Title of Invention

A MATERIAL TESTING MACHINE

Abstract

ABSTRACT A material testing machine comprising a pair of box-like posts vertically provided on opposite sides, a pair of screw rods rotatably disposed in the pair of posts respectively, a cross head laid between the pair of posts so that the cross head is engaged at its opposite end portions with the pair of screw rods through nuts respectively, and chucks attached to the cross head and a stationary portion of the machine respectively so that the pair of screw rods are driven to rotate to make the cross head displace to give a tensile load or the like to a test piece held by the chucks wherein space portions are formed on opposite end sides of the cross head and near inner sides of the screw rods respectively, and wherein plate-like covers are disposed along the screw rods so as to pass through the space portions respectively to thereby enclose the screw rods in the box-like posts respectively. At least one of the plate-like covers may be provided so as to be displaceable in the direction of the screw rods so that driving of the testing machine is stopped by displacement of the one plate-like cover.

Full Text

The present invention relates to material testing machines and particularly relates to a material testing machine having a pair of box-like posts vertically provided on opposite sides a pair of screw rods rotatably disposed in the pair of posts respectively, a cross head laid between the pair of posts so that the cross head is engaged at its opposite end- portions with the pair of screw rods through nuts respectively, and chucks attached to the cross head and a stationary portion of the machine respectively so that the pair of screw rods are rotated to make the cross head displace to give a tensile load or the like to a test piece held by the chucks. Material testing, especially static material testing by applying a tensile load or a compressing load to a test piece is carried out by means of a material testing machine as shown in Fig. 9. In Fig. 9, the material testing machine has a pair of box-like (U-shaped in section) posts M vertically provided on opposite sides, screw rods S rotatably disposed in the pair of posts M respectively a cross head K laid between the pair of posts M, the cross head K being engaged at its opposite end portions with the screw rods S through nuts N respectively. Fig. 9 a view partly in section so that the inside of only the right one of the pair of posts M is shown in section. When the pair of screw rods S are driven to rotate, the cross head K is displaced so as to move up/down to give a tensile load, or the like, to a test piece TP held between a pair of chucks Y and Y respectively attached to the cross head K and a machine stage D to thereby test tensile strength, or the like, of the test piece TP. LS is a load cell for detecting a load value. In such a material testing machine, each of the pair of posts M should be shaped like a box as perfectly as possible because it is undesirable that the respective screws are invaded by dust or foreign matters and because it is dangerous that test operator's hands, or the like, get caught in the screw portions. Because it is however necessary to lay the cross head K between the two posts M so that the cross head K is engaged at its opposite end portions with the screw rods S respectively, the facing surfaces (inner surfaces) of the pair of posts M are opened so that each of the posts M is U-shaped in section. For a measure against invasion of dust or foreign matters and for safety, a pair of bellows Z and Z acting as protective barriers are laid in the openings as shown in Fig. 9. By laying such bellows Z and Z, the up/down displacement of the cross head K can be secured and the measure against the invasion of dust or foreign matters and for safety can be realized. Although such bellows Z and Z in the conventional material testing machine serve as a measure against the invasion of dust or foreign matters and for safety, there arises a problem as follows. That is, the bellows Z and Z are produced from paper, rubber, or the like, so as to be foldable. Accordingly, the bellows Z and Z are so weak in strength that the bellows Z and Z may be deformed and hands or test operating tools may touch the screw rods dangerously when the hands or tools invade or are inserted to the bellows Z and Z accidentally. Furthermore, when the cross head K is moved up/down in testing, one of the bellows Z and Z may be expanded extremely so as to be buckled. When such buckling is repeated, break may be caused in the bellows Z and Z at the folded portion in the position of buckling. Furthermore, in the movement of the cross head K to the upper or lower level, the bellows Z and Z expand or contract but the bellows Z and Z have a predetermined thickness so that the quantity of movement (stroke) of the cross head K is limited by the thickness of the folded portion. There arises a problem that the effective stroke of the cross head K is shortened. SUMMARY OF THE INVENTION An object of the present invention is to provide a material testing machine in which the aforementioned problems are solved. According to a first aspect of the present