US3388548A - Rotating and reciprocating tool arrangement - Google Patents

Description

June 18, 1968 A. H. VIETHS 3,388,548

ROTATING AND RECIPROCATING TOOL ARRANGEMENT Filed Aug. 2' 1966 3 Sheets-Sheet 1 W1TCHE$ 22 8 HVDRAUUC 6 MOTOR y NDER 12 3 -11% TA PMNG 2O 2 HEAD NON m ROTATiNC:

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ALMAN H. VIETHS 515 I. AWOR/VEY June 18, 1968 A. H. VlETHS 3,3

ROTATING AND RECIPROCATING TOOL ARRANGEMENT Filed Aug. 2, 1966 3 Sheets-Sheet 3 L7 4 x22 I 6 I I no IQ I&

INVENTOR ALHAN H. VIETHS United States Patent ABSTRACT OF THE DISCLOSURE There is disclosed herein an improve rotating and reciprocating tool arrangement for providing a substantially constant axial force and substantially constant axial feed. This is achieved in applicants invention herein by providing a rotating shaft splined to a motor such as an electric motor that provides the rotary motion to the shaft. The spline connection allows reciprocating movement of the shaft with respect to the motor. At least a portion of the rotating shaft extends into a hydraulic cylinder and a hydraulic pump means is coupled to the rotating shaft within the cylinder. The pump means provides the axial movement for the rotating shaft and a tool bit is coupled to one end of the rotating shaft so that rotation of the shaft by the motor means rotates the tool bit and also rotates the pump means within the hydraulic cylinder. Rotation of the pump means within the hydraulic cylinder moves hydraulic fluid from one face of the piston to the other, depending upon the direction of rotation, and this movement of the fluid provides a pressure differential across the piston to move the rotating shaft in axial directions.

This invention relates to the tool art and more particularly to an improved rotating tool arrangement that is also adapted to move reciprocatingly in preselected directions during rotation thereof.

In its more specific aspects, the present invention relates to a tool arrangement such as a thread tapping tool in which the tapping tool is rotated by one source of power, for instance that furnished by an electric motor, and is simultaneously advanced and retracted by another source of power, for instance fluid power.

In many applications, such as the above-mentioned thread tapping, it is necessary that there be provided an arrangement for not only rotating the tapping head, but for moving the tapping head forward with a predetermined and controlled force. The controlled force is necessary because of the nature of the tapping operation. However, it will be appreciated, that many other appications, such as drilling, also find it advantageous to have a predetermined force applied in axial directions during the rotational movement of the tool.

Further, in tapping operations, as well as in drilling operations, and in other tool operations, it is desirable to have a predetermined feed. That is, the axial movement of the tool per revolution thereof must be accurately controlled. In addition, for versatility, the feed should preferably be variable in order that different feeds may be provided in the same basic tool setup without removing the tapping tool from a predetermined location.

To the best of applicants knowledge, the prior arrangements utilized for such tool arrangements have not been able to provide all of the above desiderata. For example, in many applications, the feed is to some extent dependent upon the axial force provided and the axial force provided for feed movement is not maintained substantially constant. Further, in other arrangements, the entire means for rotating the tool is often moved in axial directions with the tool itself, thereby increasing the weight of axially moved equipment. The increased weight, of course, tends Patented June 18, 1968 to' prevent more precise feed and force relationships for axial movement.

Accordingly, it is an object of applicants invention to provide an improved tool arrangement.

It is another object of applicants invention herein to provide a tool arrangement that may be simultaneously rotated and moved in axial directions.

It is yet another object of applicants invention herein to provide such a tool arrangement in which the rate of axial movement per revolution of the tool is accurately controlled.

It is yet another object of applicants invention herein to provide such a tool arrangement in which the axial feed force is maintained substantially constant.

It is yet a further object of applicants invention herein to provide a rotating and axially movable tool arrangement in which the feed may be changed for varying feed requirements.

The above and other objects are achieved, according to applicants invention herein, in a preferred embodiment thereof, by providing an electric variable speed reversible motor as the means for rotating a shaft. This rotating shaft is splined to the motor and therefore rotates with the motor as well as being able to move reciprocatingly with respect to the motor in axial directions of the rotating shaft. In this embodiment of applicants invention, a first end of the rotating shaft is on one side of the motor and a tool bit, such as a thread tapping tool, may be coupled to the first end of the rotating shaft. The second end of the rotating shaft, which in this embodiment of applicants invention, is on the remote side of the electric motor, is positioned in a fluid cylinder such as, for example, a hydraulic cylinder. The hydraulic cylinder is filled with hydraulic fluid and a piston arrangement is coupled to the second end of the rotating shaft inside the hydraulic cylinder.

