GB2174694A - Crank drive mechanism for straight line shear - Google Patents

Abstract

A straight line shear wherein there are two slides (24,26) for guided movement toward and away from one another, and arranged in opposed relation. The slides carry cooperating blades (28,30). The slides are driven by unidirectional rotary drive means (M) incorporating crank means (50) coupled at one end through a linkage arm (52a,52b) to at least one of the slides and at the other end to a drive unit (M) which drives the crank means. The crank means (50) is designed to complete one revolution per each cut of the shears. The drive crank system will provide a modified harmonic motion to the shear blades and does not require motor reversal to return the blades after a cut is made. <IMAGE>

Description

SPECIFICATION Crank drive mechanism for straight line shear This invention relates in general to new and useful improvements in straight line shears for cutting glass runners into individual gobs, and more particularly to improved crank drive mechanisms for such shears.

This invention, in particular, constitutes a modification on the shear drive disclosed in United States Patent No. 4 215 611 to Francis A. Dahms, granted August 5, 1980, assigned to the assignee of the present invention. The disclosure of the aforesaid patent is incorporated herein by reference.

It is known, as disclosed in the afore-noted U.S. Patent No. 4215 611, to provide a straight line shear wherein there are two slides mounted for guided movement towards and away from one another, and arranged in opposed relation. The slides carry cooperating blades. The slides are driven by racks which are interconnected by a pinion. The drive unit is in the form of a double-acting air cylinder or linear air motor which is coupled to one of the racks between that rack and an associated one of the slides.

In accordance with the present invention there is provided an improved rotary drive means incorporating crank means for straight line shears. In one embodiment of the invention a single crank is coupled at one end through a linkage arm to one slide carrying a shear blade of the straight line shears, with the second slide being a slave to the first slide through a rack and pinion mechanism, providing guided movement of the slides towards and away from one another. In this embodiment the crank is connected at its other end to a drive unit which preferably is an electric servo motor. Such an electric servo motor can be controlled by a microprocessor together with a servo control power switching device. The drive unit may be coupled directly to the crank or may be coupled thereto by way of spur gears or bevel gears.When bevel gears are utilized, the drive unit may be disposed parallel to the drive mechanism, conserving space.

In another embodiment of the present invention, two cranks tied together by a gear train driven by an electric servo motor or other controlled rotary power source are connected through separate linkage arms each to one of the opposing slides of the straight line shears to provide guided movement of the slides towards and away from one another. Preferably, as with the first embodiment, the power source will be connected to the gear train by way of spur gears or bevel gears.

In the crank shear drive mechanisms of the present invention, the crank will make one revolution per cut during which time the drive motor will make more or less revolutions depending upon the gear ratio selected for the bevel or spur gears. This gear ratio is selected to minimise the RMS motor torque. The crank drive system of this invention will provide a modified harmonic motion to the shear blades depending upon the ratio of the connecting rod length to the crank arm radius, and does not require motor reversal to return the blades after a cut is made. The drive unit which can be electronically programmed for timing, acceleration, and rotational rate will operate in three different modes as follows: (1) For high speed cutting rates, the drive motor operates at a cyclic rate to suit the feeder system rate provided that the shear blade velocity is satisfactory.

(2) For intermediate cutting rates, the drive motor is programmed to decelerate during the shear out stroke and accelerate during the glass shearing portion of the travel. The rotational frequency would match the feeder rate.

(3) For slow cutting rates, the drive motor will stop at the crank outward position of shear and then accelerate to the required velocity to provide the proper shear blade cutting rate. Each intermittent cycle will occur in time relation to the feeder rate.

There is also disclosed herein an override mechanism to prevent damage to the positive drive mechanism in the event the shear blades strike an object such as a stone. The uniqueness of the override mechanism is that within a relatively small physical size, when a pre-selected maximum design load in the mechanism is attained, the device will release and apply no further load to the drive. Very long overload strokes can be accommodated, after which the device will reset at the end of each stroke.

In the drawings, wherein throughout like numerals refer to like parts, Figure 1 is a plan view of a single crank drive for straight line shears; Figure 2 is a section taken along line 2-2 of Fig. 1; Figure 3 is an enlarged view of a portion of Fig. 1; Figure 4 is sectional view taken along line 4-4 of Fig. 3; Figure 5 is a plan view of an alternative embodiment utilising a dual crank drive for straight line shears; Figure 6 is a sectional view taken along line 6-6 of Fig. 5; Figure 7 is a wiring schematic for a servo drive unit for utilisation in accordance with the present invention; and Figure 8 is a crank velocity profile.

Referring now to the drawings in detail, reference is first made to Fig. 1 wherein there is illustrated a straight line shear generally identified by the numeral 20. This shear, in simple terms, includes a support or frame 22 which has suitable guides for a pair of opposed slides 24, 26 which are mounted within the support 22 for simultaneous reciprocation towards and away from one another. The slides 24, 26 carry blades 28, 30 which cooperate with one another for the purpose of shearing a glass runner to form gobs. The slide 24 has a bracket 32, and slide 26 has a similar bracket 36.

