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Title:
UNIVERSAL SHARPENING APPARATUS EMPLOYING PAIR OF ARCUATE BEARINGS
Document Type and Number:
WIPO Patent Application WO/2000/044530
Kind Code:
A1
Abstract:
A universal sharpening apparatus for sharpening a tool includes a grinding wheel assembly (14) and a universal clamping system (18) for clamping the tool rigidly in any of a wide range of spatial relations to the grinding wheel. The universal clamping system includes two arcuate bearings (20, 22) each having an effective axis of rotation. The arcuate bearings are mechanically interconnected so as to be deployable with their respective axes of rotation parallel such that opposing rotation of the arcuate bearings generates a non-rotational displacement of the tool relative to the grinding wheel.

Inventors:
Peled, Eli (6 Haalon St. Raanana, 43572, IL)
Application Number:
PCT/US2000/000833
Publication Date:
August 03, 2000
Filing Date:
January 13, 2000
Export Citation:
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Assignee:
INTERTOOL MACHINES LTD. (P.O. Box 91237 Jerusalem, 23811, IL)
Friedman, Mark M. (1 Alharizi St. Raanana, 43406, IL)
Peled, Eli (6 Haalon St. Raanana, 43572, IL)
International Classes:
B24B3/00; B24B41/02; (IPC1-7): B24B49/00
Foreign References:
US2394202A
US4787176A
US4841678A
US4769955A
US4667446A
US4461121A
US4142332A
US3680268A
US3626645A
US2632983A
Attorney, Agent or Firm:
Friedman, Mark M. c/o Castorina (Anthony Suite 207 2001 Jefferson Davis Highway Arlington, VA, 22202, US)
Download PDF:
Claims:
WHAT IS CLAIMED IS:
1. A universal sharpening apparatus for sharpening a tool, the apparatus comprising: (a) a grinding wheel assembly including a grinding wheel driven so as to rotate about an axis of rotation; and (b) a universal clamping system associated with said grinding wheel assembly for clamping the tool rigidly in any of a wide range of spatial relations to said grinding wheel, wherein said universal clamping system includes two arcuate bearings each having an effective axis of rotation, said two arcuate bearings being mechanically interconnected so as to be deployable with their respective axes of rotation parallel such that opposing rotation of said arcuate bearings generates a nonrotational displacement of the tool relative to said grinding wheel.
2. The apparatus of claim 1, wherein said universal clamping system further includes: (a) a tool holder configured for clamping the tool, said tool holder being configured to allow rotation of the tool about a clamping axis; and (b) a rotational adjustment mechanism interposed between at least one of said arcuate bearings and said tool holder, said rotational adjustment mechanism providing an additional axis of rotation, said universal clamping system being configured such that, when said rotational adjustment mechanism is turned to a predefined position, said clamping axis coincides with said effective axis of rotation of one of said arcuate bearings.
3. The apparatus of claim 1, wherein a first of said arcuate bearings has a radius of curvature significantly greater than a radius of curvature of a second of said arcuate bearings.
4. The apparatus of claim 1, further comprising a control system including: (a) a processor for calculating a required rotation for each of said arcuate bearings to achieve a required displacement of the tool relative to said grinding wheel; and (b) an actuator system associated with said processor and in driving relation with each of said arcuate bearings, said actuator system being responsive to said processor to drive each of said arcuate bearings through an angle corresponding to said required rotation for that arcuate bearing.
Description:
UNIVERSAL SHARPENING APPARATUS EMPLOYING PAIR OF ARCUATE BEARINGS FIELD AND BACKGROUND OF THE INVENTION The present invention relates to sharpening devices and, in particular, it concerns clamping and adjustment systems for use in a universal sharpening apparatus.

It is known to provide a universal sharpening apparatus in which a tool clamp holds a wide range of tools in the required spatial relation to a rotating grinding wheel to sharpen and renew cutting tools. In order to accommodate different tools with different forms of cutting edges, the tool clamp must provide multiple degrees of freedom in positioning the tool.

