GB2201507A

GB2201507A - Electric motor driven linear actuator with electro-magnetic release

Info

Publication number: GB2201507A
Application number: GB08719699A
Authority: GB
Inventors: Peter Norris Yeatman
Original assignee: Colt International Ltd
Current assignee: Colt International Ltd
Priority date: 1986-12-16
Filing date: 1987-08-20
Publication date: 1988-09-01
Also published as: GB8719699D0; GB8630050D0

Abstract

The actuator (19) is intended for a ventilator having an electro-mechanical control mechanism operable to open and close the ventilator via a force transmitting member (10) formed in two sections (4, 5) which are normally retained telescoped one with respect to the other by an electro-magnetic device (3) mounted on one of the sections (4, 5) and an electro-magnetic keeper plate (6) mounted-on the other of the sections (4, 5) energising means (8) being provided tending to extend the force transmitting member (10). The actuator (19) comprises co-operating screw threaded elements (2, 23) one of which is arranged to be driven by a reversible electric motor (1). <IMAGE>

Description

ELECTRIC MOTOR DRIVEN LINEAR ACTUATOR WITH ELECTRO-MAGNETIC RELEASE This invention relates to ventilators which term is to be taken to include automatic windows and doors which may be used as fire ventilators and/or for smoke control in emergencies, and concerns electro-mechanical controls for opening and closing such ventilators.

It is well known to provide ventilating systems requiring the impartation of a linear movement to a ventilator control member upon the operation of two different control systems to open or close a ventilator or a series of ventilators. Typically a ventilator may be required to be opened or closed under the control both of say a normal, day-to-day ventilation management system and opened or fully opened or closed under the control of say an emergency fire ventilation system.

GB-A-2,167,552 describes a ventilator having an electro-mechanical control mechanism capable of responding to both normal and emergency systems comprising a linear actuator operable to open and close -the ventilator via a force transmitting member formed in two sections which are normally retained telescoped one with respect to the other by an electro-magnetic device mounted on one of the sections and an electromagnetic keeper plate mounted on the other of the sections, energising means being provided tending to extend the force transmitting member.

In this prior art arrangement, the linear actuator takes the form of a pneumatic piston and cylinder of which the piston rod constitutes one section of the force transmitting member.

GB-A-2,167,552 also describes a ventilator having a control mechanism comprising an electric motor operable to drive a crank arm connected to the force transmitting member.

There is a need to provide, in a ventilator, an electric motor powered linear actuator of small dimensions capable of responding to two different control systems. Such actuators not only may conveniently be housed in the ventilator frame in direct replacement for a pneumatically operated linear actuator, but also they may be used as back-up actuators for emergency operation in substitution for failed controls.

According to the present invention and proceeding from a ventilator as described in GB-A-2,167,552 having a linear actuator, the present invention is characterized in that the actuator comprises co-operating screw threaded elements one of which is arranged to be driven by a reversible electric motor.

Preferably, one section of the force transmitting member is formed as an internally screw threaded element of said linear actuator, said motor driving an externally screw threaded rod element of said actuator, said rod element being received within the other section of the force transmitting member at least when the two sections of the force transmitting member are retained telescoped by the electro-magnetic device.

The accompanying drawing illustrates one specific embodiment of the present invention by way of example.

In the drawing: FIG. 1 shows a ventilator control comprising a linear actuator; FIG. 2 shows an elevation, in part in crosssection of the actuator; and FIG. 3 shows a modification.

With reference now to the accompanying drawing and first to Fig. 1, a linear actuator 19 for controlling the day-to-day opening and closing of a ventilator such as a louvred ventilator or an automatic window or door or again, a ducted fire ventilator, is connected to operate a member 7 of the ventilator which its bodily movable in opposite directions 9 respectively to open and close the ventilator. Spring energising means such as 8, which may be a gas spring, acts on the member 7 tending to displace the member 7 and open the ventilator. The spring means 8 may act directly or indirectly on the member 7 which may move linearly as illustrated in phantom lines in Fig. 1 or with pivoting at its. pivotal connection 12 with the actuator 19.

