1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
2、from, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2014 SAE International All rights reserved. No part of this p
3、ublication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-497
4、0 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/J684_201405 SURFACE VEHICLE STANDARD J684 MAY2014 Issued 1938-01Reaffirmed 2014-0
5、5 Superseding J684 JUL2005 Trailer Couplings, Hitches, and Safety ChainsAutomotive Type RATIONALE J684 has been reaffirmed to comply with the SAE five-year review policy. 1. ScopeThis SAE Standard includes couplings, hitches, and safety chains used in conjunction with all typesof trailers or towed v
6、ehicles whose Gross Vehicle Weight Rating (GVWR) does not exceed 4540 kg(10 000 lb). This includes such types as utility, boat, camping, travel, and special purpose trailers which arenormally towed by conventional passenger cars, light-duty commercial vehicles, light trucks, and multipurposepassenge
7、r vehicles. This document is intended primarily for ball-and-socket type of couplings and hitches. Itshould not be construed as a limitation to this type alone but should apply where appropriate to ring-and-pintle,clevis-and-pin, or any other draft means designed to serve this purpose.1.1 RationaleT
8、his document was revised to correct metric version of formulas found in Table 3.2. References2.1 Applicable PublicationsThere are no referenced publications specified herein.3. DefinitionsCoupling and Hitch NomenclatureThe following nomenclature has been adopted foruniformity in the terms used for t
9、he component parts of the trailer-coupling mechanism:3.1 HitchThat part of the connecting mechanism including the ball support platform and ball and thosecomponents that extend and are attached to the towing vehicle, including bumpers intended to serve ashitches.3.1.1 WEIGHT DISTRIBUTING HITCH (OR E
10、QUALIZING HITCH)A mechanical device that connects the trailer to thetowing vehicle and by means of leverage applied on both trailer and towing vehicle structures, when properlyadjusted, distributes the imposed vertical load at the hitch and coupling connection between structures oftowing vehicle and
11、 trailer.3.1.2 WEIGHT CARRYING HITCHA mechanical and/or structural device that connects the trailer to the towingvehicle, and that does not employ features designed to redistribute the load imposed at the hitch andcoupling connection.3.2 CouplingThat part of the trailer connecting mechanism by which
12、 the connection is actually made to thetrailer hitch. This does not include any structural member, extension of the trailer frame, or brake actuator.SAE INTERNATIONAL J684 Reaffirmed MAY2014 Page 2 of 9 4. Trailer Classification4.1 Class 1All types of trailers with a trailer Gross Vehicle Weight Rat
13、ing (GVWR) (trailer weight including itsload) not to exceed 910 kg (2000 lb).4.2 Class 2All types of trailers with a trailer GVWR of over 910 kg (2000 lb) and not to exceed 1590 kg (3500 lb)GVWR.4.3 Class 3All types of trailers with a trailer GVWR of over 1590 kg (3500 lb) and not to exceed 2270 kg(
14、5000 lb) GVWR.4.4 Class 4All types of trailers with a trailer GVWR of over 2270 kg (5000 lb) and not to exceed 4540 kg(10 000 lb) GVWR.5. Couplings5.1 Coupling ClassificationThere shall be four designations of couplings to cover all trailers up to 4540 kg(10 000 lb) GVWR. The designated classificati
15、on of the coupling shall be based on the GVWR of the trailerrather than the weight imposed vertically down on the ball by the coupling. The Class 1 coupling shall be usedon Class 1 trailers; the Class 2 coupling, on Class 2 trailers; the Class 3 coupling, on Class 3 trailers; and theClass 4 coupling
16、, on Class 4 trailers. This is not intended to limit the number or variety of couplings in a givenclass or to restrict the use of a heavier-duty coupling or hitch ball being used on a lighter class of trailer.5.2 Attachment of CouplingsAll couplings are to be attached to the trailers structural atta
17、ching member bybolting, welding, or riveting in such a manner that the loads indicated in Table 1 may be applied withoutincurring loss of attachment or distortion or failure which would affect the safe towing of trailers.5.2.1 Manufacturers of trailer couplings shall provide instructions for the att
18、achment of coupling housings totrailers.5.3 Provision for SafetyCouplings in all classes shall be equipped with a manually operated mechanism soadapted as to prevent disengagement of the unit while in operation.5.4 IdentificationTrailer couplings which meet the minimum standards set forth in Table 2
