US3648597A - Deceleration-responsive press guard device - Google Patents

Abstract

A safety device for a power press prevents an operator from reaching into the area of the press die when the press fails to stop as scheduled. The device includes a deceleration sensing arrangement which controls the operation of an actuator for a press guard, the press guard remaining in a ''''prevent'''' position unless the operating cycle of the press includes the proper deceleration period.

Description

United States Patent Van Houten [45] Mar. 14, 1972 [54] DECELERATION-RESPONSIVE PRESS GUARD DEVICE [72] Inventor: George L. Van Houten, 186 Rensselaer Road, Essex Fells, NJ. 07021 [22] Filed: Nov. 12, 1969 [21] Appl. No.: 875,632

[52] ILLS. Cl ..100/53, 74/615, 83/397, 192/133 [51] int. Cl ..B30b 15/00 [58] Field olSearch ..100/53; 74/612-615; 83/397; 192/130, 133, 134

[56] References Cited UNlTED STATES PATENTS 2,683,515 7/1954 l-lorn et al ..192/134 2,888,123 5/1959 Madden ..l92/l34 FOREIGN PATENTS OR APPLICATIONS 603,934 6/1948 Great Britain 100/53 Primary Examiner-Billy .l. Wilhite Attorney-Larson, Taylor and Hinds [57] ABSTRACT A safety device for a power press prevents an operator from reaching into the area of the press die when the press fails to stop as scheduled. The device includes a deceleration sensing arrangement which controls the operation of an actuator for a press guard, the press guard remaining in a prevent" position unless the operating cycle of the press includes the proper deceleration period.

2 Sheets-Sheet 1 mmvm'nwum GEORGE L. VAN HOUTEN ATTUIRN EWS Pmmmd arch 1% 1% 2 Sheets-Sheet 2 5 m 7 a Q 20 AND Z4 70 AIR SUPPLY INVENTOR. GEO/P65 L VAN HOUTE/V lDlECELEItATION-RESPONSIVE PRESS GUARD DEVICE FIELD OF THE INVENTION The present invention relates to power presses and the like and more particularly to an arrangement for protecting an operator of such a press against injury when the press fails to stop as scheduled.

BACKGROUND OF THE INVENTION A large number of the more serious accidents involving presses occur when a press, which is operating on a singlecycle" basis, malfunctions and fails to stop at a predetermined time in the cycle. Under these circumstances the press operator, who in many instances will have become accustomed to the rhythm of the single-cycle operation of the press, may attempt to reach into the press die, in accordance with his normal actions, to remove a finished part or to insert new blank and may, in so doing, be injured.

Single-cycle operation of a press is utilized when the parts to be formed by the press must be fed by hand into the press die, removed by hand from the die or both. To initiate such operation, the press brake is disengaged and the clutch is engaged so that the press crankshaft accelerates up to the working speed of the press and is carried through the working or closing portion of the cycle wherein the press die is closed. As the die reopens, the clutch is disengaged and brake is applied at a time such that the press crankshaft is caused to decelerate and stop at the top of the stroke. Thus for normal single-cycle operation, the stroke cycle includes a period of deceleration in last stage thereof, the precise length of this period as well as of the acceleration period being a function of the speed at which the press is to be operated as well as of the characteristics of the brake and clutch. A repeating stroke is one where there is no deceleration or insufficient deceleration to provide stop page of the press, the press continuing to operate at full working speed during what is normally the deceleration period in the cycle so that the press continues past top dead center and acts to reclose the die.

Press guards of the prior art are designed to remove the press operator from danger if and when the press is reclosing. As the operating speeds of such presses increases, the amount of time available to remove the operator from danger grows correspondingly small. Although the guards and the stops thereof must be made stronger and heavier for operation at these higher speeds, this approach is in many instances self-defeating in that as the momentum increases, the resultant wear and breakage during normal operation is correspondingly increased. Further, as these devices are made stronger to operate at increased speeds the danger from the devices themselves increases.

