US3581443A

US3581443A - Glass-grinding machines

Info

Publication number: US3581443A
Application number: US779686A
Authority: US
Inventors: Colin Clayton Mayers
Original assignee: Individual
Current assignee: Individual
Priority date: 1967-11-29
Filing date: 1968-11-29
Publication date: 1971-06-01
Anticipated expiration: 1988-06-01
Also published as: GB1253512A

Abstract

A glass-grinding machine having a holder for a glass, and a grinding wheel to cut the outer surface of the glass, in which the holder is supported on a vertically disposed spindle, rotatable about and movable along its axis, and the grinding wheel is movable towards and away from the axis. There is means to control the movement of the holder and the grinding wheel, so to cut features on the glass according to a predetermined program.

Description

United States Patent [56] References Cited UNITED STATES PATENTS 1,615,978 2/1927 Greer 51/107X 1,635,491 7/1927 Milliken 51/107 1,650,375 11/1927 Milliken 51/107 2,171,007 8/1939 Rice 51/107 Primary Examiner0thell M. Simpson Att0rneyWatson, Cole, Grindle & Watson 10 Claims, 11 Drawing Figs.

US. Cl 51/107, 51/80, 51/92 Int. Cl 1324b 5/00, B24!) 7/00, 82% 7/24 Field of Search 51/92, 94, 95, 96, 97, 80, 83, 89, 107

PATENTEDJUN Han 3581.443

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PATENTED JUN 1 I971,

SHEET 11 HF 11 GLASS-GRINDING MACHINES The invention relates to grinding apparatus, for example, grinding apparatus for grinding decorative patterns on glassware.

The various features of the invention include, a device which causes the grinding wheels to be moved in accordance with a program to follow variations of shape of the glassware, an electric stepping motor for stepwise rotation of the glassware while it is being ground, and automatic means for feeding the glassware to the apparatus.

The invention provides a glass-grinding machine of the kind comprising means to hold a cylindrical glass with the outer surface or the part thereof to be out free, a grinding wheel rotatable about an axis in a plane parallel to a tangent to the glass or at a small angle thereto, means to rotate the axis of the grinding wheel in the said plane to alter the plane of rotation of the wheel with respect to the axis of the glass, the glass holder and the wheel are relatively movable in directions axially of the glass and towards and away from one another in which the holder is supported on a vertically disposed spindle, the grinding wheel is supported for movement towards and away from the axis of the spindle, there is drive means to rotate and to move the spindle about and along its axis, and to move the grinding wheel towards and away from the axis, and there is means to control the drive meaNs in response to a predetermined program.

In one formthe 'drive means to move the grinding wheel towards and away from the spindle includes two drive elements arranged to act in series, one of which elements provides a fine control for the pressure with which the grinding wheel engages the glass, and the other of which elements moves the grinding wheel towards and away from the glass to make successive cuts.

In this form the movement caused by the first element is controlled by a feeler responsive to the shape of the glass or to a template having a profile corresponding to the shape of the glass.

Preferably there is a conveyor adjacent to or forming part of the machine, which conveyor has an upwardly facing horizontal surface, and there is means to transfer the holder from its position adjacent the grinding wheel to a position above the conveyor.

In this form the arrangement is such that the axial movement of the spindle is utilized to engage upwardly facing glasses on the aforesaid surface of the conveyor.

In this form it is preferred that the holder has means to determine whether or not a glass is secured thereto, which means is arranged to prevent movement of the holder from its position above the conveyor if a glass is not secured thereto.

There is preferably means to alter the plane of the grinding wheel with respect to the axis of the glass while a cutting operation is in progress.

In one form the control means include means responsive to the movement of the spindle and the grinding wheel, means to compare the output of the responsive means with predetermined values, and means to activate the drive means to bring the moving elements to predetermined positions correspond ing to the predetermined values.

In this form the output from the responsive means is applied to a series of relays which lock the machine against cutting action until all moving elements are correctly positioned.

Alternatively or additionally the responsive means comprise transducers connected to stepping motors each arranged to drive a magnet past a plurality of magnetic reed switches.

The various features are present in specific forms in the following examples of a grinding machine and a modification thereof, which will now be described, by way of example only, and with reference to the accompanying drawings, in which:

FIG. 1 shows a side view of part of the apparatus;

FIG. 2 shows a front view ofpart of the two grinding heads;

FIG. 3 shows a plan view of parts of the two grinding heads;

FIG. 4 shows, in diagrammatic form, control apparatus for controlling the movement of the grinding heads so that they follow the contour of the glassware;

FIG. 5 shows an end view of part of the vacuum apparatus;

FIG. 6 shows a plan view of part of the vacuum apparatus;

FIGS. 7a through 7d show, in diagrammatic form, various positions of part of the apparatus controlling rotation of the glassware and the relative positions of a tumbler for each position of the controlling apparatus;

FIG. 8 shows an electrical circuit used in the apparatus;

FIG. 9 shows a front view ofa modified version of one of the grinding heads shown in FIG. 2;

FIG. It) shows an end view of a modified version of the apparatus shown in FIG. 5; and

FIG. 11 shows a modified control system.

