Patent Publication Number: US-9895793-B2

Title: Speed-selectable hand tool

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Application No. 104210350, filed on Jun. 26, 2015. 
     FIELD 
     The disclosure relates to a hand tool, and more particularly to a speed-selectable hand tool. 
     BACKGROUND 
     U.S. Pat. No. 6,658,970 discloses a conventional screwdriver including a shaft-mounting seat, a handle, a ratchet assembly, a drive shaft, two pawls and a tubular sleeve. The shaft-mounting seat is connected fixedly to the handle. The ratchet assembly is connected to the drive shaft, and is disposed in the shaft-mounting seat. The pawls are mounted movably in the shaft-mounting seat, and are operable to engage removably the ratchet assembly. The tubular sleeve is mounted around the shaft-mounting seat, and is operable for switching states of the pawls such that the conventional screwdriver is convertible to serve as a ratcheting screwdriver or a non-ratcheting screwdriver. However, in use, the rotating speed of the drive shaft is the same as that of the handle, so that the conventional screwdriver may be laborious. 
     As shown in  FIGS. 1 and 2 , U.S. Pat. No. 5,406,866 discloses a conventional speed-selectable screwdriver  10  including a handle  11 , an insert  12 , a roller cage  13 , a plurality of first rollers  14 , a plurality of second rollers  15 , a limiting spring  16 , a knob  17 , a drive shaft  18 , an overdrive sleeve  19 , two triangular mounting plates  20 , three gear assemblies  21 , a housing  22 , a bit  23  and a bit holder  24 . The insert  12  is mounted fixedly in the handle  11 , and is formed with a non-circular hole  121 . The roller cage  13  is mounted rotatably in the non-circular hole  121 , and is formed with a plurality of channels  131 . The limiting spring  16  is mounted to the roller cage  13  for limiting the relative movement between the roller cage  13  and the insert  12 . The knob  17  is mounted fixedly around a front portion of the roller cage  13 . The drive shaft  18  is inserted into the roller cage  13 , and has a splined front end  181  and an enlarged body portion  182 . The overdrive sleeve  19  is sleeved on the drive shaft  18 , is located between the splined from end  181  and the enlarged body portion  182  of the drive shaft  18 , and has a sun gear portion  191 . The first rollers  14  are mounted respectively and movably in the channels  131  of the roller cage  13 , and are contactable with the enlarged body portion  182  of the drive shaft  18 . The second rollers  15  are mounted respectively and movably in the channels  131  of the roller cage  13 , and are contactable with the overdrive sleeve  19 . The mounting plates  20  are mounted rotatably and respectively on the drive shaft  18  and the overdrive sleeve  19 . Each of the gear assemblies  21  is mounted rotatably between the mounting plates  20 , and has a planetary gear  211  that meshes with the sun gear portion  191  of the overdrive sleeve  19 , and an auxiliary gear  212  that is co-rotatable with the planetary gear  211  and that meshes with the splined front end  181  of the drive shaft  18 . The housing  22  is mounted fixedly around the mounting plates  20 . The bit holder  24  is connected co-rotatably to the drive shaft  18 . The bit  23  is mounted co-rotatably to the bit holder  24 . 
     Referring further to  FIG. 3 , the insert  12  has a plurality of cam surfaces  122  and a plurality of slip surfaces  123 . The cam surfaces  122  and the slip surfaces  123  are arranged alternately in the circumferential direction, and cooperatively define the non-circular hole  121 . 
     For each of the gear assemblies  21 , the number of teeth of the auxiliary gear  212  is two times the number of teeth of the planetary gear  211 , and is the same as that of the sun gear portion  191  of the overdrive sleeve  19 . The number of teeth of the planetary gear  211  of each of the gear assemblies  21  is the same as that of the splined front end  181  of the drive shaft  18 . 
     When a user holds firmly the housing  22  and turns the handle  11  relative to the housing  22  in a first rotational direction (D 1 , see  FIG. 3 ), the cam surfaces  122  of the insert  12  respectively push the second rollers  15  to be in frictional contact with the overdrive sleeve  19 , such that the overdrive sleeve  19  is co-rotatable with the handle  11 . By virtue of the gear assemblies  21 , the drive shaft  18  is rotated in the first rotational direction (D 1 ) at a rotational speed four times the rotational speed of the overdrive sleeve  19 . At this time, an outer surrounding surface of the enlarged body portion  182  of the drive shaft  18  pushes the first rollers  14  to correspond respectively in angular position to the slip surfaces  123  so as to permit the relative rotation between the drive shaft  18  and the insert  12 . 
