Field of the Invention The present invention relates to flexible drive systems and flexible drive shafts.

Background of the Invention The present invention relates to flexible torque transmitting drive systems and flexible torque transmitting drive shafts. More particularly, the invention relates to drive systems and drive shafts where flexibility is required for transmitting direct torque and/or torque ratios and drive applications.

Drive shafts are used in many applications to transmit power and torque from a drive shaft to a driven shaft at a distance. Flexible drive shafts are used in situations where the drive shaft and the driven shaft are not coaxial and/or where a direct linear drive shaft cannot be connected because of intervening obstructions between the drive shaft to the driven shaft. Applications involve transmitting torque from a power source, i.e., a motor, engine, transmission, gear reduction device, etc., to a device, i.e., tool, machine, etc., at a distance, or at an obtuse or compound angle from the drive shaft. It is important, even when the drive shaft is bent at obtuse or compound angles, that the driver developed torque is equal to the delivered driven torque. Also, it is important that no backlash, or slippage, of the

flexible drive shaft occur when the desired rotational torque is applied to a device at specified angles and azimuths.

One example of an application for a flexible drive shaft is in the medical device industry. Such devices utilizing flexible drive shafts may be a part of a tool used for diagnostic survey surgery or for part of an orthopedic surgical device.

Existing devices are cumbersome and are prone to slippage. They are limited in angular application because of slippage and distortion of the flexible drive shaft.

Such limitations force a surgeon or orthopedist to take compensating precautions when using such a device in order to prevent injury to a patient during use.

Existing devices of flexible drive shafts are size- and torque-limited because of their design and construction. During particular dangerous or risky invasive surgery, such as cardiovascular or lung biopsy operations, a flexible drive shaft which is not limited in diameter and torque and which is free of backlash would be particularly useful. Such a system that would not require compensating measures to be taken by the surgeon during usage would be particularly advantageous.

It is an object of the present invention to provide a flexible drive shaft that can be utilized at obtuse and/or compound angles between the drive shaft and driven shaft.

It is a further object of the present invention to provide a flexible drive shaft that is not prone to backlash when torque is applied to the drive shaft and/or when torque is released from the drive shaft.

Another object of the present invention is to provide a flexible drive shaft that delivers literally all the developed torque from the drive shaft to the driven shaft. The new flexible drive shaft system of the present invention is particularly applicable to the medical field, especially to surgical and orthopedic devices. The new system provides for effective and efficient torque applications from the drive

shaft to the driven shaft, even when the flexible drive shaft system has one or more bends. The flexible drive shaft system of the present invention can be utilized even when the flexible drive shaft undergoes a U-bend, i.e., a bend of 1800. Another ad- vantage of the present flexible drive shaft system is that it allows substantially higher torque values or loads with proportionally smaller diameters than existing flexible drive shafts. In addition, the present invention's drive shaft system provides for precise rotational and angular forces. These forces control the rotational travel and torque of the flexible drive shaft so that the rotational travel and torque of the driven side equals that of the driver's side of the flexible drive shaft system, even when the flexible drive shaft is bent one or more times. The present invention's flexible drive shaft has a constant diameter regardless of whether it is in a bent or unbent state. Thus, the present invention's flexible drive shaft systems can follow the curve or curves of a cavity, of a conduit, of a vein, etc. without an increase in its diameter at a bend or bend irregularities.

The drive shaft system of the present invention comprises one or more substantially identical configured segments or knuckle elements adapted to inter- lock together with rotational sliding freedom regardless of polarity. The knuckle elements, because they are substantially identically configured, can be used in any numerical combination to form a chain of interlocking segments, i.e., a flexible drive shaft of virtually any length that can bridge a drive shaft to a driven shaft and that is flexible and can be bent to a desired arc or curvature.

Each segment or knuckle element is cylindrically configured, having distal end portions and proximal end portions separated by a cylinder. The distal end portion and proximal end portion are identically configured so that they directly interface and interlock, with rotational and sliding freedom, with adjacent similar segments or knuckle elements. The distal and proximal ends of the segments or

knuckle elements are castellated, having four raised bosses extending axially from the cylinder and four recessed grooves separating the bosses. The four raised bosses of an adjacent segment or knuckle element are received in the four recessed grooves in an interlocking relationship with rotational and sliding freedom.

