SE465672B - PROCEDURE SHOULD CUT GLASS WITH DIFFERENT THICKNESS MEANS A GRINDING FLUID DRAW - Google Patents

Description

465 672 10 15 20 25 30 35 2 why such openings usually have to be made by means of a diamond drill.

This method is effective in cutting relatively thin glass, whereby, due to the depth of the marking line relative to the total glass thickness, the refraction will follow the marking line. However, when cutting thicker glass by this method, the breaking line may not follow the marking line, so that an uneven edge is formed, or the glass may in fact be broken along a random line which destroys the glass sheet. The difficulty of cutting increases as the thickness increases, which is why cutting very thick glass is time consuming and expensive and the production of usable glass is relatively small. The method also means that a sharp edge is left at the surface opposite the marking line, which is a disadvantage during subsequent manufacturing steps.

Other methods, such as so-called hot line cutting, in which the glass is heated along a line and then cooled to achieve refraction along the line, and cutting with a diamond saw, have been proposed for cutting glass and especially thick glass. However, nothing has been shown to give completely satisfactory results in commercial operation, and especially not in the production of other than straight line cuts.

Such procedures tend to be slow and expensive and can create undesirable stresses in the glass. They are also not easy to adapt to cutting complex shapes in glass.

Cutting of different materials by means of a liquid jet is previously known, as is the use of abrasive particles in cooperation with the liquid jet. Although it is suggested, for example in US-A-3 888 054, that hard or brittle materials, such as glass, may be cut by a flow of abrasive particles which are transported in a fluid, it is also shown that the workpiece should be immersed in a liquid for avoiding sanding of the surface next to the cutting line. US-A-4 380 138 discloses cutting by means of an abrasive liquid jet, abrasive particles being placed adjacent to the surface of the material to be cut and then driven into the workpiece by the liquid jet, and indicating that it previously it was unknown to add abrasive particles directly to high speed liquid cutting jets. The prior art has in any case not provided cutting of glass by means of an abrasive fluid jet in the manner and at the pressure contemplated by the present invention.

Thus, it has been found that when flat glass sheets of a thickness used in ordinary commercial application are initially exposed within its periphery to an abrasive fluid jet which is pressurized to a level substantially exceeding 68.9 MPa (10,000 psi), as in the formation of holes or internal cutouts in the glass, it is likely that severe cracking or splitting of the glass occurs at the point of impact. The cracks and split edges may extend into the adjacent glass portion and render it unusable for its intended purpose. Accordingly, it has hitherto generally been considered necessary that such large-scale cutting be performed by means of a fluid under a pressure of the order of 68.9 MPa (1000O psi) or less in order to prevent damage to or destruction of the glass.

The line or cutting speed is a function of the degree of pressurization of the grinding fluid, and at this pressure the cutting speed is so limited that it makes the method marginally useful for commercial use.

It has now been determined that cutting can be advantageously accomplished by the abrasive fluid jet, which is pressurized to a much higher level, with a concomitant increase in line or cutting speed, while still obtaining cut edges of acceptable quality, which edges are equivalent with those previously obtained at the lower pressures. Grinding of the glass along the cutting line by the advanced jet occurs more precisely in the ideal case with the abrasive fluid jet pressurized to a level of the order of 137.8-241.15 MPa (ZOOOO-35000 psi) and preferably about 206.7 MPa (3000O psi), whereby cut edges of acceptable quality can be obtained at greatly increased line speeds for all glass thicknesses. However, pressures well above 241.15 MPa (35,000 psi) can result in cut edges of inferior quality regardless of line speed.

Thus, in accordance with the present invention, it is intended that chilled glass of various thicknesses should be able to be cut along any desired line, from straight lines to intricate shapes, relatively quickly and inexpensively with a resulting high quality edge grinding. The glass is therefore firmly supported along the line to be cut and a high velocity fluid jet, in which a fine abrasive is sucked in carefully controlled amounts, is directed towards the glass surface in an extremely parallel flow. Where the cutting is to begin at one edge of the glass sheet, i.e. the initial contact with the glass begins at an exposed edge, the abrasive fluid jet is discharged under the normal high working pressure and moved towards and into engagement with the glass to begin cutting at the free edge at a line speed, at which cut edges of acceptable quality are produced.

