US2177935A

US2177935A - Stamp mill

Info

Publication number: US2177935A
Application number: US95587A
Authority: US
Inventors: Benjamin B Buck
Original assignee: Individual
Current assignee: Individual
Priority date: 1936-08-12
Filing date: 1936-08-12
Publication date: 1939-10-31
Anticipated expiration: 1956-10-31

Description

Oct. 31, 1939.

B. B. BUCK 2,177,935

STAMP MILL Filed Aug. 12, 1936 3 Sheets-Sheet 5 Patented Oct. 31, 1939 UNITE srrssq PATENT orris 2,177,935 STAMIP MILL Benjamin B. Buck, Los Angeles, Calif. Application August .12, 1936, Serial No. 95,587 2 0, Claims. 01. 83 -57) This invention relates to a machine for reciprocating a plunger, and the invention is useful in any situation where the reciprocating plunger operates to give an-impulse to any part, or deliver a blow, for example, upon a die or anvil.

The invention is particularly useful when applied to the construction of stamp mills such as used in mining districts for milling ore.

The general object of this invention is to provide'a-machine for reciprocating a plunger, and particularly adaptable for use in the construction of a stamp mill, which will overcome many of the objections and drawbacks of millsconstructed in accordance with the present practice.

One of the objects of the invention is to provide a machine of simple construction, in which the impetus is given to the plunger, or stamp, by means other than gravity. In this way, with a comparatively short stroke the plunger can be given a relatively high velocity, giving a greatly increased energy of impact as compared with plungers that merely descend by gravity.

Inits general construction the invention involves the use of a power cylinder carrying a piston, which is driven forward by power, and which operates to drive forward the plunger.

One of the objects of the invention is to provide a construction and mode of operation for a machine of this type, which will enable a separation to be eifected between the power piston andthe plunger before the plunger strikes the blow. In this way shocks to the power piston and its gas rings are avoided, and the life of the mill is greatly enhanced.

Amalgamating processes are still used in reducing and refining precious metals,but it is objectionable to have oil mixedwith the milled ore, asthe presence of such ,oil interferes with the .amalgamating process. .1

One of the objects of this invention is to provide a construction forthe mill, which will effectively prevent any oil from passing into the milled ore. i

'A further object of this invention is to provide a machine of very compact construction,- capable of reciprocating a plunger at a high velocity, but without employing a rotary shaft; also to pro- ;vide a machine of thiskind particularly adapted for use as a stamp mill, and having a relatively high stamping capacity as compared with the weight of the machine.

A further object is to construct the machine in such a way that its separate parts will be sufficiently light to enable them to be readily transscribed in' thefollowing specification, while the be adapted to the special requirements of the material that is being milled; in other words, to

provide a construction which will enable the shoe to-have a relatively short travel before it strikes the die, or a relatively long travel.

A furtherobject of the invention is to provide fluid-operated means for returning the plunger 15 and the power piston after a forward stroke.

A furtherobject of the invention is to provide the necessary valves, ignition means, etc, for operating a machine of this type, and to provide means for controlling the same automatically by the return stroke of the plunger.

Although I do not limit myself to the use of a combustible fuel for operating the power cylinder, in the present specification, I have described the use of a combustible fuel for this purpose; and one of the objects of the invention is to provide a construction for the machine,'which will operate to maintain a supply of heated air to the fuel feeding apparatus.

In operating a mill that strikes a blow on an anvil, a considerable'shock occurs to the mechanism of the mill when the plunger and shoe carried thereby strikes the anvil or die. One of the objects of this invention is to provide means associated with the shoe for absorbing a portion \35 of the shock which occurs when the blow struck.

The machine embodying my invention preferably employs compressed air for returning the,

plunger and the power piston after their forward -ploy a small'quantity of compressed air in starting up the machine.

Further objects of the invention will appear hereinafter. I

The invention consists in the novel parts and 50 combination of parts to be described hereinafter, all of which contribute to produce an efficient stamp mill.

- A preferred embodiment of the invention is debroad scope of the invention is pointed out in the appended claims.

In the drawings:

Figure l is a vertical section through a machine embodying my invention, and designed particularly to function as a stamp mill.

Figure 2 is a horizontal cross-section taken on the line 22 of Figure 1, and particularly illustrating the construction at the lower end of the return cylinder that functions to return the plunger and power piston after a forward stroke.

Figure 3 is a view upon an enlarged scale similar to Figure 1, but showing only substantially the upper half of Figure 1.

Figure 4 is a view upon an enlarged scale similar to Figure 1, but showing only the lower half of Figure l.

The dot and dash line 1VIM at the top of Figure 3 and the bottom of Figure 4 is a matching line drawn through identical positions of the two figures.

Figure 5 is a fragmentary vertical section upon an enlarged scale, and illustrates the detail of an air inlet for cooling the power piston.

Figure 6 is a fragmentary vertical section taken on the line 66 of Figure 2 upon an enlarged scale, and further illustrating the details at the lower end of the return cylinder.

Before proceeding to a more detailed description of the invention, it should be stated that in accordance with the invention, I provide a power cylinder in which a power piston reciprocates. After the forward stroke, the power piston is returned automatically to its initial position. In commercial use any suitable means may be employed to utilize the power developed by the power piston in its forward stroke. When the invention is employed in the construction of a machine for delivering blows, for example, a stamp mill, I prefer to construct the power piston so that it is a separate part from the plunger, but abuts against the plunger so that when the power piston is advanced by the driving force, it also advances the plunger. In order to avoid giving a shock to the power piston when the plunger delivers a blow, in the preferred form of my invention the power piston is unattached to the plunger. The plunger is automatically returned, and while the returning plunger could be utilized to return the power piston to its initial position, in the present specification I have described the power piston as being provided with its own returning means.

