EP0067994B1

EP0067994B1 - Improved air weft insertion nozzle control system

Info

Publication number: EP0067994B1
Application number: EP81901583A
Authority: EP
Inventors: Charles W. Brouwer; Karl W. Wueger
Original assignee: Leesona Corp
Current assignee: Leesona Corp
Priority date: 1981-01-07
Filing date: 1981-01-07
Publication date: 1985-09-11
Also published as: WO1982002411A1; GB2105377A; CA1155730A; BE890668A; BR8108951A; GB2105377B; IT8124990A0; DE3172175D1; EP0067994A4; EP0067994A1; IT1139693B

Description

This invention relates to the field of air weft insertion weaving methods and apparatus in which a weft yarn is delivered from a supply to the throat of a weft insertion nozzle which is periodically pressurized to expel therefrom pressurized air or other gaseous propelling medium (the term air being employed here as a general designation for all such media for simplicity's sake) and propel a length of the weft yarn through the nozzle and across the shed of the loom under the driving force of the thus-emitted pressurized air stream, and is concerned more particularly with an improved control system for regulating the actuation of the firing of such nozzle.
In U.S. application Serial No. 64,180 of Brouwer et al, filed August 6, 1979, now U.S. Patent 4347872, commonly assigned herewith, there is disclosed and claimed a loom and weaving method embodying an air weft insertion system of the type generally defined above in which a pulse of pressurized air of abbreviated duration relative to the duration of the overall weaving cycle of the loom is delivered via a valve from a constantly pressurized air supply chamber to the throat of the weft insertion nozzle directed toward the shed of the loom, which throat is preferably contoured so as to expel such air from its exit opening at a supersonic velocity, the leading end of the weft yarn to be inserted being disposed within the throat of this nozzle for contact with the air stream passing therethrough and projection thereby into and across the shed of the loom to the opposite side thereof.
This system imposes special and demanding requirements upon the control of the actuation, i.e. opening and closing, of the nozzle valve in order to achieve the air pulse characteristics, including brief duration, needed to impart substantial thrust to the yarn and in a companion application Serial No. 64,395 of Brouwer et al, also filed August 6, 1979, now US patent 4 466 468, and commonly assigned herewith, there is disclosed and claimed a preferred control system for effecting the opening and closing of the nozzle in a manner achieving the required pulse characteristics.
The preferred control system of patent specification US-A-4 466 468 utilizes a flexible diaphragm valve closing the exit opening of the pressurized air supply chamber and opening to place the chamber exit opening into communication with the throat passageway of the nozzle wherein the leading weft yarn end is already situated. Advantageously, the air supply chamber annularly envelopes the nozzle throat passage- way so that the exit opening of the chamber is annular and is co-terminous with a coaxial annular inlet opening of the nozzle passageway so that both such openings can be closed by means of a common diaphragm valve and placed in communication when the diaphragm opens.
Movement of the diaphragm valve is determined by the application to and release from control pressure to the face of the diaphragm opposite the supply chamber and nozzle throat openings, the control pressure being preferably applied to an annular area of the opposite diaphragm face defined by means of a pilot chamber. The pilot chamber is alternately placed in communication with a source of pilot or control pressure and the ambient atmosphere, to cause closing and opening of the diaphragm valve by means of a spool servo valve arrangement which can take several different forms but in all cases incorporates a coordinated pair of rotating spool valves, one governing the pressurization of the pilot chamber and the other governing the depressurization or venting of the pilot chamber so that the closing and opening of the diaphragm valve can be carried out independently from a control standpoint. The initial angular positions of the spool valves are adjustable relative to one another, thereby permitting direct adjustment of the length of time the diaphragm valve is allowed to remain open during each cycle of spool rotation.
While the nozzle actuating control system of US-A-4 466 468 has been found to work effectively in practice, there is room for improvement. On the one hand, the diaphragm valve which is made of durable heavy rubberized fabric or the like clamped along both its center region and external margins with an intermediate annular flexible region exhibits an operating life in the order of several millions of cycles; and while this durability is certainly high by ordinary mechanical standards, a loom weaving at the rate of 400 picks per minute passes through more than one million cycles during each 48-hour week of a single shift of operation. Consequently, the diaphragm of the above control unit may require replacement after several weeks or at most a few months of use under normal conditions.
On the other hand, the construction of the rotary valve array, while decidedly advantageous in the light of the prior art nozzle control concepts, is complicated especially as regards the precise contouring of the peripheral surfaces of the respective valves to form the arrangement of lands and recesses needed to control the flow of pressurized pilot air in both directions therethrough and to impart balancing pressure forces to offset the main air flow effect and avoid premature wear.
An important object of the invention is the control of the pilot or control pressure acting on the nozzle diaphragm valve to determine the opening and closing of the same by means of a single spool servo valve of simplified construction in which the time required to reestablish control pressure to close the diaphragm valve, and thereby determine the period the latter is open, is variable in response to variation in the magnitude of the pilot pressure delivered by the spool valve.
A subsidiary object is a rotary spool servo valve which is designed to provide two different ranges of open periods merely by reversing its position in a valve housing.
A further subsidiary object of the invention is the provision of an air permeable housing for the rotary spool which is maintained under constant pressurization during operation to support the spool on an air bearing.
An additional subsidiary object is the minimization of open space within a nozzle control system to reduce the inherent capacitance and background "noise" of the system.
To attain these objects a control system for an intermittently-operating strand delivery system which includes a nozzle passageway through which the strand is guided, a supply for pressurized strand delivery medium, and conduit means connecting between said nozzle passage- way and said supply including a pressure-operated on-off flow control valve, which is normally open under the pressure of said medium and is adapted to close upon the application thereto of a generally predetermined pressure, said control system comprising a source of pressurized control medium, means for adjusting the magnitude of the pressure of said control medium, and servo valve means for alternatively applying and releasing said pressurized control medium at said adjusted pressure to and from said pressure-operated flow control valve to operate the latter according to the invention is characterized in that said servo valve means comprises a rotary spool and a housing in which said spool is rotatably disposed in generally pressure-tight relation, said housing having at a given point in the periphery thereof a delivery port in communication with said pressure-operated flow control valve, and said rotary spool having at points around its periphery separated by a predetermined arc a venting passage adapted to be in communication with the ambient atmosphere and a feed passage adapted to be in communication with said source of pressurized control medium at said adjusted pressure, said venting and feed passages being upon rotation of said spool brought successively into registry with said housing delivery port to successively release said pressurized control medium from said pressure-operated flow control valve and re-apply the same thereto via said housing port, the period required for said reapplied control medium to achieve at the flow control valve a given level of the adjusted control medium pressure varying with the magnitude of said adjusted control medium pressure, whereby the period during which the flow control valve is open to supply pressurized delivery medium to said nozzle passageway can be varied by adjusting the magnitude of said control medium pressure.
According to a prefered embodiment this system is characterized in that said supply of said pressurized delivery medium comprises a supply chamber in communication with a source of said pressurized delivery medium and having an annular exit opening therefrom and a feed conduit generally coaxial and co-terminus at its inlet end with said annular exit opening; and further characterized in that said pressure-operated flow control valve comprises a flexible diaphragm extending in close axial proximity over said annular exit opening and said feed passage inlet end, said diaphragm being movable from and a first operative position closing said exit opening and said conduit inlet end with one of its faces to and from a second operative position spaced axially away from said exit opening and conduit inlet end to bring the latter into communication and allow medium to flow from said chamber via the open exit opening thereof through said conduit via its open inlet end into said nozzle passageway; and means connecting said housing delivery port to the opposite side of said flexible diaphragm to thereby apply and release said control medium at said adjusted pressure to and from said diaphragm to control its movement between said two operative positions. This system is further preferably characterized in that said diaphragm has two coaxial radially separated generally U-shaped annular convolutions therein, said convolutions having their open ends facing toward said supply chamber with one of said open ends generally coinciding radially with said annular supply chamber exit opening and exposed to the pressure of the delivery medium in said supply chamber, the region of said diaphragm intermediate said convolutions moving bodily between said two operative diaphragm positions with the convolution walls progressively telescoping to accommodate said movement, whereby the diaphragm flexes with a generally rolling action to increase its operating life.
The above stated objects and advantages and others not specified will be more fully revealed when the following detailed description is read in connection with the accompanying drawings in which:

Fig. 1 is a longitudinal sectional view partially in cross-section and partially in elevation taken through the rotary servo valve assembly of the present invention,
Fig. 2 is a detailed perspective view of the rotary spool body of the assembly of Fig. 1;
Fig. 3 is a transverse cross-sectional view of the spool body taken generally along line 3-3 of Fig. 2;
Figs. 4-10 are detailed views showing various operative positions of the spool valve assembly, omitting drive components, in which:
Fig. 4 is a fragmentary longitudinal sectional view showing the spool valve body in position for pressurizing the pilot chamber and closing the nozzle diaphragm valve,
Fig. 5 is a side elevational view of the assembly casing showing in dotted lines one arrangement of air passages therein with arrows indicating the path of air flow during pilot chamber pressurization,
Fig. 6 is a transverse sectional view taken substantially along line 6-6 of Fig. 4 midway through the nozzle body.
Fig. 7 is a transverse sectional view taken substantially along line 7-7 of Fig. 4 and adjacent one end of the nozzle body,
Fig. 8 is a longitudinal section similar to Fig. 4 but showing the spool body in venting position,
Fig. 9 is a side elevation of the assembly similar to Fig. 5 with the arrows showing the air flow path during venting, while
Fig. 10 is a transverse sectional view similar to Fig. 6 but taken along line 10-10 of Fig. 8 and showing the nozzle body in venting position;
Figs. 11-14 are transverse sectional views similar to Figs. 6 and 10 but enlarged to show only the spool body and the surrounding portions of the air permeable housing, in which:

The spool body is shown in Fig. 11 in its position at the beginning of pilot pressure venting and consequential opening of the nozzle diaphragm valve and in Fig. 12 in its position at the beginning of pilot chamber pressurization and nozzle valve closing, but with the spool land of lesser arcuate extent in leading rotational position, while
The spool body is shown in pilot chamber venting position in Fig. 13 and in pilot chamber pressurizing position in Fig. 14, both with the arcuately long spool land in leading rotational position;

Figs. 15-18 are plots of pressure versus time in ms, from the nozzle firing pulse, for nozzle throat pressure (in solid lines) and the pilot chamber pressure (dotted lines) at two levels of pilot pressure with the short spool land in leading rotational position in Figs. 15 and 16 and in trailing rotational position in Figs. 17 and 18;
Fig. 19 is an enlarged detailed cross-sectional view through the axis of the weft insertion nozzle, showing a preferred embodiment of the convoluted "rolling action" diaphragm valve;
Fig. 20 is an enlarged end view taken partially in section substantially along line 20-20 of Fig. 19 with the diaphragm and retaining ring omitted to show the interior space between the diaphragms; and
Fig. 21 is an overall view greatly simplified of the complete nozzle control system of the present invention.

