Child Safety Engineering Solutions

         

Overview

According to the National Highway Traffic Safety Administration (NHTSA) backed website www.SaferCar.gov, children under the age of 7 (or those weighing less than 60lbs) should only be transported seated in a child’s car seat, mounted in the rear seat of the vehicle. The safest location for a child’s car seat is in the center of the back seat rather than in the side seats of a vehicle. Traditionally, for a parent or guardian to load their child into a center-mounted car seat, they must extend across either side of the vehicle while bearing the weight of the child. This can be very strenuous and can potentially hurt the parent or guardian, increase the risk of the child being injured, and could consequently result in the parent or guardian choosing to transport their child in one of the less safe side seats in order to avoid these difficulties.

Child Safety Engineering Solutions, CSES, has designed and developed a mechanical system that will easily translate a child’s car seat from the center mounted position in the rear seat of the vehicle to the passenger side seat, while also allowing the user to rotate the child’s seat 90°. This will align the front of the car seat to be directly facing the user and easily within an arms-length reach, and will permit safe and effortless loading and unloading of the child. The mechanical system is designed to safely rotate and translate a 100 pound [lb] (45.4 Kilograms [kg]) load, while requiring only a 7 pound-force [lbf] (30 Newton [N]) to operate the system.

CSES has also focused on developing the safest and easiest way to attach the product to the rear seat of the vehicle, while still maintaining an overall safety rating equal to that of a traditionally mounted child’s seat. This will be accomplished by using the vehicles manufacturer installed rear-middle seat belt to hold the CSES Car Seat Slide to the vehicles seat, while using the LATCH system that comes standard on today’s child’s seats to mount it to the top plate of the CSES product.


Child Safety Engineering Solutions Car Seat Slide

 

 

Design Problem and Objective


A child placed in the middle of the rear seat is more protected from any type of collision that occurs in a car accident. However, loading a child into the car seat at this large distance can be physically taxing. With child car seat safety requirements and recommendations continuously increasing, parent/guardian and child safety is becoming progressively important.

To ensure the child is placed in the safest place within the vehicle, and also to eliminate any unneeded strain on the parent/guardian when loading the child into this location, CSES has created a product that will perform three primary functions: translating, rotating, and securing a child’s car seat to the vehicle seat.

               

Proof of Concept

To prove the design solutions for each function worked the way intended, CSES manufactured a simplified version of the final product. This prototype included all the major functions that the team wanted the product to perform.  However, CSES used wood for the plates instead of metal. This was an inexpensive way to allow the team to see if their device on paper could be made in real life and also helped identify problems and develop solutions during the re-design phase.


What We Learned:
The proof-of-concept confirmed that the off-the-shelf components can perform the primary objectives of easily sliding and rotating a child’s car seat as well as being able to fit in the back seat of a vehicle.  The team came up with a list of problems with the proof-of-concept that required re-design:


Safety
Will our current design keep a child safe? In the event of a vehicle collision, the inner hardware which keeps the device together may break or shear.  The team had to decide if this hardware was strong enough to hold it together.


Seat Belts:
The proof-of-concept covered the passenger seat belts as shown in the picture below.  This needed to be fixed.


Attaching the Device to the Vehicle:
For attaching to the vehicle’s seat, the proof-of-concept included straps (shown in green below) that could tightly wrap around the base of the vehicles seat, along with the metal bars used with the LATCH system in newer vehicles. With many vehicle’s having the space underneath the rear seat blocked off due to some type of barricade, the team discovered this technique was not the easiest method of installing the device and would make our device uninstallable in some vehicles.

 

Safety

Car crashes are the number one killer of children 1 to 12 years old in the United States. The best way to protect children in the car is to put them in the right seat, at the right time, and in the best location. Children are always safest when they ride in a back seat, especially when placed in the middle of the back seat. The Car Seat Slide has been designed to exceed National Highway Traffic Safety (NHTSA) regulations. NHTSA, Department of Transportation Standard 571.213; Child Restraint Systems, defines that a child restraint system must be able to withstand in impact where the vehicle, in which the restraint system is installed, is traveling at 30 mph and comes to a stop in 35 milliseconds.

The Car Seat Slide meets and exceeds this standard. It has been designed to for an impact where the vehicle is traveling 5 mph faster. This impact produces a maximum force of 4,600 lbs.

In addition, when properly installed, car seats should not move more than one inch side-to-side and front-to-back. Due to the design of the top plate of the Car Seat Slide, using neoprene foam and the anchoring system a child’s car seat is able to be installed with zero free movement.

 


The Car Seat Slide has several features that are key to improving safety:

1) Box style enclosure with gate access made from aircraft grade aluminum

In a front impact the back tab could experience up to 21,538 psi of pressure. The box-style enclosure material, 7075-T6 Aluminum, has a yield strength of 73,000 psi. A thorough finite element analysis (FEA) was conducted on the back tab (shown below). Under this front impact worst-case scenario, the back tab experienced an average stress of 16,000 psi, and very small areas experienced the max stress of 68,000 psi, proving the box-style enclosure will not fail during a head on collision.

