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(11) | EP 0 369 655 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Improved screwdriver bit for Phillips-head fasteners |
| (57) A modified Phillips-type screwdriver bit is disclosed that is fully compatible with
a standard Phillips-head fastener, and is designed to significantly increase the level
of torque that can be applied to the fastener while at the same time substantially
reducing the cam-out forces normally produced by a standard Phillips screwdriver bit.
These results are accomplished by forming generated surfaces along the side walls
of the bit wings so that the included angle defined by the converging side walls of
adjoining bit wings gradually increases from the Phillips standard 92 degrees at the
base of the bit wings to approximately 105 degrees at the wing tips. This configuration
serves to confine the application of torque to the side surfaces of the bit wings
initially along contact lines adjacent and parallel to the roots of the bit wings
with the contact area gradually progressing radially outwardly as torque levels increase
and the opposing side surfaces of the recess wings in the head of the fastener begin
to deform. |
Background and Summary of the Invention
[0001] The present invention relates to screwdriver bits and in particular to an improved screwdriver bit for Phillips-head fasteners that significantly reduces the "cam-out" experienced with a conventional screwdriver bit for Phillips-head fasteners.
[0002] Conventional Phillips-head fasteners and screwdrivers were originally developed to provide a fastening system that would facilitate efficient installation of fasteners on an assembly line. In particular, as compared to conventional slotted screws, the Phillips screw was designed to center quickly and easily on the screwdriver and permit more torque to be applied to the screw so that it would hold tighter than conventional slotted screws. In addition, it was expressly contemplated that, when applied by automated screwdrivers on an assembly line, the increasing torque applied to the Phillips screw would eventually cause the driver to pop out of the recess in the screw. In other words, the original Phillips-head design was intended to cause cam-out of the driver without damaging the screw head. it is, of course, this tendency of the Phillips-head design to cause cam-out of the driver, that is a principal source of irritation for craftsmen and ordinary consumers alike.
[0003] It is, therefore, the primary object of the present invention to provide an improved screwdriver bit that satisfies standard Phillips-head geometry and, therefore, is useable with standard Phillips-head fasteners and yet is designed to significantly reduce the tendency of the driver to cam-out of the recess in the screw head.
[0004] In addition, it is an object of the present invention to provide an improved driver for Phillips-head screws that enables the application of significantly greater torque loads to a standard Phillips-head screw with minimum distortion of the shape of the recess in the screw head.
[0005] Furthermore, it is an object of the present invention to provide an improved driver for Phillips-head screws that enables the application of significantly greater torque loads to a standard Phillips-head screw equally in both rotational directions.
[0006] Additional objects and advantages of the present invention will become apparent from a reading of the following detailed description of the preferred embodiment which makes reference to the drawings in which:
Brief Description of the Drawings
[0007]
Figure 1 is a side elevational view of a standard screwdriver bit for Phillips-head screws;
Figure 2 is an end view of the Phillips bit shown in Figure 1;
Figure 3 is a sectional view taken along line 3-3 in Figure 2;
Figure 4 is a partial sectional view taken along line 4-4 in Figure 3;
Figures 5 - 11 comprise a progressive series of sectional views of a standard Phillips-type bit and screw fastening system starting from the base of the wings of the screwdriver bit in Figure 5 to the top of the head of the fastener in Figure 11;
Figure 12 is a side elevational view partially in section of a standard Phillips fastening system;
Figure 13 is a force vector diagram illustrating the cam-out force component generated by the standard Phillips fastener system;
Figure 14 is a sectional view of a standard Phillips fastener system illustrating the deformation of the recess in the head of the fastener;
Figure 15 is a enlarged view of one of the outer radial wing sections shown in Figure 14;
Figure 16 is a side elevational view of a Phillips-type screwdriver bit according to the present invention;
Figure 17 is a simplified perspective view of the bottom end of the bit shown in Figure 16;
Figures 18 - 24 comprise a progressive series of sectional views of the Phillips-type fastening system according to the present invention from the base of the wings of the screwdriver bit in Figure 18 to the top of the head of the fastener in Figure 24;
Figure 25 is an enlarged view of one of the wing sections of the Phillips-type fastening system according to the present invention;
Figure 26 is a sectional view similar to Figure 24 showing the screwdriver bit applying maximum torque to the fastener;
Figure 27 is a side elevational view partially in section of the Phillips-type fastening system according to the present invention;
Figure 28 is a force vector diagram illustrating the cam-out force component generated by the Phillips-type fastener system according to the present invention; and
Figure 29 is an enlarged side elevational view partially in section of one of the wing sections of the Phillips-type fastening system according to the present invention.
