US2545036A - Expansible drill bit - Google Patents

Description

March 13, 1951 A. w. KAMMERER ExPANsIBLE mam. BIT

2 sheets-sheet 1 Filed Aug. l2, 1948 IN VEN TOR. Aem/Ee W KAM/MERE@ March 13, 1951 A. w. KAMMERER EXPANSIBLE DRILL BIT 2 Sheets-Sheet 2 Filed Aug. 12, 1948 l I- INVENTOR. ecf/Ee W KAMMERER #Tice/5% `ward position to which Patented Mar. 13, 1951 UNITED STATES PATENT OFFICE.

' Y 2,545,036 kEXrANsIBLE DRILL Brr Archer W. Kammerer, Fullerton, Calif. Application August 12, 1948, serial No. 43,789

17 Claims. (01.;255-78) No. 597,744, filed June 6, 1945, which issued as Patent No. 2,466,991, and Expansible Rotary Drill Bits, Serial No. 686,806, led July 29, 1946, and Expansible Rotary Drill Bit and Method of Assembling the Same, Serial No. 779,592, led October 13, 1947.

An object of the present invention is' to provide an expansible drill bit embodying improved means for releasably holding the cutters of the bit initially in retracted position.

A further object of the invention is to provide an expansible drill b it embodying a positivev acting, hydraulically releasable device for initially holding three or more angularly spaced cutters inv retracted position. In this connection, the device is also applicable for holding one or two cutters in retracted position.

Another object of the invention is to provide an improved lock device in a rotary expansible drill bit for holding cutters positively in the outtheyhave been previously expanded.

This invention possesses'many other advantages, and has other objects which may be made .more clearly apparent from a consideration of a ltion; but it is to be Yunderstood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best dened by the appended claims.

- Referring to the drawings:

Figure 1 is a side elevation of a drill bit embodying the invention;

Fig. 2 is a cross-section taken along the line 2-2 on Fig. 1;

Fig. 3 is an enlarged `partial longitudinal section taken along the line 3-3 on Fig.' 2, with the cutters locked in retracted position;

Fig. 4 is a view similar to Fig. 3, withthe cutring I'I atthe upper end of the body, suitably 2 `A is attached to a string of drill pipe B, by means of which it is lowered through a well casing C in a well bore to a point below the casing shoe D at which enlargement of the bore hole is to commence. The drill bit preferably has a pilot bit I0 at its lower end for centering the bit in a hole that may have already been drilled, or for drilling' the central portion of new hole in the absence of pre-existing hole. The main portion of the bit is' capable of enlarging ther bore the drill pipe string B. This mandrel includes an lupper kelly or drill stem member I4 slidably splined to the main body I5 of the bit. As disclosed ,in the drawings, the exterior Ida of the kelly is hexagonalv inshape, and is telescopically received in a companion hexagonal socket I 5a within the body'. The mandrel has a limited range of longitudinal movement within the body, its upward v.movement being limited by engagement of an `external shoulder I 6 on the kelly with a retainer secured thereto, as by the use of welding material I8.

- vThe body I5 has a plurality of eXpansible parts .mounted on it, comprising rcutter supporting members I9 pivotally mounted in body slots 20 on pivot or hinge pins 2l suitably secured to the -body, as'by the useof welding material 22. Each cutter supporting member consists of a depend- 26, 2l are preferably placed between each cutter .25 and bearing pin 24, the roller bearing 26 transmitting radial thrusts and the ball bearings`2l in place through a passage 28 in the bearing supports, which is then closed by a plug 29 welded to the pin-"24. The plug or pin 29 depends from the Ypassage 28 and is used to hold the cutters 25 lin retracted position, as pointed out below.

Lwhich an elastic expander 3| bears.

ters released/and locked in expanded position; l

and

Figs. 5, 6 and 7 are cross-sections taken along the lines 5-5, 6-6 and I--'I',l respectively, 0f

Fig. 4.

...Each cutter supporting member I9 also includes anupwardly extending arm 36, against This eX- pander, kin the form of a compressed coil spring,

" is received within a retainer pocket 32 in the Ae .Shown in the.. ,drawing the wary dell bit body I5, and exerts its force against the arm 30,

tending to swing` it inwardly and thus urge the cutter'25 on the other side of the `fulcrum pin 2| l in an outward direction. The extents; of this 3 outward movement is limited by engagement of stop shoulders 33, 33 on opposite sides of the cutter supporting member I9v with cooperable body stop shoulders 34, 34.

