GB2202710A - Flying sound systems - Google Patents

Abstract

A stack of cabinets (20) can be flown from a suspension frame (22) by providing each cabinet with a socket at its upper and lower rear edges and two longitudinal tracks (32) on each side face, one adjacent the upper edge, and the other adjacent the lower edge of each cabinet. The stack is assembled by connecting the rear edges of the adjacent cabinets by connector plates which are held in position in the sockets by means of pip pins (44), and by connecting the upper and lower tracks on each side of adjacent cabinets by means of either flexible or rigid straps (52) which are provided with end fittings which engage at any of a plurality of distinct points along the tracks (32). The bottom edge of the lowermost cabinet is connected to a fixing point (72) on the supporting frame (22) by a webbing strap (70) which is tensioned by a device (76) in order to take up the slack in the straps (52) and produce the required bow in the stack. <IMAGE>

Description

FLYING SOUND SYSTEMS The present invention relates to flying sound systems and, more particularly, to a kit of parts to allow the assembly of a number of cabinets containing loudspeakers or other equipment into a stack for flying.

Apparatus for flying a stack of loudspeaker cabinets is described in GB-A-2 150 397. In that apparatus a stack of cabinets is supported beneath a suspension frame by means of a pair of chains, to which each of the cabinets is connected by a coupling device, which connects a link of the chain to housings permanently fixed to the sides of the cabinets.

The coupling devices can be connected to any link in the chain. The bottom of the stack is connected to the suspension frame by a webbing which can be tensioned to control the bow in the stack. A webbing strip also connects the rear edges of the cabinets to maintain these edges in register with one another.

Although this system allows some degree of bowing, it is difficult to produce a large bow in the stack without considerable inconvenience with regard to the attachment of the rear webbing. In particular, when large bows are attempted it is found that the lower cabinet tends to move forward out of alignment and may rotate about the longitudinal axis of the stack.

Bowing of the stack is important in achieving good vertical coverage in a large auditorium. A section through a typical auditorium is shown in Figure 1 in order to illustrate the need for a large vertical coverage and the advantages of using flown, bowed stacks of loudspeakers. The auditorium illustrated has a stage at ground level with a flat audience area 2 surrounded by a sloping seating area 4. Such an arrangement is typical of the conditions when a pop concert is being held in a sports arena.

If a speaker cluster 6 is mounted directly on the stage, it must provide 30 - 400 of vertical coverage in order to reach all parts of the audience. A considerable power output is also required so that audibility levels in the top of the sloping seating area are acceptable. However, this means that the audience in the flat area 2 closer to the stage is subjected to a very high sound power level. However, if a flown speaker cluster 8 having three components 12, 14, 16, arranged in one or more bowed stacks is used to provide the required vertical coverage, the power output of each component can be adjusted in accordance with the distance the sound is to be thrown by that component. The upper speaker cluster 12, which is substantially vertical, provides the long throw.This speaker cluster 12 only needs a vertical coverage of around 200 at high power in order to send sound to the sloping seating area 4. The speaker cluster 14 also has a relatively narrow vertical range of about 200. Since this speaker cluster is inclined out of the vertical by the bow in the stack, it provides the medium throw to the audience at the outer edges of the flat area 2.

Finally, the speaker cluster 16 which is most inclined out of the vertical, has a relatively larger vertical coverage of about 400 in order to provide the short throw sound to those closest to the stage. It will be appreciated that the power outputs of the three speaker clusters can be separately adjusted so that the sound power level is maintained within acceptable limits throughout the auditorium. The use of the- bowed stack 8 provides considerably better vertical coverage, which can exceed 800, than the maximum coverage of about 30 - 400 possible with speaker clusters mounted on the stage.

Another technical problem with the previous flying system is that the height of the stack is determined by the available length of chain to which the speaker cabinets are connected.

Therefore, if during the erection of a sound system, it proves necessary to add further speakers, this may be difficult with the existing system if the chain is not long enough to accommodate them.

The flying sound system of the present invention is intended to solve the technical problem outlined above of providing a way of producing a stack of cabinets which is bowed to a considerable extent while maintaining an acceptable degree of rigidity within the stack.

