EP1091031A2

EP1091031A2 - Mechanism for actuating the sley and the belts of grippers in a weaving loom

Info

Publication number: EP1091031A2
Application number: EP00120738A
Authority: EP
Inventors: Stefano Nanni
Original assignee: Promatech SpA
Current assignee: Promatech SpA
Priority date: 1999-09-23
Filing date: 2000-09-22
Publication date: 2001-04-11
Also published as: ITMI991976A0; IT1313377B1; ITMI991976A1; EP1091031A3

Abstract

In a mechanism for actuating the sley (7) and the belts (N) of grippers (Z) in weaving looms, the continuous rotary movement of the main axis (A) of the loom is transferred, by means of an angular transmission comprising a bevel gear pair (2), to a secondary shaft (1) which is perpendicular thereto. A pair of conjugate radial cams (3) is keyed onto the secondary shaft (1) and causes, by means of an associated rocker arm (9), the movement of the gear wheel (D) driving the belts (N) of the grippers (Z). A spherical cam (4) is also axially mounted on the free end of said secondary shaft (1), said cam actuating a rocker arm (6), the fulcrum of which is directly connected to the shaft of the sley (7).

Description

The present invention relates to a mechanism for actuating the sley and the belts of grippers in a weaving loom.
It is known how, in weaving looms, there is a main motor, the axis of rotation of which is arranged transversely with respect to the loom, which motor imparts movement to the most important components of the loom by means of suitable mechanisms. No problems arise in connection with the components which must perform a continuous rotating movement about an axis parallel to the main axis of the loom; in this case, in fact, the necessary kinematic chains consist of simple combinations of gear wheels which are reasonably small in size and have an excellent transmission efficiency.
The question becomes more complex, however, when the components to be actuated have an alternating rotating movement, either with the axis parallel to the main axis, as in the case of the sley, or with an axis perpendicular to the main axis, as instead is the case with gear wheels which impart the movement to the belts of the grippers. In both these cases the kinematic chain is in fact very bulky and results in a considerable power consumption for operation thereof. It in fact normally envisages firstly the transmission of the movement from the main shaft to a secondary shaft parallel therewith, which therefore also performs a continuous rotating movement. Said secondary shaft is provided with a first pair of conjugate cams which engage with a first rocker arm, for conversion of the continuous circular movement into an alternating circular movement, about an axis parallel to the main axis, suitable for actuating the sley. A second pair of conjugate cams are also keyed onto said secondary shaft and engage with a second rocker arm, the movement of which, via a kinematic multiplication chain and then an angular transmission comprising a bevel gear pair, is converted into an alternating circular movement, about an axis perpendicular to the main axis, suitable for actuating the grippers.
An example of a kinematic chain of this type is illustrated in Fig. 1. In this figure it is possible to identify the main motor M of the loom, which rotatably drives the main shaft A of the loom and therefore the secondary shaft B via the pair of gear wheels G. A first pair of cams C1 is keyed onto the shaft B and, by means of a rocker arm L1 (only partially visible in the drawing), causes the alternating rotation of the shaft P of the sley. A second pair of conjugate cams C2 is also keyed onto the secondary shaft B and, by means of a second rocker arm L2 and a kinematic chain comprising a connecting-rod/crank assembly V, a train of gears T and an angular transmission R, causes the alternating rotation of the gear wheel D driving the belt N of one of the weft insertion grippers. A corresponding mechanism is normally arranged on the other side of the loom so as to provide bilateral actuation of the sley P as well as driving of the other loom gripper.
In addition to the drawbacks associated with the dimensions and low energy efficiency considered above, the mechanisms of the known type also have other disadvantages. In fact, the kinematic chains composed of gear wheels with an alternating rotary movement - such as those arranged between the second rocker arm and the gear wheel actuating the grippers - create noise-related problems when they are operated at the high speeds required for modern-day looms. In them, moreover, the wear of the gear wheels is much more rapid and the adjustment and the elimination of the slack represents an important part of maintenance of the loom. These problems are even more accentuated when the gear wheels performing a mutual alternating movement do not have parallel axes; the abovementioned angular transmission comprising a bevel gear pair is therefore particularly critical, especially due to the high speeds involved.
The object of the present invention is therefore that of providing a mechanism for actuating the sley and the grippers which is simplified compared to the known mechanisms and in particular which allows the number of gear wheels in the kinematic chain with an alternating rotary movement to be reduced drastically and is able to eliminate completely the presence of angular transmissions with an alternating rotary movement which, as seen above, are the main sources of drawbacks in the known mechanisms.
This object is achieved, according to the present invention, by means of a mechanism for actuating the sley and the belts of grippers in weaving looms, characterized in that the continuous rotary movement of the main axis of the loom is transferred, by means of an angular transmission comprising a bevel gear pair, to a secondary shaft which is perpendicular thereto and on which a pair of conjugate radial cams is keyed, said cams causing, by means of an associated rocker arm, the movement of the gear wheel driving the belts of the grippers, and in that a spherical cam is also axially mounted on said secondary shaft, said cam actuating a rocker arm, the fulcrum of which is directly connected to the shaft of the sley.
According to a characteristic feature of the invention, the rocker arm actuated by the pair of conjugate radial cams is connected, by means of a crank/connecting-rod assembly, to an oscillating toothed crown which meshes with an axial pinion of the gear wheel actuating the belts of the grippers.
The invention will in any case now be described in more detail, with reference to the accompanying drawings which illustrate a preferred embodiment thereof and in which:
Fig. 1 is a perspective view of a mechanism according to the known art for actuating the grippers and the sley;
Fig. 2 is a schematic plan view of the mechanism according to the present invention in which, for the sake of greater clarity, the assembly actuating the gear wheel driving the grippers is not shown;
Fig. 3 is a schematic side elevation view, in the direction of the arrow III of Fig. 2, of the same mechanism, in this figure also the assembly actuating the gear wheel driving the grippers not being shown; and
Fig. 4 is a schematic side elevation view, in the direction of the arrows IV according to Fig. 2, of the mechanism according to the present invention, complete with the assembly for actuating the gear wheel driving the grippers.