Thus, the four raised bosses on one segment or knuckle element interface and interlock with the four raised bosses of an adjacent segment or knuckle element with rotational and sliding freedom. By rotational freedom, it is meant that the bosses can swivel with respect to the adjacent bosses on the sides of the bosses when two segments or knuckle elements are interfacing and interlocked together.

By rotational freedom it is also meant that the bosses can rotate with adjacent bosses on the side of the bosses as the segments are rotated about the bosses.

By sliding freedom, it is meant that the sides of the walls of a boss can slide with respect to the side walls of adjacent bosses when two segments or knuckle elements are in an interfacing and interlocking relationship. The bosses axially extending from the distal end and proximal end of a segment comprise approximately 30% of the axial length of each segment or knuckle element.

However, the length of the bosses with respect to the segment can vary, depending upon the application and degree of bending freedom desired for the flexible drive shaft. For a given flexible drive shaft, each segment will be virtually identical, preferably identical, so that each segment will have substantially identical castel- lated bosses and recesses. The drive shaft will have castellated bosses and recesses adapted to receive and interlock with the first segment or knuckle element. The driven shaft will have castellated bosses and recesses adapted to receive and interface with the last segment or knuckle element of the flexible drive shaft. For reference purposes only, the first segment or knuckle element is considered to be the segment interfacing and interlocking with the drive shaft. The

last segment, for reference purposes, is considered to be the segment that interfaces and interlocks with the driven shaft.

The interlocking bosses of the segments or knuckle elements and of the drive shaft and driven shaft are geometrically configured so that when bosses of adjacent segments and of the driven shaft and drive shaft are interlocked, and a rotational torque is applied from the drive shaft, the interlocking bosses of the drive shaft, the segments and the driven shaft will engage the adjacent interlocking bosses, causing them to react by rotating in a similar fashion. Each boss is specifically configured so that there is a radius on its crest, nose or end. This radius includes an angled surface or side at the crest or nose of the boss. This angled surface angles back from the axis or longitudinal center line of the segment or knuckle element towards the other end of the segment. Additional angles are included on either side of each boss, starting at the root or base of the boss and angling inwardly towards the radius at the crest or end of each boss. Each boss has a peripheral cylindrical angle surface or a circumferential angled side. The circumferential angled side angles radially inwardly starting at the root of each boss and taper inwardly towards the crest or nose of each boss.

All the angles of the above-described angled surfaces or sides are preferably between about 90 and 120 and may be tailored to smaller or larger angles to meet specific requirements. The radii and angles allow the segments or knuckle elements to flex longitudinally and rotate linearly, i.e., swivel and rotate with respect to adjacent segments. The cylindrical angle of the circumferential angled side of each boss allows for blended peripheral arc when the segments are flexed.

The cylindrical segments or knuckle elements may be solid. Preferably, however, each segment or knuckle element is tubular, i.e., it has an axial bore coaxial with the segment's axis, i.e., axis of rotation or longitudinal axis, extending

from the distal end to the proximal end of each segment and is coaxial with the linear axis of the segment. Advantageously, a flexible tubular member extends through the chain of segments by extending through the central bore of each segment affixing the segments together and the drive shaft to the driven shaft through the chain of segments. However, the flexible tubular member does not have to be affixed to the drive shaft and driven shaft. The tubular member can be a coiled tubular spring or it can be a flexible polymeric tube or rod. A tube or coil spring can accommodate a fiber optic element, or a tube could be utilized to transmit fluids or gases. If a coil spring wire is used as a tubular element, it can be affixed to the drive shaft and the driven shaft by crimping or brazing or the like. If a polymeric tube is employed, it can be affixed or anchored by crimping, bonding, or fusing the tube to the drive shaft or driven shaft; however, the flexible polymeric tube does not have to be affixed or anchored to shafts. If a plastic rod is employed, it can be affixed by bonding, fusing, or welding.

