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You are an expert at summarizing long articles. Proceed to summarize the following text: 
TECHNICAL FIELD 
     This invention relates to a cable tension system and more particularly to a cable tension system for operating a power sliding vehicular door. 
     BACKGROUND OF THE INVENTION 
     Power sliding doors for automotive vehicles such as minivans have seen recent popularity. The use of automatic doors is a great convenience for handicapped people, for young children and for other people who have their hands filled for example with groceries. 
     The use of pull cables have been found to be an expeditious mechanism to both open the door and close the door. When the cable system is installed, the slack of the cable needs to be taken up for the cable system to operate. Thus, it is greatly desired to maximize the ease and speed in which the cable system is installed and tensioned. 
     SUMMARY OF THE INVENTION 
     In accordance with one embodiment of the invention, a take-up guide cable tensioning system has a first take-up drum having an outer surface for pulling on a cable assembly in a first direction, i.e. an opening direction for a power door. A second take-up drum has an outer surface for pulling the cable assembly in a second opposite direction, i.e. for closing the power door. The second drum rotates with the first take-up drum. The first drum has a slot under the outer surface. A take-up guide is slideably mounted in the slot and has spring loaded ratchet teeth normally mounted to engage complementary ratchet teeth in the slot to prevent movement of the take-up guide in one direction but allow movement in a second opposite direction. Preferably, the slot is arcuate and follows under the contour of the outer surface of the drum. In addition, it is desired that the ratchet teeth on the drum are progressively larger in the second opposite direction. 
     The take up guide has a section mounted to an end of a first cable of a cable assembly and when moved in the second opposite direction in the slot, takes up slack in the first cable between the first and second drum and provides tension in the cable assembly. 
     Preferably, the ratchet teeth are cantilevered and are resiliently movable to disengage from the complementary ratchet teeth in the arcuate slot to allow sliding movement of the take-up guide in the one direction to release the tension in said cable. It is also desired that the take-up guide has a slot therein to receive a tool that provides relative motion of the take up guide with respect to the drum having the slot in the second opposite direction. 
     In accordance with another aspect of the invention, a take-up guide cable tensioning system includes a housing having apertures therethrough for allowing passage of a cable therein and tool access therethrough. A spring loaded pulley is mounted in the housing for providing a spring-loaded tension on the cable. A tool is constructed to be passed into at least two of the apertures in the housing for rotating the first drum with respect to the take up guide and for limiting the compression of the spring loaded pulley. The first drum has gear teeth about its periphery to engage a small drive gear wheel. The tool is engageable to the small drum gear wheel to rotate the first drum with respect to the take up guide. 
     In accordance with another aspect of the invention, a take-up guide tension tool includes a handle operating end and an elongated shaft. The tool also has a socket end mounted at the end of said elongated shaft. A stop assembly is mounted about the shaft in proximity to the socket end and has a first stop member for engaging a spring-loaded pulley and a second stop member for retaining a take up guide tension assembly when the socket member rotates a drum member with respect to the take up guide. The shaft member is rotatable with respect to the stop assembly. Preferably, the handle has a lever that is connected to the shaft for driving the shaft in one selected direction and is rotatable through a ratchet connection about the shaft in a second opposite direction. It is also desired that a knob is affixed on a distal end of said shaft opposite the socket end. 
     In accordance with another aspect of the invention, a take-up guide cable tensioning system includes a take-up drum having an outer surface for pulling a cable in a first direction. The take-up drum has a slot under its outer surface. A take-up guide is slideably mounted in the slot and has at least one spring loaded ratchet tooth normally mounted to engage complementary ratchet teeth in the slot to prevent movement of the take-up guide in one direction. The take up guide having a section mounted to an end of the cable and movable in a second direction in said slot to take up slack in said cable and provide tension in said cable. At least one spring loaded ratchet tooth is cantilevered on said take up guide member and is resiliently movable to disengage from the complementary ratchet teeth in the slot to allow sliding movement of the take-up guide in the one direction to release the tension in the cable. Preferably, the take-up guide has a slot therein to receive a tool that provides rotatable motion of the take up guide with respect to the drum. The slot is preferably arcuate in shape that follows the contour of the outer surface of the first drum. The ratchet teeth on the drum are progressively larger in the second direction. 
     In this fashion, the cable between the first drum and door can be have its slack taken up and place the cable system into tension to provide optimal operation of the power door opening and closing apparatus. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Reference now is made to the accompanying drawings in which: 
     FIG. 1 is a perspective view of a cable drum assembly and a tool for installation; 
     FIG. 2 is an exploded perspective view of the cable drum assembly shown in FIG. 1; FIG. 3 is front plan view of the drums illustrating the take up guide member in its initial position; 
     FIG. 4 is a view similar to FIG. 3 after the take up guide member has been moved to take up cable slack; 
     FIG. 5 is a partially segmented plan view of the drum  16  illustrating its elliptical contour section; and 
     FIG. 6 is a side elevational view of the drum shown in FIG.  5 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIGS. 1 and 2, a cable tension assembly  10  includes housing  11  is constructed to have a section  12  that rotatably houses a first drum  14  and second drum  16  that are connected to rotate together. A tool  15  can be operably mounted to the housing as shown in FIG.  1 . The housing  11  has a body section  18  and cover  20  that are fitted together to retain the two drums within. The two drums snap fit together via prongs  22  fitting into apertures  24 . 
     Both drums are rotatable via a motor not shown which rotates the drums about axis  26 . The motor and controls for the motor are conventional and form no part of this invention. 
