ARRANGMENT FOR FIXING A CUTTER

Abstract

An arrangement for fixing a pick to a cutting tool of a cutting machine includes a pick holder and a rotationally symmetrical pick sleeve, which is detachably fixed against an axial stop by surface pressure in a conical receiving element of the pick holder. The pick sleeve has an axial length that is greater than the axial length of the receiving element of the pick sleeve. A part of the pick sleeve that protrudes with respect to the edge of the receiving element when fixed has, on the outer diameter thereof, a conical bevel, which is inclined inwards.

Description

The invention relates to an arrangement for fixing a pick to a cutting tool of a cutting machine, comprising a pick holder and a rotationally symmetrical pick sleeve which is detachably fixed against an axial stop by surface pressure in a conical receiving element of the pick holder, wherein the pick sleeve has an axial length which is greater than the axial length of the receiving element of the pick sleeve, and a pick arrangement for a cutting machine.

An arrangement for fixing a pick or a pick arrangement for a cutting machine of the type referred to in the introduction is known, for example, from Austrian Patent Specification AT 404 969 B. In this document a pick holder with a pick sleeve is disclosed, into which a pick for cutting machines is located. The pick holder in this situation serves to fix the pick to cutting rollers, for example, or similar cutting tools of cutting machines, wherein the pick sleeve arranged between the pick holder and the pick is designed as a part subject to wear, and increases the service life of the pick holder. The connection of the pick to the pick holder by means of the pick sleeve in the state of the art referred to takes place by means of surface pressure of the pick sleeve, designed as slightly conical in shape, on the inner wall of a corresponding conical receiving element in the pick holder, wherein, for the assembly, the pick is inserted into the pick sleeve and knocked together with this into the pick holder. The knocking in of the pick with the pick sleeve is carried out in this situation up to a point at which the pick sleeve comes in contact with a stop at the base of the receiving element, wherein the contact with the stop during knocking in cannot be identified without further ado, due to the high surface pressure incurred. For this reason, the pick sleeve according to AT 404 969 B is dimensioned in its axial length in such a way that the pick sleeve, in the correctly located state, projects over the edge of the receiving element by a defined excess length, as a result of which a check can be made during cutting on the correct placement and correct knocking in.

During the cutting process, very high reaction forces naturally occur on the pick, which are transferred both via the shaft of the pick as well as, in particular, via the ring connection of the pick located in the immediate vicinity of the part of the pick sleeve which projects over the receiving element, onto this projecting part of the pick sleeve, as a result of which a separation of the seams of that area may occur. With the increasing wear of the pick sleeve, the forging forces cause a cold welding effect between the pick sleeve and the pick holder, such that a replacement of the pick sleeve with the pick is rendered substantially more difficult, if not completely impossible.

Starting from this prior art, the object of the present invention consists of avoiding the seam separation and consequent cold-welding of a pick sleeve located against a stop, in order to allow for improved replacement capability of the parts subject to wear, wherein, at the same time, it is intended that a simplified check on the correct placement and correct knocking in should be achieved.

To solve this object, an arrangement for fixing a pick of the type referred to heretofore being further developed according to the invention, such that the part of the pick sleeve which in the fixed state projects over the edge of the receiving element exhibits at its outer diameter a conical bevel which is inclined inwards. By means of the arrangement according to the invention of the pick sleeve in its part projecting beyond the receiving element, when the material of the pick sleeve is distorted due to the cutting forces and is pressed outwards, there is insufficient material available for seam separation to develop, which can occur in contact with the edge of the pick holder surrounding the receiving element, such that the parts which are to be detachably connected to one another, namely the pick sleeve and pick holder, do not become connected to one another in a non-detachable manner due to a cold-welding effect.

The inclination angle of the bevel is of the greatest importance for the visual guidance of the pick, while at the same time preventing the seam separation of the pick sleeve projecting over the edge of the receiving element in the pick holder. Within the framework of the present invention it is preferable in this connection that the inclination angle of the bevel against the generating line of the outer casing of the pick sleeve is between 15° and 30°, preferably 23°.

In order to allow for a visual check of the correct location of the pick sleeve, i.e. the knocking in of the pick sleeve as far as contact against the axial stop without measuring, the invention is preferably further developed in that the conical bevel begins in the position of the pick sleeve located in contact against the axial stop, directly at the edge of the receiving element. This means that the distance between the beginning of the bevel and the counter-stop surface of the pick sleeve, interacting with the stop of the receiving element, corresponds to the length of the receiving element between the edge of the receiving element and the axial stop.

Advantageously, the embodiment according to the invention is dimensioned in such a way that the surface pressure between the receiving element and the pick sleeve is essentially constantly being adjusted over the entire axial length of the receiving element, and amounts to at least 150 N/mm², this value being regarded as suitable for a secure fixing by surface pressure.

In order to facilitate the disassembly of the pick and the pick sleeve from the pick holder, the invention is preferably further developed in that the pick holder exhibits a hole, opening into the receiving element, for the introduction of hydraulic oil. When hydraulic oil is introduced under pressure via such a hole, it passes into the gap between the pick sleeve and pick holder, and exerts a certain raising force onto the pick sleeve, wherein lubrication of the contacting surfaces simultaneously takes place. In this way it becomes easier for the pick sleeve or the pick respectively to be removed.

