GB2257301A - Antenna mounting - Google Patents

Abstract

An antenna mounting comprises two parts (base 1 and body 3) connected for relative rotation on a vertical axis (2), a direct drive motor (at 10) on the axis (2) for imparting the relative rotation, and a rigid waveguide (7) for conveying antenna signals between the two parts (3,1), the waveguide extending on the axis (2) through the motor and having a rotary joint (71, 72) on the axis. The rotary drive is free of backlash. <IMAGE>

Description

Antenna Mounting This invention relates to a rotary antenna mounting including a rotary drive motor, and is particularly applicable to antenna mountings in which the rotary drive is in either direction.

In such antenna mountings, the rotary drive is conventionally applied through reduction gearing and this causes backlash whenever the rotational sense is changed, leading to imprecise positioning of the antenna and to wear in the rotary drive. However, since it is usual for the antenna signal to be guided between the relatively rotatable parts by way of a rigid waveguide with a rotary joint, which has to be on the rotational axis of the two parts, no satisfactory alternative rotary drive has hitherto been found.

The invention provides an antenna mounting comprising two parts connected for relative rotation on an axis, a direct drive motor on the axis for imparting the relative rotation, the rotor and stator of the motor being mounted in respective ones of the two parts, and a rigid waveguide for conveying antenna signals between the two parts; the waveguide extending on the axis through the motor and having a rotary joint on the axis.

The use of the direct drive motor, which is preferably a cageless ring motor, avoids any backlash in the rotary drive, and, being open-ended, allows the waveguide to extend on the axis through the motor.

Preferably, the antenna mounting further comprises a slip ring connector co-axial with the motor and having two relatively rotatable components connected to respective ones of the said two parts, for making electrical interconnections between the two parts.

In order that the invention may be better understood, a preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a side elevation of a complete antenna for mounting on the deck of a ship, and including an antenna mounting embodying the invention; Fig. 2 is a part sectional view on the arrow A of Figure 1, to an enlarged scale; and Fig. 3 is a section, to a greatly enlarged scale, in the plane of Figure 2, of the direct drive motor of the antenna mounting of Figures 1 and 2.

An antenna comprises a base 1 for mounting on the deck of a ship, from which projects vertically a column 16 rigid with respect to the base 1. A rotary body 3 is mounted over the column 16 for free rotation about a vertical axis 2 through the column 16, and is supported on two sets of roller bearings 14,15 (Fig. 2). A reflector body 5 is mounted on an upper part of the rotary body 3 for free rotary movement about a horizontal axis 6 perpendicular to the axis 4 of the reflector body 5. The reflector body 5 is driven about the axis 6 by a bidirectional direct drive frameless motor 61, through which passes a waveguide 7 for conveying antenna signals from the reflector body 5 to a receiver (not shown).

The rotary drive between the reflector body 5 and the rotary body 3 is similar in construction and function to a rotary drive between the rotary body 3 and the base 1, and accordingly only the latter will be described in detail.

The rotary drive is supplied by a bi-directional direct drive frameless motor of which the rotor 21 is connected rigidly to the frame 13 of the rotary body 3, and the stator 20 is connected rigidly to a frame of the column 16. The motor is a cageless ring motor, in which the rotor and stator are concentric and axially-coextensive rings. As shown most clearly in Figure 3, a commutator brush assembly 22 is carried by the rotor 21.

In order to provide electrical interconnections between the relatively rotatable rotary body 3 and the base 1, a power or signal capsule slip ring assembly 10 is mounted in the column 16 on the axis of rotation 2. The slip ring assembly 10 is of a conventional type, having inner and outer drums (not shown) which are open-ended on the axis 2 so as to allow the waveguide 7 to pass along the axis. The outer drum, which is stationary with respect to the base 1 and column 16, has electrical terminals 17 on its lower end plate. The inner drum is provided with a corresponding set of electrical terminals 9 on its upper end plate 11. The inner drum, which is mounted for rotation about the axis 2 relative to the outer drum, is driven by way of a pawl 12 by the frame 13 of the rotary body 3.The inner surface of the outer drum and the outer surface of the inner drum are provided with opposed ring-shaped conductive tracks (or other terminal connections) each connected to a corresponding terminal on an end plate, and brushes or other means connect the conductive tracks of one drum with corresponding conductive tracks (or other terminal connections) of the other, so as to provide a permanent connection between the two sets of terminals 9, 17.

Electrical cables 18 connect the slip ring assembly lower terminals 17 with output terminals 19 in the base 1. Electrical cables 8 connect the upper terminals 9 of the slip ring assembly with further apparatus on the rotary body 3, including the drive motor 61.

As shown in Figure 1, the waveguide 7, which is of square-section (or other rectangular section) and is rigid, is ducted through the drive motor 20,21 and slip ring assembly 10 along the axis 2. A rotary joint 71,72 in the waveguide 7 permits the relative rotation of the rotary body 3 and the base 1. The upper part 71 of the joint comprises a square-to-circular section adaptor, rigid with the rotary body 3, and the lower part 72 of the joint, which is connected rotatably to the upper part 71 by a bearing, comprises a circular-to-square section adaptor.

Claims (10)

1. An antenna mounting comprising two parts connected for relative rotation on an axis, a direct drive motor on the axis for imparting the relative rotation, the rotor and stator of the motor being mounted in respective ones of the two parts, and a rigid waveguide for conveying antenna signals between the two parts, the waveguide extending on the axis through the motor and having a rotary joint on the axis.

2. An antenna mounting according to claim 1, further comprising a slip ring connector co-axial with the motor and having two relatively rotatable components connected to respective ones of the said two parts, for making electrical interconnections between the two parts.

3. An antenna mounting according to claim 1 or 2, wherein the waveguide has a rectangular section and has a rectangular-circular-rectangular section rotary waveguide coupler on the axis.

4. An antenna mounting according to claim 1,2 or 3, wherein the motor is operable selectively in either rotational sense.

5. An antenna mounting according to any preceding claim, further comprising a third part connected for rotation relative to the second part on a further axis, and a second direct drive motor on the further axis for imparting the relative rotation between the second and third parts, the rotor and stator of the second motor being mounted in respective ones of the second and third parts, and the waveguide having a continuation extending on the further axis through the second motor and having a rotary joint on the further axis.

6. An antenna mounting according to claim 5, wherein the power supply for the further motor is sent through the slip ring connector.

7. An antenna mounting according to any preceding claim, comprising a servo system responsive to the position of the antenna, in use, to control the or each motor to position the antenna at a desired position.

8. An antenna mounting according to any preceding claim, wherein the motor is a cageless ring motor.

9. An antenna having a mounting according to any preceding claim.

10. An antenna mounting substantially as described herein with reference to the accompanying drawings.