US2500237A - Pressure intensifier - Google Patents

Description

March 14, `1950 G. s. ANDREWS PRESSURE INTENSIFIER Filed Nov. 23, 1945 Patented Mar. 14, 1950 NTED STAT TENT OFFICE Claims.

This invention relates to improvements in piston-cylinder assemblies for compressing or exerting pressure upon orthrough uids, including gases, liquids, and plastic substances, for operating hydraulic systems, and systems for such as pressure molding, die-forming, and/or extrusion oi plastics and other ductile materials.

The invention relates more particularly to immovements in compound piston assemblies, for master cylinders and the like, by the use of which successively higher degrees of compression can be obtained without the exertion of corresponding increases in the applied external operating force, and in which an initial stage of relatively low compression results from movement of the piston from starting position to an intermediate position in its cylinder as a result of initial application oi the external force to the piston, and a succeeding higher compression stage results from movement beyond said intermediate position of only a limited portion of the piston of smaller cross section than the working face' of the piston, as a result of continued application of said external force.

A primary object of the invention is to provide an improved compound piston and cylinder assembly of this character, wherein the main body oi the piston automatically locks itself in said intermediate position in the cylinder, and Will not become unlocked and recede from such int-ermediate position until after said external force has been removed or substantially reduced.

A further important object of the invention is to provide a compound piston and cylinder assembly of the character indicated above in which a plunger oi smaller cross section than the working face of the main body of the piston, and carried in said main body is free, while the main body of the piston is in locked position, to move beyond the working face of the piston, as a result of continued exertion of the external force.

A further object of the invention is to provide an improved piston and cylinder unit of the character indicated above, in which the main body of the piston involves at least two components which are axially separated while the application of external force upon the piston is relaxed and the piston is in a starting position, but which comes together when such force is applied and the piston has moved toward an intermediate position in the cylinder in such a way as to preclude further axial movement of said main body of the piston in the pressure producing direction.

A further object of this invention is to provide a piston and cylinder construction of the char'- acter indicated above in which the said components of the .main body of the piston are operatively connected with the cylinder in such a way as to be guided in and restricted to predetermined movement, relative to the cylinder and relative to each other, resulting in their locking engagement, as the piston moves as a whole away from starting position toward said intermediate position.

A still further object of the invention is the provision of a piston and cylinder construction of the character indicated above, in which the reduced cross section plunger extends through and acts as a guide and means of assembly vfor the components ofthe main body of the plunger, and as support for spring means Which operate to separate said components as the applicationl oi external force upon the piston is removed oi" relaxed below a predetermined level, and to retract said plunger from projection beyond the working face of the piston.

Other important objects and advantageous features of this invention will be apparent from the following detailed description and the drawing appended thereto, wherein, merely for purposes'of illustration, a presently preferred embodiment of the invention is set forth.

In the drawings:

Figure l is a longitudinal view with the shell and the cylinder broken away to show the components of the main body of the piston and the plung'erin their relative positions in their shell and in the cylinder before application of initial external operating 4force suiiicient to move they locking component toward locking engagement.

Figure 2 is a similar view on a somewhat smaller scale, with the shell removed, and with the components of the main body of the piston shown inlongitudinal section, and in the positions theyl occupy before application of external operating force. Figure 3 is a view similar to Figure 2, showing the relative positions of the parts upon ap plication of external force suicient to engage the locking components in locking relation in the intermediate position of the piston yin the cylinder.

Figure 4 is a View similar to Figure 3, showing the relative positions of the parts as exertion oi external operating force is continued beyond that producing locking of the piston in the cylinder, and is suicient to produce projection of the accuserv plunger beyond the working face of the piston, and,

Figure 5 is a horizontal section taken on the line 5-5 of Figure l.

