US3354588A

US3354588A - Wide belt abrasive machine

Info

Publication number: US3354588A
Application number: US413793A
Authority: US
Inventors: Phillip J Roehrig
Original assignee: SOLEM MACHINE CO
Current assignee: SOLEM MACHINE CO
Priority date: 1964-11-25
Filing date: 1964-11-25
Publication date: 1967-11-28
Anticipated expiration: 1984-11-28

Description

Nov. 28, 1967 P. J. ROEHRIG WIDE BELT ABRASIVE MACHINE 6 Sheets-Sheet 1 Filed Nov. 25. 1964 Phillip Qi- Qoehri. 6 a, cflwg sffi Nov. 28, 1967 J, ROEHRIG 3,354,588

WIDE BELT ABRASIVE MACHINE Filed Nov. 25. 1964 e sheets-sheet 2 W Qoehr'i a 710mm Nov. 28, 1967 J, OEHRIG 3,354,588

WIDE BELT ABRASIVE MACHINE Filed Nov. 25, 1964 6 SheetsSheet 5 z i W pk W "P Oew'i 4 40% cflTToimosyf Nov. 28, 1967 P. J. ROEHRIG 3,354,588

WIDE BELT ABRASIVE MACHINE Filed Nov. 25, 1964 6 Sheets-Sheet 4 f a 9. j a a.

Nov. 28, 1967 Filed Nov. 25, 1964 RQEHRIG 3,354,588

WIDE BELT ABRASIVE MACHINE 6 Sheets-Sheet 5 I 0.41,. am oqfl'omny 6 Sheets-Sheet 6 P. J. ROEHRIG WIDE BELT ABRASIVE MACHINE Nov. 28, 1967 Filed Nov. 25, 1964 Q1 Q0634 w W phdhp 7 M,

United States Patent 3,354,588 WIDE BELT ABRASIVE MACHINE Phillip J. Roehrig, Rockford, Ill., assignor to Solem Machine Company, Rockford, 11]., a corporation of Illinois Filed Nov. 25, 1964, Ser. No. 413,793 12 Claims. (Cl. 51141) ABSTRACT OF THE DISCLOSURE As a work sheet is fed along a table, an abrasive belt is supported in triangular form by three rolls, one pressing the belt against the passing workpiece, another being power driven and supported near one end for back and forth transaxial tilting about a transverse pivot to produce edgewise wandering of the belt and maintain the same centered properly on the three rolls. To control wandering, the outboard end of the drive roll is supported by an eccentric which is adjusted back and forth by a reversible power actuator whose reverse cycles are of timed duration determined by the passing of one edge of the belt back and forth across a fluid jet. The roll that drives the belt has a surface layer formed with radially disposed and angularly spaced slits which contribute to increased driving traction.

This invention relates to a so-called wide-belt sanding machine of the type in which an endless abrasive belt extends around and is supported in a generally triangular shape by three substantially parallel and rotatable rolls, namely, a pressure roll for pressing a transverse area of the belt against a passing workpiece, a power driven roll for driving the belt, and a roll urged transaxially to tension the belt. To avoid objectionable edgewise creeping of the belt, the tension roll is usually tilted alternately in opposite directions to induce edgewise and controlled oscillation of the belt back and forth along the rolls to maintain the belt in an average centered position on the rolls.

One object of the present invention is to achieve an improved belt centering or tracking action by tilting the drive roll instead of the tension roll as has been the practice heretofore.

Another object is to provide for more effective response of the belt to tilting of the drive roll by locating the axis of tilting at one end of such roll.

A further object is to provide a novel mounting of the drive roll which permits of such tilting while rotary power is being transmitted thereto by a shaft rotatable about a fixed axis.

Still another object is to effect the drive roll tilting by a novel mechanism which is located at the outboard end of the roll, which provides for automatic back and forth tilting to provide for effective tracking of the belt, and which is disposed within the path of travel of the belt so as to permit convenient edgewise removal and replacement thereof.

A further object is to incorporate in the tilting mechanism for the drive roll a novel means for effecting manual tilting of the roll to compensate for variations in the length of opposite side edge portions of the belt.

