GB2186630A

GB2186630A - Friction coupling for suspension and angular positioning of a movable unit relative to a fixed unit

Info

Publication number: GB2186630A
Application number: GB08703121A
Authority: GB
Inventors: Per-Roland Loow; Per Lundgren
Original assignee: Televerket
Current assignee: Televerket
Priority date: 1986-02-13
Filing date: 1987-02-11
Publication date: 1987-08-19
Also published as: SE8600630L; NO870504L; SE451875B; GB8703121D0; GB2186630B; SE8600630D0; NO870504D0

Abstract

A friction coupling for suspension and stepless angular positioning of a fixed unit relative to a movable unit comprises a plastic bushing fixed by means of lugs in a movable unit, e.g. a holder (5) for an LCD screen (4), and a steel or brass washer (12) fixed by lugs in a fixed unit, e.g. a casing (6) of a computer (1). The bushing and the washer are joined together to the unit by means of a rivet joint and biased by a spring washer. <IMAGE>

Description

SPECIFICATION Friction coupling for suspension and angular positioning of a movable unit relative to a fixed unit The present invention relates to a friction coupliny for suspension and stepless angular positioning of a movable unit relative to a fixed unit. More particularly, although not exclusively, it relates to a friction coupling for suspenmsion and stepless angular positioning of an LCD screen or like electronic display.

With present day technology LCD screens or displays are used to an increasing extent to display information from a computer or similar equipment. In special applications, such as number transmitters for telephones, or other similar equipment, where a display of information from electronic equipment is needed, the use of LCD screens is increasing at a very great rate.

A serious problem with LCD screens is that they are readable only in one defined direction and it is very important for the readability that the direction of the LCD screen may be adjusted accurately with respect to the present lighting conditions.

In order to solve this problem the screens are made adjustable about a horizontal axis, so that the user can position the screen angle to the desired angle. In this connection it is of utmost importance that the adjustment means is matched with the weight of the screen and that the friction torque of the friction coupling is suitably large, i.e. neither too little, as the positioning of the screen then may be changed inadvertently, nor too large, as the positioning gets stiff and difficult. Furthermore, the friction coupling should not change its friction torque in course of time, i.e. it should not get too loose in which case the screen is easily accidentally moved or too tight in which case the screen cannot be initially positioned with ease.

It is an object of the present invention to provide a friction coupling intended for an LCD screen, which coupling allows a smooth and stepless positioning of the LCD screen and wherein the wear in the coupling is low as well as the angular positioning can take place soundlessly.

In its broadest aspect the coupling comprises a plastic bushing journalled in a movable unit and a steel or brass washer, journailed in a fixed unit, the bushing and the washer being joined together to a unit by means of a rivet joint, the friction coupling being biased by a spring washer. The entrainment is accomplished in that the plastic bushing and the washer, respectively, have a shape like a wedge. The choice of material plastic against steel/brass provides a smooth and pleasant torque.

Thus, the invention relates to a friction coupliny for suspension and stepless angular positioning of a movable unit, e.g. an LCD screen, relative to a fixed unit, e.g. a number transmitter.

According to the present invention the friction coupling comprises a plastic bushing secured to the movable unit, a washer secured to the fixed unit, a rivet joint joining the plastic bushing and the washer to a unit, and a spring washer biasing the friction coupling.

Preferably the washer is either a steel washer or a brass washer.

Preferably the plastic bushing and the washer, respectively, are shaped like a wedge for mounting to the movable unit and the fixed unit, respectively.

The present invention will now be described in greater detail by way of example with reference to the accompanying drawings, wherein: Figure 1 is a side view of a number transmitter incorporating a preferred form of friction coupling in accordance with the invention; Figure 2 is a plan view of the number transmitter shown in Fig. 1; Figure 3 is a plan view of the washer which is a part of the friction coupling; Figure 4 is a side view of the washer shown in Fig. 3; and Figure 5 is an enlarged detail view of the area encircled in Fig. 4.

Referring first to Fig. 1, the number transmitter includes a friction coupling constructed in accordance with the invention. The number transmitter 1 comprises a keyboard 2 having a plurality of keys 3 and an LCD screen 4 contained in a holder 5. The holder 5 is connected to the number transmitter casing 6 via a friction coupling 7. It will be under- stood that the friction coupling made in accordance with the invention may be used in many other similar devices where alpha-numeric data are to be displayed from an electronic device, for example, an electronic typewriter, a small computer, like a home computer, or a portable computer, a so called briefcase computer.Furthermore, it is evident that the invention can be used not only in connection with LCD screens, but also in connection with other screens or other devices where an angular positioning is desired, e.g.

so called plasma screens.

In Fig. 2 the number transmitter 1 shown in Fig. 1 is shown as viewed from above. The LCD screen 4 is enclosed in a window 8 in the holder 5 in known manner and may be provided with illumination from below so as to enable satisfactory reading even in poor ambient lighting conditions.

In Fig. 3 the washer which constitutes part of the friction coupling 7 is shown. The washer 12 comprises a circular body 9 provided with a central aperture 10. Two wedges 11 are positioned on the body 9 diametrically opposite each other. The shape of these two wedges 11 will be more clearly appreciated from Figs. 4 and 5. The wedges 11 engage the corresponding grooves formed in the fixed portion of the number transmitter 1. In this way the washer 12 is prevented from rotating relative to the fixed portion, i.e. the casing 6 of the number transmitter. A bushing made of plastics material is similarly prevented from rotating relative to the movable portion viz. the holder 5 which contains the LCD screen 4 of the number transmitter.

A rivet is passed through the central aperture 1Q in the body 9 of the washer and through a corresponding aperture in the bushing and is then upset to make it impossible for the rivet to break free from the washer and the bushing.

A spring washer is provided between the rivet head and the bushing to force the bushing against the washer with a predetermined force. This spring washer is made of either steel or brass. This force is determined by the thickness of the spring washer. Thereby a friction torque results between the bushing and the washer, which prevents a change of the positioning of the LCD screen once it is adjusted.

It will be appreciated that the spring washer could equally well be provided between the washer and the inner part of the rivet in which case it will perform the same function.

With the combination of the bushing made of plastics material and the washer made of steel or brass, a relatively large resistance is obtained against starting a rotating movement, whereas, once the frictional force has been overcome, the rotating itself is somewhat easier. This facilitates the initial position of the LCD screen and prevents subsequent inadvertent changes in the position thereof.

Claims

1. A friction coupling for suspension and stepless angular positioning of a movable unit relative to a fixed unit, said friction coupling including:- (a) a plastic bushing secured to the movable unit; (b) a washer secured to the fixed unit; (c) a rivet joint joining the plastic bushing and the washer to a unit; and (d) a spring means biasing the friction coupling.

2. A friction coupling according to claim 1, wherein said washer is a steel washer.

3. A friction coupling according to claim 1, wherein said washer is a brass washer.

4. A friction coupling according to any one of the preceing claims, wherein the plastic bushing and the washer, are shaped like a wedge for respectively mounting to the movable unit and the fixed unit.

5. A friction coupling according to any one of the preceding claims, wherein the spring means is a spring washer.

6. A friction coupling according to any one of the preceding claims, wherein said movable unit is an LCD screen and said fixed unit is a number transmitter.

7. A friction coupling for suspension and stepless angular positioning of a movable unit relative to a fixed unit, constructed substantially as herein described with reference to and as illustrated in the accompanying drawings.