EP1175284B1 - Screwdriver insets - Google Patents

Abstract

The invention pertains to a screwdriver bit with a drive section ( 14 ) and a front section ( 1 ) that contains a profiled penetrating section ( 2 ) and is manufactured by compression molding and subsequently sintering a hard metal powder, where the front section is connected to the drive section. Thus, according to the invention, the length of the front section ( 1 ) is not greater than 2.5-times the length of the penetrating section ( 2 ) and/or the ratio of the length of the front section ( 1 ) to the diameter or the width across corners of the penetrating section ( 2 ) is not greater than 2.2 (FIG. 7 ).

Description

The invention relates to screwdriver inserts of the type specified in the preamble of claim 1, in particular for use in power wrenches.

Screwdriver bits of this type have heretofore been made from alloyed tool steels, usually containing carbon content and alloying additives such as silicon, manganese, chromium, molybdenum and vanadium in proportions of less than 1%. After tempering, these steels reach a working hardness of approximately 60 to 64 HRC. When used in power wrenches made of tool steel Schraubenendrehereinsaeae at the top function of a relatively high wear, because the stress is higher than a hand screwdriver. When using the screwdriver in the industrial sector, especially in the screw assembly in an automated manufacturing, it is desirable to achieve a longer service life of Schraubebdreher-inserts. Therefore, such inserts contain z. B. cylindrical intermediate portions which lie between the screwdriver tips and the present in hexagonal drive portions, the cushioning of load peaks serve and for this purpose a ratio diameter to length of 0.2 to 0.5 (EP 0 336 136 B1).

In addition, attempts have already been made to produce screwdriver inserts with cross tips made of metal powder mixtures - ie of hard metal (DE 92 11 907 U1, DE 42 41 005 A1 and DE 43 00 446 A1). Thereafter, the blanks of the screwdriver inserts are produced by injection molding, wherein the hard metal powder is mixed with a superplasticizer. The flow agent is removed from the sprayed blanks in the following treatment, then these are sintered at high temperature to the final shape and density. Although such screwdriver inserts made of carbide achieve even greater hardness than those made of high-speed steel, but in such previously known screwdriver bits brittleness is too high, so that even at lower torque values than they occur in practice, cancel.

In the VDI Journal No. 7 - 9 (1999), pages 42 to 45, the design of press tools for the production of screwdriver inserts made of carbide is described. The blanks are pressed directly from metal powder. It is reported that in the found design of the dies and the filling process using the finite element method dimensionally accurate and crack-free blanks of the screwdriver bits could be made. It is not known what load values are actually achieved with the screwdriver inserts produced in this way in mass production and whether these inserts correspond to the values required in practical use. On the market such screwdriver inserts have not become known.

In contrast to the previously mentioned one-piece screwdriver inserts, a screwdriver for Phillips screws is described in US 3,393,722, which consists of a shaft made of relatively soft steel and a tip part of an extremely hard material. The tip part made of hard metal has on its rear side a pin which engages in a bore in the end face of the shank. Both parts are connected by welding together. The tip part is preferably made of hard metal (tungsten carbide). The cross profile of the tip part is formed relatively long, about as it is in the usual manufacturing method to produce the cross profile by milling the grooves, results. However, a long shaped cross profile is unfavorable for such high carbide tip parts because carbide is more brittle compared to steel and the long shaped profile has lower torque bearing capacity and secondly this long profile is unfavorable for the manufacture of the tip parts, as explained below , The screwdriver or screwdriver bits of this embodiment have not become known in the market, although more than 30 years have passed since the application and the increasing demand for wear-resistant screwdrivers or screwdriver bits promotes market introduction. The same applies to a tool according to DE 70 44 913 U1, in which a tip part made of high-strength tool is connected to a shaft part made of inferior material. The tip portion is preformed by powder metallurgy fabrication. About the method of manufacture, shape and dimensions are given in both writings no information. It may be assumed that even for these embodiments, no manufacturing process was found, which led to satisfactory results.

Furthermore, a screwdriver insert of the type described at the outset is known (FR 2 469 250 A1), which contains a cross point made of metal powder by pressing and subsequent sintering. The cross profile of the penetrating portion rises, without any clear, shaped as a radius or slope transition, from a plane which is perpendicular to the longitudinal axis of the Spitzenenközpers. On the back of the tip body has a prismatic notch on for attachment to the corresponding end of the Schraubwerkzeuges (-schaftes), wherein the attachment is preferably carried out by brazing. The length of the crossbars should correspond to approximately half the length of the tip body. The starting material is steel or hard metal powder. The disadvantage of such an embodiment is that the crossbars pass without defined radii or bevels in the base plane. Especially with hard materials, such as carbide, edged, not gradual transitions have a notch effect, which greatly reduces the load capacity at this point, especially at a torsional load. Another disadvantage is the intended mounting method. In the cross-cutting incision self-centering of the two connecting parts is not given. It must be achieved by an auxiliary device, such as a fixed ring applied to the joint, which must not be displaced during brazing.

Based on this prior art, it is the object of the invention to produce screwdriver inserts made of hard metal in such a way that they are transmitted in the region of their Eindringabschnitte by the high hardness but also required in practice torques, compared to known embodiments significantly higher Wear resistance or service life is achieved and cost-effective production is possible.

The solution of the problem serving characterizing features are mentioned in claim 1.

In the course of leading to the solution of the problem experiments and investigations it was found that it is expedient, the screwdriver inserts not in one piece as in DE 92 11 907 U1, DE 42 41 005 A1 and DE 43 00 446 A1, but in two parts with a possible short front part made of carbide and a drive part made of steel. This is inventively achieved in that the front part consisting of hard metal is given a total length, which is determined essentially by the length of a penetrating part, which is dimensioned so that it assumes the maximum penetration depth of the inner profile in screw heads of the associated screw size and / or type , To this, relatively short length is added the length of a base part and an anchoring part, via which the front part is connected to a drive part of the screwdriver bit.

