US2644530A - Gas-operated well apparatus with expansion retarding device - Google Patents

Description

July 7, 1953 Flled Sept 20, 1948 Patented July 7, 1953 GAS-OPERATED WELL APPARATUS WITH EXPANSION RETARDING DEVICE ReubenC. Baker, Goalinga, Caliii,v assignor. to Baker Oil Tools, Inc., Vernon, Calif., a corporation of California Application September 20, 1948, Serial No. 50,194

Claims.-

The present invention relatestowell ,devices,. and more particularly to sub-surface, devices. or.-

apparatus employed in gas' and similar wells;

Certain types of sub-surface well apparatus are operated by gas pressure. Compressed air;

bore holes, such. as, oil,

hydrogen, acetylene, products of combustion and the like may constitute the motivating gaseous force. The compressedgas may not only operate the well apparatus, but may also eifeot release of the apparatus, or'part of it, from the well bore, to enable its withdrawal to the top of the well.

Heretofore; release of'all, or a portion, of the apparatus has permitted the gas, which might be under comparatively high pressure, to expand suddenly, imposing severe shock loads on the equipment, and, :attimes, inflicting damage on some of its parts; I

Accordingly, an object of the present invention isto provide improved gas operated sub-surface well apparatus, which is capable-ofretard ing expansion of the motivating gaseous me-- diu-m without preventing proper operation of the-apparatus.

Another object of the invention is to provide gas 'operatedsub-surface well apparatus, which is capable of' retarding expansion of the motivating gaseous-medium without-preventing full expansion of the medium within the limitations of the equipment;

Still another object of the'invention is vent sudden expansion of the gas which oper ates subsurface-apparatus; upon release of" a:.= large portion ofthe load on theapparatus, with out preventing the gas from expanding fully" within the limitations of theequipment.

A further object ofthe invention is' -to-provide gas operated-well apparatus capable-of'per forming its functions without substantial interference from the hydrostatic head" of fluid in thewell bore, but which still utilizes such hy drostatic head in preventingsudden expansion. of the gas in the apparatus after'the load: on

the apparatus-has beenreleased or reduced sud-. denly.

This invention possesses many other advalh tages, and has other objects which'may'be made" more clearly apparent from: a. considerationoi.v a form in which it may be embodied. This:

form is shown in the-drawingsaccompanying and forming part of the present specification.

It will now bedescribed in detail, ,forythe purposeof I illustrating thev general; principles: of: the invention'; but it". is" tobe. understood. that suchtopredetailed descriptionis not to be-taken in a lim--,

iting sense,- since the scope of the inventionis best defined by the appended claims;

Referring to the drawings:

Figures la and 1b together'constitute a longitudinal section through a well apparatus p0- sitioned in a Well casing, with the partsoccupying their-initial position for lowering theap---. paratusthrough the casing, Fig. 1b forming. a"

lower continuation of Fig, In;

Figs. 2a and Zb-are views'similar to Figs. 1a-

In the form of the invention disclosed in they drawings, it is desired to run a well packer A- to a desired location in a well casing B disposed.

within 'a bore hole. The packer is then anchored in packed-off condition against thewell casing through use of a setting tool C connect ed to it. This settingtool is attached to the lower end of a running-in string, such as-a wire,

line D extending to the top of the well bore.

The well packer A may assume any desired form. The one. disclosed in the drawings includes a tubular main body [0 whose central passage ll may be-closedby a plug 12. A guide l3v is secured to. the lower end of the body, to prevent. hanging up, of, the tool in the casing bore or coupling spaces duringv its lowering'in. the,

- well casing B.

The well, packer can be anchoredagainst the downward movement in the well casing by a plurality of lower segmental slips l4 engaging the guide I3. and the lowerxabutment or flange 15 on the body. The, inner. surfaces l6 of these slips are tapered in a downward and inward direction for slidable engagement with a corresponding, or externally tapered, surface "@011 a frusto-conic-al expander I8-slidable on the body.

This expander is connected to thelower end of f apacking sleeve l9.,,of rubber or similarmate: rial, disposed around the body Ill, the upper end of this packing. sleeve being connected toan upper expander 20 having an upwardly and in-.

wardly inclined externally tapering surface 2] engageable with corresponding tapered surfaces 22 on a plurality of upper segmental slips 23.

ing them to their associated upper and lower expanders 2B, [8.

