US1811914A - Automatic slack adjuster for brakes on railway cars and the like - Google Patents

Description

June 3Q, 1.931. BRQWALL 1 811 914 AUTOMATIC SLACK ADJUSTER FOR BRAKES 0N RAILWAY CABS AND THE LIKE Filed May 13,, 1930 I5 Sheets-Sheet l lNver Ta /4 June 30, 1931. B. H. BROWALL AUTOMATIC SLACK ADJUSTER FOR BRAKES ON RAILWAY CARS AND THE LIKE Filed may 13, 1950 5 Sheets-Sheet 2 June 30, 1931. B. 1-1. BROWALL.

AUTOMATIC SLACK ADJUSTER FOR BRAKES ON RAILWAY CARS AND THE LIKE Fil ed May 13, 1930 5 Sheets-Sheet 3 Patented June 30, 1931 UNITED STATES PATENT OFFICE BERT HENRY BROWALL, OF MALMO, SXVEDEN, ASSIGNO'R TO SV-ENSKA. AKTIELBOLAGET BROMSREGULATOB, OF MALMO, SWEDEN, A CORPORATION OF SWEDEN AUTOMATIC SLACK ADJ USTEB FOR BRAKES ON RAILWAY CARS AND THE LIKE Application filed May 13, 1930, Serial No. 452,088, and in Germany June 24, 1929 The subject of my present invention is a slack adjuster for brakes on railway cars and the like for the purpose not-only to perform a reduction but also, when required, an increase of the slacks between the brake shoes and the wheels, and the invention refers to slack adjusters of the type which embodies two actuating mechanisms, one of which is adapted for the increase, the other for the reduction of the slacks.

The characteristic of the invention is to be found therein that the actuating mechanism adapted for increase of the slacks is arranged in such a manner that it performs a certain amount of increase of the slack for each braking operation independent of the actual amountof slack then at hand, and the actuating mechanism adapted for 7 reduction of the slacks is arranged in such a manner that it becomes effective only after that the source of braking power has performed alength of movement exceeding a predetere mined value, so thatby such means the increase of the slack performed by the slack increasing mechanism is'wholly or in part eliminated, or even exceeded, whereby the result will be a reduction of the slacks. Hence, the variation of the slack is the result of-the difference between the effects of the two actuating mechanisms, and if the slack has itsnormal value, the effects of such mechanisms will be equal and thus eliminate each other.

In the following, the invention is to be explained by reference to the accompanyingdrawings whichshow some different embodiments thereof. 7

Fig. 1 showsone embodiment of the apparatus seen in longitudinalsection, and.

Fig. 2 shows a cross sectional View of the same.

In the same manner Fig. 8 shows a second embodiment of the invention seen'in longitudinal section, and

Fig. Lshows across sectional view of the latter.

Fig. 5 shows a cross section of a third em bodiment of the invention, and

Fig. 6 shows a longitudinal section of the same.

F ig. 7 shows a fourth embodiment of in ve-ntion seen in cross section, and V Fig. 8 is a diagrammatical elevation drawn to a smaller scale and showing'the apparatus according to Fig. 7 mounted in its connection with the brake cylinder structure.

In all ofthe embodiments according to the Figures 1 4 and 7 it is assumed that the variation of the slack is. to-be performed by means of a nut and screw connection known per se, and wherein the nut is supposed to be connected with a rotatable part of construction of the slack adjuster (the pitch of the nut and screw connection being chosen in such a manner that the connection is selflocking). The embodiment according to Figs. 5 and 6 is somewhat different in that the variation of the slack is adapted to be performed by means of a toothed rack which is directly slideable in its direction of length and acted upon by a toothed wheel adapted to be rotated by the slack adjuster and posi tioned in mesh with said toothed rack.

