Interconnector electrically connecting plurality of electronic device elements, fabrication method thereof, and join apparatus thereof

An interconnector includes a front surface electrode connecting portion connected to a front surface electrode of a solar cell, a back electrode connecting portion connected to a back electrode of another solar cell adjacent to the solar cell, and a stress relief portion absorbing displacement generated between the front surface electrode connecting portion and the back electrode connecting portion. A plurality of notches are formed at the front surface electrode connecting portion and the back electrode connecting portion. Since the front surface electrode connecting portion and the back electrode connecting portion have notches, an area sufficient for welding can be ensured. Reliability at the joining portion of the interconnector can be improved. Also, the interconnector can be reduced in size to allow reduction in cost.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to an interconnector to electrically connect
 a plurality of electronic device elements in a serial direction or a
 parallel direction. Particularly, the present invention relates to a
 planar type interconnector employed in the connection of solar cells for
 artificial satellites or diodes, a method of forming such an
 interconnector, and a join apparatus thereof.
 2. Description of the Background Art
 The current consumed energy worldwide corresponds to an enormous amount,
 which is mainly supplied by fossil fuel such as oil or the like. It is
 expected that the fossil fuel will be exhausted in the near future if the
 energy consumption increases at the current rate.
 In these few years, intensive research of the technology utilizing
 inexhaustible and clean solar energy has been in progress as the energy
 source to replace the fossil fuel. Development of solar cells can be
 referred to as one major technique thereof. In general, the plurality of
 solar cells constituting the solar battery are arranged adjacent to each
 other. An interconnector formed of a small piece of metal is provided in
 order to electrically connect the solar cells in the serial or parallel
 direction.
 An interconnector includes a stress relief portion that absorbs
 displacement generated between solar cells connected to each other, and at
 least two connecting portions connected to the solar cells. The invention
 disclosed in Japanese Patent Laying-Open No. 4-298082 and the invention
 disclosed in Japanese Utility Model Laying-Open No. 1-125563 can be
 enumerated as conventional art related to such an interconnector.
 FIG. 1A schematically shows a structure of an interconnector disclosed in
 Japanese Patent Laying-Open No. 4-298082. This interconnector 101 includes
 a front surface electrode connecting portion 121, a back electrode
 connecting portion 122, and a stress relief portion 110. As shown in FIG.
 1B, front surface electrode connecting portion 121 and back electrode
 connecting portion 122 have a mesh structure.
 The interconnector disclosed in Japanese Utility Model Laying-Open No.
 1-125563 includes a first stress absorption portion having a plurality of
 permeable holes arranged in the row direction with respect to the
 interconnector, and a second stress absorption portion having a plurality
 of permeable holes arranged in the column direction.
 In order to withstand the displacement generated between adjacent solar
 cells, an area for connecting or welding sufficient for the connecting
 portion is required in joining the connecting portion of the
 interconnector with the electrode portion of the solar cell. In the
 inventions disclosed in the aforementioned Japanese Patent Laying-Open No.
 4-298082 and Japanese Utility Model Laying-Open No. 1-125563, a mesh
 opening or permeable hole is provided at the connecting portion of the
 interconnector. Connection with the electrode portion of the solar cell
 was effected using the opening or permeable hole. In order to ensure a
 connection area sufficient for the connecting portion of the
 interconnector, the area of the connecting portion of the interconnector
 will become larger. In solar cells for artificial satellites, there is a
 problem that increase in the area of the connecting portion will raise the
 cost since noble metal such as gold, silver or the like is generally used
 as the material of the interconnector. Increase in the area of the
 connecting portion of the interconnector will also reduce the
 light-receiving area of the solar cell. As a result, there is a problem
 that the efficiency and output of the solar cell will be degraded.
 The provision of a mesh opening or permeable hole at the connecting portion
 of the interconnector will become the cause of crushing the mesh opening
 or permeable hole when welding is effected using a weld electrode of a
 large width. When pressure is applied with the weld electrode in contact
 with the residual portion of the mesh opening or permeable hole, i.e. the
 remaining metal portion for welding, stress concentration occurs at that
 portion to become the cause of damaging the solar cell. For the
 reliability of the weld portion, welding was effected on one connecting
 portion between the interconnector and the solar cell using a small weld
 electrode of a small width. If the area of the connecting portion of the
 connector is increased, welding must be effected many times on one
 connecting portion when a small weld electrode is used. A tremendous
 amount of time will be required for welding to degrade the productivity.
