US2018284A - Method and means for well development - Google Patents

Description

D t- 935- R. R. SCHWEITZER El Al. 2,013,234

METHOD AND MEANS FoE WELL DEVELOPMENT Filed May 21, 1954 worm zu'si RIF. CIR Spud Patented Oct. 22, 1935 PATENT OFFICE METHOD AND MEANS FOR whim.

DEVELOPMENT Reuben Richard Schweitzer and Chester Royal Sundquist, Norfolk, Wu; said Sundquist as signor to said Schweitzer Application May 21, 1934, Serial No; 726,818

10 Claims.

This invention is directed to a method and apparatus for the development of water wells of the graveled type.

In providing for the development of water wells, 5 the initial operation is the boring operation; during which the slush is delivered into the well for the purpose and with the effect of providing a mud layer over the sand stratum encountered in the boring to prevent collapse of this stratum during the well formation. As the sand stratum is the water-producing area, this stratum must be held by the inserted gravel 'to substantially the desired diameter, for if continued collapse of the sand stratum is permitted, the interstices between the gravel, forming the filtering media, will be seriously impeded and the' sand possibly reachv the screen with deleterious effects on the Pump.

It has been proposed in a well of this type'tov particularly over the sand stratum, and simultaneously replace the mud layer and such of the sand as may be washed out in the hydraulic action with a gravel body which serves to supthe same time afford the desired filtering medium' for. the water. It is, of course, well known among engineers that the area of the filtering medium directly ail'ects the capacity of the-well, the same as in all fllters.- Therefore, the larger the surrounding area between the ,sand'stratum and the screen, the larger the flow 01' water; that is to say, the larger the point or separation or separating area the less likelihood of moving the sand and the less likelihood of causing the sand to penetrate the gravel and 1111 upthe interstices' This will be evident from the known fact that the friction is reduced according to the square or the velocity and the velocity reduced directly according to the area. For instance, 'a 32 inch diameter circle would have four times the diameter area as an 8 inch diameter circle and,- therefore, the velocity to move thesand would be only one-fourth in the 32 inch diameter circle, but the friction on the sands created by the velocity would be reduced to one-sixteenth 01' the velocity around an 8 inch circle, as the square of the difl'erence of the area would'indicate' the" frictionon the sand.

It has been proposed to accomplish this e'n-' largement or under-reaming by mechanical under-reamers, but such operation has 'proven decidedly objectionable, owing to the necessity of 1 replacing the sand displaced by themechanical under-reamer with heavy drilling mud, creating hydraulically displace the mud layer of the well,

port the sand stratum against collapse and at a mud-plastered wall onithe face of the underreamed portion of the sand, with the attendant extreme difliculty if not impossibility of removing this mudwall after the space has been filled with gravel in the ordinary manner and the well 5 screen proper has been placed in position. Even in hydraulic action to displace the mud wall, with the consequent and absolutecertainty of the simultaneous displacement of more or less of 'the sand, difliculty has been encountered in 10 removing the sand particles so displaced to an extent to prevent accumulation of these sand particles'in the interstices of the gravel bed to a degreeto retard the flow oifwater through suchgravel bed. The method heretofore proposed for the removal of the mud and sand displaced through. the hydraulic action has been through a flotation process and experience has demonstrated that a definite part of the sand so displaced will not 20 readily yield tothe flotation eifect and will gradually settle into the gravel bed.- Therefore, the flotation method of removing the displaced mud and sand is not as completely efiective as is desired, with the result that the otherwise efleo- 25 tive capacity of the well is somewhat, and at times very materially, decreased.

'The primary object of. the present invention is the provision oi. means by which the hydraulic action necessary to remove the mud and displace the sand inthe sand-bearing stratum is utilized to automatically accommodate itself for the. washing of the mud'irom the sand-bearing stratum and the displacement of suflicient of the sand-bearing stratum to constitute an under-reaming oi the well in the sand stratum area, with the automatic [control of the hydraulic action gradually. in-' creasing its efiective range laterally of the wellas the sand is displaced, with the lateral range. of the hydraulic force continually increasing in 40 proportion to the displacing of the sand until the maximum limit of under-reaming desired has been reached.

