US2797601A - Thread-cutting machines - Google Patents

Description

July 2, 1957 R RENO X 2,797,601

THREAD-CUTTING MACHINES Filed March 18, 1953 5 Sheets-Sheet 1 ITS y 1957 P. E. RENOUX 2,797,601

THREAD-CUTTING MACHINES Filed March 18, 1955 5 She'ets-Sheet 2 "VZJJM 4/. 62M

July 2, 1957 Filed March 18, 1953 P. E. RENOUX THREAD-CUTTING MACHINES 5 Sheets-Sheet 3 GEM/95L. WM 40. 62M,

July 2, 1957 P. E. RENOUX 2,797,601

THREAD-CUTTING MACHINES Filed March 18, 1953 5 Sheets-Sheet 5 United States Patent or ice THREAD-CUTTING MACHINES Pierre Edouard Renoux, Argcntenil, France, assignor to Societe Anonyme dite: Cri-Dan, Paris, France, a French company Application March 18, 1953, Serial No. 343,178

Claims priority, application France January 13, 1953' 4 Claims. (Cl. 8 2-5) It has already been proposed in semi-automatic threadcutting. machines operating through the removal. of turnings by means of a simple tool executing a succession of cuts, to produce the longitudinal alternating translational movement of the tool by means of a cam, termed the pitch cam, assuming a continuous rotary movement, the main section of the cam outline producing the progression of the tool in a given direction corresponding to the active stage of the cutting, while the remaining section of the outline. corresponds to the speedy return of the tool.

Generally, the longitudinally movable carriage supporting the transverse carriage on which the tool is fitted and that is controlled by the pitch cam, is urged into contact with the latter with the interposition of a contact member such as a roller, which is urged by a spring against the cam.

The progression of the cutting tool during the operative stages of the cutting is performed generally in a direction urging the tool towards the spindle or the headstock of the machine tool.

Now, it may be of advantage. in certain cases to produce the thread through a reversal of the direction of said operative stages, i. e. to produce the turningswhile the tool moves away from the head-stock. This method of operating allows in. particular automatically releasing the turnings during the execution of a tapping.

In other cases, it :allows holding the tool in the same position, whatever may be the direction of the thread produced, whether provided with a right hand pitch or with a left hand pitch, which leads'to keeping a predetermined direction for the cutting stress, which condition is favorable for increasing the life and accuracy of the machine.

This effect may obviously be obtained through a mere reversal of the direction of rotation of the machine as provided e. g. by making its motor revolve in reverse direction; but this would result in a reversal of the tool reactionsand of the friction exerted in the slideways and, consequently, lead' to a falling out of the contact between the cam and the member driven thereby and finally, this would be a source of inaccuracy and even of damage to the'work that is being executed.

It is also possible to supply the machine with two series of cams to be used respectively for left hand threadcutting andfor righthand thread-cutting, but this arrangement would result in a supplementary expense which would increase the cost price of the work produced.

Now, the present invention has for its. object to provide for the obtention of the desired result, i. e. the production of left hand and right hand thread-cutting as desired, and this is obtained by replacing the usual pitch cam of thread-cutting machines by a reversible cam adapted to be fitted selectively in two opposed positions on the cam-carrying shaft, so as to present its operative outline either in a direction producing a movement of the longitudinal carriage from right to left e. g. and consequently, an operative movement of the tool in said direc- 2,797,601 Patented July 2, 1957 tion or else, in the opposite direction producing a displacement of the longitudinal. carriage from left to right and consequently an operative movement of the tool in said direction.

The reversible cam is advantageously constituted by a hollow sleeve the periphery of which assumes the outline of an active cam, while the end of said sleeve opposed to said cam outline is closed by a bottom section of which either side may serve as a bearing surface for assembling the sleeve on the end of the cam-carrying spindle in accordance with the direction of positioning of said sleeve for producing the thread-cutting, from right to left or from left to right respectively.