The present invention accordingly provides a kit of parts for flying a sound system, the kit comprising a suspension frame, a plurality of substantially cuboid cabinets for containing loudspeakers or other equipment, each cabinet having a rear edge connector part on upper and lower rear edges, and, on each side face of the cabinet, two tracks, one adjacent the upper edge of the side and the other adjacent the lower edge of the side and both extending parallel to the front face of the cabinet, a plurality of connector means for removably securing two cabinets by their adjacent rear edge connector parts, a plurality of flexible or rigid connector straps each having an end fitting adapted to co-operate with a side track at any one of a plurality of positions defined by said track, the suspension frame carrying top connector means for engaging the rear edge connector part and for engaging the upper side tracks on a top cabinet of a stack, and elongate, flexible means for securing the rear edge connector part of the lowermost cabinet of a stack to the suspension frame to hold a bow in an assembled stack of cabinets.

Such a kit of parts is advantageous in that it readily allows any height of stack to be built up from the components. Since there is no continuous chain to which each of the cabinets is connected there does not need to be any slack in the straps used to connect the side tracks of adjacent cabinets. The desired bow is determined by the positions at which the end fittings of the straps are connected to the tracks. Preferably the straps are all of a fixed length so that the angular displacement between the upper and lower faces of adjacent cabinets is solely determined by the positions along the track to which the end fittings are connected. In this way the degree of bow in the stack can be accurately controlled, and a stack design, once established, can readily be reproduced.

In a preferred embodiment the connector means are rigid or hinged connector plates, and the rear edge connector parts are sockets for receiving an end of a connector plate, which is releasably locked into the socket by pin means passing through aligned holes in the socket walls and plate end.

The provision of rear edge connector parts, which are connected together by rigid or hinged plates ensures that the rear edges of the adjacent cabinets of the stack are maintained firmly together in registry.

A kit of parts for assembling a flying sound system in accordance with the invention, will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a diagrammatic section through an auditorium for explaining the benefits of a flown sound system; Figure 2 is a side view of a typical stack of cabinets built up using the kit of the present invention; Figure 3 is a detail of a rear of a loudspeaker cabinet showing the rear edge connector part and a hinged connector plate; and Figure 4 is a detail of a side track and cooperating chain strap with end fitting.

The system to be described is intended for flying a stack of cabinets 20. The cabinets are substantially cuboid that is they are six sided solid cabinets of various relative dimensions. Normally the cabinets will contain loudspeaker equipment but the contents of the cabinet is not material for the purposes of the present invention. Each cabinet 20 which is to be used in forming a flown stack of cabinets is specially adapted by the provision of connector parts 36 at the upper and lower rear edges and of tracks 32 on the sides of the cabinet. These connector parts and tracks are simple in design and may readily be fitted to any existing cabinet or incorporated during manufacture of new cabinets.

Figure 2 shows a stack of cabinets in a typical flying arrangement. A suspension frame 22 is suspended by chains 24 from a hook (not shown) which is preferably connected to lifting tackle so that it can be raised and lowered during the assembly of the stack. Three chains 24 are preferably used and the length of the chains is selected so that the centre of gravity of the assembly of the suspension frame and stack lies directly beneath the hook from which the whole assembly is suspended. The suspension frame 22 preferably has a telescopically extendible rear arm 26 so that its overall length can be adjusted in dependence upon the required bow of the stack. The front part of the suspension frame is provided with top connector means to allow the upper cabinet of a stack to be secured to the frame by its standard upper rear edge connector part and its upper side tracks on each side.As illustrated, these top connector means are two laterally spaced depending plates 28 only one of which is shown in Figure 2. The plates 28 are preferably hinged to the suspension frame and are each provided with an end fitting 30 which co-operates with the upper side track 32 of the upper cabinet. The top connector means also includes a depending connector plate 34 which has an end which co-operates with the upper rear edge connector part of the upper cabinet 20. A separate chain strap may also be used in place of the plates 28. In this case the top connector means will comprise a track part to co-operate with an end fitting of the chain strap.

Each cabinet of the stack has a rear connector part 36 in the form of a socket positioned centrally of its upper and lower rear edges. Such a connector socket 36 is shown in Figure 3. The open-ended rectangular section socket is designed to receive one end 38 of a connector plate 40. A hinged connector plate 40 is shown in Figure 3. However, rigid connector plates may also be provided where there is to be no angular displacement between two adjacent cabinets.

