Abstract:
A separator for removing contaminants from compressed air, the separator including an elongate enclosure having an inlet end and an opposite outlet end, the inlet end of the separator being in flow communication with a source of compressed air, the separator defining a first air flow path between the inlet and outlet ends of the separator and a second air flow path between the outlet end of the separator and a wall member positioned adjacent outlet end of the separator for being contacted by air exiting the outlet end of the separator, wherein air traveling in the first flow path undergoes a volumetric expansion and substantial change of direction as it exits the separator and enters the second air flow path and further undergoes a change of direction as it impacts the wall member.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to air dryers. More particularly, this invention relates to devices for removing moisture and contaminants from compressed air streams. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     Compressed air is widely used in industry as an energy source. One problem associated with the use of compressed air is maintaining a relatively clean and dry supply of compressed air. For example, as atmospheric air is introduced into an air compressor, contaminants such as water vapor, dirt, particles, and oils and other lubricants associated with the compressor or the industrial setting can be introduced into the compressor. During compression, the temperature of the air increases, thus increasing the ability of the air to retain moisture. Normally, the compressed air is passed through aftercoolers and moisture separators, yet despite this the air can remain substantially saturated with oil and water and other contaminants. As the air travels through piping during use, the vapor condenses and creates corrosion. This can lead to expensive downtime and equipment failure. Accordingly, there remains a need in the art for improvements in the treatment of compressed air to dry it and otherwise remove contaminants. 
     The present invention is directed to a separator for removing contaminants from compressed air. In a preferred embodiment, the separator includes an elongate enclosure having an inlet end and an opposite outlet end. The inlet end of the separator is in flow communication with a source of compressed air and the separator defines a first air flow path between the inlet and outlet ends of the separator and a second air flow path between the outlet end of the separator and a wall member positioned adjacent outlet end of the separator for being contacted by air exiting the outlet end of the separator. Air traveling in the first flow path undergoes a volumetric expansion and substantial change of direction as it exits the separator and enters the second air flow path and further undergoes a change of direction as it impacts the wall member. 
     In another aspect, the invention relates to a air dryer for treating an inlet stream of air to remove water vapor therefrom to provide a dehumidified outlet stream of air. In a preferred embodiment, the dryer includes an air inlet for introducing the inlet steam of air into the dryer and an air outlet for removing the outlet stream from the dryer. A heat exchanger associated with the dryer includes first and second discrete air flow paths. The first air flow path has an inlet end and an opposite outlet end with the inlet end of the first air flow path being in flow communication with the air inlet. The second air flow path includes an inlet end and an opposite outlet end with the outlet end of the second air flow path being in flow communication with the air outlet and an opposite inlet end. An expansion channel is located within the dryer for expanding the flow of air exiting the first flow path. The expansion channel has an inlet end and an outlet end, the inlet end of the expansion channel being in flow communication with the outlet end of the first air flow path of the first heat exchanger. An evaporator is downstream of the expansion channel and includes a third air flow path and a refrigerant flow path. The third air flow path has an inlet end and an opposite outlet end with the inlet end of the third air flow path being in flow communication with the outlet end of the expansion chamber. The refrigerant flow path has an inlet end and an opposite outlet end. A refrigeration system is in flow communication with the refrigerant flow path of the evaporator for circulating refrigerant through the refrigerant flow path of the evaporator. A separator located downstream of the evaporator includes an inlet end and an opposite outlet end. The inlet end of the separator is in flow communication with the outlet end of the third air flow path. The separator defines a fourth air flow path between the inlet and outlet ends of the separator and a fifth air flow path between the outlet end of the separator and a wall member positioned adjacent outlet end of the separator. The wall member is located to be contacted by air exiting the outlet end of the separator. Air traveling in the fourth flow path undergoes a volumetric expansion and substantial change of direction as it exits the separator and enters the fifth air flow path and further undergoes a change of direction as it impacts the wall member. A demister is positioned in flow communication with the fifth air flow path and the inlet end of the second air flow path for receiving air traveling in the fifth air flow path and conducting it to the second air flow path for travel therethrough. 
