Abrasive Belt Control Apparatus And Method

Abstract

Apparatus and method for use with an endless abrasive belt operable to sense the position of the belt and to automatically oscillate the belt transversely in accordance with movement of a position sensor.

Description

SUMMARY BACKGROUND OF THE INVENTION

The present invention relates to apparatus for controlling the oscillatory movement of an endless abrasive belt.

In the past, apparatus has been provided for endless abrasive belts to automatically oscillate the belt transversely to its direction of travel. This prevents the belt from "walking" off the support rolls and tends to improve belt life, i.e. by more evenly distributing wear. With past constructions, the oscillation or transverse motion of the belt has been generally fixed. In the present invention a sensor is utilized which senses the position of the belt; the sensor is selectively oscillated and apparatus which is responsive to the sensor causes similar oscillation or tracking of the belt; In this manner the oscillatory motion of the belt can be controlled simply by selectively controlling the oscillatory action of the sensor. Therefore, it is an object of the present invention to provide novel apparatus and method for controlling the movement of an endless abrasive belt.

In present grinding techniques normally a belt is used which is approximately as wide as the workpiece to be ground. For extremely wide workpieces the belt is correspondingly wide and hence costly. In the present invention by use of the selective controlled oscillation the belt can be narrower and can be moved over a substantial distance to cover the width of the workpiece. Thus a substantial savings in the cost of the belt can be realized. Conversely a belt wider than the workpiece could be tracked to grind a narrow workpiece resulting in a more effective utilization of the belt. It is therefore another object of the present invention to provide novel apparatus and method for oscillating a belt on a support roll whereby a wide workpiece can be ground by a substantially narrower abrasive belt and conversely where wide belt can be more effectively utilized on a narrow workpiece.

Other objects, features, and advantages of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawing in which:

FIG. 1 is a front elevational view of apparatus embodying features of the present invention;

FIG. 2 is a side elevational view of the apparatus of FIG. 1; and

FIG. 3 is generally a schematic diagram of the apparatus of FIG. 1 and 2.

An abrading belt assembly is generally indicated by the numeral 10 and includes an endless abrasive belt 12 supported for movement on spaced rolls 14 and 16. The roll 16 can be driven by a motor 18, the actuation of which can be controlled by a motor control apparatus 20. Roll 16 is a contact roll and is generally fixed relative to the assembly 10 and backs up the abrasive belt 12 as it engages a workpiece. The roll 14 is a control and belt tension roll with the tension being selectively adjustable on the belt 12 by means of a belt tension cylinder assembly 22. The cylinder assembly 22 is fixed to a bifarcated frame 24 upon which the contact roll 16 is journaled. The control roll 14 is journaled upon a different bifarcated frame assembly 26 which is connected to the piston rod 28 of the piston assembly 22 whereby the frame 26 and hence the control roll 14 can be pivoted relative to the axis X of the rod 28 in a manner to be described.

Supported upon the frame 26 is an adjustable speed drive motor 30 which is connected to a sensor assembly 32 via a linkage assembly 34. The sensor assembly 32 is mounted for translatory and transverse motion relative to the belt 12 and to the roller 16 by means of a pair of guide or support rods 36 which are fixed to the frame 26. A sensor assembly 32 includes a fluidic sensor having an aperture 38 which is located approximate to and generally in confrontation with the back surface of the belt 12 such that air flow out from the opening 38 would be generally directed towards the back surface of the belt 12. A flexible hose 40 connects the sensor assembly 32 to a source of air pressure via a fluid line 60 and a flow regulator 43.

An actuating piston assembly 42 is fixed to a first cross bar 44 and located such that the rod of its actuating piston 46 can engage the lower end of one arm 47 of the control roll support frame 26. The bar 44 is fixed to the frame 24 such that the piston assembly 42 will be maintained stationary relative to any pivotal movement of the control roll 14 and support frame 26 relative to the axis of the piston rod 28. Thus the force from piston 46 will tend to pivot the control roll 14 about the axis X of piston rod 28. Oppositely facing the piston assembly 42 is a balance assembly 48 which is fixed to a support bar 50 which support bar 50 is also fixed to the frame 24. The balance apparatus 48 includes a moveable plunger 52 which is normally biased via spring 54 outwardly into engagement with the opposite side of arm 47 on frame 26. The bias of spring 54 can be set by a moveable plug 56. The force of the plunger 52 acting upon the frame 26 will tend to pivot the control roll 14 about the axis X of piston rod 28 in a direction opposite to that resulting from the force exerted by piston 46 and hence will react the force from piston 46. The piston 46 is normally returned to its deactuated position by means of a spring member 49. The piston 46 is actuated by air pressure on the head side via a conduit 58 which is also connected to the regulator 43 via the common fluid line 60. The regulator 43 provides for a generally constant flow of air such that the pressure in the cylinder of the piston assembly 42 will be a function of the flow through the orifice 38.