invention, the above object can be achieved by a material testing machine comprising a pair of box-like posts vertically provided on opposite sides, a pair of screw rods rotatably disposed in the pair of posts respectively, a cross head laid between the pair of posts so that the cross head is engaged at its opposite end portions with the pair of screw rods through nuts respectively, and chucks attached to the cross head and a stationary portion of the machine respectively so that the pair of screw rods are rotated to make the cross head displace to give a tensile load or the like to a test piece held by the chucks, wherein space portions are formed on opposite sides of the cross head and near inner sides of the screw rods respectively, and wherein plate-like covers are disposed along the screw rods so as to pass through the space portions respectively to thereby enclose the screw rods in the box-like posts respectively. In the above material testing machine, preferably, the cross head is moved up/down when the screw rods are driven to rotate. Preferably, slits are formed through the cross head at its opposite end portions and near inner sides of the screw rods so that the plate-like covers are disposed so as to pass through the slits respectively. Preferably, the cross head has a pair of frame portions which are disposed so as to be opposite to each other to form a single space therebetween as the space portions so that the plate¬like covers are disposed so as to pass through the single space. In the above-mentioned material testing machine according to the first aspect of the present invention, there is still a risk that a foreign matter may come into a space between the cross head and either one of the plate-like covers so that mechanical breaking or injury may occur if the testing machine is further driven in a state that the foreign matter is put between the cross head and the plate-like cover. To eliminate such a risk, according to a second aspect of the present invention, therefore, provided is a material testing machine comprising a pair of box like posts vertically provided on opposite sides, a pair of screw rods rotatably disposed in the pair of posts respectively, a cross head laid between the pair of posts so that the cross head is engaged at its opposite end portions with the pair of screw rods through nuts respectively, and chucks attached to the cross head and a stationary portion of the machine respectively so that the pair of screw rods are rotated to make the cross head displace to give a tensile load or the like to a test piece held by the chucks, wherein space portions are formed on opposite sides of the cross head and near inner sides of the screw rods respectively, and wherein plate-like covers are disposed along the screw rods so as to pass through the space portions respectively to thereby enclose the screw rods in the box-like posts respectively, at least one of the plate-like covers being provided so as to be displaceable in the direction of the screw rods so that driving of the testing machine is stopped in response to the displacement of the one plate-like cover. In the material testing machine according to the second aspect of the present invention, preferably, each of the space portions is formed so as have to a wide range. In the material testing machine according to the second aspect of the present invention, preferably, slits are formed through the cross head at its opposite end portions and near inner sides of the screw rods so that the plate-like covers are disposed so as to pass through the slits respectively. In the material testing machine according to the second aspect of the present invention, preferably, detecting means for detecting displacement of the at least one plate-like cover is provided so that driving of the testing machine is stopped in response to a signal from the detecting means. In the material testing machine according to the second aspect of the present invention, preferably, lock means are provided on the at least one plate-like cover so as to lock the at least one plate-like cover to the cross head and detecting means for detecting displacement of the at least one plate-like cover due to locking of the at least one plate-like cover to the cross head is provided so that driving of the testing machine is stopped in response to a signal from the detecting means. Accordingly, the present invention provides a material testing machine comprising a pair of box-like posts vertically provided on opposite sides, a pair of screw rods rotatably disposed in said pair of posts respectively, a cross head laid between said pair of posts so that said cross head is engaged at its opposite end portions with said pair of screw rods through nuts respectively, and chucks attached to said cross head and a stationary portion of the machine respectively so that said pair of screw rods are driven to rotate to make said cross head displace to give a tensile load or the like to a test piece held by said chucks, wherein space portions are formed on opposite end sides of said cross head and said space portions are near inner sides of said screw rods, and wherein plate-like covers are disposed along said screw rods so as to pass through said space portions respectively to thereby enclose said screw rods in said box-like posts respectively. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a front view showing, partly in section, the configuration of an embodiment of the material testing machine according to the first aspect of the present invention; Fig. 2 is a perspective view showing the configuration of a main part of the material testing machine of Fig. 1; Fig. 3 is a front view showing, partly in section, the configuration of another embodiment of the material testing machine according to the first aspect of the present invention; Fig. 4 is a perspective view showing the configuration of a main part of the material testing machine of Fig. 3; Fig. 5 is a front view showing, partly in section, the configuration of an embodiment of the material testing machine according to the second aspect of the present invention; Fig. 6 is a perspective view showing the configuration of a main part of the material testing machine of Fig. 5; Fig. 7 is a perspective view showing a detecting mechanism in the material testing machine of Fig. 5; Fig. 8 is a front view showing, partly in section, the configuration of another embodiment of the material testing machine according to the second aspect of the present invention; Fig. 9 is a front view showing, partly in section, the configuration of a conventional material testing machine. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 is a view, similarly to Fig. 9, showing the configuration of an embodiment of the material testing machine according to the first aspect of the present invention. In Fig. 1, in the material testing machine, a pair of screw rods 2 are rotatably disposed respectively in the insides of a pair of box-like (U-shaped in section) posts 1 which are vertically provided on opposite sides respectively. A cross head 3 is laid between the pair of posts 1 so that the cross head 3 is engaged at its opposite ends with the screw rods 2 through nuts 4 respectively. A pair of chucks 5 and 5 are attached on the cross head 3 and on a machine stage 6 respectively so that a test piece 7 can be held between the chucks 5 and 5. The pair of screw rods 2 are driven to rotate to make the cross head 3 move up/down to give a tensile load or the like to the test piece 7 held by the chucks to thereby test the tensile strength, or the like, of the test piece 7. The reference numeral 8 designates a load cell for detecting a load value. The cross head 3 is shaped like a box in the same manner as in the prior art but a through-hole 3H is formed in the longitudinally central portion of the cross head 3 so that the upper end portion of the upper chuck 5 is connected to the load cell 8 through the through-hole 3H in order to detect the load on the test piece 7. The reference numeral 9 designates a yoke. The aforementioned configuration is not different from that of the conventional material testing machine of Fig. 9, but this embodiment of the present invention is different from the conventional material testing machine in that slits 3S are formed on the opposite sides of the cross head 3 and near the inner sides of the screw rods 2 and that plate-like covers 10 are fixed to the posts 1 so as to pass through the slits 3S (the inside of the left one of which is not shown) along the screw rods 2 respectively. The term "near the inner sides" used herein means "inner sides of and near the two screw rods 2 respectively". Preferably, the slits 3S are provided in positions where the respective free sides of the posts 1 U-shaped in section are sealed. If each of the slits 3S is too near corresponding one of the screw rods 2, the distance between the slit 3S and the nut 4 is reduced so that mechanical strength is lowered to cause a problem such as break or the like. Accordingly, the distance is set to a proper value taking into account such circumstances. The screw rods 2 are formed so as to be enclosed in the box-like posts 1 by the plate-like covers 10 respectively. This enclosure is not perfect airtight enclosure so that gaps are generated between the plate-like covers 10 and the posts 1 but the screw rods 2 are substantially enclosed in the insides of the posts 1 respectively. The shape of each of the slits 3S in the cross head 3 is as shown in Fig. 2 which perspectively shows a main part of the embodiment of Fig. 1. That is, the slit 3S is provided so as to extend in a direction perpendicular to the longitudinal direction of the cross head 3, so that the plate-like cover 10, which is formed so as to be able to be inserted in the slit 3S, passes through the slit 3S. The cross head 3 and the cover 10 are provided so as to keep a constant distance therebetween so that they do not touch each other even in the case where the cross head 3 is displaced in the front/rear direction in testing. It is a matter of course that the cross head 3 can be moved up/down in spite of provision of the plate-like covers 10. The plate-like covers 10 not only serve as a measure against the invasion of dust or foreign matter and for safety, but also prevent occurrence of such problems that hands or test operating tools invade or are inserted to the bellows