     A significant advantage of the invention is that the dryer  10  of the invention remains effective to remove moisture and other contaminants over a wide range of flow rates. For example, the separator functions to remove contaminants by impaction and imparting Brownian Motion to contaminants, thus resulting in their separation from the flow of air. The demister further achieves separation by providing an environment wherein surface tension results in removal of contaminants from the air flow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features of preferred embodiments of the invention will become apparent by reference to the detailed description of preferred embodiments when considered in conjunction with the figures, which are not to scale, wherein like reference numbers, indicate like elements through the several views, and wherein, 
     FIG. 1 is a perspective view of an air dryer system in accordance with a preferred embodiment of the invention. 
     FIG. 2 is a detailed view of the system of FIG.  1 . 
     FIG. 3 is an exploded view of a heat exchange/drying system of the dryer of FIG.  1 . 
     FIG. 4 is a cross-sectional side view of a precooler/reheater component of the heat exchange/dryer system of FIG.  3 . 
     FIG. 5 is a cross-sectional side view of an evaporator component of the heat exchange/dryer system of FIG.  3 . 
     FIG. 6 is a perspective view of a corrugated member used in precooler/reheater component of FIG.  4  and in the evaporator component of FIG.  5 . 
     FIG. 7 is a cross-sectional side view of the corrugated member of FIG.  6 . 
     FIG. 8 is a top representational view showing separator and demister components of the heat exchange/dryer system of FIG.  3 . 
     FIG. 9 shows a preferred centrifugal component of the separator. 
     FIG. 10 is a perspective view showing the position of the separator. 
     FIG. 11 is a perspective view showing ports for entrance of the outlet air into the precooler/reheater component from the demister. 
     FIG. 12 is a perspective view showing installation of the demister component. 
     FIG. 13 is a detailed view of the demister component. 
     FIG. 14 is a bottom perspective view of the heat exchange/drying system of FIG.  3 . 
     FIG. 15 is a schematic of a compressed air system incorporating the dryer of FIG.  1 . 
    
    
     DETAILED DESCRIPTION 
     With initial reference to FIGS. 1 and 2, the invention relates to a dryer  10  having a heat exchange/drying system  12  and a refrigeration system  14  enclosed within a vented housing  16 . A drain system  18  collects and removes liquids and any entrained solids from the dryer  10 . A preferred construction material for the dryer is aluminum. 
     A significant advantage of the dryer of the invention as compared to prior art dryers is that it is able to treat variable flows of compressed air. Typical dryers are designed to cool and dehumidify air streams of a predetermined flow rate and become substantially ineffective if the flow rate varies. For example, a conventional system configured for a 100 cfm flow of air typically function effectively as long as the flow rate remains above about 60 cfm. However, in the event the flow rate drops below about 60 cfm, the effectiveness of the dryer separator dramatically decreases. To the contrary, the effectiveness of a dryer  10  of the invention configured to treat a 100 cfm stream is maintained even if the flow rate of the air stream drops significantly below 60 cfm, even to slightly above zero cfm. 
     With reference to FIGS. 3-12, the heat exchange/drying system  12  includes a precooler/reheater  20 , an evaporator  22 , a separator  24 , and a demister  26 . Air to be treated enters the system  12  via an air inlet  28 . Treated air exits the system  12  via an air outlet  30 . The system  12  as seen in FIG. 1 is preferably covered in an insulative material  32 , such as a closed cell elastomeric material. Each of the components of the system  12  is preferably of aluminum construction. 
     With reference to FIGS. 1 and 3, the system  12  is housed within an enclosure  34  having portions thereof in flow communication with the air inlet  28 , the air outlet  30 , and refrigerant outlet and outlet ports associated with the refrigeration system  14  (described below). The enclosure  34  includes a top  36 , a bottom  38 , and sidewalls  40 ,  41 ,  42 , and  43 . The components of the enclosure  34  are preferably secured together as by welds W (FIG.  11 ). Mounting brackets  44  preferably extend from the bottom  38  for mounting the system  12  to the housing  16 , as by the use of bolts  45  or other fasteners passed through apertures  46  of the brackets  44  and corresponding apertures of brackets  47  of the housing  16 . 
