Striking-mechanism body, striking mechanism and handheld power tool with a striking mechanism

Abstract

A striking-mechanism body of a handheld power tool at least a first part of the striking-mechanism body, having an impact surface and/or a lateral surface of a first material, and a second part of the striking-mechanism body of a second material, and the first material being more resistant than the second material in terms of at least one material characteristic, the striking-mechanism body being configured as a one-piece steel body so that the first material and the second material are the same, and the first material of the first part body undergoes a heat treatment that differs from that of the second material of the second part of the striking-mechanism body, or the first and the second materials are different, and the first and the second parts are joined together.

Claims

1. A method for manufacturing a striking-mechanism body of a striking mechanism of a handheld power tool having a lateral surface and an impact surface, a pulse transmittable to a pulse-receiving part via the striking mechanism, the striking mechanism body comprising: at least a first part having the impact surface and/or the lateral surface, the first part being made of a first material; and a second part being made of a second material; the striking-mechanism body being configured as a one-piece steel body, the first material and the second material being the same; the method comprising: heat treating the first material of the first part of the striking-mechanism body with a heat treatment differing from that of the second material of the second part of the striking-mechanism body.

2. The method as recited in claim 1 wherein the first and second materials are joined at a joint by an adhesive force.

3. The method as recited in claim 1 wherein the heat treatment of the first part is a heat treatment that is selected from the group consisting of tempering, carburizing, nitriding, nitrocarburizing and combinations thereof.

4. The method as recited in claim 1 wherein the second part is tempered.

5. The method as recited in claim 1 wherein the first part of the striking-mechanism body includes shot blast, pelletized or deep rolled finished steel.

6. The method as recited in claim 1 wherein the first material and/or the second material is a steel that is selected from the group consisting of the following: case-hardened steel, tempered steel, tool steel, and hard steel.

7. The method as recited in claim 6 wherein the hard steel is manganese hard steel.

8. The method as recited in claim 2 wherein the joint is a steel-bonded joint.

9. The method as recited in claim 2 wherein the joint created by adhesive force is a weld joint.

10. The method as recited in claim 9 wherein the weld joint is created by friction-welding.

11. The method as recited in claim 10 wherein the friction welding is linear friction-welding, individual or multi-orbital friction-welding.

12. The method as recited in claim 2 wherein the joint created by adhesive force is a soldered joint.

13. The method as recited in claim 2 wherein the joint created by adhesive force is a glued joint.

14. The method as recited in claim 1 wherein the impact surface comprises a planar head surface and/or the lateral surface comprises a tapered cross-sectional area.

15. The method as recited in claim 1 wherein the striking mechanism body is a striker and/or a striking pin.

16. A striking mechanism comprising; a drive acting to accelerate at least one movable striking-mechanism body manufactured according to the method as recited in claim 1, the striking-mechanism body being configured as a striker and/or as a striking pin.

17. A handheld power tool comprising: a striking mechanism as recited in claim 16; and a shank receiving a pulse from the striking mechanism.

18. The method as recited in claim 1 wherein the first part has a greater hardness than the second part.

19. The method as recited in claim 1 wherein the first part has a lower modulus of elasticity than the second part.

20. The method as recited in claim 1 wherein the first part has a front carburized part and a rear carburized part, the second part being between the front carburized part and the rear carburized part.

21. The method as recited in claim 20 wherein the first part has a further tempered part between the rear carburized part and the second part.

22. The method as recited in claim 1 wherein the second part is not heat treated.

23. The method as recited in claim 1 wherein the second part is heat treated at a lower grade than the heat treatment of the first part.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described on the basis of the drawing. The drawing does not necessarily depict the embodiments true-to-scale, but rather, the drawing is presented in schematic and/or slightly distorted form whenever necessary for the sake of clarity. Regarding additions to the teaching that can be derived directly from the drawing, reference is hereby made to the pertinent state of the art. In this context, it should be taken into account that a wide array of modifications and changes pertaining to the shape and the detail of the embodiment can be made, without deviating from the general idea of the invention. The features of the invention disclosed in the description, in the drawing as well as in the claims, either on their own or in any desired combination, can be essential for the refinement of the invention. Moreover, all combinations of at least two of the features disclosed in the description, in the drawing and/or in the claims fall within the scope of the invention. The general idea of the invention is not limited to the exact shape or details of the preferred embodiment shown and described below, nor is it limited to an object that would be restricted in comparison to the subject matter claimed in the claims. Regarding the dimensional ranges given, values that fall within the cited limits can also be disclosed as limit values and can be employed and claimed as desired. For the sake of simplicity, the same reference numerals will be used below for identical or similar parts or for parts having an identical or similar function.

