US2991835A

US2991835A - Hanger or stop for well tools and means for inserting the same

Info

Publication number: US2991835A
Application number: US668433A
Authority: US
Inventors: Carl M Schwab
Original assignee: Otis Engineering Corp
Current assignee: Otis Engineering Corp
Priority date: 1957-06-27
Filing date: 1957-06-27
Publication date: 1961-07-11
Anticipated expiration: 1978-07-11

Description

July 11, 1961 'HANGER OR STOP FOR WELL TOOLS AND MEANS FOR INSERTING THE SAME Filed June 27, 1957 F Nr Fig.|

C. M. SCHWAB KUSMH Fig.3

INVENTOR Carl M. Schwob ATTORNEY 2,991,835 HANGER OR STOP FOR WELL TOOLS AND MEANS FOR INSERTING THE SAME Carl M. Schwab, Pasadena, Tex., assignor to Otis Engineering Corporation, Dallas, Tex., a corporation of Texas Filed June 27, 1957, Ser. No. 668,433 Claims. (Cl. 166-214) This invention relates to well tools and more particularly to a hanger or stop for use in suspending or supporting a well device in the flow conductor or tubing string of a well.

In the production of petroleum products from wells it is frequently desirable to suspend or support within the well flow conductor various devices'or instruments for measuring such characteristics of the flowing stream as pressure and temperature. It is often desirable to leave the instrument or device suspended in position within the flow conductor for an extended period of time. Pressure and temperature gages or instruments are generally of delicate construction and liable to damage if subjected to shock. Because of the delicacy of such instruments it has been customary to lower them into the flow conductor by means of a flexible line, leaving the instrument suspended on the line for the desired recording period. This procedure is satisfactory but requires that the flexible line equipment used to position the instrument or device in the well conductor remain in place at the well for the :full period of time involved. Hangers or stops are presently available for suspending or supporting devices within the flow conductor, but such hangers of stops generally involve the use of jarring blows delivered to the hanger or stop, either to install or remove the same from the flow conductor.

It is accordingly an object of this invention to provide a well tool for supporting or suspending a well device within a tubular well flow conductor.

It is another object of the invention to provide a well tool adapted to be located and locked in a recess in a well pipe such as occurs at a coupling between two adjacent joints of pipe.

It is an object of the invention to provide a hanger of the type described which can be locked against displacement from position in the well pipe but which can be retrieved readily when desired. 7

An important object of the invention is to provide a hanger of the type described which can be locked in place or removed without the use of jarring blows on said hanger.

A further object of the invention is to provide a hanger of the type described wherein the hanger does not block the flow passageway of the well conductor when installed in said well conductor but permits flow around said hanger.

It is a particular object of the invention to provide a hanger of the type described having dogs or locking means biased for lateral outward movement and initially restrained from engagement with the walls of the flow conductor, but which are releasable for lateral outward movement upon upward movement of the hanger in the flow conductor, said dogs when freed being adapted to enter .disconnected from the hanger only after the locking dogs have entered the coupling recess and are in position to ,support the hanger in its well tool supporting Mens- Patented July 11, 1961 2 pending position in the well tubing, and wherein entry of the locking dogs into such recess frees the running tool from its connection with the hanger.

Additional objects and advantages of the invention will be readily apparent from the reading of the following de scription of a device constructed in accordance with the invention, and reference to the accompanying drawings thereof, wherein:

FIGURE 1 is a view, partly in elevation and partly in sect-ion, of the hanger tool showing the tool being lowered into the tubing;

FIGURE 2 is an enlarged fragmentary View of a portion of the hanger tool, showing the externally-projecting supporting lugs after being released for outward movement but before they have entered the recess in the tubing; and,

FIGURE 3 is a view, partly in elevation and partly in section, of the hanger tool showing the tool installed and locked in position in the tubing.

Referring now to the drawings, the hanger A includes an elongate cylindrical mandrel 10 having a bore 11 therethrough. The lower end of the mandrel is threadedly connected to a sub or coupling 12, the mandrel being provided with external threads 13 and the sub being provided with corresponding internal threads 13a in the upper face of the sub. Internal threads 14 are provided in the lower end of the sub for threadedly attaching thereto an instrument R such as a pressure or temperature gage or recorder.

