GB2165785A - Production of bodies of revolution having at least one groove - Google Patents

Abstract

Bodies of revolution are produced having at least one peripheral groove whose width decreases towards the floor of the groove by rotating a blank 9 about its longitudinal axis while a pressure which exceeds the yield point of the material of the blank is locally applied. To avoid excessive hardening of the blank material during shaping, pressure on the blank is reduced from a maximum corresponding to the width of the groove at the peripheral surface of the blank, to the width of the floor of the groove, in accordance with the progressing depth of impression X1 to X5. The blank is rolled between ribs on a central roller (12, Figure 18) and ribs 7 and 8 on die segments 2 to 6. The initial portion of each rib is axially wide but radially shallow and the radial height of the ribs increase while their width decreases. <IMAGE>

Description

SPECIFICATION Production of bodies of revolution having at least one groove The invention relates to a method of producing bodies of revolution having at least one groove or the like which extends substantially in the peripheral direction thereof and whose width, extending in the axial direction of the body of revolution, decreases towards the floor of the groove, wherein, with the blank being rotated about its longitudinal axis, a pressure which exceeds the yield point of the material of the blank is locally applied, and to an apparatus for carrying out the method.

The previously known methods of that kind provided for impressing a shaped rib into the blank as it rotated, the width of the rib, as considered in the direction of forward feed motion, increasing from a minimum value to a maximum value and the height thereof also increasing. In other words, in orderto produce for example a V-shaped groove, the previous method involved using a shaped rib which was impressed with its tip leading into the rotating blank, the rib increasing in width and height in the course of the forward feed motion.

The disadvantage of such a method of manufacture is that the fact that the tip of the shaped rib was impressed into the material caused the material to undergo hardening, and the hardened region had to be further deformed, so that corresponding high pressures are required and overloading of the material and thus cracking thereof may very easily occur.

The aim of the invention is to avoid such disadvantages and to propose a method of the kind set forth in the opening part of this specification, which avoids further deformation of regions of the workpiece which have already been severely deformed.

According to the invention, that is achieved in that the width of action of the presence is reduced from a width corresponding to the width of the groove to be produced at the peripheral surface of the blank, to the width of the floor of the groove to be produced, in accordance with the progressing depth of impression, wherein the reduction in the width of impression, with progressing depth of impression, is effected in accordance with the inclination of the walls of the groove.

That provides that it is only ever the regions which have been less deformed, that are subjected to further deformation, and extreme levels of hardening and consolidation of the material are avoided. In addition, deformation of the blanks in that way requires a smaller amount of energy. When producing screwthreads by means of the method according to the invention, in accordance with a further feature of the invention, it may be provided that the screwthread groove is impressed into a blank which is of the outside diameter of the desired screwthread. The material which is pressed out of the screwthread groove in that operation is displaced in the axial direction so that the finished screwthreaded pin or bolt is greater in length than the blank used for that purpose.

In relation to screwthreads, in particular trapezoidal screwthreads or the like, there is the advantage, when using blanks which are of the outside diameter, that the material does not have to flow up the flanks of the screwthread in order completely to build up the screwthread flights or ribs, which in certain circumstances can result in overloading of the material and cracking at the peripheral surface of the screwthread flights, but the material can only flow axially, thereby ensuring that the screwthread flights consist of solid material and cannot have any cracks or cavities which are covered by material which is disposed in an outward direction.

Another aim of the invention is to provide an apparatus for carrying out the method according to the invention.

In an apparatus comprising at least one roller which co-operates with a co-operating pressure surface and which is movable relative thereto, it is therefore proposed, in accordance with the invention, that the width of the shaped rib or ribs decreases in the direction of the relative movement between the roller and the co,-operating pressure surface, and the height thereof increases. That ensures that, when producing a peripheral groove or the like, the blank is first acted upon, with the maximum width of the groove to be produced, while the width of impression progressively decreases and the depth of impression increases in the course of production.

Another possible configuration of an apparatus for carrying out the method according to the invention provides that, in an apparatus comprising two rollers which can be driven in mutually opposite directions of rotation and of which at least one is provided with a raised shaped rib and between which there is a roll gap, in accordance with another feature of the invention the rib is of decreasing width and increasing height in the direction of rotation of the roller.

