Abstract:
An air diffuser for underfloor air and electrical distribution systems, which can be rapidly converted to a cable grommet assembly, is provided with a diffuser grille having generally helical slots that produce a swirling air flow pattern with low impulse, low turbulence and high induction of room air. The helical air slots allow the grille to be rotated or spun off a mold, which allows the grilles to be molded more rapidly and economically. The grille sits on a housing which contains a flow regulator. Both the housing and the flow regulator have side walls with air slots. The regulator is connected to the grille and can be rotated by rotating the grille to regulate that air flow through the diffuser. The air diffusers and cable grommet assemblies are supported by common mounting systems that can be installed through the floors overlying an air distribution and/or electrical cable plenum. The mounting system includes a trim ring installed in a hole in the floor, which supports the other components of the air diffuser or grommet assembly, and a retaining ring which is dropped through the hole before the trim ring is installed and then ratcheted onto the trim ring.

Description:
RELATED APPLICATIONS 
     This is continuation of application Ser. No. 08/899,345, filed on Jul. 23, 1997 U.S. Pat. No. 5,938,525. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to an air diffuser designed for underfloor air distribution systems, and to a mold and method for making the diffuser. The diffuser is mounted, with a specially designed mounting system, in the floor that separates the plenum of the air distribution system from the room or other enclosure to be heated, cooled or ventilated. 
     BACKGROUND 
     Underfloor air distribution has gained popularity in work environments due to its design flexibility and reconfiguration capabilities. While early underfloor air distribution systems were designed for spaces housing large computer systems, the increased use of local area networks and telecommunication systems are requiring entire buildings to be designed with underfloor air distribution systems that provide large quantities of cooling air. Also, with the trend to more frequent office reorganization, flexible offices with electrical and mechanical systems that can be easily reconfigured at minimum cost to accommodate personnel and hardware requirements are in increased demand. 
     Bottom source or underfloor air distribution systems typically include a number of small diffusers that can be moved to accommodate frequent changes in space usage and the resulting changes in ventilation requirements. The diffusers are typically mounted in a raised floor that defines the top surface of a plenum chamber. In other words, the space beneath the floor panels constitutes an enclosed plenum chamber or air space in which the air pressure is greater than in the room or other enclosure to be heated, cooled or ventilated. Air flows from the plenum chamber through the diffusers into the room or other enclosure. For optimal performance, diffusers should expel air in a swirling air pattern with little or no turbulence and, to prevent drafts, relatively low jet velocities. This pattern promotes high induction or entrainment rates that mix unconditioned air within the room with the air being supplied through the diffusers, thereby providing comfortable air movement and eliminating or reducing air stagnation and stuffiness. 
     One known underfloor air distribution system, produced by Krantz, is an injection molded device consisting of a diffuser grille, a damper, a basket, a trim frame and a retaining frame. The damper is placed within the basket, and the diffuser is placed on top of the basket. The basket is inserted into the trim frame, which is inserted into the retaining frame. The retaining frame, in turn, can be affixed to flooring panels for access to the underfloor air plenum supply. The grille is designed with a circular configuration and has air slots which extend radially from the center of the grille to the outside edge of the grille. The slots can vary in length and width, but have a uniform slope. 
     Typical underfloor air distribution systems, such as those produced by Krantz, are difficult to manufacture due to the intricate nature of the grilles. Currently, grilles manufactured from a composite material are produced in injection-type molds with retractable core pins that form the intricate pattern of slots in the grille. After molding, each core pin must be retracted from the grille so that the grille can be removed from the mold. This adds a significant increment of time, perhaps 50 to 100%, to the time that would be required to produce the grille if it could be produced on a solid mold with fixed core pins. The retractable core pins also multiply the costs to produce and maintain the equipment. The costs for molds for previous diffuser grilles, with retractable core pins, has been estimated to be at least $500,000, whereas a solid mold for producing the same grille, if this could be done, might cost less than $100,000. The retractable core pins also increase the maintenance costs substantially. With all off these costs and disadvantages, molds with retractable core pins would normally be considered cost prohibitive for this type of diffuser. Thus, to reduce equipment cost, manufacturing time and the costs of the molded grilles, there is a need for grille designs, and production equipment and methods, whereby the grille is readily and easily removed from a solid mold with fixed core pins. 
