ROLLING MILL LAYING HEAD

Abstract: A rolling mill laying head has a first tubular shaft (30) mounted on first bearings for rotation relative to a stationary housing structure (28). A second hollow shaft (34) carrying a three dimensionally curved laying pipe (38) is mounted on second bearings (36) for rotation relative to the first hollow shaft. Both hollow shafts are rotatably driven in the same direction at different speeds.

Description: This invention relates to laying heads of the type employed in rolling mills to coil products such as hot rolled rods. In the conventional laying head, as schematically depicted in Figure 1 at 10, a hollow shaft 12 is journalled on bearings 14a, 14b for rotation about an axis A. The shaft carries a three dimensionally curved laying pipe 16 having its entry end 16a arranged essentially concentric with the axis A, and its delivery end 16b located radially therefrom. Shaft 12 also carries a gear 20 on a drive shaft 22, the latter being connected to a drive motor M. A hot rolled product, e.g. steel rod, is directed at mill delivery speeds along axis A into the shaft 12. The product then continues through the laying pipe 16 and exits therefrom in the form of a continuous series of rings 24. Typically, the rings will be received in an overlapping offset pattern on a conveyor 26 where they will be cooled at a controlled rate before finally being gathered into coils. A laying head of this type is also disclosed in DE-A-3012639. This type of laying head has operated satisfactorily in the past. However, future difficulties are envisioned as a result of ever-increasing mill delivery speeds, particularly with respect to rod mills. For example, current modern day high speed rod mills are operating at mill delivery speeds of around 100 m/sec., thus requiring the laying head shafts to be driven at speeds of around 2,000 RPM. Such speeds are at the high end of the permissible operating range of the shaft bearings. Higher rod mill delivery speeds on the order of 150 m/sec. are now being planned but are in danger of not being implemented due to the inability of the conventional laying heads to accommodate further speed increases. In the present specification there is described an improved laying head which has the capability of operating at much higher speeds without overtaxing the capacity of the shaft bearings. The laying head has a first hollow shaft rotatably mounted on a first set of bearings carried by a stationary housing structure. The laying pipe is carried on a second hollow shaft which is rotatably mounted on a second set of bearings carried on the first hollow shaft. The rotational axes of both hollow shafts are coincident. The hollow shafts are each rotatably driven in the same direction but at different speeds, with the rotational speed of the second shaft and the laying pipe carried thereon in relation to the housing structure being equal to the sum of the relative rotational speeds between the second hollow shaft and the first hollow shaft, and between the first hollow shaft and the housing structure. Thus, the first and second bearing sets each experience only a percentage of the rotational speed of the laying pipe. In the accompanying drawing, by way of example only: Figure 1 is a schematic illustration of a typical prior art laying head; Figure 2 is a sectional view taken through a laying head in one embodiment of the present invention; and Figure 3 is a partial sectional view taken through a laying head in another embodiment of the present invention. With reference initially to Figure 2, a rolling mill laying head is shown comprising a stationary housing structure 28 having a base plate 28a, side walls 28b, 28c, a top wall 28d and an internal partition 28c. A first hollow shaft 30 is supported for rotation about an axis A on first bearing means including bearing sets 32a and 32b. Bearing set 32a is carried by side wall 28b, and the bearing sets 32b are carried by the housing partition 28c. A second hollow shaft 34 extends axially through the first hollow shaft 30. Second bearing means including bearing sets 36a and 36b support the second hollow shaft 34 on the first hollow shaft 30 for rotation about the same axis A. A three dimensionally curved laying pipe 38 is carried by the second hollow shaft 34 for rotation therewith. The laying pipe 38 has an entry end 38a aligned essentially concentric with axis A, and a delivery end 38b located radially from axis A. A tubular product guide 40 is fixed relative to housing side plate 28c and extends along axis A into the second hollow shaft 34 to a location proximate to the entry end 38a of the laying pipe. A drive means is employed to rotatably drive the first and second hollow shafts 30, 34 in the same direction but at different speeds. The drive means includes first and second drive gears 42, 44 keyed or otherwise fixed respectively to the first and second hollow shafts 30, 34. First and second drive gears 46, 48 are in meshed relationship respectively with the first and second drive gears. The drive gears 46, 48 are carried on a common shaft 50 journalled for rotation about an axis parallel to axis A. Shaft 50 may be driven in any convenient manner, for example via bevelled gears 52, 54 and the output shaft 56 of a drive motor (not shown). With this arrangement, the first hollow shaft 30 is driven at a first speed relative to the housing structure 28, and the second hollow shaft 34 is driven at a second speed relative to the first hollow shaft 30, with the rotational speed of the laying pipe 38 relative to the housing structure 28 being the sum of both of the aforesaid relative speeds. Thus, if the laying pipe 38 must rotate at 3,000 RPM in order to coil hot rolled steel rod exiting from a rolling mill at a delivery speed of 150 m/sec., the first bearing means 32a, 32b need only accommodate a fraction of that speed, typically 1,500 RPM, with the remaining 1,500 RPM being accommodated by the second bearing means 35a, 36b. The net effect is to dramatically increase the capacity of the laying head without exceeding the safe operating range of the bearings. In the embodiment of Figure 2, the bearing sets 32a, 36a are axially spaced and of equal diameter, as are the bearing sets 32b, 36b. This is advantageous in that it reduces spare parts requirements. In the alternate embodiment shown in Figure 3, the bearing sets 32a, 36a are of unequal diameter and are arranged in a coplanar relationship. The same relationship exists between the bearing sets 32b, 36b.

