Patent Publication Number: US-8534167-B2

Title: Super high-torque open end wrench capable of fast driving

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a super high-torque open end wrench capable of fast driving and, more particularly, to an open end wrench capable of fast driving a workpiece without the risk of undesired shifting from the workpiece and capable of withstanding super high-torque operation. 
     U.S. Pat. No. 1,320,668 discloses a wrench including a stationary jaw and a movable jaw slideable along a guide. The movable jaw is forced against an abutment at an outer end of the guide by a spring bearing against the stationary jaw. An end of the spring is received in a bore in the stationary jaw. The other end of the spring is received in another bore in the movable jaw. An intermediate portion of the spring is exposed between the stationary jaw and the movable jaw. When the user intends to tighten or loosen a nut, the wrench is turned in a driving direction, during which operation the movable jaw remains in contact with the abutment. For reengagement of the wrench with the nut, it is necessary only to turn the wrench in the opposite direction, during which operation the movable jaw slides backward against the pressure of the spring and on the edges of the nut. The movable jaw is forced forward again as soon as the bearing surfaces of the stationary and movable jaws are parallel with the sides of the nut. The nut can be tightened or loosened through repeated operations. However, the movable jaw wobbles, because the spring can not maintain the position of the movable jaw in a direction transverse to the sliding direction. Furthermore, the movable jaw is liable to disengage from the guide due to impact or falling to the ground. The spring will disengage from the wrench after disengagement of the movable jaw. Further, the exposed portion of the spring, when compressed by the movable jaw, is liable to bend and, thus, be in friction contact with the end edges of the bores of the stationary and movable jaws, leading to non-smooth compression of the spring or even permanent deformation of the spring. Further, the exposed portion of the spring is apt to be contaminated by oil to which debris easily adheres, hindering movement of the movable jaw. 
     U.S. Pat. No. 3,695,125 discloses an open end ratchet wrench including a head having a fixed jaw and an opposed pawl support portion. A pawl and a spring are mounted to an inner side of the pawl support portion. The pawl is biased by the spring and slideable between an extended torquing position and a retracted ratcheting position. Two side caps are fixed to two sides of the head to define a space receiving the pawl and the spring and to prevent disengagement of the pawl and the spring. The pawl includes a stop shoulder to prevent the pawl from moving out of the pawl support portion under the action of the spring. However, the side caps may separate from the head when the wrench falls to the ground, causing disengagement of the pawl from the pawl support portion and subsequent falling of the spring. Furthermore, the pawl merely biased by the spring is still liable to wobble, although there are two side caps on opposite sides of the pawl. Further, the spring is liable to shift from its original position due to impingement to or repeated compression of an exposed portion of the spring, causing malfunction of the spring. Further, a gap exists between the side caps and the pawl when the pawl is moved into the space. Oil and debris may enter the gap and adversely affect the compression of the spring and the movement of the pawl. 
     U.S. Pat. No. 4,706,528 discloses an adjustable wrench including a fixed jaw and an adjustable jaw. In an embodiment, a sliding jaw portion is provided on the fixed jaw. The sliding jaw includes a rectilinearly extending slot through which a pin is extended, preventing disengagement of the sliding jaw. A plate spring is mounted to an inner face of the fixed jaw to bias the sliding jaw outward. A hole is formed in an end wall of the slot and receives a coil spring to bias the sliding jaw inward. Thus, the sliding jaw is movable inward or outward and can be retained in place under action of the plate spring and the coil spring. Such a wrench is particularly suitable for rotating pipes, but not suitable for tightening or loosening fasteners such as bolts, nuts, or the like. Specifically, since a pipe has no plane surfaces and is, thus, difficult to grip, the sliding jaw is moved outward to shorten the distance between the sliding jaw and the adjustable jaw for firmly clamping the pipe to permit tightening or loosening of the pipe. The sliding jaw is returned by moving inward under the action of the coil spring. Furthermore, the pipe causes inward movement of the sliding jaw and will not rotate when the wrench is rotated in a reverse direction. However, the coil spring is redundant when the wrench is utilized on a nut or bolt head that has flat sides. In the case that the wrench drives a nut or bolt head having flat faces in a reverse direction, the nut or bolt head initially permits the sliding jaw to move inward. However, when the jaw moves inward to its innermost position, the spacing between the sliding jaw and the adjustable jaw is still smaller than the spacing between two corners of the nut or bolt head such that the nut or bolt head will be rotated in the reverse direction, which is undesired. This is because the sliding jaw moves rectilinearly along the rectilinearly extending slot along an axis at a relatively small angle to a plane on which the adjusting jaw lies. Further, formation of a hole in the inner face of the fixed jaw for receiving a small screw to position the plate spring and formation of the hole for receiving the coil spring reduce the structural strength of the wrench, such that the wrench can only be utilized in pipes that are hollow and, thus, can exert smaller reactive force (which avoids deformation of the hollow pipes) when the pipes are rotated by the wrench. Further, although the coil spring has an end received in the hole of the sliding jaw, the other end of the coil spring outside of the hole is liable to bend when the spring is compressed, leading to friction at the end edge of the opening of the hole and resulting in non-smooth compression of the spring or even permanent deformation of the spring. Further, the slot is open such that most of the reactive force imparted to the sliding jaw during driving of a pipe or nut is transmitted to and, thus, damages the pin. This is because although the sliding jaw has a plane face in sliding contact with another plane face of the fixed jaw, the plane face of the sliding jaw can not provide guidance for the inward or outward movement of the sliding jaw. As a result, the plane face of the sliding jaw transmits the reactive force to the pin instead of effectively withstanding the torque. 
