Hammer for impact tool

Abstract

A hammer for an impact tool, the hammer comprising: a body; a hammer lug including an impact surface configured to engage a corresponding impact surface on an anvil of the impact tool and to apply an impact to the corresponding impact surface; a transition surface located between the body and the hammer lug; and a hardening layer formed on at least one of the impact surface or the transition surface, the hardening layer having a higher hardness than the remainder of the hammer.

Description

[0001] This application is a divisional application of Chinese utility model patent application No. 202420775465.3, filed on April 15, 2024, entitled "Anvil for Impact Tool", filed by the same applicant.

[0002] Cross-references to related applications

[0003] This application claims priority to U.S. Provisional Patent Application No. 63 / 459,377, filed April 14, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0004] This disclosure pertains to power tool components, such as hammers used in impact tools. Background Technology

[0005] Hardening processes for tool components (such as anvils for impact tools) increase the impact strength of the components, but the increased hardness may lead to a reduction in elastic deformation under other non-impact load conditions (such as torsion). This reduction in elastic deformation can result in a shorter component lifespan. Currently, selective hardening methods for tool components are difficult to control and / or costly because they require additional steps to prepare the tool components for hardening. Utility Model Content

[0006] In some aspects, the technology described herein relates to a hammer for an impact tool, the hammer comprising: a body; a hammer lug including an 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 hardening layer formed on at least one of the impact surface or the transition surface, the hardening layer having a higher hardness than the remainder of the hammer.

[0007] In some respects, the technology described herein relates to a hammer that further includes an edge that protrudes from the front surface of the body and surrounds the hammer lug, wherein the hardened layer is formed on the inner surface of the edge.

[0008] In some respects, the technology described herein relates to a hammer in which residual compressive stress is added to the hardened layer via a laser shot peening process.

[0009] In some respects, the technology described herein relates to a hammer in which residual compressive stress is added to the hardened layer by a shot peening strengthening process following the laser shot peening process.

[0010] In some respects, the technology described herein relates to a hammer in which the hardened layer is formed by an induction heating process. Attached Figure Description

[0011] Figure 1 This is a cross-sectional view of a power tool according to an embodiment of the present disclosure, the power tool including an impact mechanism with an anvil.

[0012] Figure 2 yes Figure 1 A frontal stereoscopic view of the anvil.

[0013] Figure 3 yes Figure 1 A rear-view perspective of the anvil.

[0014] Figure 4 yes Figure 1 A cross-sectional view of the anvil.

[0015] Figure 5A yes Figure 1 The front-view perspective of the anvil shows the first processing area.

[0016] Figure 5B yes Figure 1 The front-view perspective of the anvil shows the second processing area.

[0017] Figure 5C yes Figure 1 The front-view perspective of the anvil shows the third processing area.

[0018] Figure 5D yes Figure 1 The front-view perspective of the anvil shows the fourth processing area.

[0019] Figure 6A This is a front perspective view of an anvil according to another embodiment of the present disclosure.

[0020] Figure 6B yes Figure 6A A magnified view of a portion of the anvil.

[0021] Figure 7A yes Figure 6B A top view of a magnified portion of the anvil, showing the first processed area.

[0022] Figure 7B yes Figure 6B A magnified side view of a portion of the anvil, showing the second processed area.

[0023] Figure 8 This is a perspective view of a hammer according to one embodiment of the present disclosure, the hammer being configured to... Figure 1 Use them together with power tools.

[0024] Figure 9AThis is a perspective view of a hammer according to another embodiment of the present disclosure, the hammer being configured to... Figure 1 Use them together with power tools.

[0025] Figure 9B yes Figure 9A A cross-sectional view of the hammer taken along its center.

[0026] Figure 10A It is used for Figure 1 A schematic diagram of the first step in the laser shot peening process of the anvil.

[0027] Figure 10B yes Figure 6A A schematic diagram of the second step of the laser shot peening process.

[0028] Figure 10C yes Figure 6A A schematic diagram of the third step in the laser shot peening process.

[0029] Figure 10D yes Figure 6A A schematic diagram of the fourth step in the laser shot peening process.

[0030] Figure 11 It is the first graph that plots the data of the anvil that has undergone different processing techniques.

