GB2102533A

GB2102533A - Buffer assemblies

Info

Publication number: GB2102533A
Application number: GB08121951A
Authority: GB
Inventors: Richard Cresswell
Original assignee: Marconi Co Ltd
Current assignee: BAE Systems Electronics Ltd
Priority date: 1981-07-16
Filing date: 1981-07-16
Publication date: 1983-02-02
Also published as: GB2102533B

Abstract

It may often be the case that the allowable range of angular movement of an object, such as a steerable microwave aerial, mounted for rotation about an axis needs to be finite, the end-of- range positions being defined, and mechanically constructed, using end stops (buffer units) which are fixedly secured to one of either the rotating object or its mounting and which interact with a stop abutment member (striker plate) fixedly secured to the other, and yet greater than 360 DEG . The invention seeks to allow such a range to an aerial (or other rotating object) by arranging for the interaction between buffer unit 21 and striker plate 24 to be via a buffer plate 23 slideably mounted upon an arcuate guide rail 22 extending between two buffer units; the striker plate engages not the buffer units but the buffer plate, which slides up to and engages the relevant buffer unit, so extending the movement range by the angle subtended by the two buffer units. The buffer units may contain friction ring-springs, or may be simple physical stops. As shown an aerial attached to framework 12 may be rotated through more than 360 DEG in an anti-clockwise direction before being stopped by the entrained buffer plate 23 engaging the right-hand buffer unit. <IMAGE>

Description

SPECIFICATION Buffer assemblies This invention relates to buffer assemblies, and concerns in particular mechanical buffer assemblies useful for controlling the angular range of large, relatively massive rotatably moveable objects such as steerable microwave aerials.

It may often be the case that the allowable range of angular movement of an object mounted for rotation about an axis needs to be finite, and that the end-of-range positions are defined, and mechanically constructed, using end stops (buffers) which are fixedly secured to one of either the rotating object or its mounting and which interact with a stop abuttment member equaliy fixedly secured to the other.

As a trivial example, the swing of a door is limited at one end of its range by the door catch/jamb, while at the other end it may be limited by a door stop.

The invention concerns in particular the construction of buffers - or, rather, of buffer assemblies - for use with steerable microwave aerials, especially those of the kind employed in satellite communication systems, and thus relates primarily to assemblies capable of buffering the movement of a large, heavy aerial which must usually be capable of at least 3600 movement in azimuth (in the "horizontal" plane, and about a "vertical" axis), as well as as much as 1800 in elevation (in the "vertical" plane, and about a "horizontal" axis).

For some types of microwave aerial - such as 360" scanning radar aerials, for example - it is necessary to provide the signal feed from the signal generating equipment to the aerial's antenna via one or more slip rings, so allowing the aerial to turn constantly in one direction. Where, however, a continuous turning motion is not required it is simpler and cheaper to provide a direct cable signal feed to the aerial; in a satellite communications system the aerial may need to turn up to and beyond 360" in one continuous scan, but it is unlikely to have to repeat the turn instantly (having to carry on the next turn from where it finished the last and in the same direction), and so may, after one turn, reverse itself back to the start position of the next turn.If a direct cable feed is used, however, it is generally highly desirable also to provide some means of positively preventing the aerial from being rotated continuously in one direction by accident, and so to prevent the cables becoming wound tightly around the rotational axis and perhaps breaking either themselves or some other part of the system.

In the past it has generally been considered satisfactory to buffer an aerial's rotational movement in azimuth by providing one or two (spaced) end stops, or buffers, fixedly secured usually to the aerial mounting (or on the ground itself), together with a stop abuttment member, or striker plate, fixedly secured to the aerial, the striker plate engaging the buffer(s) at either end of the aerial's allowable azimuth range so as to prevent further movement of the aerial in that direction.As will easily be appreciated, the maximum azimuth range an aerial can have using such an arrangement is a little under 360" (allowing for the thickness of the buffer and striking plate); it is presently desirable, however, that the aerial, while still positively buffered at the end of a finite range of azimuth rotation, be able to rotate by more than 360" - and perhaps as much as 540" (which is 360" plus a 1800 overlap).The invention seeks to allow such an azimuth rangeto an aerial (or other rotating object) by arranging for the interaction between buffer unit and striker plate to be via a buffer plate slideably mounted between two buffer units; the striker plate engages not the buffer units but the buffer plate, which slides up to and engages the relevant buffer units, so extending the azimuth range by the angle subtended by the two buffer units.