The machine is characterized by the use of .a floating plunger, preferably unattached to the driving power piston and not connected with any rotary shaft, and while, for a power developing mechanism this plunger could be made to operate in a horizontal direction, of course, in adapting the invention for use in the construction of stamp mills, the machine is of a vertical type, that is to say, the plunger reciprocates in a substantially vertical plane.

In the operation of the machine, on the forward stroke, means is provided for retarding the forward movement of the power piston so that when the plunger strikes a blow, it is not in contact with the power piston.

The power piston is preferably provided with its own return piston reciprocating in the return cylinder, and operating fluid admitted to the return cylinder forces the power piston back to its initial position. However, the air or other operating fluid in the return cylinder in advance of the return piston of the power piston, does not interfere with the forward advance of the power piston, due to the fact that relief valves are provided, which open automatically to permit the escape of the air before the advancing power piston, which otherwise would become highly compressed, and interfere with the development of the full force of the blow. The air forced out of the return cylinder on the down stroke of the plunger passes up to the fuel injection apparatus, thereby reducing the air volume and air pressure resistance to the striking stroke of the plunger.

The other end of the return cylinder is utilized as a compressor for compressing air, which is forced into an air reservoir, which contains a supply of compressed air for the operation of the machine. In the operation of the machine, after a blow is struck, an ample supply of operating fluid, or air, is admitted to the lower end of the return cylinder to effect the return of the power piston and plunger to their initial position; in other words, to insure the lifting of the stamp shoe to the height of its travel above the die, or anvil. The shoe of the plunger head is preferably provided with an outer sleeve, or apron, which prevents any possibility of lubricating oil passing down into the ore being milled, and during the upstroke, this outer sleeve or apron functions to control the moving parts, such as valves, and ignition means for the machine.

When the shoe has delivered a blow to the ore on the die, if the amount of material on the die is so reduced that the shoe approaches within a predetermined limit of the face of the die, then automatic means, preferably pneumatic means, is controlled to feed more ore onto the die.

The position of the reciprocating floating plunger with respect to the die, can be regulated to suit different materials being milled; in other words, if the ore is relatively diflicult to mill, the stroke of the plunger before it strikes the anvil, can be readily increased, and vice versa.

The invention as applied to a vertical type of machine, will now be described more in detail.

At the outer or upper end of the machine I provide a power cylinder I, in which power is developed to .advance a power piston 2 that drives forward a plunger 3. The cylinder I has an elongated cylindrical shell 4, and may be provided with a water jacket 5 for cooling the same. The power piston 2 is unattached to the plunger 3, and when it is driven forward by the operating fluid, it drives the plunger 3 forward, enabling the plunger to give impetus to any driven part or, as in the present instance, to drive a milling shoe, or a head 6 at the forward end of the plunger so that the same can cooperate with a die, or anvil l to reduce ore, or other material on the face of the die.

I provide means for returning the plunger after a forward stroke and, of course, the return of the plunger would effect the return of the power piston. However, I prefer to provide a return piston 8 for the power piston which is preferably carried or formed at the lower end of a long sleeve 9, which is rigidly attached to the power piston and extends down from the same within the shell 4 of the power cylinder. This return piston 8 reciprocates in a return cylinder In, the upper end of which supports the power cylinder I.

In order to provide for returning the plunger preferably compressed air, is supplied to the interior of the return cylinder ill in sufficient quantities to overcome the weight of the plunger and pheric pressure.

power piston 2, and return same to the elevated position in which they are illustrated in Fig. 1'. In the present instance, astheplunger and return piston 8 advances,,the air in the interior of the return cylinder ill and the interior of the sleeve 9, is forced out through outlet valves 13 that are mounted in an air head [4 at the lower end of the return cylinder l0. These valves l3 are preferably of a poppet type opening downwardly, and-have return springs l5 of helical form. When they open they admit the air to a valve chest it within the air head [4, and this valve chest communicates through arcuate ports I! with an air jacketspace IB surrounding the return cylinder ID. The air passes upwardly in this jacket space, and passes out of the jacket space through a pipe connection H! at the left side of the cylinder thatcarries the expelled air back toward the air reservoir, not illustrated,

but which is connected with this pipe I9. These valves l3 therefore permit the escape of the air in the return cylinder Ill, and prevent its being compressed to such a high pressure as might give too great a resistance to the forward movement of the plunger and power piston.

Themachine ispref'erably constructed so that when the head or shoe 6 strikes the ore on the anvil, or diel, the power piston Zwill be out of contact with the plunger 3. In order to ac-' complish this, I' prefer to provide an auxiliary exhaust port, or ports, such as the port in the shell 5 of the power cylinder. When the upper face of'the power piston arrives at this port 29, a quantity of the operating fluid that is propelling this piston, passes out through the port and substantially reduces the pressure in the power cylinder abovethe piston 2, to atmos- However, before this occurs I provide for a cooling effect on the piston 2 through the medium of this port 20, which is,

of course, open to atmosphere. For this purpose I provide the piston 2 with a waist 2| of reduced diameter. In other words, the piston 2 comprisesan upper head and an auxiliary lower head 22, and the outer face of the lower head 22 is formed with a scraper ring 23 in groove 23a, and the groove has a plurality of small ports 24, which extend down from the annular groove 23a, and communicate with the interior of the sleeve 9 above the return piston l2 of the plunger. The interiorof this sleeveabove the return piston I2 communicates through a passage 25 with a cooling chamber 26 cored in the main head or upper head of the piston 2. This chain-'- bercomrnunicates with the space around the pisto-ns waist, through a port 26a. This enables the cooling air that enters the annular space surrounding the waist 2|, to find its way up into the cored chamber 26.

