Specification STRUCTURE FOR PREVENTING DEFORMATION OF CAB Technical Field [0001] The present invention relates to a structure for preventing deformation of a cab capable of securing the safety of a passenger in a driver's cabin (hereafter called "cab") of a cab-over type industrial vehicle upon collision. In particular, it relates to a structure for preventing deformation of a cab capable of maintaining a passenger space by using cab frames extending longitudinally on a floor panel of the cab. Background Art [0002] In the case of a cab-over type industrial vehicle in which a cab is located at the front of the vehicle, it is necessary to maintain a space for the safety of a passenger when the cab is deformed upon collision. [0003] FIG. 1 shows an example of a cab of a cab-over type truck. A cab 1 is mounted on a front portion of a chassis frame F, and two cab frames 2 are provided extending longitudinally in the lower portion of the floor of the cab 1. At the front end of the cab frame 2, a hinge portion (not shown) is provided and supported on the chassis frame F. A tilting means 5 comprising a hydraulic cylinder/piston is provided between the chassis frame Fand the cab frame 2. The tiltingmeans 5 rotates 1 about the hinge portion and tilts up the cab 1. [0004] As its side view is shown in FIG. 1, the rear half of the cab frame 2 is inflected, being in a kick-up shape, and supporting the cab floor. Also, its plan view is shown in FIG. 2. In FIG. 2, there are provided two cab frames 2 and 2, whose front portions are close to and parallel with each other, having a wider gap between their rear portions being parallel with each other. [0005] With the above structure of the cab 1, when it collides against a wall W, as shown by dot-dash lines in FIG. 1, the cab 1 is crushed between the wall W and a carriage end Bl moving forward. Then, as shown by a broken line E, the cab frame 2 is buckled, reducing the passenger space of a driver D. (0006] In order to cope with such a problem, according to the prior art, there is proposed a technique wherein a member mounted on a cab frame engages a member mounted on an engine and the cab frame is supported by rigidity of the engine so that the cab can be prevented from being deformed (See Patent Document 1). Patent Document 1: Japanese Patent Unexamined Publication No. Hei 6-115463 [0007] The present inventors have conducted further studies to cope with the above problem and found out the followings. Namely, when the opening of the cross section being of an inverted hat-like shape or U-shape, as shown in FIG. 3, of the cab frame 2 is faced upward and the cab frame 2 extends from 2 C \NRPonbl\DCCXCAB\1251293_ .DOC-20/1W2010 the opening end horizontally and outwardly in the shape of a flange, at a portion where the cab frame 2 is inflected upon collision, vertical sides 2s and 2s being parallel with each other in the cross section of the inverted hat-like shape are bent and buckled inwardly as shown in FIG. 4, and the cab frame 2 is caused to be bent in its longitudinal direction at that point. Further, it was found out that the cab frame 2 is made stronger against buckling by reinforcing so as to prevent the both sides 2s and 2s shown in the cross section from bending inwardly. [0008] Therefore, by applying this technique, the present inventors have come to invent and propose a means allowing the strength distribution of the cab frame 2 to be optimized and space other than the passenger space to become a collapsed space for making the passenger space easier to be maintained. Disclosure of the Invention Problems to be Solved by the Invention [0009] The present invention is made in view of the above, and seeks to provide a structure for preventing deformation of a cab-over type vehicle's cab wherein the deformation of the cab is prevented so as to make it easier to maintain a passenger space upon collision. Means for Solving the Problems [0010] According to a first aspect there is provided a structure for preventing deformation of a cab of a cab-over type industrial vehicle providing a cab frame (2) having a cross section of an inverted hat-like shape and extending - 3 - C \NRPorblDCC\CAB\3251291_1 DOC-2W1120011 longitudinally in a portion of a floor of the cab, wherein a reinforcing member (3D) for preventing frame deformation is provided at an inflected portion (A) in a side view of the cab frame being a point at which the cab frame (2) is buckled