JACK

Abstract: Jack consisting of a lifting table (1) and a base (2), lifting arms (3, 4) attached to the lifting table and the base (2), and at least one lifting cylinder (5, 6), by means of which the lifting table can be lifted in an essentially horizontal position, and a preliminary lifter (15) which is so connected to one or several of the lifting arms (3) and to the lifting cylinder that a lifting motion is produced by means of it during the preliminary lifting stage. The preliminary lifter consists of a part (15b) which during the preliminary lifting is pressed against the lifting table and a part (15b) which rests against the base (2) or equivalent, the lifting motion of the preliminary lifter being thus produced by creating a mechanical contact between the lifting table and the base or equivalent.

Description: JACK The present invention relates to a jack as defined in the introductory part of claim 1. Fl-publication 871591 presents an articulated jack consist¬ ing of a frame resting on a base and a lifting table, with scissors-shaped articulated members placed between the frame and the lifting table and actuated by means of a pressure cylinder. The cylinder is located in the horizon¬ tal plane of the frame and its force is applied between one of the end beams of the frame and a connecting member link¬ ing the movable lower ends of the scissors-shaped articu¬ lated members. The body of the pressure cylinder is attach¬ ed to a transverse shaft whose ends are placed in slots provided in lugs fixed to the connecting member. This arrangement permits the shaft holding the cylinder body to move in the slots during the preliminary lifting stage while a preliminary lifter provided at the other end of the jack frame lifts the articulated members by a beam placed between them to a preliminary lifting position before the main lifting movement begins. The preliminary lifter con¬ sists of a lifting lever which is pivoted on lugs attached to the ends of flat bars and to which the preliminary lift¬ ing motion of the pressure cylinder is applied. US-publicat. an 4 899 987 presents another articulated jack which has two pairs of legs. In each pair, one end of the inner leg is turnably attached to the base while the other end is slidably mounted in the lifting table. One end of the outer leg is turnably attached to the lifting table and the other end slidably mounted on the base. The middle parts of the legs are linked togeter by a bolt. The bolt also supports a crank, one end of which is connected to a hydraulic piston and the other end to a roller which rests on the base at the preliminary lifting stage. Actuated by the piston, the crank turns and lifts the linkage point of the articulated members, thereby increasing the angle of the piston relative to the horizontal plane and thus increasing the lifting power of the piston. A corresponding solution is also presented in US publication 3 032 319. The object of the present invention is to produce a jack which enables the previously known jack solutions to be improved as regards the preliminary lifter so as to allow a sufficient preliminary lifting power to be achieved. The features characteristic of the jack are presented in the claims to follow. The jack of the invention allows vehicles such as cars to be lifted from a sufficiently low level with sufficient lifting power. In the following, the invention is described in greater detail by the aid of an example by referring to the attached drawing, in which Fig. 1 presents the jack of the invention in its high position. Fig. 2 presents the jack of the invention in its low position. The vehicle jack shown in Fig. 1 is provided with a lifting table 1 consisting of two horizontal iron plates provided with flanges on their inner edges, onto which a vehicle can be driven for repair and maintenance work, and frame beams supporting them, a base 2 resting on the floor, lifting arms 3 and 4 which lift and lower the table 1 while holding it in a horizontal position, and a pressure cylinder 5, 6 placed between the lifting arms and used as a lifting cyl¬ inder. There are four lifting arms, of which only the two foremost ones as seen in the plane of the paper are visible in Fig. 1. The lifting arms are turnably mounted by means of knuckle pins 7 - 10 in holes 11-14 provided in the frame and the lifting table so that when the table is in its high position, the arms are inclined in the same direction (left in Fig. 1 by an angle of aboυ* 60° relative to the hori¬ zontal plane. The foremost lif ^ .