EP0152125A2

EP0152125A2 - Rotary tool with cutting inserts

Info

Publication number: EP0152125A2
Application number: EP85200029A
Authority: EP
Inventors: Licio Muzzolini
Original assignee: STARK SpA
Current assignee: STARK SpA
Priority date: 1984-02-08
Filing date: 1985-01-15
Publication date: 1985-08-21
Also published as: PT79935A; EP0152125A3; IT8483317A0; IT1181163B; ES540175A0; PT79935B; ES8601001A1

Abstract

This invention concerns a rotary tool (10) with cutting inserts, which comprises for each insert (11-12-20) an anchorage block (15-120) and at least one resisting block (18) with an adjusting screw (19), such blocks (15-18-120) being lodged inside a hollow (14) which narrows towards the outside of the tool (10), in which tool (10) the anchorage block (15-120) and the resisting block (18) cooperate along a surface inclined in relation to the axis of the adjusting screw (19), which is engaged at one end in the body (110) of the tool (10) and at its other end in such resisting block (18).

Description

This invention concerns a rotary tool with cutting inserts; to be more exact, the invention concerns a rotary tool in which the inserts which constitute the cutting elements are clamped in a simple and secure manner.
Such rotary tools are, for instance, those employed to process wood or plastics, or in any event are tools which are rotated at a high speed.
Various systems are known which secure the inserts in the tools either by peripheral or frontal installation in such tools. In some of these systems the inserts are fixed to the body of the rotary tool by threaded means with a frontal action and with the interposition of a thrust block.
However, such systems are generally not self-aligning and are also not proof against violent disintegration, that is to say, in the event of bad fixture the tool does not retain the inserts, which tend to be hurled out by centrifugal force. This entails great danger for the personnel employed.
Systems for installation of inserts are known which are proof against such violent disintegration. In fact, in these systems the insert is installed by lateral insertion within a hollow having a shape which narrows outwards.
In this way, even if the fixture is not precise or the threaded fixture means becomes accidentally loose, the insert is withheld in its seating and cannot leave the rotary tool through the action of centrifugal force.
For instance, a system for fixture of inserts in a rotary tool was disclosed in patent application IT 83378 A/81 in the name of the present applicant and possesses the characteristic of being proof against violent disintegration in the manner described above.
Moreover, in such tools the inserts are self-positioning since inclined surfaces are provided in the hollow made to lodge the inserts and cooperate with blocks to retain the inserts.
When secured with threaded means, such blocks exert a thrusting action against the insert, and such action provides a self-positioning effect.
In the cited embodiment the threaded means have two threaded portions with a righthand and a lefthand thread respectively.
While such embodiments provide efficient anchorage and safety in use, yet they comprise a system of wedge-shaped surfaces which is complicated and expensive to produce and also requires complicated equipment.
Moreover, such an embodiment requires a great depth of the hollow needed to lodge the blocks that secure the cutting insert or tool bit. It is therefore not suitable in cases where a modest depth of such hollow is required; this may be so when the rotary tools have a small diameter and large central hole or where the inserts are to be secured in the front of tools having a particularly small thickness.
A first purpose of this invention is therefore to provide a rotary tool in which, for dimensional reasons, a lodgement for the block or blocks is required to have a restricted depth in both a frontal and a radial direction.
It is also necessary that the fixture of the inserts in the tool should be proof against violent disintegration and should provide self-positioning of the inserts.
Another purpose of the invention is to simplify the construction and manufacture of the hollows and of the blocks employed to secure the inserts, thus enabling equipment which is inexpensive and not very sophisticated to be used.
A further purpose of the invention is to provide a quick and simplified installation of the inserts in the tool.
The above purposes of the invention and others again which will become evident from the description are obtained by providing a rotary tool comprising a screw-threaded element having two threaded portions with a lefthand thread at one end of the element and a righthand thread at the other end, such element being engaged directly in the body of the tool at one end and in a specially shaped block at its other end.
Thus when the screw-threaded element is screwed or unscrewed, such block is displaced within the appropriately provided hollow outwards or inwards respectively.
In this way, by moving outwards the block thrusts against another adjacent block, which in turn presses against the insert.
The latter block comprises pins or teeth able to engage corresponding recesses in the insert so as to keep the insert in position.
The inclination of the surfaces of the various blocks is such as to produce a self-positioning thrust against the insert when the threaded element is tightened.
In this way even if the insert is installed by hand and is not perfectly aligned, it is positioned automatically in the correct position when the threaded element is tightened. This is very important since it permits the insert to be adjusted and replaced even by unskilled personnel.
A further p.rpose of such an embodiment is to prevent a badly positioned insert from protruding farther than the others from the working profile and thus being alone in cutting the material and therefore becoming worn quickly.
As we said before, the invention concerns mainly the frontal fixture of the inserts in the tool, especially when the rotary tool has a small thickness; however, the invention concerns also the peripheral fixture of inserts in the tool and also, in a variant, the fixture of inserts of high speed steel; as is known, the latter can be re-sharpened and are made in one piece together with the relative block.
The rotary tool of this invention comprises also another block which acts to resist the former block and which can be secured within its hollow by means of the cited screw-threaded element with two threaded portions.
This invention is therefore embodied in a rotary tool with cutting inserts, which comprises for each insert an anchorage block to position the insert and at least one resisting block cooperating with an adjusting screw having two portions with a righthand and a lefthand thread respectively, such blocks being lodged inside a hollow which narrows towards the outside of the tool, the rotary tool being characterized in that the anchorage block and the resisting block cooperate along a surface inclined in relation to the axis of the adjusting screw, which is engaged at one end in the body of the tool and at its other end in such resisting block.
We shall now describe, as a non-restrictive example, some applications of the invention with the help of the attached figures, in which:-

