Forward and backward moving impact tool with impact control

Abstract

A power tool includes a housing, an electric motor, a spindle, a mount, a back-and-forth drive assembly, a striker, and an anvil. The mount is at least partially received within the spindle. The anvil has a front anvil striking surface and a rear anvil striking surface opposite the front anvil striking surface. The mount defines a mount striking surface that contacts the front anvil striking surface when the anvil moves in a first direction along a back-and-forth axis of travel. The spindle defines a spindle striking surface that contacts the rear anvil striking surface when the anvil moves in a second direction, opposite the first direction, along the back-and-forth axis of travel. The mount striking surface and the spindle striking surface limit the amount of travel the anvil translates along the back-and-forth axis of travel.

Description

Cross-reference to related applications

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 624,954, filed January 25, 2024, and U.S. Provisional Patent Application No. 63 / 619,520, filed January 10, 2024, the disclosures of which are incorporated herein by reference in their entirety. background

[0002] A power tool (e.g., a chipping hammer, a rotary hammer, a pneumatic hammer, a drill, a pneumatic chisel, etc.) may be used to drill or strike a workpiece with an insert (e.g., to remove material from the workpiece). An output unit of the power tool may include an impact mechanism that moves the insert in an axial (i.e., linear) direction. In some applications, the impact mechanism may, for example, include a striker that moves in an axial direction to apply an impact to the tool insert (e.g., via an anvil). Overview

[0003] Some embodiments of the disclosed technology provide a power tool configured to apply axial impacts to a tool bit.The power tool may comprise: a housing, an electric motor carried in the housing, a spindle carried by the housing, a mount at least partially received in the spindle and configured to receive at least a portion of the tool bit, a back-and-forth drive assembly connected to the electric motor and configured to convert torque from the electric motor into back-and-forth movement of a drive piston at least partially received in the spindle for back-and-forth movement therein along a back-and-forth movement axis, a striker received in the spindle for back-and-forth movement in response to the back-and-forth movement of the drive piston, and an anvil at least partially received in the spindle and positioned between the striker and the tool bit.The anvil may be configured to transmit axial impacts from the firing pin to the tool bit and may include a front anvil impact surface and an opposing rear anvil impact surface proximate opposite ends of the anvil. The mount may define a mount impact surface that contacts the front anvil impact surface as the anvil moves toward the mount along the back-and-forth axis of travel. The spindle may define a spindle impact surface that contacts the rear anvil impact surface of the anvil as the anvil moves away from the mount along the back-and-forth axis of travel. The mount impact surface and the spindle impact surface may define the travel distance D. T limit the amount by which the anvil moves along the back-and-forth axis of movement.

[0004] In some aspects, the support striking surface may be spaced from the spindle striking surface by a striking surface distance DS be spaced, whereby the travel path D T less than or equal to 50 percent of the stop surface distance D S amounts.

[0005] In some aspects, the travel path D T less than or equal to 20 percent of the stop surface distance D S be.

[0006] In some aspects, the anvil may include an opening and an internal bore communicating with the opening. The internal bore may at least partially receive a shank of the tool bit.

[0007] In some aspects, the spindle may include a spindle wall defining a bore. The spindle may include a rib extending inwardly from the spindle wall and into the cylindrical bore, and the rib may define the spindle impact surface.

[0008] In some aspects, the power tool may include a retaining member connecting the mount to the spindle. In some cases, the retaining member may have a cylindrical shape.

[0009] Some embodiments of the disclosed technology may include a power tool that applies axial impacts to a tool bit. The power tool may include: a housing having an assembly comprising a gear housing and a gear housing cap connected to the gear housing; an electric motor supported in the housing; a spindle supported by the housing and defining an opening; a retainer at least partially received in the spindle and configured to receive at least a portion of the tool bit and defining a recess; a back-and-forth drive assembly connected to the electric motor and configured to convert torque from the electric motor into back-and-forth movement of a drive piston at least partially received in the spindle for back-and-forth movement therein along a back-and-forth movement axis; a striker;which is received in the spindle to move back and forth in response to the back-and-forth movement of the drive piston, and an anvil at least partially received in the spindle and arranged between the striker and the tool bit. The anvil can be configured to transmit axial impacts from the striker to the tool bit. The power tool can further comprise a retaining element connecting the holder to the spindle. The retaining element can be received in both the recess and the opening. The gear housing cover can surround the opening to retain the retaining element therein.

[0010] In some aspects, the gear housing may include a spindle housing surrounding the spindle. In some cases, the power tool may further include a collar surrounding the spindle housing.

[0011] In some aspects, the spindle housing may include a plurality of outwardly projecting ribs spaced apart from one another in the direction of the back-and-forth axis of motion. In some cases, each rib may contact the collar.

[0012] In some aspects, the retaining member may have a cylindrical shape.

[0013] In some aspects, the gear housing cap may surround at least a portion of the spindle.

[0014] In some aspects, the retaining member may be one of a plurality of retaining members, the recess may be one of a plurality of recesses, and the opening may be one of a plurality of openings.

[0015] In some aspects, the anvil may include a front anvil striking surface and an opposing and a rear anvil striking surface near the opposite ends of the anvil. The mount may include a mount striking surface that contacts the front anvil striking surface as the anvil moves toward the mount along the back-and-forth axis of travel. The spindle may define a spindle striking surface that contacts the rear anvil striking surface of the anvil as the anvil moves away from the mount along the back-and-forth axis of travel. The mount striking surface and the spindle striking surface may define the travel path D T limit the distance by which the anvil moves along the back-and-forth axis of movement.

[0016] Some embodiments of the disclosed technology provide a power tool configured to apply axial impacts to a tool bit. The power tool may include a housing, an electric motor supported within the housing, a spindle supported by the housing, a mount at least partially received within the spindle and configured to receive at least a portion of the tool bit, and a reciprocating drive assembly connected to the electric motor and configured to convert torque from the electric motor into reciprocating motion of a drive piston at least partially received within the spindle for reciprocating motion therein along a reciprocating motion axis.The back-and-forth drive assembly may include a crankshaft configured to rotate about a crank axis generally perpendicular to the back-and-forth movement axis, the crankshaft including a journal and a connecting rod connected to the journal at a first end and to the drive piston at a second end. The power tool may further include a striker received within the spindle and moving back and forth in response to the back-and-forth movement of the drive piston, and an anvil at least partially received within the spindle and located between the striker and the tool bit. The anvil may be configured to transmit axial impacts from the striker to the tool bit. The spindle may include a proximal end closest to the crank axis.The proximal end may include an upper edge and a lower edge and define a slot between the upper edge and the lower edge. At least a portion of the first end of the connecting rod passes through the slot during rotation of the crankshaft.