[0031] Figure 12 It is the second graph that plots the data of the anvil that has undergone different processing techniques.

[0032] Figure 13 It is the third curve plotted, showing the data of the anvil that has undergone different processing techniques. Detailed Implementation

[0033] Before explaining any embodiment of this disclosure in detail, it should be understood that this 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 figures. This disclosure can have other embodiments and can be practiced or implemented in various ways.

[0034] Figure 1A power tool 10 is shown, more specifically, a rotary impact tool, such as an impact wrench. The power tool 10 includes, in particular, 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 configured to strike an anvil 38 to apply torque to the anvil 38 and provide torque output to the power tool 10. Thus, the operation of the power tool 10 may lead to fatigue crack initiation, fatigue crack propagation, and eventual fracture of the anvil 38 due to repeated impacts from the hammer 34.

[0035] Figure 2 and Figure 3 An anvil 38 is shown, comprising an impact receiving portion 46, a drive portion 58 opposite to the impact receiving portion 46, and a body or shank 54 extending between the impact receiving portion 46 and the 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 the rear side 62 of the impact receiving portion 46, and the size and position of the aperture are determined to receive and support the front end of the camshaft 26 in a rotational sense during the assembly of the power tool 10. Figure 1 In other embodiments, orifice 42 may be omitted, or orifice 42 may be replaced by a protruding boss in a corresponding orifice extending into the front end of camshaft 26.

[0036] 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. An orifice 42 is defined in the back surface 70, and a shank 54 extends from the front surface 74. In the illustrated embodiment, the impact receiving portion 46 includes two lugs 50 extending away from the orifice 42 and the shank 54 in a direction perpendicular to the extending direction of the shank 54. In other words, the lugs 50 are spaced apart from each other completely opposite to the orifice 42, such that the lugs 50 extend away from each other. The lugs 50 are configured to receive impacts (i.e., torque transmission) from the hammer 34, and the anvil 38 transmits the impacts (i.e., torque) to the drive portion 58 via the shank 54.

[0037] refer to Figure 2The peripheral surface 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 may have an involute profile and is configured to be directly impacted 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 surface 78 changes at the transition surface 78c.

[0038] refer to Figures 2 to 3 The illustrated drive portion 58 includes a stepped portion 86, a body portion 87, multiple chamfers 90, multiple drive surfaces 94, multiple transition surfaces 96, and a flange 98. The stepped portion 86 extends from the shank portion 54 and converges radially inward to the body portion 87. In some embodiments, the shank portion 54 and the body portion 87 may each have a constant diameter, wherein the diameter of the body portion 87 is smaller than the diameter of the shank portion 54. In some embodiments, the shank portion 54 and / or the body portion 87 may include one or more recesses 55.

[0039] The drive surfaces 94 are formed as planar surfaces, and in some embodiments, these planar surfaces may be machined into the body portion 87. Each drive surface 94 is perpendicular to its adjacent drive surface 94, such that the drive surface 94 defines a square drive portion configured to receive a square drive tool tip, such as a socket wrench. 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 outward 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 tips.

[0040] Continue to refer to Figures 2 to 3A chamfer 90 (which may be an unmachined portion of the body portion 87) extends between adjacent drive surfaces 94 and connects them to each other. In the illustrated embodiment, a rounded end surface 102 is formed at the leading (far) end of the chamfer 90 and drive surface 94. A groove 103 is defined between the rounded end surface 102 and the flange 98. The groove 103 is configured to receive a ring (e.g., a rubber O-ring; not shown). This ring can engage the interior of the attached tool tip to provide increased friction, thereby securing the tool tip to the drive portion 58. In other embodiments, one or more of the drive surfaces 94 may include holes configured to receive locking pins (e.g., ball locking pins) to secure the tool tip to the drive portion 58. In such embodiments, the flange 98 and the groove 103 may be omitted.

[0041] During operation of the power tool 10, the anvil 38 is subjected to repetitive, localized, high-magnitude forces. Some portions of the anvil 38 (such as the impact receiving surface 78b and the drive portion 58) can benefit from high hardness to provide improved strength and wear resistance, and from high residual compressive stress to improve resistance to fatigue crack initiation. Other portions of the anvil 38 can benefit from lower hardness to provide improved toughness. Accordingly, the anvil 38 needs to have different material properties in different regions of the anvil 38.

