US2709599A - Linear actuator - Google Patents

Description

31, 1955 v C, J, MANN 2,709599 ,I LINEAR ACTUATOR Filed April 28, 1952 2 Sheets-Sheet l Hrw /n Venfor Alfio/'nevi May ZM, 1955 c.. J. MANN LINEAR ACTUATOR 2 Sheets-Sheei'l 2 Filed April 28, 1952 2,709,599 LHIJEAR ACTUATOR Charles l. Mann, Traverse City, Mich. Application April 28, 1952, Serial No. 284,757

d laims. (Cl. 279-4) The present invention provides a linear actuator. In its preferred form, this mechanism develops a high mechanical advantage, and is intended primarily for use as an actuator for a diaphragm-type chuck. This latter device has the function of holding workpieces in a lathe or similar machine, and is equipped with a plurality of jaws radially disposed about an axis of rotation. These jaws are associated with sections of a resilient plate, and opening of the jaws is accomplished by applying pressure against the sections in an axial direction. The plate is thus distorted in the manner of a diaphragm. In many of these devices, the jaws are associated with a series of separate radially-extending fingers normally disposed on a common plane or annular surface; but the action of all these tingers, when taken together, is similar enough to the deection characteristics of the diaphragm so that the name diaphragm chuck persists even though there may be no continuity of material between the fingers.

The opening and closing movements of the diaphragmtype chuck are .relatively small; and as a consequence,

this type of unit is used most frequently with special operations in which large numbers of workpieces of substantially the same size are gripped. Under these circumstances, it is only necessary that the jaws open and close a small fraction of an inch to serve their purpose. The primary purpose of the present linear actuator is to generate a large amount of force to be brought to bear against the diaphragm in response to the application oi a type of energy readily available to the conventional machine installation. It is also desirable that the actuator have a denite and positive positioning effect to the components of the chuck that is relatively independent of fluctuation in the applied forces. The preferred form of the present invention acts in response to the application of air pressure. The diiliculty of positioning a piston accurately along its travel through the application of air pressure or electro-magnetic forces is well known, and the present invention is adapted to provide a definite actuating stroke for the jaws without the necessity of exact control of the applied energy.

The present invention operates on a principle in which three basic components have their position along their paths of travel iniiuenced by the same factor. Change in position of one of the components causes change in the relative position of the other two, due to the effect of the constant factor acting between the components. In single-diaphragm actuators, one of the components is tired and another is used to apply the resultant force of the mechanism, while the third functions as the actuator. in an actuator for a double-diaphragm chuck, two of the components can apply forces to the diaphragms from a position between them, and the third component induces a change in the relative position of the l'irst two so that forces are applied from one diaphragm to another through the medium of the actuator components.

The preferred form of the present invention operates by a substantially radial movement of a series of wedging members. These members act between converging surfaces, and the radial movement of the wedging members thus causes an axial movement of the thrust member or members. The members inducing the wedging action need not (and preferably do not) have the form of a wedge. Steel balls are preferred, due to their general nited States Patent availability. They primary function is to transfer forces between the various surfaces involved, and they are therefore more appropriately identilied as force-transmitting members. The radial movement of the force-transmitting members referred to above is induced by the engagement of these members by a surface inclined to the axis of the machine and formed integrally with an actuating member slideably mounted in the frame of the chuck for movement parallel to such axis induced by air pressure and spring action. This surface, together with the surfaces on the iixed member and the thrust member, contines the force-transmitting members.

The several features of the present invention will be discussed in detail through analysis of the particular embodiments illustrated in the accompanying drawings. In these drawings,

Figure l is a section through a single diaphragm chuck embodying the present invention taken along a modified diametral plane, and showing the device with the jaws of the chuck in the open position.

Figure 2 is a section similar to that of Figure 1, but showing the components of the device in the closed position and gripping a workpiece.

Figure 3 is an elevation from the front, or working, side of the chuck, and identifying the planes of the sections aken in Figures l and 2.

