US2051400A - Mechanical brake for railway switch machines - Google Patents

Description

H. B. TAYLOR Aug. 18, 1936.

MECHANICAL BRAKE FOR RAILWAY SWITCH MACHINES Filed Dec. 23, 1951 2 Sheets-Sheet 1 Aug. 18, 1936. H. B. TAYLOR 2,051,400

MECHANICAL BRAKE FOR RAILWAY SWITCH MACHINES I Filed Dec. 23, 1951 2 Sheets-Sheet 2 FIG.3.

INVENTO fin? I MM.

/A' /ATTORNEY Patented Aug. 18, 1936 UNITED STATES MECHANICAL BRAKE FOR RAILWAY SWITCH MACHINES Herbert B. Taylor, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,

Application December 23, 1931, Serial No. 582,745

14' Claims.

This invention relates to devices used for the control of railroad track switches, and more particularly pertains to a mechanical brake employed with power driven switchmachines for operating such switches.

In the operation of track switches by power driven switch machines, it is desirable that the track switch be prevented from movement at all times except under authorized control. The usual track switch operating mechanism or switch machine is provided with means for positively looking a track switch in its extreme operated positions. However, it may happen that the switch points are operated to the desired extreme position, but the switch machine for one reason or another fails to positively look thetrack switch. Even in such a case, the switch machine should be so arranged as to prevent movement of the track switch should a train pass thereover.

In view of the above and other considerations, the present invention proposes to provide a mechanical brake associated with the switch machine in such a manner, as to prevent the movement or operation of the switch machine mechanism at all times except when power is applied to its motor. In other'words, this brake is made effective to hold the switch points in the last position to which they. are operated, irrespectiveof whether or not the switch machine has positively locked the track switch in the usual manner.-

Other objects, purposes and characteristic features will be in part'obviousirom the accompanying drawings and in part pointed out, as the description of the invention progresses.

In describing the invention in detail, reference will be made to theaccompanying drawings, in which like reference characters indicate corresponding parts throughout the several: views, and in which:-

Fig. 1 is a sectional view of a mechanical brake V constructed as one embodiment of the present invention, as taken on the lines ll ofFig. 2;

Fig. 2 is a sectional view taken on lines 2--2 ofv Fig. 1;

Fig. 3 is a sectional view taken on lines 3-3 of Fig. 4; and,

Fig. 4 is similar to Fig. 1 except certain parts have been illustrated'in their operated or released positions.

Although the mechanical brake of the present invention is contemplated as employed with a suitable switch machine, such for example as disclosed in the patent'to W. K..Howe, Patent No. 1,466,903, dated September 4, 1923, with the .brake of the present invention interposed between the driving motor and the operating mechanism of the switch machine, it is considered sufficient for an understanding of the present invention to know that the brake casing l is stationary with respect to the switch machine housing, that the 5 shaft 2 is driven by the switch machine motorin One direction or the other depending upon the operation to be accomplished, and that the pinion gear 3 suitably drives the gearing of the switch machine when the motor. rotates the shaft 2.

Also, it is to be understood thatsuitable means may be employed in connection with a switch mae chine equipped with the brake of the present invention, so as to permit the hand operation of the track switch, but the operation of such means is unnecessary for an understanding of the present invention which more particularly relates to the structure and character of the brake.

With reference to the drawings, the brake casing l isrformed so as to be securely attached to the switch machinehousing, and is provided with a web portion 5 which extends across the cavity within the casing (see Figs. ,1 and 3). A plate member 6-. has a protruding shaft! which extends through the web portion 5 forming a bearing therefor. This shaft 1 is provided with a. shoulder formed thereon againstwhich the pinion gear 3 is securely pressed by a suitable nut 8 (seeFig. 2). The pinion gear 3-is prevented from turning on the shaft 1 by suitable keys located i ak w y- Another plate 9 is secured in spaced relation with the plate Bso. that certain of the operating parts of the brake maybe mounted on the inside. More specifically, four brake shoe sectors IQ. ll,

I2 and [3 are located between the plates, and pivoted at the ,fourpoints at which the plates 6 and 9 are connected together. For example, the. plates 6 and 9; are separated by-a shouldered bolt 40 I4 which is riveted at one end toplate 9 but is detachably secured by a nut IGand asuitable lock washer H to the plate 6. Thus, a bearing surface is formed by the shoulder'of the bolt M for the brake shoe sector II. the remaining brake shoe sectors I0, I2 and I3 are supported between the plates 6 and 9 at corresponding points in the remaining quadrants of the brake.