SUMMARY OF THE INVENTION In accordance with the present invention a press is provided which includes means for sensing or detecting the effectiveness of the braking action on the press ram or, stated differently, the presence of the proper deceleration period in the operating cycle, and means for controlling the operation of a press guard, responsive to the sensing means. The press guard is movable between a first, prevent position wherein access to the press die is precluded and a second, permissive position wherein access to the press die is permitted. An actuator for the press guard which is responsive to the sensing means provides movement of the press guard to the permissive position thereof when the operating cycle includes the proper deceleration period.

The actual physical embodiment of the invention may take a number of forms. In an exemplary embodiment the press guard is formed by a plate or sheet of metal of the like which is positioned between the operator and the press die in the prevent position thereof and is movable through a 90 arc to the permissive position thereof wherein the guardplate is flush with fixed die member of the press. A pneumatic actuator for guardplate is controlled by a control switch which is actuated responsive to a deceleration sensing arrangement including a first cam member secured to the press crankshaft and a second cam member which floats with respect to the camshaft. A stop member which extends outwardly of the fixed cam is received in a slot in the floating cam and recesses in the peripheries of the cam surfaces, when aligned, permit inward movement of an actuator for the control switch. In operation the floating cam falls behind the fixed cam during the acceleration period of the operating cycle of the press to cause misalignment of the cam recesses and, consequently, prevents actuation of the control switch during this period. The floating cam should catch up with the fixed cam during the deceleration period so that the cams are aligned and the control switch is actuated. If the floating cam is not aligned with the fixed cam, the control switch is not actuated and the guard plate remains on the prevent position.

Other features and advantages of the invention will be set forth in or apparent from the detailed description of a presently preferred embodiment thereof found hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic representation of the basic operating elements of a power press;

FIG. 2 is a side elevational view of an exemplary embodiment of a simplified press incorporating the present invention;

FIG. 3 is a rear elevational view of the embodiment of FIG. 2 partially broken away to show the barrier guard;

FIG. 4 is a schematic circuit diagram of the electrical control system for the embodiment of FIGS. 2 and 3;

FIG. 5 is a perspective view of a schematic representation of one embodiment of the deceleration sensing device of FIGS. 2 and 3; and

FIGS. 6 and 7 are end views, drawn to a reduced scale, of the sensing device of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a schematic representation of a typical press, generally denoted P is shown. The press P is of conventional construction and this construction will be only briefly considered for purposes of completeness of disclosure and to provide a general background as an aid in understanding the present invention. The press P includes a die denoted D including a movable die member 10 and a fixed die member 12, a reciprocating motion being imparted to movable die 10 through a ram or slide 14 driven by a crankshaft 16. A drive l8 for crankshaft 16 may typically comprise a motor which drives a flywheel. The motor takes a certain period of time to bring the flywheel up to full speed and hence energy is stored therein, this energy being available for use during the heavy working portion of the stroke of ram 114. A clutch indicated at 20 connects drive 18 to crankshaft 16 which is connected to ram 14 through a bearing arrangement indicated schematically at 22. The reciprocating motion imparted to ram 16 is used to open and close the die D. A brake 24 is utilized to stop rotation of crankshaft I6 and to prevent rotation thereof as desired.

Referring to FIGS. 2 and 3, a simplified representation of a press incorporating the present invention is shown. The press of FIGS. 2 and 3, which is denoted 30, is of the general type shown schematically in FIG. 1 with certain elements thereof omitted for purposes of clarity of illustration. Press includes a frame 32 which rotatably supports a crankshaft 34 driven by a flywheel 36 as described hereinabove. A ram or slide 38 is drivenly connected to crankshaft 34 and carries a movable die member 40. Movable die member 40 cooperates with a fixed die member 42 mounted on a base portion of frame 32 to form a die generally denoted 44.