Where the initial penetration on the other hand is to take place in the interior of the disc, the fluid is discharged under a reduced inlet pressure level during the initial penetration of the glass, so that the cutting begins without unnecessary cracking or complete splitting of the glass at the point of insertion. the considerably higher level, as the cutting progresses to achieve maximum cutting or line speed with resulting cut edges of the desired high quality. It will be appreciated, of course, that although the invention has been shown and described herein to effect relative movement between the fluid jet and the glass by moving a nozzle assembly relative to a stationary glass sheet, the relative movement may likewise be effected by movement. of the glass relative to an immobile nozzle assembly or by combined movements of the two.

It is therefore a primary object of the invention to cut glass by means of an abrasive fluid jet.

Another object of the invention is to provide a method intended for cutting glass, in which abrasive particles are sucked into the fluid jet or flow before its discharge towards the glass.

Another object of the invention is to provide such a method in which the abrasive fluid jet strikes directly against the exposed glass surface.

Another object of the invention is to provide a method for accurate and precise cutting according to any desired pattern, from simple to complex, from a glass blank.

Yet another object is to maximize the line speed when cutting glass by means of an abrasive fluid jet.

These and other objects, which will appear from the following description, have now been achieved by a method according to the invention, which is defined in the following claim 1. Preferred variants of this method are stated in the following dependent claims.

The invention will be described in more detail in the following with reference to the accompanying drawings.

Fig. 1 is a schematic perspective view of a unit for practicing the invention. Fig. 2 is a vertical projection view on a larger scale, which from the side and partly in section shows a jet nozzle assembly, which is used in cutting glass by means of an abrasive fluid jet.

Fig. 3 is a diagram showing the relationship between the cutting or line speed and the grain size of the abrasive particles for a particular glass thickness. Fig. 4 is a graph showing the relationship between the cutting speed and the glass thickness of a particular grain size of the abrasive particles.

Fig. 1 schematically shows at 10 a unit which can be used in cutting glass sheets in accordance with the invention. More specifically, this unit is intended for cutting glass sheets or blanks along prescribed lines of any preferred shape and has an optical follower device 11 and a device 12 for cutting by means of an abrasive fluid jet.

The cutting device 12 has a support table 13, which is intended to firmly support a glass sheet S, for example on a sacrificial support plate, for cutting, as will be described in more detail in the following. Although the unit shown represents a preferred embodiment for practicing the invention, the invention is not, as will be readily appreciated, limited to use with such a unit, but may also be used with other and different equipment.

In the embodiment shown, the device 12 for cutting by means of a fluid jet has a discharge or nozzle assembly 14, which will be described in more detail in the following and which is mechanically connected to the optical tracking device 11 by means of a cross bar 15. The tracking device 11 is arranged for control of the movement of the nozzle assembly 14 in accordance with a stencil or pattern 16 on a plate part 17, which is mounted on a work table 18. The optical tracking device 11 is attached to a carriage 19, which is slidably mounted on an elongate transverse groove 20, which at its opposite ends are provided with two carriages 211 and 22. The carriages 21 and 22 are slidably mounted on parallel grooves 23 and 23, respectively. 24, which are supported by support elements 25 on a floor 26. The nozzle assembly 14 is fixed by means of a plate 27 to a carriage 28, which is also slidably mounted on the transverse groove 20. The carriage 28 is fixedly connected to the carriage 19 by means of the carriage 15 at a distance from this, the distance between the carriages 19 and 28 being such that the optical follower device 11 and the nozzle assembly 14 are located above the plate 17 and 17, respectively. the support table 13.

