Patent Publication Number: US-6209422-B1

Title: Ratchet wrench

Description:
FIELD OF THE INVENTION 
     The present invention relates to an improvement in a ratchet wrench used for tightening and loosening bolts and nuts in assembly and disassembly of automobiles, industrial machines and so on. 
     BACKGROUND OF THE INVENTION 
     An electrical or hand-operated ratchet wrench has been heretofore used for positively and quickly tightening or removing bolts, nuts or the like. A conventional ratchet wrench is disclosed in U.S. Pat. No. 5,537,899 and the main structure thereof will be explained hereinafter with reference to FIGS. 12 to 19. 
     As shown in FIG. 12, a housing  10  is internally provided with a motor  12 , a conventional motion conversion means  14  for changing rotational speed of the motor  12 , and a crank shaft  16  which is mounted for rotational motion and reciprocating sliding motion by the motion conversion means  14 . 
     As shown in FIG. 13, the crank shaft  16  is integrally formed at the extreme end thereof with a core  18  which is eccentric from the center of the shaft and parallel with the center of the shaft, and a bushing  22  having an insert hole  20  is slidably mounted on the core  18 . As shown in FIGS. 12 and 14, the housing  10  is integrally formed at the extreme end thereof with a pair of annular holding portions  24 , and an oscillating member  26  shown in FIG. 13 is provided between the pair of annular holding portions  24 . The oscillating member  26  is formed in the center thereof with a hole  28 , and the hole  28  is formed in the inner wall thereof with an internal gear  30 . The oscillating member  26  has a pair of arms  32  at the extreme end thereof, and a space  34  is formed between the pair of arms  32 . The bushing  22  is rotatably and undisengageably fitted into the space  34 . 
     As shown in FIG. 15, a shank  36  for intermittently rotating bolts or the like comprises a columnar base portion  38  and a cubical engaging portion  40  formed integral with the base portion  38 . The base portion  38  of the shank  36  is inserted into the hole  28  of the oscillating member  26 . The oscillating member  26  with the shank  36  mounted therein is held between the pair of annular holding portions  24  of the housing  10  shown in FIGS. 12 and 14. As the crank shaft  16  rotates, the oscillating member  26  oscillates about the center axis of the hole  28 . 
     In the shank  36 , the columnar base portion  38  is internally provided with two wing members  44  which are oscillatable about a pin  42 . Each wing member  44  is formed on both left and right ends thereof with a plurality of pawls  46 . The columnar base portion  38  is formed with a central axial hole  48 , and a columnar switching member  52  (FIG. 16) integrally formed with a switching knob  50  is fitted into the hole  48 . The switching member  52  is mounted for rotation through a given angular range relative to the shank  36 . 
     As shown in FIGS. 16 and 17, the switching member  52  is formed with two axially extending holes  54  with openings opposite each other by 180 degrees. Each hole  54  is internally provided with a tubular bushing pin  56  with one end closed, and one end open to receive a spring  58  internally to bias the bushing pin  56  outwardly from the switching member  52 . As shown in FIG. 17, the closed end of the bushing pin  56  is biased by the spring  58  so as to project from the hole  54  into contact with the wing member  44 , thereby pressing against the wing member  44 . 
     The switching member  52  is normally and reversely rotated, for example, by approximately 90 degrees, when fitted into the hole  48  of the base portion  38  of the shank  36 , by turning the switching knob  50  of the switching member  52 , and the switching member  52  maintains one of the two stable positions shown in FIGS. 18 and 19. In FIGS. 18 and 19, each wing member  44  is pressed by the bushing pin  56  and the spring  58  so that the pawl  46  on one of left and right sides of each wing member  46  is engaged with the internal gear  30  of the oscillating member  26 . In FIG. 18, the bushing pin  56  presses one side of the wing member  44  which oscillates about the pin  42 . The part of the wing member  44  pressed by the bushing pin  56  is shifted from one side to the other of the wing member  44  by turning the switching knob  50  from the position shown in FIG. 18 to that of FIG.  19 . By the switching with the switching knob  50 , the pawl  46  of each wing member  44  meshed with the internal gear  30  of the oscillating member  26  is switched from one side to the other, thus switching between tightening rotation and loosening rotation. 
     When the oscillating member  26  is rotated in one direction with one pawl  46  of each wing member  44  engaged with the internal gear  30  of the oscillating member  26 , wing members  44  move together with the oscillating member  26 . On the other hand, when the oscillating member  26  is rotated in an opposite direction, the pawl  46  of each wing member  44  and the internal gear  30  of the oscillating member  26  come in contact but slip so that they are not engaged, and the wing members  44  will not move together with the oscillating member  26 . 
