US1856667A - Cam gear - Google Patents

Description

May 3, 1932. .1. c. s. STUART CAM GEAR Filed April 13, 1929 5 Sheets-Sheet 1 INVENTORL JAMES CHHRLE'S STOP/7N! STUART.

" TTORNE Y5 y J c. s. STUART 1,856,667

CAM GEAR Filed April 13. 1929 5 Sheets-Sheet 2 /NYENTOR.

i J JnMEs C unmzs May-3, 1932. J. c. s. STUART CAM GEAR 5 Sheets-Sheet 4 Filed April 15, 1929 FIGM.

'80:! GIN 7GB May 3, 1932. J. c. s. STUART CAM GEAR Filed April 13, 1929 5 Sheets-Sheet 5 T- m w 5 m n w 6 mm m m m M C m T T A H m a r 2 5 6 6 7 4 Patented May 3, 1932 QNE TED STATES PATENT orries JAMES CHARLES STOPANI STUART, 0F MONKSEATON, NORTHUMBEBLAND, ENGLAND, ASSIGNGRTQ SIR W. G. ABM'ST'EONG, WHIT'WORTH & COMPANY, LIMITED, OF NEW- onsrnn-uren-nivivit, n-nennim CAM GEAR Application fiIed April 13', 1929",Seria1No. 354,889, and Great Britain April 14, 1928.

This invention relates to cam controlled val ve operating gear more particularly for use inreversible double acting engines having steamadmission and exhaust valves actuated by correspondingadmission and exhaust cams, relative'l'ongitudinal movement being provided for between the said cams and their respective valve operating levers from forward to reverse or drift positions (termed settinglU and vice versa, and between the admission cam and its associated levers for varying the steam admission (termel notching up).

The principal ob3ect of the 1nvent1on 1s to rovide a sim le and com'iact mechanismfor this purpose of minimum overall dimensionsparticularly in the dlrection or the axes ofthe cams so th'at the valve gear may a be used in a restricted space, especially that available in locomotive engines.

'A further object of the inventlon 1s to enable the longitudinal movements for setting and notching up to'be both obtained by means of a single unitary mechanism such as a control shaft which i's-mov'ed longitudinally whereby the required movements are imparted for setting, and rotated for notching up.

A further object of this invention is to minimize the overall longitudinal length of the cams and thereby assist further in obtaining a more compact mechanism and economizingin space. i

In the preferred embodiment 'of" the invention the inlet cam is stationary and has no ab1e inletvalve levers and tothe exhaust cam.

The valve levers are-respectively mounted on splined and plain portions of rocking lever shafts located on either side of the cam shaft, rocking movement of which lever shaftsis transmitted through levers to the inlet valve tappets, while the exhaust tappets are actuated by means of levers mounted on the plain portion of the rocking shaft.

Another obj ect of the invention is the pro vision of a fool proof mechanismforcontrolling the gear. Control means constructed in accordance ith' this feature of the invention comprises a hand lever for moving the control shaft to position or set the cams for forward or reverse running and a hand wheel for moving the control shaft tovarythe cut off of the inlet valves in which both lever anc wheel are mounted preferably on a common axis and the lever is arranged to have a movement relatively to the wheel to free it therefrom and permit its rotation to set the cams for forward or reverse running, means being provided for locking the lever to the wheel when it has moved into either of said positions and during rotation of the hand wheel for varying the cut The invention is illustrated in the accompanying drawings in which Figure l is a horizontal section taken on the line 1-1 on Figure 2, parts being shown in elevation.

Figure 2 is a vertical longitudinal section taken on the line 22 on Figure 1. the rocking lever shaft positioned in the line of the section and the tappet engaging levers and also the shiftable and non-shiftable cam engaging roller carrying arms carried by the shaft, and the right hand shaft bearing, all being shown in elevation, and the shiftable cam engaging arm being shown as shifted to the extreme left.

Figures 3 and 4 are vertical cross sections taken on the lines 3-3 and 4 l respectively on Figure l. I Figure 5 is a detail plan of the control: shaft. Fi rures 6 and 7 are a side and end eleva-" tion of a two cylinder simple double acting. locomotive fitted with the valve mechanism shown in Figures 15 and showing also the control mechanism. Figures 8 and 9 are an elevation'and lon-' gitudinal section to a larger scale of the control mechanism shown in Figures 6 and 7.

