Reciprocating pumps and closures therefore

Abstract

A closure for the fluid end of a reciprocating pump which uses a closure plate or assembly that is secured in a slot formed in the fluid end body so that no retaining threads must be formed in the body.

Claims

1. A fluid end apparatus for a reciprocating pump comprising: a fluid end body having one or more bores which extend inwardly into a face of the fluid end body; a closure slot which extends within the face of the fluid end body over an outer end of each of the one or more bores; the closure slot having a longitudinal length which extends between a first side of the face of the fluid end body and a second side of the face which is opposite the first side and the closure slot having an end opening in one or both of the first and the second sides of the face; an outer access opening for the closure slot which extends inwardly to the closure slot from an outer surface of the face of the fluid end body and extends longitudinally with the closure slot between the first side of the face and the second side of the face, the outer access opening having a lateral width which is (i) less than a lateral width of the closure slot but (ii) the same as or greater than a diameter of the one or more bores such that a sealing element or other object can be placed in or removed from the outer end of each of the one or more bores via the access opening; and a closure plate structure which is slideably receivable in the closure slot and has at least one width dimension which is greater than the lateral width of the outer access opening such that the closure plate structure can be placed and retained in the closure slot over the outer end of at least one of the one or more bores.

2. The fluid end apparatus of claim 1 wherein the closure plate structure is a single piece element which covers the outer ends of at least two of the one or more bores.

3. The fluid end apparatus of claim 1 further comprising a projecting structure which projects from the outer end of one of the one or more bores, wherein the closure plate structure has an aperture extending therethrough through which the projecting structure is received.

4. The fluid end apparatus of claim 3 wherein the projecting structure is a reciprocating plunger.

5. The fluid end apparatus of claim 4 wherein the aperture of the closure plate structure is threaded.

6. The fluid end apparatus of claim 5 further comprising a plunger stuffing box element which is threadedly received in the aperture of the closure plate structure, and the reciprocating plunger is slideably received through the plunger stuffing box element.

7. The fluid end apparatus of claim 3 wherein the projecting structure is a union fitting.

8. The fluid end apparatus of claim 1 wherein the closure plate structure comprises another width dimension which is less than the lateral width of the outer access opening.

9. The fluid end apparatus of claim 1 further comprising a projecting structure which projects from the outer end of one of the one or more bores, wherein the closure plate structure comprises a first plate element having a left longitudinal end and a second plate element having a right longitudinal end, the left longitudinal end of the first plate and the right longitudinal end of the second plate each have a cavity formed therein, and the first and the second plate elements are placed in the closure slot such that (i) the left longitudinal end of the first plate contacts the right longitudinal end of the second plate and (ii) the cavities formed in the left longitudinal end of the first plate and the right longitudinal end of the second plated together form an aperture through which the projecting structure is received.

10. The fluid end apparatus of claim 9 wherein the projecting structure is a seal piece extension.

11. The fluid end apparatus of claim 1 further comprising: a non-threaded bore in the fluid end body which is positioned outside of the outer access opening and extends into the face of the fluid end body to the closure slot; a threaded bore in the closure plate structure for alignment with the non-threaded bore in the fluid end body, and a bolt which extends through the non-threaded bore of the fluid end body and has a threaded distal end portion which is threadedly received in the threaded bore of the closure plate structure.

12. A fluid end apparatus for a reciprocating pump comprising: a fluid end body having one or more bores which extend inwardly into a face of the fluid end body; a sealing element for each of the one or more bores; a closure slot which extends within the face of the fluid end body over an outer end of each of the one or more bores; the closure slot having a longitudinal length which extends between a first side of the face of the fluid end body and a second side of the face which is opposite the first side and the closure slot having an end opening in one or both of the first and the second sides of the face; an outer access opening for the closure slot which extends inwardly to the closure slot from an outer surface of the face of the fluid end body and extends longitudinally with the closure slot between the first side of the face and the second side of the face, the outer access opening having a lateral width which is the same as or greater than a diameter of the one or more bores such that the sealing element for each of the one or more bores can be placed in or removed from the outer end of each of the one or more bores via the access opening; the lateral width of the outer access opening is less than a lateral width of the closure slot such that the outer access opening divides the closure slot into a longitudinally extending open central portion, a first longitudinally extending slot channel running adjacent to a first lateral side of the open central portion, and a second longitudinally extending slot channel running adjacent to a second lateral side of the open central portion which is opposite the first lateral side of the open central channel; a first elongate bar which is slideably received in the first longitudinally extending slot channel over and in contact with a first outer edge portion of the sealing element; and a second elongate bar which is slideably received in the second longitudinally extending slot channel over and in contact with a second outer edge portion of the sealing element.

