AU2014200312A1 - Fastener Driver - Google Patents

Abstract

Fastener Driver 5 The invention relates in general to a driver having a work engaging and force exerting portion adapted to be inserted into a socket of a threaded fastener. The driver having a driving portion at an extremity thereof for engagement with at least three recessed pockets in a head portion of a complimentary tamper proof fastener. The driver comprising a driver bit having a turning axis and a 10 lobe for each recessed pocket, each said lobe spaced substantially equally about the turning axis and having a driving face which is a complementary fit with the recessed pocket of the tamper-proof fastener. The driver further comprising a longitudinally extending driver shank, said shank having a first end spaced apart from a second end, said first end is adapted for connecting to a 15 driving device, said second end connecting to the driver bit. Wherein inserting said driver bit of said driver into said at least three recessed pockets of the head of said fastener results in a substantially mated engagement, such that the tamper-proof fastener can be engaged only by the driver. 20 Figure 1 to accompany the abstract. Figure 1 Figure 3 Figure 4 Figure 2

Description

1 FASTENER DRIVER FIELD OF THE INVENTION 5 This invention relates broadly to tools. More particularly, this invention relates to tools having a work engaging and force exerting portion adapted to be inserted into a socket of a threaded fastener. BACKGROUND OF THE INVENTION 10 It should be noted that reference to the prior art herein is not to be taken as an acknowledgement that such prior art constitutes common general knowledge in the art. 15 The term "screw" is used herein to refer to a threaded fastener having a screw head and a shank having a screw thread on at least a part of its length. The term includes screws and bolts. Fasteners are widely applied in many fields to attach two objects together. A 20 commonly used fastener generally includes a head portion and a threaded connecting portion extending out from one end of the fastener head portion of the fastener coaxially. The head portion defines a driving engaging hole in one end surface thereof away from the threaded connecting portion. However, the driving engaging hole of the commonly used conventional 25 fastener can be enlarged and deformed through extended use. Fasteners of various types have been developed in the art to meet various fastening requirements. Examples of conventional fasteners are screws, bolts and rivets. Depending on requirements and applications, screws and 30 bolts with various head designs and patterns such as slotted, Phillips and hex have been developed. These conventional fasteners, however, are easily operated on and therefore tampered with as driver heads with corresponding head designs and patterns are readily available.

