Patent Publication Number: US-2022226951-A1

Title: Rotary power tool

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to co-pending U.S. Provisional Patent Application No. 63/138,852 filed on Jan. 19, 2021, the entire content of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to rotary power tools, and more particularly to rotary hammers. 
     BACKGROUND OF THE INVENTION 
     Rotary hammers can include impact mechanism having a reciprocating piston disposed within a spindle, a striker that is selectively reciprocable within the spindle in response to reciprocation of the piston, and an anvil that is impacted by the striker when the striker reciprocates toward the tool bit. Rotary hammers also transfer torque to the spindle, such that the spindle can rotate the tool bit as it reciprocates in response to reciprocation of the striker. 
     SUMMARY OF THE INVENTION 
     The present invention provides, in one aspect, a rotary hammer adapted to impart axial impacts to a tool bit. The rotary hammer includes a housing, a first motor supported by the housing and defining a first motor axis, a second motor supported by the housing and defining a second motor axis that is coaxial with the first motor axis, and a spindle coupled to the first motor for receiving torque from the first motor, causing the spindle to rotate. The rotary hammer further includes a reciprocation mechanism operable to create a variable pressure air spring within the spindle. The reciprocation mechanism includes a piston configured to reciprocate within the spindle in response to receiving torque from the second motor, a striker that is selectively reciprocable within the spindle in response to reciprocation of the piston, and an anvil that is impacted by the striker when the striker reciprocates towards the tool bit. The anvil imparts axial impacts to the tool bit. 
     The present invention provides, in another aspect, a rotary hammer adapted to impart axial impacts to a tool bit. The rotary hammer includes a housing, a first motor supported by the housing and defining a first motor axis, a second motor supported by the housing, and a spindle coupled to the first motor for receiving torque from the first motor, causing the spindle to rotate. The spindle defines a rotational axis that is parallel with the first motor axis. The rotary hammer further includes a reciprocation mechanism operable to create a variable pressure air spring within the spindle. The reciprocation mechanism includes a piston configured to reciprocate within the spindle in response to receiving torque from the second motor, a striker that is selectively reciprocable within the spindle in response to reciprocation of the piston, and an anvil that is impacted by the striker when the striker reciprocates towards the tool bit. The anvil imparts axial impacts to the tool bit. 
     The present invention provides, in yet another aspect, a rotary hammer adapted to impart axial impacts to a tool bit. The rotary hammer includes a housing, a motor supported by the housing, and a spindle coupled to the motor for receiving torque from the motor, causing the spindle to rotate. The spindle has an adjustable rotation speed. The rotary hammer further comprises a reciprocation mechanism operable to create a variable pressure air spring within the spindle. The reciprocation mechanism includes a piston configured to reciprocate within the spindle in response to receiving torque from the motor. The piston has an adjustable reciprocation frequency. The reciprocation mechanism also includes a striker that is selectively reciprocable within the spindle in response to reciprocation of the piston and an anvil that is impacted by the striker when the striker reciprocates towards the tool bit. The anvil imparts axial impacts to the tool bit. The rotary hammer further comprises a first transmission configured to transfer torque from the motor to the spindle and a second transmission configured to transfer torque from the motor to the reciprocation mechanism. The reciprocation frequency of the piston is adjustable independent of the rotation speed of the spindle. The rotation speed of the spindle is adjustable independent of the reciprocation frequency of the piston. At least one of the first and second transmissions is a multi-speed transmission. 
     Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a rotary hammer according to an embodiment of the invention. 
         FIG. 2  is a cross-sectional view of the rotary hammer of  FIG. 1 . 
         FIG. 3  is an enlarged, cross-sectional view of a rotary hammer according to another embodiment of the invention. 
         FIG. 4  is a perspective view of a rotary hammer according to another embodiment of the invention. 
         FIG. 5  is a cross-sectional view of the rotary hammer of  FIG. 4 . 
         FIG. 6  is a cross-sectional view of a rotary hammer according to another embodiment of the invention. 
     
    
    
     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 is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  illustrate a rotary power tool, such as rotary hammer  10 , according to an embodiment of the invention. The rotary hammer  10  includes a housing  14 , first and second motors  18 ,  20  disposed within the housing  14 , and a rotatable spindle  22  coupled to the first motor  18  for receiving torque from the first motor  18 . The first motor  18  defines a first motor axis A 1  that is parallel with a second motor axis A 2  that is defined by the second motor  20 . In the illustrated embodiment, the rotary hammer  10  includes a quick-release chuck  23  coupled for co-rotation with the spindle  22  to facilitate quick removal and replacement of different tool bits. A tool bit  24  includes a necked section  25  or a groove in which a detent member  26  of the quick-release chuck  23  is received to constrain axial movement of the tool bit  24  to the length of the necked section  25  or groove. The rotary hammer  10  defines a tool bit axis  27 , which in the illustrated embodiment is coaxial with a rotational axis  28  of the spindle  22 . 
