[0001] This invention relates to a pilgrim-process rolling mill for hot rolling pipes of
a type which comprises a spindle formed with a seat which extends along the rolling
axis and is adapted to accommodate a mandrel.
[0002] As is known, on completion of a pipe hot rolling operation on a pilgrim-process rolling
mill, the rolled pipe fits snugly around the mandrel due to the deformations it underwent.
[0003] To enable the mandrel to be slipped off the pipe, a so-called mandrel-breaker bush
is generally used which fits slidably over the mandrel and abuts against one end of
the rolled pipe. With the bush tightened down and by applying a sharp pull to the
mandrel in the axial direction, the mandrel can be released from the pipe.
[0004] After it has been freed from the pipe, the mandrel is removed from the spindle and
sent to a cooling station, and a new mandrel is set up.
[0005] The mandrel change involves of necessity the handling of the mandrel-breaker bushes,
which is currently performed by means of specially provided devices. This, additionally
to making the rolling mill still more complex, contributes toward longer downtime
in a rolling course.
[0006] The technical problem that underlies this invention is to provide a pilgrim-process
rolling mill which has such constructional and performance characteristics as to overcome
the cited shortcomings of the prior art.
[0007] This problem is solved according to the invention by a pilgrim-process rolling mill
being characterized in that it comprises a mandrel-breaker bush of substantially cradle-like
shape mounted to the spindle in alignment relationship with said seat and being open
thereinto, said bush being movable in a guided fashion along the rolling axis between
two ledges formed on the spindle.
[0008] Advantageously in accordance with a further aspect of the invention, the rolling
mill comprises a locking means mounted on the spindle for locking the bush angularly.
[0009] The features and advantages of a rolling mill according to the invention will be
more clearly understood from the following detailed description of a preferred embodiment
thereof, to be taken by way of illustration and not of limitation in conjunction with
the accompanying drawings.
[0010] In the drawings:
Figure 1 is a fragmentary view showing schematically in side elevation and in section
a pilgrim-process rolling mill according to the invention;
Figure 2 is a sectional detail view of the rolling mill shown in Figure 1 taken along
the line II-II;
Figure 3 is a perspective view showing in longitudinal section a detail of the rolling
mill of Figure 1;
Figures 4 and 5 are cross-sectional views, corresponding to Figure 2, which show the
rolling mill of this invention at different stages of a mandrel-breaker bush assembling
to the spindle; and
Figures 6 to 10 are sectional views showing schematically the rolling mill of Figure
1 at successive stages of its operation.
[0011] With reference to the drawing views, the numeral 1 comprehensively designates a pilgrim-process
rolling mill for hot rolling seamless pipes 2.
[0012] The rolling mill 1 comprises a hydropneumatic box 3, known per se, which has a piston
4 movable in the direction of the rolling axis along guides 5 and rotatable about
its own axis by a drive means, not shown, associated with the hydropneumatic box 3.
[0013] The piston 4 has a piston rod 6 to which a spindle 7 is fitted to rotate as a unit
therewith.
[0014] The spindle 7 is formed with a cradle-shaped seat 8 which extends along the rolling
axis and is accessible from the spindle outside axially through an axial opening provided
at a forward end 7a of the spindle 7, as well radially through a longitudinal opening
bordered laterally by two longitudinal edges 7b and 7c.
[0015] The seat 8 receives a tang 9 of a mandrel 10 over which fits the pipe 2 being rolled.
[0016] The rolling mill 1 comprises, in order to hold the mandrel 10 axially into the seat
8, retainer means 11 consisting of a groove 12 formed circumferentially around the
tang 9 and having a cylindrical cross-section shape, for engagement by a raised portion
13 concentrical with the rolling axis and formed in the shape of a half-ring integrally
with the cradle seat 8 and having the same length os the groove 12 in the axial direction.
[0017] Collectively indicated at 14 are sprung means mounted on the spindle 7 and adapted
to lock the tang 9 radially within the cradle seat 8. In particular, the sprung means
14 include an eave 14a adapted to overlap the tang 9 and hold it radially within the
seat 8.
[0018] Mounted on the hydropneumatic box 3 are pusher means 15 arranged to act on the sprung
means 14 to move the eave 14a from a position where it interferes with the cradle
seat 8 to a position where it does not interfere with it, thereby the tang 9 is released
and can be removed from the spindle 7.
[0019] The rolling mill 1 comprises a so-called mandrel-breaker bush 16 mounted to the spindle
7 and effective to pull the mandrel 10 off the pipe 2 on completion of the rolling
operation.