Claims: 1. A laying head for laying an axially moving product of a rolling mill into a series of coils (24), the laying head comprising: a three dimensionally curved laying pipe (38) mounted for rotation about a predetermined axis, characterised in that the laying pipe (38) is carried by a hollow support member (30) for rotation relative thereto about the said axis, and the support member (30) is rotatably mounted in a fixed housing (28) whereby both the pipe (38) and the support member (30) are independently driven for rotation in the same direction about the said axis, the relative rotational speed of the laying pipe (38) to the housing (28) being equal to the sum of the rotational speeds of the laying pipe (38) to the support member (30) and the support member (30) to the housing (28). 2. A laying head according to claim 1 wherein the laying pipe (38) has an entry end (38a) received within the hollow support member (30) in alignment with the said axis and a delivery end (38b) disposed externally of the support member (30) and spaced radially from the said axis, the axially moving product being guided along the axis into the entry end (38a) of the laying pipe (38) and emerging from the delivery end (38b). 3. A laying head according to claim 2 wherein the hollow support member comprises a first hollow shaft (30), and the laying pipe (38) is carried by a second hollow shaft (34), at least a portion of the second hollow shaft (34) extending axially through the first hollow shaft (30). 4. A laying head according to claim 3 further comprising first bearing means (32a, 32b) for supporting the first hollow shaft (30) for rotation about the said axis, second bearing means (36a, 36b) for supporting the second hollow shaft (34) on the first hollow shaft (30) for rotation about the said axis, and drive means (42, 44, 46, 48, 50) for rotatably driving the first hollow shaft (30) in one direction at a first rotational speed relative to the said housing (28) and for driving the second hollow shaft (34) in the same direction at a second rotational speed relative to the first hollow shaft (30). 5. The laying head of claim 4 wherein the drive means comprises first and second driven gears (42, 44) carried respectively on the first and second hollow shafts (30, 34) and first and second drive gears (46, 48) meshing respectively with the first and second driven gears (42, 44), the first and second drive gears (46, 48) being carried on a common drive shaft (50) journalled for rotation about an axis parallel to the said axis. 6. The laying head of claim 4 or claim 5 wherein the first and second bearing means (32a, 32b, 36a, 36b) each include a plurality of bearings, at least some of the bearings of the first bearing means (32a, 32b) being equal in diameter to at least some of the bearings of the second bearing means (36a, 36b). 7. The laying head of claim 6 wherein the respective bearings of equal diameter in the first and second bearing means are spaced axially from one another. 8. The laying head of claim 4 or claim 5 wherein the first and second bearing means (32a, 32b, 36a, 36b) each include a plurality of bearings, at least some of the bearings of the first bearing means (32a, 32b) being arranged in a coplanar relationship with at least some of the bearings of the second bearing means (36a, 36b). 9. The laying head of claim 8 wherein the respective coplanar bearings of the first and second bearing means are of unequal diameter.

Inventors: NASRAH, CAMILLE S.
Applicants: MORGAN CONSTRUCTION COMPANY (A MASSACHUSETTS CORPORATION)
Application year: 1988
Main classification: B21B45
IPC codes: B21C47, B21B43, B21B39