Rolling mill laying head

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

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to laying heads of the type employed in rolling 
mills to coil products such as hot rolled rods. 
2. Description of the Prior Art 
In the conventional laying head, as schematically depicted in FIG. 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 18 which meshes with 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. 
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. 
The objective of the present invention is to provide an improved laying 
head which has the capability of operating at much higher speeds, without 
overtaxing the capacity of the shaft bearings. 
SUMMARY OF THE INVENTION 
The laying head of the present invention 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.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS 
With reference initially to FIG. 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 32a. 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 driven 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 driven 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 36a,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 FIG. 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 FIG. 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.