US2492934A - Internally expanding brake - Google Patents

Description

Dec. 27, 1949 a E'. HOUSE 2,492,934

INTERNALLY EXPANDING BRAKE 3 Shets-Sheet 1 Filed Feb. 5, 1945 A TTP/VEY Dec. 27, 1949 B. E. HOUSE 2,492,934

INTERNALLY EXPANDING BRAKE Filed Feb. 5, 1945 3 Sheets-Sheet 2 Dec.. 27, R949 B. E. HOUSE 2,492,934

INTERNALLY EXPANDING BRAKE 3 Sheets-Sheet 'o' Filed Feb. 5, 1945 Patented Dec. 27, 1949 INTERNALLY EXPAN DIN G BRAKE Bryan E. House, South Bend, Ind., assigner to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application February 5, 1945, Serial N o. 576,317

(Cl. 18S-152) 8 Claims.

This invention relates to brakes, and particularly to internal shoe drum-type brakes wherein a plurality of shoes are individually shiftable to anchor at either end depending upon the direction of drum rotation.

An object of the present invention is to provide an improved brake of this type, wherein a single hydraulic cylinder suffices for exerting applying force on the brake shoes.

A further object of the present invention is to provide a brake assembly having the advantage of the preceding paragraph and additionally arranged in such a way as to minimize deflections in the shoe actuating linkage.

A further object of the present invention is to provide a brake wherein the shoes are applied by a radially-acting force, without necessitating additional displacement of the applying mechanism to compensate for drum distortion.

A still further object of the present invention is to provide a simplified and inexpensive brake assembly.

Other objects and advantages of the present invention will become apparent during the course of the following description, reference being had therein to the accompanying drawings, wherein:

Figure 1 is a side elevation showing a brake assembly which incorporates my invention;

Figure 2 is a section taken on the line 2-2 of Figure 1;

Figure 3 is a view in perspective showing the lower end of the applying strut which acts on one of the shoes;

Figure 4 is a side elevationf showing a brake assembly which illustrates asecond version oi?l my invention, wherein the applying force is applied nearer one end of each shoe than the other, and the arrangement is such that the hydraulic applying cylinder may be ixed on the support member;

Figures 5, 6 and 7 are sectional views taken on the lines 5, 6-6 and respectively, of Figure 4;

Figure 8 is a side elevation showing a brake assembly which illustrates still another embodiment of my invention; and

Figure 9 is a sectional view taken on the line 9-9 of Figure 8.

Referring to Vthe vbrake assembly shown in Figures 1 to 3 inclusive, there are provided the usual vbrake drum having a cylindrical braking flange 22, and the usual support member or backing plate 24. Mounted on support member 24 are anchor members 26 and 28, the latter of which is combined with adjusting means for the shoes, similar to the adjusting means disclosed in House application Serial No. 442,407, led May 11, 1942, now Patent No. 2,381,746, issued `July 3l, 1945.

Two shoes 30 and 32, of conventional T-section construction, are provided, each of which is shiftable to anchor at either end depending upon the direction of drum rotation at the time the shoes are moved into contact with the drum. If the drum is moving in the direction indicated by the arrow A in Figure 1, shoe 30 will anchor at 28, and shoe 32 will anchor at 26. On the other hand, if the drum is rotating in the opposite, or clockwise direction, shoe 30 will anchor at 26. and shoe 32 will anchor at 28. It will be noted that each end of each shoe has sliding contact with the respective anchor thereby permitting full shoeto-drum contact during both application and adjustment of the shoes.

The shoes are normally retained in released position, or in other words, in contact with .the anchors 26 and 28, by means of spring 34 which interconnects the shoes at the left end thereof, and by means of two springs 36, each of which connects one shoe to anchor member 26.

The applying mechanism for the shoes comprises a hydraulic cylinder 38 and a thrust element or strut which extends diametrically across the brake assembly, exceptior the fact that an opening 42 is provided at the center thereof to allow clearance over the Wheel hub orl axle of the vehicle on which the brake is mounted.

