US2612756A - Means for protecting hydraulic pressure presponsive devices from the effects of fluid shock - Google Patents

Description

1952 v. w. PETERSON ET AL 2,612,755

MEANS FOR PROTECTING HYDRAULIC PRESSURE RESPONSIVE DEVICES FROM THE EFFECTS OF FLUID SHOCK Filed July 51, 1947 IN V EN TORS VICTOR W. PETERSON BY OTTO J. MAHA ATTORNEY Patented Oct. 7, 1952 es PATENT" MEANS FOR PROTECTING HYDRAULIC PRESSURE R-E SPONS IVE DEVICES FROM THE EFFECTS OF FLUID SHOCK l Victor W. Peterson and Otto J. Maha, Chicago, 111., assignors' to Hannifin Corporation, Chicago, 111., a corporation of Illinois Application July 31, 1947, Serial No. 765,206

12 Claims.

This invention relates to improvements in the control of hydraulic or other pressure actuated devices and among other objects aims to provide means for increasing the range of pressure adjustments in pressure responsive systems for controlling such devices.

Another object is to provide means tecting against hydraulic shock.

The nature of the invention may be readily understood by reference to one apparatus embodying the invention and illustrated in the accompanying drawing.

In the drawing, the figure is a schematic section, illustrating the general construction and operation of the apparatus.

For simplification in illustration and description of the invention, it is here shown applied to apparatus of the character described in greater detail in our prior Patent 2,308,712; but it will be apparent that the invention is not limited to this type of apparatus.

In hydraulic pressure actuated and pressure responsive apparatus, the hydraulicshock (caused by liquid inertia and the relatively incompressible character of the liquid) is often greater than operating pressures ,(at a given stage of a cycle); thereby causing premature and undesired operation of the pressure responsive control devices. To prevent this, it is generally the practice to set for prothe pressure responsive controls for actuation at (Cl. Gil-54.5)

pressures higher than the shock pressures. This,

however results in excessive stress or load on the pressure generating systemand the apparatus in general, because of the high pressures it is necessary to build up in the system to cause actuation of the pressure responsive control devices. This in turn makes impossible any adequate range of adjustment of the pressure responsive devices to vary the maximum or othercritical pressures according to the particular duty required of the apparatus. v

The present invention, among other advantages, provides means for temporarily (at appropriate stages in the cycle when hydraulic shock occurs) rendering the pressure responsive controls insensitive, thereby protecting the apparatus and making it possible not only to adjust the pressure responsive devices for response at the lowest practicable pressures, but to increase the range of maximum or other critical pressures exerted by the apparatus.

For example, in the illustrative apparatus, a

hydraulic pressure generator (e.g. a motor (9) driven hydraulic pump l0) supplies primary pressure to actuate a pressiln this case, a squeeze rlveter II), to close the die I2 quickly on the rivet and to exert such heading pressure thereon as can be exerted by direct pump pressure.

Thereupon, when substantially maximum pump;

pressure or such other predetermined direct pressure is developed, a valve 13 brings into operation a hydraulic intensifier la (by whichthe pump I pressure is greatly multiplied, e. g. 5 times) to apply the final squeeze on the rivet. When a;

predetermined intensified pressure is reached (deemed adequate to head the rivet), a pressure operated control device I5 reverses the rivetertool I2 to withdraw 'itirom the rivet. Upon reaching the fully returned position (engagement of the work pistonlt'with the head end I! of work cylinder [8) a control device l9 responsive to the increased line' pressure resulting from such engagement terminates'the cycle.

At various stages in the cycle-inertia of the oil (due either to setting'the' oil in motion, arresting or reversing its motion etc.) creates shock pressures suflicient under conditions heretofore existing, prematurely to actuate the aforesaid pressure responsive devices. "Additional shocks occur if the cycle be purposely-interrupted (because of improperly placed-rivets or'ior any other reason) or the work piston be revers'edintermediate the ends of its stroke. v

' Before. describing the means by which these shocks "are renderedv ineffective, fa"preliminary" brief description of the illustrative apparatus will assist in an understandingof the principle of the" invention.

