EP1334941B1

EP1334941B1 - A device for retaining the brake holder support in weft feeders

Info

Publication number: EP1334941B1
Application number: EP20030001429
Authority: EP
Inventors: Giovanni Pedrini
Original assignee: LGL Electronics SpA
Current assignee: LGL Electronics SpA
Priority date: 2002-02-01
Filing date: 2003-01-22
Publication date: 2005-03-30
Anticipated expiration: 2023-01-22
Also published as: ITTO20020023V0; DE60300425D1; CN100408738C; ITTO20020023U1; EP1334941A1; CN1435519A; DE60300425T2

Description

The present invention relates to a device for retaining the brake holder support in weft feeders for textile machines.
As is known, weft feeders comprise a stationary drum on which a swivel arm winds multiple turns of thread, which constitute a weft reserve. When requested by the loom, the turns unwind from the drum and feed said loom by passing through a braking means that controls the mechanical tension of the thread in order to keep it substantially constant. The braking means normally comprises a frustum-shaped body made of composite synthetic material, which is pushed elastically into frontal contact engagement against the drum by a brake holder support in order to engage elastically, for braking purposes, the thread that passes, in its unwinding motion, over the portion where the cylindrical surface blends with the front surface of the drum. The brake holder support comprises an annular support to which radial suspension springs are engaged at one of their ends, the opposite ends of said springs being coupled to the braking means at the smaller cross-section of its frustum-shaped body. As known from European patent EP 0826619 in the name of the same Applicant, the brake holder support, in order to adjust the static tension on the thread, is coupled to a slider, which is supported so that it can perform a rectilinear motion by a stationary arm that lies parallel to the axis of the drum. A female thread element is integral with the slider, and an adjustment screw engages therein; said adjustment screw is constituted by the threaded end portion of a pivot, which is provided with an adjustment knob, by means of which it is possible to turn the adjustment screw and cause precision movements of the slider and therefore of the brake holder support in order to adjust the static tension with which the brake acts on the drum and therefore the degree of braking applied by said brake to the thread. In order to facilitate cleaning and replacement and/or maintenance of the weft feeder, there is a pivot retention system that allows rapid disengagement of said pivot without actuating the knob; this leads to the movement of the brake holder support outwardly of the feeder and therefore to the movement of the brake away from the drum. For this purpose, the pivot is supported rotatably and so that it can perform an axial translational motion by a fixed bush integrally coupled to the stationary arm, and the end portion of the pivot lies inside a helical spring, which is accommodated in a fixed seat of the stationary arm and acts on the female thread element, actuating the slider and the brake holder support so as to move into a disengagement position. This movement is normally prevented by an annular bracket integrally coupled to an actuation lever, which is pivoted to the stationary arm at one of its ends and is subjected to the action of a spring which normally keeps the bracket engaged in a retention groove provided on the pivot. By acting on the lever, the bracket is disengaged from the groove and the entire adjustment system consequently performs a snap translational motion that places the brake in the disengagement position.
This system is not devoid of drawbacks, the first of which is that, in order to perform engagement and disengagement operations without too much difficulty, and due to the presence of coated regions, it is necessary to provide the coupling between the annular bracket and the retention groove with considerable slack, on the order of 0.5 mm, and this leads to evident inaccuracies in the adjustment of the braking system.
Another drawback of the known system is that it relies exclusively on the non-reversible nature of the screw-and-nut mechanism to fix the braking device in position, and this makes the device susceptible to unintentional movements of the adjustment knob that may occur for example during maintenance or cleaning of the various parts of the weft feeder.
The actuation lever, while making it easy to perform the release operation, also is susceptible to unintentional impacts which can lead to the unwanted disengagement of the brake and therefore to a need for repetition of the calibration operations.
The main object of the present invention is therefore to remove the above mentioned drawbacks by providing a device for retaining the brake holder support that allows greater precision in adjusting the braking means.
An object of the invention is to provide a device for retaining the brake holder support in which the braking position that is deemed optimal can be securely adjustable.
Another object of the invention is to provide a device for retaining the brake holder support that is free from risks of unwanted disengagement.
Another object of the invention is to provide said device for retaining the brake holder support so that it has a low cost and is simple to manufacture and can also be manufactured by means of equipment that is conventional in the field.
The above and other objects that will become better apparent hereinafter are achieved by the brake holder support having the features recited in claim 1, while the subordinate claims define other advantageous features.
The invention will now be described in greater detail and is illustrated by way of non-limitative example in the accompanying drawings, wherein:
Figure 1 is a partially sectional side view of a weft feeder with the device for retaining the brake holder support according to the invention;
Figure 2 is an enlarged-scale view of a detail of Figure 1, illustrating a cross-section of the device for retaining the brake holder support;
Figure 3 is a perspective view of the weft feeder, showing a partially sectional view of a detail of the retention device;
Figure 4 is a side view, similar to Figure 1, of the configuration of the device in the position for disengaging the brake holder support.
With reference to the above listed Figures, the weft feeder, generally referenced with 10, comprises a stationary base 11 and a stationary drum 12, on which a hollow swivel arm (not shown), rigidly coupled to a motor shaft (not shown) which is also hollow, winds multiple turns of thread F, which constitute a weft reserve RT. When requested by the loom (not shown), the turns unwind from the drum 12 and feed said loom, passing through a braking means that controls the mechanical tension of the thread F in order to keep it substantially constant. The nature of the braking means is not relevant to the present invention; however, reference is made to a known conical brake in order to simplify the description. Said brake is normally constituted by a continuous frustum-shaped body 15 made of composite synthetic material, which is pushed elastically into frontal contact engagement against the drum 12 by a brake holder support 17 in order to engage elastically, for braking purposes, the thread F that passes, in its unwinding motion toward a thread guiding ring G, over the portion 12b where the cylindrical surface 12a blends with the front surface 12c of the drum. The brake holder support 17 comprises an annular support, to which radial suspension springs such as 16 are engaged at one of their ends, the opposite end of said springs being coupled to the braking means at the smaller cross-section of its frustum-shaped body 15.
In a manner known per se, the brake holder support 17, in order to adjust the static tension on the thread, is coupled to a slider 18, which is supported, so that it can perform a rectilinear motion, by a stationary arm 19 that lies parallel to the axis of the drum 12. A female thread element 22 is rigidly coupled to the slider 18, and a screw engages therein to adjust the movements of the slider; said screw is constituted by the threaded end portion 23a of a pivot 23 to which an adjustment knob 24 is connected; by means of said adjustment knob, it is possible to turn the adjustment screw and produce precision movements of the slider 18 and therefore of the brake holder support 17 in order to adjust the static tension with which the brake 15 acts on the drum and therefore the degree of braking applied by said brake to the thread. The movements are indicated by an indicator 18a of the slider, which moves in a slot 13 of the stationary arm 19 along a graduated scale (not shown).
According to the invention, a system is provided for retaining the pivot 23, which can be adjusted in terms of axial slack with high precision and allows the braking position to be locked at its optimum value and to easily engage/disengage the brake holder support 17 without requiring the actuation of the knob 24. For this purpose, the pivot 23 is supported so that it can rotate and perform an axial translational motion in a stationary bushing 25, which is formed by the internal surface of a tubular body 20, which is integrally coupled to the stationary arm 19. By contrast, the end portion of the pivot 23b is rotatably housed in a centering hole 27. A slack-adjustment screw 26 is engaged in a threaded hole 14, which is formed radially in the tubular body 20, and is provided with a frustum-shaped tip 26a, which is normally engaged in a retention groove 21, which is shaped complementarily and is provided on the pivot 23.
By acting on the screw 26 it is possible to adjust the axial slack according to the requirements and reduce it to a few hundreds of a millimeter, greatly increasing the precision of the braking device. Moreover, once the ideal degree of braking has been found, the system can be locked by screwing in completely the screw 26, or by loosening the screw it is possible to move the brake holder support 17 away (Figure 4) in order to perform cleaning operations easily.
As obvious for a person skilled in the art, although the Figures show a slack-adjustment screw 26 of the Allen type, which as such requires an appropriate wrench in order to be adjusted, said screw can be replaced with other screws of a different type, so long as they end with the same frustum-shaped coupling profile, optionally connected to a knob which can be actuated manually without requiring any tool.
Moreover, it is sufficient to have a trapezoidal cross-section in either the end portion or the retention groove.
In practice it has been found that the invention fully achieves the intended aim, by providing a device for retaining the brake holder support that allows greater precision in adjusting the braking means.
Another advantage of the invention is that it provides a retention device in which it is possible to securely fix the braking position deemed optimum by tightening fully the screw 26.
Another advantage of the retention device according to the invention is that it is free from risks of unintentional disengagement.
Another advantage of the invention is that it provides a retention device that has a low cost, is simple to manufacture, and can be produced by means of equipment that is conventional in the field.

