US2604941A - Casing perforator - Google Patents

Description

July 29, 1952 A. ENGLISH EIAL 2,604,941

CASING PERFORATOR Filed April 5, 194a m M 30 MM 4 :25:2

.sv m 1 90) f. PIDGEM/AV s end of the harm and the with Patented July 29, 1952 7 UNITED STATE s PATENT;

"CASING PERFORATOR Aaron English,

Bellflowen-a'nclLeroy E; Ridgeway; I

Compton, Calif. i I

- Application April 5, 1948, Serial Nah-85996 This invention has to clo-with'a casing perforator and it is a ticularly con erned with a device for perforating casing located in a well and or the type wherein an explosive charge-is em loyee to effect the desired perforating action.

A general object. of the present invention is to; provide a casing perimeter of the type wherein ried at the forward end of the barrel; whichshell is of the rim firing type, the rim of the shell being located to be compressed between the forward I E of the casing as the barrel reaches thev casing,

- Another object or our'mve tiqn ism tro ide a well'casing' perforat'oriof the general character referred to lilllldil'lg fin mmerse construetio'n involving a tubular bodyand barrel guides in the body, which guidesare simple tubular parts extending laterally or the 'body and fixed therein,

' the structure being such a single propelling 7 charge located at any desired point in the body will act to effectively propel gun barrels carried in the u des, 1

A further object-of the ii-resent invent ons to provide a; Well casing perforator of the general character referred towhe'rei'n a giiri barrel, operable into close proximity withthe casing to be perforated; carries a I projectile -'prope1led'hy an explosive char e carried: byith-harrbli which v projectile is operable through a substantial distance in the barrel after the charge has" been ignited, with theresult thatfefietivepres'sure develops behind the iirojectile hefore n it leaves the barrel to pierce the casing. g g y Y A'fur-thei object of the present invention'is to such manner as to actuate a cap whichiigfii'tes V 5m 'IFhe ariousobjects and feature's'oIv our injve'ntion will 5 be fully under tood from'the following detailed description or .t'yi ical plieferrd forms and applications "of the" invention, throughout 16 Claims. (01. 164 905) v. f fjvw which description reference is made to.thelaccom panying drawings, in Which:.

Fig-1 is a vertical sectional viewofra typical Well showing a casingthereinand an unactuated perforator embodying the present invention eated within the casing. Fig. 2 is a sectional View similar to a portion of Fig. 1 showingithe perforator actuated. Fig-31's. an enlarged .sec-

tio'nal View ofa portion of the structure shown provide a Well casing peiforator-iwitha gun barrel of the general characterreferredto' wherein an actuating shell is carried in the noseof the barrelignited: by contact; with the casingand 1 serving to drive ,a shell rearwardin the barrel .to'strlke afiringi pinat therear of the barrel'in the barrel"- operable to projectile: J s'lidakily" carried in the gun barre a in' Figs. 1 and 2., being an enlarged view taken as indicjatedby line 3+3 on Fig. 1-. Fig; 4- is-a transverse orplai'i section taken as indicated.,.by line 4- on Fig. 3. Fig: 5 is an enlarged detailed sectional "iew taken a indicatedby line t ligon Fig. 4. Fig. 6' is a perspective. View .of vashell employed for efiecting operation ofrthe explosive charge and Fig. 7 is a detailed sectional ,vie'wjof a modified form of 'oonstructionshowing the nose portion 101" a gun barrel :carrying an explosive charge in 'such' manner that the charge: itself effects perforation of the casingv without utilizing projectile for that purpose.v

The structure provided'by the presentinvention is useful generally where it is desired. to provide perforations; or the like, .in inaccessibleobje'ots; as for instance casings located in wellsor other such Situations. Forexample, We will describe-the present invention as applied to awell casing. in which situation it is employed to, effect a pluralitylof perforations-atsuitable SDacedihterva'lsin the casing. In the particular caselillustrated a well; casing A is shownsituated ma well bore W and'jt-he perioratoremb'odying the present invention is' shown carried" byv an operating memher or. line Ccarrying an electric: control member or'wir'e: X. 3.

