Jacquard pattern control mechanism for a circular knitting machine

Abstract: A jacquard pattern control mechanism for a circular knitting machine (20) comprising a plurality of rocker bar supporting members (40) slidable in grooves (26) along which move knitting elements (27), a plurality of elongate rocker bars (44) pivotally mounted on the rocker bar supporting members (40) for movement about medial pivots, the opposite end portions of the rocker bars (44b,44c) being selectively movable between operative and inoperative positions and having magnetically attractable sections (44f,44g) thereon, and magnet attracting devices (50) operatively associated with the opposite end portions of the elongate rocker bars for selectively attracting one of the magnetically attractable sections at opposite ends of the rocker bars to pivot the rocker bars and selectively move the opposite end portions thereof to the other operative and inoperative positions. The magnetic attracting devices (50) comprise a permanent magnet and a pair of electromagnets (51,52) disposed on opposite sides of the permanent magnet and connected in series, the permanent magnet having an extension extending outwardly towards the rocker bars and having a pair of wing portions extending outwardly from the center portion of the extension, generally parallel to the rocker bar supporting members (40). The wing portions of the permanent magnet cooperate with the core parts of the electromagnets (51,52) in providing stronger magnetic fields for attraction of the magnetically attractable sections (44f,44g) of the rocker bars (44).

Description: The present invention relates to circular knitting machines. Jacquard knitting on a circular knitting machine requires needle selection of specific knitting needles being switched between active and inactive positions. Such needle selection is typically provided by jacquard pattern control mechanisms which include pattern selection devices. Such jacquard control mechanisms, including their pattern selection devices, are disclosed in our EP-A-0 752 490. As discussed in that specification, prior pattern selection devices combining a permanent magnet and an electromagnet required a plurality of control electromagnets in order to function properly. In addition, such devices were required to limit the size of the electromagnets such that the magnetic attraction generated thereby would not be stronger than that of the permanent magnet. Therefore, both the permanent magnet and the electromagnets had to be quire large which caused spatial problems in the knitting machines. Many of these problems and deficiencies have been solved by EP-A-0 752 490 by pattern selection devices embodying both a permanent magnet and an electromagnet working in concert to provide the necessary magnetic attraction while using small magnets. Our EP-A-0 874 077, which is relevant under Art. 54(3) EPC, similarly to EP-A-0 752 490, describes a jacquard pattern control mechanism for a circular knitting machine, which comprises a plurality of rocker bar supporting members slidable in the grooves along which knitting instrumentalities move. Elongate rocker bars are pivotally, mounted on the rocker bar supporting members for movement about medial pivots, the opposite end portions of the rocker bars being selectively movable between operative and inoperative positions and having magnetically attractable sections. Magnet attracting devices are operatively associated with the opposite end portions of the elongate rocker bars for selectively attracting the magnetically attractable sections in order to pivot the rocker bars and selectively move the opposite end portions thereof to the operative and inoperative positions. The magnetic attracting devices each comprises a permanent magnet and a pair of electromagnets disposed on opposite sides of the permanent magnet and connected in series, the permanent magnet having an extension extending outwardly towards the rocker bars. EP-A-0 874 077 differs from EP-A-0 752 490 in that a pair of wing portions extend outwardly from the center portion of the extension, generally parallel to the rocker bar supporting members and have outer sections disposed in attractable relation to the magnetically attractable sections at opposite ends of the rocker bars. These wing portions cooperate with the core parts of the electromagnets in providing stronger magnetic fields for attraction of the magnetically attractable sections of the rocker bars. It is an object of the present invention to provide a jacquard control mechanism for a circular knitting machine that provides an improved electromagnetic pattern selection device producing