Abstract:
To increase the occasions when fish or other aquatic animals enter an aquatic habitat extension device, a feed delivery system delivers feed through the entryway and releases it so that it floats up to an air pocket trapped in the upper portion of an aquatic habitat extension device. The delivery system employs a feeding mechanism that releases feed into the transparent habitat structure. The feeding mechanism is delivered to the habitat either through the use of a feeding pole or feeding platform.

Description:
REFERENCE TO RELATED APPLICATION 
     This is a continuation-in-part patent application of copending application Ser. No. 09/149,396, filed Sep. 8, 1998, and now U.S. Pat. No. 6,039,005. The aforementioned application is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention pertains to an apparatus that extends the habitat of aquatic life above the surface of a body of water. More particularly, the invention pertains to a device that functions as a device for viewing aquatic animals above the surface of a body of water, when used in combination with aquariums, water gardens or the like. 
     BACKGROUND OF THE INVENTION 
     Aquariums and water gardens have long been known as habitats for aquatic life. The presence of these miniature aquatic environments is often used as a way to enhance the environment in which they are placed. In addition to their decorative role, aquariums and water gardens also act as sanctuaries and instructional tools in the observation of aquatic ecology. 
     Fish bridges, swimways or other types of aquarium extensions employing a partial vacuum to hold a volume of water above the surface of an aquarium are known. These extensions provide aquarium enthusiasts with the means to expand the habitat available to their aquatic animals and may also be used as a water-filled link between two or more separate aquaria. Once in place these aquarium extensions use a partial vacuum to defy the water line, retaining a given volume of water indefinitely. As long as the entrance to the bridge or swimway remains below the surface of the water in the underlying aquarium, and the extension maintains the integrity of the partial vacuum, there is no change in the water level inside the aquarium extension. 
     Examples of bridge assemblies and other aquarium extensions are disclosed in U.S. Pat. No. 5,447,123 (Hendrickson); U.S. Pat. No. 3,991,715 (Gibson Jr.); and U.S. Pat. No. 1,943,417 (Bringman). While these patents disclose the concept of an aquarium extension above the surface of an aquarium, none of them offer a method by which the water level inside the extension attachments is quickly and easily controlled by a user. As exemplified by the above patents, the prior art discloses only manual methods for changing the water volume in an extension attachment, typically involving the manual elimination of the vacuum by the user, after which the entire extension attachment must be submerged in the underlying aquarium or other body of water to regain the partial vacuum. Due to the necessity of manually filling or emptying an extension, the resulting size and number of extensions used is limited, thereby curtailing applications of aquarium extensions in anything other than small home aquariums. 
     In addition, existing aquarium extensions make no effort to attract aquatic life directly into the extension structure where the aquatic animals are easily observed by people. Instead, existing aquarium extensions rely on the animals to move into or through the structure by chance, limiting use of the extended habitat as a primary observation platform. 
     SUMMARY OF THE INVENTION 
     Briefly stated, an aquatic extension device employs a partial vacuum created by means for reversibly changing the water level inside a clear dome or other structure located above the surface of a pool, pond, or stream bed. The invention extends the aquatic habitat available to fish and other aquatic animals, turning the hollow above-water structure into an aquatic extension device for the observation of aquatic animals. These aquatic animals, typically fish, present inside an underlying aquarium, pool or larger body of water, become easily observable for a person standing outside the pool or on a nearby shore. An individual device can be used alone or with other similar aquatic habitat extensions that can be varied in terms of size, shape, opaqueness, and the degree to which they are filled with water. 
     The water level present inside the aquatic extension can be manipulated to completely or partially fill the hollow structure through the development of a partial vacuum drawing water in to take the place of air as it is evacuated. The partial vacuum is established through the placement of means for removing or adding air, such as, for example, a tube or evacuation line with one end located within the extension device to be evacuated and the other end attached to means capable of creating a partial vacuum, such as a vacuum pump. Optionally, a partial vacuum is created by mouth siphoning, wherein a person simply withdraws air from the hollow structure through a tube. 