The perforato'r embodying the present invention' includes; generally, an elongate'tub'ular ibody B, agun barrel D, a mounting E forthe' gun barrel supporting it to shift into engagement or close proximity to the casing A,opera'tingameans F for the gun'barrelacting to shiftitiinrthe mountingv E, :an' explosive charge? G: carriedxby I effect penetratio'n bfc-tlie casing, and means'H for. ignitihgthe chargeGl' In the 7 form: of the invention. illustratdz in Figs. l to 6, inelusive, the strutur'e invoive "a carried" in the barrel behind the-proy car-fie by' the uni/er and alfii ng Din M atth'e charge w named elements are sdr'latw'tha means His actuated, as by con-tact W ing" A, the pro ectile J with the driver it is driven rearwardiyin the :guii "b suitable manner,

ing the cap L into contact with the firing pin M so that the charge G is ignited to thereupon drive or force the driver and projectile forward in the barrel in such manner as to have substantial velocity when the projectile reaches the casing.

The body B of the perfcrator is an elongate tubular structure, preferably carrying a plurality of units each involving a gun barrel D, a mounting E for the barrel, and various other elements combined therewith as herein described. It is ordinarily desirable to perforate a casing at a plurality of points spaced circumferentially ofthe casing and also longitudinally thereof. In the drawings we have shown a body B carrying a plurality of gun barrels in such manner as to perforate a casing in the manner just mentioned simultaneously, or in a Single operation.

The particular body B is shown as involving a shell l which may be in the form of 'a length.

of tubing, or the like, a head |2 closing the upper end of the shell l0, and a plug I3' closing the lower end of the shell. The shell of the body serves to support the several perforatingunits as I will be hereinafter described, that is, itsupports the several mountings which, in turn, carry the gun barrels while the .head |2 serves as an element to carry the operating means F and as an element connecting the perforator with the operating line C. The line C is shown connected with the head l2 through a suitable coupling M.

and a socket |5 in the inner end of the head open to the shell It carries the means F.

The plug l3 closing the lower end of the shell 7 I0 is preferably provided with a controlled vent opening IG so that after the means F has operated pressure is allowed to bleed from the body. In the particular case illustrated the vent opening I6 is showncontrolled by a bean or orifice member I! having an apertureor orifice of such size as toallow pressureto gradually bleed from the body after initial operation of means F has generated sufficient pressure to fully and properly operate the several gun barrels carried by the structure.

The operating means or member 0 may be of any desired form or construction so long as it is such as to handle the body B enabling it to be run into the casing A to the desired point. In

practice it is advantageous to employ a cable or fiexible line to handle the body B and in the case illustrated we have shown an operating means F involving an electrically actuated igniter and, therefore, have shown the cable or line C as including an electric operating line or wire X.

In carrying out the present invention the several perforating units carried by the body B may be alike and, therefore, one such unit will be described, it being understood that such description may apply to all of the units involved in the structure.

The guide means E provided to carry a gun barrel may be fixed in or to the body I0 and is such as to slidably support a gun barrelD. In

the preferred construction the means E involves an elongate tubular part 2| with a guideway or:

guide :opening 22 and the tubular part is supported, by or fixed in the shell Ill of the body. The guide E may be positioned or disposedin any it being preferred, however,

that it be arranged to extend laterally of; the,

body B withits opening 22 extending radially and opening at one side of the bod to face the inner wall of casing A.

'In practice the guide member 2| may be varied widely in form andconstruction and in the case illustrated the inner end 25 of the guide 2| is flat or normal to the longitudinal axis of the guide and the points or parts of the guide which closely approach the inner wall of the shell are secured thereto as by welding 26. Through the construction just described the .guide member 2| is effectively supported at both ends, the outer end of the guide being open toward the inner wall of easing A, while the inner end of the guide is open to the interior of the shell H1.

The gun barrel D is slidably carried by the means E to be shiftable from a retracted position such as is shown in Fig. 3 to an operated or extended position such as is shown in Fig. 2, where its outer or forward end is in closeproximity to, or in engagement with, the inner wall of casing A. The barrel D is provided primarily as a carrier for the explosive charge G which, when ignited serves to effect perforating of the casing A and incidental to this basic function it carries the means H and when parts such as the projectile and driver are used it carries these parts also.

