GB2273719A

GB2273719A - Heald control system

Info

Publication number: GB2273719A
Application number: GB9226922A
Authority: GB
Inventors: Malcolm Gaway Mahboubian-Jones
Original assignee: Bonas Machine Co Ltd
Current assignee: Bonas Machine Co Ltd
Priority date: 1992-12-24
Filing date: 1992-12-24
Publication date: 1994-06-29
Also published as: TW213493B; GB9226922D0

Abstract

A heald control system includes a statically mounted heald hook retention device (31) and a reciprocating heald hook (25), the device and heald hook having co-operating latch means (37, 34) which are relatively movable to cause selective retention of the heald hook at a predetermined position along said path of travel, and selectively actuatable electrostrictive motive means (10) for causing said relative movement between the co-operating latch means. As shown, a pin (37) engages an aperture (34) in the hook. In alternative embodiments a) the pin (37) may deflect the hook to engage a detent on a member (27); b) the electrostrictive element may be mounted on the hook itself and deform the latter to engage a detent; c) the electrostrictive element or a second such element may additionally control a displaceable element on the hook (25) which is selectively engaged by a lifting knife. <IMAGE>

Description

HEALD CONTROL SYSTEM The present invention relates to a heald control system and to a loom pattern control apparatus including such a system.

In our PCT application GB92/01178 we have described the use of a piezo-electric material for effecting selection in a heald control system.

The present invention is generally concerned with a similar type of heald control system wherein an electrostrictive material is used instead of a piezoelectric material.

Piezo-electricity is a bilinear coupling between mechanical and electrical variables. For the piezoelectric coefficient to be non-zero, the material must be anisotropic (which is normally a function of crystal structure), and to establish a macroscopic effect there must be a net macroscopic anisotropy (which is normally achieved by applying high fields to the material at elevated temperatures to produce a net orientation).

Piezo-electric materials therefore provide a behaviour which is directionally sensitive to the direction of the applied field. This means that the polarity of the applied field can be used to control or drive the direction of movement, or to positively return it to the zero-field state.

Electrostriction is the most common higher-order electro-mechanical coupling and is linear in respect to the mechanical variable, but quadratic in respect to the electrical variable. Electrostrictive effects exist even in isotropic materials and normally no restructuring of the material is required, the magnitude is, however, still dependent upon crystal structure. Since there is a quadratic relationship with the field, direction of movement is not dependent upon field direction. This means that returning to the zero-field state is controlled either by relaxation of the material, or by use of a mechanical return drive, but cannot be achieved by applying the reverse field to drive in the opposite direction as in the piezo-materials.

According to one aspect of the present invention there is provided a heald control system including a statically mounted heald hook retention device and a reciprocating heald hook, the retention device being located adjacent to the reciprocatory path of travel of the heald hook, the device and heald hook having co-operating latch means which are relatively movable in a lateral direction relative to said path of travel of the heald hook for controlling engagement of the co-operating latch means to cause selective retention of the heald hook at a predetermined position along said path of travel, and selectively actuatable electrostrictive motive means for causing said relative movement between the co-operating latch means.

Preferably the electrostrictive motive means comprises a stop assembly including a support strip having a layer of electrostrictive material laminated on one side thereof, the strip assembly being laterally deflected its length by application of an electric voltage to cause said relative movement between the co-operating latch means.

Preferably the support strip is formed from a resilient material such that on application of said electric voltage the strip is caused to laterally deflect from a first position to a second position and that on removal of the applied voltage the strip is returned from the second position to the first position by the resilience of the support strip.

According to one embodiment of the present invention a heald hook engagement member is provided which is movable along a path of travel between extended and retracted positions to cause retention of the heald hook, the path of travel of the hook engagement member intersecting the path of travel of the heald hook such that the heald hook engagement member moves across the path of travel of the heald hook during its movement toward its extended position.

The strip and hook engagement member may be arranged so that the first and second positions of the strip correspond the extended and retracted positions of the hook engagement member or vice versa.

The strip assembly may be directly connected to the heald hook engagement member so that displacement of the heald hook engagement member is the same as that undergone by the strip assembly. Alternatively the strip may be indirectly connected to the heald hook engagement member so that displacement of the heald hook engagement member is the same as or different to that undergone by the strip assembly.

