US3295418A

US3295418A - Balanced support for overhung table of machine tools, particularly for milling machines

Info

Publication number: US3295418A
Application number: US421906A
Authority: US
Inventors: Chiaia Paolo
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-11-17
Filing date: 1964-12-29
Publication date: 1967-01-03
Anticipated expiration: 1984-01-03

Description

CHIAIA P. 3,295,418 BALANCED SUPPORT FOR OVERHUNG TABLE OF MACHINE TOOLS, PARTICULARLY FOR MILLING MACHINES Jan. 3, 1967 v 2 Sheets-Sheet l Filed Dec.

INVENTOR ATTORNEY 3,295,418 ABLE OF MACHINE FOR 5 2 Sheets-Sheet 2 Filed Dec. 29; 1964 m mk INVENTOR ATTORNEY United States Patent 3,295,418 BALANCED SUPPORT FOR OVERHUNG TABLE OF MACHINE TOOLS, PARTICULARLY FOR MILL- ING MACHINES Paolo Chiaia, Via Ghiberti 11, Milan, Italy Filed Dec. 29, 1964, Ser. No. 421,906 9 Claims. (Cl. 9058) This invention relates to a balanced support for overhung tables of machine tools, and particularly-though not exclusivelyfor milling machines.

As already well known, machine tools are often fitted with overhung tablesusually work tableswhich can be adjusted in three directions perpendicular with respect to each other, one of such directions being vertical.

The vertical adjustment is usually that which requires a movement of the greatest mass, since the table assembly must be rather heavy to prevent any undesirable vibration from being transmitted to a workpiece. Thus, in the conventional designs of machine tools, an overhung table is provided which is guided in dovetail guides, and is lifted or lowered by an elevating spindle.

It is also well known that the stability and rigidity of an overhung table or knee in milling machines is rather uncertain, due to the fact that the whole weight of such knee assembly is usually to be supported by the elevating spindle, which is therefore subjected to an unduly high wear, and at any rate, the vertical adjustment of such knee always requires an appreciable physical effort.

To prevent the above drawbacks, the invention provides a device by which the weight of an overhung table or knee is automatically balanced.

To the above purpose, a support for overhung tables of machine tools is provided, which is characterized in that the overhung table or knee, slidingly fitted in dovetail guides, is supported by a movable arm, against the action of spring means.

One end of such arm is advantageously pivotally connected with a slipper, which is slidingly fitted in guides provided on the lower face of the knee, while the opposite end of same arm is pivotally connected with the stationary frame of the machine, and having a toothed sector, fast with latter end, in mesh with a rack, which is moved against the action of said spring means.

The invention will be better appreciated from a consideration of the following description, taken with the accompanying drawing, being both description and drawing given as a not restrictive example only.

In same drawing:

FIG. 1 is a diagrammatic side view of a machine tool equipped with the support according to the invention,

FIG. 2 is a partial section taken on the line 11-11 of FIG. 1, and

FIG. 3 shows a detail of the section taken on the line IIIIII of FIG. 2.

Referring to above figures, a machine tool 1 is equipped with an overhung table or knee 2, that is slidingly fitted on guides 3. Additional guides 4, designed to accommodate a slipper 5, are provided on one side (preferably the lower side) of said knee (see also FIG. 2). The forkshaped end 7 of a lever 8 is pivotally connected with said slider 5, while the opposite end of said lever is pivotally connected, as in 9, with the machine bed 10. A toothed sector 11, fast with 9, or directly with the related end of lever 8, is in mesh with a rack 12, that is slidingly fitted, against the action of a spring 14, on a rod 13, located within the machine bed.

Obviously, more than one toothed sector 11-and as many guides 13 and springs 14may be provided. In fact, in a preferred embodiment form, two of such sectors, symmetrically located with respect to lever 8, are provided. One end of spring 14 is set against the rack 12,

, 3,295,418 Patented Jan. 3, 1967 ice I while the opposite end of'same spring is set against an inside threaded bush 15, which is screwed onto the threaded end 16 of guide 13. One end 17 of said bush 15 projects out of machine base, thus allowing same bush to be screwed into, or out of guide 16 by means of a suitable spanner, thereby to adjust the pro-stressing of springs 14.

