PORTABLE FRICTION WELDING APPARATUS AND METHOD This application is a continuation in part of U.S. application number 08/667,843 filed June 20, 1996.
Background
The ability to join or weld various shaped workpieces together is very common in many industries. One area in which this is particularly true is in repairing systems directing the flow of fluids or gases. In petro-chemical industries for example, valves which control the flow of fluids and gases often need to be replaced, repaired, or repacked. A fitting must be attached to the housing enclosing the valve packing material to access the material while preventing excessive leaks. These fittings were previously attached through a threaded attachment, but as explained in U.S. Patent Nos. 5,062,439 and Re. 35,116 a welded attachment is preferred. However, the joining or welding process must result in creating minimal surface heat such that the resulting temperature of the side of the wall, plate, etc. potentially in contact with flammable materials does not cause combustible materials to ignite or decompose.
A traditional method to join workpieces in the valve repair industry is the drill and tap technique. First, a drill bores a hole into the second workpiece. Next, the bored hole of the second workpiece is tapped or threaded. This enables a threaded first workpiece (a fitting) to be joined to the second workpiece. There are various weaknesses with this technique. First, users are
constrained in the choice of workpieces that may be joined. A requirement of the drill and tap technique is that one must be able to bore and tap the second workpiece and have a threaded firβt workpiece to join to the bored and tapped second workpiece. Extreme care must be taken to assure the initial drill step does not penetrate too far and go into the pressure or hazardous area and cause a safety and environmental issue. The wall thickness remaining after drilling and prior to the tapping is viewed as a "safety factor". The larger this is the better. Additionally, the drill and tap technique does not provide a weld which properly seals the workpiece to workpiece interface to minimize fluid or gas leaks. There is no guarantee that the tap will take perfectly, and if the workpiece material is very strong, it may be more difficult to begin the tap and maintain it to produce a thread which will provide a sufficient junction. The final attachment may have gaps because the tap did not drive into the workpiece perfectly. If this technique is used in an environment containing flammable materials, the drill and tap technique may create a spark due to the tap's sharp metal edges thereby igniting the flammable materials.
If an attachment is made by a friction weld these problems can be overcome. However there is considerable difficulty in attempting to friction weld a first workpiece to a second workpiece. This problem is evident in welding to flat surfaces, but even more so when attempting to weld to a curved surface such as any fluid or gas pipe. Moreover, friction welding creates a fast build-up of surface heat causing the workpiece portion in
contact with flammable materials to reach a temperature which may also ignite flammable materials.
Prior friction weld techniques used to join workpieces by friction welding use an actuator located between the workpiece and motor, surrounding the spindle. This provides an indirect force on the workpiece. Through the workpiece-actuator-motor mechanism, the first workpiece is rotated and then placed in contact with a second workpiece. The combination of rotational drive, and indirect axial force causes the first workpiece to weld to the second workpiece. This indirect friction welding technique improves upon weaknesses of the drill and tap technique by decreasing gas or fluid leaks by reducing the number of possible leak points present in tap junctions, reducing the risk of creating sparks, reducing the risk of drilling through the second workpiece and offering a wider selection in workpieces which may be joined.
However, friction welding has not been successfully implemented in valve restoration due, in part, to two major weaknesses. First, the indirect means of applying force with the indirect workpiece-actuator-motor configuration does not supply the necessary amount of force to provide a sufficiently strong weld, particularly when dealing with curved surfaces. Second, the portion of the second workpiece in contact with flammable materials may reach high surface temperatures resulting in ignition of the flammable materials. Therefore, a need exists for a technique which welds workpieces together with sufficient force to provide sufficient weld strengths, minimizes fluid or gas leaks, reduces
the surface temperature of the workpiece portion in contact with flammable materials, and provides a simple and effective means to accomplish these goals using a variety of workpiece materials, shapes and configurations.
Other disadvantages of prior friction weld devices include the cumbersoroeness of the devices and methods used to attach the welder to the second workpiece, the non-universal nature of the devices or clamps and the welders require more air pressure to operate than standard plant air (more than 90 psi) .
Summary of the Invention
The present invention relates to the field of friction welding a first workpiece to a second workpiece and in one particular application relates to the friction welding of a fitting to a valve packing housing.
