Improvement in valve-gears
US 165186 A
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Description (OCR text may contain errors)
UNITED S'rA'rEs PA'rnN'r OFFICE;
GEORGE E. TOWER, OF ANNAPOLIS, MAR YLAND, ASSIGNOR OF ONE- EIGHTH HIS RIGHT TO ELI P. WETHERVVAX, OF VVEST SANDLAKE, lNEVV YORK.
IMPROVEMENT IN VALVE'GERB Specification forming part of Letters Patent No. 165,186, dated July 6, 1875 application filed April 27, 1875.
To all whom 'it may conccrn Be it known that I, GEORGE E. TOWER, of the city of Annapolis, in the county of Anne Arundel and State of Maryland, have invented certain Improvements in Valve-Gear for Steam and other Engines, of which the following is a specification:
This invention is in part the same as that ,constituting a part of the inventionv shown in my pending application for improvements in steam and other engines filed November 20, 1874, but in order to enlarge -the scope of its application, a modification, hereinafter described, has been introduced, by which it can be better applied to engines and' valves of varying design and size, though lit is -specially suited for actuating the valve shown and clainied in that application, for by the conjoint action of that valve and this valve-gear the steam can be variably cut off with a large range of expansion without changing the lead of the valve as to either the entrance to or exit from the cylinder of the steam, and without altering the width of opening of any of the ports, which is not the case with ordinary slide-Valves, moved by either the ordinary cams or eccentrics, nor with my said valve, Were it moved by either ordinary cam or eccentric action. In the drawing forming part of this specification the valve there shown is introduced merely for the sake of illustration, to show the connection of the ,valve-rod or rods with any suitable valve. In this invention a rocker-frame carrying ditferential rollers has been substituted for the reciprocating carriage carrying the same rollers shown in my application above mentioned, and also shown in Figure 5 .of the drawing accompanying this application. This rocker-frame, its use, and the parts and combination of parts constituting this invention, will now be desoribed. w
` The object of using this rocker-frame is to multiply the throw of the cams within it by means of its leverage, by which arrangement, with the same diameter of cams or eccentrics, a shorter point of cutting off the steam can be obtained, and space between the cylinder and correspondingly short.
center of cam-shaft also be saved, by reason of no increased diameter of cams or eccentrics. But with large engines, the rec'iprocating carriage might be preferable to the rockerframe, for, their steam-ports requiring' but little width, the travel of the valves would be In the figures of the drawing, R is the rocker-frame to which the valve-rods v3 are attached; but it is obvious that a single rod and link could be usedat the end of vthe rocker-frame opposite its point of oscillation, by direct attachment to the frame instead of the cross-bar H, attached thereto by links, and to which the two valverods v3 are attached, as seen in the drawing, and for which a central valve-rod may be snbstitnted if desired. But with a large valve it is obvious that space is saved by using two valve-rods, as the room required for their stuffing-boxes can be taken from space out of the line of action of the cams and rollers. But where the cross-'bar is interposed between-the rocker-frame and the valve-rod or rods it is evident that provision must be made for preserving its parallelism or rectilinear reciprocating motion. This is effected by means of the auxiliary arm L, which is fitted loosely upon the shaft S for a bearing, and which shaft revolves through its eye in one end, while its other end is attached. to one of the links h by a pin or bolt, and it is also connected to the rocker-frame at another point in the manner now to be described. -`In the drawing this auxiliary arm L is connected to the rocker-frame by means of a slot and pin, which slot and pin, provided of course with suitable bearing-brasses, may be respectivelyin either the frame or the auxiliary arm; but it is also evident that, instead of a slot and pin, the arm and frame may be connected by putting a pin in each, and connecting' said pins by a short link or' rod. It is easily seen 'that the auxiliary arm L will thus preserve the parallelism of the cross-bar H, when moved, by forming with the links h h a parallel motion for the rocker-frame, just as When a reciprocating carriag'e is used its parallelism is preserved by the well-known means of from4 the main shaft.
guides. The valve-gear for but one end of the cylinder is shown in the drawing', but it is understcod, of course, that said gear is the same at both ends ot' the cylinder. The rocker-frame being provided with the differentialrollers i' 7'2, the longer of these, v2, receives the motion and wear of both of the cams 8 82, and the shorter roller 1' that of' the full-stroke cam 8 only, 82, being the cut-off cam. These rollers, it is true, might be made of equal length, but their extremities would nevertheless require to be placed in different planes.
The operation of this valve-gear is as follows z S is an intermediate rotary shaft, such as is commonly used vfor actuatin g either ca ms or eccentrics, and taking its motion from the main shaft of the engine. This shaft may be mounted with its axis in any plane best suited to'actuate the valves of the engine, and itself 'be actuated by miter gearing or by any other suitable means for transmitting to it motion The cam 8, secured to the shaft' S, performsthe functions of an ordinary full-stroke cam; nevertheless it is of p'eculiar construction. double or two-part cam, supporting within it th'ecut-off cam 82.. An ordinary cam, whether for full stroke 01' cut-ofi', is always in contact with the connections operating the valve, whereas the cam 8 has a portion of its rear face cut away, which gives it a necessary conformation for allowing it to escape contact with roller r, when said roller is advanced by the action of' the cut-off cam 82, which, when' in action, advances the roller r by reason of the advance of the frame or carriage when the cam 82 acts upon roller V2.
The cam 82 is a cut-olfcam, con tained within- `the cam 8,' and provided with a hollow hub,l
longer than its'face. It is partially rotated by the spiral rod 83, reciprocating 'axiallythroughl itsl center, which thus protrudes it beyond the face ot'cam 8,v and causes the rocker-frame or reciprocating carriage and connections to close the main valve at any desired point of the 'stroke,-of the piston after the commencen'ient of its stroke, thus causing the main valve to" act as a cut-off valve for the ventering steam,
but allowing, at the same time, free'exit from the-cylinder for the exhaust steam.