     Thus, as shown in FIG. 18, when the oscillating member  26  is rotated in direction A, a tightening operation results, and when the oscillating member  26  is rotated in direction B slip occurs. In this manner, the tightening is carried out by repeating the tightening operation and the slip operation. Further, when switched from the FIG. 18 state to the FIG. 19 state, and when the oscillating member  26  is rotated in a direction C, the loosening operation results, and when the oscillating member  26  is rotated in a direction D, slip occurs. 
     As shown in FIGS. 12 and 14, the engaging portion  40  of the shank  36  is generally cubical in shape, and the engaging portion  40  projects, beyond one annular supporting portion  24  at the distal end of the housing  10 , in a direction perpendicular to the length of the housing  14 . A socket  60  for transmitting the intermittent rotational force of the ratchet wrench to the bolt or the like is detachably mounted on the engaging portion  40  of the shank  36 . The socket  60  is cylindrical, and one end thereof is provided with a first hole  62  which is square in section for mating with the engaging portion  40  of the shank  36 , and the other end thereof is provided with a second hole  64  which is hexagonal in section for fitting over a bolt (not shown). When the ratchet wrench is used, the socket  60  is mounted between the engaging portion  40  of the shank  36  and the bolt for tightening or loosening the bolt. 
     The operation of the ratchet wrench constructed as described above will be explained below. 
     First, when the motor  12  shown in FIG. 12 is driven, the crank shaft  16  is rotated through the known motion conversion means  14 . When the crank shaft  16  is rotated, the core  18  of the crank shaft  16  causes the bushing  22  to rotate in a planetary orbit about the center axis the crank shaft  16 . The planetary motion of the bushing  22  causes the oscillating member  26  to oscillate about the center axis of the columnar base portion  38  of the shank  36 . 
     When the oscillating member  26  is oscillated in one direction, the pawl  46  on one side of the wing member  44  mounted on the shank  36  projects and is meshed with the internal gear  30  of the oscillating member  26  to rotate the shank  36  to tighten the bolt or the like (in direction A in FIG.  18 ). When the oscillating member  26  is oscillated in the opposite direction (B in FIG.  18 ), the projecting pawl  46  does not mesh with the internal gear  30  and the shank  36  is not rotated. Thereafter, when the oscillating member  26  is rotated in the one direction again, the bolt or the like is tightened. That is, in this ratchet wrench, only when the oscillating member  26  is rotated in one direction, is the shank  36  rotated, so that the bolt or the like is intermittently tightened. 
     In the ratchet wrench having two wing members  44 , when the oscillation of the oscillating member  26  is slow, the pawl  46  of the wing member  44  moves along the internal gear  30  of the oscillating member  26  in a satisfactory manner, but when the oscillating member  26  is oscillated at high speed in order to enhance the working efficiency, a so-called resonant phenomenon caused by variation of oscillation speed occurs in the wing member  44 , and “overshoot” occurs such that, as shown in FIG. 20, the pawl  46  of the wing member  44  being meshed with the internal gear  30  of the oscillating member  26  is temporarily moved away from the internal gear  30 . When overshoot occurs, return of the wing member  44  into meshing engagement is delayed so that neither of the pawls  46  of the wing member  44  is meshed with the internal gear  30 , resulting in a failure of the tightening operation. 
     When overshoot occurs, the pawl  46 , on the side opposite the pawl  46  that should be meshed, sometimes becomes meshed with the internal gear  30  in a “ ” configuration commonly referred to as a “pigeon-toe” configuration, as shown in FIG.  21 . In the state shown in FIG. 21, the shank  36  oscillates with the oscillating member  26 , such that the tightening rotation is not produced at all. 
     In the case of operation at high speed, there is a point where the wing member  44  and the spring  58  begin to oscillate, and this oscillation is amplified (called a resonant point). This resonant point differs depending on the mass of the wing member  44  and the strength of the spring  58 , but with high speed rotation there is always a resonant point. At the resonant point overshoot occurs, as described above and as shown in FIGS. 20 and 21, such that the tightening operation cannot be performed. 
     In the ratchet wrench, the switching member  52  is rotatably mounted on the shank  36 , and the switching member  52  rotates along with the shank  36 . When the shank  36  carries out the tightening rotation and stops suddenly upon completion of tightening, the switching member  52  incorporated into the shank  36  tends to further rotate due to inertia. At this time, in the case where reaction of the spring  58  is so small that the switching member  52  is not held by the spring  58 , the switching member  52  will switch the wrench between the tightening operation and the loosening operation. To prevent such an unintended switching of the switching member  52 , a strong spring  58  is employed. 