Primary pump pressure is supplied through line 2| anddistributed by the primary valve '22 which is longitudinally slidabl'e'to direct pressure fluid either t hroughline 23 to the head end of the work cylindenorlto return'line 'Mto the plunger end of the cylindenor to shortcircuitthe fluid at practically no load .orzero pressure through discharge line 25 tothej'reservoir from which the pump draws its oil through line 2'6. Thus in' its intermediate position (that here illustrated) the pump operates at practically no lQadbetWeensuc-J cessive cycles of the riveter. In its upper orlower;

positions, when directing fluid 'for advanceor return of the work piston, respectively, the o ther lines 23. and 24 respectively, willbe connected to discharge line 25.

When the tool [2 is encountered and pump pressure. builds up either to the maximum sate: pump pressure or Thamessure, reaching intensifier.valve l3 through; line other predetermined. pump-pressure.

21, elevates the former and ,connectsisupply line one:

engages the work resistance- Yielding of spring 32 permits the oil in chamber to escape and thereby allowing the intensifier valve to move and cut in the intensifieras above described. When the small intensifier piston 34 enters the small intensifier cylinder 35, it cuts off further supply of direct primary pressure through line 23, intensifier chamber 35 and line 31 to the head end of the work cylinder. I 8. B85.-

cause of the diiferential of area between the large intensifier piston 36 and that. of :the small piston 34;(e.;;g; five-.to-one), theoil in cylinder 35- may be subjected to manytimespumppressure which 4 pressure; communicated through line 31 to the head-endoithe workcylinder supplies the intenri sified 'press ureonthe work. The maximum intensified. pressure available is the maximum pumppressure multiplied sbygthe .-ratio of the intensifier pistons.- If this ratio .bea5 and the maximum-,operating pump pressure be 1,000 pounds.

per ,square inch, :theintensified. pressure i will be 5,000: pounds, per square inch."

When the, intensified pressure reaches. the desired --value, the pressureresponsive control 'device ,-l5 :is .op erated -to.allow primary -valve.22 to be elevated as presently desqribedto reverse position,- thus connecting; the-return line .24 ,with the pump and delivering-pump pressure through line. 38 to the plunger end of work cylinder l8. The head .end :of the-cylinder is simultaneously connected-to discharge In. the present instance, control jdevicel5 .is..exposed to pump pressure through-:line-39 leading to ,a.port in the largeintensifier cylinder. Since. there .is a constant. ratio betweenfthepump pressure, and the intensified pressure, the pump pressure during the intensifyingstagelof operati'onis a measure ,of the in.-. tensified pressure.

In the .present instance, control. device. I5 .010- erates .to openan. electric .circuit. controlling solenoid.4l.. When .the...solenoid is..energized, its plunger. 42- .is elevated, thereby-depressing or low.- ering primary valve 22 through lever 43 lfulcrumedat 44.. Solenoid 4|. is preferably actuated by. closing a conveniently: located electric ,control switch, (not shown), the primary valve isv against the spring 45 lying between the, collar .46 ,on valve rod 41 and bar 48 carried on plunger 49.1 Simultaneouslywith low eringof. primary valve 22, rod 49 andbar 48 are elevated .by lever 51 fulcrumed at. 52,;thereby fur.. thercompressing spring 45.1. The purpose of'the preloading of spring .45 is to provide energy for raising of .the primary valve on deenergization of-solenoid 4| to:return-position., When rod '49 is elevated-it is latched in elevated position. by thespring latch-'53 releasable. by .the pressure responsive control l9.

Solenoid 4| is energized by appropriate circuits under the control of the operator; The details of such circuits are conventional-and need not be-describedn Included in the circuit is a switch'such as a micro switch54 whose plunger 55 is moved by the cam surface 56 on'control device l5.' The latter isfheld in its lower position by a relatively light spring '51.-

Downward movement of When work piston l6 reaches the head end of its cylinder, the increased pump pressure, built up by resistance to further movement, elevates control device l9 whose cam surface 20 withdraws latch 53 and allows primary valve 22 to riseto'its neutral, i. e., intermediate,-. position wherein thepump simply discharges into the reservoir at no load. The primary valve rod 4! falls with the bar 48 under the action of spring 58 which is somewhat compressed by the previous elevation of rod 49. Pressure of spring 58 is transmitted to the primary valve rod 41 through bar 48 bearing against the stop or pin 59 on rod 41; Spring 45 exerts no control over the primary valve during this operation since it is limited in its movement by pin 59 and the collar 46. In its extended position, it centers the valve in intermediate or neutral position.