After the cutters 25 have been expanded outwardly by the expander springs 3l to the maximum extent, they can be locked in this position by a tubular memberi3`5 of the mandrel H, which is piloted in the kelly i4. This member is provided with a lock portion 41, movable from an upper position in transverse aligmnentwith inner supporting member recesses 36, permitting retraction of the cutters, to a lower pOSition opposite lugs 3l formed on andV projecting irlwardly from the supporting member legs l2'3jp1`v'eventing retraction of the cutters.

The tubular member 3,5 is connected in swivel fashion. t the kel-1y i4., to'permit relative arcuate er lary' movement therebetween, which 'can coeur to a slight extent. However, the kelly and tubularY member are coupledA together for longitudinal movement in both directions.` is accomplished, by .providing an anti-,friction ,thrust bearing. between a boss cr Shoulder 35.1 0n the tubular member and the kelly HL The shoulder SS is received within a lower socket Mb the kellyI and has a vtoroidal raceway weon its exterin around` which; a plurality 0i bearing balls 1l. can ride. These balls are also received in; an opposed toroidal ralceway'lZ in the kelly.

The balls il are insertable into the raceways through a hole on passage` 13 extending through through the external shoulder I6 on the kelly and communicating with its internal. race 12. After the balls ,have thus been disposed in position, the lliole` is closed by Ia suitable pin'or plug 1'4, which ispreventedfrom moving outwardly `of the kelly bythe inner wall oi the surrounding body I5.

The tn bular member 35 has-fan 'upperl perti'on 35g; extending into the central bore 14dy of the keuygwith the'uuper'termines 1s Qf the member 35d ila-ring upwardly and outwardly, to guide a ball 1 6; or corresponding element, intothe central passage 35e through the' Vtubular memberl 35. Fluid pumped down the drill string B wil'flow through. the kelly ein l?, and. int@ ill?- @wel passage 35e. Itis prevented'irom flowing around the exterior of, the tubular member 35 by able 'peeking 11 disposed 'between the. @Per portion 35u', ofl the tubular member and thekjelly adjacent the upper endof the tubular member shoulder 39.

The arrangement between `the tubular member 35andkellyy i44i`s such thatboth downward and upward movement is transmitted*betweenV the kellyfid and tubular member'iltfrom oneraceway 'i0 or 12, throughthe ball bearing elements 11, to the other raceway 'l2 or il).A In this manner, the kelly i4 and tubular member 35 are caused to move jointly in both longitudinal directions, but they are free toV partake freely of relative movement therebetween.

Themandrel Il'. is normally held in its upper position with respect to the main body i5 ofthe bit and the supporting members lby a helical retractor springA 38 encircling the tubular member 35 With its upper endfengaging, the mandrel shoulder 38am@ its lower. end engaging a'sprris seat MiI at the lower endof the hexagonallbody socket a.v This spring seat ViiiI alsoserves as an upper bearing guide. for the tubular mandrel member 35, whose lower end` isslidable within a lower bearing; guide 4i below me `lugs, stumm integral. Wih Orf Securdjta tli'e. mais bodvfQf the bit. The two guides 150,4 i' form as'paced twopoint support for the mandrel member 35 and assist it in resisting inward movement of the cutter legs 23 to retracted position during the reaming or cutting operation.

Circulating iluid can pass downwardly through the string of drill pipe B and through the tubular mandrel il for ejection from its lower discharge nozle candonto the critters 25, to cleanse them of cuttings and iiush the latter from the drilling Yarea to the top of the well bore. This circulating fluid is, also availed of to unlatch the cutter supporting members I9, in the event it is desired toholdthem positively in retracted position.

The cutters may be retained initially in retrated positionsagainst the expansive forces of theI springs 3i by means of a trip device. This device includes a holding plate or member 'i8 secured tothelower endof a central rod '1.9, whose .urperend projects into the tubular member passage35e.'` A head 3U' is secured to the upper end of the rod, which/has peripheral notches 8i therein, inordertoallow fluidsy to pass upwardly into the central passage 35e and into the drill string B, The holding member 'it has spaced holes 8,2 infits outer portionV for receiving the lower ends 219e; of thelball bearing plug or pins 29.

