Four-Position open-shed jacquard machine.

Abstract: Shed forming mechanism for a jacquard machine, comprising two hooks (1), (2) both of which can be held in a bottom and a top position and through upwardly and downwardly movable raising means (13-16) can be taken out of each position into the other position, a selecting device (7-12; 17-20) provided for maintaining or allowing the raising means to change each position of each hook as desired, and a pulley device (21, 22, 26) working together with the hooks (1), (2) provided for bringing warp threads to four different heights (a, b, c, d), whereby the height of the warp threads is changed by a change in the position of each respective hook (1), (2) in proportion to the change of height (29) of the hook, and whereby the difference in height (29) between the top and the bottom position is greater for one hook (2) than for the other hook (1).

Description: This invention relates to a shed forming mechanism for a jacquard machine, comprising two hooks both of which can be held in a bottom and a top position and through upwardly and downwardly movable raising means can be taken out of each position into the other position, a selecting device provided for maintaining or allowing the raising means to change each position of each hook as desired, and a pulley device working together with the hooks provided for bringing warp threads to four different heights, whereby the height of the warp threads is changed by a change in the position of each respective hook in proportion to the change of height of the hook. Weaving with a weaving machine is principally effected by repeatedly forming a shed between warp threads and inserting into this shed one or more weft threads running in transverse direction. The successive sheds are formed by, in each case prior to every pick (i.e. the simultaneous insertion of one or more weft threads) and in accordance with the properties of the fabric to be made, bringing various warp threads to different heights. In order to bring the warp threads automatically to the desired successive heights jacquard machines are provided with shed forming mechanisms. Depending on the properties of the fabric to be made the shed forming mechanism used must be capable of bringing the warp threads to two, three, four or more different positions. This invention in particular relates to a shed forming mechanism for a jacquard machine which is provided for bringing the warp threads to four different heights. Such a jacquard machine is called a four-position jacquard machine. This invention more especially relates to a shed forming mechanism for a four-position open-shed jacquard machine. With a four-position jacquard machine which is provided for operating according to the open-shed principle the four positions of the warp threads are achievable with each pick. This signifies that a warp thread in each case prior to every pick and irrespective of the height at which this warp thread is can as desired be held at the same height or can be brought to the first, the second, or the third of the three other heights. Four-position jacquard machines exist with the characteristics mentioned in the first paragraph of this specification. The Belgian improvement patent no. 529 019 describes (with reference to figure 1) such a shed forming mechanism with a first and a second hook which can be held in a bottom and a top position, a first pulley element with two wheels which is suspended from the second hook, a second pulley element which is connected to a fixed part of the mechanism, and a pulley cord which is attached by one extremity to the first hook, is successively passed round a wheel of the second pulley element and a wheel of the first pulley element, and is connected by the other extremity to warp threads via a harness cord. This mechanism can operate according to the open-shed principle as every jacquard hook operates according to this principle, in other words if each position of each hook can be held or be changed prior to every pick. If the first hook is brought from the bottom to the top position and is moreover brought up over a well-defined height (H), then the harness cord is raised over the same height (H). One and the same raising (H) of the second hook will result in a raising (2 x H) of the harness cord over twice the aforementioned height. If both hooks are raised together over this height (H) then the harness cord is raised over a height (3 x H) which is three times as great. This device is therefore capable of bringing the warp threads to four different heights (0, H, 2 x H, 3 x H), respectively by placing both hooks in their bottom position, only the first hook in its top position, only the second hook in its top position, and both hooks in their top position. With this mechanism the pulley cord runs round two wheels which entails quite an amount of wear and tear and causes breakage of the pulley cord. Furthermore such a mechanism comprises quite a number of parts through which it is voluminous and costly. In BE-529 019 a mechanism is also described (with reference to fig. 2) with two sets of two complementary hooks. The hooks of each set are connected to each other by a respective cord which is passed under the upper wheel of respectively