1、 Ergonomic Guidelines for Carts and DolliesSAE/USCAR-41 March 2015ISBN: 978-0-7680-8187-9 TABLE OF CONTENTS 1.0 SCOPE 1 2.0 GENERAL 2 3.0 TERMINOLOGY AND CONCEPTS . 2 4.0 REQUIRED TOOLS . 2 5.0 CART / DOLLY MEASUREMENT TECHNIQUE . 3 a. Initial Push / Pull 4 b. Sustained Push / Pull 5 6.0 STRENGTH RE
2、QUIREMENTS / ANALYSIS RESULTS . 7 a. Push/Pull Force Limits and Interpretation . 7 7.0 POTENTIAL SOLUTIONS TO REDUCE PUSH / PULL FORCES 7 8.0 CART / DOLLY DESIGN RECOMMENDATIONS . 8 a. Cart / dolly handles: . 8 b. Cart / Dolly Brake Pedal: . 8 APPENDIX A. References 9 APPENDIX B. Cart / Dolly Measur
3、ement Checklist 10 APPENDIX C. Cart / Dolly Design Interface Checklist 12 1.0 SCOPE This document describes the assessment methods and physical requirements associated with the manual handling of carts and dollies, specific to material handling systems. All possible designs and applications could no
4、t be anticipated in creating these guidelines. Where there are questions of adherence to this document, such as use of an “off-the shelf” design, always consult the responsible Ergonomics Department. Force guidelines were primarily developed referencing the push/pull psychophysical Snook data contai
5、ned in A Guide to Manual Materials Handling (second edition) by Mital, Nicholson and Ayoub (NY: Taylor if the handles are vertical, locate a measurement point on the dolly chassis midway between the handles. 2. Select a gauge attachment that will provide a stable coupling at the measurement point. I
6、f the push surface is not stable, attach a push plate to the dolly handle or to the dolly chassis. The push surface must not deform when you push against it with the gage. Use a hook attachment for pull force measurements. A tool or attachment to the gauge such as the one pictured above can help in
7、taking more accurate and reliable measurements by improving the coupling with the dolly handle. 3. Load the dolly with the maximum weight the dolly will carry based on the castor / wheel rating. Make sure the load condition is safe; the load must not shift or fall when the dolly is moved. The floor
8、surface used for testing should be level and representative of the actual conditions on which the specific dolly will be used. 4. Push/Pull cart 2 3 times prior to measuring force as a means of getting familiar with the force required to push during the measurement process. For a first attempt at me
9、asuring the initial force, approach the dolly at a normal walking speed and push the dolly smoothly and gradually. Do not jerk the gauge. Read the force from the gauge within the first one or two seconds as the dolly starts to move. 5. In some cases Operators may first straighten out the swivel cast
10、ers by pulling or pushing sideways on the dolly before moving it to its destination. You may measure the initial sideways force required to straighten the swivel casters instead of the straight-on push force with the casters at right angles. Consider if line side conditions permit the operator to ma
11、neuver the dolly. 6. If you need better precision to take the measurements or if the forces are near the ergonomic limits, then consult IE for the standard time data allowed for the movement of the dolly given its weight and the specific distance(s) moved. Use this data to set up a distance and time
12、 measured test to see if the dolly can be moved the appropriate distance in the allotted time without exceeding the force limits provided below. 7. Repeat the measurement process until you can obtain at least three consistent measurements (six preferred); the measurements should not differ from each
13、 other by more than 15%. Record the measurements. 8. The dolly push forces will usually be the same as dolly pull forces. Perform a quick check for each condition that the pull forces are the same as the push forces. If the pull forces are different than the push forces, repeat the measurement proce
14、ss for pulling. 9. Use a minimum of three readings (six are preferred). SAE/USCAR-41 Issued 2015-03 ERGONOMIC GUIDELINES FOR CARTS AND DOLLIES - 5 - Figure 3. Note: Initial Force Data Collection - wheels are turned 90 degrees to the direction of travel Sustained Push / Pull Use a force gauge to take
15、 the measurements. Follow the manufacturers instructions for using the gauge. 1. Select a measurement point as follows: if the handle is horizontal, locate the measurement point at the midpoint of the handle; if the handles are vertical, locate a measurement point on the dolly chassis midway between
16、 the handles. 2. Select a gauge attachment that will provide a stable coupling at the measurement point. If the push surface is not stable, attach a push plate to the dolly handle or to the dolly chassis. 3. The push surface must not deform when you push against it with the gauge. Use a hook attachm
