Abstract:
An automatic door closing device includes a bell crank lever pivotablly mounted on the door which cooperates with a hook-shaped cam plate mounted on the door frame. A spring biased dash pot controls movement of the bell crank lever when the door is opened and closed, assuring that the door will close slowly but positively without slamming. Means is provided on the frame of the device to assure proper positioning of the bell crank lever with respect to the top edge of the door and the hook-shaped cam plate.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to automatic door closing devices. 
     2. Description of the Prior Art 
     The present inventor has suggested a Japanese Pat. No. 30920/52 published on Aug. 11, 1977 on an automatic door closing device wherein, as shown in FIG. 1, an L-lever 3 is pivoted at one end on the short piece side with both right and left pieces as bearings 2 in the upper part of a channel-shaped fitting frame 1, a piston shaft 5 of a dash pot 4 is pivoted to the bending point 6 of the above mentioned L-lever 3, a cylinder 7 is pivoted also with both pieces of the lower part of the fitting frame 1 as a bearing 8 and a piston is pressed to one side by a spring contained in the dash pot 4 so that, when a door 9 is to be opened, by a hook plate 11 fitted to a wall frame 10, the L-lever 3 may be rotated against the above mentioned spring and may be locked when a dead point is passed and, on the other hand, when the door 9 is to be closed, just before it is closed, by the hook plate 11, the L-lever may be reversely rotated and, in case it is returned by the spring past the dead point, the dash pot 4 may be operated. 
     However, in this device, the prevention of oil leakage out of the dash pot 4 is made but is not perfect. During the long use, oil will leak out of the connecting part with a lid 12 screwed with the cylinder 7 or particularly the inserting part of the piston shaft 5 with the lid 12. As a result, there have been defects that the interior of the room will be stained and air will enter the cylinder 7 to fail it. 
     Further, in fitting such automatic door closing device to the door 9, it is screwed to the door 9 with the middle piece of the channel-shaped fitting frame 1. However, as the dash pot 4 fitted to the fitting frame 1 is in the way, it has been necessary to once remove the dash pot 4 from the fitting frame 1 and then to screw it. In fitting it, it has been necessary to fit the upper end of the fitting frame 1 to the upper end of the door 9 and to vertically position the device. Therefore, it has been very difficult to fit the device. 
     Further, in the conventional automatic door closing device, in the case of closing the door, a piston 13 will slide downward, a ball 14 will close a through hole 15, the passage of the oil in the cylinder 7 will be closed but, as the L-lever is gradually rotated, the oil will be leaked little by little from around the ball 14 in the structure. However, this structure requires a precision so high that it is not adapted to mass-production. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an automatic door closing device which is perfect in preventing oil leakage, is simple to fit and is simple and cheap to make. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partly sectioned side view of a conventional automatic door closing device. 
     FIG. 2 is a side view of an automatic door closing device according to the present invention. 
     FIG. 3 is a partly sectioned magnified side view of a dash pot. 
     FIG. 4A to 4C are cross-sectioned views showing embodiments of respective oil controlling devices. 
     FIG. 5 is an elevation of a fitting frame. 
     FIG. 6 is a sectioned view on line VI--VI in FIG. 5. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     1 is a channel-shaped frame screwed to a door 9. An L-lever 3 is pivoted at one end on the short piece side to this fitting frame 1. 4 is a dash pot pivoted at one end of the piston shaft 5 to the bending point 6 of the above mentioned L-lever 3. On the other hand, the dash pot 4 is pivoted at the lower end of the cylinder 7 to the above mentioned fitting frame 1 through a bearing 8. 13 is a piston screwed to the other end of the piston shaft 5 so as to move within the cylinder 7 and to be always pressed downward by a spring 21. The interior of the cylinder 7 has a proper inclination angle so that the bore diameter may be smaller downward to control the flow of oil as shown in FIG. 3 and the minimum bore diameter is of such size as enables the piston to slide through the bore so that, just before the L-lever 3 perfectly engages with a later mentioned hook plate 11, the piston 13 may enter this minimum diameter bore. Further, the piston 13 is provided with a vertical through hole 15. A ball 14 is arranged below the hole 15 to serve as a valve to form a so-called dash pot controlling the flow of contained oil. A rubber roller 16 is pivoted to the other end of the L-lever 3 and is engaged with a hook plate 11 screwed to a wall frame 13. 
     As shown in FIG. 3, the dash pot 4 according to the present invention consists of the cylinder 7 which is a bottomed cylinder, has such proper inclination angle as reduces the bore diameter downward and has such minimum bore diameter as enables the piston 13 to slide through the bore. A female screw is provided on the inner peripheral surface at the open end of the cylinder 7. On the other hand, a lid 12 having in the center a hole 17 through which the piston shaft 5 comes in and out is connected with the above mentioned cylinder 7 through a male screw provided on its outer peripheral surface. Said cylinder 7 and lid 12 are sealed with an O-ring 18 between them. 19 is a packing of a channel-shaped section in close contact with the inner surface and inner peripheral surface of the lid 12 and integrally provided on the inner surface with a conical tubular edge part 19a projected in the direction of the piston shaft 5. The piston shaft 5 is pressed by a pressing ring 20 against the outer periphery of the end part of the edge part 19a. By the way, a concave groove for stabilizing the pressing ring 20 may be made on the outer periphery of the edge part 19a. Further, 21 is a returning spring pressing at one end on the piston 13 and at the other end on the packing 19 through a washer 22. 23 is a washer supporting the ball 14. 
