US3379352A

US3379352A - Vacuum system for multiple station tape handling apparatus

Info

Publication number: US3379352A
Application number: US535764A
Authority: US
Inventors: Harold E Hass; Robert G Nordman; Harry F Rayfield
Original assignee: Burroughs Corp
Current assignee: Unisys Corp
Priority date: 1966-03-21
Filing date: 1966-03-21
Publication date: 1968-04-23
Anticipated expiration: 1985-04-23

Description

April 23, 1968 H. E. HASS ETAL 3,379,352

VACUUM SYSTEM FOR MULTIPLE STATION TAPE HANDLING APPARATUS Filed March 21, 1966 2 Sheets-Sheet l INVENTOR.

WM mm April 23, 1968 H. E. HASS ETAL VACUUM SYSTEM FOR MULTIPLE STATION TAPE HANDLING APPARATUS Filed Mar ch 21, 1966 v 2 Sheets-Sheet 2 mm /M United States Patent dena, and Harry F. Rayfield, Arcadia, Calif., assignors to Burrough Corporation, Detroit, Mich., a corporation of Michigan Filed Mar. 21, 1966. Ser. No. 535,764 12 Claims. (Cl. 226-11) This invention relates to tape handling apparatus and, more particularly, to apparatus used in a multiple station tape handling system.

In present day high-speed tape handling apparatus it is customary to utilize slack loops held in vacuum columns to enable the tape to respond to rapid acceleration and deceleration and to reverse the direction of tape transport quickly. To sense the length of the loops for the purpose of controlling the rate of tape transport, they are placed in vacuum columns provided with vacuum operated switches according to a well-known practice.

A patent application of Harry F. Rayfield, Ser. No. 459,625, filed May 28, 1965, assigned to the assignee of the present application, and entitled, Tape Apparatus, now Patent No. 3,345,007, discloses multiple station tape handling apparatus with vacuum columns, in which a single vacuum pump serves the vacuum columns of all the stations. The vacuum pump constitutes a prime mover causing air to circulate in a closed system that includes the vacuum columns. Because the tape handling apparatus is completely closed to the atmosphere, the contamination of the apparatus and, therefore, maintenance required for it are reduced.

In multiple station tape handling apparatus that shares a single vacuum pump, a tear in the tape occupying one vacuum column or intentional removal of the tape from a vacuum column, as for example to change reels, results in a rush of air through the open vacuum column to the vacuum pump. This situation creates a danger that the remaining closed vacuum columns evacuated by the vacuum pump will become, so to speak, vacuum-starved due to th rush of air from the open vacuum column, and thus, become disabled.

According to the invention, this danger is obviated by providing plural passages for interconnecting the several vacuum columns to the vacuum pump and providing means in each passage for substantially sealing it when a vacuum column interconnected by it becomes open and unsealing the passage when all the vacuum columns interconnected by it are again closed.

In addition, a closed loop vacuum system is provided in which an absolute filter cleans the air entering the vacuum pump, a reservoir serves as an intermediate chamber between the vacuum pump and the passages, and the air exhausted from the vacuum pump is cooled before being returned to the vacuum columns. A regulator controls the operation of the vacuum pump to maintain the pressure in the reservoir substantially constant. The regulator has a neon lamp that indicates whether the regulator and the vacuum pump are properly functioning.

These and other features of the present invention are considered further in the following detailed description taken in conjunction with the drawings, in which:

FIG. 1 is a side elevation view, partially in section, of a closed loop vacuum system for multiple station tape handling apparatus;

FIG. 2 is a top plan view of multiple station tape handling apparatus with the top cover removed, showing the inlet and outlet ports of the closed loop vacuum system;

FIG. 3 is a side elevation view, in section, of a cutoff valve as shown in FIG. 1, and

FIG. 4 is a schematic diagram of the vacuum pump, its regulator, and neon lamp indicator.

