JP3027189B2 - Gas burner assembly with closed structure - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of gas burners. For details,
The present invention relates to an improvement of a gas burner assembly having a closed structure having an ignition mechanism.

2.Description of the prior art The gas burner assembly of the closed structure is received in the burner opening on the upper surface of the range, and the material that spills during the cooking process, between the burner assembly and the upper surface of the range,
It is supported around the periphery of the opening so as not to enter the burner box provided below the upper surface of the range. This type of burner assembly improves on earlier gas burners, but the improvement is that there is a large annular space between the burner head and the outer perimeter of the burner opening on the top of the range. The shape of the enclosed burner assembly has a smooth streamlined appearance that satisfies cleaning and maintenance of the top of the range.

Hermetic burner assemblies typically include a burner cap with a sidewall having a plurality of burner holes. A plurality of burner holes are formed in the side wall, and a mixture of primary air and gas passes through the burner holes to the outside of the cap so as to be burned. Electrodes connected to a suitable electrical circuit extend through the side walls of the cap to provide spark ignition of the mixture.
The use of spark ignition is increasing. This is because excessive energy consumption required for the pilot frame of the permanent ignition device used to ignite the burner on the upper surface of the gas range is prevented. The electrodes may be in the form of a wire. The wire extends upward through the base of the burner assembly, is supported within the burner assembly by an electrically insulating member, and extends outward through an electrode opening formed in a side wall of the burner cap. Within the burner cap, the electrodes are supported by a second electrically insulating support member. The burner cap is connected to the cotton swab for electrical conduction. The range top functions at ground potential and the spark electrode is connected to a higher potential via an electrical circuit to provide spark ignition between the electrode and the burner cap. The spark ignites a mixture of primary air and gas. This mixture is
Pass through the burner holes to create the desired burner flame supported by the surrounding secondary air.

There are a number of drawbacks and problems associated with conventional hermetically sealed gas burner assemblies, particularly those with spark igniters. For example, sparks generated by the electrodes fly from the electrodes to the burner body, igniting a mixture of primary air and gas flowing through the sparks. This ignition is easily recognized in the burner head formed by casting. However, it is difficult to achieve this, for example, in drawn sheet metal burner caps used in hermetic burner assemblies. This is because the main part of the electrode is housed in the burner head to protect against food leakage.
Since only the ends of the electrodes protrude from the electrode openings in the burner head, the sparks tend to scatter irregularly in all directions to the burner body. In order to solve this problem in the prior art, it is necessary to add a gas passage formed integrally with the electrode body or integrally with the opening through which the electrode projection extends. These gas passages
The gas is desirably ignited for a desired period of 4 seconds while the sparks are being scattered in various directions. This arrangement is not completely reliable, and the integral gas passage creates equipment maintenance problems.

In addition, in a conventional closed burner type range, the burner head is assembled on the top of the range with or without a clamping device. If a tightening tool is used, the burner head is mounted on the top of the range using screws or nuts. Screws or nuts
It provides more positive seal engagement but is inconvenient for cleaning and maintaining the top of the range. In these types of models, in which no clamping device is used, the positive connection of the burner head to the top of the range cannot be made to prevent food from entering the burner box located below the top of the range.

Furthermore, in conventional gas burners having an annular hole around the burner head, the secondary air required for proper combustion escapes from the hole. In a closed burner assembly, the secondary air exits between the top of the range and the bottom of the pan or cookware located on the grid above the burner head. To obtain an improved appearance, the height of the grid is preferably as low as possible. As the side walls of the enclosed burner head typically have a vertical and high profile, turbulence of the secondary air occurs at increasing combustion rates, which in turn appeals to the consumer's vision. Not to be accompanied by a very large height look.

Some examples of known, closed ignition, gas burner assemblies of the type described above are disclosed in U.S. Pat. No. 4,626,196 to Stöhrer, Jr.
And U.S. Pat. No. 4,810,1 issued to Kwiatek.
No. 88, and U.S. Pat. No. 4,846,671 to Quiretech.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved gas burner assembly having a closed structure.

It is another object of the present invention to provide an improved spark ignition of a gas burner assembly having a closed structure.

It is a further object of the present invention to provide an improved hermetically sealed gas burner having a low height profile appealing to the consumer and capable of operating at high burning rates without creating turbulence in the secondary air. To provide an assembly.

