panel apertures. One existing techniqueoffitting instrument modules into standard racking isto provide a two part casing assembly having an innercasing containing the electrical components ofthe instrument, and usually associated with the front panel ofthe complete instrument, and an outer casing in which the inner casing is a sliding fit. The outer casing can be secured permanently to the panel aperture ofthe racking and the instrument with its inner casing and front panel can be slid out from the outer casing for servicing and adjustments, etc.

A major problem with this double layer casing arrangement is the difficulty of obtaining satisfactory heat removal from the instrument, because the outer casing prevents air circulation from cooling the inner casing.

According to the present invention, a panel mounting electrical instrument casing assembly comprises an outer casing sized and arranged to be securable in a predetermined panel aperture, an inner casing for containing electrical components and circuitry of the instrument and being a sliding fit into the outer casing through a front panel ofthe outer casing, electrical connection means on a rear panel ofthe outer casing for making external electrical connections to the instrument, and plug and socket interconnection means on rear panels ofthe inner and outer casings arranged to inter-engage on pushing the inner casing fully into the outer casing to provide electrical interconnection between electrical components and circuitryintheinnercasing and said electrical connection means, said outer casing being formed with one pair only of opposed fro nt-to-rea r extending wall panels and said innercasing having a corresponding opposite pair of opposed front-to-rear extending wall panels which are arranged to co-operate with said one pair ofthe outer casing to provide also wallsforthe outer casing. With this arrangement, the plug and socket interconnection between the inner and outer casings enables the inner casing to be withdrawn from the outer casing without disturbing the external electrical connections made via the electrical connection means on the rear panel of the outer casing. Further, cooling of the instrument is considerably facilitated because at leasttwo ofthe front-to-rear extending walls ofthe inner casing itself are exposed and not covered by corresponding wall panels ofthe outer casing.

I Thus, the invention fu rther envisages an instrument having a casing assembly as described and including at least one heat dissipating electrical component mounted in close thermal contact with one of said corresponding opposite pair of opposed front-to-rear extending wall panels of the inner casing. Then, since the wall panel of the inner casing on which the heat dissipating component is mounted also forms a wall forthe outercasing, heat generated can more easily be removed.

Preferably, each of said one pair of wall panels of the outercasing comprises an extruded metal section formed with front-to-rear extending grooves, on at least one face thereof, shaped to receive and cooperate with self-tapping screws screwed into ends of the grooves to secure front and rear panels of the casing to said front-to-rear extending wall panels.

Then, where said grooves are formed on the outerface of each of said one pair of wall panels and the front panel of said outer casing extends outwardly of said one pair of wall panels to form flanges, very conve nientlyclamping elements may be provided slidable in said grooves to clamp the periphery of the predetermined panel aperture between the clamping elements and the flanges, to securethe outer casing in the panel aperture.

In a preferred embodiment, the assembly includes locking means on a front panel of said inner casing arranged to be adjustable between a closed position engaging the front panel of the outer casing and holding the inner casing fully pushed home into the outer casing, and an open position disengaging the front panel to permit the inner casing to be withdrawn from the outer casing, the locking means having a latching mechanism arranged to latch the locking means in a closed position. This arrangement can greatlyfacilitatethesecuring and removal of the inner casing and instrument from the outer casing when this is desired for adjustment or servicing. Hitherto the normal practice has beentosecurethefront panel of the inner casing against the front panel of the outer casing by means of screw fasteners.Preferably the locking means comprises a lever pivoted to the front panel of the inner casing about an axis in the plane thereof and having a tail portion extending behind the front panel and a hand grip portion extending in front ofthe front panel, when in the open position, the front panel ofthe outer casing having a rearwardlyfacing abutment surface engageable by said tail portion on rotating the leverto the closed position. Further, the latching mechanism may comprise a spring biased latch arranged to be depressed against said spring bias by part of said hand grip portion on rotating the lever into said closed position and to latch behind said partto hold the lever in the fully closed position.

Preferably the latch is releasable, to permit the lever to be rotated from the closed position, only by means of a predetermined tool. Then accidental release ofthe locking mechanism can be avoided although release is quick and easy if a suitable tool is available.

An example ofthe present invention will now be described with reference to the accompanying drawings in which: Figure lisa perspective view of a complete casing assembly illustrated mounted in a suitable panel aperture and with the inner casing partlywithdrawn; Figure 2 is a top plan view of the casing of Figure 1; Figure 3 is a cross-sectional view of the casing taken along line Ill-Ill of Figure 1; Figure 4 is a detailed perspective view of part ofthe front panels of the innerandoutercasingsillustrating the locking mechanism and showing the latch arrangement exploded for clarity; and Figure 5 is a part cross-sectional view of the front panels of the inner and outer casings illustrating the locking mechanism in the fully closed position.

Referring firstlyto Figures 1, 2 and 3, an instrument casing is illustrated formed of an outercasing 10 and an innercasing 11. The outer casing 10 is formed of a pair of metal extrusions 12 and 13. The cross-sectional shape ofthese extrusions is best illustrated in Figure 3. Each extrusion has lateral thicker edge portions 14 and 15 on the outerfaces of each of which are formed a pair of longitudinally extending grooves 16 and 17.

