Backup roll for thin walled pipe grooving device

The roll comprises a solid, cylindrical, heat-treated steel rod having a threaded stud section on one end, and an externally knurled operating section on its opposite end. The stud section is adapted to thread into a bore formed in one end of the drive or work-rotating shaft of conventional roll grooving apparatus, thereby to support the operating section in the path of a conventional grooving roll which is mounted to reciprocate radially of the drive shaft between operative and inoperative positions. A circumferential groove in the operating section of the backup roll registers with a circumferential boss on the grooving roll. When one end of a piece of thin walled pipe is inserted over the operating section and the grooving roll is advanced against the pipe, the shaft is rotated and rotates the pipe so that the grooving roll forms a groove therein.

This invention relates to a device for grooving thin walled pipe, and more 
particularly to an improved backup roll for such a device. 
In the grooving of thin walled pipe, it is customary to insert one end of 
the pipe over one end of a grooved backup roll, and then to force one or 
more grooving rolls radially into engagement with the thin walled pipe at 
the point where it overlies the grooved backup roll. Then, by rotating the 
backup roll and the overlying pipe, the grooving rolls force the thin 
walled pipe radially inwardly at the location of the underlying groove in 
the backup roll. The pipe is thus provided with a circumferential groove 
which corresponds to the groove in the backup roll. 
There are a number of known devices for grooving thin walled pipe in the 
above-noted manner. Heretofore, however, none of these known devices has 
had the capability of grooving thin walled pipes of rather small 
diameters, for example pipes having diameters of 11/2" or less. For these 
smaller pipes, it heretofore has been customary to form the grooves by use 
of a hand-operated grooving device, which is similar to a pipe cutter, and 
which does not utilize a grooved backup roll for forming the groove. 
For a typical, known pipe grooving device of the type which uses a grooved 
backup roll, reference is made to U.S. Pat. No. 3,903,722, which is cited 
merely by way of example. In the device illustrated in this patent the 
grooved backup roll (62) is typical of those currently employed in the 
industry, in that it is hollow, and has an axial bore (truncated conical 
in this particular case) which allows it to be inserted removably over one 
end of a drive shaft (28) which is employed to rotate the backup roll, and 
the surrounding work (thin walled pipe), when the device is in use. While 
this construction has been found satisfactory for roll grooving thin 
walled pipe of relatively large diameters, it has not been possible 
heretofore to use devices of this type for roll grooving pipes having 
diameters, for example, of 11/2" and less. 
The reason for the above-noted difficulties is that, in order to roll 
groove a piece of pipe by using a backup roll which projects into the bore 
of the pipe, it is necessary that the backup roll have a smaller diameter 
than the inside diameter of the groove that is to be rolled into the pipe, 
otherwise it would not be possible to withdraw the grooved pipe from the 
backup roll after the grooving operation. Obviously, therefore, in order 
to roll groove a thin walled pipe having an inside diameter of 11/2", so 
as to form in the pipe a groove having, for example, an inside diameter of 
13/8", it will be necessary to employ a backup roll having an outside 
diameter of less than 13/8". This has not been possible in devices of the 
type noted above which use a hollow, or axially-bored backup roll which is 
releasably secured over one end of the associated drive shaft, because 
this would mean that the cumulative outside diameter of both of the 
removable backup roll and the portion of the drive shaft which projects 
through its axial bore would have to be less than 13/8"; and practically 
speaking, this would mean that the portion of the drive shaft which 
projects through the bore of the backup roll would have to be reduced 
correspondingly in diameter. In order to roll groove thin walled pipe 
having a diameter of 1", this would mean reducing the diameter of the 
shaft projection to approximately 1/2" or less, which would mean that the 
shaft would no longer be strong enough to accommodate the radial load 
which would be applied to the shaft by the grooving roll during use of the 
device. 
It is an object of this invention, therefore, to provide for roll grooving 
devices of the type described a novel backup roll which is particularly 
suited for roll grooving thin walled pipes having relatively small 
diameters. 
Another object of this invention is to provide for roll grooving devices of 
the type described an improved, solid backup roll which can be removably 
attached to the drive shaft of the device for grooving thin wall pipes of 
relatively small diameter. 
Other objects of the invention will be apparent hereinafter from the 
specification and from the recital of the appended claims, particularly 
when read in conjunction with the accompanying drawing.