Detailed description of illustrative embodiment

Referring now to Fig. 1, the numeral 31 designates a casing for the improved single spool servo valve assembly of the present invention which has a cylindrical interior opening 33 passing axially therethroug but can otherwise be of any convenient exterior configuration. For example, rectangular from all sides. The casing side walls can be penetrated by spaced apertures 35 for the reception of mounting bolts for attachment to a fixed support (not shown). Fitted in the interior opening 33 adjacent one end, i.e. to the right in Fig. 1, is a spaced pair of roller or other bearings 39a, 39b and an elongated drive shaft 37 is press fitted into the inner races of these bearings for rotation therein. The inner end of shaft 37 has an enlarged head 41 to provide a shoulder retaining the inner bearing 39a, while the outer bearing 39a is retained on shaft 37 by means of a lock nut 43 anchored thereon. The bearings are held apart by a sleeve 45 and the outer race of the outer bearing is retained against axial movement relative to the casing with a retaining ring 47. A threaded aperture 48 is preferably drilled into the top wall of housing 31 to facilitate attachment of the housing in operative position to a suitable fixture (not shown) by means of a bolt or other fastening means.
Drive shaft 37 extends outside the right end of casing 31 beyond lock nut 43 and rotatably supports a driving pulley 51 encircled by a driving belt 53 driven from a source not shown. Pulley 51 is gripped for bodily rotation with shaft 37 by a friction coupling which can be released to permit initial adjustment of the relative rotational positions of the pulley and shaft. For this purpose, the pulley has a frustoconically shaped hub 55 which is adapted for mating frictional engagement with a conically shaped socket 57 in the adjacent end of a cylindrical collar 59. Collar 59 can be forced into locking frictional engagement with the pulley hub or released therefrom by means of a nut 61 in threadwise engagement with the far end of shaft 37, the movement of the nut being transmitted to collar 59 by means of a spacer sleeve 63 while the inside of pulley hub 55 abuts the lock nut 43. Preferably, the enlarged end 41 of shaft 37 is notched as at 65 so that the shaft bearings, friction coupling, etc., can be easily sub-assembled as a unit and then inserted within the end section of the interior opening 33 of casing 31.
A portion of shaft 37 adjacent head 41 is formed with an axially extending central aperture to receive one end of an elongated flexible driving rod 69 held against movement either axially or rotationally relative to shaft 37 by a set screw 71. Driving rod 69 projects exteriorly of shaft head 41 and its exterior end is adapted to make a flexible driving connection with a rotary spool body generally designated 75, the transverse cross-section of that end being preferably square or other polygonal shape to serve that purpose.
Spool body 75 is of generally cylindrical shape with a hollow interior bore 77 and the projecting end of drive rod 69 extends to about the midpoint of bore 77 and is frictionally embedded at its termination in an aperture of matching shape passing axially through a resilient lock plug 79 (see in dotted lines in Fig. 1 and in section in Fig. 3). Plug 79 has a cylindrical exterior which is press fitted within bore 77 of spool body 75. Hence, as shaft 37 is rotated with pulley 51, that rotation is transmitted by drive rod 69 to spool body 75 to rotate the same; however, drive rod 69 is sufficiently flexible as to permit lateral displacement of the spool body 72 which is thus able to "float" relative to the remainder of the assembly.
Spool body 75 fits within the central aperture 81 of a housing 83, preferably in the form of a cylindrical sleeve, which is advantageously constructed of a porous air permeable yet hard surfaced material such as porous carbon, sintered metal or the like. As will be explained shortly, the pores of air permeable housing 83 are constantly permeated by pressurized air so as to generate an air film "bearing" in the innerspace between the housing interior and the spool body exterior upon which the spool body rides during its rotation. In addition, if the permeable material has a hard surface, as preferred, it can act as a bearing for the spool body in the event air pressurization should fail for some accidental reason. Permeable housing 83 is in turn fixed in air tight engagement within the interior opening 33 of casing 31 and can be positively secured against relative axial movement with an end cap 85 having a central opening 86 communicating with spool bore 77.
As is visible in Fig. 2, spool body 75 is formed with two axially spaced circular air supply grooves 87a, 87b encircling its periphery and these peripheral grooves are interconnected by at least one, and preferably two, air supply channels or flats 89a, 89b extending axially along the otherwise solid cylindrical surface of the spool body between the circular groves 87a, b. Where two such channels are used, they are diametrically opposed and separate the spool periphery into two segments 91 and 93. In one of these segments, e.g. 91, an axially elongated air feed slot 95, located in lengthwise symmetry with the sleeve body length, passes entirely through the spool bodywall into communication with the interior bore 77 thereof, while on the other periperhal segment 93 the spool body wall is penetrated by a spaced pair of axially elongated air balancing slots 97a, 97b which are equal in length and area to one-half of the length and area of slot 95, being situated in symmetrical position intermediate the ends of the slot and the adjacent walls of circular grooves 87a, 87b. Slots 95 and 97a, b, could be located symmetrically with the arcuate length of the corresponding segment, i.e. equidistant from the channels 89a, 89b, but are preferably asymmetrically arranged so as to be closer to one channel than to the other for a reason to be explained.
Adjacent its ends, the exterior periphery of air permeable housing 83 is provided with circular manifold recesses 101a and 101b which are elongated to cover a significant portion, say about 20% each, of the housing length. Recesses 101a, b, each communicate with a peripherally spaced array, say three, of ports 103a and 103b passing radially through the thickness of housing 83 at equi-spaced points there-around, the axial location of ports 103a and b, being such as to coincide and thus communicate with the circular air supply grooves 87a, b, in spool body 75. Intermediate peripheral recesses 101a, b, sleeve 85 is penetrated by means of an elongated air feed port 105 (best seen in Figs. 5 and 10) which is in axial registration with, and generally equal in axial and arcuate dimension to, air feed slot 95 in spool body 75. The opposite side of housing 83 is similarly penetrated by two smaller air balancing ports 107a and 107b (seen in dotted lines in Figs. 6 and 10) which likewise register axially with, and are generally equal in all dimensions to, spool body air balancing slots 97a, b.