Another object is to oscillate the abrasive belt back and forth by a mechanism which, as compared to prior controls, is simpler in construction, requires a minimum tilt, and reduces the tension required to be maintained in the belt.

The invention also resides in the novel mounting of the drive roll, the novel character of the tilting mechanism therefor, and the manner of controlling the tilting of the roll.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which FIGURE 1 is a side view, partially in section, of an abrading machine incorporating the novel features of the present invention.

FIG. 2 is a fragmentary perspective view.

FIG. 3 is a partial cross-sectional view of the drive roll and belt.

FIG. 4 is a side view, partially in section, along the line 44 of FIG. 1.

FIG. 5 is a fragmentary sectional view taken along the line 5-5 of FIG. 4.

FIG. 6 is a fragmentary section taken along the line 66 of FIG. 1.

FIG. 7 is a schematic view of the tracking control circuit of the invention.

FIG. 7a is an enlarged view of a part of FIG. 7.

FIG. 8 is a sectional view of the tension roll support mechanism.

FIG. 9 is a sectional view of the self-centering bearing structure of the pressure roll taken along the line 9-9 of FIG. 5.

FIG. 10 is a fragmentary section of the belt position sensor taken along the line 101il of FIG. 5.

In the drawings, the invention is shown for purposes of illustration incorporated in a conventional so-called wide belt sander for utilizing an endless and flexible abrasive belt 11 to rough and finish sand the top surface of a work sheet 12 of wood, metal, plastic, etc., while the same is supported on and advanced by a suitable conveyor along a horizontal table 13 on the top of a rigid base 14. Rigid with and upstanding from one side of the base is a column 15 from which projects horizontally and cantilever fashion a casting 16 which supports the

usual rolls

17, 18 and 19 by which the belt is supported in a generally triangular shape, driven at high speed, tensioned, and pressed downwardly against the passing workpiece. The rolls each comprise a relatively thick sleeve 21 of resiliently yieldable material such as firm rubber covering and bonded to a rigid cylinder 22 fixed at opposite ends to a shaft somewhat longer than the cylinder.

Opposite ends of the shaft 23 of the pressure roll 19 are supported in self-alining bearings 24 (FIGS. 1 and 9) each having an outer race ring pressed into a ring 25 having an external surface 26 disposed eccentrically relative to the shaft 23. These eccentrics are journaled in parts 28 of the casting 16. Fixed to the outer ends of the eccentrics are sprockets 29 which mesh with chains 30 extending around sprockets 31 and 32 also journaled on the frame plate. By turning a crank 33 fixed to the shaft of the sprocket 32, the pressure roll may be raised and lowered in small increments to vary the pressure holding the belt against the work. The vertical position of the roll and therefore the depth of cut to be taken is gaged with reference to a scale 34.

To tension the belt and thus provide proper driving engagement with the drive and pressure rolls, the roll 18 is spaced a short distance above the work path and horizontally from the pressure roll and opposite ends thereof are yieldably urged away from the pressure roll, in this instance by compression springs 35. For this purpose, opposite ends of the shaft 36 of the roll are journaled in bearings mounted in housings 37 (FIGS. 1 and 4) on the lower ends of elongated arms 38 suspended from pivots 39 supported by the casting 16 within the triangular path of the belt.

Each of the springs 35 bears at one end against an abutment ring 41 seated in a web 42 (see FIG. 8) of the casting 16 and at the other end against an abutment 43 threaded onto a rod 44 which at one end projects through the abutment 41 and at the other end is pivoted on the 3 free end of a short crank arm 45 fast on a shaft 46 carrying a gear 47 (FIG. 4). By turning the exposed head 48 on a pinion 49 meshing with the gear (FIGS. 1 and 4),

the crank may be swung between the tensioning position shown in full in FIGS. 1 and to the position shown in full in FIG. 8. In the latter position, the tension is released and the belt freed for easy removal from the rolls.

Between the pressure and tension rolls is the usual pressure shoe 81 extending across the full width of the belt and rigidly mounted on the casting 16 for vertical adjustment through suitable means (not shown) actuated by turning a hand wheel 82 (FIG. 1). The yieldable but accurately located surface of the shoe presses the belt against the work surface after the same has been rough sanded by the action of the pressure roll. A more accurate finish of the work surface is thus produced.

The drive roll 17 is spaced well above the pressure and tension rolls so as to provide a large are a (FIG. 5), nearly 180 degrees in the present instance, of driving contact with the belt. For a purpose to more fully appear later, the projecting end of the shaft 49 of the roll is supported adjacent the end of the roll in a self-alining and anti-friction bearing 51 (FIG. 4) disposed within a housing 52 with its inner race ring secured to the shaft while the outer ring is pressed into a hole 53 in the upper end of a standard 54 secured to the column 15. The shaft end is thus supported for limited tilting about an axis extending transaxially of the shaft.

The roll 17 is driven by an electric motor 55 mounted on top of the column 15. To accommodate the tilting of the roll shaft within the bearing 51, the extended end of the shaft 49 is coupled to the motor shaft 56 through the medium of a suitable universal coupling 57.

In accordance with the present invention, an anti-friction self-alining bearing 58 (see FIG. 6) supporting the outboard end of the drive roll shaft 49 is mounted for vertical adjustment to effect a controlled tilting of the drive roll about a horizontal axis 59 (FIG. 5) defined by the center plane of the bearing 51. In the present instance, such tilting can be effected manually or automatically by separate actuation of two

concentrics

61 and 62. arranged concentrically and supporting the bearing 58 as shown in FIGS. 6 and 7.

To the foregoing ends, the inner race ring of the hearing is fixed on the shaft 49 through the medium of a sleeve 63 and a lock-nut. The outer race is pressed into a ring 64 closed at opposite ends by plates 65 to form a housing around the bearing. The ring, thus adapted to turn about its axis 72 coacts with ball-bearings 67 and a follower ring 68 to form the eccentric 61. For this purpose, these bearings separated by a spacer 69 are pressed onto the ring 64 whose outer cylindrical surface 71 is disposed eccentrically relative to the shaft, that is, its axis 72 is ofiset a short distance I) from the shaft axis 66. The bearings 67 are pressed into the follower ring 68 which is disposed between axially spaced fianges 73 formed by the margins of the plates 65.

The second and manually adjustable eccentric is formed by the ring 68 having a cylindrical external surface 74 whose axis 75 is offset from the shaft axis 66 on the same side as the first eccentric but a somewhat greater distance 0. The surface 74 is journaled in the surrounding stationary ring 76 straddled by

radial flanges

77 and 78 at opposite ends of the eccentric ring. The ring 76 is formed on the upper end of a part 79 of the frame casting 16 upstanding just beyond the outboard end of the drive roll.

With the outboard end of the drive roll supported by the two

eccentrics

61, 62, it will be apparent that turning of the outer eccentric ring 68 in opposite directions about its fixed axis 75 will raise and lower one end of the shaft 49 whose axis 66 travels along an arcuate path 84 (FIG. 7a) but through a short are disposed half above and half below a horizontal plane 89 through the axis 75. Such adjustment of the shaft, being vertical and transversely of the long are a of contact between the belt and the drive roll 17, produces a maximum amount of edgewise shifting of the belt for a given amount of tilt of the roll by either one of the

eccentrics

61, 62.

Tilting of the roll 17 by the outer eccentric 62 is made manually after a new belt has been installed or after uneven stretching of a belt in service use and for the purpose of compensating for a difference in the lengths of opposite side edge portions of the belt. To accomplish this, gear teeth 85 (FIG. 6) are formed around the periphery of the flange 77 on the eccentric ring 68 and meshed with a pinion 86 fast on a headed stud 87 which is journaled on a clamping screw 88 threaded into the support ring 76. After loosening the screw, the stud may be turned by a wrench applied to the head and the eccentric turned to correspondingly vary the transaxial position along the path 84 of the outboard end of the drive roll thus equalizing the tension in opposite side edges of the belt. After the adjustment, the screw is tightened so as to lock the eccentric in the selected position. It will be apparent that by employing the eccentric type of adjustment, the amount of the tilting can be gaged accurately since the tilt is a very small part of the angular movement of the eccentric ring.

