WIRE PRODUCTS

The proposed invention refers to a method or mechanism for the formation of spiral wire shape, which upwinds in space forming a solenoid (Fig . 3) , which is characterised by the use of a modif ed, automatic, two-dimensional wire bending machine for the formation of each spiral coil and by the use of holding mechanism for the created solenoid, which mechanism is in coordination with the bending mechanism for the upwinding of the coils and the formation of a solenoid spiral body, where the proposed method has the capability of creating unpwinding spiral shapes with uniform or different shape for each coil (Fig. 3) .

STATE-OF-THE-ART

To the best of our knowledge, there is no awarded patent similar to the proposed method . The two- dimensional wire bending machine which is considered as a pre-requisite for the method, is described in the U.S . Patent Application No . 562, 431 , for which a patent has already been granted . The most common method for production of such shapes is the following:

The formation of a plane wire frame is done in the, automatic or not , bending machine by stepwise advancements of the wire for particular lengths I _v and subsequent bending actions at angles φ _v . This is explained in Fig . 1 (a) , where the wire ( 1 ) , coming from a reel is pulled by the automatic bending machine (3 ) through the pulling/ straightening devices ( 4 ) , (5) and at point O it is bent right (or left ) by the bender (6 ) . The lengths (l _v ) are measured from point O on the OX' axis , with left/positive the clockwise direction and left/negative the counter clockwise direction . On the same figure, a plane wire is shown as an example, and it was created as follows : Advancement : l , Bending: ψ _j , Advancement : I2,

Bending: q>2 _r Advancement : l _j , Bending: φ _j . If the advancements ( lv ) and bendings (φv) of the wire are continued , then with the aid of the small inclined plane ( 7 ) [Fig - 1 (b) ] , the created wire form is occupying a second level , above the previous plane form which is seated on the upper surface (8 ) of the bending machine (3 ) . This way, a wire shape can be created which is formed of many levels one on top of each other, having a distance between each other equal to the wire thickness .

The most interesting case is the repetition of plane wire shapes, which are simply or doubly symmetric . Some of them are drawn in Fig . 1 (c) . A disadvantage of that . technique is the difficulty of formation of such geometrical forms with gradual increase of height , as it was described before, even though the surface (8 ) can be horizontal , for the following main reasons :

(a) After some time, the advancing wire cannot carry along the already created form, due to its increased weight and its subsequent friction force with the table surface .

(b) The created equal (or similar) frames which are placed on top of each other cannot keep on lying one on top of the other properly, during motion of the total formation .

We can already report that the present invention consists of the development of a special machine, which can be combined with an existing automatic, bending machine, in order to create a mechanism for the production of multilevel wire products .

DESCRIPTION OF THE METHOD

The present invention utilises an automatic, two- dimensional wire-bending machine for the production of each coil . This machine is modified in order to obtain the

working plane to be horizontal and facing downwards , so that the created wire product is "hanging" downwards due to gravitational force (Fig. 2 ) . A "table" [Fig. 2 , ( 10 ) ] is placed exactly below the working plane and the created coils are seated on it . The table has the arms ( 11 ) for the protection of the created forms against buckling or twisting . The table ' s downward motion is coordinated with the straightening and bending motions of the wire, in order to prevent bending and twisting of the wire anywhere, due to lack of synchronisation between the coil motion and the existing formation (Fig. 2 ) .

The advantages of the method are:

1 . Different machines are utilised for the production of each coil and for the support and storage of the created spiral solenoid format on, where the motion of each one is coordinated with the motion of the other . Therefore, a flexibility in production of various forms is obtained, which in general allows for the creation of different forms for each coil or for the programming of a sequence of spiral formations of various coil types .

2. The modification of the bending machine, in order to keep the bending plane horizontal but facing downwards, allows for the coils to be displaced from each other, thus eliminating the main disadvantage of common practice production of such forms . Therefore, the deformation of the coils due to their weight or motion is avoided.

3. The use of a holding table under the bender has the purpose of holding the formation and also allows for the transportation of the product to a permanent storage compartment or to a production line . Therefore, the holding table constitutes a means for automating the production process .

4. The coordinated motion of the holding table with the

advancing and bending wire motion relieves the bending and feeding mechanism from the task of advancing and twisting all the produced formation . This is a task undertaken by the holding table . This creates the following advantages :

(a ) The accelerations of the produced formation create at the point of the wire where advancement is applied , forces which are proportional to the mass of the formation and increase as the production is increased . At the same p>oint , these forces result in shear stresses which are beyond the wire yield point , resulting in plastic deformation and distortion of the coils . The motion of the table along with the holding arms protects the product from such distortion .

(b) An additional cause of deformation is the product weight , which increases as the production proceeds . Once again, the table supports and bounds the product , in order to keep deformation well inside the elastic region .

(c) Finally, the coordination of the advancing and bending movements with the holding table motion results in the reduction of the forces required for the advancement and bending (because they are no longer required to carry along all the formation ) , consequently the use of the smallest possible bending machine is required for a particular wire diameter .

