Hybrid impact tool with two-speed transmission

Abstract

A power tool that includes a housing, a motor, a planetary transmission, a first bearing and a second bearing. The motor is disposed in the housing and includes an output shaft. The planetary transmission has a sun gear, a plurality of first planet gears, a first ring gear and a carrier. The sun gear is driven by the output shaft. The first planet gears are driven by the sun gear and have teeth that are meshingly engaged to teeth of the first ring gear. The carrier includes a rear carrier plate and a front carrier plate between which the first and second planet gears are received. The rear carrier plate includes a first bearing aperture. The first bearing is received in the first bearing aperture and is configured to support the output shaft. The second bearing is received onto the rear carrier plate to support the carrier relative to the housing.

What is claimed is: 
     
       1. A power tool comprising:
 a housing; 
 a motor coupled to the housing, the motor having an output shaft; 
 an output member; 
 a power transmitting mechanism drivingly coupling the output shaft to the output member, the mechanism comprising a transmission having dual planetary stage with a sun gear, a first planet gear, a second planet gear, a planet carrier, a first ring gear and a second ring gear, the first and second planet gears being rotatably mounted on the planet carrier, the first planet gear being disposed between the motor and the second planet gear and having a pitch diameter that is smaller than a pitch diameter of the second planet gear, the first ring gear being meshingly engaged with the first planet gear, and the second ring gear being meshingly engaged with the second planet gear; and 
 a shift mechanism having a collar that is non-rotatably but axially slidably coupled to the housing for movement between a first position and a second position, wherein the collar comprises an annular collar body, a first set of external splines and a second set of external splines, the collar body being received about the first ring gear, the first set of external splines extending radially inwardly from the collar body and engaging a third set of external splines formed about the first ring gear when the collar is in the first position to thereby inhibit rotation of the first ring gear relative to the housing, the second set of external splines being coupled to an end of the collar body that faces opposite the motor, the second set of external splines engaging a fourth set of external splines formed on the second ring gear when the collar is in the second position to thereby inhibit rotation of the second ring gear relative to the housing. 
 
     
     
       2. The power tool of  claim 1 , wherein the power transmitting mechanism comprises a rotary impact mechanism having an input spindle and an anvil, the input spindle being coupled for rotation with an output of the transmission, the output member being coupled for rotation with the anvil. 
     
     
       3. The power tool of  claim 1 , wherein the shift mechanism further comprises a switch member and a pair of springs, the springs cooperating to bias the collar into a neutral position relative to the switch member. 
     
     
       4. The power tool of  claim 3 , wherein the shift mechanism further comprises a rod that is fixedly coupled to the collar, the switch member being movably mounted on the rod. 
     
     
       5. The power tool of  claim 4 , wherein the springs are mounted on the rod on opposite sides of the switch member. 
     
     
       6. The power tool of  claim 1 , wherein the first and second planet gears are unitarily formed. 
     
     
       7. The power tool of  claim 6 , wherein the first planet gear has a first quantity (Q1) of teeth, the second planet gear has second quantity of teeth (Q2) and wherein the quotient of the quantity of teeth on the second planet gear divided by the quantity of teeth on the first planet (Q2/Q1) gear is not an integer. 
     
     
       8. The power tool of  claim 7 , wherein a timing aperture is formed in at least one of the first and second planet gears, the timing aperture being indexed at a predetermined angle relative to a timing tooth on one of the first and second planet gears. 
     
