US 2849254 A
Description (OCR text may contain errors)
6, 1958 J. M. H. DOLK 2,849,254
SELF-SUPPORTING BODY, MORE PARTICULARLY FOR A MOTOR BUS JNVENTOR. JACQUES M. H. DOLK ATTORNEYS Aug. 26, 1958 'J. M. H. DOLK 2,849,254 SELF-SUPPORTING BODY, MORE PARTICULARLY FOR A MOTOR BUS Filed Feb. 28, 1955 2 Sheets-Sheet 2 S E- 7/ J Wu l2 U I L r40 I g I I I l9 V I9 I u I6 I 13 v INVENTOR. JACQUES M. H. DOLK BY ATTORNEYS ETA SELF-SUPPORTING BODY, MORE PARTICULARLY FOR A MOTOR BUS Jacques Martinus Herman Dolk, The Hague, Netherlands, assignor of one-half to N. V. Carrosseriefabriek Verheul, Waddinxveen, Netherlands, a corporation of the Netherlands Application February 28, 1955, Serial No. 491,153 Claims. 01. 296-28) This invention relates to a self-supporting body having lattice girders provided in the side walls, which body is particularly intended for a motor bus, a door case being provided in at least one of the side walls either between the front and the rear axle or behind the rear axle of the bus.
In vehicle bodies of this type the longitudinal girders of the bottom frame are of very light construction, Whereas the transverse girders have appreciable dimensions because these are to transfer the loads to which the bottom frame is subjected, viz., the weight of the motor, of the driving gear, of the floor and of the passengers, to the lattice girders provided in the side walls.
If a door case is provided in the side wall of the portion of the body between the two axles, it is necessary to interrupt the lattice girder in said side wall. The transverse forces and couples which act in said lattice girder and which are thus released, must be taken up and be transferred from the one portion to the other portion of said girder. The door case itself is not capable of accomplishing this.
Various methods have been tried to solve this problem,
but so far without any satisfactory results, for the disadvantage arises that cracks will form, especially in the corners of the door case.
In the present invention, by means of which the above disadvantage is eliminated, the portions of the lattice girder separated by the door case are connected with each other by two three-dimensional structures which transfer the couples acting in the one lattice girder portion to the other lattice girder portion through a two or three-dimensional structure located outside the plane of the lattice girder portions.
In this way the forces and couples acting in the two portions of the lattice girder are caused to by-pass the door case outside the plane of the side wall in such a manner that said two portions of the girder again function as a single girder.
In a preferred embodiment of a self-supporting body according to the invention the three-dimensional structures are formed from two three-sided pyramidal frames which are mirror images of each other and which are located one on each side of the door case and bearing on two successive transverse girders of the bottom frame of the body, said pyramidal frames being connected with each other by a two-dimensional lattice girder, which girder runs parallel or substantially parallel to the side wall containing the door case and which two-dimensional lattice girder is located between said successive transverse girders.
By the use of this construction a free space becomes available behind the door case for the provision of one or more foot boards, while the accommodation for the foot boards, as well as the space between the two longitudinal girders of the bottom frame is not obstructed.
The invention will now be further described and elucidated with reference to the accompanying drawing, in
2,849,254 Patented Aug. 26,1958
which an embodiment of a self-supporting body according to the invention is shown by way of example.
In said drawing:
Figure 1 is a perspective view of the frame of a portion of a self-supporting body according to the invention;
Figure 2 is a diagrammatic perspective view of the forces acting in the door case; and
Figure 3 is a view on a larger scale and also in perspective of an embodiment of the three-dimensional structures and the intermediate two-dimensional structure.
The bottom frame of the self-supporting body. is built up of two longitudinal girders 1 and 2 interconnected by transverse girders 3, 4, 5, 6 and 7. Between the transverse girders 3 and 4 a horizontal piston type engine 8 is suspended below the floor level of the bottom frame. The longitudinal girders 1 and 2 are slightly curved upwardly between the transverse girders 6 and 7 in order to provide a sufiicient space for the vertical movement of the rear axle (not shown).
The free ends of the transverse girders 3 are connected with the horizontal lattice girders provided in the side walls, the continuous lattice girders in the uninterrupted side wall being designated by the numeral 9 and the two portions of the lattice girders interrupted by a door case 10 in the other side wall being designated by the numerals l1 and 12.
The upper lattice girders 9 (on the side of the body without the door) and 11 and 12 (on the side with the door) define the lower edges of the window openings. Between the upper edges of the two side walls, cross-ties 13 are provided which are interconnected by a number of longitudinal ribs 14 (only partly shown), two of which define the upper edges of the window openings.
Fig. 2 shows what forces and couples are to be transferred from the one portion 11 to the other portion 12 of the lattice girder because of the interruption of the side wall by the door case 10. For purposes of illustration there will be used a two-axled motor bus with a frame resting on two points of support, which frame projects a certain distance beyond the rear axle support.
One of the points at which the sum of the moments about the longitudinal direction of the frame is zero will fall between the two points of support, i. e. the two axles, and will be closer to the most heavily loaded point axle. If said point where the moment is zero is located between transverse girders, the portions of the lattice girders adjacent the zero point are loaded by couples as well as by the vertical forces transmitted by the transverse girders.
