GB2187720A - Capping or uncapping containers - Google Patents

Abstract

A device to prevent a plastics bottle from rotating during application or removal of a screw closure has a recess defined by opposed convergent surfaces within which the neck of the bottle is received whilst capping or uncapping is taking place. The foremost one, 28, of the two surfaces in the direction of rotation of the closure is provided with backwardly facing teeth, 32 arranged to engage the bottle neck with high friction; the rear most surface 30, however, is smooth so as to act as a cam surface which drives the bottle neck against the teeth. In this way the capping or uncapping head is made to generate at least a substantial part of the lateral force by which the bottle neck is urged against the teeth. <IMAGE>

Description

SPECIFICATION Capping or uncapping containers This invention relates to the capping or uncapping of screw closures onto or from containers, particularly (but not exclusively) plastics bottles.

In the automatic application of screw closures to plastics bottles, for example, PVC bottles for fruit squashes, it is known to use a circulating, tensioned beltto force the bottle neckagainsta friction lining of a shaped recess in a rotary starwheel. With the bottle frictionally held against rotation by the friction lining, a capping head is brought down onto a closure loosely placed on the bottle neck, and rotation of the capping head screws the closure into sealing position on the bottle; alternatively,the capping head may be arranged to presentthe closuretothe bottle neck.

With such an arrangementthefrictionaltorque provided to prevent rotation of the bottle is generated bythetension in the belt, which is necessarily substantial. The belt is brought into engagement with the bottle neck before the closure is engaged overthe neck and therefore at a time when the closure is notavailableto resistany distortion (in particular, ovality) ofthe neck caused by the lateral pressure of the belt. Thus, although the neck may because of its substantial material thickness and relatively small radius of curvature be the part of the bottle which is best able to resistthe belt pressure, some distortion may in factoccurand the capping head may therefore not be effective to screw the closure into position, or the closure may subsequently be unsatisfactory in operation.

Afurther difficulty encountered with this arrangement is that the length of the bottle neck which isavailableforengagementbythebeltisoften very limited, and may not allow sufficient room for location plates (or similar devices) to be provided above and below the belt in the neighbourhood of the anti-rotation arrangement to locate the belt vertically in position,i.e. longitudinally of the neck.

Afurther known method of capping a plastic bottle is used for PET (polyethylene terephthalate) bottles having support rings on their necks. The starwheel which carries the bottle for capping has a shaped recess in which the bottle neck is received below its support ring. The recess has no friction lining, but upwardly projecting teeth are formed around its periphery in a position to frictionally engage the underside of the support ring on the bottle neck.

Downward force exerted on the bottle during capping then drives the support ring against these teeth, and so generates the necessarytorque to prevent the bottle from rotating.

The latter method of capping requires a substantial top loading bythecapping headforthe required anti-rotation torque to be generated. For some capping operations, however, the top loading which can be used is small, for example to prevent bottle collapse or distortion and/orto avoid the need for high capping torques, and on such occasions this arrangement for preventing rotation of the bottle during capping is not satisfactory.

The present invention seeks to overcome or substantially reduce in a simple and inexpensive mannerthe shortcomings of the anti-rotation arrangements described above, and accordingly provides an anti-rotation device for a container, which has two opposed surfaces arranged to define an opening within which a portion ofthe container may be received and frictionally held whilst a screw closure is being rotated on the container, the surfaces being mutually convergent and shaped to engage the said container portion at spaced parts of its periphery, the surface which is foremost in the direction of rotation of the closure being arranged for high friction engagement with the container portion whereas the rearmost surface is arranged for low friction engagement therewith, such differential frictional engagement with the surfaces and the relative position of the surfaces causing thetorque generated on the container by the closure rotation to generate force to urge the container portion laterally into the opening and against the surfaces. Usually, the device will further include means for biassing the container portion laterally against the surfaces at least until such torque-generated lateral force is effective.

Thetorque-generated lateral force produced by the anti-rotation device exists only during capping, when the closure is available to resist distortion of the container if necessary; it is essentially independent ofthe degree of top loading (if any) by the capping head.

In orderthatthe invention may be more fully understood an anti-rotation device forming an embodiment thereof will now be described, by way of example, with reference to the accompanying drawings, in which Figure 1 shows the device as seen from above; Figure2 shows the device in side elevation and when in operation; Figure 3 shows the device in perspective view; and Figure 4 shows the recess ofthe device to an enlarged scale and as seen from above.

Referring nowto the drawings, a table 10 is rotatable in a clockwise direction about a vertical axis by a drive motor (not shown). Around its periphery the table is formed with recesses of which one is shown and indicated bythe reference numeral 12.

The recesses are vertically aligned with respective capping heads which movewiththetable and of which the head associated with the recess shown is indicated in general outline by the reference numeral 14.

Athin hold-in plate 16 ofgenerallyarcuate shape is mounted adjacent the table 10so as to present its concave inner edge 17 to the table periphery. The plate 16 is fixed in position angularly of the table, but radially of the table is capable of limited movement.

It is biassed by lightcompression springs 18to a forward limiting position at which it just clears the table.

The capping head 14 is arranged for vertical movement between a raised retracted position and a forward, operative position at which to engage a closure 19 (Figure 2) which is loosely placed on the neck 20 of a bottle 22 received within the recess 12.

Rotation of the capping head whilst engaged with the closure is thereby caused to screw the closure onto the neck in known manner, so as to close and seal the bottle for subsequent despatch and sale.

The capping head may be arranged to generate little or no top (i.e. downward) loading on the bottle, so asto minimise the risk of buckling or distortion of the bottle side wall and reduce the capping torque which is required.

Figures 3to 4 showthe recess 12 in greater detail.

