Patent Publication Number: US-3874466-A

Title: Core tube placement and retrieval

Description:
United States Patent 1 1 Fulford CORE TUBE PLACEMENT AND 3 2/ 970 M 75/60 v 3,543,87 l l artinsen.... RETRIE AL 3,667,558 6/l972 Lambot l75/236X [75] Inventor: Emory Eugene Fulford, Austinvrlle, i Va. Primary Examiner-David H. Brown [73] Assignee: The New Jersey Zinc C0,, Attorney, Agennor Firm.-Colto&#39;n &amp; Stone,- Inc.  
  Austinville, Va. A 221 Filed: Apr. 19, 1974 AB TRA 2] A N 462,447 There is disclosed a drillvstring having an annular core I 1 pp 0 bit on the end thereof inside of which is placed a core tube for receiving cylindrical cores cut by the bit. The Y Cl 175/236, 175/239, 75/247 core tube is positioned in core receiving relation to I [5 the bit merely the core tube through he Field of Search 249, 3 drill string. The core tube is retrieved from the bore 175/246, 247; 166/1 156 hole by pumping a-core tube conditioning element through the drill string which engages the core tube References Cited and manipulates alatching mechanism thereof to dis- UNITED STATES PATENTS engage the core tube from the drill string. The} core 473.910 5/1892 Bullock 175/60 tube is Pumped 1&#34; 0f the drill String by P g 2145470 1 1939 into the annulus between the drill string and the-bore 2.220.554 ll/l940 hole. 3,120,283 2/1964 9Cla&#39; 6 in F 3.333.647 8/1967 Kar1ch et =11. 175/247 34/1 I [40 Dr 1; B  
  2 f 1 ?-13s 5 -|3o 4408 a a] (5 l 4114 In i &#34;&#34;0 94c 9s BO 1 122 a, i v 3. ix: 76  
 &#39; 34 lg/98 Q I 9o k b e A 1 51 Apr. 1, 1975 9/1967 Lindelofihi...  
 FATENTEDAPR 1157s 3,874,466  
 FIG. IB FIG. IA  
 PATENTEDAPR&#39; 1 ms SHEET 2 [IF 2 FIG.3  
 FIG.4  
  1 CORE TUBE PLACEMENT AND RETRIEVAL Coring devices are well known and widely used both in oil exploration activities and in hard rock mining exploration activities. These applications for core drilling have much in common with several distinct differences. One difference is that core drilling in the oilfield is typically done at substantial depths beneath the surface whereas in hard rock exploration, the distance from the core bit to the drilling machine is normally substantially less. Another substantial distinction is that oil field applications almost universally involve drilling downwardly whereas in many hard rock situations, either horizontal or upward core drilling is conducted. Upon analysis, it will be apparent that up&#34; drilling or horizontal drilling requires tool modification since gravity cannot be employed to place the core tube adjacent the bit.  
  This invention provides a core tube providing substantial flexibility in placement and retrieval thereof. Specifically, the core tube of this invention may be pumped in and pumped out of either up, horizontal or down holes. The core tube can likewise be pumped in and pulled out, as by a wire line, of either up, horizontal or down holes.  
  The provision of pump in pump out core tubes is known in the prior art as illustrated in U.S. Pat. Nos. 2.073.263; 2,145,170; 2,220,554; 2,277,989; and 3,066,748. Of some interest is the disclosure in U.S. Pat. No. 3.543.870. Of more general interest are the disclosures in U.S. Pat. Nos. 473,910; 3,120,282; 3,120,283; 3,225,845; and 3,333,647.  
  The disclosures in the prior art which provide pump in pump out core tubes usually have one or both of the following disadvantages: l) the devices employ valving structure which is subject to obstruction and/or erosion by well cuttings or drilling fluid; and (2) the latch mechanism is not positively locked but can be disengaged merely by pressure differentials.  
  It is accordingly an object of this invention to provide an improved pumpable core tube for use in the core drilling of up, horizontal or down holes.  