2 For special applications where the fasteners as applied need to be tamper proof, fasteners with special head designs and driver tools with complementary head designs must be used. 5 Whatever form of driver/recess is employed, an axial pressure is almost invariably required, a pressure, that increases with increasing torque applied in order to counter the tendency of drivers to "cam-out" of engagement with the screw recess. Craftsmen often have to work in difficult positions when fastening screws and as a result thereof have great difficulty in applying the 10 required torque. Insufficient pressure applied during fastening causes the driver to cam out and the resulting spin of the driver often damages the recess in the screw so that it becomes extremely difficult to remove or secure the damaged screw or bolt. Excessive pressure requirements reduce bit life and can cause worker fatigue or injury. 15 Clearly it would be advantageous if a fastener driver could be devised that helped to at least ameliorate some of the shortcomings described above. In particular, it would be beneficial to provide a fastener driver with a work engaging and force exerting portion adapted to be inserted into a tamper 20 proof threaded fastener. STATEMENT OF THE INVENTION In accordance with a first aspect, the present invention provides a driver 25 having a driving portion at an extremity thereof for engagement with at least three recessed pockets in a head portion of a complimentary tamper-proof fastener, the driver comprising: a driver bit having a turning axis and a lobe for each recessed pocket, each said lobe spaced substantially equally about the turning axis and having a driving face which is a complementary fit with 30 the recessed pocket of the tamper-proof fastener; a longitudinally extending driver shank, said shank having a first end spaced apart from a second end, said first end is adapted for connecting to a driving device, said second end connecting to the driver bit; and wherein inserting said driver bit of said driver into said at least three recessed pockets of the head of said fastener results 3 in a substantially mated engagement, such that the tamper-proof fastener can be engaged only by the driver. Alternatively the tamper-proof fastener may have four recessed pockets in 5 the head portion and the driver bit has four lobes spaced substantially equally about the turning axis. Or alternatively the tamper-proof fastener may have five recessed pockets in the head portion and the driver bit has five lobes spaced substantially equally about the turning axis. 10 Preferably, the driver bit may have a centrally located socket extending from an end of the driver bit which is adapted to snugly receive a complementary pin centrally located within the head portion of the tamper-proof fastener. The socket of the driver bit may have a polygon cross-section and the pin of the tamper-proof fastener has a complementary shaped pin to snugly receive 15 the socket. Likewise the pin and socket may be reversed and the pin is located on the driver and the socket is located on the screw. Preferably, the lobes extending from the driver bit having a turning axis are oriented such that they are formed turning in a clockwise direction. 20 Alternatively, the lobes may be oriented such that they are formed turning in a counter clockwise direction. Preferably, each lobe of the driver bit may comprise at least three angled facets extending from an end of the driver bit to a distance spaced from the 25 end of the driver bit, wherein the angled facets engage with complementary shaped facets in the pockets of the tamper-proof fastener. Each angled facet may be formed as an uneven surface or each lobe may be formed having irregular sized and shaped facets. 30 In accordance with a further aspect, the present invention provides a tamper proof fastener in combination with a tool comprising: a) a fastener having a threaded shank; and an enlarged drive head integral with the shank, said drive head having an internally formed driving portion with at least three recessed pockets in the drive head portion, with each said pocket having at 4 least three facets extending inwardly from the end of the drive head; and b) a tool having a turning axis and a driver bit with at least three lobes, each said lobe formed by at least three angled facets extending from an end of the driver bit to a distance spaced from the end of the driver bit, wherein the 5 angled facets engage with the complementary shaped facets in the pockets of the tamper-proof fastener. Preferably, each said lobe may be spaced substantially equally about the turning axis and a longitudinally extending driver shank, said shank having a 10 first end spaced apart from a second end, said first end is adapted for connecting to a driving device, said second end connecting to the driver bit. Preferably, each said lobe projecting from the driver bit may be separated from the next lobe by an angle of 120 degrees from each other. 15 Alternatively the tamper-proof fastener may have four recessed pockets in the head portion and the driver bit has four lobes spaced substantially equally about the turning axis. Or alternatively the tamper-proof fastener may have five recessed pockets in the head portion and the driver bit has five lobes 20 spaced substantially equally about the turning axis. Preferably, said fastener and tool may be fabricated from steel or stainless steel, and said drive head may be cold headed. 25 Preferably, each said facet in the fastener and tool have surfaces which extend substantially planar. In accordance with a further aspect, the present invention provides a driver tool for operating a tamper-proof fastener, said driver tool comprising: a 30 shank; said shank comprising: a first end and a second end; wherein said first end of said shank is adapted for connection to a driver device and longitudinally extends therefrom; said second end of said shank having a cross-sectional signature substantially complementary in size and shape to at least three recessed channels located within a head of the tamper-proof 5 fastener; and wherein inserting said second end of said shank into said three recessed channels of said head of said fastener results in a substantially matable engagement. 5 Preferably, the cross-sectional signature may comprise at least three lobes extending outward from a substantially centrally located cylinder, said lobes being equally spaced around the cylinder. Preferably, the driver tool may further comprise a socket centrally located and extending inwardly away from the second end of the shank, wherein the socket may be adapted to snugly 10 receive a complementary pin centrally located within the head portion of the tamper-proof fastener. The socket of the driver tool may have a polygon cross-section and the pin of the tamper-proof fastener has a complementary shaped pin to snugly receive the socket. 15 Alternatively the driver tool may have four lobes extending outward from a substantially centrally located cylinder, each lobe being equally spaced around the cylinder. Or alternatively the driver tool may have five lobes extending outward from a substantially centrally located cylinder, each lobe being equally spaced around the cylinder. 20 In accordance with a still further aspect, the present invention provides a driver and fastener system, comprising: a) a tamper-proof fastener having a non-twisted socket with facets, a cross-section through said socket defining an irregular polygon; and b) a driver with a shaft having a tip with an end face 25 defining at least three lobes, the lobes extending from the end face to a length along the shaft, wherein a first cross-section along said length defines an irregular polygon of a first size and a second cross section along said shaft defines a regular polygon of a larger second size, wherein when said tip is inserted into said socket, said sides of the tip of the driver adjacent entry 30 into the socket lie against said facets of the socket and said lobes of said tip contact the sides of the socket. In accordance with a still further aspect, the present invention provides a driver and fastener system, comprising: a) a tamper-proof fastener including 6 a non-twisted socket with a depth and which defines an irregular N-sided polygon shape; and b) a driver including a shaft with a tip having a length substantially corresponding to said depth, said tip extending between an end of said tip and a location on said tip, wherein a first cross-section through 5 said tip defines an irregular N-sided polygon, and a second cross section along said shaft defines a regular polygon of a larger second size. In accordance with a still further aspect, the present invention provides a driver bit for engaging with a recess of a tamper-proof screw, said recess 10 being generally depression-like and having a central portion and at least three lobe engaging portions extending outwardly from said central portion, wherein said driver bit comprising a bit central portion and at least three lobes for engaging said lobe engaging portions of said screw, said lobes extending outwardly from said bit central portion, each of said lobes 15 comprising a proximal end side portion extending outwardly in the radial direction of said driver bit and a distal end side portion extending outwardly from said proximal end side portion, said proximal end side portions of said lobes being arranged at equal angular intervals. 20 BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be understood more fully from the detailed description given hereinafter and from the accompanying drawings of the preferred embodiment of the present invention, which, however, should not 25 be taken to be limitative to the invention, but are for explanation and understanding only. Figure 1 illustrates an enlarged end view of a driver tip in accordance with the present invention; 30 Figure 2 shows a three dimensional view of a driver in accordance with an embodiment of the present invention; Figure 3 illustrates an end view of the driver opposite the driver tip end of the driver of Figure 2; Figure 4 illustrates another end view of the driver of Figure 2; 7 Figure 5 shows an enlarged drawing of a driver tip in accordance with another embodiment of the present invention; Figures 6 and 7 show two three dimensional views of the driver having the driver tip of Figure 5; 5 Figure 8 shows another three dimensional view of the driver of Figure 2; Figure 9 shows an end view of the driver of Figure 8; Figure 10 shows an enlarged end of the tip of the driver of Figure 8; Figure 11 shows a driver with the driver tip of Figure 8 but in a shortened form; 10 Figure 12 shows an enlarged end view of a driver tip in accordance with a further embodiment of the present invention; Figure 13 shows the driver with the driver tip of Figure 12; Figure 14 shows a three dimensional drawing of a driver in accordance with another embodiment of the present invention; 15 Figure 15 shows an enlarged end view of the tip of the driver of Figure 14; Figure 16 shows an enlarged end view of the driver of Figure 14; Figure 17 shows a variation of the pin type used in Figures 5 to 7 in accordance with an embodiment of the present invention; Figure 18 shows an end view of Figure 17; 20 Figure 19 illustrates another variation of the pin type used in Figures 5 to 7 of the present invention; and Figure 20 illustrates some of the variations of the drivers used in accordance with the present invention. 25 DETAILED DESCRIPTION OF THE INVENTION The following description, given by way of example only, is described in order to provide a more precise understanding of the subject matter of a preferred embodiment or embodiments. 30 Currently available tool drivers include a shank having a driver head. The shank is typically configured to be coupled to a hand tool, such as a drill. The driver head is adapted to receive, and to a certain degree retain, a 8 fastener, such as a screw. During use, an operator must align and retain the fastener with a workpiece, such as a piece of wood or steel. Referring to the screw (not shown) for use with the driver 10 of Figures 1 to 4 5 of the present invention, the screw typically includes a screw head, a shank and a male-thread. The screw head can be pan head, conical head, circular head, annular head, countersink head, oval head, truss head, etc. The screw head is provided with a drive recess, wherein the drive recess includes five symmetrical shaped channels or pockets. 10 Turning now to FIGS. 1 through 4, a driver 10 for a fastener is shown. The driver 10 includes a proximal shaft 11 which is adapted with a non-circular cross-section for engagement by a rotary tool. Alternatively, the shaft 11 may be provided with a handle for manual operation, as is well known in the 15 art. The distal end 12 of the driver 10 includes a tip 14 which is subject to a taper to step down in size to approximate the size and shape of a socket of a fastener to impart rotational force thereto. More particularly, the end 18 of tip 14 is tapered and along its length has a cross-sectional shape which corresponds to an irregular polygon with N sides, where N .three. In the 20 embodiment described in Figures 1 to 4, N = 5. When viewed end on as in Figure 4, a larger hexagon 19 defined by the end 11 circumscribes the smaller five sided irregular polygon defined by the tip 14. The tip 14 includes five lobes 15 extending from the end 18 and down 25 the tip 14 a distance which substantially corresponds to the depth of the drive recess in the screw head. As the tip 14 moves from the end 18 the depth of the groves 16 and lobes 15 decreases such that as the tip 14 approaches the cylindrical body 20 of the driver 10 the tip 14 decreases in depth to a point where the tip 14 is completely circumscribed by the cylindrical shaft 20. 30 Likewise the cylindrical shaft 20 is circumscribed by the proximal shaft 11 which has a hexagonal cross section 19 for use in a driver tool which allows the driver 10 to be driven. The end 13 of the driver 10 is rounded for ease of insertion in a driver. As shown in figures 1 and 2 the end 18 of the driver 10 is formed as a substantially flat surface and defines the start of the tip 14.