During assembly of the flexible drive shaft, each segment or knuckle element would be set over the flexible tubular member and then rotated so that each segment interlocks prior to final assembly. The flexible tubular member serves three functions. It biases the flexible drive shaft into a straight linear configuration. It assists in maintaining the distance between the driven shaft and the drive shaft and between each segment relatively constant, and it helps maintain each segment centered along the axis of rotation of the flexible drive shaft during operation.

Another element of the preferred flexible drive shaft is a length of tubular woven braid that circumferentially covers the segments or knuckle elements and is affixed to both the drive shaft and driven shaft. The woven braid is comprised of polymeric strands, such as polytetrafluoroethylene strands, polyethylene strands,

fine stainless steel or other non-corrosive metal wire, which is finely woven into a tubular configuration. A flexible polymeric tube can be used in place of woven braid. A flexible polymeric tube can also be used as a sleeve in the woven braid.

The woven braid is placed over the segments or knuckle elements and can be attached to the drive shaft and driven shaft by crimping a malleable and non- corrosive ring over the braid onto the drive shaft. During assembly of a flexible drive shaft, the woven braid is first attached either to the drive shaft or driven shaft by crimping and then crimped to the other shaft after the chain of segments and other shaft have been inserted into the tubular woven braid and slight tension has been applied to the woven braid. The woven braid is a critical component of the flexible drive shaft when each segment or knuckle element is solid. When the segments are solid, a flexible tubular element cannot be employed to keep the seg- ments together and prevent the segments from separating or deviating from the axis of rotation during rotation of the flexible drive shaft. The woven braid keeps the segments or knuckle elements in their interlocking relationship and keeps the bosses in the grooves. The woven braid keeps the bosses from extending radially and axially out of the grooves.

In the preferred embodiment of the present invention, the segments or knuckle elements and drive shaft and driven shaft, whether solid or centrally bored, are encapsulated within a length of woven braid which circumferentially covers the knuckle elements and the ends of the drive and driven shafts coupled to the string of segments. The ends of the woven braid are affixed to both the drive shaft and driven shaft by conventional means, such as by bending, crimping, soldering, welding, or the like. This woven braid comprises fine stainless steel or other non- corrosive metal wire which is finely woven into a tubular configuration. The woven braid is placed over the strings of segments or knuckle elements and is attached to

either the drive shaft or driver shaft such as by crimping a malleable and non- corrosive ring over the braid and shaft. Similarly, and after slight tension is applied to the woven braid, the woven braid is crimped to the other shaft, other the driven shaft or drive shaft, as the case may be.

The woven braid is a critical component of the drive shaft when solid segments or knuckle elements are used in the invention, i.e., segments that do not have the axial bore to receive a flexible tubular element. Additional protection and sealing of the flexible drive shaft can be accomplished by covering the woven braid and a portion of both the drive shaft and driven shaft with a flexible and thermal resistant polymeric tube, such as a plastic tube. An ideal material is high temperature resistant irradiated polyolefin. Plastic tubing extends over the woven braid and beyond the crimped joint between the woven braid and the drive shaft and driven shaft described above. The ends of the plastic tube are bonded to both the drive shaft and driven shaft beyond the crimped joint. Thermally shrinkable polymeric tubing can also be applied and thermally shrunk to bond to the flexible drive shaft. The flexible polymeric tubing protects the flexible drive elements from medical autoclave cleaning processes and precludes dust, fluids, and other foreign objects from penetrating into the working elements of the flexible drive mechanism through the wire braid. An additional benefit of this high temperature resistant plastic tube is that it protectively covers potentially harmful sharp corners associated with normal manufacturing processes of the segments and other components of the flexible drive shaft.

The flexible drive shaft of the present invention provides that the driven ro- tational travel is equal to the driving rotational travel, regardless of whether the flexible drive shaft is bent at an obtuse angle or bent where there are compound angles.

The bosses are configured to include tapered and angled sides so that a similarly configured mating boss from an adjacent segment or knuckle element can interlock with rotational freedom and sliding freedom.

The bosses are configured to include a conical angle on their crests or front surfaces or noses so that they can swivel up and down when interlocked in the groove of the adjoining segment.