The strut 40, which is preferably formed as a,

. vent relative sliding movement between member 40 and shoe 32. In order to retain member 40in' proper lateral position, the lower end thereof may be formed with projections which are bent out of the normal plane of said member 40', in order to embrace the web of shoe 32. The structure in the present case, which is shown particularly clearly in Figures 2 and 3, may include a center projection 48 extending on one side of the web of shoe 32 and end projections 50 and 52 extending on the other side of the web of shoe 32. The projection 48 may be formed by cutting along the- lines 44, 54 and 56, and bending at 58 and 60 away from the the normal plane of strut 40. The projections and 52 are formed by'cutting along the lines 82 and 64 and bending at G6 and 68 away from `the normal plane of strut 40, but in the opposite direction from projection 48. An opening 10 may be provided in projection 48 topermit the stem- 12 of a hold-down. member to extend therethrough. The head 14 of the hold-down member supports a vcompression spring 10 which acts against a oating collar 'I8 to urge the rim of shoe 32 against the backing plate 24. A similar holddown arrangement may be provided for shoe 40.

The hydraulic cylinder 38 includes two members which are adapted to be spread apart to move shoes 30 and 32 outwardly into contact with the drum.Y In the illustrated form, the cup shapedv cylinder member 80 acts directly against shoe 30, a pivotal connection between the two being provided at 82, similar to that provided at 44 in the case of shoe 32. In order to guide the cup shaped member 80, extensions 84 are provided thereon to embrace between them the web of shoe 30. Reciprocable in cylinder is a piston 06 which is slotted to receive projection 08 formed on the upper end of strut 40. and which bears against strut 40 at 90 in order that it may exert force therethrough to move shoe 32 into contact with the drum.

Admission of iluid under pressure to chamber 02 exerts a spreading force between cylinder 80 and piston 86, moving them apart substantially along a radius of the brake assembly to exert simultaneously radially outward force on shoes 30 and 32, the force on shoe 32 being transmitted through strut 40. In this connection it will be noted that the contact of strut 40 with shoe 32 is located diametrically opposite the contact point of cylinder 80 with shoe 30, thereby providing Adirect outward thrust of the shoes along a diameter of the brake assembly. Y With this arrangement, the operating characteristics of the shoes are the same, including the effectiveness, and the wear pattern. Because the force is transmitted across the brake assembly by means of direct compression acting through strut 40, the deflection of this operating member is minimized, thereby tending to avoid excessive displacement requirements in the hydraulic pressure system.

Figures 4 to 7 inclusive show a preferred version of my invention, which diifers from the preceding embodiment in several respects.

In the brake assembly shown in Figures 1 to 3 the hydraulic applying means is floating, i. e., it is not xed to support member 24, and it, together with the strut 40, is permitted tooat with the brake shoes. This has the disadvantage of causing exurein the tube or other connection which transmits uid from the master cylinder to the hydraulic motor which spreads the shoes. Where rubber tubing is used, the ilexure is not an important disadvantage, but with metallic tubing, which is preferred in many cases, exing of the tube is to be avoided if possible. Accordingly, in the brake shown in Figures 4 to 7 inclusive, I have provided a hydraulic motor 94 which is secured to the support member 24 (see Figure '1). This may be conveniently and simply accomplished by providing a boss 96 on hydraulic motor 94 having an opening 98 into which is forced a tapered cotter pin |00, said pin bearing at one side against boss 96 of the hydraulic motor and at the other side against the surface of support member 24. Pistons |02 and |04 are reciprocable in hydraulic motor 94, and are adapted to be spread apart substantially along the radius of the brake assembly by means of fluid under pressure admitted to chamber |06. In order that shoe a may move circumferentially with respect to the hydraulic motor 94. the projection |00 on shoe 30a which contacts piston |02 is permitted to slide along the outer surface of said piston. 'Ihe yoke-like strut 40a which is arranged to transmit force from piston |04 to a point diametrically across the brake assembly from projection |08, is provided with a projection ||0 which has pivotal contact with piston A |04, thus permitting the lower end of strut 40a to move with shoe 32a. Said strut, as before. contacts the web of shoes 32a at 44a,` and is provided with arms 48a, 50a and 52a which extend on opposite sides of the web of shoe 32a. With this arrangement the shoes 30a and 32a are freely shiftable to anchor at either end, while at the same time the hydraulic motor 04 is secured to the backing plate, and exure of the tube w" 'ch carries the operating fluid is unnecessary. i.. will be noted that the contact points of the hydraulic motor 94 and of the lower end of strut 40a with the respective shoes are located nearer one end of the shoes than the other. It has been found that, with the force against the shoes being applied exactly at the center thereof the lining wear along the length of the shoes is uneven. This rcsults from the fact that the greatest pressure between the shoe and the drum is along the surface between the point of application of the actuating force and the point at which the shoe anchors. Since the great majority of vehicle stops are made when the vehicle is traveling in a forward direction, the shoes tend to wear to a greater extent near the end which anchors when the vehicle is moving forward, than they do near the end which anchors when the vehicle is moving rearward. In order to overcome this tendency, and to equalize the wear along the entire length of each shoe, I have moved the point of application of force to the shoe webs nearer to the end of the shoe which anchors in reverse than to the end which anchors during forward movement. In other words, since the arrow B shown in Fig. 4 indicates the forward rotation of the vehicle wheel, the hydraulic motor 94 is spaced away from the vertical center line of the brake assembly toward the right end of shoe'30a, while the point of contact between strut 40a and shoe 32a is moved an equal distance toward the left end of shoe 32a. I have found that the best results are obtained by moving the diameter along which the applying force acts approximately 15 away from the center line of the brake assembly. or in other words, Aby ,providing an angle of approximately 15 between'the diameter on which the shoe actuatingforce is applied and the line drawn through the center of the brake shoes. This causes a certain differential in the brake effectiveness between forward braking and rear ward braking, the brakes being somewhat more effective when the vehicle is going forward than when it is in reverse. This result is desirable, since the more severe and more numerous stops are made when the vehicle is going for- Ward.