The assembly casing 31 is constructed with an arrangement of air supply passageways communicating with the peripheral recesses 101a, b, and feed passageways 105 and 107a, b, communicating with the air feed and balancing ports 105 and 107a, b, and obviously wide variation is possible in the orientation and configuration of these passageways. For purposes of illustration, one suitable arrangement is shown in Figs. 5-10. In these figures, the casing 31 is shown shaded as a single entity (forsake of better contrast with the housing and spool body) but in practice, as is suggested in these figures, the casing is constructed of several parts to facilitate the machining of the various passageways therein.
In this arrangement, casing 31 has on one side an air supply connection 111 (see especially Figs. 5 and 7) which is constantly connected by a hose or conduit (not shown) with a source of pressurized air and joins a passageway leg 113, extending vertically upward to intersect with a short lateral leg 114 which opens into a shallow axially directed (see Fig. 5) U-shaped double armed branch 115 connecting at the opposite ends of its arms via lateral branches 116a, b, with the peripheral recesses 101a, b, of the permeable housing 83. Consequently, as already stated, housing recesses 101 a, b, are constantly exposed to pressurized air which insures that the entire housing 83 is permeated by air. Also on one side of housing 31, preferably for convenience of connection on the same side as supply port 111, is a nozzle feed connection 117 which is in permanent communication via a hose or conduit (not seen) with the pilot chamber of the nozzle. Nozzle feed connection 117 joins with a vertical leg 121 which intersects with a short lateral leg 123 opening into an axially elongated arm section 125 (best seen in Figs. 5 and 9). The function of arm 125 is to feed the pressurized air to and from the air balancing slots 97a, 97b, in spool body 75 by way of housing balancing ports 108a, b, and arm 125 branches laterally as at 126a, b, in registration with housing ports 107a, b. In addition, arm 125 has a vertical branch 127 joining at its upper end with a lateral bypass 129 (see Figs. 6 and 10) that crosses to the opposite side of casing 31 where it connects with a downwardly directed vertical leg 131 that is axially enlarged at its lower end as at 133 and branches in vertical alignment with the opposite branches 126a, b. Enlargement 133 serves to establish communication with the nozzle feed slot 95 in the spool body via the corresponding housing port 105 in the permeable sleeve and branches laterally as at 135 to communicate with port 105.
From the preceding description, it will be understood that the supply connection 111 and the associated leg 114 and double armed branch 115 are maintained constantly under pressure from the air supply (not shown) and deliver this air pressure to the housing ports 101a, b, and via the port array 103a, b, to the circular recesses89a, 89b, of the rotary spool body. On the other hand, the nozzle feed connection 117 connects the nozzle pilot chamber with its associated branches and legs 121, 123, 125, 127, 129, 131,133 and 135 and thus with the feed port 105 and balancing port 107a, b, of the housing nozzle feed. The rotary spool body carries both supply channels 89a, b, and venting port 95 and the rotational position of the rotary spool body, therefore, determines the ultimate direction of air flow within these series of passages.
Assuming that the pilot chamber is initially pressurized, forcing the nozzle diaphragm valve into closed position, when spool body 75 rotates to the position of Fig. 11, at which the spool venting slot 95 has just moved into communication with the housing feed port 105, air begins to flow from the nozzle pilot chamber through the connecting conduit into connection 11 and thence via the sequence of passages 114-133 into the spool bore 77 and ultimately to the ambient atmosphere through the open ends of that bore (see also Figs. 8-10). As the pressure in pilot chamber drops due to the venting of the air therefrom in this manner, the nozzle diaphragm valve will eventually open, permitting the air supply in the nozzle supply chamber to exit into the nozzle throat to "fire" the nozzle. At the same time, air venting from the pilot chamber also passes out via the balancing slots in the spool body which have been simultaneously brought into registration with the balancing ports in housing 83 (as shown in dotted lines in Figs. 10, 11 and 13) so as to balance the pressure forces acting on the spool body to maintain the same in an equilibrium position within the sleeve opening during the venting phase.
As the spool body 75 continues to rotate, venting slot 95 will move beyond feed port 105 and the latter will become closed off by one of the segments 91, 93 of the periphery of the spool body and will remain closed until the trailing limit of that segment has rotated on to bring the leading edge of the following channel 89a, 89b, into communication with sleeve port 105 (Fig. 12). Since channels 89a, b, are constantly pressurized via circular spool grooves 87a, b, pressurized air therein now begins to escape outwardly through feed port 105 and is delivered through the series of passages 114-135 (as diagrammed by the arrows in Fig. 6) and the connecting conduit to the nozzle pilot chamber to begin re-pressurization of that chamber and cause eventual return of the nozzle diaphragm valve to closed position, ending the flow of air from the nozzle throat. Additional air needed to maintain the pressurization of the peripheral grooves 87a, b, is supplied from the source through the supply passage sequence 111-114, following the path of the arrows in Fig. 7.
