US3818799A

US3818799A - Control system for an impact device

Info

Publication number: US3818799A
Application number: US00301855A
Authority: US
Inventors: W Hague
Original assignee: Chambersburg Engineering Co
Current assignee: Chambersburg Engineering Co
Priority date: 1972-10-30
Filing date: 1972-10-30
Publication date: 1974-06-25
Anticipated expiration: 1991-06-25
Also published as: GB1428017A; DE2353952A1

Abstract

A pneumatic ram has its blow intensity varied by varying the time of opening of a valve connecting a constant pressure fluid supply to the cylinder in order to vary the fluid pressure applied to the piston driving the ram. Control means includes timing means to regulate opening of the valve and metering means. Programming is achieved by providing various stations of selected blow intensities and using counting means to count preselected numbers of blows at each selected intensity. Automatic operation depends on means to provide automatic ram return to retracted position.

Description

United States Patent [191 Hague CONTROL SYSTEM FOR AN IMPACT DEVICE [7 5] Inventor:

Wilmer W. Hague, Fayetteville, Pa.

Assignee: Chambersburg Engineering Company, Chambersburg, Pa.

Oct. 30, 1972 Filed:

Appl. No.:

U.S. Cl 91/40, 9l/l65, 91/248 Int. Cl. FlSb 21/02, FOlb l/OO Field of Search 9l/35, 37, 39, 40, 165,

References Cited UNITED STATES PATENTS 4/1961 Fillmore 91/248 6/1965 Pinsenchaum 9/1969 Weyer 9/1969 Orhawa et al. 3/1971 June 25, 1974 3,590,582 7/1971 German ..9l/35 3,613,505 10/1971 Bubula 91/35 Primary Examiner-Edgar W. Geoghegan Assistant Examiner-A. M. Zupcic Attorney, Agent, or Firm-Dorfman, Herrell and Skillman [5 7] ABSTRACT 14 Claims, 8 Drawing Figures PAIENImJuuzs-mm 50L. CaA/TROL TERMINALS-v5 E der containing a piston driving the ram of the impact device. The present invention permits not only the timing of a single blow, but the execution of sequences of blows in a repeatable variable intensity program or patpressure of the drive fluidadmitted to the cylinder.

U.S. Pat. No. 3,464,315, the invention of H. A. Weyer, entitled Pneumatic Servo Control System for High Speed lmpact Devices assigned to the assignee of the present invention discloses an impact device having mechanical controls which produce a blow impelled by the pressure of the driving fluid admitted to the cylinder. Operation of this impact device is automatic, and it will strike repeated blows if its throttle valve maintains an operating position. Fluid compressed by the piston moving the raminto impact position is collected in a reservoir as it is compressed and the energy thus stored is used for returning the ram to retracted position, the retracted position being a constant level from the point of impact.

Another U.S. Pat. No. 3,043,271 assigned to the assignee of the present invention concerns a control system for an impact device, such as a drop hammer, employing variable length strokes to achieve a pattern of blows of varying intensity as opposed to the present invention wherein blow intensity is regulated by fluid pressure driving the ram. t

Other United States patents, not owned by applicants assignee but considered-in connection with the present invention are U.S. Pat. Nos. 2,933,068 and 3,133,472. Pat. No. 2,933,068 the invention of A. R. Johnson and Joseph C. Kern concerns a pneumatically operated impact device using a mechanically adjustable retainer to hold its piston at the top of its stroke. Changing retaining force' results in a change in striking pressure'developed and a consequential change in impact intensity. No suggestion of the timing of the pneumatic impact to regulate blow intensity is found.

Pat. No. 3,133,472 does control fluid flow in a impact device using valves and regulators to vary impact frequency and impact force independently. Impact force is controlled in part by the pressure of the fluid admitted to the striking side of the piston and in part by the time interval over which fluid is allowed to enter the cylinder. The time interval is generated by the pneumatic differential pressure acting within the valve. Shifting time of this valve is adjustable and depends on spring rates, diaphragm stiflness and differential areas on which opposed pneumatic forces act. The teaching of the present invention of using timing means to control the opening and closing of a main valve is not suggested. in the present invention varying inlet time varies ram velocity.

