Umbrella

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Revision as of 19:58, 21 September 2008

Umbrella

Basic introduction information. 'Contents' box is created automatically. To skip directly to a section, use Umbrella#FMEA to create a link.

Usage and Usability

An umbrella's primary purpose is to protect the user from rain, although they are also used in some cases to protect against sun or snow. To do this, an umbrella has a long, slender shaft with a handle on one end and a collapsible canopy on the other, coming to a point at the umbrella's tip.
The umbrella's protective canopy is extended as a rider, initially located near the handle, travels up the shaft towards the tip. In a standard non-collapsible umbrella such as ours, the rider's motion is started by releasing the rider latch on the handle end of the shaft and manually moving the rider upwards until the rider engages a second latch on the tip end of the shaft, locking the rider and canopy in place.

Some improvements on the standard umbrella design have been made to overcome some of the standard umbrella's flaws.
The rider mechanism in many umbrellas, such as the golf umbrella, is spring loaded to provide one-handed automatic opening. This is an improvement over the two-handed opening that the standard umbrella offers. The canopy must be forced closed and the spring must be manually reset after use.
Because an umbrella has a very specific intended usage - outside during rain - there are times when the umbrella will not be in use but must be carried for later use, such as indoors. It is beneficial to the user for the umbrella to be lightweight and have a small footprint when not in use. One popular variation on the standard umbrella is the purse umbrella. This umbrella has a hollow telescoping shaft that extends with a button press as the spring-loaded canopy is extended. The footprint of the umbrella and its weight are reduced substantially, enough that the umbrella fits conveniently into a purse or backpack and can be carried at all times. This decrease in size comes with an increase in component complexity, as the shaft cannot be a single piece of material and the arms must be folded as well. Additional joints are needed, and the overall strength of the umbrella is reduced. Like the golf umbrella, the purse umbrella must be manually closed to reset the spring.
The most complex variant on the classic umbrella is an automatically opening and closing umbrella. This extends the functionality of the purse umbrella by using an additional mechanism to automatically close the canopy with a button press. While the canopy is automatically closed, the spring must still be manually reset.
Even with these improvements over the standard umbrella, some issues remain unaddressed. All of the umbrellas designed for personal use must be carried by hand, and even the most complex umbrellas must be forced closed manually after use. This can be a difficult task for people with motor disabilities, such as Parkinson's disease.

Parts List

Part #	Part Name	Qty	Weight (g)	Function	Manufacturing Process	Material	Picture
1	Shaft	1	59	Main support unit for umbrella	Laminated, turned	Wood
2	Handle	1	70	Provides a comfortable grip for shaft	Laminated, warped	Wood
3	Tip	1	1.5	Protects shaft & Aesthetic	injection molded	Plastic
4	Top Cap	1	1.9	Holds canopy to shaft	Stamped	Steel
5	Top Cap Retention Pin	1	<.1	Attaches top cap to shaft	Formed	Steel
6	Top Cap Skirt	1	.1	Prevents water leakage around top cap	Woven	Nylon
7	Rider Limit Pin	1	.1	Prevents upper assembly rider from traveling out of range	Formed	Steel
8	Rider Latch	2	1.6	Locks rider in place at top and bottom of range	Stamped	Steel
9	Rider Latch Pin	2	<.1	Attaches rider latch to shaft	Extruded	Steel
10	Canopy section	8	7.1	Keeps water from entering area below umbrella	Woven	Nylon
11	Canopy Latch Strap	1	.9	Thins trap to wrap around canopy when closed	Woven	Nylon
12	Canopy Latch Strap Velcro	1	.3	Allows canopy latch strap to attach to itself		Velcro
13	Upper Hub	1	3.1	Attaches arms to shaft	injection moulded	Plastic - abs?
14	Hub Pin	1	.4	Attaches upper hub to shaft	Formed	Steel
15	Bumper	1	1.9	Reduces jarring at end of rider travel, prevents contact between Arm Mainshaft and Shaft	injection moulded	Rubber
16	Connecting wire	2	.3	Attaches arms to upper hub and rider	Extruded	Aluminum
17	Rider	1	8.5	Attaches arm support rod to shaft; allows motion along shaft and attaches to latch	injection moulded	Plastic
18	Arm Mainshaft	8	14.9	Attaches canopy to upper hub	Extruded, stamped	Steel
19	Arm Support Rod	8	4.8	Attaches rider to arm mainshaft	Stamped, formed	Steel
20	Arm Support Rod Insert	16	.1	Inserts into end of support rod; adds strength at crimp point	Extruded	Steel
21	Arm Endcap	8	.7	Covers exposed end of arm mainshaft	Die cast	Steel
22	Short string	16	<.1	Loops between canopy and arm mainshaft/endcap to provide attachment	Spun	Cotton
23	Arm Joint Connector	8	.5	Connects arm mainshaft and support rod, allows rotation between the two	Stamped, crimped	Steel
24	Arm Joint Connector Pin	8	<.1	Connects arm joint connector to support rod	Extruded	Brass

