WO2000044530A1

WO2000044530A1 - Universal sharpening apparatus employing pair of arcuate bearings

Info

Publication number: WO2000044530A1
Application number: PCT/US2000/000833
Authority: WO
Inventors: Eli Peled
Original assignee: Intertool Machines Ltd.; Friedman, Mark, M.
Priority date: 1999-01-29
Filing date: 2000-01-13
Publication date: 2000-08-03
Also published as: AU2610200A

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.

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. 2 A, 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 3 A 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 3 A,

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 coπesponding 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 3 A and 3B, the vertical (z)

and horizontal (x) positions of an arbitrary center of the tool position are given

by:

Z = r. cos _n - d. cos a₀ + _n ) + b and;

X = d. sm ₀ + a_n ) - r. sin _n - 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; ₀ = initial angular position (Figure 3A); a_n = 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 α₀ = 44.56°.

The calculated values are as follows:

Table 1

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

46, 48, 50, 52 independent actuator drive mechanisms 54 user interface

56 direct data interface

60 rotational adjustment mechanism

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 non-rotational 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.