US401566A - leavitt - Google Patents

Description

5 Sheets-Sheet 1..

(No Model.)

F. M. LEAVITT.

DROP HAMMER.

Pafented Apr. 16, 1889.

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INVENTOR:

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F. M. LEAVITT.

DROP HAMMER.

No. 401,566. Patented Apr. 16, 1889.

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By his Attorneys, mgflmmm VQQ (No Model.) 5 Sheets-Sheet 3.

F. M. LEAVITT. DROP HAMMER.

No. 401,566. Patented Apr. 15, 1889.

INVENTOR:

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P. M. LEAVITT.

DROP HAMMER. No. 401,566. PatntedAphlG, 1889.

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P. M. LEAVITT.

DROP HAMMER.

No. 401,566. Patented Apr. 16, 1889.

INVENTOR:

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UNITED STATES PATENT OEEioE.

FRANK M. LEAVITT, OF BROOKLYN, NEIV YORK, ASSIGNOR TO THE E. W. BLISS COMPANY, OF SAME PLACE.

DROP-HAMMER.

SPECIFICATION forming part of Letters Patent No. 401,566, dated April 16, 1889.

Application filed December 6, 1888. Serial No. 292,793. (No model.)

T0 to whom it may concern:

Be it known that I, FRANK M. LEAVITT, a citizen of the United States, residing in Brooklyn, Kings county, New York, have invented certain new and useful Improvements in Drop-Hammers, of which the following is a specification.

This invention relates to drop-hammers, or those in which a hammer is lifted and then released and permitted to fall, so that it strikes a blow proportional to the velocity of its de' scent. Such hammers have been heretofore constructed in which the lifting mechanism consists of two opposite friction-rollers revolving continuously toward each other and engaging between them a board or upright attached to the hammer or the body of the hammer itself, and by their tractive engagement therewith lifting the hammer between them until disengaged therefrom by being moved apart. My invention relates chiefly to hammers of this class.

In drop-hammers the lifting mechanism by which the hammer is elevated is usually thrown out of action automatically upon the hammer reaching a certain predetermined height, the hammer being then in some constructions permitted to fall immediately, while in others it is held elevated by means of a pawl or other device for preventing its descent until, by the pressing of atreadle or op erating -1ever, the upholding device is re tracted, whereupon the hammer falls. \Vith both constructions it has been usual to provide means for adjusting the lift of the hammer which shall disengage its lifting mechanism, in order that the lift of the hammer, and consequently the force of its blow, may

be varied from time to time, according to the kind of work being done.

My invention provides a novel means for disengaging the lifting-gear and a novel means for upholding the hammer. It also provides a novel construction of friction-roller liftinggear and a novel construction of hammer to be lifted by a friction-roller lifting-gear.

The preferred liftingear for my improved hammer consists of oppositely-arranged continuously revolving friction rollers adj ustable toward and from each other, as heretofore, to engage between them or release the hammer, or an upright board or frame attached thereto, which rollers, however, are pressed together by springs, so that their frictional engagement with the hammer is determined by the spring-pressure applied to them. Toggle-levers or equivalent devices are employed to thrust them apart against the springpressure in order to release the hammer.

My improved means for the automatic disengagement of the lifting mechanism from the hammer is characterized by the employment of reciprocal wedging inclines, the one carried by or moving with the hammer and the other mounted on a stationary part and arranged to be displaced by the moving incline upon the ascent of the hammer to a predetermined height and by its displacement to throw the lifting mechanism out of action. Instead of two reciprocal inclines, one incline and a parallel or curved or other surface coacting with it may be used.

My improved means for holding the hammer elevated consist of wedging inclines, the one carried by the hammer and the other mounted on a stationary part, arranged to Wedge tightly together upon the ascent of the hammer to a predetermined point, so that by their wedging action a sufficiently intimate frictional engagement between them is effected to uphold the weight of the hammer. Instead of two reciprocal inclines, one incline and a frictional surfacesuch as a frictionshoe 1naybe employed to like effect. Means are provided under the control of the operator for forcibly separating said inclines, in order to disengage and drop the hammer. The inclines here referred to are or may be the same as those referred to in the preceding paragraph for effecting the disengagement of the lifting-gear.

