Title of Invention

A CRAMP BAR WITH RELEASABLY SECURED GUIDE FIXING SYSTEM

Abstract

A cramp bar with releasably secured guide fixing system for use in rolling mills comprising: trapezoidal shaped cramp bar (3) with atleast one releasably locked guide means (1,2) secured thereto, the inside portion of the said front leg i.e. toward roll is made tapered so that the leg matches with the tapered side of the cramp bar and the others leg i.e. away from the roll being straight matches with the straight vertical side of the bolt head used in the guide, the wedge portion of the bolt exactly matching with the cramp bar when the bolt is tightened making the guide fully locked with the cramp bar, said releasable lock of said guide means onto said cramp bar comprising a single bolt (4) locking means, with the loosening of the bolt having wedge shaped head, will release the guide from cramp bar and the guide will be totally free for any side wise movement on the cramp bar, each said guides having a thickness of at least 75 mm and preferably between 75 mm to 100 mm.

Full Text

The present invention relates to improvements in guides and guide fixing arrangement for rolling channels and joist in a two high reversing mill with multi pass stand. The conventional guides consists of a pair of left and right hand guides made of mild steel plate directly mounted on the rectangular shaped cramp bar with the help of locking plate and fastening with two standard bolts and nuts (fig. 1). Both the delivery and entry guides are placed on the same cramp bar on different passes. As the conventional guides consist of a pair of left and right hand guides, directly mounted on the cramp bar with the help of locking plate and fastening with two bolts and nuts. The cramp bar being rectangular in shape, the mounting of guides even after tightening does not have adequate rigidity to withstand side thrust of metal during rolling. They often get displaced sideways due to force exerted by the bars due to clearance between guide plate and cramp bar required for easy fixing of the guides. Moreover, fastening with two bolts makes it difficult to align the guides with roll pass. At times the guides get misaligned during the rolling process and cobbles, collar and mill stoppage. In case the either of the guides is inside the pass profile, it will result imbalance in reduction sequence. Due to change in drafting in the pass during structural rolling, it may so happen that at few portion of the pass, there will be tremendous loading which may lead to roll breakage. In the same manner, guide-in may also result in tearing of flanges or formation of collar around the work roll. Moreover, the existing guides are fabricated from rolled plates which wear out faster due to frictional conditions at the surface of contact with moving metal. Under such condition the gap between two guides is required to be adjusted frequently which cost time and loss of production. Thus, the known guides mounted on cramped bars suffer from the following problems/disadvantages can be summarized as - (i) Poor rigidity of the guide fixing (ii) Fast wear of guide plate (iii) High rate of cobble generation (iv) Complex guide mounting and setting process (v) High operating delay time (vi) High mill rejection It is thus the basic objective of the present invention to provide for a cramp bar with releasably secured guide fixing system for use in rolling channels/joist in rolling mills which would have good rigidity. Another object of the invention is directed to provide cramp bar with releasably secured guide fixing system for use in rolling mills which would be simple to use and will not be subject to extensive wear thereby avoiding frequent maintenance and replacement. Yet further object is directed to provide for a cramp bar with releasably secured guide fixing system for use in rolling mills which would have lower rate of cobble generation in operation and use. Another further object of the invention is directed to provide for a cramp bar with releasably secured guide fixing system for use in rolling mills which would provide for lowering the high operations delay time and also high mill rejection experience in use of known cramp bars and guide fixtures. Thus according to the present invention there is provided a cramp bar with releasably secured guide fixing system for use in rolling mills comprising : 2 trapezoidal shaped cramp bar with atleast one releasably locked guide means secured thereto, the inside portion of the said front leg i.e. toward roll is made tapered so that the leg matches with the tapered side of the cramp bar and the others leg i.e. away from the roll being straight matches with the straight vertical side of the bolt head used in the guide, the wedge portion of the bolt exactly matching with the cramp bar when the bolt is tightened making the guide fully locked with the cramp bar; said releasable lock of said guide means onto said cramp bar comprising a single bolt locking