     The dryer  10  shown and described herein is configured for treating compressed air streams generally having a flow rate of about 100 cfm at a pressure of about 100 psi. Typically, the temperature of such an air stream as it enters the system  12  is about 100° F., with a relative humidity of about 100 percent. Treatment of such an air stream using the dryer  10  as configured herein generally does not affect the flow rate or the pressure, except for a few psi drop resulting from travel through the dryer, but decreases the temperature of the air so that it is about 80° F. as it exists the dryer  10  and decreases the dew point of the air to from 33° F. to about 39° F. as it exists the dryer. However, it will be understood that the dryer  10  may be sized to treat streams of other flow rate, pressure, humidity, and temperature, or to yield outlet streams having different characteristics. 
     The precooler/reheater  20  functions to perform an initial cooling of the compressed air to be treated and to heat the treated air prior to it exiting the dryer via the outlet  30  for re-use in a compressed air system. Turning to FIGS. 3 and 4, the precooler/reheater  20  includes one or more inlet air flow channels, such as channels  46  and  48  each having an end thereof in flow communication with the air inlet  28 , and one or more outlet air or treated air channels, such as channels  50  and  52 , each having an end thereof in flow communication with the air outlet  30 . Each channel  46 ,  48 ,  50 , and  52  is preferably substantially rectangular in configuration and substantially uniform in dimension. For a system generally configured for treatment of an air stream having a flow rate of 100 cfm as described above, each channel preferably has a length of about 16 inches, a width of about 9.5 inches, and a height of about 2.5. 
     The channels  46 - 52  are enclosed by portions of the enclosure  34 , such as the top  36 , bottom  38 , and the sidewalls  42  and  43 , an interior sidewall  51 , and plates  53 ,  54 , and  55  located between adjacent ones of the channels and secured as by welding (FIG.  4 ). Inlet air (the air to be treated) travels in the channels  46  and  48  in the general direction indicated by the arrows IA. The outlet air (the treated air) travels in the channels  50  and  52  in the general direction of the arrows OA, which direction is generally countercurrent to the direction of the inlet air. 
     The inlet air is introduced into the channels  46  and  48  via inlet ends  56  and  57  of the channels  46  and  48  which are open and in flow communication with the air inlet  28 . End walls  58  and  59  located at the terminal ends of the channels  50  and  52 , respectively, prevent the inlet air from entering the channels  50  and  52 . Sides of the channels  50  and  52  adjacent the air outlet  30  are removed to place the terminal ends of the channels  50  and  52  in flow communication with the air outlet  30 . 
     The inlet air exits the channels  46  and  48  via open sides  60  and  62  thereof located at the terminal ends of the channels  46  and  48 , respectively. The sides  60  and  62  are in flow communication with an expansion channel  64  by which the air exists the channels  46  and  48  for further travel through the system  12 . The expansion channel  64  is mounted substantially normal to the channels  46  and  48  so that it thus causes the direction of the flow of the inlet air to change abruptly. The channel  64  also merges the air flows of the channels  46  and  48  and increases in dimension along its length so that the flow path of the inlet air is significantly expanded. The abrupt change in direction and expansion of the flow of the inlet air advantageously results in a decrease in moisture of the air stream as well as a loss of other entrained matter. 
     The outlet air enters the channels  50  and  52  via open sides  66  and  68  of the channels located adjacent the inlet ends of the channels  50  and  52 . End walls  70  and  72  seal the ends of the channels  50  and  52  adjacent their inlet ends to isolate the air flows of the incoming outlet air from the exiting inlet air. 
     As noted above, the precooler/reheater  20  performs an initial cooling of the air to be treated and heats the treated air prior to it exiting the dryer  10 . In this regard, for the described precooler/reheater and 100 cfm inlet stream having a temperature of about 100° F., the temperature of the inlet air is dropped to about 75° F. as it exits the channels  46  and  48  and enters the channel  64 . During travel through the channel  64 , the temperature of the air generally decreases by a few degrees, to about 72° F. The outlet air introduced into the channels  50  and  52  via the demister  26  generally has an initial temperature of about 35° F. and a temperature of about 80° F. as it exits via the outlet  30 . 
     In order to achieve the above thermal results and maintain a relatively compact configuration of the dryer  10 , each of the channels  46 ,  48 ,  50  and  52  preferably includes one or more deflection members to increase the surface area against which the air contacts as it travels through the channel, impart turbulence to the air flow, and increase the residence or contact time of the air within the channels. With reference to FIGS. 6 and 7, there is shown a preferred deflection member as provided by an elongate corrugated member  74  having a plurality of apertures  76  formed through opposite surfaces  78  and  80  of the member  74 . The apertures  76  may be uniformly spaced or non-uniformly spaced. The apertures  76  may be of uniform diameter and/or configuration, i.e., circular, or they may be of non-uniform diameter and/or configuration, i.e., some oval, circular, or other shape. 