The present invention constitutes a stroke control particularly useful for the impact devices broadly of the type described in Pat. NO. 3,464,315, but modified to be useful with the control system of the present invention. The control system of the present invention is also useful on various impact devices of the same general tern, wherein the intensity is controlled entirely by the class. Characteristically the present invention provides means for producing variable intensity blows by controlling the admission of pressurized fluid, normally air, at precisely timed intervals to drive the ram. For a fixed supply pressure, ram velocity is determined by the time interval during which pressurized air is admitted to the cylinder. Additionally, the present invention permits for the first time a preset pattern of blows, of the same or varied intensity, to be set up in advance so that the pattern is precisely repeatable. The system permits alternative manual operation, if desired, and also permits interruption of the pattern if desired, i.e., the preselected program may be interrupted between selected impressions, or groups of impressions, called stations or sequences. Alternatively, the device may continue to strike through one, or any number (including all), stations. Stations are defined as a continuous sequence of blows of the same preselected intensity.

More particularly, the present invention relates to a stroke control system for an impact device having a frame supporting at least one cylinder. A piston within that cylinder is connected by suitable means to a ram such that the ram is movable relative to the frame from a retracted position into impact position. A fluid supply system includes a driving fluid supply and valve means for admitting compressible fluid from said driving fluid supply to said at least one cylinder at a position in the cylinder to drive said ram into impact position. The control system includes operating means for opening and closing the valve means, including timing means for determining the period of time the valve means will remain open. Pressure regulating means for maintaining the fluid pressure in the fluid supply essentially constant is also provided, as is metering means in the supply system, such that flow of fluid for selected increments of time permitted by the timing means will determine the pressure in said cylinder in order to drive the ram at a different predetermined force for each selected time increment. Inherent in this system is the metering effect which prevents immediate transfer to the piston of pressure from the fixed regulated driving pressure supply. The metering causes a gradual transfer of fluid so that the pressure which enters the cylinder to drive the piston will gradually build up. Thus it is possible to control the actual driving pressure on the piston by timing the period a valve controlling flow through the metering means is open.

Preferably means is provided such as reservoir means in communication with the cylinder at such location that fluid compressed in the cylinder and reservoir means by the piston moving the ram into impact position provides stored energy to retract the ram when the fluid pressure is later exhausted from the other side of the piston.

Preferably the timing means is adjustable in order to provide blows of different predetermined energy corresponding to selected time increments. Furthermore, the timing means is preferably provided with discrete incremental positions in order to provide blows of selected repeatable blow intensities.

in order to provide a programmer, at least one counting means is provided to count a predetermined number of blows at selected blow intensity and sequencing means is provided to cause said at least one timing means to control the period of valve opening for differing predetermined times in a predetermined sequence. Stop means may be provided which interrupts the program at any time, or stop means may be provided to selectively interrupt a program at a predetermined point, permitting continuation of the program thereafter.

For a better understanding of the present invention, reference may be had to the accompanying drawings in which FIG. 1 is a diagram of an impact device and control console, showing valve means for admitting compressible fluid in position to admit fluid under pressure to drive the ram from retracted position shown to impact position;

FIG. 2 is a similar diagram showing the same impact device with its valve means in alternate position permitting exhaust of the cylinder and allowing the ram to be returned from impact to retracted position;

FIG. 2a is an enlarged sectional view of the main valve showing it in retracted exhaust position;

FIG. 3 is an enlarged front elevational view of the front panel of the control console;

FIG. 4 is an energy calibration chart wherein blow intensity as a percentage of rated size is plotted against blow intensity settings corresponding to time intervals for various constant drive fluid pressures;

FIG. 5 is a schematic circuit diagram partially in block form showing the alternating current portion of a preferred control circuit; and

FlGS. 6a and 6b together form a circuit diagram of the direct current portion of a preferred control circuit.

