Abstract:
A spray head for a coffee making apparatus having a plurality of holes at the bottom of a fluid reservoir for wetting the coffee grounds located below the spray head, the holes raised above a floor of the fluid reservoir by upwardly projecting stand pipes. The elevated hole draws water from a depth spaced from the floor where sediment and lime scaling occurs to delay clogging of the spray head. The arrangement of the holes are selected to wet the grounds evenly, and the size of the holes are preferably selected to create an impact of droplets with the grounds below while maintaining an adequate flow rate through the holes.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a coffee making apparatus, and more particularly to a spray head for a coffee making apparatus having a plurality of raised holes on the interior surface of the spray head to resist clogging by deposition of lime and other sediments. 
     2. Description of the Related Art 
     Lixiviation is a general term for the passage of hot water through a ground product, where the hot water acts as a solvent. Coffee making machines use this technique to brew coffee. In a drip filtration system for brewing coffee, coffee grounds are placed in a basket and heated water is drained into the basket to mix with the grounds and extract flavoring solubles as the water is directed into a decanter positioned below the basket. A filter is placed between the grounds and the decanter to remove sediment and prevent the grounds from entering the beverage in the decanter. 
     Brewing the most flavorful coffee requires a balancing between the strength of the brewed coffee and the degree of extraction from the ground coffee. The coffee brewing process is made up of three stages: wetting, extraction, and hydrolysis. During wetting, as the coffee bean fiber absorbs hot water gas is driven from interstitial voids inside the coffee particles preparing the coffee particles for extraction of solubles. In the extraction stage, water-soluble flavoring compounds within the coffee bean fibers dissolve and enter the water. In the hydrolysis stage, large molecules of water-insoluble carbohydrates break down into smaller molecules that are water soluble. 
     To achieve uniform wetting and extraction, the hot water contacting the bed of ground coffee must preferably lift and separate the coffee grounds with a turbulent flow. Improperly applying the water to the grounds can contribute to a poorly brewed coffee. Conventional spray heads tend to concentrate the water flow in the center of the brew basket and do not disperse the grounds with an active attempt to create turbulence. 
     Another common problem in coffee making equipment such as a drip filtration system is liming, or scaling, caused by excessive hardness or mineral content of the water. Heating water containing these minerals causes the minerals such as lime to precipitate and form scale and sediment on the piping. The precipitate is especially problematic when it accumulates around the pores of the spray head to reduce the flow of the water. When the reduction in the level of flow reaches a critical level, the equipment must be serviced at significant cost, and the equipment cannot be used during this maintenance operation. Accordingly, for commercial purveyors of coffee who use such a system it would be preferable to prolong the periods between such maintenance if possible. 
     Another problem encountered by the drip filtration systems of the prior art is the inability of the spray heads to wet the grounds evenly and completely. Typically, the pores of the spray head are centrally disposed and the flow of water through the holes is concentrated about a central stream. When the stream comes in contact with the grounds, the grounds adjacent to the central stream tend to become saturated with the water while grounds further away from the central stream may not receive adequate exposure to the water. Even if the basket begins to fill with water, the peripheral grounds may be lifting by floating grounds below and only be partially wetted. This leads grounds that are over-saturated in some places and under-saturated in others, yielding a coffee brew that is inconsistent and not optimally flavored with the right blend of solubles. Moreover, the central stream of water will typically push aside grounds immediately below the central stream and generate a pool in the displaced grounds. The pool of water that forms immerses the grounds adjacent to the pool but the static nature of the pool is not beneficial to the extraction of the flavored solubles. Rather, it is desirable to promote turbidity within the grounds environment to move the individual grounds and thereby more fully extract the solubles. Moreover, the typical spray head is made of either a high temperature plastic or stainless steel, which has a porosity that tends to promote the accumulation of scaling and liming. 
