AU702970B2

AU702970B2 - Cutter arrangement for a straight shank cutter

Info

Publication number: AU702970B2
Application number: AU11320/97A
Authority: AU
Inventors: Roman Gerer; Gottfried Siebenhofer; Alfred Zitz
Original assignee: Tamrock Voest Alpine Bergtechnik GmbH
Current assignee: Sandvik Mining and Construction GmbH
Priority date: 1995-12-21
Filing date: 1996-12-18
Publication date: 1999-03-11
Anticipated expiration: 2016-12-18
Also published as: DE29623508U1; ZA9610652B; WO1997023710A1; AU1132097A; AT406503B; ATA208995A

Description

1 Cutter Arrangement for a Straight Shank Cutter The invention relates to a cutter arrangement for a straight shank cutter comprising a cutter sleeve having a conical outer jacket and capable of being screwed into an internal thread of a cltter box.

Cutter arrangements of the initially defined kind may be taken, for instance, from AT-386 252. In that previously known configuration a cutter sleeve having a conical outer jacket was used, wherein the cutter sleeve end adjacent the cutter comprised an external thread capable of being screwed into an internal thread of the cutter box. That thread in the case of impact stresses had to absorb high deformation forces, which were taken up by the conical wall of the cutter sleeve only partially. Since the manufacture of the cutter box proper, of high-strength material involves considerable disadvantages in terms of cost and, moreover, difficulties have arisen in the welding of the cutter box with the cutting head base body in respect of a number of highly wear-resistant materials, cutter sleeves have been proposed, it being essential with a view to reducing wear that the bushes or sleeves pressed into the cutter box will not become loose within the reception bore of the cutter box. The bore of the cutter box widens due to impacts exerted by the cutter on the sleeve, thus limiting useful life. By the proposal according to AT-386 252 an external thread provided on the cutter sleeve had already been suggested, which, however, was configured in a manner that the cutter box, if necessary, could be rotated along the pitch of the thread due to impact-like stresses in order to ensure new fixing. In that manner, the conical partial region was driven more firmly into the reception bore of the cutter box. Yet, due to the simultaneously occurring rotational movement the already existing press fit was left such that, on the whole, the major portion of the respective reaction forces had to be taken up by the thread itself until a new stable press fit could be obtained.

2 Also other known configurations of cutter sleeves, such as, for instance, the configuration according to DE-Al-41 27 433, according to which inter alia double-conical outer contours of cutter sleeves have already been proposed, are altogether not suitable for preventing a cutter sleeve from rotating under excessive impact stresses, a new stable press fit position being difficult to assume after a rotational movement of the cutter box on account of said partially provided double fit.

DE-C2-30 26 930 proposed devices for retaining and bracing the reception part within the conical recess of the base portion, wherein it was possible to impede rotational movements of the cutter sleeve partially by additional measures, such as e.g.

peripheral contours deviating from the circular shape as well as additional blocking organs.

The invention aims at providing a cutter arrangement of the initially defined kind, by which a precise press fit once obtained will not be loosened again even under high impact stresses of the cutter sleeve and the respectively chosen rotary position will be safely maintained until the end of the useful life of the sleeve. At the same time, the configuration according to the invention aims at rendering as simple as possible the detachment of such a cutter sleeve for the purpose of replacement by axial pressing out. To solve this object, the configuration according to the invention essentially consists in that the cutter sleeve comprises a stop overlapping the reception bore of the cutter box and intended to limit the inward movement of the cutter sleeve, and that the thread for screwing the cutter sleeve into the cutter box has an axial play that is larger than the maximum axial stroke admitted in the deformation of the cutter sleeve.

Due to the configuration according to the invention the safe absorption of the axial forces introduced into the cutter sleeve via the cutter is ensured by the stop overlapping the edge of the reception bore, on the one hand, said stop becoming active as the conical section of the cutter sleeve is 3in the press fit within the reception bore of the cutter box.

By the fact that a thread for screwing the cutter sleeve into the cutter box is provided in addition, mounting and dismounting is substantially facilitated, said thread being kept free of axial forces by having an axial play larger than the maximum axial stroke admitted in the deformation of the cutter sleeve. In this manner, no torques whatsoever act on the sleeve under impact stresses such that the safe press fit will be maintained. On the other hand, the thread itself is not stressed by impact stresses, since the thread under an impact stress only may be relieved on account of the axial play, but will not be stressed anew.

According to a preferred further development of the cutter arrangement according to the invention, the axial length of the conical outer jacket of the cutter sleeve extends over 1/3 to 1/5 of the length of insertion of the cutter sleeve in the reception bore of the cutter box, wherein the external thread of the cutter sleeve preferably extends over an axial length that is larger than the axial length of the conical region of the jacket of the cutter sleeve. Such dimensioning ensures that the respective partial regions of the cutter sleeve merely are stressed to the extent to which they are actually able to safely absorb the forces occurring in each case, without a rotational movement of the cutter sleeve being provoked. In order to be able to additionally support eccentric forces in a better way thereby reducing wear, the configuration advantageously is devised such that the end of the cutter sleeve facing away from the end of insertion of the cutter is designed with a cylindrical jacket whose diameter is smaller than, or equal to, the smallest clear width of the internal thread of the cutter box. The region ftcitng away from the end of insertion of the cutter thus functions as a radial bearing, deformation vibrations in the axial direction being readily admissible in that case. By the fact that the cylindrical portion is provided on the inner end of the sleeve, eccentric forces may safely be taken up via a particularly favourable lever arm.

