EP0099254B1

EP0099254B1 - Heald control apparatus

Info

Publication number: EP0099254B1
Application number: EP83303989A
Authority: EP
Inventors: John Dalton Bonas Machine Company Ltd. Griffith
Original assignee: Textilma AG
Current assignee: Textilma AG
Priority date: 1982-07-10
Filing date: 1983-07-08
Publication date: 1988-12-07
Also published as: EP0099254A2; EP0099254A3; SG43689G; HK3090A; DE3378642D1

Description

The present invention relates to a retention device for a heald rod.
The U.K. patent application No. 2 047 755 discloses a heald control means including two flexible retention elements and an electromagnet located between said retention elements in order to move the retention elements with regard to the electromagnet and to engage the retention elements with the heald rods. The retention elements are fixedly mounted to a support block, to which the electromagnet is mounted, too. The retention elements are provided with a latch formation.
This device has the disadvantages that a relatively strong magnetic field has to be generated in order to draw the retention elements against the pole of the electromagnet, and that the speed of operation is limited.
The EP-A-98 428, which represents a state of the art according to article 54(3) EPC, discloses a shedding mechanism for a loom, which mechanism includes two rods which are recip- rocable between two end positions, two flexible retaining elements held on a holder and associated to the rods and an electromagnet held between the retaining elements.
The electromagnet has a double T-shaped core with flange sections of different width. An armature body is fixed to the retaining elements such that on one side the armature body abuts to the wider flange section and on the other side an air gap is provided between the armature body and the smaller flange section.
If the rod is moved by means of the knife in the upper position, the retaining element is deflected in order to adjust the air gap between the armature body and the smaller flange section to a predetermined value. The mechanism works with two exact triggering times at which the deflection of the retaining elements may be performed safely on the side necessary for the function and the power consumption of the electromagnet may be reduced and the heating may be reduced.
This mechanism has the drawback that the armature body is provided merely for optimizing the magnetic circuit.
The invention as claimed is intended to provide a remedy. It solves the problem of how to design a retention device for a heald rod, in which the response time for deflecting the retention arm is quick due to the construction of the retention device and the positive and reliable operation of retaining the selected heald rod is ensured at high speed.
Various aspects of the present invention are hereinafter described with reference to the accompanying drawings, in which:

Fig. 1 is a side view showing several side by side heald rod retention devices;
Fig. 2 is a perspective view of one of the retention devices shown in Fig. 1; and
Fig. 3 is a schematic illustration of the mechanism for operating the heald operating knives.

