Metal working – Plural diverse manufacturing apparatus including means for... – Binding or covering and cutting
Patent
1994-09-06
1996-04-02
Briggs, William
Metal working
Plural diverse manufacturing apparatus including means for...
Binding or covering and cutting
29888073, 72168, B23P 2300
Patent
active
055028802
DESCRIPTION:
BRIEF SUMMARY
This invention is concerned with a machine for manufacturing piston rings in particular piston rings for internal combustion engines, although such rings may be utilised for other purposes, eg pistons for compressors.
Piston rings for internal combustion engines are commonly formed of metal to a desired shape which is generally oval. The ring has two free ends which are closely adjacent to one another but do not touch. Each piston ring is intended to be received in a groove provided in the piston of an internal .combustion engine to provide a seal between the piston and the cylinder in which the piston reciprocates. The shape to which the piston ring is manufactured has to be precisely controlled so that the ring will provide an effective seal.
In EP 0,157,537 B1, a machine for manufacturing piston rings from metal strip is described in which a variable curvature is imparted to the strip to give the desired shape. The machine passes the strip to a fixed guide which imparts a desired minimum radius of curvature to the strip. This minimum radius of curvature is the minimum radius of curvature required anywhere on the circumference of the formed ring. After the fixed guide, the machine passes the strip to a movable guide, in the form of a roller, which bends the strip to increase its radius of curvature to the particular radius of curvature required at each point around the ring. The movable guide is moved as the strip passes it by a control system of the machine so that a ring of the required shape is achieved. In this machine, the completed ring is severed from the remainder of the strip by stopping the feed of the strip when the ring has been formed and then cutting the strip using, for example, a grinding wheel. As an alternative, it is suggested that a number of rings can be formed into a helical coil which is subsequently cut into individual rings.
GB 2,220,600 A describes a method of utilising a machine of the type described in EP 0,157,537 B1 to make more accurate rings. In this method, the strip is bent to a uniform radius of curvature, which is at least 2% below the minimum radius of curvature required, before being bent to the required radius of curvature by the movable guide. The machine utilised in this method has a high speed cropper which severs the rings from the strip without arresting feed of the strip. The movement of the strip during severing is accommodated by the elasticity of the strip.
The machines described in EP 0,157,537 B1 and GB 2,220,600 A have disadvantages concerned with the severing of the completed rings from the remainder of the strip. During bending of the strip, the metal thereof is in a plastic state so that, if the feeding of the strip is stopped to allow severing, creep can occur within the metal. The portion of the strip being formed at the instant that the feed is stopped, is then found to have a lower radius of curvature than if the feed had been continuous. The stopping of the feed also causes a lower production rate. The alternative of forming a number of rings into a coil which is subsequently cut is not desirable because the coil is awkward to handle and position correctly relative to severing means. The high speed cropper of GB 2,220,600 A is found to cause deformation of the rings from the desired shape because it stops the feed albeit only briefly. The strip is also subjected to stress as the feeding means presses the strip against the cropper during severing.
EP 0,186,072 A describes a machine for severing relatively large circular or part-circular items formed from strip, such as bicycle wheel rims, mudguards, or barrel hoops. In that machine, a pivot is provided at the centre of curvature of the item being severed and the severing mechanism is moved arcuately about said pivot to provide a match between the speed of the strip and the severing mechanism. This technique is somewhat imprecise by the standards required in piston ring manufacture but is, in any case, not suitable for use with piston rings which are not of a circular form so that there is no centr
REFERENCES:
patent: 3635063 (1972-01-01), Stern et al.
patent: 3746238 (1973-07-01), Sprague
patent: 5068963 (1991-12-01), Bruce
Briggs William
T&N Technology Limited
LandOfFree
Manufacture of piston rings does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Manufacture of piston rings, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Manufacture of piston rings will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2008569