US2077939A - Brake - Google Patents

Description

April 20, 1937. E. LA BRIE BRAKE 3 ShetS-Sheet l Filed Dec. 2l, 1932 B m .T L. F- R D Y IL April 20, 1937. E. LA BRIE 2,077,939

BRAKE Filed Dec. 2l, 1952 3 Sheets-Sheen'I 2 INVENTQR. Luoxm'E. LA BRvE A TTORNEYS.

April 20, 1937. l.. E. LA BRIE BRAKE Filed Deo. 2l, 1952 3 Sheets-Sheet 3 INVENTOR. LUDGER E. LA BRIE ATTORNEYS.

Patented Apr. 20, 1937 UNITED STATES mi'rEN'r` oFI-lcE BRAKE Ludger E. La. Brie, South Bend, Ind., assignor to Bendix Aviation Corporation, South Bend, Ind.,

a corporation of Delaware Application December 21, 1932, Serial No. @8,291 29 Claims. (Cl. 188-152) This invention relates to brakes, and is illustrated as embodied in internal expanding automobile brakes of the shiftable anchorage' type. An object of the invention is to improve the 5 smoothness and effectiveness of the control of such brakes, especially when of the type named.

According to an important feature of the invention, the primary shoe or equivalent member of the brake acts in forward braking' on the secl ond'ary shoe, or its'equivalent, through means which transmits to the backing plate or other stationary4 part a substantial predetermined portion of its thrust, while the remainder is transmitted to the secondary shoe. This gives the l5 primary shoe some of the self-energizing characteristics of an anchored shoe, and at the same time some of the characteristics of a floating servo shoe acting on the anchored secondary shoe. Preferably the above object is achieved by the '20 use of means acting in reverse braking to transmit a multiplied or intensified thrust from the secondary shoe to the primary shoe. and I prefer to arrange the applying means of the brake to have in its action on the secondary shoe in reverse braking a much greater throw or movement which makes up for the increased movement of the shoe involved in the desired action, without any increase in pedal movement, and at the same timev a reduced effectiveness which com- 30,pensates`in large part for the increased servo actionzof the secondary shoe.

lLooked at from a slightly different point of view,-I iind that the greatest simplicity in achieving Athe desired result is secured by an arrangementr which gives greater control of the servo action lin forward braking, a very great advantage, at the expense of,increased 'servo action inireverse braking whic in turn is compensated for by reducing the mec anical'advantage of the 40 applying means. 'I'his is quite satisfactory in practice, since the requirements of braking, at the low speeds usual in reverse,- are not so great as in forward braking either as to extreme smoothness of action or as to uniformity of action between the shoes.

In one desirable arrangement this result is secured by a. mechanical linkage connecting the shoes, and transmitting a predetermined part of the thrust of the primary shoe to the backing plate and the remainder to the secondary shoes, and with either another mechanical linkage, or a fluid power device (preferably with an lassociated novel mechanical emergency applying means), serving as an applying means having the desired greater throw and lessened mechanical advantage when acting on the secondary shoe.

When fluid power applying means is used, I prefer to utilize a novel ouble-diameter cylinder having a large piston (or an equivalent device 5 such as a diaphragm) acting on the primary shoe, and a smaller piston acting on the secondary shoe. When any given quantity of liquid is introduced into the cylinder by depressing the brake pedal, it will act on the large piston, if the large l0 piston is the one which moves, with a short throw but large mechanical advantage or force. whereas when the smaller piston moves it gives it a greater throw but smaller mechanical advantage or force.

In another arrangement illustrated in the l5 drawings, the samegeneral eiect is secured by using, in place of the mechanical linkage, a i'luid connection between the shoes including a doublediameter piston carried by the backing plate, and

containing a large piston acted on by the primary 20 shoe and a smaller piston acting on the secondary shoe. In this case it is preferable to use the abovedescribed novel fluid-power-applying means, in which case it will be noted that both the small pistons act on the secondary shoe and both the 25 large pistons act on the primary shoe. l

Other features o f the invention relate to the adjustment of the brake, to various important arrangements and structures of the fluid parts, and to other novel combinations and desirable 30 particular constructions which will be apparent from the following description of the illustrative embodimentsshown in the accompanying drawings, in which:

