High speed shear for end trimming rods and the like

Apparatus for shearing elongated products such as rods, bars and the like moving longitudinally along a path of travel. The apparatus includes a pair of constant diameter helical blades mounted for rotation about axes parallel to the path of travel. The rotational orientation of the blades and the spacing between their respective axes is such that segments of the blades coact along a cutting path parallel to the path of travel. The blades are rotated in opposite directions to thereby cause coacting segments thereof to move repetitively along the cutting path in the direction of product movement. A switch diverts the products from the path of travel across the cutting path for shearing by the coacting segments of the cutting blades.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates in general to continuous hot rolling mills of the 
type producing rods, bars and the like, and is concerned in particular 
with an improved shear for trimming the front and back ends from hot 
rolled rods being delivered from the finishing stands of high speed rod 
mills. 
2. Description of the Prior Art 
Conventionally, the front and back ends of hot rolled rods are trimmed by 
shears located along the rolling line in advance of the finishing stands, 
where the product is moving at slower speeds. Some trimming shears operate 
intermittently, whereas others operate continuously. Intermittently 
operable shears necessarily require complex control systems which 
precisely position the shear blades during each cut in response to rod end 
position signals generated by sensors located along the rolling line. From 
the standpoint of control complexity, continuously operating shears such 
as disc shears are far less demanding, but they commonly produce sharply 
oblique cuts with undesirable jagged ends. 
In any event, none of the conventional disc shears has been deemed capable 
of operating safely and reliably at delivery speeds on the order of 90 
m/sec. and higher. Thus, the front and back ends of finish rolled rods 
must be trimmed manually after the laying head, either while the product 
is being conveyed in overlapping ring form on the cooling conveyor, or 
after the cooled rings have been gathered into a coil at the reforming 
station. Manual trimming is labor intensive, often inconvenient, and 
potentially hazardous to operating personnel. 
SUMMARY OF THE INVENTION 
An objective of the present invention is the provision of an improved shear 
for trimming the front and back ends from rods emanating at high speed 
from the finishing stands of rod mills. 
A related objective of the present invention is the provision of a 
continually operating shear which inherently makes a single cut in 
response to diversion of the product from its normal path of travel, and 
which does not require a rod end position signal to coordinate actuation 
of tile shear blades. 
Still another objective of tile present invention is the provision of a 
continually operating shear which severs the product cleanly and at an 
angle which avoids undesirable sharp or jagged ends. 
In a preferred embodiment of the invention to be described hereinafter in 
greater detail, these and other objects and advantages are achieved by the 
provision of a shear having a pair of constant diameter helical blades 
mounted for contra-rotation about axes parallel to the path of product 
travel. The rotational orientation of the shear blades and the spacing 
between their rotational axes is such that segments of the blades coact 
along a cutting path parallel to the path of product travel. The shear 
blades are contra-rotated continually, thereby causing their coacting 
segments to move repetitively along tile cutting path in tile direction of 
and at a speed at least equal to that of products moving along the path of 
product travel. An upstream switch pipe is operable to divert products 
from their normal path of travel across the cutting path for shearing by 
the coacting segments of the cutting blades.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
Referring initially to FIGS. 1 and 2, shears 10, 12 embodying the concepts 
of the present invention are shown positioned sequentially along a path of 
product travel P.sub.2. Shear 12 operates to trim the front end of a 
product, and shear 10 operates in a similar manner to trim the back end of 
the product. Both shears are essentially identical in design and 
construction, with shear 12 being mounted at a level slightly beneath that 
of shear 10. 
As best can be seen by further reference to FIGS. 3 to 7, each shear 
includes a housing structure 16 containing a drive motor 18 with its 
output shaft coupled as at 20 to a large diameter drive gear 22. Gear 22 
meshes with a pair of idler gears 24, 26, and idler gear 24 meshes with a 
third idler gear 28. Idler gears 26, 28 mesh with pinions 30 on shafts 32 
carrying cylindrical drums 34. The shafts 32 are rotatably journalled 
between bearings 36, 38 carried on robust parallel walls 40, 42 forming 
part of the housing structure 16. The interposition of idler gear 28 
between idler gear 24 and the pinion 30 of one of the shafts 32 insures 
that the shafts are contra-rotated in response to rotation of drive gear 
22. 
Each drum 34 is provided on its exterior with a constant diameter helical 
blade 44. Each blade 44 extends from end to end along and circumscribes a 
single turn around its respective drum 34. Preferably, the axial length of 
the helix is not greater than the circumference of the circular path 
circumscribed by blade rotation. The rotational axes of the cylindrical 
drums 34 and their respective helical blades 44 are parallel to the path 
of product travel P.sub.T. The rotational orientation of the blades 44 and 
the spacing between their respective rotational axes is such that, as can 
best be seen in FIG. 7, segments of the blades coact along a cutting path 
P.sub.c parallel to path P.sub.T. 
The cylindrical drums 34 underlie an access lid 46 which closes off the top 
of the housing 16 and which may be opened for inspection of the blades 44. 
Lid 46 carries a depending guide 48 having a downwardly facing groove 49 
defining an upper guide path P.sub.u overlying the cutting path P.sub.c. 
The housing walls 40, 42 carry a similarly configured but oppositely 
disposed guide 50 having an upwardly facing groove 51 defining a lower 
guide path P.sub.L underlying the cutting path P.sub.c. 
