US2743925A - Machines for performing operations with respect to articles and control mechanisms therefor - Google Patents

Description

M y 1956 R. M. ELLIOTT ETAL 2,743,925

MACHINES FOR PERFORMING OPERATIONS WITH RESPECT L MECHANISMS THER R TO ARTICLES AND CONTRO 952 Sheets-Sheet 1 Filed July 25, l

Inventors RichardME/Ziott John LMz'nfo \1 By U2 7' May 1, 1956 Filed July 25. 1952 R. MACHINES FOR PERF' M. ELLIOTT ET AL ORMING OPERATIONS WITH RESPEC TO ARTICLES AND CONTROL MECHANISMS THEREFOR S Sheets-Sheet 3 [n ventors Pram/mm John L Minto United States Patent MACHINES FOR PERFORMING OPERATIONS WITH RESPECT TO ARTICLES AND CON- TROL MECHANISMS THEREFOR Richard M. Elliott and John L. Minto, Beverly, Massu assignors to United Shoe Machinery Corporation, Flemington, N. 1., a corporation of New Jersey Application July 25, 1952, Serial No. 300,895 7 Claims. (Cl. 271--68) This invention relates to control mechanisms, and more particularly to improvements in such mechanisms for use with apparatus comprising means for moving an article along a path, said mechanisms being adapted for initiating the operation of a device in predetermined relation to the passage past a station along the said path of a selected fractional length of articles which may vary in length.

The device to be controlled may be one which actually operates upon the article, for example, to print upon or to fold it, or it may be one which performs an operation not directly affecting the article, for example, to sound a warning when the center of the article has arrived at a given station along the path. All such devices are herein comprehended as devices for performing an operation with respect to an article or, more succinctly, operating devices.

The invention is herein illustrated as embodied in a control mechanism in combination with a hide or skin stacking machine of the type disclosed in United States application Ser. No. 251,014, filed October 12, 1951, in the names of Paul E. Morgan, Arthur R. Abbott and John J. Maciejowski, although it is understood that in its more general aspects the invention is not limited in use to machines of the type illustrated.

Machines of the type disclosed in the above mentioned application are provided with article moving means comprising conveyer belts for moving articles comprising hides or skins up an incline to a hinged arm provided with belts which are adapted to engage both surfaces of the articles to carry them to the discharge end of the arm. Means are provided for swinging the arm to move its discharge end across a horse placed below the arm, thereby to deposit the articles upon the horse. To insure that the articles remain upon the horse, it is necessary that they be placed on the horse with their centers at least approximately on the midpoint of the top bar of the horse. In order so to deposit an article, the swingof the arm must be initiated when the center of the article moving along its path of movement through the stacker reaches a predetermined station. This station is hereinafter referred to as the trip station. Certain variables such as windage, slippage, and the like make it desirable to provide for adjustment of said station.

The machine disclosed in said application is provided with a control mechanism having a delay computer controlled by feelers operative at two detector stations spaced along the said path for initiating the swing of the arm when the center of an article reaches the trip station. This mechanism, while generally effective to provide good stacking throughout a wide range of length of the articles, is not completely satisfactory in certain respects. The circuit of this mechanism is relatively complex, having a relatively large number of resistances of critical value and a relatively large number of interconnected relays, thus tending adversely to affect the reliability of operation. Additionally, since the delay computer is designed to be controlled in response to movement of the'feelers by 2,743,925 Patented May 1, 1956 the leading edge of an article at both detector stations, relatively generous spacing is required between successive skins to avoid improper operation. Further, adjustment of the trip station is difficult.

As shown and described in the copending United States application Serial No. 375,275, filed August 19, 1953, in the names of Richard M. Elliott and Edmund S. Lee Ill, such spacing limitations may be largely eliminated by employing in such control mechanism a delay computer having two delay-cycle exhausting elements controlled by two workpiece-edge detectors operating at stations spaced along the conveyor, the detector for the station first encountered by a workpiece during its passage along the conveyor being arranged to initiate the operation of one of said elements upon a predetermined response of the detector at the time the trailing edge of the workpiece passes the said station, while the second detector is arranged for response to initiate the operation of the other element at the time the leading edge of the workpiece passes the other station, whereby said elements operate jointly to exhaust the delay cycle of the computer at the time the desired fractional point (for example, the midpoint) of the workpiece arrives in predetermined relation to the leading-edge detector station. In the apparatus disclosed in said application, the elements are members which, starting from predetermined spaced positions, upon initiation by the detectors move at fixed rates toward one another to exhaust the spacing distance as the delay cycle.