l A further advantage of applying radial force against each shoe at a point spaced from the center of the shoe is the reduction of necessary displacement of the shoe actuating means due to drum distortion. When the brakes are applied while .the vehicle is moving forward, the points of maximum outward drum distortion will be approximately as indicated by the arrows C and D. The points of maximum inward drum' distortion will be approximately as indicated by the arrows E and F. A point midway between arrows C and E and another point midway between arrows D and F will be the points at which the drum dimensions will remain normal. By applying the radial force at or near these normal" points the effects of drum distortion on the displacement required for forward braking are minimized or eliminated.

In addition to the hydraulic mechanism for normally applying the brake, a mechanical brake applying mechanism may be provided. This may include a lever ||2 lying next to the web of shoe 32a and having lugs ||4 and ||0 perpendicular to the plane of the lever and located on opposite sides of the anchor 26- When lever ||2 is moved in a clockwise direction, lug ||4 acts against shoe 32a and lug IIS acts against shoe 30a to spread the shoes at the right side of the brake assembly, while they remain anchored at the left side of the brake assembly, the operation being similar to that of the shoes in a "non-servo brake. Force may be exerted on the lever ||2 bypulling on cable H8, which is attached to the lower end of the lever by means of a knob |20 iixed to the cable and bearing against the abutment |22 on the lever.V

The adjusting mechanism, which is shown in section in Figures 5 and 6, may correspond substantially to that shown and described in Goepfrich and House application Serial No. 502,858, iiled September 18, 1943, now Patent No. 2,423',- 015, issued June 24, 1947. The particular arrangement which is substantially identical with the present adjusting mechanism is shown in Figures l to 9 of said application. Briey, the adjusting mechanism includes two polygons |24 which bear against the ends of the respective shoes 30a and 32a, and which are mounted on shafts |20. The shafts |26 extend through the backing plate 24, and, being polygonal in cross section, are prevented from undesired turning by complementarily-shaped sockets in the backing plate, a spring |20 being connected between the shafts |20 to retain themin contact with the inner edges |30 of the backing plate openings. A plate |32 may be used to retain the polygons |24 in position, and also to guide the ends of the shoes.

Figures 8 and 9 illustrate a further embodiment of my invention, which has certain advantages over either of the preceding versions. Pressure is transmitted from piston |02 in hydraulic motor 94 to the web of shoe 30h by means of a compression link |34 which has pivotal contact with piston |02 at |36 and which is forked at its upper end to receive the web of shoe 30h. Contact between the shoe web and the bottom-of the slot provided in member |34 between the forks is at |40, (as shown by the dotted lines), the shoe being permitted to move lengthwise relative to the stationary hydraulic motor by either sliding or pivotal movement at contact surface |40. As in the assembly of Figure 4, strut'member 40h 4has an extension ||0 which is in pivotal contact with piston |04 in the hydraulic motor. The strut member contacts shoe 32h at |42, the contact permitting pivotal movement of strut extension |44 withrespect to the web of shoe 32h, as the shoe moves to anchor at one end or the other. As before, the lower en d of strut 40h has offset arms which receive the web of 32h, and thereby guide the strut.