Such an apparatus also ensures that the pressure firstly acts on the blank with the greatest width of the groove to be produced, and the width of action decreases as the groove is impressed in the blank. In accordance with a further feature of the invention, it may be provided that shaped ribs are disposed both on a drivable central roller and on the co-operating surface which is subdivided into segments, which ribs cross each other in the course of the mutual relative movement.

Those features make it possible for the counterpressure surface to be advanced to a greater or lesser degree towards the central roller, as required, without thereby giving rise to a roll or operative gap which varies over its arcuate length. That is due to the fact that the mutually crossing ribs only cooperate along the generatrices of the central roller and the counterpressure surface, which pass through the point of intersection of the ribs, and thus apply the necessary pressure to the blank.

In that connection, it is advantageous for the segments of the counterpressure surface to be arranged on carriages which are guided displaceably radially with respect to the central roller and which are movable preferably independently of each other by means of a control drive. In that way, it is possible to take account of wear of the ribs but also differences both in the dimensions of the blank and also in the properties of the material thereof.

It may also be provided that the control drive of the carriages is connected to a measuring means for measuring the articles when in the finally deformed condition and displaces the carriages in dependence on the detected measurement data, thereby providing for automatic adjustment of the counterpressure surface. Thus, it may be provided that random samples of the articles produced are taken from the stream leaving the apparatus, measured in the measuring means and compared to a predetermined tolerance range and the carriages carrying the counterpressure surface are adjusted such that the produced articles lie in the middle of the tolerance range.

It is fully possible for one of the mutually crossing ribs to be disposed perpendicularly to the axis of the central roller, but in that case the central roller and the counterpressure surface, besides the relative rotary movement, must also perform a relative movement having a component in the axial direction of the roller.

In order to avoid that additional movement which, in that case, can be controlled in any desired manner, and in order thereby to permit the apparatus to be simpler in construction, it may be provided, in accordance with a further feature of the invention, that each of the mutually crossing ribs of the central roller and the co-operating surface extend at an inclined angle with respect to the axis of the central roller. That arrangement ensures that the ribs constantly intersect each other during the rotary movement of the central roller, if we disregard an intake and discharge region of the apparatus, for the feed of blanks and the discharge of finished articles, which region is kept free of ribs.

In order to ensure precise entrainment and guidance of the blanks during processing thereof between the central roller and the counterpressure surface, a further feature of the invention may provide that the central roller is drivingly connected by way of transmission means to an entrainment means for the blank, which entrainment means has at least one but preferably two rotary members which are spaced from each other in the axial direction of the central roller and in which push rods or thrust members are held displaceably in the longitudinal direction thereof and engage by means of a sliding member or the like in a peripheral control groove which is disposed in a stationary part of the apparatus, wherein the thrust members which are guided in two different rotary members are axially aligned with eath other.Those features provide that the blanks are clamped and thus entrained between the thrust member and a cam, but better between a respective pair of mutually axially aligned thrust member. In that arrangement, it may further be provided that the control groove, with the exception of a feed and discharge region for the blanks and the finished bodies of revolution respectively, extends substantially parallel to the path of the points of intersection of the ribs of the central roller and the counterpressure surface during the rotary movement of the roller, wherein the control grooves which are associated with the thrust members guided in both rotary members extend parallel to each other in that region, thereby ensuring a precise guidance action forthe blanks and easy feed ofthe blanks and removal of the finished bodies of revolution.

When producing bodies of revolution with peripheral grooves, additional compacting or consolidation in the region of the walls of the groove may be desired in some cases. In such a situation, the control groove may be inclined with respect to the imaginary line which is formed from the path of the points of intersection of the ribs of the central roller and the counterpressure surface. By virtue of that arrangement, the ribs press not only radially against the blank but also axially against the walls of the groove which are being formed.

A preferred embodiment of an apparatus according to the invention further provides that at least the mutuallyfacing end regions of the thrust members are arranged to be rotatable about the longitudinal axis of the thrust members, wherein preferably the end regions of the one thrust members are springloaded relative to the coaxially aligned thrust members. That avoids friction between the end faces of the blanks and the thrust members By virtue of the end regions ofthe one thrust members being resiliently supported, that arrangement eliminates excessive pressure against the blank being processed when the blank grows in the axial direction due to the groove being impressed therein. In addition, that arrangement also makes it possible to compensate for dimensional variations in the blanks. The end regions of the thrust members may be formed by inserts.