     Another embodiment of a means of controlling the flow of oil contained within the cylinder 7 is shown in FIG. 4A. In this embodiment, the cylinder 7 has a fixed bore diameter. On the other hand, the piston 13 is provided with not only a through hole 15 but also an oil flowing passage 24 so that, even if the ball 14 perfectly closes the through hole 15, some oil flow may be made by the flowing passage 24 and the recovering action of the piston 13 may be smoothly made. Further, instead of this flowing passage 24, as in FIG. 4B and 4C, a cut part 24a may be made by cutting a part of the outer periphery of the piston 13 and a gap 24b may be provided by making the outer periphery of the piston 13 slightly smaller than the inner periphery of the cylinder 7. 
     The fitting frame for the automatic door closing device of the present invention shall be detailed in the following. 
     In the present invention, as shown in FIGS. 5 and 6, the channel-shaped fitting frame 1 is provided with fitting pieces 25 projected respectively on the right and left in the same plane of the middle piece and having respectively fitting holes 25a (two on each of the right and left in the drawing). This fitting piece 25 had better be made, for example, by cutting and raising a part of each piece. On the other hand, a locking piece 26 bent at right angles is provided on the side opposite both pieces at the upper end of the fitting frame 1. By the way, upper holes 27 made in both pieces are for the bearing 6 pivoting the L-lever 3 (See FIG. 2) at one end on the short piece side and lower holes 28 are for the bearing 8 pivoting the cylinder 7 (see FIG. 1) at one end. Further, as required, embossments 29 are provided (in four places in the drawing). 
     In fitting the fitting frame 1 of such formation to the door, when the locking piece 26 is hung on the upper end of the door 9 with the L-lever 3 and cylinder 7 as fitted as shown in FIG. 2, the vertical state of the automatic door closing device and the upper end of the fitting position will be determined and therefore the fitting frame may be fixed as it is with screws through the fitting holes 25a made in the fitting pieces 25. Needless to say, as the locking piece 26 has some clearance between the door 9 and a wall frame 10, there will be no trouble in opening and closing the door. By the way, the hook plate 11 is fitted to the end part of the wall frame 10 as fitted to the fitting frame 1 as before. 
     The operation of the automatic door closing device thus simply fitted through the fitting frame according to the present invention shall be explained. 
     When the door 2 is pushed or pulled to open in the direction indicated by the arrow from the closed door state (See FIG. 1), the L-lever 3 will rotate counterclockwise while pushing up the piston 13 against the spring 21 with its one end as an axis and the rubber roller 16 at the other end using the hook plate 11 as a guide. 
     In such case, the piston 13 will slide upward to compress the oil within the cylinder 7 but the ball 14 will operate downward to open the through hole 15 made in the piston 13. Therefore, the compressed oil will flow through this through hole 15, the clearance between the inner wall of the cylinder 7 and the piston 13, circulating hole 24, cut part 24a or air gap 24b and the L-lever 3 may have a force to overcome the force of only the spring 21. By the way, as the L-lever 3 is pivoted at one end on the short piece side to the fitting frame 1, it will serve as a lever and therefore the force to the rubber roller 16 will act with a force weaker than it. 
     When the L-lever 3 is rotated counterclockwise until the axis of the bending point passes the dead point on the straight line connecting the pivoting point 8 of the fitting frame 1 and cylinder 7 and the pivoting point 2 of the fitting frame 1 and lever 3, thereafter the L-lever will self-rotate with the force of the spring 21. However, the L-lever 3 will be locked by the fitting frame 1 to stop the rotation and will be disengaged with the hook plate 11 so that the door may be freely opened. This state is in FIG. 2. 
     The operation at the time of closing the door shall be explained. When the door is closed from the opened door state, the rubber roller 16 will engage with the hook plate 11 just before the closing and the L-lever 3 will be rotated clockwise. Soon after the rotation, the axis of the bending point of the L-lever passes the above described dead point and therefore the L-lever 3 will be automatically rotated by the spring 21. 
     In such case, the piston 13 will be moved downward and the ball 14 will close the through hole 15 but the piston 13 will move at a proper speed due to the clearance between the inner wall of the cylinder 7 and the piston, circulating hole 24, cut part 24a or gap 24b. 
     Thus, the locking operation will be fast at first, will become slow gradually and will become slower just before the door is completely closed and therefore the door will be locked quietly. In such case, even if an unreasonable external force is applied to the door, the door will not be closed quickly but will be locked quietly and will never make a noise. It is needless to say that the device of the present invention can be used also for sliding doors. 
     By the way, during the operation of the dash pot 4, the oil within the cylinder will be compressed by the upward movement of the piston 13 but the packing 14 will be strongly pressed in contact with the inner surface of the lid 12 by the spring 12, the piston shaft 5 will be always pressed on the periphery by the edge part 19a and therefore the oil will not flow out of the cylinder 7 through the piston shaft 5. Further, as the cylinder 7 and lid 12 are sealed with the O-ring 18, the oil will never flow out between them. 
     As in the above, according to the present invention, the structure is simple, the locking operation is fast, no noise is generated in locking, oil leakage can be perfectly prevented and the fitting is very simple.