GB2259511A

GB2259511A - A method of forming cullet from glass in sheet or ribbon form

Info

Publication number: GB2259511A
Application number: GB9119648A
Authority: GB
Inventors: Robert Paul Briggs
Original assignee: Pilkington PLC
Current assignee: Pilkington Group Ltd
Priority date: 1991-09-13
Filing date: 1991-09-13
Publication date: 1993-03-17
Also published as: GB9119648D0

Abstract

A conveyor (11) conveys glass sheet or ribbon towards a breaking unit (15); bar (23), to which are attached cutting units (32), is caused to reciprocate transversely across the glass sheet or ribbon, the cutters (44, 45) forming one set of parallel score lines (60, 62) in one direction of travel of the bar (23) and a further set of score lines (61, 63) during the return movement of the bar (23), thus producing a diamond pattern across the whole width of the glass. The formation of this diamond pattern, on the glass, reduces the stress needed in the breaker unit (15) and thereby much less noise is generated during fracture. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO GLASS CUTTING The invention relates to glass cutting and more particularly to scoring glass prior to breaking glass in sheet or ribbon form to form cullet.

In the production of glass in sheet or ribbon form it is known to inspect glass and that which is rejected may be broken to form cullet which in turn is resupplied to a glass melting tank for use in further glass production. Commonly glass is conveyed in a horizontal plane in sheet or ribbon form below an inspection station where the glass is checked for visible defects. Sections of the sheet or ribbon which do not pass the examination are marked and cut so as to separate the defective regions from those which have passed examination and are subsequently supplied in sheet form of desired size.

The rejected glass may be passed to a sheet breaking device such as that described in our US Patent No 4076159. The rejected glass is broken into small pieces by application of crushing forces to the glass and the broken fragments fall into a hopper below the level of a conveyor conveying the glass to the breaking unit. The crushed glass is collected in the hopper and then conveyed to the input of a glass melting tank.

Operation of such breaking apparatus to fragment rejected glass causes substantial noise due to the stresses which must be induced in the glass in order to fracture it into small pieces. Various proposals have previously been made to produce the noise which is transmitted externally of such a breaking unit.

It is an object of the present invention to provide apparatus and methods for treating rejected glass prior to entering a breaking unit such that less stress need be Indoe into the glass in order to fracture it and thereby generate less noise during fracture.

The invention provides a method of forming cullet from glass in sheet or ribbon form, which method comprises effecting relative movement between a glass sheet and an array of cutters extending transversally across a direction of transport of the glass sheet to a cullet collection station, said relative movement being both in a first direction along the direction of transport of the glass sheet and in a second direction across the said direction of transport, operating the array of cutters during said relative movement to form a first set of score lines extending in one direction between said first and second directions and to form a second set of score lines extending in another direction between said first and said second directions, said one direction and said another direction being arranged to intersect each other.

Preferably said first and second sets of score lines have a path length such that they intersect each other.

Preferably all cutters in the array are operated simultaneously.

Preferably the relative movement in said second direction is obtained by reciprocating movement of the array of cutters across said direction of transport whereby each cutter forms score lines in each of said first and second sets of score lines.

Preferably each set of score lines includes score lines formed simultaneously by cutters displaced from each other along the direction of transport of the glass sheet whereby each set of score lines comprises a similar pattern of score lines formed simultaneously at positions spaced along the direction of transport.

Preferably the two sets of score lines form a diamond shaped set of score lines.

Preferably a plurality of diamond patterns are formed side-by-side across the glass sheet in a direction transverse to the direction of transport.

Preferably the glass sheet is held in a damping device between the array of cutters and a sheet breaking unit to prevent vibrations from fracture operation extending through the sheet to the scoring operation.

