US 3487182 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
Dec. 30, 1969 L. F. GRUNDY 3,487,182
SAFETY MECHANISM FOR POWER-OPERATED PRESSES AND THE LIKE Filed Feb. 6, 1969 4 Sheets-Sheet 1 AT TORNEYS I... F. GRUNDY Dec. 30, 1969 4 Sheets-Sheet 2 Filed Feb. 6, 1969 FIQZ INVENTOR LAWRENCE E GRUNDY LLb- AT TORNEYS Dec. 30, 1969 L. F. GRUNDY 3,487,182
SAFETY MECHANISM FOR POWER-OPERATED PRESSES AND THE LIKE Filed Feb 6, 1969 4 Sheets-Sheet 5 IN VENTOF? LAWRENCE E GRUNDY AT TORNEYS Dec. 30, 1969 L. F. GRUNDY 3,487,182
SAFETY MECHANISM FOR POWER-OPERATED PRESSES AND THE LIKE Filed Feb. 6, 1969 4 Sheets-Sheet 4 I 35 B7 25 if 40 ij Q c 1 1,
IN VENTOR LAWRENCE E GRUNDY AT TORNEYS United States Patent 3,487,182 SAFETY MECHANISM FOR POWER-OPERATED PRESSES AND THE LIKE Lawrence F. Grundy, Kirtland, Ohio, assignor to The Positive Safety Manufacturing Company, Cleveland, Ohio, a corporation of Ohio Filed Feb. 6, 1969, Ser. No. 797,207 Int. Cl. H0lh 3/16 US. Cl. ZOO-61.42 Claims ABSTRACT OF THE DISCLOSURE A safety mechanism is provided for preventing actuation of the press ram in the event there is an obstruction in the work area of the press. The mechanism is characterized by the fact that it embodies a solenoid and senser mechanism responsive to energization of the solenoid, but which senser mechanism falls by gravity. Additional features include the use of a relay and limit switch, means for improving controlled movement of the senser, means for preventing misalignment or distortion of parts of the senser mechanism, and means for reducing friction at various points in the mechanism.
This invention relates, as indicated, to a safety mechanism, which is especially useful in the operation of small presses, such, for example, as used for riveting, staking, and the like.
In Cain Patent 3,315,049, a safety switch means for a machine having a power-stroking operation is disclosed, including a senser which is movable to a location opera tively in the path of a power ram of the machine, a con trol rod for movably supporting the senser, a solenoid for moving the control rod, and thus also the senser to said location (the senser being of a nature to detect an obstruction if existing along said path, so that the movement of the senser into said location assures that said path is free from obstruction), safety switches for energizing said solenoid, and an abutment on the control rod for actuating a normally-open switch which controls the movement of the ram, but operable only upon the senser having reached said location, assuring that the opera tional effect cannot be actuated if there is any obstruction preventing the senser from having reached said location.
In said Cain patent, the abutment on the control rod is adjustable along the control rod, as is the senser, and a compression coil spring is provided which holds the rod upwardly except when the solenoid is energized, the tension of this coil spring being also adjustable.
It has been found, in utilizing the safety switch means of the aforesaid patent, that there are certain disadvantages in the arrangement described in the patent, which maybe enumerated as follows:
(1) When working on sensitive material, the force of the senser being driven against an object by the solenoid may be sufficient to damage the material or compress the finger or fingers of the hand to a point at which the normally-open switch may be inadvertently closed, and the ram thus inadvertently operated.
(2) In order to achieve a desired easy working of the system, the solenoid has to be custom-designed, at a cost which is almost prohibitive, since it is difficult to find commercially available solenoids having operating characteristics necessary for the purposes of the invention described in the Cain patent.
(3) The mass or weight of the senser mechanism is so great, and the return coil spring is so strong, that the force of the solenoid required to overcome this weight and strength results in greater pressure on the senser than is desirable.
3,487,182 Patented Dec. 30, 1969 (4) No provision is made in the Cain patent for preventing misalignment or distortion of the control rod.
We have developed a safety switch system which has numerous advantages over that described in the Cain patent, including among others, the following:
1) The force required to operate or actuate the senser or sensor mechanism is considerably smaller.
