US3421770A

US3421770A - Floating holder

Info

Publication number: US3421770A
Application number: US528551A
Authority: US
Inventors: Milton L Benjamin; David D Walker
Original assignee: Erickson Tool Co
Current assignee: Erickson Tool Co
Priority date: 1966-02-18
Filing date: 1966-02-18
Publication date: 1969-01-14
Anticipated expiration: 1986-01-14
Also published as: GB1123141A; DE1552261A1

Description

J 1969 M. L. BENJAMIN ETAL 3,421,770

FLOATING HOLDER Filed Feb. 18, 1966 Sheet of 2 INVENTORS MILTON L. M/AM/N r 5' DAV/0 D. W KER ATTORNEYS M 1.. BENJAMIN ETAL 3,421,770

Jan. 14, 1969 FLOATING HOLDER Filed Feb. 18, 1966 Sheet '9 of2 INVENTORS I MILTON L. BENJAMIN DAV/D 0. WALKER ATTORNEYS United States Patent Claims ABSTRACT OF THE DISCLOSURE A floating holder in which the tool gripping bushing is mounted for limited radial movement to accommodate for axial misalignment between the tool and a workpiece, and a spring centering mechanism for yieldably maintaining the bushing in axial alignment with the holder.

The present invention relates generally, as indicated, to a floating holder and, more particularly, to a tool holder in which the tool is mounted for direct radial movement into axial alignment with a workpiece to be machined thereby.

Oftentimes when performing secondary machining operations on a workpiece such as reaming a bored or drilled hole, it is diflicult accurately to align the reamer with the hole, whereby the hole may be reamed out-of-round. This is especially true in the case of turret lathes having a plurality of tools such as drills, boring bars, reamers, and taps mounted thereon for sequential axial feeding with respect to a rotating workpiece held in the lathe spindle. To correct any axial misalignment, various types of so-called floating tool holders have been devised which permit the tool to float or shift laterally into alignment with the work.

An example of such a tool holder may be found in the patent to Milton and Stanley Benjamin, Patent No. 2,848,239, granted Aug. 19, 1958. The tool holder disclosed in such patent is capable of both parallel and angular floating movement with respect to its mounting means and for that purpose there is a pin and slot connection between the tool holder and mounting means and a spring element which urges the pin into point contact with a second retainer pin. This particular construction has proven to be quite satisfactory for most purposes, but there are occasions when it is desirable to have a tool holder in which floating movement in a lateral direction is more precisely controlled and requires less force, which is a principal object of this invention.

Moreover, those floating holders previously available could not be used with live spindles where the tool to tates and the workpiece is held stationary, since the high friction between the relatively moving parts of the holder would severely resist the rapid back and forth movements of the tool which would be required as it rotated.

Accordingly, it is another object of this invention to provide a full floating holder primarily of the rotating type.

Another object is to provide such a floating holder with novel means for permitting such lateral shifting of the tool.

Still another object is to provide a floating holder of the type indicated in which the angular position of the tool remains the same during lateral shifting thereof, whereby a simple transverse force, rather than a force couple, acting on the outer end of the tool is all that is necessary to effect such lateral shifting.

A further object is to provide such a floating holder with novel spring centering means for yieldably maintaining the tool coaxial with the holder even when rotating at high or low speeds, whereby the amount of lat- 3,421,770 Patented Jan. 14, 1969 eral shifting of the tool required to bring the same into axial alignment with a workpiece is reduced to a minimum, and depends on the extent of misalignment between the holder and workpiece.

Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.

In such annexed drawing:

FIG. 1 is a central longitudinal section of a preferred form of floating holder constructed in accordance with the present invention;

FIG. 2 is an exploded perspective view showing the floating holder of FIG. 1 in disassembled form;

FIG. 3 is a vertical transverse section through the holder of FIG. 1 taken on the plane of the line 33 thereof; and

FIG. 4 is a partial fragmentary longitudinal section of a modified form of spring centering means for yieldably maintaining the holder housing and bushing in coaxial alignment.

Referring now in detail to the drawing and first of all to FIGS. 1 and 2, a preferred form of floating holder constructed in accordance with the present invention is indicated at 1 and generally includes a cylindrical housing 2 in which there is disposed the inner end of a bushing 4 having a socket 5 for receipt of a suitable collet 6 or the like for tightly gripping the shank 7 of a rearrier 8 or similar type tool.

