US517983A - Steam-engine - Google Patents

Description

' 5 Sheets-Sheet 1. @T mm. STEAM ENGINE.

(No Model.)

f (No Model.) 5 s'heets--slwen 2.

C.T.P0RTER. 'STEAM ENGINE.

No. 517,983. Patented Apr. 10, 1894.

5 sheets-sheet a RU E T R 0 D..- mL C. d. d 0 M 0 m 4 STEAM ENGINE.

Patented Apr. 10, 1894.

STEAM ENGINE.

Patentd Apr. 10, 1894.

(No Model.) 5 sheets-sheer, 5'.

' C. T. PORTER.

STEAM ENGINE. l No. 517,983. Patented Apr. 1o, 1894.

NITED STATES PATENT OFFICE.

CHARLES T. PORTER, OF MONTCLAIR, `NEW' JERSEY.

STEAM-ENGINE.

SPECIFICATION forming part of Letters Patent-No. 517,983, dated April 10, 1894.

Appiicaion nea May 5,1893. senti No. 473.113. oto model.)

To @ZZ whom it may concern: p

Be it known that I, CHARLES T. PORTER, a citizen of the United States, residing at Mont` clair, in the county of Essex and State of New Jersey, have invented a certain new and useful Improvement in Steam-Engines, of which the following is a specification.

The object of this invention is to give a practical solution to the problem, How shall a perfect expansion diagram be produced by a steam-engine, running at any desired speed, with a single valve of moderate size, having positive movements, Working in equilibrium and so adapted to work without resistance under any desired pressure, making only one opening for admission and one opening for release of the steam, and with a very small percentage of space added to the piston displacement for clearance and port ZP In other Words, How,with asimple construction, shall all the well-known causes of waste be avoided,and the equally well-known economic features be realized, in the steam-engineol v The objection presents itself'at once, that with an equilibrium valve, which cannot be lifted from its seat, large waste room in clearance and port is a necessity, to preventbreakdown from water in the cylinder. This objection I have removed by a construction of cylinder and arrangement of steam-pipe, which are made the subject of Letters vPatent of even date therewith, and bywhich water in the cylinder, in more than a very trilling amount, is made impossible. The question can therefore be considered, quite freed from this difficulty. It is well understood that this object cannot be attained if an eccentric is employed as the means of/actuating the valve. I have succeeded in devising for this purpose a cam, which -possesses the following features:

First,-it cuts olf the steam at a fixed point in the early part of the stroke. The point which I have selected, as the most economical point of cut-off, is one-fifth of the stroke. Second,-it opens a'width of port about two and one-half times greater than is opened by an eccentric of the same throw, and cutting off at the same point, the velocity of the opening and closing movements being increasedin about the same ratio. Third,-it delays the release of the steam, if neither enhaust lap orlead be given to the valve, until eleven-twelfths of the stroke, thus permitting theexpa'nsion to continue practically to the end of the stroke; and it closes theexhaust at the same point of the return stroke, giving, in the smallwaste room space, ar good compression, while the exhaust is ample to avoid any appreciable back pressure, above 'that of the atmosphere, or in the condenser.v

Fourthf-'it compensates Vfor the inequalities of piston motion on the opposite strokes produced by the angular vibration of the connecting-rod; giving a difference in lead proportionate to the'difference in pistonvelocity near the opposite centers,and equalizing the points of cut-oft and of release. Fifth,-it is so designed that, while accomplishing these four objects, the acceleration or retardation of the valve-motion which it produces or allows, in the opposite `directions, alternatey, shall, at every point, bear a known relation to the acceleration imparted by gravity to a falling body, and shall be so moderateV in amount that at ordinaryhigh speeds contact can easily be maintained between the cam and the actuated parts. Sixth,-it permits the employment of piston valves of moderate size, so las to require, for proper admision and release of the steam, with a piston travel of six hundred feet per minute and ordinary length of stroke, only an addition of about two per cent. to the piston displacement for clearance and port.' Seventh,-it exhibits the advantages, in simplicity of construction and operation, in 4closeness of regulation', and in economy of steam, which, with suitable construction, are attainable by the system of cutting off at an early fixed point in the stroke, and regulating the speed of the engine by throttling thesteam, when already dry. As, in order to produce these results, different movements must be imparted to the valve on the opposite strokes, the cam cannot be made of aform capable of working in ayoke; and, indeed,at high'speed, such a construction would be inadmissible, on account ofv the inevitable lost motion and shock on each reversal. I have selected as the basis of my improvements, and as free from all practical objections, the style of cam f here shown, working against a roller which I hold in contact by the pressure of steam, or other elastic fluid. In a single-crank engine,