 IN THE DRAWINGS,  
  FIGS. 1A, 1B and 1C are partial longitudinal cross sectional views of a drilling apparatus constructed in accordance with the principles of this invention, which when longitudinally aligned along the lines A-A and BB illustrate the entire drilling apparatus of this invention;  
  FIG. 2 is a view similar to FIG. 1A illustrating an unlatched position between the core tube and the surrounding drill string;  
 FIG. 3 is a horizontal cross sectional view of the del vice of FIG. 1A taken substantially along line 3-3 thereof as viewed in the direction indicated by the arrow; and  
  FIG. 4 is a side elevational view, partly in section, illustrating an overshot which is used to manipulate the latching mechanism from the position shown in FIG. 1A to the position shown in FIG. 2.  
  Referring to FIGS. 1 and 2, there is illustrated a core drilling device 10 comprising a plurality of threadably connected joints of drill pipe 12, a landing nipple 14, and one or more pup joints l6, l8 constituting a drill string 20 having on one end thereof an annular or core bit 22. The core drilling device 10 also comprises a core tube 24 which is latched to the drill string 20 in the position of FIG. 1 in core receiving relation relative to the bit 22. As will be more fully explained hereinafter; the core tube 24 may be withdrawn from the drill string 20 in order to recover cores cut by the bit 22. After the core tube 24 has been removed from the drill string and the cores removed therefrom, the core tube 24 is reinserted into the drill string for additional drilling.  
  As will be apparent to those skilled in the art, the important functions of that portion of the drilling device 10 illustrated in FIGS. 1B and 1C are to receive and retain the core cut by the bit 22 with minimum damage thereto, to break the core so cut during or previous to withdrawal of the core tube 24 from adjacent the bit end of the drill string 20 and to allow circulation of drilling fluids through and around the drill string. Although that portion of the drilling device 10 illustrated in FIGS. 1B and 1C may be of any suitable design, for purposes of brevity this portion of the drilling device 10 is illustrated as a Model AQ-U coreing device made by the Longyear Company.  
  It will suffice for present purposes to state that the core tube 24 includes an inner core receiver 26 having core lifters 28 adjacent the bit and stabilizers 30 intermediate the core receiver 26 for centering the receiver 26. Adjacent the upper end of the core receiver 26 is a grease fitting 32 for injecting grease into a spring and bearing assembly 34. Above the spring and bearing assembly 34 is a dual shut-off valve arrangement&#39;36 comprised of a plurality of rubber washers 38, 40 and a pair of metallic washers 42, 44. A nut 46 above the valve arrangement 36 allows pretensioning of the washers 38, 40 in a conventional manner.  
  Above the valve arrangement 36 is an adjusting device 48 which allows the maintenance of an appropriate gap between the end of the core receiver 26 and the bit 22 as shown in FIG. 1C. The adjusting device 48 comprises a nut 50 threaded on a rod 52.  
  Above the adjusting device 48 is a valve cage and hanger assembly 54. The assembly 54 comprises a lower end 56 threaded on&#39; to the rod 52 and an upper end providing a shoulder58 for support on an insert 60 received between the mal eand female couplings of the drill string 20. The core tube 24 is accordingly restrained against further movement toward the bit 22 by the cooperation of the shoulder 58 and insert 60.  
 The assembly 54 provides an axial passage 62 com-- municatin g with a plurality of passages 64 above the insert 60 and a plurality of ;passages 66 below the insert 60. The passages 62, 64, ;6 6 accordingly provide a bypass through the assembly ;54 which is closed by a ball check valve 68 biased in the closed direction by a spring 70. An O-ring seal 72 provides a seal between the assembly 54 and the ,insert 60.  
  Those skilled in the artiwill recognize that portion of the drilling device 10 heretofore described as being-a Longyear Model AQ-U core drilling device. For a more detailed explanation thereof, reference is made to publications of the Longyear Company.  
  Referring to FIGS. 1A and 2, there are illustrated the principal features of this invention. The core tube 24 comprises a tubular shell 74 integral with or attached to the valve cage and hangar assembly 54. Inside the shell 74 are a latch mechanism 76 and a latch actuating assembly 78.  
