JPS591899B2 - static air screw - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a static air screw that ensures a theoretically and practically sufficient displacement.

Conventionally, a theoretically appropriate gap is formed as an air shaft between the flank surface of the male thread provided on the feed screw shaft and the flank surface of the female thread of the nut to be screwed into this, and an air supply throttle is used in this gap. In static pressure air screws, compressed air is sent through to form an air bearing, and the air bearing is formed through the thread groove formed between the crest of the male thread and the trough of the nut, and between the trough of the male thread and the crest of the nut. There was also a device (Utility Model Publication No. Sho 57-1169) that provided exhaust air, or made the thread groove communicate with the radial flow path of the nut in the axial direction to further exhaust air.
In either case, it was not possible to obtain the sufficient displacement that is theoretically required for an air bearing, and it was not possible to obtain the desired performance as a static pressure live air screw.

Further, the structure was complicated due to the relationship with the air supply hole passage, and processing was difficult. This invention has a simple structure by further providing a longitudinal exhaust hole as an exhaust path in the axis of the feed screw shaft, and providing a large number of exhaust holes communicating from the peaks and valleys of the male thread to the longitudinal exhaust hole. The present invention relates to a static pressure air screw that can secure a sufficient displacement volume as a static pressure air bearing.

Next, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, a feed screw shaft 4 is pivotally supported by a front end shaft support 2 and a rear end shaft support 3 which are erected on a sliding table 1. is rotated by an electric motor 8 provided at the end of the shaft.

Furthermore, a table 5 is placed on the slide table 1, and a bracket 6 fixed to the lower surface of the table can move on the slide table along a guide path 16 above the slide table 1. ing. When the guide path 16 uses a static pressure air bearing guide, high guide accuracy can be obtained. The feed screw shaft 4 has a male thread 17, and constitutes a hydrostatic air bearing between the feed screw shaft 4 and the female thread of the nut.
The nut T is attached to the bracket 6 by the side covers 18, 18, etc.
VC is fixed. In addition, 9 is a thread-shaped gap formed between the crest 12 of the male thread and the trough of the nut, and 10 is a thread-shaped gap formed between the trough 14 of the male thread and the crest of the nut. It becomes an exhaust path. The axial center of the feed screw shaft 4 has a second
As shown in detail in the figure, a separate Vc longitudinal exhaust hole 11 is bored, and the exhaust hole has an opening (not shown) at the end of the feed screw shaft on the side (opposite to the end where the motor 8 is attached). .

Furthermore, as shown in FIG. 2, there are a plurality of radial exhaust holes 13 on the outer periphery, which lead from the ridges 12 of the screw 17 to the longitudinal exhaust holes 11, and radial holes 15, which also connect from the valleys 14 to the longitudinal exhaust holes. It is perforated. The screwed state of the nut 7 and the male thread 17 is shown in an enlarged scale in FIG. As shown in FIG. 3, an annular recess is provided on the outer periphery of the nut 7, and is partitioned by the inner diameter surface of the bracket 6 to form an annular groove 19.

Further, a large number of air supply passages 20 and 21 are provided which open from the annular recess to the blank surface of the nut. In addition, the air supply path 20
, 21 has an air supply throttle part 22 necessary for the configuration of the air bearing.
, 23 are provided. Note that 24 is an air supply hole provided in the bracket 6 and opens into the annular space 19. Air supply hole 24
When air with a pressure of, for example, 5 to 7 f/Cd is introduced into the annular space 19 from the outside through the Then, air is supplied to two air bearing portions formed on the blank surface of the male thread 17 and the nut 7. When the electric motor 8 is operated in this state, the feed screw shaft 4 rotates, and the nut 7 is easily moved along the feed screw shaft 4 without causing friction on the screwing surfaces due to the presence of the air bearing film.

As the nut moves, the table 5 can be moved on the slide table 1 via the bracket 6 and along the guide path 16. Exhaust gas is exhausted through the threaded gaps 9, 10 and also through the longitudinal exhaust hole 11 of the feed screw shaft 4. In this case, the exhaust volume theoretically necessary for a static pressure air bearing is sufficiently secured by the longitudinal exhaust holes. Note that the diameter of the longitudinal exhaust hole can be appropriately selected as necessary. The present invention has a longitudinal exhaust hole in the axis of the feed screw shaft that communicates with the threaded exhaust passage formed in the crests and troughs of the nut and the male thread. It has now become possible to provide a static pressure air feed screw that can provide a large amount of displacement.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of an embodiment using the static pressure nitrogen screw of the present invention, Fig. 2 is a partial vertical sectional side view of the feed screw shaft, and Fig. 3 is a partially enlarged sectional view showing the screwed state. . 4...Feed screw shaft, 7...Nut, 9, 10...
Threaded gap (exhaust path), 11...Longitudinal exhaust hole, .
12...Male thread ridge, 13...Radial exhaust hole, 14
...Male thread valley, 15...Radial exhaust hole, 17...
・Male thread.

Claims (1)

[Claims] 1 Consists of a feed screw shaft with a male thread and a nut that is screwed into the male thread, with an air supply path on the nut side for supplying compressed air from the outside to the thread flank surface of the threaded part to form an air bearing coating. At the same time, the thread-shaped gaps formed between the crests of the male thread and the troughs of the female thread, and between the troughs of the male thread and the crests of the female thread, are used as exhaust passages. A longitudinal exhaust hole is drilled in the axis of the
A hydrostatic air screw characterized in that a large number of radial exhaust holes are provided that communicate with the longitudinal exhaust holes from the crests and valleys of the male thread.