Cutting machine for gear shaping or the like

A cutting machine includes linear electrical actuation for controlling linear reciprocating movement of a spindle and cutting tool. The cutting machine is suited for gear shaping cutting operations and the like. Linear electrical actuation may be used to control position of a hydraulic valve within the spindle, which controls hydraulic actuation and linear movement of the spindle. Linear electrical actuation may also be used to pivot the spindle to relieve the cutting and/or during the cutting stroke for gear crowning operations. A rotary actuator is also disclosed as incorporated into the pivoting saddle of such a cutting machine.

FIELD OF THE INVENTION

The present invention relates generally to automated machine tooling and more particularly to automated cutting machinery in which a reciprocating spindle iS linearly reciprocated to drive a cutting tool relative to a workpiece.

BACKGROUND OF THE INVENTION

Cutting machinery such as gear shaping machines are used to create gear teeth along the outer or inner periphery surface of gear members. As will be readily be appreciated, gears come in a wide variety of shapes and sizes, with different shapes and sizes of teeth being provided along a gear surface. Additionally, some gears will have straight gear teeth and flutes therebetween which are parallel with the rotational axis of the gear while other gears will have helical or slanted gear teeth and flutes therebetween relative to the rotational axis of the gear. Additionally, some gears will be crowned in that one or both sides of the gear will be rounded as the gear teeth and flutes approach one or both side edges of the gear.

A common approach to providing machinery for shaping gears in disclosed in Tlaker et al., U.S. Pat. No. 4,125,056, the entire disclosure of which is hereby incorporated by reference. As disclosed therein, a machine includes a hydraulically operated reciprocating spindle which drives a vertical cutter for shaping a gear. The spindle comprises a piston which is slidable in a cylinder. The spindle piston is a differential piston in that it has two faces of different area to which hydraulic fluid under pressure is controllably directed. The larger area piston face is used to drive the spindle downwardly in the cutting stroke and the smaller area piston face is used to drive the spindle upwardly in the return stroke. Further, the spindle piston has an axial bore which receives a vertically reciprocating valve. The valve is reciprocated in a manner which causes a spindle to move downwardly at a controlled lower velocity and moved upwardly on the return stroke at a much higher velocity to provide a greater overall production efficiency. The way in which the machinery is driven is through mechanical cam and inversely related lever/linkage mechanisms which require complex spring housings, mechanical linkages and adjustment mechanisms.

In a machine such as Tlaker et al., the spindle is carried for linear reciprocation within a saddle that is pivotably connected to a main frame. During the downward cutting stroke, the spindle is kept in a true vertical orientation to facilitate cutting action between the cutter and the workpiece. However, the saddle (in which the spindle linearly reciprocates) is pivotably mounted as such and during the return stroke, the saddle and spindle are pivoted slightly to a slightly offset vertical orientation by virtue of mechanical cam action to relieve the cutter from the cutting surface and thereby allow the spindle and cutter to retract free and clear of the workpiece.

As it relates to the general state-of-the-art, additional reference can be had to U.S. Pat. Nos. 3,628,359; 4,136,302; 4,254,690; 4,533,858; 4,542,638; 4,629,377; 4,784,538; and 5,345,390, the entire disclosures of which are also hereby incorporated by reference in their entireties. Additional reference can be had to U.S. Pat. No. 3,741,659.

Machinery of the type disclosed in Tlaker et al. have been commercially sold under the trademark HYDROSTROKE® and have met with substantial commercial success. With that being said, the relevant art has largely remained relatively stagnant from a mechanical cam timing, control, and hydraulic operation standpoint. As will be readily appreciated once the present invention is understood, there are several deficiencies heretofore that have not been realized in such gear shaping machines which are hereby improved upon with the present invention.

BRIEF SUMMARY OF THE INVENTION

There are several different aspects of the present invention which are believed to be independently patentable.

