US3683726A - Follower mechanism responsive to abrupt changes in cam slope in cam-controlled machines - Google Patents

Abstract

A follower mechanism for cam-controlled machine tools which is responsive to abrupt changes in the slope of the control cam. A two-link lever system carries a bearing pin and a stylus pin. The bearing pin is engaged to the sensor element of the follower mechanism, and when it is moved sufficiently far laterally in either direction by encountering an abrupt slope, such as a rising or falling shoulder relative to its travel, stops the cam motion and throws the mechanism into a condition which will cause the stylus pin to trace over the surface of the abrupt slope.

Description

United States Patent Weaver [451 Aug. 15, 1972 [54] FOLLOWER MECHANISM 3,021,740 2/1962 Treer ..82/14 A RESPONSIVE TO ABRUPT CHANGES 2,347,367 4/ 1944 Rosen ..82/14 A IN CAM-CO1 [ROLLED FOREIGN PATENTS OR APPLICATIONS [72] Inventor: Paul J. weaver, San Marino, Calif. 7 758,007 9/1956 Great Britain ..90/62 [73] Assignee: Automatic Control Systems, Inc., El Primary Examiner-Leonidas Vlachos Monte, Calif. Attorney-Angus & Mon

[21] Appl 101359 A follower mechanism for cam-controlled machine tools which is responsive to abrupt changes in the 52 us. c1. ..82/14 R, 82/14 A, 82/14 0, Slope of the Control mm A two-link lever System 90/62 ries a bearing pin and a stylus pin. The bearing pin is 51 Int. Cl. ..B23b 3/28 engaged to the Sensor e'emem 0f the follower [58] Field of Search ..82/14 A 14 B 14 c 14 R" mechanism and when it is moved sufficiently far laterally in either direction by encountering an abrupt slope, such as a rising or falling shoulder relative to its travel, stops the cam motion and throws the [56] References Cited mechanism into a condition which will cause the stylus NIT STATES PATENTS pin to trace over the surface of the abrupt slope. 3,427,906 2/1969 Berly ..82/14 R 6 Claims, 4 Drawing Figures 70 MA C/W/Vf MUTOE FOLLOWER MECHANISM RESPONSIVE T ABRUPT CHANGES IN CAM SLOPE IN CAM- CONTROLLED MACHINES This invention relates to cam-controlled machine tools. The term cam is intended to encompass flat templates as well as rotary cams, the feature involved being a profile to be followed by a follower mechanism.

Cam-controlled machines customarily include a movable cam or cams which shift or rotate, and are followed by mechanisms which appropriately shift cutting tools or other elements whose position in space is to be controlled. A familiar example of such a machine is the Swiss Automatic Lathe. A problem inherent in such machines is that the cams classically shift or rotate at a constant velocity, and should a situation arise wherein an abrupt right angle shoulder should optimally be formed on the control cam, it cannot be accommodated, because the follower would simply be snapped off.

It is an object of this invention to permit the use of abrupt shoulders in control cams, and thereby to secure the benefits attainable with such shapes. An example is the rapid positioning of a lathe slide.

A follower mechanism according to this invention is mounted to a frame and includes a movable sensor element which may, for example, be a spool valve of the type widely used in hydraulic tracer valves. A finger is attached to the movable sensor element and has an axis of motion which, when the finger moves along the axis, results in a change in setting of the sensor element. A contact surface on the finger extends laterally relative to this axis. A first link is pivoted to the frame at the first pivot either directly to the frame, or through additional links, and a second link is pivoted to the first link of the second pivot spaced from the first pivot. A stylus pin and a bearing pin are carried by and project from the second link, and both are spaced from. the second pivot. A stylus pin is adapted to contact the cam, and the bearing pin is adapted to bear against the contact surface. A deflector surface is mounted to the frame and lies in the path of the bearing pin as it moves in one direction along the contact surface, extending in an oblique angle relative to the first axis. Thus, when it is engaged by the deflector surface, the bearing pin will be deflected so as to change the setting of the sensor element in one direction. First bias means biases the first link so as to move the bearing pin away from the deflector surface, and second bias means biases the contact surface toward the bearing pin and thereby biases the sensor element in its other direction.

