US2406952A - Safety screw driver - Google Patents

Description

Sept. 3, 1946. A. M. JOSEPHO 2 SAFETY SCREW DRIVER v Filed June 7, 194; I 2 Sheets-Shut; f

'. Arm m MARCO g/osz-w/o;

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Sept. 3,1946,

A. M. JOSE PHO SAFETY SCREW DRIVER Filed June 7, 1943 2 Sheets- Sheet 2 r J nve n tr Am 70! 44mm JOSE IIO- attorney.

Patented Sept. 3, 1946 UNITED STATES PATENT OFFICE SAFETY SCREW DRIVER Anatol Marco J osepho, Pacific Palisades, Calif.

Application June 7, 1943, Serial No. 489,909

3 Claims. 1

This invention relates to a safety screwdriver and more particularly to a tool of such character that will perform two primary functions in addition to the conventional function of driving in the screw: (first), will positively retain the screw at the end of the screwdriver in correct posi tion for starting, and (second), will confine the screwdriver to the screw while it is being driven in and without any manually applied pressure so that the screwdriver will not slip off the head of the screw until the screw is completely seated.

One important application of my invention is in bone surgery where an incision is made for access to the bone and a metal plate is secured to the bone by screws. This is a diflicult operation due to the small working space and the inaccessibility of the region where the screws are to be inserted, and the instruments heretofore available for such work have been seriously deficient. Another important use for my invention is in the fabrication of airplanes in which, for example, machine screws must be threaded into plate nuts in assembling frame parts, in attaching skin to the frame, etc., which Work must frequently be done in closely confined spaces in which access is diflicult and at arms length or more from the operator, and in many instances by unskilled labor. The invention isnot only useful under the circumstances detailed, but has other general and special utility which will be obvious upon a further consideration thereof.

A more specific object of my invention is to provide a safety screwdriver of the character described which will retain its operating connection with the head of the screw whether aligned 1ongitudinally with the screw or at an angle to the axis thereof, which embodies in effect a universal driving head, and which automatically becomes freed from the screw when the screw is fully seated by a forced spreading of the chuck jaws under the wedging action of the screw head or screwdriver blade end, or both, as the ends of the jaws bear upon the surface of the object into which the screw is driven.

Another object of my invention is to provide a tool of the character described having the advantages mentioned, and which will satisfactorily operate with screws of different diameter and heads of various sizes and shapes. It will perform, for example, equally well on a flat headed tapered type of screw as well as one with an oval head or a machine screw having a slotted head otherwise similarto a bolt, also a screw head known in the trade as a Phillips head.

A still further object of the invention is to provide a tool of the character described which can be readily manufactured.

An additional object of the invention, embodied in a modified form thereof, is the provision of a screwdriver of the character described embodying a flexible cable or drive shaft enabling a screw to be driven in at places where there is not room to operate a conventional form of screw driver, and which can be used in place of an offset screwdriver.

The foregoing and additional objects and advantages of my invention will become apparent from a consideration of the detailed description and drawings.

In the drawings:

Figure 1 is a vertical elevational View of my safety screwdriver assembled.

Figure 2 is a similar view of the shaft, head, and handle of my screwdriver.

Figure 3 is a similar view of the screw retaining guide detached from the shaft and head.

Figure is a somewhat enlarged fragmentary vertical sectional view taken on the line 4-4 of Figure 1, but illustrating a screw inserted in the screwdriver ready for starting.v

Figure 5 is a'view similar to Figure 4- showing the screw driven in and the jaws of the retaining chuck sprung for release.

Figure 6 is an enlarged cross-sectional view taken on the line i-5 of Figure 3.

Figure 7 is a view similar to Figure 4 illustrating the manner in which my screwdriver will op erate at an angle to the axis of the screw.

Figure 8 is a vertical sectional view of a modi fled form of my screwdriver embodying a flexible shaft and illustrated in use in a confined spacev Referring to the drawings, I have illustrated the first form of my screwdriver lfl as comprising a shaft I l at one end of which is a head or blade end l2 and at the other end a handle it. On

,the shaft between the head and the handle is a fixed collar l4 from which project pins l5 which form part of a bayonet slot connection to be described.

The shaft H, head I2 and handle l3 are rigidly associated.

The head 12 comprises a cylindrical portion as illustrated terminating in a beveled or tapered end l6, extending from which is a fiat blade H. The blade is also tapered on each side edge, the taper forming a continuation of the taper IS. The blade I1 is the part which enters the slot in any screw.