One aspect of the present invention is directed toward a hydraulic cutting machine for driving a cutting tool in relation to a workpiece in which an electric actuator replaces the mechanical cam and spring linkage mechanisms to act upon the valve and thereby control hydraulic actuation of the spindle. A machine of this type includes a support frame, a work table mounted to the support frame and a saddle supported by the support frame above the work table. A spindle is carried by the saddle for linear reciprocation and has an output end adapted for attachment to the cutting tool. A hydraulic cylinder is integrally connected (e.g. unitarily formed with, attached and/or mounted) to the saddle. The piston is slidably mounted within the hydraulic cylinder for linear reciprocation and divides the hydraulic cylinder into upper and lower chambers. The piston is integrally connected to the spindle and is of the differential type having opposed working surfaces of different working areas. The hydraulic passageway is routed through the saddle extending from an inlet port which connects to a hydraulic pressure source; and an outlet port which connects to a hydraulic sump. The valve is carried in the saddle for linear reciprocation and regulates hydraulic flow along the hydraulic passageway to the upper chamber. The valve has a first state restricting hydraulic flow to the upper chamber (and also draining the upper chamber) to hydraulically drive the piston and spindle in a first direction and a second state facilitating hydraulic flow between the upper and lower chambers to drive the piston and spindle in a second opposite direction.

With regard to this first aspect of the present invention, a further feature may include that the electric actuator is a linear motor comprising a linear motor coil and a linear motor magnet carriage. Yet, further features may include a linear bearing system to guide sliding movement of the electric actuator, braking means for braking the linear motor carriage, and a linear encoder system to provide position feedback to an electronic controller for closed loop control over the linear motor.

Another aspect of the present invention is directed toward a cutting machine for driving a cutting tool which uses a linear electric actuator for relieving or backing off the cutting tool from the workpiece during the return stroke of the spindle and cutting tool (and for tapering or crowning a workpiece). A machine of this type includes a support frame, a work table mounted to the support frame, and a saddle pivotably mounted to the support frame via a pivot connection above the work table. A spindle is carried by the saddle for linear reciprocation and has an output end for attachment to the cutting tool. Actuation means such as a hydraulic actuator, other fluid powered actuator, electrical actuator, or mechanical linkage is provided for reciprocating the spindle linearly upwardly and downwardly. The linear electrical actuator acts between the saddle and the support frame at a location offset from the pivot connection to operatively pivot the saddle in a limited range relative to the support frame to thereby effect the back off or relieving action.

Further features of the invention according to this aspect may include pivotably mounting the saddle to the support frame with a plurality of flexure plates; using a linear motor which comprises a linear motor coil and a linear motor magnet carriage as the linear electric actuator; using a linear encoder system for providing feedback to an electronic controller for closed loop control over the linear motor. Yet a further feature which may be provided with this aspect of the invention is the provision of a back off lever that is pivotably mounted to the support frame and which has one end acting on the electric actuator and another end acting upon the saddle through flexure plates. The lever can be provided with a known ratio to effect a desired amount of pivoting movement per a linear movement of the actuator.

Another aspect of the present invention is the incorporation of an electric rotary actuator integrally with the saddle of a cutting machine for controllably rotating a cutting tool in relation to a workpiece to precise and accurate angular positions during the downward cutting stroke. The cutting machine comprises a support frame, a work table mounted to the support frame, and a saddle carried by the support frame above the work table for movement relative to the support frame. A spindle is carried by the saddle for linear reciprocation and has an output end for attachment to the cutting tool. Actuation means is provided for linearly reciprocating the spindle along a spindle axis to effectuate cutting action. An actuator is also provided which acts upon the saddle to move the saddle relative to the support frame. The electric rotary actuator is integral with the saddle and surrounds the spindle. The actuator includes a stator mounted to the saddle and a rotor rotatably mounted via bearings to the saddle for rotation relative to the saddle. The rotor is rotatably coupled (e.g. with splines) such that the rotor and spindle rotate in unison about the spindle axis while the spindle is also linearly slidable along the spindle axis relative to the rotor.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1–3illustrate in general outline a hydraulic cutting machine10which incorporates the various aspects and/or features of the invention relating to the construction, operation, and control of its vertically reciprocating spindle12. The hydraulic cutting machine as shown is particularly suited for shaping gears. The hydraulic cutting machine includes a support frame14which may include several different portions including a support base, various upright vertical supports, various support bodies/plates, and the like. Support frame14generally provides a structure for supporting various different components of the cutting machine, providing a working area enclosure, and providing orientation and fixation for various different components of the hydraulic cutting machine10.

