US2673552A - Control apparatus for steamhydraulic forging presses - Google Patents

Description

March 30, 1954 L. E. FRANcEscHlNA, JR 2,673,552

CONTROL APPARATUS FOR STEAM-HYDRAULIC FORGINO PRESSES Filed Jan. 12, 1953 3 Sheets-Sheet l l INVENTOIR jazz/s f'ancesczimJz:

and

ATTORNEY L. E. FRANCESCHINA, JR

March 30, 1954 CONTROL APPARATUS FOR STEAM-HYDRAULIC FORGING PRESSES 3 Sheets-Sheet 2 Filed Jan'. 12, 1953 FIG.3

FIG.2

ATTORNEY SES March 30, 1954 L. E. FRANcEscHlNA, JR

CONTROL APPARATUS FOR STEAMfHYDRAULIC FORGING PRES 3 Sheets-Sheet 3 Filed Jan. l2, 1953 FIG. 6

INVENTOR ATTORNEY Patented Mar. 30, 1954 UNITEDvv STATES OFFICE CONTROL APPARA HYDRAULIC FO TUS FOR` STEAM.- o RGING PRESSES,

Louis E-..Franceschina, Jr., BeaverFa'lls, Pai, as-

signor to The Babcock & Wilcox Company, New n York, N

.v Y., a corporationpf New Jersey Application January 12, 1953, serial No, 330,663 ;.o1aims..V (o1. 121-,3s)=- This invention relates to controls for metalworking presses and,

hydraulic In a which the invention control A1s particularly applicable, a vertically head is moved downwardlytoward the work, during a forging or pressing stroke,

metal forging presses.-

ram toward the starting point of vtheforglng,v or# downward, stroke.

The ram hasforging direction, resulting from the Hence, as vthe `workpiece-is successively reduced in vvertical dimension, the. starting` point ofltheMk forging stroke must be correspondingly lowered length of..` the to obtain the benet of thefull forging` or power stroke.

This re-positioning of the ing point is effected by lifting therram andi-.hen

to the hydraulic actuator. descends ey gravity, merely as a checkV opening, under pressure `from the pre-lill4 tank` to deliver .vaterto, the intensifier.

re-positioned, the forging operation- These operationsof the tvvo ranges of movement, one of which` termed the pressing ram positioning",y range.

operatively intercomlimited',

of the ram lifting pistons,and withvalves con@ trolling thev intensifierF The. present; iovention.;.. is directed.. solely, t0 i the controloi the piston type valve by the operknown steam-hydraulic forging pressto i steam operated, f hydraulic pressurev This valve, When the conpressing range, is not inators contro1-1ever.- trollever -is in` the fluenced by motion of hydraulic pressure is released.

To re-positionthe startingpoint oi the ram type valve.

When the lever positioningrange"toward the pressing range, the piston valve is moved-'tof-interconect the cylinder below the Vram lifting pistons,

coverthe pressure equalizin-g parts.

The .fact that th'efcontrolglever-must be moved through both sition; Whenever the fffullpress imlilou.;Y I meevalt@ ing one end made.: vari-ebs.. 0f a pressure cylinder to is 4novv moved through they tive lengthfao'ffuaestem preferably the outer end of the stem, this cylinder containing a piston having a piston rod carrying a stop on its outer end. A lever, interconnected by the servo mechanism to the operators control lever, has a free end carrying this piston rod. The stroke of the piston rod is so selected that, in the extended position of the rod., the stop will not be engaged by the collar in any position of the control lever but, when the piston rod is retracted, the stop will be engaged by the collar in every position of thecontrol lever or handle except the full press position.

This piston rod is normally extended so that the operators handle can be moved without operating the piston valve controlling the ram lifting pistons. To operate this piston valve to reposition the ram, the operator merely depresses a push button on the control handle. This closes an electric circuit which operates a solenoid valve to admit pressure fluid to the control cylinder retracting the piston rod and maintaining it retracted. The control handle is now effectively connected to operate the position control piston valve, due to engagement of the stop on the piston rod with the collar on the lever.

The ram positioning interconnection of the control handle and the piston valve can thus be made at any position of the control handle, except the full press position, and the handle need not be moved through full lift and the control range before the ram can be re-positioned. As the handle is moved to the full press position, the hydraulic control valve is opened in the same manner as before to supply liquid under high pressure to the hydraulic actuator. This opening of the hydraulic control valve closes a switch which effects energization of the solenoid valve in a direction to extend the stop-carrying piston rod. The ram position control piston valve can thus move back to its normal ram lift position.