A collet sleeve 15 surrounds the central part or the mandrel and is split longitudinally in its lower part to provide a plurality of dependent resilient arms 16 thereon. An ou-twardy projecting boss or supporting'member wardly projecting lug 18 is similarly provided near the 'lower end of each arm to project radially inwardly through openings 19 in the wall of the mandrel. The upper faces 17a of the lugs 17 are downwardly and outwardly beveled, while the lower faces 17b of said lugs are slightly beveled outwardly and upwardly for reasons to be hereinafter explained. The arms 16 are of such resiliency and initial configuration that the bosses on their lower ends are normally biased laterally outwardly from the mandrel to a fully expanded or projecting position.

A retainer sleeve 20 having a bore 27 is slidably positioned on the mandrel below the arms 16 of the collet sleeve and is provided with a counterbore 21 in its upper end for receiving and holding the lower ends of the arms 16 in close proximity to the mandrel 10 against the outward bias of said arms. The retainer sleeve is movable from its upper arm-retaining position, shown in FIGURE 1, to a lower position on the mandrel out of engagement with said arms, as shown in FIGURE 3, whereby said sleeve no longer retains the lower ends of the arms in retracted position. The retainer sleeve is limited in its downward movement by engagement with the upper end of the sub 12, and in its upward movement by engagement with the bosses 17.

The outwardly extending bosses 17 are of such size and configuration that, when the resilient arms 16 are held in close proximity to the mandrel, said bosses do not engage the walls of the well pipe or tubing T through which the hanger is to be lowered. But, when the resilient 'arms are released for outward movement the bosses engage the walls of the tubing and are arranged to enter a recess therein at a coupling 40 connecting adjacent lengths of tubing.

A plurality of spring fingers 22 are secured at their lower ends to the retainer sleeve by screws 23 and extend upwardly and outwardly therefrom for sliding contact :with the walls of the tubing T through which the hanger is lowered. A latch spring 24 is disposed in an external longitudinal recess 25 and is secured therein at its upper end as by welding or soldering. The latch spring extends downwardly and outwardly at its lower end so that, when unrestrained, its lower end projects from the mandrel. The lower end of the latch spring can be moved into the recess 25 and held there by the wall of the bore 27 of the retainer sleeve when said sleeve is moved upwardly to the upper position shown in FIGURE 1. When the sleeve is moved downwardly to the lower position shown in FIGURE 3, the wall of the bore 27 of the sleeve moves below the lower end of the spring 24 which is no longer retained in the recess 25 but is allowed to move outwardly into the counterbore 21 of said sleeve. Engagement of the lower end of the latch spring with the internal annular upwardly facing stop shoulder 28 formed at the bottom of the counterbore 21 of the sleeve thereafter prevents undesired upward movement of the sleeve on the mandrel.

The collet sleeve 15 is held fixed against movement on the mandrel by virtue of its being welded to the mandrel with the upper end of the collet sleeve in engagement with a downwardly facing shoulder 26 on the mandrel. An undercut external annular flange 11a at the upper end of the mandrel provides a fishing connection 11b by means of which the tool may be retrieved, as will be hereinafter explained.

A counterbore 30 in the lower end of the mandrel extends upwardly to a point slightly above the openings 19, and a plunger 31 is slidable longitudinally in the counterbore, its upward movement therein being limited by engagement with the downwardly facing annular shoulder 32 at the upper end of the counterbore. A spring 33 is confined in the counterbore between the plunger and the sub 12 and resiliently urges the. plunger .upwardly toward the shoulder 32. A vent hole 34 through the wall of the sub 12 provides fluid communication with the lower end of the counterbore of the mandrel, preventing trapping of fluid in such counterbore and permitting ready movement of the plunger therein.

A running tool 38 having an elongate central member or prong 35, provided with an enlargement or knob 36 at its lower end and with a reduced portion 36a above said enlargement, is attachable to a flexible line lowering mechanism (not shown) for lowering into or removal from the tubing T of the well. The prong, when inserted into the mandrel, engages the upper face of the plunger 31 to move said plunger downwardly against the upward urging of the spring 33. v

The diameter of the reduced portion 36a of the prong is such that, when said prong is inserted into the bore 11 of themandrel to depress the plunger, the arms 16 may be moved resiliently inwardly against said mandrel, the inwardly projecting lugs being disposed adjacent said reduced portion above the knob 36. The inwardly projecting lugs 18 thus engage the upper face of the knob 36 to hold said knob, and consequently the prong, in position in the mandrel.

