US3016982A

US3016982A - Vacuum cleaner cover latch control

Info

Publication number: US3016982A
Authority: US
Inventors: Descarries Raymond
Original assignee: Electrolux AB
Current assignee: Electrolux AB
Priority date: 1958-04-01
Filing date: 1958-04-01
Publication date: 1962-01-16
Anticipated expiration: 1979-01-16

Description

Jan. 16, 1962 R. DESCARRIES 3,016,932

VACUUM CLEANER COVER LATCH CONTROL Filed April 1, 1958 4 Sheets-Sheet 1 INV TOR W M ,wcm/w BY afmw AM ATTORNEY Jan. 16, 1962 R. DESCARRIES 3,0

VACUUM CLEANER COVER LATCH CONTROL Filed April 1, 1958 4 Sheets-Sheet 2 INVE OR F 1 m1 cw [A ATTORNEY Jan. 16, 1962 R. D ESCARRIES VACUUM CLEANER COVER LATCH CONTROL Filed April 1, 1958 4 Sheets-Sheet 3 7 1 8 FIG. 8 3r A? if :14 /2 66 F I@\\ T tx [I 66 5 X I 53 3/ 0 50x f- 7; 34

INV NTOR 1.; ATTORNEY Jan. 16, 1962 R. DESCARRiES VACUUM CLEANER COVER LATCH CONTROL 4 Sheets-Sheet 4 Filed April 1, 1958 INV NTOR BY A ATTORNEY United States Patent 3,016,982 VACUUM CLEANER CQVER LATCH CGNTROL Raymond Descarries, Montreal, Quebec, Canada, as-

signor to Aktiebelaget Electrolux, Stockholm, Sweden, a corporation of Sweden Filed Apr. 1, 1958, Ser. No. 725,730 7 Claims. (Cl. 18343) The present invention relates to vacuum cleaners and more particularly to a latch for controlling the opening and closing of a vacuum cleaner casing.

While the present invention may have other applications, it is particularly adapted for use with tank type vacuum cleaners. Such vacuum cleaners have a movable end cover for opening and closing the end of a casing for the insertion and removal of a detachable dust bag. A flexible hose has one end detachably connected to an opening in the cover and a suitable cleaning nozzle at its other end. A motor-fan unit in the casing produces a partial vacuum therein to cause dirt laden air to be drawn into the casing from the cleaning nozzle through the hose. As the dust laden air flows through the porous dust bag in the casing of the vacuum cleaner, the dust and dirt is separated from the air which is then discharged from the cleaner through an opening in the opposite end cover.

If such a vacuum cleaner is operated without a dust bag properly positioned therein, the dust removed from one area of a room is discharged with the air leaving the cleaner and distributed over the entire area of the room being cleaned. Furthermore, dust in the air accumulates on the motor-fan unit and is apt to interfere with its proper operation.

When the dust bag becomes filled with dirt and dust it should be removed and emptied as it restricts the flow of air and the capacity of the cleaner to remove dirt. However, it is also a common practice for a housewife to operate the vacuum cleaner after the dust bag has become filled and clogged with lint and dirt When this occurs, the resistance to air flow increases and the amount of air flowing through the cleaner decreases. This, in turn, lowers the capacity of the cleaner to pick up lint, dust and other materials from the surfaces being cleaned. Furthermore, a clogged dust bag produces a greater noise and a greater load, current consumption and heating of the motor-fan unit.

One of the objects of the present invention is to provide an improved mechanism in a vacuum cleaner which prevents operation of the cleaner until a dust bag is properly positioned therein.

Another object is to provide an interlocking mechanism which prevents the end cover from being latched in closed position on the casing when there is no dust bag therein.

Another object is to provide a latch mechanism which is held in a retracted, unlatching position if there is no dust bag in the casing to prevent injury to the latch and latch keeper by repeated attempts to close the cover on the casing.

