Camming device

Abstract

 Acamming device to provide a cycle of axial and rotational movements between two arms (11,33) in which the forward and return axial movements occur at different relative angular positions of the arms comprises a member (22) mounted on one of the arms and extending generally axially and tangentially beside the other of the arms, one of said member and the other of said arms being formed with a cam (23) having two oppositely directed faces (24,25) for engaging the the other said member and said other of said arms to rotate it about an axis in either direction until stopped, said cam then slipping out of engagement so that relative rotation between the arms can occur. To cause relative axial movement in one direction, a second cam (15) is fomred on one arm for engagement with the other arm, causing said relative axial movement in one direction on relative rotation of the arms in one direction. Relative axial movement in the other direction is prevented until relative rotation of arms in the other direction has occurred a predetermined distance past the relative angular position at which said relative axial movement in said one direction.
This cycle of movements may be used in connection with a button transfer device in a sewing machine, by way of example only.

Description

[0001] British Patent Specification 2138036 describes and claims button transfer apparatus including a radial arm movable about an axis, between first and second angular positions and movable axially against a resistance on interruption of the angular movement. This movement is achieved by means of a cam and a follower contacting the cam, one being mounted on the radial arm and the other on a driving arm. The combination of follower and cam causes the radial arm to be both rotated and axially moved.

[0002] According to the present invention there is provided a camming device comprising a pair of arms, one arm being movable relative to the other arm along and about a common axis, a member mounted on one of said arms and extending generally axially and tangentially beside the other of said arms, one of said member and the other of said arms being formed with a cam having two oppositely directed faces for engaging the other of said member and said other of said arms to rotate it about the axis in either direction until it encounters a resis,tance, said cam then slipping out of said engagement so that relative rotation between the arms can occur, a second cam formed on one of said arms for engagement with the other arm to cause relative axial movement in one direction on relative rotation of the arms in one direction, and means to prevent relative axial movement in the other direction until relative rotation of the arms in the other direction has occurred a predetermined distance past the relative angular position at which said relative axial movement in said one direction occurred.

[0003] An example of the invention will now be described with reference to the accompanying drawings, in which:-

Figure 1 is a side elevation of a crank arm;

Figure 2 is an underside view of the arm of Figure 1;

Figure 3 is an underside view of a latch member to be hinged to the arm of Figure 1;

Figure 4 is a side elevation of the member of Figure 3;

Figure 5 is a plan of a radial arm;

Figure 6 is a side elevation of the arm of Figure 5 looking in the direction of Arrow A;

Figure 7A is a side elevation of the assembled arms, less the hinged latch member, in one relative position; and

Figure 7B is a plan of the latch member and the radial arm in one relative angular position; and

Figures 8A and 8B are the same views in another relative angular position.

[0004] As shown in Figure 1, a crank arm 11 is fixed to a sleeve 12, which is capable of sliding and rotating on shaft 13. On the lower surface 14 of the crank arm there is provided a segment of a hollow cylinder 15 coaxial with said sleeve 12 and formed with an end caming face 16 extending at an angle of about 45° to said lower surface. A stop post 17, having an axial length slightly less than the segmental hollow cylinder, is also carried by this lower surface.

[0005] A latch member 22 is arranged to pivot about a pin, passing through the spaced arms 21 of the latch member and through a tangential bore 18 in the outer end of the crank arm 11. The member 22 is provided with a projection 23 facing towards the axis of sleeve 12, and carrying two oppositely disposed cam surfaces. Cam surface 24 has its length generally perpendicular to the pivot axis and its surface inclined at an angle of 43° to a line parallel to the pivot axis. The second surface 25 has its face 62° to the same line. A spring attachment post 26 serves to impart to the latch member, about its pivot axis, a bias towards the axis of the sleeve 12 by means of a spring (not shown). A stop screw (not shown) inserted through a threaded hole 40 passing through the thickness of the latch member 22 serves to limit the inward swing of said member towards sleeve 12 by contacting the side of the segmented hollow cylinder 15.

[0006] Rotation of radial arm 33 is conveyed to shaft 13 via the engagement of rectangular recess 32 (Fig. 5) and the mating lug 31 on the end of said shaft. The upper surface 34 of the arm 33 provides a bearing surface for the end of the segmented cylinder 15, but at one end of the tangential track of said segmented cylinder there is provided in this surface a portion 35 inclined at 45° for engagement with the camming surface 16 of the cam 15 (Figs. 7A & 8A). The stop 17 can engage surface 34 when radial arm 33 is close enough axially to crank arm 11; projection 37 is arranged to extend said surface so that stop 17 does not lose contact with same at its extremes of motion.

