Patent Publication Number: US-2021177406-A1

Title: Hand-held surgical instruments

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of and priority to U.S. Provisional Application No. 62/948,870 filed on Dec. 17, 2019, the entire contents of which are incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Technical Field 
     The disclosure relates to surgical instruments. More specifically, the disclosure relates to hand-held electromechanical surgical instruments that articulate, rotate, and actuate a variety of other functions of surgical attachments, such as, for example, end effectors configured to staple tissue. 
     2. Background of Related Art 
     Electromechanical surgical instruments include a reusable handle assembly and disposable loading units and/or single use loading units, such as, for example, surgical end effectors. The end effectors are selectively connected to the handle assembly prior to use and then disconnected from the handle assembly following use in order to be disposed of or in some instances sterilized for re-use. Some surgical instruments may be capable of articulating the end effector to adjust the angle of orientation of the end effector during a surgical procedure. There are one or more drive mechanisms within the handle assembly for carrying out the articulation of the end effector and/or the operational functions of the end effector. 
     SUMMARY 
     In one aspect of the disclosure, a hand-held surgical instrument is provided and includes a handle housing, a shaft portion extending distally relative to the handle housing, a first motor disposed within the handle housing, a ball screw operably coupled to the first motor, a ball nut non-rotationally supported in the shaft portion and operably coupled to the ball screw, and a firing shaft. The firing shaft has a proximal end portion attached to the ball nut, and a distal end portion configured to fire staples from an end effector. The ball nut is configured to translate the firing shaft along a longitudinal axis defined by the shaft portion in response to a rotation of the ball screw. 
     In aspects, the hand-held surgical instrument may further include a battery configured to power the first motor. In aspects, the battery may be configured to power all motors, LED&#39;s, and various other electronics. 
     In some aspects, the handle housing may have a barrel portion, and a handle portion extending perpendicularly from the barrel portion. The battery may be supported in the handle portion. In aspects, the battery may be supported in the barrel portion. 
     In other aspects, the handle portion may include an upper segment fixed to the barrel portion, and a lower segment pivotably coupled to the upper segment, the battery being disposed in the lower segment. 
     In further aspects, the handle portion may define a plane that extends parallel with the longitudinal axis of the shaft portion. The lower segment may be configured to pivot relative to the upper segment about a pivot axis that is parallel with the plane. 
     In aspects, the hand-held surgical instrument may further include a printed circuit board supported in the upper segment and configured to be in electrical communication with the battery and the first motor. In aspects, the printed circuit board may be in electrical communication with motion control circuitry. 
     In some aspects, the hand-held surgical instrument may further include a finger switch pivotably coupled to the upper segment. The finger switch may have an upper button and a lower button each in communication with the printed circuit board for activating the battery. In aspects, the finger switch may activate the battery and control the first motor. 
     In further aspects, the hand-held surgical instrument may further include a knob housing coupled to the handle housing, an articulation lever, and a first articulation shaft. The shaft portion may extend distally from the knob housing. The articulation lever may be rotationally coupled to the knob housing. The first articulation shaft may be operably coupled to the articulation lever, such that a rotation of the articulation lever translates the first articulation shaft to articulate an end effector. 
     In other aspects, the hand-held surgical instrument may further include a cam plate coupling the articulation lever with a proximal end portion of the first articulation shaft. The cam plate may be configured to urge the first articulation shaft in one of a proximal or distal direction upon rotation of the cam plate. 
     In aspects, the hand-held surgical instrument may further include an articulation locking assembly that includes a first ratchet gear operably coupled to the cam plate and a pawl engaged with the first ratchet gear. The pawl may be configured to restrict the rotation of the cam plate. 
     In some aspects, the first ratchet gear may be non-rotationally coupled to the articulation lever and pinned to the cam plate, such that a rotation of the articulation lever rotates the cam plate. 
     In further aspects, the cam plate may have a pin that extends through an elongate slot defined in the first ratchet gear. The first ratchet gear may be configured to rotate the cam plate after a delay. 
     In other aspects, the articulation locking assembly may include a second ratchet gear disposed between the first ratchet gear and the cam plate. The pawl may be engaged with the first and second ratchet gears. 