Figure 10 is a detailed view illustrating the control lever. Figures 11 and 12 are fragmentary face and plan views illustrating the portion of the hand wheel bearing the entrant notches.

Referring to Figures 15, 1 indicates the box or casing in which the cams are mounted. 2 is the cam shaft which is driven at the same speed as the engine crank shaft. The cam shaft is suitably mounted in bearings 3 at each end and carries two cams shown generally at 4 and 5. The cam 4 controls the inlet valves A and comprises similarly shaped cam surfaces 6 and 7 respectively for forward and reverse running. The surfaces 6 and 7 are connected to one another and are on either side of a rest cam 8. The cam 4 is fast on the shaft 2. The cam is the exhaust cam and comprises also two similarly shaped cams 9 and 10 for forward and reverse running and on either side of a rest or drift cam 11. In the embodiment of the invention illustrated in the drawings the cam 5 is splined on the shaft 2 as indicated at- 12 and is capable of sliding movement. Movement from the cams to the valves is transmitted by rollers mounted on rocking levers, which transfer the movement to the tappets. On either side of the cam shaft are rocking lever shafts 13 and 14. Two part levers 15 and 16 carry ing rollers 15 and 16 are slidably mounted on each shaft for operating the inlet valves. Sliding movement of the levers 15 and 16 is obtained. by the sleeve member 1? which is screwed upon a shaft 18 hereinafter term-ed the control shaft. The sleeve 17 is formed with arms 17 which are forked at 19 to engage between each part of levers 15 and 16 The roller on one side of the cam controls the valve at say the front end of the cylinder, and the roller on the other side of the cam controls the opposite or back end of the cylinder. In this particular showing the rollers are mounted substantially at 180 apart in relation to the axis of the cam.

At the ends of the rocking lever shafts are one armed levers 20 and 21 which bear against tappets 22. The tappets 22 engage two armed levers 23 which operate the poppet valve rods 24. By moving the rocking levers 15 and 16 along their shafts the cut off is varied as desired, for forward or reverse runnin according to with which surface 6 or 7 rollers 15 16 are in engagement.

The bell crank levers 23 are pivotally mounted on brackets 25 adjustably mounted on the sides of the casing 1 by means of shims 26, adjusting screws or other suitable means, in order that the valve centres may be adjusted to suit various cylinder lengths without in any way affecting the interchangeability of the parts. The exhaust valve centers can be varied in a similar manner,

either independently of the inlet or in conjunction with them. By means of the adjustments just described, standard and interchangeable boxes may be applied to a wide range of cylinder sizes without subordinating the design of the steam passages which can be made theoretically correct, thus adding to the overall efficiency of the gear.

In the example of the invention illustrated in the drawings in which the exhaust cam is movable along its shaft, movement is transmitted to the exhaust valves B by means of two part levers 28 and 29 carrying rollers 28 and 29, which are free to swing on the rocking lever shafts 13 and 14. One part 30 and 31 of each lever engages the tappets 32, whose outer ends engage the arms 33 of the bell crank levers similarly mounted on adjustable brackets 3 1. The other arms 35 of the levers operate the poppet valve rods. Translation of the exhaust cam 5 along the shaft 2 is effected by means of a sleeve 36 freely mounted on the control shaft 18 but constrained to follow longitudinal movement thereof by means of the collars 87. 36 is an upstanding arm forked at 38 to engage and move the exhaust cam by engagement with a groove 39.

The inlet rollers 15 and 16 consist of a cylindrical portion bounded on either side by peripheries of spherical formation radiused at the sides. lVhen in contact with any part of the cam 4 except the falling helical slope, the centre portion of the roller makes a line contact along a line parallel to the axis of the cam. vi hile passing over the falling slope of the cam, contact between the roller and the cam takes place on the spherical portion of the roller.