     According to an embodiment, an aquatic habitat extension device for use in a body of water or an aquarium includes a transparent hollow habitat structure, wherein the structure includes a lower portion and an upper portion, the lower portion has an opening therein defined by a rim, the opening is oriented downward and below a surface of the body of water, and the opening is effective to permit entrance of aquatic animals. The embodiment also includes at least one support means for receiving the rim of the lower portion of the transparent habitat structure, such that the rim of the transparent habitat structure is supported above the bottom of the body of water or aquarium, and the rim is below the surface of the body of water. 
     To increase the occasions when fish or other aquatic animals enter an aquatic habitat extension device, a feed delivery system delivers feed through the entryway and releases it so that it floats up to an air pocket trapped in the upper portion of an aquatic habitat extension device. The delivery system employs a feeding mechanism that releases feed into the transparent habitat structure. The feeding mechanism is delivered to the habitat either through the use of a feeding pole or feeding platform. 
     According to an embodiment, a feeding apparatus for an aquatic habitat extension device includes an elongated shaft having a proximal end and a distal end, wherein said distal end is attached to feeding means that can be placed in an open or closed position by a user of the feeding apparatus, wherein the feeding means is capable of containing a feed mixture, and wherein the feeding means has opening and closing means for allowing a user to open and close the feeding means. 
     According to an embodiment, a feeding apparatus for an aquatic habitat extension device includes an elongated shaft having a proximal end and a distal end, operatively connected to a feed chamber for containing a feed mixture, a feed chamber cover that can be placed in an open position or a closed position, hingeably attached to the feed chamber, securing means for maintaining the feed chamber cover in a closed position until a user opens the feed chamber, opening means for opening the feed chamber, such that a feed mixture is released, and attaching means for attaching the feed chamber to the distal end of the elongated shaft. 
     According to an embodiment, a method of feeding aquatic animals includes the steps of providing a body of water with an aquatic habitat extension device, providing the body of water with aquatic animals, and delivering feed suitable for aquatic animals to the aquatic habitat extension device. 
     The aquatic habitat extension device itself is also be used in a decorative way to enhance the aesthetic qualities of water gardens, parks or other settings. Illuminating or tinting the habitat enhances the beauty of an aquarium, pond, water garden, or other body of water. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a side elevation of an aquatic extension device with a transparent habitat structure in place. 
     FIG. 2 shows a cut-away view of the transparent habitat structure of FIG.  1  and its mating attachment to the support collar. 
     FIG. 3 shows the closed position of a feeder used to deliver feed to a transparent habitat structure. 
     FIGS. 4A and 4B show, respectively, the closed and open positions of a feeder used to deliver feed to a transparent habitat structure. 
     FIG. 5 shows a feeder operatively connected to a feeding pole. 
     FIG. 6 shows a feeder operatively connected to a feeding platform. 
     FIGS. 7A,  7 B show two embodiments of a line guide. 
     FIG. 8 shows a plurality of aquatic habitat extensions in a pond. 
     FIG. 9 shows the closed position of a feed chamber operatively connected to a bent feeding pole. 
     FIG. 10 shows the delivery of feed to an aquatic habitat extension device using a bent feeding pole. 
     FIG. 11 shows the open position of a feed chamber employing magnets. 
     FIG. 12 shows a bent feeding pole in position below a habitat structure. 
     FIG. 13 shows an alternate embodiment of the aquatic habitat structure. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, an aquatic habitat extension  1  of the invention includes a base  10  having an upper surface  12  and a substantially flat lower surface  14 . Base  10  preferably is of sufficient weight and mass to securely anchor the aquatic habitat extension  1  to a bottom  50  of a body of water  52 . Alternatively, base  10  can be secured to a support surface (not shown) capable of supporting the weight and anchoring aquatic habitat extension  1 . In operation, lower surface  14  of base  10  is parallel to and in contact with the bottom  50  of the body of water  52 . Support members  16 ,  18 ,  20  and  22  are fixedly attached to the upper surface  12  of base  10  and extend from the upper surface  12  of base  10  towards the surface of body of water  52 . Support members  16 ,  18 ,  20  and  22  are designed to fixedly attach to a support collar  24 , which in turn supports a transparent habitat structure  26 . Support members  16 ,  18 ,  20  and  22  are preferably attached to base  10  and support collar  24  through the use of a plurality of galvanized screws  17  or other suitable fastening means which preferably do not rust in water. A water tube  86  forces water into interior chamber  28  from a water pump element (not shown). 
