DEVICE FOR A VALVE SHUTTER DISPLACEMENT

Abstract

Device (10) for converting a linear motion of a first mechanical element in a rotary one of a second mechanical element, having a pin (1) which realizes a coupling between the two mechanical elements, a guide block (3) housing the pin (1) and having inclined outer side surfaces (3), two guide pads (5) provided with corresponding inclined inner side surfaces (5), which are coupled with the inclined outer side surfaces (3) of the guide block (3), and with outer side surfaces (5) configured to be coupled with corresponding wings of the Scotch yoke (9), a spring element (6), configured to generate an elastic force (Fe) on the guide pads (5) such that the guide pads (5) slide on the guide block (3), wherein the inclined outer side surfaces (3) of the guide block (3) and the inclined inner side surfaces (5) of the guide pads (5) have the same inclination angle, the distance (A) between the outer side surfaces (5) of the guide pads (5) is a function of the mutual position of the inclined inner side surfaces (5) of the guide pads (5) and the corresponding inclined outer side surfaces (3) of the guide block (3), and the outer side surfaces (5) of the guide pads (5) are parallel to each other.

Claims

1. A device (10) of a Scotch yoke mechanism for converting a linear motion of a first mechanical element in a rotary one of a second mechanical element, comprising: a pin (1), configured to realize a coupling between said first mechanical element and said second mechanical element, a guide block (3), provided with an inner hole configured to house the pin (1) and with inclined outer side surfaces (3); two guide pads (5), provided with corresponding inclined inner side surfaces (5), which are coupled with the inclined outer side surfaces (3) of the guide block (3), and with outer side surfaces (5) configured to be coupled with corresponding wings of the Scotch yoke (9), elastic means (6), configured to generate an elastic force (Fe) on the guide pads (5) such that the inclined inner side surfaces (5) of the guide pads (5) slide on the corresponding inclined outer side surfaces (3) of the guide block (3), the device being characterized in that: the inclined outer side surfaces (3) of the guide block (3) and the inclined inner side surfaces (5) of the guide pads (5) have the same inclination angle, the distance (A) between the outer side surfaces (5) of the guide pads (5) is a function of the mutual position of the inclined inner side surfaces (5) of the guide pads (5) and the corresponding inclined outer side surfaces (3) of the guide block (3), and the outer side surfaces (5) of the guide pads (5) are parallel to each other.

2. The device (10) according to claim 1, wherein on said guide pads (5), two metal sheets (4) are mounted, which are coated with self-lubricating material.

3. The Device (10) according to claim 2, wherein said metal sheets are configured to carry out both a vertical (t) and horizontal translation (s) which are function of the mutual position of the inclined inner side surfaces (5) of the guide pads (5) and the corresponding inclined outer side surfaces (3) of the guide block (3).

4. The Device (10) according to claim 1, wherein said inclined inner side surfaces (5) of the guide pads (5) and said corresponding inclined outer side surfaces (3) of the guide block (3) are conical surfaces.

5. The device (10) according to claim 1, wherein said elastic means (6) are a Belleville washer.

6. The device (10) according to claim 1, wherein said elastic means (6) are steadily connected to the pin of the Scotch yoke (1) through removable connection means.

7. An actuator with Scotch yoke kinematism, comprising a pressure rod moving in reciprocating linear motion, a rotating shaft and a device (10) for converting a linear motion of a first mechanical element in a rotary motion of a second mechanical element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] These and other advantages of the invention will be described in detail in the following, with reference to the appended drawings, in which:

[0013] FIG. 1 shows schematically an actuator with Scotch yoke kinematism according to the known art,

[0014] FIG. 2 shows a two-dimensional exploded view of an embodiment of the device according to the invention,

[0015] FIG. 3 shows a three-dimensional exploded view of the embodiment of the device,

[0016] FIG. 4 shows an axonometric view of an assembly of the device of FIG. 1,

[0017] FIG. 5 shows a detail of the device of FIG. 1, which shows the working principle thereof,

[0018] FIG. 6 shows another detail of the device of FIG. 1, which shows the transmission of the motion from the wings of the Scotch yoke.

