Camshaft for power tools

Abstract

A power tool comprising a housing, a motor mounted in the housing having an output shaft, a gear assembly, and an impact mechanism. The motor is configured to rotate the output shaft. The gear assembly is configured to be rotated by the output shaft. The impact mechanism includes a camshaft configured to be rotated by the gear assembly, a hammer, and an anvil. The camshaft has a groove, and at least a portion of the groove is defined by an equation selected from a group consisting of trigonometric equations and higher order differential equations. The hammer is coupled to the camshaft by a cam ball received in the groove. The anvil is configured to receive intermittent rotational impacts from the hammer.

Description

Cross-reference to related applications

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 620,557, filed January 12, 2024, the entire contents of which are incorporated herein by reference. Field of the invention

[0002] The present disclosure relates to power tools having impact mechanisms, and more particularly to power tools having rotating impact mechanisms ("rotary impact tools"), such as impact tools, impact wrenches, and the like. background

[0003] Rotating impact tools typically include a hammer coupled to a camshaft so that the hammer can move back and forth along the camshaft, storing energy in a spring, and can also rotate relative to the camshaft to deliver periodic rotating blows to an anvil. Summary

[0004] The reciprocating motion of the hammer along the camshaft generates axial vibrations that are uncomfortable for the user and can lead to fatigue. Accordingly, the present disclosure may provide, among other things, a camshaft configured to provide a rotating impact tool with quieter operation and less vibration.

[0005] For example, in one aspect, the techniques described herein relate to, for example, a power tool comprising: a housing; a motor mounted within the housing and having an output shaft, the motor configured to rotate the output shaft; a gear assembly configured to be rotated by the output shaft; and an impact mechanism comprising a camshaft, a hammer, and an anvil. The camshaft is configured to be rotated by the gear assembly. The camshaft has a groove, and at least a portion of the groove is defined by an equation selected from a group consisting of: trigonometric equations and higher order differential equations. The hammer is coupled to the camshaft by a cam ball received in the groove.The anvil is configured to absorb intermittent rotational impacts from the hammer.

[0006] In some aspects, the section of the groove is defined by a cosine equation. In other aspects, the hammer is configured to rotate the anvil when the cam ball is in the section of the groove defined by the cosine equation.

[0007] In some aspects, the portion of the groove is a first groove portion, and the groove includes a second groove portion defined by a linear equation. In further aspects, the first groove portion and the second groove portion meet at a transition point, and the first groove portion and the second groove portion are continuous and tangent at the transition point. In further aspects, the groove includes a third groove portion defined by an equation of a circle. In further aspects, the groove includes two second groove portions, the first groove portion extends between the two second groove portions, and the groove includes two third groove portions, each of the third groove portions extends from a corresponding one of the second groove portions.

[0008] In some cases, the entire groove is defined by an equation selected from the group consisting of: trigonometric equations and higher order differential equations.

[0009] In some cases, the camshaft extends along an axis and the groove is mirrored across the axis.

[0010] In another aspect, the techniques described herein relate to a camshaft for a striking mechanism, the camshaft including a groove configured to receive a cam ball, the groove having a first portion defined by a first equation, a second portion defined by a second equation, and a third portion defined by a third equation, wherein at least one of the first equation, the second equation, and the third equation is an equation selected from a group consisting of: trigonometric equations and higher order differential equations.

[0011] In some cases, only one of the first equation, the second equation, and the third equation is an equation selected from the group consisting of: trigonometric equations and higher order differential equations.

[0012] In some aspects, the first equation is a cosine equation with an amplitude, the amplitude of the cosine equation defining a leading point of the groove, the second groove portion extending from an end of the first groove portion opposite the amplitude, and the third groove portion extending from an end of the second groove portion opposite the first groove portion. In further aspects, the camshaft extends along an axis and the groove is mirrored about the axis such that the groove includes two second groove portions and two third groove portions. In further aspects, the second equation is a linear equation and the third equation is an equation for a circle.

[0013] In some cases, the first equation, the second equation, and the third equation are different types of equations.