Another object is to provide a latch mechanism of the type indicated which is responsive to conditions alfected either by the absence of a dust bag in proper position in the casing or the accumulation of dirt in the dust bag to prevent operation of the vacuum cleaner.

:Still another object is to provide a latch mechanism of the type indicated which is of simple and compact construction, adapted for economical manufacture and one which is reliable in operation.

These and other objects will become more apparent from the following description and drawings in which like reference characters denote like parts throughout the several views. It is to be expressly understood, however, that the drawings are for the purpose or" illustration ice only and are not a definition of the limits of the invention, reference being had for this purpose to the appended claims.

In the drawings:

FIG. 1 is a side elevational view of a tank type vacuum cleaner incorporating the novel features of the present invention;

FIG. 2 is an enlarged elevational view of the inside of the cover with the closure plate partially broken away to show the location of the latch and interlocking mechanism cooperating therewith;

FIG. 3 is a sectional view taken on line 3--3 of FIG. 2 to show the relationship of elements when the latch on the end cover is released for engagement with the latch keeper on the casing;

FIG. 4 is a plan view of the interlock bar in the position illustrated in FIG. 3 to release the latch member;

FIG. 5 is a view of the latch mechanism illustrated in FIG. 3 and showing the latch manually actuated to unlatching position;

FIG. 6 is a view similar to FIG. 5 with the cover swung away from the casing to show the interlock bar moved relative to the cover to hold the latch in its unlatching position;

FIG. 7 is a view similar to FIG. 5 showing the relationship of the latch and latch keeper as the cover is moved toward the end of the casing to closing position under one operating condition;

FIG. 8 is a view similar to FIG. 7 showing the latch held to unlatching position by the interlock bar when there is no dust bag in the casing;

FIG. 9 is a view of the lacthing mechanism as illustrated in FIG. 8 and showing the shoulder on the interlock bar overlying the tab on the latch to hold the latter in its retracted unlatching position;

FIG. 10 is a plan view of the interlock bar and tab on the latch in the interlocking position illustrated in FIG.

FIG. 11 is a view similar to FIG. 5 showing the relationship of the latch and latch keeper as the cover is moved toward the end of the casing to closing position under another operating condition;

FIG. 12 is a plan view of the interlock bar in the position illustrated in FIG. 11;

FIG. 13 is a sectional view of a part of a vacuum cleaner showing a modified form of latch and interlock bar in the latch releasing position; and

FIG. 14 is a view similar to FIG. 9 showing the latch and interlock bar in latch holding position.

Referring to FIG. 1 of the drawings, the invention is shown applied to a tank type vacuum cleaner 11 comprising a casing 12 having a front end cover 13 and a rear end cover 14-. The casing 12 is provided with a handle 15, a front wheel 16 and a pair of rear wheels 17. The front wheel 16 is mounted to rotate about a vertical axis as a caster, as well as about a horizontal axis, to adapt the cleaner to be turned.

The front end cover 13 may be removably secured on the front end of the casing 12 in any suitable manner. In the illustrated embodiment the front end cover 13 is hinged to the casing 1'2 by means of the hinge pin 19 to adapt the end cover to swing away from and open the end of the casing 12. The end cover 13 is formed with an air inlet opening 20 therein to which a suction hose (not shown) is adapted to be removably connected. Suitable cleaning appliances may be detachably mounted on a wand which, in turn, is connected to the outer free end of the suction hose and through which air flows into the casing. A dust bag 21 is mounted in the casing 12 at the rear of the front end cover 13 which acts to separate dust and other suspended material from the air as it flows therethrough.

The flow of air through the casing 12 is effected by a motor-fan unit 22 which includes a centrifugal fan 23 carried at one end of an electric motor 24. The fan 23 receives air which passes through the dust bag 21 and the air discharged from the fan flows through the motor 24 and an air outlet opening 25 in the rear end cover 14. Motor 24 is connected by suitable conductors to an electric switch located at the top of the casing 12.