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the location of the cam outside the crank, as here shown, possesses controlling advantages. It can be made small and is very accessible, the connection to the valve is direct, the solidity of the engine bed is not impaired by the requirements of this connection, the shaft lnay be shortened, and, except to supply oil to the outer bearing, the engineer has no occasion to go on the belt and {1y-wheel side of the engine for any purpose. As a construction which seems, on several accounts to be preferable, I employ two identical cams, working against two identical rollers, one on either side of the cam-rod, by which motion is communicated to the valve. These are in effect one cam, and will be designated as the cam in this specification. I make one pin to serve as a bearing pin for the rollers and a joint pin for the cam-rod. This pinis supported securely in the vibrating end of a lever, which is pivoted at its opposite end, and is of such length relatively to the throw of the cam, that the angular vibration of the rod shall be tritling. This lever, in addition to carrying the rollers and cam-rod, and determining their position, performs two other important functions. It acts as the medium through which the elastic pressure of the steam or other fluid employed is applied to the rollers to hold them in contact with the face of the cam, and through which also the rollers and cam receive their lubrication. I support the cam-shaft in line with the main shaft of the engine, the lever, and the cylinder in which the elastic pressure is exerted, on a single bracket,which is firmly bolted to the mainframing or bed-plate of the engine, by which means the relations between these parts are effectually preserved. At the end of the camrod nearest the cylinder I provide alight and simple but secure disengagng hook, which enables the engine to be started from any position except on the dead-centers, and to be run forward or backward by hand, by means of the starting-bar inserted in the end of the lever. I form the valve of two connected pistons and locate one of these at each end of the cylinder, and, except in small engines, I provide two such valves arranged side by side, connected through their stems and moving together as one valve. In compound engines the cam enables me to cut off at one-fifth of the stroke in each cylinder. I can proportion the area of these cylinders as one to five, and so obtain twenty-five eXpansions of the steam. In tandem compounds I derive the mot-ion of the valves for both cylinders from the same cam, employing a reducing lever between the cylinders for communicating its motion to the valve of the high pressure cylinder.

The accompanying drawings form a part of this specification.

Figure lis a diagram on a large scale, showing the outline of the true cam. Fig. 2 is a diagram showing the action of a corresponding eccentric. Fig. 3 is a plan view of atandem compound engine according to my invention. Fig. et is a vertical section on the line 4 4: in Fig. 6. Fig. 5 is a corresponding section showing a portion on a larger scale. Fig. 6 is a section on the line 6-6 in Fig. 4. It will be observed that this line is vertical in the lower part of the figure, and inclined at about forty-five degrees in the upper portion. Fig. 7 is a plan View, and Fig. 8 a corresponding side elevation of certain parts. Fig. 9 is a side elevation partly invertical section showing on a large scale the hook and provisions for locking -it by which the valve motion is engaged and disengaged when required. Fig. lO is an outline giving a side View of a modification.

Similar letters and numerals of reference indicate corresponding parts in all the figures where they appear.

Referring to the figures and to letters and numerals of reference marked thereon,4 A is the fixed framing or bed of the engine. i

B is the shaft, B the crank, and B2 the crank-pin.

C is the connecting-rod leading from the cross head, and through which are transmitted the strong alternate thrusting andpulling forces due to the action of the steam on the piston.

D is a double cam carried on a camshaft D in line with the shaft B, and having the form which enables it to perform all the functions which have been described by imparting movements to the valve in one direction and limiting the movements imparted to it by the constant counteracting force in the opposite direction. It is connected by a lever D2 to the main crank pin so as to be revolved with the shaft B. The arm D2 should not be connected with absolute rigidity to the crank-pin. lts junction with the cam shaft D should be absolutely firm, and its connection to the crank-pin B2 should have a little liberty lto come and go, to compensate for the possibility of the shafts B and D being slightly out of line.

E is a lever actuated bythe cam, and transmitting its motion to the valve. It turns on a center at E'. The contact with the cam is eected through the roller G. The motion is Vcommunicated to the cam-rod or link Il,

through the joint-pin F which serves also as the bearing-pin for the rollers G. This link His formed with a hook h which engages with a pin L2 carried in an idle lever L turning on a lixed center L.

Q is a rod adapted to move endwise in the link H, and with a handle or knob Q on its outer end by which it may be grasped and either lifted or moved endwise, or both, as required.