The most advantageous configuration of the cutter arrangement according to the invention consists in that the threaded section is provided axially between the conical and the cylindrical outer jacket sections of the cutter sleeve, thus providing for excellent protection also to the thread and strongly facilitating the exchange of the sleeve. Irrespective of the wear of the cutter sleeve, both mounting and dismounting by aid of a polygonal section provided in the cutter sleeve channel may be effected in a particularly simple manner. By the fact that an opening is provided in the rear end of the cutter sleeve, which opening communicates with a further opening provided in the cutter box, a tool, for instance, for exchanging a broken cutter may be inserted in a simple manner.

In the following the invention will be explained in more detail by way of an exemplary embodiment schematically represented in the drawing.

In the drawing, a cutter box 1 is illustrated, into whose reception bore 2 a cutter sleeve 3 is screwed. The cutter inserted in the cutter sleeve 3 is denoted by 4. The cuttex box 1 is connected with the cutting head base body via a weld The cutter sleeve 3 comprises a shoulder 6 overlapping the insertion end of the reception bore 2 and supported on the external edge of the cutter box 1 in the sense of arrow 7 with the cutter sleeve being axially stressed. At the same time, a first conical partial region 8 of the cutter sleeve gets into a press fit with the respectively conically designed wall of the reception bore 2 of the cutter box. For insertion, the cutter sleeve is screwed down within the reception bore 2, to which end a thread 9 is provided. Said thread has an appropriate axial play in the direction of the arrow 7 so as to safely avoid any rotational movement of the cutter sleeve 3 in the case of impact stresses exerted on the cutter in the direction of the arrow 7 and the corresponding stresses exerted on the cutter sleeve 3.

An additional support of the cutter sleeve 3, and hence of the cutter 4, against extra-axial forces is effected via a substantially cylindrical end region 10 of the cutter sleeve, which is guided in a correspondingly cylindrical partial region of the reception bore 2 so as to provide for radial support.

In order to exchange the cutter 4, a simple tool schematically indicated by 11 may be inserted. That tool 11 is designed as an appropriately curved pushrod capable of being inserted into the cutter sleeve 3 by means of an actuating lever 12 in a direction opposite to the arrow 7. Within the cutter sleeve channel 13 a polygonal section 14 is provided on the rear end, enabling mounting and dismounting of the cutter sleeve in a simple manner. Such simple dismounting of the cutter sleeve is ensured even if that part of the cutter sleeve which projects out has been worn.

Claims

1. A cutter arrangement for a straight shank cutter (4) comprising a cutter sleeve having a conical outer jacket and capable of being screwed into an internal thread of a cutter box characterized in that the cutter sleeve (3) comprises a stop overlapping the reception bore of the cutter box and intended to limit the inward movement of the cutter sleeve and that the thread for screwing the cutter sleeve into the cutter box has an axial play that is larger than the maximum axial stroke admitted in the deformation of the cutter sleeve

2. A cutter arrangement according to claim 1, characterized in that the axial length of the conical outer jacket of the cutter sleeve extends over 1/3 to 1/5 of the length of insertion of the cutter sleeve in the reception bore (2) of the cutter box

3. A cutter arrangement according to claim 1 or 2, characterized in that the external thread of the cutter sleeve extends over an axial length that is larger than the axial length of the conical region of the jacket of the cutter sleeve

4. A cutter arrangement according to claim 1, 2 or 3, characterized in that the end of the cutter sleeve facing away from the end of insertion of the cutter is designed with a cylindrical jacket (10) whose diameter is smaller than, or equal to, the smallest clear width of the internal thread of the cutter box A cutter arrangement according to any one of claims 1 to 4, characterized in that the threaded section is provided axially between the conical section and the cylindrical outer jacket section (10) of the cutter sleeve 7

6. A cutter arrangement according to any one of claims 1 to characterized in that a polygonal section (14) is provided within the cutter sleeve channel (13).

7. A cutter arrangement according to any one of claims 1 to 6, characterized in that an opening is provided in the rear end of the cutter sleeve which opening communicates with a further opening provided in the cutter box 8 Abstract: Cutter Arrangement a Straight Shank Cutter The cutter arrangement for a straight shank cutter (4) provides for a cutter sleeve including an outer jacket having a conical partial region In addition, the cutter sleeve comprises a stop overlapping the reception bore of the cutter box Furthermore, the cutter sleeve (3) is capable of being screwed into the reception bore of the cutter box by a thread having a large axial play. Finally, a cylindrical end section (10) is provided on the cutter sleeve for supporting radial forces.