The piston arrangement comprises a forward or first face and a rear or second face in spaced apart relationship. An outer race, with a bore eccentric to the axis of the rotating shaft is coupled to the first and second faces of the piston along peripheral edges thereof and is in sliding contact with the inside walls of the hydraulic cylinder. The rotating shaft is journaled in the forward or first end face of the piston and detachably coupled to the rotating shaft intermediate the first and second end faces of the piston and rotating with the eccentrically bored outer race, there is provided a vane-type pump.

Inlet and outlet ports are appropriately provided in the end caps to allow passage of hydraulic fluid from one side of the piston to the other within the cylinder. The outer peripheral surfaces of the first and second end caps and the outer race are in sliding sealing engagement with the interior Walls of the hydraulic cylinder.

Rotation of the rotating shaft rotates the vane pump in the outer race and consequently pumps hydraulic fluid from one side of the piston to the other. The increase in pressure on the second side of the piston, that is the side to which the hydraulic fluid is pumped, moves the piston and consequently the entire rotating shaft and tool in axial directions and at a substantially constant force. Further, because of the displacement nature of the vane-type pump, which is preferred in applicants arrangements, the rate at which the rotating shaft and tool advances in axial directions for a given number of rotations thereof is predetermined, constant and well known. Therefore, a very accurate feed is maintained on the tool.

In order to avoid overheating of the hydraulic fluid, applicant provides spring loaded relief ports on the piston so that when the piston approaches within a predetermined distance of the inwalls of the hydraulic cylinder, the relief ports are automatically opened and substantially equal pressure is maintained on both sides of the piston. Thus,

forward motion of the tool is stopped when this condition arises. The motor may be reversed and, because of the nature of a vane type hydraulic pump, the direction of the axis of the rotating shaft in which the rotating shaft and tool moves is also reversed and the tool is thus retracted until the piston approaches the opposite end wall of the hydraulic cylinder. A similar relief valve may be provided to stop this motion when the piston approaches within a predetermined distance of the opposite end wall of the hydraulic cylinder. In the retracted position, applicant provides, in the preferred embodiment of this invention, a by-pass port that opens additional flow passages around the piston so that temperature buildup in the retracted position, which may extend for a considerable length of time as the work piece upon which the tool operates is changed, is minimized. However, if additional cooling is required, a conventional fluid cooling jacket, together with a pump and sump, may be provided around the cylinder to remove excess heat.

In other embodiments of applicants invention, a nonrotating shaft is coupled to the second or rear face of the piston and extends through the rear wall of the hydraulic cylinder. The non-rotating shaft is keyed to the cylinder and thus prevents rotation of the piston during operation. If desired, a control means may be coupled to the external portion of the non-rotating shaft to operate a switch means for reversing the motor so that after a given axial travel, less than the total allowable by the length of the hydraulic cylinder, the motor is automatically reversed and the tool may be advanced and retracted automatically within the limit set by the control switches.

Since the motor is only splined to the rotating shaft, it will be appreciated that the motor remains fixed with respect to axial movements of the rotating shaft.

The above and other embodiments of applicants invention are more clearly understood from the following detailed description taken together with the accompanying drawings wherein similar reference characters refer to similar elements throughout and in which:

FIGURE 1 is a block diagram of one embodiment of applicants invention;

FIGURE 2 is a block diagram of another embodiment of applicants invention;

FIGURE 3 is an illustration, partially in section, of the embodiment of applicants invention shown in FIGURE 1;

FIGURE 4 is a view along the line 4-4 of FIGURE 3;

FIGURE 5 is a sectional view along the line 55 of FIGURE 3;

FIGURES 6, 7 and 8 illustrate other features of applicants invention as illustrated in FIGURE 3.

Before detailing the description of applicants invention, applicant wishes to point out that applicant has selected for illustration herein utilization of his invention in a tapping tool arrangement. However, it will be appreciated that applicants invention is not so limited and consequently maybe utilized with efiicacy in any rotating tool operation in which constant feed rates and/or constant feed forces are required. Further, it will be appreciated, that the various structural details and variations thereof illustrated for the different embodiments of applicants invention may, if desired, be equally well utilized in other embodiments of applicants invention. That is, such variations and modifications may be used interchangeably as the structure permits.

