|Title of Invention
DOUBLE START CONSTANT FLOW TAPERED SCREW WITH NONLINEARLY VARYING PITCH
|A double start constant flow tapered screw (Fig. 1) is disclosed. The thread starts on the conical hub '1' which is of diameter dl and ends at the other smaller end of diameter d2. The envelop cone '2' also has its larger diameter Dl on the same side as dl and reduces to D2 at the other end. The instantaneous starting lead is at the start of thread '3' is L1. At the other end '4' the instantaneous lead is L2. The second start of the thread '5' has similar data as first start with 180 degree rotational symmetry. Depending upon the values of Dl, D2, dl, d2, and the starting lead L1, the length of the screw and ending lead L2 are designed through simulation to meet the constant flow requirement. By using this screw, constant flow for each degree of rotation and reduction in size of the material is achieved.
| The patent invention relates to
DOUBLE START CONSTANT FLOW TAPERED SCREW WITH NONLINEARLY VARYING PITCH
The main utility/usage of the invention is in maintaining a constant flow/constant density of the material along with size variation as it passes through tapered screw. Some the applications are pug mills, and other material extrusion/transport etc.
Full Prior art details only bone screw with varying pitch as described below:
Patent number US5562672 (1996) describes a tapered bone screw with continuously varying pitch. The varying pitch of the screw causes the bone fragments in fracture to be drawn together when screw is installed across the fragments. This is a bone screw and not for material transport along with size reduction
Patent number WO9416636 (1994) also describes a tapered bone screw with continuously varying pitch. Its application is also not for material transport along with size reduction.
Patent number GB242016 (1925) describes improvements in method of milling tapered screw threads. This is not related to the present invention of material flow through the screw.
The main objective of the present invention is to provide a double start tapered screw where the hub surface and the outer envelop surfaces for the thread are conical and the volume of the material through the screw for every degree of rotation of the screw is constant, which obviates the non availability of such a screw in the earlier inventions as detailed above.
Another objective of present invention is to reduce/increase the size of the material (cylindrical shape diameter to decrease or increase) with density of the material constant as it flows out.
Still another objective of the invention is to control the volume/density of the material as it flows, to the required value through lead variation with multi start threads and or variation of hub surface and envelop surface either conical, or any surface of revolution.
Yet another objective of the present invention is to optimise the power required to drive the screw by ensuring that the volume of the material increases continuously by only +1% (form in let to out let) as it flows.
Fig.l represents a double start constant flow tapered screw with nonlinearly varying pitch, wherein Part No.l is the conical hub which is of diameter dl at one end and of diameter d2 at the other end, Part No. 2 is a generator on the envelop cone surface, which has its diameter Dl at one end and diameter D2 at the other end, Part No. 3 is the first starts of the thread with an instantaneous starting lead L1, Detail No. 4 (the other end of Part No. 3) has the instantaneous lead L2, Part No. 5, the second start of the thread, with similar data as first start with 180 degree rotational symmetry, where Detail No. 6 a represents a cross section (shown as T-section) for Part No 3 and Part No 5, and the Parts 1, 3 and 5 are held together as a single screw by welding or by machining from solid, whose non-linear lead is simulated mathematically for the required volume change (or constant volume) with in specified tolerance limits depending upon the values of Dl, D2, dl, d2, and starting lead L1, to determined the coordinate data of the threads for every incremental rotation.
Fig.2 represents the characteristics of a double start constant flow tapered screw with nonlinearly varying pitch, wherein the upper curve shows a reduction in volume with zero blade thickness and the lower portion of the curve shows almost constant volume with blade thickness (T shaped blade cross section).
Fig.3 represents the lead variation of the double start tapered screw, wherein the lead variation is non-linear.
Accordingly, present invention provides a Double start constant flow tapered screw with nonlinearly varying pitch (or lead) which comprises a simulated non linear pitch (or lead) to maintain the required volume change, or constant volume with in tolerance limits from inlet to outlet.
In an embodiment of present invention, the material of the screw is
steel or any other material depending on the application.
In another embodiment of the present invention, the screw design
can be to bring in a required volume/density change along with size
In another embodiment of the present invention, the tapers of the hub cone and envelope cone could be in the same direction or in different directions with different tapers for each.
In yet another embodiment of the present invention, the cross section of the helical blade could of any cross section, the number of starts could be one or more and the helical path of the thread can extend to any angular rotation and the length of the screw can be of any length meeting the design requirements.
The working of the screw to maintain the constant volume (or required volume change) is simulated mathematically by changing the lead nonlinearly through a mathematically and graphically simulated program for every incremental rotation of the screw. Fig.2 shows two extreme designs with decrease in volume and with almost constant volume. Fig. 3 shows the lead variation as a function of rotation, which is non-linear.
The novelty and the inventive step is to arrive at a tapered screw to transport clay like material at constant density of from inlet to outlet along with reduction or enlargement in the size (diameter of material at inlet and out let) of raw material in cylindrical form.
The mathematically simulated experiments for constant volume for every incremental of rotation as given in Fig.2, highlights the novelty of the screw.
The main advantages of the present invention are:
1. Development of a double start constant flow tapered screw along
with reduction/enlargement in size of cylindrical raw material like
2. Development of the concept of nonlinearly varying lead/pitch to
meet the requirement of density change (or density constant).
3. Development of the concept of complex screw where all the
parameters of the screw are variables, i.e., Hub surface is conical,
Envelop surface is conical, the lead is continuously varied non
linearly, with multi starts.
|Indian Patent Application Number
|PG Journal Number
|Date of Filing
|Name of Patentee
|CENTRAL MANUFACTURING TECHNOLOGY INSTITUTE
|CENTRAL MANUFACTURING TECHNOLOGY INSITITUTE TUMKUR ROAD, KARNATAKA BANGALORE 560 022.
|PCT International Classification Number
|PCT International Application Number
|PCT International Filing date