EP0420869B1

EP0420869B1 - Electronic position control system

Info

Publication number: EP0420869B1
Application number: EP19890906390
Authority: EP
Inventors: John Dalton Griffith
Original assignee: BONAS GRIFFITH Ltd
Current assignee: BONAS GRIFFITH Ltd
Priority date: 1988-05-27
Filing date: 1989-05-25
Publication date: 1993-12-22
Anticipated expiration: 2009-05-25
Also published as: DE68911682D1; WO1989011558A1; EP0420869A1; GB8812595D0

Abstract

An electronic control system for selectively positioning a controlled member (16) at one of a plurality of predetermined positions, the system including a reciprocating member (20) for driving said controlled member (16), a reciprocating drive member (22) for driving the reciprocating member (20) in one direction and being movable relative to said reciprocating member (20) in the other direction, said reciprocating member (20) being biased in said other direction, the reciprocating member (20) having a series of formations (26) spaced along the direction of reciprocation to correspond to said plurality of predetermined positions, an electronically controlled detent (25) mounted at a fixed position along the path of reciprocation, the detent (25) being movable between first and second positions, the detent (25) in said first position being arranged to engage a selected one of said formations (26) to arrest movement of the reciprocating member (20) in said other direction, and in said second position being arranged to reside at a remote position whereby it does not engage any of said formations, electronically operable means for controlling movement of the detent (25) to said first position such that engagement with one of said formations can be selected.

Description

The present invention relates to an electronic position control system and is particularly suited for electronically controlling tuft yarn selection in a carpet weaving look, in particular for an Axminster carpet weaving loom.
In such a weaving loom, for each tuft inserting position a plurality of different coloured yarns are fed to a common yarn guiding bar which is raised or lowered to different height positons to enable selection of a desired coloured yarn.
Heretofore, the controlling mechanism for selecting the height of each yarn guide bar for selecting a desired yarn has included the use of a Jacquard mechanism using punched cards and co-operating reading pins.
The present invention is primarily concerned with providing an electronically controlled arrangement which thereby enables the loom to be quickly programmed and reliably operated to weave different patterns.
GB 2189513 discloses an electronic control system for selectively positioning a yarn guide arm in a carpet loom. The system includes a lifting bar slidably mounted relative to a reciprocating lifting shaft assembly, the lifting bar having a series of formations spaced along its length and being co-operable with engagement means in the form of a solenoid for controlling driving engagement between the lifting bar and the lifting shaft assembly so that the lifting bar is moved by the lifting shaft assembly to a selected position in one direction of the reciprocative motion of the lifting shaft assembly.
According to one aspect of the present invention there is provided an electronic control system for selectively positioning a yarn guide arm, the system including a lifting bar slidably mounted relative to a reciprocating lifting shaft assembly, the lifting bar having a series of formations spaced along its length and being cooperable with a detent for controlling driving engagement between the lifting bar and the lifting shaft assembly so that the lifting bar is moved by the lifting shaft assembly to a selected position in one direction of the reciprocative motion of the lifting shaft assembly, characterised in that the detent is biased toward the lifting bar for engaging one of said formations, the detent being held by electronically controlled retention means at a non-engagement position spaced from the lifting bar, the electronically controlled retention means being selectively operable to release said detent to engage a selected formation on the lifting bar.
The lifting shaft assembly reciprocates between uppermost and lowermost positions and the control system may be designed to operate to move each lifting bar to its selected height either on the upward or the downward stroke of the lifting shaft assembly. In the former case the detent is mounted on the lifting shaft assembly and in the latter case the detent is mounted on a fixed part of the loom.
In one embodiment the lifting bar is arranged to deflect its associated detent to engage the retention means when moved in a direction opposite to said one direction of the reciprocative motion.
Preferably the retention means includes a magnetic core which is magnetically energised by a permanent magnet and an electromagnetic coilsurrounding the core, the electromagnetic coil when energised acting to nullify the magnetic effect of the permanent magnet.
Various aspects of the present invention are hereinafter described with reference to the accompanying drawings, in which:-

Figure 1 is a schematic side view showing a yarn selector mechanism according to the present invention;
Figure 2 is a more detailed view of part of the mechanism shown in Figure 1;
Figure 3 is a schematic end view of the mechanism shown in Figure 2;
Figure 4 is a schematic side view of an alternative embodiment of the present invention;
Figure 5 is a side view similar to Figure 2 of an alternative embodiment according to the present invention;
Figure 6 is a side view similar to Figure 5 showing a further embodiment according to the present invention; and
Figure 7 is a front view of the embodiment shown in Figure 6.

