GB2070652A - Apparatus for controlling the transverse movement of a fabric supporting carriage in a quilting machine - Google Patents

Abstract

A fabric supporting carriage in a quilting machine is coupled to a d.c. electric motor M for transverse movement of the carriage by a rack and pinion arrangement and the motor is fed by width modulated current pulses having fixed amplitude under control of a programmable microcomputer P, the width of the pulse being established by a comparator CP eg acting through gates A and switches T and R, the polarity of the pulse and hence direction of movement being determined by the microcomputer by means of an inverter A4 whereby the appropriate gate and switches are actuated. <IMAGE>

Description

SPECIFICATION Apparatus for controlling the transverse movement of a fabric supporting carriage in a quilting machine The present invention relates to an apparatus for controlling the intermittent and reciprocating movements of a fabric supporting carriage which are required to carry out stitching lines according to a prefixed patterns or designs in a quilting or embroidering machine. Quilting machines perform the stitching according to a particular pattern or design of two or more superimposed fabrics with insulating material therebetween. The product so obtained has several different applications, e.g. in manufacturing bed covers, sleeping bags, mattresses, etc.Said quilting machines comprise driving rolls for the fabrics and the insulating materials, a fabric-supporting carriage able to move transversally to the advancement direction of said rolls and one or more, vertically movable needle-bearing bars. Stitching is performed during the time intervals when the fabrics are still, whereas when the needle are lifted, the fabrics are longitudinally advanced by means of said driving rolls and transversally shifted by the reciprocating movements of said fabricbearing carriage.

A strong shortcoming of the known camoperated quilting machines is that limited sizes and numbers of the stitched design can be obtained since the non-rectilinear stitching is carried out through the composition of the relative advancing movements of the fabric and the lateral movements of the fabric-bearing carriage. Both said movements are rectilinear and orthogonal to each other and it is therefore obvious that the stitching shape and the distances between stitches can only be varied by changing the relative speed of the two movements (and therefore the entity of the movements).

Whereas there is no particular difficulty in controlling the driving rolls the two-way variable-length jerking movement of the fabricbearing carriage imposes strong limits to the performance of the quilting machine.

There are known apparatuses for controlling the carriage employing step by step electric motors (associated with hydraulic systems to in crease the torque) or variously shaped cams being limited as to the movement amplitude and the contour. These control systems show inconvenients and shortcomings due to the mounting clearance of cams and rolls, machine noise, wear of the components and above all, a complete lackness of flexibility of the stitching patterns. In fact it is a matter of course that a cam, however accurately designed, cannot be used but for a limited number of stitching patterns even if in combination with sophisticated programming systems which in any case do not avoid the change of the cam for each type of pattern.It is moreover impossible a gradual shift from a stitching shape to another, there are upper limits for the maximum length of the run and lower limits for the minimum allowable inversion of movement, and finally it is necessary to stock a number of cams suitable to the production requirements.

These shortcomings are overcome by the control apparatus of the present invention which provides for a rack and pinion coupling for the movements in both ways of the fabric bearing carriage, and a d.c. electric motor to drive the rack and pinion arrangement.

In order to obtain the desired displacements, the d.c. motor is fed with a prefixed amplitude current for adjustable time intervais. The rack and pinion drive allows to standardize all the transverse movements, characterizing them only by their amplitude and their sense on the transverse direction.

Therefore the system allows a complete freedom in chosing the run lengths, the inversions and the stops of the fabric bearing carriage, eliminating all the mechanical engagement and disengagement devices. This makes possible the machine to be controlled by means of a micro-computer which can be programmed in advance or modified when in use whereby in practice all types and shapes of stitch patterns can be obtained by the quilting machine in response to the operator's programmation.

The invention provides an apparatus for controlling the transverse movement of a fabric bearing carriage in a quilting machine comprising a rack fixed to the carriage and engaging with a pinion rotated by a d.c.

motor, said motor being fed by current pulses having constant amplitude, and duration and polarity depending respectively upon the requested displacement and upon its direction, supplied by a pulse width modulation (PWM) actuator controlled by a programmable microcomputer also controlling the rotation of the rolls advancing the fabric in order to obtain stitching of prefixed pattern or design. The invention will now be illustrated in a preferred embodiment with reference to the attached drawings.

Figure 1 is a schematic perspective view of a quilting machine incorporating the control apparatus of the present invention; Figure 2 shows a block diagram illustrating the working of the machine; Figure 3 shows in detail some of the component blocks; and Figure 4 shows a time diagram relating to the working of the invention.

A quilting machine 1, the main components of which are schematically illustrated in Fig.