In one aspect, therefore, this invention provides a buffer assembly for a rotatable body, comprising a buffer plate slideably mounted upon a guide rail extending between two buffer units themselves secured to one of the body and its support, the buffer plate being engageable with a striker plate secured to the other of the body and its support, such that in operation rotation of the body in either direction causes the striker plate to engage the buffer plate, pushing it along the guide rail until it is stopped by the appropriate buffer unit.

The buffer assembly of the invention may alternatively be defined as follows: A buffer assembly, for limiting the angular movement of a first body rotatably mounted upon a second body, which assembly comprises: two buffer units both of which are adapted to be fixedly secured to one of the two bodies such that they are in a plane normal to that of the rotational axis of the first body and in spaced relation one to the other equidistant from the rotational axis; a circularly arcuate guide rail fixed to and extending between the two buffer units in the plane normal to that of the rotational axis of the first body; a buffer plate mounted on the guide rail for movement therealong and for stopping engagement with either buffer unit; and a striker plate adapted to be fixedly secured to the other of the two bodies so that it is in register with the arcuate guide rail, the striker plate being of such dimensions and/or shape that it will engage with the buffer plate but will not engage with either of the two buffer units.

The invention primarily concerns the use of buffer assemblies to limit the angular movement range of aerials, specifically steerable microwave dish aerials, and for convenience will be further described herein mainly with reference to such a use. It should be noted, however, that the features specified may well be suitable for employment in connection with buffer assemblies having different uses.

Buffer units perse are of course quite common in aerial buffer assemblies, and the units employed in the assembly of the invention may in general be any of those used, or suggested for use, with aerials.

Typical such buffer units are made from a combination of those "friction spring" devices sold under the name RINGFEDER; an example of such a device is the type 1317 (though each buffer unit could be a simple physical stop against which the buffer plate

