US1810536A - Drop hammer - Google Patents

Description

J. N. sclsM DROP HAMMER Jue 16,l 19351.

Filed July 14, 1925 3 Sheets-Sheet 1 INVENTOR. v )Viver cism ATTORNEY.

J. N. sclsM `lune 16, l93'l DROP HAMMER Filed July 14, 1925 3 Sheets-Sheet 2 .INI/ENTOR. Jolzn JVz ver cz'sm ATTORNEY.

J. N. sclsM f\ Dgo? HAMMER June 16, 1931.

Filed Jul-y 14, 1923 'fly/a 3 Sheets-Sheet 3 Patented June 16, 1931 JOHN NIVER SCIS'M, OE HARTFORD, 'CONNECTICUT- Daor HAMMER Application led July 14, 192,3. kSerial No. 651,602. 'n i My invention relates to drop hammers, 'and particularly to 'what is known in the art as board drop hammers.

Such drop hammers stand high above the lloor line,and include a heavy head which slides vertically between two uprights or guides. A board isA attached to the head and extends upwardly between rol-ls which are arranged in the `frame of the drop ham'- .10 mer Vio move into and outV of engagement with the board. When a hammer is in use, the rolls are driven continually, vand by `means of suitable linkages the rolls are caused to engage frictionally the board, whereby the head is raised the desired distance.,V Thereup'om-.the rolls are moved awa-y from the board, and the head is allowed to fall freely under the forces of gravity. rlhe rolls heretofore havek been driven by beltsrunningffrom Vline shafting, and, as the hammer is raised and dropped, there are interm-ittent strains or jerks transmitted to the belts and shai'fting. From the shafting the strainsfareusuallytransmitted to some part of the buil-ding, to which the shafting i-s attached,fas wellas to the hammer itself. To,

accommodate these strains guide rods are generally connected from the hammer -to some part of the building; however, such bracing is not always possible and when it is not possible an excessive side strain is placed upon the uprights of th'efhammer. Therefore, the hammer uprights have to be made exceedingly strong, heavy and expensive.

l have mentioned in my application Serial No. 636,463, concerning a driving mechanism for drop hammer, that it is very objectionable to have these intermittent strains or jerks transmitted to the building. In the following specification I mention other objections to the use ofline shatting for driving drop hammers.-

As an example of these objections, ya long lineof shafting is often diiiicult to install where itis needed in a shop, because the roof members, or trusses, or pillars of the building are not always adapted 'for such installation'.- Aline of shafting and itsk associated belting often obstruct and close passageways, and ingeneral interferewith the installation or operation of other Ymachinery and over head constmict-ion.v 11n caseof a breakdown 'on some part 'of the fline of shating, several machines would, obviously, -beco'me tem-po rariily icl-le. v` g The ob'ject of the present invention is to provide a drop hammer having individual electric motor :and driving mechanism, whereby eachlhamm-er is voperated irl-depend ently. "Such a ihammer may be installed as a unit within a minimum oi' space, and upon a smal-l individual ifoundatien When adrop hammer is being operated-*the bilows struck by the head cause very severe `shocks and vibrations, and a furthe-r object of my invention is to provide a `cushioned `motor drive which may be placed closely to or `immediatei-y .u-pon a drop hammer. lIn so 'cushioning fand so placing thfe motor drive,

the said 4shocks and vibrations wiillbe greatly absorbed. f

Another object ofthe invention is `to provide a motor mounting 4and a anotor drive ywhich will permit 4'one ormone pairs of roilsto bedriven by direct gearing, as presently 'will be described, or by pulleys as shown my ap,- plicatifon Serial No. 636,463.