     In aspects, the first ratchet gear may have a plurality of teeth each defining an oblique surface, and the second ratchet gear may have a plurality of teeth each defining a linear surface. 
     In some aspects, adjacent teeth of the plurality of teeth of the first ratchet gear may define a triangular space therebetween, and adjacent teeth of the plurality of teeth of the second ratchet gear may define a rectangular space therebetween. 
     In further aspects, the second ratchet gear may be fixed to the cam plate, such that the cam plate and the second ratchet gear rotate simultaneously with one another. 
     In other aspects, the cam plate may define a first spiral slot, and the proximal end portion of the first articulation shaft may have a protuberance received in the first spiral slot. 
     In aspects, the hand-held surgical instrument may further include a second articulation shaft having a protuberance extending from a proximal end portion thereof. The protuberance of the second articulation shaft may be received in a second spiral slot defined in the cam plate. The first and second articulation shafts may be configured to translate in opposite directions in response to a rotation of the cam plate. 
     In accordance with another aspect of the disclosure, a hand-held surgical instrument is provided and includes a handle housing, a knob housing coupled to the handle housing, a shaft portion extending distally from the knob housing, an articulation lever rotationally coupled to the knob housing, a first articulation shaft, a cam plate, and an articulation locking assembly. The first articulation shaft is operably coupled to the articulation lever, such that a rotation of the articulation lever translates the first articulation shaft to articulate an end effector. The cam plate couples the articulation lever with a proximal end portion of the first articulation shaft. The cam plate is configured to urge the first articulation shaft in one of a proximal or distal direction. The articulation locking assembly includes a first ratchet gear operably coupled to the cam plate, and a pawl engaged with the first ratchet gear. The pawl may be configured to restrict the rotation of the cam plate. 
     In some aspects, the cam plate may have a pin that extends through an elongate slot defined in the first ratchet gear. The first ratchet gear may be configured to rotate the cam plate after a delay. 
     In further aspects, the articulation locking assembly may include a second ratchet gear disposed between the first ratchet gear and the cam plate. The pawl may be engaged with the first and second ratchet gears. 
     In other aspects, the first ratchet gear may have a plurality of teeth each defining an oblique surface, and the second ratchet gear may have a plurality of teeth each defining a linear surface. 
     In aspects, adjacent teeth of the plurality of teeth of the first ratchet gear may define a triangular space therebetween, and adjacent teeth of the plurality of teeth of the second ratchet gear may define a rectangular space therebetween, 
     In some aspects, the second ratchet gear may be fixed to the cam plate, such that the cam plate and the second ratchet gear rotate simultaneously with one another. 
     In further aspects, the cam plate may define a first spiral slot, and the proximal end portion of the first articulation shaft may have a protuberance received in the first spiral slot. 
     In other aspects, the hand-held surgical instrument may include a second articulation shaft having a protuberance extending from a proximal end portion thereof. The protuberance of the second articulation shaft may be received in a second spiral slot defined in the cam plate. The first and second articulation shafts may be configured to translate in opposite directions in response to a rotation of the cam plate. 
     In accordance with yet another aspect of the disclosure, a shaft assembly for use with a handle assembly of a hand-held surgical instrument is provided. The shaft assembly includes a knob housing, a shaft portion extending distally from the knob housing, an end effector coupled to a distal end portion of the shaft portion, an articulation lever rotationally coupled to the knob housing, a first articulation shaft, and a cam plate. The first articulation shaft is operably coupled to the articulation lever, such that a rotation of the articulation lever translates the first articulation shaft to articulate the end effector. The cam plate couples the articulation lever with a proximal end portion of the first articulation shaft. The cam plate is configured to urge the first articulation shaft in one of a proximal or distal direction in response to a rotation of the cam plate. 
     In aspects, the shaft assembly may further include an articulation locking assembly that includes a first ratchet gear operably coupled to the cam plate and a pawl engaged with the first ratchet gear. The pawl may be configured to restrict the rotation of the cam plate. 