 There was also problem that the process of etching is required to form the
 mesh opening or permeable hole at the connecting portion of the
 interconnector, resulting in increase of the processing cost. In the case
 where etching is applied on the connecting portion of the interconnector,
 automation cannot be facilitated since it is extremely difficult to work
 on components of a continuous form. Even if a continuous interconnector is
 formed by working on a continuous form, there was a problem that the cost
 of the interconnector is increased.
 In the case where a continuous interconnector cannot be formed, each
 produced interconnector must be accommodated in a pallet or the like
 individually. Extra space to install the pallet is required. There is also
 the possibility that the produced interconnector may be lost if small in
 size.
 SUMMARY OF THE INVENTION
 An object of the present invention is to provide an interconnector reduced
 in size and cost, and that has high productivity.
 Another object of the present invention is to provide an interconnector
 that facilitates the connecting task with a solar cell, and that can
 prevent reduction in the efficiency and output of the solar cell.
 A further object of the present invention is to provide a method of forming
 an interconnector that allows automated connection between an
 interconnector and a solar cell.
 Still another object of the present invention is to provide a join
 apparatus that allows automatic connection between an interconnector and a
 solar cell.
 According to an aspect of the present invention, an interconnector includes
 a first connecting portion connected to an electrode of a first electronic
 device element, a second connecting portion connected to an electrode of a
 second electronic device element adjacent to the first electronic device
 element, and a stress relief portion absorbing displacement generated
 between the first and second electronic device elements. At least one of
 the first and second connecting portions includes one or more notches.
 Since at least one of the first and second connecting portions includes at
 least one notch, sufficient weld area can be provided to allow increase of
 the reliability at the connecting portion of the interconnector. Also, the
 connector can be reduced in size to lower the cost.
 According to another aspect of the present invention, a method of forming
 an interconnector that connects a first electronic device element with a
 second electronic device element adjacent to the first electronic device
 element is provided. The method includes the steps of forming a plurality
 of interconnectors by press-working on a continuous sheet-like material,
 and accommodating the continuous sheet-like material where the plurality
 of interconnectors are formed in a reel.
 Since the continuous sheet-like material is subjected to press-working to
 form a plurality of interconnectors and accommodated in a reel, supply of
 the interconnector can be automated to allow automatic connection between
 an interconnector and a solar cell.
 According to a further aspect of the present invention, a join apparatus
 include a sever unit to cut off an interconnector formed at a continuous
 sheet-like material, a first convey unit to convey the interconnector cut
 off by the sever unit, a second convey unit to convey an electronic device
 element, and a join unit to join the interconnector conveyed by the first
 convey unit with the electronic device element conveyed by the second
 convey unit.
 Since the join unit joins a connector and a solar cell after the sever unit
 cuts off the interconnector formed on a continuous sheet-like material,
 the join between an interconnector and a solar cell can be carried out
 automatically.
 The foregoing and other objects, features, aspects and advantages of the
 present invention will become more apparent from the following detailed
 description of the present invention when taken in conjunction with the
 accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 First Embodiment
 Referring to FIG. 2, an interconnector 1 includes a front surface electrode
 connecting portion 2 connected to a front surface electrode of a solar
 cell not shown, a back electrode connecting portion 3 connected to a back
 electrode of another solar cell adjacent in a serial direction with
 respect to that solar cell, and a stress relief portion 8 between front
 surface electrode connecting portion 2 and back electrode connecting
 portion 3.
 Stress relief portion 8 absorbs and alleviates the displacement generated
 between front electrode connection portion 2 and back electrode connecting
 portion 3 by being bent at the region of round notches 40 and 41. At least
 one notch 4 extending from the opening of interconnector 1 is provided at
 front surface electrode connecting portion 2 and back electrode connecting
 portion 3. Notch 4 is formed so that the ratio of w1 to w2 (w1.div.w2) is
 not more than 1, where w1 is the width of notch 4 and w2 is the width of
 the joining portion excluding notch 4 (the width between notches 4, or the
 width from notch 4 to the edge of the joining portion).
