Patent Publication Number: US-2005135898-A1

Title: Screw and screw driver

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is a divisional application of commonly-owned U.S. patent application Ser. No. 10/385,133, filed on Mar. 10, 2003, entitled “Screw and Screw Driver”. 
    
    
     BACKGROUND  
      1. Field of the Invention  
      The present invention relates to screws and screw drivers and, more particularly, to screws and screwdrivers of the bore and pin variety.  
      2. Related Art  
      Various kinds of screws and screw drivers are well known in the art. Referring to  FIG. 1 , for example, a conventional flat-head screwdriver  100  and slot-head screw  108  are shown. The screwdriver  100  includes a generally cylindrical grip  102 , a cylindrical shank  104 , and a flat tapered blade  106  aligned along a central axis  130 . The screw  108  includes a generally flat and round head  110  at the end of a shank  114 . A slot  112  bisects the surface of the head  110 .  
      The screwdriver  100  may be grasped by the grip  102  and the blade  106  guided to engage the slot  112 . Torque may then be applied, typically in a clockwise direction  118 , to drive the screw  108  through a material (not shown). Threads  116  on the shank  114  of the screw  108  provide added shear for driving the screw  108 .  
      One problem with the conventional flat-head screwdriver  100  is that the blade  106  is susceptible to slippage within the slot  112 . Small amounts of slippage make it more difficult to drive the screw  108 , while larger amounts of slippage may cause the blade  106  to disengage from the slot  112  entirely. After each such disengagement, the blade  106  must manually be reengaged in the slot  112 , making the process of driving the screw  108  tedious and time-consuming. The problem of slippage may be mitigated by shortening the length of the slot  112 , but at the cost of reducing the torque applied to the screw  108  and making it more difficult to engage the blade  106  in the slot  112 . Although conventional Phillips-head screws and screwdrivers address the problem of slippage by incorporating cross-shaped slot and screwdriver heads, they present the same difficulty of initially positioning the screwdriver blade within the screw slot.  
      Referring to  FIG. 2A , a conventional dual-pin screwdriver  200  is shown for use with a dual-bore screw  208 . Like the conventional flat-head screwdriver  100 , the dual-pin screwdriver  200  includes a generally cylindrical grip  202  and a cylindrical shank  204 . Instead of a blade, however, the screwdriver  200  includes a pair of opposing pins  206   a - b , spaced-equidistant from central axis  230 .  
      Like the flat-head screw  108 , the screw  208  includes a generally flat and round head  210  at the end of a shank  214 . Instead of a slot, however, the screw  208  includes a pair of opposing cylindrical bores  212   a - b , spaced equidistant from central axis  230 .  
      The screwdriver  200  may be grasped by the grip  202  and the pins  206   a - b  guided so that they engage bores  212   a  and  212   b , respectively. Torque may then be applied, typically in a clockwise direction  218 , to drive the screw  208  through a material (not shown). Threads  216  on the shank  214  of the screw  208  provide added shear for driving the screw  208 .  
      Although the screwdriver  200  and screw  208  solve the problem of lateral slippage, their use requires that the two pins  206   a - b  be manually engaged in the two bores  212   a - b . This may require significant hand-eye coordination and therefore make the process of engaging the screwdriver  200  with the screw  208  difficult.  
      Referring to  FIG. 2B , a conventional single-pin screwdriver  250  is shown for use with a single-bore screw  258 . The single-pin screwdriver  250  includes a generally cylindrical grip  252  and a cylindrical shank  254 . Instead of two pins, however, the screwdriver  250  includes a single centrally-located pin  256  having a square cross-section. Although conventional screwdrivers of this variety may use shapes other than squares (such as hexagons), to apply the necessary torque the pin  256  must not be circular.  
      Screw  258  includes a generally flat and round head  260  at the end of a shank  264 . The screw  258  includes a single bore  262  located along central axis  280 .  
      The screwdriver  250  may be grasped by the grip  252  and the pin  256  guided so that it engages bore  262 . Torque may then be applied, typically in a clockwise direction  268 , to drive the screw  258  through a material (not shown). Threads  266  on the shank  264  of the screw  258  provide added shear for driving the screw  258 .  