The invention achieves two major advantages. On the one hand, a uniform, accurate and good compression when pressing the blanks and thus a good stability in the region of the Eindringabschnitts the front part relative to the bending moments acting on the crossbars when transmitting a torque is achieved. A suitable Komgrößenzusammensetzung the selected metal powder mixture according to claim 4 can contribute to this. Such a good, uniform compression has been difficult to achieve, especially in cross tips, since the crimp die is similarly filled with metal powder, as it is also required for the production of one-piece screwdriver inserts. The pressure exerted by the ram on the metal powder filling pressure then does not affect evenly into the tip region and the ridge chambers, because this pressure is reduced within the filling and by the friction of the filling at the Matrizenwänden. On the other hand, it is ensured by the design according to the invention that the compacts reach the sintering without cracking, which is necessary for good durability, in particular of cross tips. The pressed under high pressure in the die metal powder or the resultant compact obviously opposes its demolding high resistance, which is greater, the larger the surface of the compact is. This Entformungswiderstand must be overcome by acting on the central tip force of the Auswerfer- or Unterstempeis. The high specific load of the tip and the in The ejector force acting on the crossbars can lead to the formation of fine cracks, which are not even compensated during sintering and disturb the homogeneity of the microstructure. Due to the short design of the carbide front part according to the invention, however, the required ejector force is substantially reduced, so that z. B. a complicated, expensive mold can be avoided, in which the lower punch not only the profile of the central tip, but also the profile of the conical tip extending back of the cross bars, as in the above-described known method [VDI journal no. 7 - 9 (1999), pp. 42 to 45].

A feature of the invention is also that in variants, the anchoring elements, by which the front part are connected to the shaft part, are formed so that a solid, suitable for the transmission of torque connection alone by pressing, optionally using adhesive, is achieved.

Further advantageous features of the invention will become apparent from the dependent claims 2-12.

• Fig. 1 bis 3 schematische Längsschnitte durch drei unterschiedlich große Vorderteile eines erfindungsgemäßen Schraubendreher-Einsatzes für Kreuzschlitzschrauben, wobei die Kreuzstege nicht geschnitten dargestellt sind;
• Fig. 4 eine schematische Seitenansicht eines erfindungsgemäßen, analog zu Fig. 1 bis 3 ausgebildeten Vorderteils;
• Fig. 5 und 6 Schnitte längs der Linien V-V und VI-VI der Fig. 4;
• Fig. 7 eine teilweise geschnittene Seitenansicht eines erfindungsgemäßen Schraubendreher-Einsatzes mit einem Vorderteil nach Fig. 4 bis 6;
• Fig. 8 und 9 grob schematisch ein Preßwerkzeug zur Herstellung eines erfindungsgemäßen Vorderteils nach Fig. 4;
• Fig. 10 eine vergrößerte Seitensicht des Vorderteils nach Fig. 4 in Kombination mit einem zugehörigen, geschnitten dargestellten Schraubenkopf;
• Fig. 11 eine der Fig. 7 entsprechende Ansicht eines zweiten Ausführungsbeispiels eines erfindungsgemäßen Schraubendreher-Einsatzes;
• Fig. 12 einen Schnitt längs der Linie XII-XII der Fig. 11;
• Fig. 13 bis 16 jeweils teilweise geschnittene oder ungeschnittene Vorderansichten drei weiterer Ausführungsbeispiele von Verbindungsformen des Vorderteiles aus Hartmetall mit dem Antriebsteil;
• Fig. 17 bis 19 Schraubendreher-Einsätze für Kreuzschlitzschrauben verschiedener Größe;
• Fig. 20 ein Ausführungsbeispiel des erfindungsgemäßen Schraubendreher-Einsatzes, entsprechend Fig. 7, jedoch mit einem vom Antriebsteil abstehenden konvexen Verankerungselement;
• Fig. 21 einen Schnitt längs der Linie XXI-XXI;
• Fig. 22 einen der Fig. 17 entsprechenden Schraubendreher-Einsatz für Kreuzschlitzschrauben mit einer weiteren Ausführungsform des Verankerungselementes;
• Fig. 23 einen Schnitt längs der Linie XXIII-XXIII;
• Fig. 24 einen Schnitt längs der Linie XXIV-XXIV;
• Fig. 25 ein Ausführungsbeispiel analog zu Fig. 22, jedoch mit einem Vorderteil für Pozidriv-Schrauben (PZ);
• Fig. 26 einen teilweisen, stark vergrößerten Längsschnitt durch ein Vorderteil eines erfindungsgemäßen Schraubendreher-Einsatzes für TORX® -Schrauben;
• Fig. 27 eine Draufsicht (Vorderansicht) des Schraubendreher-Einsatzes nach Fig. 29;
• Fig. 28 eine Seitenansicht und Vorderansicht eines erfindungsgemäßen Schraubendreher-Einsatzes für TORX® -Schrauben mit Auslaufradius;
• Fig. 29 je eine Seitenansicht und Vorderansicht (Draufsicht) eines erfindungsgemäßen Schraubendreher-Einsatzes für Sechskant-Schrauben mit Auslaufradius;
• Fig. 30 eine Seitenansicht und Vorderansicht eines erfindungsgemäßen Schraubendreher-Einsatzes für Robertson-Schrauben mit Auslaufradius; und
• Fig. 31 eine Tabelle mit bevorzugten Maßen für die Vorderteile der erfindungsgemäßen Schraubendreher-Einsätze.