[0017] In some aspects, the back-and-forth drive assembly may further include a driven gear connected to the crankshaft, with the upper edge closest to the driven gear and the lower edge farthest from the driven gear.

[0018] In some aspects, the slot may include a first slot, and the proximal end may further define a second slot. The first and second slots may be located on opposite lateral sides of the spindle between the upper edge and the lower edge.

[0019] In some aspects, the first end of the connecting rod may pass through both the first and second slots during rotation of the crankshaft.

[0020] In some aspects, the pin may be located between the top and bottom edges when the drive piston is at top dead center in the spindle.

[0021] In some aspects, the anvil may include a front anvil striking surface and an opposing and a rear anvil striking surface near the opposite ends of the anvil. The mount may define a mount striking surface that contacts the front anvil striking surface as the anvil moves toward the mount along the back-and-forth axis of travel. The spindle may define a spindle striking surface that contacts the rear anvil striking surface of the anvil as the anvil moves away from the mount along the back-and-forth axis of travel. The mount striking surface and the spindle striking surface may define the travel path D T limit the amount by which the anvil moves along the back-and-forth axis of movement.

[0022] This overview and summary are intended to introduce a selection of concepts in a simplified form that may be described further below in the detailed description. This overview and summary are not intended to identify key features or essential features of the claimed subject matter, nor are they intended to serve as an aid in determining the scope of the claimed subject matter. Short description of the drawings

[0023] The following drawings are provided to illustrate various features of non-limiting examples of the disclosure and are not intended to limit the scope of the disclosure or to preclude alternative embodiments. Fig. 1 is an axonometric view of a power tool in accordance with aspects of the disclosure. Fig. 2 is a partial sectional view of an output assembly of the power tool of Fig. 1, along line 2-2 from Fig. 1. Fig. 3 is a partial sectional view of the output assembly of the power tool of Fig. 1, along line 3-3 from Fig. 1. Fig. 4 is a detailed view of the area around line 4-4 from Fig. 2, the details of an impact mechanism of the output assembly of the power tool from Fig. 1 shows. Fig. 5 is a partial sectional view of the output assembly of the power tool of Fig. 1, along line 5-5 from Fig. 1. Fig. 6 is an axonometric exploded view of an aging of the assembly of the power tool of Fig. 1. Fig. 7 is an enlarged cross-sectional view of a back-and-forth drive assembly of the output assembly of the power tool of Fig. 1, along line 7-7 from Fig. 1, which shows details of a drive piston in a retracted position. Fig. 8 is a cross-sectional view of the drive piston of Fig. 7 in an extended position. Fig. 9 is an axonometric view of a gearbox of the output assembly of the power tool of Fig. 1. Fig. 10 is a detailed view around the line 10-10 in Fig. 3, showing details of the drive piston in a fully extended position. Fig. 11 is a cross-sectional view of the drive piston of Fig. 10 in a first intermediate position between a fully extended and a fully retracted position. Fig. 12 is a cross-sectional view of the drive piston of Fig. 10 in a second intermediate position between a fully extended and a fully retracted position. Fig. 13 is a cross-sectional view of the drive piston of Fig. 10 in a fully retracted position. Fig. 14 is a cross-sectional view of the drive piston of Fig. 10 in a third intermediate position between a fully extended and a fully retracted position. Fig. 15 is a detailed view around the line 15-15 in Fig. 7, the details of the gearbox and a motor of the power tool from Fig. 1 shows. Detailed description

[0024] The following explanations are intended to enable those skilled in the art to make and use embodiments of the disclosed technology. Given the benefits of this disclosure, various modifications to the illustrated embodiments will be readily apparent to those skilled in the art, and the principles contained herein may be applied to other embodiments and applications without departing from the embodiments of the disclosed technology. Therefore, the embodiments of the disclosed technology are not limited to the embodiments shown, but are intended to have the widest possible applicability consistent with the principles and features disclosed herein.

[0025] The following detailed description should be read with reference to the drawings, in which the same elements have the same reference numerals in different drawings. The drawings, which are not necessarily to scale, illustrate selected embodiments and are not intended to limit the scope of the embodiments of the disclosed technique. Those skilled in the art will recognize that the examples presented herein offer many useful alternatives and are within the scope of the embodiments of the disclosed technique.

[0026] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention may be embodied and practiced otherwise. It is also to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having" and variations thereof is intended to encompass the elements listed below and their equivalents as well as additional elements.Unless otherwise specified or limited, the terms "attached," "connected," "held," and "coupled," and their variations, are used in their broadest sense and include both direct and indirect attachments, connections, mounts, and couplings. Furthermore, "connected" and "coupled" are not limited to physical or mechanical connections or couplings.

[0027] Examples of the disclosed technology can be used in all types of power tools that use removable bits. In particular, some examples can be used with impact drivers, including chipping hammers, rotary hammers, or other known designs. In this context, for example, Fig. 1-3 illustrates a power tool 100 in the form of a hammer tool (e.g., a chipping hammer), but the concepts described herein may also be applied to other types of power tools. The power tool 100 includes a housing 104 and an electric motor 108 disposed within the housing 104. The power tool 100 may also include a back-and-forth drive assembly 113 (in Fig. 2) connected to the motor 108 to convert the torque of the motor 108 (e.g., upon rotation of the motor 108 about a motor axis 120) into a back-and-forth motion. In some examples, the back-and-forth motion drive assembly 113 may be coupled to the motor 108 via a gearbox 112. An impact mechanism 114 may be coupled to the back-and-forth motion drive assembly 113 to apply repeated axial impacts to a tool bit 115 (e.g., a chisel bit or a driven tool). As shown in Fig. 1, the tool bit 115 can be slidably held by a tool holder 130 connected to the housing 104, allowing the tool bit 115 to translate along its axis to apply axial impacts to a workpiece. In the example shown, the power tool 100 includes a quick-connect mechanism 138 coupled to the tool holder 130 to enable quick release and replacement of the various tool bits 115. In other applications, other types of chucks may be used instead of the quick-connect mechanism 138, allowing for tool-in or toolless bit changes.

