US2246242A - Brake - Google Patents

Description

June 17., 1941.` w

T. P; CHASE 2,246,242

BRAKE Filed Sept. 16, 1939 :s sheets-sheet 1 -n-lilllm v1. .A

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BRAKE I 'Filed sept. 1e, l19:49 s sheets-sheet 2 zf a/ v5 75 75 N; 5l a5 :Tg y67 l Y 69' g; f 77. el 55' T; 2/ [kse I 65 l 15 ,if 7"/ j Z//// 54g. 5

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BRAKE Filed Sept. 16, 1939 3`Sheets-Sheet3 /rlllllllllllfllllq 111 Patented June 17, 1941 eral Motors Corporation, Detroit, Mich., acorporation of Delaware Application september 1s, 1939, sei-lai No. 298,205 4 Claims. (ci. iss-isz) This invention relates to friction brakes and 1s the result of eiorts to improve a brake of the kind having an assembly of shoes adapted to be spready into engagement with vthe ange of a rotating drum.

The object of the invention is to providev ashoe assembly such that each shoe is self-energized by the drum for each directionof' rotation whereby the greatest possible advantage may be taken of the energizing effect of the rotating drum-therebyY minimizing the manual eiort required to apply the brakes; so to arrange the spreading and an-4 choring mechanismv that the effective braking action of the shoes shall be substantially equalized y for each direction of drum rotation to the end of equalzing the wear of the friction 'faclngs and to avoid drum distortion; and to produce this equalized action by a servo eieot of one shoe upon the other in each direction of drum rotation without the need for a duplication of 'applying vmeans whereby the construction may becomparatively simple and inexpensive.

As anotherr object the invention aims to accomplish the major object with shoes so constructed f as to employ the well-known articulating link anchorage.

The accompanying drawings show embodiments of the invention.

In the drawings:

Figure 1 is a transverse section through the flange of a drum showing the shoe assembly in elevation.

Figure 2 is a section on line 2-2 of Fig. 1.

Figure 3 is a section on 3-3 Figure 1.l

Figure 4 is a view in elevation as seen from line 4--4 of Figure 3.

Figure 5 is a section on line 5-5 of Figure l.

Figure 6 is a section on line 6-6 of Figure l.

Figure 7 is a transverse section through the lower part of a drum flange showing a modiiied form.

Figure 8 is a section on line 8 8 oi' Figure 7.

Figure 9 is a transverse section through the lower part of the flange of a drum showing another modication.

Figure l0 is a section o n line lil-|0701 Figure 9.

Figure l1 is a transverse section through the upper part of the flange of a drum showing a modified form.

Figure 12 is a section on line I2-I2' of Figure il.

Referring to Figures 1 to 6, numeral il is used to designate a brake drum. It will be understood that in the environment for which the invention is more particularly intended, one such drum will be carried by each vehicle wheel. Mounted ad- Amitted to the `rear axle housing'orl't'ofthe 'fron ,g1 steering knuckle as the caseimayflbe; 2 4"Ihere may "cover at .IL transmits the tordueft'o. the ""cover'. As shownon the drawing-'s there are twdshoes'u I9 and .2l having webs I9'andfzi'zaand'flanges jacent `the but not forirotatinji-s''a cover plate I3 which also serves as the mediumthrough which the brake torquefroxnlthe shoes 'fis trans be a torque plate I5 betweerithe bottoniifo'ffthel-` drum and the drum -cover as shown in/iiguresijf and 3.k When sucha .torqueplat isus'ed''i't'takes I' the torqueidiruectly and,f'bein'g fastenedto-`thef provided with friction Ia'cings 23 to nange of the drumjas usual.

The objects, of thisiinvention `are'attainfedby the use` of a ysingle motory unit. 'This' ismarkedfiv" and is secured to` the vcover 'between' on'epati'rf'oi adjacent ends Yof the shoes. 'The 'motor 'unit' l shown is the so-calledlwheel-cylinder-"oiga con-l ventional hydraulic system. :It includes a cylinder 2, two pistons 29 and-29v each provided with a sealing cup 3|. Fluid frornthe master'cylinder is admitted to the space between the. two pistons.