A further object of the present invention is the.

provision oi means whereby the flotation medium 4 is subjected to pressure withdrawal in part, with the-effective withdrawal area so arranged in relation to the area of hydraulic action that the particles of sand suspended in the body of water incidentto the turbulence during hydraulic 2.0- tion will be to a large degree compelled to move upwardly to the surface of the well for discharge, and with the further relation between the ef-- fective 'ar'eagof the-withdrawal means and the Wl'blllent hodyincident'to hydraulic action so 56 located as to have the desired eifect on the sand particles and without corresponding effect on the deposited gravel.

A further object of the present invention is the provision of means for delivering the desired gravel into .the turbulent area of the hydraulic action and at a point of delivery so related to the turbulent body as to insure that the sand displaced from the sand stratum by the hydraulic action will be replaced by the gravel, so that on completion of the under-reaming the confining wall of the sand stratum defining the underreamed area will be effectively supported by a gravel body providing a clean filtering body be the hydraulic area, together with the deposit of gravel du ing these operations to insure a proper deposit of the gravel body and at the same time maintain this gravel body as free as possible of particles of sand and the like which would otherwise tend to materially clog or interfere with the passage of water through the gravel body.

The invention is illustrated in the accompanying drawing, in which:

Figure 1 is a view in vertical section, partly in elevation, illustrating the means for carrying out the method of well development forming the subject-matter ofthe present invention, the flexible jet conduits being shown inthe position inaction.

Figure 2 is a broken view showing a portion of the well formation and illustrating the automatic accommodation of the hydraulic action for the under-reaming operation.

Figure 3 is a plan of the hydraulic head.

Figure 4 is a longitudinal section of the hydraulic conduit. i

The bored well as completed by the boring action is illustrated in Figure l, in which it will be noted that there are presented well defined layers of the various materials constituting the formation, among which are indicated a waterbearing sand stratum I which constitutes the mam area through which the water is delivered to the well. Following the boring operation, the

bore of the'well is lined with a layer of mud 2- -most effective way of removing the mud wall is by hydraulic action, the jet streams of which are directed at an effective angle to displace or wash away this mud, with the hydraulic head gradually moved upwardly to displace the mud wall throughout the desired area. Of course, as the mud wall is removed from the sand-bearing stratum, there is liability, particularly under the hydraulic action, of the collapse of the sand.

which naturally would accumulate in-the bottom of the well with obvious disadvantage. and to hydraulic action, such displaced material will be automatically .replaced by the gravel or other filtering media. I

It is naturally desirable to provide within limits a material enlargement throughout the height of the sand stratum constituting the water-bearing sand in order that the final diameter through this sand stratum shall be very materially increased over the diameter of the-well bore. This is known as under-reaming and obviously tends to increase the flow of water as the larger the area of the gravel wall through which the water flows the greater the flow of water in a given time. The

difficulty of this under-reaming step, however, 20

has been, first, in taking care of the introductioh of the gravel body to prevent collapse of the sand wall and further to insure that the sand particles separated from the sand stratum in underreaming are prevented from accumulating in the gravel body to interfere with the free flow of water therethrough.

An essential feature of the present invention,

is the provision of a hydraulic method and means which will afford an effective washing away of the mud wall and which will provide for anunder-reaming of the selected sand stratum, with the under-reaming operation automatically accommodating itself as the under-reaming proceeds to insure not only an effective direction but an effective delivery of the hydraulic jets in operati'on.

The hydraulic action in the under-reaming step of the present invention is carried out through the use of a series of jets and the sand and other materials displaced by this hydraulic action are replaced substantially simultaneously with gravel introduced from the surface of the well. As this ,gravel enters the line of stream of water from the nozzles, it has a decided abrasive effect on the sand body being cut away and thus material-i ly assists in the under-reaming operation and not only assists in this operation but tends to a more effective placement of the gravel to replace the dislodged sand particles.

'In carrying out this step of the method, there is provided a hydraulic head 3 of hollow construction, the bottom wall 4 of which preferably inclines slightly upwardly from the center and the, side walls 5 of which preferably inclineupwardly and inwardly, or in other words, converge upwardly from the bottom. 'It'wlll, of course, be understood that while preferring the hydraulic head with the inclined walls as described, the use of a head with walls in other angular relations is contemplated. Thehead carries an upstanding sleeve extension 8 interiorly threaded for the reception of easing sections 1 though any type of connection is contemplated, which, of course, are

connected end to end to provide the desired length of conduit for lowering the head to the desired depth in the well.

