A composite return spring for heddles of jacquard, verdol and similar type textile looms

Abstract

 A composite return spring for heddles of textile looms, consisting of two helical springs (1,2) made of steel wire which are connected in series to each other and have different lengths and cross sections, the wire of the shorter spring (1) having a cross section 5 to 50% larger than the wire of the longer spring (2).

Description

[0001] The present invention relates to the return springs for heddles being employed in the harnesses of the textile machines of Jacquard type, Verdol type and the like; particularly, it relates to a composite spring having a higher tensile strength.

[0002] It is known that in the mechanical looms of the Jacquard type or Verdol type the heddles are subjected to a frantic reciprocating motion under the action of suitable return resilient elements which once consisted of ties in synthetic or natural rubber. The choice of this material was due to the fact that only by this it was possible to obtain return resilient elements having both load bearing and flexibility properties suitable to this purpose. But rubber ties have been with time replaced by steel springs, as these have the capability to maintain almost unchanged the load properties deriving from the high operation ratings reached in the modern textile machines.

[0003] It is also known that, due to the helical shape of the steel springs, these are manufactured by means of a very thin wire as otherwise the load and flexibility properties necessary for this particular use would not be obtained. Such springs are subjected to both high lengthwise and crosswise stresses which unavoidably involve the fatigue failure of the springs themselves, thereby impairing in such a way the quality of the fabric produced by the loom.

[0004] Researches made on purpose revealed that the crucial area where more frequently the fatigue failures occur is located near the spring anchoring point, and particularly in an area located about 10÷30 mm apart from said anchoring point. In fact, just in that area the lengthwise and crosswise stresses intersect, and hence they add to each other, the crosswise ones being extremely dangerous as being due to resonances.

[0005] Thus the object of the present invention is to provide a return spring for heddles, which is characterized by a higher tensile strength in the above described area. Such an object is attained, according to the present invention, by a spring characterized in that it consists of two helical springs made of steel wire which are connected in series to each other and have different lengths and cross sections, the wire of the shorter spring having a cross section 5 to 50%, and preferably 18 to 27%, larger than the wire of the longer spring.

[0006] The composite spring according to the present invention has the advantage of a tensile strength which is at least double compared to that of the presently used conventional springs.

[0007] The composite spring according to the present invention has the further advantage of reducing resonances, as it substantially varies the ratio between the spring natural frequency and the loom operating frequency. In fact, it is known that, by varying such ratio, the resonance is reduced and therefore also the crosswise stresses cooperating in a decisive way to the damaging of the operating springs are reduced.

[0008] These and other advantages of the composite spring according to the present invention will be clear to those skilled in the art from the following detailed description of one embodiment thereof reference being made to the annexed drawings in which:

Figure 1 shows a sectional view of a composite spring according to the present invention; and

Figure 2 shows a sectional view of a composite spring wherein the two component springs are connected to each other in a different way.

[0009] Referring to Fig.1, the composite spring according to the present invention essentially consists of two helical springs 1 and 2 connected in series to each other. The spring 1 is made of a steel wire having a 0,25 mm cross section, while spring 2 is made of a steel wire having a 0,20 mm cross section, i.e. approximately 20% smaller than the wire section of spring 1. The length of spring 2 is chosen as a function of the heddle to which it must be applied, generally said length being approximately 2/3 of the spring whole length. The length of spring 1 is instead shorter, and in the embodiment herein shown it is 10 cm. Such length depends not only upon the amplitude of the crucial zone in which the failures of the known springs mainly occur, but also upon the final elastic resultant of the composite spring.

[0010] The spring 1 has, at its external end, an eyelet for joining to the anchoring point. The spring 1 has, at its opposite end, a contracted portion 3 for joining spring 2. The spring 2 has a corresponding bell-shaped extended portion 4 cooperating with the contacted portion 3 for joining the two springs. In this embodiment spring 2 can be telescopically inserted within the spring 1 and the junction is ensured by fitting the contraction 3 of spring 1 in the extension 4 of spring 2.

[0011] It is indispensable that the material by which the two springs are formed is accurately selected as regards the wire cross section, the diameter of the coils, the pre-impressed loading, the kind of steel of the wire and so forth, in order to cause the elastic resultant of the two coupled springs to be equal, in terms of loads, to what is required by the specific employments on the heddles.

[0012] During the operation, component 1 of the composite spring according to the present invention, as being much stronger, can bear without any damage the stresses causing the failure of the known springs. In addition, as in the operating condition both components 1 and 2 are stressed by the same tensional load, their elastic response materializes through different extensions, thereby causing a mutual damping of the swingings, which involves a drastic reduction or also the elimination of the crosswise stresses.

[0013] Referring to Fig.2, a different method employed for combining springs 1 and 2 is shown. In fact, in this case spring 1 and spring 2 are connected to each other by means of a metal joint 6 having both a projection 7 suitable to engage within the end of spring 1 and, on the opposite side, a projection 8 suitable to engage within the end of spring 2. Instead of being in metal, said joint can be also provided in a different suitable material.

Claims

1. A composite return spring for heddles of textile looms, characterized in that it consists of two helical springs (1,2) made of steel wire which are connected in series to each other and have different lengths and cross sections, the wire of the shorter spring (1) having a cross section 5 to 50% larger than the wire of the longer spring (2).

2. A spring according to claim 1, characterized in that the wire of the shorter spring (1) has a cross section 18 to 27% larger than the wire of the longer spring (2).

3. A spring according to claim 1 or 2, characterized in that the shorter spring (1) has, at one end thereof, an anchoring eyelet (5), and at the opposite end a means for being connected in series to the longer spring (2).

4. A spring according to claim 3, characterized in that the shorter spring (1) has, at one end thereof, an anchoring eyelet (5), and at the opposite end a contraction (3) suitable to block a bell-shaped extension (4) present at one end of the longer spring (2) which is telescopically inserted within the shorter spring (1).

5. A spring according to claim 3, characterized in that the means for connecting the two springs (1,2) in series to each other consists of a joint (6).

6. A spring according to claim 5, characterized in that the joint (6) has both a projection (7) suitable to engage with the end of the spring (1) and, on the opposite side, a projection (8) suitable to engage with the end of the longer spring (2).

Drawing