means, with the loosening of the bolt having wedge shaped head, will release the guide from cramp bar and the guide will be totally free for any side wise movement on the cramp bar; each said guides having a thickness of at least 75 mm and preferably between 75 mm to 100 mm. In particular the releasable locking of said guide to said cramp bar is achieved by means of a single bolt having a wedge shaped head. The above disclosed single bolt locking provides for easy fixing and release of the guide from the cramp bar thereby making the system more efficient and cost effective in use. Additionally, to avoid choking of bars in the guide, taper along length of the guide is provided leaving little bearing surface on the nose of the guides to allow perfect entering of bars in the roll grooves. This provided for better fulfillment of dimensional accuracy of the product. Moreover, in the system of the invention provision was made for keeping the nose of the guides in close contact with the roll for smooth pick up. 3 Preferably, in accordance with the invention, the material for the guide has been selected to be of cast steel in order to minimize the wear of the guides and thereby increase service life of the system. The details of the system of the invention, its objects and advantages are explained hereunder in greater detail with reference to non-limiting exemplary embodiments in relation to the accompanying figures wherein : Fig. 1 is a schematic representation of an existing conventional cramp bar; Fig. 2 is an illustration of a conventional channel entry guide obtained of known cramp bar and guide fixtures ; Fig. 3 is a schematic representation of the cramp bar used in the system of the invention; Fig. 4 is an illustration of the channel entry guide obtained of the cramp bar and releasably mounted guide system of the present invention ; and Fig. 5 is an illustration of the channel delivery guide obtained of the cramp bar and releasably mounted guide system of the present invention. Referring first to Fig. 1 the known cramp bar is shown to be rectangular in shape having 203 mm. () x () 203 mm. 4 In Fig. 2 a conventional entry guide is shown obtained of the rectangular cramp bar (CB) and guide means (GM) seemed thereby with the help of locking plate (LP) and two nut and bolts (NB). Reference is now invited to fig. 3 to 5 which relate to the cramp bar and guide fixing system in accordance with the present invention. To overcome the earlier mentioned 9 limitation of earlier guides the design of entry and delivery guides of heavy channels (300 x 90 mm) and heavy joint (300 x 140 mm) a design of the guides were made. To make the guides stable and rigid with the cramp bar the thickness of the guides was increased from minimum 50 mm to 75 mm. As shown in Figs. 3 to 5 for perfect gripping of the guides, the rectangular cramp bars of the system of the invention was obtained of trapezoidal shape and the releasable locking arrangement of the guide to the cramp bar with two bolts and locking plate of the known art was replaced by a single bolt (4) with wedge shaped head. Such locking avoided the problem during guide adjustment or pass changing require two bolts to be loosened and tightened which was more time consuming as well as damage prone. In particular, in the system of the invention the guide being fixed with a single bolt, the loosening of bolt is faster and the chances of damage of the bolt is practically negligible. The material for the guides of the invention is preferably selected to be cast steel in order to minimize the wear of the guides and thus increase the service life. To avoid choking of bars in the guide, taper along length of the guide has been provided leaving little bearing surface on the nose of the guides to allow perfect entry of bars in the roll groove. This provided for better fulfillment of dimensional accuracy of the product. Provision has also been made in the system of the invention for keeping the nose of the guides in close contact with the roll for smooth pick up (fig. 4 & 5). Thus, the basic features of the cramp bar with releasably mounted guide system of the invention provides for: 5 a) high rigidity due to tapered cramp bar & wedge bolt construction ; b) elimination of bolt failure; c) least cobble generation ; d) low operating delay of the mill for guide setting ; and e) fit and forget performance avoiding regular maintenance and replacement of components. The cramp bar with releasable guide fixing system in accordance with the present invention was further tested for its suitably in actual industrial condition. For the purpose the guides for 300 x 90 mm channel and 300 x 140 mm joist were put to use in a Heavy Structural Mill. The first trial was done for 300 x 90 mm channel rolling It has been observed that average cobble generation was 1.9% against the previous figure of 2.1% ie.,reduction of cobble generation by about 10%. During the trial another achievement was the reduction of operating