Abstract:
A resonator includes an inner perforated tube, an outer shell, and a plurality of annular ribs extending radially therebetween and defining resonant chambers. Progressive stepping of ribs and grooves enables axial insertion assembly with minimal cost. The need for welding or secondary bonding operations is eliminated.

Description:
BACKGROUND AND SUMMARY  
       [0001]     The invention relates to resonators, including intake resonator silencers for internal combustion engines.  
         [0002]     Intake resonators are known in the art, and are constructed from various materials including metal and/or plastic. Blow molded bottle style resonators are known and fitted under the hood of automobiles, trucks, agricultural and construction vehicles, marine vehicles, and recreational vehicles. Various constructions employ hollow structures made of plastic which are bonded together using vibration or sonic welding or other types of friction welding. Other types of structures have additional elastomer seals, adding expense. Other structures of reduced cost are not gas tight, and therefore lack in performance.  
         [0003]     The present invention provides a simple, cost effective resonator without performance trade-off. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0004]      FIG. 1  is a perspective assembly view of a resonator in accordance with the invention.  
         [0005]      FIG. 2  is a cut-away view of the assembly of  FIG. 1 .  
         [0006]      FIG. 3  is a sectional view taken along line  3 - 3  of  FIG. 1 .  
         [0007]      FIG. 4  is a perspective view partially cut-away of the inner perforated tube of  FIGS. 1-3 . 
     
    
     DETAILED DESCRIPTION  
       [0008]      FIG. 1  shows a resonator  10  extending axially along an axis  12  between distally opposite axial ends  14  and  16  providing an inlet and an outlet, respectively, for example for receiving intake combustion air at inlet  14  and delivering the combustion air from outlet  16  to an internal combustion engine (not shown). Resonator  10  has an inner perforated tube  18 ,  FIGS. 2-4 , an outer shell  20 , and at least one and preferably two or more annular ribs such as  22 ,  24  spaced axially between inlet  14  and outlet  16  and extending radially between inner perforated tube  18  and outer shell  20 . In preferred form, inner tube  18  is an injection molded plastic member, and outer shell  20  is a blow molded or rotationally molded plastic member, and the ribs extend integrally radially outwardly from inner tube  18 . The ribs define a first resonant chamber  26  between inner perforated tube  18  and outer shell  20  axially upstream of rib  22 , a second resonant chamber  28  between inner perforated tube  18  and outer shell  20  axially downstream of rib  22  and axially upstream of rib  24 , and a third resonant chamber  30  between inner perforated tube  18  and outer shell  20  axially downstream of rib  24 . Inner perforated tube  18  has a first set of perforations  32  radially aligned with resonant chamber  26 , a second set of perforations  34  radially aligned with resonant chamber  28 , and a third set of perforations  36  radially aligned with resonant chamber  30 . The resonator attenuates sound waves in gas flow entering the resonator at inlet  14  and exiting the resonator at outlet  16 . The gas flows axially through the hollow interior of perforated tube  18  and communicates with resonant chambers  26 ,  28 ,  30  through respective sets of perforations  32 ,  34 ,  36 .  
         [0009]     The set of perforations  32  are the only inlet to and the only exit from resonant chamber  26 , such that gas flow in the hollow interior of inner perforated tube  18  can enter resonant chamber  26  only through the set of perforations  32 , and can exit resonant chamber  26  only through the set of perforations  32 . The second set of perforations  34  are the only inlet to and the only exit from resonant chamber  28 , such that gas flow in inner perforated tube  18  can enter resonant chamber  28  only through the set of perforations  34 , and can exit resonant chamber  28  only through the set of perforations  34 . The third set of perforations  36  are the only inlet to and the only exit from resonant chamber  30 , such that gas flow in inner perforated tube  18  can enter resonant chamber  30  only through the set of perforations  36 , and can exit resonant chamber only through the set of perforations  36 . The upstream inlet ends  38  and  40  of inner tube  18  and outer shell  20 , respectively, engage each other in tight fit flush relation, such that gas flow enters resonator  10  only through the hollow interior of inner tube  18 . The downstream outlet ends  42  and  44  of inner tube  18  and outer shell  20 , respectively, engage each other in tight fit flush relation, such that gas flow exits the resonator at outlet  16  only through the hollow interior of inner perforated tube  18 .  
         [0010]     Rib  22  extends radially outwardly from inner perforated tube  18  and has an outer tip  46 . Outer shell  20  has an inner surface  48  facing radially inwardly toward inner perforated tube  18  and has a sealing engagement surface  50 ,  FIG. 3 , engaging outer tip  46  of rib  22  in radially engaged tight fit relation such that inner perforated tube  18  is axially insertable (downwardly in  FIGS. 1-3 ) into outer shell  20  and held in radially engaged relation therein, to be further described. Rib  24  extends radially outwardly from inner perforated tube  18  and has an outer tip  52 . Outer shell  20  has an inner surface  54  facing radially inwardly toward inner perforated tube  18  and has a sealing engagement surface  56  engaging outer tip  52  of rib  24  in radially engaged tight fit relation such that inner perforated tube  18  is axially insertable (downwardly in  FIGS. 1-3 ) into outer shell  20  and held in radially engaged relation therein, to be further described. Outer tip  46  of rib  22  engages surface  50  in sealing relation, isolating resonant chamber  26  from resonant chamber  28 . Outer tip  52  of rib  24  engages surface  56  in sealing relation, isolating resonant chamber  28  from resonant chamber  30 .  
