US2892353A

US2892353A - Drive mechanism for power driven tool

Info

Publication number: US2892353A
Application number: US547173A
Authority: US
Inventors: Russell P Harshberger
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-11-16
Filing date: 1955-11-16
Publication date: 1959-06-30
Anticipated expiration: 1976-06-30

Description

R. P. HARSHBERGER 2,892,353 DRIVE MECHANISM FOR POWER DRIVEN TOOL June 30, 1959 Filed Nov. 16, 1955 r f 1 e m My h a b m s 17 w w w v 1 2 a a a 1 2% If 11 e A f MW 4 Q ww 3 m w RW/ e 0 I ma 4 z b. L a 0 o (W-R 2A flwfix a w a m June 30, 1959 R. P. HARSHBERGER DRIVE MECHANISM FOR POWER DRIVEN TOOL Filed Nov. 16, 1955 F -E g- 2 Sheets-Sheet 2 United States Patent DRIVE MECHANISM FOR POWER DRIVEN TOOL Russell P. Harshberger, Altadena, Calif.

Application November 16, 1955, Serial No. 547,173

9 Claims. (Cl. 74-61) This invention relates generally to a power driven tool construction, and more specifically it relates to a tool bit holder for generating gyratory motion of substantial vol time and amplitude and applying the motion generated to a tool bit.

In carrying out different wood or metal working operations with different tools, motion other than simple rotary motion may be required. For example, in cutting wood or metal with a saw blade, reciprocatory or oscillatory motion is required and power tools designed to provide such motion are well known. Another well known power tool provides a succession of rotary impacts for driving a star drill, or a tap, this tool being commonly known as an impact tool. Generally, only one form of motion is produced by any one power tool, whether it be reciprocatory to operate a saw blade, or a twist motion to operate a star drill or tap. Furthermore, motion other than simple rotary motion may be required to actuate a sifting device to separate granular materials, or for a mixing device for mixing fluids, operations other than wood or metal working. Again, only one form of motion is normally obtainable from a mechanism designed for operating one or another of these devices.

It is an object of the present invention to provide a power dn'ven tool for furnishing various forms of gyratory motion for operating different tools which are capable of performing different wood or metal working operations, or for operating different attachments requiring different forms of gyratory motion in order for the attachment to work satisfactorily.

It is another object to provide a power driven tool which is simple in construction and which furnishes gyratory motion of sufiicient force and amplitude to perform the operations rapidly and efiiciently.

It is further an object to provide the aforesaid by means of a tool bit holder, which may be made as an adaptor or built into a power tool, having a plurality of eccentric weights driven in unison directly by the spindle of a motor and which may be actuated through a yieldable connection employed to interrupt the transmission of gyrations to the motor spindle so that the motor is not subjected to the gyrations produced by the mechanism and imparted to the tool bit.

The objects of the invention generally set forth together with other objects and ancillary advantages are obtained by the construction and arrangement shown by way of illustration in the accompanying drawings, in which:

Figure l is a vertical section of a tool bit holder embodying the features of the present invention;

Fig. 2 is a vertical section taken approximately on the center line and looking toward the left in Fig. 1;

Fig. 3 is an enlarged fragmentary detail view of the connection between one of the gyration producing elements of the tool bit holder illustrated in Fig. 1 and the means for driving the element; I

Figs. 4 through 8 are diagrammatic views of different illustrative embodiment but it is to be understood that it is not thereby intended to limit the invention to the specific form disclosed, and it is intended to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention as expressed in the claims.

Referring more particularly to the drawings, there is shown in Figs. 1 and 2 a power driven tool shown in the present instance as a tool bit holder adapted to be connected to the spindle of a power drill or the like. In general this illustrative tool bit holder includes a shell or housing 10 having a shaft 11 rotatably mounted therein, and providing a member upon which a tool bit may be fastened. The tool bit may be a star drill, tap, saw blade, chisel or any other device, tool or attachment depending on the operation to be performed, the characte'ristic thereof being that one or another form of gyratory motion may be applied to operate the device in a satisfactory manner. For convenience the terms tool and tool bit will be used as generic expressions to describe the aforementioned various devices and others of the same general character and it is intended that the term be construed as broadly as defined herein. To facilitate fastening the bit on the tool bit holder a ball detent 12 is provided in the shank of the member 11 for securing the bit in place.