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Buffer assemblies This invention relates to buffer assemblies, and concerns in particular mechanical buffer assemblies useful for controlling the angular range of large, relatively massive rotatably moveable objects such as steerable microwave aerials. It may often be the case that the allowable range of angular movement of an object mounted for rotation about an axis needs to be finite, and that the end-of-range positions are defined, and mechanically constructed, using end stops (buffers) which are fixedly secured to one of either the rotating object or its mounting and which interact with a stop abuttment member equaliy fixedly secured to the other. As a trivial example, the swing of a door is limited at one end of its range by the door catch/jamb, while at the other end it may be limited by a door stop. The invention concerns in particular the construction of buffers - or, rather, of buffer assemblies - for use with steerable microwave aerials, especially those of the kind employed in satellite communication systems, and thus relates primarily to assemblies capable of buffering the movement of a large, heavy aerial which must usually be capable of at least 3600 movement in azimuth (in the "horizontal" plane, and about a "vertical" axis), as well as as much as 1800 in elevation (in the "vertical" plane, and about a "horizontal" axis). For some types of microwave aerial - such as 360" scanning radar aerials, for example - it is necessary to provide the signal feed from the signal generating equipment to the aerial's antenna via one or more slip rings, so allowing the aerial to turn constantly in one direction. Where, however, a continuous turning motion is not required it is simpler and cheaper to provide a direct cable signal feed to the aerial; in a satellite communications system the aerial may need to turn up to and beyond 360" in one continuous scan, but it is unlikely to have to repeat the turn instantly (having to carry on the next turn from where it finished the last and in the same direction), and so may, after one turn, reverse itself back to the start position of the next turn.If a direct cable feed is used, however, it is generally highly desirable also to provide some means of positively preventing the aerial from being rotated continuously in one direction by accident, and so to prevent the cables becoming wound tightly around the rotational axis and perhaps breaking either themselves or some other part of the system. In the past it has generally been considered satisfactory to buffer an aerial's rotational movement in azimuth by providing one or two (spaced) end stops, or buffers, fixedly secured usually to the aerial mounting (or on the ground itself), together with a stop abuttment member, or striker plate, fixedly secured to the aerial, the striker plate engaging the buffer(s) at either end of the aerial's allowable azimuth range so as to prevent further movement of the aerial in that direction.As will easily be appreciated, the maximum azimuth range an aerial can have using such an arrangement is a little under 360" (allowing for the thickness of the buffer and striking plate); it is presently desirable, however, that the aerial, while still positively buffered at the end of a finite range of azimuth rotation, be able to rotate by more than 360" - and perhaps as much as 540" (which is 360" plus a 1800 overlap).The invention seeks to allow such an azimuth rangeto an aerial (or other rotating object) by arranging for the interaction between buffer unit and striker plate to be via a buffer plate slideably mounted between two buffer units; the striker plate engages not the buffer units but the buffer plate, which slides up to and engages the relevant buffer units, so extending the azimuth range by the angle subtended by the two buffer units. In one aspect, therefore, this invention provides a buffer assembly for a rotatable body, comprising a buffer plate slideably mounted upon a guide rail extending between two buffer units themselves secured to one of the body and its support, the buffer plate being engageable with a striker plate secured to the other of the body and its support, such that in operation rotation of the body in either direction causes the striker plate to engage the buffer plate, pushing it along the guide rail until it is stopped by the appropriate buffer unit. The buffer assembly of the invention may alternatively be defined as follows: A buffer assembly, for limiting the angular movement of a first body rotatably mounted upon a second body, which assembly comprises: two buffer units both of which are adapted to be fixedly secured to one of the two bodies such that they are in a plane normal to that of the rotational axis of the first body and in spaced relation one to the other equidistant from the rotational axis; a circularly arcuate guide rail fixed to and extending between the two buffer units in the plane normal to that of the rotational axis of the first body; a buffer plate mounted on the guide rail for movement therealong and for stopping engagement with either buffer unit; and a striker plate adapted to be fixedly secured to the other of the two bodies so that it is in register with the arcuate guide rail, the striker plate being of such dimensions and/or shape that it will engage with the buffer plate but will not engage with either of the two buffer units. The invention primarily concerns the use of buffer assemblies to limit the angular movement range of aerials, specifically steerable microwave dish aerials, and for convenience will be further described herein mainly with reference to such a use. It should be noted, however, that the features specified may well be suitable for employment in connection with buffer assemblies having different uses. Buffer units perse are of course quite common in aerial buffer assemblies, and the units employed in the assembly of the invention may in general be any of those used, or suggested for use, with aerials. Typical such buffer units are made from a combination of those "friction spring" devices sold under the name RINGFEDER; an example of such a device is the type 1317 (though each buffer unit could be a simple physical stop against which the buffer plate abuts, most preferably it is a spring-loaded device, capable of absorbing some of the mechanical shock as it is engaged). The buffer units, between which extends the arcuate guide rail carrying the buffer plate, may be secured to the rotatable part of the aerial, the striker plate then being secured to the aerial support. However, in order to keep the complexity and weight of the rotatable part to a minimum it is preferred to secure the units to the support - and, more specifically, directly to the ground upon which the aerial stands - with only the striker plate itself secured to the rotatable part. An embodiment of such an arrangement is described in more detail hereinafter with reference to the accompanying drawings. The guide rail - which may be of any suitable construction, and is conveniently a simple bar of constant circular cross-section - is advantageously arcuate, and "concentric" with the aerial's rotational axis, so as to reduce the problem of keeping the striker plate in register with the buffer plate sliding thereon (it would be possible, but rather complicated, to have a differently-aligned guide rail, the striker plate then being mounted in a radiallyslideable fashion so as to keep in register therewith). The length of the guide rail may be any desired (up to it subtending an angle of just under 360", for a circular arc); 90" to 180" is usually sufficient. The buffer plate is (as further explained hereinafter) so dimensioned and/or shaped that its "profile" in a plane normal to the guide rail is larger than the corresponding buffer unit profiles. Most conveniently the buffer plate is generally circular, with a central aperture by which it is mounted - as a loose sliding fit- upon the guide rail, so having the overall appearance of a large washer. The striker plate is so dimensioned/shpaed that it will engage with the buffer plate but not with the buffer units. This is most conveniently arranged by forming the striker plate so that it has an aperture therein which is itself so dimensioned/shaped in the plane normal to the guide rail as to be "smaller" than the buffer plate profile but "bigger" than the buffer units profile. In this way, then, with the striker plate in register with the guide rail, and as the two move relative one to the other, the aperture in the striker plate will be large enough to enable the latter to move over/past each buffer unit but will be small enough to prevent the striker plate moving over/past the buffer plate.Thus, this relative movement will cause the striker plate to engage the buffer plate, driving the latter up to and into engagement with the appropriate buffer unit, whereby further movement both of the striker plate and of the aerial - in that direction is prevented. The operation of one embodiment of the buffer assembly of the invention is described in more detail hereinafter with reference to the accompanying drawings. The invention extends, of course, to a rotatablymounted object, especially a steerable microwave dish aerial, whenever employing a buffer assembly as described and claimed herein. An embodiment of the invention is now described, though by way of illustration only, with reference to the accompanying drawings in which: Figure lisa diagrammatic perspective view of an aerial system employing an inventive buffer assembly; Figure 2 is a diagrammatic perspective part cutaway view of the buffer assembly of Figure 1; and Figure 3 is a diagram illustrating the range of angular movement permitted to the aerial of Figure 1 by its inventive buffer assembly. The aerial system shown in Figure 1 comprises a dish antenna/reflector combination (11) mounted upon a framework (12) for rotation in elevation (by means not shown), the framework 12 itself being axially located (by means not shown) and supported by wheels (as 13) rolling on a track (14) allowing azimuth rotation. Beneath the framework 12 is a buffer assembly (generally 15 - shown in more detail in Figure 2) which allows the framework - and thus the aerial/reflector 11 - to rotate in azimuth by approximately 370" (that is, 360" + 10", or 185"to one side of a centre line and 185" to the other side, as shown in Figure 3). The details of the buffer assembly are shown in Figure 2. The assembly comprises two like springloaded buffer units (21) fixedly secured facing each other radially equidistant (see Figure 3) of the aerial's azimuth rotational axis (31) and supporting, extending between them, an arcuate guide rail (22) coaxial with the azimuth axis 31, an annular buffer plate (23) being slideably mounted thereon (so that it may slide up to but not beyond each buffer unit 21), the assembly being completed by a striker plate (24) fixedly secured to the aerial's framework 12 and having at its lower (as viewed) edge a hemispherical aperture (25) of a size which is smaller than the annular buffer plate 23 but larger than the "profile" of either buffer unit 21, this striker plate 24 being "in register" with the guide rail 22.It will be apparent that as viewed in Figure 2 the aerial may rotate clockwise in azimuth until the striker plate 24 engages with the buffer plate 23, and may then rotate further, pushing the buffer plate aiong the guide rail 22, until the buffer plate reaches - and is stopped by - the left hand (as viewed) buffer unit 21, at which point the buffer unit 21/buffer plate 23 combination prevents the striker plate 24, and thus the aerial as a whole, from rotating any further. Similarly, it will be seen that as viewed in Figure 2 the aerial may rotate anticlockwise (for almost 360") until it engages the buffer plate 23 and pushes it into stopping contact with the righthand buffer unit 21. The "overlap" this invention enables is readily apparent from Figure 3, which shows the guide rail 22 subtending an angle of just over 10" - Son one side of a centre line (32), and Son the other - and shows the positions of the buffer plate 23 and striker plate 24 at either end of the guide rail. CLAIMS