In accordance with a further feature of the invention, it may also be provided that provided for the entrainment means is a ring gear or spur gear which is non-rotatably connected to the central roller and into which engage gear transmissions drivingly connected to support shafts disposed parallel to the thrust members, wherein the support shafts are held in the pressure members guiding the thrust members, or rotary members which are non-rotatably connected thereto.

Those features provide that the blanks are driven during the operation of processing same, while, by virtue of suitable matching of the gear transmission, the peripheral speeds of the central roller and the blanks can be matched to each other.

The invention will now be described in greater detail with reference to the drawings in which: Figures 1A and 1B diagrammatically show tools for carrying out the method according to the invention and deformation of a blank using such tools, Figure 2 shows the development of the shaped ribs of the tools shown in Figures 1A and 1 B, Figure 3 is a view in vertical section of an embodiment of an apparatus for carrying out the method according to the invention, Figure 4 is a plan view of the apparatus shown in Figure 3, Figure 5 is a detail of the apparatus shown in Figures 3 and 4 on a larger scale, Figure 6 is a detail of the thrust member guide arrangement of the apparatus shown in Figures 3 and 4, on an enlarged scale, Figure 7 shows a further detail of the thrust members, Figure 8 is an exploded view of the entrainment means of the apparatus shown in Figures 3 and 4, Figure 9 is a front view of the entrainment means, and Figure 10 is a plan view of the entrainment means.

Figure 1A is a diagrammatic view of the shaped ribs 7 and 8 which are disposed on the counterpressure surface 1 which is subdivided into five segments 2, 3, 4, 5 and 6. The rib 7 serves to form the step or shoulder 10 of the finished article 9" produced from the blank 9. On the other hand, the rib 8 serves to form out the groove 11 of the finished article and has its maximum width and minimum height at the beginning of the counterpressure surface or at the boundary of the intake region for the blanks 9 which are to be handled.Along its path from the beginning of the rib 8 to the end thereof at the edge of the segment 6 which, as will be described hereinafter, is the trailing edge as considered in the direction of rotation of a central roller, the width of the rib 8 progressively decreases and it terminates in a form which is equal and opposite to the groove 10.

The central roller 12 shown Figure 1 B runs in the space enclosed by the segments 2 to 6 of the counterpressure surface, but was not shown jointly therewith, for the sake of enhanced clarity of the drawings. The roller 12 is installed in such a way that, in a position of the roller 12 relative to the segments 2 to 6 of the counterpressure surface 1 in which the beginnings of the ribs 7' and 8' are radially aligned with the beginnings of the ribs 7 and 8, they are also at the same height.

The change in the cross-sectional form of the rib 8 from segment to segment or from segment boundary to segment boundary can be clearly seen from the change in the configuration of the blank 9, to give the finished article. Thus, the intermediate products 9' corresponds to the condition of deformation of the blank 9, as occurs at the boundary xl between the segment 2 and the segment 3. That shows the cross-sectional form of the ribs in that cross-section.

In the same fashion, the intermediate product 9" corresponds to the condition of deformation of the blank in the cross-section x2, the intermediate product 9"' corresponds to the condition of deformation of the blank at the cross-section x3 and the intermediate product 9'V corresponds to the condition of deformation at the cross-section x4. In cross-section x5, the blank is formed to give the finished body of revolution 9v It will be clearly seen from the form of the intermediate products 9', 9", 9"', 9v, 9v, that the rib 8 and the ribs 8' (Figure 1 b), from their beginning, decrease in respect of their width at their location of greatest height, in their respective cross-section, whereas the ribs 7 and 7' increase in width.

It will also be seen from Figure 1Athatduring processing the blanks 9 are held between two thrust members or pushrods 14 and 14' which separate from each other in the intake and discharge region which is between the cross-sections 5x and x, and thus enable the blanks 9 to be introduced and the finished articles to be removed, such operations occurring in different planes.

Figure 1 B diagrammatically shows the central roller 12 which co-operates with the counterpressure surface 1. The roller 12 is provided with two shaped ribs 7' and 8' which correspond to the ribs 7 and 8 but which are included in the opposite direction to the ribs 7 and 8 so that when the central roller 12 is fitted between the segments 2 to 6, the ribs 7, 7' and 8, 8' respectively cross each other when the central roller 12 rotates in the direction indicated by the arrow 13.