A screw guide and retaining device 20 shown "coupled with the shaft in Figure 1 and shownseparately in Figure 3 comprises the following parts: A tube 2| is formed with a slot 22 to cooperate with the collar l4 and pins l5 to provide the bayonet slot connection for coupling the retaining member to the shaft. Fixed upon the lower end of the tube 2| is a collar 23 formed with a groove 24 which provides an annular channel 25 between the tube 2| and the lower portion of the collar 23 for the reception of a helical coil spring 26. The upper end of the coil spring 26 is firmly seated in this channel 25. It may be pressed in or secured therein in any desired manner. The opposite end of the spring 26 is fixedly mounted in an annular channel 21 provided by a collar 28 fixedly mounted upon a tube 29. A knurled sleeve 28a is rotatably mounted on the collar 28. The lower end portion. 39 of the tube 29 affords a snug but rotatable fit with the head I2 of the screwdriver shaft and functions as a bearing guide therefor. The helical spring 26 secures the collars 23 and 28 in assembled relationship, the normal separation of the collars being governed by the length of the spring when contracted. This spring may be expanded for purposes which will hereinafter appear.

Mounted upon the lower end of the collar 28 is a spring expandable chuck comprising a plurality of arcuate jaws 36 sustained upon the lower end of wire springs 31, the upper ends of which springs are mounted in the collar 28. While I have illustrated three jaws of the character designated, there may be more or fewer, and the wire springs 37 may be replaced with flat springs or any other type of springs having the requisite characteristics of normally and yielda-bly retaining the chuck jaws 36 in the closed position illustrated in Figures 1, 3, and 6.

The vertical cross-section of the jaws is illustrated in Figures 4 and 5 wherein it is shown that the jaws collectively forming the chuck embody a cylindrical cavity 38 at the lower end of which is an annular ledge 39 from which extends a conical bore M! which terminates in a circular hole 4|. The jaws are formed with feet or end faces 42 adapted to bear upon the surface of the object into which the screw is being driven as the screw nears its final position.

With the shaft l l and guide 20 uncoupled, as shown in Figures 2 and 3, a screw, an example of which is indicated at S, is inserted in the tube 2! and allowed to fall through the bore of the guide until the head of the screw rests upon the conical or tapered bore of the chuck. The relationship of the size of the screw and the tool must be such that the stem of the screw will pass through the hole M but the head of the screw will not. With these limitations in mind it will be apparent that a substantial variety of sizes and shapes of screws may be handled with a single tool of the type described.

After the screw is inserted in the guide, the shaft is next inserted into the guide, the collar 23 is grasped with one hand and the handle I3 is advanced by the other hand against the tension of the spring 26 to couple the parts together by the bayonet slot connection shown and. described. In doing this, if the screw has a small head or is a fiat headed screw with a taper which seats fairly low in the conical bore 49 of the chuck, the lower end of the tube 30 will continue to retain its normal seat upon the annular ledge 39 of the chuck, and the cylindrical walls or bore 38 of the chuck will lie in engagement with the outer wall of the tube 3'0 under influence 'of the springs 31 which serve to center the jaws. 3

4 In the coupling operation it may be necessary to give the handle a slight twist in order to seat the blade I! in the slot of the screw head. If the screw has a relatively larger head, as illustrated, for example, in Figures 4 and 5, the wedging action of the screw head upon the tapered bore 29 under pressure of the blade I! will tend to slightly spread the jaws of the chuck.

With the screw and the tool in the relationship just described and as illustrated, for example, in Figure 4, the screw may be started into a nut or other intended element, and the handle of the screwdriver rotated in the conventional manner. No manual pressure is necessary to keep the blade in the slotted head of the screw. Pressure is required only for starting the screw and until the threads have taken hold.

While the screw is being driven in there is no change in the relationship of the tool parts until the feet 42 of the chuck jaws engage the surface part 43 of the element 44 into which the screw is being driven. However, when this occurs the shaft II and its attached head 12 and blade I! advance with the screw, while advance of the chuck ceases due to the feet 42 being stopped by the part 13. The blade I! continues to be held in engagement with the head of the screw due to contracting action of the helical spring 26. As the screw head continues to advance it exerts a wedging action against the tapered bore 40 of the chuck jaws, progressively spreading them against the tension of the springs 31. This is assuming a screw of the size and general type illustrated in the drawings. If the screw has a tapered flat head or is relatively smaller than the one illustrated, the wedging action may be performed by such head, or the conical taper l6 of the head l2 and the tapered blade I! may wholly or partially perform the wedging action against the jaws.

As the screw passes the opening 4| in the chuck and becomes seated, the jaws are then sprung apart sufficiently for the head of the screw to be released through the jaws, and the jaws will spring together in normally closed position as illustrated, for example, in Figure 1. It is the entrapment of the head of the screw (or the blade end of the screwdriver shaft) which produces the wedging action.