As it can be readily appreciated, the operation of the device is unusually simple. The weight of knee 2 is balanced, through the lever 8 and the gearing 11, 12, by the springs 14, and it is to be noted that the force exerted by the weight of knee 2 on the arm 8 changes as the knee is lifted or lowered; more precisely, an increase in such force occurs when the knee is lowered, and conversely a decrease is noticed when the knee is lifted, proportionally to reaction exerted by the spring 14, which is greater when the knee is lowered, and smaller when the knee'is lifted,

There follows an automatic balancing of the system of forces acting on the lever 8, and as a final result, a balancing of knee 2.

Moreover, as it can be noticed, the spacing between the two guides 4 is progressively narrowed. A taper gib 18 is fitted between the slider 5 and one of said guides, and more precisely the guide showing the surface 4a which is inclined with respect to the longitudinal axis XX of overhung table 3. Said gib is kept firmly pressed against said surface 4a by the two screws 30, that are passed through elongated holes 31 as formed in same gib. Thus, the gib can be axially adjusted by means of the grip 19 which is fitted in a plate 32, fast with the knee 2 in such manner that it can be turned, but not axially shifted. The end of same grip 19 is threaded, and can be screwed into a suitably threaded hole of gib. Due to the taper of the gib, when it is moved in one direction, the slider 5 is locked.

It goes without saying that the knee may be lifted or lowered by any conventional system, e.g. by means of a worm, preferably fitted between the two guides 3, and that can be driven either manually or, since the weight of the knee is balanced, even by means of a fractional motor.

While the invention has been described in detail with respect to certain now preferred embodiment forms thereof, it will be understood by those skilled in the art, after understanding the invention, that various changes and modifications may be made, without departing from the spirit and scope of same invention, and is intended, therefore, to cover all such changes and modifications in the appended claims.

What I claim is:

1. In a machine tool of the type having a vertically movable carriage, in combination, support means; a cantilevered carriage having a first portion supported by said support means for substantially vertical movement therealong and having a second portion spaced from said support means; and biasing means operatively connected to said second portion of said carriage for exerting thereon an upwardly directed force in opposition to the force of gravity, said upwardly directed force remaining substantially constant during vertical displacement of said carriage so that such vertical displacement may be accomplished with relatively little effort.

2. In a machine tool according to claim 1, said biasing means comprising a slide member movable along said carriage in directions toward and away from said support means, resilient means carried by said support means and cooperating with said slide member for exerting said upwardly directed force on said carriage via said slide member, and means for increasing the bias of said resilient means in response to movement of said slide member along said carriage in a direction from said first portion toward said second portion of the latter.

3. In a machine tool according to claim 2, said biasing means further comprising motion transmitting means articulately connecting said resilient means with said slide member, said slide member being adapted to move horizontally with respect to said carriage in response to vertical displacement of the latter and to transmit to said carriage the biasing force exerted by said resilient means.

4. In -a machine tool according to claim 3, said motion transmitting means including pivot means fixed to said support means and a lever turnably mounted on said pivot means, said lever having an end spaced from said pivot means and articulately connected to said slide member so that said lever turns about said pivot means in response to horizontal movement of said slide member along said carriage when the latter is vertically displaced.

5. In a machine tool according to claim 4, wherein said pivot means is located closer to said first portion of said carriage than to said second portion.

6. In a machine tool according to claim 5 wherein the end portion of said lever in the region of said pivot means is formed as a toothed portion, said biasing means further comprising an elongated rod fixed to said support means, a rack member slidable along said rod and meshing with said toothed portion of said lever, and said resilient means comprising a coil spring surrounding said rod and biasing said rack member in a direction to produce said upwardly directed force on said carriage.

7. In a machine tool according to claim 6, said spring being a compression spring and said rack moving in a direction to compress said spring when said carriage is displaced downwardly.

8. In a machine tool according to claim 2 said combination further comprising adjusting means operatively connected to said resilient means for adjusting the bias thereof.

9. In a machine tool according to claim 2 further comprising lock means operatively connected to said slide WILLIAM W. DYER, JR., Primary Examiner.

G. A. DOST, Assistant Examiner.