US2192224A

US2192224A - Vacuum cleaner

Info

Publication number: US2192224A
Application number: US83836A
Authority: US
Inventors: Forsberg Axel Albert
Original assignee: Electrolux Corp
Current assignee: Electrolux Corp
Priority date: 1935-06-14
Filing date: 1936-06-06
Publication date: 1940-03-05
Anticipated expiration: 1957-03-05

Description

March 5, 1940- A. A. FoRsBERG VACUUM CLEANER Filed June 6, 1936 3 Sheets-Sheet 1 l //f/MVENT R' BY l /AUQRNEY.

March 5, 1940. A. A; FoRSBERc-s 2,192,224

I VACUUM CLEANER Filed June 6. 1936 3 Sheets-Sheet 2 INVENTOR.

E BY ATTORNEY.

March 5, 1940. A. A. FoRsBl-:RG 2,192,224 I VACUUM CLEANER Filed June 6, 1936 5 Sheets-Sheet 5 HUH IN VE TOR. /65 m/ We# f A BY @laf/5 Aia. ATTORNEY.

'through the member.

Patented Mar. `5, 19.40,

` UNITED STATES VACUUM CLEANER Axel Albert Forsberg, Stockholm, Sweden, assignor to Electrolux Corporation, Dover, Del., a corporation of Delaware Application June 6, 1936, Serial No. 83,836 In Germany June 14, 1935 14 Claims.

The present invention relates to vacuum cleaners and particularly to means for indicating the amount of dirt collected within a vacuum cleaner.

As dirt collects within the dust bag of a vacuum cleaner, or within adust collecting chamber one or more walls of which includes a dust separating member, the accumulated dust interferes with the ilow of air. As the dust collects it tends to clog the porcs of the dust separating member, thereby increasing the pressure drop Consequently, this pressure drop may' be employed to` indicate the amount of dirt which has accumulated. An increase in pressure drop also results in a decrease in velocity of the air passing through the cleaner unit, and hence the decrease in'velocity may be employed to indicate an increase in accumulation of dust.

In apparatus of vthis type heretofore known, the indicator member has been arranged to give a reading determined by either the pressure drop or the velocity of the air ow at the particular instance )when the indicator is observed. Consequently; the indicator gives no true indication of the amount ofv dust accumulated if it is lobserved while the fan is stationary. An indicator dependent upon pressure drop will indicate a clean dust bag whenever the fan is stationary, inasmuch as there is no pressure drop under these conditions. regardless of what the truel amount of dust accumulated may be. Likewise, an indicator responsive to air velocity will show dirty whenever the motor is stopped, regardless of how much dirtl is actual1y accu mulated. Moreover, both types of indicators give uctuating reading during. use of the vacuum cleaner, inasmuch as they are aiected to some extent by the resistance to ow through the nozzle. If the nozzle opening is substantiallyA sealed, as by being pressed against rugs of a certain type. the air flow will be substantially prevented and consequently much the same condition will exist as does when the motor is stopped. Hence, it is diflicult for the operator to know whether the o indicator at any particular instant is giving him a true reading.

One of the objects of this invention` is to provide an indicator which records maximum values. As will later appear, the maximum value of the pressure drop through the dust separating member bears a definite -.re1ationship to the amount of dust accumulated. In accordance with the present invention, the indicator records this maximum reading so that theoperator may know at (ci. iss-37) all times, even when the motor has vbeen stopped, the amount of dust in the cleaner.

Another object of the invention is to provide means for returning the indicator to a zero reading-in response to a manual operation. Preferably, the indicator is returnedto zero when the dust separating member is removed from the cleaner unit.

