METHOD AND DEVICE FOR CUTTING GLASS TUBES

Abstract

The present disclosure relates to a method and device for cutting glass tubes with a length L from a glass tubing that moves at a feed rate v.sub.1. The glass tubing is investigated for defects with an analytical device. The analytical device determines whether a glass tube to be separated is either defect-free (case 1) or contains defects (case 2). In case 1, a defect-free glass tube of the length L is separated from the glass tubing. In case 2, the device and method of the present disclosure determines a distance L.sub.A in the lengthwise direction between the defect and a free end of the glass tube to be separated. The distance L.sub.A is determined from the portion of the defect at the greatest distance from the free end of the tube. The device and method of the present disclosure then separates a piece of a glass tube or a glass tube that contains defects from the glass tubing at a distance L.sub.S from the free end of the glass tube, as a function of L.sub.A.

Claims

1. A method for cutting glass tubes having a length L from a glass tubing that moves at a feed rate v.sub.1, comprising the steps of: investigating the glass tubing with an analytical device; determining whether a glass tube of length L to be separated from the glass tubing is either defect-free (case 1) or contains defects (case 2); in case 1, separating the glass tube of the length L from the glass tubing; and in case 2, a) determining a distance L.sub.A in the lengthwise direction between the defect and a free end of the glass tube to be separated, wherein the distance L.sub.A is determined from the portion of the defect at the greatest distance from the free end of the tube; and b) separating a piece of a glass tube or a glass tube that contains defects from the glass tubing at a distance L.sub.S from the free end of the glass tube as a function of L.sub.A.

2. The method of claim 1, further comprising the steps of: subdividing the glass tubing, starting from the free end of the glass tube to be separated, into n+1 segments A.sub.1 to A.sub.n+1 of identical length L/n with n={2, 3, 4, . . . }; in case 2, determining a segment A.sub.D in which the defect lies; and separating the glass tubing at a boundary between segment A.sub.D and segment A.sub.D+1.

3. The method of claim 2, wherein n=2.

4. The method of claim 1, further comprising the step of delivering defect-free glass tubes to a transport device after separation.

5. The method of claim 4, wherein the transport device has a constant feed rate v.sub.2.

6. The method of claim 5, wherein the transport device has a multiple number of compartments for glass tubes.

7. The method of claim 6, wherein the feed rate v.sub.2 and the division of the compartments are selected so that successively cut, defect-free glass tubes are directly transferred into each compartment of the transport device.

8. The method of claim 1, further comprising the steps of: buffering the separated, defect-free glass tubes; and subsequently, removing the separated, defect-free glass tubes.

9. The method of claim 1, wherein when a glass tube piece with a length L.sub.S<L is separated, a force F.sub.U supporting a gravitational force F.sub.G is exercised on the glass tube piece to be separated.

10. The method of claim 1, wherein defect-containing glass tubes and glass tube pieces are transferred into a collecting container after separation.

11. A device for cutting glass tubes with a length L from a glass tubing that moves at a feed rate v.sub.1, comprising: an analytical device for investigating the glass tubing for defects; a separating apparatus for separating glass tubes and glass tube pieces from the glass tubing; and a transport device for removal of the separated glass tubes, wherein the analytical device determines whether a glass tube to be separated from the glass tubing is either defect-free (case 1) or contains defects (case 2), wherein, in case 1, the analytical device emits a control signal that prompts the separating apparatus to separate a defect-free glass tube of length L from the glass tubing, wherein, in case 2, the analytical device determines a distance L.sub.A in a lengthwise direction between where the defect is located and a free end of the glass tube to be separated, wherein the distance L.sub.A is determined from the portion of the defect at the greatest distance from the free end of the tube, and the analytical emits a control signal that prompts the separating apparatus to separate a defect-containing glass tube piece or glass tube from the glass tubing at a distance L.sub.S from the free end of the glass tubing as a function of L.sub.A.

12. The device according to claim 11, further comprising a collecting container for defect-containing glass tubes.

13. The device according to claim 12, further comprising a sorting apparatus to convey defect-containing glass tubes and glass tube pieces to the collecting container and to convey defect-free glass tubes to the transport device.

14. The device according to claim 11, further comprising, between the separating apparatus and the transport device, a buffering apparatus that takes up separated, defect-free glass tubes from the separating apparatus and to delivers them to the transport device.

15. The device according to claim 11, further comprising a breaking force booster that exercises a force F.sub.U that boosts the gravitational force F.sub.G on a glass tube piece to be separated, wherein the glass tube piece to be separate has a length L.sub.S<L.

16. The device according to claim 15, wherein the breaking force booster comprises at least one of a cam element, a compressed air cylinder, and a rotating arm that is equipped to press on the glass tube piece to be separated, directly or with a pressure piece.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG. 1 shows a device for cutting glass tubes according to a first embodiment.

