Design Of Hand Tools Research Articles

Electromyographic evaluation of different handle shapes of masons’ trowels

The effects of five different handle shapes of masons’ trowels on muscle activity of the arm and forearm muscles (through electromyographic measurements of the biceps brachii [BB], flexor digitorum superficialis [FDS], pronator teres [PT] and extensor carpi ulnaris [ECU]) were evaluated in a simulated masonry task. The results showed a significant effect of handle shape on the muscle activity of the BB, PT and ECU. The muscle activity of the extensor (ECU) and flexor (FDS) were generally larger than those of the supinator (BB) and pronator (PT). Some improvements were found in terms of muscular exertions with prototype designs C, D and E, which had either handles with variable diameter (designs C and E) or a slightly bent handle (design D). These findings have practical implications for the design of single-handle hand tools but may need further validation for specific contexts of use.

Design and ergonomic assessment of an infusion set connector tool used in nursing work

Nursing is a physically demanding job characterized by a high prevalence of fatigue and musculoskeletal disorders. One of the high-exertion and repetitive nursing tasks is the manual connection of an infusion set to a medical fluid bottle. Such physical work can be eased by the design of new hand tools. Correspondingly, this study designed and ergonomically assessed an infusion set connector tool (ISCT) and compared it with that of manual connection. First, a prototype of ISCT was designed to perform infusion set connecting task in the mechanical form. Subsequently, 12 nurses were asked to connect an infusion set to medical bottle in the form of manual and mechanical tasks and these tasks were evaluated using ergonomic indices including muscular activity level, force, posture, and subjective (Borg scale CR10) measures. Results showed that the activity levels (root mean square) of the extensor digitorum communis, flexor carpi radialis, biceps, triceps, and deltoid muscles remarkably decreased when the nurses used the ISCT. The postures of the wrist, arm, and shoulder regions were corrected from Rapid Upper Limb Assessment action level 3 to 2 when the designed tool was used. Additionally, the subjective perception of exertion was significantly lower with the use of the prototype.

Clockwise and Counter-Clockwise Twisting Strength in Different Operational Angles on Crown Plane

Hand tools can be seen as the extent of human hands. The evolution of hand tools was positively correlated with human development. The hand tools design affects the convenience and safety of human use. The wrenches are the most frequently used hand tools in Taiwan. However, it is lack literatures focus on the twisting force for operating hand tools. To provide reference for the hand tools design, this study surveyed the two twisting forces in five operational angles in crown plane when use wrenches. Eighty volunteer adults (half male and half female) were recruited as subjects. The maximum twisting forces of dominant hand were measured. Palm facing to ground is defined as 0 degree. Hand in supine positions are defined as positive angle and in prone positions are defined as negative angle. The five angles are: 0, 15, 22.5, 30, and 45 degrees. The two twisting forces are: clockwise and counter clockwise in vertical plane. A digital twisting force wrench was used as the measurement apparatus. The twisting forces model was constructed. In the vertical plane, the down force is greater than the up force. The forces in positive angles were greater than that in the negative angles. The force of male is greater than that of female. The results of the study can be reference for research and other hand tools design.

A case-based decision theory based process model to aid product conceptual design

In new product development, the rapid proposal of innovative solutions represents an important phase. This in turn relies on creative ideas, their evaluation, refinement and embodiment of worthwhile directions. This study aims to describe a CBDT based process model for product conceptual design that concentrates on rapidly generating innovations with the support of decision-making rationale. Case-based decision theory (CBDT), derived from case-based reasoning, is applied in this paper as a core method to aid design engineers to make an informed decision quickly, thus accelerating the design process. In the process of utilizing CBDT to support a decision, as for the similarity function, the proper value assignment methods to the selected attribute set for calculation are discussed. In order to assist with innovative solution, aspects of the theory of inventive problem solving (TRIZ) are integrated into the case-based reasoning process. Accordingly, a CBDT-TRIZ model is developed. Quality-function deployment is used to translate customer wants into relevant engineering design requirements and thus formulating the design specification. Image-Scale is used to offer an orthogonal coordinates system to aid evaluation. Finally, a case study is used to demonstrate the validity of the proposed process model based on the design of a cordless hand-tool for garden and lawn applications.