accidentally. Accordingly, the problem of buckling of the bellows in the conventional case can be solved. Furthermore, the cross head 3 can be moved up/down between the machine stage 6 and the yoke 9, so that the effective stroke can be enlarged compared with the conventional case. In this embodiment in which such slits 3S are formed, there arises an advantage that the cross head 3 can be still shaped like a box to obtain a large mechanical strength, a good appearance, etc. Fig. 3 shows another embodiment, or a modification of Fig. 1, according to the first aspect of the present invention. This embodiment of Fig. 3 is different from the embodiment of Figs. 1 and 2 in that the shape of the cross head 3 is modified. That is, the cross head 3 in Fig. 3 is not shaped like a rectangular solid as shown in Figs. 1 and 2 but the cross head 3 is constituted by a pair of cross head frames 3P disposed so as to extend in the front-rear direction in Fig. 3 and so as to be opposite to each other so that a space is formed between the pair of cross head frames 3P. The plate-like covers 11 are passed through the space. Of course, a load cell 8 is provided so as to be laid across the pair of cross head frames 3P to thereby detect a load. Fig. 4 is a view similar to Fig. 2, perspectively showing the configuration of a main part of Fig. 3. Such a configuration in which the plate-like covers 11 are passed through the space between the cross head frames 3P is not only useful for reducing the weight of the cross head 3 and easy in machining and assembling compared with the aforementioned slit configuration but also advantageous in that there is no contact between the cross head 3 and each of the plate-like covers 11 even in the case where lateral vibration of the cross head 3 occurs more or less in testing. Although the material testing machine according to the first aspect of the present invention has such a characteristic as described above with respect to the embodiments as illustrated in the drawings, other modifications using this characteristic may be included in the scope of the first aspect of the present invention. For example, the illustrated embodiments show the case where the posts are provided vertically so that the cross head 3 is moved up/down. But, it is a matter of course that the present invention can be applied to a testing machine in which posts are disposed horizontally. The present invention can be applied not only to a tensile strength testing machine but also to a compressing strength testing machine. Further, the present invention can be applied to a case where the posts are vertically provided on a machine stage. Further, it is preferable to form the plate-like covers from a metal material or a synthetic resin material from the point of view of strength, but the plate-like covers may be formed from a paper material or a rubber material. Further, the resin material may be provided as a transparent material so that the inside can be observed. The first aspect of the present invention include all these modifications. Fig. 5 is a front view showing, partly in section, the configuration of an embodiment of the material testing machine according to the second aspect of the present invention. Similarly to the first aspect of the present invention, in the material testing machine of this embodiment according to the second aspect of the present invention, a pair of screw rods 2 are rotatably disposed respectively in the insides of a pair of box¬like (U-shaped in section in a horizontal plane) posts 1 which are vertically provided on opposite sides respectively. A cross head 3 is laid between the pair of posts 1 so that the cross head 3 is engaged at its opposite ends with the screw rods 2 through nuts 4 respectively. A pair of chucks 5 and 5 are attached on the cross head 3 and on a machine stage 6 respectively so that a test piece 7 can be held between the chucks 5 and 5. The pair of screw rods 2 are driven to rotate to make the cross head 3 move up/down to give a tensile load or the like to the test piece 7 held by the chucks to thereby test the tensile strength, or the like, of the test piece 7. The reference numeral 8 designates a load cell for detecting a load value. The cross head 3 is shaped like a rectangular solid and a through hole (not shown) is formed in the longitudinally central portion of the cross head 3. The upper end portion of the upper chuck 5 is connected to the load cell 8 through the through-hole in order to detect the load on the test piece 7. The reference numeral 9 designates a yoke. In this embodiment according to the second aspect of the present invention, as shown in Fig. 5, wide-range space portions 3K are formed on the opposite end sides of the cross head 3 and near the inner sides of the screw rods 2 respectively and plate-like covers 30 are disposed to pass through the wide-range space portions 3K (the inside of the left one of which is not shown) along the screw rods 2 so as to be movable up/down relative to the posts 1 respectively. The term "near the inner sides" used herein means "inner sides of and near the two screw rods 2 respectively". Preferably, the wide-range space portions 3K are provided in positions