One of the objects of the present invention is to provide improved apparatus employing the principle of center finding as disclosed in the last mentioned application, which apparatus has a minimum of moving parts and is adapted for ease and flexibility of control, including remote control.

Accordingly, by a feature of the invention, the improved delay computing means comprises a condenser, means for establishing a predetermined initial voltage on the condenser, and circuit means controlled by leadingedge and trailing-edge detectors to vary the voltage on the condenser during the movement of a workpiece along the conveyor at such rates of change as to bring the voltage on the condenser to a predetermined operating value at the time the desired fractional point along the work piece has arrived at the leading-edge detector station.

As illustrated herein, a voltage-responsive device, shown as a relay'switch, may be connected to said con denser for control thereby to be operated when the condenser voltage has changed to the operating value.

In the illustrative embodiment the relay switch comprises a thyratron biased from the condenser, and the circuit means for varying the condenser voltage comprises a pair of resistance discharge circuits which are connected to the condenser under the control of the respective detectors to discharge the condenser at an initial rate, being one of two fixed individual rates corresponding to the two detectors, upon response by one detector, and at a final rate, being the sum of said two fixed rates, upon response by the other detector to reduce the initial cutoff bias provided by the condenser to the operating value (firing the thyratron) at the time the desired fractional point of the workpiece reaches the leading-edge detector station.

Another object of the invention is the provision of an improved detector for sensing the presence of the edge of a workpiece in a detecting station, which detector is economical and easily adjustable.

To this end, in accordance with another feature of the invention, a detector is provided comprising a pair of series-connected switches, one normally open and the other normally closed, and a pair of movable feelers adapted to engage a workpiece in a detecting station at sensing points closely spaced in the direction of movement of the workpiece, the feelers being arranged, when displaced by a workpiece, to actuate the switches so that both switches are closed only when that feeler which actuates the normally-open switch is engaged by the workpiece while the other feeler is not so engaged, in which circumstance the desired edge of the workpiece is between the sensing points.

In apparatus employing the leading-edge-trailing-edge computing principle disclosed in the aforementioned application Serial No. 375,275, the cycle of the delay computer terminates when the desired midpoint (or other desired fractional point) of the work is in line with the leading edge detector station. When an operation is to be performed on the work at this fractional point, it is frequently of a nature, such as folding, which cannot be performed at said station because of the interference of the detector means thereat. In other words, it is frequently impossible to locate the leading-edge detector means at the point where an operation is to be performed on a workpiece. However, by locating the leading-edge detector station in advance of the trip station and by combining the delay computer elements with a delay relay connected to be initiated upon the exhaustion of the computer cycle to provide a delay sutficient to allow the desired point of the workpiece to move to the operating station, the advantages of the foregoing computing principle may be obtained by the joint action of these elements even where the leading edge detector station cannot be located at the oprating (or trip) station.

Accordingly by yet another feature of the invention, the control mechanism incorporates a separate variable time delay means which is connected for initiation of its cycle by the delay computing means, and provides a convenient means for adjusting the position of the trip station.

The above and other features and advantages of the invention will best be understood by reference to the specification taken in connection with the accompanying drawings in which,

Fig. 1 is an elevational and sectional view of 2. hide and skin stacking machine embodying the present invention, a horse being shown for receiving the work;

Fig. 2 is an enlarged angular view of detector structure such as shown in Fig. 1;

Fig. 3 is a view of a left-hand portion of the conveyor as viewed in the direction of the arrow A in Fig. 1;

Fig. 4 is a diagrammatic showing of the detectors illustrated in Fig. 1 but with no Work beneath the detector feelers;

Fig. 5 is a view similar to that of Fig. 4 but with a trailing-edge detector responding to the trailing edge of a short skin;

Fig. 6 is a view similar to Fig. 4 but showing the response of the leading-edge detector to the leading edge of a skin;

Figs. 7 and 8 illustrate the responses of the leading and trailing edge detectors during the passage of long skins; and

Fig. 9 is a schematic circuit diagram of the control mechanism.

