|Publication number||US2745468 A|
|Publication date||May 15, 1956|
|Filing date||Mar 10, 1952|
|Priority date||Mar 10, 1952|
|Publication number||US 2745468 A, US 2745468A, US-A-2745468, US2745468 A, US2745468A|
|Inventors||Gideon A Kramer|
|Original Assignee||Gideon A Kramer|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (5), Referenced by (43), Classifications (16)|
|External Links: USPTO, USPTO Assignment, Espacenet|
May 15, 1956 G. A. KRAMER CHAIR WITH RESILIENT TILTING SEAT AND BACK 2 Sheets-Sheet 1 Filed March 10, 1952 FIG GIDEON A. KRAMER BY L- INVENTOR [Au-L ATTORNEYS y 1956 G. A. KRAMER CHAIR WITH RESILIENT TILTING SEAT AND BACK 2 Sheets-Sheet 2 Filed March 10, 1952 GIDEON A. KRAMER "girl ER ATTORN EYS United States Patent CHAIR WITH RESILIENT TILTING SEAT AND BACK Gideon A. Kramer, Seattle, Wash.
Application March 10, 1952, Serial No. 275,723
6 Claims. (Cl. 155-53) My invention relates to a chair which provides for automatic adjustment to the length of the lower legs of the user. This is accomplished essentially by providing a seat which is supported to tilt about an horizontal axis running transversely of the seat near the center longitudinally thereof, and a back which is supported to move vertically. The seat and back are made of a single sheet of material in a unitary structure, the material being resilient and resisting distortion. The front edge of the seat will be depressed by a user having short legs, and will raise to accommodate a user having long legs, the material forming the area of joinder of the seat and back bending due to the weight of the user.
In a chair having a full length back a basic cause for the user to assume an improper posture in a chair is the failure of the chair to adjust the height from the forward edge-of'the seat to the floor according to the length of the lower legs of the user. If the user has a long leg, the standard chair does not support the underside of the leg from the knee back and all of the weight of the user is supported by the buttocks. This is uncomfortable,
so the tall person has a tendency to slump in the chair in order to find better distribution of weight. On the other hand, the short person is troubled by the conventional chair because the front edge of the seat is not low enough, and either his legs dangle with the chair, putting uncomfortable pressure on the back side of the leg and disturbing the blood supply, or the short person rung climbs, that is, he rests his heels on the rungs of the chair. This posture problem may be solved by a proper form of tilting seat. A seat that pivots too easily is disturbing to the user as it feels unstable and the muscles may have to be used to steady the seat. If the seat pivots with too much resistance, it resembles a fixed seat and the purpose of tilting is partially or totally defeated. Therefore, the seat must have the proper resistance totilting.
The pivoting seat, even if properly adjusted as to the force required for adjustment, is still generally unsatisfactory because the back is stationary and the user has a sense of instability when the seat pivots and the back remains stationary. For that reason it is very important that the back move vertically with the rear edge of the seat so that the user may have little, if any, sense of movement because both members which his body contacts, e. g'., the seat and the back, move together giving theuser the impression of stability.
It is an object of my invention, therefore, to provide a pivoting seat for a chair that will automatically adjust the distance from the front edge of the seat to the floor according to the length of the lower legs of the user.
Another object is to provide a tilting seat with the needed amount of resistance to pivoting so that the seat will pivot under the weight of the user with a minimum sense of instability and, conversely, without excessive resistance.
Itis a further object to provide an automatically tilting' seat for a chair and a vertically moving back con- 2,745,468 Patented ill/lay 15,- 19 5 6 nected to the rear of the seat to move therewith to minimize the feeling of insecurity incident to the pivoting of the seat.