In Ithe accompanying drawings Fig. 1 is a view,-partly in side elevation and partly l vertical section, illustrating a drop hammer withl an electric motor rattached to its frame and 'geared to a shaft which extends to the top of the machine for driving the board-elevat ingro'lls. Fig. 2 is a plan view oi the drop hammer. Fig. B is a fragmentary view, partly 'in `front elevation, and partly'in vertical section, showing the upper portion of the mach-ine. Fig. 4 is a fragmentary view, partly in vertical section and partly in side elevation, showing a modification of the driving kgears for the dev-ice. Fig. 5 is a view in cross section of theksinall pinion shown in the upper portion of Fig. l, which pinion controls the pressure of the two front rolls upon the board. Fig.y 6 is a rear elevation of the vhammer, illustrating the manner in which the improved driving mechanism is Ysupported in accordance with my invention. Fig. 7 is ya fragmentary View, showing in end elevation a vportion of the motor Vmounting lshown in Fig. 6. Fig. 8 is a fragmentary view in plan, showing one of the pair of levers which is pivoted to the machine frame for supporting the motor. Fig. 9 is a plan, to larger scale, of a lock Washer, and shows in cross section the tension rod Which appears in Figs. 6 and 7. Fig. 10 illustrates in side elevation a modified motor mounting, and cushioning means therefor. Fig. 11A is a vieW in rear elevation of the modification shown in Fig. 10. Fig. 12 is a fragmentary view, showing in elevation a spring which may serve as `the cushioning means of the structure shown in Figs. 10 and 11. Fig. 13 illustrates in side elevation another form of a cushioned motor support and Fig. 14 isa rear elevation of the same. Fig. 15 is a fragmentary vieW of one of the levers Which secures the motor support to the machine frame, and Which cooperates with other motor-supporting elements, as shown in Figs. 6 and 19. Fig. 16 is a fragmentary view of a portion of the motor support Which is shown in Fig. 19. Fig. 17 is a fragmentaryvievv in plan from above, showing a pin connection Which Will presently be described in detail. Fig. 18 is a view in side elevation of still another modification of the motor support for a drop hammer; and Fig. 19 is a View of the same in rear elevation, showing fragmentarily the frame of the drop hammer. Fig. 20 is a yfragmentary view, showing in plan aportionl of the motor-supporting device of Fig. 19. Fig. 21 is a fragmentary View in rear elevation of still another modification of the motor support; and Fig. 22 is a view in side elevation of the last mentioned modification.

The v general construction Y of board drop hammers is Well known, and no attempt is, therefore, made to fully illustrate and completely describe such hammers. The invention has to do primarily With a shock-absorbing motor mounting, and in the several embodiments of the inventionillustrated heref in, I have shown the motor mounting yieldingly secured to the frame of the drop hammer. @It may be desirable, however, to use (under certain conditions) cushioning means attached to an independent frame Which is separa e from thedrop hammer frame. Such cushioning means may be arranged on a concrete base positioned closely to the hammer, similar to what is shown at the rear of the machine in my former application, above noted.

For the cushions, or for the means to obtain the desired cushioning effect, I prefer to use blocks .of rubber of about the same quality asA is generally used for automobile truck tires- Helical or elliptical springs, as Well as other forms of springs, may be employed instead of rubber blocks, or in addition to such rubber blocks. Oil-filled cylinders and dash pots may also be used in this connection.

It 'will be noted thatinstead ofthe customary one pair of rolls, I use two pair of board-driving rolls in the hammer. Such structure permits tivo rolls to be driven by one hammer, which results in a distribution of the pressure on the roll-driving Worm, whereby very heavy Work can be done Without undue Wear or injury to the gears. Of course, for lighter Work one pair of rolls may be used. It Will be further noted that the height of the hammer is much less than itcould possibly be when large pulleys are used for driving the rolls, and in so eliminating large pulleys, the hammer can be installed in buildings Where the available space is small.

The thrust of the roll-driving Worm is taken in an upward direction by thrust Washers which are provided in the gear box shown in Figs. 1 and 6. This self-contained construction eliminates all tendency for the hammer to be pulled from its base, as is usual When a. hammer is driven with pulleys and belts from line shafting. Manifestly, for the same reason guy rods are unnecessary. The two Worm Wheels shown at the top of the machine, Fig. 1, are machined to the same size and with an equal number of teeth. Hence the rolls lwill be driven at equal speed, thus obviating the objections instant to differences .in speed between the several board-elevating rolls of the hammer. Y

In Fig, 1 there is shown a portion of a drop hammer which extends above the floor line 2. A motor 3 is used for driving' the hammer, and bolts 5 securethe motor to a platform 4. The shaft 6 of the motor extends to support a fly Wheel 7 the fly Wheel being keyed at 8 to such shaft. A nut 9 is in threaded engagement With the shaft, and bears against a Washer 10 tok prevent lateral movement of the Hy Wheel. At 11 in bracket 1 2 the shaft 6 is supported. Bolts 13 secure the bracket l2 to the platform 4. A bevel gear 16 is affixed to the shaft 6, and meshes, as shown in Fig. l, with a bevel gear 18, Which latter gear is secured to shaft 21. Shaft 21 is revolubly supported in bracket 12, and at its upper end is secured to a universal joint 24.