It is yet another object of the present invention to be easily and removably coupled to a burner opening on the top of the range to provide a hermetic seal against fluids while preventing food from entering the burner box to satisfy cleaning and maintenance of the range top. An object of the present invention is to provide a gas burner assembly having an improved closed structure.

It is yet another object of the present invention to provide an improved hermetically sealed gas burner assembly with a very simple structure, low manufacturing cost and easy assembly.

Still another object of the present invention is to provide a gas burner assembly having a closed structure using spark ignition, which ignites a mixture of primary air and gas reliably and quickly.

The above and other objects of the present invention are achieved by providing a gas burner assembly having a closed structure including a burner head having a burner cap and a burner base. The head is removably supported in a burner opening on the top of the range by a rotational lock connection and includes a vertical side wall having a plurality of burner holes. The head also
Also includes curved side walls. This curved side wall allows the head to be at a low height and prevent secondary air turbulence while operating the assembly at high burn rates.
The venturi is completely contained within the interior chamber of the burner head and supplies a mixture of primary air and gas to the holes. The vertical side walls also include the electrode openings. An electrode and an insulating support member cooperating therewith are arranged through the electrode opening,
Coupled with the opening to be sealed against the fluid.
The vertical side wall includes an ignition hole. The ignition hole is arranged adjacent to the outer end of the electrode, and a gas mixture is directly supplied to the end for rapid spark ignition. The seal member is arranged between the burner head and the upper surface of the range, and prevents food from passing downward and entering a burner box disposed below the upper surface of the range.

Other objects, features and advantages of the present invention will become apparent from the detailed description of the preferred embodiments of the present invention with reference to the drawings. In the drawings, the same reference numerals are given to corresponding members in different drawings.

FIG. 1 is an exploded perspective view showing a gas burner assembly having a closed structure according to a preferred embodiment of the present invention, FIG. 2 is a top view showing the assembly in an assembled state, and FIG. 3 is a view between a burner head and a burner opening on the upper surface of a range. FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. 2, FIG. 5 is a perspective view showing a first embodiment of an electrode used in the assembly, and FIG. 6 is FIG. 7 is a front view partially showing a state in which the electrodes shown in FIG. 7 are disposed in the burner head of the assembly, FIG. 7 is a perspective view showing a second embodiment of the electrodes used in the assembly, and FIG. FIG. 4 is a front view partially showing a state of being disposed in the burner head.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1-3, a gas burner assembly 1 having a closed structure according to a preferred embodiment of the present invention will be described. As shown in FIG. 1, the assembly 1 includes a burner head 3 having a burner cap 5 and a burner base 7. Each of the head 5 and the base 7 is preferably formed by being drawn from sheet steel, that is, stamped. The head 5 has a normal circular shape, and has a flat upper surface 9 and vertical side walls 11 extending downward from the upper surface 9.
And a curved side wall 13 extending downward and outward from the side wall 11. The outer peripheral surface of the curved side wall 13 is defined by a circular flange 15 extending downward.

The burner base 7 also has a normal circular shape and is defined by an upper annular end 17. From this upper annular end 17, a curved side wall 19 is directed downwardly and outwardly to an outer peripheral end.
Extends to 21. The inner cylindrical wall 23 extends downward from the upper annular end 17 to a circular bottom wall 25. The circular bottom wall 25 has a central circular opening 27 penetrating therethrough. The shape of the curved side wall 19 matches the shape of the curved side wall 13. As a result, the base 19 is accommodated in the cap 5 and supported by the cap 5 by deforming the flange 15 of the cap 5 around the outer peripheral end 21 of the base 7.

Still referring to FIG. 1, a plurality of burner holes 29 are formed in the vertical side wall 11 of the cap 5. These burner holes 29 are circumferentially spaced for the method and purpose described below. An electrode opening 31 and an ignition hole 32 are formed in the side wall 11. This ignition hole 32 is located below the electrode opening 31.
Are positioned so as to be adjacent to. Thus, when the base 7 is attached to the cap 5 by rolling the flange 15 around the outer peripheral end 21, a substantially cylindrical inner chamber is formed between them.

