US1038521A - Pneumatic ore-stamp. - Google Patents

Description

H. G. BEHR.

PNEUMATIC om STAMP.

APPLICATION FILED NOV. 20, 1911.

Patented Sept. 17, 1912.

4 SHEETS-SHEET l.

Alim/1f] a H. C. BEHR.

PNEUMATIC ORE STAMP.

APPLICATION FILED Nov. 20. 1911.

1,038,521. Patented sept. 17, 1912.

4 SHEBTS-SHEET 2.

M L; I

gw. Harney 1 H'. C. BEHR.

PNEUMATIG ORE STAMP.

APPLICATION FILED NOV. 20, 1911. 1,038,521. Patented sept. 17,1912.

4 SHEETS-SHEET 3.

\` 7%765565' INVENTUR H. C. BEHR.

PNEUMATIC ORB STAMP.

APPLICATION FILED Nov. 20. 1911.

Patented Sept. 17, 1912.

4 SHEETS-SHEET 4.

Allomey v stant.

rrr.

srnfrns PATENT onirica.

PNEUMATIC ORE-STAMP.

-Specication of Letters Patent.

Patented Sept. 17,1912.

Application filed November 20, 1911. Serial No; 661,296.

To all whom it may concern:

Be it known that'I, HANS CHARLES BEHR,'

a citizen of the United States, residin-g at Johannesburg, in the colony of Transvaal andcountry of South Africa, have-invented certain new and useful'lmprovements in Pneumatic Ore-Stamps; and I do hereby declare the following to be a full, clear, and exact description of thev invention, such as will enable others skilled in the art to which it appertains to make and vuse the same.

This invention relatesy to percussive apparatus capable of general use, but especially adapted to ore stamps, and has for one of its objectsv to produce an apparatus of this kind which will permit a ready adjustment of the length of the operating cylinder in order to compensate for the wear of the stamp head, while at the same time. maintaining the length of the stroke con- -A further object is to produce an apparatus which will maintainT a body of air compressed in thestamp cylinder for the purpose of returning the piston while notrevta'rding the same, as will be more fully disclosed hereinafter.

lVith 'these and other objects in View the invent-ion consists in the novel details of construction and combinations of parts more fully hereinafter disclosed and par-.-A

'ticularly pointed out in the lclaims.

'Referring to the accompanying drawings forming- "a part of this specification in which like numerals designate like parts in all the views Figure 1 is a diagrammatic 'sectional view of an ore stamping machine made in accordance with my invention; Fig. 2 1s a sectional view of a modlfied form of construction of a portion of my machme:

- ,F ig. 3 is a sectional view of a further modi- 'lied form of a portion of my machine; Fig.

4 is'a view similar to Fig. 1, illust-rating a still further modied form of my invention; and, Figs. 5, 6, 7 and 8 are diagram- Ematic views of curves of pressure explaining the-pr1nc1ples underlylng myl invention.

