Abstract:
A tube heating assembly having a heating tube with proximate and distal end portions, a manifold insert disposed concentrically within the heating tube and likewise having proximate and distal end portions, and a pair of end caps removably secured to the proximate and distal end portions of the manifold insert and the heating tube respectively. The manifold insert includes a raised spiral thread on its surface. An electrical assembly such as a resistive path applied to the outer surface of the heating tube is used to heat the tube. The tube heating assembly may be embodied in a system and method for delivering an automotive fluid in a vehicle, wherein the tube heating assembly is installed as a heat exchanger in a fluid delivery path through which the fluid is pumped, preferably in pulses to enhance heating of the fluid.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is entitled to the benefit of, and claims priority to provisional U.S. Provisional Patent Application Ser. No. 60/654,701, filed Feb. 21, 2005, and entitled “System for Heating Automotive Fluids” the entirety of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE PRESENT INVENTION  
       [0002]     1. Field of the Present Invention  
         [0003]     The present invention relates generally to systems for heating automotive fluids, and, in particular, to systems, methods, and electrically-heated tubular assemblies for transferring heat to a fluid flowing therethrough.  
         [0004]     2. Background  
         [0005]     Because automobiles, trucks, and a wide variety of other motor vehicles are often used in low-temperature environments, their subsystems and components must be able to operate under conditions ranging from warm to extremely cold. In particular, automotive subsystems and components that make use of fluids, including wiper fluid systems, cooling systems, fuel lines, and the like, must be capable of reliable operation in such conditions. One primary problem faced by such systems is that of keeping the fluids flowing therethrough from congealing, freezing or the like. Thus, an ongoing need exists for heating systems, using inexpensive, lightweight and non-bulky materials for quickly and efficiently heating or warming fluids in such automotive systems.  
         [0006]     Raising the temperature of at least some automotive fluids may have other benefits as well. For example, a fluid such as wiper fluid may be comprised of water and detergent, along with a substance to lower the freezing temperature of the composition, such as an alcohol, e.g., methanol or isopropyl, and/or ethylene glycol. Higher temperatures may help ensure that such fluids are more thoroughly mixed; this may be particular critical for fluids such as wiper fluid in which the anti-freezing substance (which typically has a significantly lower boiling point than water, e.g., methanol) must be prevented from being superheated into the evaporation state and forced out of the mixture. Further, automotive studies have shown that the cleaning action of wiper fluid is increased as much as 2000% when the alcohol temperature is elevated to just under its boiling point. Also, the heating of a wiper fluid additionally provides a de-icing feature, which may be of equal or greater importance to consumers.  
       SUMMARY OF THE PRESENT INVENTION  
       [0007]     The present invention accordingly provides a system and method for delivering a heated fluid, particularly adapted for use in fluid delivery systems and methods employed in automotive vehicles. The present invention further provides a tubular assembly for heating fluids, particularly automotive fluids, and especially adapted for use in such systems and methods.  
         [0008]     Broadly defined, the present invention according to one aspect is a tube heating assembly, including: a heating tube having approximate and a distal end portion; a manifold insert having a proximate and a distal end portion and being disposed concentrically within the heating tube; and a pair of end caps removably secured to the proximate and distal end portions of the manifold insert and the heating tube respectively. In a feature of this aspect, the manifold insert may include a means for creating turbulence in the fluid, e.g., via a raised spiral thread on the surface of the manifold insert.  
         [0009]     The present invention according to another aspect is a tube heating assembly, including: a tube; an electrical assembly that heats the tube; and a manifold insert disposed concentrically within the tube. In features of this aspect, the electrical assembly is a resistive path applied to the outside of the tube; and the tube and manifold insert have proximate and distal end portions and further comprising a pair of end caps removably secured to the proximate and distal end portions of the manifold insert and the tube respectively.  
         [0010]     In one contemplated embodiment, the tube heating assembly is installed in an automotive vehicle having a fluid delivery system, wherein the tube heating system is adapted for heating a fluid conveyed in the fluid delivery system. In such an embodiment, the tube heating assembly may comprise a heating tube having a proximate and a distal end portion; a manifold insert having a proximate and a distal end portion and being disposed concentrically within the heating tube; a pair of end caps removably secured to the proximate and distal end portions of the manifold insert and the heating tube respectively, the end caps being connected respectively with inlet and outlet sections of the fluid delivery system; and an electrical assembly that heats the tube.  