This embodiment of the invention provides a grinding machine which grinds in the surface of, for example, a glass tumbler, a pattern of surface cuts to produce what is generally known as a cut glass tumbler. Many of the traditional cut glass patterns are of crisscross form which requires cutting the tumbler at an angle to the axis of the tumbler in two directions. The tumbler is indicated in the drawings by reference numeral 10.

The grinding machine comprises a main stand 11, comprising a lower part 12, an upper part 13 and an intermediate part 14 joining one side of the upper part to the same side of the lower part, thereby forming a G shaped main stand 11. Mounted above the lower part 12 is the grinding unit 16 and mounted inside and below the upper part 13 is the vacuum apparatus 17 for holding the tumbler. A conveyor belt 18 is mounted to pass adjacent the intermediate part 14 between the upper and lower parts of the main stand. A contour following apparatus is provided for controlling the movement of the grinding unit and the vacuum apparatus in accordance with the contours of the tumbler.

The grinding unit 16 (FIGS. 1, 2 and 3) comprises two

similar grinding heads

21 and 22 facing one another. One head 21 will be described, similar parts of the other head 22 being numbered on the Figures similarly but with the suffix a. The head 21 is mounted on a screwjack 23 attached to the bottom part 12 of the main stand 11. The head 21 comprises a table 24 attached to the screw of the screwjack 23. The screwjack may be rotated to vary the height of the table 24, the screw being locked in position by two locknuts 26. A further upper table 27 is situated adjacent and above the lower table 24 and is adjustable for limited rotation (in the plane of the faces of the tables) relative to the lower table 24. Slots 28 are cut in the upper table 27 so that clamping members may be passed through the upper table 27 to clamp the upper and lower tables 27 and 24 together. Mounted on the upper table are a pair of

abutments

32 and 33. A pair of slide rails 29 are mounted between the

abutments

32 and 33 and a slide member 31 is slidably mounted on the rails 29. The slide member 31 comprises a piston unit 34 which includes a closed cylinder attached to the slide member 31. A piston is situated within the cylinder. The piston is attached by members passing through the ends of the closed cylinder to the

abutments

32 and 33. If hydraulic fluid under pressure is introduced into the cylinder on one side of the piston the slide member 31 moves one way along the rail 29 and if hydraulic fluid is supplied under pressure to the other side of the piston the slide member 31 moves the opposite way along rail 29.

Mounted on and above the slide member 31 is a platform 37 on two opposite sides of which are mounted

supports

38 and 39 the support 39 being on the side of the platform 37 closest to the other grinding head 22. Rotatably mounted between the

supports

38 and 39 is an axle 41 which passes through the support 39 and projects towards the other grinding head 22. Solidly mounted around the axle 41 between the

supports

38 and 39 is a cogwheel 42. A rack 43 is slidably mounted on platform 37 so that the rack 43 engages the cogwheel 42. A hydraulic ram 44, one end of which is attached to the rack 43 and the other end of which is attached to the platform 37 may be operated to move the rack 43 and hence rotate the axle 41 through the cogwheel 42. A plate 46 is attached to the part of the axle 41 which projects beyond support 39 towards the other grinding head, the plate 46 extending transversely of the axis of axle 41. A support plate 47 extends from plate 46 substantially parallel to, but displaced from the axis of axle 41, towards the other grinding head 22. Passing through the end of this plate 47 is an axle 48 which is rotated by a motor 49 attached to the plate 47. A grinding wheel 51 is solidly mounted on the other end of the axle 48. The center part of the grinding wheel 51, (about which it is rotated by the axle 48) and the point of contact of the grinding wheel 51 with the glassware being ground, are both situated on the line of the axis of axle 41. Thus, as the axle 41 is rotated by the ram 44, point of contact of the grinding wheel on the glass does not change. The grinding wheel 51 comprises a flat disc, the cross section of the edge of which tapers usually in the shape of a 'V to a point 52. Thus the edge of the grinding wheel which has a diamondcutting surface produces a V shaped cut in the surface of the tumbler. As previously stated, the two grinding

heads

21 and 22 are similar. The

motors

49 and 49a, being on opposite sides of their associated plates 47 do not cause the

motors

49 and 49a to come into contact with each other during any rotation of the tables 27 and 27a.