     U.S. Pat. No. 7,024,971 discloses an open end ratchet wrench including first and second stationary jaws. The first stationary jaw supports a movable plate. A space is sandwiched between two face plates of the first stationary jaw to accommodate the movable plate. The movable plate includes two angled slots each receiving a pin extending through the space, avoiding disengagement of the movable plate. The wrench further includes a hole receiving a spring that has an end located outside of the hole for biasing the movable plate. Each angled slot of the movable plate includes a short section and a long section at an angle to the short section such that the movable plate can move in two stages each having a rectilinear travel. Although the two-stage movement of the movable plate increases the spacing between the movable plate and the second stationary jaw, the movable plate is liable to get stuck at the intersection of the long and short sections, adversely affecting operation of the wrench in the reverse direction. Furthermore, the spring has an exposed section that is liable to bend when the spring is compressed, leading to friction at the end edge of the opening of the hole and resulting in non-smooth compression of the spring or even permanent deformation of the spring. Further, the angled slots increase the area of the movable plate or the first stationary jaw, resulting in difficulties in reducing the volume of the open end wrench. Thus, the wrench can not be used in a small space. If the area of the movable plate is increased or the first stationary jaw is reduced in size, the short section or the longer section would be exposed outside of the first stationary jaw such that debris is apt to accumulate in the slots, adversely affecting rectilinear movement of the movable plate. Further, since the space is open in both sides, the reaction force imparted to the movable plate during driving of a workpiece is completely transmitted to the pins that can not withstand high torque. As a result, the wrench can not be used in high-torque driving operation. 
     U.S. Patent Publication No. 2009/0193941 A1 discloses first and second jaws formed on a jaw support. The first jaw can be moved by rotating a worm. The jaw support includes an open track in the form of a slot receiving the second jaw. The jaw support further includes a pin extending through the track. The second jaw includes a rectilinear opening through which the pin extends, preventing the second jaw from disengaging from the jaw support. A biasing member is mounted in the opening of the second jaw to bias the second jaw outward. Since the second jaw includes a single rectilinear opening, a change in the spacing from the second jaw to the first jaw is relatively small such that a workpiece will be rotated when the wrench rotates in a reverse direction not intended to rotate the workpiece. Thus, the first jaw must be movable, and the spacing between the first and second jaws can be adjusted by rotating the worm to avoid joint rotation of the workpiece when the wrench rotates in the reverse direction. However, the wrench of this type includes many elements, and the track, opening, and holes in the elements weaken the wrench. Furthermore, since the track is open, the reaction force imparted to the second jaw during driving of the workpiece is completely transmitted to the pin. Thus, the pin is liable to be damaged. Although the second jaw includes a surface in sliding contact with the jaw support to guide sliding movement of the second jaw, this surface merely transmits the reactive force to the pin instead of effectively withstanding the torque. Further, since the second jaw moves rectilinearly, the opening in the second jaw must be lengthened if it is desired to increase the spacing between the first and second jaws. However, this would expose the opening support such that the opening and the biasing member in the opening would easily be contaminated by oil to which debris adheres easily. Furthermore, operation of the biasing member would be adversely affected, causing non-smooth movement of the second jaw. 
     The above patents and U.S. Pat. No. 4,158,975 as well as U.S. Patent Publication Nos. 2008/0066585 A1; 2010/0071516 A1; and 2010/00873797 A1 have a common disadvantage. Specifically, the open end wrench has a limited torque-bearing capacity. This is because the open end wrench expands elastically under excessive torque. As an example, when the user finds that the torque applied is insufficient, an elongated metal tube will be coupled to the handle to increase the arm of force for large-torque operation. However, the reactive force will be larger than the elastic deforming capacity when the fastener is tightened to an extent, leading to elastic expansion in the jaws that hold the fastener during the driving operation. Thus, the jaws can not effectively hold the fastener, leading to disengagement of the movable jaw from the engaged sides of the fastener. The corners of the fastener wear easily, resulting in sliding during driving operation and in failure of the continuous driving operation. Furthermore, large-torque operation could not be performed in addition to the risk of damage to the fastener. 
     Thus, a need exists for a super high-torque open end wrench capable of fast driving of a workpiece without the disadvantages of the above conventional open end wrenches. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention solves this need and other problems in the field of super high-torque operations of fast drivable open end wrenches by providing, in a first aspect, an open end wrench capable of fast driving a workpiece. The workpiece includes first, second, third, fourth, fifth, and sixth sides respectively having first, second, third, fourth, fifth, and sixth force-receiving faces in a first rotating direction and respectively having first, second, third, fourth, fifth, and sixth force-receiving faces in a second rotating direction. The open end wrench includes a body having a handle and a jaw portion formed on an end of the handle. Spaced first and second jaws are formed on an end of the jaw portion opposite to the handle. The jaw portion includes a throat intermediate the first and second jaws. The throat and the first and second jaws together define a wrenching space adapted for receiving the workpiece. The first jaw includes a force-applying face facing the wrenching space and facing a distal end of the second jaw. The jaw portion further includes an arcuate sliding groove formed in the second jaw and facing the wrenching space. A guide is fixed in the sliding groove. A slide is slideably received in the sliding groove. The slide includes opposite first and second ends. The first end of the slide includes a first wrenching face located outside of the sliding groove. The slide further includes an arcuate guiding slot. The guide is received in the guiding slot, preventing the slide from disengaging from the sliding groove. The guiding slot includes an abutting end. The abutting end is in contact with the guide when the slide is a free position. An elastic device is mounted between the body and the slide for returning the slide to the free position. 
     When the jaw portion is not engaged with the workpiece, the slide is in the free position. The first wrenching face of the slide is located in the wrenching space. The first wrenching face is not parallel to the force-applying face of the first jaw. An extension line of the first wrenching face intersects an extension line of the force-applying face of the first jaw at a point away from the handle. 
     When the jaw portion receives the workpiece but does not drive the workpiece, the force-applying face of the first jaw abuts the first force-receiving face in the first rotating direction of the workpiece. The first end of the slide abuts the fourth force-receiving face in the first rotating direction of the workpiece. A buffering space is formed between the abutting end of the guiding slot and the guide. The buffering space has an arc length larger than a tolerance of the workpiece. 
     When the jaw portion drives the workpiece and deforms elastically, the body rotates relative to the workpiece. The slide does not rotate together with the body due to the buffering space. The buffering space allows the first end of the slide to abut the fourth force-receiving face in the first rotating direction of the workpiece when the jaw portion expands elastically. 
