Патент USA US2275202код для вставки
March 3, 1942. 2,275,202 W. P. V. ROSS ' ~ PUMP FOR MoLTEN METAL Filed July 3 , 1940 L....__ 5 Sheets-Sheet l «fliï» March 3, 1942. w. P. v. ROSS 2,275,202 PUMP FOR MoLTEN METAL Filed July 3, 1940 5 SheeÍS-Shee’tl 2 gf. /8 79 75 da r1 73 March 3, 1942. W. P. V. ROSS 2,2 75,202 PUMP FOR MQLTEN METAL Filed July 5, 1940 5 Sheets-Sheet 3 March 3, 1942. ' w. P. v. Ross 2,275,202 PUMP FOR MOLTEN METAL Filed July s,i 1940 5 Sheets-Sheet 4 :| _É. l _illlllllllh March 3, 1942.. W. P. V. ROSS 2,275,202 PUMP FOR MQLTEN METAL Filed July 3, 194()` 5 Sheets-Sheet 5 2,275,202 Patented Mar. 3, 1942 UNITED STATES, PATENT OFFICE ` 2,275,202 PUMP FOR MOLTEN METAL Y William P. V.> Ross, Battle Creek, Mich., assignor to Duplex Printing ‘ Press Company, Battle Creek, Mich., a corporation of Michigan Application Ju1ya1940, serial No. 343,905' h 15 Claims. vv(o1. .z2-7o) This invention relates to automatic pumps for molten metal or the like, and is particularly adapted for use in pumping molten stereotype metal from a melting pot into molds for casting printing plates for printing presses, although î the pump is obviously not restricted to such use; and the principal object of the invention is to provide a pump of the above type embodying certain novel features hereinafter set forth. I will explain the invention with reference to the accompanying drawings which illustrate one practical embodiment thereof, to enable others familiar with the art to adopt and use the same; and will summarize in the claims the novel features of construction, and novel -com- i binations of parts, for which protection is de In said drawings Fig. 1 is a side elevation of my novel'pump looking at the loading side thereof. - Fig. 2 is a horizontal section on the line 2_2, ' Fig. 3 is a front elevation of the pump looking towards the spout. Fig. 4 is a top plan View of the pump. Fig. 5 is a top plan view of the melting pot, detached, showing the pumping cylinder mount ed therein. ' Fig. 6 is a vertical section on the line 6_6, Fig. 5. Fig. 7 is an enlarged top plan View of the pumping cylinder, detached. Fig. 8 is a vertical section on the line 8_8, Fig. 7. ' Fig. 9 is an enlarged horizontal section on ` the line 9_9, Fig. 1, showing the means for actuating the walking beam of the pump piston _ rod. Fig, 10 is a rear elevation of the parts shown in Fig. 9. Fig. 11 is an enlarged vertical section through the loading door on the line II_I I, Fig. 1. Fig. 12 is an enlarged elevation showing the valve operating mechanism, taken on the line |2_-a2, Fig. 1. ` Fig. 13 is a top plan view of the parts shown in Fig. 12. to the upper ends of the wall members respec tively, said frame providing an inwardly directed flange. In the lower portion of the casing is a grate 8 (Fig. 1), the space below which is ac cessible through an ash pit door 9 disposed in the side wall 4 of the casing; also in wall 4 above grate 8 is a fire door I0 of suitable type. Preferably, wall members 2,` 3, 4, 5 are spaced double walls having heat insulating material 1, of granulated or other type, disposed in the space between said double walls, as indicated in Fig. 1. Preferably the walls 2, 3, 4, 5 of the casing above grate 8 are lined with ñre brick II 'extending upwardly to the underside of frame member 6, as indicated in Fig. 1. sired. Fig. 1. lower portion of the casing is open and' rec tangular frame 6 is mounted therein secured ' ' The pump preferably comprises a. substan tially rectangular casing consisting of a lower portion and an upper portion. The lower por- I tion of the casing comprises a base I, a front wall 2, a rear wall 3 and side walls 4 and 5 re spectively, connected at their lower ends to the base and connected together along their vertical- , edges in any desired manner. The top of the f _ l Suspended from frame 6 is a melting pot I2 vof substantially rectangular shape having an external peripheral flange I2a at its upper end seating upon the top of frame ß, said pot closing the upper end of the’lower portion‘of the casing. A ñue I3 is provided in the rear wall 3 adjacent the upper end adapted to be connected> to'a suitable stack or the like fornproducing- draft within the flrebox below the pot I2 and for re moving the'smoke'fumes. Í " n. Removably- mounted upon the lower member of said casing >is ,an upper member comprising a cover I4 having side walls overlapping the sides of thev casing outside the periphery of flange IZa of melting pot I2, as shown in Figs. 1 and 11, v ` said cover also having a top I4a so as to form a substantially closed chamber over pot I2. Cover I4 is provided with a flueV I5 forremov ing fumes and `gases from the molten metal in 'pot