Even after the pressure differential has been reduced to zero there is bound to be some adhesion left due to molecular interactions between the suction cup surface and the substrate. Therefore the device has to create a positive pressure differential in order to pry the device from the substrate.
In this section multiple concepts are generated that explore the amount of freedom that is still possible within the constraints of the list of requirements and the function structure. To visualize the different starting points for the concepts a strategic space has been drawn in Figure 42. This figure shows the positions fulfilled by the concepts in a graph with two axes that correspond with important keydrivers. The horizontal axis represents the keydriver ‘total costs of ownership’ while the vertical axis represents the amount of automation used by the system. This corresponds to the keydrivers ‘total benefits of ownership’, ‘performance’, ‘reliability’, ‘comfort’ and ‘ease of use’. To expand the strategic space some of the functions described in 4.2 are siphoned over from the device to the user, which makes the device less complex and reduces its cost.
47 Figure 43 - Functional Block Diagram
1.1 Perform a start- up check
1.2 Let the user set the requi red amount
of adhesi on
No pressure differential
1.3 Cal cul ate and remember the required pressure
Pressure differential
2.2 Monitor the pressure differential
1.4 Det ect when a seal is made
2.1 Create the required pressure
differential
2.5 Det ect when the device is about to let
go
2.6 Warn the user
2.7 Compensate for pressure loss
2.8 Monitor the bat tery charge
2.9 Cal cul ate the remaining adhesion
time 2.3 Cal cul ate the
amount of adhesion 2.4 Communicate the amount of adhesion 2.10 Communicate the remaining adhesion time 3.1 Equalize pressure differential
3.2 Det tach suction cup
3.2 Let user detach device
Use scenarios
Conceptual designs can best be explained by imagining how they will interact with the environment and the user. Therefore each of the concepts is first placed in a scenario that explores the use of the suction adhesion device. These scenarios are complemented by a Functional Component Diagram and drawings of the product and its functionality. Together they form a comprehensive image of the envisioned concept.
Handle concept
The handle device is a concept that tries to minimize the investment costs by assigning some of the functions seen in Figure 43 to the user. In this case the user is responsible for function 1.4, 2.1, 2.7 and 3.2. As a result of this there is no need for the device to execute function 2.9 and 2.10, as most of the energy that is needed for the device to operate is provided by the user. Scrapping the mentioned functions means that the device only requires a simple system (Figure 45) from which the most expensive parts can be left out.
Today is the big day. Chris is finally moving to his new newly build house. However before he can enjoy his new dwelling he has to move his beloved furniture to its new location. As some of the pieces are quite heavy Chris has borrowed two pairs of suction cups from his local DIY store. These were recommended to him by a friend who had to move a few weeks before him. ‘They make moving a breeze’ he recalled him saying. Time to put that to the test then. Chris switches on the suction cup by sliding down the on/off button (Figure 44). The device comes to life and shows the amount adhesion that the last user entered into its memory. LEDs above the screen also light up and then fade out again to indicate that the device is ready to use. All devices are set to 12 kg which Chris estimates should be enough to lift the sideboard. He places one of the suction cups on the side of the closet and starts to pump the air out from underneath by pushing a few times on the hand pump that sticks out of the side of the device. One by one the LEDs above the adhesion display turn on to let Chris know how much he still has to pump to reach the required level of adhesion. After a few more pumps all LEDs are brightly lit up. Chris decides to give it a try. Together with his brother, who has attached another set of suction cups at the other side of the sideboard, Chris lifts the
closet from the ground. ‘That is a lot heavier than I thought’ Chris shouts at his brother. Fortunately the rubberized grips are very comfortable and give him more than enough grip to keep the sideboard from the ground. As they start to move however the sideboards starts to rock gently and one of the suction cups has decided that it might not generate enough adhesion to keep itself attached to the closet. A loud beep fills the room, which Chris intuitively understands is a sign that he needs to increase the pressure underneath suction cup. He presses a few times on the handpump which silences the alarm. To display the effect of the extra pumps the device has changed its setting from 12 to 18 kg and the LEDs give a rough estimation of the percentage of this reading that is currently being generated. To make sure that the alarm doesn’t trip again Chris pumps the suction handles all the way to 15 kg. After that the lift goes according to plan and they reach the moving lorry without any problems. Once in place Chris detaches the suction cups by pushing a big button on the bottom of the device. This equalizes the pressure underneath the suction cup and makes it easy to detach the suction cup from the closet. ‘Let’s tackle the next lifting job.’
After a day of hard work all Chris’s furniture has traded places from his old apartment to his new home. Time for a well-deserved beer. These are well worth the few quid in rent Chris’s brother remarks. I don’t feel as shot as I normally do after a day of moving.