The side walls 5 of the head are provided with openings 8 having exterior nipples ,9 on whichare removably secured hydraulic conduits I. These conduits form an essential feature of the present invention. They are constructed of appropriate material'which will insure them maintaining a straight length in the absence of resistance while yet permitting them to flex or bendin any portion under resistance. Thus, the conduits are nei-' ther completely flexible or completely rigid but partake of both in that they are capable of being flexed and yet have an inherent tendency to straighten'out in the absence of resistance to such movement.

While it is preferred that the hydraulic conduits Ill be formed to provide a nozzle orjet effeet to a tapered bore, such, for example, as indicated in Figure 4, it is nevertheless to be understood that a hydraulic conduit of uniform bore throughout may be used. The conduits are, of course, to be constructed to straighten out on release of resistance through their inherent construction and this straightening-out function will, of course, be materially assisted by the passage of water therethrough. Furthermore, the conduits are designed to yield or flex under any reasonable or excessive resistance which will prevent their assuming a straight relation, though the conduits are to be so constructed that as they are moved gradually upwardly throughout the sand stratum to be under-reamed, the comparatively slight resistance encountered by the ends of the conduits in this movement will not tend to materially flex them. In other words, where. the conduits have assumed a straight relation incident to their reaming-out operation of the sand necessary to permit this straight relation, will ordinarily maintain this relation during pward movement necessary to under-reaming action in thetsand stratum and will not again be flexed until they encounter, in the upward movement of the head, the clay or other relatively hard stratum immediately above the sand stratum being under-reamed.

It is, of course, to be noted that the hydraulic head is provided in its wallsi with a sufficient number of openings or outlets 8 to permit the use of a considerable number of the conduits III which in the completed structure radiate fromgthe head inalldirections and are preferably so closely associated at the head that the outlet or delivery ends i I are not widely separated. It is, of course, to 'be understood that thehydraulic head and therefore the hydraulic conduits iii are designed to be raised gradually during the under-reaming of the sand strat and it is also contemplated that during this upward movement or while the head is at rest during the under-reaming action,

- the head and nozzles may be rotated either partially or completely in order to insure a completely efiective searching'of the jets of water throughout the full-' 'area of the sand stratum being subjected to the under-reaming action.

As mechanism for imparting rotation and upward movement to reamers and other well accessories are quite common in the art and, as such details form no material part of the present invention, no illustration thereof is deemed necessary.v It is sufficient to-direct attention to the fact that the hydraulic head and hydraulic conduits are designed to be gradually moved upward in use and may,- if desired, be given a rotary movement for increased-effect in underreaming. I I

. The sleeve 6 is also provided with jet outlets I2 which are directed upwardly at a somewhat less angle to the vertical than that of the conduits water finds its way under considerable pressure I casing I3 has a diameter exceeding that of the casing I andprovidesbetween it and such casing I a passage I4 opening 'at the top of the well and opening at the bottom of the well at a point above the hydraulic head. This casing ill, or more particularly the passage I4 between the casings I and I3, is designed'to provide for the pressure withdrawal of a very considerable if not greater portion of the water and materials dislodged by the jets in the under-reaming action, this casing I3 being under appropriate suction and hereinafter referred to as the withdrawalv pipe.

A pipe I5 also forms a part of the apparatus with, which the present invention is concerned, this pipe being of comparatively small diameter, at least with respect to the hydraulic casing I,

and being designed toprovide armeans for delivering gravel tojthe bottom of the well for the development of the filtering area. The pipe I5 20 terminates at its outlet end I6 below the outlet end of the withdrawal casing I3 and it is, of course, to be understood that the gravel is in- 'troduced through this pipe with water and undiameter substantially commensurate with the 'desired diameter ofthe under-reamed chamben aqgz it is, of course, apparent that during the delivery oi the hydraulic element into the well and when such element is initially positioned at the bottom of the well or adjacent the particular said stratum, these hydraulic conduits are turned upward- 4(,

ly, being flexed, of course, by contact with the wall of the well.

The water under pressureis then delivered through the casing I and into the head 3. This through the hydraulic conduits I0 and through the preferably restricted jet outlets I2, being also preferably delivered through an opening or openings I I in the bottom of the head. The initial efiect of the water jetted through the hydraulic conduits I0 is upwardly, directly in line with the mud wall. This operation cleans the mudwall away fromthe selected sand stratum and naturally will start to excavate the sand underlying the mud Wall which has beencleaned away.

