US2781677A - Resiliently mounted form rolling device - Google Patents

Description

1957 G. w. LYMAN ET-AL RESILIENTLY MOUNTED FORM ROLLING DEVICE Filed May 18, 1955 WA M mm [.9 4" mi r a m United States Patent RESILIENTLY MOUNTED FORM ROLLING DEVICE George W. Lyman, Holden, and George W. Bibber, Worcester, Mass., assignors to Reed Rolled Thread Die Company, Holden, Mass., a corporation of Massachusetts Application May 18, 1955, Serial No. 509,192

4 Claims. (Cl. 80 --6) This invention relates to a form rolling device, and more particularly to a device having a die roll arranged to be thrust directly into forming contact with the surface of a positively rotated work piece.

In a device for rolling threads, as well as forming knurls and other shapes by a rolling operation, one or two rolls are arranged with their axes substantially parallel with the work axis, depending upon the peripheral shape of the work piece. The rolls are mounted on a yoke body which is usually carried on the slide of a machine tool arranged to rotate the work positively. These rolls may be freely rotatable, or they may be connected by a gear train which forces them to rotate in synchronism. At the start of the rolling operation, the rolls engage the rotating work and then advance from the initial contact positions to one of being. substantially aligned diametrically with the work. This advance of the die rolls relative to the work applies a stress which resists the synchronized rotation of one of the die rolls. Moreover, as the die rolls penetrate the work, there is a gradual change in the work and die rolling, diameter relationship. That is, the diameter of, the axially immovable work piece may be considered as becoming smaller, so that there is a resultant axial motionof each die roll. due to the effective variation of the lead angles of the work and the rolls. Any variation in the diameter of the work blank alfectsthis axial movement, since an increase of the work diameter will cause the rolls to move in one direction and a. decrease in. diameter will result in the opposite axial movement. This applies also to the use of a single die roll which is driven by the work.

When two die rolls are positively geared together and must rotate. in synchronism, then unless some controlled degree of axial freedom is provided, an extreme side thrust will result, and the various components of the gear train will be subjected to stress which may result in broken or. badly worn drive members as well as. injure the die rolls. Heretofore, some axial freedom has beenprovided, but machine operators have. often used washers or adjusted the parts to prevent or limit endwise motion of. the rolls. Moreover, if a sliding compression spring is used to control the axial motion, this introduces errors in the rolling operation.

It is a primary object. of this invention to provide a form rolling device of this general type with: a mount which insures that a die roll may have. a controlled axial movement as required by the rolling operation and which will insure a return of the rollto a correct initial position for another rolling operation.

Another objectzis to provide aformrollingdevice which permits both an axial motion of a: die roll and a radial movement of the roll relative to its support. to compensate for variations in the position of the work axis and a changing work diameter.

A further object is to provide a construction in which a resiliently acting force permits axi'alrnoti'on' of a die roll as well as a radial movement of the roll perpendicuice lar to the line of approach towards the work axis during the forming stage and which returns the roll to an initial predetermined position for another rolling operation.

A still further object is to provide a work rolling device having two die rolls carried by a yoke and connected by a gear train so that they are rotated in synchronism by a positively driven work piece, in which the yoke is supported resiliently by fixed members which permit only a limited axial movement of the die rolls and a limited movement perpendicular thereto, so that the rolls may move laterally, if needed, to provide a correct rolling contact with the work and thereafter the rolls may move axially in either direction as required during the rolling operation. Other objects will be apparent in the following disclosure.

The drawings show a preferred embodiment of this invention in which:

Fig. l is a perspective view of a form rolling device attached to a machine tool slide, partly. broken away;

Fig. 2 is a plan view of the same with parts broken away for clarity; and

Fig. 3 is an end view of the device.

A thread rolling device, which forms no part of the present invention except as herein described, may be constructed in accordance with the patent to Scott, Reissue No. 23,897 of'November 16, 1954, or to embody the principles set forth in the copending application of Lyman and Bibber, Serial No. 505,304, filed May 2, 1955. Such a construction comprises two die rolls which are suitably shaped and mounted for forming threads, knurls or other rolled forms. These are mounted on two pairs of swinging arms 11 which may be adjusted to hold them at a correct separation for rolling a work piece of a given diameter. The arms 11 with their die rolls are pivotally mounted in a yoke body 12. The die rolls may be either freely rotatable, or they may be geared together by a gear train, as shown in said patent or application. Also, one roll may be used alone for some types of rolling operation.