The shear screws 26 attaching the upper slips 23 to the upper expander 20 have acombined shearing strength which is substantially less than the shear value of the screws 24 holding the upper expander to the body l0. These latter screws have a lesser shear value than the screws 25, 2'! securing the lower expander E8 to the body, and the lower slips 14 to the lower expander. These relative shear values are selected to secure d8.-

tachment, at first, of the upper slips 23 from the upper expander 20, and the movement of the upper slips downwardly along the upper expander and radially outward into anchoring engagement:

with the casing wall. A subsequent upward strain or pull on the packer body [D then shears the screws 24 holding the upper expander 29 to the body ID, and moves the lower expander l8 and slips l4 with the body toward the upper expander 28 and slips 23, in order to efiect compression of the packing l9 between the expanders and its outward expansion into firm sealing engagement with the wall of the casing.

Thereafter, an increase in the upward pull or force on the packer body It) substantiall simultaneously shears the screws 25, 21 holding the lower expander I8 to the body, and the lower slips M to the lower expander, to cause the lower flange I5 and, guide 13 on the body to shift the lower slips [4 upwardly along the lower expander and radially outward into anchoring engagement with the wall of the casing B. A split retractor ring 28 may be disposed in the expander for engagement with one of several buttress thread ratchet teeth 29 formed on the exterior of the body IE], to lock the latter against downward movement (see Fig, 2b)

In the form of invention disclosed in the drawings, setting of the well packer A is dependent upon the development of a gas pressure within a' setting tool C initially secured to the well packer, This gas pressure is developed within a cylinder 30, consisting of a general cylindrical sleeve 3|, an upper head 32 threaded into the sleeve, and also a lower head 33 threadedinto the sleeve. Leakage from the, oylinder'through the threaded connections may be prevented by suitable side seals 34, in peripheral grooves end of a piston rod 43 is threadedly connected to the piston, the rod extending downwardly through the lower cylinder head 33 to a point therebelow, where an anvil or cross-piece 44 is mounted within a transverse slot 45 in the'rod. Leakage between the rod 43 and lower cylinder head 33 is prevented by suitable rod packing in the form of one or more round rubber, or rubberlike, seals 46, engaging the periphery of the rod, and disposed within suitable ring'grooves 41 in 4 the head 33. The packing rings 46 prevent leakage of liquids from the well casing into the cylinder 30 below the piston 45, insuring that air under atmospheric pressure is present below the piston when the apparatus is assembled and lowered in the well casing. v v v It is desired to transfer the downward movement or force of the piston 40 and the piston rod 43 to the upper slips 23 of the packer, and the relative upward movement of the cylinder 30 to the packer body l0,in order to obtain the desired anchoring of the packer in the well casing. To

accomplish this purpose, a tubular actuating mandrel 48 is threadedl connected to the lower end of the lower cylinder head 33. The lower end 5E! of the mandrel is secured to a sleeve 49, threaded into the upper end of the body 10, through the agency of a frangible connecting pin 5 l As specifically disclosed, the lower end of the mandrel is of reduced diameter and is piloted within the sleeve 49,the pin extending transversely through the sleeve 49 and piloted mandrel portion50.

The piston rod 43 is movable downwardly within the bore 52 of the actuating mandrel 48, the cross-piece 44 projecting in opposite directions from the rod through diametrically opposed, j

longitudinally extending slots 53 formedthrough the mandrel wall. The cross-piece also extends 1 into opposed slots 58, formed through asetting ring or sleeve 56 slidably mounted on the actuating mandrel 48, to form a connection between the piston rod 33 and the setting ring 56.1 A setting sleeve or skirt 5'! is adjustably threaded on' the setting ring, its lower end 59 engaging-the tops of the upper slips, 23. v w

A fluid or gaseous force is developed within the cylinder 30 above the piston 40. This force moves the piston and piston rod 43 downwardly, and'the cylinder 30in a relative upward direction. The downwardmovement of the rod 43 is transmitted to the setting sleeve or skirt51 through the anvil 44 and setting sleeve 55; whereas, the upward movement of the cylinder 30 is,

transmitted to the packer body 10 through the actuating mandrel 48, frangible pin 51,. and the sleeve 49. Accordingly, it is apparent that the development of sufiicient pressure in the cylin-.:

der 30 will eventually shear the screws 26 holding the upper slips 23 to the expander 20, and move the slips outwardly against the casing B. Thereafter, the cylinder 30 will move upwardly, to pull the body ID in the same direction, for the purpose of "expanding the-packing sleeve l9 against the casing B, and then the lower slips I4 against the above.

