US3518030A - Fluid supply system - Google Patents

Description

June 30, 1970 G. T. KLEES I 3,518,030

FLUID SUPPLY SYSTEM Filed April 12, 1968 3 Sheets-Sheet 1 QE 4M ATTO/Q/VEY June 30, 1970 G. T. KLEES 3,518,030

FLUID SUPPLY SYSTEM Filed April 12, 1968 3 Sheets-Sheet i3 I NVEN TOR.

BY Gerard f/Vees gam A 7' TOR/V5 Y June 30, 1970 Filed April 12.. 1968 PRESSURE-PSIG IBO I70- I60 I50- I40- I30 I20- IIO- G. T. KLEES 3,518,030

FLUID SUPPLY SYSTEM I 3 Sheets-Sheet 3 PRESENT INVENTION PR|OR ART 4 6 8 IO l2 |4|6 I820 TIME-"MINUTES INVENTOR. f 7 GawmfAYees United States Patent US. Cl. 417-259 2 Claims ABSTRACT OF THE DISCLOSURE A dual chamber, two-stage compressor operated by a flexible diaphragm moved in alternate directions by an alternating pressure differential, having a movable hollow piston secured to the diaphragm and disposed within a stationary cylinder and constituting a movable cylinder that receives a stationary piston. The volume enclosed by the stationary cylinder and the movable piston forms a first-stage compression chamber and the volume enclosed by the stationary piston and the interior of the hollow movable piston forms a second-stage compression chamber. A thin end wall on the movable piston has a short length port therein for inter'communicating the compression chambers by means of a minimum volume passageway.

This invention relates to a compressor operated by a fluid pressure differential activating member and, more particularly, such compressors wherein a pressure actuated diaphragm is associated with an improved plural piston and cylinder arrangement for producing two-stage compression of fluid.

Many present day pressure actuated systems, for example, auxiliary air lift leveling systems for automobiles or the like, require a low cost, compactly arranged, pressurized fluid supply system. A problem in the past and one which the subject invention remedies is the excessive time required to bring a pressure reservoir up to a suitable working pressure.

The subject vacuum operated compressor is an improvement over the vacuum operated compressor shown in the patent to G. W. Jackson 3,253,775. Jacksons compressor is a two-stage, vacuum operated, air compressor including two pistons disposed within cylinders positioned on opposite sides of the diaphragm actuator. The two pistons are interconnected by a piston rod which itself is attached to a diaphragm actuator thus providing the means for reciprocal movement of the two pistons within the cylinders. A long axial passageway through the two pistons and the piston rod intercommunicates a first-stage compression chamber with a second-stage compression chamber. The pressurized air within the axial passageway may be referred to as dead volume air in the sense that following the first-stage compression stroke the pressurized air therein will not be discharged into the secondstage compression chamber. This volume of air will freely expand back into the first-stage compression chamber on opposite movement of the pistons. Work is thus expended in pressurizing this dead volume air during the firststage compression stroke which air is not discharged into the second-stage compression chamber. One manifestation of this inefficient use of input energy is an undesirable time delay in producing a predetermined pressure rise in a reservoir connected to the compressor outlet.

An object of the present invention, therefore, is to improve the volumetric efficiency of two-stage compressors by the provision therein of an improved piston-cylinder arrangement. The novel piston-cylinder arrangement of the subject invention eliminates the dead volume space between the firstand second-stage compression chambers. The subject invention, by eliminating this dead ice volume space, greatly reduces the time period required to produce a given volume of pressurized fluid for a given pressure differential working across an actuating diaphragm. Also, a greater peak pressure is obtainable due to more eflicient utilization of input energy.

A further object of the present invention is to improve two-stage diaphragm actuated compressors by the provision of recessed end portions of the pistons which upon reciprocation fit over and around protruding valving elements in the cylinders. This arrangement of piston head construction further helps to eliminate any dead volume space which would otherwise exist because of the interference between piston heads :and protruding valves.