The operation of the loom of the type to which the present invention particularly relates is described in the published U.K. patent application No. 2 047 755 and reference should be made thereto.
Each heald eye (not shown) is controlled by a pair of heald rods 14 in a similar manner to that shown in Fig. 1 of U.K. patent application No. 2 047 755 and each rod 14 is provided near its terminal end with an aperture 38 for selective engagement with a retention device 20.
A plurality of retention devices 20 is arranged in closely spaced rows, there being one retention device 20 for each pair of heald rods 14. The retention devices 20 are conveniently mounted on a common board (not shown) extending across the loom.
Each retention device 20 includes an electromagnet 22 which is removably mounted on a support block 23 which is secured to the board. At the upper end of the electromagnet 22 as shown in Figures 1 and 2 an angled bracket 25 is provided, one arm 25a of which is secured to the electromagnet and the other arm 25b of which seats upon the block 23 and is located on a projection 26. A similar projection 27 is provided on the support block 23 and a retaining plate (not shown) is located on projections 26 and 27 and retained in position by the bolt (not shown) passing through bore 24 in the support 23. Accordingly in the event of the electromagnet 22 failing it is a simple matter to replace it without disturbing the location of the remainder of the retention device. Conveniently the bracket 25 and support block 23 are plastics mouldings.
Secured on either side of the support block 23 and extending downwardly therefrom is a pair of retention arms 40 which co-operate with the heald rods 14 to selectively retain them in their raised position.
Each retention arm 40 includes two components, namely a resilient member 41 and a rigid member 42 which are secured to one another for instance by riveting or welding. The arms 40 may be considered to comprise three distinct portions, viz, an upper portion 43, an intermediate portion 44 and a lower portion 45.
The upper portion 43 is composed entirely of the resilient component and provides a hinge connection between the arm and the support block and provides the arm 40 with a resilient bias so that the arm 40 is normally spaced from the lower pole 46 of the electromagnet. Varying the length of portion 43 varies the amount of bias. Conveniently component 41 is a ribbon of spring steel.
The intermediate portion 44 comprises both components 41 and 42 which are rigidly connected to one another. Component 42 is preferably composed of a material which can be easily magnetised, such as soft iron, and basically acts as a pole piece for co-operation with the lower pole 46, preferably the portion 44 is arranged so that its upper end is in contact with the upper pole 47 of the electromagnet. Accordingly the intermediate portion serves to rigidify the arm below the upper portion and also provides a magnetic path so that the portion of component 42 adjacent the lower pole will be a magnetic pole thereby creating a strong attractive force due to polar attraction. Accordingly, the response time for deflection of arms 40 on energisation of the electromagnet 22 is very quick.
It is envisaged however that the portion 44 may be located in the region of the lower pole 46 alone.
The lower portion 45 of each arm 40 serves to cooperate with the heald rods 14 for selective retention thereof. The lower portion 45 includes a window 50 formed in component 41 and through which projects a hook formation 51 formed at the terminal end of component 42. The hook formation 51 on penetrating the aperture 38 formed in the operating rod 14 engages the upper edge of aperture 38 and thereby supports the rod 14. It is desirable that the hook formation 51 is resistive to impacts caused by rapid downward movement of the rods 14 and so the hook formation is constructed so as to be resistive to such impacts. In the preferred embodiment illustrated the terminal end of each component 42 is case hardened so as to provide a hook formation 51 which is resistive to such impacts.
The component 41 projects downwardly beyond the hook formation 51 and defines a guide surface 53 for guiding the terminal end of rod 14 over the hook formation 51 during upward movement of the rod 14.
In Figure 3 the mechanism for lifting the heald knives 60 is illustrated generally at 61 and includes a pair of arms 62 pivotally connected at 63 and which are caused to rise and fall relative to one another by a drive mechanism 64. Two pairs of arms 62 are provided with the knives 60 extending therebetween.
The drive mechanism 64 for each arm 62 includes a pair of cams 66 mounted on a drive shaft, one cam serving to positively raise the arm and the other cam serving to positively lower the arm. Each arm is therefore provided with a pair of cam followers 67, cam follower 67a serving to positively raise the arm and cam follower 67b serving to positively lower the arm.
The shape of cams 66 are chosen so that when each arm 62 is in its raised position (which means that the rods 14 operated thereby have been lifted so that their terminal end is above the co-operating arm 40 of the retention device) there is an extended dwell time before lowering the arm. This dwell time is advantageous in that it extends the period in which the retention device needs to operate to deflect is associated arms 40. Accordingly, since the response time for deflecting the arms 40 is quick due to the construction of the retention device and since there is a dwell time for enabling such response to take place it is possible for the loom to operate at high speeds whilst ensuring positive and reliable operation of retaining selected heald rods 14.

Claims

1. A retention device for a heald rod which is reciprocated in a linear path, the retention device including a retention arm (40) having at one end a latch formation (51) for cooperating with said heald rod (14) and being hinged to a support block (23) so that the latch formation is movable between a latch position and a non-latch position, an electromagnet (22) having at least one pole (46) positioned adjacent to the retention arm (40), a pole piece (42) mounted on the retention arm (40) to be cooperative with said pole (46) of the electromagnet (22) and biasing means for biasing the retention arm (40) so as to be normally spaced from said pole (46), said retention arm (40) is attached to the support block (23) by a resilient portion (43), which defines the hinge connection and said biasing means, said arm comprises a resilient member (41) connected to the support block (23) and a rigid member (42) fixedly secured to the resilient member (41), the rigid member (42) defining said pole piece and latch formation.

2. A retention device according to claim 1, wherein the electromagnet has a first pole located near to the said latch formation and a second pole located adjacent the arm but further from said latch formation, the pole piece extending along the arm so as to be magnetically cooperable with both poles.

3. A retention device according to claim 1 or 2, wherein the pole piece has an extended portion which forms a hook so as to define said latch formation.