A new cycle may be started by energizing solenoid 4| as above described and depressing primary valve 22. Operation of the-work-piston may be. interrupted. at any stage in the cycle simply. by de-energizing solenoid'4l. It is .unnecessary for, thework piston IE to return to its extremeposition before startinganew cycle- A new cycle may be started by the operator simply by closing said controlswitch (not shown) to energize solenoid 4|. It -istrue that .undersuch circumstances. rod 49 and bar 48,will still be latched inv their upper position but this will not prevent depression of the primary valve to its lower position. It simply makes unnecessary the simultaneous compression of spring 58 by means of the lever-5|. The latter is freeto ride above fulcrum pin 52 with theu'pwardmovement of either of the pivots onrods'41 and 49.

Premature or undesired operation of the illustrative control. devices is prevented accordingv to the present invention .by blocking communication ofpressure to suchudevices at periods in the cycle during which shock or.excessivepressures may occur. The manner of applying the principle variesdepending upon. whether movement of a plunger or other element of the existingapparatus may beutilized to blockand unblock a port or ports for, establishing or cutting oif communication of pressure. When. such movement cannot be utilized,.a separate pressure or other actuated; elements is introduced. into the line-of hydraulic communicationto block. and funblockjaccess of .pressures to the pressure responsive device.

The first method is illustrated in connection withoperation of device l5 controlling termination: of the high pressure or squeezing stage of the cycle. If, unprotected, this device wouldrespond to shock pressuressduringqthe .intensifica-. tion stage "of the cycle. As :stated above, shock pressures may occur at the beginning of intensification, i. e. when the large intensifier piston 36 is at the lower or head end of-ithe cylinder. The intensifier piston skirt is therefore advantageously used to block the passage leading from the pressure-line 28 -to control-device -l5.- As

here shown, line 39leads to a-port- 40 the lower end of the large intensifiedcylinder--where-it-is blocked from communication with the pressure in'line 28 untilit is uncovered by-a short rise of theintensifier piston. danger-of shock pressure ms passed.

- In' the present case, an adjustable relief valve 6| is interposed in line 39a- -such-valve comprises in the present instance:a simplespringloaded ball valve wherein the-load.- on spring 62 may be adjusted; The .adju'sting -means comprises: a

hand .operatedknob 63, having 'a cam surface At this time, the- 84 bearing on the spring plunger 65 to-permit 15 to operating pressures from the large inf-j tensifier cylinder. The knob 63 may advantageously have on its front face a graduated dial which in conjunction with the stationary index 66 will indicate the intensified pressure at which the ball valve will open to operate the The protection,

pressure responsive device I5. afforded by blocking line 39 during the period of shock pressures, makes it unnecessary to load spring 62 greatly in excess of what would'or'dinarily be necessary to prevent premature operation of device I5. This makes it possible to'permit easy manual adjustments of the maximum intensifier pressure in accordance with the necessities of the operation to be performed.

Spring 51 is made relatively light and suflicient only to return the device I5 to initial position at the end of the cycle when pump pressures drop practically to zero. A check valve 61, in line 39, permits escape of the small amount of oil.

displacedby device IS on return to its initial position, into line 28 and thence to discharge through line 68 when pump pressures are -reduced to zero.

The method of embodying the invention in control devices wherein no existing movable parts can v munication with the source of pressure is illustrated in connection with the intensifier valve i3 and the control device H! for restoring the primary valve to neutral position at the end of a cycle. In the present instance, these devices are advantageously effected by a single movable element H here shown in the form of a spool or shuttle valve, which, at one stage of the cycle blocks a line controlling the operation of the intensifier valve and at another stage-in the cycle, blocks a line controlling operation of 'control device l9.