17、ent for pull force measurements. A tool or attachment to the gauge such as the one pictured below can help in taking more accurate and reliable measurements by improving the coupling with the dolly handle. 4. Load the dolly with the maximum weight the dolly will carry based on the castor / wheel rat
18、ing. Make sure the load condition is safe; the load must not shift or fall when the dolly is moved. The flooring surface used for testing should be level and representative of the actual conditions on which the specific dolly will be used. 5. Push/Pull cart 2 3 times prior to measuring force as a me
19、ans of getting familiar with the force required to push during the measurement process 6. Mark off distance of 10 ft. (3.0 m) 7. Position moveable wheel in the in-line direction to measure the sustained force SAE/USCAR-41 Issued 2015-03 ERGONOMIC GUIDELINES FOR CARTS AND DOLLIES - 6 - 8. Apply force
20、 to travel 10 ft. (3.0 m) in 8 9 seconds. If you need better precision to take the measurements or if the forces are near the limits given below, then consult IE for the standard time data allowed for the movement of the dolly given its weight and the specific distance(s) moved. Use these data to se
21、t up a distance and time measured test to see if the dolly can be moved the appropriate distance in the allotted time without exceeding the force limits given below. 9. Sustained measurement set the cart or dolly in motion and apply the minimum sustained force to keep it in motion. 10. Repeat the me
22、asurement process until you can obtain at least three consistent measurements (six readings are preferred); the measurements should not differ from each other by more than 15%. Record the measurements. For an initial force value use the highest initial force reading of the consistent readings. 11. S
23、econd person can help direct cart if necessary Figure 4. Measurement Technique Pull Force Reading Figure 5. Mark off a distance of 10 ft for sustained push / pull SAE/USCAR-41 Issued 2015-03 ERGONOMIC GUIDELINES FOR CARTS AND DOLLIES - 7 - Figure 6. Sustained force data collection wheels are aligned
24、 with direction of travel 6.0 Strength Requirements / Analysis Results Push/Pull Force Limits and Interpretation This general initial and sustained force guideline applies to dollies moved manually and is designed to accommodate 75% of the female population. Initial Force Limit 180 N, 40 lbs., 18 kg
25、 Sustained Force Limit 107 N, 24 lbs., 11 kg NOTE: These limits assume relatively frequent handling of carts and dollies (handling frequency greater than once per minute) throughout a work shift. If a job involves dolly handling that is much less frequent or otherwise is much different in task compo
26、sition, distance travelled and duration, then acceptable forces should be evaluated with the Snook and Ciriello and Liberty Mutual Tables, Mital, Nicholson and Ayoub Tables. Please contact the appropriate Ergonomic Subject Matter Expert for a deep dive ergonomic analysis. If the measured forces exce
27、ed the force guidelines, then consider the suggestions below to reduce the force. If the force cannot be reduced to an acceptable level, then handling of the dolly will be confined to tugging or positioning via a powered assist such as a “Cart Caddy.” Your mobile equipment fleet manager or material
28、handling group can provide more details on Cart Caddy powered assists. 7.0 Potential Solutions to Reduce Push / Pull Forces Investigate alternative wheels / castors Investigate if wheel / castor rating is suitable for the application. Investigate if the load on the dolly can be reduced. Change stand
29、ard packs. Investigate the use of the electronic Cart Caddy to assist is pushing / stopping carts with forces greater than 40 lbs. Perform required maintenance on the casters. Take damaged equipment out of service immediately. Ensure that handling and shipping methods do not damage the casters. Prov
30、ide location aids such as guide rails for casters that may allow easier positioning of dollies and provide for proper caster orientation at the point of use. SAE/USCAR-41 Issued 2015-03 ERGONOMIC GUIDELINES FOR CARTS AND DOLLIES - 8 - Adhere to the work pattern as specified. For example, need to lim
31、it one load per cart versus double loading to be increase efficiency. Train the operators to safely handle the dollies, relative to initial force / acceleration to ensure safe speeds and stopping of the carts / dollies. Repair and level the floor surfaces along the dolly route. NOTE: uneven, broken,
32、 fissured, rutted and pitted floors can create hazards for operators handling carts and dollies! Floors should be in good repair. Ensure that materials used to repair or level floors will not wear out at a faster rate than the floor itself. Ensure proper housekeeping to maintain clean aisle ways. 8.
