Patent Publication Number: US-6658970-B2

Title: Ratchet screwdriver

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a ratchet screwdriver, more particularly to a ratchet screwdriver which has an orientation regulator that is turnable between first and second angular positions so as to permit clockwise and counterclockwise driving rotations of a drive shaft. 
     2. Description of the Related Art 
     U.S. Pat. No. 6,151,994 discloses a ratchet screwdriver that includes a handle defining a ratchet shaft receiving hole therethrough, and a ratchet shaft disposed therein. The ratchet shaft has a ratchet wheel mounted securely between first and second end portions. An engaging unit is interposed between the ratchet shaft and a drive shaft inserted in the first or second end portion to prevent relative axial displacement and permit co-rotation therebetween. A ratchet housing includes a coupling portion sleeved on the ratchet shaft and coupled to the handle for co-rotation therewith, a wheel confining portion defining a cavity for enclosing the ratchet wheel, and a shoulder between the coupling and wheel confining portions. The wheel confining portion is formed with a pawl-retaining groove in communication with the cavity to receive a pawl member which is mounted pivotally on the shoulder and which extends radially into the cavity. A biasing member biases the pawl member to engage the ratchet wheel such that when the handle is driven in a counterclockwise direction, the ratchet and drive shafts correspondingly rotate in the counterclockwise direction. 
     One disadvantage of the aforesaid ratchet screwdriver resides in that when it is desired to rotate the drive shaft in a clockwise direction, the handle is turned 180 degrees along a radial line to reverse positions of the first and second end portions of the ratchet shaft, and the drive shaft is disassembled and then re-assembled to a selected one of the first and second end portions of the ratchet shaft to permit driving rotation of the handle in the clockwise direction. 
     SUMMARY OF THE INVENTION 
     Therefore the object of the present invention is to provide a ratchet screwdriver which can solve the aforementioned problem. 
     Accordingly, the ratchet screwdriver of the present invention includes a drive shaft, a shaft-mounting seat, an elongated handle, and a ratchet assembly. The drive shaft defines a first axis, and has a coupling section, and an operating section which extends axially from the coupling section and which defines a tool-retaining hole with a non-circular cross-section. The shaft-mounting seat includes a peripheral wall that defines a shaft-receiving space to receive the coupling section of the drive shaft therein, and that has front and rear ends, and an upper wall portion formed with two spaced apart opposing spring-retaining recesses in spatial communication with the shaft-receiving space, and two spaced apart opposing pawl-limiting through-holes which are disposed between the spring-retaining recesses. Each of the pawl-limiting through-holes is confined by a hole-confining wall. The shaft-mounting seat further includes front and rear end flanges that extend inwardly and respectively from the front and rear ends of the peripheral wall in a transverse direction relative to the peripheral wall. The coupling section of the drive shaft extends through the front end flange, the shaft-receiving space, and the rear end flange. The handle is securely connected to the rear end of the shaft-mounting seat. The ratchet assembly includes a ratchet wheel, opposing left and right pawls, opposing left and right biasing members, a regulator in the form of a tubular sleeve, and a positioning unit. The ratchet wheel is disposed around and is connected securely to the coupling section of the drive shaft for co-rotation therewith in the shaft-receiving space, and has a plurality of engaging teeth formed circumferentially therearound. Each of the left and right pawls is disposed in the shaft-receiving space among the drive shaft, a respective one of the spring-retaining recesses, and a respective one of the pawl-limiting through-holes. Each of the left and right pawls has two opposite pivot ends respectively pivoted to the front and rear end flanges, a teeth-engaging portion between the pivot ends, and an actuating portion which projects from the teeth-engaging portion through a respective one of the pawl-limiting through-holes. The pivot ends of each of the left and right pawls are limitedly turnable relative to the shaft-mounting seat about a second axis that is parallel to the first axis and so as to be turnable about the first axis together with the shaft-mounting seat. The left and right biasing members are disposed in the spring-retaining recesses, respectively, for urging the teeth-engaging portions of the left and right pawls to releasably mesh with the engaging teeth of the ratchet wheel. The tubular sleeve is sleeved rotatably around the peripheral wall of the shaft-mounting seat, and has an inner wall that is formed with a sector-shaped recess defined by a recess-confining wall. The tubular sleeve is turnable about the first axis relative