[0043] FIG. 2 shows a device for cutting glass tubes according to a second embodiment.

[0044] FIG. 3 shows a device for cutting glass tubes according to a third embodiment.

[0045] FIG. 4 shows a device for cutting glass tubes according to a fourth embodiment.

[0046] FIG. 5 shows an end region of a glass tubing.

DETAILED DESCRIPTION OF THE DRAWINGS

[0047] FIG. 1 shows a device 1 for cutting glass tubes from a glass tubing 2. The glass tubing 2 is transported in the direction of the arrow at a continuous feed rate v.sub.1. The device 1 has an analytical device 21, a separating apparatus 3, which is symbolized by two arrows, a transport device 4, as well as a collecting container 5. The transport device 4 has a conveyor belt 6 on which carriers 7 are arranged. The carriers 7 form compartments 8, whereby a compartment 8 is formed between every two carriers 7.

[0048] According to the present disclosure, the glass tubing 2 is investigated for defects by means of the analytical device 21, wherein it is established, at least for the next glass tube 9 to be separated, whether it is free of defects or contains defects. If the glass tube 9 to be separated is defect-free, then it is separated from the glass tubing 2 by means of the separating apparatus 3. After the separation, the separated glass tube 9 moves further based on the feed rate v.sub.1 of the glass tubing 2, so that it reaches a free compartment 8, which is kept ready, in the transport device 4. Subsequently, the conveyor belt 6 of the transport device 4 is moved in the direction of feed R, so that a new, free compartment 8 becomes available for the next defect-free glass tube 9.

[0049] If it is established that the glass tube 9 to be separated contains defects, then a distance L.sub.A is determined of how far the defect is from the free end 10 of the glass tubing 2 (see FIG. 5). Subsequently, the glass tubing 2 is separated at a site at a distance L.sub.S from the free end of the glass tube, depending on L.sub.A. Either a defect-containing glass tube 9 of length L or a defect-containing glass tube piece of length L.sub.S<L is formed thereby. After being separated from the glass tubing 2, defect-containing glass tubes 9 and glass tube pieces are transferred to the collecting container 5. This can be achieved, for example, by way of a sorting apparatus, which is not shown.

[0050] While the defect-containing glass tube or glass tube piece is being separated and sorted out, the transport device 4 is at a standstill until the next defect-free glass tube 9 has been delivered to the next free compartment 8. In this way, in the case of the embodiment shown in FIG. 1, each compartment 8 of the transport device 4 is filled with a glass tube 9. At the same time, however a providing of defect-free glass tubes 9 to a device for the further processing of said glass tubes 9 is produced irregularly over time by the transport device 4, said further processing device connecting thereto, but not shown.

[0051] Shown in FIG. 2, the embodiment of the device 1 for cutting glass tubes 9 from a glass tubing 2 also comprises an analytical device 21, a separating apparatus 3, a transport device 4, and a collecting container 5. The glass tubing 2 again has a continuous feed rate v.sub.1. The transport device 4 here also has a conveyor belt 6 with carriers 7. In this embodiment, the conveyor belt 6 moves continuously in a feed direction R at a feed rate v.sub.2. The feed rate v.sub.2 is determined such that when a plurality of defect-free glass tubes 9 are produced sequentially one after the other, one glass tube 9 is arranged in every second compartment 8. In this case, a single empty compartment 8 is present between two compartments 8, in each of which a glass tube 9 is found.

[0052] According to the present disclosure, the glass tubing 2 is here also continuously investigated for defects 22. It is determined for each glass tube 9 to be separated whether the glass tube 9 is free of defects or contains defects. A defect-free glass tube 9 is separated from the glass tubing 2 by way of the separating apparatus 3, and automatically falls into a compartment 8 of the transport device 4, the fall brought about by the feed rate v.sub.1. In the case of a defect-containing glass tube 9, the region of the glass tube 9 in which the defect 22 is found is determined. For this purpose, the glass tubing, starting from the free end 10 of the glass tube 9 to be separated is subdivided into a multiple number of segments (in the case of the embodiment shown in FIG. 2, into three segments, n=2) and subsequently, the segment(s) in which the defect 22 is arranged is/are determined. In the present case, the glass tube 9 to be separated is composed of two segments A.sub.1, A.sub.2. It is now determined whether the defect 22 is found in segment A.sub.1 or in segment A.sub.2.

[0053] If the defect 22 is found in segment A.sub.1, then the glass tubing 2 is separated at the boundary between segments A.sub.1 and A.sub.2, so that a defect-containing glass tube piece 11 is formed. The glass tube piece 11 is then conveyed to the collecting container 5 by a sorting apparatus, which is not shown in this figure. Since the conveyor belt 6 of the transport device 4 continuously moves in the feed direction R, an additional empty compartment 8 arises. If, directly afterward, a defect-free glass tube 9 is cut from the glass tubing 2, then two empty compartments 8 are found between the latter and the previous defect-free glass tube 9.