On adjoiningportions of the brake shoe sec-. 50 tors Ill-ll and !2-.l3 suitable brake linings 20, 2!, 22. and ,23 are secured for engaging; the inside. of the casing I which acts as the stationary brake drum. These portions ofthe brake shoesectors having the brake lining are pressed 551' In a similar manner,

- 25, 2 6, 2'1 and 2s.

outwardly against the brake drum by springs The springs 25 and 26 are supported at one end by the extending portion 30 of the plate 9; and similarly the springs 21' The opposite portion of each brake shoe sector is enlarged to act'as a counter-balancing weight. Each of these weights 36, 31, 38 and 39 is of such a value that the center of the centrifugalforce acting on each brake shoe sector falls on that side of eachsector extending from its pivot point toward the weighted or enlarged porhonor the sector. In other words, as the brake shoe "sectors are revolved' whileithe motor is V spective brakeshoe sectors.

acting to drive the switch machine mechanism, the centrifugal'force acting upon the brake shoe sectors is effective to counter-act to' the desired degree the effect of the spring members of the re- The brake shoesectors II and 2 are interconnected by a bearing joint (see 'Figs. land 3) which pro vides that movement of one sector' transmits the same 'motion to the other. In

- other words, a bearingshaft wshouldered at either end fits in-thesemi-circular recesses provided in eachof the brake shoe sectors. Similarly, a bearing shaft 4| shouldered at either end fits in the semi-circular recesses located in the brake shoe sectors l and I3 so that the motion-transmitted to one brake shoe sector is imparted tothe other.

Each of the brake shoe sectors IO, 12 and .|3 has inwardly extending bifurcated arms 45, 46, V

41 and 48, within which the'roller bearings 50, 52 and 53 respectively, are suitably mounted.

1 A cam'member 60 is suitably keyed to the shaft 2; and'locat'ed between the plate members 6 and 9 'so'as to engage' in pairs the roller bearings 50,

5|, 52 and 53 depending upon the direction in which the cam is rotated. When thecam is a from the brake drum, as illustrated in Fig. 4.

, This movement or force transmitted to the sectors rotate in a clockwise direction.

turned inaclockwise direction (see Fig. 1), the

cam;member60 engages the roller bearings 5| and 53, turning the brake shoe sectors II and I3 in counter-clockwise directions, so as to move their respective brake linings 2| and 23 'away H and I3 is imparted to the sectors I2 and M respectively through the interconnecting bearing shafts 40 and 4|, so that the sectors l2 and turnain clockwise directions, which moves the brakelinings and 22 away from-the inside of. the brake drum. Thus, the frictional contact between the brake shoe sectors and the'brake drum is released allowing the plates 6 and 9 to 'The force or power imparted to the shaft 2 is now passed on to the pinion 3, inasmuch asthe brake sectors can be rotated around their pivot points only a limited distance which is determined by the bearings 5|--52 and the bearings'50-53 V making contact. In other words, the cam member 60 is rotated with respect to theplates 6 and 9 only so long as the brakeshoe sectors turn on their .pivo't poin'ts and when they cease turning and the respective pairs coincide at their bearings,gthen the cam member is stationary with respect to plates 5 and 9, but the plates 6 and 9 together with the shaft 2 rotate with respect to the brake drum or casing thereby transmitting the motion of the motor armature to the pinion gear 3.

In this connection it is noted, that the shape of the cam member 60 is such that its circular portions which engage the roller bearings 50, 5|, 52 and 53 are concentric with the roller bearings when the parts are in their operated positions (see Fig. 4). This definitely determines the limits of the cam movement, as well as prop erly directing the forces both for rotational effectiveness and for releasing effectiveness. V

The operation accomplished when the cam 60 is turned in a counter-clockwise direction is similar to that already described, and will 'be understood by analogy.

The rotation of the brake mechanism imparts centrifugal force to 'each of the parts.

in the case of the brake shoe sectors, as previously mentioned. When the motor has reached the usual operating speed, the centrifugal forces,

thus transmitted to the brake shoe sectors. added to the releasing effect imparted by the cam' GO due to the reaction of the load, counterbalance the force'of the springs with sufiicient margins to positively maintain-the brake released.

But when the power is withdrawn, as applied by the motor, the centrifugal force'alone is insufficient to maintain the brakeshoes in released or retracted positions and they are pressed by 1 their respective springs against the brake. drum. This servesto stop the rotation of the motor and switch machine mechanism with a minimum amount of overrun by absorbing the momentum of the parts in the friction created.