The invention comprises in general an arrangement of a cylinder in which the fluid upon which mechanical pressure is to be exerted; a piston working in the cylinder for compressing the fluid therein; a hollow piston rod extendingv rearwardly from the piston composed of several sections which are movable axially relative to each other, one of which is connected to or integral with the piston with Aan end section connected to the particular force applying means which is to be employed, such as a brake pedal, in the case of a hydraulic brake system; with the sections of the hollow piston rod slidably conlned in a tubular shell axially aligned with, and preferably integral with the said cylinder, suitable spring means being provided to urge the sections of the hollow piston rod apart while the force applying means is' inactiveand retracted; with means cooperating between the shell and certain of the sections of the hollow piston rod whereby such sections are conn'ed to predetermined paths of relative moveu nient in the tubular shell, as' they are moved axial'ly in the shell, that, upon actuation of the force applying means producing compressive movement of the piston in the cylinder, said certain sections will lnterengage against predetermined resistance of said spring means and in so doing lock themselves' against further movement in the shell in the compressing direction, thereby arresting further compressive movement of the piston in the cylinder, without at this point arresting further actuation of the'piston by said force applying means; and with a solid plunger of relatively small cross section, operatively connected to the said "end section and extending through intermediate sections of the hollow piston rod and through the piston in such a way that further compressive movement of the force applying means, and hence of said end section, beyond the point at which the piston is arrested produces projection of the forward end of the solid plunger beyond the working face of the piston and into the' fluid in the cylinder for quickly raising or intensifying the fluid pressure within the cylinder beyond that produced by the preceding movement of the piston in the cylinder.

The means contemplated by the present invention for eiecting interengagement of two or more sections of the hollow piston rod includes any workable arrangement wherein'the interengageable sections, while positively guided by their connection with the shell, are free to move in the shell axially relative to each other, while being confined to paths of movement such that the coming together into touching relation of these sections against the resistance of the spring means which normally urges them apart, produced by actuation of the force applying means, positively locks these sections against any further axial movement, in such a way that further movement of the piston in the compressing direction is prevented. Hence, although this disclosure shows specific embodiments of such locking means, the invention is obviously not limited thereto.

y Referring in detail to the drawings, the herein disclosed embodiment of the invention comprises a hydraulic cylinder J having the integral or otherwise suitably connected` cylindrical tubular shell H, here shown as slightly larger in diamo-- ter internally and externally than the hydraulic itil 4 cylinder J. The bore of the shell H is provided with a spiral groove i, and with two diametrically opposed straight longitudinal grooves 2, 2, only one of which appears in Figure l, the other groove 2 being in the removed half of the shell H. The straight longitudinal grooves 2 extend substantially for the full length oi the shell H, while the ends of the single spiral groove i terminate short of the. adjacent ends of the grooves 2.

Freely slidable within the upper end of sleeve H is a sleeve or head A having a boss 9 which is provided for connection with the means, not shown, used to apply force ior operating the present device; The head A is formed with an axial bore IE provided near its open lower end with a retaining shoulder l2 for retaining within the bore Il! the enlargement ii on the upper end of the plunger rod E.

Below the head A a tubular cylindrical locking member B is movably circumposed on the rod E and has an internal shoulder i3 concentrically surrounding the rod. The shoulder i3 acts as a seat for the lower end of a helical spring F which is circumposed on the rod E between head A and locking member B, and has its upper endv seated on the shoulder I2 of the head A, so as to urge head A and locking member B- away from each other. The locking member B has diametrically opposed straight ribs Ii on its sides which slidably t in the shell grooves 2, whereby the locking member B is confined to non-rotary axial sliding movement in the shell H.

Circumposed on the rod E below the locking member B is another tubular locking member C which has an internal shoulder le at its lower end concentricallyA surrounding the rod E and acting as' a seat for the lower end ci helical spring G, which is circumposed' on rod E between the upper locking member B and the lower locking member C, and has its upper end seated against the lower side of the shoulder I3 of the upper locking member B, so as to urge locking members B and C away from each other. Lower locking member C has an external spiral lug or thread 3 which slidably nts the single spiral groove l in the shell H, whereby lower locking member C is caused to rotate in a spiral path relative to upper locking member B, whenever locking member C is moved axially or longitudinally in the shell H. In the arrangement illustrated, member C is somewhat longer than member B.

The facing ends of locking members B and C have serrations 2B and 2l, respectively, which are arranged to interengage whenever these ends of the locking members are forced together, so as to preclude rotation and hence any longitudinal movement of locking member C in shell H.