Major Stakeholders and Needs

DFA

Umbrellas are a high production part and as a result a great deal of effort has been put into design for assembly. With respect to assembly, the umbrella is broken into three sub assembles: the shaft, the arms and the canopy. By breaking it into these individual sub sections this arms can be assembled independently of the shaft which can be assembled independently of the canopy, saving assembly time. Design for assembly has been considered within each sub assembly by designing the joints and parts such that there are generous tolerances with respect to part location and by designing the joints such that they are easy to make. With respect to the arms, all of the joints except that connecting the Arm Support Rod to the Arm Joint Connector are crimped connectors to reduce assembly time and part count. Additionally, all of the 8 umbrella arms are identical which improves the ease of assembly and reduces the part count of the umbrella. With respect to the shaft, design for assembly has been considered in the use of identical components for the Upper and Lower Rider Latches. Making these components identical prevents confusion during assembly and the parts are designed such that they are simply hammered onto the shaft to reduce assembly time. Also, assembly tolerances were considered with respect to attaching the Handle to the Shaft. While glue is required for this joint, there is a large tolerance with respect to how deep the shaft has to be placed inside the handle, reducing the time that is required to assembly this joint. Along with being easy to assemble individually, the umbrella sections are designed to be easy to assemble to one another, with the arms attaching to the shaft using two pieces of wire. This attachment method makes it easy for the umbrella to be assembled quickly and simply.

DFM

In order to reduce the manufacturing cost and effort the individual components of the umbrella have been designed with Design for Manufacture in mind. The majority of the metal parts on the umbrella are made through stamping premanufactured flat or round stock into the desired shape. This process is fast, efficient and removes the need for time intensive machining thereby dramatically reducing the associated manufacturing costs. Additionally by replicating components such as the Rider Latches and the arm components manufacturing costs are reduced. Similarly all of the plastic parts on the umbrella are injection molded for quick manufacturing time and reduced material cost. The umbrella also uses “off the shelf” fasteners where possible such as in attaching the top cap and upper hub to the shaft. Both of the fasteners involved in this assembly are standard brad nails which, because they do not need to be manufactured, reduce the cost of manufacturing the umbrella.

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DFE

The choices made in the design and manufacture of a standard umbrella have a variety of environment consequences. Since there are a large variety of umbrella designs, these issues may be different depending on the model and manufacturer. These comments pertain only the standard umbrella that we studied. Main Materials Used and Comments

• Wood (treated)
  • Natural wood is bio-degradable, however this wood appears laminated and chemically treated/coated to produce a desirable surface finish, which will likely impede degradation
  • Due to lamination process, it is unlikely that return these products to the manufacturer would result in recycling of materials.
• Plastic (Thermoplastic)
  • Thermoplastics can be recycled if returned to the manufacturer
  • Does not appear to be made of out of commonly recycled materials, so recycling on a large scale may be impeded.
  • Non-Biodegradable
• Steel
  • Non-Biodegradable
  • Stamping process used to create the piece is lower energy compared to other forming techniques

EIO-LCA

This is for the EIO-LCA subsection of DFE.

FMEA

This below table lists the results of our Failure Modes and Effects Analysis, followed by a brief summary of the major issues that we viewed as the most important. Only components with an RPM greater than 40 were given corrective action. The top 5 RPN components have been bolded.

Summary

The main issues seen in the FMEA deal primarily with three issues:

• Plastic Deformation of the umbrella arms
• Poor Canopy Quality
• Handle Degradation

The plastic deformation of the umbrella arms is primarily a design issue. By having a better understanding of the kind of loads that are applied to the umbrella, engineering design can redesign the arms to be more robust against yielding issues. This could mean improving the strength of the arms or, conversely, making them more flexible to allowing for more deformation before yield.

Poor canopy quality is primarily a function of the quality of the materials and the manufacturing process. By reducing variation in the quality of unprocessed fabric materials in the supply chain, this issue will be greatly reduced. It is also the job of the Manufacturing department to ensure that the machines used to process the fabric are not detrimental or add variation to the final quality of the product. There should also exist some form of quality control before the product leaves the factory in order to ensure the integrity of the woven materials.

Handle degradation is another design issue. By choosing wood as a material, the designers introduced the associated failure modes. By changing the material selection to account for a plastic or metal handle, the designers could have avoided the potential splintering of wood, and might even have been able to reduce the cost of the product. For mass production parts such as umbrellas, the tooling costs for plastic parts would not be cost prohibitive.

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Mechanical Analysis

Design Variants

Golf Umbrella

Golf Umbrella makes a big difference by having double layered canopies (upper and bottom) to avoid umbrella to fail by wind. To accomplish this purpose, wind blows under the umbrella and go out of the canopy through the gaps between outer and inner canopies. Each arm of the umbrella has canopy hook to attach the bottom canopy to the arms. Possible failure could occur from this part when too much force applied on the canopy hook. The upper canopy attaches itself on side arms extended and bent in the counter-clockwise direction from the main arms. The size of the golf umbrella is relatively bigger than regular umbrella and it has a big spring with strong stiffness on the rider to keep the umbrella opened. The shaft of the umbrella was made of carbon fiber and hollow, so that it can reduce the total weight of the umbrella compared to an umbrella with solid shaft. However, the shaft might emit harmful material when it is destroyed since it is made of carbon fiber.