The remaining features of my invention will be described. in detail hereinafter by the aid of the accompanying drawings, wherein Figure 1 is a front elevation of my improved drop-hammer in its preferred construction. Fig. 2 is a right-hand side elevation thereof,

partly in vertical section, out in the planes denoted by the lines 2 2 in Figs. 1 and 4. Fig. 3 is a left-hand side elevation thereof,

partly in vertical section, cut in the planes denoted by the lines 3 3 in 1 and 4. Fig. 4 is a horizontal section in the plane of the line 4 4 in Fig. 1. Fig. 5 is a fragmentary vertical transverse mid-section in the plane of the lines 5 5 in Figs. 1 and 4. Figs. 6, 7, and 8 are side elevations of the hammer and the lifting, upholding, and disengaging gears, the frame being omitted. Fig. 9 includes rear and side elevations of one size of frictionshoe and a side elevation of another size thereof. Figs. 10 to 12 are detail views of the lifting-gear alone, showing the improved construction of the hammer-upright, Fig. 10 being a front elevation, Fig. 11 avertical transverse mid-section, and Fig. 12 a horizontal transverse section of the upright. The re-.

maining views illustrate modifications. Fig. 13 is a side elevation answering to Fig.7 and showing a modified construction. Fig. 14 is a similar side elevation showing another modification. Fig. 15 is a vertical transverse section showing afurther modification. Fig. 16 is a fragmentary side elevation showing another modification.

I will first describe the construction shown in Figs. 1 to 9, inclusive.

Referring to these figures, let A designate in general the fixed frame of the hammer, ineluding the bed or anvil B and the two uprights or guide-pieces C O, projecting vertically upward therefrom.

D is the hammer, which moves vertically between the uprights C 0, being guided by V- slideways thereon, as heretofore. I have shown a hammer with a plain head, a, and a body,b, formed integrally therewith; but obviously the construction of the hammer may be varied according to any constructions heretofore employed-as, for example, by connecting a die to the hammer-head, or in place of the hammer-head, as is used for dropforging and drop-stamping. The body portion 1) is made with parallel. front and rear faces to be engaged by the frictional lifting-rollers E E, Fig. 5. This body portion 1) may be made integral with the hammerhead, as in my Pate'nt No. 380,808, or it may consist of a wooden board or metal plate fastened thereto, as h eretofore.

The friction lifting-rollers E E are fixed on shafts F F, which are mounted in rotative bearings in lever-frames G G, pivoted, re spectively, to the front and rear of the uprights 0 O by pintles c 0. These levers G G are drawn together by powerful. springs S S, Figs. 2, 4, and 6, so that the rollers are forced into firm frictional engagement with the front and rear faces of the hammerbody 1). One of the shafts F projects beyond its bearings at its right hand end and the other at its lefthand end, and on their projecting portions are fixed driving-p ulleys H H, which are belted to a counter-shaft, as usual, so as to be driven at equal speeds in opposite directions, as indicated by the arrows in Fig. 2.

Each of the levers G G carries a pair of friction-shoes, J J, one of which shoes is shown detached in Fig. 9. These shoes are arranged just beyond the ends of each of the frictionrollers E E, so that theybear against the ham- I merbody b, outside of the parallel faces thereof, against which the friction-rollers bear.

This outer portion of the hammer-body b is formed with wedging inclines K K on the front and rear sides thereof, as best shown in Fig. 3, which is a section through the portion of the hammer-body on which these inclines are formed. The friction-shoes J J are loosely pivoted to the lever-frames G G, so that they are permitted a suificient degree of angular motion to enable them to adjust themselves to parallelism with the inclined faces K K, against which they bear.