  The latch mechanism 76 comprises a pair of substantially identical latch elements 80, 82 mounted for pivo .tal movement about a common pin 84 for movementtends throug&#39;h the shell 74 so that the forward nose of;  
 latch elements 80, 82 rest in an anvil 88. A pair of pins 90 secure the anvil 88 to the shell 74. The latch elements 80,82 respectively comprise an upwardly facing latch shoulder 92, 94 for abutting a downwardly facing shoulder 96 provided by the configuration of the male connection of the joint 12 and an enlarged groove 98 provided by the landing nipple 14. The latch elements 80, 82 each provide an upwardly extending projection 100 providingan inclined camming surface 102 for moving and holding thelatch elements 80, 82 inthe unlatched position of FIG. 2&#39;and an abutment 104 for of the elements 80, 82. So long as the member 106 is positively held in the position of FIG. 2 against the bias of the spring120, the latch elements 80, 82 are posi- -.tively prevented from moving toward a latched position. v  
 The member 106 also includes a second section 128 comprised of a cylindrical valve body 130 connected to the first section 108 and&#34; having a plurality of inclined passages 132 opening through the side of the valve body 130. The valve body 130 and the inside of the tuholding the latch elements 80, 82v in the latched position of FIG. 1A. &#39;As will be more fully pointed out hereinaft&#39;er&#39;, the latch elements 80, 82 are positively mechanically held in the latched position which prevents movement of the core tube 24 relative to the drill string in a direction away from the&#39;bit 22.  
  The-latch actuating assembly 78 constitutes an important part of this invention and includes an actuating member 106 extending axially of the core tube.24. The merriber l0 6t includes a first generally cylindrical section 108 reciprocably slidably received in aligned axial openings afforded by a pair of bearing blocks 110, 112 which are secured to the shell 74, as by the provision of suitable set screws 114, 116. The first section 108 includes an enlargement 118 thereon positioned between the bearing blocks 110, 112. As seen in FIG. 1A, the block 110 and enlargement 118 cooperate to provide a first limit of reciprocable movement of the memher 100 at a first latched position of the latch elements 82, 84. A suitable spring 120 is disposed between the enlargement 118 and the block 112 for normally biasing-themember 106 toward the first latched position illustrated in FIG. 1A.  
  Affix&#39;ed to one end of the section 108 is a lug or protuberance 122 which acts, in the first position of the member l06,&#39;to engage the abutments 104 of the latch elements 80, 82&#39;to prevent inward pivotal movement thereofout&#39;of latching engagement with the drill string 20. As shown in FIG. 1A. the lug 122 comes into its blocking position relative to the abutments 104 as the enlargement 1 18 approaches its first limit in&#39;engagement&#39;with the bearing block 110. As will be more fully apparent; hereinafter, the lug 122 positively prevents movement ofthe latch elements 80, 82 toward the unlatched position thereof.  
  Positioned on thefirst section 108 between the enlargement 1l8 and the lug 122 is a camming element ,124 located below the bearing block 112. The camming element 124 provides&#39;an internal generally frustoconical.camm&#39;ing&#39;surface 126 adapted to engage the camming surfaces 102 of the latch elements 80, 82  
 upon downward movement of the member 106. As illustrated in FIG. 2, the camming element 124 moves the latch elements 80, 82 to the unlatched position thereof in response .to movement of the member 106 toward the bit 22. It will be seen that the limit of movement of the member 106 toward the bit 22 is determined by engagement of the camming member &#39;124 with the latch elements 80, 82 rather than &#39;coaction of the enlargement 118 and the spring 120.In any event, there is provided a second limit of reciprocable movement of the member106 at a second unlatched position bular shell 74 are sized to provide a relatively close mating fit throughout the limits of movement of the valve body 130. i  
  As is apparent from F IG. 1A, each of the, valve passages 132 registers with a passage 138 in the tubular shell 74 when the latch actuating mechanism 78 is in its latched position. It will accordingly be apparent that drilling fluid pumped down the drill string as suggested by the arrow 140 flows through the passages 134, 132, 138 into the annulus between the core tube 24 and the drill string 20 as suggested by the arrows 142.  
  Threaded onto the top of the tubular shell 74 is a collar or coupling member 144 providing a surface 146 abutting the top of the valve body 130 at the latched position of the mechanism 78. A sealing washer 148 is captivated between the collar 144 and a nut 150 for sealing against the inside of the drill string 20. For purposes more fully explained hereinafter, a fishing neck or spear point 152 is threaded onto the top of the collar 144.  
  It will be apparent that the normal position of the latch actuating mechanism 78 is the latched position of FIG. 1A because ofthe bias afforded by the spring 120. In order to place the core tube 24 in the drilling position illustrated in FIG. 1 from the floor of a drilling machine, the operator presses on the sleeve 136 to collapse the spring 120 and thereby retract the latch elements 80, 82 into the configuration shown in FIG. 2.  
