US3838541A

US3838541A - Billet grinder apparatus, particularly for contour grinding of pipe

Info

Publication number: US3838541A
Application number: US00315641A
Authority: US
Inventors: F Durst; R Zastera
Original assignee: Pettibone Corp
Current assignee: Pettibone Corp
Priority date: 1972-12-21
Filing date: 1972-12-21
Publication date: 1974-10-01
Anticipated expiration: 1991-10-01

Abstract

A billet grinding apparatus with open loop control, in which the grinding wheel head mounted on a pivotable boom is capable of following with substantially constant force a contour work surface varying rapidly in a vertical direction, presented to the wheel by the workpiece, particularly that presented by a rapidly rotating pipe having appreciable eccentricity and camber. The improvement consists in combining a boom assembly with minimal rotational inertia, a characteristic obtained by mounting the large mass, driving motor off the boom, using no counterweight for the grinding head and boom, and driving the grinding head through an intermediate drive shaft coaxial with the boom pivot; actuators having minimal frictional characteristics, a low ratio of incremental volume to total volume, and a location such that their force is applied to the boom close to the pivotal axis thus reducing the amplitude of their motion; and a master cylinder for raising the grinding head from the workpiece in case of an emergency such as loss of air pressure, but connected through a lost-motion connection permitting the boom to operate during grinding essentially free of the connection.

Description

United States Patent 1191 Durst et al.

[4;] Oct. 1, 1974 BILLET GRINDER APPARATUS,

PARTICULARLY FOR CONTOUR GRINDING OF PIPE [75] Inventors: Fred L. Durst, Palos Heights;

Rudolph J. Zastera, Glen Ellyn, both of Ill.

[73] Assignee: Pettibone Corporation, Chicago, Ill.

[22] Filed: Dec. 21, 1972 [21] Appl. No.: 315,641

[52] US. Cl. 51/79, 51/99 [51] Int. Cl B24b 5/18 [58] Field of Search 51/99, 103 R, 103 TF, 39,

[56] References Cited UNITED STATES PATENTS 2,418,737 4/1947 Talboys 51/99 2,694,274 11/1954 McGibbon 2,963,832 12/1960 Ohringer 3,143,305 8/1964 Hess et al. 51/99 Primary ExaminerAl Lawrence Smith Assistant Examiner-Robert C. Watson Attorney, Agent, or Firm-Frank B. Hall 5 7 ABSTRACT A billet grinding apparatus with open loop control, in which the grinding wheel head mounted on a pivotable boom is capable of following with substantially constant force a contour work surface varying rapidly in a vertical direction, presented to the wheel by the workpiece, particularly that presented by a rapidly rotating pipe having appreciable eccentricity and camber. The improvement consists in combining a boom assembly with minimal rotationalinertia, a characteristic obtained by mounting the large mass, driving motor off the boom, using no counterweight for the grinding head and boom, and driving the grinding head through an intermediate drive shaft coaxial with the boom pivot; actuators having minimal frictional characteristics, a low ratio of incremental volume to total volume, and a location such that their force is applied to the boom close to the pivotal axis thus reducing the amplitude of their motiom-and a master cylinder for raising the grinding head from the workpiece in case of an emergency such as loss of air pressure, but connected through a lost-motion connection permitting the boom to operate during grinding essentially free of the connection.

12 Claims, 7 Drawing Figures PAIENTEUBBI 1 I924 sum-w 5 QQE mm mm PATENIEUIIIIT H974 sIIttI no; 5'

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108 9 3' K36 K152 Ill 1 I I05 0 l NO I I g PRESSURE NORM N L 1 7 SIGNAL 7 PIPE ROTATING SIG NAL OPRATOR CONTROL v 144 n50 SIGNAL BILLET GRINDER APPARATUS, PARTICULARLY FOR CONTOUR GRINDING OF PIPE BACKGROUND OF THE INVENTION This invention relates generally to a grinding machine of the kind used to remove surface defects from billets and slabs before rolling, and more particularly to a billet grinding machine in which the grinding wheel is applied with substantially constant force for the contour surface grinding of a rotating round or pipe.

In the surface grinding of pipe and especially of stainless steel pipe to remove surface scale. it is considered desirable to contour grind. leaving wall thickness uniform and to leave the surface as smooth as possible consistent with the desired rate of metal removal.

The larger horsepower machine grinders for billet grinding developed largely from mechanization of the manually operated snag or swing grinders in which the grinding head and driving motor were balanced on a single frame. Typically the grinding head and driving motor of the machine grinders are mounted on the same pivotable boom. Commonly. the head is counterweighted, and hydraulic and pneumatic actuators are used to control the head pressure.

For a billet with an ideally straight surface, the problem of applying the grinding wheel with constant force is a simple one. However, for billets that are appreciably cambered and have badly bent ends from cropping, the work surface that the grinding wheel meets as it passes along the billet rises and falls, sometimes at a rapid rate. The same problem in greater degree is presented by a pipe supported at the ends on rotators. A cambered pipe is bent somewhat like a banana, and particularly in the middle as the pipe is rotated, the surface rises and falls with every revolution. Many pipes are not truly circular and this eccentricity adds to the problem.

If the work surface moves upward and the grinding wheel does not, the wheel will dig into the workpiece. the effect being that greater force is applied by the grinding wheel. Similarly if the work surface moves downward and the grinding wheel does not follow, the workpiece will move away from the grinding wheel leaving a lightly ground area. This will also cause the pipe to have a nonuniform wall thickness,

It is known in the art to sense an upward slope of the work from the increased motor current that results, and to apply this signal to correct the fluid power pressure to decrease the force exerted by the wheel. It is also known in the art to use relieving valves to relieve the higher pressure built up in the boom control cylinder by the workpiece surface moving upward against the grinding head. It is obvious, however, that by the time the current increases in the motor or the pressure in the cylinder, that the head has already been applied to the surface with too much force to maintain a uniform depth of cut around the circumference of the pipe.