even stronger magnetic attraction than has been achieved heretofore by comparable sized magnets. The invention resides in a circular knitting machine as set forth in claim 1 hereof. In one embodiment, the electromagnetic selecting device or mechanism of the circular knitting machine includes a rocker bar having first and second attractable portions at its opposite ends and magnetic attracting means comprising a first permanent magnet and first and second electromagnets connected to opposite sides of the permanent magnet in series. The electromagnets include first and second cores and first and second coils, with the cores having tips at one end thereof disposed in attracting relation to a portion of the first and second attractable portions of the rocker bar. The first permanent magnet includes a center tip extending therefrom into juxtaposed relation to the medial-portion of the rocker bar and having a pair of wings extending outwardly therefrom toward the tips of the cores and into juxtaposed relation to portions of the first and second attractable portions of the rocker bar. Second and third permanent magnets are mounted between the outwardly extending wings of the first permanent magnet and the core tips of the electromagnets. In order that the present invention may be more readily understood, reference will now be made to the accompanying drawings, in which:- Figure 1 is a fragmentary schematic view of an electromagnetic selecting mechanism which will be referred to for a better understanding of the present invention; Figure 2 is a side elevation of the mechanism shown in Figure 1 taken substantially along line 2-2 in Figure 1; Figure 3 is a schematic view of the mechanism of Figure 2 and illustrating the lines of magnetic force generated when a positive voltage is applied thereto; Figure 4 is a schematic view similar to Figure 3 illustrating the lines of magnetic force generated when a negative voltage is applied thereto; Figure 5 is a view similar to Figure 1 of another embodiment of the electromagnetic selecting mechanism; Figure 6 is a fragmentary, vertical sectional view taken substantially alone line 6-6 in Figure 5; Figure 7 is a fragmentary, schematic view of cams, needle, sinker and operating elements of a jacquard control mechanism embodying the present invention; Figure 8 is a fragmentary vertical sectional view taken substantially alone line 8-8 in Figure 7; Figure 9 is a fragmentary vertical sectional view taken substantially along line 9-9 in Figure 7; Figure 10A is a fragmentary vertical sectional view taken substantially along line 10-10 in Figure 7 with the sinker in its pile forming operational position; Figure 10B is a view similar to Figure 10A with the sinker in its non-pile forming operational position; Figure 11A is a fragmentary vertical section taken substantially along line 11-11 in Figure 7 with the sinker in its pile forming position; Figure 11B is a view similar to Figure 11A with the sinker in its non-pile forming position; Figure 12A is a fragmentary, vertical sectional view taken substantially along line 12-12 in Figure 7 with the sinker in its pile forming position; Figure 12B is a view similar to Figure 12A with the sinker in its non-pile forming position; Figure 13 ia a fragmentary, vertical sectional view taken substantially along line 13-13 in Figure 7; Figure 14 is an enlarged, fragmentary perspective view of the rocker bar supporting member, rocker bar, rocker bar cam and electromagnetic selection mechanism of Figure 1; Figure 15A is a schematic view of a still further embodiment of the electromagnetic selecting mechanism with wiring for the selection of even numbered knitting elements; and Figure 15B is a view similar to Figure 15A with wiring for the selection of odd numbered knitting elements; Figure 16 is a view similar to Figure 2 with portions removed for clarity of an electromagnetic selecting mechanism according to the present invention; and Figure 17 is an enlarged, fragmentary detail of the upper left-hand portion of Figure 16. Referring now more specifically to the drawings and particularly to Figures 7-14, there is illustrated schematically and sectionally the core part of a circular knitting machine, generally indicated at 20 , which incorporates the jacquard pattern control mechanism. Circular knitting machine 20 includes a rotary cylinder 21 having a multiplicity of grooves (not shown) therein. A knitting needle 22 is mounted for vertical sliding movement in each of the grooves in the needle cylinder 21 . Circular knitting machine 20 further includes a cam block 23 mounted adjacent the periphery of the needle cylinder 21 . Cam block 23 mounts a needle