Patent Description:
Cables, in particular those with a multilayer structure such as coaxial cables, are separated in a conventional manner with devices that comprise several knives or knife blades. The knives rotate together around the cable axis on a circular cutting unit. In the stripping process of such a multi-layered cable, only a defined amount of the layers must be cut. If a coaxial cable, which is an example of a multi-layered cable, for example from inside to outside from the inner conductor, dielectric, shield and sheath is constructed, then the knives must be guided, for example, so that they selectively cut the sheath without injuring the screen, or be guided in such a way that the knives selectively cut the sheath, the screen and the dielectric without injuring the inner conductor.

From <CIT> and <CIT> round cutting units are known. In the prior art, the respective knives are moved by twisting a first disc and a second disc relative to each other. At or in one disc, the knives are mounted movably, while a bolt attached to the respective knife intervenes in a groove in the second disc.

If the first and second discs do not have the same speed, the blades move in the cutting plane, i.e. towards or away from the cable. Until the first disc and the second disc have assumed the desired relative angular difference, they must rotate at exactly the same angular velocity. This is fraught with great uncertainties. There is a need for a reliable cutting unit that is simple and allows a precise cutting process.

Further prior art cutting units are disclosed in <CIT> and <CIT>.

The present disclosure relates to a circular cutting unit for partially cutting one or more layers of a cable or wire. More specifically, the present disclosure relates to a circular cutting unit that includes primary and adjustment drive units operable to rotate a knife head at a cutting speed and to adjust the position of a pair of knife blades to control the depth of cutting.

According to the invention the above given objects are achieved, by a circular cutting unit operable to partially cut a cable along a cutting plane that is perpendicular to a cable axis comprising: a drive disc rotatable about the cable axis; a pair of knife holders mounted to the drive disc, each of the knife holders configured to receive and retain a knife blade; and an adjustment disc rotatable about the cable axis, the adjustment disc including a pair of adjusting elements that each engage one of the knife holders, wherein a relative change in an angle of the adjustment disc relative to the drive disc causes movement of the knife blades in the cutting plane toward or away from each other.

According to one embodiment of the disclosure, each of the knife holders includes an adjustment groove formed in a body of the knife holder and the adjustment disc includes a pair of adjusting elements that are each received in one of the adjustment grooves formed in the body of one of the knife holders.

According to the invention, the circular cutting unit further comprises a primary drive assembly operable to rotate the drive disc and the adjustment disc at a cutting speed; and an adjustment drive assembly coupled to the adjustment disc, wherein operation of the adjustment drive assembly modifies a rotation speed of the adjustment disc relative to the rotational cutting speed of the drive disc for an adjustment period to create a change in an angle of the adjustment disc relative to the drive disc to cause movement of the knife blades in the cutting plane toward or away from each other.

According to one embodiment of the disclosure, each of the knife holders is pivotally mounted to the drive disc at a first end such that the relative change in the angle of the adjustment disc relative to the drive disc causes the knife holders to pivot about the first end.

According to one embodiment of the disclosure, the adjustment groove is substantially arc-shaped.

According to one embodiment of the disclosure, the adjusting elements move along the adjustment groove such that the pivoting of the knife holders move the knife blades along in the cutting plane.

According to one embodiment of the disclosure, the adjusting elements are rollers.

According to a further embodiment of the disclosure, the primary drive assembly includes an electric drive motor coupled to both the drive disc and the adjustment disc such that the drive disc and the adjustment disc rotate at the same speed.

Further according to the invention, the primary drive assembly includes a drive pulley connected to the drive disc by a first pulley belt and an adjustment pulley connected to the adjustment disc by a second pulley belt, wherein the drive pulley and the adjustment pulley are rotationally coupled to a primary drive shaft rotated at a cutting speed by a primary drive motor.

Further according to the invention, the adjustment drive assembly is coupled to the adjustment pulley, wherein the adjustment drive assembly is operable to modify the rotational speed of the adjustment pulley.

Further according to the invention, the primary drive shaft includes a spiral groove, and the adjustment drive assembly includes a ball nut movable along the spiral groove.

