Systems equipped with inserts for acting on hard abrasive surfaces

Abstract

A system (1) for machining hard abrasive surfaces is described, comprising a support and containment structure (3) equipped with a containment bore (5) and a spindle (7) to be inserted into the containment bore (5), the containment bore (5) being elongated and having a conical section with a first diameter (A) oriented towards the outside of the structure (1) and a second diameter (B) larger than the first diameter (A) and oriented towards the inside of the structure (1), the spindle (7) being elongated and having a conical section with a third diameter (A') oriented towards the outside of the structure (1) and a fourth diameter (B') larger than the first diameter (A') and oriented towards the inside of the structure (1), the spindle (7) being inserted into the containment bore (5) by increasing or decreasing the temperature of the support and containment structure (3).

Description

[Technical field]

[0001] The present invention refers to a system equipped with an insert for working on hard abrasive surfaces. In general, the invention relates to a system to be used in applications with tension problems caused by thermal mounting by interference. More generally, the invention can be used with all materials that develop thermal expansion. Finally, in particular, the invention refers to an improved tool for working on hard abrasive surfaces. [Background technology]

[0002] Tools are known in the art that are equipped with an insert (core) that is inserted inside the tool structure, the insert being made of a special tungsten alloy that has high hardness (up to 60 HRC) and resistance to very high temperatures (up to 500° C.).

[0003] With some measures, the service life is certainly much longer than with standard tools. During operation, wear of the insert is minimal, but it must be taken into account that the steel forming the outer part of the tool has different characteristics of hardness and heat resistance, and therefore overheating of the tool due to long stroke times must be avoided, since temperatures higher than 500°C would create problems for the part of the steel tool that holds the insert.

[0004] Optimal performance, very hard materials (800kg / cm 2 In order to achieve a minimum impact of 100% (or more), it is necessary to start the dismantling with a minimum of parts and reduced impact times, which allows a good production (in terms of material hardness), even if this requires greater responsibility and greater attention on the part of the operator.

[0005] The tungsten portion always protrudes from the rest of the steel tool and wears away when in contact with rock, so that the tool is always sharp, easier to position at the best attachment point, and it is possible to concentrate all the hammering force on a small surface, thus increasing the modulus of rupture.

[0006] However, these tools are not sufficient and, as will be seen more clearly later, have the problem that the structure cannot guarantee support for the insert (which is cylindrical in shape) and breaks after very few working cycles due to the stresses experienced by the insert itself (starting from the circular hole made in the structure to contain the insert).

[0007] EP-A2-2812532 discloses a prior art system having the above-mentioned problems. DE-U1-202005011770 discloses a cylindrical recess 11 in a receiving element 3 having a rectangular section, which has a slightly tapered shape when connected to a connecting stem 2, i.e. when in another position relative to the present invention.

[0008] Moreover, as can be clearly seen in FIG. 1 of DE-U1-202005011770, if the connection between the parts 2 and 3 were to be made by placing a receiving element 3 from the outside on the mandrel 2, the conical realization of those connections would not lead to any improvement, given the very high operating speeds of the mandrel 2, which would cause the external connecting element 3 to be detached after a short time. This is regardless of the orientation of the tapering of the mandrel 2 towards the outside or the inside of the support (mandrels are never normally conical). The operating speed would quickly chip away at the connecting element 3 (and therefore the tool connected thereto) from the mandrel 2, whatever type of tapering was adopted at that location.

[0009] DE-U1-202005011770 therefore does not in fact provide any direct teaching (from the drawings in which the air gap is cylindrical and has a rectangular section) or even any indirect teaching on how to arrive at the solution of the present invention starting from EP-A2-2812532 (even the mention of tapering in the specification is a teaching diametrically opposite to that of the present invention). [Prior art documents] [Patent documents]

[0010] [Patent Document 1] European Patent Application Publication No. 2812532 [Patent Document 2] German Utility Model No. 202005011770 Summary of the Invention [Problem to be solved by the invention]

[0011] The object of the present invention is to solve the problems of the prior art mentioned above by providing a system equipped with an insert for acting on hard abrasive surfaces, in which the connection between the insert and the supporting structure is achieved simply and effectively, avoiding any type of damage to the structure itself. [Means for solving the problem]

[0012] These and other objects and advantages of the invention, as will become apparent from the following description, are achieved by a system equipped with an insert such as that set forth in claim 1. Preferred embodiments and non-obvious variants of the invention form the subject matter of the dependent claims.

[0013] It will be understood that all of the appended claims form an integral part of this specification.

[0014] The invention will be better explained by some preferred embodiments of the invention given as non-limiting examples with reference to the attached drawings, in which: [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 is a schematic cross-sectional side view of two components of a system according to the invention in a separated position. [Diagram 2]FIG. 2 is a schematic cross-sectional side view of two components of a system according to the invention in a coupled position. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] With reference to the drawings, preferred embodiments of the insertion system of the present invention are shown and described. It will be immediately apparent that countless variations and modifications (e.g., regarding shape, size, arrangement, and parts having equivalent functions) may be made to what is described without departing from the scope of protection of the invention, which emerges from the appended claims.

[0017] The system 1 of the present invention includes: a support and containment structure 3 equipped with containment holes 5; A spindle 7 designed to be inserted into the receiving hole 5; Equipped with.

[0018] The storage hole 5 is elongated and has a conical section with a first diameter A oriented toward the outside of the structure 1 and a second diameter B larger than the first diameter A and oriented toward the inside of the structure 1.

[0019] The spindle 7 is elongated and has a conical section with a third diameter A' oriented toward the outside of the structure 1 and a fourth diameter B' that is larger than the first diameter A' and oriented toward the inside of the structure 1.