1 represents the stamp head carrying a shoe 2, and 3 the Vdie adapted to coperate with said shoe. i v 4 represents the usual mortar. box, and 5 -a guide sleeve or'other means `forguiding the head- 1. The piston rod 6 is secured by any suitable meansV to the stamp head 1 and carries atits other end the piston 'a' free to move within the cylinder 8. At the front, forward or lower end of the cylin der` 8 there is provided a port 9 from which a pipe 10, preferably of vflexible material, connects, as at`11, with a compressed air reservoir 12. The reservoir 12 is preferably cf such a sizeor character, vthat its volume is many times that ofthe cylinder 8, and therefore the reciprocation of the piston 7 does not materially compress or expand the air in said reservoir, although the pressure maintained in the same is prefer# ably above that ofthe atmospherel The` cylinder 8 is provided at its upper end, as seen in Fig. 1, with a plunger such as 13 passing through a suitable packing such as 14, an capable'of being adjusted into and out of the cylinder by means of jthe` screw 15 passing through the lock nuts 16, and the yoke 17 carried by the pillars or supports 18 secured to' lugsl 19 rigid with the said cylinder 8. The cylinder 8 is provided at or near the upward -limit of thel stroke of the piston 7 lwith 'a port 20, to which is connected pipe sections such as 21, preferably of a yielding nature, in order to form a cushion as will'appear below. In one of the pipe sections 21 there is provided a valve chamber 22 as shown, in which is located a valve 29 controlled by a spring 30, and which valve controls the port 23 leading into the operating cylinder 24 provided with the operating piston 25, connected with the rod 27 driven by the crank 26 which in turn is driven by the power pulley 28, as will be clear from the drawings. A lifting rod 31 passesthrough a stuffing boX 32 provided on one side of the cylinder 24, and is connected with a slideway block 33 guided in the slide 34 and carries on its lower end a roller 35 which is driven by` a cam 36 rigid with the crank shaft. The upper end of the said rod 31 is located below the valve 29, and is adapted to open said valve at regular intervals, and to permit the same to close as will be readily understood. A s ring 37 1s provided between the lug 3S on t e cylinder 24 and the upperl end of the slide block 33 in order to maintain the roller 35 in constant contact with the cam 36. Op-` ing boX 460 is adapted to lift the spring 44 at predetermined intervals by the means now, to be described.

450 represents a slide bar connected at its upper end with said rod 45 andcarrying at `its loweuend a roller 46, resting on the cam 47, rigid with the crank shaft 451. A spring surrounds the rod 45 between the lug 49 on said cylinder 24 and the upper end of said slide bar 450. The stern. 52 of the valve 41 is guided in the casting, as illustrated, and adapted to contact therewith is the rod 54 passing through said lug 49 and surrounded by the spring 59 resting upon the upper end of the slide bar 56 carrying'the roller 57 resting upon the cam 58 also rigid with the crank shaft 451. represents a stuffing box through which said rod 54 passes. In the head 61 of the cylinder 24 is an inlet valve 62 controlled by the spring 63 for the purpose of admitting air into .said cylinder, as will appear hereinafter. Leading from the |reservoir 12 is a pipe 64 provided with a cock 65 and connected as at- 10() with the pipe section 21, as shown.

66 represents any suit-able relief valve for the reservoir 12.

Since leakage of air during the operation of my invention is inevitable, I provide a means for automatically making up for any losses of this nature, and for this purpose I have shown a small compressor 67. Said compressor may be operated from any suitable moving part connecting with the actuating cylinder 24, but as shown, it is operated from an extension 101 of the` slide block 56, its cylinder 67 forming an extension bf the guide as illustrated. The compressor plunger 68 has a screw rod extension 69 by which it is adjustably connected through the nuts 70 to the lateral extension 101 above mentioned. vThe inlet valve4 72 controlled by a spring 103 is provided near the lower end of the cylinder 67,

and an outlet valve 73 controlled by the spring '104 is also provided and in turn controls a connection 74 between the said cylin der 67 and the reservoir 12. The lunger 68 is adjusted by means of the nuts 0 to such a height that when the lower end lof its stroke is reached, a clearance space 105 will beformed in the compressor cylinder 67. The clearance space is chosen of such a volume that when the air left in saidV space is expanded from the pressure which it is intended to maintain. in the reservoir 12 by the additional volume due to the stroke of the plunger 68, the-pressure in said space will fall to such a point that the atmosphere will open the valve. It results from this that the outer air will not enter the cylinder 67, until the pressure in said reservoir 12 does fall below a given predetermined amount. Of course, Whenever air enters the cylinder 67 it is immediately compressed and forced past the valve 73 into the reservoir 12, and thereby restores the pressure in said reservoir.

In the modied form of construction illustrated in Fig. 2, I have provided a modified form of vpipe connection 110 between the cylinders 8 and 24, and have also provided a modified form of plug 111 having a passage 112 connecting with said pipe 110. Further, the valvechamber 113 is extended upwardly, as shown.