A workpiece support table16is mounted to the support frame14and provides a support surface upon which a workpiece may be held for cutting operations effected by the spindle12. The workpiece support table16may be rotated and can also be horizontally adjusted relative to the frame in order to provide a means for positioning the workpiece relative to the spindle14. The spindle12is carried for linear reciprocation in a saddle18, which may also be referred to as the spindle support housing. The saddle18is pivotably mounted to the support frame14for pivoting movement about a pivot axis20(shown best inFIG. 2). A gap17between the saddle18and support frame14permits such pivot movement. Although pivot stub shafts may be used to facilitate the pivoting movement, one subsidiary feature of the present invention is the use of flexure plates22,24and26as shown inFIGS. 2,3,11and12which provide for a limited pivoting range of movement of the saddle18relative to the support frame14through bending or flexure of the flexure plates.

To support the saddle18with the frame14each of the flexure plates22,24and26has one end portion which is mounted to the saddle18and a second opposite end portion which is mounted to the support frame14. To provide for the limited pivot joint and pivoting movement, the first two groups of flexure plates22and24are arranged along the pivot axis20with a given orientation that allows for a limited pivoting movement illustrated inFIGS. 10 and 11. One way to accomplish this is to have the first group of flexure plates22extend horizontally forward, and rearward; and to have the second group of flexure plates24extend vertically upward, and downward; with the two groups of flexure plates22and24intersecting the common pivot axis20. For purposes of balance, and as shown inFIG. 2, preferably the flexure plates are provided on opposed lateral sides of the saddle18in order to support the saddle18and the spindle12centrally therebetween. The third group of flexure plates26are provided near the bottom of the saddle18and extend laterally as shown inFIG. 2. This third group of flexure plates26provides support for the saddle18and limits the pivoting movement of the saddle, thereby stabilizing and helping to establish a home position for the saddle18relative to the support frame14.

As shown inFIG. 4, the spindle12extends along a vertical axis28. The spindle12is slidably mounted to the saddle18such that the spindle12can be linearly reciprocated therein, and also rotated relative to the saddle18. At the bottom end of the spindle12, the spindle has a mounting end to which a cutting tool30can be removably mounted. The other top end of the spindle12is disposed near the top end of the saddle18such that the spindle is generally elongated in shape.

The spindle12is generally annular in shape and includes several stepped cylindrical and/or conical regions as is indicated in the drawings. As shown, for example, inFIGS. 6 and 4, a differential piston is integral (e.g. either unitarily formed as shown or alternatively a separate member mounted to the spindle) to provide for hydraulic actuation of the spindle12. The differential piston32includes two piston faces including an upper annular piston face34that is of a larger working area than a lower annular piston face36.

Referring toFIG. 6, the differential piston32is slidably mounted in a hydraulic cylinder38that is integrally connected (e.g. which may be in whole or in part unitarily formed with the saddle or an entirely separate component attached or mounted to the saddle) to the saddle18. The differential piston32is slidably mounted within the hydraulic cylinder38and thereby forms upper and lower piston chambers40,42to which working hydraulic fluid is directed. The upper hydraulic chamber is connected to an outlet port44which is connected to an ambient pressure hydraulic sump or reservoir46while the lower piston chamber42is connected to an inlet port which is connected to a hydraulic pressure source50that is of a higher hydraulic pressure than the sump or reservoir46. The hydraulic pressure source50provides the hydraulic actuation force necessary to drive and linearly reciprocate the spindle12within the saddle18. A hydraulic flow passageway52is defined through the saddle and components contained therein which passes from the inlet port48to each of the upper and lower piston chambers40,42into the outlet port44. It should be noted that the hydraulic flow passageway52while being fluidically connected to each of the inlet port48, the outlet port44and the piston chambers40and42, there is not continuous flow all the way through the hydraulic flow passageway and various portions of the hydraulic flow passageway52can and are in fact, blocked by the valve member54at various valve positions. Thus, it will be understood that the term hydraulic flow passageway52generally relates to areas in which fluid may be permitted to flow, which is dependent upon the position of a valve member. For example, as shown inFIG. 6, hydraulic flow according to two different modes or valve positions are indicated by solid and dashed lines, respectively.