As can be seen from Figure 2 which shows a development of the ribs 7, 8, 7' and 8', the ribs 7' and 8' are moved past the ribs 7 and 8 in the direction indicated by the arrow 13, whereby the points of intersection of the ribs move inclinedly downwardly towards the right. In that arrangement, the blank 9 is guided by the two thrust members 14 and 14' substantially along the line which corresponds to the geometrical locus of the points of intersection of the ribs 8 and 8' during the relative movement of the ribs 7 and 8 with respect to the ribs 7' and 8'.

The thrust members 14 and 14' are guided between the boundaries x and x5 of the segments of the surface 1 along the imaginary base lines 15 and 15' which are shown in dash-dotted form and which extend parallel to the ribs 8 and 8'. The lines 15 and 15' are slightly inclined with respect to the line corresponding to the geometrical locus of the points of intersection, thereby taking account of the axial growth in length of the blank 9 due to the groove 11 being impressed therein.

It will be appreciated that the blanks 9 are not guided along two different paths, but the dashdotted lines 15 only indicate the path of the blanks with respect to the ribs 7,8 and 7', and 8' respectively. In practice, as will be described in greater detail hereinafter, the blanks are in principle controlled by a groove which is provided in a stationary part of the machine and the configuration of which substantially corresponds to that of the rib 8.

With the above-described arrangement, as considered from the central roller 12, the path of movement of the blanks is parallel to the rib 8'.

As can be seen from Figures 1 B and 2, the cross-sectional shape of the ribs 7' and 8' also alters in the same fashion as that of the ribs 7' and 8', that is to say, the rib 8' increases in height from its beginning to its end and decreases in width in the region of its maximum height.

Figure 3 is a diagrammatic view of an apparatus for carrying out the method according to the invention in vertical section, in which in particular the mounting and bearing means and the installation thereof are shown in simplified form. In addition, structural groups and units which, for manufacturing reasons and for reasons of greater ease of assembly, consist of a number of parts, are shown in part as being formed as one part.

The drive motor 20 drives a shaft 23 by way of a clutch 21 of which one half is connected to a flywheel 22. The shaft 23 is supported in the housing 26 in conventional manner by way of the rolling bearings 24 and 25 and is non-rotatably connected to a bevel gear 27 and a chain wheel 29.

The bevel gear 27 meshes with a further bevel gear 28 which is non-rotatably connected to a vertically disposed main shaft 30. The main shaft 30 is held by means of two tapered roller bearings 31 and 32 in a carrier cylinder 33 connected to the housing 26.

Afirst guide member 34 is fitted on the cylinder 33 and is rigidly connected thereto. In addition, disposed on the cylinder 33 is a needle bearing 35 which is axially fixed in position by the guide member 34 and a support flange 36, and which rotatably mounts a rotary member 37 provided with a chain ring 38. The rotary member 37 or the chain ring 38 thereof is connected by way of two chains 39 to chain wheels 40 which are non-rotatably connected to the output shaft 41 of a transmission 42.

The transmission 42 is driven by way of two chains 44 and chain wheels 43 by the shaft 23 orthe chain wheels 29 connected thereto, and is held in the housing 26' by way of a bracket 46.

The rotary member 37 is connected by way of pins 45 to a further rotary member 47 and is mounted to the main shaft 30 by way of a rolling bearing 48. The two rotary members 37 and 47 are also connected together by way of slotted guide sleeves 49 in which the thrust members 14' or the guide heads 50 thereof are axially slidably guided. The guide heads 50 engage with their rotatably mounted roller 51 into a control groove in the guide member 43.

The thrust members 14' pass through the rotary member 47 and are guided therein in bushes 53. In addition, secured to the rotary member 47 is a splash ring 54 which serves to carry the oil used for lubrication purposes away into an annularly disposed oil sump (not shown).

The rotary member 47 is connected to a further rotary member 56 by way of struts 55. Like the rotary member 47, the rotary member 56 is provided with tangentially extending portions of dovetail guides which serve to accommodate sliding members which are parts of the entrainment means shown in Figures 8 to 10 and are described hereinafter with reference to those Figures. For the sake of enhanced clarity of the drawings, the corresponding reference numerals are not shown in Figure 3.

