US2156794A - Braking mechanism - Google Patents

Description

May 2, 1939.

s. SCHNELL BRAKING MECHANISM 2 Sheets-Sheet 1 Filed Dec. 16, 1936 INVENTOR B STEVE SG-HNEL L ATTo MQ'Y May 2, 1939. s. SCHNELL BRAKING MECHANISM Filed Dec. 16,- 1936 2 Sheets-Sheet 2 w a W/M m c m m "I? a 5 wm mm x m Y 2,... w mm 6 a 7 Patented May 2, 1939 I I I 7 BRAKING MECHANISM Steve Schnell, St. Louis, Mo., assignor to Wagner Electric Corporation, St. Louis, Mo., a corporation of Delaware Application Decembcr16, 1936, Serial No. 116,048

12 Claims. (Cl. 188'-78) My invention relates to. vehicle brakes and I2 in the ends of the webs of the shoes are slightly more particularly to an improved means for actueccentric to the main portion of the pins which ating the brake shoes thereof into engagement are journaled in the backing plate, thus prowith the drum. viding for adjustments during the assembling 5 One of the objects of my invention .is to prooperation of the brake shoes. Also the portions 5 vide a brake shoe withan actuating member of anchor pins H and I5 cooperating with end extending between the shoe ends and capable of surfaces I0 and I4 of the Webs of the shoes are applying pressure to the ends only of the shoe eccentric with respect to the main portion of the while at the same time permitting the shoe to plus which are journaled in the backing plate,

have relative movement with respect to said thus providing for adjustments of the shoes to 10 UNITED STATES PATENT OFFICE actuating member. compensate for Wear of the shoe linings during Another object of my invention is to provide operation of the brake. in a two shoe brake structure having both shoes The direction of rotation of the drum correacting as forward shoes, a combined fluid and sponding to the forward direction of the vehicle mechanical actuating means which will require is indicated by the arrow and under these cir-' the employment of only one fluid motor and percumstances anchor pins 9 and I3 will perform mit it to be positioned externally of the brake aso t o he anch for the brake Shoes Since sembly so as to be unaffected by the heat gener-' the brake will be employed mostly during the ated during braking. forward direction of the vehicle. When the Other objects of my invention will become apdrum is rotating in the direction opposite that 20 parent from the following description taken in indicated by the arrow, shoe 3 will anchor upon connection with the accompanying drawings in anchor pin ll and shoe 4 will anchor upon an which Figure 1 is a view of the braking mechachor pin l5. It is thus seen that the brake is nism as mounted on the front side of the backof the type in which both shoes are capable of ing plate, the drum being shown in section; Figacting as forward shoes in either direction 25 ure 2 is a view of'the rear side of the backing of rotation of the drum, thus producing a two plate showing the fluid motor and the actuating e brake of the hest efl c ency. arms; Figure 3 is a cross-sectional view on the Two trees or pressure bars l6 and I! are poline 3-3 of Figure 1; Figure 4 is a cross-sectional sitioned upo Op Sides OfWeb 5 f ra e viewon the line 4--4 of Figure 1; and Figure 5 shoe 3 and extend between the ends of this shoe. 30

is a cross-sectional view of the fiuid motor. Th s r s are somewhat haped in Referring to the drawings in detail, numeral I order to conform with the curvature of the brake indicates a dust plate or backing plate forming shoe and are so. positioned as to be p ed fIO the support for'the entire brake assembly and the lining Carrying flange. The ends of the brake being secured to some fixed part of the vehicl shoe and the adjacent ends of the trees are con- 35 as, for example, the axle or axle housing. This nested together y a pin and slot connection enplate closes the open side of the brake drum 2 erally indicated t a d 3'- In the form which is secured to the wheel of the vehicle in a wn these ons comprise an lon t well-known manner. Brake shoes 3 and 4 are slot IS in the web in which is slidably received 40 positioned within the drum in end-to-end relaa block 20 d Carried y s block s p 2| 40 tion, each shoe being identical except for their pr v e with Suitable h p s f r ma nreversed position and comprising a web 5 and a taining the ends of he r es in n a em nt with lining carrying flange B to which the lining 1 the ends of the block. The thickness of the is secured. The shoe 3 at its lo e end ha block, however, is slightly greater than that of its web notched as indicated at 8 and this notch the web in order to pe u estrained rela- 45 receives th anchor pin 9. mounted on th b ktive movement between the ends of thetrees ing plate. The .upper end of shoe 3 has its b and the ends of the shoes as the block slides in provided with a flat surface H] which is adapted its SIOt- A150 p ed up b ke shoe 4 are to abut against the anchor-pin ll. Similarly, tWO'tTEBS pressure bars 22 and 23 y ng upon the upper end of shoe 4 has its Web notched as Opposite Sides of Web 5 d extending between indicated at l2 and this notch receives the anthe ends of the shoe. These bars are identical chor pin 13 and the lower end of the shoe has in construction to those described and are conits web provided with a flat surface M for abutnected to the ends of the shoe by pin and slot ting the anchor pin l5. The portions of anchor connections 24 and 24' already described with reor pins 9 and i3 cooperating with the notches 8 and spect to shoe 3.