cam (not shown) for raising and lowering the needles 22 between an active (knitting) position and an inactive (welting) position. A rotary sinker cap or dial 25 is mounted on top of the needle cylinder 21 and has a multiplicity of grooves 26 extending radially from the outer periphery to the inner periphery thereof. A sinker 27 is slidably mounted in each of the sinker grooves 26 for movement between an active (extended) position and an inactive (retracted) position. A sinker cam block 30 is mounted above the sinker cap 25 and mounts on its lower surface an inner sinker cam 31 and an outer sinker cam 32 in facing relation to the grooves 26 and sinker cap 25 . Sinker 27 has a main section 27a and an extension section 27b . The outer end of the main section 27a defines a vertical edge 27c . A butt 27d protrudes upwardly from extension section 27b and has vertical edges 27e and 27f . The main section 27a has a nose 27g defining a first top edge 27h for forming pile loops from a pile yarn PY . Main section 27a has a second top edge 27i for forming ground or nonpile stitch loops from a ground yarn GY . Pile yarn PY and ground yarn GY are fed to the needles 22 by a yarn carrier 28 (Figures 7-12). Cam 31 has a side edge 31a that engages the vertical edge 27c of sinker 27 and a side edge 31b which cooperates with a side edge 32a on cam 32 to define a cam track 33 which receives the butt 27d and controls sinker 27 by engagement of side edge 31b with vertical edge 27e and side edge 32a with vertical edge 27f . Cam 32 has another side edge 32b , the function of which will be described presently. An intermediate member 34 is disposed in each sinker groove in sinker cap 25 outwardly of sinker 27 (Figures 8-13). Intermediate member 34 has a butt 34a thereon which has a first vertical edge 34b and a second vertical edge 34c (Figure 7). A first intermediate cam 35 is mounted on cam block 30 adjacent cam 32 and has a first side edge 35a which cooperates with side edge 32b of cam 32 to define a cam track 36 . Cam track 36 receives butt 34a on intermediate member 34 and controls and moves intermediate member 34 by engagement with side edge 32b with vertical edge 34b and side edge 35a with vertical edge 34c (Figure 7). A second intermediate cam 37 is disposed in cam track 36 and has a first side edge 37a and a second side edge 37b . Side edge 37a has a first slope or angled section 37a 1 and a second straight section 37a 2 . Side edge 37b of cam 37 is straight and parallel to side edge 35a of cam 35 . Cam 37 divides cam track 36 into two branches 36a and 36b . If butt 34a on intermediate member 34 is caused to follow branch 36a of cam track 36 , side edge 37a of cam 37 engages vertical edge 34c of butt 34a and moves intermediate member 34 into contact with sinker 27 and moves sinker 27 further toward the needles 22 . Such movement brings the nose 27g of sinker 27 into operative position to form pile loops over top edge 27h . Thereafter, side edge 32b returns intermediate member 34 back to its retracted position which corresponds to branch 36b of cam track 36 . The second intermediate cam 37 is preferably mounted on cam block 30 for movement between an extended, operative position and a retracted, inoperative position (Figures 12A and 12B). Accordingly, cam block 30 is provided with a recess 30a into which an inner end of a threaded operating member 38 extends. Cam 37 is mounted on the inner end of operating member 38 by receiving this inner end in a cavity in cam 37 . This cavity is larger than the inner end of operating member 38 such that cam 37 may move a predetermined amount longitudinally or axially of operating member 38 . A coil spring is positioned around operating member 38 between cam 37 and the bottom of recess to bias cam 37 toward the inner end of operating member 38 and toward its operative position. Thus, cam 37 protects the butt 34a from damage from outside forces which may act thereon. A rocker bar supporting member 40 (Figures 7 14) is slidably mounted in each sinker groove 26 outwardly of intermediate member 34 . Rocker bar supporting member 40 includes an inner end section 41 , the lower portion of which is received in sinker groove 26 and the upper portion of which includes a butt 41a . Butt 41a includes a first vertical edge 41b and a second vertical edge 41c . Rocker bar supporting member 40 includes a medial section 42 having a central portion 42a and opposite end portions 42b and 42c . The lower portion of central portion 42a is received in sinker groove 26 and the upper portion of which has a recess or socket 42d therein. Opposite end portions 42b and 42c of medial section 42 are of less height than central