QS is a spiral spring encircling the pin Q, and exerting a gentle` force against a collar Q2 thereon to urge the pin Q into its locked position, where it will hold the hook h en` gaged with the pin L2. So long as the parts are allowed to remain thus engaged the mo- ICO IIO

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tion of the rollers G is communicated to the 2 valves. When in starting or at any other period it is required to work the valve by hand, the knob Q' is grasped and the pin Q drawn endwise sufficiently to liberate the pin L', and then the rod H is lifted so as to disengage the hook h. Then a detachable handle L3 being inserted in a socket in the upper end of the lever L, that lever maybe moved at will, to shift thevalve rod and the attached valves I', I2 into any required positions to turn the engine forward or backward. When it is desired to again engage the parts the knob Q' is again pulled to draw the pin Q out of the notch h and that notch-is again engaged with the pin L', and the pin Q is again allowed to move endwise by the force of the spring Q3 and lock the notch h into engagement.

A' is a. hollow cylinder tixed on the bed A, and in communication through the pipe A2, with the steam-boiler, not shown. This cylinder is truly bored and receives a deep hollow piston J, having its open end partially covered and flanged, as shown by J'. The center of the bottom of the piston is formed by a removable plug J2 tapped into place, and

having its inner end finished concave. v

K is a thrust-connection or toggle, serving as a connecting-rod for this piston, one rounded end bearing against the plug J2 and the other end, also rounded, bearing in a correspondingly finished concave box E3 held in a pocket in the lever E. In the use of this mechanism, steam from the boiler exerts its pressure against the piston J, and through the toggle K on the lever E. The yielding force due to this pressure urges the lever E forward so that the roller Gis kept in contact with the surface of the cam D, in all parts of its revolution. Any leakage of steam or water. past the piston J isreceived in the circular groove a and escapes into the atmosphere by the pipe A6. The piston .I should be of such size that the pressure of the steam against it will act on the lever E with sufficient force to keep the bearing roller G always in contact with the surface of the cam.

The cam is the'chief feature of this invention. It will be seen that the design of the cam is a comprehensive one. I have discovered that it is practicable by this means to' avoid the defects which are inherentY in the Y eccentric when employed as the means for working steam expansively, and which become more serious the further the expansion is carried, and at the same time to avoid excessive acceleration or retardation of the act` uated parts at anypoint of its revolution; thus adapting the cam for use on high speed engines.

Fig. l presents an outline of one of my cams. A circle, D*, of a diameter equal to the throw of this cam is described about its center. This circle may be taken to represent on a small scale the path of the crank ot the engine, when the diameter of the circle will represent the stroke of the piston. It should be mentioned that in any cam working against a roller the real periphery of the cam is an ideal line passing through the axis of the roller, and the material cam must be of such form that, however the angle of its impingement against the roller may vary, the real periphery will always intersect this axis. This periphery is, of course, always meant in this description. In Fig. l this periphery is shown intersecting the axis of the roller G. it occupies when the piston is at the end of the cylinder farthest from the crank or when the engine is on the back center. The engine is supposed to be rotating in the direc-l tion indicated by the arrow. The events numbered from 1 to 10 occur as the points of the periphery so numbered come successively to coincide with the axis of the roller G. The four vprincipal events are numbered also on the interior circle Dk. The points of cut-olf and release and compression on each stroke The cam is shown in the position are here shown, both in the path of the crank and inl the stroke of the piston. The cam equalizes each of these latter on the opposite strokes, compensating for the inequality produced by the angular vibration of a connecting rod six cranks in length.

W and X represent the widths of the openings made for the admission of the'steam.

Fig. 2 represents the movements of an eccentric of the same throw and advanced so as to cut ott the steam at the same point as my cam. The engine is in each case supposed to be rotating inthe direction indicated lby the arrow. The inner circle is the path of the center of the eccentric. The outer circle may be taken to represent the path of the crank, whenits diameter will represent the stroke or" the piston. The eccentric has been advanced so that when the crank is on the center line at N the center of the eccentric-is at the point of opening l1. When the eccentric has arrived at the point of cut-ott' 12, the crank is at N', and the piston is at O'. When the eccentric has arrived at the point of release and compression 13, the crank is at N2, and the piston is at O2. When at the commencement ot' the return stroke, the crank is on the center line at N3 and the piston at the correspending en d O3 of its stroke, the eccentric is atthe point of opening 14. When the eccentric has arrived at the point ofcutb 15, the crank is at N4, and the piston lis at O4. Finally, when the eccentric hasreached the point of release and compression 16, the crank is at N5 and the piston is at O54. In this diagram W and X" show the width of the openings vmade by the eccentric for the admission of the steam. This figure shows what renders lthe eccentric objectionable, when employed to effect an early cut-ott. The obvious defects are, first, a too narrow opening for'admission; second, early release and compression, and third,inequality of cut-o and of release and compression on the opposite strokes. Com- IOO IIO

parison of the two diagrams will show the complete manner in which these are remedied by my cam.

