Rotary expansible chamber devices – Interengaging rotating members – Like rotary members
Patent
1995-09-15
1997-04-08
Vrablik, John J.
Rotary expansible chamber devices
Interengaging rotating members
Like rotary members
F04C 218
Patent
active
056181728
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a spinning pump for melt spinning of polyamides comprising a back plate, a front plate, a central plate with a bore of partially circular cross section for supply of the melt and a bore of partially circular cross section for removing the melt, and a pair of gear wheels.
In melt spinning of polyamide 6.6, the quality of the filaments produced can decrease, in continuous operation, after a certain time. The reason for this has been sought in the melt portion of the system and in the starting polymer. It has now been found that deposits of cracked polyamide 6.6 in the spinning pump can be one of the causes of the reduced quality, which is also expressed in high fluff counts.
Gear pumps for melt spinning of polymer melts are known (European Patent Application EP-A2 0 447 766). The known spinning pumps are connected to a spinning pump block, which serves as a connection between an extruder and the spinning nozzles. The channels of the spinning pump block communicate directly with the bore channels of the spinning pump. In the spinning of nylon, especially in the melt spinning of nylon 6.6, deposits are found in the spinning pump that can make themselves felt over the course of spinning in the form of increasing fluff counts and reduced quality. Known spinning pumps have cylindrical inlet and outlet bores in the central plate, which after relatively long periods of operation exhibit deposits of polymer and products of its decomposition.
SUMMARY OF THE INVENTION
The object of the invention is to make available a spinning pump for melt spinning of polyamide 6.6 that is free of dead zones and that makes it possible to assure encrustation-free operation so as to attain improved quality.
A further object is to increase the productivity of the continuous melt spinning process of polyamide 6.6.
This object is attained in accordance with the invention in that the bores having the partially circular cross sections on the front of the central plate are formed so that the cross-sectional area of the bores toward the back of the central plate is reduced in relation to the cross-sectional area at the front side, and the center points of the transverse partially circular cross sections of the bores are located on a parabolic arc or path from the front side of the central plate to the back side.
The parabolic shape of the bores enables continuous operation free of dead zones.
It is suitable if the profile of the bores extends in a continuous and nonlinear function, whose first derivative is continuous. The profile of a parabola has proved to be preferred.
It is also suitable if the transition of the bores from the central plate to the back plate is uninterrupted and free of kinks and represents the beginning of the profile that the bores follow.
It is especially advantageous if the profile of the center points of the partial circles forming the bores ends on the back side of the central plate in such a way that the free partial circular area of the bores is as small as possible, but preferably tends towards zero. The term "partial circular area" is to be understood according to the invention as the free cross-sectional area, which is a circle minus the imaginary two portions of the circle that are cut off from the cross-sectional area by the rotation of a tooth of the two gear wheels.
BRIEF DESCRIPTION OF THE DRAWING
The invention will now be described in further detail in conjunction with a drawing, in which:
FIG. 1, is a cross-sectional view of a spinning pump with a pump block;
FIG. 2 is a schematic cross-sectional view taken along the line II--II on the front side of the central plate in the region of the polymer inlet and outlet;
FIG. 3 is a perspective view of the central plate from the spinning pump of FIG. 1;
FIG. 4 is a cross-sectional view taken along the section line IV--IV passing through the central plate with the bores according to the invention;
FIG. 5, a schematic illustration of the bore according to the invention.
DESCRIPTION OF THE PREFERRED EMBO
REFERENCES:
patent: 2460649 (1949-02-01), Muller
patent: 3817668 (1974-06-01), Mayer et al.
Hone Poulenc Viscosuisse SA
Striker Michael J.
Vrablik John J.
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