阅读说明：本技术 一种新型阳极层离子源 (Novel anode layer ion source ) 是由 吴忠振 余浩洋 崔岁寒 刘亮亮 吴忠灿 于 2019-11-07 设计创作，主要内容包括：本发明提供一种新型阳极层离子源,包括位于轴心位置的内阴极,环绕在所述内阴极外侧的外阴极,所述内阴极和所述外阴极之间的间隙为离子束流通道；均匀排列在内阴极与外阴极之间的永磁体；位于所述内阴极和所述外阴极之间且环绕所述内阴极的阳极环,开设在所述阳极环内的通气孔,开设在所述阳极环上且连通所述通气孔的通气狭缝,所述通气狭缝朝向所述离子束流通道。通过改变离子源的通气方式,减少工作气体与阳极接触,从而降低工作气体对阳极造成污染和附着物吹出造成对沉积涂层的污染。(The invention provides a novel anode layer ion source, which comprises an inner cathode positioned at an axis position and an outer cathode surrounding the outer side of the inner cathode, wherein a gap between the inner cathode and the outer cathode is an ion beam flow channel; permanent magnets uniformly arranged between the inner cathode and the outer cathode; the ion beam current path comprises an anode ring, a vent hole and a vent slit, wherein the anode ring is positioned between the inner cathode and the outer cathode and surrounds the inner cathode, the vent hole is formed in the anode ring, the vent slit is formed in the anode ring and communicated with the vent hole, and the vent slit faces the ion beam current path. By changing the ventilation mode of the ion source, the contact between the working gas and the anode is reduced, so that the pollution of the working gas to the anode and the pollution of the deposited coating caused by the blowout of attachments are reduced.)

1. A novel anode layer ion source, comprising:

the inner cathode is positioned at the axis position, the outer cathode surrounds the outer side of the inner cathode, and a gap between the inner cathode and the outer cathode is an ion beam flow channel;

permanent magnets uniformly arranged between the inner cathode and the outer cathode;

the ion beam current path comprises an anode ring, a vent hole and a vent slit, wherein the anode ring is positioned between the inner cathode and the outer cathode and surrounds the inner cathode, the vent hole is formed in the anode ring, the vent slit is formed in the anode ring and communicated with the vent hole, and the vent slit faces the ion beam current path.

2. The novel anode layer ion source of claim 1, wherein the anode ring is provided with an anode chamfer at an inner edge of one end facing the ion beam flow channel, and the vent slit is located at an intersection of an end face of the anode ring facing the ion beam flow channel and the anode chamfer edge.

3. The anode layer ion source of claim 2, wherein the magnetic pole pieces of the inner cathode have a cathode chamfer formed at an edge facing the anode chamfer, the cathode chamfer being parallel to the anode chamfer.

4. The anode layer ion source according to claim 1, wherein a gas homogenizing chamber is arranged inside the anode, the gas homogenizing chamber is communicated with the vent hole and the vent slit, a gas homogenizing plate is arranged in the gas homogenizing chamber, and a gas homogenizing hole is arranged on the gas homogenizing plate.

5. The novel anode layer ion source of claim 4, wherein the uniform pore diameter near the vent hole location is smaller than the uniform pore diameter far from the vent hole location.

6. The anode layer ion source of claim 1, wherein two vent tubes are connected to the anode ring, and wherein the vent tubes are arranged symmetrically along the axis of the ion source.

7. The novel anode layer ion source according to claim 1, wherein the width of the vent slit is 0.5-1.5 mm.

8. The anode layer ion source of claim 1, wherein said anode ring is made of an electrically and magnetically non-conductive material; the inner cathode and the outer cathode are both made of magnetic materials.

9. The anode layer ion source of claim 1, wherein the permanent magnet is a cylindrical permanent magnet or electromagnet, one end of the permanent magnet abuts against the lower surface of the outer cathode, and the other end of the permanent magnet is connected with the magnetic yoke of the inner cathode.

10. The anode layer ion source of any one of claims 1 to 9, further comprising a bottom plate, a permanent magnet mounting bracket disposed above the bottom plate and coaxial with the inner cathode, a height limiting pillar disposed below the anode ring, wherein the vent hole penetrates the height limiting pillar and extends through the bottom plate, and a sealing assembly is disposed at a position where the vent hole penetrates the bottom plate.