Another object of the invention, is to provide means in combination of the above `for aiding in the removal of the dust separating member. Further objects of the invention will be apparent from the following description considered in connection with the accompanying'drawings, and of which:

Fig, 1 is -a side view, partially in cross-section, of one embodiment of the invention;

Fig. 2 is an enlarged view of a portion of the device shown in Fig. l;

Fig. 3 is a cross-sectional view of a part of a vacuum cleaner showing a second embodiment of the invention;

Fig. 4 is a cross-sectional View f the line 4 4 of Fig. 3;' i

Fig. 5 is a cross-sectional view of the portion of a vacuum cleaner showing a third embodiment of the invention;

Fig. 6 is a cross-sectional view showing a fourth embodiment of the invention;

Fig. l4 is a cross-sectional view showing a fth embodiment of the invention Fig, 8 is a cross-sectional view of a sixth ernbodiment of the invention:

Fig. 9 is a cross-sectional View showing a seventh embodiment, and is taken on the line 9--9 of Fig. 11;

Fig. 10 is a cross-sectional view of the device shown in Fig. 9 and is taken on the line Ill-I0 of Fig. 11;

Fig. 11 is an end View of a portion of the device shown in Figs. 9 and l0; and

, Fig. 12 is a cross-sectional View of an eighth embodiment of the invention, j

Referring more particularly to Figs. 1 and 2, reference character I0 designates a casing of a vacuum cleaner unit. Mounted vithin casing l0 is an electric motor II arranged to drive a centrifugal fanv I2 disposed within a fan housing 9 having an inlet I3. The fan exhausts through and around the motor and the air is discharged to the atmosphere through an outlet opening I4.

The left end of casing I0, asviewed in Fig. l, is provided with a ring I5 formed with an outer face I6 against which is adapted to be seated a dust bagiring I'I. l Ring l1 is formed .with an outwardly extending flange I8 carrying a packing member I9 of rubber or the like. Flange I8 and packing I9 is adapted to be clamped against the face I6 of ring I5 by means of a closure member 20, which may be secured to the casing I0 by means of spring clips 23 or the like. Closure member 20 is formed with an inlet opening 24 to which may be attached a hose 25 leading to a nozzle 26.

Secured to ring I1 is a dust separating member 21, in the form of a bag having a closed end. A perforated plate 28 is resiliently mounted on fan housing 9-by means of one or more springs 29 and the length of bag 21 with respect to the dis-` ance between ring I1 and plate 28 is so chosen that the plate prevents complete distension of the bag.

Slidably mounted in the upper part of casing I0 in the space 3| between the dust bag and the casing is a preferably tubular member 38 having a horizontal portion supported in

brackets

33, 34 and 35. Member 30 also includes a portion 36 which extends radially of the casing and has an axial portion 31 adapted to contact the central part of plate 28, but is not secured to the plate.

Mounted on the upper part of casing I0 is a handle bracket 38 having an air tight compartment 39 within which is rotatably mounted an indicator memberl 48. Indicator 40 includes the formed in member 30, whereby longitudinal 1 ,movement of the member 30 causes rotation of the indicator.

Slidably mounted within ring lI5 is a resetting rod which telescopes within the end of tubular member 30. Member 30 is formed with a. slot 46 and rod 45 is provided with a projection 41 which may slide Within the slot 46. A coil spring 48 is arranged around 'rod 45 between bracket 35 and a collar 49 formed on the rod. The left hand end as viewed in Fig. 2 of rod 45 is preferably formed .with an enlargement 50 adapted to be received in a recess formed in the face I6 of ring I5 and to press against the dust bag ring.

The operation of the above described apparatus is as follows:

- Rotation of fan I2 bythe motor II causes air to be drawn in through nozzle 26, hose 25, and

inlet opening 24 into the interior of dust bag 21. If the nozzle is passed over a dusty surface, dust will be entrained with the air and carried intoA the dust bag. 'I'he bag is made of a suitable material which is impervious with respect to.

dust, but permits the passage therethrough of` air. Consequently, the dust accumulates within the dust bag, while the air passes through the material thereof to the fan from whence it is discharged to the atmosphere through opening and therefore the closed end of the bag presses fect the indicator member.