In the modified form of construction shown in Fig. 3, I have provided a still further modified form of plug 116 which in turn provides between its outer circumference and the inner surface of the cylinder 8 a modified form of passage 118 connecting with the port 2O and the pipe sections 21, as will be clear from the drawings. It will be observed further that the plug 13 in Fig. 1

,1, and therefore the whole'cylinder may be made shorter than that illustrated in said figure. In the construction shown in Fig. 3 the plug 116 being hollow, t-he cylinder 8 may be made still shorter than even that disclosed in Fig. 2.

In the modified construction shown in Fig. 4, instead of a single reservoir 12, I haveillustrated two reservoirs 160 and 161, separated by a partition 162, provided with an opening 163 controlled by a spring pressed valve 164. Otherwise, the construction is the same as in Fig. 1, but the operation is different and it possesses many additionaladvantages, as will appear below.

The operation of my invention, referring to Fig. 1, is as follows z-As is well known or facility-as would be the case if no wearing occurred. On the other hand, it is very desirable, and practically imperative, that the stroke of the piston 7 as well as the space 149 above said piston 7, should be kept constant, in order that the strength of blow, as well as the efficiency of crushing, and the efiiciency of the operation may be maintained. Therefore, in order to remedy the ill effects of the wearing of the parts, I provide the plunger 13 which, as the said parts wear, may be adjusted into the cylinderS and thereby maintain'the space 149 above said piston 7 at any predetermined volume. As the Iparts wear, however, the lower limit 120 of the travel of the piston 7 will constantly approach the lower end of the cylinder 8, and therefore itis necessary to provide a sufficient length of cylinder below the normal travel of the piston 7 to allow for the eXtreme wear of the, shoe and die. This is indicated in Fig.

1 by the length 140 of the piston below the dot ted line 120. Further, it will be observed 10 that as the piston descends, the compressed air above the same first exerts a high pressure upon the piston, after which the piston travels so fast, owing to the combined action of gravity and the expansion of this air,

that the said air becomes raretied, and it results that the said piston is subjected to varying pressures on its -top surface. In fact, so great is the acceleratlon of the ordinary stamp piston during its -downward stroke, that the pressure on the top surface thereof frequently falls below that of the atmosphere. Since this pressure does fall 4below the atmosphere, it becomes possible to utilize atmospheric pressure to return said piston 7 But in order to derive any material aid from atmospheric pressure, .it is necessary to make the piston 7 so large in practice as to render the construction, under ordinary conditions, practically prohibitive.

Therefore, in order to reduce the size and consequently the cost of the construction, I maintain below the piston 7 a supply ofair under a pressure greater than that of the atmosphere, and which serves to return the same without ret-arding the blow, as will presently appear. This supply of air may be furnished by the reservoir 12 and connection 10, above disclosed, or by a plurality of chambers provided with a valve controlled passa e, as illustrated in Fig. 4, and it has the e ect of returning the piston 7 whenever the pressure on the top side of the latter is sufficiently diminished to enable the pressure on the under side of the same to lift the said piston and stamp. By maintaining a supply of compressed air below the piston 7, I am enabled not only to lessen the .cost of the parts, and to make them smaller, but I am also enabled to lessen the so danger of breakage of the stamp piston, which frequently occurs owing to its great inertia when very heavy blows are imparted. Therefore, this said supply of compressed air constitutes an important feature of my invention. But, to start the operation of my stamp, the system should first be charged with compressed air, and in accomplishing this I prefer to' raise the piston 7 into the position shown in Fig. 1, and to place a block, notI shown, between the shoe 2 and the die 3 in order to support said piston in iits elevated position. The piston 25 is then brought, to its extreme upper position near tile cylinder head 61, and is then caused to descend to the position shown` in Fig. 1.

