US1873807A - Elevator buffer - Google Patents

Description

E. E. ARNOLD ELEVATOR BUFFER Aug. 23, 1932.

Filed Sept. 18. 1929 Fig.2.

Fig.1.

INVENTOR Edwin E. flrnoid.

ATTORNEY Patented Aug. .23, 1932 UNITED STATES PATENT OFFICE 23 EDWIN E. ARNOLD, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA ELEVATOR BUFFER Application filed September 18, 1929. Serial No. 393,438.-

' ern elevator is toward increased speed of operation. For example, 500 to 600 feet per minute has been considered the maximum elevator speed consistent with comfort and safety. Recent developments in electrical control have demonstrated the practicability of the use of car speeds of 900 or more feet per minute.

However, when such high speeds are employ'ed, a new problem is presented to the elevator engineer in designing buffers and safety stops for insuring the gentle stopping of the car at the top and the bottom of the elevator shaft, in the event that the electrical control of the car fails.

While safety buffers have long been used for this purpose, they have all been designed with short strokes accommodated to the lower speeds ofoperation of the cars, and hence,

these old buffers are inadequate to safely stop the cars from the higher speeds, since the stored'energy to bearrested and absorbed by the bufler increases as the square of the speed.

The solution appears to be either the use of a greater force acting through the distance of the short stroke or the use of alesser force acting through a much longer stroke. T'o exert a greater force would result in the too rapid checking of the speed of the car, thereby endangering the passengers, as well as the p enclosed within a chamber which surrounds the stationary rod. The fluid provides a' equipment; A

However, to increase the length of I the stroke of the buffer presents the problem of retrieving the buffer to its extended position after its operation. The use of springs for this purposejis limited to comparatively short-stroke buffers because of the relatively short expansion characteristic of springs, and the use of combinations of springs is not satisfactory because such combinations are unwieldy and cumbersome.

An object of my invention, therefore, is to provide a buffer for elevators having a long stroke and one which does not require the use of a long spring to retrieve it after it has been operated.

Another object of my invention is to provide a bufler, the moving parts of which have a minimum weight, thereby reducingshocks due to inertia of such parts when getting them under way at the high speed of initial contacts of the mass to be brought to rest.

Another object is to employ, in such buffers, a dense fluid medium adapted to give a higher dynamic resistance than oil so that smaller pressure areas may be employed.

Another object is to eliminate the use of long springs as a restoring means to which My inventioncomprises essentially a rela-' tively long hollow buffer ram slidably mounted upon, and telescopically engaging, a relatively stationary rod or plunger. Means are provided to entrap air within the hollow ram above the plunger which is compressed during an operating stroke and expanded to retrieve the ram.

A mass of mercury or like dense fluid is force resistant to the operating stroke of the ram 4 and is bypassed along the ram toward its free end. i

A combination is thereby provided wherein two fluids are effective to yieldingly resist the motion of the buffer ram, upon an application of force thereto, and retrieve the ram to its original position upon removal of the applied force.

My invention also embodies a novel auxiliary buffer associated with the main butler,

and in series therewith, for absorbing ini- Parts having the same functions will be designated by the same reference character in both figures.

In Fig. 1 is shown an outer casing 1 within which is disposed a cylinder 2 which contains a resistance fluid 3 of high density, preferably mercury. A hollowram 4, which is the principal shock-absorbing element, has a cap l on its upper end, its lower end being fitted to 4 reciprocate in cylinder 2.

An opposing plunger 5 extends substantially the full length of the cylinder 2 and 1s centrally disposed within the latter to form a chamber therebetween and is fitted to slide within the ram 4. Plunger 5 and cylinder 2 are'held in fixed relation by being attached to a common base 6 comprising a piston in the cylindricalcasing 1.