The vacuum apparatus 17 is shown in FIGS. and 6. Extending downwardly from the upper part 13 of the main stand 11 there is a spindle 56 (see FIG. 1 also) to the bottom end of which is attached a vacuum chuck 57. The vacuum chuck 57 comprises a thick circular plate 58 the outer edge of which provides a frustoconically shaped face 59 the thicker part of the frustoconical shape being above the narrower part. A vacuum passage 61 passes through the spindle 56 and plate 58 to an aperture 62 in the undersurface of the plate 58. The spindle 56 is rotatably mounted in a bearing block 63. A plate 64 is mounted on the upper end of the spindle 56 such that the plate does not rotate with the spindle 56 but moves axially with the spindle 56. An electric stepping motor 66 is mounted on plate 64 and rotates spindle 56 through a reduction gear train 67. The overall ratio of the reduction gear train is between 25:1 .and 75:1. A ram 65, including an hydraulic cylinder 68 is attached to the bearing block 63 with the axis of the cylinder parallel to the axis of the spindle 56. The piston of the cylinder 68 is attached to the plate 64. Operation of the hydraulic ram 65 causes the plate 64 and hence the spindle 56 to move up and down relative to the bearing block 63. The bearing block 63 is mounted on a horizontal slide 69 which is attached by support beams 71 to the upper part 13 of the main stand 11, sothat the bearing block may move towards and away from the intermediate part 14 of the main stand 11. The bearing block 63 is moved along the slide 69 by a horizontally mounted hydraulic ram 72. Thus the ram 72 moves the vacuum chuck 57 between one position where the vacuum chuck is above the conveyor belt 18 and another position in which the vacuum chuck is above the grinding

wheels

51 and 51a.

The contour following apparatus is shown in FIGS. 4 and 5. A mount 73 is attached to the plate 64 and has removably mounted on it a flat template 74, the edge 75 of which corresponds to the outline of the glassware, in this case, a tumbler or wineglass 10, which is to be cut. An hydraulic cylinder 76 is mounted rigidly relative to the bearing block 63, the piston 77 of the hydraulic cylinder 76 abutting the edge 75 of the template 74. Thus as the spindle 56 moves up and down, the template 74 moves with it, thereby pushing in and out the piston 77. A slave hydraulic cylinder 78 mounted on table 27 moves its piston 79 in and out in synchronism with piston 77. Attached to the other end of piston 79 is a microswitch 81 the lever 80, of which abuts part of the slide member 31. The microswitch 81 controls the supply of fluid to the piston units 34, so that the projecting part of the slide member 31 is always adjacent the microswitch. The supply of fluid to the piston units 34a and 36a of the grinding head 22 is also controlled by the microswitch 81 and hence both of the grinding

wheels

51 and 51a move towards and away from the tumbler in synchronism with the movement of piston 77 The grinding machine operates as follows. The glass tumblers which are to be out are placed on the conveyor belt 18 with their open ends facing upwards. Successive tumblers are placed a set distance apart from one another and in a set position along the belt 18. The belt 18 moves the tumblers intermittently under the upper part 13 of the main stand 11. When a tumbler reaches the required position, the belt 18 stops. The spindle 56 is moved over the belt 18 by the contraction of the hydraulic ram 72. The spindle 56 is then lowered by expansion of the hydraulic ram 65 until the vacuum chuck 57 abuts the tumbler standing below. The size of the plate 58 on the chuck 57 is chosen so that the rim of the tumbler abuts the conical face 59 of the plate 58 everywhere around its circumference. The air within the tumbler is then withdrawn along the vacuum passage 61 and the tumbler thereby adheres to the chuck 57. The hydraulic ram 65 then raises the spindle 56 and chuck 57. When the chuck has moved a short distance a vacuum sensing device is switched on to test that there is a vacuum in passage 61. If there is little or no vacuum, then air must be entering the vacuum passage 61. This means either that the tumbler rim is not firmly sealed against the conical face 59 of the plate 58 or else the tumbler has not been picked up. Thus if little or no vacuum is detected, the ram 65 is reversed to lower the chuck S7 to try again to pick up the tumbler or to grip the tumbler more firmly held on the chuck 57. This process is repeated until sufficient vacuum is detected. When there is sufficient vacuum, the chuck continues to move upwards since this means that the tumbler is firmly secured to the chuck 57.