As shown in FIG. 1, a venturi member 33 is provided. The venturi member 33 includes a venturi tube 35, an annular ring 37, and a cylindrical tube 39. The cylindrical tube 39 extends downward from the annular ring 37. The cylindrical tube 39 has a pair of openings 41 facing each other, and a cylindrical air shutter 43 rotatably and concentrically installed in the cylindrical tube 39. The shutter 43 has a pair of openings 45 corresponding to the openings 41 and facing each other. These openings 45 are
The opening 33 can be variably positioned to take in a desired amount of air for 33. As can be seen from FIGS. 1 and 2, the venturi member 33 is incorporated into the burner head 3 by inserting a venturi tube 35 through the opening 27 of the burner base 7. This venturi
The insertion of the tube 35 is performed until the venturi tube 35 is completely accommodated in the inner chamber of the burner head 3 and closed. In this position, the annular ring 37 has a bottom wall adjacent to the periphery of the opening 27.
Contact the outer surface of 25. The member 33 is supported on the base 7 by staking or bending in a manner described later.

Burner assembly 1 also includes electrodes 47. The electrode 47 is defined by an electric wire 49, a first cylindrical electric insulating support member 51, and a second cylindrical electric insulating support 53. The second cylindrical electrical insulation support portion 53 is supported via a mounting bracket 55. The mounting bracket 55 is formed with a pair of openings 57 so as to perform appropriate mechanical tightening. One end of the wire 49 is a bent portion 59 and the other end is a terminal blade.
It is 61. The end blade 61 has a shape suitable for making an electrical connection to a conventionally used ignition circuit. As can be seen from FIG.
It is inserted through an opening 63 formed in the bottom wall 25 and is supported on the bottom wall 25 by a bracket 55 and a pair of appropriate tightening devices 65. The end 59 of the electrode 47 is inserted into the electrode opening 31 of the cap 5 and is positioned immediately near the ignition hole 32. In this assembled state, the end blade 61 and a part of the second insulating member 53 are combined with the bracket 55 with the part of the second insulating member 53 arranged so as to oppose the outer surface of the bottom wall 25. Extending downward from

When the burner head 3, the venturi member 33 and the electrodes 47 are assembled as described above, they form an assembly 1 which is removably mounted on the range upper surface 67. In particular, as can be seen from FIGS.
Includes a recessed burner recess 69. This burner recess
69 has a burner opening 71 defined by a circular vertical flange 73. A plurality of L-shaped protrusions 75 extending outward are formed on the flange 73 and are equally spaced around the flange 73. Each ridge 75 includes a vertical depression 77 and a horizontal depression 79. These bumps 75
A plurality of raised portions 81 extending outward are formed on the cylindrical wall 23 of the burner base 7 so as to correspond to FIG. The number and the circumferential spacing of the ridges 81 match those of the ridges 75. As a result, the assembly 1 replaces the raised portion 81 with the raised portion 75.
This is done simply by engaging the vertical depressions 77 in the horizontal recess 79 and rotating the assembly 1 in a clockwise direction to engage the ridges 81 with the horizontal depressions 79. The engagement of the ridges 75, 81
It essentially defines a bayonet-type connection, so that the assembly 1 can be rotated
The 67 burner openings 71 can be quickly attached or detached. Assembly 1 is top-down in this way
When mounted on the 67, a gas inlet nozzle supported in a burner body (not shown) below the top surface 67 provides gas supply to the venturi member 33 within a cylindrical tube 39 of the venturi member 33. Accepted.

The burner assembly 1 is shown in FIG. 4 in a completely assembled state, and is detachably mounted on the range upper surface 67. As described above, the burner head 3 has the base 7 arranged in the cap 5 and the outer peripheral end.
It is formed by bending the flange 15 inward so as to cover 21. The curved side walls 13, 19 are arranged so as to be laminated to each other to have the same shape, and the annular end 17 engages with an annular portion 85 of the cap 5 forming a step in the horizontal direction. The burner head 3 is inserted into the burner opening 71 and the corresponding ridge 8
It is removably supported in a burner recess 69 in the range top 67 via a rotational lock engagement between the 1,75. As is clear from FIG. 4, the Venturi tube 35 of the member 33 is completely accommodated in the inner chamber of the head 3. In this state, the member 33
It is attached so as to be supported by the bottom wall 25 via a protruding portion or bent portion shown by. U-shaped bracket 87
Is used to support a conventional gas inlet member 89. The gas inlet member 89 supports a gas inlet nozzle 83. The member 89 receives gas from the gas pipe 91. The gas pipe 91 is connected to an appropriate gas source (not shown).