[0020] The bush 16 is configured substantially cradle-like concentrically with the rolling
axis and accessible from the outside both axially, and radially through a longitudinal
opening bordered laterally by two parallel longitudinal edges 17 and 18 set at a distance
apart, thereby the mandrel 10 can be inserted and withdrawn in the radial direction.
Further, the bush 16 extends aligned to the cradle seat 8 in the spindle 7 and opens
thereinto.
[0021] Advantageously, the bush 16 can be driven in a guided fashion along the rolling axis
between two edges 19 and 20 formed on the spindle 7, as explained in detail hereinafter.
[0022] On the bush 16, there is defined a rearward section 21 having, formed integrally
on a free end thereof a radially raised collar 22 which fits slidably into a substantially
half-ring-shaped groove 23 whose angular extension exceeds 180°, being formed in the
cradle seat 8 between the raised portion 13 and the forward end 7a of the spindle
7.
[0023] The groove 23 defines two walls, facing each other and lying perpendicularly to the
rolling axis, which constitute said rearward 19 and forward 20 ledges for the collar
22. Furthermore, the axial length of the groove 23 represents, less the thickness
of the collar 22, the stroke length of the bush 16 relatively to the spindle 7.
[0024] The bush 16 also comprises, outside the spindle 7, a forward section 24 which also
extends over a predetermined distance in the direction of the rolling axis and tapers
toward it.
[0025] Between the forward section 24 and the rearward section 21, there are formed circumferentially
around the bush 16 two parallel substantially half-ring-shaped elevations 25 and 26,
also having a wider angular extension than 180°, which define a groove 27 therebetween
adapted to engage with a mandrel-breaker rest 28, known per se.
[0026] The rolling mill 1 further comprises face interfit means 29 formed on one end of
the forward section 24 of the bush 16 and adapted to engage one end of a pipe 2 being
rolled.
[0027] Advantageously according to the invention, the interfit means 29 comprise a plurality
of teeth 30 arranged annularly around the rolling axis and extending along it; furthermore,
each tooth 30 has a back 30a tapering toward its free end.
[0028] To lock the bush 16 angularly on the spindle 7, locking means, collectively indicated
at 31 are used and comprise a detent 32 affixed to the spindle 7, preferably in interfit
relationship, at the edge 7b, and an insert 33 mounted removably by means of screws
34 on the opposed edge 7c. Both the detent 32 and the insert 33 jut out of their respective
edges 7b and 7c of the spindle 7 over the cradle seat 8.
[0029] The bush 16 is mounted to the spindle 7 in the manner described herein below with
reference to Figures 4, 5 and 2. In particular, Figure 4 depicts a start condition
with the insert 33 removed from the edge 7c.
[0030] The rearward section 21 of the bush 16 is inserted into the cradle seat 8 with a
substantially pivotal movement (see Figure 5) by inserting the edge 17 of the bush
16 in between the edges 7b and 7c of the spindle 7, turning the bush 16, and sliding
it into the seat 8 until the edge 17 abuts the detent 32.
[0031] The insert 33 is then mounted on the edge 7c so as to retain the edge 18 and lock
the bush 6 angularly (see Figure 2), with the collar 22 fitted in the groove 23.
[0032] To mount the mandrel 10 to the spindle 7, the pusher means 15 is first operated to
move the eave 14a of the sprung means 14 to the position of no interference with the
cradle seat 8, and the tang 9 of the mandrel 10 is then introduced radially into the
seat 8 and the bush 16, with the groove 12 of the tang located at the raised portion
13. Thus, the mandrel 10 is retained axially by the fit of the raised portion 13 in
the groove 12.
[0033] At this stage, the sprung means 14 are released to allow the eave 14a to locate at
the interfering position so as to overlie the end of the tang 9 and hold the mandrel
10 radially.
[0034] The hot rolling of the pipe 2 on the pilgrim-process rolling mill 1 is carried out
in a conventional manner not described herein. It matters to remark, however, that
during the initial rolling steps, referred to as the tacking, the bush 10 locates
at a partway retracted position inside the spindle 7, with the collar 22 abutting
the rearward ledge 19 of the groove 23 and the face teeth 30 of the bush 16 in engagement
with the rearward end of the pipe 2 and locking the pipe angularly to the bush. Thus,
initial slip or play is advantageously prevented as may occur while the pipe 2 is
yet to fit closely over the mandrel 10 and, accordingly, not yet unitized therewith,
whereas as the rolling process progresses, the pipe 2 would tighten around the mandrel
10 by deformation.
[0035] According to the invention, moreover, the mandrel 10 can be easile uncoupled angularly
from the spindle 7, and the rotary motion required to roll the pipe 2 is imparted
by the cited drive means of the hydropneumatic box 3 on the spindle 7, then on the
bush 16 rigid rotatively with the spindle 7, and finally on the pipe 2 through the
teeth 30.
