Patent Document

BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a socket for tightening a workpiece with an adjustable torque. 
   2. Description of Related Art 
   Tighteners are generally used in the industry to rapidly tighten nuts, bolts or other workpieces to a receiving part. For example, tighteners may be used to secure spark plugs in internal combustion engines. Referring to  FIG. 1 , a conventional spark plug tightener  1  conventionally includes an elongated body  2  having a bottom end surface  3  in which a hole is formed with a hexagonal portion. In use, the hexagonal portion of the hole is engaged within the hexagonal casing  4  of the spark plug  5  and the rotation of the elongated body drives and secures the spark plug within the cylinder cover of the engine  6 . Rotation of the elongated body  2  may be done manually with a shaft  7  that is passed through the upper portion  8  of the elongated body  2 . 
   Generally, it is desirable to control the transmitted torque for properly securing the workpiece (e.g., the spark plug) to the receiving part (e.g., the engine). The workpiece should not be secured too tightly to ensure that the threads or the holding elements of the receiving part are not fractured or weakened, or that the workpiece is not damaged. Similarly, the workpiece should not be secured too loosely. In order to control the applied torque and to prevent the workpiece from being damaged during tightening, tighteners having a preset amount of torque may be used. Upon reaching that preset amount of torque, the tightener may be arranged to release and spin freely. Alternatively, or in addition, the tightener may include a device to create an audible sound when the torque for which it is set is reached. In this latter configuration, though, the tightener may not completely prevent the user from applying more torque after the signal is given. However, conventional tighteners having a preset amount of torque are generally expensive, heavy and difficult to use in tight environments such as that of many engines. As a result, simpler tools are used in current automotive repair environments and the degree of tightening of many workpieces, such as spark plugs, is left for the most part to the judgment of the user. 
   SUMMARY OF THE INVENTION 
   Embodiments of the invention include an adjustable over torque proof socket that is light, small and easy to use for engine repair and maintenance. 
   In an embodiment of the invention, there is provided an over torque proof socket including: a body having a driving portion adapted to be connected with a torque applying handle, and a receiving portion engageable with a rotatable workpiece, the driving portion being capable of relative rotation with respect to the receiving portion when a threshold amount of torque is exceeded, a first gear portion capable of being operatively driven by rotation of the driving portion in a fastening direction and an opposite releasing direction, a second gear portion functionally cooperable to drive the receiving portion for rotating the workpiece, the second gear portion being constructed and arranged to engage with and be driven by the first gear portion, the driving engagement between the first gear portion and the second gear portion being released when a torque required to drive the second gear portion exceeds the threshold amount of torque. The over torque proof socket also includes a biasing member that applies a force of engagement between the first gear portion and the second gear portion; and an adjusting member functionally cooperable with the biasing member to adjust a magnitude of the force of engagement between the first gear portion and the second gear portion so as to adjust the threshold amount of torque. 
   In another embodiment of the invention, there is provided an over torque proof socket including a body having a driving portion adapted to be connected with a torque applying handle, and a receiving portion engageable with a rotatable workpiece, the driving portion being capable of relative rotation with respect to the receiving portion when a threshold amount of torque is exceeded. The socket also includes a first gear portion capable of being operatively driven by rotation of the driving portion in a fastening direction and an opposite releasing direction; a second gear portion functionally cooperable to drive the receiving portion for rotating the workpiece, the second gear portion being constructed and arranged to engage with and be driven by the first gear portion. The driving engagement between the first gear portion and the second gear portion is released when a torque required to drive the second gear portion exceeds the threshold amount of torque. The socket further includes a biasing member that applies a force of engagement between the first gear portion and the second gear portion; .an adjusting member functionally cooperable with the biasing member to adjust a magnitude of the force of engagement between the first gear portion and the second gear portion so as to adjust the threshold amount of torque; and a magnetic ring configured to retain the workpiece. 
