GB2262199A - A security camera drive arrangement - Google Patents

Abstract

A security camera housing adapted to support a television camera mounted on a rotatable support member driven by a final drive wheel (21) thus to pan across a site to be viewed includes drive means for the support member comprising at least two motors (29, 30) which are capable of driving the support member separately or simultaneously through reduction gearboxes (28, 31) and an epicyclic gearbox (24, 25, 26) to enable rotation of the camera slowly in an automatic mode or at an increased speed to follow a moving target or to turn rapidly to a desired direction. The system utilises reliable fixed speed motors which do not require brushes or expensive variable frequency controllers or mechanical clutches and so is inexpensive to manufacture and maintain. The camera may be driven at the speed of either motor or at the sum or difference of their speeds. <IMAGE>

Description

A SECURITY CAMERA HOUSING THIS INVENTION concerns a security camera housing of the kind in which at least one television camera is mounted on a rotatable support member usually known as a satellite and adapted to pan across a site to be viewed. The camera is connected to a television monitor disposed remotely from the camera housing.

Such camera housings may be required to pan or rotate at different speeds so that, for example, in an automatic mode the speed of rotation should be slow enough to provide a clear and intelligible view of the overall site, whilst in manual mode the rotational speed may be increased to follow a moving target or turn to a desired direction as quickly as possible.

Whilst most conventional systems incorporate a reliable single fixed speed motor, some include a variable speed DC motor or a stepper motor so that different speeds may be selected. However, the control systems for such arrangements are expensive and often troublesome. Clutches and other devices to control the motor speed cause problems in operation, and it has been found that drive means of the conventional kinds using a DC motor may have a life expectancy of only 2000 to 3000 working hours.

An object of the present invention is to provide a security camera housing having a plurality of available operational speeds and in which the aforementioned disadvantages are substantially avoided.

According to the present invention a security camera housing having at least one television camera mounted on a rotatable support member and having drive means to rotate said member, is characterised in that the drive means comprises at least two motors drivingly connected to an epicyclic gearbox whose final drive is connected to the rotatable support member.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which: Fig. 1 illustrates an arrangement according to the prior art incorporating a single fixed or variable speed motor to drive a camera housing; and Fig. 2 illustrates a drive system for the camera housing, made in accordance with the invention.

Referring now to Fig. 1, in a conventional and very simple system the television camera 10 is mounted on an inclined support 11 which is rotatable about an axis 12 on a spindle 13. The spindle 13 carries a large diameter drive wheel 14 which meshes with a final drive wheel 15 attached to the output shaft 16 of a reduction gearbox 17 driven by a fixed speed electric motor 18. A fixed plate 19 serves to mount the motor gearbox as well as a bearing member 20.

In an arrangement such as this the camera 10 may be arranged to tilt about a horizontal axis thus to pan in a vertical plane, but for the sake of clarity the tilting mechanism and associated motor have been omitted.

Referring now to Fig. 2, in accordance with the invention the final drive wheel 21 is mounted on the output shaft 22 of an epicyclic gearbox indicated generally by the dotted lines 23. The spindle carries an annular wheel 24 which forms part of the epicyclic gear train including also planet gears 25 and a sun wheel 26 connected to the output shaft 27 of a first reduction gearbox 28.

This is driven by a first electric motor 29.

A second electric motor 30 is connected via a reduction gearbox 31 and output; shaft 32 to a drive wheel 33 within the epicyclic gearbox 23.

The two motors are preferably fixed speed reversible synchronous A.C motors which may be operated by either a 24-volt or 240-volt electrical supply.

As in the embodiment illustrated in Fig. 1, the final drive wheel 21 is adapted to drive the camera housing via a large diameter drive wheel similar to the wheel 14 illustrated in Fig. 1.

In operation, with motor 29 stopped, motor 30 drives the camera through the annular wheel 24 of the epicyclic gear box to provide slow speed at the final drive wheel 21. Thus the camera is panned slowly for automatic operation. The braking resistance of gearbox 28 prevents the motor 29 from back-running so that the drive to wheel 21 is not lost.

When it is required to drive the camera at a faster speed, manual control is introduced by stopping motor 30 and driving motor 29 through the planet gears 25 to provide the increased speed at the final drive wheel 21. The reduction gearbox 31 provides adequate braking resistance to ensure that motor 30 cannot be driven backwards.

Two further operational speeds are provided by running motors 29 and 30 together to achieve the sum of the slow and fast speeds or the difference therebetween.

For example, motor 30 may be preset to provide a final drive to the camera housing to produce rotation thereof at the rate of 8"/sex. If motor 29 is preset to produce rotation at the rate of 20"/sex, then additional speeds are available at rates of 12"/sex and 28"/sex by operating the two motors together through the epicyclic gearbox 23.

If reduction gearboxes 28 and 30 do not provide sufficient braking effect to prevent back-running of the motors, then additional brakes must be provided.

It will be appreciated that the advantages of the system described are that it is possible to rotate or pan a camera at a number of selectable speeds as required. The system utilises reliable fixed speed motors which do not require brushes or expensive variable frequency controllers or mechanical clutches. Thus, the system will be inexpensive to manufacture and maintain, and its life expectancy will be much greater than with conventional variable speed motordriven housings.

Claims (7)

1. A security camera housing adapted to support at least one television camera mounted on a rotatable support member, and having drive means to rotate said member, characterised in that the drive means comprises at least two motors drivingly connection to an epicyclic gearbox having a final drive connected to the rotatable support member.

2. A security camera housing according to Claim 1, wherein said motors are adapted to drive the rotatable support member at different speeds respectively.

3. A security camera housing according to Claim 1 or Claim 2, wherein each motor is adapted to drive the rotatable support member through a separate reduction gearbox.

4. A security camera housing according to Claim 3, wherein the braking resistance of each reduction gearbox is sufficient to prevent its associated motor from back-running when the other motor is driving the rotatable support member.

5. A security camera housing according to any preceding Claim, wherein said motors are fixed speed reversible synchronous AC electric motors.

6. A security camera housing according to any preceding claim, wherein said motors are adapted to be driven individually or simultaneously thus to provide, via said epicyclic gearbox, four selectable operating speeds for the rotatable support member.

7. A security camera housing substantially as hereinbefore described, with reference to and as illustrated in Fig. 2 of the accompanying drawings.