Carbide cutting tool and method of making such a tool

Abstract

The present invention concerns a rotary cutting tool (1) with a cylindrical supporting spindle (2) and several individual blades (3) with essentially radial cutting edges, helically ground and set at regular intervals on the outer surface of the spindle, each blade (3) having a rectilinear base (4) which inserts into a slot (5) of the same shape as said base, each individual blade (3) being mechanically fixed to the spindle (2), characterized in that it also comprises two covers (8, 9) fixed to the respective bases (8, 9) of the spindle (2) so as to reinforce the fixing of the blades (3).

Claims

1. Rotary cutting tool (1) with a cylindrical supporting spindle (2) and several individual blades (3) with axial cutting edges, helically ground and set at regular intervals around an outer surface of the spindle, each individual blade (3) having a base (4) which inserts into one of a plurality of slots (5) of the same shape as said base, the slots (5) being machined in the spindle (2), each individual blade (3) being mechanically fixed to the spindle (2), two covers (8, 9) fixed to two respective bases (8, 9) of the spindle (2) so as to reinforce the fixing of the individual blades (3), characterized in that the blades are attached to the spindle (2) by means of cone-headed screws (6) and in that the spindle (2) is equipped with transverse slots (7) evenly spaced and receiving the screws (6) therein, and wherein the transverse slots (7) extend circumferentially around the spindle (2) and interconnect the plurality of slots (5), wherein each transverse slot (7) extends in a continuous circular path around an outer circumference of the spindle; wherein the screws (6) extend transversely and non-parallel to a central axis of the spindle and into an outer radial periphery of the spindle, and wherein between the slots (5), the spindle (2) provides a plurality of blade supports (3) extending lengthwise between the two respective bases (8, 9), with each of the transverse slots (7) being aligned with and between the blade supports (3) with end to end pairs of blade supports (3) defining the transverse slots (7).

2. Tool as in claim 1, characterized in that the base (4) is rectangular or a parallelogram and that the slot (5) has respectively a rectangular or parallelogram-shaped cross-section.

3. Tool as in claim 1, characterized in that the mechanical fixing of the blades (3) to the spindle is achieved by screwing, tightening, brazing, shrinking, crimping or sticking.

4. Tool as in claim 1, characterized in that the screws (6) are set at regular intervals along the blades (3), in the transverse slots (7) between the end to end pairs of the blade supports (3), in such a way as to lock the blades (3) into the slots (5), by a head of the screws (6).

5. Tool as in claim 1, characterized in that the blades (3) extend along the entire length of the spindle (2) with a constant and regular cutting profile without any teeth anywhere on the whole length of the blades (3).

6. Tool as in claim 1, characterized in that the slots (5) machined into the spindle (2) are set at an angle (A) of between 0 and 15.

7. Tool as in claim 1, characterized in that the blades (3) are made of cemented carbide based on tungsten carbide, high-speed or high-strength steel, diamond, ceramics or cermet, coated with mono-or multilayered titanium nitride, titanium aluminium nitride, titanium carbonitride or chromium nitride.

8. Tool as in claim 1, characterized in that the spindle (2) is made of stainless steel.

9. Tool as in claim 1, characterized in that at least one of the two covers (9) is split radially and includes a screw hole (10) between any two splits (11) in such a way that there is a maximum of two cutting edges between any two splits (11).

10. Tool as in claim 1, characterized in that the slot (5) has a trapezoidal cross-section, the wide base (5) of the trapeze being closer to the axis of the spindle (2) than the narrow base (5).

11. Tool as in claim 1, wherein each transverse slot (7) comprises individual slot segments, each individual slot segment is open to and connects between a selected two of the slots (5).

12. Tool as in claim 1, wherein the screws (6) are received in the transverse slots (7); and each individual screw (6) provides a tightening force acting upon a selected two of the individual blades (3).

13. Tool as in claim 1, wherein the screws (6) in the transverse slots apply a tightening force to secure the blades (3) in the slots (5).

14. Tool as in claim 1, wherein the slots (5) are defined between the blade supports (3), and wherein the transverse slots (7) are formed into the blade supports (3), each transverse slot (7) comprising individual slot segments, each individual slot segment being open to and connecting between a selected two of the slots (5).

15. Method of making a rotary cutting tool as in claim 1, characterized at least by the following successive stages: blanks of blades with a base (4) are machined; the blanks of the blades with a base (4) are positioned in the corresponding slots (5) machined in the spindle (2); the blanks of the blades are mechanically fixed to the spindle (2), by cone-headed screws (6), as well as the covers (8,9); the blanks of the blades are machined so as to obtain finished blades (3) with helical grinding to provide for the cutting tool.

16. Rotary cutting tool (1) with a cylindrical supporting spindle (2) and several individual blades (3) with axial cutting edges, and set at regular intervals around an outer surface of the spindle, each individual blade (3) having a base (4) which inserts into one of a plurality of slots (5) of the same shape as said base, the slots (5) being machined in the spindle (2), each individual blade (3) being mechanically fixed to the spindle (2), characterized in that the blades are attached to the spindle (2) by screws (6), and wherein each screw (6) provides a tightening force acting upon a selected two of the individual blades (3) for securing the blades to the spindle (2), wherein the spindle is equipped with transverse slots (7) evenly spaced for the positioning of the screws (6), and wherein the transverse slots (7) extend circumferentially around the spindle (2) and interconnect the plurality of slots (5), and wherein each transverse slot (7) comprises individual slot segments, each individual slot segment is open to and connects between a selected two of the slots (5), and wherein the screws (6) extend transversely and non-parallel to a central axis of the spindle and into an outer radial periphery of the spindle, the screws being positioned in the transverse slots (7), and wherein between the slots (5), the spindle (2) provides a plurality of blade supports (3) extending lengthwise between the two respective bases (8, 9), with each of the transverse slots (7) being aligned with and between the blade supports (3) with end to end pairs of blade supports (3) defining the transverse slots (7).