Technical Field

The invention relates to the field of vacuum coating equipment, in particular to a novel anode layer ion source.

Background

An anode layer ion source is generally used in a PECVD (plasma enhanced chemical vapor deposition) reaction, and is used to ionize an inert gas such as argon to form an ion flow to be injected into a reaction vacuum chamber during the deposition of a diamond-like carbon film (DLC), and increase the ionization rate of the deposition reaction gas (acetylene), thereby increasing the proportion and deposition rate of SP3 in the DLC coating, thereby improving the quality of the deposited film and shortening the deposition time.

The existing anode layer ion source comprises an inner cathode, wherein the inner cathode is a circular disc with a chamfer, the part of the inner cathode with the chamfer is a magnetic pole shoe, an outer cathode is arranged on the outer ring of the inner cathode, an annular anode is arranged below the inner cathode and the outer cathode, a permanent magnet is arranged around the periphery below the outer cathode, and a magnetic yoke is formed by the permanent magnet and the inner cathode. When a positive voltage is applied to the anode and the inner cathode and the outer cathode are grounded, an electric field is formed between the anode and the cathode, thereby forming an orthogonal electric field and a magnetic field. The coupling of the electromagnetic field affects the motion of the charged particles in the plasma, and in particular, the electrons are most affected. The electromagnetic field acts to limit the movement of electrons, prolong the movement track of the electrons, and make the electrons confined in the annular range between the inner cathode and the outer cathode to do spinning wheel drifting movement in the range, so that the electrons are just like to be trapped on the annular runway and only drift on the annular closed runway in a cycle.

A large number of electrons drift on a 'runway' to form an annular high-density electron cloud, and when gas is injected onto the annular runway with the drift electron cloud, the probability of collision of inert gas molecules and the electrons is greatly increased, so that the inert gas molecules can be efficiently ionized. Meanwhile, the existence of the annular high-density electron cloud enables an anode layer with high potential gradient to be formed on the surface of the anode plate, and after the inert gas is ionized in the annular electron cloud, the inert gas is immediately pushed by the high potential gradient and is emitted along the normal direction of the surface of the anode plate, so that the inert gas becomes the required high-energy charged positive ions.

As shown in fig. 7, in the conventional ion source, a working gas is introduced into the bottom of the ion source, and a path of the working gas passes through the outer surface of the anode, so that the working gas is deposited on the surface of the anode under the action of plasma and heat to form contamination, and loose attachments deposited on the surface of the anode are blown out by subsequent gas flow to form large particle contamination on the coating.

Accordingly, the prior art is yet to be improved and developed.

Disclosure of Invention

The present invention provides a novel anode layer ion source, which reduces the contact between the working gas and the anode by changing the ventilation mode of the ion source, thereby reducing the pollution of the working gas to the anode surface and the coating pollution caused by the blown-out pollutant, and improving the working life of the ion source and the quality of the deposited coating.

The technical scheme adopted by the invention for solving the technical problem is as follows:

a novel anode layer ion source, comprising:

the inner cathode is positioned at the axis position, the outer cathode surrounds the outer side of the inner cathode, and a gap between the inner cathode and the outer cathode is an ion beam flow channel;

permanent magnets which are uniformly arranged between the outer cathode and the inner cathode and are positioned on the periphery below the outer cathode;

the ion beam current path comprises an anode ring, a vent hole and a vent slit, wherein the anode ring is positioned between the inner cathode and the outer cathode and surrounds the inner cathode, the vent hole is formed in the anode ring, the vent slit is formed in the anode ring and communicated with the vent hole, and the direction of the vent slit faces the ion beam current path.

Further, an anode chamfer is arranged at the edge of the inner side of one end, facing the ion beam flow channel, of the anode ring, and the ventilation slit is located at the intersection of the end face, facing the ion beam flow channel, of the anode ring and the anode chamfer edge.

Furthermore, a cathode chamfer is formed at the edge of one end, facing the anode chamfer, of the magnetic pole shoe of the inner cathode, and the cathode chamfer is parallel to the anode chamfer.