In one embodiment the latch means associated with the heald hook comprises a shoulder, for example defined by the wall of an opening, and the hook engagement member defines the co-operating latch means associated with the retention device.

The heald hook may have a resiliently deflectable portion on which the latch means associated with the heald hook are located for co-operation with static latch means mounted to one side of the reciprocatory path of travel of the hook. With such an arrangement the heald hook engagement member is adapted to engage the heald hook in order to cause its deflection and thereby cause engagement between the co-operating latch means. Alternatively, the electrostrictive material may be secured in face to face contact with the deflectable portion so that deflectable portion defines said resilient support strip and such that on application of said voltage to the electrostrictive material the deflectable portion is deflected.

Alternatively, latch means may be movably mounted on the heald hook and the hook engagement member operates to cause deflection of the latch means on the hook in order to cause engagement with the static latch means.

In one embodiment, two heald hook engagement members are provided, a first of said heald hook engagement members being operative to cause retention of the heald hook at one end of its path of reciprocal travel and a second of said heald hook engagement members being operative to cause retention of the heald hook at its opposite end of its path of reciprocal travel. Preferably the heald hook is biased in one direction of travel and is moved by a lifting knife in the opposite direction of travel, one of said heald hook engagement members being operative to cause engagement between the knife and the heald hook whilst the heald hook is located at one end of its path of travel.

Each heald hook engagement member may be moved by- a respective motive means in the form of an electrostrictive material laminated on a resilient support strip alternatively a single strip may be provided for moving both heald hook engagement members.

According to another aspect of the present invention there is provided a pattern control apparatus for a weaving loom including a heald control system as defined above.

Various aspects of the present invention are hereinafter described with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of an electrostrictive material laminated on a resilient support strip; Figure 2 is a schematic diagram of a heald retention device according to a first embodiment of the present invention within a pattern control apparatus; Figures 3 and 4 are diagrammatic representations of the embodiment of Figure 2 illustrating operational modes of selection; Figures 5 and 6 are diagrammatic representations of a second embodiment illustrating operational modes of selection; Figure 7 is a schematic illustration of a third embodiment according to the present invention; Figure 8 is a schematic illustration of a fourth embodiment according to the present invention;; Figures 9 and 10 are diagrammatic representations of a fifth embodiment illustrating operational modes of selection.

Referring initially to Figure 1, there is shown motive means in the form of a strip assembly 10 including a resilient support strip 10a having a layer of electrostrictive material lOb on one side thereof to form a laminated assembly. Electrical connections 11,12 are provided at one end of the strip assembly 10 for the application of an electric voltage. The electrostrictive material layer may be bonded to the strip lOa by adhesive or may be directly bonded thereto by for example fusion.

In the embodiment shown the electrostrictive material is applied to strip 10a so that application of the voltage causes an expansion in the layer lOb along the strip lOa.

It will be appreciated that a similar deflection of the strip 10a can be achieved by locating on the opposite side of the strip 10a an electrostrictive material which undergoes a contraction along the strip 10a.

In the example shown in Figure 1, application of either a positive voltage to connection 11 and a negative voltage to connection 12 or vice versa causes the strip 10a to deflect laterally in one direction from a central non-deflected position 0 to a deflected position D1 due to the electrostrictive effect of the electrostrictive material. Removal of the applied voltage removes the electrostrictive effect and so enables the strip 10a to return under its own resilience to position 0. The strip 10a may be formed of any suitable material and preferably is formed from spring steel.

For such a strip, having a length of 100mm, a width of 8mm and thickness of 0.5mm, a deflection d of about l.5mm (between position 0 and D1) is achieved. The applied voltage to achieve this deflection is 100 volts.

The strip assembly 10 remains in its deflected position D1 as long as voltage is applied to connections 11,12.

In Figures 2 to 4 the first embodiment of the present invention is illustrated in which healds (not shown) of a loom are raised and lowered.

The method by which the healds are lifted is similar to that described in UK Patent No. 2047755. For example, as shown in Figure 2, healds (not shown) are attached to a lifting cord 1 which passes over a pulley wheel 2 to a fixing on the jacquard frame 3. Pulley 2 is attached to a second pulley wheel 3 via a housing 4 such that both wheels can rotate but are in fixed relationship to each other.