13. The fluid end apparatus of claim 12 wherein at least one of the first and the second elongate bars has a rectangular cross-sectional shape.

14. The fluid end apparatus of claim 12 wherein the first edge portion of the sealing element includes a notch in which an elongate edge of the first elongate bar is slideably received.

15. The fluid end apparatus of claim 14 wherein the second edge portion of the sealing element includes a notch in which an elongate edge of the second elongate bar is slideably received.

16. The fluid end apparatus of claim 1 further comprising: a bore which extends laterally through the first elongate bar; a threaded bore in the sealing element of one of the one or more bores of the fluid end body for alignment with the bore which extends laterally through the first elongate bar, and a bolt which extends through the bore of the first elongate bar and has a threaded distal end portion which is threadedly received in the threaded bore of the sealing element.

17. A fluid end apparatus for a reciprocating pump comprising: a fluid end body having a bore which extends inwardly into a face of the fluid end body; a closure slot which extends within the face of the fluid end body over an outer end of the bore; the closure slot having a width dimension; an outer access opening for the closure slot which extends inwardly to the closure slot from an outer surface of the face of the fluid end body, the outer access opening having a width dimension which is (i) less than the width dimension of the closure slot but (ii) the same as or greater than a diameter of the bore; a closure plate structure having a first width dimension that is less than the width dimension of the access opening so that the closure plate structure can be placed in the closure slot through the access opening; and the closure plate structure having a second width dimension which is greater than the width dimension of the access opening but less than the width dimension of closure slot so that, after placing the closure plate structure in the closure slot through the access opening, the closure plate structure can be retained in the closure slot over the outer end of the bore by turning the closure plate structure less than a full turn in the closure slot.

18. The fluid end apparatus of claim 17 further comprising: a non-threaded bore in the fluid end body which is positioned outside of the outer access opening and extends into the face of the fluid end body to the closure slot; a threaded bore in the closure plate structure for alignment with the non-threaded bore in the fluid end body, and a bolt which extends through the non-threaded bore of the fluid end body and has a threaded distal end portion which is threadedly received in the threaded bore of the closure plate structure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A is a schematic cutaway side view of a prior art, high pressure reciprocating pump assembly 10.

(2) FIG. 1B is a perspective view of the prior art, high pressure reciprocating pump assembly 10.

(3) FIG. 2 is a cutaway elevational side view of one half of a prior art threaded closure 90 used in high pressure reciprocating pump assemblies.

(4) FIG. 3 is a cutaway elevational side view of one half of a prior art flanged closure 102 used in high pressure reciprocating pump assemblies.

(5) FIG. 4 is a plan view of a first embodiment 150 of the closure assembly provided by the present invention.

(6) FIG. 5 is a lateral cutaway view of the inventive closure assembly 150 as seen from perspective A-A shown in FIG. 4.

(7) FIG. 6 is a plan view of a second embodiment 200 of the closure assembly provided by the present invention.

(8) FIG. 7 is a lateral cutaway view of the inventive closure assembly 200 as seen from perspective 7-7 shown in FIG. 6.

(9) FIG. 8 is a cutaway view of the inventive closure assembly 200 as seen from perspective 8-8 shown in FIG. 6.

(10) FIG. 9 is a plan view of a linear half 206 of a two piece cover plate 202 used in the inventive closure assembly 200.

(11) FIG. 10 is an end view of the linear half 206 of the two piece cover plate 202 used in the inventive closure assembly 200.

(12) FIG. 11 is a plan view of a third embodiment 250 of the closure assembly provided by the present invention.

(13) FIG. 12 is a lateral cutaway view of the inventive closure assembly 250 as seen from perspective 12-12 shown in FIG. 11.

(14) FIG. 13 is a side view of a closure bar 252 used in the inventive closure assembly 250.

(15) FIG. 14 is a plan view of a fourth embodiment 300 of the closure assembly provided by the present invention.