         [0011]     The present invention according to another aspect is a system for delivering a heated fluid, basically comprising a fluid supply, a fluid delivery path comprising a heat exchanger, and an arrangement for pumping fluid in pulses from the fluid supply through the fluid delivery path. The heat exchanger may, for example, be a tube heating assembly of a type as described above. The system preferably is embodied in combination with an automotive vehicle having at least one fluid flow system in which an automotive fluid is conveyed. In such an embodiment, the pumping arrangement may comprise a pump motor and a pulse interface for cycling the pump motor between energized and non-energized states or, alternatively, may comprise a valve in the delivery path and a device for cycling the valve between opened and closed states.  
         [0012]     The present invention according to another aspect is a method for delivering a heated fluid, basically comprising the steps of providing a fluid supply, and delivering a fluid in pulses from the fluid supply along a delivery path including a heat exchanger, which may for example be a tube heating assembly of a type as described above. The method preferably is carried out in an automotive vehicle having at least one fluid flow system in which an automotive fluid is conveyed. In such an embodiment, the pulsation of the fluid may be performed by cycling a fluid pump motor between energized and non-energized states or, alternatively, by cycling a valve in the fluid delivery path between opened and closed states.  
         [0013]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     Further features, embodiments, and advantages of the present invention will become apparent from the following detailed description with reference to the drawings, wherein:  
         [0015]      FIG. 1  is a partially cut-away side elevation view of a tube heating assembly in accordance with the preferred embodiments of the present invention;  
         [0016]      FIG. 2  is a perspective view of the heating tube of  FIG. 1 ;  
         [0017]      FIG. 3  is an exploded side elevation view of the manifold insert and end caps of the tube heating assembly of  FIG. 1 ;  
         [0018]      FIG. 4  is a front elevation view of the manifold insert of  FIG. 3 ;  
         [0019]      FIG. 5  is an end elevation view of the manifold insert of  FIG. 3 ;  
         [0020]      FIG. 6  is a side elevation view of one of the end caps of  FIG. 3 ;  
         [0021]      FIG. 7  is a top elevation view of the end cap of  FIG. 6 ;  
         [0022]      FIG. 8  is a front elevation view of the end cap of  FIG. 6 ;  
         [0023]      FIG. 9  is a rear elevation view of the end cap of  FIG. 6 ;  
         [0024]      FIG. 10  is a schematic diagram depicting one contemplated exemplary embodiment of the tube heating assembly of  FIGS. 1-9  in an automobile system for delivering a windshield washer fluid;  
         [0025]      FIG. 11  is another schematic diagram depicting an alternative contemplated exemplary embodiment of the tube heating assembly of  FIGS. 1-9  in an automobile system for delivering a windshield washer fluid in a pulsed manner;  
         [0026]      FIG. 12  is a graph depicting the relationship between the flow rate of a windshield washer fluid and the temperature of the fluid at a fixed fluid pump operating voltage, such as in an automotive washer fluid system like that of  FIGS. 10 and 11 ; and  
         [0027]      FIG. 13  is a graph depicting the relationship between the pulse duty cycle of a fluid pump and the resultant temperature of the washer fluid output from the heat exchanger in an automotive windshield washer fluid system like that of  FIG. 11 , shown for differing inlet temperatures for the washer fluid. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]     Referring now to the drawings, in which like numerals represent like components throughout the several views, the preferred embodiments of the present invention are next described. The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0029]      FIG. 1  is a partially cut-away side elevation view of a tube heating assembly  10  in accordance with the preferred embodiments of the present invention. The tube heating assembly  10  includes a heating tube  12 , a manifold insert  14  and two end caps  16 . As is shown in  FIG. 1 , when assembled, the manifold insert  14  is disposed concentrically within the heating tube  12 . The manifold insert  14  and the heating tube  12  are coupled to the end caps  16 . More specifically, the two end caps  16  cinch the tube heating assembly  10  closed with a water-tight seal to the manifold insert  14  and an o-ring seal between the end caps  16  and heating tube  12 .  