Fig.1 gives a front view of a tool according to the invention, with inserts positioned frontally and perlpher- ally on the tool;
Fig.2 is an enlarged view of a section along A-A of Fig.I;
Fig.3 shows the system of fixture of an insert on the periphery of the rotary tool;
Figs.4a and 4b show views, in a radial direction, of the fixture of an insert by means of one and two resisting blocks respectively;
Fig.5 shows a high speed steel insert of a type forming one single body together with an anchorage block, the insert being fixed to the tool peripherally according to the invention.

In Fig.1 a rotary tool with cutting inserts according to the invention bears the reference number 10 and in this example contains two frontal inserts 11 and two peripheral inserts 12.
The tool 10 can comprise any number of inserts 11 and/or 12 according to its end use.
For instance, a tool 10 of this type can be employed to process window or door frames and may comprise one or more sets of frontal inserts 11 and/or peripheral inserts 12.
Fig.2 shows more clearly along the section A-A of Fig.l the fixture of the insert 11, which in its installed position presses with its lower side against an abutment surface 13 machined within a lodgement or hollow 14 that has a conformation suitable to be able to accommodate the insert and the fixture blocks.
An anchorage block 15 presses against the insert 11 and is provided with projections or pins 16 able to cooperate with corresponding recesses 17 in the insert 11.
In this way the insert 11 is thrust against its lodgement by such projections 16 and abuts against the lower abutment 13 in particular.
A resisting block 18 is able to slide substantially vertically within the lodgement 14 and is positioned by means of a screw-threaded element 19 having a lefthand thread at one end and a righthand thread at its other end.
Such screw element 19 in turn is engaged at one of its ends within the body 110 of the tool 10 itself and advantageously is of a hexagonal-head socket screw type.
In the example of Fig.1 two resisting blocks 18, each with a screw element 19, are employed owing to the considerable extent of the insert 11 in the direction of the width of the tool.
When the screw 19 is rotated in one direction, the block 18 is lowered, whereas if the screw 19 is rotated in the opposite direction, the block 18 is raised. The ascent of the resisting block 18 creates a thrust against the anchorage block 15.
Owing to the inclination of the surface 118 of contact between the blocks 18-15, such surface creates a wedge effect, the block 15 being thrust so as to clamp the insert 11.
By choosing the inclinations of the surfaces of the blocks 18-15 and hollow 14 suitably it is possible to obtain a component of thrust, directed downwards in Fig.2, against the insert 11. An effect of self-positioning of the insert 11 against the end abutment face 13 is produced in this way.
As can be seen in Fig.1, the resisting blocks 18, which are two in number in this case, have a cylindrical shape with one flat lateral face. In fact, these blocks 18 are produced from round bars and the face 118 which cooperates with the anchorage block 15 is machined with a flattening machine. The fabrication and adjustment of the resisting blocks 18 are simplified in this way.
As can be seen in Fig.2 in particular, the hollow 14 has a very small depth in the vertical direction in this figure. This is one of the purposes of the invention, which in fact is intended to make possible a secure fixture of the inserts in the event of tools which have a small thickness and therefore cannot comprise hollows of a great depth without a risk of structural weakness.
Fig.3 shows a section of a peripheral fixture of an insert 12. In this example too one anchorage block 15 equipped with projections 16 cooperating with a recess 17 in the insert 12 is employed; there is also one resisting block 18 cooperating here also with a screw element 19 having a righthand thread at one end and a lefthand thread at its other end.
Figs.4a and 4b respectively give two possible peripheral views of the embodiment of Fig.3 for tools having a small thickness and a considerable thickness respectively.
In these two examples the different widths of the cutting insert 12 cause one resisting block 18 and two resisting blocks 18 respectively to be employed. The number of blocks 18 used will therefore be proportional to the width of the insert 12.
Fig.3 shows how the depth of the hollow 14 is of a modest radial extent. This can be important, for instance, in the case of rotary tools which have a small diameter or a central hole of a considerable diameter, for in such a case the useful thickness is heavily reduced.
Lastly, Fig.5 shows an insert 20 according to the invention, which is made of high speed steel and can therefore be re-ground.
In this case the lower part 120 of the insert 20 cooperates directly with the hollow 14 and performs the functions which were carried out by the anchorage block 15 in the embodiments described above; here also a resisting block 18 is provided and cooperates with a screw 19 having two threaded portions.
In this case too the screw 19 is engaged directly in the body 110 of the rotary tool 10 so as not to create any dangerous weakening in the material.
As can be observed, in all the embodiments disclosed in this description the arrangement of the blocks 15-18 is such as to create an effect of resistance to violent disintegration of the tool 10.
Indeed, the inclination of the lateral faces of the hollow 14 is such as to retain the inserts 11-12 or re-grindable insert 20 even when the screw 19 becomes slackened or the inserts are badly fixed.
As can be seen from the examples described above, the fixture of the insert 11-12-20 is very simple since such insert is introduced laterally within the hollow 14.
The resisting block 18, with the screw element 19 in a position such as to leave such block 18 towards the bottom of the hollow 14, is positioned first of all.
In this way enough space is left to insert laterally the anchorage block 15 or the lower part 120 for fixture of an insert 20.
Next, when the insert 11-12-20 has been positioned correctly, the screw 19 is rotated, and thus the resisting block 18 is thrust outwards.
In this way, owing to the wedge-shaped conformation of the surfaces of the resisting block 18 and to the narrowing of the hollow 14 in the outward direction, a thrust effect is obtained against the anchorage block 15 or on the lower part 120 of the insert 20 respectively.
The inserts 11-12 are thus clamped against the respective cooperating walls of the hollow 14.
As we said earlier, this invention accomplishes the purpose not only of simplifying the fixture of the inserts but also of simplifying considerably the construction of the blocks 15-18 and the equipment needed to manufacture the various components of the rotary tool. n

