US1842457A - Submersible motor and reciprocating pump - Google Patents

Description

26, 1932- E. MENDENHALL ET AL SUBMERSIBLE MOTOR AND RECIPROCATING PUMP Original F lled Dec. 12. 1927 2 Sheets-Sheet /7 IWEA/TORS MENDENHHLL 5142/. a L/u/v/us 5. V4

HTTORA/EY.

Jan. 26; 1932. E. MENDENHALL ET AL 1,842,457

SUBMERSIBLE MOTOR AND RECIPROCATING PUMP Original Filed Dec. 12, 1927 2 Sheets-Sheet 2 [M/EA/Toms Err/2r. MENDENHHLL JUN/(bf 5. HIV HORN, Br 4d M fl T T023165):

Patented Jan. 26, 1932 UNITED STATES PATENT OFFICE EARL MENDENHALL AN D JUNIUS IB. VAN HORN, OF L08 ANGELES, CALIFORNIA Our invention relates to well pumps, and more particularly to a combined motor and reciprocating pump submersible in a fluid which may be injurious to the working parts of the motor should it enter therein.

Deep wells, whether of the water or oil type, are usually pumped by lowering a suitable pump to a point below the fluid-level of the well. The ciprocated by the operation of a string of sucker rods, these sucker rods extending upward to the surface of the ound where they are connected to a suita 1e prime mover. Such installations are expensive, both with respect to first cost and subsequent operation. The sucker rods of such pump installations are subjected to large stresses, and if the well is an extremely deep one, the stretch of these sucker rods becomes excessive and a large movement of the rods at the surface of the ground effects only a small movement of the pump plunger.

\Ve have found that large economies may be effected by directly connecting a pump to a prime mover and lowering the whole unit into the well, inasmuch as no sucker rods with their inevitable draw-backs are then required.

It is an object of our invention to provide a pump unit which comprises a pump directly connected to a prime mover, both the pump and the prime mover being adapted to operate submerged in a fluid.

We have found it desirable to exclude all of the well fluid from the motor in order that the windings and bearings thereof may not be injured. This is very necessary when the motor is operated submerged in a fluid which might be injurious to the working parts of the motor should it enter therein.

It is an object of our invention to provide a motor the internal parts of which are effectively separated from any fluid in which the motor is submerged.

It is, of course, necessary that some type of motion be transmitted from the motor to the pump in order to actuate the latter. Such a motion may be either rotary or reciprocatory. We have found it advisable to operate the pump by a reciprocating motion, this moplunger of this pump is re- 1 MOTOR AND REOIIPROOATING PUMP 289,428. Renewed April 15, 1881.

tion being transmitted from the motor to the pump through a flexible member which is secured both to the reciprocating member which actuates the pump and to the stationary walls of the motor.

It is an object of our invention to provide a submersible motor in which the working parts are separated from an external fluid b a flexible member,'this flexible member alowing the transmission of a reciprocating motion from the motor to a suitable means for utilizing this reciprocating motion.

Vhen using such a flexible member, there is a tendency for the volume of the motor chamber to change as the reciprocating movement takes place. We prefer to operate the motor in a motor chamber substantially filled with a neutral fluid which is not injurious to the working parts of the motor. Inasmuch as the neutral fluid is relatively incompressible, we have found it necessary to provide some means to compensate for this change in volume when usin a motor chamber substantially filled wit This may most conveniently be accomplished by another flexible member, the interior of this second flexible member communicating with the motor shell and the exterior being in contact with the well fluid.

It is an object of our invention to provide a submersible motor adapted to produce a reciprocating motion, chamber in which the motor operates being held substantially constant.

Another object of our invention is to rovide a fluid-filled submersible motor in wl iich the fluid pressures on the interior and exterior of the motor are substantiall e ual.

Still a further object of our invention is to provide a novel means of circulating and cooling a fluid in a submersible motor.

Further objects and advantages of our invention will be made evident hereinafter.

Referring to the drawings,-

Fig. 1 is a utility view of our invention, illustrating its use in the deep well pumpin art.

ig. 2 is a vertical sectional view of the combined motor and pump of our invention.

Fig. 3 is a view 0 the lower end of the neutral fluid.

the volume of the j i motor of our invention taken along the line a-a of Fig. 2.

Fig. 4 is a horizontal sectional view taken on the line 44 of Fig. 2.