against plate 28 and tends to compress the spring 29. With a clean bag the resistance to flow, and hence the pressure drop, is comparatively small and the springs 29 are designed to resist the tendency of the bag to distend. However, as dust accumulates within the bag it fills more or less the pores in the material of the bag through which the air passes, thereby increasing the resistance to flow. This in turn causes an increase in the pressure drop and the force exerted by the bag against the plate increases, and this moves the plate to the right as viewed in the figures, and compresses spring 29.- The movement in this direction of plate 28 causes tubular member 30 to move in a similar direction, thus causing indicator member 40 to rotate in a counter clockwise direction. During this movement of tubular member 30, rod 45 remains stationary, the tubularl member being able to slide with .respect thereto by virtue of the fact that projection 41 may slide within slot 46. If the motor is now stopped the flow of air through the cleaner ceases and the pressure on opposite sides of the dust bag is equalized. Consequently, the springs 28 return the plate 28 to its original position. However, member 30 does not follow the movement of plate 28 in this direction inasmuch as it is not attached to the plate, and there is no force acting on the rod tending to move it to the left. The openings in

brackets

33, 34 and 35 iit the member 30 with such tightness so that the friction prevents accidental displacement of the member 30 in either direction. Therefore, the indicator member 40 remains in the furthest position to which it was rotated by movement of member 30 to the right, and recordsA a reading proportional to the maximum pressure drop through the dust bag.

Ii the motor is again started and more dust accumulates within the bag, the increase in pressure drop causes the plate 28 and the'rod 30 to be moved further to the right and this new maximum reading is recorded by the indicator member 40.

Likewise, fluctuation in pressure drop occurring during the operation of the cleaner does not af- If the nozzle 26 is substantially sealed, the flow of. air through the unit including the iiow of air through the dust bag practically ceases, whereupon the pressure drop through the bag`amounts to practically nothing. This permits the springs 29 to move the plate 28 to the left but this movement is not communicated to the indicator member 40, which at all records the maximum pressure drop which has occurred through the bag since the machine was rst started. When a suicient amount of dust has been accumulated in the bag to require the cleaning thereof, this fact is made known to the operator by the position of the indicator member 40. To clean the bag closure member 20 is removed by unfastening clip 23, whereupon the dust bag ring I5 may be grasped and the bag removed from the casing IIJ. As soon as the ring is moved away from the end 50 of rod 45, spring 48 moves the rod to the left, as viewed in the figure, and projection 41 on the rod engages the left hand end of slot 46 in member 38, thus causing member 30 to be moved to the left. Thisrotates indicator member 48 in la clock-wise direction and resets it in a position to indicate a clean bag. It will be noted that the indicator member may be reset only in response to the manual operation of removing the dust bag.

Spring '48 may be made to have sufficient vstrength so that, when closure member 20 is detached from the casing I0, the spring will force rod 45 to the left, thus moving dust bag ring I1 out of contact with ring I5. This facilitates grasping the packing I9 on the ring with-- out placing the hand within the ring. This is advantageous inasmuch as the interior of the ring is apt to be covered with dust.

The embodiment shown in Figs. 3 and 4 differ from that above described only in the nature of the indicator member. In this embodiment, the indicator member comprises a flat plate 55 rigidly secured to tubular member 30, and arranged to move longitudinally with the member underneath an air tight window 56. Otherwise, the construction of the two embodiments is the same, and their operation is identical.

It will be noted that in the embodiments above described the dust bag itself has been utilized as the distensible member movable by means of the pressure drop for imparting movement to the indicator.

In the following embodiments a separate distensible diaphragm is provided for this purpose and is arranged to be subjected on one side to the pressure existing within the dust bag and on the other side to the pressure existing within space 3| in the casing.

Referring to Fig. 5, reference character I0 again designates the casing of the vacuum cleaner` unit provided with an end ring I5. Ring I5 has an enlarged portion forming a recess opening from the space 8| within the casing. Mounted within this recess is a cylindrical member 6| having a flat end 62 and an open end 63 of reduced diameter. End 63 is received within an opening formed in a member 64 secured to ring I5, and a bolt 65 is arranged vto press 'against the end 62 to hold the member 6| in position. Ring I5 is formed with a passageway 66 communicating with the open end 63 and with an annular groove 61 formed in the face I6 of ring |5. Closure member 20 is formed with a similar groove 68 and the flange I8 and packing I9 of dust bag ring I1 are formed with one or more openings 69 which establish communication between grooves 61and 68. `A passage 10 connects grooves 68 with the space within closure member 20 and hence with the` interior of dust bag 21. A distensible member in the form of a flexible diaphragm 13 is secured within cylindrical member 6| by means of a ring 14 clamping the circumference of the diaphragm against a shoulder 15 of member 6I. Diaphragm 13 divides member 6| into a chamber 16 which is in communication with the interior` of the dust bag through open end 63, passage 66, groove 61, opening 69, groove 68 and passage 10, and a chamber 11 which is in communication with the space 3| through an opening 18 formed in the lower side of member 6

I. Reinforcing discs

19 and 80 are preferably secured to the central part of diaphragm 13 by means of a rivet 83. A spring 84 is disposed between disc 80 and the bottom 62 and is preferably secured in place around a cylindrical member 85 fastened to the bottom 62.