The invention will be explained in more detail below in connection with the accompanying drawings of exemplary embodiments. Show it:

• 1 to 3 are schematic longitudinal sections through three different sized front parts of a screwdriver insert according to the invention for Phillips screws, wherein the cross bars are not shown cut;
• 4 shows a schematic side view of a front part according to the invention, designed analogously to FIGS. 1 to 3;
• Figures 5 and 6 are sections taken along lines VV and VI-VI of Figure 4;
• 7 shows a partially sectioned side view of a screwdriver insert according to the invention with a front part according to FIGS. 4 to 6;
• 8 and 9 roughly schematically a pressing tool for producing a front part according to the invention according to Fig. 4;
• FIG. 10 is an enlarged side view of the front part of FIG. 4 in combination with an associated screw head shown in section; FIG.
• 11 is a view corresponding to FIG. 7 of a second embodiment of a screwdriver bit according to the invention;
• Fig. 12 is a section along the line XII-XII of Fig. 11;
• 13 to 16 are each a partially sectioned or uncut front view of three further embodiments of connection forms of the front part of hard metal with the drive part;
• 17 to 19 screwdriver inserts for Phillips screws of various sizes;
• 20 shows an exemplary embodiment of the screwdriver insert according to the invention, corresponding to FIG. 7, but with a convex anchoring element projecting from the drive part;
• Fig. 21 is a section taken along the line XXI-XXI;
• FIG. 22 shows a screwdriver insert corresponding to FIG. 17 for Phillips screws with a further embodiment of the anchoring element; FIG.
• Fig. 23 is a section along the line XXIII-XXIII;
• Fig. 24 is a section along the line XXIV-XXIV;
• FIG. 25 shows an embodiment analogous to FIG. 22, but with a front part for Pozidriv screws (PZ); FIG.
• 26 shows a partially, greatly enlarged longitudinal section through a front part of a screwdriver insert according to the invention for TORX® screws;
• Fig. 27 is a plan view (front view) of the screwdriver bit of Fig. 29;
• 28 shows a side view and front view of a screwdriver insert according to the invention for TORX® screws with outlet radius;
• 29 each a side view and front view (top view) of a screwdriver insert according to the invention for hexagonal screws with outlet radius;
• 30 is a side view and front view of a screwdriver insert according to the invention for Robertson screws with outlet radius. and
• Fig. 31 is a table of preferred dimensions for the front parts of the screwdriver bits according to the invention.

Fig. 1 shows a front part 1 of a screwdriver insert according to the invention. The front part 1 is provided at its front end with a penetration portion 2 in the form of a conventional cross tip, which serves to penetrate into the corresponding inner profile of a Phillips screw. The cross point comprises four cross-shaped ribs or webs 3 with upper edges 4, which taper towards each other towards the front and terminate at a for the purposes of the invention insignificant, flattened end portion 5. Between the webs 3, there are arranged cross grooves or grooves with groove bottoms 6, which are also conical up to the end section 5 and which, on the side remote from the end section 5, bulge radially outwards or bevelled, starting at a point 7 which defines the rear end of the penetrating section 2 and thereby form a subsequently designated as outlet 8 section.

At the outlet 8 closes backwards z. B. cylindrical base portion 9, which terminates at a rear end face 10, which is generally perpendicular to a central or rotational axis 11 of the front part. From the end face 10 is still an anchoring portion 12 in the form of a pin from behind, which has a reduced compared to the construction section 9 cross-section, wherein the penetration portion 2, the base portion 9 and the anchoring portion 12 are arranged coaxially to the axis 11. This basic shape of the front part 1 is essentially the same in all screwdriver inserts of the invention, but the outer design and dimensions of the different sections 2, 4 and 6 in particular are adapted to the inner profile of the respectively assigned screw and the sections 12 to the selected ones Anchoring must be adapted, as explained below.

Fig. 2 shows an analogous to Fig. 1 front part 1 and its essential for the invention dimensions. Then, a dimension L0 denotes the length of the penetrating portion 2 between the end portion 5 and the spout 8, L1 the length of the front portion 1 between the end portion 5 and the end surface 10, LP the profile length, which is the sum of the length L0 and the length LA of the spout 8, and LB the length of the base section 9 such that LP + LB = L1. For the length LA of the spout 8, it follows that LA = L1 - L0 - LB = LP - L0). All lengths are measured in the direction of the longitudinal axis 11 (FIG. 2). In addition, a comparison of Figs. 1 to 3, in which like parts are provided with the same reference numeral, that the point 7, 7 a and 7 b at the end of the conical portions of the groove bottoms 6 of the penetrating 2 and enter the outlet 8, in Fig. 1 is in the same height with the lower end of the upper edges 4 of the webs 3, while the corresponding point 7a and 7b in Fig. 2 below and in Fig. 3 above the lower end of the upper edges 4. This is a consequence of the fact that normally both a measure D1, which indicates the diameter of the front part 1 at the end of the length L1, ie in the region of the base portion 9 and the end face 10, as well as the cone angles, under which the upper edges 4 of the webs 3 and the groove bottoms 6 extend, are predetermined by standards or the like. The upper edges 4 therefore end downwards, respectively, where they intersect an imaginary peripheral cylinder of the base section 9. Finally, d0 denotes the diameter at the end of the length LO, ie at the points 7, 7a or 7b.

Front part 1 (Fig. 4 to 6) and a likewise separately produced drive member 14 (Fig. 7) composed, the z. B. is used to attach the insert in the lining of a motor screwdriver. In this case, the front part 1 made of hard metal, the drive member 14, however, made of a usual for this purpose tool steel. For the coaxial connection of these two parts 1, 14 to a screwdriver insert (FIG. 7), the drive part 14 is provided on a front side facing the front part 1 with a surface incorporated in its, adapted with its inner cross section to the outer cross section of the anchoring part 12 recess 15 , The connection then takes place in that the anchoring part 12 is inserted into the recess 15 and pressed in this way, soldered or fastened in any other way that the drive member 14 can transmit the required torques on the front part 1. As shown in FIG. 7, the recess 15 in a z. B. cylindrical or slightly conical transition portion 16 may be formed, which adjoins a portion 17 with a conventional hexagonal outer profile of the drive member 14 and causes a flush transition from the section 17 to the base portion 9.