In the construction illustrated, the yoke body 12 may have a dovetailed slide 13' suitably mounted in slideways '24 on a carrier 15 and held in place by means of the slide clamp 15 secured by set screws 17. This adjustment moves the rolls axially parallel with the work W. The carrier 15 is resiliently supported, as will be described, by a rigidly mounted support 18. This support 18 carries a body 20 adjustably mounted thereon by a dove-tailed part 21 arranged to move the die rolls perpendicular to the directions of adjustment provided by the slideway 14. A suitably shaped clamp 22 forms one side of the dovetailedconnection between the bodies 18 and 2t? and. may be held in place by a set screw 23, thus permitting the part 20 to be held rigidly in position after a desired adjustment. This part 26 and its associated body 18' constitute a primary support which is movable linearly relative to the work.

The support 18 is suitably secured to the machine tool,

slide 25, so that the die rolls may be forced into operative relationship with the work to roll a form thereon. The slide 25 may have one or more T slots 26 formed therein, and in which a nut 27 may be slidably mounted.

This nut is connected to the yoke by means of a bolt 28 This is accomplished by mounting the die roll support on a further support by means of parallel fiat springs rigidly connected at their ends to the two supports, so that only a linear motion can be had. The construction further comprises a movable mount which provides for a lateral movement of the die roll relative to the work surface. If only a single die roll is used, we may employ only the parallel plates, which permit the axial movement of the die roll. For both of these motions, we provide three supports, one being a primary end support or base and another being an end support which serves as a carrier for the die roll or rolls. Between these two is an intermediate support carried by the primary support and on which the carrier support is mounted. Two parallel fiat springs are rigidly connected at their respective ends to two adjacent supports and are arranged to provide for the axial motion. The other two adjacent supports are connected by a means which provides for the lateral motion of the die roll into a proper rolling contact with the work. The preferred embodiment comprises separate springs which are so mounted rigidly in a relatively perpendicular arrangement that the die rolls or their slide supports may move axially and/or radially in straight line motions. These springs preferably comprise two pairs of resilient flat springs 30 and 32, each of which is a flat plate or a multiple of plates of a stifily resilient metal, such as spring steel, and the resilient plates are of such size and arrangement as to hold the die rolls almost rigidly in position and yet permit a slight linear movement thereof under the form rolling conditions. The use of a pair of plates rigidly connected at. their ends to both the support and the support body insures that the rolls may move only linearly or axially, so that the die roll axis cannot be tilted.

The two spring leaves or plates 30 101 the laminations of thin plates are attached rigidly to the slide 20 at their inner ends by means of bolts or rivets 34. The slide 20 is provided with two slots 35 (Fig. 2) in which the edge portions of the steel plates 30 are inserted, and the bolts or rivets 34 are then secured in suitably aligned holes in the plates and the supporting body 20. At their outer ends, the plates 30 likewise project into slots in the :outer T portion 36 of an intermediate support 38 which is movable between and separate from the carrier and the inner support fixed on the slide mount 18. The springs are secured to the intermediate support by the rivets or bolts 39. Thus, the intermediate support 38 is mounted securely on the slide 20 solely by means of the stifily resilient leaves or plates 30. sure a rigid fastening for both ends of each plate 30.

The intermediate support 38 has a projecting T portion 40 at the two sides of its inner end, and these carry the spring leaves or plates 32. Each leaf 32 is mounted in a slot on the related projecting end 40 and it is held rigidly in place by means of a rivet or bolt 41 in the same manner as the other plates are mounted. The outer ends of these leaves 32 are similarly connected to the carrier slide 15 which adjustably carries the yoke 12 on which the die rolls are mounted. These plates 32 are rigidly fastened in the slots in the body 15 by rivets 42. The inner edges of the spring plates 32 and the interme diate support 38 are close to the slide 20, so as to save space and permit the use of relatively long springs with a consequent flexibility of action. Thus the intermediate support 38 is supported solely by the springs 30, and it in turn is the sole mount for the carrier 15 through the springs 32.

The springs may be suitably constructed. A set of thin laminated steel plates of the thickness of a single steel plate will provide enough flexibility and yet resist adequately the high pressure involved in a direct thrust of the die rolls into the work without buckling, as well as provide resistance and yet permit axial movement of the die rolls, as required. As an example of a suitable spring Various expedients may be adopted to in- I mount, each leaf spring 30 or 32 may be made of five to eight laminations of resilient steel strips about 0.015 to 0.020 inch thick, and the plate may be about two inches, more or less, on a side, or as is found desirable.

In its operation, the die rolls are initially located as determined by the adjusted positions of the slides 13 and 20 which are mounted above and below the two pairs of springs 30 and 32. These slides 13 and 20 are respectively parts of the carrier and the primary support and they are spaced from and solely connected by the intermediate support 38 and the two pairs of springs. If the die rolls should not be correctly positioned after such adjustment of the slides so as to touch both sides of the work at the same time, :or to touch only one side, if thus desired, the springs 30 will bend as needed (shown exaggerated in Fig. 2 by the dotted lines) as soon as one die roll touches the work and permit the yoke head to move slightly laterally but in a straight line motion and thus bring both die rolls into proper engagement with the work.