As will be readily appreciated, the follower device 11 together with the carriage unit described above can perform movement in any direction longitudinally, laterally or diagonally, the carriage 28 and the nozzle assembly 14 following the same movement depending on the connection between the carriages 19 and 28 by the crossbar 15 and the groove 20. When the follower device 11 in operation follows the contour or pattern 16, the nozzle 14 for cutting is caused by a fluid jet via the carriage 28 to move correspondingly over the support table 13 and the glass plate S thereon. For illustration purposes, the cut line along the disc S has been shown beginning at an edge and running diagonally across the disc. It will be appreciated, of course, that since the line is prescribed by the stencil or pattern 16, it may equally well describe a closed, inner cutout or circular opening, if so prescribed by the stencil. Operation of the following device's functions, such as power on / off, speed, automatic and manual operation, etc., can be performed from a suitably placed control panel 29.

The actual device for cutting by means of a fluid jet, as shown schematically in Fig. 1, has an electric motor 30, which drives a hydraulic pump 31, which in turn supplies working fluid via a line 32 to a pressure boosting unit 33. The function of the pressure boosting unit 33 is to in fluid (e.g. deionized water) from a suitable source, such as a container 34, and placing it under a very high pressure, which can be adjusted in a variable manner, preferably in the order of 68.9-206.7 MPa (10000-30000 psi) for discharge via a conduit 35. The nozzle assembly 14 is mounted at the outlet end of the conduit 35 for directing a very high velocity, small diameter fluid jet toward the glass sheet S on the support table 13. The nozzle assembly 14 has , as best seen in Fig. 2, a substantially rectangular casing 36 with a threaded bore 37 at its upper end, which axial bore is aligned with a flow channel 38 extending through casing jet. An externally threaded connector 39 with a flow channel 40 extending therethrough is suitably attached to the outlet end of the conduit 35 for connecting the conduit to the housing.

A recess 41 is arranged in a projection 42 at the threaded end of the connector 39, inside which the recess a fluid jet opening 43 is mounted, which opening has an outlet mouth 44 of very small diameter, for example in the order of 0.10-0.46 mm (0.004-0.018 inches) and preferably about 0.35 mm (0.014 inches). When the connector 39 is securely screwed into the bore 37, it duly places the opening 43 in the upper portion 45 of reduced diameter of the flow channel 38. The lower end of the channel 38 has a portion 46 of increased diameter for receiving a nozzle or mixer tube 47. The nozzle tube has a longitudinally extending channel 48 of relatively small diameter, for example in the order of 1.0-1.57 mm (0.040-0.062 inches) and preferably about 1.57 mm (0.062 inches), and a conical inlet opening 49 to more easily receive the fluid jet from the opening 43.

A bore 50 for supplying abrasive, as will be described in more detail below, in the path of the fluid jet flow is obliquely aligned with the channel 38. A controlled supply of the abrasive is transported from a storage container 51 and a regulator 52 to the bore 50 by means of a flexible conduit or a transport tube 53. The abrasive is sucked into the fluid jet stream as the flow passes through the channel 38, where it is mixed and accelerated in the high pressure flow before entering the channel 48 in the nozzle tube 47. will be described in more detail below, in order to minimize the scattering of the fluid jet flow and thus to provide a minimum cutting or impact surface width. It will be appreciated that the nozzle assembly described above is intended to be used only as representative of those assemblies which may be practiced in the invention.

In order to provide a cut edge of acceptable quality fluid jet, it is absolutely necessary that a number at a high speed by means of an abrasive parameters in the process are properly correlated and regulated. Thus, it has been found that such factors as the type and particle or grain size of the abrasive, the type of fluid medium and the degree to which it is pressurized, the feed rate, the diameter of the outlet orifice 44, the length and diameter of the channel 48 in the nozzle tube 47, the distance of the nozzle from the glass surface, the thickness of the glass and the feed rate of the cutting beam along the glass all affect each other and must be properly correlated to achieve a high quality cut at a suitable line speed.

