reference is now made to fig1 illustrating the endless loop conveyor system 10 with a screw driving means 20 incorporating the principles of the present invention . as will become apparent by reviewing the description below , the endless loop conveyor system 10 provides an effective means for transporting articles along an uninterrupted , full loop flow path in a smooth , efficient , and reliable manner . as best shown in fig1 a modular conveyor belt 11 forms the endless conveying loop ( part broken away for simplicity ). as should be appreciated , the entire conveyor belt 11 is preferably disposed in a horizontal plane and provides a continuous conveying surface 12 . upon further inspection , it can be seen that the total conveying surface 12 of the conveyor belt 11 is at all times available for transporting articles in an endless feed path . advantageously , this significantly promotes material handling efficiency . articles are capable of being transported between various work stations utilizing a minimum length of conveyor belt . significant operational efficiency is realized because the screw driving means 20 of the present invention provides for exceptionally smooth driving of the conveyor belt 11 . the requirement for a inverted return run of the belt is eliminated , thus cutting the power needed , and at the same time assuring a smooth operation of the system . the elimination of transfer zones for the moving of articles from one conveyor to another along the flow path also enhances the efficiency and promotes smoothness . in the preferred embodiment , and as best shown in fig4 the conveyor belt 11 is comprised of a plurality of substantially identical composite modular links 14 . each link 14 includes tip or apex 21 and pairs of legs 22 , 22 &# 39 ; extending at an angle therefrom . transverse connectors 25 are provided to interconnect and retain the links 14 together , thereby forming the modular link conveyor belt 11 . specifically , the apexes 21 of the links 14 include transversely oriented slots 29 for receiving the connectors . the distal end of each leg 22 includes a transverse hole 30 for also receiving the connector 25 . the holes 30 are coaxial such that each connector 25 passes freely through all aligned holes 30 and slots 29 . when properly connected , the connectors 25 join the legs 22 of the links 14 in one row with the apexes 21 of the links in the adjacent row . as will be realized , this combination forms the interlocking modular conveyor belt 11 . according to an important aspect of this invention , the conveyor belt 11 is equipped with a special shaped modular center link 100 having an angled depending cleat 102 , as best shown in the bottom perspective view of fig4 a . the depending cleat 102 is positioned at an approximately 45 ° angle on the underside of the link 100 spanning across legs 104 , 104 &# 39 ;. the preferred embodiment described herein uses the center link 100 having a single depending cleat 102 for illustrative purposes only , and it should be appreciated that single or multiple depending cleats could be positioned on various links across the width of the conveyor belt 11 , if desired ( see , for example , fig7 ). furthermore , screw driving means 20 is mounted beneath the conveyor belt 11 and includes a drive shaft 106 and a screw 108 having a thread 110 ( see fig1 & amp ; 2 ). as can be seen in fig2 and 3 , the screw 108 is positioned in such a manner so that thread 110 extends upwardly toward the bottom surface of conveyor belt 11 . more particularly , the thread 110 has an approximately 45 ° lead angle and mates with the depending cleats 102 for applying a driving force to conveyor belt 11 . an electrical motor m provides the driving force to the shaft 106 . as best shown in fig5 the depending cleat 102 is angled so that its rear face 114 is substantially parallel to the front driving face 116 of the thread 110 . this allows for transfer of a smooth , continuous driving engagement . this in turn translates into maintenance of a steady conveying surface 12 during operation so that the articles are transported in an efficient and reliable manner . in addition , and as best shown in fig4 a , the lateral edges of the depending cleats 102 are preferably tapered . these tapered edges contribute to the smooth , uninterrupted engagement and disengagement with thread 110 during operation . the thread 110 continuously engages successive depending cleats 102 as the conveyor belt 11 is pushed forward . as a result of this advantageous thread 110 and depending cleat 102 relationship , the conveyor belt 11 is driven forward to effect article movement in a smooth and efficient manner . as a further means to provide a smooth and efficient conveyor operation , fig3 best shows that the pitch p of thread 110 is gradually reduced to pitch p &# 39 ; near the distal end 112 . this pitch reduction provides for a smooth , uninterrupted exit or disengagement of the thread 110 from the depending cleats 102 . in addition , the gradual pitch reduction allows for a gradual reduction in the pulling force at the distal end 112 of the thread 110 further enhancing the smooth operation in this area where the modular links 100 are no longer under full tension from the screw driving means 20 . several operational benefits are realized by driving the conveyor belt 11 by means of the described screw driving means 20 . first , the conveyor belt 11 does not require both forward and return runs , as is common in prior art sprocket driven conveyor systems . accordingly , the conveyor system 10 of the present invention is less expensive all around . secondly , it requires less power to drive , generally operates smoother and more efficiently and does not experience the problems of excessive wear . thirdly , the conveyor system 10 of the present invention eliminates the need for utilizing transfer zones between separate conveyors in order to provide an endless loop and continuous conveying surface . as best shown in fig1 and 2 , the screw driving means 20 preferably engages a plurality of cleats 102 over an extended length of the conveyor belt 11 . accordingly , each and every depending cleat 102 bears a portion of the stress and loading associated with conveyor system operation . this necessarily alleviates a substantial amount of the associated strain at the driving interface of the conveyor belt 11 . accordingly , because of this efficient means of extending and evenly distributing the conveyor loading , reduced component strain and longer conveyor life , as well as a smoother , more even and predictable operation is realized . as best shown in fig6 guide rails 27 are provided to support and guide the conveyor belt 11 . a plurality of side links 23 on the belt 11 are provided with depending arms 24 for locating and guiding the belt 11 along the corresponding guide rails 27 . advantageously , the side links 23 are provided with transversely extending tabs 25 at the distal end of the depending arms 24 to further maintain the position of the conveyor belt 11 . as mentioned above , more than one driving means 20 may be used . thus , as shown in fig7 an alternate embodiment is provided utilizing dual screw driving means 118 , 120 . the screw threads have opposite leads and are driven in opposite directions ( as shown by the directional arrows ). as shown , each thread 122 , 124 engages the depending cleats 126 , 128 , respectively , on different rows of links . the depending cleats 126 , 128 on the engaged links are angled and positioned in an opposite manner so as to accommodate the rotational direction of the mating threads 122 , 124 . advantageously , in this alternate embodiment the lateral force vectors cancel each other to enhance the smooth operation of the conveyor system . in summary , numerous benefits have been described which result from employing the concepts of the invention . the conveyor system 10 of the present invention exhibits improved material handling capabilities and includes an endless conveyor belt 11 having an uninterrupted conveying surface with no inverted return run . accordingly , the conveyor system 10 represents an improvement in terms of lower cost , easier installation and less maintenance , as well as smoother and more efficient operation . finally , the present conveyor system 11 is capable of transporting a wide variety of articles around a full loop with no transfer zones in an economically more efficient , more productive , and more reliable manner . the foregoing description of a preferred embodiment of the invention has been presented for purposes of illustration and description . it is not intended to be exhaustive or to limit the invention to the precise form disclosed . obvious modifications or variations are possible in light of the above teachings . the embodiment was chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as is suited to the particular use contemplated . all such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with breadth to which they are fairly , legally and equitably entitled .