US2889668A - Work holders of the centerless type for grinding machines - Google Patents

Description

June 9, 1959 G. GLUCHOWICZ ET AL WORK HOLDERS OF THE CENTERLESS TYPE FOR GRINDING MACHINES Filed Feb. 9, 1956 2 Sheets-Sheet l June 9, 1959 G. GLUCHOWICZ ET AL WORK HOLDERS OF THE CENTERLESS TYPE FOR GRINDING MACHINES Filed Feb. 9, 1956 F lg. 2

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A ftor'n ey WORK HOLDERS OF THE CENTERLESS TYPE FOR GRINDING MACHINES Gerszon Gluchowicz, Hagersten, and Holger Villielm Axelsson, Bromma, Sweden, assignors to Ulvsunda Verkstader Aktiebolag, Bromma, Sweden, a joint-stock company of Sweden Application February 9, 1956, Serial No. 564,579 Claims priority, application Sweden April 7, 1955 3 Claims. (Cl. 51-236) This invention relates to a work holder of the centreless type for grinding machines, wherein the workpiece while bearing against a surface of the holder extending at right angles to the holder axis is supported in a radial direction by means of rigid supports, that is, supports not rotating together with the holder. In such constructions the workpiece is entrained in the rotation of the holder by being subjected to axial pressure against the above-mentioned surface, which pressure produces a frictional drag between the surface and the workpiece.

It is known to produce this pressure by means of rollers requiring accurate adjustment so as not to give rise to radial force components, which rollers also tend to wear relatively soon. This is due to the fact that the stresses on the rollers are high because the axial pressure must be of a high value to produce suflicient frictional drag between the holder surface and the workpiece.

To avoid such wear it has also been proposed to replace the rollers by members producing axial pressure on the workpiece by means of fluid under pressure. These members comprise supply conduits from a source of compressed air opening into a stationary element containing an annular channel. The channel receives a flange on a ring element with some play, the ring element bearing against the workpiece and rotating therewith.

When compressed air is supplied to the chamber formed by the channel and the flange, the latter is subjected to axial pressure and the play between the flange and the walls of the channel is selected with respect to the leakage of high pressure fluid continuously passing therethrough. The rotating element slides in contact with the stationary channel wall thus setting up undesirable frictional drag. Due to the fact that grinding particles and the like enter between the sliding surfaces, the friction is increased with the result that the operation of the device is unsatisfactory and liable to interruption.

One main object of tthe invention is to provide a construction avoiding such disadvantages of the kind lastdescribed, wherein direct contact between the members forming the chamber is entirely eliminated, so that said members are always separated by high pressure fluid.

Further objects and advantages of the invention will be apparent from the following description considered in connection with the accompanying drawings which form part of this specification, and of which:

Fig. 1 shows a part-longitudinal section of a work holder constructed according to the invention.

Fig. 2 shows a similar section through a modified embodiment of the invention.

Referring to Fig. 1, designates the support pillar of a grinding machine havng a rotary work holder 12 formed wth a surface 14 extending at right angles to the holder axis, said surface in the present construction being of annular form. The workpiece 16 is caused to bear against the surface 14 in order to rotate therewith during the grinding of its internal surface 18, which in the present case is conical. The radial position of the worknited States Patent piece relatively to the surface 14 is ensured by means of two stationary supports (not shown) located so that the axis of the workpiece is disposed somewhat eccentrically with respect to that of the work holder 12. Thus a force is created which keeps the workpiece bearing against the supports, which since they are well known, are not shown in the drawings.

The pillar 10 carries a number of, for example three, axially extending brackets 20 uniformly distributed round a circle on the pillar. Each bracket includes a chamber 22 having a supply channel 24 for fluid under pressure, preferably compressed air, opening into said chamber. A sleeve 26 is fitted into the Wall of the chamber and clamped between the sleeve and wall is the outer peripheral portion of a resilient diaphragm 28 of annular form. A similar diaphragm 30 is clamped at its outer peripheral portion between the sleeve 26 and a ring 32 at the outer end of the cylinder. A bolt 34, which may be surrounded by a sleeve 36 with which it is in threaded engagement, extends into the chamber 22, wherein the bolt is centered by the two annular diaphragms 28 and 30. For this purpose, the inner peripheral portions of the diaphragm members 28, 39 are clamped between a flange 38 on the sleeve 36, a sleeve 40 and a plate 42, respectively. The diaphragms permit longitudinal movement of the bolt 34 and of the sleeve 36 but fix their radial positions.

