US3073194A - Attachment for chasing threads on horizontal lathes - Google Patents

Description

Jan. l5, 1963 DON PIETRO clccARELLl 3,073,194

ATTACHMENT FOR CHASING THREADS oN HORIZONTAL LATHEs Filed April 6, 1956 a" J "6 1 f l if mm2 l: l; iT5 7 la. f

5 9* /2 9( .qui-V y d lum 9 United States Patent iltice l A3,073,194 Patented Jan. 15, 1963 3,073,194 ATTACHMENT FOR CHASING THREADS N HORIZONTAL LATHES Don Pietro Ciccarelli, Turin, Italy, assigner to Istituto Salesiano Rebaudengo, Turin, Italy Filed Apr. 6, 1956, Ser. No. 576,565 Claims priority, appication Italy Apr. 8, 1955 3 Claims. (Cl. 82-5) This invention concerns an attachment for chasing threads on horizontal lathes, and relates particularly to an attachment of the type described in British Patent 764,926, which includes a feed cam determining the pitch of cutting and driven by means of a telescopic transmission rod from the lathe feed shaft, said transmission rod being provided with at least one universal joint to operate a longitudinal tool carriage in opposition to spring arrangements adapted automatically to restore said carriage to its initial position at the end of its working stroke, and a second cam mounted coaxially of and rotating with the iirst cam to effect disengagement of the tool from the workpiece at the end of its working stroke in opposition to spring arrangements on a transverse carriage, and to bring the tool back to its initial position automatically at the start of a succeeding cutting operation, the required transverse feed of the tool on the transverse slide being controlled by hand by the operator. In one embodiment of the. attachment above referred to, the second cam operates a lever pivotal about a fixed point in order to move the transverse carrage so as to disengage the tool from the workpiece.

' lt is an object of the present invention to ettect advance of the transverse carriage automatically during the return stroke of the longitudinal carriage, through the medium of a controllable device acting on said transverse carriage in dependence upon the movement of the longitudinal carriage.

Another object of the invention is to effect outward and inward motion of the tool with respect to the workpiece, not by a lever pivotal about a iixed point, but by an oblique lever integral with the longitudinal tool carriage and operated by a bar sliding in said longitudinal carriage so as to act at the appropriate moment on a pin integral with the transverse tool carriage.

These and other objects of the invention will become more apparent in relation to three preferred forms of construction, given by way of example only and in no way intended to limit the scope of the invention, described with reference to the accompanying drawings, in which:

FIG. 1 is a longitudinal cross-sectional view taken on the line I-I of FIG. 3 showing la rst form of construction of the attachment,

FIG. 2 is a side elevation of said attachment partly in section showing the auotmatic advancing device of the transverse carriage,

FIG.V 3 is a plan View, partly in section, of the attachment illustrated in the preceding iigures,

FIG. 4 is a cross-section taken on the line IV-IV of FIG. 2.

With reference to the form of construction of improved cutting device as shown in FIGS. 1 to 4, 1 is the end of a telescopic transmission rod or shaft provided with a universal joint la, which rod is driven by the feed shaft of the lathe, as described in British Patent 764,926, and transmits rotary motion via a worm, not shown, engaged with the gear 2 to a pin or shaft 3 piv- Oted on the longitudinal carriage 1b. Shaft 3 has a cam 4 removably iixed thereto, which, at the furthest point from the centre of the pin 3 has a catch or second cam surface 4a, which is an extension which projects outward and sidewards relative to cam 4 as best seen in sion rod 1 and the cam 4 as also decribed in Britih Patent The catch 4a operates through a bearing wheel 8 on the end of a sliding bar 9, guided for translation by and between a pair of parallel guides 9a mounted on the slide 6, and positioned parallel to the direction of sliding thereof. The opposite end of bar 9 is provided with an oblique groove or guideway 9b into which slidably iits a slide or follower 10 ixed on the transverse carriage 7 by means of a threaded pin 11. The slide 6 has a cavity between the two parallel guides 9a and this is used for housing a compression spring 12, one end of which bears on an end of said cavity, that is, the left end as the parts are viewed upon FIGURES l and 3, and faces the direction of motion of the transverse carriage, whilst the other end of said spring abuts the iiattened side surface of a pin 9c integral with bar 9. The catch or second cam surface 4a of cam 4 effects, therefore, translation of the shaft 9 toward the left at the end of the travel of cutting tool, and, consequently, the disengagement of the tool from the workpiece by motion of the slide 10 in the oblique groove 9b; the spring 12 which becomes compressed during this sliding motion provides for the return of bar 9 towards the right after the point of the catch 4a rotating with cam 4 has passed the bearing wheel 8, said spring thus also controlling the consequent return to the starting position of the slide 10 and of the transverse carriage 7 integral with it. The catch 4a is provided with a slope so formed that the approach of the cutting tool to the workpiece takes place after the longitudinal carriage, shifted to the left by the cam 4, has been brought into the starting position by restoring spring 13 secured between the bed and the carriage and acting on said carriage.