The taper IS on the head l2 and the taper on the blade I! correspond, and while the angle of this taper may be the same as the angle of taper in the bore 40, I prefer to make the taper slightly greater than in the bore 40 as I am thereby better enabled to prevent any binding of the blade in the chuck and to better exert a wedging action for spreading the chuck jaws, a function which is more important in the case of small headed screws than with large ones. In this connection the function of the helical spring 26 should be further emphasized. It not only provides the necessary yielding tension whereby the two major parts of the tool may be coupled together by the pins I5 and slots 22, but provides an automatic tensioning of the head l2 against the screw head regardless of the shape or size of the screw head so long as it is within the range of sizes which can be handled by the tool. Thus the screw is at all times firmly maintained in position at the end of the tool, and there is no tendency or opportunity for the blade I"! to slip out of the slot of the screw head. This latter is extremely important in many operations where a slip of the conventional screw-driver might cause irreparable damage.

This last safety feature is present even when the tool is operated at an angle from the axis of the screw as shown in Figure '7. It is assumed, of course, that the blade I! is sufficiently thinner than the width of the slot in the screw head so that it has some play therein. With such condition prevailing the tool may be operated at an angle from the axis of the screw and the blade will nevertheless drive in the screw with the effect of a universal coupling, while at the same time the independent spring mounting of the chuck jaws will permit certain of the jaws to yield more than others necessary to accommodate the rotation of the shaft H while held at an angle, yet the jaws retaining their resilient grip upon the head of the screw until it is finally seated.

In the modified *form of the invention illustrated in Figure 8 the essential elements of the device are present as before but with the substitution of a flexible shaft for the shaft or rod ll. Thus the device is shown operating on a screw Si being threaded into a plate nut 58 in a fabrication 51. The shaft or rod corresponding generally to the rod H has two sections, an upper section lid and a lower section Hb which are integral but are defined by a collar Ma which is fixed thereon. This flexible shaft is connected at its lower end to the head IM and at its upper end to the handle I311. The collars 23a and 28b are similar to those illustrated in the first form of the invention and these are joined by a helical spring 26a which is also similar. A knurled bearing sleeve 280 is likewise mounted on the collar 28a. The head l2a and other working parts illustrated are similar to the first form except as differentiated by explanation and as in other instances is obvious from the drawings. The tube Zla fits over the collar I4a and is coupled by a bayonet slot connection embodying pins a.

From the more detailed description of the operation of the first form of the invention the operation of the modified form should be obvious. The knurled sleeve 230 can be held stationary by the operator while the screw is being started in.

Power is transmitted from the handle i3a through the flexible shaft [la and III) to the head 12a. Manual power may be applied for turning the handle |3a in various positions remote from the location of the screw SI and quite irrespective of the longitudinal direction in which the screw progresses. The illustration is by way of example only, as the modified tool may be employed in all kinds of positions in which it would be impossible to operate a conventional screwdriver.

Although I have herein shown and described my invention in what I have conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of my invention, which is not to be limited to the details disclosed herein 6 but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a device of the character described, the combination of: a screw driving element comprising a shaft having a blade on one end, a handle on the other end, and one part of a coupling device intermediate the end, and a tubular screw guide and retaining element for retaining a screw in operative engagement with said blade comprising a plurality of tapered jaws enclosing said blade and diametrically yieldable under wedging action of either the blade end of said shaft or the head of said screw as they advance relatively to said jaws and releasing said screw head when the latter is advanced into its final seat, said jaws being spring mounted on a collar which encloses said shaft, a tubular member depending from said collar for guiding a screw and for centering said jaws, a complementary part of said coupling device adapted to cooperate with said first part to releasably retain said elements in assembled relation, and a helical spring interconnecting said complementary part and said tubular member.

'2. In a device of the character described, the combination of: a screw driving element comprising a flexible shaft having a blade on one end and a handle on the other end, a screw guide and retaining element for entrapping a screw in operative engagement with said blade comprising a plurality of jaws enclosing said blade, tapered means rendering said jaws diametrically yieldable under wedging action of either the blade end of said shaft or the head of a screw when said jaws bear upon the object into which the screw is being driven to pass said screw head as it advances when turned by said blade and releasing said screw head when the latter is advanced into its final seat, said guide element having a flexible portion and means for releasably coupling said elements together.

3. The combination of a screwdriver blade and a screw retaining means detachably connected therewith for continuously tensioning the blade in a screw head slot during operation, said screw retaining means including a separate screw head engaging chuck comprising a plurality of jaws encircling a screw, said jaws having inner faces tapering outwardly from the base of each and engaging under the head of the screw, spring mounts on the retaining means for each jaw, and the jaws being diametrically yieldable under wedging action of either the blade or the head of the screw when said jaws bear upon the surface of an element into which the screw is being driven to release the screw from the retaining means.

ANATOL MARCO JOSEPHO.

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