[0028] In some cases, the housing 104 includes various pieces that hold different parts of the power tool 100. For example, the housing 104 may include a pair of shell halves that form an outer cover for the power tool 100. In some cases, the housing 104 may include a gear housing 200 that houses the gearbox 112, the back-and-forth drive assembly 113, or the impact mechanism 114. In the example shown, the gear housing 200 includes an upper gear housing cover 204, a middle gear housing cover 206, a lower gear housing cover 208, and a gear housing cap 212.

[0029] In the illustrated example of the power tool 100, the motor 108 may be configured as a direct current (DC) motor that receives power from a built-in power source (e.g., a battery pack 118). The housing 104 may define a battery receptacle 117 that removably receives the battery pack 118. The battery pack 118 may comprise any nominal voltage (e.g., 12 V, 18 V, etc.) and may be configured with a lithium-based chemistry (e.g., lithium, lithium-ion, etc.) or other suitable chemistry. Alternatively, the motor 108 may be powered from a remote power source (e.g., a household outlet) via a power cord, or the motor 108 may be another type of motor, such as an alternating current (AC) motor. The motor 108 is selectively activated by pulling a trigger, which in some cases activates an internal switch.The switch may be electrically connected to the motor 108 via a master control device 198 (e.g., a microcontroller) or one or more circuits to control the operation of the motor 108.

[0030] With particular reference to Fig. 2 and Fig. 3, the gear housing 200 includes a spindle housing 214 that can support a spindle 160 (e.g., a drum). The spindle housing 214 is covered by a sleeve 216. In some cases, the sleeve 216 can be made of a heat-insulating material (e.g., rubber, fiberglass, mineral wool, cellulose, polyurethane, polystyrene, etc.). In some cases, the sleeve 216 can include a gripping portion 220 that can be grasped by the user (e.g., during operation of the power tool 100). During operation of the power tool 100, for example, frictional forces, vibrations, the expansion and contraction of an air pocket within the spindle 160, the operation of the motor 108, or other factors can generate heat that can increase the temperature of the gear housing 200. Accordingly, the sleeve 216 can provide an insulating layer for the user's hand from the gear housing 200.In some cases, the sleeve 216 may include a relatively high coefficient of friction in the grip area 220 and prevent the power tool 100 from slipping out of the user's hand during operation.

[0031] In addition, the handle portion 220 includes heat-dissipating elements. For example, the spindle housing 214 may include a wall 224 and a plurality of ribs 228 extending from the wall 224. In this case, the wall 224 and the ribs 228 are configured as a cylindrical wall and as circumferential ribs, respectively, although other wall-rib configurations are also possible. The ribs 228 may project outwardly from the wall 224 toward the sleeve 216 and are spaced apart in a direction parallel to a back-and-forth movement axis 168 (e.g., a striking axis). As shown in Fig. 2 and Fig. 3, the ribs 228 in the gripping portion 220 of the sleeve 216 abut the sleeve 216 and minimize the contact area between the sleeve 216 and the gear housing 200. Accordingly, a smaller amount of heat can be transferred directly from the gear housing 200 to the sleeve 216 and insulate the user's hand when positioned on the gripping portion 220.

[0032] With further reference to Fig. 2 and Fig. 3, a reciprocating drive assembly may be configured to convert the rotational motion of an engine (e.g., via a transmission) into linear reciprocating motion of a piston. In the depicted example, the reciprocating drive assembly 113 includes a crankshaft 132, a reciprocating piston 156, and a connecting rod 144. The connecting rod 144 is connected to the crankshaft 132 at a first end 148 and a second end 152 opposite the first end 148. In some cases, the connecting rod 144 may be pivotally connected to the crankshaft 132 at both the first end 148 and the second end 152. The crankshaft 132 is configured to receive torque from the engine 108 and to rotate about a crankshaft axis 136.In the illustrated example, the crankshaft 132 includes a crankpin 140 connected to the first end 148 of the connecting rod 144, which may be coupled to the piston 156 at the second end 152. Accordingly, as the crankshaft 132 rotates about the crankshaft axis 136, the connecting rod 144 drives the piston 156 for back-and-forth movement along the back-and-forth movement axis 168 and within the spindle 160 supported within the housing 104. In the illustrated example, the spindle 160 is stationary. However, in other examples, such as hammer drills, the spindle 160 may be rotated by the motor 108 to effect rotation of a tool bit.

[0033] In some embodiments, the back-and-forth drive assembly 113 may be implemented by other mechanisms, including mechanisms known in the art for converting rotary motion into back-and-forth motion (e.g., a Scotch yoke mechanism, a wobble drive mechanism, a swash plate mechanism, etc.). Although the various tool holders described below may be used in combination with the illustrated back-and-forth drive assembly 113 for back-and-forth drive, various other implementations are also possible.

[0034] A back-and-forth drive assembly moves back and forth to produce an impact on a tool via an impact mechanism. That is, the impact mechanism moves in response to the movement of the back-and-forth drive assembly to produce an impact on a tool bit. In the depicted example, the impact mechanism 114 includes a striker 164 and an anvil 172 movably received within the spindle 160. The striker 164 is located between the piston 156 and the anvil 172 and selectively moves back and forth within the spindle 160 in response to the back-and-forth movement of the piston 156. The anvil 172, which engages the tool bit 115, is struck by the striker 164 as the striker 164 moves back and forth toward the tool bit 115.The impact from the firing pin 164 on the anvil 172 can be transmitted to the tool bit 115, causing the anvil 172 to move back and forth with the tool bit 115 and work a workpiece (e.g., impact a workpiece). In the illustrated example, the anvil 172 has an internal bore 174 that receives a shank 177 of the tool bit 115. Furthermore, in the illustrated construction of the power tool 100, the spindle 160 is hollow and defines an internal chamber 162 (e.g., a bore) in which the firing pin 164 is received. An air spring 190 (e.g., an air pocket or air cushion) may be formed between the piston 156 and the firing pin 164 as the piston 156 moves back and forth within the spindle 160, whereby the expansion and contraction of the air spring 190 causes the back and forth movement of the firing pin 164.That is, as the piston 156 moves toward the firing pin 164, the volume of the air spring 190 decreases, thereby increasing the pressure within the air spring 190. This increase in pressure may be sufficient to move the firing pin 164 in the same direction as the piston 156 and cause the firing pin 164 to impact the anvil 172 to apply a blow to a workpiece via the insert 115. Conversely, as the piston 156 moves away from the firing pin 164, the volume of the air spring 190 may increase, thereby decreasing the pressure within the air spring 190. This decrease in pressure may be sufficient to move the firing pin 164 in the same direction as the piston 156, causing the firing pin 164 to retract and move away from the anvil 172.

