Patent Publication Number: US-9849577-B2

Title: Rotary hammer

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 13/757,090 filed on Feb. 1, 2013, now U.S. Pat. No. 9,308,636, which claims priority to U.S. Provisional Patent Application No. 61/594,675 filed on Feb. 3, 2012, Application No. 61/737,304 filed on Dec. 14, 2012, and Application No. 61/737,318 filed on Dec. 14, 2012, the entire contents of all of which are incorporated herein by reference. 
     This application further claims priority to U.S. Provisional Patent Application No. 61/846,303 filed on Jul. 15, 2013, the entire content of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to power tools, and more particularly to rotary hammers. 
     BACKGROUND OF THE INVENTION 
     Rotary hammers typically include a rotatable spindle, a reciprocating piston within the spindle, and a striker that is selectively reciprocable within the piston in response to an air pocket developed between the piston and the striker. Rotary hammers also typically include an anvil that is impacted by the striker when the striker reciprocates within the piston. The impact between the striker and the anvil is transferred to a tool bit, causing it to reciprocate for performing work on a work piece. This reciprocation may cause undesirable vibration that may be transmitted to a user of the rotary hammer. 
     SUMMARY OF THE INVENTION 
     The invention provides, in one aspect, a rotary power tool including a housing, a spindle defining a working axis, and a motor supported by the housing. The motor is operable to drive the spindle. The rotary power tool also includes a handle movably coupled to the housing and a vibration isolating assembly disposed between the housing and the handle. The vibration isolating assembly attenuates vibration transmitted from the housing to the handle. A battery pack is removably coupled directly to the handle and configured to provide power to the motor. 
     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 a portion of the rotary hammer of  FIG. 1 . 
         FIG. 3  is a perspective cutaway view of an upper joint of a vibration isolating assembly of the rotary hammer of  FIG. 1 . 
         FIG. 4  is a cross-sectional view of the upper joint of  FIG. 3  taken through line  4 - 4 . 
         FIG. 5  is a cross-sectional view of the upper joint of  FIG. 3  taken through line  5 - 5  in  FIG. 1 . 
         FIG. 6  is a perspective view of a battery pack removed from the rotary hammer of  FIG. 1 . 
     
    
    
     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 
       FIG. 1 . illustrates a rotary hammer  260  according to an embodiment of the invention. The rotary hammer  260  includes a housing  262  and a motor  264  disposed within the housing  262 . A tool bit  266 , defining a working axis  268 , is coupled to the motor  264  for receiving torque from the motor  264 . The motor  264  receives power from a rechargeable battery pack  270 . 
     In the illustrated embodiment, the motor  264  is a brushless direct-current (“BLDC”) motor and includes a stator (not shown) having a plurality of coils (e.g., 6 coils) and a rotor (not shown) including a plurality of permanent magnets. Operation of the motor  264  is governed by a motor control system  265  including a printed circuit board (“PCB”) (not shown) and a switching FET PCB (not shown). Alternatively, the motor  264  can be any other type of DC motor, such as a brush commutated motor. 
     The motor control system  265  controls the operation of the rotary hammer  260  based on sensed or stored characteristics and parameters of the rotary hammer  260 . For example, the control PCB is operable to control the selective application of power to the motor  264  in response to actuation of a trigger  272 . The switching FET PCB includes a series of switching FETs for controlling the application of power to the motor  264  based on electrical signals received from the control PCB. The switching FET PCB includes, for example, six switching FETs. The number of switching FETs included in the rotary hammer  260  is related to, for example, the desired commutation scheme for the motor  264 . In other embodiments, additional or fewer switching FETs and stator coils can be employed (e.g., 4, 8, 12, 16, between 4 and 16, etc.). 
     The design and construction of the motor  264  is such that its performance characteristics maximize the output power capability of the rotary hammer  260 . The motor  264  is composed primarily of steel (e.g., steel laminations), permanent magnets (e.g., sintered Neodymium Iron Boron), and copper (e.g., copper stator coils). 