According to a preferred but optional feature of the invention, means is provided for effecting the operation of the cam drive comprising power cutoff means having a central position with one transmission condition and two positions on opposite sides thereof having a different transmission condition, the control position being transmissive or non-transmissive, and the others being the opposite. A crank assembly has an arm engaged to the bearing pin and an arm engaged to the power cutoff means (which may be a switch), whereby deflection of the stylus pin to a sufficient extent, and thereby also of the bearing pin, will turn the crank and change the condition of the power cutoff means so as to effect transmission of power to a circuit controlling the cam drive.

The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawings, in which:

FIG. 1 is a top view, partly in schematic notation and partly in cut-away cross-section, showing the presently preferred embodiment of the invention;

FIG. 2 is a fragmentary showing of a portion of FIG.

FIG. 3 is a simplified showing of an optional feature useful in FIG. 1 taken at line 3-3 of FIG. 4; and

FIG. 4 is a side view of the device of FIG. 3.

A follower mechanism 10 according to the invention is shown in FIG. 1. It includes a frame I 1 adapted to be mounted to a machine tool, the frame serving to mount a sensor element 12, which includes a valve sleeve 13 and a spool 14. It is a typical four-way valve of the type used in tracer controls. Details of such a valve are well known in the trade andwill not be discussed in detail here. A complete disclosure of this type of valve and its operation may be found by reference to US. Pat. No. 2,753,145, issued to Rosebrook on July 3, 1956. Suffice it to say that the sleeve and the spool together form a sensor element, which has an axis 16, movement of the spool along this axis causing a variable setting of the valve itself. As is well known in the art, this valve operates machine components in a manner tending to restore the valve to a null position. Such a valve characteristically has inlet and outlet ports and conduits which connect with control grooves 17 in the sleeve and spool, and the flow through which is determined by the spool position in the sleeve. When the spool is centered in the sleeve as illustrated, flow is balanced and there is no net flow to the controlled element. When it is offset from null in either direction, then certain combinations of grooves will overlap and cause a resultant power flow in a selected direction to a machine tool element. Further details of this class of relationship, both as to the machine tool and to the internal construction of the valve, may be found by referring to the said Rosebrook patent.

The purpose of the follower mechanism is to react with the reference surface 20 of a cam 21 (sometimes called a template), which template moves laterally relative to axis 16 along its own axis 22. In FIG. 1, for simplicity of exposition, the cam is shown moving laterally as though flat, which indeed it may be. However, in the preferred embodiment, as shown in FIG. 3, it is a rotary cam whose reference surface moves laterally. In either case, the cam will be driven by a motor 19. There is no particular problem involved in tracing slopes relative to axis 22, but when an abupt change occurs, such as a right angle shoulder 23 to he climbed or a second right angle shoulder 24 which is to have its reverse side machined in a falling as opposed to a climbing condition, then the matter becomes more difficult, because unless the cam motion is stopped, the stylus would be snapped off. This is the condition which is solved by this invention.

Frame 11 extends to a first pivot 25 to which is pivotally attached a first link 26. A second pivot 27, spaced from the first pivot, mounts a second link 28, and these links form an angle between them. A brace surface 29 is formed which limits the movement of the second pivot in a downward direction in FIG. 1. In the specification and claims, where it is said that the first pivot joins the first link to the frame, it does not necessarily mean directly to the frame. Instead, there may be intermediate linkages between the frame and the first pivot, but there is a mounting such that the first link can swing relative to the frame. Therefore, while the illustrated direct mounting is shown and described, this is not intended as a limitation on the generality of the claims or of the invention.

A stylus pin 30, which is intended to contact and follow the reference surface of template 21 (see FIG. 3), is attached to and projects from the second link at a location spaced from the second pivot.

Similarly, a bearing pin 31 is attached to the second link spaced from the second pivot and is adapted to engage a contact surface 32 carried by the sensor element. This contact surface extends laterally relative to axis 16, and it will now be seen that the bearing pin can move laterally along the contact surface. A deflector surface 35 is formed adjacent to the bearing pin and lies in its path as it moves laterally. Preferably, it forms about a 45 angle with the axis 16.

First bias means 36 biases the first and second links so that the bearing pin tends to move away from the deflector surface. Second bias means 37, which may conveniently comprise a coil spring mounted around a stud 38 on the valve sleeve and biased against the frame, tends to move the contact surface toward and against the bearing pin, and biases the sensor spool to the left toward one of its off-null positions.