The grooves have a keyhole section as illustrated in Figure 3 and are arranged to receive self-tapping screws 18 which secure front and rear panels 19 and 20 of the outer casing.

Outer edges of the extrusions 12 and 13 are extended slightly inwardly relative to one another perpendicularly to the general plane of the respective extrusion to form flanges 21. The inner casing 11 is formed substantially as a rectangular section box having fourfront-to-rear extending panels 22, 23, 24 and 25. The inner casing is sized to form a sliding fit through an aperture 26 in the front panel 19 ofthe outer casing. Furthermore, the extrusions 12 and 13 formed the opposed front-to-rear extending wall panels of the outer casing are sized and shaped with theflanges 21 to receive and support the innercasing 11 as it is slid into the outer casing. However it can be seen from Figure 3 that the outer casing 10 has itself no integral upper and lowerwall panels interconnecting the extrusions 12 and 13.When the inner casing 11 is pushed fully home, the wall panels 22 and 24 ofthe inner casing form also exterior wall surfaces of the outer casing. This greatly facilitates cooling of heat generating components within the instrument which may be mounted on one of wall panels 22 and 24 as shown at 27.

Only one groove 17 in each portion 14,15 ofthe extrusions 12 and 13 is used for securing the front and rear panels. The second groove 16 may be used to receive a clamping member62which is slid into the groove and arranged to engagewith one end the inner face ofthe panel 63 of the racking in which the instrumentcasing is mounted. The clamping member 62 is forced againstthe panel 63 clamping it behind a peripheral flange 64 of the front panel 19 ofthe outer casing by means of a self-tapping screw 65 bearing againstthe other end of the member. Normally just two clamping members 62 are employed atdiametri cally opposed corners of the casing as shown in Figure 3.

The rear panel 20 of the outer casing has mounted thereon connectors 28, 29 and 30 which provide external electrical connections to the instrument.

However, connection between the connectors 28, 29 and 30 and the electrical components and circuitry within the inner casing 11 of the instrument is made by means of plug and socket or edge connectors 31 to 36, illustrated in Figure 2. Thus, electrical connection is madetotheinstrumentwhen theinstrumentis pushed fully home into the outer casing 10. However the instrument and the inner casing 11 can readily be withdrawn, disconnecting the connectors 31 to 36, without disturbing the external connections by means of connectors 28, 29 and 30.

Referring now to Figures 4 and 5, these illustrate the locking mechanism forsecuring the inner casing pushed fully home into the outer casing.

As shown in Figure 1,theouterfrontpanel ofthe instrument is constituted by a front panel 40 of the inner casing. The locking mechanism comprises a lever 41 pivoted to the front panel about a pin 48 and shown in the open position in Figures 1 and 4. Figure 4 showstheframe or bezel 42 ofthefront panel. When in the open position, the lever 41 provides a grip to enable the inner casing ofthe instrumentto be pulled out disconnecting the connectors 31 to 36 atthe rear.

The lever 41 is formed with atail portion 43 which extends rearwardly beyond the front panel bezel 42 when the lever is in the open position as illustrated in Figure 4. The lever can be pivoted between the open position illustrated in Figure 4 and a closed position illustrated in Figure where the leversubstantiallyfills a slot 44 provided in the bezel 42.

Figure 4 illustrates the bezel 42 of the front panel of the inner casing in relation to a lower portion of the front panel 19 ofthe outercasing when the inner casing is pushed only partly home. The front panel 19 isformed substantially as a frame encompassing the opening 26. The lower edge 45 ofthe frame has a cutaway portion 46which co-operates with the lever 41 when the inner casing is pushed fully home. Then, the tail 43 of the lever passes justoverthe upperface ofthe portion 46 (as illustrated in Figure 4), so that when the lever 41 is rotated anticlockwise in Figures 4 and 5,thetail 43 engages a rearwardlyfacing abutment surface 47 provided by the lower edge 45 of the frame.

Mounted in the bezel 42 of the front panel ofthe inner casing is a spring loaded latch 50 arranged to hold the lever 41 in the closed position. The latch 50 can slide againstthe loading of a compression spring 51 in a cavity 52 provided in a mounting block 53 formed in the bezel 42. The latch 50 is retained in position in the cavity 52 by means of a front panel 54 secured by projections 55 which are staked over. The latch 50 is formed with a bevel 56 at the bottom edge thereofwhich is arranged to be engaged by a correspondingly beveled leading edge 57 on a prot ruding part 58 of the lever 41,on rotating the leverto the closed position.

The part 58 of the lever41 is soformed that on pushing the lever into the closed position to lockthe inner casing into the outer casing,the latch 50 is lifted by engagement between the beveled surfaces 56 and 57 and then drops down again behind the part 58to latch the lever 41 in the closed position. When in the closed position, the lever41 appears to form part of the bezel 42.