A flap or barrier guard 46 is positioned between an operator indicated at 48 and the die 44, the operator of the press 30 facing the press as shown in FIG. 2.. Flap guard 46 is constructed of sheet metal, plastic or the like and is mounted on a metallic shaft 50 by suitable means (not shown) such as inino-l mu brackets. The shaft 50 is mounted in bearings (not shown) secured in the sides of press frame 32. Flap guard 46 in the vertical or prevent position thereof, shown in solid lines in FIG. 4, prevents access to die 44 whereas in the horizontal or permissive" position thereof, shown in dashed lines in FIG. 4, permits access to die 44. In the permissive position thereof, guard 46 forms a horizontal table which is even with the lower, fixed die member. Movement of flap guard 44 is controlled by a rotary actuator 52 which provides 90 angular displacement of guard 46 between the vertical and horizontal positions thereof.

It will be appreciated that a number of devices may be utilized in providing rotation of shaft 50 and hence of guard 46. For example, actuator 52 may be pneumatically operated and may as shown in FIG. 4, include a series of vanes 52a located within a cylindrical housing 52b, which vanes, responsive to air pressure from a solenoid-controlled valve 53, provide rotation of shaft 50 through a 90 arc and consequent rotation of guard 46 between the prevent and permissive positions thereof. As is described in more detail hereinbelow actuation of actuator 52 is controlled by a control device 54 in accordance with the acceleration and deceleration cycle of the press 30.

Referring again to FIG. 4, the electrical control circuit for press 30 is shown. The circuit includes input terminals 56 and 58 which are connected to a source of electrical energy (not shown). A double-pole, single-throw foot switch 60, actuated by the operator of the press, completes a circuit through a first set of contacts 60b in a first line 64 in a first (or at rest) position thereof and completes a circuit through a second set of contacts 60a in a second line 62 for a second (or actuated) position thereof, line 62 being open for the first position of switch 60 and line 64 being open for the second position of switch 60.

A flap switch 66 and a press clutch solenoid 68 are connected in series in line 62. Flap switch 66 comprises a normally open microswitch mounted as indicated in FIG. 4 such that actuation thereof is effected in response to movement of flap guard 46 to the permissive position thereof. Switch 66 is shown in the actuated position thereof in dotted lines in FIG. 4 and is, as stated, actuated by movement of flap guard 46 to the prevent position thereof, this position of flap guard 46 also being indicated in dotted lines in FIG. 4. As shown in FIG. 4, press clutch solenoid 68 controls actuation of an air valve 77 and air cylinder 79 for controlling operation of a press clutch corresponding to clutch of FIG. 1. Energization of solenoid 68 causes engagement of the press clutch and operation of the press 30 and deenergization thereof causes disengagement of the press clutch and stopping of press 30.

Line 64 includes a ram switch 70, a set of relay contacts 72a and a flap valve solenoid 74. Relay contacts 72a are normally open and actuation thereof is controlled by a relay 72 connected in parallel with flap valve solenoid 74 and foot switch contacts 60b. Relay contacts 720 are connected in parallel with a deceleration signal-responsive switch 76. Ram switch 70 comprises microswitch responsive to movement of press ram 38, switch 70 being normally open and being closed with ram 38 (indicated schematically in FIG. 4) in the extreme upward position thereof. Flap valve solenoid 74 is used in controlling four-way air valve 53 which in turn controls actuation of flap guard actuator 52 described hereinabove. With solenoid 74 deenergized, flap guard 46 is in the prevent position thereof. Thus it is necessary to energize solenoid 74 before flap guard 46 is moved to the permissive" position wherein access is provided to the press die 44.

With the press at rest, the crankshaft 34 at top dead center, and switch 60 in the first, or at rest position, relay 72 and solenoid 74 are energized through contacts of ram switch 70, relay contacts 720, and switch contacts 60b. As the switch 60 is moved to the second (or actuating) position, contacts 6011 are opened'and contacts 60a are closed. Solenoid 74 is deenergized, causing the four-way valve (not shown) to shift and cause rotation of flap guard 46 to the prevent position.