[0020] The first diameter A and the third diameter A' are substantially identical; similarly, the second diameter B and the fourth diameter B' are substantially identical.

[0021] Inserting the spindle 7 inside the containment hole 5 is done by increasing the temperature of the support and containment structure 3 to achieve an expansion of a first diameter A, which allows the spindle 7 to enter the hole 5. The same objective is achieved by decreasing the temperature of the spindle 7, thus reducing the diameter B'. All the diameters and temperatures are precisely designed to obtain the functional expansions and contractions for the desired objectives.

[0022] The operative coupling of the spindle 7 to the inside of the storage hole 5 is achieved through the uniformity of the temperature of the two structures, returning them to their original measurement, thereby preventing the spindle 7 from coming out of the hole 5.

[0023] In particular, the second diameter B is greater than the first diameter A, and the fourth diameter B' is greater than the third diameter A'.

[0024] The spindle 7 is preferably made of a tungsten alloy having a hardness higher than 60HRC and a resistance to temperatures up to 500°C, while the support and containment structure 3 is made of steel.

[0025] The present invention therefore relates to a system equipped with a special insert, made with a mechanical solution for the hot and interference assembly of the spindle 7, which must remain fixed in position without being subjected to the effects of loads and tensile stresses to which both the spindle 7 and the mutual seat 5 are subjected due to the mechanical interference caused by the assembly taking advantage of the thermal expansion of the hole 5 into which they are inserted.

[0026] Usually, prior art solutions adopted for hot interference assembly provide that the parts to be assembled are cylindrical and not conical as in the solution of the present application, where the spindle 7 has a larger diameter than the hole 5, especially when the two objects are at the same temperature. The degree of increase depends on the thermal expansion obtained at the hole 5 by applying heat up to a temperature allowed by the technical specifications. The thermal expansion is a very precise value that is tied to the type of material and the temperature.

[0027] The diameter of hole 5 upon reaching the heating temperature increases by an expected amount, and when it becomes larger than the diameter of spindle 7 (which is at a lower temperature), spindle 7 can be inserted without effort.

[0028] Once both parts are back at the same temperature, an extremely rigid assembly is created which exerts a very high radial force between the two parts, preventing any relative movement.

[0029] This very high load has been found to have a contraindication in some applications, for example when the part is used under shock or vibration, since it causes failure, pulling the fibers of the material under very strong tension, which gradually starts to flex until they completely break.

[0030] The proposed solution achieves assembly without the possibility of pulling out the spindle 7, but with minimal or even zero radial load.

[0031] In the situation shown in the drawings, in hole 5, the first diameter A is smaller than the second diameter B, and in spindle 7, the third diameter A' is smaller than the fourth diameter B', and at the same temperature, the fourth diameter B' of spindle 7 is larger than the first diameter A of hole 5, making it impossible to connect the parts (Figure 1). By heating structure 3 to the temperatures estimated in this project, the first diameter A increases until it exceeds the fourth diameter B' of spindle 7, and spindle 7 can then be freely inserted into hole 5.

[0032] The same effect can be obtained by lowering the temperature of the spindle so that the diameter B' is smaller than A, and the spindle 7 can be inserted into the hole 5.

[0033] Once both parts have returned to the same temperature, we have an extremely rigid assembly which does not allow the spindle 7 to be pulled out, but which does not exert significant radial loads, since the two tapers are connected but not in interference (Figure 2).

[0034] This solution solves the problems caused by tensions caused by interference fits.

[0035] Several preferred embodiments of the present invention have been shown and described above. Obviously, numerous variations and modifications that are functionally equivalent to the previous embodiments and fall within the scope of protection of the present invention as emphasized in the appended claims will be immediately apparent to those skilled in the art.

Claims

1. A system (1) for processing hard abrasive surfaces, comprising: A support and containment structure (3) with a containment cavity (5), a spindle (7) designed to be inserted into said receiving hole (5); In a system (1) comprising: the containment hole (5) is elongated and has a conical section with a first diameter (A) oriented towards the outside of the structure (1) and a second diameter (B) larger than the first diameter (A) and oriented towards the inside of the structure (1); the spindle (7) is elongated and has a conical section with a third diameter (A') directed towards the outside of the structure (1) and a fourth diameter (B') larger than the first diameter (A') and directed towards the inside of the structure (1); the first diameter (A) and the third diameter (A') are substantially identical; the second diameter (B) and the fourth diameter (B') are substantially identical; said spindle (7) is inserted inside said containment hole (5) by expanding said hole by increasing the temperature of said support and containment structure (3) until said first diameter (A) is greater than said fourth diameter (B'), so that said spindle (7) can enter said containment hole (5); The operative connection of the spindle (7) inside the containment hole (5) is achieved by equalizing the temperature of the support and containment structure (3) with the spindle (7) to ensure that the fourth diameter (B') returns to its original size, which is greater than the first diameter (A), thereby preventing the spindle (7) from coming out of the containment hole (5). A system (1).

2. 2. The system (1) according to claim 1, characterized in that the spindle (7) is inserted inside the storage hole (5) by lowering the temperature of the spindle (7) so that the fourth diameter (B') becomes smaller than the first diameter (A) and then the spindle (7) can be inserted into the hole (5).

3. 3. The system (1) according to claim 1 or 2, characterized in that the first diameter (A) is smaller than the second diameter (B) and the third diameter (A') is smaller than the fourth diameter (B').

4. 4. The system (1) according to any one of claims 1 to 3, characterized in that the spindle (7) is made of a tungsten alloy having a hardness higher than 60 HRC and a resistance to temperatures up to 500°C.

5. A system (1) according to any one of the preceding claims, characterized in that the support and containment structure (5) is made of steel.

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