 . The core tube 24 is then inserted into the open collar of the drill pipe joint exposed at the drilling machine until the latch elements 80, 82 are inside this joint. The inner diameter of the drill pipe 12 is small enough to prevent the latch elements 80, 82 from opening a sufficient distance to allow the lug 122 to enter between the abutments 104. v  
  The core tube 24 is pushed completely into the joint of drill pipe exposed at the drilling machine and a cap is threaded onto this joint. Suitable pressure connections are afforded by the cap so that water or other drilling fluid may be pumped into the drill string 20. Pumping into the cap acts against the seal 148 to pump the core tube 24 through the drill string 20 toward the bit 22. As the core tube 24 approaches the bit end of the drill string 20, the shoulder 58 engages the insert 60 and prevents further movement of the core tube 24 toward the bit 22..The spacing between the insert 60 and the landing nipple 14 is such that the latch elements 80, 82 are aligned with the shoulder 96. As the latch elements 80, 82 become free to move about their pivot pin As the drill string is rotatedand advanced, the core cut by the bit 22 enters the .core receiver 26 thereby tending to move the coreqtube 24 away from the bit 22 which is prevented-by, engagement of the shoulders 92, 94, 96.  
  After a core of sufficient length has been cut, it is of course necessary to retrieve the core tube&#39;24 so that the core may be removed from the receiver 26 and examined. Accordingly, circulation of drilling fluid down the drill string 20 is stopped and the circulating head removed from the joint of drill pipe at the drilling machine. An overshot 154 as shown in FIG. 4 is placed into the drill string 20.  
  The overshot 154 comprises abody 1.56 having a pair of latch arms 158, 160 mounted for rotation about a pivot pin 162. The arms 158, 160 provide grappling shoulders 164, 166 respectively for latching onto a shoulder 168 (FIG. 2) of the fishing neck 152. The body 156 carries a member 170 positioned relative to the shoulders 164, 166 for engaging and depressing the sleeve 136 from the position shown in FIG. lA.to the position shown in FIG&#39;. 2 in response to latching of the overshot 154 onto the fishing neck 152.  
  A spring 172 biases the arms 1&#39;58, 160 toward &#39;a latched position for snapping about the shoulder 168. It will be seen that the inclined surface 174 on the fishing neck 152 acts to spread the arms 158, 160 preparatory to latching onto the shoulder 168. For sealing against the inside of the drill string 20 the body 156 carries a washer 176 capivated by a nut 178. The upper end of the overshot 154 includes a cap 180 having a spear point or fishing neck 182 thereon for purposes more fully explained hereinafter.  
  After the overshot 154 is placed inside the drill string 20, a circulating head and tube catcher adapted to latch onto the fishing neck 182 are attached to the joint of drill pipe exposed at the drilling machine. Drilling fluid is then pumped into the drill string 20 which acts against the washer 176 to move the overshot 154 through the drill string 20 toward the bit 22. Drilling fluid captivated in the drill string between the washers 148, 176 moves through the passages 134, 132, 138 in the manner suggested by the arrows 140, 142.  
  As the overshot 154 reaches the fishing neck 152, the member 170 engages the sleeve 136 and moves the same toward the bit end of the drill string fromthe position illustrated in FIG. 1A to the position illustrated in FIG. 2. As the member 170 abuts the top of the fishing neck 152, the shouldersl64, 166 of the latch arms 158,  
 I60 engage&#39;under the shoulder 168 to positively mechanically hold the sleeve 136 in the position illustrated in FIG. 2. It is apparent&#39;that movement of the sleeve 136 toward the bit end of the drill string&#39;20 effects movement ofthe member 106 toward the position illustrated in FIG. 2. Consequently, the valve body 130 moves so that the passages 132,138 are no longer in registry. Thus,fluid communication across the sealing washer 148 is interrupted. Contemporaneously, the camming member 126 engages the projections 100 of the latch elements 80, 82 thereby retracting thesame out of engagement with the shoulder 96&#39;provided by the landing nipple 14. It is accordingly apparent that the core tube 24 is free for movementin thedrill string 20 away from the bit end thereof.  