19、 shall be permanentlymarked with the following information:5.4.1 Coupling manufacturers name, initials, or trademark.5.4.2 Part, style, or model number.5.4.3 SAE coupling classification and maximum trailer GVWR.5.4.4 Ball diameters for which coupling is designed.TABLE 1STRENGTH TEST LOADSFOR COUPLIN
20、G ATTACHMENTSModeMinimum StaticTest LoadLongitudinal Tension and Compression 1.5 x Maximum Trailer GVWRTransverse Thrust 0.5 x Maximum Trailer GVWRVertical Tension and Compression 0.5 x Maximum Trailer GVWRSAE INTERNATIONAL J684 Reaffirmed MAY2014 Page 3 of 9 5.5 Coupling RatingsThere shall be a min
21、imum strength test for couplings by class as indicated in Table 2.5.6 Test FixtureBasic drawings of typical test fixtures (Figure 1) for use in determining conformance ofcouplings to the minimum strength test load requirements of Table 2 are included in this document to promoteuniformity in test res
22、ults by various testing laboratories.TABLE 2STRENGTH TEST LOADS FOR BALLS AND TRAILER COUPLINGS(1)(2)1. Vertical Tension Load RequirementThe vertical tension load requirement is extremely important because of the mechan-ics of holding the ball in the socket. On vertical-tension (or pullout) testing,
23、 the major portion of the tensile load is transferred from the lip of the coupling to the ball clamp and its supporting bolt, rivet, or inclined plane. While relatively little distortion occurs in the coupling housing, the ball clamp is forced back and downward until the final restricting force reta
24、ining the ball is lost and pullout occurs. The load at which retention is maintained is highly critical and loss of purchase on the ball occurs suddenly, going from safe retention to complete separation.2. Coupling versus Hitch Static Bench Test Load RequirementsCoupling strength design criteria are
25、 necessarily different than those for hitches and will be greater because of the stresses to which each is subjected. Couplings are welded or bolted to trailer tongues with only the socket and latching mechanism exposed. The coupling socket must take the concen-trated dynamic shock load as well as t
26、he varying stresses induced from normal trailering, and is the point of highest stress.The hitch load is distributed through the hitch components, spring deflections in the towing vehicle, shock absorbers, and the vehicle structure, and is affected by entirely different force distribution than the c
27、oupling. Hitches are actually subjected to much lower unit forces than are the coupling and the ball.TrailerClassificationTrailerCouplingDesignationTypical BallDiameter, mm (in)(where ball-typehitch is used)Minimum Test LoadRequirements, kN (lb)Class 1 Class 1 47.6 (1-7/8) Longitudinal Tension: 26.7
28、 (6000)Longitudinal Compression: 26.7 (6000)Transverse Thrust: 8.9 (2000)Vertical Tension: 11.1 (2500)Vertical Compression: 11.1 (2500)Class 2 Class 2 50.8 (2) Longitudinal Tension: 46.7 (10 500)Longitudinal Compression: 46.7 (10 500)Transverse Thrust: 13.3 (3000)Vertical Tension: 20.0 (4500)Vertica
29、l Compression: 20.0 (4500)Class 3 Class 3 50.8 (2) Longitudinal Tension: 66.7 (15 000)Longitudinal Compression: 66.7 (15 000)Transverse Thrust: 17.8 (4000)Vertical Tension: 31.1 (7000)Vertical Compression: 31.1 (7000)Class 4 Class 4 Ball and bolt shall be of suchsize and strength as to conformto the
30、 minimum breaking strength requirements of themating coupling required for thespecific load of Class 4 trailerLongitudinal Tension: Gross trailer Weight, N (lb) x 3Longitudinal Compression: Gross trailer weight, N (lb) x 3Transverse Thrust: Gross trailer weight, N (lb) x 1Vertical Tension: Gross tra
31、iler weight, N (lb) x 1.3Vertical Compression: Gross trailer weight, N (lb) x 1.3SAE INTERNATIONAL J684 Reaffirmed MAY2014 Page 4 of 9 FIGURE 1TYPICAL TRAILER COUPLING TEST FIXTURE ARRANGEMENT5.7 Coupling Test ProcedureA coupling or ball shall withstand the test loads indicated in Table 2 withoutinc
32、urring failure. For the purpose of this section, failure is defined as the point at which the coupling or ball willaccept no additional test load without separation of the ball from the coupling ball socket, or the occurrence ofa metal fracture of either coupling ball or coupling assembly which resu
33、lts in separation of the ball from thecoupling ball socket. Distortion or bending of the ball or of a coupling assembly component occurring duringtesting does not constitute a failure as defined herein unless actual separation of the ball from the couplingsocket occurs prior to the designated test l
34、oads indicated in Table 2. When conducting tests, a new coupling orball shall be used for each mode of load application.6. Hitches6.1 Hitch Strength RequirementsThe hitch shall meet the test load requirements indicated in Table 3 of thisdocument.SAE INTERNATIONAL J684 Reaffirmed MAY2014 Page 5 of 9