   In yet another embodiment of the invention, there is provided an over torque proof socket including a body having a driving portion adapted to be connected with a torque applying handle, and a receiving portion engageable with a rotatable workpiece, the driving portion being capable of relative rotation with respect to the receiving portion when a threshold amount of torque is exceeded. The socket also includes a first gear portion capable of being operatively driven by rotation of the driving portion in a fastening direction and an opposite releasing direction; a second gear portion functionally cooperable to drive the receiving portion for rotating the workpiece, the second gear portion being constructed and arranged to engage with and be driven by the first gear portion. The driving engagement between the first gear portion and the second gear portion is released when a torque required to drive the second gear portion exceeds the threshold amount of torque. The socket further includes a biasing member that applies a force of engagement between the first gear portion and the second gear portion; and an adjusting member functionally cooperable with the biasing member to adjust a magnitude of the force of engagement between the first gear portion and the second gear portion so as to adjust the threshold amount of torque. In this embodiment, the driving portion is constructed and arranged to be removably engaged with the first gear portion. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which corresponding reference symbols indicate corresponding parts, and in which 
       FIG. 1  is a schematic representation of a spark plug and a conventional spark plug tightener; 
       FIG. 2  is a perspective view, partly in section, of the over torque proof socket in accordance with an embodiment of the invention; 
       FIGS. 3   a - d  show several views of the main body of the socket in accordance with an embodiment of the invention; 
       FIGS. 4   a - d  show an adjusting member in accordance with an embodiment of the invention; 
       FIG. 5  shows a biasing member for use in the socket in accordance with an embodiment of the invention; 
       FIGS. 6   a - b  show several views of a workpiece retaining element in accordance with an embodiment of the invention; 
       FIG. 6   c  shows a view of a workpiece retaining element mounted to the adjusting member in accordance with an embodiment of the invention; 
       FIG. 6   d  shows a view of a workpiece retaining element mounted to the workpiece retaining portion in accordance with an embodiment of the invention; 
       FIGS. 7   a - c  show several views of the bottom gear plate for use in the socket in accordance with an embodiment of the invention; 
       FIGS. 8   a - f  show several views of the top gear plate for use in the socket in accordance with an embodiment of the invention; 
       FIG. 9  shows a steel ball for use in the socket in accordance with an embodiment of the invention; 
       FIGS. 10   a - c  show several views of an outside ring for use in the socket in accordance with an embodiment of the invention; 
       FIGS. 11   a - f  show several views of a driving portion for use in the socket in accordance with an embodiment of the invention; 
       FIG. 12  is a perspective view, partly in section, of the over torque proof socket in accordance with an embodiment of the invention; and 
       FIG. 13  is an exploded view of the over torque proof socket shown in  FIG. 12 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 2  shows a perspective view, partly in section, of the over torque proof socket, generally shown as  100 , for selectively applying a torque to a workpiece, and which embodies the principles of the present invention. In an embodiment of the invention, the workpiece is a spark plug and the over torque proof socket  100  is configured to secure the spark plug to an engine. However, it will be appreciated that the over torque proof socket  100  may be configured in other embodiments of the invention to secure any type of workpiece or fastener such as, for example, a bolt or a nut. 
     FIG. 2  shows the main components of the socket  100  which includes a body  200 . The body  200  includes a driving portion  1000  and a receiving portion, generally shown at  110 . The receiving portion  110  has at one end  112  thereof a peripheral interior surfaces  114  defining multi-faceted interior shape, for engaging a multi-faceted workpiece. In the embodiment shown, surfaces  114  define a hexagonal interior shape for engaging the hexagonal casing of a workpiece to be rotationally secured. The workpiece may be a spark plug such as the one shown in  FIG. 1 . An outside ring  900  is slideably arranged on a protruding portion, generally shown as  210 , of the receiving portion  110 . As shown, protruding portion  210  has a thinner wall thickness than portions of the body  200  therebelow. In particular, it has a smaller outer diameter to accommodate the thickness of outer ring  900 , which has an outer diameter of approximately the same dimension as the lower portions of body  200 , so that the outer surfaces are generally flush. The driving portion  1000  has a lower surface that is constructed and arranged to rest on the top radial surfaces  201  and  901  of, respectively, the receiving portion  110  and the outside ring  900 . A torque applying member, such as a conventional wrench, may be used to engage the top square cavity  1015  of the driving portion  1000  such that torque applied to the driving portion  1000  is transmitted to the body  200  to effect rotation thereof. In an embodiment, a square drive wrench such as a ratchet wrench may be used to engage the top square cavity  1015 . In another embodiment, square drive wrench handles without a ratchet may also be used to engage the top square cavity  1015 . 
   The socket  100  also includes an adjusting member  300 , a biasing member  400 , a first gear portion  700  and a second gear portion  600  that are arranged inside the body  200 . The driving portion  1000  is constructed and arranged to drive the first gear portion  700 . In the embodiment shown in  FIG. 2 , the driving portion  1000  is secured to the first gear portion  700  via a pin  1040  that is inserted into the lateral holes  1035  and  740  of respectively the driving portion  1000  and the first gear portion  700  (see  FIGS. 8   a ,  11   b  and  11   f ). The driving portion  1000  may be disengaged from the first gear portion  700  by removing the pin  1040 . In that way, the driving portion  1000  can easily be switched from one size to another, for example, from a ½″ drive to a ⅜″ drive. 
