Babyproof door knob lock

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Revision as of 01:43, 21 September 2007

Executive Summary

Babyproof door knob locks are a common method in many households to restrain children within a certain area. This information page analyzes both the babyproof lock in addition to type of door knob to which it is attached. By fully understanding the consumer needs in addition to the exact function and manufacturing methods of the system under study our team hopes to innovate and improve upon products already available for purchase. By not only analyzing the babyproofing cover but also studying the complex mechanism of the doorknob itself, this study is provided extra depth.

A doorknob's primary purpose is to allow selective entry and exit between connected rooms. This simple of objective has evolved a complex mechanism with many points for possible failure. Locking and unlocking, the doorknob-to-door interface, and even the impact of rotation must be accommodated by the doorknob within a reasonable failure tolerance. Via product dissection, a deeper understanding of each item of the assembly is gained. FMEA allowed possible failure areas to be outlined and ranked while DFMA structured possible improvements in a systematic fashion.

A babyproof door knob lock's initial simplicity is complicated by its defined interaction with the doorknob mentioned previously. Deconstruction and analysis must always take into consideration what effect each component has upon a doorknob. Varying standards in size, quality and complexity of doorknobs themselves complicate the manufacture of the door knob locks. By combining the information from both of these products, a comprehensive improvement plan can be produced that minimizes parts and cost while maximizing effectiveness.

Customer Needs

(include what you know that can help the client)

Product Use

System Function

(include pictures)

Bill of Materials (Doorknob)

#	Name	Origin	Weight	Material	Manufacturing Process	Function
1	circular wedge	latch	--	Aluminum	stamped	access a wedge to keep latch assembled in place inside door
2	pop rivot	latch	--	brass	molded	holds latch case
3	turning shaft	outer doorknob	--	steel	molded	functions key lock
4	screws x2	outer doorknob	--	brass plated	cold heading, thread wooling	locks inner and outer doorknobs in place
5	latch plate	latch	--	brass	stamped	attaches to door jam (on door side)
6	strike plate	latch	--	brass	stamped and bent	attaches to door jam, allows latch to fit in hole
7	spring	inner doorknob	--	harden steel, nickel based alloy	wound, prehardened or hardened during fabrication	guides the lock by creating resistance in a locking shaft and keeping it aligned in a locking or unlocking position
8	lock shaft	inner doorknob	--	plastic and brass	two molded parts, press fitted	turns shaft into lock/unlock positions
9	ring	inner doorknob	--	aluminum	stamped	serves as a buffer between knob spring and spring housing
10	inner doorknob torsional spring	inner doorknob	--	steel	molded and wrapped	creates resistance when turning doorknob, prevents free spinning
11	spring housing	inner doorknob	--	brass	stamped and bent	houses and secures torsional spring
12	outer plate locking mechanism	latch	--	brass	stamped	attaches to door, similar to strike plate
13	inner plate locking mechanism	latch	--	brass	stamped	wedges between #12 and the door
14	latch	latch	--	steel	molded	latches door to door jam
15	lock attachment	latch	--	steel	molded	attaches to latch, does not slide when locked
16	face for outer doorknob	outer doorknob	--	brass	stamped	aesthetically pleasing
17	hook	latch	--	brass	stamped	hooks to latch or lock attachment
18	large hooks x2	latch	--	steel	stamped	pulls back latch
19	hook mechanism plate	latch	--	plastic	molded/injection molding	hooks #18 to latch
20	small hook from lock	latch	--	brass	molded	(unknown use)
21	pin	latch	--	brass	stamped and bent	adjusts locking mechanism between two different lengths
22	black plastic	inner doorknob	--	plastic	molded	(unknown use)
23	locking mechanism housing	latch	--	brass	molded and hole punched	houses small pieces in latch
24	short pin	latch	--	brass	molded	slides back and forth when size is adjusted
25	plastic hooks	latch	--	plastic	molded	slides back and forth when size is adjusted, may pull back when hook is tilted to latch
26	latch housing	latch	--	brass	molded and hole punched	houses mechanism controlling hooks for latch
27	sliding plate	latch	--	brass	molded and hole punched	slides back and forth, may align holes to those in the door or second housing piece
28	two lock springs	latch	--	steel/nickel alloy	wound	impacts latch mechanism
29	inner doorknob ring	inner doorknob	--	aluminum	stamped and molded	locks doorknob into rose, locks doorknob's cylindrical connector
30	inner doorknob rose plate	inner doorknob	--	brass	stamped and bent	attaches doorknob to door, acts as faceplate
31	inner doorknob rose	inner doorknob	--	brass	stamped and bent	connects door to doorknob, attaches and connects inner and outer doorknobs
32	inner doorknob	inner doorknob	--	brass	molded/pressed/clamped	it is gripped by the user to engage latch from inside the door
33	spring housing	outer doorknob	--	brass	stamped and bent	houses spring mechanism on the outer doorknob
34	bottom spring plate	outer doorknob	--	steel	stamped	spring pushes against it to create torque
35	top spring plate	outer doorknob	--	steel	stamped	spring pushes against it to create torque
36	outer knob torsional spring	outer doorknob	--	steel	molded/wrapped	creates resistance when turning doorknob to prevent free spinning of the knob
37	outer doorknob rose plate	outer doorknob	--	brass	stamped and bent	attaches doorknob to door, acts as a faceplate
38	outer doorknob rose	outer doorknob	--	steel	molded and tapped	houses screws and connects inner doorknob to outer doorknob
39	outer doorknob ring	outer doorknob	--	aluminum	stamped and molded	secures doorknob connector into rose
40	cylindrical connector	inner doorknob	--	steel	molded	connects doorknob to rose and secured with ring
41	spindle	outer doorknob	--	brass plated steel	molded	semi-cylinder that wraps around the turning shaft
42	outer doorknob	outer doorknob	--	brass	molded/pressed/clamped	is gripped by user to engage latch from outside the door
43	cone-shaped connector	outer doorknob	--	steel	molded	secures outer doorknob to rose and houses locking mechanism, spindle, and locking shaft
44	lock mechanism	outer doorknob	--	steel/aluminum/other	stamped/sealed/molded/assorted	mechanism engages lock

