GB2049824A

GB2049824A - Apparatus for Controlling a Component of a Machine for Making Textile Webs

Info

Publication number: GB2049824A
Application number: GB8015009A
Authority: GB
Original assignee: Sulzer AG; Gebrueder Sulzer AG
Current assignee: Sulzer AG
Priority date: 1979-05-10
Filing date: 1980-05-06
Publication date: 1980-12-31
Also published as: FR2456154A1; DE2919749A1; IT1131443B; IT8021850A0; JPS55152847A; BR8002853A

Abstract

Apparatus for programming a servo-element for controlling a component of a machine for making a textile web, for example for positioning a guide bar of a knitting machine, comprises a hydraulic servomotor (16) comprising a movable wall in the form of a piston (25) which is connected to the guide bar (11) and having at least one input device (18, 19, 20) having a movable wall also in the form of a piston (30, 31, 32). The total content of hydraulic fluid (33) in the two is constant. The input device (18, 19, 20) displaces hydraulic fluid (33) which is received by the servomotor (16) and moves the servomotor piston (25) and guide bar (11). During the return motion, the servomotor piston (25) pushes the hydraulic fluid (33) back into the input device (18, 19, 20) and thus moves the input device back to the starting position. <IMAGE>

Description

SPECIFICATION Apparatus for Controlling a Component of a Machine for Making Textile Webs This invention relates to apparatus for controlling a component of a machine for making textile webs, more particularly for programming the guide bars of textile machines for producing knitted fabrics, the apparatus comprising a hydraulic servomotor having a movable wall such as a piston connected to the component.

In apparatus described in German Offenlegungsschrift 20 1 2 734 the motion of a hydraulic servomotor piston is varied by supplying hydraulic fluid to or removing hydraulic fluid from the servomotor. The flow of fluid is controlled by valves in lines connected to a pressure source of hydraulic fluid and to an outlet. The disadvantage of this patterning device is the expense of the control means.

According to a first aspect of the present invention, apparatus for controlling a component of a machine for making a textile web comprises a hydraulic servo-motor having a movable wall connected to the component, the servomotor being in flow connection with at least one input device, the total content of hydraulic fluid in the servomotor and the input device being constant, and the input device comprising a hydraulic-fluid displacement element, whereby the servomotor receives hydraulic fluid displaced by the control device resulting in motion of the movable wall, whereas the control element moves back when the control device receives hydraulic fluid displaced by the movable wall, resulting in a movement of the displacement element. The invention thus provides control apparatus which can be made relatively cheaply and with great reliability.It can be applied to various components but is particularly applicable to the control of components which adjust the pattern of the web being made, for example guide bars of a knitting machine. Thus, according to a second aspect of the invention, a knitting machine has a control bar and apparatus for controlling the control bar, the apparatus being according to the first aspect of the invention.

The invention may be carried into practice in various ways but a number of forms of control apparatus embodying the invention and applied in each case to the control of a control bar of a knitting machine will now be described by way of example with reference to the accompanying somewhat diagrammatic drawings, in which: Figure 1 shows control apparatus incorporating a cam drive; Figure 2 shows control apparatus with a crank drive; Figure 3 shows apparatus with a return line between the servomotor and input device; Figure 4 shows a servo-piston and a control piston in the form of bellows; Figure 5 shows an electromagnetically actuated input device; Figure 6 shows apparatus with a device disposed axially relative to the servomotor; Figure 7 shows apparatus with an input device driven by rotation; and Figure 8 shows apparatus having an input device comprising a control element made of flexible material.

Figure 1 shows the parts of a warp knitting machine which are relevant to the invention. The position of a guide bar 11 is adjusted by a servodevice 1 5 in dependence on information provided by a data store 10. The date store 10 includes a film strip constituting the information carrier and this contains data for the positions of the controlled member of the servo mechanism, i.e.

the guide bar 11, which is movable longitudinally relative to a needle 12 in order to produce the desired elongated pattern of the knitted article.