Circumposed on the plunger rod E below the lower locking member C is the tubular piston body D, which has a relatively long internal shoulder iii at its upper end circumferentially surrounding the rod E, and constituting an abutment or stop for the fixed collar or enlargement il on the rod E. The upper end of the piston body D is of substantially the same diameter as the members A, B and C and constitutes a head 5, which like the members A, B and C slides in the shell H. The piston body head 5 has two diametri-cally opposed ribs e which are slidably confined in the straight shell grooves 2, 2 so that the piston is prevented from rotating in shell H.

The piston body D below the head e comprises a smaller diameter tubular shank 6, having a relatively long internal shoulder 22 at its lower end, presenting an abutment or stop for the lower modas? end of the rod enlargement I1'. 'I'he shank 6 extends into the hydraulic cylinder J. The lower end of the shank I5 is externally enlarged to provide the piston head 'I working within the hydraulic cylinder J, and having on its working face the packing ring 8, through which projects the smooth lower end I 8 of the plunger rod E. The upper end of piston body D may be separated from the lower end of lower locking member C by a gasket I5, or connected thereto.

The components of the device are shown in Figures 1 and 2 in the separated positions they occupy before operating force is applied to move the piston D in hydraulic cylinder J, wherein spring G maintains upper locking member B pushed upwardly away from lower locking member C; wherein spring F maintains the head A pushed upwardly away from the upper locking member B; and wherein the upward movement of head A produced by expansion of spring F has withdrawn plunger rod E upwardly, so that its lower end IB projects only slightly below the working face of the piston D.

Figure 3 shows the positions the components of the device reach when only suflicent force has been applied to the head A to collapse springs F and G and produce interengagement of the serrations 20, 2l of the locking members B and C, respectively, and sufcient downward movement of the piston D to put the fluid in cylinder J under pressure, Without causing the lower end I8 of plunger rod E to become projected substantially beyond the lower end of piston D. In this disposition of the components the locking members B and C cannot move in shell H either upwardly or downwardly because of the interengagement of their serrated ends, and freedom for such movement thereof cannot be resumed except by release of the pressure exerted on upper locking member B by spring F suiciently to permit spring G to move locking member B upwardly away from lower locking member C.

If force be applied to the head A beyond that producing the above described positioning of the components shown in Figure 3, the spring F will be further collapsed and the upper end of the bore I [I of head A will forcibly engage the enlargement II on the upper end of plunger rod E and force rod E downwardly through the components, so as to project the lower end I8 of the rod beyond the working face of piston D into the hydraulic cylinder J and thereby intensify the fluid pressure within the cylinder. Since the cross sectional area of plunger rod E at the lower end I8 is less than the cross sectional area of the working face of piston D, each additional pound of force exerted on head A will exert greater pressure on the lluid in the master cylinder J than was the case before members B and C became locked, and such additional pressure will be effective since the locking of members B- and C will prevent the ring portion of the piston head from receding in the cylinder J.

To the point where the members B and C become locked, as shown in Fig. 3, the pressure per square inch on the uid in the cylinder J is equal to the force exerted on member A, divided by the sum of the areas of the piston working faces and I 8.

After the members B and C become locked, as shown in Figure 3, the pressure on the fluid in the cylinder J, is intensied by piston I8 so that the unit pressure in J is equal to the force exerted on member A, divided by the area of piston I8 only.

Therefore, if the diameter of plunger El is 1/3 of the overall diameter of piston head 1, each pound of pressure exerted on member A after the members B and C have become locked will exert 9 times as much pressure on the fluid in the cylinder J as was exerted thereon by each pound of pressure exerted on member A prior to the time of locking of members B and C, less pressure consumed in collapsing spiral spring F.

