摘 要螺旋輸送機(jī)由多個(gè)首尾相連的組件和同一的整體塑造構(gòu)件組成。每一個(gè)組件由一種合適的塑性材料塑造，它有與之相對(duì)的固有成形加工圓柱體，其中有同軸的管子，在同軸管子和圓柱體之間有螺旋體。首尾相配合的組件使螺旋輸送機(jī)成為具有合適長度和旋轉(zhuǎn)的整體。每個(gè)模塊上面會(huì)有一槽輪以便用于V型帶驅(qū)動(dòng)。或者，由焊接在更適宜于首尾相配合的非圓形中心管上的敞面式螺旋卷筒使螺旋輸送機(jī)具有適宜的長度。這種開放式螺旋輸送機(jī)很容易使具有傳統(tǒng)金屬制螺旋體系統(tǒng)改裝翻新。 標(biāo)準(zhǔn)螺旋輸送機(jī) 發(fā)明園地和螺旋輸送機(jī)相關(guān)的發(fā)明還有10多種專門的由塑性材料制成的螺旋輸送組件。 發(fā)明背景眾所周知，螺旋輸送機(jī)用于輸送散塊物體。像這種在外罩內(nèi)含有螺旋體的螺旋輸送機(jī)通常通過縱向軸的螺旋使散塊物體沿螺旋體向前傳輸。通常輸送機(jī)的結(jié)構(gòu)由金屬構(gòu)造它們有合適的長度使輸送機(jī)具有適當(dāng)?shù)拈L度。螺旋輸送機(jī)也可以由模塊塊或者部件構(gòu)成組件從而制成具有滿意長度的輸送機(jī)。在U.S.Pat.Nos349,233; 525,194; 1,867,573; 2,394,163; 2,492,915 and 3,178,210.中可以看到這樣結(jié)構(gòu)的螺旋輸送機(jī)。發(fā)明概要該發(fā)明使螺旋輸送機(jī)有了同一的首尾相配合的單元，每一單元都是塑性構(gòu)造件。每一單元包括一個(gè)圓柱型輪廓其中有同軸的管子開放型向外延伸，在它們之間是螺旋體。在圓柱體和同軸管的末端被配合成一體，螺旋體各自的尾部包括配合的表面。模組軸向連接形成具有合適長度的螺旋輸送機(jī)，相配合的組件通過成直線的同軸管子約束以及提供合適壓力成為一整體。或者，組件通過其他方式例如機(jī)械凸緣約束在一起。組件，同軸管和螺旋部分都由合適塑性材料塑造而成，尤其通過噴射摸塑法制造。每個(gè)組件含有一個(gè)帶V型槽的槽輪以便配合外部V型帶驅(qū)動(dòng)?；蛘?，組件帶有鏈齒以便使用鏈條驅(qū)動(dòng)，也可以通過其他方式驅(qū)動(dòng)。對(duì)于上述結(jié)構(gòu)體，螺旋部分通過螺旋管形成螺旋。本發(fā)明的輸送部分同樣可以通過中心管采用非圓開放形式，這些螺旋部分鑄造而成。中心管和螺旋套首尾配合使輸送機(jī)具有合適長度。組件通過例如非圓形橫截面的延伸軸約束成型，這個(gè)桿同樣可以為組件從當(dāng)驅(qū)動(dòng)軸。由中心軸驅(qū)動(dòng)的開放型螺旋輸送機(jī)適應(yīng)于現(xiàn)有傳統(tǒng)螺旋輸送機(jī)系統(tǒng)。 這種螺旋輸送機(jī)明顯優(yōu)于具有傳統(tǒng)結(jié)構(gòu)的螺旋輸送機(jī)。被裝配的模組在運(yùn)送機(jī)的長度各處沿著輸送表面以沒有硬件或其他的障礙提供光滑的有效連續(xù)的表面。新型的運(yùn)送機(jī)很容易被清理，而且能相容多種材料和進(jìn)行特殊的操作目的。和很多輸送機(jī)一樣該輸送機(jī)不能生銹和受腐蝕，它的重量比相同規(guī)格的要輕。組件結(jié)構(gòu)允許一個(gè)單一的統(tǒng)一模式制造和安裝成組件以實(shí)現(xiàn)輸送不同的長度。該模塊可以方便地被輸送到安裝現(xiàn)場組裝使用。傳送帶也可以很容易分解成它的組成模塊以便清潔，搬運(yùn)，或者修理。 圖形說明 從以下結(jié)合所附圖紙的詳細(xì)說明中我們將會(huì)更加充分地理解該發(fā)明，其中：圖1是體現(xiàn)發(fā)明的螺旋模塊示意圖；圖2是圖1所示模塊的端面圖；圖3是圖2沿3-3的橫截面圖；圖4是類似圖1的具體示意圖，還包括一個(gè)整體成型輪；圖5是圖4模型的端面圖；圖6是圖5沿6-6線的截面圖；圖7是一個(gè)體現(xiàn)由圖1-3所示模型組成的螺旋輸送機(jī)的側(cè)面斷面圖；圖8是擁有不同安裝方式的模塊的剖側(cè)圖；圖9是進(jìn)一步體現(xiàn)螺旋輸送機(jī)模塊發(fā)明的局部正視圖；圖10是圖9所示模型的端面圖；圖11是圖9和圖10組成體現(xiàn)螺旋輸送機(jī)發(fā)明的一個(gè)側(cè)面圖；圖12是這種發(fā)明的螺旋模塊的進(jìn)一步體現(xiàn)。 發(fā)明的詳細(xì)說明圖1-3可以顯示整體成型模塊是由配合的模塊組成實(shí)現(xiàn)螺旋輸送機(jī)的合適長度。該模塊是由合適的成型塑料材料，如聚乙烯，聚丙烯或聚氨酯等制作，并已整體形成需要的所有基本成分的螺旋輸送機(jī)。該模塊包括一個(gè)具有管狀結(jié)構(gòu)的兩端有圓形凹槽12和16的機(jī)構(gòu)，這種O形圈密封單元分別用于模塊之間配合的。在柱體10內(nèi)有同軸的管子16，還有開放型延伸的管18，在柱體10內(nèi)表面和管子16外表面之間有20螺旋部分。管16包括在各自的有圓形槽5和17的O形圈密封。該螺旋20的長度略小于一個(gè)螺距，它終止于包括平行表面26的22和24。因此，螺旋末端10和22的表面26用于配合相鄰模塊末端24的邊緣。如圖所示，該螺旋末端延伸至構(gòu)件10的1 / 2壁厚。螺旋15的長度略小于螺距使模塊可以按常規(guī)方法組裝如圖2所示，兩半的注塑模具可以打開軸向的模塊，因?yàn)樗穆菪L度略少于1螺旋間距。一般來說，螺旋長度比軌跡長度少1%以便給模具提供充足的空間。類似圖1-3所示圖4-6包括一體成型輪的傳送帶模塊示意。該輪是各地的機(jī)構(gòu)提供集中處置各自的兩端之間的機(jī)構(gòu)，滑輪組成的交替部分。第一部分是一系列的處置機(jī)構(gòu)在間距圓周上排列。如圖所示，第二部分同軸空間布置，并且沿環(huán)形間隔錯(cuò)開。在圖6中很容易可以看出，對(duì)立面、各自部分和V 型凹槽配合以便外部V帶驅(qū)動(dòng)。該模塊和圖1-3所示描述一樣。允許使用常規(guī)注塑成型注塑技術(shù)，因此模塊采用交錯(cuò)安排，如圖4-5所示允許多半組合成開放型同軸部件。模塊圖1-3是軸向交配與像模塊，而如圖7所示，形成一個(gè)傳送帶的長度。每個(gè)單元是符合兩端相鄰的機(jī)構(gòu)參與了插嘴O形圈，并與兩端相鄰管參與了插嘴O形圈。螺旋部分有其邊緣面對(duì)提供有效持續(xù)長度。螺旋處置的連續(xù)管機(jī)構(gòu)形成的交配模塊。由于螺旋部分是略少于一螺旋間距長度，小空間之間的兩端交配模塊。通常情況下，之間的差距是每8英寸直徑差0.1英寸。螺旋相對(duì)末端之間的小空間不具備輸送大部分物品的能力。這小小的空間可以填充和模塊相同或者兼容的材料。例如，塑性材料制作的模塊螺旋末端之間可以通過氣體保護(hù)焊焊接以形成螺旋連續(xù)表面。在一些要求下例如衛(wèi)士要求，這些小的排泄間隔是很有用的。對(duì)于大部分的輸送目的來說，這些小的空間不是沒有任何作用的。配合的模塊通過開口管子內(nèi)部的拉伸部件保持。這通常是一個(gè)金屬桿41兩端有螺紋緊固件42和44來提供一個(gè)預(yù)加強(qiáng)壓縮力來組裝模塊。另外，在管16內(nèi)的開口18管內(nèi)的拉伸部件可以是鋼絲線，塑料，后者其他管。這種情況輸送可以適應(yīng)變化的溫度，它有一個(gè)允許膨脹和收縮輸送的拉伸部件，同時(shí)輸送的結(jié)構(gòu)可以為配合提供軸向壓力。拉伸部件的熱膨脹和收縮特性應(yīng)和模塊材料相關(guān)以保持配合模塊即使在溫度循環(huán)下也呢過承受壓載荷。通過拉伸部件這些模塊可以保持在一起。這樣的一個(gè)辦法如圖8所示，其中包括機(jī)構(gòu)10的兩端有一個(gè)不可分割的法蘭45和緊固件47是通過插入能夠緊密配合在一起。 