As shown in FIGURE 3, the dust bag 21 is of a selfsealing type composed of paper. The paper bag 21 is air permeable but the interstices between the fibers of the paper are of such small dimensions as to separate all dust particles from the air. Bag 21 fits in a perforated inner casing sleeve 30 supported in the outer casing 12 by a ring flange 31. The edges 32 of the open end of the paper bag 21 are adhesively attached to a front plate 33 of cardboard or the like which projects beyond the bag to provide a peripheral flange for engagement with a resilient sealing gasket 34. Gasket 34 is carried by an annular fitting 35 attached to brackets 36 on the easing 12 by means of screws 37. The cardboard front plate 33 is provided with a circular opening 38 at its center which is closed by a thin resilient membrane 39 of rubber, or the like, having a diamctrical slit therein.

Projecting rearwardly from the front end cover 13 is a tube 42 surrounding the air inlet opening 20. The end of the rearwardly projecting tube 42 is adapted to penetrate the slitted membrane 39 as the front end cover 13 is swung to closed position on the end of the casing 12 and the membrane stretches over the outer periphery of the tube to seal the joint therebetween.

A closure plate 43 is attached to the front end cover 13 by means of screws 44, see FIGURES 2 and 3, to close the open end of the cover. An annular gasket 45 is positioned between an opening in the closure plate 43 and tube 42 to seal the joint therebetween. The opposite end of the gasket 45 is flared outwardly to provide a yielding circular edge which engages the front face of the cardboard plate 33 of the dust bag to resiliently hold its outer periphery in sealing engagement with the gasket 34 on the casing 12. Thus, when the front end cover 13 is swung to open position, the dust bag 21 may be stripped from the end of the tube 42 at which time the membrane '39 returns to its original position to close the end of the dust bag and prevent dirt from falling therefrom while the bag is removed from the cleaner. The dust bag 21 filled with dust and dirt is then discarded and a new dust bag mounted in the end of the casing 12. The end of the tube 42 automatically penetrates the slitted membrane 39 of the new bag 21 as the end cover 13 moves to closed position on casing 12 and properly positions the dust bag in the casing.

Gaskets

34 and 45 engage the opposite sides of the front cardboard plate 33 of the dust bag 21 to seal it in the casing.

In accordance with the present invention a latch is provided for latching the end cover to the casing which is held in a retracted unlatching position when there is no dust bag in the casing and released for latching engagement when a dust bag is properly positioned in the casing. In another aspect, the invention provides a latching mechanism responsive to the presence or absence of a dust bag and the condition of the dust bag to control operation of the vacuum cleaner.

The latching mechanism comprises a latch member 50 on one of the casing 12 and cover 13 parts and a latch keeper 51 on the other part. In the embodiment illustrated in FIGURES 1 to 10, the latch member 50 is mounted on the cover 13 and the latch keeper 51 is mounted on the casing 12. As illustrated in FIGURES 2 and 3, the latch member 50 comprises a thin sheet metal plate pivotally mounted at one end on a pin 52 and having a latching detent or catch 53 adjacent its other end. Pin 52 is mounted between

bosses

54 and 55 in the cover, see FIGURE 2, and a hairpin spring 56 surrounds the pivot pin at the side of the latch member 50 with one leg 57 engaging the latch member and the other leg 58 engaging a stop 59 on the cover. Thus, spring 56 yieldingly rocks the latch member 50 toward latching position.

An integrally formed lug 60 extends upwardly from the latch member 50 between the pivot pin 52 and catch 53 and projects into an opening 61 in the cover 13. A push button 62 is mounted on the lug 60 for manually pressing the latch member against the action of spring 56 to an unlatching position as illustrated in FIGURE 5. Latch member 50 also has a depending arm 63 with a laterally projecting tab 64. As will be observed by reference to FIGURES S and 6, the end of the latch member 50 adjacent the detent or catch 53 has a rearwardly projecting nose with a curved edge to provide a cam surface 66 for rocking the latch member to unlatching position as it engages the latch keeper 51.