The shoes 3 and 4 are maintained in their retracted or ofi" position and against the anchor pins by suitable retractile springs 25 and 26, the connection between the shoes and springs being by means of pins 2| which form part of the pin and slot connections I 8, I3, 24 and 24'.

An actuating shaft 21 is journaled in the backing plate adjacent the central portion of shoe 3 by means of a suitable bearing 28, and the inner portion of this shaft has integral therewith an arm 29 on which is mounted a crankpin 3|]. This crankpin extends through openings in the center of trees 16 and I1 and a suitable C-washer 3| holds the trees and crankpin in position. In order that the crankpin may have suflicient free movement to actuate the trees, web 5 of the shoe is cut away as is indicated at 32. The outer end of shaft 21 exterior to the backing plate has secured thereto an arm 33 for rotating the shaft to actuate the trees through the crankpin.

As best shown in Figure 3, the opposite side of the backing plate adjacent the central portion of shoe 4 has a bearing 35 and journaled therein is a shaft 35, the inner end of which has integral therewith an arm 31 and a crankpin 3B. This crankpin extends through suitable openings 39 and 40 in the center of trees 22 and 23 and the outer end carries a c-washer 4| for holding the trees and the crankpin in position. The web 5 of shoe 4 is notched as indicated at 42 in order to give, free movement to the crankpin. The exterior end of shaft 36 has secured thereto an arm 43 extending upwardly and substantially parallel with the previously mentioned arm 35.

It is desirable that arms 33 and 43 be simultaneously operated and with equal pressure, and the structure I have employed to perform this operation is a fluid pressure motor generallyindicated at 44, although other and equivalent means may be used. The fluid motor comprises a head 45 pivoted to the upper'end of arm 33 and screwthreaded in this head is a cylinder 46 having a reduced open end 41 into which is slidably fitted the piston rod 48 pivotally connected to arm 43. The inner end of the piston rod carries a piston 49 having an integral axial projection 50 upon which is mounted an annular rubber sealing cap 5|, this projection also acting as a stop means for the end of the piston. The head of the cylinder is formed with a suitable boss 52 to which is secured a conduit 53 connected to a suitable source of pressure as, for example, a master cylinder device (not shown). The head is also provided with a bleeder valve 54 for bleeding the system of any air when it is being filled with a suitable operating fluid. In order to protect the piston from the elements and exclude dust and dirt from the sliding parts of the fluid motor, a corrugated boot 55 surrounds the end of cylinder 45 and has one end connected to the cylinder and the other end to the piston rod.

In addition to the fluid operating means for simultaneously operating arms 33 and 43, I have also disclosed a mechanical connection for operating arm 33, when it is desired to actuate the brake shoe 3 and employ the brake as a parking or emergency brake. This mechanical connection comprises a flexible rod 56 pivotally con nected to an extended portion 51 on arm 33, and the rod is enclosed within a suitable sheath 58 which has its end clamped to a supporting member 59 riveted to backing plate I as best shown in Figure 2. A coil spring 60 surrounds the rod and is positioned between the end of the sheath where it is connected to the support and the end of .the rod where it is connected to extension 51. This spring provides suitable return movement for arm 33 after rod 56 has been released by the operator of the vehicle.

In the operation of my brake when it is desired to apply the brake shoes to the drum, fluid under pressure is admitted into the operating end of the fiuid'mo'tor through conduit 53. This will cause cylinder 46 and piston 49 to move in opposite directions, thus rotating arm 33 in a counter-clockwise direction and arm 43 in a clockwise direction as viewed in Figure 1. Rotation of these arms causes crankpins 30 and 38 to move the central portions of the two sets of trees toward the drum. Since the trees only engage the shoes at their ends, pressure to force the shoes into engagement with the drum can only be applied to the shoes through these ends. If the drum is rotating in the forward direction of the vehicle as indicated by the arrow, shoe 3, when moved into engagement with the drum, will anchor uponanchor pins 9, and shoe 4, when moved into engagement with the drum, will anchor upon anchor pin I 3. Both shoes will be free to move with respect to the trees to engage these anchors because of the pin and slot connections between the ends of the trees and the adjacent ends of the shoes. The notches 8 and I2, however, do not permit the anchored ends of the shoes to have radial movement. Since the crankpins are applying pressure to the trees at their center and the trees engage the ends only of the shoes, the pressure which is-being applied to each shoe end will 'be only one-half of that which is being applied to the center of the trees. The pressures on the unanchored ends of the shoes will be the only pressures which are effective in applying the brake shoes as the pressures on the anchored ends are insuflicient to overcome the braking drag on the shoes which maintains them against anchors 9 and I3. The pin and slot connections i8 and 24, therefore, become fulcrum points for the trees when the brake is applied in' the direction of rotation indicated by the arrow. The application of pressure to the end of the shoe remote from the anchor instead of the center of the shoe is very desirable as it permtis the employment of the maximum self-energizing action of the shoe.