upon collision and/or being an inflected portion (B) in a plan view; and wherein the reinforcing member (3D) is a molded steel plate inserted between two sides (2s, 2s) of the cab frame (2) and one side of the reinforcing member (3D) is provided downward from a frame flange portion (2f) along the side (2s) of the frame in an overlapping manner (3a to 3b), extending horizontally (3c) between two sides (2s, 2s) of the frame, further extending upward (3d) along an opposing inner side (2s) of the frame in an overlapping manner and being fixed to the cab frame, thereby preventing the cab frame (2) from being deformed. According to another aspect, there is provided a structure for preventing deformation of a cab (1), wherein a reinforcing member (3) for preventing frame deformation is provided at a point where a cab frame (2) is buckled; and wherein the point at which the cab frame is buckled is a portion (A) where the cab frame (2) is inflected as seen in its plan view and also a portion (B) where the cab frame (2) is inflected as seen in its side view. [0011] According to another aspect, the reinforcing member for preventing the frame deformation is provided near a portion (C) where the cab frame (2) and tilting means (5) are connected. [0012] Thus, the cab frame is made stronger against buckling upon collision by providing the reinforcing member for preventing the frame deformation near the portion where - 4 - C \NRPonbl\DCC\CABN3251293_1 DOC-20W102010 the cab frame is buckled or the portion where the tilting means is connected. In particular, by making the passenger seat area stronger than the edge portion, it becomes easier to maintain the passenger space even when the cab is deformed, thereby securing the safety of the passenger. Preferred other aspects of the reinforcing member for preventing frame deformation are as follows. [0013] According to another aspect, a cross section of the cab frame (2) is of an inverted hat-like shape opened upward; and the reinforcing member (3A) for preventing frame deformation is formed in a rib-like shape by connecting both sides (2s, 2s) of the frame. According to another aspect, the reinforcing member (3B) for preventing frame deformation is formed in a pipe like shape by connecting both sides (2s, 2s) of the frame. According to still another aspect, the reinforcing member (3C) for preventing the frame deformation is formed in a plate-like shape by connecting both sides (2s, 2s) of the frame. [0014] According to yet another aspect, a cross section of the cab frame (2) is of an inverted hat-like shape opened upward; and the reinforcing member (3D) for preventing frame deformation is formed such that its portion (3c) fitted into the cab frame (2) with the cross section of the inverted hat-like shape and extending in the horizontal direction prevents the deformation of the cab frame (2). [0015] With the above structure, both sides of the cab frame whose cross section is of an inverted hat-like shape are connected so that the inward buckling is prevented and the cab frame is made stronger against the buckling. - 5 - C \NRPonbIOlCC\CAB\3251291 DOC-21VlIV2UI) Therefore, the safety of the passenger can be secured by applying the above structure to the invention according to claim 1. Alternatively, troubles related to the mounting of the tilting means can be dealt with by applying it to the invention according to claim 2. Advantages of the Invention [0016] According to the present invention, following operation/working-effects can be obtained. - 5A- (1) When the reinforcing member of the present invention is provided in the cab frame, even if it is of an open cross-section which is easily manufactured, both sides are connected so that the inward buckling is prevented and the strength is secured without being formed as the one with a closed cross-section. (2) In particular, if the strength of the driver's seat portion of the cab frame is increased so that the space other than the passenger space may be deformed, it becomes easier to maintain the passenger space upon collision. (3) Further, the joint portion between the cab frame and the floor panel can be prevented from being damaged. Description of the Preferred Embodiments [0017] By referring to the attached drawings, embodiments of the present invention will be described. In a first embodiment, the cab frame 2 is formed from steel plate whose side view and plan view are as shown in FIGS. 1 