US3799298A

US3799298A - Safety brake assembly for elevators and the like

Info

Publication number: US3799298A
Application number: US00266445A
Authority: US
Inventors: W Loomer
Original assignee: HARTMAN METAL FABRICATORS Inc
Current assignee: HARTMAN METAL FABRICATORS Inc
Priority date: 1972-06-26
Filing date: 1972-06-26
Publication date: 1974-03-26
Anticipated expiration: 1991-03-26

Abstract

Each brake assembly comprises a plurality of elongate, metal files that are releasably secured side by side to a flat surface on a metal plate, which is resiliently mounted on a reciprocable carrier. The carrier slides on inclined wedging surfaces on a housing between active and inactive positions. The housings of each of a plurality of these brake assemblies are secured on an elevator with their file teeth normally disposed in spaced, confronting relation to braking surfaces on the mast on which the elevator travels. When the elevator descends at an excessive speed, the reciprocable carriers are shifted to active positions by sliding along the inclined, wedging surfaces. This causes the files to be shifted laterally to engage the file teeth resiliently with the mast to stop the elevator.

Description

United States Patent 1191 Loomer 1 Mar. 26, 1974 SAFETY BRAKE ASSEMBLY FOR Primary Examiner-Duane A. Reger ELEVATORS AND THE LIKE Attorney, Agent, or Firm-Shlesinger, Fitzsimmons & [75] Inventor: Weston R. Loomer, Candaigua, shlesmger I [57] ABSTRACT [73] Assignee: f Mela Fabricators? Each brake assembly comprises a plurality of elon- Vlctorl gate, metal files that are releasably secured side by 22 Filed; June 2 72 side to a flat surface on a metal plate, which is resiliently mounted on a reciprocable carrier. The carrier [21] Appl. No.: 266,445 slides on inclined wedging surfaces on a housing between active and inactive positions. The housings of [52] US. Cl. 188/189 each of e plurellly of these brake assemblies are 51 Int. Cl. F1681 59/02 cured all elevator with their file teeth normally [58] Field of Search 188/136, 188, 189; 187/89 Posed in spaced, confronting relation to braking faces on the mast on which the elevator travels. When 5 References Cited the elevator descends at an excessive speed, the recip- UNITED STATES PATENTS rocable carriers are shifted to active positions by sliding along the inclined, wedging surfaces. This causes 3,706,361 12/1972 Paulssen et a1. 188/189 the files to be shifted laterally to g g the me teeth 1,165,583 12/1915 Farmer 188/189 3,215,231 11/1965 Lodige 188/189 reshemly the mast to Stop the elevator' 8 Claims, 3 Drawing Figures SHEEI 2 0F 2 9G mm ATENTEU MARZB I974 SAFETY BRAKE ASSEMBLY FOR ELEVATORS AND THE LIKE This invention relates to braking devices, and more particularly to a safety brake or brake shoe assembly particularly suitable for use in conjunction with the vertically movable elevators of automatic stackers.

It is customary to employ automatic safety or braking devices for the elevators of the automatic stackers or load carriers employed in modern warehousing systems. Usually the stacker comprises a trolley that travels horizontally in an aisle between a pair of spaced storage racks, and an elevator which moves vertically on a mast that is carried by the trolley. The elevator carries a retractable, load-bearing fork mechanism which can be projected out of either side of the elevator to insert a load into, or retract a load from, a registering bin in one of the racks.

To prevent excessive damage in the event of a failure in the elevator control mechanism, it is common practice to employ one or more safety brakes between the elevator and mast which operate automatically in event the downward velocity of the elevator exceeds a predetermined value. When actuated, the safety brake shoes are pressed firmly against the mast to generate a braking force sufficient to halt fall of the elevator.

Heretofore it has been customary to manufacture such brake shoes from conventional, industrial brake lining material. However, this type of brake shoe has proved to be rather unsatisfactory, particularly in the case of load-bearing stackers. To improve the performance and wear resistant characteristics of conventional brake shoes, bits of tungsten carbide have been braised on thebraking surfaces of the shoes; but even this has not produced a satisfactory braking device for the stacker elevators.