It was generally recognized that it is preferable to reduce friction at all bearing surfaces, and considerable work has been done in development of control circuits to keep the fluid power pressure in the head cylinder constant in the belief that to accomplish that goal would solve the problem of keeping the head force constant. But this was not sufficient.

Analysis showed that more basic considerations were necessary, and it was decided that with certain developments an open loop system might prove more success ful than a closed loop servo system operating on the pressure. Opposing the change in the position of the grinding head are the following forces: rotational inertia of the grinding head. its counterweight. the boom. and the driving motor; static (coulomb) friction and stiction (starting friction) in the cylinder actuators caused by movement of the piston seals andv rod packing and increased by the pressure of the oil or airi and movement of the actuator, the change in the volume causing a change in pressure at least until the relieving valve can operate to restore the pre-set pressure. To remove counterweighting from the grinding head would introduce another problem in that in case of failure of the oil or air system pressure. the head would drop onto the work under the full weight of the boom grinding head.

SUMMARY OF THE INVENTION.

The grinding head and boom are not counterweighted, and the driving motor is mounted on the saddle which also pivotally supports the boom. Rotational inertia is thus minimized, The means for driving the pivoting grinding wheel from the stationary drivingmotor is through an intermediate shaft mounted on the v about the pivot axis is applied by a short moment arm.

so that the grinding head travel is approximately four times greater than the actuator travel. Additionally, the air bag actuators are oversized so that their ratio of incremental volume to total volume is very small. thus the change in pressure because of actuator travel is minimized. For retracting the non-counterweighted boom with grinding head in case of failure of the air pressure supply to the actuator, or under other mailfunction conditions such as failure of rotation of the pipe or travel of the pipe, a master cylinder is used. The master cylinder is connected between boom and saddle through a lost motion device and is supplied with air from an air storage tank. For some types of grinding of billet contours, the degree of constant force needed can be obtained with ordinary fluid power cylinder actuators if the rotational inertia is minimized in the manner described. However, for successful grinding of pipe, it has been found necessary to combine the minimizing of the actuator reactions as described above, with the minimal rotational inertia characteristics of the boom mounted grinding head.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a side elevation view taken on section lI of the billet grinder apparatus shown as applied to grinding of pipe on a rotator car traveling beneath a stationary grinding unit, The rotator car isshown in phantom outline inasmuch as it is no part of the, invention. f

FIG. 2is an enlarged representation of conventional components making up the jack screw assembly.

FIG. 3 is a top plan view of the billet grinder apparatus. Section lines 1l, 44, and 55 j I ShQyvn, in this view. I

FIG. 4 is an enlarged sectional view taken on section line 44 of FIG. 3. This figure particularly shows the assembly of the boom pivot shaft into the boom for pivoting on the saddle, and the coaxial mounting of the intermediate drive shaft.

FIG. 5 is a front elevation view taken on section line 5-5 of of FIG. 3. It particularly shows the air actuators, the boom control plate, control rods. shock absorbers. and their mountings.

DESCRIPTION OF THE PREFERRED EMBODIMENT General Description. FIG. 1.

In this figure the billet grinding apparatus is shown applied to the grinding of pipe supported and rotated on a traveling car. The grinding head can be brought into contact with the work first by bringing the whole boom vertically within range, and then by pivoting the boom. Phantom views shows the grinding wheel at several positions. The entire grinder unit in this application is fixed while the work is moved under it. but equally practical would be a moving grinder with a stationary rotator. FIG. 1. shows the entire grinder unit I, mounted on a beam base 2, together with the car 3 which rotates the workpiece pipe 4 and is simultaneously propelled along the rails 5 on the wheels 6 under the grinding wheel. Inasmuch as the invention resides in the grinder unit 1, so much only of the car is exhibited as will suffice to show the connection of the invention therewith.

Guide Shafts for the Saddle. Figs. 1, 3.

The frame 7 which is the supporting member of the grinder unit 1 is in the form of a topless box and consists of a weldment of steel plates for sides and bottom.

Four upright shafts 8 are positioned at the four inside corners of the frame 7. Each shaft Sis turned down at the ends to a smaller diameter leaving shoulders at the transitions. The smaller diameter of each shaft 8 fits into a hole 9 in the bottom of the frame 7 just large enough to receive it, the shaft then being retained but supported on the shoulder. At the top of each shaft a shaft cap 10 with a hole just large enough to fit over the smaller diameter of the shaft at the top, bolts to frame 7, and when bolted in place bears against the shoulder of the shaft 8 and retains the shaft in place.

Jack Screw Assembly. FIGS. 1, 2.

The jack screw 11 is an assembly of conventional parts on a mounting plate 12 which is bolted to the bottom of the frame 7. The load bearing screw 13 is driven by a worm gear unit 14 having a double shaft extension. A hydraulic motor 15 drives the worm shaft-right extension 16 through a coupling 17. A rotary limit switch 18 connected to the worm shaft extension 19 through a coupling 20 is set to actuate at the limits of travel up and down of the saddle 21. A well 22 in the base 2 allows for downward extension of the screw 13 when the saddle 21 is lowered. The travel of the saddle 21 is approximately forty inches vertically. The controls for the hydraulic drive motor 15 are conventional and are not shown. However. they incorporate the limit switch 18 contacts to limit the travel so that the operator cannot overdrive the saddle upward or downward.

