Patent Publication Number: US-5293010-A

Title: Sound dampening device for horns

Description:
FIELD OF THE INVENTION 
     The present invention relates to a horn housing mountable to a structure which directs sound generated by the horn through an opening in the housing and absorbs sound propagating sideways from the horn towards the structure. 
     BACKGROUND OF THE INVENTION 
     High decibel horns or sirens are used on trains and ships as a warning that the vehicle is approaching. When the horn is mounted to an outside of the structure in which crew or passengers are located, the sound propagating from the horn as well as the vibration generated by the horn is partially transmitted sideways to the structure and can be disturbing to the crew or passengers after prolonged exposure to the sound or vibration. 
     Usually, the horns or sirens are mounted to the structure of the vehicle or vessel with some sort of vibration absorbing member to absorb the primary high amplitude mechanical vibrations coming from the horn. Such vibration absorbing mountings serve to prevent damage to the structure as a result of the vibration. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a horn housing capable of reducing substantially the amount of sound and mechanical vibration emanating from a horn to a structure containing crew or passengers. It is furthermore an object of the present invention to provide a horn housing in which sound emanating from a horn in directions other than a principal direction of the horn is either absorbed or reflected in the principal direction of the horn. 
     According to the invention, there is provided a horn housing comprising an inner solid horn containing box having an opening at one end, an outer dense solid box having an opening at one end, the outer box containing the inner box, an intermediate low density sound absorbing filler for filling a space between the inner and the outer boxes, means for connecting the inner box to the outer box, the connecting means transmitting little vibration from the inner box to the outer box in a frequency range of the horn, and means for mounting a side of the outer box to a person containing structure, the mounting means transmitting little vibration from the outer box to the structure. In this way, one or more horns can be installed inside the inner box for directing sound through the opening of the inner box and through the opening of the outer box, the housing absorbing most of the sound propagating sideways towards the structure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will become better understood by way of the following non-limiting detailed description of a preferred embodiment with reference to the appended drawings in which: 
     FIG. 1 is a transverse cross-sectional view of the preferred embodiment; 
     FIG. 2 is a longitudinal cross-section of the preferred embodiment; 
     FIG. 3 illustrates a detailed partial cross-sectional view of a safety mounting bolt according to the preferred embodiment; and 
     FIG. 4 is a detailed partial cross-sectional view of the connecting means according to the preferred embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIGS. 1 and 2, the horn housing (10) according to the preferred embodiment comprises an inner solid shell or box (12) made of stainless steel having a hexagonal cross-section and an opening at one end. Horns (14) are mounted inside box (12). An outer dense solid box (18) is molded from a composite material such as a polymer resin and a filler. The horns (12) are solidly connected to inner box (12) by mounting stems (16) which are welded to box (12). As shown, there may be more than one horn (14) contained within housing (10). Inner box (12) is connected to outer box (18) by means of vibration dampening mounting bolts (40). The space inbetween inner box (12) and outer box (18) is filled with a synthetic filler such as neoprene foam (20) which acts as a good vibration and sound absorber. The outer box (18) is connected to a roof (30) of a train by mounting means (22). 
     Mounting means (22) comprise a bracket (24) interconnecting rubber pads (25) and (26) between bracket (24) and the outer box (18) and roof top (30) respectively. The vibration dampening mounting bolts (40) are also shown in FIG. 1 to be positioned on the upper and lower side walls of the housing such that the upper bolts (40) lift the inner shell (12) and the lower mounting bolts (40) push up inner shell (12). In the preferred embodiment, there are three bolts (40) per side one bolt at each end of housing (10) on the upper side, and a single bolt in the middle of the side on the lower portion. 
     As particularly illustrated in FIG. 4, the vibration dampening mounting bolt (40) according to the preferred embodiment has a vibration absorbing rubber member (42) sandwiched between and fastened to an outer bolt (44) and an inner bolt (46) which fit through holes provided in outer box (18) and inner box (12) respectively. Nuts (not shown) may be fastened to the ends of bolts (44) and (46) to complete the mounting. 
     With reference to FIG. 3, a cross-sectional view of the safety mounting bolt (32) is illustrated which passes through a sleeve (34) provided in the bottom side wall of housing (10). Bolt (32) is bonded to roof top (30), and nut (36) is secured to the end of bolt (32) to provide an additional fastening. 
     Of course, the rubber pads (25) and (26) can be replaced by vibration dampening bolts (40) in which case, bracket (24) may be bolted to roof (30) and to outer box (18). Preferably, four bolts (40) could be used per mounting (22).