Reciprocating Drives For The Movable Members Of Shut-off Elements

Abstract

A reciprocating drive for the movable member of shut-off element wherein the driving element 2 made in the form of at least one wire turn heated by a source of electric current and resting on two supports 3, 4 one of which (3) is secured in the body 1 while the second one (4), connected with the movable member, moves when the driving element 2 is elongated due to heating. The second support 4 is fastened to one end of the spring-loaded part 5 whose other end is secured in the body 1. Such an installation of the second support makes it possible to increase several times the travel of the movable member as compared to the elongation of the driving element due to heating. Shown in FIG. 1 is the reciprocating drive for the movable member of shut-off element, realized in accordance with the present invention.

Description

The present invention relates to reciprocating drives for the movable members of shut-off elements.

Most expediently the drive according to the present invention can be used for the remote control of the shut-off elements in pneumatic or hydraulic systems.

Known in the art are reciprocating drives for the movable members of shut-off elements whose operating principle is based on mechanical deformation of the driving element of the drive. The driving element of such drives is made in the form of a rod resting on two supports, one of which is secured in the body and the other one is connected to the movable member of the shut-off element. The movable member of the shut-off element is moved owing to mechanical deformation (elongation) of the driving element of the drive, said deformation being performed by a mechanical method (see, for example, Pat. No. 719,058, Belgium).

These drives are not suitable for remote control of the reciprocating motion of the movable member in the shut-off element.

Also, widely known are electromagnetic drives wherein the movable member of the shut-off element is actuated by a core located inside an electric coil. The core is pulled into the coil by electromagnetic forces when the coil is energized.

These drives are difficult to manufacture and have large weight.

An object of the present invention resides in eliminating the aforesaid disadvantages.

The main object of the invention is to provide such a reciprocating drive for the movable member of a shut-off element wherein the elengation of the driving element of the drive can be controlled remotely while a small elongation of the movable element will be transformed into a considerably larger travel of the movable member of the shut-off element.

This object is achieved by providing a reciprocating drive for the movable member of a shut-off element comprising a driving element mounted in the body on two supports one of which is secured while the other one is connected to the movable member of the shut-off element and can move when the driving element of the drive is elongated in which; according to the invention the driving element is made of at least one turn of an electric wire, heated by a source of electric current, the second support being located on one end of the spring-loaded part working in compression and installed at an acute angle to the longitudinal axis of the wire turn, while the other end of said spring-loaded part is secured in the drive body.

It is practicable that the spring-loaded part be made in the form of a leaf spring with one end secured rigidly in the drive body.

Such an arrangement simplifies the design of the drive and somewhat reduces its size.

Most efficiently the present invention can be carried into effect when the drive body is pressuretight and vacuumized.

Such a design of the body increases the working travel of the movable member without changes in the power consumption, due to the absence of heat transfer by convection.

It is no less practicable that the turns of the driving element be coated with a layer of a material with a low coefficient of blackness.

This arrangement ensures a considerable further increase of the working travel of the movable member at a constant power, especially in case of a vacuumized body.

The drive realized in accordance with the present invention is simple to manufacture, has a considerably lighter weight and is much cheaper that the known drives described above.

Now the invention will be described by way of example with reference to the accompanying drawings in which:

FIG. 1 is a longitudinal section of a reciprocating drive for the movable member of shut-off element according to the invention;

FIG. 2 is a section taken along line II--II of FIG. 1;

FIG. 3 is similar to FIG. 1 with the spring-loaded part being made in the form of a leaf spring;

FIG. 4 is similar to FIG. 1 with a vacuumized body of the drive; and

FIG. 5 is a graphic representation of motions of the drive elements.

Accommodated in the drive body 1 (FIGS. 1, 2) is a driving element 2 which is made in the form of a piece of wire coiled over two cylinder-shaped supports 3, 4. In this design either the wire or the support may be insulated.

The driving element of the drive may also be made of at least one turn of a metal strip or any other type of conductor.

Arranged in the body 1 at an angle .alpha. to the driving element 2 is a part 5 one end of which is secured to support 4. The other end of the part 5 is fastened by a joint 6 in the body 1. The end of the part 5 has a rod 7 connecting it with the movable member 8 of the shut-off element 9.

A spring 10 is installed between the body 1 and the part 5 to hold the driving element 2 in a constantly stretched state and constantly stresses the part 5.

The driving element 2 is connected by wires 11 to a D.C. (or A.C.) source of power supply (not shown) for elongating it by heating.