The uniformity in adjustment of the two shoes is provided by locating both adjustors |40 and |48 at the heel ends of the respective shoes, or, in other words, at the ends which anchor during forward movement of the vehicle. Note that the arrow G which indicates forward rotation is oppositely directed as compared with the arrows A and B of Figs. 1 and 4. Eachof the adjustors bears against an anchor member |50 which may 4the support member.

be `secured to support member 24 by means of a rivet head |52 (see Fig. 9) formed on the boss |04 of the anchor member which extends through an opening in support member 24. A reinforcement plate |50 may be provided adjacent each anchor member, said plate being spot welded to A locating nib |00 provided on the support .member extends into an opening |00 in the anchor member to prevent the same from turning about the axis of boss |04.' A spring |02 retains the selected face of each adjuster in contact with the anchor member.

The hydraulic motor 04 may be secured to support member 24 in the same manner as illus-v trated in Figure 7.

I'he emergency brake applying means may in' clude a lever |04 which contacts adjustor |40 at |00 and which contacts shoe 30h at |00. Force applied by' cable |10 tending to turn lever |04 in a eounterclockwise direction, exerts a spread@ ing force between the shoes at the left side of the brake assembly.

Two return springs |12 are connected between the shoes at opposite sides of the brake assembly.

to retain them normally in released position. Resilient hold-down devices |14 are provided for retaining the shoes inproper lateral position.

Although particular embodiments of my invention have been described, it will be understood by those skilled in the art that the object. of the invention may be attained by the use of constructions diii'erent in certain respects from those disclosed without departing from' the underlying principles of the invention. I therefore desire by the following claims to include within the scope of my invention all such variations and modifications by which substantially the results of my invention may be obtained through the use of substantially the same or equivalent means. l

I claim: l. For use in cooperation with a rotatable brake drum, a brake'comprising two T`section shoes which are individually shiftable to anchor at one end or Atheother depending upon the direction of tween the ends of one of the shoes 'Hand having oppositely disposed members which move radially apart under the iniiuence of fluid pressure, and a thrust member extending diametrically across the brake assembly from themotor to the oppo- 55 site shoe, said thrust member being constituted by a stamping having a portion which is co-planar with and which contacts the web of said opposite shoe, said stamping having integral ofl'set arms which embrace the web of said opposite shoe to guide the thrust member, one of said oppositely disposed members of the motor acting on the adjacent shoe to thrust the same against the drum, and the other of said members acting through the thrust member to move the opposite shoe against the drum.

2'. For use in cooperation with a rotatable brake drum, a brake comprising two T-se'ction shoes which are individually shiftable to anchor at one -end or the other depending upon the.` direction of drum rotation, fixed anchors at both of iiuid pressure, and a thrust member extending diametrically across the brake assembly from the motor to the opposite shoe, said thrust member being constituted by a stamping having a portion which is co-planar with and which contacts the web of said opposite shoe. said stamping having integral oiset arms which embrace the web of said opposite shoe to guide the thrust member. one of said oppositely disposed members oi' the motor acting on the adjacent shoe to thrust the same against the drum, and the other of said members acting through the thrust member to move the opposite shoe against the drum.

3. For use in cooperation with a rotatable brake drum, a brake comprising two shoes which are individually shiftable to anchor at one end or the other according to the direction of drum rotation, ilxed anchors at both ends of both shoes, each of said shoes extending substantially half the circumference of the drum. a hydraulic motor disposed within the drum between the ends of one of the shoes and having oppositely disposed members which move radially apart under the inuence of uid pressure, a thrust member extending diametrically across the brake assembly from the motor to the opposite shoe, one of said oppositely disposed members of the motor acting directly on the adjacent shoe to thrust the same against the drum, and the other of said members acting through the thrust member to move the opposite shoe against the drum, and auxiliary mechanical applying means located adjacent one of said iixed anchors and arranged to actdirectly on the shoes at one end thereof.

4. For use in cooperation with a rotatable brake drum, a brake comprising two shoes which are individually shiftable to anchor at one end or the other according to the direction of drum rotation, xed anchors at both ends of both shoes, each of said shoes extending substantially half the circumference of the drum, a hydraulic motor disposed within the drum between the ends of one of the shoes and having oppositely disposed members which move radially apart under the influence of fluid pressure, a thrust member extending diametrically across the brake assembly from the motor to the opposite shoe, one of said oppositely disposed members of the motor acting directly on the adjacent shoe to thrust the same against the drum, and the other of said members acting through the thrust member to move the opposite shoe against the drum, and auxiliary mechanical applying means adapted to spread the shoes at one end thereof, said mechanical applying means including a lever pivotally associated with one end of each shoe and a cable connected to the lever for rotating the same.