According to one embodiment of the disclosure, the adjustment drive assembly is operable to move the ball nut along the primary drive shaft such that movement along the primary drive shaft rotates the ball nut and the ball nut is coupled to the adjustment pulley.

One aspect of the present disclosure is related to the circular cutting unit. The circular cutting unit is configured to partially cut one or more layers of a cable or wire along a cutting plane. The cable is defined by its cable axis. The cutting plane runs approximately perpendicular to the cable axis. The circular cutting unit has a knife head including a pair of knife holder, a drive disc and an adjustment disc. Each knife holder has an integrated adjustment groove and is designed to hold a knife blade. The drive disc is mounted to rotate around a disc axis that runs approximately parallel to the cable axis. The adjustment disc is also mounted to rotate around the disc axis. The adjustment disc is also configured to act on the adjustment groove of the knife holder. An angle is defined between the discs mounted on the common disc axis, i.e. the adjustment disc and the drive disc. The action of the adjustment disc on the adjustment groove is carried out in accordance with the present disclosure in such a way that a change of the angle between the drive disc and the adjustment disc causes a movement of the knife blades in the cutting plane.

The described configuration facilitates a synchronous rotation of the drive disc and the adjustment disc around the disc axis, or drive axis. This makes it easy to precisely approach the blades to an inserted cable and to selectively cut the desired layers.

In embodiments of the present disclosure, the adjustment groove in each knife holder is arc-shaped. Alternatively or additionally, the adjustment groove is formed to match a circular arc, which describes an associated section of the adjustment disc. For example, an adjusting member is provided on the adjustment disc, and the adjusting element moves along the adjustment groove.

According to the invention, the circular cutting unit includes a primary drive assembly. The primary drive assembly is coupled to the drive disc by means of a transmission device for a drive force and is configured to drive the drive disc. The primary drive assembly is also coupled to the adjustment disc by means of a transmission device for an adjustable force. For example, the transmission device coupled with the drive disc is a drive belt and the transmission device coupled with the adjustment disc is an adjustment belt. The primary drive assembly is configured to drive the drive disc at a cutting speed and to drive the adjustment disc at the same cutting speed. During cutting, the angle between the adjustment disc and the drive disc is constant. In an adjustment period, the angle between the adjustment disc and the drive disc is changed. This change moves the knife blades in the cutting plane. In the adjustment period, the angular position of the adjustment disc is adjusted relative to the drive disc.

The circular cutting unit includes an adjustment drive assembly that is operable to adjust the angular position between the adjustment disc and the drive disc. Typically, there is an open blade position in which the knife blades are further away from the cable axis as an external circumferential position of the cable sheath of an inserted cable. In other words, in the open blade position, the blade does not touch the cable sheath (an outer layer of a multi-layer coaxial cable). Further there is a closed blade position. In the closed blade position, the knife blades are approximately in the area of the cable axis. In other words, in the closed blade position, the knife blade - or a cutting surface of the knife blade - is in contact with the outer layer or layers of the cable or wire being processed.

The circular cutting unit of the present disclosure is operable to cut a cable or wire along a cutting plane that is perpendicular to a cable axis. The cutting unit includes a drive disc and an adjustment disc that are both rotatable about the cable axis. The drive disc includes a pair of knife holders pivotally mounted to the drive disc. Each of the knife holders can include an adjustment groove that is formed in the body of the knife holder and has a substantially arc shape.

The adjustment disc includes a pair of adjusting elements that are each received in one of the adjustment grooves. During operation, the position of the adjustment disc can be adjusted relative to the drive disc to cause the movement of the knife blades in the cutting plane toward or away from each other.

The circular cutting unit can include a primary drive assembly that rotates both the drive disc and the adjustment disc at the cutting speed. An adjustment drive assembly is separately operable to modify the position of the adjustment disc to cause movement of the knife blades in the cutting plane toward or away from each other.

Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.

The drawings illustrate the best mode presently contemplated of carrying out the disclosure. In the drawings:.