With the prong thus inserted and the plunger depressed, and with the arms 16 moved laterally inwardly to close proximity to the mandrel, the lower end of the latch spring 24 may be depressed into the recess 25 and the retainer sleeve 20 moved upwardly to the position shown in FIGURE 1 to telescope over the lower ends .of the spring arms to hold the arms in such retracted positions. The lower ends of the spring arms frictionally engage the counterbore 21 of the sleeve 20 to assist in holding the sleeve in its upper position.

In use, the prong is inserted in the bore of the mandrel of the hanger and secured therein as previously described, the desired instrument or recorder R is threadedly attached to the sub 12 as shown, and the running tool 38 is threadedly attached to the string of flexible line operated tools. This string of tools (notshown) may consist of a rofisocket or member for attachment to the flexible line, a sinker bar, and the sub 38. 'The conventional stroke jars are preferably omitted fromthis string of tools as it is neither desired nor necessary to deliver jarring blows to the hanger.

The flexible line operated tools, the hanger and the attached instrument are inserted into and lowered in the tubing T, the upwardly and outwardly extending spring fingers 22 of the retainer sleeve contacting the wall of said tubing. The externally projecting bosses 17 of the resilient arms 16 do not, as previously pointed out, project to such extent as to engage the walls of the tubing, and the bevels -1-7b on the lower faces of said lugs prevent undesired engagement of said bosses with internal obstructions or recesses in the tubing.

When the level is reached at which it is desired to install the hanger and the attached instrument, the tools are raised by means of the flexible line. As the hanger moves through the coupling 40 next above in the tubing T, the projecting upper ends of the spring fingers 22 enter the coupling recess and engage the lower end 41 of the joint of the tubing T above the coupling, the retainer sleeve 20 being thus stopped from further upward movement. Continued upward motion of the hanger causes the mandrel to be moved upwardly relative to the retainer sleeve until said sleeve engages the sub 12 as shown in FIGURE 3. The lower end of the latch spring 24 is freed and moves laterally outwardly into the counterbore 21 of the sleeve and thus engages the upwardly facing annular shoulder 28 to retain the sleeve in its lower position on the mandrel. The lower ends of the arms 16 are also freed to move laterally outwardly, the external bosses 17 contacting the inner wall of the tubing T as shown in FIGURE 2. The length of the inwardly projecting lugs 18 and the diameter of the knob 36 of the prong are such that said inwardly projecting lugs continue to engage said knob to retain said prong in the mandrel as long as the arms 16 are prevented from further lateral outward movement by the engagement of the external bosses with the walls of the tubing.

The hanger is then lowered to the level of the coupling 40 at which time the resilient arms 16 move the external bosses 17 laterally outwardly into the annular coupling recess or space between the adjacent tubing sections. Alternatively, the hanger could be elevated to the coupling next above so that the external bosses 17 could be move outwardly into the recess between the tubing sections next above. In the event this latter course is followed, the spring fingers 22 are fractured or bent back upon themselves by the pull of the flexible line so that the hanger can be thus elevated. The further outward movement of the arms 16 as the bosses '17 enter the coupling recess moves the inwardly-projecting lugs 18 outwardly as shown in FIGURE 3 so that said lugs no longer engage the knob 36 of the prong, whereupon said prong is removed upwardly from the mandrel. The external bosses 17 support the hanger in position by virtue of their entry into the recess between the adjacent tubing sections, the lower faces of said lugs engaging the upper end of the lower tubing section. With the arms moved fully outwardly into the space between adjacent tubing sections, the lugs 18 no longer protrude into the counterbore 30, and the plunger 31 moves upwardly under the biasing of the spring 33 to a position between the inwardly-projecting lugs 18 and 'until said plunger contacts the downwardly facing annular shoulder 32 in the mandrel.

The arms 16 are locked in their outer positions inasmuch as the plunger 31 prevents inward movement of the inwardly-projecting lugs 18, the hanger thus being locked in position in the tubing T against movement in either an upward or downward direction. The running tool and the string of flexible line operated tools are then removed from the well, and the hanger with its attached instrument is left in position for the time desired.

