a main body includes a roller 2 at a bottom thereof and a suction fan motor 3 in a lower portion of the body . a floor nozzle 4 is pivotally mounted on main body 1 at the lower portion , and a handle 5 projects upwardly from the main body . a dust collector case 6 is disposed at a suction side of fan motor 3 and detachably mounted on a front portion of main body 1 . dust - laden air flows through floor nozzle 4 and a flexible hose 7 into dust collector case 6 , where dust is filtered . filtered air is discharged through fan motor 3 out of an air discharge opening 9 located in bottom of main body 1 . the dust collected in dust collector case 6 can easily be disposed of by periodically removing the dust collector case from main body 1 removing filter 8 , and opening the lower portion of the case . floor nozzle 4 is shaped to sandwich the lower portion of main body 1 at both sides thereof . nozzle 4 is rotatably mounted on hollow shafts 10 projecting outwardly from both sides of main body 1 ( fig3 ). a suction chamber 11 has a suction port 12 opening at a bottom of floor nozzle 4 and housing therein a rotary brush 13 . a suction tube 14 extends from the suction chamber 11 and has a distal end located in the rear of the floor nozzle 4 where a joint tube 15 mounted on one end of flexible hose 7 is detachably connected to the suction tube . a power transmission belt 16 extends under tension around and between a shaft 17 of fan motor 3 and rotary brush 13 . a lower end of dust collector case 6 has a projection removably engageable in a slot 18 in main body 1 , and an upper grip 21 having a tail lock 20 removably engageable with the main body . a rear suction hole 24 formed in case 6 is held in communication with an air passage hole 23 in back of the main body 1 through an airtight gasket 22 . an elbow pipe 25 provides communication between air passage hole 23 and the other end of flexible hose 7 . air flows from suction port 12 in floor nozzle 4 into suction chamber 11 , and then through suction tube 14 , joint tube 15 , flexible hose 7 , elbow 25 , and thence through air passage hole 23 , suction hole 24 into dust collector case 6 . thereafter , air flows through filter 8 , an air duct 26 , and fan motor 3 , for discharge through discharge opening 9 . fan motor 3 is fixedly mounted in position in main body 1 by resilient supports 27 , 28 as of rubber . for cleaning tight places not reachable with floor nozzle 4 joint tube 15 on flexible hose 7 is disconnected from suction tube 14 and equipped with a crevice tool 29 as illustrated in fig9 . flexible hose 7 should be used instead of another hose to allow easy cleaning operation within a certain area . a bypass air passage 30 is disposed at suction side of the fan motor 3 for permitting communication between the atmosphere and the suction side of the fan motor without passing through filter 8 . bypass air passage 30 has one end vented directly to atmosphere and the other end opening into air duct 26 at suction side of the fan motor 3 . more specifically , the bypass air passage 30 comprises an air conduit 31 fixedly mounted in one of hollow shafts 10 on main body 1 , conduit 31 has one end connected to a valve casing 33 having a circumferential wall integral with air duct 26 and opening into the air duct . the circumferential wall includes air outlet ports 32 . air conduit 31 is joined at the other end thereof to a sound producing cylinder 34 having open ends . the sound producing cylinder 34 is composed of a pair of semicylindrical members 35 , 36 molded integrally of plastics and joined together ( fig5 - 8 ). the semicylindrical members 35 , 36 have oblong holes 37 , 38 respectively , extending in the axial direction and integral vibratory members 39 , 40 facing the oblong holes 37 , 38 , respectively , each including free ends . the sound producing cylinder 34 has one end press - fitted in and secured to the inner peripheral surface of air conduit 31 , and is fixed to main body 1 by a screw 42 extending through mounting fin 41 ( projecting from one of semi - cylindrical members 35 , 36 ), as illustrated in fig8 . a sound control cylinder 43 having open opposite ends is rotatably inserted in sound producing cylinder 34 . cylinder 43 has in a circumferential wall therefore axial control slots 44 , 45 which can be held in registration with oblong holes 37 , 38 , and further includes an external manipulator 47 projecting outwardly through an opening 46 defined in a top wall of floor nozzle 4 . a pressure - responsive valve 48 is accommodated in valve casing 33 and is normally urged by a spring 49 to close one end of air conduit 31 . when the pressure in air duct 26 drops below a predetermined value , valve 48 is displaced to open end of the