A number of products are commercially available for use as abrasives, such as those marketed under the tradenames Biasil, AMA Zircon, Zircon M, Florida Zircon, Zircon 'T', Idaho Garnet, Barton Garnet, O-I Sand and Rock Quartz. The products are available in a nominal size range, ranging from a grain size of 250 μm (60 grit) or coarser to a grain size of 63 μm (220 grit) or finer. It has been found that although glass can be successfully cut in accordance with the invention by using abrasive particles of any of the above sizes by appropriately varying mutually correlated parameters, such as line velocity and fluid pressure, the use of abrasive particles within a special size range to provide a high quality cut edge at higher line speeds than other grain sizes in glass of commonly used thicknesses. The diagram of Fig. 3 thus illustrates the experimentally determined relationship between the grain size of the abrasive particles and the line or cutting speed when cutting glass with a thickness of 6.0 mm (0.235 inch) at a fluid pressure of 206.7 MPa (30000 psi). in accordance with the invention. The upper, dashed curve represents the maximum speed of the cutting head, i.e. the line speed, at which the advanced grinding jet will maintain a cut completely through the glass. At such a speed, the cut glass edges tend to split and develop unwanted notches and cracks, which run into the adjacent glass, so that the cut does not become of acceptable quality. The lower, solid curve represents the achievable speed at which the cut glass edges will have a uniform, uniformly high quality. As will be appreciated, maximum speed is achieved, while obtaining both complete separation and good quality edges, with a grain size for the abrasive particles in the range 97-115 μm (150-130 grit). The curve family representing the cutting speed as a function of the grain size for commercial glass thicknesses below 6.0 mm (0.235 inch) is substantially similar to that shown in Fig. 3, while the curves for thicker glass, especially with a thickness of 12.7 mm (0.500 inches) and 19.1 mm (0.750 inches), tend to be more flat and horizontal. Abrasive particles in the intermediate grain size range are thus very suitable for cutting glass of varying, commonly used thicknesses. As pointed out above, abrasive particles with different grain sizes can be used in the practice of the invention by varying other parameters, such as the line speed. For convenience, however, abrasives with a single grain size are preferably used in cutting the various thicknesses and a grain size in the above-noted range is very suitable for this purpose. It is easy to obtain abrasives with a grain size of 97 μm (150 grit) and such an abrasive is granite, for example granite with the trade name Barton yarn, which can be used to advantage in cutting glass in accordance with the invention.

The diagram according to Fig. 4 shows the relationship between the line speed in mm / min and the glass thickness when cutting different glass thicknesses in accordance with the invention, using an abrasive with a grain size of 97 μm (150 grit) as an abrasive in a fluid, which is pressurized to about 206.7 MPa (30,000 psi).

The upper dashed line again represents the maximum line velocity at which the advanced grinding jet will penetrate completely through the glass, while the solid line represents the line velocity at which the cut glass edges will have a uniform, uniformly high quality. In completing the experimental data, it was found that the maximum line speed for complete separation of very thin glass, i.e. glass with a thickness of less than about 3.8 mm (1.05 inch), exceeded the maximum line speed capacity of the machine according to Figures 1 and 2, which were used for cutting the glass. In other words, glass with a thickness of less than about 3.8 mm (0.1 inch) can be cut at speeds in excess of 2.54 m / min (100 inches / min). The device used in cutting the glass according to Figs. 3 and 4, as best shown in Fig. 2, had a jeweled opening 43 made of industrial gemstone, which has an outlet orifice 44 with a diameter of 0.36 mm. (0.014 inch), together with a nozzle tube 47 having a length of 76.2 mm (3 inches) and a thereby extending channel 48 having a diameter of 1.57 mm (0.062 inch). The end of the nozzle tube was located 1.27 mm (0.050 inch) from the glass surface. Deionized water was used as the fluid jet and the abrasive particles of the abrasive were absorbed into the fluid stream at a feed rate of about 0.454 kg / min (1 lb / min).

In the practice of the invention, the fluid medium, usually deionized water, is pressurized in the pressure boosting unit for discharge via the nozzle assembly.