Fig. 3 shows in schematic form the basic elements of the mechanism for actuating the sley and the belts of the grippers according to the present invention. This mechanism consists of a secondary shaft 1 perpendicular to the main shaft A or - which is the same thing - to a shaft branched from the latter and parallel thereto. The shaft 1 receives its movement from the shaft A via a bevel gear pair 2 and therefore performs a continuous rotary movement.
Two radial cams 3 are keyed onto the secondary shaft 1 in a known manner, while a spherical cam 4 is fixed, endwise, to the end of said shaft. The spherical cam 4 is provided with two rolling tracks, i.e. an outer track 4e and inner track 4i, on which rollers 5e and 5i, i.e. an outer roller and inner roller, of a rocker arm 6 provided with a counterweight 6a travel. As schematically shown in Fig. 2, the fulcrum of the rocker arm 6 is rigidly fixed to the axis of rotation P of the sley 7 which supports the reed 8 to which the desired alternating oscillating movement about the axis P, parallel to the main shaft A of the loom, is therefore imparted in a direct manner.
The radial cams 3 co-operate, in a manner known per se, with a rocker arm 9 comprising rollers, as illustrated in Fig. 4. Owing to the fact that the kinematic chain of the present invention is based on an axis perpendicular to the main axis A, instead of parallel thereto as was the case in the prior known art, also the oscillating movement of this second rocker arm may be used immediately and directly to impart the alternating rotary movement to the gear wheel D driving the belt N of the grippers Z. This system comprises, in fact, the rocker arm 9 which converts the continuous rotary movement of the conjugate cams 3 with which it is engaged into an alternating rotary movement; this movement is then transmitted to a crank 10 which is rigidly associated with the fulcrum of the rocker arm 9. The free end of the crank 10 then causes in turn the oscillating movement, by means of a connecting rod 11, of the vertex of a toothed sector 12 pivotably mounted on the loom at 13. Finally, the toothed crown 12a of the sector 12 engages with a pinion 14 which is integral and coaxial with the hub 15 of the gear wheel D. The desired multiplication ratio between the oscillating movement of the rocker arm 9 and that of sector 12 is obtained by adjusting the position of the base of the connecting rod 11 on the crank 10, while the choice in the position of the fulcrum 13 of the sector 12 determines the desired multiplication ratio between the travel of the connecting rod 11 and the much greater travel of the toothed crown 12a, thereby eliminating completely the train of gears provided for this purpose in the mechanisms of the known type, which is replaced by the single coupling between the toothed crown 12a and the pinion 14 of the gear wheel D.
As emerges clearly from the above description, the actuating mechanism according to the present invention therefore consists of a single secondary shaft - the shaft 1, which is arranged perpendicularly with respect to the main shaft A - and is entirely devoid of angular transmissions between shafts performing an alternating movement; it therefore has minimum dimensions, a high degree of compactness and an optimum transmission efficiency. The actuating mechanism according to the present invention may therefore be used with particular success both in an asymmetrical arrangement on one side only of the loom, where the height of the loom is low, and in a symmetrical arrangement - in which the said mechanism is duplicated and symmetrically arranged on both sides of the loom, as illustrated in Fig. 2 - where the height of the loom is such as to require bilateral operation of the sley 7 in order to avoid possible misalignment thereof during beating-up by the reed 8. With the actuating mechanism according to the present invention, used in the symmetrical version, the sley may have a very lightweight structure, to the advantage of the maximum speeds which can be achieved, while maintaining limited lateral dimensions of the loom owing to the compactness of the said mechanism.
The actuating mechanism according to the present invention is also able to achieve an excellent balance between the internal stresses of the various components of the mechanism, such as to minimise the stresses transmitted to the support bearings of the mechanism which are fixed to the loom structure. The inclination of the helix of the bevel gear pair 2 may in fact be designed so that the component F - parallel to the shaft 1 - of the force exchanged in the gearing has a value equal to the minimum value assumed by the component S of the variable force exchanged in the engagement between the spherical cam 4 and the rollers 5 of the rocker arm 6. In this way, the resultant of the forces S and F will never have an excessively high value and moreover will always have the direction of the force S, thus avoiding in the most absolute manner any possible longitudinal oscillation or vibration of the shaft 1.
It should also be noted that in the embodiment comprising the symmetrical arrangement shown in Fig. 2, the components G - along the main shaft A - of the forces exchanged in the bevel gear pairs 2 cancel out each other, thus avoiding the presence of an unbalanced axial load on said shaft which must be transmitted to the support bearings of the said shaft.
Finally, engagement of the rollers 5 of the rocker arm 6 with the spherical cam 4 should preferably occur with a predefined preloading force. As a result, in fact, it is possible to achieve always a contact force between rollers and cam which is greater than zero and thereby eliminate any problem of knocking of these elements and therefore noisiness of the mechanism. Preloading of the rollers 5 is achieved, in a manner known per se, by means of an eccentric pin on the outer roller 5b, or by using rollers 5e and 5i of different sizes or, finally, by axially displacing the spherical cam 4 with the insertion of suitable spacers.
The form of the lateral surface of the rollers 5 must also be designed with particular care. Since, in fact, the rolling tracks of the rollers 5 on the cam 4 are inclined with respect to the axis of the shaft 1, the peripheral speed of the cam 4 is obviously variable at different points of the track simultaneously making contact with each roller 5. In order to avoid, therefore, excessive slipping between part of the lateral surface of the rollers and the cam, the lateral surface of the said rollers is shaped so as to have a convex instead of a cylindrical profile; in this way, in fact, the area of contact between roller and cam is an elliptical area having its greater axis - albeit with smaller dimensions - arranged tangentially with respect to the cam such that the problem of partial slipping between these components in relative movement is greatly reduced.
From the above description it is obvious how the present invention has fully achieved the pre-set object. The mechanism according to the present invention is in fact extraordinarily compact and is able to achieve direct actuation both of the sley and of the gripper belts, eliminating entirely the presence of angular transmissions between gearings with an alternating rotary movement - the sole angular transmission being in fact that, with a continuous rotary movement, between the main shaft and the secondary shaft - and reducing the number of coupling between gearings with an alternating rotary movement to only one, i.e. that between the toothed sector and pinion of the gear wheel driving the gripper belts. This mechanism, owing to its features, is therefore particularly suitable for use in high-speed looms, thus ensuring an excellent performance, a high degree of compactness and a reduced noise level.