[0014] In another aspect, the techniques described herein relate to a power tool comprising a housing, a motor mounted in the housing and having an output shaft, a gear assembly, and an impact mechanism. The motor is configured to rotate the output shaft. The gear assembly is configured to be rotated by the output shaft. The impact mechanism includes a camshaft, a hammer, and an anvil. The camshaft is configured to be rotated by the gear assembly. The camshaft has a groove having a first groove portion and a second groove portion that meet at a transition point. The first groove portion and the second groove portion are continuous and tangential at the transition point. The hammer is coupled to the camshaft via a cam ball received in the groove.The anvil is configured to absorb intermittent rotational impacts from the hammer.

[0015] In some aspects, the first groove portion is defined by a first equation and the second groove portion is defined by a second equation, wherein the first equation and the second equation are different. In further aspects, one of the first equation and the second equation is an equation selected from a group of equations consisting of: trigonometric equations and higher-order differential equations, and the other of the first equation and the second equation is a linear equation.

[0016] In some aspects, the transition point is a first transition point, the groove further comprising a third groove portion such that the second groove portion and the third groove portion meet at a second transition point, and the second groove portion and the third groove portion are continuous and tangent at the second transition point. In further aspects, each of the first groove portion, the second groove portion, and the third groove portion is defined by a different equation than the others of the first groove portion, the second groove portion, and the third groove portion. Short description of the drawings Fig. 1 is a perspective view of an impact wrench according to an embodiment of the disclosure. Fig. 2 is a cross-sectional view of the impact wrench of Fig. 1 along line 2-2. Fig. 3 is a perspective view of a camshaft and a hammer for the impact wrench of Fig. 1. Fig. 4 is a plan view of the camshaft of Fig. 3. Fig. 5 is a schematic view of a cam groove for the camshaft of Fig. 4. Fig. Figure 6 shows a graph with position, speed and acceleration curves for a camshaft according to the state of the art. Fig. 7 shows a graph with position, speed and acceleration curves for the camshaft of Fig. 4. Fig. 8A is a plan view of a camshaft according to another embodiment of the disclosure. Fig. 8B is another top view of the camshaft of Fig. 8A. Fig. 8C is a perspective view of the camshaft of Fig. 8A. Fig. 9 shows a graph with position, velocity and acceleration curves for a camshaft according to another embodiment of the disclosure.

[0017] Before any embodiments of the invention are explained in detail, it should be understood that the invention is not limited in its application to the details of construction and arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. It is understood that the phraseology and terminology used herein is for the purpose of description and should not be considered limiting. Detailed description

[0018] In the Fig. 1 and Fig. 2, a power tool in the form of an impact wrench 10 is shown. The impact wrench 10 includes a housing 14 having a drive unit housing portion 18, a handle housing portion 22 extending downwardly from the drive unit housing portion 18, an intermediate housing 26, and an impact housing or front housing portion 30 coupled to and extending forwardly from the drive unit housing portion 18. In the illustrated embodiment, the drive unit housing portion 18 and the handle housing portion 22 are defined by cooperating first and second half-shells or housing portions. The drive unit housing portion 18 houses a drive unit 34 configured to output or generate torque. The handle housing portion 22 defines a handle configured to be grasped by a user to operate the impact wrench 10.The intermediate housing 26 houses a gear assembly 38 configured to receive torque from the drive unit 34. The drive unit 34 and the gear assembly 38 form a drive assembly. The front housing portion 30 houses an impact mechanism 42 configured to receive torque from the gear assembly 38 and provide or deliver torque to an output end 46 of the impact wrench 10.

