GB2044347A - High Pressure Plunger Pump - Google Patents

Abstract

The pump assembly comprises a plunger rod (1) and pressure sealing means (10) housed in a thick-walled monoblock cylinder (5) of high strength metal alloy which is cooled by means of forced liquid coolant flow through an annular jacket (30). The pump is designed for use at pressures of 1400 kilo/sq.cm. or more, and for pumping chemically active fluids. <IMAGE>

Description

SPECIFICATION High Pressure Fatigue and Wear Resistant Cylinder Assembly This invention relates to high pressure pumps of the reciprocating plunger rod type and particularly to the high pressure cylinder assembly in which such a plunger rod performs its pumping action.

Background of the Invention Although plunger type pumps are prized for their positive fluid delivery characteristics, most such units are not recommended for use at pressures much above 20,000 psi. In fact, even at lower pressures, the pliable seal ring packings generally used in such equipment have at best rather limited service life and, of course, deteriorate even faster at higher pumping speeds and/or when used with chemically active fluids. At operating pressures appreciably above 20,000 psi, fatigue cracking failures of even the steel components of the cylinder assemblies constitute an additional problem limiting the service life of such equipment even further.

Accordingly, there are many high pressure and/or corrosive fluid applications where the use of a reciprocating plunger type pump would be of great commercial interest were it not for the unacceptably short sevice life of such equipment and the prohibitive maintenance costs associated therewith.

Summary of the Invention A principal object of this invention is to improve the durability and service life of high pressure cylinder assemblies used in reciprocating plunger type pumps. Another object is to provide such cylinder assemblies having sufficient fatigue resistance and durability to be used commercially at pressures of well over 20,000 psi.

A further object is to provide packing ring seals for such cylinder assemblies which are effective at very high pressures and sufficiently wear reisistant and corrosion resistant to have adequate service life even when used in pumps handling chemically active fluids.

An overall object is to provide reciprocating plunger type pumps which are durable even under severe service conditions. A more specific object is to provide multiplex plunger pumps which can be operated economically on a sustained basis to deliver a controlled volume of fluid steadily at a very high pressure without significant pulsation.

Still other objects and advantages of this invention will be apparent from the full disclosure thereof which follows.

In accordance with the present invention, an exceptionally durable, long wearing and easily serviced cylinder, plunger rod and annular sealing means assembly having a good corrosion resistance and suitable for use as a high pressure pumping element of a reciprocating plunger type pump comprises: (1) an elongated cylindrical plunger rod of hard, high modulus material equipped at its rear accessible end portion with means for connecting same to a suitable drive mechanism to impart reciprocating motion thereto;; (2) a thick-walled, cylindrical monoblock housing of high tensile strength, corrosion resistant metal alloy surrounding the working portion of said plunger rod, said housing having a smooth internal bore slightly larger than the diameter of said plunger rod extending axially from a point near its front end rearwardly for a distance slightly longer than the reciprocating stroke of said plunger rod and, immediately to the rear of said bore, a similar coaxial bore of substantially larger diameter in order to accommodate annular seal elements; (3) pressure sealing means filling the annular space in said coaxial bore around said plunger rod and comprising a plurality of solid pliable packing rings of good lubricity backed up to the rear by a simple spacer ring of hard, substantially nonpliable material;; (4) adjustable connection means at the rear end of said housing for applying thrust against said follower ring which thereby in turn transmits compressive force against said series of packing rings; and (5) a relatively light weight, annular jacket concentrically surrounding said housing but of thinner walled construction having an inside diameter which is no more than a minor fraction of an inch larger than the outside diameter of said housing thereby defining a narrow annular passageway around most of said housing with peripheral seal rings between said jacket and housing at either end and a pair of openings through said jacket suitable for use as inlet and outlet connections in passing coolant liquid through said passageway.

For maximum fatigue resistance of the assembly, which is of vital importance for prolonging service life at the higher pressures contemplated, said monoblock housing should be subjected to autofrettage treatments involving application of internal pressures sufficient to initiate partial yielding or cold working of at least the inner layers of metal surrounding the bores therein which serve as the working pressure chambers thereof.