9 In this embodiment the driver 10 is shown having a hexagonal section shank 19 for fitting in a conventional socket to rotationally drive the driver 10 about its longitudinal axis 50. On the end of the shank 19 is a driving tip 14. The tip 14 comprises five drive elements 15. Between each drive element is a 5 channel 16. In transverse section, each channel 16 is substantially s shaped. Each channel 16 and lobe or drive element 15 are symmetrically aligned and equally spaced around the longitudinal axis 50. Each drive lobe 15 has a flat front face 21 which is inclined from the end 18 of the driving tip 14 to a point 22. 10 The driving tip 14 is shaped to fit a recess of a screw so as to transmit drive from the driver 10 to the screw. Since the shape of the driver 10 and recess is rotationally symmetrical, drive can be transmitted in either direction. 15 By virtue of the lobes 15 and the mating surfaces of the drive pockets a particularly tight fit between them is achievable. Moreover, because the drive lobes 15 can wedge between adjacent drive pockets, slipping of the driver in the recess is resisted. 20 The relative dimensions of the recess can be maintained in larger or smaller screws, a different driver being required for each change in overall dimensions. However, with the same relative dimensions, there is still opportunity to adjust the recess size depending on the size of screw. Likewise the number of lobes 15 located symmetrically around the driver tip 25 14 can also be varied as is described further below. Another variation which is utilised for the drivers of the present invention is the orientation of a centrally located pin socket in the end face 18 of the driver 40 and a complementary pin in the screw. This is illustrated in Figures 30 5 to 7. Furthermore and as described below the pin and socket can be of any cross-sectional shape. Figures 5 to 7 show the further embodiment in which a socket 30 is centrally located extending from the end 18 of the driver 40 and to within the driver tip 10 14. In use, the driver 40 would be paired with screw which had a complementary pin for insertion into the socket 30. Figures 8 to 10 show the driver 10 as shown in Figures 1 to 4 in which there 5 is no centrally located socket. Figure 11 shows a shorter version of the driver 10 in which the driver has five lobes 15 and with a shorter shank 19. 10 Figures 12 and 13 illustrate another embodiment of the present invention in which N 4. That is the driver 70 has four lobes 15 for insertion and mating with a screw having four sockets. Also shown in Figure 12 and 13 is socket 30 which allows the driver 70 to be paired with a screw with four sockets. As can be expected the driver 70 can include a socket of any cross-sectional 15 shape or not include a socket at all. Figures 14 to 16 show a driver 80 with three lobes extending symmetrically around the centre axis of the driver 80. Once again the driver 80 includes a socket 30 into which the pin of the mating screw is placed. 20 Figures 17 and 18 show a further embodiment of the cross-sectional shape and the orientation of the socket/pin is in the shape of a pentagon with slightly curved sides. As above and as shown in Figures 17 and 18 the pin and socket are interchangeable. For example the pin 60 is located on the 25 driver and the complementary socket would be located on the screw. This embodiment has pin 60 having five sides 61 located around a central recess 62. As illustrated in Figure 19 the pin or socket may have the cross-sectional 30 shape of a triangle. The driver 70 has a pin consisting of three sides 71 with a central recess 72. Also and as above the pin maybe located on either the driver or the screw or vice versa.