By reason of the reduction of pressure in the gas that is driving the piston 2 forwardly at the time the same passes the port 28, there willbe a retarding effect tending to reduce the acceleration of the power piston 2.. This effect is enhanc'edby reason of the fact that in the design of the machine the effective area of the under side of the return piston 8 is considerably greater than the effective area on the under side of the return piston [2 0f the plunger. On this account the resistance to the advance of the power piston by the air in the cylinder [0, is considerably greater than the resistance to the advance of the return piston I2. In this way a separation between the power piston and the plunger is effected. --One of the main advantages of this is that when the plunger delivers its blow, there is little or no shock from the blow imparted to the power piston, and this considerably increases the life of the packing rings 21 of the power piston 2.

It is necessary to provide for lubrication of the return piston l2 as it reciprocates within the sleeve 9 of the power piston 2. For'this purpose I provide a lubrication connection 28 thatadmits a lubricant such as oil into the space surrounding the waist 2| and into the annular groove 230i whenever the power piston passes this lubricator and this oil is scraped down by the ring 23, and passes down through the ports 24 into the interior of the sleeve 9 above the return piston l2 of the plunger.

As many milled ores are subjected to cyaniding processes, andas the presence of oil in such a milled ore is objectionable, I prefer to construct this machine so that lubricating oil used in the machine cannot pass down into the vicinity of the die I where the ore is milled. In order to accomplish this, I prefer to provide the shoe 6 with a shell-form cap 29 secured rigidly to it, and this cap 29 is formed with a long upwardly extending outer sleeve 39, which reciprocates within an outer tubular casing 3i, said casing 3| being preferably formed with an external flange 32 near its lower end for supporting the same above a mortar box 33, as will be described more in detail hereinafter; This sleeve 35! not only prevents the passage of oil down to the shoe 6, but also afiords means for operating the automatic mechanism of the machine when in operation, as will be described hereinafter; The machine is constructed so that it feeds ore onto the die I automatically, and this automatic feed is controlled through the agency of the proximity of the shoe 6 to the die I after the blow has been tical movement so that it 'cancontrol flow of ore down a chute 35 into the mortar box 33. If the ore on the die 1 requires replenishing, theupper edge 38a: of the-sleeve 38 will pass below the inner end of a trip lever 36, which trip lever, with the roller on its forward end, will be projected forwardly by a coil spring 3'! so that the roller at its forward end will be in the path of the edge 30a when the plunger starts its upward movement. This trip lever 36 is preferably formed with a wide central slot as shown, which guides the lever so that it can slide on a fixed roller 38. The axial pin of this roller is mounted for adjustment in a vertical slot 39 in the frame of the machine. When the inner end of the trip lever 36 is rocked upwardly, its upper side operates a rock lever ill pivoted on a pin 4!, and this lever engages a collar on a valve stem .62, thereby opening the airvalve 43 admitting air from an air chest 44 down a pipe connection 65, so that this airis admitted under the piston 46 moving in an air cylinder 41. This piston 46 fits loosely in its cylinder and has a stem 48 extending downwardly, and attached to the gate 36. With this construction it will be evident that when the trip lever 36 is actuated, compressed air will be admitted under the piston 36, thereby raising the gate and admitting a quantity of ore through the chute 35. After the gate has been opened in this way, and the piston 48 rises above the outlet port 47a in the wall of cylinder 37, it will be returned to its closed position by a coil spring 49 associated with the stem 48.

The air chest M is connected by a suitable connection 50 with the air pipe l9 already described. An adjustable stop i for the trip lever 36 is provided, and this stop may be clamped in any desired position in a vertical slot 52 in the frame of the machine. The rocker lever 19 is held in contact with the trip lever 36 through the agency of a coil spring 53 disposed around the stem 54 guided through a small block 55.

The head 56 of the power cylinder l is provided with a main exhaust valve 51, the stem of which is guided through the head 56 so as to be actuated by a rock lever 58. This valve 5'! is normally held closed by a coil spring 59. This valve 51 is opened automatically during the up-stroke of the plunger through the agency of the sleeve 30. For this purpose I provide a trip lever 69 that is pivotally attached near its middle point to the lower end of a slide bar SI, and the outer end of this lever is pivotally attached to a holding lever 82, which is pivoted at its upper end in an adjustable frame 83, the lower end of the lever 62 being provided with a small coil spring 64 that holds a roller on the forward end of the lever 99 against the side of the sleeve 39 while the plunger is elevated, and the spring 64 will, of course, force the roller on the forward end of the trip lever 60 into the path of the edge 39a of the sleeve 39 when the plunger is near the lower end of its down stroke. Hence on the upward movement of the plunger 3, the upper edge 39a of the sleeve 39 will trip the trip lever Gil in an upward direction. This will cause the slide bar 6! to move upwardly and open an air admission valve 65, which admits air from an air chest 66 to the under side of the piston 61, moving in a small air cylinder 68. The rod of this piston is extended to form an actuating stem 69 that thrusts against the long arm of the rock lever 58. In order to actuate the valve 65, the slide bar 6i carries a stem '59 with an adjustable collar H that engages the lower end of the stem of the valve 65. This valve 95 is normally held closed by a coil spring 6512; and, furthermore, the actuating stem 79 is returned by a small coil spring 19a. The actuating stem 69 for the rock lever 58 is also returned, together with the piston 68, by a coil spring 99a. In this way, soon after the plunger 3 commences its rip-stroke, the exhaust valve 51 is open to atmosphere to permit exhaust of the operating fluid, or spent gases of combustion, in the power cylinder I.