The stacking machine illustrated in Fig. 1 is similar to the machine shown in the patent application Ser. No. 251,014 referred to above.

Accordingly it comprises a base 10 to which is secured, in inclined disposition, an elongated frame 12. At the lower end of the frame 12 is a conveyer belt roll 14 extending transversely of the frame nearly the width thereof. A similar roll 16 is mounted in the upper end of the frame. A conveyer arm 18 is pivoted substantially coaxially with the roller 16 and carries at its free, or discharge, end a belt roller 20. A plurality of conveyer belts 22 are arranged on the rollers 14, 16 and to be driven by a motor M for moving an article S up the incline over a supporting platform 24 and to the discharge 4 end of the conveyer arm. Means, whose operation is controlled by a solenoid 25, are provided for swinging the arm in an are starting from the position shown in Fig. l to discharge an article such as a skin or hide across a horse 26 positioned beneath the arm. Supplementary belts 28 on the arm 13 cooperate with the belts 22 to retain the article on the arm during its swing.

In order that an article may be dropped with its center approximately on the midpoint of the top bar of the horse, it is necessary to initiate the swing of the arm when the center of the article on the belts 22 reaches a predetermined trip station along its path of movement. An improved control mechanism provided by the present invention for performing this function will now be described.

Referring to Fig. 9, the control mechanism comprises a delay computer A controlled by a trailing-edge detector 30 and a leading-edge detector 32 associated with the conveyer, a variable time delay relay B, and a power supply C. The computer, relay and power supply may conveniently be disposed in a housing H (Fig. 1) secured to the frame 12.

The detectors 3i) and 32 are supported respectively on channel bars 34 and 36 which are secured on the frame 12 by brackets 37 to extend transversely across and above the platform 24. Each bar carries brackets in which are journaled two rods 38 extending parallel to the bar and spaced from each other in the direction of feed. Each detector comprises a pair of series-connected switches 49 each having a plunger 42 by which the switch is actuated. A switch arm 44 secured to each rod 38 is arranged to engage the plunger of one of the switches for operating the switch by rotation of the rod. From each rod a set of three elongated lightweight feelers 46 extend toward the platform 24, spaced cars 43 at one end of each feeler pivoting freely on the rod while the free curved end of each feeler normally lies in a depression 50 in the platform 24, the feeler then being in an inactive position.

Between the ears of each feeler, an arm 52 is secured to the rod 38 and carries a set screw 54 to engage the feeler so that movement of any feeler from its inactive position to an active position in which the feeler is lifted, for example, by engagement of its free end by an article, is effective to rotate the rod 38 without lifting the other feelers of the same set. This minimizes the weight and inertia presented to the leading edge of a rapidly moving skin.

The more advanced detector, that is, the one whose feelers are first intercepted by an article moving on the belts 22, is the trailing-edge detector 30 which has its switches arranged so that the front switch is normally closed and the rear switch is normally open as shown in Fig. 4. Accordingly, the only condition in which both switches are closed is that in which one of the rear set of feelers rests on a skin while all the front feelers are clear (Figs. 5 and 8), hence this detector provides a response comprising a connection through both switches only during the passage of the trailing edge of an article between the points of engagement of the front and rear feelers, the aligned curved ends of the front feelers establishing approximately the station on the path of movement of an article at which the detector is responsive to the trailing edges. The leading-edge detector 32 also has a normally-closed and a normally-open switch, but these switches are associated with the front and rear feelers in a relation reversed from that of the trailing edge detector so that it responds only to leading edges (Figs. 6 and 7) at a second station spaced along the path of movement from the first station, said second station being established approximately by the aligned points of engagement of the front feelers of the detector 32. While we have described an improved embodiment for detecting the edges of articles, it is obvious that other means could be employed for this purpose, and in its more general aspects the invention is not limited to use with the specific detectors described.