The operation is as follows: Assuming the hammer to have fallen to the bottom of its stroke,- the friction-rollers E E are drawn together by the tension of the springs S S and engage the opposite faces of the hammerbody with sufficient force to enable them to propel it upwardly at a rapid speed, so that it acquires considerable momentum. When the ascending hammer approaches its highest position, its inclines K K, which previously have moved freely between the shoes J J, as indicated in Fig. 6, begin to wedge themselves against these shoes, so as to force the latter, and consequently the lever-frames G G, apart. The momentum of the hammer is such that its upward movement continues in spite of the retardation due to engagement with the shoes until the lever-frames G G are pressed sufficiently apart to move the rollers E E out of contact with the parallel faces of the hammer -body, after which, the momentum of the hammer being expended,it comes to rest. This pressing apart of the friction-rollers E E enables them to continue their revolution freely without grinding or chafing against the hammer-body. The friction between the faces of the shoes J J and the wedging inclines K K on the hammer is sufficient consequent upon the tension of the springs S S to hold the hammer elevated, as shown in Fig. 7. When the operator desires to drop the hammer, he forcibly separates the leverframes G G still farther than they have been separated by the action of the wedging inclines, in order that the friction-shoes shall loosen their grip upon the said inclines and enable the hammer to fall. To enable the operator to thus separate the frames G G against the powerful pressure of the springs S S, I provide toggle-links d d, jointed at their outer ends to the respective levers G G and engaged at their inner ends or knuckle-joint by a pull-rod, f, which extends downwardly and is connected to an operating-treadle, T. The operator, by pressing down on this treadle, pulls downwardly on the rod f, and thereby straightens out the toggle-links dd, as shown in Fig. 8, whereupon the hammer falls. If it is desired that the hammer shall reascend immediately, the operator will release the treadleTimmediately upon the striking of the hammer, whereupon the latter will immediately reascend and will remain suspended until the operator again depresses the treadle. If repeated falls of the hammer are desired, the operator will repeatedly depress the treadle, the hammer falling after each depression thereof. The connection of the rod f to the treadle T, just referredto, may be a direct connection, if desired; but the in direct connection shown is preferable. Referring to Fig. 1, the rod f, extending down about half-way toward the treadle, is jointed to a lever, e, to the end of which another rod, f, is jointed, and this latter rod extends down and is jointed at its lower end to the treadle-lever T. This inter mediate lever, e, not only increases the lever age against the rod f, but enables the rod f and treadle T to be carried out sufliciently to one side to avoid the base of the machine. This construction has also another function. The lever 12 is formed with an upwardly-proj ecting arm, 0', which is engaged by a catchlever, g, which is pivoted to the right-hand upright C by a bolt or stud, i, in such manner as to be removable at will. The hammer being elevated and suspended, the operator depresses the treadle T, and thereby tilts the lever e sufficiently to release the hammerholding device and permit the hammer to fall. This tilting movement of the lever c brings its arm 2' beyond the end of the catchlever g, whereupon the latter drops and prevents the lever e tilting back, so that the operator may immediately release the treadle T. Thelever-frames G G are thus held spread apart until the hammer falls to the bottom of its stroke, whereupon an incline, h, formed on the hammer-body, working against the tail g of the catch-lever, tilts the latter sufficiently to disengage the lever e, which consequently frees the lever-frames G G, and the latter, being instantly drawn together by their springs, cause the friction-rollers to engage with the hammer-body and quickly lift the hammer again. This device insures the fall of the hammer until it strikes the blow without necessitating that the operator shall hold the treadle depressed until the hammer is fully down, as would otherwise be necessary, because of the fact that the springs S S will immediately bring the friction-rollers against the hammer-body if left free to do so.

It is an important advantage of my invention that under no possibility can the hammer fall while the machine is in operation until, by the depression of the treadle, the friction-rollers are forcibly separated. If the hammer in its ascent should have insufficient momentum to wedge itself closely enough between the shoes J J to frictionally hold it sus pended, so that it slips out from between them and begins to descend, this movement brings the friction-rollers e (2 together and into contact with the hammer-body, so that they lift it again and prevent its falling. If the hammer should thus slip back, the operator will know that the machine is running too slowly, and he will accordingly speed it up faster in order that the hammer shall be lifted at a greater velocity.

The pressure of the springs S S may be applied to the lever-frames G G at any convenient point, either above or below the axes of the rollers E E. The springs might be connected directly, as tensile springs,.in the manner shown in Fig. 13; but I prefer to employ compression-springs, as shown in Fig. 2. A yoke, j, is pivoted on a pintle, k, to one of the lever frames G, and a bolt, 'm, is passed through the other frame, against the exterior of which its head is seated, its shank passing through an eye, Z, in the front end of the yoke j, and its threaded end screwing into a crosshead, it, having notched ends engaging the sides of the yoke. The spring S is compressed between the free end of the yoke'and the cross-head a, its tension being adjusted by turning the bolt m by means of its head, so that its threaded end draws the crosshead a toward the rear.

The friction-shoes J are preferably constructed, as shown best in Fig. 9,with a cylindrical boss, 13, projecting on the side opposite to the frictional face,which boss enters a semicylindrical seat or bearing-recess, q, in the lever-frame G, and is retained in place therein by a vertical pin, '1", driven tightly through holes in the lugs above and below the recess q and entering loosely a hole, 5, formed vertically through the boss 19 of the shoe, all as best shown in Figs. 3, 6, and 9. Any other pivotal connection for these shoes offering a sufficiently unyielding engagement with the levers G G and allowing sufficient freedom of motion for the shoes may be substituted for the particular construction shown.

