Strength of Door of Horizontal Rotation Axis

Doors of horizontal rotation axis are used in furniture fulfilling the function of bars and davenports. Their work tops in addition to mass and concentrated loads also shift the load equally distributed on the surface of the board. The strength of the door suspension is determined by the hinges mounted in horizontal partition of the body. A tangible indicator of this strength is the value of the force aiming to break out the hinge box from the partition. Taking into account the actual conditions of the furniture use, two calculation schemes can be applied. The first, shown in Fig. 7.78, describes a condition in which a correctly operating guide shifts

operational loads, at the same time relieving the box hinge. Rules for first class lever, which are valid for this calculation scheme, clearly indicate that the durability of the door suspension will be greater when the distance x of mounting the guide from the hinge will be similar to the width of the door b. By making calculations for half of the value of the operational load (per one hinge), and taking into account the weight of the door, the value of the resultant force W acting on the hinge, must be written in the form:

W = Rw = Ra = 2X 2b – x Vqg + 2P 1 – 2c + qAbl, (7.264)

where

W resultant force, b width of the door, c 50 mm, g 9.81 m/s2, l length of the door,

p density of element material,

qA surface load,

V volume of the door board and x distance of mounting the guide.

Calculation scheme in Fig. 7.79 shows the door suspension in which the guides work faultily, not shifting the relevant operational loads. As a consequence, the result is that the edge of the door and horizontal partition, by pushing each other, trigger a particularly high concentration of forces gathered in the hinge. Value of this force can be written down as

W = Ha = 4hb(vpg – 2P( 1 – b) – qAbl), (7.265)

where

h thickness of the door board,