1. A muffler for an exhaust gas system of an internal combustion engine comprising:
a housing having at least one exhaust inlet and at least one exhaust outlet;
a control device;
a silencer system;
a first and a second pipe on said exhaust inlet or outlet ends, said first pipe being switchable at least between an open state and a closed state by said control device, and being acoustically coupled to said silencer system such that said silencer system is active when said first pipe is opened as well as when said first pipe is closed, said silencer system having a different damping characteristic when said first pipe is opened than when it is closed,
wherein at least one of said first and second pipes is permanently open, and
wherein said housing is partitioned into a first, second and a third chamber, said third chamber being between said first and second chambers, and said at least one permanently open pipe passes through said third chamber and is acoustically coupled to said third chamber.
2. The muffler according to claim 1, wherein said silencer system has a volume that is acoustically coupled to said first switchable pipe.
3. The muffler according to claim 2, wherein said volume comprises at least one pipe volume of at least one branching pipe that branches off from and communicates with said first switchable pipe.
4. The muffler according to claim 2, wherein said volume comprises a chamber volume of a first chamber of said housing through which said first switchable pipe passes, said chamber volume communicating with the said first switchable pipe.
5. A muffler for an exhaust gas system of an internal combustion engine comprising:
a housing having at least one exhaust inlet and at least one exhaust outlet;
a control device;
a silencer system;
a first and a second pipe on said exhaust inlet or outlet ends, said first pipe being switchable at least between an open state and a closed state by said control device, and being acoustically coupled to said silencer system such that said silencer system is active when said first pipe is opened as well as when said first pipe is closed, said silencer system having a different damping characteristic when said first pipe is opened than when it is closed,
wherein said silencer system has a volume that is acoustically coupled to said first switchable pipe,
wherein said volume comprises at least one pipe volume of at least one branching pipe that branches off from and communicates with said first switchable pipe,
wherein said branching pipe is sealed at its remote end from said first switchable pipe, said sealed branching pipe forming a lambda4 resonator.
6. A muffler for an exhaust gas system of an internal combustion engine comprising:
a housing having at least one exhaust inlet and at least one exhaust outlet;
a control device;
a silencer system;
a first and a second pipe on said exhaust inlet or outlet ends, said first pipe being switchable at least between an open state and a closed state by said control device, and being acoustically coupled to said silencer system such that said silencer system is active when said first pipe is opened as well as when said first pipe is closed, said silencer system having a different damping characteristic when said first pipe is opened than when it is closed,
wherein said silencer system has a volume that is acoustically coupled to said first switchable pipe,
wherein said volume comprises at least one pipe volume of at least one branching pipe that branches off from and communicates with said first switchable pipe,
wherein said branching pipe communicates with a first chamber of the housing through which said first switchable pipe passes, said branching pipe and said first chamber forming a Helmholtz resonator.
7. The muffler according to claim 3, wherein said branching pipe further comprises a perforated plate on an end, said end being remote from said first switchable pipe.
8. The muffler according to claim 4, wherein said first pipe has an opening or a perforation or an interruption in said first chamber, said first pipe communicating with said first chamber through said opening or said perforation or said interruption.
9. The muffler according to claim 3, wherein said first switchable pipe communicates with said branching pipe at a point between an open end of said first switchable pipe and said control device.
10. The muffler according to claim 3, wherein said first switchable pipe communicates with said first chamber at a point between an open end of said first switchable pipe and said control device.
11. The muffler according to claim 1, wherein said at least one permanently open pipe passes through said first chamber.
12. The muffler according to claim 1, wherein said first switchable pipe passes through said third chamber.
13. The muffler according to claim 1, wherein said third chamber is separated from said first chamber by a first partition and from said second chamber by a second partition.
14. The muffler according to claim 1, wherein said first and second pipes have their open ends in said second chamber of said housing.
15. The muffler according to claim 1, wherein said control device further comprises at least one valve arranged in said first switchable pipe.
16. The muffler according to claim 15, wherein said control device is situated inside said housing.
17. The muffler according to claim 15, wherein said control device is situated outside said housing.
18. The muffler according to claim 1, wherein said control device controls said first switchable pipe passively as a function of exhaust gas pressure.
19. The muffler according to claim 1, wherein said control device controls said first switchable pipe actively as a function of rotational speed of said internal combustion engine.
20. The muffler according to claim 1, wherein said control device controls said first switchable pipe actively as a function of load of said internal combustion engine.
21. The muffler according to claim 1, wherein said silencer system is adapted such that interfering frequencies are dampened, said interfering frequencies occurring while switching said first switchable pipe due to a change in the flow through the muffler.
22. The muffler according to claim 1, wherein said silencer system acts as a bypass resonator when said first switchable pipe is opened as well as when said switchable pipe is closed.
23. The muffler according to claim 22, wherein said bypass resonator is a Helmholtz resonator or a \u03bb4 resonator or a combination of a Helmholtz resonator and a \u03bb4 resonator when said first switchable pipe is opened as well as when said first switchable pipe is closed.
24. The muffler according to claim 1, wherein said first and second pipes branch off from a first common pipe inside or outside of said housing.