     For suppressing the overshoot phenomenon, in the conventional ratchet wrench, either a strong spring  58  is employed, or a stopper may be provided to limit motion of the wing member  44 . Further, for preventing unintended switching, the spring  58  may be strengthened. However, in the case of the conventional small spring  58 , its strength cannot be adequately increased. Further, while a stopper might be provided to prevent the wing member  44  from moving to an improper position, there is inadequate space for the stopper. 
     Accordingly an object of the present invention is to provide a ratchet wrench which is free of occurrence of overshoot and unintended switching. 
     SUMMARY OF THE INVENTION 
     For achieving the aforementioned object, according to the present invention, there is provided a ratchet wrench, comprising: a housing, an oscillating member having an internal gear mounted oscillatably on the housing, a shank provided with a wing member having pawls meshed with the internal gear on both left and right sides thereof, a switching member mounted on the shank for rotation through given angle, a hole formed in the switching member, a bushing pin provided within the hole, and a spring provided within the hole for pressing said wing member in a direction bringing said pawls of said wing member into contact with said internal gear through said bushing pin, wherein an elastic member inhibiting movement of said bushing pin internally within said hole is provided within said hole. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of main parts of a ratchet wrench according to one embodiment the present invention; 
     FIG. 2 is an enlarged sectional view of the main parts shown in FIG. 1; 
     FIG. 3 is a sectional view showing a further embodiment of the bushing pin according to the present invention; 
     FIG. 4 is a sectional view showing yet another embodiment of the bushing pin according to the present invention; 
     FIG. 5 is a sectional view showing still another embodiment of the bushing pin according to the present invention; 
     FIG. 6 is a sectional view showing a further embodiment of the bushing pin according to the present invention; 
     FIG. 7 is a sectional view showing another embodiment of the bushing pin according to the present invention; 
     FIG. 8 is a sectional view showing yet another embodiment of the bushing pin according to the present invention; 
     FIG. 9 is a sectional view showing a further embodiment of the bushing pin according to the present invention; 
     FIG. 10 is a sectional view showing another embodiment of the bushing pin according to the present invention; 
     FIG. 11 is a sectional view showing still another embodiment of the bushing pin according to the present invention; 
     FIG. 12 is a front view of a conventional ratchet wrench; 
     FIG. 13 is an exploded perspective view showing the connection between a crank shaft and an oscillating member used in FIG. 12; 
     FIG. 14 is a perspective view showing a socket mounted on the ratchet wrench shown in FIG. 12; 
     FIG. 15 is a perspective view of a shank used in FIG. 12; 
     FIG. 16 is a sectional view of main parts of the ratchet wrench shown in FIG. 12; 
     FIG. 17 is an enlarged sectional view of the main parts shown in FIG. 16; 
     FIG. 18 is a sectional view showing a state of good meshing of the oscillating member and the wing member in the ratchet wrench shown in FIG. 12; 
     FIG. 19 is a sectional view showing a good meshing state of the other of the oscillating member and the wing member in the ratchet wrench shown in FIG. 12; 
     FIG. 20 is a sectional view showing a state in which the oscillating member and the wing member in the ratchet wrench shown in FIG. 12 are disengaged; and 
     FIG. 21 is a sectional view showing an inadequate meshing state between the oscillating member and the wing member in the ratchet wrench shown in FIG.  12 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     A first embodiment of present invention will be described hereinafter with reference to FIGS. 1 AND 2 of the drawings. 
     In FIGS. 1 and 2, the same reference numerals as those used in FIGS. 12 to  19  indicate the same members, respectively. In the present invention, a switching member  52  is formed with two holes  54  which are perpendicular to the central axis and are axially spaced. The holes  54  open at positions opposite each other, i.e. 180 degrees from each other. Each hole  54  has one end closed and is internally provided with a tubular bushing pin  56 , and a spring  58  within each bushing pin  56  to bias the bushing pin  56  outwardly. As shown in FIGS. 1 and 2, the closed end of the bushing pin  56  is biased by the spring  58  so as to project from the hole  54 , and the outer surface of the closed end of the bushing pin  56  presses against a wing member  44 . The structure mentioned so far is the same as the prior art. 
     In the present invention, an elastic member, such as rubber, is provided within the hole  54  to resist movement of the bushing pin  56 . In FIGS. 1 and 2, an elastic member  66  in the shape of a solid rod extends axially within the inner space of the spring  58 . 