5. Finally, an advantage of the present method over the state-of-the-art is the following:

In common practice, as production progresses , small advancement and bending speeds are applied , because the accelerations created by the subsequent advancements and bendings result in larger forces, as the mass of the formation increases . As a result , smaller sp>eeds are applied, hence the production rate, i . e . the number of products in the unit of time , is reduced .

With the present method, speed reduction is no longer necessary, hence production increases. The fact that it can be included in a production line, certainly increases the production capabilities.

INVENTION EMBODIMENT

A first invention embodiment is shown in Fig. 2. At first, it must be reported that the bending machine (3) is placed in such a way that the horizontal surface (8) is facing downwards and not upwards (as it is common practic ) and the product (9) is practically hanging from the bender (6).

However, just a few product (9) coils are really hanging since most "coils" are seated on the hanging table (10). The product (9) is protected from deforming by the holding arms (11). The most suitable number of arms is 4, as they successfully enclose most shapes, but any number can apply. The arms may be placed at any suitable distance from centre K of the hanging table (10) in order to enclose the product (9). The hanging table

(10) consists of a square or circular upper surface and it is connected with the arms (11) in such a way so that it can slide moving vertically upwards or downwards , while the arms

(11) remain immovable to the vertical movement.

In order to have the sides of the continuously produced coil (9) smoothly seated, the hanging table (10) and the arms (11) make the appropriate movements. The movements of the hanging table (10) and the arms (11), connected with the table, may be understood by the following remarks:

I. The hanging table move in a direction parallel to the axis OX' (or OX) and remain parallel to itself during the l _v advancement of the wire. Also the table movement is of the same speed as the wire movement advancing (Fig. 2).

II. The table turns around a vertical axis passing from the center O of the bender during the rotation at an angle φ _v , of the side l _v , simultaneously , with the same angle φ _v and having the same angular speed.

There are no other movements, since, as already mentioned, the formation of a wire shape is effected by consecutive advancements and bendings of the wire. We shall prove that both movements I and II will be made if we give to the table (10) three options of movement i.e.:

a) at the direction of axis O ^' X

b) at the direction of axis O'Y

c) rotating around a vertical axis passing through its centre K (Fig. 2)

One (among many) engineering way for achieving above movements , is shown in Fig. 2 wherein the hanging table (10) turns by rotation of the arms (11) which are supported through the ball bearings (12) on the fixed body (13), driven by the servomotor (15). Moreover, the table (10), based on the fixed body (13), participates to the latter' s (13) movement along the axis O'Y driven by the servomotor (16) and the chain (17), and by its sliding on the axes (18) of the fixed body (18). Finally, the table

(10), also based on the fixed body (18), participates to the latter' ε (18) movement along the axis O'X driven by the servomotor (19) and the chain (20) and by its sliding on the axes (21) of the immovable fixed body (21).

I. This parallel movement is only driven by the servomotor (19) which finally moves the table along the axis O'X. The said servomotor is synchronised with the servomotors used for the wire (4) and (5) straightening and advancement in order to achieve the same speed and length with the movement 2 _y of the wire, when moving along axis O'X

of the table. In Fig. 1 (d) the position (v+1) of the table's (10) centre moving to the position (v+2) is shown

( ^κ v+l ^>κ v+2) ^~

II. For this movement, the synchronised operation of servomotors (14), (17) and (19) is required. During the rotation of table (10) with the centre of symmetry of shape K, which coincides with the centre of the table, the radius OK performs the same rotation with the side of the coil, and this rotation is identical to the one performed by radius KO, measured from an axis passing through K and being parallel to OX', and this rotation is to be driven by the servomotor (14) based on the fixed body (13).

If OK= R _v : Known, then

Xκ - XQ + R _v .cosφ _κ Yκ = Y _Q + R _v .sinφ _κ

Since XQ, YQ should remain constant, upon differentiation of the above equations is obtained: dXκ = -R _v .sinφ _κ .dφ _κ dYκ = R _v .coεφ _κ .dφ _κ

In practice we consider constant increases of φ _κ , let's call them Δφ, therefore:

Vκr <?κ0 ^{+ Δ(} P-

and thereafter:

sinφ _κl , cosφ _κl , ΔX _χl , ΔY _χl , X _κl , Y _κl ,

<Pκ2 = <Pκl ^{+ Δ(} P ^{~ sln<} Pκ2' ^cosζ Pκ2' ^ΔX κ2' ^~ ∞κ2> ^x 2' ^γ κ2 ^etc ' upto the final position X _{κ v+j} , Y _v + _j r commencing from X _{κ v} , Y _{κ v}

The table (10) is based on the screw (22), which can rotate driven by the servomotor (24) through the sprockets and the

chain (23). Thus, the descent of the hanging table (10) is adjusted , in combination to its rotation driven by the servomotor (14), in order to have adequate space for placing the product being continuously produced. The screw (22) is supported by the ball bearings (25) on the fixed body (13). It is noted that the fixed body (13) may be supported sliding on an arm rotating around O' moving on the plane YO'X, therefore we may also use for K, "a polar coordinate system" instead of "the cartesian coordinate system" already described .