As here-shown, at the beginning'ofthe cycle, valve H blocks passage 12 leading from the in-' tensifier operating valve 29 to discharge line 13. Thus the oil in passage 12 prevents valve 29 fromleaving its seat and therefore prevents operation of the intensifier by shock pressures occurring at the beginning of a cycle whether such cycle starts with the work piston in midstroke or at the head end of its strokep Spool II is longitudinally slidable in its cylinder 14 and in this instance'is moved to unblocking position by line pressuredeliver-ed thereto through line 15 as the workpiston starts its forward stroke. The rate of such movement is limited by interposing in line 15 a restricted orifice 16 (in this case in the form of a plug inserted in the end of cylinder 14), thereby delaying the unblockingof passage I2 until the work piston [6 has advancedwell beyond any point at which shock pressures could occur. When spool H reaches the limits of its retarded movement a passage therein (here provided 'by a circumferential groove 11 in the spool) registers with passage '12 to connect thelatter with-passage 13. In the present case, groove 17 communicates with radial and axial passages 18 and 19 in the spool to providea continuous passagefrom line 12 to line 13. f I i In its extreme position, as aforesaid spool ll blocks communication of line 13 with line Bl leading to control device l9, and the latter is therefore cut off from any shock pressures developed at the beginning of the reverse or rebe used to block and unblock comturn travel of the work piston and existing in return line 24 with which line 13 communicates."

Pressure in the latter linemo'ves spool H toits initial position lay-displacing oilthroughthe-r'e' stricted orifice'lS which therefore retards'such movement and the unblocking of line-=81 untildanger of development of shock pressures'has passed. When the spool reaches its initial position wherein passage 11 communicates with line 8| (whichoccurs after the work piston I6 is. well along on its returnstroke) line 8| and control device 19 are placed in communication with and made responsive to the pressures in return line 24 Spring 82 controlling the operation of device 19 is set to allow the latter to move'when pump pressure builds up (and is communicated to plunger 19 through lines 13 and 8!) 'as a result of the work piston reaching the head end of its stroke. The setting of the latter spring need=not require the development of excessive pressure but' instead maybe adjusted to permit actuation by pressures which are only nominally higher than line pressures required for return of the work piston. This again minimizes un-. necessary load on the pressure generator.

Protection of intensifier operating valve 29 also permits setting of this valve for operation at any desired pump pressure without regard to the problem of shock pressures.

Where, as in the present apparatus, the means for reversing the work piston is responsive to pump pressure (and not to intensifier pressure), an auxiliary safety valve 83 is advantageously employed to protect the apparatus against development of excessive pressures in the event of failure of operation of solenoid M or other electric controlling elements. Such auxiliary safety valve is in thesecondary circuit, e. g., line 28, and would respond more quickly-in case of failure of switch 54 or solenoid ll than would the main safety valve 84, and more quickly than the usual overload devices with which the pump motor is regularly equipped. The main safety valve, on the other hand, affords protection during portions of the cycle wherein'auxiliary valve 83 is ineffective. However, it is advantageously set to operate somewhat above normal maximum pump pressure so that it will not be responsive to the incidental shocks occurring during the cycle. For example, if the normal maximum pump pressure be 1,000 pounds per square inch, valve 84 is advantageously set to operate at 1500 pounds per square inch. 1 I

The foregoing will serve to illustrate the'principle of the invention and the manner in which it may be adapted for various hydraulic pressure systems controlled by pressure responsive devices and wherein the latter devices may be subjected to shock pressures.

The improved apparatus thus makes possible a much wider range of adjustment than has heretofore been possible. I i

Obviously, the invention is not limited to details of the illustrative apparatus since these may be variously modified. Moreover, it is not indispensable that all features of the invention be used conjointly since various features may be used to advantage in different combinations and sub-combinations. I

Having described our invention, we claim:

. 1. In hydraulic pressure actuated apparatus plying intensified hydraulic pressure to said work cylinder during a portion of its cycle, pressure Supp y means for supplying hydraulic pressure;

to said'intensifier cylinder, a hydraulically actuated controldevice operable to interrupt-supp -f pressure to, said intensifier cylinder, a n c draulic line leading from, said intensifier cylinder to said control devices to supply the-latter with actuatin hydraulic pressure, a normally closed valve in said line and responsive to-,pressure in said intensifier cylinder and adapted tq open to permit hydraulic pressure from said intensifiercylinder to, operate said control device, said' valve being adjustable to vary thepressure at which it; opens. thereby to limit the maximum pressure in, said intensifier cylinder and correspondingly tolimit the maximum. intensified pressureinsaid work; cylinder, and a line connecting said valve to saidintensifier cylinder at a point where it iscovered and blocked by said intensifier piston,