The latch keeper 51 is in the form of a pin extending between spaced lugs 65 projecting forwardly from the fitting 35 on the casing 12. The latch keeper 51 projects into an opening in the cover 13 above the closure plate 43 for engagement by the catch 53 of the latch member 50.

An interlocking bar 68 is slidably mounted on the cover 13 which cooperates with the tab 64 on the depending arm 63 of the latch member 50 to hold the latch in retracted or unlatching position or release the latch for engagement with the latch keeper 51. As shown in FIG-

URES

4 and 10, the interlocking bar 68 is bifurcated at one end to provide

special legs

69 and 70 slidably mounted in

slots

71 and 72 in the opposite sides of a boss 73 projecting rearwardly from the front wall of the cover 13. The rearwardly projecting end of the interlocking bar 68 is provided with a plurality of stepped

portions

74 and 75. The outermost and narrower stepped portion 75 of the bar 68 projects through an opening 76 of substantially the same size in the closure plate 43 of the cover 13. The intermediate stepped portion 74 provides shoulders projecting laterally from narrow portion 75 and adapted to engage the closure plate 43 to limit the rearward movement of the bar 68. When the intermediate stepped portion 74 is engaged with the closure plate 43 in the rearwardly extending position of the interlock bar 68, the shoulder 77 forwardly of the intermediate stepped portion 74 overlies the tab 64 on depending arm 63 of the latch member 50, see FIGURE 10, When the interlock bar 68 is moved forwardly relative to the end cover 13 the intermediate stepped portion 74 provides a clearance space for tab 64 on the depending arm 63 of the latch member 50 as illustrated in FIGURE 4 to release it for latching engagement with latch keeper 51. The hairpin spring 56 also has a leg 78 engaging the forward edge of the interlocking bar 68 to bias it rearwardly to its extended position illustrated in FIGURE 10 while permitting forward sliding movement to the position illustrated in FIGURE 4.

As illustrated in FIGURE 2, the arm 63 depending from the latch member 50 is inclined laterally and has a loop 79 at its end engaging a stem 80, which is provided with an enlarged head 81 and project from a flexible diaphragm 82. The diaphragm 82 overlies one face of a chamber 83 (not shown in detail) which is connected by a tube 84 to a fitting on closure plate 43. The fitting, in turn, connects with a tube 84a, see FIGURE 3, extending into the space in the casing 12 between the dust bag 21 and fan- 23. When the dust bag 21 become clogged by the accumulation of dust and dirt therein the partial vacuum between the bag 21 and motor 24 increases and flexes diaphragm 82 sufficiently to rock the arm 63 and latch member 50 to its unlatching position. One form of the invention having now been described in detail, the mode of operation is explained below.

Assuming, for purposes of description, that the vacuum cleaner has been used for a period of time and is about to be opened to remove the dust bag 21 therefrom. This may be accomplished by manually depressing the push button 62 on the latch member 50 to the position illustrated in FIGURE 5 and swinging the end cover 13 away from the casing 12 to the position illustrated in FIGURE 6. As the cover 13 moves away from the casing 12 the interlock bar 68 is actuated rearwardly relative to the cover by the leg 78 of the hairpin spring 56 until the shoulder 77 overlies the tab 64 on the depending arm 63 of the latch member. Thus, when the push button 62 is released, the :latch member 50 is then held in its retracted unlatching position by the interlock bar 68. The cover 13 then may be swung to its full open position and the dust bag 21 stripped from the tube 42. As the dust bag 21 is withdrawn from the tube 42, the flexible membrane 39 closes the end of the bag so that no dirt is spilled during removal of the dust bag.

