The invention is concerned with a loom including weft yarn guide which guides an air flow for directing a weft yarn across a warp sheet.
When directing a weft yarn along a weft yarn guide it is desirable to provide auxiliary air jets along the guide which serve to help project the yarn along the guide.
The weft yarn guide is usually mounted on the reed shaft and so during operation the auxiliary jets move in unison with the reed shaft. This creates the problems of providing a connection between the source of pressurised air and each auxiliary jet which is reliable and interferes as little as possible with the running of the loom.
It has been proposed to arrange the auxiliary jets into groups, each group being supplied from a single source an air distributor. The air distributor may be mounted on the loom frame as for instance disclosed in published U.K. Patent Application 2065727A or on the reed shaft as disclosed in published U.K. Patent Application 2027066A. In both of these types of construction it is necessary to provide a valve means to control each distributor and the valve means is mounted on the loom frame.
Both of these types of construction suffer the disadvantage that the air supply connection either from the static air distributor to the moving auxiliary air jets or between the moving air distributor and the static valve means is achieved using flexible pipes. These are undesirable as they can suffer from fatigue caused by being repeatedly flexed; they can wear by rubbing against adjacent machine parts, and they tend to clutter the internal working space of the loom.
It is a general aim of the present invention to overcome these drawbacks.
According to the present invention there is provided a fluid jet weaving loom comprising a reed shaft rotatably mounted in the loom frame for oscillatory rotary motion, a reed mounted on the reed shaft, a weft insertion channel mounted adjacent to the reed, jet nozzles spaced along the weft insertion channel for carrying the weft yarn along the channel during weft insertion, the jet nozzles being arranged in groups of nozzles spaced along the length of the channel, the nozzles of each group communicating with a source of pressurised fluid via a common valve means, characterised in that each valve means is mounted on and adjacent the reed shaft, each valve means including cam follower means which is movable mounted to actuate the valve means, and in that a cam shaft is rotatably mounted on the loom frame at a position so as to co-operate with the cam follower means during weft insertion.
Reference is now made to the accompanying drawings in which:-
In Figures 1 and 2 there is shown an air guide channel 10 for weft yarn insertion which extends across the warp sheet of a loom 12. The channel 10 is composed of a plurality of individual guide teeth 13 which will be described hereinafter. Spaced along the channel 10 are auxiliary air jets 15 which are spaced apart by a desired number of guide teeth 13.
The guide teeth 13 and auxiliary jets 15 are mounted on the reed shaft 18 of the loom so as to be located in front of the beat-up reed 19. Conventionally the guide teeth 13 have a base portion 20 which is received in a rebate 21 formed in a support member 22 secured to the beat-up shaft 18. Individual clamp plates 23 are provided along the support member 22 and each is secured thereto by a pair of bolts 25 so that individual clamp plates 23 may be removed to permit removal of blocks of guide teeth 13. The guide teeth include a pair of arms 60, 61 which have internal edges defining the sides and upper confines of the channel. The lower confine of the channel is defined by the upper edge of the upper portion 20a and the base portion 20. The lower portion 20b of the base portion is a greater thickness than the remainder of the tooth so that abutting lower portion 20b of adjacent teeth serve to space the respective arms 60, 61 of the adjacent teeth apart by a predetermined amount. The lower portion 20b are provided with projections 20c on one side and complimentary recesses on the opposite side so that abutting teeth are maintained in correct alignment. Conveniently the teeth 13 are moulded in one piece from a suitable plastics material.
The auxiliary air jets 15 are arranged in groups along the length of the channel 10 wherein the air jets in each group are supplied with air from a common valve 30. Only one group and valve 30 are shown in Figure 2. During insertion of weft yarn the valves 30 are operated sequentially by the cam shaft so that auxiliary jets are operated sequentially along the channel as the weft yarn end travels therealong. Conventiently the auxiliary jets are each mounted on a guide tooth having one arm removed to permit its inclusion. Preferably the auxiliary jet is moulded with the tooth so that its position may be accurately attained.
To operate the valves 30, a cam 31 is provided for each valve 30 and operates a cam follower 34. Each cam follower 34 is in the form of a lever having a roller 35 at one end and an abutment face 36 at the other end for operating a plunger 37 in valve 30. The lever is biased by a spring 34a so that the plunger 37 is normally depressed, in which position the plunger urges a ball 38 against a conical seat 39 surrounding an air inlet port 40 to a chamber 43 in which ball 38 is housed.