     When the user turns the handle  11  in the first rotational direction (D 1 ) without holding firmly the housing  22 , the cam surfaces  122  of the insert  12  respectively push the first rollers  14  to be in frictional contact with the enlarged body portion.  182  of the drive shaft  18 , such that the drive shaft  18  is rotated by the handle  11  at the same rotational speed. Additionally, when the user turns the handle  11  in a second rotational direction (D 2 , see  FIG. 3 ) without holding firmly the housing  22 , the slip surfaces  123  are rotated to correspond respectively in angular position to first rollers  14 , such that the drive shaft  18  would not be rotated by the handle  11 . 
     However, the conventional speed-selectable screwdriver  10  cannot serve as a non-ratcheting screwdriver, and has a relatively complex structure. Moreover, since the handle  11  rotates the drive shaft  18  by virtue of the frictional contact between each of the first rollers  14  and the enlarged body portion  182  of the drive shaft  18 , or the frictional contact between each of the second rollers  15  and the overdrive sleeve  19 , an output torque of the drive shaft  18  may be insufficiently large. 
     SUMMARY 
     Therefore, an object of the disclosure is to provide a speed-selectable hand tool that can overcome at least one of the aforesaid drawbacks associated with the prior arts. 
     According to the disclosure, the speed-selectable hand tool includes a handle, a cage member, a shaft member, an overdrive unit, a pawl unit, a knob, an outer casing and a head unit. The cage member has a cage section and a connecting section. The cage section has a front portion, a rear portion that is spaced apart from the front portion along an axis, an intermediate portion that is connected between the front and rear portions, a retaining space that is formed, in the front portion and the intermediate portion and that extends along the axis, four through grooves each of which is formed in the intermediate portion and extends in the radial direction of the axis, and a first shaft hole portion that is formed in the rear portion. The connecting section extends along the axis from one end of the rear portion distal from the from portion, is connected fixedly to the handle, and is formed with a second shaft hole portion that is in spatial communication with the first shaft hole portion. The shaft member extends along the axis, is rotatable relative to the cage member, and has a first ratchet wheel section that is retained in the retaining space, a rod section that extends through the first and second shaft hole portions, and a first gear section that is located at a front side of the first ratchet wheel section opposite to the rod section. The overdrive unit includes a sleeve member that is sleeved rotatably on the shaft member, that is located at the front side of the first ratchet wheel section opposite to the rod section, and that has a second ratchet wheel section retained in the retaining space and proximate to the first ratchet wheel section, and a second gear section distal from the first ratchet wheel section, two spaced-apart and substantially polygonal support frames that are mounted rotatably and respectively on the sleeve member and the shaft member, and a plurality of transmission members each of which is mounted rotatably between the support frames, and has a small gear section meshing with the second gear section of the sleeve member, and a large gear section meshing with the first gear section of the shaft member. The pawl unit includes a mounting plate that is mounted in the front portion of the cage section of the cage member, first and second shaft pawls that are partially retained in the retaining space, and first and second sleeve pawls that are partially retained in the retaining space. The first shaft pawl has a main body that is mounted pivotally between the mounting plate and the rear portion of the cage section of the cage member, an engaging section that extends from the main body, and a driven section that extends from the main body and out of the cage section of the cage member through a corresponding one of the through grooves, and is operable to switch between an enabled state where the engaging section of the first shaft pawl engages separably the first ratchet wheel section of the shaft member for preventing the shaft member from rotating relative to the cage member in a first rotational direction, and a disabled state where the engaging section of the first shaft pawl is separated from the first ratchet wheel section. The second shaft pawl has a main body that is mounted pivotally between the mounting plate and the rear portion of the cage section of the cage member, an engaging section that extends from the main body, and a driven section that extends from the main body and out of the cage section of the cage member through a corresponding one of the through grooves, and is operable to switch between an enabled state where the engaging section of the second shaft pawl engages separably the first ratchet wheel section of the shaft member for preventing the shaft member from rotating relative to the cage member in a second rotational direction opposite to the first rotational direction, and a disabled state where the engaging section of the second shaft pawl is separated from the first ratchet wheel section. The first sleeve pawl has a main body that is mounted pivotally between the mounting plate and the rear portion of the cage section of the cage member, an engaging section