Anvil for an impact tool

Abstract

An anvil for an impact tool, the anvil comprising: an impact receiving portion at an end of the anvil, the impact receiving portion comprising a lug having an impact receiving surface that receives an impact from a hammer of a rotating power tool; a handle portion extending from the impact receiving portion; a drive portion located at an end of the handle portion opposite the impact receiving portion, the drive portion including a plurality of drive surfaces configured to engage a tool bit; and a hardened layer formed on at least one of the driving portion or the impact receiving surface, the hardened layer having a higher hardness than a remaining portion of the anvil. The hardened layer is formed by a heating process.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 459,377 filed on April 14, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to power tool components, such as anvils for impact tools. Background Art

[0004] Hardening processes for tool components (e.g., anvils of impact tools) increase the impact strength of the component, but the increase in hardness may result in a reduction in elastic deformation under other non-impact load conditions (e.g., torsion). The reduction in elastic deformation may result in a shortened component life. Current methods for selective hardening of portions of tool components are difficult to control and / or costly due to the need for additional steps to prepare the tool component for hardening. Utility Model Content

[0005] In some aspects, the technology described herein relates to an anvil for an impact tool, the anvil comprising: an impact receiving portion located at an end of the anvil, the impact receiving portion including a lug having an impact receiving surface, the impact receiving surface receiving an impact from a hammer of the impact tool; a shank portion extending from the impact receiving portion; a drive portion located at an end of the shank portion opposite the impact receiving portion, the drive portion including a plurality of drive surfaces configured to engage a tool bit; and a hardened layer formed on at least one of the drive portion or the impact receiving surface, the hardened layer having a higher hardness than the remainder of the anvil, wherein the hardened layer is formed by a heating process.

[0006] In some aspects, the technology described herein relates to an anvil wherein residual compressive stress is added to the hardened layer by a shot peening process.

[0007] In some aspects, the techniques described herein relate to an anvil wherein the peening process is a laser peening process.

[0008] In some aspects, the technology described herein relates to an anvil wherein the residual compressive stresses are added to the hardened layer at a location below the surface of the anvil.

[0009] In some aspects, the technology described herein relates to an anvil wherein the hardened layer is formed on the entire drive portion by the heating process, and wherein the residual compressive stresses are added only at a portion of the drive portion via the shot peening process.

[0010] In some aspects, the technology described herein relates to an anvil in which the residual compressive stresses are added to at least one quarter of the area of ​​each of the drive surfaces.

[0011] In some aspects, the technology described herein relates to an anvil wherein the hardened layer is formed on both the drive portion and the impact receiving surface.

[0012] In some aspects, the technology described herein relates to an anvil wherein the hardened layer does not extend along the shank portion.

[0013] In some aspects, the technology described herein relates to an anvil for an impact tool, the anvil comprising: an impact receiving portion located at an end of the anvil, the impact receiving portion including a lug having an impact receiving surface that receives an impact from a hammer of the impact tool; a shank portion extending from the impact receiving portion; and a drive portion located at an end of the shank portion opposite the impact receiving portion, the drive portion including a plurality of drive surfaces configured to engage a tool bit, wherein at least one of the impact receiving portion or the drive portion includes a region having residual compressive stresses; and wherein the residual compressive stresses are applied to the region by a laser peening process.

[0014] In some aspects, the technology described herein relates to an anvil wherein the zone having residual compressive stress is located below a surface of the anvil.

[0015] In some aspects, the techniques described herein relate to an anvil wherein, in addition to the residual compressive stresses, the zone is treated with a heating process to produce a hardened layer.

[0016] In some aspects, the technology described herein relates to an anvil wherein the drive portion includes the zone, and wherein the hardened layer extends along the entire length of the drive portion.

[0017] In some aspects, the technology described herein relates to an anvil wherein the drive portion includes the zone, and wherein the zone includes a corner of each of the plurality of drive surfaces located closest to the shank.

[0018] In some aspects, the technology described herein relates to an anvil wherein the zone comprises more than one quarter of the entire area of ​​each of the plurality of drive surfaces.

[0019] In some aspects, the technology described herein relates to an anvil wherein the zone includes the entire area of ​​each of the plurality of drive surfaces.

[0020] In some aspects, the techniques described herein relate to an anvil wherein the residual compressive stresses are applied to the zone by performing a shot peening process subsequent to the laser peening process.

[0021] In some aspects, the technology described herein relates to an anvil for an impact tool, the anvil comprising: an impact receiving portion located at an end of the anvil, the impact receiving portion including a lug having an impact receiving surface, the impact receiving surface receiving an impact from a hammer of the impact tool; a shank portion extending from the impact receiving portion; a drive portion located at an end of the shank portion opposite to the impact receiving portion, the drive portion including a plurality of drive surfaces configured to engage a tool bit; and a hardened layer formed on at least one of the drive portion or the impact receiving surface, the hardened layer having a higher hardness than the remainder of the anvil, wherein the hardened layer is formed by a diffusion process.

[0022] In some aspects, the techniques described herein relate to an anvil wherein the remainder of the anvil is masked during the diffusion process.

[0023] In some aspects, the techniques described herein relate to an anvil wherein a remainder of the anvil is ground after the diffusion process.

[0024] In some aspects, the techniques described herein relate to an anvil wherein the diffusion process includes carburizing.

[0025] In some aspects, the techniques described herein relate to an anvil wherein the diffusion process includes nitriding.

[0026] In some aspects, the technology described herein relates to an anvil wherein residual compressive stress is added to the hardened layer by a shot peening process.

[0027] In some aspects, the techniques described herein relate to an anvil wherein the peening process is a laser peening process.

[0028] In some aspects, the technology described herein relates to an anvil wherein the peening process includes a laser peening process and a subsequent shot peening process.

[0029] In some aspects, the techniques described herein involve generating a plasma wave within at least one of the impact-receiving portion or the driving portion.

[0030] In some aspects, the technology described herein relates to a hammer for an impact tool, the hammer comprising: a body; a hammer lug, the hammer lug including an impact surface, the impact surface configured to engage a corresponding impact surface on an anvil of the impact tool and apply an impact to the corresponding impact surface; a transition surface located between the body and the hammer lug; and a hardened layer formed on at least one of the impact surface or the transition surface, the hardened layer having a higher hardness than the rest of the hammer.

