US2313602A - Railway car hand brake - Google Patents

Description

March 9, 1943. E. E. VAN CLEAVE I "RAILWAY CAR HAND BRAKE Filed May 8 1941 2 Sheets-Sheet 1 Jr/em; gin 2'26 Wazzfiaue,

wrzgya E. E. VAN CLEAYE RAILWAY CAR HAND BRAKE March 9, 1943.

Filed May 8,1941 2 Sheets-Sheet 2 Patented Mar. 9, 1943 UNITED STATES PATENT OFFICE RAILWAY CAR HAND BRAKE Edwin E. Van Cleave, Chicago, Ill.

Continuation of application Serial No. 352,256, August 12, 1940. This application May 8, 1941,

Serial No. 392,960

3 Claims.

This application is a continuation of my pending application, Serial No. 352,256, filed August The invention relates generally to railway car brakes and more particularly to mechanism for operating the brakes by hand.

The general object of the invention is to provide a novel mechanism for manually operating the brakes of a railway car, arranged to provide increase in the braking effort by relatively small increments so that the effect of differences in the physical strength of different brakemen may be minimized.

More specifically, it is an object to provide a hand brake including a one-way holding device, utilized in setting up the brake, which is so constructed that holding is effected at a large number of points in turning the handwheel of the brake, whereby the increase in force required to turn the handwheel from one such point to the next is relatively small, thereby permitting the brake to be held substantially at the maximum point to which a brakeman is capable of turning the handwheel.

Another object is to provide a hand brake which requires a minimum effort on the part of the brakeman to release.

A further object is to provide a hand brake which may be partially released by hand and then automatically relocks under the effect of the load, and which is so constructed that the efiort required to release the brake at any point is relatively small so that, regardless of the strength required of the brakeman in setting up the brake, it may be easily released by one not so strong.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawings, in which:

Figure l is a vertical sectional view of a railway car hand brake embodying the features of the invention.

Fig. 2 is a fragmentary sectional view taken on the line 22 of Fig. 1.

Fig. 3 is a fragmentary sectional view similar to Fig. 1 but showing a modified form of the device.

Fig. 4 is a sectional view similar to Fig. 3 but showing another modified form of the device.

Railway car brake systems in use at the present are adapted to be operated either by air or by hand. The braking mechanism is mounted under the car and is connected to a hand brake, mounted on the end of the car, by a flexible connection such as a chain. The hand brake comprises a housing in which is rotatably mounted a winding drum for the chain. The winding drum is connected usually through a gear reduction to a handwheel, and a one-way holding means such as a pawl and ratchet deviceis provided so that the chain may be wound upon the drum and held in such position by the pawl and ratchet.

As hand brakes are usually made, most of the turning movement of the drum is utilized in taking up slack in the chain and braking mechanism, while only a comparatively small part of the drum rotation is utilized in applying pressure to the brakes. Such slack is necessary so that operation of the brakes by air will not be interfered with. Thus only a comparatively small turning of the handwheel is utilized for raising the brake pressure from zero to the maximum. The pawl and ratchet device, if of suiiicient strength to carry the load, will thereby have relatively few points at which holding may be effected, and consequently the increment of brake pressure caused by movement of the pawl and ratchet device from one such point to the next will be relatively large. With such large increments of brake pressure, one brakeman may be capable of setting the brake to its maximum pressure, while another brakeman, lacking the strength of the first, may not be quite able to set the brake to its maximum pressure. In such case the result is that the weaker brakeman is able to set the brake only to a point far below the maximum.

To illustrate the foregoing by a specific instance, the chain may be required to be moved 8 inches to take up the slack necessary for proper actuation of the air brake. Further movement of the chain is utilized for applying the power to the brake. Specifications of the American Association of Railroads require a hand brake to be capable of applying a maximum brake pressure of 3950 lbs. when the hand brake is operated by a man of ordinary strength. Such maxi mum brake pressure will be applied by a chain movement of only approximately Z2 inch after the slack has been taken up. The total winding drum rotation to provide for chain movement of 8 inches for taking up slack and approximately inch for applying the power amounts to a little more than a one-half turn of the drum. Therefore the amount of turning of the drum which actually causes the application of pressure is only a few degrees.

The gear ratio of the gear reduction between the drum and the handwheel may, for example, be /2 to 1. Thus the rotation of the handwheel which moves the chain the last /2 inch to apply the pressure is only about /3 to /2 a turn. Because of space restrictions and strength requirements, the ratchets commonly used on hand brakes have in the neighborhood of twenty teeth.