     SUMMARY OF THE INVENTION 
     The present invention provides a diffuser for underfloor air distribution with a grille having generally helical slots with substantially straight sides along arcuate sections through said slots. These slots produce a swirling air flow pattern with high induction. Unlike previous diffusers for this type of flow pattern, however, the helical air slots of this invention allow the grille to be rotated or spun off a solid mold core. The ability to quickly remove the grille from the mold core is a dramatic improvement over current manufacturing techniques in which each individual mold insertion must be separately retracted from the respective air slot in order to remove the grille. Since the grille of this invention can be produced with a solid mold, the costs of the mold and molding time are both significantly lower than with prior art molds with retractable core pins. 
     In the preferred embodiment, the diffuser grille sets on a dust receptacle or basket-shaped housing that is supported by a mounting assembly in the floor. A flow regulator or damper nests inside the housing. Both the housing and the flow regulator have vertically extending air slots extending through their side walls. Air from the underfloor air plenum passes through these slots into the diffuser and is forced through the helical slots in the grille into the room above the diffuser. The air flow rate can be adjusted by rotating the flow regulator within the housing so that the slots in the flow regulator are either in or out of registry with the slots in the housing. 
     The preferred grille for this diffuser rests on top of the rim of the housing, and the flow regulator has a series of pins that project into grille slots. The rim of the housing and the outer surface of the grille have mating rings of shallow, generally V-shaped teeth. The slopes of the sides of these teeth are designed to allow the grille to be rotated, thereby adjusting the air flow rate, with gentle manual pressure. The grilles will not rotate, however, if a heavier weight such as a person or a piece of furniture is on the diffuser. 
     The invention also provides a mounting system for securing the diffusers in floors above underfloor air distribution systems. The mounting system includes a trim ring that extends through a hole in the floor and a retaining ring. The trim ring has a rim that rests on the floor. The retainer ring is shaped so that it can be dropped through the hole in the floor and then pulled up onto the trim ring, with the floor gripped between the retaining ring and the rim of the trim ring. The preferred retainer ring is movably fixed to the trim ring by a ratchet-like latching mechanism that allows the retainer ring to be rotated about and onto the trim ring. This accommodates various thicknesses of flooring panels. Once the trim ring is properly positioned, the retainer ring is ratcheted onto the trim ring to securely attach the diffuser to the floor. 
     The diffuser can be rapidly converted to an electrical power/data port by removing the grille, flow regulator and housing, and replacing them with a power/data port cover with one or more openings for electrical cables. The power/data port cover is supported by the trim ring that also supports the housing, flow regulator and grille of the air diffuser. This further improves the flexibility of the system by allowing a fixture that had been an air diffuser to be quickly converted into an electrical power/data port, or vice versa. Other features and advantages of this invention will be apparent from the following description. 
    
    
     DRAWINGS 
     FIG. 1 is an exploded perspective view of an underfloor air diffuser embodying this invention. 
     FIG. 2 is a partially sectioned elevation view of the diffuser in FIG. 1, installed in the floor panel of an underfloor air distribution system. 
     FIG. 3 is an enlarged detail view, along lines  3 — 3  of FIG. 4, of the rims of the grille and the housing on which it rests, showing the teeth between the grille and housing. 
     FIG. 4 is an enlarged cross-sectional view, along lines  4 — 4  of FIG. 3, showing the connection between grille and flow regulator in the diffuser in FIGS. 1 and 2. 
     FIGS. 5 and 6 are top and bottom plan views of the grille. 
     FIG. 7 is an exploded perspective view of the grille, the mold core on which it is produced, and a mating collar ring used to remove the grille from the mold core. 
     FIG. 8 is a fragmentary cross-sectional view of the grille, the mold core, the mating collar ring and the mold cap that defines the basic shape of the grille in the molding process, along lines  8 — 8  in FIG.  9 . 
     FIG. 9 is a fragmentary cross-sectional view along lines  9 — 9  in FIG.  8 . 
     FIG. 10 is a top plan view of the mold core. 
     FIG. 11 is an enlarged plan view of a fragment of the mold in FIG. 10, showing the geometrical configuration of the core pins. 
     FIGS. 12 and 13 are enlarged cross-sectional views along lines  12 — 12  and  13 — 13  in FIG.  11 . 