Further objects and advantages of the present invention will be apparent from the following description, reference being bad to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIG. 1 is a phantom view in side elevation of a vehicle with a fluid pressurized automatic leveling system including the compressor of the present invention;

FIG. 2 is a view partly in elevation and partly in section taken along lines 2-2 of FIG. 3 and showing the piston-cylinder relationship at the beginning of the second-stage compression stroke;

FIG. 3 is a fragmentary, enlarged, view partly in elevation and partly in section of the compressor of the present invention looking in the direction of the arrows in line 33 of FIG. 2;

FIG. 4 is a fragmentary view in vertical section like FIG. 2 showing the piston-cylinder relationship at the beginning of the first-stage compression stroke;

FIG. 5 is a fragmentary, enlarged View in vertical section of the end-wall structure of the movable piston;

FIG. 6 is a schematic drawing revealing the novel piston-cylinder arrangement which eliminates dead volume between the first-stage and second-stage compression chambers;

FIG. 7 is a graph plotting outlet pressure in pounds per square inch versus time in minutes required to bring the automatic leveling system of FIG. 1 up to its operating pressure.

In FIG. 1 of the drawings, a vehicle 1 is illustrated as including a sprung assembly comprising a chassis frame 2 having a body 3 supported thereon. An unsprung assembly comprising ground engaging wheels 4 is supported on axle housing 5 in a conventional manner. Chassis frame 2 and the body 3 are supported relative to the axle housing 5 by means schematically illustrated as including a pair of spaced control arms 6, only one of which is shown, each pivotally secured by a pin 7 to a bracket 8 fixed to the suspended chassis frame 2. The opposite end of each control arm 6 is rigielly secured to the axle housing 5 through a bracket 9. Each control arm 6 serves as a support for one of a pair of coil-type primary suspension springs 10 mounted between the control arm 6 and the frame 2, thus, providing spring support between sprung and unsprung masses. In addition to the supporting action of each coil-type chassis spring 10, automatic vehicle chassis leveling control is provided by shock absorber and air spring auxiliary suspension units 11 located on each of the control arms 6. Each of the units '11 is pivotally secured at its opposite ends to one of the control arms 6 and the frame 2.

Details of a typical combination shock absorber air spring auxiliary suspension unit 11. are more particularly set forth in US. Pat. 3,042,392. Each of the suspension units 11 basically includes a direct acting hydraulic shock absorber 12 having an inflatable element, or air spring, 13 thereon. When inflated, the air spring 13 supplements the load carrying capacity of the coil springs 10 so as to prevent excessive engagement of the chassis 2 with conventional bump stops, not shown, on the vehicle axle 1. In addition, undue elevation of the front end of the vehicle 1 caused by heavy loading in the vicinity of the axle '5 is prevented. The above described system, of course, is merely illustrative, it being fully understood that the improved features of the compressor of the present invention are equally well suited for association with arrangements having pressure actuated components equivalent to air spring means 13.

Referring now to FIGS. 2 through 4, a pressurized fluid system 14 is illustrated including an elongated cylindrical pressure reservoir 15 having a closed end 16 and an open end 17. The end 17 has a ring-like reinforcing bracket 18 connected thereto for supportingly receiving an outwardly directed flange 19 upon a first housing portion 20 of a pressure differential powered compressor 21. Between the bracket 18 and the flange 19 an annular sealing element 22 of a resilient material is located in sealing engagement therebetween. For a more detailed explanation of the pump-reservoir combination as described above, reference is made to the United States Pat. 3,215,339. In that patent a two-stage double action pump forms one end of a cylindrical reservoir.

In the illustrated embodiment, the first housing portion 20 has a reservoir outlet 23 directed therethrough interconnecting the reservoir 15 with a pressure regulator 24. A conduit 25 transports the pressurized fluid from regulator 24 to a three position height control valve 26 located adjacent the suspension unit 11. Control valve 26, which is operably connected to the control arm 6, either directs pressurized fluid to the air spring 13, directs the fluid from the air spring -13, or prohibits escape of the fluid from the air spring 13. The control valve 26 thus automatically pressurizes or deflates the air springs 13 by mechanical interpretation of the angular position of control arm 6 in relation to chassis 2. For a more detailed explanation of the height control valve 26, reference is made to U.S. Pat. 2,967,547. For a more detailed explanation of the pressure regulator valve 24, reference is made to U.S. Pat. 3,285,617.

Referring now more particularly to the pressure differential powered compressor 21, in FIGS. 2 through 4, an unusually compact two-stage compressor is illustrated. A second housing portion 27 is joined to the first housing portion 20 and to the bracket 18 on the reservoir 15 by screw and nut fasteners 28 directed through the peripheral parts of portions 20, 27.