Fig. 5 is a horizontal sectional view taken along the line 5-5 of Fig. 2.

Fig. 6 is a horizontal sectional view taken along the line 66 of Fig. 2.

Fig. 7 is an alternative form of our 1nvention.

Our invention finds numerous applications in numerous industries. A particularly valuable ap lication of the invention is in the deep-wel pumpin art, and it is in this relation that it will be described, it being understood that we are not limited to this use.

Referring particularly1 to Fig. 1, a casing 10 is set in a well 11, t is casing extending from the surface of the ground to a point some distance below a fluid-level 13 in the well. Extending downward in the casing 10 is a discharge pipe 15, carr ing at its lower end a pumping unit 16. T e pumping unit 16 comprises a motor unit 17 directly connected to a reciprocating 1pump 18. When the motor 17 is energized, e pump 18 forces the well fluid through the discharge pipe to the surface of the ground, this well fluid bein discharged through a suitable elbow 18a.

e motor unit 17 of our invention may best be understood by reference to Figs. 2, 3, and 6. Referring to these figures, a shell 19 provides a motor chamber 20 which encloses the working parts of the motor. This shell comprises a cylindrical portion 21, this 0 lindrical portion being shaped so as to form ribs 22 at the lower art thereof, these ribs being adapted to ho d the cylindrical portion 21 a distance away from the well casing 10 when the motor is lowered therein. The central portion of each of these ribs 22 is hollow, as best shown in Figs. 2 and 5, these ribs defining longitudinal channels 23 there- The lower ortion of the shell 19 has a bore 24 exten mg therethrough. Secured in the bore 24 is a stator 25 of the motor unit 17. This stator comprises laminations 26 which are encased in a sleeve 27, this sleeve 27 engaging the walls of the bore 24 to hold the stator in place. Windings 28 are placed on the laminations 26. Openings 29 are formed longitudinally through the sleeve 27, these openin forming cooling ducts for the fpurpose 0 allowing a assage of a fluid mm the upper portion 0 the motor to the lower portion thereof. The stator 25 has an openmg 30 in which a rotor 31 is adapted to rotate, there being an air gap between the rotor and the stator. The rotor 31 is suitably journalled in bearings 32 and 33, these bearmgs being mounted respectively in u perand lower bearing members 35 an 36 w ich' are suitably secured in the shell '19. Holes 38 are formed in the upper bearing member 35. Mounted on the upper end of a shaft 40 of the rotor 31 is a worm 41. This worm is adapted to engage a worm gear 43 which is keyed to a shaft 44. The shaft 44 is pivoted in a pair of bosses 46 which are formed at the upper end of a plate 47 extending upward from the upper bearing member 35. Also keyed to the shaft 44 is a pair of arms 49, one of these arms being outside of each of the bosses 46. The arms 49 are adapted to rotate, with the worm gear 43, these arms, when in a horizontal position pointing away from the worm 41, extending mto one of the lon itudinal channels 23.

ivoted to the outer end of each arm 49.is an arm 51 of a connecting yoke 52. The uper end of the connecting yoke 52 is attached y means of a in 53 to a oke 54 of a reciprocating mem er 55. his reciprocating member is circular in cross-section and is adapted to slide vertically in a boss 56 of an intermediate wall 57 extending across the cylindrical ortion 21 at the upper end of the motor cham r 20.

A primary flexible member 60 in the form of a collapsible bellows is secured to the upper face of the intermediate wall 57. This flexible member has a thin corrugated wall 62 closed at its upper end by a late 63. The plate 63 is connected in fluid-tight relationshi with the reciprocating member 55 and is t us reciprocated with the member 55 when the motor 17 is energized. As the late 63 moves downward from the position s own in Fig. 2, the corrugations of the wall 62 are folded on one another in a manner similar to the action of any well known bellows. The corrugated wall 62 and the plate 63 define a rimary fluid-chamber 65 in communication with the motor chamber 20 through openin s 66 in the intermediate wall 57 he up er portion of the cylindrical ortion 21 o the shell 19 forms an u per ub 71 to which is threadedly attache a. cylin-' der sleeve 7 2 of a cylinder 73. The cylinder 73 is lined with a suitable wear-resistm lining 74. To the upper end of the cylinder sleeve 72 is secured a standing valve 76. This standing valve may be of any wellknown construction, the ty illustrated in Fig. 2 being particularly ada ted to this form of pump. An 0 ening 7 is formed centrally through a b y 78 of the standin valve 76. Closing the top of the o ning 77 is a ball 79 the maximum up)ward position of this ball being determined y a cage 80 of conventional design. This standin valve is adapted to allow a passage of fiui upward therethrou h in the direction of an arrow 81, as indicate in Fig. 2. The ball 79, however, will seat in the top of the opening 77 to prevent any reverse flow of fluid therethrough.