配合的模塊可以支持旋轉(zhuǎn)的輥46。通常情況下，一系列的三輥環(huán)間隔是每端附近的輸送機(jī)構(gòu)。附加輥可提供必要的，這取決于輸送距離的長短。通過輸送體末端的滾筒48輸送體的軸向位置得到保持，這些滾筒被環(huán)形間隔在輸送體的外部。法蘭50被連接到傳送帶末端模塊，其中包括一個(gè)與滾筒48配合的圓形表面52以保證軸向位置?；y可以被機(jī)加工或者成型于外部模塊的外部。在描述結(jié)構(gòu)體中，滑閥的形式是一個(gè)環(huán)形槽54結(jié)束于管子56，這樣使得螺旋體旋轉(zhuǎn)。進(jìn)料管56通常是連接到一個(gè)漏斗58以便進(jìn)料（如箭頭所示）從而用于運(yùn)輸。驅(qū)動(dòng)器60包括可攜帶滑輪62和可旋轉(zhuǎn)的軸64，其支持軸承為66，而且被電機(jī)驅(qū)動(dòng)（未顯示）。軸64和輸送機(jī)構(gòu)體平行，而且每滑輪62和各自傳送帶模塊相連。V型帶68與驅(qū)動(dòng)器62相配至傳送帶模塊而且通過動(dòng)力傳遞至輸送體用于旋轉(zhuǎn)。在描述的裝置中，每一個(gè)模塊是由相關(guān)的輸送帶驅(qū)動(dòng)。并不是所有傳送帶模塊都需要驅(qū)動(dòng)，而驅(qū)動(dòng)的數(shù)量將取決于應(yīng)用特殊要求的驅(qū)動(dòng)動(dòng)力。如果圖4-6所示模塊被使用，則滑輪28用于確保V型帶68驅(qū)動(dòng)輸送。這種輸送可以被除V型帶以外的其他輸送帶驅(qū)動(dòng)。例如，鏈鏈輪可配合模塊以便利用鏈驅(qū)動(dòng)。另一個(gè)體現(xiàn)了結(jié)構(gòu)發(fā)明所示如圖9和10 ，并包括螺旋輸送機(jī)模塊有一個(gè)中心管70圓柱形外觀形式， 非圓形開放形式5和72形成螺旋型中心管。螺旋部分在長度上略小于一個(gè)螺旋間距，如描述所示，并終止在74和76的邊緣，這些邊緣適應(yīng)于相應(yīng)邊緣相鄰模塊。通過中央管的非圓截面部分78位于80末端并在中央部分逐漸趨于非圓截面82 。這是輕微錐形提供“拔模角”以方便拆除模塊的軸向可分離鑄模。這種開口配合非圓軸以充當(dāng)拉伸件以鎖定模塊軸向接觸，同時(shí)為螺旋輸送擔(dān)任主驅(qū)動(dòng)軸。在圖9和10所示中，開六角形口還有其他非圓形狀的開口可提供管使用以防止輪換從事模塊相對(duì)軸。由模塊9和10圖組成的螺旋輸送機(jī)可以在圖11中顯示。每個(gè)模塊是符合兩端相鄰的帶有插嘴O形圈84的中心管70，并與螺旋72末端面對(duì)35以提供了一個(gè)有效的連續(xù)螺旋。86軸通過開口80和管70安裝并被緊固件保證，如螺母88與軸86兩端螺紋配合，這樣提供一個(gè)合適壓縮力給相互關(guān)聯(lián)的模塊，如上所述。圖11所示裝備可以用來改造現(xiàn)有金屬螺桿輸送單驅(qū)動(dòng)系統(tǒng)不會(huì)發(fā)生重大變化。Abstract A screw conveyor composed of a plurality of modules mated end to end and of identical integrally molded construction. Each module is molded of a suitable plastic material and has integrally formed therewith a cylindrical body, a coaxially disposed tube within the body, and a web helically disposed between the coaxial tube and the cylindrical body. The module includes ends mateable with corresponding ends of like modules to provide a screw conveyor of intended length and which is rotatable as a single unitary structure. Each module may have a sheave integrally molded thereon for mating with a V-belt drive. Alternatively, the modules can be of open form each having a helical web molded on a central tube preferably having a non-circular and adapted for end to end mating with like modules to provide a screw conveyor of desired length. This open type of screw conveyor can be readily retrofitted to systems having conventional metal conveyor screws. MODULAR SCREW CONVEYOR.FIELD OF THE INVENTIONThis invention relates to screw conveyors, and more 10 particularly to an integrally constructed modular screw conveyor molded of a plastic material.BACKGROUND OF THE INVENTIONScrew conveyors are well known for the transport of bulk material. Such conveyors generally include a helical screw disposed within housing, often of trough like form, and rotatable about its longitudinal axis to cause propulsion of bulk material along the length of the screw. Conveyors of known construction are usually fabricated of metal and are constructed to an intended finished size to provide a conveyor of intended length. Screw conveyors have also been constructed of modular or segmented form to provide sections which can be assembled into a complete conveyor of a desired length. Examples of segmented or modular conveyors are shown in U.S. Pat. Nos. 349,233; 525,194; 1,867,573; 2,394,163; 2,492,915 and 3,178,210.SUMMARY OF THE INVENTIONThe present invention provides a screw conveyor composed of identical end to end mated modules, each module being of integral plastic molded construction. Each