GB2134221A

GB2134221A - Motor-driven valve

Info

Publication number: GB2134221A
Application number: GB08325885A
Authority: GB
Inventors: Ekkehard Brzoska; Klaus Traeger
Original assignee: Deutsche Babcock Werke AG
Current assignee: Deutsche Babcock Werke AG
Priority date: 1982-12-22
Filing date: 1983-09-28
Publication date: 1984-08-08
Also published as: IT8349544A0; GB8325885D0; GB2134221B; DE3247490C2; DE3247490A1; FR2538497B1; CS239946B2; FR2538497A1; DD210731A5; IT1197761B

Abstract

In a motor-driven valve comprising a valve closure element displaceable between end settings by a rising spindle (12) connected by a nut (11) with the output shaft (10) of an electric motor (9) capable of being switched off by limit switches, a torque-absorbing spring such as a torsion bar (19) is connected between the nut (11) and the output shaft (10) in order to protect the valve element and the motor, in the event of failure of either of the limit switches, against overload through excess torque, and spaced abutments (16, 17) co- operate with the torsion bar by coming to bear against a respective countersurface, for example on the nut (11), if the closure element is displaced beyond a respective one of the end settings. <IMAGE>

Description

SPECIFICATION Motor-driven valve The present invention relates to motor-driven valve, and has particular reference to, for example, a valve with a valve element displaceable by a spindle connected through a spindle nut with the output of an electric motor, which in the end settings of the valve element is able to be switched off through limit switches.

In valves of this kind, limit switches can act in dependence on torque and/or travel according to the kind of armature and system.

They are set so that the motor switches off in the end settings of a predetermined setting travel. Through this limitation of torque or travel, the valve is protected against an overload as long as the limit switch is serviceable.

In the event of failure of a limit switch, the motor would, after the seating of the valve element, load the spindle by a constantly increasing moment before the motor would stop in consequence of overload. The same would occur when the valve element in its open setting lies against a rear seal. This creates a danger that the valve components as well as the motor could be damaged or destroyed. In order to counter this danger, the valve components and the motor would have to be designed for this excess momemt, which would however significantly increase their cost. This disadvantage could be avoided through the incorporation of a predetermined fracture point, but in the event of fracture at this point, the valve would no longer be serviceable.

There is thus a need for protection of the motor against overload in such a manner that the valve is undamaged and remains serviceable after the occurrence of an excess moment.

According to the present invention there is provided a motor-driven valve comprising a spindle carrying a valve element, a spindle nut drivable to cause the spindle to displace the valve element between two end settings thereof, an electric motor which is operable to drive the spindle nut by way of a torqueabsorbing spring element connected between the nut and output means of the motor and which is controllable to be switched off on attainment of the valve element end settings, and two abutments arranged on the spindle at a spacing from each other to each engage a respective stop surface after attainment of a respective one of the valve element end settings.

In the case of a valve according to a preferred embodiment of the invention, if a limit switch fails and the motor remains switched on even though the valve element bears agains a sealing seat and a spring bias required for maintenance of the sealing tightness has been exerted, then the relevant abutment thereafter comes onto a counter surface at the housing side, for example on the spindle nut. The further moment exerted by the motor is now absorbed by the spring element and converted into deformation work until the motor stops by reason of the overload and is switched off, for example through a thermal switch at the drive side. The moment still acting on the armature is absorbed in the upper part of the armature. In such an embodiment, only this part and not the entire valve need be designed for the excess moment.After the assumed case of damage of a failure of the limit switch, the motor and the armature remain serviceable. If the valve element entid setting that is exceeded is due to a failure of a limit switch during opening of the valve, the spring element and the other abutment co-operate in analogous manner.

The valve can be of any type, including a slide, actuated by an electric motor setting drive and, for example, provided with a limit switch dependent on torque and/or travel.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Figure 1 is a sectional front elevation of a valve embodying the invention; and Figure 2 is a detail view, to an enlarged scale, of the area X in Fig. 1.

Referring now to the drawings, there is shown a valve which comprises a housing 1 with an inlet 2 and an outlet 3. The valve is closed by a closure element, guided in a cylinder 4, in the form of a cone 5, which is pressed with a certain positioning moment against a seating surface 6 at the housing side. The cylinder, together with a housing attachment 7, are screwed onto the valve housing 1. An electric motor 9 is mounted on the attachment 7 by an intermediate flange 8.