The stored data are read from the strip 10 by a reading head 13 and the resulting signals are supplied via an amplifier 14 to the servo-device 1 5. The servo-device comprises a hydraulic servomotor 1 6 having input piston-and-cylinder units 18, 19, 20 actuated by cams 21,22,23 respectively. The motor 1 6 has an output piston 25 connected by a piston-rod 26 to the guide bar 11. The other end of the bar is supported on a machine frame 28 and a compression spring 27 is interposed between the bar and the frame. Each of the units 18, 19, 20 has a displacement element, i.e. a control piston 30, 31 and 32. The servomotor and the input units are filled with the same fluid, e.g. a hydraulic oil 33.The total content of hydraulic oil in the servomotor and input units is therefore constant. The spring 27 maintains the hydraulic oil under a certain pressure. The piston 30 in the input unit 1 8 has a rod 34 with a roller 35 at its free end. The roller 35, acted upon by the pressure of the hydraulic oil 33, follows the periphery 36 of the cam 21. The cam 21 can be connected to or disconnected from a drive shaft 37 by a clutch (not shown).

The cam 21 can be locked in either of two positions A and B separated by 1 800. To this end it has a locking disc 38 formed with two diametrically opposite recesses 40 and 41 for receiving a pawl 42. The pawl is biased towards engagement by a spring 43.

When, as a result of a signal from the store 1 0, the respective clutch couples the cam 21 to the shaft 37, the cam is rotated, e.g. anticlockwise.

The radius of the portion of the cam beneath the roller 35 is increased, thus raising the piston-rod 34 and consequently raising the piston 30 of the input unit 1 8. The volume of oil displaced by the piston 30 is added to the oil behind the piston 25.

If the servo-piston 25 and the piston of the input unit have the same diameter, the resulting change in length of the oil column in the motor 16, i.e. the control motion a, is equal to the change in length of the oil column in the input unit 18. The guide bar 11 is consequently pushed to the left by the same distance, against the pressure of the spring 27. After rotating through 180 , the cam 21 is released from the shaft 37, whereupon the pawl 42 engages in the recess 41 and holds the cam in position.

If the guide bar 11 has to remain in the same position during the next machine cycle, the data store does not generate any signal to couple the shaft 37 to the cam 21, which is thus not rotated.

If, on the other hand, the bar 11 has to return to its starting position, the data store gives a corresponding signal and the cam is again coupled to the shaft 37 and rotated through a further 1800 until the pawl 42 engages in the recess 40. The resulting free space in front of the downward-moving piston 30 is occupied by oil from the motor 16, since the spring 27 simultaneously pushes the bar 11 and consequently the piston 25 by the same distance to the right.

Additional input units 1 9 and 20 are provided for producing a number of different strokes by the guide bars 11. The units 19 and 20 are constructed and operated in the same manner as described in the case of the unit 1 8. Each of the three input units, either alone or in combination with one or both of the others, is coupled with an associated drive shaft 37, 44, 45 in accordance with a program and signals delivered by the data store, as described in the case of the input unit 18.

If the eccentricity of the cams 21, 22 and 23 doubles from one to the next, the guide bar 11 can have one, two, three, four, five, six or seven different strokes (in general 2"--1 strokes where n is the number of cams). The motion a of the servo-piston 25 produced by the cam 21 is here termed the unit stroke and is equal to the needle spacing.

The strokes of bar 11 produced by sucessive input units 1 8, 1 9 and 20 are therefore greater than the unit stroke by the factors 2 and 4, in the sequence towards the right. The factors are place values in the binary system. If two or more slides are actuated, the resulting stroke of the servopiston or guide bar is equal to the sum of the strokes caused by the individual input units.

The cams 21,22 and 23 need not be disposed as in Figure 1 so that the eccentricity increases from left to right, but can be in any order.

In Figure 1 the oil displaced by the input unit pistons acts on the side of the servo-piston 25 remote from the guide bar 11. However, alternatively, it could act on the other side of the servo-piston, in which case the guide bar would be pulled by the servo-motor and the compression spring 27 would be replaced by a tension spring.

Of course, the input units do not need to be integral with the servomotor as shown, but can be connected thereto by ducts. They can then be spatially separate, which may be important if there are many servomotors.

Instead of using cams, the pistons of the input units can be driven by cranks, as shown in Figure 2. A piston 50 of an input unit 51 associated with a servomotor 52 (only partly shown) and servopiston 53 is pivotally connected to one end of a rod 54 the other end of which is pivotally connected to a disc 55 which can be coupled to or uncoupled from a drive shaft 56. The coupling (not shown) between the disc 55 and drive shaft 56 is controlled by a data store 57. The disc 55 has two peripheral recesses 58, 59 co-operating with a spring-loaded pawl 60. The operation of this embodiment is similar to as described in connection with Figure 1.

