Acer Inc., the world’s No. 2 PC manufacturer, unveiled a range of tablet computers to help it compete with Apple Inc.’s iPad.

The tablet computer market is becoming crowded as more companies produce the new devices, which fall between traditional PCs and smartphones.

Chief Executive Gianfranco Lanci announced at a news conference in New York Tuesday that the tablets would have 5-, 7- and 10-inch screens, running on Google’s Android software. A second 10-inch tablet will run on Microsoft’s Windows.

The company said the Wi-Fi-only models of the tablets would come out in April 2011, while the 3G-capable models would arrive about a month later. The 5-inch tablet doubles as a smart phone.

Separately Tuesday, Acer’s rival Dell Inc. announced a new tablet that runs on Microsoft’s Windows software.

Acer, based in Taiwan, said it was in talks with U.S. phone carriers for 3G connectivity for its tablets.

No prices had been set for the devices, the company added.

“It’s a gold rush right now,” said NPD analyst Ross Rubin. “Everyone wants to get a tablet product out there.”

Apple’s iPad, a touchscreen tablet that began selling in April, has an overwhelming lead in the market. It controlled 95 percent of it in the July-to-September quarter, according to research firm Strategy Analytics.

“PC vendors and hardware vendors are looking at this market and saying ‘how will I compete with Apple?’ ” Gartner analyst Carolina Milanesi said.

Tablet sales are expected to grow to 54 million units in 2011 and more than 100 million units in 2012, according to a forecast by research firm Gartner.

Acer also unveiled a screen laptop with two 14-inch LCD touch screens called the Iconia, along with a media store and software called Clear.fi that lets customers stream content on different Acer devices.

Dell’s new 10-inch touchscreen Inspiron Duo looks and runs like a tablet but can also be popped into a laptop shell and used like a notebook, similar to one of the new Acer tablets. The Duo starts at $550.