Referring to FIGS. 1, 2 and 3 there is shown a pneumatic impact device which, in its preferred form constitutes a high speed sequence program controlled die forger with suitable controls. The device depicted is highly schematic in that the hammer itself is to a large degree of the same general construction as that hammer shown in US. Pat. No. 3,464,315, to which reference may be had for further details of construction. FIG. 1 depicts the preferred embodiment of the present invention schematically with its ram in retracted position. FIG. 2 depicts the same hammer with its ram in impact position.

The device shown is a high speed forging hammer for flat die work and impression die work controlled by an electrical sequence program controlled system as opposed to the mechanical pneumatic servo control system of the aforesaid patent, which accounts for a number of differences in the control feature.

Like the earlier device the major parts of the hammer are the anvil 10, a pair of upright frame members 12 and a yoke 14. These parts are bolted together in conventional fashion for a machine of this type to accomodate heavy impact vibration forces. The anvil and frame members are generally standard cast construction but the yoke is modified and of the general type taught by Pat. No. 3,464,315. The yoke 14 is provided with various cavities, the largest of which is centrally located cylinder 16, which is of generally right circular cylindrical form with a vertically oriented axis. In this cylinder is located a piston 18, which is moved up and down within the cylinder by introduction of air under pressure. Air is introduced and removed from the cylinder through ports in its walls. The piston 18 is connected by piston rod 20 to a ram 22. The piston rod passes through suitably gasketed bushings to prevent leakage of air from the cylinder along the piston rod.

The ram is always in contact or close proximity with and guided by guide pieces 24 which are bolted onto the frame members 12, four of which guide pieces are preferably used in order to assume the same ram positioning at impact, blow after blow. The anvil 10 and the ram 22, respectively, carry forging dies 26a and 26b between which is fed metal stock to be forged in conventional manner. The piston 18 is provided with suitable piston rings which effectively prevent flow around the edges of the piston between it and the cylinder walls. The cylinder preferably has a replaceable cylinder liner providing a uniform cylinder wall and wear surface for cooperation with piston 18. The top of the cylinder is closed by a suitable cylinder head 28, preferably bolted to the yoke 14. A reservoir or surge tank 30 communicates with the cylinder 16 through passage 32 at the bottom of cylinder 16. Air under pressure is fed into the reservoir 30 through suitable feed means (not shown) provided with pressure regulating means which is arranged to admit air only when pressure drops below a predetermined value. When greater air pressure is applied to the impact (upper) side of piston 18 to urge the piston downward driving the ram 22 to impact, air is forced out of the bottom of the cylinder through passage 32 into reservoir 30 and in this process the total volume of air is compressed. Then when air is exhausted from the cylinder above the piston the pressure of the air in this reservoir 30 drives the piston back upwardly. Ordinarily the piston is retained in its retracted position shown in FIG. 1 solely by the pressure of air beneath the piston and in reservoir 30. This pressure is sufficient without other mechanical restraint to hold the ram ready for use until driving air is reintroduced above the piston.

The present invention provides a constant fluid pressure supply 34, which is used directly to supply pressure to pilot valves and which is regulated to the selected pressure for use by the main cylinder by an adjustable pressure regulator 36. Regulator 36 permits a change in the constant pressure supplied by fluid pressure supply 34 to the inlet duct 38. Located in the inlet duct is a trip valve 40. Ordinarily in the course of operation the trip valve 40 is initially mechanically opened to make the system ready to operate. However, a solenoid actuator 46 responds to an emergency pushbutton to close the trip valve to shut off fluid pressure supply, exhaust downstream pressure and stop or retard the progress of the ram toward impact. At the end of the inlet duct 38 is the main valve 42. The main valve has three positions. In the open position shown in FIG. 1 the valve spool 41 is held by pilot air against spring pressure in its lower position so that the air from duct 38 communicates directly with the cylinder 16 above the piston 18 through duct 37. In its closed position shown in FIG. 2 the spool 41 has been moved up by spring pressure so that the inlet is shut off from duct 37, and the cylinder 16 through duct 37 communicates with exhaust duct 44. The main valve 42 is operated into open position shown in FIG. 1 by a solenoid 50 operating a pilot valve 48 in the pilot supply line directly from fluid pressure supply 34.