portion 42a such that the top edges thereof are recessed below the top edge of the central portion 42a . Finally, rocker bar supporting member 40 includes an outer end section 43 , the lower portion of which is received in sinker groove 26 . A rocker bar 44 is mounted on the medial section 42 of rocker bar supporting member 40 for pivotal movement by a circular pivot protrusion 44a which is received in socket 42d . Rocker bar 44 has symmetrical opposite end portions 44b and 44c which are beveled, wedge-shaped at their outer extremities at 44d and 44e . The lower portions of opposite end portions 44b and 44c are bulbous-shaped and serve to engage the upper ends of end portions 42b and 42c of medial section 42 of rocker bar supporting member 40 to limit the pivotal movement of rocker bar 44 . The upper sections 44f and 44g of end portions 44b and 44c are magnetically attractable and are raised above the central portion of rocker bar 44 . A rocker bar supporting member cam 46 is carried by cam block 30 adjacent cam 35 . Cam 46 has a side edge 46a which is straight and spaced from a second side edge 35b of cam 35 to define therewith a cam track 47 which receives and controls butt 41a on rocker bar supporting member 40 . Cam 35 has a concave section 35c in its second side edge 35b corresponding to the location of second intermediate cam 37 . Cam 46 has a second side edge 46b which is positioned to engage wedge-shaped end 44d of rocker bar 44 when rocker bar 44 is pivoted to have end portion 44b extended to maintain the rocker bar 44 and rocker bar supporting member 40 in the inactive, retracted position. A rocker bar actuating cam 48 is mounted on cam block 30 and has a side edge 48a spaced from side edge 46b a distance equal to the length of rocker bar 44 . Side edge 48a engages the wedge-shaped end 44e when rocker bar 44 is pivoted to position end portion 44c in extended position. Cam 48 has a protruding portion 48b in side edge 48a in alignment with and of the same shape as the concave section 35c in side edge 35b of cam 35 . The protruding portion 48b preferably has a trapezial-shaped cross section corresponding to the wedge-shaped end 44e of rocker bar 44 . Upstream of protruding portion 48b of cam 48 , a cancelling cam 49 is positioned above the path of travel of rocker bar 44 and includes an upperly and outwardly sloped surface 49a to engage a pivoted or tilted rocker bar 44 and cam rocker bar 44 back to a level or neutral position. Cancelling cam 49 will function irrespective of the direction in which rocker bar 44 is pivoted. Preferably, cancelling cam 49 is constructed of an antimagnetic material so that it effectively weakens leaking magnetic attraction from the permanent magnet. A magnetic attraction selection device, generally indicated at 50 , is positioned immediately downstream of cancelling cam 49 and above the path of travel of rocker bar 44 such that the rocker bar. 44 on the rocker bar supporting member 40 passes closely therebeneath. Selection device 50 is positioned upstream of protruding portion 48b of cam 48 . Selection device 50 includes two magnetic attraction means 51 and 52 (Figures 2, 7 and 14) disposed in position to attract magnetically the magnetic attractable section 44f and 44g , respectively, of rocker bar 44 when rocker bar 44 passes therebeneath (Figures 1, 2, 3 and 4 are shown with the elements upside down). Preferably, magnetic attraction selection device 50 comprises a permanent magnet 53 in the center and first and second electromagnets 54 and 55 on opposite sides thereof, which define the magnetic attraction means 51 and 52 . Permanent magnet 53 and electromagnets 54 and 55 are all supported by a support member 56 (Figure 2). Preferably, the permanent magnet 53 has an extension 53a which extends toward rocker bar 44 and has a central section 53b which engages the medial portion of rocker bar 44 to stabilize the same. Extension 53a also has two wing portions 53c and 53d extending generally parallel to rocker bar support member 40 and into overlying relation to portions of the magnetically at tractable sections 44f and 44g , respectively, of rocker bar 44 when rocker bar 44 is passing therebeneath. The extension 53a must be of a magnetic material and may be part of the permanent magnet 53 and, therefore, will be of permanent magnetic material. The wings 53c and 53d are tapered or beveled outwardly and upwardly from the center section 53b to the outer ends such that, when rocker bar 44 is pivoted, the lower surfaces of the wings 53c and 53d will be parallel to the magnetic attractable sections 44f and 44g and spaced therefrom a gap distance of between about 0.5 mm and about 