The invention refers to a transmission arm particularly suitable for actuating devices of gates or doors. In known actuating devices for gates (see figures 1 and 2) there is a transmission arm transmitting the rotary movement of a motor M, usually fixed to the ground or to a wall or to a column, to a gate GT. The arm is composed of two rigid segments 12, 14: the free end of the segment 12 is fixed to the output shaft of the motor M, the free end of the other segment 14 is rotatably pivoted to the gate GT by a bracket SF. The two segments are rotatably connected with each other at an end thereof. This system has the drawback of providing a predetermined arm for every type of motor and thus it excludes every kind of adjustment. The features of the two segments 12, 14 and especially the length thereof are set by the maximum operating ratings of the motor. Said ratings are mainly the torque exerted by the motor and the weight of the gate to be moved. These parameters, settled during the design phase, determine the actual length of the segments 12, 14. The known gate actuating devices prove to be remarkably hard to install in all those cases where a wall or the like is present alongside the actuating device (see wall in broken lines in fig. 1): in these circumstances the gate cannot be opened. It follows that homes cannot be equipped with these actuating devices, above all those recently constructed for which the residential market offers gardens and perimetrical fencings with ever decreasing dimensions.

Other kinds of articulated joints are used in JP 7.269.219, EP 1 854 953, US 5.040.331 or e.g. the lifting arms of US 6.378.249.

In all these documents the solved problem is to allow the adjustment of the arm length (or part thereof) in order to better adapt it to the gate or door to be moved. An insufficient arm length does not allow to exploit the whole travel of the gate; a length in excess too, and/ or can even cause collisions between the arm and fixed obstacles like the wall the motor is attached to or a near wall W, or another gate leaf when present.

Some solutions of the cited documents teach to make the arm, or a segment thereof, telescopic. Such a segment is manufactured with two semi-segments, slidable with respect to each other and lockable in desired position. For instance, US 5.040.331 describes (see its fig. 9) a rectilinear arm formed by two segments and extendable thanks to a sliding connection.

To produce two semi-arms also capable of mutual fixing entails a complex and expensive structure, determined above all by the complementary shape to be given to them, by the observance of tolerances and by the number of necessary pieces.

Object of the invention is to obtain a different transmission arm of the kind described being of simple and cheap construction. Another object of the invention is a different transmission arm of the kind described being easily and quickly assembled into actuating devices of gates and doors of different dimensions.

These objects are achieved by a transmission arm for actuating devices of gates and doors, comprising a first rigid segment connectable to a motor, a second rigid segment rotatably pivoted at one end to the first segment and at the other end to the gate or door, characterized in that it comprises means for longitudinally adjusting inside the first and/ or second segment the position of a relevant rotation axis (about which one and/ or the other rotates).

Thus, by the invention the first and/ or second segment can be shortened by moving one or each axis towards the center of the same segment.

If the adjustable axis is the common rotation axis of the first and second segment, the two segments can be misaligned so that the excess portion of a segment projects from the other and can then be removed, e.g. cut. Generally, it is preferable for the axis to be adjustable on the second segment, given the greater easiness for arranging suitably adapted means thereon, and for the truncated segment to be again the second, because of the easiness in shortening it snugly and because, in the dynamics of the forces at play during the motion, the modification of the first segment could entail stress variations able to alter the proper functioning of the motor, thereby causing potentially dangerous situations.

If the adjustable axis is the axis pivoting on the gate it suffices to direct properly the second segment in order to be able to remove the excess portion thereof.

With the invention the telescopic rigid construction of the segments used in the known art is avoided, wherein a segment must by necessity have a seat or a length to receive the other. Instead of producing sundry arms for different gates, with the invention always the same segment can be used and adapted permanently to the actual installation (it is not to be forgotten that the cost for producing a telescopic arm is much higher than that of the invention).

In the sense above, the invention allows a method for mounting a, or modifying a preexisting, transmission arm for actuating devices of gates or doors, comprising a first rigid segment connectable to a motor, and a second rigid segment rotatably pivoted at one end to the first segment and at the other end to the gate or door, characterized by installing the second segment, resolving the proper length of the second segment by fixing inside the second segment the position of the rotation axis in common with the first and /or the pivoting axis on the gate, cutting the excess part of the second segment. The adjustment of the position of an axis may be continuous

(capability of even millimetric adjustment) or with discrete steps (capability of adjustment predefined in factory). In the former case there is greater freedom of choice but the assembling operations require a greater commitment; in the latter the positions are fixed in advance but the installation is immediate.

The invention and its advantages will be however clearer from the 5 description of a preferred embodiment of a transmission arm, together with the attached drawings wherein

Figures 1 and 2 show a known arm for actuating devices of gates in two different positions;

Figures 3 and 4 show an arm according to the invention in two 10 different positions;

Figure 5 shows an exploded view of the arm in figures 3 and 4;

Figures 6 and 7 show a variant of the arm of the invention in two different positions.

The arm of figures 3 and 4 is composed of a first segment 20,

15 connected to a motor 26 for receiving a momentum, and a second segment 22, hinged both with the first segment and with a bracket

24, integral with a gate GT. The segment 22 has a pass-through longitudinal loop or slot 30 extending for most of the length thereof.

An end of the segment 22 is clasped between a lower plate 40

20 and an upper hub 42, which has on one side two equal diametrical fins 44, spaced apart each other as the width of the segment 22 so as to receive in the middle thereof the end of the segment 22, and on the other side a central pin 46 with which the hub 42 rotatably pivots into a ring 50 integral with an end of the segment 20. The hub 42, the pin

25 46 and the plate 40 have respective pass-through coaxial holes in which a screw 32, having a diameter a bit smaller than the width of the slot 30 and being tightenable by a nut 54, can be inserted. In the mounted assembly the screw 32 places itself inside the slot 30 and allows the hub 42, which is integral with the segment 22, to rotate

30 constrained in the ring 50 about a vertical axis X (which is in common between the first and second segment).

During assembling one can either directly measure the correct length for the segment 22 and cut it at once or it can be placed inside the hub 42, between the fins 44, and then the plate 40 and the nut 54 on one side and the screw 32 on the other are mounted. The segment 22 can slide in the hub 42 by leaving the screw 32 slack, so as to adjust the length of the segment 22 with respect to the hub 42 (and therefore the position of axis X). When such a position is perfectly established (and, notice, by an adaptive manner to the actual installation), the screw 32 can be tightened in order to permanently fix the length of the segment 22 with respect to the axis X. The portion of the segment 22 which has passed through the hub 42 is in excess, and can be easily removed, e.g. by cutting it (see cut- line L). A filling end-member 52 can make the cut end of the segment 22 and the borders of the plate 40 and the hub 42 fit together, with also the advantage of covering any sharp burrs and unsatisfactory finishes. In this manner the esthetic appearance of the arm remains always the same even after any working, cut and adjustment.

A variant of the second segment (see fig. 6 and 7, reference 22 bis) provides in it for discrete positions for the axis X, in the example represented by an aligned series of pass-through holes 60 on which the screw 32 can be inserted (the remaining construction is identical to the preceding one). Such segment 22bis can be manufactured advantageously with standard length and, after determining during installation that hole corresponding to its desired length, the excess portion can be cut (see cut-line Lbis). In the two variants, at the end of the installation the overall arm turns out to be of optimal length, without dangerous pointed and/ or bulky parts, and maintaining unaltered esthetical appearance. It is to be noted above all that with the invention the gate GT can open completely without the arm hitting against a surrounding wall W (in dashed lines in figures 3-4 and 6-7).