1. A buffer assembly for a rotatable body, comprising a buffer plate slideably mounted upon a guide rail extending between two buffer units themselves secured to one of the body and its support, the buffer plate being engageable with a striker plate secured to the other of the body and its support, such that in operation rotation of the body in either direction causes the striker plate to engage the buffer plate, pushing it along the guide rail until it is stopped by the appropriate buffer unit.

2. A buffer assembly as claimed in claim 1, which assembly is for limiting the angular movement of a first body rotatably mounted upon a second body, with comprises: two buffer units both of which are adapted to be fixedly secured to one of the two bodies such that they are in a plane normal to that of the rotational axis of the first body and in spaced relation one to the other equidistant from the rotational axis; a circularly arcuate guide rail fixed to and extending between the two buffer units in the plane normal to that of the rotational axis of the first body; a buffer plate mounted on the guide rail for movement therealong and for stopping engagement with either buffer unit; and a striker plate adapted to be fixedly secured to the other of the two bodies so that it is in register with the arcuate guide rail, the striker plate being of such dimensions and/or shape that it will engage with the buffer plate but will not engage with either of the two buffer units.

3. A buffer assembly as claimed in either of the preceding claims and for limiting the angular movement range of a steerable microwave dish aerial, wherein the buffer units are secured to the ground upon which the aerial stands, the striker plate being secured to the rotatable part of the aerial.

4. A buffer assembly as claimed in any of the preceding claims, wherein each buffer unit is a spring-loaded device, capable of absorbing some of the mechanical shock as it is engaged.

5. A buffer assembly as claimed in any of the preceding claims, wherein the guide rail is a simple arcuate bar, of constant circular cross-section, "concentric" with the body's rotational axis.

6. A buffer assembly as claimed in any of the preceding claims, wherein the buffer plate is generally circular, with a central aperture by which it is mounted - as a loose sliding fit - upon the guide rail.

7. A buffer assembly as claimed in any of the preceding claims, wherein the striker plate is so formed that it has an aperture therein which is itself so dimensioned/shaped in the plane normal to the guide rail as to be "smaller" than the buffer plate profile but "bigger" than the buffer units profile.

A buffer assembly as claimed in any of the preceding claims and substantially as described hereinbefore.

9. A rotatably-mounted object, especially a steerable microwave dish aerial, whenever employing a buffer assembly as claimed in any of the preceding claims.