delay time of the mill by more than 20%. In the 2nd trial the reduction of cobble generation and operating delay time by more than 25% and 20% respectively was achieved. A further 3rd trial showed that there was a lowering of cobble generation and operating delay time by approximately 20% and 25%. In a further test the modified guides for 300 x 140 mm joist were installed in the intermediate stand Cobble generation was reduced marginally by 10% and operating delay time lowered by more than 25%. The 2nd trial of this guides were carried out wherein modified guides were tried both in the intermediate and the finishing stand and as a result of which cobble generation was reduced by more that 25% and the operating delay time was lowered by 30% approximately. 6 The dimensional accuracy of the rolled products also improved significantly after introduction of modified guides. In case of channel, the mill rejection was lowered from 2.3% to 1.4% and in case of joist from 4.3 to 4.1 %. Thus the cramp bar with releasably secured guide fixing system in accordance with the present invention provide for the following advantages : i) The modified cramp bar provide for fixing the guides more rigidly as well as positioning the guides accurately ; ii) The modified guide system provide for feeding the bar smoothly to the pass resulting in better product quality and productivity of the mill; iii) The releasable locking of the guides provide more user friendly and rigid locking of the guide to the cramp bar; iv) The robust and rigid guides provide for reduced cobble generation to about 10-20% for different sections ; v) The system of the invention provides for simple guide adjustment and consequently guide adjustment time has also been reduced to 15-30% for different sections; vi) Requirement of spares like bolts etc. is much less than the existing guides. 7 It is thus possible by way of the system of the invention to provide a simple to operate and cost-effective cramp bar with reteasably locked guide fixing system for use in rolling mills. 8 We Claim: 1. A cramp bar with releasably secured guide fixing system for use in rolling mills comprising trapezoidal shaped cramp bar with atleast one releasably locked guide means secured thereto, the inside portion of the said front leg i.e. toward roll is made tapered so that the leg matches with the tapered side of the cramp bar said releasable lock of said guide means onto said cramp bar comprising a single bolt locking means, with the loosening of the bolt having wedge shaped head, will release the guide from cramp bar and the guide will be totally free for any side wise movement on the cramp bar; each said guides having a thickness of at least 75 mm and preferably between 75 mm to 100 mm. 2. A cramp bar with releasably secured guide fixing system as claimed in claim 1 wherein said guide means is adapted to allow perfect entry of bars in the roll grooves. 3. A cramp bar with releasably secured guide fixing system as claimed in anyone of claims 1 or 2 wherein the nose of the guide is adapted for close contact with the roll for smooth pick up. 9 4. A cramp bar with releasably secured guide fixing system as claimed in anyone of claims 1 to 3 wherein said guide means taper along its length. 5. A cramp bar with releasably secured guide fixing system as claimed in anyone of claims 1 to 4 wherein said guide means is obtained of cast steel. 6. A cramp bar with releasably secured guide fixing system substantially as hereindescribed and illustrated with reference to the accompanying figures. 4. Dated this 8th Day of March 1999 S. Majumdar Of S. MAJUMDAR & CO. Applicants Agent 10 A cramp bar with releasably secured guide fixing system for use in rolling mills comprising: trapezoidal shaped cramp bar (3) with atleast one releasably locked guide means (1,2) secured thereto, the inside portion of the said front leg i.e. toward roll is made tapered so that the leg matches with the tapered side of the cramp bar and the others leg i.e. away from the roll being straight matches with the straight vertical side of the bolt head used in the guide, the wedge portion of the bolt exactly matching with the cramp bar when the bolt is tightened making the guide fully locked with the cramp bar, said releasable lock of said guide means onto said cramp bar comprising a single bolt (4) locking means, with the loosening of the bolt having wedge shaped head, will release the guide from cramp bar and the guide will be totally free for any side wise movement on the cramp bar, each said guides having a thickness of at least 75 mm and preferably between 75 mm to 100 mm.

Documents:

00188-cal-1999 abstract.pdf

00188-cal-1999 assignment.pdf

00188-cal-1999 claims.pdf

00188-cal-1999 correspondence.pdf

00188-cal-1999 description(complete).pdf

00188-cal-1999 drawings.pdf

00188-cal-1999 form-1.pdf

00188-cal-1999 form-18.pdf

00188-cal-1999 form-2.pdf

00188-cal-1999 form-3.pdf

00188-cal-1999 form-5.pdf

00188-cal-1999 pa.pdf