The preparation of the front part 1 is effected by means of a in Fig. 8 and 9 schematically indicated pressing tool 19. This contains a press bushing 20, which at one end with a z. B. cylindrical receiving opening 21 for a z. B. also cylindrical ram 22 and at the other end is provided with a Preßmatrize 23 inserted into it, which at one of the receiving opening 21 coaxial opposite side as a negative mold 24 for the front part 1 to be produced, d. H. is formed in the embodiment as a negative mold for a cross point. Between the female mold 24 and the receiving opening 21, the press bush 20 has a cavity 26. In addition, the Preßmatrize 20 is provided with a central passage into which an ejector 25 is inserted. The ram 22 is provided on its side facing the Preßmatrize 22 end face with a recess 27 which is formed as a negative mold of the anchoring part 12.

To produce the front part 1, the cavity 26 is first filled with the desired cemented carbide powder when the ejector 25 has been inserted and pushed up to the die 24, as indicated in FIG. 8 by the reference numeral 28. Subsequently, the ram 22 is inserted into the receiving opening 21 and pre-pressed with the pressure required for the compression of the hard metal powder 28 in the direction of the Preßmatrize 23, whereby the hard metal powder 28 is compressed and brought into the shape of the front part 2 (Fig. 9). Thereafter, the ram 22 is removed, the ejector 25 is advanced to eject the front part 2 of the Preßmatrize 22 and the Preßbuchse 20, and the front part 2 obtained in such conventional pressing method, for. B. sintered at 1100 ° C to 1200 ° C: The hard metal powder mixture contains z. B. cobalt, molybdenum, and tungsten carbide and optionally iron and leads through the pressing and sintering process to an extremely hard and wear-resistant front part. 2

Due to the two-part design of the screwdriver inserts 2, 14 according to the invention, it is achieved that the actual functional or active zone, which is contained in the front part 1, is produced with a comparatively simple, cost-effective method, but nevertheless achieves optimum pressing conditions become. After the connection of the front part 1 with the drive member 14 then creates a screwdriver insert which also withstands high loads.

To achieve a uniform pressure distribution and thus a homogeneous microstructure in the front part 1, it is considered necessary in the context of the invention to form the front part 1 as small as possible in order to cause the lowest possible friction losses in the tool 19. Since the shape and the size of the actual penetration section 2 depends on the internal profiling in the head of the respective associated screw, the following considerations are used to achieve this objective:

First of all, it is clear that the portions and sizes discussed above in the context of the invention, as will be apparent from the later description, apply not only to the Phillips system of FIGS. 1 to 3, but also to other bit / screw pairings. These include z. As the Phillips and Pozidriv Phillips systems, the usual hexagonal systems, further the TORX® or square Robertson polygonal, multi-tooth or waveform systems as well as various special systems such. B. Tri-Wing and Torque-Set.

For the dimensioning of the penetration sections 2 of the bits or the associated inner profiles of the screws there are z. As DIN / ISO standards or other standards and regulations, the z. B. were given by the original developers of the respective profile systems.

These standards and regulations are adopted for the purposes of the invention, as far as this is required for a good function or a good pairing bit / screw. It is based on the DIN standards 967, 7996 and 7997 and / or EN-ISO 7045 to 7047, according to which the screws of different thread diameters are divided into cross-slit sizes 0 to 4 and for each size screws with different heads and Internal profiles and therefore different penetration depths can belong in these.

Important for the good fit of Phillips and inner profile of the screw is that the cross point with the flanks of the webs 3 (Fig. 1) on the flanks of the inner profile of the screw has surface contact. The supporting profile of the cross point must be so long that it can dive into the cross profile of the screw, without about the cross point at its outlet 8, which no longer corresponds to the correct contour of the Eindringabschnitts 2, seated on the edge of the Phillips profile of the screw. This is schematically indicated in Fig. 10, which shows a front part 1 according to FIGS. 1 to 7, which dips into the profiled opening of a screw head 29 having a penetration depth T, which is smaller than the length L0 of the penetrating portion 2 corresponds. The point 7, at which the Kreuznutenböden 6 pass into the outlet 8, is located sufficiently far outside the screw head opening. If L0 <T, the penetration section 2 would lie only in a part of the screw head opening because the outlet 8 would rest on the screw head 29. In addition, this would mean that the good surface contact between the penetration portion 2 and the associated surfaces of the screw head opening would be lost and the insert would sit with some play in the screw, which is unfavorable for the transmission of high torques. Finally, with L0 = T, the case L0 <T can also be set depending on the respective tolerances.
In this determination, on the other hand, it is understood, of course, that the profile dimensions of the penetrating portions in the area provided for penetration into the screw correspond in cross section to the specified standards in association with the respective cross-slot type and size.

In order to arrive at a practicable compromise in the design of the inserts according to the invention, the length L0 on the basis of that screw head one of Profile size of the Eindringabschnittes assigned screw series, which has the largest penetration depth T according to the relevant standard or other rule. First, it is assumed that the screw type, through whose head shape, the largest penetration depth T results. These are in the case of Phillips screws z. B. Lens countersunk screws according to EN-ISO 7047. As with all other types of screws, the penetration depth T is significantly smaller, measured on the basis of the lens sinker screws sized inserts also on the same inner profile having heads of other screws.

If there are screws that lead to different penetration depths T due to different head shapes for any size of a particular cross-slot profile, the screw that has the greatest penetration depth T is selected to design L0.

This will be explained below with reference to a concrete embodiment.

According to EN-ISO 7045 - 7047 (type Z, Pozidriv), z. B. countersunk square head screws with Phillips differently standardized penetration depths of the teaching, which the areas T _MIN to T _MAX of 1.48 / 1.93 mm to 2.9 / 3.35 mm are assigned. According to the invention, the largest occurring area of the largest screw head shape is used for the design of L0 by L0 is 3.35 mm. This ensures that the front part 1 can dive into all screw heads with full penetration depth T. An advantage of this L0 design is that L0 is not made larger than required for the desired function.

