IMPROVED ACTUATOR FOR ACTUATING VALVES

Abstract: The actuator comprises an actuator body (2) including a cavity (3) in which there are housed two pistons (4,5) movable in opposite directions and including toothed portions (20,21) meshing with a toothed pignon (22) rigid with a shaft (23) to be coupled to the spindle of the valve element to be actuated,there being moreover provided end of stroke abutment members which can be adjusted from the outside of the body (2) and which are engaged by the pistons (4,5) in order to adjust the opening and closing strokes of the valve element.

Description: BACKGROUND OF THE INVENTION The present invention relates to an improved actuator for actuating a valve element in general. As is known, there are commercially available actuators for opening and closing valve elements of several types which actuators usually comprise either hydraulic or pneumatic elements suitable to drive the driving spindle of the valve element to be acuated. These known actuators are generally very complex construction-wise and,moreover, they do not afford the possibility of precisely adjusting, depending on requirements, the rotation angle of the valve element spindle. Document WO-A- 8 403 129 discloses an actuator having the features of the pre-characterizing portion of the maine claim. SUMMARY OF THE INVENTION Accordingly, the main object of the present invention is to overcome the above mentioned drawbacks by providing an improved valve actuator affording the possibility of easily and quickly adjusting the end of stroke positions of the valve element actuated thereby. Another object of the present invention is to provide such an improved valve actuator which has a very reduced size and a high response speed so as to quickly switch from the valve element closing to the valve element opening position and/or vice versa. Another object of the present invention is to provide such an improved actuator which is very reliable in operation and can be easily made,at a comparatively low cost,starting from easily available elements and materials. According to one aspect of the present invention, the above mentioned objects,as well as yet other objects,which will become more apparent herein-after,are achieved by an improved actuator for actuating valve elements in general having the features of the characterizing portion of the main claim. SUMMARY OF THE INVENTION Further characteristics and advantages of the present invention will become more apparent from the following detailed description of a preferred embodiment of an improved valve actuator according to the invention,which is illustrated,by way of an indicative but not limitative example,in the figures of the accompanying drawings,where: figure 1 is a partially cross-sectioned elevation view illustrating the valve actuator according to the present invention; figure 2 is a cross-sectional view taken along the line II-II of figure 1; figure 3 is another cross-sectional view of the subject actuator,taken along the section line III-III of figure 1; and figure 4 is a plan top view illustrating the actuator according to the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the figures of the accompanying drawings, the improved actuator for actuating valve elements in general according to the present invention,which is overally indicated at the reference number 1,comprises a body 2 in which there defined a preferably cylindrical cavity 3. In this cavity two pistons 4 and 5 respectively can move in opposite directions:more specifically these pistons tightly move in a first and second chambers 6 and 7 which are opposite to one another and coupled to the longitudinal ends of the body 2. To the cavity 3 a first pressurized air delivery duct 10 leads,and further air delivery duct, indicated at the reference number 11,communicate with the head portions of the chambers 6 and 7 so as to displace the pistons 4 and 5 in opposite directions. The pistons 4 and 5 are provided, at the coupling side thereof,with toothed portions indicated respectively at 20 and 21 which extend according to rectilinear portions parallel to the piston sliding direction and engaging with a toothed pinion 22 which is rigidly mounted on a shaft 23, in turn rotatably supported by the body 2. As shown, the shaft 23 tightly projects from the body 2 and, at its bottom portion, defines a seat 24, broached in its inside, in which can be engaged a fitting 25, provided with a corresponding outer broached portion for coupling with the spindle of a valve element on which the actuator must be applied. Thus, the fitting 25 can be interexchanged so as to easily and quickly engage different shape valve spindles. A main feature of the present invention is that there are provided end of stroke elements which can be directly adjusted from the outside of the body 2 and directly engage,by contact,with the pistons. Said end of stroke elements,as is clearly shown in figure 2,are provided with a first stem 30 which engages with the head of the portion of the chamber 6;this threaded stem 30 engaging,by contact, with the first piston 4 and operates as an abutment member for the displacement in a first direction of this first piston. It should be apparent in this connection that,as the first piston is locked,also the other piston will be automatically locked because of the coupling between the mentioned toothed portions and the toothed pignon. More specifically,the other piston 5 is provided with a cap bush 35 which is restrained on said piston 5 and engages with a second threaded stem 36 coupled to the other head of the chamber 7 and provided with an enlarged head portion 38 which butt engages with an annular narrowed portion 39 formed at the end of the bush. Thus, the head portion 38 of the second stem will operate as a stop element for the displacement of the piston in the opposite direction to the direction in which the stem 30 operates as a stop member for the first piston. It should be moreover be pointed out that the cap bush 35 is tightly coupled to the piston 5 and that,advantageously,said cap bush is provided with a closing plug 40 at that portion of the bush facing the too thed pinion. A micrometric adjusting can be carried out by means of nuts,indicated at 50,which allow for the stems to be properly arranged so as to cause the pistons to perform the desired stroke before the operation of said stems as end of stroke elements. On the two stems,moreover,there is provided a respective locking nut,indicated at 51. By operating the stems 30 and 36 it will be possible to micrometrically change the positions of said stems,to precisely stop the pistons at the desired places,with a perfect adjusting of said pistons. From the above disclosure, it should be apparent that the invention fully achieves the intended objects.

Claims: 1. An actuator for actuating valve elements comprising an actuator body (2) including a cavity (3) in which first and second pistons (4, 5) can move in opposite directions, said pistons (4, 5) being provided with toothed portions (20, 21) meshing with a toothed pinion (22) rigid with a shaft (23) suitable to be coupled to a spindle of a valve element to be actuated, there being moreover provided separated end of stroke adjustment means (30, 35, 36) which can be adjusted from the outside of said body (2) and contact engaged by said pistons (4, 5) to adjust the opening and closing strokes of said valve element, said end of stroke adjustment means (30, 35, 36) comprising two end of stroke adjustment assemblies, one of said assembly (30) at one end of said actuator body (2) including a threaded stem (30) engaging, by contact, with one (4) of said pistons and operating as an abutment member for the displacement in a first sliding direction of said one piston (4), characterized in that said assemblies can be adjusted independently from each other and that the other (35, 36) of said assemblies (30, 35, 36) at the other end of said actuator body (2) comprises on the other piston (5) a cap bush (35) tightly coupled to one (5) of said pistons (4, 5) and including a closing plug (40) at that portion of said bush (35) facing said toothed pinion (22) said bush (35) being moreover provided with an inner seat therewithin engages a heat portion (38) of a threaded stem (36) which is screwably supported at one end of said ends of said actuator body (2), there being moreover provided an annular abutment member (39) formed at one end of said bush (35) thereagainst said head portion (38) can abut so as to define an end of stroke position of said other piston (5) in a second sliding direction opposite to said first sliding direction of said one piston (4). 2. An actuator according to Claim 1, characterized in that said shaft (23) is provided, at one end thereof projecting from said actuator body (2), with a seat suitable to removably receive a fitting member (25) for coupling with said spindle of said valve, said seat having an inner broached portion engaging with a corresponding outer broached portion of said fitting member (25).

Inventors: MESSINA, AURELIO
Applicants: MESSINA, AURELIO
Application year: 1989
Main classification: F15B15
IPC codes: F15B15