When it is desired to remove the hanger from the tubing, a suitable pulling tool (not shown) is attached to the string of flexible line operated tools in lieu of the run; ning tool 38, and the prong 35 is threaded into the lower end of said pulling tool. The pulling tool is lowered into the tubing T' until the prong entersthe bore 11 of the mandrel and engages and depresses the plunger 31 against the force of the spring 33. The prong is inserted to such depth that the knob 36 is moved below theinwardly-projecting lugs 18 whereby said lugs are no longer locked against lateral inward movement. At the same time the pulling tool engages and grasps the fishing connection 11b of the mandrel, retaining the prong in the position just described. The hanger is removed by means of a steady upward pull on the flexible line, the beveled upper faces 17a of the external bosses 17 camming said bosses inwardly as the hanger is elevated past succeeding collars. As previously mentioned, the spring fingers 22 on the retaining sleeve are of such strength and stilfness that they are fractured or bent back to inoperative position by an upward pull on the flexible line.

It is noteworthy that the lower face 17b of the externally-projecting supporting members or bosses 17, are only slightly beveled. The remainder of the lower face 17b is approximately normal to the spring arms 16 whereby the 'bosses, when in position in a recess at a coupling in the tubing, support the hanger and the instrument carried thereby.

Although the hanger has been described as being installed and locked in position in a tubing at a recess at a coupling between adjacent joints of tubing, obviously the hanger could be installed at any other recess in the tubing of depth and length sufiicient to permit the bosses 17 to move outwardly therein in the manner described.

From the foregoing it will be seen that a hanger has been described which admits of installation in and removal from a well conductor for the purpose of suspending or supporting in said conductor a well device such as a gage or instrument or the like. It is seen that the hanger can be installed and removed by means of a flexible line and that the line can be disconnected from said hanger and removed from the well conductor while the hanger remains installed therein. Further it will particularly be seen that the installation and removal of the hanger from the well conductor can be accomplished without any use of jarring blows but simply by the steady application of force in the desired direction; and that, when the hanger is installed in the well bore, it is locked therein against displacement in either direction until it has been unlocked for removal. It will also be seen that the hanger may be of such dimensions and of such configuration that the flow passage through the well conductor is not obstructed whereby the readings of the instrument or gage may be made while the well is flowing in a normal manner.

It will further be seen the retaining sleeve 20 is held in a position below the lower ends of the arms 16 whereby said sleeve does not interfere with inward movement of said arms to retracted position.

The foregoing description of the invention is explanatory only, and changes in the details of the construction illustrated may be made by those skilled in the art, within the scope of the appended claims, without departing from the spirit of the invention.

What is claimed and desired to be secured by Letters Patent is:

1. A well tool including: a tubular body; support means mounted exteriorly on said body adapted for lateral movement from an inner retracted position to an outer projecting position; said support means having inwardly projecting lug means thereon and said body having an aperture therein adjacent said support means through which said lug means is movable to project into the bore of said tubular body; means biasing said support means outwardly; retaining means slidable on said body from body movable from a position spaced from -saidaperture in said body to a position in registry with said aperture and adapted to engage saidinwardly projecting lugmeans of'said support means to hold said support means in'pro jecting position, said lock means being movable from an initial non-engaging position to an engaging positionto engage said inwardly projecting lug means of said support means after said support means is moved to projecting position; and means carried by said body for moving said locking means into engagement with said inwardly projecting lug means of said support means.

2. A well tool including: a tubular body having a lateral aperture formed in the Wall thereof; support means mounted exteriorly onsaid body adapted for lateral movement from an inner retracted position to an outer projecting position; said support means having inwardly pro-, jecting lug means thereon disposed to project inwardly through said lateral aperture in said bodyinto the bore of said body; means biasing said supportmeans outwardly; retaining means slidable on said body from an-upper position engaging and retaining said support means in retracted position to a-lower position releasing said support meansifor lateral movement toward projecting position; lock means movably mounted'within said body adapted to engage said inwardly projecting lug means of said support means to hold said support means in projecting position, said lock means being movable from an initial non-engaging position to an engaging position to engage said inwardly projecting lug means of said support means after said support means is moved to projecting position; and means biasing said lock means from said non-engag ing position to said engaging position, v