Housing portion 27 has an outwardly directed extension thereon which serves as a first-stage stationary cylinder 29. A cylindrical bearing sleeve 30 is press fitted within the cylinder 29. Across the peripheral juncture of housing portions 20, 27 which define a chamber therebetween is disposed a contoured flexible diaphragm 31 which divides this chamber into first and second power chambers 32, 33. The diaphragm 31 is directed transversely of the housing portions 20, 27 so that its outer periphery is secured between adjoining edges of portions 20, 27 by fasteners 28. A pair of apertured reinforcing discs 34, 35 are located on opposite faces of diaphragm 31 and define therethrough a central axial opening. Secured to the diaphragm 31 and extending through the central opening is one end of a movable dual purpose hollow piston 36. More particularly, the movable piston 36 is attached to the diaphragm 31 and discs 34, 35 by an annular snap ring 37 disposed over the inward end of the piston 36. The snap ring 37 biases the discs 34, 35 and the diaphragm 31 against a radially outwardly extending shoulder of the movable piston 36. The other end of the movable piston 36 is slidably sealingly disposed in the sleeve 30 within the coaxial stationary cylinder 29 of the housing portion 27. This same end of the movable piston 36 is closed by a thin end wall 38, the significance of which will be explained hereinafter. A hearing sleeve 39 similar to the sleeve 30 is press fitted within a cylindrical bore of piston 36. Because sleeves 30, 39 are made from a material which has a low coefficient of friction, the limited quantity of input work available from a given pressure differential across the diaphragms 31 is not dissipated by frictional losses. Directed outwardly from the housing portion 20 and coaxially with stationary cylinder 29 is a hollow stationary piston 40 fixedly secured at one end to the housing portion 20. The other end of the piston 40 is directed through the central opening of the diaphragm 31 and coaxially into the cylinder formed by sleeve 39 within the bore of the movable piston 36.

The variable volume space defined by stationary cylinder 29 and movable piston 36 constitutes a first-stage compression chamber 41. The variable volume space defined by the bore of piston 36 and stationary piston 40 constitutes a second-stage compression chamber 42. An alternating pressure differential across diaphragms 31 effects reciprocal movement of piston 36, to vary the volumes of the firstand second-stage compression chambers 41, 42 to compress and move the fluid through the pump.

An outer end of the movable piston 36 supports an annular seal 43 made of Teflon that sealingly slidably engages sleeve 30. The seal 43 is radially outwardly biased against sleeve 30 by a radially inwardly compressed O-ring 44. The outer end of the stationary piston 40 also supports an annular seal 45 made of Teflon that sealingly slidably engages the sleeve 39. Seal 45 is radially outwardly biased against sleeve 39 by a radially inwardly compressed O-ring 46.

The thin end wall of the movable piston 36 has an axially directed short length port 47 intercommunicating the first-stage compression chamber 41 with the secondstage compression chamber 42. A check valve 48 is biased outwardly against port 47 by a coil spring 49. Valve 48 controls the flow of first-stage compressed fluid through the port 47 into the second stage compression chamber 42. Because of the thin end wall 38 of the piston 36 and the resulting close proximity of the firstand second-stage compression chambers 41, 42, the intercommunication passageway between the compression chambers 41, 42 is reduced to a minimum volurne. An axially extending inlet opening 50 within the end portion of the stationary cylinder 29 permits air from the atmosphere to be drawn into the first-stage compression chamber 41. An air inlet valve 52 is disposed within the cylinder 29 and is biased outwardly by a coil spring 51 against inlet opening 50. An axially extending outlet opening 53 within the end portion of the stationary piston 40 provides for the discharge of compressed fluid directly from the second-stage compression chamber 42 into the reservoir 15. Disposed within the interior of hollow piston 40 and seated against opening 53 is an outlet valve 54. Coil spring 55 biases valve 54 outwardly against opening 53.