Slidably disposed within cylindrical member 6| is an indicator member 86 having a reduced end 81 adapted to be cont..:ted by disc 80 of the diaphragm 13. Casing GII is formed with an air tight window 81 in alignment with an opening 88 in the upper side of member 6| through which vthe position of indicator member 86 may be observed. A resetting rod 89 is sliu'ably supported within a stationary member 90 rigidly secured to member 6I. The left hand end of rod 89, as viewed in Fig. 5, is provided with a head 93 adapted to press against the dust bag ring I1. Spring 94 is disposed between member 90 and head 93 and tends to move the rod 89,l to the left. The right hand end of the rod is formed as a ring 95 slidable within cylindrical member 6|.

'I'he operation of this embodiment is as follows:

As described in connection with the previous embodiments, the dust bag 21 offers a resistance to the flow of air therethrough which is proportional to the amount of dust accumulated therein, thus causing a lower pressure to exist Within space 3| than within the dust bag. The higher pressure within the dust bag is communicated to chamber 16 as previously described, and this pressure is exerted on the left hand face of diaphragm 13, while the lower pressure within space 3| is communicated to chamber 11 and acts upon the right hand face of the diaphragm. Consequently,

as the diterence in these pressures increases, the

central portion of diaphragm 13 is moved to the right against the increasing resistance oiered by spring 84. This movement causes indicator member 86 to move to the right. In the event of a subsequent decrease of the pressure drop, caused, for instance, by stopping the motor, spring 84 will move the diaphragm 13 back to its original position but indicator member 86 will remain in the furthest position to which it has been `moved, thus giving a reading which is proportional to the maximum pressure drop which has occurred through the bag since the machine was started.

When indicator member 86 indicates that the bag should be cleaned, closure member 20 is unfastened and bag 21 removed. Spring 94 is now able to move rod y,89 to the left and the ring 95 connected to the rod moves indicator member 86 back to its original position. As was the case in the first embodiment described, if spring 94 is stiff enough, it will eject the dust bag ring a short distance when the closure member 2.0 is unfastened, thus making it easier for the operator to grasp the ring to remove the bag. v

The embodiment shown in Fig. 6 diiers from that illustrated in Fig. 5 only in that the head 93 of rod 89, contacts-the dust bag ring I1 directly instead of having a portion of the dust bag material interposed therebetween. This may b e accomplished by turning the material of the ring I1 back on itself as shown at 96 and securing the end of the bag 21 between the main part of the ring and the portion 96.

Stem |01 is Yslidably mounted in an opening formed in ring I5 and a spring IIO is disposed between the right hand end of the stem and the bottom of member IUI. Stem |01 is formed with a bore ||3 extending axially from its left hand end Vand communicating with a radial bore ||4 which establishes communication with the space to the left of diaphragm |03. The left end of Stem |01 is provided with a packing ring I I5 which seals the end'of the stem against the inner face of closure member 20, the latter being formed with a passage I I6 which establishes communication between bore I I3 and the interior of the dust bag 21. Any suitable means may be provided for positioning closure member 20 with respect to ring I5 so that passage |I6 will be in alignment with the end of stem |01 when the closure member is secured in place. For instance, the closure member may be permanently hinged to the ring.

Rigidly secured to the central part of diaphragm 03 and indicator member |08 is a pin II1 having a portion of reduced diameter II8. Loosely mounted on stem |01 is disc ||9 having a projecting edge |20. The reduced portion I|8 of pin II1 extends loosely through the hole formed in disc ||9 and a spring |23 is disposed between the diaphragm and disc ||9. Due to the loose t of stem |01 and pin II1 in the disc, the latter can be tilted a limited amount by spring |23.