In its simplest form, the pressure sealing means of the present invention may be constituted by the basic combination defined in sub-paragraph (3) above. The service life of even such an elementary sealing means will generally be significantly improved by use of forced liquid cooling through an annular jacket around the monoblock housing for said sealing means as defined in sub-paragraph (5) above, and the resultant improvement is particularly worthwhile when operating at higher pressures and/or pumping speeds. However, the most effective pressure sealing means for use in the present invention, particularly at the higher pressurescontemplated, has been found to be of the general type described in my U.S.Patent 3,834,715 involving a pressurized sealing fluid which is distributed by means of a lantern ring around and within a series of packing ring elements some of which have a chevron shape or other cross-sectional shape providing a concave profile facing toward said lantern ring. The full disclosure of U.S. 3,834,715 is herewith explicitly incorporated herein by this specific reference thereto.

Although a detailed explanation of the relevance of various features and modifications of said patent reference to the particular needs of the present invention will be presented in the more comprehensive description which follows, one of the most fortunate advantages resides in the unusually large degree of improvement in service life of this preferred, fluid-pressurized-type of sealing means which is achieved by applying said forced liquid cooling through the annular jacket surrounding said monoblock housing.

Detailed Description of the Invention A more complete understanding of the present invention and the practical details involved in constructing actual working embodiments thereof can be obtained from the following description in conjunction with the accompanying drawing which is a sectional view along its axis of a unitary cylinder assembly incorporating not only the essential features of the present invention but also certain highly preferred optional measures of special value in optimizing performance, especially under exceptionally rigorous and demanding service conditions.

Referring now to said drawing, there is depicted full bodied and unsectioned an elongated cylindrical plunger rod 1 shown in a position just short of the most forward point (represented by dotted outline 2) reached by its forward end during reciprocating (the most rearward position reached in its stroke being correspondingly indicated by dotted outline 2').

Said plunger rod 1 is made of tungsten carbide or other hard, abrasion resistant material. The rear portion of said rod 1 which remains readily accessible for connection to a suitable drive mechanism is equipped with an annular collar or yoke 4 (shown in section).

The working portion of rod 1 operates within a heavy, cylindrical monoblock housing 5 the main working pressure chambers of which are two uniform axial bores 6 and 7. Bore 6 in the forward portion of housing 5 has a length exceeding the stroke of rod 1 and an inside diameter just slightly larger than the diameter of said rod. In order to provide a smooth sliding fit, bores 6 and 7 are truly concentric and coaxially aligned with a highly polished surface finish (e.g. no more than 1 6 micro inches). Preferably, the surface finish of said bores is about 8 micro inches. Likewise, the outer surface of the working portion of rod 1 is unusually smooth, i.e. at least about equal to the smoothness of said bores and preferably even better (e.g. no more than about 2 micro inches).

Bore 7 is of substantially larger diameter than bore 6 so as to provide space for annular seal pack 10 which serves as the pressure seal between rod 1 and housing 5.

Seal pack 10 in the full form illustrated in the drawing embodies the preferred, fluid pressurized type of sealing means which includes lantern ring 12 and other specialized additional elements over and above the minimal essential construction defined in sub-paragraph (3) of the summarized statement of invention hereinabove. Thus, over and above the plurality of pliable packing rings basically required, the depicted embodiment involves a plurality of such rings, including cooperating types 11, 13 and 14, at either end 6f said lantern ring 12 thus forming two separate sets of such packing rings. The forward set in this embodiment contains three individual rings 11 of generally V-shaped or chevron cross section, while the rearward set contains four such rings 11, all such chevron type rings being oriented with their concave end faces toward lantern ring 12.In this preferred type of packing means, each of said sets should have at least two such chevron rings 11 fitted between a middle follower ring 13 and an end follower ring 14 having flat radial faces on the ends away from said chevron rings.

Packing rings 11, 13 and 14 are formed of an inert plastic, e.g. a fluorinated hydrocarbon polymer such as Teflon, reinforced with a finely divided, higher melting solid filler material characterized by better thermal conductivity and heat resistance, such as graphite, molybdenum disulfide, powdered metals, glass fibers, carbon black and the like. As a further optional preferred embodiment in the present illustration, follower rings 13 and 14 are formed of Teflon reinforced with copper powder while chevron rings 11 are of graphite filled Teflon so as to provide a balanced combination of lubricity, pliability and thermal stability.