The end wall, or head, of the movable piston 36 has a cylindrical recess 56 as best seen in FIG. 5. Upon reciprocation of piston 36 outwardly in the stationary cylinder 29 the recessed end portion 56 moves over and around the protruding inlet valve 52. Because of this arrangement, substantially all of the air within the first-stage compression chamber 41 is expelled into the second-stage compression chamber. This piston head construction, in addition to promoting compactness, expells fluid from the chamber 41 which otherwise would remain after the first-stage compression stroke. Any such unexpelled fluid expands back into the first-stage compression chamber 41 during the first-stage inlet stroke. Without a recessed piston head construction, some input work would be wasted on the compression of such dead volume fluid. Serving :a similar function in regard to fluid within the second-stage compression chamber 42 is a recess 57 with in the end, or head, of stationary piston 40. Recess 57 receives protruding valve 48 located on end wall 38. By this means essentially all the fluid within the second-stage compression chamber 42 is swept into the reservoir 15.

By virtue of the provision of val'ving elements of the aforedescribed type in association with the reciprocating diaphragm-actuated recessed piston, an efficient compact compressor is obtained. A limited pressure differential such as established by the manifold vacuum of an automobile acting alternately on opposite sides of the flexible diaphragm 31 provides the activating force for compression of a fluid such as air. An alternating pressure differential across diaphragm 31 is obtained under the control of a reversing valve assembly 58.

The fluid flow in the illustrated embodiment of the compressor 21 begins with the passage of fluid through a port 59 for-med within a cover 60 of the reversing valve assembly 58. The fluid then passes into compartment 61 defined by cover plate 60 and the second housing portion 27. The fluid next passes from compartment 61 through the inlet opening 50 past inlet valve 52 into the ever increasing volumetric space of the first-stage compression chamber 41. This first-stage inlet stroke occurs upon reciprocation of the movable piston 36 toward stationary piston 40. Following a predetermined stroke during which time the variable volume first-stage compression chamber 41 progresses to a predetermined maximum volume, the movable piston 36 will be reciprocated in an opposite direction by reversing the pressure differential across diaphragm 31. During this opposite reciprocation, movable piston 36 slides away from stationary piston 40 which progressively reduces the volume of the first-stage compression chamber 41. During this first-stage compression stroke fluid is forced from the first-stage compression chamber 41 through the port 47 formed in the thin end wall 38 of the piston 36. The fluid flows by the check valve 48 into the ever increasing volume of the secondstage compression chamber 42. Reference is now made to the Jackson patent, herein'before mentioned, which is the predecessor of the subject improved compressor. That compressor contained a long axial passageway between the firstand second-stage compression chambers. Fluid pressurized within this axial passageway during the firststage compression stroke could not be expelled into the second-stage compression chamber. Rather than being expelled, the pressurized air in the passageway re-expanded into the first-stage compression chamber during the firststage inlet stroke. It can be readily understood that the present improvement on the prior Jackson compressor greatly reduces this wasteful use of input work by eliminating the long axial passageway by the substitution of a short length port 47 within the thin wall 38 of the movable piston 36 separating the compression chambers.

The following data concerning the volumetric characteristics of the prior Jackson compressor and the subject compressor emphasizes the dramatic reduction of dead air volume in the improved compressor. Jacksons prior compressor contains approximately thirty-six thousandths of a cubic inch of dead air within the long axial passageway which joins the compression chambers. With substantially the same size firstand second stage compression chambers in both compressors, the volume of dead air withinthe short length port of the subject invention is approximately thirty-eight ten thousandths of :a cubic inch. Thus, the subject compressor has improved volumetric characteristics by an approximate ten fold reduction in dead air space. The following parameters of compressor performance and efliciency are calculated on the basis of stated tolerance limits which accounts for the range of values. The ratio of volume of the first-stage compression chamber to the volume of the unswept dead air space in the prior Jackson compressor lies between 19 and 22 to 1. The same ratio in the subject compressor ranges between 168 and 256 to 1. The first-stage volumetric efficiency of the prior Jackson compressor is approximately .947 while the subject invention has an improved first-stage volumetric efliciency of .994. The volume of port 47 varies from 390% to 596% of the volume of the first-stage compression chamber. In Jacksons compressor the volume of the axial passageway varies from 4.50% to 5.22% of the volume of the first-stage compression chamber. FIG. 7 reveals a forty-two percent decrease in time necessary to achieve a working pressure of psi. realized by the subject compressor in test comparison with Jacksons prior compressor. Another benefit resulting from the elimination of dead air volume is a 13% increase in peak pressure attained by the subject improved compressor.