[0019] With continued reference to the Fig. 1 and Fig. 2, the drive unit 34 includes a motor 50, an output shaft 54 configured to be driven by the motor 50 to provide output torque, a printed circuit board assembly ("PCBA") 58 for controlling the operation of the motor 50, and a fan 62 mounted on the output shaft 54. The motor 50 is a brushless direct current ("BLDC") motor. As such, the motor 50 may include a stator and a rotor. The output shaft 54 defines a motor axis A1. The output shaft 54 is supported by a rear bearing 66 and a front bearing 70. Both the rear bearing 66 and the front bearing 70 are supported by the drive unit housing portion 18. In the illustrated embodiment, the PCBA 58 is disposed between the motor 50 and the front bearing 70. In other embodiments, the PCBA 58 may be disposed elsewhere.The fan 62 is mounted on the output shaft 54 at a position between the motor 50 and the rear bearing 66. The motor 50 is configured to rotate the fan 62. As the fan 62 rotates, the fan 62 can create a flow of cooling air that flows past the motor 50 to cool the motor 50 and the PCBA 58.

[0020] The handle housing portion 22 defines the handle and a battery receptacle 74 that receives a battery 78 configured to power the motor 50. The battery 78 may be a power tool battery generally used to operate a power tool, such as an electric drill (e.g., an 18-volt rechargeable battery or an M18 REDLITHIUM battery sold by Milwaukee Electric Tool Corporation). The battery 78 may include lithium-ion (Li-ion) cells. In alternative embodiments, the battery 78 may have a different chemistry (e.g., nickel-cadmium (NiCa or NiCad), nickel-hydride, and the like). In the illustrated embodiment, the battery 78 may be a 4-volt battery pack, a 28-volt battery pack, a 40-volt battery pack, or a battery pack having a different voltage suitable for operating the impact wrench 10.The handle supports a switch 82 (e.g., a trigger switch) that can be actuated to electrically connect the motor 50 and the battery 78 and to supply DC power to the motor 50. Thus, a user can actuate the switch 82 to send a signal to the PCBA 58 to energize the motor 50 so that the drive unit 34 begins to generate torque.

[0021] As in the Fig. 2-4, the gear assembly 38 includes a planetary carrier 86, a plurality of planetary gears 90, and a ring gear 94. The planetary carrier 86 supports the plurality of planetary gears 90. The planetary carrier 86 may include a back wall 86a, a front wall 86b, and a plurality of pins 98 extending between the back wall 86a and the front wall 86b such that each of the planetary gears 90 is mounted or coupled to a corresponding one of the pins 98 between the back wall 86a and the front wall 86b. Each of the planetary gears 90 has a gearing that meshes with a pinion gear 54a of the output shaft 54 such that rotation of the output shaft 54 drives the movement and rotation of the planetary gears 90. Each of the planetary gears 90 is also in meshing engagement with ring gear teeth formed on an inner surface of the ring gear 94.The output shaft 54 is configured to rotate the planetary gears 90 about the ring gear 94 such that the planetary gears 90 orbit the pinion gear 54a of the output shaft 54. Due to the coupling between the planetary gears 90 and a corresponding one of the pins 98, the planetary gears 90 provide a constant rotational force or torque to the planetary carrier 86.

[0022] With continued reference to the Fig. 2 to 4, the impact mechanism 42 is configured to convert the constant rotational force or torque provided by the gear assembly 38 into a percussive rotational force or intermittent application of torque at the output end 46 of the impact wrench 10 for application to the workpiece 102. The impact mechanism 42 includes a camshaft 106, a hammer 110, an anvil 114, and a spring 118. The camshaft 106 is integrally formed with the planetary carrier 86 of the gear assembly 38 so that the motor 50 can apply a constant rotational force or torque to the camshaft 106 through the meshing engagement between the output pinion 54a and the planetary gears 90. The camshaft 106 extends along a rotational axis A2. The rotational axis A2 may also be referred to as the output axis. In the illustrated embodiment, the rotation axis A2 is coaxial with the motor axis A1.The camshaft 106 includes at least one cam groove 122 defined within the camshaft 106, which is configured to receive at least one cam ball 126. The cam ball 126 is positioned in driving engagement with the hammer 110 such that movement of the cam ball 126 within the cam groove 122 enables relative axial movement of the hammer 110 along the camshaft 106. In particular, the hammer 110 is configured to move axially along the camshaft 106 to intermittently apply a percussive rotational force or rotational impact to the anvil 114. The spring 118 extends from the planetary carrier 86 to the hammer 110 and urges the hammer 110 toward the anvil 114.