(16) FIG. 15 is a lateral cutaway view of the inventive closure assembly 300 as seen from perspective 15-15 shown in FIG. 14.

(17) FIG. 16 is a plan view of a cover plate 304 used in the inventive closure assembly 300.

(18) FIG. 17 is a cutaway view of the cover plate 304 as seen from perspective 17-17 shown in FIG. 16.

(19) FIG. 18 is another plan view of the inventive closure assembly 300 as seen from perspective 18-18 shown in FIG. 19.

(20) FIG. 19 is a lateral cutaway view of the inventive closure assembly 300 as seen from perspective 19-19 shown in FIG. 18.

(21) FIG. 20 is a plan view of a fifth embodiment 350 of the closure assembly provided by the present invention.

(22) FIG. 21 is a lateral cutaway view of the inventive closure assembly 350 as seen from perspective 21-21 shown in FIG. 20.

(23) FIG. 22 is a plan view of a cover plate 352 used in the inventive closure assembly 350.

(24) FIG. 23 is a cutaway view of the cover plate 352 as seen from perspective 23-23 shown in FIG. 22.

(25) FIG. 24 is a cutaway view of an embodiment 180 of the inventive closure assembly which is a variation of the embodiment 150 illustrated in FIGS. 4 and 5.

(26) FIG. 25 is a plan view of an embodiment 240 of the inventive closure assembly which is a variation of the embodiment 200 illustrated in FIGS. 6-10.

(27) FIG. 26 is a cutaway view of the inventive closure assembly 240 as seen from perspective 26-26 shown in FIG. 25.

(28) FIG. 27 is a plan view of an embodiment 400 of the inventive closure assembly.

(29) FIG. 28 is a cutaway view of the inventive closure assembly 400 as seen from perspective 28-28 shown in FIG. 27.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(30) A first embodiment 150 of the inventive closure assembly is illustrated in FIGS. 4 and 5. The inventive closure assembly 150 comprises a cover plate 152 having a longitudinal length 153 which is sufficient to cover the outer end opening 154 of at least one bore 155, or to cover the outer end openings 154 of a series of two, three, or more bores 155a, 155b, and/or 155c, which are provided in one face 156 of the fluid end body 158 of a high pressure reciprocating pump. The longitudinally extending lateral sides 160 and 162 of the cover plate 152 are preferably linear and can have a rectangular cross-sectional shape as indicated in FIG. 5 or can be beveled or rounded or can have other cross-sectional shapes. In addition, the cross-sectional shapes of the longitudinally extending lateral sides 160 and 162 of the cover plate 152 can be the same (e.g., both squared) or different (e.g., one squared and one beveled).

(31) It will be understood that, unless otherwise specified, the term plate as used in reference to element 152, or in reference to other elements described herein, is an inclusive term covering structures of the type shown or described, regardless of whether the element was cut from or formed as a metal plate, cut from or formed as a metal bar, or cut or formed in any other manner from any desired material.

(32) The cover plate 152 is slidably received in a cover plate slot 164 which is formed within the face 156 of the fluid end body 158 over, and preferably perpendicular to, the outer end openings 154 of the bore(s) 155 or 155a, 155b, and 155c. By way of example, but not by way of limitation, the slot 164 for the cover plate 152 can be formed in the fluid end body 158 by standard machining processes such as milling.

(33) As seen in FIG. 5, the lateral cross-sectional shape of the cover plate slot 164 preferably corresponds to the lateral cross-sectional shape of the cover plate 152. In addition, the slot 164 preferably has a longitudinal length which extends within the face 156 of the fluid end body 158 from one side 159 of the face 156 to the other side 161 so that the corresponding longitudinal ends 166 and 168 of the slot 164 are open for slidably receiving the cover plate 152. Once inserted into either of the longitudinal ends 166 or 168 of the slot 164, the cover plate 152 can be moved into a closing position over one or more of the bore openings 154.

(34) Alternatively, it will be understood that the cover plate slot 164 can be milled or otherwise formed such that the slot 164 does not extend the entire distance from side 159 to the other side 161 of the face 156 of the fluid end body 158 but instead has a closed end. The closed end will preferably be located between side 161 of the face 156 and the bore 155a which is closest to the side 161.

