EP0771934A2 - Coupling for percussion rods - Google Patents

Abstract

The drilling tool has parts which can be connected to one another using a thread (8,8'). The thread connection is in the form of a modified round thread. In order to avoid high wedge forces on the external thread of a threaded spigot (6) and/or on the internal thread of a threaded nut (7), threaded sections (14,15,15') are arranged with parallel axes on each shaft raised surface (11,11') and/or in each shaft depression (12,12'). The region (18,18') between the threaded sections is formed by a continuous curved groove.

Description

The invention relates to a drilling tool, in particular for a rotational impact for processing rock or the like according to the preamble of claim 1.

State of the art

Depending on the size of the borehole, so-called breakthrough drills with a type of crosshead are used for the rotary impact processing of rock, as is shown, for example, in US Pat. For larger borehole diameters, so-called drill bits are used, the cup-shaped housing of which has carbide cutting inserts on the front and which have an additional centering drill in the center. Such drill bits can also be subjected to striking stresses for rock processing. For this purpose, reference is made, for example, to DE-U 85 21 577. Finally, conventional rock drills for striking rock have become known which have a one-piece (DE 43 14 868 A1) or an interchangeable conveying helix (DE 23 48 847).

In the case of rock drills with impact stress, there is basically the problem that the drill head and in particular the hard metal cutting inserts are subjected to high mechanical and thermal loads. Furthermore, the tools must be adapted to the respective circumstances both in the area of the drill head and in the area of their helical shank and their clamping end for the hammer drill. This often leads to the drill head being formed in two parts with the adjoining drill shaft, which can be equipped with or without a conveying helix or with an exchangeable conveying helix. In all of the known rock drills mentioned above, this exchange usually takes place by means of a threaded connection between the drill head and drill shaft, the threaded pin or threaded bolt with its external thread generally being arranged on the drill shaft and the associated threaded bore or threaded nut with its internal thread being arranged in the drill head. However, designs have also become known in which the threaded pin on the drill head and the threaded bore are positioned on the associated threaded shaft. From DE 25 43 578 a breakthrough drill has become known, the connection between the drill head and the drill shank is made via a mere cone connection.

The type of connection thread must be optimized depending on the application. Common thread types such as metric thread, trapezoidal thread, saw thread or even round thread are suitable for this. Each thread type has its specific properties and advantages. Round threads are used in particular where there is a high risk of contamination and damage. This can certainly be the case in the rough everyday operation of such drilling tools. According to the figure 3 of the aforementioned US Pat. No. 4,262,762, a conventional round thread is also used in such a drilling tool.

These generally have advantages in terms of insensitivity to dirt and corrosion. Despite these conditions, they must be easy to open and close.

Object and advantages of the invention

The invention has for its object to propose a rock drilling tool for a particularly striking load, the threaded connection has been optimized in particular between the drill head and drill shank compared to the prior art, so that considerable advantages are achieved.

The object of the invention is achieved by the features of claim 1.

Advantageous and expedient developments of the drilling tool according to the invention are specified in the subclaims.

The basic idea of the invention is that the use of a modified round thread and thus a special thread is generally advantageous in order to be able to handle the contamination, corrosion loads or the like that occur. A disadvantage of a kind of round thread connection, however, are the transmission losses generally associated with this. These losses are higher the higher the impact energy to be transmitted is converted into frictional heat and sound energy. The frictional heat arises especially in those contact sections that have a steep lead angle. This means that there is a high efficiency of the transmission of the impact energy with the smallest possible pitch angle, that is to say the impact surface is as flat as possible. Losses due to sound energy are caused by excessive play and the associated impact of the parts on each other.

The use of a conventional round thread has the advantage that it is highly insensitive to dirt and corrosion. However, it has the disadvantage that the surface sections lying one on top of the other are extremely small due to the constant curvature of the flank sections of the round thread, for example compared to a trapezoidal thread with high surface parts lying on top of each other.

In order to eliminate in particular the surface sections with steeper thread pitch in the round thread and the associated clamp connection, the invention provides that a modified round thread or a special thread is used in which in the area of the wave crests and / or the troughs of such a thread, axially parallel thread sections are provided, through which a round thread is straightened axially parallel in these sections. Sections parallel to the axis cannot absorb axial forces, so that there is no jamming in these threaded areas and thus excessive wear with a corresponding heating of these threaded sections. The coordinated threaded sections of the external thread of the threaded pin and the internal thread of the threaded bore are designed in such a way that they nestle on the side of each threaded groove facing away from the force direction over a high surface section similar to a trapezoidal thread and form a continuous curve, while the wave crests and Wave troughs in particular can also be used for correct axial guidance and not for axial force transmission due to their respective lateral flattening. In the area of the side of each thread groove facing the direction of force, a play can also be provided between the respective thread pairing. This results in an optimal one Relationship between power transmission and durability of the system.