The platform t is secured to tWo levers 26, 27 by means of bolts 13 and 28. TWO opposed levers 32 and 33 are pivotally secured, intermediate their length, to the frame 39 of the drop hammer. A shaft 31, being of reduced diameter at its two end positions, interconnects the levers 26, 27, 32, 33, as shown in Fig. 1. The shaft 3l serves as a spacer for the outer ends of levers 32 and 33, as Well as serving for the pivotal inner connection of the four levers. Nuts 34 and Washers 35 retain the levers in this assembled position, While cross rods 29 and 30 interbrace the platform et and levers 26, 27. As shown in Figs. 6 and 7, the levers 32 and 33 are conveniently connected to the frame 39 by means of a shaft-36. The levers are keyed to shaft 36 at 58, and are laterally held thereon by ILS lmachin-e at 43. A plurality of rubber bloc-ks 44l serve as cushions-between the washers 45 and the arms 32and 33. r1`he washers are held on the .rods 42 by nuts v46. Advantal`geously, ythe rods 42 are flattened at 52 (see Figs. 6 and 9), whereby lock washers 50 in `engaging the flattened portion of the rods prevent .the rods from rotating out of threaded engagement at 43, and in general hold the parts in their illustrated position. Rubber cushions 47 and 48 are located between levers 26 and 32 and between levers 27 and 33, as indicated in Figs.6 andu8. These rubber cushions are wedge shaped, as shown in Fig. 8.

yFrom the universaljoint'24 there extends upwardly a shaft 53. The shaft 53 is pinned to the upper portion of the universal joint at 54. This universal joint 24 is not of unusual structure `and will not be described further.

The upper end yofthe rod 53 is affixed by means of a feather key 57 within sleeve56 ofa universal joint 55. Relative axial movement between the universal joint-55 and shaft 53 is permitted to accommodate the Vvertical oscillations of the motor when the hammer head of the machine delivers al blow. Of course, theV universal joints associated with shaft 53 will ,admit of such horizontal movement of the motor 3 as the blows of the hammer. head create.

The ymotor and motor support as awhole areborne by the shaft 36, and in Fig. 6 it will be seeny that the motor is so supported relatively to the shaft that its weight, as ywell as the weight of the links, will tend constantly to rotate the links 32 and 33 in a counter-clockwise direction.' The rubber washers .44, however, are in effect a yielding stop to prevent such rotation. There is, manifestly, a similar tendency for the motor and its supporting links 26 and 27 to rotate clockwise upon the shaft 31, and the 'rubber blocks 47 Vresiliently prevent such rotation. Such mechanical linkage is effective to prevent the shocks which are created by the operation of the hammer from harming the ymotor 3. If desired, the. Ybearings for the shaft (within the ribs 41) may be of resilient material, or `resiliently.mounted to enhance the shock absorbing characteristics of the motor support as a whole. Iniaddition a resilient washer 60 (Fig. 7) may be interposed between th-e ,links 32 and 33 and the frame39 to cushion. shocks which tend to produce lateral movementof .saidlfinks upon the supporting shaft 36.

Adjacent the top of .thehammeigand with-` in the gearbox 62, there is trunnioned a worm 161. The shaft 59 of the worm is keyed to the universal joint 55, and manifestly positiveconnections for driving the worm are had with the motor 3. The gear box 62 is secured to dro-p hammer frame by means of a'tongue portion 76. lThe shafts 78 and 80 of the two V'driven rolls y86 andk 91 extend into the lgear box 62, andtherein the shafts are provided with` fixedlgear- s 82 and 83 respectively in mesh with ythe worm 161. 1n Figs. 2 and 6,

l show ythe shaft passing through top por- 'l tions 84 and 85 of vthe hammer, and show the roll 86-keyed at 87 to said shaft. The shaft 80 also passes through a bushing` 88 which permits the shaft and key to be pushed through the roll 86 beforethe bushing 88 is assembled. T35

A spur gear y89 is also keyed to shaft 80 by means of a gib key 90. rihe shaft 78 is keyed lto roll 91 in the same manner as the shaft 80 is keyed to the roll 86, and is assembled similarly by using a bushing 92 having the head 93 bearing .against the portion 85 of the hammer. A spur gear94is keyed at 95 to shaft 78. In Fig. 2 the spurgears 89 and 94 are shown in position for driving spur gears 96 and 97 respectively,whiclr latter gearsV are keyed to shafts k98 and 99. Opposed toroll 86 is a roll 104, andopposed to roll 91 i-s a roll 105,v and the diameter `of all the rolls and the gearing are such that the peripheral speeds of all the rolls are equal. As sho-wn in Figs.