[0042] Figure 4 A cross-section of an anvil 38 is shown. Anvil 38 has a first region A, which has a length along the rotation axis X of anvil 38 from its front end 105 to its end surface 102. Anvil 38 has a second region B, which has a length along the rotation axis X of anvil 38 from its end surface 102 to its transition surface 96. The second region B thus includes a drive surface 94. Anvil 38 further has a third region C, which has a length along the rotation axis X of anvil 38 spanning the transition surface 96. Finally, anvil 38 has a fourth region D, which has a length along the rotation axis X of anvil 38 from the rear end of the transition surface 96 toward the stepped portion 86. In some embodiments, the fourth region D may span the entire length between the transition surface 96 and the stepped portion 86. In other embodiments, the length of the fourth region D may be less than the length between the transition surface 96 and the stepped portion 86. In the illustrated embodiment, the length of the second region B is greater than the length of the first region A, the length of the first region is greater than the length of the fourth region D, and the length of the fourth region is greater than the length of the third region C.

[0043] Continue to refer to Figure 4The anvil 38 shown has a core 107 and a hardened layer 109 surrounding the core 107. In the shown embodiment, the hardened layer 109 has a thickness T and extends to the length of each of the second region B, the third region C, and the fourth region D. In each of regions B, C, and D, the thickness T may be substantially uniform. Alternatively, the thickness T may vary (e.g., the thickness T may be greater in region B than in regions C and D, etc.). In some embodiments, the thickness T in each of regions B, C, and D may be between 0.7 mm and 2.0 mm. In some embodiments, the thickness T in each of regions B, C, and D may be between 1.0 mm and 1.5 mm.

[0044] The anvil 38 can be integrally formed from 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 casting or powder metallurgy (PM) manufacturing processes. 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 core 107 has a lower hardness than the hardened layer 109. For example, in some embodiments, the core 107 can have a hardness of 35 to 54 HRC, while the hardened layer 109 can have a hardness of 55 to 62 HRC. This provides high toughness to the core 107 to reduce the likelihood of breakage. The hardened layer 109 provides high strength and wear resistance at the portion of the anvil 38 that may contact the tool tip. In some embodiments, the lug 50 may also include a hardened layer that 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 to the portion of the anvil 38 that contacts the hammer 34.

[0045] Figure 5A A first region 110a 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 first region 110a). 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 lower hardness to provide increased toughness to the lug 50. In other embodiments, the first region 110a may extend into the end portion 78a and / or the transition surface 78c.

[0046] Figure 5BA second region 110b of the anvil 38 is shown, which can be locally hardened via the processes described herein (e.g., to form a hardened layer 109 in the second region 110b). In the illustrated embodiment, the second region 110b includes a body portion 87, a chamfer 90, a drive surface 94, a transition surface 96, and an end surface 102. In the illustrated embodiment, the second region 110b does not include a flange 98, a stepped portion 86, or a shank 54. The second region 110b corresponds to the surfaces of the drive portion 58, which can engage with the tool tip or another type of workpiece when attached to the anvil 38. The drive surface 94 may be subjected to high compressive and tensile stresses, and the transition surface 96 may be subjected to high stress concentrations due to its geometry and axial impact loads, which may occur if the end of the tool tip presses against the transition surface 96. The hardening of the body portion 87 and the end surface 102 can promote more uniform hardening of the driving surface 94 and the transition surface 96, making the thickness T of the hardened layer 109 approximately uniform. Figure 4 In the illustrated embodiment, flange 98 is not surface hardened, thus remaining part of the softer core 107. Because flange 98 is relatively thin and defines the front end 105 of anvil 38, it is more prone to breakage if flange 98 has the high hardness of the hardened layer 109 and the power tool 10 is dropped. During operation, the maximum stress of the locally hardened anvil 38 in the second region 110b is reduced by approximately 30%.

[0047] 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 but less than half of the total area of ​​the chamfers 90. Additionally, a portion of each of the drive surfaces 94 included in the third region 110c is at least one-quarter but less than half of the total area of ​​the drive surfaces 94. The third region 110c does not include the body portion 87, the flange 98, the stepped portion 86, or the shank 54. During operation, the maximum stress of the anvil 38 locally hardened at the third region 110c is reduced by approximately 16.5%.