Means is provided for automatically closing this valve 57 near the termination of the upstroke of the plunger and power piston 2. For this purpose I provide a trip lever l2 that is engaged by the upper edge Eta of the sleeve 39. Fig. 1 shows this edge 39a engaging this lever. This will cause the lever 72 to rock in an upward direction, and against a slide bar 53 that is pivotally attached to it, said slide bar operating to raise the valve stem i l of an air exhaust valve 75 connected with the valve chest 69. The raising of this valve 75 permits the air under the piston 67 to exhaust to atmosphere through the port'lfi. This valve 15' is normally held closed by a coil spring 14a around the stem 14.

The upper end of the slide bar 73 has a roller 11 rolling on the inner side of a guide bar 18, and the slide bar 13 is normally held up against the guide bar 18 by a coil spring 19. This coil spring also operates to pull the slide bar 13 and the lever 12 down to an extreme low position. In other words, the spring 19 will hold the inner end of the lever 72 against the outer face of the sleeve 39 when the upper edge 30a, of the sleeve is located above this trip lever.

The exhausting of the compressed air from under the piston 68 of course, permits the exhaust valve 51 to be closed by its spring 59.

During all the time that the plunger 3 is below the position in which it is shown in the drawings, compressed air, or other operating fluid, is admitted to the interior of the return cylinder It]. This air, however, is not admitted through the pipe I9, but through another pipe connection 80, which admits air to a valve chest 8| in which a gate valve 82 slides. This gate valve is housed in a post 8| a that passes up through the valve chest. In the position of the parts illustrated in the drawings, the upper end of the gate valve 82 is below two aligning ports 83 that permit air to flow across the upper face of the gate, and into an air passage 89, also housed in post Bla, and duct 85 in the upper end of the return cylinder l8, which duct 85 communicates with a tube 86 that extends down through air jacket space l8, and admits air into the lower end of the return cylinder near the air head M. However, on the up stroke when the edge We of the sleeve 39 engages a trip lever 81, it moves the valve 82 upwardly, and closes the ports 83. For this purpose the trip lever 81 carries a link 88, the upper end of which is pivotally attached to a slide block 89, said slide block being secured to the stem 99 of the gate valve 82. This gate valve 82 is normally held in a depressed position by a coil spring fllla disposed around the stem 99.

Thesupporting pin 9| for the trip lever ill, is preferably mounted for adjustment in a slot 92 in a portion of the frame of the machine.

The time of operation of this cut-off valve 82 determines the amount of power employed in the return of the plunger 3, and the power piston 2; and if more travel in return of these parts is required, the trip lever 87 should be adjusted so as to give a later cut-01f for the valve 82. This trip lever 81 is preferably also utilized to control the admission of operating fluid, or combustible fuel, to the power cylinder l, as will be described hereinafter.

The return piston 8 is preferably utilized to enable this machine to supply its own compressed air to keep it running after the machine has once been put into operation. For this purpose the upper end of the return cylinder 19 is surmounted by an air head 93 having an air inlet valve 94, which admits free air from the atmosphere on the down stroke of the return piston 8, and this air head is also provided with an outlet valve 95, which opens on the up stroke to permit compressed air in the upper end of the return cylinder it to pass out into the valve chest Bl already described; and this air, forced into valve chest 8| past the valve 95, passes up around the post am. as indicated by the arrow in Fig. 1, and thence back into pipe 86 back to the air reservoir.

This air pipe 9?.leads up to a fuel injecting device 98, preferably including a valve 99 which, when opened, admits the air under pressure into spring 0912.

anfair admission duct I-that-leads through a poppet valve .IOI into the interior of the power cylinder I; The seat of the valve 99 has a countersunk fuel groove I I la with passages I I lb leading onto the seat, and to which liquidfuel may be admitted from the fuel reservoir I02. When the valve 99 is open, air rushes through-the inlet port I03 for this fuel, and carries a quantity of fuel with the air down through the duct I00 and past the valve IOI into the interior of the power cylinder. This valve. 99 is opened automatically at'the proper time through the agency of the rock lever 01, already described. For this,

purpose. the rock lever 81 carries a stem I04, which stem shoves upwardly against a rock lever I05, said rock lever pivotally carrying an actuator I06, which is formed with a cam edge I01 cooperating with a roller I08 adjustably mounted in'a slot IBM ina fixed bracket IIlBb. The actuator is held against the roller by a coil spring IIlGa. The upper end of the actuatorIIlB will thrust against the shoulder I09 and raise: the rocker IIO. However, the latter part of the movement of the actuator I06, and its cam edge I01, will cause it to swing outwardly at its upper end, thereby disengaging the shoulder I09 and permitting the rocker II 0 to fall. 7 The rockerI I0 through an adjustable set screw, engages the stem 99a of the valve 99, which stem has a return The valve 99 is opened and the fuel admitted just before the termination of the up stroke. of the prior closing of ports-33, a quantity of air from the lower end of the return cylinder will flow up through tube 86 and follow up the air flowing into the power cylinder from air pipe 91.,

The charge of fuel and compressed'air admittedinto the power cylinder I, is'ignited-automatically, preferably by means of a spark plug III, the circuit of which is closed. at the proper instant, by means of a pivoted circuit closer I I2,

which is shoved upwardly at the proper instant by a small plunger H3 actuated. by a linklld, the lower end of which is jpivotally' attached to the rocker I05.

an adjustable set screw. IIIla; I

When the circuit closer H2 engages the ter minal H5, thecircuit through the spark plug I and through a spark coil H6, will be closed;

thereby producing an ignition spark in a recess This igniin the wall of the power cylinder. tion, however, will take place after the admission of the'fuel and air through the duct I00 has terminated,'and the valve IOI has closed. 4

The air pipe 91 extends over to the right sid of the machine as'illustrated in Fig. 1, and is provided with abentiend am that is connected into the airchest 00 associated with the admission valve 65' that admits air underthe piston 01 for operating the exhaust valve 5'I.

