Tool sharpener with web thickness determination capability

Method and apparatus for sharpening a tool, such as a drill bit. A tool sharpener includes a tool holder subassembly which retains and presents the tool against a grinding wheel subassembly. A sensor locates a cutting edge of the tool while the tool is retained by the tool holder. A circuit, preferably comprising a programmable processor, determines a web thickness of the tool from the located cutting edge. The cutting edge is preferably located by detecting at least first and second points at different radii along the cutting edge. A cross-feed subassembly preferably moves the sensor into position, and the tool holder subassembly preferably rotates the tool to facilitate detection of each of the at least first and second points. The tool holder subassembly thereafter presents the tool against the grinding wheel subassembly in response to the determined web thickness of the tool.

FIELD OF THE INVENTION

The present invention is directed to a tool sharpener, and, more particularly to an automated tool sharpener especially for use in sharpening drills.

BACKGROUND

Tool sharpeners for sharpening the tips of drills and the cutting faces of other cutting tools have heretofore been developed in the art. Such tool sharpeners extend the operating life of drills and other cutting tools, in that a tool having dull cutting surfaces will not perform with the desired precision or speed, and, if not sharpened, must be discarded even though the tool has a considerable amount of usable material left to work with.

Particularly in industrial applications, the drills or other cutting tools are expensive items, and where change out and resharpening is not part of the normal equipment operating procedure, there is a tendency to try to prolong the useful life of the drill by using it after it has dulled and is not performing optimally. This adversely affects the quality of the products being produced. Accordingly, commercial grade or industrial grade tool sharpeners have been developed in order to prolong the useful life of drills and other cutting tools, and in order to permit the equipment to be operated substantially continuously with a drill or cutting tool of proper sharpness.

A recent example of a commercial-grade tool sharpener is disclosed in U.S. Pat. No. 5,400,546, which is assigned to the assignee of the present application. The disclosure of that patent is hereby expressly incorporated by reference herein. That tool sharpener has enjoyed considerable commercial success, and is capable of providing highly precise sharpening of a drill. The sharpener does, however, require that several operations be carried out manually, or involve manual manipulations, including aligning the drill properly in the chuck (aided by an alignment device on the sharpener), tightening the drill in the chuck, and then manually manipulating the chuck and drill in one or more sharpening or dressing ports.

Use of this sharpener is somewhat labor intensive, and despite the fact that the design of the sharpener greatly reduces the potential for operator error, and limits the degree of possible error which can result in an improperly sharpened drill, that possibility continues to exist.

Modern cutting tools are high performance, complex and expensive devices that can not readily be sharpened manually without a great deal of effort and skill.

Accordingly, a need has been identified by the present inventors to provide a tool sharpener that automates most, if not all, of the operations necessary to properly sharpen a drill or other cutting tool. The automation of the majority of the operations results in the sharpening operation being less labor-intensive and less prone to sharpening errors committed by the person operating the sharpener. This will also permit a less-skilled laborer to be entrusted with the tool sharpening function, resulting in potentially reduced labor costs.

SUMMARY OF THE INVENTION

In accordance with preferred embodiments, a method and apparatus are provided for sharpening a tool, such as a drill bit.

A tool sharpener includes a tool holder subassembly which retains and presents the tool against a grinding wheel subassembly. A sensor locates a cutting edge of the tool while the tool is retained by the tool holder. A circuit, preferably comprising a programmable processor, determines a web thickness of the tool from the located cutting edge.

The cutting edge is preferably located by detecting at least first and second points at different radii along the cutting edge. A cross-feed subassembly preferably moves the sensor into position, and the tool holder subassembly preferably rotates the tool to facilitate detection of each of the at least first and second points.

The tool holder subassembly thereafter preferably presents the tool against the grinding wheel subassembly in response to the determined web thickness of the tool.

These and various other features and advantages which characterize the claimed invention will become apparent upon reading the following detailed description and upon reviewing the associated drawings.

DETAILED DESCRIPTION

FIG. 1illustrates the tool sharpener according to a preferred embodiment in an exploded or breakaway view. The casing or housing100comprises a main base102and an electronics housing104which connects to the main base to complete the overall base.