Simple block shaped spacer rings 1 5 and 16 form the terminal elements of seal pack 10 and, like lantern ring 12, are fabricated of metal or other hard, nonpliable material in order to support the pliable packing ring elements and help to maintain their uniform cooperative alignment as well as the concentricity of the entire assembly including the reciprocating plunger rod. In addition, the rear spacer ring 16, which is an essential feature even in the minimal basic sealing means construction, also serves as a free, sliding contact element against the final pliable packing ring of the seal means (i.e. follower ring 14 in the instant construction). This insures even transmittal of forwardly directed axial thrust designed to take up any slack which may develop in the annular sealing means due to compressive set, yielding or other dimensional changes in the pliable packing rings thereof.

Said axial thrust is provided by the advancement of externally threaded annular bushing member 18 as it is screwed into matching internally threaded section 9 at the rear end of housing 5, the relative dimensions thereof being such that radial end face 1 9 on the front of bushing 1 8 contacts follower ring 14 well before it is fully engaged with threaded section 9.

Heavier reliance is normally placed upon the adjustable connection device represented by this screw thread mounting of bushing 1 8 in the rear end of housing 5 in conjunction with the basic elementary seal ring construction than in the preferred, fluid pressurized type actually shown here. Thus, in the more basic construction it may prove desirable to apply sufficient axial thrust by this means to effect sufficient compressive shaping of the pliable packing rings to achieve improved sealing of contact surfaces and thereby reduce leakage through the sealing means. On the other hand, in a fluid pressurized sealing means, the principal counter pressures being applied in achieving improved sealing contacts come from the pressurizing fluid.In this case, therefore, the main function of said adjustable connection means is to insure maintenance of a good snug fit between adjacent packing ring elements so that proper cooperative interaction is realized.

The purpose of lantern ring 12 is to distribute said pressurizing fluid adequately through the interior of said pressure sealing means. To this end, a rather wide, shallow recessed groove 22 is provided in the median portion of lantern ring 12 with plural passageways 24 (two shown) leading inwardly from said groove to the outer periphery of plunger rod 1. Since said pressurized fluid must be supplied from outside the cylinder assembly, radial bore 8 through housing 5 is included for delivering said fluid in accordance with this preferred embodiment.

Concentrically surrounding housing 5 is annular jacket member 30 the walls of which are substantially thinner than housing 5 but still thick enough to provide structurally stable rigidity under the mechanical forces to be applied. The inside diameter of jacket 30 is substantially uniform along its main median portion and exceeds by a small fraction of an inch the outside diameter of the main body of said housing 5 (i.e.

its full length except for short enlarged head section 28) thus providing narrow annular passageway 32 around most of said housing.

However, the inside diameter of jacket 30 is reduced at points 31 and 33 to form short sections having an inside diameter just slightly larger than the outside diameter of the main body of housing 5 so as to provide a close sliding fit therewith. Finally, at its front end, jacket 30 also has an enlarged head section 34 the front portion of which is recessed sufficiently to fit over head section 28 of housing 5.

Thus, jacket 30 is designed so that it can be installed in working position by simply sliding it over housing 5 from the rear after first sliding on two elastic 0 rings 21 and positioning them in slots 20 in the outer periphery of housing 5 adjacent the minimum diameter sections of jacket 30 so as to form the needed peripheral seals at either end of annular passageway 32. Threaded openings 35 and 36 are provided through jacket 30 leading into said passageway 32 near the rear and front ends thereof for use as inlet and outlet connections for passing coolant fluid through said passageway. Jacket 30 is additionally modified by boring larger port 38 therethrough in concentric alignment with smaller bore 8 through housing 5 in order to allow convenient access to bore 8 by pressurized fluid from an external supply.

After jacket 30 has been slipped into place around housing 5, completion of described assembly involves installation of a few peripheral connection elements as detailed in the following steps: (1) Jacket 30 is slipped into cap member 40 so that it completely surrounds enlarged head section 34 by means of its appropriately sized forward axial bore 42 and concentrically aligned smaller rear bore 44.

(2) The nose portion of connection stem 50 containing fluid passageway 52 from the valve chamber (not shown) is inserted into appropriately dimensioned front recess 29 in housing 5 so that tapered end face 54 on said nose portion can seat on flat radial annular shoulder 3 at the bottom of said recess 29.

