1 / 50

Hand Tools I

Hand Tools I. Rad Zdero, Ph.D. zradovan@uoguelph.ca University of Guelph. Outline. Hand Anatomy & Injury Design Principles Shape Orientation Size Weight Grip Strength Vibration Texturing and Gloves. Hand Anatomy & Injury. Bones of the Hand. [Hall, 1999]. Nerves & Arteries of

aizza
Download Presentation

Hand Tools I

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Hand Tools I Rad Zdero, Ph.D. zradovan@uoguelph.ca University of Guelph

  2. Outline • Hand Anatomy & Injury • Design Principles • Shape • Orientation • Size • Weight • Grip Strength • Vibration • Texturing and Gloves

  3. Hand Anatomy & Injury

  4. Bones of the Hand [Hall, 1999]

  5. Nerves & Arteries of the Hand Transverse Carpal Ligament Ulnar Nerve Pisiform Bone Radial Artery Ulnar Artery Median Nerve Tendons [Tichauer, 1978]

  6. Movements of the Hand Neutral Neutral [Hall, 1999]

  7. Hand Injury and Disorder Traumatic “One Time” Injuries • impact, crush, cut • 9 % of all work-related injuries • 260,000 hand tool related injuries in U.S. each year • $ 400 million associated medical costs • 21% of hand injuries are power tool related • Most common: knives, wrenches, and hammers • Mostly “one time” traumatic injuries (U.S. Statistics by Aghazadeh & Mital, 1987)

  8. Hand Injury and Disorder • Repetitive Injuries • 4.8 % of workers in meat packing industry suffer from repetitive injuries (Bureau of Labor Stats, 1986) • 13 repetitive injuries per 200,000 work hours in poultry processing plant (Armstrong et al., 1982) • Often go unreported but show up as … • reduced worker output • poor quality work • increased absence from work • “one time” trauma injuries

  9. Hand Injury and Disorder Carpal Tunnel Syndrome • hand held in fixed position for prolonged time • repetitive exertion with flexed or hyperflexed wrist with low or high forces • pressure at base of palm • vibration Tendinitis • repetitive motion, especially in combination with ulnar deviation with fixed thumb Hammer Syndrome • vibration, push, twist, hand hammering, catching

  10. Hand Injury and Disorder • Trigger Finger • excessive flexion and extension of digits • overuse of finger with pistol airtool • Gamekeeper’s Thumb • thumb abduction/extension with force • Pronator Teres Syndrome • repeated gripping and grasp • tight gripping, turning of tools • forceful flexion with finger flexion and/or elbow extension

  11. Design Principles

  12. Factors to Minimize • Soft tissue, artery, and nerve compression • Grip/Finger/Torque/Push/Pull strength required to perform task successfully • Vibration levels • Temperature changes (+/- 2 degrees) • Repetitive motion • Prolonged performance of task • Prolonged maintenance of “fixed position” • Angle deviation away from “neutral” hand position • Pinching, sharp corners, edges • Cost

  13. Factors to Maximize • General feeling of “comfort” • Adjustability of design • Ease of use • Factors to Consider Depending on Use • Weight of tool • Texturing, gloves, bracing/support, padding • Size of tool and hand anthropometrics • Subgroups: Lefthanders, women, physically impaired, young, elderly • Safety and protection features (e.g. flange, safety latch, plastic guard, etc.) • Material selection – What’s it made of? Why? • Power Specs: Manual vs. powered, Battery vs. plug-in, North American vs. European standards

  14. Shape

  15. Conventional Handle Modified Handle

  16. [Lewis and Narayan, 1993]

  17. Orientation

  18. [Chaffin et al., 1999] Thumb Switch Finger Switch

  19. Size

  20. [Chaffin et al., 1999]

  21. Weight

  22. Bicep Muscle Force Tool + Arm Weight Tool Weight (WT) Tool-to-Elbow Length (L) Added Torque from Tool Weight Total Elbow Torque, T [N-m] T = To + (WT)(L) } To = Net Torque on Elbow without tool Weight of tool may work AGAINST task performance • e.g. torque or moment around arm joints may eventually cause muscle fatigue, etc. Tool Weight (WT)[N]

  23. Arm Weight and Push Force Tool Weight (WT) Required Total Push Force Needed For Task, P [N] P = Po - WT Po = Net Push Force without Tool weight Tool Weight (WT)[N] • Weight of tool may work FOR task performance • e.g. less pushing force required in using a chain saw, electric sander, drill, hammer, etc.

  24. Grip Strength

  25. Vibration

  26. Lower temperature associated with loss of sensitivity, dexterity, and grip

  27. Texturing and Gloves

  28. [Chaffin et al., 1999]

  29. Performance (time to complete) for a task while wearing gloves made from various materials. % time shown in comparison to bare handed performance time (Weidman, 1970)

  30. Sources 1 • Aghazadeh and Mital, “Injuries due to handtools”, Applied Ergonomics, 18(4):273-278, 1987. • Armstrong, An ergonomics guide to carpal tunnel syndrome, AIHA Ergonomic Guide series, American Industrial Hygiene Association, 1983. • Armstrong et al., “Investigation of cumulative trauma disorders in a poultry processing plant”, American Industrial Hygiene Association Journal, 43(2):103-116, 1982. • Chaffin, “Localized muscle fatigue—definition and measurement”, J.Occup.Med., 15(4):346-354, 1973. • Chaffin et al., Occupational Biomechanics, 1999. • Greenberg & Chaffin, Workers and their Tools, 1976. • Hall, Basic Biomechanics, 1999. • Hansson et al., “Vibration in car repair work”, Applied Ergonomics, 18(1):57-63, 1987. • Johnson, “Evaluation of of powered screwdriver design characteristics”, Human Factors, 30(1):61-69, 1988.

  31. Sources 2 • Koradecka, “Peripheral blood circulation under the influence of occupational exposure to hand-transmitted vibration”, In: Proceedings of the International Occupational Hand-Arm Vibration Conference, NIOSH, 1977. • Knowlton & Gilbert, “Ulnar deviation and short-term strength reductions as affected by a curve-handles ripping hammer and a conventional claw hammer”, Ergonomics, 26(2):173-179, 1983. • Lewis & Narayan, “Design and sizing of ergonomic handles for hand tools”, Applied Ergonomics, 24(5):351-356, 1993. • Terrell & Purswell, “The influence of forearm and wrist orientation on static grip strength as a design criterion for hand tools”, Proceedings of the Human Factors Society 20th Annual Meeting, pp.28-32, 1976. • Tichauer, “Ergonomics: The state of the art”, American Industrial Hygiene Association Journal, 28:105-116, 1967. • Tichauer, The Biomechanical Basis of Ergonomics, 1978.

  32. Sources 3 • Wang et al., “Grip strength changes when wearing three types of gloves”, Proceedings of Interface 87, Human Factors Society, pp.349-354, 1987. • Webb Associates, Anthropometric Source Book (Vol.II), NASA Reference 1024, Washington, DC, 1978. • Weidman, Effect of safety gloves on simulated work tasks, 1970.

More Related