The-machine is constructed so that the length of stroke of the shoe 6 canbe adapted to the character of the ore beingmilled. If the ore is relatively hard, or difficult to mill, the plunger Sshould havethe greatest possible stroke so-as to increase the energy'of the blow delivered to the ore on the die 1. On theother hand, if

:themilling operation is easy, the length ofstroke When the valve 99 is opened, by reason maybe shortened. In order to. enable this to be accomplished,.al1 of the connections for the rocking 'partscontrolled by the'sleeve 30, should be adjustable. In order to regulate the stroke of the plunger, I prefer to employ a series of distance rings II'I. These rings are preferably formed in sections, which may be put in place under the flange 32 of the casing 3I. They operate to support the casing 3| at a more or of the mortar box 33 is preferably protected bymeans of a liner I22 in which the die I is set; The milled material floats, out through a screen I23 on one or more sides of the mortar box, said screen being clamped in place by a frame I24 and wedges I25 applied at the ends of the frame.

In order to assist in preventing any oil from passing down into the mortar box, and also so as to provide efiicient guiding means for the plunger stem 3a that extends down from its return piston I2, I prefer to provide the air head M with an upwardly extending long tubular sleeve I26, which fits closely to the diameter of the stem 3a, which is preferably slightly enlarged at this point. The upper end of this enlarged neck of the stem 3a is preferably provided withsuitable packing rings I21.- I

In order to enable the trip levers -36, 60, I2, andfil to cooperate with the upper edge a of the sleeve 30, the wall of the outer casing Si is provided with openings such as the opening I28, that pass through the same.

The shoe 6 is preferably connected to the lower end of the stem 3a in such a way that a certain amount'of cushioning effect is obtained in impartingthe thrust of the plunger to the shoe. For this purpose I prefer to form the lower end of the stem 3a with a substantially spherical ball head, or ball I29, and this ball is received in cooperating sockets formed between a lowerblock I30 and an upper block I3 I, the said upper block being provided with an over-size opening I32 through which the stem 3dr passes downwardly.

These blocks fit down into a cylindrical chamber I33 in the upper side of the shoe. The blocks I30 and ISI are also cylindrical in horizontal cross-section, and are held in place in a steel shell,.or sleeve I34, on-the outerside of which a shell I35 of relatively soft packing material such as fiber, or similar material, is provided. The upper block I3I is held in position by means i of the usual arcuate locking segments I36 that are dropped down through arcuate slots I31 on the upperside of the block, and then pushed circumferentially around in an arcuate chamber formed between two annular grooves, namely, a groove I3'I formed in the inner face of the wall of the shoe at this point, and a cooperating groove I38 formed in the outer face of the upper block I 3L,

Between the lower face of the lower block I30 and the upper face of the body of the shoe 6, I provide a plurality of cushioning discs I39. These discs I39 give a slight amount of cushioning effect,- and while they do not detract from the blow given by the shoe 6 to the material on the die I, they give a certain amount of follow-up to the blow, and they also relieve the upper mechanism of the machine of considerable shock.

I shall now describe briefly the mode of operation of the machine in passing through a complete cycle.

It should be understood that in the position illustrated in Fig. 1 for the power piston 2 and the plunger 3, these parts have traveled downwardlyapproximately an inch, or thereabouts, from the extreme upward limit of their travel. In other words, the explosion of the fuel has taken place, and the power piston 2 and plunger 3 are commencing their downward stroke. As this movement continues, a high amount of acceleration is imparted to these parts. As the waist 25 of the power piston 2 arrives opposite the port 26, atmospheric air is admitted around the waist 2!, which tends to cool the power piston. As the movement continues, as soon as the upper face of the power piston 2 arrives at this port 28, an auxiliary exhaust of the propelling gases behind the piston 2, occurs. This reduces the impelling power on the power piston, and tends to check the advance of this piston with the plunger 3. Furthermore, by reason of the fact that the effective area of the under side of the return piston 8 is considerably greater than the effective area of the under side of the return piston 52 of the plunger 3, the air within the return cylinder It] will offer greater resistance to the advance of the return piston 8, and this will assist in retarding it and eiTect a separation between the upper end of the stem 3a and the power piston 2, and hence when the blow is delivered to the material on the die I, the power piston 2 will be out of contact with the plunger, and will not receive any shock from the sudden arrest of the plunger. Of course, the power piston will continue its forward movement, but its acceleration will have been retarded by the partial exhaust through the port 26, so that although the power piston 2 will follow up and strike the plunger, it will not be greatly jarred from strik ng it. Furthermore. 1