It is within the scope of the present invention to arrange the radial axes of the spool valve body vent port 95 symmetrically with the central radial axis of the spool segment 91, but it will be recalled that preference has already been expressed for an asymmetrical relationship between these axes whereby the feed slot is displaced nearer one edge of the spool peripheral segment than the other. In this way, it becomes possible to employ the same spool to achieve two different ranges of response times for the diaphragm valve and consequently for the duration of the air pulse emitted from the nozzle throat and an understanding of this feature will be facilitated by a comparison of Figs. 11 and 12 with Figs. 13 and 14. With the radial axes of spool slots and peripheral segments asymmetrically disposed, each segment is separated into an arcuately short land 91 a, 93a, and an arcuately long land 91 a, 91 b. In Figs. 11 and 12, the spool body 75 is disposed within the housing bore 81 with a short land 91 a, 93a, in leading position to feed slot 95 relative to the direction of rotation. In this case, after the pilot chamber pressure has been vented while spool vent slot 95 registers with housing feed port 105, feed port 105 becomes closed by the trailing segment 91 b, 93b and remains closed until that segment clears the feed port 105. If the trailing segment, therefore, is extended, the closure of port 105 will likewise be extended and re- pressurization of the pilot chamber is delayed.
Contrariwise, if spool body 75 is inverted or reversed in endwise position within the housing bore 81 to place a long land 91 b, 93b, in leading position rotationally speaking to vent slot 95, as illustrated in Figs. 13 and 14, port 105 will remain closed for a shorter period of time due to the lesser arc of the trailing short segment 91a, 93b, and re-pressurization of the pilot chamber will start at an earlier time when the spool body rotates to the position of Fig. 14.
Obviously, the difference in arcuate length of the leading segments of the spool valve body for its two positions with the housing 83 will have no influence on the point in the rotation of the spool valve body at which venting, and consequential firing of the gun, will take place, since this point is determined by the location of housing feed slot 105 which is fixed.
When re-pressurization of the nozzle venting chamber begins, with the spool valve body in position shown in either of Figs. 12 and 14, it will be appreciated that a finite period of time will elapse before the pressure of the air being re-supplied to the nozzle venting chamber has built up to a sufficient level to cause displacement of the nozzle diaphragm valve to closed position, in the manner explained in more detail in the related US-A-4 466 468 identified above. The length of this finite re-pressurization period will be influenced to some extent by the capacitance of the delivery system which affects the rate at which air can flow along its path from the pressure supply to the pilot chamber itself. An advantage of the present invention compared to that of the just mentioned prior application, is a reduction in the inherent capacitance of the control valve unit. Another factor determining the duration of the re-pressurization period, however, is the magnitude of the supply pressure being delivered via the spool valve to the pilot chamber, and an important objective of the present invention is the utilization of supply pressure variation to adjust the overall length of the re-pressurization period and thus the ultimate duration of the air pulse emitted from the nozzle throat.
As is explained more fully in US-A-4 466 468 the magnitude of the pressure required in the pilot chamber needed to achieve closure of the diaphragm valve can be altered by appropriate design of the overall nozzle, particularly as regards the relationship of the effective area on the opposite sides of the diaphragm valve (or valve sub-assembly where plural spaced diaphragms are employed) since it is the effective ratio of the opposite diaphragm regions against which the opposed nozzle supply and pilot chamber pressure bear that establishes the operative ratio between these pressures at which the diaphragm valves opens and/or closes. The effective ratios of the exposed areas of the opposite diaphragm faces can be varied not only by selection of the relative dimensions of the chambers communicating with those opposite faces but, more preferably, by the interposition of a floating ring in an interspace within a dual diaphragm sub-assembly. The end faces of this ring make contact with adjacent faces of the two diaphragms of the dual diaphragm sub-assembly so that the respective areas of these end faces determines the transmission of opposing pressure forces between the diaphragm pair. By selecting different areas for these end faces, the effective area ratio of the diaphragm valve can be changed so that, as is preferred, a greater nozzle air supply pressure can be controlled with a lesser pilot chamber pressure.
These design considerations thus establish a minimum pilot chamber pressure necessary for a given supply chamber pressure to return the diaphragm valve from open to closed position against the resistance of the pressure of the air passing from the supply chamber through the open valve to the nozzle throat, and this minimum applies in any case. However, the magnitude of the pilot chamber supply pressure above this minimum can be effectively employed to alter within a certain rate the re-pressurization period of time of the pilot chamber and hence the duration of the air pulse emitted from the nozzle throat. This concept is illustrated graphically in Figs. 15-18 which plot pilot chamber pressure (broken lines) and nozzle throat pressure (solid lines) against time, starting at the beginning of venting of the pilot chamber and thus actuation of the nozzle (P_o), for a nozzle containing an air supply at 69,1 bar (70 psig) and an effective pilot chamber actuation pressure, i.e. at which the diaphragm valve opens and closes, of 44,4 bar ((45 psig) at two levels of pilot chamber supply pressure (i.e. 49,3 bar (50 psig) and 64,1 bar (65 psig) and for the two possible endwise positions of the spool valve, i.e. with the short segment land 91a, 91 b, leading in Figs. 15 and 16 and with the long land 91 b, 93b, leading in Figs. 17 and 18. In the region of each of these curves between A-B, the diaphragm valve is opening due to venting of the pilot chamber to the atmosphere and nozzle throat pressure is rising, which begins slowly and then because of the avalanching diaphragm behavior described in the above identified application Serial No. 64,395, rapidly accelerates to reach peak throat pressure at time B. As Figs. 15-18 show, the response of the diaphragm valve and nozzle during time A-B is substantially, if not exactly, constant in all four cases since the pressure vents rapidly from the pilot chamber via venting slot 95 notwithstanding the presence of resilient plug 79 blocking a part of the interior opening of slot 95 and variations in pilot chamber pressure have only