     A discussion of the type of coffee makers that utilize spray heads can be found in U.S. Pat. No. 5,910,205 to Patel, the disclosure of which is incorporated fuilly by reference herein,and U.S. Pat. No. 5,477,775 to Delbom et al., the disclosure of which is incorporated fully by reference herein. Mork, U.S. Pat. No. 6,279,459 incorporated herein by reference, discloses a coffee maker with a rotating grounds basket in an attempt to disperse the water more evenly about the grounds basket. However, the complications associated with a spinning grounds basket make its implementation and use problematic. Dahmen, U.S. Pat. No. 6,244,162 incorporated herein by reference, discloses a coffee making apparatus with a spray head having an inner ring of pores and a ring of pores along an outer edge adapted to spray the grounds in a fan shaped pattern. These disclosures do not adequately address the problem oft he accumulation of lime and scaling at the pores of the spray head. The present invention seeks to overcome the shortcomings of the prior art systems discussed above. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a spray head for a coffee making apparatus that distributes a water flow pattern evenly over a surface area of grounds located below the spray head, and includes a configuration for reducing the accumulation of lime and sedimentation at the spray head exit holes by elevating the inlet of the holes above a lowermost surface. The raised holes allow the formation of lime and scaling to occur below and away from the inlets such that the inlets are not clogged as quickly and maintenance of the spray head can be deferred for longer periods of time. The raised holes are spaced from the lowermost floor by stand pipes having a vertical channel therethrough for communicating water at an accumulation level equal to the height of the stand pipe. The stand pipes can be cylindrical in shape at a base and include a tapered or beveled upper portion leading to the entrance of the vertical channel. The exit of the channel may include a frusto contical annul projection depending downward from the outside surface of the sprinkler member to resist water from adhering to the outside surface. The two-piece spray head of the present invention is preferably made of a polyetherimide material with a low surface porosity to further resist the accumulation of lime and other sedimentary deposits. 
     These and other features and advantages of the present invention will become apparent from the following detailed description of a preferred embodiment which, taken in conjunction with the accompanying drawings, illustrates by way of example the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevated perspective view of a preferred embodiment of the spray head of the present invention in exploded view; 
     FIG. 2 is a bottom view of the preferred embodiment of FIG. 1; 
     FIG. 3 is a cross sectional view of the sprinkler member taken across line A—A of FIG. 2; 
     FIG. 4 is a cross sectional view of the sprinkler member taken across line B—B of FIG. 2; 
     FIG. 5 is a sectional cut-away view of the edge of the sprinkler member and further illustrates the raised holes on the interior surface; 
     FIG. 6 is a top view of the preferred embodiment of the present invention shown in FIG. 1; 
     FIG. 7 is a cross sectional view of the cover of the present invention taken along line A—A of FIG. 6; 
     FIG. 8 is an enlarged view of the socket of the cover shown in FIG. 6; 
     FIG. 9 is a sectional cut-away view of the socket of the cover of FIG. 7; and 
     FIG. 10 is a bottom view of the cover of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a cover  15  and a sprinkler member  20  that cooperate to form a spray head  10  of the present invention. The cover  15  is circular disk that opens at a threaded inlet flange  25  on the upper surface  30  for receiving an exterior-treaded conduit (not shown) that communicates hot water to the spray head  10 . The cover  15  snaps to a sprinkler member  20  and forms a water distribution reservoir inside, where water typically under pressure enters the inlet  25  and collects on the interior surface of the sprinkler member in a pool. The lowermost surface of the sprinkler member can preferably be flat, where the circumferential wall  75  collects the accumulating water and allows the water to pool. The interior sprinkler member includes risers or stand pipes  35  dispersed over the interior surface  30 . When the water level in the fluid reservoir rises to the height of the stand pipes  35 , water will flow down the stand pipe through holes or channels  55  to distribute the pressurized hot water to a basket of grounds (not shown) positioned below the spray head. The stand pipes are elevated from the interior surface to allow sediment and liming scales to collect on the interior surface  30  away from the openings of the channel  55  to preserve the openings from clogging. 
     As can be seen in FIGS.  1  and  3 — 5 , the interior surface  30  of the sprinkler member  20  includes a plurality of stand pipes  35  that project upwardly from the interior planar surface  30 . For reference it should be noted that the sprinkler member  20  is shown inverted in FIGS.  3 — 5  from its operational position opposite the cover  15 . That is, the interior surface  30  of the sprinkler member faces the bottom of the page in FIGS.  3 — 5  and the outer surface  40  faces the top of the page. As seen in FIG. 5, the stand pipes  35  comprise a cylindrical base  45  and a tapered or beveled top portion  50  forming a frusto conical end portion extending from the cylindrical base  45 . The stand pipe surrounds a channel  55  that passes completely through the sprinkler member  20  to allow water to exit the fluid reservoir and wet the coffee grounds below. The channel  55  can be formed with interchangeable pins during the molding process. The channel  55  is preferably 0.073 inches in diameter and the height of the stand pipe  35  is preferably 0.025 inches. The angular slope of the stand pipe&#39;s beveled portion  50  is forty-five degrees and the outer diameter of the stand pipe&#39;s cylindrical base  45  is 0.125 inches. 
     As seen in FIGS. 2 and 5, the outer surface  40  of the sprinkler, member  20  also includes projections  60  in a frusto conical shape about the exit of channel  55 . The projection&#39;s taped conical shape limits the exiting water&#39;s contact with the lower surface  40  and the water resists collecting on the bottom of the sprinkler member, which keeps the sprinkler member relatively clean and clog free on the outside surface  40 . The height of the outer surface&#39;s projections are approximately 0.025 inches with an outer diameter of approximately 0.175 inches and an inner diameter of approximately 0.088 inches. The angular slope of the conical portion  65  is thirty degrees. The stand pipes  35  are preferably arranged in a first inner ring, and then radially extending to a second intermediate ring, and further radially extending to an outer third ring spaced circumferentially over the sprinkler member. 