It should be understood that somewhere between the regulator 36 and the cylinder 16 above piston 18 is located appropriate metering means which prevents immediate transfer to the piston of the full regulated pressure. Metering can be provided by the size of the inlet duct 38, by limiting the size of opening of main valve 42 or even by introducing a metering orifice into the system. ln a manner to be described hereafter, by timing the period the trip valve 40 is open the pressure applied to the piston can be selected and controlled within narrow limits.

FIG. 2a shows the main valve 42 in a special expansion position achieved by applying pilot pressure to and cup-shaped valve member 43 to raise it into the position shown against spring pressure. Pilot valve 52 when positioned by energization of solenoid 54 connects fluid pressure supply to the expansion valve 43 which moves to the position shown in FIG. 2a to impede the flow of air out of the cylinder 16 in a situation such as the last blow of a series where fluid pressure may not be fed into the cylinder 16 above the piston, to cushion its upward motion. The expansion valve 43 may also be used to allow air to expand in the cylinder to conserve compressed air. Solenoids 50 and 54 and their

pilot valves

48 and 52 for operating main valve 42 are preferably shock mounted atop the crown of the machine.

below the duct 37 of the main valve 42. As shown in FIG. 2, when the die forger is operating the safety plunger 56 is withdrawn by solenoid 58.

In the position of the ram 22 during its upward rise a position-sensing switch 60 is provided at a predetermined position along the upward path of travel of the ram to be actuated by the ram at that point. The switch 60 may be adjustably positioned along its support rod by which it is attached to the frame 12. The switch 60 is used to initiate the return of the main valve to open position to allow fluid to flow from the fluid supply 34 into the cylinder 16. As will appear hereafter this switch also initiates a timing relay which determines howlong the valve 42 remains inopen condition and thus determines the intensity of the impact.

The operation of the machine as described is initiated by use of a foot treadle 64 which provides a switch which may be operated at the will of the operator to manually actuate the ram when it is set for manual actuation, or to interrupt and reinitiate.

Also shown in FIG. 1 is a control console generally designated 66 which contains the electrical circuitry for operating the die forger in a preprogrammed sequence of blows in a fashion determined by the manual selection means occupying the panel, generally designated 68, which is shown in greater detail in FIG. 3.

Before giving detailed consideration to the selection and indicator means shown in FIG. 3 it is desirable to understand the capabilities of the control means contained within the control cabinet 66. The control means of the present invention enable an operator to select blow intensity of the ram in a particular die forging operation by timing the period during which the main valve 42 is open to the fluid supply. Since the flow from the fluid supply to the cylinder 16 is restricted and requires a finite time to reach the full pressure of the fluid supply, the longer the valve is open to a certain point the greater will be pressure supplied cylinder 16 above the piston 18 for a given fluid supply pressure. For the sake of repeatability and reliability of setting, discreet increments of time are provided corresponding to increasing blow intensity settings for increasing time the trip valve 40 is allowed to remain open.

FIG. 4 illustrates the effect of varying the blow intensity setting for a given supply pressure where the blow intensity is expressed as a percentage of rated size. In passing it should be noted that this chart assumes a fixed lifting air pressure beneath the piston, since a variation in that pressure will also cause a variation in the effect illustrated in the chart of FIG. 4. Ordinarily, however, lifting air pressure supplied beneath the piston 18 is kept at a constant predetermined amount which may be observed on a lifting air pressure gauge 70 on console 66. This pressure is kept constant by a lifting pressure regulator. If desired, lifting pressure may be modified by knob 72. Similarly the driving or striking air pressure is shown on a gauge 74. Again the air pressure is regulated to maintain it constant at a fixed setting, but the regulated pressure may be changed by an adjustment knob 76.