module includes a body of cylindrical configuration, a tube coaxially disposed within the cylindrical body and having an opening extending there through, with a web helically disposed between the coaxial tube and cylindrical body. The ends of the body and coaxial tube are configured to seemingly engage like ends of mated modules, and the respective ends of the helical web include surfaces mateable with corresponding surfaces of the modules. The modules are axially mated to form a conveyor of desired length, the mated modules being retained in engagement by a tensile member such as a rod disposed through the aligned openings of the coaxial tubes and operative to provide an intended compressive force on the engaged modules. Alternatively, the modules can be secured in engagement by other means such as flanges on the ends of the body. The module body, coaxial tube, and helical web are integrally molded of a suitable plastic material, typically by an injection molding process. Each module may include a sheave integrally formed with the body which is composed of a plurality of spaced segments to define a V-groove configured to mate with a V-belt of an exterior drive. Alternatively, sprocket teeth may be integrally formed with the module body to mate with a chain drive, or other driving means can be employed.In the embodiment described above, the helical web is integrally formed within a surrounding tube which provides a self-enclosure for the helical screw. The conveyor of the present invention can also be embodied in open form in which the module comprises a central tube preferably having a non-circular opening, about which the helical web is integrally molded. The ends of the central tube and ends of the web are mateable with the ends of the modules to provide a conveyor of desired length. The modules are retained in compressive engagement by a tensile member such as a shaft of non- circular cross-section extending through the aligned non-circular openings of the central tubes, the rod also serving as a tensional drive shaft for the mated modules. This open type of screw conveyor driven by a central shaft is adapted to be readily retrofitted to existing conveyor systems which presently employ conventional metal conveyor screws.The molded plastic conveyor of this invention offers major benefits over screw conveyors of conventional construction. The assembled modules offer smooth effectively continuous surfaces throughout the length of the conveyor with no hardware or other obstructions along the conveying surfaces. The novel conveyor is easily cleaned and can be molded of a variety of materials compatible with and suitable for particular operational purposes. The conveyor is not subject to rust or corrosion, as with many conveyors, and is of much less weight than a metal conveyor of the same size. The modular construction allows a single unitary module to be manufactured and stocked for assembly as necessary to achieve conveyors of different lengths. The modules can be easily shipped to an installation site and assembled on site for use. The conveyor can also be readily disassembled into its component modules such as for cleaning, shipping, or repair. DESCRIPTION OF THE DRAWINGSThe invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG. 1 is a pictorial view of a screw conveyor module embodying the invention; FIG. 2 is an end view of the module of FIG. 1; FIG. 3 is a sectional view taken along