2.0 mm. Electromagnets 54 and 55 include first and second exciting coils 54a , 55a on opposite sides of permanent magnet 53 and first and second cores 54b , 55b inside and extending to the left and right, respectively, of the coils 54a, 55a . The outer tips 54c , 55c of the cores 54b , 55b are slanted upwardly and outwardly from the inside to the outside to accommodate sufficient pivotal movement of rocker bar 44 without contact with these tips 54c, 55c . Also preferably, the magnetically attractable sections 44f and 44g of rocker bar 44 slant downwardly and outwardly for this same reason, with the same gap distance as stated above. The coils 54a , 55a are connected in series (Figures 3 and 4). By applying positive or negative voltage to the electromagnets 54, 55 , the tips 54c, 55c selectively attract magnetically attractable sections 44f , 44g of rocker bar 44 . For example, when positive voltage is applied from A to B (Figure 3), the magnetic field of the permanent magnet 53 is shut off by a flux generated by the first electromagnet 54 and this shut off first magnetic field and a flux generated by the second electromagnet 55 are added to the magnetic flux of the first electromagnet 54 creating a stronger magnetic field. At this time, the core 54b of the first electromagnet 54 selectively attracts the attractable section 44f of the rocker bar 44 . As shown in Figure 4, when a negative voltage is applied from B to A , the magnetic field of the permanent magnet 53 is shut-off by the flux generated by the second electromagnet 55 and the shut-off magnetic field from the permanent magnet 53 and the flux generated by the first electromagnet 54 are added to the first magnetic flux of the second electromagnet 55 , creating a stronger magnetic field. At this time, the core 55b of the second electromagnet 55 selectively attracts the attractable section 44g of the rocker bar 44 . Referring now to Figures 5 and 6 , another embodiment of the electromagnetic selection device 50' is illustrated in which like parts are referred to by like reference characters with the prime notation added. The electromagnetic selection device 50' includes two magnetic attraction means 51' and 52' disposed in position to attract magnetically the magnetic attractable sections 44f and 44g respectively of rocket bar 44 when rocket bar 44 passes therebeneath. Preferably, magnetic attraction selection device 50' comprises a first permanent magnet 53' in the center and first and second electromagnets 54' and 55' on opposite sides thereof, which define the magnetic attraction means 51' and 52' . Permanent magnet 53' and electromagnets 54' and 55' are identical to the permanent magnet 53 and electromagnets 54 and 55 described above and will, therefore, not be described again. Electromagnets 54' and 55' include first and second cores 54b' and 55b' . Cores 54b' and 55b' include second and third permanent magnets 70, 71 . By providing the second and third permanent magnets 70, 71 underneath the tips 54c' and 55c' , even when the next signal for attraction of the rocker bar 44 is sent to the electromagnets 54', 55' , the second and third permanent magnets 70, 71 continue attracting the attractable sections 44f and 44g of the rocker bar 44 . As a result, when the electromagnetic selection device is used in a circular knitting machine, after a needle selection has been performed, the electromagnetic selection device will receive no influence of the next needle selection signal. Therefore, there will be much less needle selection errors even at high speed operation. Referring now to Figures 16 and 17 , an embodiment of the present invention is illustrated and like reference characters with the double prime notations are used with respect to like elements. An electromagnetic selection device 50" includes two magnetic attraction means 51" and 52" disposed in position to attract magnetically the magnetic attractable sections 44f and 44g , respectively, of rocker bar 44 when rocker bar 44 passes therebeneath. Preferably, magnetic attraction selection device 50" comprises a first permanent magnet 53" in the center and first and second electromagnets 54" and 55" on opposite sides thereof, which define the magnetic attraction means 51" and 52" . Permanent magnet 53" and electromagnets 54" and 55" are identical to permanent magnet 53 and electromagnets 54 and 55 described above and will, therefore, not be described again. Permanent magnet 53" has an extension 53a" with wing portions 53c" and 53d" . Electromagnets 54" and 55" include first and second cores 54b" and 55b" with upper tips 54c" and 55c" . The second and third permanent magnets 70" and 71" are mounted