To release the lever 41,a suitable tool is inserted undertheface plate 54to engage underthe latch at point 61 adjacent the exposed bevelled face 56 and lift the latch sufficiently to allow the lever to be with drawn. Afinger depression 59 is formed in the under face of the bottom part of the bezel 42 to permit a downwardly extending flange portion 60 of the lever 41 to be engaged and pulled out simultaneously with raising the latch 50. Aspecifically designed tool may be provided to engage and lift the latch 50to allow the inner casing to be removed. However, any tool which can be inserted underthe face plate 54to engage the bevel 56 can be used, such as a small screwdriver.On the other hand the bevel 56 is sufficiently inaccessible to avoid accidental release of the latch and thereby prevent accidental unlocking ofthe inner casing.

Onefurtheradvantage ofthe locking mechanism as described with reference to the accompanying drawings is thatthe entire mechanism is contained within the width ofthe usual bezel ofthefront panel ofthe instrument and thereby allows the front panel area available to beusedfordisplaysandcontrolsforthe instumentto be maximised.

The instrument provided in the casing assembly may include provision on the instrument front panel for adjusting one or more presettable operating parameters ofthe instrument. To avoid accidental or unauthorised alteration ofthe settings of these parameters, a set-up lock may be provided within the instrument behind the front panel or bezel and accessible only on unlocking the innercasing and slightly withdrawing itfrom the outer casing. The set-up lock can be switched to inhibitfurtheradjustment ofthe presettable parameters and lockthe settings. Then to change settings, the latch 50 must be released to allow the inner casing to be unlocked and withdrawn, so that the set-up lock can be switched out. The instrument is then pushed back into the outer casing to complete the connections at the rear ofthe casing, and the parameters can then be adjusted on the front panel. To lockthe parameters at the new setting, the instrument is again withdrawn, the set-up lock switched in again and the instrument pushed back and locked in position.

Claims (11)

1. A panel mounting electrical instrument casing assembly comprising an outer casing sized and arranged to be securable in a predetermined panel aperture, an inner casing for containing electrical components and circuitry of the instrument and being a sliding fit into the outer casing, to be supported thereby, through a front panel ofthe outer casing, electrical connection means on a rear panel of the outer casing for making external electrical connectionstothe instrument and plug and socket interconnection means on rear panels of the inner and outer casings arranged to inter-engage on pushing the inner casing fully into the outer casing to provide electrical interconnection between electrical components and circuitry in the inner casing and said electrical connection means, said outer casing being formed with one pair only of opposed front-to-rear extending wall panels and said inner casing having a corresponding opposite pair of opposed front-to-rear extending wall panels which are arranged to cooperate with said one pair of the outer casing to provide also walls forthe outer casing.

2. A casing assembly as claimed in Claim 1 wherein each of said one pair of wall panels of the outercasing comprises an extruded metal section formed with front-to-rear extending grooves, on at least onefacethereof, shaped to receive and cooperate with self-tapping screws screwed into ends ofthe grooves to secure front and rear panels of the casing to said front-to-rear extending all panels.

3. A casing assembly as claimed in Claim 2 wherein said grooves are formed on the outer face of each of said one pair of wall panels, the front panel of said outer casing extending outwardly of said one pair ofwall panels to form flanges, and clamping elements being providedslidableinsaidgroovesto clamp the periphery of the predetermined panel aperture between the clamping elements and the flanges, to securethe outer casing in the panel aperture.

4. A casing assembly as claimed in any of Claims 1 to 3 and including locking means on a front panel of said inner casing arranged to be adjustable between a closed position engaging the front panel ofthe outer casing and holding the inner casing fully pushed home into the outer casing, and an open position disengaging the front panel to permitthe inner casing to be withdrawn from the outer casing, the locking means having a latching mechanism arranged to latch the locking means in the closed position.

5. A casing assembly as claimed in Claim 4 wherein the locking means comprises a lever pivoted to the front panel oftheinnercasing about an axis in the plane thereof and having a tail portion extending behind the front panel and a hand grip portion extending in front of the front panel, when in the open position,thefrontpaneloftheoutercasing having a rearwardlyfacing abutment surface engageable by said tail portion on rotating the leverto the closed position.

6. A casing assembly as claimed in Claim 5 wherein its latching mechanism comprises a spring biassed latch arranged to be depressed against said spring bias by pair of said hand grip portion on rotating the lever into said closed position and to latch behind said part to hold the lever in the fully closed position.

7. Acasing assemblyasclaimed in Claim 6 wherein the latch is releasable, to permit the leverto be rotated from the closed position only by means of a predetermined tool.

8. A casing assembly as claimed in Claim 6 or Claim 7 wherein said lever is shaped to form, when in the closed position, part of the frame or bezel of the front panel of the inner casing of the instrument.

9. A panel mounting electrical instrument casing assemblysubstantiallyas hereinbeforedescribed.

10. An electrical instrument having a casing assembly as claimed in any preceding claim.

11. An instrument as claimed in Claim 10 and including at least one heat dissipating electrical component mounted in close thermal contact with one of said corresponding opposite pair of opposed front-to-rear extending wall panels ofthe inner casing.