that extends from the main body, and a driven section that extends from the main body and out of the cage section of the cage member through a corresponding one of the through grooves, and is operable to switch between an enabled state where the engaging section of the first sleeve pawl engages separably the second ratchet wheel section of the sleeve member for preventing the sleeve member from rotating relative to the cage member in the first rotational direction, and a disabled state where the engaging section of the first sleeve pawl is separated from the second ratchet wheel section. The second sleeve pawl has a main body that is mounted pivotally between the mounting plate and the rear portion of the cage section of the cage member, an engaging section that extends from the main body, and a driven section that extends from the main body and out of the cage section of the cage member through a corresponding one of the through grooves, and is operable to switch between an enabled state where the engaging section of the second sleeve pawl engages separably the second ratchet wheel section of the sleeve member for preventing the sleeve member from rotating relative to the cage member in the second rotational direction, and a disabled state where the engaging section of the second sleeve pawl is separated from the second ratchet wheel section. The knob is mounted rotatably around the cage section of the cage member and the pawl unit, and has a surrounding wall that surrounds the pawl unit, a base wall that is dispose at an end of the surrounding wall distal from the handle, two first driving protrusions that are formed on an inner surface of the surrounding wall for respectively driving the driven sections of the first and second shaft pawls so as to switch the states of the first and second shaft pawls, and two second driving protrusions that are formed on the inner surface of the surrounding wall for respectively driving the driven sections of the first and second sleeve pawls so as to switch the states of the first and second sleeve pawls. The first driving protrusions and the second driving protrusions are angularly spaced apart from each other about the axis. The outer casing is formed with a substantially polygonal hole for retaining co-rotatably the support frames therein. The head unit is connected to and driven by the shaft member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment with reference to the accompanying drawings, of which: 
         FIG. 1  is an exploded, perspective view of conventional speed-selectable screwdriver disclosed in U.S. Pat. No. 5,406,866; 
         FIG. 2  is a sectional view of the conventional speed-selectable screwdriver; 
         FIG. 3  is a sectional view of the conventional speed-selectable screwdriver taken along line III-III in  FIG. 2 ; 
         FIG. 4  is a schematic side view of an embodiment of a speed-selectable hand tool according to the disclosure; 
         FIG. 5  is a rear view of the embodiment omitting a handle; 
         FIG. 6  is a fragmentary, partly exploded perspective view of the embodiment; 
         FIG. 7  is another fragmentary, partly exploded perspective view of the embodiment; 
         FIG. 8  is still another fragmentary, partly exploded perspective view of the embodiment; 
         FIG. 9  is a fragmentary assembled perspective view of a portion of the embodiment; 
         FIG. 10  is a schematic fragmentary sectional view of the embodiment taken along line X-X in  FIG. 5 ; 
         FIG. 11  is a schematic sectional view of the embodiment taken along line XI-XI in  FIG. 4 ; 
         FIG. 12  is another schematic sectional view of the embodiment taken along line XII-XII in  FIG. 4 ; 
         FIG. 13  is still another schematic sectional view of the embodiment similar to  FIG. 12 ; and 
         FIG. 14  is still another schematic sectional view of the embodiment similar to  FIG. 12 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 4 to 10 , an embodiment of a speed-selectable hand tool  3  according to the disclosure includes a handle  30 , a cage member  40 , a shaft member  50 , an overdrive unit  60 , a pawl unit  70 , a knob  80 , a positioning unit  90 , an outer casing  100  and a head unit  110 . 
     With particular reference to  FIG. 8 , the cage member  40  has a cage section  41  and a connecting section  42 . The cage section  41  has a front portion  411 , a rear portion  412  that is spaced apart from the front portion  411  along an axis (I), an intermediate portion  413  that is connected between the front and rear portions  411 ,  412 , a retaining space  414  that is formed in the front portion  411  and the intermediate portion  413  and that extends along the axis (I), four through grooves  415  each of which is formed in the intermediate portion  413  and extends in the radial direction of the axis (I), a first shaft hole portion.  416  (see  FIG. 10 ) that is formed in the rear portion  412 , a limiting block  417  that projects outwardly from an outer surface of the intermediate portion  413 , and an installation hole  418  that is formed in the front portion  411  and that extends in the radial direction of the axis (I). The installation hole  418  is configured as a blind hole. The connecting section  42  extends along the axis (I) from one end of the rear portion  412  distal from the front portion  411 , is connected fixedly to the handle  30 , and is formed with a second shaft hole portion  421  (see  FIG. 10 ) that is in spatial communication with the first shaft hole portion  416 . 
