Power tool

Abstract

A power tool includes: a housing; the driving mechanism is supported in the shell; a spindle operably coupled with the output of the drive mechanism such that torque from the drive mechanism rotates the spindle about an axis; and a clutch assembly configured to selectively limit torque transmitted from the drive mechanism to the spindle. The clutch assembly includes: a plurality of rolling elements; a biasing member configured to bias the plurality of rolling elements into engagement with an output of the drive mechanism; and a sleeve movable along the axis to adjust a torque limit of the clutch assembly by varying a preload of the biasing member. The sleeve is made of high-temperature engineering thermoplastic plastics.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to co-pending U.S. Provisional Patent Application No. 63 / 234,358 filed on August 18, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to power tools and, more particularly, to clutch assemblies for rotary power tools. Background Art

[0004] Some power tools (particularly rotary power tools) may include a clutch assembly for limiting the amount of torque transmitted to a workpiece by the power tool. These tools typically include a clutch setting selector that allows an operator to select different torque limits.

[0005] Some clutch assemblies on rotary power tools can be selectively enabled and disabled to enable the tool to have different modes (e.g., a drilling mode in which the clutch assembly is disabled or "locked", a drive mode in which the clutch assembly is enabled and can slip at a desired torque setting). Such clutch assemblies include a locking ring that blocks movement of a shiftable clutch element to prevent the clutch from slipping, thereby disabling or "locking" the clutch assembly. However, the locking ring adds additional axial length to the tool. Utility Model Content

[0006] In one aspect, the present disclosure provides a power tool comprising: a housing; a drive mechanism supported within the housing; a spindle operably coupled to an output member of the drive mechanism such that torque from the drive mechanism rotates the spindle about an axis; and a clutch assembly configured to selectively limit torque transmitted from the drive mechanism to the spindle. The clutch assembly comprises: a plurality of rolling elements; a biasing member configured to bias the plurality of rolling elements into engagement with the output member of the drive mechanism; and a sleeve movable along the axis to adjust the torque limit of the clutch assembly by varying the preload of the biasing member. The sleeve is made of high temperature engineering thermoplastic.

[0007] In another aspect, the present disclosure provides a power tool comprising: a housing; a drive mechanism supported within the housing; a spindle operably coupled to an output member of the drive mechanism such that torque from the drive mechanism rotates the spindle about an axis; and a clutch assembly configured to selectively limit torque transmitted from the drive mechanism to the spindle. The clutch assembly comprises: a plurality of rolling elements; a biasing member configured to bias the plurality of rolling elements into engagement with the output member of the drive mechanism; and a sleeve movable along the axis to adjust the torque limit of the clutch assembly by changing the preload of the biasing member. The sleeve is movable to a locked position in which the biasing member is fully compressed to prevent axial displacement of the plurality of rolling elements, and the biasing member comprises a wave spring.

[0008] In another aspect, the present disclosure provides a power tool comprising: a housing having a gearbox; a drive mechanism at least partially supported within the gearbox; a spindle operably coupled to an output member of the drive mechanism such that torque from the drive mechanism causes the spindle to rotate about an axis; and a clutch assembly configured to selectively limit torque transmitted from the drive mechanism to the spindle. The clutch assembly comprises: a plurality of rolling elements; a biasing member configured to bias the plurality of rolling elements into engagement with the output member of the drive mechanism; and a sleeve movable along the axis to adjust the torque limit of the clutch assembly by changing the preload of the biasing member. The sleeve comprises an internal thread defining a first pitch width, the gearbox comprises an external thread defining a second pitch width and meshing with the internal thread, such that rotation of the sleeve about the axis relative to the gearbox causes the sleeve to move relative to the gearbox along the axis, and the first pitch width is greater than the second pitch width.

[0009] Other features and aspects of the present disclosure will become apparent by consideration of the following detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a perspective view of a rotary power tool including a clutch assembly according to an embodiment of the present disclosure.

[0011] Figure 2 yes Figure 1 An enlarged cross-sectional view of a portion of a rotary power tool.