Although two sets of blades 28, 30 have been illustrated in the drawing, it is to be understood that the shear may incorporate but a single set or may include three or more sets of blades.

Also as shown in Figs. 1, 3 and 4, support 22 has attached thereto a mounting frame 42 which carries a shaft 44 and an electric servo motor M. A shaft S on motor M is coupled to a spur gear 46 which drives gear 48 on shaft 44. A crank 50 is coupled at one end of its arm to the end of shaft 44. The other end of crank 50 is coupled through shaft 51 to bearing and bearing block 92. Bearing and bearing block 92 is coupled to one end of connecting rods 52a and 52b. Connecting rods 52a and 52b are, in turn, coupled through an override mechanism generally designated 90, to be fully described later, to shaft 54. Shaft 54 is attached through block 56 to bracket 36 on slide 26.

An idler rack and pinion mechanism, generally designated 60, is connected to bracket 36 by rod 38 and to bracket 32 on slide 24 by rod 34. This idler mechanism includes a housing 62 having mounted therein in a guide tube 64 in which there is guidedly mounted one end of rod 38. The terminal portion of rod 38 carries a rack 66. The housing 62 carries a second guide tube 68 in which there is a guide for reciprocation of an end portion of rod 34. The end portion of rod 34 is also provided with a rack 70 which opposes rack 66. A pinion 72 is positioned between the racks 66, 70, and is meshed therewith. The pinion 72 is keyed to a drive shaft 74 which is suitably rotatably journalled within the housing 62.

As best shown in Fig. 3 and 4, connecting rods 52a and 52b are coupled to crank 50 through bearing and bearing block 92. Tie rods 52a and 52b are, in turn, coupled through bearing and bearing block 94 to shaft 54. Shaft 54 is integral to mounting block 56 which is fixed to bracket 36 and drives slide 26. Connecting rods 52a and 52b are positively attached to block 92 and plates 96, and are slideable in block 94. Fingers 98 are attached to plate 96, the individual fingers being a set of multiple cantilevered beams arranged in a circle. The fingers 98 can be deflected radially inward a significant amount with a relatively low load.

The fingers are prevented from moving radially inward by a retainer 100 which is springloaded by a spring 102 against keeper 104 which attached to block 94. The fingers are restrained outwardly by a spring seat 106 which is spring-loaded against keeper 104 and block 94 by spring 108. The other end of override spring 108 is restrained by seat 110 and retainers 112. Override spring 108 is preloaded to near the maximum load that will be applied to blades 28, 30.

As will be apparent, the override mechanism attachment at blocks 92 and 94 could be reserved. Further, the fingers can be single leaf or multiple leaf, with the finger design being arranged for outward deflection rather than inward deflection as shown in Fig. 4. Further the design of the device can be modified so as to be arranged as a tension or compression override device.

In operation of the device shown in Figs. 1 through 4, non-reversible electric servo motor M will drive gear 48 through spur gear 46 which, in turn, will cause the rotation of crank 50. Crank 50, in turn, through connecting rods 52a and 52b will cause slide 26 to reciprocate. For each revolution of crank 50, the blades of the shears will make one cut during which time the drive motor will make more or less revolutions depending upon the gear ration selected for spur gear 46.

As is best shown in Figs. 1 and 2, the movement of slide 24 will follow or be a slave to the movement of slide 26 as a result of idler rack and pinion mechanism 60 being tied through rod 38 to bracket 36, and rod 34 being tied to bracket 32.

With respect to the override mechanism, in the event blades 28, 30 strike a solid object such as a stone, block 94 is prevented from continued forward movement. Block 92 being attached to a positive drive continues in motion to the left toward block 94. This, in turn, carries fingers 98 and spring seat 106 which starts to compress the override spring 108.

After moving a short distance to the left, the fingers will have cleared retainer 100 and in so doing are able to deflect radially inward and slide past spring seat 106. At this point the fingers then clear the seat and are free to move to the left unrestricted along with the connecting rods and bearing block 92, as shown in Fig. 3 in phantom lines. When the motion reverses, fingers 98 will eventually enter the spring seat and be deflected inward by the ramp on the seat. As they go over the ramp and are deflected inward, they contract retainer 100, pushing it back thus allowing the fingers to relatch into position. When relatched, the spring-loaded retainer can move back into position and positively lock the mechanism until the next override condition occurs. A full open bumper restricts the opening movement of the shear in case the rod or finger latching friction should want to carry the shear further open than desired before relatching. As is apparent, therefore, the override mechanism prevents damage to the shear mechanism in the event a solid object is en countered by the shear blades.

Referring now to Figs. 5 and 6, there is shown a second embodiment of the present invention utilising a dual crank drive. In this embodiment each of slides 24 and 26 carrying blades 28 and 30 is positively driven by the drive unit power source such as the electric servo motor M through bevel gears 130 and 132 which drive the gear train comprising gears 134, 136 and 138. As shown, gears 134 and 138 are coupled through shafts 135 and 137 to dual cranks 50. Dual cranks 50 are coupled through connecting rods 52a and 52b (generally indicated by 52 in Fig. 5), and override mechanisms 90 directly to brackets 32a and 36a. These brackets 32a and 36a in carrying slides 24 and 26 are guided on guide rod 35. As will be apparent, the crank on the right hand side carries slide 24; whereas crank 50 on the left hand side carries slide 26.Each crank will make one revolution per cut during which time the drive motor again will make more or less revolutions depending upon the gear ratio selected for bevel gears 130 and 132. This gear ration is selected to minimise the RMS motor torque.