The formation of the threaded connection is particularly advantageous in that, in particular, the shaft belly of the threaded pin has an axially parallel thread section which, like the alternative or supplementary axially parallel section in the trough of the threaded pin, comprises a length range which is approximately 1/5 to 1/4 of the pitch of the Thread is. The associated internal thread in the threaded bore is a mirror image, that is, the radially outer, axially parallel section on the shaft crest of the threaded pin corresponds to an associated radially outer, axially parallel section in the trough of the internal thread.

The design of the drilling tool according to the invention is particularly advantageous in that the drill head generally has an attached threaded pin with an external thread and the adjoining drill shaft has an associated bore with an internal thread. Such an arrangement has the advantage that the drill head is not weakened by an additional hole for receiving an internal thread, so that, for example in the embodiment of the invention as a drill bit, this area can be used excellently for receiving an inner hole for a center drill.

It is also advantageous that the connection between the drill head and the drill shank additionally receives a high degree of force transmission of the impacting energy via a circumferential collar via a corresponding modified round thread according to the invention. The circumferential collar arranged between the bore for the internal thread and the outer diameter of the shaft part with its circular ring surface is supported over a large area on an opposite corresponding one Collar on the drill head in order to transmit the axial impact energy to a large extent from the drill shaft on the drill head. In this case, the modified round thread is relieved of energy transmission and is also used to a large extent for axial guidance between the drill shank and drill head.

Further details of the invention can also be found in the drawings, to which express reference is hereby made. In the following description, these drawings are explained in more detail with details of and advantages of the invention.

Fig. 1a, 1b

ein Ausführungsbeispiel für eine Gewindeverbindung zwischen einem Bohrerschaft (Fig. 1a) und einem Bohrerkopf (Fig. 1b) und

Fig. 2

eine vergrößerte Darstellung der zusammengefügten Gewindeabschnitte über etwa einen Gewindegang.

Show it

1a, 1b

an embodiment of a threaded connection between a drill shank (Fig. 1a) and a drill head (Fig. 1b) and

Fig. 2

an enlarged view of the assembled thread sections over about a thread.

Description of the embodiment

1 shows a two-part drilling tool 1, for example with a drill head 2 in FIG. 1b and, for example, a drill shaft 3 in FIG. 1a. The drill head 2 can comprise any other type of drill head and in particular a drill head as described in all of the prior art documents mentioned at the beginning. 1b indicates, for example, the use of a drill bit as the drill head.

Likewise, the drill shaft 3 can be any boring bar or the like with or without an integrated one Include conveying helix, wherein a separate attachable conveying helix could also be used, for example, with a cross boring head.

In the exemplary embodiment according to FIG. 1 b, the drill head 2 has a cup-shaped drill bit 4, the drill bit shaft 5 of which is designed as a threaded pin or threaded bolt 6. Likewise, the drill shaft 3 has an internal thread 7 which is designed as a threaded nut 7 and which interacts with the threaded pin 6.

beträgt. Gleichermaßen ist in Fig. 1b ein Außendurchmesser d_A der Bohrkrone 4, ein Nenndurchmesser d_N und ein Kerndurchmesser d_K für den Gewindezapfen 6 angegeben, wobei die Nutentiefe ${\text{t2 = d}}_{\text{N}}{\text{- d}}_{\text{K}}$

beträgt.The threaded pin 6 and the threaded nut 7 have a modified round thread 8, 8 '- hereinafter also called "round thread" - with a thread pitch h and a thread depth t1. In Fig. 1a, an outer diameter D _{A of} the drill shaft 3, a nominal diameter D _N and a core diameter D _{K of} the internal thread 7 is shown, the groove depth ${\text{t}}_{\text{1}}{\text{= D}}_{\text{N}}{\text{- D}}_{\text{K}}$

is. Likewise, an outer diameter d _{A of} the drill bit 4, a nominal diameter d _N and a core diameter d _K for the threaded pin 6 are indicated in FIG. 1b, the groove depth ${\text{t2 = d}}_{\text{N}}{\text{- d}}_{\text{K}}$

is.

FIG. 1a also shows the borehole depth L1 and an axial inlet section L2.

Fig. 1b shows an entire pin length l1, a thread length l2 and a thread run-out length l3.

The round thread 7 shown in FIG. 1a has a radius of curvature R1. Furthermore, the lower inlet angle α1 for the round thread and the upper cone angle α2 for the cone tip are shown.

1b shows the transition radius R2 to the circumferential collar 9 between the threaded pin 6 and the drill bit 4. The end Thread runout of the threaded pin 6 has a pitch angle α3.