When the hydraulic ram 65 has lifted up the spindle 56 sufficiently, hydraulic ram 72 extends to move the spindle, chuck and tumbler towards the grinding

wheels

51 and 51a. At this stage, the grinding heads 21 and 22 are spaced well apart from one another so that the tumbler may enter between the grinding wheels to the position in which it is to be cut, hereinafter called the operating position. The table 27 has previously been manually rotated relative to the table 24, the axis of this rotation passing vertically through the operating position, so that the grinding wheels are in the necessary relative positions for a particular style of tumbler or glassware. The grinding wheels have previously been rotated to the required angle relative to the tumbler by movement of the rack 43.

When the tumbler is in the operating position hydraulic fluid at relatively high pressure is applied to the piston unit 34 and 34a and the

slide members

31 and 31a move the grinding wheels rapidly towards the tumbler. However, the piston 77 of hydraulic cylinder 76 contacts the edge of template 74 and is stopped just before the grinding wheels reach the tumbler and thus the forward motion of the

slide members

31 and 31a is checked. There is, however, a further low pressure supply of hydraulic fluid supplied to the piston units 34 and 34a to move them slowly forward so that the grinding wheels touch the glass relatively slowly. The rapid movement of the grinding wheels towards the tumbler reduces the total time the tumbler is in the grinding machine. The two grinding wheels are rotated by hydraulic motors 49 before they contact the tumbler. The grinding wheels both contact the tumbler and cut the surface of the tumbler simultaneously. The grinding pressure i.e. the pressure exerted by the grinding wheels on the tumbler, is provided by the low pressure supply of hydraulic fluid to the piston units 34 and 34a.

To produce a line cut the tumbler is moved by movement of the stepping motor 66 and hydraulic ram 65. Since the tumbler is not normally cylindrical the diameter of the tumbler changes at the point of contact of the grinding wheels as the grinding wheels move up and down the surface of the tumbler. Since the piston 76 is also moving up and down the template 74 in unison with the grinding wheels the grinding wheels are thereby moved in and out relative to the cutting position to compensate for these changes of diameter by the slave hydraulic cylinder 78 and microswitch 81.

To produce a spaced crisscross pattern of diagonal cuts on the tumbler, the grinding wheels are rotated by the rack 43 to the required angle and the first cut made by each grinding wheel. This involves the stepping motor 66 rotating the tumbler a fixed distance. If the diagonal cuts are to be relatively close to one another, the stepping motor 66 must then rotate the tumbler backwards (when the grinding wheels are clear of the tumbler) a fixed distance. The process is then repeated. The method of controlling the stepping motor 66 to perform this operation automatically will be described later in the specification. When all of the cuts in one direction are complete (since there are two grinding wheels, this will be after half a revolution of the tumbler), the grinding wheels are rotated by the rack 43 to the angle required to produce the other set of diagonal lines in the pattern.

When the required pattern has been cut on the tumbler, the tumbler is moved back onto the belt 18 by operation of the ram 65 and ram 72. When the tumbler has reached the conveyor belt 18, the vacuum is released in the vacuum chuck 57. To ensure that the tumbler is dislodged from the chuck, low pressure air is blown through pipe 61. A pressure sensitive switch 132 will prevent the machine continuing to cycle until a drop in pressure indicates the tumbler has been released. The belt then moves forward so that the next tumbler on the belt may be picked up by the vacuum chuck 57.

When different glassware is to be cut, for example, wineglasses, a template corresponding to this glassware is mounted on the mount 73.

The method of controlling the stepping motor 66 to cut a spiral groove on the tumbler will now be described with reference to FIGS. 7a-d. The stepping motor 66 rotates the tumbler during the cutting stroke and at the same time the hydraulic ram 76 moves it linearly along the line of the tumbler axis. These two motions, compounded, twist the tumbler diagonally or helically between the grinding wheels 51, 5111. A further stepping motor 91 (FIG. 8) is controlled to rotate an arm 86 at the same rate as the stepping motor 66 rotates the tumbler 10. Spaced around the arc swept out by the arm 86 are three

switches

87, 88 and 89. The arm 86 is initially adjacent the switch 87 (FIG. 7a). When the cutting of a diagonal line on the tumbler begins, the stepping motor 66 and the other stepping motor 91 rotate the tumbler and the arm 86 (clockwise in FIG. 7) in synchronism with each other. The rotational position of the switch 89 is adjusted so that when the tumbler has been rotated to produce the required cut, the arm 86 reaches the switch 89 (FIG. 7b). The arm 86 then switches off and switch 89 which reverses the direction of motion of the stepping

motors

66 and 91. The closing of the switch 89 also controls the hydraulic valves that actuate the