In order to obtain the desired operational sequence, a combustible fuel 69 may be contained within the upper end of the cylinder 30. The combustion charge, such as a railway flare of cylindrical or stick form, is placed in the head end 32 of the cylinder within a combustion chamber 10 formed therein. This combustion charge is ignited by a blank cartridge H contained within a gun barrel 12 inserted within the upper end of the cylinder head 32. Leakage between the barrel and head is prevented by a suitable side seal 13 on the barrel engaging the wall of the The barrel [2 is threaded into a firing head, which, in turn, is threadedly secured to the upper end of'the cylinder head 32. The wire line running-in string D is suitably secured to the firing head'74, in a known manner, and has, the lower,

cas ng, in the manner described end of its electrically conductive wire or core connected electrically to a heating filament 13 contained within the cartridge H.

The apparatus is lowered in the well bore with the parts disposed in the position shown in Figs. 1a and lb. When the point in the casing is reached at which the well-packer A is to be set, the circuit through the cartridge filament I6 is completed, which fires the cartridge H. The flame issuing therefrom ignites the upper end of the combustible charge 69, initiating its combustion. The charge burns and develops a gaseous pressure within the cylinder 30. As the pressure increases, the piston 40 is urgeddown-v wardly and the cylinder 3:] relatively upwardly. The force of the piston 40 is transmitted through the rod 43, cross-piece 44 and setting ring 56 to the sleeve 51, which bears against the upper slips 23. When sufficient pressure has been developed within the cylinder to overcome the shear strength of the screws 26, and also the hydrostatic head of fluid acting upwardly on the piston rod 43, the slips 23 are released from the expander and are pushed downward- 1y along the latter into outward engagement with the casing B. v

As the combustible charge continues to burn. the gas pressure within cylinder increases to a further extent. Since the upper slips 23 are wedged against the casing B, the piston can,- not move downwardly to any further appreciable extent. Instead, the cylinder 35, actuating mandrel 48, sleeve 49, and packer body II] are urged in an upward direction. When the pressure and force within the cylinder has increased suificiently to overcome the shear strength of the screws 24 holding the upper expander 2!! to the body, such screws are disrupted and the packer body In is moved upwardly within the upper expander 20 to compress the packer sleeve l9 between the upper and lower expanders 23, I8, forcing it into firm sealing engagement with the casing wall.

If the cylinder gas pressure increases further, as a result of the continued combustion of the charge 69, the screws 25, 21, attaching the lower expander Hi to the body In and the lower slips-l4 to the lower expander, are disrupted, allowing the cylinder 30 to move upwardly and carry the body I!) and lower slips l4 in an upward direction, to shift the latter radially outward into engagement with the casing B. The pressure in the cylinder continuest increase as combustion of the charge 69 proceeds, and all of the packer elements are engaged more firmly with the casing B. When the pressure A, the piston has not been moved downwardly. to its fullest extent within the cylinder 39.

Shearing of the pin 5| releases the load on the cylinder 30 and piston 40, and ordinarily allows the gas in the cylinder to partake of a sudden expansion, which shifts the piston '40 relatively downwardly to the extent limited by its engagement with the lower cylinder head 33.

When it is realized that comparatively high pressures, of the order of 5000 p. s. i. and higher, may be developed in the cylinder 3|), in order to disrupt the connector pin 5|, it is evident that a tremendous blow would be struck by the piston 40 upon the cylinder head 33. The reaction of this blow and the sudden movement of the cylinder 3|] and piston 40 introduce a recoil or shock load on all of the equipment in the well bore, which sometimes results in damage to some of the parts.

The present invention overcomes the above noted disadvantages. A liquid 80, preferably of a non-combustible variety, such as water, is placed in the cylinder 30 below the piston 40. The liquid level 8| terminates a substantial distance belowv the lower end of the piston, in order to permit 5 relative downward movement of the piston in the cylinder in efiecting full setting of the well packer A against the casing B and shearing of the frangible connector pin 5|, which releases the setting tool C from the bridge plug. The liquid level 8| is so chosen that the lower end of the piston is closely adjacent the liquid in the cylinder when the frangible pin 5| is sheared. Following such shearing, the piston 4|) may move relatively downward to a further extent, until it engages theupper end of the liquid column 80 in the cylinder. Before the piston can move downwardly in the cylinder to any further extent; it must displace or force this liquid from the cyline der 30; otherwise, the piston must remain on top of the incompressible liquid 80.