[0007] A radial shoulder 39, directed oppositely from camming surface 35, is carried at the end of arm 33 remote from sleeve 12. This shoulder 39 is engaged by face 25 of the latch member 22. A flange 41 is provided along the bottom edge of the arm 33 remote from the sleeve 12 to engage the bottom edge of the projection 23, and carries a notch 42 shaped to allow the projection 23 on latch member 22 to pass axially through the flange at teh appropriate relative angular positions of the arms 11 and 33.

[0008] Figure 7A shows a side elevation and Figure 7B a plan of the camming surfaces of the arms 11 and 33 and the latch member 22 in one relative position, during movement of the arm 11 and member 22 to the right. Figures 8A and 8B show the same views of the components in a second relative position during movement to the left. It will be seen that the axial spacing of the arms 11 and 33 is less in Figure 7 than in Figure 8.

[0009] When the components are in the position shown in Figure 7, the crank arm 11 drives the radial arm 33 to the right through the engagement of the projection 23 with the notch 42. The flanks of the projection and the notch imparting rotation to the radial arm 33 in this direction are inclined at only a small angle to the direction of motion, so that when the arm 33 hits a stop (not shown) to limit its rightward movement, the projection 23 is forced out of the notch 42 and the latch member 22 moves to the right relative to the arm 33 beyond the position shown in Figure 8B until the stroke of arm 11 is completed. During this relative movement of the arms 11 and 33, the cam surface 16 moves into contact and along surface 35, forcing the arms 11 and 33 apart axially to the position shown in Figure 8A. Furthermore projection 23 is carried above the flange 41 by such movement, allowing the spring bias to carry said projection 23 into contact with the inner circumferential face 43 of the radial arm 33.

[0010] When the arm 11 starts to move to the left from the position shown in Figure 8, the surface 25 of the projection 23 moves into engagement with the shoulder 37 on the arm 33, imparting movement to said arm until arm 33 contacts a stop (not shown) defining the leftward limit of its stroke.

[0011] The projection 23 is then forced out of contact with the shoulder 37 against the bias of the spring acting on post 26 and the arm 11 and latch member 22 move to the left relative to the arm 33, the axial separation being maintained by the bottom face of latch 22 riding on the top surface of flange 41. Upon the projection 23 moving into alignment with the notch 42 in flange 41, the two arms 11 and 33 can move axially towards each other under the bias of a spring (not shown) or gravity. This motion is allowed since meanwhile cam 15 has moved past caming surface 16, the flange 41 preventing axial movement until alignment between the projection 23 and notch 42 is reached. This completes the cycle which comprises relative rotation between the two arms in one direction accompanied by an increase in axial separation, and then relative rotation to the other direction accompanied by a decrease in axial separation, the two relative axial movements occurring at different relative angular positons.

[0012] The latch 22 not only imparts rotary motion to radial arm 33 in both directions, but also serves to prevent any motion other than axial from taking place on the occasion of radial arm 33 contacting the stop controlling leftwards rotation of the radial arm, during the continued leftwards motion of crank arm 11, due to the inclination of its face 25.

[0013] The movement of the arms may be used to operate button transfer apparatus described in my earlier patent specifications, or any other form of article transferer, or for any other purposes.

Claims

1. A camming device comprising a pair of arms (11,33), one arm being movable relative to the other arm along and about a common axis, a member (22) mounted on one of said arms and extending generally axially and tangentially beside the other of said arms, one of said member and the other of said arms being formed with a cam (23) having two oppositely directed faces (24,25) for engaging the other of said member and said other of said arms to rotate it about the axis in either direction until it enc/ounters a resistance, said cam then slipping out of said engagement so that relative rotation between the arms can occur, a second cam (15) formed on one of said arms for engagement with the other arm to cause relative axial movement in one direction on relative rotation of the arms in one direction, and means (41) to prevent relative axial movement in the other direction until relative rotation of the arms in the other direction has occurred a predetermined distance past the relative angular position at which said relative axial movement in said one direction occurred.

2. A device as claimed in Claim 1, wherein said preventing means comprises a flange (41) on said other of said member and said other of said arms, said flange being formed with a notch (42) to allow said cam to move axially relative to said flange.

3. A device as claimed in Claim 1 or Claim 2, wherein said member (22) is pivotally mounted on said one arm about an axis extending at right angles to the common axis of the arms and the radius of said one arm.

4. A device as claimed in any one of Claims 1 to 3, wherein said oppositely directed faces (24, 25) are inclined at angles between 30° and 45° from a plane through said common axis.

Drawing