The announcement by the Richmond, Va.-based company sent the price of its stock soaring by nearly 33%. Robertshaw, which said it retained the investment firm Goldman, Sachs & Co. to seek a buyer, is a leading manufacturer of automatic controls used in residential and commercial buildings, appliances and cars. The company's stock soared $14.87 1/2 a share to $61.50 in New York Stock Exchange composite trading. At that price, Robertshaw is worth about $338.3 million. Reynolds Metals owns 41% of the firm's common stock. Robertshaw did not indicate what price it would seek, and it cautioned that there was no assurance a deal would be completed.