[0031] In some aspects, the technology described herein relates to a hammer further comprising a rim protruding from a front surface of the body and surrounding the hammer lug, wherein the hardened layer is formed on an inner surface of the rim.

[0032] In some aspects, the technology described herein relates to a hammer in which residual compressive stress is added to the hardened layer by a laser peening process.

[0033] In some aspects, the technology described herein relates to a hammer wherein residual compressive stress is added to the hardened layer by performing a shot peening process after the laser peening process.

[0034] In some aspects, the technology described herein relates to a hammer wherein the hardened layer is formed by an induction heating process. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a cross-sectional view of a power tool including an impact mechanism having an anvil according to an embodiment of the present disclosure.

[0036] Figure 2 yes Figure 1 Front view of the anvil.

[0037] Figure 3 yes Figure 1 Rear perspective view of the anvil.

[0038] Figure 4 yes Figure 1 Cross-sectional view of anvil.

[0039] Figure 5A yes Figure 1 Front perspective view of an anvil showing the first processed area.

[0040] Figure 5B yes Figure 1 Front perspective view of an anvil showing the second processed area.

[0041] Figure 5C yes Figure 1 Front perspective view of the anvil showing the third warp processing zone.

[0042] Figure 5D yes Figure 1 Front perspective view of the anvil showing the fourth warp processing zone.

[0043] Fig. 6A is a front perspective view of an anvil according to another embodiment of the present disclosure.

[0044] Figure 6B yes Fig. 6A An enlarged view of a portion of the anvil.

[0045] Fig. 7A yes Figure 6B A top view of an enlarged view of a portion of an anvil showing a first processed zone.

[0046] Figure 7B yes Figure 6B A side view of an enlarged view of a portion of an anvil showing a second processed zone.

[0047] Figure 8 is a perspective view of a hammer according to one embodiment of the present disclosure, the hammer being configured to Figure 1 Use with power tools.

[0048] Fig. 9A is a perspective view of a hammer according to another embodiment of the present disclosure, the hammer being configured to Figure 1 Use with power tools.

[0049] Fig. 9B yes Fig. 9A A cross-sectional view of a hammer taken along the center of the hammer.

[0050] Fig. 10A is used for Figure 1 Schematic representation of the first step of the laser peening process of the anvil.

[0051] Fig. 10B yes Fig. 6A Schematic diagram of the second step of the laser peening process.

[0052] Fig. 10C yes Fig. 6A Schematic diagram of the third step of the laser peening process.

[0053] Fig. 10D yes Fig. 6A Schematic diagram of the fourth step of the laser peening process.

[0054] Fig.11 is a first graph that plots data for anvils that have undergone different processing variations.

[0055] Fig.12is a second graph that plots data for anvils that have undergone different processing variations.

[0056] Fig.13 is a third graph that plots data for anvils that have undergone different processing variations. DETAILED DESCRIPTION

[0057] Before explaining any embodiments of the present disclosure in detail, it should be understood that the present disclosure is not limited in its application to the construction details and component arrangements set forth in the following description or shown in the following drawings. The present disclosure is capable of other embodiments and can be practiced or carried out in various ways.

[0058] Figure 1 A power tool 10 is shown, and more specifically, a rotary impact tool, such as an impact wrench. The power tool 10 includes, among other things, a housing 14, a motor 18, a gear assembly 22, a camshaft 26, and an impact mechanism 30. The motor 18 transmits torque to the gear assembly 22 and the camshaft 26 and drives them to rotate. The gear assembly 22 and the camshaft 26 transmit torque to the impact mechanism 30 and drive it to rotate. The impact mechanism 30 has a hammer 34 that is configured to strike an anvil 38 to apply torque on the anvil 38 and provide a torque output for the power tool 10. As such, operation of the power tool 10 may cause fatigue crack initiation, fatigue crack growth, and eventual fracture of the anvil 38 due to repeated strikes of the hammer 34.

[0059] Figure 2 and Figure 3 Anvil 38 is shown including an impact receiving portion 46, a drive portion 58 opposite impact receiving portion 46, and a body or shank 54 extending between impact receiving portion 46 and drive portion 58. The impact receiving portion 46 shown includes a central hole or aperture 42 and a pair of lugs 50. The aperture 42 is formed on a rear side 62 of the impact receiving portion 46 and is sized and positioned to receive and rotationally support a front end ( 60 ) of the camshaft 26 when the power tool 10 is assembled. Figure 1 In other embodiments, the aperture 42 may be omitted, or the aperture 42 may be replaced with a protruding boss that extends into a corresponding aperture in the front end of the camshaft 26 .

[0060] The impact receiving portion 46 includes a back surface 70, a front surface 74, and a peripheral surface 78 extending between the back surface 70 and the front surface 74. The aperture 42 is defined in the back surface 70, and the shank 54 extends from the front surface 74. In the illustrated embodiment, the impact receiving portion 46 includes two lugs 50 that extend away from the aperture 42 and the shank 54 in a direction perpendicular to the direction of extension of the shank 54. In other words, the lugs 50 are diametrically spaced apart from each other relative to the aperture 42 so that the lugs 50 extend away from each other. The lugs 50 are configured to receive an impact (i.e., torque transmission) from the hammer 34, and the anvil 38 transmits the impact (i.e., torque) to the drive portion 58 through the shank 54.

[0061] refer to Figure 2 , the peripheral face 78 of the impact receiving portion 46 includes an end portion 78a defined at the distal end of each lug 50, an impact receiving surface 78b extending from the end portion 78a, a transition surface 78c extending from the impact receiving surface 78b, and a central portion 78d. In some embodiments, the impact receiving surface 78b can have an involute profile and is configured to be directly struck by the hammer 34 during operation of the power tool 10. In the illustrated embodiment, the central portion 78d has a constant radius, and the transition surface 78c provides a smooth transition between the impact receiving surface 78b and the central cylindrical portion 78d. In the illustrated embodiment, the concavity of the peripheral face 78 changes at the transition surface 78c.