The bosses are configured to included a tapered peripheral angle so that when two or more of the segments or knuckle elements are interlocked together, they form a circular arc with no protrusions interrupting the curvature of the arc to the bent flexible drive shaft.

The bosses' grooves include suitable radii so that when two or more of the segments or knuckle elements are interlocked together, they smoothly flex and arc without interruption to the uniformity of the flexing and arcuate motion.

Brief Description of the Drawings Figure 1 is a plan view of the segments or knuckle elements of the present flexible drive shaft system; Figure 2 is a partial fragmentary plan view of the segment of Figure 1 that has been rotated 450.

Figure 3 is an end view of the segment of Figure 1; Figure 4 is a fragmentary top sectional view of the flexible drive shaft of the present invention; Figure 5 is a perspective view of the segment of Figure 1; Figure 6 is the driver end of another embodiment of the flexible drive shaft of the present invention;

Figure 7 is the driven end of another embodiment of the flexible drive shaft of the present invention; and Figure 8 Is a plan view of the drive shaft of the present invention.

Detailed Description of the Invention Referring to Figures 1, 2, 3 and 5, the flexible drive shaft system 10 of the present invention is comprised of a number of components, including segments or knuckle elements 18. The segments 18 comprise a cylinder 48, which can be solid or bored axially with bore 54, as shown in Figure 1 in phantom. Each segment has four bosses 50 extending axially outward from each end of the cylinder 48. Each boss has a base or root 57, angled sides 58 which extend axially outward from the cylinder, a conical front side 60, a bottom or inner circumferential side 62, and a top or outer circumferential angle side 64. The bosses are separated by recessed grooves 52. The length of the bosses is selected to accomplish specific functions of the flexible drive shaft, i.e., degree of bending. For drive shafts that will bend relativeiy sharply, the bosses will be shorter than for drive shafts that will have moderate or mild curvature. Likewise, the axial length of the cylinder 48 will be selected for a particular purpose for the flexible drive shaft . For drive shafts that will have sharp bends or curvatures, the axial length of the cylinder 48 will be shorter than for flexible drive shafts having moderate or mild bends or curvatures.

It has been found that bosses having an axial length of about 15% of the total length of the segment work out satisfactorily and permit the flexible drive shaft to be bent into obtuse angles or two or more compound angles. Preferably, the segments will be identical. The lengths of the segments can vary, but the diameter of the segments and the shapes and dimensions of the bosses and grooves should be substantially identical. The recessed groove 52 of a segment is designed to

receive a boss from an adjacent substantially identical segment. Thus, each end of a segment is adapted to receive the end of an adjacent segment in an interlocking relationship for freedom of rotational motion and freedom of sliding motion between the bosses. In other words, the four recessed grooves 52 at the end of one segment will receive the four bosses 50 of the adjacent segment, and the four recessed grooves of the adjacent segment will receive the four bosses of the one segment in an interlocking relationship as described above.

The angled sides 58 of each boss are angled inwardly from the base 57 towards the nose or crest of the boss at an angle 80 (see Figure 1). The conical front side 60 of each boss is radially angled back from the longitudinal axis or axis of rotation 56 of the segment back towards the other end of the segment at an angle 82 (see Figure 1). The top circumferential angled side 64 of each boss is angled downwardly from the root of the boss towards the axis 56 at an angle 84 (see Figure 1).

Each groove 52 has a back wall 66. The back wall 66 and the angled side 58 blend together via fillet 68. The conical front side 60 has a blended radius which blends the conical front side into the angle sides 58 as shown in Figures 1, 2 and 5.