   A plurality of ball bearings  800  are arranged between the intermediate portion  710  of the first gear portion  700  and the cylindrical inner surface  230  of the protruding portion  210  of the receiving portion  110 . The ball bearings  800  are constructed and arranged to secure the first gear portion  700  to the receiving portion  110 . Specifically, the ball bearings  800  are constructed and arranged such that a portion thereof can be retained in the equally spaced holes  220  (see  FIG. 3   a ) while another portion thereof can rest on the curved lower portion  711  of the intermediate portion  710  (see  FIG. 8   d ). The curved lower portion  711  of the intermediate portion  710  may be shaped to conform the surface of the ball bearings  800 . The ball bearings  800  secure the first gear portion  700  to the receiving portion  110  despite the axial force exerted by the biasing member  400  to the first gear portion  700  via the second gear portion  600 , which force acts to move the second gear portion  600  and the first gear portion  700  towards the end  111  of the receiving portion  110 . 
   The first gear portion  700  is engaged with the second gear portion  600 . The second gear portion  600  is rotationally secured within the receiving portion  110  so that rotation of the second gear portion  600  about axis AA′ rotates the receiving portion. The rotation of the second gear portion  600  is translated into rotational movement of the receiving portion  110  as a result of the conforming shapes of the exterior surface  615  of the second gear portion  600  and interior surface portion  250  of receiving portion  110 . These conforming surface shapes prevent relative rotation between parts, but permit some degree of axial movement of second gear portion  600  relative to receiving portion  110 . 
   The first gear portion  700  and the second gear portion  600  are provided at their confronting faces with a plurality of teeth  720 ,  620 , which, as viewed in one direction of turning the socket  100 , have flanks  721 ,  630 , of shallow inclination and, as viewed in the opposite direction, have sharp flanks  722 ,  635 . In the tightening or fastening direction (labeled as “T” in  FIG. 2 ), the flanks of shallow inclination  721  of the first gear portion  700  are biased against the flanks of shallow inclination  630  of the second gear portion  600 . By contrast, in the loosening or releasing direction (labeled as “L” in  FIG. 2 ), the sharp flanks  722  of the first gear portion  700  are biased against the sharp flanks  635  of the second gear portion  600 . The biasing member  400  is slideably arranged inside the body  200  and biases at one end thereof (e.g.,  405 ) the lower surface  625  of the second gear portion  600  and rests at the other end thereof (e.g.,  410 ) on an end bearing surface  330  of the adjusting member  300 . The biasing member  400  and the adjusting member  300  are intended to work in unison to set the desired threshold level of torque for the socket  100 . 
   Operation of the socket  100  will now be described in greater detail with reference to  FIGS. 3-11 . The adjusting member  300  is provided with an exterior surface threaded portion  310  that is received by threads  241  formed on an exterior surface portion  240  of the receiving portion  110 . In addition, the adjusting member  300  has a hexagonal cavity  320  defined by six surfaces  321  (see  FIG. 4   b , illustrated three of such surfaces). The cavity  320  is accessible through the open end  112  of the body  200 . Engaging the hexagonal surfaces defining cavity  320  enables adjusting member  300  to be screwed up or down inside the body  200  in order to set the required level of torque. A displacement of the adjusting member  300  toward the driving portion  1000  compresses the biasing member  400 , thereby increasing its level of stress. Conversely, a displacement of the torque adjusting member  300  toward the opposite end  112  of the body  200  loosens the biasing member  400 , thereby reducing its level of stress. The biased force exerted by the biasing member  400  on the second gear portion  600  is transmitted to the first gear portion  700 . 
   As the driving portion  1000  is rotated in the tightening or fastening direction with a torque applying member, such as a wrench, it directly drives the first gear portion  700 , which is rotationally fixed relative to the driving portion  1000 . Since the plurality of teeth  720  of the first gear portion  700  are engaged with the plurality of teeth  620  of the second gear portion  600 , rotation of the first gear portion  700  drives the second gear portion  600 , which in turn drives the receiving portion  110  until the torque exerted by the torque applying member exceeds the torsional resistance offered by the biasing member  400  via the engagement between the first and second gear portions  700  and  600 . During rotation of the socket  100  in the tightening or fastening direction, the flanks of shallow inclination  721  of the first gear portion  700  will begin to slide over the flanks of shallow inclination  630  of the second gear portion  600 , as the threshold force set by the adjusting member  300  is approached. 