         [0030]      FIG. 2  is a perspective view of the heating tube  12  of  FIG. 1 . An electrically resistive path  18  is applied to the outside surface of the heating tube  12 . When current flows through the resistive path  18 , heat is generated, thereby heating a fluid flowing through the tube  12 . An example of a heating tube  12  suitable for use in the preferred embodiments of the present invention is described in U.S. patent application Ser. No. 10/871,117, the entirety of which is incorporated herein by reference.  
         [0031]      FIG. 3  is an exploded side elevation view of the manifold insert  14  and end caps  16  of the tube heating assembly  10  of  FIG. 1 . The manifold insert  14  is preferably formed from a material capable of being injection molded; more particularly, however, it is preferably formed from an elastomer that is capable of expanding inward in the event of fluid expansion during a fluid freezing condition or a heating cycle. The manifold insert  14  is tubular in shape with spiral threading  20  arranged around its outer surface. The spiral threading  20  preferably extends along most of the length of the manifold insert  14 , with only the end portions of the manifold insert  14  not having the spiral threads  20  around the outer surface, thus allowing for the end portions of the manifold insert  14  to be coupled with the end caps  16 . However, the end portions of the manifold insert  14  are preferable configured for secure coupling with the end caps  16 . For example, the inner surface of the end portions of the manifold insert  14  may be threaded  22  (best seen in  FIG. 4 ) for coupling with correspondingly threaded projections  28  extending from the end caps  16 . Alternatively, the end portions of the manifold insert  14  and the end caps may be configured for assembly via a snap-type fitting of respective portions thereof, or via any other suitable assembly means. The end caps  16  is also preferably formed from a material capable of being injection molded; more particularly, however, they are preferably formed from polyester or another elastomer capable of expansion. When the manifold insert  14  and end caps  16  are coupled together, the seal formed therebetween is a water-tight seal. While  FIG. 3  shows the manifold insert  14  and end caps  16  as three separate components, one of ordinary skill in the art will understand that the manifold insert  14  and one of the end caps  16  may be formed together as a single piece.  
         [0032]      FIG. 4  is a front elevation view of the manifold insert  14  of  FIG. 3 . In an exemplary embodiment that is suitable for a windshield wiper fluid heater, the length of the manifold insert  14  would be 5.5 inches, but one of ordinary skill in the art will understand that other dimensions would be suitable for the length of the manifold insert  14  in other applications. The length of the manifold insert  14  may also be affected by the length of the heater tube  12  into which the manifold insert  14  is placed. The dimensions of the spiral threading  20  may vary with the application of the tube heating assembly  10 . In a preferred embodiment, the width  24  of the thread  20  is related to the width  26  of the open space between threads and to the depth of the thread  20  such that the cross-sectional area of the fluid flow channel defined by the thread  20  substantially matches the cross sectional area of incoming and outgoing fluid supply lines connected to the end caps  16 , as more fully described hereinafter.  
         [0033]      FIG. 5  is an end elevation view of the manifold insert  14  of  FIG. 3 . In an exemplary embodiment that is suitable for a windshield wiper fluid heater, the outer diameter of the manifold insert  14  would be 0.545 inches, but one of ordinary skill in the art will understand that other dimensions would be suitable for the outer diameter of the manifold insert  14  in other applications.  
         [0034]      FIG. 6  is a side elevation view of one of the end caps  16  of  FIG. 3 . As noted previously, each end cap  16  has a threaded projection  28  extending outwardly from a proximal end for threaded coupling with the manifold insert  14 . On the distal end of each end cap  16 , the end cap  16  has a fitting  30  projecting outwardly for connection with a windshield wiper fluid supply line (not shown in  FIG. 6 ; see line  48  in  FIGS. 10 and 11 ) or other tube or supply line. The interior of the end cap  16  is defined by a T-shaped flow path  32  for routing the windshield wiper fluid to the outside of the manifold insert  14 . The T-shaped flow path  32  includes a central concentric bore  34  connecting the distal end of the end cap  16  to a cross-bore  36  disposed adjacent the threaded projection. The end cap  16  has small openings  38  near the outer edges of each end of the cross-bore  36  of the T-shaped flow path  32 , or alternatively a stepped down diameter, to route fluid flow into the heating tube  12 .  