For an understanding of the invention principles, reference is made to the following description and the accompanying drawings. In the drawings:

Fig. 1 is a somewhat schematic elevation view, partly in section, of a steam-hydraulic forging press and controls of the type to which the present invention is applicable;

Figs. 2 through 5 are partially schematic sectional views of the ram position control piston valve, illustrating the usual releasable latch interconnection with the operators control handle in certain key positions of the latter; and

Fig. 6 is a partially schematic elevation view of the invention control arrangement for the ram position control piston Valve, including a schematic illustration of the control circuits.

Referring to Fig. 1 of the drawing, a steamhydraulic forging press Ill is illustrated as comprising a bed II on which is a support I2 for a workpiece I3 such as an ingot or bloom. Extending upwardly from bed II are columns I4 which act as guides for a vertically movable pressing ram I5. Ram I5 is moved under high pressure toward bed II, to forge workpiece I3, by a hydraulic actuator mounted in a superstructure or head structure I6 tied rigidly to bed I I by columns I4. The hydraulic actuator'compresses a cylinder i1 in which is movable a piston I8 receiving the stem I9 of ram I5.

Ram I5 is forced in the downward or forging direction by the hydraulic actuator I1-I8, control of the ram being effected byan operatorfs control handle or lever 20. Upward mOYEmQpt QI a collar slidable along ram I5, and positioning of the starting point of the power or forging stroke, is effected by double acting pistons 2I movable in cylinders 22 mounted in superstructure I4, the pistons having piston rods 23 connected to ram I5.

Hydraulic fluid under high pressure is supplied to actuator II--I8 from a pressure intensifier 24 through a hydraulic control valve 25 mechanically interconnected to control handle 20. Intensier 24 includes a large diameter, lov.1 pressure steam operated piston 26 operating in a cylnder 21 and tied by rods 28 to a head 3l on the outer end of the stem 32 of a small diameter piston 33 operating in a cylinder 34 connected to valve 25. Also connected to this latter valve is a pre-fill tank or accumulator 30.

The operators control handle is also operatively connected to four steam flow control valves through the medium of suitable servo mechanisms. Three of these valves control the operation of intensifier 24, these being an equalizer valve 36, an exhaust valve 31, and an inlet valve 38. The fourth valve 40 is a piston type valve controlling lifting and positioning of ram I5, and this piston valve is connected for operation by handle 20 through a releasable latch. This latch is released when handle 20 is moved from the solid line position of Fig. l clockwise through the pressing range. To re-engage the latch mechanism, in order to re-position the starting point of the forging stroke, lever 20 must be moved counterclockwise through the solid line position of Fig. 1 into the ram positioning range and to substantially the extreme counterclockwise position of this range.

The steam exhaust and inlet valves 31 and 38 are operated, responsive to operation of control lever 20 from the standing or neutral position shown in Fig. 1 clockwise through the pressing range, to admit steam under pressure beneath piston 26 and connect the space above the piston to exhaust. At this time, hydraulic valve 25 is in a position closing off tank 30 and connecting intensifier 24 to hydraulic actuator I1-I 8. The steam pressure raises piston 26 forcing piston 33 into cylinder 34 and delivering hydraulic fluid under very high pressure through valve 25 to actuator I1-I8. At the same time, valve 43 will be in a position admitting steam to the undersides of pistons 2I and connecting the space above these pistons to exhaust. Piston I8 and ram I5 are forced downwardly, to deliver the forging stroke, and compressing the steam beneath pistons 2|. 'I'his occurs in the extreme clockwise, or maximum pressing, position of handle 20. At the limit of the forging stroke, handle 20 is moved counterclockwise to a position short of the neutral position of Fig. 1. This closes the steam inlet and exhaust valves 31-38, and opens equalizing valve 36 which equalizes the pressure above and below intensifier steam piston 26. Piston 26 falls, moving piston 33 downwardly in cylinder 34. The steam pressure beneath pistons 2| moves these pistons and ram I5 upwardly to the starting point of the power stroke, the hydraulic fluid flowing from actuator I1-'I8 through valve 25 into cylinder 34. The forging stroke may be repeated from the same starting point by moving handle 20 clockwise to its limiting position.