Figure 1 is a vertical section, just inside the 35 head of the brake drum and showing the shoes in side elevation, of a modification having a mechanical applying linkage and a mechanical connecting linkage between the shoes;

Figure 2 is a partial section on the line 2-2 40 of Figure 1, showing the applying linkage;

Figure 3 is a partial section on the line 3-3 of Figure 1, showing the connecting linkage;

Figure 4 is a iigure corresponding to Figure l, but showing a mechanical connecting linkage 45 and a fluid (hydraulic) applying device, with an auxiliary mechanical emergency applying device;

Figure 5 is a partial section, on the line 5--5v of Figure 4, showing the auxiliary mechanical 50 applying device;

Figure 6 is a partial section, on the line 6 6 oi' Figure 4, showing the connecting linkage;

Figure '7 is a figure corresponding to Figures 1 and 4, but showing a 4brake with a fluid 55 (hydraulic) connecting device as well as a uid (hydraulic) applying device;

Figure 8 is a partial section through the fluid applying device, on the line 8--8 of Figure 7; 5 Figure 9 is a partial section through the uid connecting device, on the line 8--8 of Figure '7; and

Figure 10 is a section corresponding to Figure 9, and showing a connecting device embodying a 10 novel automatic brake adjustment.

The'brake illustrated in Figures 1-3 includes a rotatable drum I2, at the open side of which is a support such as a backing plate I4, and within which is arranged the shiftable-anchorage friction means, shown as including a primary shoe I6 connected as described below to a secondary shoe I8. The shoes are held, when the brake is released, by a heavy return spring and a lighter return spring 22 against a brake anchor 20 or post 24, carried by the backing plate, in positions determined by suitable adjustable eccentric stops or the like 26. The shoes are urged laterally irictionally against the backing plate by anti-rattle springs 28. An auxiliary spring 38 25`holds the shoe assembly yieldingly against the anchor 24. The ends of the shoe webs are notched to embrace the anchor 24 between them. 'I'he brake is applied by a linkage or means such as a floating lever 32, arranged between the web of shoe I6 and the backing plate, and having at its end laterally-projecting lugs 34 engaging the ends of the shoe webs on opposite sides of the anchor 24. Lever 32 is shown operated by a cable 36 passing through the backing plate I4 35 into a ilexible Bowden conduit (not shown). It should be noted that lugs 34 are so related-to the upper end of the lever that the mechanical Y advantage of the lever in acting on the primary shoe I6 is greater than in acting on the secondary shoe I8, whereas the movement of the right-hand lug 34 in applying shoe I6 is less than the movement of the left-hand lug 34 in applying the shoe I8. In other words, during forward rotation, a certain movement of lever 32 produces a movement of shoe I6 a lesser distance but,

with greater effective force, than the same movement of lever 32 produces in shoe I8 during 4reverse rotation, and this results from the fact that the right hand lug 34 is farther than the left hand lug from the effective pivotal points at the left hand ends of the shoes I6 and I8.

The novel connection, in this case a mechanical linkage, between the shoes at the other side of the brake is shown as including a lever 36 notched to fulcrum at its inner end on a xed p ivot 38 carried by the backing plate, and having its outer end rounded to form a thrust surface engaging the rounded'end of a projection 40 formed on the web of the secondary shoe I8. The end of the rim of shoe I8 is shown extended past the end of the shoe at 42 and slotted, guidingly to embrace the outer end of the short radial lever 36.

Between its ends, the lever 36 carries a transverse pin 44 pivotally engaged by notched arms straddling lever 36 and formed on a member 46 having a central socket forming a bearing rotatably receiving the lower end of an adjusting member 48. The adjusting member 48 is adjustably threaded into a socket formed in an upper member 60 having a slotted upper end embracing a seat on the end of the web of shoe I6.