„.ng arms 3 are connected to the pressure cylinder 5, 6 by means of a preliminary lifter 15, which is turnably connected to the middle part of the lifting arms 3 and to the end of the piston 5 by means of knuckle pins 18, 19 mounted with slide bearings in holes 16, 17. The lower end of the cylinder 6 is turnably mounted in a hole 21 in the frame 2 by means of a knuckle pin 22. When the jack is in its high position, the pressure cylin¬ der has an angle of inclination, in the opposite direction relative to the lifting arms, of about 45° relative to the horizontal plane. The holes 16, 17 in the preliminary lifter, as shown in Fig. 1, are so placed that hole 17, which is connected to the piston 5, is above the level of the other hole 16, to which the legs 3 are connected. The preliminary lifter 15 has a slide-like body consisting of a lower end 15a and an upper end 15b. In the case of Fig. 1 , with the jack in its high position, the preliminary lifter is in a vertical position. In the case of Fig. 2, with the jack in its low position, the preliminary lifter is in a horizontal position. When the jack is in its low position (Fig. 2), the lower end of the lifter has a * rizontal bottom 22 and a rear end 23 with an upward slope (about 30° relative to the horizon¬ tal plane) . The hole 16 for the lifting arms and the hole 17 for the lifting cylinder are both located in the middle region of the lifter body. Similarly, when the jack is in its low position, the upper end of the lifter consists of an upper edge 24 facing the lifting table and a rounded front end 25. In addition, both ends are provided with rollers 26 - 29 to reduce friction :n the low position of the jack, the lifting cylinder 5, 6 is at an angle of about 3° - 5° relative to the horizontal plane. Moreover, the lifting table is provided with ascending plates 30 to enable the vehicle to get onto the lifting table. In addition, the lifting table and the ascending plates are provided with stopper plates 31, 32 at the ends of the lifting table to prevent the vechicle from falling down. To lift the table, the lifting cylinder is activated by its control circuit (not shown) so that the piston 5 is pushed out of the cylinder 6. At the same time, it exerts a push on the preliminary lifter 15, which was initially in a horizontal position, causing it to be inclined with its rear end 23 resting against the base 1. As a result, a triangular arrangement is formed by the lifting cylinder, the rear part of the preliminary lifter and the base. Correspondingly, the front end 25 is pressed against the lifting table 1. Thus, the lift produced during the pre¬ liminary lifting stage by means of the preliminary lifter acting as a slide (lever) is based on mechanical lift be¬ tween the base 2 and the lifting table as the preliminary lifter is in mechanical contact with both. After the pre¬ liminary lifting stage, the lifting cylinder 5, 6 is at a sufficient angle relative to the horizontal plane and the lifting operation is continued by the lifting cylinder in a known manner. It is obvious to a person skilled in the art that different embodiments of the invention are not restricted to the ex¬ ample described above, but that they may instead be varied within the scope of the following claims

Claims: CLAIMS 1. Jack consisting of a lifting table (1 ) and a base (2), lifting arms (3,4) attached to the lifting table and the base (2), and at least one lifting cylinder (5,6), by means of which the lifting table can be lifted in an essentially horizontal position, and a preliminary lifter (15) which is so connected to one or several of the lifting arms (3) and to the lifting cylinder that a lifting motion is produced by means of it during the preliminary lifting stage, characterized in that the preliminary lifter consists of a part (15b) which during the perliminary lifting is pressed against the lifting table and a part (15b) which rests against the base (2) or equivalent, the lifting motion of the preliminary lifter being thus produced by creating a mechanical contact between the lifting table and the base or equivalent. 2. Jack according to claim 1, characterized in that both the part of the preliminary lifter pressed against the lifting table and the part resting against the base or equivalent is provided with a bevelled or rounded edge (23,25) which lies closest to the lifting table or the base or equivalent. 3. Jack according to claim 1 or 2, characterized in that the edges of the preliminary lifter are provided with rollers (26-29) to reduce the friction.

Inventors: VIERTO RAINE, VIERTO, RAINE
Applicants: VIERTO RAINE, VIERTO, RAINE
Application year: 1991
Main classification: B66F7
IPC codes: B66F7