[0035] In some cases, the firing pin 164 or the anvil 172 may form a seal against an inner surface of the spindle 160 via one or more sealing rings (e.g., an O-ring 166). In some examples, maintaining the seal between the firing pin 164 and the spindle 160 may help maintain the air spring 190 formed in the inner chamber 162.

[0036] In some non-limiting cases, the motor 108 may be positioned within the housing 104 (e.g., within a gear housing disposed within the housing 104), and the spindle 160 may be coupled to the housing 104. In some non-limiting cases, the motor 108 may be disposed within the housing 104, and the spindle 160 may be rotatable. For example, the gearbox 112 between the motor 108 and the spindle 160 may transmit torque from the motor 108 to the spindle 160 such that the spindle 160 rotates when the motor 108 is activated. The gearbox 112 may be a gear transmission, although other types of transmission systems may be used, such as belt drives, chain drives, and the like.

[0037] Furthermore, the power tool 100 includes retaining features that guide axial movement of the anvil 172 along the back-and-forth movement axis 168. As in Fig. 4, for example, a mount 176 is provided at a distal end of the spindle 160. The mount 176 defines a bore 180 (e.g., a cylindrical bore) that can receive the tool bit 115. In the example shown, the mount 176 is connected to the spindle 160 via fastening means (e.g., fasteners or retaining members). The mount 176 has a mount striking surface 188 that can engage a corresponding surface of the anvil 172. In the example shown, the anvil 172 defines a front anvil striking surface 184 that generally faces the front of the power tool 100 (e.g., the tool holder).As the anvil 172 moves along the fore-and-aft axis 168 toward the front of the power tool 100, the holder's support striking surface 188 may engage the front anvil striking surface 184 and stop further movement of the anvil 172 toward the front of the power tool 100. In the example shown, a profile of the front anvil striking surface 184 generally corresponds to the profile of the support striking surface 188. For example, each of the striking surfaces 184, 188 may have a frustoconical shape. In other embodiments, the profiles of the front anvil striking surface 184 and the support striking surface 188 may be different or include various shapes (e.g., pyramidal, cylindrical, spherical, cubic, cuboid, conical, etc.).

[0038] Furthermore, the anvil 172 is configured to engage the spindle 160 during the back-and-forth movement of the power tool 100. As in Fig. 4, the anvil 172 defines a rear anvil striking surface 268 located at a rear end of the anvil 172, generally opposite the front anvil striking surface 184. The rear anvil striking surface 268 includes a first rear surface 269 that can engage (directly) the firing pin 164 during back-and-forth movement, and a second rear surface 270 that can engage the spindle 160. In some aspects, the rear anvil striking surface 268 can be arranged to generally face the rear of the power tool 100 (e.g., toward the firing pin 164). In the example shown, the second rear surface 270 is generally conical in shape, and the first rear surface 269 projects from the second rear surface 270 toward the firing pin 164. Additionally, the second rear surface 270 engages a corresponding surface of the spindle 160.In particular, the spindle 160 may include a rib 272 protruding from a spindle wall 232 of the spindle 160 and extending circumferentially along an inner surface of the spindle wall 232. The rib 272 may define a spindle striking surface 276 disposed toward the second rear surface 270 of the rear anvil striking surface 268. As the anvil 172 moves along the fore-and-aft axis of travel 168 toward the rear of the power tool 100, the spindle striking surface 276 may engage the second rear surface 270 and stop further movement of the anvil 172 toward the rear of the power tool 100. In some cases, the profile of the spindle striking surface 276 may generally correspond to a profile of the second rear surface 270. For example, each of the striking surfaces 270, 276 may have a frustoconical shape.In other embodiments, the profiles of the rear anvil striking surface 268 and the spindle striking surface 276 may be different or include different shapes (e.g., pyramidal, cylindrical, spherical, cubic, cuboid, conical, etc.).

[0039] In some configurations, the mount 176 or spindle 160 may absorb an impact force exerted by the striker 164 on the anvil 172 along the back-and-forth movement axis 168 when the anvil 172 directly or indirectly contacts the mount 176 or spindle 160. For example, repeated impacts of the striker 164 on the anvil 172 may cause the anvil 172 to move back and forth between the mount 176 and the spindle 160. When the anvil 172 strikes the mount 176, the impact force may be absorbed by the spindle 160, which is coupled to the anvil 172 via the retaining members 192.

[0040] Under these circumstances, the mount 176 and spindle 160 may include shock-absorbing features that absorb at least a portion of the impact force exerted by the striker 164 or the reaction force exerted by a workpiece during operation. For example, as the anvil 172 moves back toward the spindle 160, the rear anvil striking surface 268 may contact the spindle striking surface 276. The impact force may be transferred to the spindle 160, with the force dissipated by the spindle 160. As the anvil 172 moves forward toward the mount 176, the front anvil striking surface 184 may contact the mount striking surface 188. The impact force exerted by the firing pin 164 can be transmitted to the anvil 172, wherein the transmitted impact force can then be transmitted via the holding elements 192 to the holder 176 and the spindle 160.Accordingly, the impact force exerted by the firing pin 164 can be reduced by directing the force to the spindle 160 or other parts of the power tool 100.

[0041] With conventional power tools, impacts can occur even when the tool bit is not in contact with a workpiece, resulting in idle impacts. To prevent impacts from occurring when a power tool is not contacting the workpiece with a tool bit, which can reduce operator fatigue and tool wear, conventional impact tool designs incorporate a parking feature that prevents the striker from moving back and forth within the spindle. For example, O-rings are included to restrict anvil movement and prevent contact between the striker and the anvil. However, such parking features increase the complexity of the manufacturing process and the overall size of the tool.According to aspects of the present disclosure, by providing a support for an anvil and a protruding wall in a spindle, the need for a parking feature (e.g., to prevent idle impacts) can be reduced or eliminated, which can typically result in increased length of the power tools. By disposing an anvil between a support (e.g., support 176) and a protruding wall (e.g., rib 272), the travel of the anvil between the support and the protruding wall can be limited or reduced, improving the efficiency of the power tool.