     FIG. 14 is a perspective view of the trim ring and retaining ring in FIG. 1, illustrating the ratcheting mechanism that holds them together, so that the diffuser is secured in a hole in a floor panel as shown in FIG. 2, yet allows them to be separated so that the diffuser can be moved. 
     FIGS. 15 a  and  15   b  are schematic perspective views, showing the installation of the trim ring and retaining ring in the floor of an underfloor air distribution system. 
     FIG. 16 is an exploded, partially sectioned side elevation view of the trim ring and retaining ring. 
     FIG. 17 is a bottom plan view of the trim ring and retainer ring. 
     FIG. 18 is an enlarged detail view of the ratcheting mechanism in FIGS. 14 and 16. 
     FIG. 19 is a still further enlarged detail view of the ratcheting mechanism, showing how the locking tooth is moved for removal of the retaining ring. 
     FIGS. 20 a ,  20   b  and  20   c  are fragmentary side elevation views of the trim ring and retaining ring, illustrating the assembly of these components. 
     FIG. 21 is a perspective view of an electrical power/data port that may be used with the same mounting structure as the diffuser illustrated in foregoing Figures. 
     FIG. 22 is a cross-sectional elevation view of the power/data port in FIG.  21 . 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 is an exploded perspective view of an underfloor air diffuser embodying this invention. The diffuser, referred to generally as  24 , has a grille  30  supported by a dust receptacle or basket shaped housing  60 . As show in FIG. 2, housing  60  is mounted in the floor  25  above the plenum  28  of the air distribution system by a trim ring  80  and a retaining ring  100 , described in more detail below. In the preferred diffuser  24 , a flow regulator or damper  70  nests inside the basket-shaped housing  60 . The side walls  72  of flow regulator  70  and the side walls  62  of housing  60  are complementary surfaces of revolution, such as stepped, slightly tapered cylinders or truncated cones, that allow the side walls  72  of the flow regulator to contact and rotated with respect to the side walls  62  of the housing. The illustrated flow regulator  70  has an upper sloping shoulder  75  and a lower sloping shoulder  77  that rest on sloping shoulders  65  and  67  in housing  60 . The upper and lower pairs of sloping shoulders  75 ,  65  and  77 ,  67  providing mating surfaces that reduce surface contact and allow the flow regulator to rotate easily within the housing. 
     The side walls  62  of housing  60  and the side walls  72  of flow regulator  70  have mating longitudinally extending air slots  64 ,  74 , separated by solid portions  66 ,  76  of their respective side walls  62 ,  72 . When the flow regulator is rotated so that the slots  74  in the flow regulator are in registry with the slots  64  in housing  60 , air can flow from the underfloor air plenum  28  into the diffuser. This flow can be reduced or stopped by rotating the flow regulator  70  so that solid portions  76  of the flow regulator side walls  72  partially or totally cover the air slots  64  in the housing. 
     Vertical tabs or pins  78  protrude from the upper rim  79  of air flow regulator  70 , extending above the top of housing  60  into air slots  42 ,  44  or  46  in the grille  30 . The pins  78  are spaced to correspond to the spacing of the slots in the grille, so that each pin will engage one of the air slots whenever the grille is placed on the housing  60  and flow regulator  70 . When the grille is rotated, an inner wall of an air slot engages each of the pins, and the flow regulator is rotated with the grille. As the flow regulator rotates within housing  60 , the air slots  74  in the side walls of the flow regulator and the solid portions  76  of the flow regulator side walls open and close the air slots  64  in the side walls of the housing. Thus, the air flow from the plenum through the diffuser can be controlled by simply rotating the grille by hand. 
     As may be seen in FIGS. 3 and 6, there is a ring of shallow, V-shaped teeth  48  around the outer edge of the bottom of grille  30 . There is a mating ring of teeth  68 , shown in FIGS. 1 and 3, around a flange  61  that extends laterally from the top of housing  60 . Grille  30  rests on flange  61 , and the teeth  48  on the bottom of the grille mesh with the teeth  68  on the top of the flange. The sides  52  of the illustrated teeth  48 ,  68  define angles of about 150° at the tips  54  and bases  56  of the teeth  48 ,  68 . This shallow angle allows the grille to be rotated with gentle pressure on the top of the grille, thereby rotating flow regulator  70  and opening or closing the air slots  64  in housing  60 . Thus, the flow rate can be adjusted quickly without removing the grille. However, when a greater force such as the weight of a piece of furniture or a person is placed on the grille, the teeth  48 ,  68  lock the grille and prevent inadvertent movement. 