where the respective free sides of the posts 1 U-shaped in section are sealed. If each of the wide-range space portions 3K is too near corresponding one of the screw rods 2, the distance between the end portion of the wide-range space portion 3K and the nut 4 is reduced so that mechanical strength is lowered to cause a problem such as break or the like. Accordingly, the distance is set to a proper value taking into account such circumstances. The screw rods 2 are formed so as to be enclosed in the box-like posts 1 by the plate-like covers 30 respectively. This enclosure is not perfect airtight enclosure so that gaps are generated between the plate-like covers 30 and the posts 1 but the screw rods 2 are substantially enclosed in the insides of the posts 1 respectively. Further, the embodiment of the second aspect of the present invention has an important characteristic in that the plate-like covers 30 are disposed so as to be movable up/down. Specifically, each of the upper and lower ends of the plate-like covers 30 is T- shaped and elastic bodies 12A and 12B (for example, coiled springs) are interposed between the T-shaped end surfaces of the plate-like covers 30 and the machine frame. The coiled springs 12A and 12B may be forcedly disposed as compressing springs or may be laid as tensile springs. A signal may be outputted in response to the up-down movement of the plate-like covers 3 0 so that the test driving state can be stopped on the basis of this signal. That is, as shown in Fig. 5, lock members 13 and 14 are attached on each of the plate-like covers 30 by means of fixing screws 15 and 16 respectively so as to be located in upper and lower positions with respect to the cross head 3. The fixing screws 15 and 16 pass through a slit 30S formed in the plate-like cover 30 as shown in Fig. 6 and thread-engage with nut mechanisms 17 and 18 respectively on the rear surface side of the plate-like cover 30. Though not shown in detail, the nut mechanisms 17 and 18 are formed so that nuts to be thread-engaged with the fixing screws 15 and 16 respectively are made to elastically contact with the plate-like cover 30. Furthermore, the lock members 13 and 14 can be moved along the slit 30S while the fixing screws 15 and 16 are loosened so that the lock members 13 and 14 can be fixed in desired positions. In the aforementioned configuration, not only the cross head 3 abuts on the lock member 13 (14) when the cross head 3 is moved greater than a predetermined quantity after the completion of testing but also the plate-like covers 30 are moved against the elastic force of the coiled springs 12A and 12B when the cross head 3 is moved further greater. The movement is detected by a detecting mechanism SK. Fig. 7 shows the configuration of the detecting mechanism SK in detail. As shown in Fig. 7, a U-shaped frame 19 having a light-emitting portion 20 and a light-receiving portion 21 is fixed to the rear surface of the plate-like cover 30. A shading plate 22 provided on a seat 23 disposed on the machine stage 6 is inserted into the U-shaped frame 19. In a state shown in Fig. 7, shading is performed so that no signal is transmitted from the light-receiving portion 21. When the plate-like cover 30 is then moved against the elastic force of the coiled springs 12A and 12B, the shading state is eliminated so that the movement of the plate-like cover 30 is detected. Further, when, for example, a foreign matter is put between the plate-like cover 30 and the nut 4 of the cross head 3, the cross head 3 is integrated with the plate-like cover 3 0 so that the plate-like cover 3 0 is moved by the operation of the cross head 3. Also in this case, the light-receiving portion 21 outputs a detection signal. Although Fig. 5 shows the case where wide-range spaces 3K are provided in the cross head 3, such wide-range space portions are not always necessary to be formed in the cross head 3 but slits may be provided so long as the slits have only areas which allow the plate-like covers 30 to pass through the slits respectively. In this case, as shown in Fig. 8, the slit 3S is provided so as to extend in a direction perpendicular to the longitudinal direction of the cross head 3, so that the plate-like cover 30, which is formed so as to be able to be inserted in the slit 3S, passes through the slit 3S. The cross head 3 and the cover 30 are provided so as to keep a constant distance therebetween so that they do not touch each other even in the case where the cross head 3 is displaced in the front/rear direction in testing. It is a matter of course that the cross head 3 can be moved up/down in spite of provision of the plate-like covers 30. The plate-like covers 10 not only serve as a measure against the invasion of dust or foreign matter and for safety, but also prevent occurrence of such problems that hands or test operating tools invade or are inserted to the bellows accidentally. Accordingly, the problem of buckling of the bellows in the conventional case can be solved. Furthermore, the cross head 3 can be moved up/down between the machine stage 6 and the yoke 9, so that the effective stroke can be enlarged compared with the conventional case. In this embodiment in which such