The collar 10 corresponding to the collar 9 of the drill head 2 on the end face of the drill shaft 3 has corresponding dimensions.

For a selected exemplary embodiment, the variables specified above are compiled as examples.

The peculiarity of the modified round thread of the threaded pin 6 and / or the threaded nut 7 is that axially parallel sections are provided in the wave crests and / or in the troughs of the round thread as shown in FIGS. 1 and 2. For example, the threaded pin 6 has on its round thread 8 radially outer wave crests 11 and radially inner wave troughs 12. Similarly, the internal thread 8 'of the threaded nut 7 has radially inwardly projecting wave crests 11' and radially outwardly directed wave troughs 12 '. In the exemplary embodiment according to FIG. 1b, the wave crests 11 each have axially parallel linear sections, that is to say the radially outer region of the round thread 8 of the threaded pin 6 is flattened and arranged parallel to the longitudinal axis of symmetry 13. This axially parallel section is designated in FIG. 1b, FIG. 2 with reference number 14 with a width s1. In Fig. 1a, the radially inward wave crest 11 'of the round thread 8' there also has an axially parallel section 15 with the width s2. The shaft crest 11 of the round thread 8 of the threaded pin 6 therefore interacts with its axially parallel section 14 with a corresponding axially parallel section 15 'in the trough 12' of the round thread 8 'of the threaded nut 7, with a continuous curve such as one in the remaining area of the thread, for example usual round thread may be present. Furthermore can however, also an axially parallel section 15 of the radially inwardly pointing crest 11 'of the threaded nut 7 cooperate with a corresponding axially parallel section 14' in the trough 12 of the threaded pin 6. Across the axial length, axially parallel sections 14, 14 'of the crest 11 and of the trough 12 of the threaded pin 6 or axially parallel section 15, 15 'of the crest 11' or of the trough 12 'of the threaded nut 7. Between these axially parallel sections 14, 14', 15, 15 'there are continuous curves of the respective modified round thread 8, 8' where cavities 16, 17 may also be formed. No forces can be transmitted in the axially parallel areas via an axial section s1, s2. This leads to a very significant reduction in the surface pressure of the threaded connection.

As can be seen in particular from FIG. 2 with the details described above, the threaded nut 7 with its round thread 8 ′ lies closely and positively on the almost identical cam section 18 of the threaded pin 6, in particular on the curve area 18 ′ remote from the force P over an axial height area s3 at. In this area 18, 18 'with a continuous curve, the force transmission takes place during the impact load.

The curve area 19 of the threaded pin 6 lying below the axis-parallel section 14 and the associated curve section 19 'of the threaded nut 7 can have a cavity 20 or gap 20, that is to say no force transmission takes place in this area. The same applies to the curve area above the axially parallel section 15 of the threaded nut 7.

The power transmission and, in particular, optimal guidance between the drill head 2 and drill shank 3 therefore take place over the round thread 8, 8 'with axially parallel surface sections 14, 14', 15, 15 'on the respective wave crests 11, 11' or the wave troughs 12, 12 ', or over the rest of the curve 18, 18' and 19, 19 ' of the modified round thread, which is formed continuously or continuously.

The essential part of the power transmission of the force P from the drill shank 3 to the drill head 2 takes place via the two stop collars 9, 10 which, when the round threads 8, 8 'are joined together, lie on one another in a positive and non-positive manner. This power transmission is shown in Fig. 1a, 1b with P1, P2.

The above consideration can also be carried out by corresponding axially parallel sections in only the respective wave crests 11, 11 'or the respective wave troughs 12, 12' of the two round threads 8, 8 '. This is to be applied accordingly.

In a preferred embodiment, the length L1 has a dimension which corresponds approximately to 1 to 1.3 times the outer diameter d _{A of} the drill bit 4. The difference between the nominal diameter d _{N and} the core diameter d _{K of} the threaded pin 6 corresponds to approximately 10% of the core diameter.

The inlet zone or the inlet section 21 has a length L2 which corresponds to approximately 30% of the length L1. As a result of this measure, the area in which the radius R2 lies at the transition from the threaded pin 6 to the drill bit 4 is not unnecessarily braced when the threads are joined.

In addition to the axially parallel sections 14, 15 in their respective specified areas, the two round threads 8, 8 'are designed in accordance with conventional round threads, the flank radius R1, r1 in the respective thread being approximately 0.1 to 0.15 times the respective nominal diameter D _N or d _N corresponds. The respective cylindrical section 14, 15 on the wave crests 11, 11 'has an axial length s1, s2 which corresponds to 0.1 to 0.4 times the pitch h.

Apart from the axially parallel sections, the round thread is therefore a continuous curve.

