ADAPTABLE POOL LIFT SEAT FOR THE ARC OF MONROE COUNTY

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1 Multi-Disciplinary Engineering Design Conference Kate Gleason College of Engineering Rochester Institute of Technology Rochester, New York Project Number: P07005 ADAPTABLE POOL LIFT SEAT FOR THE ARC OF MONROE COUNTY Alecia Eppelsheimer/Mechanical Eng. Jeffrey Klaus /Mechanical Eng. Brian Walsh/Mechanical Eng. David Alas /Mechanical Eng. Myong Choi/Industrial and Systems Eng. Michael Webb/Industrial and Systems Eng. ABSTRACT The Adaptable Pool Lift Seat Project is a joint effort between RIT and the Arc of Monroe County to design a reclining pool lift seat for use in the therapy pool at the Al Sigl Center in Rochester, NY. The chair is designed to be comfortable, easy to use, transportable, and safe for both the user and operator(s). A prototype was developed and manufactured based on structural and ergonomic simulations. Testing was performed to verify key customer requirements and to ensure that the system complies with all ADA regulations. redesign the base of the lift from the previous project to resolve some design problems. The lift built by the previous senior design group is shown below. INTRODUCTION The objective of this design team is to develop a fully functional seat, integrated with the existing ARC pool lift system, and able to accommodate individuals with different disabilities and body types. The team must provide complete documentation of the analysis, design, manufacturing, fabrication, test, and evaluation of the seat. This project is part of the Assistive Devices and Bioengineering track which focuses on the application of technology to improve the quality of life for individuals with disabilities. The need for this seat came from the Al Sigl Center which is part of the ARC of Monroe County. The Al Siegel Center was lacking a fully functional pool lift, causing some of their patients to travel to other facilities for access to a therapeutic pool, while some patients were unable to use a pool at all. This project, 07005, builds upon the work of another project, 06216, from the previous year which completed the construction of the pool lift mechanism. Another objective of this project is to Figure 1: Pool Lift and Seat from P06216 The seat visible in this picture was built by the previous team to attach to the lift. This seat, however, did not meet all of the ARC s requirements, as they have a wide variety of patients, 2007 Rochester Institute of Technology

2 Proceedings of the Multi-Disciplinary Engineering Design Conference Page 2 each with specific needs. For example, some patients could not sit up straight and would need to be in a reclined position while being lowered into the pool and vice versa. The other customer need that made this previous seat impractical was that loading the patient into the pool lift seat at the edge of the pool was extremely dangerous. This reason, coupled with the fact that the ARC wanted the ability to get one person ready in a seat, while at the same time be lowering another person into the pool, created the need for the seat to provide transportation to and from the locker room as well as easily connect to and disconnect from the lift. DESIGN PROCESS From the needs assessment it was determined that the major project design specifications were that the seat needed to be safe, comfortable, transportable, and needed to provide support for a wide range of users. A full list of specifications and their corresponding engineering metrics can be seen in the figure below. For the Comfort category, the team examined a number of existing pool lift seats as well as other pool and lawn furniture and assessed the ergonomic qualities of those products. pool lift seat that met all of these criteria. To do this each specification was assigned a sub-category corresponding to which major customer need it fulfilled: safety, support, transporting the user, comfort, and integration into existing pool lift. Each of these categories was then further researched in order to find existing products and systems that provided similar results in meeting the specifications. These products were used as the benchmarking metrics. For the Transporting the User category, a number of different wheeled products were compared to find a suitable candidate. The wheel setups on wheelchairs, shopping carts, office chairs, and hand dollies were all considered as possible solutions to the problem. For the Safety category, various seatbelts and other securing devices were used in benchmarking including car seat belts, 5- point racing harnesses, rollercoaster overhead harnesses, and also a simple lap belt. For the Integration category, the team chose to look at universal gym equipment and forklifts as possible solutions to the integration issue. The final design used a combination of both to integrate the chair into the existing system. Using research gathered on existing pool lift systems, and the above specifications, it was the team s task to design a reclining Customer Need Engineering Metric Units of Measure Provides support for different back angles Reclining Range Range from degrees The seat must be comfortable Safety 0 dangerous points for user Fit the existing pool lift system Easily attaches to existing lift Less than 5 steps Fit in the pool environment Seat must be waterproof Waterproof Yes Accommodate an adult user Effective Load 350 lbs. Seat must be safe Minimum Dimensions (Seat width x back height) (18x23) (24x32) User should not slip out of seat Restraints (Minimum number of touch points) 2 Secure User is Seat Minimize Slipping Support the arms and side of the user Armrest and Footrest Removable Seat must be easy to install into lift Time to install seat into pool lift <2 min Light weight Weight Max 20 lbs. Allow transportation from dressing room Transportable with user Yes Comply with ADA regulations Comply with all ADA regulations Yes Seat should look nice Appearance Presentable Overall easy to use Number of Operators One Seat should be reliable Time between maintenance 1 yr (About 348 hrs of usage) System should have an instruction manual Instruction manual Describe Processes and Maint. Table 1: Customer Needs Evaluation Paper Number P07005

