Knitting machine

Abstract

There is provided a warp knitting machine with summing drive for the displacement of a guide bar in which at least one addition member is made operative by an eccentric cam which, with the assistance of a switchable coupling, is rotated 180° by a drive shaft. The mean rate of rotation of the drive shaft depends upon the main drive shaft and which rate, at the switching moment, is substantially reduced to 0. A sensor obtains the rate of rotation and the turning angle position of the main shaft and provides an appropriate sensor signal. A motor control mechanism for an electric motor includes an input port for the sensor signal. In addition to storing at least one movement curve, which is read out dependent upon the angular position of the main shaft for the formation of a control signal, and which has at least one segment of reduced angular rotational speed, the machine is provided with synchronization means for stopping the rotation in timely correspondence with the switching moment

Description

BACKGROUND

[0001] It is known to provide a warp knitting machine with a summing drive for the achievement of guide bar displacement in which at least one addition member is activated by an eccentric cam with the help of a switchable coupling which is rotated 180° by a drive shaft whose mean rate of rotation depends on that of the main shaft and which, at the moment of switching, is reduced, suitably to 0 (see, for instance, German Patent No. 3,117,653). In order that the couplings switch securely and that the parts to be moved out of the at rest position (e.g., eccentric cam, shaft and the like) are not subject to high accelerative forces, the drive shaft is driven by the main shaft of the warp knitting machine via a so called stepping drive, which uses a system of transmissions and gears to reduce the rate of the revolution of the drive shaft until, at the switching moment, it reaches the value of approximately 0 and thereafter, is substantially increased, Such a stepping drive is disclosed in a publication entitled “Warp Knitting Production” by Dr. S. Raz (see FIG. 36 and the accompanying text on page 56).

[0002] The stepping drive described above is disadvantageous because it has a relatively complex mode of construction and requires a very high degree of precision in its production and thus, expensive parts. A further disadvantage resides in that a resetting of the “at rest” time of the stepping drive and the summing aggregate relative to each other, is costly and must take place mechanically.

[0003] German Patent No. 2,741,200 discloses, in one embodiment, how a pair of eccentric cams may be rotated along a predetermined turning angle by a mechanical system which includes a grooved drive shaft.

SUMMARY

[0004] An object of the invention is to produce a warp knitting machine whose construction is simpler that than of the prior art. This object is achieved by the present invention in that a sensor monitors the rate of revolution and angle of rotation of the main shaft and generates a sensor signal, so that the drive activation is achieved by an electric motor, and that a motor control arrangement is provided, which comprises an entry point for the sensor to signal, a storage means for at least one movement curve, which, for the formation of control signal, is read out in dependence of the rotational angle of the main shaft and has a segment of reduced rotational speed, and a synchronizing step which holds the mentioned segment in timely correspondence with the switching moment.

[0005] By utilizing the novel construction described above, the conventional way in which the drive shaft of the summing drive is mechanically permitted to be taken along by the drive shaft is abandoned and in place thereof a servor motor is utilized, which is connected by the main shaft only via a signal path which is utilized to introduce a simple mode of operation for the desired switching This occurs in that the stored movement curve is checked and followed. In this way, the so called “at rest” time can be achieved with very little space consumption and its adjustment is greatly simplified.

[0006] It is advantageous, in accordance with the present invention, that in the motor control arrangement, means are provided for adjusting the movement curve, In this way, different accelerations and decelerations may be taken into account as they occur when the drive shaft of the summing drive is driven at different rates of rotation. It is further advantageous that means on the sensor are provided for adjustment of the segment of reduced rotational speed relative to the switching moment. These means may be utilized to synchronize the resting of the drive shaft for the summing drive with the switching moment, as well as for an exact setting of an optimal arrangement.

[0007] A preferred embodiment provides that the coupling comprises a groove in a transfer shaft driven by an electric motor and, at least at the switching moment, a latch dropping into the groove which is rotatable about a pivot in an eccentric cam and, is removable from the groove after 180°. In the utilization of the latch, it is essential that the groove at the switching moment moves rather slowly past the latch.

[0008] In a very simple embodiment, the summing drive comprises a cam disk and an addition member. The cam disk controls the usual overlaps and underlaps, while the addition member moves this control by a predetermined number of needle spaces. With the utilization of an addition member for one needle space, which is switched at every second main shaft revolution, there is provided, for example, a fabric comprised of pillar stitches, but whose stitches are secure. This also shows that the addition members may be combined, not only with the same, but with other pattern forming elements, such as cam disks.

[0009] The invention may be further explained in the drawings which show the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a switching diagram of the warp knitting machine of the present invention.

[0011] FIG. 2 is a graphical exemplification of the movement curve.

[0012] FIG. 3 is a partial downward perspective view of a summing drive which may be utilized in the present invention.

[0013] FIG. 4 is the adjustment of the eccentric cam with a connecting rod,

DETAILED DESCRIPTION OF THE DRAWING

[0014] FIG. 1 shows a warp knitting machine 1 with a guide bar 2 which by means of summing drive 3 is moved in one direction and by means of spring 4 is returned again, as is indicated by double arrow 5. The warp knitting machine 1 further comprises a main shaft 6 with appropriate sensor 7 which generates signals indicating the rate of rotation and the angular position of the main shaft 6. Such sensors are generally speaking known and operate, for example, by reading bar codes.