Shoes I6 and I8 are shown as being interchangeable, both of them having thrust portions 48, slotted extensions 42, and seats for receiving the slotted end of member 58. Parts 46, 48, and

60 jointly form an adjustable rigid thrust link connecting primary shoe I8 and the center of lever 36. The adjusting member 48 is shown with a star-wheel or serrated collar 52, by which it can conveniently be operated, and which is yieldingly locked in adjusted position by engagement with a spring 64 tensioned between the shoes and holding the shoes and their oating mechanical linkage connecting means inassembled position. m

It will be seen that, in forward braking with the drum turning counterclockwise in Figure l, the primary shoe transmits part of its thrust through link 60-48-46 and lever 36 to the iixed anchor post 38 carried by the backing plate, and 15 to that extent the shoe acts with a self-energizi ng or` wrapping effect like an anchored shoe. The remainder of the thrust of the primary shoe I6 is transmitted to the secondary shoe I8, which is anchored on the anchor post 24. 20

In reverse braking, with the drum turning clockwise, the -secondary shoe I8 acts, through lever 36 with a power multiplication of approximately two, on the anchored primary lshoe I6. The power multiplication is partially or wholly 25 compensated' for by the lessened mechanical advantage of the lever 32, and the additional movement of shoe I8 due to the movement of lever 36 being compensated for by the greater throw of the right-hand lug 34. :in

In the arrangement of Figures 4, 5, and 6, a primary shoe 60 is connected to a secondary shoe 62 through a mechanical linkage including an adjustable link comprising an adjusting member 64, having an operating star-wheel and right- 35 and-left threaded ends, threaded into socket members 66 and 68 slotted at their ends to embrace respectively the end of the web of shoe 60 and a short radial lever 18.'

Lever 10 is fulcrumed on its outer end on a 4f) fixed pivot 'I2 carried by the backing plate, and at its inner end is rounded for thrust engagement with the end of the web of the secondary shoe 62. Lever 10 may have welded to its upper end a pair of guide plates I4 guidingly embracing the 4,-, web of shoe 62. A spring I6 holds the parts together, and yieldingly locks the adjusting member 64 in adjusted position.

In this embodiment the shoes are urged against an anchor 'I8 by a main return spring 88 ten- 50 sioned between the shoes and an auxiliary spring 82 tensioned between the secondary shoe and the anchor. Theapplying means illustrated is of the iluid type, being in its details adapted for hydraulic rather than air or vacuum operation 55 but in principle suited for either. It includes a stationary double-diameter cylinder 84 bolted or otherwise secured to the backing plate between the ends of the shoes and-having the usual communication through a flexible conduit (not 60 shown) with the hydraulic lines on the chassis frame.

Within the left end of the conduit is a largediameter piston 66, faced with a rubber cup packing 88. The piston 86 has a piston rod 8l, 65 passing through a flexible rubber boot 82 mounted on the end of the cylinder, and notched at its end to embrace a seat formed on the web of the primary shoe 60.

Within the right or small-diameter end of the 70 cylinder is arranged a smaller piston 84, faced by a rubber sealing cup 86 which, with cup 88, is held in place by a spring 88. Piston 84 has a piston rod |00, passing through another boot 82, and notched at its end to embrace a seat formed 75 on the end of the web of the secondary shoe 62.

With this arrangement, in forward braking and with shoe 62 anchored, the forcing of a given quantity of liquid into cylinder 84 acts on piston 86 with a high mechanical advantage (due to its large area) and a relatively short stroke. The forcing of the same quantity of liquid into the cylinder in reverse braking, when shoe 60 is anchored, acts with a lesser mechanical advantage but greater stroke on the smaller piston 94.

I prefer to utilize in this brake, also, a mechanical connection from the usual hand emergency brake lever, including a cable |02 housed exteriorly of the brake in a flexible Bowden conduit, and which' passes through the backing plate and is connected to the end of a relatively long auxiliary floating applying lever |04. Lever |04 is pivoted to the end of the secondary shoe at |06, and has between its ends a connection such as a rigid thrust link |08 pivoted thereto at one end, and which is arranged below and parallel to the cylinder 84. At its opposite end the link |08 may be slotted to vembrace a seat formed on the web of the shoe 60, being provided if desired with a light anti-rattle spring ||0 compressed between the shoe web and a shoulder on the link |08.

In the modification of Figures 7, 8, and 9, the brake has both fluid applying means (preferably with an auxiliary mechanical emergency applying linkage the same as in Figure 4), and fluid (hydraulic) connecting means between the unanchored ends of the shoes.

