问题 问答题 简答题

X62W万能铣床具有哪些联锁和保护?为何要有这些联锁与保护?

答案

参考答案:

左右进给与上下、前后进给的联锁控制。

在控制进给的两个手柄中,当其中的一个操作手柄被置定在某一进给方向后,另一个操作手柄必须置于中间位置,否则将无法实现任何进给运动。这是因为在控制电路中对两者实行了联锁保护。如当把左右进给手柄扳向左时,若又将另一个进给手柄扳到向下进给方向,则行程开关SQ5和SQ3均被压下,常闭触点SQ5-2和SQ3-2均分断,断开了接触器KM3和KM4的通路,从而使电动机M2停转,保证了操作安全。

单项选择题
单项选择题

"You are not here to tell me what to do. You are here to tell me why I have done what I have already decided to do," Montagu Norman, the Bank of England’s longest-serving governor (1920-1944), is reputed to have once told his economic adviser. Today, thankfully, central banks aim to be more transparent in their decision making, as well as more rational. But achieving either of these things is not always easy. With the most laudable of intentions, the Federal Reserve, America’s central bank, may be about to take a step that could backfire.

Unlike the Fed, many other central banks have long declared explicit inflation targets and then set interest rates to try to meet these. Some economists have argued that the Fed should do the same. With Alan Greenspan, the Fed’s much-respected chairman, due to retire next year-after a mere 18 years in the job-some Fed officials want to adopt a target, presumably to maintain the central bank’s credibility in the scary new post-Greenspan era. The Fed discussed such a target at its February meeting, according to minutes published this week. This sounds encouraging. However, the Fed is considering the idea just when some other central banks are beginning to question whether strict inflation targeting really works.

At present centra1 banks focus almost exclusively on consumer-price indices. On this measure Mr. Greenspan can boast that inflation remains under control. But some central bankers now argue that the prices of assets, such as houses and shares, should also somehow be taken into account. A broad price index for America which includes house prices is currently running at 5.5%, its fastest pace since 1982. Inflation has simply taken a different form.

Should central banks also try to curb increases in such asset prices Mr. Greenspan continues to insist that monetary policy should not be used to prick asset-price bubbles. Identifying bubbles is difficult, except in retrospect, he says, and interest rates are a blunt weapon: an increase big enough to halt rising prices could trigger a recession. It is better, he says, to wait for a housing or stockmarket bubble to burst and then to cushion the economy by cutting interest rates-as he did in 2001-2002.

And yet the risk is not just that asset prices can go swiftly into reverse. As with traditional inflation, surging asset prices also distort price signals and so can cause a misallocation of resources-encouraging too little saving, for example, or too much investment in housing. Surging house prices may therefore argue for higher interest rates than conventional inflation would demand. In other words, strict inflation targeting-the fad of the 1990s-is too crude.

Which of the followings would be the best title for the text()

A. American Monetary Conundrums Are Readily Deciphered

B. American Central Banks Are on the Verge of Extinction

C. Conventional Inflation Target Is Best Employed in Transparent Environment

D. America’s Monetary Policy Is off Target