The collet 6 shown is of a conventional form, axially slotted from opposite ends and having axially spaced parallel frusto-conical surfaces 10 and 11 which are adapted to be moved into engagement with corresponding

frustoconical seats

12 and 13 in the bushing socket 5. Threaded onto the forward end of the bushing 4 there is a nosepiece 14 having a nose ring 15 disposed therein. As apparent, when the nosepiece 14 is tightened, the nose ring 15 is forced against the collet 6 to cause such collet to move inwardly against the frusto-

conical seats

12 and 13, causing the collet to be radially contracted into tight gripping engagement with the tool shank 7,

The bushing 4 with tool 8 carried thereby is mounted for limited lateral movement within the cylindrical housing 2 while maintaining the angular position of the bushing and tool coaxial with the housing through a novel connection including a driver 16 and driver plate 17, in a manner which will become readily apparent in the discussion to follow. The driver 16 is of cylindrical form, snugly received within the housing bore 18 adjacent the back wall 19, and has a pair of diametrically opposed, axially extending slots 20 in the outer surface thereof for keying the driver 16 to the housing 2 by means of dowel pins 21 extending through oppositely disposed openings 22 in the housing 2 and into the slots 20.

The driver plate 17 is also cylindrical, but is loosely disposed in the housing 2 between the driver 16 and bushing 4 due to a slight diametral clearance between the driver plate 17 and housing bore 18, and the forward face 23 of the driver 16 is centrally slotted thereacross at 24 for receipt of a central projection 25 from the rear' face 26 of the driver plate 17 so as to permit limited lateral shifting of the driver plate 17 with respect to the driver 16, but not relative rotational movement therebetween.

Ball bearing assemblies 29 each comprising a plurality of ball bearings 30 contained in a U-shaped retainer 31 with openings 32 in the sides thereof through which the ball bearings 30 project may be positioned between the

adjacent surfaces

33 and 34 of the slot 24 and central projection 25, respectively, to reduce substantially the friction between the driver 16 and driver plate 17 for ease of sliding movement therebetween.

There is a similar connection between the driver plate 17 and bushing 4 which permits transverse movement of the bushing 4 across the driver plate 17 in a direction perpendicular to that in which the driver plate 17 may be moved, or substantially so. More specifically, the front face 35 of the driver plate 17 has a central slot 36 thereacross similar to the slot 24 in the driver 16-, but running in a direction perpendicular to the central projection 25 on the opposite or rear face 26, and the bushing 4 has an annular flange 37 the rear face 38 of which is cut away to provide a central projection 39 of a size to be received within the central slot 36 with additional ball bearings 30 contained in apertured retainers 31 disposed between the adjacent edges 40 and 41. As shown in FIG. 3, the ends of the retainers 31 are beveled at 42 so as not to interfere with assembly of the driver plate 17 and bushing 4 in the housing 2. The same is true of the retainers 31 between the driver 16 and driver plate 17.

The diametral clearance between the bushing flange 37 and housing bore 18 is preferably the same as between the driver plate 17 and housing bore 18, whereby the bushing 4 may be laterally shifted to the same extent in two directions perpendicular to each other; i.e. with the driver plate 17 in the direction of the driver slot 24, and in the direction of the driver plate slot 36. As apparent, these perpendicular movements will permit lateral shifting of the bushing 4 in any direction to bring the tool 8 into axial alignment with a workpiece. The diametral clearance between the driver plate 17, bushing 4 and housing bore 18 should be suflicient to accommodate the maximum amount of axial misalignment which is ordinarily encountered with a workpiece as when drilling and reaming holes in a workpiece on a turret lathe or other machine.

The driver 16, driver plate 17, and annular flange 37 of the bushing 4 are retained within the cylindrical housing 2 by a locknut 45 which is threaded onto the outer end of the housing 2 and may be secured in place by a setscrew 46 or the like. The bushing 4 extends through a central opening 47 in the locknut 45 with a sufficient clearance between the locknut opening 47 and the adjacent bushing surface 48 so as not to interfere with the desired lateral shifting of the bushing 4, and an O-ring 49 disposed in a groove in the locknut 45 engages the bushing surface 48 to guard against moisture and dust particles entering the interior of the housing 2.

Axial shifting of the

various parts

16, 17 and 4 within the housing 2 is prevented by a stress washer 50 and thrust bearing 51 inserted between the locknut 45 and bushing flange 37.