     The diameter of the channels  55  has been selected to produce a stream of water through the air below the exit at the exterior surface  40  of the sprinkler member  20  for an inch or two, but breaks, up into droplets before reaching the coffee grounds. The breakup of the stream creates multiple, impacts by the falling droplets that move the grounds and introduce turbulence into the grounds basket. A channel diameter too small will break up the stream too early may inhibit the water flow and may reduce the kinetic energy of the falling liquid as it passes through the exit of the channel  55 . Conversely, if the water stream does not break up until it reaches the grounds the steady impact of the stream will typically move the grounds away from the point of impact and scatter the grounds without sufficiently wetting the grounds. Accordingly, the selection of the channel diameter is important in creating a stream of water that breaks up at a height sufficiently above the grounds to promote greater turbulence. The preferred channel diameter is 0.073 inches. 
     The inner surface  30  of the sprinkler member  20  can also include a centrally disposed cup element  70  shown in FIG.  3 . Water from the inlet  25  of the of the cover  15  is partially directed by gravity directly into the cup element  70  and water quickly flows over the edges of the cup element  70  as it fills. The cup forms a first trap for larger impurities that can collect at the bottom of the cup as water rises over the edge of the cup. The flow of water over the edge of the cup also reduces the turbulence in the spray head  10  and thus fewer air bubbles are formed in the fluid reservoir that can impede flow through the channels  55 . 
     The cover  15  and the sprinkler member  20  connect together by a press fit between the circumferential wall  75  of the sprinkler member  20  and the outer circumferential flange  80  of the cover  15 . The flange  80  fits tightly over the sprinkler member&#39;s wall  75  to provide an initial engagement. The sprinkler member  20  is also provided with lateral bosses  85  (see FIGS. 1 and 5) depending from the circumferential wall  75  that engage and interlock into mating sockets  90  on the cover&#39;s outer circumferential flange  80  (see FIG.  9 ). When snapped together, the bosses  85  on the sprinkler member  20  slide over the inner shoulder  95  leading to the socket&#39;s slot  100  and resiliently enter the slot  100 . The slot  100  is provided with an opening  105  on the upper surface  110  on the socket  90  such that a screwdriver or other bladed instrument (not shown) can be inserted into the opening  105  to eject the lateral boss from the slot  100  and disengage the cover  15  from the sprinkler member  20 . 
     The inlet  25  to the cover  15  includes a threaded section  115  that leads to a neck portion  120  that tapers radially outward to the inner planar surface  125  of the cover  15 . In the radially tapered region of the neck is a plurality of radially directed triangular fins or guides  125  that direct the flow of water radially outward between the guides  125  into discrete radial flow channels  130 . The water is communicated to the periphery of the fluid distribution reservoir between the interior surface  125  of the cover  15  and the interior surface  30  of sprinkler member  20  so that it will be passed through the three rings of stand pipes  35  and the grounds below will be wetted uniformly at every angular position. FIG. 10 shows the guides  125  and the radial channels  130  therebetween, where the flow channels  130  are spaced approximately thirty degrees apart radially and are approximately 0.060 inches wide. 
     In operation, the present invention is connected to a supply line for delivering hot water to the coffee making apparatus. The size of the inlet is selected based on the requirements for the particular coffee brewing machine, and water enters the inlet and passes though the neck into the fluid reservoir between the sprinkler member and the cover. The radial flow channels on the upper surface of the cover immediately below the neck aid in distributing the hot water peripherally to the outside edges of the sprinkler member. Water begins to accumulate in the bottom of the sprinkler member and rise until the level of the water reaches the stand pipe opening. As the water level rises further, water will flow over the upper edge of the stand pipes and pour down the vertical channels out of the spray head. As the water exits the spray head, the frusto conical projections at the exits limit the accumulation of water on the outside surface as the steams of water through the vertical channels exit the spray head. The size of the vertical channel is preferably selected such that the stream of water is continuous through the channel and partially along its trip to the coffee grounds below, whereupon the stream begins to break up into discrete droplets due to interaction with the air molecules. The breakup of the stream into droplets creates distinct impacts on the coffee grounds, promoting turbulence and mixing of the water and coffee grounds. When the supply of water is pressurized, mixing is further promoted by the additional velocity of the liquid above the velocity due to the falling liquid. 
     While a particular form of the invention has been illustrated and described, it will also be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited except by the appended claims.