     In some aspects, the first ratchet gear may be non-rotationally coupled to the articulation lever and pinned to the cam plate, such that a rotation of the articulation lever rotates the cam plate. 
     In further aspects, the cam plate may have a pin that extends through an elongate slot defined in the first ratchet gear. The first ratchet gear may be configured to rotate the cam plate after a delay. 
     In other aspects, the articulation locking assembly may include a second ratchet gear disposed between the first ratchet gear and the cam plate. The pawl may be engaged with the first and second ratchet gears. 
     In aspects, the first ratchet gear may have a plurality of teeth each defining an oblique surface, and the second ratchet gear may have a plurality of teeth each defining a linear surface. 
     In some aspects, adjacent teeth of the plurality of teeth of the first ratchet gear may define a triangular space therebetween, and adjacent teeth of the plurality of teeth of the second ratchet gear may define a rectangular space therebetween. 
     In other aspects, the second ratchet gear may be fixed to the cam plate, such that the cam plate and the second ratchet gear rotate simultaneously with one another. 
     In accordance with yet another aspect of the disclosure, a hand-held surgical instrument is provided and includes a handle housing, a shaft portion extending distally relative to the handle housing, a first articulation shaft supported in the shaft portion, a barrel cam, and an articulation motor. The first articulation shaft has a distal end portion configured to operably engage an end effector. The barrel cam is coupled to a proximal end portion of the first articulation shaft. The articulation motor may be operably coupled to the barrel cam and configured to rotate the barrel cam. A rotation of the barrel cam translates the first articulation shaft. 
     In aspects, the hand-held surgical instrument may further include a knob housing coupled to the handle housing. The knob housing may have the shaft portion extending distally therefrom. A manual rotation of the knob housing may rotate the shaft portion and the attached end effector. 
     In some aspects, the barrel cam may have an inner annular surface defining a helical cam slot. The proximal end portion of the first articulation shaft may have a protuberance received in the helical cam slot. 
     In further aspects, the hand-held surgical instrument may further include a ring gear non-rotationally coupled to the barrel cam. The articulation motor may have a motor gear operably coupled to the ring gear, such that a rotation of the motor gear results in a rotation of the barrel cam. 
     As used herein, the terms parallel and perpendicular are understood to include relative configurations that are substantially parallel and substantially perpendicular up to about + or −10 degrees from true parallel and true perpendicular. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the disclosure are described herein with reference to the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a hand-held electromechanical surgical instrument including a handle assembly, a shaft portion coupled to the handle assembly, and a surgical end effector coupled to the shaft portion, in accordance with an embodiment of the disclosure; 
         FIG. 2  is an enlarged side view, with a handle housing half removed, of the surgical instrument of  FIG. 1 ; 
         FIG. 3  is a rear perspective view illustrating a handle portion of the surgical instrument in an open state for removing a battery; 
         FIG. 4  is a side cross-sectional view of the handle portion of  FIG. 3 , as taken through  4 - 4  of  FIG. 3 ; 
         FIG. 5  is a longitudinal cross-sectional view, as taken through  5 - 5  of  FIG. 1 , illustrating a drive motor and a ball screw assembly for operating a stapling function of the end effector; 
         FIG. 6  is a perspective view, with parts separated, of a ball nut of the ball screw assembly of  FIG. 5 ; 
         FIG. 7  is a side perspective view illustrating the shaft assembly of the surgical instrument of  FIG. 1 ; 
         FIG. 8  is a perspective view, with parts separated, illustrating components of an articulation assembly of the shaft assembly of  FIG. 7 ; 
         FIG. 9  is an enlarged perspective view, of the indicated area of detail of  FIG. 8 , illustrating first and second articulation shafts of the articulation assembly of  FIG. 8 ; 
         FIG. 10  is a perspective view, with parts separated, illustrating a camming mechanism of the articulation assembly of  FIG. 8 ; 
         FIG. 11  is a perspective view, with parts separated, illustrating an articulation locking assembly of the shaft assembly of  FIG. 7 ; 
         FIG. 12  is a top view illustrating the articulation locking assembly of  FIG. 11 ; 
         FIG. 13  is a side view illustrating another embodiment of a hand-held electromechanical surgical instrument including a handle assembly, a shaft portion coupled to the handle assembly, and a surgical end effector coupled to the shaft portion; and 
         FIG. 14  is a perspective view, with parts separated, illustrating components of an articulation assembly of the surgical instrument of  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the presently disclosed surgical instruments are described in detail with reference to the drawings, in which like reference numerals designate identical or corresponding elements in each of the several views. As used herein the term “distal” refers to that portion of the surgical instrument, or component thereof, farther from the user, while the term “proximal” refers to that portion of the surgical instrument, or component thereof, closer to the user. 