The exemplary tool bit holder has a rotatable spindle 13 axially aligned with the shaft 11 and extending from the upper end of the housing 10, which is adapted to be received in a chuck 14 fastened on the spindle of a power drill or the like or which may be connected in any other manner, as will be apparent, to the power drill spindle to provide a source of power for driving the tool bit holder.

The illustrative tool incorporates an improved construction and arrangement of components to generate gyratory motion of substantial volume and amplitude for operating a tool bit. Thus, transversely disposed within the housing 10, is a shaft 16 having mounted thereon for revolution about the shaft axis axially spaced

eccentric weights

17, 18 which are rotatable in unison by the shaft, to generate gyrations for application to the tool bit. For mounting the shaft 16 for rotation within the housing 19, there is provided a gear frame 19 disposed along the vertical longitudinal axis of the housing 10 and rigidly mounted therein by means of a

ring

20, 21 at the upper and lower ends of the gear frame 19, respectively, the ring in turn being connected by means of spot welds or rivets to the housing. The lower end of the gear frame 19 is provided with an axial bore in which the tool bit member or shaft 11 fits snugly, preferably with a press fit, the shaft 11 thus receiving gyrations produced by the revolution of

weights

17, 18 and which are transmitted directly to thetool bit.

As can be seen in Fig. 1, the shaft 16 is journaled in the gear frame 19 by means of

bushings

22, 23 and turns freely within the housing 10. To rotate the shaft 16 and thus the

weights

17, 18, a drive is provided connecting the spindle 13 in driving relation with the shaft 16. In the present instance, the drive comprises a driving member or shaft 24 arranged longitudinally of the vertical axis of the housing 10 and journaled for rotation within the horizontal cross member 25 of the gear frame 19 connecting the

vertical yoke members

26, 27 of the gear frame in which shaft 16 is journaled for rotation. The extreme lower end of the driving member or shaft Patented June 30, 1959 24 extends below the cross member 25 to receive a bevel gear 28 which meshes with a similar bevel gear 29 coaxial and rigid with the shaft 16. Thus the driving member or shaft 24 is operatively connected at all times to drive the shaft 16 and rotatethe

weights

17, 18 mounted thereon. Although a one to one drive ratio between the

bevel gears

28, 29 is employed in this instance, the drive ratio may be varied as desired, depending on the form of gyration required and the speed available from the driving motor.

. In the preferred form of the invention, the drive member 24 is connected for rotation by spindle 13 through a resilient coupling which comprises a helical coil spring 30 anchored at its upper end to the enlarged head 31 on spindle 13, and anchored at its lower end to an enlarged head 32 formed on the upper end of shaft 24 to receive the spring and also serving to prevent the shaft 24 from dropping through the bore in the cross member 25 of the gear frame. To facilitate anchoring the spring in place on these two members, the enlarged head on the spindle 13 is provided with a spiral groove for wrapping or winding the end of the spring 30 about and in intimate contact with the head of the spindle. Likewise the enlarged head of driving member 24 is also provided with a spiral groove in order that the lower end of the spring may be wound in intimate engagement with the driving member 24. Normal clockwise rotation of the spindle 13 by the drill motor chucked thereto causes the spring to wind up and grip more tightly the heads on both the spindle and the driving member. The spring thus is wound as a right hand helix for operation of the mechanism in a clockwise direction, and is bent at its very extremities in a right angle turn, the end portions 30a, 30b, anchored in radial drilled holes 24a, 31a, provided in the driving member 24 and spindle 31 respectively.

This resilient or yieldable connection is employed between the spindle adapted to be connected to the drill powering the tool bit holder, and the driving member 'operatively coupled to the shaft on which the eccentric weights are mounted, to interrupt the transmission of gyrations generated by the revolving weights, to the spindle 13 and thus to the power drill or the like used to power the mechanism. To maintain the spindle 13 and driving member 24 substantially in axial alignment, required because of the resilient connection therebetween, the gear frame 19 is provided with a vertically extending sleeve fastened by means of the flanges 20 to the shell or housing and enclosing the ends of the spindle, the

driving member, and the spring. A predetermined and limited amount of transverse play is permitted between the spindle 13 and the driving member 24, however the sleeve 33 prevents substantial mis-alignment.