[0062] refer to Figures 2 to 3 , the illustrated drive portion 58 includes a step 86, a body portion 87, a plurality of chamfers 90, a plurality of drive surfaces 94, a plurality of transition surfaces 96, and a flange 98. The step 86 extends from the shank 54 and converges radially inward to the body portion 87. In some embodiments, the shank 54 and the body portion 87 can each have a constant diameter, wherein the diameter of the body portion 87 is less than the diameter of the shank 54. In some embodiments, the shank 54 and / or the body portion 87 can include one or more grooves 55.

[0063] The drive surfaces 94 are formed as planar surfaces that, in some embodiments, may be machined into the body portion 87. Each drive surface 94 is perpendicular to its adjacent drive surface 94 such that the drive surfaces 94 define a square drive portion that is configured to receive a square drive tool bit, such as a socket wrench or the like. Thus, in the illustrated embodiment, the drive portion 58 includes four drive surfaces 94. A transition surface 96 is formed at the rear (proximal) end of the drive surfaces 94 and curves outwardly toward the body portion 87 to transition between the square cross-sectional shape defined by the drive surfaces 94 and the circular cross-sectional shape defined by the body portion 87. In other embodiments, the drive surfaces 94 may have other geometries to engage other types of tool bits.

[0064] Continue to refer Figures 2 to 3 , chamfers 90 (which may be unmachined portions of body portion 87) extend between adjacent drive surfaces 94 and interconnect them. In the illustrated embodiment, rounded end surfaces 102 are formed at the front (distal) ends of chamfers 90 and drive surfaces 94. A groove 103 is defined between the rounded end surface 102 and flange 98. The groove 103 is configured to receive a ring (e.g., a rubber o-ring; not shown). The ring may engage the interior of an attached tool bit to provide increased friction, thereby retaining the tool bit on drive portion 58. In other embodiments, one or more of the drive surfaces 94 may include a hole configured to receive a locking pin (e.g., a ball locking pin) to retain the tool bit on drive portion 58. In such embodiments, flange 98 and groove 103 may be omitted.

[0065] During operation of the power tool 10, the anvil 38 is subjected to repeated, localized, high-magnitude forces. Some portions of the anvil 38, such as the impact receiving surface 78b and the drive portion 58, may benefit from high hardness to provide increased strength and wear resistance, and from high residual compressive stresses to increase resistance to fatigue crack initiation. Other portions of the anvil 38 may benefit from lower hardness to provide increased toughness. Accordingly, it is desirable for the anvil 38 to have different material properties in different regions of the anvil 38.

[0066] Figure 4 38 is shown in cross section. The anvil 38 has a first zone A having a length from the front end 105 of the anvil 38 to the end surface 102 along the rotation axis X of the anvil 38. The anvil 38 has a second zone B having a length from the end surface 102 to the transition surface 96 along the rotation axis X of the anvil 38. The second zone B thus includes the drive surface 94. The anvil 38 further has a third zone C having a length spanning the transition surface 96 along the rotation axis X of the anvil 38. Finally, the anvil 38 has a fourth zone D having a length from the rear end of the transition surface 96 toward the step 86 along the rotation axis X of the anvil 38. In some embodiments, the fourth zone D may span the entire length between the transition surface 96 and the step 86. In other embodiments, the length of the fourth zone D may be less than the length between the transition surface 96 and the step 86. In the illustrated embodiment, the length of the second zone B is greater than the length of the first zone A, the length of the first zone is greater than the length of the fourth zone D, and the length of the fourth zone is greater than the length of the third zone C.

[0067] Continue to refer Figure 4, the anvil 38 shown has a core 107 and a hardened layer 109 surrounding the core 107. In the embodiment shown, the hardened layer 109 has a thickness T and extends to the length of each of the second zone B, the third zone C, and the fourth zone D. In each of the zones B, C, and D, the thickness T can be substantially uniform. Alternatively, the thickness T can vary (for example, the thickness T can be greater in zone B than in zones C and D, etc.). In some embodiments, in each of the zones B, C, and D, the thickness T can be between 0.7 mm and 2.0 mm. In some embodiments, in each of the zones B, C, and D, the thickness T can be between 1.0 mm and 1.5 mm.

[0068] The anvil 38 can be formed as a whole body by a single type of material. For example, in some embodiments, the anvil 38 can be formed via a forging process. In other embodiments, the anvil 38 can be formed via a casting or powder metal (PM) manufacturing process. The anvil 38 can be made of hardenable steel. For example, in some embodiments, the anvil 38 can be made of medium carbon steel. In other embodiments, the anvil 38 can be made of tool steels such as S7, H13, YXR33, CMP3V, A9, etc. The hardness of the core 107 is lower than the hardness of the hardened layer 109. For example, in some embodiments, the core 107 can have a hardness of 35 to 54HRC, and the hardened layer 109 can have a hardness of 55 to 62HRC. This provides high toughness for the core 107 to reduce the possibility of fracture. The hardened layer 109 provides high strength and wear resistance on the portion of the anvil 38 that may contact the tool bit. In some embodiments, the lug 50 may also include a hardened layer, which may have the same or similar properties as the hardened layer 109. The hardened layer on the lug 50 provides high strength and wear resistance on the portion of the anvil 38 that contacts the hammer 34 .

[0069] Figure 5A A first region 110a of the anvil 38 is shown that can be locally hardened (e.g., to form a hardened layer 109 in the first region 110a) via the process described herein. In the illustrated embodiment, the first region 110a includes only the impact receiving surface 78b of the peripheral face 78 of each lug 50. That is, in some embodiments, the first region 110a does not include the end portion 78a, the transition surface 78c, or the central portion 78d. Because only the impact receiving surface 78b is contacted by the hammer 34, the remainder of the lug 50 can have a lower hardness to provide improved toughness to the lug 50. In other embodiments, the first region 110a can extend into the end portion 78a and / or the transition surface 78c.