Figure 3 shows an embodiment which does not require a spring for returning the guide bar.

Figure 3 shows a servomotor 65, a servo-piston 66 and three input units 67, 68 and 69. The piston 66 is connected to a guide bar 70. The cylinder space 71 at the cover end of the servomotor is connected by a line 72 to the cylinder space 73 at the cover end of the input unit 67. The cylinder spaces 74, 75 at the cover ends of units 68, 69 are connected by a line 76 to one another and by a line 77 to the space 73. If, for example, the input unit 69 is actuated and the piston 69' is moved upwards, so that the piston 66 and guide bar 70 move to the left, the oil displaced by the piston 66 flows through the lines 72, 76 and 77 into the expanding space 75.

When the piston 69' moves downwards so as to return the bar 70, the oil flows back into the space 71. The same applies when the other two slides are actuated.

Figure 4 shows an embodiment of a servomotor 79 in which the piston has been replaced by a flexible wall, in this case a bellows 80, connected by a rod 81 to the guide bar. An input unit 82 (for simplicity, only one is shown) has a piston in the form of a bellows 83. The bellows is actuated by a cam 84 via a rod 85 connected to the bellows. The result is a completely closed servomotor and control-device assembly in which no oil losses can occur, thus preventing the fabric from being contaminated with oil.

Figure 5 shows a servomotor 87 and piston 88 with an electromagnetic input unit 89 which comprises a control piston 91 constituting the armature of an electromagnet 92 and floating on the oil 90 in the input unit. When the electromagnet is energized, the piston 91 is pulled downwards and thus drives some of the oil 90 into the servomotor, thus moving the piston 88 and the guide bar 93 connected thereto. When the current is switched off, the oil column in the servomotor is pushed to the right by a compression spring 94 acting on the guide bar and is driven back into the input unit 89 so that the piston 91 returns to its starting position.

Figure 6 shows an in-line arrangement which is advantageous when a number of servomotors have to be disposed close beside one another as in a knitting machine. A servomotor 95 with a piston 96 have an axially aligned input unit 97 comprising a plunger 98 actuated by an electromagnet 99. The plunger 98 carries a permanent magnet 100 constituting the armature of the electromagnet 99. The electromagnet is actuated by an electric control device (not shown) connected to a pattern store (also not shown).

The plunger is driven-by an amount depending on the strength of the energizing current-out of the electromagnet into the servomotor 95, thus axially displacing a corresponding amount of oil 101 and axially moving the piston 96 and the guide bar 103, which is loaded by a compression spring 102.

An energizing current having a given strength corresponds to a unit stroke of the guide bar.

Twice or three times the strength corresponds to twice or three times the guide-bar stroke. As soon as the current has been switched to a lower strength, the spring 102 pushes the guide bar and consequently the piston 96 back to a position corresponding to the new current. When the current is switched off, the guide bar and piston return to the starting position. The electromagnet 99 is electrically coupled to an electromechanical locking device 104, having an armature 104' which can engage in any of a plurality of recesses 98' in the plunger 98 and stops the plunger as soon as it has penetrated to the required depth into the servomotor. Of course, the servomotor can have a number of control plungers.

Instead of using an electromagnet, the control plunger can be driven by an electromechanical stepping motor, e.g. with geared transmission, in which case the control plunger will be provided with a rack. Alternatively, the control plunger can be driven by a linear motor. Of course, the control plunger can be driven by a cam, eccentric or crank drive. Finally, the control plunger can be sealed by a bellows.

Figure 7 shows a servomotor 110 and piston 111 and a rotating control device. The motor is open at one end 112 and has a thread 113 on its outer periphery. An internal thread 114 on a cylinder 11 5 engages the thread 11 3. The cylinder 11 5 is divided by a partition 11 6 into two halves 11 5a and 11 sub. The motor 110 and the half 11 5a are filled with hydraulic oil 117. The other half 11 sub contains a boss 11 8 on a rotor 11 9a of an electric motor 119. The half 11 sub and boss 11 8 are interconnected by a sliding key 118a.During clockwise motion, the half 115a is screwed further on to the servomotor, so that oil 11 7 is driven from the half 11 spa into the servomotor, whereupon the piston 111 and the guide bar connected thereto are pushed to the left. When the rotor 11 9a rotates in the reverse direction, the volume in the half 11 spa increases, so that the piston 111 moves to the right, back to the starting position, as a result of the pressure on the spring acting on the guide bar.