To control fluid flow along the hydraulic flow passageway52, a valve member54is provided. The valve member54is received through a cylindrical stepped bore56formed through the central region of the spindle12. The valve member includes a valve stem58that projects through a top side of the spindle12and a lower flow regulating valve spool60that is contained in a valve cage assembly60. The valve cage assembly60is mounted and trapped in a central or lower region of the bore56of the spindle12. The valve member54is linearly slidable within the spindle12and regulates hydraulic fluid flow along and through the hydraulic flow passageway52in an operative manner in order to alternatively pressurize and depressurize the upper piston chamber40in a manner generally discussed in U.S. Pat. No. 4,125,056 to Tlaker et al. Generally, when the high pressure hydraulic fluid is communicated to the upper and larger piston face34, the generated force will overcome hydraulic pressure exerted on the lower piston face36to drive the spindle downwardly in the cutting stroke. When the high pressure source is restricted and blocked from the upper piston face, and instead vented to the sump/reservoir46, hydraulic pressure acting upon the lower piston face36will drive the spindle12upwardly thereby providing for the return stroke of the cutting tool.

While the hydraulic operation of the spindle12is much like or can be identical to that disclosed in the aforementioned Tlaker et al. patent, an entirely new way of controlling and actuating the valve member54is disclosed in accordance with one aspect of the present invention. In particular, and referring toFIGS. 4–5, an electrical linear actuator in the preferred form of a magnetic drive linear motor64is directly coupled to the valve member54for linearly stroking the valve member54in direct relation. The linear motor64can do so without the need for complex spring housings, cam mechanisms and linkages as has been done in the prior art through mechanical cam motion. The linear motor64is supported by and mounted to the support frame14and extends vertically along an axis that is parallel to the vertical axis of the valve member54. The output of the linear motor64is coupled to the valve member54through a stroke motor link arm66, which is rigidly mounted to the linear motor64. The other end of the link arm64is slidably inserted into a linear translation joint68(or connected via a flexure) which is mounted to a top end of the valve stem58to allow for limited horizontal and pivoting movement therebetween to accommodate the pivoting movement of the saddle18, while not losing the precision and accuracy of the linear stroking movement of the valve member54.

Referring in greater detail to the linear motor64, reference can be had toFIG. 5. As shown inFIG. 5, the linear motor includes a linear motor coil70which is mounted to the support frame14and fixed relative thereto. The linear motor64also includes a linear motor magnet carriage72which is linearly moveable relative to the motor coil70. The motor carriage includes a linear motor magnet plate74and a linear slide plate76. To guide the linear sliding movement of the motor carriage72, a linear bearing system is provided which includes two parallel linear bearing rails78mounted to the slide plate76of the carriage72and linear bearing blocks80that are securely mounted to the support frame14. As shown in the attached drawing, the motor carriage72is moveable between the linear motor coil70and the linear bearing blocks80. Although the linear bearing rails are shown mounted to the carriage and the linear bearing blocks mounted to the frame, the reverse may be done such that the rails would be mounted to the frame and the bearing blocks mounted to the carriage. Similarly, the linear motor magnet carriage could also be mounted stationary to the frame with the linear motor coil being moveable and mounted to the link arm66to drive the valve.

Further associated with the linear motor64is a braking means which comprises a brake that acts between the linear motor coil70and the linear motor magnet plate carriage72. The brake is better shown in greater detail inFIGS. 14 and 15which illustrate an enlarged horizontal cross-sectional view of the linear motor64and its related assembly components. As shown therein, the brake includes brake pads84which are carried on brake calipers86which are moveable relative to one another. The calipers86are movable toward and away from each other to selectively engage and brake against a fin88that extends from the linear slide plate76. Thin flexure mounting plates90are used to mount the brake calipers86to the support frame14and a twin spring pack brake clamping mechanism92and a hydraulic piston brake release94are provided for operating the brake82. The brake82is automatically engaged to brake and stop the motor carriage72relative to the linear motor coil70when there is no electrical power to prevent the linear motor magnet plate carriage72from simply dropping down out of position. As shown inFIG. 14, opposed pairs of brakes82act on opposed sides of the assemblage associated with the linear motor64for balance purposes.

