REAR VIEW APPARATUS

Abstract: The rear view apparatus according to the invention is of the periscopic type and consists of at least three separate mirrors, of which the first mirror (1) is placed higher than the cabin roof (4), while the design and positioning of the three mirrors is such that the drawbacks of the periscopic rear view apparatuses known at present are prevented or greatly reduced and that it is possible to fit the apparatus into common passenger cars without extensive alterations.

Description: Rear view apparatus The invention concerns a rear view apparatus for vehicles, especially passenger cars, and bears a resemblance to periscopic viewing apparatuses. Periscopic rear view apparatuses in themselves are known. Use in passenger cars, however, has taken place hardly or not at all, because the known appartuses have drawbacks attached to them. These drawbacks concern, among other things, the restricted horizontal angle of vision of the known periscope, consisting of a tubular housing contai- ning an optical apparatus by which an upright rear view image is obtained by means of mirrors and/or prisms and/or lenses. A drawback of enlarging the angle of vision by using convex or cylindrical mirrors and the like is that image reduction takes place, whereby distances to the rear can no longer be properly estimated, which can pose a threat to road safety. Enlarging the angle of vision by strongly widening the periscope raises the drawback of increasing air resistance of the periscope which rises above the car roof, while the large dimensions also hinder the fitting and positioning of the periscope tube. Apart from this, the high costs of the known apparatuses are also a con¬ sideration. The drawbacks mentioned are avoided or greatly reduced in the apparatus according to the invention, characterized in that the apparatus consists of at least three mirrors of which the first mirror is placed higher than the car roof with the mirror surface inclined towards the rear, the third mirror is placed in the driver's cabin in front of the head of the driver and with the mirror surface direc¬ ted towards the driver and the second mirror is placed in such a way that the rays of light inciding from the rear reach the eye of the driver via the first mirror, subse- quently via the second mirror and finally via the third mirror, wherein the cabin roof is provided with a transpa¬ rent part through which passes the course of the rays between the first and the third mirror. A second important characteristic of the apparatus accor- ding to the invention is that at least two of the mirror surfaces of the mirrors which are used are twisted. This torsion makes it possible to obtain such a field of vision that an optimal part of the total rearward field of view can be seen by the driver when the first mirror has a limited height. The optical image blurr which is caused by torsion of one of the mirror surfaces is corrected by an opposed torsion of the second and/ or the third mirror. The torsion also allows for correction of the inclination of the image as well as the optical effect of a limited non-parallelism of the longitudinal axes of the mirror surfaces. The invention will be described and explained in more detail by means of the following figures: Fig. 1 : illustrates the arrangement of the three mirrors, Fig. 2 : shows a second possible arrangement of the three mirrors, Fig. 3 : shows a third arrangement of the three mirrors, Fig. 4 : shows how use can be made of a transparent sliding- or tilting roof which is already present, Fig. 5 : illustrates the torsion of the mirrors and the effect thereof on the rearward field of vision, Fig. 6 : shows some constructional details for the as¬ sembly of the mirrors. In figure 1, the first mirror (1) is secured higher than the car roof (4) as a separate mirror with the mirror surface directed backwardly and inclined downwardly. The second mirror surface (2) is secured immediately below the window (5) in the car roof, with the mirror surface direc¬ ted towards the front. The third mirror (3) is situated in front of the head of the driver (6) , with the mirror surface directed towards the driver. The course of the rays has been indicated in the figure (21) . The figure shows that at its lower side, the bottom line of vision (7) is bordered by the rearside (8) of the car roof (4) . The upper line of vision (9) has, for practical purposes, been restricted to such an extent that vision is possible upto a sufficient height above the road surface situated behind the car. Figure 2a shows an arrangment of the three mirrors wherein the second and the third mirror have been placed closely together, the mirror surface of the second mirror (2) has been directed upwardly and the second mirror (2) has been placed lower than the third mirror (3) . This embodiment creates more space above the head of the driver but re¬ quires more space in front of the head of the driver. Figure 2b indicates how the arrangement which has been described here allows for using the front window of the vehicle as the transparent part of the cabin wall. This utilisation of the front window is desirable when there is a relatively short distance between the head of the driver and the top side of the front window (15) . Figure 3 shows an arrangement wherein the second mirror (2) has been placed higher than the first mirror (1) , the mirror surface of the second mirror is directed downwardly and the mirror surface of the first mirror (1) is inclined and directed upwardly. The figure shows that this arran¬ gement, too, can be employed in order to use the front window as the transparent part of the cabine wall through which pass the rays between the first and the third mir¬ ror. In this case, the mirror surface of the first mirror (1) defines an angle α with the horizontal. This angle α has a value of between 5° and 85°, but preferably of 60°, because in that case the height of the first mirror and the second mirror together can reach its minimum. Figure 4 shows how an existing transparent sliding- or tilting roof (10) can be used. In view of the usual dimen¬ sions and positioning of such a roof, the rear view ap- paratus can