     The shaft member  50  extends along the axis (I), is rotatable relative to the cage member  40 , and has a first ratchet wheel section  51  that is retained in the retaining space  414 , a rod section  52  that extends through the first and second shaft hole portions  416 ,  421 , and a first gear section  53  that is located at a front side of the first ratchet wheel section  51  opposite to the rod section  52 , and a splined section  54  that is located at a front side of the first gear section  53  opposite to the first ratchet wheel section  51 . 
     The overdrive unit  60  includes a sleeve member  61  that is sleeved rotatably on the shaft member  50 , that is located at the front side of the first ratchet wheel section  51  opposite to the rod section  52 , and that has a second ratchet wheel section  62  retained in the retaining space  414  and proximate to the first ratchet wheel section  51 , and a second gear section  63  distal from the thirst ratchet wheel section  51  such that the second ratchet wheel section  62  is between the second gear section  63  and the first ratchet wheel section  51 , two spaced-apart polygonal support frames  64  that are mounted rotatably and respectively on the sleeve member  61  and the shaft member  50 , and a plurality of transmission members  65  each of which is mounted rotatably between the support frames  64 , and has a small gear section  651  meshing with the second gear section  63  of the sleeve member  61 , and a large gear section  652  meshing with the first gear section  53  of the shaft member  50 . The second gear section  63  of the sleeve member  61  and the large gear section  652  of each of the transmission members  65  have the same number of teeth. The first gear section  53  of the shaft member  50  and the small gear section  651  of each of the transmission members  65  have the same number of teeth. In this embodiment, the number of teeth of the large gear section  652  of each of the transmission members  65  is two times that of the small gear section  651  of the transmission member  65 , such that when the sleeve member  61  rotates relative to the support frames  64 , the shaft member  50  is driven to rotate relative to the support frames  64  at a speed four times that of the sleeve member  61  via the transmission members  65 . Further note that, in this embodiment, the sleeve member  61  is not a one-piece element, but is an assembly of two components (see FIGS.  8  to  10 ). 
     In this embodiment, each of the support frames  64  is triangular-shaped, and the overdrive unit  60  includes three transmission members  65 . 
     With particular reference to  FIGS. 8 and 10 , the pawl unit  70  includes a mounting plate  71  that is mounted in the front portion  411  of the cage section  41  of the cage member  40 , first and second shaft pawls  72 ,  72 ′ that are partially retained in the retaining space  414 , first and second sleeve pawls  73 ,  73 ′ that are partially retained in the retaining space  414 , and an abrasion-resistant plate  74  that is retained in the retaining space  414 . 
     The first shaft pawl  72  has a main body  721  that is mounted pivotally between the mounting plate  71  and the rear portion  412  of the cage section  41  of the cage member  40 , an engaging section  722  that extends from the main body  721 , and a driven section  723  that extends from the main body  721  and out of the cage section  41  of the cage member  40  through one of the through grooves  415 , and is operable to switch between an enabled state where the engaging section  722  engages separably the first ratchet wheel section  51  of the shaft member  50  for preventing the shaft member  50  from rotating relative to the cage member  40  in a first rotational direction (R 1 , see  FIG. 13 ), and a disabled state where the engaging section.  722  is separated from the first ratchet wheel section  51 . The first shaft pawl  72  further has a recess  724  that corresponds in position to the second ratchet wheel section  62  of the sleeve member  61  such that the first shaft pawl  72  is prevented from engaging the second ratchet wheel section  62  of the sleeve member  61 . 