Between the two pistonsis a spring 33 to hold the cups 3| against the pistons.. At `vone end ofthe cylinder. Threaded to the disk 35 is a plunger 39 having a forked end engagingthe web I9. The other piston 29' has asocket 4I to receive the f rounded end 43 of a link 45 pivoted' to shoe 2| at 4l. The link is formed from two plates' 45 and 45" of which plate 45'? continues beyond the pivot 4l and carries a pin 49 extending through a somewhat enlarged opening "5I, in the` web 2|'. A spring 53 surrounds the pin and presses the plate 45'A frictionally against the web 2 I By this construction the angular relation between the shoe and the link 45 may vary to `obtain the`most eiective irictional engagement between the shoe and the drum flange without the occurrence of undesired rotation of the links at 4l. A spring 55 is terminally connected to the shoes I9 and 2l to bias the assembly to its released position. Other springs 5l and 59 connect the shoes tothe torque plate, these springsv being located near the other pair of shoe ends. It will be noted-that by the rotation of disk 35 adjustment is provided to accommodate the lining wear of kshoe I9. 'I'he disk 35 by its engagement with the end of cylinder 21 limits the release movement of the shoe toward the cylinder whereby the cylinder becomes a torque receiving abutment. In a similar way piston 279' has an annular ange 29 which may .so applied to the link pin 1I engaging the end of slot el and apart actsfss aservo force `to 'apply'l shoe i! which, 75

engage the end of cylinder 21 for a like purpose. Torque plate il has three elongated openings in the region adjacent the pair of shoe ends relmote from cylinder 21. These are radially spaced and are marked Il. Il and Il respectively. A 5

pin l1 extend'sthrough Il. Onthesides of torque plate il are links Il. It supported on pin t1. Rotatably supported by links II' are pins 1| and 13 which pass through torque plate openings Il and II respectively. Other l0 slots 11 and 1I. the registering slots 11 openl5 ing toward shoe I while the slots ll open toward shoe 2l. Retainer plates Il, Il' arealso carried by pins l1 and 18. 'Ihese plates cover the slots and are held in piace by the heads of the pins and by fastening means such as snap rings Il. The several links and plates constitute a lever operable for a purpose to be explained.

A pair of plates Il, Il' form an articulating link for shoe II. These plates lie on opposite sides oi' the web of the shoe and are pivoted. 25 thereto by a pin l1. Near the end of the shoe is a spring device comprising a spring surrounding a pin Il, the device functioning to permit a limited swinging of the linkageresisted when so applied, is additionally energised by the rotating drum. This reverstbilityin action is made possible by the oating support of the 'lever between the shoes. The specific structure of this lever is of importance. It the articulating llnksattheendsoftheshoesweretoengaga the links 1l and 1l' at distances from the-ad- Jacentpinsgreaterthantheradiusofthesepins the pins would obviously need a greater spacing than in the arrangement to obtain the desired leverage. By the arrangement illustrated it is possible to secure the desired ratio of lever armswithalevernottoogreatinlengthtobe installed in the conventional brake. It will be seen from Figure 3 andligure that the linkage ss. ss'straddles the end 'orpln 1| at adistance from its axis intersects the linkage thecenteroi'pinli lessthantheradiusthereof. This is made possible by the association of links Il and 1l. In the'case of linkage l2 the forks also 'engage links 18,15' but engge the links in the plane of the reduoedparts 1I.; oi the pin 1I and in this case. the samerelatbn prevails relative to the radius of the pinll.

Inl'lgures'l andisshownaseeon'dandsimplined form which, being simpler. may be regarded as apreferred embodiment.' Inthese the drum is marked lli and numerals iis and I2I- designatethe shoes. 'Ihe backing piatevii by friction between the web and the linkage.l The so is vformed as iin Figure 8 andan anchor plate ill'at its is shaped as shown by ends ci' link It and Il' are tapered and seat in'- the dared slots 11 as best shown by Figure 4, Similarly seated in slots 1l are the furcations of a thrust member l2." A stem Il is seated in 'an opeling of member l2. It is provided with a notched annulus Il and its other endis threadedto engage a threaded openingll in a link II pivoted to the web 2i' of shoe 2| at lli.