Detailed Description of the Preferred Embodiment
[0008] The structure, significance, and advantages of the present invention are believed best understood if described in relation to a standard Phillips screwdriver bit. Accordingly, Figure 1 in the drawings illustrates a standard No. 2 Phillips bit 10 and will be used as a starting point for the description of the present invention. A standard Phillips bit 10 has a cross-shaped tip that is formed through the creation of four wedge-shaped concave recesses that converge toward the tip 11 of the bit. The recesses define four evenly spaced wings 12 that are tapered along their outer radial surfaces 14 toward the tip of the bit. The angle of this taper is referred to as the "wing angle" and in a standard No. 1, 2, or 3 Phillips bit is equal to 26 degrees 30 minutes relative to the vertical axis of the bit. The radially innermost part 16 of each recess is referred to as the "root" 16 and the angle at which the root diverges from the tip relative to the axis of the bit is referred to as the "root angle". In a standard No. 2 Phillips bit, the root angle of that portion of the bit 10 adapted to engage the fastener is 5 degrees 45 minutes, as shown in Figure 3. The root angle in a standard No. 3 Phillips bit is also 5 degrees 45 minutes; however, the root angle is 7 degrees in a standard No. 1 Phillips bit. Addition, as best illustrated in Figure 4, the angle formed by the adjoining interior wing surfaces 18, referred to as the "included angle", is 92 degrees in a standard No. 1, 2, or 3 Phillips bit and remains constant along the entire axial length of the bit wings 12. Finally, the tip 11 of a standard Phillips bit is conically shaped as shown in Figure 1 to form a point, the conical surface diverging from the point at an angle of 19 degrees relative to the plane normal to the axis of the bit. The specifications and dimensions for standard Phillips-type bits are defined in literature published by the Screw Research Association.
[0009] Given the above geometry for a standard Phillips bit 10, it is important to bear in mind, as shown in Figures 5 - 11, that the cross-shaped recess 20 formed in the head 22 of a standard Phillips-head fastener 24 is created with a punch having precisely the same dimensional characteristics. Accordingly, the standard Phillips screwdriver bit 10 is adapted to fit precisely into the recess 20 formed in the head 22 of a standard Phillips fastener 24, except for a designed-in tolerance clearance which enables the bit to fit readily into the recess 20. This relationship is clearly demonstrated in Figures 5 - 11 which comprise sectional views of a standard Phillips-type fastening system progressing in the axial direction from the base of the bit wings 12 in Figure 5 to the top of the head 22 of the fastener 24 in Figure 11.
[0010] In view of the precise conformity between the driver 10 and the recess 20 in the head 22 of the fastener in a standard Phillips-type fastening system, it will be appreciated that as the screwdriver bit 10 is rotated in the clockwise direction, torque is applied to the head 22 of the fastener 24 along the outer radial edges 18 of the bit wings 12, as indicated by the arrows appearing in Figures 5 - 11. This occurs due to the simple geometric fact that the points farthest from the center of rotation move the greatest distance. Therefore, assuming a substantially uniform tolerance gap between the bit 10 and the recess 20, the outer radial edges 18 of the bit wings 12 will take up the tolerance gap first and engage the opposing outer recess wing surfaces, establishing lines of contact therealong. The concentration of torque along the outer radial edges 18 of the bit wings 12 results in the recess wings 21 in the head 22 of the fastener 24 deforming in these areas as torque levels increase. This deformation is illustrated in somewhat exaggerated form in Figures 14 and 15. Once this deformation occurs, the radially outward facing end surfaces 14 of the bit wings 12 come into contact with the newly formed opposing surfaces 26 in the deformation areas, thereby generating a significant force in the vertical direction (i.e., out of the paper relative to Figures 14 and 15) causing the driver 10 to "cam out" of the screw-head recess 20.