3 Proceedings of the KGCOE Multi-Disciplinary Engineering Design Conference Page 3 These benchmarking samples were then used by each team member to create a design concept that would fulfill the specifications for each category. Each design was then put through a Pugh Analysis in order to determine the design that best addressed all specifications. An example Pugh Matrix is shown below: Concepts Criteria Weight Reclining Range Comfort Attach to Lift Waterproof Effective Load Fit Pool Environment Safe Light Weight Ease of Transportation Allow to 2 Users 1 Reliable Feasibility Easy to Use Weighted Total Table 2: Sample Pugh Analysis Concepts 1, 2, and 3 correspond to three alternative designs which were eventually combined and refined to arrive at the team s final design. The finalized concept consisted of a PVC frame with a custom hinge design that allows the seat to operate in the upright and reclined position. Six removable stainless steel casters allow the chair to transport the user from the locker room to the pool deck and a forklift-like linkage allows the integration of the new chair into the existing lift system. Figure (2) shows the final chair design. Figure 2: Model of Final Seat and Caster Assemblies with Linkage Once a final design concept was chosen, calculations were performed to determine the minimum PVC pipe size that would support the weight of the user. The entire system was then modeled and simulated using ANSYS. The system was determined to be feasible, passing with a maximum Von Mises Stress that was well below the yield stress of the PVC with a factor of safety of 2. ENGINEERING MODEL The seat was modeled using Pro Engineer as a set of subassemblies. The seat frame was the primary component, with the seat back, two hinge sections, armrests, and footrest attached to it. Several model iterations were created as the hinge mechanism and footrest were refined. Finally, the linkage and caster assemblies were integrated. Upon finalization of the design, the first prototype was constructed using PVC pipe and fittings. This was not glued during the initial phase of construction, so that pipe lengths could be adjusted to allow proper alignment of all sections of the seat assembly. Once the entire seat was assembled properly, it was disassembled and all sections of pipe were measured for final length and labeled. Copyright 2007 by Rochester Institute of Technology The seat was then reassembled using PVC cleaner and cement. The seat was assembled from the inside out, with the front hinge glued first, followed by the rear hinge and seat back subassemblies which were had sections passing through the front hinge. The armrests, footrest, and diagonal braces were built next. The main seat frame was built last, with sections passing through all of the other subassemblies. The adjustable end of the footrest and the caster assemblies were constructed separately and attached with removable stainless steel pins. This process was repeated for the second prototype. The seat material (Phifertex Plus, a PVC coated polyester mesh) was sewn to fit the completed assemblies by Steve s Custom Canvas Etc. The three sections (seat bottom, seat back, and foot rest) were then attached to the seat assemblies using Sta-Set polyester rope.

4 Proceedings of the Multi-Disciplinary Engineering Design Conference Page 4 The linkage was constructed of stainless steel tubing. Four square tubing sections were welded together to form a rectangle. Two round tubing sections were then welded perpendicular to the rectangle to form the forklift arms. On the back of the rectangle, two rectangular sections were welded vertically in the middle to form an attachment point for the lift. 3 Point Bending Experimental Setup and Procedure Figure 4: Drop Test Diagram Figure 3: 3-Point Bending Diagram Initially, our concern was the effect the chemicals in the pool particularly bromine might have on the adhesive strength in the PVC joints. To test such effects, we simulated a 2 year aging period by increasing the bromine concentration in a bath of water and leaving the test samples in the bath for one week. After the aging simulation period, the aged samples were tested against non aged samples to see if bromine had any affect on the adhesive strength of the PVC joints. We conducted a 3 point bending test similar to the set-up shown above. A hydraulic testing machine was used to apply an increasing load (P) at a rate of 0.1 /min until the pipe joint failed. Failure was considered a significant crack or complete separation of the joint. The frame was originally dropped from a height of three feet and progressively increased in order to have the frame fail. Again, a failure was considered a significant crack in the pipes or a separation of the joints. Weight Drop A 50 lb weight was dropped on the same L-shaped frame from varying heights while the frame rested and supported on the ground. Impact A 16 L x 22 W x 13 H L-shaped PVC frame was constructed using 2 diameter PVC pipes, 2 three way fittings and 4 elbows. The frame was dropped from varying heights to simulate a sharp impact or blow to the chair frame. Figure 5: Weight Drop Diagram Data Analysis 3 point bending This test reveals that bromine did not affect the strength of the adhesive in the PVC joints as both test samples failed under fairly similar loads. In fact, the PVC coupling failed before the adhesive bonding. In both the aged and non aged samples, the Paper Number P07005