The operation of the control system in re-positioning the starting point of the power stroke of ram I5 will be best understood by reference to Figs. I through 5, `r"g.2 4shows the piston valve 40 in 'the position it occupies when lever 20 is interconnect ports 43 'and '44.

moving through the pressing range. Valve port 4| is connected to steam under pressure, preierably through inlet valve 3'8, and valve port 42 is connected to exhaust, preferably through exhaust valve 37. Valve port 43 is connected to the space beneath ram lifting pistons 2| and valve port 44 is connected to the space above ram lifting pistons 2|. The valve 40 includes a piston 4 5 having longitudinally extending grooves 4S and 4l in its periphery, these grooves having a length such that they can selectively interconnect ports 4| and 43 or ports 43 Yand 44. The upper edge of piston valve 45 has a recess 43 and of such dimension that, in the lowermost position of valve 45 (Figs. 2 and 3) port 44 is connected to exhaust port 42. The relation of the parts is such that in such lowermost position of piston valve 45, port 43 is connected to steam inlet port 4l.

The piston valve 45 has an upwardly extending stem provided with a guide 52 yslidably receiving a latch 'bar 53 having notch 54 near its upper end. 'The upper end of bar 54 is pivotally connected to a lever 53 pivoted to a fixed point at 56 and carrying a weight 51 on its free end. The other end of the lever` isschematically illustrated as connected by servo mechanism '58 to control handle 20. Guide 52 has pivotally mounted thereon a latch 55 having a keeper 6| adapted to engage in notch 54 and a forked operating arm 62 embracing a rod 63 extending 40 parallel to guide 52. Rod 63 has a stop l65 adjustably mounted on its and arranged to engage arm 62, dur of latch bar 53, to release keeper from notch 54.

In the position of valve 40 shown in Fig. 2, it is assumed that lever 59 is moved clockwise due to movement of press position e toward the ram positioning range of lever 23. 'During such movement of handle 20, steam flows from port 4| through grooves 46, 4;? to port 43 and thus to the space beneath lifting pistons 2|. is thus moved upwardly, as previously described, following the completion of a forging stroke.

It is assumed lthat it is desired to re-position the starting point of the forging stroke. As ccunterclockwise movement of handle 2d is continued, through the positions d, c and b of Fig. 1, the hydraulic control valve is opened mechanically when handle A2i? reaches position h, and connects the pre-fill tank 3|) intoI the hydraulic system. This permits water from the so that piston v45 closes port 4|, interrupts the connection between ports 42 and 44andbegins` to Inlet steam is now shut off from beneath the pistons 2| and steam begins to bleed from beneath the pistons through ports 43, grooves 45, 47, and ports 44 to the space above pistons 2|. The resulting gradual equalization ofthe pressure above and beneath the pistons 2| allows the ram I5 to drop, with valve 25 acting as a check valve as the hydraulic iiuid flows out of actuator l'l-IB. Further movement of handle 20 clockwise toward the power range increases the bleed-01T rate as will be noted from Fig. 5, and increases the rate of drop of ram I5. The maximum rate of bleed-off is illustrated in Fig. 5.

After ram l5 engages workpiece of handle 20 to position d causes ward movement of bar 53 that arm 62 of latch 55 engages stop 65 on bar 63. This swings latch 55 counterclockwise disengaging keeper 6| from notch 54, and allowing piston to drop back to the position of Fig. 2. The control handle 20 is now in the pressing range and may be moved back and `forth therein to raise and lower the ram withou again interconnecting valve 4D to itself. In the position of Fig. 2, as explained, the space beneath pistons 2| is connected to steam under pressure and that above the piston to exhaust.

The required movement of handle 2U to substantially the far extreme of the ram positioning range in order to re-position the starting point of the forging stroke results in undue delay and in unnecessary use of steam to lift the ram beyond the desired starting point for the next forging stroke. This delay may be avoided, and the ram starting point re-located at any position of control handle Y20, except the maximum press position, by the modified control of this invention as shown in Fig. 6.

Referring to Fig. 6, which shows only the valve stem 5|' connected to valve piston 45, a cylinder lli has a swivel connection 1| to the upper end of stein 5|. A piston l5 operating in cylinder 'l has a piston rod 76 projecting upwardly there from. Admission of pressure fluid to either side of piston l5 is controlled by valves 12, i3 which are operable by intel-locked solenoids '.I'l, i8. The upper end of rod 'I6 has a stop 74 adiustably secured thereto.