[0011] This phenomenon is illustrated and the related force vectors diagrammed in Figures 12 and 13. In particular, as the torque applied along the outer radial edges 18 (Figure 11) of the bit wings 12 increases and deformation of the outer radial areas of the recess wings 21 occur, a force is generated by the radially outward facing end surfaces 14 of the bit wings 12 against the deformed surfaces 26 of the recess wings 21 in a direction normal to the end surfaces 14, as indicated by the arrows 27 in Figure 12. This, in turn, creates an equal and opposite force from the deformed surfaces 26 against the radially outward facing wing surfaces 14. This opposing force, designated "Z" in the force diagram illustrated in Figure 13 is comprised of a horizontal force component, designated "X", and a vertical force component, designated "Y". Given the Phillips-standard wing angle of 26 degrees 30 minutes, the resulting cam-out force, "Y", generated by the application of torque from the screwdriver bit 10 to the fastener 24 is equal to a factor of 0.43 (i.e., sin 26o 30′) times the magnitude of the force vector "Z". In other words, the greater the application of torque, the greater the force tending to cam the screwdriver bit 10 out of the recess 20 in the head 22 of the fastener 24.
[0012] To obviate this cam-out tendency of the standard Phillips fastening system, the improved Phillips-type screwdriver bit according to the present invention has been designed so that torque loading between the bit and the recess in the head of a standard Phillips fastener is confined to the side faces of the bit wings. This is accomplished in the manner described below. Referring now to Figures 16 and 17, an improved Phillips-type screwdriver bit 30 according to the present invention is shown. At the outset it is important to note that the present screwdriver bit 30 retains the same root angle (either 5 degrees 45 minutes for a No. 2 or No. 3 Phillips fastener, or 7 degrees for a No. 1 Phillips fastener) and the same wing angle of 26 degrees 30 minutes according to standard Phillips specifications to ensure that the present bit 30 is fully compatible with standard Phillips-head fasteners. Thus, it will be appreciated that the present invention does not require a uniquely configured fastener to achieve its increased torque loading capabilities. Moreover, due to the radial symmetry of the present screwdriver bit 30, the increased torque loading capabilities of the present invention apply equally in both rotational directions of the driver.
[0013] Returning to the drawings, it will be noted from an examination of Figure 16 that the width of the radially outward facing surface 34 of the bit wing 32 remains substantially constant from the base 31 of the wing to the wing tip 35. This is contrary to the configuration of a standard Phillips bit, as illustrated in Figure 1, whose corresponding surface 14 gradually increases in width from the base 11 of the wing 12 to the wing tip 15 due to the geometry of the Phillips-standard root angle and the constant Phillips-standard included angle. Specifically, the improved Phillips-type bit 30 according to the present invention does not maintain a constant included angle from the base 31 of the wing 32 to the wing tip 35. Rather, as illustrated in Figure 17, the included angle between the bit wings 32 in the present screwdriver bit 30 is equal to the Phillips-standard 92 degrees at the base 31 of the bit wings 32 and progressively increases to approximately 105 degrees at the wing tips 35. In other words, rather than the side surfaces of the bit wings 12 being defined by flat planes as in the standard Phillips bit 10, the side surfaces of the bit wings 32 in the present bit 30 comprise generated surfaces. As a result, when the screwdriver bit 30 according to the present invention is inserted into the recess 20 of a standard Phillips-head fastener 24, a gradually increasing gap 38 (Figure 25) is defined between the bit wings 32 and the recess wings 21 in the radially outward direction. This is due to the fact that the thickness of the recess wings 21 in the standard Phillips-head fastener 24 diminishes more gradually in the radially outward direction due to the constant Phillips-standard included angle, which becomes progressively smaller than the increasing included angle of the present bit 30. In other words, the gap 38 shown in Figures 24 and 25 results from the fact that the included angle between the sidewalls of the recess wings 21 corresponds to the Phillips-standard 92 degrees whereas the included angle between the bit wings 32 at this illustrated axial position of bit 30 corresponds to approximately 103 degrees. (Note that the 103-degree angle referred to corresponds to the included angle at an axial position somewhat below the wing tip 35 as the entire bit portion typically does not fit into the recess 20 in the head of the fastener 24, as shown in Figure 27.) In addition, it is important to note that the radial dimension of the bit wings 32 when the bit is fully inserted into the recess 20 is less than that of the recess wings 21 so that a slight space is maintained between the radially outward facing surfaces 34 of the bit wings 32 and the opposing surfaces 44 of the recess wings 21. In the preferred embodiment of the present invention, the roots 36 of the recesses between adjoining bit wings 32 are also formed somewhat deeper so that an additional gap 40 (Figure 25) is created between the root 36 of the bit 30 and the root 42 of the recess 20 in the standard Phillips-head fastener 24. Finally, as illustrated in Figures 16 and 27, the base 31 of the present screwdriver bit 30 is preferably truncated as shown to prevent the bit 30 from bottoming out when inserted into the recess 20 of a standard Phillips-head fastener 24.