When the closed burner assembly 1 is used for cooking, a suitable grid (not shown) is supported on the range upper surface 67 so as to cover the recess 69 and directly above the burner head 3.
This serves to support the cooking utensil at a distance from the upper surface of the burner head 3, which allows secondary air to flow between the cooking utensil and the upper surface 9. The primary air, the gas, and the air-fuel mixture enter the inner chamber of the burner head 3 through the venturi tube 35 and are distributed outside through the burner holes 29 and the ignition holes 32. When the air shutter 43 is rotated with respect to the cylindrical tube 39 of the member 33, the air is sent to the Venturi tube 35.
The ratio of secondary air to gas can be as desired.

Due to the closed structure of the burner assembly 1 with respect to the range top 67, food spatters that occur during cooking are usually
Since it is collected at 69 and does not directly access the burner box below the range upper surface 67, it can be removed from the recess 69. It is preferable to provide an annular seal member 93 near the outer surface of the head 3 to ensure the fluid tightness between the burner head 3 and the range upper surface 67. In addition, the sealing member 93 is formed so as to be adjustable at an annular joint between the cylindrical wall 23 of the base 7 and the flange 73 of the range upper surface 67 so that a fluid seal against the rotation lock engagement of the raised portions 75, 81 can be confirmed. You may do it. Sealing member 93 may be formed of any material known in the art, such as rubber or plastic, and considered suitable for practicing the present invention as disclosed herein.

As can be seen particularly from FIG. 4, the structural shape of the burner assembly, in particular the side walls 13, 19 of the burner head 3 which are laminated outwardly curved, have a large diameter at a low height relative to the burner head 3. Therefore, a grid having a low height can be used. These features can significantly improve the appearance of the assembly 1 to appeal to the consumer and adapt to the general requirements of the gas range. Burner head 3
The curved side walls have a significant effect of eliminating the turbulence of the secondary air, thereby increasing the burner rate capacity for the assembly 1.
This effect is incorporated with the installation of the venturi tube 35 at a low position in the burner head 3, the sealing of the venturi tube 35, and the arrangement of the burner hole 29 in a manner to be described later. The assembly 1 can be operated in a state where it is increased to the same degree as the thermal energy unit (BTU).

The shape, structure, and operation of the electrode 47 with respect to the burner head 3 will be described with reference to FIGS. Referring first to FIG. 5, the first cylindrical insulating member 51 has a large diameter rear portion.
95 and a coaxial small diameter front portion 97, between which a lateral annular surface 99 is defined. When the electrode 47 is installed in the burner head 3, as shown in FIG.
Is approximately the same as, but slightly smaller than, the diameter of the front wall 97 so that the front part 97 can slide through the electrode opening 31 until the annular surface 99 abuts against the inner surface of the vertical side wall 11. It has become. This helps to substantially define the fluid tightness between the member 51 and the opening 31 and thus prevents the mixture of primary air and gas from passing therethrough. The position of the electrode 47 directs the downwardly bent portion 59 toward the front of the ignition hole 32. As a result, when a spark is generated between the portion 59 and the burner head 3,
The spark initially occurs in the area adjacent to the ignition hole 32. From this adjacent area, a mixture of primary air and gas is sent directly to section 59. This results in a very quick and controlled ignition. In this way, irregular splashing of sparks from the electrodes to other areas of the burner head, which would normally occur with conventional burner assemblies of the same type, is prevented by the present invention. The insulating member 51 and / or the opening 31 allow gas to pass between the member 51 and the opening 31 for the ignition hole 32.
The formation of integral gas passages in the interior and the maintenance of equipment caused by such a design are completely eliminated by the simple and effective structure of the present invention.