A second cord 5 which passes round wheel 3 connects two heald hooks in the form of rods 6. These heald rods are raised and lowered alternately by knives 8 and 9 which press against knife hooks or abutments 100.

The sequence of operation of the hooks is described in Patent Nos UK 2047755 and European Patent 0119787 as are the knife drive means and the method of mounting and arranging the heald control devices.

As illustrated in Figure 2, the upper portion 25 of each heald hook is reciprocated between an upper limit position UL and a lower limit position LL and a heald hook retention device 20 is located between each pair of connected heald hooks 6 in the region between positions UL and LL. The upper heald hook portions 25 are guided in a channel 26 formed by a spacer element 27 adjacent to each side of the retention device 20. In use, a plurality of side by side retention devices 20 spaced apart by spacer elements 27 are provided across the width of the loom.

The retention device 20 illustrated in Figures 2 to 4 includes a body 31 in which is housed a pair of electrostrictive strip assemblies 10. One end of each strip 10a is fixedly mounted in a connection block 32 to which appropriate connections 11 and 12 are made. Each strip assembly 10 independently operates in the same manner to cause retention of an adjacent heald hook 6. For simplification of description retention of single heald hook 6 only will hereinafter be described.

The upper portion 25 of the heald hook 6 is provided with an elongate aperture 34 and the retention device 20 is provided with a hook engagement member 36 in the form of a sheer pin 37. The pin 37 is axially movably mounted in a bore 38 formed in the body 31 for movement between extended and retracted positions. One end of the pin 37 is directly connected to the free terminal end of the strip assembly 10 so as to be axially moved thereby so that when strip assembly 10 is at positions D1,0 the pin 37 is located at its fully extended and retracted positions respectively.

The spacer element 27 is provided with a bore 28 which is in axial alignment with bore 38 such that on movement of the pin 37 from its fully retracted position (as seen in Figure 3) to its fully extended position (as seen in Figure 4) it enters into the bore 28. The pin 37 is moved from its retracted position to its extended position during movement of the aperture 34 passed bore 28. The length of the aperture 34 and the position of pin 37 relative to the reciprocal path of the hook 6 between positions UL and LL is chosen to permit sufficient time for the pin to enter the aperture 34 and reside in its fully extended position prior to the upper edge of the aperture engaging the pin 37. In the extended position of pin 37 it is received in both bores 28 and 38 on either side of channel 26.The pin 37 is therefore self-supporting in this position and does not transmit loadings onto the strip assembly 10 which are imparted onto the pin 37 when supporting the hook 6. The strip 10 is therefore isolated from loadings which might otherwise cause damage. Isolation from loadings may be improved by adopting a loose connection between the strip 10 and pin 37.

In order to release a hook 6 retained on a pin 37, the hook 6 is raised toward its UL position and in so doing lifts the upper edge of aperture 34 from the pin 37. The strip assembly 10 is then deflected to position 0 by its inherent resilience on the removal of the applied voltage and thereby moves pin 37 to its fully retracted position.

The hook 6 is then free to move to its lower position LL.

Preferably the length of the aperture 34 is such that the lower edge of the aperture 34 is located below the pin 37 when the hook 6 is located at its upper position UL. In this way a maximum length of time can be provided for retracting the pin 37.

Typically the width of channel 26 is 0.5mm and the thickness of the upper portions of hook 6 is 0.3mm. Since the maximum displacement between positions D1 and 0 is utilised the stroke of movement of pin 37 is about 1.5mm.

This enables a substantial length of pin 37 to be supported at either end in bores 28 and 38 to accommodate loadings applied by an engaged hook 6.

In order to reduce inertia, the pin 37 is preferably made from a light weight material and is of small cross-sectional area, typically about 3mm diameter if circular. Preferably the upper edge of aperture 34 and the face of pin 37 which engages the upper edge are of complimentary profile so as to provide maximum contact surface. The material chosen for pin 37 is preferably a suitable hard wearing plastics or composite. A suitable plastics material is polyetheretherketone.

An alternative embodiment is illustrated in Figures 5 and 6 wherein the pin 37 is utilised as a means for deflecting the hook 6 rather than being used as a latch.