It the cover 13 is closed against the end of the casing 12 without inserting another dust bag 21, the interlock bar 68 holds the latch member 56 in its retracted unlatching position so that it cannot engage the latch keeper 51 as illustrated in FIGURES 7 and 8. This immediately indicates to the housewife that there is no dust bag present in the casing. However, should the cover 13 be successively slammed to closed position on the casing 12 in an attempt to latch the cover in closed position, no damage will occur to the latch member 50 as the catch portion 53 is held by the interlock bar 68 in its Withdrawn unlatching position and does not contact the keeper 5'1. When a new dust bag 21 is inserted in the perforated sleeve 30 and the cover 13 is moved to closed position, the projecting end 75 of the interlock bar 68 will engage the front plate 33 of the dust bag 21 and move relative to the cover 13 as the latter is swung toward closed position to release the latch member 50. In this retracted position of the interlock bar 68 the slotted side of the intermediate stepped portion 74 provides :a clearance for the tab 64 on the depending arm 63 of the latch member 50 as illustrated in FIGURES 3 and 4 and releases the latter. Leg 57 of the spring 56 then rocks the latch member 50 counterclockwise to engage the latch keeper 51 and latch the end cover 13 in closed position on the casing.

Operation of the vacuum cleaner 11 is initiated by depressing the push button switch 26 which energizes the motor-fan unit 22. Dust laden air is then drawn through the opening 20 in the front cover 13 and through the tube 42 into the interior of the dust bag 21. The air then flows through the porous dust bag 21 which separates the dust from the air and the air is exhausted through the outlet opening 25 in the rearward end cover 14 of the cleaner.

The vacuum cleaner 11 is used from time to time as required until the dust bag is filled with lint and dust. The dust bag 21 may be removed and replaced manually in the manner explained above. However, if the dust bag 21 becomes so filled with dust and lint as to impair the proper operation of the vacuum cleaner the latch member 50 is automatically tripped to release the end cover 13. This operation is performed by the flexible diaphragm 82 which is connected to the end of the depending arm 63 of the latch member 50. As the permeability of the dust bag 21 decreases, due to clogging of the bag with dust and lint, the pressure drop across the bag increases and the amount and velocity of air flowing to the bag decreases with a corresponding decrease in the capacity of the cleaner. Simultaneously, the partial vacuum between the dust bag 21 and fan 23 increases. When the partial vacuum between the dust bag 21 and fan 23 increases to a predetermined value, it acts through the diaphragm 82 and depending arm 63 against the action of spring 56 to rock the latch member 50 and release the catch 53 from engagement with the latch keeper 51. The cover 13 then automatically swings to its open position and renders the vacuum cleaner inoperative. This indicates to the housewife that the dust bag 21 needs replacement. Accordingly, the dust bag 21 is withdrawn from the tube 42 and a new dust bag placed in the perforated sleeve 30.

During the forward swinging movement of the cover 13 with the latch retracted, the interlock bar 68 is held in its rearwardly extended position by the leg 78 of spring 56 to position its shoulder 77 over the tab 64 on latch arm 63 to lock and hold the latch member 54} in its unlatching position. Without a dust bag 21 mounted in the casing 12, the interlock bar 68 will remain in its extended position, as illustrated in FIGURES 7 and 8. However, when a new dust bag 21 is inserted in the sleeve 36 of the casing 12 and the cover 13 moved to closed position the projecting end 75 of the interlock bar 68 will engage the front plate 33 of the dust bag and be moved relative to the cover 13 to release the latch member 56. Upon release, the spring 56 rocks the latch member 5a into latching engagement with the latch keeper 51. The vacuum cleaner then may be operated in the manner as previously explained.

Let us assume that the cover 11 is in its wide open position and the latch member 50 is held in its retracted unlatching position by the interlock bar 68, as illustrated in FIG. 7. If the part of the interlock bar 68 projecting outside the closure plate 43 should be pushed a suflicient distance into the cover 13 under these conditions, either accidentally or otherwise, the shoulder 77 of the interlock bar will move toward the left in FIG. 7 and provide clearance for the tab 64 on the depending arm 63 of the latch member. Leg 57 of the spring 56 then rocks the latch member 54) counterclockwise to its released position illustrated in FIG. 11, the head 81 on the stem limiting the movement of the depending arm 63 serving as a stop to arrest counterclockwise movement of the latch member 50.