The illustrated embodiment includes a pri' mary shoe ||2 and a secondary shoe ||4, each having an anchor. ||6 carried by the backing plate and arranged in a lost motion slot H8 formed in the shoe web. The shoes are applied, against the resistance of an inclined return spring |20, by uidmeans shown as including a double-diameter hydraulic cylinder |22 bolted to the backing plate and having therein alarge piston |24 in direct thrust engagement with the l rounded end of the web of the primary shoe H2, and a smaller piston |26 similarly engaging the rounded end of the web of shoe H6. Shoes ||2 and ||4 are shown as being identical ,and interchangeable. Cylinder |22 has a connection |28, the details of which are shown in Figure 8, leading to its uppermost point from the hydraulic system on the chassis.

An auxiliary hydraulic line |30 leads' from the lowermost point of the cylinder |22, and communicates with an intake passage |32 (Figure 9) of a connecting double-diameter cylinder |36 mounted on the backing plate between the lower ends of the shoes. Cylinder |30 hasarranged therein a large piston |36 in direct thrust engagement with the rounded end of the web of the primary shoe H2, and a smaller piston |30 in similar engagement with the secondary shoe llt. The parts are all held in assembled relationship by a spring |40 tensioned between the shoes, a pair of the stops 26 being used to determine the released positions of the shoes. In the same Way as in the applying means, the large piston |36 has a relatively short throw, and a relatively high mechanical'advantage (or leverage or power factor), whereas the small piston |38 has a greater throw but a lesser mechanical advantage.

The cylinder is shown with a bleeder passage |42 at its uppermost point, having therein avalve seat and an enlarged threaded portion in which is threaded a bleeder plug |44 having at its end a solid conical valve adapted for sealing engagement with said seat, and having passages |46 therethrough for the bleeding of the cylinder when the plug is loosened.

The communication between connection and passage |32 is past a spring-held rubber-ball check valve V|48 which seals off all communication between the cylinder and the connection |30 as soon as any substantial pressure builds up in the cylinder. Before such pressure builds up, the pressure in line |30 can force liquid past the check valve to keep the cylinder full of liquid.

In Figure is shown a modification of the structure of Figure 9, intended for automatic adjustment of the brake to compensate for wear of the brake shoes. In this modification, the liquid enters through passages |50, forcing to the left a small sliding piston |52 faced at its ends with small rubber sealing cups which in effect form oppositely-opening check valves.

If the brake has worn unduly, the piston moves far enough to the left to uncover a cored by-pass |54 formed in the cylinder casting. By-pass |54 communicates, through an annular groove around piston |52 and grooves or other passages therefrom opening under the left-hand rubber cup, with passage |32, and additional liquid is therefore forced into the cylinder until the shoes engage the drum. The pressure then building up 'in the'cylinder shifts 'piston |52 to the right against a stop |56 (into the position shown in Figure l0), sealing off the passage |54 and also the connection |30.

In .both of the embodiments of Figures '7-10. primary shoe ||2 acts in forward braking to force the large piston |36 further into the cylinder, creating a considerable pressure in the liquid therein. Part of the thrust created by this pressure is taken by the cylinder itself, and to that extent the shoe ||2 acts like an anchored shoe. The remainder of the pressure is exerted on the small piston |38, and thence with a servo effect to the secondary shoe H6.

In reverse braking, shoe ||4 moves the pisto |38 to build up a pressure in the cylinder, which pressure acts on the larger area of` piston |36 to give a multiplied pressure on' the anchored primary shoe ||2.

In either forward or reverse braking, if the shoes have Worn beyond a predetermined clearance, during the initial stage of application of the brake when the pressure in conduit exceeds the pressure in the cylinder, the arrangement of Figure 10 will introduce into the cylinder sufficient additional liquid to compensate for the wear, piston 52 acting as a check valve to prevent subsequent escape of the additional liquid. Y

In the foregoing description,it should befundierstood that the illustrated hydraulic brakes are intended for use with a standard hydraulic system having a pressure of from four to eight pounds in the system even when the'brakes'are released.

While several illustrative embodiments have been described in detail, it is not my intention to limit the scope of the invention to those particular embodiments, or otherwise than by the terms of the appended claims.

