GB2067651A

GB2067651A - Device for locking a sliding element relative to a bar

Info

Publication number: GB2067651A
Application number: GB8040217A
Authority: GB
Original assignee: Olivetti SpA
Current assignee: Olivetti SpA
Priority date: 1979-12-19
Filing date: 1980-12-16
Publication date: 1981-07-30
Also published as: FR2471865A1; DE8033674U1; FR2471865B1; IT7969436A0; IT1119615B; GB2067651B

Abstract

The device is suitable for locking a sliding element such as a pin-wheel drive unit for continuous, perforated forms relative to a bar 32 and includes a pair of abutment projections 40 and 41 on the element which are oppositely arranged relative to the bar 32. A locking lever 44 pivoted on the bar, carries at one end two semi- circular cam extensions 45, 46 of varying thickness which are disposed between the cross-bar and the abutment projections 40, 41. Rotation of the lever effects the locking of the drive unit relative to the bar by wedge action of the extensions 45, 46. <IMAGE>

Description

SPECIFICATION Device for locking a sliding element relative to a bar of an office machine The present invention relates to a device for locking a sliding element relative to a bar of an office machine which element may be a pin-wheel drive unit for continuous, perforated forms movable along a fixed crossbar to accommodate various paper widths.

A device is known in which a locking lever is hinged on a pin fixed laterally to the drive unit and has a slot eccentric relative to its pin in which the cross-bar is housed with some play. A spring stretched between the drive unit and the lever normally draws the lever towards a locking position. A handle enables the operator to release the lever, causing it to rotate relative to its pin, against the action of the spring.

This device has the drawback that, in the locking position, the force exerted by the spring on the fixed bar and on the drive unit in order to lock them mutually, tends to skew the drive unit relative to the fixed bar, with consequent misalignment of the drive unit relative to the continuous form and hence damage to the latter.

In addition, the parts of the driver which rotate relative to the fixed bar are also subject to considerable wear.

The object of the present invention is to provide a simple locking device, in which the forces are distributed over the fixed bar and on the sliding element in such a manner that they have no influence upon the correct positioning of the one relative to the other. The invention is defined in claim 1 below.

The invention will be described in more detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic plan view of two drive units for continuous, perforated forms in which a locking device embodying the invention is mounted; Figure 2 is a side view, partly in section, of the locking device; Figure 3 is a section along line 3-3 of Figure 2, on an enlarged scale, and Figure 4 is a magnified detail of Figure 2.

Referring to Figure 1 , the locking device is shown applied on a pair of drive units 10 and 11 of a continuous form 12 perforated close to the edges.

Each drive unit 10, 11 (Figure 2) comprises a pair of flanges 1 3 and 14, made of a plastics material, which have an elongated shape and enclose, by positive engagement, in any convenient manner, two pulleys 15 and 1 6 between which runs a belt 17, provided externally with drive studs 1 8.

The pulley 15 is a motor pulley and has a central hole 1 9 in which a square-section bar 20 is lodged, having its ends 21 and 22 rotatably mounted on the sides 23 and 24 of the machine.

The bar 20 is coupled, for example by means of a transmission belt 25, to an electric motor 26 which is used to control the rotation of the belts 1 7 and therefore the forward movement of the form 12.

The other pulley 1 6 has a hole 30 in which a cylindrical bar 32 is lodged, parailel with the bar 20 and fixed to the sides 23 and 24.

Each drive unit 10, 11, comprises in addition a pair of paper press plates 33, 34 hinged on the flanges 1 3 and 14 and kept horizontal by a spring 35 stretched between them.

The drive units 10 and 11 are slidable along the bars 20 and 32 in such a manner that their spacing can be adjusted by the operator in accordance with the width of the form 1 2 used.

The locking device comprises two abutments constituted by a pair of projections 40 and 41, fixed to the flange 13, which are also of plastics material, and which are oppositely arranged relative to the fixed bar 32. The projections 40 and 41 have their inner surfaces 42 and 43 coaxial with the bar 32 and separated by a distance R from the axis 48 of the bar 32 (Figure 4), where R is larger than the radius of the bar.