a certain quantity of air from the annular space surrounding the waist 2! will find its way into the space between the power piston 2 and the end of the plunger 3, thereby giving an air cushion effect. When the blow is struck on the ore on the die I, if it should happen that the ore on the die needs replenishing, then the plunger will have descended to such an extent that the upper edge 38a of the sleeve 38 of the plunger will have passed below the forward end of the trip lever 36. If this occurs, then when the plunger commences its return stroke, the edge 38a of the sleeve 38 will rock the trip lever 36 upwardly, thereby actuating the rock lever 48 and thereby raising the valve stem 42 to open the valve 43. This will admit compressed air from the pipe 19 and connection 50 to the pipe connection 45 that delivers air under the piston 46 in the cylinder 41. This will raise the piston, and the stem 49 of the piston will pull up the gate 34 and permit some ore to pass down the feed chute 35 into the mortar box. When the piston 46 passes the exhaust port 41a, the compressed air under the piston escapes and the spring 48 returns the gate 34. As this occurs the air in the cylinder escapes past the loose piston 46.

Referring again to the downward stroke of the plunger 3 and power piston 2, it should be understood that compressed air is present in the return cylinder I0, and a quantity of this compressed air is forced out through the valves [3 in the air head. This air passes up through the ports I2 into the air jacket space I8 around the cylinder IE, and thence passes through the pipe I9 back to the air reservoir.

The plunger and the power piston commence to rise immediately after striking, by reason of the fact that compressed air will flow through the air supply pipe 88 and through the ports 83 of the valve chest 8|, and thence through the

passages

84 and 85 to communicate with the tube 86, which will deliver air at the lower end of the cylinder l and under the return piston 8. This air, of course, will commence to raise the power piston by reason of the force which it exerts upon the under side of the return piston 8; it will also commence to raise the plunger by reason of the force which it exerts on the under side of the return piston I2.

During the downward movement of the plunger, as it approaches the bottom of its travel, the upper edge 38a of the sleeve 38 will pass below the inner end of the trip lever 60, and hence the spring 64 will pull the trip lever 60 inwardly so that the roller on its forward end projects into the path of the edge 30a. Hence during the up-stroke, when the edge 38a strikes the lever 68, it will rock the lever on its pivotal support on the hanging lever 62, thereby exerting an upward thrust in the slide bar 6|. This will cause the collar II to open the air admission valve 65, which will admit compressed air under the piston 61, raise the stem 69, and thereby rock the rock lever 58, which will open the exhaust valve 51. This reduces pressure of the gas of combustion above the power piston 2, and enables the piston as it rises, to completely exhaust the power cylinder I. As the upward movement continues, the edge 38a eventually strikes the trip lever I2, which raises the slide bar I3, and this opens the air release valve 75, permitting the air under the piston 61 to exhaust. This permits the exhaust valve 51 to close preparatory to the power cylinder I receiving the explosive or combustible charge which is to be consumed for causing the next down stroke of the plunger.

Referring again to the down stroke of the plunger, it should be understood that as the return piston 8 moves downwardly in the return cylinder I0, the upper end of the return cylinder I0 operates as a compressor cylinder, atmospheric air being admitted through the inlet valve 94; and when the up-stroke commences, this air is forced out through the delivery valve 95, and passes through the air chest 8| and around post 8Ia as indicated by the arrow, and thence through pipe 80 back to the air tank, or reservoir. Just before the up stroke of the plunger and power piston is completed, the edge 38a of the sleeve 38 strikes the trip lever 81, the first effect of which is to actuate the link 88 that shoves the gate valve 82 upwardly and closes the ports 83. After these ports close, the fuel valve 99 opens and air flows into the power cylinder I from air pipe 91, followed up by air that flows out of the lower end of return cylinder ID. This air is for combustion of the fuel when ignited in the power cylinder I above the power piston 2. The movement of the trip lever 87, through the stem I84 housed in post 3Ia, actuates the rock lever I05, thereby moving the actuator I06, the upper end of which engages on shoulder Hi9, causing the rock lever IIOj-to rise,

thereby opening the air admission valve 99. and

then permitting the same to close quickly by reason of the cam edge Hill on the actuator I85 that moves it back out of engagement'with the shoulder Hit; The opening of this Valve 99, of course, permits the compressed air to flow in past the valve 99 into the air duct lflfl, thereby entraining liquid fuel from the fuel reservoir Hi2. This duct lliil'also operates as a vaporizing chamber and mixer for the fuel and air;.the air blowing into the duct or chamber lilil, opens the.

valve lfll, thereby bringing the explosive charge into the power cylinder As soon as the valve 99 is permitted to close, of course, the valve 5M isimmediately closed by its own spring. A continued upward movement of the rock lever [05 will push the plunger i it far enough up to cause the circuit closure l2 to touch the terminal H5, thereby closing the circuit through the spark plug H l and igniting the charge.

The stroke of the plunger is regulated withrespect to the die l, by. changing the distance rings I H and I it underthe flange 32 of the outer casing 3| of the machine. When the material .being milled is soft, or easily milled, the stroke of theplunger should be reduced by removing the distance rings and permitting the flange 32 to rest on .the base ring H9. i

The feature in the mode ofoperation of thi mill involving the withdrawal of air from the under side of the return piston 8 for admission into the power cylinder for burning the fuel' therein, is highly'advantageous'because it substantially. reduces the pressure of the air under the return piston 8, and under the return piston I?! of theplunger. Thisgreatlyreduces the resistance to the plunger on itsdown stroke, and enablesa blow of a given amount of energy to be delivered with arelatively small quantity of guidingthe same, a power cylinder, a power piston unattached to the plunger and located back of the plunger, meansfor developing pres- I sure in the power cylinder to drive the power piston and the plunger forward. and means for returning the plunger.