   Specifically, the engaged shallow flank surfaces apply an axial force upon second gear portion  600 . When that force increases towards the threshold level set by the axial position of adjusting member  300 , the spring  400  starts to compress under the force of axial movement of second gear portion  600 , which axial movement is imparted to second gear portion  600  through the forced engagement between the shallow teeth surfaces  721 ,  630  of first and second gear portion  700  and  600 . 
   Upon exceeding the torsional resistance offered by the biasing member  400 , the plurality of teeth  720  on the first gear portion  700  disengage from the plurality of teeth  620  on the second gear portion  600  and the manual force applied by the torque applying member rotates the assembly formed by the driving portion  1000  and the first gear portion  700  relative to the receiving portion  110 . Conversely, when the driving portion  1000  is rotated in the loosening direction or the releasing direction, i.e., the direction opposite the tightening direction, the sharp flanks  722  of the first gear portion  700  are forced against the sharp flanks  635  of the second gear portion  600  such that substantially no axial forces are transmitted to second gear portion  600  and no slippage between the first gear portion  700  and the second gear portion  600  can occur. In one embodiment, the sharp flank surfaces  722  and  635  are parallel to the axis AA′ of the device  100 . 
   Referring now to  FIGS. 3   a - d , these figures show different views of the receiving portion of the socket  100  in accordance with an embodiment of the invention. The receiving portion  110  includes a cylindrical housing  205 , which at the upper end thereof is provided with the protruding portion  210  at the indicated recess  215 . The protruding portion  210  includes a cylindrical outer surface  225  and a cylindrical inner surface  230 , which are provided with a plurality of equally spaced holes  220 . The plurality of equally spaced holes  220  are constructed and arranged to receive a portion of the ball bearings  800 , while another portion thereof is arranged in the intermediate portion  710  of the first gear portion  700 . The curved lower portion  711  of the intermediate portion  710  may be shaped to conform the surface of the ball bearings  800 . The ball bearings  800  secure the first gear portion  700  to the receiving portion  110 . 
   As best seen in  FIG. 3   b , the interior part of the cylindrical housing  205  also includes a lower portion  235 , the intermediate threaded portion  240 , a cylindrical housing  245 , and an upper surface portion  250 . The lower portion  235  of the receiving portion  110  is constructed and arranged to engage the casing of the workpiece to effect rotation thereof. In  FIGS. 3   a - d , the inner wall or surfaces  114  of the lower portion  235  is hexagonally shaped. However, it will be appreciated that any shape suitable to engage the casing of the spark plug may be used for the lower portion  235 . 
   Referring now more particularly to  FIGS. 4   a - d , the intermediate threaded portion  240  is configured to receive the external threaded portion  310  of the adjusting portion  300 . The adjusting member  300  consists of a cylindrical hollowed housing  305  including at one end thereof the external threaded portion  310 . The inner part of the cylindrical hollowed housing  305  is substantially divided between a first portion  320  having an hexagonal shaped wall defined by surfaces  321  and a second portion  325  having a cylindrical shaped wall. The first portion  320  is dimensioned so as to receive the correspondingly shaped surfaces of the workpiece, e.g., a spark plug, during operation of the socket  100 . The adjusting member  300  is rotated by detachable connection with, for example, a ratchet via a head thereof which fits into the cavity formed by the first portion  320 . The cylindrical hollowed housing  305  includes an end bearing surface  330  that is arranged at one end of the external threaded portion  310 . The bearing surface  330  extends inwardly from the external threaded portion  310  to the hexagonal shaped wall of the second portion  325  and is configured to bear one end of the biasing member  400  shown in  FIG. 5 . 
   As can be seen in  FIG. 5 , the biasing member  400  may be a compression spring. In one embodiment, the spring comprises between two and three coils. The compression spring  400  is grounded at both extremities thereof to provide a first flat extremity  405  and a second flat extremity  410 . One of the first and second flat extremities  405  and  410  rests on the aforementioned bearing surface  330  of the driving member  300 , while the other extremity is configured to bias the bottom gear plate  600 , shown in  FIG. 7 , so as to keep the second gear portion engaged with the first gear portion  700 . The ground surfaces increase the surface area of contact between the compression spring  400  and the second gear portion  600  or the torque adjusting member  300 . As a result, the efforts generated by rotation of the torque adjusting member  300  will be more equally distributed throughout the compression spring  400  and the second gear portion  600 . 
