IMPROVEMENT FOR CIRCULAR KNITTING MACHINES

Abstract: The invention relates to an improved knitting machine, either with latch or with compound needles, in which for each feeding station a thread guide (16) is provided which is placed at a certain distance above the rising zone of the needles (11) and is fitted with a horizontal supporting cam (23) preventing the thread from fluttering while it is fed, the sinkers (13) of the ma­ chine being fitted with an additional bearing sur­ face (35) designed to support the thread as it is fed by the thread guide (16) till it is picked up by the needles (11) on their down path immediately after their upward motion.

Description: The present invention relates to some improvements on knitting machines using compound needles or latch needles and in particular to some improvements on the means used to feed the yarn to be knitted on said machines. On circular knitting machines the yarn to be knitted is fed by means of thread guides normally positioned within the zones where the needles are first lifted and then lowered to catch the yarn and at any rate at the highest level reached by the needles during their upward motion. In US-A-2 263 530 a yearn feeding means for a knitting machine is disclosed as including a vertically operable finger of rectangular cross-section having a flat surface from which projects a boss, an opening through which a yarn is to be threaded adjacent the boss and at substantially the same height as the center of the boss and from which it would emerge to be taken by knitting machine needles said boss has an outermost, flat surface parallel to the surface of the finger and bevelled sides leading back from said outer flat surface to the surface of the finger from which a feeding yarn would emerge. In GB-A-2 096 181 a yearn carrier for a circular knitting machine is disclosed and shown (Figs.1 and 3) as arranged where the needles reach the highest level during their rising motion. It is however known that this position of the thread guides in respect to the needles may prevent a correct positioning of the yarn to be picked up by the needle hooks and also create some problems of interference and wear of the needles themselves. These problems and inconveniences already arise when using latch needles where the moving latch is usually able to recover the yarn even if it is misplaced and put it into the hook of the relevant needle while it is moving downward to cast off the previous loop, but they are much worse when using compound needles without a latch to recover that position of an incoming yarn. It is instead the object of the present invention to solve said problems and to improve the feeding conditions of the yarn on circular knitting machines and in particular to eliminate the inconveniences due to interference and wear of the needles caused by the thread guides on conventional machines. The presente invention therefore relates to a circular knitting machine comprising a needle cylinder with at least one plurality of needles cooperating with an equal number of sinker means or any other kind of intercalated elements designed to knit threads fed in a plurality of feeding stations, said needles being operativaly displaceable on the needle cylinder by means of lifting and lowering cams, while said sinkers or the like are displaceable by egress and ingress cams, characterized in that: for each feeding station a thread guide is placed at some distance above the rising zone of the needles; each thread guide is fitted outside the circumference of the needle cylinder with at least one guide bush orientated substantially radially to the central axis of the cylinder and with one inner supporting cam flush with said bush, said supporting cam comprising a front bearing surface to hold the yarn as it is fed to and extending towards the rising zone of the needles substantially in a vertical plane in a direction which is parallel to a tangential plane on the needle cylinder. Advantageously, each thread guide is placed in an intermediate position between two needle rising zone, and where the front bearing surface of cam (23) has an initial bevel (24′) on its side directed to the guiding bush. As in the circular knitting machine sinker means are used each having a normal working face and a beak portion extending above said working face and having a length shorter than said working face, said working face and said beak portion defining an interweaving gap, each sinker means has an additional supporting aurface designed to support the thread coming from thread guide even beyond said supporting cam and till the thread is caught by the needles during their path following their rising zone and immediately after the thread guide. Said additional supporting surface of each sinker means is composed of a top section of the beak placed above the normal working face and a bevelled portion at the and of the sinker beak. The invention may be applied to circular knitting machines both with compound and with latch needles, as well as to machines with a single or double knitting head and needles or other knitting elements. By placing