GB2174693A - Straight line shear with non-reversible rotary drive means - Google Patents

Abstract

A straight line shear wherein there are two slides (28,30) for guided movement toward and away from one another, and arranged in opposed relation. The slides carry cooperating blades (32,34). The slides are driven by unidirectional rotary drive means incorporating crank means (44) coupled through a connecting rod (42) to at least one of the opposed slides and at the other end to a drive unit (M). The crank means 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 Straight line shear with non-reversible rotary drive means 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 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. 4,215,611, 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 gear. 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 for straight line shears incorporating a crank drive system which imparts a modified harmonic motion to the shear blades by controlling the ratio of the connecting rod length to the crank arm radius. The crank drive system rotates in one direction only so that the blade reversal does not require drive system reversal.

In one embodiment of the invention a single crank drive is coupled directly to one shear arm rack with the opposing shear arm rack driven by means of an idler gear to provide guided movement of the slides towards and away from one another. In this embodiment the crank is coupled at its other end to a drive unit which preferably is an electric servo motor.

In another embodiment of the present invention, a separate crank is coupled to each of the slides of the shears. The cranks are tied together by a gear train driven by an electric servo motor or other controlled rotary power source to provide guided movement of the slides towards and away from one another.

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 de pending upon the gear ratio selected for the drive system. The drive unit which can be electronically programmed for timing, acceleration, and rotational rate will operate in three different modes as foliows: 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.

In the drawings, wherein throughout like numerals refer to like parts.

Figure 1 is a plan view of a dual crank drive for straight line shears; Figure 2 is a fragmented plan view of an alternative embodiment utilising a single crank drive for straight line shears; Figure 3 is a sectional view, partly broken away, taken along line 3-3 of Fig. 2; Figure 4 is a wiring schematic for a servo drive unit for utilisation in accordance with the present invention; and Figure 5 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 guide rods 24, 26 for carrying a pair of opposed slides 28, 30 which are mounted within the support 22 for simultaneous reciprocation towards and away from one another. The slides 28, 30 carry blades 32, 34 which cooperate with one another for the purpose of shearing a glass runner to form gobs.

Although two sets of blades 32, 34 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 Fig. 1, support 22 has attached thereto a mounting frame 21 which, along with support 22, carries shafts 41, 41a, 61, 63 and 65, and an electric servo motor M. Shaft 65 coupled to motor M is coupled through drive gear 68 to a gear train comprising gears 60, 62, 64 and 66 which drives shafts 41 and 41a As seen, shafts 41 and 41a which are spaced behind slides 28, 30, respectively, are mounted in frame 21 and support 22. A crank assembly, generally identified by the numeral 40, is coupled to each of shafts 41 and 41a. The crank assembly in referring to the right side of Fig. 1 includes connecting rod 42 tying crank 44 to slide 30 through slot 36 and pin 38. Crank assembly 40 further includes counterweights 46 on either side of crank 44.

An identical assembly ties slides 28 to shaft 41.

In operation, non-reversible servo motor M, through gear 68 and the gear train, drives cranks 44 in one direction, reciprocating slides 28, 30 toward and away from each other.

One complete revolution of each crank 44 constitutes one complete reciprocation of slides 28, 30, and constitutes one shear cut.

The motion of the shear blades is controlled by adjusting the ratio of the connecting rod length to the crank arm radius.

Referring now to Figs. 2 and 3, there is shown a second embodiment of the present invention utilising a single crank drive. In this embodiment slide 30 is attached to rack 52 through bracket 25, and slide 28 is attached to rack 54 through bracket 23. Slide 30, carrying blades 34, is positively driven by servo motor M through gear 56 and crank 44a which drives rack 52 through connecting rod 42a. Opposing shear rack 54 is driven in reverse order by means of idler gear 58. Similar to the assembly of Fig. 1, one complete revolution of crank 44a constitutes one complete reciprocation of slides 28, 30, and constitutes one shear cut.

The drive unit shown in the drawing is electronically programmed. Referring to Fig. 4, it will be seen that there is illustrated a wiring schematic of the drive for electrical servo motor M. Actuation of the servo motor M is primarily by means of a microprocessor 80 which provides the shear motion profile. The microprocessor 80 has an output 82 connected to a servo controller 84 which effects power switching. The servo controller 84 has an output 86 connected to a controlling head 88 of the servo motor M for controlling actuation of the servo motor M.

The control system includes a feedback 90 from the controlling head 88 to the microprocessor 80. There is also a tachometer feedback 92 from the controlling head 88 to the servo controller.

The velocity of the shear blades is a function of crank speed, crank arm radius, and connnecting arm length. These parameters are related by the well-known equations of mechanics. As an example and as shown in Fig.

5, on one type of application for 200 cycles per minute cranks 44 may be made to accelerate from rest to 250 rpm, a 45" of travel being required; continue at 250 rpm for 270 , and decelerate to rest during the remaining 45 , for a total crank travel of 360 . 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 (9)

1. A straight line shear for forming glass gobs and the like, said shear comprising a pair of opposed slides (28,30) carrying opposed blades (32,34), guide means (24,26) mounting said slides for movement along a predetermined path, and drive means (M) 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 (44;44a) having at least one rotary crank, a rotary drive unit (M) coupled to said crank for rotating said crank in one direction, and a connecting rod (42;42a) directly coupled to said crank and to one of said slides for positively driving said slide, said crank means being designed to complete one revolution per 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 motion control (80).

5. A shear according to any one of claims 1 to 4, characterised in that there is a gear coupling (60,62,64,66,68) between said crank (44;44a) and said rotary drive unit (M).

6. A shear according to claim 5, characterised in that said gear coupling is a spur coupling.

7. A shear according to any one of claims 1 to 6, characterised in that said opposed slides (28,30) are each attached to separate racks (52,54), and said connecting rod (42a) is directly connected to one (52) of said racks to drive said rack, and the other (54) of said racks is driven in reverse order by an idler gear (58) for movement of said opposed slide.

8. A shear according to any one of claims 1 to 7, characterised in that said crank means includes a pair of cranks (44) each being positively driven by said rotary drive unit (M) through a gear train (60,62,64,66,68) coupled to said drive unit, each of said cranks being balanced by counterweights (46).

9. A shear substantially as hereinbefore described with reference to and as shown in the accompanying drawings.