     According to a second aspect, an open end wrench is provided and capable of fast driving a workpiece. The workpiece includes first, second, third, fourth, fifth, and sixth sides respectively having first, second, third, fourth, fifth, and sixth force-receiving faces in a first rotating direction and respectively having first, second, third, fourth, fifth, and sixth force-receiving faces in a second rotating direction. The open end wrench includes a body having a handle and a jaw portion formed on an end of the handle. Spaced first and second jaws are formed on an end of the jaw portion opposite to the handle. The jaw portion includes a throat intermediate the first and second jaws. The throat and the first and second jaws together define a wrenching space adapted for receiving the workpiece. The first jaw includes a force-applying face facing the wrenching space and facing a distal end of the second jaw. The jaw portion further includes an arcuate sliding groove formed in the second jaw and facing the wrenching space. A guide is fixed in the sliding groove. A slide is slideably received in the sliding groove. The slide includes opposite first and second ends. The first end of the slide includes a first wrenching face located outside of the sliding groove. The slide further includes an arcuate guiding slot. The guide is received in the guiding slot, preventing the slide from disengaging from the sliding groove. The guiding slot includes an abutting end. The abutting end is in contact with the guide when the slide is a free position. An elastic device is mounted between the body and the slide for returning the slide to the free position. 
     When the jaw portion is not engaged with the workpiece, the slide is in the free position. The first wrenching face of the slide is located in the wrenching space. The first wrenching face is not parallel to the force-applying face of the first jaw. An extension line of the first wrenching face intersects an extension line of the force-applying face of the first jaw at a point away from the handle. 
     When the jaw portion receives the workpiece but does not drive the workpiece, the force-applying face of the first jaw abuts the first force-receiving face in the first rotating direction of the workpiece. The first end of the slide abuts the fourth force-receiving face in the first rotating direction of the workpiece. A buffering angle is formed between the first wrenching face and the fourth force-receiving face in the first rotating direction of the workpiece. 
     When the jaw portion drives the workpiece to rotate and deforms elastically, the body rotates relative to the workpiece. The buffering angle allows the body and the slide to gradually rotate relative to the workpiece such that the first wrenching face of the slide abuts the fourth force-receiving face in the first rotating direction of the workpiece, providing surface contact between the first wrenching face of the slide and the fourth force-receiving face in the first rotating direction of the workpiece. 
     The present invention will become clearer in light of the following detailed description of illustrative embodiments of this invention described in connection with the drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The illustrative embodiments may best be described by reference to the accompanying drawings where: 
         FIG. 1  shows a partial, perspective view of an open end wrench of a first embodiment according to the preferred teachings of the present invention. 
         FIG. 2  shows a partial, exploded, perspective view of the open end wrench of  FIG. 1 . 
         FIG. 3  shows a partial, cross sectional view of the open end wrench of  FIG. 1 . 
         FIG. 4  shows a perspective view illustrating use of the open end wrench of  FIG. 1  on a workpiece. 
         FIG. 5  shows a partial, cross sectional view illustrating rotation of the open end wrench of  FIG. 4  in a driving direction to drive the workpiece in the same direction. 
         FIG. 6  shows a partial, cross sectional view illustrating further rotation of the open end wrench of  FIG. 5  in the driving direction through use of an extension tube. 
         FIG. 7  shows a partial, cross sectional view illustrating further rotation of the open end wrench of  FIG. 6  in the driving direction. 
         FIG. 8  shows a partial, cross sectional view of an open end wrench of a second embodiment according to the preferred teachings of the present invention. 
         FIG. 9  shows an enlarged view of a circled portion in  FIG. 8 . 
         FIG. 10  shows a partial, cross sectional view illustrating use of the open end wrench of  FIG. 8  on a workpiece with the open end wrench rotated in a driving direction. 
         FIG. 11  shows a partial, cross sectional view illustrating further rotation of the open end wrench of  FIG. 10  in the driving direction through use of an extension tube. 
         FIG. 12  shows a partial, cross sectional view illustrating further rotation of the open end wrench of  FIG. 11  in the driving direction. 
         FIG. 13  shows a partial, cross sectional view illustrating further rotation of the open end wrench of  FIG. 12  in the driving direction. 
         FIG. 14  shows an enlarged view of a circled portion in  FIG. 13 . 
         FIG. 15  shows a partial, cross sectional view illustrating further rotation of the open end wrench of  FIG. 13  in the driving direction. 
         FIG. 16  shows an enlarged view of a portion of an open end wrench of a third embodiment according to the preferred teachings of the present invention. 
     
    
    
     All figures are drawn for ease of explanation of the basic teachings of the present invention only; the extensions of the figures with respect to number, position, relationship, and dimensions of the parts to form the preferred embodiments will be explained or will be within the skill of the art after the following teachings of the present invention have been read and understood. Further, the exact dimensions and dimensional proportions to conform to specific force, weight, strength, and similar requirements will likewise be within the skill of the art after the following teachings of the present invention have been read and understood. 
     Where used in the various figures of the drawings, the same numerals designate the same or similar parts. Furthermore, when the terms “first”, “second”, “third”, “fourth”, “fifth”, “sixth”, “lower”, “upper”, “inner”, “outer”, “side”, “end”, “portion”, “section”, “spacing”, “clockwise”, “counterclockwise”, “length”, “width”, “height”, and similar terms are used herein, it should be understood that these terms have reference only to the structure shown in the drawings as it would appear to a person viewing the drawings and are utilized only to facilitate describing the invention. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1-7  show an open end wrench  10  of a first embodiment according to the preferred teachings of the present invention. Open end wrench  10  includes a body  20 , a slide  30 , and an elastic device  40 . 
     Body  20  includes a handle  21  and a jaw portion  22  formed on an end of handle  21 . Jaw portion  22  can hold a workpiece  90 , such as a hexagonal head of a bolt, a nut, or the like. Workpiece  90  includes first, second, third, fourth, fifth, and sixth sides respectively having first, second, third, fourth, fifth, and sixth force-receiving faces in a first rotating direction  91 A,  92 A,  93 A,  94 A,  95 A, and  96 A. The first, second, third, fourth, fifth, and sixth sides of workpiece  90  respectively have first, second, third, fourth, fifth, and sixth force-receiving faces in a second rotating direction  91 B,  92 B,  93 B,  94 B,  95 B, and  96 B. A user can grip the handle  21  and rotate body  20  as well as jaw portion  22  about an axis of workpiece  90  to tighten or loosen workpiece  90 . 