[0048] Figure 5DA fourth region 110d 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 fourth region 110d). In the illustrated embodiment, the fourth region 110d includes the area where the body portion 87, chamfer 90, drive surface 94, and transition surface 96 intersect. In other words, the fourth region 110d includes the corner of each of the square drive surfaces 94 and a portion of each of the body portion 87, chamfer 90, and transition surface 96 adjacent to the corner of the drive surface 94. During operation, the maximum stress of the anvil 38 locally hardened at the fourth region 110d is reduced by approximately 12.2%.

[0049] Figure 6A and Figure 6B An anvil 238 according to another embodiment of this disclosure is shown. Apart from the differences described herein, anvil 238 may be substantially similar to... Figure 2 and Figure 3 The anvil 38. like Figure 6A and Figure 6B As shown, the anvil 238 includes an impact receiving portion 246, a drive portion 258 opposite to the impact receiving portion 246, and a body or shank portion 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-locking anvil; however, the anvil 238 may alternatively be formed as a spherical locking anvil, or an anvil having another type of tool head retention interface.

[0050] 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. Similar to... Figure 3 The orifice 42 may define a central hole or opening in the back face 270 to facilitate engagement with the camshaft. The impact receiving portion 246 includes two lugs 250 extending away from the shank 254 in a direction perpendicular to the extending direction of the shank 254. The lugs 250 are configured to receive impacts (i.e., torque transmission) from the hammer, and the anvil 238 transmits the impacts (i.e., torque) to the drive portion 258 via the shank 254. In some embodiments, the lugs 250 may have an involute profile.

[0051] The illustrated drive portion 258 includes a stepped portion 286, a body portion 287, multiple chamfers 290, multiple drive surfaces 294, multiple transition surfaces 296, and an end surface 302. The stepped portion 286 extends from the shank portion 254 and converges radially inward to the body portion 287. In some embodiments, the shank portion 254 and the body portion 287 may have a constant diameter, wherein the diameter of the body portion 287 is smaller than the diameter of the shank portion 254. In some embodiments, the shank portion 54 and / or the body portion 287 may include one or more grooves.

[0052] The drive surfaces 294 are formed as planar surfaces, and in some embodiments, these planar surfaces may be machined into the body portion 287. Each drive surface 294 is perpendicular to its adjacent drive surface 294 such that the drive surface 294 defines a square drive portion configured to receive a square drive tool tip, such as a socket wrench. 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 engagement with a tool tip or another type of workpiece. The pin receiving portion 306 is configured to receive a pin 306a that secures 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 (near) end of the drive surface 294 and curves outward 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 tips.

[0053] Continue to refer to Figure 6A and Figure 6B A chamfer 290 (which may be an unmachined portion of the body portion 287) extends between adjacent drive surfaces 294 and connects them to each other. In the illustrated embodiment, the chamfer 290 extends to an end surface 302. The end surface 302 is oriented perpendicular to the extension direction of the shank 254. Thus, a transition collar 308 connects the chamfer 290 and the end surface 302. Specifically, the transition collar 308 bends from the chamfer 290 toward the end surface 302.

[0054] During operation of the power tool, the anvil 238 is subjected to repetitive, localized, high-magnitude forces. Some portions of the anvil 238 (such as the drive portion 258) may benefit from high hardness to provide improved strength and wear resistance, and from high residual compressive stress to improve resistance to fatigue crack initiation. Specifically, due to the movement of the locking pins 304a and 306a within the locking pin receiving portions 304 and 306, respectively, the areas surrounding the locking pin receiving portions 304 and 306 may experience variable high stress.

[0055] Figure 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 forming or defining a locking pin receiving portion 304 and a transition surface 296 adjacent to the drive surface 294 forming the locking pin receiving portion 304. Specifically, the first region 310a includes strips along each of the edges of the drive surfaces 294, the strips extending parallel to the extending direction of the shank 254. These strips extend from the transition surface 296 adjacent to the drive surface 294 forming the locking pin receiving portion 304 to a region of the drive surface 294 adjacent to the transition collar 308.