[0070] Figure 5BA second region 110b of the anvil 38 is shown that can be locally hardened (e.g., to form a hardened layer 109 in the second region 110b) via the processes described herein. In the illustrated embodiment, the second region 110b includes the body portion 87, the chamfer 90, the drive surface 94, the transition surface 96, and the end surface 102. In the illustrated embodiment, the second region 110b does not include the flange 98, the step 86, or the shank 54. The second region 110b corresponds to surfaces of the drive portion 58 that can engage with a tool bit or another type of workpiece when the tool bit or another type of workpiece is coupled to the anvil 38. The drive surface 94 can be subject to high compressive and tensile stresses, and the transition surface 96 can be subject to high stress concentrations due to its geometry and axial shock loads that can occur if the end of the tool bit is pressed against the transition surface 96. The hardening of the body portion 87 and the end surface 102 can promote a more uniform hardening of the drive surface 94 and the transition surface 96, so that the thickness T of the hardened layer 109 is substantially uniform ( Figure 4 ). In the illustrated embodiment, the flange 98 is not subjected to surface hardening, so that the flange 98 remains part of the softer core 107. Because the flange 98 is relatively thin and defines the front end 105 of the anvil 38, if the flange 98 has the high hardness of the hardened layer 109 and the power tool 10 is dropped, the flange will be more easily broken. During working operation, the maximum stress of the anvil 38 partially hardened at the second area 110b is reduced by about 30%.

[0071] Figure 5C A third region 110c of the anvil 38 is shown, which can be locally hardened via the process described herein (e.g., to form a hardened layer 109 in the third region 110c). The third region 110c includes a portion of each of the chamfers 90, a portion of each of the drive surfaces 94, and a transition surface 96. In the illustrated embodiment, a portion of each of the chamfers 90 included in the third region 110c is greater than one quarter of the total area of ​​the chamfers 90 but less than one half of the total area. Additionally, a portion of each of the drive surfaces 94 included in the third region 110c is at least one quarter of the total area of ​​the drive surfaces 94 but less than one half of the total area. The third region 110c does not include the body portion 87, the flange 98, the step 86, or the shank 54. During working operation, the maximum stress of the anvil 38 locally hardened at the third region 110c is reduced by approximately 16.5%.

[0072] Figure 5DA fourth region 110d of the anvil 38 is shown that can be locally hardened via the process described herein (e.g., to form a hardened layer 109 in the fourth region 110d). In the illustrated embodiment, the fourth region 110d includes the area where the body portion 87, the chamfer 90, the drive surface 94, and the transition surface 96 meet. In other words, the fourth region 110d includes the corners of each of the square drive surfaces 94 and a portion of each of the body portion 87, the chamfer 90, and the transition surface 96 that is adjacent to the corner of the drive surface 94. During working operation, the maximum stress of the anvil 38 locally hardened at the fourth region 110d is reduced by approximately 12.2%.

[0073] Fig. 6A and Figure 6B Anvil 238 is shown in accordance with another embodiment of the present disclosure. Anvil 238 may be substantially similar to Figure 2 and Figure 3 The anvil 38. like Fig. 6A and Figure 6B As shown, the anvil 238 includes an impact receiving portion 246, a drive portion 258 opposite the impact receiving portion 246, and a body or handle 254 extending between the impact receiving portion 246 and the drive portion 258. In the illustrated embodiment, the anvil 238 is formed as a pin-lock anvil; however, the anvil 238 may alternatively be formed as a ball-lock anvil, or an anvil having another type of bit retention interface.

[0074] The impact receiving portion 246 includes a back surface 270, a front surface 274, and a peripheral surface 278 extending between the back surface 270 and the front surface 274. Figure 3 The aperture 42 of the anvil 238 may define a central hole or aperture in the back face 270 to facilitate coupling with the camshaft. The impact receiving portion 246 includes two lugs 250 extending away from the shank 254 in a direction perpendicular to the extension direction of the shank 254. The lugs 250 are configured to receive an impact (i.e., torque transfer) from the hammer, and the anvil 238 transfers the impact (i.e., torque) to the driving portion 258 through the shank 254. In some embodiments, the lugs 250 may have an involute profile.

[0075] The illustrated drive portion 258 includes a step 286, a body portion 287, a plurality of chamfers 290, a plurality of drive surfaces 294, a plurality of transition surfaces 296, and an end surface 302. The step 286 extends from the shank 254 and converges radially inward to the body portion 287. In some embodiments, the shank 254 and the body portion 287 can have a constant diameter, wherein the diameter of the body portion 287 is less than the diameter of the shank 254. In some embodiments, the shank 54 and / or the body portion 287 can include one or more grooves.

[0076] The drive surfaces 294 are formed as planar surfaces, which in some embodiments can be machined into the body portion 287. Each drive surface 294 is perpendicular to its adjacent drive surface 294, so that the drive surfaces 294 define a square drive portion that is configured to receive a square drive tool bit, such as a socket wrench, etc. Thus, in the illustrated embodiment, the drive portion 258 includes four drive surfaces 294. A locking pin receiving portion 304 is formed or defined in one of the drive surfaces 294, and a pin receiving portion 306 is formed or defined in the drive surface 294 adjacent to the drive surface 294 including the locking pin receiving portion 304. The locking pin receiving portion 304 is configured to receive a locking pin 304a to facilitate coupling with a tool bit or another type of workpiece. The pin receiving portion 306 is configured to receive a pin 306a that fixes the locking pin 304a relative to the anvil 238. Thus, the locking pin receiving portion 304 and the pin receiving portion 306 are in fluid communication. A transition surface 296 is formed at the rear (proximal) end of the drive surface 294 and curves outwardly toward the body portion 287 to transition between the square cross-sectional shape defined by the drive surface 294 and the circular cross-sectional shape defined by the body portion 287. In other embodiments, the drive surface 294 may have other geometries to engage other types of tool bits.

[0077] Continue to refer Fig. 6A and Figure 6B , chamfer 290 (which may be an unmachined portion of body portion 287) extends between adjacent drive surfaces 294 and connects them to each other. In the illustrated embodiment, chamfer 290 extends to end surface 302. End surface 302 is oriented perpendicular to the direction of extension of shank 254. Thus, transition collar 308 connects chamfer 290 and end surface 302. Specifically, transition collar 308 bends from chamfer 290 to end surface 302.