In the embodiment according to Figs. 1 and 2, the part of construction adapted to be rotated by the apparatus: consists of a sleeveshaped or tubular rod 1 connected with a nut (not shown in the drawings), such nut in the common manner, at its rotatiombeing adapt- 7 ed to cause an axial displacement of another rod provided with corresponding threads, as

by such means to provide for a variation of the inter-distance between the ends of the brake rigging rod, in which the apparatus is mounted. In a manner known per se, the movement is alsotransmittedto the'apparatus by means of a crank member 2 affixed to a housing 3 enclosing the parts of the apparatus, such housing 3 being rotatably mounted around the axis of the rod 1. At its one end the said rod is rigidly connected witha pin 4, which is rotatably mounted in the connection eye member 6 together with the head 5, although said pin is prevented from axial displacement in any substantial degree, the head 5 serving the purpose of taking up the stress arising when braking. Two pawls 7 and 8 respectively are hingedly mounted within the housing 3 onfixedipivot pins therein, the first mentioned pawl 7 serving as an actuating member for the purpose of lncreasing the slack, and the second mentioned pawl 8 serving as actuating member for reduction of the same. Both of the pawls are spring-actuated so as permanently to tend to engage a ratchet wheel 9 fixed to the rod member 1 or to the pin l. The pawl 7 is provided with a laterally extending lug 10 adapted for coaction with a cam disc 11 fixedly mounted in the connection eye, and the pawl S is provided with a similar lug 12 for coaction with a cam disc 13, which is nor mally rigidly connected with the connection eye but carried by a sleeve 14 rotatably mounted on the connection eye and coacting with a set screw or the like so thatit may be locked in different positions, and thereby it is possible to adjust the relative position of the cam 13 in relation to the lug 12 on the pawl 8, so that the normal value of the slack may be varied according to will.

In order to understand the manner of action of the apparatus it may be assumed that the crank 2, from the original position shown in Fig. 2, is rocked in a clock-wise direction when braking,so as by releasing the brake to be rocked back again into said orig inal position, and the means for performing such rocking movements of the crank may be constructed in a manner known per se.

If starting from the original positions of the parts shown in Fig. 2, the pawl 7, when rocking the crank in a clockwise direction (when braking), will turn the ratchet wheel 9 a small angle before the lug 1O strikes the cam 11 and thereby lifts the pawl 7 out of engagement with the ratchet wheel. The ratchet wheel 9, a d hereby also the tubular rod member 1 will thus be given a certain rotation corresponding to an increase of the slack with a certain amount. At the continuation of the braking, the manner of action of the apparatus will be dependent on the length of stroke of the source of braking power. If such stroke is too small, the crank :2 will not be turned so far that the lug 12 leaves the cam 13, and consequently the pawl 8 will then never come into engagement with the ratchet wheel 9. When releasing the brake again, the parts of construction will return to their positions shown in the drawings and the result of the action will thus be an increase of the slack performed by means of ti e pawl 7. This manner of action will be repeated at each braking, until the said stroke has reached its normal value.

If the stroke is normal, the pawl 8 will be moved beyond the cam 13 to an equal extent as the pawl 7 takes a position in advance of the cam 11 when the brake is released. Consequently the pawl 7 will increase the amount of slack with a certain value when braking,

but when the brake is released the increase of slack will be eliminated again by the pawl 8 previous to the disengagement of said pawl by means of the cam 13, and therefore the slack will be withheld at its original value.

If the stroke is too large, an increase of the slack will nevertheless be performed when braking by means of the pawl 7 in the manner described above, but the crank 2 will then be rocked so far, that the pawl 8 has been moved a greater angle beyond the cam 13. At the release of the brake, the slack will consequently be reduced with an amount that is greater than the increase of slack performed by the pawl 7, and the result will be that a reduction of slack is performed answering to the difference bet-ween the amount of work performed by the two pawls.

As the cam 13 is adjustable in peripheral direction by turning and locking of the sleeve ll in a different position, the normal value of the working stroke, at which the work .erformed by one pawl is eliminated by the other, may be varied, and in this manner it is possible to adjust the apparatus according to any desired value of the working stroke.

In relation to the construction, the embodiment according to Figs. 3 and 4 is generally the same as that according to Figs. 1 and 2, and the same references are used on corresponding parts of construction.