between the outer ends of the wings 53c", 53d" and the upper tips 54c", 55c" . Preferably, the configuration of the extension 53a" of first permanent magnet 53" , second and third permanent magnets 70", 71" and the outer tips 54c", 55c" is such that the upper surfaces thereof are in a straight line. The second and third permanent magnets 70" and 71" are mounted and held in place by any suitable means, such as an adhesive. Also, the poles of the second and third permanent magnets 70" and 71" are symmetrical. With this arrangement, increased magnetic fields are achieved. For example, the magnetic field generated by the selecting mechanism illustrated in Figure 2 has a strength at the needle selection point of 1200 gauss, while the strength of the magnetic field generated by in the embodiment of the invention illustrated in Figures 16 and 17 is 1600 gauss at that point. The operation of the mechanisms discussed above will now be described. When sinker 27 is to be advanced, a signal from a controller (not shown) is sent to the magnetic selection device 50, 50' or 50" to cause electromagnetic electromagnet 55 to attract magnetically attractable section 44g of rocker bar 44 to pivot rocket bar 44 and move wedged-shaped end 44e in extended position (Figure 14). By this time, ground yarn GY is supplied from yarn carrier 28 and crosses over top edge 27i of sinker 27 and is fed to the knitting needle 22 . As rocker bar 44 moves with rotating sinker cap 25, wedge-shaped end 44e engages the protrusion 48b of cam 48 and rocker bar 44 and rocker bar supporting member 40 are pushed inwardly toward the cylinder 21 . Rocker bar supporting member 40 engages and pushes inwardly intermediate member 34 such that butt 34a engages the inwardly slanting section 37a 1 of side edge 37a of second intermediate cam 37 which pushes intermediate member 34 even further inwardly toward cylinder 21 . Intermediate member 34 engages sinker 27 and advances sinker 27 to its most extended inward position in which nose 27g is in position to receive pile yarn PY from yarn carrier 28 across the top edge 27h thereof to form a pile loop in concert with needle 22 . When butt 34a reaches the straight section 37a 2 of side edge 37a of second intermediate cam 37 , the tip of nose 27g of sinker 27 is preferably at least 0.3 mm inward from the circumferential action line L (Figure 7) of the knitting needle 22 . Therefore, formation of a pile loop at least 0.3 mm from the tip of nose 27g is ensured and will prevent such pile loop from prematurely slipping off of top edge 27h of sinker 27 . While intermediate member 34 is being pushed further out by second intermediate cam 37 , butt 41a on rocker bar supporting member 40 engages the outwardly slanting portion of concave section 35c of first intermediate cam 35 which returns rocker bar supporting member 40 and thus rocker bar 44 to their original retracted positions. Of course, it is possible to omit intermediate member 34 and have rocker bar supporting member 40 act directly on sinker 27 . Suitable modification of the cam system would also be required. When sinker 27 is not to be advanced, a signal is sent to electromagnet 54 so as to attract magnetically attractable section 44f of rocker bar 44 to pivot rocker bar 44 to extend wedge-shaped end 44d . Rocker bar 44 does not engage rocker bar actuating cam 48 and, therefore, rocker bar 44 and rocker bar supporting member 40 do not move inwardly in groove 26 of sinker cap 25 . Consequently, intermediate member 34 is not pushed inwardly and butt 34a thereon remains in branch 36b of cam track 36 . Sinker 27 is thus only controlled by cam track 33 and both the pile yarn and ground yarn GY are fed to needle 22 and form ground stitch loops across the second top edge 27i of sinker 27 . The action line L 2 (Figure 7) shows the action of sinker 27 forming pile and nonpile loops in the knitted fabric. As each rocker bar 44 approaches the electronic attracting device 50 , the rocker bar 44 is preferably aligned to be horizontal by the cancelling cam 49 . The rocker bar 44 is thus always in the neutral position when it reaches the magnetic selecting device 50, 50' or 50" . In the electromagnetic selecting device 50 , 50' and 50" , the North pole and the South pole of the permanent magnet 53 are arranged outward and inward respectively. When this electromagnetic selecting device 50 , 50' , or 50" is employed as a sinker control in a circular knitting machine, alternating the poles between mutually adjacent yarn feeders eliminates residual magnetism in the rocker bar 44 . In this manner, if a positive voltage applied to electromagnets 54 and 55 (Figure 15A) at one yarn feeder is