Referring to the drawings, a single diaphragm-type chuck is illustrated having a main body portion or frame 1b and a series of jaws 11, 12, 13, 14, 15 and 16 adapted to grip a workpiece 17. The jaws 11 through 16, inclusive, are respectively secured to substantially radiallyextending resilient members 18 through 23, inclusive. These radial members, in the form of the chuck illustrated in the drawings, are joined at their outer extremities to form a single structural unit secured to the frame lib of the chuck by the screws indicated. at 24 through 29, inclusive. i

The frame 1t) of the chuck is provided at its rear face with a recess 30 adapted to engage a suitable member associated with the spindle of the machine on which the chuck is used. The frame is formed with a solid transverse plate 3l, and with a cylindrical bore 32 opening toward the front of the device. The plate 31 acts as the head of the cylinder established by the cylindrical surface 32. A xed plate 33 closes oli the front of the cylinder defined by the surface 32, and is positioned by the screws 34 through 39, inclusive. The screws 24 through 29 also operate to secure the plate 33 in position.

An actuating member 4t) is slidably received within the cylinder defined by the surface 32. The actuating member 4t) is essentially a piston, and is provided with the sealing rings 41 on its inner diameter and 42 on its outer diameter. Air pressure is admitted through the central opening 43 in the chuck, and a radially-extending channel 44 is also formed in the frame lll to provide for transmitting the pressure to the space behind the actuating member dit. A series of springs 45 biases the actuating member di) toward the fixed transverse plate portion 31 of the frame, the springs being positioned in suitable recesses 46 in the fixed plate 33. It is preferable that openings as indicated at 47 be provided in the plate .33 for the escape of air trapped ahead of the actuating member i0 during its axial movement.

A fixed member 48 is formed in the shape of a cup and is secured at its base to the frame 10 of the chuck by the screws 49, 50, and 51. This fixed member has an annular face surface S2 concentric with the axis 53 of the chuck. A thrust member 54 in the general shape of a collar is slideably received within the :inner diameter of the cup-shaped fixed member 48, and is: provided with annular conical shoulder 55 on its outer periphery. In the illustrated form of the invention, the surface 52 is in a plane perpendicular to the axis 53, but it may also be formed as a conical surface, The important feature is the divergence between the surface 52 and the shoulder 55. A series of hardened steel balls 56 is positioned in the area defined by the surface 52 and the conical shoulder 55. Another conical surface 57 completes the confinement of the balls 56, the surface 57 being formed integrally with the actuating member 40. Axial movement of the actuating member 40 under air pressure will cause the conical surface 57 to move toward the jaws of the chuck and thereby move the balls 56 radially inward. Such movement of the balls 56 induces an axial separation between the shouder 55 and the face 52 of the fixed member 48, and thereby forces the thrust member 54 toward the jaws of the chuck and urges them forward. Such forward movement induces a rotation about the flexible portions of the chuck with which the jaws are associated, and results in expanding the operating diameter of the jaws. The forward movement of the actuating member is preferably limited by its engagement with the fixed plate 33, giving a uniform open" position of the jaws.

The particular modification of the present invention illustrated in the accompanying drawings is also provided with auxiliary positioning equipment shown in section in Figure 2. A stud 58 is secured to the plate 33, and is provided with a hollow bore 59 in which the pin 60 is slideably received. The pin 60 serves the purpose of angularly locating the workpiece 17 about the axis 53 of the chuck. A set screw 61 bears against a flat area on the pin 60 and secures the axial position thereof within the bore 59. The stud 58 is positioned between the radially-extending areas 21 and Z2, and these components are machined out as indicated at 62 and 63 in cases where the dimensions of the stud exceed the space between the members 21 and 22.

The particular embodiments of the present invention illustrated in the accompanying drawings and discussed herein are for illustrative purposes only and are not to be considered as a limitation upon the scope of the appending claims. In these claims, it is my intention to claim the entire invention disclosed herein except as I am limited by the prior art.