     With reference to  FIGS. 1 and 2 , a surgical instrument, in accordance with an embodiment of the disclosure, is generally designated as  10 , and is in the form of a powered hand-held electromechanical surgical instrument configured for selective coupling thereto of a plurality of different surgical end effectors, for example, the surgical end effector  20 . The end effector  20  is configured for actuation and manipulation by the powered hand-held electromechanical surgical instrument  10 . 
     The hand-held electromechanical surgical instrument  10  includes a handle assembly  12  and a shaft portion  14  extending distally from the handle assembly  12 . The shaft portion  14  is configured for selective connection with a surgical attachment, such as, for example, the end effector  20 . The handle assembly  12  has a fire switch  16  configured to actuate the various functions of the end effector  20 . In addition, the handle assembly  12  has a safety switch  18  for preventing an inadvertent actuation of the fire switch  16 . A knob housing  22  is rotationally coupled to the handle assembly  12  and configured to be manually rotated about a longitudinal axis “X” defined by the shaft portion  14  to rotate the end effector  20 . An articulation lever  24  is rotationally coupled to the knob housing  22  and is configured to articulate the end effector  20  (e.g., move the end effector  200  along a horizontal plane between a position coaxial with the shaft portion  14  and multiple positions out of alignment with the shaft portion  14 . The angular orientation of a longitudinal axis of the articulation lever relative to the longitudinal axis “X” corresponds to an angular orientation of a longitudinal axis of the end effector  20  relative to the longitudinal axis “X.” As such, the end effector  20  may articulate in the same direction and to the same angular extent as the articulation lever  24 . 
     With reference to  FIGS. 2-4 , the handle assembly  12  includes a handle housing  26  consisting of a barrel portion  28  substantially aligned with the longitudinal axis “X,” and a handle portion  30  extending perpendicularly downward from the barrel portion  28 . The handle portion  30  includes an upper segment  32  fixed to and extending downwardly from the barrel portion  28 , and a lower segment  34  pivotably coupled to the upper segment  32 . The handle assembly  12  includes a printed circuit board  36  supported in the upper segment  32  and a battery  38  disposed in the lower segment  34 . The printed circuit board  36  is configured to be in electrical communication with the battery  38  and a drive motor  40 . The motor  40  may be wirelessly connected, connected via a wire, or otherwise electrically connected to the printed circuit board  36  and the battery  38 . The fire switch  16  may be a finger switch pivotably coupled to the upper segment  32  and has an upper button  16   a  and a lower button  16   b  each in communication with the printed circuit board  36  for activating the battery  38  to ultimately actuate an open/close and staple firing function of the end effector  20 . 
     As shown in  FIGS. 3 and 4 , the upper segment  32  of the handle portion  30  has a flange  42 , such as, for example, a tab, extending downwardly therefrom, and the lower segment  34  defines a cutout  44  configured for receipt of the flange  42 . The flange  42  has an inner surface having a deflectable latch hook  46  at an end thereof, and the lower segment  34  includes a release button  48  having a tab  50  extending into the cutout  44 . The tab  50  of the release button  48  defines a notch  52  configured to selectively receive and lock with the latch hook  46  of the upper segment  32 . In some aspects, the upper and lower segments  32 ,  34  may detachably couple to one another via any suitable fastening connection, such as, for example, a bayonet-type connection. The upper and lower segments  32 ,  34  are pivotably coupled to one another about a hinge  54 , such as, for example, a pivot pin. The handle portion  30  defines a plane that extends parallel with the central longitudinal axis “X” of the shaft portion  14 , such that the lower segment  34  is pivotable relative to the upper segment  32  about a pivot axis “Y” ( FIG. 2 ) that is parallel with the plane. 