A fluid seal is maintained between the ram 4 and the plunger 5 by means of a sealing ring 7, disposed adjacent to the upper end of the plunger 5, together with a small amount of mercury 7 placed above its ring. By means of this seal, air is entrapped within the ram 4, thereby forming a cushion below it. The chamber between the cylinder 2 and the plunger 5 is filled with mercury or like dense fluid. .Vhen mercury is employed as the resistant fluid, it will have considerable buoyant effect on the ram l which, as will be seen, is always partially immersed therein. With the buoyancy of the mercury assisting the air cushion in supporting the ram l, only a slight air pressure is necessary to maintain it in an extended position. As will be explained below, the mercury and entrapped air operates on the associated elements to retrieve the ram 4 after it has been. forced into its retaining cylinder 2. It is apparent that the pressure of the air forming said cushion may be suflicient to retrieve and support the ram 4.

When the ram 4 is forced downwardly, its movement is resisted by the mercury, or other fluid, in cylinder 2 which is displaced and escapes through an annular space between the outer wall of the ram and the inner wall of the cylinder, and into overflow chamber 8. This space is provided by fitting the ram l into the cylinder 2 with the proper amount of clearance. By making the clearance greater or less, any desired resistance may be secured.

The same clearance is maintained between ram 4 and cylinder 2 throughout their entire lengths. As the ram is forced down into the cylinder, the above mentioned annular space is lengthened. Owing to the high surface tension of mercury and the increase in length of the space through which it must flow, its resistance to flow is correspondingly increased. 1 thereby obtain the desired characteristic of increased resistance of the shockabsorbing element as it approaches its limit of travel.

It is desirable, in heavy duty high-speed buffers of this type, to absorb the initial shock of impact of the applied force, by utilizing the combined shock-absorbing effect of two bufl'ers operating in series at the instant of impact and for a limited portion of the stroke. This I accomplish by using a long-stroke fluid-resistance buffer comprising a solid plunger and a short-stroke auxiliary bulier with a spring retrieving means associated therewith. This provides a sufficiently effective arrangement wherein a relatively large amount of fluid is displaced.

Such an auxiliary buffer may comprise an auxiliary buifer chamber 9 at the bottom of the casing 1, as shown in Fig. 1, and this chamber is filled with oil or like fluid. Base,

operates, through cylinder 2, to retrieve base- 6 and the parts moving in unison therewith.

Base 6 is depressed by the force exerted upon ram 4, which force is transmitted to the piston 6 through the fluid in cylinder 2 and the air above ram 5, whereupon piston 6 is. moved downwardly upon the oil 1n chamberv 9 and, at the same time, compresses spring 10 in the chamber 11. The downward movement of the piston 6 in chamber 9 is resisted by the oil in the chamber as it flows around the piston passing from below to above it as it descends. Upon removal of the applied force, spring. 10 acts against the base of chamber 8 to force piston 6 and its associated parts upwardly, and the displaced oil will be returned from casing 11 into chamber 9, thereby restoring the base 6 to its original position.

Fig. 2 shows another form of my inven tion wherein the auxiliary bufier is attached to the upper or free end of ram 4. This modification also includes a series buiier action, as is embodied in Fig. 1, except that the applied force is first exerted on the auxweight.

ilia'r-y bufii'er instead of on the main buffer.

The adding of inertia to ram 4, bythis con-l struction, is large-1y compensated because the initial shock is absorbed mainly by the auraliary buffer, very little of it being transmitted.

tion,to' correspondingelements in Fig. 1.

Casing 1, cylinder 2, and ram 5 are concentricallymounted on base 6 which, in this embodiment, does notreciprocate as a piston butis integral with the pedestal of the buffer. Ram 4' reciprocates in cylinder 2 and functions in the same manner as in the structure shown in Fig. 1. I provide a fluid seal-7 adjacent to the upper end of ram 5 to entrap air within ram4. This air, aided by the resistance .fiuid, operates to, retrieve ram 4 in the same manner as in Fig. 1. Overflow chamber 8 receives the displaced fluid from cylinder 2.