Because of the unique design of each segment or knuckle element, each end of each segment can interlock with the end of an adjacent segment regardless of the polarity between the two segments. A segment with side angles 58 on either side of its four bosses 50 permits interlocking segments or knuckle elements 18 to swivel both vertically and horizontally at a prescribed angle which is fixed by the side angle 80. A segment with conical angles 82 at the nose of the four bosses 50 allow interlocking segments 18 to swivel both vertically and horizontally to a maximum angle fixed by the conical angle 82. In other words, if angle 82 is 100, the two adjacent segments in interlocking relationship with respect to each other

cannot bend more than 200 with respect to their longitudinal axes. Each segment with its circumferential angle 84 on each boss at both ends of the segment permits interlocking segments to smoothly arc when curved or bent vertically and horizontally (see Figure 4). The blended radius at the nose of each boss 50 and the fillet radii 68 at the base of each boss at the back wall of each groove allow for a smooth transition of the interlocking bosses during the vertical and horizontal flex- ure actions of the segments during rotation. Moreover, the combination of the angles 80, 82 and 84 for the angled sides 58, conical front side 60, the blended radius of the nose of each boss, and the radii of the fillet 66 eliminates backlash or swivel interruption during vertical and horizontal flexure actions of the flexible drive shaft during rotation of the drive shaft.

The grooves 52 are always slightly larger than the bosses 50 in circumfer- ential width 44, 42 respectively (see Figures 1 and 2). As the angled side walls 58 of each boss angle inwardly as they extend axially outward from the cylinder 48, each groove 52 defined by the side walls 58 angles outwardly as it extends axially outward from the cylinder 48. Thus, the grooves and bosses of adjacent segments complement each other and are designed to dovetail when the segments are interlocked. The tolerances can be adjusted as deemed fit to minimize or maximize play in the flexible drive shaft. For a flexible drive with little play or rotational movement, tolerances between interlocking bosses can be less than 1 mil. For drive shafts with more play for rotational movement, the tolerances can be greater than 1 mil.

The flexible drive shafts of the present invention with all their components are illustrated in Figures 4, 6, 7, and 8. However, Figures 4, 6, and 7 show alternative embodiments of the flexible drive shaft of the present invention. The flexible drive shaft of Figure 4 has no central flexible tubular element running the

length of the drive shaft. The flexible drive shaft of Figure 6 has a flexible tubular element running through the central bore of the segments and into the drive coupler 34. In this embodiment of the invention, the flexible tubular element is a coiled spring 21 which runs the entire length of the flexible drive shaft from the drive coupler 34 to the driven coupler (not shown) at the driven end of the flexible drive shaft.

The flexible drive shaft of Figure 7 also has a flexible tubular element 20 running the length of the flexible drive shaft (not shown) from the driven shaft 24 through the bores of the segments 18 to the drive shaft at the other end of the flexible drive shaft. The flexible tubular element in the embodiment shown in Figure 7 is a polymeric tube 19.

As shown in Figure 4, the drive shaft has a driving end assembly 12 at one end and a driven end assembly 14 at the other end which are interconnected with tubular wire braiding 28 and the string of interlocking segments as described above. A drive shaft 38 is shown in Figure 8. The drive shaft and the driven shaft are normally identical. The drive shaft is comprised of the main shaft 90 which is normally connected to the powering device or the device to be powered, a mid portion of reduced diameter 92, and a coupling head 94 which has bosses 50 and grooves 52 which are substantially identical in shape and size to the bosses and grooves in the segments of the flexible drive shaft. The first segment of the flexible drive shaft, which is coupled to the drive shaft 38, has four of the bosses at one end interlocking with the four bosses of the coupling head 94 of the drive shaft in an interlocking relationship with freedom of rotation and freedom of sliding motion.

Likewise, the last segment of the flexible shaft 40 that is coupled to the driven shaft so that its bosses 18 interlock with the bosses of the driven shaft 40 the same manner as the bosses of adjacent segments of the flexible drive shaft.

The flexible drive shaft of Figure 4 is assembled by securing one end of the tubular wire braiding 28 to the driven shaft or drive shaft 40 or 38, respectively.

The end of the wire braiding butts against the shoulder 96 of the shaft. The tubular wire braiding can be affixed to the shaft in any manner, including soldering, silver soldering, and the like. The braiding can be secured to the shaft quickly and securely with a crimping or ferrule 30. The segments are then inserted into the interior of the tube in interlocking relationships to form the string of segments. The flexible polymeric sheath 32 is then pulled over the tubular wire braiding and affixed to the drive shaft and driven shaft. As mentioned before, in this embodiment, the flexible drive shaft has no flexible tubular element. However, if a flexible tubular element were to be provided, the drive shaft and driven shaft would have axial bores (shown in phantom as 98 in figure 4), and the string of segments in interlocking relationship would first be assembled on the flexible tubular element, which would be secured in axial bore 98 of the shaft, and then the tubular wire braiding would be slid over the segments and secured to the drive shaft or driven shaft as described above.

