Clamshell pipe lathe having improved bearing arrangement

A clamshell machining lathe for cutting and finishing pipes in industrial settings comprises a split-ring assembly, including a clamping ring that is positioned about the pipe, and journaled to the clamping ring is a rotatable gear ring that supports a tool block carrying a cutting tool. The improvement resides in the bearing arrangement used to journal the gear ring to the stationary clamping ring. One face of the gear ring includes an annular groove whose side walls define a bearing race. The race is dimensioned to receive a plurality of roller bearings therein, the roller bearings being affixed to a planar surface of the clamping gear in a circumferential arrangement so as to fit into the bearing race when the gear ring is coupled to the clamping ring. The arrangement can support greater loads without canting, thus reducing wear on the moving parts.

BACKGROUND OF THE INVENTION 
I. Field of the Invention 
This invention relates generally to a machining lathe, and more 
particularly to a split frame clamshell-type portable machining lathe for 
cutting and finishing relatively large diameter pipes. 
II. Description of the Prior Art 
Split frame clamshell lathes of the type described herein are known in the 
art. My earlier U.S. Pat. Nos. 4,739,685 and 4,939,964 are illustrative of 
the technology involved. The split frame pipe machining lathe generally 
comprises first and second semicircular halves that are designed to be 
joined together so as to surround the pipe to be machined. The resulting 
annular assembly includes a stationary ring portion that becomes clamped 
to the pipe and an abutting rotatable portion including a ring gear that 
is journaled to the stationary portion for rotation about the 
concentrically disposed pipe. An air-operated, hydraulically-operated or 
electrically-operated motor is operatively coupled to the assembly and 
includes a drive gear designed to mesh with the ring gear on the rotatable 
segment of the pipe lathe. Also mounted on the rotatable segment of the 
pipe lathe is a tool block for supporting a cutting tool that can be made 
to advance in the radial direction against the pipe to be machined in 
incremental steps upon each revolution of the ring gear. 
A problem has heretofore existed in the prior art in the manner in which 
the ring gear has been journaled to rotate relative to the stationary 
clamping ring. It FIG. 2 of my earlier U.S. Pat. No. 4,739,685, which is 
reproduced herein as FIG. 1, there is shown a cross-section illustrating 
the manner in which the gear member 10 is journaled for rotation relative 
to the stationary ring member 11. A first set of roller bearings 12 
cooperate with the straight arcuate surface of a circular race member 14, 
which is bolted onto the ring gear member 10 by bolts 13. The race member 
14 also cooperates with a second set of bearings 15. The bearings in set 
15 have opposed beveled segments for cooperating with a W-shaped surface 
16 formed on the race member 14 and with a V-shaped extension or 
protuberance 17 formed on the inner side wall of the cavity 18. 
It has been found that under load, the race member 14 behaves like a 
fulcrum, allowing the ring gear 10 to rock back and forth which results in 
undue wear on the bearings and slight variation in the cutting circle as 
the ring gear orbits the pipe being finished. Moreover, the assembly is 
costly to manufacture because of the intricacies in the machining required 
to produce the ring gear 10 and the tolerances that need to be maintained 
between the ring gear 10 and the circular race member 14 so that these 
parts will provide the appropriate contact with the associated bearings 12 
and 15. 
In the low clearance pipe lathe described in my earlier U.S. Pat. No. 
4,939,964, the problems inherent in the journaling of the ring gear to the 
stationary member described in the '685 patent were partially resolved. 
FIG. 2 herein taken from the '964 patent shows the way the ring gear is 
journaled in that earlier invention. The problem of undue wear occasioned 
by the ability of the ring gear 19 therein to rock under loads was still 
present. Again, the race member 20 was fabricated separately from the ring 
gear 19 and affixed to it by bolts which made it difficult to maintain the 
desired degree of contact between the race member 20, the W-shaped segment 
21 on the ring gear and the notched roller bearings 22 affixed to the 
stationary member 23. 
OBJECTS 
It is accordingly a principal object of the present invention to provide an 
improved split frame clamshell pipe lathe. 
Another object of the invention is to provide a portable, clamshell-type 
pipe lathe having an improved bearing/bearing race design that resists 
rocking under load. 
A further object of the invention is to provide an improved bearing 
structure for a portable pipe machining lathe of the clamshell type whose 
rotatable ring gear includes a simplified one-piece bearing race milled 
into the flat side surface of the ring gear and cooperating with roller 
bearings that are eccentrically mounted on an axis whereby the clearance 
between the bearing surface and its associated race can be adjusted to a 
desired tolerance to thereby inhibit any tendency of the ring gear to rock 
relative to the stationary ring member even under heavy loads. 
A still further object of the invention is to provide an improved portable 
clamshell-type pipe machining lathe including a rotatable ring gear having 
a bearing race machined therein and whose side surfaces define a bearing 
race that cooperates with first and second sets of roller bearings that 
are slightly radially offset from one another to thereby increase the span 
and spread the load, thereby minimizing any undue wear during use. 
