US2174443A

US2174443A - Vacuum cleaner

Info

Publication number: US2174443A
Application number: US52027A
Authority: US
Inventors: Lofgren Gustaf Einar
Original assignee: Electrolux Corp
Current assignee: Electrolux Corp
Priority date: 1935-11-29
Filing date: 1935-11-29
Publication date: 1939-09-26
Anticipated expiration: 1956-09-26
Also published as: GB479740A; GB485932A; FR814158A

Description

3 Sheets-Sheet 1 Sept. 26, 1939. G. E. LOFGREN VACUUH CLEANER Filed Nov. 29, 1935 Sept. 26, 1939. t G. E. LOFGREN 2.174.443

VACUUM CLEANER rund nov. 29. 1935 s sheets-sheet 2 a@ ATTORNEY4 Sept. 26, 1939. G. E. LOFGREN VACUUM CLEANER Filed Nov. 29, 1935 3 Sheets-Sheet 3 .5- ATTORNEY.

Patented Sept. 26, 1939 UNITED STATES VACUUM CLEANER Gustar Einar Lofgren, Riverside, Conn., assignmto Electrolux Corporation, Dover, Del., a corporation oi Delaware Application November 29, 1935, Serial No. 52,027

l Claims. (Cl. 183-37) My invention relates to vacuum cleaners and more particularly to vacuum cleaners oi the kind having a cleaner unit including a casing or housing enclosing a motor and a i'an, a nozzle, and a 6 tubular member including a hose for establishing communication between the casing and the nozzle, the casing being pulled by the hose on a carpet or surface.

The invention aims to provide a more eillcient construction oi' vacuum cleaner unit both from manufacturing and operating points oi view. In my novel construction, I preferably make the housing of two stampings of such character with relation to the unit that they can have endless l5 .iointing seams or edges. This provides rigidity of structure. I ilnd that this is feasible if the housing is made oi' an upper deep shell and a lower shallow shell joined near the iloor. 'I'hus the Joining line is below the dust bag opening and can be continuous.

An object of the invention is to utilize a minimum of structural parts. The shell is made of a minimum number oi stampings and yet the housing is strong. The housing is subdivided by transg5 verse bulkheads which serve to stiien the shell,

act as supports for the motor-fan unit, and provide pressure demarcation as well as space demarcation. Due to the construction, only the dust bag space is under suction. The enclosure for 30 the motor and fan is under atmospheric pressure.

A further object is to provide an improved motorfan.unit, which is better protected than heretofore.

The nature of my invention will be understood 35 from the following description taken in conjunction with the accompanying drawings forming part of this speciilcation and of which:

Fig. 1 is a vertical longitudinal sectional view through a vacuum cleaner unit embodying the 40 invention and also parts attached thereto;

Fig. 2 is an enlarged longitudinal sectional View; taken on line 2 2 oi' Fig. 4;

Fig. 3 is a transverse sectional view taken on the line 3 3 of Fig. 1; Fig. 4 is a transverse sectional view taken dn the line 4 4 of Fig. l;

Fig. 5 is a horizontal. sectional view taken on the line 5 5 of Fig. 1;

o Fig. 6 is a sectional view taken on the line 8 8 oi Fig. 4;

Fig. '1 is a sectional view taken on the line 'I l of Fig. 4;

Fig. 8 is a cross-sectional view of a portion of a 55 vacuum cleaner in accordance with my invention.

including a dust indicator, and shows the handle and switch arrangement more in detail; and

Fig. 9 is a cross-sectional view taken on the line 3 9 oi' Fis. 8.

The vacuum cleaner includes a cleaner unit Il to which is connected a flexible hose I i, by which the cleaner unit may be pulled by the operator, and a hollow wand I2 to which is connected the nozzle I3. This general type of cleaner and its mode of use are known. The cleaner unit to which the present invention is directed, rests on the floor. 'I'he operator generally holds the wand I2 with the iiexible hose loose between the cleaner unit and the wand.

