GB2296386A - Control panel assembly and spindle stabilising device - Google Patents

Abstract

A device (16) for stabilising a spindle (32) of a potentiometer or switch passes through an aperture (42) in a control panel (36). The device comprises a body (16) having a bore through which the spindle is slidably passable, and a flange which co-operates with the display panel (36) to maintain the device located in the aperture in use. The body is provided with gripping ribs projecting radially into contact with sidewalls of the aperture. The leading edges of the bore and ribs are shaped to aid insertion of the device and spindle. The device is useful in a control panel assembly (1) of an audio mixing console, the potentiometer being mounted on a pcb attached to the rear of the control panel. <IMAGE>

Description

CONTROL PANEL ASSEMBLY AND STABILISING DEVICE The invention relates to a control panel assembly and to a device for stabilising controls1 and particularly for stabilising spindles of control devices such as are used in potentiometer knobs used on analog mixing consoles or other apparatus, against excessive side to side movement (wobble).

Analog mixing consoles are used in sound recording studios, for example, to amplify and mix a plurality of audio input signals. Such consoles generally comprise a large number of controls such as potentiometers to enable gain control, for example, of different frequency bands in a signal. It is usual to mount the printed circuit board carrying much of the electronic circuitry including the controls to the underside of the front control panel of the console by using he controls such as potentiometers as part of the fixing solution.

Conventionally this is done using a threaded bush around a potentiometer spindle and a nut which is used to co-operate with the threaded bush to fix the potentiometer against the front panel of the console with the potentiometer spindle protruding through an aperture in the panel. However, potentiometers which carry a threaded bush and require a nut to lock them in position are relatively expensive.

It is also known to provide separate mounting screws to connect a circuit board to the underside of the control panel. In these systems, however, a control knob attached for example to a potentiometer spindle can wobble excessively due to the absence of the threaded bush and nut. To avoid this problem of wobble it is known to reduce the diameter of the apertures in the control panel through which the spindles of the controls must pass thereby to restrict the amount of movement of the spindles. However, the use of such small apertures requires each control device, such as a potentiometer or other variable devices, like variable switches for example, to be accurately located on a circuit board prior to mounting onto a console panel. This presents considerable difficulties in the manufacture and assembly of circuit boards and control apparatus.Another system is disclosed in GB 1373606 which uses the knob to fill the aperture in the front panel.

However, accurate location of the devices is again required in order to enable smooth rotation of the knobs in the apertures. Also, this system is unsightly since the apertures are visible in the front panel and the associated gap allows ingress of material into the apparatus. It is also noted that GB 1373606 does not provide for direct mounting of the potentiometers directly on a printed circuit board.

It is also known from US4495547 to provide a control panel assembly in which a stabilising device in the form of a bushing is used as a support for a potentiometer spindle at the point at which the spindle passes through an aperture in the control panel. The bushing extends into a cylindrical recess in the control knob so that the control knob must therefore be of a particular configuration having a suitable recess. The bushing also has a cylindrical barrel portion having a diameter adapted to closely match the inner diameter of the aperture in the panel. The aperture therefore must be accurately formed in both position and shape to receive the bushing.

According to the present invention there is disclosed a control panel assembly comprising a panel defining an aperture, a circuit board mounted in spaced relationship to the panel, a control device mounted on the circuit board and having an actuating spindle extending via the aperture into engagement with a control knob mounted slidably on the spindle, and an annular stabilising device defining a bore and coaxially mounted in sliding contact with the spindle, wherein the stabilising device comprises an annular body extending through the aperture and projecting from the panel towards the circuit board and an annular first end portion extending axially between the panel and the control knob and having a diameter greater than that of the aperture, and wherein the body comprises a plurality of circumferentially spaced gripping formations projecting radially into contact with the panel.

An advantage of such an assembly is that the gripping formations allow for tolerance in the aperture size, position and shape, the stabilising device being generally formed of a plastics material and dimensioned such that the gripping formations pass through the aperture as an interference fit.

Preferably the gripping formations comprise axially extending ribs.

Any misalignment or shape irregularity of the aperture can therefore be tolerated by deformation of one or more of the ribs during fitting.

Preferably the ribs have tapered end portions for ease of assembly through the aperture.

This elevates the problem of inserting the stabilising device within a closely fitting aperture as an interference fit.

Conveniently the ribs are circumferentially equispaced.

Preferably the first end portion of the stabilising device has an end face which is planar and abutted by a co-operating planar end surface of the control knob.