 FIG. 3 shows the case where interconnector 1 of FIG. 2 is connected to a
 solar cell. Front surface electrode connecting portion 2 of interconnector
 1 is connected to the front surface electrode connecting portion of solar
 cell 6 by welding or the like. Back surface electrode connecting portion 3
 of interconnector 1 is connected to the back electrode connecting portion
 of solar cell 7 adjacent to solar cell 6 in the serial direction by
 welding or the like. Since width w1 of notch 4 formed at front surface
 electrode connecting portion 2 and back electrode connecting portion 3 is
 smaller than width w2 of the joining portion excluding notch 4, decrease
 in the weld area by notch 4 is small. A weld area large enough can be
 obtained. Thus, sufficient mechanical join strength between interconnector
 1 and solar cell 6 or 7 can be obtained.
 The influence of the residual stress during welding can be dispersed since
 the connecting portion is divided by notches 4. In the case where the
 solar cell is greatly displaced due to the effect of the thermal stress or
 external force during production to result in generation of a crack 10 at
 the connecting portion (for example, at front surface electrode connecting
 portion 2) of interconnector 1, further development of the crack can be
 suppressed by notch 4. Therefore, degradation of the reliability of weld
 portion 5 of interconnector 1 can be prevented.
 Interconnector 1 of the present embodiment is not limited to the
 configuration shown in FIG. 2. A configuration shown in FIGS. 4A-4E, for
 example, may be employed. An interconnector 1a of FIG. 4A has the depth of
 the notch in front surface electrode connecting portion 2 and back
 electrode connecting portion 3 gradually increased. An interconnector 1b
 of FIG. 4B has the notch of front surface electrode connecting portion 2
 and back electrode connecting portion 3 formed oblique with respect to the
 connecting portion. An interconnector 1c of FIG. 4C has the notch formed
 in the lateral direction of front surface electrode connecting portion 2
 and back electrode connecting portion 3. An interconnector 1d shown in
 FIG. 4D has notches formed in a zigzag manner at front surface electrode
 connecting portion 2 and back electrode connecting portion 3. An
 interconnector 1e of FIG. 4E has the number of stress relief portions
 between front surface electrode connecting portion 2 and back electrode
 connecting portion 3 increased.
 According to the interconnector of the present embodiment, the weld area is
 not reduced by notch 4 and of a sufficient area can be obtained to allow
 reduction in the size and cost of an interconnector. Also, the influence
 of the residual stress during welding can be dispersed since the
 connecting portion is divided by notches 4. Therefore, reliability at the
 connecting portion can be improved.
 Second Embodiment
 FIG. 5 shows the case where an interconnector of the present embodiment is
 connected to a solar cell. The configuration of the interconnector of the
 present embodiment is identical to that of the interconnector shown in
 FIG. 2 or 4. Therefore, detailed description thereof will not be repeated.
 In a solar cell 12, a rod-like front surface electrode 11 is elongated
 laterally. Therefore, a join area of a certain level can be ensured even
 if the distance of the connecting portion of solar cell 12 in the vertical
 direction is reduced. It is therefore possible to reduce the element of
 decreasing the light-receiving area of solar cell 12. Thus, the efficiency
 and output of solar cell 12 can be further improved.
 Third Embodiment
 The configuration of an interconnector according to a third embodiment of
 the present invention is identical to that of the interconnector shown in
 FIG. 2. The connection between the interconnector of the present
 embodiment and a solar cell is similar to that of FIG. 3 or 5. Therefore,
 detailed description of the same structure or function will not be
 repeated.
 In the joining operation of interconnector 1 with a solar cell 12 by
 welding, a plurality of interconnectors 1 are joined to solar cell 12 to
 connect adjacent solar cells. The welding is generally carried out by a
 pair of weld electrodes arranged in parallel. However, when a mesh opening
 or permeable hole is provided at the connecting portion of the
 interconnector as described in the conventional art, the weld electrode
 must be pressed against the joining portion of the interconnector with a
 great force if the width of the weld electrode is increased. This may
 cause stress concentration at the metal-remaining portion for welding to
 damage the solar cell. Conventionally, welding was carried out using one
 pair of small weld electrodes urged a plurality of times.
