US3033384A

US3033384A - Hydraulic draft gear

Info

Publication number: US3033384A
Application number: US857615A
Authority: US
Inventors: Andrey L Zanow; Catherine A Overbeke
Original assignee: National Castings Co
Current assignee: National Castings Co
Priority date: 1959-12-07
Filing date: 1959-12-07
Publication date: 1962-05-08
Anticipated expiration: 1979-05-08
Also published as: NL109985C; NL258769A; ES263051A1; BE597802A; GB914563A; CH364662A

Description

May 8, 1962 A. l.. zANow ETAL HYDRAULIC DRAFT GEAR 2 Sheets-Sheet 1 Filed Dec. 7. 1959 www May 8, 1962 A. l.. zANow ErAL 3,033,384

HYDRAULIC DRAFT GEAR Filed Dec, 7, 1959 2 Sheets-Sheet 2 @Y 4free/Vey 3,033,34 HYDRAULIC DRAFT GEAR Andrey L. Zanow, Cleveland, Ohio, and .lohn W. Uverbeke, deceased, late of La Jolla, Calif., by Catherine A. (lverbelre, administratrix, La Jolla, Calif., assignors to National Castings Company, a corporation of Ohio Filed Dec. 7, 1959, Ser. No. 357,615 7 Claims. (Cl. 213-43) This invention relates to an improved railway draft gear. In particular, it is a draft gear that relies on the energy-absorbing attributes of a hydraulic mechanism to cushion the greater-than-average impacts delivered to the mechanism during railroad switching and humping operations.

Currently employed resilient type draft gears function adequately under the compressive forces induced by impacts, but they have little capacity for energy absorption. The resilient type of railway draft gear is characterized, in operation by its recoil after compression. A major part of the kinetic energy initially applied to this type of draft gear during the compressive stroke is stored by the gear in the form of potential energy. This energy is then returned to the train in the form of a jolting recoil during the expansion stroke of the draft gear. This recoil is responsible for much of the damage done to lading carried by the railroads.

The friction-type draft gears extensively employed by American railroads have a greater energy absorption level than the resilient type, but they, too, are characterized by a pronounced recoil. The jolting recoil that is present in the aforementioned types of railway draft gears is one that is generally inherentin any draft gear relying upon spring means to serve as the force cushioning means. The friction-type draft gear, however, does have 4an advantage over the resilient type in that it is able to dissipate a substantial portion of the compressive forces as frictional energy which is not returned to the train in the form of recoil, but it has not solved the problem entirely.

The ideal draft gear would be one having the ability to absorb all the compressive forces to which it is likely to be subjected, coupled with the ability to restore the draft gear to its extended uncompressed position without any recoil.

vlt is the primary object of this invention to provide a hydraulic energy-absorbing device adapted for use as a railway draft gear that is capable of sustaining high energy level impacts as well as being capable of automatic recovery with a minimum of recoil.

A specilic object of this invention is to provide a hydraulic energy-absorbing device adapted for use as a railway draft gear comprising two containers, one enclosing the other with a piston disposed in the inner container, the piston having a reservoir to receive uid upon compression of the mechanism, and means to restore the piston to its extended position with a minimum of recoil.

A more specific object of this invention is to provide a metering device for use in a hydraulic railway draft gear comprising a hollow tube having an exteriorly disposed flute of varying cross-section adapted for slidable insertion in an opening with a fixed perimeter during operation.

Other objects and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawings.

Referring to the drawings:

FIG. l is a longitudinal section illustrating the draft gear in its fully extended uncompressed position.

FIG. 2 is a longitudinal section illustrating the draft gear in a compressed position.

FIG. 3 is a cross section taken along line 3 3 of FIG. l.

FIG. 4 is a cross section taken along line 4-4 of FIG. 2.

FIG. 5 is a perspective of the draft gear metering device. f

The improved hydraulic draft gear comprises an outer container 2 and an inner container 4, both containing a fluid. The outer container encloses the inner container and is connected thereto at its open end by means of a duid-tight seal. Slidably dispose-d within the inner container is a piston member 6 that is reciprocable from an extended position of the gear to a compressed position. The travel of the piston member is from the extended position of the gear, shown in FIG. 1, to the compressed position, shown in FIG. `2. It is during this travel that energy absorption by the gear is effected.

