US3462024A - Draft gear - Google Patents

Draft gear Download PDF

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Publication number
US3462024A
US3462024A US638911A US3462024DA US3462024A US 3462024 A US3462024 A US 3462024A US 638911 A US638911 A US 638911A US 3462024D A US3462024D A US 3462024DA US 3462024 A US3462024 A US 3462024A
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United States
Prior art keywords
piston
cylinder
orifice
hollow piston
head
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Expired - Lifetime
Application number
US638911A
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English (en)
Inventor
Erwin H Hartel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Cleveland Pneumatic Tool Co
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Cleveland Pneumatic Tool Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Cleveland Pneumatic Tool Co filed Critical Cleveland Pneumatic Tool Co
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Publication of US3462024A publication Critical patent/US3462024A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B61—RAILWAYS
    • B61G—COUPLINGS; DRAUGHT AND BUFFING APPLIANCES
    • B61G7/00—Details or accessories
    • B61G7/06—Coupling heads constructed to facilitate alignment

Definitions

  • This invention relates to hydropneumatic draft gear for railroad cars.
  • Such operating mode in draft provides virtually solid-train operation, thereby minimizing the increase in train length which has been experienced and found objectionable in many conventional end-of-car cushioning devices.
  • Another object is to provide such hydropneumatic draft gear including improved relief valve protection against overload, for example, in the event of greater than normal impact.
  • FIGS. 1 and la are longitudinal sections which together show a full draft gear in accordance with the present invention:
  • FIG. 2 is a transverse cross-sectional view of the plane of which is shown by the line 22 in FIG. 1;
  • FIG. 3 is a further transverse section as viewed from the plane of the line 3-3.
  • the illustrative embodiment of the invention is a gear basically comprising a coupler head section 10, which can be of any known type, a cylinder 11 welded to and extending from the coupler head, a hollow piston 12 within and projecting from the cylinder, and a piston fitting or cap 13.
  • the fitting 13 is a forging or casting welded to the outer end of the hollow piston and having a cavity 14 which complements the latter in the sense of forming a closed and extension of the piston interior.
  • This fitting is further formed with a horizontal lug 15 in which there is a vertical aperture 16 for pin connection of the gear to the railway car.
  • the dashed outline 17 represents a standard freight car sill, and it will be appreciated that the gear is simply inserted in such a sill and supported in any suitable manner.
  • a solid plate, such as shown by the further dashed outline 18, which closes the sill bottom over the full length of the gear is recommended to protect the piston in particular from direct impingement of debris, and it is also preferred that antiturn blocks 19, 20 and 21 be secured to the exterior of the cylinder to prevent rotation of the coupler.
  • the bottom block 19 engages the hanger plate, while the other blocks 20 and 21 are separate angular projections respectively adjacent the upper corners of the sill.
  • a piston head 22 is threaded on the inner end of the hollow piston 12 and locked by one or more dowel pins 23 which extend radially through the internally threaded skirt part 24 of the piston head and into the piston.
  • the periphery of this portion 24 is relieved by a multiplicity of circumferentially spaced axial slots 25, cooperably with the inner surface of the cylinder 11, and also a clear annular space 26 at the outer side of such slotted part.
  • the piston head is supported for relative movement in the cylinder by a split bronze ring bearing 30 seated partially in a peripheral groove in the piston head, and a central metering orifice 31 is provided in the piston head for fiow of hydraulic fluid from the cylinder to the interior of the piston.
  • This flow is programmed by a metering pin 32 which extends from a secondary piston head 33 in a direction away from the coupler head 10 or inwardly of the gear with a progressively decreasing external diameter.
  • Such pin which is in sealed threaded engagement with the secondary piston head as shown, extends through the metering orifice 31 of the piston head and its free end 34 within the piston is flared to engage the head about the orifice and accordingly limit the relative extension of the pin.
  • the pin is also provided with a through bore 35, with a relief 36 provided in the face of the coupler head 10 which affords communication with the pin bore 35 even when the secondary piston is in the illustrated condition against such coupler face.
  • the hollow piston is sealed in the cylinder by a main gland preferably of chevron type and shown as comprising a series of rings 37 of V-shaped cross-section held in compression between machined bronze packing rings 38, 39.
  • These rings or chevrons are interleaved with bronze or Teflon spacers 40 to maintain their shape under load, and the compressive load is applied by a wave spring 41.
  • the assembly is held in place by a retainer washer 42 and a snap ring 43, with positive retention of the latter assured by machining a recess in the end of the retaining washer and thus making it necessary to physically compress wave spring 41 before snap ring 43 can be removed.
  • the gland further includes a conventional wiper and scraper assembly 44 external to the chevron seal unit for removing any foreign material which might adhere to the extended piston, and a grease cavity 45 is incor porated between the chevron unit and the wiper ring to keep the outboard chevrons from drying. This is an added precaution to assure long seal life, since if the inboard chevrons seal effectively, the remaining rings will be found to run almost completely dry. It is preferred for this purpose to employ a light grease to minimize wear and operating friction, and the cavity 45 is fairly large in volume compared to the amount of the grease needed so that servicing at frequent intervals should not be required.
  • the full assembly is contained in a gland nut 46.