(2) Additional advantages, features and individual details of the invention ensue from the description below of preferred embodiments as well as from the drawings; these show the following:

(3) FIG. 1: a striking-mechanism body in the form of a striker which, in a first embodiment according to the first variant of the invention, is configured as a one-piece steel body made of identical steel material but partially having undergone different heat treatments;

(4) FIG. 2: a striking-mechanism body in the form of a striking pin which, in a first embodiment according to the first variant of the invention, is configured as a one-piece steel body made of identical steel material but partially having undergone different heat treatments;

(5) FIG. 3: a striking-mechanism body in the form of a striker which, in a second embodiment according to the second variant of the invention, is configured as a one-piece steel body made of two different materials joined by adhesive force;

(6) FIG. 4: a striking-mechanism body in the form of a striking pin which, in a second embodiment according to the second variant of the invention, is configured as a one-piece steel body joined by adhesive force from two different materials.

(7) FIG. 5: a schematic depiction of a handheld power tool having a striking mechanism and a tool, whereby the striking mechanism has a striker and a striking pin according to one of FIGS. 1 to 4.

DETAILED DESCRIPTION

(8) Starting with reference to FIG. 5, it can be seen that said figure schematically shows a handheld power tool 1000 having a striking mechanism 100. The striking mechanism 100, which in the case presented here is configured so as to operate pneumatically, has a schematically depicted drive A. The drive A converts a rotational motion of an electric motor into a back-and-forth motion of a piston 300 which, in turn, acts pneumatically on the striker 10, 30 and causes it to execute a back-and-forth motion. In a guide 50, the striker 10, 30 in turn, transmits its pulse to the striking pin 20, 40 of the striking mechanism 100 via an impact surface not shown in greater detail in FIG. 5. The striking pin 20, 40 transmits its pulse to the shank 200 of the tool W that is held in a receptacle of the tool 1000 not shown in greater detail here.

(9) A first embodiment of the striker 10 and of the striking pin 20 is shown in FIG. 1 and FIG. 2 according to the first variant of the concept of the invention. A second embodiment of the striker 30 and of the striking pin 40 is shown in FIG. 3 and FIG. 4 according to a second variant of the concept of the invention.

(10) Now making reference to FIG. 1, it can be seen that said figure shows a striker 10 having a one-piece steel body 11, which in the case presented here, is made of a tempered steel, although, in another embodiment not shown here, it can also be advantageously made of a case-hardened steel. Here, a front first part 12 of the striking-mechanism body is formed on the striking-pin side and a rear first part 13 of the striking-mechanism body is formed on the drive side, said part comprising a front impact surface 12.1 on the striking-pin side and a rear impact surface 13.1 on the drive side. The thus designated front and rear first parts 12, 13 of the striking-mechanism body here have been carburized within the scope of a partial heat treatment for the steel body 11. This results in a particularly effective hardening of the front or rear impact surface 12.1, 13.1. This is particularly advantageous especially in the case of the front impact surface 12.1 since, when in contact with an associated impact surface of the striking pin 20, it transmits the pulse of the striker 10 to the striking pin 20. Both impact surfaces 12.1, 13.1 are thus highly impact-resistant, resistant to wear and tear, and they are configured with a relatively low modulus of elasticity.