     The illustrated BLDC motor  264  is more efficient than conventional motors (e.g., brush commutated motors) used in rotary hammers. For example, the motor  264  does not have power losses resulting from brushes. The motor  264  also combines the removal of steel from the rotor (i.e., in order to include the plurality of permanent magnets) and windings of copper in the stator coils to increase the power density of the motor  264  (i.e., removing steel from the rotor and adding more copper in the stator windings can increase the power density of the motor  264 ). Motor alterations such as these allow the motor  264  to produce more power than a conventional brushed motor of the same size, or, alternatively, to produce the same or more power from a motor smaller than a conventional brushed motor for use with rotary hammers. 
     With reference to  FIG. 2 , the tool bit  266  is secured to a spindle  274  for co-rotation with the spindle  274  about the working axis  268  (e.g., using a quick-release mechanism). The rotary hammer  260  further includes an impact mechanism  276  having a reciprocating piston  278  disposed within the spindle  274 , a striker  279  that is selectively reciprocable within the spindle  274  in response to reciprocation of the piston  278 , and an anvil  280  that is impacted by the striker  279  when the striker  279  reciprocates toward the tool bit  266 . The impact between the striker  279  and the anvil  280  is transferred to the tool bit  266 , causing it to reciprocate for performing work on a work piece. The spindle  274  and the impact mechanism  276  of the rotary hammer  260  can have any suitable configuration for transmitting rotary and reciprocating motion to the tool bit  266 . 
     With reference to  FIG. 1 , the rotary hammer  260  further includes a handle  282  having an upper portion  284  and a lower portion  286  coupled to the housing  262  via a vibration isolating assembly  287  including an upper joint  288  and a lower joint  290 . The handle  282  has an upper bellows  292  disposed between the upper portion  284  and the housing  262 , and a lower bellows  294  disposed between the lower portion  286  and the housing  262 . The bellows  292 ,  294  protect the joints  288 ,  290  from dust or other contamination. The handle  282  is formed from cooperating first and second handle halves  282   a ,  282   b , and includes an overmolded grip portion  298  to provide increased operator comfort. In other embodiments, the handle  282  may be formed as a single piece or may not include the overmolded grip portion  298 . 
     Operation of the rotary hammer  260  may produce vibration at least due to the reciprocating motion of the impact mechanism  276  and intermittent contact between the tool bit  266  and a work piece. Such vibration may generally occur along a first axis  302  parallel to the working axis  268  of the tool bit ( FIG. 3 ). Depending upon the use of the rotary hammer  260 , vibration may also occur along a second axis  306  orthogonal to the first axis  302  and along a third axis  310  orthogonal to both the first axis  302  and the second axis  306 . To attenuate the vibration being transferred to the handle  282 , and therefore the operator of the rotary hammer  260 , the upper and lower joints  288 ,  290  of the vibration isolating assembly  287  each permit limited movement of the handle  282  relative to the housing  262 . Although a specific embodiment of the vibration isolating assembly  287  is described in detail herein, it should be understood that the vibration isolating assembly  287  can have any configuration or construction suitable for attenuating vibration transmitted from the housing  262  to the handle  282 . 
     With reference to  FIG. 6 , the handle  282  includes a battery receptacle  414  adjacent the lower portion  286  of the handle  282 , proximate the lower joint  290 . The battery receptacle  414  defines an insertion axis  416  along which the battery pack  270  is slidable that is oriented substantially parallel to the working axis  268  of the spindle  274  (see also  FIG. 1 ). As such, the battery pack  270  is slidable in a forward direction along the insertion axis  416  to insert the battery pack  270  into the receptacle  414  and in a rearward direction along the insertion axis  416  to remove the battery pack  270  from the receptacle  414 . The battery pack  270  includes a housing  418  and a plurality of rechargeable battery cells (not shown) supported by the battery housing  418 . The battery pack  270  also includes a support portion  426  for securing the battery pack  270  within the battery receptacle  414 , and a locking mechanism  430  for selectively locking the battery pack  270  to the battery receptacle  414 . 
     In the illustrated embodiment, the battery pack  270  is designed to substantially follow the contours of the rotary hammer  260  to match the general shape of the handle  282  and housing  262  of the rotary hammer  260  ( FIG. 1 ). Because the battery pack  270  is supported on the handle  282 , the vibration isolating assembly  287  also substantially isolates the battery pack  270  from the vibration produced during operation of the rotary hammer  260 . The mass of the battery pack  270  adds inertia to the handle  282  which further reduces the vibration experienced by the operator of the rotary hammer  260 . 