The height to which the hammer will ascend before it is stopped. by wedging between the friction-shoes will be governed by the distance apart of these shoes relatively to the thickness of the inclined portion K K of the hammer. The adjustment of the drop of the hammer may consequently be effected by inserting thicker or thinner shoes J J, according as it is desired that-the hammer shall ascend to a less or greater elevation. In Fig. 9 the middle view shows a thicker shoe designed to be substituted for the thinner one shown in the right-hand View when it is desired that the hammer shall not rise so high. The same adjustment might be otherwise attained, as will be obvious to any mechanic as, for example, by inserting re-enforce bushings behind the half-round pivotal bosses p p of the shoes, or to the same effect by facing the inclines K K with thickening-plates. Any device which will change the relation of the friction-rollers E E to the inclines K K when the hammer is at the bottom of its stroke will cause the disengagement of the fric tion-roller and the wedging fast of the hammer to occur at a higher or lower point in the stroke.

Figs. 10, 11, and 12 show a detail of construction of the hammer-body b, which is omitted from the other figures for the sake of clearness. The hammer-body is faced on its opposite parallel sides with plates or boards to w, of any suitable material for affording a frictional surface against which the liftingrollers E E may bear-such, for example, as any suitable metal, or some fibrous composition or wood. These plates 20 w are preferably applied by being driven downwardly from the top into undercut recesses formed in the front and rear faces of the hammerbody, the shape of these recesses being best shown in Fig. 12. The plates should fit so tightly as to prevent their displacement. If driven down until their lower ends come in contact with the bottoms of the undercut remer-body should be of a width equal to the length of the roller or slightly in excess thereof, as shown in Fig. 10. Outside of this width sufficient space must be left for the undercut flanges by which the plate 111 is held and for the wedging inclines K K.

In the description of my improved means for disengaging the lifting mechanism and for holding the hammer suspended I have described the wedging inclines K K as being formed on the hammer and the shoes J J as being carried by the lever-frames G G. These parts J and K might, however, be transposed that is, instead of the inclines being formed on the hammer they may be formed on the levers G G, and instead of the shoes being carried by these levers or other stationary part they may be carried by the hammer. Such a construction is shown in Fig. 14, where the lever-frames G G are formed with two wedging inclines, K K and the hammer D carries friction-shoes J J", pivoted to it on a stud, P. Pins q are arranged to limit the vibratory movement of these shoes.

It is not essential that friction-shoes, properly so called, shall be used as the part -or incline which reciprocally coacts with the wedging inclines K K. In Fig. 13 I have shown a simple projecting block, J, carried by the hammer and entering between the wedging inclines K K, in order to force apart the levers G G. The engaging-surfaces of thls block may be either curved or straight. This construction is subject to the disadvantage that a less extended frictional surface is provided than if pivoted shoes were employed, which are so mounted that they can adjust themselves to parallelism with the face of the wedging incline. Fig. 14 shows a modified means for spreading apart the levers G G upon depressing the treadle, such means consisting of a lever-arm, d bearing a wheel or roller, (1, and to the projecting end of which arm the rod f is jointed. On pulling down this rod the roller (1 rolls against the face of the opposite lever G, and as the arm (i approaches the horizontal it forces the two levers apart.

Fig. 15 shows how my invention may be applied to an existing construction of drophammer of the type having a wooden board fastened to the hammer-head and projecting upward between the two friction rollers. One of the friction-rollers is stationary, the other roller alone being moved toward or from it, motion being communicated to it by oscillating an eccentric bearing-sleeve, M, which turns in bearings in the supportingframe. Such a construction of oscillating bearing-sleeve is well known in the art,being illustrated in my Patent No. 380,808, dated April 10, 1888, and in other patents. I have therefore not shown this construction in detail in Fig. 15. There is only one wedging incline K, (here lettered K which is formed on a separate piece or block, L, which is clamped or fastened to the upright board at any desired point. A friction-shoe, J, (here lettered J'**,) is arranged to be displaced by this wedging incline, and is pivoted to an elbowlever, N, against which a spring, S, presses in order to force the shoe J 3 toward the upright board of the hammer. A stop, If, is provided to limit the movement of the lever N. This lever is connected by a link, a, to a lever-arm, Q7, projecting from the eccentric-sleeve M, so that the latter is oscillated by the vibratory movement of the leverN. When the lever N is drawn down, the movable friction-roller E is moved toward the immovable roller, thereby clamping the hammer-board between them and elevating the hammer. of its movement, its incline K encounters the shoe J 3 and presses it outwardly, thereby tilting the lever N against the tension of the spring S, and also through the link a, moving up the arm 1; and oscillating the sleeve M in such direction as to move the movable friction-roller sufficiently away from the immovable roller to release the hammer-board. The hammer then remains suspended, held by the friction between the shoe J 3 and incline K. This modification is introduced simply to show that only one incline K and shoe J may be employed in place of two, and that other means of relatively moving the friction-rollers in order to release or engage the hammer may be employed with my present invention. Any known means for releasing the hammer may be used with this construction, that shown consisting of an arm, (1 on the lever N, drawn down by the rod f.