3. A well tool including: a tubular body; support means on said body adapted for lateral movement from an inner retractedposition toan outer projecting position; means biasing said support means outwardly; retainingmeans slidable on said body from an upper position engaging and retaining said support means in retracted position to a lower. position releasing said support means for lateral movement; lock means movable in said body adapted to engage said support means to hold said supportmeans in'projecting position, said lock means being. movable from an initial non-engaging position to an engaging position to engage said support means when said support means is moved to projecting position; a means biasing said lock means from said non-engaging position to said engaging position; a rod member slidably inserted in said tubular body; and means on said support meansengaging said rod member when said support means .is in retracted position to hold said rod in said body. i A A 4. A well tool adapted for locating and locking in a recess in a tubular well pipe, said well tool including; a tubular body having a lateral aperture formed in'th'e wall thereof; support means mounted exteriorly on said body movable laterally from an inner non-supporting position to an outer projectingposition for entry .into said pipe recess; said support means having inwardly projecting lug means thereon disposed to project inwardly through said lateral aperture and said tubular body when in retracted position to project into the bore of said body; means biasing said support means to said outer position; retaining means movable on said body downwardly relative to said body from an upper position engaging and retaining said support means in inner position to a lower non-retaining position to release said support means for lateral movement; holding means on said body and-said retaining means coengageable on movement of said retaining means to said lower position on said body to hold said retaining means in said lower position; and lock means in said body movable in the bore thereof from a lower non-locking position to anupper lockingposition, said lock means being engageable by said inwardly projecting lug means of said support means when said lock means is in locking position to prevent said support means from movement inwardly from-Said Qllter position, said lock means being movable to said locking position only after movement of said support means to said outer position; and means carried by said body for moving'said locking means into engagement with said inwardly projecting lug means of said support means.

5. A well tool adapted for locating and locking in a recess in a tubular well pipe, said well tool including: a tubularbody having a lateral aperture in the wall thereof; support means mounted exteriorly on said body movable laterally from an'i'nnernon-supporting position to an outer projecting position for entry into said pipe recess; said support means having inwardly projecting lug means thereon disposed to move through said aperture into the bore of said body when said support means is moved to inner nonsupporting positionymeans biasing said support means to said outer position; retaining means on said body engaging and releasably retaining said support means in said inner position, said retaining means being movable downwardly relative tosaid body member from an upper retaining position to a lower non-retaining position to release said support means for lateral movement; holding means'on saidbody and said retaining means eoengageable 'on movement'of saidretaining means to said lower position to hold said retaining means in said lower position; lock means in said body movable in the bore of said body from a lower non-locking position to an upper lockingposition; said inwardly projecting lug means on said support meansbeing engageable with said lock means when said lock means is in upper locking position, whereby'saidsupport'means is prevented 'cfrom'movement from said outer positiomsaid lock means being movable to said upper position only after movement of said support means to said outer position; and means in said body biasing said lock meanstoward said upper position.

6. A well tool adapted for locating and locking in a recess in a tubular well pipe, said well tool including: a tubular body; support means on said body movable laterally from an inner non-supporting position to an outer projecting position for entry into said pipe recess; means biasing said support means to said outer position; retainingmeans on said body engaging and releasably retaining said support'means in said inner position, said retaining meansbeing movable downwardly relative to said body from, an upper retaining position to a lower non-retaining position releasing said support means for lateral movement; holding means on said body and said retaining means coengageable on movement of said retaining means to said lowerlposition to hold said retaining means in said lower position; lockmeans in said body movable relative thereto from a lower non-locking position to an upper locking position; said support means having an inwardly projecting lug thereon 'engageable with said lock means when said lock means is in upper locking position to prevent inward movement of said support means from said outer-position; said lock means being movable to said upper position only after movement of said support means to said'outerposition; means biasing said lock means toward said upper position; and arod member slidably inserted in said body and having a knob thereon engageable by said inwardly projecting lug on said support meanswhen said support means is in said inner position; said lug holding said rod member in said body member when said support means is in said inner position; said rod member being releasable and removable from said body upon movement of said support means to said outer position.

