Geometrical instruments – Gauge – Circular size
Reexamination Certificate
2001-02-13
2002-11-05
Bennett, G. Bradley (Department: 2859)
Geometrical instruments
Gauge
Circular size
C033S529000, C033S555100, C072S031010
Reexamination Certificate
active
06473981
ABSTRACT:
FIELD OF THE INVENTION
This invention concerns a tool and a method for indicating when an external circumferential groove formed in a pipe has a desired outer diameter.
BACKGROUND OF THE INVENTION
Mechanical pipe coupling systems which do not require welding, brazing or soldering for joining piping, find widespread use throughout industry, especially in petroleum and chemical applications where it may be hazardous and/or forbidden to use an open flame or an electrical arc. Such mechanical coupling systems are also more conveniently employable in the field or in remote locations where primitive environmental conditions and a lack of access to available services and supplies such as electricity or acetylene gas and oxygen inhibit traditional arc or gas welding techniques.
FIG. 1
shows an example of one mechanical pipe coupling system wherein pipe ends
20
and
22
are joined together by a coupling
24
. Coupling
24
comprises segmented semi-circular collar segments
26
and
28
which are clamped together around the pipe ends. Each collar segment is roughly U-shaped in cross section as shown, the ends of the “U” forming a pair of flanges
30
and
32
which engage grooves
34
and
36
formed circumferentially in the pipe wall
38
on each pipe end. A pressure energized elastomeric seal
40
is positioned within the coupling to effect a fluid tight joint between the pipe ends.
In addition to providing a fluid tight joint, the mechanical coupling system shown in
FIG. 1
also provides a strong connection between the pipe ends which allows the joint to withstand bending, axial and torsional loads on the pipes without joint separation or blowout.
To ensure a fluid tight and robust connection via the mechanical system, fairly tight tolerances must be maintained between the flanges
30
and
32
of the collar segments
26
and
28
and the grooves
34
and
36
in the pipe ends
20
and
22
. Groove depth uniformity is also an important parameter affecting the connection. While the tolerances of the flanges are relatively easily controlled during manufacture of the collar segments, it is more difficult to control the outer diameter of the grooves, as well as the uniformity of the groove depth to within a desired tolerance. There are several factors which affect the accuracy of the grooves, such as the tolerance on the pipe outer diameter, the tolerance on the wall thickness and, for pipes having an outer diameter greater than 6 inches, the roundness of the pipe is also significant.
Groove
34
is formed by a cutting process which removes material from the pipe wall
38
. This may be done, for example, on a lathe. The pipe is held in the lathe chuck and rotated about its longitudinal axis while a cutting tool engages the surface at the appropriate distance from the end of the pipe and cuts the wall
38
to the desired depth to form the groove
34
having a desired outer diameter appropriate for the particular pipe and coupling
24
. Although lathes produce an accurate outer groove diameter, the groove often has non-uniform depth around the pipe circumference due to the inherent out of roundness of the pipe.
In contrast, groove
36
is formed by cold working the material comprising the pipe wall
38
beyond the yield point. Such grooves are most advantageously formed in the pipes by means of a grooving tool
21
, shown in
FIGS. 1A and 1B
. Grooving tool
21
comprises a grooving roll
23
which cooperates with a backup roll
25
to permanently deform the pipe wall
38
. The pipe wall is positioned between the grooving and backup rolls, and the rolls are forced toward each other while they are rotated around the pipe, either by rotating the tool
21
relatively to the pipe
20
or the pipe relatively to the tool. The grooving roll
23
has a hardened circumferential surface
27
which engages and permanently deforms the pipe wall
38
into a trough
29
positioned circumferentially around the backup roll
25
and in registration with the grooving roll
23
. As the rolls rotate around the circumference of the pipe and pressure is applied to force them together, the groove
36
is deepened, making the outer diameter of the groove smaller. A hydraulic system may be used to force the grooving roll toward the backup roll, but other means, such as a manually turned jackscrew
31
, are also feasible.
While the cold working process produces a groove of uniform depth, establishing the proper diameter of the groove
36
is usually a trial and error process. A variably adjustable depth gage
37
on the grooving tool
21
which limits the travel of the grooving roll toward the backup roll is used initially to form the groove
36
to a depth yielding a groove diameter near to, but short of, the desired diameter. The groove is then made progressively deeper in stages, and multiple hand measurements of the groove circumference or diameter are made between the stages until the groove is formed having a diameter within the allowable tolerance. However, this requires that the pipe being grooved must be removed and remounted on the tool between each stage, leading to significant inefficiencies in the formation of the grooves. These inefficiencies become especially costly when large numbers of pipes are required. Furthermore, the method using depth gages and hand measurements is prone to human error, leading to pipes in which the grooves are made too deep or too shallow. Grooves which are too deep allow the coupling
24
to reposition itself eccentrically on the pipe ends
20
and
22
when the pipe joint experiences bending loads. The coupling tends to move toward the side of the joint which is in tension, thus, reducing the engagement of flanges
30
and
32
on that side. This weakens the joint and may lead to joint separation. Conversely, grooves which are too shallow do not allow the coupling
24
to fully close around the pipe ends
20
and
22
. Consequently, flanges
30
and
32
have less engagement with the side walls of the grooves
34
and
36
. This reduces the load carrying capability of the joint which may also lead to joint separation, particularly blowout type failures. The seal
40
is also under less radial compression and is, therefore, more prone to leakage when the grooves are too shallow.
There is clearly a need for a more precise method and apparatus for forming grooves in pipe ends which avoids the time consuming trial and error procedure of multiple stages of alternating deformation and measurement and allows the grooves to be formed in one attempt efficiently, reliably and precisely at the proper diameter within the desired tolerances.
SUMMARY AND OBJECTS OF THE INVENTION
The invention concerns a tool for indicating that an external circumferential groove of a desired outer diameter has been formed in a pipe, for example, by cutting or cold forming. The pipe has an external surface into which the groove is cut or cold formed and a longitudinal axis arranged lengthwise along the pipe. In its preferred embodiment, the tool comprises a first arm pivotally mountable adjacent to the pipe for rotation about a pivot axis substantially parallel to the longitudinal axis. The pipe and the first arm are relatively rotatable to one another about the longitudinal axis. For example, for a cut groove the pipe may be mounted in the chuck of a lathe and the arm may be fixedly mounted on the lathe, the pipe turning relatively to the arm. For a cold formed groove, the arm may be mounted on a grooving tool which orbits around the pipe to form the groove.
A first feeler surface is mounted on the first arm and is engageable with the external surface of the pipe within the circumferential groove. The first feeler surface traverses the pipe circumference within the groove upon relative rotation of the pipe and the first arm. The first arm is pivotable to a predetermined angular position when the first feeler surface is engaged with the external surface of the pipe within the groove and the groove has the desired outer diameter.
The invention also concerns a tool for forming an external circumferent
Bennett G. Bradley
Synnestvedt & Lechner LLP
Victaulic Company of America
LandOfFree
Diameter indicator for use with groove forming tools does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Diameter indicator for use with groove forming tools, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Diameter indicator for use with groove forming tools will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2980478