The difference is to be found therein, that the two pawls are'arranged in such a manner that the reduction of the slack is performed when braking, the increase of the same being performed when releasing the brake. This construction involves the advantage, that the braking stress arising when the brake shoes are in contact with the wheel rims in a simple manner may be utilized for the purpose of limiting the action of the apparatus at the reduction of the slack, so that the effect of the apparatus will onl be dependent on that part of the stroke of the source of brake power, the length of which corresponds to the amount of slack actually at hand, that part of the stroke, however, which is dependent on deformations in the brake rigging due to elasticity, or other movements perhaps occurring due to the stresses, being without influence on the result of the adjustment. For such purpose an elastic or resilient member, in a manner known per so, can be mounted for instance in the transmission means adapted for causing the movement of the crank, so that such resilient member accumulates the continued actuating movement appearing after that the stress .has arisen and the ratchet wheel cannot be further rotated due to the same.

Another difference is to be found therein 7 llb period of working of the pawl 7 Hereby a manua-l adjustinent of the slack is facilitated, and the tube 1 can be rotated both directions without the necessity of first disengaging the pawls fromthe ratchet wheel.

In order to understand the manner of actionof the apparatus, it mustbe assumed that the crank 2 in Fig. 4, when braking, is rocked a certain angle in a counter-clockwise direction, and when releasing the brake it is rocked a corresponding angle in the opposite direction. hen braking, both of the pawls will at first run idle for a certain angle. If the slack is too small, a locking stress will arise in the apparatus before the pawl 8, or itslug 12, has slid off from the cam 13, and consequently such pawl will not perform any amount of work. The pawl 7 continues'in sliding back over the cam 11, over the recess 11 and perhaps alsoup again on the cam. hen thecrank 2, at the release of the brake, is rocked back again as described above, the pawl? will consequently perform an increase of the slack corresponding to the peripheral length of the rece'ss11 If the slack is normal, the pawl 8, when braking, will slide down from the cam 13 and is moved a certain angle further correspondingto the peripheral length of the recess 11 and thereby it performsa. reduction of the slack, Hereby'the pawl 7 will, however, slide back past the recess 11 and when it is returned into its original position at the release of the brake, it will perform an increase of the slack corresponding to the length of the recess 11-, and therefore the actions of the two pawls will eliminate each other so that the slack will finally remain unaltered. hen the slack is too large, the pawl 8 will pass a rather great angle beyond the'end of the cam 13, and it will performa reduction of the slack, which is considerably greater than theiconstant increase of the same performed by the pawl 7 at the brake release, as the amount of said increase can never exceed a value corresponding to the length of the recess 11 i I Also in thisembodiment it will be possible, by adjustment of the position of the cam '13, to vary the moment at which the 'pawl 8 goes into engagement, and thereby also to vary the amount of normal slack, same as in the embodiment' according to Figs. 1 and 2 andin I both embodiments it is the difference between the constant value of the increase of slack and the changeable value of the reduction of slack, which performs'theadjustment of the actual amount of slack. V

The embodiment according to Figs. '5 and 6 is based on the same principles as those described above but applied to anothertype of apparatus, in whichthe variation of the length of the pull rod, in which'the apparatus is mounted, is performed by'a direct sliding mov ment of the rod parts without relative rotation of the same. V I

' Inthis instance, the rod part or member 15 is vshaped into a toothed rack which is telescopically 'slidable in the other red part or member 16 which is sleeve-shaped. A housing 17 is aflixed to the rod member 16, such housing forming bearings for a shaft 18 carrying a toothed wheel 19 positioned in mesh with the aforesaid toothed rack. That part of the shaft 18 directly carrying the toothed wheel 19 is provided with threads 18 the hub portion of the toothed wheel forming a nut on said threads. The crank 2 is carried by a sleeve 20 freely rotatab-ly mounted on the shaft 18, such sleeve being rigidly connected with two arms supporting ' thepawls 7 and 8 respectively, the pawls acting in opposite directions and coacting with a ratchet wheel 23 fiXed on the shaft 18. Be-