 Interconnector 1 of the present embodiment can have the area of the
 connecting portion increased. Even if welding is carried out using a weld
 electrode of a large width, the stress concentration at the connecting
 portion of interconnector 1 is small. Therefore, solar cell 12 will not be
 damaged
 FIG. 6 is a table of the strength measured when interconnectors 1 of the
 present embodiment are welded at one time with a weld electrode of a large
 width. The solar cell was of a cell type BSR (Back Surface Reflector) with
 a thickness of 0.15 mm. The pad size of the weld portion was 1.5.times.2.5
 mm.sup.2. The ratio of width w1 of notch 4 of the connecting portion to
 width w2 of the joining portion excluding notch 4 was 1.0. Silver system
 material was employed for interconnector 1. Four notches were provided
 with w1=0.25 mm, w2=0.25 mm and a slit length of L=0.9 mm. The values in
 the table show the result of such a solar cell connected with
 interconnectors 1 by one-time welding, and subjected to a 45.degree.
 tensile test. A weld electrode of 0.3.times.2.7 mm.sup.2 was used.
 The tensile test was carried out on three solar cells of cell numbers 1-3.
 It is appreciated from the table of FIG. 6 that the smallest value of the
 tensile strength was 985 g. The conventional standard of the tensile
 strength of a solar cell is at least 500 g. Therefore, this condition is
 satisfied sufficiently.
 FIG. 7 is a diagram to describe the dimension of the weld electrode. In
 welding interconnector 1 to solar cell 6, a pair of weld electrodes 37 is
 used. A gap g of approximately 0.1-0.3 mm is provided for the pair of weld
 electrodes 37. When gap g is 0.1 mm, the total width T of the pair of weld
 electrodes 37 is 0.7 mm. The length from the edge of interconnector 1 to
 weld electrode 37 is the positioning dimension Y.
 When interconnector 1 is to be welded with solar cell 6, the slit length L
 of interconnector 1 is represented by L=T+.alpha.+Y, where .alpha. is the
 length from the end of weld electrode 37 to an end 38 of notch 4. When Y
 takes a constant value, the dimension of slit depth L is defined by the
 value of .alpha.. FIG. 8A shows the relationship between value .alpha. and
 the weld strength as a result of the measurement of the weld strength
 after welded interconnector 1 is subjected to a thermal shock test. Y is
 set to 0.3 mm, and the cycle of -196.degree. C..about.130.degree. C. was
 carried out 1,000 times for the thermal shock test. It is appreciated from
 FIG. 8A that a weld strength of at least 500 g is obtained by at least
 .alpha.=0 mm. A thermal shock test was carried out while altering
 dimension Y in the range of -0.3.about.3 mm. The welded strength after the
 test was identical to that of Y=0.3 mm. Therefore, slit length L of notch
 4 is to be at least (width T of the weld electrode+positioning dimension
 Y).
 A silver sheet of 30 .mu.m in thickness was employed in the present
 embodiment. It is appreciated that a weld strength of at least 500 g can
 be obtained if the thickness of the silver sheet is at least 5 .mu.m as
 shown in FIG. 8B. If the thickness of the silver sheet is 100 .mu.m or
 more, the cover glass, if attached to solar cell 6, is inclined to cause
 generation of an unattached portion between the cover glass and solar cell
 6, whereby solar cell 6 or the cover glass was damaged in connecting solar
 cells 6 with each other in series or in parallel by welding. Therefore, a
 test for an interconnector of 100 .mu.m or greater in thickness was not
 carried out.
 FIG. 8C shows the relationship between the total of the length of the weld
 portion and the weld strength when the weld strength was measured after
 welded interconnector 1 was subjected to a thermal shock test. The total
 length of the weld portion is the weld portion length w2.times.(number of
 notches 4+1). When the weld portion total length (weld portion length
 w2.times.(number of notches 4+1)) is at least 0.8 mm, a weld strength of
 500 g is obtained as shown in FIG. 8C. Here, the number of notch 4 is 1.
 More specifically, sufficient strength can be obtained if interconnector 1
 has at least one notch, and the length of the weld portion is at least 0.8
 mm.
 According to the interconnector of the present embodiment, a weld strength
 of a sufficient level can be obtained by setting the length and the number
 of notches 4 appropriately.