5. For use in cooperation with a rotatable brake drum, a brake comprising a non-rotatable support member, two shoes mounted on the support member which are'individually shiftable to anchor at one end or the other depending upon the direction of drum rotation. fixed anchors provided on the support member at both ends of both shoes, a hydraulic cylinder secured to the support member and disposed within the drum between the ends of one of the shoes, said cylinder having opposed pistons reciprocable therein which move radially apart under the influence of fluid pressure, a thrust member extending across the brake assembly and adapted to transmit force from one of the pistons to the more remote shoe, a short compression link adapted to transmit force from the other piston to the adjacent shoe, said thrust member actins on said remote shoe at a point approximately 8 diametrically opposite the point at which the compression link acts on the adjacent shoe, whereby pressure developed in the hydraulic cylinder simultaneously exerts a radial thrust against both of the shoes.

6. For use in cooperation with a rotatable brake drum, a brake comprising a non-rotatable support member, two shoes mounted on the support member which are individually shiftable to anchor at one end or the other depending upon the direction of drum rotation, xed anchors provided on the support member at both ends of both shoes, a hydraulic cylinder secured to the support member and disposed within the drum between the ends of one of the shoes. said cylinder having opposed pistons 'reciprocable therein which move radially apart under the inuence of iiuid pressure, a thrust member extending across the brake assembly and adapted to transmit force from one of the pistons to the more remote shoe, said thrust member having pivotal engagement at one end with said piston and having pivotal engagement at the other end with said shoe, a short compression link adapted to transmit force from the other piston to the adjacent shoe, said compression link being in pivotal engagement at one end with the respective piston and being in pivotal engagement at the other end with said adjacent shoe, said thrust member acting on said remote shoe at a point approximately diametrically opposite the point at which the compression link acts on the adjacent shoe, whereby pressure developed in the hydraulic cylinder simultaneously exerts a radial thrust against both of the shoes.

7. For use in cooperation with a rotatable brake drum, a brake comprising a non-rotatable support member, two shoes mounted on the support member which are individually shiftable to anchor at one end or the other depending upon the direction of drum rotation, fixed anchors provided on the support member at both ends of both shoes, a hydraulic cylinder secured to the support member and disposed within the drum between the ends of one of the shoes, said cylinder having opposed pistons reciprocable therein which move radially apart under the influence of iluid pressure, a thrust member extending across the brake assembly and adapted to transmit force from one of the pistons to the more remote shoe, said thrust member having pivotal engagement at one end with said piston and having both pivotal and sliding engagement at the other end with said shoe, a short compression link adapted to transmit force from the other piston to the adjacent shoe, said compression link being in pivotal engagement at one end with the respective piston and being in both pivotal and sliding engagement at the other end with said adjacent shoe, said thrust member acting on said remote shoe at a point approximately diametrically opposite the point at which the compression link acts on the adjacent shoe, whereby pressure developed in the hydraulic cylinder simultaneously exerts a radial thrust against both of the shoes.

8. For use in cooperation with a rotatable brake drum having a cylindrical braking surface, c brake comprising two arcuate shoes which form a substantially complete cylindrical surface facing the drum and which are individually shiftable to anchor at either end depending upon the direction of drum rotation at the time they contact the drum, a hydraulic motorpositioned l 9 l0 inside the brake drum and near one of the shoes, said motor having two' parts which may be ra- REFERENCES CITED y dially Spread apart, by fluid pressure, and a thrust The following references are of record in the member extending across the brake assembly me 0f thisl mirent:

and having pivotal vengagement; with the more UNITED STATES PATENTS remote shoewhereby it transmits force thereto from one of the parts of the hydraulic motor, the Number Name Date other part of the hydraulic motor having pivotal 1160921 Sanford Mar' 15 1927 engagement with the adjacent shoe, said thrust 2,381'746 Hmse Aug' 7 1945 member acting' on said opposite shoe at a point 10 4231,15 Goepfnch June 24 1947 diametrically opposite the point at vwhich said FOREIGN PATENTS other part of the hydraulic motor acts on the adjacent shoe, whereby pressure developed in the motor simultaneously exerts a radial thrust against both of the shoes. 15

BRYAN E. HOUSE.

Number Country Date 698,577 Germany Nov. 13, 1940

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