Saddle and Motor Mounting. Figs. 1, 3.

The saddle 21 is a structural weldment of brackets. mounting plates. and channel. The saddle 21 moves vertically inside the frame 7. and is guided by the four upright shafts 8. It has at each corner accommodation for an upper ball bushing 23 secured by a lock ring 23 and a lower ball bushing 25 secured by a lock ring 26. The entire saddle 21, guided in this way for vertical movement. is supported on the screw 13 and connected to it by an adaptor plate 27. Bolted on top of the motor mounting sub-base 28. but separated from it by vibration mounts 29 is the intermediate motor plate 30. The adjustable speed. dc motor 31 with driving sheave 32 on its output shaft is enclosed and is force cooled by separate motor driven fans in order to utilize a smaller frame size. The fans. fan motors. conduit box. and ducting are conventional and are not shown. The adjustable speed controls for the dc motor 31 are conventional and allow the drive speed to be increased as the grinding wheel wears down to a smaller diameter. thus maintaining constant peripheral speed of the grinding surface. Such controls are well known and are there fore not shown. The motor 31. the motor mounting plate 33, and the intermediate motor plate are bolted together, slotted holes in the intermediate motor plate permitting the motor 31 with the motor mounting plate 33 to be slidably adjustable on the intermediate motor plate 30, for tensioning the motor drive belts 86. Milled slots in the motor mounting base 28 provide clearance for the bolt heads. The adjustment for tensioning is made by two adjustment screws 34, each of which is engaged in a threaded bracket 35 of the intermediate motor plate 30. The shank end of each screw 34 is grooved and is rotatably retained in a hole of bracket 36 on the motor mounting plate by two roll pins 37 engaging the groove above and below. Two hex nuts allow the adjustment to be secured. The motor mounting sub-base 28 is bolted to the top of the saddle 21, slotted holes in the saddle allowing a forward and backward adjustment of the motor mounting sub-base. The adjustment is made by two adjustment screws 38 which have a similar function and construction to the two adjustment screws 34. The two adjustment screws 38 permit tensioning of the spindle drive belts 85.

Boom weldment. FIG. 6.

The boom 39 is a weldment consisting of a horizontal. square tubular member. the boom extension 40, terminating in a round tubular flange 41, a hub member 42 having a keyway 43. and an arm 44 extending rearward and downward. Two slotted holes 45 in the arm 44 form a yoke. On the side of the hub 42 away from the boom extension 40, a gap 46 is cut into the hub 42. Brackets 47 welded to the hub above and below the gap 46 are drilled and enable the parted back section of the hub 42 to be drawn together with clamping bolt and nuts 48 for clamping purposes. Two bracket type rod clevises 49 and two drilled shock absorber brackets 50 are located on the boom extension 40.

Boom Pivot Assembly. FIG. 4, 6.

At the front of the saddle 21 the weldment includes two vertical side plates 52 surmounted by a flat top bridge member 53 which form a yoke, in which the boom hub 42 is supported by pivoting of the boom 39. A boom pivot shaft 54 is keyed to the boom hub 42 by key engaging keyway 43 (FIG. 6) in the hub, after which the hub is clamped by clamping bolts and nuts 48. A keyway clearance groove 55 in the vertical side plates 52 allows this assembly to be made. The boom pivot shaft 54 is tapered at 56 to receive roller bearing 57 which are retained in place position in bearing caps 58, which in turn are bolted to the vertical side plates 52. Shims 59 are used to center the boom hub 42 in this assembly. The lock nuts 60 and lock washers 61 are used to preload the bearings from an initial clearance of approximately .008 inch to 0.004 inch. End covers 62 having an oval opening are bolted to the bearing caps 58. The boom pivot shaft 54 is hollow and has oval.

openings like the bearing caps 62, the opening beings wider than high, the purpose being to allow forward and backward adjustment movement of the intermediate drive shaft 63 which passes through the boom pivot shaft 54, being adjusted by adjusting screws 38.

Intermediate Drive Shaft and Grinding Wheel Head Assembly. FIGS. 3,4.

The intermediate drive shaft 63 passes through the pivot boom shaft 54 and is supported on two anchor bearings 64 which are bolted to the motor mounting sub-base 28. On one end of the intermediate drive shaft 63 is a driven sheave 65 secured by a key 66, a lock washer 67, and a lock nut 68. On the other end of the intermediate drive shaft 63 is a driving sheave 69, secured by a key 70, a lock washer 71, and a lock nut 72. The grinding wheel head assembly 73 is of conventional design and no claim is made herein to any novelty associated with it. The grinding wheel head assembly 73 is bolted to the boom flange 41 with hex head bolts 74 and lock washers 75. The grinding head assembly 73 consists of the spindle 76. the sheave 77, the spindle housing 78, and means for mounting the grinding wheel 79 to the spindle.

Master Cylinder. FIGS. 1,6.

The master cylinder 80 is pivotally mounted at the blind end to a bracket clevis 81 of the saddle. A rod-eye 82 screwed on the end of the cylinder shaft 83 is connected to the slottedholes 45 in the arm 44 of the boom 39 by means of a pin 84, thus providing a lostmotion connection between the cylinder shaft 83 and the arm 44 of the boom 39. With the cylinder rod 83 in its extended position, the boom can pivot downward, giving the grinding wheel a vertical movement of approximately 8 inches.

Drive Belts. FIG. 3.