     Air is discharged from the diffuser through slots  42 ,  44 , and  46  in grille  30 . Unlike conventional grilles for this type of underfloor diffuser which, because of manufacturing limitations, have generally had straight slots, the grilles of this invention have a pattern of curved, helical slots with substantially straight side along arcuate sections through said slots. These slots extent generally inwardly from near the outer rim of the grille  30 , with the longest slots  42  terminating at the central hub  36  of the grille. These long slots  42  are separated from each other by medium length slots  44  and short slots  46 . This pattern facilitates production of a grille with slots comprising a relatively high percentage of its face, while maintaining desired structural integrity. When constructed of an engineered plastic, the illustrated grille, with slots covering more than 20% of the surface of the grille, is capable of supporting loads in excess of 1400 lbs., which makes it entirely suitable for underfloor air diffusers. 
     The slots in the grille are sloped so that the sides  45  of the slots function as air deflectors that help provide the desired flow pattern. The curvature and slope of the slots provide a swirling air flow with low jet velocities, low impulse, minimal turbulence and high induction. As shown in FIGS. 7-13, the slots are produced in an injection mold with a mold core  140  with an intricate pattern of core pins  142 ,  144 ,  146 , extending from a base  141 . The mold also has a cap  132  (shown in FIG. 8) with a cylindrical cavity that defines the general shape of the grille. 
     Molten resin is injected into the mold around the core pins, which form the slots  42 ,  44 ,  46  in the grille. As best seen in FIG. 8, the base  141  of the mold core also has an outer ring of teeth  148  that form the inner portions  481  of the teeth  48  around the outside of the bottom of grille  30 . The outer portions  482  of the teeth  48  on the grille are formed by a mating collar ring  136  with a ring of teeth  138  that are aligned with the teeth  148  on the base  141  of mold core  140 . 
     Upon completion of the molding process, lid  132  is removed and the molded grille  30  is rotated and extracted from the mold core  140  by lifting and rotating the mating collar ring  136 , which is shown in FIG.  7 . The teeth  138  on the collar ring, engaged with the teeth  48  on the bottom of the grille, ensure that the grille rotates with the collar ring at the desired rate. The rotation of the mating collar ring is coordinated with its vertical movement so that the arcuate movement of the grille corresponds to the slope of the slots. This allows the grille to be rotated or “spun” off the fixed core pins  142 ,  144 ,  146  of the mold core  140 . Ejector pins (not shown) in the base  141  of the core also contribute to the extraction of the grille. 
     Core pins  142 ,  144  and  146  are preferably formed by electrostatic discharge machining. A carbon electrode which corresponds to the slots in the grille machines material from a block of tool steel by electrostatic discharge to form the pins. This process produces a mold core that, in comparison to other molding processes used to form similar geometry, such as molds with retractable core pins, is much less expensive in original fabrication of the mold, in maintenance requirements, and in operating costs. 
     In the illustrated mold core and grille, the left side of each core pin defines an acute angle with the top of the mold that varies from about 27° to about 5° along the length of the core pin and along the length of the corresponding grille slot. The right hand side of the illustrated core pins  142 ,  144 ,  146  and grille slots  42 ,  44  and  46  meet the mold top or grille face at obtuse angles ranging from about 147° to about 101°. The difference between the angles on the two sides of the core pins and slots provides a draft angle of about 3° (per side), which might be between about 3° and about 5° in other embodiments. This facilitates removal of the grille from the mold. 
     As shown in FIGS. 9-11, each slot and core pin of the illustrated grille and mold core is designed so that the lateral offset from a point along the top edge of any slot or core pin to the bottom edge of the same side of the slot or core pin at the same radial distance from the center of the grille or mold core or, in other words, the width of the base of a right triangle lying substantially in an arcuate section through the points, with the right corner of the triangle directly beneath the point on the top edge, is a function of the distance from the center. As seen in FIGS. 10 and 11, the width W, of a base of a right triangle formed by a first arcuate section extending through any slot or pin and the width W 2  of a base of a right triangle formed by a second arcuate section extending through the slot or core pin at another point or through another slot or pin satisfy the equation 
     
       
         
           W 
           1/ 
           W 
           2 
           ≅R 
           1/ 
           R 
           2 
         
       
     
     where R 1  and R 2  equal the distance from a center point of the grille to the first and second arcuate sections. As a result, an angle ∝ formed between a first radial line intersecting the top of a slot or core pin and a second radial line through a projection of the bottom of the slot or core pin is substantially equivalent to the angle between two comparable projections at the top and bottom of the slot at any other point. 