The invention also provides apparatus for forming cullet from glass sheet or ribbon which apparatus comprises a glass breaking unit for breaking glass into small pieces for cullet, a transport system for supporting a glass sheet and moving it in a direction of transport to said breaking unit, a cutter array having a plurality of scoring devices extending across said transport system in a direction across the direction of transport, and reciprocating means for effecting relative movement between said scoring devices and a glass sheet supported by the transport system so as to form a plurality of score lines in more than one direction across the glass sheet inclined to the direction of transport.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 is a view from above of a sheet scoring and fracturing apparatus in accordance with the present invention Figure 2 is a section on the line II-II of Figure 1, Figure 3 is a view of a dual cutter carriage she in Figure 1, Figure 4 shows an end bearing and drive cylinder for a cutter bar of Figure 1, Figure 5 shows an end mounting unit for a damping bar used in Figure 1, Figure 6 is a section through a single cutter of Figure 1, and Figure 7 is an enlarged view of part of the arrangement shown in Figure 1 illustrating a diamond score pattern formed by operation of the apparatus.

The apparatus of Figure 1 comprises a horizontal conveyor 11 comprising a plurality of rows of conveyor wheels 12 arranged to convey a sheet or ribbon of glass 13 lying in a horizontal plane past an examination booth 14 which extends transversely across the direction of transport of the glass on the conveyor 11. The conveyor 11 leads to a glass fracture or breaking unit 15 mounted at the end of the conveyor 11 over a hopper 16 for collecting broken glass in the form of cullet.

Glass may be conveyed from the hopper 16 to the input of a glass melting tank for re-use. The glass breaking unit 14 is of conventional construction and may comprise a plurality of rotary crushing members arranged to apply stress to fracture the glass so that it breaks into small pieces prior to falling into the hopper 16. The unit 15 may include sound absorbing walls and roof to minimise the noise emitted from the housing as the glass is broken inside the housing.

The examination booth 14 has secured thereto an access platform 20 extending over the glass ribbon 13. Mounted cn the access platform 20 is a cutter assembly 21 having an array of cutters extending transversely across the ribbon perpendicular to the direction of transport of the glass on the conveyor 11. The cutter assembly 21 is mounted horizontally and parallel to a damping bar 22 which extends over the glass ribbon immediately prior to entry into the breaking unit 15. The bar 22 is parallel to the cutter assembly 21 and extends horizontally.

The structure of the cutter assembly is shown more clearly in Figures 3, 4, 6 and 7. A bar 23 of rectangular cross-section extends across the full width of the glass ribbon 13 and projects at both sides of the glass ribbon. The projecting ends of the bar 23 are each mounted in respective bearing assembly 25 as shown in Figure 4. The bearing assembly comprises a housing 26 with four upper wheels 27 and four lower wheels 28 arranged to engage the bar 23 as it reciprocates in a sliding movement through the housing 26. At the left-hand side only as seen in the direction of transport of the glass ribbon, the bearing assembly 25 is provided with a drive piston and cylinder device 29 having a piston connected by a coupling 30 to the bar 23. The cylinder is fixed at 31 to the housing 26 which is in turn secured to the platform 30. In this way, operation of the hydraulic piston and cylinder 29 causes the bar 23 to reciprocate horizontally.

Mounted at equally spaced intervals along the length of the bar 23 are six cutter carriages 32. Each cutter assembly is in the form of a trolley 33 mounted on four free rotatable wheels 34. The trolley 33 has two guide walls 35 and 36 which are arranged to engage in sliding contact with opposite side walls of the rectangular bar 23. The upper face of te bar 23 is provided with an elongated channel 38 and each trolley 33 is provided with a clamping bolt 29 passing through an upper wall 40 of the trolley with a retaining nut 41 located in channel 38. Rotation of the clamping bolt ray aster tre no 41 in the channel 38 so as to clamp the trolley in the desired longitudinal position along the bar 23 when the trolley has been adjusted to the required position.Each trolley has an upstream cutter 44 and a downstream cutter 45 mounted on the upstream and downstream edges of the trolley. Each cutter is of similar construction and comprises a cylindrical body 47 secured to an upstream or downstream wall of the trolley with an inner slidable tube member 48 on which is mounted a cutting wheel 49 at its lower extremity. The tube 48 is connected to an oil reservoir 50 for providing cutting oil to the cutting wheel 49. The wheel 49 is mounted off-centre from the axis of a pillar post 51 which is rotatably mounted within a socket 54 at the lower end of the tube 48. The vertical position of the piller post 51 is adjustable under pneumatic pressure from inlet and outlet apertures 52 and 53. The post 51 is also spring-mounted by use of a compression spring 55 surrounded by an adjusting nut 56.The nut 56 may be adjusted to compress the spring 55 to achieve the desired cutting load. In compressing the spring 55 the tube 48, socket 54 and cutter 49 are urged downwardly relative to the body 47 so that the cutter 49 engages the glass surface to effect a scoreline.