     
       9. A power tool comprising:
 a housing; 
 a motor coupled to the housing, the motor having an output shaft; 
 an output member; 
 a power transmitting mechanism drivingly coupling the output shaft to the output member, the mechanism comprising a transmission having dual planetary stage with a sun gear, a compound planet gear, a planet carrier, a first ring gear and a second ring gear, the compound planet gear being rotatably mounted on the planet carrier and having first and second planet gears that are fixedly coupled to and integrally formed with one another, the first planet gear being disposed between the motor and the second planet gear and having a pitch diameter that is smaller than a pitch diameter of the second planet gear, the first ring gear being meshingly engaged with the first planet gear, and the second ring gear being meshingly engaged with the second planet gear, wherein the first planet gear has a first quantity (Q1) of teeth, the second planet gear has second quantity of teeth (Q2) and wherein the quotient of the quantity of teeth on the second planet gear divided by the quantity of teeth on the first planet (Q2/Q1) gear is not an integer; and 
 a shift mechanism with a collar that is non-rotatably but axially slidably coupled to the housing for movement between a first position and a second position, wherein the collar non-rotatably couples the first ring gear to the housing in the first position and non-rotatably couples the second ring gear to the housing in the second position. 
 
     
     
       10. The power tool of  claim 9 , wherein a timing aperture is formed in at least one of the first and second planet gears, the timing aperture being indexed at a predetermined angle relative to a timing tooth on one of the first and second planet gears. 
     
     
       11. A power tool comprising:
 a housing; 
 a motor in the housing, the motor including an output shaft; 
 a planetary transmission having a sun gear, a plurality of first planet gears, a first ring gear and a carrier, the sun gear being driven by the output shaft, the first planet gears being driven by the sun gear and having teeth that are meshingly engaged to teeth of the first ring gear, the carrier including a rear carrier plate and a front carrier plate between which the first planet gears are received, the rear carrier plate including a first bearing aperture; 
 a first bearing received in the first bearing aperture and being configured to support the output shaft; and 
 a second bearing received onto the rear carrier plate to support the carrier relative to the housing. 
 
     
     
       12. The power tool of  claim 11 , wherein the planetary transmission includes a plurality of second planet gears. 
     
     
       13. The power tool of  claim 12 , wherein each of the first planet gears is coupled for rotation with a corresponding one of the second planet gears. 
     
     
       14. The power tool of  claim 13 , wherein each of the first planet gears has a first pitch diameter and each of the second planet gears has a second pitch diameter that is larger than the first pitch diameter. 
     
     
       15. The power tool of  claim 13 , wherein the first ring gear includes a plurality of external teeth that are axially spaced apart from the teeth that are meshingly engaged by the teeth of the first planet gears. 
     
     
       16. The power tool of  claim 15 , wherein the external teeth are positioned at least partly vertically in-line with at least one of the first and second bearings. 
     
     
       17. The power tool of  claim 15 , further comprising an axially slidable collar that is movable between a first position, in which the collar is engaged to the external teeth of the first ring gear, and a second position in which the collar is engaged to a second ring gear that is meshingly engaged to the second planet gears. 
     
     
       18. The power tool of  claim 17 , wherein the collar is non-rotatably coupled to the housing. 
     
     
       19. The power tool of  claim 18 , further comprising a switch member, a first spring ( 224 ) and a second spring, the first spring ( 224 ) being compressed when the switch member is moved from a first switch position to a second switch position without a corresponding movement of the collar from the first position to the second position, the second spring being compressed when the switch member is moved from the second switch position to the first switch position without a corresponding movement of the collar from the second position to the first position. 
     
     
       20. The power tool of claim 11, wherein the second bearing is engaged to a bearing support plate that is received in the housing. 
     
     
       21. The power tool of claim 11, wherein the second bearing is substantially axially aligned with the first bearing. 
     
     
       22. The power tool of claim 11, wherein the rear carrier plate comprises an annular structure with a first portion and a second portion, the first portion having a larger diameter than the second portion. 
     
     
       23. The power tool of claim 22, wherein the first portion abuts against a rear surface of the first planet gears. 
     
     
       24. The power tool of claim 22, wherein the second portion receives the first bearing therein. 
     
     
       25. The power tool of claim 24, wherein the second bearing is received onto the second portion. 
     
     
       26. The power tool of claim 11, wherein the output shaft has a front end portion supported axially forward of the motor by the first bearing and a rear end portion supported axially rearward of the motor by a third bearing received in a rear mount of the housing. 
     