'I'he cleaner unit I 0 includes a housing made essentially of an upper shell I5 and a lower shell IB. Preferably the shells are made from fiat sheet metal stock by die forming in a punch press. The lower shell is shallow and is formed with ridges Il on the under sides to act as runners when pulling the cleaner unit on the carpet or oor. The lower shell has a continuous or endless top edge at IB, which, when the cleaner unit is resting normally, is in a horizontal plane. 'Ihe upper shell I5 is a deep drawn shell which is a sort of inverted dish and which also has a continuous or endless edge I9. When the cleaner unit is resting normally, the edge I8 is likewise ina. horizontal plane. The edges IB and I9 are joined as by welding. Both the upper and lower shells preferably widen from the center-line to the jointure so that the plane oi joining is at the horizontal crosssection of maximum area. The plane of joining-is close to the iloor.

At the forward end of the cleaner unit is a cover 20 which controls access to the dust bag 2l and to which the hose II is connected by a suitable coupling member 22.

The housing of the cleaner unit is subdivided by two partitions or bulkheads and SII. Bulkhead 25 may be termed the forward bulkhead and bulkhead the rear bulkhead. Each of the bulkheads is flanged around its periphery and welded to the shell all the way around to form an air-tight `ioint. The bulkheads' divide the housing into three distinct compartments. namely-a dust compartment 26, a motor-ian compartment 2l, and a illter compartment 28. The bulkheads are imperforate except for center openings 3| and I2.

Positioned in opening 3l is a motor-fan unit suspension ring 33, preferably made oi rubber. Ring 33 also extends within a metal ring I4 secured to a case 35 for the motor-fan unit. A cap ring 3B is placed over ring l2 and held in place by a member 31 fastened to the bulkhead as by a screw, as shown. A spacer ring 38 may be used between ring 34 and the center flange 39 of bulkhead 25.

The other or exhaust end of the motor-fan unit is similarly supported by means of a rubber cushioning ring 4I mounted in the central opening 32 of bulkhead 36. A seating ring 42 holds ring 4I in place. This ring is fastened to bulkhead 30 by screws 43. Ring 4I seats in a fibre or Bakelite end cap 44 forming part of the case 35.

The bottom shell I6 is provided with an opening 45 covered by means of a removable cap 46 whereby the case 35 can be inserted and removed from the motor-fan compartment. In inserting the motor-fan unit, the case 35 is held in alignment with openings 3l and 32 and rubber rings 33 and 4I are ther'i inserted by pushing them toward the case 35 from within compartments 26 and 23 respectively, after which the

caps

36 and 42 are applied. The case 35 and the connections between the same and the bulkheads are air-tight wherefore, due to the air-tight connection of the bulkhead 25 with the shell, the only one of the compartments which is subjected to suction is compartment 26. Thus substantially one-half of the shell is relieved of stress due to preponderance of external pressure. It will be understood that the bulkheads greatly strengthen the shell.

The dust bag 2| is provided with a ring 43 which is held between cover 20 and a iiange on the upper shell. Suitable mechanism may be employed to clamp cover 20 onto the housing with the dust bag ring therebetween. Clips may be used as shown in United States Patent No. 1,757,239 of May 6, 1930. The dust bag is preferably large so as to wrinkle within chamber 26 and distention of the dust bag is resisted by a plate 43 and a spring 5I attached thereto and to member 31. Member 49 may be utilized to operate a signal as disclosed in United States Patent No. 2,022,250 of November 26, 1935.

Upper shell I5 is formed with a ridge 52 at the top which is a continuation of a handle part and which provides space for dust indicating mechanism. Ridge 52 extends longitudinally and is preferably initially stamped into the upper shell.

The handle is formed as a separate piece 53. Handle part 53 overlaps and is secured to ridge 52 and is suitably secured as by screws to the shell at about the place of bulkhead 36. One preferred arrangement for securing the handle is described in detail in connection with Figs. 8 and 9. The shell may be recessed at 54 and the part 53 is cut away for grasping by the hand. The handle is abpve the motor-fan compartment which is at the center of gravity of the cleaner unit.

The rear end of part 53 is open at 56 for reception of the plug of an electric cord. A step switch 51 is incorporated in part 53 and includes a step button 58. The step switch can readily be connected to the motor through an opening in the shell. The step switch and contact points are removable with the part 53, for instance. as described in connection with Fig. 8.

A hole 6I is provided for access to compartment 26. This hole is normally closed by means of a cover 62 which may be made as a die casting and which includes a discharge opening 63 into which the hose I I may be secured for blowing purposes. Compartment 28 may have a special nlter pad 64 therein or may be loosely i'llled with iiltering material.