(3) The seal between connection stem 50 and cylinder housing 5 is made tight and jacket member 30 is simultaneously fixed in position by tightening into mating threaded holes 45 in cap member 40 a set of stud bolts (not shown) extending through symmetrically placed holes 55 in flange 56 which presses against tapered shoulder 58 on stem 50.

(4! Cooling fluid supply (not shown) can be connected to inlet 35 and a suitable discharge handling system for same (not shown) can be connected to outlet 36.

(5) Lastly, in order to activate the preferred fluid pressurized type of sealing means, the delivery means for said fluid must be completed by making a pressure tight connection to bore 8 in housing 5 via access port 38. In the present embodiment this is accomplished by use of an auxiliary force ring 60 which is slip fitted around the periphery of jacket 30 so that radially directed threaded opening 61 therethrough is concentrically aligned with access port 38 and bore 8. Cylindrical fitting 66 with enlarged front portion 68 being just slightly smaller than port 38 is inserted through said port so that the blunt end face 69 thereon seats on flat spot face 39 on housing 5 at the outer end of bore 8.Gland nut 70 concentrically surrounding fitting 66 by means of the internal recesses therein which closely follow the contours of the shoulder area 67 at the back of said fitting is then engaged with threaded opening 62 until a tight, high pressure seal is effected between end face 69 and spot face 39.

The low pressure seal between jacket 30 and fitting 66 is accomplished by means of 0 ring 65 in peripheral groove 63 located in the part of enlarged portion 68 which is surrounded by the wall of jacket 30.

As indicated in U.S. Patent 3,834,715, a good general rule of thumb in operating fluid pressurized sealing means of the type preferred herein is to feed the pressurizing fluid to the seal pack at a counter pressure substantially equal to the pressure to which the working fluid is being pressurized. Indeed, in most cases optimum performance is achieved when said counter pressure is within + 10% of the operating pressure of the pumping elements. However, excellent results may sometimes be achieved with greater than 10% differentials in counter pressure, particularly on the minus side. Much depends on the particular combination of variables in use in a particular situation, e.g. pumping speed, number, character and design of packing ring elements in the seal pack, general operating pressure levels, etc.

Another feature of primary importance in the present invention is the achievement of outstanding improvements in high pressure fatigue resistance. Special attention is, therefore, directed to the discussion which follows of the factors responsible for this achievement, most of which are concerned with the design and fabrication of the main cylinder housing since this is the element which is exposed to the full brunt of the maximum fatigue stresses involved in high pressure reciprocating plunger pumping units.

The basic approach from which improved fatigue resistance is ultimately evolved in accordance with this invention is the use of a unitary, monoblock cylinder housing for both plunger rod and sealing means in combination with a simple annular jacket for forced liquid coolant to remove internally generated heat readily through the walls of said housing.

Other closely related, major considerations of pervading importance in the ultimate realization of the present concept are the materials of construction and methods of fabrication of said cylinder housing. I have found that the best materials of construction for this use are the high tensile strength, iron based alloys, especially those containing significant amounts of chromium and some nickel. Preferably, the concentration of chromium should be at least about 10% by weight and the content of nickel should be at least about 4% by weight Such materials provide an added advantage of excellent corrosion resistance, which contributes further to long term integrity under severe service conditions.

Ideally, whatever alloy is used should be in a highly refined form, free of all dirt and discrete foreign matter in order to avoid even small discontinuities which might serve as points for initiating stress concentration. Accordingly, the alloy billet from which the cylinder housing is fabricated should be produced by a technique such as vacuum arc or electro slag remelting.

Such iron based alloys containing about 11- 19% chromium and about 39% nickel as the major additives are good choices.

Excellent results have also been obtained from similar alloys containing a small amount of molybdenum and which are precipitation hardened by appropriate heat treatment. One such alloy containing about 13% chromium, about 8% nickel and about 2% molybdenum together with 0.05% carbon and other minor constituents has proved to be ideal.

In fabricating the cylinder housing, it is vitally important to provide a smooth, polished internal surface finish on the high pressure bore chambers, as already described. It is also desirable to avoid sharp edge corners within the high pressure chambers thereof. For maximum fatigue resistance, these high pressure chambers of said housing should be subjected to an autofrettage treatment sufficient to initiate cold flow or yielding of the boundary layers of metal adjacent the bores thereof, after which the inner surface of said bores should not be disturbed by machining, honing or polishing, etc.It will be apparent, therefore, that in units such as that depicted in the drawing where the outer diameter of seal pack 10 is much larger than the plunger rod diameter, the autofrettage treatment should be done in two stages because of the great difference in internal pressure required to effect yielding in the area surrounding bore 6 compared to the area surrounding bore 7.