DETAILED DESCRIPTION OF THE INVENTION

[0019] As it is shown in FIGS. 2 to 6, object of the present invention is a device 10 which allows to eliminate all the possible mechanical clearances in the elements which transform the linear motion in rotary motion, and in particular between the guide pads and the wings of the Scotch yoke. The device according to the invention is also able to balance possible clearances due to wear occurring during the life cycle of the actuator. The elimination of the clearances allows a high mechanical resolution of positioning, and as a consequence an improvement in precision and possibility to repeat the position control. Said device allows also to eliminate casual movements of the valve connected to the actuator avoiding variations of valve positioning with consequent change of parameters of the main flow through the valve, flow rate and load losses.

[0020] The device 10 is shown in exploded view in FIGS. 2 and 3 and in FIG. 4 after mounting. The device 10 is made up of a pin 1, which can rotate in a hole of a housing 2 realized in a block 20, integral with the stem of the actuator, of known type and for this reason not shown in figure, or anyway integral to an element moving in linear motion. On the pin of the Scotch yoke, at both ends, as it is shown in FIG. 4, in the areas where the pin of the Scotch yoke is coupled with the wings of the slotted link, further elements are mounted which allow, as it is explained in the following, the possible coupling clearances between pin and wings of Scotch yoke to be balanced, which are coupling clearances existing both when new, i.e. due to tolerances of piece working, and during the life cycle of the actuator, due, in such case, to wear occurred among the various elements. In particular, directly on the pin a guide block 3 is mounted, provided with an inner hole for housing the same pin. The guide block 3 is characterized by inclined side surfaces 3 which are coupled with similar inclined surfaces 5 of two guide pads 5. The outer side surfaces 3 of the guide block 3 and the inner side surfaces 5 of the guide pads 5 have the same inclination.

[0021] Advantageously, on the guide pads there are introduced two metal sheets 4 coated with self-lubricating material to lower and reduce the wear of the elements.

[0022] Elastic means 6, preferably a Belleville washer, generate a force on the guide pads 5 such that possible clearances are balanced between the device 10 and the wings of Scotch yoke 9, which form the seat of the device, as it is shown in FIG. 6. The elastic means 6 exert its force on the guide pads 5, since it is blocked with respect to the pin of the Scotch yoke 1 by a screw 8 with suitable washer 7.

[0023] During the life cycle of the actuator possible clearances due to wear will be equally balanced by the device, thanks to the translation of the guide pads 5, i.e. the sliding of the inclined surfaces 5 of the guide pads on corresponding inclined surfaces 3 of the guide block 3. So, as a consequence the balancing of coupling clearances will cause an increasing distance A between the outer side surfaces 5 of guide pads 5, which will remain always parallel to each other, keeping the mechanical coupling without clearances with the wings of the Scotch yoke.

[0024] As it is shown in FIG. 5, the irreversible motion between the inclined surfaces 5 of the guide pads 5 and the corresponding inclined surfaces of the guide block 3 due to the force Fe of the elastic means 6 allow both the vertical t and horizontal s translation of the sheets 4, eliminating all the clearances between the parts with mechanical transmission.

[0025] This embodiment of the invention is described as a way of example, clearly it is possible to eliminate the coupling clearances between guide pads of the pin of the Scotch yoke and the wings of the Scotch yoke also in the opposite manner, i.e. by reducing the distance between the surfaces of the wings of the Scotch yoke.

[0026] In addition to the embodiments, as above described, it is to be intended that there exist many other variants. Further, it is to be intended that said embodiments are only example and do not limit in any way the object of the invention and its applications or configurations. On the contrary, even if the above described description makes possible for the experts in the field to provide the present invention in at least an embodiment, it is to be intended that many variations of the elements described can be made, without departing from the object of the invention, as it is encompassed by the appended claims and/or technical/legal equivalents thereof.