In the embodiment of Figures 5 and 6, instead of the spacer element 27 being provided with a bore 28 it is provided with an inclined deflection surface 40 which is inclined at an acute angle e with the side wall 27a of spacer element 27 defining channel 26.

A static latch 42 formed on the spacer element 27 projects above surface 40 and is located at a position laterally offset from the path of travel of the hook 6 such that if undeflected the hook 6 does not engage latch 42.

In this embodiment, since the static latch 42 is located on element 27, this element defines a retention device.

To retain hook 6 on latch 42, the strip assembly 10 is actuated, whilst the upper portion 25 of hook 6 is in its upper region of travel, to move pin 37 from its fully retracted position (as shown in Figure 5) to its fully extended position (as shown in Figure 6). In moving to its fully extended position, the pin 37 engages the upper portion 25 of hook 6 and causes it to bend about the transition edge 44 between surface 40 and sidewall 27a.

In deflecting upper portion 25 in this manner, the aperture 34 surrounds the latch 42 so that on downward movement of the hook 6 the upper edge of aperture 34 engages latch 42 and thereby retains the hook 6 at an upper position.

Preferably the upper portion of latch 42 which engages with the upper edge of aperture 34 is shaped to resist lateral separation between the hook and latch 42. This may be achieved as shown by the provision of an inclined support face 43. After retention of hook 6 on latch 42, the knife 8 descends and the hook 6 becomes suspended from the latch which thereby maintains engagement to restrain lateral separation.

Thus after engagement of the upper edge of aperture 34 with latch 42 the pin 37 may be retracted to its fully retracted position.

To release a retained hook 6, the pin 37 is retracted to its fully retracted position and the hook 6 is raised toward its upper position UL. Such movement raises the upper edge of aperture 34 away from latch 40 and enables the upper portion 25 to return under its inherent bias to an undeflected condition. The hook 6 is then free to move to its lower position LL without engaging latch 42.

For the embodiment of Figures 5 and 6 at least the upper portion 25 of hook 6 is formed from a resilient material such as spring steel and is in the form of a thin strip. By changing the thickness of the strip and/or the position of the transition edge 44 below the pin 37 it is possible to change the force needed to be applied by pin 37 for bending the upper portion 25.

In the embodiment of Figures 2 to 6 the pin 37 is directly connected to the strip assembly 10 and as such the axial displacement of pin 37 is the same as that undergone by the strip 10.

It is envisaged that the hook engagement member may be indirectly connected with the strip assembly 10. This enables the strip to be isolated from loadings applied to the hook engagement member and also enables the displacement undergone by the hook engagement member to be different to that undergone by the strip assembly 10. Thus for the embodiments of Figures 2 to 6 wherein the hook engagement member is pin 37, this enables the displacement stroke of the pin to be varied and also enables the applied force on pin 37 to be varied.

An example of an indirect connection is illustrated in Figure 7 wherein the strip assembly 10 is connected to the pin 37 via a lever 50 which is pivotally mounted on the body 31 via a pivotal connection 52. Functioning of the pin 37 for causing retention of the hook 6 is the same as that described in the embodiment of Figures 2 to 4, or Figures 5 and 6.

The embodiment of Figure 7 further illustrates use of a single hook 6 for controlling movement of a heald (not shown) between its upper and lower shed positions.

In the embodiment of Figure 7 the single hook 6 is connected to a heald to cause its movement between upper and lower shed positions in response to movement of a single knife 55. In the embodiment illustrated the hook 6 is biased to toward its lower position LL and is retained in this position by virtue of a stop 56 mounted on the hook 6 engaging with a shoulder 57 on body 31.

The hook 6 is provided with a laterally deflectable knife hook 60 which is biased to a retracted position. In the retracted position, the knife hook 60 is off-set from the path of travel of the knife 55 and so is not engaged by the knife 55. Accordingly whilst knife hook 60 is retracted the hook 6 remains at its lower position LL.

A hook engagement pin 70 is provided which is axially slidably located in a bore 72 of the body 31 at a position facing the knife hook 60 when the hook 6 is at its lower position LL.

The pin 70 is connected to one end of the strip assembly 10 so as to be moved thereby between extended and retracted positions.

In order to raise hook 6, the strip assembly 10 is arranged so that in its biased position 0 the pin 70 is located at its extended to engage knife hook 60 to move it to an extended position (see Figure 7). In its extended position, the knife hook 60 projects into the path of travel of the knife 55 and is accordingly engaged thereby.