While in the accompanying drawing, member B is provided with straight projections which mesh in straight grooves in the bore of the shell H, which prevent member B from rotating when slid in the shell, and members C' is provided with a spiral projection which meshes in spiral groove in the bore of the shell H, which causes member C to rotate when slid in the shell, however, this invention and protection claimed thereon is not limited to this means of causing said members to become locked. The same locking elfect can be secured by having member B to rotate and member C not to rotate, or by having member B rotate in one direction and member C rotate in the opposite direction, or by having members B and C both rotate in the same direction but with different pitches, and grooves in the bore of the shell and projections or threads on members B and C to accomplish any of these combinations may be used as will best accomplish the desired results; also members C and D may be formed as one member; also members B and C may be equipped with one or more projections, and the shell H with one or more grooves with which said projections will mesh. The invention is not limited to the form of serrations 2li and ZI of mem bers B and C as shown in the accompanying drawing.

It is also to be understood that the invention and protection claimed thereon is not limited to the interior design of members A and D or the form of plunger E as shown in the accompanying drawings, but the same may be changed or modifled to better accomplish the functions of said two members in combination with plunger E.

For example, the upper end of plunger rod E may be formed differently, in which case the bore I0 in member A could be diiferently formed. Also, the stop collar I 'I on plunger E may be diierently located, such as on the lower end I8 thereof, in which event the collar I'I would abut the face of piston head 'I or packing ring 8, instead of the shoulder I6, for preventing recession of the lower end 4of rod E into the piston head or packing ring; and it is understood that any of such changes may be made in the form of said members and plunger as will best accomplish the desired results.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a fluid pressure producing device, a fluid containing cylinder, a piston movable in said cylinder to compress the uid therein having a hollow piston rod projecting rearwardly i'rom said cylinder, said piston comprising a plurality of tubular sections movable axially relative to each other, a tubular shell supported in axial extension of said cylinder and enclosing said sections, a plunger rod extending rearwardly through said tubular sections and forwardly through a longitudinal bore provided in said piston, spring means urging said tubular sections apart, the rearmost of said sections having connection means thereon for operatively connecting force applying means thereto for moving said rearmost section forwardly so as to compress said scctionslongitudnallyytoward*eachother against the resistance of said spring means and .thereby move said piston forwardly to compress the fluid in said cylinder, two adjacent onesof said sectionsfbeing operatively connected to said shell to movein different paths as they are moved longitudinally togetherY so as to interengage and lock themselves l against further longitudinal movement 1in ,either` direction in said shell, thereby'locking said pistonina forwardly compressing position insaid-cylinder; .a lost motion connection between said rearmost section and said plunger-rod whereby initial actuating movement ofisaidffforce applying meanscan produce forwardxmovement of said'hollow piston rod and compressive movement of said piston in said cylinder against the resistance of said spring means without producing forward movement of saidplunger rod with relation to said piston, and further actuating movement of said actuating means can produce forward movement of said plunger rod upon locking of said two adjacent sections, so as to project the forward vend of said plunger rod into thefluid cylinder beyond the working face of said piston, and thereby intensify the compression of the fluid therein.

2. In afluid pressure-producing device, a cylinder, a piston movable therein and having a tubular piston rod, a tubular shell through which said piston rod slidably extends, said piston rod comprising a plurality of axially separable tubular sections, compressible spring means normally yieldably separating said sections, the foremost-,section being.- operatively engageable with said piston and the rearmost section having connectinggmeans for -theoperative connection thereto of force applying means, a plunger rod eX- tendingeforwardly' through saidtubular piston rod-andthrough abore#` provided in said piston, alost motion connection-,between said rearmost section and the rearward Aend .of said plunger rod permitting saidfrea-rmostsectionto move .forwardly relative to said plunger rod for a limited distance-before rnovingsaidl plunger rod forwardlyfwhereby said spring means is .compressed suiciently to cause saidsections-to move toward each other and compress said springmeans suiiiciently to move said piston Iforwardly in said cylinder and compress the fluid therein, and means,*operativelyccnnecting some of saidsections to said shell whereby such sections are conned to rdifferent-paths of'lmovement relative to each other-as theyy are'm0vedforwardly, so that some'A of ,said sectionsinterengage and interlock so as to preclude their further longitudinal `movementin said shell and thereby arrest said .piston in the position in said cylinder achieved by the preceding forwarddnovement ofsaidpiston rod while permitting said plunger rod to move forwardly against thevresistance. of said spring means untilthe forward end of said plunger rod projects beyond `said piston and intensifies the. uid pressure insaid cylinder.