The schematic illustrated in FIG. 6- clearly reveals the fluid path through the compressor during operation of the subject invention. During the first-stage compression stroke the movable piston 36 moves away from housing portion 20. Inlet valve 52 is biased against the end of stationary cylinder 29 by the pressure build-up within the first-stage compression chamber 41 and by the inlet spring 51 to thereby prohibit fluid leakage from the first-stage compression chamber 41. Fluid compressed within the first-stage compression chamber 41 is forced through the short length port 47 into the second-stage compression chamber 42. Check valve 48 which is biased against port 47 by spring 49 allows one-way fluid flow from the first-stage compression chamber 41 into the second-stage compression chamber 42. On opposite reciprocation of the piston 36 toward stationary piston 40 the fluid is further compressed within the second-stage compression chamber 42. Movement of the piston 36 towards the stationary piston 40 reduces the volume of the second-stage compression chamber 42 and forces the compressed fluid through outlet opening 53. Outlet valve 54 normally biased outwardly against outlet opening 53 by spring 55 yields to the increasing pressure in the second-stage compression chamber 42 allows the fluid to pass intodischarge passageway 62. The discharge passageway 62 is an axially extending bore within stationary piston 40 which communicates the second-stage compression chamber 42 with reservoir 15.

Alternate reciprocal movement of the piston 36 is provided by an alternating pressure differential across diaphragm 31. This is accomplished by a piston driven reversing valve assembly 58 that alternately fluidly connects the power compartments 32, 33 with a vacuum or atmospheric source. The various parts of the reversing valve assembly 58 are made of a material possessing a low coefficient of friction so as to operate without materially effecting the efliciency of the compression portion of the system. More particularly, the reversing valve assembly 58 is illustratively shown as being associated with a pressure port 63 in housing portion 27. Pressure port 63 is fluidly connected with a source of subatmospheric (or superatmospheric) pressure. The vacuum manifold on the internal combustion engine of an automobile may be conveniently used for this purpose. The housing portion 27 is further provided with two ports 64, 65 positioned equidistantly on each side of the pressure port 63. Port 65 communicates power chamber 32 with atmospheric through a port extension formed in the housing portions 20, 27. Port 64 communicates power chamber 33 with atmosphere through a port extension in the housing portion 27.

A reversing valve 66 is pivotally' secured to the housing portion 27. The function of valve 66 is to alternately communicate the pressure port '63 with ports 64, 65. Reciprocal motion of the piston 36 causes shoulder portions 36a, b on pison 36 to alternately engage a crank arm 67 which produces a limited alternate oscillatoiy motion of the crank arm 67. The motion of crank arm 67 in turn produces limited rotative oscillatory motion of an operatively connected bent swivel arm 68. An end 69 of the bent swivel arm 68 projects through a pivoted actuating arm 70. Thus, motion of the end '69 of the bent swivel arm 68 in a limited rotative oscillatory motion imparts the same movement to the actuating arm 70. Because of a pin and slot mechanism (not shown) on facing sides of the actuating arm 70 and the valve 66,

respectively, oscillatory rotative motion of the pivoted actuating arm 70 is transferred to the valve 66. It is this oscillatory rotative motion of valve 66 which alternately connects ports 64, 65 with the pressure port 63. A snap action is imparted to the valve 66 by a spring 71 extending from the end of the best swivel arm 68 to a pin 72 positioned at the outer end of the pivoted actuating arm 70. For a more detailed explanation of the reversing valve assembly 58, reference to is made tothe U.S. Pat. 3,200,844. To insure that the limited power derived from a given pressure differential across diaphragm 3-1 will not be substantially dissipated in actuating the reversing valve assembly 58, light weight components made from a material with a low coefficient of friction are utilized. These characteristics allow the reversing assembly to quickly respond to limiting actuating force produced by the engagement of crank arm 67 with the piston 36.

In order to protect the operating parts of the reversing valve assembly 58, cover 60 is secured to the end face of the housing portion 27 by a screw fastener 74.

While the embodiment of the present invention as herein described constitutes a preferred form, it is to be understood that other forms might be adapted.