An object of my invention is to .provide a chair .for use in class rooms and the like which is conducive to, proper posture and to provide maximum comfort in a chair which may be used for several hours at. a time. 7 A further object is to provide a chair whichis self.- adjusting to the length of the lower leg of the user and which is economical to manufacture, aesthetically pleasing, and is of durable andsturdy construction. Further objects, advantages and capabilities will beap-. parent from the description and disclosure in the; draw-t ings, which may be comprehended as inherent in the de-, vice. i
Inthe drawings: ,1, Figure 1 is a perspective view taken from above. and in front of a chair showing a specific embodiment of my invention; 4 V
Figure 2 is a perspective view of the chair shown in Figure 1 taken from an opposite pointbelow and to the rear of the chair;
Figure 3 is a view showing the chair in perspective taken from a point below and behind the chair showing the parts thereof in exploded form; t Figure 4 is a fragmentary view, partly in section, and enlarged, showing the seat-supporting structure; and r Figure 5 is a view from the side, partly infsection, showing in full lines the chair as .it appears with the front edge of the seat in its lowermost position and showing in dotted lines the chair with the front edge of the seat in its uppermostposition. v
The drawings show a construction in which the seat 10 and the back 12 are formed of a single sheet of material in a unitary structure. The material of this sheet could be one of various plastic materials,.or one of the resilient metals, but it is preferred to form these members from a sheet of vulcanized fiber. Vulcanized-fibenas it is known in the trade, is formed of cotton cellulose fiber. This is a multilayered construction and has the property of resiliency and is distortable under a-medium amount of pressure. I have found that /8 "to 71 inch:
vulcanized fiber is preferable, the thinner material being various ways but it is preferred to use the method, well known to the art, of soaking the vulcanized fiber in water and then placing it on a form in proper position, to
dry in the presence of heat. As will be discussed later,- the chair could be formed with a separate seat and backconnected together in a hinged, spring-loaded construc-- tion to simulate the action obtained by the unitary structure of the resilient material shown. However, this would be an expensive construction, subject to deterioraw tion in use and it is deemed very important to provide the economical structure shown and described, requiring,
practically no adjustment or maintenance.
Back 12 is a full length back which is importantbecause a person sitting in a chair with a low back has a.
tendency to slump because of lack of support. of his shoulders. Transversely the back has a generous curve to the end that the backbone will not come into contact with the chair back. A chair in which the backbone contacts the chair back is uncomfortable for long periods.
and the person has the tendency to pivot his body in what might be called a side saddle position in order to protect his back. Seat 10 is curved longitudinally and on either 5 side has depending wings 14.
- The seatand'back' are supported by a metal framework.
.This framework includes a first L-shaped rod 20 having Second'rod 30 has a horizontal portion 32 and two legs 34-and 36 depending therefrom forming an inverted U shape; Horizontal portion 32 runs transversely of seat 10' near the'longitudinal center thereof and is secured, as
by welding-to said portion 24 of L-shaped rod 20. Third rod 38 is shaped and positioned similarly to rod 30, having a horizontal portion 40 and two legs 42 and 44, but is positioned tothe rear of second U-shaped rodv 30 and welded to horizontal portion 24 of L-shaped rod '20 near its junction 'with 'upright portion 22. Discs 46 are secured to the lower end of legs 34, 36, 42, 44 and have their lower surfaces disposed in 'a common plane. To avoid damage to the floorsurface, a'snap-on rubber glide may be positionedlolr discs 46. These rods are rigid and formed preferably of a chrome-coated steel.
A: central portion 50 ofback 12 has an opening therethrongh-and is cut away from the remainder of the back on three sides and is bent rearwardly forming an outsleeve. This may be formed by'routing or may be punched. A metallic collar 52 is secured in'the openingand upright rod portion22 is positioned in the metal collar or sleeve 52 whereby back 12 is supported by upright rod portion 22 to move longitudinally thereof. To prevent unpleasant noise due to the sliding of sleeve 520i the rod, a grommet 54. of vulcanized fiber is secured to upright rod' portion 22.: The relative movement between back 12 and upright portion 22 being in the form of sliding contactbetween grommet 54 and the metal of collar 52, unplea'sant noise will'be avoided.
children or adults. It has been found that /8 inch vulcanized fiber sheet has approximately the correct amount of resiliency for the use of the chair with children. The short-legged person sitting in the chair will cause forward edge 80 of seat 10 to assume the lowermost position in Figure and, conversely, a long-legged person will cause the forward edge of seat to assume the uppermost position shown in Figure 5. With the pivotal support for the seat position substantially as shown, the weight is balanced about the pivot of seat 10. Of course there is more weight in the trunk of the body than in the legs, but much of the weight of the leg will be borne by the seat near front edge 80, whereas the weight of the trunk of the body will not be applied to the seat 10 by the buttocks completely V Thistype of support for back 12 not only provides for s'npport'in vertical movement thereof but also serves an additional purpose. The additional purpose is. to provide for a limited pivoting action of back 12 about uprightrod portion 22; This. movement is restricted because of the nahlre'of' the vulcanized fiber, or other material having similar? resilient properties, the upper portion of back 12 has retarded pivoting action as the user shifts in his chair, as,ifor'instance,'if the user turns to the side to observe something to the rear of him. When a person sits in a chairfora considerable length of time, of course he may wish to assume various positions, and it'will be understoodthat it is advantageous to have this restricted pivoting-of the back about a substantially verticalaxis.