When the flap guard 46 is in the full prevent position, flap switch 66 is closed. An electrical signal is now transmitted through the switch contacts 60a and flap switch 66 to press clutch solenoid 68, causing press clutch 20 to be engaged and press brake 24 to be released. At this time press crankshaft 34 starts rotating, causing slide 38 to descend and close press die 44. The first downward motion of slide 38 causes ram switch 70 to open and deenergize relay 72. The operator then releases switch 60, which returns to the first, or at-rest, position thereof, with contacts 60b closed and contacts 60a open. As the press cycle is completed and ram 38 again returns to the upper position thereof ram switch 70 is closed. If the proper braking action, and therefore deceleration occurs at this time, the deceleration-responsive switch 76 will close and energize relay 72, and at the same time, through switch contacts 60b, energize solenoid 74. Solenoid 74, now energized, causes the four-way valve (not shown) to shift position and cause flap guard 46 to move to the permissive" position, and permit the operator to have access to the die area. If the driving force through clutch 20 is not released, or the braking action of press brake 24 is not effective, deceleration does not occur in the proper amount and the deceleration-responsive signal switch 76 will not close. Under these conditions, relay 72 and flap valve solenoid 74 remain deenergized and the guard remains in the prevent" position.

Referring to FIGS. 5 to 7, one form of deceleration-respom sive control device 54 indicated in FIGS. 2 and 3 is shown. Control device 54 is mounted on, or driven by, crankshaft 34 and includes first and second disclike cam members 80 and 82. Cam member 80 is rigidly affixed to crankshaft 34 and rotates therewith whereas cam member 82 although mounted concentrically with crankshaft 34 floats with respect thereto. Floating cam 82 includes an outwardly extending stop member or projection 82a which is received in an arcuate slot 800 in fixed cam 80. Slot 80a and stop projection 82a thus cooperate to limit movement of floating cam 82 with respect to fixed cam 80. Floating cam 82 includes a recess or notch 82b in the periphery thereof whereas fixed cam 80 includes a similar notch or recess 80b. Deceleration-responsive sensing switch 76, shown schematically in FIG. 4, includes an actuator 76a adapted to be received in recesses 80b and 82b upon alignment thereof as shown in FIGS. 5 and 6 and biased toward the periphery of cams 80 and 82 as is indicated schematically by spring 76b in FIG. 4. Switch 76, which is normally open, is closed in the position for actuator 760 shown in FIGS. 5 and 6, that is, upon alignment of recesses 80b and 82b.

Considering the operation of control device 54, upon rotation of crankshaft 34 floating cam 82 will fall behind fixed cam 80 and, assuming clockwise rotation of shaft 34, stop member 82a will be positioned near or at the rearmost portion of slot 80a. As indicated in FIG. 7, under these conditions, switch actuator 76a will be held outwardly of the periphery of floating cam 82, recess 82b being positioned rearwardly of recess 80b. In this position switch 76 is open and flap guard 46 is in the prevent position thereof. If the press 30 decelerates, the floating cam 82 will forge ahead of the previous position thereof and will approach a position wherein stop member 82a is positioned near or at the frontmost or leading portion of slot 80a. Under these circumstances recesses 80b and 82b are near alignment and switch actuator 76a is permitted to move inwardly as shown in FIGS. 5 and 6 so that switch 76 is closed.