[0012] Figure 3 yes Figure 1 An exploded detailed view of the clutch assembly of a rotary power tool.

[0013] Figure 4 It is shown Figure 1 An exploded perspective view of an inner sleeve and a gear box of a rotary power tool.

[0014] Figure 5 It is shown Figure 4 Cross-sectional view of the thread geometry of the inner sleeve and gearbox.

[0015] Before explaining any embodiments of the present disclosure in detail, it should be understood that the present disclosure is not limited in its application to the construction details and component arrangements set forth in the following description or shown in the following figures. The present disclosure can have other embodiments and can be practiced or performed in a variety of different ways. In addition, it should be understood that the words and terms used herein are for descriptive purposes and should not be considered restrictive. DETAILED DESCRIPTION

[0016] Figure 1 A rotary power tool 10 is shown in the form of a drill. The power tool 10 includes a housing 12 having a motor housing portion 14, a handle portion 16 extending from the motor housing portion 14, and a front housing portion or gear box 17 coupled to the front side of the motor housing portion 14. A battery receptacle 19 is located at the bottom end of the handle portion 16 and is configured to receive a battery (e.g., a rechargeable power tool battery pack, not shown).

[0017] Driving mechanism 18( Figure 2 ) is disposed within the housing 12 and includes an electric motor 22 and a transmission 26, the electric motor being supported within the motor housing portion 14, the transmission being coupled to an output shaft 27 of the electric motor 22 and being at least partially supported within the gearbox 17. In the illustrated embodiment, the transmission 26 is a multi-speed planetary transmission that is shiftable to provide different output speeds for the power tool 10. In other embodiments, other types of transmissions may be used.

[0018] Continue to refer Figure 2 , the transmission 26 shown includes an output member 29 (i.e., the last stage ring gear, which in some embodiments may be a last stage carrier or other rotating output member). The output member 29 of the transmission 26 is operably coupled to the main shaft 30 via a clutch assembly 50 (described in more detail below) so that torque can be transmitted from the output member 29 to the main shaft 30 to rotate the main shaft 30 about the rotation axis A. The clutch assembly 50 selectively limits the torque transmitted from the output member 29 of the transmission 26 to the main shaft 30. In some embodiments, the transmission 26 can be shifted between a low speed setting and a high speed setting. In some such embodiments, the clutch assembly 50 can be bypassed when the transmission 26 is in the high speed setting. In the illustrated embodiment, the rotation axis A of the main shaft 30 is coaxial with the motor output shaft 27; however, in other embodiments, the orientation of the motor output shaft 27 can be parallel or perpendicular to the rotation axis A of the main shaft 30.

[0019] Continue to refer Figure 2 The drive mechanism 18 shown further includes a chuck 34 located at the end of the spindle 30 opposite the transmission 26 and coupled to the spindle 30 for common rotation. The chuck 34 includes a plurality of jaws 38 configured to support a working tool bit (e.g., a drill bit, a screwdriver bit, etc., not shown). Torque is transmitted from the electric motor 22 through the transmission 26 and the spindle 30 to the chuck 34 to be applied to the workpiece.

[0020] The illustrated clutch assembly 50 includes a plurality of spherical rolling elements 54 supported within a cage 58 that is coupled for common rotation with the spindle 30 (e.g., keyed to the spindle 30 via one or more intermediate spline rings that may allow the spindle 30 to move axially relative to the cage 58). Each of the plurality of spherical rolling elements 54 is disposed within a corresponding aperture 62 formed in the cage 58 ( Figure 3 The holes 62 are evenly spaced apart in the circumferential direction of the retainer 58 .

[0021] refer to Figure 3 , the rolling elements 54 engage with a plurality of forwardly extending projections or detents 66 on the output member 29 of the transmission 26. That is, each of the plurality of detents 66 interacts with the rolling elements 54 to transfer torque through the rolling elements 54 to the cage 58, the spindle 30, and the chuck 34. As will be described in greater detail below, the rolling elements 54 are biased to engage with the detents 66 but are displaceable away from the detents 66 to pass over (or "slide over") the detents 66, thereby allowing relative rotation between the output member 29 of the transmission 26 and downstream components of the drive mechanism 18 when the torque transmitted between the output member 29 and the spindle 30 exceeds the selected torque limit of the clutch assembly 50.

