Title: Melting lead fuse.

This invention relates to a melting lead fuse, particularly applicable in combination with a linear actuator, preferably of the pre stressed type, e.g. comprising a gas spring or mechanical spring. With said use the fuse keeps the linear actuator in its pre stressed condition. The invention is particularly applicable to an emergency ventilation system for a building. ^" In that case the fuse functions as a releasing system to ^" become active in case 'of a fire and release ^' the pre stressed linear actuator. ^*" The energy stored in the linear actuator is then released, e.g. by extension of a piston rod, with which a ventilationTeqiiipment in e.g. the roof or a wall can be opened.

The fuse preferably has components which are substantially immovably fixed to each other by a material which looses its strength due to a relatively small temperature increase above ambient temperature, e.g. in the range below 140 or 100 or 70 and above 30 or 40 degrees Celsius, e.g. weakens or melts. This material preferably is or contains lead or a lead alloy or some other soldering material.

The fuse preferably provides a substantially symmetrical or balanced load of the component which due to the fuse is kept in the pre stressed condition, wherein said component preferably contains a pre stress means, e.g. a spring or pressurised gas.

The fuse preferably comprises two or more releasing members at different sides, e.g. at both sides and/or diametrically opposite each other from a component connected to it which at increasing temperature are activated, the releasing members are preferably positioned such that the component obtains a substantially symmetrical retaining or holding force from the arrangement of these releasing members and/or is substantially symmetrically loaded by the combination of the pre stress load and the retaining or holding force from the arrangement of these releasing members. Thus in use a low mechanical load is applied.

The fuse can comprise a circumferential wall. The fuse preferably keeps two mutually displaceable/movable components mutually substantially immovable until a determined temperature, e.g. 70 degrees Celsius, is obtained, wherein said mounting to the one component breaks at said determined temperature, e.g. i

since the mounting is made by melting material, while the mounting to the other component only breaks at a temperature substantially higher then said determined temperature, e.g. since the mounting is provided by steel or aluminium.

A fuse of melting type preferably comprises a gap located between two relatively movable parts which is ^" filled ^" with a material' with- retaining capacity - to hold the ^' -two - relatively movable 'parts," and which material looses its retaining capacity at -low_temperature, e.g. „melts. ^■ = - - * - _» ,-,[ -<χ _^ .-_-o _» -„ _] • -^I ^{n an} application, e.g. to a gas spring or mechanical spring, the fuse comprises a part that is mounted to the one component of the linear actuator, such as the cylinder or shell that contains pressurised gas or a mechanical spring. Preferably this part projects beyond this one component and is mounted by melting material to another part of said fuse which is mounted to the other component of the linear actuator, or is directly mounted to said other component through said melting material. In that case said other component xs the pre stressed, axially relative to the one component displaceable extension element, such as piston rod.

The releasing system can be prefabricated, e.g. comprising a cap to be located across the end of the piston rod or a stop, keeping a gap at both sides, wherein said gap is filled with melting material while the part is easily mountable to the cylinder.

In an embodiment the releasing system can comprise substantially concentrically within each other located elements which are mutually mounted by melting material . The one element is mounted to or is part of the one component the other element is mounted to or is part of another component of the actuator which can be moved relative to the one component. The one component is e.g. the cylinder, the other component the piston rod of a cylinder/piston assembly. The elements are e.g. within each other fitting shells or bushes. Or the one element is a shell or bush and the other element is a stop fitting in it.

Preferably the fuse comprises a recess and/or an into it fitting projection, wherein preferably the recess and/or projection are covered with melting material. The projection e.g.

projects from the recess such _^ that substantially everywhere the space between said two parts is filled with melting material. Preferably said projection or said recess an engaging or retaining operation.