[0036] To break the mandrel 10 axially off the pipe 2 at the end of the rolling process,
and enable the mandrel to be withdrawn, the mandrel-breaker rest 28 is first positioned
in the groove 27 of the bush 16 (see Figure 6). Then, a first pull is applied in the
axial direction, using conventional means and causing the spindle 7 and mandrel 10
to move back by a distance equal to the stroke length of the bush 16 as locked by
the rest 28 relatively to the spindle 7, until the collar 22 abuts against the forward
ledge 20 (see Figure 7), thereby the mandrel 10 is disengaged partway from the pipe
2.
[0037] Subsequently, the spindle 7 with the mandrel 10 is again advanced while still holding
the bush 16 locked with the rest 28, by a distance equal to the bush stroke, to disengage
the teeth 30 from the end of the pipe 2, which end is substantially bell-shaped on
completion of the rolling process (see Figure 8).
[0038] At this stage, the rest 28 is released from the groove 27, the spindle 7 with the
mandrel 10 is again moved backward, with the bush 16 also no longer retained by the
rest 28, and said rest is positioned between the bush 16 and the pipe 2 (see Figure
9).
[0039] Lastly, the spindle 7 is moved farther back until the mandrel 10 is drawn fully out
of the pipe 2 as held back by the mandrel-breaker rest 28 (see Figure 10).
[0040] On the pilgrim-process rolling mill according to this invention, the mandrel-breaker
bush is mounted directly to the spindle and does not require, therefore, to be manipulated
and replaced on the occasion of a change of a mandrel at the end of a rolling course.
As a result, additionally to the advantage of eliminatin bush handling devices, with
a rolling mill according to the invention, tool handling, and specifically mandrel
changes, is made much easier, which reflects in improved reliability of the rolling
mill.
[0041] In addition, it has proved particularly advantageous to provide a forward section
of the bush with an elongate shape that tapers toward the rolling axis to enable rolling
of a longer section of the pipe bell-shaped end and reduce scrap.
[0042] A further advantage afforded by a pilgrim-process rolling mill according to the invention
is that by providing face interfit means between the mandrel-breaker bush and the
pipe to be rolled, the rolling operations can be performed in an optimum manner even
at the tacking stage, by eliminating any play or slip of the pipe.
[0043] Furthermore, due to the teeth engaging in the pipe being rolled, the pipe itself
is made to cooperate mechanically with the bush, thereby the latter may have reduced
size and weight to bring about lower costs.
1. A pilgrim-process rolling mill for hot rolling pipes of a type comprising a spindle
(7) formed with a seat (8) which extends in the direction of the rolling axis and
is adapted to accommodate a mandrel (10), characterized in that it comprises a mandrel-breaker
bush (16) of substantially cradle-like shape mounted to the spindle (7) in alignment
relationship with said seat (8) and being open thereinto, said bush (16) being movable
in a guided fashion along the rolling axis between two ledges (19,20) formed on the
spindle (7).
2. A rolling mill according to Claim 1, characterized in that it comprises locking
means (31) mounted to the spindle (7) to lock the bush (16) angularly.
3. A rolling mill according to Claim 1, characterized in that said bush (16) comprises
a rearward section (21) fitted slidably in said seat (8) on the spindle (7).
4. A rolling mill according to Claim 3, characterized in that said rearward section
(21) of the bush (16) is provided with a raised collar (22) fitting into a groove
(23) formed in said seat (8) and defining two facing walls which constitute said edges
(19,20).
5. A rolling mill according to Claim 4, characterized in that said bush (16) includes
outside the spindle (7) a forward section (24) extending along the rolling axis and
tapering toward it.
6. A rolling mill according to Claim 5, characterized in that it includes a groove
(27) formed circumferentially around the bush (16) outside the spindle (7) between
said rearward section (21) and said forward section (24).
7. A rolling mill according to Claim 4, characterized in that it comprises face interfit
means (29) formed on one end of the forward section (24) of the bush (16) and adapted
to engage a pipe (2) being rolled.
8. A rolling mill according to Claim 7, characterized in that said interfit means
(29) comprise a plurality of teeth (30) arranged into an annulus and extending along
the rolling axis.
9. A rolling mill according to Claim 8, characterized in that said teeth (30) have
tapering backs (30a).
10. A rolling mill according to Claim 2 characterized in that said locking means (31)
comprise a detent (32) attached to the spindle (7) on one side of said seat (8) and
an insert (33) removably mounted on the other side of said seat (8).