1- and 2 the shaft 98 is eccentrically mounted infshafts 108 and 110, and the shaft99 is similarly located y, ineccentric bushings 107 and 109. .The shafts 107, 108, 109 and 110 are Y rigidly connect-ed at their inner ends to levers i 111, 112, 113 and 114 respectively. These levers are respectively formed with bosses 115, 116, 117 and 118, and the upper pair of levers form bearings for a shaft 119,'which shaft lies within the'upper end of a rack 120.

In a similar manner a shaft 121 is arranged with a rack 122 and bosses 115 and 117.

VEach of` said racks has a round rod solidly unitedwith it, one rod .being numbered 123 and the other 124. y These 'rods are fitted into the larger 'ends of racks 122 and 120 respectively, in whichracks the rods are free to slide. The said' rods 123 and 124 are each provided with a nut (,125 and 126) which nuts are spaced from the racks to allow a limited amount of relative sliding movement of the racks. The said racks have teeth in mesh with a small spurggearfpinion 127,

whichr pinion has'shanks 128 of reduced diameter, as shown' in Fig. 5. A control rod 129 includes at its upper end the forked legs 130 and 131, and the Shanks 128 of the ypinion 127 kare retained in the legs 130 and 131 of thecontrol rod. [As indicated in Figs. 2 and 3 a bushing 132 is driven into leg 1.30 of the control rod. The control rod 129 is connected to a lever 133 which is pivoted at 135 to operate in controlling the elevating of the board 106 and its associated hammer 137.

The two upper levers 112 and 114 act in unison or as a unit, and the two levers 111 and 113 also act together. These levers are connected, as said above to the two lracks 120 and 122, and by means of the pinion 127, with which pinion the racks are in mutual engagement, the raising or lowering of the control rod 129 will effect respectively the outward or inward movement of the rolls 104 and 105. That is to say, upon lowering the control rod 129 the two pair of levers will be rotated counter-clockwise to effect the movement of the rolls 104 and 105 into engagement with the board 106. Upon the raising of the control rod, the levers will be rotated in a clockwise direction to move the rolls out of engagement with the board. So, in moving the rotating rolls 104 and 105 into and out of engagement with the board 106, the hammer` head of the machine may be caused to rise and fall and do its work. The racks 120 and 122 with the pinion 127 will, upon downward pull of the control rod 129, equalize 'the pressures with which the rolls 104 and 105 engage the board 106. In Fig. 3 the control rod 129 shown in its extreme upward position,l and in this position the lever 133 rests upon a pin 136, thepin 136 being secured in the hammer head 137. In operation the hammer head 137 and rod 129 are raised (F ig. and held in such raised position by board clamps. The board clamps to which I refer are known to the art and are .not shown in the drawings. Sufiice it to say,

Y the board clamps are released by the operator of the machine, and so the hammer head is released to drop by force of gravity.

A modification of the hammer driving means is shown in Fig. 4. A fragmentarily indicated motor 138 has its shaft 139 keyed at 141 to a bevel gear 140. A shaft 143 is aligned with shaft 139, and is revolubly supported in a bracket 144. Upon the outer end of shaft 143 is secured a-fiy wheel 146, and, as shown in the drawings, a bevel gear 147 is secured to the shaft intermediate its length. In the bracket 144 there is trunnioned the shaft 150 which has securedto its lower end a bevel gear 152 in mesh with the gears 140 and 147. The shaft 150 may be secured to a universal joint, as the shaft 21 is secured to the universal joint 24, for driving thel drop hammer.