I claim:

1 A brake having a rotatable drum, a pair of shoes within the drum, a pivoted lever having one part enga-ging the end of one of the shoes, an adjustable connection between another part of said lever and the adjacent end of the other shoe, a two-diameter cylinder between the opposite ends lau of said shoes, and a large and a small piston in said cylinder arranged to act on said shoes respectively, the small piston acting onl the shoe engaged by said lever and the large piston acting 5 on the shoe engaged by the adjustable connection. 2. A brake having a rotatable drum, a pair of shoes within the drum, a pivoted lever having one part acting on the end of one of the shoes and having a different part acting on the adjacent lo end of the other shoe, the action on the two shoes being at different leverages, a two-diameter cylinder between the opposite ends of said shoes, and a large and a small piston in said cylinder arranged to act on said shoes respectively, the small 15 piston acting on the shoe engaged by the part of said lever furthest from its fulcrum.

3. A brake comprising a pair of shoes, a lever fulcrumedat one end and having its other end acting on the end of one of the shoes, an adjust- 20 able connection between an intermediate part of the leverand the adjacent end of the other shoe,

a two-diameter cylinder between the other ends of the shoes, a large and a small piston in said cylinder acting on said shoes respectively, the 25 small piston acting on the shoe which engages the end of the lever.

4. A brake comprising a pair of shoes, a lever fulcrumed at one end and having its other end acting on the end of one of the shoes andv having 30 an intermediate part acting on the adjacent end of the other shoe, a two-diameter cylinder between the other ends of the shoes, a large and a small piston in said cylinder, acting on said shoes respectively, the small piston acting" on the 35 shoe which engages the end of the lever.

5. A brake comprising a pair of shoes, a lever fulcrumed at one end and having its other end acting on the end of one of .the shoes and having an intermediate part acting on the adjacent end of the other shoe, a two-diameter cylinder between the other ends of the shoes, a large and a small piston in said cylinder acting on said shoes respectively, the small piston acting on the shoe which engages the end of the lever, a relatively 45 long auxiliary operating lever pivoted to one of the shoes adjacent its piston end, a connection from said lever to the other shoe adjacent and paralleling said cylinder, and an operating cable adjacent said first level and connected to said long lever.

6.` A brake having a pair oi connected shoes, an anchor between the ends of the shoes, a twodiameter piston adjacent said anchor, a large and a small piston in said cylinder and acting on 55 said shoes respectively, an auxiliary lever pivoted to one of the shoes adjacent the anchor and a connection from said lever to the other shoe adjacent and paralieling said cylinder.

7. A brake having a pair of connected shoes, anchorage means engaging the ends of the shoes, a two-diameter piston adjacent said means, a large and a small piston in said cylinder and acting on said shoes respectively, an auxiliary lever pivoted to one of the shoes adjacent the-anchor. 65 and a connection from said lever to the other shoe adjacent and paralleling said cylinder.

8. A brake comprising a drum, a pair of shoes, a two-diameter piston between the ends of the shoes at one side of the drum, a large and a small piston in the cylinder acting on said shoes respectively. and means between the ends of the shoes at the other side of the drum and acting on one shoe with one mechanical advantage and on the other shoe with a different mechanical u advantage.

9. A brake comprising a drum, a pair of shoes, a two-diameter piston between the ends of the shoes at one side of the drum. a large and a small piston in the cylinder acting on said shoes respectively, and means including another twodiame'ter cylinder and a large and a small piston therein between the ends of the shoes at the other side of the drum, the large piston acting on one shoe with one mechanical advantage and the small piston acting on the other shoe with a different mechanical advantage.

10. A brake comprising a drum, a pair of shoes. a -two-diameter piston'between the ends of the shoes at one side of the drum, a large and a small piston in the cylinder acting-on said shoes respectively, and means including another twodiameter cylinder and a large and a small piston therein between the ends of the shoes at the other side of the drum, the large piston acting on one shoe with one mechanical advantage and the small piston acting on the other shoe with a dii'- ferent mechanical advantage, both of the small pistons being arranged to act on the same shoe.

ll. A brake comprising a drum, a pair of shoes, a two-diameter piston between the ends of the shoes at one side of the drum, a large and a small piston in the cylinder acting on said shoes respectively, and means including another twodiameter cylinder and a large and a small piston therein between the ends of they shoes at the other side of the drum, the large piston acting on one shoe with one mechanical advantage and the small piston acting on the other shoe with a different mechanical advantage, together with anchorage means for the ends of the shoes.