[0014] As a result of this configuration, when the present screwdriver bit 30 is inserted into the recess 20 of a standard Phillips-head fastener 24 and rotated in a clockwise direction, torque is applied to the fastener 24 along lines of contact 46 between the side surfaces of the bit wings 32 and the opposing side surfaces of the recess wings 20, as indicated by the arrows appearing in Figures 18 - 24. In addition, it will be appreciated that these initial lines of contact 46 between the side surfaces of the bit wings 32 and recess wings 20 are essentially parallel to the root 36 of the bit 30, as illustrated by the dashed lines in Figure 27. In other words, these lines of contact 46 form substantially the same 5-degree 45-minute angle with respect to the axis of the bit 30 corresponding to the Phillips-standard root angle. Moreover, as the level of applied torque increases and the bit 30 begins to deform the recess 20, the lines of contact expand radially outwardly in parallel fashion along the side faces of the bit wings 32, as indicated by the shaded portion 50 illustrated in Figure 29. This serves to significantly increase the level of torque that can be transmitted from the screwdriver bit 30 to the fastener 24 while confining the areas of engagement to the side surfaces of the bit wings 12. This distinction between the present invention and the standard Phillips bit is illustrated in Figures 14 and 26.
[0015] Significantly, the deformation of the recess 20, as illustrated in Figure 26, along the sidewalls of the recess wings 21 does not add to the relatively small cam-out forces generated by the application of torque along the initial lines of contact 46 between the bit 30 and recess 20. Accordingly, driving engagement between the screwdriver bit 30 and the fastener 24 can easily be maintained with the application of a modest amount of downforce. This phenomenon of the present invention is illustrated and diagrammed in Figures 27 and 28. As previously noted, the application of torque from the bit 30 to the fastener 24 along the initial lines of contact 46 on the side surfaces of the bit wings 32 is represented by the dotted lines in Figure 27. The application of force in this manner results in the generation of an outwardly directed force component perpendicular to the lines of contact, as indicated by the arrows 45 in Figure 27. This, in turn, results in the generation of an equal and opposite force vector designated "Z" in the accompanying vector force diagram shown in Figure 28. In view of the approximated 5-degree 45-minute angle of the force vector "Z" relative to the axis of the bit 30, the force vector "Z" is comprised predominantly of a horizontal force component, labeled "X", and a relative small vertical force component, labeled "Y". In fact, the vertical force component "Y" tending to cause the bit 30 to cam-out of the recess 20 is only equal to approximately a factor of 0.10 (i.e., sin 5o 45′) times the magnitude of the force vector "Z". Accordingly, when compared to a standard Phillips bit 10, significantly less downward force is required from the operator to retain the present bit 30 in the recess 20 of a standard Phillips-head fastener 24, even at high levels of applied torque.
[0016] From the above discussion, it will be appreciated that the screwdriver bit 30 according to the present invention is able to significantly reduce the cam-out force associated with a standard Phillips screwdriver bit 10 by preventing the radially outward facing bit wing surfaces 34 from contacting the recess 20 in the head 22 of the fastener 24. Due to the angle of these bit wing surfaces 34, the application of force along these surfaces is believed to be the greatest cause of cam-out in a standard Phillips design. Therefore, the present screwdriver bit 30 is capable of deforming the recess wings 21 in a Phillips-head fastener 24 to the degree illustrated in Figure 26 before significant cam-out forces will be generated. At the stage illustrated in Figure 26, torque is being applied along virtually the entire side surfaces of the bit wings 32 from the initial lines of contact 46 adjacent the root 36 of the bit to the outer radial edges 48 of the bit wings 32.