Figure 8 shows an embodiment comprising a servomotor 120 and piston 1 21 and a control device comprising an eccentric 1 22 and a diaphragm 123. The diaphragm is secured in an aperture 124 in the wall of a housing 125 of the servomotor, so that the control device is oil-tight.

When the eccentric 122 rotates, the diaphragm 1 23 is pressed inwards, corresponding to the instantaneous eccentricity, and displaces a corresponding volume of oil, so that the piston 121 and the guide bar connected thereto are pushed to the left. A ring 1 26 rotates freely on the periphery of the eccentric, so that the ring does not move relative to the diaphragm and the diaphragm does not become worn.

Although the described embodiments relate only to the control of guide bars, the invention of course can be applied to the control of other components of machines for making textile webs and adapted to be controlled in accordance with various controlled conditions each of which may be made up of a number of factors.

Claims

1. Apparatus for controlling a component of a machine for making a textile web comprising a hydraulic servomotor having a movable wall connected to the component, the servomotor being in flow connection with at least one input device, the total content of hydraulic fluid in the servomotor and the input device being constant, and the input device comprising a hydraulic-fluid displacement element, whereby the servomotor receives hydraulic fluid displaced by the control device resulting in motion of the movable wall, whereas the control element moves back when the control device receives hydraulic fluid displaced by the movable wall, resulting in a movement of the displacement element.

2. Apparatus as claimed in Claim 1 in which the component is a pattern-adjusting component.

3. Apparatus as claimed in Claim 1 or Claim 2 in which the displacement element of the input device is a movable wall actuated by a cam.

4. Apparatus as claimed in Claim 1 or Claim 2 in which the displacement element of the input device is a movable wall actuated by a crank drive.

5. Apparatus as claimed in Claim 3 or Claim 4 in which the movable wall of the control device is a piston.

6. Apparatus as claimed in Claim 5 in which the piston of the servomotor and the piston of the control device are double-acting pistons, each having a piston rod extending through a wall at one end of the piston, the cylinder spaces surrounding the two piston rods being interconnected.

7. Apparatus as claimed in any of Claims 1 to 4 in which at least one of the movable walls is a flexible wall.

8. Apparatus as claimed in Claim 7 in which the flexible wall is a bellows.

9. Apparatus as claimed in Claim 1 or Claim 2 in which the displacement element of the input device is a piston which constitutes the armature of an electromagnet and which floats on the hydraulic fluid.

10. Apparatus as claimed in Claim 1 or Claim 2 in which the input device includes a plunger whose axis passes through and is parallel to the direction of movement of the movable wall of the servomotor.

11. Apparatus as claimed in Claim 10 in which the plunger carries a permanent magnet which constitutes the armature of an electromagnet.

12. Apparatus as claimed in Claim 10 or Claim 11 in which the input device has locking means.

13. Apparatus as claimed in Claim 10 or Claim 11 or Claim 12 in which the plunger is sealed by a bellows.

14. Apparatus as claimed in Claim 1 or Claim 2 in which the servomotor comprises a sleeve divided by a partition into two sections, the first section having an internal thread engaging an external thread on a servomotor cylinder containing a piston constituting the movable wall of the servomotor, and the first section and the cylinder forming a common cavity filled with hydraulic fluid, and the second section containing a drive element connected for rotation by the rotor of an electric motor, the drive element being connected to the second section by means which transmit rotation but not axial movement.

15. Apparatus as claimed in Claim 1 or Claim 2 in which the control device comprises a resilient element disposed in an aperture in the wall of the servo-motor and an eccentric acting on the flexible element.

16. Apparatus as claimed in Claim 15 in which there is a freely rotatable ring on the periphery of the eccentric.

1 7. Apparatus for controlling a component of a machine for making a flat textile web, the apparatus being substantially as described herein with reference to any one of the Figures of the accompanying drawings.

18. A knitting machine having a control bar and apparatus for controlling the control bar, the control apparatus being as claimed in any of the preceding claims.