     In the normal state, preferably, one end of the elastic rod  66  is brought into contact with the closed end of a tubular bushing pin  56 , and the other end thereof is brought into contact with switching member  52 . With the elastic rod  66  incorporated into the axial inner space of the spring  58 , a compressive force may be either applied or not applied to the elastic rod  66 . One end of the elastic rod  66  is brought into contact with the closed end of the bushing pin  56 , and the other end is brought into contact with the switching member  52  as previously mentioned, but in the normal state, either end of the elastic rod  66  may not be in contact. 
     With the structure as described above, when an overshooting force is exerted on a wing member  44 , the bushing pin  56  is pressed by the wing member  44  so that the elastic rod  66  and the spring  58  are compressed. Reaction against the compression is generated in the elastic rod  66  and the spring  58 , and this reaction force prevents a pawl  46  of the wing member  44  from separation from internal gear  30  to the extent of overshooting. 
     The material for the elastic rod  66  is preferably less elastic under compression than spring  58  so that the elastic rod  66  functions as a stopper for the wing member  44  to prevent the pawl  46  of the wing member  44  from separating from the internal gear  30  to prevent an occurrence of overshooting. 
     Further, there sometimes appears a frequency at which vibrations of the wing member  44  and the spring  58  are amplified at the time of high speed rotation. In this case, since the rod  66  functions as a stopper or a damper relative to the wing member  44 , it is possible to prevent an occurrence of overshooting even at the time of high speed rotation. 
     Besides, at the time of high speed rotation, the elastic rod  66  extends quickly relative to motion of the wing member  46 , and even in the elastic rod  66  formed of elastic material, there occurs a large reaction force according to the pressing force with respect to the wing member  46 . For this reason, since at the time of high speed rotation, the elastic rod  66  functions as a stopper or a damper, it is possible to prevent occurrence of overshooting even at high speed rotation. 
     Further, when the bushing pin  56  is pressed, the compressed elastic rod  66  comes in contact with the spring  58 , and the vibrations of the bushing pin  56  and the spring  58  are absorbed by the elastic rod  66  to enable the suppression of the resonant phenomenon. Thus, it is possible to prevent an occurrence of overshooting also by suppressing the resonant phenomenon. 
     Furthermore, since the holding force of the switching member  52  with respect to the shank  36  is increased by the elastic rod  66 , it is possible to prevent occurrence of unintended switching of the switching member  52 . 
     While in the foregoing embodiment the shank  36  has been described as provided with two wing members  44 , it is to be noted that the invention can be applied to an arrangement wherein one wing member  44  is provided. 
     Second Embodiment of the Invention 
     Next, FIG. 3 shows a further embodiment of the ratchet wrench according to the present invention. 
     Also in this embodiment, an elastic member is provided in a space along the center axis of the spring  58 , similarly to FIGS. 1 and 2. In the bushing pin  68 , a surface  70  facing the spring  58  is formed with a projecting pin  72  projecting internally of the hole  54 . A tubular elastic member  74  is provided within an internal space of the spring  58 , and the projecting pin  72  is fitted internally of the tubular elastic member  74   
     In the bushing pin  68 , the surface  70  has a size so that both one end of the spring  58  and one end of the elastic member  74  may both contact same. 
     Also in this embodiment, when an overshooting force is exerted on the wing member  44 , the tubular elastic member  74  is compressed along with the spring  58  by the bushing pin  68 , and the reaction force of the elastic member  74  and the spring  58  prevents the pawl  46  of the wing member  44  from separating from the internal gear  30  to the extent of overshooting. 
     Third Embodiment of the Invention 
     FIG. 4 shows another embodiment of the ratchet wrench according to the present invention. In this embodiment, a tubular elastic member is provided externally of the spring  58 . 
     This embodiment uses a tubular bushing pin  56  with one end closed as shown in FIGS. 1 and 2. The spring  58  and a tubular elastic member  76  are mounted in the internal space of the tubular bushing pin  56 . The tubular elastic member  76  is arranged externally of the spring  58 . 
     Also in this embodiment, when an overshooting force is exerted on the wing member  44 , the tubular elastic member  76  is compressed along with the spring  58  by the bushing pin  56 , and the reaction force of the elastic member  76  and the spring  58  prevents the pawl  46  of the wing member  44  from separating from the internal gear  30  to the extent of overshooting. 
     Fourth Embodiment of the Invention 
     FIG. 5 shows another embodiment of the ratchet wrench according to the present invention. Also in this embodiment, a tubular elastic member is provided externally of the spring  58 . 