With regard to the measure L1 is required according to the invention that it should be as small as possible to ensure the desired uniform pressure distribution during the pressing process. This is ensured according to the invention by choosing L1 not greater than 2.5 * L0, preferably not greater than 2.2 * L0, and with very particular advantage less than 2.0 * L0, which in the above example is L1 = 8.5 mm or 7.48 mm or 6.80 mm. Among other things, the size of L1 in cross-hatch profiles depends on how large the values for LP and LB should be (FIG. 2). With regard to LP has proved to be expedient to choose the outlet 8 significantly smaller than that in conventional Bits is possible. If, however, the outlet 8 is chosen to be too small, unfavorable pressure distributions result during the pressing process as a result of the steep transition from the base section 9 to the penetration section 2, while excessively large values of LP would increase the overall length L 1 too much. Considered by itself, a short profile length LP, especially at cross tips, means that the overall surface becomes significantly smaller. As a result, the friction when ejecting the pressed part from the die considerably smaller, on the other hand increases a short profile length LP and the load capacity. Ratios of Lp / Lo in the range of approx. 1.25 to 1.55 are considered favorable. In the above case, with a length LB of about bit size by about 0.8 mm to 1.5 mm and not more than 2.5 mm, a value LP of about 5.00 to 5.25 mm has proven to be expedient, which is sufficient large value L1 = 6.00 to 6.25 mm, ie L1 = 1.76 · L0 to 1.84 · L0 leads to a short and therefore easily compressible front part 1.

Größe 1:

Hier liegt der Bereich ET_MIN bis ET_MAX bei 1,22 bis 1,47 mm für kleinere und bei 1,83 bis 2,08 für größere Schraubenköpfe. Erfindungsgemäß wird L0 = 2,1 mm, LP = 3,0 mm und L1 = 3,8 mm gewählt.

Größe 3:

Hier liegt der Bereich ET_MIN bis ET_MAX bei 2,73 mm bis 3,18 mm. Erfindungsgemäß wird L0 = 4,4 mm, LP = 6,6 mm und L1 = 8,1 mm gewählt.

Größe 4:

Hier liegt der Bereich ET_MIN bis ET_MAX bei 3,87 mm bis 4,32 mm für kleinere und bei 5,6 mm bis 6,05 mm für größere Schraubenköpfe. Erfindungsgemäß wird L0 = 6,6 mm LP = 8,8 mm und L1 = 10,3 mm gewählt.

For the other three sizes 1, 3 and 4 according to EN-ISO 7045 - 7047 (type Z, Pozidriv), the following values have proven to be suitable:

Size 1:

Here, the range ET _MIN to ET _MAX is 1.22 to 1.47 mm for smaller and 1.83 to 2.08 for larger screw heads. According to the invention, L0 = 2.1 mm, LP = 3.0 mm and L1 = 3.8 mm are selected.

Size 3:

Here, the range ET _MIN to ET _MAX is 2.73 mm to 3.18 mm. According to the invention, L0 = 4.4 mm, LP = 6.6 mm and L1 = 8.1 mm are selected.

Size 4:

Here, the range ET _MIN to ET _MAX ranges from 3.87 mm to 4.32 mm for smaller and 5.6 mm to 6.05 mm for larger screw heads. According to the invention, L0 = 6.6 mm LP = 8.8 mm and L1 = 10.3 mm are selected.

It can be seen from the above values that none of the values for L1 is greater than 2 - L0 mm, and particularly for the smaller sizes, very small values for L1 can be obtained, even when L1 is rated at 2.5 · L0. Very particularly preferred dimensions are shown in FIG. 31.

For other screw heads [z. B. type H (Phillips) according to EN-ISO 7045 - 7047] can be proceeded in a similar manner.

The base portion 9 consists of a short, plate-shaped portion, which serves mainly for Anformung the anchoring elements 12. These may consist of convex, protruding from the end face 10 (FIG. 1) or concave, sunken into the end face 10 form elements. Reference to FIGS. 11 to 24, some exemplary embodiments are explained in more detail below, in which the front parts 1 substantially correspond to the front part 1 according to FIGS. 1 to 9 except for partially different base sections. In an analogous manner, the drive parts 14 substantially correspond to the drive part 14 according to FIG. 7, for which reason only the different parts are denoted by different reference numbers than before. While, as anchoring element 12 of FIG. 1 to 9 is a Cylindrical pin, the front part 1 of FIG. 11 and 12 with a Vertically provided by the other end face of the base portion 9 projecting anchoring element 31 with a TORX profile, which is inserted into a recess 32 of the drive member 14, which has a corresponding inner profile. The solid compound of both parts 1,14 z. B. by gluing, soldering, pressing od. Like., Where the non-circular cross-section of the anchoring elements 31, 32 has the advantage that a rotationally fixed, the transmission of high torques enabling connection is achieved by Formschiuß.

FIG. 13 shows a concave anchoring element 33 in the base section 9 and a corresponding but convex anchoring element 34 on the drive part 14. B. by gluing or soldering.

Fig. 14 shows two anchoring elements in the form of flat surfaces on the underside of the base portion 9 and at the top of the transition portion 16 of the drive member 14. The two anchoring parts are here along an interface 35 by welding firmly connected.

According to Fig. 15, the front part 1 is provided with an anchoring element 36 in the form of a raised from the base portion 9 V-rib, while a drive member 37 is provided on its base portion 9 facing end face with an anchoring element 38 in the form of a corresponding, concave keyway. The attachment of the two anchoring elements 36, 37 to each other by soldering along a Lötnaht 39. The embodiment of FIG. 15 also differs from those of FIG. 7 to 14, that the drive member 37 is cylindrical.

In the embodiment according to FIG. 16, the cylindrical drive part 37 is connected to the front part 1 analogously to FIG. 14 by welding along a weld seam 40. In contrast to FIGS. 7 to 14, the cross section of the drive part 37 according to FIGS. 13 and 14 is slightly larger than that of the base section 9 or the diameter D1 in FIG. 2.