- Also, it will be obvious from the above description that any force applied to the pinion 3 in either direction when the motor isnot actuated,

These 7 centrifugal forces are preferably balanced except will be transmitted directly through the brake shoe members to the brake drum I through the frictional contact between the brake linings and the drum, thuspreventingmovement of the pin ion 3. v

The actual weight, the'degreeof balancing, the

forces, the' moments of torque, and the like are .of course considered asengineering details and adjustment, the particular values of which are not necessary for an understanding of the present invention.

This brake when applied to switch machines,

:as contemplated in accordancewith the present invention, will adequately prevent the movement of the track switch points due to externally applied forces, but will allow proper operation when forces are applied thereto through the medium of the switch machine mechanism asdriven by its'power operated motor. The brake'of, the' present invention also serves to limit the overrun at the end of an; operation.

Having thus shown a brake for railroad switch machines, as one specific embodiment of the present invention, it is desired to be understood i that this form is selected to facilitate in the disclosure of the invention rather than to limit the 7 number of 'forms which it may assume; and, itis to befurther understood that various modifications, adaptations and alterations may be applied to the specific form shown tomeet the requirements of practice, withoutin any manner departing from the spirit orscopeof'the present invention except as limited by the appended claims.

What I claim is:

1. For use with a power driven switch machine for railroad track switchesa mechanicalbrakeplurality of brake shoes for compressing said coil springs to disengage said brake shoes from said brake drum and for rotating said pinion. drive member withsaid power driven, shaft after said brake shoes are disengaged, and means re-'v sponsive to the synchronous, rotation of said shaft and said pinion drive member for maintainingsaid coil springs compressed.

2. For use with a power driven switchmachine for railroad track switches, a mechanical, brakeincluding, a fixed brake drum, a pinion drive member, a plurality of brake Shoes pivotally attached to said pinion drive member'andnormally biased to engage said brake drum, a shaft, operating means connecting; said shaft with a plurality of brake shoes for disengaging said brake shoes from said brake drum and for rotating said pinion drive member when power is applied to said shaft, and means effectively only while said pinion drive member is being rotatedfor maintaining said brake shoes disengaged from said brake drum.

3. For use with a power driven switch machine for railroad track switches, a mechanical brake including, a fixed brake drum, a pinion drive member, a plurality of brake shoes each having an unbalancing weighton one end and'a braking surface on the other end, and each being pivotally attached to said pinion drive member at a point between its unbalancing' weight and its braking surface, means normally biasingsaid brake shoes so that their respective,brakingsurfaces engage said brake drum, a shaft, and operating means,

shoes for initially disengaging said brake shoes from said brake drum and for rotating said pinion drive member when power is applied to said shaft, whereby the revolving of said pinion drive member and said unbalanced brake shoes is effective to counteract said normal bias on said brake shoes.

4. In combination, a driven member, a driving member, a brake for preventing operation of said driven member, means for releasing said brake when power is applied to said driving member, said means operatively connecting said driving member to said driven member when said brake is released, and means dependent upon the speed of operation of said driven member for maintaining said brake released during operation.

5. For use with a power driven switch machine for railroad track switches, a mechanical brake including; a fixed brake drum; mounting means rotatably supported with respect to said brake drum; a pinion gear attached to said mounting means; a plurality of brake shoe sectors pivotally supported on said mounting means; brake linings on each brake shoe sector for engaging said fixed brake drum, said linings being on one side of the pivot point of each brake shoe sector; weight means on the other side of the pivot point of each brake shoe sector; spring biasing means for normally causing said brake shoe linings to engage said brake drum; a power driven shaft; and operating means connecting said power driven shaft and said brake shoe sectors for compressing said spring biasing means and for rotating said brake shoe sectors, said mounting means: and said; pinion gear being in synchronism with said power driven shaft when, power is applied thereto; whereby said pinion gear is prevented from rotation except. when power is applied to said'shaft; and whereby the centrifugal force acting on said unbalanced brake shoe sectors due'to the rotation thereof is effective to counter-act said spring biasingmeans.

6. For use with a power driven switch machine for railroad track switches, a mechanical brake including; a fixed brake drum; mounting means rotatably supported with respect to said brake drum; a pinion gear attached, to said mounting means; apluralit of brake shoe sectors pivotally supported on said mounting means; brake linings on each brake shoe sector for engaging said fixed, brake drum, said linings being on one side of the pivot point of each brake shoe sector; weight means on the other side of the pivot point of each brake shoe sector; spring biasingv means for normally causing said brake linings.

to engage saidbrake drum; a power driven shaft; and a cam on said shaft adapted to engage said brake shoe sectors for compressing said spring biasing means andfor rotating said brake shoe sectors, said mounting means and said pinion gear being in synchronism therewith when power is applied thereto for rotation in either direction; whereby said pinion gear is prevented from rotation except when power is applied to said shaft; and whereby the centrifugal force acting on said unbalanced brake shoe sectors due to the rotation thereof is effective to counteract said spring biasing means.

