Patent Application
20050045241
The present invention relates to the forming of a coil spring having pigtails at each end, and more particularly to a machine for efficiently forming the pig tails.
In many instances, it is desirable to have reduced diameter ends or “pigtails” on a wound coil spring. One example application for such springs is in automotive suspension systems. A reduced diameter at one end of the spring can be beneficial for efficiency in spring height and operating travel.
In a typical coil spring forming manufacturing method, a cut-to-length bar is wound around a solid mandrel that sets the inside diameter of the coil spring. One end coil of the spring can be formed smaller than the next coil of the spring using this technique to provide a pigtailed spring. The mandrel for such springs typically has a smaller diameter on one end to form the reduced end of the spring.
It is also beneficial in many circumstances to also reduce the diameter of the opposite coil of the spring for similar size and performance reasons. A secondary pigtailing operation is performed after the mandrel has been removed. Typically a separate pigtailing machine performs the pigtailing operation.
Conventional pigtailing machines typically include an A head which receives the previously pigtailed coil and a B head which forms the second pigtail coil. Between the heads, are numerous adjustable fixtures, supports, and clamping arrangements. The adjustable components allow a pigtail of a desired shape to be formed onto an opposite end of coil springs of various sizes and shapes.
Disadvantageously, setup for conventional pigtailing machines is quite extensive.
Each adjustable component must be accurately and precisely aligned relative the heads. The setup time for each spring type increases the overall production cycle time and results in a lower manufacturing efficiency. Additionally, the adjustable components may shift over time due to the aggressive environment in which a pigtailing machine operates. Shifting in any of the adjustable supports may result in marking of the spring surface which may lead to a stress concentration and potential early fatigue of the spring during service.
Accordingly, it is desirable to provide a pigtailing machine and forming approach that provides for a double pigtail while reducing cycle time, minimizes marking and assures an accurately formed double pigtailed coil spring.
The pigtailing machine according to the present invention provides an A forming head, a B forming head, a drive system for the B forming head, a base, a support pedestal, and a controller. The B forming head and the pedestal are secured to a cassette base. The cassette base is located upon the base to provide for a relatively quick changeover should another double pigtail coil spring type need be manufactured. By fixing the forming head and the support pedestal to the cassette base, alignment and proper manufacture of the spring is assured. Alternatively, the A forming head may also be mounted to the cassette base.
The present invention therefore provides a pigtailing machine and forming approach that provides for a double pigtail while reducing cycle time, minimizes marking and assures an accurately formed double pigtailed coil spring.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:
Preferably, the B forming head 18, and the pedestal 22 are secured to a cassette base 26 through fasteners 28 such as bolts or the like. The cassette base 26 is located upon the base 18 and locked thereto through locks (illustrated schematically at 30) to provide for a relatively quick changeover should another double pigtail coil spring need be manufactured. That is, a cassette 32 which includes at least the B forming head 18 and the pedestal 22 secured to the cassette base 26 is a dedicated die for the manufacture of a single specific double pigtail coil spring. By fixing the B forming head 18 and the support pedestal 22 to the cassette base 26 alignment and proper manufacture of the spring is assured.
The A forming head 16 may be mounted directly to the base 18 to minimize expense of the cassette 32. Alternatively, a pigtailing machine 10′ may mount the A forming head 16, the B forming head 18, and the support pedestal 22 to the cassette base 26 as a cassette 32′ at a slight increase in expense (
Referring to
The B forming head 18 includes a face plate 38 and a B die 40 mounted to the face plate 38. The B die 40 is preferably mounted offset from axis X. The B forming head 18 further includes a dog latch 42 mounted axially along the B forming head 18 to lock the opposite coil (initially the non-pigtailed coil 14;
The B forming head 18 preferably rotates and axially translates relative axis X as indicated by arrows RB. and TB The drive system 20 for the B forming head 18 preferably rotates the B forming head 18 about axis X which rotates B die 40 in an eccentric path relative axis X to form the second pigtailed end of the coil spring 12.
The A die 36 and the B die 40 include a step 44, 46 which respectively receive and abut the distal end of the coil spring 12 (also illustrated in
The support pedestal 22 includes a first and a second roller 48a, 48b mounted thereto. The rollers 48a, 48b are preferably located adjacent axis X and spaced therefrom. The rollers 48a, 48b assure that the shape of the spring 12 is maintained during the forming operation which includes rotating the B die 40 such that the (initially not pigtailed) coil of the coil spring 12 is rotated about the B-die 40 to form the pigtail coil. The rollers 48a, 48b are mounted directly to the support pedestal 22 without the heretofore requirement of an adjustment mechanism which may shift position and potentially mark the spring.
A tangent clamp 50 is located between the support pedestal 22 and the B forming 18 to further support the coil spring during the forming operation. The tangent clamp 50 preferably engages the second to the last coil of the coil spring.
A lifter 52 is preferably located between the rollers 48a, 48b. The lifter 52 selectively extends from the support pedestal 22 in response to the controller 24 (
The foregoing description is exemplary rather than defined by the limitations within. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.