FIGS. 17 and 18 show in a direct comparison two screwdriver inserts according to the invention, which differ in the region of a base section 9 and 41, respectively. While the base portion 9 in Fig. 17 is formed as shown in Figs. 1 to 9, the base portion 41 immediately adjacent to a spout 42 has a radially expanding zone 43 which then merges into a zone 44 corresponding to the base portion 9. In contrast, the embodiment shown in direct comparison with Fig. 17 and 18 of FIG. 19 differs from the embodiments of FIGS. 7 to 14 in that a drive member 45 is connected via a transition section 46 with a base portion 47 of a front part 48. The base portion 47 here has a dimension D1 (FIG. 2) which, in contrast to FIG. 7, is larger than the diameter of the hexagonal portion of the drive part 45, and the transition portion 46 in this case serves to make the smaller cross section of the hexagonal portion larger Cross section of the base portion 47 to connect. The anchoring element is exemplified here as described for FIGS. 22 to 24.

FIGS. 20 and 21 show an anchoring element 48 projecting from the upper end face of the drive part 14 and inserted in a corresponding anchoring element 49 incorporated in the end face of the base section 9 in the form of a recess.

21, the anchoring elements 48 and 49 have a bow star profile analogous to FIG. 12. The connection of the two anchoring elements 48, 49 takes place, for example, in FIG. B. by soldering along a solder seam 50th

Referring to FIGS. 22 to 24, a raised protruding anchoring element 52 having a cross-shaped profile is formed on the base portion 9 of the front part 1, which is in a corresponding anchoring element 53 in the form of a Phillips, which is formed in the upper end face of the transition portion 16 of the drive member 14 , The attachment is z. B. by gluing or soldering. This embodiment is currently considered the best variant of anchoring elements.

Finally, FIG. 25 shows an exemplary embodiment analogous to FIG. 17, in which a front part 1a is provided with a penetration section 2a with a Pozidriv profile, which is designed as in FIGS. 22 to 24. A base portion 9a is provided with a projecting anchoring element 12a which projects into a corresponding anchoring element 15a in the form of a recess which is machined into the upper end face of the transitional section 16 of the drive part 14. The connection of the two anchoring elements 12a, 15a takes place by soldering in the region of the contact surfaces.

Incidentally, the same applies to the Pozidriv inserts (PZ) of Fig. 25 as to the other Phillips (Ph) Phillips inserts. As shown in Fig. 25, L0 is the length of the penetrating portion 2a extending to a spout 8a, while L1 is the total length of the front portion 1a except for the length of the anchoring member 12a. The same applies to the measures of L0 and L1 of the Pozidriv bets as for the Phillips bets, ie. H. it is L1 ≤ 2.5 · L0, preferably L1 ≤ 2.2 · L0 and with very particular advantage L1 <2 · L0, wherein L0 is determined analogously to the above description.

If, for some reason, only a single range ET _MIN to ET _MAX for the penetration depth is specified or specified for a screw size or cup form, L0 may also be chosen equal to ET _MAX plus a small allowance for tolerance compensation, since in this case length L0 will always be would be suitable.

Moreover, it is clear that the length of the anchoring elements, in the direction of the axis 11 (Fig. 2) measured, should be as small as possible, so as not to hinder the homogeneous pressure distribution during the pressing process. However, since the anchoring elements are arranged on the side of the front parts 1, 1a facing the ram, their length is less critical than that for the lengths L0 and L1. Apart from this, it can be provided if necessary to include the anchoring elements in the measure L1.

What has been explained above with screwdriver inserts with cross-slot profile, applies to screwdriver inserts with other profiles accordingly, z. For hexagon socket, TORX® and Robertson screws. In these screwdriver inserts have the penetration sections in the axial direction in cross-section evenly - in Robertson slightly conical - extending profile. The profile with rounded outlet goes over into a base part. This has the advantage that the cross section of the hard metal tip (the hard metal functional part) in the area in which the torsional forces are effective in use reinforced. The anchoring in the drive part takes place in the same way as has been described in detail above.

For TORX® screws, the minimum lengths L0 of the penetration section are also specified by the manufacturer's standards or other regulations, such as: B. an associated data sheet. The function lengths for the different profile sizes are derived from this, if necessary with a surcharge. Similarly, in other profiles such. B. hexagonal or Robertson profiles. In this case, the penetration sections with outlet can pass into a base section in accordance with the outlet 8, 8a (eg, FIGS.

The application of the invention to TORX® - and other profiles will be explained in more detail with reference to FIGS. 26 to 30.

FIGS. 26 and 27 show, analogously to FIGS. 1 and 2, a front part 58 of a screwdriver insert according to the invention intended for TORX® screws on a much larger scale. The front part 58 is arranged coaxially to a longitudinal or rotational axis 59 and provided at its front end with a penetration portion 60 having a conventional TORX® profile whose wave-shaped course is shown in particular in FIG. 27, and for penetrating into the corresponding Internal profile of a TORX® screw is used. The TORX® profile is characterized by webs 61 and grooves 62 (FIG. 27) which follow one another in the circumferential direction and are parallel to the axis 59, with rounded edges which give the profile an undulating course along an imaginary circle. The TORX® profile is the same throughout the penetration section 60 in the direction of the axis 59 and terminates at a conical, for the purposes of the invention insignificant, flattened end portion 63. At its end remote from the end portion 63 back of the groove bottoms are from a point 64, the defined rearward end of the Eindringabschnitts 60, curved radially outwardly, whereby analogous to the spouts 8,8a an outlet 65 is formed which terminates at a base portion 66 which substantially corresponds to the base portion 9 of FIG. 1 and has a rear end face 67, which is usually perpendicular to the axis 59. An anchoring element 68 projects backwards from the end face 67 in one embodiment, as described in relation to FIGS. 22 to 24.