49
Manual vacuum pump Inlet/outlet valves Detachment button Suction cup Pressure sensor Suction cup controller LED controller Display controller Display LEDs AA batteries Air Airflow Exhaust Intake Flow reversal Adhesion Air Pressure Pressure reading LED commands Display commands Display signal 2.5V DC Adhesion pad and air
filter
Airflow
Suction system componenents Control system components Interface components Input Output Speaker Warning signal 4.5 V DC On/Off switch
51
Harness concept
The harness concept is aimed at creating a mobile device that fulfils all the functions seen in Figure 43. This means that the concept requires a higher investment as it is inherently more complex (Figure 45), but also delivers better performance, safety and use comfort. To justify the higher total costs of ownership the device is aimed at professionals since they can use it more frequently. This increases the benefits associated with the system. Another strategy to improve the benefits of ownership is the incorporation of a lifting harness in the concept which is similar to the one shown in chapter 3.4. The use of a harness allows the user to lift objects that are above the NIOSH weight limit more safely by transferring the load to stronger areas of the body. The following scenario explains how the device is used and how it is able to provide the benefits mentioned in section 4.1.
Peter has been a self-employed furniture mover for almost 20 years. During this period his business has steadily grown. He now employs about 10 to 15 people depending on how much work is available. Throughout his career the moving business has been more or less the same. Although some furniture pieces like televisions have gotten lighter and smaller it is still a matter of bringing heavy pieces of furniture from point A to point B without damaging them. A few years ago Peter used to help his guys out during large jobs but due to a hernia he now manages his business from the office. Furniture moving is a back-breaking job and most of his employees have to stop doing it way before they reach their retirement age. This is a costly problem and it has forced Peter to look for ways to reduce injuries amongst his personnel.
Peter therefore decided to buy a set of powertools from a company that claims they can alleviate the problem. The kit consists out of a two self-powered suction cups and lifting harnesses. Today is the first time his team will use them and therefore Peter has decided to come along. After a short drive they arrive with their lorry at their client’s apartment. The apartment is on the third floor, which means they will have to carry all the objects through a narrow stairwell.
After introducing themselves to their client they quickly get going. First a medium sized wardrobe needs to be lifted. Two of Peter’s employees strap on their lifting harness
while Peter explains how the suction cup works. ‘First you turn this ring to set the device to how much you think the object weighs and then you push the suction cup onto the closet. If you place it correctly the suction cup will automatically start to suck itself against the surface. These LEDs show you how long it takes until the device reaches your required setting, but from what I’ve been told that shouldn’t take too long.
When Peter’s employee has finished putting on his vest he turns on his suction cup by pushing the on/off button, which is located on the side of the suction cup. When the device comes to life he turns it up to 40 kg by sliding the ring that surrounds the display. A number he thinks should be more than enough for this type of closet. ‘How do you turn it on Peter?’ the employee asks. ‘Just push it onto the closet and it will turn on automatically’ Peter replies. Peter’s employee pushes the suction cup onto a flat section of the closet and the cup immediately begins to hum. Quickly the LED’s around the display start the light up and after a few seconds the device has reached the intended pressure differential. ‘I think we’re good to go’. Both movers attach their lifting harnesses to the handle of the suction cup which requires them to squat down. When they rise again they lift the closet with their leg muscles and only have to use their hands to keep the object balanced. This gives the movers the freedom to unlock doors, give non-verbal directions with their hands and wave at attractive female passer- by’s. A big advantage for any well respected mover.
After making their way down the stairwell, Peter’s employees reach the van with the wardrobe and detach themselves from it by pushing the pressure settings ring downward (Figure 46). This releases the suction cup by pumping air back into the suction cavity. With their first successful lift completed, Peter’s men move back to the apartment to tackle the next lifting job. For carrying light objects they use the suction cup’s handgrips while heavier items are more convenient to carry by using the harness. At the end of the day all items have been successfully moved to the clients’ new home and on their way back Peter and his employees talk about their experiences with the device. ‘I still feel as fresh as a daisy’, one of Peter’s employees remarks. ‘These things really take the strain out of lifting.’
53 Vacuum pump Vacuum pump engine Transmission Battery Engine controller Inlet/outlet valves Detachment button Suction cup Pressure sensor Suction cup controller LED controller Display controller Display LEDs Battery charging station Battery dock Converter Input RPM Output RPM Airflow Airflow Exhaust Intake Flow reversal Adhesion Air Pressure Pressure reading Detachment signal Engine commands Modulated 12V AC 5V DC 14V DC 14V DC LED commands Display commands Display signal 2.5V DC 14V DC 14V DC 230V AC
Suction system componenents Control system components Interface components Input
Output
Adhesion pad and air
filter Airflow Suction cup control interface Suction cup settings Speaker Warning signal