33、0 Cart / Dolly Design Recommendations 1. Cart / dolly handles: a. The push handle must be between heights of 92 to 155 cm (36” and 45”), with 102-107 cm (40 - 42”) preferred. b. Handle diameter of 3.2 cm (1.25”) to 4.5 cm (1.75”) and must permit a minimum of 2.5” hand clearance to grasp the handle t
34、o ensure good hand/wrist posture. c. The handle should run most of the length of the side that it is mounted on minimum length-71 cm (28 in.). d. The handle is recommended to be coated or covered with an insulating, compressible substance. e. The dolly must be free of sharp edges and/or pinch points
35、 on surfaces that the operators hands or body can contact. f. There must be at least 3.5 cm (1.4 in.) of clearance around any hand control or mechanism requiring manipulation by the operator. g. The forces required to operate latches, locks or handles (operated with finger or thumb) must be under 45
36、 N (10 lbs.). h. Finger/thumb-operated controls must be at least 1.3 cm (0.5 in.) in diameter i. The forces required for one-handed operation of levers or controls (including force to rotate a loaded rack on a turntable on a dolly if only one hand must be used) must be under 75 N (17 lbs.) j. The fo
37、rces required for two-handed operation of levers, handle releases or controls on the dolly/cart (including two-handed rotation of turn tables) or manual push/pull of loads onto or off of dollies/carts must be under 134 N (30 lbs.). k. The grasping surface of all hand-operated controls/handles at lea
38、st 2.5 cm (1.0 in.) and no more than 3.8 cm (1.5 in.) in diameter? l. Finger/hand clearances under nested parts must be at least 30 mm (so as to allow the operator to lift the part) and preferably 50 mm (2.0 in.). 2. Cart / Dolly Brake Pedal: m. The pedal must be placed at a maximum height of 7” abo
39、ve the floor. n. The pedal dimensions must be 3” long x 3.5” wide o. The foot lever must be a minimum of 1.3 cm (0.5 in.) in width. p. The foot lever must be positioned no higher than 38 cm (15.0 in.) above the floor surface at any point in the lock/unlock cycle. q. Horizontal and vertical clearance
40、s must be at least 6.4 cm (2.5 in.) around the foot lever for unobstructed access. r. The brake must require less than 312 N (70 lbs.) of force exerted by the foot to set. SAE/USCAR-41 Issued 2015-03 ERGONOMIC GUIDELINES FOR CARTS AND DOLLIES - 9 - APPENDIX A. References 1.0 Key References Chrysler,
41、 Material Delivery Dolly Standard Ergonomic Requirements Ford Motor Company (2012), Cart Measurement Technique General Motors (2011), Ergonomic Design Guidelines for Global Dolly Delivery do not apply force with a sudden jerk. 4. Record the peak push and pull force reading obtained during the first
42、2.0 seconds of pushing. Sustained force: The force required to keep the cart in motion.1. Bring the cart up to a normal pushing speed. 2. Remove hands, place force gauge against the center of the handle and orient to deliver a horizontal force to the handle. 3. Apply force to the gauge to sustain th
43、e carts movement.4. Record the force required to maintain the normal pushing / pulling speed. To allow the cart to reach a steady state speedit is often best to record the sustained force after the cart has traveled 3 ft from the “at rest“ location in a time of 8 - 9 seconds.Comments / Notes:SAE/USC
44、AR-41 Issued 2015-03 ERGONOMIC GUIDELINES FOR CARTS AND DOLLIES - 11 - APPENDIX B. Continued Cart / Dolly Measurement Checklist Checklist Stage of Review: 100% Design 100% Build Vendor Floor Plant Floor Post Unique Review Completed By: Supplier Name:Name / Number of Cart: Cart Description: Yes No*Do
45、es the handle diameter range between 30mm and 45mm (1.25“ - 1.75“)?Are handle edges rounded and smooth?Does handle orientation maintain neutral wrist posture throughout manipulation of cart?Is the vertical hand height within 850mm and 1335mm (31“ - 50“) throughout cycle?Is the Operator able to maint
46、ain hands within 500mm ( 20“) (measured from side of hips)? Yes No*Is avg initial push force less than 40 lbs (180N)?Is avg sustained push force less than 25 lbs (107N )?Is avg initial pull force less than 45 lbs (180N)?Is avg sustained pull force less than 24 lbs (107 N)?Yes No*Does the load fall w
47、ithin the acceptable caster / wheel rating?Is the test floor condition representative of cart location? Include plant location Max weight / load on cart (record in comments section)100% DesignPlant FloorAdditonal Comments / Data Collection100% Build VendorFloorBUY-OFF PHASE REQUIRED SIGNATURESData C
48、ollection (Trials 1 - 6) Average ForceMiscellaneousComments / DataComments / DataComments / DataHANDLE DESIGNPUSH / PULL FORCES (assumption is two hands are used to manipulate cart)SAE/USCAR-41 Issued 2015-03 ERGONOMIC GUIDELINES FOR CARTS AND DOLLIES - 12 - APPENDIX C. Cart / Dolly Design Interface
49、 Checklist This checklist is intended for use as a design guideline for future dollies and carts as well as racks on wheels and carts. Not all guideline features will be applicable or practical for all designs of dollies and carts. In a case where a dolly does not meet an applicable guideline, investigate options to allow for correction or otherwise for safe and ergonomically acceptable operation. INTERFACES AND HAND CONTROL FUNCTIONS ON DOLLY/CART Is the dolly free of sharp edges (6.0 mm/0.25 i