SUMMARY OF THE INVENTION 
The foregoing objects and features of the invention are achieved by 
providing a clamshell machining lathe for cutting or finishing pipes used 
in industrial applications where the machining lathe comprises a first 
stationary annular member that is adapted to be concentrically clamped 
about the periphery of a cylindrical pipe segment to be finished. This 
first stationary annular member has an inner arcuate face, an outer 
arcuate face and a planar surface extending therebetween. A plurality of 
sets of roller bearings having plural rollers rotatably mounted on a 
common axes are designed to have a predetermined outer diameter. The 
members of the set are affixed to the stationary annular member with the 
axes thereof disposed perpendicularly to a planar surface of the first 
annular member to define a generally circular track. Completing the 
assembly is a second, rotatable, annular member having an inner arcuate 
face, an outer arcuate face and a planar surface extending therebetween. 
The outer arcuate face includes gear teeth thereon. The planar surface of 
the second annular member includes a circumferential bearing race 
comprising a groove of a depth and width to receive therein the plurality 
of roller bearings when the first and second annular members are 
juxtaposed with the planar surface of the first annular member in facing 
relationship to the planar surface of the second annular member. The outer 
diameter of the plurality of roller bearings cooperate with the opposed 
walls defining the circumferential bearing race to rotatably support the 
second annular member relative to the first annular member. 
In accordance with one embodiment, the plurality of roller bearings are 
arranged in first and second sets with the roller bearings in the first 
set each rotatable about an axis that is radially offset relative to a 
corresponding axis of the second set. In a second embodiment, the axes of 
each of the roller bearings lies on the same bearing circle of the 
stationary member but are eccentrically mounted on their axes of rotation 
so as to be adjustable in establishing rolling contact between them and 
their associated race surfaces.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 3, there is shown a perspective view of clamshell-type 
pipe lathe constructed in accordance with the present invention. It is 
indicated generally by numeral 30 and is seen to comprise a first annular 
member 32 that is adapted to be concentrically clamped about the periphery 
of a cylindrical pipe to be finished (not shown). The annular member 32 is 
shown as being split diametrically along lines 34 and 36, with the two 
semicircular segments being fastened together by swing bolts as at 38. 
While the assembly 30 is shown as being comprised of two semicircular 
halves, to increase its portability, the device can be constructed as four 
quarter segments that may be joined together about the pipe. For proper 
centering, a plurality of pads 40 are positioned about the interior wall 
surface of the stationary ring member 32 and held in place by bolts 42 
(FIG. 4). 
Rotatably journaled to the interior face of the stationary ring member 32 
is a second, rotatable, annular member 44 also comprised of two 
semicircular halves 46 and 48 held together by swing bolts as at 50. 
Enclosed within a protective shroud 52 attached to the stationary annular 
member is a ring gear 54 having a pattern of gear teeth formed in the 
outer peripheral surface thereof. As will be explained in greater detail 
hereinbelow, the ring gear 54 is journaled to the stationary annular 
member 32 and cooperates with a spur gear 56 which is driven by a suitable 
motor 58, the motor being mounted on a bracket 60 secured to the 
stationary annular member 32. The spur gear 56 meshes with the teeth on 
the ring gear 54 and when the motor 58 is driven, the ring gear 54 rotates 
within the shroud 52. The motor used may be air driven, hydraulically 
driven or electrically driven. 
Affixed to the exterior face 62 of the ring gear 54 is a tool slide block 
assembly indicated generally by numeral 64. The tool slide block 64 
supports a metal cutting tool 66 therein and upon each rotation of the 
gear ring, as the cutting tool orbits the pipe being finished, a star 
wheel 68 on the slide block assembly engages a pin 70 disposed in the path 
of travel of the star wheel, causing the threaded shaft to which the star 
wheel is affixed to rotate through a predetermined angle and thereby 
advance the slide block 64 in the radial direction. In this fashion, the 
tool 66 can be advanced in incremental steps through the wall thickness of 
the pipe being finished to cut off an end segment thereof. 
Also shown in FIGS. 3 and 4 is a bracket 71 attached to the exposed side 
face surface of the ring gear 54. Bracket 71 supports an end finishing 
tool 72 mounted in a threaded arbor 74 and adjustable in the longitudinal 
direction by rotation of a crank wheel 76. The crank wheel 76 is shown as 
being manually operated to advance the tool 72 against a cut end surface 
of a pipe, but those skilled in the art can appreciate that the tool can 
also be advanced using a step-motor drive, if desired. 
Turning next to FIGS. 5 and 6, a first embodiment of the invention will be 
explained, showing the improved manner in which the ring gear assembly 54 
is journaled for rotation relative to the stationary annular member 32. 
The stationary member 32 and the rotatable annular gear ring member 54 
abut one another along a line 78 which are machined flat. An annular 
recess 80 of a predetermined depth dimension is also machined into the 
stationary member 32 and formed inwardly therefrom are a series of 
threaded bores as at 82 which are adapted to receive a threaded spindle or 
axle 84 of a roller bearing assembly 86. The bearing assembly itself 
comprises upper and lower ball bearing mounted rollers 88 and 90 separated 
from one another by a washer-type spacer 92. The outer race of the roller 
bearings 88 and 90 are inwardly beveled to form a V-shaped notch, as 
shown, when the two roller bearings 88 and 90 are juxtaposed on the 
threaded axle 84. 
Formed inwardly from the interior face of the ring gear 62 is an annular 
groove 93, having a pair of opposed side walls 94 and 96. Each of the 
walls 94 and 96 is provided with an annular protuberance 98, which has a 
cross-sectional appearance of a truncated isosceles triangle, and, as 
such, conforms to the shape of the V-notch 92 formed in the roller bearing 
assemblies 86. 
FIG. 6 illustrates an alternative roller bearing configuration from that 
shown in FIG. 5. Instead of positioning the individual roller bearings 88 
and 90 with their beveled ends facing one another as in FIG. 5, in the 
arrangement of FIG. 6, the roller bearings are inverted such that the 
beveled ends thereof are directed away from one another and the spacer 
washer 99 is relocated to be adjacent the surface 80 of the housing 32. By 
configuring the roller bearings 88 and 90 as indicated in FIG. 6, it 
obviates the need for a somewhat difficult-to-form, projecting, annular 
ridge as at 98 in FIG. 5. Instead, the gear 62 has angled corner edges as 
at 95, 97, 101 and 103 in FIG. 6. Thus the bearing race formed in the gear 
62 is made to conform closely to the outer profile of the roller bearings 
88 and 90. 
With reference to the cross-sectional view of FIG. 7, it can be seen that 
the roller bearing assemblies 86 do not lie on a common bearing circle, 
but instead, have their rotational axles 84 radially offset. That is to 
say, a first set of roller bearings labeled 86a lie on a first bearing 
circle, such that the peripheries thereof engage the wall 96 of the 
bearing race 93 while the roller bearings labeled 86b fall on a bearing 
circle radially displaced from the bearing circle in set 86a whereby their 
peripheral surfaces engage the bearing race wall 94. The roller bearings 
of the set labeled 86a alternate with those in the set labeled 86b around 
the circumference of the annular member 32. 
It has been found that the staggered arrangement of the roller bearings and 
their cooperation with the walls on the bearing race 93 prevents any 
lateral shifting of the rotatable ring member 54 relative to the 
stationary ring member 32, even when subjected to relatively high loads as 
the ring gear and attached tool assemblies are driven to orbit the pipe 
being finished. Also, the construction of the assembly is greatly 
simplified in that it does not require a separate race member bolted to 
the ring gear as in the prior art arrangements of FIGS. 1 and 2. 
ALTERNATIVE EMBODIMENT 
Referring next to FIGS. 8 and 9, an alternative embodiment is illustrated. 
In this arrangement, there is again a ring gear member 100 journaled for 
rotation on an interior planar surface 102 of a stationary annular member 
104. More particularly, the stationary annular member 104 has its surface 
102 provided with regularly, circumferentially spaced bores or wells 105 
which are dimensioned to receive with a slip fit an eccentric cam member 
107. The cam 107 is cylindrical and has a threaded bore 109 into which is 
screwed the stud 84 of the bearing assembly 106. The threaded bore 109 is 
offset from the center line of the cylindrical cam by a predetermined 
eccentricity and, as such, when eccentric cam 107 is rotated within the 
bore 108, the bearing assembly 106 is shifted. When a desired position for 
the bearing assembly is established, it is locked in place by a set screw 
124. 
Formed inwardly from the interior surface of the ring gear 100 is a bearing 
race 114 having opposed side walls 116 and 118. Again, the side walls of 
the bearing race may include a triangular protuberance, as at 120 and 122, 
which conform to a V-notch in the bearing assembly resulting when the 
beveled surfaces of the upper and lower roller bearing members 110 and 112 
are juxtaposed. If the bearing assembly of FIG. 6 is used, no such 
triangular protuberance is required. Because of the eccentric mount, the 
individual roller bearing assemblies 106 can be adjusted by rotating the 
eccentric cam 107, using an Allen wrench or the like and then subsequently 
advancing a threaded lock screw 124 in a threaded, radially extending bore 
against the eccentric cam to lock the eccentric orientation. As such, the 
roller bearing assemblies 106 can be adjusted to engage the triangular 
protuberances 120 and 122 and the walls 116 and 118 of the bearing race 
114 with a desired clearance therebetween. It is found that this 
alternative embodiment also provides the desired stability under load of 
the ring gear as it is driven in its orbital path. Moreover, this desired 
result is achieved with a simpler, less expensive implementation compared 
to the prior art. 
This invention has been described herein in considerable detail in order to 
comply with the Patent Statutes and to provide those skilled in the art 
with the information needed to apply the novel principles and to construct 
and use such specialized components as are required. However, it is to be 
understood that the invention can be carried out by specifically different 
equipment and devices, and that various modifications, both as to the 
equipment details and operating procedures, can be accomplished without 
departing from the scope of the invention itself.