Claims

Mechanism for actuating the sley and the belts of grippers in weaving looms, characterized in that the continuous rotary movement of the main axis of the loom is transferred, by means of an angular transmission comprising a bevel gear pair, to a secondary shaft which is perpendicular thereto and on which a pair of conjugate radial cams is keyed, said cams causing, by means of an associated rocker arm, the movement of the gear wheel driving the belts of the grippers, and in that a spherical cam is also axially mounted on said secondary shaft, said cam actuating a rocker arm, the fulcrum of which is directly connected to the shaft of the sley.
Actuating mechanism according to Claim 1, in which the rocker arm actuated by the pair of radial cams is connected, by means of a crank/connecting-rod assembly, in the vicinity of the vertex of a toothed-crown sector which is pivotably and centrally mounted on the loom and which meshes, via said toothed crown, with an axial pinion of the gear wheel driving the belt for the grippers.
Actuating mechanism according to claim 1) or 2), in which the inclination of the helix of said angular transmission comprising a bevel gear pair is such that the component - along the secondary shaft - of the meshing force of said bevel gear pair has a value which is substantially equal to and a direction opposite to the component - in the same direction - of the minimum value of the variable force of engagement between said spherical cam and the rocker arm co-operating therewith.
Actuating mechanism according to claim 1) or 2), in which engagement between said spherical cam and the rollers of the rocker arm co-operating therewith occurs with a predefined preloading force.
Actuating mechanism according to claim 1) or 2), in which the lateral surface of said rollers is a convex surface.
Mechanism for actuating the sley and the belts of grippers in weaving looms, comprising a pair of actuating mechanisms as described in any one of the preceding claims, symmetrically arranged on both sides of the loom, each of said mechanisms actuating one end of the sley and a gear wheel driving the belt of one gripper.