12. A brake comprising a pair of floating shoes, an anchor for the end of the shoe, two iluidpower applying means having iluid connections and acting on the adjacent ends of the shoes at opposite sides of the brake, one of said means being cut off from the connections when the brake is applied, and an auxiliary mechanical applying linkage acting on the two shoes.

13. A brake comprising primary and secondary -tloating shoes, a backing plate, applying and anchoring means acting on the shoes at one side ofthe brake, and fluid-pressure connections between the ends of the shoes at the other side of Ithe brake arranged to transmit part of the thrust of the primary shoe to the backing plate and the remainder of the thrust to the secondary shoe.

14. A brake comprising primary and secondary oating shoes, a backing plate, applying and anchoring means acting on the shoes at one side of the brake, and fluid-pressure connections between the ends of the shoes at the other side of the brake arranged to transmit part of the thrust of the primary shoe to the backing plate and the remainder of the thrust to the secondary shoe, said connections including an adjustment' compensating for wear of the brake shoes. 4

15. A brake comprising primary and secondary iloating shoes, a backing plate, applying and anchoring means acting on the shoes at one side of the brake, and fluid-pressure connections between the ends of the shoes at the other side of the brake arranged to transmit part of the thrust of the primary shoe to the backing plate and the remainder of the thrust to the secondary shoe.

said connections including a self-filling cylinder automatically compensating for wear of the brake shoes.

. 16. A brake comprising a pair of shoes. a stationary cylinder between the ends of the shoes which has two diameters and which is cut oil from all outside connections at least when the brake is applied, a large piston in the cylinder acted on by one shoe, and a small piston in the cylinder acting on the other shoe, part of the thrust of said one shoe being transmitted by the large piston to the cylinder and the remainder through the small piston to said other shoe.

17. A brake comprising a pair of shoes, a stationary cylinder between the ends of the shoes which has two dimeters and which is cut oi from all outside connections when the 'brake is applied, a large piston in the cylinder acted on by one shoe, a small piston in the cylinder acting on the other shoe, part of the thrust of said one shoe being transmitted by the large piston to the cylinder and the remainder through the small piston to said other shoe, and outside fluid connections communicating with the cylinder when the brake is released and replenishing the iiuid therein.

18. A brake comprising a pair .of shoes, a stationary cylinder between the endslof the shoes which has two diameters and which is cut 01T from all outside connections when vthe brake is applied, a large piston in the cylinder acted on by one shoe, a small piston in the cylinder acting on the other shoe, part of the thrust of said one shoe being transmitted by the large piston to the cylinder and the remainder through the small piston to said other shoe, and outside iluid connections communicating with the cylinder through a check valve when the brake is released and automatically replenishing the fluid therein.

19. A b-rake comprising a pair of shoes, a stationary cylinder; between the ends of the shoes which has two diameters and which is out off from all outside connections at least when the brake is applied, a large piston in the cylinder acted on by one shoe, and a small piston in the cylinder acting onthe other shoe, part of the thrust vof said one shoe being transmitted by the large piston to the cylinder and the remainder through the small piston to said other shoe, together with means automatically operated during the application of the brake to vary the quantity of liquid in the cylinder to limit the release movement of the shoes to a predetermined clearance regardless of wear.

20. A brake comprising shiftable-anchorage primary and secondary shoes, anchorage means for said shoes at one side of the brake, a brake backing plate carrying the anchorage means, means carried by the backing plate at the other side of the brake and acted on in forward braking by the primary shoe to transmit part of its thrust to the backing plate and the remainder to the secondary shoe and acted on in reverse braking by the secondary shoe to transmit a multiplied thrust to the primary shoe, and applying means at the rst side of the brake acting on said shoes and having a greater mechanical advantage but a lesser throw in its action on the primary shoe than in its action on the secondary shoe.