a first and second pulley element with two wheels. A third pulley element is connected to a fixed part. A pulley cord is attached by one extremity to the first pulley element, successively passed round a wheel of the third pulley element and a wheel of the second pulley element and by the other extremity connected to warp threads via a harness cord. Here four positions can also be obtained according to the open-shed principle. This mechanism also comprises many parts - four hooks and three pulley elements - and is therefore very voluminous and costly. Here the pulley cord also runs round two wheels resulting in great wear and tear and breakage of the pulley cord. In EP-0 665 312 a shed forming mechanism is described with two sets of two complementary hooks, two electromagnetic selection elements, two pulley elements and two reversal wheels in order to create a four-position open-shed jacquard machine. A raising (H) of one of the hooks of the left-hand set causes a raising (2 x H) of the harness cord (fig. 1) which is twice as great. One and the same raising (H) of one of the hooks of the right-hand set causes a raising (H) of the harness cord over the same height. One and the same raising (H) of both hooks causes a raising (3 x H) of the harness cord which is three times as great. This device can therefore generate four positions. This mechanism has however a large number of parts and is therefore rather costly. The lower pulley cord is passed round a large number of wheels through which this is subject to great wear and tear. Furthermore two sets of two complementary hooks are provided, through which the jacquard machine becomes rather large in dimensions. This is a great disadvantage, in particular for carpet weaving with three weft insertion means (e.g. grippers). For this purpose a large number - up to 12 0000 - of usable harness cords must indeed be capable of being brought to four different heights. The object of this invention is to provide a shed forming mechanism for a four-position jacquard machine without the above mentioned disadvantages of the known mechanisms. This object is achieved by providing a shed forming mechanism with the characteristics mentioned in the first paragraph of this specification, whereby the height difference between the top and the bottom position is greater for one hook than for the other hook. Because of the fact that the height difference between both positions is different for the two hooks, and since changing the height of a hook results in a proportional change in the height of the warp threads, a four-position mechanism can be obtained by passing the height changes from both one and the other hook on to one and the same cord. This is for example possible by means of one pulley element. If both hooks are in their bottom position a warp thread working together with the mechanism is in a first position. By only bringing the hook with the smaller height difference between both positions into the top position the aforementioned warp thread comes up to a second height. By only bringing the hook with the greater height difference between both positions into the top position that warp thread comes up to a third height. By bringing both hooks into their top position the warp thread comes up to a fourth height, since the change in height of the warp thread which is the result of the raising of one hook and the change in height of the warp thread which is the result of the raising of the other hook are combined. This mechanism can therefore be implemented with less parts than the known mechanisms. A mechanism according to this invention can consequently be made for a lower cost price than the existing mechanisms. Furthermore a jacquard machine with shed forming mechanisms according to this invention can also be built much more compactly than the known mechanisms. Because of the fact that each mechanism also takes up less room large numbers of shed forming mechanisms can be provided next to each other in one and the same jacquard machine without any problem. Moreover the mechanism can be so implemented that the pulley cord only has to pass round one wheel, so that the wear and tear of the pulley cord can be appreciably limited. According to this invention a very advantageous shed forming mechanism is obtained if it is so implemented that the difference in height between the top and the bottom position for one hook is almost twice as great as for the other hook. Because of this between the first and the second height of the warp threads, between the second and the third height, and between the third and the fourth height of the warp threads in each case one and the same difference in height is obtained. The shed forming mechanism according to this invention is preferably so implemented that each hook can be engaged by each of two in opposition upwardly and downwardly movable blades so that the position of each hook can be changed during every half movement cycle of the blades. Because of this, working according to the open-shed principle, twice one or more weft threads can be inserted per full movement cycle of the blades. The mechanism according to this invention has a preferred embodiment with a selecting device which is provided in order to move each hook brought