Bearingplatefil) is positioned between horizontal rod portion 320i U-shaped rod 30 and seat 10. Plate has downwardly turned' ends 62 and 64 and is secured to wings1'4' as byrivets 66. Bearing plate 60. has a longitudinal lip to add rigidity thereto. Secured to the lower side of bearing plate 60 are two saddle members 68' which are secured thereto by rivets 70. Bearing plate 60 and saddles 68 form a bearing for horizontal rod portion 32'of' U-shaped rod .30 which is journaled therebetweempermitting pivoting of seat 10 about a horizontal transverse axisimmediately below the seat. In addition to-its function as'a bearing for rod 30, plate 60 has a load distributing function for distributing the weight of the user.
Figure 5, shows the limits of tilting of seat ltlfound in adjustment of the chair to various persons. lip 65 abutting theforward end of horizontal rod portion 24 as the seat tips forward and the rear of the seat abutting horizontal rod portion 2421s the seat tips backward. The forward edge. 80' of seat 10 may move. as much as two inches from its lowermost. position to. its uppermost position.
The material forming seat 10 and back 12: must have no more resistance to distortion than can be overcome by the weight of the persons for which thechair is designed, i. e.,
' the seat of the chair.
at the rear of seat 10, but rather will center at some position between the center of the seat and the back of the seat. Therefore we have in effect a long arm and a short arm of a lever; the short arm being from the horizontal rod portion 32 toedge 80, and the long arm being from the horizontal rod 32 to a point shortof the rear of seat 10, the former supporting less weight, and the latter supporting more weight, by which means substantially an equilibrium is reached, as is well known in the working of levers.
The exact point, longitudinally of seat 10, at which horizontal rod portion 32 is positioned will be determined by consideration of the weight distribution on the seat and the amount of resistance to distortion of the material of seat 10 and back 12. The weight of the legs of the shortlegged person will press edge of seat 10 downward to the position shown in Figure 5 so that the forward edge of the seat will not put excessive pressure on the back of the leg. For the long-legged person, the forward edge 80 V will raise to the uppermost position shown in Figure 5 and will gently support the back of the leg in this position;
This adjustment will be understood to those skilled in the art.
There is a second adjusting action of the seat, which; is part of the adjustment of the chair to the length of the leg. The second action is dependent on the angle the legs present to the floor. If the legs are extended completely forward, they have the same efiect as a shorter leg disposed at right angles to the floor. Again, the legs have the same action as a shorter leg if they are folded under In each case the front edge of theseat will adjust to the distance from the knee to the floor.
When a person sits in the adjustable chair, he will probably be unconscious of this adjustment as he has no index by which this movementmay be measured. This may be explained by contrast with the type of chair wherein the seat pivots and the back remains in position. v latter construction, as the person takes the seat, his back moves longitudinally of the chair back as the seat tilts, and he is conscious of the pivoting of the seat with an accompanying sense of instability. In the present chair, the only movement of the part which the person could. possibly feel is the change in angle between the seat. 10 and back 12 and this is hardly noticeable.
With the shoulders supported by the high back, the.
back-bone in floating position, the weight distributed over the seat. so that excessive and uncomfortable pressure is. not placed on any part of the body, as for instance the buttocks, and with the distance from the forward edge of. the chair to the floor adjusted'to the length of the lower legs of the. person so that only slight pressure is placed under the back of the legs, a most comfortable chair: is,
Thesea.. chair, such as efiiciency, strength and economy, the" specific embodiment shown in the drawings has proven to.
be a very satisfactory construction. Advantages include the easy stacking; of the chair, the pleasing appearance and-J Inth'is.