[0078] During operation of the power tool, the anvil 238 is subjected to repeated, localized, high magnitude forces. Some portions of the anvil 238, such as the drive portion 258, may benefit from high hardness to provide increased strength and wear resistance, and from high residual compressive stresses to increase resistance to fatigue crack initiation. Specifically, the areas surrounding the lock pin receiving portion 304 and the pin receiving portion 306 may be subjected to variable high stresses due to the movement of the lock pin 304a and the pin 306a within the lock pin receiving portion 304 and the pin receiving portion 306, respectively.

[0079] Fig. 7AA first region 310a of the anvil is shown, which can be locally hardened (e.g., to form a hardened layer in the first region 310a) via the processes described herein. In the illustrated embodiment, the first region 310a includes a drive surface 294 that forms or defines a lock pin receiving portion 304 and a transition surface 296 adjacent to the drive surface 294 that forms the lock pin receiving portion 304. Specifically, the first region 310a includes a band along each of the edges of the drive surface 294 that extends parallel to the extension direction of the handle 254. These bands extend from the transition surface 296 adjacent to the drive surface 294 that forms the lock pin receiving portion 304 to an area of ​​the drive surface 294 adjacent to the transition collar 308.

[0080] Figure 7B A second region 310b of the anvil 238 is shown that can be locally hardened (e.g., to form a hardened layer in the second region 310b) via the processes described herein. In the illustrated embodiment, the second region 310b includes the drive surface 294 that forms or defines the pin receiving portion 306 and the transition surface 296 adjacent to the drive surface 294 that defines the pin receiving portion 306. Specifically, the second region 310b includes the entire transition surface 296 adjacent to the drive surface 294 that forms the pin receiving portion 306 and the entire drive surface 294 that forms the pin receiving portion 306, except for the region 294a of the drive surface 294 that directly surrounds the pin receiving portion 306. The region 294a of the drive surface 294 that directly surrounds the pin receiving portion 306 may be curved or chamfered and, therefore, may not be suitable for local hardening. Although the first and second regions 310a, 310b of the anvil 238 are described separately, it should be understood that the anvil 238 may be locally hardened at both the first and second regions 310a, 310b via the processes described herein. For example, the entire drive portion 258 may be locally hardened.

[0081] Figure 8A hammer 434 according to one embodiment of the present disclosure is shown. The hammer 434 includes a body 438 and a hammer lug 442 protruding from a front surface 438a of the body 438. The body 438 defines a mounting aperture 446 configured to receive a camshaft for slidably mounting the hammer 434 to the camshaft. The hammer lug 442 includes impact surfaces 450 configured to engage and impact corresponding impact surfaces on an anvil. A transition surface 454 is disposed between the front surface 438a of the body 438 and each of the hammer lugs 442. Specifically, the transition surface 454 is disposed between the front surface 438a and each of the impact surfaces 450 on each of the hammer lugs 442. In some embodiments, the transition surface 454 may form a groove that undercuts the lug 442 and the front surface 438a of the body 438.

[0082] Continue to refer Figure 8 , the first region 510a of the hammer 434 can be locally hardened (e.g., to form a hardened layer in the first region 510a) via the processes described herein. In the illustrated embodiment, the first region 510a includes the impact surface 450 of each of the hammer lugs 442. The second region 510b of the hammer 434 can additionally or independently be locally hardened (e.g., to form a hardened layer in the second region 510b) via the processes described herein. The second region 510b includes a transition surface 454 positioned between the front surface 438a of the body 438 and the hammer lugs 442. The impact surface 450 of the hammer lugs 442 may be subject to high compressive and tensile stresses, and the transition surface may be subject to high stress concentrations due to its geometry. In this way, the first region 510a and the second region 510b can be hardened individually or in combination via the processes described herein to offset the respective stresses.

[0083] Fig. 9A and Fig. 9BA hammer 634 according to another embodiment of the present disclosure is shown. The hammer 634 includes a body 638 and a rim 642 protruding from a front surface 638a of the body 638 and positioned around the periphery of the body 638. The body 638 defines a mounting aperture 646 configured to receive a camshaft for slidably mounting the hammer 634 thereon. The body 638 additionally defines a spring receiver 650 on a rear surface 638b of the body 638 and a recess or groove 654 in a front surface 638a of the body 638. The spring receiver 650 is configured to receive a hammer spring. The groove 654 slopes from the front surface 638a of the body 638 into the aperture 646. The end surface 650a of the spring receiver 650 and the sloped surface 654a of the groove 654 are disposed adjacent to each other such that a relatively narrow portion 658 of the body 638 extends between the spring receiver 650 and the groove 654. The rim 642 includes hammer lugs 662 that protrude inwardly from the outer periphery of the body 638. The hammer lugs 662 include impact surfaces 666 that are configured to engage and impact corresponding impact surfaces on the anvil. In the illustrated embodiment, the impact surfaces 666 on the hammer lugs 662 are formed such that each of the hammer lugs 662 has an involute profile.

[0084] Fig. 9A A first region 710a of the hammer 634 is shown that can be locally hardened (e.g., to form a hardened layer in the first region 710a) via the processes described herein. In the illustrated embodiment, the first region 710a includes the inner surface 642a of the rim 642. As such, the first region 710a includes the impact surface 666 of each of the hammer lugs 662 and the portion of the inner surface 642a of the rim 642 that connects the hammer lugs 662 together. The impact surfaces 666 of the hammer lugs 662 can be subject to high compressive and tensile stresses, and the portion of the inner surface 642a of the rim 642 that connects the hammer lugs 662 can be subject to radial forces generated by the involute hammer lugs 662. As such, the impact surfaces 666 and the portion of the inner surface 642a of the rim 642 that connects the hammer lugs 662 can be hardened via the processes described herein to counteract the corresponding stresses and forces.