Each shear housing 16 is preceded by a pedestal 52 carrying a bracket 54. 
The brackets 54 pivotally support the upstream ends of switch pipes 56, 
the downstream ends of which are adjustable vertically by pneumatic 
cylinders 58 supported on the housings 16. The cylinders 58 operate to 
adjust the downstream ends of their respective switch pipes 56 between 
free running positions aligned with the path P.sub.T of product travel as 
indicated by the full lines in FIG. 1, and angularly disposed positions 
56' depicted by the broken lines. 
As can best be seen in FIG. 1, the difference in elevation of shears 10, 12 
with respect to the path of product travel P.sub.T results in the 
following relationships: shear 10 has its lower guide path P.sub.L aligned 
with the path of product travel P.sub.T, with its cutting path P.sub.c and 
upper guide path P.sub.u located respectively thereabove, and with the 
upper guide path P.sub.u leading to an exit pipe 60 for sheared back ends. 
In contrast, shear 12 has its upper guide path P.sub.u aligned with the 
path of product travel P.sub.T and leading to a downstream guide pipe 61, 
and has its cutting path P.sub.c and lower guide path P.sub.L arranged 
therebeneath, the latter leading to an exit pipe 62 for sheared front 
ends. 
A front and back end shearing operation will now be described with 
reference to FIGS. 8A-8C. As shown in FIG. 8A, the front end of a product 
has passed through shear 10 along its lower guide path P.sub.L and has 
been deflected by the angularly disposed switch pipe 56' of shear 12 along 
its lower guide path P.sub.L, into the front end exit pipe 62. 
At the appropriate time, and as illustrated in FIG. 8B, the switch pipe of 
shear 12 is shifted vertically into alignment with its upper guide path 
P.sub.u, thus effecting a single cut X.sub.1 as the product is directed 
across the cutting path P.sub.c. The severed front end exits through pipe 
62, and the remainder of the product continues on through pipe 61. 
As shown in FIG. 8C, as the back end of the product approaches shear 10, 
its switch pipe is adjusted to position 56', thereby deflecting the 
product across its cutting path P.sub.C to effect a single cut X.sub.2. 
The product continues along the lower guide path P.sub.L, while the 
severed back end is directed along upper guide path P.sub.u into exit pipe 
60. 
With reference to FIG. 9, it will be understood that the velocity V at 
which the coacting cutting segments of the helical blades 44 traverse the 
cutting path P.sub.C must at least equal the speed of the product moving 
along the path of product travel P.sub.T. The velocity V is a function of 
several variables, including the diameter D of the blade helix, the helix 
angle .varies., and the rotational speed N of the drums 34. 
FIG. 10 graphically depicts a shear blade unrolled about its axis. 
##EQU1## 
If one assumes a product speed of 20,000 f.p.m., a roll diameter of 8 in. 
(0.67 ft) and a helix angle of 45.degree. C., which is the practical 
minimum for producing a satisfactory end cut, then the value of N is 
calculated as 
##EQU2## 
As the helix angle increases in order to produce blunter end cuts, so must 
the rotational speed of the blades increase. Thus, for a helix angle 
60.degree., N becomes 
##EQU3## 
A range of helix angles between about 45.degree.-60.degree. is considered 
to be optimum for the helical shear blades 44. Below 45.degree., the 
resulting cuts will be excessively sharp, whereas above 60.degree., the 
rotational drum speeds will exceed practical limits. 
Referring now to FIGS. 11 and 12, an alternative embodiment is shown having 
slotted guide pipes 64, 66 lining the grooves 49, 51 of the upper and 
lower guides 48, 50. The guide pipes are provided at their discharge ends 
with pinions 68 meshing with segmented gears 70. The gears 70 are 
rotatable about axes 72 and are driven through 90.degree. strokes by 
piston-cylinder units 74. A 90.degree. rotation of the gears 70 produces 
180.degree. rotation of the pinions 68. 
As shown in FIG. 12, the upper guide pipe 64 is rotatably adjusted to its 
open position, with its slotted side wall ready to accept product being 
diverted upwardly across the cutting path P.sub.C into the upper guide 
path P.sub.u. Product is shown running along the lower guide path P.sub.L, 
with the lower guide pipe 66 rotatably adjusted to confine the product 
within the lower guide groove 51. 
In preparation for effecting a cut of the product, the lower guide pipe 66 
will be rotated 180.degree. to its open position, thus clearing the way 
for the product to be switched upwardly across the cutting path P.sub.C 
into the open upper guide pipe 64. As soon as the cut has been effected, 
the upper guide pipe 64 is rotated to capture the product within the upper 
guide groove 49, and the lower guide pipe 66 is rotatably returned to its 
closed position. The guide pipes 64, 66 thus provide assurance that the 
product will not vibrate or otherwise stray unintentionally into the 
cutting path P.sub.C. 
In light of the forgoing, it now will be appreciated by those skilled in 
the art that the present invention offers significant advantages as 
compared to shears of the prior art. For example, the helical shear blades 
44 operate continuously, yet inherently produce single cuts in response to 
diversion of the products from their paths of travel P.sub.T across the 
shear cutting paths P.sub.C. This obviates any necessity for precisely 
coordinating blade orientation and speed with respect to the locations of 
the front and back ends of the product. Various combinations of helix 
angles, helix diameters and rotational drum speeds can be selected to 
accommodate different product speeds and cutting angles.