A typical example of such an apparatus is shown schematically in Figure 1. The apparatus shown employs three linear adjustments and four rotational adjustments to provide the range of required clamping positions. Specifically, a primary linear adjustment 100 along a main axis, tilting adjustment 102 about the main axis and a rotational adjustment 104 about a vertical axis are used together to achieve the correct positioning and inclination of the tool. A second linear adjustment 106 and swivel adjustment 108 are provided along and around the length axis of the tool. These latter adjustments are typically used for following the contours of a cutting edge such as a spiral drill bit.

One particular shortcoming of existing universal sharpening apparatuses is that they do not generally provide a vertical adjustment. In order to provide

such an adjustment, the entire main axis would typically need to mounted on a vertically adjustable platform, making the entire structure extremely heavy and expensive.

Reference is made to U. S. Patent No. 5,139,245 to Bruns et al. which is marginally relevant to the present invention to the extent that it employs arcuate bearings. Bruns et al. discloses a jig for clamping workpieces which includes a vacuum clamping head with two arcuate bearings the axes of which are crossed at 90°. Separate mechanisms are provided for displacing each clamping head linearly in elevational, longitudinal and transverse directions.

There is therefore a need for a universal sharpening apparatus which provides a simple, compact and effective mechanism for vertical adjustment of the position of a tool relative to a grinding wheel.

SUMMARY OF THE INVENTION The present invention is a universal sharpening apparatus employing pair of arcuate bearings.

According to the teachings of the present invention there is provided, a universal sharpening apparatus for sharpening a tool, the apparatus comprising: (a) a grinding wheel assembly including a grinding wheel driven so as to rotate about an axis of rotation; and (b) a universal clamping system associated with the grinding wheel assembly for clamping the tool rigidly in any of a wide range of spatial relations to the grinding wheel, wherein the universal clamping

system includes two arcuate bearings each having an effective axis of rotation, the two arcuate bearings being mechanically interconnected so as to be deployable with their respective axes of rotation parallel such that opposing rotation of the arcuate bearings generates a non-rotational displacement of the tool relative to the grinding wheel.

According to a further feature of the present invention, the universal clamping system further includes: (a) a tool holder configured for clamping the tool, the tool holder being configured to allow rotation of the tool about a clamping axis; and (b) a rotational adjustment mechanism interposed between at least one of the arcuate bearings and the tool holder, the rotational adjustment mechanism providing an additional axis of rotation, the universal clamping system being configured such that, when the rotational adjustment mechanism is turned to a predefined position, the clamping axis coincides with the effective axis of rotation of one of the arcuate bearings.

According to a further feature of the present invention, a first of the arcuate bearings has a radius of curvature significantly greater than a radius of curvature of a second of the arcuate bearings.

According to a further feature of the present invention, there is also provided a control system including: (a) a processor for calculating a required rotation for each of the arcuate bearings to achieve a required displacement of the tool relative to the grinding wheel; and (b) an actuator system associated with the processor and in driving relation with each of the arcuate bearings, the

actuator system being responsive to the processor to drive each of the arcuate bearings through an angle corresponding to the required rotation for that arcuate bearing.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: FIG. 1 is a schematic representation of a universal sharpening apparatus according to the prior art; FIGS. 2A, 2B and 2C are schematic isometric views of a universal sharpening apparatus, constructed and operative according to the teachings of the present invention, employing two arcuate bearings to achieve an intermediate position, a raised position and a lowered position, respectively; FIGS. 3A, 3B and 3C are schematic side views of a universal clamping system from the apparatus of Figures 2A, 2B and 2C, respectively; FIG. 3D is a schematic side view similar to Figure 3A but with a tool holder of the system rotated through 90° about a vertical axis; and FIG. 4 is a block diagram of the apparatus of Figures 2A-2C in an automated implementation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a universal sharpening apparatus employing pair of arcuate bearings.

The principles and operation of a universal sharpening apparatus according to the present invention may be better understood with reference to the drawings and the accompanying description.

Referring now to the drawings, Figures 2-4 illustrate a universal sharpening apparatus, generally designated 10, for sharpening a tool. Generally speaking, apparatus 10 includes a grinding wheel assembly 12 including a grinding wheel 14 driven so as to rotate about an axis of rotation 16. Associated with grinding wheel assembly 12 is a universal clamping system 18 for clamping the tool rigidly in any of a wide range of spatial relations to grinding wheel 14 so as to effect grinding of the tool in the required manner.