I2. Preferably cover I4 is also heat in sulated as shown in Fig. 11 by means of insula tion I1, similar to insulation ‘I, for the purpose of preventing loss of heat by excessivel radiation. In the loading side of 'cover I4 is a swinging door I6 (Figs. 1 and 1l) pivoted on a horizontal axis adjacent the top thereof so that said door can be swung inwardly as hereinafter described to permit the operator to skim the> dross from the surface of the molten metal in pot I2, andr said door being sufficiently large to permit in sertion of a used stereotype plate P (Fig. 11) for the purpose of re-melting to replenish the melting pot I2 with metal M. Door I6 is pref erably also double-walled withv heat insulation therebetween, in a manner similar to the walls >of the cover. Extending over the top of coverk I4, when posi tioned upon the casing, kand extending down 2 2,275,202 the rear walls of the cover and casing, is a re movable hood I8, having an enlargement I3 at will clear the return bore 2Ie as shown in dotted lines in Fig. 7, but when said end of valve 22h covers return bore 2Ie the other end will clear outlet 22e as shown in dot-and-dash lines in Fig. 7. Valve rod 22x is actuated automatically its lower end seating upon an extension Ia of base I at the rear thereof. The main portion of hood I8 is of relatively narrow width, for the purpose hereinafter described, and extending and may be adjusted as hereinafter described. laterally from the hood on the top of cover I4 A walking beam is provided in the upper por adjacent the front end thereof is an enlarge tion of hood I8 comprising a pair of parallel ment 20, for the purpose hereinafter described. swinging levers 21, 21a (Figs. l and 2) pivoted at Within melting pot I2 adjacent the front of 10 their centers on a bracket 28 mounted on the the casing is mounted a pumping cylinder 2| top I 4a of cover I 4, said levers extending from closed at its upper end by plate 2|a, and open at its lower end which terminates adjacent the bottom of pot I2, as shown in Figs. 1 and 6. A removable head 22 is removably secured to plate 2Ia by bolts 22a. Cylinder 2| is positioned in pot I2 by means of arms 221:» and 22e formed integrally with cylinder head 22, said arms being disposed at angles to the side walls of pot I 2, as shown in Fig. 5, so as to avoid interference with the spout, hereinafter described. a point adjacent piston rod 23 to the rear end of hood I8. The front ends of the levers 21, 21a, are pivotally connected to a plate 23 having an elongated slot 29a in its front edge and slidably receiving a pin 30a on a head 30 secured on the upper end of piston rod 23, whereby as levers 21, 21a are swung the piston rod 23 will move up and down with an approximate straight line motion. The rear ends of levers 21, 21a are piv otally connected to a plate 3| to which is con nected the upper end of an actuating rod 32 extending down through hood> I8 at the rear of the casing and having its lower end pivotally Extending through a bore 22d in head 22 and through a registering bore 2Ib in plate 2Ia of cylinder 2| is a piston rod 23 (Figs. 1, 5 and 6) carrying a piston 24 on its lower end, said piston 25 connected to an eccentric pin 33a on a crank rod extending upwardly through a gland 23a wheel 33 (Figs. 9 and 10) mounted on the driven (Fig. 1) in the top |4a of cover I4 and into the shaft 34a of a reducing gear 34. Gear 34 is hood I8, opposite enlargement 2|). When piston driven by an electric motor 35 mounted upon ex rod 23 is at thelower end of its stroke, piston 24 tension Ia of base I, by means of a -belt 36 run is disposed below the lower open end of cylin 30 ning over pulleys 35h and 34h on the drive shafts der 2|, so that molten metal within pot I2 may of motor 35 'and reducing gear 34 respectively, as freely enter the cylinder, whereby when the pis shown in Figs. 9 and l0. By the above construc ton rod is raised a predetermined amount of tion, as motor 35 is actuated, the walking beam molten metal will be forced upwardly within the 21, 21a Will be oscillated to reciprocate piston rod cylinder and into and through spout 25 (Fig. 1) 35 23. Preferably the hood I8 and its enlargements connected with an outlet 22e in the valve chest I9 and 20 are provided with suitable louvres as formed between cylinder plate 2Ia and a recess shown in Figs. l and 3 to allow circulation >of air 22j (Fig. 8) in the underside of cylinder head 22. therethrough to prevent undue heating of the Spout 25 extends through a` large opening- |42: motor and other operating parts of piston rod (Fig. 1) in the wall of cover I4 at the front of 40 23 and the automatic Valve actuating means. the casing, and preferably the portion of spout