rams

34, 34a and 65 so that the grinding wheels withdraw from the glass and it is lifted up to its original position. Thus the tumbler rotates backwards (the indexing stroke) in synchronism with the backwards rotation of the arm 86. When the arm 86 reaches switch 88 on this backward rotation, (FIG. 70) the switch 88 is operated which thereby cuts off pulses to the stepping motor 66 which stops rotation of the tumbler. However, the arm continues to be rotated backwards by the motor 91 until it reaches the switch 87 (FIG. 7d) which reverses the stepping motor 91 and starts the motor 66. The operation then repeats itself. During this operation the tumbler has been moved forward by a first angle, and backwards by a second angle, the second angle being smaller than the first angle. The diagonal cuts on the tumbler are therefore displaced by a distance y (FlG. 7d) relative to one another and the two angles and hence the distance y" can be altered by moving the

switches

88 and 89 around the arc swept out by the arm 86. Movement of the switch 89 around the arc varies the length of the diagonal cut on the tumbler.

An electrical circuit is required to operate the stepping motors and various other parts of the apparatus and the method of operation of the electrical circuit will now be described with reference to FIG. 8. In this diagram the following switches are biassed towards an open position, 101, 104, 106, 109,87, 88, 89, 124, 127, 131 and 132.

Switches

108, 89 and 134 are biassed to a closed position.

The switch 101 is momentarily closed to start the operation of the machine. The closure of the switch 101 allows the voltage on input line to be connected to relay 102. Both relays 102 and 111 (see later) are of the kind which are flipped from one state (in which the relay connects the input to one output) to a second state (in which the relay connects the input to a second output) by a voltage pulse. The voltage on line 100 thereby switches the relay 102 to a position in which it provides an output along line 103 to the valve controlling the input to cylinder 68. This causes the cylinder 68 to extend and lower the chuck 57 onto the tumbler and vacuum is applied along vacuum passage 61. When the chuck reaches the tumbler it closes switch 104. This operates relay 107 by applying voltage from line 100 through closed switch 108 and switch 104. The operation of relay 107 reverses the direction of ram 65. To ensure that the tumbler :is correctly seated on the chuck a vacuum-sensing device is incorporated in the circuit. This consists of switch 108 which is. opened by the chuck when it has been raised some 3 inches above the belt and switch 106 which is an aneroid-type switch closing when the vacuum in the vacuum chuck reaches a certain level. If the tumbler is incorrectly held, or not held at all, the vacuum will have dropped below a certain level and switch 106 will be open. Thus on opening switch 108, no voltage is applied via switch 104 to control relay 107 which therefore changes to its other state, thereby reversing the valve-controlling cylinder 68. Thus the motion of the piston in cylinder 68 is reversed so that the vacuum chuck is lowered and the process is repeated. The vacuum chuck will not lift any higher than switch 108 allows it to until the tumbler is firmly adhering to the vacuum chuck.

When the vacuum sensing switch 106 and switch 108 indicate that the glass is firmly adhering to the vacuum chuck, the ram 65 contracts to raise the vacuum chuck fully. When the vacuum chuck is fully raised it momentarily closes switch 109. This switches relay 102 which in turn switches relay 111 to a position in which the input on line 112 is fed to line 113 which operates a valve to extend! ram 72. The tumbler is thereby moved to the grinding position.

When the tumbler reaches the grinding position, the switch 114 is switched to a second position in which it cuts off the supply to the part of the electrical circuit so far described. The input line 100 is then connected to line 116. The momentary closing of switch 87 initiates the cutting cycle by l. passing the input voltage along line 117 to a valve which extends the ram 65.

ll. changing the relay 118 to the position in FIG. 8 in which no signal is passed along line 119 to the valve controlling the piston units 34 and 34a. In this case the spring loaded valve operates the piston units to move them inwards so that the grinding wheels move in towards the tumbler.

lll. changing the relay 118 to the position in FIG. 8 which starts both of the stepping

motors

66 and 91.

The relay 118 when in the position shown in FIG. 8 is held in that position since voltage is applied along line to the relay control line even when switch 87 is open.

The stepping

motors

66 and 91 are fed by pulses by an oscillator 121. The pulses are fed to the two stepping motors through amplifiers and pulse shapers and provision can be made for counting these pulses in order to achieve a form of numerical control over the machine. The oscillator has two outputs one of a fast rate of pulses and one of a slow rate of pulses for rapid and slow rotation of the spindle. The stepping motors work at two speeds, a relatively slow speed during the cutting stroke and a relatively fast speed during the indexing stroke to minimize the time the machine is not actually cutting the tumbler. The fast pulse rate is passed along line and the slow rate which gives the slow variable speed for cutting along line 122. The relay 118 controls which rate is fed to the stepping motors.