The pick arrangement according to the invention for a cutting machine with a pick holder, a rotationally symmetrical pick sleeve which is detachably fixed against an axial stop by surface pressure in a conical receiving element of the pick holder, and a pick, wherein the pick sleeve has an axial length which is greater than the axial length of the receiving element of the pick sleeve, and exhibits a part which protrudes with respect to the edge of the receiving element when fixed, on the outer diameter thereof, a conical bevel which is inclined inwards, is characterized in that the pick is in contact on a ring-shaped face surface of the pick sleeve with a ring-shaped contact surface formed at a ring connection, and the diameter of the ring connection does not exceed the outer diameter of the face surface. By this measure, the ring connection of the pick comes in contact over its entire radial extent with the face surface of the pick sleeve, as a result of which the forces are conducted optimally into the pick sleeve and tilting is prevented.

In order to allow for the use of the cutting tool in salt water also, provision is preferably made for the pick sleeve to be made of stainless steel, e.g. X17CrNi 16-2.

The invention is explained in greater detail hereinafter on the basis of an embodiment represented schematically in the drawings. In the drawings, FIG. 1 shows a representation of the pick arrangement according to the invention in a pre-fitted state of the pick sleeve, FIG. 2 shows a detailed view of FIG. 1, FIG. 3 the state of the arrangement after final assembly, and FIG. 4 a detailed view of FIG. 3.

In FIG. 1, a pick arrangement according to the invention is designated by 1, wherein a pick sleeve 2, in which a pick 3 is held, is located into a pick holder 4. The pick holder 4 can be fixed, by means not represented in greater detail, to a cutting tool, such as, for example, a cutting roller. The pick holder 4 exhibits a receiving element 5 with a conical inner surface, such that the inner diameter of the receiving hole becomes larger in the direction of the pick tip. Fixed in the receiving element 5 are the pick sleeve 2 and the pick 3, which is held by a clip ring 6 in the pick sleeve 2, wherein the pick sleeve 2 exhibits a conical outer surface which interacts with the conical inner surface of the receiving hole. When the pick sleeve 2 is knocked in, in the direction of the arrow 7, due to the conicity and the dimensions of the pick holder 4 and the pick sleeve 2 increasingly high surface pressures arise between the pick sleeve 2 and the pick holder 4. In FIG. 1 it can be seen that the pick sleeve 2, in the pre-fitted state represented in FIG. 1, has not yet been brought into contact against the stop 8 of the receiving element 5.

The dimension A in the area of the stop 8, i.e. the distance between the stop 8 and the counter-stop surface of the pick sleeve 2 in this situation corresponds to the same dimension A at the edge of the receiving element 5, i.e. the distance between the edge of the receiving element 5 and the beginning of the conical bevel 10 of the pick sleeve 2, which is represented in more precise detail according to FIG. 2.

If now, as represented in FIG. 3, the pick 3, together with the pick sleeve 2, is knocked further into the pick holder 4, until no more free dimension is present between the edge of the receiving element 5 of the pick holder 4 and the bevel 10 on the pick sleeve 2, it is also ensured that the pick sleeve 2 comes in contact with the stop 8 at the base of the receiving element 5.

In FIGS. 1 and 3, the reference number 9 designates a hole for the introduction of hydraulic oil, and the reference number 11 designates a ring connection of a pick.

Claims

1. An arrangement for fixing a pick to a cutting tool of a cutting machine, comprising: a pick holder; anda rotationally symmetrical pick sleeve is detachably fixed against an axial stop by surface pressure in a conical receiving element of the pick holder, the pick sleeve having an axial length which is greater than an axial length of the receiving element of the pick sleeve, wherein a part of the pick sleeve protrudes with respect to an edge of the receiving element when fixed, the part exhibiting at its outer diameter a conical bevel which is inclined inwards.

2. An arrangement for fixing of a pick according to claim 1, wherein an inclination angle of the bevel against a generating line of an outer casing of the pick sleeve is between 15° and 30°, preferably 23°.

3. An arrangement for fixing of a pick according to claim 1, wherein the conical bevel begins at the position of the pick sleeve when it is in contact against the axial stop, directly at the edge of the receiving element.

4. An arrangement for the fixing of a pick according to claim 1, wherein a surface pressure between the receiving element and the pick sleeve is constantly adjusted over the entire axial length of the receiving element, and amounts to at least 150 N/mm2.

5. An arrangement for the fixing of a pick according to claim 1, wherein the pick holder includes a hole, opening into the receiving element, for the introduction of hydraulic oil.

6. An arrangement for the fixing of a pick according to claim 1, wherein the pick sleeve is made of stainless steel, such as X17CrNi 16-2.

7. A pick arrangement for a cutting tool of a cutting machine, comprising: a pick; andan arrangement for fixing the pick to a cutting tool including a pick holder and a rotationally symmetrical pick sleeve detachably fixed against an axial stop by surface pressure in a conical receiving element of the pick holder, the pick sleeve having an axial length that is greater than an axial length of the receiving element of the pick sleeve, wherein a part of the pick sleeve protrudes with respect to an edge of the receiving element when fixed, the part exhibiting at its outer diameter a conical bevel that is inclined inwards, the pick being in contact on a ring-shaped face surface of the pick sleeve with a ring-shaped contact surface formed at a ring connection, and the diameter of the ring connection does not exceed the outer diameter of the face surface.