     Spaced first and second jaws  23  and  24  are formed on an end of jaw portion  22  opposite to handle  21 . First and second jaws  23  and  24  can withstand reactive force from workpiece  90 . First and second jaws  23  and  24  face each other. Furthermore, first and second jaws  23  and  24  and jaw portion  22  are integrally formed as a single and inseparable component of the same material to provide jaw portion  22  with excellent structural strength and to increase the torque bearing capacity of jaw portion  22 . 
     Jaw portion  22  further includes a throat  25  intermediate first and second jaws  23  and  24 . Throat  25  and first and second jaws  23  and  24  together define a wrenching space  26 . Jaw portion  22  can enter wrenching space  26  by moving jaw portion  22  in a direction perpendicular to one of the six sides of workpiece  90  or by moving jaw portion  22  along the axis of workpiece  90 . 
     First jaw  23  includes a force-applying face  231  facing wrenching space  26  and facing a distal end of second jaw  24 . Force-applying face  231  corresponds to first force-receiving face in the first rotating direction  91 A of workpiece  90 . Second jaw  24  includes first and second faces  241  and  242 . First face  241  faces wrenching space  26  and throat  25 . Second face  242  faces wrenching space  26  and a distal end of first jaw  23 . First face  241  is at an angle of 120° to second face  242  such that first and second faces  241  and  242  correspond respectively to fourth and third force-receiving faces in the first rotating direction  94 A and  93 A. In this embodiment, first face  241  of second jaw  24  is substantially parallel to force-applying face  231  of first jaw  23 . Namely, an extension line L 241  of first face  241  is parallel to an extension line L 231  of force-applying force  231 . Thus, jaw portion  22  has an opening spacing α 0  between first face  241  and force-applying face  231 . 
     Throat  25  includes a push face  251  facing wrenching space  26 . Push face  251  is at an angle of 120° to force-applying face  231  of first jaw  23  such that push face  251  corresponds to second force-receiving face in the first rotating direction  92 A. Second face  242  is intermediate first face  241  and push face  251 . 
     Jaw portion  22  further includes a first evasive portion  221  between force-applying face  231  of first jaw  23  and push face  251  of throat  25 . First evasive portion  221  can receive first force-receiving face in the second rotating direction  91 B of workpiece  90 . Jaw portion  22  further includes a second evasive portion  222  between push face  251  of throat  25  and second face  242  of second jaw  24 . Second evasive portion  222  can receive second force-receiving face in the second rotating direction  92 B of workpiece  90 . Furthermore, jaw portion  22  includes a third evasive portion  223  between first and second faces  241  and  242  of the second jaw  24 . Third evasive portion  223  can receive third force-receiving face in the second rotating direction  93 B of workpiece  90 . 
     An arcuate sliding groove  27  is formed in second jaw  24  and faces wrenching space  26 . Sliding groove  27  includes spaced, first and second support walls  272  and  273  and a concave, arcuate sliding wall  271  extending between first and second support walls  272  and  273 . Sliding wall  271  is free of holes, grooves, recesses, etc., providing a complete concave, arcuate surface and enhancing the structural strength of second jaw  24 . Thus, jaw portion  22  can withstand high-torque operation. Furthermore, a center of an arcuate face of the sliding wall  271  is located in wrenching space  26  such that sliding wall  271  can be easily and rapidly processed with a single cutter at low costs while assuring structural strength of jaw portion  22 . First and second support walls  272  and  273  are parallel to each other and have a spacing therebetween. 
     A circular through-hole  274  is extended through first and second support walls  272  and  273  and in communication with sliding groove  27 . Through-hole  274  is located adjacent to throat  25  and receives a cylindrical guide  28  in the form of a pin. Two ends of guide  28  are received in two ends of through-hole  274  in first and second support walls  272  and  273  to retain guide  28  in sliding groove  27 . Guide  28  has a diameter D 28 . 
     Slide  30  is slideably received in sliding groove  27  and can drive workpiece  90  to rotate in a driving direction or slide along a perimeter of workpiece  90  in an opposite direction opposite to the driving direction without driving workpiece  90 . Slide  30  is substantially arcuate in cross section and includes a side having a convex, arcuate sliding face  31  slideably abutting sliding wall  271  of sliding groove  27 , allowing relative arcuate sliding movement between slide  30  and jaw portion  22 . Sliding face  31  is free of holes, grooves, recesses, etc., providing a complete arcuate surface and enhancing the structural strength of slide  30 . Thus, slide  30  can withstand high-torque operation. 
     Sliding face  31  of slide  30  has a curvature the same as that of sliding wall  271  of sliding groove  27  to allow smooth sliding of sliding face  31  on sliding wall  271 . Furthermore, when slide  30  is subjected to reactive force from workpiece  90 , the reactive force from the workpiece  90  can be transmitted to sliding wall  271  through a large area of sliding face  31  due to the same curvature. Thus, the force imparted to slide  30  can be distributed, avoiding stress concentration and increasing the torque bearing capacity of slide  30  when workpiece  90  is driven by body  20 . 
     Slide  30  includes opposite first and second ends  303  and  304  for driving workpiece  90 . First end  303  of slide  30  includes a first wrenching face  32  located outside of sliding groove  27 . Second end  304  includes a second wrenching face  33  located outside of sliding groove  27 . First and second wrenching faces  32  and  33  are located on the other side of slide  30  opposite to sliding face  31 . First wrenching face  32  is at an angle of 120° to second wrenching face  33  for the purpose of driving workpiece  90 . An evasive portion  34  is formed between first and second wrenching faces  32  and  33  and can receive third force-receiving face in the second rotating direction  93 B of workpiece  90 . 