Referring to FIG. 1, outer container 2 serves as the reservoir and overflow chamber for the fluid in inner container 4. Movement of the iluid from the outer container to the inner container may be effected by any suitable pressure producing means. In the embodiment illustrated, kgravity is relied upon as the pressure producing means to move the fluid to the inner container. The inner container functions as a cylinder in which piston member 6 is, as aforementioned, reciprocable from the extended position or the mechanism to the compressed position thereof.

The outer container 2 comprises a cylindrically shaped side wall S having an opening litt and screw cap l2 therefor providing means for the easy addition of iiuid to the reservoir chamber. Container 2 has a flat end wall 14 provided with inwardly facing, reinforcing ribs 16 so located as to strengthen end wall 13 of inner container 4 as well as to firmly stabilize the inner container within the outer container. Each reinforcing rib 16 has an opening 29 permitting fluid to pass readily from the reservoir chamber through a hollow fluted tube 22a into the piston and ultimately into the inner container.

As aforementioned, inner container 4 is located within the outer container and engages ribs 16 on the llat end wall y14 at the forward end of the outer container. At the other end, the inner container is tightly encircled by the outer Ycontainer and a substantially fluid-tight seal is provided by sealing element 17. Flat end-wall 18 of the forward end of the inner container has a centrally located circular aperture 24 which receives an end of the metering device 22, comprising the hollow uted tube 22a. The fit of tube 22a in the aperture 24 is substantially fluid-tight, and the tube is held in a Xed position within aperture 24 by snap-rings 26. The forward end of tube 22a is spaced from the opposing wall4 14 to allow ow of uid between the tube and outer con-V tainer 2. Extending into the open end of the inner container 4 is the hollow piston member 6, which is cylindrically shaped and is the movable element ofthe draft gear mechanism. The piston member may be squareor rectangular in cross-section. The only restriction on its shape is that it must be complemental to the inner container. However, in the preferred embodiment of the invention, Ias shown in the drawing, the piston member t is cylindrical in shape. At its forward end piston 6 has an end wall 28 provided with centrally disposed circular opening 30 kthat slidably receives hollow fluted tube 22a. Preferably, a snug lit exists between tube 22aand opening 3i). ln addition to circular opening 30, openings 32 of any suitable shape are provided in end-wall 28 to permit uid to pass, either during the `compression stroke of the mechanism, or `during the expansion stroke, or both. The embodiment illustrated in FIGS. 1 and 2 permits iiuid to ow through openings 32 during the expansion stroke only. Washer 34, mounted on tube 22a,- is adapted to engage front face 2SC of wall 28 to close the openings 32 during the compression` stroke while @al snap-ringv 36 secured to the forward ange 28a on wall 28 limits washer 34 in its movement away from the openings during the expansion stroke.

Within the piston the rearward end of the metering device 22 is formed with a cap member 38 which is inl tegral with tube 22a. This cap serves'a two-fold purpose: first, it forms a wall beyond which the fluid may not pass, and secondly, it serves as a stabilizing member for `tube 22a and the piston. An oil ring 40 is placed around the outer periphery of cap 38 to form a fluidtight seal between the cap and the inner surface 6a of the piston. Within the piston member is oil sump 42 which provides lubrication to thecap. The sump extends from cap 38 to transverse wall y54 which is aihxed to the piston by snap rings 56 and 58. Cap 38 is provided with a forwardly extending projection 38a having openings communicating with the opening 23 in tube 22a, thus permitting uid in the-piston to move to and fromV the reservoir, as indicated by the arrows in FIGS. 1 and 2. n

The rearward end of piston 6 is closed by an end plate 48 which is secured to the piston walls. Plate 48 is provided with lateral shoulders 48a which are in abutting relationship with the rearward end of coil spring 46. The spring surrounds portions of thepiston 6 and outer container 2wat its forward end and abuts against the shoulders 2a onvthe outer container; It is this spring that furnishes the'force to'restore the draft gear mechanism to its extended position after compression.