A three-piece cover106is provided in this embodiment. A side cover element108and rear cover element110are secured in fixed position overlying main base102and electronics housing104. The third cover element is a guard door112which is pivotably mounted to rear cover element110. Guard door112has a semi-circular peripheral wall114, as does rear cover element110. The guard door112is sized such that it can pivot between an open position in which it substantially overlies the rear cover element110, leaving grinding chamber10exposed to the external environment, and a closed position in which the grinding chamber10is substantially closed off or sealed off from the external environment.

The guard door112is preferably provided with a window113on an upper surface thereof, which permits an operator to view the sharpening operation with the guard door closed.

The cover106is preferably provided with an operator interface. As shown, side cover element108is provided with a touch screen118and one or more operator input buttons120at the front portion of the cover. Details regarding the function and operation of the operator interface will be discussed later in this specification. The side cover element108may preferably also be provided with an elongated (rectangular) recess122having a rubber or polymeric mat124disposed on a floor thereof, which may be used to hold tools or drills awaiting sharpening and/or tools or drills that have been sharpened. The recess is also preferably sized such that the recess can be used to determine whether a particular drill is too long to be sharpened in the unit. This may be accomplished by forming the recess such that it can receive therein drills or tools up to the maximum length that can be accommodated in the grind chamber.

A further external feature of the device is the provision, in main base102, of a grinding wheel storage recess126. This recess is preferably sized to retain a plurality of spare grinding wheels, and/or grinding wheels having different grinding characteristics, in a series of slots128provided in the recess. The slots128are adapted to retain the additional grinding wheels in an upright, spaced-apart relation.

Turning to the internal operating components of the tool sharpener,FIGS. 1 and 2illustrate that the sharpener preferably employs an infeed stage subassembly200, a cross-feed stage subassembly300, a swing subassembly400, a grinding wheel subassembly500, a chuck subassembly600, and an electronics subassembly700.

The infeed stage subassembly200is operably connected to the chuck subassembly600, and is adapted to move the chuck in an “axial” direction (along an axis parallel to the axis on which the grinding wheel rotates) toward or away from the grinding wheel subassembly500. The cross-feed stage subassembly300is operably connected to the grinding wheel subassembly500, and is adapted to move the grinding wheel subassembly in a “transverse” direction (normal to the axis on which the grinding wheel rotates), in order to position the grinding wheel502and/or honing brush510relative to the tool being sharpened.

Both the infeed stage subassembly and the cross-feed stage subassembly operate using step motors and lead screws to drive guide covers along guide rails. Looking first at the infeed stage subassembly200(seeFIGS. 1,2and3) a motor-end plate202and a switch-end plate204are mounted in main base102, with a guide rail206extending therebetween. The guide rail may preferably be mounted to rail supports208,210disposed at the two end plates. A step motor212is mounted at one end of the subassembly, and is operatively coupled to a lead screw214extending within the subassembly200from motor end-plate to a distance sufficient to give guide cover216the necessary range of motion along the axial direction.

An infeed stage sensor218(FIG. 3) is mounted by sensor mount220to the switch-end plate204. The function of this sensor will be discussed later in the specification.

Referring now especially toFIG. 3, it can be seen that the moving components of the infeed stage subassembly200are preferably to be fully enclosed. It was determined, in designing the infeed stage subassembly200, and cross-feed stage subassembly300, which are more generically referred to as “linear stages”, that known schemes for protecting bearing components, including the guide rail, would not provide adequate protection in this environment. The infeed stage subassembly is thus provided with two bellows elements222,224, which are secured between the motor-end plate202and a facing end of guide cover216, and between the switch end plate204and the end of the guide cover216facing that plate. The assembly of the two end plates202,204, the two bellows elements222,224and the guide cover216completely surrounds and isolates the guide rail206and virtually eliminates the intrusion of grinding debris into this area. The bellows elements222,224, may be constructed in a known manner, with rigid or semi-rigid mounting plates226at the two ends, and a flexible or pliant material forming the bellows.