[0017] Finally, it will be appreciated that, in view of the radially symmetrical design of the invention, the present screwdriver bit 30 is capable of applying significantly greater torque loads than a standard Phillips bit in either rotational direction. Therefore, unlike certain existing modified Phillips designs which radially offset the bit wings and are, therefore, primarily useable in only one rotational direction, the present invention is equally useful for tightly setting standard Philips screws and for "breaking free" and removing "frozen" Phillips fasteners.
1. A driver for applying torque to a fastener having a standard Phillips cross-shaped
recess formed in the head of the fastener, the standard Phillips cross-shaped recess
comprising four equally radially spaced recess wings, the outer radial surfaces thereof
converging toward a common point at a predefined standard wing angle relative to the
axis of the fastener, the converging side surfaces of adjoining recess wings defining
a predefined standard included angle that remains substantially constant from the
bottom of said recess wings to the top of said recess, and wherein the sidewalls of
said recess wings are angled at a predefined standard root angle relative to said
axis;
the driver including a bit portion adapted for insertion into said recess comprising:
four radially symmetrical bit wings having radially outward facing surfaces that are tapered at an angle relative to the axis of said bit substantially equal to said standard wing angle, and wherein the converging side surfaces of adjoining bit wings define a root that is oriented relative to said axis at an angle substantially equal to said standard root angle, and further wherein said converging side surfaces of adjoining bit wings define an included angle that increases gradually in the axial direction from approximately said standard included angle at the base of said bit wings to a predetermined greater included angle at an axially spaced distance therefrom, such that when said bit is inserted into the recess of a standard Phillips-head fastener, contact is created between the recess and said bit at the side surfaces of said bit wings along lines of contact substantially parallel to said adjacent roots with a gradually increasing gap formed between the side surfaces of said bit wings and the corresponding side surfaces of said recess wings in a radially outward direction from said lines of contact.
the driver including a bit portion adapted for insertion into said recess comprising:
four radially symmetrical bit wings having radially outward facing surfaces that are tapered at an angle relative to the axis of said bit substantially equal to said standard wing angle, and wherein the converging side surfaces of adjoining bit wings define a root that is oriented relative to said axis at an angle substantially equal to said standard root angle, and further wherein said converging side surfaces of adjoining bit wings define an included angle that increases gradually in the axial direction from approximately said standard included angle at the base of said bit wings to a predetermined greater included angle at an axially spaced distance therefrom, such that when said bit is inserted into the recess of a standard Phillips-head fastener, contact is created between the recess and said bit at the side surfaces of said bit wings along lines of contact substantially parallel to said adjacent roots with a gradually increasing gap formed between the side surfaces of said bit wings and the corresponding side surfaces of said recess wings in a radially outward direction from said lines of contact.
2. The driver of claim 1 wherein the contact area between the recess and said bit
expands progressively radially outwardly from said lines of contact as the torque
levels applied by said driver to said fastener increase.
3. The driver of claim 1 wherein said radially outward facing surfaces of said bit
wings have a substantially uniform width from the base of said bit wings to the end
of said taper.
4. The driver of claim 3 wherein a gap is formed between said radially outward facing
surfaces of said bit wings and said opposing outer radial surfaces of said recess
wings when said bit portion is fully inserted into said recess.
5. The driver of claim 1 wherein a gap is formed radially inward from said lines of
contact between the roots of said bit portion and the opposing surfaces of said recess
when said bit portion is fully inserted into said recess.
6. The driver of claim 1 wherein the base of said bit portion is truncated.
7. A driver for a standard Phillips-head fastener having a cross-shaped recess formed
in the head thereof, the driver including a bit portion adapted for insertion into
said recess and comprising four bit wings, the radially outwardly facing surfaces
of said bit wings converging toward a common point at the Phillips-standard wing angle,
the bit portion comprising:
generated side surfaces on said bit wings such that the converging side surfaces of adjoining bit wings define an included angle in a plane substantially normal to the axis of said bit that increases in the axial direction from approximately the Phillips-standard included angle at the base of said bit wings to a predetermined greater included angle at an axially spaced distance therefrom.
generated side surfaces on said bit wings such that the converging side surfaces of adjoining bit wings define an included angle in a plane substantially normal to the axis of said bit that increases in the axial direction from approximately the Phillips-standard included angle at the base of said bit wings to a predetermined greater included angle at an axially spaced distance therefrom.