     Optionally, aquatic habitat extension  1  includes a light source  60  mounted on base  10  such that light source  60  is focused up from base  10  through inlet  30  and into an interior chamber  28 . Light source  60  allows a more decorative display and aids in the observation of animals in transparent habitat structure  26  at night or in other low-light conditions. Power for the operation of light source  60  is supplied through a watertight powerline  62  that runs with an evacuation line  36  underneath line guides  38  through guide grooves  39  to an electrical power source (not shown). Evacuation line  36  is preferably made of a clear plastic or resin of the type typically employed in supplying air to aquarium filters and runs from an apex  37  of interior chamber  28  along the inner surface of transparent habitat structure  26  downward and out of habitat extension  1  through inlet  30  to attach to a circulation assembly (not shown), through which a user can control the water level in habitat extension  1 . The user of habitat extension device  1  regulates the use of light source  60  to illuminate aquatic habitat extension  1  as desired. Light source  60  is fixedly attached to base  10  through the use of a plurality of galvanized screws  17  or other suitable fastening means that preferably do not rust in water. Optionally, light can be delivered into interior chamber  28  through the use of a fiber optic cable (not shown) connected to an electrical power source. 
     Preferably, four support members  16 ,  18 ,  20 , and  22  are used to receive support collar  24  and provide the structural support necessary to maintain transparent habitat structure  28  above the surface of body of water  52 . However, in alternate designs employing transparent habitat structures of variable size, the number and dimensions of support members used to structurally support a volume of aqueous media above a body of water larger is altered to maintain the structural integrity of the invention. For example, in an extremely small transparent habitat structure  28 , only two support members may be needed to maintain structural integrity. In contrast, if a very large transparent habitat structure  28  is employed, larger and/or more numerous support members may be employed, as necessary. 
     Transparent habitat structure  26 , support collar  24 , and support members  16 ,  18 ,  20 , and  22  are preferably made of a transparent plexi-glass, glass, thermoplastic resin, extruded acrylic compound, or equivalent transparent material sufficiently strong to maintain structural integrity and a partial vacuum when substantially filled with aqueous media. Any conventional means can be used to fixedly attach the transparent components of aquatic habitat extension  1  to base  10  and to other extensions  10 , although galvanized screws  17  are preferred. 
     The length of, and distance between, support members  16 ,  18 ,  20 , and  22  is preferably sufficient to allow aquatic animals of interest to move between them and into inlet  30 . A partial vacuum must be established in transparent habitat structure  26  to maintain a volume of water above the surface of a body of water  52 . The first step in the attachment of assembled base  10  and transparent habitat structure  26  to develop the completed aquatic habitat extension  1  is to mate peripheral rim  32  of transparent habitat structure  26  with support collar  24 . During this mating, peripheral rim  32  is oriented in a downward orientation detachably connecting with and extending through support collar  24 . Thereafter, peripheral rim  32  is preferably fixedly attached to support collar  24  through the use of a plurality of galvanized screws  17  or other rust proof conventional means. The leading edge  34  of peripheral rim  32  must be below the surface of body of water  52  in which base  10  rests. A transparent water tube  86  is used to force water into interior chamber  28  from a water pump element (not shown). 
     In a second embodiment of the aquatic habitat extension  1  the transparent habitat structure  26  is tinted so as to lessen the amount of external light entering interior chamber  28 . Tinting protects any aquatic animals entering the habitat extension device  1  from bright sunlight magnified by the curvature and transparency of the transparent habitat structure  26 . By making external observers of aquatic habitat extension device  1  less visible to aquatic animals inside interior chamber  28 , tinting enhances the value of the habitat as a hiding place for aquatic animals. In this way aquatic animals are more likely to enter and remain in the habitat for viewing. However, in combination with the illumination provided by light source  60  aquatic animals in interior chamber  28  remain readily visible to external observers. 
     In a third embodiment, the transparent material used to fashion the aquatic extension device  1  is selected so that it magnifies in size any aquatic animal present in interior chamber  28 . This magnification aids in the recreational value of the aquatic habitat extension device  1  since it makes the aquatic animals more visible to the observer. 