into the bottom position either up and down as desired in a non-selection position in which the hook cannot be engaged by a raising means, or to hold it at a fixed height so that the hook takes on a pre-selection position at this fixed height in which the hook is ready to be taken along by an upward moving raising means to the top position, while each hook in a non-selection position can be retained at the fixed height for each cycle of its upward and downward movement in order to bring the hook into the pre-selection position. Such a selecting device operates very efficiently and is quite simple. In a particularly preferred embodiment the selecting device comprises at least one upwardly and downwardly movable motive element provided with at least one wing with a sloping top surface, and each hook comprises at least one supporting element provided in order to rest on the sloping top surface of a wing of a motive element in order to perform the aforementioned up and down movement in a non-selection position, so that each hook which, being in a pre-selection position, arrives with a supporting element on the sloping top surface of a wing, slides on this sloping surface to a non-selection position. Changing the position of each hook, from a pre-selection position to a non-selection position is because of this effected automatically by releasing the hook. The means provided for that purpose are very simple and inexpensive. Furthermore the mechanism can also be so implemented that each hook is provided with a protrusion while at least one motive element comprises at least one wing with a sloping underside, so that each hook which, being in a non-selection position, is held at the fixed height, is moved during a downward movement of the motive element to a pre-selection position because of the fact that the aforementioned sloping underside presses against the aforementioned protrusion. Changing the position of each hook, from a non-selection position to a pre-selection position, is because of this effected automatically by holding the hook at the fixed height. The means provided for that purpose are likewise very simple and inexpensive. Each hook is preferably provided in order to be retained at more than two different heights. This is particularly advantageous if a so-called progressive shed is to be formed. Since the hooks of different shed forming mechanisms have moreover to be capable of being brought to different top and bottom positions. In a particularly efficient embodiment the selecting device for each hook comprises a holding means that can be brought into a holding position or into a non-holding position as desired, while each hook comprises a series of teeth provided one above the other, which can hook into a holding means brought into the holding position. In a special embodiment of the shed forming mechanism according to this invention for each hook a set of two mutually in opposition upwardly and downwardly movable blades, and a set of two motive elements mutually movable in opposition to and in phase with a respective blade are provided, while these blades and motive elements are so provided that each hook when in its bottom position which is not held at a fixed height, is alternately moved up and down by one and the other motive element of its set in a non-selection position at a rate which is almost twice the rate of the up and down movement of each blade. This makes it possible to place each hook in a pre-selection position prior to each upward movement of a blade working together with this hook. The mechanism according to this invention is in one of its most preferred embodiments provided with a pulley device which comprises a pulley element with a first and a second wheel, while the hooks are connected to each other by a first cord that is passed round a first wheel of the pulley element, and while a second cord is passed round the second wheel of the pulley element, on the one hand is attached to a fixed part of the mechanism, and on the other hand is provided for the connection to a harness cord on at least one warp thread. The second cord is only passed round one wheel and is therefore less subject to wear and tear. This invention is further explained in the following detailed description of an embodiment thereof. This however in no way signifies that the invention can be considered as being solely restricted to this embodiment. In this specification reference is made to the figure attached hereto, Fig. 1 in which a side view of the specified mechanism is schematically presented. This shed forming mechanism comprises two identical, narrow, elongated parts (1), (2), called hooks, which extending almost in vertical direction, can be held in a top and a bottom position, and can be brought from one position to the other position by means of up and down moving blades (13, 14), (15, 16). On the flanks of the hooks (1), (2) directed towards each other a series of sawtooth-shaped protrusions (3), (4) are provided, which extend according to the longitudinal direction of the hook over a specific length of the hook from the upper extremity of the hook. On the lower extremity of each hook (1), (2) a respective extremity of one and the same cord (21) is attached so that both hooks are connected