When the holding device` 'I8 is disposed over the pinsf 29, the cutter'supporting members i9 arepreventedirom expanding under the influence of the springs 3|, thereby holding the cutters 25 in retracted position. It is to benoted that the pinsA 2,9 are inclined initially in a downward and outwardrdirection, so as tov prevent the holdingl memberA 'lilv and the" rod 79 connected theretofrom moving downwardly until purposely released, which do wnv'va'rd'4 movement-would allow outward expansion of the'cutters 25. Such releasefcan oscuras a result of fluid pressure acting dgni/nwardly` onr the ball "i6, which 'can fest. Qthahead.-

During low` ling of the cutting tool to the point at which the reaming operation Aisto begin, the holding device T3, 13 4retains the cutters 25 in retracted position: During't'his lowering operation huidV may flowv Yupw'arizlly aroundthe device rod 'lil vandthrough the notches or recesses 8i in' the head {it} 'into the tubular member passage 35e. The fluid lifts the ball "i6 upwardly withi't, as limited by a rscreen 83 secured tethe upper end of the pin /I2 by screws 84, and then continuesits upward'fiowing to fill the tubular drill string B with the drilling fluid.

when the peint in the weil 'here has been reached at which the rearning operation is vto begin, the pumps at the toprof the well bore are started and drilling iuid'pumped down the drill string B- The ball is then forced down through the passage 35eA onto the head.v 80. Since the diameter of the ball is preferably equal to the diameter of passage 35e, it substantially closes the passage 35eA to rdev vn.ward flow 'of iiuids, which allows the pumps at the topogf the well bore to exert a pressure on the fluid in the drillvstring B and tubular member 35'. ThisA pressure acts dofvvnwardly ony thehall 1B, which correspondingly exerts a, downward.` force on vthe holding 4device '19,` 78, shiftingA the letterina downward direction ofi. theririsjZS., andtheballl and rod 19 @0m- 'pletely out 'f the `passage 35e. The pins 29 are thereby releasedgallowing the springs 3l to expand the cuttersv 25outwardly, while at the same (time.Vv the p ,isSage 35e 'isn free from, restrictions,

, shifts its connected mandrel within the body I against the action of the reits ends being held together by a clip 86, in a manner well known to warehousemen. A jarring action, such as that incident to rotation of the bit, is sufficient to break or snap the strap 85,

which is thus released from the legs 23.

If desired, the band 85 may be used to holdv the cutters retracted in lieu of the trip device 18,

In the operation of the device the tool A is mounted on the lower end of the drill string B, with its parts held in retracted position by the latch or trip device 18, 1S, and also, if desired, by the strap 85, as shown in Fig. 3. In this position of operatiom the compressed retractor spring 38 holds the mandrel II and its kelly I4 in an upward position with respect to the body I5, as determined by engagement of the kelly shoulder I6 with the body retainer ring I1. With the mandrel in this position, its lock portion 41 is elevated above the lugs 31 on the cutter supporting members I9, being received within the inner recesses 36 in the supporting members, which permits the latter to be held inwardly against the action of the expander springs 3I.

The tool is lowered through the well casing C, and upon reaching the position in the well bore below the casing shoe D at which the drilling operation is to begin, the pumps are started at the surface of the well bore, the fluid under pressure in the drill string and bit A forcing the trip device 18 off the pins 29, releasing the cutting supporting members I9 for outward expantion under the iniiuence of the springs 3|. If the bandor strap 95 is used, rotation of the bit by the drill pipe B will break the band and release the cutter supporting members I9.

The drill string B is then rotated to rotate the main bit body I5 through the splined kelly and body connection Ida, I5a, the expander springs 3l forcing the arms 30 inwardly and the cutters 25 outwardly against the formation. Rotation is continued without moving the drill string longitudinally until the side cutters 25 enlarge the diameter of the hole to the maximum extent, as determined by the eventual abutting of the supporting member stop shoulders 33 with the companion body stop shoulders 34. Thereafter, the drill string is lowered to cause the formation shoulder E, produced in the well boreby the cutters 25 under the action of the expander springs 3I, to support the cutter members I9 and body I5, and prevent their downward movement.