In FIG. 1 a closed loop vacuum system for the vacuum columns of four station tape handling apparatus, as disclosed in the above mentioned Rayfield patent, is formed by a reservoir 10, an absolute filter 11, a vacuum pump 12, an air cooling unit 13, interconnecting conduits 14, 15 and 16, four passages such as 19 and 20, and the chamber defined by a tape deck 50, a vacuum column cover 51, and vertical sides (not shown). Vacuum pump 12 draws air into reservoir from a vacuum column 21 associated with one station through a cutoff valve 22 mounted in passage 19 and from a vacuum column 23 associated with another station through a cutoff valve 24 mounted in passage 20. Air is similarly drawn from the vacuum columns associated with the other stations through passages, each provided with a cut off valve. The mode of operation of the cutoff valves is explained in connection with FIG. 3. Vacuum pump 12 thus creates an evacuated region in the vacuum columns such as 21 and 23 so that the lengths of the loops therein can be sensed for the purpose of controlling the rate of tape transport according to well-known practice. Air sucked from reservoir 10 by vacuum pump 12 is cleaned by absolute filter 11 and, after being exhausted by vacuum pump 12, is applied to air cooling unit 13, in which, either by refrigeration or by an air-to-air heat exchanger, the exhausted air is cooled to room temperature. The necessity forair cooling in the closed loop arises from the fact that the same air is continually recirculated in the system, 'being heated each time in vacuum pump 12, and from the requirement that the ambient temperature of the tape handling apparatus must be approximately at room temperature. The cooled air is carried by conduits 15 and 16 to Y-joints 17 and 18 respectively, which supply the cooled air to the top of tape deck 50 through four ports such as the ports shown at 31 and 32, one port leading to each station. Air from these four ports then circulates through the vacuum columns such as 21 and 23 back to vacuum pump 12 through four passages such as 19 and 20. A parallel path for air flow from each station of tape deck 50 is formed by a groove 25, that is located in a post 26 mounted on tape deck 50 in the path of tape transport and a conduit 27. The tape during its transport, passes across post 26 and is cleaned by the air passing through groove 25. A regulator 28 controls the operation of vacuum pump 12 so as to maintain substantially constant pressure in reservoir 10. The operation of regulator 28 is described in more detail in connection with FIG. 4.

In FIG. 2 a partial layout of the top of the four stations is shown. The tape and its transport system are not shown because they are not necessary to the understanding of the invention. Four pairs of tape reels such as the two ,pairs designated 29 and 30, are mounted adjacent the corners of tape deck 50. Each pair of reels has associated with it two vacuum columns, designated 21a and 21b in the case of reels 29, and designated 23a and 23b, in the case of reels 30. The two vacuum columns associated with each station are connected to form an L-shaped compartment. The four L-shaped compartments are then arranged to form a cross, as illustrated in FIG. 2. At the intersection of the arms of each L-shaped compartment is a passage, such as those designated 19 and in FIGS. 1 and 2, to permit communication of all the vacuum columns with vacuum pump 12. Each station also has a port, such as those designated 31 and 32 in FIGS. 1 and 2, located outside of the vacuum columns to deliver air to tape deck from air cooling unit 13.

Each of the four passages connecting vacuum pump 12 such as 19 and 20, is provided with a cutoff valve such as 22 and 24 in FIGS. 1. In FIG. 4 the construction of this cutoff valve is shown in detail. The valve body 33, which is cylindrical in shape, has a flange 34, the

outside surface of which rests against a circular abutment 35 in the passage. A perforated disc 36 rests upon the inside surface of flange 34. The lower end of valve body 33 tapers and then terminates in an opening 37. A valve plug 38, tapered at one end to correspond to the taper of valve body 33, is connected by a tension spring 39 to perforated disc 36. Longitudinal openings 40 are provided along the periphery of valve plug 38. These openings are placed so that they are blocked by the tapered portion of valve body 33 when valve plug 38 is located against the lower end of valve body 33. Bypass openings 41 are situated in valve body 33 above valve plug 38 so that a small passage from the vacuum columns to reservoir is maintained at all times.

Under normal operating conditions, that is to say, when both vacuum columns of a station are closed by unbroken slack loops of tape, the pressure difference between the vacuum columns of a station and reservoir 10 is not sufficient to oppose tension springs 39. As a result,

air is drawn through the perforations of disc 36 and

d openings

40 and 37 into reservoir 10. An increase in the pressure difference between the vacuum columns of the station and reservoir 10, which would be caused by an opening due to an intentional removal or unintentional tearing of tape in a vacuum column, creates a force sufficient to overcome spring 39. Valve plug 38 is thereby driven to the lower end of valve body 33, thus blocking

openings

40 and 37. Air continues to flow through bypass openings 41, but because of their small size the quantity of air is not sufficient to disable the operation of the other, properly working, vacuum columns. When an unbroken slack loop of tape is again placed in the vacuum column associated with the closed cutoff valve, the pressure difference between this vacuum column, now closed again, and reservoir 10 is returned to normal by the passage of air through bypass openings 41. As the pressure difference between the vacuum column and reservoir 10 returns to its normal value the force upon valve plug 38 becomes insufficient to oppose sprin 39. Thus, valve plug 38 retreats from the lower end of valve body 33 and a normal flow of air through

openings

40 and 37 is resumed.