[0023] In the illustrated embodiment, with reference to Fig. 4, the cam groove 122 has a first groove portion 130, a second groove portion 134, and a third groove portion 138. The designation "first," "second," and "third" groove portions is arbitrary, so that the groove portions 130, 134, and 138 may be referred to in any other order. For example, the first groove portion 130 could be referred to as the third groove portion, and the third groove portion 138 could be referred to as the first groove portion. The first groove portion 130 defines a first end of the cam groove 122. When the cam ball 126 is positioned in the first portion 130 of the cam groove 122, the hammer 110 may be in a rearward-most position along the camshaft 106. The second groove portion 134 extends between the first portion 130 and the third groove portion 138. The third groove portion 138 defines a second end of the cam groove 122.When the cam ball 126 is positioned in the third groove portion, the hammer 110 is in a forwardmost position along the camshaft 106, allowing the hammer 110 to strike the anvil 114. In the illustrated embodiment, the cam groove 122 is arranged along a circumference or outer surface of the camshaft 106, mirroring the output axis A2. As such, the cam groove 122 includes two first groove portions 130 and two second groove portions 134. The third groove portion 138 extends between the two second groove portions 134 and interconnects the second groove portions 134 such that the cam ball 126 can move sequentially from the first groove portion 130 and the second groove portion 134 on one side of the output axis A2, across the third groove portion 138, and along the second groove portion 134 and the first groove portion 130 on the opposite side of the output axis A2.In other words, each of the second groove portions 134 extends from an end of the third groove portion 138 opposite to the output axis A2 (ie, the amplitude or the foremost position of the third groove portion 138), and each of the first groove portions 130 extends from an end of a corresponding one of the second groove portions opposite to the third groove portion 138.

[0024] The first groove portion 130 is defined by a first equation, the second groove portion 134 is defined by a second equation, and the third groove portion is defined by a third equation. In the illustrated embodiment, each of the first equation, the second equation, and the third equation are different. In other words, the first groove portion 130, the second groove portion 134, and the third groove portion 138 are each defined by different equations. In some embodiments, the first equation, the second equation, and the third equation may all be the same. In other embodiments, the groove may have only one portion defined by a single equation. As described in more detail below, the third equation is an equation selected from a group consisting of trigonometric equations and higher order differential equations.

[0025] With reference to the Fig. 4 and Fig. 5, each of the first groove portions 130 and the second groove portions 134 will be described below with respect to only one of the portions 130, 134 (i.e., the portion 130, 134 on one side of the output axis A2). It should be understood that the description of the first groove portion 130 and the second groove portion 134 on one side of the output axis A2 equally applies to the corresponding portion 130, 134 on the opposite side of the output axis A2. In some embodiments, the portions 130, 134 on one side of the output axis A2 may differ from the corresponding portions 130, 134 on the opposite side of the output axis A2. In the illustrated embodiment, the first groove portion 130 is defined by a particular radius. In other words, the first groove portion 130 is defined by a portion of a circle having that radius.Thus, the first groove portion 130 follows the equation of a circle, as follows:. r2=(x−A)2+(y−B)2

[0026] In this equation, variables A and B specify the location of the center of the circle. For example, variable A specifies the x-coordinate in an xy coordinate system, and variable B specifies the y-coordinate in an xy coordinate system. Thus, variables A and B can be adjusted to specify the starting position of the first groove portion 130 (e.g., to align it with the second groove portion 134). The variable r is the radius of the circle. As such, variable r can be adjusted to specify the curvature of the first groove portion 130 from the starting position (e.g., to align it with the second groove portion 134). In particular, the first groove portion 130 and the second groove portion 134 meet at a transition point, and the equation of the circle can be determined such that the first groove portion 130 and the second groove portion 134 are continuous and tangent at the transition point.The transition point between the first groove portion 130 and the second groove portion 134 may be referred to as a first or second transition point.