, As the sand is displaced under the hydraulic action, the hydraulic conduits I0 tend to straighten-out. This deflectse the jet of water flowing through the conduits or each of them outwardly with respect to the bore of the well and as the displacementof the sand under the jets is progressing, the conduits te'nd more and more to seek a normal straight position during .which the sand is displaced laterally and progressively until the maximum or straight position ofthe conduits is reached, when the effect of the water'jets is more nearly laterally and the enlargement 'Qrunder-reamEng of the sand stratum is completed at the effective limit of the water jet with the hydraulic conduits Ill in their straight. positions. The hydraulic head and conduits are, of course, gradually raised to insure a complete under-reaming throughout the mittently, the hydraulic head and conduits may their gravital action,

be rotated, as previously stated.

During the entire hydraulic action, gravel is being delivered into the well through the space l5. This gravel incident to gravital action and to the movement of the gravel under the turbulence of the water in the hydraulic area will spread out to take the place of the displaced sand. This spreading out of the gravel body is in effect substantially simultaneous with the displacement of the sand and as the sand displacement continues, the direct substitution of the gravel body also continues until finally, when the under-reaming operation is completed, all displaced sand has been replaced by the gravel body.

A portion of the displaced material, particularly the mud, is floated to. the surface of the well under the natural upward movement of the water delivered for the hydraulic action. It has been found, however, from experience that there is a proportion of the material of the sand stratum, that is, certain particles ordinarily found in such stratum, which while readily moved and held more or less in suspension within the direct turbulent area of the hydraulic action, will not respond to a natural flotation action and. will not, therefore, float upwardly and out the top of the well but will tend to eventually gravitate to the gravel bed. These particles have a tendency to effect a clogging or partial closing of the interstices between the gravel of the gravel bed and thus interfere with the flow of thewater through such gravel bed and correspondingly reduce the volume capacity of the-well.

It will, of course, be apparent that the turbulence created through the action of the water in the under-reaming process will naturally tend to substantially classify the solid materials in the turbulent area. The 'finer muds and finer sands would quickly reach the top of the area, the medium and coarser sands will reach substantially the mid-height of the area, and the heavier gravels and filtering media will naturally, owing to take their placeat the bottom of the area.

To avoid this result, the withdrawal function of the pipe 13 isutilized. As this pipe is under sitillcient suction to cause a steady withdrawal of I the water and other material in the well to the pipe, it follows that, except under -capacity of the the suction or withpredetermined conditions,

drawal effect of the pipe 13 might seriously displace and as a. matter of fact tend to a withdrawal of no inconsiderable part of the gravel or filtration bodies introduced throughthe pipe l5. As. it is important to avoid this result, it follows th'at the pipe l3 must be arranged so that its loweror inlet end is accurately placed with rela-'- tion to the turbulent area of the hydraulic action, under any varied conditions in the well be-, ing developed.

In other.words, the lower or inlet end of the pipe must be so arranged that it will serve to draw into the pipe, under the suction provided, those particles floating in the turbulent area which are light enough to be held in more .or less suspension in the .water in such area and y t too heavy to be floated to the surface in the natural flotation'movement. The particular par-. ticles under consideration are those of, thesand stratum which experience has demonstrated will not float to the surface and which will otherwise tend to gravitate to the gravel bed. -With this purpose in view and in the light of the classifi cation 'of materials in the turbulent area as above pointed out, it is proposed that the inlet of the withdrawal pipe l3 shall be located'in the mid-area of the turbulent body which will insure the withdrawal, under appropriate suction, of the finer muds and sands and of the coarser sands, all of which are located either at substantially the middle area or above such area of the turbu- 10 lent body.

Therefore, the lower or inlet end of the withdrawal pipe must be so located and changed with respect to the turbulent area that these particles of sand, grit and like material will be drawn into the pipe and so brought to the surface of the well for discharge without, however, affecting the gravel Or other filtration bodies. In actual practice, this can be readily accomplished by lowering the pipe and starting the action and determin- 2O ing by the outflow whether the sand particles are being reached without affecting the gravel. If the gravel is being withdrawn, the pipe is raised slightly until practically no gravel is discharged through the pipe. In any event, the essential feature in this particular is that the inlet end of the withdrawal pipe must be so located with respect to the turbulent area of the hydraulic action as to effectively withdraw those particles at least of the displaced sand which would not otherwise yield to the flotation action without any appreciable disturbance and particularly without any considerable withdrawal of the gravel of the gravel body.