' the little maintenance required. However it will be apparent thechair could be formed in various ways within the conception shown and described herein. In other wards, the supporting structure could be of a difierent type, for instance, wood construction, the essential requirement being the providing of the horizontal pivot for seat and the support for vertical movement of back 12. The various ways in which this might be done will be apparent without elaboration. Likewise, as has been mentioned before, the seat 10 and back 12 do not have to be made in a unitary structure as they could be hingedly connected and the resistance to relative movement therebetween could be effected by means of springs or friction joints. However, for economy and efiiciency, it is believed to be an important feature of this invention that the aforesaid characteristics have been possible of attainment with the use of a single sheet of material selected from one of the materials having resilient properties inherent in the material.
This chair may be characterized as affording adjustment to the size and posture of the user as distinguished from conventional practice where in general the user must accommodate himself to the shape of the chair.
It is believed that it will be clearly apparent from the above description and the disclosure in the drawings that the invention comprehends a novel construction of a chair.
Having thus disclosed the invention, I claim:
1. A chair, comprising: a sheet of material forming a seat and a back in a unitary structure, said seat and back joining at an angle which is close-to a right angle, a central portion of said back having an opening therethrough and being cut away from the remainder of said back on three sides and being bent rearwardly forming an outstanding, rigid sleeve; a portion of the sides of said seat being bent downwardly forming depending wings; a rigid metal framework including a first rod having two portions forming an L-shape, one of said portions of said first rod being disposed upright and positioned in said sleeve for sliding movement of said sleeve longitudinally thereof and the second of said portions being positioned under said seat and longitudinally thereof, a second rod having a horizon- 'tal portion and two legs depending therefromformin'g an inverted U-shape, said horizontal portion running transversely of said seat near the longitudinal center thereof and being secured to said second portion of said first rod with said legs forming the forward supports of said chair, a third rod shaped and positioned similarly to said second rod only being secured to said first rod behind said second horizontal portion of said second rod joumaled therebetween permitting tilting of said seat about said horizontal mitting bending between said seat and back'when said seat is tilted by the weight of user but said sheet resuming its normal position in the absence of such weight.
2. A chair, comprising: a sheet of material forming a seat and a back in a unitary structure; means forming a sleeve positioned on the central rear portion of said back; a metal supporting framework including a first rod having two portions forming an L-shape, one of said portions of said first rod being disposed upright and positioned in said sleeve for sliding movement of said sleeve longitudinally thereof and the second of said portions being positioned under said seat and longitudinally thereof, a second rod having a horizontal portion and two legs depending therefrom forming an inverted U-shape, said horizontal portion running transversely of said seat near the longiportion; and said sheet of material being resilient perward supports of said chair, a third 'rod shaped and positioned similarly to said second rod only being secured to said first rod behind said second rod with the legs thereof forming the rear supports of said chair; bearing means secured to said seat, said horizontal portion of said second rod being journaled in said heating means permitting tilt? ing of said seat about said horizontal portion; and said sheet of material being resilient and resisting deformation but permitting bending between said seat and back as said seat is tilted under force and said back moves longitudinally of said upright portion of said first rod, and permitting some bending of said back about said upright rod, said seat and back resuming their original position when such forceis removed.
3. A chair, comprising: a sheet of material forming a seat and a back in a unitary structure, a central portion of said back having an opening therethrough and being cut away from the remainder of said back on three sides and being bent'rearwardly forming an outstanding, rigid sleeve; a supporting framework including leg means and an upright rod positioned at the rear of said back, said upright rod being positioned in said sleeve for sliding movement of said sleeve longitudinally thereof; pivotal heating means between said seat and said supporting framework disposed near the longitudinal center of said seat and providing securing means therebetween permitting tilting of said seat about a horizontal axis running transversely of said seat therebelow; and said sheet of material being resilient and resisting deformation but permitting bending between said seat and back as said seat is tilted under force and said back moves longitudinally of said upright rod, said seat and back resuming their original position when such force is removed.