Referring initially to Figure 1, there is schematically illustrated a warp sheet 10 carried on a weaving loom. The warp sheet is shown as being separated to form a shed having a fell point F.
Mounted on the frame of the loom (not shown) in a conventional manner is a series of yarn clamps 15 each of which co-operate with a movable yarn guide bar 16. Each guide bar 16 is fed with a plurality of yarns 18 of differing colours. The height of each guide bar 16 is adjusted on each weaving cycle so as to present a desired coloured yarn to the co-operating yarn clamp 15. The yarn clamp 15 grips the protruding end of the selected yarn 18 and holds it whilst the end is severed to form a short tuft of yarn. The yarn clamp 15 then carries the tuft of yarn to the fell point F where it remains whilst weft yarn is inserted for trapping the tuft into the weave. The yarn clamp releases the tuft and then returns to obtain a further tuft from the yarn guide bar.
Since a large number of tufts have to be inserted simultaneously across the width of the weave, it will be appreciated that a large number of side by side yarn clamps and associated yarn guide bars are provided which are closely spaced to one another across the width of the loom.
As seen in Figures 1 and 2 each yarn guide bar 16 is suspended from an associated lifting bar 20, there being one lifting bar 20 for each guide bar 16. As seen in in Figure 1 the connection between the associated guide bar 16 and lifting bar 20 may be via a flexible connection such as a length of wire 21 or alternatively as seen in Figure 4 the lifting bar 20 may be formed as an extension to the yarn guide bar 16.
Each lifting bar 20 is slidably received in a common lifting shaft 22. The lifting shaft 22 extend across the width of the loom and is provided with spaced grooves each of which slidingly receive a respective lifting bar and serve to space adjacent lifting bars apart. Each lifting bar 20 is provided with a projection 23 which abuts against the upper surface of the lifting shaft 22. During each cycle of the weaving loom, the lifting shaft 22 reciprocates from an upper position (as shown in full lines) to a lower position as shown in broken lines in Figure 2. During such movement, all the lifting bars 20 are lowered and raised by the lifting shaft. Each lifting bar 20 is biased in the downward direction of reciprocation and thus maintain contact with the lifting shaft 22 in that direction.
Below the lower position of the lifting shaft 22 there is provided a series of detents 25, one detent being provided for co-operation with an associated lifting bar 20. Each lifting bar 20 is provided with a series of downwardly facing shoulders 26 which are spaced from one another by the same spacing as the yarns 18 carried by the associated yarn guide 16.
The detent associated with each lifting bar is biased toward the edge of the guide bar having the shoulders so that as the lifting bar is lowered the detent engages a selected shoulder and holds the lifting bar against further downward movement. Continued downward movement of the lifting shaft is unaffected since each lifting bar is slidably received therein.
In the illustrated embodiment, the detent comprises a length of spring wire which is fixedly retained at one end in a clamp 28 mounted on the loom frame. However it will be apprreciated other forms of detent providing a similar function may be adopted if desired. For instance, a pivoted lever biased by a spring may be adopted.
Also positioned below the lower position of the lifting shaft is a stationary guide bar 24 having laterally projecting shims 24a projecting therefrom. The shims 24a are interposed between adjacent lifting bars 20 for guiding their motion and also project beyond the lifting bars to provide guideways for receiving the upper portion of respective detents. Accordingly the shims help to ensure alignment between each lifting bar and its associated detent.
Control of each detent to engage a selected shoulder is achieved using an electronically controlled magnet arrangement 30. A single arrangement 30 is provided for cooperation with an associated detent and each arrangement includes a permanent magnet 34 and a magnetic core 35 extending fromthe magnet toward the detent. A coil 36 of an electrically conducting wire is wound about the core 35 in such a way that when an electric current is passed the magnetic affect of the core which is induced by the permanent magnet is nullified.
Each lifting bar 20 is provided with a cam face 38 which engages the associated detent when the lifting bar is raised toward its uppermost position so as to move the detent into contact with its associated magnetic core 35. The detent is made of a magnetic material and so is retained in contact with the core 35 by magnetic attraction induced by the permanent magnet. In this position, the detent is clear of the series of shoulders and so would not interfere with the subsequent downward motion of the lifting bar.