A portable welder which is capable of being carried by a human operator for friction welding a first workpiece to a second workpiece includes a lightweight hydropneumatic actuator which produces a direct axial thrust upon an air motor. The air motor produces a direct axial thrust and a rotational drive upon a spindle. The spindle produces a direct axial thrust and a rotational drive upon the first workpiece. The actuator, air motor and spindle are contained within a housing. A clamp base is made integral with the housing. With this arrangement the pounds force produced by the actuator will be equivalent to the pounds force
translated between the fitting and the valve packing housing less any minimal decrease due to drag.
As used in this application, the term "portable" indicates the welder is lightweight such that it can be carried by a human operator. The welder should weigh less than thirty pounds and, preferably, the welder will weigh less than twenty pounds. The welder is designed to operate on a supply of standard shop air which means it must operate at less than 120 psi while producing an axial force or welding thrust of 1000 lbs. or greater. As used herein, the fitting may be referred to as a first workpiece and the valve packing housing may be referred to as a second workpiece, although, the meaning of a first workpiece and a second workpiece is not necessarily limited to a fitting and a valve packing housing, respectively. The welder can be used to friction weld any configuration of workpieces which may be accommodated by the welder.
The invention may also be improved such that an acceptable friction weld can be accomplished in less than ten seconds while the temperature of any portion of a workpiece in contact with a flammable material does not reach a temperature of 500 deg. F. This is accomplished by applying the force of the actuator/ram prior to initiating rotational drive to the first workpiece, having the ability to adjust the ram force as dictated by the nature of the first and second workpieces, initiating a rotational drive with a sufficient torque to overcome the ram force and cause the first workpiece to rotate with respect to the second at a
sufficient RPM to friction weld.
Brief Description of the Drawings
Fig. 1 is a cross sectional view of the portable friction welding apparatus with a clamping mechanism to attach to a valve packing housing. Fig. 2 is a view similar to Fig. 1 showing a second embodiment of a portable friction welding apparatus. Fig. 3 is a schematic view of the controls used with the portable friction welder. Fig. 4 is an end view of a fitting. Fig. 5 is a cross-sectional view of the fitting taken along line 5-5 of Fig. 4. Fig. 6 is a view showing a third embodiment of the welder. Fig. 7 is an end view of the embodiment shown in Fig. 6. Fig. 8 is a cross section view of a first workpiece or fitting welded to a curved plate or second workpiece. Fig. 9 is a schematic view of another embodiment of a control system used with the welder shown in Fig.6. Figs. 10-27 are charts and graphs showing data taken from tests of the welder shown in Figs.6-9. Detailed Description
Referring to Fig. 1, one embodiment of the portable welder 10 is shown. In one application, the portable welder 10 is to be clamped to a valve packing housing 12 for welding a fitting 14 (Fig. 4) to the valve packing housing 12. The portable welder 10
generally comprises a housing 20, an actuator 30, an air motor 40, a spindle 50 and a clamp 60. The actuator 30, air motor 40 and spindle 50 are all aligned such that the welding force is always applied along the axial centerline of each component or, in other words, such that the force generated by the actuator 30 is directed along the center axis of the air motor 40, the spindle 50 and the fitting 14. This results in the translation of the axial force produced by the actuator directly to the fitting 14 less any negligible forces which are lost due to friction or drag, etc.
The housing 20 generally includes an upper housing 22 and a lower housing 24. The housing defines an axial cavity and is open at both ends for containing the actuator 30, the air motor 40, the spindle 50, and various other parts as will be discussed below. The upper housing 22 may be disconnected from the lower housing 24 with or by bolts (not shown) or by releasing some other suitable means of attachment. The end 26 of the lower housing 24 is made integral with the clamp base 62 either by manufacturing a lower housing 24 and the clamp base 62 as one piece or by securely bolting the clamp base 62 to the lower housing 24. By making the lower housing 24 integral with the clamp base 62 vibrations and misalignment between the spindle 50, fitting 14 and the valve packing housing 12 are inhibited during the welding cycle.