The recess is defined by a thin stainless steel plate 24 which is screwed to the table 10 above a generally corresponding but somewhat larger recess 26 formed in the table. The recess 12 is open to the periphery ofthe table and is formed by two opposed but convergent surfaces so asto be generally v-shaped in plan view.

Of the two surfaces forming the recess, the one which is foremost in relation to the direction of rotation ofthe capping head 14andthe closure 19 is generally indicated by the reference numeral 28, the rearmost ofthetwo surfaces being generally denoted 30. The direction of rotation ofthe capping head is indicated by the arrow A. in Figure 1.

As can be seen from Fig ure 4 i n particular, the foremost surface 28 is straight but inclined by typically 15" to the table radius RR which passes through the centre of the recess 12. The part ofthe surface 28 which is operative during capping is formed by a series of teeth 32 which are provided by a detachable insert 34 of hardened stainless steel which is removably attached to the plate 24 by a screw 35. Preferably, as shown in Figure 1, the hole 36 formed through the insertforthe screw 35 is in the form of a slot, and the insert is adjustable in the direction towards and away from the recess 12 to accommodate different bottle neck diameters and/or to enable the operation of the device to be optimised.

In the described embodiment the teeth 32 are four in number. They are angled backwardly in relation to the direction of rotation A of the capping head so as to be best capable of resisting rotation of the bottle in that direction byfrictional engagementwiththe surface of the bottle neck as will become apparent.

The rearmost surface 30 of the recess 12 is partly straight and partly curved, the straight and curved parts merging smoothly with one another and being respectively indicated by the reference numerals 38,40 respectively in Figure 4. The curved part 40 meets the inner end of the surface 28 at an elbow42 forming the base of the recess 12. From the elbow 42 the curved part extends, in concave relation to the recess, to the junction at which it merges with the straight part 38. The straight part 38 is inclined to the radius RR by the same angle as the surface 28 but on the opposite side ofthe radius RR. (The radius RR is central in relation to the surface 28 and the straight part 38 of the surface 30).

Features ofthe arrangement other than these described above will become apparent from the following description ofthe anti-rotation device when in operation.

The bottle neck 20 is presented to recess 12 by relative movement of the bottle 22 and recess atthe right hand side of Figure 1, the surfaces 28,30 at the mouth ofthe recess providing any necessary centering action for the neck. Further peripheral movement ofthe table 10 to the left as shown in Figure 1 then carries the bottle neck againstthe rounded leading end of the concave inner edge 17 of the hold-in plate 16. The edge 17 is shaped so that as the table rotatesfurtherthe hold-in plate will urgethe bottle neck into the recess 12 and bias it resiliently againstthe surface 30 and the teeth 32 of the surface 28.The biassing force is light,forexample 5- 10 kg, but sufficient to ensurethat, when the capping head 14 is operative to rotate the closure 19 on the bottle neck in the direction of the arrow A, the capping torque as transmitted to the bottle neckwill cause the latterto becomefirmly wedged in the recess 12 by the differential frictional engagement of the surfaces 28,30. To achieve this the rearmost surface 30 is smooth so as to act as a cam surface which drives the bottle neck into firm engagement with the teeth 32; the teeth themselves act frictionally to preventthe bottle from rotating whilst acting in combination as a fulcrum about which the capping torque acts to drive the bottle firmly against the surface 30.During capping, therefore, a substantial part ofthe lateral force required to maintain the bottle neck in contact with the teeth 32 and so prevent the bottle from rotating is generated bythecapping head; in comparison, the contribution from the hold-in plate 16 is small.

After capping has been completed the capping head is lifted, and continued rotation ofthe table 10 brings the bottle neck beyond the trailing end ofthe hold-in plate. The closed and sealed bottle is then carried away by a suitable conveying device such as a take-off starwheel. The curved part 40 ofthe surface30 acts during capping to present a stop to excessive penetration ofthe bottle neck into the recess; following capping, it assists the ejection of the bottle neck from the recess by reaction against the neck when the PET material of the neck relaxes on removal ofthe capping torque.

Although specifically described in relation to capping plastics bottles and to use of a toothed friction surface, the invention may have application to uncapping operations, to screw-threaded containers otherthan bottles (e.g. jars), to containers otherthan of plastics materials (e.g. glass), and to use offriction surfaces other than teeth; for example, in one modificatiion of the described arrangement the metal insert 34 is replaced by a rubber lining which providesthe required friction surface.

Claims (7)

1. An anti-rotation device for a container, which has two opposed surfaces arranged to define an opening within which a portion of the container may be received and frictionally held whilst a screw closure is being rotated on the container, the surfaces being mutually convergent and shaped to engage the said container portion at spaced parts of its periphery, the surface which is foremost in the direction of rotation of the closure being arranged for high friction engagement with the container portion whereas the rearmost surface is arranged for low friction engagement therewith, such differential frictional engagement with the surfaces and the relative position of the surfaces causing the torque generated on the container by the closure rotation to generate force to urge the container portion laterally into the opening and againstthesurfaces.

2. A device according to claim 1 for a plastics container, wherein for making the said high friction engagement with the container portion the foremost surface has a plurality of backwardly directed teeth.

3. A device according to claim 1 wherein the foremost surface has elastomeric material for making the said high friction engagement with the container portion.

4. A device according to any preceding claim which further includes means for biassing the container portion laterally against the surfaces at least until such torque-generated lateral force is effective.

5. A device according to claim 4, wherein the bottle is moved along a predetermined path during the closure rotation and the biassing means comprises a resiliently mounted member having a cam face arranged to engage the containerwhilst travelling along the predetermined path, and to urge it resiliently against the surfaces.

6. A device according to any preceding claim, wherein the closure rotation is in the sense to screw the closure onto the container.

7. An anti-rotation device for a container, substantially as hereinbefore described with reference to the accompanying drawings.