Inthe form of the invention illustrated the barrel D is shown as an elongate element corresponding in cross section with the guide opening 22 in guide member 2|. The guide'opening or bore 22 in member 2| is shown as round in cross section and, therefore, the exterior 3|) of the gun barrel D is turned or round in cross section and is slidably fitted in the bore 22. The barrel is of such length that when in an in or retracted position its rear end is opposite or at the rear end 25 of the guide member 2| while its forward end or nose 3| is within the forward end portion of the guide 2| as shown in Fig. 3. In the preferred construction the forward end portion or nose 3| of the gun barrel is rounded so that when the barrel is operated or moved to an out position the means H carried by the barrel, preferably centrally thereof, is moved into contact with the casing, without interference from the nose portion of the barrel. 7 j

The gun barrel D is provided with a bore 35 that receives or holds the means H and with a charge opening or chamber 36 that carriesthe explosive charge G. In the preferred arrangement the bore 35 and chamber 3'5 are centrally located in the'barrel or are concentric with the longitudinal axis of the barrel and they are in communication with each other, the chamber 36 being in communication with the inner or rear end of the bore 35 while the forward endof the bore 35 is such as to receive and hold :the

means-EL- In the form of the invention under consideration,' that is, where a projectile J and drive K are employed, the bore 35 is of substantial length,

attach aforward position adjacent the means H to-a rear 'positionwhere they are at the chamber 36. 1 The gun" barrel 35'as' above describedisopen atboth ends, that is, its forward end isopen toward or at thenose of the-gun barrel so that-it facesthe wall of the casing, while the rear end of the bore is open and in communication with the chamber 36. The chamber 36 is in the nature of anenlargement or cavity in the rear end portion of the gun barrel and its rear end-is closed by-a closure or plug 40 which is preferablyremovable, being in the nature of a threaded plug having screw threaded engagement-- with therear end-portion of the gun barrel, -The operating'means F carried'by bodyf'B is a pressure means-preferably involving a pressure generating charge 4| carried in the socket or openingl5 provided in-the' head 12 of thebody B. The charge All may be a body of suitable pow-- der and in the case illustrated it-is' suchasto be ignited by an electrically actuated ignite'r' which is-imbedded in the charge. The igniter 20 is shown suitably connected with the operating line or wire X so that when it is desired toactuate the perforator the line X is energized, 'causingthe igniter 20 to operate, which in turn ignites charge 4|.

.When the charge M is ignited a substantial pressure generates in the body B,in 'fact, enough pressurev is developed in the body so that the several barrels D carried thereby are propelled or driven forward or outward in their mountings v E, bringing the nose portions into engagement with or into close proximity with the inner wall of easing A. The charge 4! is such as to propel the barrels D forward with sufficient pressure .to insure. proper operation of the: means'H carried by the gun barrels for igniting the charges-G. The charge G carried by gun barrel D is preferably a powerful or high explosive such for example as a body of black pistol powder, or the like. In the preferred form of the invention the charge G is in the form of a cake orblock of .the desired powder-and is fashioned to'occupy .the charge chamber 36;in'a manner such as is clearly illustrated in Fig. 4 of the'drawings. VWith the construction above described the plugJfl is removed to allow for introduction of thecharge G into the chamber 36,and when the plugyM) has been reapplied or arranged in place the -charge chamber is closed, confining the charge; G in the .chamber so that when the; charge is ignited the pressure generated thereby can escape only ,through the bore of the gun barrel.

The means H provided for igniting the explosive charge G involves primarily a percussion eap orshell carried in the forward end por- V- tion of; the gun barrel 35. In accordance'with -..the preferred form of the invention the shell 50 isof the rim-firingtype and has a case 51 slid-= bly fitted into the forward end portion'of barrel 35 and has a head 52 on the outer end of the case. The head projects somewhat radially from the case to overlie the end of the gunbarrel beyond the bore. The rim portion of the head is such as to carry a percussion charg ignitedwhen the gunbarrelis forced forward causingthe rim of the head tobe put under-pressure between the '"noseo'r; the barrel and the wall of the casing. A'suit'able powder "charge in the .case 5! is ignited by the head developing pressure, which effects "ignition of i the charge G.