Due to the leverage relation between arms 29 and 33 and arms 31 and 43, the pressures applied by the fluid motor to arms 33 and 43 are less than the pressures which are actually being applied to the ends of the brake shoe by the ends of the trees. For example, if the lever ratios between arms 29 and 33 and arms 31 and 43 is 4 to 1, then the pressure upon each end of the brake shoe is twice the pressure which is being applied to the ends of arms 33 and 43 by the fluid motor. Because of this arrangement, it is seen that the pressure input to the brake may be easily varied in many ways by either varying the size of the motor, the lengths of arms 33 and 43 and/ or the short arms '29 and 31.

When the drum is rotating in the opposite direction and the fluid motor is operated to move the shoes into engagement, with the drum through the trees, shoe 3 will anchor against anchor pin ll, shoe 4 will anchor against anchor pin l5, and the trees will apply pressure ,tothe shoes at the ends remote from the anchors in a manner already described. The notched end 8 of shoe 3 and the notched end l2 of shoe 4 willmove away from their anchor pins and the anchored ends of the shoes will be free to move radially into engagement with the drum as these ends will not be restrained due to the flat surfaces l0 and M.

Because of this freedom of radial movement, the shoes will not be as well controlled as they were in the other direction of rotation of the drum but this is not required since braking in reverse is not generally performed when the wheels are rotating at high speeds.

When the pull rod 56 is actuated, arm 33 will be the only onewhich is operated and, consequently. shoe 3 will be the only one that will be moved into engagement with the drum. Under these circumstances only one-half of the braking torque, of the brake is employed. However, since it is only intended to use this portion of the brake for parking purposes, the braking effect of shoe 3 has been found to be suflicient for this purpose. When arm 33 only is moved by the pull rod, cylinder 46 will be carried with arm 33 and there will be relative movement between the piston and cylinder, the piston being restrained from movement with the cylinder by arm 43 which is held from movement by'the ends of trees 22 and 23 acting through the ends of shoe 4 and against anchor pins l3 and I 5. During relative 'movement of the pistonand cylinder, fluid from the master cylinder will be free to flow into the cylinder through conduit 53 and thus prevent a suction efiect on the piston.

The brake just described has been found to be 1pull rod for actuating one of the leversemployed in actuating one of the shoes. Also by means. of the treeconstruction the pressure applied to the shoes is alwaysfat their ends regardless of the direction of rotation of the drum and this tree I construction does not restrain the shoes fromhavis opposed, in fact, the radius of curvature of the shoe will even be increased by the actuating pressure at the shoe ends, thus compensating for the increase in the drum diameter as a result of increased temperatures.

Being aware of the possibility of modifications in the particular structure herein described without departing from the fundamental principles of my invention, 1 do not intend that its scope be limited except. as set forth by the appended claims.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent of'the United States is:

1. In braking mechanism, a backing plate, a brake drum, two continuous shoes positioned in end-to -end relation and adapted to cooperate with the drum, means carried by the backing plate adjacent each end of each shoe for anchoring said ends depending upon the direction of rotation of the drum, an actuating member for each brake shoe, each member extending between and enends into engagement with the drum, and fluid pressure-operated means comprising a fluid motor exterior to the backing plate and having a movable element connected to each actuating member for simultaneouslyapplying pressure to each of said actuating members.

2. In braking mechanism, a support, a rotatable drum, a continuous brake shoe cooperating with the drum, actuating means independent of the anchor means for the shoe for moving said shoe into engagement with' the drum and comprising a pressure applying member having its ends only engaging the ends of the shoe, 9. connection between each end of the member and the adjacent shoe and permitting the shoe to shift relatively to the member, an arm pivoted to the support, means pivotally connecting the central portion of the pressure applying member to the arm, and means for actuating the arm.