Non-rotatably disposed on the main shaft 30 is a chuck body 57 on to which is fitted the roller 12 which bears the ribs 7' and 8', being held in position non-rotatably by means of a key and groove connection. Screwed to the roller 12 is a ring gear of spur gear 58 from which the drive for the entrainment means is derived, as will be described in greater detail hereinafter with reference to Figures 8 and 10.

A sleeve 59 is fitted on a stepped portion of the main shaft 30 and non-rotatably connected thereto by way of a key and groove connection. Mounted on the sleeve 59 by way of a rolling bearing 60 is a rotary member 62 which is screwed to an internal ring gear 61. As can be seen from Figure 5, the ring gear 61 meshes with intermediate gears 63 which in turn mesh with further gears 64 which serve only to reverse the direction of rotation and which, like the intermediate gears 63, are mounted rotatably in a ring 66 disposed in the interior of a further guide member 65 which is fixed with respect to the housing. The gears 64 in turn mesh with a ring gear which is disposed on the sleeve 59 and which provides for the drive for the rotary member 62 by way of the gears 63 and 64 and the ring gear 61 which supports the guide member 64 by way of a rolling bearing 60'.

The rotary member 62 is connected by way of pins 67 and a sleeve 68 to a ring 69 in which are mounted bushes 53 in which the thrust members 14 are rotatably and axially displaceably guided, just as in the rotary member 62.

The guide member 65 is of a two-part construction and supports the main shaft 30 by way of a rolling bearing 69'. In addition, the guide member 65 is provided with a control groove 70 into which engages a rotatable roller 51 carried in each guide head 71 of the thrust members 14, as shown on a larger scale in Figure 6. As shown in Figure 6, the pin 72 carrying the roller 51 engages with an extension portion into a peripheral groove 73 is the thrust member 14 whereby the latter is mounted rotatably but axially displaceably in the guide head 71.

Over the major part of the periphery of the guide member 65, the control groove 70 extends parallel to the control groove 52 of the guide member 34. It is only in the intake and discharge region which was described with reference to Figure 1A that the above-indicated parallel condition does not occur and in that region the two control grooves move apart and back towards each other again.

The guide member 65 can be connected by way of a flanged member 74 to a support arm 75 in which the main shaft 30 is supported in a plain bearing. The support arm 75 is supported on a carrier pillar 76 which is fixed on the housing 26'. Disposed in the pillar 76 is a spindle 77 which is supported relative to the inside wall surface of the pillar 76 and relative to a cylindrical bore 79 of the support arm 75 by means of a centering ring 78 in its upper region. The support arm 75 is clamped to the pillar 76 by means of a nut 80.

After unscrewing and removing the nut 80 and releasing the connection between the flanged member 74 and the support arm 75, the latter can be lifted and pivoted whereby it is possible to dismantle the apparatus, in order for example to replace the roller 12 by another roller with ribs of a different configuration in order to be able to produce different bodies of revolution.

Also arranged on the housing 26' are five carriages 81 which carry the segments 2 to 6 of the co-operating surface 1. The carriages 81 are guided in housings 82 in each of which is disposed a screw-threaded spindle 84 supported in a bearing arrangement 83 comprising thrust and radial rolling bearings. The spindle 84 is driven by a stepping motor 86 by way of a transmision 85 and it passes through two nuts 87 which are braced relative to each other to compensate for play atthe spindle, which in turn is connected to the carriage or slide body 88 which is guided in the housing 82 and which incorporates a weak location 89 for carrying wire strain gauges.

Mounted at the end of the body 88 is an adjustable-height support, which, together with the adjusting spindle associated therewith, is generally denoted by reference numeral 90. Secured to the support 90 is a segment of the co-operating surface 1 which bears the ribs 7 and 8.

A peripheral cam 92 is mounted to the carriages 81 and the pillar 76 by way of mounting arms 91. As will be described in greater detail hereinafter with reference to Figures 8 and 9, the cam 92 is provided for controlling the entrainment means.

The feed means for the blanks to be worked upon, which can be better seen from Figure 4, is indicated generally by reference numeral 93 and is driven by the transmission 42 by way of a chain wheel 94 and a chain 95.

The step-up ratio of the transmission 42 and the chain wheels 40 and 38 as well as that of the transmission formed by the ring gear 61 and the ring gear of the sleeve 59 and the gears 63 and 64 is such that the rotary members which are driven by those transmissions, on the path of movement described by the thrust members 14 and 14' which are mounted in the rotary members, move at half the peripheral speed of the peripheral surface of the roller bearing the ribs.