     The second shaft pawl  72 ′ has a main body  721 ′ that is mounted pivotally between the mounting plate  71  and the rear portion  412  of the cage section  41  of the cage member  40 , an engaging section  722 ′ that extends from the main body  721 ′, and a driven section  723 ′ that extends from the main body  721 ′ and out of the cage section  41  of the cage member  40  through one of the through grooves  415 , and is operable to switch between an enabled state where the engaging section  722 ′ engages separably the first ratchet wheel section  51  of the shaft member  50  for preventing the shaft member  50  from rotating relative to the cage member  40  in a second rotational direction (R 2 , see  FIG. 14 ) opposite to the first rotational direction (R 1 ), and a disabled state where the engaging section  722 ′ is separated from the first ratchet wheel section  51 . The second shaft pawl  72 ′ further has a recess  724 ′ that corresponds in position to the second ratchet wheel section  62  of the sleeve member  61  such that the second shaft pawl  72 ′ is prevented from engaging the second ratchet wheel section  62  of the sleeve member  61 . 
     The first sleeve pawl  73  has a main body  731  that is mounted pivotally between the mounting plate  71  and the rear portion  412  of the cage section  41  of the cage member  40 , an engaging section  732  that extends from the main body  731 , and a driven section  733  that extends from the main body  731  and out of the cage section  41  of the cage member  40  through one of the through grooves  415 , and is operable to switch between an enabled state where the engaging section  732  engages separably the second ratchet wheel section  62  of the sleeve member  61  for preventing the sleeve member  61  from rotating relative to the cage member  40  in the first rotational direction (R 1 ), and a disabled state where the engaging section  732  is separated from the second ratchet wheel section  62 . The first sleeve pawl  73  further has a recess  734  that corresponds in position to the first ratchet wheel section  51  of the shaft member  50  such that the first sleeve pawl  73  is prevented from engaging the first ratchet wheel section  51  of the shaft member  50 . 
     The second sleeve pawl  73 ′ has a main body  731 ′ that is mounted pivotally between the mounting plate  71  and the rear portion  412  of the cage section  41  of the cage member  40 , an engaging section  732 ′ that extends from the main body  731 ′, and a driven section  733 ′ that extends from the main body  731 ′ and out of the cage section  41  of the cage member  40  through one of the through grooves  415 , and is operable to switch between an enabled state where the engaging section  732 ′ engages separably the second ratchet wheel section  62  of the sleeve member  61  for preventing the sleeve member  61  from rotating relative to the cage member  40  in the second rotational direction (R 2 ), and a disabled state where the engaging section  732 ′ is separated from the second ratchet wheel section  62 . The second sleeve pawl  73 ′ further has a recess  734 ′ that corresponds in position to the first ratchet wheel section  51  of the shaft member  50  such that the second sleeve pawl  73 ′ is prevented from engaging the first ratchet wheel section  51  of the shaft member  50 . 
     In this embodiment, each of the driven sections  723 ,  723 ′,  733 ,  733 ′ of the first and second shaft pawls  72 ,  72 ′ and the first and second sleeve pawls  73 ,  73 ′ extends out of the cage section  41  of the cage member  40  through a respective one of the through grooves  415 . 
     The abrasion-resistant plate  74  is disposed adjacent to the rear portion  412 , and has a ring section  741  that surrounds the rod section  52  of the shaft member  50 , and four position arms  742  that extend from the ring section  741 . The abrasion-resistant plate  74  is for alleviating the abrasion of the cage member  40  due to the relative rotation between the shaft member  50  and the cage member  40 . 
     Referring to  FIGS. 4, 7, 10 and 12 , the knob  80  is mounted rotatably around the cage section  41  of the cage member  40  and the pawl unit  70 , and has a surrounding wall  82  that surrounds the pawl unit  70 , a base wall  81  that is dispose at an end of the surrounding wall  82  distal from the handle  30 , two first driving protrusions  83  that are formed on an inner surface of the surrounding wall  82  for respectively driving the driven sections  723 ,  723 ′ of the first and second shaft pawls  72 ,  72 ′ so as to switch the states of the first and second shaft pawls  72 ,  72 ′, and two second driving protrusions  84  that are formed on the inner surface of the surrounding wall  82  for respectively driving the driven sections  733 ,  733 ′ of the first and second sleeve pawls  73 ,  73 ′ so as to switch the states of the first and second sleeve pawls  73 ,  73 ′. The first driving protrusions  83  and the second driving protrusions  84  are angularly spaced apart from each other about the axis (I). The first driving protrusions  83  are adjacent to each other. The second driving protrusions  84  are adjacent to each other. The knob  80  further has three positioning grooves  85  that are formed in the inner surface of the surrounding wall  82  and that are located between the first driving protrusions  83 , and a limiting space  86  (see  FIG. 12 ) that is defined between one of the first driving protrusions  83  and one of the second driving protrusions  84  for extension of the limiting block  417  of the cage member  40  so as to limit the range of relative rotational movement between the cage member  40  and the knob  80 . The positioning grooves  85  are arranged in a circumferential direction of the knob  80 . The knob  80  further has an annular wall  87  (see  FIG. 10 ) that extends from the base wall  81  away from the surrounding wall  82 . 