A.ttached to the upper end of the reciprocatin member 55 is a piston 83 of the pump 18. his piston is adapted to reciprocate in the cylinder 73 when the member 55 is reoiprocated. The piston 83 has a central longitudinal opening 84 therethrough, this opening communicating with the fluid in which the pump is submerged through the ports 85 formed in the shell 19 just below the ub 71. Serewedinto the upper end of the piston 83 is a. working valve 86 having an openin 87 formed therethrough, this opening 87 1s ada ted to be closed by a ball valve 88, this ball eing held in position by means of a ca e 89. The working valve 86 is adapted to al ow a passage of well fluid throu h the opening 87 in a direction indicated b t e arrow 90 of Fig. 2, but any reverse ow will be immediatel checked by the seating of the ball 88 in t e top of the opening 87. The lower portion of the standing valve 76 is shaped to conform to the upper end of the cage 89, there being a small clearance space 92 above the working valve 86 when the piston 83 is in its uppermost position.

We prefer to operate the motor unit 17 of our invention substantially filled with a neutralfluid which is non-injurious to the windings of the motor and which will at the same time act as a lubricating medium for the bearings 32 and 33 and the crank mechanism previously described. This neutral fluid may be supplied through a pipe 100 extending upward in the well to a point above the surface of the liquid 13 therein. In most instances, it is preferable to extend this pipe 100 to the surface of the ground. This pipe 100 is in open communication with the motor chamber 20, this motor chamber including that ortion of the shell 19 between the lower caring member 36 and the intermediate wall 57. The pipe 100 also forms a convenient means of supplying energy to the motor unit 17, this energy being supplied through wires 103 which are preferably joined together in a lead cable 104. This lead cable extends from a suitable electrical source at the surface of the round downward through the pipe 100 am? through a passage 106 in the cylindrical portion 21, the lead cable 104 then passing through the upper portion of the motor chamber 20 and entering one of the openings 38 in the bearing member 35, finally being connected to the windings 28 of the motor.

Inasmuch as the neutral fluid filling the chamber and the motor chamber 20 is relatively incompressible, it is necessary that may convenient] be of the same design as the primary flexi le member 60, in which case it will have thin corrugated side walls 113 closed at the bottom by a plate 114. The side walls 113 and the plate 114 define a secondary fluid-chamber 116, the volume of which is variable by changing the vertical position of the plate 114. The chamber 116 communicates with the motor chamber 20 through the air gap, the openings 29, and through holes 118 formed in the lower bearing member 36. The cylindrical portion 21 has ports 120 formed in the lower end thereof, these ports allowing the external surface of the flexible member 112 to communicate with the fluid in the well, the interior of this flexible member being, of course, filled with neutral fluid. A guard 121 is formed on the extremelowcr end of the shell 19, this guard protecting the lower flexible member 112 from injury.

The operation of our invention is as follows:

In installing the unit of our invention, we prefer to fill the motor chamber 20 and the chambers 65 and 116 with neutral fluid before the motor is submerged. The correct amount of neutral fluid may best be determined by compressing the flexible member 112 into a position shown in Fig. 3 and turning the motor until the plate 63 of the primary flexible member 60 is in its uppermost osition. These positions of the flexible mem ers are clearly shown in Figs. 2 and 3. When in this position, the chambers 65. 20 and 116 are filled with neutral fluid. The motor and attached pump are then lowered to a point below the level 13 of the fluid in the well 11. When submerged, the fluid in the well comes into contact with the exterior surface of the plates 63 and 114 of the flexible members, and will force these plates toward each other until a pressure, equal to the pressure of a surrounding well fluid, builds up in the chambers 65, 20, and 116. lVhen this occurs, the internal and external surfaces of the flexible members are under equal pressures so that there is no tendency for these members to be deformed, thus allowing the use of very thin material in forming these flexible members.