When the vehicle is at restand the brake not applied. the springs sl, s1 and ls hold the mL shoes `away from the drum. Disk II and flange 20"v determine the release position at the wheel cylinder end of the shoes and the end walls of slots I8 and Il determine the corresponding position at the other ends of the shoes. The forces 5- exerted by spring l1 and II are applied to the iioating link means 1I and 15' constitute a couplel to hold the parts in the position shown in Figure l. If the brake is applied while the vehicle is standing the linkage Il., 8l' for one shoe 50 .and l2 for the other constitute the anchoring means and the two shoes are spread apart each being equally eii'ective to holdthe car against rolling.` If on the other hand the vehicle is moving and the drum rotating counterclockwise (Figure 1-) the pressure applied aty 39 to shoe il` is supplemented bythe self-energizing eirect upon shoe Il nfthe rotating drum. The engagement of pin 1lwith thewall of theislot 'takes one Figure '1. plate H1 is' welded to the cover plate lil. I tqhol an axial-'aange Il! provided with an'elansated'openmg m. The openonevmarginalwali bent up as at' |23.

A pivot piaf-III is mountedfinvthe cover plate c lili and the lower portionV ofv the anchor yplate notched as at 4III on 1 notch are engaged by the furcations at-the' e`nd of a link l0.v Thelink" includes an int`e'rnally,"""` threaded socket I4I,'a stem il] threaded there-v in, the stem having .vnotehedrmg m 'and s' smooth surface extension III.l 'I'he stem III vis rotatably supported in a socket III having the .bifurcated end embracing the web of shoe l2l. Springs ill and Ill are attached to the shoes and to" the lanchor plate -Ill to hold the shoes in their brake released position. It .will be un'- derstood thatl thershoes are expanded by means part of .the Vforce so applied buifsince the force so at. their opposite pair. o adiacent ends as in port of the force which is applied to shoe 2| 65 when supplemented by the `self-energizing force applied by the drum to shoe 2i ,causes the brak ing eiiect of the two shoes to be substantially equal. In this way the whole drum are is used and-the required pedal pressure is reduced to a minimum. In the case of reversedrum' rotation the effect is substantially thesame. A part of J the pressure of the energized shoe v2i is anchored isa-short distancetous.wf..A

Figure 1. In this form of the invention, counter'ciockwise drum rotation causes the dium to supplement the pressure applied to shoe ill. 'I'he force derived from ythe wheel cylinder and the self-energization isltransmitted by the shoe in part to the abutment l!! and in part is transmitted to the secondary shoe through `theinstrumentality of the link i, mitted to the secondary shoe is supplemented'by the self-energizing eiIect of the drum, the secondary shoe anchoring as in Figure l at the end of the wheel cylinder or upon some other' convenient anchorage, and using preferably the wellknown articulating Thus by the use of VThe force transdate themselves to the outline of the drum exerting a maximum force at the mid-points of theirl arcs. the presence of the anchorage for each and the 4resistance offered to drum rotation is substantially the same in the case of each shoe, this being accomplished by properly determining the lengths of the arms of lever |21. Upon reverse rotation of the drum the brake operates in substantially the same way. It will be seen that this embodiment of the invention so spaces the iulc'ra |23 and |26 that it becomes unnecessary to resort to the expedient shown by'Figure i where the ends. of pin 1| are overlapped by the articulating links 2l, Il'. 'Ihe construction is thus greatly simplified.