     The corrugated member  74  preferably has a width corresponding substantially to the width of the channels  46 - 52  and a height substantially corresponding thereto. In FIG. 7, one of the corrugated members  74  is shown installed in the channel  50 , intermediate the plates  53  and  54 . As will be noted, the air is constrained to travel through the apertures  76  to advance along the length of the channel. This results in a relatively turbulent flow of air, as the air expands as it exits each aperture and must thereafter constrict to enter the next aperture  76 . Thus, the corrugated member  74  serves to impart turbulence to the air flow, as represented by the arrows T, to increase the surface area available for contacting the air, and to increase the contact time. Each of these factors aids in improving thermal transfer between the channels and their adjacent surfaces to promote heat transfer for cooling the inlet air and heating the outlet air. 
     The evaporator  22  further cools the air to be treated. Continuing with the example herein, the evaporator generally cools the air from its entrance temperature of about 72° F. to an exit temperature of about 35° F. Turning to FIG. 5, the evaporator  22  includes one or more air channels, such as air channels  82  and  84 , and one or more refrigerant channels, such as channels  86 ,  88 ,  90 , and  92 . The construction of each of the channels  82 - 92  is substantially similar to that previously described in connection with the channels  46 - 52 , with each channel being substantially enclosed (except as to provide the desired ingress and egress of fluid such as air or refrigerant) and including a corrugated member  74 . In this regard, an interior sidewall  93  is provided (similar to sidewall  51 ). 
     As will be noticed, however, each air channel  82  and  84  is sandwiched between at least two of the refrigerant channels  96 - 92 . Thus, each layer of air is in contact from top to bottom with two layers of refrigerant. In addition, the flow of refrigerant is counter-current to the flow of air. This is advantageous to enhance the heat transfer between the air and the refrigerant to rapidly decrease the air temperature over a relatively short distance. This is advantageous to reduce the size of the system. The sandwiched construction of the air channels relative to the refrigeration channels is also advantageous to protect the refrigeration compressor from liquid back flush. For example, the two layers of refrigerant promote evaporation of the refrigerant due to its contact with the higher temperature air stream on both sides. 
     Air to be treated (the inlet air from the channels  46  and  48  of the precooler/reheater  20 ) is introduced from the expansion channel  64  into the channels  82  and  84  via openings in the sides of the channels  82  and  84  and flows as indicated by the arrows A. The terminal ends of the channels  82  and  84  are closed as by walls  94  and  95 , and the air exists the channels  82  and  84  via openings in the sides of the channels for travel to an air outlet  96  by which it is introduced into the separator  24 . 
     Refrigerant, such as R134A, R404, R407C or the like is introduced from the refrigeration system  14  via refrigerant inlet  98  in flow communication with the ends of the channels  86 - 92  for travel in the direction indicated generally by the arrows R. The flow of the air and the flow of the refrigerant is preferably counter-current. The refrigeration exits the channels  86 - 92  via their terminal ends, which are in flow communication with refrigerant outlet  100  for travel back to the refrigeration system  14 . The ends of the channels  82  and  84  are closed as by walls  102  and  104 . 
     The separator  24  removes liquids and contaminants from the air stream transferred thereto from the evaporator  22  via the outlet  96 . Turning to FIG. 8, the separator  24  includes an elongate cylinder  110  having opposite closed ends  112  and  114 . An entrance for the travel of air into the cylinder  110  is provided as by an aperture  116  extending through the sidewall and an exit is provided as by an aperture  118  through the sidewall adjacent the opposite closed end  114 . A brace  120  preferably extends between the cylinder  110  and the sidewall  93  for strength and to restrict the travel of air toward the end  112  after it exits the cylinder  110  via the aperture  118 . In a preferred embodiment and for the configuration described herein, the aperture  118  is preferably spaced from about 1.25 inches to about 1.5 inches from the sidewall  93 . An additional aperture  121  is preferably provided opposite the aperture  118  so as to flow air toward the sidewall  51 . The sizing o the aperture  121  and spacing relative to the sidewall  51  preferably substantially corresponds to that described fo the aperture  118 . 