The reversibility of the cam may be associated, in accordance with the invention, with a reversibility of the tool-returning means which hold permanently in. contact with the cam, a member. carried by the longitudinal carriage, said. member being constituted by a roller or the like follower.

The tool-returning means may be constituted by a single spring engaging selectively one of two stops that may recede when desired and that are provided on the transverse carriage of the machine.

The tool-returning means may again be constituted by a double acting hydraulic or the like jack, carried by the transverse carriage and the piston of which, rigid with the longitudinal carriage, is submitted tofiuid pressure on either of its surfaces selectively. The reversal of the direction of the fluid pressure on the piston-ends in the-jack may be obtained by means of a distributor, the location of which may be defined by that of the reversible cam.

Further features of the invention will appear in the reading of the following description of various embodiments of the latter, given byway of examples and by no means in a limiting sense, reference being made to accompanying drawings, wherein:

Fig. 1 is a general view of a thread-cutting machine;

Figs. 2 and 3 are two diagrammatic axial cross-sections of the reversible cam carried by the cam-shaft in order to allow selectively a right-hand and a left-hand thread.- cutting;

Fig. 4 is a longitudinal sectional view of reversible means returning the longitudinal carriage into its starting position through the agency of a spring;

Fig. 5 is a longitudinal cross-sectional view of a modified reversible means returning the longitudinal carriage into its stationary position and operating through the agency of a hydraulic jack;

Fig. 6 is a sectional view through line VI'VI. of Fig. 5

Figs. 7 and 8 are two sectional views of the distributor feeding fiuid under pressure to the hydraulic jack, corresponding to the cases where the reversible cam is positioned for thread-cutting in either direction respectively;

and

Fig. 9 is a diagram illustrating a conventional reversible drive for cam shaft 8.

Fig. 1 which is, "as stated, a general view of a threadcutting machine of conventional type, shows at 1 the frame of the machine, having a spindle 2 driving the. work in which the thread is to be cut, and a center 3. The transversely moving carriage 4 carries a longitudinally moving carriage 5; the cross tool carrier is shown at 6 and the pitch cam controlling the longitudinal movement of the carriage 5 is shown at 7, while 8 designates the shaft controlling the rotation of the pitch cam and 9 the roller fitted underneath the end of the longitudinal moving carriage and which is constantly urged against the pitch cam.

Figs. 2 and 3 illustrate diagrammatically a reversible cam 10 according to my invention; this cam is constituted by a hollow sleeve the bottom transverse wall 11 of which has two sides, a and b, constituting selectively, according to the manner in which the sleeve is fitted on the camcarrying shaft 8, the surface assembling the cam with the terminal bearing section 12 of said shaft. The sleeve is provided, furthermore, at its periphery, with a camshaped outline 13 adapted to be engaged by the roller 9 carried on a spindle 14 rigid with a member 15 fitted in side an arm 16 rigid in its turn with the longitudinally moving carriage 5, said member 15 being held fast in the arm 16 by a screw 17 engaging an annular groove 18 in said member.

According as to Whether the sleeve 10 forming the reversible cam is mounted on the camshaft 8 in a manner such that its terminal surface a or b engages the terminal surface of the bearing 12 carried by the said shaft 8, the reversible cam 10 has its operative outline directed either towards the right hand side as in the case of Fig. 2, or towards the left hand side, as shown in Fig. 3, and it produces consequently through the agency of the roller 9 an operative movement of the cutting tool mounted on the carriage 6 from left to right, as shown in Fig. 2, or from right to left, as shown in Fig. 3. The sleeve 10 forming the reversible cam may be provided with an annular recess at 19. In either of its positions illustrated in Fig. 2 or in Fig. 3, its central bottom section 11 is secured to the cam shaft 8 through the agency of screws 20.