2. In a machine for reciprocating a plunger, the combination of a floating plungenmeans for guiding the same,a power cylindena power piston unattached to the plunger and located back of the plunger, an admission valve for the power cylinder, an exhaust valve for the power cylinder, and

means controlled by the plunger for controllin the said valves. I

3. In a machine for reciprocating a plunger, the combination of a floating plunger, guiding means for the same, a power cylinder adjacent the rear end of the plunger, a power piston in the power cylinder unattached to the plunger and mounted to reciprocate in the power cylinder, means foradrnitting combustible fuel and igniting. the .same in. the .power cylinder to .drive forpneumatic means for. returning the. plunger and the power piston.

4. In a machine for striking blows, the combination of a floating plunger, guiding means for the same, a power cylinder adjacent the rear end of the plunger, a power piston mounted to reciprocate in the power cylinder means for developing gas pressurein thepower cylinder to drive forward the power piston and the plunger,

, ward the power piston and the 1 plunger, andi axreturn piston connected with the power piston, and means for admitting fluid to the return piston for returning the same.

5. In a machine for striking blows, the combination of a floating plunger, guiding means for the same, a combustion cylinder, a power piston mountedto reciprocate therein, means for feeding a combustible mixture intothe combustion cylinder and for igniting the same to drive forward the power piston and the plunger, a sleeve carried by the power piston and'sliding in the power cylinder, a return piston on the plunger within the sleeve, a return cylinder for the power piston, a return piston on said sleeve mounted to reciprocate in the said return cylinder, and

means for admitting a fluid to said return pistons to return the same after the plunger has struck ablow.

6. In a machine for striking blows, the combination of a floating plunger, guiding means for the same, a combustion cylinder, a power piston mounted to'reciprocate therein, means for feeding acombustible fuel into the combustion cylinder and for igniting the same to drive forward thepower piston and the plunger, a sleeve carried by the power piston and sliding in the power.

cylinder, a return'piston on the plunger within the sleeve, 2. return cylinder for the power piston,

a return piston on said'sleeve mounted to reciprocate in the said return cylinder, means for admitting a fluid to said return pistons to return the same afterthe plunger has struck a blow, and automatic means for effecting the exhaust of the spent gases of combustioncontrolled by the return movement of the plunger.

'7. .A machine constructedin accordance with claim 4, in which means is provided for per- .der beforethe blow is struck.

8. In a machine for striking blows, the com- 7 bination of a floating plunger, guiding means for mitting the exhaust of gas from the power cylinthe same, a combustioncylinder, a power piston mounted to reciprocatetherein; means for feeding a combustible mixture into the combustion cylinder and for igniting the same to drive forward the power piston and the plunger, a sleeve carried by the power piston and sliding in the power cylinder, areturn piston on the plunger within the sleeve, a return cylinder for the power piston, a return piston on said sleeve mounted to reciprocate in the said return cylinder, means for. admitting air in the return, cylinder to exert pressure on the forward sidesof the return pistons on the return stroke, and means for effecting a partial exhaust of the gas pressure from the power cylinder before the end of the forward stroke, and cooperating with the air pres-.

sure in the return cylinder toretard the power piston and separate the same from the plunger before the blow isstruck, p i l 9. In a machine for striking blows, the combination of a floating plunger, guiding means for the same, a combustioncylinder, a power piston mounted to reciprocate therein, meansfor feeding a. combustiblemixture into'the combustion cylinder and for igniting the same to drive forward the power piston and the plunger, a sleeve carried by the power piston and sliding in the power cylinder, a return piston on the plunger within the sleeve, a return cylinder for the power piston, a return piston on said sleeve mounted to reciprocate in the said return cylinder, means for admitting air to the return cylinder to exert pressure on the forward sides of the return pistons on the return stroke, the area of the return piston of the power piston being greater than the area of the return piston of the plunger so that as the power piston and the plunger advance, the power piston will be retarded and out of contact with the plunger when the blow is struck.

10. In a machine for striking blows, the combination of a floating plunger, guiding means for the same, a combustion cylinder, a power piston mounted to reciprocate therein, means for feeding a combustible fuel into the combustion cylinder and for igniting the same to drive forward the power piston and the plunger, a sleeve carried by the power piston and sliding in the power cylinder, a return piston on the plunger within the sleeve, a return cylinder for the power piston, a return piston on said sleeve mounted to re ciprocate in the said return cylinder, means for admitting a fluid to said return pistons to return the same after the plunger has struck a blow, said plunger having a head at the forward end thereof, and said head having an outer sleeve extending therefrom and toward the power piston, and means actuated by the outer sleeve for effecting the exhaust of the spent gases of combustion during the return movement of the plunger.

11. In a machine for striking blows, the combination of a floating plunger, guiding means for the same, a combustion cylinder, a power piston mounted to reciprocate therein, means for feeding a combustible fuel into the combustion cylinder and for igniting the same to drive forward the power piston and the plunger, a sleeve carried by the power piston and sliding in the power cylinder, a return piston on the plunger within the sleeve, a return cylinder for the power piston, a return piston on said sleeve mounted to reciprocate in the said return cylinder, means for admitting a fluid to said return pistons to return the same after the plunger has struck a blow, said plunger having a head at its forward end and said head having an outer sleeve extending therefrom and toward the power piston, an exhaust valve for the power cylinder, pneumatic means for opening the exhaust valve actuated by the said outer sleeve during the return movement of the plunger, and means also actuated by the outer sleeve in the return movement of the plunger for effecting the closing of the exhaust valve toward the end of the return movement of the plunger and the power piston.

