Elevator cars used at present are generally not of the so- called monocoque car type; instead, they have a load-bearing frame to which the car is fixed. Moreover, the car top has to be strong enough to withstand the weight of installers and maintenance people working on the car top, and the car floor must support the elevator passengers or loads of other types.

The walls of the car are generally made of thin metal sheet provided e. g. with longitudinal bendings, and in practice they do not have to carry any loads at all. One of the drawbacks with an elevator car provided with a car frame is its rather large cross-sectional area and, due to the car frame, also a large weight. A further drawback is that the car is difficult to install in narrow shaft spaces. As the dimensions of the bent sheet metal elements and other components are not very accurate, the components to be joined by screwed connections are generally provided with elongated mounting holes so that the components can be successfully joined together at instal- lation time. Although the components are firmly tightened in place during installation, the use of elongate holes involves the drawback that the components move somewhat with respect to each other during use. Especially during the obligatory test- ing of safety gear operation, the fixation of the components undergoes changes as the elongate holes permit some movement of the components. This results in extra jar in the car and may cause other problems as well. A further problem is the large number of components needed, which contributes towards making the car relatively expensive.

To solve the problem described above, monocoque elevator cars have also been proposed, primarily for small elevators. A prior-art elevator car of monocoque design is disclosed in British patent no. 1495610. The solution according to this patent comprises two rigid panels, one of which forms the floor and the other the roof of the elevator car. The floor

and the roof are connected to each other by vertical wall ele- ments, which have a load-bearing strength. According to the patent, the floor and the roof are made from steel sheets re- inforced with various profiled steel elements. Similarly, the walls are made from steel sheets, of which the interior sheet is bent at its edges towards the exterior sheet and the exte- rior sheet is bent towards the interior sheet. The space re- maining between the steel sheets is filled with a material that functions both as reinforcement and as sound insulating material. The wall elements are fastened to the roof and the floor from inside the car. Beyond this, the patent does not contain any detailed description of how the car elements are to be fastened, but since the wall elements are made from sheets bent at their edges, it is obvious that the fixing holes have to be elongate in shape to ensure that small inac- curacies produced e. g. when the sheets are being bent should not prevent the assembly of the elevator car. Although the car solution in question, being of monocoque construction, is akin to the solution of the present invention, it has not been widely endorsed in practice. This may be due to the very fact that the fixing of the elements is not immovably implemented, with the result that in practice there appear problems before long as the components begin to move in relation to each other.

The object of the present invention is to eliminate the above- mentioned drawbacks and to achieve an advantageous elevator car that is easy to install, of good quality and rigid but light in weight, for use in elevator solutions of different types. The elevator car of the invention is characterized by what is presented in the preamble of claim 1. Other embodi- ments of the invention are characterized by what is presented in the other claims.

The solution of the invention has the advantage that the ele- vator car is easy to install at the installation site from components made to accurate dimensions at factory. In addi-

tion, the number of components is small as compared with prior-art solutions. A further advantage is that the compo- nents are easy to transport to the installation site, and the transportation does not require much space. One advantage is also that the monocoque elevator car of the invention is lighter in weight and smaller in cross-section than currently used elevator cars because no car frame is needed. One of the consequences is that an elevator car designed for the same load can be installed in a shaft of smaller dimensions than at present. This brings savings to the constructor, among others, and allows more flexible space utilization in buildings. An- other advantage is the fact that the car is rigid and quiet and, thanks to its rigidity, sturdy as well. The rigid con- struction also allows the use of thinner decorative elements than in prior art. For example, stainless sheet steel with a thickness of only 0.3 mm may be used as decoration. Similarly, stone panels intended for the floor may be thinner than at present, and the panels will not crack as their deflections are insignificant, thanks to the rigid construction. The car also gives passengers the impression of reliability, and thus it provides better traveling comfort than the cars used at present.

Yet another advantage is that the construction of the car ele- ments allows the fixing points of the elements, such as holes, attachment surfaces of accurate shape etc. , to made at exactly the right positions. For example, the fixing holes of the ele- ments can be made round instead of elongate in shape and tight enough in size to just barely permit the fixing devices, such as screws or rivets, to fit in the holes. Likewise, electric conduits and other ducts, cutouts for push-button boxes etc. can be made at exactly the right positions. This guarantees that the car will be easy to install as the components can be mounted directly at correct positions with respect to each other by virtue of the fixing, lead-through and other holes and fixing points accurately made at factory using automatic working machines. As the wall elements are manufactured from

straight sheets, the above-mentioned fixing points can be made at exactly the right positions before the assembly of the ele- ments. An additional advantage afforded by accurate dimension- ing is, among other things, the fact that the components com- prised in the car equipment, such as electric cables and push- button boxes etc. , can be made from parts of standard length and size. This means savings in component prices, too. Accu- rate dimensioning also allows the use of various bayonet con- nections.