In addition to the selection of force of blow through adjustment of the timing in accordance with the present invention, it is also possible to select the number of blows at the given blow intensity, the number of blows selected for a given intensity being known as a station of the control program. In accordance with the present invention it is possible to have multiple stations in each of which is provided a selectable number of blows of selected intensity. In the control panel shown in FIG. 3 provision has been made for five stations. Controls for the various stations are designated by the numerals to the left of the rows in their sequence of operation. The first column 78 provides indicator lights 78-], 78-2, 78-3, 78-4 and 78-5, only one of which will be illuminated at a time to designate which particular station is in progress. The second column 80 contains selector switch dials 80-1, 80-2, 80-3, 80-4 and 80-5, by which in this particular embodiment, a selection of up to fifteen sequential blows of the same intensity may be made for each station. The third column 82 contains selector switch dials 82-1, 82-2, 82-3, 82-4 and 82-5 having ten positions providing ten discreet preselected intensities of blow determined by the timing period of the associated timer means in each case. The final column 84 contains restart/continue selector switches 84-1, 84-2, 84-3 and 84-4 which permit a choice between stopping at the end of the selected number of blows of each station or automatically continuing on to the blows of the next station. Not all of the stations, or sequences, need to be used. The number of stations employed in a particular process is selected by the sequence selector switch 86. As the blows actually take place, the blows of the currently active station are counted by a binary counter and displayed by a binary blow count indicator 88, consisting of four lights representing from left to right I, 2, 4, and 8 blows, which are added to determine the equivalent number of blows in decimal units.

The panel also provides for a blow set control 90, a no-blow safety switch 92, both of which function as safety control. The blow set control must be pressed before the ram can be initiated. In the event of emergency the no-blow safety switch is pressed to interrupt the operation at any point. Overall operation may be manual, simply using the foot switch 64, or automatic, using the program set up by the control panel 68, according to which one of two positions is assumed by the manual-automatic selector switch 94. If desired, an automatic lubricator system may be provided and an indicator light 96 on the panel will show when it is functioning.

Referring now to FIGS. 5, 6a and 6b, there is shown in highly schematic form the control circuitry for the control programmer of the present invention. FIG. shows a step-down power transformer 98 connecting a 60 cycle power source to the control circuit such that the control circuit is provided with l volt, 3 amp. service across the

lines

100, 102. In this circuit the blow set switch 90 is normally open and when it closes it connects the blow set relay BSR across the 1 15 volt power lines through the no-blow safety switch 92, which is normally closed and can be opened at any time, in case of emergency, to disrupt the operation of the control circuit. The function of the blow set relay functions to close the normally open contacts BSR-l in series with the trip valve solenoid 46 across the power lines to thereby energize the trip valve solenoid, opening trip valve 40 as previously described. The relay BSR provides normally open contacts BSR-2 in the power line 100 so that, until the blow set switch 90 is closed, power is not supplied across the transformer/rectifier 104 which produces 24 volt dc for operation of the control function circuitry shown in FIGS. 6a and 6b. The closing of contacts BS R-2 also places power across the foot switch indicator lamp 106 through normally closed relay contacts FSR-Z of the foot switch relay and normally closed contacts 2P1, 3P1, 4P1, SP1 and normally closed contacts 1PS-]. At the same time the sequence l indicator lamp 78-1 is illuminated indicating that the first sequence is set up to begin. The foot switch 64 when closed energizes foot switch relay FSR which closes normally open contacts FRS-l to energize safety plunger release solenoid 58 to withdraw the safety plunger 56.

Inlet timer 107 and exhaust timer 108 are both enabled across the

power lines

100 and 102. The exhaust timer 108 is normally a single timer which, once set, retains its setting but is normally deterred until contacts of the last blow relay close to enable it to function during the last blow of a sequence. Its function is to energize the solenoid 54 for a predetermined time to impede the flow of exhaust air through valve 52 in order to retard the return of the ram on the last blow of a sequence of on other occasions when it is probable that the return of the piston 18 will not be opposed by new fluid entering the cylinder. The exhaust timer can also be used, if desired, to control expansion of air in the main cylinder.

The inlet timer usually performs a far more complicated function. In certain embodiments the inlet timer may, in fact, be a plurality of timers, one for each sequence, or station. In the present embodiment the inlet timer is preferably a single timer, with multiple settings. Variable resistances, one for each of the respective stations or sequences, are successively switched into a timing circuit with a fixed capacitance, to provide the needed timing represented by the respective RC circuits for each of the sequences. The resistances are adjustable by conventional potentiometer means, but are preferably provided with detents to give discreet repeatable settings for the selector dials of column 82 representing blow intensity. Other means of providing the desired timing will occur to the man skilled in the art in view of the advanced stage of the timer art.