     As a result of the unique shape of these helical core pins  142 ,  144 ,  146  and helical grille slots  42 ,  44  and  46 , the finished grille can be simply rotated or “spun” off the mold when the molding process is finished. This is a radical departure from previous molding processes for grilles for this type of diffuser, which employed complicated, cumbersome and expensive molding equipment and techniques with individual retractable mold core pins for each slot. These core pins had to be retracted individually at the end of the molding process before the grille could be removed from the mold. The simplicity of the mold and process of this invention, in which the grille is simply rotated off a substantially less expensive solid mold core, thereby shortening the molding process significantly to provide even greater savings, is in stark contrast to the complexity and inefficiency of the prior art equipment and practices. 
     As shown in FIG. 2, the diffuser  20  is designed to be mounted, with the trim ring  80  and retaining ring  100  illustrated in FIGS. 14-19, in a hole  26  in the floor  25  above an air distribution plenum  28 . The trim ring and retaining ring are designed so that the entire installation process can be performed from above the floor, which shortens installation and relocation of the diffusers substantially. This diffuser can be installed in less than 1 minute, whereas installation of prior art diffusers that required parts of the installation to be performed from beneath the floor typically required at least 5 minutes. In an office building with many diffusers, the time savings are significant. 
     Referring to FIGS.  2  and  14 - 17 , trim ring  80  has a cylindrical section  82  that extends through the hole  26  in the floor, and a tapered flange  84 , extending laterally from the top of cylindrical section  82 , that is larger than the hole in the floor. The surface of the cylindrical section  82  of the trim ring has three series of latching teeth  94  and three camming grooves  88  that hold the trim ring and retaining ring together in the installed position. Retaining ring  100  has a cylindrical section  102  whose inner diameter is slightly larger than the outer diameter of the cylindrical section  82  of the trim ring. A flange  104  extends from the upper end of the cylindrical section  102  of the retaining ring and, as seen in FIG. 2, presses against the bottom of floor  25  in the installed position. Flange  104  differs from the flange  84  on the trim ring in that it does not have a uniform diameter or width. In one direction flange  104  is longer than the width of the hole  26  in which it is to be installed. Thus, the flange spans the hole and holds the diffuser in place. In another direction, as best seen FIG. 17, the width of flange  104  is only slightly greater than the outer diameter of the cylindrical section  102  of the retaining ring, and less than the width of hole  26 . This means that the retaining ring can be slipped through the hole in the installation process, and the entire process can be performed from above the floor. 
     Three pins  108 , which may be seen in FIGS. 14,  16 - 18 ,  20   a ,  20   b , and  20   c , extend from the inner surface of retaining ring  100 . As best seen in FIGS. 20 a ,  20   b , and  20   c , these pins  108  are positioned to enter vertically extending mouths  89  of the camming grooves  88  on the trim ring when the retaining ring is placed on the bottom of the trim ring. When the pins reach the top of the vertically extending mouths of the camming grooves, the retaining ring may be rotated with respect to the trim ring and the pins  108  ride up inclined spiral sections  91  of camming grooves  88 , pulling the retaining ring onto the trim ring until it reaches the installed position shown in FIG.  2 . 
     Retaining ring  100  has a latching mechanism  112  that engages one of the series of latching teeth  94  on the trim ring. Latching mechanism  112  comprises a latch tooth  114  that engages the teeth  94  on the trim ring, a release tab  116  used to disengage the latch tooth  114  from teeth  94 , and a resilient arm  118 , extending from the cylindrical section  102  of the retaining ring, on which the latch tooth and release tab are mounted. There is an opening in the retaining ring flange  104  at the latching mechanism to facilitate access. 