         [0035]      FIG. 7  is a top elevation view of the end cap  16  of  FIG. 6 . The end cap  16  is configured to be fitted to the opposite ends of the heating tube  12 . For example, as can be seen in  FIG. 7 , the end cap  16  may have a lip  40  around its outer circumference sized to fit over and in surrounding relation to the outer diameter of the heating tube  12  when the tube heating assembly  10  is assembled. Alternatively, the end cap  116  may be formed with a tapered lead to be slidable into the end of the heating tube  12  via a friction press fit. A seal (not shown) is disposed between the heating tube  12  and the end cap  16  to cinch the tube heating assembly  10  closed. Also seen in  FIG. 7 , is an air outlet  46  that may be utilized during operation to release any excess pressure that could otherwise lead to damage of the circuitry  18  printed on the heating tube  12 .  
         [0036]      FIG. 8  is a front elevation view of the end cap  16  of  FIG. 6 , and  FIG. 9  is a rear elevation view of the end cap  16  of  FIG. 6 . In an exemplary embodiment that is suitable for a windshield wiper fluid heater, the outer diameter of the end cap  16  would be 0.85 inches, but one of ordinary skill in the art will understand that other dimensions would be suitable for the outer diameter of the end cap  16  in other applications.  
         [0037]     In operation, the heating tube assembly  10  operates as follows. Windshield wiper fluid enters one end cap  16  and flows through the concentric bore  34  of the T-shaped flow path  32  within the end cap  16 . Then the fluid is directed to the outside edges of the of end cap  16  by the cross-bore  36  of the T-shaped flow path  32 . The fluid then exits the end cap  16  via the openings  38  at the ends of the cross-bore  36  of the T-shaped flow path  32 . The end cap openings  38  direct fluid flow to an outer flow path located between the outside surface of the manifold insert  14  and the inside surface of the heating tube  12 .  
         [0038]     The fluid flows through the outer flow path for the extent of the length of the manifold insert  14  and heating tube  12 . It then exits through the end cap  16  at the other end of the tube heating assembly  10  by passing through the openings  38  and into the cross-bore  36  and from there through the central concentric bore  34  and out into the fluid line or pipe (not shown) connected thereto.  
         [0039]     As the fluid flows through the tube heating assembly  10 , it is heated by the heating tube  12 . In fact, the tube heating assembly  10  of the present invention provides improved heat transfer capabilities as compared to conventional tube heating assemblies. The present invention provides reduced fluid volume, increased fluid velocity, increased turbulent flow and increased heating area. More specifically, the flow path available within the tube heating assembly  10  is limited in volume because the manifold insert  14  displaces most of the volume within the heating tube  12 . Because the volume available for the fluid flow is limited, the fluid velocity increases as the fluid enters the outer flow path. Increased fluid velocity aids in improving heat transfer of the tube heating assembly. Additionally, the reduced fluid volume within the tube heating assembly requires less power to raise the fluid temperature than conventional heating assemblies. The spiral threading  20  of the manifold insert  14  creates a spiraled path for fluid flow and increases the turbulence of the fluid flow through the tube heating assembly  10 . The turbulent flow forces more fluid to contact the surface of the heating tube  12  thus heating the fluid more quickly. Turbulent flow also causes the fluid to mix more thoroughly, which is particularly beneficial for a fluid mixture comprising multiple fluid types, e.g., windshield wiper fluid. The tube heating assembly  10  of the present invention increases the heating area of the heating tube  12  by using a heating tube  12  with an outer diameter larger than that of a conventional heating tube; however, the actual fluid volume within the tube heating assembly  10  is reduced because of the presence of the manifold insert  14  disposed within the tube heating assembly  10 .  