Referring now to FIGURE 1, there is shown one embodiment of applicants improved tool arrangement, generally designated 10, in block diagram form. As shown in FIGURE 1, there is provided a tapping head 12 which is coupled to a first end 14 of a rotating shaft 16. The rotating shaft 16 passes through and is splined to a motor means 18. The motor means 18 may, for example, be an electrically driven variable speed reversible motor and the spline connection allows the reciprocating motion of the rotating shaft 16, in axial directions as indicated by the arrow 20 during the rotation thereof by the motor means 18 as indicated by the arrow 22. Thus, the rotating shaft 16 may be moved both in axial directions for linear motion and simultaneously rotated about its axis.

The rotating shaft 16 extends into a hydraulic cylinder 24 and the second end 26 of the rotating shaft 16 is posi tioned therein.

A non-rotating shaft 28 that moves in axial directions as indicated by the arrow 20 with the rotating shaft 16, but does not rotate, protrudes from the opposite side of the hydraulic cylinder and has a control means 30 coupled thereto. The control means 30 is adapted, for predetermined axial movements thereof, to engage switches 32 which control the motor means 18. Thus, for example, the switches 32 may alternately reverse the direction of rotation of the motor means 18 or start and stop the motor means 18 or any desired combination thereof.

As shown on FIGURE 1, both the hydraulic cylinder 24 and the motor means 18 are fixed with respect to the movement of the rotating shaft 16 and tapping head 12. The tapping head 12 is adapted to engage a work piece 34 to provide, for example, a threaded hole therein. It will be appreciated that the hydraulic cylinder 24 is essentially a fluid cylinder and full of a fluid means which, in this embodiment of applicants invention may comprise hydraulic fluid.

In another embodiment of applicants invention, illustrated in block diagram on FIGURE 2 and generally designated 40, there is shown a slightly diiferent arrangement of applicants invention. As shown on FIGURE 2, there is a tapping head 42 which, for example, may

be similar to the tapping head 12 coupled to a first end 44 of a rotating shaft 46. The rotating shaft 46 extends through a hydraulic cylinder 48 and has a second end 50 splined to a motor means 52. The motor means 52 may be similar to the motor means 18 described above, and, for example, may be an electrically powered variable speed. reversible motor. In this embodiment of applicants invention, the rotating shaft 46 and the tapping head 42 are adapted to move in axial directions as indicated by the arrow 54 simultaneously with rotation thereof about the axis of the rotating shaft 46 as indicated by the arrow 56. The motor means 52, as does the motor means 18 for the embodiment shown on FIG- URE 1, provides the rotational motion to the rotating shafts 46 and .16, respectively, and, as described below in greater detail, the rotation of the rotating shafts provides the axial movement desired.

A control means 58 is also shown on the rotating shaft 46 and is adapted to engage, alternately, switches 60 after predetermined axial motions of the rotating shaft 46. The switches 60 may be similar to the switches 32 shown on FIGURE 1 and similarly control the electric motor to reverse the direction of rotation thereof, start or stop or the like.

As noted above, it is desired that the axial motion of the rotating shaft of applicants improved tool arrangement be with a substantially constant feed for a given setting and also be with a substantially constant force. Applicant achieves these desidera-ta by providing a piston coupled to the rotating shaft and positioned within the hydraulic cylinder and the piston comprises, in part, a hydraulic pump means, which, in the preferred embodiment of applicants invention, is a vane-type pump.