Referring more particularly to the motor-Ian assembly. the motor is supported on two

rings

44 and 65 made of Bakelite or iibre or other suitable electrical insulating material. A sheet metal cylinder 68 extends between

parts

44 and 65. Mounted on part 65 are members 61 and 6l. Member 66 is a stationary member between ian rotors 69 and 1I). Intermediate directing vanes are mounted on member 66. The case 35 is like a can and it can be supported in any position radially.

Figs. 6 and '7 show how the motor is supported. Pins 12 and 13 extend axially from the motor casing 14. There are several pins 12 and several pins 13, disposed about the motor housing. Conical springs 15 extend between pins 13 and rings 44 and 65 and are seated in recesses in the rings. Caps 16 hold the apices of the springs in position. Caps 16 and pins 13 may be made of electrical insulating material.

Rods 16 pull the

rings

44 and 65 together and members 61 and 66 are secured to ring 65 as by screws 19. The motor includes the usual armature 32 and shaft 63 carrying the fan rotors and mounted in ball bearings 6I.

The operation is as follows:

The motor is set in operation by stepping on switch button 56. The motor rotates the fan and causes flow of air. The nozzle I3 is applied to the object or surface to be cleaned. Dust-laden air passes through nozzle I3, wand I2, tube Ii and through union 22 into the dust bag 2i. Here the dust is deposited and cleaned air passes on through the fan and past the motor, cooling the same, and out through the filter chamber 26 where fine particles are removed which are not caught in the dust bag. The iilter chamber also acts as a mufer.

Chamber 26 is under suction which may be oi'` a value exceeding thirty inches of water lift. Consequently, the total pressure diil'erential on the walls oi' Achamber' 26 (atmospheric pressure on the outside less suction pressure on the inside) will be high. The shell is assisted from buckling by the variations in its wall structure. The welded joint between the shells is oi' assistance in this respect. The ridge 52 is also advantageous in this respect. Additional ridges or reenforcements may be provided in the side walls to the extent found necessary.

With a properly air-tight case 35 and tight connections, compartment 21 will be at atmospheric pressure. This is due to the separate assembly of motor and fan and the bulkheads, as above explained. Should there be some leakage through case 35, it would not affect the relief of stress on the walls of compartment 21.

Compartment 26 is at somewhat above atmospheric pressure but the pressure is slight. This compartment is essentially free of wall stress. Thus the suction is confined to the chamber containing the dust bag, and no part of the motor or fan is positioned in this chamber It will be noted that the outer housing and the motor-fan case are entirely separate. The motor-fan assembly is a separate sub-assembly. All the electric parts are in one sub-assembly. This facilitates original manufacture and repairs. The generally continuous outward flare of the shells is of assistance since the shells can be nested in the process oi manufacture and for shipment of parts. This also facilitates insertion of the bulkheads.

In Figs. 8 and 9, there is shown, on a somewhat enlarged scale, a portion of a cleaner similar to that shown in the preceding gures, but including dust indicator mechanism and a removable handle and switch assembly.

Member 49, against which dust bag 2| presses when inflated, is resiliently supported by means of a plurality of conical springs 99 suitably secured thereto. The opposite ends of springs 99 engage grooves formed in the heads of bolts 9| which are threaded into bulkheads 25.

Secured within ridge 52 of upper stamping |9, preferably by welding, is a bracket 92 having apertures for receiving prongs 93 of a frame 94. Frame 94 includes a pair of spaced side bars 95, one end of each of which terminates in the prongs 93. The other ends of bars 95 are integral with a portion 99, to the free end of which is secured a spring 91. The other end of this spring is supported by a bracket 99 welded within ridge 92. Spring 91 holds portion 99 against a projection 99 secured within the casing and the slight inclination oi' the spring urges the entire frame 94 to the right, as viewed in Fig. 8, and maintains the ends oi' prongs 93 in contact with the interior of the casing. Thus. the frame is held securely in place.

Extending between the side bars 99 are shafts |99 and |9|. Rotatably mounted on shaft |99 is a bell crank lever |92 having arms |93 and |94. The end of arm |93 contacts the central portion of member 49 and consequently movement of member 49 to the right, as viewed in Fig. 8, causes bell crank lever |92 to pivot in a counter-clockwise direction about shaft |99. A spring |99 encircles shaft |99 and has one end in engagement with frame 94, and the other end in engagement with the under side of arm |94, thereby tending to rotate the bell crank lever |92 clockwise and maintaining the end o! arm |93 in contact with member 49. The end of arm |94 is provided with a rack |99 which engages a gear |91 mounted on shaft |9|. Rotatable with gear |91 is a sector |99 constituting a visual indicator. For instance. one part of the outer surface of sector |99 may be red, as indicated at |99, while the other part ||9 may be white. An air-tight window is set in the casing above sector |99 so that the position of the latter may be seen therethrough. A pin ||2 limits the movement of bell crank |92 in clockwise direction.