     The cylinder  110  preferably has a length of about 6 inches and a diameter of about 2 inches. The apertures  116 ,  118 , and  121  each preferably have a diameter of about 1.5 inches. The cylinder  110  preferably includes one or more internal impact members as structure against which the air impacts as it travels through the cylinder and which promotes a centrifugal orientation to the flow. A preferred impact member is a spiral or auger-like member  122  located within and substantially filling the cylinder  110  (FIG. 9) having a plurality of flights  124  along its length. Impaction of the air as by use of an impaction member such as the spiral member  122  is advantageous to cause the flow to change direction repeatedly (while still retaining a general direction of travel along the length of the cylinder) to cause contaminants to separate from the air flow. 
     For example, as the air enters the separator housing it is forced in a circular motion around the inner wall. By incorporating a spiral or auger structure inside the separator, a centrifugal separation occurs, dependent in part upon the entering velocity of the air. The air then moves toward the outlets provided by the apertures  118  and  121  and undergoes abrupt changes of direction as it exists the separator, which further enhances separation. The construction of the separator incorporating structure for changing flow direction thus also yields separation characteristics that are not directly dependent upon the air velocity. 
     With additional reference to FIG. 8, it will be seen that as the air exits the cylinder  110  via the aperture  118 , the flow of air expands (thereby slowing) and undergoes a sudden and substantial change of direction as compared to its direction of travel within the cylinder. For example, it will be appreciated that the travel of the air within the cylinder generally has a direction of travel corresponding to the length axis of the cylinder, as well as directional components imparted by the impact member. However, to exit the cylinder, the flow of air must make a sudden and substantial change of direction, toward a direction that is substantially normal to the length axis of the cylinder. It will be appreciated that greater or lesser changes of direction will suffice, so long as the desired dewatering affect is achieved. This sudden change of direction, coupled with a loss of velocity from the enlargement of the flow area exterior to the cylinder generally results in a loss of liquids and solids from the air stream. In addition, the flow thereafter impacts the sidewall  93  resulting in another sudden change of direction of the flow. In combination, the slowing of the air flow and the sudden changes of direction results in significant dewatering and removal of contaminants. Under such circumstances, moisture and other contaminants generally cannot remain with the air flow and fall out or cling to the sidewall. 
     For example, it has been observed that water vapor and other contaminants entrained in the air will tend to drop out of the flow as the flow slows. Next, the impact of the flow against the sidewall and the associated change in direction causes solids to drop out and for liquids to cling to the sidewall and run down the sidewall to the bottom  38 . Without being bound by theory, it is believed that the flow imparted to the air flow by the structure also results in so-called “Brownian Motion” of the entrained particles, resulting in their separation from the air. In this regard, the term “Brownian Motion” will be understood to refer generally to a random movement of microscopic particles suspended in liquids or gases resulting from the impact of the molecules of the fluid surrounding the particles. 
     Next, the air flow A travels through the demister  26  and into the channels  50  and  52  of the precooler/reheater  20 , from which it is expelled from the dryer  10  via the outlet  30 . The demister is preferably a mesh material that divides the flow of air into a plurality of flow paths as it travels through the mesh. Turning to FIGS. 10-13, the demister  26  includes a top  126  and a body portion  128  extending substantially perpendicular away from a lower surface of the top  126 . The body portion  128  is preferably provided as by a stainless steel mesh material having a mesh size of about 40 microns, with the body portion having a width W of about 1.25 inches, a length L of about 5 inches, and a height H of about 3.5 inches (FIG.  13 ). The body portion  128  is removably positionable within the enclosure  34  so that air must travel through the demister to reach the channels  50  and  52 . In a preferred embodiment, one length surface of the body portion  128  is adjacent the end  114  of the cylinder  110  and the other length surface of the body portion is adjacent the open sides  66  and  68  of the channels  50  and  52 . However, it will be understood that other positioning of the demister may be utilized to cause the air to travel through the demister before reaching the channels  50  and  52 . 