to the shaft-mounting seat between a first angular position, where the actuating portion of the left pawl is pushed by the recess-confining wall of the tubular sleeve against biasing action of the left biasing member so as to turn about the second axis to abut against the hole-confining wall of the respective one of the pawl-limiting through-holes and so as to permit the teeth-engaging portion of the left pawl to disengage from the engaging teeth of the ratchet wheel, and where the teeth-engaging portion of the right pawl engages the teeth of the ratchet wheel, and a second angular position opposite to the first angular position, where the actuating portion of the right pawl is pushed by the recess-confining wall of the tubular sleeve against biasing action of the right biasing member so as to turn about the second axis to abut against the hole-confining wall of the other one of the pawl-limiting through-holes and so as to permit the teeth-engaging portion of the right pawl to disengage from the engaging teeth of the ratchet wheel, and where the teeth-engaging portion of the left pawl engages the engaging teeth of the ratchet wheel. The positioning unit is disposed between the shaft-mounting seat and the tubular sleeve for releasably engaging the shaft-mounting seat and the tubular sleeve once the tubular sleeve is moved to the first and second angular positions. As such, when the tubular sleeve is moved to the first angular position, rotation of the handle in a clockwise direction results in synchronous rotation of the shaft-mounting seat and the drive shaft in the clockwise direction, and rotation of the handle in a counterclockwise direction results in idle rotation of the handle relative to the drive shaft. Accordingly, when the tubular sleeve is moved to the second angular position, rotation of the handle in the counterclockwise direction results in synchronous rotation of the shaft-mounting seat and the drive shaft in the counterclockwise direction, and rotation of the handle in the clockwise direction results in idle rotation of the handle relative to the drive shaft. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of this invention will become more apparent in the following detailed description of the preferred embodiments of this invention, with reference to the accompanying drawings, in which: 
     FIG. 1 is a fragmentary exploded perspective view of a preferred embodiment of a ratchet screwdriver according to the present invention; 
     FIG. 2 is a fragmentary sectional view of the preferred embodiment; 
     FIG. 3 is a cross-sectional view of the preferred embodiment taken along lines III—III in FIG. 2; 
     FIG. 4 is a cross-sectional view of the preferred embodiment taken along lines III—III in FIG. 2 when turned in a clockwise direction during use; 
     FIG. 5 is a cross-sectional view of the preferred embodiment taken along lines III—III in FIG. 2 when turned in a counterclockwise direction during use; 
     FIG. 6 is a fragmentary sectional view of a modified preferred embodiment according to the present invention; and 
     FIG. 7 is a fragmentary sectional view of another modified preferred embodiment according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Before the present invention is described in greater detail with reference to the following preferred embodiments, it should be noted that same reference numerals have been used to denote similar elements throughout the specification. 
     Referring to FIGS. 1,  2  and  3 , a preferred embodiment of a ratchet screwdriver according to the present invention is shown to include a drive shaft  40 , a shaft-mounting seat  10 , an elongated handle  20 , and a ratchet assembly  30 . 
     As illustrated, the drive shaft  40  defines a first axis, has a coupling section  41 , and an operating section  42  which extends axially from the coupling section  41  and which defines a tool-retaining hole  421  with a non-circular cross-section to receive a tool-bit  90  therein. 
     The shaft-mounting seat  10  includes a peripheral wall  11  that defines a shaft-receiving space  12  to receive the coupling section  41  of the drive shaft  40  therein, and that has front and rear ends  111 ,  112 , and an upper wall portion  114  formed with two spaced apart opposing spring-retaining recesses  113  in spatial communication with the shaft-receiving space  12 , and two spaced apart opposing pawl-limiting through-holes  116  which are disposed between the spring-retaining recesses  113 . Each of the pawl-limiting through-holes  116  is confined by a hole-confining wall  116 W. The shaft-mounting seat  10  further includes front and rear end flanges  16 ,  15  that extend inwardly and respectively from the front and rear ends  111 ,  112  of the peripheral wall  11  in a transverse direction relative to the peripheral wall  11 . The coupling section  41  of the drive shaft  40  extends through the front end flange  16 , the shaft-receiving space  12 , and the rear end flange  15 , and is fastened to the shaft-mounting seat  10  via two C-shaped retainer rings  33  so as to be prevented from axial removal from the shaft-mounting seat  10 . 