<FIG> and <FIG> illustrate portions of a circular cutting unit constructed in accordance with the present disclosure. The circular cutting unit includes a knife head <NUM> that is configured to rotate about a cable axis <NUM> and to selectively cut through one or more layers of a cable being processed. The knife head <NUM> shown in <FIG> and <FIG> is coupled to a primary drive assembly such that the knife head <NUM> rotates about the cable axis <NUM> at a cutting speed. The details of the primary drive assembly will be described in much greater detail below.

As illustrated in <FIG>, the knife head <NUM> includes a pair of knife holders <NUM> that each are designed to receive and retain a knife blade <NUM>. Each knife blade <NUM> includes a cutting edge <NUM> that is used to cut through one or more layers of a wire or cable as the knife head <NUM> rotates about the cable axis <NUM>. The pair of knife blades <NUM> are located on opposite sides of the cable axis <NUM> and are each movable along a cutting plane that is perpendicular to the cable axis <NUM>. The pair of knife holders <NUM> are designed such that the position of the knife holders <NUM> relative to each other can be adjusted such that the distance between the cutting edges <NUM> of the pair of knife blades <NUM> can be adjusted. The distance between the pair of cutting edges <NUM> defines the depth of cut when the knife head <NUM> is being used to cut one or more layers from either a wire or cable that extends along the cable axis <NUM>.

Referring again to <FIG> and <FIG>, each of the knife holder <NUM> includes an adjustment groove <NUM>. As illustrated, the adjustment groove <NUM> has an overall arcuate shape that is defined by an inner guide surface <NUM>. The shape of the adjustment groove <NUM> is designed to create linear movement of the knife blades <NUM> during movement of the knife holders <NUM> as will be described below.

Each of the pair of knife holders <NUM> is formed from a durable metal material. As illustrated in <FIG>, each of the knife blades <NUM> is attached to the respective knife holder <NUM> by one or more connectors <NUM>, which can be screws, rivets or other connectors that are able to secure the knife blade <NUM> in place along the knife holder <NUM> while allowing the knife blade <NUM> to be removed and replaced when desired.

Each of the pair of knife holders <NUM> includes an attachment ear <NUM> that is formed on a first end <NUM> of the knife holder <NUM>. An opposite, outer second end <NUM> of the knife holder <NUM> includes the terminal end of the adjustment groove <NUM>. As best shown in <FIG>, the attachment ear <NUM> includes an opening <NUM> that is sized to receive a pivot pin <NUM>. The pivot pin <NUM> extends through the opening <NUM> and is received within a receiving opening <NUM> formed in an extending hub <NUM> formed as part of a drive disc <NUM>. The drive disc <NUM> includes a pair of hubs <NUM> that each receive one of the pair of pivot pins <NUM> such that each of the pair of knife holders <NUM> are pivotally mounted to the drive disc <NUM>.

As can be understood in <FIG>, the knife head <NUM> further includes an adjustment disc <NUM> that is located between the drive disc <NUM> and the pair of knife holders <NUM>. The adjustment disc <NUM> includes a pair of adjusting elements <NUM> that each protrude past an outer face <NUM> of the adjustment disc <NUM>. In the embodiment illustrated in <FIG> and <FIG>, each of the adjusting elements <NUM> is a roller that includes an outer surface that rotates about a fixed center portion. However, the adjusting element <NUM> could be any one of multiple different types of components other than the roller shown in <FIG>. As an example, the adjusting element <NUM> could be a fixed circular protrusion having a wear resistant outer surface.

As illustrated in <FIG>, when the drive disc <NUM> and adjustment disc <NUM> are assembled together, the adjusting elements <NUM> are each received within one of the adjustment grooves <NUM>. As will be described in greater detail below, movement of the adjustment disc <NUM> relative to the drive disc <NUM> causes the adjusting element <NUM> to move along the adjustment groove <NUM>. Since the adjustment groove <NUM> has an arcuate shape, the movement of the adjusting element <NUM> within the adjustment groove <NUM> causes the pair of knife blades <NUM>, and thus the cutting edges <NUM>, to move toward or away from each other depending upon the direction of movement of the adjusting element <NUM> within the adjustment groove <NUM>. The movement of the adjusting elements <NUM> within the adjustment grooves <NUM> is controlled by the relative rotational movement of the adjustment disc <NUM> relative to the drive disc <NUM>.