[0022] In more detail, the clutch assembly 50 is configured to limit the amount of torque that can be transmitted to the main shaft 30. The clutch assembly 50 shown includes a plurality of pins 70 that are biased toward the rolling elements 54 by a biasing arrangement that, in the illustrated embodiment, includes a washer 74 and a wave spring 78. The washer 74 and the wave spring 78 each surround a nose 79 of the gearbox 17. The washer 74 is disposed against the front end of the respective pin 70 to transmit a rearward axial biasing force from the wave spring 78 to the pin 70, and in turn to the rolling elements 54. In other embodiments, the biasing arrangement may include one or more coil springs, one or more disc springs, etc., for biasing the pins 70 toward the rolling elements 54, and in turn biasing the rolling elements 54 toward the output 29 of the transmission 26.

[0023] The clutch assembly 50 further includes an adjustment mechanism 82 that allows a user to change the upper limit of torque transmitted through the clutch 50 before the clutch 50 slips. The adjustment mechanism 82 shown includes an outer collar 86 and an inner sleeve 90. The outer collar 86 is axially fixed relative to the gearbox 17 and is rotatable relative to the gearbox 17 about the axis A. The inner sleeve 90 is coupled to the outer collar 86 for common rotation, but is axially movable relative to the outer collar 86. The rear side of the inner sleeve 90 has an annular recess 92 that receives the end of the wave spring 78.

[0024] refer to Figure 4 , the inner sleeve 90 and the nose 79 of the gearbox 17 each have threads 94, 98 that engage so that rotation of the outer collar 86 and the inner sleeve 90 relative to the gearbox 17 causes the inner sleeve 90 to move axially along the nose 79 of the gearbox 17. Thus, rotation of the collar 86 in a first direction to move the inner sleeve 90 axially rearward (toward the motor 22) compresses the wave spring 78, thereby increasing the force applied to the rolling elements 54. Similarly, rotation of the collar 86 in an opposite second direction to move the inner sleeve 90 axially forward (away from the motor 22) reduces the preload on the wave spring 78, thereby reducing the force applied by the wave spring 78 to the rolling elements 54. In some embodiments, the outer collar 86 may include a detent mechanism and / or indicia to provide a tactile and / or visual indication to the user of the amount of adjustment or torque setting applied to the clutch assembly 50.

[0025] In some embodiments, the clutch assembly 50 can be adjusted to a locked position that prevents the clutch assembly 50 from sliding. In some embodiments, the clutch assembly 50 may include a locking ring (not shown) that is rotatable to selectively block the axial displacement of the rolling element 54 and / or the pin 70. However, providing such a locking ring increases the overall length of the power tool 10. The embodiment of the power tool 10 shown does not include a separate locking ring, which makes the overall length shorter. In order to lock the clutch assembly 50, the collar 86 is rotated in a first direction to move the inner sleeve 90 backward until the wave spring 78 is fully compressed. When fully compressed, the wave spring 78 acts as a solid body. Therefore, the wave spring 78 prevents the rolling element 54 and the pin 70 from shifting away from the pawl 66, thereby preventing the clutch assembly 50 from sliding.

[0026] Due to the geometry of the wave spring 78, the wave spring 78 provides a flat, stable configuration when fully compressed without plastic deformation, as opposed to a coil spring, which may tend to warp outward to one side and may be susceptible to plastic deformation to the detriment of future performance. The wave spring 78 can also be shorter in axial length than a coil spring and have a smaller tolerance stack-up than a laminated disc spring.

[0027] In the illustrated embodiment, the inner sleeve 90 may be made of a plastic material, which reduces cost, and is also designed to control any failure that may be caused by high axial forces within the clutch assembly 50 when the clutch assembly 50 is in the locked position. That is, the threads 94 on the plastic inner sleeve 90 may be designed to yield before the threads 98 on the gear case 17 (which is made of a metal material such as an aluminum alloy).