• 1. Schaftteil:
  • L1 = 38 mm
  • L2 = 10 mm
  • d_A = 32 mm
  • D_N = 22,1 mm
  • D_K = 20 mm
  • α1 = 30°
  • α2 = 27°
  • R1 = 2,5 mm
  • t1 = 0,4 mm.
• 2. Gewindezapfen 6:
  • 11 = 30 mm
  • 12 = 27 mm
  • d_N = 22 mm
  • d_K = 20 mm
  • t2 = 0,4 mm.

In the embodiment of the round thread according to the invention, that flank region of the round thread with steep surface sections is relieved of impulse forces of the hammer due to the axially parallel surface sections, so that the shock wave for the most part runs over the cross-sectional area 22 laterally of the round thread 8 'in the threaded nut 7 and over the contact surfaces 9 , 10 is transferred to the drill head. This results in few friction losses in the thread and thus a noticeably lower heat development and a longer service life of the connection. The measures according to the invention achieve a 25% improvement in power transmission compared to comparable tool interfaces, also with a round thread. However, the use of this type enables a good fit of both joining partners. No sharp-edged transitions are created, which entail an increased risk of breakage. Furthermore, the external thread on the tool side, that is, in the area of the drill head, saves installation space that enables strength reserves in this area. After all, the entire connection is insensitive to dirt and corrosion. For an exemplary embodiment, the following dimensions are given below for a drill bit.

• 1st shaft part:
  • L1 = 38 mm
  • L2 = 10 mm
  • d _A = 32 mm
  • D _N = 22.1 mm
  • D _K = 20 mm
  • α1 = 30 °
  • α2 = 27 °
  • R1 = 2.5 mm
  • t1 = 0.4 mm.
• 2.Thread 6:
  • 11 = 30 mm
  • 12 = 27 mm
  • d _N = 22 mm
  • d _K = 20 mm
  • t2 = 0.4 mm.

The invention is not restricted to the exemplary embodiment shown and described. Rather, it also encompasses all professional further training within the framework of intellectual property rights claims.

In particular, the axially parallel sections 14, 15 are carried out directly next to one another, that is to say the axially parallel section 14 on the wave crest 11 interacts with an axially parallel section 15 'arranged in the trough 12 in FIG is indicated. In this way, an optimal axially parallel guidance of the threaded parts to one another is achieved. The same applies to corresponding axially parallel sections 14 'in the troughs 12 of the threaded pin 6. Alternatively, such arrangements can only be arranged on the shaft crests 11 and / or only in the troughs 12 of the threaded pin 6, with associated sections in the threaded nut 7.

Claims (6)

Drilling tool, in particular for a rotational impact for machining rock or the like, the tool being of multiple parts and the parts being connectable to one another via a thread (8, 8 '), characterized in that the thread connection is a modified round thread or a special thread (8, 8 '), and to avoid high wedge forces on the external thread of a threaded pin (6) and / or on the internal thread of a threaded nut (7), axially parallel threaded sections (14, 14'; 15, 15 ') on the respective shaft crest (11, 11') and / or are provided in the respective trough (12, 12 ') and that the area (18, 18') between the threaded sections (14, 14 '; 15, 15') is formed by a continuous curve. Drilling tool according to claim 1, characterized in that at least the shaft crest (11, 11 ') of the threaded pin (6) has an axially parallel threaded section (14) which is connected to a curved section (12, 12') of the associated threaded partner (7) or with a corresponding axis-parallel section (15 ') of the threaded partner cooperates to an axial guide. Drilling tool according to claim 1, characterized in that the drilling head (2) is designed as a drill bit equipped with cutting elements, as a through-hole drill with a cross-drilling head or as a conventional rock drill and is provided with a threaded pin (6) with an external thread (8) and that the associated drilling tool shaft (3 ) has an internal thread (8 ') adapted to it. Drilling tool according to claim 3, characterized in that the drill shank (3) of the drilling tool with an internal thread (8 ') has a circumferential cross-sectional area (22) with an end collar (10) which, in the case of a tensioned threaded connection (8, 8'), for transmitting the impact forces (P) on a circumferential cuff (9) on the drill head (2) positively and non-positively. Drilling tool according to one of the preceding claims, characterized in that the axially parallel section (14, 14 ') on the external thread (8) of the threaded pin (6) and / or the axially parallel section (15, 15') on the internal thread (8 ') of the threaded nut (7) has an axial length s1 ≈ s2 of 1/5 to 1/4 h, with h = pitch or pitch of the round thread. Drilling tool according to one of the preceding claims, characterized in that the thread depth t1 ≈ t2 of the round threads (8, 8 ') is approximately 1/6 to 1/7 of the pitch height h.

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