Patent GB-581148-A (GB)
Title: Improvements in or relating to milling and like profiling machines
IPC: B23Q35/18
Filed: 1943-09-02
Abstract: 581,148. Copying by milling. STEVENS, A. H. (Cincinnati Milling Machine Co.). Sept. 2, 1943, No. 14355. [Class 83 (iii)] [Also in Group XXIX] A milling or like machine for copying from a pattern has a rotatable tracer which is biassed towards the edge of the pattern and actuates, by its rotation, two throttle valves which control two fluid pressure cylinders causing relative movement between the tool and work so as to traverse the tool round the edge of the work. A slide 12, Fig. 4, carries the tracer and cutter whilst a slide 13 carries the work and pattern, or vice versa, the flow of fluid from a constant pressure pump 35 to the cylinders 14, 16, being controlled by throttle valves 24, 29 respectively which are arranged at right angles to each other as shown with their plungers 59, 53 pressed by springs 86 into contact with two similar eccentrics 67 attached to rotate with the tracer 100. The eccentrics lie in different planes as shown in Fig. 1, or one eccentric only may be used to engage both valves in the same plane. In the position of the valves shown in Fig. 4 each plunger lies against a radius of the eccentric which is less than the mean radii 90, 91 so that plunger 53 is to the left of its neutral position and plunger 59 is ,below neutral. This allows flow of fluid from the pump to proceed by ports 32, 27 to the left hand end of cylinder 16 whilst exhaust from the right hand end passes through ports 28, 40 and allows fluid to flow by ports 31, 23 to the top of cylinder 14 whilst connecting the bottom to exhaust through ports 22, 39, the spools 60 of the plungers having bevelled edges so that both the supply and exhaust are throttled and the speed of movement of the slides varies with the displacements of the plungers. Movement of slide 12 downwards and of slide 13 to the right, both at the same speed, gives a resultant movement of the cutter relatively to the work in a S.W. direction as indicated by an arrow 97 on a hand wheel 95 attached to the tracer. If the eccentric is rotated clockwise as seen in Fig. 4 the plunger 59 moves upwardly towards its neutral position and plunger 53 moves towards theleft to increase the pressure difference at opposite ends of cylinder 16 whereby the speed of slide 12 will decrease and the speed of slide 13 will increase, producing a change in resultant direction of the cutter and work which will still be indicated by the arrow 97. When the mean radius 90 or 91 is opposite either plunger the movement of the corresponding slide will cease whilst the other slide will be moving at its maximum speed and when the effective radius changes from below to above the mean the direction of movement of the corresponding slide will be reversed. The eccentrics consist of rings 65, Fig. 1, mounted by anti-friction bearings on a sleeve 72 having an axial cylindrical exterior and an inclined cylindrical bore engaging an inclined surface on a sleeve 74 which is vertically adjustable to vary the eccentricity of the rings 65 from zero to their maximum. When the eccentricity is zero, the plungers 53, 59 are in their neutral positions and the slides 12, 13 are stationary, increase of the eccentricity serving to increase the speed of movement of the slides in their respective directions and being indicated by a graduated dial 88 on a handle 87 which is attached to a crank 85 for adjusting the sleeve 74. A tracer head 76 is rotated in bearings 92, 93 in a housing 10 movable on a supporting arm 11 and is connected by a key 81 to the sleeve 74, and to a gear wheel 80 which is also connected by a pin and radial slot 82 to the sleeve 72 so that all will be rotated together to adjust the settings of valves 24, 29 when the gear is rotated through an idler from a fluid .pressure motor 128. The head may also be rotated by the hand wheel 95 attached to the head and having a pin and slot connection 102 with the ball joint 99 by which the tracer 100 is mounted in the head for universal lateral movement. Lateral pressure of the pattern on the tracer rocks it about the joint 99 and causes a ball'110 on the upper end thereof to raise the plunger 111 of a valve mounted in the housing 10 and give automatic copying control of the cylinders 14, 16 from the supply ports 114, 115. A selector valve 46 is interposed between the ports 116, 117, connectable with ports 114, 115, and the supply leads 126, 127 of the motor 128. In operation, with the parts as shown in Fig. 4, the tracer is steered by means of the hand wheel 95 into contact with the pattern and on contacting the latter the tracer is deflected to raise the valve 111 against a spring 151 through a central neutral position into a position in which it connects supply port 115 to port 117 to deliver fluid to a cylinder 137 and raise a plunger 138. This rocks a trip lever 139 about its pivot 140 against the pressure of a spring 141 and releases a pawl 142 which allows a spring to depress the valve 46 until it is locked in the lowered position by a detent 153. The ports 116, 117 are now connected through the selector valve 46 to the motor 128 so that movement of the valve 111 up or down from this position, due to increased or reduced pressure of the pattern on the tracer, will control the speed and direction of rotation of the motor, exhaust from the motor taking place through a port 132. The valve 46 in its lower position also connects the exhaust lines 41, 42 from the cylinders 14, 16 to ports 146, 147 of the tracer valve 111, but in the present position of valve 111 these ports are cut off from the exhaust line 133, so that motion of the slides 12, 13 is stopped. The lower portion 105 of the tracer is pivoted to the port 100 at 106 and may be adjusted angularly by screws 109, 109<1> so as to project in front of the tracer axis in the plane con. taining the radius of maximum eccentricity of the eccentrics 67 so that rotation of the tracer by the motor 128 will carry the lower end of the tracer away from the pattern until the deflected portion lies parallel to the pattern at the point of contact. In this position of the tracer, due to the relief of pressure thereon by the pattern, the valve 111 is lowered sufficiently to stop the motor 128 and start the slides 12, 13 to move the tracer parallel to the edge of the pattern. If the tracer meets a depression in the pattern the relief of pressure thereon will permit the valve 111 to approach its lowest position, in which the motor 128 is started to rotate the tracer towards the pattern and the exhaust from the cylinders 14, 16 is throttled to slow down or stop the slides 12, 13, whilst if a projection on the pattern is encountered the valve 111 is raised to rotate the tracer away from the pattern and simultaneously slow or stop the slides, until the required change in direction has been effected. If the edge of the pattern in front of the tracer extends parallel to the plane containing the angularly adjusted portion 105 of the tracer the slides 12, 13 will be moved to traverse the tracer parallel to the edge of the pattern at a speed determined by by the setting of the sleeve 74. On completion of the copying operation the operator manually deflects the tracer to cause rotation of the head 76 in a direction to steer the tracer away from the pattern whereupon the valve 111 assumes its lowest position as shown in Fig. 4, the cylinder 137 is connected to exhaust and the detent 153 is disconnected from the plunger 46 which may then be raised into the manual control position by rotation of a handle connected to the pawl 142. The traverse of the slides 12, 13 may be stopped at any time by raising the sleeve 74 through the handle 87 to centralize the eccentrics 67. During manual control, with the valve 46 in the raised position shown in Fig. 4, exhaust from the cylinders 14, 16 takes place through pipes 41, 42 and resistances 51, 52 to the pipes 134, 133 and during automatic control the pipes 41, 42 are connected to ports 146, 147 of the tracer valve 111, the resistances at 51, 52 being equal to those at 146, 147.