[0028] Compared with the gearbox 17, it is simpler and more cost-effective to replace the plastic inner sleeve 90. However, the inventors have determined that traditional plastic materials may not be suitable for constructing the inner sleeve 90. Therefore, in some embodiments, the inner sleeve 90 is formed by a plastic having a glass transition point of at least 70 degrees Celsius, a Young's modulus of at least 10000 MPa at 120 degrees Celsius, and a tensile strength of at least 140 MPa at 120 degrees Celsius, so that the inner sleeve 90 has sufficient strength and can withstand the high temperatures (e.g., up to 120 degrees Celsius) that may occur in the gearbox 17 during the operation of the power tool 10. Suitable materials include, but are not limited to, polyphthalamide ("PPA"), polyphenylene sulfide ("PPS"), or polyamide 46 ("PA46"). These materials can also be reinforced with fibers (such as glass fibers or polyaramid fibers) to make them stronger. In some embodiments, the inner sleeve is formed by PPA having at least 50% glass fibers by weight. The material was found to have a tensile strength of 159 MPa at 120 degrees Celsius and a modulus of 15,300 MPa at 120 degrees Celsius.

[0029] To further increase the strength of the inner sleeve 90, the threads 94, 98 may have different geometries. That is, the threads 94 on the inner sleeve 90 and the threads 98 on the gearbox 17 may be asymmetric (ie, different from each other). Figure 5 As shown, the thread 94 of the inner sleeve has a pitch width P1, and the outer thread 98 of the gear box has a pitch width P2 that is smaller than the pitch width P1. The threads 94 and 98 both have the same total pitch PT and the same depth D from the root to the crest, so that the threads 94 and 98 can be properly meshed. The pitch width P1 of the thread 94 of the inner sleeve can be 10% to 30% larger than the pitch width P2 of the outer thread 98 of the gear box, and in the embodiment shown, the pitch width P1 is about 24% larger than the pitch width P2. This increases the axial strength of the thread 94 of the plastic inner sleeve 90 compared to the case where the pitch widths of the threads 94 and 98 are the same.

[0030] Thus, although the inner sleeve 90 and the gearbox 17 are formed of different materials, the construction of the high temperature engineering thermoplastic of the inner sleeve 90 and the asymmetric thread configuration (e.g., the pitch width P1 is larger) can enable the threads 94 on the inner sleeve 90 and the threads 98 on the gearbox 17 to have similar yield strengths, and enable the power tool 10 to have a high torque capacity with a minimum overall length of the clutch assembly 50. In some embodiments, the peak torque capacity of the clutch assembly 50 before locking can be about 1200 inch pounds. Optionally, the threads 94 on the inner sleeve 90 can be configured to fail before the threads 98 on the gearbox 17, thereby allowing any failure of the clutch assembly 50 to be more predictable and cheaper to repair. For example, the yield strength of the threads 94 can be 1% to 5% less than the yield strength of the threads 98. Finally, the clutch assembly 50 can be locked without the need for a separate locking ring, thereby further shortening the overall axial length of the power tool 10.

[0031] Various features and aspects of the invention are set forth in the following claims.

Claims

1. A power tool comprising: case; a drive mechanism supported within the housing; a spindle operatively coupled to an output of the drive mechanism such that torque from the drive mechanism causes the spindle to rotate about an axis; as well as A clutch assembly configured to selectively limit torque transmitted from the drive mechanism to the main shaft, the clutch assembly comprising Multiple rolling elements; a biasing member configured to bias the plurality of rolling elements into engagement with an output of the drive mechanism; as well as a sleeve movable along the axis to adjust the torque limit of the clutch assembly by varying the preload of the biasing member, Wherein, the sleeve is made of high-temperature engineering thermoplastics.

2. The power tool according to claim 1, wherein: The housing includes a gearbox formed of metal having a nose through which the spindle extends, and wherein the drive mechanism is at least partially supported within the gearbox.

