Patent Publication Number: US-8973471-B2

Title: Three-protuberance open-end wrench

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to an open-end wrench, and more particularly to an open-end wrench, which is applicable to both an ordinary bolt and a worn bolt. 
     2. Description of the Related Art 
     A conventional open-end wrench has two jaws. The two jaws respectively have two holding plane faces in parallel to each other for holding and wrench an ordinary hexagonal bolt. The holding plane faces can be toothed to provide larger wrenching force. However, such wrench can hardly wrench a worn bolt. This is because the head section of the worn bolt is irregularly blunt. When making the holding plane faces of the jaws of the open-end wrench abut against the head section of the bolt to wrench the same, the holding plane faces are likely to slip over the corners of the head section of the bolt. Therefore, it is inconvenient to use such open-end wrench. 
     Taiwanese Patent Publication No. 319139 discloses an antislip open-end wrench as shown in  FIG. 1 . The head section of the open-end wrench  1  has a first jaw  11 , a second jaw  12  and a bottom  13 . Two recesses are formed on an inner face of the first jaw  11  in a position spaced from a free end of the first jaw  11  by a certain length and in a position close to the bottom  13  respectively. A boss section  111  is defined between the two recesses. Two arcuate protuberance sections  121  are formed on an inner face of the second jaw  12 . A worn bolt head  3  can be held between the first and second jaws  11 ,  12  of the open-end wrench  1 . The bolt head  3  has a width L. The inscribed circle of the bolt head  3  has a radius R. When making the inner faces of the jaws of the open-end wrench abut against the bolt head  3  to wrench the same, the effort point of the boss section  111  to the bolt head  3  will move so that the boss section  111  will still slip over the corners of the bolt head  3 . Moreover, with respect to different bolts worn to different extents, the effort point of the boss section  111  can be hardly fixed. As a result, the boss section  111  is very likely to slip over the corners of the bolt head. 
     Therefore, it is inconvenient to use such open-end wrench. It is therefore tried by the applicant to provide a wrench, which is applicable to both an ordinary bolt and a worn bolt to easily wrench the same. 
     SUMMARY OF THE INVENTION 
     It is therefore a primary object of the present invention to provide a three-protuberance open-end wrench, which is applicable to both an ordinary hexagonal bolt to more easily wrench the bolts, for user-friendly manipulation. 
     It is a further object of the present invention to provide the above three-protuberance open-end wrench, which can provide fixed effort points on the bolt to minimize the possibility of slippage. 
     To achieve the above and other objects, the three-protuberance open-end wrench of the present invention includes a head section. The head section has a first jaw and a second jaw. A throat is formed between the holding faces of the first and second jaws for receiving a threaded member therein. The open-end wrench is characterized in that two first protuberances are front-and-rear side by side formed on the holding face of the first jaw. A second protuberance is formed on the holding face of the second jaw. The second protuberance of the second jaw is not positioned in a central bisector of the two first protuberances of the first jaw. Two lateral sides of the threaded member are respectively held by the protuberances of the first and second jaws. 
     Still to achieve the above and other objects, the three-protuberance open-end wrench of the present invention includes a head section. The head section has a first jaw and a second jaw. Two first protuberances are front-and-rear side by side formed on a holding face of the first jaw. A second protuberance is formed on a holding face of the second jaw. A throat is formed between the holding faces of the first and second jaws for receiving a threaded member therein. The protuberances of the first and second jaws serve to hold two lateral sides of the threaded member. The protuberances form a non-isosceles triangle. 
     The present invention can be best understood through the following description and accompanying drawings, wherein: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view showing that a conventional open-end wrench is used to wrench a worn bolt; 
         FIG. 2  is a front view of the open-end wrench of the present invention; 
         FIG. 3  is a front view of the open-end wrench of the present invention, showing that the open-end wrench is used to wrench an ordinary bolt; 
         FIG. 4  is an enlarged top view of a worn bolt; and 
         FIG. 5  is a front view of the open-end wrench of the present invention, showing that the open-end wrench is used to wrench the worn bolt. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Please refer to  FIGS. 2 ,  3 , and  5 . According to a preferred embodiment, the three-protuberance open-end wrench  20  of the present invention includes a handle (not shown) and at least one head section  21 . The head section  21  includes a first jaw  22  and a second jaw  23 . The first jaw  22  has a first planar surface P 1 , while the second jaw  23  has a second planar surface P 2 . The first planar surface P 1  and the second planar surface P 2  are parallel and are separated a distance D. The first planar surface P 1  includes a first holding face  25 , two first protuberances  27 ,  27 ′ and three first recesses  51 ,  51 ′,  51 ″. The second planar surface P 2  includes a second holding face  26 , a second protuberance  28  and two second recesses  52 ,  52 ′. The first holding face  25  and the second holding face  26  are parallel. The two first protuberances  27 ,  27 ′ protrude inwardly above the first planar surface P 1  toward a center of the head section  21 . The second protuberance  28  protrudes inwardly above the second planar surface P 2  toward the center of the head section  21 . The three first recesses  51 ,  51 ′,  51 ″ protrude outwardly below the first planar surface P 1  away from the center of the head section  21 . The two second recesses  52 ,  52 ′ protrude outwardly below the second planar surface P 2  away from the center of the head section  21 . A throat  24  is formed between the first and second holding faces  25 ,  26  of the two jaws  22 ,  23 . 