The dual crank drive system shown in Figs.

5 and 6 will provide a modified harmonic motion to the shear blades depending upon the ratio of connecting rod length to the crank arm radius and does not require motor reversal to return the blades after a cut is made.

The drive unit may be electronically programmed to start, accelerate, continue at constant speed, deceleration, and stop to achieve a desired shearing velocity and cut rate as, for example, in accordance with the wiring schematic shown in Fig. 7 to provide a crank RPM profile as shown in Fig. 8.

Referring specifically to Fig. 7, it will be seen that there is illustrated a wiring schematic of the drive for the electrical servo motor M. Actuation of the servo motor M is primarily by means of a microprocessor which provides the motion which translates to the shear motion profile, the microprocessor being identified by the numeral 140. The microprocessor 140 has an output 142 connected to a servo controller 144 which effects power switching.

The servo controller 144 has an output 146 connected to a control head 148 of the servo motor M for controlling actuation of the servo motor M.

The control system includes a feedback 80 from the control head 148 to the microprocessor 140. There is also a tachometer feedback 150 from the control head 148 to the servo controller.

Fig. 8 is a graph plotting crank RPM against crank rotation. As an example, crank 50 may be made to accelerate from rest to 250 rpm, a 45-degree of travel being required; continue at 250 rpm for 270 degrees, and decelerate to rest during the remaining 45 degrees, for a total crank travel of 360 degrees. At this crank speed of 250 rpm and with connecting rod length of 6" (15.24 cms) and a crank radius of 2-1/8" (5.4 cms), shearing velocity will be 55'/ second (139.7 cms/second) with a total shearing cycle of 0.30 seconds. This will provide a cut rate of 200 per minute.

Lower cut rates with the same shearing cycle can be achieved by inserting a dwell between the cuts.

Claims (12)

1. A straight line shear for forming glass gobs and the like, said shear comprising a pair of opposed slides (24,26) carrying opposed blades (28,30), guide means mounting said slides for movement along a predetermined path, and drive means for first simultaneously moving said slides together in a shearing operation and then simultaneously moving said slides apart to a starting position, characterised in that said drive means comprises crank means (50) having at least one crank with a first and second end, a rotary drive unit (M) coupled to a first end of said crank (50) for rotating said crank, and a connecting linkage (52a,52b) having a first end coupled to the second end of said crank, and a second end coupled to one (26) of said slides (24,26) for driving said slide, said crank means (50) being designed to complete one revolution for each cut of said shearing operation.

2. A shear according to claim 1, characterised in that said rotary drive unit comprises a servo motor (M).

3. A shear according to claim 1, characterised in that said rotary drive unit comprises an electric servo motor (M).

4. A shear according to claim 1, characterised in that said rotary drive unit comprises an electric servo motor (M) having a microprocessor (140) controlling its motion.

5. A shear according to any one of claims 1 to 4, characterised in that there is a gear coupling (46,48;1 30,132,134,136,138) between said crank (50) and said rotary drive unit (M).

6. A shear according to claim 5, characterised in that said gear coupling is a bevel gear coupling (130,132,134,136,138) whereby said drive unit (M) is positioned parallel to the blade movement of the shear.

7. A shear according to any one of claims 1 to 6, characterised in that said one slide (26) is also coupled to one rack (66) of a rack and pinion mechanism, comprising two racks (66,70) meshed with a pinion (72) for movement in opposite directions, and the other (24) of said opposed slides is connected to the other rack (70) of said rack and pinion mechanism for movement of said opposed slide.

8. A shear according to any one of claims 1 to 6, characterised in that said crank means (50) includes a pair of cranks (50) each having first and second ends, with a first end of each being coupled to said rotary drive unit (M) dnd the second end of each crank being coupled to a separate connecting linkage (52a,52b) which is in turn coupled to one or the other of said opposed slides (24,26) for driving said slides.

9. A shear according to any one of claims 1 to 8, characterised in that said connecting linkage (52a,52b) comprises rod means, said rod means being fixedly secured at one end to a first bearing and bearing block (92) and proximate to the other end being slideably secured to a second bearing and bearing block (94), said first bearing block being connected to said crank (50) and said second bearing block being associated with override means (98,100,102,104,106,108,110,112), said override means comprising means (98) for fixedly retaining said rod means from sliding in said block (94) at relatively low load and permitting said rod means to slide in said blocks at high load.

10. A shear according to claim 9, characterised in that said rod means comprise two parallel rods (52a,52b).

11. A shear substantially as hereinbefore described with reference to and as shown in Figs. 1 to 4 of the accompanying drawings.

12. A shear substantially as hereinbefore described with reference to and as shown in Figs. 5 and 6 of the accompanying drawings.