My invention may be in part availed of by the employment of a partial equivalent for hen the hammer nears the top the wedging inclines K K and shoes J J. Such a construction is shown in Fig. 16. In this figure the lever-frames G G (here lettered G G) are inverted, being pivoted to the frame at their upper ends, and their lower ends carry toggle-arms z z, which are normally held at the angle shown by stops a: 00, formed on the lever-frames. \Vhen the hammer ascends, shoulders 1 formed on it, encounter the free ends of these toggle-arms and form therewith a knuckle-joint, forcing the toggle-arms into a straight line, in order to separate the levers G G, and they may move sufficiently beyond a straight line, so that the opposite inclination of the toggle-arms z 2 will suffice under the tension of the springs S S to hold the 11ammer suspended, or the hammer may simply straighten the toggle-arms and be held suspended by pawls or otherwise in any manner heretofore employed. The particular means for releasing the hammer here shown consists of toggles d d, one of them prolonged to form an arm, 01*, which is pulled down by the rod f.

It will be understood that although in the preferred construction of my invention the action of the wedginglinclines effects two purposes-via, the automatic release of the lifting mechanism and the suspending of the hammeryet these two functions are not necessarily united, since the action of the wedging inclines may serve only to disengage the lifting mechanism or only to suspend the hammer. In either of these cases any mechanism formerly employed may be substituted for effecting the other function.

It will also be understood that with reference to the function of disengaging the lifting mechanism the wedging inclines will find their equivalents in any mechanical devices by which the momentum of the ascending hammer is converted into a lateral thrust sufficient to overcome the action of the springs in pressing the friction-rollers together and thereby to force these rollers apart. The construction shown in Fig, 16 illustrates 'one such equivalent device.

I claim as my invention the following-defined improvements in drop-hammers, essentially as hereinbefore specified, viz:

1. The combination, with the hammer and its lifting mechanism, of a wedging incline arranged in connection therewith to act by the ascent of the hammer to its highest position to disengage said lifting mechanism.

2. The combination, with the hammer and its lifting mechanism, of a wedging incline and a coacting part arranged to be displaced by said incline upon the ascent of the hammer and connected to the lifting mechanism, so that upon being so displaced it throws the latter out of action.

3. The combination, with the hammer and revolving friction-rollers for lift-ing it, of a movable bearing-frame carrying one of said rollers, and a wedging incline arranged in connection with the hammer and. said bearing-frame and adapted upon the ascent of the hammer to displace said bearing-frame and move its roller out of action.

4. The combination, with the hammer and revolving friction-rollers for lifting it, of a pivoted lever-frame carrying one of said rollers, and a wedging incline arranged in con- .nection with the hammer and said leverframe and adapted upon the ascent of the hammer to force said lever-frame outwardly and move its roller out of contact with the hammer.

5. The combination, with the hammer and its lifting mechanism and supporting-frame, of reciprocally-wedging surfaces carried, re-

spectively, by the hammer and frame and arranged to be wedged together by the ascent of the hammer to its highest position and thereby to hold the hammer suspended.

6. The combination, with the hammer and its lifting mechanism and supporting-frame, of reciprocally-wedging parts carried, respectively, by the hammer and frame and arranged to be wedged together by the ascent of the hammer to its highest position, and a spring against which one of said parts is seated, so that it yields to the wedging action of the other of said parts.

7. The combination, with the hammer and its lifting mechanism and supporting-frame, of reciprocally-wedging parts carried, respectively,by the hammer and frame and arranged to be wedged together by the ascent of the hammer to its highest position and thereby to hold the hammer suspended, and a releasing mechanism for retracting one of said parts from the other in order to drop the hammer.

