the present invention has being provided for business application and protection from patent law . referring to fig2 which is the first embodiment of the present invention . fig2 a shows a usb connector 23 being fit into a case 27 ; the usb connector 23 connects to a pcb 25 , and a bottom of the pcb 25 has a spring 29 for withstanding between the bottom of the pcb 25 and an internal surface of a bottom of the case 27 . meanwhile the spring 29 is depressed by a positioning structure 21 . a buckling piece 215 inserts into a buckling hole 273 , other components as a poking piece 217 , an extended arm 213 and a pushing button 211 are actually with the buckling piece 25 in one body so as to keep the pcb 25 staying with the present status . when the poking piece 217 is poked up , the buckling piece 215 is then taken off from the buckling hole 273 , shown as fig2 b ; continuously usb connector 23 is protruded out from a usb exit 271 . referring to fig3 which is the second embodiment of the present invention . fig3 a shows a usb connector 33 being hidden in a case 37 ; the usb connector 33 connects to a pcb 35 , and a top of the pcb 35 has a plurality of springs 39 for withstanding between an internal surface of a top of the case 37 and the top of pcb 35 . meanwhile the springs 39 are elongated . depressing and pushing a pushing button 311 of a positioning structure 31 upward makes that a buckling piece 315 being inserted into a buckling hole 373 because of the pushing button 311 , an extended arm 313 and the buckling piece 315 are in one body ; on the other hand , pushing button 311 connects with pcb 35 so as to that usb connector 33 is protruded out from a usb exit 371 , shown as fig3 b . at the moment , the springs 39 are depressed , and slightly poking up a poking piece 317 to take buckling piece 315 off the buckling hole 373 for recovering back to the status shown as fig3 a via spring force . referring to fig4 which is the third embodiment of the present invention . as shown in fig4 a , a case 47 comprises a fixing case 473 and a moving case 472 . an upper part of the fixing case 473 are wrapped in the moving case 472 , and moving case 472 is capable of sliding up and down on fixing case 473 . in the meantime , plural springs 49 withstand between a pcb 45 and a top of moving case 472 and are in elongation . to press moving case 472 downward is to let that a usb connector 43 goes out of moving case 472 via a usb exit 471 , as shown in fig4 b . referring to fig5 which is the fourth embodiment of the present invention . as shown in fig5 a , a usb connector 53 is hidden in an empty place of a case 57 . the usb connector 53 pivots on a pcb 55 via a pivotal structure 59 for both structure connection and electrical connection , such as pivotal means of keyboard and lcd of general portable computer , and there are several wires in the pivotal means . the pivotal structure 59 is able to have pivotal connection with usb connector 53 for turning usb connector 53 over so as to that usb connector 53 being protruded out from a usb exit 571 , as shown in fig5 b . referring to fig6 which is the fifth embodiment of the present invention . the embodiment adopts a screw mechanism to protrude a usb connector out of a case . as shown in fig6 a , a usb connector 63 connects with a pcb 65 , which lodges with a guiding rod 611 ; namely the pcb 65 has a toothlike structure , which is just matched with the guiding rod 611 . a rotational base 61 wraps over a bottom of a case 67 , and a protruding object on the rotational base 61 cooperates with a slot on the case 67 to make that rotational base 61 can circulate on case 67 . guiding rod 611 and rotational base 61 are in the same body , rotational base 61 is able to move pcb 65 and the usb connector 63 up and down via guiding rod 611 ; continuously usb connector 63 goes out of case 67 through a usb exit 671 . to conclude the above embodiments , the present invention adopts simple design to approach the protection purpose , such as spring and positioning structure , pivotal structure and rotational structure . as it can be seen , the present invention is capable of saving cost and manufacturing processes . the above - descriptions are the preferable embodiments of the present invention , however , the covered scope of the present invention is not limited to the embodiments shown in this invention . any changes according to the content of the present invention and the resulted functions and characteristics are similar to the embodiments of the present invention and the ideas created by all such technology well - known persons are all belonged to the covering scopes of the present invention .