Claims

A device for retaining the brake holder support (17) in weft feeders for textile machines, wherein the brake holder support (17) is rigidly coupled to a slider (18), which is supported, so that it can perform a rectilinear motion, by a stationary arm (19) and is integrally provided with a female thread element (22) in which a screw for adjusting the movements of the slider is engaged, said screw being constituted by the end portion (23a) of a pivot (23), which is supported so that it can rotate and perform an axial translational motion in a bushing (25) rigidly coupled to said stationary arm (19), characterized in that it comprises a slack-adjustment element (26), which can perform a radial translational motion with respect to said pivot (23) and has an end portion (26a) that can be inserted in a retention groove (21) formed on said pivot (23), said end portion (26a) and/or said retention groove (21) having a substantially trapezoidal cross-section.
The device of claim 1, characterized in that said end portion (26a) and said retention groove (21) both have a substantially trapezoidal cross-section.
The device of anyone of claims 1 or 2, characterized in that said adjustment means is a screw (26), which is engaged in a threaded hole (14), which is formed radially in a portion that is rigidly coupled to said stationary arm (19) and is provided with a frustum-shaped point (26a) which forms said portion having a substantially trapezoidal cross-section.
The device of anyone of the preceding claims, characterized in that said bushing (25) is formed by the internal surface of a tubular body (20) rigidly coupled to said stationary arm (19), and in that said threaded hole (14) is formed in said bushing (25).
The device of anyone of the preceding claims, characterized in that it comprises an adjustment knob (24), which is connected coaxially to said pivot (23).
The device of anyone of the preceding claims, characterized in that said slack adjustment screw (26) is of the Allen type.
The device of anyone of the preceding claims, characterized in that the end portion (23b) of said screw for adjusting the movements of the slider (23a) is rotatably housed in a centering hole (27) formed in a transverse wall, which is integrally coupled to said stationary arm.