to each other by means of the cord (21). Furthermore each hook also comprises a supporting element (5), (6) that forms a protruding nose (40) on both sides of the hook, of which the underside slopes downwards from the flank of the hook. The shed forming mechanism furthermore also comprises a pulley element (22) that principally consists of two wheels (24), (25) which are rotatably attached one above the other to one and the same body (23). The cord (21) that connects both hooks (1), (2) to each other is passed round the upper wheel (24) of the pulley element (22) so that the down-hanging loop formed by the cord (21) carries the pulley element. A pulley cord (26) is attached by one extremity to a fixed part (28) of the mechanism, and is passed round the lower wheel (25) of the pulley element (22). The free part of the pulley cord (26) hanging down from the wheel (25) is connected to a harness cord (27), which in turn is provided for bringing one or more warp threads (not shown in the figure) upwards or downwards. On both sides of each hook (1), (2) an almost horizontally disposed blade (13, 14), (15, 16) is provided. The two blades of each hook can move up and down mutually in opposition along the opposite flanks of the hook. Each blade (13, 14) of one hook (1) moreover moves in phase with a respective blade (15), (16) of the other hook (2). Each blade has a lower edge (41) along the side of the hook (1), (2) working together therewith which slopes upwards in the direction of the hook so that the lower part of each blade has a hook-shaped profile. The edge (41) is provided for supporting the hook working together with the blade. The underside of the nose (40) of the hook directed towards the edge then rests on the edge (41), and the hook is engaged by the blade. The blades (13, 14), (15, 16) of each hook (1), (2) are provided in order to move up and down mutually in opposition between an upper and a lower dead point. The vertical distance (29) between the upper and the lower dead point of the blades is called "the raising" of the blades. The blades (15, 16) of the right hook (2) have a raising (29) which is twice the raising (29) of the blades (13, 14) of the left hook (1). Each hook (1), (2) can be taken along by each of its blades (13, 14), (15, 16) from its bottom position to its top position, or vice versa, during the upward or downward movement of these blades. Between the two positions of each hook (1), (2) there is a difference in height which is almost equal to the raising (29) of the blades which can engage this hook. On top between the two hooks (1), (2) a selector (7), (8) is provided for each hook. Each selector has a holding means (9), (10) underneath that can as desired be placed in a holding position (the right holding means (10) in the figure) or in a non-holding position (the left holding means (9) in the figure) by means of an electromagnetic element that can be actuated in order automatically to take on the desired successive positions. Each holding means (9), (10) has a lower hook-shaped part that is provided in order - when the holding means is in the holding position - to retain a respective hook by hooking under one of its sawtooth-shaped protrusions (3), (4). By placing a holding means in the non-holding position it moves away from the hook (1), (2) so that the sawtooth-shaped protrusions (3), (4) of the hook can no longer rest on the hook-shaped part of the holding element. Each hook (1), (2) can with each sawtooth-shaped protrusion (3), (4) rest on a holding means (9), (10) placed in the holding position, so that each hook can be retained at a rather large number of different heights (as many as the number of sawtooth-shaped protrusions). Because of this it is possible to use the mechanism according to this invention for forming a so-called progressive shed, whereby the hooks of different mechanisms, depending on the position of the mechanism in the jacquard machine, must be capable of being retained at different heights. On both sides of each hook two motive elements (17, 18), (19, 20) are also provided which are movable in opposition up and down along the hook. The motive elements move up and down with an amplitude (z) which is much smaller than the raising (29) of the blades (13, 14) of the left hook. Each motive element moves in phase with a respective blade and is under that blade at every moment during its movements. The upper dead point of each motive element almost corresponds to the lower dead point of the blades. Each motive element has two wings (30) extending sideways in opposite directions which in the direction of their free extremity have an upwardly sloping top surface (31) and an upwardly sloping underside (32). The wing (30) directed towards a hook is provided for supporting this hook. The underside of the nose (40) of the hook directed towards the edge then rests on the aforementioned top surface (31) of this wing (30), and the hook is engaged by the motive element. In its bottom position each hook (1), (2) can either be moved up and down by its two motive elements (17, 18), (19, 20) (like the left hook (1) in the figure), of be retained at a fixed height by the holding element (9, 10) of its selector (7, 8) (like the right hook (2) in the figure). When