Since pin 37 is also connected to strip assembly 10, when strip 10 is at its biased position 0, pin 37 is located at its fully retracted position in readiness for causing retention of the hook 6 at its upper position.

This is achieved at the appropriate time by deflecting strip 10 to its position D1 to move pin 37 to its extended position and cause retention of the hook 6 as described in the previous embodiments. Preferably the strip 10 is operated by application of a reduced voltage (compared with that for causing deflection to D1) to reside at a deflected position intermediate D1 and 0 so as to hold both pins 37,70 at a retracted position.

The knife hook 60 is preferably in the form of a swinging latch which is biased under its own weight to its retracted position. Preferably the swing latch is arranged to engage a side face of body 31 or an appropriately positioned cam face for maintaining the knife hook 60 at its extended position whilst the hook 6 is retained at its upper position and the knife 55 has been lowered.

An alternative arrangement to embodiment of Figure 7 is illustrated in Figure 8 wherein instead of using a single strip assembly 10 to move pins 37 and 70 simultaneously, two strip assemblies 10c,10d are provided for independently moving pins 37,70 respectively.

Operation of the device shown in Figure 8 is otherwise the same as that for the device shown in Figure 7.

It is envisaged that in the embodiments of Figures 2 to 6, if desired, the upper end of strip 10a may be anchored to the connection block and the lower end of the strip 10a be connected to the hook engagement member. The position of the hook engagement member relative to the path of reciprocatory travel of the hook 6 would remain the same. Such an arrangement further isolates transmission of loadings onto the strip assembly 10 from the hook engagement member.

Furthermore it is possible to arrange the strip assemblies 10 of within one body 31 in a "head to toe" manner ie one strip assembly with its lower end in a connection block and the other strip assembly with its upper end in a connection block.

In the embodiments described above, the fully extended and retracted positions of the hook engaging pins correspond to the displacement positions D1,0 respectively of the strip assembly 10. This means that the pins are positively held at their extended/retracted positions and this ensures reliability of operation.

A fifth embodiment is illustrated in Figures 9 and 10 which operates in a similar manner to the embodiment of Figures 5 and 6, i.e. the latch means 34 is located on a deflectable portion 25 of the heald hook 6 and the portion 25 is deflected to bring about engagement of the latch means 34 with latch means 42.

In the embodiment of Figures 9 and 10, the layer of electrostrictive material is laminated, for example by bonding or fusion, in face to face contact with the upper deflectable portion 25. The upper portion 25 thereby defines a support strip similar to strip 10a.

Voltage is applied to the electrostrictive material 10b by for example an electrical contact 80 which is slidingly contacted by the electrostrictive material 10b as the hook 6 approaches its upper position UL. Other alternative means for charging the electrostrictive material may be adopted if desired, for example, electromagnetic induction, capacitive coupling etc. Preferably the hook 6 is formed of an electrically conductive material and is conveniently earthed. Accordingly a voltage may be applied via contact 80 to initially cause deflection of the upper portion 25 from the position shown in Figure 9 to that shown in Figure 10.

Once the co-operating latch means 34,42 have been engaged, the voltage applied via contact 80 may be removed.

Thus on subsequent raising of hook 6 the upper portion 25 of hook 6 will return to its undeflected state (as shown in Figure 9) under its own bias.

Due to the use of electrostrictive motive means the power consumption is extremely low and no heating or electrical interference problems arise. This means that the devices can be compact and closely spaced. In addition, the electrostrictive material always retains it electrostrictive properties and so does not deteriorate with time.

It is envisaged that the applied voltage for deflecting the strip assembly 10 may be applied in a constant manner or by pulse.

It will be appreciated that the upper wall of aperture 34 which forms the latch means 34 associated with the heald hook acts as a stop shoulder for location on the latch means associated with the retention device. It is envisaged that other constructions of shoulder may be formed on the hook in order to achieve the same function.

In the above described embodiments, the electrostrictive material is mounted on a resilient strip 10 made of spring steel. It will be appreciated that the strip 10a may be formed from other resilient materials such as plastics. Desirably the resilient force of the support strip is chosen so as to not exceed about 20% of the force generated by the electrostrictive material.