air conduit 31 against bias of the spring 49 . when the vacuum cleaner is in operation for cleaning with floor nozzle 4 , and as long as filter 8 remains unclogged , the pressure in air duct 26 is higher than the predetermined value , and hence pressure - responsive valve 48 is closed ( see fig3 ). as the amount of dust in collector case 6 increases , or if filter 8 clogs , the pressure in duct 26 at the suction side of fan motor 3 becomes lower than the predetermined value , causing valve 48 to open the end of air conduit 31 against the force of spring 49 as illustrated in fig4 . the aforesaid movement of valve 48 opens bypass air passage 30 , permitting air to flow towards fan motor 3 in bypassing relation to filter 8 , thus preventing the fan motor from burning out due to operation under an excessive load . the bypassing air flows partly through oblong holes 37 , 38 in sound producing cylinder 34 and control slots 44 , 45 in sound control cylinder 43 , and partly through the open end of the sound control cylinder . the bypassing air as it enters slots 37 , 38 and control slots 44 , 45 causes vibratory members 39 , 40 to emit a sound ( see fig5 and 7 ), informing the user that the amount of dust collected has been increased to capacity , or filter 8 has been clogged , so that the user can throw away the collected dust or dust off the filter . when the vacuum cleaner is used to clean tight places such as corners of a room with crevice tool 29 attached to joint tube 15 of flexible hose 7 as disconnected from suction tube 14 in floor nozzle 4 , pressure - responsive valve 48 opens air conduit 31 since the crevice tool has greater air flow resistance therethrough even when the amount of dust collected is within a tolerable range , or the filter 8 is free of any clogging . at this time , however , external manipulator 47 is actuated to angularly move sound control cylinder 43 until control slots 44 , 45 are brought fully out of registration with oblong holes 37 , 38 in sound producing cylinder 34 . consequently , oblong holes 37 , 38 are closed by sound control cylinder 43 and no air flow is permitted therethrough . vibratory members 39 , 40 are then prevented from vibrating and giving off sound . while unwanted generation of an alarm sound is being supressed , the bypassing air continues to flow through the open and of the sund control cylinder 43 , so that there is no danger for the fan motor 3 to be operated under an excessive load . the amount of air drawn through the filter 8 is reduced by the amount of bypassing air during opening of the air conduit 31 . the speed of flow of air which is large enough to draw dust is however maintained due to the constricted opening in the crevice tool 29 . since the mode of operation in which the crevice tool 29 is employed is a supplemental operation and is effected in a relatively short period of time , it has no substantial adverse effect on the efficiency of the vacuum cleaner . although in the embodiment the sound control cylinder 43 is angularly movable with respect to the sound producing cylinder 34 , the sound control cylinder 43 may be slidable axially or may be arranged otherwise provided it can open and close the oblong holes 37 , 38 in the sound producing cylinder 34 while maintaining a required amount of bypassing air . furthermore , two or more vibratory members 39 , 40 may be provided which are of different thicknesses for varying tones so that the vibratory members will jointly produce a pleasing chord . as described above , the present invention resides in that when the load imposed on the fan motor exceeds a predetermined value , a bypassing flow of air is introduced to prevent the fan motor from being burned out , and such an excessive load condition is indicated by sound to allow the user to take a necessary measure quickly against the undesirable condition . generation of an alarm sound can be prevented by the user at will . thus the vacuum cleaner of the invention is quite convenient to handle . even if the fan motor is subject to an increased load while an adjustment is made to stop the emission of an alarm sound , the fan motor is nevertheless supplied with bypassing air . therefore the fan motor is prevented from burning out in any case .
the present invention relates to a vacuum cleaner in which an alarm sound is generated by introducing air from the exterior in bypassing relation to a filter 8 when a suction load imposed on a fan motor 3 exceeds a predetermined value . the alarm sound can be emitted or stopped without adversely affecting the introduction of bypassing air toward the fan motor 3 . with such an arrangement , the vacuum cleaner can be used conveniently , and the fan motor 3 is prevented from being burned out .