     The positioning unit  90  includes a positioning set  91  and a spring set  92 . The positioning set  91  includes a resilient member  911  that is retained in the installation hole  418 , and a positioning ball member  912  that is biased resiliently by the resilient member  911  to engage an alternative one of the positioning grooves  82  so as to position the knob  80  relative to the cage member  40 . The spring set  92  includes four pawl springs  921  each of which is disposed between an inner surface of the intermediate portion  413  of the cage member  40  and the engaging section.  722 ,  722 ′,  732 ,  732 ′ of a respective one of the first and second shaft pawl s  72 ,  72 ′ and the first and second sleeve pawls  73 ,  73 ′ for retaining the corresponding one of the first and second shaft pawls  72 ,  72 ′ and the first and second sleeve pawls  73 ,  73 ′ at the enabled state. In this embodiment, each of the resilient member  911  and the pawl springs  921  is configured as a compression spring. 
     Referring to  FIGS. 6 and 10 , the outer casing  100  is formed with a polygonal hole  101  for retaining co-rotatably the support frames  64 . In this embodiment, the outer casing  100  includes interconnected front and rear casing parts  102 ,  104 . The from casing part  102  is formed with the polygonal hole  101  and three insertion holes  103 . The polygonal hole  101  and the insertion holes  103  open toward the rear casing part  104 . The rear casing part  104  is mounted rotatably around the sleeve member  61 , is located at one side of the knob  80  opposite to the handle  30 , and has three insertion rods  106  that are respectively inserted into the insertion holes  103 , and an annular groove  105  (see  FIG. 10 ) that opens toward the knob  80  for retaining the annular wall  87  of the knob  60  therein. 
     The head unit  110  is connected to and driven by the shaft member  50 , and includes a connecting tube  111  that is connected co-rotatably to the splined section  54  of the shaft member  50 , and a bit  112  that is connected co-rotatably and detachably to the connecting tube  111  for tightening or loosening a fastener (not shown). 
     Referring to  FIGS. 4, 10, 11 and 12 , when the positioning ball member  912  engages the middle one of the positioning grooves  85  (see  FIGS. 11 and 12 ), the speed-selectable hand tool  3  of this disclosure serves as a non-ratcheting screwdriver. Each of the first and second shaft pawls  72 ,  72 ′ and the first and second sleeve pawls  73 ,  73 ′ is in the enabled state, such that the shaft member  50  is prevented from rotating relative to the cage member  40  and that the sleeve member  61  is prevented from rotating relative to the cage member  40 . As a result, rotation of the handle  30  drives synchronous rotation of the shaft member  50  via the cage member  40  and the first and second shaft pawls  72 ,  72 ′. It is noted that, at this time, each of the driven sections  723 ,  723 ′ of the first and second shaft pawls  72 ,  72 ′ abuts against the corresponding one of the first driving protrusions  83 , each of the driven sections  733 ,  733 ′ of the first and second sleeve pawls  73 ,  73 ′ abuts against the corresponding one of the second driving protrusions  84 , and the limiting block  417  of the cage member  40  is located at a middle portion of the limiting space  86 . 
