Patent GB-608128-A (GB)
Title: Improvements in and relating to profiling machines
IPC: B23Q35/125
Filed: 1945-02-14
Abstract: 608,128. Copying by milling. TRIGGS, W. W. (Nilea-Bement-Pond Co.). Feb. 14, 1945, No. 3731. [Class 83 (iii)] [Also in Groups XXXV and. XXXVIII] In a profile copying machine wherein a tracer engaging a template has its support movable, under electrical control, along two lines at right angles, one being a leading movement and the other a movement toward and away, these being electrically controlled by the pressure of the tracer against the template, a single tracer is alone employed which controls means changing the direction of the leading movement from one line to another when the movement in one line becomes longer than that in the other. As described, when the movement in a leading direction becomes smaller than the movement of the tracer in the next toward or away movement, the direction of the leading movement is changed from one line to the other. Thus, when a downward leading movement takes the tracer away from the point x on the outside periphery of the template in Fig. 3, the tracer allows the contacts a and f (Fig. 1) to energize the "toward" relay 1 and cause a movement to the right until the tracer pressure separates contacts a and f, when the downward movement is resumed; these alternate movements go on until, at point m, the leading movement is shorter than the other movement, when the leading movement is automatically changed to a movement to the right. The greater pressure on the tracer then brings contacts b and g (Fig. 1) into engagement to energize the " away " relay 6 and cause a downward movement until contacts band g separate and the leading movement to the right is resumed. When, by alternate small movements downwards and to the right, the point m of tangency to the template curve is reached, movement to the right allows contacts a and f to energize relay 1 and cause an upward movement. At the point n, the leading movement is again less than the other movement and is automatically changed to an upward movement. These movements in alternate small steps-so short as to be invisible in the work-piece produced by a cutter moving with the tracercontinue, automatic changes of direction taking place at points o and p, until the tracer has traversed the entire periphery of the template. The movements to right, to left, up and down, are imparted through magnetic clutches which are engaged by the energizing of coils RC, LC, UC and DC respectively (Fig. 2). Thus, the machine may be as set forth in Specification 233,747, [Class 83 (iii)]. The coils RC, LC, UC and DC are selectively energized through the contacts of one of four relays 21-24 which are successively energized by the cam-operated switch device D, E, F, G. The latter is turned through one step by the motor H each time the tracer passes one of the points x, n, o, p. At the start from point x, the relay 21 is energized and so coil DC is energized for the leading movement. The " towards " relay 1 de-energizes coil DC and energizes coil RC. While relay 1 is closed, the condenser 35 is charged from the constant voltage produced across the regulator tube R by the generator P, and during the leading movement the condenser discharges through the resistance 37a. When, with the tracer at point m, the leading step is shorter than the toward step, condenser 35 attains such a charge that through the grid 30 the gas-filled discharge device N becomes conductive, energizing relay 33 which, in conjunction with relay 42 closed by the action of relay 1, energizes the relay 40 to start the motor H. The relay 33 discharges the condenser 35. The motor H, through the further cam-switch T driven thereby, maintains relay 40 until the switchgear has moved through one step, and, through cam-switch O (Fig. 2) it de-energizes relay 33. Relay 21 is now de-energized and relay 23 is operated. Consequently, coil RC is energized for the leading movement, and the away relay can de-energize coil RC and energize coil DC. Further rotational steps of the camoperated switchgear are produced at points A and B to energize relays 22 and 24 in succession. At the points of tangency, when control is passing, for example, from relay 1 to relay 6, and relay 43 is energized before relay 42 drops out, these relays momentarily open the circuit of tube S and also discharge the condenser 53, thereby de-energizing relay 39 and opening the charging circuit of condenser 35 until the condenser 53 has re-charged and re-ignited the. tube S; this prevents unwanted operation of device N by charging of the condenser 35 ifas a result, for example, of backlash in screw mechanism driving the tracer support-the "toward" step after passing the tangent point is unduly long. In an alternative to the use of device N, a contact arm, driven backward by a motor during the leading motion and forward while relay 1 or 6 is energized, ultimately reaches a forward position wherein it energizes the relay 33. Undue pressure on the tracer after engagement of contacts band g will separate contacts k and l to de-energize relays 21-24 and stop the movement of the tracer. To start the tracer movement, the switch J is temporarily moved to interrupt the circuit of relay 4 and prepare the circuit of relay 2, and the tracer is then moved to right, to left, up or down (until the tracer engages the work and de-energizes relay 1) by pressing the appropriate button RS, LS, US or DS, which energizes relays 2 and 5 and also sets the switchgear D-E-F-G in correct initial position. The reversing switch M for the motor H determines the direction of subsequent steps of switchgear D-E-F-G and selects one of the two lower banks of contacts of relays 21-24 in Fig. 2 according to the direction in which the tracer is to traverse an external or an internal periphery. The automatic tracer movement can be stopped by pressing " away " button K to energize the relay 3, which maintains itself, de-energizes relay 4 and energizes relay 6 to cause an "away" motion until the switch J is moved to de-energize relay 4.