In FIGS. 11 and 12 it will be seen that the tab 64 is in the path of movement of the interlock bar 68 so that, when the outer projecting end thereof is pushed a sufficient distance into the cover, the latch member 50 will move counterclockwise to its released position and the tab 64 will then become eifective to hold the interlock bar 68 in the retracted position shown in FIGS. 11 and 12. Under these conditions, as the cover 13 is moved towards closed position on the casing 12 from the position illustrated in FIGURE 11 to that illustrated in FIGURE 8 the cam surface 66 on the nose of the latch member will engage the latch keeper 51 and automatically rock to latch releasing position. If there is no dust bag 21 properly positioned in the casing 12, the interlock bar 68 then will slide to the latch holding position illustrated in FIGURE 8 and prevent the cover from being latched to closed position. If a bag is present in the casing 12, the interlock bar 68 is moved relative to the cover 13 to latch releasing position as illustrated in FIGURE 4.

FIGURES 13 and 14 illustrate an interlocking latch mechanism of modified construction. The modified form of latch mechanism 85 is generally similar to that illustrated in FIGURES l to 12 comprising a latch member 85 mounted at one end on pivot pin 52 and having a catch 53 at its other end as in the previously described form. The latching member 85 is biased to latching position by the hairpin spring 56 and has a push button 62 for operating the latch to releasing position against the action of the spring. However, the arm 86 depending from the latch member 85 is wider and has a slotted opening 87 therein so shaped as to provide a lower horizontal edge 38, an upper horizontal shoulder 39 and inclined cam surface 9t) between the upper and lower surfaces.

An interlocking bar 91 is mounted to slide in an opening in the closure plate and has a laterally projecting end 92 projecting into the slotted opening 87 in the depending arm 86. A spring bellows 93 is connected between an annular wall 94 projecting forwardly from closure plate 43 and an enlarged head 95 at the rearward end of the interlocking bar 91 to bias the bar to its rearwardly extended position and seal the joint between the bar and wall. The enlarged head 95 on the rearward end of the interlocking bar 91 is adapted to engage the peripheral 7 rim 96 of a dust bag 97. In the illustrated embodiment an open mouth bag 97 of a type having an annular gasket 98 is shown for engaging the gasket 34 on the fitting 35 of the casing 12. The gasket 98 on the dust bag 97 has a sealing flange 99 for engagement with the closure plate 43 on the cover 13 to seal the joint therebetween.

The depending arm 86 of the latch member 85 has its lower end 100 bifurcated to straddle a stem 101 projecting from a flexible diaphragm 102 at one side of the chamber 103. The stem 101 attached to the diaphragm 102 has an enlarged head 104 at its end engaging the side of the bifurcated lower end portion 100 of the depending arm 86.

As in the previously described embodiment, th diaphragm 102 is responsive to the partial vacuum between the dust bag 97 and fan 23. To the chamber 103 is connected one end of a tube 105 which is connected to a fitting 106 on the closure plate 43. The fitting, in turn, connects with a tube 107 extending into the space in the casing 12 which is outside the dust bag 97 and between the latter and the motor-fan unit.

The construction illustrated in FIGURES 13 and 14 operates in a manner similar to the construction illustrated in FIGURES 1 to 12. The interlock bar 91 is normally biased to its rearwardly extended position illustrated in FIGURE 12 by the spring bellows 93 and the laterally projecting end 92 acting on the inclined cam face 90 in the slotted opening 87 in the depending arm 86 rocks the latch member 85 to unlatching position.

When the cover 13 is swung to open position, either by manual operation of the push button 62 or the rocking of the latch by the diaphragm 10-2 the interlock bar 91 is projected rearwardly by spring bellows 93 and acting through the laterally projecting end 92, automatically rocks and holds the latch member 85 in its retracted unlatching position illustrated in FIGURE 14. Thus, the latch member 85 is held in its retracted unlatching position until the cover approaches a closed position on the casing 12 at which time the interlocking bar 91 is either actuated by engagement with a bag 97 to release the latch for engagement with the keeper 1 or is not actuated if no bag is present to hold the latch member in its unlatching position.

