From the Congressional Research Service
http://www.senate.gov/CRSReports/crs-publish.cfm?pid=%26*2%3C4QLS%3E%0A">report on cloture:
"There are several stages to the process of invoking cloture.
- First, at least 16 Senators sign a cloture motion (also called a cloture petition)
that states: “We, the undersigned Senators, in accordance with the provisions of
Rule XXII of the Standing Rules of the Senate, hereby move to bring to a close
the debate upon .”
- To present a cloture motion, a Senator may interrupt another Senator who is
speaking. When the motion is presented, the clerk reads it.
- The cloture motion then lies over until the second calendar day on which the
Senate is in session. For example, if the motion is filed on Monday, it lies over
until Wednesday, assuming the Senate is in session daily. If the motion is filed on
Friday, it lies over until Tuesday unless the Senate was in session on Saturday or
Sunday.
- The Senate votes on the cloture motion one hour after it convenes on the second
calendar day after the cloture motion was filed, and after a quorum call has
established the presence of a quorum. The time for the cloture vote may be
changed by unanimous consent, and the required quorum call is routinely
waived.
- The presiding officer presents the cloture motion to the Senate for a rollcall vote
at the time required by Rule XXII, even if the Senate had been considering other
business between the time the cloture motion was filed and the time for voting on
the motion arrives.
- The majority required to invoke cloture is three-fifths of the Senators duly chosen
and sworn, or 60 votes if there are no vacancies in the Senate’s membership.
However, invoking cloture on a measure or motion to amend the Senate’s rules
requires the votes of two-thirds of the Senators present and voting, or 67 votes if
all 100 Senators vote.
This is in accordance with Rule 22 (XXII) of the
http://rules.senate.gov/public/index.cfm?FuseAction=RulesOfSenate.View&Rule_id=b53f00ae-eaf3-4382-a827-097360cb1c93&CFID=5239000&CFTOKEN=74671706">Standing Rules of the Senate. (The CRS report is easier to read than the Standing Rules of the Senate, imho.)