     Slide  30  further includes a top face  301  and a bottom face  302  respectively at upper and lower sides thereof. First and second wrenching faces  32  and  33  extend between top and bottom faces  301  and  302 . Top and bottom faces  301  and  302  are parallel to each other and respectively in contact with first and second support walls  272  and  273  of sliding groove  27 . Slide  30  has a height H 30  between top and bottom faces  301  and  302  in a height direction. Ignoring the tolerance, height H 30  of slide  30  is the same as the spacing between first and second support walls  272  and  273  of sliding groove  27 . This allows top and bottom faces  301  and  302  of slide  30  to be symmetrically supported by first and second support walls  272  and  273  of sliding groove  27 , avoiding wobbling of slide  30  while sliding in sliding groove  27  along an arcuate path and increasing operational stability of open end wrench  10 . 
     Slide  30  further includes a guiding slot  35  extending from top face  301  through bottom face  302 . Guiding slot  35  is arcuate in cross section and has a curvature the same as the curvature of sliding wall  271  of sliding groove  27 . Since guiding slot  35  extends from top face  301  through bottom face  302 , a height of guiding slot  35  in the height direction of slide  30  is the same as height H 30  of slide  30 . Furthermore, guiding slot  35  has a width W 35  (between inner and outer arcuate surfaces thereof) in a width direction perpendicular to the height direction of slide  30 . Namely, width W 35  is equal to a difference between a radius of the outer arcuate surface and a radius of the inner arcuate surface of guiding slot  35 . Ignoring the tolerance, width W 35  of guiding slot  35  is the same as diameter D 28  of guide  28 . The height of guiding slot  35  is larger than 1.5 times width W 35  of guiding slot  35  (i.e., width W 35  of guiding slot  35  is smaller than 0.66 times the height of guiding slot  35 ). In this embodiment, the height of guiding slot  35  is larger than two times width W 35  of guiding slot  35  (i.e., width W 35  of guiding slot  35  is smaller than 0.5 times the height of guiding slot  35 ). 
     Guiding slot  35  receives guide  28  to prevent slide  30  from disengaging from sliding groove  27 . Since the curvature of sliding face  31  of slide  30  is the same as those of guiding slot  35  and sliding wall  271  of sliding groove  27 , smooth sliding movement between guiding slot  35  of slide  30  and guide  28  in sliding groove  27  can be obtained while sliding face  31  of slide  30  is moving along sliding wall  271  of sliding groove  27  along the arcuate path. Undesired interference between slide  30 , guide  28 , and sliding wall  271  is avoided. 
     Guiding slot  35  further includes an abutting end  351  and a pressing end  352 . When slide  30  is in a free position, abutting end  351  is in contact with guide  28 , and pressing end  352  is in contact with elastic device  40 . Since all of the surfaces of guiding slot  35  are free of holes, grooves, recesses, etc., stress concentration is avoided, and the structural strength of slide  30  is assured. Thus, slide  30  can withstand high-torque operation. Furthermore, since sliding face  31  and all of the surfaces of guiding slot  35  of slide  30  are free of holes, grooves, recesses, etc., the manufacturing costs of slide  30  can be reduced while providing open end wrench  10  with high-torque capacity and allowing open end wrench  10  to be produced at low costs for wider industrial application. 
     Elastic device  40  is mounted between body  20  and slide  30 . Elastic device  40  has two ends respectively abutting guide  28  and pressing end  352  of guiding slot  35  for returning slide  30  to the free position. Elastic device  40  includes an elastic element  41  mounted in guiding slot  35  of slide  30 . After mounting, elastic element  41  is completely received in guiding slot  35 . Elastic element  41  has a height in the height direction of slide  30  not larger than the height of guiding slot  35  but larger than width W 35  of guiding slot  35 . Furthermore, the height of elastic element  41  is larger than 0.5 times the height of guiding slot  35 . Thus, rotation of elastic element  41  in guiding slot  35  is avoided, preventing slide  30  from shifting from the free position after returning. 
     In this embodiment, elastic element  41  is a resilient plate having Z-shaped cross sections. At least one force-storing unit  401  is provided between two ends of elastic element  41 . Each force-storing unit  401  is in the form of a metal plate having substantially V-shaped cross sections. Each force-storing unit  401  includes first and second legs  402  and  403  and a compression section  404  between first and second legs  402  and  403 . Compression section  404  can store energy when first and second legs  402  and  403  are compressed, providing force-storing unit  401  with an elastic returning function. First leg  402  of each force-storing unit  401  is connected to second leg  403  of an adjacent force-storing unit  401 . Thus, compression section  404  of each force-storing unit  401  possesses an elastic returning function. First leg  402  on an end of elastic element  41  abuts guide  28 , and second leg  403  on the other end of elastic element  41  abuts pressing end  352  of guiding slot  35 . Thus, slide  30  can be automatically returned to the free position. 
     Slide  30  is in the free position before jaw portion  22  is engaged with workpiece  90  (see  FIG. 3 ). First wrenching face  32  of slide  30  is located in wrenching space  26 . First wrenching face  32  of slide  30  is not parallel to force-applying face  231  of first jaw  23 . Abutting end  351  of guiding slot  35  is in contact with guide  28 . 
     As can be seen in  FIG. 3 , an extension line L 32  of first wrenching face  32  is not parallel to extension line L 231  of force-applying face  231 . Thus, extension line L 32  of first wrenching face  32  intersects extension line L 231  of force-applying face  231  at a point away from handle  21  of body  20 . 
     When jaw portion  22  is engaged with workpiece  90  but does not drive workpiece  90  (see  FIG. 4 ), force-applying face  231  of first jaw  23  abuts first force-receiving face in the first rotating direction  91 A of workpiece  90 , and first end  303  of slide  30  abuts fourth force-receiving face in the first rotating direction  94 A of workpiece  90  such that first wrenching face  32  of slide  30  is parallel to force-applying face  231  of first jaw  23 . 
     As can be seen in  FIG. 4 , extension line L 32  of first wrenching face  32  is parallel to extension line L 231  of force-applying face  231 . Thus, force-applying face  231  and first wrenching face  32  can respectively abut first and fourth force-receiving faces in the first rotating direction  91 A and  94 A of workpiece  90 . 