In the carriage 81 shown in section in Figure 4, a vibration generator 96 is screwed into the segment of the counterpressure surface 1 and causes the counterpressure surface to be displaced with highfrequency vibrations or oscillations, thereby facilitating deformation of the blanks 9 which are guided between the segments of the surface 1 and the roller 12 by means of an entrainment arrangement which is not shown in Figure 4 for the sake of enhanced clarity of the drawing.

As can be seen from Figure 4, the supply means 93 has an inclinedly extending channel 97 which guides the blanks 9 into the star wheel 98. The star wheel 98 transports the blanks to a further star wheel 99, while for the purposes of transferring the blanks the arrangement includes a guide plate 100 which is secured to the housing 26' by way of a holder which is not shown for the sake of enhanced clarity of the drawings.

Punches 101 of which only two are illustrated are guided in the star wheel 99 which rotates in a plane which is displaced with respect to the star wheel 98.

The punches 101 project beyond the upper face of the star wheel 99 and slide against the cam 102. The cam 102 which is stationary causes the blanks to be pushed out into the path of the thrust members 14 and 14' by which they are engaged or clamped.

Disposed in a horizontal plane which is different from that of the feed means is a magnet 103 which, after the finished bodies of revolution 9v are released by the thrust members 14 and 14', conducts them into a further channel 104.

Incorporated into the channel 104 is a switching means 105 which permits a body of revolution to be selectively removed from the channel by a deflection plate 106 being inserted thereinto by means of the piston-cylinder arrangement 107. The body of revolution which is removed from the channel in that way then passes by way of a channel 108 to a measuring device 109 in which the body of revolution is pushed by means of a piston 110 into a measuring position in which it bears against an abutment 111 which is pivotable by means of a piston-cylinder arrangement 112. The measuring operation itself is carried out by means of an optical measuring head 113which produces the measuring result in the form of electrical signals which are passed to a control means (not shown) for example a process computer.In the case where the measurement values obtained are towards the limits of a predetermined tolerance range, the control means passes suitable control instructions to the stepping motors 86 of the carriages 81, to provide for suitable adjustment thereof. That makes it possible to observe very close tolerances.

After the operation of measuring the body of revolution, the abutment 111 is pivoted by the piston-cylinder arrangement 112 and the pistoncylinder arrangement 110 pushes the body of revolution which has already been measured to the opening 114 through which it slips to the exterior by way of the channel 115.

Figure 7 shows the end regions of the members 14 and 14' on an enlarged scale, said end regions being rotable about the longitudinal axis of the members 14 and 14'. In that arrangement, screwed into the thrust member 14 in the end thereof is an insert 116 in which atip 117 is held by means of a pin 119 which passes through a transverse 118 in the tip 117 and which also passes through the walls of the insert 116. The tip 117 is axially displaceably held in the insert 116 and is subjected to the force of a spring 146. As the transverse bore 118 is large in diameter than the tip, this arrangement provides for a slight amount of axial displacement of the tip 117 relative to the insert or the casing thereof.That makes it possible to compensate for slight dimensional variations in the blanks 9 and to compensate for the growth in length of the blanks while they are being deformed by the ribs 7,8 and 7', 8' respectively of the counterpressure surface 1 and the roller 12.

A sleeve 121 is screwed oh to the screwthreaded spigot 120 of the thrust member 14'. A slide bush 122 is fitted into the sleeve 121 and secured therein with an insert member 123. A tip 124 is rotatably carried in the bush 122, the collar on the tip being supported against a slide ring 125 which in turn is supported against a shoulder of the sleeve 121.

The arrangement of the rotatable tip 124 of the thrust members 14' and the rotatable mounting of the thrust members 14 in the guide heads 71 thereof ensures that friction between the thrust members 14, 14' and the blanks 9 which are held therebetween is eliminated.

The entrainment means will be described in greater detail with reference to Figures 8,9 and 10.

The rotary members 47 and 56 are provided in a section-wise manner with tangentially extending, radially projecting dovetail guides 126. Two slide members 127 are displaceably disposed on each of the sections of the dovetail guides. The thrust members 14 and 14' pass between the projections on the rotary members whereas the support rollers 128 are rotatably mounted in the bores 129 of the slide members 127. The slide members 127 which are mounted in different rotary members 47 and 56 respectively are connected together by way of the pressure members 130 which are screwed to the slide members 127.