The basic shape of the front part 58 substantially corresponds to that of the front part 1 according to FIG. 1, for which reason the same lengths L0, L1, LP and LB and the diameter D1 are assigned to it for the purposes of the present invention, as described in detail above with reference to FIG was explained.

According to the invention, a screwdriver insert for TORX® screws according to FIG. 28 from the separately and integrally manufactured front part 58 and a likewise separately produced drive member 69 composed, the z. B. in a section 70 has a conventional hexagonal profile and analogous to Fig. 1 to 27 by means of a Übergangsab-section 71 is connected to the front part 58. The transition section 71 is provided for this purpose with a corresponding anchoring element 72 in the form of a recess formed in its front end surface. The connection of the two anchoring elements 68, 72 is analogous to the above description by gluing, welding, soldering or other connection methods.

The production of the front part 58 is analogous to the Kreuzspitz front parts 1 from a hard metal powder and with the aid of a press tool according to Fig. 8 and 9, the press bushing 20 and optionally Preßmatrize 23 are adjusted accordingly.

To ensure a uniform pressure distribution during the pressing process, the dimension L0 is again as short as possible and preferably measured according to those of the embrasures T which the supplier of the respective TORX® system specifies in a data sheet or the like. In this case, the length L0 is preferably dimensioned at least equal to the predetermined penetration depth, wherein an additional addition for tolerance compensation is expediently added. The length L1 is then measured analogously to the cross tips to a maximum of L1 = 2.5 · L0, preferably a maximum of L1 = 2.2 · L0 and with very particular advantage to L1 <2.0 · L0. This is true regardless of whether the prescribed (minimum) penetration depth T or a slightly greater or a slightly smaller value is used for L0, because for the front part 58 only very short, even with full utilization of the range L1 = 2.5 · L0 give suitable values for the application of the described pressing process.

For example, reference is made to TORX® systems of sizes 15, 20, 30, 40 and 50, for which the manufacturer or supplier specifies minimum penetration depths of 2.16 mm, 2.29 mm, 3.18 mm , 3.30 mm and 4.57 mm, which are to guarantee a sufficiently deep penetration of the TORX® profiles into the screw heads and a transmission of the required torques. According to the invention for these five sizes, the length L0 z. B. to 2.40 mm, 2.50 mm, 3.50 mm, 3.65 mm and 5.05 mm and the length L1 to 4.1 mm, 4.8 mm, 5.8 mm, 6.95 mm and 8.35 mm, in which case the L1 values are well below twice the LO value lie. Very particularly preferred dimensions are shown in FIG. 31.

With regard to the values LP, LB and D1, the same considerations apply as explained above with reference to the Kreuzspitz inserts.

Fig. 29 shows a screwdriver insert for screws with hexagon internal profiles. This differs from the screwdriver insert according to FIGS. 26 to 28 only in that it has a front part 74 with a penetration section 75, which is provided with a conventional hexagonal profile. Incidentally, the various parts are the same, and therefore, in FIG. 29, like parts are provided with the same reference numerals as in FIGS. 26 to 28. An outlet is provided with the reference numeral 76. Also for the sizes L0, L1, etc., the same applies as with screwdriver inserts for TORX® screws, and also with regard to the design of these sizes to achieve an optimum microstructure in the pressing process of FIG. 8 and 9.

30 shows a two-part screwdriver insert having a Robertson-profile front part 77, which has a penetration section 78 with a quadratic square profile, which can be seen from the top view. The front part 77 is connected along an arcuate radially outwardly curved outlet 79 with a base portion which is provided on its rear side with the anchoring element 68 which is inserted into the recess formed as an anchoring element 72 of the drive element 69 preferably made of normal tool steel and fixed therein becomes. Since the arrangement is the same as in FIGS. 28 and 29 except for the penetration section 78, the same reference numerals are again provided to simplify the illustration. It is clear that z. B. the transition portion 71 depending on the shape of the respective Eindringabschnitts 60, 75 and 78 may have different shapes.

With regard to the dimensions L0, L1, etc. (see Fig. 30), the same applies as for the TORX® and hexagonal inserts (see also Fig. 31).

Opposite one-piece, z. As described by injection molding screwdriver inserts (eg, DE 42 41 005 A1), the described two-part design has the advantage that the small front part of carbide press technology and dimensionally accurate to produce and in the plane of the highest torsional stress, ie in the Plane of the front face of the Drive parts, no indentations, which increase the risk of breakage by notch stress. As such indentations z. B. the immediate transitions of the cross bars in the face in the one-piece design to DE 42 41 005 A1.

In principle, the insights gained for the cross-slit profiles also apply to other profiles. Pressing technology, however, profiles are cheaper with a uniform cross-section in the axial direction than the cross slot profiles. Therefore, in the evenly extending profiles, a greater length to diameter ratio is permissible, especially as the diameter of the ejector punches can be made with a round cross-section and / or can be almost equal to the profile diameter. The discharge conditions of Auswerferkraft in the compact are therefore cheaper.

According to the invention will be affected to the extent that should be about 1.0 to 1.2 at Phillips profiles, the ratio L1 / d = ⁰ (Fig. 2), ie L1 and d0 should be approximately the same size. Ratios L1 / d0 (Figures 26, 27) of about 0.9 to 1.4 have been found to be useful in TORX® spouted outlets, ie, L1 may generally be slightly larger than d0. In the case of hexagonal profiles with outlet, favorable ratios of L1 (FIG. 29) to d0 are approximately 1.4 to 1.9, where d0 is the angular dimension according to FIG. 29 in millimeters. Robertson profiles result in favorable front parts with L1 / d0 (Figure 30) from about 1.3 to 1.5, where d0 is again the girth in millimeters (Figure 30).

The invention is not limited to the described embodiments, which can be modified in many ways. This applies initially to the shape of the anchoring elements, whereby the application of two or more anchoring elements per bit would be conceivable if these z. B. would be formed as a plurality of pins.