As shown on FIGURE 3, which is an illustration of the invention shown in block diagram on FIGURE 1 and illustrating the principles of applicants invention, partially in sectional view, there is shown a sectional view of the hydraulic cylinder 24. As shown on FIGURE 3, the hydraulic cylinder 24 is comprised of a first portion 60 which is threadingly attached to a second or rear portion 62. The interior 64 of the hydraulic cylinder 24 is substantially full of hydraulic oil, in this embodiment of applicants invention. The rotating shaft 16 extends into the interior 64 of the hydraulic cylinder 24 through, for example, Oilite bearings 66, passes through and is journaled for rotary motion in a forward or first end cap 68 of a piston assembly 70. The second end 26 of the rotating shaft 16 is detachably secured, for example by pin means 72, to a hub portion 74 of a vane pump 76. The vane pump '76 comprises, in addition to the hub '74 a slotted inter race '78 in which vanes 80 are free to move under the influence of centrifugal force in directions indicated by the arrow 82, that is, towards and away from the eccentrically bordered outer race 34. As shown more clearly in FIGURE 4, the outer race 84 has an eccentric bore that allows the vanes 89 in the vane pump 76 to move inwardly and outwardly in radial directions during rotation thereof. Because of the eccentric bore, rotation of the vanes 80 induces a pumping action which, for the arrangement shown on FIGURES 3 and 4, pumps hydraulic oil from areas adjacent the forward face 68 of the piston assembly 70 through the rear or second end cap 86 to regions intermediate the second end cap 86 and the second portion 62 of the hydraulic cylinder 24, as indicated by the arrow 88. Because of the nature of the vane pump 76, it will be appreciated that reversal of the direction of rotation thereof will pump oil in the opposite direction to that indicated by the arrow 88. As the oil is pumped from the first side of the piston to the second side of the piston assembly 79, pressure is built up against the rear face of the piston assembly 76 and, consequently, the piston assembly 743 and the rotating shaft 16 move in axial directions to move the tapping head 12 towards the work piece 34. Since the displacement of the vane-type pump per revolution thereof is an accurately known parameter the feed or forward motion of the tapping head 12 towards the work piece 34 per revolution of the rotating shaft 16 is accurately known. Further, because of the constant pressure rise through the pump 76, the force acting against the rear face 86 of the piston assembly 70 provides a constant forcefor moving the tapping head during engagement with the work piece 34.

In one embodiment of applicants invention, there may be provided a non-rotating shaft 28 that is detachably coupled, for example by a screw 90 to the second or rear end cap 86 of the piston assembly 70. The nonrotating shaft 28 moves reciprocatingly in directions indicated by the arrow 20, but, as noted above, does not rotate since the piston assembly 74 does not rotate. Thus, arm means 92 may be utilized to engage a slot 94 in the non-rotating shaft 23. The arm means 92 is coupled to the second portion 62 of the hydraulic cylinder assembly 24 and thus prevents rotation of the non-rotating shaft which, since it is secured to the piston assembly '70, prevents rotation of the rear or second end cap 86, the outer race 34 which is secured to both the rear end cap 86 and to the first or forward end cap 68.

Outer peripheral edges 96 of the first and second end cap 68 and 86 and the outer race 84 slidingly, sealingly engage the inner wall portions 98 of the hydraulic cylinder 24 and substantially prevent leakage therebetween.

In the preferred embodiment of applicants invention, applicant provides a pair of spring loaded pressure relief valve means 106 in the piston assembly 70. As shown in FIGURE 3 and in more detail on FIGURE 6, the pressure relief valve ltlt) comprises an elongated shaft 162, having a first end 104 that is adapted to sealingly engage the rear end face of the rear end cap 86 under the influence of a spring means 106 that urges the second end 138 of the elongated shaft 102 away from the first end cap 68 of the piston assembly 70. A plurality of holes 110 extend through the first and second end cap 68 and 86 respectively and the outer race 84 and are sealed during movement of the piston assembly 70 towards the forward wall 112 of the hydraulic cylinder 24 by the first end 104 of elongated shaft 102. When the piston assembly 70 approaches within a predetermined distance of the first end wall 112 of the hydraulic cylinder 24, the second end 108 of the elongated shaft 1432 engages the first or forward wall 112 and continued movement of the piston assembly 70 opens up the holes to allow movement of hydraulic fluid through the holes 110 past the second end 104 of elongated shaft 102 to equalize the pressure on both sides of the piston assembly 70. Therefore, even though rotation of the rotating shaft 16 continues under the influence of motor 18 forward motion of the rotating shaft 16 is terminated. The other pressure relief valve shown adjacent the bottom portion of the hydraulic cylinder 24 operates in identical manner for movement of the piston assembly 70 towards the rear wall 114 of the second portion 62 of the hydraulic cylinder assembly 24. Therefore, the pressure relief valves 106 provide the structure for terminating axial motion of the rotating shaft 16 even though rotary motion thereof continues. I

The control means 3h may be coupled to the end of the non-rotating shaft 28 that is external of the hydraulic cylinder 24 and may be adapted to engage the switches 32 which are connected to motor 18. The switches 32 may sequentially reverse the direction of rotation of the motor 13 and consequently the rotating shaft 16 as desired. O-rings 116 may be provided for sealing the non-rotating shaft 28 where it passes through the second portion 62 of the hydraulic cylinder 24.