(35) The cover plate slot 164 is spaced inwardly below, and runs parallel to, the outer surface 170 of the face 156 of the fluid end body 158. However, a centralized, longitudinally extending outer access opening 172 for the slot 164 extends inwardly from the outer surface 170 of the face 156 of the fluid end body 158 to the slot 164. The lateral width 174 of the outer access opening 172 is the same as or preferably slightly greater than the diameter 177 of the outer end openings 154 of the bore(s) 155 or 155a, 155b, 155c so that sealing members 176 can be inserted through the outer access opening 172 into the bore(s) 155 or 155a, 155b, 155c.

(36) However, the lateral width 174 of the outer access opening 172 is less than the lateral width 178 of the slot 164 and is also less than the lateral width of the cover plate 154. As a result, the longitudinally extending outer access opening 172 divides the longitudinally extending slot 164 into (a) a longitudinally extending open central portion 167, (b) a first longitudinally extending slot channel 169 running adjacent to one lateral side of the open central portion 167, and (c) a second longitudinally extending slot channel 173 adjacent the opposite lateral side of the open central portion 167. The longitudinally extending slot channels 169 and 173 extend longitudinally within the face 156 of the fluid end body 158 either (a) from one side 159 of the face 156 to the other side 161 such that both ends of each of the slot channels 169 and 173 are open or (b) at least a portion of the distance from side 159 to side 161 such that the slot channels 169 and 173 each have a closed end, which will preferably be located between side 161 and bore 155a. The slot channels 169 and 173 slidably receive and retain the longitudinally extending lateral side edges 160 and 162 of the cover plate 152.

(37) A variation 180 of the closure plate assembly 150 is illustrated in FIG. 24. In the assembly 180, a slot channel 182 is milled or otherwise formed along only one lateral side of the longitudinally extending access opening 184. In this variation 180, the lateral depth of the slot channel 182 and the milling tolerances used for forming the slot channel 182 and the cover plate 186 prevent the cover plate 186 from the pivoting in the slot channel 182 so that that the cover plate 186 and the sealing member 188 are firmly retained in the bore 190.

(38) By way of example, but not by way of limitation, the inventive closure assemblies 150 and 180 can be used for closing the access bores, discharge bores, or valve cover bores of the fluid end body 158.

(39) A second embodiment 200 of the inventive closure assembly is illustrated in FIGS. 6-10. The inventive closure assembly 200 is similar to the inventive closure assembly 150 shown in FIGS. 4 and 5 except that the cover plate 202 of the inventive closure 200 is a two piece cover plate having a first linear half 204 and a mating second linear half 206. The two piece cover plate 202 can be used, for example, for covering a single bore opening in the fluid end body 208, or for covering the center bore 210b of a series of bores 210a, 210b, and 210c, wherein the single bore or the central bore 210b of the series of bores includes, for example, a sealing element 212 having a seal piece extension 214 which must project from the attached closure assembly 200 for attaching a pressure gage or for attaching any other instrument, element or structure. The mating ends 216 and 218 of the first and second linear halves 204 and 206 of the two piece cover plate 202 have corresponding cavities 220 and 222 formed therein which, when assembled in the cover plate slot 224 of the fluid end body 208 over the bore(s) 210a, 210b, and/or 210c, form an aperture 226 having a circular shape or other shape suitable for retaining the seal piece extension 214.

(40) In addition to being useful, for example, for closing a single access bore having a seal piece extension 214, or for closing a series of bores wherein a central one of the bores has a seal piece extension 214, the inventive closure assembly 200 can also be used for closing a single bore or a series of bores wherein the single bore or a central one of the series of bores has, for example, a union fitting or other fitting projecting therefrom for attaching a flow line.

(41) The longitudinally extending lateral side edges 228 and 230 of the mating first and second linear halves 204 and 206 of the two piece cover plate 202 shown in FIGS. 6-10 have beveled outer surfaces 232 and 234. However, as with the cover plate 152 of the closure assembly 150 shown in FIGS. 4 and 5, the side edge portions 228 and 230 of the two piece cover plate 202 can be rectangular or can have other lateral cross-sectional shapes.