In: Figure 2'it' has beenassumed that the point where the moments are zero is located between the transverse girders Sand 6, since this is more complex than where the zero point occurs at one of the transverse girders. To the right of said point, the side on whichthe door case is positioned, the couple to be taken up is positive, while to the left of the point it is negative.
In Figure 2 the couple which is exerted there by the lattice girder portion 12 is shown as a positive couple M. A couple N is exerted on the side of the door case by the lattice girder portion 11, which couple is negative. This is also the case if, for example, the Zero point lies exactly at the transverse girder 5 or within the door case, and the couple M=O or is negative.
The free forces P and Q are thus generated, which are equal to each other but in the opposite directions, so that in the case shown P and Q form a positive couple R. It stands to reason that the couples M, N and R must be in equilibrium. This, however, presents difficulties, because obviously it is not possible to provide a diagonal bar across the door case since it would obstruct the door frame.
The lower edge 15 of the door case 10 forms the lowermost footboard and it consists of a horizonal flat plate 15 which to have a small stepping height should not have any appreciable thickness in vertical direction. This plate, therefore, cannot take up a couple acting in a vertical plane. The roof of the motor bus cannot take up such a couple either, because no diagonal bars can be provided between the lattice girder and the roof, for such bars would run through the bays in which the Windows are provided.
The profile of the longitudinal girder 1 cannot be made heavier because the vertical dimension thereof is limited. In addition it should be borne in mind that a displacement of the forces P and Q and the couples M and N to a vertical plane through said girder would result in a load which would bend said girder portion.
Since the transverse girders 5 and 6 are located in a plane they can only transfer a couple if they act as levers having the lattice girder 9 as a fixed fulcrum. The application of the theorem of moment to the force P and the two vectors of the couple M teaches that all of these are multiplied by an amount obtained by dividing the distance between the longitudinal girder 1 and the lattice girder 9 into the distance between the lattice girder 9 and lattice girder parts 11 and 12.
The result is that large moments will manifest themselves in the points 16 and 17 of the girder 1. By taking up said moments by making the girder 1 heavier would also detract from the purpose of a self-supporting body which is to keep the weight as low as possible.
In addition the moment of resistance against bending would hardly be increased, so that the body will not remain rigid adjacent the door case.
A reinforcement of the bottom frame girder 1 by converting it into a lattice girder, which reinforcement would have to be effected between the transverse girders 3 and 6, is not possible either because of the presence of the engine 8.
According to the invention the problem is solved by effectively making the two lattice girder portions 11 and 12 into a single girder again. This is effected by the interposition of three-dimensional structures that are connected with said lattice girder portions.
In Figures 1 and 3 a preferred embodiment of said structures is shown, according to which embodiment said elements consist of two frames in the form of a tetrahedron or three-sided pyramid, which frames form mirror images of each other and the ribs of which are constituted by the bars 18, 19, 20, 21, 22 and a portion of the transverse girder 4 and by the bars 18, 19', 20, 21', 22' and a portion of the transverse girder 5 respectively.
In this connection it should be noted that the bars 18 and 18 are portions of the lower lattice girder portions 11 and 12.
The two tetrahedrons are connected by a two-dimensional lattice girder formed by the bars 21, 21, 23, 24
and the diagonal 25. This two-dimensional lattice girder is generally sufficient, because the forces S and T which, upon the transfer of the forces P and Q to the longitudinal girder 1, are exerted on the ends of the transverse girders 4 and 5 connected with the lattice girder 9, are sufficiently small so that the couples U and V resulting from the transfer of said forces to the girder 1 have little influence. Said couples act in planes normal to the girders 1 and 2.
However, it is also possible to effect the connection between the two tetrahedrons by a three-dimensional structure.
1. In a self-supporting vehicle body having a frame of longitudinal and transverse girders, side walls with lon' gitudinal lattice girders therein and a door case provided in one of said side walls between successive transverse girders and interrupting the lattice girders in thatside wall, that improvement comprising two rigid three-dimensional couple transferring structures, one attached to a lattice girder on each side of the door frame for transferring couples from the lattice girder out of the plane of the lattice girder, and a rigid couple transferring structure connecting said two rigid three-dimensional couple transferring structures outside of the plane of the lattice girder.
2. The improvement as claimed in claim 1 in which said rigid couple transferring structure connecting said two rigid three-dimensional couple transferring structures is two-dimensional.
3. The improvement as claimed in claim 2 in which said rigid couple transferring structure comprises a rectangular frame with a diagonal brace therethrough.
4. The improvement as claimed in claim 1 in which said rigid three-dimensional couple transferring structures are tetrahedral frames which are mirror images of each other, each frame being connected at two points of the frame to one of the successive transverse girders between which the door frame is positioned.
5. The improvement as claimed in claim 4 in which one edge of each of the tetrahedral frames is formed by a portion of the lower edge of the lattice girder which is interrupted by the door case, a second edge is formed by a portion of the transverse girder against which the tetrahedral frame bears, and a third edge is formed by an edge of the rigid couple transferring structure.
References Cited in the file of this patent UNITED STATES PATENTS 973,366 McKeen Oct. 18, 1910 2,191,572 Maier Feb. 27, 1940 FOREIGN PATENTS 621,640 Germany July 24, 1932