8. The combination, with a vertically-mow ing hammer and its lifting mechanism and supporting-frame, of a wedging incline and a friction-shoe, the one connected to the hammer and the other arranged relatively thereto to be wedged against it by the ascent of the hammer to its highest position, whereby the hammer is held suspended by their frictional contact.

9. The combination, with the hammer and its lifting mechanism and supporting-frame, of a frictional projection carried by the hammer and opposite frictional parts carried by the frame and between which said projection enters, said frictional projection and parts constructed to reciprocally wedge together as the hammer] ascends to its highest position and thereby to hold the hammer suspended, and a releasing mechanism for retracting said parts from frictional engagement to drop the hammer.

10. In a drop-hammer, the combination, with the hammer and revolving friction-rollers for lifting it, of springs arranged to press said rollers together with a force sufficient to give the requisite tractive adhesion to lift the hammer between them. I

11. In a drop -hammer, the combination, with the supporting-frame, the hammer, and revolving friction-rollers for lifting it, of a lever-frame in which one of said rollers has its bearings pivoted to said frame and movable toward and from the opposite roller, and a spring acting against said frame and pressing its roller against the opposite roller with a force sufficient to "give the requisite tractive adhesion to lift the hammer between them.

12. The combination, with the supportingframe, the hammer, and revolving frictionrollers for lifting it, of two lever-frames carrying the respective friction-rollers pivoted to the supporting-frame and movable toward and from each other, and springs acting against said lever-frames forpressing the rollers together.

13. The combination, with the supportingframe, the hammer, and revolving frictionrollers for lifting it, of two lever-frames carrying the respective friction-rollers pivoted to the supporting-frame and movable toward and from each other, and springs arranged each to react in opposite directions against the opposite lever-frame for pressing the rollers together.

let. The combination,with the supportingframe, the hammer, and revolving frictionrollers for lifting it, of two lever-frames carrying the respective friction-rollers pivoted to the supporting-frame and movable toward and from each other, springs acting against said lever-frames for pressing the rollers to gether, and the hammer arranged relatively to said lever-frames, as described, so that in its ascent its momentum is utilized to force them apart and disengage said rollers from the hammer.

15. The combination, with the supporting frame, the hammer, and revolving frictionrollers for lifting it, of two lever-frames carryin g the respective friction-rollers pivoted to the supporting-frame and movable toward and from each other, springs acting against said lever-frames for pressing the rollers together, and reciprocal opposite wedging inclines in connection with said hammer and leverfraines respectively constructed to come into engagement during the ascent of the hammer and thereby to force said levers and rollers apart.

16. The combination of the hammer formed with opposite wedging inclines, its frictional lifting-rollers, lever-frames carrying said rollers and arranged to be thrust apart by said inclines upon the ascent of the hammer to its highest position, and springs acting against said lever-frames for pressing the rollers together.

17. The combination of the hammer formed with opposite wedging inclines, its frictional lifting-rollers, lever-frames carrying said rollers, and friction-shoes borne by said leverframes and arranged to bear against said inclines and to be thrust apart thereby upon the ascent of the hammer to its highest position, and springs acting against said lever-frames for pressing the rollers together.

18. The combination, with the supporting frame, the hammer, and revolving frictionrollers for lifting it, of two lever-frames carrying the respective friction-rollers pivoted to the supporting-frame and movable toward and from each other,and springs acting against said lever-frames for pressing the rollers together, and a releasing mechanism consisting of toggle-links acting, upon being straightened, to force said frames apart.

19. The combination, with the hammer, revolving friction-rollers for lifting it, springs for forcing said rollers together, and a releasing mechanism for pressing said rollers apart, of a catch for holding said releasing mechanism in order to prevent the ire-engagement of the rollers during the fall of the hammer, and a projection on the hammer arranged to displace said catch on the striking of the hammer, whereby it is immediately relifted.

20. The combination, with opposite revolvin g friction-rollers, of the hammer-body projecting between them and constructed with detachable plates on its opposite sides to receive the tractive bearing of said rollers.

21. The combinatiomwith opposite revolving friction-rollers, of the hammer-body projecting between them and constructed with vertical dovetailed recesses on its opposite sides, and plates fastened in said recesses to receive the tractive bearing of said rollers.

In witness whereof I have hereunto signed my name in the presence of two subscribing witnesses.

FRANK M. LEAVITT.

Witnesses:

CHARLES K. FRASER, GEORGE H. FRASER.

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