Also each shoe is self-energizing due to" Figures-,.9 and 1o snow a simuarbut slightly different form. In this embodiment numeral ry,21| is used to designate the drum and k212 the cover. 'I'he anchor plate is made up of two laminae 2N, 2li' in close contact with each other in the region where they are secured tothe cover but spaced at the lower end of the drum where they straddle the lever 2I1. A spacer 2|9 is secured by fastening means 22 between the extremities of plates 2id and 2|5' and this spacer is formed with an elongated slot 222 which receives the end of lever-2H. At its upper end thedever has an elongated slot 225 embracing a pin 221 supported by the laminae 2|5, 2|5'. The lever 211 is formed on its opposite faces with recesses, one near the lower end and the other near the upper end. The recesses receive the ends of adjustable links 222 and 22| connested to the shoes 2,22 and 2li. springs 221, 222 connect the shoes to the anchor plate and bias the parts tothe position shown in Figure 9. Esch articulating link is composed of three parts, a shoe engaging Dart 24| having a biiurcated end and a pivot pin 243. a stem 2l! hav- .ing one end unthreaded and received within a pocket of part 24| and a lthreaded end adjustsbly received with the third part, a socket .2, *which is seated. as 'stated above. in a recess of the lever. The operation of the parts described will be understood from the description of the embodiment illustrated in Figure '1.

It will be observed that in Figure 9 there ls an adjustment in each of the shoe articulating links 229 and 23|, this arrangement diiering from the embodiment shown in Figure 'I in which but one of the articulating links is made adjustable. 4When the articulating link for one shoe only is adustable a second 'adjustment is provided for the other shoe at its end remote from the adjustment for the nrst shoe.' This construction is shown in Figure 1, the second adjust- 'ment being seen at 32. The construction shown by Figure 9 provides another use for the laminated anchor plate. Where. as in Figure 1, the

ends of the `wheel cylinder take the brake torquef the cylinder must necessarily be quite rigid. It is possible to make a wheel cylinder ofl sheet metal insofar as its hinction of applying the brake is concerned, especialiy in a brake where the applied force may be low as in the present brake where self-energization is` used to supplement the applied force.

In Figures 11 and l2 there has sheet metal wheel cylinder to ser with an anchorageior the shoes inrispende t ci the cylindex'. The anchorage is in he s. pin 251 een shown a carried by the spaced upper ends 253 25T-of the anchor plates. By this construction the thrust of one or the other of the brake shoes is transmitted directly to the pin 25| and is not transmitted to the ends of the cylinder. It is therefore possible to make the cylinder of light weight material. Inasmuch as the cylinder does 4not receive the brake torque a simplified form for its support is made possible. The plates 253 and 253' are cut out as at 255 and oneither side of the opening so formed the plates are bowed away from each other to form cooperating pockets 251 and 25| within which the sheet metal cylinder 26| is mounted. This cylinder carries pistons 263 and plungers 265 as before.

Within the opening 255 the cylinder is embraced by a block 251.A The block has an opening 269 registering with an opening in the cylinder and also communicating with a conduit 21| from the master cylinder. A bleed plug is shown at 212. The pin 25| is formed with an axial extension 216 to which the ends of springs 215' and 211 are connected, the other ends of these springs being connected to the shoes. By this means the shoes 219 and 28| are normally heldin contact with the anchor pin' 25 I. While this arrangement for supporting the cylinder and providing the adjacent anchor pin for the shoes may be used with other arrangements at the opposite ends of the shoes it is particularly useful with an arrangement corresponding to that of Figure 9 since that, form makes use of a two-part anchor plate.

I claim: f 1. In a brake. a drum, a pair of shoes friction- -ally to engage the drum. spreading means beact as a servo device to actuate the other shoe,

said mechanism comprising a lever positioned between the second pair of adjacent ends. two pivot members about either of which said lever may rotate. a link pivoted to each shoe, said links engaging said lever. one near each pivot member and at a distance from the axis oi said pivot member less than the radius thereof.

2. In a brake. a drum, a pair of shoes, a tlxed anchorage spreading means between one pair of shoe ends, said anchorage having radially spaced slots, first and second pins in said slots, a lever including first links rotatably mounted on said pins, one on each side of the anchorage. second links overlying said iir'st links and the ends of one of said pins, said second links being rotatably supported on reduced ends of the other of said pins,.other pin and slot connections between said rst and second links andthe anchorage, said Second links having oppositely directed slots between said flrst and second pins, and articulating links pivoted to said shoes and engaging in said f slots. o

with retainer links mounted .alongside sec-.

ond links vto close the siete therein.

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