     This embodiment also has a tubular bushing pin  56  with one end closed as shown in FIGS. 1 and 2. One end of the spring  58  is mounted in the internal space of the bushing pin  56  and its opposite end extends out of pin  56 . A tubular elastic member  78  is provided surrounding that opposite end of the spring  56  and aligned with tubular portion  77  of the bushing pin  56 , within the hole  54 . The inside diameter and the outside diameter of the tubular elastic member  78  are preferably substantially the same as those of the tubular portion  77  of the bushing pin  56 , but are not limited thereto. 
     Also in this embodiment, when an overshooting force is exerted on the wing member  44 , the tubular elastic member  78  is compressed along with the spring  58  by the bushing pin  56 , and the reaction force of the elastic member  78  and the spring  58  prevents the pawl  46  of the wing member  44  from separating from the internal gear  30  to the extent of overshooting. 
     While in FIG. 5 the bushing pin  56  and the tubular elastic member  74  are shown separated from each other, it is to be noted that normally they may be placed in contact. 
     FIG. 6 shows a modified example of FIG.  5 . In FIG. 6, the bushing pin  56  is in contact with a tubular elastic member  80 , but the contact surface between the bushing pin  56  and the tubular elastic member  80  is stepped, with a shoulder  82  formed at the free end of the tubular portion (wall)  77  of the bushing pin  56 , and a shoulder formed on the elastic member  80 , which exactly mates with the shoulder  82  of the bushing pin  56 . While the shoulder  82  of the bushing pin  56  is shown as external, with a central portion, it is to be noted that the shoulder may be internal so that an external portion extends from the shoulder. 
     FIG. 7 shows another modification of FIG.  5 . In FIG. 7, as in FIG. 6, a shoulder  82  is formed at the tubular free end of the bushing pin  56 . A tubular elastic member  84  is fit around the outside of an inner projecting portion  85  projected lengthwise in an axial direction from the shoulder  82  of the bushing pin  56 . The wall-thickness of the elastic member  84  is about half of that of the elastic member  78  of FIG.  5  and the elastic member  80  of FIG.  6 . 
     While in FIG. 7, the projecting portion  85  projected lengthwise in an axial direction from the shoulder  82  is an inner portion of tubular wall  77 , the shoulder  82  may be internal to tubular wall  77  so that the tubular elastic member  84  is fitted internally of the projecting portion  85  of the bushing pin  56 . 
     Fifth Embodiment of the Invention 
     FIG. 8 shows another embodiment of the ratchet wrench according to the present invention. Also in this embodiment, a tubular elastic member is provided externally of the spring  58 . In this embodiment, the bushing pin  68  is provided with the projecting pin  72  as shown in FIG.  3 . The internal space at one end of the spring  58  is fitted over the projecting pin  72 . A tubular elastic member  86  is provided externally of the spring  58 . One end of the spring  58  and one end of the elastic member  86  abutt the annular surface  70  of the bushing pin  56 . 
     Also in this embodiment, when an overshooting force is exerted on the wing member  44 , the tubular elastic member  86  is compressed along with the spring  58 , and the reaction force of the elastic member  86  and the spring  58  prevents the pawl  46  of the wing member  44  from separating from the internal gear  30  to the extent of allowing overshooting. 
     Sixth Embodiment of the Invention 
     FIG. 9 shows still another embodiment of the ratchet wrench according to the present invention. FIG. 9 shows a solid elastic member  88  with a spring  56  embedded therein. The elastic member  88  with the spring  56  embedded therein is formed by molding. In this case, the bushing pin may be the tubular bushing pin  56  with one end closed as shown in FIGS. 1 and 4, or may be the tubular bushing pin  68  provided with the surface  70  as shown in FIGS. 3 and 8. 
     Also in this embodiment, the reaction force of the spring  58  and the elastic member  88  prevents the pawl  46  of the wing member  44  from separating from the internal gear  30  to the extent of allowing overshooting. 
     In place of the arrangement shown in FIG. 9, there can be used an annular elastic member  90  having the spring  56  molded therein as shown in FIG.  10 . Further, there can be used an arrangement wherein a tubular elastic member  92  is molded externally of the spring  56  as shown in FIG.  11 . 
     As described above, according to the present invention, an elastic member such as rubber, which resists movement of a bushing pin into a hole, is provided within the hole along with a spring for biasing the bushing pin outwardly. As a result, even if an overshooting force is exerted on the wing member, or even if there appears a frequency at which vibrations of the wing member and the spring are amplified at the time of high speed rotation, it is possible to prevent the pawls of the wing members from separation from the internal gear to the extent of allowing overshooting by the combined reaction force the elastic member and the spring, and by the stopping function of the elastic member having a compression rate. 
     Furthermore, in the present invention, since the holding force of the switching member with respect to the shank can be increased by the spring and the elastic member, it is possible to prevent an unintended switching of the switching member.