[0042] In particular, with continued reference to Fig. 4 a travel path D T as the difference between a stop surface distance D S and an anvil-face distance D A be defined (ie D T = D S - D A), wherein each of the respective distances is measured along the same line extending in the axial direction (e.g., approximately parallel to the axis 168). The stop surface distance D S is measured, for example, between the support striking surface 188 and the spindle striking surface 276, and the anvil striking surface distance D A is measured between the front anvil striking surface 184 and the rear anvil striking surface 268. In some aspects, the travel distance D T be the distance that the anvil 172 can travel along the back-and-forth movement axis 168 between the holder 176 or the spindle 160, or which is limited by other components of the power tool 100. In the embodiment shown, the stop surface distance D S be a small distance greater than the anvil-face distance D A . Accordingly, the travel path D Tof the anvil 172 must be smaller than the stop surface distance D S In some embodiments, the travel distance D T for example, less than or equal to 50% of the stop surface distance D S In other embodiments, the travel distance D T less than or equal to 25% of the stop surface distance D S In the embodiment shown, the travel distance D T less than or equal to 20% of the stop surface distance D S In further embodiments, the travel distance D T less than or equal to 10% of the stop surface distance D S By dissipating the impact forces generated during operation of the power tool 100 into the holder 176, the holding elements 192 and the spindle 160, the need for a parking feature can be reduced or eliminated and the travel distance D T in relation to the stop surface distance D Swhich advantageously allows a reduction in the overall length of the power tool 100 compared to conventional chisel hammers.

[0043] Fig. 5 and Fig. 6 show details of the holder 176 and the features surrounding it. In particular, the spindle 160 may include the spindle wall 232, which defines a bore 236 in which the drive piston 156, the firing pin 164, and the anvil 172 move back and forth. The spindle 160 includes a proximal end 240 (e.g., in Fig. 2 and Fig. 3) located proximate the motor 108 and a crank axle 136 about which a gear 128 rotates, and a distal end 244 remote from the motor 108 and toward the front of the power tool 100. The mount 176 may include a mount wall 248. A portion of the mount wall 248 may be received within the bore 236 at the distal end 244 of the spindle 160 in a close fit with the spindle wall 232 (e.g., a nominal sliding fit).

[0044] The support 176 may include features and elements for coupling to the spindle 160. For example, the support wall 248 may define a plurality of recesses 252 that are circumferentially spaced apart and axially aligned with respect to the back-and-forth movement axis 168. In some cases, the recesses 252 may be sized and shaped to receive the support members 192. In the illustrated embodiment, the support members 192 are cylindrically shaped, and the recesses 252 may be correspondingly cylindrically shaped to receive corresponding portions of the support members 192. In other embodiments, the support members 192 may instead comprise other shapes (e.g., ovoid, spherical, frustoconical, prismatic, arcuate, etc.) and the recesses 252 may be correspondingly shaped to closely receive the guide members.

[0045] Similarly, the spindle 160 may include features and elements for coupling to the support 176. For example, the spindle wall 232 may include a plurality of openings 256 extending therethrough such that the bore 236 is accessible through the plurality of openings 256. The openings 256 may be circumferentially spaced from one another and axially aligned with respect to the axis of movement 168. The openings 256 may be sized and shaped to receive corresponding portions of the retaining members 192. In the illustrated embodiment, the retaining members 192 are cylindrically shaped, and the openings 256 are correspondingly cylindrically shaped to closely receive the respective portions of the retaining members 192. In other embodiments, the openings 256 may include different shapes to closely receive correspondingly shaped retaining members, which may not be cylindrical.

[0046] With further reference to Fig. 5 and Fig. 6, the recesses 252 of the bracket 176 may be aligned with the openings 256 of the spindle 160. The retaining elements 192 may be provided through the recesses 252 and the openings 256. In particular, a first portion of each retaining element 192 may be disposed in a corresponding recess 252 and a second portion (e.g., the remaining portion) of each retaining element 192 may be disposed in the corresponding aligned opening 256. Therefore, the retaining elements 192 may provide a coupling mechanism to couple the bracket 176 to the spindle 160.

[0047] In some cases, the gear housing cap 212 may be provided at the distal end 244 of the spindle 160 and retain the retaining elements 192 in the recesses 252 and the openings 256. The gear housing cap 212 may include a flange 260 and a cap wall 264 extending axially from the flange 260. In some cases, the cap wall 264 may be cylindrically shaped, but other shapes are also possible. The cap wall 264 may be fitted over the distal end 244 adjacent the retaining elements 192 and retain the retaining elements 192 in the recesses 252 and the openings 256. In some cases, the flange 260 may be attached to the gear housing 200 (for example, by fasteners such as screws or adhesives).

[0048] In some cases, the support members 192 may be formed from a first material having a first modulus of elasticity. The spindle 160 may be formed from a second material having a second modulus of elasticity. The bracket 176 may be formed from a third material having a third modulus of elasticity. In some cases, the first, second, and third materials may each comprise a hard and stiff material (e.g., metals, hardened steel, etc.). In other embodiments, various types of materials with different stiffness may be used, such as an elastomer, rubber, wood, plastic, concrete, glass, high permeability materials, low permeability materials, ferrous material, and the like. In some embodiments, the first Young's modulus may be equal to or greater than the second Young's modulus and equal to or greater than the third Young's modulus.In some cases, two or more of the first, second and third materials may be the same or different.

[0049] In the illustrated embodiment, the power tool 100 includes eight retaining members 192 and eight corresponding recesses 252 and openings 256 arranged at equal intervals circumferentially around the spindle 160. In other embodiments, the power tool 100 may include a fewer number of retaining members, corresponding recesses, and corresponding openings (e.g., one, two, three, four, five, six, or seven). In some embodiments, the power tool 100 may include a greater number of retaining members, corresponding recesses, and corresponding openings (e.g., more than eight).