Since the body I5 cannot move downwardly, drilling weight imposed on the drilling string B II downwardly tractor spring 38 until' the lower end 48 of the kelly I4 engages the upper spring seat and guide 40. This downward movement also shifts the tubular member downwardly, because of the interlocking ball thrust bearing 10, 1I, 12, to position the mandrel or tubular member lock portion 41 opposite and in alignment with the lugs 31 on the inner portions of the cutter supporting members I9, providing a positive lock by prevent- Ving inward movement of the cutters. So long as down weightis imposed on the drill string B, and the cutters 25 rest on the formation shoulder E, the cutters are prevented from moving inwardly by engagement of their lugs 31v with 4the mandrel lock portion 41. It is also to beA noted that further outward movement 'of the cutters beyond the predetermined maximum reaming diameter is prevented by contact between the supporting member shoulders 33 and the body shoulders 34, through which the drilling weight is transmitted to the roller cutters 25, thusV` relieving the hinge pins 2| of this load.

Drilling is continued by rotating the drill bit and imposing the proper drilling weight on the cutters to' cause theirremoval of the formation material and reaming of the hole in a downward direction for the desired extent or length. When the drill bit is to be retracted and removed to the top of the well bore, all that need be done is elevate the drill string B, which moves the side cutters 25 above the formation shoulder E, and permits the retractor spring 38 to press downwardly on the body I5 and move it, together with the cutter-supporting `members I9, downwardly with respect to the mandrel I I. This action repositions the mandrel lock portion 41 opposite the supporting member recesses 36 and above their lugs 31, because of the ball bearing coupling 1I, permitting inward swinging of the cutters 25 and their supporting members' I9 when the tool passes back into the casing C, upon elevation of the drill string. The cutters 25 and their supporting members I9 will ride the wall of the casing C during elevation of the string until the tool is removed from the top of the well bore.

The lock portion 41 of the tubular member preferably has flat faces 41a engaging corresponding fiat faces 31a on the lugs 31 extending inwardly from the cutter supporting members; These at faces are preferred, to present a surface contact between the members, and thus `increase the lead carrying capacity lof the lock device, enabling it to resist to a greater extent the reactive force of the formation tending to press the cutters 25 inwardly from their expanded positions. The remaining portions of the-tubular members 35, namely, the shoulder 39, the upper section 35a above the shoulder, and the portions which ride inthe upper and lower bearing guides 40, 4I are all circular in cross-section to permit relative rotation, even to a slight extent, between the tubular member 35 and the kelly I4 within which it is received.

The relative rotation of the tubular member 35 and its locking portion il with respect to the driving kelly I4 is important, since it permits the lock portion 41 to adjust itself with respect to the lugs 31 on the cutter supports I3 and thus insures a surface contact therebetween. There is a slight play of the supporting members i3 on their hinge pins 2I, permitting a slight angular adjustment of the supporting member about a longitudinal axis with respect to the expander portion 41. In the event that an error has been made in the mounting of the pin 2 I in the body I 5, the supporting member i9 may pivot slightly about the lcngitudinal axis, and this pivoting action, coupled with the swivel arrangement ofthe tubular member 35 and lock portion i1 with respect to the kelly I4 (which permits the tubular member 35 to rock or move about the body axis), Yonere assurance that the contact between the lock portion 41, 41a and the lugs 31, 31a will be a surface contact. The swivel action of the tubular member 35 in the kelly I4 is facilitated and is kept free by the ball bearings 1I.

` The inability of the tubular member 35 to swivel or move about the bit axis might merely result in a line contact between the cutter lugs seemed hole ofeiesser @lamelle ;izillingfoperationf and@ niiaeizf'bejeweeh. allieL leekwmlllon an,

feather.enanfthe;desieahle :.sufffaee Gema fiswivel; oonneeeioo'neeveete lille liaesmiesion Of sters r; 2 5 inwandily frlm .-Suohwear would @Crm1 Wardl, and. would :resille pro on ofi a dates@ runnen to the body l5 need not pass throngh themizibq a annehriber135 :and its loeklllel verlieh 4l Onto lille supporting members 1.9.