1, comprises a support table 2 on which a carriage 3 is arranged for the transverse shifting of the fabric fed from one or more rolls 5 and longitudinally advanced by means of driv ing rolls 6. The quilting machine further comprise needle bearing bars 7 (one of which shown in Figure) suitably connected to an impending frame (comprising also lifting and lowering devices for the needles and not shown) and a d.c. electric motor 10 for transverse movements, as well as management and programming circuits housed in cabinet 12'. For sake of simplicity the drawing does not show the control and driving elements for the rolls as well as the several rolls over which the material to be stitched is wound and also the protecting covering of the members generating the transverse movements has been removed.In working stitching according to predetermined patterns and designs are accomplished by suitably lowering the needle bearing bar in the time intervals when the fabric is still, said fabric actually comprising at least two distinct sheets enclosing the padding material, each of said sheets being fed from a roll such as the one shown with reference 5.

The transverse movement of carriage 3 is accomplished by means of d.c. motor 10 through pinion 14, rack 1 6, plate 1 8 and bars 20 along horizontal guides 1 2.

The movements to be accomplished by the carriage are both ways displacements ranging from about 1 mm to several centimeters.

To these displacements there correspond different angular rotations in both directions of motor 10 and gears interposed between the motor and the rack. For simplicity in the figure, pinion 1 4 is shown as directly splined to the shaft of motor 10. Angular rotation of motor 10 is obtained by energizing the latter for suitable time intervals upon control of the management and programming circuits in cabinet 12' and through driving means housed in the lower portion 1 3 of supporting table 2. The working of the machine will now be described with reference to Figs. 2 to 4.

The block diagram of Fig. 2 illustrates a motor M driven by an actuator 1 2 of the electronic type, controlled by unit GC which in turn is subordinated to a microcomputer ME programmable for controlling both the fabric bearing carriage and the driving rolls (the latter by means of the rolls control unit CR).

An esemplificatory basic cycle for accomplishing a single stitch (referring to each needle) is shown in Fig. 4. It comprises at least three time intervals, respectively T1, T2 and T3. At the starting time, corresponding to the origin of the t axis, the rolls and the carriage are brought into movement, the needle bearing bars being lifted. After a time T1 the carriage is stopped and after a time T2 the rolls too are stopped. In the remaining part (T3) of the basic interval there occur the lowering and the lifting of the needles together with the further required preparation operations. In the diagram of Fig. 4 on the ordinates axis it is shown the speed of the carriage which must go down to zero within interval T1.

The block diagram of the circuit accomplishing the feeding of the d.c. motor is shown in Fig. 3. The output signal from the microcomputer consists of a synchronizing signal S and of a binary code with sign transmitted through leads P. The binary code on leads P is stored in a register R whereas the synchronizing signal is applied to a flip-flop or bistable circuit F. When the synronizing signal becomes active, e.g. by passing from a logic 0 to a logic 1, AND gate A3 is enabled and clock pulses from a unit CK, also comprising suitable frequency dividers, are fed to counter CC changing its configuration accordingly. At the same time the output of flip-flop F is applied to gates Al and A2, each having three inputs.Register R and counter CC are connected to the inputs of a comparator CP having the output connected to Al and A2, said gates also receiving in input the sign bit from R. More particularly the sign bit is fed through inverter A4 to an input of gate A2.

Comparator CP compares the code stored in register R with the binary configurations successively present in counter CC, generating a logic 0 upon detecting identity. The outputs of gates Al and A2 are connected respectively to two electronic switches Ii and 12 supplying a current from a current generator G, respectively to one or the other of the control terminal of switches R1 and R2, for example two dry-reed relays. The closing of switch R1 or R2 causes a reference voltage VR1 or VR2 respectively to be applied to the power supply AL of the electronic actuator AZ for the motor. Said feeding of the motor furthermore depends upon safety and check signals, schematically represented by unit CT, to ensure proper operation of the motor.

The working of the circuit shown in Fig. 3 is the following. Supposing that the displacement required is in a direction characterized by a sign bit equal to 1 and of a length proportional to the bit configuration present on P, when synchronizing signal turns from level 0 to level 1 gate Al is enabled causing switch Ii to close and a drive current is applied to the winding of relay R1. Reference voltage VR1 being applied to AL, a constant value current having a certain plarity is supplied by power supply AL to the motor in order to get a movement in the wished direction. Said current supply from AL continues until the opening of switch R1, i.e. until the binary configuration of counter CC is equal to the one stored in register R.

At this point the output of comparator CP becomes low blocking also gate Al and causing therefore the opening of switch 11. Of course the time during which the switches were closed is proportional to the value of the binary configuration of program signal on leads P. If a displacement in the opposite direction is required the sign bit will be 0 and thanks to inverter A4 switches 12 and R2 will be closed causing a drive current for the movement in the opposite direction.

