Tamping shoe for a vibration rammer

Abstract: A tamping shoe (1) for a vibration rammer : has a plurality of through holes (7, 11) communication between an under surface and an upper surface. The through holes (7, 11) permit the escape of air trapped between the under surface and a surface being tamped, and thereby reduce the amount and pressure of air compressed under the tamping shoe. This reduces noise pollution produced during tamping. In a preferred embodiment, the through holes are tapered outward in the direction of air flow. Air passing through a through hole (11) into a mount (2) is released through a further through hole (12) bored through a wall of the mount (2).

Description: The present invention relates to a tamping shoe for a vibration rammer, more particularly, a tamping shoe for a rammer for flattening and tamping soil and gravel on a road or other surface. As described, for example, in Japanese Utility Model Publication No. 20645/1985, conventional vibration rammers have a tamping shoe attachable to the bottom of a rammer body so that vibration of the excitation mechanism of the rammer is conveyed to the tamping shoe, thus permitting it to tamp the ground. Conventional tamping shoes have a generally rectangular, flat shape, which produces impulse sounds during rolling compaction of the ground because of the compression of air trapped between the tamping shoe and the surface being tamped. Such impulse sounds cause noise pollution, resulting in restriction on working times, especially at night. The most relevant prior art known is disclosed in US-A-2771012, with respect to which claim 1 is characterised. However, US-A-2771012, while having some general features in common with the present invention, does not address the problem of noise attenuation. It is an object of the present invention to provide a tamping shoe of a vibration rammer which is capable of reducing the compression of air under the tamping shoe, thereby reducing impulse sounds caused by such compression of air. Accordingly there is provided a tamping shoe for a vibration rammer comprising: an under surface for contacting a surface to be tamped; an upper surface a plurality of through holes communicating between said under surface and said upper surface, characterised in that said through holes are tapered outwardly in a direction from said under surface to said upper surface to permit the escape of air trapped between said under surface and said surface to be tamped whereby impulse sounds caused by the compression of air are attenuated. When a tamping shoe of a vibration rammer according to the present invention is driven forward and backward by an excitation mechanism of the rammer to flatten and compact the surface, air is released upward through the holes so that the impulse sound, caused by compressed air, is reduced. Dirt and sand entering the throughholes is discharged from the opening at the top of each through hole. The through holes are tapered outward in the direction of air flow to improve the noise reduction, and to enhance the ability of dirt to escape through the through holes. Air passing through a through hole in a mounting part of the tamping shoe may be released through a further communicating through hole bored through a wall of the mounting part. An embodiment of a tamping shoe for a vibration rammer will now be described, by way of example, with reference to the accompanying drawings; in which, Fig. 1 is a vertical section view of a tamping shoe for a vibration rammer according to an embodiment of the present invention. Fig. 2 is a plan view of the tamping shoe of Fig. 1. Fig. 3 is a vertical section view of a part of the vibration rammer usable with the tamping shoe of Figs. 1 and 2. Referring to Figs. 1 to 3, a tamping shoe 1 is a flat rectangular plate made of wood, steel, light alloy, rubber, urethane resin or other synthetic resin. A front part of the tamping shoe 1 (to the left in the figures) is curved upward. A generally cylindrical mount 2, is formed at the center top of tamping shoe 1. An upper end of cylindrical mount 2 is inclined upward from the front to the rear end (from left to right in the figures). A bottom of a movable cylinder 5 of an excitation mechanism, 4 of a rammer body 3 is bolted onto mount 2 of tamping shoe 1. A fixed cylinder (not shown in the drawings) in excitation mechanism 4 receives movable cylinder 5 in a sliding manner effective to permit movable cylinder 5 to advance and retreat therein. Coil springs 6 extend between the bottom of movable cylinder 5 and the fixed cylinder. A piston and a piston rod (not shown ) are disposed between the fixed cylinder of the excitation mechanism 4 and the movable cylinder 5. The piston is driven to advance and retreat by a motor. The piston moves the movable cylinder 5 in one direction, and a restoring force acting in the opposite direction is provided by the springs 6 to move the movable cylinder 5 in the opposite direction to produce an up and down movement. Downward movement of movable cylinder 5 causes tamping shoe 1 to flatten and compact the ground surface. A plurality of through holes 7 are bored through the tamping shoe 1, from the bottom to the top thereof, outside the perimeter of the mount 2. The diameter of each through hole 7 tapers outward from the bottom to the top such that the upper diameter of each through hole is larger than its lower diameter. Reinforcement materials 8 and 9 may be fixed, if necessary, to the upper and lower surfaces, respectively, of tamping shoe 1 by bolts 10. A central through hole 11 is vertically bored through shoe 1, inside the perimeter of mount 2, near the center thereof. A through hole 12 is bored through the rear of mount 2. Through hole 11 and through hole 12 communicate with an open volume on mount 2, below movable cylinder 5, whereby air communication is provided between these two through holes. When the movable cylinder 5 is driven downward by the excitation mechanism 4, the tamping shoe 1 is pounded against the ground surface, thus compacting and tamping the ground. As the lower surface of tamping shoe 1 contacts the surface, air trapped between the tamping shoe 1 and the ground surface is compressed. A substantial part of the air escapes through the through holes 7 of the tamping shoe 1, thereby reducing the amount of compressed air, and reducing the pressure reached by the air that fails to pass through the through holes. As a result the impulse noise caused by the compressed air is reduced. The silencing effect is enhanced by the increasing tapered diameters of through holes 7. Air passing through through hole 11, located generally at the center of mount 2, passes out from mount 2 through through hole 12 at the rear part of mount 2. This avoids blocking through hole 11 by rammer body 3 covering the top of mount 2. According to the present invention, during reciprocating drive of a tamping shoe to flatten and compact the ground surface, air that would otherwise be trapped under tamping shoe 1 passes upward through the through holes to the outside of the machine. As a result, the amount of compressed air trapped between tamping shoe 1 and a surface being tamped is reduced substantially. As a consequence, impulse noise caused by compressed air under tamping shoe 1, is reduced. This reduction in impulse noise makes it possible to use a vibration rammer at night without disturbing the neighborhood.

Claims: A tamping shoe (1) for a vibration rammer comprising: an under surface for contacting a surface to be tamped; an upper surface a plurality of through holes (7, 11) communicating between said under surface and said upper surface, characterised in that said through holes (7) are tapered outwardly in a direction from said under surface to said upper surface to permit the escape of air trapped between said under surface and said surface to be tamped whereby impulse sounds caused by the compression of air are attenuated. A tamping shoe according two claim 1, wherein said tamping shoe (2) is generally rectangular. A tamping shoe according to any one of the preceding claims comprising: a mount (2) centered on said upper surface; said mount (2) enclosing a center portion of said upper surface; at least one of said through holes (11) extending from said under surface to said center portion; and means for communicating said center portion to a location outside said mount. A tamping shoe according to claim 3, wherein; said means for communicating includes a further through hole (12) thorugh said mount (2); and said further through hole (11) communicates with an open volume disposed above said center portion.

Inventors: YAMAGUCHI HITOSHI, YAMAGUCHI, HITOSHI
Applicants: YAMAGUCHI HITOSHI, YAMAGUCHI, HITOSHI
Application year: 1992
Main classification: E01C19
IPC codes: E01C19, E02D3