     Referring to FIG. 2, transparent habitat structure  26  has interior chamber  28  that fluidly communicates with body of water  52  through inlet  30 , as shown by arrow “a”. Interior chamber  28  preferably is of sufficient size to allow the display of animals or other aquatic phenomena of interest. The size and shape of inlet  30  is variable but must be sufficient to allow the entry and exit of aqueous media and animals of interest into interior chamber  28 . Inlet  30  is bounded by a peripheral rim  32  extending in a plane that is perpendicular to the flow of arrow “a” and away from transparent habitat structure  28 . 
     Referring to FIG. 3, an open end of transparent evacuation line  36 ′ extends from an apex  37  of interior chamber  28  along the inner surface of transparent habitat structure  26  downward through inlet  30  along the bottom  50  of body of water  52  to attach to a circulation assembly  82  or other means of establishing a partial vacuum through evacuation line  36 , it is used to remove residual air from interior chamber  28 . Through circulation assembly  82  a user can control the water level “b” in the habitat extension  1  by manipulating the partial vacuum present in interior chamber  28 . Circulation assembly  82 , through the establishment of a partial vacuum by a vacuum pump element  88  is employed to raise or lower the water level in interior chamber  28  by adding or removing air on the interior of habitat extension  1  through evacuation line  36 . Circulation assembly  82  includes or is reversibly attached to a conventional power source  64  and contains vacuum pump element  88  a water pump element  90 , and an air pump element  92 . A user can attach these pump elements to evacuation line  36  as needed to achieve a desirable water level in habitat extension  1 , dependent upon the desire of the user to evacuate air from transparent habitat structure  26  or force air or water into transparent habitat structure  26 . Between vacuum pump element  88  and a second flow valve  85  a water  94  is positioned to prevent any water from the interior of habitat extension  1  from entering vacuum pump  88 . Optionally, the water pump element can provide water to the transparent habitat structure  26  through evacuation line  36  that has first been cleaned or filtered through conventional means. 
     Circulation assembly  82  includes a first flow valve  83  operable to add, remove or maintain the air in an individual habitat. In an open position, first flow valve  83  permits air to enter the habitat from air pump element  92 , or optionally the outside environment. In a closed position, first flow valve  83  prevents air from entering or leaving interior chamber  28 . In a “vacuum” position, circulation assembly  82  removes air from the transparent habitat structure  26  through the use of vacuum pump element  88 . In this position second flow valve  85  is opened to allow vacuum pump  88  to evacuate air from interior chamber  28  of habitat extension  1 . When air is removed from an transparent habitat structure  26  a partial vacuum in the transparent habitat structure is created, strengthened or maintained concurrently with the diminishing amount of air in interior chamber  28 . When a vacuum is established in the interior chamber  28  of habitat extension  1  any water entering evacuation line  36  is accumulated in water collector  64 , thereafter being eliminated by conventional means when second flow valve  85  is closed. 
     In a variation of the preferred embodiment, circulation assembly  82  also includes a third flow valve  87  operable to introduce water into transparent habitat structure  26  through transparent water tube  86  and water pump element  90 . In a closed position third flow valve  87  prevents any water from entering interior chamber  28 . In an open position third flow valve  87  forces water through a transparent water tube  86  into transparent habitat structure  26 . If the habitat is sufficiently free of water, the effect created by water pump element  90  is that of a fountain present inside the transparent aquatic habitat  26 . Transparent water tube  86  is inserted into interior chamber  28  through inlet  30  and reversibly attached to support members  16 ,  18 ,  20 , and  22  through the use of a plurality of galvanized screws  17  or other rustproof conventional means. Evacuation line  36  and transparent water tube  86  are held in place on the bottom  50  of body of water  52  through the use of a plurality of line guides  38 . In the context of this invention water is a generic term applying to any aqueous medium capable of supporting aquatic life. 
     With an increase in the water pressure supplied by water pump element  90  through third flow valve  87  the water emanating from transparent water tube  86  is used to partially clean or remove debris found on the inner surface of transparent habitat structure  26 . Alternatively, transparent water tube  86  is used to deliver compounds capable of cleaning the inner surface of transparent habitat structure  26 , such as algicide, fungicides, or detergents. Other methods of cleaning the interior of transparent habitat structure  26  include the removal of transparent habitat structure  26  for manual cleaning or disposal. Alternatively, if the transparent habitat structure  26  is large enough, an individual can enter the interior chamber to clean the inner surface of transparent habitat structure  26 . 