(42) The illustration of the inventive two piece cover plate assembly 200 in FIGS. 6-10 also differs from the illustration of the one piece cover plate assembly 150 shown in FIGS. 4 and 5 in that one or more, preferably a plurality, of bolts 236 may be used to secure each of the mating linear halves 204 and 206 of the two piece cover plate 202 in the cover plate slot 224. In each of the bolt attachments, the bolt 236 is inserted through a non-threaded bore 238 which extends into the face 240 of the fluid end body 208 outside of the centralized outer linear access opening 242 and is threadedly received and tightened in a threaded bore 244 which is provided in one of the longitudinally extending lateral side edge portions 228 or 230 of the linear half 204 or 206 of the two piece cover plate 202.

(43) A variation 240 of the closure assembly 200 for covering a single bore 243 is illustrated in FIGS. 25 and 26. Variation 240 comprises a two piece cover having mating halves 241 and 242 sized to cover a single bore 243 having, e.g., a union fitting 244 or other fitting projecting therefrom for attaching a flow line, a seal piece projecting therefrom for attaching a pressure gage, or other structure projecting therefrom. A further variation of the closure assembly 240 is that the assembly 240 is secured in the slot 239 over the bore 243 using a plurality of bolts 246 (preferably 2 bolts 246 per each half 241 and 242 of the cover) which extend through non-threaded bores 245 provide through the halves 241 and 242 of the cover and are threadedly received and tightened in corresponding threaded bores 247 formed in a radial flange 248 provided at the base of the union fitting 244. An O-ring or other sealing element 249 is also provided around the flange 248 of the union fitting 244 for sealing the bore 243.

(44) A third embodiment 250 of the inventive closure assembly is illustrated in FIGS. 11-13. The inventive closure assembly 250 is similar to the inventive closure assembly 150 shown in FIGS. 4 and 5 except that, rather than using a cover plate 152, the inventive closure assembly 250 uses a pair of longitudinally extending closure bars 252 and 254 which are slidably received in the laterally opposing side channels 256 and 258 of the cover slot 260. The slot channels 256 and 258 extend longitudinally within the face 262 of the fluid end body 264 from one side 266 of the face 262 to, or at least a portion of the distance to, the other side 268 thereof such that the ends of the slot channels 256 and 258 at or approaching the side 268 of the face 262 can be open or closed.

(45) The cross sectional shape of each channel 256 and 258 corresponds or substantially corresponds to the cross-sectional shape of the closure bar 252 or 254 or is otherwise suitably shaped for receiving the closure bar 252 or 254 therein. The cross-sectional shapes of the bars 252 and 254 can be the same or different. In the embodiment 250 illustrated in FIGS. 11-13, the closure bar 252 is entirely rectangular whereas the closure bar 254 has a greater thickness and also has a beveled outer surface 270.

(46) In the assembly 250, the sealing member(s) 272 illustrated in FIG. 12 each comprise a cover element 271 which is surrounded by an O-ring or other sealing element 273 for sealing the bore(s) 274. The sealing members 272 can differ from the sealing members 176 used in the assembly 150 in that side notches 276 and 278 can optionally be formed in the outer end 280 of the cover element 271 for receiving the side edges 282 and 284 of the closure bars 252 and 254 so that (a) the closure bars 252 and 254 prevent the sealing member 272 from rotating in the fluid end bore 274 and (b) the notched sealing member 272 also assists in holding the closure bars 252 and 254 in the longitudinally extending slot channels 256 and 258.

(47) To further secure the components of the closure assembly 250 in operating position, the closure bar 254 is preferably bolted to the sealing member 272 using a bolt 288 which extends through a bore 290 formed through the closure bar 254 and is threadedly received and tightened in a corresponding threaded bore 292 provided in the outer end 280 of the sealing member 272. In addition, a lateral holding plate 294 can also be bolted to the longitudinal ends 296 and 298 of the closure bars 252 and 254. Preferably, a similar holding plate will also be bolted to the opposite ends of the closure bars 252 and 254 unless the opposite ends of the slot channels 256 and 258 are blind.

(48) By way of example, but not by way of limitation, the inventive closure assembly 250 can be used for closing the access bores, discharge bores, or valve cover bores of the fluid end body 264.