The socket is preferably formed in an L-shaped metal member which is positioned in a cut-out 41 in the rear face of the cabinet. The L-shaped arms of the member may then be fixed to the interior of the rear and adjacent top or bottom face of the cabinet by nuts and bolts 43. Both side walls of the socket of the connector have aligned central holes 42 sized to just receive the shaft of a npipn pin 44. Each end 38 of the connector plate 40 is provided with an elongate slot 46 which aligns with the holes 42 when the end 38 of the connector plate is received within the socket.In order to lock the end of the plate into the socket, the pip pin 44, which is provided with retractable detents 48, is operated by pulling on the ring 50 in order to retract the detents into the outer profile of the shaft of the pin so that the shaft can be passed through the holes 42 in the socket and the elongate slot 46 in the connector plate. The operating ring 50 is then released to allow the retractable detents to resume their normal position as shown in Figure 3 thereby holding the pin 44 in position retaining the end of the connector plate 40 within the socket 36.

Each cabinet 20 is provided with four tracks 32. Two tracks are provided on each side face of the cabinet. Each track is aligned with its longitudinal direction parallel to the front and rear faces of the cabinet and is mounted a fixed distance from the rear longitudinal edge of the cabinet whatever the depth of the cabinet so that the side tracks of a stack of cabinets are always vertically aligned when the rear edges are aligned. An upper track is mounted closer to the upper edge and a lower track is mounted closer to the lower edge on each side. Adjacent cabinets of the stack are connected together by straps 52 which are provided with an end fitting 54 at each end. As shown in Figure 2, rigid plates may be used as the straps where the cabinets are to be close coupled as in the two uppermost cabinets of the stack shown.In particular where two cabinets are always flown together as part of a system the cabinets may be permanently bolted together by rigid plates so that the combined unit may be rigged as a single cabinet. This makes for more rapid rigging. Where the upper and lower faces of the adjacent cabinets are to be inclined relative to one another, it is more convenient to use a chain strap.

The connector arrangement using an elongate track and straps with end fittings is required so that, by positioning the end fittings at different positions along the tracks, a number of different angular spacings between the upper and lower faces of adjacent cabinets can be achieved. The particular design of the connector is therefore not important provided the end fittings 54 can be positioned at a plurality of different discrete positions along the length of the track. The type of connector illustrated in Figure 4 is suitable for this purpose. It is a system sold under the trade name AEROQUIP for use in securing loads in aircraft.

The track 32 is secured by means of fixing screws 56 to the side walls of the cabinets. The track is substantially Ushaped with inturned upper edges defining a channel which is accessible through an upper, open slot 58. The slot has alternating narrower and wider sections. The wider sections define circular openings. The end fitting 54 has two downwardly-projecting cylindrical pins 60 each provided with an enlarged diameter head. The size of the main body of each pin is such that it can be received in the narrower sections of the slot but the head is only capable of passing through one of the circular openings. A section 61 between the pins 60 is formed as a piston and can be retracted into the body by pulling on a ring 62.With the piston 61 retracted and the pins 60 aligned with respective circular openings of the slot, the fitting is pushed into the track channel and slid along the length of the track to the required position. By releasing the ring 62 so that the piston 61 is projected from the body of the end fitting when the pins are aligned with narrower sections of the slot, the heads of the pins 60 engage with the inside of the upper wall of the channel to prevent removal of the end fitting from the track. The piston 60 has chamfered edges to engage with a circular opening in the track slot when it is projected in order to prevent further sliding of the fitting along the track. As shown, each track has six circular openings permitting the end fitting to be positioned in any of four longitudinally spaced positions in each of which the heads of both pins 60 engage with the upper wall of the channel. Stops may be provided on the track to prevent the end fitting 54 from being moved to a position in which only one of the pin heads engages wholly with the track. The combined effect of the engagement of the pins and piston with the track is such as to resist movement of the end fitting regardless of the direction of any force applied to the fitting by the chain.

A webbing strap 70 has one end connected to a central fixing point 72 at the rear of the rear extension 26 of the suspension frame 22. The other end of the webbing strap is provided with a connector 73 which can be removably coupled to the rear edge connector part 36 at the lower edge of the bottom cabinet of the stack. For example the webbing strap may be provided with a hook member that engages into the socket 36 and is held therein by a pip pin 44 passing through a slot in the hook and the holes 42 of the socket walls.A tensioning device 76 is provided between the ends of the strap so that once the ends are connected to the frame and bottom of the stack respectively, the tensioning device can be used to reduce the length of the strap by an appropriate amount in order to produce the required bow which is determined by the position in which all the straps 52 are taut so that the load is mainly carried through the straps 52 and not by the strap 70.