In Fig. 2, the auxiliary bulfer is located on: the'free end of ram 4. An oil. reservoir 9 'is formed within the upper portion of ram 4, by a partition 12, within. which an auxiliary plunger 13 is slidably mounted in concentric spaced relation thereto. A spring 10 is provided to support the auxiliary plungerv 13 and retrieve the latter after a downward stroke thereof. A chamber 11, in communication with the open end of chamber- 9, serves as an overfiow reservoir and. also provides a base for seating spring 10, the upper end of which bears against a shoul- 1 fer-elements are concerned, but their cooperader'14 onauxiliary plunger 13.

Either embodiment of my invention, when used in connection with elevators, is placed inthe well of the elevator shaft at the end of travel of the elevator car or the counter- The object is to check the movement of the car or the like before it comes against the bottom of the elevator shaft. The car, proceeding downwardly in the shaft at a sub stantial rate of speed, strikes the buffer cap 4 with high initial shock, causing the ram 4'to suddenly start moving downwardly.

My-device provides for initial rapid move ment of the ram 4 through the use of buffers ;in series with low initial fluid resistance which increases rapidly toward the end of the stroke, as hereinbefore described.

1 In the operation of the embodiment shown in Fig. 1 the force of the downwardly moving body is transmitted, through ram 4, to the cylinder assembly 2 and thence to piston 6. Under the action of the applied forcc,.re sistancefluid 3'will begin to yield and bypass around ram 4 to chamber 8. At the-same time, the fluid in chamber 9 will begin to yield and pass around piston 6 through the annular clearance space, shown in Fig. 1, thereby allowing piston 6 and ram 4 to move simultaneously. I V j For the first portion of the stroke, and

until piston 6 reaches'the bottom of chamber 9, the action of the twov buffers will be in series, which will-allowa comparatively rapid movement of ram 4. By the time the auxiliary bufl'er has completed its stroke-,the initial impact shock will have been absorbed, and the inertia of the falling body. will havebeen somewhat checked. -The complete retarda-- tion of thecar will be accomplished by the action of theresistance'fluid 3 alone asthe rain 4 is forced fartherinto cylinder 2. Owing to the increased resistance of the fluid, as the ram .4 moves downwardly in cylinder 2,- the inertia of the falling car will be rapidly absorbed, and the car brought to rest-without shock.

Duringv the downward movement of .ram 4, air, entrapped therein by. the'seal'7' on the upper end of ram 4, is compressed. At the same time,thedepth of the immersion of the ram inthe fluid 3 .is increased, and spring-1O is compressed.

lVhen the car is lifted from the bufferyth-e ram 4 will be retrievedto its original position by the action of the compressed air with in it, aided by the buoyant effect of the resistance fluid 3 upon it. The spring 10 will operate to force the piston Gland elements assembled therewith upwardly to their original position, thereby completely restoring the bufl'er'to its original condition.

The operation of the modified structure shown in Fig. 2, in which the auxiliary but fer is placed free at'the end of ram 4,. is similar, so far as the action of the main bufauxiliary plunger to the overflow chamber 11.

The flow of the liquid around the auxiliary plunger 13 at a high rate of speed affords considerable'resistance which reacts downwardly on theram 4 and the latter is accelerated.

By the time the auxiliary plunger 13 is'completely depressed, the ram 4 has been accelerated to move at a speed substantially equal to that of the car. Since the hollow ram 4 was not instantly accelerated to the speed of the car by direct engagement therewith, but was gradually accelerated to the speed'of the car during the stroke of the auxiliary plunger After the car is lifted from the bufler, the buoyancy of the resistance fluid 3 and the action of the compressed air entrapped in the hollow ram 4 restores the latter to its nor- 5 mal elevated position. 'The spring and the liquid associated with plunger 13 also restores it to its normal position and the device is reset for another operation.