slits 3S are formed, there arises an advantage in that the cross head 3 can be still shaped like a rectangular solid to obtain a large mechanical strength, a good appearance, etc. Also in this embodiment, the plate-like covers 30 are disposed so as to be movable up/down. That is, the upper end portion of each of the plate-like covers 30 passes through the lower surface of the yoke 9 whereas the lower end of the plate-like cover 30 passes through the machine stage 6. In this case, the size of the through-hole of the machine stage 6 is made to approach the size of the plate-like cover 30 as extremely as possible to reduce the distance between the machine stage 6 and the plate-like cover 30. Further, T-shaped plates 30T are formed at respective end portions of the plate-like covers 30. Coiled springs 24 and 25 are interposed between the T-shaped plate 3 0T and the yoke 9 and between the T-shaped plate 30T and the machine stage 6 respectively. Accordingly, the plate-like covers 30 are urged so as to be moved up/down elastically. Further, micro-switches 26 and 27 are disposed on the yoke 9 and the machine stage 6 respectively so as to face the T-shaped plates 30T. In the aforementioned configuration, the plate-like cover 30 moves up/down following the movement of the cross head 3 when, for example, a foreign matter is put in a gap between the cross head 3 and the plate-like cover 30. Then, the micro-switch 26 (27) operates soon to output a signal so that the driving mechanism provided on the machine stage 6 can be emergency-stopped to prevent the machine from breaking, injuring, or the like. Even in the case where an operator makes a mistake so that his or her hands or tools are put between the cross head 3 and the plate¬like cover 30, testing is stopped immediately safely. Although the material testing machine according to the second aspect of the present invention has such a characteristic as described above with respect to the embodiment as illustrated in the drawings, other modifications using this characteristic may be included in the scope of the second aspect of the present invention. Particularly the characteristic of this second aspect of the present invention is in the space portions formed in the cross head. The space portions may have intermediate size between the size of the wide-range spaces and the size of the slits. For example, spaces each shaped like a triangle having a slit as its bottom side may be used. Further, as the lock means, in Fig. 5, lock members are disposed so that displacement is given to the plate-like cover in response to abnormal movement of the cross head 3. In this case, however, the shape of the lock members is not limited to such a plate-like shape as illustrated in the drawings. For example, the functions of the lock members may be given to the fixing screws of the lock means. Further, the detecting means for detecting the movement of the plate-like cover is not limited to such optical detecting means or micro-switches as employed in the described embodiments. For example, the detecting means may be formed as a switching mechanism in which the driving circuit (constituted by an electric circuit) of the testing machine is opened/closed in response the displacement of the plate-like cover. Further, also in the case where lock members are disposed like in the illustrated embodiment, the lock members may be fixed, while they are attached in a manner so that the positions of attachment of the lock members are changeable in the illustrated embodiment. Even in the case where the positions of attachment of the lock members can be changed, a plurality of holes may be provided instead of the slits which are provided in the plate-like covers in the illustrated embodiment. Further, the illustrated embodiment shows the case where the posts are provided vertically so that the cross head 3 is moved up/down. But, it is a matter of course that the present invention can be applied to a testing machine in which posts are disposed horizontally. Further, the present invention can be applied not only to a tensile strength testing machine but also to a compressing strength testing machine. Further, the present invention can be applied to a case where the posts are vertically provided on a machine stage. Further, it is preferable to form the plate-like covers from a metal material or a synthetic resin material from the point of view of strength, but the plate-like covers may be formed from a paper material or a rubber material. Further, the resin material may be provided as a transparent material so that the inside can be observed. The second aspect of the present invention include all these modifications. As has been described above, in the material testing machine according to the first aspect of the present invention, the problem of the bellows in the conventional material testing machine is solved. That is, the covers provided to protect the screw rods have sufficient strength so that the covers are not deformed even in the case where hands or test operating tools invade or are inserted to the covers accidentally. Accordingly, there is no risk that the hands or tools touch the screw rods. Furthermore, there is no problem of