Patent ID: 8752603

Claim:
An apparatus for connecting at least a supporting plate having a higher strength than a supported plate located on top of the supporting plate by means of a connecting element having a collar and shaft provided, respectively, on an upper end and a lower end thereof, the apparatus comprising: a rotational feeder unit including: a down holder which rests in a fixed non-rotatable position directly on an upper surface of the supported plate and exerts pressure on the supported plate and the supporting plate, and a plunger which is rotatable within the down holder and moveable in an axial direction of the down holder, wherein the plunger is connectable to an upper portion of the collar of the connecting element, so that when the plunger connected to the connecting element is rotated within the down holder, the plunger rotates and presses the shaft of the connecting element onto the upper surface of the supported plate, causes the shaft to penetrate though the supported plate to an upper surface of the supporting plate, and produces a friction welding connection on the upper surface the supporting plate, wherein the rotational feeder unit includes adjustable operational parameters which are set based on a thickness and physical characteristics of each of the supported and supporting plates arranged on the frame, the operational parameters of the rotational feeder unit including rotational speed, feeding distance, and axial force of the rotating plunger, the rotational feeder unit further comprising: a measurement device operatively connected to the plunger for measuring the axial force exerted by the rotating plunger and a respective feeding distance of the plunger based on the thickness and the physical characteristics of each of supported and supporting plates, and when the plunger, upon pressing the shaft of the connecting element to the upper surface of the supported plate causes the measurement device to detect an increase in pressure encountered therein, the rotational feeder unit adjusts a downward feed motion of the plunger at least to three sequential connecting stages, wherein: in the first stage, the rotational feeder unit causes the shaft of the connecting element to penetrate through the thickness of the supported plate, in the second stage, the rotational feeder unit initiates a friction welding process of the shaft with the upper surface of the supporting plate, and in the third stage, the rotational feeder unit finalizes the friction welding process by increasing the axial force of the shaft of the connection element to the supporting plate, during and first stage, the plunger moves downwardly within the down holder by an amount of at least the thickness of the supported plate, and during the second and third stages, the plunger continues to move downwardly until the collar of the connecting element rests on an upper surface of the supported plate.