A set of first belts 85 connect the spindle sheave 77 with the driving sheave 69 of the intermediate shaft 63. A set of second belts 86 connects the driven sheave 65 of the intermediate shaft 63 with the motor sheave 32.

Boom Control with Actuators. FIGS. 5,6.

The boom control plate 87 is connected to the boom extension 40 by two control rods 88, having bushed holes at each end. At the upper end of each rod, a pin 89 connects it to a clevis bracket 49 on the boom extension 40. At the lower end of each rod 88 a pin 90 connects it to a clevis bracket 91 of the boom control plate 87. Two vertical shafts 92 form guides for the boom control plate 87, ball bushings 93 being used to minimize friction. Each shaft 92 is held in an vertical position by an upper bracket 94 and a lower bracket 95 of the saddle 21. Keeper plates 96 are used to retain the shafts in position, each keeper plate fitting into a transverse groove in the upper end of each shaft. The keeper plates are then bolted to the upper brackets 94 An upper air actuator 97 and a lower air actuator 98 suspend the boom control plate 87 between the upper actuator bracket 99 of the saddle 21 and the lower actuator bracket 100 of the saddle 21. The air actuators are commercial units. the upper actuator 97 being a model 1T15T-1, the lower actuator 98 being a model lTlSM- 2, manufactured by Firestone Industrial Rubber Products Co.. under the trademark of Airstroke. The port 101 on the top of the upper actuator 97, and a port 102 on the bottom of the lower actuator 98 are-connections for air lines. The

air actuators

97, 98, have studs at top and bottom by which they are secured to the bracket 99, the boom control plate 87, and bracket 100. Four mechanical stops 51 on top and bottom of the boom control plate 87 limit its vertical travel. and prevent crushing of the air actuators by over-travel. Each of two commercial automobile type shock absorbers 103 is pivotally connected to a bracket 50 on the boom extension 40 at one end and at the other end is pivotally connected to a bracket 104 on the saddle 21.

Pneumatic Operation of the Master Cylinder. FIG. 6.

Air under pressure is supplied to the machine at line 105. From the filter with automatic drain 106, air passes through line 107 to the adjustable. relieving. airline pressure regulator 108 and from there through line 109 to the lubricator with drain 110 and then to line 111. Air pressure passes through check valve 112 through line 113 to air tank 114, through line 115 through the normally open, two-way valve 116 through line 117 to the combination valve 118 which consists of a check valve 119 in parallel with an adjustable flow control valve 120. The air under pressure is directed through line 121 to the rod end of cylinder 80.

The cylinder rod 83 is thus retracted. the pin 84 moving to the bottom of the slotted hole 45 in the arm 44 of the boom 39 and forcing the boom extension 40 to a horizontal position. This is definedas retracting the head.

Line 122 which is connected to the pilot port of valve 116 and to the blind end of cylinder 80 is at this time vented to atmosphere through valve 123.

Valve 123 consists of a two position, four way, directional, pilot operated, spring return valve 124, piloted through internal porting 125 from a three-way two position, spring return. solenoid valve 126 with solenoid coil 127. The pressure port of valve 124 is connected thru line 128 to check valve 129 which in turn is connected to line 111. The pressure port of valve 126 is connected directly to line 111. When solenoid 127 is energized, the valve 126 opens, allowing pressure through porting 125 to operate valve 124.

This air pressure through 111, check valve 129, line Y 128 is thus applied through valve 124, through line 122 to pilot operate valve 116 to the closed position and through line 122 to the blind end of cylinder 80. Simultaneously line 117 is vented to atmosphere through valve 124. Check valve 119 prevents air from the rod end of the cylinder 80 from returning through check valve 119 to line 117, but it can return through flow control valve to line 117 and through valve 124 to atmosphere under controlled conditions. The cylinder rod 83 thus extends slowly. When it is at the end of its stroke, the boom can pivot freely within the limits of the slotted hole 45, being controlled then by means of varying the pressure in the

air actuators

97, 98. as will be explained further.

However, if at any time solenoid 127 is de-energized. the conditions described initially are present again. and the cylinder retracts fully, bringing the boom extension back into horizontal position-Also. should air pressure fail during grinding, so that pressure in line 111 falls to atmospheric pressure which would lose control of the boom 39 by the air actuators.

check valves

112 and 129 remain checked, and the air stored in the air tank 114 operates the cylinder rod 83 to its retracted position, again restoring the boom extension 40 back into horizontal position. Note that even though the solenoid 127 of valve 126 might remain energized. there is no pressure in line 111 to operate valve 124 through porting 125 and hence the valve would spring return to the condition shown in the drawing.

Pneumatic Control of the Lower Actuator. FIG. 6.

Valve consists of a two position, four way, directional, pilot operated, spring return valve 131, piloted through internal porting 132 from a three way, two position, spring return, solenoid, normally closed valve 133 with solenoid 134. Line 111 is connected through valve 131 in its spring returned position to line 139 and thus keeps line pressure on lower actuator 98, adding an upward force to the boom extension 40. One port of valve 131 is plugged as indicated by the When solenoid 134 is energized, line 111 pressure is connected through valve 133 to porting 132 to operate valve 131 which then connects line 139 to line 135 which connects to a large remotely controlled, venting regulator 136 controlled by the pressure in line 137, which in turn is controlled by manually adjustable venting regulator 138. In this condition, the pressure in the lower actuator 98 is regulated by the manual adjustment of regulator valve 138.

Pneumatic Control of the Upper Actuator. FIG. 6.

