What mechanism makes a cell phone or pager vibrate, and where can I
purchase that component?

The device which enables pagers and cell phones to vibrate is a tiny,
very simple motor which is unevenly balanced. As it rotates on its
shaft, the deliberately uneven weighting causes it to shake or thump.
Continuous rapid rotation results in a steady vibrating movement. The
same concept is often used in other types of vibrators, from personal
massagers to vibrating beds and chairs.

"Plurality of electromagnetic windings are positioned on said rotor
assembly, said rotor unbalance being effected by at least one of said
windings being substantially different in size and weight than the
other windings."

Free Patents Online: United States Patent 4931765
http://www.freepatentsonline.com/4931765.html

"Pager or cell phone vibrator motors ...
the way they do it is the output shaft of a vibrator motor has a
non-uniform weight attached to it so as the shaft spins, the weight
causes a vibration."

Board Game Designers Forum
http://www.bgdf.com/modules.php?name=Forums&file=viewtopic&t=1264

I've found several online sources for such motors:

Electronic Goldmine: Our Smallest Pager Motor
http://www.goldmine-elec-products.com/prodinfo.asp?number=G15615

MPJA Online: 6mm CELL PHONE VIBRATOR MOTOR 
http://www.mpja.com/category/DC__Motors/6mm_CELL_PHONE_VIBRATOR_MOTOR_16053_MD.asp

VOTI: very small pager vibrator motor (surplus)
http://www.voti.nl/shop/catalog.html?MOT-06

You'll find many sizes and styles of small vibrator motors listed here:

EC Plaza Global: micro vibrator motor
http://www.ecplaza.net/ecmarket/list.asp?cmd=search&keywords=micro+vibrator+motor

My Google search strategy:

Google Web Search: "vibrator motor" pager OR phone
://www.google.com/search?hl=en&q=%22vibrator+motor%22+pager+OR+phone

Google Web Search: "micro vibrator motor OR motors"
://www.google.com/search?hl=en&q=%22micro+vibrator+motor+OR+motors%22

I hope this is helpful! If anything is unclear or incomplete, please
request clarification; I'll gladly offer further assistance before you
rate my answer.

Best regards,
pinkfreud

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Request for Answer Clarification by ohmann37-ga on 05 Apr 2006 19:59 PDT

I have an application for this type of motor...how would I find out
which one is best for my use?

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Clarification of Answer by pinkfreud-ga on 06 Apr 2006 10:30 PDT

There are basically two types of small vibrator motors: cylindrical
ones and coin-shaped ones. The choice will probably depend upon the
contours of the space allotted for the motor. Since these motors are
quite inexpensive, it would be quite feasible to purchase several of
them and give them a real-world trial.

If you are looking for technical specifications, you may want to
contact manufacturers of this type of motor. Two major manufacturers
are SANYO and DOOCO:

SANYO MICRO MOTORS
General Sales Inquiries & Tech Support

DC Micro Motor Division
SANYO E&E America Company
1062 Thorndale Avenue
Bensenville, IL 60106 

motors@sss.sanyo.com
Tel: (630) 694-8230
Fax: (630) 595-7028
8:30am - 5:00pm CST Mon - Fri
English and Japanese spoken

http://www.sanyo.com/industrial/micro_motors/contact.cfm?showFileID=285

DOOCO USA

Address
1287 Barclay Blvd.
Buffalo Grove, IL 60089
USA
 
Phone   (847) 419-9200  
Fax   (847) 419-9209  
e-mail   info@doocousa.com

http://www.doocousa.com/contact.htm