All the overall operation of the press is believed to be apparent from the foregoing description, this operation will be very briefly reviewed. Under normal conditions, press 30 will operate as described, the normal operating cycle including a period of acceleration, a working period and a period of deceleration. If, for example, a malfunction occurs in the control system for controlling braking of crankshaft 34, the die 40 will reclose after the ram 38 again passes through top dead center. Reclosing of die 40 in this manner could cause possible injury to the press operator were it not for the presence of barrier guard 46. As discussed hereinabove when decelerationsensing device 54 senses that the proper braking of the rotational movement of crankshaft 34 is occurring, a release signal is applied to actuator 52 which causes movement of guard 46 to the permissive" position thereof so that the operator can gain access to die $0. lf, however, no such braking is detected by sensing device 54 a release signal is not applied to actuator 52 and guard 46 remains in the prevent position thereof so that the operator is protected.

Thus, although the invention has been described in detail with respect to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that, in addition to the modifications specifically described, other variations and modifications may be effected within the scope and spirit of the invention.

lclaim:

l. A safety device for a press comprising a die including a stationary die member and a movable die member, rarn means for causing movement of the movable die member, and a crankshaft for driving said rams means, said safety device comprising guard means movable between a first, prevent position wherein access to the die is precluded, and a second, permissive position wherein access to the die is permitted, guard actuator means for, upon actuation, causing movement of said guard means between said first and second positions, and control means for controlling actuation of said actuator means, said control means comprising sensing means driven by the crankshaft for sensing deceleration of said ram means, and switch means responsive to said sensing means for controlling actuation of said guard actuator means, said sensing means including a first cam member fixed relative to the crankshaft, a second, floating cam member movable relative to said first cam member, shaft means for coaxially mounting said first and second cam members in spaced relationship, and a stop member rigidly secured to one of said first and second cam members, the other of said first and second cam members including a slot therein for receiving said stop member, said first cam member including a peripheral cam surface including a first arcuate recess therein and said second cam member including a peripheral cam surface including a second arcuate recess therein, and said switch means comprising a switch for controlling actuation of said guard actuator means and a cam follower in engagement with the peripheral surfaces of said first and second cam members for controlling actuation of said switch, said cam follower being movable between a first, nonactuating position and a second, actuating position, said cam follower, in the second, actuating position thereof, entering into said first and second arcuate recesses when said recesses are in alignment and movement of said cam follower into said recesses causing actuation of said switch and corresponding actuation of said guard actuator means, said cam follower being held in the first, nonaetuating position thereof when said arcuate recesses are out of alignment and hence preventing actuation of said guard actuator means and corresponding movement of said guard means to the second, permissive position thereof,

Claims (1)

1. A safety device for a press comprising a die including a stationary die member and a movable die member, ram means for causing movement of the movable die member, and a crankshaft for driving said rams means, said safety device comprising guard means movable between a first, prevent position wherein access to the die is precluded, and a second, permissive position wherein access to the die is permitted, guard actuator means for, upon actuation, causing movement of said guard means between said first and second positions, and control means for controlling actuation of said actuator means, said control means comprising sensing means driven by the crankshaft for sensing deceleration of said ram means, and switch means responsive to said sensing means for controlling actuation of said guard actuator means, said sensing means including a first cam member fixed relative to the crankshaft, a second, floating cam member movable relative to said first cam member, shaft means for coaxially mounting said first and second cam members in spaced relationship, and a stop member rigidly secured to one of said first and second cam members, the other of said first and second cam members including a slot therein for recEiving said stop member, said first cam member including a peripheral cam surface including a first arcuate recess therein and said second cam member including a peripheral cam surface including a second arcuate recess therein, and said switch means comprising a switch for controlling actuation of said guard actuator means and a cam follower in engagement with the peripheral surfaces of said first and second cam members for controlling actuation of said switch, said cam follower being movable between a first, nonactuating position and a second, actuating position, said cam follower, in the second, actuating position thereof, entering into said first and second arcuate recesses when said recesses are in alignment and movement of said cam follower into said recesses causing actuation of said switch and corresponding actuation of said guard actuator means, said cam follower being held in the first, nonactuating position thereof when said arcuate recesses are out of alignment and hence preventing actuation of said guard actuator means and corresponding movement of said guard means to the second, permissive position thereof.

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