It will be seen that all of the dust indicator mechanism, with the exception of arm |93, is contained within the space within ridge 92. It is thus entirely out of the way of the dust bag and does not interfere with the expansion of the latter.

'I'he operation of the dust indicator will -be largely apparent. As dust accumulates within bag 2|, it reduces the flow of air through the walls of the bag, thus increasing the pressure drop therethrough. This causes the bag to exert more force against member 49, thus moving this member to the right, as viewed in Fig. 8 against the force of springs 99. Bell crank |93 is thereby pivoted counter-clockwise and rotates gear |91 and sector |99 in a clockwise direction, thus bringing the rod portion |99 into view through window This is an indication vto the operator that suiilcient dust has been collected in the bag to make the emptying thereof desirable'.

Handle 93 includes an end portion l5 which extends over and conforms generally to the outer contour of the higher end of ridge 92. Portion H9 is formed with an opening |i9 in registry with window A cylinder ||1 is secured by means of a strap ||9 to the outer end of ridge 92. Strap i|9 may be welded to the casing and to the cylinder. Received within cylinder are two buttons H9 having outer ends |29 of reduced diameter. A spring |2| tends to force buttons ||9 outwardly. Portion U5 of the handle'ls formed with skirts |22, which extend down to the top oi' stamping I5, and which are formed with apertures for receiving the ends |29 of the buttons. Thus, the forward end of the handle is removably secured to the casing.

The other end of the handle is formed with a recess in which is positioned the step switch assembiy 91. This assembly includes the usual chassis |29L of insulating material in which is mounted a snap switch mechanism |29 and electric contact pins |21 positioned in opening 99. A step button 59 is reciprocably mounted in a recess |29 in the chassis and is urged upwardly by a spring |39. Upward movement of the button is limited by a flange thereon contacting the top of the handle stamping. A pin |3| is pivoted on button |29 and is arranged to engage notches, formed in one opening I 33 is formed in the upper part of stamping |5 between

bulkheads

25 and 39 and consequently communicates with motor-fan compartment 21. The electric leads froxmthe motor within case 39 may be thus connected to binding screws |34. Inasmuch as atmospheric pressure prevai's at all times within compartment 21, there is no necessity for sealing opening |33.

A bracket |39 is welded to the top of stamping i9 and extends between the switch chassis |29 and a portion |39 of the handle stamping. A screw |31 passes through openings formed in por tion |39 and bracket |39 and has threaded engagement with chassis |29, thus securing the rear end of the handle to the casing and holding the switch assembly rigidly in place. A sleeve |33 fits snugly within the opening 99 in the rear pox'- tion of the handle stamping and surrounds contact pins |21. A member |39 is welded to stamping i5 and a screw passes through sleeve |39 and has threaded engagement with member |39. Thus, sleeve |39 is secured in place which, by virtue of its close tit in opening 59, gives additional support to the rear oi' the handle.

It wil be seen that the handle and switch assembly may be installed or removed as a unit. Removal, for instance, may be accomplished by unscrewing screws |31 and |49 'and by pressing in buttons H9 until the ends |29 thereof are disengaged from the handle. 'I'he motor leads are still attached to the switch, but suillcient slack may be provided in the leads so that the handle and switch may be removed far enough to give access to screws |34.

While, in the foregoing, I have described a more or less specific embodiment of my invention, it is to be understood that this has been done for purposes of illustration only, and that the scope of my invention is not to be limited in any manner thereby, but is to be interpreted as broadly as is commensurate with the appended claims when considered in relation to the prior art.

What I claim is:

1. A vacuum cleaner unit including a casing, said casing being horizontally elongated, a motor. fan and dust separator in said casing in horizontal alignment, said casing having an air in let and an air outlet, and said casing including upper and lower shells having mating edges, each of said shells being essentially formed as sheet metal pans having their widest portions at the mating edges, the lower shell having elongated depressions therein extending below the remainder of the lower shell to form runners.