In case eccentricsare used instead of cams, 'they' would be placed side by side, instead of one within the other. The spiral rod 83 is Vinserted within the shaft S, which is bored out to receive it farv enough to allowforits axial' movem'ent in Operating the cut-offcams at both ends of the cylinder. Ehisspiralrod's3 has'a cross-section whose con'tour is threeside'd, and formed of lines either straight or Curved, as`V may b'e desired. The object of making the spiral-rod three-sided Will be herei'nafter explained; but a spiral rod havinga' section of any suitable shape may be used without departing from the principle, here applied, of actuating the cut-off cam by a spiral rod passin g within and throughthe inter- It is in 'reality a and the cross-bar or sliding carriage.
mediate shaft S. This spiral rod is itself directly actuated by the slidin g collar T, which is connected to it by the pin or key t, traveling in a slot in shaft S, as is clearly seen in the drawing. The revolution of shaft S, therefore, causes cam 82 to revolve, through the iiite'rvention of the pin t in the sliding collar T, and this collar itself may either be moved by hand longitudinally on shaft S, and be secured at any fixed point, and thus set cam 82 to cut off, at any desired point, by the action upon it of the spiral rod, or it may be connected by any suitable device to la governor, and thus, by the actionof the governor, be caused to traverse on the shaft S, and automatically and momentarily, if necessary, change the point of cutting off the steam through the joint action of cam 82 and the governor.
The spring I), interposed between the crossbar H and the steam-chest, performs an important office, hereinafter mentioned, besides that of taking Lip lost motion due to wear in the joints of the valve-gear, and thereby preventing noise and jars.
I arn aware that ysprings and weights have been used to prevent valves from hanging up or sticking in their seats, and also with rollers to keep them in contact with cams; but I ani not aware that Springs have been used in connection with governors to obviate a del'ect.
likely to be made manifest when connected to cut-off Valves instead of to throttle-valves.
In rolling-mills and in other machinery sudden obstructions are liable to be presented to the movement of the engine after the cut ofi' of the steam has been effected by the governor.
In such case the governor can no longer act to reopen the cut-off valve before the completionof the stroke, hence the engine isliable to stop immediately. This difficulty, however, is obviated in my valve-gear by the use of the spring P, interposed between the steam-chest A weighted lever might, however, if desired, be usedv instead of the spring, and the use of either of which in a small engine might dispense 'with the use of the roller r, for the valve would then make the return-stroke by the action of either-of them, instead of by the action of the cam 8 upon the roller r,- but should the -engine be in danger of stopping, through the closing of the cut-off valve by the governor,
the reaction of the spring P, or an equivalent weighted lever, will instantly cause the cut-off `valve to` reopen and'afi'ord the necessary steam vto move the piston to the end of its stroke, =when the valve-gear will operate for the return-stroke. w
The object of making-the spiral rod 83 threesided in cross-section is this: It will be ob- 'served that the cut-off cam 82 has a pocket formed in one side of its interior bearing-surface, which conforms generally with the perimeter of the spiral rod. This pocket is filled by the step or shoe g, which is set up or ad- -justed by the screw e. By this device anylost motion due to the wear of both the cam and the rod can be taken up, and thus noise ,and jars be prevented.
Having thus Afully described this valve-gear as of my invention, I claim- 1. The combination, with the hollow rotary cam-shaft S, of the collar T and its pin t, and a spiral rod within said shaft, and rotated by it by means of said collar and pin, said rod being bounded longitudinally by helicoidal faces,
and neither helically grooved or threaded, nor' longitudinally toothed, Whereby rotary motion is transmitted by said rod to the cut-off cam of the engine, in the manner substantially as described and set forth.
2. The combination of a spiral rod, 83, contained within the hollow rotary cam-shaft S, With the cut-off cam 82, sliding collar T, and pin t, and any suitable adjusting device for said collar, whereby said cam is adjusted to cut off the steam in proportion to the work to be performed, in the manner substantially as described and set forth.
3. The combination of the three-sided spiral rod 83, gib or step g, and adjusting-screw e with the 'hub of an eccentric, wheel, or cam,
whereby the rod is allowed a longitudinal spi-` ral motion through said hub, and provision is made for tightenin g the hub on the rod,,in the manner substaiitially as described and set forth.
4. The combination of the three sided spiral rod 83 and cut-oif cam 82, provided with the adj usting device e g, whereby provision is made for the Wear of the cam and the rod, in the manner substantiall y as described and set forth.
5. The combination of the differential rollers 7' W, mounted in a suitable rocker or carriage, with the cams 8 82, whereby motion is transmitted from both cams by the longer roller, and from the full-stroke cam only, by the shorter roller, in the manner and for the purpose -substantially as described and set forth.
6. The combination of a full-stroke cam having a portion of one side of its rear face cut away, a cut-off cam contained Within it, and the rollers r 72,' of different depths, mounted in a suitable rocker or carriage, whereby allowance is made for the contact and clearance of said cams and rollers, in the manner and for the purposes substantially as described and set forth.
7. The combination, with the cross-bar H and rocker R, of the vibrating auxiliary arm L, connected to said rocker by any suitable device, whereby the parallelism of the crossbar-is preserved, in the manner substantially as described and set forth.
8. The combination, With a cut-off valve, of the cross-bar H, the cut-off cam 82, and the elliptic spring P interposed between said bar and the steam-chest, whereby the valve is reopened, if required, after cutting off the steam before the end of the stroke, and lost motion in the joints of the Valve-gear taken up, in the manner substantially as described and set forth.
' GEO. E. TOWER.