Further, an air homogenizing chamber is arranged inside the anode and is communicated with the vent hole and the vent slit, an air homogenizing plate is arranged in the air homogenizing chamber, and air homogenizing holes are formed in the air homogenizing plate.

Further, the diameter of the uniform air hole close to the position of the vent hole is smaller than that of the uniform air hole far away from the position of the vent hole.

Furthermore, the anode ring is connected with two vent pipes, the vent holes are formed in the vent pipes, and the two vent pipes are symmetrically arranged along the axis of the ion source.

Furthermore, the width of the ventilation slit is 0.5-1.5 mm.

Further, the anode ring is a strip-shaped annular body or a circular annular body made of an electric conducting and non-magnetic conducting material, and the inner cathode and the outer cathode are made of magnetic conducting materials.

Further, the permanent magnet is a columnar permanent magnet or electromagnet, one end of the permanent magnet abuts against the lower surface of the outer cathode, and the other end of the permanent magnet is connected with the magnetic yoke of the inner cathode.

Further, still including the bottom plate, set up bottom plate top and with the coaxial permanent magnet mounting bracket of interior negative pole is located anode ring below and with the coaxial limit for height post of air vent, anode ring's air vent link up limit for height post and extend and link up the bottom plate is located the air vent link up be provided with seal assembly in the position of bottom plate.

The beneficial effect who adopts above-mentioned scheme is: the invention provides a novel anode layer ion source. Working gas is directly discharged through the vent holes in the anode ring, the working gas is uniformly ejected to the electromagnetic coupling area through the vent slits, the working gas is directly ejected from the outer surface of the anode ring, a small part of the working gas is in contact with the surface of the anode ring close to the inner cathode side, and most of the working gas enters the electromagnetic coupling area for ionization treatment. The pollution of active gas to an anode ring, an inner cathode and other parts of the ion source in the process of coating the anode layer ion source and the pollution of a coating caused by blowing out of pollutants which are not firmly bonded are reduced. Meanwhile, the uniformity and cleanliness of the ion beam in the processes of processing, heating, cleaning, etching, sputtering, ion implantation and the like can be effectively improved.

Drawings

Fig. 1 is a cross-sectional view of a snorkel position of an embodiment of a novel anode layer ion source of the present invention.

Fig. 2 is an enlarged view of a portion a of fig. 1.

Fig. 3 is a cross-sectional view of the position of the inlet tube of a novel anode layer ion source embodiment of the present invention.

Fig. 4 is a top view of a gas distribution plate in an embodiment of a novel anode layer ion source of the present invention.

Fig. 5 is a magnetic field profile for an embodiment of a novel anode layer ion source of the present invention.

Fig. 6 is a gas flow diagram for a novel embodiment of an anode layer ion source of the present invention.

Fig. 7 is a gas flow diagram of the prior art.

Fig. 8 is a top view of an inner cathode in an embodiment of a novel anode layer ion source of the present invention.

Fig. 9 is a top view of an outer cathode in an embodiment of a novel anode layer ion source of the present invention.

Fig. 10 is a top view of an anode ring in an embodiment of a novel anode layer ion source of the present invention.