The inlet cam as stated above comprises two surfaces of the same shape, one being mounted on either side of a rest cam. This rest cam has a periphery of such formation that when the rollers are in contact with it, the valves will be held open, partly open or closed, as may be predetermined to give the best results when drifting or when in mid gear, during a complete revolution of the crank shaft.

The cams as illustrated have been arranged to give the conditions usually found on locomotives, that is, the drift or mid gear position is between the forward and backward cams, and the minimum cut off end of each cam is against the rest position.

To start the engine from the midgear position the rocking lever carrying the roller is moved axially until the roller is opposite an inlet portion of the cam and in usual practice this would be at the maximum cut off position. The exhaust phase is at the same time properly adjust-ed but this will be described later. The feature of this cam that the inlet portion is the development of an infinite number of cams, side by side, each trol shafts 18 of each cam box are connected cam being of .such profile that it gives the theoretically correctvalve vents or openings. The inlet lift and therefore the lead, is constant for all cut oils and the rising and falling peripheral slopes are identical. This is our preferred arrangement, but it could be varied without in any way detracting from the features of the gear.

For example, the rising slope could be varied to give increasing or decreasing-lead, while the falling slope could be varied to give a bigger valve opening atsmall cut offs. In the preferred arrangement con stant lead is obtained for all cut off positions, and full valve opening may be maintained down to as low as cut off and this gives good theoretical and practical results.

It will be understood that a similar cam to the one described is disposed on the shaft at 180 to the forward cam and turned end for end for backward running.

The exhaust valve control as stated above consists of a rest cam of the same or similar profile to the inlet rest cam, and two identical cams arranged so that one controls the forward and the other the backward running. Since for practical purposes the timing of the exhaust valves once determined need not be altered, these exhaust cams are of the ordinary constant profile type.

Referring now more particularly to. Figures 612, C indicates the cylinders, D the crank shaft, E the cabin wherein is mounted the control mechanism showngenerally at F (Figures. 6 and 7).

The cam shafts 2 of each cylinder are connected by a transverse shaft toxwhich drive is imparted by a shaft 41 through suitable gearing from the crank shaft D. I The conby a transverse shaft to which rotational and longitudinal movement isv imparted from the control mechanism F.

Rotational movement is obtained from the bevel. pinion and sprocket chain drive 42,

43, at The sprocket wieel 44 is fast on a shaft (see Figures 8 and 9) on the other end of which is a. pinion 46 meshing with teeth l7 formed on the inner periphery of the hand wheel 48. Rotation of the hand wheel will thus cause rotation of the control shafts 18. and hence cause sliding movement of the rocking levers 15 and 16owing. to the sleeve 17 being mounted on the screwed portion of the control. shaft 18 (see Figure It will be not-ed thatthe sleeves 36 at this time will not be affected.

Longitudinal movement of the controlshaft is obtained by means ofthe lever -19 link andlever 51 which is fast on the end of a sleeve 52 carried by the shaft 45. The sleeve 52 at its other end carries a lever 53 the. stub shaft 56,0n which the hand wheel stops 58 when the lever 57 is in a forward 7 position towards the hand wheel l8 as shown in Figure 9. There are four stops one on each side of the two lateral positions of the lever 57 thus constituting three notches so that when the arm 69 engages in anyone of these notches the lever cannot be moved in either direction of rotation. The three notches correspond to the mid-position and two lateral positions respectively of the lever as shown in Fgure 8. The hand lever 57 has three positions, reverse, mid and forward (see also Figures 11 anl 12). Corresponding with the mid position is a notch 59 on the periphery of the hand wheel l8 with which is adapted to engage a stud 60 on the hand lever. On either side of the notch 59 are similar notches ,(31 and 62 corresponding to the reverse and forward positions. Notches 61 and 62 are connected to each half of a peripheral groove 63. All the notches have rearwardly entrant slots.

The hand lever 57 in order to lock the cam gears at any desired cut oil between maximum and minimum is provided with a pin 6% normally spring pressed by spring 65 into engagement with teeth 66 around the rim of the hand wheel 48. A grip lever 67 is pro-- vided for disengaging the pin 64.