The sleeve 33 also serves as a support for a handle 35 adapted to be gripped by the operator to hold the tool bit holder against the torque applied to the spindle 13 from the drill motor. Thus, the sleeve 33 projects above the top of the shell or housing 10 containing the mechanism for generating gyratory motion, to receive the handle 35 whichcomprises a grip portion 36 and an elongated arm provided adjacent the free end thereof with an opening 37 conforming substantially to the outer diameter of the sleeve 33 and receiving the sleeve therein.

In this instance, the handle 35 is mounted for rotary adjustment thereof either in a right hand or left hand direction and may be locked by means of the pawl 38 in various positions with respect to the housing 10, the

pawl 38 being slidably supported on a pin 39 carried in a slot 39a in the handle, and engageable with teeth 40 on an annular member 41 carried on the upper end of the sleeve 33.

In the illustrative form of the invention, the shell 10 is also provided with an eyelet 43 threaded therein, to

provide means for fastening a cable or linkage. securely fastened at its other end, to the tool bit holder torestrain the torque of the motor. The revolving

weights

17, 18

' are of substantial mass and serve to impart gyratory motion to the housing 10 of the tool bit holder and to the tool bit. The form of the gyratory motion generated by the revolving weights is subject to control by adjusting the angular phase relation between the

weights

17 and 18 and means for adjusting the angular phase relation of the weights is included as a feature of this invention, and will be hereinafter described. With the weights offset 180 as shown in Fig. 1, the vertical component of gyration is substantially neutralized. Intermediate positions of relative phase adjustment between this angular relation of the weights and the arrangement where the weights are disposed on the same side of the shaft axis, and producing maximum gyration, results in proportional variations in the vertical component of gyration.

For example, referring to Fig. 6, a diagrammatic illustration of the form of motion produced with the weights positioned offset 180 is there shown where the vertical component of gyration is substantially neutralized producing back and forth oscillatory gyrations which might be applied to a brush 45 for washing.

The gyratory motion produced wth the weights disposed on the same side of the shaft axis is diagrammatically illustrated in Figs. 4, 5 and 8, applied to

chisels

46, 47 in Figs. 4 and 5 respectively, and to a saw blade 48 in Fig. 8. With the arrangement of the weights on the same side of the shaft axis, although it is difiicult specifically to define the exact form of motion produced it appears that gyration vertically in a generally circular orbit is obtained. This form of gyratory motion applied to a chisel 46 as shown in Fig. 4, where the edge of the chisel is disposed substantially parallel with the axis of the shaft supporting the weights, causes the head of the tool to follow a rocking motion with a sidewise or transverse reciprocatory component causing the edge of the chisel to scrape the surface of the work against which the tool bit is held.

With the edge of the chisel disposed transversely to the axis of the shaft supporting the weights, as shown in Fig. 5, a rocking motion is imparted to the head of the tool with a reciprocatory component acting substantially parallel with the edge of the blade of the chisel. Thus the chisel would rock and also would nibble along the surface of the work against which the chisel is held.

To provide motion to operate a saw blade 48, shown in Fig. 8, the blade of the saw should be arranged substantially in a plane perpendicular to the plane formed by the axis of the shaft carrying the weights and the axis of the tool bit holder itself, where the weights are illustrated in angular position to produce oscillatory motion in a generally circulatory orbit enabling the teeth of the saw to bite into the wood or metal on the forward stroke and clear on a return stroke of the saw blade, the reciprocatory component of the motion always tending to further penetrate the teeth of the saw blade into the work.

An intermediate angular relation between the eccentric weights carried by the shaft, is shown in Fig. 7, where the weights are positioned out of phase with respect to each other. The motion produced by the tool bit holder with the weights so arranged may be described as having longitudinal and transverse components, the tool bit head following generally orbital paths in both a longitudinal and a transverse direction. The motion produced would be useful in operating a tool bit such as a star drill for cement or the like. A star drill is shown as 49 in Fig. 7, and with the weights positioned as shown in Fig. 7 is twisted in an oscillatory fashion and also is gyrated vertically tending to penetrate the star drill further into the work as the operation is continued.

In the present preferred embodiment of the invention, to adjust the weights to various angular positions, weight 17 is made rigidly and permanently fixed to the shaft 16 by means of a cross pin extending through the weight and shaft and pressed into place.