Non-powered hand tool improvement research for prevention of work-related problems: a review

Purpose. In lower-middle-income countries, most of the work is performed manually using non-ergonomic hand tools which results in work-related health problems. Using hand tools designed in line with ergonomic principles may play an important role in reducing work-related health concerns significantly. Methods. Scientific databases (PubMed, EBSCOhost) and e-publishers were searched for articles from 1985 to 2015 using the following keywords: ‘hand tool’, ‘ergonomics’, ‘usability’ and ‘design’. After applying selection criteria to 614 articles, 58 articles related to the physical design of hand tools were selected. Results. Seventeen articles were related to hand tool improvement in the manufacturing sector. Musculoskeletal disorders were found to be the most frequently occurring work-related health problems. Most of the articles focused on product and qualitative variables for improvement in hand tools, while few articles considered human and task variables. Conclusions. Literature shows that hand tool improvement studies have been given less importance in low-income and lower-middle-income countries. However, some work of significance is reported in the agriculture sectors of these countries. Hence, it is concluded that ergonomic intervention in hand tools is much needed for those industries which employ traditional methods of working.

Comparison of physiological load among different sizes of computer mouse

The purpose of this study is to compare the difference in physiological load among three different sizes of computer mouse. The mouse is one of the most commonly used input devices for controlling computer system. However, due to the fact that there are many different sizes of mice available to consumers and the hand size of each consumer is quite different from each other, so this study is trying to determine the suitability of different mouse sizes with consideration of the parameter of hand size of each person. A series of operation experiments will be conducted to collect the data of EMG of hand muscles for evaluating physical load of computer mouse. Twelve adults were recruited according to the two genders and six size combinations of hand length and hand width distribution. The results showed that gender, computer operating activities and hand width may affect the EMG (% MVC) on four groups of muscle. It could apply to computer mouse design and other related hand tool design.

Investigation of grip and pinch strengths in Iranian adults and their correlated anthropometric and demographic factors.

Grip and pinch strength measurement is important for objective evaluation of the function of the upper extremities in upper limbs injuries treatment and also for ergonomists as a way of optimizing the requirements of hand tool design. The present study was conducted to investigate the correlation of anthropometric and demographic factors with hand strength as well as to develop regression models for grip and three types of pinch strengths including Tip, Key and Palmar in Iranian adult population. The study population consisted of 1008 Iranian adults aged 20 to 107 years. Participants were selected using a stratified random sampling method from crowded places of the cities with the highest number of Persian ethnic group. Strength measurements were undertaken according to recommendations by the American Society of Hand Therapists (ASHT). This study found a positive and significant correlation between all measured strengths and anthropometric factors. The regression equations of grip and pinch strengths were developed for dominant and non-dominant hands. The results of this study provided more information about correlated factors of grip and pinch strengths. The regression equations developed in this research are applicable to clinical treatment and ergonomics programs.

Anthropometric characteristics of female smallholder farmers of Uganda – Toward design of labor-saving tools

Sub-Saharan African women on small-acreage farms carry a disproportionately higher labor burden, which is one of the main reasons they are unable to produce for both home and the market and realize higher incomes. Labor-saving interventions such as hand-tools are needed to save time and/or increase productivity in, for example, land preparation for crop and animal agriculture, post-harvest processing, and meeting daily energy and water needs. Development of such tools requires comprehensive and content-specific anthropometric data or body dimensions and existing databases based on Western women may be less relevant. We conducted measurements on 89 women to provide preliminary results toward answering two questions. First, how well existing databases are applicable in the design of hand-tools for sub-Saharan African women. Second, how universal body dimension predictive models are among ethnic groups. Our results show that, body dimensions between Bantu and Nilotic ethnolinguistic groups are different and both are different from American women. These results strongly support the need for establishing anthropometric databases for sub-Saharan African women, toward hand-tool design.