While I have described my invention as applied to elevators, it is obvious that it may 2 in said cylinder operative to bypass the ram and produce a buffer action with respect to the movement of said ram, with means associated with said ram to form an air chamber, and means tocompress the air in said chamber during an operative. stroke of said ram, whereby the air, when compressed, is eflec tive to retrieve said ram.

2. In a fluid-resistance buffer, the combination of a cylinder, a hollow ram disposed gfftO reciprocate within said cylinder, and a fluid of high density within said cylinder, said fluid being displaced upon a movement of said ram to yieldingly retard the motion thereof, with means for .entraining air with-' 35; in said ram, and means associated with said ram for compressing said air during an operative stroke of said ram, whereby the air,-

when compressed, is effective to retrieve said ram.

3. A buffer comprising a cylinder containing a fluid, an overflow chamber at the upper end thereof, a plunger centrally disposed within said cylinder and held in a fixed relation thereto, a hollow ram arranged to slide .over said plunger and other fluid means compressible between said. plunger and ram for yieldably holding said hollow ram in a raised position.

buffer comprising a cylinder-con- 'itaining a fluid, an overflow chamber at the upper end thereof, a hollow ram slidable within said cylinder, an opposing. plunger slidable in said hollow ram, said cylinder and said opposing plunger having a common base,

and means tending to hold said hollow ram in a raised position comprising air entrapped within said hollow ram by said opposing plunger;

5. A buffer comprising a cylinder con- .ta-ining mercury, an overflow chamber at the upper end thereof, a rod centrally disposed within said cylinder, a base common to said cylinder and said rod, a hollow ram slidable within said cylinder and over said rod,

whereby the buoyancy ofsaid mercury acts upon said hollow ram to maintain the latter in a raised position.

6. A fluid-resistance buffer comprising a cylinder containing a fluid, a hollow ram normally held in an extended position and slidable within said cylinder in contact with said fluid, an opposing plunger disposed to slide withinsaid hollow ram and an air cushion between said ram and plunger, said air cushion and the buoyancy of said fluid being effective to restore said hollow ram to its extended position after displacement thereof.

7. In a buffer, an outer casing, a rod centrally disposed within said casing, a hollow cylinder intermediate said casing and said rod and spaced from the latter, a fluid within said space, a hollow ram slidable over said rod to engage and displace said fluid and an air cushion within said hollow ram above said rod.

' 8. In a buffer, an outer casing, a rod centrally disposed within said casing, a hollow cylinder intermediate said casing and said rod and spaced from the latter, mercury within said space and a hollow ram slidable over said rod to engage and displace said mercury, whereby the buoyancy of said mercury tends to maintain said ram in its raised position.

9. A buffer comprising a cylinder, a plunger centrally disposed within said cylinder and 'Xed with respect to the same to form an annular space between them, a hollow ram slidable within said annular space, mercury within said space tending to float said hollow ram and acting as a resistance fluid during the downward stroke of said ram, an air space within said hollow ram and above said mercury and sealing means carried by said centrally disposed ram and interposed between said air space and said mercury to entrain air within said space, whereby the compression of said air between the plunger and the ram acts to return the said hollow ram toits raised position.

10. In a buffer, an outer casing, a rod centrally disposed within said casing, a cylinder intermediate said casing and said rod and spaced from the latter, a fluid within said space, a hollow ram slidable over said rod to engage and displace said fluid, and an air cushion within the hollow ram above said rod, said cylinder and said rod being mounted on a common base to form a unit slidable within said casin and an auxiliary fluid reservoir within said casing and below said base.

11. In a buffer, an outer casing, a rod centrally disposed within said casing, a cylinder intermediate said casing and said rod and spaced from the latter, a fluid within said space, a hollow ram slidable over said rod to engage and displace said fluid, an air cushion within the hollow ram above saidrod and an auxiliary buffer mounted on said hollow ram.

up the initial shock upon sudden actuation thereof.

In testimony whereof, I have hereunto subscribed my name this 4th day of September,

EDWIN E. ARNOLD.

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