The weight 18 on the other end of the shaft 16, however, is angularly adjustable relative thereto, and to enable such angular adjustment a clutch is provided for dis engaging the weight 18 from the shaft 16, Comprised in the preferred form shown, of toothed driving and driven members 50, 51 fastened on the shaft 16 and the weight 18. respectively. The driving member 50 of the clutch comprises a collar or sleeve 52 splined on the shaft 16 to prevent relative rotary movement thereof and to permit relative axial movement thereof, and having teeth 53 on the inner end of the collar adapted to interengage with teeth 54 formed on the driven member 51 of the clutch. As shown, the driven member 51 of the clutch is formed by a bushing 55 fixed within a bore in the weight 18 sufiicient in size to accommodate the bushing which is provided with an annular flange supporting the teeth 54 of the driven member of the clutch assembly. As shown in Fig. 3, the collar 52 supporting the teeth of the driving member of the clutch assembly may be moved axially to withdraw the teeth thereon out of engagement with the teeth on the driven member 51, against the action of a spiral compression spring 56 bearing against shoulder 57 formed on the collar and the inside wall of the housing and normally biasing the driving and driven members of the clutch assembly together. The spline connection between the collar 52 of the driving member 50 and the shaft 16 is formed by a cross pin 58 disposed, when the driving member is in position to engage the clutch, at the bottom of a slot 59 formed in the end of the shaft 16. When the clutch assembly is disengaged, the weight 18 is freely rotatable about shaft 16, being journaled thereon by the bushing 55 pressed into .place in the weight.

Thus, normally the clutch comprised of the driving and driven members 50, 51 respectively, is operable to connect in driving relation the shaft 16 and the eccentric weight 18 through the spline connection consisting of the cross pin 58 connected to the collar 52 and lying in the slot 59 extending axially of and substantially bisecting the shaft 16. In the present instance, the collar 52 is relatively movable axially with regard to the shaft 16 and to enable such movement manually the collar extends outward of the housing 10 and may be grasped between the thumb and forefinger and pulled outwardly to separate the driving and driven interengaging teeth on the face of the driving and driven members 50, 51 respectively. The collar 52 is so arranged that it may be pulled outwardly with consequent removal of the pin 58 from the slot 59 allowing the collar 52 to be then rotated with "respect 'to th'e shaft 16. For convenience, "a shallow groove 60 is formed in the end of the shaft 16 adjacent the slot '59 to receive the pin 58 when the collar has been thus rotated, the groove 60 in the preferred embodiment of the invention illustrated being arranged at substantially 90 to the slot 59. The position of the members with the pin 58 in the groove 60 is shown in Fig. 3 and it will be observed that with the parts arranged as shown, the teeth on the driving and driven members 50, 51 respectively of the clutch assembly are out 'of engagement. When so stationed, the driving member 50 of the clutch assembly rotates with the shaft 16, the fixed rotary relation being established by the transverse groove 60 in the end of the shaft and the cross pin 58 located therein.

As described hereinbefore, normally gyratory motion for driving the tool bit is produced by rotating the

eccentric weights

17, 18 in unison, the angular phase relation of the said weights being adjustable to produce gyratory motion with different've'rtical and horizontal components, in order to provide motion for operating dilferent tool bits for performing different operations. Thus a feature of this invention is that the mechanism is adapted to produce gyratory motion preferably through the joint drive of axially spaced and 'angularly offset eccentric Weights.

The mechanism in the present instance, however, is also adapted to produce gyratory motion by the drive of 'a single eccentric weight, the second weight of the assembly being then disposed in idle relation with regard to the rotating assembly. Such an arrangement is shown in Fig. 3, where power applied to the driving spindle results only in rotation of the single weight 17 which is fixed to the shaft 16.

In order to adjust the weights angularly with respect to each other, and provide a gyratory motion for a particular tool bit the result of the joint drive of the eccentrically disposed Weights, the clutch assembly is first operated to disengage the weight 18 from driving relation with the shaft 16 by pulling the collar 52 toward the right in Fig. 1. Due to the weight 18 being freely rotatable, the weight 18 then drops below the shaft 16 to the position shown in Fig. 3. The weight 17, then, by manual rotation of the chuck 14 or the shank 13 of the spindle extending from the upper side of the tool bit holder, can be rotated to any angular position relative to the weight 18. The clutch may then be re-engaged. Thus the

weights

17, 18 may be disposed in a particular angular relation with respect to each other.