It will be remarked that this positioning of the reversible cam with reference to the shaft 8 allows it to have selectively its operative section on the right hand A side, as shown in Fig. 2, or on the left hand side, as shown in Fig. 3, but that such a change in position modifies by no means the normal ends of the stroke of the longitudinal carriage 5 corresponding to the lines G and D occupied by the axis 14 of the roller 9 for the two extreme positions of said roller respectively.

If A and B are the distances between the extreme outer points of the operative outline 13 of the cam and one of the assembling surfaces a or b in either of the positions corresponding respectively to Figs. 2 and 3 and if H designates the sum of said distances A and B and if, further, R is the radius of the contact roller 9 and C the thickness of the central bottom section 11 of the cam between the two bearing-engaging surfaces a and b, calculation shows that the following equations are true:

GX=AR and XD=B+R and in the case of Fig. 3,

GX=B+R and XD=AR-|C In both cases, the following equation is consequently true:

and

GX+XD=GD=A+B whatever may be the location of the reversible cam on its shaft.

The extreme positions occupied by the carriage 5 remain consequently unchanged when the cam 10 is reversed.

According as to whether the thread is to be cut with a left hand pitch or with a right hand pitch, the cam 10 is secured to the end of the cam shaft 8 in a manner such that the surface engaging the bearing on said shaft is either the surface a (Fig. 2) or the surface b (Fig. 3).

By reason of this relative positioning, it is possible to obtain the desired effect by means of a single cam without inserting any further member for the drive of r 4 the longitudinal carriage 5 and without any modification in the extreme positions of the latter.

The reversal of the cam 10 implies, of course, a reversal of its direction of rotation.

The roller 9 on the movable carriage 5 which is controlled by the rotation of the cam 10, may be held fast permanently in contact with the latter through the agency of a spring 21 having a reversible action, as illustrated in Fig. 4 and as described hereinafter.

The transverse carriage 4 carries between two supports 22 a spindle 23 fitted with two adjustable nuts and counternuts 24, 25 and 26, 27 engaged normally by stops 28, 29 under the action of the compressed spring 21 wound round the spindle 23. Each stop 28, 29 is provided with an annular groove 30 adapted to be engaged by a spring-urged projection 33 of the longitudinal carriage 5. A bayonet or the like system allows holding the projection 31 or 32 raised in a receding position through mere action on the terminal knob 34 carried by said projection, said knob being drawn out and then rotated through one quarter of a revolution for instance. A rotation of the knob 34 by an equal amount in the opposite direction allows releasing the latter so as to let the projection 31 or 32 drop back into the annular groove 30 of the corresponding stop 28 or 29.

According to the direction of the pitch to be cut, the projection 31 or the projection 32 is brought into its receding position and the longitudinally movable carriage 5 controlled by the rotation of the cam 10 is held in contact with the latter through the follower 9 by the spring 21 acting on said carriage through the agency of the stop 29 or of the stop 28, as the case may be. In Fig. 4, it has been assumed that the pitch was being cut from right to left and that the carriage 5 was held in contact with the cam 10 through the agency of the spring 21 and of the stop 29, moving in unison with said carriage by reason of the projection 32 engaging said stop.

In Fig. 5, the reversible tool and carriage-returning means urging the carriage against the roller 9 contacting with the cam 19 include a double acting hydraulic jack. This jack includes a stationary cylinder 35 rigid with the transverse carriage 4 and inside which may move a piston 36 carried by a rod 37 passing through the bottom of the cylinder 35 and engaging a member 38 rigid with the movable carriage 5.

39 and 40 designate pipes feeding fluid under pressure into the cylinder 35 near the corresponding ends thereof, so as to act selectively on the opposite surfaces of the piston 36. The piston 36 is driven in unison with the carriage 5 rigid therewith towards the right hand side or towards the left hand side, whenever the fluid under pressure acts correspondingly on the left hand side or on the right hand side of the piston 36.