Although one embodiment of the knife holders <NUM> is shown in which the knife holders <NUM> are each pivotable about one end and include an arcuate adjustment groove to direct the movement, other embodiments of the knife holders are contemplated. For example, the knife holders could be configured such that the knife holders move in a linear direction along a groove or track toward and away from the cable being cut. The movement of the knife holders could be controlled by a cam or other similar element on the adjustment disc <NUM>. In the contemplated alternate configuration, each of the knife blades would move in a linear manner toward and away from each other in the cutting plane as in the embodiment shown and described.

Referring back to <FIG>, in addition to the adjusting element <NUM>, the adjustment disc <NUM> includes a pair of support rollers <NUM> that are positioned adjacent to the adjusting element <NUM>. Each of the support rollers <NUM> is mounted to a bracket <NUM> that is pivotally mounted at a pivot end <NUM>. The opposite end of the bracket <NUM> is connected to a bias spring <NUM>. The bias spring <NUM> is configured to press the support roller <NUM> into contact with the guide surface <NUM> of the adjustment groove <NUM> to help eliminate the mechanical play that could be present between the knife holder <NUM> and the adjusting element <NUM>.

The outer circumference <NUM> of the drive disc <NUM> and the outer circumference <NUM> of the adjustment disc <NUM> both include a series of teeth <NUM>. The number of teeth on both the drive disc <NUM> and the adjustment disc <NUM> are the same. The outer circumference of both of the drive disc and the adjustment disc are identical such that when the drive disc <NUM> and the adjustment disc <NUM> are connected to a primary drive assembly through a pair of separate pulley belts, the drive disc <NUM> and the adjustment disc <NUM> rotate at the same rotational speed.

<FIG> illustrates the inclusion of the circular cutting unit <NUM> of the present disclosure as part of a larger wire processing system <NUM>. The larger wire processing system <NUM> shown in <FIG> includes various wire processing equipment that feeds a wire or cable for cutting utilizing the circular cutting unit <NUM> of the present disclosure. The types of wire processing equipment can vary depending upon the specific wire processing process being carried out. The wire processing equipment can include wire cutting units, wire stripping units, wire feeding units and others. In the embodiment shown in <FIG>, the components of the wire processing system <NUM> are mounted to a support wall <NUM> which also provides a mounting location for the support frame <NUM> of the circular cutting unit <NUM>.

<FIG> and <FIG> further illustrate the construction and components that form the circular cutting unit <NUM> of the present disclosure. As shown in <FIG>, both the adjustment disc <NUM> and the drive disc <NUM> of the knife head <NUM> are connected to a primary drive assembly by a pair of pulley belts <NUM> and <NUM>. The pulley belt <NUM> is coupled to the outer circumference of the adjustment disc <NUM> while the pulley belt <NUM> is coupled to the outer circumference of the drive disc <NUM>. The pulley belt <NUM> is further entrained around an adjustment pulley <NUM> while the pulley belt <NUM> is entrained around a drive pulley <NUM>. Both the adjustment pulley <NUM> and the drive pulley <NUM> are rotatably connected to a primary drive shaft <NUM>. The primary drive shaft <NUM> extends through a motor mounting plate <NUM> and is connected to an idler pulley <NUM>. The idler pulley <NUM>, in turn, is connected to a primary drive pulley <NUM> through a pulley belt <NUM>.