35、TABLE 3HITCH TEST LOADS(1)(2)1. V = Vertical Force (kN lb)L = Longitudinal Force (kN lb)T = Transverse Force (kN lb)M = Spring Bar Moment (kN m in-lb) (Leveling Force Couple)R = Hitch Rating in terms of trailer GVWR (kN lb) (Gross Vehicle Weight Rating)X = Hitch Rating for Maximum Vertical Load on H
36、itch (kN lb) (Tongue Weight)2. NotesHitch Test Force Applications(See Table 3 and Figure 2)Apply the forces in any sequence as follows:a. Apply the specified downward vertical force concurrently with the specified compressive longitudinal force orspring bar moment.b it includes linkchain and all att
37、aching means, or an alternative system (see 7.6). The purpose of Safety Chain is to retainconnection between the towing vehicle and trailer in the event of separation of the trailer coupling from the ballor the ball from the hitch, long enough to bring the vehicles to a stop. It should not be constr
38、ued that safetychains can ensure that vehicle control or connection will be maintained in the event of vehicle incidents such asloss of control, rollover, jackknife, collision, etc.For the purpose of this section:a. The “hitch” assembly (including ball and ball support platform) is considered part o
39、f the towing vehicle.b. The “safety chain” is considered part of the trailer.c. “Attaching means” are defined as the hooks, bolts, anchorages, or other devices used to fasten orconnect link chain, or its equivalent, to the trailer tongue and to the rear of the towing vehicle includinghitch assembly
40、devices provided for such connection.7.2 Strength RequirementsEach individual safety chain, and all attaching means, shall meet the minimumbreaking force tensile load as indicated in Table 4, and where applicable such load shall be applied in adirection parallel to the trailers or towing vehicles lo
41、ngitudinal axis. Any operation performed on safety chainsubsequent to its manufacture shall not reduce its strength below the requirements of Table 4.7.3 Wire Rope ThimblesWhen wire rope is used as safety chain, the strands of the rope shall be protected fromdamage by use of a wire rope thimble in t
42、he areas of its attaching means.TABLE 4STRENGTH REQUIREMENTS FOR SAFETY CHAIN ANDATTACHING MEANS(1)1. When conducting a tensile strength test of a length of chain or equivalent and its attaching means, when the minimum load specified in Table 4 is applied, such load shall be maintained for a minimum
43、 of 1 min.Safety Chain orTrailer Classification Breaking ForceMinimumClass 1 8.9 kN (2000 lb)Class 2 15.6 kN (3500 lb)Class 3 22.2 kN (5000 lb)Class 4 The strength rating of each length of safety chain or its equivalent and its attachments shall be equal to or exceed in minimum breaking force the GV
44、WR of the trailer.SAE INTERNATIONAL J684 Reaffirmed MAY2014 Page 8 of 9 7.4 Chain Application and IdentificationSafety chain assemblies shall be classified and applied to trailers asshown in Table 4. Safety chain assemblies for individual sale shall be identified with the applicable trailerclassific
45、ation and GVWR on the specifications, packaging, or the safety chain assemby itself; alternatively thisinformation may be incorporated in catalogues or other specifications where safety chains are selected byservice personnel.7.5 Installation7.5.1 Two safety chains shall be permanently fastened (i.e
46、., bolted, anchored) to the trailer tongue, one on eachside. The safety chains shall be connected from the trailer tongue to the hitch assembly or to other towingvehicle members meeting the strength requirements of 7.2.7.5.2 Safety chain shall be connected to the towing vehicle and trailer so that t
47、he slack for each length of chain isapproximately the same when the vehicles are aligned on a common front to rear centerline. There shall beno more slack than necessary to permit proper turning of the vehicles. The safety chains shall be crossedunder the trailer tongue and connected to the hitch as
48、sembly or to other towing vehicle members.NOTECrossing the chains under the tongue typically reduces the probability of stressing or breaking thechains when turning. See Figure 3. FIGURE 3TYPICAL SAFETY CHAIN INSTALLATION7.5.3 Safety chains shall not be attached to the towing vehicle by use of the f
49、asteners that secure the ball to itssupporting hitch member, nor shall they be connected directly to any part of the ball.7.6 Equivalency7.6.1 Nothing in Section 7 shall preclude the use of an alternative connecting arrangement which will effectivelymaintain connection between towing vehicle and trailer in the event of separation of the coupling from the ballor the ball from the hitch.7.6.2