The delay computer comprises a condenser 60 arranged to be charged from a power supply C (Fig. 9), one side of the condenser being connected to the positive lead through a charging resistor 62 while the other side is connected to the negative (grounded) lead through the normally-closed contacts 64, 64' of relays 7t) and 72 which relays are respectively connected to be controlled by the detectors 30 and 32. Across the condenser 60 are connected a first discharge circuit comprising a resistor 76 and a second discharge circuit comprising a resistor 78, the circuits being arranged to be connected respectively by the closure of contacts 80 of relay 70 and contacts 82 of relay 72. Each relay 7G, 72 is provided with a set of holding contacts 84 which hold the relay circuit closed around the detector switches whereby the momentary response of either detector is effective to maintain the corresponding discharge circuit connected until the relay coil circuit is broken by the opening of the normallyclosed contacts 86 of a relay 9d.

The relay 90 is arranged to be energized from the power supply C under the control of a switch tube 92 having a control grid 94 connected to the negativelycharged side of the condenser 60. The cathode 96 of the tube 92 is biased through a regulator tube 93 so that its potential is substantially above ground. The tube 92, which may as illustrated be a thyratron, is thus rendered ineffective to conduct current to energize the relay 90 until, by discharge of the condenser 64 through its delay cycle, the grid 94 reaches a predetermined voltage. It will readily be seen from Fig. 9 that the response of either detector, that is, a response either to the passage of the trailing edge of an article past a first station on its path of movement or to the passage of the leading edge of the article past a second station, is effective to initiate the operation of a delay element and hence to initiate the operation of the computer in its delay cycle at one rate, and that the response of the other detector, by initiating joint operation of the discharge circuits, is effective to establish a different final rate of operation, which different rate is the sum of the individual rates. Accordingly, the time required for the condenser 60 to discharge to the aforesaid predetermined voltage varies in proportion to the length of the article.

In order that the computer may indicate the arrival of the center of an article at the second, or leadingedge, detector station, the individual rates of discharge are adjusted by properly fixing the values of the resistors 76, 78 so that each individual discharge rate is sufficient to run out the computer cycle in the time required for the conveyor belts to move the distance d (Fig. 4) between the detector stations.

It will be seen that for so indicating the center of articles, the range of length of articles accommodated lies between a theoretical minimum of zero and a maximum length twice the distance (1 along the path between the detector stations. The maximum length accommodated and the rate of discharge established by the leadingedge detector vary with the fractional portion whose passage past the second detector station (or subsequent passage past the trip station) is to be indicated, while the discharge rate established by the trailing-edge detector remains fixed. For example, if it is desired to indicate the passage of one-quarter of the length of the article, the discharge rate established by the leading-edge detector is three times the other rate and the maximum length accommodated is 4/3 a. If a three-quarter length is to be indicated, the discharge rate established by the leading edge detector is one-third the other rate and the maximum length is 4:3.

The relay 90 is provided with operating cont-acts 100 which could be used directly to control an operating device. However, for this particular application it is desired that the operating device, i. e. the swinging arm,

have its operation initiated when the center of the article passes a trip station which is rearward of the leadingedge detector station. Accordingly, the contacts are connected to initiate the operation of a time delay relay B, Fig. 9. This relay comprises a condenser normally connected for charging from the power supply and having the negatively-charged side thereof connected to the grid 112 of a thyratron tube normally maintained non-conductive by cathode bias. The condenser 110 has connected across it a discharge circuit comprising a variable resistor 122. The contacts 100 of relay 90 are connected to operate a relay switch which disconnects the negative side of the condenser 110 from the negative side of the power supply. Upon such interruption, the discharge of the condenser through the resistor 122 raises the potential of the grid 112 until the tube 120 fires to operate relay switch having operating contacts 142 connected to control the energization of the solenoid 25. Thus the position of the trip station may conveniently be varied by means of the variable resistor 122. It will be noted that relay switch 90 also has restoring contacts 144 for interrupting its connection to the positive side of the power supply, relay 130 has holding contacts 146 for continuing its energization after the opening of contacts 100, and the relay 140 has restoring contacts 148 and 150 respectively for deenergizing relays 130 and 140. Relays 90 and 146 are also provided with a shunt condenser and resistor for delaying the time of release.