[0027] In the illustrated embodiment, the second groove portion 134 extends linearly between the first groove portion 130 and the third groove portion 138. Specifically, the second groove portion 134 extends at an alpha angle R1 relative to a horizontal axis (e.g., an x-axis in an xy coordinate system). As such, the second groove portion 134 is defined by a linear equation in terms of the slope intercept, as follows: y=Cx+D

[0028] In this equation, variable C is the slope at which the second groove section 134 extends. As such, variable C can be adjusted according to a desired value for the alpha angle R1. Variable D sets the initial position of the second groove section 134. Variable D can be adjusted according to the desired starting and ending positions of the second groove section 134.

[0029] In the illustrated embodiment, the third groove portion 138 extends between the two second groove portions 134. In particular, the third groove portion 138 curves between the two second groove portions 134 such that the third groove portion 138 is mirrored at the output axis A2. More specifically, the third groove portion 138 curves from each of the second groove portions 134 to the output axis A2 according to one of a group of equations including trigonometric equations and higher-order differential equations. In other words, the third groove portion 138 is defined by one of a group of equations including trigonometric equations and higher-order differential equations. The trigonometric equations may include one or more trigonometric ratios of an angle, such as sine, cosine, tangent, cotangent, secant, or cosecant.The higher-order differential equations may, for example, be second- or third-order differential equations. In the illustrated embodiment, the trigonometric equation defining the third groove portion 138 is the cosine equation, so that the third groove portion 138 is a cosine curve, as follows: Y=(−E)cos(F(x−G))+H

[0030] In this cosine curve equation, the variable E defines the amplitude of the cosine curve. Thus, the variable E can be set to specify the height of the cosine curve's curvature and thus the foremost point of groove 122. The variable F defines the period of the cosine curve. The variable F can be set to specify the length of the cosine curve's curvature. The variable G defines the phase shift of the cosine curve. The variable G can be set to specify the x-coordinate of the cosine curve in an xy-coordinate system. The variable H defines the vertical shift of the cosine curve. The variable H can be set to specify the y-coordinate of the cosine curve in an xy-coordinate system.

[0031] The one equation may also be referred to as a first equation, and the group of equations may also be referred to as a first group of equations. Thus, the second groove portion 134 extends between the first groove portion 130 and the third groove portion 138 according to another equation (e.g., a second equation) from a second group of equations, which includes at least the linear equation or the slope-intercept equation. In other words, the second groove portion 134 is defined by a second equation from a second group of equations. The second group of equations may, for example, also include the equation of a circle. In some embodiments, the second group of equations does not include trigonometric equations or higher-order differential equations.

[0032] The third groove portion 138 provides a continuous and tangential transition between the second groove portion 134 and the third groove portion 138, which eliminates sudden jerks or accelerations of the hammer 110 during operation of the striking mechanism 42. Fig. For example, Figure 6 shows a graph 142 showing a position curve 146, a velocity curve 150, and an acceleration curve 154 for a camshaft with a conventional cam groove defined in part by a circular function (radius) and a linear equation. As shown in Fig. 6, a line A3 shows the position of a transition point between a second groove portion and a third groove portion for the conventional cam groove (e.g., where the second groove portion and the third groove portion meet) relative to the position, velocity, and acceleration curves 146, 150, 154 of a cam ball moving along the conventional cam groove. When the cam ball reaches the transition point during operation of the camshaft with the conventional cam groove, the movement of the cam ball may encounter or be interrupted by a sudden change in acceleration between the second groove portion and the third groove portion, which is represented as a step in the acceleration curve 154. This sudden change in acceleration, shown in line A3 in Fig. 6, leads to a jerk of the cam ball and thus of the hammer.

[0033] Fig. 7 shows a graph 158 showing a position curve 162, a speed curve 166 and an acceleration curve 170 for the camshaft 106 of the illustrated embodiment with the cam groove 122 ( Fig. 4). With reference to the Fig. 4 and Fig. 7 shows a line A4 ( Fig. 7) the position of a transition point between the second groove portion 134 and the third groove portion 138 (e.g., where the second groove portion 134 and the third groove portion 138 meet) relative to the position, velocity, and acceleration curves 162, 166, 170 of the cam ball 126 moving along the cam groove 122. Due to the cosine curve geometry of the third groove portion 138, the cam groove 122 does not include a step in the acceleration curve 170 that would otherwise cause a jerky movement of the cam ball 126, as in the embodiment described above with reference to Fig. 6. Therefore, the acceleration of the cam ball 126 can smoothly decrease to zero as the cam ball 126 moves from the third groove portion 138 to the second groove portion 134.