The direction of the thrust thus exerted on the piston 36 and, consequently, on the carriage 5 rigid with said piston, by the compressed fluid, may be reversed through the operation of the four-way distributor illustrated in Figs. 6 to 8. Insaid figures isshown the cam-carrying shaft 8 with its reversible cam 10, said cam being assumed in the case of Fig. 7 as positioned for left-to-right thread cutting and in Fig. 8 for right-to-left thread cutting. 9 designates again the roller carried by the longitudinally movable carriage 5 for engagement with said cam 10.

To the frame 41 supporting the camshaft 8 is secured the body 42 of a distributing cylinder inside which may move a piston 43 provided with an annular peripheral recess 44 and with an axial bore 45 subdivided into two arms 46 diverging to either side of a rod 47 rigid with the piston 43. Said rod 47 is rigid with a terminal strap 48 on the outside of the carrying frame 41, said strap carrying a spindle 49 to which is revolubly secured a roller 50.

' The roller 50 may, for the position of the reversible cam 10 shown in Fig. 7, roll over the rear end of the said 5 reversible cam 10. A coil spring 51- urges constantly the piston 43 towardsthe right hand side of Figs. 7 and 8'.

The cylinder 42 is provided with ports 53, 54, 55' and 56 communicating respectively with the pipes 39' and 40 opening: into the cylinder 35 of the hydraulic jack, with a pipe 57 feeding fluid under pressure and finally with a pipe 58 serving for the exhaust of said fluid.

In the position occupied by the distributing piston 43, as illustrated in Fig. 7, and corresponding to a drive towards the right hand side of the movable carriage 5 under the action of the cam 10, the fluid under pressure admitted through the pipe 57 passes through the port 56 into the annular recess 44 and thence through the port 53 and the pipe 39 into the cylinder 35 of the jack so as to act on the right hand side of the piston 36, which urges thus constantly the roller 9 carried by the movable carriage 5 against the reversible cam 10 during the displacement of said carriage. The fluid under pressure contained in the cylinder on the other side of the piston 36 is exhausted through the pipe 40 and the ports 54, 46, and 55 into the exhaust pipe 58.

In Fig. 8, the movable carriage 5 is assumed to have been driven towards the left hand side by the reversible cam 10 that is positioned correspondingly while the spring 51 has urged into its extreme right hand position the strap 48 with the roller 50 thereon and the distributor piston 43. The fluid under pressure acts then on the left hand side of the jack piston 36 through the agency of the port 56, of the annular recess 44, of the port 54 and of the pipe 40, while the fluid under pressure is exhausted away from the other side of the piston 36 through the pipe 39, the ports 53 and 55 and the exhaust pipe 58.

While various reversible drives may be provided for cam shaft 8, a satisfactory arrangement is diagrammed in Fig. 9 wherein is illustrated a reversible electric motor energized by a source 62 of three-phase voltage to which it is coupled through a reversing switch 64, it being apparent that motor 60 will rotate in the selected rotative direction in accordance with the position of reversing switch 64. Speed gearing 66 coupled by belt 68 to motor 60 and speed-controlled by lever 70 has its drive shaft 72 geared as at 74 to cam shaft 8, so that cam 10 is rotated in one direction or the other in accordance with the position of reversing switch 64.

The present invention covers also a thread-cuttting machine incorporating at least part of the above disclosed improvements insofar as they are claimed in accompanying claims.

What I claim is:

1. In a thread-cutting machine, a frame; a tool carriage supported on said frame for sliding movement in opposite longitudinal directions; a camshaft rotatably mounted with its longitudinal axis extending longitudinally of the direction of movement of the carriage, means for selectively rotating said camshaft in either of its two opposite rotative directions; a cam comprising a substantially sleeve-shaped body having a cam surface at one end; means for mounting said body on said camshaft selectively in either of two positions, in the first of which positions said cam surface faces one axial direction of the cam shaft and in the second of which said positions said cam surface faces the opposite axial direction, a cam follower on said carriage, said cam follower being adapted to engage said cam surface when the latter is mounted in either of said positions, whereby said carriage is positively driven in said one longitudinal direction or the other in accordance with the selected mounting of said cam on said camshaft; and reversible bias means engaged between said frame and said carriage for selectively biasing said carriage contra to the direction of positive drive of said cam, whereby to return said carriage in the direction opposite to the positive drive thereof.