It is a particular feature of the present invention that universal clamping system 18 includes two arcuate bearings 20 and 22 supporting the tool holder 24. The significance of this structure is most clearly understood with reference to Figures 3A-3C. Arcuate bearings 20 and 22 each have an effective axis of rotation, denoted 26 and 28, respectively. Arcuate bearings 20 and 22 are mechanically interconnected so as to be deployable with their respective axes of rotation parallel such that opposing rotation of arcuate bearings 20 and 22 can be used to generate a non-rotational displacement of the tool relative to the grinding wheel.

In this context, the term"non-rotational"is used to refer to a pure translation in which the orientation or"tilt"of the tool is unchanged. It should be noted that the translation may be achieved in two separate steps during

which the orientation changes. However, for the purposes of the present description and claims, the displacement is still referred to herein as"non- rotational"so long as both the initial position and the final position have the tool in the same orientation. Furthermore, it is important to understand that the present invention is fully capable of achieving combinations of displacement with rotation. However, the invention is characterized by its additional capability of employing two arcuate bearings to achieve a non-rotational displacement when required.

It should also be noted that the use of arcuate bearings provides great advantages of compactness. The fact that rotation occurs around an axis remote from the bearing element allows the axes of rotation to be located close to tool holder 24 without obstructing the work area. In certain cases, tool holder 24 actually moves through the axis of rotation (see Figure 2C), thereby providing a range of motion which would be impossible with other forms of rotational bearings. Additionally, the use of rotational elements to achieve the required vertical displacement adds to the compactness and economy of machine parts.

Preferably, system 18 employs a large radius first arcuate bearing 20 to achieve the primary vertical displacement while the second arcuate bearing 22 has a relatively small radius of curvature, acting as a compensator to correct tilt of the tool holder 24 introduced by movement of bearing 20. Thus, bearing 20 preferably has a radius of between about 10 cm and about 30 cm, and most

preferably between about 15 cm and about 25 cm, while bearing 22 preferably has a radius of between about 5 and about 10 cm.

Specifically, in the example illustrated here, first arcuate bearing 20 may be rotated from its initial position as shown in Figure 3A through an angle of typically up to about 30° or 40° to the position of Figure 3B, thereby raising tool holder 24. If a non-rotational displacement is required, second arcuate bearing 22 is also rotated in the opposite sense through an equal angle, thereby returning the tool holder to its initial orientation. To lower tool holder 24, bearing 20 is rotated in the opposite direction from its initial position by as much as 40° or 50° to the position of Figure 3C with bearing 22 again being used to compensate for the induced tilt.

It will be noted that the displacements between the states of Figures 3A, 3B and 3C include components both vertically and horizontally. If a pure vertical displacement is required, the conventional horizontal adjustment mechanism (s) may be used to compensate for the horizontal component.

Turning now to Figure 3D, it should be noted that the vertical adjustment of the present invention is primarily applicable to configurations in which axes of rotation 26 and 28 are parallel. However, universal clamping system 18 preferably also includes at least one rotational adjustment mechanism 60 which is interposed between arcuate bearings 20 and 22. When adjustment mechanism 60 is turned such that arcuate bearings 20 and 22 are not

aligned, the two bearings may be used independently to provide two different tilt adjustments.

One particularly valuable configuration is illustrated in Figure 3D. In this preferred embodiment, universal clamping system 18 is configured such that, when rotational adjustment mechanism 60 is turned through 90° so that the axes of rotation of arcuate bearings 20 and 22 are orthogonal, a clamping axis of tool holder 24 is coincident with effective axis of rotation 26 of arcuate bearing 20.

As a result of this structure, arcuate bearing 20 provides a second rotational adjustment about the axis of the tool being sharpened. Since the conventional primary axial rotation offered by the structure of tool holder 24 is frequently required for following a helical groove or the like, adjustment of the tool position about its axis by conventional techniques such as for grinding clearance angles is non-trivial, requiring extensive setting-up time. To avoid this problem, the axial position can be adjusted using arcuate bearing 20 in the configuration shown without in any way affecting the vertical or horizontal alignment of the tool.

Turning now to Figure 4, it should be noted that the present invention may be implemented either in a manually adjustable form or as an automated device. One preferred example of an automated implementation is represented in Figure 4.