Switch 124 is provided to prevent: the tumbler, when it is in the grinding position, being moved by the ram 65 before the grinding wheels have engaged the tumbler. This prevents skid marks at the start of each cutting stroke.

When the switch 89 is momentarily opened a voltage is applied to relay control line 115 and thus relay 118 changes to its second position. This causes voltage to be applied to the valve controlling the piston units 34 and 34a which thereby removes the grinding wheels from the tumbler, the speed of the stepping motors is changed (this is controlled by the position of relay 118), and the direction of rotation of both stepping motors is reversed. When switch 88 is closed by the returning arm 86 is operates relay 126 which switches off the pulses being fed to motor 66. When the vacuum chuck has completed a complete half cycle, (i.e. the tumbler has been rotated through 180) switch 127 is tripped closed which then changes relay 128..This relay then operates via line 129 and a valve controlling the hydraulic ram 64 changes the angle of the grinding wheels. The relay 128 also reverses

connections

122 and 125 reversing the stepping motors.

When the complete pattern has been cut on the tumbler, switch 131 is automatically closed. This operates via line 113 the valve to contract the ram 72. Thus the vacuum chuck is moved away from the grinding wheels to a position above the belt. Switch 114 is then tripped to switch over. When the chuck reaches the belt, switch 109 is momentarily closed and thus the ram 65 is moved downwards since the closure of switch 109 alters relay 102 to pass a voltage along line 103. When the tumbler reaches the belt, the ram 65 is reversed and the vacuum turned off allowing low pressure air to pass through the vacuum piping to the vacuum chuck. If the tumbler does not fall off the chuck, air pressure will build up in the vacuum line and this will close the pressure sensitive switch 132. As before, switch 108 opens on the upward stroke of the vacuum chuck, and, if an excess air pressure indicates that the tumbler has not been ejected, by switch 132 remaining open the relay 107 is changed so that the vacuum chuck returns to the belt. When the tumbler has been ejected the ram 65 lifts the chuck to its uppermost position. Switch 109 is again tripped which changes relay 102 so that relay 105 is changed. Thus a voltage pulse is passed onto line 133 which causes the conveyor belt 18 to move forward so that a new tumbler is placed beneath the vacuum chuck.

In automatic working of this grinding machine, the belt moving forward may close switch 134 thereby initiating the cycle again. Thus, once the start switch 101 has been closed operation of the grinding machine is completely automatic.

A manual switch, 133, is incorporated in this circuit to allow the machine to perform spot cuts e.g. the tumbler is not moved at all during cutting. This switch 135 simply breaks the connection between the line 122 and stepping motor 66.

In this case a timer must be incorporated to obtain the same depth of cut each time.

The invention is not restricted to details of the foregoing example. For example, different size chucks may be used for different size tumblers and for other glassware. Also the grinding machine may be used to give cuts along the axis of the tumbler.

A further stepping motor operating a lead screw may be used to replace ram 65.

A pulse shaper may be included between the oscillator 121 and the stepping motors.

Several grinding machines may be linked in series, one machine cutting, say, the foot of a wineglass, and another the bowl of the wineglass.

A disc brake may be provided on plates 46 to lock it firmly in position during cutting to prevent vibration of the grinding wheels.

An alternative method of cutting a groove of equal depth in the wall of a curved tumbler is as follows: Instead of employing a template of the shape of the tumbler to be followed for varying the position of the

slide members

31 and 31a, a feeler placed near the tip of the grinding wheel senses alterations in shape of the tumbler and transmits any such variation to the slide members. To avoid scratching the glass the feeler can take the form ofa low pressure air pipe. Any build up of pressure in this pipe (which would result when its tip came close to the surface of the tumbler) switches the hydraulic valve controlling the hydraulic rams 34 and 34a and these move the slide members into or away from the tumbler as required. If two such air sensors were used, one to each side member, the machine could cut irregularly shaped glassware, for example, wineglasses with bent stems.

In FIG. 9 there is a fixed table 201 which is rigidly mounted on the frame. This arrangement differs from that shown in FIG. 2 in that the screwjack and swingable upper table are eliminated. The table supports a fixed abutment 202 which holds a central part of a piston unit 203. At the ends of the piston unit there are downwardly extending

arms

204 and 205 which are attached to the ends of a mounting plate 206. The plate 206 is thus movable in response to the movement of the piston unit 203, which is arranged to move the guiding wheel towards and away from the glass.

The plate 206 supports two

further arms

207 and 208 which hold the ends of a high pressure cylinder 209. The cylinder 209 has a hollow piston 210 to which a grinding wheel (not shown) is attached. The power and fluid supplied to the grinding wheel are fed through the hollow piston. The end of the piston 210 away from the grinding wheel is connected through a flexible coupling 21] to a gear box 212. A motor (not shown) is arranged to rotate the piston 210 through the gear box 212, thus replacing the rack and

cog wheel

43 and 42 respectively of FIG. 2. This provides angular adjustment for the plane of the grinding wheel.