It is apparent that the liquid 80 prevents further relative downward movement of the piston 45 within the cylinder 35, and does not permit the piston to move downwardly to the full extent determined by its engagement with the lower cylinder head 33. As a result, the gaseous medium in the cylinder cannot expand to any appreciable extent after the connector pin 5| has been sheared, and is incapable of imparting a substantial velocity to the parts of the setting tool C, which impose the shock loads on the apparatus referred-to above. Thus, the liquid level can be used to regulate the length of the downward move-. ment of the piston in the cylinder.

Although the liquid medium 80 can be used for the latter purpose and to prevent sudden and full expansion of the gaseous medium, it is preferred to displace such liquid medium in a comparatively slow manner from, the cylinder 30 after, it has been engaged by the piston 40.

As indicated above, air at substantially atmospheric pressure is initially contained in the cyl-- inder 35 between the piston 40 and the liquid medium Bil. The gas underpressure in the cyl inder above the piston will, of course, compress this air during downward movement of the piston 40 in the cylinder, and it must also overcome the hydrostatic head of fluid in the well casing acting upwardly across the cross-sectional area of the piston rod 43. The area of this rod, however, is substantially less than the cross-sectional area of the piston 45; so-that only a slightly additional load is imposed by the hydrostatic head upon the apparatus, which must be overcome by the com--v bastion gas under pressure. The hydrostatic head of fluid is prevented from entering the cylinder 30 below the piston why the various packing rings 46 around the piston rod 43 and by othersuitable seal rings 35.

' Despite the fact that the hydrostatic head does not substantially interfere with the operation of the apparatus, it is still desired to take advan-. tage of this hydrostatic head in cushioning the equipment after theconnector pin 5| has been disrupted. It is also desired to utilize the liquid 80 in the cylinder 30 below the piston 40 as a cushioning medium, by allowing it to escape, comparatively slowly, from the cylinder 30 upon its engagement by the piston 40.

For the purpose of accomplishing the above noted purposes, a port or orifice 82 is provided in the cylinder sleeve 3| adjacent the lower cylinder head 33. This port or orifice is of relatively small cross-section and is initially closed by a plug 83, made of steel or other suitable material. The plug is of the type that can be forced outwardly by the liquid 8!! in the cylinder upon its being subjected to sufficient pressure, but it cannot be forced inwardly by the hydrostatic head of fluid in thewell casing. As specifically disclosed, the plug 83 has an inner cylindrical portion 84 received within a companion cylindrical bore portion of the orifice 82, there being a suitable seal ring 85 in the cylinder sleeve 3! engaging the cylindrical plug portion 84 to prevent leakage therealong in both directions. The plug is prevented from being shifted inwardly by the hydrostatic head of fluid by tapering its outer head 86 and causing this tapered portion to engage a companion seat 81 in the cylinder sleeve.

It is apparent that the hydrostatic head of fluid is prevented from entering the cylinder 30 below the'piston 40 by the plug or closure member 83. However, after the well packer A has been set in the well casing B and the connector pin sheared, the piston 45 moves a slight distance downwardly into engagement with the liquid 80 in the cylinder, the pressure of the gas in the cylinder above the piston being transmitted to the cushioning liquid 80, and from this liquid to the plug 83. When sumcient force has been exerted to overcome the hydrostatic head of fluid in the well casing, the plug 83 is blown out of the orifice 82, which then allows the cushioning liquid 80 to escape from the cylinder 30. Such escape is not instantaneous because of the restricted area of the orifice 82, the piston 40 lowering in a comparatively gradual manner under the impetus of the gaseous medium, and eventually coming to rest against the lower cylinder head 33, or immediately thereabove.

Thus, the cushioning liquid 80, by being exhausted in a gradual manner through the orifice 82, retards expansion of the gaseous medium by slowing down the rate at which the piston 40 can approach the lower cylinder head 33. Accordingly, the gaseous medium does not expand suddenly after disruption of. the connector pin 5|, which prevents shock loads from being imposed on the equipment. Not only does the liquid medium 80 function as a cushioning agent in preventing sudden expansion of the gaseous medium upon release of the load on the setting tool C, but the removal of the plug 83 from the orifice 82 subjects the entire cross-sectional area of the piston 40 to thehydrostatic head of fluid in the well casing, thereby introducing further retarding forces to full movement of the piston 40 to its lowermost position in the cylinder 30.