[0034] With reference to the Fig. 4 and Fig. 5, the variables C, D in the slope-intercept equation and the variables E, F, G, H in the cosine equation are determined to align the second groove portion 134 and the third groove portion 138 based on a desired alpha angle R1 that minimizes the vibrations and efficiency losses experienced by the operator when operating the impact mechanism 42. Specifically, the variables C, D, E, F, G, H are determined such that the value of the slope-intercept equation defining the second groove portion 134 and the value of the cosine curve equation defining the third groove portion 138 are equal at a transition point between the second groove portion 134 and the third groove portion 138 (i.e., at a position along the cam groove 122 where the second groove portion 134 and the third groove portion 138 meet).In other words, the variables C, D, E, F, G, H are determined such that the second groove portion 134 and the third groove portion 138 are continuous at the transition point. The variables C, D, E, F, G, H are additionally determined such that the slope (i.e., the derivative) of the equation in the form of the slope intercept that defines the second groove portion 134 and the slope (i.e., the derivative) of the equation of the cosine curve that defines the third groove portion 138 are equal at the transition point. In other words, the variables C, D, E, F, G, H are determined such that the second groove portion 134 and the third groove portion 138 are tangent at the transition point.Thus, the orientation of the cam groove 122 is advantageously determined so that the cam ball 126 can move smoothly from the second groove portion 134 to the third groove portion 138 (and vice versa) without sudden jerks caused by impacts between the cam ball 126 and a step of the camshaft 106. The transition point between the second groove portion 134 and the third groove portion 138 may be referred to as the first or second transition point.

[0035] To determine the variables C, D, E, F, G, and H based on a desired alpha angle R1, the slope-intercept equation and the cosine curve equation are first solved based on a hypothetical transition point with values a and b. The value a is the x-coordinate of the transition point in an xy coordinate system. The value b is the y-coordinate of the transition point in an xy coordinate system. The xy coordinate system is representative of a position on the outer surface of the camshaft 106 where the output axis A2 forms the y-axis. Thus, the value a is equal to the value of the adjacent line in a triangle with respect to the alpha angle R1, and the value b is equal to the value of the opposite line in the same triangle with respect to the alpha angle R1. Thus, the alpha angle R1 and the transition point are related by the following equation. tan(A1)=ba

[0036] Starting with the variables E, F, G, and H of the cosine curve equation, the variable E, which represents the amplitude of the cosine curve, is determined based on the value b. In particular, the variable E is set directly equal to the value b. The variable F, which represents the period of the cosine curve, is determined based on the value a. In particular, the variable E is set equal to π / (2a). The variable G, which represents the phase shift (e.g., the shift along the x-axis of an xy coordinate system) of the cosine curve, is set equal to zero so that the third groove portion 138 is centered on the output axis A2. In some embodiments, the phase shift may be set to a non-zero value so that the third groove portion 138 is not centered on the output axis A2. The variable H, which represents the vertical shift of the cosine curve, is determined based on the value a.In particular, the variable D is set directly equal to the value b. y1=−(b)(cos(π2ax)+b)

[0037] The variables C, D of the slope intercept equation can then be determined from equation y1. The variable C, which represents the slope of the equation in slope intercept form, is determined from the derivative of equation y1. Since the second groove portion 134 and the third groove portion 138 are tangent at the hypothetical transition point, the slope of the equation in slope intercept form is directly equated to the derivative of equation y1 at the hypothetical transition point. Therefore, after deriving equation y1 and solving the derivative at the hypothetical transition point, the variable C or slope is (πb) / (2a) . The variable D, which represents the y-intercept of the equation in slope intercept form, is determined by both the value a and the value b.Specifically, the variable D is determined by substituting the value a for x, the value b for y, and the derived value of the variable C for the slope, as described above. Solving the slope-intercept equation for the variable D with these substitutions yields the value b - (πb) / (2) for the variable D. The slope-intercept equation can therefore be simplified to the following equation. y2=πb2a(x)+(−b−)πb2