Farmers’Injuries, Discomfort and Its Use in Design of Agricultural Hand Tools: A Case Study from East Java, Indonesia

Abstract Farmers in East Java, Indonesia have opinions of the agricultural hand tools that they wear. In farming activities they get injured due to the use of agricultural equipments. The most injury was in hand. Farmers feel fatigue/discomfort in different levels of their body part when using agricultural tools. Majority of farmers complained to suffer fatigue in upper back (92.8%), mid back (93.6%), and lower back (91.8%), respectively. The third major criteria's design of agricultural hand tools base on survey resulted are be safe, good and fit in hand, and easy to use. The ergonomic evaluation suggests their handle length and diameter to be 12.4 cm and 3.0 cm, respectively.

Anthropometry of male agricultural workers of western India for the design of tools and equipments

Agricultural workers and farmers in India perform most of the agricultural operations manually. Hence, for the design of farm equipments, hand tools and machinery involving human efforts, region specific anthropometric data is needed. A survey was conducted to collect anthropometric dimensions of male agricultural workers in the state of Maharashtra in India in the age group of 18–60 years. Almost 59 body dimensions were selected for the measurement from the recommendations by All India Coordinated Research Project (AICRP) on Human Engineering and Safety in Agriculture (HESA) and requisite by digital human manikin modeling. Total 303 male agricultural workers were selected from 23 districts of Maharashtra by convenience sampling. Repeatability of the measurements was checked by paired samples t test. From the measured dimensions, the values of minimum, maximum, mean, standard deviation (SD), standard error of mean (SEM), coefficient of variation (CV), 5th and 95th percentile values were determined. The results of the survey were compared with results of other regions of India and other countries. Relevance to industryThe anthropometric data of user population is very utile for the design/improvement of farm equipments/implements for agricultural workers in order to reduce drudgery, increase efficiency, safety and comfort.

Hand anthropometry survey of rural farm workers in south-eastern Nigeria

The importance of hand anthropometry as it relates to design of hand tools particularly for farm workers have been established; however, anthropometric data for this group of agricultural workers have continued to remain scarce. A survey of hand anthropometry relevant in design of agricultural hand tools was carried out on 200 male and 100 female adult farm workers in south-eastern Nigeria. Comparison of the male and female data obtained showed that male dimensions were higher than that recorded for the females. The hand anthropometric data of the male and female farm workers were compared with that of other populations but no clear distinction was observed. It was however clear that the following hand dimensions, 2nd Joint to root digit 3 and width at tip digit 3 recorded for Nigerian farm workers were highest and lowest, respectively, compared to other populations.Practitioner Summary:Hand anthropometric data relevant in design of hand tools have continued to remain scarce particularly for farm workers. Hand anthropometry survey of farm workers carried out in south-eastern Nigeria revealed higher dimensions for males than females; however, no clear distinction was observed in comparison with other populations.

The relationship between hand anthropometrics, total grip strength and individual finger force for various handle shapes

The design and shape of hand tool handles are critical factors for preventing musculoskeletal disorders (MSDs) caused by the use of hand tools. We explored how these factors are related to total force and individual finger force in males and females with various hand anthropometrics. Using the MFFM system, we assessed four indices of anthropometry, and measured total force and individual finger force on various handle designs and shapes. Both total force and individual finger force were significant according to gender and handle shape. Total grip strength to the handle shape indicated the greatest strength with D shape and the least with A shape. From the regression analysis of hand anthropometric indices, the value of R was respectably high at 0.608–0.696. The current study examined the gender and handle shape factors affecting grip strength based on the force measurements from various handle types, in terms of influence on different hand anthropometric indices.

Effects of Working Environment Factors and Operator Experience on Upper Extremity Mechanical Properties During Powered Hand Tool Use