(2) Means are provided which slow down the operation sufficiently to provide better control of the senser.
(3) By eliminating a driven senser, and utilizing a gravity-actuated senser, in which pivotal connection between components are utilized, very little wear is effected at pivot points in the system.
(4) Commercially available solenoids, purchasable at low cost, can be used.
(5) Means have been provided for preventing or minimizing misalignment and distortion of the senser controd rod and senser.
(6) A relay is used, which prevents actuation of the machine by manually operating the senser.
(7) An adjusting collar is provided which limits the return movement of the senser control rod, and, at the same time, provides a means of adjusting the stroke of the senser.
(8) The senser control rod is independently adjustable, that is to say, it is infinitely adjustable.
Other objects and advantages of my invention will be apparent during the course of the following description.
In the accompanying drawings forming a part of this specification, like numerals are employed to designate like parts throughout the same.
FIG. 1 is a fragmentary perspective view of a press or press device embodying the safety means of the present invention, but with the cover of the safety means removed to more clearly show details thereof;
FIG. 2 is a fragmentary cross-sectional view, taken on the line 2-2 of FIG. 1;
FIG. 3 is a fragmentary elevational view, as seen in the direction indicated by the arrows 3-3 of FIG. 1;
FIG. 4 is a fragmentary cross-sectional view, taken on the line 4-4 of FIG. 3, and
FIG. 5 is a wiring diagram of the safety means, and circuitry therefor.
Referring more particularly to the drawings, there is illustrated a press 1, shown diagrammatically as having a base or bed 2 having an upright supporting column 3, which carries a fixed press-head 4. From the head 4, there extends downwardly an axially-movable power ram or punch 5 designed to coact with work-holding means 6, which is secured to the bed 2 in any suitable manner.
Electric power for actuation of the ram 5 is provided by an external two-wire or three-wire electric supply 7 (see FIG. 5), as required by electrical codes.
Normally open foot or hand switches 8 and 9', are provided in the electric supply circuit, for the purpose of actuating the safety means, which then provides a source of power to the ram 5. In other cases, these would control a source of power for, or actuation of the ram.
The components thus described form no part of the present invention, except in their relation to and their cooperation with the safety means of the invention.
In accordance with the invention, there is provided a senser or probe comprising a vertical rod 10 and a member extending angularly to the rod 10 and terminating in a loop 11. This senser is caused to feel or test the work area prior to any possibility of actuation of the ram 5; and only if the work area is operationally free of any foreign object can the senser cause the ram to be actuated. This action is subject to proper adjustment of the safety means, which adjustment will be presently described.
The senser 11 is shown, in this instance, as in the shape of a loop, the axis of which is coaxial with the axis of travel of the ram 5, and the rod is adjustably secured in an actuator block 12, by means of a set screw 12a.
The block 12 is secured, as by means of a hollow head screw 13, to a senser control rod or shaft 14, having a flattened area 15, against which the stem of the screw 13 bears, to preclude rotation of the shaft 14 in the block 12.
The shaft 14 is mounted for reciprocal slidable movement in a pair of vertically-spaced bearing blocks 16 and 17 which are secured to a base plate 18.
The block 16 has secured thereon, as by a screw 18a, a leaf spring 1811, to the upper end of which is secured, as by a screw 180, a drag block 18d. This block bears resiliently and frictionally against the shaft 14 and thus acts to slow the movement of the shaft sufiiciently to provide better control of the senser. This drag block, in conjunction with a latch spring to be presently described, functions to provide such improved control of the senser.
The base plate 18 forms the base or back of a housing which is mounted on the head 4 of the press, as shown in FIG. 1, the cover of this housing being omitted in FIG. 1, for purposes of clarity. The base plate 18 has mounted thereon all of the elements comprising the safety means of the invention.
The shaft 14 has adjustably secured thereto, as by means of a screw 19, a collar 20, on which is superimposed a rubber bumper 20a, which is designed to engage the lower surface of the bearing block 16 to thereby limit the upward movement of the shaft 14. This rubber bumper prevents metal to metal contact between the collar and bearing block, in addition to its normal shockreducing function.