8. The driver of claim 7 wherein said bit wings are radially symmetrical such that
equal levels of torque can be applied from said driver to the fastener in both rotational
directions.
9. The driver of claim 7 wherein said bit wings define roots therebetween that are
oriented relative to the axis of said bit at an angle substantially equal to the Phillips-standard
root angle.
10. The driver of claim 9 wherein said bit portion is adapted to engage said recess
at the side surfaces of said bit wings along lines of contact adjacent and substantially
parallel to said roots.
11. The driver of claim 10 wherein a progressively increasing gap is formed between
the generated side surfaces of said bit wings and the corresponding side surfaces
of said recess in a radially outward direction from said lines of contact when said
bit portion is inserted into said recess.
12. The driver of claim 11 wherein the area of engagement between the recess and said
bit expands progressively radially outwardly from said lines of contact as the torque
levels applied by said driver to said fastener increase.
13. The driver of claim 11 wherein said radially outward facing surfaces of said bit
wings have a substantially uniform width.
14. The driver of claim 11 wherein a gap is formed between said radially outward facing
surfaces of said bit wings and said opposing outer radial surfaces of said recess
wings when said bit portion is fully inserted into said recess.
15. The driver of claim 11 wherein a gap is formed radially inward from said lines
of contact between the roots of said bit portion and the opposing surfaces of said
recess when said bit portion is fully inserted into said recess.
16. The driver of claim 11 wherein the base of said bit portion is truncated.
17. The driver of claim 11 wherein said included angle between said bit wings increases
progressively from approximately 92 degrees at the base of said bit wings to approximately
105 degrees at the tip of said bit wings.
18. A driver for a standard Phillips-head fastener having a cross-shaped recess formed
in the head thereof defining recess wings having outer radial surfaces that are tapered
toward a common point at a predefined standard wing angle relative to the axis of
the fastener and sidewalls oriented at a predefined standard root angle relative to
said axis such that the thickness of said recess wings expands in the radial outward
direction and in the axial direction from the bottom of the recess to the top of the
recess; said driver including a bit portion adapted for insertion into said recess
comprising:
four bit wings having radially outward facing surfaces that are tapered toward a common point at an angle substantially equal to said standard wing angle relative to the axis of said bit and wherein the thickness of said bit wings adjacent the roots of said bit wings increases gradually in the axial direction in accordance with said standard root angle but remains substantially constant along said tapered radially outward facing surfaces.
four bit wings having radially outward facing surfaces that are tapered toward a common point at an angle substantially equal to said standard wing angle relative to the axis of said bit and wherein the thickness of said bit wings adjacent the roots of said bit wings increases gradually in the axial direction in accordance with said standard root angle but remains substantially constant along said tapered radially outward facing surfaces.
19. The driver of claim 18 wherein said bit wings define roots therebetween that are
oriented relative to the axis of said bit at an angle substantially equal to said
standard root angle.
20. The driver of claim 19 wherein the converging side surfaces of adjoining recess
wings define a predefined Phillips-standard included angle that remains substantially
constant from the bottom of said recess to the top of said recess, and further wherein
the side surfaces of said bit wings comprise generated surfaces that define an included
angle in a plane substantially normal to said bit axis that progressively increases
in the axial direction from approximately said Phillips-standard included angle at
the base of said bit wings to a predetermined greater included angle at an axially
spaced distance therefrom.
21. The driver of claim 20 wherein said bit is adapted to engage said recess when
said bit portion is inserted into said recess at the generated side surfaces of said
bit wings along lines of contact adjacent and substantially parallel to said roots.
22. The driver of claim 21 wherein the area of engagement between the recess and said
bit portion expands progressively radially outwardly from said lines of contact as
the torque levels applied by said driver to said fastener increase.
23. The driver of claim 18 wherein a gap is formed between said radially outward facing
surfaces of said bit wings and said opposing outer radial surfaces of said recess
wings when said bit portion is fully inserted into said recess.
24. The driver of claim 18 wherein a gap is formed radially inward from said lines
of contact between the roots of said bit portion and the opposing surfaces of said
recess when said bit portion is fully inserted into said recess.