In the form of the invention under considerati'on' heoperation of means I -I indirectlyfeffects "ignition" of charge GI" In this case the'means" Facts" to drive or'propel the projectile- 3 rearwardly ili the barrl'35 from; a; fo ward or initial "position in the forward end-portion OilthB-bhreel; As the'projectilefi is initiallylocate'd in the barrel it is adjacent therneans H and the driver K is"; preferably adjacent the rear end-of the p'ojectile and i's'-'co'nsequeht1y in a forward positio The percussioncap' L'- is carriedby the rear end of the=driver-being carried in a'socltet 55 m r er? v 4 t, e j When the means is actuated the charge carried thereby developssiiificient pressure todrive or th'rust the projectile J and driver K rearwardly in thebarrel in-suchmanner as to move the cap L intooperating engagement with the firing pin M.- I The firing pin M is shown as carriedby'the plug or closure in such manneras to extend *throughthe cha'rgeG'and has an exposedtip facing the rear end of thebore =35.-

-When the driver K' reaches the firing pin" as a resultof a;ctu'ation" by'means H, the firingpin engages; the percussion cap L in the driver so that the cap is ignited. When the cap is thus ignited it is immediately adjacent'or in; contact '-'with the'charge G and v consequently causes A ignition 10f the charge G." Upon ignition of charge Ga high pressure is rapidly developed in the ch ar'ge chamber 36 which can escape only through the barre1' 35- and as a result 'the'dri'ver K, which is preferably a'slug of lead, or the like, acts behind "the projectile'J as it remain theboretfi forcing the projectile J forward in the bore and into engagement with the 'casing A to pierce the casing and pass completely through it.

. ln-practime the projectile J-may be-ofany suitable form or type, it being preferred ordinarily "to employa'projectile with a pointed nose such as -t enectively penetrate the ca'sing -Ae- In accordance'with the preferred for'm 'or construction the projectile is a subs'tantial distanceinward of the forward end of the barrel--35 when the driver moves the-cap Linto operating engagement withthe firingpin M, with the result that the projectile moves a substantial distance forward I withinthe barrel "35 before reaching the casing;-so that a substaiiti'ai pressureds developed by the c'hargeG in the'barrel 35 behind -the projectile, effectively driving the projectile throughthe-casing as the projectile 50 reaches :the I casing to penetrate it. i

Intheyfo'rm of the invention illustratedin -Fign7 of the drawi-hgs the projectile J; driver K, percussion cap L and firing-pin'M'areeliminated and the explosive charge 1G "instead of being located at the rear of the gun barrel is located in-a charge chamber 36 at the forward end portion orjno'se portion of thegun barrel.

The .guni-barrel in this .case has :a removable v tip .orinose end" Hlwwhichiconfin'es the'charge G in the charge chamber-36 and' thezbore- '35 of thegunbarrel; is-.formed in 1 or; through; :the :tip end 10'. Thelbore 35 is suchlias toca-rry -the meansH! which, aszin" the case aboverdescribed, involves a shell 50 of the rimfiring'wype.

. With the arrangementjust described when the shell=50 is ignited by-contac't of itsrimw'ith the casing A or between the nose of the barrel andthe casing A, the charge in the shell immediately and directly ignites the explosive charge G" and the force generated by ignition of the charge G is confined and directedby the barrel 35 onto or at the wall of -o asi ngA in such manner that the charge directly'p'ehetrates the casing making 'aprojectile unnecessary. r

In the'forrn of the invention shown in Fig.1 the explosive charge G may ;bedynamiteor other high explosive such as will generatea force or pressure effective in penetrating the casing without utilizing a projectile. V 7

Having described only typical preferred forms andapplications of our invention, we do notwish to be limited or restricted to the specific details herein set forth, but wish to reserve to ourselves any variations or modifications that mayappear tothose skilled in the artand fall within the scope of-the following claims: 7 v

.I-Iaving described our invention, we claim:

l. A casing perforator. including, a body insertable into the casing, an elongate barrel. with a chamber therein open at the forward end of the barrel, means mounting the barrel in the body to shift laterally of the casing from a retracted position spaced a substantial distance from the wall of the casing to an extended position where the forward end of the barrel is immediately adjacent the wall of the casing, a

charge carried by the barrel and generating force delivered through the opening at the forward end of. the body to effect penetration of the casing, and means for igniting the charge including an explosive shell carried by the muzzle portion of the barrel and having an igniting head seated on the forward end of .the barrel to be. actuated by compression between the end of the barrel and the wall of the casing when the barrel is moved to the extended position,