When it is desired to hold the lifting bar in a desired position, an electric pulse is fed to the coil 36 tonullify the magnetic attraction of the core and to release the detent which then moves under its bias toward the lifting bar to engage the selected shoulder. The position of each lifting bar is electronically sensed to that it is known when to activate the coil 36. It is therefore possible to electronically program actuation of all the coils of the respective magnetic arrangements 30 to select desired yarns for each yarn clamp 15. Since the coils 36 are only actuated momentarily no heating problems occur.
As illustrated in Figures 2 and 3, the plurality of cores 35 are preferably mounted on a non-magnetic plate 40 (such as aluminijm) which is secured to the frame of the loom. Conveniently a single elongate permanent magnet is secured to the plate 40 by a bracket 46. Preferably as seen in Figures 2 and 3 cores 35 are arranged in two or more rows with each core of one row being located between adjacent cores of the other row in order to enable close spacing between immediately adjacent cores.
The embodiments described above in relation to Figures 1 to 4 operate to retain each lifting bar at a selected height during the downward movement of the lifting shaft 22.
Figures 5 to 7 show alternative embodiments wherein upward movement of a lifting shaft assembly 100 is utilised to raise each lifting bar 20 to a selected height.
In Figure 5 each lifting bar 20 is supported in a lowermost position by engagement of its projection upon a fixed support shaft 121 which extends across the loom. Guide fingers 122 extend from the support shaft 121 to extend between adjacent lifting bars 20 to thereby define guideways for guiding sliding reciprocal motion of each lifting bar 20.
The detent 25, clamp 28 and magnet arrangement 30 are assembled as a unit to define a lifting shaft assembly which is arranged to be reciprocated between a lowermost position (as illustrated in solid lines in Figure 5) and an uppermost position (as illustrated in broken lines in Figure 5). In the lowermost position of the lifting shaft assembly, the detents for each lifting bar 20 are located beneath the lowermost shoulder 26.
Operation of the embodiment shown in Figure 5 is as follows. When a lifting bar 20 is in its lowermost position, the associated detent will be in contact with and heldin a non-operative position by the associated magnet and core 35.
During upward motion of the lifting shaft assembly, the associated coil 36 is activated to release the detent to engage a selected shoulder 26 thereby causing the lifting bar 20 to be raised. On downward movement of the lifting shaft assembly, the lifting bar 20 is lowered until its projection 23 rests on support shaft 121 and thereafter continued downward movement of the lifting shaft assembly results in a relative motion between the detent and the lifting bar thereby causing the detent to be moved back into contact with its associated core 36 by engagement with a cam face 38. Thus at the lowermost position of the lifting shaft assembly each detent is held by its respective core 35 in readiness for the next cycle.
An alternative embodiment is illustrated in Figures 6 and 7 wherein an alternative method for engaging the detents onto their respective cores 35 at the lowermost position of the lifting shaft assembly is provided.
In the embodiment of Figures 6 and 7, the lifting shaft assembly includes a rotatable support shaft 120 which extends in the weft direction across the loom and is supported at opposite ends in a frame 125. The frame 125 has side members 126, and a cross member 127 and is arranged to reciprocate between an uppermost and a lowermost position.
The magnets 34, coils 35, etc. for controlling release of each detent are mounted between the side members 126 and the detents 25 are mounted onto the support shaft 120. Fixedly mounted on each end of the shaft 120 is a lever 130 which is biased by a spring 131 into contact with a stop 132 formed on the adjacent side member 126. In this position of each lever 130 the shaft 120 is resiliently held at a predetermined rotational working position. In this working position the detents when released by their associated core 35 project from the shaft 120 to engage a respective lifting bar 20 and when held by their respectively core 35 are held in a deflected biased condition. It is envisaged that lever 130 may be biased into contact with stop 132 by means of weights instead of spring 131.
Operation of the embodiment of Figures 6 and 7 during the upward stroke of the lifting shaft assembly is the same as that for the embodiment of Figure 5.
On the downward stroke of the lifting shaft assembly, as the assembly approaches the lowermost position, a roller 138 mounted on each lever 130 is arranged to engage an associated fixed stop and thereby cause deflection of each lever 130 against the bias of springs 131. The deflection of levers 130 cause the shaft 120 to rotate to move each detent into contact with its associated core. As the lifting shaft assembly rises from its lowermost position, levers 130 return to engage their associated stops 132.
It is envisaged that the permanent magnet may be dispensed with and that the detents may be held in contact with their respective cores 35 by the action of coils 36. In such a case coils 36 need to be maintained in an active condition until release of the detent is required.