DFMA

FMEA (doorknob)

Who Are the Stake Holders?
- Homeowners, families
- Anyone who wishes to enter or exit a door
- Anyone who wants to secure a door

What it Does and How it is Used
Secures a door
- Allows selective entry or exit
- Steps:
1. Walk to a door
2. Lift hand
3. Grasp doorknob firmly
4. Twist the knob away from door jam
5. Push or pull the door open/close

Potential Failures
- If latch disconnects or mis-aligns, door does not open
- Loosening of the knob
- Material fatigue
- Rusting and sticking
- Loss of spring constant

How Failure Affects Consumers
- Doorknob becomes difficult or impossible to operate
- Doors may or may not be opened
- Repair or replacement

How Dangerous the Failures Would Be
- Cannot leave room during an emergency
- No longer reserving privacy
- Small parts may be swallowed by children

How Likely/Often Failure Would Occur
- 5~60 years

FMEA (doorknob protector)

i think we should combine the FMEA's (doorknob and doorknob protector) into a chart...
don't edit anything under the FMEA's yet, i'll get back to it tomorrow~

DFE

Quantitative Mechanical Analysis

EIOLCA

Production	Transportation	Use	End of Life
cell 1,1	cell 1,2	blank	blank
cell 2,1	cell 2,2	blank	blank

Bill of Materials (doorknob protector)

#	Name	Origin	Weight	Material	Manufacturing Technique	Function
45	blank	blank	--	blank	blank	blank
46	blank	blank	--	blank	blank	blank
47	blank	blank	--	blank	blank	blank
48	blank	blank	--	blank	blank	blank
49	blank	blank	--	blank	blank	blank
50	blank	blank	--	blank	blank	blank

24-441 Engineering Design Course, Fall 2007, Carnegie Mellon University

@@ Line 5: / Line 5: @@
 A doorknob's primary purpose is to allow selective entry and exit between connected rooms. This simple of objective has evolved a complex mechanism with many points for possible failure. Locking and unlocking, the doorknob-to-door interface, and even the impact of rotation must be accommodated by the doorknob within a reasonable failure tolerance. Via product dissection, a deeper understanding of each item of the assembly is gained. FMEA allowed possible failure areas to be outlined and ranked while DFMA structured possible improvements in a systematic fashion.
-A babyproof door knob lock's initial simplicity is complicated by its defined interaction with the doorknob mentioned previously. Deconstruction and analysis must always take into consideration what effect each component has upon a doorknob. Varying standards in size, shape and complexity of doorknobs themselves complicate the manufacture of the door knob locks. By combining the information from both of these products, a comprehensive improvement plan can be produced that minimizes parts and cost while maximizing effectiveness.
+A babyproof door knob lock's initial simplicity is complicated by its defined interaction with the doorknob mentioned previously. Deconstruction and analysis must always take into consideration what effect each component has upon a doorknob. Varying standards in size, quality and complexity of doorknobs themselves complicate the manufacture of the door knob locks. By combining the information from both of these products, a comprehensive improvement plan can be produced that minimizes parts and cost while maximizing effectiveness.
 == Customer Needs ==