[0038] Using the derived theoretical equations y1, y2, the actual equations for the second groove portion 134 and the third groove portion 138 can be determined by substituting a known or desired value (e.g., an independent variable) into the equations y1, y2. In the illustrated embodiment, the actual equations are determined by substituting a desired alpha angle R1, which determines the actual pitch, into the derived equations y1, y2 and solving the value a and the value b of the transition point using a system of equations. In some embodiments, the actual equations can be determined by substituting a known or desired transition point into the derived angles y1, y2 and solving the alpha angle R1.The system of equations may include equation y1, equation y2, the derivative of equation y1, and the derivative of equation y2, as well as other relationships described herein. Once equations y1 and y2 are solved with respect to the desired alpha angle R1, the second groove portion 134 and the third groove portion 138 may be formed (e.g., manufactured) in the camshaft 106 based on the resulting actual equations.

[0039] Fig. 8A-8C show another embodiment of a camshaft 206 for the power tool 10 of Fig. 1. The camshaft 206 can be connected to the camshaft 106 of Fig. 4 be substantially similar, except for the differences described here. As described in the Fig. 8A-8C, the camshaft 206 includes at least one cam groove 210 defined in the camshaft 206, which is configured to receive at least one cam ball 214. The cam ball 214 can be drivingly engaged with a hammer, such as the one shown in Fig. 3. The movement of the cam ball 214 in the cam groove 210 allows relative axial movement of the hammer along the camshaft 206. In particular, the hammer is configured to move axially along the camshaft 206 to intermittently apply a percussive rotational force or a rotational impact to an anvil, such as the one shown in Fig. 2 shown anvil 114.

[0040] The cam groove 210 is defined by one equation from a group of equations comprising trigonometric equations and higher-order differential equations. In particular, the cam groove 210 is formed uniformly according to one equation from the group of equations comprising trigonometric equations and higher-order differential equations. In the embodiment shown, the cam groove 210 is formed uniformly according to the equation of a cosine curve, as described above with respect to the Fig. 4 shown third groove section 138. In other words, the cam groove 210 of the Fig. 8A-8C is entirely defined by the equation of a cosine curve. Due to the uniformity of the cam groove 210, the cam ball 214 can move smoothly between the ends 210a, 210b of the cam groove 210. That is, the cam groove 210 does not contain any steps that would otherwise cause a jerky movement of the cam ball 214 as the cam ball 214 moves along the cam groove 210. In some embodiments, the cam groove 210 may be uniformly shaped according to the equation of a sine curve. In other embodiments, the cam groove 210 may be uniformly shaped according to the equation of a higher-order differential equation.

[0041] Fig.9 shows a graph 250 depicting a position curve 254, a velocity curve 258, and an acceleration curve 262 for a camshaft according to another embodiment of the disclosure. The camshaft includes a cam groove smoothly formed according to a higher-order differential equation. The higher-order differential equation may be a second-order, third-order, fourth-order, fifth-order, or higher-order differential equation. In particular, the higher-order differential equation may be manipulated so that the curvature of the position curve 254 mimics the curvature of a sine curve or a cosine curve. As such, the graph 250 further includes a cosine curve 266 as a reference relative to the position curve 254. In the illustrated embodiment, the position curve follows the equation for a general linear differential equation, as shown below. L(y)=(∂n)(y)∂(t)+p1(t)(∂n−1)(y)∂(t)+p1−n(t)(∂)(y)∂(t)+pn(t)(y)

[0042] The above equation can be modified if necessary to make it essentially similar to a trigonometric equation.