In the figure: 100. an inner cathode; 110. chamfering the inner cathode; 200. an outer cathode; 210. an ion beam flow path; 300. a permanent magnet; 400. an anode ring; 410. chamfering the anode; 420. a breather pipe; 430. a vent hole; 440. a vent slit; 500. an air homogenizing chamber; 510. a gas homogenizing plate; 520. air homogenizing holes; 600. a base plate; 610. a permanent magnet mounting rack; 620. a height limiting column; 700. a seal assembly; 800. an ion source housing; 900. a water inlet pipe; 910. and (5) discharging a water pipe.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in fig. 1 and fig. 2, the present embodiment provides a novel anode layer ion source, which is arranged in an axisymmetric manner, and includes an inner cathode 100 located at an axial center position, an outer cathode 200 located at an outer side of the inner cathode 100, the outer cathode 200 surrounding a circumference of the outer side of the inner cathode 100, a gap being provided between the inner cathode 100 and the outer cathode 200, the gap being an ion beam flow channel 210 for emitting an ion beam current, the outer cathode 200 in this embodiment being specifically located at a position above the outer side of the inner cathode 100; the inner cathode 100 and the outer cathode 200 are both made of magnetic conductive materials, a plurality of permanent magnets 300, specifically 16 in this embodiment, are uniformly arranged between the inner cathode 100 and the outer cathode 200, the permanent magnets 300 surround the outer cathode 100 for a circle, the permanent magnets 300 are columnar permanent magnets or electromagnets, in the specific structure of this embodiment, one end of each permanent magnet 300 abuts against the lower surface of the outer cathode 200, and the other end of each permanent magnet 300 is connected with a magnetic yoke of the inner cathode 100. Be located interior negative pole 100 with be provided with anode ring 400 between the outer negative pole 200, anode ring 400 encircles interior negative pole 100, anode ring 400 is for adopting electrically conductive and not magnetic material preparation, and anode ring 400 can be for no magnetism stainless steel or chromium nickel titanium alloy material, and in the concrete structure of this embodiment, interior negative pole 100 is cylindrical, outer negative pole 200 is the ring shape, and anode ring 400 adopts circular ring shaped structure, and other parts of novel anode layer ion source set up for the shape of cooperation interior negative pole 100, outer negative pole 200 and anode ring 400. It is easily conceived that the inner cathode 100 is not limited to a cylindrical shape, but may be a square shape, such as a stripe race track shape shown in fig. 8, or other shapes symmetrical about the axis; the outer cathode 200 and the anode ring 400 are not limited to circular ring structures, but may have a ring race track shape as shown in fig. 9 and 10 or other ring structures symmetrical with respect to the axial center. The inner cathode 100 is positioned above the anode ring 400, and the lower surface of the inner cathode 100 is higher than the upper surface of the anode ring 400. The anode ring 400, the inner cathode 100, and the outer cathode 200 form a discharge chamber. A vent hole 430 is formed in the anode ring 400, the vent hole 430 is used for connecting working gas provided from the outside, a vent slit 440 is formed in the anode ring 400, the vent slit 440 is communicated with the vent hole 430, the vent slit 440 faces the ion beam channel 210, the external working gas enters the anode ring 400 from the vent hole 430 and is ejected into the discharge chamber from the vent slit 440; the width of the ventilation slit 440 is 0.5-1.5 mm, and the width of the slit is 1mm in this embodiment.

In this embodiment, as shown in fig. 1 and 5, a closed magnetic circuit is formed by the permanent magnet 300 disposed between the inner cathode 100 and the outer cathode 200, and a magnetic field parallel to the anode chamfered surface is formed between the inner cathode 100 and the outer cathode 200. The anode ring 400 is connected with a positive voltage to form an anode, the inner cathode 100 and the outer cathode 200 are grounded to form a cathode, an electric field is formed in a region between the cathode and the anode, namely, an electric field is formed between the anode ring 400 and the inner cathode 100, between the anode ring 400 and the outer cathode 200, the direction of the electric field is perpendicular to the direction of the magnetic field to form an electromagnetic coupling field, and under the action of the electromagnetic coupling field, the electron cloud cluster can perform closed drift in the range of the electromagnetic coupling field, so that the number of collisions is increased, and the ionization rate is remarkably increased. The existence of the high-density electron cloud enables an anode layer with a high potential gradient to be formed on the surface of the anode ring 400, and when the working gas is ionized in the annular electron cloud, the working gas is immediately pushed by the high potential gradient and is emitted along the normal direction of the surface of the anode plate, so that the working gas becomes the required high-energy charged positive ions. As shown in fig. 6, since the working gas is directly discharged through the vent holes 430 in the anode ring 400, the working gas is uniformly emitted to the electromagnetic coupling field through the vent slits 440, the working gas is directly emitted from the outer surface of the anode ring 400, a small portion of the working gas contacts the surface of the anode ring 400 near the inner cathode 100, and a large portion of the working gas enters the electromagnetic coupling region for ionization. The pollution of active gas to the anode ring 400, the inner cathode 100 and other parts of the ion source in the process of coating the anode layer ion source and the pollution of coating caused by blowing out of the pollutants which are not firmly bonded are reduced. Meanwhile, the uniformity and cleanliness of the ion beam in the process of processing, heating, cleaning, etching, sputtering, ion implantation and the like can be effectively improved.