Preferably the fuse is designed to retain an axial load as long "as the melting ^" material is in tact while a part ^" is present which is mounted'by the -melting material and can move/displace in radial'direction if the-melting material no longer is in tact. Preferably,.jsaid_part ,is _^ mounted ,to the _^ one component and said part can move in.radial direction away from the other component or a part connected thereto. If a projection and/or recess is applied, -preferably a provision is made such that by movement/displacement in radial direction said projection or recess becomes disengaged.

Preferably the fuse has two or more parts which are mounted to the one component, wherein said parts are mounted by melting material and can move/displace relative to each other if the melting material is no longer in tact. Preferably said parts can move radially or outward/inward away from each other. One or both said parts preferably have a projection or recess.

The projection or recess could also be provided by surface roughness.

Preferably the fuse comprises an axially extending Shell or bush which circumferentially is divided into two or more parts which preferably are mutually independent and are mounted to a preferably common support through melting material which is e.g. provided to be mounted to a piston rod, such that after the melting material is molten, it allows that said parts move radially.

Preferably the fuse has one or more openings to allow passage of a mounting element, e.g. to mount the fuse, e.g. with the aid of a resilient bracket, easily removable.

The actuator can be a gas spring. In that case both gas filled spaces within the cylinder at both sides of the piston are sealed relative to the environment and are pressurised at a level higher than the environmental pressure. These spaces are mutually communicating. At the one side of the piston the piston rod is mounted, which projects outside the cylinder. Due to this

structure the piston rod is naturally pre_ loaded to the extended direction. . . . .. ..

The invention is further illustrated by way of the enclosed drawing, showing in:

Fig. Ia and b a melting fuse;

Fig. 2 a different fuse; ^' ' ^"

Fig. 3a and b an ^* actuator ⁵ with stop ^" member; -• ^■ - ^" Fig. ^" 4a and b a ^ventilation?system in -two .positions;

Fig. 5-7 _a ventilation _, system integrated .in ₍ a building; -Fig. 8-12 a .further different melting fuse.

The fuse of fig. 1 is mounted to the end of a cylinder or the piston rod, respectively. The fuse is made of two fixedly to the cylinder mounted end beyond the cylinder extending parts that are part of a circumferential wall. These parts are diametrically opposite at both ^" sides of the piston rod. They provide with the piston rod, or enlargement of it, a gap diametrically opposite at both side of the piston rod. Said gap is filled with melting material, e.g. lead.

In this embodiment the fuse comprises a bush which is mounted to the cylinder through mounting means. In the embodiment shown the bush has for that a groove opposite a groove in to cylinder and in which grooves a pin fits such that by within each other fitting shapes the bush is fixed to the cylinder. An inner stop fits into the bush and is mounted to the piston rod by mounting means. Between bush and stop an annular gap is present, filled with melting material .

Fig. Ia shows the situation before, fig. Ib after melting of the melting material within the annular gap, with the application at a to the extended position pre stressed piston rod.

Fig. 2 shows an alternative mounting. The bush is fixed to the cylinder by way of a wall deformation.

Fig. 3 shows a gas spring with the fuse of fig. 2 and a stop member. The stop member comprises a strip or different elongated part that is fixed to the -end of the piston rod. The free end of the strip comprises a hooking edge and is radially inward pre stressed by the integral, bend mounting flange. Fig. 3a shows

the initial stage, with the piston rod completely withdrawn and by the fuse retained in said position. The hooking edge applies radial inward pressure to the outer side of the cylinder wall. Fig. 3b shows the end stage after the fuse has released the piston rod and the rod has obtained the completely extended position due to the pre load at the piston. The hooking edge of the strip is axially beyond the bush of the fuse and radially inward displaced and co-operates in a^retaining manner with a, component of the bush or cylinder such -that it is not possible, -or only over a small distance possible, to retract the piston rod back.