[0056] Figure 7B A second region 310b of the anvil 238 is shown, which can be locally hardened (e.g., to form a hardened layer in the second region 310b) via the process described herein. In the illustrated embodiment, the second region 310b includes a drive surface 294 that forms or defines the pin receiving portion 306 and a transition surface 296 adjacent to the drive surface 294 defining the pin receiving portion 306. Specifically, the second region 310b includes the entire transition surface 296 adjacent to the drive surface 294 forming the pin receiving portion 306 and the entire drive surface 294 forming the pin receiving portion 306, except for the region 294a of the drive surface 294 directly surrounding the pin receiving portion 306. The region 294a of the drive surface 294 directly surrounding the pin receiving portion 306 may be curved or chamfered, and therefore may not be suitable for local hardening. Although the first region 310a and the second region 310b of the anvil 238 are described separately, it should be understood that the anvil 238 can be locally hardened at both the first region 310a and the second region 310b via the processes described herein. For example, the entire drive portion 258 can be locally hardened.

[0057] Figure 8A hammer 434 according to one embodiment of this disclosure is shown. The hammer 434 includes a body 438 and hammer lugs 442 projecting 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 onto the camshaft. The hammer lugs 442 include impact surfaces 450 configured to engage corresponding impact surfaces on an anvil and apply impact to these impact surfaces. 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 lugs 442 and the front surface 438a of the body 438.

[0058] Continue to refer to 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 process 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 be locally hardened (e.g., to form a hardened layer in the second region 510b) additionally or independently via the process 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 surfaces 450 of the hammer lugs 442 may be subjected to high compressive and tensile stresses, and the transition surface may be subjected to high stress concentrations due to its geometry. Thus, the first region 510a and the second region 510b can be hardened individually or in combination via the process described herein to counteract the respective stresses.

[0059] Figure 9A and Figure 9BA hammer 634 according to another embodiment of this disclosure is shown. The hammer 634 includes a body 638 and an edge 642 projecting 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 onto the camshaft. The body 638 additionally defines a spring receiving portion 650 on a rear surface 638b of the body 638 and a notch or groove 654 in the front surface 638a of the body 638. The spring receiving portion 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 receiving portion 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 receiving portion 650 and the groove 654. Edge 642 includes a hammer lug 662 projecting inward from the outer periphery of body 638. The hammer lug 662 includes impact surfaces 666 configured to engage corresponding impact surfaces on anvil and apply impact to these impact surfaces. In the illustrated embodiment, the impact surfaces 666 on the hammer lug 662 are formed such that each of the hammer lugs 662 has an involute profile.

[0060] Figure 9A A first region 710a of the hammer 634 is shown, which can be locally hardened (e.g., to form a hardened layer in the first region 710a) via the process described herein. In the illustrated embodiment, the first region 710a includes an inner surface 642a of an edge 642. Thus, the first region 710a includes an impact surface 666 of each of the hammer lugs 662 and a portion of the inner surface 642a of the edge 642 that connects the hammer lugs 662 together. The impact surfaces 666 of the hammer lugs 662 may be subjected to high compressive and tensile stresses, and the portion of the inner surface 642a of the edge 642 that connects the hammer lugs 662 may be subjected to radial forces generated by the involute hammer lugs 662. Thus, the impact surfaces 666 and the portion of the inner surface 642a of the edge 642 that connects the hammer lugs 662 can be hardened via the process described herein to counteract the corresponding stresses and forces.

[0061] Figure 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 process 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 surface hardened layer of the hammer 634 (i.e., the distance between the tip 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 surface hardened 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 breakage of the relatively narrow portion 658. Thus, the second region 710b of the hammer 634 can be advantageously hardened to reduce breakage along the end surface 650a of the spring receiving portion 650 and along the inclined surface 654a of the groove 654.

[0062] The following is a description of the processing techniques used to form the hardened layer in the anvils 38, 238 and / or hammers 434, 634 described herein. For the sake of brevity, regarding... Figures 1 to 3 These processes are described using the anvil 38. However, it should be understood that these processes can be equally applied to... Figure 6A The anvil 238, Figure 8 Hammer 434, and / or Figure 9A Hammer 634. During manufacturing, the anvil 38 undergoes one or more processing steps to form a hardened layer 109 in the first region 110a and / or the second region 110b. These processing steps may be localized so that only desired portions of the anvil 38 are targeted and hardened, while other portions of the anvil 38 have lower hardness to improve toughness.