[0050] In Fig. 7-9, the engine 108, the transmission 112, and the fore-and-aft drive assembly 113 are shown in more detail. In particular, the crankshaft 132 includes a counterweight 280 and a crank 284 that includes the crankpin 140. The counterweight 280 may be defined by a distance L1 (e.g., a radial distance) measured along a direction of the fore-and-aft axis 168 between the crank axis 136 and a first distal edge of the counterweight 280. The crank 284 may also be defined by a distance L2 (e.g., a radial distance) measured along the direction of the fore-and-aft axis 168 between the crank axis 136 and a second distal edge of the counterweight 280 on a side that includes the crank 284. In the example shown, the distance L1 of the counterweight 280 is shorter than the distance L2 of the crank 284.In some cases, the shorter distance L1 may allow the counterweight 280 to avoid contact with the drive piston 156 when the drive piston 156 is in a fully retracted position (for example, in a bottom dead center position, as shown in FIG. Fig. 7). In some cases, the larger distance L2 of the crank 284 may increase a crank radius of the crank pin 140. However, the example shown contemplates an arrangement of the crank 284 in which the crank 284 may be positioned closer to the transmission 112 or rotated away from the drive piston 156 in the bottom dead center position without interfering with the drive piston 156, the spindle 160, or other parts of the transmission 112.

[0051] In particular, the proximal end 240 of the spindle 160, as in Fig. 9, include a plurality of cutouts or slots 292 located on each respective lateral side of the spindle 160. In some cases, each of the slots 292 may be defined between an upper edge 296 of the spindle 160 and a lower edge 300 of the spindle 160. In the example shown, the spindle 160 is disposed below the gear 128, and the crank 284 may at least partially overlap with the upper edge 296 and the lower edge 300 in a direction parallel to the crank axis 136 when the drive piston 156 is in a fully extended position (e.g., in a top dead center position, as in Fig. 8-10). In other words, as the drive piston 156 approaches or returns from the fully extended position, at least a portion of the crank 284 of the crankshaft 132 may pass between the upper and lower edges 296, 300 of the spindle 160. Accordingly, the slots 292 may allow the crank 284 to rotate about the crank axis 136 and impart translational motion to the drive piston 156 without disturbing the spindle 160 (which remains stationary, for example, in chipping hammers) or the drive piston 156. In some cases, the illustrated configuration of the spindle 160 may allow for a compact arrangement of the reciprocating drive assembly 113 or the gearbox 112 within the gearbox housing 200 and a shorter overall length of the power tool 100.

[0052] Fig. 10-14 show functional views of the gearbox 112 and the reciprocating drive assembly 113 in various positions. As generally described above, the spindle 160 may include features that allow rotational movement of the crank 284 without interference between a fully extended position and a fully retracted position of the drive piston 156.

[0053] Fig. 10 shows the drive piston 156 in a fully extended position (e.g., in the top dead center position). In the illustrated example, the rod 144 is aligned along the fore-and-aft axis 168. A portion of the crank 284 and the crank pin 140 are at least partially disposed within the spindle 160 at the proximal end 240. For example, the crank 284 and the crank pin 140 at least partially overlap the upper edge 296 (e.g., in Fig. 7-9) and the lower edge 300. The counterweight 280 is arranged towards a rear end of the power tool 100 (for example, towards the motor 108).

[0054] Fig. Figure 11 shows the drive piston 156 in a partially retracted (or, for example, partially extended) first intermediate position between the fully extended position (for example, in Fig. 10) and the fully retracted position (for example in Fig. 13). In the example shown, the crankshaft 132 is rotated in a 45-degree counterclockwise position from the fully extended position about the crank axis 136, and the rod 144 is disposed at an oblique angle relative to the fore-and-aft axis 168. In some cases, at least a portion of the rod 144 may be disposed in one of the slots 292 formed between the upper edge 296 (e.g., in Fig. 7-9) and the lower edge 300. In this position, the crank 284 and the crank pin 140 are arranged outside the spindle 160. The counterweight 280 can be rotated 45 degrees about the crank axis 136.

[0055] Fig. 12 shows the drive piston 156 in a further, partially retracted, second intermediate position in which the drive piston 156 is displaced further toward the motor side of the power tool 100. In the illustrated example, the crankshaft 132 is rotated counterclockwise from the 45-degree position about the crank axis 136 to a 90-degree position. The rod 144 is arranged at an oblique angle relative to the back-and-forth movement axis 168. In this position, at least a portion of the rod 144 may be arranged in the slot 292. The crank 284 and the crank pin 140 are arranged outside the spindle 160, and a portion of the counterweight 280 is arranged inside the spindle 160 between the upper edge 296 (for example, in Fig. 7-9) and the lower edge 300. In particular, the counterweight 280 can be slid into the slot 292 when the crankshaft 132 is rotated from the 45-degree position to the 90-degree position. Accordingly, the crankshaft 132 can rotate without interfering with the spindle 160 or the piston 156, and the piston 156 can continue to move within the spindle 160 along the fore-and-aft axis 168.

[0056] Fig. 13 shows the drive piston 156 in a fully retracted position. In the example shown, the crankshaft 132 is rotated counterclockwise from the 90-degree position about the crank axis 136 to a 180-degree position. In this position, the drive piston 156 may be in the bottom dead center position. A portion of the drive piston 156 may axially overlap the slots 292 and be positioned between the upper edge 296 and the lower edge 300. In some cases, the upper and lower edges 296, 300 may protrude beyond the drive piston 156 in this position, i.e., be closer to the crank axis 136. Additionally, the counterweight 280 may be located near the proximal end 240 of the spindle 160 and disposed outside the spindle 160. The rod 144 may axially overlap with the counterweight 280 above the counterweight 280, and the rod 144 may extend along the fore-and-aft movement axis 168.

[0057] Fig. 14 shows the drive piston 156 in a partially retracted, third intermediate position between the fully extended position and the fully retracted position of the drive piston 156. In the illustrated example, the crankshaft 132 is rotated counterclockwise from the 180-degree position about the crank axis 136 to a 270-degree position. In this position, a portion of the rod 144 may be disposed in one of the slots 292 and a portion of the counterweight 280 may be disposed in the other of the slots 292.

[0058] In some cases, the drive piston 156 may be moved from the 270 degree position as in Fig. 14, to complete one stroke of the drive piston 156. In some cases, the crankshaft 132 may rotate clockwise, the opposite direction to that described above. By allowing portions of the crankshaft 132 to slide through the slots 292 while the crankshaft 132 rotates about the crank axis 136, the drive piston 156 can continue its back-and-forth motion without interference and while maintaining a compact arrangement of components within the power tool 100.