17. Tool as in claim 16, wherein each transverse slot (7) extends in a continuous circular path around an outer circumference of the spindle.

18. Tool as in claim 16, characterized in that the tool (1) also comprises two covers (8, 9) fixed to two respective bases (8, 9) of the spindle (2) so as to reinforce the fixing of the individual blades (3).

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows an exploded perspective view of the cutting tool according to a preferred embodiment of the present invention.

(2) FIGS. 2A and 2B show respectively an elevation view and a cross-section view of the supporting spindle of the cutting tool as in FIG. 1.

(3) FIGS. 3A and 3B show respective views of the bases of the above-mentioned spindle.

(4) FIGS. 4A and 4B show respectively a cross-section view and a plan view of the cover corresponding to the base in FIG. 3A.

(5) FIGS. 5A and 5B show respectively a cross-section view and a plan view of the cover corresponding to the base in FIG. 3B.

(6) FIG. 6 shows a cross-sectional view of one embodiment of the cutting tool according to one aspect of the present application.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

(7) As shown in FIG. 1, the cutting tool 1 according to a first preferred embodiment of the invention comprises a cylindrical spindle 2 supporting blades, made for example of ordinary steel or stainless steel. The blades 3, on the other hand, are made of a material with great resistance to wear such as, for example, tungsten carbide (WC), ceramics, high-speed steel etc., possibly coated with titanium nitride (TiN), titanium carbonitride (TiCN), titanium aluminium nitride (TiAlN), chromium nitride (CrN) etc.

(8) The rough blades or blade blanks (not shown) are essentially in the form of rectangular parallelipeds or bars with rectilinear bases that are roughly ground and fixed on the side surface of the cylindrical spindle 2 in slots 5 by mechanical means, for example by locking by means of cone-headed screws 6. The blades 3 are orientated parallel to each other at an angle of about 10 degrees relative to the axis of the cylinder 2. This angle will allow the grinding blades with a helical finish to have a spiral angle greater than the blades positioned axially.

(9) The spindle 2 is equipped with several rectilinear, flat-bottomed slots 5, allowing the blanks of the blades 3 to be fixed, said blades having bases 4 of a corresponding shape, that is, rectangular or in the shape of a parallelogram (FIGS. 1, 2A and 2B). Once these are fixed to the spindle, it is then easy to do the final grinding of the blades in accordance with the required tolerances.

(10) Between the slots, the spindle 2 therefore shows blade supports 3 that themselves show several, for example three, transverse slots 7 evenly spaced and allowing the insertion of the above-mentioned cone-headed screws 6.

(11) The invention is not restricted to the fixing of the blanks of the blades by screws but rather any mechanical means such as crimping, tightening, hot shrinking, clamping, brazing, sticking etc. may be considered within the limits of the invention.

(12) As an advantage, the blanks of the blades 3 and the spindle 2 may be sized in such a way that a blade with two cutting edges (not shown) may be inserted across the width of the rectilinear slots 5 machined in the spindle.

(13) According to a preferred embodiment of the invention, the fixing of the blades 3 is reinforced by the additional fixing of two covers 8, 9 with inverted tapers relative to the bases 8, 9 of the spindle 2.

(14) The blades 3 therefore have at least one cone-headed end 4 which fits, when the whole is fixed, into an inverted taper machined into the corresponding cover 8.

(15) In order to cover the entire length of the blades, at least one of the two covers (cover 9, FIGS. 1 and 5B) is split radially and shows a screw hole 10 between any two splits 11 in such a way that there is a maximum of two blades between two splits, given what is explained here. These arrangements allow to counteract the exit of the rotating knife under the action of the centrifugal force.

(16) According to a second preferred embodiment of the invention shown in FIG. 6, the slots 5 are of trapezoidal cross-section, the wide base of the trapeze 5 being closer to the axis of the spindle 2 than the narrow base 5. Thus, the secure fixation of the blades 3 is further reinforced, said blades having a tendency to be ejected when the spindle is moving as a result of the centrifugal force. As an advantage, the spindle 2 is then designed to take movable locking parts 3 presented in the form of bars of the same lengths as the blades 3 that can be set axially along the blades 3 and form slots 5 when they are in position. Shoulders are cut into the spindle and the blades 3 are placed against said shoulders. The locking parts 3 of the blades also have spaces for inserting fixing screws 6 on the spindle 2. These fixing screws may be of any type well known to the person skilled in the art.

(17) In applications where the angular pitch between the blades may be sufficiently wide, a locking part 3 may be provided for fixing two adjacent blades 3, as shown in FIG. 6.

(18) The invention shows the following advantages.

(19) The use of carbide allows the working life of the blades to be greatly increased and therefore reduces the production downtimes.

(20) The blades are interchangeable and movable. Because of the individual fixing of each blade to the blade support, any defective blade may be separately replaced, which considerably reduces the cost of repair compared with a monobloc device. Moreover, each tool may be supplied with two sets of blades.

(21) The cost of machining a spindle and separate bars is less than that of a monobloc piece.

(22) The fact that the blades are movable is taken into account with regard to the effect of the centrifugal force by appropriate measures (reinforcement covers, trapezoidal slots narrowing towards the outside of the spindle).