         [0040]     Because of the improved heat transfer rate of the tube heating assembly  10  of the present invention, the tube heating assembly  10  is capable of providing heated fluid on demand, i.e., no heat is required until fluid flow begins. However, the tube heating assembly  10  may also be operated to maintain fluid at an elevated temperature. It is contemplated that the heating assembly  10  may be equipped additionally with a thermal feedback arrangement, e.g., SMD thermistors, attached directly to the outer surface of the heating tube  12 , to provide feedback to a control system associated with the assembly. It is also contemplated to provide a means for heat transfer from heat generating control elements which may be associated with the assembly, e.g., field transistors, so as to further improve the heating efficiency of the heating assembly.  
         [0041]     An additional improvement of the present invention is the end cap design that allows for air to be released from the manifold insert  14  during high pressure events such as fluid freezing or boiling. The manifold insert  14  can absorb pressure from frozen fluid or boiling fluid and release the pressure though the air outlets  46  in the end caps  16 .  
         [0042]      FIG. 10  depicts schematically a typical installation of the tube heating assembly  10  for heating a windshield washer fluid in a washer fluid delivery system of an automobile. The tube heating assembly  10  is installed in a fluid delivery line  48  extending from a washer fluid reservoir  50  to a nozzle or other spray head (indicated only representatively at  52 ) disposed to emit the washer fluid onto the windshield of the automobile, with the fittings  30  of the tube heating assembly  10  being connected in-line in the fluid delivery line  48 . The fluid delivery system further includes a fluid pump  54  in the fluid delivery line  48 , driven by an electrically operated pump motor  56 .  
         [0043]     The tube heating assembly  10  is electrically connected in the electrical system of the automobile to heat the washer fluid as it is delivered by the pump  54  through the manifold in the heater assembly  10 . The tube heating assembly  10  is connected in the ignition circuit of the automobile between the ignition switch assembly  60  and the alternator or other source of operating voltage energized when the automobile engine is in operation (indicated only symbolically at OV) to provide power to the heating assembly  10  only when the ignition switch is in the closed position with the automobile engine in operation. The tube heating assembly  10  is connected, directly or indirectly, to the positive and negative terminals of the ignition battery  58  of the automobile electrical system to provide direct current electrical voltage to the heating assembly  10  when the ignition circuit is closed during engine operation. A disabling switch sub-circuit  62  is connected in the ignition circuit and to the tube heating assembly  10 . The disabling sub-circuit  62  is normally closed during ongoing normal operation of the automobile electrical system, but is configured to open if the total operating amperage draw on the system reaches a level which endangers the minimum voltage required to supply electrical operating current to the critical systems of the automobile engine, e.g., to insure correct firing of the engine spark plugs. As depicted in  FIG. 10 , each of the ignition switch assembly  60  and the disabling switch circuit  62  are shown in their open condition as occurs when the automobile engine is not operating.  
         [0044]     As is conventional, the windshield washer fluid delivery system is provided with a warning circuit  64  to monitor the fluid level in the reservoir  50  and to generate a warning signal, e.g., via an illuminated warning lamp, in the event the quantity of fluid in the reservoir falls below a predetermined minimum level. The tube heating assembly  10  is also connected in the warning circuit  64  to deactivate operation of the tube heating assembly  10  in the event there is insufficient fluid in the reservoir for normal operation of the fluid delivery system.  
         [0045]     As is also conventional, the operating motor  56  to the fluid pump  54  is also connected in the ignition circuit of the automobile between the ignition switch assembly  10  and the operating voltage source OV and includes a manually operated switch  66  for selectively actuating and deactuating the windshield washer fluid delivery system when desired. The switch  66  is also shown in its normally open deactuated position.  
         [0046]     The operation of the tube heating assembly  10  in conjunction with the windshield washer fluid delivery system of  FIG. 10  may thus be understood. Upon closing of the ignition switch assembly  60  to start operation of the automobile engine, the disabling sub-circuit  62  is closed and electrical power is supplied to the tube heating assembly  10 . The warning circuit  64  and the operating circuit to the pump motor  56  are also enabled. Upon manual closing of the pump motor switch  66  (e.g., via a switch lever or the like provided as part of the driver&#39;s controls in the passenger compartment of the automobile), washer fluid is pumped under pressure from the reservoir  50  through the fluid line  48  and through the tube heating assembly  10 , which thereby acts as a heat exchanger to heat the fluid to an elevated temperature as it flows through the manifold of the tube heating assembly  10 .  