11 Figure 20 shows a photograph of some of the variations for the driver. As shown driver 10 is shown with the five lobes and no centrally located pin, driver 40 has five lobes with a socket for the pin, driver 70 has four lobes with a recess or socket for a pin and finally driver 80 had three lobes with a recess 5 for a pin. Furthermore figures 1 to 11 show different embodiments of the lobes 15, wherein the lobes are rotate around the turning axis in a clockwise direction. Alternatively, and in figures 12 to 16 the lobes are oriented such that they are 10 formed turning in a counter clockwise direction. ADVANTAGES The present invention provides a driver for tamper-proof fasteners which 15 provide another level of security by their unique drive designs to prevent removal with ordinary screw drivers and commonplace tools. The term ''screw" is used to refer to a threaded fastener having a screw head and a shank having a screw thread on at least a part of its length. 20 The driver is designed to mate tightly with a complementary screw having sockets in which the lobes of the driver will snugly fit. The driver has been designed so that it will only mate with a particular complementary shaped screw. Therefore a screw which has 3 sockets will only mate with a driver which has three lobes of complementary cross-sectional shape. 25 VARIATIONS It will be realized that the foregoing has been given by way of illustrative example only and that all other modifications and variations as would be 30 apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as herein set forth. In the specification the term "comprising" shall be understood to have a broad meaning similar to the term "including" and will be understood to imply the 12 inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations on the term "comprising" such as "comprise" and "comprises".