A lever 53, made of plastics material, is shaped in such a manner as to have, at one end, a handle 44 and, at the other end, two locking shoes for the bar 32, which consist of two semi-circular extensions 45 and 46.

The two extensions 45 and 46 have an internal profile 47 coaxial with the fixed bar 32 and an external profile 49 and 50 respectively, which is semi-cylindrical and has a radius R equal to the radius of the internal surfaces 42 and 43 of the fixed projections 40 and 41. The centres of the radii of curvature R of the external profiles 49 and 50 lie along a median axis 52 of the lever 53 and are equidistant from the axis 48. In this way the thickness of the projections 45 and 46 varies linearly from a minimum to a maximum. In particular, the minimum thickness of each extension 45, 46 is smaller than the distance between the fixed bar 32 and the internal surface 42, 43 of the corresponding projection 40, 41; while the maximum thickness is greater than this distance.In addition, it will be noted that nearest the handle 44 the thickness of the extension 45 is at its minimum, whilst the thickness of the extension 46 is at its maximum.

The operation of the locking device described above is as follows. In a first position, represented in Figures 2, 3 and 4, the lever 53 has the grip 44 raised. In this position, the extensions 45 and 46 are located with their minimum thicknesses interposed between the bar 32 and the projections 40 and 41. There is play between the projections 40 and 41 and the extensions 45 and 46 and between the internal surface of the latter and the bar 32. The drive units 10, 11 can therefore slide easily on the bars 20 and 32.

To lock the driver 10, 11 in the desired position relative to the bar 32, the lever 53 is rotated anticlockwise (Figure 4) about the bar 32, bringing the handle 44 into the position represented by dashes in Figure 4, which corresponds to the locking position. In this position, the extensions 45 and 46 of the lever 53 are situated with their greater thickness between the projections 40, 41 and the bar 32. The extensions 45 and 46 exert a pressure on the projections 40 and 41, pushing them both outwards, with equal force, and effect the locking of the driver 10, 11 relative to the bar 32. In this way the thrust exerted by the lever 53 in its locking position is transmitted to the bar 32 from diametrically opposed areas and with equal intensity, and has no influence upon the correct positioning of the drive unit 10, 11 relative to the bar 32.

The device described above may also be used to lock other members and sliding parts of an office machine relative to a matched-up element such as, for example, a writing head relative to the drive shaft or a sheet guide, or an inserting device for cards, or the like, relative to a fixed axis.

Claims

1. A device for locking a sliding element relative to a bar of an office machine, comprising a pair of abutment members fixed to the element and disposed in opposite positions relative to the bar, and a lever having a pair of extensions of varying thickness, between the abutment members respectively and the bar in an arrangement such that rotation of the level wedges the two extensions against opposite sides of the bar.

2. A device according to claim 2, wherein the abutment members are two projections of the said element.

3. A device according to claim 2, wherein the locking force exerted by the lever on the projections is symmetrical relative to the bar.

4. A device according to any of the foregoing claims, wherein the extensions are of substantially semi-circular section.

5. A device according to claim 4, wherein the radius of curvature of the internal surface of each extension has its centre along the axis of the bar, while the radii of curvature of the external surfaces of the extensions have their centres away from, and equidistant from, the said axis.

6. A device according to claim 5, wherein the radii of curvature of the internal surfaces of the projections and the radii of curvature of the external surfaces of the extensions are equal.

7. A device according to any of claims 4 to 6, in which the lever has a handle, and the two extensions have their minimum and maximum thicknesses respectively nearest the handle.

8. A device according to any of the foregoing claims, in which the bar is fixed and the said element comprises a drive unit for continuous and perforated forms.

9. A device according to any of the foregoing claims, wherein the bar has a substantially cylindrical section, and the internal surface of the extensions are coaxial with the cylindrical bar.

10. A device for locking a slidable element relative to a bar of an office machine, substantially as described, with reference to the accompanying drawings.