[0063] In one embodiment, the anvil 38 is carburized to form a hardened layer 109. During carburizing, the anvil 38 is heated in a high-carbon atmosphere. The exposed surfaces of the anvil 38 absorb carbon from the high-carbon atmosphere, which increases the carbon content of the steel in the anvil 38 (and thus its hardness) to form the hardened layer 109 (after the anvil 38 has been quenched). Prior to carburizing, a protective masking material (in some embodiments, the protective masking material may include paint or tape) may be applied to portions of the anvil 38 to prevent the formation of the hardened layer 109 in these portions. For example, a protective masking material may be applied to the anvil in addition to the first region 110a and the second region 110b. Thus, only the first region 110a and the second region 110b absorb carbon during the carburizing process. In other embodiments, the anvil 38 may additionally or alternatively undergo a nitriding process or other diffusion hardening process to form the hardened layer 109. In such embodiments, a similar protective masking 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 lower surface hardness is desired.

[0064] In other embodiments, the anvil 38 is locally hardened via a heating process to form a 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 high percentage of martensite, thereby providing 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 to induction heating, lasers are able to target the complex geometry of the first region 110a and the second region 110b of the anvil 38 more precisely. Furthermore, laser hardening eliminates 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 high percentage of martensite.

[0065] In some embodiments, instead of or in addition to a local hardening step, the anvil 38 may additionally or alternatively undergo one or more surface finishing steps. In some embodiments, the surface finishing steps may include a shot peening process (e.g., a shot peening strengthening process), which can generate residual compressive stress on the outer surface of the anvil 38. In some embodiments, the anvil 38 is shot peened via a targeted laser shot peening process at specific locations (e.g., regions 110a, 110b). In some embodiments, the anvil 38 undergoes not only a laser shot peening process but also a subsequent shot peening strengthening process.

[0066] refer to Figures 10A to 10D The laser shot peening process generates residual compressive stress in the specific target area on the anvil 38 to modify the mechanical properties of the metal in the target areas 110a and 110b on the anvil 38, such as improving fatigue resistance.

[0067] like Figure 10A The laser peening process shown includes providing laser pulses 806 at target regions 110a and 110b. The laser pulses 806 generate plasma shock waves that exert pressure on the metal at the target regions 110a and 110b, thereby introducing strain, shock waves, and / or dislocations into the microstructure of the anvil 38 at the target regions 110a and 110b. Specifically, refer to... Figure 10B The plasma shock wave mechanically modifies the metal in target regions 110a and 110b from the first state 814a to the second state 814b. For example... Figure 10C As shown, in the second state 814b, target areas 110a and 110b are pushed upwards against the surrounding areas of the anvil 38, which are not considered targets during the laser peening process. (Reference) Figure 10D The surrounding area then elastically recovers to fit the metal around the target areas 110a and 110b. Therefore, tensile stress S1 is generated in the area surrounding the anvil 38, while the area surrounding the anvil 38 also provides residual compressive stress S2 on the target areas 110a and 110b. The net force provided by these stresses S1 and S2 helps reduce the net internal stress, thereby extending the life of the anvil 38 by providing resistance to fatigue cracking and crack propagation.

[0068] During the laser peening process, a cooling fluid (such as water) can flow over the anvil 38, and more specifically, over the target areas 110a and 110b. Introducing water into the laser peening process helps maintain the plasma in the proper position to create compressive stress S2. Adhesive tape can also be applied to the outer surface of the anvil 38 during the laser peening process. A layer of tape provides an opaque surface to the anvil 38, which amplifies the peening effect to aid in the formation of stress within the anvil 38.

[0069] Laser shot peening process ( Figures 10A to 10D ) is superior to similar anvil 38 forming processes, such as shot peening or laser ablation, because the laser pulse ( Figure 10A Laser peening can penetrate deeper into metal, can deliver higher power and sustain longer durations, and can target more precise areas (i.e., target areas 110a and 110b). For example, laser peening can generate residual compressive stress at depths of 1 mm to 12 mm below the metal surface, while other processes may only be able to impact the surface of the anvil 38. Residual compressive stress S2 ( Figure 10D ) offset the potential impact on power tools 10 ( Figure 1 The stress applied to the anvil 38 during operation. Additionally, the laser pulse can target a specific spot size of approximately 1 mm on the anvil 38. Thus, the laser peening process allows the user or manufacturer to successfully create very fine residual stress zones within and / or on the anvil 38, thereby improving the performance of the anvil 38. Figure 2 This improves wear resistance and extends overall lifespan.