As shown in fig. 1 and 2, an anode chamfer 410 is provided at an inner edge of one end of the anode ring 400 facing the ion beam flow channel 210. When the anode ring 400 adopts a circular structure, the surface of the anode chamfer 410 is a conical surface, the ion beam flow channel 210 is also a cathode gap formed between the magnetic pole piece of the inner cathode 100 and the magnetic pole piece of the outer cathode 200, the cathode gap (ion beam flow channel 210) is axisymmetric with respect to the central axis, the outgoing direction of each cathode gap is almost perpendicular to the surface of the anode chamfer 410 of the anode ring 400 below the cathode gap, and the magnetic field generated by the permanent magnet 300 is released at the cathode gap formed by the inner cathode 200 and the outer cathode 200 through the outer cathode 200 and the inner cathode 100. An anode layer with high potential gradient is formed on the surface of the anode chamfer 410 of the anode ring 400, and after inert gas is ionized in the annular electron cloud, the inert gas is pushed by the high potential gradient and is emitted along the normal direction of the surface of the anode chamfer 410, so that required high-energy charged positive ions are formed. The ventilation slit 440 is located at the intersection of the end surface of the anode ring 400 facing the ion beam flow channel 210 and the edge of the anode chamfer 410, and the ventilation slit 440 is arranged at the intersection of the end surface and the anode chamfer 410, so that working gas enters the electromagnetic coupling region to generate an ion beam, and due to the clearance action of the anode chamfer 410, when the generated ion beam moves towards the direction of the inner cathode 100, the generated ion beam does not contact the end surface of the anode ring 400 facing the inner cathode 100, so that the working gas does not pass through the outer surface of the anode ring, thereby reducing the pollution of the working gas to the surface of the anode and further improving the cleanliness of the generated ion beam.

The edge of one end of the magnetic pole piece of the inner cathode 100 facing the anode chamfer 410 is provided with a cathode chamfer 110, and the cathode chamfer 110 is parallel to the anode chamfer 410. The provision of the cathode chamfer 110 can reduce the area of the outer circumferential surface of the magnetic pole piece of the inner cathode 100, thereby reducing the contact between the ion beam and the outer circumferential surface of the inner cathode 100 and further improving the cleanliness of the ion beam.

The anode ring 400 is internally provided with a gas homogenizing chamber 500, the gas homogenizing chamber 500 is communicated with the vent holes 430 and the vent slits 440, the gas homogenizing chamber 500 is used for concentrating working gas in the vent holes 430, the anode ring 400 is connected with a plurality of vent pipes 420 which can be connected, in the embodiment, the vent pipes 420 are arranged in two, the vent holes 430 are inner cavities of the vent pipes 420, namely, the vent holes 430 are arranged in two, the two vent holes 430 are communicated with the gas homogenizing chamber 500, and the two vent pipes 420 are symmetrically arranged along the axis of the ion source, so that the working gas in the gas homogenizing chamber 500 can be distributed more uniformly. The gas homogenizing plate 510 is arranged in the gas homogenizing chamber 500, the gas homogenizing plate 510 is located between the ventilation slit 440 and the ventilation pipe 420 and divides the gas homogenizing chamber 500 into two parts, the gas homogenizing plate 510 is provided with gas homogenizing holes 520, the gas homogenizing holes 520 are symmetrically distributed around the axis, the gas homogenizing holes 520 are communicated with the two parts of the gas homogenizing chamber 500, working gas firstly enters the lower space of the gas homogenizing chamber 500 through the ventilation holes 430 and then enters the upper space through the gas homogenizing plate 510, the working gas is buffered by the gas homogenizing plate 510, gas homogenizing is further achieved, the uniform working gas in the upper space flows out of the ventilation slit 440 and enters the electromagnetic coupling field for ionization.