A diaphragm seal 44 of annular shape is clamped at its outer periphery between the ring 32 and a ring 46 and at its inner periphery between the plate 42 and a Washer 48 that is threaded on to the sleeve 36. The diaphragm seal 44 closes the chamber 22. On the other hand, the resilient diaphragms 28, 30 are formed with slots so that the compressed air has free access to both sides of the diaphragms. A spring 50 tends to move the bolt 34 into contact with the end of the chamber 22.

An annular plate element 52 is formed with a centering cone 54 at the inner peripheral portion thereof which ensures the radial position of the element 52 relatively to the workpiece 16. Another annular plate element 56 is formed with three lugs 58 apertured to engage the sleeves 36 and locked by means of nuts 60, 62. The element 56 thus assumes a fixed radial position with respect to the work holder axis but is movable axially together with the bolt 34.

The element 56 is formed with an annular channel 64 with which communicates a supply passage 66 for a fluid under pressure from a pum which may be of the centrifugal type. The fluid under pressure preferably comprises a liquid which also serves for cooling purposes during the grinding operations. The channel 64 together with the element 52 forms a chamber 68, which however is not closed as there is always a clearance between the elements 52 and 56 at each side of the channel. This clearance, which is in a radial plane, is at a minimum when the bolt 34 bears against the end of the chamber 22.

When the element 56 has moved a small distance to the right away from the element 52, as viewed in Fig. 1, stops 70 on the element 56 come into contact with the element 52 and carry this element along in the axial direction.

On completion of the grinding operation compressed air is introduced into the chamber 22 so that the bolt 34 and thus the element 56 are displaced in a direction away from the workpiece 16; and simultaneously with the admission of compressed air to the chamber 22, the flow of fluid under pressure to the chamber 68 is stopped. During this displacement the element 52 is carried along a sufficient distance to ensure that the workpiece 16 is unobstructed by said element and can be removed from the work holder. Then another workpiece 16 is intro- -movement of the element 56.

diic'ed and "the chamber 22 relieved of load so that the springs SO'then'move'the elements 56 and 52in a direction toward the workpiece. Liquid under pressure is then again admitted to the chamber 68, and the flow of "compressed air to the chamber 22 is stopped and the element 52 is thus subjected to an axial pressure and due to the centering cone 54 the element 52 assumes a fixed radial position relatively to the'workpiece 16.

The axial pressure is determined by the liquid pressure in'the chamber 68which is chosen in such manner as to create a frictional drag between the workpiece 16 and the surface -14 of suflicient magnitude to cause the work- 'piece to be entrained in the rotary movement. By virtue 'of the clearances between the elements 52 and 56 existing on both sides of the chamber 68 there will be a continuous leakage of liquid under pressure. The size of the clearances, which is adjustable by means of the bolts 34 is chosen with respect to any divergences possibly arising in the axial dimensions of the workpieces and may amount to one or a few tenths of a millimetre. The pressure acting on the workpiece 16 may be adjusted at the same time by variation of the width of the clearance. It will beunderstood that contact between tthe elements 52 and '56 cannot take place and the active pressure is maintained by the cushion of liquid under pressure always existing in the chamber 68, during grinding.

The clearance between the peripheral cylindrical surface of the element 52 and the confronting, radiallyspaced surface of the element 56 issuflicient that there is normally no contact between these surfaces, and consequently, no frictional drag. The liquid that escapes between the elements 52, 56, respectively, during grinding, prevents this contact and also lubricates these confronting surfaces.

When the grinding operation has been completed, the supply of liquid to the chamber 68 will be cut off and compressed air introduced into the chamber 22 in the manner above-described.

The embodiment shown in Fig. 2 differs from that of Fig. 1 in that bolts 72 are rigidly and immovably connected to the brackets 20, said bolts carrying an annular plate element 74 secured to the bolts by means of the nuts 60, 62. An annular diaphragm 76, for instance of rubber, is sealingly connected at its outer peripheral portion to the element 74 and at its inner peripheral portion to the element 56. This diaphragm provides a closure for a chamber 78 while permitting some axial A fluid under pressure, primarily air, is supplied to the chamber 78 through a conduit 80.

The element 56, which together with the element 52 forms the chamber 68, as in the preceding embodiment, is connected at its outer peripheral portion with an annular diaphragm 82, also secured to the stationary element 74. Bearing against the inner peripheral portion of the diaphragm is a rin 84, which is screwed securely in the element 56, and hearing at the outer peripheral portion of the diaphragm is a ring 86, which is screwed securely on the element 74. The ring 84 may also serve for the radial centering of the element 56. The ring 86 has 'a lip 88 to limit the axial movement of the element 56 in a direction toward the element 52.