Valve 140 consists of a two position. four way, directional, pilot operated, spring return valve 141, piloted through internal porting 142 from a three way, two position, spring return, solenoid, normally closed valve 143 with solenoid 144. On port of valve 141 is plugged as indicated by the X. Line 149 connects to port 101 of the upper actuator 97 and is normally vented to atmosphere through valve 141. Line 145 at such time is blocked at valve 141. When solenoid 144 is energized, line 111 pressure is connected through valve 143 to porting 142 to operate valve 141 which then connects line 149 to line 145, which in turn is connected to a large remotely controlled venting regulator 146 con trolled by the pressure in line 147 which in turn is controlled by manually adjustable venting regulator 148. In this condition the pressure in the upper actuator 97 is regulated by manual adjustment of regulator valve 148.

Conditions for Actuating the Master Cylinder. FIG. 7.

The derivation of an electrical signal from the rotation or movement of a body through an appropriate sensor is well known in the art, as is the derivation of an electrical signal from the operation of an operators control switch or from the operation of a pressure switch such as 152. Similarly, it is well known how to combine such signals into circuits that will energize solenoids only when all such signals are present. These controls are therefore not shown, but FIG. 7 illustrates graphically such conventional controls being used to energize

solenoids

127, 134, and 144, through amplifier 151. The conditions are that the air pressure is normal. the pipe is rotating and the ear is moving. combined with the signal from the operator. Should any one of these signals fail. the solenoids will be deenergized, and the master cylinder 80 will retract the grinding wheel from the work. In this way. should rotation or travel of the car cease. which would ordinarily cause the wheel to grind in one spot. the wheel will be retracted from the work. Similarly. should the air pressure fail, the wheel will not drop upon the work. but will be retracted.

Discussion of Design.

By making the boom pivot shaft of large diameter, the boom load is distributed over multiple rollers of the roller bearings 57. In addition. the roller bearings 57 are preloaded to reduce their normal clearance to an operational minimum by tightening them onto the tapered 56 part of the shaft 54 with the lock nuts 60. This results in a more rigid mounting of the boom and is permissible because this is not a high speed shaft but is held for relatively slow motion. The incremental volume of the actuator is defined as being the difference in volume with the actuator at one end of its permitted stroke and the volume at the other end of its permitted stroke. In a cylindrical actuator. the smaller the ratio of incremental travel to total length of actuator chamber. the less change such travel will make in the ratio of original pressure to resulting pressure.

By mounting the control rods 88 of the actuator assembly so that they act close to the pivotal axis of the boom. their travel is a fraction of the grinding wheel travel. The moment is considered to have a short mo-' ment arm when the actuator travel is one quarter or less of the grinding wheel travel.

When the grinding surface moves upward. the force against the wheel must exceed the sum of ths stiction and friction of the actuator before the wheel will move. and hence cannot affect the pressure of the actuator until that happens. This is the fallacy behind the attempt to control head force by constant pressure of the actuator. The stiction and friction must be minimized. Conventional fluid power cylinders are characterized by appreciable friction and stiction. The internal seals and packing cause such effects and the result is intensified by the pressure used. Rubber bag actuators have very low hystersis and minimal friction and stiction characteristics. Cylinders of the rolling diaphragm type such as Bellorfram cylinders have similarly desirable characteristics. In the claims the work frictional shall be construed to include both stiction and friction as defined earlier. The configuration of two air bags operating a suspended plate between them is conventional and novelty is not claimed for the structure which is a double acting actuator.

Fluid power is used in the conventional sense of air or oil under pressure for the actuation of devices.

To obtain even large metal removal rates with a smooth finish, two such billet grinder apparatuses as described herein can be used with a single rotater car. The first grinding wheel is set for a heavier cut, and the trailing grinding wheel is set for the lighter grinding.

Operation.

In grinding a pipe, the rotation and travel of the car 3 are first established. the drive motor 31 is adjusted to the correct speed, and the operator brings the saddle 21 down vertically until the grinding wheel is approximately four inches from the rotating pipe. The grinding wheel has a total vertical travel of eight inches so that this adjustment puts the wheel in the mid range of that travel. He now actuates the control for grinding. and the master cylinder 80 extends its rod 83. allowing the boom to be controlled by

actuators

97, 98. He then brings the grinding wheel down onto the work by adjusting

valves

138 and 148. He gradually reduces the pressure from valve 138 and increases the pressure from valve 148 until the grinding wheel is in contact with the workpiece under the desired force. The grinding should take place in the mid range so that the head can respond adequately.

The invention is not to be construed as limited to the particular forms disclosed herein. since these are to be regarded as illustrative rather than restrictive.

Definition of words for construction of claims. The incremental volume of the bag actuator is defined as the difference in volume with the bag actuator at one end of its permitted stroke and the volume of the bag actuator at the other end of its permitted stroke. Permitted stroke means simply the maximum allowable stroke or travel of the actuator as determined by mechanical or control means of the machine and is to be distinguished from the working stroke which in nearly all cases will be much less. The moment of the boom produced by the bag actuators is considered to have a short moment arm when the bag actuator travel is no more than one quarter of the corresponding travel of nation has means for producing relative movement of the grinding wheel along the workpiece, and particularly the combination for contour grinding of rounds and pipe wherein the combination also simultaneously rotates the workpiece about its own axis, the improvement for maintaining a substantially constant force of the wheel against a work surface that changes its vertical position rapidly, comprising:

a. a frame,

b. a saddle,

c. means for supporting the saddle in the frame,

d. a boom extending outwardly from the saddle,

e. a grinding wheel mounted for rotation about its central axis, on the outer end of the boom,

f. means pivotally mounting the inner end of the boom on the saddle for moving the grinding wheel onto the workpiece, thereby also establishing a piv otal axis of the boom.

g. a motor mounted on the saddle,

h. means for driving the grinding wheel from the motor,

i. an upper air bag actuator secured at its upper end to the saddle,

j. a lower air bag actuator secured at its lower end to the saddle,

k. main fluid power pressure means to control the force exerted by each actuator for producing a differential force between them.