Claims

An electronic control system for selectively positioning a yarn guide arm (16), the system including a lifting bar (20) slidably mounted relative to a reciprocating lifting shaft assembly (22), the lifting bar having a series of formations (26) spaced along its length and being cooperable with a detent (25) for controlling driving engagement between the lifting bar and the lifting shaft assembly so that the lifting bar is moved by the lifting shaft assembly to a selected position in one direction of the reciprocative motion of the lifting shaft assembly, characterised in that the detent (25) is biased toward the lifting bar for engaging one of said formations, the detent being held by electronically controlled retention means (30) at a non-engagement position spaced from the lifting bar, the electronically controlled retention means being selectively operable to release said detent to engage a selected formation on the lifting bar.
A system according to claim 1, wherein the retention means comprises a magnetic core (35) which magnetically holds the detent at said non-engagement position, the magnetic core being electronically controlled to release the detent.
A system according to claim 2, wherein the magnetic core is formed by a permanent magnet (34) and electrical windings (36) surround the core which on passage of electrical current nullify the magnetic effect of the permanent magnet to cause the release of the detent.
A system according to claim 2, wherein the magnetic core is defined by an electromagnet which on activation retains the detent and on de-activation releases the detent.
A system according to any of claims 1 to 4, wherein the lifting shaft assembly reciprocates between first and second positions and said detent is mounted on a fixed part of the loom to engage a selected formation on the lifting bar during its movement toward said second position and thereby arrest motion of said lifting bar until return of the lifting shaft assembly towards said first position.
A system according to claim 5, wherein the lifting bar includes a cam formation (38) arranged to deflect the detent toward the non-engagement position to engage the retention means when the lifting bar approaches said first position.
A system according to any of claims 1 to 4, wherein the lifting shaft assembly (100) reciprocates between first and second limit positions and said detent is mounted on the lifting shaft assembly to engage a selected formation on the lifting bar during movement of the lifting shaft toward said first limit position and thereby move the lifting bar to a desired position intermediate said first and second limit positions.
A system according to claim 7, wherein the detent, lifting shaft assembly and retention means are mounted in a reciprocally movable frame (125), the detent being mounted on a shaft (120) rotatably mounted on said movable frame, the shaft being biased in one rotational direction to bias the detent into engagement with the lifting bar, the shaft being provided with at least one lever arm (130) which engages a fixed stop (132) on the loom as the movable frame approaches said second position and thereby causes the shaft to rotate against said bias to move the detent toward the non-engagement position to engage the retention means.
A system according to claim 7, wherein the lifting bar includes a cam formation (38) arranged to deflect the detent toward the non-engagement position to engage the retention means when the lifting shaft assembly approaches said second position.
A system according to any preceding claim, wherein each detent comprises a length of spring wire (25).