Secured to the actuator block 12, as by means of screws 21 and 22, is a switch actuator 23, which is designed to engage a switch closing arm 24 of a limit switch 24a, when the shaft 14 descends. The limit switch 24a is mounted on the base plate 18, in spaced relation to such plate.
The safety means further includes a solenoid 25 which is mounted on the base plate 18, and the armature of which is designated by reference numeral 26. The lower end of the armature 26 is secured, as by a pivot pin 27, to the arms of a spring yoke 28, so that the yoke has a slight degree of pivotal movement relatively to the armature. Mounted on the pivot pin 27, between the arms of the yoke 28 is a roller 27a (see FIG. 4), which serves a purpose to be presently described.
The lower end of the yoke 28 is secured to one end of a coil spring 29, the lower end of which is secured, as by a screw 30, to a post 31, which is mounted on the base plate 18.
The upper end of the shaft 14 is provided with a pin 32 which extends through a slide or bearing block 32a (FIG. 4), which, in turn, is mounted for slidable movement in a slot 33, at the rear of a pivot beam 34. The beam 34 is mounted for pivotal movement on a post 35, which is mounted on the base plate 18.
The beam 34 has mounted thereon adjacent its forward end, a latch spring 34a (FIG. 4), which, when the beam 34 is rotated in a clockwise direction, as viewed in FIG. 4, resiliently embraces the roller 27a, to thereby provide improved control of the action of the senser.
The safety means further includes a relay 36, which is supported by a bracket 36a, which is attached to the base! plate 18.
A terminal block 37 is also provided, which is secured to the base plate 18 by means of screws 37a, and is provided with bridged terminals A, B, C and D.
Reference to the wiring diagram of FIG. 5 shows that the switches 8 and 9 are respectively secured, as by wires 38 and 39, to the terminals A and B of the terminal block 37, and that these terminals are secured, as by wires 40 and 41, to the solenoid 25.
The wires 40 and 41 are secured, as by Wi$ 42 and 43, to the relay 36.
The relay 36 is also provided with normally open contacts 44 and 45, which are connected, through the limit switch 24a, to the terminals C and D of the terminal block 37, these terminals being connected, through the wires 46 and 47, to the machine or press control unit 48 which controls the action of the ram 5. This control unit 48 is illustrated diagrammatically, and might be a solenoid clutch actuator, a solenoid valve (either pneumatically or hydraulically operated), or, in the case of a solenoidactuated press, would be a solenoid winding or control.
The use and operation of the safety means may now be described as follows:
With the ram or punch 5 in the elevated position, and the senser 11 in the position shown in FIG. 1, the various parts of the safety means will be disposed in the position shown in this figure.
When the operator closes the switches 8 and 9, the solenoid 25 and the relay 36 are activated, permitting the shaft 14 and senser 10-11 to be released and to descend by gravity. The senser weighs only a few ounces and the drop is controlled to prevent discomfort to the fingers of the operator should they be in the path of the senser.
If the senser is obstructed by an object, such as a finger of the operator or a misplaced part, and thus is not permitted to complete its full travel, the control circuit (FIG. 5) remains open and the punch or ram 5 will not be activated. This results from the fact that the limit switch 24a cannot close, due to such obstruction, and the portion of the circuit which is controlled by the limit switch 24a and relay 36 is not energized.
If the senser encounters no obstacle and is permitted to travel its complete pre-selected distance, the circuit controlled by the limit switch 24a and relay 36 is completed, and the ram or punch 5 is activated. The control relay 36 is used to prevent the operator from cycling the machine by hand by pulling the senser down manually.
The vertical position of the senser is adjustable to compensate for differences such as material thickness and height of the dies. This adjustment for height and stroke is permitted by means of the set screws 12a and 19.
Upon completion of the downstroke of the ram or punch, the coil spring 29 contracts, thereby returning the senser 10-11 to its initial position preparatory to another cycle of operation of the press.
Since the senser mechanism falls by gravity, the force required to operate or actuate the senser mechanism is considerably smaller than that required to operate the corresponding mechanism in the aforesaid Cain patent.
The provision of the drag block 18d and the latch spring 341: slows the movement of the shaft 14 sufiiciently to provide better control of the senser.