OCCUPATIONAL APPLICATIONS Powered hand tools are widely used during assembly operations. The hand displacement during powered hand-tool use has been identified as a potential risk factor for upper extremity musculoskeletal disorders. In the current study, the mechanical properties of the upper extremity were identified, which represent muscle capacity to react to an impulsive power tool torque loading and affect the responsive hand displacement. These properties were obtained from among experienced and inexperienced participants under various operating configurations, including working heights, horizontal working distances, tool moments of inertia, and joint type. The results indicated that operating configurations and experiences affected the mechanical properties of upper extremities in different ways. This research may help in future studies on powered hand-tool work-station design, for example by improving parameters in biomechanical models.TECHNICAL ABSTRACT Rationale: Hand-tool displacement during powered hand-tool use is a potential risk factor for upper extremity injuries and is correlated to the subjective discomfort level. The upper extremity has been modeled as a second-order linear system to describe the hand-tool response. While previous studies have found that working environment factors and operator experience significantly affect the hand-tool response during powered tool use, how those factors affect the mechanical properties of the upper extremity has not been investigated. Purpose: This study assessed the mechanical properties of the upper extremity under various working environment factors and operator experience levels. Method: A least-squares method was used to identify the mechanical properties of the upper extremity during powered hand-tool use, directly from the dynamics of hand-tool response. Results: Working heights, horizontal working distances, hand tool moments of inertia, joint type, and experience significantly affected some mechanical properties of the upper extremities in various operating configurations. In addition, stiffness and damping coefficients of the upper extremities were greater than those values identified from a free oscillation system in a previous study. Conclusions: Mechanical properties of the upper extremities can be used to predict hand displacement during powered hand-tool use. The current results provide additional information to improve the understanding of operator reactions to powered hand tools.

Hand cumulative trauma disorders in Nigerian custom tailors: the need for redesign of manual scissors

Cutting scissors are important working tools for Nigerian custom tailors (CTs) but its usage apparently does not meet the ergonomics need of these artisans. A survey was carried out amongst CTs using questionnaires to obtain their background social-occupational demographics and observation methods to study their work performance, use of scissors and any cumulative trauma disorder (CTD) in their hands. Thicknesses of various fabrics were measured and comparison between Western world's custom tailoring job and the Nigerian type was done. The results showed some CTD risk factors with finger contusions on the 71 CTs evaluated. The right-hand contusions were traced to the constant usage of unpadded manual scissors with ungloved hands. Disparity between Western and Nigerian tailoring practice may account for the high occurrence of disorders in Nigerian CTs. Since hand dimensions are crucial in the design of hand tools, it is therefore concluded that hand anthropometry of Nigerian CTs and soft padding of manual scissors may mitigate CTD burdens on CTs' hands.

Ergonomic Analysis of a Firearm According to the Anthropometric Dimension

The paper summarizes the results of an ergonomic analysis of firearms with regard to anthropometric dimensions of selected populations. For evaluation 3D digital human models, which represent currently the best technology, have been used. Analyses are performed for three major population groups (Americans, Europeans and Asians). Ranges to controls (e.g. lock, trigger, etc.) are critically evaluated. The grip of the firearm according to the position of shooters wrist is also a subject to critical analysis. At the end of the paper the deficiencies found are discussed as well as a bad situation regarding the availability and timeliness of anthropometric dimensions of Czech population. Further work that is described will be focused on the creation of national anthropometric database. The database shall include the dimensions of the hand and will be created according to the rules of EN ISO 15535. The data will be suitable for the design of other hand tools from various sectors.

The effects of tool handle shape on hand performance, usability and discomfort using masons' trowels

The effects of five new different handle shapes on hand performance capabilities, usability and discomfort, and also the relationship between these variables were evaluated in the context of masonry work and using masons’ trowels as an exemplar hand tool. The prototype handles were designed to provide different patterns of grip so that they could be suited to the hand/tool interaction in particular hand areas. The results showed significant effect of tool handle shape on the hand grip effort, usability, and hand and finger discomfort assessments, but not on the time to complete the masonry task. The hand grip effort and usability were negatively correlated with subjective assessment of hand and finger discomfort, so that a lower level of hand and finger discomfort corresponded to higher hand grip exertion and usability. These findings provide a better insight into the performance and usability issues when using hand tools which can be applied by tool manufacturers to improve industrial hand tool design. Relevance to industryThese findings present a unique insight into the handle design for industrial hand tool use and support the general conclusion that objective measurements should be supplemented by qualitative subjective assessments to provide a more holistic approach where specific and additional details about the hand tool design characteristics are incorporated from the workers' perspective.