In other words, in fabricating a cylinder housing of this hyper pressure type, a bore the size of bore 6 would be drilled through the entire body of housing 5 first and after honing and polishing at least the required front portion thereof, the necessary very high pressure autofrettage treatment would be effected. Then after fashioning larger bore 7 as shown in the rear portion and honing and polishing same properly and completing any other interior machining such as radial bore 8, etc., the second atuofrettage treatment at the lower pressure needed for the section of housing 5 surrounding bore 7 would be effected.

One of the most promising applications for the pumping elements of this invention is in delivering catalyst solutions to polymerization reactors operating at very high pressures, e.g. typically from about 25,000 psi to about 50,000 psi. In such chemical reaction related fields of service, steady delivery at an accurately controllable rate with minimal pressure pulsations is highly desirable. At lower pressures, it appears that the combination of two of the described cylinder assemblies through a suitably phased drive mechanism would be adequate. However, at pressures of 25,000 psi and above, the compressibility of liquids becomes a significant factor so that a combination of three or more cylinder assemblies is preferred.

For example, a combination of three equal sized cylinders assemblies each built as shown in the drawing with a 3/8" diameter plunger rod was operated from a common crank shaft providing a 4-inch stroke for each rod and a 60C differential in phase angle of strokes between cylinders 1 and 2 and cylinders 2 and 3. The resulting unit was tested in pumping a dilute solution of organic peroxides in hexane solvent supplied at a suction pressure of about 1 50 psi and delivered at a reactor pressure of about 30,000, using a variable speed direct current motor connected to said crank through a reduction gear train allowing crank shaft speeds of 10 to 200 rpm.Resulting performance was excellent with exceptionally accurate delivery rates, and pulsation in delivery pressures seldom exceeding 3%, especially in the mid range of crank shaft operation of from about 40 to about 120 rpm, which represents the more normal range of practical interest.

A particularly suitable type of variable speed motor for this service is a DC shunt motor in which the speed can be varied by changing the armature voltage while maintaining constant field voltage. The speed of such motors can be very accurately controlled through the use of electrical sensing and feed back circuits which are commercially available. For example, such speed control equipment is sold by Reliance Electric Company under the trade name MAXPAK SOLID STATE DC V*S DRIVE.

Although pumping units built in full accordance with this invention have not been in sustained use for a sufficient period to establish their ultimate fatigue life, no signs of incipient failure have been found in my preliminary inspections thus far. Also, it is already clear that average service life of pressure seals has been greatly increased by the use of forced liquid cooling of the cylinder housing wall surrounding same.

Having described my basic invention generally as well as preferred specific embodiments thereof, the principles thereof will now be clearly understood. Accordingly, it is intended that the appended claims apply to all modified and related forms of my invention representing clear equivalents or design variations thereof obvious to those skilled in the art.

Claims (22)

Claims

1. A durable cylinder, plunger rod and annular sealing means assembly having good resistance to corrosion and fatigue when used as a high pressure pumping element of a reciprocating plunger type pump comprising: (1) an elongated cylindrical plunger rod of hard, high modulus material having an accessible portion to the rear equipped with means for connecting same to a suitable drive mechanism to impart reciprocating motion thereto;; (2) a thick-walled, cylindrical monoblock housing of high tensile strength, corrosion resistant metal alloy surrounding the working portion of said plunger rod, said housing having a smooth internal bore slightly iarger than the diameter of said plunger rod extending axially from a point near its front end rearwardly for a distance slightly longer than the reciprocating stroke of said plunger rod and, immediately to the rear of said bore, a similar coaxial bore of substantially larger diameter; (3) pressure sealing means filling the annular space in the said coaxial bore around said plunger rod and comprising a plurality of solid packing rings of good lubricity and pliability and having a follower ring of hard, substantially nonpliable material at the rear end thereof;; (4) Adjustable connection means at the rear end of said housing for applying thrust against said follower ring which thereby in turn transmits compressive force against said series of packing rings; and (5) an annular jacket concentrically surrounding said housing but of thinner walled construction, having an inside diameter which is no more than a minor fraction of an inch larger than the outside diameter of said housing thereby defining a narrow annular passageway around most of said housing with peripheral seal rings between said jacket and housing at either end and a pair of openings through said jacket suitable for use as inlet and outlet connections for passing coolant liquid through said passageway.