The actuator 30 is mounted in one end of the housing 20 with its axis of force directed along a centerline through the cavity in housing 20. The thrust end 32 of the actuator 30 which produces the axial force impinges upon an air motor body 42. It has been
discovered that a hydropneumatic clamp sold under the brand name CompAir by CompAir North America, located in Kittery, Maine should be incorporated as the actuator 30 in the welder 10. This hydropneumatic clamp or any other acceptable actuator should be lightweight (approximately two pounds) , capable of producing an axial force greater than one thousand lb.F. using a supply of standard shop air.
The air motor body 42 generally includes a sidewall housing
41, a first end 43 and a second end 44. The second end 44 includes a collar 49. The sidewall housing 41, the first end 43 and the collar 49 define a cavity for housing the air motor 40. An o-ring 45 is located in a groove in the sidewall housing 41. The first end 43 includes an upper sleeve 46 to stabilize and guide the air motor 40. The rotational axis of the air motor 40 is aligned with the centerline through the cavity of housing 20. As the end 32 of actuator 30 impinges upon the first end 43 of the air motor body
42, the air motor body 42 will be moved through the cavity in housing 20. The air motor 40 will generate a rotational drive about a rotational axis which coincides with the axis of thrust. The thrust is translated through the second end 44 to the spindle 50. The rotational shaft (not shown in Fig. 1) of the air motor 40 may be splined to the spindle 50. Guide pins 47a and 47b may be located on the collar 49. The guide pins 47a, b move into holes 48a, b in the lower housing 24 to function as a guide and to provide stability to the air motor body 42 as the air motor 40 produces rotational drive and is thrusted within the housing 20.
A radial bearing 51 and a thrust bearing 52 are positioned around the spindle 50. A front sleeve 53 is fitted between the bearings 51, 52 and the lower housing 24. The end 54 of the actuator rod 50 may be made with a hex connector, a spline connector, a threaded connector (Fig.2) or any other suitable connector for the fitting 14. As shown, a hex connector 55 includes a socket 56 for connecting to end 54 of spindle 50, and hex socket 57 for connecting to fitting 14. Socket 56 and hex socket 57 may each include a retention means such as a ball plunger.
A clamp base 62 is made integral with the lower housing 24 preferably by bolting the clamp base 62 to the lower housing 24. A clamp bracket 64 is bolted to the clamp base 62 around valve packing housing 12. The clamp bracket 64 may be made in a number of configurations as needed to clamp to the second workpiece. The clamp bracket 64 is clamped to the valve packing housing 12 by three clamping devices 66 a, b, c which may comprise worm gear crank vices or hydraulic cylinders.
Referring now to Fig. 2 another embodiment of the portable welder 10 is shown. In this embodiment housing 120 includes upper housing 122 and lower housing 124. Actuator 130 is mounted in the upper housing 122 and produces an axial thrust along a axial centerline of the cavity through housing 120. The thrust end 132 of actuator 130 impinges upon a connector 134 along the axial centerline of the connector 134. The air motor 140 having a sidewall housing 141 is of a type made by Ingersoll Rand (yielding approximately 8,500 rpm) having- a rotational shaft 148 which runs
through the air motor 140. The air motor 140 and its rotational drive shaft 148 are supported by an end thrust bearing 136 and a rear guide sleeve 138. A bearing retainer 139 is placed against end thrust bearing 136.
Actuator 130 produces an axial force via connector 134 on the axial centerline of the rotational drive shaft 148 at the first end 143 of air-motor 140. The rotational drive shaft 148 of the air motor 140 is connected to the spindle 150 by a spline connector 154. The spindle 150 is supported and allowed to rotate and thrust by radial bearings 151 and thrust bearing 152. A front sleeve 153 is placed between the bearings 151, 152 and the lower housing 124. Guide rods 147a and 147b are mounted on the front sleeve 153 and penetrate openings (not shown) in the lower housing 124 as the air- motor 140 and front sleeve 153 are thrusted. The axial force produced on the air motor 140 is translated from the rotational drive shaft 148 through the second end 144 to the spindle 150.