     The two first protuberances  27 ,  27 ′ inward protruded from the first holding face  25  are front and rear, side by side formed. A front one of the first protuberances  27  is close to the opening of the throat  24 . The distance between the front first protuberance  27  and a bottom side  29  of the throat  24  is defined as H 1 . A rear one of the first protuberances  27 ′ is close to the bottom side  29  of the throat  24 . The distance between the rear first protuberance  27 ′ and the bottom side  29  of the throat  24  is defined as H 2 . The second protuberance  28  inward protruded from the second holding face  26  is formed. The distance between the second protuberance  28  and the bottom side  29  of the throat  24  is defined as H 3 . The second protuberance  28  of the second jaw  23  is not positioned in a central bisector M of the two first protuberances  27 ,  27 ′ of the first jaw  23 . Therefore, the triangle formed of the protuberances  27 ,  27 ′,  28  is asymmetrical, that is, is a non-isosceles triangle. 
     Referring to  FIG. 3 , the throat  24  has a working width L for receiving a threaded member. The working width L is the distance between the protuberances of the two jaws. A bottom end of the threaded member abuts against the bottom side  29  of the throat. In this embodiment, the threaded member is an ordinary hexagonal bolt  30  for illustration purposes only. 
     The first protuberances  27 ,  27 ′ of the first jaw  22  and the second protuberance  28  of the second jaw  23  together hold two lateral sides of the hexagonal bolt  30 , at which three holding points A, A′ and B are defined respectively. The lateral side of the hexagonal bolt  30 , which is held by the first protuberances  27 ,  27 ′, is defined with a front end point E 1  and a rear end point E 2 . The distance between the front end point E 1  and the holding point A is h 1 . The distance between the rear end point E 2  and the holding point A′ is h 2 . The distance h 1  is larger than the distance h 2 . The distance between the holding point B and the central bisector M of the two holding points A, A′ is h 3 . The holding point B is offset from the central bisector M to on one hand, ensure force balance relationship between the holding points A, A′, B and always keep the force unified. For example, the effort point to the threaded member can be always kept in the same position so as to minimize the possibility of slippage of the bolt. On the other hand, a moment T 1  is created by the offset between the holding point B and the central bisector M of the two holding points A, A′ to increase the wrenching force applied to the hexagonal bolt  30 . 
     In this embodiment, the second protuberance  28  of the second jaw  23  is positioned above the central bisector M of the two first protuberances  27 ,  27 ′ of the first jaw  22 , that is, positioned between the central bisector M and the first protuberance  27 . Alternatively, the second protuberance  28  of the second jaw  23  can be positioned below the central bisector M of the two first protuberances  27 ,  27 ′. 
     In this embodiment, the hexagonal bolt  30  has a side length S. The width of the hexagonal bolt  30  is equal to the working width L of the throat  24 , that is, √3S (about 1.73 S). 
       FIG. 4  shows a worn bolt  40 . In comparison with an ordinary hexagonal bolt  30 , the corners of the bolt  40  are worn and blunted. The wear ratio of the worn bolt  40  can be calculated and obtained on the basis of the distance D between the inscribed circle I of the hexagonal bolt  30  and the bottom end C 1  and the wear distance d of the worn bolt  40 . Provided that the worn bolt  40  has a wear ratio x, then the wear ratio x=(d/D)*100%, wherein D=[1−(√3/2)]S, S=(√3/3) L. Accordingly, D is about 0.077 L. 
     The distance h 3  between the holding point B and the central bisector M of the two holding points A, A′ is larger than the wear distance d of the bolt. 
     In the preferred embodiment of the present invention, the three-protuberance open-end wrench is applicable to a worn bolt  40  with a wear ratio up to about 40%, which can cover most of the wear states of the bolts. In the case that the wear ratio is 40%, the wear distance d is about 0.031 L. The bottom end C 2  of the worn bolt  40  abuts against the bottom side  29  of the throat to provide a secure wrenching condition. Accordingly, when applied to the worn bolt  40 , the distance between the front first protuberance  27  of the first jaw  22  and the bottom side  29  of the throat is preferably not larger than 0.834 L. The distance between the rear first protuberance  27 ′ of the first jaw  22  and the bottom side  29  of the throat  24  is preferably not smaller than 0.257 L. 
     In addition, the distance between the second protuberance  28  of the second jaw  23  and the bottom side  29  of the throat  24  can range from 0.257 L to 0.834 L. In this embodiment, the distance ranges from 0.577 L to 0.834 L. Preferably, the second protuberance  28  is formed in a position spaced from the bottom side  29  of the throat  24  by a distance of 0.706 L. 
     According to the above arrangement, by means of the offset between the holding point B and the central bisector M, the open-end wrench of the present invention is applicable to both an ordinary hexagonal bolt  30  and a worn bolt  40  to provide fixed effort points in the form of an asymmetrical triangle. This minimizes the possibility of slippage and makes it easier to wrench the bolt. 
     Moreover, as shown in  FIGS. 3 and 5 , the holding point B is kept spaced from the central bisector M by a distance h 3  to create moments T 1 , T 2  for increasing the wrenching force applied to the threaded member. Accordingly, the threaded member can be more easily wrenched. 
     The above embodiments are only used to illustrate the present invention, not intended to limit the scope thereof. Many modifications of the above embodiments can be made without departing from the spirit of the present invention.