the thread guides outside the operative zone of the needles the above mentioned problems due to interference and wear are eliminated. The presence of a supporting cam flush with the guiding bush and extending towards the rising zone of the needles has the advantage of eliminating any kind of fluttering, vibration or oscillation of the yarn and to keep it in such a position that the rising needle will not touch it, while it will take the yarn to the correct position to be caught by the hook of the needles while they are moving downward. The purpose of the additional bearing surface of each sinker is to support the function of the cam provided on the thread guide in order to prevent the yarn from oscillating and in particular to keep the incoming yarn at the correct level to be surely picked up by the hook of the needles during their downward motion to form the loops. After that the sinker goes back to allow the yarn to go down on the usual looping plane and to form loops according to the standard sequence.All these measures have the additional advantage of allowing the feeding of the yarn at a much lower tension than that usually required, thus reducing the risk of thread breakages. The present invention will be more apparent from the following description of a machine with radially moving horizontal sinkers, without however excluding the possibility to apply the invention to machines fitted with vertical sinkers moving in a different way. The enclosed drawing shows an embodiment of the invention and in particular: Fig. 1 is a partial vertical section of a schematically represented knitting machine fitted with thread guides; Fig. 2 is a top view of the detail shown in Fig. 3, with three consecutive thread guides; Fig. 3 is a partial vertical section with the thread guides inside the machine; Fig. 4 is the side view of a sinker with additional supporting surface; Fig. 5 is the corresponding cams controlling the up and down movements of the needles and the egress and ingress of the sinkers; Figures 6 to 11 are some positions of a sinker with reference to the operating motions of a needle and corresponding to positions a,b,c, d,e,f in Fig. 5. The represented circular knitting machine comprises, like any other machine of the kind, at least a plurality of needles (11) mounted and vertically guided in slots on the periphery of a rotating cylinder (12) and cooperating with an equal number of intercalated down sinkers (13) assembled on a sinker ring (14) fitted on cylinder (12) and turning with same. Needles (11) and sinkers (13) are interacting to knit threads (15) which are fed in a number of feeding stations distributed around cylinder (12), each of them including a thread guide (16), the different thread guides being mounted on a stationary ring (16′). The needles may be of the type featuring a hook (11′) and a piston (11″) to open and close said hook at shown in the drawing or of the latch type. In any case the needles (11) are operatively displaced by stationary rising and lowering cams (17) assigned to each feeding station, while sinkers (13) are displaced by stationary egress and ingress sinkers cams (18). Both said cams are partially represented in Fig. 5 of the enclosed drawing, while the rising and lowering paths (19, 20) respectively of the needles (11) are also schematically shown in Fig. 3, where arrow (F) indicates the sense of rotation of the cylinder. Now, according to the present invention, the thread guide (16) for each feeding station is placed at some distance above - see Fig. 3 - the rising zone (19) of needles (11) in the corresponding feeding station. In other words, each thread guide (16) is placed above the needles in an intermediate position between two consecutive needle rising zones (19) and in any case outside the operative zone of the needles. Each thread guide comprises a substantially vertical supporting stem (21) with at least one guiding bush (22) fitted to its bottom end at a given level A above the sinkers (13) and radially directed towards the cylinder. At the bottom end of stem (21) a supporting cam (23) is fixed, which is substantially at the same level as bush (22) and has a front bearing surface (24) against which the thread (15) fed through said bush (22) is obliged to rest. The front bearing surface (24) of supporting cam (23) is vertically directed and parallel to the outer circumference of cylinder (12), from which it is displaced to some extent as shown in Fig. 2. In addition, said front surface (24) of supporting cam (23) approximately extends from guiding bush (22) towards the upward path (19) of needles (11), nearly to the top of said upward path. Surface (24) may also present an initial bevel (24′) on its end facing guiding bush (22), while stem (21) may have a bevel (21′) at its bottom end directed to the upward path (19) of needles (11), as shown in Fig. 3, in order to prevent eventually broken needles from interfering with the thread guide. As mentioned above, the supporting cam (23) prevents the thread (15) coming from bush (22) and travelling towards the needles in their upward path (19) from fluttering and also