US2338589A - Locomotive valve gear - Google Patents

Description

Jan- 4, 1944- T. KNOWLES LOCOMOTIVE VALVE GEAR 17172021502 A. TA7Y0M5 Filed Nov 21, 1941 .17550 rney Patented Jan. 4, 1944 UNITED STATES PATENT? OFFICE LOCOMOTIVE VAL E GEAR Louis Thomas Knowles, Minneapolis, Minn. Application November 21, 1941, SerialNO. 419,843 6 Claims. (01. 121-163) This invention relates to a. valve gear for a locomotive. While the invention might be applied to various types of valve gears, in the embodiment of the same illustrated, it is shown as a modification of the well known Walschaert valve gear.

It is a well known fact that the valve gears including the well known Walschaert valve gear which are now used on a great number of locomotives, do not efliciently distribute the steam 01' accomplish the valve events in an efiicient manner. The valve gears have not been developed to properly handle the high steam pressures now used in modern locomotives. With the present high pressures and super heat the steam in the cylinders could be much more efiiciently used and expanded if proper valve events could be secured. With the valve gears now in use the compression periods are too long at the working cutoffs and said periods increase rapidly as the cut or: is shortened. This is true to such an extent as to prohibit the use of out offs of less than 25 percent. If lesser cut offs are used, counter stresses and excessive vibrations develop to such an extent as to make the shorter cut offs impractical. It is an object of this invention therefore, to provide a locomotive valve gear which will permit the use of a short out off of approximately as short as 10 percent, without developing excessive compression or developing objectionable vibration or stresses.

It is a further object of the invention to provide a locomotive valve gear by the use of which very short cut offs may be used without excessive preadmission of steam as well as not increasing the length of the compression stroke.

It is still another object of the invention to provide a valve gear by means of which short cut oils may be used with a subsequent greater expansion of the steam and the use of a great deal less fuel.

Another object of the invention is to provide a valve gear of the general radial type in which an additional movement is given to the combination or the lap and lead lever usually moved in synchronism with the piston by the use of an extra movable element which is connected to the combination lever and main cross head.

t is more specifically an object of the invention to provide an improved valve gear of the general radial type in which the usual combination or lap and lead lever is connected to the main cross head by a link and a movable member, which member is given motion by engaging with a fixed portion of the locomotive cross head guide or frame.

These and other obiectsand advantages ofthe invention will be fully set forth in the following description made in connection with the-accompanying drawing in which like reference characters refer to similar parts throughout the several views and in which:

Fig. 1 is a view in side elevation of the device;

Fig. 2 is a vertical section taken on line 2--2 of Fig. 1 as indicated by the arrows;

Fig, 3 is a partial top plan view; and

Fig. 4 is a partial view in side elevation showing a modification.

Referring to the drawing the driving wheel of a locomotive is indicated at If! to which is secured the usual crank pin H. Crank pin II is embraced by one end of the usual main driving rod l2 which is pivotally connected at its other end by the pivot bolt IS with the cross head M, which cross head is carried in and slides in the usual cross head guide l5. Said cross head in the standard practice and in the embodiment of the invention illustrated, is shown as having one or more guide ribs or portions I do receivable in a groove la in the cross head guide, said cross head being retained in place by the guide cover plate l6. Plate 16 is secured to the cross head guide by a plurality of headed bolts IT. The main piston rod 20 is secured to cross head I4 as usual and extends into the steam cylinder, one end of which is shown at 2|.

The eccentric arm 22 for imparting motion to the valve mechanism is secured to pin I i and has pivotally secured to its end by a pivot 23 the eccentric rod 24. Rod 24 is pivotally connected at its other end to an extension 25a shown as integral with the valve operating link 25. Link 25 is pivotally mounted on the locomotive frame at its central portion by the trunnions 26. Link 25 as usual is provided with an arcuate slot 25b in which is slidable a block 21. Block 2'! is pivotally connected to the link or radius rod 29. Rod 29 is shown as having a reduced end portion 29a of cylindrical form on which is slidable a block 30. Block 30 has one or more pins 3i projecting therefrom and extending into the bore in one end of a bell crank lever 32. Lever 32 is pivotally mounted on a pivot pin 33 fixed in the frame of the locomotive and has its other arm 32a pivotal- 1y connected to a link 34 which is pulled or pushed upon by the engineer by use of an appropriate lever or other mechanism. Link 25 in practice is usually provided With a housing or cover plates at one or both sides, but these are not shown. The structure of the link per seis not involved in any specific manner with the present invention. The radius rod 29is pivotally connected at its other end as usual to the upper end of the combination lever 36 of the valve gear which is sometimes called the lap and lead lever. The lever 36 is pivotally mounted intermediate its ends on the end of the valve rod 3'! which is guided in a guide 38 carried on a bracket 39 secured to the front portion 40 of the valve chamber. The valve chamber is shown as for a cylindrical inside admission valve. The lever 35 1s pivotally connected at its lower end to a link 42 by a suitable pivot 43. Link 42 is pivotally connected at its other end by an appropriate pivot 64 to one end of a comparatively small bell crank lever 45. Bell crank lever 45 is oscillatably mounted on a pivot pin it carried in a bracket 47 secured to the main cross head It by bolt l3 and additional bolts or screws 48. Bell crank 45 at the end of its other arm is provided with a stud 59 on which is mounted a roller 5i. Roller 5| is disposed inwardly of crank lever L5 and is arranged to travel in a curved or sinuous groove or slot 52a in a guide bracket 52 which is secured to the cross head guide by the bolts [1.