[0085] Fig. 9BA second region 710b of the hammer 634 is shown, which can be locally hardened (e.g., to form a hardened layer in the second region 710b) via the processes described herein. In the illustrated embodiment, the second region 710b includes the end surface 650a of the spring receiving portion 650 and the inclined surface 654a of the groove 654. In other words, the second region 710b includes the outer surface of the relatively narrow portion 658 of the body 638. In some cases, increasing the depth of the hardened surface layer of the hammer 634 (i.e., the distance between the front end of the edge 642 and the front surface of the body 638) can be beneficial to the operation of the hammer 634. Increasing the depth of the hardened surface layer may reduce the size of the relatively narrow portion 658 of the body 638 between the spring receiving portion 650 and the groove 654, thereby increasing the risk of fracture of the relatively narrow portion 658. In this way, the second region 710b of the hammer 634 can be advantageously hardened to reduce fracture along the end surface 650a of the spring receiving portion 650 and along the inclined surface 654a of the groove 654.

[0086] The following is a description of the process for forming a hardened layer in the anvil 38, 238 and / or hammer 434, 634 described herein. Figures 1 to 3 However, it should be understood that these processes can also be applied to Fig. 6A The anvil 238, Figure 8 Hammer 434, and / or Fig. 9A During manufacturing, the anvil 38 undergoes one or more treatment processes to form a hardened layer 109 in the first region 110a and / or the second region 110b. These treatment processes can be localized so as to target and harden only desired portions of the anvil 38 while leaving other portions of the anvil 38 with a lower hardness to increase toughness.

[0087] In one embodiment, the anvil 38 is carburized to form a hardened layer 109. During carburization, the anvil 38 is heated in a high carbon atmosphere. The exposed surface of the anvil 38 absorbs carbon from the high carbon atmosphere, which increases the carbon content of the steel in the anvil 38 (and therefore increases its hardness) to form a hardened layer 109 (after the anvil 38 is quenched). Before carburization, a protective mask material (in some embodiments, the protective mask material may include a coating or tape) may be applied to portions of the anvil 38 to prevent the formation of a hardened layer 109 in these portions. For example, a protective mask material may be applied to the anvil in addition to the first region 110a and the second region 110b. Therefore, during the carburization process, only the first region 110a and the second region 110b absorb carbon. In other embodiments, the anvil 38 may additionally or alternatively undergo a nitriding process or other diffusion hardening process to form a hardened layer 109. In such an embodiment, a similar protective mask material may be applied to protect portions of the anvil 38 other than the first region 110a and the second region 110b. In other embodiments, portions of the anvil 38 may be ground after the diffusion hardening process to selectively remove the hardened layer from areas where a lower surface hardness is desired.

[0088] In other embodiments, the anvil 38 is locally hardened via a heating process to form the hardened layer 109. For example, in some embodiments, the first region 110a and the second region 110b of the anvil 38 are locally heated via induction. After being heated by induction, the first region 110a and the second region 110b can be quenched to maintain a higher percentage of martensite, thereby providing a higher hardness. In other embodiments, the first region 110a and the second region 110b of the anvil 38 are locally heated via one or more lasers. Compared with induction heating, the laser can more accurately target the complex geometries of the first region 110a and the second region 110b of the anvil 38. In addition, laser hardening can eliminate the need for a separate quenching step because the locally heated area is small compared to the remaining volume of the anvil 38. Therefore, the anvil 38 acts as a heat sink to quickly dissipate the heat applied by the laser, thereby providing a self-quenching function that maintains a higher percentage of martensite.

[0089] In some embodiments, the anvil 38 may additionally or alternatively undergo one or more surface processing steps instead of or in addition to the local hardening step. In some embodiments, the surface processing step may include a peening process (such as a shot peening process), which may produce residual compressive stresses on the outer surface of the anvil 38. In some embodiments, the anvil 38 is peened via a targeted laser peening process in specific locations (e.g., areas 110a, 110b). In some embodiments, the anvil 38 is not only subjected to a laser peening process but is subsequently subjected to a shot peening process.

[0090] refer to FIG. 10A to FIG. 10D The laser peening process generates residual compressive stresses in specific target areas on the anvil 38 to modify the mechanical properties of the metal at the target areas 110a, 110b on the anvil 38, such as improving fatigue resistance.

[0091] like Fig. 10A As shown, the laser peening process includes providing a laser pulse 806 at the target region 110a, 110b. The laser pulse 806 generates a plasma shock wave that applies pressure to the metal at the target region 110a, 110b, thereby introducing strain, shock waves and / or dislocations into the microstructure of the anvil 38 at the target region 110a, 110b. Specifically, referring to Fig. 10B , the plasma shock mechanically modifies the metal at the target regions 110a, 110b from a first state 814a to a second state 814b. Fig. 10C As shown, in the second state 814b, the target areas 110a, 110b are pushed upward against surrounding areas of the anvil 38 that are not targeted during the laser peening process. Fig. 10D , the surrounding area then elastically recovers to adapt around the metal at the target area 110a, 110b. Therefore, a tensile stress S1 is generated in the surrounding area of ​​the anvil 38, and the surrounding area of ​​the anvil 38 also provides a residual compressive stress S2 on the target area 110a, 110b. The net force provided by these stresses S1, S2 helps to reduce the net internal stress, thereby extending the life of the anvil 38 by providing resistance to fatigue cracking and crack propagation.

[0092] A cooling fluid, such as water, may flow through the anvil 38, and more specifically, through the target areas 110a, 110b, while the laser peening process is being performed. The introduction of water into the laser peening process helps maintain the plasma in place to form the compressive stress S2. Tape may also be applied to the outer surface of the anvil 38 while the laser peening process is being performed. A layer of tape provides an opaque surface for the anvil 38 that amplifies the peening effect to assist in forming stress in the anvil 38.

[0093] Laser shot peening process ( FIG. 10A to FIG. 10D ) is superior to similar anvil 38 forming processes, such as shot peening or laser ablation, because the laser pulse ( Fig. 10A ) can penetrate deeper into the metal, can be provided at higher powers and for longer durations, and can target more precise areas (i.e., target areas 110a and 110b). For example, the laser peening process may be able to produce residual compressive stresses 1 mm to 12 mm below the metal surface, while other processes may only be able to impact the surface of the anvil 38. The residual compressive stress S2 ( Fig. 10D ) offsets the possible Figure 1) during operation. Additionally, the laser pulses can target a specific spot size of approximately 1 mm on the anvil 38. Thus, the laser peening process enables a user or manufacturer to successfully create very fine residual stress regions in and / or on the anvil 38, thereby improving the anvil 38 ( Figure 2 )’s wear resistance and extends overall life.