lines 33 of FIG. 2; FIG. 4 is a pictorial view of an embodiment similar to that of FIG. 1 and including an integrally molded sheave thereon; FIG. 5 is an end view of the module of FIG. 4; FIG. 6 is a sectional view taken along lines 66 of FIG. 5; FIG. 7 is a sectional side view of a screw conveyor embodying the invention and composed of the modules of FIGS. 1-3; FIG. 8 is a cutaway side view of a module having alternative mounting means; FIG. 9 is a sectional elevation view of a further embodiment of a screw conveyor module of the invention; FIG. 10 is an end view of the module of FIG. 9; FIG. 11 is a side view of a screw conveyor embodying the invention and composed of the modules of FIGS. 9 and 10; and FIG. 12 is a pictorial view of a further embodiment of a screw conveyor module of the invention.DETAILED DESCRIPTION OF THE INVENTION Referring to FIGS. 1-3 of the drawing, there is shown an integrally molded module which is mated with like modules to form a screw conveyor of intended length. The module is molded of a suitable plastic material such as polyethylene, polypropylene or polyurethane and has integrally formed therewith all essential constituents of the screw conveyor. The module includes a body of tubular configuration having on the ends thereof circular grooves 12 and 16, respectively, for accommodation of an O-ring seal between mated modules. A tube 16 is coaxially disposed within body 10 and having an opening 18 extending there through, with a web 20 helically disposed between the inner surface of body 10 and outer surface of tube 16. The tube 16 includes on the respective ends thereof circular grooves 5 17 for accommodation of an O-ring seal. The web 20 is slightly less than one helical pitch length terminating in respective ends 22 and 24 which include radically parallel surfaces 26 adapted to confront corresponding surfaces of like modules. Thus, the surface 26 of helix end 10 22 is adapted to confront the oppositely facing edge of end 24 of an adjacent module. The web ends extend outward of the confronting ends of body 10 typically by approximately 1/2 the wall thickness of the web, as illustrated. By having the length of the helical web 15 slightly less than the helical pitch it is possible to injection mold the module by conventional molding techniques since as seen from FIG. 2 the two halves of an injection mold can open axially of the module which, because its helical length is slightly less than one helical pitch, presents no undercuts to the mold halves. Typically, the web length is about one percent less than the pitch length to provide sufficient clearance for mold tooling.An embodiment similar to that of FIGS. 1-3 is shown in FIGS. 4-6 and includes a sheave integrally molded with the conveyor module. The sheave is provided around the body centrally disposed between the respective ends of the body, the sheave being composed of alternating segments. A first array of segments is disposed around the body in spaced circumferential arrangement. A second array of segments is axially spaced from the segments and is circumferentially disposed about body in spaced position staggered from the position of the segments, as illustrated. The confronting surfaces and of respective segments and define a V-groove, best seen in FIG. 6, configured to mate with a V-belt of an exterior drive. The module is otherwise the same as described above with respect to FIGS. 1-3. The staggered arrangement