This embodiment operates in general in the same mannet as that according to Fig. 1 but with the difference that fluid under pressure is supplied to the two chambers 68 and 78 during the grinding operation. The pressurized liquid flowing to the chamber 68 through the element 52 produces that frictional drag on the surface 14 which entrains the workpiece in the rotary movement. The lip 88 determines the smallest clearance existing between the elements 52 and 56 through which the liquid escapes from the chamber 68. During replacement of workpieces -16 the supply of fluid is interrupted, at least to the chamber 78. The elements 56 and 52. are removed axially iii) away from the workpiece 16 by means of the two resilient diaphragms 76 and 82.

Slots may be provided in the clearances between the elements 52 and 56, so that a kind of labyrinth sealing efiect is obtained. In some cases, the lip limiting the movement of the element 56 in a direction toward the workpiece may be omitted. The clearances between the elements 52, 56 then automatically adjust themselves to a definite width determined in part by the pressure in the chamber 78 and in part by the characteristics of the pump for the liquid. This construction may be utilised particularly where the workpieces vary greatly with respect to their axial dimension or where it is desired to limit the clearance width to a minimum so as to cut down the consumption of liquid. In the embodiment described With reference to Fig. 1, the minimum width of the clearances is decided by the power of the springs 56 instead of by the pressure in the chamber 78 as in the embodiment shown in Fig. 2.

If the workpiece has a radial dimension corresponding approximately to that of thte element 52, the latter may be omitted, the chamber 68 then being bounded by the workpiece. The outlet clearances for the liquid under pressure introduced into the chamber 68 are in this case formed between the element 56 and the workpiece.

While two more or less specific embodiments of the invention have been described, it is to be understood that this is for purpose of illustration only, and that the invention is not to be limited thereby, but its scope is to be determined by the appended claims.

What we claim is:

1. in combination with a rotary spindle carrying a face plate at one end presenting a face transverse to the axis of said spindle against which a workpiece to be ground may be pressed for rotation With said spindle, a rotatable element mounted for movement toward and away from said face to press one surface of the workpiece against said face, a member mounted axially outwardly of said element and for limited axial movement toward-and away from said face, spring means mounted constantly to urge said member in one direction relative to said face, lost motion means interconnecting said member and said element for limited independent relative axial movement, said member and said element having opposed surfaces in radial planes defining a space therebetween, and means to supply fluid under pressure to said space to urge said element axially toward said face, said spring means being operative simultaneously resiliently to hold said member against axial movement away from said face.

2. In combination with a rotaryspindle carrying a face plate at one end presenting a face transverse to the axis of said spindle against which a generally cylindrical workpiece to be ground may be pressed for rotation with said spindle, a rotatable disc element formed with a conical central recess in which aworkpiece can engage to align the axes of said element and said workpiece, said element having larger radial than axial dimension and being mounted for movement toward and way from said face to engage said workpiece'to press one surface of the workpiece against said face in frictional contact therewith to rotate said workpiece upon rotation of said spindle, a member held against rotation and mounted axially outwardly of said element, said member being axially movable relative to said face and said element, resilient means mounted constantly to urge said member in one direction relative to said face, means mounted adjustably to regulate the axial spacing between said member to said face, said member and said element having opposed surfaces in radial planes defining a space therebetween, means to supply fluid under pressure to said space to urge said element axially toward said face to engage said workpiece to press said workpiece against said face, means to move said member axially away from said face, and lost motion means slidably interconnecting said element and said member for limited axial movement apart-and operative to move said element with said member away from said face to release said workpiece.

3. In combination with a rotary spindle carrying a face plate at one end presenting a face transverse to the axis of said spindle against which a generally cylindrical workpiece to be ground may be pressed for rotation with said spindle, a rotatable disc element formed with a conical central recess in which a workpiece can engage to align the axes of said element and said workpiece, a member held against rotation and mounted axially outwardly of said element for mial movement relative to said face, said member being formed with a recessed, radially extending annular face in the surface thereof nearer said face, said element having larger radial than axial dimension and having a radial face disposed to confront said recessed face of said member to define a space, means to supply fluid under pressure to said space to move said element toward said transverse face to engage said workpiece to press one surface of the workpiece against said transverse face in frictional contact therewith to rotate said workpiece upon rotation of said spindle, resilient means mounted constantly to urge said member in one direction axially toward said transverse face, means mounted adjustably to regulate the axial spacing between said memher and said transverse face, means to move said member axially from said transverse face, and lost motion means interconnecting said member and said element for limited axial movement apart to move said element with said member away from said transverse face to release said workpiece.

References Cited in the file of this patent UNITED STATES PATENTS 2,078,416 Sauer Apr. 27, 1937 2,478,607 Theler et a1. Aug. 9, 1949 2,706,369 Dix Apr. 19, 1955 2,715,304 Dix Aug. 16, 1955

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