In operation, the link will be oscillated as usual through link 26 from the eccentric arm 22. This will reciprocate rod 29, the amount of movement depending upon the position of block 27 in the link 25. The block will be positioned by the engineer in the usual manner by movement in link Movement will thus be transmitted to valve rod 3'! from link 25 through the lever 36. .As the main cross head M reciprocates bracket ll is moved therewith and bell crank lever :5 is bodily moved with bracket 41. As bell crank lever is thus reciprocated with bracket 47 it is given an oscillating motion about its pivot it by roller 5! moving in its groove 52a. This gives additional movements to the combination lever The movement transmitted to lever 3% therefore, from the cross head is a combination of the movement which is caused by the bodily movement of lever to or the reciprocating movement of cross head 5 with the additional movement given by the oscillation of bell crank lever 45. The additional movement given by the oscillation of hell crank lever 4-5 results in a greatly improved positioning of the valve or a great improvement in the sequence of valve events. With the high steam pressures now used in locomotives a shorter cut off in the main cylinder is feasible and desirable. The steam pressures used are sufficient to furnish the necessary power with a very short cut off and a long expansion period. With the present type of Walschaert valve gears commonly used as well as other types of radial valve gear including modified Walschaert types, it is impossible to use a short cut off of less than 25 percent without getting an objectionably long compression period. These excessive compression periods develops counter pressures and stresses together with excessive vibrations. These are all objectionable as a matter of practice, and cut offs of less than 25 percent are now not practical without devel ping prohibitive and excessive counter stresses and vibration. Also in the valve gears now commonly used, if a very short cut off with leads now standard is attempted there is excessive preadmission which also develops un-- desirable stresses and vibration. With the present invention these objections are eliminated and a cut on as low as 10 percent can be used with no more preadmission or compression than now occurs with the 30 percent cut oil. A carefully measured comparison of the present valve gear and one of the common types now used of the W alschaert type made by the Lima Locomotive Company and used on an engine of the Minneapolis, St. Paul and Sault Ste. Marie Railway Company, showed the following events: With a 10% cut off with applicants valve gear there was a preadmission port opening 0 1% of an inch. The cut off occurred at 3.2 inches from the beginning of the stroke and on the forward stroke compression began at 8% inches from the end of the stroke and on the back stroke compression began at 7 inches. With the standard Walschaert gear it wa impossible to set the valve to get a 10% cut off. With a l2 cut off, or a out 01f after four inches of piston travel, the preadmission opening of the port on the standard Walschaert valve gear was 2% inches. The compression stroke was 13 inches from the end of the piston stroke, or in other words, the exhaust valve closed with the piston 13 inches from the end of its stroke. With applicants valve gear the preadmission port opening was only it of an inch and the compression stroke was only 7%; inches long. It will thus be seen that with the 12 70 out off, applicants valve gear maintained a small preadmission opening and reduced the compression stroke almost by half. This is a very desirable condition. The short cut off gives ample power with the steam pressures used and the steam is allowed to expand efficiently. This will result in a great saving of fuel. With fast heavy trains it is now a practice to govern the tonnage rating by acceleration and sustained power at high speeds. With applicants valve gear therefore, the tonnage rating on present 10- comotives would be greatly increased. The advantage obtained by applicants valve gear as set forth above on the l2 /2% cut off continues through the various sets of the gear. lowing table showing the valve events with cut oils from 12 to 50 percent illustrates forcibly the great advantage attained in the sequence of valve events with applicants gear. In said table the numeral F indicates the measurement on the back stroke. As is well known, all valve gears may have a slight difference on the two strokes due to the necessary ofiset position of the parts.

Prcadmission Port opening Compression Outofis F B F B F B Inches Inches Inches Inches $44 it 13 is %4 %2 7 A 6% it %4 11 12A /1 6% 5% /64 %2 10% 10 /46 /32 %4 6 5% 3-64 %4 We 8 16 %4 %2 57 16 49 16 %2 /64 8% 7% 9s %4 5 4% 9i 0 2 %2 6 5% 1 A c %4 4% s 3% %2 %2 5V0 4%;

In the above chart the letter A at the left designates applicants device, while the letter S designates the standard Walschaert valve gear used in comparison. The figures given are in inches and fractions thereof.