What is claimed is as follows:

1. A two-stage compressor, comprising: a first housing portion and a second housing portion; said housing portions joined together to form a chamber; a flexible diaphragm extending transversely Within said chamber and held at its outer periphery between said housing portions; said diaphragm dividing said chamber into first and second power chambers; means for producing a pressure differential across said diaphragm; means for reversing said pressure differential upon opposite movement of said diaphragm within said housing; a stationary cylinder in said housing; a hollow movable piston slidably supported within said stationary cylinder and forming therewithin a variable volume first-stage compression chamber; said hollow movable piston having an inner cylindrical bore with one end closed by an end wall and the other end left open; means connecting said hollow movable piston with said diaphragm for reciprocation therewith; an elongated hollow stationary piston in said housing and coaxial with said stationary cylinder; said stationary piston slidably sealingly extending into said bore of said hollow movable piston and forming therewith a variable volume secondstage compression chamber; said end walls of said hollow movable piston having a short length port inter-communicating said first-stage compression chamber with said second-stage compression chamber; said port through said end wall characterized by a small volume; said volume not to exceed .60 percent of the volume of said first-stage compression chamber; protruding valve means coacting with said port for controlling flow from said first stage compression chamber to said second-stage compression chamber upon reciprocation of said hollow movable piston in a direction to expand the second-stage compression chamber thus constituting a first-stage compression stroke; said stationary cylinder having an inlet opening therethrough; an inwardly, protruding inlet valve coacting with said inlet opening to control the flow of fluid into said first-stage compression chamber upon reciprocation of said hollow movable piston in a direction to expand the first-stage compression chamber thus constituting a second-stage compression stroke; said hollow stationary piston having an outlet opening therethrough; an outlet valve coacting with said outlet opening to control the flow of fluid out from said second-stage compression chamber during said second-stage compression stroke; said hollow stationary piston serving as a discharge passageway from said second-stage compression chamber; recess means within the said end wall of said hollow movable piston for reception of said protruding inlet valve; and recessed end means on said stationary piston for reception of said protruding outlet valve.

2. A two-stage compressor, comprising: a first housing portion and a second housing portion; said housing portions joined together to form a chamber; a flexible diaphragm extending transversely within said chamber and held at its outer periphery between said housing portions; said diaphragm dividing said chamber into first and second power chambers; means for producing a pressure differential across said diaphragm; means for reversing said pressure differential upon opposite movement of said diaphragm within said housing; a stationary cylinder in said housing; a hollow movable piston slidably supported within said stationary cylinder and forming therewithin a variable volume first-stage compression chamber; said hollow movable piston having an inner cylindrical bore with one end closed by an end wall and the other end left open; means connecting said hollow movable piston with said diaphragm for reciprocation therewith; an elongated hollow stationary piston in said housing and coaxial with said stationary cylinder; said stationary piston slidably sealingly extending into said bore of said hollow movable piston and forming therewithin a variable volume second-stage compression chamber; said end wall of said hollow movable piston having a short length port intercommunicating said first-stage compression chamber with said secondstage compression chamber; said port through said end wall characterized by a small volume; protruding valve means coacting with said port for controlling flow from said first-stage compression chamber to said second-stage compression chamber upon reciprocation of said hollow movable piston in a direction to expand the second-stage compression chamber thus constituting a first-stage compression stroke; said stationary cylinder having an inlet opening therethrough; an inwardly, protruding inlet valve coacting with said inlet opening to control the flow of fluid into said first-stage compression chamber upon reciprocation of said hollow movable piston in a direction to eX- pand the first-stage compression chamber thus constituting a second-stage compression stroke; said hollow stationary piston having an outlet opening therethrough; an outlet valve coacting with said outlet opening to control the flow of fluid out from said second-stage compression chamber during said second-stage compression stroke; said hollow stationary piston serving as a discharge passageway from said second-stage compression chamber; a recess within the said end wall of said hollow movable piston for reception of said protruding inlet valve; and a recess on the end of said stationary piston for reception of said protruding valve means.

References Cited UNITED STATES PATENTS 495,348 4/1893 Lawson 230200 2,669,186 2/1954 Parker 10353 2,880,927 4/1959 Ploegert 230-200 3,151,805 10/1964 Pribonic 230200 3,253,775 5/1966 Jackson 23052 WILLIAM L. FREEH, Primary Examiner U.S. Cl. X.R. 417-399, 549

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