     A cable  28  has one end secured  27  onto the second drum  16  at point  30  as shown in FIG.  5  and wraps about the outer surface  32  a plurality of times, extends about tension pulley  34  and out through an aperture  36  to exit the housing and be connected to the door (not shown). 
     Another cable  29  is then attached to the door and has its end  40  return back into the housing through aperture  38  and about a second tension pulley  42  and into the drum  14  through an aperture  44  in the drum. The end  40  then is connected to a tension take up member  46  that is mounted in an arcuate slot  48  within the drum  14 . The take up member  46  has resiliently mounted ratchet teeth  50  on a cantilevered section  49  that normally engage complementary ratchet teeth  52  about the outer wall  54  of the slot  48 . The cantilevered section  49  has some resilient flex. 
     The take up member is initially positioned in proximity to one end  56  of slot  48  as shown in phantom in FIG.  3 . Furthermore there is sufficient length of cable  29  such that there is plenty of length of cable to easily reach end  40  of cable  29  into the slot  48  and be securely attached to tension take up member  46  without placing any tension onto cable  29 . 
     The take up member is initially positioned in proximity to one end  56  of slot  48  as shown in phantom in FIG.  3 . Furthermore there is sufficient length of cable  29  such that there is plenty of length of cable to easily reach end  40  of cable  29  into the slot  48  and be securely attached to tension take up member  46  without placing any tension onto cable  29 . 
     A tool  15  and a gear wheel  62  expedite the take up of slack and the tensioning of the cable  28 . The gear wheel  62  is rotatably mounted adjacent the drum  16  and has gear teeth  64  that engage teeth  66  about the perimeter  68  of drum  16 . The gear wheel has an integral hex nut section  69  that can be engaged by tool  15 . The tool  15  socket engaging section  70  is mounted on a distal end of a shaft  72  that is moved by a lever handle  73  that is connected through a ratchet connection  74 . A knob  75  is also mounted on an opposing end of the shaft. A stop assembly  76  is rotatably mounted about the shaft and has one stop member  78  that protrudes through aperture  80  that limits the compression of the spring loaded pulley  34  to about one-half its travel capacity. Tool  15  also has a second stop member  82  that protrudes through aperture  84  and protrudes into slot  86  of take up guide member  46 . 
     In operation, after the cable  28  has been attached to the door, the door is positioned so that the slot  86  is visible through the aperture  84 . The installer then places tool  15  into position and cranks on lever handle  73  to rotate the shaft  72  which in turn rotates the nut  69  and gear wheel  62 . The gear then rotates the drum  14  and drum  16 . The tool simultaneously retains the take up member such that the take up member slides in slot  48  in the direction indicated by arrow  58  with the teeth  50  and  52  causing clicking indicating sounds. The excess cable is taken up onto the drum  16  as both drums rotate. Pulley  42  has its spring fully compressed and pulley  34  is limited by stop member  78 . When the tool is disengaged the tension on both pulleys  42  and  54  re-balances to provide equal spring resiliency in both pulleys  34  and  42 . The take up guide member remains positioned to be accessed through aperture  84  when the door is in the closed position. 
     If tension in the cable ever needs to be released, the drums  14  and  16  are positioned to align slot  86  with aperture  84 . A screw driver is then placed into slot  86  to flex the cantilevered section to disengage the teeth  50  from teeth  52 . Once the teeth are disengaged from each other the drums are free to rotate to release the tension of the cable system. 
     Drum  16  is used to pull cable  28  such that as the cable  28  wraps about its outer surface  90 , the door is moved to its closed position. As the door is moved to its fully closed position, the driving motor must overcome the higher torque forces caused by sealing members and the closure latch in the last few centimeters of travel. The extra torque is provided by decreasing the effective outer radius of the drum  16  for the last few centimeters of travel. 
     The drum  16  as more clearly shown in FIGS. 5 and 6 has a normal circular first outer surface section  92  normally referred to as a drum helix with a first radius indicated at  94 . A second outer surface helix section  96  has an elliptical contour that is tangent to the first outer surface section  92  at point  99  in proximity to the major axis  98  of the contour. The minor axis  100  of the elliptical contour intersects the axis of rotation  26 . The axis of rotation  26  is interposed between the defined center  102  of the elliptical contour and the elliptical contour surface  96 . The elliptical contour is positioned such that the effective radius continually decreases from the tangent point  99  to the minor axis  100  to it&#39;s minimum radius indicated at  104 . 
     It can be readily seen that the motor thus can provide for more torque to overcome the resisting forces of seals and latches by placing the cable along a smaller radius  104 . 
     In this fashion, when the door is closed and the most tension is placed on the cable, the highest bending stresses occur near the tangent point  99  near the major axis  98  and the highest tensile forces are in proximity of the minor axis  100 . However, the bending stress at the minor axis  100  is lowered due to its flattened elliptical contour. The most bending stress occurs along the major axis  98  where the tensile forces are lower. In this fashion, the location of the highest tensile force and the highest bending stress are displaced from each other along different sections of the cable  28 . By displacing the location of these two highest forces from each other, one lowers the peak stress along any given point along the cable and thus provides for a more durable cable. 
     Variations and modifications are possible without departing from the scope and spirit of the present invention as defined by the appended claims.

Summary:
An automatic sliding door cable mechanism with a take up guide member ( 46 ) mounted in a drum ( 14 ) for taking up slack of a cable during installation of the cable. A second drum ( 16 ) has an elliptical profile drum helix ( 96 ) for increasing durability of the operating cable for the automatic door.