The actuator 19 comprises a small reversible 24V d.c. elecric motor 1 which is directly coupled to drive an externally screw threaded rod 2, the rod 2 extending with its longitudinal axis along the axis of rotation of the motor. A force transmitting member 10, formed in two tubular sections 4, 5 is normally retained with its section 5 telescoped within its section 4 by an electro-magnetic device 3 mounted on the section.4 and an electro-magnetic keeper plate 6 mounted on the section 5. De-energisation of the electro-magnetic device 3, e.g. under the control of an automatic fire or smoke ventilation system releases the keeper plate 6 and allows the ventilator to open under the action of the spring means 8, the plate 6 then moving to the phantom line position shown in Fig.

1 of the drawing.

Subsequent operation of the motor 1 rotates the rod 2 to advance a nut 23 fixed to the section 4 and screw-threadedly engaged with the rod 2 to extend the section 4 of the force transmitting member 10 from a tubular casing 25 of the actuator to move the electromagnetic device 3 into contact with the plate 6.

Re-energisation of the electro-magnetic device 3 then re-sets the ventilator for automatic operation.

In normal day-to-day operation of the ventilator the motor 1 is driven to extend and retract the force transmitting member 10 from the casing 25 to open and to close the ventilator, the section 5 of the member being retained telescoped within the section 4 of the member and over the rod 2 by the electro-magnetic device 3 magnetically holding the keeper plate 6. Thus, the section 5 of the force transmitting member telescopically receives the rod 2 in order to foreshorten the actuator.

The actuator 19 is operable to impart a predetermined start and finish for the displacement of the distal end of the force transmitting member 10. Thus, a pair of spaced apart, electrical limit switches 27, e.g. micro-switches, are each adjustably mounted as to position in a housing 30 on the casing 25 to be operated by a rod 32 fixed to the device 3 and movable lengthwise in the housing 30.

By adjusting the positions of the switches 27, the member 10 may be set for linear movement by the actuator accurately to fully open, and to fully close, the ventilator as well as to reset the ventilator after its automatic operation in which the device 3 is de-energised. The position of the left-hand switch 27 in Fig. 2 determines the closed position of the ventilator and the position of the right-hand switch in Fig. 2 determines the fully open position of the ventilator.

Fig. 3 illustrates a modification in which the keeper plate 6 is loosely mounted on the section 5 of the member 10 to allow the keeper plate to align itself with the armature of the device 3. Alternatively, the keeper plate 6 may be mounted to the section 5 by means of a flexible coupling.

In the event of a power failure, the ventilator "fails safe" as a fire ventilator and moves to its fully open position.

Claims

CLAIMS:

1. A ventilator having an electro-mechanical control mechanism comprising a linear actuator operable to open and close the ventilator via a force transmitting member formed in two sections which are normally retained telescoped one with respect to the other by an electromagnetic device mounted on one of the sections and an electro-magnetic keeper plate mounted on the other of the sections, energising means being provided tending to extend the force transmitting member characterised in that the actuator comprises co-operating screw threaded elements one of which is arranged to be driven by a reversible electric motor.

2. A ventilator as claimed in claim 1, wherein one section of the force transmitting member is formed as an internally screw threaded element of said linear actuator, said motor driving an externally screw threaded rod element of said actuator, said rod element being received within the other section of the force transmitting member, at least when the two sections of the force transmitting member are retained telescoped by the electro-magnetic device.

3. A ventilator as claimed in claim 1 or 2, wherein the electric motor directly drives the screw threaded rod, the rod extending with its longitudinal axis along the axis of rotation of the motor.

4. A ventilator as claimed in any preceding claim, wherein carried with said one of said sections of said force transmitting member is a switch operating member for operating limit switches carried by a casing of said actuator, said switches being adjustably positionable along the casing to pre-set the start and finish of the displacement of the force transmitting member.

5. A ventilator as claimed in any preceding claim, wherein the keeper plate is flexibly or loosely mounted to the other of the sections of the force transmitting member.