7. For use with a. power driven switch machine for railroad track switches, a mechanical brake including, a fixed brake drum having a cavity, two spaced plates pivotally supported within said cavity, a pinion gear fixedto said plates, four:

brake shoe sectors each being pivotally supported between said plates at intermediate points near their periphery and having inwardly projecting arms, a brake lining attached to each of said brake shoe sectors on one side of its pivot point, a weight attached to each of said brake shoe sectors on the opposite side of its pivot point, coil springs associated with each of said brake shoe sectors for causing said brake linings to engage the inside of said brake drum, a power driven shaft pivotally supported having the same axis as said plates, and a movement limiting cam on said power driven shaft for engaging said inwardly projecting arms, whereby said coil springs are compressed for disengaging said brake linings from said brake drum, whereby said plates, said brake shoe sectors and said pinion are all rotated when power is applied to said shaft, and whereby the centrifugal force acting on said weights assists in maintaining said coil springs compressed.

8. In combination, a driven member capable of being rotated in either direction, a plurality of unbalanced sectors so pivotally attached to said driven member that their heavier portions move outwardly when said driven member is rotated, biasing means for drawing the heavier portions inwardly when said driven member is not rotated, and a friction brake drum engaged by said unbalanced sectors when their heavier portions are drawn inwardly by said biasing means to thereby prevent rotation of said driven member in either direction.

9. In combination, a driven member capable of being rotated in either direction, a plurality of unbalanced sectors so pivotally attached to said V anced sectors when their heavier portions are drawn inwardly by said biasing means to thereby prevent rotation of said driven memberin either drivenmembers that their heavier portions move outwardly when said driven member is rotated,

biasing means for drawing the heavier portions inwardlywhen saiddriven member is not rotated, a'friction brake drum' engaged bysaid unbaldirection, and mechanical releasing means for counteracting said biasing 'means, whereby saidpendent upon the speed of rotation of said 'driven member for maintainingsaid brake released. 11. In combination, 'a driven member capable of being rotated, a brake for preventing rotation of said driven member, a driving member,

"means automatically releasing said brake upon the tendency of said driving 'member" to rotate .and then directly transmitting rotation tendency from said driving member to said driven memher; and centrifugal means dependent upon the speed of rotation of 'saiddriven' member for effectively maintaining said brake'released' during 7 the rotation of said driven member.

12. In combination, a driven member capable of being rotated, a driving member disconnected from said driven member and capable of rotation when power is applied thereto, a friction brake for preventing rotation of said driven member in either direction, means automatically releasing said brake upon the application of power to'said driving member to cause it to tend to rotate,

whereby said brake is released to allow the rotation'of. said driven member, means directly 7 driving member.

transmitting rotational tendency from said driv ing member to said driven member when said brake is released, and centrifugal means dependent' upon the speed of rotation of said driven member for maintaining said brake released by supplementing said automatic, releasing means.

13. In combinatioma driven member capable I of being rotated in at least one direction, a friction brake for preventing rotation of said driven member in said one direction, a driving member,

automatic mechanical means for initially releasing said brake when driving torque is applied to said driving member, means operatively connecting said driven member and said driving member for the transference of driving: torque from said driving member to said driven member when said brake is released, and centrifugal means dependent upon the speed of rotation of said driven member for effectively maintaining said brake released during saidrotation of said driven member. r

14. In combination, a driven shaft capable of being rotated, 'a driving member capable of rotation when power is applied thereto. a friction brake for normally preventing-rotation of said driven shaft inboth directions while driving torque is removed .from said driving 'member, means automatically releasing said brake upon the application of driving torque to said driving member, whereby said brake is released to allow transmitting torque fromsaid driving member to said driven shaft when saidbrake is released, and centrifugal means'responsive to the speed of rotation of said driven shaft for maintaining said 7 the rotation of said driven shaft, means directly brake released by supplementing the releasing effeet or said'automatic'releasing means, whereby torque can be transferred from said driving mem her to said'driven shaft, but cannot be transferred from said driven shaft to said driving member while driving torque is removed'fromsaid HERBERT B. TAYLOR.

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