slight effect. Between B-C, pilot chamber pressure remains at a minimum, being closed off during this interval by the trailing land of the spool valve body, and this minimum is constant in each pair of curves. The nozzle continues to emit pressurized air during this period and thereafter. At time C, a pressurizing channel 89a, 89b, has just moved into coincidence with the housing feed port 105 and repressurization of the pilot chamber now begins and continues until the pressure of the pilot chambersupply has been achieved at time E. The slope of the plot of pilot chamber pressure for the interval C-E will vary as a function of the magnitude of the pilot supply pressure, and while the actuation point D is fixed (in all four cases at 44,4 bar (45 psig) the location timewise of point D along slope C-E will accordingly change with differing pilot supply pressure. For example, in Figs. 15 and 16 repressurization begins in both cases at about 37 ms after venting but re- pressurization takes about 23 ms at 49,3 bar (50 psig) pilot supply pressure and about 11 ms for 64,1 bar (65 psig) pilot supply pressure.
Further insight as to the execution in practice of the concept of regulating pilot chamber re- pressurization time (and nozzle pulse duration) by pilot supply pressure variation will be obtained from the following tabulation showing the pulse widths or duration that have been obtained in tests carried out on 127 cm (50 inch) width loom operating at 320 cycles per minute using a spool valve constructed according to the drawings in this application in both possible endwise positions over a pilot supply pressure range 44,4-74,0 bar (45-75 psig).
Obviously, the results of any such tests are specific to a given test configuration and cannot be precisely extrapolated to other configurations; they do, however, illustrate clearly the effect on pulse duration of pilot supply pressure variation and are indicative of the degree of that effect under different combinations of significant conditions.
The second major improvement of the present invention concerns the configuration of the dual diaphragm sub-assembly, as preferred, and the details of this aspect, reference is now made to Figs. 19 and 20. Apart from the diaphragm configuration, the nozzle assembly here is quite similar to that disclosed in above-mentioned US-A-4 466 468 and a fuller understanding of the specifics of the nozzle will be found in the explanation appearing in that application. For present purposes only, the general components of the nozzle apart from the diaphragm will be identified. Thus, the nozzle has an exterior casing 150 to which air under pressure is supplied via an inlet port 152. A two part central core 154a, b, extends through the interior of the nozzle, and the space between the core and casing serves as a supply chamber 156 for pressurized air. The two parts 154a, b, of the core define therebetween a tapering annular throat passageway 158 beginning at an annular rim 160 of the outer core part 154a which rim acts as the valve seat against which the control diaphragm rests in its closed position. When the diaphragm is displaced away from rim 160, throat passageway 158 is placed in communication with supply chamber 156 and the pressurized air accumulated in the chamber is free to pass through throat 158 and out the exit opening 162 of the throat.
Preferably, as is more fully explained in the above mentioned application Serial No. 64,180 now U.S. Patent 43 47 872, throat passageway 158 is contoured, as at 164, with a diverging region to achieve expansion of the air stream passing therethrough with a consequential increase in air stream velocity, preferably up to supersonic speeds. The nozzle body is completed at the end opposite exit opening 162 by a head or cover 166 threaded or otherwise engaged upon the upper end of casing 150, and head 166 is penetrated along its axis by means of a hollow thread insertion tube 168 by means of which the leading end of the weft yarn to be projected by the nozzle is inserted into the nozzle throat. Preferably, insertion tube 168 projects beyond the point of minimum convergance of the throat passage into the divergent region 164 and, more preferably, at least to the exit opening of the nozzle (the yarn itself being omitted from the drawings), The interior face of head 166 is cut away as an annular recess 170 which defines a pilot chamber 171 for the nozzle to which pressurized air is applied and released via the port 172.
Turning now to the details of the diaphragm sub-assembly itself, exterior and interior spacer rings 174, 176 of annular shape are interposed between outer and inner margins of head 166 and the ends of casing 160 and inner core part 154b and clamped between the opposed surfaces thereof on both sides of the rings are the exterior and interior margins of two axially separated diaphragms 180, 210. The inner and outer edges of each such diaphragm are thickened to form beads at 178a, 178b, which are adapted to fit within corresponding annular grooves 179a, 179b, machined for that purpose in the faces of spacer rings 174, 176 so as to positively grip the opposite margin of each of the two diaphragms when the nozzle head 166 is secured on casing 150.
The diaphragm adjacent the supply chamber 156 and closing the end opening thereof is designated 180; it is deformed in its intermediate region into two radially spaced apart annular convolutions 182, 184, each generally U-shaped in cross-section and opening towards supply chamber 156.
In its region between the spaced pair of convolutions 182, 184, the outer face of diaphragm 180 is clamped between the inner face of a "floating" pressure transmitting ring 190, which has differential end face areas in order to achieve the mechanical operating advantage referred to above in connection with the working differential between the nozzle supply pressure and the diaphragm actuation pressure and an annular retaining ring 192, which is anchored in place on floating ring 190 for movemement therewith by a peripherally spaced series of pins 194 brazed or welded at one of their ends to the ring and penetrating through openings provided for that purpose in the diaphragm. Pins 194 extend through ring 190 and are encircled at each of their outer ends by a Truarc split washer 196 seated in peripheral grooves formed on the pin ends, a resilient Belleville spring washer 198 being interposed therebetween to bias the retaining ring and floating ring together. Retaining ring 192 has an unbalanced or lopsided "flying U" cross-sectional contour, the outermost leg 200 of which projects partially into the interior of convolution 182 with a re-entrantly curved termination, while it innermost leg 202 extends along the adjacent wall of convolution 182, both legs, however, ending short of the bottom of the respective convolutions to permit some freedom for relative axial telescoping movement of the convolution walls.