only be applied in this case when at least one of the longitudinal axes of the mirrors is parallel to a horizontal line (11) which defines an angle (β) with the vertical (13) which splits the vehicle longitudinally. The angle (β) is between 90° and 50° and preferably 70°. In the preferred embodiment with parallel longitudinal axes, all longitudinal axes are parallel to said line (11) . In the embodiment described here, all mirrors will be posi¬ tioned on the side of the driver which faces the middle of the cabin. Figure 5 indicates how the lines of vision (7) and (9) can be twisted from the centre of the first mirror (1) to both sides in a downward direction to the position indicated by (7') en (9') . This twisting is obtained by twisting the mirror surface of the first mirror. The mirror surface of the first mirror is thereby rotated downwardly from the middle to both sides. This twisting of the field of vision is effective because, nearer the side of the field of vision, the edge of the car roof restricts the downward vision less. The downward twisting from (7) to (7') there- fore provides an increased view of the road surface im¬ mediately behind and beside the car and thereby a better view of overtaking traffic which is near the car and diagonally behind it. At a given height (14) of the first mirror (1) , the torsion of the mirror surface of the first mirror makes it possible to view a relatively larger part of the sides of the lower section of the rearward field of vision. Consequently, the first mirror can have a relati¬ vely lower height (14) , whereby the air resistance of the first mirror (1) becomes as low as possible. In view of the importance of a low air resistance, the first mirror is also surrounded by an aero-dynamic hood (16) or a spoiler. The image blurr which is a consequence of the twosided torsion of the mirror surface of the first mirror is compensated in the case drawn here by opposed twosided torsion of the mirror surface of the third mirror (3) . By such a twosided and opossed torsion at the first and the third mirror, both an optimal field of vision and a rela¬ tively low height of the first mirror and a high picture- clarity can be achieved. A further improvement of the pic¬ ture quality is achieved by increasing the degree of torsion (meant as angle rotation per unit of length of the mirror) from the centre of the mirrors to both sides. A gradual increase of the degree of torsion from the centre thereby causes the transition from left to right torsion in the centre of the mirrors to take place gradually as well, and does not lead to problematic image deformation in the centre. Figure 6 indicates how the rear view apparatus can be constructed in such a way that it can quickly be installed in cars which are already provided with a transparent sliding- or tilting roof. The mounting of the second and third mirror is done by clamping a frame (17) to the edge (18) of the roof opening, on which the mirrors (2) and (3) are slidably and/or rotatably secured. The frame can be enlarged or reduced longitudinally and/ or cross-section- ally by means of a thread end and nut (19) . Lips are secured to the frame (17) , the shape of the lips corre¬ sponding to the shape of the edge of the roof opening (18) . By enlarging the frame longitudinally and/ or cross- sectionally, the lips (20) clamp against the edge of the roof opening. The frame offers ample opportunity for secu¬ ring the mirrors. Instead of a frame round the roof openi¬ ng, a smaller frame is also possible. The first mirror can be mounted higher than the roof by means of legs which are secured onto the roof such as the legs of a car roof rack. To allow for setting of the correct width, the legs should be slidably secured onto the mirror. When a fixed position on the car roof is concerned, it is desirable that the mirror can be swung down by means of pivots in the secu¬ ring means. In order to obtain the above-described torsion of the mirror surface, the mirror glass can be moulded into the desired shape when it is hot. It is, however, also pos¬ sible to twist a flat glass mirror mechanically, for instance, by clamping at least one longitudinal side in a bent setting. In order to obtain a gradually increasing degree of torsion starting from the centre of the mirror, a circularly bent setting is then required on a longitu¬ dinal side in combination with a straight or circularly bent setting on the other longitudinal side. The intended gradually increasing torsion can also be obtained by bending the glass longitudinally over a cross support wherein a strip has been placed under the glass, the strip having such a section that a circular bendingline is formed on the one longitudinal side while the other lon¬ gitudinal side is clamped in a straight position. The glass can also be clamped or glued onto a strip of metal or another form-retaining material which has previously been moulded into the desired shape. The field of vision of the rear view apparatus according to the invention can be further increased by using conve - ly or cilyndrically curved mirror surfaces. An additional cylindrical curvature on the sides of the first mirror and a cylindrical curvature, with a horizontal cylinder axis, of the second mirror, is preferred. It is also possible to superpose the described opposed torsion from the centre on a torsion which is constant over the length of the mirror, said latter torsion serving to compensate a certain inclination of the image. In figure 1 a lightscreen (22) has been indicated above or on the outer top side of the car roof, preventing distur¬ bing direct incidence of light on the third mirror. It goes without saying that, when mention is made in the preceding paragraphs of the mirror surface or the mirror, this also refers to a mirror surface which is made up of several separate surfaces which, together, provide a reasonably continuous image. The direction of the mirror surface here means the direc¬ tion of the perpendicular line on the mirror surface. In relation to the indicated direction, a directional tole¬ rance applies of plus and minus 40°. The directional indication "inclined" means a directional deviation of 45°.