7. A well tool adapted for locating and locking in a recess in a tubular well pipe, said well tool including: a tubular body; support means on said body movable lateral- 'ly'from aninner non-supporting position to an outer projecting position for entry into said pipe recess; means biasing'said" support means tosaid outer position; retaining means movable'on said body and engageable with said' snpport'means for "retainingsaid support means in said inner position whenin an upper position "on said body; said retaining means being movable downwardly relative to said body from an upper retaining position to a lower non-retaining position releasing said sup port means for lateral movement; holding means on said body and said retaining means coengageable on movement of said retaining means to said lower position on said body to hold said retaining means in said lower position; lock means in said body member movable relative thereto from a lower position to an upper locking position; said support means having an inwardly projecting lug thereon engageable with said support means to hold said support means in said outer position, said lock means being movable to said upper position only after movement of said support means to said outer position; means biasing said lock means toward said upper position; and a rod member inserted in said body and having a knob disposed to be thereon engaged by the inwardly projecting lug on said support means when said support means is in said inner position, said rod member being held in position in said body by said engagement of said lug with the knob of said rod member; said rod member being releasable and removable from said body upon movement of said support means to said outer position; said support means being movable upon release by said retaining means outwardly into contact with the wall of the well pipe, the lug on said support means holding said rod member in position in said body member when said support means is in contact with the wall of the well pipe, said well tool being movable longitudinally in said tubular pipe to position said support means in said recess; said support means moving outwardly to full projecting and supporting position in said recess and releasing'said central rod member for removal from said body.

8. A well tool adapted for locking in a recess in a tubular well pipe, said well tool including: a tubular body having a plurality of lateral apertures formed at radially spaced positions in the wall thereof; a plurality of support members mounted exteriorly on said tubular body and movable laterally from an inner non-supporting position to an outer projecting position for supporting engagement with said pipe recess; means biasing said support members toward said outer position; retaining means on said body movable longitudinally thereon between an upper and a lower position; arresting means on said retaining means engaging said well pipe; said arresting means permitting downward movement of said retaining means in said well pipe but preventing upward movement of said retaining means therein; said retaining means being moved to said lower position on said body when said arresting means prevents upward movement of said retaining means in said well pipe and said body is raised therein; said support members being retained in said inner position by said retaining means when said retaining means is in said upper position and being freed for lateral movement when said retaining means is in said lower position; holding means on said body coengageable with said retaining means when said retaining means is in said lower position to hold said retaining means in saidlower position; lock means in said body movable longitudinally in the bore of said body from a lower to an upper position; means biasing said lock means toward said upper position; said support members each having an inwardly projecting lug projecting inwardly through one of said lateral apertures in said tubular body so as to be engageable with said lock means when said lock means is in upper position to prevent inward movement of said support members from projecting position.

9. A well tool for locking in a well pipe, said well tool including: a tubular body member; a central rod member having a knob on the lower end thereof and inserted downwardly into said tubular .body; a plunger slidable longitudinally in said body between an upper anda lower position; firstbiasing means urging said plunger'toward said upper positiongsaidrod'member engaging said plung- 9 er when said rod is inserted into said body to move said plunger to said lower position; support members on said body movable laterally from an inner position to an outer position; second biasing means on said body urging said support members to said outer position; inwardly extending projections on said support member engageable with said knob to hold said rod member in position in said body when said rod member is inserted into said body and said lugs are in said inner position; said plunger being engageable by said projections to prevent inward movement of said support member from outer position when said plunger is in said upper position; a sleeve on said body member slidable from an upper to a lower position thereon; arresting means on said sleeve projecting outwardly and upwardly for engagement with the wall of said well pipe to permit downward movement of said sleeve in said well pipe; said arresting means being engageable with a downwardly facing shoulder in said well pipe to prevent upward movement of said sleeve in said pipe to move said sleeve to said lower position on said body upon upward movement of said well tool in said well pipe; and holding means on said body engageable with said sieeve when said sleeve is in said lower position on said body member to hold said sleeve in said lower position; said sleeve retaining said support members in inner position when said sleeve is in said upper position on said body and releasing said support members when said sleeve is in said lower position on said body; said inwardly'extending projections disengaging said knob only when said support members are in said outer position.

10. A well tool of the type described in claim 9 in which the arresting means is deformable upon exertion of a predetermined upward force on said .tool for removal of said tool upwardly from the well pipe.

References Cited in the file of this patent UNITED STATES PATENTS 2,153,812 Newton Apr. 11, 1939 2,401,119 Taylor May 28, 1946 2,644,527 Baker July 7, 1953 2,726,724 Wilhoit et a1 Dec. 13, 1955 2,790,395 Garrett et al. Apr. 30, 1957 2,800,186 Tausch July 23, 1957 2,828,698 Bryan Apr. 1, 1958