Normally in operation, the edge of the belt 12 is located such as to be partially blocking the aperture 38. In this condition, the flow of fluid out from the aperture 38 will be reduced resulting in a pressure rise in the cylinder assembly 42 causing the piston 46 to move outwardly to pivot the control roll frame 26 and hence the control roll 14 about axis X. This causes the belt 12 to twist slightly increasing the pressure on its outer most edge causing the belt 12 to move in a direction away from the opening 38 as the rolls 14 and 16 rotate. Looking now to FIGS. 1 and 2 for example, if the fluid sensor assembly 32 is moved to the right along the guide rods 36, the opening 38 will continuously be moved in the direction to be at least partially blocked by the black of the belt 12. The result will be pressurization of the cylinder assembly 42 whereby the piston 46 will be actuated to pivot the control roll 14 to twist of belt 12 causing the belt 12 to be moved transversely to the right along the control roll 14. This motion will continue at least until the belt 12 exposes a sufficient portion of the aperture 38 such that the pressure in the piston assembly 42 will be reduced and the face of piston 46 balanced or overcome by the balance force of the spring loaded plunger 52. The motion of the sensor assembly 32 is controlled by the adjustable speed gear motor 30 via the linkage 34 such that its transverse motion will continue in a selected or programmed manner resulting in selective movement of the belt 12 to the right. At the end of the stroke of linkage 34, the motion of sensor 32 will be reversed and it will be moved toward its original position at the left. As this occurs, the opening 38 will be moved in the direction tending to expose the aperture 38 resulting in a loss of pressure in the cylinder assembly 42 resulting in the control roll 14 and control roll frame 26 being pivoted in an opposite direction whereby the belt 12 will be oppositely twisted and will move to the left. Note that in this way the belt 12 can be automatically oscillated transversely across the control roll 14 and contact roll 16 in accordance with the speed and type of motion selected for the sensor assembly 32; in the example shown this is determined by the motor 30 and linkage 34.

The apparatus in the embodiments of FIGS. 1 and 2 are shown schematically in FIG. 3. It can be seen that with the apparatus shown a simple means can be used to control the transverse motion of a belt and with this apparatus a relatively narrow belt can be used to grind or finish a wide workpiece obviating the need for wider, more expensive belts.

While it will be apparent that the preferred embodiments of the invention disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the invention.

Claims

What is claimed is:

1. In an endless abrasive belt supported for translational movement on a pair of spaced support rollers, apparatus for causing controlled movement of the belt transversely to its direction of translational movement, said apparatus comprising: sensor means movably supported relative to one edge of said belt for providing a first output signal when the belt and said sensor are in first determinable positions relative to each other; first means drivingly connected to said sensor means for cylically displacing said sensor means in a first direction between first and second spaced, transversely located points; and second means responsive to said output signal for effecting transverse movement of the belt in said first direction whereby the belt will substantially track the movement of said sensor means as it is displaced in said direction between said first and second points.

2. The apparatus of claim 1 with said second means effecting the transverse movement of the belt in the opposite direction in response to a second control signal, said sensor means providing said second control signal with the belt and said sensor means are in second determinable positions relative to each other.

3. The apparatus of claim 2 with said first means including drive means connected to said sensor means for moving said sensor means in said one and opposite directions in a preselected manner between said first and second spaced transversely located points.

4. The apparatus of claim 3 with said sensor means comprising a fluidic sensing member operable from a source of pneumatic pressure.

5. The apparatus of claim 4 with said sensor means including an aperature normally located in confrontation with the belt and with said first and second determinable positions being determined by the position of the aperature relative to the belt.

6. The apparatus of claim 1 with said second means comprising piston means actuable in response to said first signal to pivot one of the support rolls.

7. The apparatus of claim 6 with said second means comprising balancing means for reacting the force of said piston means.

8. The apparatus of claim 6 with said sensor means comprising a fluidic sensor operable from a source of pneumatic pressure and with said piston means actuable from the same source.

9. The apparatus of claim 8 with said sensor means including an aperature normally located in confrontation with the belt and with said first determinable positions being determined by the degree of direct confrontation of the aperature with the belt with said first signal being a pressure having a magnitude varying with the magnitude of said degree of confrontation and with the pressure to said piston means varying in accordance with the magnitude of said first signal.

10. The apparatus of claim 9 with said second means comprising balancing means for reacting the force of said piston means.

11. The method of grinding a workpiece with an endless abrasive belt supported for translational movement on a pair of spaced support rollers, comprising the steps of providing an output signal by means of sensing apparatus movably located relative to one edge of the belt, driving the sensing apparatus between first and second spaced transversely located points, moving the belt transversely relative to the rollers in response to the output signal, whereby the belt will generally track the movement of the sensing apparatus.

12. The method of claim 11 further comprising the steps of utilizing a belt for grinding a workpiece surface which surface is substantially wider than than the width of the belt and moving the sensing apparatus to cause the belt to traverse over the complete width of the workpiece surface.

13. The method of claim 11 further comprising the steps of utilizing a belt for grinding a workpiece surface which surface is substantially narrower than the width of the belt and moving the sensing apparatus to cause substantially the entire width of the belt to traverse over the workpiece surface.

14. In an endless abrasive belt supported for translational movement on a pair of spaced support rollers, apparatus for causing translational movement of the belt transversely to its direction of translational movement, said apparatus comprising: a sensor operable from a source of pneumatic pressure and movably supported relative to one edge of said belt for providing a first output signal when said sensor confronts a surface of the belt and a second signal when said sensor is spaced outside of the surface of the belt, drive means connected to said sensor for continuously displacing said sensor between first and second transversely spaced points; and second means operable from said source of pneumatic pressure and responsive to said first output signal for effecting transverse movement of the belt in a first direction and to said second output signal for effecting transverse movement of the belt in an opposite transverse direction.

15. The apparatus as set forth in claim 14 wherein said drive means includes an adjustable speed drive motor for displacing said sensor in said first and opposite direction.