The automatic tilting of the drive roll to cause controlled edgewise wandering of the belt and maintain the same properly centered on the three rolls is effected by rocking the eccentric ring 64 back and forth intermittently about its axis 72 whose position is fixed when the eccentric 62 is locked. In response to such rocking, the shaft axis 66 traverses a short part, usually somewhat less than of an inch, of an arcuate path 91 whose radius is equal to the spacing b of the shaft and eccentric axes. As before, the range of the arcuate travel is preferably disposed half above and half below the plane 89 and therefore transversely of and about midway between the ends of the are a of belt and drive roll contact area.

Rocking of the eccentric 61 in opposite directions is effected in the present instance by selectively energizing two power actuators 92, 93 (FIGS. 1 and 7) under the control of a single device 94 (FIGS. 7 and 10) for sensing edgewise shifting of the belt in opposite directions past a predetermined position 95 as a result of opposite tiltings of the drive roll. While the actuators may take various forms, the ones shown herein comprise a cylinder 96 having a piston 97 slidable therein and fixed to a rod 98 disposed generally tangentially of the eccentric ring 64 with its outer end pivotally connected at 99 to a stud 101 projecting from the housing 65 parallel to the shaft 49 and near the periphery of the ring. A yoke 102 (FIG. 2) projecting from the head end of the cylinder is pivoted at 103 on a stud 104 projecting from the end of the frame casting 16 within the triangular path traversed by the belt. By employing a reversible actuator of the rectilinear type and thus positioned, it will be apparent that eccentric 61 may be oscillated back and forth within a range d (FIG. 7) in all angular positions of the manually adjustable eccentric 62. The relatively wide range of rocking of the eccentric 61 produces a substantially smaller movement, usually somewhat less than of an inch, of the outboard end of the drive roll thus enabling the tilting of the roll to be controlled with extreme accuracy.

Preferably the sensing device 94 (see FIGS. 2, 5, 7 and 10) is arranged to respond to changes in the position of the edge 105 of the belt at the inboard ends of the rolls and between the tension and drive rolls. The operating parts are supported by and enclosed in a housing 106 secured to a bracket 107 projecting from the arm casting 38. The device includes a nozzle 108 communicating with a source 109 of compressed air for detecting a jet of air perpendicular to the path of edgewise travel of the belt along the supporting rolls. When the jet is unobstructed as shown in FIG. 10, the air passes through a hole 111 in the housing 106 and impinges against a disk 112 on the free end of an arm 113 of a switch 114 in a casing mounted within the housing 106. The switch which is urged open by a spring 115 is thus held closed completing a circuit 116 for energizing a solenoid 117 whose armature is on the outwardly projecting end of the plunger 118 of a reversing air valve 119.

When the jet is unobstructed by the belt as shown in FIG. 7, the switch 114 is closed, the solenoid is energized, and the plunger is shifted to the position shown for admitting compressed air from a supply line 109 to a line 121 leading to the head end of the cylinder 96 through a check valve 122 which opens automatically. At this time, the rod end of the cylinder is connected through an unobstructed line 123 and the valve to a low pressure area 124. Thus, when the switch becomes closed by the belt uncovering the air jet in moving in the direction of the full arrow in FIG. 7, the actuator 92 formed by the piston 7 and the head end of the cylinder 96 is energized and the eccentric 61 is shifted rapidly through the range d to the end 125 thereof. As a result, the outboard end of the drive roll 17 is moved rapidly through the full tilting range e (FIG. 7a) thus reversing the direction of edgewise creeping of the belt. Such creeping in the direction of the dotted arrow (FIG. 7) continues at a relatively rapid rate so long as the drive roll is held in the new tilting position or tilted in such direction sufficiently to induce the shifting of the belt to continue.

In the initial part of this reverse belt shifting, the edge 105 of the belt passes the air jet and intercepts the latter thus permitting the spring 115 to open the switch 94, deenergize the solenoid, and reverse the position of the valve plunger 118 thus admitting high pressure air into the rod end of the cylinder 96 while connecting the head end to the low pressure are-a 124 through the passage 121 which includes a by-passage 126 controlled by a needle valve 127 adjusted to restrict and slow the outflow of air from the cylinder. The actuator 93 formed by the piston and rod end of the cylinder 96 is thus energized to initiate reverse tilting of the roll but the creeping beyond the jet continues until the belt reaches the other limit of the tilt range, the eccentric ring 64 then being at the end 125 of the range d. Then, when the roll, in its mverse movement, passes the center of the range and the tilting is reversed, the direction of creeping is reversed and the edge 105 of the belt starts to move back toward the jet. This movement continues until the jet becomes uncovered causing the switch 114 to be closed and the actuator 92 to be reenergized to again cause rapid movement of the eccentric ring 64 to the limit 125 in the manner described above.