With the handwheel making only /3 to /2 of a revolution to actually apply the pressure, the pawl and ratchet device has only seven to ten points of holding during such rotation of the handwheel. Translating this into the increments of brake pressure caused by movement of the pawl and ratchet device from one point to the next, each increment therefore is between 400 and 600 lbs.

Obviously all brakemen are not of equal strength. A strong brakeman may be able to turn the handwheel to such extent that the pawl and ratchet device will hold the brake pressure at its maximum. Another brakeman of less strength may not quite be able to turn the handwheel to the maximum brake pressure and therefore will have to let the handwheel turn back to the last point of holding of the pawl and ratchet device. Such point of holding may be 490 to 600 lbs. less than the maximum, or, in other words, 3550 or 3350 lbs. of brake pressure. Obviously such a large difference in the setting of the brake will have a material effect in stopping the car. However, had the pawl and ratchet device been capable of finer adjustment, there would not have been such large difference between the different settings, and the weaker brakeman would be able to set the brake more nearly to the point at which the stronger brakeman could set it.

The present invention provides a structure for decreasing the size of the increments of brake pressure without sacrificing any strength in the ratchet teeth. In fact, ratchet teeth of exactly the same size as heretofore used may be utilized in the present structure. To this end I provide a brake housing l3 adapted to be mounted on the end of a car in the usual manner. Within the housing 13 is rotatably mounted a drum l5 on which a chain I! is adapted to be wound. The chain I! is connected to the bar brakes in the usual manner. The drum l5 carries a gear wheel 16 adapted to mesh with a manually operated pinion 5.

In the preferred form of the invention, the pinion 5 is threaded on an operating shaft I, as indicated at 3. The shaft is journaled at its rear end in the housing l3 and extends through the front wall of the housing to receive a handwheel 4 mounted on the end of the shaft.

Mounted on the shaft 1 adjacent the pinion is a one-way holding device adapted to be clamped to the pinion when the brake is set, and adapted to be released therefrom when it is desired to release the brake. To this end the pinion 5 is provided with a flange having a clutch disk 8. Spaced therefrom is a flange 2 rigid with the shaft and also provided with a clutch surface Q. Mounted between these two clutch disks is the one-way holding device. Thus when the handwheel is rotated clockwise, such rotation first causes the shaft to be threaded into the pinion thereby clamping the one-way holding device between the clutch disks 8 and 9. When such clamping occurs, further rotation causes the pinion to be rotated with the one-way holding device to set the brake.

To release the brake, the handwheel 4 is turned counterclockwise and the one-way holding device the usual 7 to 10 points of holding.

is thereby unclamped so that the pinion is no longer held against rotation by said device. So long as the handwheel is rotated counterclockwise, the pinion may correspondingly rotate and the winding drum will turn in the direction to release the brake. However, when rotation of the handwheel is stopped, the load of the brake transmitted back to the pinion causes the pinion to rotate relative to the shaft l and thereby move into clamping engagement with the one-way holding device to stop release of the brake.

As mentioned above, an important feature of the invention is to provide a one-way holding device which provides a large number of points of holding so that the brake pressure may be applied in relatively small increments. Thus the one-way holding device in the present instance comprises a pawl carrier 1 loosely mounted on the shaft I between the clutch disks 8 and 9, the respective faces of the pawl carrier 1 cooperating with said clutch disks when the parts are clamped together. Mounted in a peripheral groove in the pawl carrier is a plurality of pawls Ill, each pivotally supported for radial swinging movement and urged outwardly by a spring Id. The pawls ID are adapted to cooperate with ratchet teeth l2 formed internally on a flange I l integral with the front wall of the housing 13. The ratchet teeth l2 are of the same strength and size as normally employed, but the pawls ID are so spaced that they successively engage the teeth of the ratchet. Thus only one pawl is in holding engagement with the ratchet at one time. But while said one pawl is passing from one ratchet tooth to the next, the other two pawls will successively engage ratchet teeth. In effect therefore I obtain the equivalent of a ratchet of three times as many teeth but without sacrificing any of the strength or size of the teeth.

With this construction, the last or turn of the handwheel causes the application of brake pressure, and with the twenty-two ratchet teeth shown in the present construction, there will be from 20 to 30 points of holding as compared with This means that the brake pressure may be increased from zero to the maximum in increments of roughly 133 lbs. to 200 lbs. instead of the former increments of 400 to 600 lbs. Thus a brakeman, even though lacking the strength of others, may set the brake at a pressure more nearly approaching the maximum pressure.