2. A casing perforator including, a body insertable into the casing, an elongate barrel with a chamber-therein openat the forwardend of the-barrel, means :mountingthe barrel in the ,body to shift. from a retracted'position spaced vto-an extended position wherethe forward-end asubstantialdistance from the wall of the casing of the-barrel isimmediately adjacent the wall of the casing; means carried by the body adapted to goperate the barrel to the extended position,

a.-charge carriedbygthe barrel and generating force delivered through the opening atthe for- ,ward end of-;the body to effect penetration of the casing, and means .for ignitingthe charge jincluding a rim firedexplosive shell. carried by the muzzle p'ortionof the-barrel .andghaving an .igniting head with itsrim seated on thejforward end of the barrel to be actuatedby compression between the end of thebarrel and; the wall of thefcasing :whenthe barrel is moved to the extended-position;1 i a 3;:Aflcasing perforatorfincluding, aibodyinsertable into the casing; .anelongate barrel with iachamber therein openat the forward end of the: barrel, means :mounting thebarrel. in the .bodyto shiftefrom. a retracted positionrspaced a esubstantialdistance from the wall of thecasing to an extended position immediately adjacent the e 'iwalliof-zthe casing including; a'tubular guide and means-fixing the. guide to the. body with an. open .iend ofzthe guide facing. the :wall' of. the casing,- a

. delivered-through-the opening at the forward-end charge carried, by .the barrel-and generatingzforce of uthetbody to effect;.penetration f ithe'i casing,

a dmea sf 'is iti ez ber h ree i lud a explosive shellgcarriedby-the muzzle portion of the barrel and having an igniting-head seated-on theforward end of the barrel tobe actuated by 'on lpression between; the endof thebarrel and tubularbody insertable into the casing,;an-;elonithe wall of the casingwhenthe barrelis moved ,tov'the extended position.

f4. A casi g perforator including, anelongate :8 satshantel wi h; a, cha ber. the ein pen. at the war a d. :91 the bar el; an mea t m the barr l. inth b d wsh r m a jrst i s r ion a iae b iam al di nc rom th wa o z'the cas o. a ex ended p si on, immed ate y' a i s tth W l. .o the b s nc u in tubu ar sn de-e t n n ran ve ly of he body and means fixing theguide'in the body ,with an open end of the guide facing the wall .of 10 the casing, a charge carried by the barrel and generatingforcethrough the opening at the forward end of the body to effect penetration of the casing, and means for igniting thegcharge including. an explosive shell carried by the muzzle portion of the barrelandhaving-anigniting head-seated on the forwardendof the barrel to be actuated by compression between; the. end of the barrel"; and the. wall of the casing when the barrel is moved to, they extendedlposition'. ,1;

- 5. A .casi ng perforator includin an elongate from a retracted position spaced a substantial distance from the wall of the casingtoian extended position immediately adjacent the wallof the casing including a. tubular guide extending transversely of the body and supported thereby 3 with-anjopen endfacing the wall of the-casing, charge .carried-by'the barrel, and means for igniting the charge carried bythe. muzzle portion of the barrel. and .adaptedzto engage the casing. i 6. A- casing perforator including, a tubular body insertable into the casing, an elongate barrel with a charge carrying chamber therein open at the forward end of'the barrelpmeans mounting the barrel in the body to-shift from a retracted position spaced a substantial'idistance from the wall of the. casing to ane'xtendedposb tion immediately adjacent the wall of theeasing including. a tubular guide "extendingtransversely of the body and supported: thereby with an open end facing the wall: of theca'singfime'ans carried by the body'opera'ting' to shift the barrel to the extended position, a charge carried by the barrel, and means for igniting the charge carried by thenmuzzle portion of the'- barrel and adapted to engage the casing.

' 7; A "casing perforat'or includingfa'tubular body 'insertable' into the casing, I an'elongate' barrel with a charge carrying chamber therein open at the forward end of the barrel, and means mounting the'barrel in'the-body to shift from -a retracted position spaced a substantial dis- -tancefrom the wall of the casing to an" extended position immediately adjacent the wall 'of'the leasing. including a tubular {guide extending transversely of theibody-and'having its forward -'e'n'd fixed to the body'* and oped-toward -the easing, a charge carried by the barrel, and means for igniting the charge carried by" the muzzle portion of th'e barrel adapted "to engage thecasing'.