   The biasing member  400  is dimensioned so as to be slideably arranged within the cylindrical housing  245  of the receiving member shown in  FIG. 3 . As the adjusting member  300  is screwed up in the direction of the driving portion  1000  shown in  FIG. 2 , the stress level in the biasing member  400 , or compression spring, is increased. The assembly formed by the biasing member  400  and the adjusting member  300  may be calibrated to inform the operator of the socket  100  of the target torque at which the socket  100  operates. To that effect, markings  335  showing the target torque may be provided on the exterior surface of the cylindrical hollowed housing  305 . Such markings may be visible through a window  255  arranged in the body  200  of the socket. In an embodiment of the invention, a transparent cap  256  may be inserted in the window  255  to protect the markings  335  during operation of the socket  100 . 
   A workpiece retaining element  500  may be used in an embodiment of the invention to retain the workpiece once it is removed, e.g., to retain the spark plug. The workpiece retaining element  500  may be a magnetic ring such as the one shown in  FIGS. 6   a - b , which is slideably inserted around the exterior surface of the cylindrical hollowed housing  305 , as shown in  FIG. 6   c . Alternatively, the workpiece retaining element  500  may be an o-ring arranged in the lower portion  205  of the receiving portion  110 , as shown in  FIG. 6   d . Where a magnetic ring is used for the retaining element  500 , as shown in  FIG. 6   c , the magnetic ring  500  includes an outer wall  510  and an inner wall  505  that has substantially the same diameter as that of the exterior surface of the cylindrical hollowed housing  305 . The magnetic ring  500  may be positioned so as not to impair reading of the markings  335  through the window  255 . Alternatively, the magnetic ring  500  may be positioned proximate the threaded portion  310  of the cylindrical hollowed housing  305  and the markings may be provided on the magnetic ring  500 . 
     FIGS. 7   a - c  show several views of the second gear portion  600  in accordance with an embodiment of the invention. The second gear portion  600  includes a cylindrical inner wall portion  605  and an outer wall portion  615  having a male hexagonal spline. The male hexagonal spline consists of a plurality of arcs  610 , which define the contour of the outer wall portion  615 . In this embodiment of the invention, the male hexagonal spline includes six connected arcs  610  that have substantially the same radius of curvature. However, it will be appreciated that a second gear portion  600  with a male polygonal spline including fewer or more than six arcs can also be used in another embodiment of the invention. 
   The second gear portion  600  includes a plurality of teeth  620  provided at one end thereof and a bias surface  625 , which is contacted by one of the first and second flat extremities  405  and  410  of the biasing member  400 . The teeth  620  have a trapezoidal shape and extend from the outer wall portion  615  to the cylindrical inner wall portion  605  of the second gear portion  600 . The teeth  620  also have flanks of shallow inclination  630  and sharp flanks  635  that are substantially perpendicular to the upper surface  640  that extends between adjacent teeth. The second gear portion  600  is arranged in the upper portion  250  of the receiving portion  110 . The interior wall of the upper portion  250  includes a corresponding polygonal spline to prevent rotation of the second gear portion  600 . It will be appreciated that a different outer wall profile and corresponding interior wall of, respectively, the second gear portion  600  and the receiving portion  110  may also be used in other embodiments of the invention. 
   The plurality of teeth  620  of the second gear portion  600  are configured to engage the corresponding plurality of teeth  720  of the first gear portion, generally shown as  700  in  FIGS. 8   a - f . The first gear portion  700  has a cylindrical hole formed therethrough and includes an upper portion  705 , the intermediate portion  710 , and a toothed circular plate  715  on which the corresponding plurality of teeth  720  is provided. The intermediate portion  710  is arranged at the indicated recess  725  between the upper portion  705  and the toothed circular plate  715 . The inner wall  730  defining the hole extends from one end  723  to the other end  724  of the first gear portion  700 . The outer wall upper portion  705  has a generally cylindrical shape on which two parallel flat portions  735  and  740  are provided. The flat portion  735  includes a lateral hole  741  formed therethrough for attachment, via a pin  1040 , with the driving portion  1000  shown in  FIG. 11 . 