12. In a vertical type machine for striking blows and capable of being used as a stamp mill, the combination of a floating plunger, guiding means for guiding the same to reciprocate along a substantially vertical axis, a power cylinder coaxial with said plunger, a power piston mounted to reciprocate therein, means for feeding a combustible fuel into the power cylinder and for igniting the same to drive forward the power piston and the plunger, a sleeve carried by the power piston and sliding in the power cylinder, a return piston on the plunger within the sleeve,

,a return cylinder for the power piston, a return piston for the power piston mounted to reciprocate in the said return cylinder, means for admitting a lubricant to the interior of the power cylinder to lubricate the power piston and its sleeve, means for admitting an operating fluid to said return pistons to return the same after the plunger has struck a blow, said plunger having a head at its lower end, said head having an outer sleeve extending upwardly therefrom of larger diameter than the return piston of the sleeve, and operating to prevent passage of any of the lubricant downwardly past the plunger head.

13. In a machine for striking blows, the combination of a floating plunger, guiding means for the same, a power cylinder, a power piston mounted to reciprocate therein, means for feeding a combustible fuel into the power cylinder and for igniting the same to drive forward the power piston and the plunger, a sleeve carried by the power piston and sliding in the power cylinder, a return piston on the plunger within the sleeve, a return cylinder for the power piston, a return piston on said sleeve mounted to reciprocate in the said return cylinder, means for maintaining air in the return cylinder in advance of the return pistons, means for permitting exhaust of the said air as the return pistons advance in the forward stroke, an air admission valve for admitting air to the return cylinder for returning the plunger and the power piston, and means controlled by the plunger in its return movement for closing said air admission valve.

14. In a machine for striking blows, the combination of a floating plunger, guiding means for the same, a power cylinder, a power piston mounted to reciprocate therein, means for feeding a combustible mixture to the power cylinder including an air duct, means for igniting the mixture within the power cylinder to drive forward the power piston and the plunger, a sleeve carried by the power piston, a return cylinder with a compression chamber in its upper end, a return piston on the sleeve, sliding in the return cylinder, means for admitting air to be compressed in the compression chamber when the power piston and plunger move forwardly, means for admitting air to the under side of the return piston to return the same and thereby return the plunger, and deliver air from the compression chamber.

15. In a machine for striking blows, the combination of a floating plunger, guiding means for the same, a power cylinder adjacent the rear end of the plunger, a power piston mounted to reciprocate in the power cylinder, means for developing gas pressure in the power cylinder to drive forward the power piston and the plunger, a return piston connected with the power piston, and means for admitting fluid to the return piston for returning the same, said power cylinder having a port opening to atmosphere through the wall thereof adapted to be passed by the power piston in. its forward stroke, and operating to permit exhaust of gases of combustion from the power cylinder, said power piston having a reduced waist, said port also operating to admit air around the said reduced waist when the power piston is passing the said port, and thereby cooling the power piston.

16. In a machine for striking blows, the combination of a floating plunger, guiding means for the same, a combustion cylinder, a power piston mounted to reciprocate therein, means for feeding a combustible mixture into the combustion cylinder and for igniting the sameto drive forward the power piston and the plunger, a sleeve carried by the power piston and sliding in the power cylinder, a return piston on the plunger within the sleeve, a return cylinder for the power piston, a return piston on said sleeve mounted to reciprocate in the said return cylinder, said return cylinder having an air head at the end thereof remote from thereturn pistons, valve means carried in the air head to permit air to be forced out of the return cylinder as the returnpistons advance therein, said return cylin der having a jacket with means for circulating the air expelled through the said air head, and means for conducting the said air back to an air reservoir.

17. In a machine for striking blows, the combination of a floating plunger, guiding means for the same, a combustion cylinder, at power piston mounted to reciprocate therein, means for feeding a combustible mixture into the combustion cylinder and for igniting the same to drive forward the power piston and the plunger, a sleeve carried by the power piston and sliding in the power cylinder, a return piston on the plunger within the sleeve, a return cylinder for the power piston, a return piston on said sleeve mounted to reciprocate in the said return cylinder, said return cylinder having a head at its end remote from the return pistons, said head having a sleeve extending toward the power cylinder, and said plunger having a stem guided in the lastnamed sleeve.

18. In a machine for striking blows, the combination of a floating plunger, guiding means for the same, a power cylinder adjacent the rear end of the plunger, a power piston mounted to recip-- rocate in the power cylinder, a return cylinder,

a return piston for the plunger cooperating with the return cylinder for returning the floating plunger after the same has delivered a blow, means for admitting compressed air under the return piston to return the floating plunger, valve means for admitting a combustible charge and air into the power cylinder at about the termination of the return stroke of the plunger, and means for effecting the delivery of a quantity of air from the under side of the return piston to the valve means for combustion in the power cylinder, thereby reducing the volume of air under the return piston on the down stroke, and reducing the air resistance to the plunger in its down stroke.

19. Amachine constructed in accordance with claim 15, in which the power piston has a chaml rear end of the plunger, a power piston mounted to reciprocate in the power cylinder, means for compressing a charge and exploding the same in the power cylinder to drive forward the power piston and the plunger, a die cooperating with the forward end of the plunger to crush material, means for compressing air by the reciprocation of said power piston, with means for confining the same, and a pneumatically-controlled feeding device to receive a portion of said compressed air, for feeding material to the die, with means for controlling the admission of the compressed air to the same, brought into action by the proximity of the plunger to the die.

BENJAMIN B. BUCK.