     At the same time, a buffering space  36  is formed between abutting end  351  of guiding slot  35  and guide  28 . Buffering space  36  assures abutting of first end  303  of slide  30  against fourth force-receiving face in the first rotating direction  94 A of workpiece  90  when jaw portion  22  expands elastically. Since first wrenching face  32  of slide  30  is at an angle of 120° to second wrenching face  33  and since buffering space  36  is formed between abutting end  351  of guiding slot  35  and guide  28 , first wrenching face  32  of slide  30  still abuts fourth force-receiving face in the first rotating direction  94 A of workpiece  90  when jaw portion  22  expands elastically. 
     Buffering space  36  has an arc length AL 36  larger than the tolerance of workpiece  90 . Namely, ignoring the tolerance difference of the same specification of workpiece  90 , arc length AL 36  must be larger than the tolerance of workpiece  90 . By such an arrangement, buffering space  36  maintains abutting of slide  30  against fourth force-receiving face in the first rotating direction  94 A of workpiece  90  when jaw portion  22  expands elastically. 
     More preferably, arc length AL 36  is larger than half of width W 35  of guiding slot  35 . Namely, arc length AL 36  is larger than half of diameter D 28  of guide  28 . 
       FIG. 4  shows engagement of jaw portion  22  of open end wrench  10  according to the preferred teachings of the present invention with workpiece  90  in the form of a bolt extended through a first board  98  and then screwed through a second board  99 . Before driving workpiece  90 , workpiece  90  is entered wrenching space  26  of jaw portion  22  with force-applying face  231  of first jaw  23  abutting first force-receiving face in the first rotating direction  91 A of workpiece  90  and with first end  303  of slide  30  abutting fourth force-receiving face in the first rotating direction  94 A of workpiece  90 . 
     At the same time, buffering space  36  is formed between abutting end  351  of guiding slot  35  and guide  28  and is larger than the tolerance of workpiece  90  of its specification. 
     When workpiece  90  enters wrenching space  26 , first end  303  of slide  30  is pushed by workpiece  90  and compresses elastic device  40 . Slide  30  slides along an arcuate path relative to body  20  until workpiece  90  comes in contact with second wrenching face  33  of slide  30 . In this case, slide  30  is pushed by elastic device  40  such that first wrenching face  32  of slide  30  is in intimate contact with fourth force-receiving face in the first rotating direction  94 A of workpiece  90 , providing surface contact therebetween. Since fourth force-receiving face in the first rotating direction  94 A of workpiece  90  is parallel to first force-receiving face in the first rotating direction  91 A of workpiece  90 , first wrenching face  32  of slide  30  is substantially parallel to force-applying face  231  of first jaw  23 . 
       FIG. 5  shows driving of workpiece  90  by jaw portion  22  of open end wrench  10  according to the preferred teachings of the present invention towards first jaw  23  (in the clockwise direction in  FIG. 5 ). Workpiece  90  is driven by jaw portion  22  to rotate about the axis of workpiece  90 . The force applied by the user is transmitted to first force-receiving face in the first rotating direction  91 A of workpiece  90  via force-applying face  231  of first jaw  23  and transmitted to fourth force-receiving face in the first rotating direction  94 A of workpiece  90  via first wrenching face  32  of slide  30 . Thus, workpiece  90  rotates together with jaw portion  22 . Second wrenching face  33  of slide  30  abuts third force-receiving face in the first rotating direction  93 A of workpiece  90  to assist in driving of workpiece  90 . 
     Since first jaw  23  and jaw portion  22  are integrally formed as a single and inseparable component of the same material, force-applying face  231  of first jaw  23  can effectively withstand the reactive force from first force-receiving face in the first rotating direction  91 A of workpiece  90 . Furthermore, since second jaw  24  and jaw portion  22  are integrally formed as a single and inseparable component of the same material and since sliding face  31  of slide  30  and sliding wall  271  of sliding groove  27  are free of holes, grooves, recesses, etc., and have the same curvature and are in surface contact with each other, first wrenching face  32  of slide  30  can effectively withstand the reactive force from fourth force-receiving face in the first rotating direction  94 A of workpiece  90 . Thus, open end wrench  10  according to the preferred teachings of the present invention can withstand high-torque operation. 
     In this embodiment, second wrenching face  33  of slide  30  abuts third force-receiving face in the first rotating direction  93 A of workpiece  90 . Since second jaw  24  and jaw portion  22  are integrally formed as a single and inseparable component of the same material and since sliding face  31  of slide  30  and sliding wall  271  of sliding groove  27  are free of holes, grooves, recesses, etc., and have the same curvature and are in surface contact with each other, second wrenching face  33  of slide  30  can effectively withstand the reactive force from third force-receiving face in the first rotating direction  93 A of workpiece  90 . Thus, open end wrench  10  according to the preferred teachings of the present invention can withstand high-torque operation. 
     In this embodiment, second wrenching face  33  of slide  30  abuts third force-receiving face in th first rotating direction  93 A of workpiece  90 . since second jaw  24  and jaw portion  22  are integrally formed as a single and inseperable component of the same material and since sliding face  31  of slide  30  and sliding wall  271  of sliding groove  27  are free of holes, grooves, recesses, etc and have the same curvature and are in surface contact with each other, second wrenching face  33  or slide  30  can effectively withstand the reactive force from third force-receiving face in the first rotating direction  93 A of workpiece  90 . Thus, open end wrench  10  according to the preferred teachings of the present invention can withstand high-torque operation. 
     Since the user applies the force through handle  21 , if the arm of force and the force remain the same, workpiece  90  can be driven by the torque in the clockwise direction until a torque in the counterclockwise direction acting on workpiece  90  is equal to the clockwise torque. In this case, workpiece  90  is stopped after having been rotated through 10° relative to first and second boards  98  and  99 , as shown in  FIG. 5 . 
     With reference to  FIGS. 6 and 7 , to further tighten workpiece  90 , an extension tube  97  is engaged with handle  21  to provide an increased arm of force equal to or more than twice the original arm of force, providing double (or higher) toque with the same force. 