As previously stated, return duct 2|@ in cylin 25 projecting out of cover I4 in enclosed in a der plate 2Ia returns excess metal delivered by casingY 26 which- is> enlarged at its inner end and the cylinder 2| back into melting pot I2. The is connected to the side of cover I 4 covering the proportion of metal raised by piston 24 which opening |41', so that the hot fumes in the cover passes into delivery spout 25 through outlet I4 above the melting pot I2 may circulate freely openingA 22e is regulated by the setting of Valve along and around spout 25> and prevent the plate 22h within the valve chest at the top of molten metal therein from solidifying before cylinder 2| and which Valve 22h is secured to same has'reached the outer end of spout 25. the lower end of valve rod 22x. When the full A valve is providedY in the valve chest formed 50 quantity of molten metal raised by piston 24 is between the plate 2Ia and recess 22j in cylinder not permitted by valve plate 22h to pass into head 22, for the purpose of regulating the amount spout 25, the overñow descends through duct 2|e of molten metal forced into spouty 25 on each up back into pct I2, agitating the molten metal ward stroke of piston 24'. As shown, the valve therein and keeping its components well mixed chest communicates constantly withA cylinder 2| 55 without requiring any additional mechanical or through two open ports 2 Ic, 2|d (Fig. '7) in plate manual means for suchpurpose. The upper end 2 Ia within the area of recess 22]c of head 22, said of valve rod 22:0 is journaled in a bearing 39a ports 2Ic, 2Id permitting entry of molten metal in a frame 39 secured to the top I 4a, of cover I4 from cylinder 2| into the valve chest. In the of the casing within the hood enlargement 20. A plate 2Ia, offset from outletY 22e, is a bore 2Ie lever 36 (Figs. 12 and 13) on the upper end of (Figs. '7 and 8) forming a return duct for the valve rod 22x within hood I8 is connected by an molten metal from the valve chest to pot I2, the extensible link 3'! to a lever 33 on rock shaft 40 walls of said bore A¿Ie extending downwardly journaled in bearing 33h so that when said> shaft through an exteriorr enlargementv 2| f of> cylinder is rocked, valve rod 22h will be shifted to con 2| and terminating adjacent the lower open end 65 trol the relative amounts of uncovered areas of of the cylinder 2 I, whereby the metal discharged through said bore into pot I2 will agitate' the molten metal therein keeping the components therein well mixed‘without necessitatingY addi« outlet 22e and the return duct 2 ie (Fig. 7) .. Link 31 is equipped with a threaded section 31a for initially adjusting the limits of swinging move ment of valve 22h to provide different ratios of tional mechanical or manual means. Journaled 70 uncovered portions of outlet 22e and duct 2| e. in a bearing 22g (Fig. 8) in head 22 between the Shaft 40 carries a gear 4| meshing with a gear axes of bore 2| e and outlet 22er is a valve plate 42, twice the diameter of gear 4I, said gear 42 22h mounted on a valve rod 22x and being of being mounted on a shaft 43 journaled in bearing such shape and area that when one end thereof 39e of frame 39 and parallel with shaft 40. Piv covers~the outlet 22e of head 22 the other end 75 ‘ oted on shaft 43 is a rocker arm 44 connected by 2,275,202 3 a link 45 to one arm 46a of a bell-crank lever lines in Fig. 7.' By adjustment of link 3'I'-.-3'Ia. journaled at 47 in a bearing 39d of frame 39, the other arm 48h of the bell-crank lever having an elongated slot 46c therein which slidably receives of the 'valve mechanism the relative amount of opening of both ports 22e-2Ie may be varied, to wit, the movement of the valve 22h may be regulated to entirely close return duct 2 Ie in one position and leave outlet 22e wide open, or to close outlet 22e leaving duct 2|e> wide open, or the'valve 22h may be regulated to partially close both ports. Thus the valve 22h may be initially set to deliver all the metal back to the pot I2, or to deliver all the metal to the spout 25; or with both ports partially opened to delivery only sufficient metal to the spout to forma complete a roller 30a: on the head 38 at the upper end of piston rod 23 .within hood I8. As bell-crank lever 46a-48h is rocked by the vertical motion of head 38, link 45 rocks the arm 44 which is freely mounted on the shaft 43 and which car vries at its outer end a hinged member 44a equipped at its free end with an elongated roller 44h freely journaled on a stud 44C, where-by as arm 44 is rocked the roller 44h will roll on the periphery of a four-toothed ratchet disk 48 hav plate, the surplus metal being returned to melt ing pot I2. ing undercut teeth indicated