sides, a locking pawl 24 is 'hingedly mounted on a fixed pin in the housing17, this locking. pawl acting in the same direction as the actuating pawl 8 and coactin'g' with a toothed locking wheel 25 freely rotatably mounted on the shaft 18. The shaft 18 isprovided with an abutment or collar 26 forming an axial supporting face for the ratchet wheel 23 and the locking wheel'25 at one side, the nutshaped toothed wheel 19'being provided with a friction flange 27 supporting the locking wheel 25 at the opposite side. A guide flange 28 is provided within the housing 17, andthe pawls 7 and 8 are each provided with a latreleasing the brake,it is rockedback the same anglein opposite'direction. WVhen braking, the crank 2 by means of the pawl 7 will rotate the ratchet wheel 23a small angle, until the pawl is disengaged by the guide flange '28. At this small rotation of the ratchet'wheel 23, theshaft 18 will also be rotated,'and the screw 18 forming part thereof is screwed out frointhe nut-shaped wheel 19. As the ratchet wheel 23 and the locking wheel 25 cannot be axially displaced towards the right in Fig. 5, the wheel-nut 19 must consequently be displaced towards the left, and hereby the contact pressure between the friction disc 27 and the wheel 25 will be relieved, whereupon the rod 15, due to the stress arising when braking, may be pulled a certain amount tojwards the left in Fig.6, i. e. the slack is increased toa certain extent. Thetlispljacement ofthe rod 15 just described will, howerally extending lug for coaction with said ever, perform a corresponding rotation of the wheel-nut 19 in such a direction, that the latter will again be axially displaced towards the right, and will be jammed against the locking wheel 25 due to the action of the friction disc 27 and since the said wheel is locked by the pawl 24, the pulling out of the rod 15 will cease. This functioning will continue until the pawl 7 is disengaged by the guide flange 28, so that it cannot longer rotate the shaft 18, and consequently it can neither disconnect the wheel 19 for a further increase of the slack, as described above. At the continuation of the braking, the crank 2 is further rotated in a clockwise direction according to Fig. 6, so that the pawl 8 will finally slide off from the guide flange and go into engagement with the ratchet wheel a greater or smaller angle beyond the end of the guide flange 28, and thereafter the pawl 8, when releasing the brake, will move in opposite direction to that referred to above, so as thereby, to a. greater or smaller extent, to eliminate the increase of slack caused by the pawl 7. The locking wheel 2-5, which hereby must take part in the said movement, is not locked in this direction by the pawl 24.

If the slack is too small, the pawl 8 will not move beyond the guide flange, and consequently the increase of slack performed by the pawl 7 will be withheld. If the slack is normal, the pawl 8 will just move so far beyond the guide flange 28 as required for eliminating the increase of slack performed by the pawl 7, and hereby the slack is again reduced to the same amount as the increase of the same performed by the pawl 7 On the contrary, if the slack is too large, the pawl 8 will move still further beyond the guide flange 28, and it will reduce the slack a greater extent than the increase of the same by means of the pawl 7, the actual reduction of the slack being then equal to the difference between the amounts of work performed by the two actuating pawls. Hence, it will be seen that the manner of action of this apparatus in point of principle is in conformity with the manner of action of the embodiment according to Figs. 1 and 2, and by the addition of a resilient member it may naturally also be converted so as to correspond to the embodiment according to Figs. 3 and 1.