1. a boom control member between said actuators, secured to the lower end of the upper actuator and to the upper end of the lower actuator so as to move between them in response to the differential force exerted by said actuators,

m. means for guiding the motion of said boom control member between the actuators.

n. means for limiting the travel of the boom control member.

0. means pivotally connecting said boom control member to the boom for producing a moment of the boom about the pivotal axis of the boom.

p. emergency means having a lost motion connection to the boom. operable upon loss of pressure of main fluid power means to retract the boom for removing the grinding wheel from the workpiece. and

q. power means for storing energy during the operation of the main fluid power means and for supplying energy to said emergency means during loss of pressure of main fluid power means.

2. The machine defined in claim 1, wherein the means for driving the grinding wheel from the motor includes.

a. an intermediate shaft which is substantially coaxial with the pivotal axis of the boom.

b. a driven sheave on one end of said shaft.

c. a driving sheave on the other end of said shaft.

d. a first set of belts connecting the motor and the driven sheave.

e. a second set of belts connecting the driving sheave with the grinding wheel.

3. The machine defined in claim 2, wherein the means pivotally mounting the inner end of the boom on the saddle includes a hollow pivotal shaft. and the intermediate shaft passes through said pivotal shaft.

4. The machine defined in claim 1, wherein the moment of the boom produced by the bag actuators, boom control member. and connecting means has a short moment arm.

5. The machine defined in claim 1, wherein the bag actuators. the boom control member, and the means pivotally connecting the boom control member to the boom are so positioned with relation to the pivotal axis of the boom that the arcuate travel of the grinding wheel axis is no less than four times the corresponding travel of the boom control member.

6. The machine defined in claim 1, wherein the distance between the pivotal axis of the boom and the axis I of the grinding wheel, to the distance between said pivotal axis and the pivotal connection on the boom of the connecting means. is in the ratio of no less than four to one.

7. The machine defined in claim 1, wherein the incremental volume of the actuator to the volume of the actuator at that end of its permitted stroke when its vol ume is greatest. is in the ratio of no more than six to ten.

8. The machine defined in claim 3, wherein the bag actuators, the boom control member. and the means pivotally connecting the boom control member to the boom are so positioned with relation to the pivotal axis of the boom that the arcuate travel of the grinding wheel axis is no less than four times the corresponding travel of the boom control member.

9. The machine defined in claim 8, where in the incremental volume of the actuator to the volume of the actuator at that end of its permitted stroke when it volume is greatest, is in the ratioof no more than six to ten.

10. In a billet grinding machine including a cooperating unit for holding the workpiece wherein the combination has means for producing relative moment of the grinding wheel along the workpiece, and particularly the combination for contour grinding of rounds and pipe wherein the combination also simultaneously rotates the workpiece about its own axis. the improvement for maintaining a substantially constant force of the wheel against a work surface that changes its vertical position rapidly, comprising;

a. a frame,

b. a saddle,

0. means for supporting the saddle in the frame.

d. a boom extending outwardly from the saddle,

f. means pivotally mounting the inner end of the boom on the saddle for moving the grinding wheel onto the workpiece, thereby also establishing a pivotal axis of the boom, said means including a hollow pivotal shaft,

g. a motor mounted on the saddle,

h. means for driving the grinding wheel from the motor, including an intermediate shaft which is substantially coaxial with the pivotal axis of the boom and which passes through the hollow pivotal shaft; a driven sheave on one end of said shaft; a driving sheave on the other end of said shaft; a first set of belts connecting the motor and the driven sheave; and a second set of belts connecting the driving sheave with the grinding wheel,

i. An upper air bag actuator secured at its upper end to the saddle,

j. a lower air bag actuator secured at its lower end to the saddle,

k. main fluid power pressure means to control the force exerted by each actuator for producing a differential force between them,

l. a boom control member between said actuators. secured to the lower end of the upper actuator and to the upper end of the lower actuator so as to move between them in response to the differential force exerted by said actuators,

m. means for guiding the motion of the boom control member between the actuators.

n. means for limiting the travel of the boom control member,

0. means pivotally connecting said boom control member to the boom for producing a moment of the boom about the pivotal axis of the boom, said bag actuators, boom control member, and pivotally connecting means being so positioned with relation to the pivotal axis of the boom that the arcuate travel of the grinding wheel axis is no less than four times the corresponding travel of the boom control member,

p. emergency means having a lost motion connection to the boom, operable upon loss of pressure of main fluid power means to retract the boom for removing the grinding wheel from the workpiece, and

q. power means for storing energy during operation of the main fluid power means and for supplying energy to said emergency means during loss of pressure of main fluid power means.

11. in a billet grinding machine including a cooperating unit for holding the workpiece wherein the combination has means for producing relative moment of the grinding wheel along the workpiece, and particularly the combination for contour grinding of rounds and pipe wherein the combination also simultaneouslyrotates the workpiece about its own axis. the improvement for maintaining a substantially constant force of the wheel against a work surface that changes its vertical position rapidly. comprising.

a. a frame.

. a saddle.

c. means for supporting the saddle in the frame.

d. a boom extending outwardly from the saddle.