As noted above, applicant prefers that the rate of feed for a given number of revolutions of the rotating shaft 16 be adjustable. Applicant achieves this by providing that the vane pump 76 is detachably coupled to the rotating shaft 16 by the pin means 72. Thus, the second portion 62 of hydraulic cylinder 24 may be removed and the said screw 90 and pin '72 removed and a different vane pump 76 installed. Other vane pumps that may be installed will provide variations in the eccentricity of the bore of the outer race 84 since the amount of eccentricity in the bore determines the rate of feed of the rotating shaft 16 and consequently the tapping head 12. Thus, as desired, either the outer race alone may be replaced or the entire piston assembly 76 may be replaced, as desired in any particular application.

As shown in both FIGURE 3 and FIGURE 5, applicant provides a by-pass port arrangement 118 in the retracted or rearward position of the piston assembly 7-9. The by-pass port arrangement 118 provides a pair of ports 120 and 122 in the wall of the hydraulic cylinder 24 that span the piston assembly '70 in a desired position. A floating plate 124 is provided with a notch therein above the port 120. When the piston is in the position as indicated in FIGURE 3, the piston has been traveling in the rearwardly direction, that is, towards the second portion 62 of the hydraulic cylinder 24. Consequently, there was a higher pressure on the first or forward face and end cap 63 of the piston assembly '78 than on the second or rear end cap 86 thereof. When the piston assembly reaches the position indicated in FIGURE 3, the high pressure is ported completely around the piston assembly '70 through the port 122 past the floating plate 124 and then through the port 120. Thus, the pressure on both sides of the piston assembly 70 is balanced and there is no further movement thereof. However, when the direction of rotation is reversed, there is a pressure buildup adjacent to rearward or second end cap 86 of the piston assembly 76 and the floating plate 124 is forced downwardly, due to the higher pressure on the upper face thereof, exerted by the hydraulic fluid flowing through port 120 and the notch in floating plate 124, against and sealing the port 122 and forward motion of the piston assembly 70 occurs.

If desire-d, a cooling jacket 126 may be provided to additionally remove heat that may be generated during extended periods of operation of applicants invention. The cooling jacket 126 comprises a jacket means 128 filled with a circulating fluid 130. Circulating fluid 130 may, of course, be hydraulic oil but the hydraulic oil 130 is completely separate from the hydraulic oil contained within the hydraulic cylinder 24.

As shown in block diagram form on FIGURE 3, the cooling jacket 126 further comprises a pump means 132 that pumps oil from a sump means 134 into the jacket means 128. The cooling hydraulic fluid 130 leaves the jacket means 128 and passes through a conventional heat exchanger 136 before flowing back into the sump 134.

The structural arrangement indicated for the block diagram embodiment shown on FIGURE 2 is similar to the structure utilized in the detailed drawing shown on Fl"- URES 3 through 7. The difference is that the piston assembly inside the hydraulic cylinder 43 is prevented from rotation by means other than a non-rotating shaft since the rotating shaft 46 extends completely through the piston assembly. Thus, the rotating shaft 46 would be journaled for rotation in both the forward and rear end caps of the piston assembly and be detachably coupled to the hub of a vane-type pump. The rotating shaft then continues through the hydraulic cylinder 48 and its second end 50 is connected to the motor 52 and is rotated thereby. Thus, the entire rotating shaft 46 rotates and also moves in axial directions to move the tapping head 42 into and out of engagement with a work piece 34.

This concludes the description of applicants improved tool arrangement. As described above, it can be seen that applicant has provided a tool arrangement in which the feed or axial movement per rotation thereof is accurately controlled and, further, that the axial movement is under a substantially constant force. Further, the improved tool arrangement of applicants invention is provided with automatic safeguard features to prevent overheating of the hydraulic or other fluid utilized to move the tool in axial directions as well as automatic stopping, starting and reversing of direction of rotation thereof. In addition, as shown above, the means providing the rotary motion of the rotating shaft for rotation of the tool coupled to the rotating shaft does not move in axial directions with the axial movement that is provided.