     The battery cells can be arranged in series, parallel, or a series-parallel combination. For example, in the illustrated embodiment, the battery pack  270  includes a total of ten battery cells configured in a series-parallel arrangement of five sets of two series-connected cells. The series-parallel combination of battery cells allows for an increased voltage and an increased capacity of the battery pack  270 . In other embodiments, the battery pack  270  can include a different number of battery cells (e.g., between 3 and 12 battery cells) connected in series, parallel, or a series-parallel combination in order to produce a battery pack having a desired combination of nominal battery pack voltage and battery capacity. 
     The battery cells are lithium-based battery cells having a chemistry of, for example, lithium-cobalt (“Li—Co”), lithium-manganese (“Li—Mn”), or Li—Mn spinel. Alternatively, the battery cells can have any other suitable chemistry. In the illustrated embodiment, each battery cell has a nominal voltage of about 3.6V, such that the battery pack  270  has a nominal voltage of about 18V. In other embodiments, the battery cells can have different nominal voltages, such as, for example, between about 3.6V and about 4.2V, and the battery pack  270  can have a different nominal voltage, such as, for example, about 10.8V, 12V, 14.4V, 24V, 28V, 36V, between about 10.8V and about 36V, etc. The battery cells also have a capacity of, for example, between about 1.0 ampere-hours (“Ah”) and about 5.0 Ah. In exemplary embodiments, the battery cells can have capacities of about, 1.5 Ah, 2.4 Ah, 3.0 Ah, 4.0 Ah, between 1.5 Ah and 5.0 Ah, etc. 
     The vibration isolating assembly  287  will now be described in more detail with reference to  FIGS. 3-5 . To attenuate the vibration being transferred to the handle  282  and the battery pack  270 , and therefore the operator of the rotary hammer  260 , the upper and lower joints  288 ,  290  of the vibration isolating assembly  287  each permit limited movement of the handle  282  relative to the housing  262  in the directions of the first axis  302 , the second axis  306 , and the third axis  310  ( FIG. 3 ). For example, the upper and lower joints  288 ,  290  enable movement of the handle  282  relative to the housing  262  along the first axis  302  between an extended position and a retracted position. The extended position and the retracted position correspond with the respective maximum and minimum relative distances between the handle  282  and the housing  262  during normal operation of the rotary hammer  260 . The upper and lower joints  288 ,  290  are structurally and functionally identical, and as such, only the upper joint  288  is described in greater detail herein. Like components are identified with like reference numerals. 
     With reference to  FIG. 4 , the first and second handle halves  282   a ,  282   b  each include a front wall  314 , a rear wall  318 , an upper wall  322 , and a lower wall  326  that collectively define a cavity  330  when the first and second handle halves  282   a ,  282   b  are attached. The upper joint  288  includes a rod  334  having a distal end  338  coupled to the housing  262 , a head  342  opposite the distal end  338 , and a shank  346  extending through the cavity  330 . The distal end  338  is coupled to the housing  262  by a first, generally T-shaped bracket  350 . The bracket  350  includes a rectangular head  354  and a post  358  extending from the head  354 . In the illustrated embodiment, the rod  334  is a threaded fastener (e.g., a bolt), and the post  358  includes a threaded bore  362  in which the threaded end  338  of the rod  334  is received. In other embodiments, the rod  334  may be coupled to the bracket  350  in any suitable fashion (e.g., an interference fit, etc.), or the rod  334  may be integrally formed as a single piece with the bracket  350 . In the illustrated embodiment, the bracket  350  is coupled to the housing  262  using an insert molding process. Alternatively, the bracket  350  may be coupled to the housing  262  by any suitable method. 