Under the hydraulic action of the hydraulic 3:! jets i0 and the consequent turbulent action of the hydraulic area, the sand and like refuse particles would naturally tend to eddy toward the center and thus accumulate .in line with the hydraulic head. In order, however, to prevent such accumulationand to maintain a' more or less turbulent and suspension relation of the particles in the water, the jets l2 are provided. These jets direct water under pressure more or less upwardly and thus tend to keep these particles, which would to otherwise accumulate'under eddy action at the center ofthe turbulent area, in more or less active movement in an upward'direction, so that they are more easily and in greater volume subject to the withdrawal action of the pipe I3.

After the well is completed by the under-reaming and graveling, the usual screen in conventionalform and of appropriate area is bailed down in the conventional way through the gravel cylinder to its appropriate position and the well is complete. The hydraulic casing or conduit I, the gravel conduit l5-and the withdrawal pipe II are appropriately connected at the top of the well by an element indicated at l8 which maybe provided with lifting ,means ll so that all these parts may be moved upwardly as desired in operation. Of course, it is understood that the hydraulic head is gradually moved upwardly during the hydraulic action in order to effectively remove. the mud-'wall from the desired sand stratum and under-ream such sand stratum throughout the desired vertical extent, If the hydraulic conduits l0 yield or fl'exsumciently to permit their movement to a position to remain in the well, as they will not seriously iii der-reaming of the well with the automatic combination of the hydraulic action to such under-reamin'g action and the forced withdrawal of. certain particles dislodged in the under-reaming which are incapable of flotation to the surface of the well, provides for an extended area of the chamber in the sand-bearing stratum to materially increase the quantity flow of the water and furthermore in the accumulation in this chamber of. a gravel body which not only supports the wall of the chamber against collapse but acts as a filtration for the incoming water, with this gravel body maintained in a natural open condition without material clogging of the sand and. other particles to interfere with water flow. There is thus produced a well presenting the maximum capacity in volume and which will remain at the maximum for amaterially longer time by-reason of the .fact that the interstices of the filtration body are not interfered with. The method including the step of withdrawing the displaceable but non-floatable particles of sand from the sand stratum results in amaterial increase' in the volume flow of the water as it prevents the accumulation of these particles in the water body and the consequent interference with the maximum flow of water.

While the invention is described in connection with wells as initially developed, it is quite apparent that the hydraulic under-reamingaction is equally effective with wells which are already in production but in which the volume flowjs materially less than that expected from the nature of the formation in which the well is cated. In these uses, the screens in the well may be withdrawn, the hydraulic element introduced and the well hydraulically underreamed according to the method of this invention, with the result already demonstrated in practice of materially increasing the volume flow from the particular well.

Further, while 'the method .andapparatus are particularly. applicable to water wells, it is not intended to be limited to this use, as it is designed for use in connection with any well designedto produce a fluid flow and in which such fluid flow can be increased by the use of the method and means described.

What'is claimed as new is:

1. A means for hydraulically under-reaming a bored well, including a hydraulic head for' the reception of fluid under pressure, outlets leading from the head,, and flexible conduits'leading from the outlets and radiating from the head, the distance between the outlet ends oi the condiameter of the bore of the well, said conduits being of a character to automatically assume an inherently straight relation when relatively ,free of resistance. 65 2. A means for developing a bored well, in-

cluding a hydraulic. head for the reception of fluid under pressure, hydraulic conduits radiating from the head and in communication therewith, the diameter 0! the head and conduits together materially exceeding the normal diameter of the bore of the well, said conduits being inherently straight and capable of flexing under pressure without interfering with the fluid discharge, and a conduit terminating above the 75 head and providing a passage for the delivery duits being materially greater than the normal of filtering media to the area of the well including the head and hydraulic conduits.

3. A means for developing a bored well, including a hydraulic head for the reception of fluid under pressure, hydraulic conduits radi- 5 'ating from the head anddn communication therewith, the diameter of the head and conduits together materially exceeding the normal diameter of the bore of the well, saidconduits being inherently straight and capable of flexing under pressure without interfering with the fluid discharge, and a withdrawal pipe subject to suction and terminating within the well in an inlet above the hydraulic head.