keeps threads outside the needles to allow the latter to surely pass behind the thread and thus catch it by their hook (11′) when coming down, exactly as requested. Sinkers (13) are in turn supporting the operation of thread guide cams (23) in correctly guiding the thread (15) towards the needles (11). To this purpose each sinker (13) is fitted, above its normal upper working face (33), with at least one beak (34) which is shorter than said working face and includes a bivelled portion (34′) and an additional top supporting surface (35) which is designed to support the thread (15) coming from thread guide (16) and moving toward the rising needles - see Figures 6 and 7 - which will move downward immediately after said thread guide. Said sinkers are controlled by sinker cams (18) - see Fig. 5 - in such a way that their beak (34) is placed below the thread coming from the thread guide and will go back only when the thread is going to be caught by the needle hook. Now the additional top face supporting surface (35) of each sinker (13) is supporting the thread (15) to prevent it from unduly fluttering along the whole path from thread guide (16) to the down path (20) of the needles, where it will be picked up as shown in Figures 6 to 11 representing some positions of sinker and needle corresponding to positions a,b,c,d,e,f in Fig. 5 along the path of the two elements as it is defined by the relevant cam. Thus the above stated purposes and advantages are achieved owing to an "eccentric" position of the thread guides in respect to the peak of the rising path of the needles in the various feeding stations. As the thread is caught by the needle hook the sinkers move rearwards and progressively release the thread while accompanying it to the needle hook by means of their bevelled portion (34′). The thread, once it is taken in by the needle hook and slipped down from bevel (34′) - see Figures 8 and 9 - may rest on upper working face (33) of the sinkers to be knitted in a conventional manner - see Figures 10 and 11. In addition, the thread guides may be used as parts of an electric circuit to check eventual needle breakages, holes in the knitted fabric or to any other useful purpose and to stop the machine through an additional control circuit as soon as a needle breaks or as a mesh is faulty, any fault being immediately detected in any point of the cylinder circumference.

Claims: A circular knitting machine comprising a needle cylinder (12) with at least one plurality of needles (11) cooperating with an equal number of sinkers means (13) or any other kind intercalated elements designed to knit threads (15) fed in a plurality of feeding stations, said needles being operatively displaceable on the needle cylinder by means of lifting and lowering cams, while said sinkers or the like are displaceable by egress and ingress cams, characterized in that: for each feeding station a thread guide (16) is placed at some distance above the rising zone of the needles; each thread guide (16) is fitted outside the circumference of the needle cylinder with at least one guide bush (22) orientated substantially radially to the central axis of the cylinder and with one inner supporting cam (23) flush with said bush, said supporting cam (23) comprising a front bearing surface (24) to hold the yarn as it is fed to and extending towards the rising zone of the needles substantially in a vertical plane in a direction which is parallel to a tangential plane on the needle cylinder (12). A circular knitting machine as claimed in claim 1, characterized in that each thread guide (16) is placed in an intermediate position between two needle rising zones, and where the front bearing surface (24) of cam (23) has an initial bevel (24′) on its side directed to the guiding bush (22). A circular knitting machine as claimed in claims 1 and 2, and wherein sinker means (13) are used each having a normal working face (33) and a beak portion (34) extending above said working face and having a length shorter than said working face, said working face and said beak portion defining an interweaving gap, further characterized in that each sinker means (13) has an additional supporting surface (35) designed to support the thread coming from thread guide (16) even beyond said supporting cam and till the thread is caught by the needles during their path following their rising zone and immediately after the thread guide. A circular knitting machine as claimed in claim 3, characterized in that said additional supporting surface (35) of each sinker means (13) is composed of a top section of the beak (34) placed above the normal working face (33) and a bevelled portion (34′) at the and of the sinker beak (34). A circular knitting machine as claimed in claims 3 and 4, characterized in that said sinkers are moving rearwards to get out and remove their additional supporting surface (35, 34′) from the thread as soon as the latter is picked up by the hook of the needles while they are moving downward.

Inventors: VIGNONI, CESARE
Applicants: VIGNONI S.R.L.
Application year: 1989
Main classification: D04B15
IPC codes: D04B15, D04B9