The operation of this embodiment is as follows:

The pressure within dust bag 21 is communicated to the left hand side of diaphragm |03 through passage I|6 and the bores I| 3 and |I4` and'stem |01, while the lower pressure existing within space 3| is communicated to the right hand space of the diaphragm through opening |02. The pressure difference acting on the diaphragm causes the central part thereof to move to the right against the force of spring |09 and indicator member |08 is caused to move in the same direction by virtue of the fact that it is rigidly secured to the center part of the diaphragm. During such movement bushing |06 slides on stem |01 and disc ||9 likewise slides on the stem. Due to the tilted position in which the disc is held by spring |23, the disc does not bind against stem |01 during movement in this direction. Upon a reduction in the diilerence in pressuresacting on opposite sides of the diaphragm the spring |09 tends to move the central part of the diaphragm and the indicator member |08 attached thereto to the left. However, when pin I1 attempts to slide disc |I9 along the stem |01, by applying force to the lower edge of the disc, the latter does bind and locks against the stem, thus preventing movement of the diaphragm to the left. Consequently, the indicator member |00 is retained in the furthest position to which it has been moved. When the closure member 20 is removed in order to take out the dust bag, spring ||0 moves stem |01 to the left and diaphragm |03 and indicator |08 move along therewith, and thus return to their original position. When the projection edge |20 of disc ||9 strikes the bottom of member |05, it is tilted to a more vertical. position thus releasing the locking action between the disc and stem 01. Spring ||0 is not absolutely necessary, and if it is omitted spring |09 will move both the diaphragm and stem |01, which are locked together by disc II9, to the left when closure member 20 is removed. However, if spring |I0 is omitted, stem |01 must be extended so as to abut against the bottom of member. |0| when the closure member is in place in lorder to maintain a tight seal at packing ||5.

In the embodiments shown in Figs. 8 through 12, the indicating mechanism is located within closure member 20,` instead of within the casing |0. An advantage of this is that if the indicating mechanism gets out of order, it is not neces'- sary to return the entire vacuum cleaner unit for repairs but a new closure member may be substituted and only the old closure member need bereturned.

Referring to Fig. 8, closure member 20 is formed with an inwardly projecting cylindrical member |25 which is arranged to receive the hose 25. An annular flexible diaphragm |26 has its inner part secured in air tight relation to the inner end of member |25 while its outer circumference is secured to a member v|21 supported by cylindrical member |25,'the part of the diaphragm in between being movable. A member |29 is slidably supported on cylindrical member |25 and forced against diaphragm |26 by means of a spring |30. Closure member 20 is formed with an outwardly projecting portion |33 provided with an air tight window |34. A pin |35 is rigidly secured in portion |33 and an indicator member |36 is slidably mounted on the pin, and engages the pin with suflicient friction so that it is not movable accidentally. Indicator member |36 is provided with an extension |31 adapted to be contacted by member |29 when the latter is moved to the left as viewed in Fig. 8.

A cylindrical member 38 is slidably mounted y within closure member 20 and a spring |39 tends to move member |38 to the right. However, when closure member 20 is secured to ring I5, member |38 presses' g'aii'st 'a packing ring |40 which prevents member |38 from moving with respect to the closure member. Member I 38 isV provided with a radially extending portion |43 which is will not be so sudden as to cause the diaphragmv to strike the indicator with such force as to knock it further to the left than the diaphragm itself moves. Dust bag ring I1 is clamped between ring I5 and the outer circumference of diaphragm |26.

The operation of this embodiment is asY fol-v lows:

The right hand face of diaphragm |26 is subjected to the pressure existingwithin dust bag 21 while the opposite face of the diaphragm is subjected to the lower pressure existing within space 3|. This difference in pressure tends to move the diaphragm. and member |28 to the left against the force of spring |30. Such movement causesindicator member 38 to be moved to the left, but movement of diaphragm |26 and member |29 in the opposite Ldirection hasA no eect on the indicator. Consequently, the indicator records the maximum pressure drop which has occurred through the dust bag.v When closure member 20 is removed in order to take out the dust bag, spring |39 is able to move member |38 to the right, whereupon extension |43 strikes collar |44 of the indicator and moves the latter to the right, thus returning` it to its original position.