In as much as the pipe 100 communicates with the chamber 20. it should be apparent that as the unit is being lowered, and as the internal pressure is being built up to correspond to the external pressure, the neutral fluid will be forced upward in this pipe 100 until the pressure-head of this neutral fluid equals the pressure of the well fluid. The neutral fluid will then have an upper surface level such as indicated by the numeral 132 of Fig. 1, and, inasmuch as the densities of the well fluid and the neutral fluid are usually nearly the same, this level 132 will be substantially the same as the level 13 at all times, the only difl'erence existing being due to the difference in density of the two E fluids. Inasmuch as the diameter of the pipe 100 is relatively small, a very slight decrease in volume of the chambers and 116 will cause a large movement of the level 132,

so that no additional neutral fluid need be added through the pipe 100 unless the unit is installed at a great distance below the surface of the well fluid.

The motor windings are then energized, thus turning the worm 41 and the worm gear 43. The shaft 44 is thus caused to slowly rotate in the bosses 46 and as it rotates it carries the arms 49 therewith. As the arms 49 turn, the member 55 is reciprocated due to the connection of the yoke 52. The reciprocation of the member 55 raises and lowers the plate 63 and the piston 83. When the mechanism is in the position shown in full lines in Fig. 2, the chamber 65 has a maximum volume, while the chamber 116 has a minimum volume. As the piston 83 moves downward, a portion of the well fluid enters the opening 84 in the piston and passes through the working valve 86, accumulating in the clearance chamber 92. At the same time, the volume of the chamber 65 begins to decrease, thus forcin some of the neutral fluid through the opening 66 into the motor chamber 20. This displlaced fluid causes a flow of neutral fluid t rough the o enings 38 and 29 and the holes 118, this flui entering the chamber 116 and forcing the plate 114 of the secondary flexible member 112 downward a sufficient distance to compensate for the downward movement of the plate 63 of the primary flexible member. When-the piston is in its extreme lowermost position, the volume of the chamber 65 is a minimum, the neutral fluid displaced therefrom now causing a corresponding increase in volume of the chamber 116, a flow taking place through the stator 25. This lowermost position of the crank mechanism is indicated by dotted lines 130 of Fi 2. When the member 55 is again pushe upward, the ball 88 seats in the opening 87 and forces the oil in the clearance chamber 92 upward through the standing valve 7 6 and into the discharge pipe 15 communicating therewith. At the same time the volume of the chamber 65 increases, and fluid is drawn thereinto from the motor chamber 20, the secondary flexible member 112 compressing a sufficient distance to compensate for the increase in volume of the chamber 65.

It should thus be noticed that an actual flow of the neutral fluid takes place through the stator 25. This flow of fluid has two paths, one through the air gap, and the other through the openings 29. Inasmuch as the openings 29 are of much larger cross section than the air gap, most of the flow takes place through these openings. This flow of fluid through the stator has a decided cooling efiect thereon, especially as the fluid flowing therethrough comes into contact with the walls of the shell 19. These walls are, of course, kept cool by contact with the fluid in the well inasmuch as the fluid bein pumped is drawn upward around the shefl 19 between the shell and the casing 10, this well fluid usually being of a low temperature. This very eflicient cooling action of our motor makes it possible to obtain an amount of dpower from the motor which is very consi erably larger than the amount obtained through the operation of a similar air-cooled motor.

It is preferable that the clearance space 92 be made as small as is practical inasmuch as certain fluids being umped might contain gases. If a body 0 gas should accumulate in the clearance space 92, and if this clearance space were sufliciently large, no pumping action would take place, inasmuch as the body of gas in the clearance chamber would simply be expanded and compressed as the piston was reciprocated.

It should be further apparent that if some obstruction should impede the downward movement of the plate 114 of the secondary flexible member 112, the pressure of the neutral fluid in the motor will be raised as the plate 63 is lowered on the downward stroke of the piston. Should this occur, neutral fluid will rise in the pipe 100 to allow for the decrease in volume of the chamber 65. It is possible, by making the pipe 100 of a size larger than that shown in Fig. 2, to entirely dispense with the secondary flexible member 112, allowing the surface 132 of the neutral fluid to be forced upward and downward in the pipe 100 as the volume of the chamber 65 is changed. This would, of course, subject the primary flexible member 60 to a difference in pressure between the interior and exterior thereof, such a difference in pressure being undesirable in most installations.

It is also possible to dispense with the secondary flexible member 112 and the pipe 160 by using an alternative form of our invention, such as shown in Fig. 7.