the-combination comprising a work cylinder andv piston, pressure means for supplying pressure to opposite ends of said work cylinder, for advancing said piston on its work stroke and; returning the same atv the conclusion of its work stroke, a pressure,responsivecontrol-device for interrupting supply of pressure, to said; work cylinder when the work piston reaches the end of'its return, stroke, a line connectingsaid pressure responsive device with the line iorqsupplying pressure for returning said work piston and, adapted to supply pressure fluid for operatingsaid control device at a predetermined pressure, a slidable valve in said line blockin transmission of pressure to said; control-device-during the intermediate portion ofthe returnstroke of said work piston, and means for supplying pressure fluid to move said valve to unblocking, position at, a limited rate but sufiicient to move said valve to unblocking position by the time said work piston reaches the end of itsv return, stroke.

3. In hydraulic pressure actuated apparatus the combination comprising a double acting work cylinder and piston, means for supplying pres; sure fluid to the opposite ends of saidwork cylinder to advance said piston on its work stroke and return the same on completion ofv its work stroke, a pressure actuated pressure responsive control device for controllingan, operation dur; ing the work stroke of said pis'ton in response to predetermined pressure in said work cylinder, and other pressure actuated pressure responsive control device for interrupting supply of prese sure for returning said work piston uponpredetermined'pressures generated when said work piston reaches the end of its return stroke, means, including fluid lines for subjecting said respective control devices to the pressures existing respectively in the work cylinder on the work stroke and on the return stroke, a slidable valveand cylinder in said lines and. constructed and arranged to block the line leading to said first mentioned control device during the first portion of the work stroke of the workpiston-soas to prevent operation of said first namedconti-ol device in response to shock pressures duringthe first portion of the stroke of 'saidf'work pi'ston, said slidable valve being movable during-the work stroke of said piston to a position blocking the line leading to said secondnamedcontrol device, and lines for supplying pressure-to 7-0pposite ends of the latter cylinder from-themes- 8. sure supplied to said work cylinder for the respective work and returnstrokes of. said Work piston so as to move said slidable valve duringthework stroke from its position blocking operation of said first named control device to. a position blocking the second named control device and in the opposite direction during the return,

stroke of said work piston.

. 4. Inhydraulic pressure actuated apparatus-,, the;combination comprising a'work cylinder and,v

charge and filled with hydraulic fluid preventingmovement of said control device until displacedthereby, a slidable cylindrical valveclosing said line at thebeginning of the work piston stroke to prevent displacement of. said fluid to discharge and thereby preventing operation of said control device, means for subjecting said valve to pressure delivered to said work cylinder tending to open said valve, and a throttling orifice for limiting the rate of' fluid flow to said valve to retard its, movement to open position until the Work piston has substantially advanced on its work stroke.

5. In hydraulic pressure actuated apparatus, thecombination comprising a work cylinder and piston, means for supplying hydraulic pressure-to said work cylinder, an intensifier piston and cylinder for intensifying the pressure in said work cylinder; during a portion of its stroke, a pressure responsive valve movable, on a predetermined pressure in said work cylinder for connecting the pressure supply, to said; intensifier cylinder, a line connected with saidpressure responsive valve for the, escape of. hydraulic fluid necessary for the opening of, said, valve, a slidable cylindrical element closing said-line.- at the beginning of the stroke of the work piston to prevent said escape andthereby prevent opening of said valve, a line connecting saidrslidable element with the pressure in said, work, cylinder; to move said element toopen. position, and, a restricted orifice in said line, tolimitthe, rate of movement of said cylindrical: element. to open position until the: work piston; has. substantially advanced on itsv work stroke.

6;, In pressure actuated apparatus, the combination: comprising. a. work cylinder; and piston, a pressure responsive. control device. for controllingan operativemovement of said work piston in response to predetermined pressure in said work cylinder, a line subject. to shock pressures exceeding said predetermined pressure for communicating pressure to. said control device to actuate the latter at said predetermined pressure, a movable device insensitive tothe pressure in said line and closing said line during portions of said workpiston stroke when shock pressures occur in said line, thereby to prevent operation of said control device during said periods of the cycle, a passage-for supplying pressure tosaid movable -device-to-move the latter to-open position-to open'saidline, and means for regulating the rate of said movement of saidmovable device.

