OVERHEAD PROJECTOR

Abstract: The objective of the invention is an overhead projector (1) supplied with acetate film rolls (4), to which projector belongs a body (2) onto which is fixed a projection arm (16) equipped with a lens/lenses (21) and a flat mirror (20). The body (2) is supplied with an openable top part (3) into which roll spaces are arranged for the acetate film rolls (4). The acetate film rolls (4) are installed on axle rods (26) which are supplied with rotating cylinders (5) and mounted in the top part (3) at opposite ends in the shaped spaces with the aid of a bent spring and fixing hole. In the inner side of the body (2) is also arranged at least one shutter screen element (10-13) that stays inside the body (2) in all cases of use, and which is installed to cover the projected part of the acetate film (6) fully or partially. The screen elements are moved in a flat level on guiding rods (15) inside the body (2) in the directions of the length and/or width of the body (2) with the help of levers (14).

Description: OVERHEAD PROJECTOR The objective of this invention is an overhead projector ( OHP ) fitted with an acetate film roll, which consists of a body and its relevant projection arm fitted with a lens or lenses and a mirror. In the existing OHP's, the acetate film rolls are usually assembled as extra elements onto fixed holders. These holders are usually fixed onto the body of the,projector. One disadvantage of fixing the acetate film rolls in this con¬ ventional way is that when it is necessary to perform maintenace work, like changing a lamp, it is necessary to take the rolls off before being able to open the top and have aceess to the inside of the body. There is a further problem in the conventional OHP's and that is that when there is a need to cover part of the projected image, like in lectures and demonstrations, this is done by using extra sheets of paper or equivalent on top of the image. This makes the use of the OHP quite clumsy. The main o. active of the invention being presented is to decrease or eliminate the above causes of problems or disadvantages, and generally to improve the usefullness of the OHP. In order to implement the main objectives of the inven¬ tion, the iters presented in the patent claim 1 are characteristic of this OHP. The invention is shown in relation to the enclosed drawings as follows : Fig. 1 shows the OHP, according to the invention, open and presented in a perspective view. Fig. 2 shows the OHP, according to the invention, closed and presented in a perspective view. Fig. 3 shows some features of the OHP, according to the i .ventions, viewed from Fig. 2 , arrow A. Fig. 4 and 5 show, ace ding to the invention, the ?'s projection arm, with its fixing base and moving knob seen from front and top. Fig. 6 shows some details of the invention seen from the top. According to Fig. 1 and 2, the OHP consists of a body 2, which is supplied with an openable top part 3. Onto the body 2 is also connected a projection arm 16 with the help of a fixing base 18 and the moving knob 17. The top part of the projection arm 16 is made of a base unit 22, lens/lenses 21 and a flat mirror 20 on a holder 19. The openable top part 3 is supplied with a glass plate 8 with its holder and the acetate film rolls 4 with their holders. According to Fig. 3, the acetate film rolls are installed on axle rods 26, which are supplied from one end with rotating cylinders 5. The acetate film rolls 4, which are installed on the axle rods 26, are mounted in the ώpenable top part 3 at opposite ends in the shaped spaces with the help of a bent spring 27 and fixing hole 28. The roll space is shaped so that when the y.op part 3 is in the closed position, the acetate film rolls 4 can be rotated from the rotating cylinder 5. The open- able top part 3 is fixed to the body 2 with a hinge 9. In the inner part of the body 2 is arranged four shutter screens 10-13 advanta¬ geously. The screens can be moved in a flat level with guiding rods situated in the inner side of the body 2 on all four sides so that the screens 10-13 stay, in all cases of use, inside the body 2. According to Fig. 1 and 6, the form of operation of screens 10 and 12 is such, that they move in the same direct of the movement of the acetate film, while screens 11 and 13 move in a direction perpendicular to that of the movement of the acetate film. Each of the shutter screens 10-13 is so arranged that it can, when needed, cover all the area of the image being projected. The shutter screens 10-13 are moved with the help of the levers 14, which are easily situated in two adjacent sides of the body 2 of the OHP 1. In the inside of the body 2 is also installed a Fresnel lens7 between the edge rims 25 and 24. The openable top part 3 is locked with the aid of the locking unit 23. The projection arm 16 is a square section aluminium tube whose top part is bent so that the base unit 22 is always maintaied in a level exactly parallel to the glass plate 8. The projection arm 16 is fixed to the body 2 with the fixing base 18. The fixing base 18 is a cylindrically shaped plastic piece into which is cut a vertical hole 18b of the same square section of the projection arm 16, and in the other direction is cut a cylindrical hole 18a perpendicular to the square section hole. The fixing base 18 is itself fixed to the body 2 by screws or rivet The moving knob 17 consists of a cylindrical part 17b and a rim 17a, to be inserted into hole 18a. Between these rims 17a, the projection arm 16 is situate By turning the moving knob 17, the projection arm 16 moves vertically. According to the invention, the OHP is also supplied with an electronic circuit which measures the light condition in the room and adjusts the intensity of the lamp of the OHP 1 accordingly. The light intensity needed in a dark room from the lamp of the OHP 1 is less than that in a lit room, and in this case the light intensity of the lamp can be decreased, thus extending the life of the lamp noticeably. In order to improve the moving, storage and handling of the OHP, a retracting power cable is installed in the OHP.

Claims: AMENDED CLAIMS [received by the International Bureau on 22 October 1990 (22.10.90)., original claims 1-10 replaced by the amended claims 1-8 (2 pages)] 1. An overhead projector (1) supplied with acetate film rolls (4), consisting of a body (2), a projection arm (16) equipped with a lens/lenses (21) and flat mirror (20), the body (2) being provided with an openable top part (3), characterized in that the acetate film rolls (4) are assembled on axle rods (26) provided with rotating cylinders (5), and mounted in the openable top part (3) at opposite ends in the shaped spaces with the help of a bent spring (27) and fixing hole (28). 2. An overhead projector, according to claim 1 wherein the inner side of the body (2) is provided at least one shutter screen element (10-13) that stays inside the body (2) in all cases of its use the screens being installed to cover the projected part of the acetate film (6) fully or partially, characterized in that the shutter screens (10-13) are four pieces, which are moved in a flat level on guiding rods (15) inside the body (2) in the directions of the length and/or width of the body (2) with the help of levers (14). 3. An overhead projector, according to claim 2, characterized in that the levers (14) of the shutter screens (10-13) are situated on two sides of the body (2) of the overhead projector (1). 4. An overhead projector, according to claims 1 - 3, characterized in that the smooth surfaced projection arm (16) is situated by friction action between the fixing element (18, 18a, 18b) and the moving element (17, 17a, 17b). 5. An overhead projector, according to claim 4, characterized in that the projection arm (16) is square in cross section. 6. An overhead projector, according to claim 4 or 5 , characterized in that the material of the projection arm (16) is aluminium or aluminium alloy. 7. An overhead projector, according to one of the claims 1 - 6, characterized in that the lamp of the overhead projector (1) is supplied with an automatic element to adjust the intensity of the lamp according to the light condition in the room. 8. An overhead projector, according to one of the claims 1- 7, characterized in that the overhead projector (1) is provided with a retracting power cable.

Inventors: TARIK AL-ANI, TARIK, AL-ANI
Applicants: EDUCATEK OY
Application year: 1989
Main classification: G03B21
IPC codes: G03B21