21. A brake comprising shiftable-anchorage primary and secondary shoes, anchorage means for said shoes at one side of the brake, a brake backing plate carrying the anchorage means, a mechanical linkage carried by the backing plate at the other side of the brake and acted on in forward braking by the primary shoe to transmit part of its thrust to the backing plate and the remainder to the secondary shoe and acted on in reverse braking by the secondary shoe to transmit a multiplied thrust to the primary shoe, and applying means at the rst side of the brake including another mechanical linkage acting on said shoes and havinga greater mechanical advantage but a lesser throw in its action on the primary shoe than in its action on the secondary shoe.

22. A brake comprising a pairof floating shoes, two fluid power ap-plying means acting on the adjacent ends of the shoes at opposite sides of the brake, one of which cylinders includes means for applying the shoes acting on oneyshoe with a different force from the force with which it acts on the other, anchorage means for the ends of the shoes adjacent one of the fluid power applying means, and an auxiliary mechanical applying linkage acting on the two shoes, said linkage comprising a lever pivoted to one of the shoes adjacent the anchorage means, and a connection from said lever tothe other shoe adjacent and paralleling said one uid power applying means.

23. A brake comprising primary and secondary shoes; a backing plate; applying and anchoring means acting on the shoes at one Aside of the brake; and means at the other side of the brake comprising a threaded screw rotatably connected at one end to one of the shoes, and a lever to an intermediate portion of which the other end of the threaded screw is rotatably connected and which bears at one end on one end of the other shoe, and at the other end on the backing plate, fortransmitting part of the thrust of the primary shoe to the backing plate and the remainder of the thrust to the secondary shoe.

24. A brake comprising a drum, a pair of shoes, a two-diameter piston between the ends of the shoesv at one side of the drum, a large and a small piston in the cylinder acting on said shoes respectively, means including another twodiameter cylinder and a large and a small piston therein between the ends of the shoes at the other side of the drum, the large piston acting on one shoe with one force and the small piston acting on the other shoe with a different force for applying said shoes hydraulically, anchorage means for the ends of the shoes, and means for applying said shoes mechanically.

25. A brake comprising a drum, a pair of shoes, a two-diameter piston between the ends of the shoes at one side of the drum, a large and a small piston in the cylinder acting on said shoes respectively, means including another two-diameter cylinder and a large and a small piston therein between the endsof the shoes at the other side of the drum, the large piston acting on one shoe with one force and the small piston acting on the other shoe with a different force for applying said shoes hydraulically, anchorage means for 'the ends of the shoes, and means for applying said shoes mechanically, one with a greater force than the other.

26. A brake comprising a drum, a pair of shoes, a two-diameter piston between the ends of the shoes at one side of the drum, a large and a small piston in the cylinder acting on said shoes i respectively, means including another two-diameter cylinder and a large and a small piston therein between the ends of the shoes at the other side of the drum, the large piston acting on one shoe with one force and the small piston acting on the other shoe with a diierent force for applying said shoes hydraulically, anchorage means for the ends of the shoes, and means GOmprising a lever and a link having one end of the link nearer to the drum than the vother end for applying said shoes mechanically.

27. A brake comprising a pair oi floating shoes, an anchor i'or the ends oi' the shoes. two fluid 5 power applying means having fluid connections and acting on the adjacent ends o!V the shoes at opposite sides of the brak'e, and means for applying iluid cutting of! one said applying means from theiiuid connection when the brake is l0 applied.

28. A brake comprising primary and secondary iioating shoes, a backing plate, applying and anchoring means acting on the shoes at one side of the brake, uid pressure connections between l5 the ends of the shoes at the other side of the brake arranged to transmit a thrust from the primary shoe to the secondary shoe in forward braking, an adjustment for compensating for wear ot the brake shoes included in said connections, and means for trapping iiuid in said uid pressure connections when the brakes are applied.

29. A brake comprising shiftable anchorage primary and secondary shoes, anchorage means for said shoes at one side of the brake, a brake backing plate carrying the anchorage means. means also carried by the backing plate at the other side of the brake for transmitting thrust from the primary shoe to the secondary shoe in one direction of braking and for transmitting thrust from the secondary shoe to the primary shoe in the other direction of braking, and applying means at the first side of the brake acting on said shoes and having a greater mechanical advantage but a lesser throw in its action on the primary shoe than in its action on the secondary shoe.

LUDGER E. LA BRIE.

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