Fastener Retainer and Driver

This application claims priority to U.S. Provisional Application No. 60/707,864, filed August 12, 2005. The disclosure of this prior application is incorporated by reference in its entirety.

TECHNICAL FIELD This invention relates to a fastener retainer and driver.

BACKGROUND

It is often desirable to be able to retain a fastener to a driver without having to use one's hand, such that only one hand need engage the driver leaving the other hand free to, for example, hold a work piece into which the fastener is being driven.

SUMMARY

In one aspect, a driver includes a shank split in a distal region of the shank to form spring members normally spaced apart a first distance. The members form a fastener mating portion and are configured such that when a force is applied to the members, the mating portion forms a regular polygon for mating with a fastener, and when the force is removed, the members grip the fastener due to a return toward their normally spaced distance.

Embodiments of this aspect may include one or more of the following features.

The members form the regular polygon when compressed. Alternatively, the members form the regular polygon when expanded. The members are substantially equally dimensioned. The shank is one piece and is solid. The split does not extend a full length of the shank, for example, the split is only in the distal region of the shank. The members include complementary shapes configured to limit relative slipping between the members. The driver includes an assisting mechanism for applying an inward, compression force to the members. Alternatively or in addition, the driver includes an assisting mechanism for applying an outward, expansion force to the members.

According to another aspect, a driver includes a one-piece shank split in only a distal region of the shank to form substantially equally dimensioned spring members.

The distal region of the shank includes a fastener mating portion configured to mate with a fastener. The members are configured such that when the members are collapsed, the mating portion forms a regular polygon.

According to another aspect, a driver includes a solid shank split in only a distal region of the shank to form substantially equally dimensioned spring members such that in a free state the members are normally spaced apart a first distance. The distal region of the shank includes a fastener mating portion configured to mate with a fastener. The members are configured such that when a force is applied to the members, the shank can receive the fastener, and the members grip the fastener due to a return toward their free state.

According to another aspect, a method of manufacturing a driver includes forming a material into a polygonal shape, and splitting the material to form substantially equally dimensioned spring members, such that when the members are brought into contact, the members form a regular polygon. Advantages may include one or more of the following.

Regular shape of the mating portion and thus the close fit of the mating portion with the fastener, reduces any likelihood of breakage of the members, which are under shear stress when the driver rotates the fastener.

The fastener retainer and driver is particularly useful in orthopaedic applications where it is difficult or impossible to use one's hand to retain a fastener to the driver, for example, when advancing the driver and fastener through a guide tube.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

Fig. 1 is an illustration of a driver for retaining and driving a fastener.

Fig. 2 is an end view of a mating portion of the driver of Fig. 1 shown in an unstressed state. Fig. 3 is an end view of the mating portion of Fig. 2 shown in a stressed state.

Fig. 4 is an end view of the mating portion shown prior to forming a slit in the driver shank.

Fig. 5 shows alternative configurations of the slit.

Figs. 6-8 are illustrations of various alternative profiles on the faces of spring members of a driver.

Figs. 9 and 10 are illustrations of an alternative embodiment of a driver.

Figs. 11 and 12 are illustrations of another alternative embodiment of a driver. Figs. 13-15 show various alternative embodiments for assisting in the collapse of spring members of the drivers of Figs. 1 and 11.

Fig. 16 is an illustrations of a mechanism for assisting in the expansion of spring members of the driver of Fig. 9.

Fig. 17 illustrates screw head configurations. Fig. 18 is an illustration of the driver of Fig. 1 in use in a medical application.

DETAILED DESCRIPTION

Referring to Fig. 1, a driver 10 for retaining and driving a fastener (not shown) includes a shank, for example, a one-piece, solid shank 12m having a distal region 14 that is split in two by a slit 16 to form substantially equally dimensioned spring members 18a, 18b. In a free state, the spring members 18a, 18b are normally spaced apart a first distance, X (Fig. 2), selected to be a value within the range of , for example about 0.001" to 0.012", preferably about 0.006" to 0.012". The distal region 14 of the shank 12 includes a fastener mating portion 20 at a distal end portion 22 of the shank. The fastener mating portion 20 has a profile, for example, a polygon such as the hexagon of Fig. 1, that corresponds to the drive head of the fastener. Various configurations of the mating portion are contemplated (see, for example, Fig. 17).