of the segments and allow injection molding by conventional injection molding techniques since the staggered arrangement as seen from FIGS. 4-5 permits the mold halves to open axially of the module and presents no undercuts to the mold halves. The module of FIGS. 1-3 is axially mated with like modules, as shown in FIG. 7, to form a conveyor of desired length. Each of the modules is aligned with the ends of adjacent bodies in engagement with an interposed O-ring, and with the ends of adjacent tubes in engagement with an interposed O-ring. The helical webs have their edges confronting to provide an effectively continuous helical screw disposed within the continuous tubular body formed by the mated modules. Since the web is slightly less than one helical pitch length, small spaces exist between the confronting web ends of mated modules. Typically, the gap between confronting web ends is about 0.1 inch for a web of eight inch diameter. The small spaces between the confronting ends of the helical web are of little consequence to the ability of the assembled screw to convey most products. The small spaces may be filled in with material which is the same as or compatible with that of the module. For example, molded strips of plastic material can be inserted into the small spaces between web ends and fused therein, such as by hot gas welding, to produce a helical web having fully continuous surfaces. The elimination of the small gaps is useful in some applications such as where sanitary conditions require. For most conveying purposes, the small spaces are not of any consequence.The mated modules are maintained in engagement by a tensile member disposed within the openings of tubes. This member typically is a metal rod 41 having threaded ends 42 and fasteners 44 which are tightened to provide an intended compressive force on the engaged modules. Alternatively, the tensile member can be a wire, plastic, or other rope disposed within the openings 18 of tubes 16 and tensioned by appropriate fasteners on the respective ends of the rope. In cases where the conveyor is subject to changes in temperature, it would be preferable to have a tensile member which allows for expansion and contraction of the conveyor while maintaining the axial compressive force on the mated modules. The tensile member should be of a material having thermal expansion and contraction characteristics in relation to those of the modules to maintain a compressive load on the mated modules even during temperature cycling.The modules can alternatively be secured together by means other than a tensile member. One such alternative is illustrated in FIG. 8 in which the body 10 includes on each end thereof an integral flange 45 having openings 47 disposed about the circumference of the flange and through which fasteners are insert able for securing mated ends together.The mated modules may be supported for rotation on rollers 46. Typically, an array of three circumferentially spaced rollers is provided near each end of the conveyor body. Additional rollers can be provided as necessary, depending upon the length of the particular conveyor. Axial positioning of the conveyor body is maintained by horizontally disposed rollers 48 at each end of the body, these rollers being circumferentially spaced about the periphery of the body. A flange 50 is attached to the end modules of the conveyor and includes a circular surface 52 which is cooperative