5 Proceedings of the KGCOE Multi-Disciplinary Engineering Design Conference Page 5 coupling fractured completely under the given loads while the adhesive bonding still held. Load supported (lbf) Non aged test sample Aged test sample Table 3: 3-Point Bending Results Mesh Tensile strength In order to test the strength of the mesh, we used a hydraulic testing machine to test the tensile strength by applying an increasing tensile load at a rate of 0.3 in/min until there was a significant tear in the mesh at which point it was considered a failure. We used 7.5 L x 1.5 W mesh strips reinforced at the ends with nickel plated brass grommets. Figure 6: Mesh Tensile Testing at Failure Test sample Cross sectional area (in 2 ) max load (lbf) Tensile strength (psi) Average Table 4: Mesh Tensile Test Results Impact Height (ft) Time (s) Failure (Y/N) V (ft/s) N N N N N N N Table 5: Drop Test Results Weight Drop Height (in) Failure (Y/N) 6 N 12 N 18 N 24 N 30 N 36 N 42 N 48 N 54 N 60 N 66 N 72 N Table 6: Weight Drop Test Results Both of these tests reveal that even with a significant force, applied abruptly to the frame, the frame and all of the joints are able to withstand the impact Tipping For safety, the chair should not tip over while the patient is sitting in it. Therefore, when it is stationary with locked wheels, we performed a tipping test where a load of 300 lbs is placed on the seat while being pushed from the sides. The outcome is the chair did not tip over. Results and Interpretation Our finite element analysis demonstrated that the selected PVC pipe diameter was sufficient to withstand a load of 300 lbs with a factor of safety of 2 for a total weight capacity of 600 lbs. Our testing revealed that the selected PVC was not only able to meet our expectations but exceed them by 200%. Furthermore, our concern about the strength of the PVC adhesive affected by the bromine in the water was eliminated by the fact that the adhesive did not fail under twice the amount of loading we were attempting to support. Although not taken into account into our preliminary design, the impact and weight drop tests were done to mimic the chair frame hitting a wall or an obstacle in the way. Both tests served to simulate a sharp impact against the chair frame and both confirmed that the PVC frame could handle a significant amount of abuse. Copyright 2007 by Rochester Institute of Technology

6 Proceedings of the Multi-Disciplinary Engineering Design Conference Page 6 Conclusion The chair has been successfully designed and tested. This unique design has met all but a few customer needs. More importantly, our model has satisfied the main function that the customer desires, which is to develop a chair that has two positions for comfort and is compatible with the current system safe within a bromine-water environment. Other needs achieved are described below. Aside from the main functions being satisfied, the needs related to safety and comfort are just as important. The customer requested that for safety the seat must be comfortable, safe, non-slip so that patient stays in seat, and that it complies with the ADA regulations and for comfort it must accommodate 95% of the population and have removable armrests and footrest. Other than simply building a chair, in respect to the customer needs, the seat was also designed to make setup easier by designing it to be mobile with removable wheels and a linkage that connects the chair to the lift with a simple push. Furthermore, an instruction manual will support the setup, which can be done by one person, and supply simple instructions for maintaining functionality. versatile and should be able to be adapted easily for most locations. It is also very possible that the location is flat, and therefore the designed base will be applicable. When the final location is determined, the design will need to be reevaluated and then built. ACKNOWLEDGEMENTS This material is based upon work supported by the National Science Foundation under Award No. BES Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation. Steve Polis (Steve s Custom Canvas, Etc) for sewing; Phifer Incorporated for donating material; Lowe s; Caster City; Justin Stabb for welding; Brian Fornell; Nick Valerio. In addition to simplifying setup, our customer had mentioned the need of setting one patient on the lift while preparing and transporting another patient from the locker room. This was satisfied by creating two identical chairs. However, this led to an unsatisfied need of staying within the budget. Another unsatisfied need is maintaining the weight of the chair between 20 lbs to 50 lbs was not satisfied. Although this affects the max load in which the lift can operate, the original design considered a factor of safety of 2. Thus, the current system with the new chair design can handle the same weight, but with a safety factor of 1.5. The other unsatisfied need is the redesign of a new base for the lift. The current base is designed to go below ground level, which causes issues such as corrosion due to water being trapped in it. Since the current system is not made corrosion resistant, the customer has decided to make the product inoperable. Even though there were some issues with the design of the lift, the assembly of the chair is a success. RECOMMENDATION FOR FUTURE WORK The complete system is now complete except for the base of the lift. The base is dependent on the location that the lift will be put in. Since the location is not currently determined, it is impossible to build the lift. A base has been designed to detail for a perfectly flat surface. The original location was not perfectly flat, so if the lift was to go to this location the design would have to be slightly modified. But again, the location is not yet determined. However, the design for the base is fairly Paper Number P07005