Referring now to the drawing by numerals of reference, 10 denotes generally 
the frame of a roll grooving device having a horizontal platform section 
11 on which is secured the base 12 of a conventional needle bearing 
housing 13. Rotatably journaled adjacent its forward end in needle 
bearings (not illustrated) contained in housing 13 is a circular drive 
shaft 15, the rear end of which is drivingly connected in known manner to 
an electric motor (not illustrated), or the like, which is used to drive 
the shaft and the work as noted hereinafter. 
Releasably secured to the forward end of shaft 15, and projecting coaxially 
therefrom beyond the forward edge of the platform section 11, is an 
improved backup roll 20 made according to one embodiment of this 
invention. Roll 20 is made, for example, from a steel rod, or the like, 
and has intermediate its ends a circumferential shoulder section 21, which 
has an outside diameter substantially equal to that of the diameter of 
shaft 15. Roll 20 has a reduced-diameter, externally threaded shank 
portion 22, which projects coaxially rearwardly from one side of the 
shoulder section 21, and which is removably threaded into an internally 
threaded blind bore 23, which is formed in the outer end of shaft 15 
coaxially thereof. When the shank portion 22 of the backup roll 20 has 
been fully threaded into the bore 23 so that the rear surface 24 on 
shoulder 21 engages the outer end of the drive shaft 15, a diametral 
opening 25 in the threaded shank 22 registers with opposed radial openings 
26 in the shaft 15, so that a lock pin 27 can be inserted into the 
registering openings 25 and 26 to lock the roll 20 against rotational 
movement relative to shaft 15. 
Projecting coaxially forwardly from the opposite or outer end of the 
shoulder 21 is another reduced-diameter, cylindrical section 28, which is 
externally knurled so as to function as a driving surface for the pipe of 
work W, that is to be grooved as noted hereinafter. Intermediate its ends 
the operating or driving section 28 of the backup roll 20 has therein a 
circumferential groove 29, which is used for the actual grooving operation 
as noted hereinafter. 
Bolted or otherwise secured to the lower end of a post 31, which is mounted 
in a conventional manner (not illustrated) on the frame 10 for vertical 
reciprocation above the operating section 28 of the backup roll 20, is a 
bifurcated yoke member 32. Member 32 has a pair of downwardly projecting 
legs 33 having in the lower ends thereof registering openings in which a 
headed bolt 34 is secured by a nut 35, so that the bolt extends between 
legs 33 above and parallel to the operating section 28 of the backup roll 
20. 
Mounted to rotate on bolt 34 coaxially thereof between the legs 33 of the 
yoke 32 is an annular grooving tool or roll 37, which has intermediate its 
ends an integral, circumferential boss or grooving section 38, which has 
an outside diameter larger than that of the remaining outer peripheral 
surface of roller 37. The yoke member 32, of course, is mounted so that 
the embossed surface 38 on roller 37 registers with the groove 29 on the 
backup roll 20, with the axes of both the roller 37 and the backup roll 20 
lying in a common plane and being parallel to each other. Moreover, the 
shoulder 21 on the backup roll 20 is designed so that its outer or right 
hand end 41 is disposed in a plane parallel to, and nearly coplanar with, 
the plane containing the inner or left hand end 42 of the grooving roll 
37, as illustrated in FIG. 1. 
In operation the post 31 is elevated from its position as illustrated in 
FIG. 1 to withdraw the grooving roll 37 to an upper or inoperative 
position in which it is spaced above the operating section 28 of the 
backup roll 20. One end of a thin walled pipe or tube W, which is to be 
grooved, and which is relatively small in diameter, is then inserted over 
the operating section 28 of the backup roll 20 until the outer end thereof 
(the left end of the work as illustrated in FIG. 1) engages the plane 
surface 41 formed on the outer end of the backup roll shoulder 21. The 
post 31 is then lowered to engage its boss or grooving surface 38 with the 
work W in the area immediately located around the outside of the groove 29 
in the backup roll; and shaft 15 is then rotated so that the downward 
pressure exerted by post 31 causes the work W to rotate with the shaft 15, 
while the roll 37 also rotates relative to the work. The pressure of roll 
31 is progressively increased in order to cause the work W to be forced or 
bent downwardly into the groove 29 in the backup roll 20, thereby 
producing the groove W' in the work at a point axially spaced slightly 
from its outer or left end (FIG. 1). 
After the groove W' has been formed in the work, the post 31 is elevated 
back into its inoperative position, and the work is withdrawn from the 
forward end of the backup roll 20. It will be noted (FIG. 1) that the 
inside diameter of the groove W' which is formed in the work by this 
operation, is slightly larger than the external diameter of the driving 
section 28 of the backup roll 20, so that the work can be readily 
withdrawn from the roll after the grooving operation has taken place. 
From the foregoing it will be apparent that the instant invention provides 
a relatively simple and inexpensive means for enabling the roll grooving 
of thin wall pipe of very small diameters, for example diameters ranging 
11/2 and less. This, as above noted, was not possible heretofore except by 
using apparatus of the type which does not employ a backup roll to support 
the work during the grooving operation. But with applicant's invention, 
however, it is now possible to support thin walled pipe of relatively 
small diameter internally during a roll grooving operation so that the 
resulting grooving operation can be performed substantially more 
accurately and rapidly than was heretofore possible. Moreover, since the 
work is supported internally by the backup roll it is possible to control 
more accurately the cross sectional configuration of the resulting groove 
in the work. 
For example, as noted in FIG. 1, the embossed grooving surface 38 on the 
grooving roll 37 has beveled edges 38' which form corresponding beveled 
edges in the groove W' that is finally formed in the work W. This is made 
possible through the use of the backup roll 20, which enables the 
concentration of substantially greater grooving pressures in localized 
areas of the pipe or work W during the grooving operation, as compared to 
grooving apparatus of the type which does not utilize an internal backup 
roll or arbor for internally supporting the work during a grooving 
operation. When a backup roll is not employed, it is not possible rigidly 
to support both portions of the work which are located immediately 
adjacent opposite sides of that portion of the work which is engaged by 
the grooving boss 38, and consequently it is not possible to form a very 
accurate groove in the work. 
Still another advantage of applicant's novel backup roll is that it can be, 
if necessary, readily removed and replaced by a backup roll of different 
diameter, or by a backup roll having a groove 29 of different 
configuration, location or depth. In any case, each such backup roll 20, 
will consist of a solid, cylindrical member which, in practice, is 
preferably heat treated to increase its strength and resistance against 
bending during the actual roll grooving operation, when the upper grooving 
roll 37 is being urged downwardly against the work, and at which time the 
upper grooving roll obviously tends to apply a rather large moment or 
bending force transverse to the axis of rotation of the backup roll 20. 
While this invention is particularly suitable for use in the grooving of 
thin walled pipe, it is to be understood that it could be used for 
grooving standard wall pipe as well. Moreover, while the invention has 
been illustrated and described in connection with a preferred embodiment 
thereof, it will be apparent that it is capable of still further 
modification, and that this application is intended to cover any such 
modification that may fall within the scope of one skilled in the art or 
the appended claims.