Since the weight 17 is not visible from the outside of the housing 10, a means is provided to give an outward indication of the angular position of the weight 17. In the present instance, the cross slot 59 in the shaft 16 gives such a visible indication of the position of the weight 17. For example, as shown in Fig. 1, when the weight 17 is in a vertical position, the slot 59 is horizontally disposed, and thus to position weight 17 in a vertical position, the spindle 13 is rotated until the slot 59 is located horizontally. In the arrangement shown, it is noted that the weight 17 may be in either of two vertical positions when the slot 59 is located horizontally, either in the position shown in Fig. l where the weight 17 is located above the shaft 16, or in the position with the weight 17 located therefrom. Due to the unbalance of the weight 17, the difference in position is always manifested in the tendency of the weight to rotate to the lower position, which may be felt by rotating the spindle 13 or chuck 14 by hand.

Although the invention in its present form uses @e cross slot 59 to indicate the position of weight 17, it is intended that other obvious modifications could be effected to give a clear indication of the position of weight 17, for example, on the outside of the housing and surrounding the collar 52 with an arrow or pointer on the shaft 16, either inscribed thereon or fastened thereto, so as to give a positive outward indication of the position of the weight.

To select different angular relations of the

weights

17, 18 first the clutch is disengaged by pulling the collar 52 outwardly, and then the weight 17 positioned as desired with respect to the then suspended weight 18. The weights may be positioned, as shown in Figs. 4 through 7 in dilferent angular relations.

It is also clear from the above description that the weight 18 may be disposed in idle relation with respect to the shaft 16, so that in place of joint drive of the two weights axially spaced and in angular phase relation with respect to each other, only a single weight may be driven to produce the gyratory motion for driving the tool bit.

In Figs. 4 through 7 various positions of the weights to obtain various forms of gyratory motion are diagrammatically illustrated. By positioning the weights in other angular phase relations than shown, dilferent forms of gyratory motion may be produced, with slightly different vertical or horizontal components of gyration. Such forms of gy'ratory motion may be useful in operating different tools or work-producing devices than those illustrated and it is not intended that the invention be limited to the specific examples illustrated.

A one to one drive ratio between the bevel gears 28, 29 is used in the illustrative form of the invention, although as noted hereinbefore, this may be varied as desired, to obtain forms of gyratory motion of different frequency and amplitude. For general application, it has been found that a rotational speed of approximately 1000 r.p.m. for the weights has proven satisfactory. Thus the drive ratio for the bevel gears may be selected in relation to the speed of the driving motor available for operating the tool bit holder and the particular application intended for the tool bit holder.

It will be apparent from the foregoing that a tool bit holder made in accordance with the present invention is capable of providing different forms of gyratory motion for operating diverse tool bits. The relatively simple character and construction of the apparatus permits of trouble free operation, long life, and economical manufacture.

I claim:

1. In a power driven tool construction, a tool bit holder having a' transversely disposed rotatable shaft, a first eccentric weight rigidly supported on said shaft, a second eccentric weight axially spaced from said first weight on said shaft and normally supported in driving engagement with said shaft, drive means for rotating said shaft, a driving spindle, a yieldable drive connection between said driving spindle and said drive means to transmit rotary movement therebetween and to interrupt the transmission of gyrations to the spindle, and means for selectively disengaging said second weight from driving engagement with said shaft to permit rotative movement of said shaft relative to said second weight for changing the angular phase relation of the eccentric weights so as to alter the characteristics of the gyratory motion produced by rotation of the eccentric weights for operating tool bits of different types.

2. In a power driven tool construction, a tool bit holder having a hollow housing, a shaft support fixedly mounted inside the housing, a transverse shaft rotatably mounted on said support in said housing, axially spaced eccentric weights mounted for rotation in unison by said shaft to generate gyratory motion transmitted to said shaft support and housing, means for mounting a tool bit on said housing so as to receive said gyratory motion, a longitudinal driving spindle mounted in said housing, a longitudinal drive member arranged coaxially of said driving spindle and connected in drive relation with said shaft, and a yieldable drive connection between said driving spindle and said driving member to transmit rotary movement therebetween and to interrupt the transmission of gyrations to said spindle. r

3. In a power driven tool construction, a tool bit holder having a housing, a transverse shaft rotatably journaled in said housing, an eccentric weight supported on said shaft for rotation, a second eccentric weight axially spaced from said first weight on said shaft and supported normally in driving engagement with said shaft, means for disengaging said second weight from driving engagement with said shaft, to provide for rotative movement of said shaft relative to said second weight for changing the angular phase relation of the eccentric weights a longitudinal driving spindle mounted in said housing, a drive member for said shaft mounted for rotation about an axis extending longitudinally of said driving spindle and connected for drive with said driving spindle, and means for fastening a tool bit on said housing.