Those skilled in the art may find many variations and adaptions of applicants invention. Applicant intends that the preferred embodiment comprising the best method known to applicant for taking advantage of his invention described above be considered as an illustrative embodiment only and applicants invention is to be limited only by the scope of the appended claims.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A tool arrangement comprising, in combination:

a motor means;

a rotating shaft means splined to said motor means for rotation by said motor means, and said rotating shaft means reciprocally movable in axial directions with respect to said motor means during rotation thereof;

a cylinder substantially full of fluid and said rotating shaft having a portion extending into said cylinder;

a pump means positioned in said cylinder and coupled to said portion of said rotating shaft in said cylinder for moving said shaft in said axial directions;

and tool means coupled to said rotating shaft for movement therewith into and out of engagement with a work piece.

2. The arrangement defined in claim 1 wherein:

said rotating shaft means has a first end and a second end and is splined to said motor means intermediate said first end and said second end;

said tool means is coupled to said first end of said rotating shaft and said pump means is coupled to said second end of said rotating shaft.

3. The arrangement defined in claim 2 wherein:

said pump means is detachably coupled to said second end of said rotating shaft and said pump means comprises a vane-type hydraulic pump, and said fluid means comprises hydraulic fluid;

said motor means is an electrically powered reversible variable speed motor, and said vane-type pump moves said rotating shaft in said axial directions at a substantially constant force.

4. The arrangement defined in claim 3 wherein:

a plurality of vane-type pumps are sequentially dctachably coupled to said first end of said rotating shaft and each of said vane-type pumps has a different axial movement distance for each revolution thereof whereby the rate of axial movement of said rotating shaft and said tool means is variable depending upon the particular vane-type pump detachably coupled to said rotating shaft.

5. The arrangement defined in claim 3 wherein:

said vane-type pump comprises a portion of a piston in said cylinder and said piston further comprises:

a first non-rotating end cap, a second non-rotating end cap spaced apart from said first non-rotating end cap and a non-rotating outer race coupled to said first end cap and said second end cap in peripheral portions thereof, and said vane pump is positioned intermediate said first end cap and said second end cap and rotates interior said outer race, and said first end cap and said second end cap have fluid passages therethrough in preselected locations thereof;

said rotating shaft is journaled for rotational motion in said first end cap and drivingly coupled to said vane pump to rotate said vane pump;

a non-rotating shaft is keyed to said cylinder and coupled to said second end cap to prevent rotation of said first end cap, said second end cap and said outer race, and said non-rotating shaft having a portion extending extenrally of said cylinder.

6. The arrangement defined in claim 5 wherein:

said piston further comprises a pair of spring loaded relief valves for terminating axial movement of said piston and said rotating shaft at predetermined portions of said axial movement.

7. The arrangement defined in claim 6 and further comprising a by-pass port in said cylinder adjacent one end thereof for by-passing said fluid around said piston to a position adjacent said first end cap thereof for the condition of rotation of said rotating shaft and said vane pump in a first direction, and said by-pass port for allowing by-passing of said fluid around said piston to a position adjacent said second end cap thereof for the condition of rotation of said rotating shaft and said vane pump in a second direction opposite said first direction.

8. The arrangement defined in claim 1 wherein said rotating shaft has a first end and a second end and said pump means is coupled to said rotating shaft intermediate said first end and said second end and said rotating shaft is splined to said motor means adjacent a second end thereof and said tool means is coupled to said rotating shaft adjacent a first end thereof.

9. The arrangement defined in claim '8 wherein said pump means comprises a vane-type hydraulic pump detachably coupled to said rotating shaft means in said cylinder and said fluid comprises hydraulic fluid.

10. The arrangement defined in claim 7 wherein said non-rotating shaft means has a control means coupled to said second end thereof;

switch means activated by said control means for re- 60 versing the direction of rotation of said motor means to reverse the direction of axial movement of said rotating shaft means, and said control means engaging said switch means after a predetermined axial movement thereof.

References Cited UNITED STATES PATENTS 1,490,633 4/1924 Peters 91-399 1,911,138 5/1933 Clute et al 9161 XR 2,261,444 11/1941 Neubert 91---401 XR 2,622,372 12/1952 I'Moulden 9l61 XR 2,643,555 6/1-953 Steibel 60-6 XR 2,750,816 6/1956 Mott 91-61 XR EDGAR W. GEOGHEGAN, Primary Examiner.

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