The outer face of floating ring 190, through which the ends of anchoring pins 194 project is covered by an annular hub 204, recessed on its inner face to accommodate those pin ends, and hub 204 defines the actual outer end face area of ring 190 which effectively receives the pilot chamber pressure. Thus, in effect, the floating differential area ring is constituted in two parts, the main part 190 and hub 204, for two reasons, first to facilitate assembly and second to allowthe ratio between the end face areas of the ring to be easily altered by interchanging hubs of different annular radius.
Hub 204 is associated with the outer flexible diaphragm 210 closing pilot chamber 170 and similarly to nozzle supply chamber diaphragm 180 diaphragm 210 is deformed into two radially spaced U-shaped convolutions 212 and 214 opening toward the pilot chamber. The region of pilot chamber diaphragm 210 between the convolutions 212 and 214 is in contact with the outer end face of hub 204 and clamped thereagainst by means of an inverted lopsided "flying U" retaining ring 216 similar to ring 192 and having its legs 218, 220 contoured roughly the same as legs 200, 202 of ring 192 to project into the convolutions to maintain their contour while still affording some freedom of axial displacement thereto. Inverted retaining ring 216 is affixed in place to hub 204 by peripherally spaced bolts 222 in threadwise engagement at their inner ends with the floating ring body 190.
Although the two diaphragms are made of tough, strong, durable, flexible weaving material, such as a rubberized fabric or a polymer film and the lips of the respective retaining rings 192, 216 function in projecting into the interior of the web convolutions to maintain to some degree the shape of those convolutions, it is nonetheless advisable to furnish backing support to the side walls of the several convolutions and thereby substantially eliminate any possibility for any of these convolutions to spread out or balloon laterally which would tend to reduce their effectiveness during operation and significantly decrease their working life. To this end, the opposed inner and outer sides of the floating ring 190 and the respective spacer rings 174,196 have their surfaces adjacent the walls of legs of the respective diaphragms shaped to provide shoulders contoured to follow the shape of the diaphragm walls and tightly juxtaposed thereagainst. In this manner, the respective U-shaped diaphragm convolutions, in effect, lie within open ended annular channels and are positively prevented thereby from significant distortion of their U-shaped configuration. In this same connection, it is preferred that the interior wall of each interior convolution 184, 214 each be engaged by a circular tongue 186, 221 projecting axially from the inner core part 154 and the nozzle head 166, respectively. Similar circular tongues could be provided on the outer edges of nozzle casing 150 and head 164 to project into the interior of the adjacent convolutions 182, 212 if desired, but it has been found that approximately the same function can be performed by the re-entrantly curved termination of the outer retaining lips 200, 218 without the necessity for providing an additional set of circular tongues.
Preferably, a separate valve seat plate formed of wear resistant resilient material such as high density polyurethane or the like is adhered to the exposed surface of retaining ring 192 to seat directly upon the nozzle rim 160 and receive the wear imparted by such rim during operation rather than the diaphragm fabric itself.
It will be appreciated that when the pilot chamber 170 is vented to the atmosphere through port 172, the nozzle supply pressure in supply chamber 156 which bears against the nozzle diaphragm 180 will at some point exceed the falling pilot chamber pressure and force the exposed region of diaphragm 180 to move axially away from the nozzle rim 160 and consequently open nozzle passageway 138 to the flow of air from the supply chamber 156 and out through its exit opening 162. As diaphragm 180 undergoes such displacement, convolutions 182, 184 each flex with a rolling or progressively advancing action as the individual convolution walls telescope with respect to one another, to shorten the innermost wall while lengthening the outermost wall in contrast to the simple vibratory behavior of an ordinary diaphragm. Pilot chamber diaphragm 210 behaves in a similar but inverted fashion, the innermost walls of its two convolutions 212, 214 becoming shorter and the outermost walls extended as they telescope relative to one another following the same rolling or progressively advancing action. When the pilot chamber is re-pressurized to restore the diaphragms to starting position to close the nozzle, the two diaphragms behave in precisely the opposite manner to that just described.
Naturally, the diaphragm convolutions should open in the direction of the higher pressure to which they are exposed since otherwise the applied pressure would tend to force the convolutions in the opposite working direction and greatly increase the severity of wear received by the diaphragms and consequently substantially shorten their life. In operation, the diaphragm valve of the invention, of course, necessarily has the higher effective pressure applied alternately to both of its opposite sides, the problem that would otherwise exist is resolved in accordnce with the invention by the provision of dual diaphragms, each isolated to receive the higher pressure on only one of its faces and oriented as best suited to bear that pressure. For the same reason, the pressure acting on the sides of each of the diaphragms opposite the high pressure side should be minimized and for this purpose the interior space between the two diaphragms 180, 210 not occupied by floating ring 190 preferably vented to the atmosphere by means of one or more vents 224 passing through the outer ring 174 and nozzle head 166. In addition, the clearance between the opposite peripheral surfaces of floating ring 190 and the inner and outer spacing rings 174, 176, which are preferably restricted in order to limit bodily lateral movement of ring 190, are prevented from entrapping air and thereby increasing resistance to the free movement of the diaphragms by cutting axial slots as at 226a, b, as needed at peripherally spaced points therearound (see especially Fig. 20).