One of the problems with prior braking devices is that the brake shoes tend to generate large quantities of heat upon being applied, due to the sliding movement of their friction surfaces against the stacker mast.

One object of this invention is to provide an improved safety brake which is more durable and reliable than prior such devices.

Another object of this invention is to provide an improved braking device of the type described which operates primarily as an energy absorbing device, rather than an energy (heat) generating device. To this end it is an object also to provide a novel brake shoe which generates substantially less heat, when applied, than prior brake shoes.

A further object of this invention is to provide an improved brake shoe assembly which is particularly adapted for use as a safety device for the elevators of automatic stackers.

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawings.

In the drawings:

FIG. 1 is a side elevational view of a safety brake made in accordance with one embodiment of this invention, portions thereof being broken away and shown in section;

FIG. 2 is a sectional view of this device taken along the line 2-2 in FIG. 1 looking in the direction of the arrows; and

FIG. 3 is a fragmentary elevational view of a stacker elevator assembly having a plurality of braking devices made in accordance with this invention, portions of the assembly being broken away and shown in section.

Referring now to the drawings by numerals of reference, and first to FIGS. 1 and 2, denotes generally a brake shoe device comprising three major components: a housing or wedge box 11, a spring box 12, and a brake shoe assembly 13.

Wedge box 11 has elongate, spaced,

parallel side walls

15 and 16, which are secured adjacent opposite ends of the box (FIG. 1) to opposite sides of two, rectangular blocks or spacers 17. A rigid end plate 18 is secured transversely across the upper ends of

walls

15 and 16 to extend laterally beyond the inside or right hand edges of these walls as shown in FIG. 1. Longitudinally spaced notches 19 and 20 are formed in the inner or right hand edge of each

wall

15 and 16 so that the notches 19 and 20 in one of the walls register laterally with the corresponding notches 19 and 20, respectively, in the other wall. Each notch 19 and 211 has a rounded bottom, and is bounded on one side by a short, rounded projection 21 and on its opposite side by an inclined camming or wedging surface 22 for a purpose to be described hereinafter.

The spring box 12, which is mounted for limited movement in box 11 between its

walls

15 and 16, has elongate, spaced,

parallel side walls

24 and 25, which are secured at opposite ends to the spaced,

parallel end walls

26 and 27. Secured between the side walls 24 and and extending only part-way of the height of these side walls, is the front wall 28 of the spring box 12 which constitutes a support for the brake shoe assembly 13. One leg of a right angle bracket 30 is secured by screws 32 to the outside of wall 28 intermediate its height, and the other leg of bracket 30 projects laterally outwardly beyond the wedge box 11 for a purpose described hereinafter.

Mounted on studs 35, which are fastened in

walls

24 and 25 by nuts 36 and washers 37, are four rollers 34, which engage in the rounded bottoms of the notches 19 and 20 in the

sides

15 and 16 of the wedge box 11. Also secured in the

side walls

24 and 25 adjacent their lower ends (FIG. 1), and projecting laterally outwardly through the notches 20 in the

wedge box walls

15, 16, are two pins or bolts 38. These pins 38 are connected by a pair of tension springs 40 to two similar pins or bolts 39, which project from

walls

24 and 25 adjacent their upper ends. As described hereinafter, under certain circumstances the springs 40 operate to draw the spring box 12 upwardly relative to the wedge box 11, thus causing the rollers 34 to slide on the inclined surfaces 22.

Brake assembly 13 comprises an elongate base plate 42, which is recessed at 44 on its inside and is slightly wider but shorter than the wedge box 11. On its outer side plate 42 has a plane surface 43. Six stub shafts 45 are secured to the plate 42 at equi-spaced points along its height to project through registering openings 46 (FIG. 2) in the front wall 28 of spring box 12. A washer 47 is secured over the projecting end of each shaft 45 by a screw 48, which threads into a tapped hole in this end of the shaft. A coiled compression spring 49, which surrounds each stub shaft 45, has opposite ends thereof seated against the plate 42 and the wall 2%, respectively, so that springs 49 urge plate 42 resiliently toward the right in FIGS. 1 and 2 relative to the spring box 12 to the extent permitted by the washers 47.

