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(11) | EP 0 426 173 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Rotary diamond dresser |
| (57) A rotary diamond dresser (1) for dressing a grinding wheel, includes a body (1) made
of a sintered alloy, and a multiplicity of single crystal diamond pieces (2) embedded
in the body in a circumferentially equally spaced relationship. These diamond pieces
project radially from the outer peripheral surface of the body. The direction in which
each diamond piece has resistance to wear is parallel to a line extending tangentially
of the outer peripheral surface of the body so as to minimize the amount of wear during
dressing operation. |
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to a rotary diamond dresser for use in shaping and sharpening a grinding wheel.
2. Discussion of the Prior Art
[0002] A single-point diamond dresser has hitherto been used to dress a grinding wheel with super abrasive grains, such as a diamond grinding wheel and a cubic boron nitride (CBN) grinding wheel. The tip of such a single-point dresser is subject to substantial wear. The prior art dresser is thus unable to shape the grinding wheel after a long period of use. Also, a contact area between the dresser and the grinding wheel increases as the tip of the dresser is worn. This results in the rise of dressing resistance and thus, adversely affects not only the efficiency of dressing operation, but also the abrasive action of the grinding wheel.
[0003] In order to provide an improved wear resistance, there was developed a rotary diamond dresser as shown in Fig. 7. The dresser includes a body 11 which has a dressing layer 13 on its outer periphery. A multiplicity of diamond grains 12 are uniformly embedded in the dressing layer 13. In the dresser shown in Fig. 7, however, separation of the diamond grains 12 from the dressing layer 13 is likely to occur during use. This results in the change of the number and distribution of the diamond grains. In addition, the amount and manner of dressing are not constant since crystals of the diamond grains on the dresser are oriented in a different fashion.
[0004] This results in the change of dressing action, and the dressing can not constantly be effected. This adversely affects the abrasive action of the grinding wheel. It is, therefore, difficult for the grinding wheel to grind a workpiece in an accurate manner.
SUMMARY OF THE INVENTION
[0005] Accordingly, it is an object of the present invention to provide a rotary diamond dresser which has a long service life and can dress a grinding wheel in a constant manner.
[0006] In brief, a rotary diamond dresser of the present invention includes a body having an outer peripheral portion in which a multiplicity of diamond pieces are radially embedded in a circumferentially egually spaced relationship. Crystals of the diamond pieces are oriented in such a manner as to maximize its resistance to wear.
[0007] With the rotary diamond dresser thus constructed, the diamond pieces are firmly held by the body and will not be released therefrom. Also, the cross section of each diamond piece remains the same if worn. This enables a grinding wheel as dressed to perform the abrasive action in a constant manner. Crystals of all diamond pieces are oriented in such a manner as to maximize its resistance to wear. This substantially reduces the amount of wear to which the dresser is subject and allows the diamond pieces to be uniformly worn.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0008] Various other objects, features and many attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description of the preferred embodiment when considered in connection with the accompanying drawings, in which:
Fig. 1 is a front view of a rotary diamond dresser according to one embodiment of the present invention;
Fig. 2 is a sectional view taken along the line II-II in Fig. 1;
Fig. 3 is a fragmentary view looking in the direction of the arrow III in Fig. 1;
Fig. 4 is a view showing the manner in which single crystal diamond pieces are made;
Fig. 5 is a view showing the direction in which the diamond piece has resistance to wear;
Fig. 6 is a sectional view showing the manner in which the rotary diamond dresser shown in Fig. 1 is produced; and
Fig. 7 is a sectional view of a conventional rotary diamond dresser.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0009] The present invention will now be described by way of example with reference to the drawings.
[0010] In Figs. 1 and 2, the reference numeral 1 denotes a stepped body in the form of a disk and made of a sintered alloy. The reference numeral 2 denotes a multiplicity of diamond pieces. Each diamond piece 2 has a square section and is 0.2 mm wide and 2.0 mm long. These diamond pieces 2 are embedded in the outer periphery of the body 1 in a circumferentially equally spaced relationship. The tip of each diamond piece 2 projects radially therefrom.
[0011] Crystals of the diamond pieces 2 are oriented circumferentially of the body 1 to increase its resistance to wear. In other words, each diamond piece 2 is positioned about a longitudinal axis such that the direction in which the diamond piece 2 receives a force from a grinding wheel is aligned with the direction in which the diamond piece 2 has resistance to wear.
[0012] In this embodiment, the diamond piece 2 has resistance to wear in a direction at right angles to a lateral side 2a as shown in Fig. 5. To this end, the diamond piece 2 is embedded such that the lateral side 2ais oriented circumferentially of the body 1 as shown in Fig. 3. This arrangement improves its resistance to wear, and the diamond piece 2 may uniformly be worn if any.
[0013] Next, reference will be made to the manner in which the rotary diamond dresser is produced.
(1) One face or direction of a single crystal diamond is worn several hundred times
much more than the other face or direction. To this end, a large single crystal synthetic
diamond D is split in a fixed direction by a cleaving process or by a laser, as shown
in Fig. 4, to provide a plurality of diamond pieces, each being 0.2 mm wide and 2.0
mm long.
The diamond D is split in such a direction as to maximize its resistance to wear.
Such a direction is at right angles to one side of the diamond piece 2 which extends
in parallel to its longitudinal axis 2. Each diamond piece 2 has resistance to wear
in a direction at right angles to one side 2a as shown by the arrow in Fig. 5.
(2) Cu, Sn; Co, and Ag, all in powder form, are mixed under pressure to provide an alloy. This constitutes a disk portion 1a of the body 1.
(3) A multiplicity of diamond pieces 2 are radially arranged on the edge of the disk portion 1a in a circumferentially equally spaced relationship. The lateral side 2a of the diamond piece 2 is oriented circumferentially of the body 1 since the diamond piece 2 has resistance to wear in a direction at right angles thereto.
(4) Cu, Sn, Co and Ag, all in powder form, are mixed under pressure to provide an alloy. This constitutes a step portion 1b. The step portion 1b is placed on the disk portion 1a.
(5) The disk portion 1a, the diamond pieces 2 and the step portion 1b are now integrated and sintered under the influence of heat.
(6) Thereafter, the outer peripheral surface of the body 1 is dressed to remove an outer peripheral portion 1c. As a result, the forvard or outer ends of the diamond pieces 2 uniformly project therefrom. It will be noted that the outer peripheral portion 1c needs not necessarily be removed prior to its use since it is removed when the grinding wheel is dressed.
[0014] The diamond piece 2 is not limited to a square rod and may be in the form of a round rod or column. Also, a plurality of arrays of diamond pieces 2 may be used. In such a case, the steps (3) and (4) are repeated, but disk portions 1a are arranged one above the other, and the step portion 1b is then added thereto.
[0015] With the rotary diamond dresser as stated above, the diamond pieces 2 are deeply embedded in the body 1. This prevents release of the diamond pieces 2 from the body 1. Also, the cross section of the diamond piece 2 remains the same if worn. The crystals of all the diamond pieces 2 are oriented in an identical manner so as to maximize its resistance to wear. This substantially reduces the amount of which the diamond pieces 2 are worn and allows the diamond pieces 2 to be uniformly worn. The rotary diamond dresser of the present invention has a long service life and is able to dress the grinding wheel in a constant manner for a long period of time.
a circular body having a cylindrical outer peripheral surface; and
a multiplicity of diamond pieces embedded in an outer peripheral portion of said body in a circumferentially equally spaced relationship;
said multiplicity of diamond pieces being radially embedded and angularly positioned about a longitudinal axis such that all of said diamond pieces have resistance to wear in the same direction.