     Referring further to  FIG. 13 , when the knob  80  is rotated relative to the cage member  40  in a first operating direction  120  to engage the left one of the positioning grooves  85  with the positioning ball member  912 , the speed-selectable hand tool  3  of this disclosure serves as a ratcheting screwdriver. The driven section  723 ′ of the second shaft pawl  72 ′ is pushed by the corresponding one of the first driving protrusions  83  such that the second shaft pawl  72 ′ is switched into the disabled state. The driven section  733 ′ of the second sleeve pawl  73 ′ is pushed by the corresponding one of the second driving protrusions  84  such that the second sleeve pawl  73 ′ is switched into the disabled state. The driven section  723  of the first shaft pawl  72  is separated from the corresponding one of the first driving protrusions  83 , and the first shaft pawl  72  is retained in the enabled state. The driven section  733  of the first sleeve pawl  73  is separated from the corresponding one of the second driving protrusions  84 , and the first sleeve pawl  73  is retained in the enabled state. When a user rotates the handle  30  in the first operating direction  120  without holding the outer casing  100 , the shaft member  50  is rotated in the first operating direction  120  at a rotational speed the same as that of the handle  30  via the cage member  40  and the first shaft pawl  72 . When the user holds firmly the outer casing  100  and rotates the handle  30  relative to the outer casing  100  in the first operating direction  120 , the sleeve member  61  is rotated in the first operating direction  120  at a rotational speed the same as that of the handle  30  via the cage member  40  and the first sleeve pawl  73 . Since the support frames  64  are fixed in the outer casing  100 , the rotation of the sleeve member  61  drives the shaft member  50  to rotate in the first operating direction  120  at a rotational speed four times that of the sleeve member  61  via the transmission members  65 . As a result, the shaft member  50  is rotated at a rotational speed four times that of the handle  30  in the direction the same as that of the handle  30 . It is noted that, at this time, the engaging section  722  of the first shaft pawl  72  is pushed outwardly by the first ratchet wheel section  51  of the shaft member  50 , and slides on the first ratchet wheel section  51 . When the user rotates the handle  30  in a direction opposite to the first operating direction  120 , the engaging section  722  of the first shaft pawl  72  would be pushed outwardly by the first ratchet wheel section  51  of the shaft member  50  to slides around the first ratchet wheel section  51 . As a result, rotation of the handle  30  in the direction opposite to the first operating direction  120  may not drive rotation of the shaft member  50 . 
     Referring further to  FIG. 14 , when the knob  80  is rotated relative to the cage member  40  in a second operating direction  130  to engage the right one of the positioning grooves  85  with the positioning ball member  912 , the speed-selectable hand tool  3  of this disclosure serves as a ratcheting screwdriver as well. The driven section  723  of the first shaft pawl  72  is pushed by the corresponding one of the first driving protrusions  83  such that the first shaft pawl  72  is switched into the disabled state. The driven section  733  of the first sleeve pawl  73  is pushed by the corresponding one of the second driving protrusions  84  such that the first sleeve pawl  73  is switched into the disabled state. The driven section  723 ′ of the second shaft pawl  72 ′ is separated from the corresponding one of the first driving protrusions  83 , and the second shaft pawl  72 ′ is retained in the enabled state. The driven section  733 ′ of the second sleeve pawl  73 ′ is separated from corresponding one of the second driving protrusions  84 , and the second sleeve pawl  73 ′ is retained in the enabled state. Similarly, when the user rotates the handle  30  in the second operating direction  130  without holding the outer casing  100 , the shaft member  50  is rotated in the second operating direction  130  at a rotational speed the same as that of the handle  30  via the cage member  40  and the second shaft pawl  72 ′. When the user holds firmly the outer casing  100  and rotates the handle  30  relative to the outer casing  100  in the second operating direction  130 , the shaft member  50  is driven to rotate in the second operating direction  130  at a rotational speed four times that of the handle  30  via the cage member  40 , the second sleeve pawl  73 ′, the sleeve member  61  and the transmission members  65 . When the user rotates the handle  30  in a direction opposite to the second operating direction  130 , the shaft member  50  may not be driven to rotate. 
     The advantages of the speed-selectable hand tool  3  of this disclosure are as follows. 
     1. The speed-selectable hand tool  3  is operable to serve as a non-ratcheting hand tool or a ratcheting hand tool. 
     2. When the speed-selectable hand tool  3  serves as a ratcheting hand tool, the rotational speed of the shaft member  50  is selectable to be the same as or four times that of the handle  30  through operation of the outer casing  100 . 
     3. The handle  30  drives rotation of the shaft member  50  by geometric engagement rather than by frictional contact, so that an output torque of the shaft member  50  can be relatively large. 
     4. The structure of the speed-selectable hand tool  3  of this disclosure is simpler than that of the conventional speed-selectable screwdriver 10 ( FIG. 1 ) of U.S. Pat. No. 5,406,866. 
     While the disclosure has been described in connection with what is considered the exemplary embodiment, it is understood that this disclosure is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.