Textiles: weaving – Weft manipulation – Weaving with stationary weft supply
Patent
1982-06-29
1985-11-05
Jaudon, Henry S.
Textiles: weaving
Weft manipulation
Weaving with stationary weft supply
D03D 4730
Patent
active
045507520
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to a method for conveying a flexible thread by means of a pressurized gas, particularly for inserting a weft thread into the weaving shed of a weaving machine, by utilizing an injector of the type comprising a chamber connected to a source of the pressurized gas, a first channel extending from said chamber for a primary gas flow, a second channel merging with said first channel, in which the thread to be conveyed is supplied together with a secondary air flow, from any known source and a third channel in which both flows after have been joined are combined into a single gas flow taking along the thread to be conveyed.
In the method as known up till this moment and which are applied in the modern pneumatic weaving machines generally injectors are used in which the third channel, also indicated by "mixing tube", has a constant cross-sectional area.
With a view to an as economic air consumption as possible and therefore a low air consumption the diameter of the mixing tube is generally minimized. A small mixing tube diameter moreover has the advantage that the path of movement followed by the conveyed thread will deviate relatively little from a predetermined average conveying path so that the injector will present a thread with large certainty within a relatively narrowly limited area at the entrance of the weaving shed of the weaving machine.
The invention aims at improving the method as performed up till now such that with a given pressure and a given air consumption the force imparted by the flowing gas to the thread to be conveyed in the conveying direction is increased and thereby the effectiveness of weft thread insertion is improved.
According to the invention it is assumed that the force F imparted by the flowing gas to the thread may be considered to be in direct proportion with velocity of the flowing gas.
An obvious idea would be to increase the mixing tube length. However, in a cylindrical mixing tube the velocity of the flowing gas, as seen in the direction of the axis, is not the same everywhere.
Therewith there has to be distinguished between flow of the combined conveying gas flow and establishing a supersonic flow of the combined conveying gas flow.
In the first case, like in the second case, as long as the pressure used is too low to actually arrive at a supersonic flow, a pressure decrease will occur in the conveying direction under the influence of the friction experienced by the flowing gas from the (cylindrical) mixing tube wall which simultaneously produces a density decrease. With a stationary flow, as a like mass quantity flows through each cross-section, the velocity in the cylindrical mixing tube has to be inversely proportional to the density. This implies that the velocity is maximum at the exit end of the tube.
If the feed pressure is increased the velocity initially will increase until at a predetermined value of pressure the speed of sound is reached at the end of the mixing tube. If the feed pressure is still further increased this velocity cannot further increase but only the density will increase.
It follows from the above given consideration of the factors determining the value of the force imparted to a thread, that the largest contribution to force is given at the exit end of the mixing tube. A prolongation of the mixing tube will have increasingly less effect since the contribution is added at the side where the velocity is minimum. At the same time, with an equal pressure drop, less gas will be permitted to flow through the tube so that the density along the full length will be lower than may be realized with a shorter tube. Thereby a lower force contribution per unit of length will occur.
The invention now proposes to use in case of conveying a thread in a subsonic gas flow an injector in which the channel for the combined gas flow is constructed such that the ratio of the cross-section and the mass quantity flow as seen in the flow direction increases such that in each point of the flow path through the m
REFERENCES:
patent: 4347872 (1979-08-01), Brouwer et al.
patent: 4353397 (1982-10-01), Teva et al.
Journal of the Textile Machinery of Japan, pp. 28-36, Jul. 1961, A Study on Air Jet Looms, by Minoru Uno et al.
Jaudon Henry S.
Ruti-Te Strake B.V.
LandOfFree
Method for conveying a flexible thread by means of pressurized g does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for conveying a flexible thread by means of pressurized g, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for conveying a flexible thread by means of pressurized g will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-291684