Claims (26)

1. A driver having a driving portion at an extremity thereof for engagement with at least three recessed pockets in a head portion of a complimentary 5 tamper-proof fastener, the driver comprising: a driver bit having a turning axis and a lobe for each recessed pocket, each said lobe spaced substantially equally about the turning axis and having a driving face which is a complementary fit with the recessed pocket of the tamper-proof fastener; 10 a longitudinally extending driver shank, said shank having a first end spaced apart from a second end, said first end is adapted for connecting to a driving device, said second end connecting to the driver bit; and wherein inserting said driver bit of said driver into said at least three recessed pockets of the head of said fastener results in a substantially mated 15 engagement, such that the tamper-proof fastener can be engaged only by the driver.

2. A driver as claimed in claim 1, wherein the tamper-proof fastener has four recessed pockets in the head portion and the driver bit has four lobes 20 spaced substantially equally about the turning axis.

3. A driver as claimed in claim 1, wherein the tamper-proof fastener has five recessed pockets in the head portion and the driver bit has five lobes spaced substantially equally about the turning axis. 25

4. A driver as claimed in any one of claims 1 to 3, wherein the driver bit is a centrally located socket extending from an end of the driver bit which is adapted to snugly receive a complementary pin centrally located within the head portion of the tamper-proof fastener. 30

5. A driver as claimed in claim 4, wherein the socket of the driver bit is a polygon cross-section and the pin of the tamper-proof fastener has a complementary shaped pin to snugly receive the socket. 14

6. A driver as claimed in claim 4 or claim 5, wherein the pin and socket are reversed and the pin is located on the driver and the socket is located on the screw. 5

7. A driver as claimed in claim 1, wherein the lobes extending from the driver bit having a turning axis are oriented such that they are formed turning in a clockwise direction.

8. A driver as claimed in claim 1, wherein, the lobes extending from the 10 driver bit having a turning axis are oriented such that they are formed turning in a counter clockwise direction.

9. A driver as claimed in claim 7 or claim 8, wherein each lobe of the driver bit comprises at least three angled facets extending from an end of the driver bit 15 to a distance spaced from the end of the driver bit, wherein the angled facets engage with complementary shaped facets in the pockets of the tamper-proof fastener.

10. A driver as claimed in claim 9, wherein each angled facet is formed as 20 an uneven surface or each lobe is formed having irregular sized and shaped facets.

11. A tamper-proof fastener in combination with a tool comprising: a) a fastener having a threaded shank; and an enlarged drive head 25 integral with the shank, said drive head having an internally formed driving portion with at least three recessed pockets in the drive head portion, with each said pocket having at least three facets extending inwardly from the end of the drive head; and b) a tool having a turning axis and a driver bit with at least three lobes, 30 each said lobe formed by at least three angled facets extending from an end of the driver bit to a distance spaced from the end of the driver bit, wherein the angled facets engage with the complementary shaped facets in the pockets of the tamper-proof fastener. 15

12. A tamper proof fastener in combination with a tool as claimed in claim 11, wherein each said lobe is spaced substantially equally about the turning axis and a longitudinally extending driver shank, said shank having a first end spaced apart from a second end, said first end is adapted for connecting to a 5 driving device, said second end connecting to the driver bit.

