Turning – Severing or cut-off – Processes
Reexamination Certificate
2001-03-12
2003-01-28
Ackun, Jacob K. (Department: 3712)
Turning
Severing or cut-off
Processes
C082S124000, C082S129000
Reexamination Certificate
active
06510769
ABSTRACT:
TECHNICAL FIELD
This invention relates in general to multi-spindle machines. Specifically, this invention relates to a multi-spindle machine having attachments for pick-up and back machining operations.
BACKGROUND ART
Multi-spindle machines are known in the prior art. Multi-spindle machines are used to mass produce standardized types of components. A multi-spindle machine typically has several work stations at which machining operations are performed. A piece of raw stock, such as a bar stock, enters the machine at a first station and as the machine indexes, various machining operations are performed. Once the station is indexed completely through the machine, a completed part is formed. The part is released, and the process is repeated for that station with a new piece of raw stock. An advantage of multi-spindle machines is that all stations in the machine are producing parts simultaneously, resulting in high production.
Multi-spindle machines (also referred to as multiple spindle machines) typically have a large indexing spindle drum with four, five, six or eight work spindle stations thereon. Each of the stations carries a work piece. Generally in all but one of the stations, where a new piece of stock enters, a machining operation is performed. After each machining operation is completed, the drum is rotated so that each work piece moves sequentially through the locations where the various machining operations are performed. Machining operations that are typically performed at a multi-spindle machine include milling, turning, and threading.
Most multi-spindle machines are very efficient in terms of producing standardized parts at a high rate. However, one drawback associated with a multi-spindle machine is that the entire machine operates off of a single main motor. The main motor simultaneously drives all of the devices and processes in the machine. Multi-spindle machines typically include one or more timing shafts with cams for the coordination of multiple machine operations.
There is always a risk that one of the mechanisms within the machine will not function properly. If such a malfunction should occur and not be detected by an operator in time to shut the machine off, the machine will continue with its next cycle. In such a case, an attempt by the machine to index to its next position could cause severe damage. This is why it is common for an operator to be required to closely monitor multi-spindle machines.
Typically, the speed of multi-spindle machines changes from high to low speed and back again during the course of the operating cycle. High speed is normally used for times in the machine cycle when critical machining operations are not occurring. High speed operation is desirable when the stations are indexing, or when the tools are moving toward or away from the work pieces and are not performing work thereon. Low speed operation is generally used when the tools in the machine are forming the metal. Any attempt to operate the machine at a high speed when such forming work is being performed is likely to cause a problem or jam the machine.
In many multi-spindle machines at the final station the completed work piece is cut off from the stock. The completed work piece is dropped onto a conveyor or other device to move it away from the machine. It is common to have to perform additional operations on the completed part before it is ready for use. These additional operations are often done by hand or in other machines and add substantial cost to making the part. In many machines the movement of the work piece after cut off is unpredictable and may result in nicks on the ejected work piece. Therefore, work pieces sometimes become damaged and unusable. Furthermore, because the work piece is released from a rotating collet, large work piece catchers are required in order to ensure catching of the falling work pieces. Additionally, the large catchers have to be situated in a crowded tool zone, which often makes it difficult to control the cut off part and avoid damage to parts and other machine components.
In some multi-spindle machines pick-up attachments are available for pick-up of work pieces in the station where the completed work piece is cut off from the stock. Sometimes back machining operations in which a single minor back machining operation after cut off, such as finishing, reaming, chamfering, recessing, and deburring is performed by the machine. A pick-up attachment may include a dead length collet type with the collet operated by twin toggles controlled by a special cam mounted on the main camshaft in front of the main drive housing. The collet may be attached to a pick-up spindle. A pick-up collet is able to grip and eject the work piece. The movement of the pick-up attachments is typically set with the timing of the multi-spindle machine.
The pick-up spindle has one rotational speed which is generally mechanically gear driven. The rotational speed is set one to one with the spindle speed. During a pick-up operation, the pick-up spindle with the collet is moved axially up to the workpiece and is rotated at the same speed as the workpiece. The collet is moved over the work piece to hold it so that the work piece may be cut off. Later the work piece may be dropped in a relatively controlled manner from the pick-up spindle. However because the pick-up spindle is rotating the work piece there is still often difficulty preventing damage to work pieces and machine components when the part is released by the pick-up spindle.
The axial movement of the pick-up spindle is generally controlled by mechanically driven cams and levers. Timing changes are difficult because a mechanical cam must be altered or adjusted. Movement is limited by the travel of the cams and related levers. The cam actuated movement of a pick-up spindle is often restricted to less travel than would be desirable. Often the limited ability to control and move the pick-up spindle necessitates that additional operations on parts be done in subsequent operations in other machines or by hand.
In a back machining or forming operation of the prior art multi-spindle machines the pick-up and back machining operations are controlled by the mechanical cams and actuating devices in the machine. Thus, back machining operations are limited. Every work piece is picked up at the same position and speed, and any back machining operation is done at the spindle speed of the spindle from which the part has separated by the cut off operation. The operations are repeatedly performed based on the multi-spindle machine's timing device. The pick-up spindle collet is constantly rotating at the speed of the work piece collet. This pick-up collet is axially driven by cams and levers to position the collet over the work piece held by the work spindle. The pick-up spindle collet grippingly engages the work piece which is then cut from the remaining stock. The rotating or spinning work piece may then have a back machining operation performed thereon. An ejector plunger may be used for removal of the work piece from the pick-up spindle. The pick-up spindle is axially retracted toward a stationary ejector plunger so that the work piece is pushed out of the pick-up collet by the ejector plunger. However, the work piece is ejected from the collet while it is still rotating. Therefore, large work piece catchers are required to catch the ejected rotating work piece because of its unpredictable drop location.
A disadvantage with the prior art multi-spindle machines is that the rotational speed and the axial movement of the pick-up spindle are limited. Thus, the types and character of back machining operations are limited. For example, because the prior art pick-up spindle is constantly rotating, the drilling of a hole transversely through the work piece while it is held in the machine is not readily achievable. Similarly the performance of multiple back machining operations in the multi-spindle machine after part cut off is not achievable because of the limited ability to control part position and machining speeds.
Another dis
Ackun Jacob K.
Jocke Ralph E.
Logan Clutch Corporation
Walker & Jocke
Wasil Daniel D.
LandOfFree
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