EP1918039A1

EP1918039A1 - Rolling rack

Info

Publication number: EP1918039A1
Application number: EP06807881A
Authority: EP
Inventors: Jaume Morell Miro
Original assignee: INDUSTRIAS METALURGICAS JEM SA
Current assignee: INDUSTRIAS METALURGICAS JEM SA
Priority date: 2005-08-02
Filing date: 2006-07-24
Publication date: 2008-05-07
Also published as: CN101296761A; EP1918039A4; ES2251324B1; ES2251324A1; KR20080063745A; WO2007017536A1

Abstract

The invention relates to a rolling rack of the type that comprises a toothed rolling surface. The invention is characterised in that one of the ends of the toothed surface comprises a strip of material having a coefficient of friction that is greater than that of the material forming the toothing of the rolling surface, said strip forming a non-zero oblique angle in relation to the teeth of the toothed surface. In this way, the strip extends through a certain number of teeth of the toothed surface, the height of said strip being at least equal to that of the teeth through which it extends.

Description

The present invention relates to a rolling rack and a to shaft rolling machine comprising said rolling rack.
A rolling rack is a tool, usually with a general parallelepiped shape, which has a toothed rolling face. Rolling racks are used to manufacture toothed, splined and threaded shafts. A shaft rolling machine usually has two of these racks which are separated by a distance known as a machine opening and which move longitudinally in opposite directions, in such a way that each one makes contact with the shaft to be rolled on opposite sides of the lateral surface of the shaft and compresses it. The shaft rotates owing to contact with the racks, in such a way that, as the racks pass in a movement tangential to the shaft to be rolled, a toothing or groove is formed in the shaft.
The toothed rolling faces of rolling racks usually have three different zones. The first zone or entry zone is where the shaft to be rolled first makes contact. Said zone is usually recognised by the height of the rack teeth which gradually increases, in such a way that, in operation, this zone gradually compresses the shaft to be rolled whilst just as gradually grooving or toothing the shaft. Next is the finish zone, its function being to calibrate the shaft grooving or toothing so that the teeth or grooves have the desired shape and size. The teeth in the finish zone are therefore usually the same shape and size. Lastly, after the finish zone is the outlet or decompression zone, where the teeth gradually lose height. The function of the outlet zone is to gradually decrease contact between the part and the rack.
For the teeth on the shaft to be correctly formed, the linear velocity of the racks needs to be identical to the velocity of the shaft on the tangential surface in the contact zone. Given that the transmission of movement between the racks and the shaft to be rolled is achieved via contact of the rack teeth with the lateral surface of the part, it is extremely important to prevent slipping during the initial moments of contact between the racks and the shaft to be rolled.
To prevent slipping between the racks and the shaft to be rolled, sandblasting of the toothed surface at the start of the rack entry zone is known. In the same way, according to the known art, the first teeth in said entry zone need to have a planar tooth shape, for the purpose of providing better contact and capacity to transmit movement. The two known steps are problematic in that the rolling of the shaft is excessively jerky, which leads to high fatigue in the tool and a shorter service life thereof.
With the aim of solving the aforementioned problems, the present invention consists of a rolling rack, of the type which comprises a toothed rolling face. The rack according to the present invention is characterised in that at one of the ends of its toothed face, which is also known as the entry zone, it has an insert bar made of a material with a coefficient of friction greater than that of the toothing material of the rolling face, said insert bar forming a non-zero oblique angle in relation to the teeth of the toothed face, in such a way that the insert bar passes over a number of teeth of said face, the height of said insert bar being at least equal to that of the teeth over which it passes.
Preferably, the insert bar is made of a resilient material. More preferably, said insert bar is made of a material with a high coefficient of friction, such as for example a rubber.
According to the present invention, the zone with the greater coefficient of friction, when making contact with a shaft to be rolled, prevents slipping between the shaft to be rolled and the rack or racks, thus accurately synchronising the rotating movement of the shaft to be rolled and the linear movement of the rack. The angle of the insert bar in relation to the teeth prevents there being any areas which are not rolled. In different embodiments, an angle between the insert bar and the teeth is selected in such a way that, during operation, at the moment when contact between the insert bar and the shaft to be rolled is lost, the depth of the grooves formed in the shaft means that there is no slipping between the rack and the shaft being rolled. Therefore, said angle is determined as a function of the different operating parameters of each application in particular, such as materials, width to be rolled, exerted pressure, etc.
Also preferably, for the purpose of producing contact between the shaft to be rolled and the insert bar, the insert bar will protrude above the teeth over which it passes. In another preferred embodiment, the height difference between the insert bar and the teeth will gradually increase from the furthest point of the toothed face until it reaches a peak and gradually decreases at the end of the insert bar.
The present invention moreover has the advantage of allowing acute shapes to be formed in the teeth of the entry zone without loss of the anti-slipping properties of the rolling rack, which is not possible with previously known rolling racks. By means of the present invention, it is possible for the rack teeth to roll much more smoothly over the shaft, and consequently further decrease fatigue in the tool.
The present invention also comprises a machine for rolling shafts, which is characterised in that it comprises at least one rack according to the present invention.
For a better understanding of the invention, embodiments of the present invention are illustrated, by way of an explanatory but not limiting example in the accompanying drawings in which:

Figure 1 is a perspective view of a rolling rack according to the present invention.
Figure 2 is a view in lateral elevation of the rack in Figure 1.
Figure 3 is a top plan view of the rack in Figure 1.
Figure 4 schematically shows the operation of a rolling machine equipped with racks according to the present invention, at a moment immediately prior to the first contact of the racks with the shaft to be rolled.
Figure 5 schematically shows another moment of the operation of a rolling machine, at an intermediate moment of contact between the rolling racks and the shaft to be rolled.
Figure 6 schematically shows a moment during the operation of a rolling machine when the shaft, now rolled, is no longer in contact with the rolling racks.

Figures 1 to 3 show an embodiment of a rolling rack according to the present invention. In the example given, the rolling rack 1 has a body which is generally parallelepiped in shape 2, which has on its upper face 3 a number of teeth, such as those indicated in the various figures by the numeral 4. The rack in the example has an insert bar 5 at one of the ends of the rack. The insert bar forms a non-zero oblique angle with the teeth 4 over which it passes. The end of the toothed surface 3 on which the insert bar 5 is located is, during operation, where the shaft to be rolled first makes contact (entry zone). According to known art, the teeth 4 in the zone can increase in height from said end. However, unlike previously known rolling racks, said teeth 4 of the entry zone can have an acute shape, which has been illustrated schematically in the figures.
The insert bar 5 is made of a material with a coefficient of friction greater than that of the teeth 4 of the toothed face 3, for example a rubber, which is a material favoured for its resilience and high coefficient of friction. On the other hand, in the example given, as is seen in Figure 2, the insert bar 5 is higher than the teeth 4 over which it passes, the height difference between the insert bar 5 and the teeth 4 increasing from the end of the toothed face 3 until it reaches a peak, which in the case of the example occurs at the second tooth, and then gradually decreases until it almost becomes nothing at the end of the insert bar 5.
Figures 4 to 6 schematically show the process for forming a toothed shaft on a shaft rolling machine which comprises at least one rack according to the present invention, more specifically, two racks 1, 1' according to the present invention. The components which are similar to those shown in the example in Figures 1 to 3 are indicated with identical numerals 2, 3, 4, 5 on the lower rack 1, whilst said components are also indicated with identical numerals, followed by a prime 2', 3', 4', 5' on the upper rack 1'.
Figure 4 shows a shaft 10, to be rolled, before each rack 1, 1' makes contact via respective longitudinal movements in the opposite direction 11, 12 with the lateral surface 14 of the shaft 10 to be rolled. It is important to avoid slipping between the shaft 10 to be rolled and the racks 1, 1'. This is achieved, according to the present invention, by means of contact between the lateral surface 14 of the shaft 10 to be rolled and the insert bars 5, 5' of the racks.
The contact with the insert bars 5, 5', as is shown in Figure 4, ensures that the longitudinal linear movements of the racks 11, 12 are synchronised with the rotating movement 13 of the shaft 10 to be rolled, in other words the slipping speed of each rack 1, 1' is equal to the linear velocity on the lateral surface 14 of the shaft 10 to be rolled. Contact of the racks 1, 1' with the insert bar or insert bars 5, 5' is maintained until the lateral surface 14 of the shaft 10 to be rolled has a depth such that there is no slipping between the shaft 10 being rolled and the racks 1, 1', and the shaft 10 being rolled passes over the entire toothed surfaces 3, 3' of the racks 1, 1' until the toothed shaft 10 shown in Figure 6 is achieved.

Claims

Rolling rack, of the type which comprises a toothed rolling face, characterised in that one of the ends of its toothed face or entry zone has an insert bar made of a material with a coefficient of friction greater than that of the material of the toothing of the rolling face, said insert bar forming a non-zero oblique angle, in relation to the teeth of the toothed face, in such a way that the insert bar passes over a number of teeth of said face, the height of said insert bar being at least equal to that of the teeth over which it passes.
Rack according to claim 1, characterised in that the insert bar is made of a resilient material.
Rack according to either claim 1 or claim 2, characterised in that the insert bar is made of a material with a high coefficient of friction.
Rack according to claim 3, characterised in that the insert bar is made of rubber.
Rack according to any one of claims 1 to 4, characterised in that the insert bar protrudes above the teeth over which it passes.
Rack according to claim 5, characterised in that the height difference between the insert bar and the teeth over which it passes gradually increases from the furthest point of the toothed face until it reaches a peak and gradually decreases toward the end of the insert bar.
Rack according to any one of claims 1 to 6, characterised in that the teeth over which the insert bar passes gradually increase in height.
Rack according to any one of the claims 1 to 7, characterised in that the rack has a parallelepiped body, the toothed face with the insert bar being located on one of its faces.
Shaft rolling machine, characterised in that it comprises at least one rolling rack according to any one of claims 1 to 8.