In Fig. 4 a modified arrangement of the valve gear is hown in which a rack 69 is secured to the main cross head guide 15 by the bolts El. A stud i2 is carried by the main cross head M on which is journalled a pinion 63. with rack 60 and has pivotally connected thereto at one side of its center, a link 64. The other The fol- Pinion 63 meshes end of link 64 is pivotally connected to the lower end of the combination lever 36.

In operation of the device shown in Fig. 4, the main cross head [4 will be reciprocated as shown in its guide l5 and pinion 63 will be carried bodily therewith. Pinion 63 will also be oscillated by its movement along the rack 60. This will give additional movement to link 64 so that the movement of lever 36 will be a combination of the movement imparted of the reciprocation of cross head I4 and the oscillation of pinion 63.

The efiect of this device on the movement of the main steam valve is to accelerate its movement near the ends of its stroke and retard it near mid stroke. This change from the standard practice now in use will cause valve events that bring about the following highly desirable results:

It will permit the use of a longer steam lap without shortening maximum cut off.

It will give a larger port opening at the shorter cut offs.

It will greatly shorten compression periods, especially at the short cut off positions.

It will cause far later release of exhaust at the short cut oil positions, thus giving longer expansion periods.

It will give a quicker opening and closing of both intake and exhaust with less wire drawing at running positions.

It will permit the use of more lead with much less preadmission than the standard now in use.

From the above description it will be seen that I have provided a simple and highly improved valve gear and one that will give the sequence of events in the valve which are most desired. Not

only is a short out off possible with an efiicient expansion of the stroke and the compression stroke reduced, but the other desirable events of the valve are not particularly changed. The desired lead and lap can be had and this will remain substantially constant. The possibility of using greatly reduced cut ofis and a short compression stroke results in a great advantage over present valve gears and this will also result in a great saving of fuel. As above stated, locomotives equipped with applicants gear can be given a much higher tonnag rating. The valve gear is easily operated and works with great eificiency. The device has been amply demonstrated and found to be very successful and efficient.

It will, of course, be understood that various changes may be made in the form, details, arrangement and proportions of the parts, without departing from the scope of applicants invention, which generally stated, consists in a device capable of carrying out the objects above set forth, in the parts and combinations of parts disclosed and defined in the appended claims.

What is claimed is:

1. In a valve gear of the radial type having a lap and lead lever, a movable means entirely supported by and carried bodily by the main cross head to reciprocate therewith, a link connected to said means and to said lap and lead lever, a stationary means for moving said means in addition to its reciprocation by its cross head to move said lap and lead lever and valve.

2. A valve gear for a locomotive, of the radial type having a link operated by an eccentric, a lap and lead lever connected to said link and to the valve rod, a bell crank lever, a member about which said bell crank lever oscillates connected to the main cross head, stationary means for acting on one arm of said bell crank lever in the reciprocation of said cross head to oscillate said bell crank lever and means connecting the other arm of said bell crank lever to said lap and lead lever.

3. In a valve gear for a locomotive, of the radial type having a lap and lead lever, a bell crank lever, a member about which said bell crank lever oscillates connected to the main cross head, stationary means for acting on one arm of said bell crank lever in the reciprocation of said cross head to oscillate said bell crank lever and a link connecting the other arm of said bell crank lever to the lower end of said lap and lead lever.

4. In a valve gear of the radial type having a link operated by an eccentric, a lap and lead lever connected to said link and to the valve rod, a bell crank lever, a member about which said bell crank lever oscillates connected to the main cross head, a roller carried by one arm of said bell crank lever, a stationary member having a sinuous groove in which said roller travels whereby said bell crank lever is oscillated in the reciprocation of said cross head and means connecting the other arm of said bell crank lever to said lap and lead lever. I

5. In a valve gear of the radial type for a locomotive having the usual link oscillatable from the crank pin, a radius rod connected to said link, a valve rod and a lap and lead lever connected at its upper end to said radius rod and at an intermediate portion to said valve rod, the combination of a movable member carried by the main cross head, a link connecting said member to the lower end of said lap and lead lever, and means engaged by said movable member in the movement of said cross head for giving additional movement to said movable member and said lever.

6. A valve gear of the radial type for a locomotive having the usual link oscillated from the crank pin, a radius rod connected to and adjustable relatively to said link, a valve rod and a lap and lead lever pivotally connected to said radius rod and said valve rod, an oscillating member carried by the main cross head and bodily movable therewith, a link connecting said member to the lower end of said lap and lead lever and stationary means engaged by said oscillating member for giving additional movement thereto and to said lap and lead lever in the reciprocation of said cross head.

LOUIS THOMAS KNOWLES.

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