(11) In this context, the material of the thus designated first parts 12, 13 of the striking-mechanism body is configured to be more resistant than the other material of the steel body 11 in a second part 15 of the striking-mechanism body that is adjacent to the part 12 or to the part 13. The latter second part 15 of the striking-mechanism body has not undergone a separate heat treatment, but rather, it is formed out of the tempered steel of the steel body 11, which has not undergone a heat treatment. The embodiment of the striker 10 shown in FIG. 1 has another first part 14 of the striking-mechanism body that is formed adjacent to the rear first part 13 of the striking-mechanism body on the drive side and whose tempered steel of the steel body 11 has been partially heat-treated by means of tempering in the area of the other first part 14 of the striking-mechanism body. Here, too, hardening occurs through carbon diffusion which, however, is not as strong as in the previously mentioned first front and rear parts 12, 13 of the striking-mechanism body. On the contrary, in the other first part 14 of the striking-mechanism body, an especially advantageous toughness predominates for this partial area with its lateral surface 14.1 of the striker 10.

(12) FIG. 2 likewise shows an embodiment of a striking pin 20 that falls under the concept of the first variant of the invention, and this striking pin is configured as a one-piece steel body 21 made of tempered steel, and it has a front first part 22 of the striking-mechanism body on the tool side as well as a rear first part 23 of the striking-mechanism body on the striker side and also another first part 24 of the striking-mechanism body. As is the case with the striker 10, the thus designated first front and rear parts 22, 23 of the striking-mechanism body each have a front and rear impact surface 22.1 and 23.1, and they are carburized within the scope of a partial heat treatment in order to impart the front and rear impact surfaces 22.1 and 23.1 with an especially high degree of hardness. The other first part 24 of the striking-mechanism body is tempered within the scope of another partial heat treatment, and this imparts a relatively high level of toughness to this part 24 of the striking-mechanism body and to the lateral surface 24.1. The other areas of the steel body 21, as second parts 25.1 and 25.2 of the striking-mechanism body, are not heat-treated and they exhibit the usual high-quality properties of a tempered steel. As a result, for the striker 10 and the striking-pin 20, the only first parts 12, 13, 22, 23 or 14, 24 of the striking-mechanism body that are carburized or tempered within the scope of a partial heat treatment are those that actually need to have greater strength or toughness, namely, due to the impact surfaces 12.1, 13.1, 22.1 and 23.1 as well as the lateral surfaces 14.1, 24.1 that are present there. In contrast to this, the areas of a second part 15, 25.1, 25.2 of the striking-mechanism body that are exposed to less stress can make do without an additional resistance-enhancing heat treatment.

(13) In greater detail, the other first part 14 and 24 of the striking-mechanism body on the striker 10 and on the striking pin 20 respectively is provided with a plurality of grooves 16, 26 which, as needed, serve to place a gasket or to guide sonic-pressure amplitudes in a guide chamber 50 for the striker 10, 30 and for the striking pin 20, 40. Particularly, the cross sections of the lateral surfaces 14.1, 24.1 which are tapered by the grooves 16, 26 have diameter transitions and are consequently subject to more stringent requirements in terms of their reverse fatigue strength. In view of the more stringent requirements, the present greater toughness of the other first part 14, 24 of the striking-mechanism body prevents fatigue fractures. Such fractures are caused primarily by notch effects at the above-mentioned diameter transitions of the grooves 16, 26. It has proven to be advantageous to counter the notch effect by means of tempering within the scope of a partial heat treatment, especially at least on the greatly tapered areas of the grooves 16, 26.

(14) In summary, when it comes to the present embodiment which uses tempered steel for the one-piece steel body 11, 21 of the striker 10 or of the striking pin 20, the first parts 12, 13, 22, 23 of the striking-mechanism body are carburized within the scope of a partial heat treatment, while the other parts 14, 24 of the striking-mechanism body are tempered.

(15) All in all, a marked improvement of the service life of the striker 10 and of the striking pin 20 can be expected as a result of the targeted adjustment of the material characteristics as a function of the position, and also of the stress of the parts of the striking-mechanism. The striking mechanism 100, which is configured with a striker 10 and a striking pin 20, permits greater energy densities than the striking mechanisms known so far.

(16) In another embodiment not shown here, the steel body 11, 21 of the striker 10 or of the striking pin 20 can be made of case-hardened steel. In this case, it has proven to be advantageous to more strongly carburize the first parts 12, 13 and 22, 23 of the striking-mechanism body. The other first parts 14, 24 of the striking-mechanism bodyor at least the grooves 16, 26 that are exposed to a greater notch effectshould be carburized to a lesser degree, but at the very least they should be tempered partially more strongly.