      Referring to  FIG. 3 , a conventional square-head screwdriver  300  is shown for use with a square-head screw  308 . Like the conventional flat-head screwdriver  300 , the square-head screwdriver  300  includes a generally cylindrical grip  302  and a cylindrical shank  304 . Instead of a blade, however, the screwdriver  300  includes a hollow square head  306  forming a cavity  332  having a square cross-section. The screw  308  includes a square head  310  at the end of a shank  314 .  
      The screwdriver  300  may be grasped by the grip  302  and the screwdriver head  306  guided so that it engages the screw head  310 . Torque may then be applied, typically in a clockwise direction  318 , to drive the screw  308  through a material (not shown). Threads  316  on the shank  314  of the screw  308  provide added shear for driving the screw  308 . The heads  306  and  310  may be polygonal shapes other than squares, such as hexagons.  
      Although the screwdriver  300  and screw  308  are easier to engage and are less prone to slippage than the screwdrivers  100  and  200  and screws  108  and  208  illustrated in  FIGS. 1 and 2 , respectively, the square head  310  of the screw  308 , when exposed on the surface into which the screw  308  has been driven, may present a facade that is less aesthetically pleasing than the circular face of the flat-head screw  108 . Screws having circular faces, however, require slots (as in the case of the slot  112  in the flat-head screw  108 ), dual and symmetrical opposing bores (as in the case of the bores  212   a - b  in the screw  208 ), or a central but non-circular bore (as in the case of the bore  262  in the screw  258 ) to apply the techniques of the prior art. Screws having such features have the disadvantages described above.  
      What is needed, therefore, is a combination of screw and screwdriver which are easily engaged with each other, not prone to slippage, and which result in an aesthetically pleasing exposed screw face.  
     SUMMARY  
      Various screws and corresponding screwdrivers are disclosed. For example, in one embodiment a screwdriver having a single, circular, non-axial pin is disclosed, and a corresponding screw having a single, circular, non-axial bore is disclosed. In another embodiment, a screwdriver (and corresponding screw) having a plurality of pins arranged asymmetrically about the central axis of the screwdriver is disclosed. In yet another embodiment, a screwdriver (and corresponding screw) having an irregularly-shaped and centrally-located pin is disclosed. Techniques for combining these and other features in various ways are also disclosed.  
      One aspect of the present invention features a screw that includes a threaded shank having a lengthwise central axis and a head coupled to one end of the shank. The head includes a forward surface and a single bore. The single bore defines a region forming a gap in the forward surface. The centroid of the region is located a non-zero distance from the central axis. The bore may, for example, be circular. Another aspect of the present invention features a screwdriver for driving the screw just described. The screwdriver includes a grip, a shank coupled at one end to the grip and having a first lengthwise central axis, and a single pin coupled to the other end of the shank and having a second lengthwise central axis, wherein the first and second lengthwise central axes are not coincident. The screwdriver may include a head coupled at a first end to the other end of the shank and at a second end to the single pin. The head may include a guide-skirt having an inner surface defining a depression in the head, and the single pin may extend outward from the depression.  
      Another aspect of the present invention features a screw including a threaded shank having a lengthwise central axis and a head coupled to one end of the shank. The head includes a forward surface and at least two bores, which may be circular, non-circular, or a combination thereof. The at least two bores define at least two regions forming at least two gaps in the forward surface. The centroids of the at least two regions are located asymmetrically about the central axis. In another aspect of the present invention, a screwdriver is provided which includes pins appropriately shaped and arranged to engage the bores of the screw just described.  
      Another aspect of the present invention features a screw including a threaded shank having a lengthwise central axis and a head coupled to one end of the shank. The head includes a forward surface and at least one bore. The at least one bore defines at least one region forming at least one gap in the forward surface. The at least one region has an outline (such as a letter of the alphabet) that is not a regular polygon. In another aspect of the present invention, a screwdriver is provided which includes one or more pins appropriately shaped and arranged to engage the one or more bores of the screw just described.  