Referring to FIG. 7, an electrode 101 according to a second embodiment is disclosed. The first cylindrical insulating member 103 has a large diameter rear part 1.
05 and an insulated front hood 107 having a semi-cylindrical shape directed downward. The effective outer diameter of the hood 107 is
105 so as to define a transverse annular surface 109 between
Is smaller than the diameter. In this embodiment, the electrode wire 49 terminates at the vertical end face 111. This vertical end face 111 is spaced from and surrounded by the hood 101. When the electrode 101 is disposed in the burner head 3, as shown in FIG. 8, the hood 107 extends through the opening 31, and the outer diameter of the hood 107 substantially matches the diameter of the opening 31, It is slightly smaller than this. In this way, the annular surface 109 is arranged in a substantially fluid tight engagement with the rear surface of the vertical side wall 11 and the member 103 and the opening 31
To prevent any mixture of primary air and gas from passing therethrough. By providing the hood 107,
Sparks are restricted to the area between the ignition hole 32 and the vertical end face 111, thereby preventing the sparks from scattered irregularly around the burner head 3 and providing a quick and effective ignition.

As is clear from FIGS.
Are preferably circular in shape and include an upper row, each having a uniform large diameter, and a lower row, each having a uniform small diameter. These burner holes 29
The upper row and the lower row are alternately spaced along the periphery of the vertical side wall 11. The shape and arrangement of the burner holes 29 are included in the unique features of the assembly 1 described above, which also significantly increases the annual turnover rate according to the present invention.

The distal blade 61 of the electrodes 47, 103 may be connected to any known ignition circuit. For example, this circuit is disclosed in U.S. Pat. No. 4,626,1 to Stöhrer, Jr.
No. 96 may be used. The entire disclosure of this patent is incorporated herein by reference.

The burner head 3 may also be provided with a durable porcelain enamel finish to prevent fading, which is enabled by the present invention, to accommodate applications with high annual sales rates in British thermal units. The individual components of burner assembly 1 may be formed of any suitable material known in the art and deemed optimal for practicing the invention as disclosed herein.
Suitable such materials are disclosed in U.S. Pat. No. 4,810,188 to Kwiatek and U.S. Pat. No. 4,846,671 to Kwiertek. The entire disclosures of these patents are incorporated herein by reference.

Although the present invention has been described herein with reference to details of a preferred embodiment thereof, changes in the form, size, shape, configuration, arrangement, etc. of the components may depart from the invention in which the concept and scope are defined in the claims. Otherwise, it may be performed by those skilled in the art of the present invention.

──────────────────────────────────────────────────の Continued on front page (72) Inventor Stevens, William E. T., United States, 37311, Tennessee, Cleveland, Reed Mine Valley Road 2378 (72) Inventor, Barnes, Shelton Tee United States, Edgefield Drive, Chattanooga, Tennessee 37421 7337 (56) References US Patent 5002038 (US, A) (58) Field of Study (Int. Cl. ⁷ , DB Name) F23Q 3/00 102

Claims (20)