[0070] Therefore, to manufacture the anvil 38, a material blank (e.g., medium carbon steel, tool steel, etc.) is processed via metal forming steps (e.g., forging, casting, PM manufacturing processes, etc.) to form the integral shape of the anvil 38. The anvil 38 can then be machined to form the driving surface 94, transition surface 96, 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 its carbon content, thereby generating greater residual stress in subsequent hardening processes. Thus, if the anvil 38 is carburized, the carburizing must be performed before subsequent localized surface hardening processes 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.

[0071] After carburizing, a local surface hardening process (e.g., diffusion surface hardening, laser heating, or induction heat treatment as described above) can then be performed to form a hardened layer 109 with higher hardness relative to the remaining core 107 of the anvil 38. Figure 4 Specifically, refer to Figure 4 Each of regions A, B, C, and D can undergo a localized surface hardening process (e.g., induction hardening). By treating each of regions A, B, C, and D, the induction hardening process offers greater tolerance for inaccuracies, ensuring that the transition between regions of different shapes, where stress may be highest, is induction hardened.

[0072] After the hardened layer 109 is formed, the anvil 38 may undergo additional processes (such as laser peening) to create residual compressive stress in target regions 110a, 110b, 110c, 110d and / or other desired regions of the anvil 38, and in some embodiments, subsequently undergo a shot peening strengthening process. The resulting anvil 38 can combine high toughness and high wear resistance in appropriate regions to extend the life of the anvil 38 and allow the anvil 38 to transmit a larger amount of torque.

[0073] The process described in this article regarding anvil 38 can also be applied to other power tool components, such as hammer 34 (e.g., Figure 8 Hammer 434 and / or Figure 9AThe hammer 34 (634) and camshaft 26. For example, the impact surface of the hammer lug can be locally hardened and / or machined using the methods described herein to add residual compressive stress, thereby improving the wear resistance and fatigue crack resistance of the hammer 34. In some embodiments, the camshaft 26 and the hammer 34 each include cam grooves that receive balls that engage 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 using the methods described herein to improve wear resistance. In other embodiments, other power tool parts with complex geometries and thin features can be manufactured according to the methods described herein, which may otherwise be prone to through-hardening and brittleness when subjected to conventional hardening or processing techniques.

[0074] Figures 11 to 13 Graphs 1010, 1110, and 1210 are shown, which include curves of data for anvils that have undergone various hardening processes. Specifically, each of graphs 1010, 1110, and 1210 plots the residual compressive stress of the anvil relative to the depth from the outer surface of the anvil.

[0075] Figure 11 The 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 yet undergone shot peening. The third line 1016 shows the stress-depth relationship of an anvil that has undergone both shot peening and induction heat treatment. Figure 11 As shown, compared to the anvils that have undergone shot peening as shown by the first line 1012 and the anvils that have not undergone shot peening as shown by the second line 1014, the anvils that have undergone both shot peening and induction heat treatment, as shown by the third line 1016, exhibit higher maximum residual compressive stress and higher residual compressive stress at the surface. Therefore, the first graph 1010 demonstrates that combining shot peening and induction heat treatment on the anvil can advantageously increase the residual compressive stress of the anvil.

[0076] Figure 12 The second graph 1110 is shown. The second graph 1110 includes the first line 1112, the second line 1114, the third line 1116, the fourth line 1118, and the fifth line 1120. The first line 1112 shows the stress-depth relationship of anvils that have undergone carburizing and shot peening. The second line 1114 shows the stress-depth relationship of carburized anvils that have not yet undergone shot peening. The third line 1116 shows the stress-depth relationship of carburized anvils that have not yet undergone shot peening but have already undergone shot peening. Figure 5CThe stress-depth relationship of the carburized anvil, subjected to laser shot peening, is shown in the third region 110c. The fourth line 1118 shows the stress-depth relationship of the carburized anvil before shot peening, but already undergoing similar conditions. Figure 5B The stress-depth relationship of the carburized anvil undergoing laser shot peening is shown in the second region 110b of the anvil. The fifth line 1120 shows the stress-depth relationship of the carburized anvil that has not yet undergone shot peening but has already been subjected to laser shot peening. Figure 5D The stress-depth relationship of the carburized anvil that underwent laser shot peening in the fourth region 110d of the anvil is shown.