     The first and second motors  18 ,  20  are configured as DC motors that receive power from on-board power sources, such as first and second battery packs  29 ,  30  that are respectively selectively coupled to first and second receptacles  31 ,  32  on the housing  14 . In some embodiments, only the first battery pack  29  is coupled to the first receptacle  31 , and the first and second motors  18 ,  20  both receive power from the first battery pack  29 . In other embodiments, only the second battery pack  30  is coupled to the second receptacle  32  and the first and second motors  18 ,  20  both receive power from the second battery pack  30 . In other embodiments, the first and second battery packs  29 ,  30  are both respectively coupled to the first and second receptacles  31 ,  32 , and the first motor  18  receives power from the first battery pack  29 , and the second motor  20  receives power from the second battery pack  30 . 
     The first and second battery packs  29 ,  30  may include any of a number of different nominal voltages (e.g., 12V, 18V, etc.), and may be configured having any of a number of different chemistries (e.g., lithium-ion, nickel-cadmium, etc.). Alternatively, the first and second motors  18 ,  20  may be powered by a remote power source (e.g., a household electrical outlet) through a power cord. The first and second motors  18 ,  20  are selectively activated, either simultaneously or separately as described in further detail below, by depressing an actuating member, such as a trigger  34 . 
     The rotary hammer  10  further includes an impact mechanism  36  ( FIG. 2 ) having a reciprocating piston  38  disposed within the spindle  22 , a striker  40  that is selectively reciprocable within the spindle  22  in response to reciprocation of the piston  38 , and an anvil  42  that is impacted by the striker  40  when the striker reciprocates toward the tool bit  24 . Torque from the first motor  18  is transferred to the spindle  22  by a first transmission  46 . In the illustrated embodiment of the rotary hammer  10 , the first transmission  46  includes a first gear  50  rotatable on a stationary shaft  52  and engaged with a pinion  54  on an output shaft  58  that is selectively driven by the first motor  18 . The first transmission  46  further includes a second gear  60  in meshing relationship with the first gear  50 , and a drive shaft  62  coupled for rotation with the second gear  60  and having an drive pinion  64  engaged with and configured to drive an output gear  66  coupled for co-rotation with the spindle  22 . The drive shaft  62  is rotatably supported within the housing  14  by a bearing  70  arranged between the second gear  60  and the drive pinion  64 . The output gear  66  is secured to the spindle  22  using a spline-fit or a key and keyway arrangement, for example, that facilitates axial movement of the spindle  22  relative to the output gear  66  yet prevents relative rotation between the spindle  22  and the output gear  66 . 
     The impact mechanism  36  is driven by a second transmission  74  that receives torque from the second motor  20 . The second transmission  74  includes an input gear  78  that is engaged with a pinion  80  on an output shaft  82  that is selectively driven by the second motor  20 . The impact mechanism  36  includes a crankshaft  84  that is coupled for co-rotation with the input gear  78  and is rotatably supported within the housing  14  by bearings  86 ,  88  and a bushing  92 . The crankshaft  84  includes an eccentric pin  110  and the impact mechanism  36  further includes a connecting rod  116  interconnecting the piston  38  and the eccentric pin  110 . 
     With reference to  FIG. 1 , the rotary hammer  10  includes a mode selection switch illustrated schematically at  120  in electrical communication with the first and second motors  18 ,  20 , to allow an operator to switch between three modes. Both of the first and second motors  18 ,  20  are activated by a controller  122  (also illustrated schematically) in response to the trigger  34  being depressed and the mode selection switch  120  being set to a “hammer-drill” mode, to simultaneously and respectively rotate the spindle  22  and reciprocate the piston  38 . Only the first motor  18  is activated by the controller  122  in response to depression of the trigger  34  and the mode selection switch  120  being set to a “drill-only” mode, such that the spindle  22  is rotated by the motor  18  while second motor  20  is deactivated and the piston  38  is thus inactive. Only the second motor  20  is activated by the controller  12  in response to the trigger  34  being depressed and the mode selection switch  120  being set to a “hammer-only” mode, such that the piston  38  is reciprocated while the first motor  18  is deactivated, such that the spindle  22  does not rotate. 