buckling of the bellows which had occurred in the conventional material testing machine. In addition, because there are no bellows interposed for making the up-down movement of the cross head, the cross head can be moved up and down between the machine stage and the yoke so that the effective stroke of the cross rod can be enlarged compared with the conventional case. Further, in the material testing machine according to the second aspect of the present invention, the plate-like covers are formed so as to be displaceable in addition to the features of the first aspect of the invention, and the driving of the testing machine is stopped in response to detection of the displacement of the plate-like covers to thereby limit the quantity of movement of the cross head. Accordingly, in addition of the effect of the configuration according to the first aspect of the invention, the configuration according to the second aspect of the present invention has such an advantage that prevention of the breaking of the testing machine and safety can be secured by stopping the driving of the testing machine when an abnormal situation is generated by interposition of a foreign matter between the plate¬like cover and the cross head. WE CLAIM; 1. A material testing machine comprising a pair of box-like posts vertically provided on opposite sides a pair of screw rods rotatably disposed in said pair of posts respectively, a cross head laid between said pair of posts so that said cross head is engaged at its opposite end portions with said pair of screw rods through nuts respectively, and chucks attached to said cross head and a stationary portion of the machine respectively so that said pair of screw rods are driven to rotate to make said cross head displace to give a tensile load or the like to a test piece held by said chucks, wherein space portions are formed on opposite end sides of said cross head and said space portions are near inner sides of said screw rods, and wherein plate-like covers are disposed along said screw rods so as to pass through said space portions respectively to thereby enclose said screw rods in said box-like posts respectively. 2. The material testing machine according to claim 1, wherein said crosshead forming a through-hole in its longitudinally central portion is moved up/down when said screw rods are driven to rotate. 3. The material testing machine according to claim 1, wherein slits are formed through said cross head at its opposite end portions and said space portions are near inner sides of said screw rods so that said plate-like covers are disposed so as to pass through said slits respectively. 4. The material testing machine according to claim 1, wherein said cross head has a pair of frame portions which are disposed so as to be opposite to each other to form a single space therebetween as said space portions so that said plate¬like covers are disposed so as to pass through said single space. 5. The material testing machine according to claim 1 wherein space portions are formed on opposite end sides of said cross head and said space portions are near inner sides of said screw rods, and wherein plate-like covers are disposed along said screw rods so as to pass through said space portions respectively to thereby enclose said screw rods in said box-like posts respectively, at least one of said plate-like covers is provided with displaceable means to displace in the direction of said screw rods in order to stop driving of said testing machine by displacement of said at least one plate-like cover. 6. The material testing machine according to claim 5, wherein each of said space portions is formed so as to have a wide range, by keeping a distance between the end portion of the wide-range space portion and the nut proper value so that mechanical strength is not lowered. 7. The material testing machine according to claim 5, wherein slits are formed through said cross head at its opposite end portions and near inner sides j{ said screw rods so that said plate-Iike covers are disposed so as to pass through said slits respectively. 8. The material testing machine according to claim 5, wherein detecting means is provided for detecting displacement of said at least one plate-like cover so that driving of said testing machine is stopped by a signal from said detecting means. 9. The material testing machine according to claim 5, wherein lock means are provided on said at least one plate-like cover for locking said at least one plate-like cover relative to said cross head and detecting means for detecting displacement of said at least one plate-like cover due to locking of said at least one plate-like cover to said cross head is provided so that driving of said testing machine is stopped by a signal from said detecting means. 10. A material testing machine substantially as herein described with reference to the accompanying drawings.

Documents:

1835-mas-1996 abstarct.pdf

1835-mas-1996 claims.pdf

1835-mas-1996 correspondence others.pdf

1835-mas-1996 correspondence po.pdf

1835-mas-1996 description (complete).pdf

1835-mas-1996 drawings.pdf

1835-mas-1996 form-1.pdf

1835-mas-1996 form-26.pdf

1835-mas-1996 form-4.pdf

1835-mas-1996 petition.pdf