   The first gear portion  700  is arranged within the protruding portion  230  of the receiving portion  110  and abuts the second gear portion  600 , as best seen in  FIG. 2 . A plurality of ball bearings  800  having a portion thereof retained by the plurality of holes  220  are disposed within the intermediate portion  710  to secure the first gear portion  700  to the receiving portion  110 .  FIG. 9  shows a steel ball that can be used in an embodiment of the invention. In another embodiment, cylindrical rollers may be substituted for the ball bearings  800  to secure the first gear portion  700  to the receiving portion  110 . Specifically, the cylindrical rollers may be constructed and arranged such that a first end portion thereof is retained in the plurality of holes  220  while a second end portion thereof is engaged with the intermediate portion  710  of the first gear plate  700 .  FIGS. 10   a - c  show the outside ring  900  that is slideably arranged on the outer portion  225  of the receiving portion  110 . 
   Referring now to  FIGS. 11   a - e , these figures show several views of the driving portion that is constructed and arranged to be cooperatively engaged with the first gear portion  700  to drive the receiving portion  110 . The driving portion, generally shown as  1000 , may be a hexagonal cap that includes a hexagonal portion  1005  having an outward flange  1010  at one end thereof. The driving portion  1000  includes a first cavity  1015  provided at a first end thereof and a second cavity  1020  provided at a second end thereof. The second cavity  1020  has a generally cylindrical interior wall with parallel flat portions  1025  and  1030  that is configured to engage the upper portion  705  of the first gear portion  700 . The driving portion  1000  is rotated by detachable connection with a head of a ratchet (not shown) that engages the first cavity  1015 . Lateral recesses  1017  may be arranged on each side  1016  of the first cavity  1015 . Those lateral recesses  1017  may be used to cooperate with protruding portions of the ratchet head (not shown) to secure such head to the driving portion  1000 . A lateral hole  1035  is formed through the flat portion  1025  to cooperate with the lateral hole formed in the flat portion  735  of the first gear portion  700 . A pin  1040  may be used to secure the first gear portion  700  with the hexagonal cap  1000 , as shown in  FIG. 11   f.    
   The assembly formed by the second gear portion  600  and the first gear portion  700  enables the operator to accurately control tightening/fastening of the workpiece. In the tightening or fastening direction, the shallow inclined flanks  721  of the first gear portion  700  are forced against the shallow inclined flanks  730  of the second gear portion  600 . The inclination of these flanks may in the range of about 111°-121° in an embodiment of the invention. When the torque transmitted by a torque applying member to the first gear portion  700 , via the driving portion  1000 , reaches the target or threshold torque exerted by the biasing portion  400 , the shallow inclined flanks  721  of the top gear plate  700  begin to slide over the shallow inclined flanks  730  of the second gear portion  700 . Upon exceeding the target torque, the plurality of teeth  720  of the first gear portion  700  disengage from the plurality of teeth  620  of the second gear portion  600  and the assembly formed by the first gear portion  700  and the driving portion  1000  freely rotates about the central axis A-A′ of the body  200 . In the loosening direction, the plurality of teeth  720  of the first gear portion  700  remains engaged with the plurality of teeth  620  of the second gear portion  600  irrespective of the applied torque because the sharp flanks  722 ,  635  prevent any slippage between these two portion. 
     FIGS. 12 and 13  show respectively a perspective view, partly in section, and an exploded view of the over torque proof socket  100 ′ in accordance with another embodiment of the invention. Similarly to the embodiment shown in  FIG. 2 , the socket  100 ′ includes a body  200 ′, which includes a driving portion  1000 ′ and a receiving portion, generally shown at  110 ′. The workpiece receiving portion  110 ′ has at one end  112 ′ thereof a peripheral interior surfaces  114 ′ defining multi-faceted interior shape, for engaging a multi-faceted workpiece. In the embodiment shown, surfaces  114 ′ define a hexagonal interior shape for engaging the hexagonal casing of a workpiece to be rotationally secured. The workpiece may be a spark plug such as the one shown in  FIG. 1 . 