A clamp base 62 is made integral with the lower housing 124 preferably by bolting the clamp base 62 to the lower housing 124. A clamp bracket 64 is bolted to the clamp base 62 around valve packing housing 12. The clamp bracket 64 may be made in a number of configurations as needed to clamp to the second workpiece. The clamp bracket 64 is clamped to the valve packing housing 12 by three clamping devices 66 a, b, σ which may comprise worm gear crank vices or hydraulic cylinders. The clamp 60 can be set prior to initiating the welding procedure since it includes three points of attachment. The clamp 60 could also be made with clamping
devices which are jaws (not shown) such that only two clamping devices would be needed to clamp the portable friction welder 10 to the valve packing housing 12. The portable welder 10 can be clamped to the second workpiece in a vertical alignment, a horizontal alignment as shown or at any other angle therebetween. Since the clamp base 62 is made integral with housing 20, the welder 10 is stabilized for clamping to valve housing 12 and for subsequent welding. The air motor 140 is moved back to its start position after the weld is completed by applying pressure on the end of spindle 150 (e.g. place the end of spindle 150 on a hard surface and push on housing 120).
Since the welding force is always applied along an axial centerline and perpendicular to the surface of each adjacent component, any tendency toward transverse movement due to rapid rotation generated by the air motor during the welding cycle will be inhibited. Transverse movement is also minimized by making all components in the portable welder 10 symmetrical about the centerline.
Referring to Fig. 3, a control system 70 which may be used to control the portable welder 10 is shown. The control system 70 includes a control block 71, an air chamber block 72 connected to the control block 71, a supply line 73 to be connected to a supply of standard shop air 74, a feed line 75 to be connected to the air motor 40, a feed line 76 to be connected to the actuator 30, a timer 77, a pressure meter 78, a start button 79 and a stop button 80. A suitable control block 71 is commercially available from
companies such as HapeCo model 59895 and Aro Corporation located in Bryan, Ohio (Flex 6 brand) and the implementation of same into the control system 70 would be known to one of ordinary skill in the art. A suitable timer 77 is also commercially available from the Aro Corporation of Bryan, Ohio. The time needed to complete a weld varies according to the materials to be welded. The control system 70 through the timer 77 allows for a pre-determined weld time to be applied, with an emergency shut down. Preferably, the legend for the pre-determined weld time settings will be labeled by weld material (e.g. a setting for carbon steel) as opposed to time. The emergency shut-down may be implemented through a volume chamber in air chamber block 72 attached to the control block 71 which would stop the welding process after a predetermined time (e.g. ninety seconds). The control system 70 also includes a pilot valve 82 and a flow control valve 81. Flow control valve 81 controls the pressure buildup on the actuator 30 which delays the initial axial thrust of the actuator, because it is desirable to increase the RPM of the air motor 40 to maximum RPM before applying axial thrust of the fitting 14 against the valve packing housing 12 and it is desirable to ramp up the pressure of the fitting 14 against the valve packing housing 12 as opposed to thrusting the fitting against the valve packing housing at full pressure upon initial contact.
Referring to Figs. 4 and 5, a fitting 14 which may be mounted in the spindle 50 for welding to the valve packing housing 12 is shown. The fitting includes a weld face 15 and a weld effected
area 16 for use in welding the fitting 14 to the valve packing housing 12. The end 17 to be driven by spindle 50 may be engaged by the spindle 50 through a threaded connector, a splined connector, a hex connector, etc. If the connector 17 is threaded, then it will be preferable for motor 40 to be reversible such that when the weld process is completed the clamp base 62 can be unbolted from clamp bracket 64 and the directional drive of motor 40 can be reversed for detaching the spindle 50 from the fitting 14.