Removably secured side by side against the plane surface 43 of plate 42 are three, elongate,

flexible metal files

52, 53 and 54. These files, which may be any standard, flexible variety having, for example, eight teeth per inch, are removably fastened at opposite ends thereof to plate 42 by screws 55, and nuts 56, so that at one end of the device (the upper end in FIG. 1) the aligned edges of all three files abut against a plane, transverse surface 57 formed by a right angular back stop 58, which is fastened over the upper end of the base plate 42 to prevent vertical shifting of the

files

52, 53 and 54 during use.

FIG. 3 illustrates schematically one manner in which a plurality of braking devices may be used with the elevator of a stacker. In this figure 60 denotes a portion of the stacker elevator, which rides vertically on a hollow, rectangular mast 61 that projects upwardly from the trolley portion (not illustrated) of the stacker. At least two safety brake devices 10 are mounted in spaced, vertically disposed housings 63, which are carried by elevator 60 to flank opposite sides of the mast 61. The wedge box 11 of each such device 10 is fixed in its associated housing 63; but the bracket 30 on each such device projects slidably through a slot 65 in this housing 63, and is attached by a line or cable 66 to a conventional safety mechanism that need not be described in detail here.

Under normal operations of the stacker its safety mechanism maintains sufficient tension in the cables 66 to cause the attached brackets 30 to be held downwardly (FIG. 3) in their lowermost or inactive positions, wherein the attached spring boxes 12 are also held in their lowermost positions as shown in FIGS. 1 and 2. Normally, therefore, the rollers 34 of these devices are fully seated in the lower, rounded ends of notches l9 and in the associated wedge box 11, and the teeth T (FIG. 1) on the

associated files

52, 53 and 54 are spaced anywhere from 1/16 inch to V3 inch from the adjacent, confronting surface on the mast 61, so that these teeth T (FIG. 1) do not interfere with vertical movement of the elevator on the mast.

However, if the elevator happens to exceed a predetermined velocity during its descent (for example approaches 130 per cent of its normal rated top (veloc- .ity), the safety mechanism will operate in known manner to release the tension on cables 66. This permits the springs 40 (FIG. 1) in the associated brake assemblies 10 (FIG. 3) to draw the attached spring boxes 12 upwardly so that their rollers 34 ride upwardly on the inclined wedging surfaces 22 of the associated wedge boxes 11, thus urging these spring boxes 12 inwardly toward opposite sides of the mast 61. Since each brake assembly 13 is connected by shafts 45 and springs 49 to the associated spring box 12, the movement of the latter toward the mast 61 will cause the teeth or serrations of the

files

52, 53 and 54 of each assembly 13 resiliently to engage the confronting side of the mast. As certain of the teeth on the files penetrate or scrape against the now-engaged mast, they tend to shift the associated plate 42, and the attached spring box 12, vertically relative to the associated wedge box 11, thereby driving the rollers 34 further along the associated wedging surfaces 22, and consequently increasing the lateral pressure exerted by the file teeth T against the mast 61. The springs 49, however, transmit this lateral force resiliently against the mast, and enable each plate 42 to recoil slightly away from the mast, thus applying a gradual braking force against the mast. These teeth or serrations are inclined downwardly from their bases to their tips, that is, in the direction of descent of the elevator so that when they are moved to braking position they do not dig into the confronting surface of the mast until first they exert through their tips a frictional braking action.

During an actual braking operation it has been found that the

files

52, 53 and 54 tend to flex slightly in a longitudinal direction. To permit this slight flexing, and to minimize breakage of the files, it has been found advisable to secure those ends of the files, which confront the back stop member 58, snugly to the base plate 42, but to allow the screws 55 at the opposite ends of the files (the lower ends in FIG. 1) to remain slightly loose. For this purpose two nuts 56 may be secured to the inner end of each of the last-mentioned screws as shown in the lower right hand corner of FIG. 1. The backstop 58 is also important for the purpose of reinforcing the

files

52, 53 and 54 against any axial movement which might tend to shear the screws 55 during a braking operation. With this construction it has been found that, when the safety device operates to apply the brake shoes or

files

52, 53 and 54, the associated elevator experiences a brief free fall i.e., the file teeth T do not immediately grab against the mast but immediately following the free fall the teeth T dig into and scrape along the confronting surface of the mast before the elevator is finally brought to rest. In other words, instead of instantly halting the elevator, thus applying extremely heavy dynamic loading to the structure, the brake assemblies 10 operate as energy absorbing devices which reliably but gradually bring the elevator to rest, without generating an intense amount of heat between the brake shoes and the mast, in contrast to prior brake shoes.