The primary drive pulley <NUM> is securely connected to a motor shaft <NUM> of a primary drive motor. As illustrated best in <FIG>, the primary drive motor <NUM> is mounted to the motor mounting plate <NUM>. The primary drive motor <NUM> is preferably an electric motor that is operable to rotate the primary drive pulley <NUM> at a controllable speed. The rotation of the primary drive pulley <NUM> rotates the idler pulley <NUM> through the pulley belt <NUM>. The idler pulley <NUM>, in turn, rotates the primary drive shaft <NUM> which is coupled to both the adjustment pulley <NUM> and the drive pulley <NUM>. Since the adjustment pulley <NUM> and the drive pulley <NUM> are both connected to the drive disc <NUM> and the adjustment disc <NUM>, during normal operation, the rotating speed of both of the drive disc <NUM> and the adjustment disc <NUM> are controlled by operation of the primary drive motor <NUM>. When the pair of knife blades are in the desired position relative to each other to perform a cutting operation, the primary drive motor <NUM> controls the rotational speed of the drive disc <NUM> and the adjustment disc <NUM> to cut through the desired layers of a cable or wire.

As can be seen in <FIG> and <FIG>, the primary drive shaft <NUM> includes a spiral groove <NUM> formed in its outer surface. The spiral groove <NUM> extends along the length of the primary drive shaft <NUM> and is used to adjust the rotational speed of the adjustment pulley <NUM> in a manner which will be described in greater detail below.

Referring again to <FIG> and <FIG>, the circular cutting unit <NUM> further includes an adjustment drive assembly <NUM> that is operable to adjust the position of the adjustment disc <NUM> relative to the drive disc <NUM>. The adjustment drive assembly <NUM> includes an adjustment drive motor <NUM> that includes a motor shaft received by a shaft coupler <NUM>. In the embodiment illustrated, the adjustment drive motor <NUM> is an electric motor. The shaft coupler <NUM> provides a coupling between the drive shaft of the adjustment drive motor <NUM> and an adjustment shaft <NUM>. The adjustment shaft <NUM> includes a threaded outer surface <NUM>. The threaded outer surface <NUM> is received within an internally threaded barrel <NUM> formed as part of an adjustment bracket <NUM>. The adjustment bracket <NUM> further includes a guide plate <NUM> having a slide block <NUM> that is designed to move linearly along a guide rail <NUM>. The slide block <NUM> and guide rail <NUM> provide stabilization for the adjustment bracket <NUM> during movement of the adjustment bracket <NUM>. In other embodiments, the guide plate <NUM>, slide block <NUM> and guide rail <NUM> could be eliminated if stabilization is not required. As can be understood in <FIG> and <FIG>, when the adjustment drive motor <NUM> operates, rotation of the motor shaft causes rotation of the adjustment shaft <NUM> through the shaft coupler <NUM>. Since the outer surface <NUM> of the adjustment shaft <NUM> is threaded, the rotational movement of the adjustment shaft <NUM> causes the entire adjustment bracket <NUM> to move in a linear manner along the guide rail <NUM>. The direction of movement of the adjustment bracket <NUM> is controlled by the direction of operation of the adjustment drive motor <NUM>.

Referring now to <FIG>, the adjustment bracket <NUM> provides rotational support for a ball nut <NUM>. The ball nut <NUM> is rotatably supported by a bearing retainer <NUM> shown in <FIG>. The ball nut <NUM> includes an internal pin or ball that is received within and travels along the spiral groove <NUM>. Thus, when the adjustment bracket <NUM> moves in the linear direction shown by the arrow in <FIG>, the linear movement of the ball nut <NUM> causes the ball nut <NUM> to rotate within the bearing retainer <NUM> due to the movement of the internal pin or ball along the helical groove <NUM>.

Referring back to <FIG>, the portion of the ball nut <NUM> that extends through the adjustment bracket is joined to a rod holder <NUM>. The rod holder <NUM> is connected to a pulley driver <NUM> through a pair of support rods <NUM>. As can be seen in a comparison between <FIG> and <FIG>, the support rods <NUM> are press fit into the rod holder <NUM> and move into and out of the pulley driver <NUM> as the ball nut <NUM> moves along the drive shaft <NUM>. The pulley driver <NUM> is securely connected to the adjustment pulley <NUM>. In this manner, as the entire adjustment bracket <NUM> moves linearly as indicated by the arrow in <FIG>, the linear movement of the adjustment bracket <NUM> causes rotational movement of the ball nut <NUM>. The rod holder <NUM> joined to the ball nut <NUM> imparts rotation to the pulley driver <NUM> through the pair of support rods <NUM>. The rotation of the pulley driver <NUM> thus slows down or speeds up the rotational speed of the adjustment pulley <NUM>. The direction of this rotational movement depends upon the direction of linear movement of the adjustment bracket <NUM>. The movement of the adjustment bracket <NUM> can thus cause the relative movement of the adjustment disc relative to the drive disc <NUM>. As described previously, the relative movement of the adjustment disc <NUM> relative to the drive disc <NUM> controls the distance between the knife blades. The relative movement of the adjustment disc <NUM> relative to the drive disc <NUM> causes the knife blades <NUM> to move toward or away from each other in a direction perpendicular to the wire axis.