     The body portion of the demister  26  may be installed as by inserting it through a slot  130  extending through the top  36 . The slot  130  is surrounded by a raised rib  132  having a plurality of threaded openings  134  for receiving bolts  136 . The bolts  136  pass through corresponding openings  138  of the top  126 . A gasket  140  is preferably located to seal between the top of the rib  132  and the lower surface of the top  126 . Openings  142  of the gasket  140  correspond to the openings  134  and  138 . As will be appreciated, the demister  26  may be readily removed, such as for cleaning or replacement. 
     As air travels through the separator, changing direction, a majority of the water will be dropped, leaving primarily a fine mist in the form of a fog or vapor. As this mist passes through the demister, the mist tends to cling to the mesh and develop droplets that increase in size over time. When a droplet is sufficiently large, it tends to drop from the mesh and is collected in the drain system  18 . This action is believed to be relatively independent of the air velocity, so that the demister is effective to remove water for virtually any experienced flow rate. In addition, it has been observed that oil and other contaminants also tend to release from the air flow and cling to the mesh and thus separate from the air flow. 
     Returning to FIG. 2, the refrigeration system  14  preferably includes a compressor  150 , a condenser  152 , a receiver  154 , a filter/dryer  156 , a thermostatic expansion valve  158 , a hot gas by-pass valve  160 , and a suction accumulator  162 . Refrigerant is fed from the refrigeration system  14  to the evaporator  22  via conduit  164  in flow communication with the refrigeration inlet  98 . Refrigerant is returned from the evaporator  22  to the refrigeration system  14  via conduit  166  in flow communication with the refrigerant outlet  100 . A temperature gauge  168  is preferably located in-line on the conduit  164  and/or  166  for monitoring of the refrigerant temperature. 
     The compressor  150  pumps hot, high pressure gaseous refrigerant to the condenser  152 . The condenser  152  cools and liquifies the refrigerant. From the condenser the refrigerant flows through the receiver  154 , then the filter/dryer  156 , and through the expansion valve  158  where pressure and temperature are reduced. This reduction in pressure causes the liquid refrigerant to boil until it reaches the saturation temperature which corresponds to its pressure. As the low pressure refrigerant passes through the evaporator  22 , the refrigerant continues to boil until all refrigerant is vaporized. Refrigerant gas is returned to the compressor and the cycle is repeated. The by pass valve  160  may be used to control temperature in the evaporator  22 . 
     With reference to FIGS. 2 and 14, the drain system  18  includes a sump  170  having a drain opening  172 . The sump  170  is preferably formed as part of the bottom  38  at a location directly beneath the slot  132  so that the bottom of the demister  26  sits over the sump  170 . A conduit  174  is in flow communication with the sump  170  via the opening  172  for draining fluids and solids from the sump  170 . The drain system  18  also preferably includes a check valve  176  and a solenoid valve  178 . The check valve  176  inhibits back-flow and the valve  178  is preferably operated via a timer to periodically enable emptying of the sump. If desired, a suction may be applied to the conduit  174  to facilitate drainage. 
     Turning now to FIG. 15, the dryer  10  is shown connected to a compressed air system  180  having a source of compressed air, such as a compressor  182  feeding an air receiver tank  184 . As will be appreciated, use of the dryer  10  advantageously enables treatment of a stream of compressed air to remove moisture and other contaminants. A significant advantage of the invention is that the dryer  10  of the invention remains effective to remove moisture and other contaminants over a wide range of flow rates. To the contrary, conventional dryers typically are only effective when the flow rate remains within a relatively close range of the flow rate with which the dryer was designed to operate. For example, in the case of a dryer of the invention designed to handle a flow rate of air of about 100 cfm, it has been observed that the dryer effectively removes water and other contaminants even in the event the flow rate drops to very small flow rates of 5 cfm or less, as well as higher flow rates of up to about 115 cfm. 
     Without being bound by theory, it is believed that the ability of the dryer to remain effective even for low flow rates is due, at least in part, to the ability of the separator  24  to provide a plurality of dewatering environments. For example, as noted earlier, the separator functions to remove contaminants by providing structure which achieves removal of contamination by impaction, Brownian Motion, and by surface tension. 
     The foregoing description of certain exemplary embodiments of the present invention has been provided for purposes of illustration only, and it is understood that numerous modifications or alterations may be made in and to the illustrated embodiments without departing from the spirit and scope of the invention as defined in the following claims.