     In operation, if “hammer-drill” mode is selected with the mode selection switch  120  and the trigger  34  is depressed, both of the first and second motors  18 ,  20  are activated. In response to activation of the first motor  18 , rotation of the pinion  54  of the output shaft  58  causes the first gear  50  to rotate. Rotation of the first gear  50  causes the second gear  60  and thus the drive shaft  62  to rotate, such that the drive pinion  64  drives the output gear  66  on the spindle  22 , causing the spindle  22  and the tool bit  24  to rotate. In response to activation of the second motor  20 , the input gear  78  is rotated by the pinion  80 , such that the crankshaft  84  and thus the eccentric pin  110  are rotated as well. Rotation of the eccentric pin  110  causes the piston  38  to reciprocate within the spindle  22  via the connecting rod  116 , which causes the striker  40  to impart axial blows to the anvil  42 , which in turn causes reciprocation of the tool bit  24  against a workpiece. Specifically, a variable pressure air pocket (or an air spring) is developed between the piston  38  and the striker  40  when the piston  38  reciprocates within the spindle  22 , whereby expansion and contraction of the air pocket induces reciprocation of the striker  40 . The impact between the striker  40  and the anvil  42  is then transferred to the tool bit  24 , causing it to reciprocate for performing work on workpiece. 
     In operation, if “drill-only” mode is selected with the mode selection switch  120  and the trigger  34  is depressed, only the first motor  18  is activated by the mode selection switch  120 , such that the spindle  22  is rotated by the motor  18  while second motor  20  is deactivated and the piston  38  is thus inactive. In operation, if “hammer-only” mode is selected with the mode selection switch  120  and the trigger  34  is depressed, only the second motor  20  is activated by the mode selection switch  120  in response to depression of the trigger  34 , such that the piston  38  is reciprocated, while the first motor  18  is deactivated, such that the spindle  22  does not rotate. 
     Advantageously, by using first and second motors  18 ,  20  to respectively and separately control rotation of the spindle  18  and reciprocation of the piston  38 , the reciprocation frequency of the piston  38  may be controlled independently of the rotational speed of the spindle  22 . In other words, the rotational speed of the spindle  22  may be kept constant by keeping the speed of the first motor  18  constant, while the reciprocation frequency of the piston  38  may be increased or decreased by increasing or decreasing the speed of the second motor  20 . By adjusting the reciprocation frequency of the piston  38 , the blow pattern of the tool bit  24  may conveniently be adjusted independent of the rotational speed of the spindle  22 , before or during the operation, depending on a size, cutter, or geometry of the tool bit  24 . Thus, a ratio of the rotational speed of the spindle  18  to the reciprocation frequency of the piston  38  can be optimized to allow the tool bit  24  to drill at an optimal, maximum speed for a certain operation type. 
       FIG. 3  illustrates a rotary hammer  10   a  according to another embodiment of the invention. The rotary hammer  10   a  is identical to the rotary hammer  10 , with like parts having the same annotation plus the letter “a”, and the following differences explained below. In the rotary hammer  10   a , the first motor axis A 1   a  is coaxial with the second motor axis A 2   a , and the output shaft  82   a  of the second motor  20   a  extends through a bore  124  in the output shaft  58   a  of the first motor  18   a . A first end  128  of the output shaft  82   a  of the second motor  20   a  is rotatably supported by a first bearing  132  arranged within a heat sink  136 . An opposite, second end  134  of the output shaft  82   a  of the second motor  20   a  is rotatably supported by a second bearing  140  arranged within a gearcase  144 . An intermediate portion  146  of the output shaft  82   a  of the second motor  20   a  is rotatably supported within the output shaft  58   a  of the first motor  18   a  by a bearing  148  set in a bearing pocket  152  of the output shaft  58   a . A first fan  156  is coupled for rotation with the first end  128  of the output shaft  82   a  to axially draw a cooling airflow through the first and second motors  18   a ,  20   a  during operation. Instead of being engaged with an input gear, the pinion  80   a  of the output shaft  82   a  of the second motor  20   a  is engaged with a driven gear  157  having the eccentric pin  116   a , such that in response to rotation of the output shaft  82   a  of the second motor  20   a , the driven gear  157  is rotated by the pinion  80   a . The driven gear  157  includes a stem  158  that is rotatably supported within the gearcase  144  by a bearing  159  set in the gearcase  144 . Instead of being arranged on a stationary shaft, the first gear  50   a  is arranged on the first output shaft  58   a.    