1n Figs. 10 and 11 is shown a modification in the motor supporting and cushioning means. In such modification the levers 155 are pivotally borne upon a shaft 157, which shaft isv secured to the drop hammer base 156. That is, blocks 158 are fitted into lugs 159 which are solid with the base 156, and the shaft 157 extends through the blocks.

dvantageously, the blocks 158 are provided with rubber cushions 162, lying between the blocks and the lugs 159. The levers 155 rest against lugs 163, at 164. To the top of levers Y 155 there is attached a platform 165, and secured to this platform are four rods 167 Upon these rods there are fitted steel washers 168 and between the steel washers 168 there are interposed rubber washers 169. On top of these washers is placed a platform 170 which is formed with four holes to slip over the rods 167. A gear bracket 171 and a motor 172 (both being fragmentarily indicated) are secured to the platform 170. The horizontal shocks from the hammer are cushioned by the lateral yielding of the rods 167, while the vertical shocks will be absorbed by the washer assemblies 168, 169. Fig. 12 indicates a spring 174 which may serve in place of the washers 168, 169 on the rods 167 Figs. 13 and 14 illustrate another embodiment of driving mechanism which is generally similar to the mechanism shown in Figs. 1, 2, 3 and 6. The latter modified structure (Figs 13, and 14) includes a lever 17 5 which comprises two side members integrally connected by means of a cross piece 189. A rubberblock 176 is interposed between each side member of this lever and a'base 177 of the hammer. From said base, lugs 178 project and form a packing for each of the rubber blockse176. In appropriate lugs 180, integral wth tlie base 177, blocks 179 are fitted to form bearings for a shaft 181, upon which the lever 17 5 is pivotally secured to the drop hammer. Immediately below the shaft 181 there are pivoted two links 184, said pivotal connection being made by means of pins 185 extending into lugs 180. These links 184 are also pivotally connected at 186 to a member 187. Member 187 is pivotally supported by a shaft 188. Manifestly the four centers of inter-connection (181, 185, 186, 188) are so disposed as to create a parallelogram hinge, and the member 187 will always remain in vertical position, irrespective of the movement of, levers 175 and 184. The member 187 includes ahorizontal extension 190 and, of course, they member 187 in remaining vertical position will cause the extension 190 to remain in a horizontal position. To the extension 190 there is pivotally secured at 193 a pair of arms 191 and 192. In the upper portion of arms 191 and 192 the shafts 195 cooperate with lugs 200 and 202 to support a platform 201. Betweenthese lugs and the arms 191 and 192 the ruber blocks 204, .having the diverging sides 205, are fitted. The rubber blocks are held in place by the screws 206. The reference numerals 207 and 208 represent respectively fragments of a gear bracket and a motor-which are borne by the platform 201. This arrangement also protiveV of whether the shocks are vertical or horizontal in eect,` and "in all positions of the motor supporting linkage the platform 201 will remain in a horizontal plane. That is to say, the arms 191 and 192 being angularly arranged with respect to the vertical,

will yield upon the rubbers 204 to both horizontal and vertical shocks, and since they are pivotally secured to the extension 190, which extension will also yield to shocks (against the cushions 17 6)', the driving mechanism, obviously, is well protected against both vertical and horizontal shocks. show vadditional rubber washers 209 upon the shafts 195. These washers 209 are intended to cushion the platform from shocks which are effective in a line parallel to the axis of the shafts 195.

The modification shown in Fig. 15 indicates fragmentaril a lever 212, which lever corresponds to t e lever 32 of Fig. 6. VThere are in fact two levers 212 which are pivotally attached and cushioned to the hammer frame 213, in a manner generally similar to that in which the levers 32 are secured to the frame 39. Figs. 15, 16 and 19- should be considered together in the following description. The floor upon which the hammer rests is indicated by the numeral 214, and numeral 215 indicates the base upon which the hammer frame 213 is secured. The lever 216 corresponds generally to the lever 26 of Figs. 1

.` and 6, except that it is adapted to be fastened to a cross bar 217 by means of bolts 218. The lower terminal portions of the levers 216 (there being, obviously, a pair of levers 216) are forined'tosupport a platform 219. Fig. 16 represents fragmentarily the upper portion of levers 216 which are provided with holes 220 kfor the receptionv of a shaft, such as the shaft 31 of Figs. 1 and 6. Upon the middle portion of cross bar 217 lugs 221 are formed. Between these lugs 221 there is pivotally secured upon a pin 223 a link 222.