      Another aspect of the present invention features a screw including a threaded shank having a lengthwise central axis and a head coupled to one end of the shank. The head includes a forward surface and at least three bores. The at least three bores define at least three regions forming at least three gaps in the forward surface. The centroids of the at least three regions are located symmetrically about the central axis. In another aspect of the present invention, a screwdriver is provided which includes pins appropriately shaped and arranged to engage the bores of the screw just described.  
      Other features and advantages of various aspects and embodiments of the present invention will become apparent from the following description and from the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of a prior art flat-head screwdriver and screw;  
       FIG. 2A  is a perspective view of a prior art dual-pin screwdriver and screw;  
       FIG. 2B  is a perspective view of a prior art single-pin screwdriver and screw;  
       FIG. 3  is a perspective view of a prior art square-head screwdriver and screw;  
       FIG. 4  is a perspective view of a single-pin screwdriver according to a first embodiment of the present invention;  
       FIG. 5  is a perspective view of a single-bore screw for use with the screwdriver of  FIG. 4  according to the first embodiment of the present invention;  
       FIG. 6  is a perspective view of the screwdriver of  FIG. 4  in engagement with the screw of  FIG. 5  according to the first embodiment of the present invention;  
       FIG. 7  is a perspective view of a single-pin screwdriver according to a second embodiment of the present invention;  
       FIG. 8  is a perspective view of a single-bore screw for use with the screwdriver of  FIG. 4  according to the second embodiment of the present invention;  
       FIG. 9  is a perspective view of the screwdriver of  FIG. 4  in engagement with the screw of  FIG. 5  according to the second embodiment of the present invention;  
       FIG. 10  is a perspective view of a single-pin screwdriver according to a third embodiment of the present invention;  
       FIG. 11  is a perspective view of a single-bore screw for use with the screwdriver of  FIG. 10  according to the third embodiment of the present invention; and  
       FIG. 12  is a perspective view of the screwdriver of  FIG. 10  in engagement with the screw of  FIG. 11  according to the second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION  
      Referring to  FIG. 4 , a single-pin screwdriver  400  is shown according to one embodiment of the present invention. The screwdriver  400  includes a generally cylindrical grip  402 , a cylindrical shank  404 , and a head  406 . A guide-skirt  411  on the head  406  has an inner surface  410  which defines a depression for engaging a corresponding screw (see  FIG. 5 , below). Central axis  414  intersects surface  412  at the center  416  of surface  412 . A single non-axial pin  408  extends from forward surface  412  of head  406 . Pin  408  is offset from center  416  by a distance which may be freely chosen.  
      Referring to  FIG. 5 , a single-bore screw  420  is shown for use with the screwdriver  400  according to one embodiment of the present invention. The screw  420  includes a generally flat and round head  422  at the end of a shank  426 . The screw  420  includes a single cylindrical bore  424  extending into the head  422  from forward surface  434  of head  422 . Central axis  430  intersects surface  434  at the center  432  of surface  434 . Bore  424  is offset from center  432  by a distance which is equal to the distance of pin  408  from the center  416  of the forward surface  412  of the screwdriver  400  ( FIG. 4 ). Bore  424  may or may not penetrate through the full depth of head  422 , may or may not overlap in whole or in part with the shank  426 , and may or may not penetrate into the shank  426 .  
      Referring to  FIG. 6 , the screwdriver  400  of  FIG. 4  is shown in engagement with the screw  420  of  FIG. 5  according to one embodiment of the present invention. The screwdriver  400  may be grasped by the grip  402  and the head  406  guided so that the pin  408  engages the bore  424  and so that the screw head  422  engages the depression in the screwdriver head  406 . The inner diameter of the guide-skirt  411  is equal to or slightly larger than the diameter of the screw head  422 .  