4. In a power driven tool construction, a tool bit holder having a housing,'a transverse shaft rotatably journaled in said housing, an eccentric weight supported on said shaft for rotation, a second eccentric weight axially spacedfrorn said first weight on said shaft and supported normally in driving engagement with said shaft for rotation in unison with said first weight to generate gyratory motion for operating a tool bit, means for disengaging said second weight from driving engagement with said shaft to provide for adjustment of the angular phase relation thereof relative to said shaft and said first eccentric weight, a longitudinal driving spindle mounted in said housing, a drive member for said shaft mounted for rotation about an axis extending longitudinally of said driving spindle and connected for drive with said driving spindle, and means for fastening a tool bit on said housing.

5. In a power driven tool construction, a tool bit holder having a housing, a transverse shaft rotatably journaled in said housing, a plurality of eccentric weights axially spaced on said shaft and supported for rgtation to generate gyratory motion for operating a tool bit, means for disengaging one of said weights from driving relation with said shaft to provide for adjustment of the angular phase relation thereof relative to said shaft, said means extending outwardly of said housing to permit manual operation thereof, a driving spindle rotatably mounted in said housing, a drive member for said shaft connected for drive with said driving spindle, and means for fastening a tool bit on said housing.

6. In a power driven tool construction, a tool bit holder having a housing, a transverse shaft rotatably journaled in said housing, a plurality of eccentric weights axially spaced on said shaft and supported for rotation in unison to generate gyratory motion for operating a tool bit, means for disengaging one of said weights from driving relation with said shaft to provide for adjustment of the angular phase relation thereof relative to said shaft, a longitudinal driving spindle rotatably mounted in said housing, a drive member for said shaft mounted for rotation about an axis extending longitudinally of said driving spindle, and a helical spring wrapped around said driving spindle and said driving member forming a yieldable drive connection therebetween to transmit rotary movement and to interrupt the transmission of gyrations to the driving spindle.

7. In a power driven tool, the combination comprising, a housing, means for fixedly securing a tool bit on the housing, and means in said housing for generating gyratory motion and for transmitting said motion to the housing and the tool bit including a pair of spaced eccentric weights mounted in the housing for rotation about a common axis, a driving spindle adapted to be rotated by a separate power source, and a drive connection between said driving spindle and said eccentric weights for operating the latter including a yieldable element for isolating the driving spindle so as to interrupt the transmission of gyrations to the spindle.

8. In a power driven tool, the combination comprising, a housing, means for fixedly securing a tool bit on the housing, and means in said housing for generating gyratory motion and for transmitting said motion to the housing and the tool bit including a shaft support fixed to the housing and arranged in longitudinal alinement with the tool bit, a pair of spaced eccentric weights mounted in the housing for rotation about an axis transverse to the shaft support and tool bit, each weight being mounted on a shaft section carried for rotation by said shaft support and arranged on a common axis transverse to the shaft support, a driving spindle alined with the shaft support and tool bit and adapted to be rotated by a separate power source, and means connecting said driving spindle to said shaft sections for rotating the latter including a yieldable element for isolating the driving spindle so as to interrupt the transmission of gyrations to the spindle.

9. In an adaptor for a power tool, for generating gyratory motion and applying the motion to a tool bit, the combination comprising, a tool bit holder having means for securing a tool bit thereon, a driving spindle supported by said tool bit holder in alinement with the tool bit and adapted to be driven by the power tool, and motion generating means supported by said tool bit holder and operated by said driving spindle for generating gyra- 2,892,353 9 10 tory motion, said motion generating means including a duced by rotation of the eccentric weights for operating pair of spaced eccentric weights, each weight being i001 bits of different YP mounted on a shaft section carried by said tool bit holder transverse to the driving the spindle, means connecting References Cited In the file of thls Pawnt said driving spindle to said shaft sections for rotating the 5 UNITED STATES PATENTS latter, and clutch means whereby the phase relation be- 1 55 332 pederson et 1 1 1926 tween said eccentric weights may be selectively changed 1,779,923 Wagner Oct 28, 1930 to alter the characteristics of the gyratory motion pro- 2,350,921 Pinazza June 6, 1934