 


2) Rolled edges to keep seat belts from being damaged.

Vertical edges of the back tab of the enclosure are hemmed to keep the seat belt safe from snags or fraying. Also, all exposed edges were rounded before the powder coating process to ensure no possibility of scrapping or cutting the child or guardian during use.

 


3) Locking drop pin

The locking drop pin secures the gate and is key to connecting the front tab of the enclosure to the back tab, allowing for a much greater stress distribution during a car accident. The drop pin has a shear rating of 9,200 lbs and goes through 5 sheets of aluminum (top plate not shown in the inside view of the picture below).


4) Heavy Duty Drawer Slides

 CSES testing shows that as long as the combined weight of the child and car seat is less than 140 lbs, the parent or guardian will be able to pull out or push in the mechanism with less than 7 lbs force, making the Car Seat Slide easy and safe to operate.

 

Additionally, the mechanism is capable of moving a child 16” closer to the passenger door, decreasing parent or guardian strain with loading a child.


5) Industrial Strength Turntable

 CSES testing shows that as long as the combined weight of the child and car seat is less than 120 lbs, the parent or guardian will be able to rotate the child and car seat with 7 lbs force. The max force required is required for the turntable to escape built in divots, and the actual force required for rotation is less than half of the max, also making the Car Seat Slide easy and safe to operate.

 

References:
http://www.iihs.org/research/topics/child_restraints/default.html
http://www.safekids.org/safety-basics/little-kids/on-the-way/car-seats-and-booster-seats.html
http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmcsrruletext.aspx?reg=571.213

 

 

 

Solution: The Car Seat Slide

The Proof of Concept was a very important step in re-design because of the number of things we learned.


One of the most pressing issues was how we were going to prevent our product from spinning when we don’t want it to, and to prevent an internal component failure (such as the hardware, turntable, or the drawer slides) during an impact. This was solved by creating a box-style enclosure to hold all components in place when in the locked / traveling position.


We learned from our Proof of Concept that the locking feature in the drawer slides was not going to be strong enough. We redesigned and came up with a “Gate” design to add superior strength during any type of side impact; however, the gate feature also greatly increases the strength of the entire enclosure, as it connects the back tab to the front tab.


We needed a way to keep the gate closed so we decided to use a drop pin that would go through all the plates and would hold the mechanism closed. This pin also greatly assists in helping prevent any unwanted side-to-side translation that could occur from a side impact.
Final Product:

These new features also greatly improved the safety of the design since the tabs, the gate, and the drop pin would endure the most stress in the event of a vehicle collision.


As for attaching the Car Seat Slide to the vehicle’s seat, we learned that the method used with our proof of concept was not going to be very practical for all cars, and thus defeated the universality of the Car Seat Slide that we were striving for. We had to design a new way to hold our mechanism in the car.
Weaving the rear middle seat belt through the back tab of the box-style enclosure ensured the highest level of safety, and the easiest installation process possible for the Car Seat Slide (while also making the product universal for all vehicles). After attaching the corner side tab (which prevents the seat belt from moving once installed), and tightening the seat belt, the installation process of the Car Seat Slide is complete.


The new design needed a stronger way of keeping the baby seat attached to the device, so three 0.25 in. thick stainless steel D-rings were included on the top plate. These D-rings will be the anchor points used with the The LATCH system, which comes standard on all of today’s modern car seats, to securely mount the car seat to the top plate of the Car Seat Slide.


The final design solves every problem identified from the Proof-of-Concept.

 

 

The Team

Cameron Bellamy Cameron Bellamy is a senior mechanical engineering student at the University of Nevada, Reno, graduating in May of 2013. Along with his scholastic achievements, Mr. Bellamy has over seven years of business experience, being the president of a local corporation based out of Reno, Nevada. Mr. Bellamy also brings his leadership and management principles acquired from previous presidential and secretarial positions held in state charter of a professional society. Mr. Bellamy also has several years of construction, manufacturing, metal fabrication, and welding experience from past jobs and internships.
Mike Goodrick Mike Goodrick is also a mechanical engineering student that will be graduating in May. Mike has also accumulated a business administration minor during his time at UNR. Mike has had worked in a variety of fields such as construction for five years, geothermal energy, and composite manufacturing.  Mike brings a different dynamic to the team as he will be going to grad school to get his MBA and MS in Management information systems.
Alex Gould Alex Gould is a senior mechanical engineering student at UNR and has a year of engineering experience, as well as several years of experience in customer service related jobs.
Robert Green Robert Green is currently a senior mechanical engineering student at University of Nevada, Reno, graduating in May of 2013. Mr. Green has over 8 years of experience working in manufacturing engineering, engineering design, and engineering support roles.
Kyle Klino Kyle Klino is graduating from the University of Nevada, Reno in May 2013 with a B.S in Mechanical Engineering.  He has developed a wide range of skills in various aspects of Engineering and Manufacturing.  His experiences include the high production manufacturing of plastics using Computer Numerical Control Routers, as well as Composite Manufacturing.  He has obtained many skill sets using engineering software, CNC machines, Manual machines, Inspection equipment and all the tools to manufacture quality products.