In point of principle, the embodiment according to Figs. 7 and 8 acts in the same manner as that according to Figs. 3 and 4, although by influence from air pressure. will be seen from Fig. 8, the brake cylinder 29 is combined with two compressed air cylinders 30 and 31, the cylinder 30 of which being shorter than the other and directly connected with the cylinder cover by means of a pipe 32, the other cylinder 31 being longer and connected with the cylinder 29 by means of a pipe 33 at a point between the ends of said cylinder, this point corresponding to rs1r914 the length of stroke normally to be travellex by the brake piston for the purpose of advancing the brake shoes towards the wheels, under the provision that the slack is normal. This point may naturally be chosen according to the desired amount of normal slack, .and by suit-able means it may also be adjustable so as to vary the location of the same. The slack adjuster can be supposed to consist of a screw 34: provided with a connection means for the brake lever, the osition of such connection means being varia le (see Fig. 8), and then the said connection means may be given the shape of a nut mounted on the said screw, so that it is displaceable in the direction of length of the screw by means of a relative rotation. Besides, the screw is also provided with a ratchet wheel 35 (Fig. 7) fixed thereto and preferably surrounded by a housing 36 combined with the cylinder structure 30,31. The cylinder 30 is provided with a reciprocable piston 37, the piston rod of which is hingedly connected with a pawl 38 adapted for coaction with the ratchet wheel 35, and the cylinder 31 in a similar manner is provided with a piston 39 connected with another pawl 40 .adapted for coaction with said ratchet wheel, the housing 36 being interiorly provided with an abutment face 41, which by coaction with a lug 4C2 on the pawl 38 performs a disengagement of the said pawl after a certain .amount of displacement of the same. Both of the pistons are acted upon by return springs tending normally to keep them in the positions shown in Fig. 7, and the pawl 38 may be in engagement with the ratchet wheel 35, when the brake is release-d, but the pawl 4L0 being then out of engagement therewith. Finally it is to be assumed, that the pitch of the screw is chosen in such amanner, that it is self-locking.

The manner of action is as follows 2- Y'Vhen braking, a pressure will at once be transplanted to the cylinder 30, and the pawl 38 rotates the ratchet wheel 35 and the screw 34 for the purpose of performing a certain amount of increase of the slack, until the pawl is disengaged by means of the abutment face. As long as the slack is so small, that the piston within the brake cylinder 29 does not arrive in the position required for connection of the pipe 33, no compressed air will be introduced into the cylinder 31, and consequently the increase of slack performed by the piston 37 will be maintained. In case A the slack is normal, the piston within the brake cylinder 29 will arrive at the position just required for connect-ion of the pipe 33, whereby the piston 39 will come into action and by means of the pawl 40 it will rotate the ratchet wheel 35 and the screw 34: the same amount back as the rotation caused by the pawl 38. This being performed, the brake rigging (due to the normal value of the slack) will be set under so great a stress that the piston 39 cannot rotate the ratchet wheel 35 any further, and the continued braking will cause an increase of pressure within the cylinder 31 only, such increase of pressure acting in the same manner as the resilient member described above and adapted for mounting in the transmission means connected with the crank 2. In case the slack is too large, the brake piston will also travel past the point of connection of the pipe 33, but on account of the amount of slack the braking stress will not arise so early, and the piston 39 is able to rotate the ratchet wheel 35 still further, and since the piston 39 has a greater length of stroke than the piston 37, the former will perform a greater reduction of the slack than the increase of the same performed by the latter, before the braking stress has increased to such'a value that it prevents the further rotation of the ratchet wheel 35.

What I claim and desire to secure by Let-- ters Patent is 1. In an automatic slack adjuster of the character described, an actuating means adapted to actuate the slack adjuster in a direction for increasing the slack, another actuating means adapted for actuation of the adjuster in an opposite direction for reduction of the slack, the said two actuating means being arranged independent of each other in such a manner that both of them 7 and adapted to actuate the adjuster in an op-.

posite direction for reduction of the slack, means adapted for causing both of said actuating means to actuate the slack adjuster when braking, so that the result will be dependent on the difference between the actuations thus performed, and guide means combined with at least one of the actuating means and adapted for controlling the moment and duration of the actuation of said means.

4. In an automatic slack adjuster according to claim 3, the additional feature that the guide means are adjustably mounted and adapted to control the effect of the adjust ment desired.

5. In an automatic slack adjuster of the character described, an actuating means adapted to actuate the slack adjuster in a direction for increasing the slack, a driving means for such actuating means, another actuating means independent of the former and adapted to actuate the adjuster in an opposite direction for reduction of the slack, a second driving means for such other actuating means and independent of the first mentioned driving means, means adapted for causing both of the aforesaid actuating means to actuate the slack adjuster when braking, so that the result will be dependent on the difference between the actuations thus performed, and means adapted to disengage each of the actuating means after performance of its actuation.

In testimony whereof I have signed my name to this specification.

BERT HENRY BROWVALL.

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