Noise silencer assembly

A noise silencer covering an air discharge opening in front of a radiator is used for noise control for an earthmoving vehicle. The silencer encloses a radiator grill which is removably attached to a forward end of an engine enclosure. The noise silencer is provided with upper and lower discharge openings with the open area of the upper opening being larger than that of the lower opening. The walls of the silencer are lined with sound absorbing materials.

BACKGROUND OF THE INVENTION 
This invention relates to noise control for an earthmoving vehicle and more 
particularly to a noise silencer provided forwardly of the radiator and 
removably attached to an engine enclosure. 
In general, an enclosure for an engine compartment in an earthmoving 
vehicle consists of a hood, enclosures (side covers), dash board, radiator 
guard and an under guard. The enclosure protects the engine and its 
accessories from damage due to pebbles, branches of trees, and the like as 
well as shields noise emanating from the engine. 
Recently the noise control for earthmoving vehicles has come to the 
forefront and a demand for a countermeasure to reduce the noise has 
arisen. As a result, strict limitations or regulations have been imposed 
on the earthmoving vehicles such as for instance the noise levels of 
vehicles which should be less than 65 db (A) as measured at a point 30 m 
apart from a vehicle in its nonmovable condition and less than 75 db (A) 
as measured at a point 30 m apart from a vehicle in its operating 
condition. 
Prior art references having noise control apparatuses are U.S. Pat. No. 
3,812,927 and Japanese Laid-open Utility Model SH051-3733. The former 
discloses a radiator in which a radiator mask in front of the radiator is 
of such shape that noise from the engine is guided upwardly through a top 
opening with sound absorbing material being bonded to the inner surfaces 
of the mask. The latter discloses a radiator in which there is provided an 
opening in the front portion of a radiator with the aforesaid opening 
being covered with ducts having a sound absorbing material bonded to the 
inner surfaces of the ducts. The above both attempts are successful as a 
noise control means to some extent. However, the radiator mask (the former 
attempt) and the ducts (the latter attempt) can not be removed as required 
and, in addition, the opening is directed only upwards with the result 
that foreign matter such as pebbles, sand, soil, rain, water and the like 
pollute or damage the sound absorbing materials provided inside and in 
some cases such foreign matter enters the engine compartment. 
Japanese Laid-open Utility Model Publication SH052-105 improves the 
aforesaid shortcomings by providing upper and lower openings for a 
radiator mask. However, the aforesaid openings are large in diameter so 
that air being blown from the fan through the lower opening impinges on 
the ground and thus blows dust and sand upwardly causing discomfort for 
the operator. 
SUMMARY OF THE INVENTION 
According to the present invention there is provided a noise silencer 
assembly for use in an earthmoving vehicle. A noise silencer encloses a 
radiator grill which is removably attached to an engine enclosure and 
covers an air discharge opening which is open toward the front in front of 
a radiator. The noise silencer is provided with upper and lower air 
discharge openings with an open area of the upper opening thereof being 
larger than that of the lower opening. The internal space of the silencer 
diverges from the bottom toward the top. The walls of the silencer are 
lined with sound absorbing materials.