25. The muffler according to claim 1, wherein said first and second pipes are brought together to form a second common pipe inside or outside of said housing.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A sign comprising:
a main body having a first surface and a second surface;
an overlay removably attachable to the first surface or the second surface of the main body; and
at least two fasteners attached to the overlay for removably securing the overlay to the first surface or the second surface, each fastener passing through an oversized hole in the overlay and movably secured to the overlay with a washer, each washer spacing the overlay from the main body when the overlay is attached to the main body.
2. The sign of claim 1, wherein the main body includes at least one selected from the group of polycarbonate, plywood, plastic, and aluminum.
3. The sign of claim 1, wherein the overlay includes at least one selected from the group of polycarbonate, sheet metal, wood, fabric, fabric reinforced polyvinyl chloride, plastic, and polymeric film.
4. The sign of claim 1, further comprising a retroreflective sheeting disposed on the main body and the overlay for retroreflecting light back toward a light source.
5. The sign of claim 4, wherein the retroreflective sheeting includes glass beads.
6. The sign of claim 4, wherein the retroreflective sheeting includes a plurality of air-backed cube-corner prisms, each prism having three facets extending to an apex.
7. The sign of claim 4, wherein the retroreflective sheeting includes a plurality of cube-corner prisms each having three facets extending to an apex, wherein substantially all of the facets have a reflective coating thereon.
8. The sign of claim 4, further comprising a barrier film disposed between the overlay and the retroreflective sheeting.
9. The sign of claim 8, wherein the barrier film includes at least one selected from the group of polyester, polyethylene, polypropylene, and polystyrene.
10. The sign of claim 8, further comprising a first adhesive disposed between the barrier film and the overlay and a second adhesive disposed between the barrier film and the retroreflective sheeting.
11. The sign of claim 1, wherein the sign is slit on a back side and formed from a substantially flexible material such that it can be folded in half.
12. The sign of claim 1, wherein the sign is mounted on a mounting device.
13. The sign of claim 1, wherein the fasteners snap-fit into the main body.
14. The sign of claim 1, wherein each fastener includes an expandable shank that passes through a hole in the main body to deform the shank, wherein the shank expands after passing through the hole to secure the overlay to the main body.
15. The sign of claim 1, wherein the main body includes a plurality of hollow cells within the main body.
16. A sign comprising:
a main body having a first surface and a second surface and a plurality of hollow cells within the main body;
an overlay removably attachable to the first surface or the second surface of the main body; and
at least two fasteners attached to the overlay for removably securing the overlay to the main body, each fastener passing through an oversized hole in the overlay and movably secured to the overlay with a washer, each washer spacing the overlay from the main body when the overlay is attached to the main body;
wherein each fastener includes an expandable shank that deforms when passing through a hole in the main body and expands after passing through the hole to removably secure the overlay to the main body.
17. A sign comprising:
a main body having a first surface and a second surface;
an overlay removably attachable to the first surface and the second surface of the main body; and
at least two fasteners for removably securing the overlay to the first surface and the second surface.
18. The sign of claim 17, wherein each fastener passes through an oversized hole in the overlay.
19. The sign of claim 18, wherein each fastener is movably secured to the overlay with a washer, each washer spacing the overlay from the main body when the overlay is attached to the main body.
20. The sign of claim 17, wherein the main body includes a plurality of hollow cells within the main body.
21. The sign of claim 17, wherein the fasteners are movably attached to the overlay.
22. A sign comprising:
a main body having a first surface;
an overlay removably attachable to at least the first surface of the main body; and
at least two fasteners for removably securing the overlay to the first surface, each fastener passing through an oversized hole in the overlay and movably secured to the overlay with a washer.
23. A method of providing an overlay on a sign comprising:
forming a main body having a first surface and a plurality of hollow cells within the main body; and
removably attaching an overlay to the first surface of the main body with at least two fasteners attached to the overlay, each fastener passing through an oversized hole in the overlay and movably secured to the overlay with a washer, each washer spacing the overlay from the main body when the overlay is attached to the main body.
24. The method of claim 23, further comprising providing a retroreflective sheeting on the main body and the overlay for retroreflecting light back toward a light source.
25. The method of claim 23, wherein the retroreflective sheeting includes a plurality of air-backed cube-corner prisms.
26. The method of claim 23, wherein the retroreflective sheeting includes a plurality of cube-corner prisms each having three facets extending to an apex, wherein substantially all of the facets have a reflective coating thereon.
27. The method of claim 23, further comprising providing a barrier film between the overlay and the retroreflective sheeting.
28. The method of claim 27, further comprising providing a first adhesive between the barrier film and overlay and further providing a second adhesive between the barrier film and the retroreflective sheeting.
29. The method of claim 23, further comprising folding the sign in half.
30. The method of claim 23, further comprising mounting the sign on a mounting device.
31. The method of claim 23, further comprising removably attaching the overlay to a back side of the main body.
32. A method of providing an overlay on a sign comprising:
forming a main body having a first surface and a second surface; and
removably attaching an overlay to the first surface or the second surface of the main body with at least two fasteners attached to the overlay, each fastener passing through an oversized hole in the overlay and movably secured to the overlay with a washer, each washer spacing the overlay from the main body when the overlay is attached to the main body.