Fig. 4 shows an arrangement of a first and second linear actuator, in this example a single or double acting pressurised air cylinder and a gas spring which is kept in the retracted position by a fuse. This arrangement can be used to open the ventilation opening in the wall or roof of a building. The pressurised air cylinder, which is connected to a pressurised air source through conduits, is used to open and close the ventilation during typical operating conditions. The gas spring becomes active during a fire. The piston rods of both actuators extend parallel in the same direction. An arm is present at the end of the piston rod of the first actuator to which the piston rod of the second actuator will engage as soon as it extends. Thus the piston rod of the first actuator is always extended by the piston rod of the second actuator, by which a simple drive of the ventilation by the second actuator is ensured.

Fig. 4a shows both actuators retracted, fig. 4b the first actuator extended and the second retracted.

The arrangement of fig. 4 is in fig. 5-7 applied to a louvre system. The gas spring is, as in fig. 3, provided with a retaining member for blocking in the extended position. Fig. 5 shows the closed position, fig. 6 the open position during ventilating during typical operating conditions and fig. 7 the open position during a fire, after the fuse is molten. In fig. 7 both piston rods are extended.

The fuse of fig. 8 is mounted to the end of the cylinder 1 or the piston rod 2, respectively, of a linear actuator. In fig. 8 the fuse is only partly shown. The fuse consists of an

inner _bush 3 which is fixedly mounted to the end of the piston rod 2, e.g. by means of a screw mounting. An outer bush is placed over te inner bush 3, such that they are mutually co-axial. The outer bush is made from two substantial identical bush halves 4 of which in fig. 8 only one is shown. Thus the outer bush is divided in two parts 4 in the circumferential direction. Each part provides more or less a shell halve. The outer bush is substantially longer to completely overlap with the inner bush 3 and also to overlap with the one end of the cylinder 1 of the linear- actuator.

Each part 4 contains at its inner side a projection 5 which fits into a recess 6 at the outer side of the inner bush 3, and a gap like opening 7 which joins with a recess 8 at short distance from the end of the cylinder 1. The legs of a U-shaped spring (not shown) can engage through these openings 7 with the recesses 8 such that in this manner the bush is fixed with the cylinder 1 in the axial direction.

The inner bush 3 and the outer bush 4 keep a spacing. Also the projection 5 and recess 6 keep a spacing. These spacings are filled with a melting material, such that the bushes 3, 4 provide a united unit.

By the presence of the projection 5 and/or recess 6 the melting material is able to keep the linear actuator in pre stressed condition, as long as the melting material is in tact. Since the outer bush 4 is divided in circumferential direction the projection 5 can move radially away from the recess 6 if the melting material is no longer in tact, such that if the melting material is molten, the outer bush 4 releases the inner bush 3 and the piston rod 2 can extend in axial direction from the cylinder 1, drawing the inner bush 3 with it.

Fig. 9 shows a top view and fig. 10 a side view of one of the parts 4. Fig. 11 shows a perspective of the complete fuse and fig. 12 shows a perspective of one of the parts 4.

Different embodiments also belong to this invention. While in the enclosed drawings the parts 3, 4 have a curved shape, they also could have an angled shape. While the parts 4 are, in the embodiment of the drawing, merely mutually mounted through the

melting material, an embodiment is feasible wherein _: they also remain mounted to each other after melting of the melting material through mounting means which allows (radial) displacement of one or both parts 4, e.g. a mounting means which allows mutual pivoting of the parts 4. The recesses 6 are preferably located substantially diametrically opposite each other, but also a different location is 'feasible'. In ^' stead of mounting the -inner-bush 3 to the piston ^" 'rod 2, It could be mbunted-to -the cylinder 1 _in another example, such that the _. outer bush_(parts _V 4) after melting of the melting material remains mounted to the piston rod 2 and then moves along with the rod 2.

For all applications it is preferred that from the projection

5 and/or recess 6 a preferably ^" in the environment debouching channel extends to allow melting material to exit, to ensure the reliability of the fuse. Fig. 8 shows that channel 8 extends from

6 to 2.