用來防止由於司機操作失誤或其它原因引起的吊鉤過卷揚
，從而可能造成拉斷起升鋼絲繩、鋼(gang)絲(si)繩(sheng)固(gu)定(ding)端(duan)板(ban)開(kai)裂(lie)脫(tuo)落(luo)或(huo)擠(ji)碎(sui)滑(hua)輪(lun)等(deng)造(zao)成(cheng)吊(diao)鉤(gou)與(yu)重(zhong)物(wu)一(yi)起(qi)下(xia)落(luo)的(de)重(zhong)大(da)事(shi)故(gu)。為(wei)此(ci)雙(shuang)梁(liang)起(qi)重(zhong)機(ji)必(bi)須(xu)裝(zhuang)有(you)起(qi)升(sheng)高(gao)度(du)限(xian)位(wei)器(qi)，當(dang)吊(diao)鉤(gou)起(qi)升(sheng)到(dao)一(yi)定(ding)高(gao)度(du)時(shi)能(neng)自(zi)動(dong)切(qie)斷(duan)電(dian)動(dong)機(ji)電(dian)源(yuan)而(er)停(ting)止(zhi)起(qi)升(sheng)。

    常用的有壓繩式限位器

、螺杆式限位器與重錘式限位器。

    壓ya繩sheng式shi限xian位wei器qi是shi將jiang起qi升sheng鋼gang絲si繩sheng通tong過guo小xiao滑hua輪lun槽cao卷juan繞rao到dao卷juan筒tong上shang，小xiao滑hua輪lun套tao在zai光guang杆gan上shang，隨sui著zhe卷juan筒tong上shang鋼gang絲si繩sheng卷juan上shang與yu放fang下xia

，帶dai動dong小xiao滑hua輪lun在zai光guang杆gan上shang左zuo右you移yi動dong，在zai光guang杆gan兩liang端duan裝zhuang有you行xing程cheng開kai關guan。當dang起qi升sheng（或下降）到極限位置時，小滑輪碰壓起升（或下降）限位開關
，使電動機斷電停止工作。

    zhongchuishixianweiqishiyouyigejuyoudaipinghengchuidegangganshihuodongbidexianweikaiguan
，dangshuangliangqizhongjidiaogoushengzhizuigaoweizhishi，diaogoushangdepengganjiangpinghengchuituoqigangganshihuodongbizhuanguoyigejiaodu，shixianweikaiguanchudiandongzuo，qieduandianyuan
，diandongjitingzhigongzuo。