frotary;drillhittlias heenlprovidedsin Whlelleesllr- Yance is fhad; that thegoufterS- Willabe lleld rellelled .in 1a positivermanner duringlowering of the bll :through the well leasing and well hole io the llesiredpointat which-the holesehlerglneoperallen :is to;o 111 11ll enoel .Thereaten theholdinelevlee .isf -rem oved hy lpositivehydranlleelly opelelele ;means, which, nevertheless, does not interfere with automatiolllne ofrthef-drlllfserihawlfihlhe fters -clisposed T120 Adegrees apart) to befheld -posimore cutters insures appropriailecentering-oithe biifin tnewellfbore, arnetltsfpsoduollen-'Offan er1- larged hole circular ln erossfeeolell- ;1; r1 eddiftion, assurance; is had-'phafgthe i lockl device may aooommodateiteeleedily, tonrovielelllefpreleel -oontactbetween the look'portionlll' andg the ings 31 OIL-the cutter supportinggnembeijs.

-V`The Vinventor claims:

1, Ina rotary drill,bitainainbody-haying a fluid passage; outtelvmeans Gel-fried byeadllqdy for lateral; movement with :respect to said body;

means engaging saixieutten zineans`- ior-exnangilng said cutter means laterallyfellllwerd; end elch Y lmeans connected Vtoy said cutters means-and-extending into said passage, andv releasablebyA 4the cutter means in an inward position.

afina roraryfdrillbitr amelnf bodylieville e fluid passage-r ouitermeans carried loaseid body x means engaging. said cutter lineagel for expanding said clutter means Alae rally Outward A1a teh means connected to said; cutter fmeansgandfezgtnenging into said fluid passage for releasablyfholdingsad 8 1e e-:laelely ellll bll= e leale body-fon lelelel ,moy/,eugene in; res-neet zo 'saidfboiy' havn eine eaeeeew ellllel* meen'e erlledlbsr seid bpdy; means elle'eelllle seid bulle? means for ."e'xpallllle s eend Sluiter ineens lelelelly beware? le'l'eh mees eonneetedio fsaid cu-tter means yand"extending intodsailnid lnassage `for yreleasably liolilriig ysaid. onizteijmeans yin ijetifaclzed posibionilancl la ball moyable in said passage inf/o engagement .l0 een leleh f lleees* for -enehllrlesui'd iiider pressage in said passage Ytorelease ygrid latch means from said cutter means. A j'. I n 1anotar-y drill baitga inan body having a leid-Rennie; `,miller eeeeee d Joy Szllliedl l5 lelelael movement Wllh'le el :lee-iid belli' i eirleellsv eneeelee seid Cutler means fsr exlnd- @nasale weer ineens laterally' onlwed eid leiehfmeelle eoflneelied le Sallellile d ller releesoely llellllle eeldeuller meelflslln .ll 2o inward, position, and loelrullelilelllle moieble wlthinselel Passage eeeeeeeble 'with eeidlaih means to V,release Seid leleh lleen's" fromhldlng v said eener means .in eileh @Walid poelllerlf 5. 4In a rotary/ drill bit: y.a main Qbody; :cutter :Zanieans l innund on said body for lateral .,rnoy- Ymerli: wllhreseeee lo Seid body: .Serine eheesineseld eviter means fer `l eno ,anelllle said Cult-er meellel-eterallx outward :el-mandrel heling f aifllllllnessaee and aeleoled ,lo be. oonneeledlo 30 a,tubulei-dnllshha eelimenllrelll ne elf'l'ebly -lsplined lo eeid bold? and movable lh one lonelniellnel ollreellen alone .Seiidlwdy lo ,-eos'itlell Anr renting ieweldmovement ofiSeld-eulleiineens .f .fiom llsolilwardly expended. posltlenk, andhyaulieelln operable leech means extending V4hilo lelfflilld :passage and oo rllleeled .loeeldj eller Ineens fior fleleasebly holding Seid Cutler lleells f hf-an inward position ,eeensethe eellonfoffeaid spring means.

6- In e enters drill ibllfesmeln body; .llllel meensmoullted en lseld bodyfor laieelfbi/e- ,.Airleni with reepeel lo said b9dy; sp1l1lsmahs :engaging :seid ellller. means `f 9r exoelld l rie sld eener -lelerellyeutweldl,emehelrellialf- `assagea clY dantL d to lee1 onnected 1 lelrllleylieelll--reelldrel her @ably en fled flo Seid hed-y fend-movable' elirlel eifeelloaeloeeSeidl-belli@ I Epreventing l inward moi/lement; -ofeeldrotatable on said supporting member; ball bearing elementsv between said cutter and supporting member; said supporting member having a hole through which said elements are insertable in their bearing position between said cutter and supporting member; means closing said hole; means connected to said hole closing means for holding said supporting member and cutter in retracted position and means carried by said body engageable with said holding means for releasing the same.