Referring now to <FIG>, the operation of both the primary drive assembly and the adjustment drive assembly in modifying the distance between the pair of cutting blades will now be described. Referring first to <FIG>, the fully retracted position of the pair of knife holders <NUM> is illustrated. In this retracted position, the pair of knife blades <NUM> are positioned at a maximum distance away from a cable <NUM> positioned for processing. In the retracted position, the adjusting elements <NUM> are positioned at an inner end <NUM> of the adjustment groove <NUM>. If it is desired to close the gap between the pair of knife blades <NUM>, the adjustment drive motor <NUM> shown in <FIG> is operated in a manner that causes the adjustment bracket <NUM> to move in the direction shown by arrow <NUM> in <FIG>.

As the adjustment bracket <NUM> moves in the direction shown by arrow <NUM>, such movement causes the pulley driver <NUM> to rotate. <FIG> shows such rotation of the pulley driver <NUM>. In the embodiment shown in <FIG>, the pulley driver <NUM>, and thus the adjustment pulley <NUM>, rotates in a counterclockwise direction, as shown by arrow <NUM>. The counterclockwise rotation of the adjustment pulley <NUM> causes relative movement of the pulley belt <NUM> in the direction shown by arrow <NUM>. The movement of the pulley belt <NUM> causes the adjustment disc <NUM> to rotate in the counterclockwise direction. Such rotation of the adjustment disc <NUM> relative to the drive disc causes the adjusting element <NUM> to move away from the inner end <NUM> of the adjustment groove <NUM> as illustrated in <FIG>. The movement of the adjusting element <NUM> within the adjustment groove <NUM> causes the knife blades <NUM> to move toward each other. In the embodiment illustrated, such linear movement of the knife blades <NUM> is caused by the pivoting movement of each of the knife holders <NUM> about the pivot pin <NUM> mounting the first end of the knife holder <NUM> to the drive disc. In alternate embodiments, the knife holders can have different configurations that also allow for the linear movement of the knife blades <NUM> as was discussed above.

<FIG> and <FIG> illustrate further operation of the adjustment drive motor <NUM> to cause further rotation of the pulley driver <NUM> and the connected adjustment pulley <NUM> in the counterclockwise direction. Again, this rotation results in similar movement of the pulley belt <NUM> and thus further counterclockwise movement of the adjustment disc <NUM> relative to the drive disc. This further rotation causes the adjusting elements <NUM> to move further along the adjustment groove <NUM> toward the outer end <NUM> of the adjustment groove <NUM>. As can be seen in <FIG>, such movement causes the knife blades <NUM> to move toward each other in a cutting plane that is perpendicular to the cable axis. As illustrated in <FIG>, the knife blades <NUM> move close enough to each other to engage the cable <NUM> to cut one or more outer layers of the cable <NUM>. As can be understood in <FIG> and <FIG>, although relative movement of the adjustment disc <NUM> relative to the drive disc is shown and described, it should be understood that both the adjustment disc <NUM> and drive disc <NUM> are rotating at the cutting speed as the adjustment disc <NUM> is moved relative to the drive disc.