1 8; A casing-" perforator including, a tubular body linsertablejihto the. casing, an elongate barend of the guide being open to the casing and the other end of the guide being open to the interior of the body and supported thereby with igniting the charge carried by the muzzle portion of the barrel and adapted to engage the casing.

9. A casing perforator including, an elongate tubular body insertable into the casing, an elongate barrel with a charge carrying chamber therein open at the forward end of the barrel, a guide slidably supporting the barrel extending transversely of the body and having its outer end opening toward the wall of the casing and having its inner end in communication with the interior of the body, and means carried by the body generating pressure in the body to enter the guide and operate the barrel therein, a charge carried by the barrel, and means for igniting the charge carried by the muzzle portion of the barrel and adapted to engage the casing.

10. A casing perforator including, an elongate tubular body insertable into the casing and including an elongate tubular shell, a plug closing the lower end of the shell and a head closing the upper end of the shell, a barrel, a guide slidably supporting the barrel, means supporting the guide in the body with the guide extending transversely of the body and having its outer end opening toward the wall of the casing and having its inner end in communication with the interior of the body, and means carried by the head of the body generating pressure in the body to enter the guide and operate the barrel therein, the guide having its outer end fixed to the shell of the body, a charge carried by the barrel, and means for igniting the charge carried by the muzzle portion of the barrel and adapted to engage the casing.

11. A casing perforator including, an elongate tubular body insertable into the casing, a plurality of elongate barrels each with a charge chamber open at the forward end of the barrel, guides slidably supporting the barrels, the guides being tubular elements spaced axially of the body and extending transversely of the body with their outer ends opening toward the wall of the casing, and means carried by the body generating pressure in the body to operate the barrels outwardly in the guides, a charge carried by the barrel, and means for igniting the charge carried by the muzzle portion of the barrel and adapted to engage the casing.

12. A casing perforator including, an elongate body insertable in the casing, a barrel carried by the body and operable relative thereto in a direction transversely thereof to a position immediately adjacent the casing and having a charge chamber therein opening toward the easing, means shifting the barrel relative to the body, an explosive charge in the chamber, and means operating to ignite the charge and including an exposive shell carried by the barrel at the muzzle portion thereof and adapted to engage the casing, the barrel having a jet opening directed toward the casing and directing the force of the ignited charge at the casing to penetrate it.

13. A casing perforator including, a body insertable into the casing, an elongate barrel hav- I ing a chamber therein and including a detachable head at the forward end of the barrel and closing the chamber, the head having a jet opening therein extending longitudinally of the barrel and in connection with the chamber, an explosive charge in the chamber and confined thereto by the head, means mounting the barrel in the body to shift laterally of the casing from a retracted position where the head is spaced a substantial distance from the wall of the casing to an extended position where the head is immediately adjacent the wall of the casing, means adapted to shift the barrel from the retracted to the extended position, and means adapted to ignite the charge including an explosives shell carried by the head and adapted to engage the wall of the casing upon the barrel being operated to the extended position.

14. A casing perforator including, a body insertable into the casing, a barrel slidably carried by the body and operable relative thereto to a position immediately adjacent the casing and having a bore and a charge chamber at the rear end of the bore, means shifting the barrel relative to the body, a projectile operable in the bore, an explosive charge in the chamber, and an explosive shell carried in the forward end portion of the bore with an igniting head engageable with the casing, the shell being adapted to propel the projectile rearwardly in the bore to effect ignition of the charge so the projectile is propelled from the forward end of the barrel by the charge.

15. A casing perforator including, a body insertable into the casing, a barrel slidably carried by the body and operable relative thereto to a position immediately adjacent the casing and having a bore and a charge chamber at the rear end of the bore, means shifting the barrel relative to the body, a projectile operable in the bore, an explosive charge in the chamber, a percussion cap to ignite the charge, and a shell carried by the forward end portion of the barrel and adapted to propel the projectile rearwardly in the barrel to ignite the cap.

16. A casing perforator including, a barrel operable to a position immediately adjacent the casing and having a bore and a charge chamber REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,145,231 Alzner Jan. 31, 1939 2,210,125 Raymond et a1 Aug. 6, 1940 2,408,419 Foster Oct. 1, 1946 2,457,277 Sehlumberger Dec. 28, 1948 2,462,784 Smith Feb. 22, 1949 2,517,560 Hambly Aug. 8, 1950

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