     
       27. The power tool of claim 11, further comprising an output spindle configured to be rotationally driven by rotation of the carrier. 
     
     
       28. The power tool of claim 27, further comprising an impact mechanism disposed between the carrier and the output spindle, wherein the carrier rotationally drives the output spindle via the impact mechanism. 
     
     
       29. The power tool of claim 28, wherein the impact mechanism has an input spindle that is coupled for rotation with the front carrier plate. 
     
     
       30. The power tool of claim 27, further comprising a chuck coupled for rotation with the output spindle. 
     
     
       31. The power tool of claim 11, wherein the sun gear is coupled for rotation with the output shaft axially forward of the first bearing. 
     
     
       32. The power tool of claim 11, further comprising a controller configured to control distribution of electrical power to the motor. 
     
     
       33. The power tool of claim 32, wherein the controller is configured to select between at least a first control scheme and a second control scheme based on a user input, wherein, in the first control scheme, the controller causes rotation of the motor at a first rotational speed, and in the second control scheme, the controller causes rotation of the motor at a second rotational speed that is lower than the first rotational speed. 
     
     
       34. The power tool of claim 33, wherein the housing is instrumented to receive the user input of a selection between the first control scheme and the second control scheme. 
     
     
       35. The power tool of claim 33, wherein, in the first control scheme, electrical power is provided to the motor by a pulse-width-modulation signal having a relatively large ratio of on-time relative to the total time of the duty cycle, and, in the second control scheme, electrical power is provided to the motor by a pulse-width-modulation signal having a relatively smaller ratio of on-time relative to the total time of the duty cycle. 
     
     
       36. A power tool comprising:
 a housing;   a motor in the housing, the motor including an output shaft having a forward end portion and a rear end portion;   a planetary transmission having a sun gear, a plurality of planet gears, a ring gear and a planet gear carrier, the sun gear being driven in rotation by the output shaft, the plurality of planet gears being driven in rotation by the sun gear and having teeth that are meshingly engaged to teeth of the ring gear, and the carrier being driven in rotation by motion of the planet gears, the carrier defining a first bearing aperture;   an impact mechanism having an input shaft that is fixedly coupled for rotation with the carrier and an output spindle;   a first bearing received in the first bearing aperture and being configured to support the forward end of the output shaft; and   a second bearing received onto the carrier to support the carrier relative to the housing.   
     
     
       37. The power tool of claim 36, wherein the carrier comprises a rear carrier plate axially rearward of the planet gears and a front carrier plate axially forward of the planet gears. 
     
     
       38. The power tool of claim 37, wherein the first bearing aperture is defined in the rear carrier plate axially rearward of the planet gears. 
     
     
       39. The power tool of claim 36, wherein the second bearing is engaged to a bearing support plate that is received in the housing. 
     
     
       40. The power tool of claim 36, wherein the second bearing is substantially axially aligned with the first bearing. 
     
     
       41. The power tool of claim 36, wherein the rear end portion of the motor shaft is supported axially rearward of the motor by a third bearing received in a rear mount of the housing. 
     
     
       42. The power tool of claim 36, further comprising a controller configured to control distribution of electrical power to the motor. 
     
     
       43. The power tool of claim 42, wherein the controller is configured to select between at least a first control scheme and a second control scheme based on a user input, wherein, in the first control scheme, the controller causes rotation of the motor at a first rotational speed, and in the second control scheme, the controller causes rotation of the motor at a second rotational speed that is lower than the first rotational speed. 
     
     
       44. The power tool of claim 43, wherein the housing is instrumented to receive the user input of a selection between the first control scheme and the second control scheme. 
     
     
       45. The power tool of claim 43, wherein, in the first control scheme, electrical power is provided to the motor by a pulse-width-modulation signal having a relatively large ratio of on-time relative to the total time of the duty cycle, and, in the second control scheme, electrical power is provided to the motor by a pulse-width-modulation signal having a relatively smaller ratio of on-time relative to the total time of the duty cycle.