. means pivotally mounting the inner end of the boom on the saddle so that substantially all of the weight of the boom and grinding wheel produces a moment of force about the pivotal axis in the same direction for moving the grinding wheel onto the workpiece. thereby also establishing a pivotal axis, said means including a hollow pivotal shaft,

g. a motor mounted on the saddle,

i. an upper air bag actuator secured at its upper end to the saddle.

j. a lower air bag actuator secured at its lower end to the saddle.

m. means for guiding the motion of the boom control member between the actuators,

n. means for limiting the travel of the boom control member, and

0. means pivotally connecting said boom control member to the boom for producing a moment of the boom about the pivotal axis of the boom, said bag actuators, boom control member, and pivotally connecting means being so positioned with relation to the pivotal axis of the boom that the arcuate travel of the grinding wheel axis is no less than four times the corresponding travel of the boom control member.

12. In a billet grinding machine including a cooperating unit for holding the workpiece wherein the combination has means for producing relative movement of the grinding wheel along the workpiece, and particularly the combination for contour grinding of rounds and pipe wherein the combination also simultaneously rotates the workpiece about its own axis, the improvement for maintaining a substantially constant force of the wheel against a work surface that changes its vertical position rapidly, comprising:

a. a frame, b. a saddle, c. means for supporting the saddle in the frame,

d. a boom extending outwardly from the saddle.

e. a grinding wheel mounted for rotation about its central axis, on the outer end of the boom.

f. means pivotally mounting the inner end of the boom on the saddle so that substantially all of the weight of the boom and grinding wheel produces a moment of force about the pivotal axis in the same direction for moving the grinding wheel onto the workpiece, thereby also establishing a pivotal axis. said means including a hollow pivotal shaft.

g. a motor mounted on the saddle.

h. means for driving the grinding wheel from the motor.

i. an upper air bag actuator secured at its upper end to the saddle,

j. a lower air bag actuator secured at its lower end to the saddle,

k. main fluid power pressure means to control the force exerted by each actuator for producing a dif-.

Claims

1. In a billet grinding machine including a cooperating unit for holding the workpiece wherein the combination has means for producing relative movement of the grinding wheel along the workpiece, and particularly the combination for contour grinding of rounds and pipe wherein the combination also simultaneously rotates the workpiece about its own axis, the improvement for maintaining a substantially constant force of the wheel against a work surface that changes its vertical position rapidly, comprising: a. a frame, b. a saddle, c. means for supporting the saddle in the frame, d. a boom extending outwardly from the saddle, e. a grinding wheel mounted for rotation about its central axis, on the outer end of the boom, f. means pivotally mounting the inner end of the boom on the saddle for moving the grinding wheel onto the workpiece, thereby also establishing a pivotal axis of the boom, g. a motor mounted on the saddle, h. means for driving the grinding wheel from the motor, i. an upper air bag actuator secured at its upper end to the saddle, j. a lower air bag actuator secured at its lower end to the saddle, k. main fluid power pressure means to control the force exerted by each actuator for producing a differential force between them, l. a boom control member between said actuators, secured to the lower end of the upper actuator and to the upper end of the lower actuator so as to move between them in response to the differential force exerted by said actuators, m. means for guiding the motion of said boom control member between the actuators, n. means for limiting the travel of the boom control member, o. means pivotally connecting said boom control member to the boom for producing a moment of the boom about the pivotal axis of the boom, p. emergency means having a lost motion connection to the boom, operable upon loss of pressure of main fluid power means to retract the boom for removing the grinding wheel from the workpiece, and q. power means for storing energy during the operation of the main fluid power means and for supplying energy to said emergency means during loss of pressure of main fluid power means.

2. The machine defined in claim 1, wherein the means for driving the grinding wheel from the motor includes, a. an intermediate shaft which is substantially coaxial with the pivotal axis of the boom, b. a driven sheave on one end of said shaft, c. a driving sheave on the other end of said shaft, d. a first set of belts connecting the motor and the driven sheave, e. a second set of belts connecting the driving sheave with the grinding wheel.

3. The machine defined in claim 2, wherein the means pivotally mounting the inner end of the boom on the saddle includes a hollow pivotal shaft, and the intermediate shaft passes through said pivotal shaft.

4. The machine defined in claim 1, wherein the moment of the boom produced by the bag actuators, boom control member, and connecting means has a short moment arm.

5. The machine defined in claim 1, wherein the bag actuators, the boom control member, and the means pivotally connecting the boom control member to the boom are so positioned with relation to the pivotal axis of the boom that the arcuate travel of the grinding wheel axis is no less than four times the corresponding travel of the boom control member.

6. The machine defined in claim 1, wherein the distance between the pivotal axis of the boom and the axis of the grinding wheel, to the distance between said pivotal axis and the pivotal connection on the boom of the connecting means, is in the ratio of no less than four to one.

7. The machine defined in claim 1, wherein the incremental volume of the actuator to the volume of the actuator at that end of its permitted stroke when its volume is greatest, is in the ratio of no more than six to ten.

8. The machine defined in claim 3, wherein the bag actuators, the boom control member, and the means pivotally connecting the boom control member to the boom are so positioned with relation to the pivotal axis of the boom that the arcuate travel of the grinding wheel axis is no less than four times the corresponding travel of the boom control member.

9. The machine defined in claim 8, where in the incremental volume of the actuator to the volume of the actuator at that end of its permitted stroke when it volume is greatest, is in the ratio of no more than six to ten.