  • a floating piston 47 is disposed in sealed relation within the hollow piston 12 to define a variable volume accumulator chamber 48 therein isolated from the end portion of the piston having communication through the metering orifice 31 with the main interior of the cylinder and also through the passages 29 and slots 25 with the annular chamber 49 about that portion of the hollow cylinder which is inboard of the main gland.
  • the cylinder will be filled with oil, and a charge of pressurized air will be provided in the hollow piston chamber.
  • Dual seals are employed for sealing of the floating piston 47, with each preferably comprising a standard O-ring 50 in assembly with dual polytetrafluoroethylene backup rings 51 and a quad ring 52.
  • These quad rings serve not only to preload the O-rings for most efiicient sealing, but also provide two added sealing surfaces and thereby three lines of contact instead of the usual single contact in a conventional O-ring installation.
  • the backup rings 51 are recommended to insure long life, since they prevent extrusion of the O-ring into the clearance gap during dynamic operation at high pressures. These backup rings are closely fitted to both the bore and the O-ring groove, with the polytetrafluoroethylene selected for long life and minimum friction.
  • a felt wiper 53 is also used on the air side of the floating piston to maintain a thin oil film in the piston-accumulator bore, with this also helping to enhance long life and leak-free operation.
  • the floating piston 47 is provided with one or more passages 54 which extends from a peripheral relief 55 between the two seals commonly to an axial passage 56 from which a hollow pilot tube 57 extends into the main bore 35 of the metering pin 32.
  • the pilot tube which is of course movable relative to the pin, has a head 58 at its free end sealed to the bore.
  • This tube and passage arrangement provides an atmospheric bleed between the seals completed by vent passage 59 from the coupler head relief 36 to the exterior, with the result that full charge pressure is always experienced by both to avoid the potential difficulty of providing leak-free sealing with essentially zero differential pressure.
  • the gear is also protected against overload, in the event of greater impact than normally expected, by a relief valve arrangement mounted on the piston head 22.
  • This assembly comprises two valve blocks 60 against the end face of the head and spaced 180 apart. Each block contains a small stepped piston 61 controlling a large relief passage 62 extending to a radial passage 29 and thus in bypass relation to the head metering orifice 31.
  • the pistons 61 are loaded by circular spring segments 63 designed to provide a specific load stroke curve over the required deflection, and the step dimensions on the pistons are established by the spring load and by the desired pressure for the relief.
  • the springs 63 will be seen normally to maintain the pistons 61 in extended outward relation, with radial inward movement against the spring load resulting in the uncovering of the relief ports.
  • the latter will be sized to accept the high flow rates that will be encountered at impacts in excess of the normal design value.
  • This new draft gear is filled and charged in the following manner.
  • the gland nut 46 is backed off from contact with the cylinder end and a small air charge is introduced at a fitting 64 in the piston end 13, so that the accumulator will hold the unit in the neutral position during filling.
  • the gland nut has two fill passages 65 closed by plugs 66, and the latter are removed, with oil supplied through one with the unit vertical and interior air displaced through the other until overflow occurs, the plugs then being reinstalled.
  • the piston head can be provided with a plurality of same holes 67 to facilitate the filling operation.
  • the unit After this filling and the tightening of the gland nut 46, the unit is then charged to the full air pressure. However, if desired for handling, the unit can be retracted by reducing the charge and subsequently recharged for extension to the neutral position.
  • the displaced oil after passing through the piston head 22, enters the end of the hollow main piston 12 and forces the floating piston 47 inwardly to compress the air charge. Part of the oil also flows outwardly through the relatively large radial passages 29, thereby forcing open the ring valve 27, so that the flow continues through the slots 25 around the head and increases the volume in the annular cavity 49.
  • the air pressure built up in the accumulator will extend the unit to the neutral position.
  • the draft gear is designed so that the gland nut 46 actually bottoms on the piston end or fitting 13 before any of the internal parts come into contact. In this manner, the load is transferred directly into the outer cylinder eliminating external bump stops required by most other cushioning devices. The operation of the relief mechanism has already been described.
  • the coupler With respect to the draft operation, as the coupler is pulled out, it carries the cylinder 11 with it while the metering pin 32 and secondary piston 33 are, however, restrained by the primary piston 12 and do not move relative to the car frame.
  • the volume of oil between the heads of the two pistons accordingly does not change, but the volume of annular cavity 49 between the primary piston and the gland nut is reduced.
  • the only path for the oil displaced by this reduction is through the snubbing holes 28 in the ring valve 27, and again this action prevents the unit from being extended rapidly.
  • the air charge pressure acts on the secondary piston area to provide a very high pullout force which may, for example, be on the order of about 63,000'lbs. and increase about 2,000 lbs.
  • the new design can provide a stroke of 13 in buff and 3" in draft, which will be seen to provide over-all performance superior to conventional end-of-car cushioning devices.
  • This unit can provide protection for a car Weighting 222,000 lbs. to at least 10 miles per hour, within the standard couplerforce specification of 500,000 lbs. when bumped into a car equipped with conventional friction type draft gear.
  • the pivotal attachment of the new gear to the car is,