         [0047]      FIG. 11  depicts schematically an alternative embodiment of an installation of the tube heating assembly  10  for heating a windshield washer fluid in a washer fluid delivery system of an automobile. The installation of  FIG. 11  is similar to that of  FIG. 10  and embodies many identical components and operational characteristics which are as described above in the embodiment of  FIG. 10 . Accordingly, corresponding components in  FIG. 11  are identified by like reference numerals as in  FIG. 10 , the description of which need not be repeated. The embodiment of  FIG. 11  differs from that of  FIG. 10  by the provision of a pulse interface device  68  in the portion of the ignition circuit through the pump motor  56 , and also connected to the output from the warning circuit  64 . The pulse interface device  68  is operable to cycle the pump motor  56 , when actuated via closing of the switch  66 , between energized and non-energized states, thereby creating a pulsed flow of the washer fluid through the fluid delivery line  48  and through the tube heating assembly  10 . Of course, those persons skilled in the relevant art will readily recognize and understand that various alternative arrangements may be utilized for accomplishing a cyclical pulsing operation of the fluid delivery system, for example but without limitation, the provision of a solenoid valve in the fluid delivery line  48  and actuable to cycle between closed and open states, e.g., via the control of a microprocessor or other suitable control system such as commonly provided in conventional motor vehicles.  
         [0048]     The advantages of the provision of the fluid heating capabilities of the present invention will be understood with reference to the graphs of  FIGS. 12 and 13 , which depict empirical test data derived from operation of prototype embodiments of the systems of  FIGS. 10 and 11 . The graph of  FIG. 12  plots a curve representing the relationship between the flow rate of a typical water-methanol windshield washer fluid mixture and the temperature of the fluid mixture, at a constant voltage of operation of a fluid pump motor operating at 14.5 volts of direct current. As will be seen, the flow rate of the fluid measured in liters per minute more than doubles as the temperature of the fluid increases from just above the freezing point of the mixture (−28 degrees C.) to a generally flat plateau at about 25 degrees C. The benefits of heating the fluid mixture in cold environments and conditions will therefore be readily apparent. The performance of a windshield washer system is directly dependent on the maintenance of a minimum outlet velocity of the fluid from the spray nozzle, yet absent heating of the fluid, the graph of  FIG. 12  shows that the flow rate at a given pump speed can be reduced by more than half under conditions of extreme cold temperatures. Conversely, by provision of the heating system of the present invention, the flow rate and output velocity of the fluid can be maintained within a much more narrow range generally unaffected by ambient temperature changes.  
         [0049]      FIG. 13  reflects that the advantages of the present invention are even more enhanced in an embodiment utilizing a pulsing delivery of the washer fluid. The graph of  FIG. 13  plots a number of curves, each representing a differing starting temperature of the fluid mixture, showing the relationship between the heated output temperature achieved in a typical water-methanol windshield washer fluid mixture at differing on-off duty cycles of the fluid pump motor wherein each duty cycle operates the pump alternatingly between an energized state for 0.1 second and a deenergized state ranging from 0.1 second to 0.5 second. Each curve also shows the heated output temperature achieved by a continuous operation of the pump motor, represented as a 0.0 second off cycle. As will be seen, the cyclical operation of the pump motor achieves an increase in output fluid temperature over continuous flow pump operation, with the out put temperature progressively increasing as the off cycle is lengthened, regardless of starting fluid temperature.  
         [0050]     Based on the foregoing information, it is readily understood by those persons skilled in the art that the present invention is susceptible of broad utility and application. Many embodiments and adaptations of the present invention other than those specifically described herein, as well as many variations, modifications, and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the foregoing descriptions thereof, without departing from the substance or scope of the present invention. Accordingly, while the present invention has been described herein in detail in relation to its preferred embodiment, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for the purpose of providing a full and enabling disclosure of the invention. The foregoing disclosure is not intended to be construed to limit the present invention or otherwise exclude any such other embodiments, adaptations, variations, modifications or equivalent arrangements; the present invention being limited only by the claims appended hereto and the equivalents thereof. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for the purpose of limitation.