10. In a billet grinding machine including a cooperating unit for holding the workpiece wherein the combination has means for producing relative moment of the grinding wheel along the workpiece, and particularly the combination for contour grinding of rounds and pipe wherein the combination also simultaneously rotates the workpiece about its own axis, the improvement for maintaining a substantially constant force of the wheel against a work surface that changes its vertical position rapidly, comprising; a. a frame, b. a saddle, c. means for supporting the saddle in the frame, d. a boom extending outwardly from the saddle, e. a grinding wheel mounted for rotation about its central axis, on the outer end of the boom, f. means pivotally mounting the inner end of the boom on thE saddle for moving the grinding wheel onto the workpiece, thereby also establishing a pivotal axis of the boom, said means including a hollow pivotal shaft, g. a motor mounted on the saddle, h. means for driving the grinding wheel from the motor, including an intermediate shaft which is substantially coaxial with the pivotal axis of the boom and which passes through the hollow pivotal shaft; a driven sheave on one end of said shaft; a driving sheave on the other end of said shaft; a first set of belts connecting the motor and the driven sheave; and a second set of belts connecting the driving sheave with the grinding wheel, i. An upper air bag actuator secured at its upper end to the saddle, j. a lower air bag actuator secured at its lower end to the saddle, k. main fluid power pressure means to control the force exerted by each actuator for producing a differential force between them, l. a boom control member between said actuators, secured to the lower end of the upper actuator and to the upper end of the lower actuator so as to move between them in response to the differential force exerted by said actuators, m. means for guiding the motion of the boom control member between the actuators, n. means for limiting the travel of the boom control member, o. means pivotally connecting said boom control member to the boom for producing a moment of the boom about the pivotal axis of the boom, said bag actuators, boom control member, and pivotally connecting means being so positioned with relation to the pivotal axis of the boom that the arcuate travel of the grinding wheel axis is no less than four times the corresponding travel of the boom control member, p. emergency means having a lost motion connection to the boom, operable upon loss of pressure of main fluid power means to retract the boom for removing the grinding wheel from the workpiece, and q. power means for storing energy during operation of the main fluid power means and for supplying energy to said emergency means during loss of pressure of main fluid power means.

11. In a billet grinding machine including a cooperating unit for holding the workpiece wherein the combination has means for producing relative moment of the grinding wheel along the workpiece, and particularly the combination for contour grinding of rounds and pipe wherein the combination also simultaneously rotates the workpiece about its own axis, the improvement for maintaining a substantially constant force of the wheel against a work surface that changes its vertical position rapidly, comprising; a. a frame, b. a saddle, c. means for supporting the saddle in the frame, d. a boom extending outwardly from the saddle, e. a grinding wheel mounted for rotation about its central axis, on the outer end of the boom, f. means pivotally mounting the inner end of the boom on the saddle so that substantially all of the weight of the boom and grinding wheel produces a moment of force about the pivotal axis in the same direction for moving the grinding wheel onto the workpiece, thereby also establishing a pivotal axis, said means including a hollow pivotal shaft, g. a motor mounted on the saddle, h. means for driving the grinding wheel from the motor, including an intermediate shaft which is substantially coaxial with the pivotal axis of the boom and which passes through the hollow pivotal shaft; a driven sheave on one end of said shaft; a driving sheave on the other end of said shaft; a first set of belts connecting the motor and the driven sheave; and a second set of belts connecting the driving sheave with the grinding wheel, i. an upper air bag actuator secured at its upper end to the saddle, j. a lower air bag actuator secured at its lower end to the saddle, k. main fluid power pressure means to control the force exerted by each actuator for producing a differential force between them, l. a boom control member between said actuators, secureD to the lower end of the upper actuator and to the upper end of the lower actuator so as to move between them in response to the differential force exerted by said actuators, m. means for guiding the motion of the boom control member between the actuators, n. means for limiting the travel of the boom control member, and o. means pivotally connecting said boom control member to the boom for producing a moment of the boom about the pivotal axis of the boom, said bag actuators, boom control member, and pivotally connecting means being so positioned with relation to the pivotal axis of the boom that the arcuate travel of the grinding wheel axis is no less than four times the corresponding travel of the boom control member.

12. In a billet grinding machine including a cooperating unit for holding the workpiece wherein the combination has means for producing relative movement of the grinding wheel along the workpiece, and particularly the combination for contour grinding of rounds and pipe wherein the combination also simultaneously rotates the workpiece about its own axis, the improvement for maintaining a substantially constant force of the wheel against a work surface that changes its vertical position rapidly, comprising: a. a frame, b. a saddle, c. means for supporting the saddle in the frame, d. a boom extending outwardly from the saddle, e. a grinding wheel mounted for rotation about its central axis, on the outer end of the boom, f. means pivotally mounting the inner end of the boom on the saddle so that substantially all of the weight of the boom and grinding wheel produces a moment of force about the pivotal axis in the same direction for moving the grinding wheel onto the workpiece, thereby also establishing a pivotal axis, said means including a hollow pivotal shaft, g. a motor mounted on the saddle, h. means for driving the grinding wheel from the motor, i. an upper air bag actuator secured at its upper end to the saddle, j. a lower air bag actuator secured at its lower end to the saddle, k. main fluid power pressure means to control the force exerted by each actuator for producing a differential force between them, l. a boom control member between said actuators, secured to the lower end of the upper actuator and to the upper end of the lower actuator so as to move between them in response to the differential force exerted by said actuators, m. means for guiding the motion of said boom control member between the actuators, n. means for limiting the travel of the boom control member, and o. means pivotally connecting said boom control member to the boom for producing a moment of the boom about the pivotal axis of the boom.