  • a railroad car draft gear including a cylinder and hollow piston, with a coupler head carried by one and the other adapted to be attached to the car, a floating piston within the hollow piston, the inner end of the latter having an orifice providing communication with the interior of the hollow piston at one side of the floating piston, the cylinder being filled with oil and the hollow piston at the other side of the floating piston containing compressed air, metering pin means movable relatively in said orifice to control the area thereof, said metering pin means having an axial passage, and a pilot member attached to the floating piston and slidably extending into the passage of the metering pin means for stabilizing relative movement of the floating position.
  • pilot member is a tube forming part of said passage means
  • pin means passage is another part which extends to the atmospheric vent.
  • hollow piston a coupler attached to one of the cylinder and hollow piston, means for pivotally attaching the other of the cylinder and hollow piston to a railroad car in sill structure of the same, a floating piston within the hollow piston dividing the interior thereof in first and second chambers, an orifice in the hollow piston providing communication between the first chamber and the cylinder interior, metering pin means movable relatively in said orifice to vary the area thereof, a secondary piston relatively movable within the cylinder to which the pin means is attached, and stop means for preventing full relative withdrawal of the pin means from the orifice, the first chamber and cylinder being filled with liquid and the second chamber containing a charge of pressurized air which maintains the cylinder and hollow piston in a neutral partially extended condition.
  • the hollow piston has further orifices means therethrough in bypassing relation to the first-named orifice, and relief valve means applied to the end face of such hollow piston normally closing said further orifice means and opening the same when the liquid pressure in the cylinder reaches a preselected value, said relief valve means including a valving member and a curved spring segment biasing the same in the closing direction.
  • the relief valve means comprises a pair of pistons and curved spring segments loading the same, said pistons being stepped to provide small differential areas to overcome the spring forces.
  • a railroad car draft gear including a cylinder and hollow piston slidable therein, with one carrying a coupler head and the other adapted for attachment to the car, a floating piston within the hollow piston and dividing the interior thereof into first and second chambers, first orifice means providing communication between the first chamber and the cylinder interior, metermg pin means movable relatively in said orifice to vary the area thereof with relative movement of the cylinder and hollow piston, second orifice means in bypassing relation to the first orifice means, and relief valve means applied to the end face of the hollow piston and controlling the second orifice means, said relief valve means comprising a body forming a continuation passage for the second orifice means generally normal to said end face, the passage having a side opening, and the valve means further including a traversely movable differential area piston normally closing said opening and hence the second orifice means, and a curved spring segment actlng at one end against said differential area piston for loading the same and being anchored at the other end to the end face of the hollow piston.
  • railroad car draft gear comprising a cylinder, a hollow piston slidable in said cylinder, a coupler head affixed to one of said cylinder and piston and the other being adapted for attachment to a railroad car, first packing means engaging the inner end portion of the hollow piston and the interior of the cylinder, second packing means engaging the cylinder adjacent its free end and the exterior of the hollow piston, with the latter formed to provide with the cylinder an annular cavity between the first and second packing means, a floating piston movable within the hollow piston to define first and second chambers of variable volume therein, first and second spaced seals carried by the floating piston in engagement with the hollow piston, passage means extend- 1ng from the exterior of the floating piston between said first and second seals to an atmospheric vent, first ori fice means in the hollow piston providing communication between said first chamber and the cylinder interior, piston-position responsive means for controlling the area of said first orifice means, second orifice means hetween said first chamber and said annular cavity, the cylinder and first chamber being filled with liquid and the second
  • railroad car draft gear comprising a cylinder, a hollow piston slidable in said cylinder, a coupler head affixed to one of said cylinder and piston and the other being adapted for attachment to a railroad car, first packing means engaging the inner end portion of the hollow piston and the interior of the cylinder, second packing means engaging the cylinder adjacent its free end and the exterior of the hollow piston, with the latter formed to provide with the cylinder an annular cavity between the first and second packing means, a floating piston movable within the hollow piston to define first and second chambers of variable volume therein, first orifice means in the hollow piston providing communication between said first chamber and the cylinder interior, a metering pin carried by a secondary piston relatively movable within the cylinder and through said first orifice means to control the area thereof, said metering pin having stop means for limiting retraction thereof from the first orifice means, second orifice means between said first chamber and said annular cavity, the cylinder and first chamber being filled with liquid and the second chamber containing a pressure air charge
  • pilot member is a tube and part of passage means extending to the exterior of the floating piston, and the pin passage leads to an atmospheric vent.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Fluid-Damping Devices (AREA)
  • Turning (AREA)
US638911A 1967-05-16 1967-05-16 Draft gear Expired - Lifetime US3462024A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US63891167A 1967-05-16 1967-05-16