.Lever is replaced by a modified lever 5t' pivotally mounted to a xed point at and interconnected by servo mechanism 58 to the control handle '2B'.

Intermediate point 5S and weight 5l, a bracket 5| on vlever 5i is pivotally connected to a collar 82 sl-idable on rod 7B. The relation of parts is so extended `position of rod i3, will remain ineffective to operate valve 45 throughout the entire operating range of the control lever; and in the retracted position of rod '16, stop 'I4 will remain engaged with collar 32 in every position of control handle 25' except the maximum pressing position.

Operation -of piston 'l5 is under the conjoint control of a push button 811i on the end of lever 2H' and hydraulic control valve 25. This valve is modied from valve 25 so that when valve 25' closes under its spring loading, `it closes a switch 83. Push button 86 has a 84 'a1-ranged, when 'the push button is depressed, to momentarilyclose contacts 85 to connect solenoid 18 across a `suitable source of voltage S6. The push button has a second bridging member 8T which normally engages contacts 83 connected, in series with switch 8-3 v'and solenoid "71, across source '86. A imain contini I3, movement sulicient upvic-ed in the eircuia-ana-isnerina11y closed when`- first bridging member the steam-hydraulic press is in operation. To re-position the ram at any position of control handle 28, the operator merely depresses button 8D. This cuts the switch 83 out of circuit by opening contacts 88, and energizes solenoid 18 through closing of contacts 85. Solenoid 18 is interlocked with solenoid 11 so that valve 13 is opened to pressure and valve 12 is opened to exhaust. The valves remain in such position until the next operation of solenoid 11. This retracts piston 15 into cylinder 10 so that stop 14 engages collar 82 and stem 5l of valve piston 45 is effectively connected for operation by control handle When the ram l5 has been lowered on to the workpiece and the hydraulic system has been filled, hydraulic control valve closes in the same manner as previously. This closing of valve 25' closes switch. 83 which completes the energizing circuit for solenoid 11. Solenoid 11 interlocked with solenoid 18 now opens valve 12 to pressure and opens valve 13 to exhaust to extend rod 15. The piston valve 45 is thus effectively disconnected from control handle 2D so that ram l5 is in the normal power stroke operating position.

Thus, the press operation is greatly speeded up as there is no necessity for moving handle '20 completely through the ram positioning range in order to re-position the ram starting point. The ram starting point may be re-positioned at any point in the range of operation of handle 20', except in the maximum press position. Furthermore, no unnecessary lifting of the ram results, as is the case with the arrangement shown in Figs. 1 through 5.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the invention principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

l. A control for a steam-hydraulic press of the type comprising a vertically movable pressing ram, a hydraulic actuator operable to move said ram in the pressing direction, piston means connected to said ram and operating in cylinders connectible to a source of elastic fluid under pressure, said piston means being operable to retract said ram and control its position for the start of the pressure stroke, a hydraulic uid control valve controlling flow of hydraulic iuid under pressure to and from said actuator, a piston valve controlling admission to and exhaust from said cylinders, and an operators control handle operatively interconnected with said control valve and movable through a pressing range and a ram positioning range, said handle having a press position in the pressing range in which said control valve is operable to admit hydraulic fluid under pressure to said actuator, and a lift position in the pressing range in which said control valve is operable to exhaust hydraulic fluid from said actuator; said control comprising a longitudinally extendable and retractable stem connected to said piston valve; a stop on the outer end of said stem; a slider movable along said stem by said handle during movement of the latter in either range; said stop being beyond the path of movement of said slider when said stem is extended and engageable by said slider to move said stem outwardly when said stem is retracted; said piston valve, in its innermost position, connecting the undersides of the piston means to pressurea'nd the uppersides to exhaust whereby said piston means will lift said ram when the control handle is in the lift position; said piston valve, when moved outwardly, interconnecting the spaces above and beneath said piston means to equalize the pressures thereon to provide for lowering of said ram by gravity; mechanism selectively operable to extend and retract said stem; and a control element on said handle selectively operable to condition said mechanism to fully retract said stem to engage said stop with said slider.