The air inlet port 40 communicates via a conduit 41 with a bore 18a within a shaft 18 which is supplied with compressed air. During rotation of the camshaft 33 the cam 31 operates cam follower 34 to move away from plunger 37 and accordingly air pressure at the inlet port 40 forces the ball 38 away from seat 39 and into contact with a conical seat 45 surrounding the bore housing plunger 37. Air from conduit 41 enters chamber 43 and flows via exit ports 46 to auxiliary jets communicating therewith.
In order to permit all the auxiliary jets to be operated, say during a setting up procedure, a shaft 50 having a plurality of radial arms 51 for cooperation with the cam followers 34 is provided. On rotation of shaft 50 in an anti-clockwise direction as seen in Figure 1 the radial arms strike the cam-followers to deflect them away from their associated valve 30.
As mentioned above the guide teeth 13 each have two arms 60, 61 which have internal edges which define opposed sides and top of the channel 10. The bottom of the channel 10 is defined by the upper edge of the base portion 20. The arms 60, 61 have terminal ends spaced apart to define a mouth 63 through which weft yarn may escape from the channel during beat-up.
The auxiliary jets 15 are each provided with a nozzle 65 (see Figure 3) which is arranged to direct a flow of air toward an internal edge 70 of the guide tooth 13a adjacent to and downstream of the jet 15 so that a curtain of air 65a extends across the mouth 63 of tooth 13a to discourage exit of weft yarn through that mouth. The internal edge against which the flow of air is directed is shaped so as to deflect the flow of air along the channel 10. At least one of the remaining internal edges is preferably shaped so as to encourage removal of air from the channel between adjacent teeth. In this way the weft yarn is encourage to move toward those edges.
In Figure 3, the nozzle 65 directs a flow of air toward the lower part of the internal edge 70 defined by arm 60. The edge 70 defined by arm 60. The edge 70 is inclined to the axis of the channel so that it progressively approaches the centre of the channel in the direction of travel of the weft yarn. The angle of inclination between the edge 70 and longitudinal axis of the channel is about 10°.
Edge 10 may alternatively be rounded as shown in Figures 4d or 4e. The flow of air is deflected by edge 70 towards internal edge 71 of arm 61. This edge 71 can be shaped to encourage air loss between adjacent teeth so as to encourage the main flow of air whilst travelling toward the next auxiliary jet to remain close to edge 71.
Examples of cross sectional edge shapes suitable for edge 71 are illustrated schematically in Figures 4a to 4f. Each of these edges is designed to cause a negative pressure immediately downstream of the tooth to cause turbulence and thus loss of air from channel 10. The outer internal edges 72 and 73 may be shaped so as to encourage the desired air flow, for instance edge 72 may be inclined in a similar manner to edge 70 so that flow of air impinging on edge 72 is deflected downwardly toward edge 73 and edge 73 may be shaped in a similar manner to edge 71 so that air loss is achieved between adjacent teeth at the bottom of channel 10. Accordingly flow of air along channel 10 between adjacent auxiliary jets is in the main encouraged to flow near to the corner between edges 71 and 73 which urges the weft yarn to travel along the channel 10 at a location which is remote from the mouths 63 of adjacent teeth.
However, it is not essential to have edges 70, 71, 72 and 73 of different shape. They could all be of a shape which allows edge 70 to deflect the air from the nozzle, but which also allows sufficient air escape from all the edges to prevent a pressure build up inside the guides and consequent air escape from gap 63.
It will be appreciated that by directing a flow of air against an internal edge for deflecting the flow along the channel, it enables the auxiliary jets to be arranged to direct the flow of air upwardly across mouth 63 for subsequent deflection toward the bottom of the channel as schematically illustrated in Figure 5.
It is appreciated that the effect of the auxiliary jets directing a flow of air against an internal wall for subsequent deflection can cause the air flow within the channel to circulate, in a vortex fashion, as it moves along the channel. Accordingly, arms 60, 61 are shaped so that the exit mouth 63 does not permit the yarn to exit therethrough should it be gyrating due to the circulating flow of air within channel 10. Thus in Figure 3 it is assumed gyration of the yarn would be anti-clockwise whereas in Figure 5 it would be clockwise. Figure 6a illustrates an alternative guide tooth having a stepped mouth 63 for replacement of the teeth illustrated in Figure 3 whereas Figure 6b illustrates an alternative guide tooth having a stepped mouth 63 for replacement of the tooth illustrated in Figure 5. Figure 6a illustrates a tooth which could be used as an alternative for either of the teeth illustrated in Figures 3 and 5.