As a result of the alternate reversals of the valve 119 and the accompanying rapid and slow tilting of the drive roll 17, the belt is oscillated back and forth along the rolls within a range considerably narrower and more positively controlled than has been possible heretofore. By tilting the drive roll about one end, the belt is more reactive to the tilting with the result that the tendency of the belt to flutter or become rippled during the tracking action is reduced considerably. This not only prolongs the service life of the belt but also makes for greater uniformity in the finished work surface.

It will be apparent from the foregoing that the eccentrics for manually and automatically tilting the drive roll as well as the supports for the tension roll and the means for adjusting the same are'all disposed within the triangular path traversed by the belt and are easily accessible from the outboard end of the supporting casting 16. All of the adjustments required in service use may be made easily from one end of the machine. During service operation, the free end of the casting 16 is preferably clamped rigidly to the base 14 by a bar 131 (FIG. 2.) spanning side rails 132 on the top of the base and clamped to the latter and the free end of the casting by screws 133. These are loosened and the bar removed when it is desired to replace a worn out belt. As a preliminary to this, the tension is relieved by drawing the roll 18 inwardly to the position shown in full in FIG. 8. The belt may then be drawn edgewise off from the three rolls and the shoe 81. After substituting a new belt, the roll 18 is swung outward to tension the belt after which the eccentric 62 is adjusted to tilt the drive roll and equalize the tension at opposite side edges of the belt.

It will be apparent from the foregoing that the eccentrics automatic tilting of the drive roll 17 through the eccentric 61 as above described may be increased and the range of edgewise shifting by the belt to achieve the desired centering or tracking may be reduced considerably by a simple modification of the surface of the drive roll to increase the traction between this roll and the belt. To this end, the rubber or other resiliently yieldable material forming the surface layer 21 of the roll is slitted along parallel lines 134 (FIGS. 2 to 5) closely spaced angularly around the roll and extending longitudinally thereof but terminating at 135 short of the side edges of the belt in all edgewise positions of the latter. The slits are simple straight cuts about one-eighth of an inch deep made by pressing a thin and sharp blade into the rubber and drawing the same along the roll. The slits are spaced about one inch apart and opposite side walls thereof are left in face to face contact since none of the material of the surface layer is removed in the slitting process. The outer portion of the yieldable layer 21 is divided into segments which are flexible circumferentially of the roll.

It is believed that the improved traction resulting from such slitting of the drive roll is attributable to the differenial distortion of the

areas

136, 137 on the leading and trailing sides of the slits 134 under the forces to which these areas are subjected during high speed rotation of the roll within the tensioned belt. It is believed that the rubber areas 136 trailing the slits become compressed and denser as illustrated by the shading in FIG. 3 and push forward against the trailing walls of the slits thus causing the areas 137 to be forced outwardly and increase the contact pressure between these areas and the belt. A noticeable increase in the driving friction is observed through the use of the slits. By confining the slits to the area of the roll 17 which is always disposed between the side edges of the belt, the forces resulting from radial compression of the areas 137 are transmitted forwardly to expand these areas rather than being applied uselessly to distort the areas longitudinally.

I claim as my invention:

1. In a Wide belt abrading machine having, in combination, an endless belt, a roll disposed within said belt for pressing a transverse area of the belt against a passing workpiece, a roll within the belt paralleling the pressure roll and adapted to drive the belt, a roll within the belt paralleling said pressure and drive rolls and adapted for bodily transaxial adjustment to tension the belt around the rolls, a self-alining bearing supporting one end of said drive roll for tilting of the roll about a transverse axis perpendicular to the roll axis and disposed substantially in the plane of said bearing, a power driven shaft mounted outwardly beyond said transverse axis for rotation about a fixed axis approximately alined with the drive roll axis, and a universal coupling connecting said shaft and the end of said drive roll for transmitting rotary power to the roll while permitting tilting of the roll about said transverse axis during such rotation.