The floating holder 1 thus far described permits lateral shifting of the bushing 4 and tool 8 carried thereby to compensate within limits for any axial misalignment between the tool and a workpiece to be machined thereby.

As an example the shank 52 of the housing 2 may be mounted in a live spindle and the tool 8 may be a reamer or other such tool. In use, if there is slight misalignment between the tool and a hole in a stationary workpiece to be reamed thereby, the ball bearing assemblies 29 will permit substantially unrestricted shifting of the tool back and forth as the tool and holder are rotated to compensate for misalignment. Of course, the housing shank 52 may also be mounted at one of the stations of a turret lathe for reaming holes or the like in a workpiece drilled at another of the turret stations. In actual practice, when the turret head is indexed to bring the reamer into position for reaming the hole, there is usually a slight misalignment therebetween, whereby if the tool were not mounted for lateral shifting movement to compensate for the misalignment, the hole would be reamed out-of-round. However, with the floating holder 1 of the present application, the tool will shift radially in any direction to compensate for the misalignment.

Moreover, only a simple force of small magnitude acting on the end of the tool is required to effect such radial movement of the tool, rather than a high force couple, because of the bearings 30 and the keying of the housing 2, driver 16, driver plate 17, and bushing 4 together as described above in such a manner that the angular position of the tool is always the same; i.e., parallel to the axis of the cylindrical housing 2.

Another important feature of the floating holder 1 not yet mentioned is the spring centering mechanism 55 which is effective to center the tool in the housing 2 upon release of the lateral shifting force on the tool as when the tool is removed from a misaligned hole subsequent to the reaming operation while the tool is rotating at high or low speed or even stationary. This reduces to a minimum the amount of lateral shifting of the tool required to bring it into axial alignment with any workpiece, and is determined by the amount of misalignment between the holder and workpiece. Moreover, with the tool ordinarily held coaxial with the holder, such holder may be used in situations where no axial shifting is required.

Referring next to the details of the spring centering mechanism 55, such mechanism includes a plunger 56 disposed in a counterbore 57 in the reduced end portion 58 of the bushing 4 which extends through

central apertures

59 and 60 in the drive plate 17 and driver 16, respectively, with suflicient clearance between such end portion 58 and the walls of the

apertures

59, 60 so as not to interfere with the desired lateral shifting movement. Preferably, there is a ball sleeve 61 with a plurality of ball bearings 62 contained therein surrounding the plunger 56 for permitting ready axial sliding movement of the plunger 56 within the counterbore 57, and there is a compression spring 63 disposed in a recess 64 in the plunger 56 for maintaining the plunger in engagement with a ball bearing 66 located in a socket 67 in the back wall 19 of the housing 2. The end surface of the plunger 56 which engages the ball bearing 66 has a frusto-conical depression 68 formed therein, whereby when a lateral or transverse force is applied to the tool to cause the tool and bushing 4 to shift laterally, the plunger 56 also moves laterally a corresponding amount and in addition moves axially inwardly against the bias of the spring 63. Later on when the lateral shifting force is removed from the tool, the action of the compression spring 63 tending to return the plunger 56 to its original position causes the plunger and bushing 4 to be moved laterally in the reverse direction until the ball bearing 66 is once again properly seated within the depression 68 and the plunger and bushing are coaxial with the housing 2.

If desired, a backup screw 70 for the spring follower 71 may be threaded through the base 72 of the bushing 4 which when adjusted will vary the force applied by the spring 63 against the plunger 56.

While in the preferred form shown in FIG. 1 the spring centering mechanism 55 is carried by the bushing 4, such centering mechanism may just as easily be disposed in the cylindrical housing 2, as in the FIG. 4 embodiment wherein the plunger 56', ball sleeve 61 with ball bearings 62 therein, spring 63', and adjusting screw 70 are shown positioned in the shank portion 52, with the ball bearing 66 located in a socket 67' in the reduced end section 75 of the bushing 4. Otherwise the structure of the FIG. 4 embodiment is the same as the FIG. 1 embodiment and accordingly no further discussion is thought to be necessary.

From the above, it can now be seen that the device of the present invention is a full floating holder of a unique construction which permits lateral shifting of the tool carried thereby to compensate for any axial misalignment between the tool and a workpiece whether the tool be rotating or stationary. At the same time the angular disposition of the tool is maintained so as to reduce to a minimum the amount of force required to effect such lateral shifting. Moreover, such holder is provided with a unique spring centering mechanism for centering the tool within the tool holder housing while rotating at high or low speeds or stationary upon releasing of the lateral shifting force, whereby the amount of lateral shifting of the tool required to bring the same into axial alignment with a workpiece is reduced to a minimum, and the holder may be used in situations where no axial shifting is necessary.