     When workpiece  90  is tightened to a certain extent by using extension tube  97 , the reactive force imparted from workpiece  90  to jaw portion  22  increases and causes elastic deformation of jaw portion  22 . Workpiece  90  no longer rotates together with open end wrench  10 , and body  20  gradually rotates clockwise relative to workpiece  90 . In this case, the slide  30  does not rotate together with the body  20  in the clockwise direction due to existence of buffering space  36 . Thus, first wrenching face  32  of slide  30  remains in surface contact with fourth force-receiving face in the first rotating direction  94 A of workpiece  90  while arc length AL 36  of buffering space  36  is reduced. 
     Opening space of jaw portion  22  increases (see opening spacing α 1  in  FIG. 6 ) such that the stress acting on the deforming jaw portion  22  increases to resist deformation. When the stress resisting deformation of jaw portion  22  becomes larger than the reacting force from workpiece  90 , jaw portion  22  no longer deforms. In this case, slide  30  can be driven again by jaw portion  22  to proceed with supper high-torque operation of open end wrench  10 . 
     Then, the user rotates jaw portion  22  in the driving direction by using extension tube  97  to drive workpiece  90  to rotate about the axis of workpiece  90 . The force applied by the user is transmitted to first force-receiving face in the first rotating direction  91 A of workpiece  90  via force-applying face  231  of first jaw  23  and transmitted to fourth force-receiving face in the first rotating direction  94 A of workpiece  90  via first wrenching face  32  of slide  30 . Thus, workpiece  90  continues to rotate together with jaw portion  22 , proceeding with super high-torque operation until workpiece  90  is tightened. During the operation, push face  251  of throat  25  abuts second force-receiving face in the first rotating direction  92 A of workpiece  90  to assist in driving of workpiece  90 . 
     It can be appreciated that open end wrench  10  according to the preferred teachings of the present invention can be rotated in an opposite, non-driving direction without driving workpiece  90 . Namely, open end wrench  10  is moved in the opposite direction back to a position ready for driving workpiece  90  without the need of disengaging workpiece  90  from wrenching space  26  of jaw portion  22  and subsequent reengaging workpiece  90  in wrenching space  26 , allowing fast driving of workpiece  90 . 
       FIGS. 8-15  show an open end wrench  10  of a second embodiment according to the preferred teachings of the present invention that is substantially the same as the first embodiment except that the angle between first and second wrenching faces  32  and  33  of slide  30  is smaller than 118°. 
     When jaw portion  22  receives the workpiece  90  but does not drive workpiece  90 , first end  303  of slide  30  abuts second force-receiving face in the first rotating direction  92 A of workpiece  90  such that a buffering angle θ is formed between first wrenching face  32  of slide  30  and fourth force-receiving face in the first rotating direction  94 A of workpiece  90 . The buffering angle θ is larger than 2°. Namely, the angle between first and second wrenching faces  32  and  33  of slide  30  is smaller than 118°. Buffering angle θ allows body  20  and slide  30  to gradually rotate relative to workpiece  90  when jaw portion  22  expands elastically, such that first wrenching face  32  of slide  30  abuts fourth force-receiving face in the first rotating direction  94 A of workpiece  90 , providing surface contact between first wrenching face  32  of slide  30  and fourth force-receiving face in the first rotating direction  94 A of the workpiece  90 . 
       FIGS. 8 and 9  show engagement of jaw portion  22  of open end wrench  10  according to the preferred teachings of the present invention with workpiece  90  in the form of a bolt extended through a first board  98  and then screwed through a second board  99 . Before driving workpiece  90 , workpiece  90  enters wrenching space  26  of jaw portion  22  with force-applying face  231  of first jaw  23  abutting first force-receiving face in the first rotating direction  91 A of workpiece  90  and with first end  303  of slide  30  abutting fourth force-receiving face in the first rotating direction  94 A of workpiece  90 . 
     At the same time, buffering space  36  is formed between abutting end  351  of guiding slot  35  and guide  28  and is larger than the tolerance of workpiece  90  of its specification. 
     When workpiece  90  enters wrenching space  26 , first end  303  of slide  30  is pushed by workpiece  90  and compresses elastic device  40 . Slide  30  slides along an arcuate path relative to body  20  until workpiece  90  comes in contact with second wrenching face  33  of slide  30 . In this case, slide  30  is pushed by elastic device  40  such that first end  303  of slide  30  abuts fourth force-receiving face in the first rotating direction  94 A of workpiece  90 . Since fourth force-receiving face in the first rotating direction  94 A of workpiece  90  is parallel to first force-receiving face in the first rotating direction  91 A of workpiece  90 , buffering angle θ is formed between first wrenching face  32  of slide  30  and force-applying face  231  of first jaw  23 . 
       FIG. 10  shows driving of workpiece  90  by jaw portion  22  of open end wrench  10  according to the preferred teachings of the present invention towards first jaw  23  (in the clockwise direction in  FIG. 10 ). Workpiece  90  is driven by jaw portion  22  to rotate about the axis of workpiece  90 . The force applied by the user is transmitted to first force-receiving face in the first rotating direction  91 A of workpiece  90  via force-applying face  231  of first jaw  23  and transmitted to fourth force-receiving face in the first rotating direction  94 A of workpiece  90  via first end  303  of slide  30 . Thus, workpiece  90  rotates together with jaw portion  22 . Second wrenching face  33  of slide  30  abuts third force-receiving face in the first rotating direction  93 A of workpiece  90  to assist in driving of workpiece  90 . 
     Since first jaw  23  and jaw portion  22  are integrally formed as a single and inseparable component of the same material, force-applying face  231  of first jaw  23  can effectively withstand the reactive force from first force-receiving face in the first rotating direction  91 A of workpiece  90 . Furthermore, since second jaw  24  and jaw portion  22  are integrally formed as a single and inseparable component of the same material and since sliding face  31  of slide  30  and sliding wall  271  of sliding groove  27  are free of holes, grooves, recesses, etc., and have the same curvature and are in surface contact with each other, first wrenching face  32  of slide  30  can effectively withstand the reactive force from fourth force-receiving face in the first rotating direction  94 A of workpiece  90 . Thus, open end wrench  10  according to the preferred teachings of the present invention can withstand high-torque operation. 