Design, Analysis and Fabrication of Conceptual Innovative Hand Tool

Dioscorea hispida is a poisonous plant normally found in forest where scientific studies have shown that its tuber contains toxic poison and can be consumed after its poison is removed. Traditionally the tubers were placed in flowing river water for several days. In the harvesting aspect, an innovative hand tool were conceptually designed to replace the traditional hoe or “cangkul”. Using IMADA digital force gauge to measure the force required for pulling out the tuber and reverse engineering methods, an innovative hand tool were designed and developed. The results from experiments showed that the force required for harvesting the Dioscorea hispida tuber is found significant with its weight versus regression squared (R2) of 0.86. The information of optimum force required from field experiment is used to model the simulation and practicality in Computer Aided Design (CAD) environment system. The finite element on stress distribution on selected material of hand tool was simulated by uploading the material characteristic on simulation program embedded in Solidworks software. The end result of the simulation is based on visualization of analysis in Solidworks while producing the hand tool for designing and fabrication from material which is lighter and stronger.

Anthropometry and Agricultural Hand Tool Design for Javanese and Madurese Farmers in East Java, Indonesia

This study revealed that anthropometric measurements of Javanese farmers are mostly higher than that of Madurese farmers. The minimum, mean, and the maximum stature values are 146.3, 159.0, 174.6cm for Javanese male farmers and 143.0, 156.3, 173.8cm for Madurese male farmers, respectively. The minimum, mean, and the maximum stature of Javanese and Madures female farmers are 137.7, 152.5, 167.3cm and 137.4, 150.1, 167.7cm, respectively. The mean of Relative Sitting Height (RSH) of Javanese and Madurese, male is 0.49, 0.49, respectively, whereas the mean of RSH of Javanese and Madurese female is 0.52, 0.51, respectively. The mean values of body surface area (BSA) of Javanese, Madurese, male are 1.57, 1.54, and for female are 1.47, 1.44 m2, respectively. Whereas, the body mass index (BMI) is 22.4, 22.88 for male and 22.38, 22.75kg/m2 for female Javanese and Madurese farmers, respectively. By using Principal Component Analysis (PCA) with varimax rotation, the first rank preference of farmers is safety for hand tools, and then followed by good fit in hand, easy to use, reliable and to no inflamed skin in the last. For agricultural hand tools, farmers prefer utilitarian performance than hedonic performance.

Optimal Grip Span of A-type Pliers in a Maximum Gripping Task

Objective: The objective of this study is designing an optimal hand tool through maximum grip force study accordance to the hand grip span. Background: In order to prevent musculoskeletal diseases, studies on hand tool design are proceeding based on grip strength, finger force, and contribution of individual finger force on total grip strength. However, experimental apparatus using a tool that is actually used in work place was almost non-existent. Method: 19 males were participated in an experiment. Using the load cell inserted real plier, finger force, grip strength, and subjective discomfort rate of both hands (dominant and non-dominant) were measured in 5 different hand grip span(45mm, 50mm, 60mm, 70mm, and 80mm). Results: There was significant difference(p<0.001) of total grip strength, individual finger force and subjective discomfort rating according to various hand grip span(45, 50, 60, 70, and 80mm). Also, statistically significant different(p<0.001) was shown between the dominant hand and non-dominant hand. In addition, individual finger force in maximum grip was in order of middle finger, ring finger, index finger, and little finger. Conclusion: Optimal grip span of pliers that exerting maximum grip strength is 50~60mm. Application: This finding is expected to be used for designing proper pliers.

The Effects of Different Tactile Sensations on Pinch Effort

Failure in proper design of ergonomic hand tools can lead to the prevalence of hand-related injuries. In order to improve the ergonomics of hand tools, numerous studies have been done on causal factors related to these injuries such as grip postures, grip forces and torque directions. Nevertheless, there appears to be limited studies concerning how pinch effort can change with different types of tactile sensations. Therefore this study aims to determine the effects of different tactile sensations on pinch effort. A total of 110 manual workers from the wooden pallets and furniture manufacturing firm participated in the study. The descriptive analyses were conducted in Microsoft Excel 2010 and the reliability of data was verified using Cronbach's alpha reliability analyses. The results show that individuals can produce a greater pinch effort while gripping objects that have a high friction coefficient between the fingers and the grip surface. This study improves our understanding on the implications of different tactile sensations and potentially decreases workplace hazards for eventual improvements on safety, health and medical costs.