Installed in the motor 9 are limit switches (not shown) which are dependent on torque and which serve to switch off the motor when one of the end settings of the closure element is reached.

The output shaft 10 of the motor 9 is connected with a spindle nut 11 in a manner which will be later described in more detail.

The spindle nut 11 surrounds the upper part of an upright spindle 1 2 and is resiliently rotatably mounted in the housing attachment 7. The spindle 12 extends through the housing attachment 7 and the cylinder 4 with sealing relative thereto and carries the valve cone 5 at its lower end. Springs 13, which are arranged between the spindle nut 11 and the intermediate flange 8, provide a certain bias of the spindle 1 2 when the cone 5 has seated.

At its end face facing the cone 5, the cylinder 4 is provided with a rear seat 14, against which the cone 5 lies in the open setting of the valve. Springs 15, which are arranged between the housing attachment 7 and the spindle nut 11, provide a certain bias of the spindle 1 2 when the valve cone 5 is raised.

An abutment 1 6 is provided on the head of the spindle 1 2. The abutment 1 6 can consist of a nut which is threaded onto the spindle 1 2 and locked in place. The abutment 1 6 is so adjusted that it comes to bear on a counter surface at the housing side after the spindle 1 2 has placed the cone 5 onto the seating surface 6 whereby the valve is closed. The end face of the spindle nut 11 is preferably utilized as the counter surface at the housing side.

A further abutment 17, also in the form of a nut, is fastened on the spindle 1 2 underneath the nut 11. This further abutment 1 7 is so adjusted that it comes to bear against the lower end face of the nut 11 as a counter surface on the housing side after the spindle 1 2 in open setting of the valve has driven the upper end face of the valve cone 5 against the rear seating 14.

The spindle nut 11 is connected with a drive sleeve 18, to which a spring element, for example a torsion bar 19, is fastened. The torsion bar 1 9 lies in an extension of the longitudinal axis of the spindle 1 2 and is connected through an intermediate piece 20 with the output shaft 10 of the motor 9.

In normal operation of the valve, the positioning moment of the motor 9 is transmitted through the intermediate piece 20, the torsion bar 1 9 and the drive sleeve 1 8 to the spindle nut 11. In the event that one of the limit switches fails and the motor remains switched on although the spindle 1 2 has reached one of its end settings and the valve cone 5 is thereby pressed against the seating surface 6 or the rear seating 14, the abutment 16 or 17 has also laid itself against the spindle nut 11.

Thereby, any further loading of the spindle 1 2 and valve cone 5 is inhibited. The loading from the motor is absorbed in the upper part of the housing attachment 7 and through the intermediate piece 20 and trranslated into deformation of the torsion bar 1 9. At the same time, however, the required sealing force is also present through the biassed springs 1 3 and 1 5 at the seating surface 6 or the rear seating 14. The torsion bar 1 9 is so dimensioned that it can absorb 1.5 to 10 times the value of the setting moment of the motor 9.

Since the transmission of torque from the motor to the spindle in a slide takes place in the same manner, the spring element can also be used in conjunction with the abutments for slides.

Claims

1. A motor-driven valve comprising a spindle carrying a valve element, a spindle nut drivable to cause the spindle to displace the valve element between two end settings thereof, an electric motor which is operable to drive the spindle nut by way of a torqueabsorbing spring element connected between the nut end output means of the motor and which is controllable to be swiched off on attainment of the valve element end settings, and two abutments arranged on the spindle at a spacing from each other to each engage a respective stop surface after attainment of a respective one of the valve element end settings.

2. A valve as claimed in claim 1, wherein each of the abutments is adjustable in its position on the spindle.

3. A valve as claimed in claim 2, wherein each of the abutments comprises a nut threadedly engaged on the spindle.

4. A valve as claimed in any one of the preceding claims, wherein the stop surfaces are provided by surface portions of the spindle nut.

5. A valve as claimed in any one of the preceding claims, wherein the spring element is a torsion bar.

6. A valve as claimed in any one of the preceding claims, wherein the spring element is constructed to absorb 1.5 to 10 times the torque of the motor.

7. A valve substantially as hereinbefore described with reference to the accompanying drawings.