The high pressure cylinder 209 is operable to withdraw the grinding wheel from the glass between successive cuts, and the piston unit 203 is operable as an air spring in response to feeler means 77 which follows the profile of the glass being cut. The piston unit 203 thus controls the depth of the cut made on the surface of the glass.

A modified glass-raising device is shown in FIG. 10. In this device two fixed

sidewalls

231 and 232

support guide rails

233 and 234 respectively; each guide rail has upper and lower running surfaces. A carriage 235 is mounted on rollers 236- 237 which engage the running surfaces of the

guide rails

233 and 234. The carriage 235 is formed of a cylinder 246 and an upright guide 245. The cylinder surrounds a ram (not shown) which is mounted on a spindle 238 to the lower end of which a glass 10 may be attached. At the upper end of the spindle there is a gearbox 239 and a motor 240. The motor is arranged to drive the gearbox through a flexible coupling 24], and so to rotate the spindle 238. The gear box 239 has

guide wheels

242 and 243 which engage the upright guide 237 to resist rotation of the motor 240 about the spindle. The spindle 238 is hollow to receive the vacuum line to secure the glass.

A revised control system will now be described with reference to FIG. 11. This system includes sensors or transducers on the elements of the machine that move the glass holder or the grinding wheel. These elements may be termed glass raise, glass rotate, wheel angle", and wheel infeed.

The movement elements in this example are illustrated as follows. The glass raise" is provided by the ram 68, or the ram in the cylinder 246, which raises and lowers the glass. The glass rotate" is provided by the motor 66 or the motor 240 which rotates the glass. The wheel angle" element is provided by the ram 44, or the motor driving the gearbox 212, which elements rotate the grinding wheel about an axis in its plane of rotation and passing through the axis of the spindle. The wheel infeed element may be a hydraulic ram to index the wheel into and away from the glass and an air spring to control the grinding pressure. This is given as the

pistons

203 and 209 which move the grinding wheel towards and away from the glass. In FIG. 11 the glass raise sensor or transducer is designated 300 and the glass rotate sensor or transducer is designated 301.

Each transducer produces a train of impulses, the number of impulses being proportional to the movement of the element, and these are fed into stepping motors causing them to rotate. There is one motor to each element and the angular displacement of its rotor is proportional to the movement of that element.

Each motor has a magnet fitted to an arm on its rotor and so this magnet sweeps around an arc of a circle as the element moves. A ring of reed switches is packed around this circle so that the switch that is nearest to the rotor arm is closed by the magnet. There are as many such switches as there are steps to a complete revolution of the stepping motor. In this instance, the motor used has 48 steps to a revolution and such a motor, with its attendant ring of reed switches, acts as a 48 way selector switch.

In any subsequence of the cutting operation in which a cut is formed, a pair of reed switches will be selected on each of these stepping motor arrays. The first switch of each pair (called the a" switch on the diagram) dictates the position its element should take up at the start of the cutting stroke, c.g. it controls the indexing movement of the element between cuts. Similarly, the second switch (b) dictates the movement of its particular element during cutting.

The signals from the a" and b switches are fed into a series of interlocking relays 303. These determine that all the elements have completed their indexing stroke before cutting begins. At the end of the cutting stroke only one b" signal is used to switch to the next subsequence. This prevents damage to the grinding wheel through one element stopping prematurely.

The positions of each element that are controlled during a subsequence areas has already been stated-dictated by the pair of switches selected on each stepping motor array. A new pair of switches is selected for the different subsequences and this is done by a programming uniselector 302. However, as most out decorations are made up of a relatively few number of similar cuts, repeated many times, this programming uniselector is linked with a second uniselector 304 that controls a step and repeat function. This allows up to 50 similar cuts to be made on the glass at one single program station.

Not every program station controls a cutting operation. The first station controls the pickup of a glass from the feed belt and the last controls the ejection of a cut glass onto this same belt.

This is done by controlling the glass raise

element

72 or 236 only and interlocking the signals its stepping motor array produces with those from four limit switches. These are designated with reference to the first embodiment:

I at the take-out position on ram 72 1 on a pressure sensitive switch attached to the vacuum pipe 61 which leads to the chuck holding the glass 1 a vacuum sensitive switch on the same pipe, 61

1 on the feed belt, which signals when a fresh glass is correctly positioned beneath the chuck.