The members 130 are controlled by respective cam shafts 131 whose cylindrical projections 132 extend through and are rotatably mounted in the bores 133 disposed in the radially projecting portions of the rotary members 47 and 56. The upper cylindrical projections 132 are each non-rotatably clamped in a respective control lever 134 while the projections 132 engage into the bores 135 which define a slot 136. The control levers 134 slide along the stationary cam 92 upon rotary movement of the two rotary members 47 and 56.

Over the arcuate region over which the counterpressure surface 1 extends, the cam 92 describes substantially a circular arc. In the region of the feed and discharge area for the blanks 9 and the finished bodies of revolution respectively, the cam 92 has a depression 137 which permits pivotal movement of the control levers.

The support rollers 128 have a region which is provided with knurling and which comes into contact with and drives the blanks 9. The support rollers are driven by the gears 138 which are non-rotatably connected to the support rollers. The gears 138 mesh with intermediate gears 139 which are rotatably mounted with a respective gear 138 in a holder 140, the intermediate gears 139 meshing with the gear 58 connected to the roller 12 carrying the ribs 7' and 8'. In that arrangement, because of the difference in speed between the gear 58 and the holders 140 which are also moved by virtue of the driving connection to the rotary members 47 and 56 which is provided by the support shafts 128, a rolling movement of the intermediate gears 139 is produced and thus the support shafts are driven.

As can be seen from Figures 9 and 10, the respectively associated holders 140 are connected together by a pin 141,with the two holders 140 being braced towards each other by two springs 142.

As long as the control levers 134 slide along the arcuate region of the cam 94, they are deflected and the cam shafts 131 which are non-rotatably con nectedthereto urge the members 130 and the support shafts 128 which are held therewith in the slide members 127 against the thrust members 14 and 14' and thus against the blanks 9 to be deformed. When that happens, the holders 140 are urged apart againsttheforce of the springs 142.

When one of the control levers 134 slides into the depression in the cam, that control lever can be deflected and the springs 142 can urge the support shafts 128 away from the thrust members whereby, by way of the pivotal movement of the cam shaft 131, the control lever 134 is also caused to pivot, being held in contact with the cam 92 by the springs 142.

As can be seen from Figure 10, the intermediate gears 39 rotate in two different horizontal planes and are rotatably fixed on axle journals which are held at one end in the respective holders 140. The step-up ratio of the transmissions 58, 139, 138 and the support shaft 128 or the diameter of the knurled region thereof are matched to each other in such a way that the peripheral speed ofthe knurled region of the support shafts 128 and thus also that of the blanks 9 bearing thereagainst is equal to the peripheral speed of the periphery of the roller 12 carrying the ribs.Although the blanks 9 are caused to rotate solely by the rolling movement against the stationary co-operating surface 1 and the peripheral surface of the roller 12, as indicated by the arrows in Figure 10, nonetheless a certain sliding movement of the blank against such surfaces may also occur during working of the blank. That is prevented by the additional drive for the blanks by the support shafts, while, as can be seen from Figure 10, the blank 9 is always supported and driven between the support shafts 128 which are mounted in adjacent pairs of holders 140.

As can be seen from Figure 8, the pressure members 130 have a groove which is towards the support shafts 128 and which extends in the axial direction and in which are disposed rolling members 144 which project beyond the outer edges of the groove 145. That substantially eliminates friction between the support shafts and the pressure members 130.

When the control levers 134 go from the arcuate region of the cam 92 into the depression 137 therein, the intermediate gears 139 also perform an additional movement relative to the gear 58, by virtue of the two holders 140 connected by the pin 141 moving towards each other, due to the springs 142. Although that additional movement results in a change in the speed of rotation of the support shafts, that is however of no importance as in that situation the support shafts 128 are moved away from the blank 9.

The control grooves 52 and 70 which determine the path of the blanks 9 extend as indicated by the line 15 in Figure 1A or parallel thereto, in the region covered by the co-operating surface 1. Outside that region, the paths of the control grooves have deviations in opposite directions, the control grooves 52 and 70 moving further apart from each other and moving towards each other again so that in that region there is no clamping in respect of the blanks 9 or the bodies of revolution 9V and the blanks can be introduced and the finished bodies of revolution can be removed.