      Torque may then be applied to the grip  402 , typically in a clockwise direction  440  about central axis  414 . Torque is transferred through the pin  408  to the inner surface of bore  424 , thereby causing the screw  420  to rotate and be driven through a material (not shown). Threads  428  on the shank  426  of the screw  420  provide added shear for driving the screw  420 . Engagement of the screw head  422  in the guide-skirt  411  prevents lateral slippage of the screw  420  while it is being driven.  
      The limits of the torque applied by the screwdriver  400  derive from materials strengths and dimensions. In particular, the shear strength of the pin or bore materials must be matched to the forces applied. If the width of the screwdriver skirt  1011  is minimized in order to allow close spacing between screw heads and mechanical obstacles, then the strength of the skirt  1011  must be carefully accounted for as well. In general, the pin and skirt materials should be harder than the bore material since the screwdriver  400  is typically used to drive many screws and therefore must be more durable than the bore material against both wear and accidental breakage. The shear forces on the pin  408  and bore  424  are directly proportional to the torque applied divided by the distance from the bore  424  and pin  408  to the central axis  1014 . Thus, given constant constraints on materials, designs in which the bore  424  and pin  408  are farther from the central axis  1014  will allow greater torque to be applied to driving the screw  420 . Shear strength of the pin  408  and bore  424  also increase with increasing cross-sectional area. Therefore, larger-diameter pins and bores will allow greater torques to be applied.  
      Referring to  FIG. 7 , a single-pin screwdriver  700  is shown according to one embodiment of the present invention. Like the screwdriver  400  illustrated in  FIG. 4 , the screwdriver  700  includes a generally cylindrical grip  702 , a cylindrical shank  704 , and a head  706 . A guide-skirt  711  on the head  706  has an inner surface  710  which defines a depression for engaging a corresponding screw (see  FIG. 8 , below). As with screwdriver  400 , central axis  714  intersects surface  712  at the center  716  of surface  712 . A single non-axial pin  708  extends from forward surface  712  of head  706 . Pin  708  is offset from center  716  by a distance which may be freely chosen.  
      Unlike pin  408 , which is free-standing, pin  708  abuts inner surface  710  and may even be molded integrally with inner surface  710  so that pin  708  effectively forms a protuberance extending from inner surface  710 . If, however, screwdriver  700  is implemented without the guide-skirt  711 , the pin  708  may be implemented as a free-standing pin having a circular or semi-circular cross-section.  
      Referring to  FIG. 8 , a single-bore screw  720  is shown for use in conjunction with the screwdriver  700  according to one embodiment of the present invention. The screw  720  includes a generally flat and round head  722  at the end of a shank  726 . The screw  720  includes a single semi-circular notch  724  extending from the outer edge of forward surface  434  of head  422 . Central axis  730  intersects surface  734  at the center  732  of surface  734 . Although bore  724  is semi-circular in shape, it is defined in cross-section by a circle which is offset from center  732  by a distance which is equal to the distance of pin  708  from the center  716  of the forward surface  712  of the screwdriver  700  ( FIG. 7 ).  
      Referring to  FIG. 9 , the screwdriver  700  of  FIG. 7  is shown in engagement with the screw  720  of  FIG. 8  according to one embodiment of the present invention. The use of the screwdriver  700  to drive the screw  720  may be understood by reference to the description above with respect to  FIG. 6 .  
      Referring to  FIG. 10 , a single-pin screwdriver  1000  is shown according to one embodiment of the present invention. Like the screwdriver  400  illustrated in  FIG. 4 , the screwdriver  1000  includes a generally cylindrical grip  1002 , a cylindrical shank  1004 , and a head  1006 . An optional guide-skirt  1011  on the head  1006  has an inner surface  1010  which defines a depression for engaging a corresponding screw (see  FIG. 11 , below). A single pin  1008  extends from forward surface  1012  of head  1006 . As with screwdriver  400 , central axis  1014  intersects surface  1012  at the center  1016  of surface  1012 . Pin  1008  is located centrally on the axis  1014 . Alternatively, pin  1008  may be offset from center  1016  by a distance which may be freely chosen.  