2. An assembly as described in claim 1 wherein said cylindrical plunger rod is constructed of tungsten carbide.

3. The assembly of claim 2 wherein the outside of said rod is honed to a smooth surface finish of not more than 1 6 micro inches.

4. The assembly of claim 3 wherein said surface finish is not over about 2 micro inches.

5. An assembly as described in claim 1 wherein the means for connecting said plunger rod to said drive mechanism comprises a collar shaped element which is shrink-fitted around the accessible rear portion of said rod.

6. An assembly as described in claim 1 wherein the metal alloy of which said monoblock housing is constructed is a highly fatigue resistant iron based alloy containing at least about 10% chromium and at least about 4% nickel by weight.

7. The assembly of claim 6 wherein said alloy also contains a significant amount of molybdenum and is precipitation hardened through appropriate heat treatment.

8. An assembly as described in claim 1 wherein the metal alloy of which said monoblock housing is constructed has been vacuum arc remelted to eliminate discrete foreign matter and resultant discontinuities therefrom.

9. An assembly as described in claim 1 wherein each of said two bores in said monoblock housing is subjected to high pressure autofrettage treatment after completion of all required machining thereon including honing of the surfaces of the bores therein.

10. An assembly as described in claim 1 wherein said sealing means includes a centrally positioned lantern ring having a shallow recessed groove of substantial width in the median portion of its outer periphery with connecting passageways therefrom leading to the inner periphery thereof at several points and means to provide a sealing fluid under pressure to said groove, and at least one of the solid packing rings in said sealing means in either direction from said centrally positioned lantern ring having a generally chevron shaped cross-section, all such chevron shaped rings being aligned so that their concave ends face toward said lantern ring.

11. The assembly of claim 10 wherein said lantern ring is made of metal and said solid packing rings are constructed of a fluorocarbon polymer, nylon or other low friction plastic resin reinforced with fine solid filler material of higher melting point.

12. The assembly of claim 11 wherein said fine solid filler material is chosen from the group consisting of graphite, molybdenum disulfide, carbon black, glass fiber, and finely powdered metals.

13. An assembly as described in claim 1 wherein said adjustable connection means comprises a short terminal section at the rear end of said housing which is internally threaded and an annular bushing externally threaded to mate with said internally threaded terminal section so that the forward portion of said bushing can contact said follower ring after it has become firmly engaged but before complete engagement with said internally threaded section.

14. An assembly as described in claim 1 wherein said annular jacket has limited portions at either end having a reduced inside diameter which is just sufficiently greater than the outside diameter of said housing to provide a close sliding fit therebetween and said low pressure seals are provided within said portions by 0 rings located in circumferential grooves in one of the interfacing surfaces involved in said sliding fit.

1 5. An assembly as defined in claim 1 wherein said annular passageway is less than about 1/4 inch in depth.

1 6. The assembly of claim 1 5 wherein the depth of said annular passageway is between about 1/1 6 and about 3/16 of an inch.

17. An assembly as described in claim 1 wherein said inlet connection is located slightly in front of said rear end peripheral seal ring and said outlet connection is located slightly to the rear of said front end peripheral seal ring.

1 8. A multiplex reciprocating plunger type pump each of the individual pumping elements of which is constructed in accordance with claim 1 and the drive mechanism is a common crank shaft operated through a suitable gear train by a variable speed electrical motor.

19. The multiplex plunger pump of claim 18 wherein said electrical motor is a d-c shunt motor the speed of which is controlled by varying the armature voltage thereto.

20. The multiplex plunger pump of claim 19 wherein an automatic feedback sensing and control circuit is applied to regulate voltage to the armature of said motor thereby permitting the speed of said motor to be maintained within very close tolerances.

21. A cylinder, plunger rod and annular sealing assembly constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

22. A multiplex pump including a plurality of individual pumping elements each of which comprises an assembly according to any preceding claim and constructed and arranged to operate substantially as hereinbefore described with reference to the accompanying drawing.