3,` A# pressure producing device, comprisinga plunger made of aplurality of longitudinally divided tubular sections, the forward section terminating in a pistonoperating in a cylinder, a tubular shell in which said sections are slidably confined, a plunger rod slidably extending through said plunger, the rear end of said plunger rod being'connected-with therearmost slidable section upon which the actuating force is applied in the operation of the device, compressible spring means positioned between adjacent sections yieldably ulgnxsa-id sections@ apart andgacting to f retract saidA plungerA rod., rearwardlyin. said plunger; two adjacent ones of said sections being operatively connected to said shell to move in different paths as they are moved longitudinally together qso to interengage and lock themselves against further longitudinal movement in the shell, thereby locking said plunger in its forward compressing position, said spring ymeans between adjacent sections ofsaid plunger being graded in tension to cause -a ypredetermined amount of pressure to be exertedrby the forward section of the plungeron the contents of the cylinder before the plunger becomeslocked, and after the plunger becomes so locked further actuating force exerted on the rearmost section to cause said plunger rod to be projected forwardlywith relation to said plunger, thereby intensifying the compression of the contents of said cylinder.

4. A uidpressure'producing device comprising acylinder, a piston movable therein, a piston rod engageable Withsaid piston for moving it forwardly to-compress fluid in said cylinder, said piston rod comprising a plurality of longitudinally divided tubular sections, a tubular shell aligned with saidcylinder in'which said sections areislidably confined, a plunger rod slidably eX- tendingthrough saidv pistonrod and through a bore provided in said-piston, a lost motion connection between the rearward end of said plunger rod and the rearmost one of said sections whereby said rearmost section can be moved forwardly for a limited distance before forward movement is imposed upon said plunger rod, said lost1 motion'y connection having means for the operative connection thereof of actuating means, compressible spring means positioned betweenadjacent ones of said sections yieldably urging said sections apart and .acting to retract said plunger rod rearwardly to a point whereat the forward end of said plunger rod projects only slightly beyond the working face of said piston in said cylinder, portions of saidfspring means between adjacent sections of said piston rod being graded in tension to cause a predetermined amount of forward movement of said piston in said cylinder when said spring means is compressed by forward actuation of said rearmostsection, in advance of any forward movement of said plunger rod, followed by forward movement of said plunger rod whereby its forward end is projected forwardly in said cylinder to intensify the compression of the iiuid therein, and means for locking said piston rod against rearward movement and against further forward movement when said piston has moved forwardly said predetermined amount, said locking means comprising guide means cooperatively arranged on said tubular shell and on two adjacent ones of said piston rod sections imparting divergent paths of movement to such adjacent sections as they are moved forwardly in said shell, whereby such adjacent sections become frictionally interengaged and locked against either rearward or forward movement in said shell, until the compression of said spring means is relaxed by, sufficient withdrawal of actuating force from said rearmost piston rod section.

5. A fluid pressure producing device comprising a cylinder, a piston movable therein, a piston rod engageable with said piston for imparting forward compressive movement thereto in said cylinder, said piston rod comprising a plurality of tubular axially separable sections, a tubular shellv aligned with saidk cylinder within which said sections are slidable, av plunger rod extending slidably through said sections and through a bore provided in said piston, helical springs circumposed on said plunger rod between adjacent ones of said sections and yieldably urging such sections apart, two of said adjacent sections having lateral ribs working in divergent longitudinal grooves formed in said tubular shell, whereby said two adjacent grooves move in divergent paths so as to lockably interengage when moved forwardly in said shell whereby any further 'orward movement of said pistons in said cylinder is arrested, a lost motion connection between the rearmost one of said sections and the rearward end of said plunger rod and having means for connecting actuating means thereto, said lost motion connection permitting initial operation of said actuating means to move said rearmost section forwardly and compress said spring means so as to move said piston forwardly in said cylinder and impart pressure thereto in advance of any forward movement of said plunger rod, and providing for forward movement of said plunger rod subsequent to the forward movement of said piston so as to project the forward end of said plunger rod beyond the working face of said piston in said cylinder whereby the compressing of the fluid therein is intensified.

GARNETT S. ANDREWS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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