13. A tamper proof fastener in combination with a tool as claimed in claim 11 or claim 12, wherein each said lobe projecting from the driver bit is separated from the next lobe by an angle of 120 degrees from each other. 10

14. A tamper proof fastener in combination with a tool as claimed in any one of claims 11 to 13, wherein the tamper-proof fastener has four recessed pockets in the head portion and the driver bit has four lobes spaced substantially equally about the turning axis. 15

15. A tamper proof fastener in combination with a tool as claimed in any one of claims 11 to 13, wherein the tamper-proof fastener has five recessed pockets in the head portion and the driver bit has five lobes spaced substantially equally about the turning axis. 20

16. A tamper proof fastener in combination with a tool as claimed in any one of claims 11 to 15, wherein said fastener and tool are fabricated from steel or stainless steel, and said drive head is cold headed. 25

17. A tamper proof fastener in combination with a tool as claimed in any one of claims 11 to 16, wherein each said facet in the fastener and tool have surfaces which extend substantially planar.

18. A driver tool for operating a tamper-proof fastener, said driver tool 30 comprising a shank; said shank comprising a first end and a second end, wherein said first end of said shank is adapted for connection to a driver device and longitudinally extends therefrom, said second end of said shank having a cross-sectional signature substantially complementary in size and shape to at least three recessed channels located within a head of the tamper-proof 16 fastener, and wherein inserting said second end of said shank into said three recessed channels of said head of said fastener results in a substantially mated engagement. 5

19. A driver tool as claimed in claim 18, wherein the cross-sectional signature comprises at least three lobes extending outward from a substantially centrally located cylinder, said lobes being equally spaced around the cylinder.

20. A driver as claimed in claim 18 or claim 19, further comprises a socket 10 centrally located and extending inwardly away from the second end of the shank, wherein the socket is adapted to snugly receive a complementary pin centrally located within the head portion of the tamper-proof fastener.

21. A driver as claimed in claim 20, wherein the socket of the driver tool has 15 a polygon cross-section and the pin of the tamper-proof fastener has a complementary shaped pin to snugly receive the socket.

22. A driver as claimed in claim 20, wherein the socket of the driver tool has four lobes extending outward from a substantially centrally located cylinder, 20 each lobe being equally spaced around the cylinder.

23. A driver as claimed in claim 20, wherein the socket of the driver tool has five lobes extending outward from a substantially centrally located cylinder, each lobe being equally spaced around the cylinder. 25

24. A driver and fastener system, comprising: a) a tamper-proof fastener having a non-twisted socket with facets, a cross-section through said socket defining an irregular polygon; and b) a driver with a shaft having a tip with an end face defining at least 30 three lobes, the lobes extending from the end face to a length along the shaft, wherein a first cross-section along said length defines an irregular polygon of a first size and a second cross section along said shaft defines a regular polygon of a larger second size, wherein when said tip is inserted into said socket, said 17 sides of the tip of the driver adjacent entry into the socket lie against said facets of the socket and said lobes of said tip contact the sides of the socket.

25. A driver and fastener system, comprising: 5 a) a tamper-proof fastener including a non-twisted socket with a depth and which defines an irregular N-sided polygon shape; and b) a driver including a shaft with a tip having a length substantially corresponding to said depth, said tip extending between an end of said tip and a location on said tip, wherein a first cross-section through said tip defines an 10 irregular N-sided polygon, and a second cross section along said shaft defines a regular polygon of a larger second size.

26. A driver bit for engaging with a recess of a tamper-proof screw, said recess being generally depression-like and having a central portion and at least 15 three lobe engaging portions extending outwardly from said central portion, wherein said driver bit comprising a bit central portion and at least three lobes for engaging said lobe engaging portions of said screw, said lobes extending outwardly from said bit central portion, each of said lobes comprising a proximal end side portion extending outwardly in the radial direction of said driver bit and 20 a distal end side portion extending outwardly from said proximal end side portion, said proximal end side portions of said lobes being arranged at equal angular intervals.