The sub-circuit of FIGS. 60 and 6b, provides 24 volts dc across the

power lines

110 and 112 from the transformer/rectifier 104 of FIG. 5. The manual automatic selector switch 94 is left open as shown for manual operation and closed for automatic operation of the program controller. Closing switch 94 actuates automatic control relay ACR.

The normally open contacts FSR-3 of foot switch relay are closed by action of the foot switch 64, initiating operation and energization of start sequence relay SSR, to energize relays 1P and IP. Energization of relay SSR also closes contact SSR-1 and another contact of relay SSR to initiate a cycle reset timer 3TR (not shown) which, like

timers

107 and 108, is placed across the

power lines

100, 102. Energization of a relay ACR opens contacts ACR-l to permit sequencing of subsequent relays, which cannot occur during manual operation when contacts ACR-1 remain closed. Contacts ACR-2 and ACR-3 close to complete an altemate path to relays IP and 1? through normally closed switch contacts of relays ESR and LBR and through contacts 3TR-l and SSR-l. Relay 1? provides normally open contacts lP-l which close to energize the first sequence light 78-1. Relay 1P enables the restart or continue selector 84-1 and also sets up the trigger and timing circuit for the first station of inlet timer 107 in the manner previously described. Relay 1P through contacts lP'-3 sets up the number selected by the number of sequences selector 86. Relay 1P also sets up through contacts lP'-4 (FIG. 6b) the number of blows selector 80-1, readies relay lPS for the end of the first sequence through contacts lP'-2, (FIG. 6a) and enables the second sequence of light 78-2 through contacts lP-5 (FIG. 5). However, the second sequence light is held off by other contacts until the last blow of the series.

Relay 1? also triggers inlet timer 107. It will be ap preciated that when the inlet solenoid 50 triggers the main valve 42 by feeding pilot air to the main valve to open the fluid supply to the top of the main cylinder 16, fluid from supply 34 immediately begins to feed into the cylinder. The amount of pressure and the amount of force imparted to the ram is proportional to the time thatvalve 42 is open, in the position shown in FIG. 1. When the inlet timer 107 times out, it functions to drop out the inlet solenoid 50 and pilot valve 48 at which point the main valve 42 closes off the cylinder 16 from the inlet supply and opens the cylinder to the exhaust duct 44, the ram inertia and pressure continuing through this advanced period of ram travel to drive the ram toward impact. As the ram rebounds air is flowing out the exhaust of the cylinder and compressed air beneath the piston 18 and in the reservoir 30 forces the ram to rise.

When the ram rises, if more than one blow is called for by selector switch 80-1, the timer 107 is again triggered by the rising ram through switch 60 causing a repetition of the sequence described. That is, the main valve 42 is opened to fluid pressure supply 34 through regulator 36 for a period determined by blow intensity selector 82-1. The time during which the valve is open will be the same for each blow of the first station or sequence. On repeated blows the timer is triggered again and again. In practice the timer 107 pulls in other relays such as one which serves a number of auxiliary functions including pulsing the relay which drives the blow counting counter-circuit 114. Each count is indicated at binary indicator 88. The respective l, 2, 4 and 8 outputs of the binary counter, which may be composed of flip-flops, when turned on, also activate control relays lCR, ZCR, 4CR and 8CR. Those relays lCR, 2CR, 4CR and 8CR, energized by the counter, close contacts designated by their relay number in the blow selector circuit shown in FIG. 6b, in a pattern which represents the count. When a coincidence of the blow selector setting and the count indicated by an appropriate combination of closed contacts of control relay lCR, 2CR, 4CR and 8CR occurs, the circuit provides a continuous path to energize the last blow relay LBR. In the restart condition LBR is ordinarily maintained by the foot switch contacts through relay SSR contacts SSR-2 and the restart contacts and contacts lP-2 of relay 1P (or the corresponding contacts for later sequences).

