JPS6012172B2 - Support mechanism for horizontal girder lifting screws - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a support mechanism for a lifting screw that maintains the inclination of a crossbeam of a portal machine tool at a maximum of 4° even when the crossbeam moves up and down and changes its position.

Generally, the elevating mechanism for the cross beam of a portal machine tool is one in which screws vertically provided along the left and right columns are rotated by a single drive source via a phase adjustment device.

The screw is trapezoidal, and the thrust load is received by either the top or bottom. There is no problem if the load is applied equally to these two trapezoidal screws, but
If the spindle head is biased to either the left or right side, or if the copying device is attached to one end face of the crossbeam (see item 4)
There is a problem. In other words, if there is a large difference in the loads between the two trapezoidal screws, if the bearing is at the top, there will be a difference in the amount of tensile displacement, if it is at the bottom, there will be a difference in the amount of compressive displacement, and if the bearing is at the bottom, there will be a difference in the amount of compression displacement, or there will be a difference in the surface pressure acting on the screws. Related to the difference in the amount of heat generated during lifting and lowering, the parallelism between the groove girder and the table varies greatly depending on the lifting and lowering position of the cross beam, as shown in Figures 1 and 2, which has a significant negative impact on machining accuracy. . For this reason, in the past, in order to correct this, load reduction methods using a balancing method, electrical correction methods, hydraulic correction methods, mechanical correction methods that involve position detection, etc. have been considered, and these methods have been implemented using methods that are suitable for the machine. was.
However, all of them have drawbacks such as complicated structures, high manufacturing costs, and sometimes malfunctions. In view of the above, the present invention has been made to eliminate these drawbacks, and its object is to provide a support mechanism for a lifting screw of a crossbeam that stabilizes processing accuracy and is inexpensive to manufacture.

Next, the embodiment will be explained with reference to the drawings.

The figure shows a portal-shaped vertical boring and milling machine with a copying device attached thereto, and a table 2 that is reciprocated is rested on a bed 1. A column 3 having a vertical sliding guide surface on the front side is fastened to both sides of the bed across the table 2, and a top beam 4 is vertically attached to the top surface of the column to form a gate shape. . A cross beam 5 is provided across the front surface of the column 3 and guided in the vertical direction along a sliding guide surface. The cross beam is moved in the vertical direction by a pair of left and right trapezoidal screws 7 provided vertically along the column via nuts 6 built into both ends thereof. The support structure for the trapezoidal screw 7 is a feature of the present invention, and thrust bearings 8 and 9 are provided at the upper and lower ends of the screw portion, respectively. The upper bearing 8 is fixed to the top beam 4 and receives the flange portion of the trapezoidal screw. The lower bearing 9 is fixed by a thrust support piece 10 and receives a stepped portion of a trapezoidal screw. Each thrust bearing is installed in such a way that the elongation of the screw due to thermal displacement is released upward. The upper and lower bearings are also adjusted to carry the load together when the weight of the crossbeam is applied. The uppermost ends of the trapezoidal screws 7 are each connected to a gear box 11, and the rotation of the drive punch 12 supported on the top beam 41 is transmitted. The driving village 12 is a gear 1 provided in the center.
3 and is rotated by an electric motor (not shown). Left and right 2
Since the trapezoidal screws 7 horizontally support the crossbeam 5, a phase adjustment device 14 for adjusting the phase of the screws is interposed in the middle of the drive punch 12. On the other hand, a horizontal guide surface is provided on the cross beam 5, and a spindle head 16 having a vertical spindle 15 on which a tool is mounted is mounted, and is moved left and right by an electric motor and a feed screw (not shown). Further, an auxiliary cross beam 17 is attached to the left end of the cross beam, and a tracer head 18 for copying is provided. A model pet 19 is arranged below the feeler of the tracer head 18, and a model table 2 is placed above it, which can be moved synchronously in the same direction as the table 2.
0 is layered. The model is fixed to this upper surface. In this configuration, the workpiece is fixed on the table 2, the model is fixed on the model table 20, and the table 2 and the model table 20 are moved synchronously by commands from the control device.

The electric motor/drive village 12 is rotated by a command from the control device based on a signal of the movement of the feeler of the tracer head 18 in contact with the model. As a result, the left and right trapezoidal screws 7 are rotated via the gear box 11, the crossbeam 5 is moved up and down following the feeler, and the workpiece is machined by the tool of the main shaft 15. In this way, when the auxiliary cross beam 17 and the tracer head 18 are attached to the cross beam 5, and the spindle head 16 moves toward the tracer head side depending on the machining position, the weight distribution will be biased toward the tracer head side, and the trapezoidal screw on the left side will be A large load will be applied.
In this state, if the thrust bearing is at the bottom as shown in Figure 1, the compression span will increase as the crossbeam moves upwards, and the difference in compression displacement of the trapezoidal screw due to the difference in left and right loads will be large and the levelness will be poor. Become. Further, as shown in FIG. 2, if the thrust bearing is located at the upper part, the lower the machine girder moves, the larger the tension span becomes, the difference in the amount of tension displacement becomes larger, and the levelness becomes worse. However, in this embodiment, since a pair of upper and lower thrust bearings are provided, the mutual effect of the respective advantages of FIGS. 1 and 2 makes it possible to reduce the amount of displacement as shown in FIG. By fixing only the lower side of the thrust bearing, the expansion of the screw due to heat is not restricted, which prevents the negative effects of the screw from loosening, and also reduces the amount of heat generated due to the difference in load applied to the left and right screws. A remarkable feature is that the effect of automatically correcting the difference in upward elongation caused by the difference in load is also applied.This support mechanism is suitable for machines that use the copying method by moving the main shaft quill and other machines. Of course, it can be applied.

[Brief explanation of the drawing]

Fig. 1 shows a support type with a thrust bearing at the bottom of the girder lifting screw, Fig. 2 shows a support type with a thrust bearing at the top of the cross girder lifting screw, and Fig. 3 shows the support type of the present invention. FIG. 4 is a diagram showing the type, and FIG. 4 is a diagram explaining the use in a portal machine tool. FIG. 5... Cross beam, 7... Trapezoidal screw 8, 9... Thrust bearing. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. In the horizontal girder lifting mechanism of a portal machine tool, thrust bearings for the pair of left and right cross girder lifting screws along the column are provided at the upper and lower ends of the threaded parts, respectively, and the thrust bearings are fixed only on the lower side that receives the load. A support mechanism for a horizontal girder lifting screw, characterized in that the screw is incorporated in a state in which upward movement of the screw is not restricted.