I claim:

1. In combination with a diaphragm-type chuck, said chuck having a frame, diaphragm means, and a plurality of jaws secured to said diaphragm means and adapted to grip workpieces on an axis perpendicular to said diaphragm means, an actuator comprising: a first member, said first member having an annular surface; a second member, said second member being slideably mounted with respect to said first member for movement parallel to" said axis and adapted to engage said diaphragm means, said second member having an annular surface, said first and second member annular surfaces forming a diverging space therebetween; an actuating member slideably mounted in said frame for movement parallel to said axis, said actuating member having an annular surface inclined to said axis and disposed opposite the said diverging space; means for inducing axial movement of said actuating member; force-transmitting means confined between said annular surfaces whereby axial movement of said actuating member induces movement of said forcetransmitting means and relative axial movement between said first and second members to apply axial force to said diaphragm means; and biasing means urging said actuating member in a direction to remove axial force from said diaphragm means.

2. In combination with a diaphragm-type chuck, said chuck having a frame, cylinder means in said frame, diaphragm means, Vand a plurality of jaws secured to said diaphragm means and adapted to grip workpieces on an axis perpendicular to said diaphragm means, an actuator comprising: a4 rst member, said first member having an annular surface; a second member, said second member being slideably mounted with respect to said first member for movement parallel to said axis and adapted to engage said diaphragm means, said second member having an annular surface, said first and second member annular surfaces forming a diverging space therebetween; an actuating member slideably mounted in said frame for movement parallel to said axis, said actuating member having a piston portion cooperating with said cylinder, and also having an annular surface inclined to said axis and disposed opposite the said diverging space; force-transmitting means confined between said annular surfaces whereby axial movement of said actuating member induces movement of said force-transmitting means and relative axial movement between said first and second members to apply axial force to said diaphragm means; and biasing means urging said actuating member in a direction to remove axial force from said diaphragm means. l

3. In combination with a. diaphragm-type chuck, said chuck having a frame, cylinder means in said frame, diaphragm means, and a plurality of jaws secured to said diaphragm means and adapted to grip workpieces on an axis perpendicular to said diaphragm means, an actuator comprising: a first member, said first member having an annular surface about said axis; a second member, said second member being slideably mounted with respect to said first member for movement parallel to said axis and adapted to engage said diaphragm means, said second member having an annular surface about said axis, said first and second member annular surfaces forming a diverging space therebetween; an actuating member slideably mounted in said frame for movement parallel to said axis, said actuating member having a piston portion cooperating with said cylinder, and also having an annular surface inclined to said axis and disposed opposite the said diverging space; ball means confined between said annular surfaces whereby axial movement of said actuating member induces movement of said ball means and relative axial movement between said first and second members to apply axial force to said diaphragm means; and biasing means urging said actuating member in a direction to remove axial force from said diaphragm means.

4. In combination with a diaphragm-type chuck, said chuck having a frame, cylinder means in said frame, diaphragm means, and a plurality of jaws secured to said diaphragm means and adapted to grip Vworkpieces on an axis perpendicular to said diaphragm means, an actuator comprising: a fixed member having an annular surface about said axis; a member slideably mounted with respect to said fixed member for movement parallel to said axis and adapted to engage said diaphragm means, said slideable member having an annular surface about said axis, said xed and slideably member annular surfaces forming a` diverging space therebetween; an actuating member slideably mounted in said frame for movement parallel to said axis, said actuating member having an annular surface inclined to said axis and disposed opposite the said diverging space; means for inducing axial movement of said actuating member; ball means confined between said annular surfaces whereby axial movement of said actuat ing member induces movement of said ball means and axial movement of said slideable member to apply axial force to said diaphragm means; and biasing means urging said actuating member in a direction to remove axial force from said diaphragm means.

References Cited in the file of this patent UNITED STATES PATENTS 614,951 Hoffman Nov. 29, 1898 887,779 Dixon May 19, 1908 2,577,656 Hohwart et al. Dec. 4, 1951 g FOREIGN PATENTS 638,215 Great Britain 1950

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