Actuation of last blow relay LBR or the release of the relay SSR triggers the exhaust timer 108. Exhaust timer 108 energizes exhaust solenoid 54 when a last blow occurs as was previously explained. Then solenoid 54 acts on valve 52 to partially occlude the exhaust duct 44, thereby cushioning the upward travel of the ram. Last blow relay LBR, through nonnally open contacts LBR- l, energizes relay lPS to discontinue the first sequence. Before timing can be completed the sequence of the next station must be started by reactuating the foot switch 64 to energize relay SSR. Another timing relay initiated by the foot switch (and by relay SSR) may be provided to prevent work from being forged after cooling too much by timing out a time within which a decision about continuing or restarting the sequence must be made when the selector 84-1 is put in restart position.

If the selector 84-1 is in the continue position another timer (not shown) reduces the normal time required by exhaust timer 108 to hold the main valve in the exhaust position and allows the next sequence to proceed immediately. In the continue position of switch 84-1 the last blow relay is maintained by contacts of exhaust timer 108.

As seen in FIG. 6b, all restart-continue switches 84-1, 84-2, 84-3, and 84-4 are shown in the restart" position. ln this position the operator must interrupt the contact of the foot switch (and FSR) in order to permit the sequence of the next station to continue. In the continue position which closes another set of contacts through a timer (not shown) as long as the operator maintains the foot switch closed, there will be no interruption in operation between stations. In the restart position shown, when the respective relay contacts such as lP-2 are closed by energization of their respective relays and, through relay contacts SSR-2, a holding circuit is set up for the last blow relay through contacts LBR-l.

After the first sequence is completed, normally open contacts lP'-2 remain closed so that, upon closing of the contact LBR-l, relay lPS is energized closing contacts lPS-l for holding purposes, and IFS-2 is closed to energize

relays

2P and 2P through the normally closed contacts 2PS-l and 3PS-l. Upon energization of relay 2P, contacts 2P-2 act as holding contacts to keep the relays energized.

As can be seen from FIG. 6a, the circuit of station 2 is like that of station 1 and its sequence of operation is essentially the same. The same thing is true of

stations

3 and 4, which are therefore shown in block form, it being understood that the pattern of contacts and relays is the same. Station requires only one relay 5?, since there is no need to set up additional relays. Where relay contacts have not been described the relay is indicated without numbering the contacts so that circuit operation can be determined by inspection of relay circuits to determine when each relay will be effective.

The system has been described omitting details and alternative possibilities which can be provided as options with the system of the present invention. The means to accomplish the results described and modification of these results are well within the skill of the art and will be obvious to the man skilled in the art, so that he can readily modify the controls to perform many varieties of function and the same functions in a variety of different ways. All such variations and modifications within the scope of the claims are intended to be within the scope and spirit of the present invention. Description of the specific embodiment is intended by way of example of a preferred embodiment and is not intended by way of limitation.

I claim: 1. A stroke control system for an impact device having a frame supporting at least one cylinder, a piston within said cylinder and means connecting said piston to a ram such that said ram is movable relative to said frame from a retracted position into impact position and a driving fluid system, including a driving fluid supply and valve means for admitting compressible fluid from said driving fluid supply to said at least one cylinder at a position in the cylinder to drive said ram into impact position, comprising operating means for opening and closing said valve means including timing means for determining the period of time the valve means will remain open,

pressure regulating means for maintaining essentially constant the fluid pressure in said driving fluid supply, and

metering means in the supply system such that flow of fluid for selected increments of time permitted by the timing means will determine the pressure in said cylinder in order to drive the ram at a different predetermined force for each selected time increment.

2. The stroke control system of claim 1 in which exhaust means is provided to exhaust driving fluid from the impact side of the piston driving the ram into impact position and lift means is provided to retract the ram after each impact following exhaust.

3. The stroke control system of claim 2 in which the lift means includes reservoir means in communication with said cylinder at such location that fluid is compressed by the piston moving the ram into impact position whereby, following exhaust of driving fluid, compressed fluid in the cylinder and reservoir means provides force to retract the ram.

4. The stroke control system of claim 1 in which means is provided to adjust the driving fluid supply pressure and to regulate it.