(49) A fourth embodiment 300 of the inventive closure assembly is illustrated in FIGS. 14-17. The inventive closure assembly 300 is essentially the same as the inventive closure assembly 150 illustrated in FIGS. 4 and 5 except that a threaded cylindrical bore 302 is provided through the rectangular cover plate 304 of the closure assembly 300. By way of example, as shown in FIG. 15, the threaded bore 302 provided through the cover plate 304 allows a gland nut 306 or other element of a plunger stuffing box assembly to be threadedly installed in the cover plate 304 against one or more packing seal components 305. Consequently, the closure assembly 300 can be used in a plunger bore 308 of the fluid end body 310 for receiving and allowing the reciprocating pumping movement of the plunger 312 through the cover plate 304.

(50) In addition to being used for closing a plunger bore 308, the inventive closure assembly 300 can also be used as illustrated in FIGS. 18 and 19, for example, in a discharge bore 320 of the fluid end body 322 for threadedly receiving a union fitting 324 for attaching a discharge flow line (e.g., a high pressure flow line to a well head). The closure assembly 300 illustrated in FIG. 19 also optionally includes a locking nut 326 on the fitting 324.

(51) A fifth embodiment 350 of the inventive closure assembly is illustrated in FIGS. 20-23. The inventive closure assembly 350 is essentially the same as the inventive closure assembly 300 illustrated in FIGS. 14-19 except that, rather than being rectangular, the cover plate 352 of the closure assembly 350 has an opposing pair of flat sides 354 and 356 and an opposing pair of rounded, preferably semicircular, sides 358 and 360 wherein (a) the width 362 of the cover plate 352 between the flat sides 354 and 356 is less than the width 364 of the cover plate 352 between the rounded sides 358 and 360 and (b) the width 362 of the cover plate 352 between the flat sides 354 and 356 is also less than the lateral width 366 of the longitudinally extending access opening 368 of the cover retaining slot 370. This allows the partially rounded cover plate 352 to be inserted through the slot access opening 368 onto the bore and then rotated such that the rounded sides 358 and 360 are received in the outer, longitudinally extending channels 374 and 376 of the slot 370.

(52) In this embodiment 350, the cover retaining slot 370 in the face 380 of the fluid end body 382 preferably extends across the outer openings of all of the bores 389 in the face 380; however, the cover retaining slot can be open at both ends, open on one end and closed on the other, or closed at both ends.

(53) To prevent the partially rounded cover plate 352 from rotating during operation, the rounded cover plate 352 is preferably bolted in place using a bolt 378 which (a) extends through a non-threaded bore 372 in the face 380 of the fluid end body 382 outside of the longitudinally extending access opening 368 and (b) is threadedly received and tightened in a threaded bore 385 which extends into the outer surface 384 of the rounded side portion 360 of the partially rounded cover plate 352.

(54) A sixth embodiment 400 of the inventive closure assembly for closing a single bore 402 in a fluid end body 404 is illustrated in FIGS. 27 and 28. The assembly 400 comprises a lobed pressure closure element 406 which is removably securable for retaining a sealing member 408 between the lobed element 406 and an interior radial shoulder 410 in the outer end of the bore 402.

(55) By way of example, but not by way of limitation, the sealing member 408 can comprise a cover body 412 having a surrounding seal element groove 414 formed therein in which an O-ring or other sealing element 416 is received. Alternatively, it will be understood that the lobed closure element 406 and the cover body 412 can be formed together as a single closure and sealing element.

(56) The lobed closure element 406 is preferably substantially circular except for a single lobed portion 418 which projects radially outward on only one side of the closure element 406.

(57) A cavity 420 having an outer opening 421 with a shape corresponding to the shape of the lobed closure element 406 is provided in the face 422 of the fluid end body 404 for receiving the sealing member 408 and the lobed closure element 406. The cavity 420 further includes a radially projecting lobe channel 425 provided on one side of the cavity 420 beneath the outer surface 426 of the face 422 of the fluid end body 404.

(58) Consequently, the closure element 406 can be inserted through the outer opening 421 of the cavity 422 over the sealing member 408 and then rotated so that the projecting lobe 418 of the closure 406 is received in the lobe channel 425 of the cavity 420 to thereby lock the closure 406 and sealing member 408 in place.

(59) Thus, the present invention is well adapted to carry out the objects and attain the ends and advantages mentioned above as well as those inherent therein. While presently preferred embodiments have been described for purposes of this disclosure, numerous changes and modifications will be apparent to those in the art.