[0077] Continue to refer to Figure 12 Compared to each of the anvils that have not undergone shot peening at their surface (i.e., the second line 1114, the third line 1116, the fourth line 1118, and the fifth line 1120), the anvils that have undergone shot peening, as shown by the first line 1112, have much higher residual compressive stress. Thus, the second graph 1110 illustrates the benefits of shot peening when high residual compressive stress is required at the surface of the anvil. The second graph 1110 also illustrates the benefits of laser peening when higher residual compressive stress is required below the surface of the anvil, regardless of where the laser peening is performed. Specifically, compared to the anvils that have not undergone laser peening, represented by the first line 1112 and the second line 1114, the third line 1116, the fourth line 1118, and the fifth line 1120, representing the anvils that have undergone laser peening, each have higher residual compressive stress at a depth of approximately 0.1 mm or greater from the surface.

[0078] Figure 13 The third curve 1210 is shown. The third curve 1210 includes the first line 1212, the second line 1214, the third line 1216, and the fourth line 1218. The first line 1212 shows the stress-depth relationship of the anvil that has undergone shot peening and induction heat treatment. The second line 1214 shows the stress-depth relationship of the anvil that has undergone shot peening and induction heat treatment, and has already undergone... Figure 5C The stress-depth relationship of the anvil at the third region 110c of the anvil, as shown, is that it has undergone laser shot peening. The third line 1216 shows the anvil that has undergone shot peening and induction heat treatment, and has already been... Figure 5D The stress-depth relationship of the anvil at region 110d in the fourth region of the anvil, which underwent laser shot peening, is shown. The fourth line 1218 shows the anvil that has undergone shot peening and induction heat treatment, and has already been... Figure 5B The stress-depth relationship of the anvil at the second region 110b of the anvil, which is subjected to laser shot peening, is shown.

[0079] The third curve 1210 illustrates the benefits of laser peening at various target regions 110b, 110c, and 110d. Specifically, as shown by the third line 1216, in the fourth region 110d ( Figure 5D Laser peening at a depth of approximately 0.35 mm results in relatively high residual compressive stress on the anvil between its surface and a depth of about 0.35 mm. However, at depths greater than 0.35 mm, the anvil begins to exhibit relatively low residual compressive stress, as indicated by the third line 1216. Thus, different combinations of localized heat treatment processes and target areas for laser peening may be desired under different conditions. That is, for any given operation, the optimal combination of hardening processes can be determined based on the depth at which the highest stress occurs. Furthermore, incorporating a shot peening strengthening process after laser peening can advantageously provide high residual compressive stress both on and below the treated surface of the anvil.

[0080] While this disclosure has been described in detail with reference to certain preferred embodiments, variations and modifications may be made within the scope and spirit of one or more independent aspects of the described disclosure.

[0081] The various features and aspects of this disclosure are set forth in the appended claims.

Claims

1. A hammer for an impact tool, the hammer comprising: main body; A hammer lug, the hammer lug including an impact surface configured to engage a corresponding impact surface on the anvil of the impact tool and apply an impact to the corresponding impact surface; and A transition surface, located between the body and the hammer lug; characterized in that, A hardened layer is 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.

2. The hammer as described in claim 1, characterized in that, It further includes an edge that protrudes from the front surface of the body and surrounds the hammer lug, the hardened layer being formed on the inner surface of the edge.

3. The hammer as described in claim 1, characterized in that, Residual compressive stress is added to the hardened layer using a laser shot peening process.

4. The hammer as described in claim 3, characterized in that, The residual compressive stress is added to the hardened layer by a shot peening strengthening process following the laser shot peening process.

5. The hammer as described in any one of claims 1 to 4, characterized in that, The hardened layer is formed using an induction heating process.

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