The other end of the link 222 is pivoted to the lugs 224 which are integral with the machine frame. It may be remarked that the'hori'- zontal and perpendicular planes passing through the centers of the pins (226, 220, 225 and 223) of the pivotal interconnection of the linkage form a parallelogram, and theA levers 216 -will always remain in a vertical position. The levers 216 are formed each with a leg 227 which extends therefrom in y a horizontal plane. To these legs there are loosely pivoted the arms 228 `and 229, and these arms are maintained in a vertical position by meansV of rubber blocks adjacent their upper ends. As shown in Figs. 19 and 20, a rubber block 232 is held betweenV a lug 233, a projecting part of the leg 227, and the arm 228. `4Similarly, the rubber blocks 234. 235. 236 and 237 are positioned in the leg 227. Fig. 20 illusin Fig. is i trates in plan' a portion of' the , horizontalleg 2,27; that is, before the platform 219 has been mounted thereon.'A As Vshown in Figs, 18 and 19, speciallwashers; 239hold'` all the Vrubber blocks,',iiiplace.4 Th'efupper portions of 228,1and" 229 (Fig. 19)` are loosely fitted to turn uponpins241and242, which' pins are drivenl into'lugs 24,3:and '244 of the platform 219. D ue to the aforesaid parallelogramiarof the motor-supporting linkage, the platform willL alwaysremain Vin ahorizontal plane. `1n view of the fact that the fixed centfersjoffpins230 yand 2,31 lie in a horizontal p lanewhich isparallel to legs 227 and since the Lcenters offpins 241 andf242 are respectively arranged at equal intervals of space from the centersA 2 31 and 230, the `said fourV centers must always be inthe lines ofY intersection of parts whichforma parallelo* kThe platform 219 will "always lielin my invention. v The lei/'er 245vw'hich correspondsto :the lever of the 'deviceillustratedfiirFi'g. `14, includestwovend inem' bers which arepivotall'y connected by means of a shaft 247 to the lever 2,46. The lever 245 is secured to the frame ofthe drop hammer ina manner! similar to that in which the lever`17'5 is secured, and the lever 246 isgatt'ached Vtoi the lever 245, as themember 187'is attached to the -lever 175. As shown in Fig. 21,` the lever'246 includes an angular exten'- sion 250, to which extension four arnis248 are pivtally secured at249. Tothe lower end of leversv 248 there isconnected on pins 252 a motor-supporting platform 251.- Here again the platform forms with its supporting linkages a parallelograim and obviously the platform will always remain in a horizontal plane, regardless of its swinging motion about the points 249. l Such linkage permits the platform 251 (the connections at 249 being loose) to yield to horizontal shocks. A. motor 253 and a gear bracket 254v are secured tothe platform 251, and suitable connections, such as thosefshown in Fig. 1, are made to theroll-operating means of the hammer. The linkage shown' in Figs. 21 and 22 is provided `with cushioningl means Vto absorb vertical shocks by means of rubber said frame, cushioning means interposed between said armsand saidfraine, ka motor supporting platform, supporting- `arms pivotally connecting said platform with the lever arms inr said frame, and cushioning meansinterposed betweensaid platform and supporting arms.

V2. AV yielding motor support comprising a frame, lever arms pivotally mounted in said frame, tension members secured in said frame and maintaining said lever arms in substantially fixed position withrespect to said frame, yielding means between said tension members and said lever arms, a motor supporting platform, supporting arms pivotally connecting said platform with the m lever arms in said ram'e, and cushioning means interposed bet-Ween said platform and the supporting arms connected thereto.

3. A yielding motor support comprising a frame, a lever arm pivotally mounted insaid frame, a motor-supporting member, means pivotally suspending said motor-supporting member from said lever arm ata point removed from the pivotal mounting of the lever arm, a stop on said frame arranged to 2o limit positively angular movement of said lever arm under the weight of said motorsupporting member, and cushioning means effectively disposed between said lever arm' and said stop. fr 4. A motor mounting comprising a frame, a lever pivotally connected to said frame, a motor-supporting member borne by connections to said lever, said connections joining the lever at a point remote from the pivotal IH connection of said lever tothe frame, which motor-supporting memberby reason of its weight and location with respect to said pivotal connection tends constantly to produce angular movement of said lever, together 35- with means for yieldingly resisting and positively preventingsuch angular movement.

In testimony whereof I alx my signature.

JOHN NIVER SCISM.

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