     With reference to  FIGS. 5 and 6 , the surgical instrument  10  further includes a ball screw assembly  56  operably coupled to the motor  40  for carrying out an open/close and stapling function of the end effector  20  ( FIG. 1 ). The ball screw assembly  56  includes a ball nut  58 , a ball screw  60 , and a firing shaft  62 . The ball screw  60  is drivingly coupled to the motor  40  such that an actuation of the motor  40  results in a rotation of the ball screw  60 . The ball nut  58  is non-rotationally supported in the shaft portion  14  and operably coupled to the ball screw  60 . In particular, the ball nut  58  may have first and second planar lateral sides  58   a ,  58   b  that inhibit rotation of the ball nut  58  relative to the shaft portion  14 , and the ball nut  58  has an inner surface defining threading  64  that houses bearings (not shown). The bearings are captured between the threading  64  of the ball nut  58  and a threaded outer surface of the ball screw  60 . 
     The firing shaft  62  defines a conduit  66  through a proximal end portion  62   a  thereof. The ball screw  60  extends through the conduit  66  and the proximal end portion  62   a  is fixed to the ball nut  58 . In this way, the firing shaft  62  moves with the ball nut  58  as the ball nut  58  moves axially within the shaft portion  14  and relative to the ball screw  60 . The firing shaft  62  has a distal end portion  62   b  configured to operably couple to an axially-driven member (not shown) of the end effector  20 . The ball nut  58  has a cap or cover  68  for containing the ball bearings therein. 
       FIGS. 7-10  illustrate a shaft assembly  70  of the surgical instrument  10 . The shaft assembly  70  includes the knob housing  22 , the shaft portion  14 , and the end effector  20 . The knob housing  22  supports an articulation assembly  72  configured to effect the articulation of the end effector  20  relative to the shaft portion  14 . The articulation lever  24  of the articulation assembly  72  is accessible from outside of the knob housing  22  and is configured to be manually rotated. 
     The articulation assembly  72  generally includes first and second articulation shafts  74 ,  76  and a cam plate  82 . The first and second articulation shafts  74 ,  76  are axially movable within the shaft portion  14  and each has a proximal end portion  74   a ,  76   a  operably coupled to the articulation lever  22 , and a distal end portion (not explicitly shown) operably coupled to opposite sides of the end effector  20 . As such, a rotation of the articulation lever  22  translates the first and second articulation shafts  74 ,  76  in opposite directions to articulate the end effector  20 . The proximal end portion  74   a ,  76   a  of each of the articulation shafts  74 ,  76  has a respective protuberance  78 ,  80 . The cam plate  82  defines first and second spiral slots  82   a ,  82   b  for receiving the respective protuberances  78 ,  80 . The spiral cam slots  82   a ,  82   b  are oriented so that a rotation of the cam plate  82  results in an axial movement of the first and second articulation shafts  74 ,  76  in opposite directions. A helical coil  84  may be attached to the proximal end portion of the shaft portion  14  for guiding an electrical cable (not shown) thereabout that runs from the motor  40  ( FIG. 5 ). The helical coil  84  rotates with a rotation of the shaft portion  14  and prevents the cable from bunching and eliminates the need for an electrical slip ring. 
       FIGS. 11 and 12  illustrate an articulation locking assembly  88  for selectively locking the articulation lever  22  in a rotational position to prevent backdriving of the articulation lever  22 . The articulation locking assembly  88  generally includes a ratchet assembly  90  operably coupling the cam plate  82  and the articulation lever  22 , and a pawl  92  engaged with the ratchet assembly  90  and configured to restrict the rotation of the cam plate  82 . The pawl  92  has a proximal end portion  92   a  slidably supported on the spiral coil  84 , and a free distal end portion  92   b  having an elongated distal tip  94 . The pawl  92  is slidable along a longitudinal axis defined by the pawl  92 . A detent spring  96  ( FIG. 10 ) is provided to resiliently bias the distal tip  94  of the pawl  92  in a distal direction. In aspects, the pawl  92  may be resilient or rigid. 