Claims: Claims 1. Rear view apparatus for vehicles, especially passenger cars, characterized in that the apparatus consists of at least three mirrors, of which the first mirror (1) is placed higher than the car roof with the mirror surface inclined towards the rear, the third mirror (3) is placed in the driver's cabin in front of the head of the driver and with the mirror surface directed towards the driver, while the second mirror (2) is placed in such a way that the rays of light inciding from the rear reach the eye of the driver via the first mirror, subsequently via the second mirror and finally via the third mirror, wherein the cabin roof is provided with a transparent part through which passes the course of the rays between the first and the third mirror. 2. Rear view apparatus according to claim 1, characterized in that the longitudinal axes of the mirror are parallel to the horizontal. 3. Rear view apparatus according to claims 1 and 2, cha- racterized in that the second mirror (2) is placed im¬ mediately below the cabin roof and, as far as height is concerned, between the first (1) and the third (3) mirror and with the mirror surface of the second mirror directed towards the front. 4. Rear view apparatus according to claims 1 and 2, cha¬ racterized in that the second mirror (2) is placed lower than the third mirror (3) , while the mirror surface of the second mirror (2) is directed upwardly. 5. Rear view apparatus according to claims 1 and 2, cha¬ racterized in that the second mirror (2) is placed higher than the first mirror (1) , while the mirror surface of the second mirror (2) is directed downwardly and the mirror surface of the first mirror is inclined and directed upwardly. 6. Rear view apparatus according to claims 1 to 5, charac¬ terized in that at least two of the mirror surfaces are twisted longitudinally. 7. Rear view apparatus according to claims 1 to 6, charac¬ terized in that the longitudinal axes of the mirror are parallel in relation to each other. 8. Rear view apparatus according to claims 1 to 7, charac- terized in that at least one of the longitudinal axes of the mirrors is parallel to a line (11) which defines an angle β of 50° to 90° with the plane (13) which longitudi¬ nally cuts the vehicle though the middle. 9. Rear view apparatus according to claims 1 to 8, charac¬ terized in that the transparent part of the cabin roof through which passes the course of the rays between the first and the third mirror, consists of a transparent sliding- or tilting roof or of a transparent part of a sliding- or tilting roof or of the front window of the vehicle. 10. Rear view apparatus according to claims 1 to 9, cha¬ racterized in that the torsion of the mirrors is opposed from the centre to the sides of the mirrors. 11. Rear view apparatus according to claims 1 to 10, characterized in that the opposed torsion increases from the centre to the sides of the mirrors, preferably in pro¬ portion to the distance to the middle. 12. Rear view apparatus according to claims 1 to 11, cha¬ racterized in that the torsion consist of a torsion which is constant over the length of the mirror, on which a torsion which is opposed from the centre to the sides is superposed. 13. Rear view apparatus according to claims 1 to 12, cha¬ racterized in that the second and the third mirror are secured on a frame (17) which is clamped by means of lips (20) which are adapted to the edge of the roof opening. 14. Rear view apparatus according to claims 1 to 13, cha¬ racterized in that the first mirror is secured by legs and fastening clamps as is usual with car roof racks. 15. Rear view apparatus according to claims 1 to 14, characterized in that the mirror are secured slidably and/ or rotatably. 16. Rear view apparatus according to claims 1 to 15, characterized in that the first mirror is provided with an aero-dynamically formed hood with a awning-shaped upper edge extending towards the rear. 17. Rear view apparatus according to claims 1 to 16, characterized in that the torsion of the mirror surfaces is obtained by mechanical deformation of flat mirror glass. 18. Rear view apparatus according to claims l to 17, characterized in that an opposed degree of torsion which gradually increases from the centre is obtained by clam¬ ping one or both longitudinal sides of the mirror glass in a circularly bent setting, or by securing or clamping ag¬ ainst a twisted strip of metal or another material. 19. Rear view apparatus according to claims 1 to 18, characterized in that one or more of the mirror surfaces are curved in a convex, concave, cylindrical, spherical or other manner.

Inventors: POTMA THEODORUS GERHARDUS, POTMA, THEODORUS, GERHARDUS
Applicants: POTMA THEODORUS GERHARDUS, POTMA, THEODORUS, GERHARDUS
Application year: 1992
Main classification: B60R1
IPC codes: B60R1, F02B71