In this embodiment, the lead cable passes through a suitable insulator 150 in the intermediate wall 57, and from thence through the motor chamber 20 to the windings 28. So, also, the lower bearing member consists of a solid bottom plate 152 closing the lower end of the shell 19. In installing the apparatus shown in Fig. 7, the motor chamber 102 is filled with neutral fluid to a level indicated by the numeral 157. Above the level 157 is a body of air or other gas 158. When the motor is set into operation, the raising and lowering of the plate 63 causes an increase and decrease in the volume of the primary chamber 65, as previously explained. Inasmuch as this chamber 65 is filled with the air 158, such a decrease in volume is possible by compressing the air above the level 157 of the neutral fluid. The coolin action in this form of our invention is much less than that shown in the preferred form, and also the upper flexible member 60 is subjected to diflerences in pressure between its external and internal surfaces, thus requirin a more substantial form of flexible member t an that required in the preferred form of our invention. This form has the added disadvantage that insulators are necessary, and the insulator 150, of course, must be so designed as to prevent any escape of air or gas therearound.

We claim as our invention:

1. In a submersible structure, the combination of: walls forming a motor chamber; a motor in said chamber; mechanism in said chamber for transforming a rotary movement developed by said motor into a reciproeating movement; a flexible member secured to said walls, said flexible member transmitting said reciprocating movement to the exterior of said motor chamber; and means for keeping the volume of said motor chamber substantially constant.

2. In a submersible structure adapted to be filled with a neutral fluid, the combination of: a shell; a stator supported in said shell, said stator being provided with longitudinal openings communicating between spaces above and below said stator; a rotor adapted to rotate in said stator; and means for orcing a portion of said neutral fluid from one of said spaces to the other of said spaces and back again through said openings.

3. In a submersible structure, the combination of: walls forming a motor chamber; a primary flexible member, said flexible member defining a primary chamber communL eating with said motor chamber; a motor in said motor chamber mechanism in said motor chamber for transferring the rotation of said motor into a reciprocating motion, said reciprocating motion being transmitted to the exterior of said submersible motor structure through said primary flexible member; and a secondary flexible member, said secondary flexible member defining a secondary chamber communicating with said motor chamber, said'primary and secondary chambers and said motor chamber being substantially filled with a neutral fluid.

4. In a submersible structure, the combination of: walls forming a motor chamber; a primary collapsible bellows, said collapsible bellows defining a primary chamber communicating with said motor chamber; a motor in said motor chamber; mechanism in sai motor chamber for transferring the rotation of said motor into a reciprocating motion, said reciprocating motion eing transmitted to the exterior of said submersible motor structure through said primary collapsible bellows; and a secondary collapsible bellows,

said secondary colapsible bellows defining a. secondary'chamber communicating with said motor chamber, said primary and secondary chambers and said motor chamber being substantially filled with a neutral fluid.

5. In a submersible structure, the combination of: walls forming a motor chamber; a primary bellows above said motor chamber, said p'imary bellows defining a primary cham r in communication with said motor chamber; a motor in said motor chamber; a crank mechanism operable by said motor, said crank mechanism being connected to said rimary bellows; and a secondary bellows 1n communication with the lower end of said motor chamber, said secondary bellows defining a secondary chamber in communication with said motor chamber, said primary and secondary chambers and said motor chamber being substantially filled with a neutral fluid.

6. A combination as defined in claim 5 in which, said motor contains cooling ducts through which said neutral fluid is forced as said crank mechanism reciprocates said primary bellows.

7 In combination: a shell; a motor means in said shell; a reciprocable member adapted to be reciprocated by said motor means; and a flexible member secured in fluid-tight relationship to said reciprocable member and to said shell.

8. In a submersible structure, the combination of: walls forming a chamber, said walls includin a flexible member; a motor means in said chamber, said motor means actuating said flexible member in a manner to change the volume of said chamber; and means into which the fluid in said chamber may flow to compensate for said change in volume.

9. In a submersible structure, the combination of: walls forming a motor chamber substantially filled with a neutral fluid; a motor means in said motor chamber a flexible member communicating with said motor chamber means for operatively connecting said motor means and said flexible member in a manner to reciprocate said flexible member and displace said catin with said motor chamber at the opposite side of said motor means from said flexible member into which said displaced neutral fluid may flow after passing said prime mover in cooling relationship.