2. A vacuum cleaner unit including a casing, said casing being horizontally elongated, a motor, fan and dust separator in said casing in horizontal alignment, said casing having an air inlet and said and edges, each of said shells being essentially formed as pans having their widest portions at the mating edges, said upper shell being arched both longitudinally and transversely.

3. A vacuum cleaner unit including a casing, said casing ing having an air inlet and an air outlet, said casing including an upper deep shell arched both longitudinally and transversely and a shallow shell in a continuous joint below said inlet and outlet, said shell widening to the joint, interior vertical transverse bulkheads in said casing providing a separator chamber and a motor chamber and a rear chamber, a motor unit mounted on said bulkheads in said motor chamber, and an opening in said bottom shell providing access to said motor chamber.

4. A vacuum cleaner unit including a casing, said casing being horizontally elongated, said casing having an air inlet and an air outlet, said casing including an upper deep shell arched both longitudinally and transversely and a shallow bottom shell joined to said upper shell in a continuous joint below said inlet and outlet, said shell widening to the joint, interior vertical transverse bulkheads in said casing providing a separator chamber and a motor chamber and a rear chamber, and a motor unit mounted on said bulkheads in said motor chamber.

5. A vacuum cleaner unit including a casing, said casing being horizontally elongated, said casing having an air inlet and an air outlet, said casing including an upper deep shell arched both longitudinally and transversely and a shallow bottom shell joined to said upper shell in a continuous joint below said inlet and outlet, said shell widening to the joint, interior vertical transverse bulkheads in said casing providing a separator chamber and a motor chamber and a rear chamber, said bulkheads being air-tight except for interior openings, a motor housing mounted on said bulkheads in said motor charnber and having inlet and outlet openings in registry with the bulkhead openings, a motor-fan unit in said housing, and an opening in said bottom shell providing access to said motor chamber.

6. A vacuum cleaner unit including a casing, said casing being horizontally elongated, said casing having an air inlet and an air outlet, said casing including an upper deep shell arched both longitudinally and transversely and a shallow bottom shell joined to said upper shell in a continuous joint below said inlet and outlet, said shell widening to the joint, interior vertical transverse bulkheads in said casing providing a separator chamber and a motor chamber and a rear chamber, a motor unit mounted on said bulkheads in said motor chamber, said upper shell being so formed that the separator chamber is higher than the motor chamber, and a handle member above said motor chamber.

7. A vacuum cleaner unit including a casing,

being horizontally elongated, said cassaid casing being horizontally elongated, said casing having an air inlet and an air outlet, said casing including an upper deep shell arched both longitudinally and transversely and a shallow bottom shell joined to said upper shell in a continuous joint below said inlet and outlet, said shell widening to the joint, interior vertical transverse bulkheads in `said casing providing a separator chamber and a motor chamber and a. rear chamber, a motor unit in said motor chamber, said upper shell being so formed that the separator chamber is higher than the motor chamber, a handle member secured to said shell and extending above said motor chamber, said handle having a hollow portion, and a switch member in said hollow portion.

B. A vacuum cleaner unit including a casing, said casing being horizontally elongated, said casing having an air inlet and an air outlet, said casing including an upper deep shell arched both longitudinally and transversely and a shallow bottom shell joined to said upper shell in a continuous joint below said inlet and outlet, said shell widening to the joint, interior vertical transverse bulkheads in said casing providing a separator chamber and a motor chamber and a rear chamber, a motor unit lmounted on said bulkheads in said motor chamber, ridges in said bottom shell forming runners, an upwardly extending ridge in the portion of said upper shell above said separator chamber, and a handle member above said motor chamber in longitudinal alignment with and secured at one end to said ridge.

9. In a vacuum cleaner. an elongated casing having an air inlet in one end and an air outlet in the other end, transverse bulkheads in said casing having air openings, said bulkheads being air-tight with respect to said casing and providing a chamber therebetween, an air-tight housing in said chamber having end openings in air-tight registry with the openings in said bulkheads, said housing being mounted on said bulkheads, and a motor-ian unit mounted in said housing, whereby the walls of said chamber are unaffected by air pressure diierence caused by said motor-fan unit.