It is, accordingly, apparent that apparatus has been provided for preventing damage to the equipment; which cushions the shock incident to sudden release of the load on the apparatus; and which prevents sudden expansion of the generating gases by limiting the extent to which such gases can move the parts of the apparatus, following release of the load on the apparatus; or by retarding the rate at which such gases can move the apparatus parts, following release of the load to which it has been subjected.

The inventor claims:

1. In well apparatus: a well device adapted to be operated in a well bore; fluid actuated prime moving means operatively connected to said well device and adapted to be lowered in the well bore with said device to operate'the same therewithin, comprising a cylinder and piston means slidable in said cylinder; means sealing a crosssectional area of said cylinder to provide a completely enclosed space in said cylinder on the low pressure side of said piston means and to prevent the well fluid externally of said cylinder from entering said enclosed space during lowering of the apparatus in the well bore; means providing a motivating force in said cylinder on the 'high. pressure side of said piston means to slide said piston means relatively in said cylinder; and a fluid medium in said enclosed space on the low pressure side of said piston means engageable by said piston means for arresting relative movement of said piston means in said cylinder, said fluid medium comprising a liquid.

2. In well apparatus: a well device adapted to be operated in a well bore; fluid actuated prime moving means operatively connected to said well device and adapted to be lowered in the well bore with said device to operate the same therewithin, comprising a cylinder and piston means slidable in said cylinder; means sealing a cross-sectional area of said cylinder to provide a completely enclosed space in said cylinder on the low pI'BS-. sure side of said piston means and to prevent the well fluid externally of said cylinder from entering said enclosed space during lowering of the apparatus in the well bore; means providing a motivating force in said cylinder on the high pressure side of said piston means to slide said piston means relatively in said cylinder; and a fluid medium in said enclosed space on the low pressure side of said piston means engageable by said piston means for arresting relative movement of said piston means in said cylinder, said fluid medium comprising a liquid, there being a space initially between said liquid and piston means to allow initial movement of said piston means In said cylinder free from interference from said liquid.

3. In well apparatus: a well device adapted to be operated in a well bore; fluid actuated prime moving means operatively connected to said well device and adapted to be lowered in the well bore with said device to operate the same therew thin, comprising a cylinder and imperforate p ston means slidable in said cylinder; means closing said cylinder to provide a closed space therewithin on the low" pressure side of said piston means and to prevent well fluid externally of said cylinder from entering said closed space during lowering of the apparatus in the well bore said cylinder having an orifice on the low pressure side of said piston means; means providing a motivating force in said cylinder on the high pressure side of said piston means to slide said piston means relatively in said cylinder; closure means closing said orifice against entr of well fluid into said cylinder from the exterior of said cylinder; a fluid medium in said closed space on the low pressure side of said piston means engageable by said piston means for opening said closure means and arresting relative movement of said piston means in said cylinder, said fluid medium comprising a, liquid, there being a space initially between said liquid and piston means to 9 allow initial movement of said piston means in said cylinder free from interference from said liquid.

4. In well apparatus: a well device adapted to be operated in a well bore; fluid actuated prime moving means operatively connected tosaid well device and adapted to be lowered in the well bore with said device to operate the same therewithin, comprising a cylinder and imperforate piston means slidable in said cylinder; means closing said cylindertoprovide a closed space therewithin on the low pressure side of said piston means and to prevent well fluid externally of said cylinder from entering said closed space during lowering of the apparatus in the well bore means providing a motivating force in said cylinder above said piston means to slide said piston means relatively downward in said cylinder; and

a fluid medium in said closed space below said piston means engageable by said piston means for arresting relative downward movement of said piston means in said cylinder, said fluid medium comprising a liquid.

5. In well apparatus: a well device adapted to be operated in a well bore; fluid actuated prime moving means operatively connected to said well device and adapted to be lowered in the well bore with said device to operate the same therewithin, comprising a cylinder and piston means slidable in said cylinder; means closing said cylinder to provide a closed space therewithin on the low pressure side of said piston means and to prevent fluid from entering said closed space; said cylinder having an orifice in its lower end; an outwardly removable plug initially closing said orifice; means providing a motivating force in said cylinder abov said piston means to slide said piston means relatively downward in said cylinder; and a fluid medium in said closed space below said piston means engageable by said piston means for displacement through said orifice to arrest relative downward movement of said piston means in said cylinder, said fluid medium comprising a, liquid.