On the glass eject sequence at the end of the cutting operations ram 72 is signalled to withdraw the glass holding spindle shown in FIG. 5 from the grinding position to a point above the feed belt. At the same time, this glass hold actuator is extended so that the glass is 1 inch above the belt.

When both these two movements are complete, e.g., switch 1 on the ram 72 and a on the glass raise stepping motor array are both closed, the vacuum applied to the chuck is turned off and low pressure air is injected into pipe 61. This blows the glass off the chuck onto the belt. When the glass is released, there will be a fall in pressure in pipe 61 which will be sensed by 1 This signals the machine to turn itself off and also signals the uniselectors to return to their zero position.

However, for fully automatic operation, this signal can be diverted from switching off the controller to moving the feed belt until a new glass is presented to the chuck. l then switches vacuum back into pipe 61 and lowers 68 until the chuck engages with the rim of the glass. It then halts until 1 on the vacuum sensor indicates that the glass is finnly attached to the chuck. 68 then lifts the glass off the belt and 72 extends to the grinding position where the grinding cycle is repeated.

Should the vacuum fail at any time during the cutting operation-and this would indicate either that the glass has become unseated on the chuck or that is has broken-the program will be cancelled and this last movement will be reversed, bringing the chuck back to the belt.

lClaim:

l. A glass-grinding machine of the kind comprising means to hold a glass so that a portion of its outer surface may be cut unobstructed, a grinding wheel rotatable about an axis in a plane parallel to a tangent to the glass or at a small angle thereto, means to rotate the axis of said grinding wheel in said plane to alter the plane of rotation of said wheel with respect to the axis of the glass, a vertically disposed axially movable spindle arranged to support said glass-holding means, linear bearing means to support said grinding wheel for movement toward and away from the axis of said spindle, whereby said glass holder and said grinding wheel are relatively movable in directions axially of the glass and toward and away from one another drive means provided to rotate said spindle about its axis, drive means provided to move said spindle vertically along its axis, drive means provided to move said grinding wheel linearly toward and away from said spindle axis, and means provided to control each of said drive means in response to a predetermined program.

2. A machine as claimed in claim 1 in which said drive means to move said grinding wheel linearly toward and away from said spindle axis includes two drive elements arranged to act in series, one of said elements providing a fine control for controlling the pressure with which said grinding wheel engages the glass, the other of said elements moving said grinding wheel toward and away from the glass to make successive cuts.

3. A machine as claimed in claim 2 in which the movement caused by said one element is controlled by a feeler responsive to a template having a profile corresponding to the shape of the glass.

4. A machine as claimed in claim 1 wherein a conveyor is provided adjacent to the machine, said conveyor having an upwardly facing horizontal surface, and there being means provided to transfer said holder from its position adjacent said grinding wheel to a position above said conveyor.

5. A machine as claimed in claim 4 in which the axial movement of said spindle is effective to engage upwardly facing glasses resting on said conveyor surface.

6. A machine as claimed in claim 5 in which said holder has means to determine whether a glass is secured thereto, said determinative means comprising an electric circuit arranged to prevent movement of said holder from its position above said conveyor if a glass is not secured thereto.

7. A machine as claimed in claim 1 further including a geared motor to alter said plane of the grinding wheel with respect to the axis of the glass while a cutting operation is in progress.

8. A machine as claimed in claim 1 in which said control means include electrical circuits responsive to the rotary and linear movements of said spindle supporting said glass holder and also of the linear movements of said grinding wheel, as it is fed into and disengaged from the glass, said circuits comparing these movements with predetermined values programmed into the machine.

9. A machine as claimed in claim 8 in which the output from said control means is applied through a series of relays which lock the machine against cutting action until all moving elements are correctly positioned and a glass securely held on said holder.

10. A machine as claimed in claim 8 in which the responsive electric circuits comprise transducers connected to stepping motors each arranged to drive a magnet past a plurality of magnetic reed switches.

Claims

1. A glass-grinding machine of the kind comprising means to holD a glass so that a portion of its outer surface may be cut unobstructed, a grinding wheel rotatable about an axis in a plane parallel to a tangent to the glass or at a small angle thereto, means to rotate the axis of said grinding wheel in said plane to alter the plane of rotation of said wheel with respect to the axis of the glass, a vertically disposed axially movable spindle arranged to support said glass-holding means, linear bearing means to support said grinding wheel for movement toward and away from the axis of said spindle, whereby said glass holder and said grinding wheel are relatively movable in directions axially of the glass and toward and away from one another drive means provided to rotate said spindle about its axis, drive means provided to move said spindle vertically along its axis, drive means provided to move said grinding wheel linearly toward and away from said spindle axis, and means provided to control each of said drive means in response to a predetermined program.