Actuator AZ is a conventional one and will not be described in detail as well as motor M which is a series excitated d.c. motor fed by a pulse width modulated current.

From the above it is clear that the running of the motor occurs in jerks, i.e. by swift and exact short rotations in one direction or the other.

Even the stitch length can be controlled by motor 10 and moreover it is possible to check the real displacement of the carriage by means of a feedback loop. In fact, through a unit EL comprising a linear encoder shown in Fig. 2, the real displacement of the carriage can be measured and this information, forwarded to the management control or directly to the microcomputer, is used to correct possible errors with respect to the wished values.

Let us suppose for example that a string of stitches each being spaced apart by 2 mm it to be applied and for any reason one of the stitches takes place at 1, 5 mm only, then the information of such error in defect from EL will produce a signal to cause the following stitch to be spaced by 2,5 mm, thereby correcting the error of the previous stitch and keeping unchanged the overall lengths of the design which must be kept constant all over the width of the fabric, so that each locally effected stitches in a same design coincides with the ones effected by different needles.

As for the running times of the motor, they depend upon the working speed of the machine and upon the length of the stitches and the design to reproduce. Tipically the base interval made up by T1, T2 and T3 is in the order of about 80 millisec, corresponding to 7,000 jerks/minute for the motor. It is possible to increase the speed up to about 1,000 jerks/minute and to obtain length changes in the order of a few hundredths of millimeter.

Further advantages of the control devices will be illustrated more particularly in the following.

Practically there are no limits for the carriage run but the ones imposed by the machine size; there is no limitation for the reverse run of the carriage however short, such as it happens in the known machines using a suitably shaped cam. The complete correspondence between mechanical movements and electric signals allows to employ a rea electronic processor to control the quilting machine, programmed and run directly by the operator who can moreover modify the same through the input/output devices in form of a keyboard and visually check over suitable displays in order to obtain particularly complicated stitching patterns, hardly obtainable through conventional controls.The linear relation between the carriage run and the pulse length allows to realize in a simple way the programs for different stitching patterns even in case they provide for quite variable lengths and directions of the displacements.

The control apparatus according to the invention, completely eliminating the'change-speed to change the stitch length, tipically allows to change the length of the stitch from a minimum of 0.2 mm to a maximum of 17 mm with increments in the order of the hundredths of millimeter. Furthermore the number of movements can increase up to about 1000 per minute, well above the number of a conventional quilting machine. Finally another possible use of the control apparatus according to the invention may be for the longitudinal movement of the fabric, i.e. replacing at least partially the driving rolls with a sub-unit of the carriage longitudinally driven by a rack apparatus according to the invention. This would allow for longitudinal backrunning of the carriage in order to obtain complicated design of the embroidery type.

Claims (7)

1. An apparatus for controlling the transverse movement of a fabric supporting carriage in a quilting machine, including driving rolls for longitudinally advancing the fabric characterized by that it comprises a rack fixed to the carriage, engaging with a pinion rotated by a d.c. electric motor and by that said motor is fed by means of current pulses having fixed amplitude but duration and polarity depending respectively upon the length and the direction of the desired displacement of the carriage, supplied by a pulse width modulation actuator under control of a programmable microcomputer also controlling the advance of the driving rolls for the fabric to obtain stitches according to predetermined designs of patterns.

2. An apparatus according to claim 1, characterized by that it comprises, in order to generate the current pulses having fixed amplitude and variable duration and polarity, an electronic actuator to which either one or the other of two reference voltages is applied for predetermined time intervals.

3. An apparatus according to claim 2 characterized by that the sources supplying the reference voltages are connected to the inputs of the actuator power supply through two electronic switches (R1, R2) under control of one or the other of two control signals for a duration proportional to the length of the carriage displacement.

4. An apparatus according to claim 3 characterized by that each of said two electronic switches (R1, R2) comprises a dry-reed relay connected to a current generator through a corresponding electronic switch (11, 12) controlled by a decoding and comparison circuit.

5. An apparatus according to claim 4 characterized by that the decoding and comparison circuit includes a register for storing a binary configuration containing the information about the displacement, a counter enabled to count clock pulses by a synchronizing signal and a comparator that, upon detecting identity of the binary configurations stored in the register and in the counter, opens the one of the two electronic switches (11, 12) previously closed by said synchronizing signal.

6. An apparatus for controlling a fabric supporting carriage according to claim 5 characterized by that it comprises a unit having a linear encoder measuring the real displacement of the carriage, said unit emitting a binary code with sign when detecting an error with respect to the desired displacement which is added to or subtracted from the binary code of the subsequent displacement in order to correct an error in excess or in defect of the carriage displacement.

7. An apparatus for controlling the transverse movement of the fabric to be stitched in a quilting machine substantially as described and illustrated.