and 2. As shown in FIG. 3, its basic cross section is of an inverted hat-like shape. Namely, two sides 2s and 2s which are substantially parallel in the vertical direction (certain degrees of draft may be given) and a bottom surface 2b form a U-shape opened upward. Flange surfaces 2f and 2f extend in horizontal directions from the opening ends. [0018] Further, there is provided a reinforcing member 3A (hereafter, the numeral 3 denotes a reinforcing member) in an inflected portion ("A" in FIG. 1) in the plan view being a point 6 at which the cab frame 2 is buckled and also being an inflected portion ("B" in FIG. 2) in the side view. As shown in FIGS. 5 and 6, the reinforcing member 3A is fitted between two sides 2s and 2s of the cab frame, being formed in a rib-like shape in the hat-like cross section, and its two ends are fixed to the sides 2s and 2s. [0019] In a second embodiment shown in FIGS. 7 and 8, the reinforcing member is provided at the same position as in the first embodiment. A pipe-like reinforcing member 3B is inserted between the two sides 2s and 2s of the cab frame and its both ends are fixed. The cross section of the pipe-like reinforcing member 3B may be circular or squire. [0020] Also, in a third embodiment shown in FIGS. 9 and 10, the reinforcing member is provided at the same position as in the embodiments described above. Two sides 2s and 2s of the cab frame are connected by a plate-like reinforcing member 3C. Further, besides the flat plate as shown in FIGS. 9 and 10, the reinforcing member may be of an I-shaped steel or an L-shaped steel. [0021] According to a fourth embodiment, as shown in FIGS. 11 and 12, there is provided a reinforcing member 3D of a molded steel plate inserted between two sides 2s and 2s of the cab frame 2. As shown in the cross section of FIG. 12, one side of the reinforcing member 3D is provided downward from the frame flange portion 2f along the side 2s of the frame in an overlapping manner (3a to 3b), extending horizontally (3c) between two sides of the frame, further extending upward (3d) 7 along the opposing inner side 2s of the frame and being fixed, thereby preventing the frame 2 from being deformed. [0022] Thus, the closed cross-section is formed by combining the cab frame 2 of the open cross-section and the reinforcing member 3D, thereby increasing the torsional strength. Therefore, in addition to the same operation/working-effect as in the above embodiment, troubles such as the one where the joint (for example, by spot welding) with a floor panel (not shown) is separated by the torsional stress can be solved. [0023] In each of the above embodiments, the points A and B at which the cab frames 2 are buckled are close to the joint of the tilting means 5. However, even in a structure where the joint C of the tilting means and the point of buckling are not close, by providing any of those reinforcing members 3 near the joint C of the tilting means 5, local concentration of stress due to the mounting of the tilting means 5 or loads caused by the tilting operation can be coped with. Brief Description of the Drawings [0024] FIG. 1 is a side view showing a cab and cab frames; FIG. 2 is a plan view of the cab frames of FIG. 1; FIG. 3 is a cross section of the cab frame of FIG. 1; FIG. 4 is a cross section of the cab frame of FIG. 3 in its buckled state; FIG. 5 is a cross section of a first embodiment of the cab-frame reinforcing member according to the present 8 invention; FIG. 6 is a cross section taken along line a-a of FIG. 5; FIG. 7 is a cross section of a second embodiment of the cab-frame reinforcing member according to the present invention; FIG. 8 is a cross section taken along line b-b of FIG. 7; FIG. 9 is a cross section of a third embodiment of the cab-frame reinforcing member according to the present invention; FIG. 10 is a cross section taken along line c-c of FIG. 9; FIG. 11 is a perspective view of a fourth embodiment of the cab-frame reinforcing member according to the present invention; and FIG. 12 is a cross section square to frame of FIG. 11. [Explanations of letters or numerals] [0025] 1 ... Cab 2 ... Cab frame 3, 3A to 3D ... Reinforcing member 5 ... Tilting means 9 C NRPonibl\DCC\CAB\l251293_ .DOC-20/10/2010 [0026] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as, an acknowledgement or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. [0027] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. - 9A-