  When drilling an up, down or horizontal hole,&#39;the circulation of drilling fluidrri ay bereversed in&#39;a conventional manner top&#39;um&#39;p down the annulus between the drill string 20 and the bore hole. Consequently, fluid enters the drill string 20 at the bit end thereof and flows upwardly in the drill&#39;string&#39; Because of the reactive surfaces exposed to the pressures of reverse circulation such as-the ,wallthickness oftheshelli74 and the shoulder of the washer 148, the core tube2 4 is pumped out of the drill string2 0. As the core tube 2 4&#39;rea ches the drilling machine, it is retained by the tube catcher for subsequentmemovalf i -&#34;&#34;l&#39;he device of this invention provides severaldesirableua-dvantages. First, the latch 76 is positively mechanically held in both the latched arid uiilatched posi-&#39; I tions and does not depend on fluid p&#39;re&#39;ssure&#39;diffeientials to maintain the latch mechanism in either of its positions.  
  Second the valve particularly insensitive to erosion from drilling fluid and/or cuttings; When the provided by the exterior of the valve body and the interior of the tubular shell 74. Thus, the sealing sur-- faces are not themselves subject to erosion from drilling. fluid during drillings. In the collapsed or movable configuration of the core tube 24, as illustrated in FIG. 2, the interiorsurface of the tubular shell 74 is exposed to drilling fluid. It will be apparent, howeverfthat the drilling fluid does not-flow through the shell 74 during retrieval of the core tube 24. It will also be apparent that the position of the passage 138 may be adjusted slightly so that it is closed by the upper portion of the valve body 130 during retrieval ofithe core tube 24 so that the sealing surfaces are not exposed todrilling fluid during either configuration of the core tube 24.  
 Third, the overshot 154 at the core tube latched thereto can be retrieved from inside the drill string ei- .ther by .reverse circulation, as mentioned previouslymr by wireline. In the latter event,- a wi&#39;reline maybe at-- tached by a pull-out socket to the neck 182 before pumping the overshot 154into thedrill string 20. In the alternative a separate wireline retrievableovershot may be placed into the drill string 20 to retrieve the overshot 1&#39;54 and core tube 24 attached thereto.  
 I claim:  
  .1. A coring tool for attachment to a hollow drill string havingithe-reon an annular bit operative inside a bore hole, the tool comprising an elongate pumpable core tube,;mounted for movement between a first position in core receiving relation to the bit and a second position spaced axially along the drill string from the first I position, the tube comprising:  
 means for sealing between the tube exterior and the drill string interior for driving the tube toward the a first element on the member operative in the first position thereof for engaging the latch and holding the same in the latched position; and  
 a second element on the member operative in the second position thereof for engaging the latch and holding the same in the unlatched position; and  
 means for moving the member beween the first and second positions thereof including means normally biasing the member toward the first position thereof; and  
 means pumpable down the drill string for securement to the core tube for moving the member to the second position thereof upon securement to the core tube.  
  2. The coring tool of claim 1 wherein the core tube includes a tubular shell housing the latch and the member.  
  3. The core tube of claim 2 further comprising means for allowing circulation of drilling fluid through the drill string past a sealing means when the latch is in the latched position thereof, the circulation allowing means including a valve body, inside the shell, carried by the member for reciprocable movement and defining the first passage opening through the side thereof;  
 a sleeve rigid with the valve body extending longitudinally of the core tube, and spanning the sealing means, the sleeve providing a second passage communicating at one end thereof with the first passage and opening at the other end thereof exteriorly of the core tube; and  
 the tubular shell providing therethrough a third passage registering with the first passage in the first position of the member.  
  4. The core tube of claim 3 wherein the circulation allowing means includes means for preventing circulation of drilling fluid through the drill string past the sealing means when the latch is in the unlatched position, the circulation preventing means including means for moving the valve body relative to the tubular shell and misaligning the first and third passages contemporaneously with movement of the member away from the first position toward the second position.  
  5. The core tube of claim 4 further comprising a coupling member attached to one end of the tubular shell providing an opening therethrough receiving the sleeve. the sleeve extending beyond the end of the coupling member in the first position of the actuating member.  
