DE SCRIPTION

Background and summary of the invention

The present invention relates to a motion transmissio n device for movable members o f mechanical equipment or structures .

As is known, various systems are present in essentially mechanical equipment or structures by means o f which two operating members opposed to each other are alternately moved away from and towards each other in order to execute specific op erations . These operating members are generally associated with sliding blocks or pads which slide along guides and are normally driven by means o f actuators . In order to move these operating members towards or away from each other at variab le speeds, it is frequently necessary to combine the actuators with complex operating and control systems; furthermore , these actuators are o ften very bulky, expensive and inefficient.

The object o f the present invention is therefore to provide a motion transmission device for movable members o f mechanical equipment or structures which, by using a single drive motor, enables the rotary motion of this motor to be converted into an alternating linear motion o f any pair o f operating members , thereby also allowing them to be moved away from or towards each other at variable sp eed if required.

This obj ect is achieved by the present invention by means o f a motion transmission device for movable members o f mechanical equipment or structures according to C laim 1 .

Other advantageous features o f the present motion transmission device for movable members o f mechanical equipment or structures are described in the dependent claims .

By using the present motion transmission device for movable members of mechanical equipment or structures , therefore, a single drive motor can be used, and, by means o f a pair o f suitably shaped levers , the rotary motion o f the motor is converted into linear motion o f the two operating members , which pass, alternately, from a situation in which they are moved away from each other to a situation in which they are moved towards each other. Additionally, for a given speed o f the motor, the speed o f the operating members changes in the different stages o f movement towards and away from each other, and, in particular, when the members are distant from each other, their sp eed o f movement towards each other is relatively high, whereas , when they are close to each other, the speed o f movement towards each other is relatively low.

Brief description of the drawings

Other features and advantages o f the present invention will be made clear in the course of the following description, to be considered as a non- limiting example , which refers to the attached drawings, in which :

- Fig . 1 shows a first front view o f a motion transmission device for movable members o f mechanical equipment or structures, in a comp letely open position and with a maximum distance or gap between two movable members supported by the device;

- Fig . 2 shows a view from above o f the present device o f Fig . 1 in the open position;

- Fig . 3 shows a second front view of the present device in a completely closed position and with a minimum distance or gap between the operating members;

- Fig. 4 shows a view from above of the present device of Fig.3 in the closed position; and

- Figs. 5a, 5b, 5c and 5d show, in schematic views from above, the sequence of the movement from a completely open position, with a maximum gap or distance between the operating members, to a completely closed position, with a minimum gap or distance between the operating members. Description of the preferred embodiment of the invention

With reference to the attached drawings, and with particular reference to Figures 1 and 2 thereof, the number 1 indicates a support structure for a pair of parallel guides 2 and 2'. A pair of sliding blocks or pads 3 and 3' slides on each of the guides 2 and 2'. The pad 3 and the pad 3' positioned on each guide 2 and 2' are translated simultaneously in opposite directions to each other, and are therefore moved away from or towards each other. Additionally, the two pads 3' placed on the right-hand side of the device, as it appears to the viewer of the drawings, are positioned in a position which is a mirror image of that of the two pads 3 placed on the left-hand side relative to a median plane M of the device. The two pads 3' located on the right-hand side support a first essentially L-shaped plate 4', placed in a position which is a mirror image, relative to the median plane M, of that of a second essentially L-shaped plate 4 carried by the pair of pads 3 located on the left-hand side of the device. Each of these plates 4 and 4' supports an operating member which must be translated in one or the other direction, in other words the operating member 5 and the operating member 5'. These operating members 5 and 5' could be, for example, heads for welding the tops and bottoms of packages for packaging machines, these heads, as is known, being generally aligned and opposed to each other and moving towards and away from each other. These operating members 5 and 5' are in positions which form mirror images relative to the median plane M of the device. Each of the plates 4 and 4' is connected by means of a plate 6 and 6', provided with a corresponding pin 7 and 7', to a first end part of a corresponding curved lever: the pin 7 is connected to the first free end part 108 of a first curved lever 8, while the pin 7' is connected to a first free end part 108' of a second curved lever 8'. These first end parts 108 and 108' of the curved levers are in diametrically opposed positions. The curved levers 8 and 8' can take the form of circular arcs, elliptical arcs, or the like, and are preferably identical. Each of these curved levers 8 and 8' comprises a second end part 208 and 208', fastened to a support plate 9, which in this case is circular. The second end part 208 of the curved lever 8 is connected to the plate 9 by means of a pin 10 about which the lever 8 can rotate, while the second end part 208' of the curved lever 8' is connected to the plate 9 by means of a pin 10' about which the lever 8' can rotate. The pins 10 and 10', and therefore the end parts 208 and 208' of the levers 8 and 8', are located in the proximity of the periphery of said plate 9 and in diametrically opposite positions relative to this plate. This support plate 9 is connected centrally to the shaft 11 of an electric motor 12, provided with a bush 13 for its support on the structure 1. In this structure 1, a cavity 14 is provided to allow the circular plate 9 to pass partially through it.