From the foregoing it will be apparent that the instant invention provides an improved brake shoe assembly, which is more reliable and durable than prior such devices. Moreover, since the

files

52, 53 and 54 are removably fastened to the base plate 42 by the screws 55 and nuts 56, they can be readily removed and replaced if they become unduly worn or damaged. Furthermore, the springs 49, together with the inclined wedging surfaces 22 on the wedge box 11, operate resiliently and snugly to drive the teeth T of the files against the braking surface, such as the side of the mast 61, whenever the brake cables 66 are released by the stacker safety mechanism.

Obviously the slope of the wedging surfaces 22, and the tension strength of the springs 49, will affect the interval that it takes to halt the elevator 60 on the mast 61 after the brake devices have been released. Moreover, the shape and the quantity of the teeth on the files will also affect this interval. In actualpractice, the use of vixen milled curved tooth files having eight to ten teeth per inch have been found to operate very satisfactorily.

While the invention has been described in connection with a specific embodiment thereof and a specific use therefor, it will be understood that it is capable of further modification and uses, and this application is intended to cover any modification and adaptations of the invention coming within the disclosure and the recital of the appended claims.

Having thus described my invention, what 1 claim is:

l. A safety brake assembly for braking the descending motion of a vertically movable member relative to a stationary member, comprising a wedge box secured to said movable member,

a spring box vertically reciprocable on said wedge box,

a rigid plate having an elongate braking surface on one side thereof confronting said stationary member,

means mounting said plate on said spring box so that said plate moves vertically with said spring box,

resilient means connecting said spring box with said wedge box and constantly urging said spring box vertically upwardly on said wedge box,

means holding said spring box against upward movement so long as a predetermined velocity of descent of said vertically movable member is not exceeded, and operative normally to hold said braking surface spaced from and out of engagement with the confronting surface of said stationary member,

resilient means interposed between said plate and said spring box constantly urging said plate and its braking surface in a horizontal direction toward engagement of said braking surface with the confronting surface of said stationary member, and

means operative positively to move said spring box horizontally toward said stationary member upon movement of said spring box vertically on said wedge box, thereby positively to engage said braking surface, against the resistance of the last-named resilient means, with the confronting surface of said stationary member upon such vertical movement,

said braking surface comprising a plurality of spaced metal teeth projecting from said one side of said plate toward said confronting surface and operative to engage and dig into said confronting surface when said braking surface is engaged therewith.

2. A safety brake assembly as defined in claim 1, wherein a plurality of elongate, flexible metal files are removably secured in side-by-side, coplanar relation on said plate to extend lengthwise in the direction of movement of said movable member, and to form said braking surface.

3. A safety brake assembly as defined in claim 1, wherein said means for moving said spring box positively comprises sliding surfaces on one of said wedge box and said spring box, respectively, which are inclined to the direction of movement of said movable member, and are operative,.when said spring box is moved vertically, to guide said spring box and said plate diagonally toward said stationary member to brake-engaging position.

4. A safety brake assembly as defined in claim 1, in-

cluding means for releasably securing said files on said frame to permit slight flexing thereof in their longitudinal directions when saidplate is in its active, braking position.

5. A safety brake assembly as defined in claim ll,

wherein said means mounting said plate on said spring box comprises a plurality of pins secured at one end to said plate and projecting at their opposite ends slidably through registering openings in said spring box,

means is provided on said opposite ends of said pins to prevent withdrawal thereof from the last-named Openings, and

said last-named resilient means comprises a compression spring surrounding each of said pins and engaged at opposite ends thereof with said spring box and said plate, respectively.