the hook is taken along by its motive elements (17, 18), (19, 20) it alternately rests with its nose (40) which (in the figure) extends from the left flank of the hook on the motive element (17), (19) which is on the left of the hook (1), (2), and with its nose (40) which extends from the right flank on the motive element (18), (20) which is on the right of the hook (1), (2). Approximately halfway through the downward movement of each motive element (17, 18), (19, 20) a hook (1), (2) taken downwards by the motive element is taken back upwards by the other motive element. The frequency of motion of the hook is therefore twice the frequency of motion of the blades (13, 14), (15, 16) and of the motive elements (17, 18), (19, 20), and it moves up and down with an amplitude which is almost half the vertical distance (z) between the upper and lower dead point of the motive elements (13, 11), (15, 16). A hook taken along by a motive element (17, 18), (19, 20) is in a non-selection position because of the fact that the hook each time slides down as far as possible with its nose (40) on to the sloping top surface (31) of the wing (30) of the motive element, so that the opposite nose (40) remains out of reach of the edge (41) of the blade moving along that side of the hook. In order to bring a hook (1), (2) which is in its bottom position out of a non-selection position into a pre-selection position the selector (7), (8) is actuated in order to bring the holding element (9), (10) of the hook into the holding position at the time that the hook (1), (2) is brought by one of its motive elements (17, 18), (19, 20) approximately to the upper dead point of its up and down movement. Because of this the hook (1), (2) with a sawtooth-shaped protrusion (3), (4) will be able to hook on to the hook-shaped extremity of this holding means (9), (10), and remain suspended at a fixed height while the motive element that brought the hook up moves downwards. The sloping underside (32) of the wing (30) of this motive element (17, 18), (19, 20) now presses against a protrusion (11), (12) provided on the hook (1), (2) through which the hook is pushed away from the motive element. Because of this the opposite nose (40) of the hook (1), (2) can be taken upwards by the edge of the opposite blade which is under this nose (40) at that time. When a blade (13, 14), (15, 16) is approximately in its upper dead point a hook (1), (2) taken along by it can be retained by its holding element (9), (10) while the blade moves back downwards. The hook is then in its top position. When the holding element (9), (10) is placed in its non-holding position the hook (1), (2) will rest on the blade and it will be taken back down. If the holding element (9), (10) remains in the non-holding position the hook (1), (2) arrives with a nose (40) on one of its motive elements (17, 18), (19, 20) and it slides downwards on the sloping top surface (31) of the wing (30) until it is in the non-selection position. If the holding element (9), (10) on the other hand is placed in the holding position the hook continues to be retained, through which it cannot slide down on the sloping top surface (31) of the wing (30), and remains in the pre-selection position, ready to be taken upwards by the next upward movement of a blade. Each hook (1), (2) can therefore after every half movement cycle of the blades (13, 14), (15, 16) be in a bottom and a top position as desired. This mechanism can therefore operate according to the open-shed principle. If both hooks (1), (2) are in their bottom position (as shown in the figure), then the harness cord (27) is at a first height (I), through which the warp threads (not shown in the figure) come into a first position. When the left hook (1) is in its top position - a vertical distance (h) higher than in its bottom position - while the right hook (2) is in its bottom position, the harness cord (27) is at a second height (II), one and the same vertical distance (h) higher than the first height (I). The warp threads then come into a second position. When the right hook (2) is in its top position - a vertical distance (2 x h) higher than in its bottom position - while the left hook (1) is in its bottom position, the harness cord (27) is at a third height (III), a vertical distance (2 x h) higher than its bottom position. Because of this the warp threads come into a third position. When both hooks (1), (2) are in their top position, the harness cord (27) is at a fourth height (IV), a vertical distance (3 x h) higher than in its bottom position. With that a fourth position of the warp threads is obtained. With this machine the warp threads can therefore be placed as desired in one of four possible positions prior to every insertion of weft threads. This mechanism can therefore be used for the implementation of a four-position open-shed jacquard machine. This four-position jacquard machine can be built compactly and only has two hooks and one pulley device, whereby the pulley cords in each case only run round one reversal wheel just as with the known three-position devices. There are therefore fewer pulley cords subject to wear and tear and the jacquard machine can be built for a lower cost than the known four-position open-shed mechanisms.