Since the force required to operate or actuate the senser mechanism is considerably smaller than that required to operate or actuate the corresponding mechanism in the aforesaid Cain patent, it is not necessary to utilize expensive, custom-designed, armatures for use in the present mechanism, and it is possible to use, instead, low-cost, commercially available or standard solenoids.
The use of the bearing blocks 16 and 17 and actuator block 12, as well as the manner in which these are associated with the shaft 14 and senser rod 11, insures against misalignment and distortion of the senser rod and the senser loop.
The use of the relay prevents the operator from cycling or operating the press by manually-actuated means, such as the hands of the operator, or a manually-controlled switch.
The use of the collar 20 is advantageous in that it provides an adjustable means of limiting the return movement of the shaft 14.
The senser is independently and infinitely adjustable.
Wear of the mechanism is reduced to a minimum, since there are only two pivotal connections employed,
and the pivotal movement between the pivotally-connected parts is relatively slight.
Friction is reduced by reason of the rolling contact between the pivot beam and the roller 27a. The sliding block 32a provides a bearing with a minimum amount of free movement. This reduces the total amount of backlash in the shaft 14 and the senser or probe assembly, and controlling the senser assembly produces a more positive actuation of the limit switch.
It is to be understood that the form of my invention, herewith shown and described, is to be taken as a preferred example of the same, and that various changes may be made in the shape, size and arrangement of parts thereof, without departing from the spirit of the invention or the scope of the subjoined claims.
Having thus described my invention, I claim:
1. Safety means for a machine having an operational eflFect along a path, said safety means comprising senser means operatively movable to a location in said path, movable support means movably supporting said senser means, said support means and said senser means being movable by gravity into said location, control means for actuating the power stroke of the machine, said senser means being responsive to the presence of an obstruction in said path to prevent actuation of said control means, the control means being cooperative with said movable support means to be actuatable to energize said operational effect only if said senser means has reached said location without sensing any such obstruction, solenoidactuated means, and means connected to said support means and responsive to selective operation of said solenoid actuated means for moving said support means and said senser means to their uppermost position and for releasing these means from said position to fall by gravity to said location.
2. Safety means, as defined in claim 1, including springactuated means operative in opposition to said solenoidactuated means for returning said support means and senser means to their uppermost position, when said solenoid-actuated means is not energized.
3. Safety means, as defined in claim 2, including relay means for delaying the actuation of said control means.
4. In a safety device of the character described, a base plate, a control shaft mounted on said base plate for slidable movement, a senser supported by said control shaft, a limit switch, means connected to said control shaft for closing said limit switch upon reaching a limit position, said shaft and senser being entirely movable downwardly by gravity, and means releasably holding and preventing said gravity movement of said shaft and senser.
5. A safety device, as defined in claim 4, wherein said last-named means comprises an armature, a yoke secured to said armature, and a spring for pulling said yoke downwardly.
6. A safety device, as defined in claim 5, wherein a relay is provided in association with said limit switch for controlling the effect of said switch.
7. In a safety device of the character described, a base plate, vertically-spaced bearing blocks mounted on said base plate, a shaft mounted for reciprocal sliding movement in said bearing blocks, an actuator block adjustbly secured to said shaft, a senser carried by said block, a limit switch mounted on said base plate, means mounted on said actuator block for closing said limit switch, and spring-actuated means including means for releasably holding said shaft and senser in an elevated position to prevent free falling of said shaft through said bearing blocks.
8. A safety device, as defined in claim 7, wherein said last mentioned means includes a beam pivotally mounted on said base plate and pivotally connected to said shaft, said beam bearing against said spring-actuated means.
9. A safety device, as defined in claim 8, wherein said pivot beam has a slot in one end thereof, a slide block is mounted for slidable movement in said slot, and a pivot pin is provided which extends through said block.
10. A safety device, as defined in claim 9, wherein a drag block is mounted on one of said bearing blocks, said block being in frictional contact with said shaft, and a latch spring is mounted on said beam for engagement with said spring-actuated means.
References Cited FOREIGN PATENTS 731,051 6/1955 Great Britain.
ROBERT K. SCHAEFER, Primary Examiner M. GINSBURG, Assistant Examiner US. Cl. X.R. 192-134