The automatic advancing device of the cutting tool for successive cutting operations is enclosed in a box which is carried by siide 6 and the details of which are shown in FIGS. 2, 3 and 4. On the front end of the transverse carriage there is iitted a 'push-rod 14, FIG. 4, co-acting with an eccentric cam 15a integral with a shaft 15 parallel to the direction of sliding motion of slide. Said shaft 15 at its opposite end has a bevel pinion 16 geared with another bevel pinion 17 journaled on a bearing pin 18. This latter pinion 17 -is connected to a disc 19 provided with teeth on part of its circumference. The same pin 18 acts as a pivot for a right-angular plate 20. A moving catch 21 is pivotally mounted on a plate which is connected to plate 20 and positioned to engage an extension 20a of the intermediate plate. Plate 20 is urged into counterclockwise rotation, as the parts are viewed upon FIG. 2 by a spring 22 and bears a pawl 23 pressed against the toothed disc 19 by means of a spring 24. A stop 20h limits the counter-clockwise rotation of the plate 20.

Furthermore, pin 18 acts as a pivot for a second plate 25, the ends of which are bent to extend axially over the periphery of disc 19 so as partly to cover it. The left arm of plate 25, as seen in FIG. 2, is formed as a toothed section which meshes with a pinio-n 26 operable by hand by a button 27 protruding from the box containing the device. The longitudinal carriage also has a stop 28, FIG. 2, to engage catch 21 when the carriage moves into first position in the retrograde position. A button 29 integral with pinion 17 allows the device to be operated by hand.

The automatic advancement device functions as fol- 3. lows: At each return. of the longitudinal carriage the catch 21 abuts against the fixed stop 28and pressing against the extension 20a of the plate 20, causes said plate to rotate in a clockwise direction. The pawl 23 fixed to the plate 20 and engaged with the toothed disc 19 4effects rotationof the disc 19., which drives the pinion 17 and, through thepinon 16 and shaft 15, rotate the cam V15a` collaborating with push-rod 14. The angle of rotation of the disc 19, and` therefore also of the cam 15a can beA regulated .bymeans of button 27 acting throughthe toothed wheel26 on the plate 25. According to the position given to said plate 25 with respectto the pawl 23, the latter, in the oscillating motion of constant amplitude of the plate 20., therefore engages with a greater or lesser number of teeth of the disc 19 and consequently causes said disc to ro-tate in a clockwise direction by a greater or lesser angle for each stroke of the carriage. The transverse carriage which is being pressed against the workpiece by means `of the slide and the connecting pin -11 to a degree determined by the momentary position of the cam 15awith respect to the push-rod 14, will therefore move forward after each return stroke through a distance determined by the shape of the cam. 15a and by its angle of rotation, until it has reached its maximum allowed depth, corresponding to the position represented in FIG.,4 through the .cooperation of cam 15a.and push rod14. This position being reached i.e. the follower actionhaving been completed, the .cam V15a is caused by the'advance device to rotate through a further vangle in aclockwise direction as viewed upon FIG. 4, so that the push-rod 14 engages vin the extensiongof tsaidcam, so impeding the cutting tool from approaching the workpiece. In4 addition to this, the disc 19 kpresents to the pawl 23, its non-toothed section, andA said catch will henceV not operate. At the beginning of the. cutting operation of the following workpiece, the `advance device is restored to the starting position with the ,aid of the button 29V and eventually by the button 27. suitably provided with control notches.v

The mechanism describedy can be utilised either for internal or external thread cutting, while permitting the latheitself to be `utilised for conventional turning operations..r

In practice, such details of construction as dimensions, materials, the shape and. the like of the device, may be varied without departing from the scope of the invention as defined in the appended claims. Thus, for example, in order to facilitate the sliding movements of-the carriages there. can be used straight and inverted superpcsed V-shaped guides .in which are arranged cylindrical rollers with .theirshafts askew andY reciprocally olf-set at 90, said rollers running freely betweensaid guides.