     It is important to note that when one of the three flow valves  83 ,  85  or  87  are open, the other two flow valves must be closed. When closed the various flow valves from an airtight and watertight seal between their respective element of circulation assembly  82  and habitat extension  1 . 
     Referring to FIG. 4A-4B, a feeding assembly  40  is used to deliver feed (not shown) to a point just below inlet  30  of habitat extension  1  (see FIG.  1 ), to draw animals of interest into the interior chamber  28  of transparent habitat structure  26 . The feeder  42  of feeding assembly  40  optionally is operatively connected to a feeding pole or a feeding platform. 
     Referring to FIG. 5, feeding pole  44  has a proximal end  46  held by the user during use and a distal bent end  48  that is inserted through support members  18 ,  20 , and  22  to a position below inlet  30  of transparent habitat structure  26  (see FIG.  1 ). Feeding pole  44  is used to deliver to aquatic habitat extension  1  feed (not shown) contained in a feeder  42  placed at the distal end of pole  44 . When feeder  42  is in position under inlet  30 , a trigger  49  is reversibly actuated to release feed. Upon the opening of feeder  42 , any feed contained therein is freed to float upwards to the top of the water in transparent habitat structure  26  through inlet  30 . To encourage the entrance of animals into the interior chamber  28 , the feed used in this application should be somewhat buoyant. In addition, some air is typically left at apex  37  of interior chamber  28 , so that when feed is released into interior chamber  28  it floats normally to the surface of the water remaining within interior chamber  28 . 
     Referring to FIG. 6, in an alternate embodiment of feeding assembly  40 , a feeding line  70  is used to deliver feeder  42  from a feeding platform  72  to a point under transparent habitat structure  26 , such that when feeder  42  is opened, the feed contained therein (not shown) is freed to float upwards to the surface of the water remaining in interior chamber  28 . Feeding line  70  is a flexible closed loop that can be manipulated to reversibly move feeding assembly  40  from aquatic habitat extension  1  to a feeding platform  72  located external to aquatic habitat extension  1 . Feeding line  70  extends from a feeding platform  72  to a location below inlet  30  of transparent habitat structure  26 , where line  70  is held in place by a curved guide  74 . Curved guide  74  redirects line  70  toward the bottom of body of water  52 ; line guides  38  thereafter return to feeding platform  72  through a curved guide  78 . In this embodiment, line guides  38  are equipped with a plurality of eye loops  76 . Eye loops  76  allow the movement of line  70  while preventing line  70  from tangling along the bottom  50  of body of water  52 . Curved guides  74  and  78  and the plurality of eye loops  76  allow the movement of line  70  through them, but are too small to allow feeding assembly  40  to pass through. Feeding assembly  40  is fixedly attached to feeding line  70 , such that when the closed loop that comprises feeding line  70  is manipulated, feeding assembly  40  is moved. Preferably, platform  72  is located out of body of water  52 , such that when feeding line  70  is used to return feeding assembly  40  to feeding platform  72 , the user can easily open an empty feeder  42  and replace feed therein. Curved guide  78  restricts the movement of feeding assembly  40  such that feeding assembly  40  can only be moved between platform  72  and aquatic habitat extension  1 , and will not pass through line guides  38 . The movement of line  70  can be actuated either manually by a user, or the process can use a motor (not shown) or other well known means to automate the movement of feeding line  70 . 
     When line  70  is manipulated such that feeder  42  touches curved guide  74 , feeder  42 , fixedly attached to line  70 , is halted in its progression and stopped beneath inlet  30 . With additional force applied to line  70  to move feeder  42  towards curved guide  74 , swing arms  80  of feeder  42  are forced open and the feed is released to float upward through inlet  30  and into interior chamber  28 . 