In FIG. 4 regulator 28 is shown connected in series with vacuum pump 12 between terminals A and C of a three-phase voltage source. The anode-cathode circuit of a silicon controlled rectifier 42 is connected between terminal A and vacuum pump 12. The terminals of a vacuum-operated switch 43 and a current limiting resistor 44 are connected in series between terminal A and the control element of silicon controlled rectifier 42 and a resistor 45 is connected between the control element and vacuum pump 12. When the absolute pressure in reservoir 10 becomes too high the terminals of vacuum-operated switch 43 close, thus firing silicon controlled rectifier 42 and starting up vacuum pump 12- When the absolute pressure in reservoir 10 is again reduced below a predetermined value, the terminals of vacuum-operated switch 43 open, silicon controlled rectifier 42 turns off, and vacuum pump 12 shuts off. A circuit to indicate whether regulator 28 and vacuum pump 12 are properly functioning is formed by the series combination of a neon lamp 46 and a resistor 47 connected across the anode-cathode terminals of silicon controlled rectifier 42. When negligible current flows through neon lamp 46 neither of its illuminating elements is lit. This condition indicates that silicon controlled rectifier 42 is short-circuited and thus regulator 28 is not properly functioning. When the current flowing through neon lamp 46 goes above a lower threshold, one of its elements becomes lit. This indicates that silicon controlled rectifier 42 is turned on and thus vacuum pump 12 is operating. When the current passing through neon lamp 46 exceeds an upper threshold both elements become lit, thus indicating that silicon controlled rectifier 42 is turned ofl and vacuum pump 12 is shut off. Under normal operating conditions neon lamp 46 flickers, indicating continual starting and stopping of vacuum pump 12.

What is claimed is:

1. In a multiple station tape handling system having vacuum columns normally closed by slack loops of unbroken tape the combination comprising a single vacuum pump to serve all the stations, plural means for interconnecting the vacuum columns and the vacuum pump, and means individual to each interconnecting means for substantially sealing it off when a vacuum column which it interconnects becomes open.

2. In a multiple station tape handling system the combination comprising vacuum columns normally closed by slack loops of unbroken tape, a single vacuum pump to serve all the stations, plural means interconnecting the vacuum pump with the vacuum columns, and means individual to each interconnecting means for substantially sealing it off when a vacuumcolumn which it interconnects becomes open and unsealing it when each vacuum column which it interconnects is again closed.

3. In multiple station tape handling apparatus having vacuum columns normally occupied by slack loops of unbroken tape the combination comprising a single vacuum pump to serve all the stations, plural passages providing communication between the vacuum pump and the vacuum columns, a cutoff valve mounted in each passage, the cutoff valve blocking the passage against fluid flow when the pressure in a vacuum column provided communication by the passage exceeds a predetermined limit and unblocking the passage when the pressure in the vacuum column again falls below the predetermined limit, and bypass means individual to each cutoff valve providing communication between the vacuum pump and the vacuum columns to enable the return of pressure to a Vacuum column after it becomes closed.

4. In a multiple station tape handling system the combination comprising a single vacuum pump having a reservoir, a plurality of pairs, of vacuum columns, a passage interconnecting the reservoir to each pair of vacuum columns, a cutoff valve sensitive to pressure difference and mounted in each passage, a valve cutting off when the pressure difference between at least one of the vacuum columns that it interconnects and the reservoir exceeds a preselected value and opening again when the pressure difference between all of the vacuum columns and the,

reservoir is below the preselected value, and means integral with each cutoff valve to permit bleedoff of fluid from the associated pair of vacuum columns to the reservoir.