Once the cutting blades <NUM> are in the desired location, both the drive disc and adjustment disc continue to rotate at the cutting speed to cut through the outer layers of the cable <NUM>. The movement of the cutting blades <NUM> is controlled by the operation of the adjustment motor. The adjustment motor is a high precision electric motor that is bi-directional and is controlled by a control unit as is conventional. As an example, the adjustment motor could be a stepper motor or a servo motor that is controlled by a control unit in a conventional manner. Once a complete cut has been created, the adjustment motor <NUM> is operated in a reverse direction to cause the cutting blades <NUM> to move from the cutting position shown in <FIG> back to the retracted position shown in <FIG>. In this manner, the operation of the adjustment drive motor <NUM> can be controlled to accurately control the movement of the cutting blades to a precise cutting location such as shown in <FIG>.

<FIG> illustrate an alternate embodiment of the circular cutting unit of the present disclosure. In the alternate embodiment shown in <FIG>, the location and configuration for the connection of both the primary drive motor <NUM> and the adjustment drive motor <NUM> is illustrated. In this alternate embodiment, the primary drive motor <NUM> is connected to the motor drive pulley <NUM> and the idler pulley <NUM> through the belt <NUM>. In this manner, the primary drive motor <NUM> drives the rotation of the similar primary drive shaft <NUM>. The primary drive shaft <NUM> is connected to both the drive pulley <NUM> and the adjustment pulley <NUM>. The drive pulley <NUM> and adjustment pulley <NUM> are connected to the same pulley belts as described previously.

In the embodiment shown in <FIG>, the adjustment drive motor <NUM> is connected in a linear relationship to the primary drive shaft <NUM>. The adjustment drive motor <NUM> is connected to the shaft coupler <NUM> and a similar adjustment shaft <NUM>. However, when the adjustment shaft <NUM> rotates, a coupler <NUM> moves along the threaded outer surface <NUM> of the adjustment shaft <NUM>. The coupler <NUM> includes a coupler shaft <NUM> that is connected to a ball nut <NUM>. The ball nut <NUM> includes an internal pin or ball that moves along the spiral groove <NUM>. The movement of the ball nut <NUM> as illustrated in a comparison of <FIG> imparts the desired rotational movement of the adjustment pulley <NUM> in the same manner as described in the first embodiment. In this manner, the operation of the adjustment drive motor <NUM> can selectively rotate the adjustment pulley <NUM> in either a clockwise or counterclockwise direction depending upon the desired movement of the knife blades <NUM>.

Claim 1:
A circular cutting unit (<NUM>) operable to partially cut a cable (<NUM>) along a cutting plane that is perpendicular to a cable axis comprising:
a drive disc (<NUM>) rotatable about the cable axis;
a pair of knife holders (<NUM>) mounted to the drive disc, each of the knife holders configured to receive and retain a knife blade (<NUM>);
an adjustment disc (<NUM>) rotatable about the cable axis, the adjustment disc including a pair of adjusting elements (<NUM>) that each engage one of the knife holders,
wherein a relative change in an angle of the adjustment disc relative to the drive disc causes movement of the knife blades in the cutting plane toward or away from each other; and
a primary drive assembly operable to rotate the drive disc and the adjustment disc at a cutting speed;
an adjustment drive assembly (<NUM>) coupled to the adjustment disc,
wherein operation of the adjustment drive assembly modifies a rotation speed of the adjustment disc relative to the rotational cutting speed of the drive disc for an adjustment period to create a change in an angle of the adjustment disc relative to the drive disc to cause movement of the knife blades in the cutting plane toward or away from each other;
wherein the primary drive assembly includes a drive pulley (<NUM>) connected to the drive disc (<NUM>) by a first pulley belt (<NUM>) and an adjustment pulley (<NUM>) connected to the adjustment disc (<NUM>) by a second pulley belt (<NUM>), wherein the drive pulley and the adjustment pulley are rotationally coupled to a primary drive shaft (<NUM>) rotated at a cutting speed by a primary drive motor (<NUM>), wherein the adjustment drive assembly (<NUM>) is coupled to the adjustment pulley (<NUM>),
wherein the adjustment drive assembly (<NUM>) is operable to modify the rotational speed of the adjustment pulley,
characterized in that the primary drive shaft (<NUM>) includes a spiral groove (<NUM>), and the adjustment drive assembly (<NUM>) includes a ball nut (<NUM>) movable along the spiral groove (<NUM>).