at 48a, 48h, 48o and 48d: and in the positions of the parts as shown in Fig. 12, roller 44 would engage the uppermost tooth 48a at the top of disk 48 if such engage ment Were not obstructed. Preferably disk 48 is secured directly to gear 42 so that the gear may be mounted freely on shaft 43. On the v outer face of disk 48 are tWo diametrically op posed studs 48e and 48j. A dog 55 (Fig. 12) prevents disk 48 from ro tating in the wrong direction by engagement of the projection 55a thereof with the teeth 48a, 48h, 48e and 48d in succession, said dog swing ing on a stud 53 as the disk 48 is rotated by roll 44h in the direction of the arrow (Fig. 12). A guard leverA 49 is shown in Fig. 12 in its ob structing position, said lever being fulcrumed on a stud 50 ñXed in the frame 39 beside disk 48, and said lever being provided with projections 49a and 49h. Projection 49D is adapted to be normally engaged by a tooth i'slbI on the upper f end of a pawl 5I, which pawl swings on a stud 52 fast in the frame 39, and is provided with a lower projection 5Ia which, until the pawl is released, engages with lowermost stud 48e (Fig. 12) on disk 4B to positively hold the disk against When ready to cast, the handle 52h (Figs. 1 and 13) is rotated through one complete turn (360°) thereby rotating cam 52a, and swinging tooth 5Ib of pawl 5I out of locking engagement with the end 49h of guard lever 49, and lugv 5Ia of pawl 5I out of engagement with stud 48e of disk 48, thereby allowing guard lever 49 to rock on stud 50‘so that its outerl end lies below the tooth 48a and below the path of the roller 44h. On the subsequent up-stroke of Ipiston rod 23, roller 44h drops into the uppermost tooth 48a of the disk 48, so that on the following down stroke the lever 44 will turn the disk 48 one quarter revolution and through the gears 42 and 4I will rotate the shaft 40‘ one-half revolution, and through lever 38, link 3l, and arm 36 on valve rod 22x, will swing valve 22h to uncover outlet 22e to the spout 25 and close the return duct 2Ie. The next upstroke of the piston rod 23 forces the molten metal in the cylinder into the spout 25 and causes the roller 44h to engage the next tooth 48h of disk 48 which is then in the position formerly occupied by tooth 48a. The Il) rotation, while the diametrically opposite stud 48j (Fig. 12) is adapted, as the disk 48 is ro tated in the direction of the arrow in Fig. 12, to engage the underside of projection 49a of guard lever 49 and swing said lever so that its end 49h will be engaged by the pawl tooth 5Ib‘. The edge 5Ic of the pawl 5| is engaged with next downstroke of piston rod 23 therefore ro tates the disk 48 and gear 42 another quarter turn, thereby rotating gear 4I and shaft 48 a secondhalf revolution. During such latter ro tation of disk 48 the stud 481‘ will engage the underside of guard lever 49 and raise said lever into position to be engaged by tooth 5Ib of pawl 5I, thus restoring the different members to the a cam 52a mounted on a manually operable shaft positions shown in Figs. 12 and 13 upon the com pletion of a full half rotation of disk 48. 'I‘hus 52 rotatably mounted in the frame 39, said shaft while the -piston rod 23 is reciprocated by the 52 having one end projecting through casing 20 "1* motor 35, the valve 22h will remain stationary and journaled in a bearing 53 (Fig. 1) and hav and covering outlet 22e until crank 52h is again ing a crank 521) (Figs. 1 and 13) which may be rotated to permit actuation of the valve mecha equipped with the trip handle for the convenience nism. of the operator. I claim: 1. In a metal pump having a casing contain Operation To operate the pump the motor 35 is actuated by closing a manually operated switch (not shown), thus reciprocating the pump piston 23 through the rod 32 and walking beam 21, 21a. The valve 22h in normal position closes outlet 22e to spout 25 causing the entire flow of molten metal from cylinder 2I to be discharged through the return duct 2Ie, thereby agitating the metal in pot I2, the valve operating parts normally be- v’ ing in the positions shown in Figs. 12 and 13. Enough molten metal for casting a stereotype plate must pass, through the pumping cylinder ing a melting pot having a pumping cylinder and having a continuously reciprocating piston in said cylinder; a valve chest having an inlet from said cylinder and having an outlet provided with a spout; said valve chest having a return duct discharging into the pot; a valve in said chest adapted to be moved by the piston into posi tions across the outlet and return duct; means for normally holding said valve in position to close the outlet and to open the return duct; and manually operable means for releasing the holding means to permit said valve to be shifted into position to close the return duct and open and through the outlet 22e in the valve chest to the spout 25 and into the mold or casting box the outlet. (not shown), the surplus metal passing through said holding means comprising normally inactive valve actuating mechanism actuated by the pis ton and adapted when activated to open the out return duct 2Ie back into melting pot I2. Nor mally valve 22h closes the outlet 22e and main- ’ . 