2. An abrading machine asde-fined in claim 1 in which said drive roll is spaced a substantial distance from said' pressure and tension rolls to provide for driving contact between the belt and drive roll over an arc of substantially a half revolution, and mechanism for moving the outboard end of said drive roll alternately back and forth and correspondingly tilt the roll about said axis and along a path disposed intermediate the ends of said arc.

3. An abrading machine as defined in claim 1 including a second self-alining hearing supporting the opposite end of said roll, means supportingv said second bearing for bodily transaxial shifting to tilt the roll about said axis.

4. An abrading machine as defined in claim 3 including a device for sensing edgewise shifting of the belt to opposite limits of a narrow tracking range, and means controlled by said device for shifting said second bearing alternately in opposite directions about said axis.

5. In a wide belt abrading machine having, in combination, an endless belt, a pressure roll disposed within said belt for pressing a transverse area of the belt against a passing workpiece, a drive roll within the belt paralleling the pressure roll and adapted to drive the belt, said drive roll having first and second shaft ends, a tension roll within the belt paralleling said pressure and drive rolls and adapted for bodily transaxial adjustment to tension the belt around the rolls, a self-aligning bearing supporting said first shaft end for tilting of the drive roll about a transverse axis perpendicular to the drive roll axis, means for transmitting rotary power to said first shaft end While permitting tilting of the drive roll about said transverse axis during such rotation, a second self-aligning bearing supporting said second shaft end, an eccentric ring surrounding and rotatably supported by said second bearing and having a cylindrical periphery with its axis paralleling but ofiset from the axis of said shaft ends, a second normally stationary ring in which said eccentric ring is supported to turn about its axis whereby to shift said second end transaxially to thereby tilt said drive roll about said first axis.

6. An abrading machine as defined in claim in which said second ring is journaied on and rotatable relative to said eccentric ring and formed with a cylindrical outer surface whose axis is offset laterally from said shaft and eccentric axes, and a stationarily mounted ring in which said second ring is journaled for rotation to swing said first eccentri ring and said shaft about the axis of the stationary ring.

7. In a wide belt abrading machine having, in combination, an endless belt, a pressure roll disposed within said belt for pressing a transverse area of the belt against a passing workpiece, a drive roll within the belt paralleling the pressure roll and adapted to drive the belt, said drive roll having first and second shaft ends, a tension roll within the belt paralleling said pressure and drive rolls and adapted for bodily transaxial adjustment to tension the belt around the rolls, a self-aligning bearing supporting said first shaft end for tilting of the drive roll about a transverse axis perpendicular to the drive roll axis, means for transmitting rotary power to said first shaft end while permitting tilting of the drive roll about said transverse axis during such rotation, a stationary support ring beyond the opposite end of said drive roll and having a cylindrical internal surface, an eccentric ring journaled in said support ring surface for turning about an axis offset laterally from the axis of said drive roll, a second eccentric ring journaled in said first eccentric ring to turn about an axis offset laterally from said drive roll axis and also the axis of said first eccentric ring, a second self-aligning bearing supporting said second shaft end and supported by and within said second eccentric ring, and independently operable means for turning the respective eccentric rings whereby to move said second bearing transaxially and thereby tilt said drive roll correspondingly.

8. In a wide belt abrading machine. having, in combination, an endless belt, a pressure roll disposed within said belt for pressing a transverse area of the belt against a passing workpiece, a drive roll within the belt paralleling the pressure roll and adapted to drive the belt, said drive roll having first and second shaft ends, a tension roll within the belt paralleling said pressure and drive rolls and adapted for bodily transaxial adjustment to tention the belt around the rolls, a self-aligned bearing supporting said first shaft end for tilting of the drive roll about a transverse axis perpendicular to the axis of the drive roll, means for transmitting rotary power to said first shaft end while permitting tilting of the drive roll about said transverse axis during such rotation, a stationary support beyond said drive roll opposite said axis, an eccentric journaled on said support to turn about an axis offset laterally from said drive roll axis, a second eccentric journaled in said first eccentric to turn about an axis offset laterally from said drive roll and first eccentric axes, a self-aligning bearing disposed within and supported by said second eccentric and supporting said second shaft end for independent rotation of the drive roll, and independently operable means for angularly adjusting the positions of said first and second eccentrics, the position of said drive roll being determined by the combined positions of the two eccentrics.