Claims: Shed forming mechanism for a jacquard machine, comprising two hooks (1), (2) both of which can be held in a bottom and a top position and through upwardly and downwardly movable raising means (13-16) can be taken out of each position into the other position, a selecting device (7-12; 17-20) provided for maintaining or allowing the raising means to change each position of each hook as desired, and a pulley device (21, 22, 26) working together with the hooks (1), (2) provided for bringing warp threads to four different heights, whereby the height of the warp threads is changed by a change in the position of each respective hook (1), (2) in proportion to the change of height (29) of the hook, characterised in that the difference in height (29) between the top and the bottom position is greater for one hook (2) than for the other hook (1). Shed forming mechanism for a jacquard machine, according to claim 1, characterised in that the difference in height (29) between the top and the bottom position for one hook (2) is almost twice as great as for the other hook (1). Shed forming mechanism for a jacquard machine, according to claim 1 or 2, characterised in that each hook (1), (2) can be engaged by each of two in opposition upwardly and downwardly movable blades (13, 14), (15, 16) so that the position of each hook can be changed during every half movement cycle of the blades (13-16). Shed forming mechanism for a jacquard machine, according to any of the preceding claims characterised in that the selecting device (7-12; 17-20) which is provided in order to move each hook (1), (2) brought into the bottom position either up and down as desired in a non-selection position in which the hook cannot be engaged by a raising means (13-16), or to hold it at a fixed height so that the hook takes on a pre-selection position at this fixed height in which the hook is ready to be taken along by an upward moving raising means (13-16) to the top position, and that each hook (1), (2) in a non-selection position can be retained at the fixed height for each cycle of its upward and downward movement in order to bring the hook into the pre-selection position. Shed forming mechanism for a jacquard machine, according to claim 4 characterised in that the selecting device (7-12; 17-20) comprises at least one upwardly and downwardly movable motive element (17-20) provided with at least one wing (30) with a sloping top surface (31), and that each hook (1), (2) comprises at least one supporting element (5), (6) provided in order to rest on the sloping top surface (31) of a wing (30) of a motive element (17-20) in order to perform the aforementioned up and down movement in a non-selection position, so that each hook (1), (2) which, being in a pre-selection position, arrives with a supporting element (5), (6) on the sloping top surface (31) of a wing (30), slides on this sloping surface (31) to a non-selection position. Shed forming mechanism for a jacquard machine, according to claim 4 or 5 characterised in that each hook (1), (2) is provided with a protrusion (11), (12), and that at least one motive element (17-20) comprises at least one wing (30) with a sloping underside (32), so that each hook (1), (2) which, being in a non-selection position, is held at the fixed height, is moved during a downward movement of the motive element (17-20) to a pre-selection position because of the fact that the aforementioned sloping underside (32) presses against the aforementioned protrusion (11), (12). Shed forming mechanism for a jacquard machine, according to any of the preceding claims characterised in that each hook (1), (2) is provided in order to be retained at more than two different heights. Shed forming mechanism for a jacquard machine, according to claim 7 characterised in that the selecting device (7-12; 17-20) for each hook (1), (2) comprises a holding means (9), (10) that can be brought into a holding position or into a non-holding position as desired, and that each hook (1), (2) comprises a series of teeth (33) provided one above the other, which can hook into a holding means (9), (10) brought into the holding position. Shed forming mechanism for a jacquard machine, according to claim 4 up to and including 8 characterised in that for each hook (1), (2) a set of two mutually in opposition upwardly and downwardly movable blades (13-14), (15-16), and a set of two motive elements (17, 18), (19, 20) mutually movable in opposition to and in phase with a respective blade (13-14), (15-16) are provided, that these blades and motive elements are so provided that each hook (1), (2) when in its bottom position which is not held at a fixed height, is alternately moved up and down by one (17), (19) and the other motive element (18), (20) of its set in a non-selection position at a rate which is almost twice the rate of the up and down movement of each blade. Shed forming mechanism for a jacquard machine, according to any of the preceding claims, characterised in that the pulley device (21, 22, 26) comprises a pulley element (22) with a first (24) and a second wheel (25), that the hooks (1), (2) are connected to each other by a first cord (21) that is passed round a first wheel (24) of the pulley element (22), and that a second cord (26) is passed round the second wheel (25) of the pulley element (22), on the one hand is attached to a fixed part (28) of the mechanism, and on the other hand is provided for the connection to at least one warp thread.

Inventors: DEWISPELAERE ANDRE, DEWISPELAERE, ANDRE, Dewispelaere, André
Applicants: WIELE MICHEL VAN DE NV, N.V. MICHEL VAN DE WIELE
Application year: 1998
Main classification: D03C3
IPC codes: D03C3