Purse Umbrella

The Purse umbrella, also called a Compact umbrella, extends upon standard umbrella design by adding the capability of folding up into a greatly reduced size when closed. This design variation is the result of greater emphasis on customer needs for portability and compactness not typically found in standard umbrellas. The primary features which gives the purse umbrella it's unique ability lies in a complex collapsable arm design and a telescoping shaft. An overview of these two features is provided below:

Collapsable Arm Design

The basic function of the collapsable arm design involves using a combination of linkages to translate a small amount of vertical movement on the shaft into a large amount of radial movement of the arm tip. Unlike standard umbrellas, which have large shafts on which the rider has a large range of motion, purse umbrellas have limited range along the shaft with which to extend the umbrella arms. In order to accomplish the extension the arm is composed of a series of linkages, connected by pins, which transmit moments to other members creating relative rotation. Pictures of the linkage sub-assembly are included below, as well as a depiction of how the pieces create relative rotation.

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Telescoping Shaft Design

The function of the telescoping shaft is to provide a shaft that has the ability to extend to different lengths depending on the needs of the user. When the umbrella is closed the shaft retracts to a smaller length improving storage and portability. When the umbrella is open the shaft extends to full length allowing the user to comfortable hold the umbrella during operation. The key features of this design include concentric hollow steel shafts with a spring loaded locking feature to maintain the extended position. A few examples of specific design features are pictured below: The telescoping shaft is made up of 5 shafts of decreasing diameters. Each shaft is shown with different lengths, with the associated locking mechanism.

In order to facilitate the telescoping movement, a brass insert is placed on the inside of the shaft. This brass insert creates lower friction between the shafts, making the telescoping movement easier and more reliable.

Auto Open Close

The Auto Open Close umbrella is a double fold collapsible shaft variant of the standard umbrella which has additional mechanisms in order to allow it to both open and collapse with the touch of a button. The opening of the umbrella is achieved through a large spring which is compressed inside the shaft. When the open close button is pressed a latch releases the upper shaft, causing the spring to extend the shaft. At the same time the umbrella canopy is opened by a string which is latched inside the handle of umbrella. This string passes through the shaft, around a pulley at the top of the umbrella and is anchored inside the lower hub of the umbrella. By this means when the umbrella shaft is extended it causes the string to pull the lower hub upwards, extending the arms and opening the umbrella canopy. The collapsing of the umbrella canopy is achieved through tension springs located in each arm. When the open close button is pressed a latch attached to the button releases the string from inside the handle, this frees the lower hub, causing the tension springs in the arm to compress, collapsing the umbrella canopy.

Part #	Part Name	Qty	Weight (g)	Function	Manufacturing Process	Material	Picture
1	Shaft Spring	1	17.2	Causes the shaft to extend	Coiled	Steel
2	Button	1	1.1	Releases umbrella mechanisms	Injection Molded	Plastic
3	Button Spring	2	0.1	Returns the Button to its original position	Coiled	Steel
4	Button Tab	1	0.4	Releases the String Bulb	Stamped	Steel
5	Button Tab Shaft	1	0.3	Attaches Button Tab to Button	Formed	Steel
6	Button Tab Spring	1	1	Return the Button Tab to its original position	Coiled	Steel
7	Shaft Clip	1	1.2	Locks shaft in the collapsed position	Stamped	Steel
8	Handle Frame	1	10	Houses and locates all of the handle mechanical parts	Injection Molded	Plastic
9	Shaft Clip Spring	1	<0.1	Locates and locks Shaft Clip	Stamped	Steel
10	String Bulb	1	0.5	Locks String into handle of Umbrella	Injection Molded	Plastic
11	String Bulb Latch	1	1.3	Locks String Bulb into handle	Injection Molded	Plastic
12	String Bulb Spring	1	0.3	Locks String Bulb into String Bulb Latch	Stamped	Steel
13	String	1	0.7	Links Lower Hub to Umbrella Handle	Woven	Nylon
14	String Guide	1	4.9	Protects string and pushes String Bulb into String Bulb Latch	Extruded/Injection Molded	Steel
15	Pulley	1	0.2	Reduces string frictionand wear	injection moulded	Plastic
16	Pulley Shaft	1	0.3	Connects Pulley to String Guide	Formed	Steel
17	Pulley Cap	1	0.1	prevents String from slipping off Pulley	injection moulded	Plastic
18	Lower Hub	1	6.4	Attaches lower arms supports to shaft. Opens and collapses umbrella by translating along the shaft	Injection Molded	Plastic
19	String Clip	1	0.3	Attaches String to Lower Hub	Injection Molded	Plastic
20	Arm Spring	7	0.7	Collapses arm when string is released	Coiled	Steel