9. An abrading machine as defined in claim 8 including manually operable means for adjusting and holding the angular position of one of said eccentrics, a device operatively associated with one edge of said belt and operable to detect movement of such edge in opposite directions to opposite limits of a predetermined tracking range, and mechanism controlled by said device to move the other of said eccentrics alternatively in opposite directions.

10. In a wide belt abrading machine having, in combination, an endless belt, a roll disposed within said belt for pressing a transverse area of the belt against a passing workpiece, a roll within the belt paralleling the pressure roll and adapted to drive the belt, a roll within the belt paralleling said pressure and drive rolls and adapted for bodily transaxial adjustment to tension the belt around the rolls, means supporting said drive roll for back and forth tilting about a transverse axis to induce edgewise oscillation of said belt, mechanism associated with the mounting of said drive roll for automatically tilting the same back and forth about said axis between first and second positions, said mechanism comprising one actuator adapted when activated to tilt the drive roll quickly and uninterruptedly to said first position and thereby initiate shifting of the belt edgewise in a corresponding direction, a second actuator adapted when activated to urge the drive roll in the opposite direction and toward said second position at a slow and restricted rate, and a device for sensing changes in the edgewise position of said belt and operating to activate said first actuator when the roll reaches said second position by the action of said second actuator when said roll, while being tilted in the opposite direction by said first actuator, moves away from said second position.

11. An abrading machine as defined in claim 10 in which said first actuator is unrestrained in its movement and the second actuator includes means for controllably restraining the motion of the actuator.

12. An abrading machine as defined in claim 10 in which said actuators comprise a cylinder, a piston reciprocated therein and coupled to said drive roll, and a valve and passages controlled by said sensing device for admitting pressure fluid to opposite ends, one of said passages permitting the free flow of pressure fluid therethrough while the other passage includes a restriction for limiting the fiow of fluid therethrough.

References Cited UNlTED STATES PATENTS 2,592,581 4/1952 Lorig. 2,597,256 5/1952 Murray. 3,008,276 11/1961 Kile 51135 X 3,110,989 11/1963 Dawson 51-435 3,153,306 10/1964 Robischung 51-135 ROBERT C. RIORDON, Primary Examiner.

D. G. KELLY, Assistant Examiner.

Claims

1. IN A WIDE BELT ABRADING MACHINE HAVING, IN COMBINATION, AN ENDLESS BELT, A ROLL DISPOSED WITHIN SAID BELT FOR PRESSING A TRANSVERSE AREA OF THE BELT AGAINST A PASSING WORKPIECE, A ROLL WITHIN THE BELT PARALLELING THE PRESSURE ROLL AND ADAPTED TO DRIVE THE BELT, A ROLL WITHIN THE BELT PARALLELING SAID PRESSURE AND DRIVE ROLLS AND ADAPTED FOR BODILY TRANSAXIAL ADJUSTMENT TO TENSION THE BELT AROUND THE ROLLS, A SELF-ALINING BEARING SUPPORTING ONE END OF SAID DRIVE ROLL FOR TILTING OF THE ROLL ABOUT A TRANSVERSE AXIS PERPENEDICULAR TO THE ROLL AND DISPOSED SUBSTANTIALLY IN THE PLANE OF SAID BEARING, A POWER DRIVEN SHAFT MOUNTED OUTWARDLY BEYOND SAID TRANSVERSE AXIS FOR ROTATION ABOUT A FIXED AXIS APPROXIMATELY ALIGNED WITH THE DRIVE ROLL AXIS, AND A UNIVERSAL COUPLING CONNECTING SAID SHAFT AND THE END OF SAID DRIVE ROLL FOR TRANSMITTING ROTARY POWER TO THE ROLL WHILE PERMITTING TILTING OF THE ROLL ABOUT SAID TRANSVERSE AXIS DURING SUCH ROTATION.