In the illustrated embodiment, the co-operating surface 1 is of a curved configuration corresponding to the roller 12, but that is in no way absolutely necessary. Thus, it is also possible to use a flat counterpressure surface over which the roller moves, in which respect it is irrelevant whether the counterpressure surface is moved with respect to the axis of the roller or whether the roller is moved in parallel relationship with the counterpressure surface.

Claims (11)

1. A method of producing bodies of revolution having at least one groove or the like which extends substantially in the peripheral direction thereof and whose width, extending in the axial direction of the body of revolution, decreases towards the floor of the groove, wherein, with the blank being rotated about its longitudinal axis, a pressure which exceeds the yield point of the material of the blank is locally applied, characterised in that the width of action of the pressure is reduced from a width corresponding to the width of the groove to be produced at the peripheral surface of the blank, to the width of the floor of the groove to be produced, in accordance with the progressing depth of impression, wherein the reduction in the width of impression, with progressing depth of impression, is effected in accordance with the inclination of the walls of the groove.

2. A method according to claim 1 for producing screwthreads characterised in that the screwthread groove is impressed into a blank which is of the outside diameter of the desired screwthread.

3. Apparatus for carrying outthe method according to claim 1 or claim 2, which comprises at least one roller which co-operates with a counterpressure surface and which is movable relative thereto, wherein a raised shaped rib is disposed on the roller and/or on the counterpressure surface, characterised in that the width of the shaped rib or ribs (7,8; 7', 8') decreases in the direction of the relative movement between the roller (12) and the counterpressure surface (1) and the height thereof increases.

4. Apparatus according to claim 3 characterised in that shaped ribs (7, 8; 7', 8') are arranged both on a drivable central roller (12) and on the co-operating surface (1) which is subdivided into segments (2,3, 4; 5, 6), which ribs cross each other in the course of the mutual relative movement.

5. Apparatus according to claim 4 characterised in that the segments (2,3,4,5,6) of the co-operating surface (1) are arranged on carriages (81) which are guided displaceably radially with respect to the central roller (12) and which are movable preferably independently of each other by means of a control rive (85,86).

6. Apparatus according to one of claims 3,4 or 5 characterised in that each of the mutually crossing ribs (7,8; 7',8') of the central roller (12) and the co-operating surface (1) extends at an inclined angle with respect to the axis of the central roller (12).

7. Apparatus according to one of claims 3 and 4 to 6 characterised in that the central roller (12) is drivingly connected by way of transmission means (42; 61,63,64) to an entrainment means for the blanks (9), which entrainment means has at least one and preferably two rotary members (37, 47; 62, 69) which are spaced from each other in the axial direction of the central roller (12) and in which thrust members (14, 14') are held displaceably in the longitudinal direction thereof and engage by means of a sliding member or the like into a peripheral control groove (52, 70) which is disposed in a stationary part of the apparatus, wherein thrust members (14, 14') which are guided in two different rotary members (37,47; 62, 69) are axially aligned with each other.

8. Apparatus according to claim 7 characterised in that at least the mutually facing end regions of the thrust members (14, 14') are mounted rotatably about the longitudinal axis of the thrust members (14,14'), wherein preferably the end regions ofthe individual thrust members (14) are spring-loaded relative to the coaxially aligned thrust members (14').

9. Apparatus according to claim 7 characterised in that provided for the entrainment means is a gear ring (58) which is non-rotatably connected to the central roller (12) and into which engage gear transmissions (139, 138) drivingly connected to support shafts (128) disposed parallel to the thrust members (14, 14'), wherein the support shafts (128) are held in the rotary members guiding the thrust members (14, 14'), or rotary members (47,56) which are non-rotatably connected thereto.

10. Apparatus according to claim 8 characterised in that the control groove (52,70), with the exception of a feed and discharge region for the blanks (9) and the finished bodies of revolution 9V respectively, extends substantially parallel to the path of the points of intersection of the ribs (8,8') of the central roller (12) and the counterpressure surface (1) during the rotary movement of the roller (12), wherein the control grooves (52, 70) associated with the thrust members (14, 14') guided in both rotary members (37, 47; 62, 69), extend parallel to each other in that region.

11. Apparatus according to claim 5 characterised in that the control drive of the carriages (81) is connected to a measuring means (109) for measuring the finished bodies of revolution and adjusts the carriages (81) in dependence on the measurement data obtained.