4. A chair, comprising: a sheet of material forming a seat and a back in a unitary structure, said seat and back joining at an angle which is close to a right angle; a rigid metal framework including leg means and an upright rod positioned at the rear of said back and substantially aligned with the longitudinal axis of said back; means positioned on the central rear portion of said back connecting said back to said upright rod permitting movement of said back longitudinally of said upright rod and restricting movement of said back transversely of said upright rod; pivotal bearing means between said seat and said rigid metal framework disposed near the longitudinal center of said seat and providing securing means therebetween permitting tilting of said seat about horizontal axis running transversely of said seat therebelow; and said sheet of material being resilient and resisting deformation but permitting bending between said seat and back as said seat is tilted under force and said back moves longitudinally of said upright rod, and permitting some bending of said back about said upright rod, said seat and back resuming their original position when such force is removed.
5. A chair, comprising: a single resilient sheet of material shaped to form a seat and a back in a unitary, integral structure; supporting means for said seat and back including substantially vertically oriented guide means engaging said back permitting movement of said back in a substantially vertical direction and preventing movement of the back laterally of the guide means in a substantially horizontal direction, the resiliency of said sheet permitting limited pivoting and return of said back about an upright axis formed by said guide means so that the back resiliently yields to turning of the user in the chair, said supporting means including pivotal bearing means pivotally supporting said seat on an axis running transversely of said seat approximately half way between the front and the rear of said seat, the resiliency of said sheet resisting deformation but permitting limited bending between said seat and back as said seat is tilted under the force of the weight of the user and as said back moves upward and downward in said guide means, the resiliency 7 of the sheet returning said seat and back to the originalgosi t ion when such forceis removed. y a
6. 1% chain, comprising: a single resilient sheet of materialhshapedltoronn a seat and a-back in a unitary; integral structure having an L-shaped outline when viewed from the side: supporting means for said seat: and back including guide means substantially vertically oriented permitting movement of saidback in a substantiallyvertical" direction and preventing movement ofithe back laterally of the guide means in a substantially horizontal direction, said supporting means including. pivotal bearing'mean's pivotally supporting said'seat on an axis running transversely of said seat approximatelylhalf way be-, tween the front and the rear of' said seat; saidsheet throughout the major extent of the seat and-back being bent transversely excepting at the area of joinder of the seat and back at the bend of'said L-shape where the sheet is transversely straight whereby the sheet is more easily longitudinally bent in'said area of joinder'than inrothei areas, the resiliency of said sheetpermitting limited bend- 1 ing' betweensaid seattandsaid' back as saidseat'is tilted original position when the Weight is rem o ved.
References Cited in thelfile of this natent UNITE STATES PATENTS
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US964012 *||Jul 1, 1909||Jul 12, 1910||Frank E Folts||Chair.|
|US1201844 *||Feb 24, 1916||Oct 17, 1916||Robert L Margolyes||Factory-chair.|
|US1409212 *||Dec 10, 1920||Mar 14, 1922||Behr Claus F Y||Device for repose|
|US2544800 *||Apr 3, 1947||Mar 13, 1951||Karl Michaelis||Chair|
|AU184726A *||Title not available|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US3036861 *||Mar 30, 1960||May 29, 1962||Galloway Ralph M||Reclining chair|