[0059] With reference to Fig.15, examples of the present disclosure may provide an arrangement of the gearbox 112 that may reduce or eliminate translation of a rotor of the motor 108 along the motor axis 120 during operation of the power tool 100. The gearbox 112 includes, for example, a central gearbox cover 206 disposed adjacent the motor 108 and defining a bearing pocket 310. In some cases, a bearing 314 having an outer race 316 may be disposed within the bearing pocket 310. A bearing retainer 312 may be attached to the central gearbox cover 206 (e.g., via fasteners such as bolts) and may engage the outer race 316 to secure the outer race 316 within the bearing pocket 310. An inner race 318 of the bearing 314 can engage the pinion gear 124 as the pinion gear 124 rotates relative to the outer race 316 and the center gear housing cover 206.In some cases, the pinion gear 124 may be connected to one end of the motor shaft 116 and include a flange 322 that abuts an axial end surface of the inner race 318. A retainer 320 (e.g., a snap ring, an E-clip, etc.) may be provided in a groove 126 formed in the pinion gear 124. The retainer 320 may engage an opposing axial end surface of the inner race 318. Accordingly, translational movement of the pinion gear 124 may be limited by disposing the bearing 314 between a head portion of the pinion gear 124 and the retainer 320. In some cases, the axial position of the inner race 318 may be determined by the axial position of the outer race 316. In some cases, the axial position of the outer race 316 may be determined by the center gear housing cover 206 and the bearing retainer 312.Accordingly, the arrangement of the central gear housing cover 206 can determine the axial position of the pinion gear 124.

[0060] Additionally, the motor 108 may include a stator assembly 330 and a rotor assembly 332 rotatably mounted on the motor shaft 116 relative to the stator assembly 330. The rotor assembly 332 may include a rotor core 334 (e.g., such as a lamination stack) disposed on the motor shaft 116 (e.g., by press fitting or nominal interference). The rotor core 334 may define a first axial face 336 that contacts a corresponding second axial face 338 defined on the pinion gear 124. Thus, the pinion gear 124 fixes the rotor core 334 against forward displacement (i.e., toward the central transmission housing cover 206).

[0061] During operation of the power tool 100, the rotor core 334 may tend to slip on the motor shaft 116. In some cases, the rotor core 334 may shift axially toward the central gear housing cover 206 due to the repeated back-and-forth movements and impact forces acting on the drive piston 156, the striker 164, the anvil 172, or the tool bit 115. In some cases, the contact between the pinion gear 124 and the rotor core 334 may prevent the rotor core 334 from slipping and moving toward the central gear housing cover 206 during operation of the power tool 100.

[0062] In some embodiments, the devices or systems disclosed herein may be used, manufactured, or installed using methods embodying aspects of the invention. Accordingly, any description herein of particular features, capabilities, or intended purposes of a device or system is generally intended to include disclosure of a method of using such devices for the intended purposes, a method of otherwise applying such capabilities, a method of manufacturing relevant components of such device or system (or the device or system as a whole), and a method of installing disclosed (or otherwise known) components to support such purposes or capabilities.Similarly, unless otherwise stated or limited, discussion of a method of making or using a particular device or system, including installation of the device or system, as an embodiment of the invention is intended to include disclosure of the utilized features and applied capabilities of such device or system.

[0063] Unless otherwise limited or defined, the term "or" as used herein refers to a non-exclusive list of components or acts that may be present in a variety of combinations, rather than an exclusive list of components that may be present only as alternatives to one another. For example, a list of "A, B, or C" indicates the following options: A; B; C; A and B; A and C; B and C; and A, B, and C. Accordingly, the term "or," as used herein, is intended to indicate exclusive alternatives only when preceded by expressions of exclusivity such as "either," "one of," "only one of," or "exactly one of." For example, the list of "one of A, B, or C" indicates the following options: A, but not B and C; B, but not A and C; and C, but not A and B.A list preceded by the word "one or more" (and variations thereof) and separated by "or" indicates the possibility of choosing one or more of the listed items. For example, the phrases "one or more of A, B, or C" and "at least one of A, B, or C" indicate the following options: one or more A; one or more B; one or more C; one or more A and one or more B; one or more B and one or more C; one or more A and one or more C; and one or more of A, one or more of B, and one or more of C. Similarly, a list preceded by "a plurality of" (and variations thereof) and separated by "or" indicates options for multiple instances of one or all of the listed items.For example, the expressions “a plurality of A, B, or C” and “two or more of A, B, or C” indicate the following options: A and B; B and C; A and C; and A, B, and C.

[0064] Unless otherwise defined or restricted, the directional terms used herein are used to simplify the discussion of specific drawings or examples or to clarify spatial relationships to specific other components or contexts, but not to indicate absolute orientation. For example, references to downward, forward, or other directions, or to the top, back, or other positions (or features) may be used to discuss aspects of a particular example or drawing, but do not necessarily require a similar orientation or geometry in all installations or configurations.

[0065] Unless otherwise defined, "substantially parallel" means a direction that is within ± 12 degrees of a reference direction (for example, within ± 6 degrees or ± 3 degrees), inclusive. Similarly, unless otherwise limited or defined, "substantially perpendicular" means a direction that is within ± 12 degrees of a reference direction (for example, within ± 6 degrees or ± 3 degrees), inclusive. Accordingly, "substantially vertical" means a direction that is substantially parallel to the vertical direction as defined relative to the reference frame (for example, by default, a local direction of gravity), with a similarly derived meaning for "substantially horizontal" (relative to the horizontal direction). When reference is made to directions "transverse" to a reference direction, this means directions that are not substantially parallel to the reference direction.Accordingly, some transverse directions may be perpendicular or substantially perpendicular to the reference direction in question.

[0066] Unless expressly stated otherwise, ordinal numbers are used herein for ease of reference, generally based on the order in which particular components are presented in that portion of the disclosure. For example, in this context, designations such as "first," "second," etc., generally indicate only the order in which a so-designated component is presented for discussion and generally do not imply a requirement for any particular spatial, functional, temporal, or structural precedence or order.