         [0011]     Resonant chamber  26  is sealed at its upstream end by the flush tight fit engagement of ends  38  and  40  of inner tube  18  and outer shell  20 , respectively, and is sealed at its downstream end by the engagement of rib tip  46  and surface  50 . Resonant chamber  28  is sealed at its upstream end by the engagement of rib tip  46  and surface  50 , and is sealed at its downstream end by the engagement of rib tip  52  and surface  56 . Resonant chamber  30  is sealed at its upstream end by the engagement of rib tip  52  and surface  56 , and is sealed at its downstream end by the flush fit tight engagement of downstream ends  42  and  44  of inner tube  18  and outer shell  20 , respectively.  
         [0012]     Each of sealing engagement surfaces  50  and  56  is a detent engaging the respective outer tip  46  and  50  of the respective rib  22  and  24  in snap-fit relation upon the noted axial insertion. Outer shell  20  has an outer surface  58  with an annular groove  60  recessed radially inwardly toward inner perforated tube  18  and providing the noted sealing engagement surface  50  on inner surface  48 . Outer shell  20  has an outer surface  62  with an annular groove  64  recessed radially inwardly toward inner perforated tube  18  and providing sealing engagement surface  56  on inner surface  54 .  
         [0013]     Inner perforated tube  18  is a two-piece member having first and second pieces  66  and  68  abutting each other at first and second axially extending abutment lines  70  and  72  in assembled condition in outer shell  20 . Pieces  66  and  68  are preferably held in assembled condition in outer shell  20  solely by outer shell  20 , without bonding or welding of pieces  66  and  68  to each other. Further preferably, pieces  66  and  68  are identical, which enables the use of a single tool for forming same, to reduce tooling cost. One axially extending edge of each piece, such as edge  74 ,  FIG. 4 , along abutment line  70 , is concave as shown at  76 , while the other axially extending edge  78  at abutment line  72  is convex or bulged as shown at  80  to mate in the concave edge of the other piece. Other types of interlocking engagement of pieces  66  and  68  may be used to provide proper alignment of the pieces during axial insertion into outer shell  20 , whereafter the pieces are held in assembled condition by engagement of ribs  22  and  24  with respective detents  50  and  56 .  
         [0014]     Inner perforated tube  18  and outer shell  20  have the noted upstream axial ends  38  and  40  mating at an upstream joint  82 ,  FIG. 3 , blocking gas flow therepast at inlet  14  such that gas flow at inlet  14  can only flow into the hollow interior of perforated inner tube  18  and not into the space between inner tube  18  and outer shell  20 . Inner perforated tube  18  and outer shell  20  have the noted downstream axial ends  42  and  44  mating at a downstream joint  84  blocking gas flow and sound therepast at outlet  16  such that gas flow at outlet  16  can only flow from the hollow interior of inner perforated tube  18  and not from the space between inner tube  18  and outer shell  20 . The upstream axial end of inner perforated tube  18  has first and second different diameter portions  86  and  88 ,  FIG. 3 , and a transition portion  90  therebetween. The diameter of portion  86  is larger than the diameter of portion  88  and mates with outer shell  20 . Transition portion  90  extends radially inwardly from first diameter portion  86  to second diameter portion  88 . The downstream axial end of outer shell  20  has third and fourth different diameter portions  92  and  94  and a transition portion  96  therebetween. The diameter of portion  94  is smaller than the diameter of portion  92  and mates with inner perforated tube  18 . Transition portion  96  extends radially inwardly from third diameter portion  92  to fourth diameter portion  94 .  
         [0015]     The number of ribs  22 ,  24  equals N, the number of grooves  60 ,  64  equals N, and in preferred form, N is greater than or equal to 2, and the number of resonant chambers  26 ,  28 ,  30  equals N+1, and the number of sets of perforations  32 ,  34 ,  36  equals N+1. The ribs  22 ,  24  have a radial height between inner perforated tube  18  and outer shell  20 , which radial height progressively increases from rib to rib. As seen in  FIGS. 3 and 4 , the radial height of rib  22  is greater than the radial height of rib  24 . The ribs extend radially outwardly from inner perforated tube  18 . Outer shell  20  has the noted plurality of annular grooves  60 ,  64  axially spaced from each other and serially axially spaced between inlet  14  and outlet  16  and radially aligned with and engaging respective ribs  22  and  24 . The grooves have a radial depth progressively increasing from groove to groove in inverse relation to the progression of the progressively increasing height of the ribs. As seen in  FIGS. 2 and 3 , the radial depth of groove  64  is greater than the radial depth of groove  60 . The shortest radial height rib  24  engages the deepest radial depth groove  64 . The tallest radial height rib  22  engages the shallowest radial depth groove  60 . This construction facilitates axial insertion of inner perforated tube  18  into outer shell  20 , and enables such axial insertion without a draft on inner tube  18 .  
         [0016]     In the present method for assembling a resonator, the inner perforated tube  18  is axially inserted into outer shell  20  (downwardly in  FIGS. 1-3 ). First and second pieces  66  and  68  are abutted at axially extending abutment lines  70  and  72  to a pre-assembled condition. The first and second pieces  66  and  68  in the pre-assembled condition are inserted axially into outer shell  20  such that pieces  66  and  68  are held in assembled condition in outer shell  20 , preferably solely by outer shell  20 , without bonding or welding of pieces  66  and  68  to each other. Radial retention force is provided by the snap-fit detent engagement of ribs  22 ,  24  and detent sealing engagement surfaces  50 ,  56 , respectively. The noted progressive stepping of the ribs and grooves facilitates the noted axial insertion, including without drafting.  
         [0017]     It is recognized that various equivalents, alternatives and modifications are possible within the scope of the appended claims.