4. A means for developing -a bored well, including a hydraulic head for the reception of water under pressure, hydraulic conduits radiating from the head and in communication therewith, the diameter of the head andconduits together materially exceeding the normal diameter ofthe bore of the well, said conduits being inherently straight and capable. of flexing under pressure without interfering with the water discharge, and a withdrawal pipe subject'to suction and terminating in an inlet between the delivery end of the filtering media conduit and the hydraulic head.

Y 5. A means for developing a bored well, includ-' ing a hydraulic head open to water under pressure, a series of hydraulic-conduits radiating from the head and in open communication therewith, said conduits being inherently straight and capable of flexing under pressure without interfering with water flow, the distance between the discharge ends of the opposing conduits exceeding the normal diameter of the bore of the well, a conduit leading into the well-and terminating abovethe head for the deliveryof gravel to that portion of the well afiected by hydraulic action,

means carried by the head for directing jets of g water upwardly with respect. to the head to maintain the particles dislodged by the jets of the hydraulic conduits in suspension in the water, and means arranged beyond the gravel conduit for forcibly withdrawing the suspended particles to the top of the well,

6. A means for developing 35. bored well, in eluding a hydraulic head open to water under pressure, a series of hydraulic conduits radiating from the head and in open communication therem)v with, .said conduits being inherently straight and capable of flexing under pressure without interfering with the water flow, the distance between the discharge ends of the opposing conduits exceeding the normal diameter-of the bore of the .well, a conduit leading into the well and terminatingabov the head forthe delivery of gravel to that'p'ortion of the well aflected by hydraulic f action means carrie'd by the head for directing jets of waterupwardly withrespect to the head to maintain the particles dislodged by the Jets of the hydraulic conduits in suspension in the water, and means arranged beyond the gravelconduit for forcibly withdrawing the suspended particles to the top of the well, said means having aninlet end in such'relation to the hydraulic head as to permit withdrawal of the jet-dislodged particles without creating withdrawal action on the incoming gravel.

7. A means for developing a gravel type, including a member for creating a hydraulic action against the wall 'of the well bore in any predetermined area of such bore, said member including jet-directing means having a 1 length exceeding the diameter of the'boreof the u bored well of the well and inherently straight when free of resistance, said jet-directing means being capable of fiexing under resistance, a pipe for delivering water under pressure to the hydraulic member, a casing encircling and spaced from said pipe provided for the delivery of gravel to that area of the well within the hydraulic action, and a withdrawal pipe open to suction and having an inlet end terminating above the hydraulic member for the forcible withdrawal of dislodged material not susceptible to discharge by flotation.

8. A means for developing a bored well of the gravel type, including a member for creating a hydraulic action against the wall of the well bore in any predetermined area of such bore, said member including jet-directing means having a length exceeding the diameter of the bore of the well and inherently straight when free of resistance, said jet-directing means being capable of flexing under resistance, a pipe for delivering water under pressure to the hydraulic member, a withdrawal casing encircling and spaced from said pipe provided for the forcible withdrawal of dislodged material not susceptible to discharge by flotation, a pipe open to pressure and having an outlet end terminating below the withdrawal pipe for the delivery of gravel to that area of the well within the hydraulic action, and independent jet means carried-by the member for maintaining the turbulence at the hydraulic area to present dislodged material within the eflective range of the withdrawal pipe.

9. A method of under-reaming a' bored well, consisting in directinga plurality'oi' jets initially against and at a slight angle relative to the wall of the well bore and upwardly, and thereafter increasing the angular relation of the jets relative to the well bore as more and more of the material of the bore is displaced.

.10; A means for under-reaming the waterbearing stratum of .a water well, comprising jetting conduits having an inherenttendency' to assume a maximum angle position approximating a right angle to the wall of the well bore, the normal wall of the well bore serving to hold the jets at a minimum angle, the jet impact increasing the displacement of material as the jetting conduits move from the minimum angle position to the maximum angle position, the displacement of the material from the wall under the jet impact serving to permit the jetting conduits under their inherent tendency to move from the minimum angle position to the maximum angle position.

REUBEN RICHARD SCHWEITZER.

CHESTER ROYAL SUNDQUIST. [r..s.]

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