6. A safety brake for an' elevator which is movable vertically on a mast, comprising a plate,

a flexible, serrated braking member secured to said plate in confronting relation to said mast and fastened to said plate rigidly at its upper end and with some permissible movement between plate and serrated member at its lower end a spring box,

resilient means interposed between said plate and said spring box for mounting said plate on said box and constantly urging said plate and the serrated member mounted thereon toward engagement with said mast,

a wedge box on which said spring box is mounted,

second resilient means normally operative to lift said spring box upwardly on said wedge box,

means for holding said spring box in a down, disengaged position, against the resistance of said second resilient means, and operative, when said elevator descends at a rate in excess of a predetermined speed, to release said spring box to cause said second resilient means to move said spring box upwardly on said wedge box, and

guide means between said spring box and said wedge box operative upon lifting of said spring box to move said spring box toward said mast to cause said serrations to engage and brake said elevator.

7. A safety brake as claimed in claim 6, wherein said guide means comprises a slot in said wedge box inclined upwardly toward said mast, and a roller on said spring box engaging in said slot.

8. A safety brake as claimed in claim 6, wherein the teeth of said serrations are inclined downwardly from their bases to their tips in the direction of descent of the elevator.

Claims

1. A safety brake assembly for braking the descending motion of a vertically movable member relative to a stationary member, comprising a wedge box secured to said movable member, a spring box vertically reciprocable on said wedge box, a rigid plate having an elongate braking surface on one side thereof confronting said stationary member, means mounting said plate on said spring box so that said plate moves vertically with said spring box, resilient means connecting said spring box with said wedge box and constantly urging said spring box vertically upwardly on said wedge box, means holding said spring box against upward movement so long as a predetermined velocity of descent of said vertically movable member is not exceeded, and operative normally to hold said braking surface spaced from and out of engagement with the confronting surface of said stationary member, resilient means interposed between said plate and said spring box constantly urging saId plate and its braking surface in a horizontal direction toward engagement of said braking surface with the confronting surface of said stationary member, and means operative positively to move said spring box horizontally toward said stationary member upon movement of said spring box vertically on said wedge box, thereby positively to engage said braking surface, against the resistance of the last-named resilient means, with the confronting surface of said stationary member upon such vertical movement, said braking surface comprising a plurality of spaced metal teeth projecting from said one side of said plate toward said confronting surface and operative to engage and dig into said confronting surface when said braking surface is engaged therewith.

3. A safety brake assembly as defined in claim 1, wherein said means for moving said spring box positively comprises sliding surfaces on one of said wedge box and said spring box, respectively, which are inclined to the direction of movement of said movable member, and are operative, when said spring box is moved vertically, to guide said spring box and said plate diagonally toward said stationary member to brake-engaging position.

4. A safety brake assembly as defined in claim 1, including means for releasably securing said files on said frame to permit slight flexing thereof in their longitudinal directions when said plate is in its active, braking position.

5. A safety brake assembly as defined in claim 1, wherein said means mounting said plate on said spring box comprises a plurality of pins secured at one end to said plate and projecting at their opposite ends slidably through registering openings in said spring box, means is provided on said opposite ends of said pins to prevent withdrawal thereof from the last-named openings, and said last-named resilient means comprises a compression spring surrounding each of said pins and engaged at opposite ends thereof with said spring box and said plate, respectively.

6. A safety brake for an elevator which is movable vertically on a mast, comprising a plate, a flexible, serrated braking member secured to said plate in confronting relation to said mast and fastened to said plate rigidly at its upper end and with some permissible movement between plate and serrated member at its lower end a spring box, resilient means interposed between said plate and said spring box for mounting said plate on said box and constantly urging said plate and the serrated member mounted thereon toward engagement with said mast, a wedge box on which said spring box is mounted, second resilient means normally operative to lift said spring box upwardly on said wedge box, means for holding said spring box in a down, disengaged position, against the resistance of said second resilient means, and operative, when said elevator descends at a rate in excess of a predetermined speed, to release said spring box to cause said second resilient means to move said spring box upwardly on said wedge box, and guide means between said spring box and said wedge box operative upon lifting of said spring box to move said spring box toward said mast to cause said serrations to engage and brake said elevator.