In FIG. l the draft gear mechanism is illustrated in its uncompressed position. IUpon compression of the mechanism, in response to draft or bui forces applied thereto, piston Vmember 6 moves into inner container 4. As the mechanism Vis compressed, washer 34 on tube`22 is forced Vagainst `flat surface 28e on end-wall 28 of the piston by the fluid in inner container 4, thereby closing openings 32. By thus closing openings 32, uid in the inner container is necessarily forced through the orifice formed by a pair of flutes 50 provided on the outer side of. tube 22a and circular opening 30 in end-wall 28 of the piston. It is to be understood that iiutes are formed inthe outer side of the tube and are of -a depth less than the thickness of the tube wall. The outerV surface of tube 22d is in` slidable contact withthe inner surface of opening 30'. The-utes are so shaped as -to form an orifice that is larger in cross-section at the beginning of thecompression stroke thanat the end of the stroke; Each flute commences at a point on tube 22d Where endvva11`28'- of the piston is positioned when the mechanism is fully extended,as in FIG;v l.l At this point, the crosssectional larea of the -u'te is greatest and likewise the aforementioned orifice formed by the'utes and opening 30 is fa maximum.- The flute decreases in cross-sectional area. in a. forward direction until it reaches the point along the tube where end-wall28 is positioned when the' mechanism is fully compressed. At the latter point, the orifice formed is `a minimum inA-cross-sectional area. By ythus changing the orifice size, the mechanism closes with ever-decreasing speed during the compression stroke, Up'on cessation of lthe compressive force, thedraft gear mechanism is restored to its'fully extended position by spring 46.

Dining the restoration stroke; washer 34 moves forwardly-away fromopenings 32 into contact with ,ring 36 of thepiston, thus enabling a rapid flow of fluid from the piston through openings 32 into the inner container 4 as the piston 'moves outwardly from the inner container. The maximum distance of extension of the gear isdetermined by abutment surfacefSZron projections 38a of the tube capwhich engages the rearward surface 28b of piston end-wall 28.VA However, the limitation could just yas well Vbe imposed by `the size of the draft'gear pocket in a railway car before end-wall 28 ever abuts against surface 52A.. j

During the energy-absorbing compression stroke, Huidiiow from the inner container is through the orifice formed by flutes 50 and opening 30 into the piston, thence into tube 22a via opening 44 and out into the the reservoir 2. The fluid-flow, as is indicated in FIG. 2, is due to a reduction in'thefavailable space within the inner container 4 caused by the movement of the piston walls into container 4. The volume of uidzdisplaced is equal, approximately, to the volume of the piston walls entering the inner container. During the extension or restoring stroke, fluid Vmoves from reservoir 2 into inner container 4 via the iluted tube and piston, as is shown by the arrows in FIG. l. Reservoir capacity is greater than the needs imposed by the changing inner container volume; tlie excess capacity being available to replace any fluid loss that may result due to protracted periods of use without preventive maintenance;

Although this invention is described in an Vembodiment calling for a cylindrically shaped inner and outer container, the only limitation as to shape is that the piston must be complemental to the inner container 4.

The terms and expressions which havebeen employed are used as terms of'description and not of limitation,

and there is no intention of excluding su'ch equivalents of the invention described or of the portions thereof as fall within the purview of the claims.

What is claimed is:

l. A hydraulic shock absorbing mechanism comprising an outer container and an inner container joined together at their open ends, fluid disposed in at least one of said containers, said outer container providing a fluid reservoir aboutsaid inner container, pressure means to move said fluid from the outer to the 'inner container, a hollow piston member reciprocable within said inner container, a fluid metering device extending within'said inner container and said piston member, said device comprising a longitudinal hollow tube secured to said'inner con-V tainer and slidably extending through an opening in the head of said piston, one end of said tube extending into said reservoir, said tube having in its sides a longitudinal flute of varying cross-section, said ute in conjunction' with said opening in the piston head forming an orificev of decreasing cross-sectional area as said piston member moves into said inner container during compression of said mechanism. l

2. A hydraulic shock absorbing mechanism comprising an outer container and an inner container oriented in the same direction, fluid disposed in at least one of said containers, said containers being sealed together at' their open ends, said outer container providing a uid reservoir, pressure means to move said fluid from the outer to the inner container, a longitudinal hollow tube member within said inner container and secured thereto, one end of said tube extending into said reservoir, said tube member having an exterior-ly disposed flute of varying cross-section, a piston member reciprocable within said inner container from an extended position to a compressed position of said mechanism, said piston member projecting longitudinally outward through the open end of said inner container, said piston member comprising a hollow cylinder closed at both ends, one of said ends having an opening to slidably receive said rod member during compression of the mechanism, said opening and said ilute forming an orifice of variable cross-sectional area upon compression or extension of the mechanism, and resilient means disposed in abutting relationship to said piston and said outer container to maintain the mechanism in an extended position.