[0015] The summing drive 3 comprises a cam disk 8 whose circumference determines the appropriate activation of the guide bar 2 for one or more working cycles. The rate of rotation of the cam disk 8, is thus equivalent to that of main shaft 6, or an integral proportion thereof, and is generated via a conventional coupling arrangement, for example, mechanical combination via a transmission. The summing drive 3 further comprises a schematically indicated addition element 10 which is activated with the help of a switch coupling 11 and can then displace the guide bar 2 over a predetermined number of needle spaces. This occurs by way of an electric motor 12 which drives a drive shaft (not shown) which, in the switching moment, is connected with the eccentric cam and is rotated by 180° and thus, activates a displacement element via a connecting rod.

[0016] It is essential that the rate of rotation of the electric motor 12 is not constant, but at the switching moment can be reduced to substantially 0. Thus, there is provided movement curve 13, rate of rotation n of the electric motor 12 relative to the rotational angle &agr; of the main shaft 6, as is shown in FIG. 2. It has a segment R of reduced turning angle speed. The minimum of the curve 13 should occur at the switching moment S.

[0017] The control arrangement 14 comprises a data storage means 15 for a plurality of such movement curves 13. By means of an input port 16, the desired curve 13 can be chosen or altered. The sensor signal is led over a further port 17 of a synchronizing step 18, which on the one hand, via conduit 19 activates the switch coupling 11 at the moment of switching S and on the other hand reads off the rotational angle &agr; of the main shaft 6 of movement curve 13 by means of computer 20. The thus measured values of the rate of rotation of the electric motor 12 are converted by an output switch means 21 into a control signal for the electric motor 12. The control signals are transferred via conduit 22 to the electric motor 12, whose “Is value” is signaled to the switch means 21 via a further conduit 23 so that the control circuit for the present position of electric motor 12 is closed.

[0018] The lie and form of movement curve 13 are preferably selected dependent upon the mean rate of rotation of the electric motor 12, so that not only is a rate of rotation close to 0 obtained at the switching time S, but also the previous deceleration and subsequent acceleration of the mass and speed of the moving parts is adequately selected. The adjustment of the at rest period is obtained by a simple adjustment of sensor 7.

[0019] In FIG. 3, reference numerals increase by one hundred are utilized for parts corresponding to those of FIG. 1. A guide bar 102 is activated via a angle lever 130 of push rod 131 whose position is determined by the summing of a number of addition members 132. The addition members 132 are activated by the push rods 133, whereby by means of eccentric cams 134 the rods are pushed or removed from the series of addition members 132. Each of the eccentric cams 134 is rotated 180° by means of a catch 138 rotatably attached thereto, which catch falls into a groove in transport shaft 135. The transport shaft 135 is operably connected with a gear wheel which via drive wheel 136 is attached to drive shaft 137 and driven thereby. The drive shaft 137 is driven by an electric motor 112. This electric motor is controlled in a similar manner to the electric motor 12 in FIG. 1.

[0020] In the embodiment of FIG. 1, the cam disk 8 was so provided to build two rows of pillar stitches. Then the guide bar 2, by means of the addition member 10, is displaced over one needle space. There follow two further pillar rows and thereafter, the return of the guide bar 2.

[0021] In this manner there is always obtained pillar stitch goods which are immune to stitch running. In this mode of working only a single addition member 10 is utilized that operates a switching of the switch coupling 11 during every second rotation of the main shaft 6. Accordingly it is only at the second rotation of the main shaft 6 that a reduction of the rate of rotation of electric motor 12 occurs.

Claims

1. A warp knitting machine with summing drive for the displacement of a guide bar in which at least one addition member is made operative by an eccentric cam which, with the assistance of a switchable coupling, is rotated 180° by a drive shaft whose mean rate of rotation depends upon the main drive shaft and which rate, at the switching moment, is substantially reduced to 0, comprising a sensor which obtains the rate of rotation and the turning angle position of the main shaft, said sensor providing an appropriate sensor signal; an electric motor; a motor control mechanism having an input port for the sensor signal; data storage for at least one movement curve which is read out dependent upon the angular position of the main shaft for the formation of a control signal, said curve having at least one segment of reduced angular rotational speed; and synchronization means for stopping the rotation in timely correspondence with the switching moment.

2. A warp knitting machine according to

claim 1, wherein said motor control mechanism includes means for changing said movement curve.

3. A warp knitting machine according to

claim 1, wherein said sensor includes means for adjusting the reduced rotational speed of said at least one segment with respect to the timing of the switching moment.

4. A warp knitting machine according to

claim 1, further comprising a coupling which includes at least one groove in a transmission shaft driven by said electric motor and at at least the switching moment, a knob falls into the groove which is rotatable about the fulcrum of the eccentric cam and after 180° of rotation is removable from the groove.

5. A warp knitting machine according to

claim 1, further comprising a summing drive which includes a mirror cam disc and an addition member.