7. In hydraulic pressure actuated apparatus subjected to shock pressures duringcertain periods of itscycle of operations, the combination comprising a workcylinder and piston, means for supplyinghyd-raulic pressure to saidwork cylinder, a pressure responsive control-device insensi- CJI device, a valve closing said line to prevent dis- I placement of said hydraulic fluid and insensitive to said shock pressures for preventing operation of said device during periods of shock pressure, and a passage for communicating pressure from said work cylinder to said valve to open the same during other periods in the cycle of operation to permit displacement of said hydraulic fluid.

8. In hydraulic pressure actuated apparatus, the combination comprising a cylinder and piston, 'means for supplying hydraulic pressure to said cylinder to advance said piston, a hydraulically actuated control device for interrupting supply of pressure to said cylinder, a normally closed valve responsive to pressure in said cylinder and adapted to open under hydraulic pressure in said cylinder to admit hydraulic pressure to said control device to actuate the latter, a hydraulic line connecting said valve with said cylinder through a port in the latter to deliver cylinder pressure to said valve, said port being positioned so that it is closed by said piston for a portion of its stroke to render said valve during such portion of the stroke insensitive to pressure in said cylinder, said valve being adjustable to vary the pressure at which it opens, thereby to vary the maximum operating pressure in said cylinder.

9. In hydraulic pressure actuated apparatus, the combination comprising a working member movable in a cylinder by hydraulic pressure, means for supplying hydraulic pressure to said cylinder to move said member, a hydraulically actuated control device for interrupting supply of pressure to said work cylinder, a normally closed valve responsive to pressure in said work cylinder to admit hydraulic pressure to said control device, a hydraulic line connecting said valve with said cylinder through .a port in the latter to deliver cylinder pressure to said valve, said port being positioned so that it is closed by said work member for a portion of its movement to render said valve during said portion of move ment insensitive to pressure in said work cylin der.

10. In hydraulic pressure apparatus subjected to p-ressureshocks in excess of norm-a1 operating pressures during a portion of the cycle of operations, the combination comprising a work piston, a supply of hydraulic pressure, a pressure responsive device sensitive to said pressure shocks for controlling supply of pressure to said work piston and adapted to be actuated when operating pressures rise to a predetermined sure shocks occur to render said device insensi ,tive and inoperative, and means for unblocking said communication during other portions of said cycle so that during said other portions of the cycle said device, is operative to control supply of pressure to said work piston in response to operating pressures.

11. In hydraulic pressure apparatus subjected during a portion of the cycle of operations to pressure shocks in excess of normal operating pressures, the combination comprising a supply of hydraulic pressure; a cylinder with piston therein actuated by said pressure, a pressure responsive device sensitive to said pressure shocks and adapted to be actuated when operating pressures rise to a predetermined pressure to control an operative movement of said piston, a hydraulic line connecting said cylinder with said pressure responsive device to subject the latter to the hydraulic pressure in said c5 r Number inder, said. line being connected with said cylinder at a point covered by said piston during the said portion of the cycle, thereby to cut off connection of pressure to said pressure'responsive device during said portion of the cycle wherein said shocks occur.

12. In hydraulic pressure apparatus subjected during a portion of the cycle of operations to pressure shocks in excess of normal operating pressures, the combination comprising a supply of said piston, thereby to cut off connection of pressure to said pressure actuated device durin said portion of the cycle, and means associated with said pres-sure responsive device to vary the predetermined pressure at Which said device will operate.

VICTOR W. PETERSON. OTTO J. MAHA.

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

UNITED STATES PATENTS Name Date 902,723 1,660,720 1,347,889 2,113,161 2,303,712

Osborne Feb. 28, 1928 Osborne Mar. 1, I932 Osborne Apr. 5, 1938 Peterson et a1 Jan. 19,, 1943 Cole Mar. 2, 1948 "Sedgwick Mar. 29, 1949 Gauer Nov. 3, 1908 Tucker Jan. 25, 1949,v

Images