In Fig. 3 I have shown a brake embodying the foregoing feature but of somewhat different form. In this brake the pinion 5 is provided with an integral extension l9 threaded at 28 into a sleeve 21 formed on the shaft l. The pinion 5 carries a clutch disk 8, and the shaft I carries a clutch disk 9, while the pawl carrier 7 is mounted between these clutch disks and is rotatable on the extension l9. The operation of this form is substantially the same as in the preceding form.

In Fig. 4 I have illustrated another modified form generally similar to the form shown in Fig. l and utilizing a similar pawl carrier and ratchet. The form illustrated in Fig. 4, however, embodies another feature of the invention, the broad aim of which is to facilitate release of the brake. When the brakes shown in Figs. 1 and 3 are set to apply the maximum brake pressure, the pawl carrier 1 is rigidly clamped between the clutch disks 8 and 9. Release is effected by rotation of the clutch disk 9 relative to the clutch disk 8 and consequently the clutch disk 9 must rotate relative to the pawl carrier 1. If the brake has been set to its maximum by a brakeman of considerable strength, a brakeman of less strength may have difficulty in releasing the brake because of the friction between the clutch disk 9 and the pawl carrier 1.

The structure illustrated in Fig. 4 reduces the friction between the pawl carrier and the flange 2 of the shaft, without affecting the clamping pressure of the pinion clutch disk 8 against the pawl carrier. To this end an antifriction bearing I8, preferably in the form of a roller bearing, is interposed between the pawl carrier 1 and the flange 2 of the shaft l. The antifriction bearing l8 carries the clamping pressure, which is in the nature of a thrust load, but facilitates relative rotation between the flange 2 and the pawl carrier 1. Thus the weaker brakeman may readily release a brake of this character no matter to what pressure it has been set. Moreover, the ease with which the handwheel 4 may be turned in the releasing direction with this construction, permits a brakeman to exercise much more accurate control of the braking pressures exerted on the car since he does not have to exert an impulsive effort to cause release of the flange 2 from the pawl carrier. With the small fraction of a turn of the handwheel necessary to cause complete release of the brake, the ease with which the brakeman may turn the handwheel out of clamping position permits a much more sensitive control of the brake.

I claim as my invention:

1. A railway car hand brake comprising, in combination. winding mechanism. and operating mechanism therefor comprising a pinion, a handwheel, shaft means connecting said pinion and handwheel and including a clamping member, a pawl carrier mounted between said pinion and said clamping member, said shaft means including means to effect clamping of said pawl carrier between said pinion and said clamping member upon relative rotation between said handwheel and said pinion, and a fixed ratchet surrounding said pawl carrier, said pawl carrier comprising a disk provided with a peripheral groove. pawl means pivotally mounted in said groove for movement outwardly thereof. and spring means tending to cause said pawl means to move outwardly.

2. A railway car hand brake comprising, in combination, winding mechanism, and operating mechanism therefor comprising a pinion, a handwheel, shaft means connecting said pinion and handwheel and including a clamping member, a pawl carrier mounted between said pinion and said clamping member, said shaft means including means to effect clamping of said pawl carrier between said pinion and said clamping member upon relative rotation between said handwheel and said pinion, and a fixed ratchet surrounding said pawl carrier, said pawl carrier comprising a disk having a peripheral groove forming a pair of radially extending flanges, a plurality of pawls in said groove, pivots for said pawls fixed in said flanges and extending across said groove, and a plurality of springs seated in sockets in the bottom of said grooves and tending to force said pawls outwardly.

3. A railway car hand brake comprising, in combination, a housing comprising front and rear walls, winding mechanism mounted in the lower part of said housing, and operating mechanism therefor mounted in the upper portion of said housing comprising a handwheel located exteriorly of the housing, a pinion within the housing, shaft means connecting said pinion and handwheel and including a clamping member, said shaft means being journaled in the front and rear walls of said housing, a pawl carrier mounted between said pinion and said clamping member within said housing, said shaft means including means to effect clamping of said pawl carrier between said pinion and said clamping member upon relative rotation between said handwheel and pinion, and a ratchet comprising an annular flange integral with and extending inwardly from the front Wall of the housing and surrounding said pawl carrier.

EDWIN E. VAN CLEAVE.

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