  6. The core tube of claim 5 wherein the coupling member includes a fishing neck thereon.  
  7. The core tube of claim 6 wherein the securement means comprises means for attachment to the fishing neck.  
  8. A core drilling tool for attachment to a hollow drill string comprising an elongate pumpable core tube mounted for movement between a first location for receiving a core and a second location spaced axially along the drill string from the first location, the tube comprising a core receiving end and an other end; means for sealing intermediate the two ends between the tube exterior and the drill string interior; a latch movable between a latched position for securing the tube at the first location to the drill string and an unlatched position freeing the tube for movement through the drill string;  
 means for holding the latch in the latched position and for holding the latch in the unlatched position, the holding means including an actuating member extending longitudinally of the core tube and mounted for reciprocable movement between first and second positions corresponding respectively to the latch and unlatched positions of the latch;  
 means biasing the actuating member toward the first position thereof;  
 means for allowing circulation of drilling fluid through the drill string past the sealing means when the latch is in the latched position thereof and preventing circulation of drilling fluid through the drill string past the sealing means when the latch is in the unlatched position thereof, the circulation means comprising a valve body, rigid with the actuating member, in-  
 cluding a first passage opening through the side thereof and a sleeve connected to the valve body providing a second passage communicating at one end thereof with the first passage and opening at the other end thereof exteriorly of the core tube at a location away from the sealing means toward the other end of the core tube;  
 the core tube providing a third passage opening exteriorly of the core tube at a location between the sealing means and the core receiving end, aligned with the first passage in the first position of the actuating member for allowing fluid travel past the sealing means in the first position of the actuating member and misaligned with the first passage in the second position of the actuating member for preventing fluid travel past the sealing means in the second position of the actuating member; and  
 means pumpable through the drill string for securement to the other end of the core tube; and  
 means carried by the pumpable means for moving the sleeve and the actuating member to the second position thereof in response to securement of the pumpable means to the core tube and for holding the sleeve and the actuating member in the second position thereof during securement of the pumpable means to the core tube.  
  9. A coring tool for attachment to a hollow drill string, the tool comprising an elongate pumpable core tube, mounted for movement between a first position in core receiving relation to a bit and a second position spaced axially along the drill string from the first position, the tube comprising:  
 means for sealing between the exterior of the tube and the drill string for driving the tube toward the bit upon application of pressure thereto through the drill string;  
 a latch movable between a latched position for securing the tube at the first position to the drill string and an unlatched position freeing the tube for movement;  
 means for holding the latch in the latched position and for holding the latch in the unlatched position including an actuating member extending longitudinally of the core tube;  
 means reciprocably mounting the member between first and second positions corresponding respectively to the latched and unlatched positions;  
 a first element on the member operative in the first position thereof for engaging the latch and holding the same in the latched position; and  
 a second element on the member operative in the second position thereof for engaging the latch and holding the same in the unlatched position;  
 means for moving the member between the first and second positions thereof including means normally biasing the member toward the first position thereof; and  
 means pumpable down the drill string for securement to the core tube for holding the member in the second position thereof upon securement to the core tube;  
 means for allowing circulation of the drilling fluid through the drill string past the sealing means when the latch is in the latched position thereof and for preventing circulation of drilling fluid through the drill string past the sealing means thereof when the latch is in the unlatched position thereof, the circulation means including a valve body, inside the shell, carried by the member for reciprocable movement therewith and defining a first passage opening through the side thereof;  
 a sleeve rigid with the valve body, extending longitudinally of the core tube and spanning the sealing means, the sleeve providing a second passage communicating at one end thereof with the first passage and opening at the other end thereof exteriorly of the core tube;  
 a tubular shell providing therethrough a third passage registering with the first passage in the first position of the actuating member; and the sleeve being positioned exteriorly of the core tube for engagement with the securement means for moving the valve body relative to the tubular shell and misaligning the first and third passages contemporaneously with movement of the actuating member away from the first position toward the second position thereof.  
  UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,874,466 DATED April 1, 1975 INVENTOR(S) 1 Emory Eugene Fulford It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:  
  In column 7, line 20 of claim 3, &#34;a&#34; should read -the.  
  In column 7, line 24 of claim 3, &#34;the&#34; should read a. r  
  In column 8, line 9 of claim 8, &#34;latch&#34; should read -latched.  
 Signed and sealed this 20th day of May 1975.  
 (SEAL) Attest:  
 C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks