Sucker rod machining system

A machining system for oil well sucker rods wherein the rod end to be machined is held in a non-rotating fixture rigidly without release throughout rough machining, finish machining and roll threading operations including a conveyor system for transporting fixtures with rods to successive stations for performing successive operations.

BACKGROUND OF THE INVENTION 
In machining the threaded coupling ends of sucker rods which are employed 
in pumping oil from deep wells, e.g. sometimes extending to depths as 
great as 14,000 feet; extreme precision is required to assure pumping 
operation under the high tensile loads involved without any possibility of 
"working" at the coupling joints which might cause failure and separation 
within the well. Precision threads axially normal to shoulder engaging 
surfaces of the rod ends for press fit machining with end surfaces of 
couplings free of any radial plane angularity which could limit full 
contacting engagement of adjacent coupling surfaces is a critical 
requirement. 
Conventional prior art systems for machining the ends of sucker rods have 
employed typical barstock machines with rotating rod and stationary 
tooling techniques. Rotary indexing heads hold the tooling for successive 
operations on rod lengths in the range of 23 to 30 feet and rod diameters 
in the range of 5/8" to 11/8". 
Limitations in the speed and accuracy of performing the required successive 
operations led to the development of an alternative "unwrapped" system 
wherein each rod is transported horizontally to successive stations at 
each of which the rod is axially moved to a shoulder gauge stop and 
clamped against rotation whereupon rotating tooling performs the required 
operation. While such system has proved commercially successful in 
improving productivity and accuracy over the prior conventional rotating 
rod machining method, the requirement for clamping, unclamping and 
relocating the axial position of the bar at each station has failed to 
achieve the total benefits of the present system wherein the bar end is 
clamped and retained in a single accurately located fixturized pallet 
throughout all operations. 
Thus, in clamping and releasing at each station, initial axial registration 
of the rod takes place against a forged shoulder surface followed by 
lateral clamping and removal of the axial gauge to provide access for 
rough machining the shoulder. Due to variations in forgings, clamp release 
of the rod for transport between stations, possible different rotational 
orientation at successive stations, possible rebound from the axial gauge 
surface, and other potentials for mislocation, maximum precision in 
relative inter-station location of the rods has involved practical 
tolerances in the order of plus or minus 0.020" even in the absence of any 
malfunction of the locating tooling. Furthermore, occasionally where 
workpiece variations cause gross mislocations, substandard machining out 
of tolerance may result in an undesirable percentage of scrapped sucker 
rods. 
SUMMARY OF THE PRESENT INVENTION 
By developing the present system of rigid fixturized clamping of the sucker 
rod end in a precision fixturized pallet which is transported from station 
to station and rigidly clamped in precise orientation relative to the 
operational tooling at each station without ever releasing the rod from 
its fixture between stations, a marked improvement in accuracy of 
inter-station locations, and dependability of meeting all tolerance 
requirements as well as increased productivity has been obtained. For 
example, locating tolerances within plus or minus 0.005" are readily and 
reliably obtained with minimized possibility for any scrapped rods. 
The preferred transport system involves a pair of continuously running 
horizontal chain conveyors for frictional drive of fixturized pallets at 
one rod end and like drive of tailstock carriers at the other which 
respectively register against lateral retractable stops aligned with the 
respective stations. Clamping within the fixture takes place on a square 
rod section behind all surfaces to be machined so that precision pallet 
registration with a fixed axial stop and complete rigidly clamped 
orientation of locating pallet surfaces at each station can assure 
dependable inter-station fixture location without any loss of workpiece 
orientation within the fixture throughout all sequential machining 
operations. 
In the preferred system for maximum productivity a rod locating and fixture 
clamping station is followed by a pair of rough machining stations, a pair 
of finish machining stations, and a single thread rolling station in order 
to take advantage of the relatively shorter cycle time for thread rolling. 
Also, in order to provide a through horizontal system for complete 
machining of both ends without requirement for rotating the sucker rods 
end for end, repeat stations for machining the second end are located in 
horizontally and axially displaced relation to the stations for machining 
the first end so that only minor axial repositioning and reclamping of 
each sucker rod is required between machining stations for each end.

With reference to FIG. 1 a first embodiment of the sucker rod machining 
system of the present invention is schematically illustrated in a plan 
view showing a first horizontal fixturized pallet conveyor 30 passing a 
load and fixture clamping station, adjacent rough and finish turning 
stations, a thread, gauge and unlock station and a pallet reposition and 
unload station. A tailstock conveyor 31 is adapted to cooperate with 
conveyor 30 in transporting individual sucker rods horizontally disposed 
across the two conveyors to the successive stations. A return path 32 for 
fixturized pallets and 33 for tailstock V-blocks is provided by the 
respective conveyors. The system for machining the first end of the sucker 
rod generally indicated as 34 is duplicated in a second system 35 for 
machining the other end so arranged as to permit simple transfer without 
reversing the position of the second end to be machined. 
A typical end of sucker rod SR as illustrated in FIGS. 2 and 3 comprises a 
cylindrical rod portion 36 a forged square cross-section clamp engaged 
portion 37, a forged annular flange 38 having an accurately machined face 
39 extending exactly at right angles to axis 40 of roll threaded end 41 
terminating at reduced cylindrical necked portion 42. A coupling (not 
shown) for joining two identically machined ends of adjacent sucker rods 
is provided with a through thread terminating in ends exactly normal to 
the axis which tightly engage each shoulder 39 in assembled relation and 
must bear with substantially uniform pre-stressed compressive engagement 
over the full shoulder surface in order to meet American Petroleum 
Institute standards established to minimize possibilities of any play 
developing which could result in the coupling working loose during 
cyclical operation or in developing overstressed fatigue failures through 
slightly cocked engagement. Thus, very close to absolute precision is 
required in the normality of shoulder 39 relative to thread axis 40 as the 
prime objective of the entire machining system. 
Since rough forged square cross section surfaces are involved in clamping 
the workpiece for machining, any release and reclamping at successive 
stations offers the potential for slight misalignment of the axis angle 
and/or displacement relative to previously machined surfaces with a 
resultant light cocking of shoulder surface 39 with the adjacent threaded 
coupling end. In addition the use of shoulder 39, initially a rough forged 
surface, for gauging the axial position of the sucker rod for each 
machining operation offers the possibility of variations in axial location 
from operation to operation leading to objectionable variations in the 
threaded ends as well as occasional gross mislocations leading to scrapped 
rods. The significant improvement of the present system in securely 
clamping the end of the sucker rod to be machined in a fixture rigidly 
mounted on a precisely machined pallet capable of accurate registry and 
rigid clamping at each successive machining station will now be described. 
With reference to FIG. 6 illustrating a station for automatic registry of a 
pallet for rough turning operation on successive sucker rods and with 
reference to FIGS. 7A and 7B illustrating longitudinal stops for arresting 
successive pallets at respective longitudinal positions 43 and 44, 
retractable stop lever 45 is engageable with leading depending pallet 
projection 46 trapped against rebound by spring loaded deflectable plunger 
47 having ramp surface 48 to accommodate passage of the pallet to a 
trapped position. Similar simultaneously retractable stop 49 serves to 
prevent any overtaking successive pallet 50 from entering the station 
until both stops 45 and 49 are retracted through common linkage 50 
actuated by cylinder rod 51. With leading and back stops 52 and 53 
retracted by similar linkage 54 and piston rod 55, a pallet in position 
43, when released by retraction of step 45, may advance to a position for 
leading projection 56 to pass stop 53 whereupon restoration of stop 52 to 
the position shown will effectively stop and trap the pallet in position 
44 as shown. The stop mechanism illustrated in FIGS. 7A and 7B accomplish 
an approximate longitudinal positioning of each fixturized pallet relative 
to an operating station within limits accommodating precision location and 
clamping of the pallet by supplemental registry means. 
With reference to FIG. 8, a station for locating each pallet includes 
housing 56 for vertical register pin 57 actuated by retraction of rod 
extension 58 pulled by power cylinder 59 into pallet locating and clamping 
position shown which, as later described with reference to the pallet 
illustrated in FIGS. 15, 16 and 17 serves to center, laterally shift and 
raise the pallet as shown at 60 in FIG. 9 into accurately clamped position 
against ramp surface 61 and rigidly fixed clamp rail 62 on one side and 
clamp rail 63 on the other side. Pallets are transported by frictional 
engagement to such station position on horizontal conveyor plates 64 at 
the top of roller drive chain 65 traveling between fixed guide rails 66. 
FIG. 10 provides a sectional view showing provision of air passages 67, 68 
for blowing off any chips on the surface of the incoming pallet to further 
assure accurate registration. 
For control purposes to signal a pallet in registered position, pin 69 
projecting from the bottom of the pallet engages button 70, as shown in 
FIG. 13, actuating linkage 71 for rotating rod 72, lever 73 and limit 
switch 74 shown in FIGS. 11 and 12 remote from chips and coolant which 
would provide an adverse environment for a more directly actuated limit 
switch. With reference to FIGS. 8 and 14 additional controls signal the 
operation of register pin 57 through linkage 75 from rod extension 58 to 
adjustable cam 76 for actuating limit switch 77. 
With reference to FIGS. 15, 16 and 17 pallet assembly P having fixture F 
rigidly mounted thereon rides on conveyor plates 64 driven by roller 
conveyor chain 65 and is provided with guide rollers 78 for engaging fixed 
guide rail 79, beveled edge 80 for engaging station ram surface 61, 
machined pad surfaces 81 for registration with bottom surface 82 of clamp 
rail 62, machined pad surfaces 83 for engaging bottom surface 84 of clamp 
rail 63, angular beveled engagement surface 85 for receiving machining end 
of clamping pin 57 shown in FIG. 8 and registration pad 85a (FIG. 16) 
secured to the bottom of the pallet. 
With reference to FIGS. 6, 8, 9, and 16 it will be understood that the 
matching angular beveled surface at the end of clamping pin 57 will (1) 
create a backward longitudinal force moving vertical transverse surface 8b 
of pallet registration pad 85a against vertical transverse locating 
surface 85c of clamping pin 57; (2) create a transverse force wedging the 
pallet laterally against ramp surface 61 into clamped engagement of pallet 
pads 81 with bottom surface 82 of clamp rail 62; and (3) force pallet pads 
83 directly upwardly into engagement with bottom surface 84 of clamp rail 
63, thus fully and precisely orienting and rigidly clamping the pallet 
with the single vertical movement of clamping pin 57. 
With reference to FIGS. 18 to 21 fixture assembly F for holding an end 86 
of sucker rod SR is rigidly mounted on pallet P which moves into the 
loading and clamping station shown in FIGS. 18, 19 and 20 where it is 
accurately positioned by station clamping means previously described. 
During movement into the station clamp setting head 87 is retracted by 
piston 88 under control of binocular guide rods shown in phantom at 89, 
and end gauge 90 carried by clamping head 87 is likewise retracted. With 
fixture F clamped into position, power cylinder 91 moves piston rod 88, 
head 87 and gauge 90 into full line position shown in FIG. 19 whereupon 
sucker rod SR is manually or otherwise loaded on V-blocks 92 and 93, 
clamping arms 94 of the fixture being held open by springs 95, and end 
shoulder 39 of sucker rod 86 is moved into registration with gauge 90 
whereupon slotted clamp setting tools 96, best shown in FIG. 20, engage 
projections 97 and through opposite screw drives in gear boxes 98 actuated 
by hydraulic motor 99 move clamp jaws 100 into clamping engagement with 
square necked portion 101 of sucker rod SR. Clamp retaining wedges 102 are 
next actuated into holding position by power cylinders 103 and piston rods 
104 whereupon clamping head 87 is again retracted and fixturized pallet 
released for travel to the first machining station. 
With reference to FIGS. 22 and 23 rough and finish turning stations 105 and 
106 are mounted on common base 107 where a pair of successive fixturized 
pallets can be located for successive rough and finish machining 
operations in accordance with the disclosure of FIGS. 6 to 17. 
With reference to FIGS. 24 and 25 similar rotating turning heads 108 and 
109 driven by motor and belt drives 110 and 111 are mounted on slides 112 
and 113 actuated after arrival and clamping of a rod fixturized pallet to 
an operating position as shown. At the rough turning station separate 
tools fed within rotating head 108 turn the annular flange 38 (FIG. 3), 
the adjacent chamfer, end shoulder 39, and the cylindridal end extending 
from shoulder 39. At the finish turning station, separate finish tools fed 
within rotating head 109 finish shoulder 39, finish turn the projecting 
end for the roll threading diameter, and under the axial control of an 
auxiliary feed rod 115 actuated by hydraulic motor 117 turn the reduced 
cylindrical necked portion 42. 
With reference to FIGS. 26, 27 and 28 each fixturized pallet with clamped 
rod end next moves to the thread rolling station and rigidly located 
without intermediate rod release. Prior to completion of the thread 
rolling operation, gauge 19 verifies the accuracy of the preceding 
operations whereupon the thread rolling head 114 of station assembly 118 
advances to roll the thread and retracts to clearance position. and clamp 
release levers 120 are actuated by power cylinders 121 to drive release 
extensions 122 of the clamp wedges into release position 123. Upon 
retraction of the clamp wedges positive release of clamp jaws 94 is 
effected by vertical slide 124 having tapered sides 125 for engaging 
matching tapers on clamp jaws 100 having tapered sides 125 for engaging 
matching tapers on the clamp jaws 100, slide 124 being actuated by 
cylinder 126. The unclamped fixturized pallet with rod supported in 
V-blocks is finally released to an unload station for manual or other 
removal to the second end machining system 35. 
In the duplicate system 35 the same accommodation of different length 
sucker rods may be provided so that the only variation in the processing 
of different length rods will be variations in the distance of axial 
shifting in transferring between the first and second end segments of the 
total system. 
With reference to FIGS. 4 and 5 illustrating the higher capacity 
embodiment, load and clamp station 127 is the same as in the first 
embodiment. A pair of roughing stations 128 will be programmed to bypass a 
fixturized pallet to the second roughing station when both are empty so 
that the next fixturized pallet may enter the first roughing station while 
the second is operating; likewise a pair of finish turning stations 129 
will provide double capacity with the relatively faster single thread 
rolling station 130 adapted to handle the output of the dual roughing and 
finishing stations. 
FIG. 5 will be seen to illustrate the angular relationship of sucker rod SR 
to accommodate overpassing the return flight of the horizontal conveyor 
with respect to both the main fixturized pallet and the supplemental 
V-block conveyor. It will also be seen that by locating the support 
V-block inboard of the shortest sucker rod to be handled by the system a 
variety of lengths can be accommodated.