This has the advantage of allowing any conventional control knob to be utilised with the stabilising device in a control panel assembly, there being no specific adaptation of the control knob since it is common for such control knobs to have a planar end surface.

Preferably the end face of the stabilising device and the end surface of the control knob have substantially the same external diameter conforming to the maximum diameter of the control knob.

By this arrangement, the face to face contact between the end face and the end surface provides a seal preventing the ingress of dust or other contaminant, thereby effectively sealing the aperture.

Preferably the control knob defines a socket receiving the spindle having a depth which is greater than the axial extent of the spindle in the socket.

In use, the control knob will therefore be slidably received on the spindle in known manner and will be urged into face to face contact with the stabilising device, thereby absorbing any axial load placed on the control knob by contact with the stabilising device which in turn is supported by the panel. Axial loading to the control knob is therefore not transmitted to the spindle or to the control device.

Preferably the stabilising device is formed of a low friction material, thereby allowing the spindle to freely rotate and allowing the control knob to rotate freely.

According to a further aspect of the present invention there is disclosed a stabilising device comprising an annular body, an annular first end portion at one axial extremity of the body and having an enlarged diameter relative to the body, and a plurality of circumferentially spaced gripping formations projecting radially from the body.

The gripping formations preferably comprise axially extending ribs having a semicircular profile when viewed in axial projection.

Preferably the bore has a length of about 4mm and preferably in the range 5 to 6mm.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIGURE 1 is a cross-sectional, side elevation view of a stabilising device according to the invention; FIGURE 2 is a plan view from beneath of part of the device shown in Figure 1; and FIGURE 3 is a sectional view of the device shown in Figures 1 and 2 fitted in a control panel assembly of a mixing console.

Figure 1 shows a stabilising device 10 according to the invention which comprises a tubular body 16 through which passes a bore 12 having first and second openings 22 and 26 at opposite ends thereof. A first end portion 13 of the device has an annular flange 14 projecting radially from one end of the body 16. An outer cylindrical wall of the body 16 is provided with paraxially extending ribs 18. For example, five ribs might be equidistantly spaced around device 10. The lower end 20 of each of the ribs 18 is chamfered to enable the device 10 easily to be inserted in an aperture in a control panel 36 shown in Figure 3. The rim 24 of the first opening 22 can also be chamfered in order to allow device 10 easily to be placed over a spindle 32 of a control device such as a potentiometer.For example, chamfer angle A can be in the order of 30 as shown in Figure 1. The device 10 is in other words provided with a second end portion 33 defining a throat 35 of tapering cross section merging with the bore 12.

The stabilising device 10 can be made of various materials such as entirely of nylon for example. Alternative materials could be used and indeed, the device could be made from a number of materials each for different parts of the device. However, in order to minimise costs, a single piece device can be moulded from a single material. The overall length I of the device 10 is 5.7mm with a bore diameter of 6.05mm.

As shown in Figure 3 a printed circuit board 40 comprising a potentiometer 34 is spaced from the panel 36 using spaced connectors 38 attached to both the panel 36 and printed circuit board 40 by screws. In the absence of stabilising device 10 the spindle 32 would be able to wobble about a pivot located near the printed circuit board 40 due to the space between spindle 32 and sidewalls of the aperture 42.

The stabilising device 10 prevents such movement by filling the space between the spindle 32 and the sidewalls of the aperture to provide relatively rigid support for the spindle whilst at the same time allowing it to rotate about the spindle axis 44 thereby to effect a change in the resistance of the potentiometer 34. During assembly the stabilising device 10 is passed over the spindle 32 as shown in Figure 3 and passed through the aperture 42 in a control panel 36 of the audio mixing console. The ribs 18 are adapted to abut the inner rim of aperture 42 thus maintaining the device 10 in position whilst bore 12 is adapted to closely fit the spindle 32 thereby minimising the extent to which it can move readily away from central axis 44.

The spindle 32 has a free end 46 which is received in a cylindrical socket 48 defined within a control knob 30. The depth of the socket 48 is greater than the axial extent of the spindle within the socket so that the free end 46 is spaced from a blind end of the socket.

The control knob 30 has an end surface 50 which is planar and circular in profile, the outer diameter of the end surface being the maximum diameter of the control knob. The end surface 50 abuts in face to face contact a planar end face 52 of the first end portion 13, the end face 52 having an external diameter equal to that of the end surface 50 of the control knob such that a face to face seal is formed against the ingress of contaminant such as dust.