As the said piston 25 descends, air is drawn in past the valve 62, and upon forcing said piston 25 upwardly again, the air thus taken in is forced past the valve 29 through the cock 65 which has been opened by hand, and into the reservoir v12. The piston 25 is repeatedly reciprccated until the said reservoir 12\is charged to a predetermined pressure, which will be indicated by the blow-ofi'k of the safety valve 66. The system being 75 thus charged with compressed air, the block, not shown, may be removed from the shoe 2, and the said shoe allowed to rest upon the die 3. When in operation, if we assume the piston 7 has traveled to the lower end of its 80 stroke the parts are so timed that it will dwell there a brief period before the piston 25 completes its upward stroke. For this position of the parts, the timing is also such that the valve 41 is still open, it hav- 85 ing been previously forced open'by the rod 54 through the cam 58, as will appear farther on. As soon, however, as the piston 25 moves downward the valve 41 closes. The parts are also so timed that when the piston 25 has reached the limit of its upward stroke the valve 29 has begun to open owing to the upward movement of the rod 31 through the cam 36. This latter valve remains held open until the piston 7 is near the end of its upward stroke, but closes just before said stroke is completed, and it therefore permits air to be trapped above said piston 7 and compressed, thereby forming a cushion for the upward stroke of said piston. The final pressure of this trapped air, however, is not greater than the pressure of the compressed air'which is maintained belowsaid piston 7, as will presently appear. In the meantime the piston 25 begins to move downwardly 105 and to rarefy the air above it, and since the valve 29 is open during this early downward movement, las above stated, the air above the piston 7 also expands while the said pist-on 7 is approaching the upward 110 limit of its stroke. In other words, if we consider the descent of the piston 25, reinembering that the piston 7 is at its lowest position, it will be clear that as the said piston 25 moves downward, the air in the cyl- 115 inder 24, and above the piston 7, will at first continually diminish in pressure. It will, therefore, be clear that a point will soon be reached at which the pressure of the said air above the piston 7 will be suili- 120 ciently small'to permit the compressed air below said piston to lift the same. It will now be clear that the piston 7 dwells at the end of its downward stroke for a brief period while the piston 25 begins to move 125 downwardly. It will further be understood that the timing of the parts causes the valve 29 to close just before the completion of the downward stroke of the piston 25, and that,`

therefore, the air above said piston 25 is 13o p of the latter.

further slightly expanded after the said valve 29 closes. This air, however, is again compressed on the return or upward stroke ceeds the pressure of the trapped air above said piston 7, .the valve 29 will be forced open automatically and the piston 7 forced downwardly. It will thus be seen that the air which was originally trapped above the piston 7, was compressed by the pressure of the air below the piston 7, and that consequently the pressure in the cylinder 24 during this upward movement of the piston 25 need not greatly exceed t-he pressure of the compressed air below the piston 7 before the piston 7 begins to descend. lIt is very desirable, of course, to deliver the heaviest blow possible, and in order to do this the piston 7 should gain in velocity during its entire downward stroke. Accordingly the parts are further so timed that during theV beginning of the downward stroke of the piston 7, the piston 25' has reached its maximum velocity, or is at about its mid stroke. After passing its mid stroke, owing to its crank motion, the said piston 25 of necessity loses velocity up to the end of its upper stroke, but the air which was compressed whilev the said piston 25 was at its maximum velocity continues to expand above the piston 7, and thereby accelerates the velocity Since the velocity of the piston 7 'continues to increase, and the velocity of the piston 25 continues to decrease, there will come a period during the strokes of both pistons at which the volume of air inclosed behind them will increase. From this period on, therefore, instead ofV a compression taking place there will be an expansion of the air above both pistons. Fur' ther, it could'happen that such expansion might cause the pressure above the piston 7 to fall to such a degree that the compressed air below said piston would have a retarding eHect, and would cause the said piston to have a lower final velocity and to deliver a correspondingly weaker blow. In order to prevent reduction of pressure leading to such a result, airis automatically admitted above the pistons 25 vand 7 through the valve 41 from the reservoir 12, whenever the pressure above said pistons drops to a given point, all as will now appear. To accomplish this admission of air automatically, the par'ts are so timed that the pressure of the spring 44 is taken oil'- the valve 41 by the rod 45 before the pressure above the'pistons falls to that in the receiver 12. It results from this that the said valve 41 will open whenever the pressure in the said receiver 12 slightly exceeds the pressure in the cylinder 24. The opening of the valve 41, supposing a single chambered receiver 12 is employed,