Other modes of applying the principles of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

. We therefore, particularly point out and distinctly claim as our invention:

1. A floating holder comprising a housing having a cylindrical opening in one end, a bushing having means for tightly gripping a tool loosely disposed in said cylindrical opening, and means interconnecting said bushing and housing for permitting limited lateral shifting of said bushing within said housing to accommodate for axial misalignment between the tool and a workpiece, said means for permitting limited lateral shifting of said bushing as aforesaid comprising a driver plate disposed in said cylindrical opening inwardly of said bushing and having a slight diametral clearance with the wall of said cylindrical opening, a cylindrical driver having a close fit in said cylindrical opening and keyed to said housing inwardly of said driver plate, one of said driver plate and driver having a transverse slot therein and the other of said driver and driver plate having a projection extending into said transverse slot for permitting limited radial movement of said driver plate between diametrically opposed surfaces on the wall of said opening, a central transverse slot in one of said bushing and driver plate, and a central projection on the other of said bushing and driver plate extending into said slot for permitting limited radial movement of said bushing in a direction at an angle with respect to the direction of movement of said driver plate.

2. The floating holder of claim 1 further comprising bearing elements disposed between the adjacent surfaces of said slots and projections for permitting ready sliding movement therebetween, said bearing elements being contained in elongated U-shaped retainers with openings in the side walls through which said bearing elements project, the ends of said retainers being beveled to provide adequate clearance with said housing to permit such radial movements of said driver plate and bushing.

3. The floating holder of claim 1 further comprising a spring centering means interconnecting said housing and bushing for yieldably maintaining said bushing in coaxial alignment with said housing, said spring centering means comprising a plunger disposed in a recess in the inner end of said housing, said inner end of said bushing projecting through aligned openings in said driver and driver plate, bearing elements located between said plunger and the wall of said recess to permit ready axial sliding of said plunger in said recess, another bearing element disposed in a socket in said housing, the inner end of said plunger having a frusto-conical depression therein, and spring means between said bushing and plunger for maintaining the surface of said frusto-conical depression in engagement with said another bearing element.

4. A floating holder comprising a housing having a cylindrical opening in one end, a bushing having means for tightly gripping a tool loosely disposed in said cylindrical opening, means interconnecting said bushing and housing for permitting limited lateral shifting of said bushing within said housing to accommodate for axial misalignment between the tool and a workpiece, and spring centering means interconnecting said housing and bushing for yieldably maintaining said bushing in axial alignment with said housing, said spring centering means comprising a plunger disposed in a recess in the inner end of said bushing, bearing elements located between said plunger and the wall of said recess to permit ready axial sliding of said plunger in said recess, another bearing element disposed in a socket in said housing adjacent the inner end of said plunger, said inner end of said plunger having a frusto-conical depression therein, and spring means between said bushing and plunger for maintaining said inner end of said plunger in engagement with said another bearing element.

5. A floating holder comprising a housing having a cylindrical opening in one end, a bushing having a means for tightly gripping a tool loosely disposed in said cylindrical opening, means interconnecting said bushing and housing for permitting limited lateral shifting of said bushing within said housing to accommodate for axial misalignment between the tool and a workpiece, and spring centering means interconnecting said housing and bushing for yieldably maintaining said bushing in axial alignment with said housing, said spring centering means comprising a plunger disposed in a recess in said housing, bearingelements located between said plunger and the wall of said recess to permit ready axial sliding of said plunger in said recess, another bearing element disposed in a socket in the inner end of said bushing, the outer end of said plunger having a frusto-conical depression therein, and spring means between said housing and plunger for maintaining said outer end of said plunger in engagement with said another bearing element.

References Cited UNITED STATES PATENTS 1,027,520 5/1912 Blood 27916 1,377,663 5/1921 Brown et a1. 279-16 X 1,398,679 11/1921 Clark 276-16 1,424,535 8/1922 Watts 27916 1,818,622 8/1931 Hoeh 27916 2,460,210 1/1949 Barrett 279-16 2,475,386 7/1949 Frisco 2791'6 2,826,053 3/1958 Munn 279-16 X ROBERT C. RIORDON, Primary Examiner.

J. C. PETERS, Assistant Examiner.