In the situation shown in Figs. 1 and 2, the present device is shown in the open position, in other words with the operating members 5 and 5' at the maximum distance from each other. As mentioned, these operating members could be, for example, heads for welding the tops and bottoms of packages for packaging machines, and the present motion transmission device is particularly advantageous if used for translating these welding heads in one or the other direction. In the situation shown in Figures 1 and 2, the package welded at the top and bottom can pass freely through the free space left between the operating members 5 and 5', owing to the size of the distance L.

In Figures 3 and 4, the present device is shown in the closed position, in other words with the operating members 5 and 5' at the minimum distance from each other, which may ultimately be equal to zero, if for example the operating members come into contact with each other as a result of their operation. If these movable members are heads for welding the tops and bottoms of packages for packaging machines, in this situation the heads are able to weld the top of one package and the bottom of a subsequent package.

The present device can move at the desired speed from the open to the closed position, and vice versa. In order to move, for example, from the open position of Figures 1 and 2 to the closed position of Figures 3 and 4, the motor 12 is operated in such a way that the shaft 11 causes the plate 9 to rotate through about 90° in the direction of the arrow R of Fig. 1. Simultaneously with the rotation of the plate 9, there is a synchronized rotation of the curved levers 8 and 8' about the respective rotation pins 10 and 10', in the opposite direction to the direction R of the support plate 9. At the end of this rotation of the plate 9, the terminal parts 208 and 208' of the levers 8 and 8' have also rotated through 90° in the direction of the arrow R, while the end parts 108 and 108' of the levers have moved towards each other; see Figures 1 and 3 and Figures 2 and 4. In the movement from the open to the closed position, or vice versa, one of the two levers passes under the other, with the curved lever 8' passing under the lever 8 in the present case, and therefore, as is apparent, the 8 and 8' can cross each other without any mutual interference. In order to move from the closed to the open position, the motor must be operated in such a way that the plate 9 undergoes a rotation of about 90° in the direction of the arrow R' of Fig. 3, which is opposite to the direction of the arrow R of Fig. 1. As can be seen, at the end of the rotation the rotation pins 10 and 10' of the end parts 208 and 208' of the respective curved levers 8 and 8' are still in diametrically opposed positions on the plate 9.

Depending on the size and shape of the curved levers, and the distance between the corresponding movable parts, the angle of rotation imparted by the motor 12 to the plate 9 can be other than 90°.

A further advantageous aspect of the present device is that the speed at which the operating members move towards or away from each other is variable for a given rotation speed of the motor 12. Fig. 5a shows a situation similar to that of Fig. 1, with the present device in the open position and the operating members 5 and 5' associated with the two curved levers 8 and 8' at the maximum distance L. When the motor is operated in the direction of the arrow R, the curved levers 8 and 8' rotate in a synchronized way about the respective rotation pins 10 and 10', and when they have covered approximately 50% of their curved path (see Fig. 5b), in other words when they have travelled through an angle A of approximately 45°, the two operating members will have covered approximately 80% of their linear path towards each other, thus arriving at a distance L' equal to approximately 20% of the distance L in the open position. When the curved levers 8 and 8' move through a further angle B of approximately 22.5° (see Fig. 5c), the operating members 5 and 5' move towards each other by a further 10%, and therefore the new distance L" between them will be equal to approximately 10% of the initial distance L. Consequently, the initial speed of the movement of the two operating members 5 and 5' towards each other, and also the final movement away from each other in the opposite stage, is high, whereas, when the operating members are at a sufficiently small distance, their movement towards each other becomes markedly slower, until the situation of minimum distance, or of contact in the ultimate case, is reached as shown in Fig. 5d. This aspect of the present device, in other words the fact that the operating members move at different speeds towards and away from each other for the same motor speed, may prove to be very important in some possible applications. For example, if the operating members 5 and 5' are heads for welding the tops and bottoms of packages for packaging machines, the heads will move rapidly towards each other and to the flaps of a package to be welded, whereas, when the heads are in the proximity of the flaps and come into contact with them, they slow down markedly, in such a way that sufficient time is provided for carrying out the weld. In the same way, during their movement away from each other, there is essentially a first, relatively slow, stage of detachment from the flaps of the package , and a second, relatively fast, stage o f movement away from each other, in such a way that the package can pass through the operating members when they are again in the open position. Clearly, the arrangement described above is only one o f the possible multiple applications o f the present motion transmission device for movable members o f mechanical equipment or structures .