9. In a rotary drill bit: a main body/having a fluid passage therein; a supporting member mounted on said body for lateral movement with respect to said body; a cutter rotatable on said supporting member; rollable bearing elements between said cutter and supporting member; means for preventing removal oi said elements from their bearing position between said cutter and supporting member; means eng-ageable with said supporting member for expanding said cutter outwardly; and latch means extending into said passage and connected to said preventing means for initially holding said supporting member and cutter in retracted position, said latch means being releasable from said preventing means by the pressure of fluid in said passage.

10. In a rotary drill bit: a main body having a iluid passage; cutter means carried by said body for lateral movement with respect to said body; means engaging said cutter means for expanding said cutter means laterally outward; latch means connected to said cutter means and extending into said passage, and releasable by the pressure of iiuid in said passage, for initially holding said cutter means in an inward position; and a readily breakable band encompassing said cutter means to hold said cutter means in retracted position.

11. In a rotary drill bit: a body; cutter means mounted on said body for lateral movement with respect to said body; means for expanding and holding said cutter means laterally outward, comprising a iirst member connectable to a drill string and slidably snlined to said body: .a second member rotatable with respect to said rst member and engageable with said cutter means for holding said cutter means laterally outward; and rollable elements between Said rst member and second member coupling said members together for .ioint longitudinal movement.

12. In a. rotary drill bit: a body; cutter means mounted on said body for lateral movement with respect to said body; means for expanding and holding said cutter means laterally outward, coroprising a rst member connectable to a drill string-and slidably splined to said body; a second member rotatable with respect to said first member and engageable with said cutter means for holding said cutter means laterally outward; said first member and second member having opposed raceways; and balls in said raceways coupling said members together for joint longitudinal movement.

13. In a rotary drill bit: a body; cutter means mounted on said body for lateral movement with respect to said body; means forexpanding and holding said cutter means laterally outward, comprising a rst member connectable to a drill string, said first member being positioned in and slidably splined to said body, a second member within said rst member and engageable with said cutter means for holding said cutter means laterally outward, said first member and second member having opposed raceways; balls in said raceways coupling said members together for joint longitudinal movement; said rst member having a hole therein through which said balls are insertable in said raceways; and .a plug in said hole.

14. In a rotary drill bit: a main body ha'ving a fluid passage; cutter means carried by said body for lateral movement with respect to said body; means engaging said cutter means for expanding said cutter means laterally outward; releasable latch means connected to said cutter means for holding said cutter means in an inward position, said latch means including instrumentalities extending into said pass-age and subject to the force of fluid in said passage to remove said instrumentalities from said passage and release said latch means from cutter means holding position.

15. In a rotary drill bit: a main body; a plurality of supporting members mounted on said body for lateral movement with respect to said body; a cutterJ rotatable on each of said supporting members; a set of rollable bearing elements between each of said cutters and companion supporting members; individual means for preventing removal of each set of elements from their bearing position between an Iassociated cutter and supporting member; means engageable with said supporting means for expanding said cutters outwardly; means interconnecting said individual preventing means for releasably holding said supporting members and cutters in retracted position and means carried by said body engageable with said holding means for releasing the same.

16. In a` rotary drill bit as dened in claim 13, said plug being engageable with said body for preventing removal of said plug from said hole.

17. In a rotary drill bit: Ia main body having a iluid passage; a plurality of supporting members mounted on said body for lateral movement with respect to said body; a cutter rotatable on each of said supporting members; a set of rollable bearing elements between each of said cutters and companion supporting members; individual means for preventing removal of each set of elements from their bearing position between an associated cutter and supporting member; means engageable with said supporting means for expanding said cutters outwardly; means interconnecting said individual preventing means for releasably holding said supporting membersY and cutters in retracted position; and means extending `into said passage and subject to the force of fluid in said passage for releasing, said interconnecting means from holding said supporting members and cutters in retracted position.

ARCHER W. KAMMERER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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