2. In a metal pump as set forth in claim 1, tains the return duct 2Ie opened, the valve 22h let and close the return duct during one pump normally assuming the position shown in dotted ing stroke of the piston. 4 2,275,202 metal discharged from the pump may be regu lated, the excess pumped metal returning to the claim 3. In1,combination means for initially with a;pump settingas the set 4valve forth to pot through the return duct. , 9. In a metal pump as set forth in claim 8, expose various-ratios of uncovered areas of said outlet and return duct while the molten vmetal is being passed to the spout, whereby the amount of metal passed thereinto may be regulated,y the excess pumped metal being returnedv to the pot through the return duct. said holding means comprising normally inactive valve actuating mechanism actuated by the piston and adapted when actuated to open the outlet and close the return duct during one pumping i stroke oi the piston. 4. In a pump as set forth in claim 1, said’hold . 10. In a metal pump having a melting pot con taining a pumping cylinder and having a con tinuously reciprocating piston in said cylinder; a valve chest having an inlet port from the cylinder ing means comprising a rotatable member jour naled on said casing; means actuated byV said member for moving the valve; a ratchet on said member having peripheral teeth; Van arm pivoted coaxially of said ratchet; means for> oscillating and having an outlet provided with a spout; said said arm; a yieldable pawl on said arm engaging the teeth of said ratchet; means for normally valve chest having a return duct discharging into the pot; a valve in said chest movable by the piston between the outlet and duct; said cylinder having its lower end open and terminat ing adjacent the bottom of the pot, and having its preventing the pawl from engagingthe teeth; and said manual means shifting the preventing means. upper end closed; a head on said closed upper end having a recess in its underside forming with said end the valve chest; and said return duct 5. In a metal pump having a casing contain ing a melting pot having a. pumping cylinder and having a reciprocating piston in said cylin der; a valve chest having> an inlet from said cylinder and having an outlet provided with a spout; said valve chest having a return duct discharging into theY pot; a valve in said chest adapted to be moved into positions across the discharging adjacent the bottom of the pot whereby the flow of molten metal from the vvalve chest into the pot will maintain the contents of the pot agitated. 1l. In a metal pump having a melting pot containing a pumping cylinder and having a reciprocating piston therein; a valve chest hav ing an inlet from the cylinder and having an out let and having a return duct discharging into the pot; a valve in said chest adapted to be moved into positions to cover thev outlet and return duct, said valve normally closing the outlet and open ing the returnV duct; a gear journaled on said pump; means actuated by said' gear for moving the valve; a second gear meshing with the ñrst outlet and return duct; normally _inactive valve actuating mechanism holding the valve in posi tion to close the outlet and to open the return duct; normally inactive means actuated bythe piston for actuating the valvel mechanism; and manual means for releasing said inactive means for actuating the valve actuating mechanism and shift the valve to close the return duct and open the outlet on one down stroke ofl the -pis ton, and on the next down stroke» to restore the gear; a ratchet on» said second gear having pe ripheral teeth; an arm besideV the ratchet; means valve to normal position. 6. In combination with a pump as set forth in claim 5, means in said valve actuating mechanism actuated by the piston for oscillating said arm; a yieldable pawl on said arm adapted to engage a tooth of the ratchet and rotate the ratchet a for initially setting the valve into position to ex pose various ratios of uncovered areas of said outlet and return duct while the molten metal is being passed to the spout, whereby the amount of metalv discharged from> the spout may-be regu- - lated, the excess pumpedmetal being returned tc the pot through the return duct. 7. In a pump-as set forth in claim 5, said valve actuating mechanisrnincluding a rotatable mem ber journaled on said casing; means actuated by e said member> for moving the valve; a ratchet on said member having peripheral teeth; and said 12. In a pump as set forth in claim il., said preventing means comprising a pivoted guard beside the ratchet normally positioned to pre vent the pawl from engaging said teeth until the guard is shifted by said manual means. 