In operation, with the conveyor belts 22 moving at their normal feed speed and the arm 18 extended in its position shown in Fig. 1, an article may be disposed on the belts at the lower end of the frame to be carried thereby up the incline. As the article passes up the incline it first intercepts the feelers 46 of the trailing-edge detector and proceeds thereunder toward the feelers of the leading-edge detector. As soon as the trailing edge of the article passes out from beneath all the front feelers of the trailing-edge detector 30, the resistor 76 is connected across condenser 60. Similarly as soon as the leading edge of the article engages one of the front feelers of the leading edge detector 32, the resistor 78 is similarly connected. Which resistor is connected first depends, of course, on the length of the article. When the voltage of condenser 60 has discharged to its critical value, the thyratron 92 fires, energizing relay 90 to close contacts 100 to energize relay 130. Relay 130 in turn initiates the operation of the time delay relay which at the expiration of its cycle energizes relay 140 to close the operating contacts 142 to the solenoid 25. Meanwhile, the center of the article has moved along its path from the leading-edge detector station (where it was when thyratron 92 fired) to the trip station, so that when the energization of the solenoid 25 initiates the swing of the arm 18, the article is deposited across the horse 26 with the center of the article on the bar of the horse. If it is required to adjust the position of the trip station, this may be done by adjusting the variable resistor 122.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent of the United States is:

1. Control apparatus adapted for use with a workpiece conveyor to initiate the operation of a device upon passage of a predetermined fractional length of a workpiece past a station on said conveyor, said control apparatus comprising, in combination, trailing-edge and leading-edge detector means adapted for association with a conveyor for response to the passage respectively of the trailing edge of a workpiece past a first station and of the leading-edge of the workpiece past a second station on said conveyor, said second station being spaced from the first station in the direction of movement of workpieces on the conveyor, a device controllable by a control voltage to effect switching action in response to change of said control voltage from a non-operating value to a predetermined operating value, means for supplying to said device a control voltage at a predetermined non-operating value, circuit means controlled by said detector means and arranged upon response of either of said detector means to change said control voltage toward the operating value at an initial rate, being one of two predetermined rates corresponding to the two said detector means, and at a final rate upon response of the other of said detector means, said final rate being the sum of said two predetermined rates.

2. Control means for use with apparatus comprising means for moving an article along a path, said control means being adapted to initiate the operation of a device in relation to the position of said article along said path, said control means comprising, in combination, a condenser, means for charging said condenser to a predetermined initial voltage, a device connected to said condenser for operation in response to the discharge of said condenser to a predetermined trip voltage, first and second independent resistance discharge circuits connectable across said condenser, first and second detectors adapted to be associated with said moving means at first and second stations spaced along said path, said detectors being operable respectively to connect the first discharge circuit across the condenser in response to passage of the trailing edge of an article past said first station and to connect the second discharge circuit across the condenser in response to passage of the leading edge of said article past said second station, and means operable to render the charging means ineffective during the discharge of said condenser through either discharge circuit.

3. In a machine for performing an operation with respect to an article, means for moving an article along a feed path, a delay computer having two separate elements operable individually to run out a delay cycle at a predetermined individual rate and operable jointly to run out said cycle at a rate which is the sum of the individual rates, a first detector connected to initiate the operation of one element upon the passage of the trailing edge of an article past a first station on said path, a second detector connected to initiate the operation of the other element upon the passage of the leading edge of said article past a second station on said path, and a time delay relay connected for initiation of its operation under the control of said delay computer at the end of the delay cycle.