The portable welder 10 may be used as follows. The human operator will carry the portable welder 10 onto the worksite such as a refinery requiring a fitting 14 to be welded to a valve packing housing 12. The operator will use the clamp 60 to align the spindle 50 and fitting 14 with the location of the valve packing housing 12 where the fitting 14 is to be welded. The clamping devices 66a, b and c will be used to set the clamp 60 once a proper alignment is achieved. Line 73 of the control system 70 should then be connected to a supply of shop air 74. Then based on the type of material which makes up the fitting 12 and the type of material which makes up the valve stem 12, the operator can make a setting according to the weld material legend which will determine the welding time required to complete the weld. For example, the welding time should be set for one minute or less for stainless steel and carbon steels. The welding times will also vary according to different grades for a material. Other factors must also be accounted for when determining the welding times such as, for
example, the size of the weld face 15 on the fitting 14 and the thickness of the second workpiece. The timer 77 on the control system 70 will then be set accordingly. The control system 70 is started and air will be supplied by line 75 to the air motor 40 such that the spindle 50 will begin to rotate. The thrust of actuator 30 will be impeded by flow control valve 81 until the spindle and fitting are rotated at full r.p.m. The end 32 of the actuator 30 will produce an axial force which will be applied perpendicular to the first end 43 of motor body 42. The air motor 40 will then advance within the cavity of housing 20 causing the guide pins 47a, b to penetrate the openings 48 a,b in the lower housing 24. Simultaneously, the second end 44 (rotational shaft) of the air motor 40 will produce an axial force which is perpendicular to the end of spindle 50 while spindle 50 is being rotated by the rotational shaft. Also simultaneously, the spindle 50 will rotate the fitting 14 and create an axial force perpendicular to the end of fitting 14. Consequently, the fitting 14 will be thrusted against the valve packing housing 12 to achieve sufficient friction heat to forge a weld. Full forge pressure is maintained after the air motor stops rotating for a given time to help achieve a stronger weld. The check valve 83 is in the air line 76 to the actuator 30 to allow the pressure to be maintained after the shut down of the air motor 40, then the pressure is released by vent valve 84.
For a description of the friction welding process please refer to U.S. Patent Application No. 08/191,618 which is incorporated
herein by reference. For more information relating to the need and use of the fitting 14 when welding to the valve packing housing 12 please refer to U.S. Patent No. 5,062,439 and U.S. Re. No. 35,116 which are incorporated herein by reference.
Referring to Figs. 6-9 the present invention may be enhanced as described below. The enhancements enable the welder 210 to complete an acceptable friction weld in less than ten seconds and more particularly within a time range of three to seven seconds. By way of example, an acceptable friction weld between a fitting 214 and a valve body 212 is a weld which withstands a torque of 100 ft/lbs, a load of 100 lbs and a tensile force greater than 35,000 PSI.
Such a friction weld may be accomplished by welding a first workpiece 214 (e.g. a fitting or stud) to a second workpiece 212 (e.g. a flat plate, a curved plate, a beam) . When the second workpiece 212 is a valve body the wall or plate to be welded to may have a thickness 213 as small as 0.300 inches. The surface 216 of the wall 218 opposite the surface 220 in contact with the first workpiece 214 typically remains below the temperature of 500 deg. F. during the entire friction weld process of the present invention so long as the wall thickness is greater than 0.300 inches. Therefore, the welder 210 can be used to make a certified hazardous weld.
These features must be achievable in a variety of applications using a variety of materials. By way of example, the friction welder 210 could be used for welding a fitting 214 to a valve body
/1
212, for welding a stud to an I-beam, for welding instrument connections, and for automotive, railroad or underwater applications, any or all of which may be performed in a flammable environment.
A friction welder 210 of this embodiment having these characteristics includes:
1. An adjustable ram or actuator 230. Preferably the axial force of the ram 230 is adjustable between zero and 10,000 PSI (in this embodiment; different components may be substituted to increase this range) . Two acceptable rams 230 which can be used are model nos. C53C and C51C sold by POWER TEAM located in Owatonna, MN, USA. These rams are hydraulic rams powered by a hydraulic air pump, model no. PA4R also sold by POWER TEAM. The rams 230 may also be powered by a hand control pump. This pump may be powered by a supply of standard shop air ranging from seventy to ninety PSI.
2. A motor 240 having a sufficient torque to overcome the ram force and having a sufficient RPM to form a friction weld. One acceptable motor 240 is a model 4800M air motor sold by Ingersoll Rand. Such a motor 240 can be powered by a supply 222 of standard shop air to achieve 1050 RPM free or maximum speed, 560 RPM at maximum load, and sixty-nine ft./lbs. of torque.
