Textiles: braiding – netting – and lace making – Apparatus – With take up
Patent
1997-09-19
1999-06-08
Stryjewski, William
Textiles: braiding, netting, and lace making
Apparatus
With take up
87 8, 87 13, 87 14, 87 50, D04C 348
Patent
active
059102047
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for the production of packing for stuffing boxes, including a step in which the elementary yarns are braided to form the packing at an assembly point.
BACKGROUND INFORMATION
It is known that packings produced by the method specified above are wound around pump shafts or valve rods within a stuffing box to reduce or eliminate liquid losses. The packing thus arranged is compressed by a gland with a predetermined force so that it presses against the surface of the shaft or rod.
As a result of the curvature imposed by the winding, the elementary yarns on the extrados surface of the packing are in traction while the elementary yarns on the intrados surface are compressed so that the cross-section of the packing, which initially is square or rectangular, deforms into an isosceles trapezium with its larger base on the intrados side.
As a result of this deformation, the compressive force is not transmitted uniformly through the packing. Thus it is necessary to increase the force to achieve adequate hydraulic sealing at the expense of greater wear of the packing itself due to yielding and friction.
WO-A-94/11555 discloses a packing which has a cross-section in the form of an isosceles trapezium with its larger base on the extrados side. The deformation induced by the winding makes the section square or rectangular, improving the uniformity of transmission of the compressive forces.
The elementary yarns in such a packing are however subject to yielding as in conventional packing and are, in any case, under traction and compression. Moreover, in pumps, the friction is increased since the elementary yarns on the intrados surface are pressed together by the overlying yarns and pressed onto the surface of the shaft with a consequent loss of energy and overheating of the packing.
SUMMARY OF THE INVENTION
The technical problem which is at the root of the present invention is to provide a method for the production of packing for stuffing boxes, which packing is able to avoid the problems mentioned with reference to the prior art.
This problem is solved by a method of the type specified which is characterised in that it includes a step of winding the packing starting at the assembly point.
The main advantage of the method of the invention lies in the fact that packing is obtained which enables compressive forces to be transmitted uniformly through adjacent turns while at the same time eliminating forces within the packing.
BRIEF DESCRIPTION OF THE DRAWINGS
Further characteristics and advantages will become clear from the description of one preferred embodiment of the method of the invention, given below by way of non-limitative example, with reference to a machine for carrying out the said method and packing formed as illustrated in the appended drawings, in which:
FIG. 1 is a schematic perspective view of a machine for carrying out the method for the production of packing for stuffing boxes according to the invention;
FIG. 2 is a perspective view of a detail of the machine of FIG. 1;
FIG. 3 is a cross-section of the detail of FIG. 2;
FIG. 4 is a close-up perspective view of the step in which packing is braided in the machine of FIG. 1;
FIG. 5 is an enlarged perspective view of packing formed by the method for the production of packing for stuffing boxes according to the invention;
FIG. 6 is a perspective view of a portion of the packing of FIG. 5 in a rest condition; and
FIG. 7 is a sectional view of the packing of FIG. 5 within a stuffing box.
DETAILED DESCRIPTION
With reference to FIG. 1, a machine for the production of packing for stuffing boxes by means of the method for the production of packing for stuffing boxes according to the invention is indicated 1.
The machine 1 includes a frame 2, a horizontal thread guide plate 3 supported by the frame 2, a plurality of reels 4 of elementary yarns 5 rotatably engaged on respective fixed pins 6 of the frame 2 beneath the thread guide plate 3.
The thread guide plate 3 has a plurality of thread guide
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patent: 4333380 (1982-06-01), Kozlowski
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patent: 5417138 (1995-05-01), Morris
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