5. In a four-station tape handling system a tape deck, a pair of L-shaped vacuum columns provided for each station, the pairs being arranged on the tape deck to form a cross, a single vacuum pump to serve all the stations located below the tape deck, an opening in the tape deck for each vacuum column pair to interconnect it with the vacuum pump, each opening being located at the intersection of the arms of a different column pair, and means individual to each opening for sealing it off when the pressure in at least one of the columns interconnected by it exceeds a preselected value.

6. A cutoff valve adapted to be mounted in a passage interconnecting areas having different air pressures comprising a hollow substantially cylindrical body member having a taper at its bottom end'and a flange at its top end, a valve plug adapted to move axially along the inside of the body member, the bottom face of the valve plug being tapered to form upon contact a substantially airtight fit with the tapered portion of the body member,

longitudinal passages in the valve body to permit fluid flow between the two portions of the body member separated by the valve plug, a perforated circular disc having a diameter such that the disc rests upon the flange at the upper end of the body member, a tension spring fastened between the circular disc and the valve plug,

and bypass means to permit a controlled fluid flow through the valve regardless of the position of the valve plug.

7. The cutoff valve of claim 6 in which the bypass means are openings in the body member located between the circular disc and the valve plug when the spring is unexpanded.

8. In a multiple station tape handling system having vacuum columns normally closed by slack loops of unbroken tape the combination comprising a single vacuum pump to serve all the stations, an absolute filter to clean the air entering the vacuum pump, a reservoir which is evacuated by the vacuum pump, plural means for interconnecting the vacuum columns with the vacuum pump through the reservoir, means individual toeach of the interconnecting means for substantially sealing it off when a vacuum column which it interconnects becomes open, means for cooling the exhaust air of the vacuum pump, and means for carrying the cooled air to each of the vacuum columns to form a closed loop system.

9. In a tape handling system with vacuum columns normally occupied by slack loops of unbroken tape the combination comprising a vacuum pump, an absolute filter to clean the air entering the vacuum pump, a reservoir which is evacuated by the vacuum pump, means for interconnecting the vacuum columns with the vacuum pump through the reservoir, means for cooling the exhaust air of the vacuum pump, and means for carrying the cooled air to each of the vacuum columns to form a closed loop system.

10. In a tape handling station according to claim 9 a regulator for controlling the operation of the vacuum pump so as to maintain a substantially constant pressure in the reservoir.

11. The combination of claim 10 in which the regulator comprises a silicon controlled rectifier, the anodecathode circuit of which is in a series with the source of power of the vacuum pump, a vacuum actuated switch connected in the control circuit of the silicon controlled rectifier to cause it to fire when the absolute pressure in the reservoir exceeds a predetermined value, and start up the vacuum pump and a neon lamp having two indicating elements connected in parallel with the silicon controlled rectifier, both elements of the neon lamp being off when the current through it is below a lower predetermined level indicating that the silicon controlled rectifier is short circuited, one element of the neon lamp being lit when the current through it is between the lower predetermined limit and an upper predetermined limit indicating that the silicon controlled rectifier is firing, and both elements of the neon lamp being lit when current through it exceeds the upper predetermined limit indicating that the silicon controlled rectifier is open.

12. In a four-station tape handling system, an enclosed tape deck, a pair of L-shaped vacuum columns provided for each station, the pairs being arranged on the tape deck to form a cross, a single vacuum pump located below the tape deck to serve all the stations, an absolute filter located below the tape deck to clean the air entering the vacuum pump, a reservoir located below the tape deck and evacuated by the vacuum pump, a first opening in the tape deck for each vacuum column pair interconnecting it through the reservoir with the vacuum pump, the first opening being located at the intersection of the arms of the pair of vacuum columns it interconnects, means individual to each opening for sealing it olf when the pressure in at least one of the vacuum columns interconnected by it exceeds a preselected value, means located below the tape deck for cooling the exhaust air of the vacuum pump, a second opening in the tape deck for each station located outside of the pair of vacuum columns, and conduits for carrying the cooled air to each of the second openings to form a closed loop system.

References Cited UNITED STATES PATENTS 2,927,789 3/1960 Walsh 242-55.12 X 3,122,162 2/1964 Sands 137-498 3,185,400 5/1965 Maxey 226-11 8 X 3,310,249 3/1967 Bryer 226118 X 3,329,364 7/1967 Brettell 22697 X M. HENSON WOOD, JR., Primary Examiner.

R. A. SCHACHER, Assistant Examiner.