causes the pressure from the said reservoir to be equalized above and below the piston 7, and the said piston 7 therefore completes its stroke without any retarding pressure beneath it. As above stated, the said piston 7 strikes its blow and comes to rest before the` piston 25 has completed its upward stroke, so that there is more air above the pistons than therewas when the cycle of one full revolution began with the piston 25 at the extreme end of its upward stroke. Consequently, the air taken in during the downward stroke of the pist-on 7 must be expelled by the piston 25 passing the valve 41, and forced back into the reservoir 12 during the completion of its upward stroke. In order to accomplish this with the least loss 4of power, the valve 41 must be prevented from closing automatically upon the be-. ginmng of the expulsion of air back int-o the reservoir` 12. Consequently, the rod 54 has been provided and the parts are so timed that the said valve 41 will not be permitted to close until the piston 25 has reached the end of its upward stroke, when the cam 5S permits the rod 54 to fall, and the valve 4l to close. There isl then the same pressure above the pistons as in the reservoir 12, and also the same pressure as there was for the same position o-f-the two pistons as when the cycle of operation started. All succeeding cycles will operate in the same manner. When, however, a reservoir having a plurality of chambers such as 100 and 161 shown in Fig. 4, is employed, the operation differs somewhat from the foregoing, owing to the fact that the pressures from said reservoirs above and below the piston 7 may vary independently, and that therefore, the pressure above said piste-11 on its up stroke can be made less than the pressure below the same, while on the down stroke the pressure below the said piston 7 can be neutralized so as to prevent the blow from being cushioned. A number of vadvantages llow from this modification of my construction, as will presently appear.

In order that the exact principles underlying` the operation of my ore stamp may be understood, I have graphically illustrated in Figs. 5 to 8 by pressure curves, the operation when a plurality'of reservoirs or receivers are employed, and these curves will also render clear the operation when a single reservoir or receiver 12 is employed.

Referring to the diagram shown in Fig. 5, in which the ordinates represent pressure land the. abscissae represent time :-the'dot weight ol the piston and its co-acting parts. The line 204 represents the pressure in the cylinder 2d when the upward stroke of the piston 25 begins, the valve 29 being closed. 'lhe line 205 represents theline ot n0 pressure. o represents the period at 'which the piston 25 begins its upward moyement. 206 is a curve representing the increasing pressure oi the air in the cylinder 2d until it reaches a pressurev equal to the edective pressure at which time the valve 29 lifts and communication is. established with the space 149 above the piston 7. The curve 207 represents the increasing pressure of the air above the two pistons up to the period b, after which the volume increase due to the accelerated downward movement of the piston 7, exceeds the volume decrease due to the upward movement ot piston 25 down to the period c, as indicated by the curve 208. The line 212 represents the constant pressure which is maintained above said pistons by the opening of the valve 41 during the remainder of the downward stroke ot piston 7 and the upward stroke of piston 25. The point den the line 212, designates the end et the stroke ot the piston 7. Further, 'the portion c-d of the line 212 represents the period during which air has been taken in from the reservoir 161 to maintain the pressure owe constant; and the line Zw-fp represents the period during which the rexpulsion of the same amount of 'air at the same pressure takes place, during the period after the completion of the downward stroke ot piston 7, to the completion of the upward stroke ci piston 25.

Referring to Fig.- 6:'-a represents the` same period as in Fig.` 5. The line 215 rep-` resents the increasing pressure under which.

the piston 7 begins to move downward at the period a. rlhe curve 216 represents the increasing pressure above the piston 7 until the period in Fig. 5 is reached; and the curve 217 represents the decreasing pressure above the piston until the period c in Fig.; 5 is reached. Said curve 217 down to the, point c also represents the period of time.

during which the pressure decreases, due to the increase of volume displacement ot pis-I, ton 7 being at a more rapid rate than the:

Referring now to Fig. 7, which is a dia-v gram of the pressures during the down stroke of the piston 25, the point p represents the pressure above the piston 25 which existed at the end of-its upward stroke. The curve 221 represents the expansion ofthe air as the piston 25 descends until the period fis reached, corresponding to the pressure ff, which is the effective lifting pressureunderneath the piston 7..- 'lhe curve 222 represents the ex ansion of the air above both pistons as t e piston 25 continues to descend until the period g is reached, at which period the valve 29 closes, and the pressure above the piston 7 increases somewhat. .de the piston 25, however, continues to descend, the'pressure above the same continues to diminish, as is indicated by the curve 224, until the point o is reached again and the cycle is completed.

Referring now to Fig. 8, which shows a curve of pressures above the piston 7 on its upward stroke, the point f corresponds to the same point in Fig. 7, and the curve 225 represents the expansion of the air above both pistons owing to the continuedrdescent ciT the piston 25, until the point g is reached, which is the same period as that illustrated in Fig. 7 At the period g, valve 29 closes, so that the air is trapped and compressed by the kinetic energy et piston 7. rllhe pnessure oithis trapped air hrst rises above and then drops down to the edective pressure h h beneath the said piston, and the cycle is completed. l

lt will thus lne-seen that in all forms of my invention, l am enabled to adjust the length of the cylinder d as the'shoe 2 and die 3 wear, and thereby maintain the stroke or the pistonv 7 substantially constant, as well as the space 1&9 above the same. l, therefore, am enabled to attain a maximum eliiciency in cushionin in the operation of the stamp. Further, y adding additional length 140 to the cylinder 8, l am enabled to return the said piston 7 by the action of compressed air, while at the same time, I

yavoid all cushioning ot the said piston during its downward stroke. lt results from this that the parts vmay be made much lighter and smaller, and therefore the cost is greatly 8 may be still further shortened, and the construction still lessened in cost and in dimensions. ln addition to the above, when a plurality ont chambers are employed, as is illustrated 'in Fi d, the reservoir pressure above the pistong on its return stroke may be lessened to any desired degree below the pressure beneath said piston, and therefore l am further enabled to cause the periods o the up and down strokes to vary. rlhis variation in the periods of the up and down strokes enables me to secure any desired reduction in the eriod of dwell or rest of the piston 7, at t e bottom of the cylinder 8, .and therefore, enables me to secure 'a maximumperiod for the introduction of ore underneath the stamp head. lt results from this that the capacity of the stamp is greatly increased. In other words, it will be ob-4 served from the foregoing disclosure, that I am enabled to produce a machine of a minimuml size at a minimum cost, and one which will deliver a maximum blow of great suddenness, and that the stamp shoe 2 will dwell a minimum period after striking the ore. Further, since the system is a closed one, it i's'evident that any energy which may be expended in .compressing the air is also recovered in the subsequent expansions munication with said extension; a piston' in said cylinder; a stamp head associated with sald plston; means comprlsing an operating piston and cylinder 'whereby air of greater pressure than that in said reservoir may be delivered to one side of said piston; and means whereby the pressure on said side is prevented from remaining below that in said reservoir during the downward stroke, substantially as described.

2. In a percussive apparatus the combination of a cylinder 'provided with an eXtension; a reservoir of compressedair in communication with said extension; a. piston in said cylinder; a stamp head associated with lsaid piston; means comprisingan o erating piston; a cylinder in which said ast mentioned piston reciprocates; and a valved connection between said cylinders whereby air of greater pressure'than that in said reservoir may be delivered to one side of said piston; and means whereby the pressure in said side is prevented from remaining below that in said reservoir during the downward stroke, substantially as described.