The linear motor64is further associated with a linear encoder system96which comprises a linear scale98and a reader head100. As shown, the reader head100is mounted to the motor carriage72while the linear scale98is mounted to a plate extending from the linear motor coil and/or the frame14. In operation, as the motor carriage72moves, the reader head100will move therewith and read the linear scale98which is fixed relative to the linear motor coil70and support frame14. The reader head100then provides position feedback indicating the precise linear position of the motor carriage72and thereby the valve member54which is coupled to the motor carriage72. Of course, the components of the encoder system96can be reversed such that the linear scale98can alternatively be mounted to the motor carriage72(either directly or indirectly through an additional assembly or through the linear bearing rail) and the reader head can alternately be mounted in a fixed position to the support frame14either directly or indirectly through the linear motor coil housing.

The encoder system96and more specifically the reader head100is in communication with an electronic controller102(e.g. a microprocessor, programmable logic device, computer numerical controller system, or other similar types of controllers) as shown inFIG. 4. The controller102is operative to use the position feedback for closed loop control over the linear motor64. The controller102can thus controllably position the valve member54as desired and thereby control the resulting hydraulic actuation movement and position of the spindle12. The stroking of the valve member54can be done by the controller102according to the same general movement and timing principles outlined in Tlaker et al., U.S. Pat. No. 4,125,056, but instead of doing it through mechanical motion, the motion can be done electronically. An advantage of this is that the adjustment can be done electronically. Also more control over the relative speed stroking length and movement of the valve and thereby the spindle can be accomplished electronically as opposed to mechanical cam action.

Turning towards another aspect of the present invention, the cutting machine10includes a novel actuation system for controllably pivoting the saddle18relative to the support frame14about the pivot axis20. The components of the actuation system and the operation thereof are best shown with reference toFIGS. 8–11. As shown therein, the pivoting system includes a linear electrical actuator in the form of a linear motor104. The linear motor104is in many respects similar to the linear motor64and can include the same motor and braking mechanism discussed above and as shown inFIGS. 14–15. As shown, the linear motor104is mounted to the support frame14by being carried on the back of the stationary motor coil housing for the first linear motor64discussed previously.

The linear motor104includes a linear motor coil106that is mounted to the frame14and a motor carriage108that is linearly slidable relative to the linear motor coil106. The linear motor magnet carriage108includes a linear motor magnet plate110mounted to a linear slide plate112. A linear bearing system is also provided for guiding the linear reciprocation of the linear motor. The bearing system includes linear bearing blocks114mounted to the support frame14and linear bearing rails116mounted to the linear motor carriage108. The blocks114and rails116slidably engage each other to guide linear movement. These may be oriented vertically as shown or can alternatively take a different orientation if desired. Additionally, the linear bearing rails may be mounted stationary to the frame and the linear bearing blocks could be mounted to the motor carriage as an alternative. Similarly, the linear motor coil could also be mounted for movement with the motor magnet carriage being mounted stationary to the support frame.

To provide for closed loop control over the linear motor104, an encoder system118is provided which includes a reader head120and scale122which is positioned in association with the reader head120to be read thereby. The reader head120is either mounted to the stationary component or the moving component and the scale is mounted to the other component. As shown herein, the reader head120is mounted to the linear motor magnet carriage108while the scale122is shown mounted to the linear motor coil106. In operation, movement of the motor carriage108causes the reader head120to move therewith. Such movement and the position of the motor carriage108is therefore read by the reader head120which is operative communication with the encoder scale122. Feedback is provided to the electronic controller102(seeFIG. 4) which provides for closed loop control over the linear motor104.

The linear motor104acts upon the saddle18through a back off lever124. The back off lever124is pivotably connected to the support frame14. To provide for this pivot connection, cooperating flexure plates may be used including vertical flexure plates126having opposed ends mounted to the back off lever124and support frame14, respectively, and horizontal flexure plates128having opposed ends mounted to the back off lever124and the support frame14, respectively. The flexure plates126,128intersect along a common pivot axis130over which the back off lever124can pivot relative to the support frame14. The back off lever124is driven by the linear motor104. As shown, a flexure plate132connects the linear motor magnet carriage108to an end portion of the back off lever124. This flexure plate132accommodates the linear motion facilitated by the linear motor while also allowing for the slight arc created when the back off lever is pivoted about the pivot axis130.