The cross-feed stage subassembly300is constructed in much the same way as is infeed stage subassembly200. A main difference is that the infeed stage subassembly is mounted to main base102such that the lead screw moves guide cover216in an axial direction, whereas the cross-feed stage subassembly300is oriented at a right angle to the infeed stage, so that the guide cover316is moved in the transverse direction. The other main difference is that these two subassemblies are operatively coupled to different subassemblies or components disposed within grinding chamber10.

The cross-feed stage subassembly has a motor end plate302, a switch-end plate304, a guide rail306, rail supports (one shown at308), a step motor312, a lead screw314operatively coupled thereto, and a guide cover316. The cross-feed stage subassembly300will also preferably have a fully enclosed guide rail, employing bellows as does the infeed stage subassembly. These are not shown inFIGS. 1 and 2, however, in order that the internal components may be seen.

Turning back to the infeed stage subassembly, it can be seen that infeed guide cover216is operatively coupled to lead nut228(FIG. 3), and thus guide cover216moves along lead screw214as step motor212turns the lead screw214. As can best be seen inFIG. 2, guide cover216has a swing step motor404mounted to an upper surface thereof. Swing step motor404is operatively coupled, through an opening between wall130of main base102and side cover108, to a housing406of swing subassembly400. The swing step motor404and swing subassembly400(which houses chuck subassembly600as well) are thus moved in the axial direction by infeed stage subassembly200.

Swing step motor404operates to swing or tilt the swing subassembly400, to tilt the tool to be sharpened in a substantially vertical plane normal to an axis of rotation of the shaft of step motor404. This allows the tool or drill being sharpened to be presented at a range of angular orientations relative to the grinding wheel502. Swing step motor404is operatively connected to and is controlled by central processor20, as are all of the step motors employed in the sharpening device.

FIGS. 2 and 4are used to illustrate the swing subassembly400in greater detail. The housing406of swing subassembly houses chuck subassembly600and a belt drive system408for rotating the chuck, and the drill or other tool held therein, about the longitudinal axis of the drill or other tool.

Swing subassembly housing406has a mounting flange410extending forwardly therefrom, which is used to mount housing406to step motor404. Positioned above mounting flange410is a tool rotation step motor412having a shaft414protruding through opening416in housing406. The step motor shaft414is operatively connected to drive gear418, and a drive belt420loops around drive gear418and a chuck drive gear604disposed on chuck subassembly600, and passes over idler roll424. In this manner, tool rotation step motor412, under the control of central processor20, can rotate the chuck600, and thus the tool retained therein, about the longitudinal axis of the tool, in order to present different parts of the tool point surface to the grinding wheel during sharpening. The tool rotation step motor is also used at the beginning of the sharpening cycle to properly orient the drill to the proper grind position.

The swing subassembly400also contains a solenoid422which is operable to lock the chuck to prevent the chuck from rotating during the time that the operator is installing and removing the drill. The solenoid422is automatically actuated to lock the chuck when the guard door112is open, and when no sharpening cycles are active. This makes the loading and unloading of the drill or other tool by the operator a very simple exercise, in which the drill is inserted into the central opening608of chuck600, and chuck knob610is turned to tighten the chuck jaws612against the drill (see alsoFIG. 6).

The grinding wheel subassembly500is operatively coupled to and carried by the cross-feed stage subassembly300. In particular, a grind motor504is mounted to the guide cover316, and a drive shaft506and drive pulley508(FIG. 5) extend through a wall132in main base102, and into the grind chamber10. The drive pulley is operatively coupled to grinding wheel502and honing brush510, such that the drive pulley will rotate these elements. Honing brush510may be secured to grinding wheel502in a preferred embodiment, and thus would be operatively coupled to the drive pulley via the grinding wheel.

Grinding wheel502and honing brush510are preferably enclosed within a grind housing512comprising a rear housing member514and a front cover516which, when joined to rear housing member514, encloses all but a small portion of the grinding wheel and honing brush. The front cover516is designed to be easily removable from rear housing member514, in order that the grinding wheel and/or the honing brush may be replaced as necessary or as desired.