 Fourth Embodiment
 FIG. 9 shows an example of an interconnector according to a fourth
 embodiment of the present invention. FIG. 9 corresponds to interconnector
 1 of the first embodiment shown in FIG. 2, formed at a continuous
 sheet-like material. Interconnector 1 of the present invention is formed
 repeatedly at a continuous sheet-like material by press working. By
 severing two cut away sections 14, one interconnector 1 can be extracted.
 When a mesh opening or permeable hole is to be provided in the connecting
 portion of the interconnector, a connector must be fabricated one by one
 since it is necessary to form the mesh opening or permeable hole by
 etching. In contrast to the conventional interconnector that does not
 allow continuity to negate reduction in cost, interconnector group 15 of
 the present embodiment can be formed by press working. Therefore, the cost
 can be lowered.
 Interconnector group 15 of the present embodiment having a length of at
 least 10 m can be fabricated easily. Interconnector group 15 can be
 accommodated wound in a reel 20' as shown in FIG. 10C. Several ten
 thousand interconnectors 1 are accommodated in reel 20'. Therefore, the
 space for storage can be reduced than the conventional case where
 interconnectors are accommodated in a pallet. The number of
 interconnectors 1 can be identified by identifying the length of
 interconnector group 15. Therefore, administration of interconnectors 1 is
 extremely simple.
 A pilot hole 13 (refer FIG. 9) for positioning is provided with respect to
 interconnector group 15. The position of forming interconnector group 15
 is determined according to pilot holes 13. Therefore, automation of the
 weld task is possible as will be described afterwards. Description of
 forming interconnector 1 of FIG. 1 continuously has been provided.
 However, the present embodiment is applicable to interconnectors 1a-1e
 shown in FIGS. 4A-4E. Furthermore, formation of interconnector group 15 is
 not limited to press working, and etching or the like may be employed
 instead.
 According to the interconnector of the present embodiment, the cost can be
 reduced since interconnector group 15 is formed by press working.
 Fifth Embodiment
 FIG. 10A is a diagram to describe a broad projection (burr) generated in
 forming interconnector group 15 of FIG. 9 by press working. FIG. 10A shows
 a cross section of the formed interconnector 1. When interconnector group
 15 is formed by press working, a broad projection 22 is generated between
 interconnector 1 and drop portion 16. If interconnector 1 is connected to
 a solar cell with broad projection 22 still formed, a scratch or crack may
 be generated in the cover glass that covers the solar cell or in the base
 plate that secures the solar cell when the solar cell is deformed by heat.
 It was therefore necessary to distinguish the front surface from the back
 surface of interconnector 1 to prevent any scratches or cracks as much as
 possible.
 FIG. 10 is a diagram to describe an apparatus removing broad projection 22
 of interconnector 1 according to the fifth embodiment of the present
 invention. This apparatus includes a reel 20 in which continuous
 sheet-like material 19 is stored, a press work die 21 forming
 interconnector group 15 at a continuous sheet-like material 19, a flat
 punch 17 to crush projection 22, and a reel 20' accommodating the formed
 interconnector group 15.
 By the move of press work die 21 and punch 17 in the direction of arrow 18,
 interconnector 1 is formed at sheet-like material 19 on press work die 21,
 and also broad projection 22 generated around interconnector 1 is crushed
 in the die by punch 17 located downstream.
 When the thickness of the sheet is small, projection 22 generated at the
 cross section of interconnector 1 shown in FIG. 10A has a length of
 approximately 10-50% the sheet thickness depending upon the material. For
 example, when the material is silver and the thickness is 30 .mu.m, the
 height 36 of broad projection 22 is approximately 15 .mu.m when press
 working is carried out.
 It is known that projection 22 generally becomes harder than the hardness
 of the parent material by work-hardening. Solar cells used for artificial
 satellites are susceptible to severe temperature environment under the
 usage status. It is required that such solar cells can withstand the
 thermal cycle condition of several thousand to several ten thousand cycles
 at -140.degree. C..about.+100.degree. C. Since the interconnector
 expands/contracts under such a severe environment, there is a possibility
 that the substrate or the cover glass of the solar cell is damaged by
 broad projection 22 to result in breakage of the panel per se, in the
 worst case. It is therefore, necessary to remove or bend laterally this
 broad projection 22.