[0094] Therefore, in order to manufacture the anvil 38, a material blank (e.g., medium carbon steel, tool steel, etc.) is processed via a metal forming step (e.g., forging, casting, PM manufacturing process, etc.) to form the overall shape of the anvil 38. The anvil 38 can then be machined to form the drive surface 94, the transition surface 96, the groove 103, and / or other features of the anvil 38. After machining, the anvil 38 can undergo a combination of hardening processes. For example, the anvil 38 can first undergo carburizing to increase the carbon content of the anvil 38, thereby causing a subsequent hardening process to produce greater residual stresses. Thus, if the anvil 38 is carburized, the carburizing must be performed before the subsequent local surface hardening process to obtain the benefits of the increased carbon content in the anvil. In the illustrated embodiment, the ideal carbon content of the anvil 38 can be 0.3% or higher.

[0095] After carburizing, a local surface hardening process (e.g., a diffusion surface hardening process, a laser heating process, or an induction heat treatment process as described above) may then be performed to form a hardened layer 109 ( ) having a higher hardness relative to the remaining core 107 of the anvil 38. Figure 4 ). Specifically, refer to Figure 4 , each of the zones A, B, C, and D can undergo a localized surface hardening process (e.g., induction hardening). By treating each of the zones A, B, C, and D, the induction hardening process has a greater tolerance for inaccuracies to ensure that the transitions between zones of different shapes, where stresses may be highest, are induction hardened.

[0096] After forming the hardened layer 109, the anvil 38 may undergo additional processes such as laser peening to form residual compressive stresses in the target areas 110a, 110b, 110c, 110d and / or other desired areas of the anvil 38, and in some embodiments, subsequently undergo a shot peening process. The resulting anvil 38 may combine high toughness and high wear resistance in appropriate areas to extend the life of the anvil 38 and allow the anvil 38 to transmit a greater amount of torque.

[0097] The process described herein with respect to the anvil 38 may also be applied to other power tool components, such as the hammer 34 (e.g., Figure 8 Hammer 434 and / or Fig. 9AThe hammer 34 of the camshaft 26 can be partially hardened and / or machined to add residual compressive stresses to improve the wear resistance and fatigue crack resistance of the hammer 34 using the methods described herein. In some embodiments, the camshaft 26 and the hammer 34 each include cam grooves that receive balls that couple the hammer 34 to the camshaft 26. In such embodiments, the grooves in the camshaft 26 and / or the hammer 34 can be locally hardened to improve wear resistance using the methods described herein. In other embodiments, other power tool components with complex geometries and thin features that may otherwise be susceptible to through-hardening and brittleness when subjected to conventional hardening or treatment processes can be manufactured according to the methods described herein.

[0098] Figures 11 to 13 Graphs 1010, 1110, 1210 are shown that include graphs of data for anvils that have undergone various hardening processes. Specifically, each of the graphs 1010, 1110, 1210 plots residual compressive stress of an anvil versus depth from the outer surface of the anvil.

[0099] Fig.11 A first graph 1010 is shown. The first graph 1010 includes a first line 1012, a second line 1014, and a third line 1016. The first line 1012 shows the stress-depth relationship of an anvil that has undergone shot peening. The second line 1014 shows the stress-depth relationship of an anvil that has not undergone shot peening. The third line 1016 shows the stress-depth relationship of an anvil that has undergone shot peening and induction heat treatment. Fig.11 As shown, an anvil that has undergone shot peening and induction heat treatment, as shown by the third line 1016, has a higher maximum residual compressive stress and a higher residual compressive stress at the surface than an anvil that has undergone shot peening, as shown by the first line 1012, and an anvil that has not undergone shot peening, as shown by the second line 1014. Therefore, the first graph 1010 shows that combining shot peening and induction heat treatment of an anvil can advantageously increase the residual compressive stress of the anvil.

[0100] Fig.12 A second graph 1110 is shown. The second graph 1110 includes a first line 1112, a second line 1114, a third line 1116, a fourth line 1118, and a fifth line 1120. The first line 1112 shows the stress-depth relationship of an anvil that has been carburized and shot peened. The second line 1114 shows the stress-depth relationship of a carburized anvil that has not been shot peened. The third line 1116 shows the stress-depth relationship of an anvil that has not been shot peened but has been shot peened. Figure 5CThe stress-depth relationship of a carburized anvil that has been laser peened at a third region 110c of the anvil is shown. The fourth line 1118 shows the stress-depth relationship of a carburized anvil that has not been shot peened but has been laser peened at a third region 110c of the anvil. Figure 5B The stress-depth relationship of a carburized anvil that has been laser peened in the second region 110b of the anvil is shown. The fifth line 1120 shows the stress-depth relationship of a carburized anvil that has not been shot peened but has been laser peened in the second region 110b of the anvil. Figure 5D The stress-depth relationship of a carburized anvil subjected to laser peening is shown in a fourth region 110d of the anvil.

[0101] Continue to refer Fig.12 , anvils that have undergone shot peening, as illustrated by the first line 1112, have much greater residual compressive stresses than each of the anvils that have not undergone shot peening at the surface of the anvil (i.e., the second line 1114, the third line 1116, the fourth line 1118, and the fifth line 1120). Thus, the second graph 1110 illustrates the benefits of shot peening in situations where high residual compressive stresses are desired at the surface of the anvil. The second graph 1110 also illustrates the benefits of laser peening in situations where higher residual compressive stresses are desired below the surface of the anvil, regardless of where the laser peening is performed. Specifically, the third line 1116, the fourth line 1118, and the fifth line 1120, representing anvils that have undergone laser peening, each have higher residual compressive stresses at a depth of about 0.1 mm or more from the surface than the anvils represented by the first line 1112 and the second line 1114 that have not undergone laser peening.