2. A control for a steam-hydraulic press of the type comprising a vertically movable pressing ram, a hydraulic actuator operable to move said ram in the pressing direction, piston means connected to said ram and operating in cylinders connectible to a source of elastic fluid under pressure, said piston means being operable to retract said ram and control its position for the start of the pressure stroke, a hydraulic fluid control valve controlling ow of hydraulic fluid under pressure to and from said actuator, a piston valve controlling admission to and exhaust from said cylinders, and an operators control handle operatively interconnected with said control valve and movable through a pressing range and a ram positioning range, said handle having a press position in the pressing range in which said control valve is operable to admit hydraulic fluid under pressure to said actuator, and a lift position in the pressing range in which said control valve is operable to exhaust hydraulic fluid from said actuator; said control comprising a longitudinally extendable and retractable stem connected to said piston valve; a

stop on the outer end of said stem; a slider movable along said stem by said handle during movement of the latter in either range; said stop being beyond the path of movement of said slider when said stem is extended and engageable by said slider to move said stem outwardly when said stem is retracted; said piston valve, in its innermost position, connecting the undersides of the piston means to pressure and the upper sides to exhaust whereby said piston means will lift said ram when the control handle is in the lift position; said piston valve, when moved outwardly, interconnecting the spaces above and beneath said piston means to eoualize the pressures thereon to provide for lowering of said ram by gravity; mechanism selectively operable to extend and retract said stem; a control element on said handle selectively operable in any position of said handle to condition said mechanism to fully retract said stem to engage said stop with said slider; and means operable by said control valve, responsive to movement of the control handle to the press position, to condition said mechanism to fully extend said stem.

3. A control for a steam-hydraulic press of the type comprising a vertically movable pressing ram, a hydraulic actuator operable to move said ram in the pressing direction, piston means connected to said ram and operating in cylinders connectible to a source of elastic fluid under pressure, said piston means being operable to retract said ram and control its position for the start of the pressure stroke, a hydraulic fluid control valve controlling flow of hydraulic fluid under pressure to and from said actuator, a piston valve controlling admission to and exhaust from said cylinders, and an operators control handle operatively interconnected with said control valve and movable through a pressing range and a ram position in the positioning rangepsaid handler having `ia fpress pressing.` range in-@Whichf'saidzcontrol valve isV operableito fadmit hydraulic .ui'd under pressure to said actuator; and a liftrposi said stein said piston valve, in itsinnermostpositionfcom necting the undersides of the piston zmeans z to position; 'saidpisoutwardly, interconnecting the spaces above'and `beneath :said piston means to equalize the pressures thereontoprovide for lowering of saidv ram'by gravity; mechanism selectively operable toextend and: retract said stem; a controll elementfon said handle semovement of the control handle -to thel press position, to conditionsaid mechanism to fully extend said stem; Vanclian interlock device operder said last-named'means ineffective.

4. A control for ra steamhydraulicpress-of the type comprising a .vertically :movable pressing ram, a hydraulic `actuator operable to movesaiol ram in the 'pressing direction, piston means conmoved outwardly, interconnecting the spaces above and beneath said piston means to equalize the pressures thereon to provide for loweringof said .ram .bv` gravity; and-.a control element-on outwardly when said'. stem is retracted;

vpiston and stem slider.

. handle `operatively Ytrol valve and movable through a pressing range .and -a ram'positioning range, said handle hav- `comprising a cylinder connected said handle selectively operable toadmit pressure fluid; to-saidvalvecylinder to retract said valve to ,engage said stop with said i 5. A control forla-steam-hydraulic press of the type comprising a `vertically movable pressing ram, a hydraulic 'actuator operable to move said ram inthe pressing direction, piston means ccnnected to said ram and operating in cylinders yconnectible 'to a source of elastic duid under pressure,V said piston means being operable to retractsaid ram and control its position for the start of theV pressure stroke, a hydraulic uid control valve controlling flow of hydraulic uid under pressurefto and from said actuator, a piston valve controlling admission to and exhaust fromsaid cylinders, andan operators control interconnected with said condraulic iiuid from'said actuator; said control to said piston 6. A control for a steam-hydraulic press of the type comprising -a vertically movable pressing connected to said piston valve; a piston operable in said cylinder and having a stem projecting therebeyond; a stop on the outer end of said stem; a slider movable along said stem by said handle during movement of the latter in either range; said stop being beyond the path of movement of said slider when said stem is extended and engageable by said slider to move said stem outwardly when said stem is retracted; said piston valve, in its innermost position, connecting the undersides of the piston means to pressure and the upper sides to exhaust whereby said piston means will lift said ram when the control handle is in the lift position; said piston valve, when moved outwardly, interconnecting the spaces above and beneath said piston means to equalize the pressures thereon to provide for lowering of said ram by gravity; a control element on said handle selectively operable to admit pressure fluid to said valve cylinder to retract said valve piston and stem to engage said stop with said slider; means operable by said control valve, responsive to movement of the control handle to the press position, to admit pressure fluid to said valve cylinder to fully extend said valve piston and stem; and an interlock device operable conjointly with said control element to render said last-named means ineffective.