The installation of the part 5 at an acute angle .alpha. to the driving element 2 increases the working travel of the movable member 8 of the shut-off element 9 many times as compared with the elongation of the driving element 2 through heating.

To simplify the design of the drive, the part 5 and the spring 10 may be replaced by a leaf spring 12 (FIG. 3). The spring 12 is installed in the body in such a way that one of its ends mounts the support 4 and the rod 7 which latter connects it with the movable member 8, while its second end is fastened rigidly in the drive body 1. Provision of such a spring simplifies the design of the drive and reduces its dimensions to a certain extent.

In order to still further increase the working travel of the movable member 8 of the shut-off element 9 at the same consumption of electric power or to reduce the power consumption for the same travel of the movable member 8, it is preferred that the drive be located in a pressuretight body 1 as shown in FIG. 4.

At the point where the driving element 2 is connected with the movable member 8 of the shut-off element 9, the body 1 is sealed by a flexible element 13, for example, a bellows.

The installation of the drive in vacuumized body reduces the heat exchange between the heated driving element 2 and the ambient medium, thereby increasing the working travel of the movable member 8 of the shut-off element 9.

For this purpose, it is preferred to coat the wire from which the turns of the driving element 2 are made with a material having a low coefficient of blackness, for example gold or silver. The term "coefficient of blackness" denotes the ratio of heat radiated by a given body to the amount of heat radiated by a perfectly black body at equal temperatures. If the coefficient of blackness of the turns of the driving element 2 is reduced, the quantity of heat radiated by them is sharply decreased. This ensures additional elongation of the driving element 2 and, consequently, increases the working travel of the movable member 8 of the shut-off element 9 at equal power consumptions, compared to a drive whose turns are not coated with a layer of gold or silver.

The reciprocating drive for the movable member of the shut-off element operates as follows.

Before the driving element 2 is energized, all the parts of the drive occupy positions shown in FIG. 1 and represented graphically in FIG. 5 by triangle ABC. As the driving element 2 is energized from the source of power supply (not shown), said element is heated and elongated from the length of AB TO AB' . As a result, the support 4 moves from point B to point B' . Being actuated by the spring 10, the part 5 turns clockwise around the joint 6. The rod 7 moves the movable member 8 of the shut-off element 9 downwardly.

The force of the drive depends on the characteristics of the spring 10.

In view of the fact that angle .alpha. is acute, the displacement BB' in the direction of movement of the movable member 8 is larger than the elongation of the driving element 2, as seen from the relation CB/AC.

If angle .alpha. is diminished, the relation CB/AC increases and, consequently, the travel of the movable member 8 becomes longer at the same elongation of the driving element 2.

When the power supply is cut off, the driving element 2 cools and becomes shorter. All the parts of the drive move in the direction opposite to that described above.

The reciprocating drive for the movable member of a shut-off element realized according to the present invention is ten times lighter and approximately as many times cheaper than an electromagnetic drive consuming the same power, ensuring the same travel of the movable member and developing the same forces. The drive realized according to the present invention is simple to manufacture, reliable in operation and can use both direct and alternating current. Besides, as distinct from an electromagnet, this drive can hold the movable member of the shut-off element in any intermediate position, thus regulating the amount of heat supplied to the driving element 2 of the drive.

Claims

What is claimed is:

1. A reciprocal drive for a shut-off element, said drive comprising a pressuretight and vacuumized body; a driving element in said body and including at least one wire turn extending along a longitudinal axis, and electrical supply means connected to the wire turn to heat the same; two supports for said driving element, one of which is secured in said body while the other one is free for movement when the length of said driving element changes due to heating thereof; a displaceable actuator member for said shut off member extending within said body; and means coupling the movable support with the actuator member to follow the movement of the support, the latter means comprising a spring-loaded member disposed on said body at an acute angle relative to the longitudinal axis of said driving element, means attaching one end of said spring-loaded member to said body, and means attaching said spring-loaded member to said second support remote from said one end.

2. A drive according to claim 1 wherein said spring-loaded member comprises a leaf spring whose one end is rigidly secured in the drive body.

3. A drive according to claim 1 wherein said wire turn of the driving element is coated with a layer of a material with a low coefficient of blackness.

4. A drive according to claim 1 wherein said spring-loaded member is in contact with the actuator member at a location remote from the location where the spring-loaded member is attached to said body.

5. A drive according to claim 1 wherein said supports are each cylindrical and said wire turn extends around the supports.