Iclaim: Y

1. A .threading attachmentr for a lathe adapted to mount and rotate a workpiece about a first longitudinal axis, a carriage, a slide mounted'on -said carriage for guided translation parallel. withsaid first axis, a bar mounted Y Y on said slide for guided translation relatively thereto parallel rwith said first axis, a tool carrier mounted .on saidY Slide for -guidedtranslation toward .and from said firstl axis, a pin-and-slot connection between said bar andv ,toolcarrier and operating to translatevsaid tool carrier by V.and in response ,to translationV of saidbar, arst cam journaled on said carriage,vsaid first cam having a first surfaceengaging and `:translating said slide in a work p and rotate a workpiece about a first longitudinal axis,

stroke. said first cam also having a second surface engaging said bar at a predetermined rotational position of said first cam, to thereby retract said tool carrier from said first axis, spring means between said slide and bar urging said tool carrier toward said first axis, a second cam journaled on said slide on a second axis parallel with said first axis, a follower fixed with said to l carrier and urged into engagement with said second cam by said spring means, means responsive to retrograde translation of said slide when released by said first cam, to rotate said second cam and thereby free said tool carrier to measured advancement toward said first axis by said spring means, and means urging said slide into retrograde translation.

2. A threading attachment for a lathe adapted to mount a carraige, a slide mounted on said carriage for guided translation parallel with said first axis, a bar mounted on said slide for guided translation relatively thereto parallel with said first axis, a tool carrier mounted on said slide for guided translation toward and from said rst axis, a pin-and-slot connection between said bar and'tool carrier and operatingv to translate said tool carrier by and in responsel to translation of said bar, a first cam journaled on said carriage, said first cam having a first surface engaging and translating said slide in a workstroke, said rst cam also having a second surface engaging said Abar at a predetermined rotational position of said first cam, to thereby retract said tool carrier from said first axis, spring means between said slide and bark urgingsaid tool carrier toward said first axis, a seco-nd cam journaled on said slide on a second axis parallel with said first axis, a follower fixed with said tool carrier and urged into engagement with said second cam by said spring means, meansurgingsaid slide into retrograde translation, a toothed disc journaled on said slide and connected to rotate said second cam, pawl means engageable with the teeth of said disc to rotate the same, a stop fixed with said carriage, and an abutment carried byV said pawl means, said abutment engaging said stop during retrograde translation ofsaid slide when released by said trst cam, to rotate said dise and second cam, thereby to free said tool carrier to measured advancement toward said first axis by said spring means.

3. A thread cutting attachment as in claim 2, and means manually adjustable to vary the angle of rotation of said disc effected by said pawl means, foreach retrograde stroke of said slide.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. A THREADING ATTACHMENT FOR A LATHE ADAPTED TO MOUNT AND ROTATE A WORKPIECE ABOUT A FIRST LONGITUDINAL AXIS, A CARRIAGE, A SLIDE MOUNTED ON SAID CARRIAGE FOR GUIDED TRANSLATION PARALLEL WITH SAID FIRST AXIS, A BAR MOUNTED ON SAID SLIDE FOR GUIDED TRANSLATION RELATIVELY THERETO PARALLEL WITH SAID FIRST AXIS, A TOOL CARRIER MOUNTED ON SAID SLIDE FOR GUIDED TRANSLATION TOWARD AND FROM SAID FIRST AXIS, A PIN-AND-SLOT CONNECTION BETWEEN SAID BAR AND TOOL CARRIER AND OPERATING TO TRANSLATE SAID TOOL CARRIER BY AND IN RESPONSE TO TRANSLATION OF SAID BAR, A FIRST CAM JOURNALED ON SAID CARRIAGE, SAID FIRST CAM HAVING A FIRST SURFACE ENGAGING AND TRANSLATING SAID SLIDE IN A WORK STROKE, SAID FIRST CAM ALSO HAVING A SECOND SURFACE ENGAGING SAID BAR AT A PREDETERMINED ROTATIONAL POSITION OF SAID FIRST CAM, TO THEREBY RETRACT SAID TOOL CARRIER FROM SAID FIRST AXIS, SPRING MEANS BETWEEN SAID SLIDE AND BAR URGING SAID TOOL CARRIER TOWARD SAID FIRST AXIS, A SECOND CAM JOURNALED ON SAID SLIDE ON A SECOND AXIS PARALLEL WITH SAID FIRST AXIS, A FOLLOWER FIXED WITH SAID TOOL CAR-

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