7. A control as claimed in claim 6 in which the admission of fluid to said valve cylinder is controlled by a pair of interlocked solenoid valves, said control element is a push button controlling energization of one solenoid valve, said lastnamed means is a switch controlling energization of the other solenoid valve, and said interlock device is a circuit closure of said push button in series with said switch and the source of elective potential.

8. In a steam-hydraulic press of the type comprising a hydraulically actuated vertically movable pressing ram, a control valve controlling application of hydraulic pressure to said ram, piston means connected to said ram and operating in cylinders connectible to a source of elastic fluid under pressure, said piston means being operable to retract said ram and control its position for the start of the pressure stroke, a piston valve controlling application of pressure to said piston means and having a retracted position applying v pressure beneath said piston means and an extended position equalizing pressure above and beneath said piston means, and means, including an operators control handle movable through a pressing range and a ram positioning range; a ram retracting and positioning control comprising, in combination, a longitudinally extendable and retractable stem connected to said piston valve; a stop on the outer end of said stem; a slider movable along said stem by said handle during movement of the latter in either range; said stop being beyond the path of movement of said slider when said stem is extended and engageable by said slider to move said stem outwardly when said stem is retracted; mechanism selectively operable to extend and retract said stem; and a control element on said handle selectively operable to condition said mechanism to fully retract said stem to engage said stop with said slider.

9. In a steam-hydraulic press of the type comprising a hydraulically actuated vertically movable pressing ram, a control valve controlling application of hydraulic pressure to said ram, piston means connected to said ram and operating in cylinders connectible to a source of elastic uid under pressure, said piston means being operable to retract said ram and control its position for the start of the pressure stroke, a piston valve controlling application of pressure to said' piston means and having a retracted position applying pressure beneath said piston means and an extended position equalizing pressure above and beneath said piston means, and means, including an operators control handle movable through a pressing range having a press position and a ram positioning range; a ram retracting and positioning control comprising, in combination, a longitudinally extendable and retractable stem connected to said piston valve; a stop on the outer end of said stem; a slider movable along said stem by said handle during movement of the latter in either range; said stop being beyond the path of movement of said slider when said stem is extended and engageable by said slider to move said stem outwardly when said stem is retracted; mechanism selectively operable to extend and retract said stem; a control element on said handle selectively operable in any position of said handle to condition said mechanism to fully retract said stem to engage said Stop with said slider; and means operable by said control valve, responsive to movement of the control handle to the press position, to condition said mechanism to fully extend said stem.

10. In a steam-hydraulic press of the type comprising a hydraulically actuated vertically movable pressing ram, a control valve controlling application of hydraulic pressure to said ram, piston means connected to said ram and operating in cylinders connectible to a source of elastic fluid under pressure, said piston means. being operable to retract said ram and controlr its position for the start of the pressure stroke, a piston valve controlling application of pressure to said piston means and having a retracted: position applying pressure beneath said pistonA means and an extended position equalizing pressure above and beneath said piston means, and means, including an operators control handle movable through a pressing range having a press position and a ram positioning range; a ram retracting and positioning control comprising, in combination, a longitudinally extendable and retractable stem connected to said piston valve; a stop on the outer end of said stem; a slider movable along said stem by said handle during movement of the latter in either range; said stop being beyond the path of movement of said slider to move said stem outwardly when said stem is retracted; mechanism selectively operable to extend and retract said stem; a control element on said handle selectively operable in any position of said handle to condition said mechanism to fully retract said stem to engage said stop with said slider; means operable by said control valve, responsive to movement of the control handle to the press position, to condition said mechanism to fully extend said stem; and an interlock device operable conjointly with said control element to render said last-named means ineffective.

LOUIS E. FRANCESCHINA, JR.

Number Name Date Crowe ,July 19, 1904il

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