10. In a submersible structure, the combination of: walls forming a motor chamber substantially filled with aneutral fluid; a motor means in said motor chamber; a pair of flexible members communicating with said motor chamber on opposite sides of said motor means; and means for operatively connecting one of said flexible members and said motor means whereby this flexible member is reciprocated in a manner to alternately expand and contract the other of said flexible members in a manner to circulate said neutral fluid in cooling relationship with said motor means.

11. A combination as defined in claim 8 including a pi e in open communication with the interior oi said shell and extending u ward to a point above the level of the fluid in which said motor is submerged.

12. In a submersible structure, the combination of: a shell adapted to be submerged in an external fluid; a rotor rotatably mounted within said shell; mechanism for converting the rotation of said rotor into a reciprocating movement; and a flexible member adapted to be reciprocated by said reciprocating movement, said flexible member separatilfig 1said external fluid from the fluid in said s el 13. In a submersible structure, the combination of: a shell; a rotor rotatably mounted within said shell; mechanism for converting the rotation of said motor into a reciprocating movement; a flexible member secured to said shell and adapted-to be reciprocated by said reciprocating movement; and means for substantially equalizing the internal and external pressures on said shell.

14. In a submersible structure, the combination of: a shell; a rotor rotatably mounted in said shell; a member reciprocable in said shell; mechanism for operativel v connecting said rotor and said member; and a flexible member secured to said member, said flexible member closing a portion of said shell.

15. In a submersible structure, the combination of: a shell; motor means in said shell and having arotatably mounted rotor; mechanism for converting the rotation of said rotor into a reciprocating movement; and a collapsible bellows mounted in lationship with said shell, said reciprocating movement being transmitted through said bellows to a point outside of said shell.

16. In a submersible structure, the combination of: a shell; a rotor rotatably mounted within said shell; mechanism for converting the rotation of said rotor into a reciprocating movement; a collapsible bellows mounted in fluid-tight relationship with said shell, said reciprocating movement being transmitted through said bellows; and means for equalizing the internal and external pressures on said shell.

17 In a submersible structure, the combination of: a shell; a rotor rotatably mounted within said shell; mechanism for converting the rotation of said rotor into a reciprocating movement; a primary flexible member mounted in fluid-tight relationship with said shell, said reciprocating movement being transmitted through said primary member to a lpoint outside said shell; and a secondary flexi le member se arating the interior and the exterior of sai shell.

8 In a submersible structure, the combifluid-tight re- 1 nation of: a shell; a rotor rotatably mounted within said shell; mechanism for converting the rotation of said rotor into a reciprocating movement; a flexible member adapted to be reciprocated by said reciprocating movement; and a pipe communicating with the interior of said shell and extending upward to a point above the surface of the fluid in which said motor is submerged.

19. In combination: a fluid-filledshell surrounded by an external fluid; deformable means secured in fluid-tight relationship to said shell and adapted when reciprocated to maintain the volume of said shell substantially constant: and a reciprocating member secured in fluid-tight relationship with a portion of said deformable means.

20. In combination: a shell; deformable means completely closing said shell, said shell and said deformable means being substantially filled with a relatively incompressible neutral fluid; an electric motor in said shell and comprising a rotor and a stator operatmg in said neutral fluid; and means in said shell for converting a rotary motion of said rotor into a reciprocating movement, said means imparting said reciprocatin movement directly to a portion of said do ormable means.

21. In a submersible structure, the combination of: walls providing a motor chamber completely filled with a substantially incompressible neutral fluid; a collapsible bellows forming a part of said walls and being contacted on the exterior by the fluid in which said structure is submerged and on the inside by said internal fluid whereby a pressure transfer between said fluids takes lace through said bellows; a motor in said 0 amer and transmitting motion to a position beyond said walls; and a pipe means in open communication with said motor chamber the internal fluid extending upward therein until a static balance is obtained, said pipe means serving to supply additional neutral fluid to said motor chamber to control the amount of expansion of said llows:

In testimony whereof, we set our hands at Los Angel-es, 5th day of December, 1927.

EARL MENDENHALL. JUNIUS B. VAN HORN.

have hereunto California, this CERTIFICATE or CORRECTION.

Patent No. 1,842,457. Granted January 26, 1932, to

EARL MENDENHALL ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 6, line 4, claim 11, for the numeral "8" read 20; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 22nd day of March, A. D. 1932.

M. J. Moore, (Seal) Acting Commissioner of Patents.

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