Grind housing512is preferably shaped to provide a lower chamber518adjacent the area in which grinding wheel502and honing brush510are located. Front cover516has an opening and an annular protrusion520adjacent this chamber518, in order to permit a vacuum hose522(FIGS. 11,12) to be fastened thereto. Main base102has an opening134leading to an exterior of the unit, to allow the vacuum hose522to connect at one end to protrusion520, and to extend out of the unit to a quiet, low speed vacuum system524. The vacuum system pulls the debris generated in the sharpening operation and falling into chamber518out of the sharpener. The vacuum system524preferably includes a filtration system526which protects the operating parts of the vacuum system from the potentially damaging grit and debris, and further protects the machine operator from any health risks associated with this debris.

Front cover516has a slot530extending laterally from a point near the center of the grinding wheel502out past the outer peripheral edge of the grinding wheel. This slot530thus exposes a portion of the grinding wheel502and honing brush510, to permit those elements to engage a tool to be sharpened and honed, as desired. Slot530must be of sufficient width to accommodate the larger drill and tool diameters, and to provide adequate clearance for the grinding wheel, taking into account the range of angles that the drill points will be sharpened to and the position of the drills when presented to obtain such angles. The slot530is preferably not oversized to any extent, in that this would result in more of the debris from the sharpening operation possibly escaping into the grind chamber10.

Grind motor504is provided with a cooling shroud560, through which cooling air is passed, in order to lower the operating temperature of the motor. This will have the effect of maximizing motor performance and increasing brush life. In the present design, it was found to be advantageous to employ a small amount of bleed air from the vacuum system, introduced into the shroud at a vacuum nipple562, which passes between the shroud560and the motor casing (inside of shroud560) and is exhausted. The drawing of this air over the motor casing was demonstrated to be an effective way of maintaining the motor temperature under a specified maximum temperature.

Another feature of the grind motor560is that the current drawn by the motor, which may preferably be a DC motor operating on 115/230 VAC supply and having a nominal current consumption of 1.5 A, is monitored in order to determine and control the force being exerted on the grind wheel while a drill or other tool is being sharpened. The rate of change and magnitude of the grind motor current consumption is then used to modulate (e.g., slow down and possibly stop) the motion of the infeed stage subassembly, the swing subassembly, the tool rotation subassembly, and the cross feed stage subassembly simultaneously. This will operate to prevent excessive grinding pressure being exerted, which leads to degradation of the grinding wheel surface, as well as to overheating and burning of the tool. The control of this coordinated motion will be dependent on both the diameter of the tool and the material from which the tool is made.

A compact chuck subassembly600is illustrated inFIG. 6. Once assembled, this chuck subassembly is fitted onto swing assembly400, as is best seen inFIGS. 2 and 4. Chuck subassembly600comprises a chuck knob610and a chuck spindle614which retain therein a plurality (preferably six) chuck jaws612and their respective jaw springs616. The chuck jaws are maintained in their radial orientation by slots618provided on an internal tapered surface of chuck spindle614, as well as by radial slots620provided on backing screw or closing screw622. A jaw spring retainer624is also provided at the rearward end of the jaw springs616.

An annular drive gear604is mounted to the exterior of the chuck spindle614, so that the chuck subassembly can be rotated during the sharpening process. A bearing structure628is also mounted to the chuck subassembly600to facilitate rotation thereof once mounted in swing subassembly housing406.

A diameter detect rod630is attached to backing or closing screw622, which will, once chuck subassembly600is fully assembled, protrude through the chuck spindle614. Since backing screw622is moved forward as the chuck knob is turned to tighten the chuck jaws onto the drill which has been placed in the chuck, the distance to which diameter detect rod630protrudes from the chuck subassembly will have a direct relation to the diameter of the drill retained therein. This feature is advantageously used to detect the diameter of the drill to be sharpened without the need for very sophisticated and expensive sensors.