2. In a thread-cutting machine, a frame; a transverse carriage transversely shiftable on said frame; a tool carriage supported on said transverse carriage for sliding movement in; opposite directions longitudinally of the frame; a cam shaft rotatably mounted on said transverse carriage with its longitudinal axis extending longitudinally of the direction of movement of the tool carriage, means for selectively rotating said shaft in either of its two opposite rotative directions; a cam comprising a substantially sleeve-shaped body having a cam surface at one end; means for mounting said cam on said camshaft selectively in either of two positions, in the first of which positions said cam surface faces one axial direction of the camshaft and in the second of which said positions said cam surface faces the opposite axial direction; a cam follower on said carriage; said cam follower being adapted to engage said cam surface when the latter is mounted in either of said positions, whereby said carriage is positively driven in said one longitudinal direction or the other in accordance with the selected mounting of said cam on said camshaft; and a double-acting jack including a cylinder member and a piston member, one member being mounted on said transverse carriage and the other member being mounted on said tool carriage; and means for feeding fluid to said cylinder member selectively on either side of said piston member, whereby to hold said cam follower against said cam surface and to return said carriage in the direction opposite to the direction in which it is positively driven by said cam.

3. The combination claimed in claim 2, the means for selectively feeding fluid to said cylinder member on either side of said piston member comprising a pair of fluid pipes leading respectively to opposite sides of said cylinder member, fluid supply and return conduits, a multi-way distributor valve connected to said pipe and conduits and selectively actuatable for establishing fluid flow from said supply conduit to either one of said pipes while simultaneously establishing communication between the other pipe and the return conduit, and means engaging said cam body responsive to the position thereof on said camshaft for actuating said distributor valve.

4. In a thread-cutting machine, a frame; a transverse carriage transversely shiftable on said frame, a tool carriage supported on said transverse carriage for sliding movement in opposite directions longitudinally of the frame; a camshaft rotatably mounted on said transverse carriage with its longitudinal axis extending longitudinally of the direction of movement of the tool carriage; means for selectively rotating said camshaft in either of its two opposite rotative directions; a cam comprising a substantially sleeve-shaped body having a cam surface at one end; means for mounting said cam on said camshaft selectively in either of two positions, in the first of which positions said cam surface faces one axial direction of the camshaft and in the second of which said positions said cam surface faces the opposite axial direction of the camshaft; a cam follower on said carriage, said cam follower being adapted to engage said cam surface when the latter is mounted in either of said positions, whereby said carriage is positively driven in said one longitudinal direction or the other in accordance with the selected mounting of said cam on said camshaft; an elongate compression spring mounted on said transverse carriage with its length extending longitudinally of the direction of movement of said tool carriage; a pair of abutments on said transverse carriage respectively adjacent opposite end portions of said spring and adapted to be engaged thereby;

and independently operable catch means longitudinally spaced along said tool carriage, said catch means being respectively engageable with the opposite end portions of said spring, whereby a selected one of said catches may be engaged with one end portion of said spring so that the spring is compressed between the selected catch and the abutment at the opposite end portion of the spring as a result of the positive drive of said cam.

(References on following page) 7 8 References Cited in the file of this patent 1 2,417,091 Smith Mar. 11, 1947 2,462,126 Peat Feb. 22, 1949 UNITED STATES PATENTS 2,468,478 Ardoin Apr. 26, 1949 1,454,554 M1tche1l May 8, 1925- 2,527,397 Castelli Oct. 24, 1950 2,291,591 Medholdt July 28, 1942 5 2,627,618 Holmes Feb. 10, 1953

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