It will be seen that the hand lever 57 cannot be disengaged during rotation of the hand wheel 48 (termed notching up) and thereby impart longitudinal movement to the control shaft 18, owing to the engagement of the stud 60 with'the groove 63. The stud 60 cannot leave the groove 63 until it is opposite the entrant notches 61 and 62 i. e. at either minimum cut off position when the hand lever 57 may be moved backwards and out of engagement with the hand wheel 48. At this period a pin 68 is depressed by a linger 69'into a hole 70 in the stub shaft 56 against the action of a spring 71. The pin 68 passes through a hole 7 O in a sleeve on the stub shaft with which the hand wheel is fast.

the stud 60 will leave the notch 59. It is now moved sideways to the reverse or forward position i. e. until stud 60 is opposite entrant notch 61 or 62. This rotational movement of the hand lever from mid (59) to re-- verse or forwardposition (61 or 62) causes the sleeve 52 to be rocked through lever link mechanism 53, 54, 55 and hence impart longitudinal or sliding movement to the control shaft 18 and with it the rocking levers 15 and 16 and rollers 15 and 16 and the exhaust cam 5.

The distances and travels are so arranged that when the lever of the hand wheel is moved from mid to forward or from mid to back gear, the inlet rollers take up the positions of minimum cut off forward and backward respectively, while the exhaust cam is at the same time pushed along the roller until forward or backward position is reached. No further travel of the lever 57 being possible after forward or backward position on account of the stops 58, any further movement of the rocking levers 15 and 16 has to be made by the rotation of the control shaft 18. This is caused by the rotation of the hand wheel 48. The wheel et8 can move independently of the lever 5'? as the lever 67 is pressed towards the lever 57 thus releasing the dog 64; from the teeth 66 on the hand wheel. As already stated, the exhaust phase is constant for all cut offs so that by arranging the sleeve 36 with a plain bearing, rotation of the control shaft does not affect it while the out of is being varied. While the control shaft is being slid bodily it is essential that no relative motion takes place between the pinion 4c and the teeth 47 of the hand wheel. This is pre vented by the pin 68 which comes into action immediately the hand lever is moved backward to come out of engagement with the hand wheel.

The above described arrangement of parts provides a fool proof device for the driver and is therefore an improvemen over known types of poppet valve gear controls which are not positive.

In some cases it may be necessary to provide means for compensating for the effect of the angularity of the connecting rod and for this purpose the positions of the rocking lever shafts or the rocking levers themselves may be adjustable so that the point of contact of the rollers around the axis of the cam may be varied.

It will be seen from the foregoing description that owing to the avoidance of the necessity for shifting the comparatively lengthy inlet controlling cam, and the arrangement whereby the levers bearing againstthat cam can be shifted longitudinally of the cam without needing to shift their associated levers which transfer the movement to the valves, 1 am enabled to provide a valve opera-ting gear which can be housed in a casing of minimum dimension in the direction of the cam shaft, and this dimension is not materially increased if the exhaust cam is shiftable as in the example illustrated owing to the comparatively narrow width of that cam in the direction of its axis. Moreover by the described means of control I am enabled to pro vide for the shifting movements in relation to both the cam and lever combinations for setting, and also the further shifting movement in relation to the inlet cam, whether for forward or reverse travel, for so-called notching up, all through one unitary control device.

Various modifications may be made by those skilled in the art without departing from the spirit of this invention which is not restricted otherwise than in accordance with the appended claims.

W hat I claim is 1. In a cam controlled valve operating gear for a reversible double acting engine the combination of a cam shaft, an inlet cam of predetermined shape to give varying cut offs for both forward and reverse running and fast on said shaft, a constant phase exhaust cam for forward and reverse running slidably mounted on said shaft, slidably mounted levers for transmitting movement from the inlet cam to the inlet valves, stationar' levers for transmitting movement from the exhaust cam to the exhaust valves, a control shaft having av screwed and plain portion, arms on the screwed portion for transmitting movement to the inlet valve levers and an arm on the plain portion for transmitting movement to the exhaust cam.