As before, apparatus 10 includes a grinding wheel assembly 12 and a universal clamping system 18. Clamping system 18 is shown here to include first arcuate bearing 20 and second arcuate bearing 22, as well as a number of other adjustments exemplified here by a first linear adjustment 36 and a rotational adjustment 38. Additionally, apparatus 10 here includes a control system 40 which features a processor 42 for calculating a required rotation for each of arcuate bearings 20 and 22 to achieve a required linear and/or angular displacement of the tool relative to the grinding wheel. Control system 40 also features an actuator system 44 which is deployed in driving relation with each of the arcuate bearings. Actuator system 44 is responsive to processor 42 to drive each of arcuate bearings 20 and 22 through the corresponding required rotation.

Typically, actuator system 44 is implemented as a number of independent actuator drive mechanisms 46,48,50,52 etc. associated with corresponding arcuate bearings or other adjustment features of universal clamping system 18. The mechanisms may be implemented in a range of forms generally known in the art including, but not limited to, electromechanical, hydraulic and pneumatic mechanisms.

Input to processor 42 may be provided in a number of forms. Preferably, a user interface 54 including a user input device such as a keyboard and an output such as a display screen allow a user to set the required parameters of absolute or relative position for the tool holder. Alternatively, or additionally, a

direct data interface 56 may be provided to allow apparatus 10 to operate as part of a larger automated system such as a CNC system.

A range of implementations of processor 42 and interfaces 54 and 56 to perform the operations described above are well within the capabilities of one ordinarily skilled in the art. In particular, the calculation of the required angular displacements for bearings 20 and 22 may be performed using custom hardware or software operating on any conventional computer system according to algorithms based on straightforward geometry, or may be obtained by use of calculated or empirically established look-up tables stored in any suitable data storage medium.

By way of example, with reference to Figures 3A and 3B, the vertical (z) and horizontal (x) positions of an arbitrary center of the tool position are given by: Z= r. cosan-d. cos (aO +an) +b and; X = d. sin (ao + an)-r. sinan-a where: r = radius of curvature of small arcuate bearing 22; d = distance from center of rotation of bearing 20 to a point on bearing 22; ao = initial angular position (Figure 3A); °Gn = angular displacement of bearing 20; and a and b are constants.

An example of a partial table based upon these calculations is shown in Table 1 below. These figures correspond to a universal clamping system for which: R = 188 mm; r = 62 mm; d = 111.15 mm; a = 78 mm; and oc0 = 44.56°.

The calculated values are as follows: Table 1 a,, (deg.) cc, (deg.) x (mm) z (mm) 0 44.56-0.009 0.000 2 46. 56 0. 544 2.732 4 48. 56 1. 001 5.482 8 52. 56 1. 626 11.021 12 56. 56 1. 863 16.590 15 59. 56 1. 785 20.770 20 64. 56 1. 171 27.710 25 69.56-0.047 34.569 30 74. 56-1. 857 41.297 -2 42.56-0.657-2.711 -4 40.56-1.399-5.398 -8 36.56-3.161-10.686 -20 24.56-10.594-25.635 -30 14.56-19.056-36.689

Clearly, additional values can readily be calculated and, given sufficiently close values, intermediate values can readily be estimated by interpolation. Thus, it will be clear that this information could readily be expanded into a sufficient look-up table for operation of processor 42.

Clearly, control system 40 may readily be configured to additionally correct the listed x displacement, thereby providing a pure vertical displacement of tool holder 24.

It will be appreciated that the above descriptions are intended only to serve as examples, and that many other embodiments are possible within the spirit and the scope of the present invention.

LIST OF NOMENCLATURE Prior Art 100 primary linear adjustment 102 tilting adjustment 104 rotational adjustment 106 second linear adjustment 108 swivel adjustment 10 universal sharpening apparatus 12 grinding wheel assembly 14 grinding wheel 16 axis of rotation 18 universal clamping system 20 large radius first arcuate bearing 22 second arcuate bearing 24 tool holder 26 effective axis of rotation 28 effective axis of rotation 36 first linear adjustment 38 rotational adjustment 40 control system 42 processor 44 actuator system independent actuator drive mechanisms 54 user interface 56 direct data interface 60 rotational adjustment mechanism