GB2330005A - Traverse drive for antennae - Google Patents

Abstract

An improved traverse drive (i.e. horizon to horizon) for antennae has an endless drive chain 16 running on a driven chain pulley 12 and an idler pulley 14. The chain 16 incorporates a connecting link 18 to which is attached the jack end of a powered linear actuator 10. Operating the actuator 10 causes linear movement in the chain resulting in rotational movement of the pulleys 14 and 16. The antennae 20 is mounted as one with the driven pulley 16 and can consequently be traversed as desired according to the operation of the actuator.

Description

IMPROVED TRAVERSE DRIVE (H to H) FOR ANTENNAE This invention relates to an improved traverse drive for antennae.

Traverse drives are well known for the purpose of rotating antennae or satellite dishes in a horizontal plane. These frequently take the form of rotary actuators consisting of electric motors acting through some form of geared reduction. These are however expensive because of the need to design and manufacture them specially for each application whilst reducing freeplay and backlash to the necessary minimum for precision movement. Linear actuators usually comprising a motor gearbox unit driving a screwjack may be cheaply and readily bought as standard assemblies, precision being achieved by selective or controlled manufacture of certain parts and these have been used in order to provide limited traverse. If a crank is used, it is difficult to convert precision linear movement into precision rotary movement because the thrust of the jack becomes less effective in proportion to the amount it moves out of perpendicular to the crank. In order to achieve the desired rotation, a pair of cranks and linear actuators have been used in tandem but the effect is still present.

According to the present invention there is provided an improved traverse drive for antennae comprising an electrically operated linear actuator, an endless drive chain or toothed timing belt on two pulley wheels, one of which drives the shaft or member on which the antenna is mounted and the other of which is an idler. The actuator is mounted parallel to and either directly above or to one side of one leg of the drive chain or belt, it's jack end being connected rigidly to it by a linking member so that both move as one when the former is operated. If desired the movement may be further controlled in order to eliminate any tilting due to out of line forces by making the linking member move on a suitably shaped slide provided for the purpose. If further desired in order to reduce overall length of the assembly, the actuator may be mounted nearer to the antenna end of the drive and connection made between the jack end and the linking member on the chain by a connecting rod. The antenna drive pulley is sized to give the desired amount of angular movement from the available stroke of the jack and the pulleys spaced to accomodate the latter. Either pulley may be used for the purposes of chain or belt tension adjustment and additional pulleys inserted if desired.

By the means just described, linear motion of the actuator jack imparts corresponding linear motion to the straight leg of the chain, which in turn causes rotation of the pulley wheels such that where D is the pitch circle diameter of the pulley which rotates with the antenna mounting spindle, a linear movement of H (3.142) x D units ofjack and chain will result in 360" rotational movement of the antenna on it's mounting spindle or otherwise in direct proportion thereto.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which :- Figure 1 shows the drive in plan.

Referring to the drawing the drive comprises an electric linear actuator 10, a driven chain pulley 12 which rotates as one with the antenna 20, an idler chain pulley 14 and a drive chain 16 to which is attached or clamped the jack end of the actuator 10 by a link 18 itself rigidly attached to the actuator jack. If desired the link 18 may be made to slide on a guide [not shown] mounted parallel to the adjacent leg of the chain but this is not obligatory. If further desired, the actuator 10 in order to save space may be positioned nearer to to the driven chain pulley 12 and made to move the link 18 by means of a connecting rod [not shown]. The Operation of the actuator 10 causes a to and fro movement ofthe chain 16 with consequent rotation ofthe pulleys 12 and 14. If desired a toothed timing belt and pulleys may be substituted for the chain 16 and the chain pulleys 12 and 14.

Claims (1)

1. CLAIMS 1 An improved traverse drive (horizon to horizon) for antennae comprising a powered linear actuator, an endless drive chain or toothed timing belt on two sprockets or toothed pulley wheels, one of which drives the shaft or member on which the antennae is mounted and the other of which is an idler.