This face to face contact between the control knob 30 and the first end portion 13 imparts stability to the control knob by virtue of the peripheral contact therebetween and prevents the accumulation of dust under the periphery of the control knob.

Figure 3 therefore shows a control panel assembly 1 consisting of the control panel 36, the circuit board 40, a control device in the form of a potentiometer 34, a control knob 30 and a stabilising device 10. In use, the control knob 30 will be exposed to axial, radial and oblique forces during normal use and due to accidental impacts. The control panel assembly in accordance with the present invention prevents relative movement of the spindle and circuit board 40 in response to such forces since the spindle is supported against radial motion relative to the aperture 42 by the presence of the stabilising device 10 and axial forces on the knob 30 are applied only to the end face 52 of the first end portion 13 of the stabilising device.It would be apparent that the control knob 30 is required to be received as a push fit axially on the spindle 32, there being sufficient friction to retain the control knob against falling away from the spindle.

The diameter of bore 1 2 should not be such that spindle 32 is restricted from rotating about axis 44 when a user turns knob 30. A low friction material for body 1 6 is preferably used to enable the diameter of bore 12 to be minimised. The device 10 is additionally retained in position against panel 36 by flange 14 which acts on the upper surface of the panel as shown in Figure 3. Also, the length of bore 12 can be important to restrict wobble and is preferably as long as possible. The distance device 10, or aperture 42, is away from the lower pivot of the spindle is also important since the further apart they are the easier it is to reduce any wobble.

To assemble the system it is possible to assemble a circuit on a printed circuit board 40, attach the board to panel 36 and then attach device 10 to each spindle and insert into an aperture 42. The knob 30 can then be attached to the spindle.

Of course, device .10 might be used with other control devices such as variable switches, for example, and used in control panels electronic equipment other than audio mixing consoles.

Claims (15)

Claims:

1. A control panel assembly comprising a panel defining an aperture, a circuit board mounted in spaced relationship to the panel, a control device mounted on the circuit board and having an actuating spindle extending via the aperture into engagement with a control knob mounted slidably on the spindle, and an annular stabilising device defining a bore and coaxially mounted in sliding contact with the spindle, wherein the stabilising device comprises an annular body extending through the aperture and projecting from the panel towards the circuit board and an annular first end portion extending axially between the panel and the control knob and having a diameter greater than that of the aperture, and wherein the body comprises a plurality of circumferentially spaced gripping formations projecting radially into contact with the panel.

2. A control panel assembly as claimed in claim 1 wherein the gripping formations comprise axially extending ribs.

3. A control panel assembly as claimed in claim 2 wherein the ribs have tapered end portions for ease of assembly through the aperture.

4. A control panel assembly as claimed in any of claims 2 and 3 wherein the ribs are circumferentially equispaced.

5. A control panel assembly as claimed in any preceding claim wherein the first end portion has an end face which is planar and abutted by a co-operating planar end surface of the control knob.

6. A control panel assembly as claimed in claim 5 wherein the end face and the end surface have substantially the same external diameter conforming to the maximum diameter of the control knob.

7. A control panel assembly as claimed in any preceding claim wherein the control knob defines a socket receiving the spindle, the depth of the socket being greater than the axial extent of the spindle in the socket.

8. A control panel assembly as claimed in any preceding claim wherein the stabilising device is formed from a low friction material.

9. A control panel assembly as claimed in any preceding claim wherein the stabilising device comprises a second end portion defining a throat of tapering cross section merging with the bore.

10. A stabilising device for use in a control panel assembly as claimed in claim 1, the stabilising device comprising an annular body, an annular first end portion at one axial extremity of the body and having an enlarged diameter relative to the body, and a plurality of circumferentially spaced gripping formations projecting radially from the body.

11. A stabilising device as claimed in claim 10 wherein the first end portion has a planar end face orthogonal to the axial extent of the body.

12. A stabilising device as claimed in any of claims 10 and 11 wherein the gripping formations comprise axially extending ribs.

13. A stabilising device as claimed in claim 12 wherein the ribs have a substantially semicircular profile when viewed in axial projection.

14. A control panel assembly substantially as hereinbefore disclosed with reference to and as shown in Figure 3 of the accompanying drawings.

15. A stabilising device substantially as hereinbefore disclosed with reference to and as shown in any of the accompanying drawings.