with the rollers 48 to maintain the axial position of the rot able body. A slip seal can be machined or otherwise formed in the outer end of the outermost module. In the illustrated embodiment, the slip seal is in the form of an annular groove 54 into which an end of a feed tube 56 is inserted, and with respect to which the conveyor body is rotatable. The feed tube 56 is typically connected to a hopper 58 into which a product is fed (as shown by the arrow) for conveyance.The drive assembly 60 includes sheaves 62 carried by and rotatable with a shaft 64 which is supported on bearing blocks 66 and which is driven by a motor (not shown). The shaft 64 is spaced from and parallel to the conveyor body, and each sheave 62 may be in association with a respective conveyor module. V-belts 68 couple the drive sheaves 62 to the conveyor modules and by which power is transmitted to the conveyor body for rotation thereof. In the illustrated embodiment, each of the modules is driven by an associated conveyor belt coupled to the drive assembly. All of the conveyor modules need not be driven, and the driven number will be determined in accordance with the motive force necessary to rotate the conveyor for particular applications.If the modules of FIGS. 4-6 are employed, the sheaves 28 are operative to engage the V-belts 68 for driving the conveyor. It is appreciated that the conveyor can be driven by other than V-belts. For example, chain sprockets can be formed on or attached to the modules for cooperation with a chain drive.Another embodiment of the invention is shown in FIGS. 9 and 10 and includes a screw conveyor module having a central tube 70 of cylindrical exterior form, 5 with a non-circular opening there through and with a web 72 helically disposed about the central tube. The helical web is slightly less in length than one helical pitch length, as described, and terminates at edges 74 and 76, these edges being adapted to confront corresponding edges of adjacent modules. The opening 78 through the central tube is of non-circular cross-section at end portions 80 and tapers to a non-circular cross-section at a central portion 82. This tapering is slight and is provided as "draft angle" to facilitate removal of the 15 module from axially separable molds. The opening is configured to mate with a non-circular shaft which serves as a tensile member to lock the modules into axial engagement and which also serves as a positive drive shaft for rotation of the conveyor. In the embodiment of FIGS. 9 and 10, the opening is illustrated as hexagonal, although other noncircular shaped openings can be provided in tube for use with a correspondingly shaped shaft to prevent rotation of the engaged modules relative to the shaft. A screw conveyor composed of the modules of FIGS. 9 and 10 is shown in FIG. 11. Each of the modules is aligned with the ends of adjacent central tubes 70 in engagement with an interposed O-ring 84, and with the helical webs 72 having their ends confronting to 35 provide an effectively continuous helical screw. A shaft 86 is fitted through the openings 80 through the tubes 70 and is secured by end fasteners, such as nuts 88 threaded onto threaded ends of shaft 86, which are tightened to provide an intended compressive force on the interconnected modules, as described above. This embodiment of FIG. 11 can be employed to retrofit existing metal screw conveyors without material change to the drive system.