3. A hydraulic shock-absorbing mechanism comprising an outer container and an inner container oriented in the same direction, said outer container enclosing said inner container and spaced therefrom, said containers being sealed together at their open ends, a uid disposed within saidA containers, pressure means vto move said fluid from the outer to the inner container, a piston member reciprocable from an extended to a compressed position of said mechanism disposed in said inner container and projecting longitudinally outward through the open end of said inner container, said piston member comprising a cylinder closed at both ends, one of said ends having an opening therein, a hollow rod member secured within said inner container and having an end extending into said outer container, said rod member projecting through the opening in the piston member to permit the latter to slidably receive the rod, said rod member having an exteriorly disposed ilute of varying cross-section extending lengthwise of the rod, stiel piston opening and said flute forming an orifice of varying crosssectional area upon compression or extension of said mechanism, and resilient means disposed in abutting relationship to said piston and said containers to maintain the mechanism in an extended position.

4. A hydraulic shock-absorbing mechanism comprising an outer container and an inner container oriented in the same direction, fluid disposed in at least one of said containers, said outer container enclosing said inner container and spaced therefrom, said containers being sealed together at their open ends, pressure means to move said lluid from the outer to the inner container, a piston member reciprocable within said inner container from an extended position to a compressed position of said mechanism and projecting longitudinally outward through the open end of said inner container, said piston member comprising a cylinder closed at both ends, one or said cylinder ends having a circular opening therein, a longitudinal hollow rod member disposed within said inner container and being secured thereto, one end of said rod member extending into said outer container, the other end of said rod member projecting through the opening in the piston member and having disposed thereon an annular cap, said cap sealing said hollow rod, an opening in said rod adjacent said cap and connecting with the opening in said rod member, the outer side surface of said cap being in slidable relationship with the interior surface of said piston member, said rod member having an exteriorly disposed flute of varying cross-section extending lengthwise of the rod, said piston opening and said ilute forming an orifice through which said fluid may pass upon compression or extension of said mechanism, and resilient means disposed in abutting relationship to said piston and said containers to maintain the mechanism in an extended position.

5. A hydraulic shock-absorbing mechanism comprising an outer container and an inner container oriented in the same direction, said outer container enclosing said inner container and spaced therefrom, said containers being sealed together at their open ends, a fluid disposed within said containers, pressure means to move said fluid from the outer to the inner container, the end-wall of said inner container having a circular aperture, a piston member reciprocable from an extended position to a compressed position of said mechanism disposed in said inner container and projecting longitudinally outward throng-'.1 the open end of said inner container, said piston member comprising a cylinder closed at both ends, one of said ends havin." a circular opening therein, a hollow rod member disposed within said circular aperture and connected to the end-wall of said inner container, theV other end projecting through the opening in the piston member, said rod member having an exteriorly disposed flute of varying cross-section extending the length of the rod, said piston opening and said flute forming an orice through which said iluid may pass upon compression or extension of said mechanism, an annular collar disposed on the outward end of said piston, resilient means disposed in abutting relationship to said collar. and said onter container to maintain the mechanism in an extended position.

6. The hydraulic shock-absorbing mechanism of claim 4 further characterized by said other end of the rod member having disposed thereon an annular cap, said cap sealing said hollow rod, an opening in said rod adjacent said cap allowing iluid to pass therethrough, the outer perimeter' of said cap in slidable abutting relationship with the inner surface of said piston member.

7. A hydraulic shock absorbing mechanism comprising a lltu'd reservoir container and a second container adjacent said reservoir container, uid disposed in at least one of said containers, pressure means to move said iluid rorn the reservoir container to the second container, a hollow piston member reciprocable within the second container, said piston member having an opening in the head thereof, a fluid metering device disposed within the second container and piston member, said metering device comprising a hollow tube-like rod secured to said second container and slidably extending through said opening, means on said rod cooperating with said openingl to form a fluid metering orii'ice varying in cross-section as said piston moves into said second container, said rod connecting said reservoir container to said piston member to allow fluid to pass therebetween.

References Cited in the iile of this patent UNITED STATES PATENTS 770,128 Teal Sept. 13, 1904 770,537 Raders Sept. 20, 1904 782,964 Hopkinson Feb. 21, 1905 1,378,281 Ross May 17, 1921 2,726,773 Fitz-lohn Dec. 13, 1955 FOREIGN PATENTS 366,156 Italy Dec. 20, 1938