[0102] Fig.13 A third graph 1210 is shown. The third graph 1210 includes a first line 1212, a second line 1214, a third line 1216, and a fourth line 1218. The first line 1212 shows the stress-depth relationship of an anvil that has undergone shot peening and induction heat treatment. The second line 1214 shows the stress-depth relationship of an anvil that has undergone shot peening and induction heat treatment and has been Figure 5C The stress-depth relationship of an anvil that has been laser peened at a third region 110c of the anvil is shown. The third line 1216 shows the stress-depth relationship of an anvil that has been laser peened at a third region 110c of the anvil. Figure 5D The stress-depth relationship of an anvil that has been laser peened at a fourth region 110d of the anvil is shown. The fourth line 1218 shows the stress-depth relationship of an anvil that has been shot peened and induction heat treated and has been laser peened at a fourth region 110d of the anvil. Figure 5B The stress-depth relationship of an anvil subjected to laser peening is shown at a second region 110b of the anvil.

[0103] The third graph 1210 illustrates the benefits of laser peening at various target areas 110b, 110c, 110d. Specifically, as illustrated by the third line 1216, at the fourth area 110d ( Figure 5D) can cause the anvil to have a relatively high residual compressive stress between the surface of the anvil and approximately 0.35 mm from the surface. However, at a depth greater than 0.35 mm, the anvil represented by the third line 1216 begins to have a relatively low residual compressive stress. Thus, in different situations, different combinations of localized heat treatment processes and target areas for laser peening may be desired. That is, for any given work operation, the optimal combination of hardening processes can be determined based on the depth at which the highest stresses occur. In addition, including a shot peening strengthening process after the laser peening process can advantageously provide high residual compressive stresses both at the treated surface of the anvil and below the treated surface of the anvil.

[0104] Although the disclosure has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of one or more independent aspects of the disclosure described.

[0105] Various features and aspects of the disclosure are set forth in the following claims.

Claims

1. An anvil for an impact tool, the anvil comprising: an impact receiving portion located at an end of the anvil, the impact receiving portion including a lug having an impact receiving surface that receives an impact from a hammer of the impact tool; a handle portion extending from the impact receiving portion; a drive portion at an end of the shank portion opposite the impact receiving portion, the drive portion including a plurality of drive surfaces configured to engage a tool bit; as well as a hardened layer formed on at least one of the drive portion or the impact receiving surface, the hardened layer having a higher hardness than the rest of the anvil, The invention is characterized in that the hardened layer is formed by a heating process.

2. An anvil according to claim 1, characterized in that Residual compressive stresses are added to this hardened layer by the shot peening process.

3. An anvil according to claim 2, characterized in that The shot peening process is a laser shot peening process.

4. The anvil according to claim 2, characterized in that The residual compressive stresses are added to the hardened layer at a location below the surface of the anvil.

5. The anvil according to claim 2, characterized in that The hardened layer is formed on the entire driving portion through the heating process, and wherein the residual compressive stresses are added only at a portion of the driving portion through the shot peening process.

6. An anvil according to claim 5, characterized in that The residual compressive stresses are added to at least one quarter of the area of ​​each of the drive surfaces.

7. The anvil according to claim 1, wherein: The hardened layer is formed on both the driving portion and the impact receiving surface.

8. An anvil according to any one of claims 1 to 7, characterized in that The hardened layer does not extend along the shank portion.

9. An anvil for an impact tool, the anvil comprising: an impact receiving portion located at an end of the anvil, the impact receiving portion including a lug having an impact receiving surface that receives an impact from a hammer of the impact tool; a handle portion extending from the impact receiving portion; as well as a drive portion at an end of the shank portion opposite the impact receiving portion, the drive portion including a plurality of drive surfaces configured to engage a tool bit, characterised in that at least one of the impact receiving portion or the driving portion includes a region having residual compressive stress; and Among other things, these residual compressive stresses are applied to the zone by a laser peening process.

10. An anvil according to claim 9, characterized in that The zone having residual compressive stress is located below the surface of the anvil.

11. The anvil according to claim 9, characterized in that In addition to these residual compressive stresses, this zone is treated using a heating process to produce a hardened layer.

12. An anvil according to claim 11, characterized in that The drive portion includes the zone, and wherein the stiffening layer extends along the entire length of the drive portion.

13. The anvil according to claim 9, characterized in that The drive portion includes the zone, and wherein the zone includes a corner of each of the plurality of drive surfaces located closest to the shank.

14. An anvil according to claim 13, characterized in that The zone comprises more than one quarter of the entire area of ​​each of the plurality of drive surfaces.

15. An anvil according to claim 14, characterized in that The zone includes the entire area of ​​each of the plurality of drive surfaces.

16. An anvil according to any one of claims 9 to 15, characterized in that These residual compressive stresses are applied to the zone by performing a shot peening process after the laser peening process.

17. An anvil for an impact tool, the anvil comprising: an impact receiving portion located at an end of the anvil, the impact receiving portion including a lug having an impact receiving surface that receives an impact from a hammer of the impact tool; a handle portion extending from the impact receiving portion; a drive portion at an end of the shank portion opposite the impact receiving portion, the drive portion including a plurality of drive surfaces configured to engage a tool bit; as well as a hardened layer formed on at least one of the drive portion or the impact receiving surface, the hardened layer having a higher hardness than the rest of the anvil, The invention is characterized in that the hardened layer is formed by a diffusion process.

18. An anvil according to claim 17, wherein: The remainder of the anvil is masked during the diffusion process.

19. The anvil according to claim 17, wherein: The remainder of the anvil is ground after the diffusion process.

20. An anvil according to any one of claims 17 to 19, characterized in that The diffusion process includes carburizing.

21. An anvil according to any one of claims 17 to 19, characterized in that The diffusion process includes nitriding.

22. An anvil according to any one of claims 17 to 19, characterized in that Residual compressive stresses are added to this hardened layer by the shot peening process.

23. An anvil according to claim 22, characterized in that The shot peening process is a laser shot peening process.

24. The anvil of claim 22, wherein: The shot peening process includes a laser shot peening process and a subsequent shot peening strengthening process.

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