In the embodiment shown in Figs. 9 through 11, a diaphragm |50 `has its outer periphery secured within closure member 20, while its central closure member. A spring |48 is disposed between the diaphragm and wall |52 and the diaphragm may be supported by a perforated plate |49 when the air pressures in opposite sides of the diaphragm are equalized. Ring I is formed with a passageway |53 communicating with a .groove |54 formed in the face of the ring, while closure member 20 is formed with a similar groove |55, communication between these grooves being established by one or more openings |56 in the dust bag ring. A passage |51 connects groove |55 with the space to the left of diaphragm |50. Pivotally mounted on wall |52 is an indicator member |58. The friction caused by turning of the indicator about its pivot is sufficient to retain it in any position in which it may be set. An air tight Window |59 makes the indicator |58 visible to the operator. An arm |66 connected to the indicator is arranged to be contacted and rotated in counterclockwise direction by movement of pin |5| to the left. Inasmuch as an increase in pressure drop through the dust bag causes diaphragm |50 to move to the left, indicator |58 records the maximum pressure drop which has occurred through the bag. The indicator is returned to its original position when the closure member 20 is removed by means of an arm |6| rigidly secured to a pin |62 which is slidably supported within the closure member, as will appear more clearly from Fig. 11. Pin |62 is provided with an enlarged head |63 and a spring |64 tends to move pin |62 to the right. Hence, when the closure member is removed the spring does move the pin to the right and arm |6| contacts arm` |60 and rotates indicator |58 in a clockwise direction back to its original position.

In the embodiment shown in Fig. 12, a diaphragm |65 is mounted in closure member 20 so as to be subjected on one side to the pressure existing within the dust bag while the pressure of space 3| is communicated to the other side of the diaphragm through a passage |66 in ring I5 and a passage |61 in the closure member. A spring |68 tends to move the diaphragm to the right, while the pressure diierence tends to move it in opposite direction. An indicator pin |69 is slidab-ly mounted in an opening formed in closure member 20 and is arranged to be moved to the left by similar movement of the diaphragm. However, there is no connection between pin |69 and the diaphragm, and hence movement of the latter to the right will not move the pin. Inasmuch as the pin projects through the closure member to the atmosphere, a packing diaphragm is provided for preventing leakage of atmospheric air. phragm |10 is subjected on one side to the low pressure existing within space 3| and on the other side to atmospheric pressure it will tend to resist movement of the pin |69 to the left. However, diaphragm |65 is made of sufficiently larger area so that the total force exerted by this diaphragm is larger than the force exerted by diaphragm |10. Friction producing means |1| are provided for retaining the indicator pin |69 in the furthest position to which it has been moved by the diaphragm |65. The distance that the outer end of'indicator pin.|69 projects is an indication of the maximum pressure drop which has occurred through the dust bag. In this embodiment the indicator member is not returned to its original position by removal of the closure member but must be pushed in by the operator.

Inasmuch as the dia- While there have been described several more or less specic embodiments to my invention, it is to be understood that these have been for purposes of illustration only and that the scope of the invention is not to be limited thereby, but is to be limited only by the appended claims viewed Ithrough said member, a movable indicator member, means for moving said indicator member in one direction upon an increase in pressure drop through said dust separating member, said indicator member being arranged to remainin the position to which it is moved by the second mentloned means regardless of subsequent decrease in pressure drop, and means independent of said second mentioned means for moving said indicator member in the opposite direction.

2. In a vacuum cleaner', a dust separating member, means for producing varying iiow of air through said member, a movable indicator member, means for moving said indicator member' in one direction upon an increase in pressure drop through said dust separating member, said indicator member being arranged to be frictionally held in the furthest position to which it is moved by the second mentioned means, and manually operable means for moving said indicator member in the opposite direction.

3. In a vacuum cleaner, a removabledust separating element, means for producing iiowI of air through said element, an indicator member movable in one direction in resonse to an increase in pressure drop through said element, and means operable by removal of 'said dust sepa'.-

opposite direction.