Attention needs to be called to another defect which is not obvious on inspection but which is serious. The velocity of the piston, with a connecting rod six cranks in length, is forty per cent. greater at the end of its stroke farthest from the crank than it is at the end of its stroke nearest the crank. This difference in piston velocity calls for a very considerable difference in the lead given to the valve on the.opposite strokes. Vith the eccentric the greater lead required at the back end can be given only by adding less lap to that end of the valve. This, however, causes it to close later, and so increases the already greaterlength of the admission. This defect also is seen to be remedied by my cam.

The cylinder A is secured to the block A3, which is, in turn, stiiy supported upon the same bracket A4 which carries the bearings for the cam shaft D and for the center E. This bracket is stiflly bolted to the bed of the engine and the block A3 is bolted upon the bracket.

To effect the detachable union of the cylinder A with the block A3, I form a female screw thread in the cylinder and tit therein a plug P having a corresponding male thread, and a large square head P by which it can be strongly inserted. The extension P2from this plug, of much smaller diameter, is eX- tended through a hole bored in the block A8 and secured by a nut A5.

I attach importance to thev provisions for supporting the cam-shaft D', lever E, cylinder A and their several attachments on the single bracket A4 which can be removed and replaced at will. The considerable strain exerted on the piston J urging the rollers G into contact with the cam, is received and supported by the deep web of this bracket. Its removable character allows the work thereon to be executed by ordinary tools entirely disconnected from the heavy bed-plate. The connection of this bracket to the bedplate, and again the connection of the block, A3 to this bracket, are maintained stiflly in position by keys or tongues fitted in grooves.

Modifications may be made without departing from the principle or sacrificing the ad vantages of the invention.

Parts of the invention can be used without the whole.

I can substitute a half-round rolling or swiveling pin in place of the roller G, when the real cam will be employed bearing against the hat surface of said pin, to give the required motions.

I consider compressed air or other fluid as the equivalent of steam, and any chamber containing vapor or gas under tension of sufiicient capacity to maintain a practically uniform pressure in all positions of the piston, an equivalent of the boiler. It is important that the fluid be light and elastic, and of sufficient pressure.

In engines with an overhanging pulley at each end of the shaft, the cam will be placed on a short extension of the shaft at one end, of reduced diameter, but requiring no supporting bearings, and the connection to the valve will be through levers on a rock-shaft behind the pulley. I have indicated one-fifth as the preferable point of cut-olf, and the cam shown is adapted to attain that degree, and I have shown five to one as the relative volumes of the two cylinders, but these points may be varied Within wide limits.

1 am aware that steam-pressure has heretofore been employed to hold the valve connections in contact with acam, such pressure being exerted in the valve-chamber itself, and transmitted through the valve connections. My construction ditfers in that I employ a separate cylinder, in which either steam or compressed air or any other elastic fluid may be used, and locate this cylinder close to the cam, and provide a special connection between them. By this arrangement the great pressure required, often amounting to several thousand pounds, is transmitted through a rigid connection, and the valve connections are free from such pressure and strain.

I claim as my invention- 1. As a means of applying the pressure of steam or other elastic fluid to maintain contact between the cam and the valve connections, the cylinder A', piston J, and thrustrod K, in combination with the lever E, all arranged for joint operation substantially as herein specified.

2. In the valve motion of a steam-engine the connecting link Il, reciprocated as shown, having a hook h,`and the axial rod Q, and means as the knob Q' for both moving it axiallyand raising and lowering it, and the spring Q3 urging it into the locked position, in combination with each other and with the pin L2 and the valve rod I, all arranged for joint operation substantially as herein specified.

3. In a steam-engine having the valves actuated by a cam, the detachable bracket A4 supporting the cam-shaft D', lever E and cylinder A', with a web extending between the camshaft and the cylinder support, adapted to serve as herein specified.

In testimony that Iclaim the invention above set forth I affix my signature in presence of two witnesses.

GHAS. T. PORTER.

Witnesses:

CHARLES R. SEARLE, M. F. BoYLE.

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