The purpose of the resilience of the strip 10a is to bias the strip assembly 10 to position 0 in the absence of an applied voltage.

It is envisaged that the support strip 10a may be made of a non-resilient flexible material and that the biasing force for returning the strip assembly 10 to the nondeflected position may be in the form of a separate mechanical compression or extension spring which is compressed or extended when the strip 10 is moved toward its deflected position Dl.

Claims

1. A heald control system including a statically mounted heald hook retention device and a reciprocating heald hook, the retention device being located adjacent to the reciprocatory path of travel of the heald hook, the device and heald hook having co-operating latch means which are relatively movable in a lateral direction relative to said path of travel of the heald hook for controlling engagement of the co-operating latch means to cause selective retention of the heald hook at a predetermined position along said path of travel, and selectively actuatable electrostrictive motive means for causing said relative movement between the co-operating latch means.

2. A system according to claim 1, wherein the electrostrictive motive means comprises a strip assembly including a support strip having a layer of electrostrictive material laminated on one side thereof, the strip assembly being laterally deflectable relative to its length by application of an electric voltage to cause said relative movement between the co-operating latch means.

3. A system according to claim 2, wherein the support strip is formed from a resilient material such that on application of said electric voltage the strip is caused to laterally deflect from a first position to a second position and that on removal of the applied voltage the strip is returned from the second position to the first position by the resilience of the support strip.

4. A system according to claim 2 or 3, including a heald hook engagement member which is movable along a path of travel between extended and retracted positions to cause retention of the heald hook, the path of travel of the hook engagement member intersecting the path of travel of the heald hook such that the heald hook engagement member moves across the path of travel of the heald hook during its movement toward its extended position.

5. A system according to claim 4, wherein the strip assembly is deflectable between a first and second position corresponding to the extended and retracted positions of the hook engagement member.

6. A system according to claims 4 or 5, wherein the strip assembly is directly connected to the heald hook engagement member so that displacement of the heald hook engagement member is the same as that undergone by the strip.

7. A system according to claims 4 or 5, wherein the strip assembly is indirectly connected to the hook engagement member so that displacement of the hook engagement member is the same as or different to that undergone by the strip.

8. A system according to claims 4 or 7, including a body having a bore in which the hook engagement member is slidingly received, a spacer member being located adjacent to the body and spaced therefrom to define a channel in which the heald hook is reciprocally received, the spacer member having a recess opposed to the bore so that in its extended position the hook engagement member extends across the channel and is supported at opposite ends in said bore and said recess, said hook engagement member thereby defining the latch means associated with the retention device.

9. A system according to any of claims 4 to 7, wherein the heald hook has a resiliently deflectable portion having latch means for co-operation with static latch means mounted to one side of the reciprocatory path of travel of the hook, the heald hook engagement member being adapted to engage the heald hook in order to cause its deflection and thereby cause engagement between the co-operating latch means.

10. A system according to any of claims 4 to 7 wherein latch means are movably mounted on the heald hook and the heald hook engagement member operates to cause deflection of the latch means on the hook in order to cause engagement with static latch means mounted to one side of the reciprocatory path of travel of the hook.

11. A system according to claim 4, including two heald hook engagement members for each heald hook, a first of said heald hook engagement members being operative to control retention of the heald hook at one end of its path of reciprocal travel and a second of said heald hook engagement members being operative to control retention of the heald hook at its opposite end of its path of reciprocal travel.

12. A system according to claim 11, wherein the heald hook is biased in one direction of travel and is moved by a lifting knife in the opposite direction of travel, one of said heald hook engagement members being operative to cause engagement between the knife and the heald hook whilst the heald hook is located at one end of its path of travel.

13. A system according to claim 11 or 12, wherein the first and second hook engagement members are each connected to a respective strip assembly.

14. A system according to claim 11 or 12, wherein a single strip assembly is connected to both the first and second hook engagement members.

15. A system according to claim 1, wherein the heald hook includes a deflectable portion on which its associated latch means are located, the motive means comprising a layer of electrostrictive material laminated on one side of the deflectable portion such that application of a voltage to said material causes a lateral deflection of the deflectable portion of the heald hook.

16. A pattern control apparatus for a loom including a heald control system according to any preceding claim.