It will now be observed that the present invention provides a novel latching mechanism which prevents operation of a vacuum cleaner until a dust bag is properly positioned in the casing. It will also be observed that the present invention provides an interlocking mechanism responsive to the presence or absence of a dust bag in the casing for holding the latch member retracted if there is no bag present to prevent injury to the latch and keeper by repeated attempts to close the cover on the casing. It will also be observed that the latching mechanism of the present invention is responsive to a condition effected either by the presence of a dust bag properly positioned in the casing or the accumulation of dirt in the dust bag to prevent operation of the vacuum cleaner. It will still further be observed that the present invention provides selective latching mechanism of the type indicated which is of simple and compact construction, adapted for economical manufacture and reliable in operation.

While two embodiments of the invention are herein illustrated and described, it will be understood that further modifications may be made in the construction and arrangements of elements without departing from the spirit or scope of the invention. Therefore, Without limitation in this respect, the invention is defined by the following claims:

I claim:

1. Latching mechanism for use on a vacuum cleaner of the type having a casing open at one side for the insertion and removal of a dust bag and a cover for closing the open side of the casing in which the latching means is rendered inoperative in the absence of a dust bag in the casing comprising, a latch keeper on the casing, a latch pivotally mounted on the cover for rocking movement to latching and unlatching positions in an arc with respect to the latch keeper on the casing, spring means for rocking the latch to latching position, an interlock bar mounted to slide on the cover in a linear path intercepting the arcuate path of at least a portion of the latch and having an end projecting forwardly of the cover, spring means for moving the interlock bar to an extended position, said latch and interlock bar being positioned in sideby-side relation, and interlocking shoulders on the latch and interlock bar overlying each other when the bar is extended for holding the latch in unlatching position and offset when the bar is slid on the cover relative to the latch by engagement with the dust bag for releasing the latch for movement to latching position whereby to prevent the cover from being latched to the casing in the absence of a dust bag in the casing.

2. Latching mechanism in accordance with claim 1 in which the latch has a depending arm adjacent at least one side of the interlock bar, the latch has a push button for manually operating the latch to unlatching position, and a pressure responsive device connected to the depending arm of the latch for moving the latch to unlatching position independently of the push button and interlock bar.

3. Latching mechanism in accordance with claim 1 in which the spring means for the latch and interlock bar is a single spring mounted on the latch pivot and connected to rock the latch member to latching position and slide the interlock bar to extended position.

4. Latching mechanism in accordance with claim 2 in which the interlocking shoulder on the latch is a tab on the depending arm extending at righ angles to the plane of the arm, the side of the bar adjacent the depending arm of the latch being stepped to form the shoulder for engaging the tab on the latch when in its extended position and providing a clearance for the tab in its releasing position.

5. Latching mechanism in accordance with claim 4 in which the projecting end of the interlock bar extends through an opening in a plate on the cover, and a stepped portion of the bar forming a shoulder engaging a plate to limit its movement to extended position.

6. Latching mechanism in accordance with claim 1 in which the interlocking shoulder on the latch is formed by a slot in the latch, and the shoulder on the interlock bar projecting laterally into the slot in the latch to overlie the shoulder.

7. Latching mechanism in accordance with claim 6 in which the slot has an inclined side adjacent the shoulder and constitutes a cam face engaged by the laterally projecting shoulder on the interlock bar for actuating the latch to unlatching position.

References Cited in the file of this patent UNITED STATES PATENTS 1,090,305 Hoffman Mar. 17, 1914 1,475,526 Waskins Nov. 27, 1923 1,788,016 Desplats Jan. 6, 1931 2,322,948 Lofgren June 29, 1943 2,742,105 Dow Apr. 17, 1956 2,814,358 Beede et al Nov. 26, 1957 2,860,725 Cawl et a1. Nov. 18, 1958