[0043] Various features and advantages of the invention are set forth in the following claims. 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 / 620,557

[0001]

Claims

[1] A power tool comprising: a housing; a motor mounted in the housing and having an output shaft, the motor configured to rotate the output shaft; a gear assembly configured to be driven into rotation by the output shaft; and a striking mechanism comprising a camshaft configured to be driven into rotation by the gear assembly, the camshaft having a groove, at least a portion of the groove being defined by an equation selected from a group consisting of: trigonometric equations and higher order differential equations, a hammer coupled to the camshaft via a cam ball received in the groove, and an anvil configured to absorb intermittent rotational impacts from the hammer. [2] The power tool according to claim 1, wherein the portion of the groove is defined by a cosine equation. [3] The power tool of claim 2, wherein the hammer is configured to rotate the anvil when the cam ball is in the portion of the groove defined by the cosine equation. [4] The power tool according to any one of claims 1 to 3, wherein the portion of the groove is a first groove portion and wherein the groove includes a second groove portion defined by a linear equation. [5] The power tool of claim 4, wherein the first groove portion and the second groove portion meet at a transition point, and wherein the first groove portion and the second groove portion are continuous and tangential at the transition point. [6] The power tool according to claim 4 or 5, wherein the groove has a third groove portion defined by an equation for a circle. [7] The power tool of claim 6, wherein the groove has two second groove portions and the first groove portion extends between the two second groove portions, and wherein the groove has two third groove portions and each of the third groove portions extends from a corresponding one of the second groove portions. [8] The power tool of claim 1, wherein the entire groove is defined by the equation selected from a group consisting of: trigonometric equations and higher order differential equations. [9] The power tool according to any one of the preceding claims, wherein the camshaft extends along an axis and the groove is mirrored transversely to the axis. [10] A camshaft for a striking mechanism, the camshaft comprising: a groove configured to receive a cam ball, the groove comprising a first groove section defined by a first equation, a second groove section defined by a second equation, and a third groove section defined by a third equation, wherein at least one of the first equation, the second equation, and the third equation is an equation selected from a group consisting of: trigonometric equations and higher order differential equations. [11] The camshaft according to claim 10, wherein only one of the first equation, the second equation and the third equation is an equation selected from the group consisting of: trigonometric equations and higher order differential equations. [12] The camshaft of claim 10, wherein the first equation is a cosine equation having an amplitude, the amplitude of the cosine equation defining a leading point of the groove, the second groove portion extending from an end of the first groove portion opposite the amplitude, and the third groove portion extending from an end of the second groove portion opposite the first groove portion. [13] The camshaft of claim 12, wherein the camshaft extends along an axis and wherein the groove is mirrored transversely to the axis such that the groove comprises two second groove portions and two third groove portions. [14] The camshaft according to claim 12 or 13, wherein the second equation is a linear equation and the third equation is an equation for a circle. [15] The camshaft according to any one of claims 10 to 14, wherein the first equation, the second equation and the third equation are each different types of equations. [16] A power tool comprising a housing; a motor mounted in the housing and having an output shaft, the motor configured to rotate the output shaft; a gear assembly configured to be driven into rotation by the output shaft; and a striking mechanism comprising a camshaft configured to be driven into rotation by the gear assembly, the camshaft having a groove with a first groove portion and a second groove portion meeting at a transition point, the first groove portion and the second groove portion being continuous and tangential at the transition point, a hammer which is coupled to the camshaft via a cam ball received in the groove and an anvil configured to absorb intermittent rotational impacts from the hammer. [17] The power tool of claim 16, wherein the first groove portion is defined by a first equation and the second groove portion is defined by a second equation, and wherein the first equation and the second equation are different. [18] The power tool of claim 17, wherein one of the first equation and the second equation is an equation selected from a group of equations consisting of: trigonometric equations and higher order differential equations, and wherein the other of the first equation and the second equation is a linear equation. [19] The power tool according to any one of claims 16 to 18, wherein the transition point is a first transition point, wherein the groove further comprises a third groove portion, wherein the second groove portion and the third groove portion meet at a second transition point, and wherein the second groove portion and the third groove portion are continuous and tangential at the second transition point. [20] The power tool according to claim 19, wherein the first groove portion, the second groove portion, and the third groove portion are each defined by an equation different from the others of the first groove portion, the second groove portion, and the third groove portion.

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