[0054] If, for a defect-containing glass tube 9, it is determined that the defect 22 is arranged in segment A.sub.2, then a complete, but defect-containing glass tube 9 of length L is separated and transferred to the collecting container 5 by the sorting apparatus.

[0055] FIG. 3 schematically shows a device 1 for cutting glass tubes 9 from a glass tubing 2, in a lateral view. The glass tubing 2 is moved in the direction of the arrow at the continuous feed rate v.sub.1 by means of a feed apparatus 12. The feed apparatus 12 has for this purpose two or more drawing rollers 13 or other suitable feed systems such as drawing chains or belts, which draw the glass tubing 2 from the hot forming operation connected upstream (not shown) and support the tubing at the same time.

[0056] The device 1 has an analytical device 21, a separating apparatus 3, as well as a transport device 4. The separating apparatus 3 has a scoring unit 14 and a breaking force booster 15. The glass tubing 2 is scored at the desired separating site by means of the scoring unit 14. The initial crack in this case is usually produced with diamond tools and preferably on the upper side of the glass tube, i.e., at the 12:00 o'clock position. In this way, microcracks are produced in the glass tube. Since the glass tubing 2 is not supported against gravitational force F.sub.G in the region of the free end 10, a bending moment arises due to the tube weight that is present, and this leads to the broadening of the crack. An encircling crack arises along which the tube breaks. Water supports the process by temperature shock and penetration into the crack. The glass tube 9 is thus separated from the glass tubing 2 and subsequently the cut glass tube 9 can be delivered to the transport device 4 and conveyed to further processing. The transport device 4 here also has a conveyor belt 6 with carriers 7.

[0057] The breaking force booster 15 is preferably applied exclusively for separating glass tube pieces 11. Glass tube pieces 11 have a shorter length than glass tubes 9 and thus also have a lower weight. Without the breaking force booster 15, it may happen that a cracked glass tube piece 11 is not separated from the glass tubing 2 or has a deviating breaking behavior. Thanks to the breaking force booster 15, a force that supports the gravitational force F.sub.G is exercised on a glass tube piece 11, so that the latter is separated from the glass tubing 2 and has the same breaking behavior as a complete glass tube 9. The breaking force booster 15 has for this purpose a rotating arm 16 that presses on the glass tube piece 11 to be separated, preferably from the top, by means of a pressure piece 17.

[0058] The fourth embodiment of the device 1 for cutting glass tubes 9 from a glass tubing 2, which is shown in FIG. 4, has a separating apparatus 3, a transport device 4 and a buffering apparatus 18 arranged between the separating apparatus 3 and the transport device 4. The glass tubing 2 again has a continuous feed rate v.sub.1, so that defect-free glass tubes 9 are irregularly cut due to rejects that arise. The transport device 4 has a continuous feed rate v.sub.2.

[0059] In order to equilibrate the irregular supply of glass tubes 9 from the separating apparatus 3 and the regular removal operation of the glass tubes 9 by the transport device 4, the buffering apparatus 18 is provided, which has a conveyor belt 23, a conveyor belt 24, and an intermediate storage unit 19 having a third conveyor belt 25. Each conveyor belt 23, 24, 25 has a multiple number of carriers 27, between which are formed compartments 28. A single glass tube 9 can be arranged in each compartment 28. Along an axis arranged perpendicular to the plane of the drawing, the carriers 27 of the first conveyor belt 23 and of the second conveyor belt 24 are each offset relative to the carriers 27 of the third conveyor belt 25, so that the carriers 27 of different conveyor belts 23, 24, 25 do not come into contact with one another during a movement of one or more of conveyor belts 23, 24, 25.

[0060] The first conveyor belt 23 transports defect-free glass tubes 9, which have been separated from the glass tubing 2 by means of the separating apparatus 3, along a feed direction R1 to the intermediate storage unit 19 by way of a conveyor belt 25. The second conveyor belt 24 transports glass tubes 9 from the intermediate storage unit 19 along a feed direction R2 to the transport device 4, by means of which the glass tubes 9 are supplied for further processing. The third conveyor belt 25 moves along a feed direction R3. In order to equilibrate the deviation between supply and removal, the intermediate storage unit can be moved along an equilibration direction R4.

[0061] The conveyor belt 25 is mounted in a floating manner for this purpose and is joined to an internal chain system. The chain from belt 23 and the left half of the chain from conveyor belt 25 are linked and run at the same speed. The chain from belt 24 and the right half of the chain from conveyor belt 25 are linked and also run at the same speed. If the speed of conveyor belt 23 is slower than that of conveyor belt 24, then the entire module 25 moves downward; the left side thus takes up fewer tubes than the right side delivers. A storage reduction occurs. In this case, the transfer positions of conveyor belt 23 on 25 and 25 on 24 remain at the same site. In contrast, the entire module 25 moves upward, if conveyor belt 23 runs faster than conveyor belt 24. A storage increase occurs.