     In this embodiment, second wrenching face  33  of slide  30  abuts third force-receiving face in the first rotating direction  93 A of workpiece  90 . Since second jaw  24  and jaw portion  22  are integrally formed as a single and inseparable component of the same material and since sliding face  31  of slide  30  and sliding wall  271  of sliding groove  27  are free of holes, grooves, recesses, etc., and have the same curvature and are in surface contact with each other, second wrenching face  33  of slide  30  can effectively withstand the reactive force from third force-receiving face in the first rotating direction  93 A of workpiece  90 . Thus, open end wrench  10  according to the preferred teachings of the present invention can withstand high-torque operation. 
     Since the user applies the force through handle  21 , if the arm of force and the force remain the same, workpiece  90  can be driven by the torque in the clockwise direction until a torque in the counterclockwise direction acting on workpiece  90  is equal to the clockwise torque. In this case, workpiece  90  is stopped after having been rotated through 10° relative to first and second boards  98  and  99 , as shown in  FIG. 10 . 
     With reference to  FIGS. 11 and 12 , to further tighten workpiece  90 , an extension tube  97  is engaged with handle  21  to provide an increased arm of force equal to or more than twice the original arm of force, providing double (or higher) toque with the same force. 
     When workpiece  90  is tightened to a certain extent by using extension tube  97 , the reactive force imparted from workpiece  90  to jaw portion  22  increases and causes elastic deformation of jaw portion  22 . Workpiece  90  no longer rotates together with open end wrench  10 , and body  20  gradually rotates clockwise relative to workpiece  90 . In this case, slide  30  does not rotate together with body  20  in the clockwise direction due to existence of buffering space  36 . Thus, first end  303  of slide  30  remains in contact with fourth force-receiving face in the first rotating direction  94 A of workpiece  90  while arc length AL 36  of buffering space  36  reduces. 
     The opening space of jaw portion  22  increases (see opening spacing α 1  in  FIGS. 11 and 12 ) such that the stress acting on the deforming jaw portion  22  increases to resist deformation. When the stress resisting deformation of jaw portion  22  becomes larger than the reacting force from workpiece  90 , jaw portion  22  no longer deforms. In this case, slide  30  can be driven again by jaw portion  22  to proceed with supper high-torque operation of open end wrench  10 . 
     Then, the user rotates jaw portion  22  in the driving direction by using extension tube  97  to drive workpiece  90  to rotate about the axis of workpiece  90 . The force applied by the user is transmitted to first force-receiving face in the first rotating direction  91 A of workpiece  90  via force-applying face  231  of first jaw  23  and transmitted to fourth force-receiving face in the first rotating direction  94 A of workpiece  90  via first end  303  of slide  30 . Thus, workpiece  90  continues to rotate together with jaw portion  22 , proceeding with super high-torque operation until workpiece  90  is tightened. During the operation, push face  251  of throat  25  abuts second force-receiving face in the first rotating direction  92 A of workpiece  90  to assist in driving of workpiece  90 . Workpiece  90  in  FIG. 12  has been rotated 10° in the clockwise direction relative to first and second boards  98  and  99 . 
     With reference to  FIGS. 13 and 14 , during tightening of workpiece  90 , the reactive force from workpiece  90  also increases continuously. When the reactive force from workpiece  90  becomes larger than the stress resisting deformation of jaw portion  22 , workpiece  90  stops again. In this case, the opening space of jaw portion  22  further increases due to elastic deformation of jaw portion  22  (see opening spacing α 2  in  FIG. 13 ) such that the stress acting on the deforming jaw portion  22  increases again to resist the deformation, and workpiece  90  does not rotate together with open end wrench  10 . Body  20  and slide  30  gradually rotate relative to workpiece  90  in the clockwise direction while buffering angle θ reduces gradually. 
     Then, the stress acting on jaw portion  22  increases to continuously resist deformation of jaw portion  22 . When the stress becomes larger than the reacting force from workpiece  90 , jaw portion  22  no longer deforms. In this case, first wrenching face  32  of slide  30  abuts and is in surface contact with fourth force-receiving face in the first rotating direction of workpiece  90 . Slide  30  can be driven again by jaw portion  22  to proceed with super high-torque operation of open end wrench  10 . 
     With reference to  FIG. 15 , the user rotates jaw portion  22  in the driving direction by using extension tube  97  to drive workpiece  90  to rotate about the axis of workpiece  90 . The force applied by the user is transmitted to first force-receiving face in the first rotating direction  91 A of workpiece  90  via force-applying face  231  of first jaw  23  and transmitted to fourth force-receiving face in the first rotating direction  94 A of workpiece  90  via first wrenching face  32  of slide  30 . Thus, workpiece  90  continues to rotate together with jaw portion  22 , proceeding with super high-torque operation until workpiece  90  is tightened. Workpiece  90  in  FIG. 15  has been rotated 10° in the clockwise direction relative to first and second boards  98  and  99 . The operation continues until workpiece  90  is tightened. 
     In this embodiment, the timing of actuation of buffering space  36  prior to buffering angle θ is not limited to the driving procedures mentioned above. It can be appreciated that buffering angle θ can be actuated prior to buffering space  36  due to differing friction between workpiece  90  and slide  30 . The above driving procedures are provided to assist in understanding the technique of the present invention. The same effect can be achieved through other driving procedures. 
       FIG. 16  shows an open end wrench  10  of a third embodiment according to the preferred teachings of the present invention that is substantially the same as the first and second embodiments except that first wrenching face  32  of slide  30  includes at least one cavity  37  (two in this embodiment) having V-shaped cross sections. Cavities  37  increase friction between first wrenching face  32  of slide  30  and fourth force-receiving face in the first rotating direction  94 A of workpiece  90 , further increasing the driving torque to be higher than that in the first and second embodiments. 
     Thus since the invention disclosed herein may be embodied in other specific forms without departing from the spirit or general characteristics thereof, some of which forms have been indicated, the embodiments described herein are to be considered in all respects illustrative and not restrictive. The scope of the invention is to be indicated by the appended claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.