3. In a percussive apparatus the combination of a cylinder provided with an eXtension; a piston reciprocating in said cylinder above said extension; .a stamp head associated with said piston; a compressed air reservoir connected to said extension; an operating piston and cylinder adapted to deliver compressed air to said rst mentioned cylinder above said piston; a valved connection between said cylinders; a valved connection between said operating cylinder and said reservoir; and automatic means timed with said operating piston for controlling said connection, substantially as described.-

4. In a percussive apparatus the combina'- tionvof a cylinder provided with an eXtension; a piston reciprocating in said cylinder above said extension; a stamp head associated with said piston; a compressedair reservoir connected to said extension; an operating piston andV cylinder adapted to deliver compressed air to said first mentioned cylinder above said piston; a valved connection between said cylinders; a valved connection between said operating cylinder and said reservoir; and. automatic means comprising reciprocating rods and cams for controlling said connections, substantially as described.v

5. In a percussive apparatus the combination of a cylinder provided with an eX tension.; a pistonreciprocating in said cylinder. above said extension; a stamp head rshoe associated with said piston; means to lessen the space above said piston as said shoe wears; a compressed air reservoir connected to said extension; an operating piston an'd cylinder adapted to Vdeliver compressed air to said rst mentioned cylinder above said piston; a valved connection between said cylinders constituting a cushioning means; a valved connection between said operating cylinder and said reservoir; and automatic means comprising reciprocating spring controlled rods and cams for controlling said connections, substantially as described. I

6. In a percussive apparatus the combination of a cylinder provided with an eXtension; a stamp piston in said cylinder; a reservoir .of compressed air adapted to supply a constant pressure on the lower side oi said piston to return the same; means to supply air at a pressure higher than that in said reservoir to the top side of said stamp piston duringits downward stroke; and

means adapted to prevent said constant pressure from retarding the` downward stroke of said stamp piston, substantially las described. 7 In a percussive apparatus the combination of a cylinder provided with an eXtension; a stamp piston in said cylinder; a reservoir of compressed air adapted to supply' `a constant pressure on the lower side of said piston to return the same; means comprising an operating-cylinder and piston to supply air at a pressure higher than that in said reservoir to the topl side of said' stamp piston during its downward stroke; and valve controlled means adapted to prevent said constant pressure from retarding the downward stroke of said stamp piston, substantially as described. 8. In a percussive apparatus the combination of a cylinder provided with an eX- tension; a stamp piston in said cylinder; a reservoir of compressed air adapted to supply a constant pressure on the lower side of said piston to return the same; means to supply air at a pressure higher than that in sald reservoir to the top side of said stampl piston during its downward stroke; and additicnal means for supplying compressed airv above said piston adapted to prevent said constant pressure from retarding the downward stroke of said stamp piston, substantially as described.l l,

9. In a percussive apparatus the combination of a cylinder provided with an exten* sion; a stamp piston in said cylinder; an operating cylinder and piston adapted to deliver compressed air above said stamp piston during its downward stroke; a reservoir and connections adapted to maintain a constant pressure of air below said stamp piston and to return the same; and additional means provided with a valved connection to said operating cylinder adapted to supply air at predetermined intervalsI above said stamp piston at a pressure less than that in said reservoir, whereby the dwell at the end of the down stroke of said stamp piston may be lessened, substantially as described. v

10. n a percussive apparatus the combination of a cylinder provided with an extension; a stamp piston in said cylinder; an operating cylinder and piston adapted to deliver compressed air above said stamp piston during its downward stroke; a res-V ervoir and connections adapted to maintain a constant pressure of air below said stamp piston and to return the same; a valved con nection between said cylinders; additional means provided with a valved connection to lrigid with said` piston; means .adapted to enter said cylinder above said piston when said shoe wears; a reservoir connected to said cylinder adapted to`maintain a constantressure of compressed air beneath said piston; an operating piston and cylinder adapted to supply compressed air to said stamp cylinder.; a valve and connection between said cylinders; automatic means for opening said valve at predetermined eriods; a second reservoir; a second va vc and connection between said second reservoir and said operating cylinder; automatic means for opening said second valve at redetermined intervals; and means for positively closing said second valve at other predetermined inter vals, substantially as described.

y In testimony whereof, aix my s1gnature, in presence of two witnesses.

HANS CHARLES BEHR. Witnesses:

T. A. WrrHnRsPooN, R. M. PARKER.

said operating cylinderadapted to supply

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