EP0496966A1

EP0496966A1 - Actuator

Info

Publication number: EP0496966A1
Application number: EP91119727A
Authority: EP
Inventors: Silvio Carmeli
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-01-31
Filing date: 1991-11-19
Publication date: 1992-08-05
Also published as: IL97108A0

Abstract

The invention relates to a piston type actuator which acts by transforming a linear movement into a rotational one. The actuator comprises a cylindrical casing (1) in which is provided a piston (2). A shaft (3) which passes through the centre of said piston (2) is provided with splines (3b) mating with grooves provided in said piston (2). Helical curved ridges (12) provided with said cylindrical casing (1) are mating with grooves (13) provided on the outer surface of said piston (2). Pressurized fluid is introduced alternatively to the upper and lower parts of said cylinder causing reciprocating movement of said piston (2) and consequently alternatively turning movement of said shaft (3).

Description

The present invention relates to an actuator, i.e. to a device by means of which another mechanical arrangement can be operated by imparting movements to mechanical elements forming part of the said other arrangement. More particularly the invention concerns actuators of the piston type which act by transforming a linear movement into a rotational one.
There are many known constructions of actuators of that type, all being rather complicated and in most cases huge constructions representing relatively high initial expense.
It is the object of the present invention to provide an actuator of the piston type which is of simple construction, which includes a relatively small number of parts and which is most convenient to operate.
According to the invention the actuator comprises a casing defining a cylindrical interior in which is provided and in which plies a piston, a shaft being passed through a central passage in the said piston, the said shaft having a multiple number of specially profiled splines on its outer circumference while the inner wall of said central passage in the piston has the same number of equally profiled axially intruding grooves, two or more helically curved ridges extending from the uppermost region of the said cylindrical internal space of the said casing to its lowermost region, an upper and a lower stub extending from the respective upper and lower circular surfaces of the said shaft and extending out of the casing through top and bottom walls thereof, the piston having two or more slots which are matingly entered by the said helically curved ridges, a packing being provided ensuring air tightness in the cylindrical interior space which packing has recesses of the same profile as that of the helical ridge permitting its movement past the ridge, inlet ports being provided at the upper and the lower region of the casing, leading respectively into the interior of the latter into the space above and the space below the piston for the alternate introduction of pressurized fluid into said spaces.
These and further features of the invention will become clear from the following description of the device shown in the annexed drawings.
In the drawings Fig. 1 is a schematical, sectional view of the new device, while Fig. 2 is an isometric, partially sectional view thereof. Fig. 3 is a schematical, sectional view of the cylindrical space in the casing. Fig. 4 is a horizontal plan view thereof. Fig. 5 is a horizontal plan view of the piston. Fig. 6 is an elevational view of the piston with its packing. Fig. 7 is a section on line A-A of Fig. 6.
In the drawings the reference sign 1 indicates a casing the interior of which defines a cylindrical space 1a. In that space plies a piston 2. The up-and-down movement is caused by the introduction of pressurized fluid as will be described. The piston 2 has a central aperture 2a through which passes a shaft 3. The shaft 3 has at its outer circumferential surface axially extruding splines 3b. At the interior wall of aperture 2a are provided slots (not referenced) into which the spline 3b enter in radial direction. The shaft has at its upper and at its lower face stubs 8, which pass out of the casing through top and bottom walls 9 and 10 respectively of the casing. Tightness of passage of the stubs is assured by packing rings 8'. Reference sign 7 relates to an "O" ring seal.
On the interior of the wall of the cylindrical space 1a there extends, from top to bottom, helically curved ridges 12, a section of whose end portion is indicated in Fig. 2.
The piston 2 has a cut out 13 in which at passage of the piston, the profile of the ridge is matingly received.
A packing 4,seated within a groove 14, ensures tightness between cavities 1a and 1b. This packing is of peculiar shape, having periodical passages over the ridges of the cylinder. The passage over the ridges is accomplished according to the "shortest distance" and thus it passes perpendicularly relative to every one of the ridges. Passing thus perpendicularly to the ridges, and the ridges being inclined at a certain angle to the axis of the cylinder, the seal cord forms two basic periodic shapes: the one that circumvents the ridge and the second which follows the inner circumference of the cylinder. The recessed portions, those which circumvent the ridges, are interconnected top to bottom by the intermediate circumferential portions thus forming an uninterrupted seal.
Summarizing this, the general shape of the seal is an 'O' ring upon which recesses have been made and those recesses have been twisted so that the cord of each one has an inclination perpendicular to the angle of the helix.
An inlet 15 for pressurized fluid and one 16 for pressurized fluid are provided at top and bottom walls 9, 10 respectively. These inlets lead into the space above and that below the piston 2.
The new device functions as an actuator in the following way: Assuming that in the position of Fig. 2 pressure fluid is introduced at inlet 15, the piston 2 would be caused to move in a downward direction; however, the movement of the piston is a twofold one:

1. Pressure of the introduced fluid acting on the piston's top surface cause it to move downwardly, but
2. its being functionally connected via helical ridge 12 and groove 13 with the cylinder wall 1, it is caused to also perform a rotational movement.
This movement is transmitted by the meshing splines 3b and corresponding grooves at the inner wall of aperture 2a to the shaft 3 and the stubs 8. The torque imparted to a stub can be employed by transferring it by whatever conventional means to a mechanical element, the rotational movement of which is desired.

The upward movement of the piston can be brought about by introducing pressurized fluid to entry 16 which acts upon the lowermost circular surface of the piston, forcing it upwardly and imparting torque, but in reverse direction, which means that the rotational movement caused to a mechanical part by the down movement of the piston is now reversed.
The magnitude of torque available at the stubs is dependent on the pitch of the helical ridge. This latter is of smaller linear length when its curvatures are shallow and is of greater magnitude with more pronounced curves.

Claims

An actuator comprising a casing defining a cylindrical interior in which is provided and in which plies a piston, a shaft being passed through a central passage in the said piston, the said shaft having a multiple number of specially profiled splines on its outer circumference while the inner wall of said central passage in the piston has the same number of equally profiled axially intruding grooves, two or more helically curved ridges extending from the uppermost region of the said cylindrical internal space of the said casing to its lowermost region, an upper and a lower stub extending from the respective upper and lower circular surfaces of the said shaft and extending out of the casing through top and bottom walls thereof, the piston having two or more slots which are matingly entered by the said helically curved ridges, a packing being provided ensuring air tightness in the cylindrical interior space which packing has recesses of the same profile as that of the helical ridge permitting its movement past the ridge, inlet ports being provided at the upper and the lower region of the casing, leading respectively into the interior of the latter into the space above and the space below the piston for the alternate introduction of pressurized fluid into said spaces.
The actuator claimed in Claim 1, wherein the packing on the piston is formed to permit its passage over the curved ridges thereby that it is formed on the principle of the shortest distance as defined.
The actuator claimed in Claim 2 wherein the said packing is an 'O' ring upon which recesses have been made and those recesses have been twisted so that the cord of each one has an inclination perpendicular to the angle of the helix.