Further, the described quantities L0, L1, d0, etc. can be dimensioned differently than exemplified above. In particular, the ratios of length to diameter should always be chosen so that the smallest possible circumferential or contact surfaces arise with the pressing tool, so favorable friction conditions and small Auswerferkräfte be obtained. Furthermore, it is not possible to base the design of L0 on the absolutely largest occurring penetration depth. Rather, this could also z. For example, the largest T _MAX / T _MIN range is used and the length L0 is chosen to be a value that is approximately in the middle of that range. Then penetrate the penetration of the largest screws, although not fully, but still sufficiently deep into the recesses of the screw heads to achieve a good fit. Which dimensioning is particularly favorable in the individual case can easily be determined from the above explanations both by calculations and by tests. It turns out that the ratio L1 / d0 should preferably be less than 2.2 and with particular advantage less than 2.0. For inserts with spout even ratios of L1 / d0, which are smaller than 1.5, have proven to be particularly advantageous, the size d0 is bestimnit by the respective associated screw head. Furthermore, the short length L1 according to the invention is advantageous not only in the case of pressing and immediately following sintering, but also in front parts produced by injection molding. As in the pressing process, demoulding by means of an ejector is usually also desired in injection molding, and therefore a reduction of the demolding resistance by reducing the length is expedient. To promote the injection molding process, a proportion of thermoplastic flux (eg wax or plastic) is added to the cemented carbide powder mixture, which is removed from the blank more savagely before sintering. To even out the microstructure of the inserts, the selected grain size composition of the cemented carbide powder mixture has also proved to be important. Grain gradations in the mixture of 0.5 μm to 8 μm are particularly advantageous. Finally, it should be understood that the various features and sizes may be applied in combinations other than those described and illustrated.

Claims (12)

1. Screwdriver bit having a drive section (14, 37, 45, 69) and a front section (1, 1a, 58, 74, 77) of length (L1) which is manufactured by moulding or by injection-moulding and subsequently sintering a hard metal powder (28) and which has a profiled penetrating section (2, 2a, 60, 75, 78) with a profile length (LP), and on its rear side a base section (9, 9a, 41, 47, 66) secured to the drive section (14, 37, 45, 69) and of length (LB), characterised in that the groove bases of the penetrating section (2, 2a, 60, 75, 78) are connected to the base section (9, 41, 47, 60) by a continuation (8, 8a, 42, 65, 76, 79) which is determined during moulding to avoid unfavourable pressure distributions and in each case is curved radially outwards, wherein

   - a length (LA) of the continuation measured in the direction of the longitudinal axis arises from the difference between the profile length (LP) and the length (LO) of the groove bases (6) measured in the direction of the longitudinal axis (11) as far as the continuation,

   - a diameter or width across corners (dO) of the penetrating section is measured in a plane perpendicular to the longitudinal axis (11) which lies at the end of the length (LO) and contains a point (7, 7a or 7b) at which the groove bases (6) merge into the continuation,

   - the size ratio of (L1) to (LO) is between 1.00 and 2.5,

   - the size ratio of (L1) to (dO) is between 0.9 and 2.2, and

   - the length (LB) of the base section is 2.5 mm at the most.
2. Screwdriver bit according to claim 1, characterised in that the base section (9, 41, 47, 66) has a length (LB) of 0.5 mm to 2.5 mm.
3. Screwdriver bit according to claim 1 or 2, characterised in that the penetrating section (2, 2a, 60, 75, 78) has a cross-tip profile, a TORX profile, a hexagonal profile or a Robertson profile and its length (LO), measured up to the continuation (8, 8a, 42, 65, 76, 79), if an associated screw size contains heads (29) having different required or desired penetrating depths (T), is selected as a function of the respectively largest minimum and maximum penetrating depths (T) for that screw size.
4. Screwdriver bit according to one of claims 1 to 3, characterised in that the hard metal powder mixture (28) has a grain size of between 0.5 µm and 8 µm.
5. Screwdriver bit according to one of claims 1 to 4, characterised in that the front section (1, 1a, 58, 74, 77) and the drive section (14, 37, 45, 69) are interconnected by means of bonding, soldering, pressing or welding.
6. Screwdriver bit according to one of claims 1 to 5, characterised in that the facing end surfaces of the front section (1, 1a, 58, 74, 77) and of the drive section (14, 37, 45, 69) are provided with anchoring elements (12, 31 to 34, 36, 38, 48, 49, 52, 53, 68, 72) which engage with each other.
7. Screwdriver bit according to claim 6, characterised in that the anchoring elements (31 to 34, 36, 38, 48, 49, 52, 53, 68, 72) fix the front section (1, 1a, 58, 74, 77) and the drive section (14, 37, 45, 69) so that they cannot be turned relative to one another due to engaging with each other in an interlocking manner.
8. Screwdriver bit according to one of claims 6 or 7, characterised in that the anchoring elements (31 to 34, 36, 38, 48, 49, 52, 53, 56, 68, 72) have non-circular cross-sections.
9. Screwdriver bit according to one of claims 6 to 8, characterised in that the anchoring elements comprise a portion (31, 36, 52) protruding from an end surface of the front section (1) and a recess (32, 37, 53) formed in an end surface of the drive section (14).
10. Screwdriver bit according to one of claims 6 to 8, characterised in that the anchoring elements comprise a portion (34, 38) protruding from an end surface of the drive section (14) and a recess (33, 49) formed in an end surface of the front section (1, 1a).
11. Screwdriver bit according to one or more of claims 1 to 10, characterised in that the anchoring element and the recesses are so matched to one another in respect of form and dimensions that a fixed force-locking and/or interlocking connection for transmitting torques which coaxially centres the two parts is produced by pressing the two parts together.
12. Screwdriver bit according to one of claims 1 to 11, characterised in that the front section (1, 1a, 1b, 58, 74, 77) is produced by compression moulding.

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