alternated with a negative voltage applied to the electromagnets 54, 55 at the next yarn feeder (Figure 15B), control signals for other action or nonaction from the control apparatus can have the same polarity for every yarn feeder. As described above, by using the sinker control mechanism of the present invention, it is possible to select "pile" or "non-pile" in accordance with the pattern signal output from the controller and knit a jacquard pile fabric with a profiled surface. The application of the present invention, however, is not restricted to knitting machines for manufacturing jacquard pile fabrics. The present invention contemplates application of the jacquard selection mechanism to a wide variety of knitting machines in which knitting elements, such as sinkers, cylinder needles, dial needles and jacquards, to name just a few, are selectively controlled in at least two different paths. The electronic magnetic selection devices described above minimize needle selection errors by minimizing the influence from the previous or subsequent signals to the electronic selection device 50 , 50' or 50" . Previously, when a rocker bar 44 and its associated electromagnetic selection means 51 and 52 receive a first signal at a needle selection point, this first rocker bar 44 moves for a certain distance in the rotational direction of the knitting machine before a subsequent signal is sent to the electromagnetic selecting device 50 or 50' for the next rocker bar 44 . When the subsequent signal is sent to the electromagnetic selecting device 50 or 50' is of opposite polarity from the immediately preceding signal, the potential for the second signal being influenced by the first signal was present. In general, the length of the moving distance of the previous rocker bar, i.e. the longer the pitch between the rocker bars, and the lower the needle-selection current to the electromagnetic selection device 50 , the less influence from the previous or subsequent signals occurs and, therefore, a more stable needle selection is achieved. Tests have been conducted which have measured the moving distance required for stable needle selection. The performance test results of the control mechanism of the present invention are shown below in Table 1, whereas the performance test results of the control mechanism of U.S. Patent No. 5,689,977 are shown in Table 2. It is evident from Table 2 that heretofore a minimum pitch between rocker bars was 0.8 mm before stable needle selection was achieved. With the present invention, a pitch of only 0.4 mm is necessary to obtain stable needle selection as is shown in Table 1. Accordingly, fine gauge, high speed operation with a short rocker-bar-to-rocker-bar pitch is possible (e.g., a minimum of 32 needles per inch with a pitch distance of 0.79 mm or less). The chart contained in Table 3 below illustrates test results where the performance of the electromagnetic selecting mechanism 50 are shown. In this chart, the X axis represents current values while the Y axis represents the attraction between the tips 54c , 55c of the cores 54 , 55 and the attractable sections 44f and 44g of the rocker bar 44 . Model 1 represents a gap distance between the tips of 54c and 55c and the attractable sections 44f and 44g to be 1.0 mm with a single permanent magnet 53 associated therewith. Model 2 shows a gap of 1.0 mm with two permanent magnets 70 and 71 associated with the cores 54b' , 55b' of the electromagnets 54' and 55' , while Model 3 employs a gap of 5.0 mm and one permanent magnet 53 . As shown in this chart, Model 3 has the weakest attraction while Model 1 has a stronger attraction than Model 3. However, Model 2 has the strongest attraction of all. The electromagnetic selecting mechanism 50, 50' or 50" , when used in a jacquard circular knitting machine, occupy considerable less space within the knitting machine. Further, because these electromagnetic selecting mechanisms have a strong magnetic field, needle selection errors are minimized. A further advantage is that the rocker bar 44 does not employ a projecting butt, but instead the end portions 44d and 44e of the rocker bar 44 engage directly against the rocker bar raising cam 48 . Therefore, the rocker bar 44 does not slip off of the rocker bar raising cam 48 and this eliminates selection errors. In addition, the danger of butt breakage is minimal or nonexistent. Finally, because the rocker bar 44 is the only item to be controlled, the magnetic attracting means 51 and 52 may also be made compact. The electronic magnetic selecting device 50, 50' or 50" can be computer controlled and, therefore, fabrics of a wide variety of patterns can be produced.