The maximum cutting load which can be achieved by compression of the spring 55 is determined by the proportion of the dead weight of the cutter beam assembly over each of the cutter wheels 49. The spring 55 can be compressed to provide a cutting load up to that proportion of the dead weight. The pneumatic supply through the apertures 52 and 53 is used to raise the cutter 49 and tube 48 against the downward action of the compressed spring 55 when it is not required to effect a scoreline. As the adjustment nuts 55 for the cutting load are externally accessible the load can be adjusted as required without stopping operation of the cutting system.

The post 51 is freely rotatable relative to the socket 5; so that as the cutting wheel 43 is mounted off-centre the cutters can be moved in any direction across the surface of the glass ribbon with free rotary movement of the pillar 51 to allow the cutting wheel 49 to lie in the plane of movement of the cutter relative to the glass ribbon. The relative movement between the ribbon and the cutter will automatically cause the pillar 51 to rotate until the cutting wheel 49 is lying in the correct plane to effect a score line on the surface of the glass ribbon along the direction of travel of relative movement between the glass ribbon and the cutter.

As can be seen from Figures 1 and 7, the cutter units 32 are mounted at equi-distant positions along the bar 23 and the separation between adjacent cutter units is equal to the reciprocating travel of the piston and cylinder device 29 which is driving the bar 23 in a reciprocating movement through the end bearings 25.

In use glass is conveyed by driven rollers in the conveyor 11 in the direction of transport towards the housing 15 and the bar 23 is caused to reciprocate transversely across the ribbon with the vertical height of the cutters adjusted so that each of the cutting wheels 49 forms a score on the surface of the glass when examination in the examination booth 14 has indicated that the section of glass leaving the examination booth is defective and is to be scored ready for breaking into cullet.

Figure 7 shows only one half of the width of the glass ribbon but the score pattern formed on the other half is the same as that shown in Figure 7. From this it can be seen that all the cutters are operated simultaneously with the upstream cutters 44 forming a set of parallel score lines 60 indicated in solid lines during one direction of travel of the bar 23 and a further set of score lines 61 indicated in soiiv ines during the return movement of the bar 23. The acwr.s~e~.

cutters 45 form similar lines 62 which are parallel to the lines 60 during one direction of travel of the bar 23 and a further set of score lines indicated by broken lines 63 during the return movement of the bar 23. It can be seen from Figure 7 that all the lines 60, 61, 62 and 63 are inclined across the glass ribbon between the direction of transport of the glass ribbon and the transverse direction in which the bar 23 is recipricated. The score lines formed during opposite preciprocating movements of the bar 23 are formed in directions which intersect each other.The length of travel of the bar 23 is so arranged in relation to the spacing between the separate cutter assemblies that the score lines formed by the upstream and downstream cutters meet so as to form a plurality of intersecting score lines having a diamond pattern across the whole width of the glass ribbon to be broken into cullet.

The scored glass leaves the cutter region on the conveyor 11 and passes under the damper bar 22. The bar 22 has mounted on it at spaced intervals along its length a ball castor 70 immediately above a corresponding wheel 12 of the conveyor 11. In this way the glass ribbon passes between the castors 70 and wheels 11 of the conveyor entering the breaker unit 15. At opposite ends of the bar 22 it is mounted on an assembly as shown in Figure 5. The bar 22 is mounted on a frame 71 secured to the housing 15 and having a screw jack 72 rotatable in a nut 73 fixed to the bar 22 so that rotation of the jack 72 may cause the bar 22 to rise or fall against upper and lower compression springs 74 and 75 mounted on the frame 71. In this way the bar 22 is adjusted by the jack 72 but is resiliently mounted by virtue of the springs.The height adjustment of the bar 22 is controlled so that the ball castors 70 press the ribbon against the conveyor wheels 12 and absorb vibration which may be induced downstream in the braking unit 15. This acts to dampen any vibraticn in the glass ribbon induced by the breaker unit 50 and prevent those vibrations affecting the scoring operation by the cutter assemblies.