4. In a vacuum cleaner, a casing, a distensible member mounted in said casing, air flow means for producing a varying pressure diierential on opposite sides of said member, means yfor limiting distension of said member to an amount proportioned to the pressure diierential, an indicator movable in one direction to record the maximum distension of said member, and means responsive to a manual operation for moving said indicator in the opposite direction. f

5 In a vacuum cleaner, avcasilng,`a distensible dust separating member mounted in said casing,

Arating element for moving said indicator in the air flow means for producing a varying pressure dierential on opposite sides of said merf'iber,A

resilient mechanism arrangedA to resist distcnsion'g .of said member 'and to be mOVed by distensin thereof, an indicator movable in one direction to record the maximum movement of said mechanism caused by distension of said member, and.A

means independent of said mechanism for moving said indicator in the opposite direction.

6. In a vacuum cleaner, a casing, a dust separating member removably mounted in said casing, air ow means for producing apressure differential on opposite sides of said'member, a movable member subjected on opposite sides to said pressure differential, means for limiting movement of said movable member to an amount proportioned to the pressure dilerential, an indicator movable in one direction to record the maximum movement of said movable member caused by the pressure dierential, and means operable by removal of said dust separating member for moving said indicator in the opposite direction.

7. In a vacuum cleaner, a casing, a dust separating member in said casing, air ow means for producing a varying pressure diierential on opposite sides of said member, structure movable in one direction by an increase in pressure differential, resilient means for limiting said movement to" an amount proportional to said increase, means for locking said structure against movement in the opposite direction upon a decrease in pressure differential, and means for releasing the locking means.

8. In a vacuum cleaner, a casing, a dust separating member removably mounted in said casing, air flow means for producing a pressure differential on opposite sides of said member, structure movable in one direction by an increase in pressure diierential, resilient means for limiting said movement to an amount proportional to said increase, means for locking said structure against movement in the opposite direction upon a decrease in pressure dilerential, and means' operable by removal of said dust separating member for releasing the locking means.

9. In a Vacuum cleaner, a casing having an opening, a closure member for said opening, a dust separating member including a rim adapted to be clamped between said casing and said closure member, means for producingvow of air through said dust separating member, an indicator, means for moving said indicator in one direction upon an increase in pressure drop through said dust separating member to record the maximum pressure drop, and resilient means maintained under stress by said rim in clamped position for moving said indicator in the opposite direction and for moving said rim away from said casing when the stress is relieved by unclamping the rim.

10. In a vacuum cleaner, a casing having an opening, a closure member for said opening, a dust separating member including a rim adapted to be clamped between said casing and said closure member, and resilient means maintained under stress by said rim in clamped position for moving said rim away from said casing when said closure member is removed.

11. In a vacuum cleaner, a dust separating element, means for producing flow of air through said element, a member movable in one direction in response to an increase in pressure drop through said element, a spring for resisting said movement and for moving said member in the opposite direction upon a decrease in pressure drop, an indicator for recording the maximum movement of said member in said one direction, and'a manually releasable spring for resetting said indicator.

12. In a vacuum cleaner, a dust separating element, means for producing ow of air through said element, an indicator movable in one direction in response to an increase in pressure drop through said element, a spring for resisting said movement and for tending to move said indicator in the opposite deriction upon a decrease in pressure drop, locking means for preventing movement in said opposite direction whereby said indicator records the maximum movement `in said one direction, and manually operable means for releasing said locking means.

13. In a vacuum cleaner, a casing having an open end, a removable closure for said open end formed with an inlet port, a dust bag having a iianged rim, said rim being adapted to be disposed between said closure and said casing with the bag within the casing, means in said casing for producing flow of air through said bag, said bag oiering resistance to the flow of air whereby a higher pressure exists in said bag than inthe space within said casing and outside said-bag, a pressure responsive member mounted in said casing with one side thereof communicating with said space, said casing, said rim and said closure being formed with communicating passages establishing communication between the opposite side of the pressure responsive member and the in-4 teriorof said dust bag whereby said pressure responsive member is responsive to the pressure drop through said bag,- and means for recording the response of said member corresponding to the highest pressure drop to which it is subjected.

14. In a vacuum cleaner, a distendible dust separating element, means for producing iiow crfl air through said element, said element being arranged to be distended by the flow of air therethrough, means for yieldably resisting the distension of said element, a member for indicating and recording the maximum distension of said dust separating element, and means operable by removal of said element for resetting said4 member. y

AXEL ALBERT FORSBERG.