INDEX

*****

10 - rotary tool
110 - body of tool
11 - frontal insert
12 - peripheral insert
13 - abutment
14 - lodgement hollow
15 - anchorage block
16 - pins or projections
17 - recesses
18 - resisting block
118 - inclined surface
19 - screw with double thread
20 - re-grindable insert
120 - lower part.

Claims

1 - Rotary tool (10) with cutting inserts, which comprises for each insert (11-12-20) an anchorage block (15-120) to position the insert (11-12-20) and at least one resisting block (18) cooperating with an adjusting screw (19) having two portions with a righthand and a lefthand thread respectively, such blocks (15-18-120) being lodged inside a hollow (14) which narrows towards the outside of the tool (10), the rotary tool (10) being characterized in that the anchorage block (15) and the resisting block (18) cooperate along a surface inclined in relation to the axis of the adjusting screw (19), which is engaged at one end in the body (110) of the tool (10) and at its other end in such resisting block (18).

2 - Rotary tool (10) with cutting inserts as claimed in Claim 1, in which the anchorage block (15) has a shape which can be likened to a parallelepided.

3 - Rotary tool (10) with cutting inserts as claimed in Claim 1 or 2, in which the resisting block (18) is substantially cylindrical.

4 - Rotary tool (10) with cutting inserts as claimed in Claims 1 and 3, in which a surface (118) of cooperation between the anchorage block (15) and resisting block (18) is flat.

5 - Rotary tool (10) with cutting inserts as claimed in any claim hereinbefore, in which the action of the resisting block (18) on the anchorage block (15) comprises a component which thrusts the insert (11-12) towards an abutment surface (13) provided in the hollow (14).

6 - Rotary tool (10) with cutting inserts as claimed in any claim hereinbefore, which provides for fixture of a frontal insert (11) (Figs.1 and 2).

7 - Rotary tool (10) with cutting inserts as claimed in any of Claims 1 to 5 inclusive, which provides for fixture of a peripheral insert (12) (Figs.3 and 4).

8 - Rotary tool (10) with cutting inserts as claimed in any claim hereinbefore, in which the anchorage block (15) is separate from the insert (11-12).

9 - Rotary tool (10) with cutting inserts as claimed in any of Claims 1 to 7 inclusive, in which the anchorage block (120) is integrally united to the insert (20) (Fig.5).