2. In a cam controlled valve operating gear suitable for a reversible double acting engine, the combination of steam admission and exhaust valves, corresponding admission and exhaust cams, levers for actuating said valves and transmitting movement from the cams to the1r corresponding valves, said cams and levers being relatively adjustable longitudinally with respect to each other for effecting setting and notching-up movements, a control shaft for controlling the adjustment between the cams and levers, and means for rotating and moving the control shaft longitudinally to effect said setting and notching-up movements.

3. In a cam controlled valve operating gear suitable for a reversible double acting engine, the combination of steam admission and exhaust valves, corresponding admission and exhaust cams, levers for actuating said valves and transmitting movement from the cams to their corresponding valves, said cams and levers being relatively adjustable with respect to each other for the purpose of setting the cams and providing for notchingup with respect thereto, means for effecting said relative movement between the cams and levers in order to set the cams, and other means for effecting said relative movement between the cams and levers to provide for notching-up with respect to one of the cams.

4:. In a cam controlled valve operating gear iio suitable for a reversible double acting engine, the combination of steam'admissi'on and exhaust valves, an admission valve control cam and an exhaust valve control cam, levers for actuating said valves and transmitting movement from the cams to their corresponding valves, the cams and levers being relatively adjustable longitudinally with respect to each other for the purpose of efi'ecting setting and notching-up movements, :1 control shaft for controlling the adjustment between the cams and levers, and means for rotating and moving the control shaft longitudinally to effect setting and notcl'iing-up move-- ments, said cams and their associated levers being relatively movable to bring about reverse and forward valve setting positions, and said inlet levers being movable for notching-up.

5. Cam controlled valve operating gear as pointed out in claim 2 in which the notchingup is accomplished by movement of the admission valve associated levers effected by rotation of the control shaft.

6. Cam controlled valve operating gear as pointed out in claim 2 in which the admission cam is stationary relative to the exhaust cam and'the exhaust cam movable relative to the admission cam, and in which the levers cooperating with the admission cam are slidable and the levers cooperating with the exhaust cam are relatively stationary.

7. Ina cam controlled valve operating gear suitable for a reversible double acting engine, the combination of steam admission and exhaust valves, corresponding admission and exhaust cams, levers for actuating said valves and transmitting movement from the cams to their corresponding valves, said cams and levers being relatively adjustable longitudinally with respect to each other for effecting setting and notching-up movements, a control shaft for controlling the adjustment between the cams and levers, and means for rotating and moving the control shaft longitudinally to effect said setting and notching-up movements, said control shaft having a threaded portion and a non-threaded portion, means engaging the threaded portion of the control shaft to move the admission valve associated levers relative to the inlet cam, and means engaging the nonthreaded portion of the control shaft and adapted to effect setting movement of both cams. 8. In a cam controlled valve operating gear for a reversible double acting engine, the combination of a cam shaft, an inlet cam of predetermined shape to give varying cut-offs for both forward and reverse running and fast on said shaft, a constant phase exhaust cam for forward and reverse running slidably mounted on said shaft, rocking lever shafts on either side of the cam shafts having splined and plain portions, inlet levers slidably mounted on the splined portions of said rocking lever shaftsfor transmitting movement from the inlet cam to the inlet valves, stationary levers mounted on the plain portions of said rocking lever shafts for transmitting movement from the exhaust cam to the exhaust valves, 21 control shaft having screwed and plain portions, arms on the screwed portion for transmitting movement to the inlet valve levers, and an arm on the plain portion for transmitting movement to the exhaust cam.

9. In a cam controlled valve operating gear for a reversible double acting engine, the combination of a cam shaft, an inlet cam of predetermined shape to give varying cut-offs for both forward and reverse running and fast on said shaft, a constant phase exhaust cam for forward and reverse running slidably mounted on said shaft, rocking lever shafts on either side of the cam shafts having splined and plain portions, inlet levers slidably mounted on the splined portions of said rocking lever shafts, levers fast on said rocking lever shafts for transmitting the cam movements to the inlet valves, stationary levers mounted on the plain portions of said rocking lever shafts for transmitting movement from the exhaust cam to the exhaust valves, a control shaft having screwed and plain portions, arms on the screwed portion for transmitting movement to the inlet valve levers, and an arm on the plane portion for transmitting movement to the exhaust cam.