      In the example illustrated in  FIG. 10 , the cross-section of pin  1008  is in the shape of the letter “A.” The pin  1008  may, however, have any shape, such as a letter of the alphabet, a heart shape, or a corporate logo. As illustrated below with respect to  FIG. 11 , the pin  1008  is shaped to engage a screw including a depression having a shape corresponding to the shape of the pin  1008 .  
      Referring to  FIG. 11 , a single-bore screw  1020  is shown for use in conjunction with the screwdriver  1000  according to one embodiment of the present invention. The screw  1020  includes a generally flat and round head  1022  at the end of a shank  1026 . The screw  1020  includes a single centrally-located depression  1024  extending into head  1022  from forward surface  1034  of head  1022 . Central axis  1030  intersects surface  1034  at the center  1032  of surface  1034 .  
      In the example illustrated in  FIG. 11 , the depression  1024  is in the shape of the letter “A,” thereby to engage the pin  1008  of the screwdriver  1000 . The depression  1024 , however, may have any shape, such as a letter of the alphabet, a heart shape, or a corporate logo. More generally, the depression  1024  may be in the shape of a silhouette of an image desirable for aesthetic reasons. Note that the depression  1024  may, for example, be so far offset from the central axis  1014  that the letter “A” is effectively cropped by the outer edge of the head  1022 , resulting in a bore (and corresponding pin) whose shape is that portion of the letter “A” which falls within the boundary defined by the outer edge of the head  1022 .  
      Although the depression  1024  illustrated in  FIG. 11  extends only partway through the head  1022  of the screw  1020 , the depression  1024  may extend fully through the screw  1020 , in which case the depression  1024  is a bore. Furthermore, the depression  1024  need not be centrally located. Rather, the depression  1024  (and the corresponding pin  1008 ) may be offset from the center  1032  by a distance which may be freely chosen.  
      Referring to  FIG. 12 , the screwdriver  1000  of  FIG. 10  is shown in engagement with the screw  1020  of  FIG. 11  according to one embodiment of the present invention. When the pin  1008  and depression  1024  are not centrally located, the use of the screwdriver  1000  to drive the screw  1020  may be understood by reference to the description above with respect to  FIG. 6 . When the pin  1008  and depression  1024  are centrally located, as illustrated in  FIGS. 10-12 , the torque is transferred through the head  1006  to the inner surfaces of depression  1024 , thereby causing the screw  420  to rotate and be driven through a material (not shown). When the pin  1008  and depression  1024  are centrally located, and assuming that the center of torque of the driving pattern is concentric with the central axis of the screw, then the guide skirt  1011 , while possibly desirable in some cases for ease of alignment, etc., is not necessary since the torque is conveyed entirely by the driving pattern.  
      The embodiments illustrated in  FIGS. 4-12  above are illustrative only and do not constitute limitations of the present invention. Rather, various other embodiments fall within the scope of the claims below. For example, the cross-sections of pin  408  and bore  424  need not be circular, but rather may be any shape, such as a triangle, square, rectangle, arc, or heart.  
      Similarly, the cross-sections of pin  708  and notch  724  need not be circular sections, but rather may be any shape, such as a rectangle, “V,” or oval. Other cross-sectional shapes that may be used include, but are not limited to, the following: clovers, spades, diamonds, hearts, clubs, fleur d&#39;alis, musical notes or instruments, depictions of the moon (e.g., half-moons or quarter-moons) or sun, leaves (such as maple leaves or oak leaves), flags, portraits, flowers or other plants, animals, machinery or components thereof, seashells, snowflakes, sports equipment, geographical features (such as outlines of countries, states), stars, letters or words in any language, alchemical symbols representing elements from the periodic table, signs of the zodiac, traffic sign shapes (e.g., one way, U-turn, caution), emoticons (e.g., happy face, sad face, mad face), mathematical symbols, ideographs, and any combination thereof. Furthermore, the pins  408  and  708 , bore  424 , and notch  724  may be any size.  