After the braiding and segments have been assembled, the remaining shaft, either the drive shaft or driven shaft, as the case may be, is inserted into the tubular wire braiding 28. The shaft is rotated so that the coupling head of the shaft interlocks with the end segment. The tubular wire braiding is secured to the mid- portion 92 of the shaft after the braiding is placed under mild tension to keep the segments together in interlocking relationship with the coupler heads 94 of the drive shaft and driven shaft.

As discussed previously, the angles 80, 82 and 84 and length of the seg- ments are selected so that the flexible drive shaft in Figure 1 can accomplish a

function. The angles 80, 82 and 84 can be 92° and the length of each segment can 3 be 18 inch with a diameter of 8 inch, so that the flexible drive shaft over a distance of 18 inch can be bent at a radius angle of 500, i.e., an angle of 500 between the axis at the first segments 18A and 1 8B out of the bend (see Figure 4). By selecting other angles, other segment lengths, and diameters, in operation, the flexible drive shaft delivers substantially all the torque from the drive shaft to the driven shaft.

There is very little, if any, backlash.

Referring to Figure 6, the flexible drive shaft 10A has a flexible tubing 20, a coil spring 21 in this case. When a flexible tubular member is utilized in the flexible drive shaft, the ends of the flexible tubular member must be secured to the driving end assembly and the driver end assembly. The driver end assembly 12A is differ- ent from the driver assembly 12 of the flexible drive shaft of Figure 4. The end of the spring is secured within the axial bore 33 of the driver to a coupler 34 which in turn is threadingly received by the drive shaft 38A by the screwed insert. Similarly (but not shown), the other end of the coiled spring 21 is secured in the axial bore 98A of a driven coupler which is received in a threaded relationship by the driven shaft (not shown). The drive shaft 38A and the driven shaft are virtually identical.

The flexible tubular element assists in keeping the chain of segments together and biases the flexible drive shaft to a straight linear position. In Figure 6, the seg- ments are shown within the casing of tubular wire braiding which is secured to the drive shaft 38A by crimping ring 30. In the embodiment shown, the flexible drive shaft has no flexible outer sheath or covering 32 as the flexible drive shaft 10 of Figure 4. In the preferred embodiment of the invention, the drive shaft would be equipped with such a sheath to protect the flexible drive shaft from corrosion, moisture, dust, fluids, and other foreign material getting into the flexible drive shaft.

Referring to Figure 7, the flexible drive shaft 10B has a flexible tubular member 20. In this case, however, the flexible tubular member 20 is a flexible polymeric tubular member 19. The tubular member is secured within the axial bore 98B of the driven shaft 40 by bonding, fusion or welding. The bottom of the tubular member can be secured by heat bonding or bonding with adhesive members. The tubular member extends the length of the flexible drive shaft through bores 54 of the segments 18. The tubular member assists in keeping the segments in interlocking relationship and biases the flexible drive shaft into a straight linear orientation. The flexible drive shaft of Figure 7 is shown without an outer sheath to protect the flexible drive shaft. In the preferred embodiment of the invention, the tubular wire braiding would be ensheathed in a polymeric tubular member which would cover the entire tubular wire braiding and be bonded to the driven shaft 40, which would be secured to the driven shaft and drive shaft.

Although not the preferred embodiment of the invention, the invention can be utilized without the tubular wire braiding when a coiled spring is utilized as the flexible tubular element. In an alternative embodiment of the present invention (not shown), the flexible tubular element would be a polymeric tubing supported on the inside by a coiled spring.

In the preferred embodiment of the present invention, protective plastic sheathing 32 is hermetically bonded to the tubular wire braid and the crimping and over the shoulder 96 of the drive shaft and driven shaft so that the plastic sheathing and the drive shaft and driven shaft essentially form one homogenous and continu- ous surface.