To retain the fastener to the driver 10, the user applies an inward force to the spring members 18a, 18b to collapse the spring members, inserts the spring members into the fastener head, and releases the spring members to grip the fastener. Thus, when the spring members 18a, 18b are collapsed, the fastener can receive the driver 10, and when the spring members are freed upon removal of the inward force, the driver retains the fastener. To remove the driver 10 from the fastener, the user need only pull back on the driver with or without concurrently applying an inward force to the spring members 18a, 18b. When the spring members 18a, 18b are collapsed, the spring members are in contact along a length of, for example, about 0.001" to 0.25", of the spring members measured proximally from their distal ends 24. This portion 26 of the driver 10 forms the shape of the fastener head, for example, a regular polygon (Fig. 3), when the

spring members are collapsed such that the fastener mating portion can receive the fastener. When the inward force on the spring members 18a, 18b is removed, the natural tendency of the spring members to return to their free state provides the retaining force needed to grip the fastener. The slit 16, and thus the split in the shank 12, does not extend a full length of the shank, for example, the split is only in the distal region 14 of the shank 12. The length of slit 16 is, for example, about 0.01" to 5", preferably about .25" to 1.25", depending on the shaft length (for example, in the range of about 3 to 50% of the shaft length, preferably about 9 to 25% of the shaft length, and most preferably about 15% of the shaft length), and is selected to provide a desired amount of retaining force while not being too stiff, which would make it difficult to compress the spring members.

The driver 10 includes a handle (not shown) that can be of any conventional type.

To manufacture driver 10, the raw material, for example, 400 series stainless steel for medical applications and hardened tool steel for other applications, in the form of rod stock is cut to the desired length and lathe turned or centerless ground to the desired diameter. For the hex driver of Fig. 1, a six-sided tip is milled or broached to the proper specification along distal end 22. For example, referring to Fig. 4, six- sided tip 30 has four sides 32a-32d of equal length, and two sides 34a, 34b that are longer. The slit 16 is made in the shaft 12 in distal region 14 using a microtome or EDM process to remove the material within dashed lines 36 to form spring members 18a, 18b. The width of slit 16 is selected such that when the spring members are brought into contact, a regular hexagon is formed.

As shown in Fig. 5, the slit 16 need not be machined through the center of the long sides 34a, 34b, but could be at an angle as shown by line 40. Alternatively, four sides of the six-sided tip could be longer and the slit 16 machined through the apex where each of two sides meet, as shown by line 42. However the slit is oriented, the resulting spring members are substantially equally dimensioned. For example, the ratio of the dimensions of the spring members can be 25 to 75% of the cross-section area, 30 to 70%, 35 to 65%, 40 to 60%, 45 to 55%, anywhere within the range of 25 to 75% to 50 to 50%, and preferably 50 to 50% of the cross-sectional area to provide the greatest torque transfer capability.

Referring to Figs. 6-8, to limit any tendency of the spring members to slip past each other when placed within a screw head and torquing the screw, various shape

modifications can be made in the surfaces of the spring members where the slit is formed. For example, in Fig. 6, spring members 18 'a, 18'b have complementary stepped formations; in Fig. 7, spring members 18 "a, 18"b have complementary wavy surfaces; and in Fig. 8, spring members 18"'a, 18"'b have complementary notches 46 forming an opening in which a pin 48 is received. The complementary shapes reduce the likelihood of stripping of the fastener or driver, and reduce the likelihood that the spring members would break.

The split shank concept described above can also be applied to drivers in which the screw head is received within the driver rather than the driver being received within screw head. Referring to Figs. 9 and 10, a driver 110 for retaining and driving a fastener (not shown) includes a one-piece, solid shank 112 having a distal region 114 that is split in two by a slit 116 to form substantially equally dimensioned spring members 118a, 118b. In a free state, the spring members 118a, 118b are normally spaced apart the first distance, X. The distal region 114 of the shank 112 includes a fastener mating portion 120 at a distal end portion 122 of the shank. The fastener mating portion 120 defines an internal profile, for example, a polygon such as the hexagon shown, that corresponds to the drive head of the fastener to be received within mating portion 120. Various configurations of the mating portion are contemplated. To retain the fastener to the driver 110, the user applies an outward force to the spring members 118a, 118b using the fastener head to spread the spring members, and inserts the fastener head into the mating portion 120. The natural tendency of the spring members to return to their free state provides the force to grip the fastener. To remove the driver from the fastener, the user need only pull back on the driver. In their free state, the spring members 118a, 118b form a split hexagon having two sides 134a, 134b that are shorter than the other sides. When expanded to receive the fastener head, the sides 134a, 134b are slightly longer than the other sides. Once the fastener is within mating portion 120 and gripped by spring members 118a, 188b, the six sides of the split hexagon are of equal length to form a regular polygon. As discussed above, the slit 116 need not be machined through the center of sides 134a, 134b.