Claims: A circular knitting machine (20) having knitting instrumentalities (22,27,34) for forming knit fabric including a rotating member (21,25) having a plurality of grooves (26) in which said knitting instrumentalities are slidably mounted, comprising control means for controlling said knitting instrumentalities to produce jacquard knit fabric, said control means comprising a plurality of rocker bar supporting members (40) each slidably mounted in one of the grooves (26) along with one of said knitting instrumentalities, each of said plurality of rocker bar supporting members including at least one butt (41a) protruding therefrom, a plurality of elongate rocker bars(44) formed free of butts and having magnetically attractable opposite end portions (44b,44c), each elongate rocker bar being pivotally mounted on one of said plurality of rocker bar supporting members for movement about a medial pivot (44a) and having its opposite end portions (44b,44c) selectively movable between operative and inoperative positions, magnetic attracting means (50") operatively associated with the opposite end portions (44b,44c) of said elongate rocker bars (44) for selectively attracting one of said magnetically attractable opposite end portions to pivot said elongate rocker bars and selectively move one of the opposite end portions to said operative position and the other of the opposite end portions to said inoperative position, said magnetic attracting means (50") comprising a permanent magnet (53") and a pair of electromagnets (54",55") disposed on opposite sides of said permanent magnet and connected in series, said permanent magnet (53") having an extension (53a") extending outwardly toward said rocker bars (44) and having a pair of wing portions (53c",53d") generally parallel to said rocker bar supporting members (40) and having outer sections disposed in attractable relation to said magnetically attractable end portions (44b,44c) of said rocker bars (44), and said electromagnets (54",55") comprising cores (54b",55b") and coils wound about portions of said cores, said cores having core tips (54c",55c") disposed in magnetically attractable relation to said attractable end portions (44b,44c) of said rocker bars, rocker bar operating cam means (46,48) engageable with the end portions (44b,44c) of a rocker bar (44) in said operative position for either moving the rocker bar and the rocker bar supporting member assembly from a retracted position to an extended position for engagement and movement of the associated knitting instrumentality or maintaining the rocker bar and the rocker bar supporting member assembly in said retracted position, and control cam means (31,32,35) engageable with said knitting instrumentalities for controlling said knitting instrumentalities and for moving each instrumentality to at least one knitting position upon movement of the associated rocker bar supporting member (40) to the extended position and for maintaining said knitting instrumentality in a nonknitting position when the rocker bar supporting member is in the retracted position, characterised in that said core tips (54c",55c") of the cores of the electromagnets (54",55") are in spaced relation to and in alignment with said wing portions (53c",53d") of said extension (53a") of said permanent magnet (53") and second and third permanent magnets (70",71") are mounted between said wing portions (53c",53d") of said extension of said permanent magnet and said core tips (54c",55c"). A circular knitting machine according to claim 1 wherein said wing portions (53c",53d") of said extension of said permanent magnet (53") are slanted upwardly and outwardly to accommodate pivotal movement of said rocker bars (44) without being touched thereby. A circular knitting machine according to claim 2 wherein said magnetically attractable end portions (44b,44c) of said rocker bars (44) slant downwardly and outwardly substantially to the same degree as the slant on said wing portions (53c",53d") of said extension of said permanent magnet. A circular knitting machine according to claim 2 or 3 wherein said core tips (54c",55c") of said electromagnets (54",55") are slanted upwardly and outwardly substantially to the same degree as the slant on said wing portions (53c",53d") of said extension of said permanent magnet (53"), whereby upon pivotal movement of said rocker bars (44) a gap is maintained between said magnetically attractable end portions (44b,44c) of said rocker bars and said wing portions and said core tips. A circular knitting machine according to claim 4 wherein said gap has a width of between about 0.5 mm and about 2.0 mm. A circular knitting machine according to any preceding claim wherein said second and third permanent magnets (70",71") bridge the spaces between said wing portions (53c",53d") and said core tips (54c",55c") A circular knitting machine according to any preceding claim wherein upper surfaces of said wing portions (53c",53d"), said second and third permanent magnets (70",71") and said core tips (54c",55c") are in a straight line.

Inventors: SHIBATA TAKAO, SHIBATA, TAKAO
Applicants: PRECISION FUKUHARA WORKS LTD, PRECISION FUKUHARA WORKS, LTD
Application year: 1998
Main classification: D04B15
IPC codes: D04B15