(57) [Claims] 1. A burner cap having a side wall having a plurality of burner holes and an electrode opening, means for supplying a mixture of primary air and gas to the burner hole, and an opening provided in the electrode opening. An electrically insulating support member having an electrode passage therethrough, a spark electrode extending through the electrode passage and completely surrounded by the support member, and a spark electrode having a distal end directed toward the outer periphery of the support member. Means for maintaining a substantially fluid-tight connection between a support member and an electrode opening to prevent a mixture of primary air and gas from passing through the opening in an enclosed gas burner assembly of the type including: A gas burner assembly having a closed structure, further comprising: 2. A burner cap formed on the side wall and positioned directly near the end of the spark electrode.
2. The burner assembly according to claim 1, further comprising an ignition hole for supplying a mixture of secondary air and gas. 3. The electrode opening is formed in a circular shape, the insulating support member is formed in a substantially cylindrical shape defined by a large-diameter rear portion and a small-diameter front portion, and a lateral annular surface is formed between both portions. And the electrode opening is to receive the front,
And having substantially the same diameter as the front portion, such that the annular surface is disposed in sealing engagement with the inner surface of the side wall surrounding the electrode opening.
The burner assembly according to claim 1. 4. The burner assembly according to claim 3, wherein the small diameter front portion is formed substantially in the shape of a semi-cylindrical hood surrounding the distal end of the spark electrode. 5. Each of the burner holes is formed in a circular shape with a first set of large diameter burner holes and a second set of small diameter burners.
And the first set is positioned higher than the second set, and the holes of the set include:
The burner assembly according to claim 1, wherein the burner assemblies are spaced apart from each other along a circumference of the side wall so as to be staggered. 6. A burner assembly having a closed structure, comprising: a) a burner head defined by a cap and a base; b) a vertical side wall having a plurality of burner holes; and an electrode opening formed in the vertical side wall. Said cap including a first curved sidewall extending downwardly and outwardly from the vertical sidewall and terminating at a first circumferential edge; c) an annular end; and extending downwardly and outwardly from the annular end; A second curved side wall terminating at a second circumference;
Said base including a cylindrical side wall disposed inside a second curved side wall, extending downwardly from the annular end and terminating in a bottom wall having a central opening; d) said cap and said base; The first and second sidewalls are supported together at corresponding circumferential edges so as to be arranged in a stacked relationship, whereby the cap and the base together define an interior chamber therebetween; e) primary air and gas and A venturi member for directing the air-fuel mixture into the inner chamber; and a burner assembly having a closed structure. 7. The Venturi member comprises: a Venturi tube;
A cylindrical tube, and a venturi tube and an annular ring disposed between the cylindrical tubes, wherein the venturi tube extends through a central opening in the bottom wall and is disposed substantially completely within the interior chamber; 7. The burner assembly according to claim 6, wherein the ring is positioned to abut against an outer surface of the bottom wall, and wherein the venturi member includes means for supporting the venturi member to the bottom wall. 8. The cylindrical tube includes at least one opening formed in the cylindrical tube for circulation of primary air, and means for changing an amount of primary air flowing through the opening.
The burner assembly described in 1. 9. An electrode according to claim 9, further comprising an electrically insulating support member and an electrode, wherein said support member includes an electrode passage extending through the electrode opening and penetrating through the support member. The burner assembly according to claim 7, further comprising a distal end extending outside the burner head. 10. The insulating support member is disposed in a substantially fluid tight connection with respect to the electrode opening, thereby preventing the passage of a mixture of primary air and gas through the opening, and providing an ignition port. 10. A gasket is formed on a vertical side wall of the cap, wherein the igniter is positioned directly adjacent an end of the electrode and supplies the end with a mixture of primary air and gas. Burner assembly. 11. The burner assembly according to claim 6, including a range top with a burner opening for receiving the burner head, and removable locking means for supporting the burner head in the burner opening. 12. The burner opening is defined by an upright circular flange, and the removal locking means includes a common means formed on the cylindrical side wall of the base, said upright circular flange defining a rotational locking engagement therebetween. The burner assembly according to claim 11, wherein: 13. The joint means includes a plurality of first projections formed on the cylindrical wall and extending outward and spaced apart along the circumference, and a plurality of first projections corresponding to the first projections and extending outward and along the circumference. 13. The burner assembly according to claim 12, including a plurality of second protrusions formed in a spaced apart, upright circular flange, the second protrusions being defined by vertical and horizontal depressions. 14. The burner assembly according to claim 12, further comprising a sealing means disposed between the burner head and the upright circular flange to prevent food from passing therebetween. 15. The burner assembly according to claim 11, further comprising a sealing means disposed between the burner head and the top of the range to prevent food from passing therebetween. 16. The burner assembly according to claim 6, wherein at least said cap has a heat-resistant coating thereon. 17. The heat resistant coating is porcelain.
The burner assembly according to 16. 18. A gas burner assembly having a closed structure, comprising: a) a burner head having a cap and a base defining an inner chamber therebetween; b) disposed within the inner chamber and extending outside the cap. A spark electrode with a protruding end; c) a range top including a recess and at least one burner opening formed in the recess; d) said burner opening defined by an upright circular flange; e. And b. A joint means supported by the burner head and the upright vertical flange to provide a releasable rotational locking engagement between the head and the flange. 19. The joint means includes a plurality of first ridges formed on the burner head and a second ridge formed on the flange corresponding to the first ridges, each of the first ridges being formed on the flange. 19. The burner assembly according to claim 18, wherein the second ridge is defined by a vertical depression and a horizontal depression. 20. The joint means generally defines a bayonet-type engagement between the burner head and the flange.
19. The burner assembly according to claim 18.