Mounted to the exterior of grind housing512is an alignment subassembly550, which includes an alignment plunger assembly552, a fiber optic sensor554, and a material take off sensor556. The alignment subassembly is used by the tool sharpener, in conjunction with the central processor20, to automatically determine certain pertinent parameters or details of the drill or other tool to be sharpened. Alignment plunger assembly552is used to aid in sensing the length of the portion of diameter detect rod630protruding from chuck subassembly600. This is accomplished by advancing the swing subassembly housing406toward alignment plunger552, with the alignment plunger552positioned to engage the tip of the advancing diameter detect rod. Once contact is made, the plunger is pushed into plunger housing553, and trips or triggers a switch551in the alignment plunger assembly552, and a signal is sent to the infeed stage subassembly to cease advancing the swing subassembly. The length of the protruding portion of rod630is determined by the position at which the swing subassembly housing is stopped. Central processor20is programmed to be able to correlate this stopped position to a length of the protruding portion of rod630, and also to correlate this length to a diameter of the drill or other tool retained in the chuck. The thus-determined drill diameter information is later used by the central processor in controlling the various aspects and stages of the sharpening process.

The length of the portion of the drill01protruding through chuck subassembly600is also automatically determined through the use of alignment plunger552. In this case, the alignment plunger552and the drill01are brought into axial alignment by shifting the alignment plunger transversely, and the drill01is advanced into contact with the front surface of plunger552, triggering the switch551in the pin, and halting the advance of the swing assembly. Again, the position of the swing subassembly housing on the infeed stage assembly is used by central processor20to determine the length of the portion of the drill extending forwardly or sticking out of chuck subassembly600. This information is used by central processor20in controlling the amount of infeed to use during the sharpening process, which controls how much material is to be ground off in the sharpening process.

The fiber optic sensor554is employed to characterize (or crudely map or image) the cutting edge of the drill to be sharpened. The fiber optic sensor554is preferably constructed and installed on the subassembly to have a focal point on the order of several millimeters, for example seven millimeters, in front of the lens555of the sensor. The cross-feed subassembly300is used to move the sensor into axial alignment with the drill, and the infeed subassembly is used to move the cutting edge of the drill into the focal region of the fiber optic sensor554. These steps, as are nearly all others, are preferably performed automatically, under the control of central processor, which has these pre-sharpening data gathering routines programmed or embedded therein.

The fiber optic sensor554is used to detect multiple points along the cutting edge of the drill01as the drill is rotated into different positions. Processor20is provided with an embedded algorithm or program that is capable of determining the web thickness of the drill using the data obtained by the fiber optic sensor. In addition, this data enables processor20to determine the orientation of the drill being held by the chuck. The processor20is then able to send a command to the tool rotation step motor412to rotate the drill as necessary to properly orient the drill for the ensuing sharpening operation. The processor20uses the calculated web thickness in controlling the position of the drill during the sharpening operation.

As a further pre-sharpening data gathering step, material take-off (MTO) sensor556is used to determine when the drill will first contact the grinding wheel, so that the processor20, infeed stage subassembly200, and grind motor subassembly500, will have advance notice as to when the contact and grinding will actually begin as the drill is advanced toward the grinding wheel. In this step, cross-feed stage subassembly300moves laterally to axially align the MTO sensor556with the drill01. Processor20controls swing subassembly to position the drill at the appropriate orientation to sharpen the drill to the angle selected by the operator. The infeed stage subassembly advances the drill into contact with MTO sensor556, which has a switch557that operates to cause cessation of the advance of drill01. Processor20is thus able to determine from the stopped position of the swing subassembly when contact will first be made between the thus-positioned drill and the grinding wheel.

This feature is especially useful when a drill is to be sharpened to a different point angle than it originally had. When this information is known, the processor20can slow the infeed rate just prior to the anticipated contact, so that the drill is not advanced at an excessive speed, and the processor can begin monitoring the current reading of the grind motor, so as to further control the infeed rate to prevent excessive pressure being exerted on the grind wheel. This further prevents overheating and burning of the cutting edge of the drill. The use of the disclosed MTO sensor556is an inexpensive way to obtain this initial process control.