[0067] The foregoing description of the disclosed embodiments is intended to enable one skilled in the art to make or use the invention. In light of this disclosure, various modifications to these embodiments will be readily apparent to those skilled in the art, and the principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. The invention is therefore not limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 624,954

[0001] US 63 / 619,520

[0001]

Claims

[1] Power tool comprising: a housing; an electric motor held in the housing; a spindle supported by the housing; a holder at least partially received in the spindle and configured to receive at least a portion of a tool bit of the power tool; a back-and-forth drive assembly coupled to the electric motor and configured to convert the torque of the electric motor into back-and-forth movement of a drive piston at least partially received in the spindle for back-and-forth movement therein along a back-and-forth movement axis; a firing pin received in the spindle and moving back and forth in response to the back and forth movement of the drive piston; and an anvil at least partially received in the spindle and positioned between the striking pin and the tool bit, the anvil being adapted to transmit axial impacts from the striking pin to the tool bit, and the anvil comprising a front anvil striking surface and a rear anvil striking surface opposite the front anvil striking surface, wherein the support defines a support striking surface that contacts the front anvil striking surface of the anvil in response to movement of the anvil in a first direction along the back-and-forth movement axis, the spindle defines a spindle striking surface that contacts the rear anvil striking surface of the anvil in response to movement of the anvil in a second direction along the back-and-forth axis of movement, the second direction being opposite to the first direction, and the holder striking surface and the spindle striking surface have a travel path D T limit the amount by which the anvil moves along the back-and-forth axis of movement. [2] Power tool according to claim 1, wherein the holding striking surface is spaced apart from the spindle striking surface by a stop surface distance D S and the travel path D T less than or equal to 50 percent of the stop surface distance D S amounts. [3] Power tool according to claim 2, wherein the travel path D T less than or equal to 20 percent of the stop surface distance D S amounts. [4] The power tool of claim 1, wherein the anvil defines an opening and an internal bore, the internal bore at least partially receiving a shank of the tool bit. [5] The power tool of claim 1, wherein the spindle includes a spindle wall defining a bore, the spindle including a rib extending inwardly from the spindle wall and into the bore, the rib defining the spindle striking surface. [6] Power tool according to claim 1, wherein the holder is connected to the spindle via a holding element. [7] Power tool according to claim 6, wherein the holding element has a cylindrical shape. [8] Power tool comprising: a housing having a gear housing and a gear housing cap connected to the gear housing; an electric motor held in the housing; a spindle supported by the housing, the spindle defining an opening; a holder at least partially received in the spindle and configured to receive at least a portion of a tool bit of the power tool, the holder defining a recess; a back-and-forth drive assembly coupled to the electric motor and configured to convert the torque of the electric motor into back-and-forth movement of a drive piston at least partially received in the spindle for back-and-forth movement therein along a back-and-forth movement axis; a firing pin received in the spindle and moving back and forth in response to the back and forth movement of the drive piston; an anvil at least partially received in the spindle and positioned between the firing pin and the tool bit, the anvil being adapted to transmit axial impacts from the firing pin to the tool bit; and a retaining element connecting the holder and the spindle, the retaining element being received in both the recess and the opening, and the gearbox cap surrounds the opening to hold the retaining element therein. [9] The power tool of claim 8, wherein the gear housing comprises a spindle housing surrounding the spindle, and the power tool further comprises a collar surrounding the spindle housing. [10] The power tool of claim 9, wherein the spindle housing includes a plurality of outwardly projecting ribs spaced apart in a direction parallel to the back-and-forth axis of movement, each rib contacting the collar. [11] Power tool according to claim 8, wherein the holding element has a cylindrical shape. [12] A power tool according to claim 8, wherein the gear housing cap surrounds at least a portion of the spindle. [13] The power tool of claim 8, wherein the retaining member is one of a plurality of retaining members, the recess being one of a plurality of recesses and the opening being one of a plurality of openings. [14] Power tool according to claim 8, wherein: the anvil comprises a front anvil striking surface and a rear anvil striking surface opposite the front anvil striking surface; the bracket defines a bracket striking surface that contacts the front anvil striking surface of the anvil as the anvil moves toward the bracket along the back-and-forth axis of movement; the spindle defines a spindle striking surface that contacts the rear anvil striking surface of the anvil as the anvil moves away from the support along the back-and-forth axis of movement; and the holder impact surface and the spindle impact surface have a travel path D T limit the amount by which the anvil moves along the back-and-forth axis of movement. [15] Power tool comprising: a housing; an electric motor held in the housing; a spindle supported by the housing; a holder at least partially received in the spindle and configured to receive at least a portion of a tool bit of the power tool; a back-and-forth drive assembly coupled to the electric motor and configured to convert the torque of the electric motor into back-and-forth movement of a drive piston at least partially received in the spindle for back-and-forth movement therein along a back-and-forth movement axis, the back-and-forth drive assembly comprising: a crankshaft adapted to rotate about a crank axis substantially perpendicular to the back-and-forth movement axis, the crankshaft including a journal, and a connecting rod connected at a first end to the pin and at a second end to the drive piston; a firing pin received in the spindle and moving back and forth in response to the back and forth movement of the drive piston; and an anvil at least partially received in the spindle and arranged between the firing pin and the tool bit, the anvil being adapted to transmit axial impacts from the firing pin to the tool bit; wherein the spindle includes a proximal end closest to the crank axis, the proximal end including an upper edge and a lower edge, and the proximal end defining a slot between the upper edge and the lower edge; and at least a portion of the first end of the connecting rod passes through the slot during rotation of the crankshaft. [16] The power tool of claim 15, wherein the back-and-forth drive assembly further comprises a driven gear coupled to the crankshaft, and the upper edge is located closest to the driven gear and the lower edge is located farthest from the driven gear. [17] The power tool of claim 16, wherein the slot is a first slot and the proximal end further defines a second slot, the first and second slots being defined on opposite lateral sides of the spindle between the upper edge and the lower edge. [18] A power tool according to claim 17, wherein the first end of the connecting rod passes through both the first slot and the second slot during rotation of the crankshaft. [19] A power tool according to claim 15, wherein the pin is located between the upper edge and the lower edge when the drive piston in the spindle is in a top dead center position. [20] A power tool according to claim 15, wherein: the anvil comprises a front anvil striking surface and a rear anvil striking surface near the opposite ends of the anvil; the bracket defines a bracket striking surface that contacts the front anvil striking surface of the anvil as the anvil moves toward the bracket along the back-and-forth axis of movement; the spindle defines a spindle striking surface that contacts the rear anvil striking surface of the anvil as the anvil moves away from the support along the back-and-forth axis of movement; and the holder impact surface and the spindle impact surface have a travel path D T limit the amount by which the anvil moves along the back-and-forth axis of movement.

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