Publications (1)

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US3462024A true US3462024A (en) 1969-08-19

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US638911A Expired - Lifetime US3462024A (en) 1967-05-16 1967-05-16 Draft gear

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US (1) US3462024A (show.php)
BE (1) BE715249A (show.php)
DE (1) DE1755278A1 (show.php)
FR (1) FR1558763A (show.php)
GB (1) GB1212562A (show.php)
NL (1) NL6814282A (show.php)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3598249A (en) * 1969-01-27 1971-08-10 Smith Corp A O Railway draft appliance
CN114761303A (zh) * 2019-12-06 2022-07-15 亚历山大·亚历山大罗维奇·安德烈夫 减震单元

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2737301A (en) * 1952-12-01 1956-03-06 Levitation Ltd Buffers for railway, tramway and like vehicles
US2994442A (en) * 1960-06-20 1961-08-01 Bendix Corp Kinetic energy absorbing device
US3152699A (en) * 1963-05-27 1964-10-13 Smith Corp A O Railway draft appliance
US3216592A (en) * 1964-05-25 1965-11-09 Pullman Inc Hydraulic draft gear
US3378149A (en) * 1966-02-14 1968-04-16 Acf Ind Inc Railway car cushioning device

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2737301A (en) * 1952-12-01 1956-03-06 Levitation Ltd Buffers for railway, tramway and like vehicles
US2994442A (en) * 1960-06-20 1961-08-01 Bendix Corp Kinetic energy absorbing device
US3152699A (en) * 1963-05-27 1964-10-13 Smith Corp A O Railway draft appliance
US3216592A (en) * 1964-05-25 1965-11-09 Pullman Inc Hydraulic draft gear
US3378149A (en) * 1966-02-14 1968-04-16 Acf Ind Inc Railway car cushioning device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3598249A (en) * 1969-01-27 1971-08-10 Smith Corp A O Railway draft appliance
CN114761303A (zh) * 2019-12-06 2022-07-15 亚历山大·亚历山大罗维奇·安德烈夫 减震单元

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NL6814282A (show.php) 1970-04-07
DE1755278A1 (de) 1971-12-02
GB1212562A (en) 1970-11-18
BE715249A (show.php) 1968-10-16
FR1558763A (show.php) 1969-02-28

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