6. In well apparatus: a well deviceadapted to be operated in a well bore; fluid actuated prime moving means for operating said well device and adapted to be lowered in the well bore with said device to operate the same therewithin, comprising a cylinder and piston means slidable in said cylinder; means sealing a cross-sectional area of said cylinder to provide a completely enclosed space in said cylinder on the low pressure side of said piston means and to prevent the well fluid externally of said cylinder from entering said enclosed space during lowering of the apparatus in the well bore; means releasably securing said fluid actuated means to said well device; means providing a motivating force'in said cylinder on the high pressure side of said piston means to slide said piston means relatively in said cylinder; and a fluid medium in said enclosed space on the low pressure side of said piston means engageable by said piston means for arresting relative movement of said piston means in said cylinder upon release of said securing means, said fluid medium comprising a liquid.

'7. In well apparatus: a well device having normally retracted means engageable with a well casing; fluid actuated prime moving means for expanding said normally retracted means against the casing, comprising a cylinder and a piston slidable in said cylinder, means closing said cylinder to provide a closed space therewit-hin on the low pressure side of said piston and to prevent well fluid externally of said cylinder from entering said closed space during lowering of the apparatus in the well casing; said cylinder having an orifice therein on the low pressure side of said piston and closure means normally closing said orifice against entry of fluid into said cylinder from; the exterior thereof; means releasably securing said fluid actuated means to said well device; and a fluid medium in said closed space engageable with said piston for retarding relative movement of said piston in said cylinder, said fluid medium, comprising a liquid subject to pres-.- sure by said piston to effect opening of said closure means and to be expelled from said cylinder through said orifice, there being a space initially between said liquid and piston to allow initial movement of said piston in said cylinder free from interference from said liquid until after release of said securing means.

8. In well apparatus: a well device having normally retracted means engageable with a well casing; fluid actuated prime moving means for expanding said normally retracted means against the casing, comprising a cylinder and a piston slidable in said cylinder, said cylinder and piston providing a closed fluid tight space on the low pressure side of said piston into which Well fluid externally of the cylinder cannot enter during lowering of the apparatus in the well casing, said cylinder having an orifice therein on the low pressure side of said piston and closure means normally closing said orifice against entry of well fluid externally of said cylinder into said closed space; means releasa-bly securing said fluid actuated means to said well device;-and a fluid medium in said closed space engageable with said piston for retarding relative movement of said piston in said cylinder, said fluid medium comprising a liquid subject to pressure by said piston to effect opening of said closure means and to be expelled by said piston from said cylinder through said orifice.

9. In well apparatus; a well device having a body and normally retracted means for engagement with a well casing; fluid actuated means for setting said device in said well casing comprising a piston means for exerting a downward force on said normally retracted means and a cylinder for exerting an upward force on said body; said cylinder and piston means providing a closed fluid tight space on the low pressure side of said piston means; frangible means for transmitting said upward force between said cylinder and body; said cylinder having an orifice at its lower end; closure means for preventing entry of fluid through said orifice into said cylinder; and a fluid medium in said closed space below said piston means for shifting said closure means to open position upon being subjected to pressure by said piston means, said fluid medium comprising a liquid spaced initially from said piston means and engageable by said piston means after disruption of said frangible means to be expelled by said piston means from said cylinder through said orifice.

10. In well apparatus: a well device having a body and normally retracted means for engagement with a well casing; fluid actuated means for setting said device in said well casing comprising a piston means for exerting a downward force on said normally retracted means and a cylinder for exerting an upward force on said body; said cylinder and piston means providing a closed fluid tight space on the low pressure side of said piston means; frangible means for transmitting said upward force between said cylinder 'fiuid through said orifice into said cylinder; and

a fluid medium in said closed space, said medium being spaced initially a substantial distance below said piston means and adapted to be subjected to the pressure of said piston means, upon disruption of said frangible means, to shift said closure means to orifice opening position and retard relative movement of said piston means in said cylinder, said fluid medium comprising a liquid ejectable by said piston means through said orifice and from said cylinder.

, REUBEN C. BAKER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Scott July 15, 1913 Flynn Apr. 21, 1936 Wells et a1 Apr. 6, 1937 Coshow Dec. 28, 1937 Baker Nov. 7, 1939 Broyles Feb. 13, 1940 Futral July 6, 1943 Baker Apr. 3, 1945

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