 As mentioned above, the length of projection 22 that is generated becomes
 approximately 15 .mu.m when the sheet thickness is 30 .mu.m. High accuracy
 is required for the vertical-motion press machine and the bottom dead
 center of the die in the case where projection 22 is to be crushed by
 press working. In the conventional press machine, a bottom dead center
 accuracy of only .+-.10 .mu.m could be achieved. However, it has become
 possible to achieve a bottom dead center accuracy of .+-.1-2 .mu.m in
 accordance with improvement of the press technique. Using a press machine
 having a bottom dead center accuracy of .+-.1 .mu.m in the present
 embodiment, projection 22 can be bent laterally as shown in the cross
 sectional view of FIG. 10D to suppress the height 36 of projection 22 to
 be not more than 1 .mu.m. As a result of carrying out a thermal shock test
 under the above-described embodiment using an interconnector formed
 according to the present embodiment, it was confirmed that the cover glass
 or substrate were not broken or damaged.
 By removing broad projection 22 and eliminating the difference between the
 front side and the back side of interconnector 1, fabrication of a solar
 cell panel is facilitated and reliability thereof is improved. More
 specifically, removal of broad projection 22 in interconnector 1 prevents
 generation of scratches and cracks in the cover glass covering the solar
 cell panel or in the base plate securing the solar cells when the solar
 cell panel is deformed by heat. Thus, reliability of the solar cell panel
 is improved.
 As shown in FIG. 10C, the formed interconnector group 15 is accommodated
 and stored in reel 20'. Reel 20' in which interconnector group 15 is
 accommodated is used in the fabrication of a solar cell panel as will be
 described afterwards.
 According to the apparatus of the present embodiment, broad projection 22
 of interconnector 1 is removed. Therefore, generation of scratches and
 cracks in the cover glass covering the solar cell panel and the base plate
 fixing the solar cells during deformation of the solar cell panel caused
 by heat can be prevented.
 Sixth Embodiment
 FIG. 11 is the diagram to describe a schematic structure of a join
 apparatus of a solar cell panel according to a sixth embodiment of the
 present invention. This join apparatus includes a sever device 27 severing
 interconnector group 15 accommodated in reel 20' to cut off interconnector
 1, a reel 20" winding and collecting sheet-like material 35 after
 interconnector 1 is cut off therefrom, a convey stage 29 conveying the cut
 off interconnector 1, a welding machine 26 welding interconnector 1 to a
 solar cell 23, a welding stage 33 on which solar cell 23 and
 interconnector 1 are mounted when welded by welding machine 26, a cell
 cassette 24 in which solar cells 23 are accommodated, a cell convey device
 30 conveying solar cells 23, and a positioning camera 34 installed above
 welding stage 33.
 Sever device 27 is provided with a sever unit 28 formed of a die end, an
 edged tool and the like to cut off interconnector 1 by severing two
 regions of interconnector group 15 shown in FIG. 9 with sever unit 14. At
 convey stage 29, interconnector 1 that is cut off is held by a convey hand
 31 provided below to be conveyed on welding stage 33. In cell convey
 device 30, solar cell 23 accommodated in cell cassette 24 is held by a
 cell convey hand 32 to be transported on welding stage 33.
 Positioning camera 34 shoots the region above welding stage 33, whereby
 convey hand 31 and cell convey hand 32 are controlled so that connecting
 portion 3 of interconnector 1 and the connecting portion of solar cell 23
 are placed at a predetermined position. Following the positioning between
 interconnector 1 and solar cell 23, welding machine 26 controls a weld
 electrode 25 to apply welding as shown in FIG. 3 or 5. Interconnector 1
 and solar cell 23 subjected to welding are transported by cell convey
 device 30 again to be stored in cell cassette 24. Since positioning is
 effected by pilot hole 13 in the generation of interconnector group 15, it
 is not necessary to carry out positioning again on welding stage 23 after
 interconnector 1 severed by sever device 27 is conveyed by convey stage
 29.
 According to the join apparatus of the present embodiment, interconnector 1
 is severed from interconnector group 15 stored in reel 20' and then welded
 to solar cell 23. It is therefore possible to automate the welding process
 between interconnector 1 and solar cell 23. A join apparatus can be
 realized by a simple structure.
 Although the present invention has been described and illustrated in
 detail, it is clearly understood that the same is by way of illustration
 and example only and is not to be taken by way of limitation, the spirit
 and scope of the present invention being limited only by the terms of the
 appended claims.