     The handle  20  is connected securely to the rear end  112  of the shaft-mounting seat  10  so that the shaft-mounting seat  10  co-rotates with the handle  20  in case the handle  20  is rotated. 
     The ratchet assembly  30  includes a ratchet wheel  31 , opposing left and right pawls  50 , opposing left and right biasing members  60 , a regulator in the form of a tubular sleeve  70 , and a positioning unit  80 . The ratchet wheel  31  is disposed around and is connected securely to the coupling section  41  of the drive shaft  40  for co-rotation therewith in the shaft-receiving space  12 , and has a plurality of engaging teeth  311  formed circumferentially therearound. Each of the left and right pawls  50  is disposed in the shaft-receiving space  12  among the drive shaft  40 , a respective one of the spring-retaining recesses  113 , and a respective one of the pawl-limiting through-holes  116 . Each of the left and right pawls  50  has two opposite pivot ends  51  pivoted to circular holes  161 ,  151  in the front and rear end flanges  16 ,  15 , a teeth-engaging portion  52  between the pivot ends  51 , and an actuating portion  53  that projects from the teeth-engaging portion  52  through a respective one of the pawl-limiting through-holes  116 . The pivot ends  51  of each of the left and right pawls  50  are limitedly turnable relative to the shaft-mounting seat  10  about a second axis that is parallel to the first axis and so as to be turnable about the first axis together with the shaft-mounting seat  10 . 
     The left and right biasing members  60  are respectively disposed in the spring-retaining recesses  113  of the shaft-mounting seat  10  for urging the teeth-engaging portions  52  of the left and right pawls  50  to releasably mesh with the engaging teeth  311  of the ratchet wheel  31 . 
     The tubular sleeve  70  is sleeved rotatably around the peripheral wall  11  of the shaft-mounting seat  10 , and defines an axial hole  711  to permit extension of the operating section  42  of the drive shaft  40  therethrough. The tubular sleeve  70  has an inner wall  71  that is formed with a sector-shaped recess  74  defined by a recess-confining wall  741 . The tubular sleeve  70  is turnable about the first axis relative to the shaft-mounting seat  10  between a first angular position, as best shown in FIG. 4, where the actuating portion  53  of the left pawl  50  is pushed by the recess-confining wall  741  of the tubular sleeve  70  against biasing action of the left biasing member  60  so as to turn about the second axis to abut against the hole-confining wall  116 W of the respective one of the pawl-limiting through-holes  116  and so as to permit the teeth-engaging portion  52  of the left pawl  50  to disengage from the engaging teeth  311  of the ratchet wheel  31 , and where the teeth-engaging portion  52  of the right pawl  50  engages the engaging teeth  311  of the ratchet wheel  31 , and a second angular position opposite to the first angular position, as best shown in FIG. 5, where the actuating portion  53  of the right pawl  50  is pushed by the recess-confining wall  741  of the tubular sleeve  70  against biasing action of the right biasing member  50  so as to turn about the second axis to abut against the hole-confining wall  116 W of the other one of the pawl-limiting through-holes  116  and so as to permit the teeth-engaging portion  52  of the right pawl  50  to disengage from the engaging teeth  311  of the ratchet wheel  31 , and where the teeth-engaging portion  52  of the left pawl  50  engages the engaging teeth  311  of the ratchet wheel  31 . Preferably, the rear end flange  15  is integrally formed with the rear end  112  of the peripheral wall  11 . The front end flange  16  is mounted securely in a flange-receiving groove  131  defined by the peripheral wall  11  adjacent to the front end  111  thereof. The tubular sleeve  70  has an annular flange-retention rib  73  which projects inwardly and axially from a periphery of a front open end of the tubular sleeve  70  to abut against the front end flange  16  and prevent removal of the front end flange  16  from the shaft-mounting seat  10 . 