10. In apparatus of the character described, inlet and exhaust valves, means to actuate the valves including a control element movable longitudinally to effect opening of the inlet and exhaust valves and movable in, a rotary direction. to vary the degree of opening of the inlet valves.

11. In apparatus of the character described, inlet and exhaust valves, means to actuate the valves including a control ele ment movable longitudinally to effect opening of the inlet and exhaust valves and movable in a rotary direction to vary the degree of opening of the inlet valves, and means to actuate said control element from a remote point.

12. In apparatus of the character described, inlet and exhaust valves, means to actuate the valves including a control element movable longitudinally to effect opening of the inlet and exhaust valves and movable in a rotary direction to vary the degree of opening of the inlet valves, and means to actuate said control element from a remote point, said last-named means including devices for securing the control element against rotary movement when it is being moved longitudinally.

13. In a cam controlled valve operating gear, the combination of a rotary cam having a variable throw effecting cam surface,

a lever arm non-movable in axial direction and adapted to operate a valve, a second lever arm adapted to coact with the cam surface and movable in axial direction, said lever arms being axially connected as a pair for simultaneous angular movement.

ll. In a cam controlled valve operating gear, the combination of a rotary cam having a variable throw effecting cam surface, a lever arm non movable in axial direction and adapted to operate a valve, a second lever arm adapted to coact with the cam surface and movable in axial direction, said lever arms being axially connected as a pair for simultaneous angular movement, and control means for shifting the axially movable lever arm along its axis.

15. In a cam controlled valve operating gear, the combination of a rotary cam having a variable throw effecting cam surface, a lever arm non-movable in axial direction and adapted to operate a valve, a second lever arm adapted to coact with the cam surface and movable in axial direction along a line parallel to the axis of said am, said lever arms being axially connected as a pair for simultaneous angular movement.

16. In a cam controlled valve operating gear, the combination of a rotary cam having a variable throw effecting cam surface, a lever arm non-movable in axial direction and adapted to operate a valve, a shaft carrying said lever arm, a second lever arm on said shaft adapted tocoact with the cam surface and movable in axial direction along said shaft, said axially non-movable lever arm and said axially movable lever arm being axially connected by said shaft for simultaneous angular movement, and control means for shifting the axially movable lever arm along the shaft.

17. In a cam controlled valve operating gear, the combination of a rotary cam having a plurality of varying surface contours, a shaft, a lever arm fixed on said shaft and adapted to operate a valve, a second lever arm slidably mounted on said shaft and adapted to coact with the surface contours of'said cam whereby to rock said shaft and consequently the first mentioned lever arm for operating the valve, and control means for shifting the slidably mounted lever arm along said shaft.

18. In a cam controlled valve operating gear for reversible engines, the combination of a rotary cam, said cam having a plurality of surface contours for forward control intermediate dwell contour and surface contours for reverse control, a lever arm nonmovable in axial direction and adapted to operate a valve, a second lever arm adapted to coact with the cam surface contour and movable in axial direction along a line parallel to the axis of said cam, said lever arms being axially connected as a pair for simultaneous angular movement, and control means for shifting the axially movable lever arm along its axis.

19. In a cam controlled valve operating gear for double acting steam engines, the combination of a rotary cam having a variable throw effecting cam surface, lever arms non-movable in axial direction and adapted to operate inlet valves, other lever arms adapted to coact with opposite sides of the cam surface and movable in axial direction, said axially non-movable lever arms and said axially movable lever arms being axially connected in pairs for simultaneous angular movement.

20. In a cam controlled valve operating gear for double acting steam engines, the combination of a rotary cam having a variable throw effecting cam surface, lever arms non-movable in axial direction and adapted to operate inlet valves, other lever arms adapted to coact with opposite sides of said cam surface and movable in axial direction, said axially non-movable lever arms and said axially movable lever arms being axially connected in pairs for simultaneous angular movement, and control means for shifting the axially movable lever arms simultaneously along their axes.

In testimony that I claim the foregoing my invention I have signed my name this 28th day of March, 1929.

JAMES CHARLES STOPANI STUART.

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