     As the retaining ring is rotated onto the trim ring, the latch tooth engages the teeth on the trim ring and locks the retaining ring in place. As best seen in FIGS. 18 and 19, the leading sides  95  of the trim ring teeth  94 , i.e. the sides that are contacted first by the latch tooth  114  as the retaining ring rotates onto the trim ring, and the leading side  115  of latch tooth  114 , are sloped or beveled to allow the latch tooth to pass over the trim ring teeth in the installation process. The trailing sides  97  of the trim ring teeth and the trailing side  117  of the latch tooth are substantially at right angles to the direction of movement of the latch tooth to reduce the risks of inadvertent release. 
     The trim ring and retaining ring can be installed quickly and easily from above the floor, a marked advantage over the processes required with earlier underfloor diffusers. As shown in FIG. 15 a , the retainer ring  100  is inserted through the hole  26  in floor  25  and allowed to rest on the bottom of the plenum  28 . The trim ring  80  is then placed in hole  26 , as shown in FIG. 17 b . The installer reaches through the central opening in the trim ring, picks up the retainer ring, inserts the retaining ring pins  108  into the vertically extending mouths  89  of the trim ring camming grooves, and rotates the retaining ring to move pins  108  up the inclined spiral sections  91  of the camming grooves and pull the retaining ring up the trim ring until the floor is gripped securely between the trim ring flange  84  and the retaining ring flange  104 . With the trim ring and retaining ring secured in place, housing  60  is placed inside the trim ring. As shown in FIGS. 2 and 4, the flange  67  at the top of housing  60  rests on an annular shoulder  86  that extends from the inside wall of trim ring  80 . The flow regulator  70  is placed inside the housing, the grille  30  is placed on top, and the unit is ready for service. The entire installation process can be performed in less than one minute, which is substantially less than the time required for previous underfloor diffusers. 
     The diffuser can be removed just as easily. The grille, flow regulator and dust basket are removed. The worker then reaches through the central opening in the trim ring and grasps the release tab  116  on the retaining ring locking mechanism. As shown in FIG. 19, pulling back on the release tab flexes arm  118  and allows the latch tooth  114  to clear the teeth  94  on the trim ring  80  so that the retaining ring can be rotated back off the trim ring. 
     The illustrated air diffuser  20  can be rapidly converted to the electrical power/data port  160  shown in FIGS. 21 and 22 by simply removing the diffuser grille  30 , flow regulator  70  and dust receptacle  60 , and replacing them with them with the electrical power/data port cover  162 , pivot cover  170  and, if desired, one or more of the electrical power/data port seals  180  shown in FIG.  19 . This conversion to an electrical power/data port can be utilized when remodeling of an office space, or other changes, makes it desirable to use the opening  26  in the floor panel for electrical cables, fiber optic cables, or the like. As seen in FIG. 21, the electrical power/data port has several openings  164  that will accommodate many types and sizes of cables. 
     Electrical power/data port cover  160  has several locking tabs  166  with grooves  167  that snap on the annular shoulder  86  inside the trim ring  80 . The locking tabs  166  are designed so that the electrical power/data port cover can be removed by inserting a tool into a central opening  168  in the electrical power/data port cover and pulling upward. The flexibility of the locking tabs allows them to snap off the shoulder in the locking ring. 
     When secured to shoulder  86 , the electrical power/data port cover rests slightly beneath the top of the trim ring flange  84 . Pivot cover  170 , which has a central boss  172  that fits into the central opening  168  in the electrical power/data port cover, is then placed on top of the electrical power/data port cover and within the trim ring  80  so that the top of the pivot cover is substantially flush with the top surface of the trim ring. The pivot cover may be rotated about its center boss  172  to cover one or more of the openings of the electrical power/data port cover, depending on the number and area of openings required for cables. As shown in FIG. 19, optional adhesive backed grommet seals  180  may be used for small cabling to prevent or reduce the loss of air from the plenum. 
     It should be apparent that the air diffuser and electrical power/data port described above provide substantial advantages in furnishing, rearranging and updating modern offices and other commercial buildings with underfloor air and electrical distribution systems. These diffusers and electrical power/data port can be installed in a fraction of the time required for previous components, and can be moved, modified or switched just as readily to suit almost any conceivable configuration. The diffusers provide a superior air flow pattern and the helically slotted grilles can be molded more quickly and economically than prior art structures. As those skilled in the art will recognize, the diffusers, molds and molding processes described herein can be adapted to suit a wide variety of applications. Many adaptations, modifications may be made to the embodiments described above without departing from the spirit and scope of this invention, which is defined by the following claims.