As shown in fig. 3 and 4, among the air uniforming holes 520 on the air uniforming plate 510, the diameter of the air uniforming holes near the positions of the air uniforming holes is smaller than that of the air uniforming holes far from the positions of the air uniforming holes, that is, the diameter of the air uniforming holes far from the air uniforming holes 430 is larger and denser, and the diameter of the air uniforming holes near the air uniforming holes 430 is smaller and sparser. The gas enters the gas homogenizing chamber 500 through the symmetrically distributed vent holes 430, passes through the gas homogenizing holes 520 on the gas homogenizing plate 510 in the gas homogenizing chamber 500, and the gas homogenizing holes 520 are arranged according to the flowing rule of the gas, so that the working gas can uniformly enter the vent slits 440 and enter the discharge chamber, and the purpose of homogenizing the gas is achieved. The air homogenizing effect is tested after simulation, and the effect is good. Therefore, after passing through the gas homogenizing chamber 500, the gas is uniformly distributed and has consistent gas speed when entering the electromagnetic coupling field after passing through the ventilating slit 440 at the intersection of the conical anode chamfer 410 surface and the end surface on the anode ring 400, so that the discharge uniformity and the discharge stability in the discharge area are promoted, and the bad phenomena of film coating influence, such as sparking and the like in the discharge area, are avoided.

As shown in fig. 4, the anode ring is further connected with a water inlet pipe 900 and a water outlet pipe 910, the water inlet pipe 900 and the water outlet pipe 910 are symmetrically arranged about the central axis, a gap is left between the gas homogenizing chamber 500 and the inner wall of the anode ring 400, the channels of the water inlet pipe 900 and the water outlet pipe 910 are communicated with the gap to form a cooling channel, and cooling water enters the gap between the gas homogenizing chamber 500 and the inner wall of the anode ring 400 from the water inlet pipe to cool the anode ring and the gas homogenizing chamber.

The novel anode layer ion source in the scheme further comprises a bottom plate 600, wherein the bottom plate 600 is disc-shaped, the inner cathode 100 is coaxially and fixedly arranged in the middle of the bottom plate 600, a permanent magnet mounting frame 610 is arranged above the bottom plate 600, the permanent magnet mounting frame 610 and the inner cathode 100 are coaxially arranged, the permanent magnet 300 is arranged on the permanent magnet mounting frame 610 and is positioned above the bottom plate, a height limiting column 620 is arranged below the lower surface of the anode and coaxially with the water inlet pipe 900, the water outlet pipe 910 and the vent pipe, the vent pipe 420, the water inlet pipe 900 and the water outlet pipe 910 are communicated with the height limiting column 620 and extend to communicate with the bottom plate 600, the height limiting column 620 enables the inner cathode 100 to be spaced apart from the anode ring 400, a sealing assembly 700 is arranged at the position where the water inlet pipe 900, the water outlet pipe 910 and the vent pipe 420 are communicated with the bottom, The gap between the water outlet pipe 910 and the bottom plate 600 is provided with the ion source shell 800 on the bottom plate 600, the ion source shell 800 is sleeved on the outer side of the permanent magnet mounting frame 610, and the upper part of the ion source shell 800 is sleeved on the outer side of the outer cathode 200. The novel anode layer ion source is preferably of an axisymmetric structure formed about a central axis, and the symmetric structure has uniform overall magnetic field distribution, simple structure and easy processing.

In summary, the present invention provides a novel anode layer ion source, wherein the working gas is directly discharged through the vent holes 430 in the anode ring 400, the working gas is uniformly emitted to the electromagnetic coupling region through the vent slits 440, the working gas is directly emitted from the outer surface of the anode ring 400, a small portion of the working gas contacts the surface of the anode ring 400 near the inner cathode 100, and a large portion of the working gas enters the electromagnetic coupling region for ionization. The pollution of active gas to the anode ring 400, the inner cathode 100 and other parts of the ion source in the process of coating the anode layer ion source is reduced, and meanwhile, the pollution caused by blowing out of pollutants which are not firmly bonded on the surfaces of the parts in the ion source discharge chamber is avoided. The uniformity and cleanliness of the ion beam in the process of processing, heating, cleaning, etching, sputtering, ion implantation and the like can be effectively improved. Meanwhile, an anode layer with a very high potential gradient is formed on the surface of the anode chamfer 410 of the anode ring 400, and after inert gas is ionized in the annular electron cloud, the inert gas is pushed by the high potential gradient and is emitted along the normal direction of the surface of the anode chamfer 410, so that the inert gas becomes required high-energy charged positive ions.

In summary, the structure of the anode layer ion source satisfying the principle should be within the scope of the present patent application, and is not affected by the size and position of the gas outlet, the material, size, shape and other deformation structure of other parts of the ion source.

It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.