FIGS. 3 and 4 show means to control motor 19, and thereby the operation of the cam drive. Characteristically and classically, the device of FIG. 1 will be utilized to control some machine tool motion, such as the cross-motion of a lathe. When the stylus moves along and encounters an abrupt change in slope, such as either of shoulders 23 or 24, the cam drive is to be stopped until the sensor element can cause the machine tool element to undergo the requisite change in position, during which event the stylus pin will have followed the abrupt slope, and after which the cam motion will be resumed.

This device includes a yoke 40 which embraces the bearing pin and which is responsive to motion of the bearing pin as it moves laterally relative to axis 16. The yoke is formed as a part of a crank system 41 which is mounted by pivot 42 to the frame. Another arm 43 includes a switch contactor 44 which engages the actuator 45 of a power cutoff means 46, such as a common electrical switch. This switch has a first and a second contact 47, 48 respectively, and accordingly has a pair of control positions. The first, central, position is illustrated in FIG. 4, and it will be seen that the switch is open. Were arm 43 to be pivoted sufficiently in either direction from this central position, it will be seen that the switch will be closed. Leads 49, 5.0 are connected to the switch, and to motor 19 or to some circuit controlling this motorQIt will be seen that in one condition this switch is transmissive and the other condition is non-transmissive. This condition may be communicated to the power supply of the cam drive motor 19, and the change of condition will result in the shutdown of motion of the cam until the operation of the machine has restored the sensor means to a position such that the bearing pin and stylus are no longer sufficiently deflected that arm 43 will leave the switch in one of its alternative conditions. This will occur when the movement, such as a rapid positioning movement of the machine tool element, has been substantially completed, and the cam motion will then be resumed.

The operation of the device of FIG. 1 will now be described. It is shown in equilibrium operating along the reference surface moving substantially parallel to axis 22. At that time the sensor element is in equilibrium and in its null condition, and there is no requirement for motion of the machine tool under its control. However, when the stylus strikes shoulder 23, which must be climbed, then the second link will be pressed back against the second pivot and against the first bias means until the bearing pin strikes the deflector surface. Thereafter, further such motion will cause the bearing pin to climb along the deflector surface and move the contact surface and the sensor means to the right, actuating the tracers sensor.

As best illustrated in FIG. 2, there will be initial motion of the bearing pin from initial point 55 to point 56 (speaking of the center of the bearing pin), after which it will move along the deflector surface until it is deflected to a center shown at 57, at which time the sensor spool will be shifted to the right in FIG. 1, setting the flow conditions to the machine motor such that the machine element will move to restore the sensor element to null.

During this time, arm 43 will have been swung so as to change the condition of the switch, and motor 19 will have stopped moving the cam. Therefore, the stylus pin will have climbed shoulder 23 with no risk of being snapped off.

When the stylus pin reaches the position numbered 60, it will have cleared shoulder 23 and the two bias means will tend to restore the bearing pin to the relative position shown in FIG. 1. Then the switch will have swung to the central position of FIG. 1, and motor 19 will again drive the cam.

When the stylus pin reaches an abruptly falling shoulder, such as shoulder 24, the second bias means pulls the bearing pin to the position shown in FIG. 2 by numeral 31. Then the sensor means will have moved in its other control direction, and arm 43 will have swung away from the central position and changed the switch condition. Again, cam motion will have been stopped until this abrupt shoulder has been followed by the stylus pin. After the stylus pin reaches a surface such as surface 65, the central positions of the sensor element and of the switch will have been assumed, and cam drive will resume.

It will be recognized that a deflection of the bearing pin equal to that shown as X in FIG. 2 will have been needed to actuate the switch. The switch, therefore, has a central dwell region within which the sensor element exerts its control and the cam drive motor is not affected. This enables the machine to operate without interruption for more gradual slopes, and for the cam drive to be affected only for slopes of a given abruptness, usually meaning a right angle rise.

Further details of devices which can use this invention to control motions and cam drives will be found in applicants United States patent application, Ser. No. 872,492, filed Oct. 30, 1969, and now abandoned entitled Machine Control Utilizing a Plurality of Control Templates and Tracer Mechanisms, and in the copending continuation-impart thereof, Ser. No. 101,338, filed Dec. 24, 1970, entitled Machine Control Utilizing a Plurality of Control Templates and Tracer Mechanisms.

Commonly, a number of cams are driven from a single drive so they are in synchronism. When one cam should stop, all should stop. Therefore, when a plurality of follower mechanisms is used, their power cutoff means will all be interposed in the cam drive motor circuit.