3. The power tool according to claim 2, wherein: The sleeve comprises an internal thread, and wherein, The gearbox includes external threads that mesh with the internal threads such that rotation of the sleeve about the axis relative to the gearbox moves the sleeve along the axis relative to the gearbox. 4 . The power tool of claim 3 , further comprising a collar coupled to the sleeve for common rotation.

5. The power tool according to claim 3, wherein: The internal thread has a first pitch width, wherein the external thread has a second pitch width, and wherein the first pitch width is greater than the second pitch width.

6. The power tool according to claim 5, wherein: The first pitch width is 10% to 30% greater than the second pitch width.

7. The power tool according to claim 1, wherein: The high temperature engineering thermoplastic is selected from the group consisting of polyphthalamide, polyphenylene sulfide and polyamide 46.

8. The power tool according to claim 1, wherein: This high temperature engineering thermoplastic is reinforced with glass fibers.

9. The power tool according to claim 1, wherein: The high temperature engineering thermoplastic contains 50% by weight glass fibers.

10. The power tool according to claim 1, wherein: The biasing member includes a wave spring.

11. A power tool comprising: case; a drive mechanism supported within the housing; a spindle operatively coupled to an output of the drive mechanism such that torque from the drive mechanism causes the spindle to rotate about an axis; as well as A clutch assembly configured to selectively limit torque transmitted from the drive mechanism to the main shaft, the clutch assembly comprising Multiple rolling elements; a biasing member configured to bias the plurality of rolling elements into engagement with an output of the drive mechanism; as well as a sleeve movable along the axis to adjust the torque limit of the clutch assembly by varying the preload of the biasing member, wherein the sleeve is movable to a locked position in which the biasing member is fully compressed to prevent axial displacement of the plurality of rolling elements, and Wherein, the biasing member comprises a wave spring.

12. The power tool according to claim 11, wherein: The clutch assembly further includes a cage coupled for common rotation with the main shaft, and wherein the plurality of rolling elements are received in corresponding apertures formed in the cage.

13. The power tool according to claim 12, wherein: The clutch assembly further includes a plurality of pins aligned with the plurality of rolling elements and a washer engaged with a front end of each of the plurality of pins.

14. The power tool according to claim 13, wherein: The first end of the biasing member abuts the sleeve and the second end of the biasing member abuts the washer.

15. The power tool according to claim 14, wherein: The sleeve is made of high temperature engineering thermoplastic.

16. The power tool according to claim 15, wherein: The high temperature engineering thermoplastic has a glass transition point of at least 70 degrees Celsius, a Young's modulus at 120 degrees Celsius of at least 10,000 MPa, and a tensile strength at 120 degrees Celsius of at least 140 MPa.

17. The power tool according to claim 11, wherein: The sleeve includes threads.

18. A power tool comprising: a housing including a gear box; a drive mechanism at least partially supported within the gear housing; a spindle operatively coupled to an output of the drive mechanism such that torque from the drive mechanism causes the spindle to rotate about an axis; as well as A clutch assembly configured to selectively limit torque transmitted from the drive mechanism to the main shaft, the clutch assembly comprising Multiple rolling elements; a biasing member configured to bias the plurality of rolling elements into engagement with an output of the drive mechanism; as well as a sleeve movable along the axis to adjust the torque limit of the clutch assembly by varying the preload of the biasing member, wherein the sleeve comprises an internal thread defining a first pitch width, wherein the gearbox comprises an external thread defining a second pitch width and meshing with the internal thread, such that rotation of the sleeve relative to the gearbox about the axis causes the sleeve to move relative to the gearbox along the axis, and Wherein, the first pitch width is greater than the second pitch width.

19. The power tool according to claim 18, wherein: The sleeve is movable to a locked position in which the biasing member is fully compressed to prevent axial displacement of the plurality of rolling elements.

20. The power tool according to claim 18, wherein: The first pitch width is 10% to 30% greater than the second pitch width.

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