25. The driver of claim 18 wherein the base of said bit portion is truncated.
26. The driver of claim 18 wherein said bit wings are radially symmetrical such that
equal levels of torque can be applied from said driver to the fastener in both rotational
directions.
27. A driver for a standard Phillips-head fastener having a cross-shaped recess formed
in the head thereof, the driver including a bit portion adapted for insertion into
said recess comprising:
radially symmetrical wing means defining roots therebetween for rotationally driving said fastener intially adjacent said roots and progressively radially outward therefrom as the torque levels applied by said driver to said fastener increase.
radially symmetrical wing means defining roots therebetween for rotationally driving said fastener intially adjacent said roots and progressively radially outward therefrom as the torque levels applied by said driver to said fastener increase.
28. The driver of claim 27 wherein said wing means comprises four equally radially
spaced bit wings defined by generated side surfaces that in turn define an included
angle between adjoining bit wings that progressively increase from a first predetermined
angle at the base of said bit wings to a second greater predetermined angle at an
axially spaced distance therefrom.
29. The driver of claim 28 wherein the radially outwardly facing surfaces of said
bit wings are tapered toward a common point at an angle relative to the axis of said
bit portion substantially equal to the Phillips-standard wing angle.
30. The driver of claim 29 wherein the roots of said bit portion are oriented relative
to said bit axis at an angle substantially equal to the Phillips-standard root angle.
31. The driver of claim 30 wherein a gap is formed between said radially outward facing
surfaces of said bit wings and the opposing outer radial surfaces of said recess when
said bit portion is fully inserted into said recess.
32. The driver of claim 30 wherein a gap is formed between the root areas of said
bit portion and the opposing surfaces of said recess when said bit portion is inserted
into said recess.
33. The driver of claim 30 wherein the base of said bit portion is truncated.
34. A driver for a standard Phillips-head fastener having a cross-shaped recess formed
in the head thereof, the driver including a bit portion adapted for insertion into
said recess comprising:
radially symmetrical wing means defining roots therebetween for rotationally driving said fastener adjacent said roots in both rotational directions.
radially symmetrical wing means defining roots therebetween for rotationally driving said fastener adjacent said roots in both rotational directions.
35. The driver of claim 34 wherein said wing means comprise four equally radially
spaced bit wings defined by generated side surfaces that in turn define an included
angle between adjoining bit wings that progressively increases from a first predetermined
angle at the base of said bit wings to a second greater predetermined angle at an
axially spaced distance therefrom.
36. The driver of claim 35 wherein the radially outwardly facing surfaces of said
bit wings are tapered toward a common point at an angle relative to the axis of said
bit portion substantially equal to the Phillips-standard wing angle.
37. The driver of claim 36 wherein the roots of said bit portion are oriented relative
to said bit axis at an angle substantially equal to the Phillips-standard root angle.
38. The driver of claim 37 wherein a gap is formed between said radially outward facing
surfaces of said bit wings and the opposing outer radial surfaces of said recess when
said bit portion is fully inserted into said recess.
39. The driver of claim 37 wherein a gap is formed between the root areas of said
bit portion and the opposing surfaces of said recess when said bit portion is inserted
into said recess.
40. The driver of claim 37 wherein the base of said bit portion is truncated.
41. The method of applying torque to a standard Phillips-head fastener having a standard
Phillips cross-shaped recess formed in the head thereof, including the steps of:
inserting into said standard Phillips-head recess the bit portion of a driver having four radially symmetrical bit wings that are adapted to engage said recess exclusively along lines of contact on the side surfaces of said bit wings adjacent and substantially parallel to the roots of said adjoining bit wings, and
rotating said driver so that torque is initially applied to said fastener along said lines of contact.
inserting into said standard Phillips-head recess the bit portion of a driver having four radially symmetrical bit wings that are adapted to engage said recess exclusively along lines of contact on the side surfaces of said bit wings adjacent and substantially parallel to the roots of said adjoining bit wings, and
rotating said driver so that torque is initially applied to said fastener along said lines of contact.
42. The method of claim 41 further including the step of progressively expanding the
areas of contact between said bit portion and said recess in a radially outward direction
along said side surfaces of said bit wings as the level of torque applied by said
driver to said fastener increases.