The outer springs 32 are particularly important in providing for the axial movement of the die rolls. Ordinarily, if the relative diameters of the work and die rolls are correct, the rolls tend to move axially first in one direction, then in the other during the rolling cycle, as is permitted by a stifiiy resistant bending of the springs 32, as shown in exaggerated condition by the dotted lines in Fig. 3. The rolls return to their original positions when removed from the work due to the spring action. Thus this axial freedom compensates both for a change in ap parent work diameter and for the stress condition resulting from the advance of the rolls relative to the work, which causes one of the die rolls to move axially, without imposing undue stress on the die roll threads or the gear train which synchronizes the rolls. A single die roll used alone or a pair of freely rotatable die rolls will follow this same action. Also, since the two die rolls or a single roll may be so mounted and moved that the rolls are initially properly aligned with the work, we may provide for only an axial movement of the die rolls by means of springs 32, and in that case the construction will be simplified by the omission of springs 30 and associated parts.

Hence this double spring mount for the die roll carrier holds the die rolls in an exact preset position for straddling the work, or correctly positions a single die roll as required for the beginning of the thread rolling operation. Such positioning may be adjusted by means of the various clamping dove-tailed slides which carry the yoke. It will also be noted that the spring mount is for the roll supporting structure and that it does not permit the roll to move relative thereto. Hence the die roll can move only linearly and not angularly as is permitted by motion of the entire support. There are no sliding or tilting parts for the roll movement and all permitted motion is controlled by the parallel springs.

This construction permits a free axial movement of the die rolls which cannot be prevented during a normal use of the device. Any attempt to restrict the axial motion of the rolls invites various defects, such as drunkenness of the thread, a poor roll life and excessive stress upon the roll thrust washers, as well as improper relationship with the work. The spring mount insures an optimum behavior of the die rolls so that they will follow the same track or helix throughout the entire formation of the thread. This prevents the formation of slivers, scufi': marks, stepped roots and unequal spacing of the threads which gives a false pitch line and a non-symmetrical thread crest. The ultimate goal of matching is to insure that when the rolls have advanced to a full straddle position on a completed thread, the ends of the rolls will be aligned in the same plane.

It will now be appreciated that various modifications of this constmction may be employed to embody the invention herein set forth, comprising a pair of leaf springs, each of which may be either a single plate or a lamina tion of thin plates, connected rigidly in a parallel arrangement to the carrier and to a support therefor and so arranged that a lateral thrust relative to the springs permits the carrier and its associated die roll to move linearly relative to the work. It further comprises two pairs of leaf springs so arranged that the die roll carrier may move only linearly in directions axially parallel to the die roll and perpendicular thereto. This construction preferably includes an intermediate support connected between the carrier and a primary support by the pairs of leaf springs arranged at right angles for a two directional movement of the carrier under the form rolling requirements. Slides may be associated with the carrier and the primary support which provide for adjustment of the carrier for the die rolls in directions which are either parallel with the work axis or transversely thereof, so that the die rolls may be properly positioned for the rolling operation. Hence, the above disclosure is to be interpreted as setting forth the principles of this invention and a preferred embodiment thereof and not as imposing limitations on the appended claims.

We claim:

1. A form rolling device comprising -a carrier, a primary support therefor which is movable linearly relative to a rotated piece of work, a die roll rotatably mounted on the carrier for rolling a form on the work, a movable intermediate support between and spaced from the carrier and primary support, !a pair of leaf springs rigidly con nected to the primary support and the intermediate support which permits a limited linear movement of the die roll in one direction, and a pair of leaf springs rigidly connected to the intermediate support and the carrier which permit a limited linear movement of the die roll in a direction perpendicular to the other.

2. A form rolling device comprising a yoke, a pair of die rolls rotatably mounted thereon for rolling a form on a positively rotated piece of work, a carrier slidably supporting the yoke for linear adjustment of the rolls relative to the work, a support arranged to be moved relatively towards the work, a slide mounted on the support for adjustably moving the die rolls at right angles to the carrier adjustment, said support and slide constituting a primary support, an intermediate support between and movable relative to the carrier and primary support, a A

parallel flat springs which are rigidly connected at their respective ends to the intermediate support and an end support, said springs being arranged to provide only a yielding axial movement of the die roll during a forming operation and a return to an initial position, and means which provides for a lateral movement of the die roll and its support relative to the work.

4. A form rolling device comprising two end supports and an intermediate support therebetween, one end support being a primary support mountable on the machine tool and the other end support being a carrier, a die roll rotatably mounted on the carrier for rolling a form on a work piece, a pair of parallel fl-at springs rigidly connected at their ends to the intermediate support and one of the end supports which are arranged to provide only a yielding axial movement of the die roll, and means including a flat spring connected at its ends to the intermediate support and the other end support which provides for a yielding lateral movement of the die roll relative to the work piece.

References Cited in the file of this patent

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