Claims

1. A control system for an intermittently-operating strand delivery system which includes a nozzle passageway (164) through which the strand is guided, a supply (156) for pressurized strand delivery medium, and conduit means (158) connecting between said nozzle passageway and said supply including a pressure-operated on-off flow control valve (180), which is normally open under the pressure of said medium and is adapted to close upon the application thereto of a generally predetermined pressure, said control system comprising a source of pressurized control medium, means for adjusting the magnitude of the pressure of said control medium, and servo valve means (31) for alternately applying and releasing said pressurized control medium at said adjusted pressure to and from said pressure-operated flow control valve to operate the latter, characterized in that said servo valve means (31) comprises a rotary spool (75) and a housing (83) in which said spool is rotatably disposed in generally pressure-tight relation, said housing (83) having at a given point in the periphery thereof a delivery port (105) in communication with said pressure-operated flow control valve, and said rotary spool having at points around its periphery separated by a predetermined arc a venting passage (95) adapted to be in communication with the ambient atmosphere and a feed passage (89a, 89b) adapted to be in communication with said source of pressurized control medium at said adjusted pressure, said venting and feed passages being upon rotation of said spool brought successively into registry with said housing delivery port to successively release said pressurized control medium from said pressure-operated flow control valve and re-apply the same thereto via said housing port, the period required for said reapplied control medium to achieve at the flow control valve a given level of the adjusted control medium pressure varying with the magnitude of said adjusted control medium pressure, whereby the period during which the flow control valve is open to supply pressurized delivery medium to said nozzle passage-way can be varied by adjusting the magnitude of said control medium pressure.

2. The system of claim 1, characterized in that said spool venting and feed passages are in constant communication respectively with said ambient atmosphere and said control medium source.

3. The system of claim 1, characterized in that said spool includes two separate feed passages (89a, 89b) around its periphery spaced on either side of said venting passage (95) by different predetermined arcs whereby the elapsed time between venting and re-applying control medium pressure during spool rotation at a given rotational speed can be changed by axially inverting the spool within said housing.

4. The system of claim 2, characterized in that said housing comprises a porous sleeve (83) surrounding said spool (75) with said delivery port passage (105) therethrough and means (101a, 101b) for permeating said porous sleeve with said control medium to provide a bearing film of said medium around said spool.

5. The system of claim 1, characterized in that said supply of said pressurized delivery medium comprises a supply chamber (156) in communication with a source (152) of said pressurized delivery medium and having an annular exit opening therefrom and a feed conduit (158) generally coaxial and co-terminus at its inlet end with said annular exit opening; and further characterized in that said pressure-operated flow control valve comprises a flexible diaphragm (180) extending in close axial proximity over said annular exit opening and said feed passage inlet end, said diaphragm being movable from and to a first operative position closing said exit opening and said conduit inlet end with one of its faces to and from a second operative position spaced axially away from said exit opening and conduit inlet end to bring the latter into communication and allow medium to flow from said chamber via the open exit opening thereof through said conduit via its open inlet end into said nozzle passageway; and means (111, 117, 172) connecting said housing delivery port to the opposite side of said flexible diaphragm to thereby apply and release said control medium at said adjusted pressure to and from said diaphragm to control its movement between said two operative positions.

6. The system of claim 5, characterized in that said diaphragm (180) has two coaxial radially separated generally U-shaped annular convolutions (182, 184) therein, said convolutions having their open ends facing toward said supply chamber (156) with one of said open ends (182) generally coinciding radially with said annular supply chamber exit opening and exposed to the pressure of the delivery medium in said supply chamber (156), the region of said diaphragm (180) intermediate said convolutions moving bodily between said two operative diaphragm positions with the convolution walls progressively telescoping to accommodate said movement, whereby the diaphragm flexes with a generally rolling action to increase its operating life.

7. The system of claim 6, characterized in that said flow control valve comprises a pair of axially spaced diaphragms (180, 210) each including a radially separated coaxial pair (182, 184; 212, 214) of said convolutions, the open ends of the convolutions in the diaphragm adjacent said supply chamber facing toward the supply chamber (156) and the open ends of the convolutions in the diaphragm remote from said supply chamber being exposed to said control medium at said adjusted pressure, and a mechanical connection (190, 194, 222) between the respective regions of said diaphragms intermediate the respective pairs of convolutions thereof.

8. The system of claim 7, characterized by rigid retaining means (192, 216) projecting into the interior of each of said diapragm convolutions to maintain its general shape and limit the extent of relative telescoping movement of its walls.

9. The system of claim 8, characterized by means (224) for venting the space axially separating said pair of diaphragms to the atmosphere to maintain resistance to the movement thereof.