[0062] In standard function when mostly all tubes are good, conveyor belt 23 and conveyor belt 24 run at the same speed. If a defect-containing glass tube 9 is separated and discarded, the first conveyor belt 23 does not move until the next good tube is delivered. This storage reduction can continue until the storage unit has reached a lower minimum position. If the storage unit is emptied, the belt 24 must run faster for a short time when a defect-containing glass tube 9 is separated and rejected, or temporarily run at twice the speed if a good tube is separated. The storage of tubes is increased in this way.

[0063] The frequency of the removal operation is selected so that it is less than the frequency with which defect-free glass tubes 9 would be cut at the glass tubing 2, if no defects were present. The difference in the frequencies of the supply and the removal balances out the waiting times that are caused by the separation of defect-containing glass tube pieces during production.

[0064] The device 1 also has a sorting apparatus 20, by means of which defect-containing glass tubes 9 are sorted out and conveyed to a collecting container 5. The sorting apparatus or defective tube sluice has an electrically or pneumatically driven flap, which is placed by pivoting between the tube segment to be separated and the conveyor belt for good tubes when a defect-containing glass tube is determined by means of the analytical device, and the defect-containing glass tube is steered to the collecting container 5.

[0065] FIG. 5 schematically shows the end region of a glass tubing 2 with the free end 10. The glass tubing 2 has a principal axis X about which the glass tubing 2 is rotationally symmetrical. The separating site at the axial distance L from the free end 10 of the glass tubing 2 where the defect-free glass tube 9 would be separated is plotted as a dotted guide line. The glass tubing 2 is further subdivided (n=3) into four segments A.sub.1, A.sub.2, A.sub.3 and A.sub.4 along the principal axis X, starting from the free end 10. The segments A.sub.1, A.sub.2, A.sub.3, A.sub.4 each have a uniform length of L/3. The separating site at the distance L thus coincides with the boundary between segments A.sub.3 and A.sub.4, or stated another way, the glass tube 9 to be separated is composed of the segments A.sub.1, A.sub.2, A.sub.3.

[0066] The glass tubing 2 or the glass tube 9 to be separated has a defect 22. The defect 22 has a distance L.sub.A, measured in the lengthwise direction, from the free end 10 of the glass tubing 2 and is found in the segment A.sub.2. Taking into consideration the position of the defect 22 or the distance L.sub.A, the glass tubing 2 is separated according to the present disclosure at the boundary between the segments A.sub.2 and A.sub.3, whereby a glass tube piece 11 of length L is formed. The segment A.sub.3 then forms the new segment A.sub.1 for the next glass tube 9 to be separated. In this example, when compared to the known methods in which an entire glass tube of length L would be separated and discarded, the reject is reduced by L.

[0067] Statistically, the defect is found with the same probability in each of the three segments A.sub.1 to A.sub.3, if one disregards overlapping defects, so that the rejects can also be reduced overall approximately by L to L (=( L+ L+1 L)). With an increase of n, i.e., the number of segments, the rejects are further reduced; of course, the reduction cannot go below L for statistical reasons.

[0068] While the present disclosure has been described with reference to one or more particular embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope thereof. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment(s) disclosed as the best mode contemplated for carrying out this disclosure.

LIST OF REFERENCE CHARACTERS

[0069] 1 Device [0070] 2 Glass tubing [0071] 3 Separating apparatus [0072] 4 Transport device [0073] 5 Collecting container [0074] 6 Conveyor belt [0075] 7 Carrier [0076] 8 Compartment [0077] 8 Empty compartment [0078] 9 Glass tube [0079] 10 Free end [0080] 11 Glass tube piece [0081] 12 Feed apparatus [0082] 13 Drawing rollers [0083] 14 Scoring unit [0084] 15 Breaking force booster [0085] 16 Rotating arm [0086] 17 Pressure piece [0087] 18 Buffering apparatus [0088] 19 Intermediate storage unit [0089] 20 Sorting apparatus [0090] 21 Analytical device [0091] 22 Defect [0092] 23 First conveyor belt [0093] 24 Second conveyor belt [0094] 25 Third conveyor belt [0095] 27 Carrier [0096] 28 Compartment [0097] A.sub.1 to A.sub.4 Segment [0098] F.sub.G Gravitational force [0099] L Length [0100] R Feed direction [0101] R1 Feed direction [0102] R2 Feed direction [0103] R3 Feed direction [0104] R4 Equilibration direction [0105] v.sub.1 Feed rate [0106] v.sub.2 Feed rate [0107] X Principal axis