     The ratchet assembly  90  includes a first ratchet gear  98  and a second ratchet gear  100 . The first ratchet gear  98  has a plate  102  and a stem  104  extending from the plate  102 . The stem  104  is received in a correspondingly shaped aperture (not explicitly shown) defined in the articulation lever  22  to non-rotationally couple the first ratchet gear  98  to the articulation lever  22 . The plate  102  of the first ratchet gear  98  has a plurality of teeth  106  arranged around the outer periphery of the first ratchet gear  98 . Each of the teeth  106  defines an oblique surface  108 , such that adjacent teeth  106  define a triangular space  110  therebetween configured for selective receipt of the free distal tip  94  of the pawl  92 . 
     The plate  102  of the first ratchet gear  98  is coupled to the cam plate  82 , such that a rotation of the articulation lever  22  rotates the cam plate  82 . For example, the cam plate  82  has a pair of pins  112 ,  114  that extend through a respective elongate slot  116 ,  118  defined in the first ratchet gear  98 . The elongate slots  116 ,  118  define a length that is approximately 1.5 times greater than a diameter of the pins  112 ,  114  of the cam plate  82 . In this way, a rotation of the first ratchet gear  98 , in response to a rotation of the articulation lever  22 , results in a rotation of the cam plate  82  after a delay. 
     The second ratchet gear  100  is disposed between the plate  102  of the first ratchet gear  98  and the cam plate  82 . The second ratchet gear  100  is fixed to the cam plate  82  (e.g., via the pins  112 ,  114 ), such that the cam plate  82  and the second ratchet gear  100  rotate simultaneously with one another. The second ratchet gear  100  has a plurality of teeth  120  arranged around an outer periphery thereof. The teeth  120  of the second ratchet gear  100  each define a linear surface  122 , such that adjacent teeth  120  of the second ratchet gear  100  define a rectangular space  124  therebetween configured for selective receipt of the distal tip  94  of the pawl  92 . The distal tip  94  of the pawl  92  may be configured to wedge into the space  124  to resist rotation of the second ratchet gear  100  relative to the pawl  92 . 
     The first and second ratchet gears  98 ,  100  are angularly oriented relative to one another so that the triangular spaces  110  of the first ratchet gear  98  overlap with the respective rectangular spaces  124  of the second ratchet gear  100 . In aspects, the spaces  110  of the first ratchet gear  98  may assume the same shape as the spaces  124  of the second ratchet gear  100  and/or the spaces  110 ,  124  may assume any suitable shape, such as, for example, arcuate. 
     In operation, to articulate the end effector  20 , the articulation lever  22  may be manually rotated in the direction intended for the end effector  20  to articulate. Rotation of the articulation lever  22  rotates the first ratchet gear  98 , whereby one of the oblique surfaces  108  of the teeth  106  of the first ratchet gear  98  cams the free distal tip  94  of the pawl  92  proximally and out of the space  110  between the teeth  106  of the first ratchet gear  98  and the space  124  between the teeth  120  of the second ratchet gear  100 . A tooth  106  of the first ratchet gear  98  is rotated into overlapping alignment with a space  124  defined between adjacent teeth  120  of the second ratchet gear  100 , whereby the first ratchet gear  98  engages the pins  112 ,  114  of the cam plate  82  to drive a rotation of the cam plate  82 . As described, rotation of the cam plate  82  translates the first and second articulation shafts  74 ,  76  in opposite directions. The opposing translation of the first and second articulation shafts  74 ,  76  drives the articulation of the end effector  20 . 