      In the following discussion, references to the pin  408  may also be applicable to the other pins and heads disclosed herein (such as those illustrated in  FIGS. 7-12 ), and any references to the bore  424  may also be applicable to the bores, notches, and depressions disclosed herein (such as those illustrated in  FIGS. 7-12 ). The pin  408  and bore  424  may be any distance from the center points  416  and  432 , respectively. The present invention is not limited to screws and screwdrivers having the numbers of pins/bores shown in  FIGS. 4-12 . Furthermore, the present invention is not limited to screws and screwdrivers having pins/bores arranged in the particular spatial configurations shown in  FIGS. 4-12 .  
      For example, a screw may include both a plurality of bores arranged symmetrically about the central axis of the screw head and one or more additional bores which are not symmetrically arranged about the central axis. Alternatively, the screw may include a centrally-located (circular or non-circular) bore in addition to one or more non-centrally located (and optionally non-symmetrical) bores. Alternatively, the screw may include a set of three or more (circular or non-circular) bores arranged symmetrically about the central axis. Alternatively, for example, there may be, three pins in a “Y” or “V” configuration or four pins in a rectangular configuration, with bores in a corresponding configuration.  
      There may be fewer pins on the screwdriver  400  than bores on the screw  420 . For example, there may be one pin and three bores, thereby obtaining the advantages of the screwdriver  400  and screw  420  illustrated in  FIGS. 4 and 5 , respectively, with the additional advantage of facilitating the engagement of the screwdriver  400  in the screw  420 . A single screwdriver  400  may therefore be used with screws having different numbers of bores in different configurations, so long as a subset of the bores on each screw are located to allow engagement with the screwdriver pin(s).  
      The screwdriver  400  may be implemented with a head having a flat forward surface rather than the guide-skirt  411  illustrated in  FIG. 4 . Although the pin  408  and bore  424  illustrated in  FIGS. 4 and 5 , respectively, are cylindrical, the pin(s) and bore(s) may be any shape. Furthermore, a single screwdriver may include pins of varying shape. A single screw may include both bores and notches in any combination and configuration.  
      The bore  424  need not fully extend through the screw head  422 . The pin  408  may be longer or shorter than the corresponding bore. For example, a pin that is longer than the bore through which it extends may provide extra stability and therefore eliminate or reduce the need for the guide-skirt  411 . Such an extended pin may, for example, extend into the shank  426  of the screw  420 . The pin  408  need not be fixed in location or length. For example, the pin  408  may be partially or entirely retractable. Examples of centrally-located retractable pins are disclosed in U.S. Pat. No. 4,314,489 to Arcangeli, entitled “Screwdrivers,” issued on Feb. 9, 1982.  
      It should be appreciated that each screw feature described above implicitly define complementary screwdrivers and vice versa.  
      Among the advantages of the invention are one or more of the following.  
      The non-central location of the pin  408  and bore  424  allow torque to be transferred from the screwdriver  400  to the screw  420  using a single pin/bore combination. One advantage of using a single pin/bore combination is that it may simplify and reduce the cost of designing and/or manufacturing the screwdriver  400  and screw  420 . Another advantage of the screws and screwdrivers disclosed herein, which is particularly applicable to coarsely threaded screws, is that the screw can be engaged in an exactly known rotational phase of the screwdriver, a property that is not shared by conventional screwdrivers that have 2-fold (slot), 3-fold, 4-fold (Robertson), 5-fold (Allen), or 6-fold (Allen) rotational symmetries.  
      A further advantage of using a single pin/bore combination is that the screw  420 , once driven into the desired material, presents a surface (i.e., forward surface  434 ) exposing the single bore  424 . One or more screws exposing such surfaces may present a more aesthetically pleasing facade than screws having slotted surfaces or surfaces having dual opposing bores. Furthermore, as described above, screws with various numbers of bores having various shapes and arranged in various configurations may be implemented in accordance with the present invention, thereby presenting further opportunities for increasing the aesthetic appeal of the surface on which the screws are exposed.  
      It is to be understood that although the invention has been described above in terms of particular embodiments, the foregoing embodiments are provided as illustrative only, and do not limit or define the scope of the invention. Various other embodiments, including but not limited to the following, are also within the scope of the claims.