   An outer cylindrical ring  1200  is slideably arranged on a protruding portion, generally shown as  210 ′, of the receiving portion  110 ′. As shown in  FIG. 12 , when the outer cylindrical ring  1200  is fully engaged with the protruding portion  210 ′, the outer cylindrical ring  1200  abuts the recess portion  215 ′ such that the bottom radial surface  1202  of the cylindrical ring  1200  rests on the recess portion  215 ′ of the receiving portion  110 ′. As shown, protruding portion  210 ′ has a thinner wall thickness than portions of the body  200 ′ therebelow. In particular, protruding portion  210 ′ has a smaller outer diameter to accommodate the thickness of outer cylindrical ring  1200 , which has an outer diameter of approximately the same dimension as the lower portions of body  200 ′, so that the outer surfaces are generally flush. The driving portion  1000 ′ has a lower surface that is constructed and arranged to rest on the top radial surfaces  201 ′ and  1201  of, respectively, the receiving portion  110 ′ and the outer cylindrical ring  1200 . A torque applying member, such as a conventional wrench, may be used to engage the top square cavity  1015 ′ of the driving portion  1000 ′ such that torque applied to the driving portion  1000 ′ is transmitted to the body  200 ′ to effect rotation thereof. In an embodiment, a square drive wrench such as a ratchet wrench may be used to engage the top square cavity  1015 ′. In another embodiment, square drive wrench handles without a ratchet may also be used to engage the top square cavity  1015 ′. 
   Similarly to the embodiment of  FIG. 2 , the socket  100 ′ also includes an adjusting member  300 ′, a biasing member  400 ′, a first gear portion  700 ′ and a second gear portion  600 ′ that are arranged inside the body  200 ′. The driving portion  1000 ′ is constructed and arranged to drive the first gear portion  700 ′. In the embodiment shown in  FIGS. 12-13 , the driving portion  1000 ′ is secured to the first gear portion  700 ′ via a pin  1040 ′ that is inserted into the lateral holes  1035 ′ and  740 ′ of respectively the driving portion  1000 ′ and the first gear portion  700 ′. The driving portion  1000 ′ may be disengaged from the first gear portion  700 ′ by removing the pin  1040 ′. 
   As can be seen in  FIGS. 12-13 , a plurality of linear rollers  800 ′ are arranged between the intermediate portion  710 ′ of the first gear portion  700 ′ and the cylindrical inner surface  250 ′ of the protruding portion  210 ′ of the receiving portion  110 ′. The linear rollers  800 ′ have a generally cylindrical shape and are constructed and arranged to secure the first gear portion  700 ′ to the receiving portion  110 ′. Specifically, the linear rollers  800 ′ are constructed and arranged such that a first end portion thereof  801 ′ is retained in the equally spaced holes  220 ′ located on the protruding portion  210 ′ while a second end portion thereof  802 ′ is engaged with the intermediate portion  710 ′ of the first gear plate  700 ′. 
   In this embodiment, the intermediate portion  710 ′ is dimensioned to receive the second end portion  802 ′ and has a height (labeled as “H” in  FIG. 12 ) that is slightly larger than a diameter of the linear rollers  800 ′. The first end portion  801 ′ of the linear rollers  800 ′ is slideably arranged within the equally spaced holes  220 ′ such that the linear rollers  800 ′ are allowed to rotate about their longitudinal axis that extends from the first end portion  801 ′ to the second end portion  802 ′. 
   The linear rollers  800 ′ secure the first gear portion  700 ′ to the receiving portion  110 ′ despite the axial force exerted by the biasing member  400 ′ to the first gear portion  700 ′ via the second gear portion  600 ′, which force acts to move the second gear portion  600 ′ and the first gear portion  700 ′ towards the end  111 ′ of the receiving portion  110 ′. The axial force exerted by the biasing member  400 ′ applies a force of engagement between the bottom surface  711 ′ of the intermediate portion  710 ′ and the linear rollers  800 ′, such that when the first gear plate  700 ′ rotates about the AA′ axis, the linear rollers  800 ′ rotate about their longitudinal axis. During rotation of the linear rollers  800 ′ about their longitudinal axis, the second end portion  802 ′ of each roller  800 ′ rolls over the bottom surface  711 ′ of the intermediary portion  710 ′. 
   The first gear portion  700 ′ is engaged with the second gear portion  600 ′. The second gear portion  600 ′ is rotationally secured within the receiving portion  110 ′ via a plurality of cylindrical wedges  1205  so that rotation of the second gear portion  600 ′ about axis AA′ rotates the receiving portion  110 ′. The inner surface  250 ′ of the protruding portion  210 ′ is substantially cylindrical and is configured to receive the exterior surface  615 ′ of the second gear plate  600 ′. The cylindrical wedges  1205  are constructed and arranged such that a portion thereof is retained in the equally spaced holes  1215 , which are radially arranged on the exterior surface  615 ′ of the second gear plate  600 ′, while another portion thereof is retained in the equally spaced holes  1210 , which are radially arranged on the protruding portion  210 ′ of the retaining portion  110 ′. 