5. The stroke control of claim 1 in which said timing means is adjustable in order to time valve openings to provide blows of different predetermined force corresponding to selected time increments.

6. The stroke control system of claim 5 in which the timing means has a predetermined number of selectable discreet incremental positions, each position corresponding to a predetermined blow intensity.

7. A stroke programmer control system employing the control system of claim 6 in which counting means is provided to count a preselected number of blows at a selected intensity and to cause the control function to be repeated to repeat the operating cycle for the preselected number of blows.

8. The stroke programmer control system of claim 7 in which the preselected number of blows at a selected intensity may be preselected by adjustment of an ad justable counter means.

9. The stroke programmer control system of claim 7 in which the system is provided with means for automatically sensing the return of the hammer to retracted position.

10. The stroke programmer control system of claim 7 in which the system is provided with means for automatically sensing the return of the hammer to retracted position and the preselected number of blows at a selected intensity may be preselected by adjustment of an adjustable counter means.

11. The stroke programmer control system of claim 10 in which a plurality of adjustable timing means are provided, each with selectable predesignated timing positions to permit blows of predetermined intensity, and sequencing means is provided to cause said timing means to be effective in predetermined sequence.

12. The stroke programmer control system of claim 11 in which each adjustable timing means is provided with a separate counter permitting multiple blows of the same intensity determined by each such counting means before the sequencing means is effective to select another timing means.

13. The stroke programmer control system of claim 12 in which stop means is provided to interrupt the system manually at any time.

14. The stroke programmer control system of claim 13 in which various selectable stop means are provided to permit automatically stopping a sequence at a predetermined time and means is provided to reinitiate the sequence when desired.

UNHED snares PATENT @FHQE QEE'HHQATE e5 @QERREEFTWN Patent No. 3, 81 799 Dated June 25 1974 Inventor(s) Wilmer W. Hague Sheet 1 Of 2 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

i 1 Correct F180 6a as lam.

may;

Sheet 2 of 2 UNITED STATES PATENT OFFICE 1, CERTIFICATE OF CORRECTION Patent 3 818 799 Dated June 25 1974 Inventor(s) Wilmer W. Hague It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below;

Column 1, line 55 "pressure" should be pressures 0 Column 5 line 63, Column 6, line 38, column 7,

line 60 and column 10, line 62 change "discreet" to -discrete--.

Column 7, line 31 "FRS-l" should be -FSRl- Signed and Sealed this twenty-seventh D a) Of April 1976 [SEAL] Atiesr:

RUTH C. MASON C. MARSHALL DANN Arresting Officer (mnmissinner uj'larvnls and Trademarks UNHED snares PATENT @FHQE QEE'HHQATE e5 @QERREEFTWN Patent No. 3, 81 799 Dated June 25 1974 Inventor(s) Wilmer W. Hague Sheet 1 Of 2 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

i 1 Correct F180 6a as lam.

may;

Sheet 2 of 2 UNITED STATES PATENT OFFICE 1, CETIFICATE OF CORRECTION Patent 3 818 799 Dated June 25 1974 Inventor(s) Wilmer W. Hague It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below;

line 60 and column 10, line 62 change "discreet" to -discrete--.

RUTH C. MASON C. MARSHALL DANN Arresting Officer (mnmissinner uj'larvnls and Trademarks

Claims

1. A stroke control system for an impact device having a frame supporting at least one cylinder, a piston within said cylinder and means connecting said piston to a ram such that said ram is movable relative to said frame from a retracted position into impact position and a driving fluid system, including a driving fluid supply and valve means for admitting compressible fluid from said driving fluid supply to said at least one cylinder at a position in the cylinder to drive said ram into impact position, comprising operating means for opening and closing said valve means including timing means for determining the period of time the valve means will remain open, pressure regulating means for maintaining essentially constant the fluid pressure in said driving fluid supply, and metering means in the supply system such that flow of fluid for selected increments of time permitted by the timing means will determine the pressure in said cylinder in order to drive the ram at a different predetermined force for each selected time increment.

8. The stroke programmer control system of claim 7 in which the preselected number of blows at a selected intensity may be preselected by adjustment of an adjustable counter means.