4. In apparatus for handling workpieces, said apparatus comprising conveyor means for moving a workpiece along a path at a uniform speed, an operating device controllable by an electric voltage to efiect initiation of a predetermined operation of said device in response to change of said control voltage from a non-operating value to a predetermined operating value, and computing control means adapted to initiate the operation of said device in relation to the position of a predetermined fractional point of said article along said path, said control means comprising, in combination, a condenser, means for connecting said condenser to said device to control it by the voltage on said condenser, means for charging said condenser to a predetermined initial voltage of non-operating value, a leading-edge detector and a trailing-edge detector associated with said conveyor means, said detectors being arranged for response respectively to the presence of the leading edge and the trailing edge of a work piece in detector stations spaced along said path, and circuit means controlled by said detectors and arranged upon response of either of said detectors to change the voltage on said condenser toward the operating value at an initial rate, being one of two predetermined rates corresponding to the two said detectors and at a final rate upon response of the other of said detectors, said final rate being the sum of said two predetermined rates.

5. In apparatus for handling workpieces, said apparatuscomprising conveyor means for moving a workpiece along a path at a uniform speed, an operating device controllable by an electric voltage to efiect initiation of a predetermined operation of said device in response to change of said control voltage from a non-operating value to a predetermined operating value, and computing control means adapted to initiate the operation of said device in relation to the position of a predetermined fractional point of said article along said path, said control means comprising, in combination, a condenser, means for connecting said condenser to said device to control it by the voltage on said condenser, means for charging said condenser to a predetermined initial voltage of nonoperating value, a leading-edge detector and a trailingedge detector associated with said conveyor means, said detectors having means for sensing, respectively, the presence of the leading edge and the trailing edge of a workpiece in detector stations spaced along said path, first circuit means operable individually to change the voltage on said condenser toward the operating value at a predetermined rate efiective to change said voltage to the operating value in the time required for the conveyor means to move a workpiece the distance between the detector stations, said first circuit means being connected to said trailing-edge detector for initiation of its operation when the trailing edge of a workpiece reaches the trailing-edge detector station, and second circuit means operable individually to change the voltage on said condenser toward the operating value at a predetermined rate, said second circuit means being connected to said leading-edge detector for initiation of its operation when the leading edge of a workpiece reaches the leadingedge detector station, whereby said device will be operated when a predetermined fractional point of a workpiece within a predetermined range of length is moved by the conveyor means to the leading edge detector station, said fractional point and said range of length being predetermined by the rate of operation of said second circuit means.

6. In apparatus for handling workpieces, said apparatus having conveyor means for moving a workpiece along a path and having leading-edge and trailing-edge detectors operative at stations spaced along the path of movement of the work, computing control means adapted to provide a control voltage which drops to a predetermined operating value when a predetermined fractional point of a workpiece reaches the leading-edge detector station after having passed the trailing-edge detector station, said control means comprising, in combination, a condenser, means for charging said condenser to a predetermined initial voltage higher than said operating value, a first resistance discharge circuit operable when connected across the condenser to discharge it to the operating value in the time required for the conveyor means to move a workpiece the distance between the detector stations, means controlled by the trailing-edge detector for connecting said first discharge circuit across the condenser when the trailing edge of a workpiece reaches the trailing-edge detector station, a second resistor discharge circuit, means controlled by the leading-edge detector for connecting said second discharge circuit across the condenser when the leading edge of a workpiece reaches the leading-edge detector station, and means rendering said charging means ineffective during operation of either discharge circuit.

7. In workpiece handling apparatus having a conveyor to move progressively rearward a workpiece having a leading edge and a trailing edge, detector means adapted to complete an electric circuit during the passage of one of said edges of a workpiece through a detector station on said conveyor comprising, in combination, a pair of series-connected switches, one switch being normally open and the other being normally closed, and a pair of movable members each adapted to engage a workpiece in the detector station at one of a pair of sensing points closely spaced along the path of movement of the workpiece, one member being arranged to actuate one of said switches when displaced by the work and the other member being arranged to actuate the other switch when displaced by the Work.

References Cited in the file of this patent UNITED STATES PATENTS Kahn Nov. 26, 1935 Cumfer July 29, 1941 Preston Aug. 8, 1944 Preston May 1, 1945 Preston July 2, 1946

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