(17) In a modification, it is also possible to employ other heat-treatment methods that are associated with diffusion processes such as nitriding or nitrocarburizing at least for the first parts 12, 13, 22, 23 of the striking-mechanism body and, to a lesser extent, for the other first parts 14, 24 of the striking-mechanism body. As a result, greater hardness can be achieved for the former while especially greater toughness can be achieved for the latter. Other surface-finishing methods are likewise possible such as shot blasting, pelletizing, deep rolling or the like for purposes of further partially influencing especially the above-mentioned first parts 12, 13, 22, 24 of the striking-mechanism body.

(18) FIG. 3 and FIG. 4 show second embodiments of a striker 30 or of a striking pin 40. In the case of the striker 30, the part 32, 35 of the striking-mechanism body are made of different materials. In the case of the striking pin 40, the parts 42, 43 of the striking-mechanism body on the one hand, and 44 on the other hand, are made of different materials. In order to create the striker 30 as a one-piece steel body 31, a first part 32 of the striking-mechanism body and a second part 35 of the striking-mechanism body are joined together at a steel-bonded joint 37. When it comes to the striking pin 40, in order to create a one-piece steel body 41, in each case, a steel-bonded joint 47 is created between a first part 42 of the striking-mechanism body and the second part 44 of the striking-mechanism body, or between a first part 43 of the striking-mechanism body and a second part 44 of the striking-mechanism body. The steel-bonded joint 37, 47 is formed here by a multi-orbital friction-welding joint. As a result, the adjacent parts 32, 31, 35 of the striking-mechanism body in the case of the striker 30 and the parts 42, 44, and 43, 44 of the striking-mechanism body in the case of the striking pin 40 are joined to each other in such a way that, on the one hand, a homogenous bond is created over the entire surface, irrespective of the cross section of the joint, and so that, on the other hand, even materials that are difficult to weld can be joined together. In the case here, the multi-orbital friction-welding at the joints 37, 47 also allows the steel-bonded joining of a manganese hard steel as the first material of the first part 32 or 42, 43 of the striking-mechanism body, and a case-hardened steel as the second material of the second part 35 or 44 of the striking-mechanism body.

(19) Even larger components can be joined with relatively low heat input and virtually independently of the joint geometry in the area of the joint 37, 47 by means of multi-orbital friction-welding. This translates into an additional positive influence on the structure properties owing to plastic deformation during friction welding. In the present case, a first part 32, 42, 43 of the striking-mechanism body is made of a first material in the form of manganese hard steel and consequently, it exhibits a particularly favorable combination of cold-hardening capacity and ductility. This causes the first part 32, 42, 43 of the striking-mechanism body of the striker 30 or of the striking pin 40 to have superior strength and resistance to wear and tear, coupled with a high level of ductility, which is especially beneficial for the creation of impact surfaces 32.1, 42.1 and 43.1 that are highly resistant to wear and tear as well as impact-resistant.

(20) A second part 35, 44 of the striking-mechanism body of the striker 30 or of the striking pin 40 is made here of a case-hardened steel. In a modification not shown herein a manner similar to that explained with reference to FIG. 1 and FIG. 2a second part 35, 44 of the striking-mechanism body made of case-hardened steel that serves to increase the toughness on the lateral surfaces 34.1. 44.1 can be tempered within the scope of a partial heat treatment, especially in the area of the grooves 36, 46, which are particularly stressed by notch effects, or else carburized to a small extent in order to increase the toughness in the cited areas.

(21) Altogether, a striker 30 according to the second embodiment of FIG. 3 has a second part 35 of the striking-mechanism body that still has a comparatively high level of reverse fatigue strength with a high density. By the same token, a striker 30 has a first part 32 of the striking-mechanism body that is impact-resistant and resistant to wear and tear with a relatively low modulus of elasticity. Analogously, this holds true for the first parts 42, 43 of the striking-mechanism body or for the second part 44 of the striking-mechanism body of the striking pin 40 of FIG. 4.