13. In a pump as set forth in claiml 1l, said preventing means comprising a trip and a guard beside the ratchet and having one end normally normally inactive means comprising an arm pivoted coaxially of said ratchet and` oscillated by the piston; a yieldable pawl on said- arm adapted to engage a tooth of the ratchet and rotate the ratchet a partial turn; a guard nor engaging the trip and its other end positioned to bridge the ratchet tooth; said manual means when actuated shifting the trip to permit the ratchet to be turned successive partial turns; mally preventing the pawl from engaging said tooth; and said manual means shifting said guard. partial turn; means for normallypreventing the pawl from engaging said teeth; and manual meansV for shifting the preventing' means'to per mit the ratchet to-be rotated-to clese'the return duct and open'the outlet. 60 and means on the ratchet adapted to restore the 8. In a metal pump having a casingv containing a melting pot having a pumping cylinder and having a continuously reciprocating piston in said cylinder; a valve chest having an inlet from said cylinder and having an outlet provided with a spout; said valve chest having a return duct dis charging into the pot; a valve in said chest; means for normally holding the valve in position to close the outlet and to open the return duct; means operated by the piston for shifting the 70 guard and trip to normal positionsV after a pre determined number of partial turns. 14. In a metal pump having a melting pot con taining a pumping cylinder and having a continu ously» reciprocating piston therein; a valve chest provided with an inlet fromthe cylinder,` an out let, and a return duct tothe pot; a valve in said chest normally closing the outlet and opening the return duct; a rotatable member; means actuated by said member for moving the valve; a toothed ratchet on said member; an oscillating valve to pass molten metal pumped on the up arm beside the ratchet actuated bythe piston; a stroke of the piston through the spout; and means yieldable pawl on said arm adapted to engage for initially setting the valve into position to ex a ratchet tooth and intermittently rotate the pose various ratios of uncovered areas of the outlet and return duct, wherebyY the amount of 75 ratchet during a down stroke of the piston; a 2,275,202 5 trip; , a pivoted guard beside the ratchet normally means actuated by said member for moving the maintained by the trip into position to bridge the adjacent tooth; and manual means for shifting valve; a toothed ratchet on said member; an the trip to permit the ratchet to be rotated and thereby close the return duct and open the out let; said ratchet teeth being spaced 90° apart; and a pair of diametrically opposed lugs on the ratchet adapted to engage the guard as the oscillating arm beside the ratchet actuated by the piston; a yieldable paWl on said varm adapted to engage a ratchet tooth and intermittently rotate the ratchet during a down stroke of the piston; a trip; a pivoted guard beside the ratchet normally maintained by the trip into positio-n to ratchet turns and restore the guard and trip to bridge the adjacent tooth; and manual means for normal positions, whereby the ratchet will be rotated through two successive quarter turns by two successive down strokes of the piston before the guard is restored to normal position. shifting the trip to rotated and thereby open the outlet; said 90° apart; a pair of permit the ratchet to be close the return duct and ratchet teeth being spaced diametrically opposed lugs 15. In a metal pump having a melting pot con on the ratchet adapted to engage the guard as taining a pumping cylinder and having a con the ratchet is turned and restore the guard and trip to normal positions; means for preventing tinuously reciprocating piston therein; a valve chest provided with an inlet from the cylinder, an outlet, and a return duct to the pot; a valve in said chest normally closing the outlet and opening the return duct; a rotatable member; backward rotation of the ratchet; and means co operating with said l-ugs to prevent forward rota tion of the ratchet until the trip is shifted. WILLIAM P. V. ROSS.