|US3127221 *||Jul 16, 1962||Mar 31, 1964||Chair|
|US3133765 *||Aug 30, 1962||May 19, 1964||Ion Corp||Chair|
|US3304121 *||Aug 10, 1965||Feb 14, 1967||Soc Civ D Rech Etudes Ind||Metal chairs|
|US3874727 *||Mar 13, 1973||Apr 1, 1975||Rudolph Baresel Bofinger||Chair|
|US3951451 *||Jul 19, 1973||Apr 20, 1976||Dr. -Ing. H.C.F. Porsche Aktiengesellschaft||Shell seat for passenger motor vehicles|
|US4557521 *||Nov 24, 1982||Dec 10, 1985||Gebr. Thonet Gmbh||Chair having a resiliently interconnected seat and back|
|US4776633 *||Apr 10, 1986||Oct 11, 1988||Steelcase Inc.||Integrated chair and control|
|US4783121 *||May 11, 1987||Nov 8, 1988||Luyk Harley E||Improved chair with convex upper backrest and forward seat surfaces|
|US5318346 *||Apr 30, 1993||Jun 7, 1994||Steelcase Inc.||Chair with zero front rise control|
|US5320410 *||Jan 14, 1992||Jun 14, 1994||Steelcase Inc.||Chair control|
|US5540481 *||May 2, 1994||Jul 30, 1996||Steelcase, Inc.||Chair with zero front rise control|
|US5611598 *||Jan 26, 1996||Mar 18, 1997||Steelcase Inc.||Chair having back shell with selective stiffening|
|US5630643 *||Jun 1, 1993||May 20, 1997||Steelcase Inc||Upholstered chair with two-piece shell|
|US5662381 *||Jun 6, 1995||Sep 2, 1997||Steelcase Inc.||Chair construction and method of assembly|
|US5725277 *||Jul 18, 1996||Mar 10, 1998||Steelcase Inc.||Synchrotilt chair|
|US5842264 *||Aug 27, 1997||Dec 1, 1998||Steelcase Inc.||Chair construction and method of assembly|
|US6471293||Mar 8, 2001||Oct 29, 2002||Michigan Tube Swagers & Fabricators, Inc.||Stackable chair with flexible back support|
|US6679551||Oct 24, 2002||Jan 20, 2004||Michigan Tube Swagers And Fabricators, Inc.||Stackable chair with flexible back support|
|US6805412||Aug 30, 2002||Oct 19, 2004||Burgess Furniture Ltd.||Stackable chair with flexible back|
|US6820934||Oct 22, 2003||Nov 23, 2004||Michigan Tube Swagers & Fabricators, Inc.||Chair having flexible back support|
|US7275788||Aug 5, 2005||Oct 2, 2007||Wenger Corporation||Music posture chairs|
|US7841666||Nov 30, 2010||Herman Miller, Inc.||Back support structure|
|US8449037||Apr 11, 2011||May 28, 2013||Herman Miller, Inc.||Seating structure with a contoured flexible backrest|
|US9049936 *||Jan 14, 2011||Jun 9, 2015||Currier Plastics||Integral coccyx and lumbar support system|
|US9301615||Nov 25, 2014||Apr 5, 2016||Herman Miller, Inc.||Seating structure with a contoured flexible backrest|
|US20030047981 *||Aug 30, 2002||Mar 13, 2003||Roth Peter Simon||Stackable chair with flexible back|
|US20040080199 *||Oct 22, 2003||Apr 29, 2004||Ware R. Duane||Chair having flexible back support|
|US20060103198 *||Aug 5, 2005||May 18, 2006||Thomas Dettmann||Music posture chairs|
|US20090127905 *||Sep 16, 2008||May 21, 2009||Herman Miller, Inc.||Back support structure|
|US20120181840 *||Jan 14, 2011||Jul 19, 2012||Massimo Angelo Leone||Integral coccyx and lumbar support system|
|USD637423||May 10, 2011||Herman Miller, Inc.||Chair|
|USD639091||Jun 7, 2011||Herman Miller, Inc.||Backrest|
|USD650206||Dec 13, 2011||Herman Miller, Inc.||Chair|
|USD652657||Jan 24, 2012||Herman Miller, Inc.||Chair|
|USD653061||Jan 31, 2012||Herman Miller, Inc.||Chair|
|USD657166||Apr 13, 2010||Apr 10, 2012||Herman Miller, Inc.||Chair|
|USD668469 *||Oct 9, 2012||Early Learning Resources, Llc||Chair|
|DE102010051692A1||Nov 15, 2010||Oct 31, 2012||Tile Geismar||Sitzm÷bel mit rasch verformbarem Gestell|
|DE102010052496A1||Nov 22, 2010||Jan 17, 2013||Tile Geismar||Sitzm÷bel mit rasch verformbarem Gestell|
|EP2921080A1 *||Mar 6, 2015||Sep 23, 2015||Wilkhahn Wilkening + Hahne GmbH + Co. KG||Chair|
|EP2962602A1 *||Mar 6, 2015||Jan 6, 2016||Wilkhahn Wilkening + Hahne GmbH + Co. KG||Chair|
|WO2011060766A1||Nov 15, 2010||May 26, 2011||Tile Geismar||Seat furniture having a rapidly adjustable frame|
|U.S. Classification||297/285, 297/452.12, 297/DIG.200, 297/452.14|
|International Classification||A47C5/06, A47C3/12, A47C3/021|
|Cooperative Classification||A47C5/06, A47C3/12, A47C3/021, Y10S297/02, A47C7/44|
|European Classification||A47C3/021, A47C5/06, A47C3/12, A47C7/44|