     The first motor  18   a  includes a first stator  160  and a first rotor  164  to which the output shaft  58   a  of the first motor  18   a  is coupled for rotation. The first stator  160  includes a first stator core  168  around which a plurality of first windings  172  are wrapped. In response to activation of the first motor  18   a , electrical current passes through the first windings  172 , thus generating a first electromagnetic field that causes rotation of the first rotor  164 . The second motor  20   a  includes a second stator  176  and a second rotor  180  to which the output shaft  82   a  of the second motor  20   a  is coupled for rotation. The second stator  176  includes a second stator core  184  around which a plurality of second windings  188  are wrapped. In response to activation of the second motor  20   a , electrical current passes through the second windings  188 , thus generating a second electromagnetic field that causes rotation of the second rotor  180 . By arranging the first and second motors  18   a ,  20   a  to have coaxial axes A 1   a , A 2   a , and by arranging the output shaft  82   a  of the second motor  20   a  within the output shaft  58   a  of the first motor  18   a , the design envelope for the rotary hammer  10   a  is advantageously reduced, thus making the rotary hammer  10   a  easier to use and store. 
     In the embodiment illustrated in  FIG. 3 , the first and second stators  160 ,  176  are separated by an intermediate member  192  that includes electromagnetic shielding (e.g., a brass ring) to inhibit the first electromagnetic field generated by the first windings  172  from affecting rotation of the second rotor  180 , and to inhibit the second electromagnetic field generated by the second windings  188  from affecting rotation of the first rotor  164 . Thus, in “hammer-drill” mode, when both of the first and second motors  18   a ,  20   a  are simultaneously activated, activation of the first motor  18   a  does not affect or interfere with operation of the impact mechanism  36   a  (not shown in  FIG. 3 ), and activation of the second motor  20   a  does not affect or interfere with rotation of the spindle  22   a  (not shown in  FIG. 3 ). In other embodiments, the first and second stator cores  168 ,  184  may be formed together, but electromagnetic shielding is still arranged between the first windings  172  and second windings  188 . 
     A first portion  196  of the output shaft  82   a  of the second motor  20   a  is rotatably supported by a bearing  200  arranged in the intermediate member  192 . An opposite second portion  204  of the output shaft  82   a  of the second motor  20   a , is rotatably supported by a bearing  208  arranged in the gearcase  144 . In some embodiments, a second fan is arranged on the output shaft  82   a  of the second motor  20   a  between the second rotor  180  and the bearing  208 . 
     In other embodiments, the first rotor  164  is arranged on top of the second rotor  180  via bearing elements and the second rotor  180  uses the first rotor  164  as a mount. In such an embodiment, the first and second stators  160 ,  176  are formed as a single staged stator with separate first and second windings  172 ,  188 . 
       FIGS. 4 and 5  illustrate a rotary hammer  10   b  according to another embodiment of the invention. The rotary hammer  10   b  is identical to the rotary hammer  10 , with like parts having the same annotation plus the letter “b”, and the following differences explained below. The housing  14   b  includes an upper housing portion  212  in which the first motor  18   b  is arranged and on which the first receptacle  31   b  is arranged. The first motor axis Alb is parallel with the rotational axis  28   b  of the spindle  22   b . And, a drive gear  216  on the output shaft  58   b  of the first motor  18   b  is engaged with the output gear  66   b . The crankshaft  84   b  is rotatably supported within the housing  14   b  by a pair of bearings  220 ,  224  set on a stationary post  228 . Advantageously, instead of having to use spiral bevel gears  64 ,  66  as in the rotary hammer  10 , in the rotary hammer  10   b , drive gear  216  is a spur gear and output gear  66   b  is a spur gear, thus reducing cost. Also, by positioning the first motor  18   b  on the opposite side of the rotational axis  28   b  of the spindle  22   b  as the second motor  20   b , the length of the rotary hammer  10   b  (measured along the axis  28   b ) is reduced compared to the rotary hammer  10 . 
       FIG. 6  illustrates a rotary hammer  10   c  according to another embodiment of the invention. The rotary hammer  10   c  is identical to the rotary hammer  10 , with like parts having the same annotation plus the letter “c”, and the following differences explained below. The rotary hammer  10   c  does not have a second motor or second receptacle for a second battery. Rather, in rotary hammer  10   c , the schematically illustrated first motor  18   c  provides torque to each of the schematically illustrated first and second transmissions  46   c ,  74   c . And, the first and transmissions  46   c ,  74   c  are both multi-speed transmissions, such as a continuously variable transmission (“CVT”) or an intelligent variable transmission (“IVT”). A CVT is an automatic transmission that can change seamlessly through a continuous range of gear ratios, in contrast with other transmissions that provide a limited number of gear ratios in fixed steps. Similar to a CVT, an IVT performs continuous shifts, correlating to a broader ratio of operation than many other, similar transmissions. Thus, just as in the previous embodiments of the rotary hammers  10 ,  10   a , and  10   b , in the rotary hammer  10   c , the first and second transmissions  46   c ,  74   c  are used to respectively and separately control the rotational speed of the spindle  18   c  and the frequency of reciprocation of the piston  38   c.    
     Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of one or more independent aspects of the invention as described. 
     Various features of the invention are set forth in the following claims.