In order to provide a mechanically continuous connection from the suspension frame down through the cabinets, a metal reinforcing plate is provided on the inside side face of the cabinets and connected to the upper and lower tracks through the wall of the cabinet. This provides a strong mechanical connection throughout the length of the stack in order to minimize the risk of a failure within a cabinet resulting in the stack falling down.

The webbing strap 70 is preferably treated so as to be fireresistant or may be replaced by a chain or a wire rope with appropriate tensioners.

A method of assembling a stack of loudspeaker cabinets for flying will now be described.

The suspension frame 22 is connected by chains 24 to a hook which is then lowered by lifting tackle (not shown) to a convenient height above the ground allowing the topmost cabinet of the stack to be moved to a position underneath the lifting frame. This topmost cabinet is then connected to the frame by side straps 28, which are preferably permanently connected to the lifting frame, which couple to the upper tracks 32 on each side of the cabinet. A rigid connector plate 34 is received into the socket at the upper rear edge of the cabinet and locked therein by means of a pip pin.

The lifting tackle is then used to raise the lifting frame with its one suspended cabinet so that another cabinet can be moved into position underneath. The next cabinet is connected to the bottom of the upper cabinet by means of a connector plate which has one end received in the rear edge connector socket at the lower edge of the top cabinet and its other end received in the rear edge connector socket at the upper edge of the new cabinet. Both ends of the connector plate, which, in the example illustrated, is a rigid connector plate, are retained in their respective sockets by means of pip pins. The adjacent upper and lower tracks of the two cabinets on each side are connected by means of rigid connector straps 52 which each have end fittings which engage with the tracks 32.Of course, if these first two cabinets were premanently coupled, they would have been coupled directly as a single top cabinet to the suspension frame as in the previously described step.

Again the lifting tackle is used to raise the stack of two cabinets in order to allow a third cabinet to be moved into a position just beneath the lower surface of the second cabinet. This time a hinged connector plate is used to connect the rear edge connector sockets and flexible chain straps 52 are used to connect the tracks on each side of the cabinet.

The process of lifting the suspension frame and the so far completed stack and connecting further cabinets can be continued until the required stack has been completed. Once the stack is completed, the free end of the webbing strap 70 is connected to the rear edge connector socket at the bottom of the lowermost cabinet and the strap tensioned in order to take up the slack in all the connecting straps 52 so that the stack has the required bow. The completed stack can then be raised by means of the lifting tackle to the required position.

It will be appreciated that a stack design can readily be reproduced by noting the positions for the end fittings of the straps 52 in the side tracks of the cabinets. A completed stack can be lowered for the addition of a further cabinet or for rearrangement which can be achieved quickly and with minimum delay due to the nature of the connectors described.

Claims (7)

1. A kit of parts for flying a sound system, the kit comprising a suspension frame, a plurality of substantially cuboid cabinets for containing loudspeakers or other equipment, each cabinet having a rear edge connector part on upper and lower rear edges, and, on each side face of the cabinet, two tracks, one adjacent the upper edge of the side and the other adjacent the lower edge of the side and both extending parallel to the front face of the cabinet, a plurality of connector means for removably securing two cabinets by their adjacent rear edge connector parts, a plurality of flexible or rigid connector straps each having an end fitting adapted to co-operate with a side track at any one of a plurality of positions defined by said track, the suspension frame carrying two connector means for engaging the rear edge connector part and for engaging the upper side tracks on a top cabinet of a stack, and elongate, flexible means for securing the rear edge connector part of the lowermost cabinet of a stack to the suspension frame to hold a bow in an assembled stack of cabinets.

2. A kit according to claim 1 wherein the connector means are rigid or hinged connector plates, and the rear edge connector parts are sockets for receiving an end of a connector plate which is releasably locked into the socket by pin means passing through aligned holes in the socket walls and plate end.

3. A kit according to claim 2 wherein at least some of the connector plates are hinged so that the two ends may adopt various angular positions relative to one another.

4. A kit according to any one of the preceding claims wherein at least some of the connector straps are chain lengths.

5. A kit according to any one of the preceding claims wherein the flexible means is a webbing strap.

6. A kit according to any one of the preceding claims wherein the upper and lower tracks on each side face of a cabinet are connected together by means of a reinforcing plate.

7. A kit of parts for flying a sound system substantially as herein described with reference to the accompanying drawings.