     With continued reference to  FIG. 4 , the upper joint  288  includes a biasing member  366  disposed between the upper portion  284  of the handle  282  and the housing  262 . The biasing member  366  is deformable to attenuate vibration transmitted from the housing  262  along the first axis  302 . In the illustrated embodiment, the biasing member  366  is a coil spring; however, the biasing member  366  may be configured as another type of elastic structure. The upper joint  288  also includes a second, generally T-shaped bracket  370  coupled to the rod  334 . The bracket  370  includes a rectangular head  374  and a hollow post  378  extending from the head  374  through which the shank  346  of the rod  334  extends. The head  342  of the rod  334  limits the extent to which the shank  346  may be inserted within the hollow post  378 . A sleeve  382 , having a generally square cross-sectional shape, surrounds the rod  334  and the posts  358 ,  378  of the brackets  350 ,  370  to provide smooth, sliding surfaces  386  ( FIG. 5 ) along the length of the rod  334 . The rectangular head  374  of the bracket  370  is configured to abut the rear walls  318  of the respective handle halves  282   a ,  282   b  in the extended position of the handle  282  and to be spaced from the rear walls  318  of the respective handle halves  282   a ,  282   b  as the handle  282  moves towards the retracted position. 
     With continued reference to  FIG. 5 , the upper joint  288  also includes a first guide  390  and a second guide  394  positioned within the cavity  330  on opposing sides of the sleeve  382 . The guides  390 ,  394  are constrained within the cavity  330  along the first axis  302  by the front and rear walls  314 ,  318  of the handle halves  282   a ,  282   b  such that the guides  390 ,  394  move with the handle  282  along the sliding surfaces  386  of the sleeve  382  as the handle  282  moves along the first axis  302 . A first bumper  398  is disposed within the cavity  330  between the first guide  390  and the first handle half  282   a , and a second bumper  402  is disposed within the cavity  330  between the second guide  394  and the second handle half  282   b . The bumpers  398 ,  402  are formed from an elastic material (e.g., rubber) and are deformable to allow the handle  282  to move relative to the housing  262  a limited extent along the second axis  306  (see also  FIG. 4 ). The bumpers  398 ,  402  resist this movement, thereby attenuating vibration transmitted from the housing  262  to the handle  282  along the second axis  306 . 
     With reference to  FIG. 3 , the upper joint  288  includes a gap  406  between the sleeve  382  and the upper walls  322  of the handle halves  282   a ,  282   b , and another gap  410  between the sleeve  382  and the lower walls  326  of the handle halves  282   a ,  282   b . The gaps  406 ,  410  allow the guides  390 ,  394  to slide relative to the sleeve  382  a limited extent along the third axis  310 . The gaps  406 ,  410  therefore allow the handle  282  to move relative to the housing  262  a limited extent along the third axis  310 . The biasing member  366  resists shearing forces developed by movement of the handle  282  along the third axis  310 , thereby attenuating vibration transmitted to the handle  282  along the third axis  310 . In addition, the upper bellows  292  is formed from a resilient material and further resists the shearing forces developed by movement of the handle  282  along the third axis  310 , thereby providing additional vibration attenuation. Similarly, the lower bellows  294  attenuates vibration transmitted to the handle  282  along the third axis  310  in conjunction with the lower joint  290 . 
     In operation of the rotary hammer  260 , vibration may occur along the first axis  302 , the second axis  306 , and/or the third axis  310  depending on the use of the rotary hammer  260 . When the handle  282  (and therefore, the battery pack  270 ) moves relative to the housing  262  along the first axis  302  between the extended position and the retracted position of the handle  282 , the biasing member  366  of each of the joints  288 ,  290  expands and compresses accordingly to attenuate the vibration occurring along the first axis  302 . Additionally, the bumpers  398 ,  402  of each of the joints  288 ,  290  elastically deform between the handle halves  282   a ,  282   b  and the guides  390 ,  394 , respectively, to permit limited movement of the handle  282  and the battery pack  270  relative to the housing  262  along the second axis  306 , thereby attenuating vibration occurring along the second axis  306 . Finally, the gaps  406 ,  410  defined by each of the joints  288 ,  290  allow for limited movement of the handle  282  and the battery pack  270  relative to the housing  262  along the third axis  310 , and the biasing member  366  and the upper and lower bellows  292 ,  294  resist the resulting shearing forces to attenuate the vibration occurring along the third axis  310 . 
     Thus, the invention provides a battery-powered rotary hammer having a housing, a handle, a vibration isolating assembly between the housing and the handle for attenuating vibration transmitted from the housing to the handle, and a battery pack removably coupled to the handle such that the battery pack is also at least partially isolated from the vibration. 
     Various features of the invention are set forth in the following claims.