Detailed Description 
Referring to FIG. 1, an earthmoving vehicle 10 has a radiator guard 12 as 
part of an engine enclosure 18 positioned at the forward end of the 
vehicle. As shown in FIG. 4, a radiator 14 is installed within an engine 
compartment 28. An air discharge opening 19 is provided in the radiator 
guard in front of the radiator. Brackets 16, FIG. 2A, are provided at a 
suitable spacing about a peripheral portion of the air discharge opening 
19. A radiator grill 24 is attached to the bracketsby fastening means such 
as bolts and nuts, not shown, for protecting the radiator. As shown in 
FIGS. 2A and 2B, bolt holes 17 and 26 are provided in the brackets and 
radiator grill, respectively, for receiving the fastening means. 
A noise silencer 30 is positioned in front of the radiator grill 14 and is 
removably attached to the engine enclosure 18. A plurality of forwardly 
projecting hinge members 20 are secured to the radiator guard 12 at 
opposite sides thereof. The hinge members are provided in pairs with each 
pair receiving one of a plurality of rearwardly directed hinge plates 32 
secured to the noise silencer 30. The hinge plates are removably attached 
to the hinge members by hinge pins 22. 
The noise silencer 30 has an internal capacity sufficiently large for the 
radiator 14 and includes a forward outer wall plate 30" which is inclined 
forwardly at the top at an angle selected from a range of from about 
20.degree. to about 30.degree. to the vertical in opposed relation to the 
radiator guard 12. Each of a pair of side wall plates 30' is bent at a 
right angle to the forward outer wall plate 30". A top plate 44 and a 
bottom plate 44' extend rearwardly from the top and bottom edges 
respectively of the forward outer wall plate. The noise silencer is 
provided with an upper air discharge opening 34 between the top plate and 
the top portion of the radiator guard and a lower air discharge opening 36 
between the lower plate and the lower portion of the radiator guard. 
The forward outer wall plate 30" and the side wall plates 30' of the noise 
silencer 30 are lined with sound absorbing materials 42. The sound 
absorbing materials are backed with screen members or perforated plates 40 
at the internal portion of the noise silencer. Thus, the sound absorbing 
materials are sandwiched between the walls of the noise silencer and the 
perforated plates 40. 
Each of the perforated plates 40 is removably attached to the respective 
wall by bolts 38 which are secured to pin bosses 48 secured to the walls 
at a suitable spacing. 
The perforated plates 40 have an at least 40% opening ratio that prevents 
the sound absorbing material from being stained and damaged due to foreign 
matter entering the noise silencer. In addition, the perforated plates 40 
direct part of the sound upwardly through the upper air discharge opening 
34. 
The sound absorbing material 42 should preferably be thick. However, 
materials having thicknesses selected from the range of about 25 mm to 
about 50 mm are sufficient for this purpose. Such sound absorbing 
materials can be glass wool, or the like. 
The upper air discharge opening 34 of the noise silencer 30 has a large 
open area as compared with the lower discharge opening 36 which has a 
small open area. Thus, the noise silencer has an internal space which is 
diverging upwardly from its bottom so that air and noise passing through 
the air discharge opening 19 may be directed upwardly through the upper 
air discharge opening as indicated by the arrows in FIG. 4. The lower air 
discharge opening 36 is provided in the noise silencer so that pebbles, 
sand, soil, rain water, or foreign matter carried by the air from the 
engine or falling into the noise silencer from above will be discharged 
through the lower air discharge opening. 
The lower air discharge opening 36 has a longitudinally small dimension 
"d", i.e., narrow width as shown in FIG. 3. This is because if the width 
"d" is increased excessively, then air discharged from the lower air 
discharge opening 36 blows sand or soil on the ground immediately under 
the opening 36. 
In this respect, the width of the lower discharge opening 36 should 
desirably be in the order of 30 mm. 
The lower edge 44" of the noise silencer 30 as shown in FIG. 3 extends 
linearly. However, since the front surface of the radiator guard 12 is 
curved along an arcuate form, the lower edge 44" of the bottom plate 44' 
could preferably be formed into an arcuate shape. 
The removal of bolts 38 allows easy cleaning and replacement of the 
perforated plates 40 as well as cleaning and replacement of the sound 
absorbing materials 42. Normally, the noise silencer 30 is supported by 
the hinge pins 22 at both sides of the noise silencer. However, for easy 
repair of the silencer, maintenance and checking of the cooling fan, other 
engine accessories, radiator grill 24 and radiator 14, the hinge pins at 
one side of the noise silencer can be removed so that the silencer can be 
pivotally moved or turned about the hinge pins on the other side. 
As is apparent from the foregoing description, the silencer 30 is provided 
forwardly of the radiator guard 12 and has the upper air discharge opening 
34 of an open area larger than that of the lower air discharge opening 36 
so that part of the sound stemming from the engine compartment 28 may be 
absorbed by the sound absorbing materials 42 through perforations in the 
perforated plates 40 while the remaining portion of the sound may be 
reflected by the perforated plates 40 upwardly for diffusion. In addition, 
the silencer 30 is formed with the lower air discharge opening having a 
small open area so that only a low level of sound and air is discharged 
therethrough. 
While the present invention has been described herein with reference to a 
certain exemplary embodiment thereof, it should be understood that various 
changes, modifications and alterations may be affected without departing 
from the spirit of the scope of the present invention as defined in the 
appended claims.