The power cutoff means could, of course, be other than an electric switch, and the sensor means other than a hydraulic valve. These are merely the preferred examples of means having the desired control functions.

This invention thereby provides a convenient means for deflecting the sensor element of the tracer mechanism to follow abrupt contours, and to control the cam drive means during the time these contours are being followed.

This invention is not to be limited by the embodiment shown in the drawings and described in the description which is given by way of example and not of limitation, but only in accordance with the scope of the appended claims.

I claim:

1. A follower mechanism responsive to abrupt changes in cam slope, comprising: a frame; a sensor mechanism mounted to said frame, said sensor mechanism including a movable sensor element; a finger attached to the movable sensor element and having an axis of motion which, when the finger moves along said axis, results in a change in setting of the sensor element; a contact surface on said finger extending laterally relative to said axis; a first link pivoted to the frame at a first pivot; a second link pivoted to the first link at a second pivot spaced from the first pivot; a stylus pin and a bearing pin carried by and projecting from the second link, spaced from the second pivot, the stylus pin being adapted to contact a cam, and the bearing pin being adapted to bear against said contact surface; a deflector surface mounted to the frame lying in the path of said bearing pin as it moves in one direction along said contact surface, extending at an oblique angle relative to said axis; first bias means biasing the first link so as to move the bearing pin away from the deflector surface, and second bias means biasing the contact surface toward the bearing pin.

2. A tracer mechanism according to claim 1 in which the sensor element comprises a spool in a valve sleeve, the second bias means comprises a spring biasing the spool away from the bearing pin, and in which the links form an angle with one another.

3. A tracer mechanism according to claim 1 in which means is provided for stopping motion of the cam com prising power cutoff means having a central position with one power transmission condition and two posi tions on opposite sides thereof having a different power transmission condition, one being transmissive and the other preventing transmission, and in which an arm is engaged to the bearing pin and to the switch, whereby deflection of the stylus pin to a sufficient extent, and thereby the bearing pin, will move the arm to change the condition of the power cutoff means so as to cut off power to the motor driving the cam.

4. A tracer mechanism according to claim 3 in which the power cutoff means is an electrical switch.

5. A tracer mechanism according to claim 4 in which the sensor element comprises a spool in a valve sleeve, the second bias means comprises a spring biasing the spool away from the bearing pin, and in which the links form an angle with one another.

6. A tracer mechanism according to claim 2 in which the deflector surface lies at approximately 45 to the said axis.

Claims (6)

1. A follower mechanism respoNsive to abrupt changes in cam slope, comprising: a frame; a sensor mechanism mounted to said frame, said sensor mechanism including a movable sensor element; a finger attached to the movable sensor element and having an axis of motion which, when the finger moves along said axis, results in a change in setting of the sensor element; a contact surface on said finger extending laterally relative to said axis; a first link pivoted to the frame at a first pivot; a second link pivoted to the first link at a second pivot spaced from the first pivot; a stylus pin and a bearing pin carried by and projecting from the second link, spaced from the second pivot, the stylus pin being adapted to contact a cam, and the bearing pin being adapted to bear against said contact surface; a deflector surface mounted to the frame lying in the path of said bearing pin as it moves in one direction along said contact surface, extending at an oblique angle relative to said axis; first bias means biasing the first link so as to move the bearing pin away from the deflector surface, and second bias means biasing the contact surface toward the bearing pin.

2. A tracer mechanism according to claim 1 in which the sensor element comprises a spool in a valve sleeve, the second bias means comprises a spring biasing the spool away from the bearing pin, and in which the links form an angle with one another.

3. A tracer mechanism according to claim 1 in which means is provided for stopping motion of the cam comprising power cutoff means having a central position with one power transmission condition and two positions on opposite sides thereof having a different power transmission condition, one being transmissive and the other preventing transmission, and in which an arm is engaged to the bearing pin and to the switch, whereby deflection of the stylus pin to a sufficient extent, and thereby the bearing pin, will move the arm to change the condition of the power cutoff means so as to cut off power to the motor driving the cam.

4. A tracer mechanism according to claim 3 in which the power cutoff means is an electrical switch.

5. A tracer mechanism according to claim 4 in which the sensor element comprises a spool in a valve sleeve, the second bias means comprises a spring biasing the spool away from the bearing pin, and in which the links form an angle with one another.

6. A tracer mechanism according to claim 2 in which the deflector surface lies at approximately 45* to the said axis.

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