3. A control system 270 powered in part by a supply of standard shop air including: controls to adjust and set an initial axial or ram force; a control to start and stop the motor for a desirable length of time (e.g. a timer to set the duration of the weld); and a preweld controlled air purge to the weld purge chamber/
shield/shroud assembly 250. An instrument control panel 272 includes a master on off switch 273 having a key 274; start 275 and stop 276 buttons; and pressure gauges. A suitable control system similar to Fig. 3 is shown in Fig. 9.
The welder 210 is operated by fixing the mounting clamp 260 to the second workpiece 212 and to the welder 210. The ram 230 is activated to force the first workpiece 214 against the second workpiece 212. Presently, the ram force is set at 2,500 lbs. By forcing the first workpiece 214 against the second workpiece 212 prior to activating rotational drive a quality weld is further ensured since the workpieces are stabilized together prior to their relative rotation. The duration of the weld is set with a timer. The air purge to the weld area 215 is activated. Next the motor 240 is activated. Friction heat to forge a weld is created as a result of the high torque motor 240 overcoming the force between the workpieces 212,214. The motor 240 is activated for a preset period of time, preferably three to seven seconds.
Since the hydraulic force on the ram 230 is preset (e.g. 2500 lbs) any movement or elongation of the ram 230 will cause the hydraulic pressure to drop. For example, as the contact interface between the first and second workpieces becomes fluid during the friction weld process, the ram 230 will advance. Presently it is preferable for the ram 230 to travel about 1/4 inch causing the preset hydraulic force which began at 2500 lb to drop to, for example, 1000 lbs. Deformation of the first 214 or second workpieces 212 is suggested if the hydraulic pressure drops prior
to activation of the rotational drive. A final pressure less than, for example, 1000 lbs suggests the weld may not be of a sufficient quality.
Tests have been conducted using the embodiment of the invention shown in Figs. 6-7. The results of such tests may be seen by referring to the graphs shown in Figs. 10-27. The tests were conducted using an initial ram force of 2,500 lbs. The fittings 214 were welded to curved plates 212 having a radius of curvature as little as one inch. Under such conditions when welding to an approximate 0.312 inch schedule 80 pipe, the distal surface 216 peaked at a temperature of 284 deg. F. when rotationally driving for three seconds, 387 deg F when rotationally driving for five seconds, and 462 deg F when rotationally driving for seven seconds.
A clamp 260 which is adjustable for clamping to plates having a diameter ranging from one to fifty inches and adjustable to clear an obstacle (not shown) proximate to the second workpiece 212 may be used in the invention. A mounting chain clamp 260 may be used to achieve same and includes a single chain 261 which is prelocked to the second workpiece 212. Some example types of chains 261 which may be used are a mechanical link type or a sprocket chain. The links 262 are attached over teeth 263a and 263b. One or both teeth 263a and b may be adjustable with respect to a mounting plate 264 by, for example, a threaded piece 265. The length of the chain 261 is variable as needed to clamp to the second workpiece 212. The clamp 260 includes cam type locks 266 having a swivel knuckle
267 (a 1/4 turn quick connect) to lock the welder 210 to the mounting chain clamp 260. The mounting chain clamp 260 includes a seat (not shown) to stabilize the welder 210. The seat terminates and transcends into a shroud 250. The shroud 250 functions as an air purge chamber around the first workpiece 214 directing air to the region of the weld 215 when forming the friction weld. The length of the shroud 250 may be varied by, for example, a threaded or telescoping piece (both not shown) so that the outer diameter of the mounting chain clamp 260 or welder 210 will not interfere with a bonnet, etc. The first workpiece 214 may be mounted in the welder 210 in a hex socket 228 which may have an internal magnet, or the first workpiece 214 may be threaded to the welder 210. A cap or extension piece may be placed in the socket 228 to adjust the position of the first workpiece 214 allowing it to clear the shroud 250 after the shroud 250 has been lengthened.
In conclusion, it is seen that the present invention and the embodiments disclosed herein are well adapted to carry out the objectives and obtain the ends set forth. Certain changes can be made in the subject matter without departing from the spirit and scope of the invention. It is realized that changes are possible within the scope of this invention and it is further intended that each element or step recited is to be understood as referring to all equivalent elements or steps. The description is intended to cover the invention as broadly as legally possible in whatever form it may be utilized.