3. In braking mechanism, a support, a rotatable drum, a continuous brake shoe for-cooperating with the drum, an anchor for each end of the brakmsho'e and carried by the support, a tree. independent of the anchors for the shoe and extending between the ends of the shoe and-pivotally connected to said ends, said pivoted connection permitting relative movement between the tree and shoe, and means for applying pressure to the central portion of the tree.

4. In braking mechanism, a support, a rotatable drum, a continuous brake shoe for cooperating with the drum, anchoring means for each end of the brake shoe and carried by the support, a tree independent of the anchor means for the shoe and extending between theends of the shoe, a pivotal connection between each end of the tree and the adjacent shoe end and including means for permittin'g the shoe and tree to move relatively longitudinally with respect to each other, and means for applying pressure to the central portion of the tree.

5. In braking mechanism, a support, a rotatable drum, a brakeshoe for cooperating with the drum and provided with a lining carrying portion and a web, anchoring means for each end of the brake shoe and carried by the support, two trees extending between the ends of the shoe and positioned on opposite sides of the shoe web, a pin and slot connection between each shoe endand the adjacent tree ends, and meansfor applying pressure to the central portions of the trees.

. 6. In braking mechanism, a support, a rotatable drum, a brake shoe cooperating with the drum, means on the support providing an anchor for each end of the shoe depending upon the direction of rotation of the drum, a tree extending between the ends of the shoe and having its ends only engaging the shoe, a shaft journaled in the support, an eccentric portion on said shaft engaging the central portion of the tree, and an arm for rotating said shaft.

7. In braking mechanism, a support, a rotatable drum, a brake shoe for cooperating with the drum, anchoring means for each end of the brake shoe and carried by the support, a tree extending between the ends of the shoe, a pivotal connection between each end of the tree and the adjacent shoe end and including means for permitting the shoe and tree to move relativelylongitudinally with respect to each other, a shaft journaled in the support, an eccentric portion on said shaft engaging the central portion of the tree, and an arm for rotating said shaft.

8. In braking mechanism, a support, a rotatable drum, a brake shoe for cooperating with the drum and provided with a lining carrying portion and a web. anchoring means for each end of the brake shoe and carried by the support, two trees extending between the ends of the shoe and positioned on opposite sides of the shoe web, a pin and slot connection between each shoe end and the adjacent tree ends, a shaft journaled in the support, an eccentric portion on said shaft engaging the central portions of the trees, and an arm for rotating said shaft.

9. In braking mechanism, a support, a brake drum, a pair of shoes positioned in end-to-end relation and adapted to cooperate with the drum, means carried by the support for anchoring each end of each shoe, a tree extending between the ends of each shoe, each tree engaging the ends only of the shoe with which it is associated, two

shafts journaled in the support, an eccentric portion on each shaft and adapted to engage a tree, and fluid-operated means for simultaneously rotating the shafts.

10. In braking mechanism, a backing plate, a brake drum, a pair of shoes positioned in end-toend relation and adapted to cooperate with the drum, four adjustable anchor pins carried-by the backing plate, each pin adapted to cooperate with a shoe end, a tree extending between the ends of each shoe, each tree end being connected to its adjacent shoe end by a pin and slot connection permitting relative longitudinal movement between each shoe and the associated tree, two

shafts journaled in the backing plate and each provided with an eccentric portion for engaging the central portion of a. tree, an arm secured to the exterior end of each shaft, and a fluid motor interposed between said arms for, rotating the shafts in opposite directions to cause the trees to force the ends of the shoes into engagement with the drum.

11. In braking mechanism, a backing plate, a drum, a brake shoe for cooperating with the drum, anchor pins carried by the backing plate for the shoe ends, one of said shoe ends being provided with a notched portion surrounding the anchor pin associated therewith and restraining radial movement of the shoe end when it engages the anchor pin, the other shoe end being provided with a substantially flat surface for abutting the other anchor pin and said last named shoe end being unrestrained by the anchor pin from moving substantially radially toward said drum when said surface engages the pin, and means for applying pressure to the shoe to force it into engagement with the drum.

12. In braking mechanism, a backing. plate, a drum, a brake shoe for cooperating with the drum, anchor pins carried by the backing plate for the shoe ends, one of said shoe ends being provided with a notched portion surrounding the anchor pin associated therewith and restraining radial movement of the shoe end when it engages the anchor pin, the other shoe end being provided with a substantially flat surface for abutting the other anchor pin and'said last named shoe end being unrestrained by the anchor pin from moving substantially radially toward said drum when said surface engages the pin, means for adjusting said anchor pins with respect to the backing plate and drum, and means for applying pressure to'the shoe to force it into engagement with the drum.

STEVE SCHNELL.

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