There is no standard pattern for an emergency(see Pondlife's answer), I suppose if you were really bored you could spell out "HELP" on somebodies radar scope, but if you are operating VFR in the US a controller really isn't going to notice that you are flying a triangular pattern. This would be dangerous though around airfields, since you want to remain in the standard pattern so you aren't confusing or surprising other pilots by coming in from odd angles. The best thing to do in this situation is to fly normally in a manner which other pilots can anticipate.
Squawking 7600 is the code for "Communications Failure" and this is the procedure I was taught for VFR (in the US), although it should hold for any ICAO airspace/field:
- Set Transponder to 7600
- Say intentions over the radio, the transmit may still work but the receive may be dead
- Enter the traffic pattern with a standard pattern entry
- Watch the tower for light-gun signals.
- Acknowledge Signals by rocking wings or flashing landing/taxi lights.
For an un-towered field, you enter the pattern as normal and follow the traffic flow in to land, taking care to watch for other aircraft on a straight-in or other odd approach.
Class-B offers other issues, if you are outside of class-B and lose your radio you cannot enter the class-B airspace even squawking 7600. If you are already in class-B then you may be able to continue but personally if the aircraft is otherwise flyable I'd head for the nearest class-D or C. There may be some exceptions to this for IFR flight plans, but that should be spelled out in the information in the link below.
Here is a good read of the Radio Loss Procedures and exceptions to the ICAO standard procedures for different operational areas below it.
By the way, you should be flying with a current AFD, and using your cell-phone to contact the tower is a perfectly acceptable way of establishing communications.