The limit switches used in the various subassemblies merit special discussion. Limit switches are provided in each of the infeed stage and cross-feed stage subassemblies, the switches being mounted in sensor housings or mounts220,802, for the infeed and cross-feed stages, respectively, as well as in the swing subassembly (not shown), and in the chuck or tool rotation subassembly, where the switch is designated at806(FIG. 4). These switches are preferably inexpensive optoelectronic sensors, however, with the control logic employed, these inexpensive sensors will allow fast and highly accurate operation.

The fast, accurate operation is obtained by using two sensing stages. First, a digital logic level is used, whereby motion into the limit switch may be fast, and is digitally detected, albeit not with high accuracy. Once a preset digital trip point is hit, the speed is reduced and the sensing changes to an analog sensing. Motion of the slowed element is then stopped at a preset analog voltage, which is highly accurate and precise.

FIGS. 14Aand B illustrate an example of the operator interface900presented at console118.FIG. 14Ais the main setup screen, andFIG. 14Brepresents a subsequent screen that is presented to the operator after the operator has initially selected the “quick start” feature at the main setup screen, which is expected to be used in most instances in sharpening drills. The other choices presented on the main startup screen are provided for advanced users to customize the sharpening operation to their specific and unique needs.

FIG. 14Ashows a point angle selection button/icon902, a material removal icon904, a drill diameter size icon906, a web thickness selector icon908, a hone selection icon910, a point type grind selector icon912, a split point selector icon914, a relief angle selector916(for lip relief), a drill material selector icon918, a memory open icon (for settings stored in memory)920, the “quick start” icon922, and a maintenance icon924.

As noted previously, the central processor is programmed with defaults and automated routines to handle most of these functions and selections automatically. For example, the material removal in the sharpening process has a default value (used in the “quick start” routine, and if not otherwise overridden in manual mode) that will minimize the amount of material removed in the sharpening process, for example, in the range of about 0.005 to 0.008 inches. This will prolong the life of the drill, by permitting more resharpenings. However, if the cutting edge of the drill is damaged, as by a nick or gouge, then additional drill material would need to be removed in order to present a uniform new cutting edge. In such instances, the material removal icon would be pressed, in order to provide the operator with additional choices as to the amount of material that is to be removed during the sharpening operation.

In continuing with the example of the primary mode of operation, the operator would insert a drill to be sharpened into the chuck, and the operator would tighten the chuck and close the guard door112. The operator would then touch the “quick start” icon922, and would be presented with the interface or screen illustrated inFIG. 14B. At this screen, the operator would select one of four standard point styles or types (conic or facet: no split or X-split), and one of the two point angles (defaults to1180, toggles to135upon touching). The operator would then press a “cycle start” button (one of those shown at120), and the tool sharpener will automatically sharpen the drill. Without any overrides being made, the automated sharpening process will include the following steps (which have previously been described in discussing the components that perform the steps):

determining the diameter of the drill to be sharpened;

determining the length of the portion of the drill protruding from the chuck;

determining the web thickness of the drill;

properly orienting the cutting edge of the drill for the sharpening procedure;

determining the point of infeed at which contact will be initiated between the drill and the grinding wheel;

controlling the infeed stage subassembly, the swing subassembly, the tool rotation subassembly, and the crossfeed stage subassembly as necessary to grind the cutting edge of the drill to remove material therefrom in sharpening the drill;

monitoring the current drawn by the grind motor in order to control the amount of pressure being exerted on the grinding wheel; and

when a honing step is to be performed, moving the grinding wheel assembly laterally to present the honing brush to the newly sharpened drill cutting edge.

The central processor20in this tool sharpener is also capable of storing a number of custom sharpening routines programmed by the operator by using the various options presented at the main setup screen on console118.

The sharpener is preferably provided with both cubic boron nitride (CBN) and diamond coated or plated wheels, which are standard in the field. The wheel coatings, typically known as a superabrasives, permit the sharpening of high strength steel (HSS), cobalt and carbide cutting tools.

Additional features and functions provided by the tool sharpener described and shown herein will be readily apparent to those having ordinary skill in the art upon reading this disclosure. The foregoing discussion of the preferred embodiments of the invention is for illustrative purposes only, and is not intended to limit the scope of the invention.