Groove rolling of piping elements

Details Groove rolling of piping elements Groove rolling of piping elements

1999-07-30

2001-03-06

Larson, Lowell A. (Department: 3725)

Metal deforming

By use of tool acting during relative rotation between tool...

During rotation of work

Reexamination Certificate

active

06196039

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to groove rolling of piping, tubing, and fitting elements.
A grooved end pipe coupling, e.g. of the type illustrated in
FIGS. 1 and 1A
, is used for joining together ends of pipe elements in a leak tight assembly by use of grooves that are cut, cast or formed in the ends of the pipe elements. The terms “pipe elements”, “pipes”, and “piping”, refer herein to sections of pipes, tubes, fittings, valves bodies, and the like, both in the plural and the singular. Referring to
FIGS. 2 and 3
, critical parameters of a grooved end connection include: the gasket seat diameter, D
s
, groove diameter, D
g
, gasket seat width, W
s
, and groove width, W
g
. In the case of wrought metal piping elements, e.g. tubing, fittings, or valve bodies, the grooved end of the piping element, P, is conventionally produced by either a cutting (machining) operation or a rolling (contour roll forming) operation as shown in piping element P
CUT
, of
FIG. 2
, and piping element P
ROLL
, of
FIG. 3
, respectively. In the case of a cast fitting or valve body, the grooved end connection is normally either cut in the configuration of a piping element, P
CUT
shown in
FIG. 2
, or cast in the dual outward step configuration of a piping element, P
CAST
, shown in FIG.
4
. Each piping element includes a groove
30
a distance at least W
s
from an end. P
ROLL
includes an indented region
32
on its inner surface underneath groove
30
.
Cut grooves for use with grooved end pipe couplings are typically prepared by the use of a turning process.
Roll grooves for use with grooved end pipe couplings have been prepared by an apparatus similar in function to that described in Kunsman U.S. Pat. No. 3,995,466 and Dole U.S. Pat. No. 5,279,143. Both of these patents describe a means for contour roll forming a groove in the end of the pipe element by which a segment of the pipe is press formed or stretched into the desired configuration by forcing a shaped die roller located outside of the pipe against a form roller located inside of the pipe.
Other examples of contour roll forming of pipes are presented in Constantine, Great Britain Patent 18201, Pritchett, et al. U.S. Pat. No. 3,191,416 and Vaill, et al. U.S. Pat No. 3,290,914. Although these latter three patents describe devices which force a die roller located inside the pipe against a form located outside of the pipe, the contour roll forming principle is the same as for the previous two patent references. That is, the pipe is locally shaped by radial press forming or stretching, into the desired contour.
Referring again to
FIGS. 1
,
1
A, and
2
-
4
, a typical grooved end pipe coupling assembly
10
consists of two or more housing segments
12
,
14
, a gasket
16
, and fastening means, e.g. nuts
18
and bolts
20
, for securing assembly
10
together with the end connections to be joined. Housing segments
12
,
14
have keys
22
around the inner periphery at both ends, a shoulder
24
also around and just inside each key, and a gasket cavity
26
. Keys
22
fit into grooves
30
formed in each pipe end to axially and transversely retain the end connections. Keys
22
and shoulders
24
are involved to varying degrees in maintaining coupling assembly
10
generally centered about the grooved end connection. Shoulder
24
fits closely around the gasket seat diameter to prevent gasket
16
from extruding outwardly under the internal pressure of the piping system, gasket
16
being retained in gasket cavity
26
and producing a seal on gasket seat surfaces
34
to form a leak tight assembly.
SUMMARY OF THE INVENTION
According to one aspect, the invention provides groove rollers for use with a roll grooving device for forming a groove in an outer surface of a pipe near an end of the pipe. The groove rollers include an outside roller and an inside roller. The outside roller has a surface that includes a first protrusion for forming the groove a first distance from the end of the pipe and a second protrusion positioned to contact the pipe a second distance from the end of the pipe when forming the groove, wherein the second distance is shorter than the first distance. The inside roller has a surface including a grooving notch configured to receive the first protrusion. The inside roller surface may include a second notch configured to receive the second protrusion.
In one feature, one of the outside and inside rollers includes a pipe abutment surface against which the end of the pipe is positioned when forming the groove.
In another feature, the outside roller includes a first aligning element and the inside roller includes a second aligning element configured to interact with the first aligning element to align the outside and inside rollers when forming the groove. The first aligning element may include a first alignment surface facing the first protrusion, and the second aligning element may include a second alignment surface which contacts the first alignment surface when forming the groove. The first alignment surface may be formed on a side of an alignment bead and the second alignment surface may be formed on a wall of an alignment slot which receives the alignment bead when forming the groove. In one embodiment, the second alignment surface is formed on a side of a second alignment bead, and the first alignment surface is formed on a wall of a second alignment slot which receives the second alignment bead when forming the groove, the second alignment slot being located between the second protrusion and the first mentioned alignment bead. The second alignment bead can include the pipe abutment surface.
In yet another feature, the second protrusion includes a chamfered surface which faces the first protrusion.
In a further feature, the first protrusion, a surface of the second protrusion and the grooving notch are configured to form an arcuate surface on the pipe adjacent to the groove when forming the groove. A tangent to the arcuate surface intersects an adjacent wall of the groove at an angle &dgr;. The surface of the second protrusion is configured to decrease &dgr;. In one embodiment, the surface of the second protrusion faces the first protrusion at an angle &bgr; from a perpendicular to the rotational axis of the outside roller, wherein &bgr; is in a range between about 0° and 70°.
According to another aspect of the invention, groove rollers include an outside roller and an inside roller. The outside roller has a surface which includes a first protrusion configured to form the groove, a second protrusion configured to inhibit flaring at the end of the pipe, and a first aligning element. The inside roller has a surface including a first notch configured to receive the first protrusion, a second notch configured to receive the second protrusion, and a second aligning element configured to interact with the first aligning element to align the outside and inside rollers during groove rolling. The first aligning element can include a first alignment surface formed on a side of an alignment bead and facing the first protrusion, and the second aligning element can include a second alignment surface formed on a wall of an alignment slot which receives the alignment bead when forming the groove. The second alignment surface contacts the first alignment surface when forming the groove.
The second alignment surface, in one embodiment, is formed on a side of a second alignment bead. In this instance, the first alignment surface is formed on a wall of a second alignment slot which receives the second alignment bead when forming the groove. The second alignment slot is located between the second protrusion and the first mentioned alignment bead. The second alignment bead can include a pipe abutment surface against which the end of the pipe is positioned when forming the groove, wherein the pipe abutment surface is at a small angle &agr; from a perpendicular to the rotational axis of the inside roller. In a different embodiment, the side of the alignment bead also includes a pipe abutment surface against which the end o

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