Y 10. In a vacuum cleaner, an elongated non-circular casing, a pair o! spaced transverse partitions disposed within said casing and secured in air-tight relation therewith to provide separate compartments within said casing capable of sustaining diflerent pressures. a motor-fan unit supported from said partitions in the central compartment therebetween and arranged to produce a sub-atmospheric pressure in one of the other compartments, said partitions serving to strengthen said non-circular casing against atmospheric force acting on the exterior of said other compartment, and a dust separating member disposed in said other compartment in the path of air flow therethroug l1. In a vacuum cleaner, an elongated non-circular casing, a pair of spaced transverse partitions disposed within said casing and secured in air-tight relation therewith to provide separate central and end compartments within said casing capable of sustaining diierent pressures, a motor-fan unit supported from said Partitions in said central compartment and arranged to produce sub-atmospheric pressure in one of said end compartments and to produce pressure higher than atmospheric in the other of said end compartments, said partitions serving to reenforce said non-circularcasing against atmospheric pressure acting on the exterior of said one end compartment and against internal pressure acting on said other end compartment. and a dust separating member in said one end compartment disposed in the path of flow of air therethrough.

12. In a vacuum cleaner, an elongated noncircular casing formed with an inlet opening at one end and an outlet opening at the other, a pair of spaced transverse partitions disposed within said casing and secured in airtight relation thereto to provide separate central and end compartments, each partition being formed with an opening therethrough, a motor-fan unit including an airtight case having an intake opening at one end and an exhaust opening at the other end, said unit being supported between said partitions in said central compartment with the intake opening sealed to the opening in the partition adjacent to the end compartment communicating with the inlet opening in the casing and with the exhaust opening sealed to the opening in the other partition, whereby atmospheric pressure exists within said central compartment and said motor-fan unit is capable of maintaining subatmospheric pressure in the first mentioned end compartment and of maintaining pressure higher than atmospheric in said other end compartment, said partitions serving to strengthen said non-circular casing against atmospheric pressure acting on the exterior of said iirst mentioned end compartment and against internal pressure acting on the interior of said other compartment. and a dust separating member in said first mentioned compartment in the path of air iiow from the inlet opening of said casing to the intake opening of said motor-fan unit.

13. A vacuum cleaner as dened in claim 412 having the casing formed with an aperture'communicating with said central compartment through which insertion and removal o! said CERTIFICATE 0F Patent No. 2,l7h,lili5.

motor-ian unit may be e'ected, and a closure member for said aperture.

14. In a. vacuum cleaner, a hollow casing, a pair of spaced partitions secured in said casing and deiinlng a motor chamber, a motor-fan unit in said chamber having an inlet opening and an outlet opening, each of said partitions being formed with an opening, means for connecting said inlet opening to the opening in one partition and means for connecting said outlet opening to the opening in the other partition whereby atmospheric pressure may exist in said chamber, an electric switch mounted on said casing, said casing being formed with an aperture theremrough into said chamber, and electric conductors extending through said aperture for connecting said switch in the motor circuit.

15. In a vacuum cleaner, a hollow casing having flattened wall portions, a pair of spaced bulkheads secured in said casing for defining a motor chamber and for reenforcing said casing, a motor-fan unit in said chamber having an inlet opening and an outlet opening, each of said bulkheads being formed with an opening, means for connecting said inlet opening to the opening in one bulkhead and means for connecting said outlet opening to the opening in the other bulkhead, whereby atmospheric pressure may exist in said chamber, an electric switch adapted to be operated by downwardly directed foot pressurel mounted on the exterior of the upper part of said casing in the neighborhood of one of said bulkheads, whereby the bulkhead prevents deformation of said casing by excessive foot pressure, said casing being formed with an aperture therethrough into said chamber, and electric conductors extending through said aperture for connesting said switch in the motor circuit.

GUSTAF EINAR. DOFGREN.

CORRECTIN.

September 26, 1959 GUSTAF EINAR LGFGREN. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page i4., first column, line 9, claim 2, strike out the words "and an air inlet", and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 31st day of October, A. D. 1959.

(Seal) V Henry van Arsdale, Acting Commissioner of Patents.

partment and against internal pressure acting on said other end compartment. and a dust separating member in said one end compartment disposed in the path of flow of air therethrough.

motor-ian unit may be e'ected, and a closure member for said aperture.

GUSTAF EINAR. DOFGREN.

CORRECTIN.

Signed and sealed this 31st day of October, A. D. 1959.

(Seal) V Henry van Arsdale, Acting Commissioner of Patents.