     Due to the second ratchet gear  100  being fixed to the cam plate  82 , the second ratchet gear  100  rotates with the cam plate  82  to maintain the teeth  106  of the first ratchet gear  98  in overlapping alignment with respective spaces  124  of the second ratchet gear  100 . In this way, the distal tip  94  of the pawl  92  is maintained in a proximal position and out of the spaces  110 ,  124  of the ratchet gears  98 ,  100  while the articulation lever  22  is being rotated. However, upon removing the application of a rotational force on the articulation lever  22 , the resilient bias of the pawl  92  (due to detent spring  96 ) will cam the first ratchet gear  98  to reposition the teeth  106  of the first ratchet gear  98  into overlapping alignment with the teeth  120  of the second ratchet gear  100 . This is caused by the first ratchet gear  98  being free to rotate relative to the second ratchet gear  100  a selected distance. Despite any backdriving force exerted on the second ratchet gear  100  via the cam plate  82 , rotation of the second ratchet gear  100  is resisted due to the engagement of the distal tip  94  of the pawl  92  in the space  124  of the second ratchet gear  100 . More specifically, the adjacent teeth  120  of the second ratchet gear  100  capture the distal tip  94  of the pawl  92  therebetween, thereby resisting rotation of the second ratchet gear  100  and, in turn, the cam plate  82 . 
       FIGS. 13 and 14  illustrate another embodiment of a hand-held surgical instrument  210 , similar to the surgical instrument  10  described above. The surgical instrument  210  is different by having a powered articulation mechanism  220  rather than being manually actuated. Due to the similarities between the two surgical instruments, only those elements of the surgical instrument  210  deemed necessary to elucidate the differences from the surgical instrument  10  will be described in detail. 
     The surgical instrument  210  generally includes a handle housing  212 , a knob housing  222  coupled to the handle housing  212 , a shaft portion  214  extending distally from the knob housing  222 , and an end effector, such as, for example, the end effector  20 , operably coupled to a distal end portion of the shaft portion  214 . An articulation switch  216  is pivotably coupled to the handle housing  212  for actuating an articulation of the end effector  20 . The knob housing  222  may be manually rotated to thereby rotate the shaft portion  214  and the attached end effector  20  about a longitudinal axis defined by the shaft portion  214 . The shaft portion  214  has a first articulation shaft  274  and a second articulation shaft (not explicitly shown) each supported therein. 
     The articulation mechanism  220  is received at least partially in the knob housing  222  and includes a barrel cam  224 , a barrel cam gear  226 , and an articulation motor  228 . The barrel cam  224  consists of first and second semicircular half sections  224   a ,  224   b  together forming a tubular barrel cam  224 . The barrel cam  224  is received within and fixed to the barrel cam gear  226 . In some aspects, the barrel cam  224  may be monolithically formed with the barrel cam gear  226 . Each of the first and second semicircular half sections  224   a ,  224   b  of the barrel cam  224  defines opposing helical cam slots  230  in an inner annular surface  232  thereof. The helical cam slots  230  receive a respective protuberance extending from the proximal end portion of the first and second articulation shafts  274 . As such, a rotation of the barrel cam  224  results in axial translation of the first and second articulation shafts  274  in opposite directions. 
     The barrel cam gear  226  has a tubular body  226   a  and a ring gear  226   b  fixed about the tubular body  226   a . The articulation motor  228  has a drive shaft  236  and a drive gear  238  non-rotationally coupled to the drive shaft  236 . The drive gear  238  of the articulation motor  228  is operably coupled to the ring gear  226   b  to rotate the barrel cam  224  to translate the first and second articulation shafts  274 . 
     In operation, an articulation switch  217  may be actuated to activate the articulation motor  228  to rotate the drive gear  238 . Rotation of the drive gear  238  drives a rotation of the barrel cam  224  via the ring gear  226   b . Due to the protuberances or pins of the articulation shafts  274  being received in the opposing helical cam slots  230  of the barrel cam  224 , rotation of the barrel cam  224  drives an axial translation of the first and second articulation shafts  274  in opposing directions to articulate the end effector  20  relative to the shaft portion  214 . 
     Any of the components described herein may be fabricated from either metals, plastics, resins, composites or the like taking into consideration strength, durability, wearability, weight, resistance to corrosion, ease of manufacturing, cost of manufacturing, and the like. 
     It will be understood that various modifications may be made to the embodiments of the presently disclosed surgical instruments including switch assemblies. Therefore, the above description should not be construed as limiting, but merely as exemplifications of embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the disclosure.