     Referring to FIG. 7A-7B, line guides  38  are constructed such that their lower surface is substantially flat except for a guide groove  39 . Line guides  38  are preferably of sufficient weight and mass to securely anchor evacuation line  36 , power line  62 , and transparent water tube  86  to the bottom  50  of a body of water  52  simultaneously. Alternatively, line guides  38  and base  10  can be secured to an artificial surface (not shown) such that aquatic habitat extension  1  can be used in a body of water flowing past or around aquatic habitat extension  1 . Guide grooves  39  prevent any line running to aquatic habitat extension  1  from leaving the bottom  50  of body of water  52  or becoming tangled. 
     Referring to FIG. 8, a plurality of aquatic habitat extensions  1  are in a pond. Each of the individual extensions I can be independently controlled with regard to water level and consequent presence or absence of a vacuum, size or dimensions of transparent habitat structure  26 , light source  60 , or tinting. If desired, multiple extensions  1  are used simultaneously in aquaria, water gardens, or ponds. Particularly in outdoor applications, the use of multiple habitat extensions greatly enhance the recreational and aesthetic value of aquaria, water gardens, or ponds. When appropriately secured, extensions  1  are used in flowing streams, rivers or other occasions in which an underlying body of water  52  is moving as long as leading edge  34  of the peripheral rim  32  remains below the surface of said body of water  52 . 
     Preferably, the transparent habitat structure  26  is spherical in shape. However, any enclosed shape that retains a partial vacuum can be used as a habitat structure. This variety of shapes can extend from those strictly geometric in dimension to purely decorative such as in the shape of a golf ball, football, globe or an artistic rendering. The spherical design provides structural integrity and extensive magnification due to the curvature of the habitat walls. Likewise, a rectangular design is used to prevent extensive magnification. 
     In a variation of the habitat herein disclosed, the size of the habitat is such that it allows the entry individuals to enter interior chamber  28 . This embodiment is useful in diving instruction or other recreational applications. 
     In a variation on the use of evacuation line  36  an excess length of flexible tubing is used as evacuation line  36 . To end  35  of this tubing  36  a watertight flotation ball  41  is fixedly attached such that the end  35  is kept above the level of water present in interior chamber  28  of transparent habitat structure  26 . As air is removed from interior chamber  28  through evacuation line  36 , flotation ball  41  will exert an upward force on end  35  moving the excess length of evacuation line  36  upwards towards the apex  37  of interior chamber  28 . In this manner the flexible tubing extension line  1  evacuation line  36  is able to reversibly remove water from the interior of transparent habitat structure  26 . A fountain like effect can also be created through the use of floatation ball  41 . If the water level in transparent habitat structure  26  is sufficiently free of water, water can be forced through evacuation line  36  and into chamber  28  by a conventional water pump element  90  or other means. Since the air remaining inside interior chamber  28  is not removed the water level is maintained and a fountain like 
     Referring to FIG. 9-10, a bent pole feeding apparatus includes an extended shaft  102  having a bent distal end  104  attached to a feed chamber  106  using a feed chamber attachment  108 . The bent pole feeder optionally includes a water inhibitor  109  between feed chamber  106  and chamber attachment  108 . A feed chamber cover  1   10  is hingeably attached to feed chamber  106 . A pole connector  116  connects the extended shaft  102  and the bent distal end  104 . A monofilament pull line  112 , is affixed to feed chamber cover  110 , thus providing opening means for a user to open the feed chamber such that feed is released into an aquatic habitat extension device. In a variation on the use of extended shaft  102 , feed chamber  106  and feed chamber attachment  108  are removed and extended shaft  102  is used as an evacuation line to remove or add air or water to transparent habitat structure  26 . 
     Referring to FIG. 11, magnets  114  hold feed chamber cover  110  in a closed position, until a user is ready to release the feed into a transparent habitat structure. Feed for aquatic animals is placed inside the feed chamber  106 ; feed chamber cover  110  is closed by hand. Magnets  114  hold the feed chamber cover  110  in a closed position. The user then manipulates the feeding apparatus such that the feed chamber  106  is placed under an aquatic extension device. The user then gently pushes up on the feeding apparatus such that the monofilament pull line  112  contacts the top ring of the globe base, thus causing the feed chamber cover  110  to open and allowing the feed to float into the globe (see FIG.  12 ). 
     Referring to FIG. 13, in a simple alternate embodiment of the invention, the transparent hollow habitat structure rests on a plurality of support structures. 
     Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments are not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.