     The positioning unit  80  is disposed between the shaft-mounting seat  10  and the tubular sleeve  10  for releasably engaging the shaft-mounting seat  10  and the tubular sleeve  70  once the tubular sleeve  70  is moved to the first and second angular positions. As such, when the tubular sleeve  70  is moved to the first angular position of FIG. 4, rotation of the handle  20  in a clockwise direction (shown by the headed arrow in FIG. 4) results in synchronous rotation of the shaft-mounting seat  10  and the drive shaft  40  in the clockwise direction, and rotation of the handle  10  in a counterclockwise direction results in idle rotation of the handle  10  relative to the drive shaft  40 . Accordingly, when the tubular sleeve  70  is moved to the second angular position of FIG. 5, rotation of the handle  20  in the counterclockwise direction (shown by the headed arrow in FIG. 5) results in synchronous rotation of the shaft-mounting seat  10  and the drive shaft  40  in the counterclockwise direction, and rotation of the handle  10  in the clockwise direction results in idle rotation of the handle  10  relative to the drive shaft  10 . 
     Preferably, the inner wall  71  of the tubular sleeve  70  is further formed with spaced apart left and right engaging grooves  82 ,  84  which are disposed at a position opposite to the sector-shaped recess  74 , and an intermediate engaging groove  83  between the left and right engaging grooves  82 ,  84 . The positioning unit  80  includes a spring-loaded ball  81  which is mounted on shaft-mounting seat  10  and which engages the right engaging groove  84  when the tubular sleeve  70  is moved to the first angular position and which engages the left engaging groove  82  when the tubular sleeve  70  is moved to the second angular position. 
     The inner wall  71  of the tubular sleeve  70  is further formed with a pair of diametrically disposed limiting grooves  75  at two opposite sides of the sector-shaped recess  74 . The shaft-mounting seat  10  further includes a pair of opposing limiting tabs  17  which radially and outwardly project from the peripheral wall  11  and which extend into the limiting grooves  75 , respectively, so as to limit angular rotation of the tubular sleeve  70  to the first and second angular positions relative to the shaft-mounting seat  10 . 
     Referring to FIG. 6, a modified preferred embodiment of the present invention is shown to have a structure similar to that of the previous embodiment. The main difference resides in that two opposite end portions  41 ′,  42 ′ of the drive shaft  40 ′ define two bit-retaining holes  411 ′,  421 ′ with a non-circular cross-section to receive tool-bits  90 ′ of different configurations for driving different screws. The ratchet wheel  31 ′ and the drive shaft  40 ′ are coupled detachably to each other by tongue-and-groove arrangement  43 ′,  331 ′ such that the drive shaft  40 ′ can be reversed relative to the shaft-mounting seat when it is desired to use the tool bit  42 ′ disposed within the handle  20 ′. 
     Referring to FIG. 7, an another modified preferred embodiment of the present invention is shown to have a structure similar to that of the previous embodiment. The main difference resides in that each of the left and right pawls  50  has a constricted neck portion  54  between the actuating portion  53  and the teeth-engaging portion  52 . The upper wall portion of the peripheral wall  11  further has an inner protrusion  18  extending inwardly from an inner wall surface confining the shaft-receiving space  12  (see FIG. 1) and located between the pawl-limiting through-holes  116 . The inner protrusion  18  has opposing left and right flat faces  181 . The right flat face  181  abuts against the constricted neck portion  54  of the right pawl  50  so as to prevent bending of the right pawl  50  when the tubular sleeve  70  is turned about the first axis relative to the shaft-mounting seat  10  to the first angular position. The left flat face  181  abuts against the constricted neck portion  54  of the left pawl  50  so as to prevent bending of the left pawl  50  when the tubular sleeve  70  is turned about the first axis relative to the shaft-mounting seat  10  to the second angular position. 
     While the present invention has been described in connection with what is considered the most practical and preferred embodiments, it is understood that the present invention is not limited to the disclosed embodiments 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.