Referring to Figs. 11 and 12, in another embodiment, a driver 210 for retaining and driving a fastener 211 includes a one-piece, solid shank 212 having a distal region 214 that is split in three by three slits 216 to form substantially equally dimensioned

spring members 218a, 218b, 218c. The distal region 214 of the shank 212 includes a fastener mating portion 220 at a distal end portion 222 of the shank. The spring members each end in a prong 224 for mating with holes 226 in the fastener head. Driver 210 functions as described above with reference to driver 10. To assist in applying an inward compression force, the driver can include an assisting mechanism such as finger pads 250, 252 (Fig. 13) for applying direct manual compression, or, as shown in Fig. 14, the driver shank can have an increased diameter in a region 254 of the shank corresponding to the proximal portion of the slit, and a sleeve 256 that is extendable over the shank to engage the region 254 and compress the spring members.

Referring to Fig. 15, a driver 258 includes a shaft 260, a moveable member 262, a first passage 264, a first guide 266, a second passage 268, a second guide 270, at least one spring 272, and at least one retaining device 274. In the depicted embodiment, there are two springs 272, such as helical springs, that bias the moveable member 262 away from the shaft 260. The springs 272 bias the moveable member 262 away from the shaft 260 so as to form a slot 280. The first and second guides 266, 270 are mounted to the moveable member 262. For example, the first and second guides 266, 270 may be pressed fit to the moveable member 262. Optionally, the moveable member 262 may further include one or more mounting devices 276 to retain the first and second guides 266, 270. The first and second guides 266, 270 are received in the respective first and second passage 264, 268. The retaining devices are attached to the guides 266, 270 and limit the travel of the guides 266, 270 within the passages 264, 268. Thus, the guides 266, 270 allow the moveable member 262 to move relative to the shaft 260 but the retaining devices 274 keep the components from separating.

Fig. 16 shows an assisting mechanism that can be used to assist in spreading the spring members. The assisting mechanism can be used to lock the spring members within the screw head in which the spring members are received (as illustrated in Fig. 16), or the assisting member can be used in the embodiment of Fig. 9 to spread the spring members 118a, 118b to receive the screw head within the spring members 118a, 118b. The shaft 312 of Fig. 16 defines a central lumen 314 that ends in a tapered region 316 at the distal end of the shaft. The tapered region 316 has a diameter that enlarges distally. Located within the tapered region 316 is a bead 318, and attached to and extending proximally from the bead 318 within the lumen 314 is a

rod 320. The bead 318 is smaller in diameter than the distal end 322 of the tapered region 316 but larger in diameter than the apex 324 of the tapered region. By moving the rod 320 proximally, the bead 318 is moved longitudinally along the tapered region to expand the spring members. Rod 320 can be moved distally and proximally using a handle 330. Handle

330 includes a stationary grip 332 and a lock knob 334 that is coupled to the grip by a snap ring 336. The lock knob 334 is rotatable relative to the grip 332. The lock knob 334 defines a threaded central lumen 338. The rod 320 has a threaded proximal tip 340 that threadedly engages the threaded wall of lumen 338. Formed between the rod 320 and the shaft 312 is a key/keyway arrangement 342. When the user rotates the lock knob 334, the key/keyway arrangement 342 forces the rod 320 to move axially along the shaft, thus moving the bead 318 proximally to expand the spring members or distally to allow the spring members to collapse. The grip 332 and the shaft 312 have corresponding flats 344 such that rotation of the lock knob 334 does not cause rotation of the grip .

When applied to the embodiment of Fig. 9, the tapered region and the bead are located proximally of mating portion 120.

Referring to Fig. 18, in use in an orthopaedic application, the surgeon grips a fastener 400 with the driver, for example, the driver 10 of Fig. 1, and advances the fastener 400 to the surgical site through a drill guide tube or tissue protector 402. The driver 10 provides the ability to actively retain the fastener to the driver even when the surgeon cannot access the fastener because the fastener is within the tube 402 or out of reach within the patient's body.

A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, in the embodiments of Figs. 1-10 and 13-16, the shaft can be split to form more than two spring members, for example, three of four spring members, and the embodiment of Figs. 11 and 12 can have other than three spring members, for example, two or four spring members. The shaft can be split by two parallel slits to form three spring members. The above described drivers can mate with and grip objects other than a fastener. For example, rather than directly coupling to a fastener, the driver of Fig. 9 can receive a driving bit, which in turn can include any of the above described configurations for mating with and gripping a fastener.

Accordingly, other embodiments are within the scope of the following claims.