It is found that the formation of a multiple diamond pattern over the full width of the ribbon which is to be broken, particularly where the diamonds are of relatively small dimensions in relation to the width of the ribbon so that a plurality (in this case six) diamonds are formed across the width of the ribbon, the stress needed to break glass in the breaker unit 15 is much reduced with corresponding noise reduction during the fracturing operation.

The invention has not been limited to the details of the foregoing example.

Claims

1. A method of forming cullet from glass in sheet or ribbon form which method comprises effecting relative movement between a glass sheet and an array of cutters extending transversely across a direction of transport of the glass sheet to a cullet collection station, said relative movement being both in a first direction along the direction of transport of the glass sheet and in a second direction across the said direction of transport, operating the array of cutters during said relative movement to form a first set of score lines extending in one direction between said first and said second directions and to form a second set of score lines extending in another direction between said first and said second directions, said one direction and said another direction being arranged to intersect each other.

2. A method according to claim 1 in which said first and said second sets of score lines have a path length such that they intersect each other.

3. A method according to claim 1 or claim 2 in which all cutters in the array are operated simultaneously.

4. A method according to any one of the preceding claims in which the relative movement in said second direction is obtained by reciprocating movement of the array of cutters across said direction of transport whereby each cutter forms score lines in each of said first and said second sets of score lines.

5. A method according any one of the preceding claims in which each set of score lines includes score lines formed simultaneously by cutters displaced from each other along the direction of transport of the glass sheet whereby each set of score lines comprises a similar pattern of score lines forked simultaneously at positions spaced along the direction of transport.

6. A method according to any one of the preceding claims in which the two sets of score lines form a diamond shape set of score lines.

7. A method according to any one of the preceding claims in which after scoring, the glass sheet is moved to a sheet breaking unit to fracture the scored sheet to form cullet.

8. A method according to claim 7 in which the glass sheet is held in a damping device between said array of cutters and said sheet breaking unit to prevent vibrations from the fracture operation extending through the sheet to the scoring operation.

9. Apparatus for forming cullet from glass sheet or ribbon which apparatus comprises a glass breaking unit for breaking glass into small pieces for cullet, a transport system for supporting a glass sheet and moving it in a direction of transport to said breaking unit, a cutter array having a plurality of scoring devices extending across said transport system in a direction across the direction of transport, and reciprocating means for effecting relative movement between said scoring devices and a glass sheet supported by the transport system so as to form a plurality of score lines in more than one direction across the glass sheet inclined to the direction of transport.

10. Apparatus according to claim 9 in which the cutter array comprises a plurality of devices mounted for linear reciprocating movement across the direction of transport while a sheet is moved in the direction of transport toward the breaking unit.

11. Apparatus according to claim 9 or claim 10 in which each scoring device comprises a planar cutter freely rotatable about a vertical axis so that the plane of the cutter may lie in the direction of relative movement of the cutter and glass sheet.

12. Apparatus according to claim 11 in which each planar cutter is mounted on a support rotatable about said vertical axis at a position off-set from said vertical axis so that relative movement between the cutter and the glass sheet causes the cutter to rotate the support to a position where the plane of the cutter lies in the direction of relative movement.

13. Apparatus according to any one of claims 9 to 12 in which the cutter array comprises two banks of scoring devices extending across the direction of transport, one bank being located upstream of the other.

14. Apparatus according to claim 13 in which the scoring devices of the upstream bank are aligned in the direction of transport with the scoring devices of the downstream bank.

15. Apparatus according to any one of claims 9 to 14 in which the scoring devices are separated across the direction of transport by a distance which is at least equal to the the length of reciprocating travel of the scoring devices.

16. Apparatus for forming cullet from glass sheet or ribbon which apparatus is substantially as hereinbefore described with reference to the accompanying drawings.