A further advantage is that connections to external elements, such as controllers etc. , are easy to accomplish, thanks to accurate dimensioning.

Yet another advantage achieved by the use of thin and strong sheet steel is that such sheets are more economical in price than the normal sheet steel used in elevator cars.

In the following, the invention will be described in detail by the aid of an embodiment example with reference to the at- tached drawings, wherein Fig. 1 presents a simplified oblique top view of an ele- vator car according to the invention provided with a doorframe, Fig. 2 presents a simplified oblique top view of a walk- through elevator car according to the invention, Fig. 3 presents elements of light-weight construction for an elevator car according to the invention, Fig. 4 presents a more detailed illustration of the joint between a wall and the roof of the elevator car of the invention in side view, Fig. 5 presents a more detailed illustration of the joint between a wall and the floor of the elevator car of the invention in side view, Fig. 6 presents a more detailed illustration of a joint between two walls of the elevator car of the in-

vention in top view, Fig. 7 presents a more detailed illustration of another joint between two walls of the elevator car of the invention in top view, and Fig. 8 presents a more detailed illustration of a joint between two walls of the elevator car of the in- vention in oblique top view, In the solution according to Fig. 1, the elevator car is de- picted in a simplified form in oblique top view. The elevator car consists of six main parts: a roof 1, a floor 2, two side walls 3, a doorframe 4 and a back wall, which is not visible in the figure. All the walls are implemented as substantially thin sandwich structures or sandwich panels, each of which comprises two thin and strong face sheets 14,15 and a layer of reinforcing material 10 between them. Due to their con- struction, the walls are accurately dimensioned, light and rigid self-supporting structures. Likewise, the roof 1 and the floor 2 are implemented as self-supporting sandwich panels. In the solution presented in Fig. 1, the doorframe 4 stiffens the elevator car so that the result is a monocoque car. The door- frame structure is similar to the wall structures. Attached directly to the self-supporting roof is a supporting beam 5 serving as a reinforcing structure and provided with an- chorages for the hoisting ropes 6. The ends of the supporting beam 5 in the upper. part of the car are provided with guides 7, and guides 8 are placed at the lower corners on the sides of the elevator car to guide the movement of the elevator car on guide rails in the elevator shaft. There is no need for a separate car frame, which is a complex, heavy and space- consuming structure.

The elevator car presented in Fig. 2 corresponds to the car in Fig. 1 in respect of its wall, roof and floor structures. How- ever, this elevator car is of a so-called walk-through design, which has no doorframe and no back wall corresponding to it.

However, the walk-through model may have a doorframe both on

the front side and on the back side. The walls 3 are now se- cured to the roof 1 and the floor 2 in such a way that the resulting elevator car is a rigid monocoque frame structure that does not require any doorframe 4 or back wall 9 to strengthen it. The supporting beam 5 and the guides 7,8 may be identical to those in the elevator car presented in Fig. 1 and fastened in the same way.

Those parts of the car that need reinforcing are provided with so-called local reinforcements. One of these parts is the area where the supporting beam 5 is secured. Other local reinforce- ments are needed e. g. at the mounting places of the guides, mounts on the car walls for a handrail possibly to be provided inside the car, and so on. A feature of the local reinforce- ments is that they are each concentrated on a very small area.

Fig. 3 presents the six main elements of an elevator car with a doorframe, shown apart from each other to give a better vis- ual idea but still close to their proper places. All the ele- ments are independent, self-supporting elements that are easy to assemble at factory. The figure also shows the back wall element 9, which is not visible in the preceding figures.

Fig. 4 shows the joint between the roof element 1 and a wall element 3. Each of the aforesaid main elements is a sandwich construction consisting of an interior face sheet 15, an exte- rior face sheet 14 and a filling material 10 firmly attached between the face sheets to stiffen the panel. Both face sheets 14,15 are smooth and straight in their entire surface, thus forming a flat outer surface of the element. At least one, but suitably both of the face sheets 14,15 are substantially thin metal sheets, e. g. steel sheets, and made of a very strong material, substantially stronger than normal sheet steel. The strong steel sheets allow lighter elements to be achieved by using face sheets 14,15 as thin as possible. A suitable sheet thickness is at least below 1 mm, preferably between 0.3-0. 8 mm. Sheets with a thickness below 0.3 mm are not robust

enough, whereas sheets thicker than 0. 8-1 mm increase the weight of the element unnecessarily. The most suitable face sheet thickness is below 0.7 mm and preferably even below 0.6 mm, e. g. 0.5 mm or even 0.4 mm. An essential point is that the face sheets 14,15 are not bent during manufacture, but the elements are shaped in a manner that allows the face sheets to remain straight, a good and permanent accuracy of dimensioning being thus achieved. A special requirement regarding the roof element 1 is that it should withstand the loads imposed by installation and maintenance personnel working on the roof.