Abrasive particles, for example abrasives with a grain size of 97 μm (150 grit), are sucked into the fluid jet at a speed of about 0.454 kg / min (1 pound / min). Where the advanced grinding jet is to initially strike the glass at one of its exposed edges, the fluid medium in the pressure boosting unit is pressurized to an ultra-high pressure in the order of 137.8-241.15 MPa (20000-35000 psi), preferably about 206.7 MPa ( 30000 psi), and the cutting device 12 and the nozzle assembly 14 are advanced so that the grinding jet begins cutting at the edge and follows the line prescribed by the stencil 16. In these circumstances, where the grinding jet initially engages the glass at an internal position, the fluid medium to a level of the order of 68.9 MPa (10000 psi) until the grinding jet has made the initial cut through the glass. Thereafter, the pressure in the booster unit increases considerably, for example to a level of the order of 137.8-241.15 MPa (20,000-35,000 psi), preferably about 206.7 MPa (30,000 psi). The cutting device 12 and the nozzle assembly 14 are then advanced along the line prescribed by the stencil 16 to cut the prescribed opening in the glass sheet S. the aforementioned ultra-high pressure, * obviously due to the successive removal of glass fragments. Depending on the speed at which the ultra-high pressure grinding jet cuts through the glass, the line speed or movement of the nozzle assembly 14 relative to the glass can be significantly increased while still producing uniformly high quality cut edges. Grinding particles with a grain size of 97 μm (150 grit) are, as described above, particularly suitable for cutting glass with a thickness which is in the glass thickness range most commonly used in commercial contexts at high line speeds in accordance with the invention. It will be appreciated, however, that high quality cut edges may be obtained by using abrasive particles of a different grain size by appropriately varying other parameters. It has thus been noted that smaller abrasive particles, for example with a grain size of 65 or 80 μm (220 or 180 grit), will produce very smooth, cut edges, but that the line or cutting speed will be lower than with abrasives with a grain size of 97 μm. (150 grit). Conversely, it is possible to cut through glass at higher overall line speeds with coarser abrasives with a grain size of 149 or 250 μm (100 or 60 grit), but the cut edge will, due to edge splitting and matting at the higher speeds, have poorer quality.

In order to obtain an edge quality comparable to that obtained with abrasives with a grain size of 97 μm (150 grit), it will be necessary to reduce the line speed. The cone angle of the cutting edges depends on both the grain size of the abrasive particles and the line speed of the cutting device. The cone angle of the cut edge thus increases as the abrasive particles are made finer and the line speed increases.

Claims (9)

465 672 10 15 20 25 30 14 PATENT REQUIREMENTS A method of cutting glass of different thicknesses along a desired path or line by means of an abrasive fluid jet at the maximum speed compatible with the production of cut edges of acceptable quality, characterized in that an extremely collimated fluid jet is discharged from a pressure source, which is maintained at an ultra-high pressure level, that abrasive particles are entrained in the fluid jet, that the glass is exposed to the abrasive particle-containing fluid jet, that the abrasive jet is moved relative to said glass and thereby advanced along said line, and that the abrasive jet the glass along said line at the maximum speed at which the cut glass edges have acceptable quality. 2. A method according to claim 1, characterized in that the grinding jet initially engages an edge of the glass before the beginning of the cutting. 3. A method according to claim 2, characterized in that about 137.8 MPa and 241.15 MPa, preferably about 206.7 MPa. A method according to any one of claims 1-3, e.g. in the range 65-250 μm. that the ultra-high pressure level is between the senses - that the abrasive particles have a grain size 5. A method according to claim 4, characterized in that the abrasive particles consist of garnet or zircon. ' Method according to claim 4 or 5, characterized in that the abrasive particles have a grain size of about 100 μm. Method according to one of the preceding claims, characterized in that the pressure source is initially kept at a lower pressure level, in that the grinding jet is directed towards a larger surface of the glass in order to initially penetrate 465 672. into the glass with the pressure source at the lower level and that the pressure of the pressure source is subsequently increased to the ultra-high pressure level for advancing the grinding jet along said line. 8. A method according to claim 7, characterized in that the grinding jet while it is still directed towards the glass is advanced along said line at the second pressure level. A method according to claim 8, in that the first pressure level is less than about 68.9 MPa.