   In the embodiment shown in  FIGS. 12-13 , the wedges  1205  are arranged such that an end portion  1206  of the wedges  1205  and the outer surface of the protruding portion  210 ′ are substantially flush. Similarly, the outer cylindrical ring  1200  is constructed and arranged to be slideably arranged within the protruding portion  210 ′ and has an outer diameter of approximately the same dimension as the lower portions of body  200 ′, so that the outer surfaces are generally flush. 
   Operation of the socket  100 ′ is performed substantially the same way as in the embodiment of the  FIG. 2 . The adjusting member  300 ′ is provided with an exterior surface threaded portion  310 ′ that is received by threads formed on an exterior surface portion of the receiving portion  110 ′ (not shown in  FIGS. 12-13 ). The adjusting member  300 ′ may be screwed up or down inside the body  200 ′ in order to set the required level of torque. A displacement of the adjusting member  300 ′ toward the driving portion  1000 ′ compresses the biasing member  400 ′, thereby increasing its level of stress. Conversely, a displacement of the torque adjusting member  300 ′ toward the opposite end  112 ′ of the body  200 ′ loosens the biasing member  400 ′, thereby reducing its level of stress. The biased force exerted by the biasing member  400 ′ on the second gear portion  600 ′ is transmitted to the first gear portion  700 ′. 
   As the driving portion  1000 ′ is rotated in the tightening or fastening direction with a torque applying member, such as a wrench, it directly drives the first gear portion  700 ′, which is rotationally fixed relative to the driving portion  1000 ′. Since the plurality of teeth  720 ′ of the first gear portion  700 ′ are engaged with the plurality of teeth  620 ′ of the second gear portion  600 ′, rotation of the first gear portion  700 ′ drives the second gear portion  600 ′, which in turn drives the receiving portion  110 ′ until the torque exerted by the torque applying member exceeds the torsional resistance offered by the biasing member  400 ′ via the engagement between the first and second gear portions  700  and  600 . During rotation of the socket  100 ′ in the tightening or fastening direction, the flanks of shallow inclination  721 ′ of the first gear portion  700 ′ will begin to slide over the flanks of shallow inclination  630 ′ of the second gear portion  600 ′, as the threshold force set by the adjusting member  300 ′ is approached. 
   Specifically, the engaged shallow flank surfaces apply an axial force upon second gear portion  600 ′. When that force increases towards the threshold level set by the axial position of adjusting member  300 ′, the spring  400 ′ starts to compress under the force of axial movement of second gear portion  600 ′, which axial movement is imparted to second gear portion  600 ′ through the forced engagement between the shallow teeth surfaces  721 ′,  630 ′ of first and second gear portion  700 ′ and  600 ′. 
   Upon exceeding the torsional resistance offered by the biasing member  400 ′, the plurality of teeth  720 ′ on the first gear portion  700 ′ disengage from the plurality of teeth  620 ′ on the second gear portion  600 ′ and the manual force applied by the torque applying member rotates the assembly formed by the driving portion  1000 ′ and the first gear portion  700 ′ relative to the receiving portion  110 ′. Conversely, when the driving portion  1000 ′ is rotated in the loosening direction or the releasing direction, i.e. the direction opposite the tightening direction, the sharp flanks  722 ′ of the first gear portion  700 ′ are forced against the sharp flanks  635 ′ of the second gear portion  600 ′ such that substantially no axial forces are transmitted to second gear portion  600 ′ and no slippage occur between the first gear portion  700 ′ and the second gear portion  600 ′. 
   The assembly formed by the biasing member  400 ′ and the adjusting member  300 ′ may be calibrated to inform the operator of the socket  100 ′ of the target torque at which the socket  100 ′ operates. To that effect, markings  335 ′ showing the target torque may be provided on the exterior surface of the cylindrical hollowed housing  305 ′. Such markings may be visible through a circular window  255 ′ arranged in the body  200 ′ of the socket  100 ′. 
   It will be appreciated that the present invention is not limited to the sockets  100 ,  100 ′. Other arrangements are contemplated which can accommodate control of the tightening of a spark plug or any other workpiece or device for which it is desirable to control torque during tightening. The foregoing specific embodiments have been provided to illustrate the structural and functional principles of the present invention and are not intended to be limiting. To the contrary, the present invention is intended to encompass all modifications, alterations, and substitutions within the spirit and scope of the appended claims.

Technology Category: 7