Despite the thinness of the face sheets, wall elements accord- ing to the invention with a sufficient resistance to impacts and indentation will be achieved by making the face sheets from high-strength sheet steel.

The edges of each element are provided with a profiled joint reinforcement 11, which has been bent into the appropriate shape before being mounted on a side edge or end edge of the element. The shape of the joint reinforcement 11 varies de- pending on the element and its intended use. In side view, an ordinary joint reinforcement has the shape of e. g. a substan- tially even-bottomed rectangular letter U whose one prong ex- tends as an arm 17 parallel to the bottom plane of the letter U. The elements are fixed together via the joint reinforce- ments. In Fig. 4, a side wall element 3 has been fastened to the roof element 1 by means of fixing devices 13, such as screws. The joint reinforcement of the roof element is pro- vided with joining pieces 12 attached to the joint reinforce- ment 11 during manufacture of the element 1. The joining piece is provided with threaded holes machined at exactly the right positions. The joint reinforcement of the wall element 3 is provided with corresponding accurate round fixing holes made at factory at exactly the right positions. The fixing holes have a diameter such that the fixing device 13 exactly fits in the hole. This makes accurate and easy installation possible and allows a sturdy car structure to be achieved.

The wall element 3 is so attached to the roof element 1 that a small gap 16 is left at the joint between the elements to pro- vide for ventilation of the car. The gap is easily achieved e. g. by using joining pieces 12 of suitable length.

The floor element 2 and the wall element 3 presented in Fig. 5 are secured to each other by a joint in principle identical to the above-described joint between the roof element and the wall element. The floor element 2 is a sandwich panel contain- ing stiffening material 10 between the two face sheets 14,15.

At least one of the face sheets is made of thin high-strength sheet steel having a thickness between 0.4-1. 5 mm, most suitably e. g. about 0.5 mm. This is a substantially smaller thickness than in prior-art floor solutions, in which the face sheets generally have thickness between 2.5-3 mm. In the solution of the invention, the stiffening material of the floor element may consist of e. g. balsawood, which is light and can be used in this structure to produce a rigid and strong element. The profiled edge elements consist of joint reinforcements 11 appropriately manufactured. By means of fix- ing devices 13 and a joining piece 12, the floor element and the wall element are so connected to each other that a suffi- cient air gap 16 is left between the elements for ventilation of the elevator car. The wall elements 3 and 9 are provided with a horizontal batten 18 placed near the lower edge and secured to the wall elements by means of securing blocks 23 inserted through the elements. Each securing block comprises a fastening sleeve and a fastening screw. The fastening sleeve is secured either at factory or only in connection with the mounting of the batten to a round hole 24 of accurate dimen- sions made in the wall element at factory during manufacture of the element. Such accurately dimensioned round holes 24 are made in the elements in appropriate places, e. g. for the above-mentioned battens, handrails, local reinforcements, e. g. those for the supporting beam 5 and the guides 7, and for similar structures.

Figures 6-8 illustrate different methods of fastening the wall elements. All these figures show a joint between the back wall element 9 and a side wall element 3. Fig. 6 presents a joint implemented on the inside of the wall elements, which forms a decorative rounded interior corner. The joining ele- ment is a strip 19 of curved profile, provided with round fix- ing holes disposed at accurate positions matching the disposi- tion of corresponding fixing holes 21 and 22 in the joint re- inforcements 11. The elements are secured together with fixing devices 13, such as screws or rivets. The round fixing holes allow a very firm attachment to be made quickly and easily using e. g. blind rivets. Mounted on top of the strip 19 is additionally a decorative fillet 20 that covers the heads of the fixing devices.

Fig. 8 visualizes the round fixing holes 21 and 22 provided in the joint reinforcements 11 as well as their distribution in relation to each other. In the case illustrated by this fig- ure, the joint between the elements can be further strength- ened by applying a layer of glue between the joint reinforce- ments 11.

It is obvious to the person skilled in the art that the inven- tion is not limited to the example described above, but that it may be varied within the scope of the claims presented be- low. Thus, for example, the joint reinforcements may have a shape and construction differing from those described above.

Likewise, the structure of the elements may be such that only one of the face sheets is thin while the other one is thicker.

In addition, the face sheets 14,15 may be made of some other suitable material than metal.