When the linear motor magnet carriage is reciprocated, this movement pivots the back off lever124about the pivot axis130which in turn pushes and pulls the saddle18as shown schematically inFIGS. 9 and 10to pivot the saddle18about its pivot axis20as shown for example inFIGS. 11–12. To provide for the pushing and pulling action through the back off lever124, further flexure plates134are provided which have one end mounted to the back off lever124at a point offset from the pivot axis130and a second portion mounted to the saddle18. These flexure plates134accommodate the slight arc created by virtue of the pivoting action about pivot axis130while maintaining proper spacing between the back off lever124and the saddle18. As shown inFIGS. 8–10, the linear motor104and back off lever124are used to control the relative position of the spindle12and cutting tool30relative to a workpiece136. During the downward cutting stroke as shown inFIG. 11, the spindle12and cutting tool30may be kept truly vertical along the vertical axis28. Also any profile can be generated normal to the gear tooth profile. After the cutting stroke is finished, it is desirable to relieve the cutting tool from the workpiece136as shown inFIG. 12. Accordingly the linear motor104is actuated to slightly pivot the saddle and thereby move the spindle12and cutting tool30away from the workpiece136. This allows the spindle and cutting tool to retract without engaging the workpiece thereby extending cutting tool life.

An additional benefit of the linear motor104is that it can be actuated during the downward cutting stroke to effect crowning of a workpiece. According to this operation, as the cutting tool is being moved and driven downwardly against the workpiece, the linear motor104is controllably driven to round the top of the workpiece or “crown” the gear in the case of a gear shaping machine. The cutting tool is thus driven horizontally inward and/or outward relative to the rotational axis of the gear during the vertically downward cutting stroke. Heretofore, this has not previously been possible with such a gear shaping machine of this type. The electronic controller102thus coordinates the linear motion of the spindle12with the pivoting motion of the saddle18(by controlling linear motors64and104simultaneously) to effect the desired shape or crowning action.

A further aspect of the present invention is the integration of a rotary electrical actuator138into the saddle18that controls and sets the relative angular position of the spindle12relative to the saddle18. This rotary actuator138can also work in coordinated movement with the linear motors104and64(e.g. being simultaneously controlled by controller102) to effectuate a spiral or helical cutting action (e.g. to shape spiral or helical shaped flutes into a gear workpiece126), if desired.

The rotary actuator138includes an integral motor stator140which is mounted internally of the body of the saddle18. An integral motor rotor142is mounted internally of the stator140and surrounds the spindle12. The rotor142is carried for rotation by a guide bushing hub144, which is rotatably mounted to the saddle18through a bearing ring146. The guide bushing hub144also has mounted thereto a spindle guide housing148that is splined through keys to the spindle guide150, which is secured to the spindle12. By virtue of the spline keys152, the spindle12can linearly reciprocate relative to the rotor142and spindle guide150, but is rotatably coupled thereto and thus rotates when the rotary actuator138rotates.

To provide for closed loop control over the rotary actuator138, a rotary encoder system is also provided which includes a rotary encoder ring154to which an encoder scale156is mounted and a reader head158which is mounted to the stator140or saddle18. This encoder system provides feedback to the electronic controller102to indicate the angular position of the integral rotary actuator138and thereby provide for closed loop control such that the rotary actuator can accurately and precisely rotate the spindle12and thereby the cutting tool30during linear movement of the spindle12and the cutting tool30during the cutting stroke.

An alternative embodiment of a cutting machine is depicted inFIG. 16which shows a non-hydraulic gear shaping machine210. This machine similarly includes the integral rotary actuator on the saddle212and the linear motor system214which drives a back off lever to selectively pivot the saddle212. However, the spindle218and cutting tool220are not hydraulically driven, but instead are directly driven through electrical actuation in the form of one or more linear motors222arranged in series and acting upon the spindle218directly. As shown, three linear motors222shown in series (e.g. either stacked or arranged at different angular orientations about the central axis) are preferably inline with the spindle218to directly drive the spindle218. Multiple linear motors are typically needed to provide sufficient force in order to drive the spindle218directly as applied to gear shaping machines. Thus, it will be noted that this is a further additional aspect of the present invention.

It should also be noted that linear motors are not the only type of electrical actuators which may be used and that for micro-machining or where a very short movement may be desired that voice coil motors in place of linear motors may be used. Other appropriate electrical actuators that meet the requirements of a practical machine may also be used.