US2102557A

US2102557A - Safety mechanism

Info

Publication number: US2102557A
Application number: US753321A
Authority: US
Inventors: Hoffman Jacob
Original assignee: Individual
Current assignee: Individual
Priority date: 1934-11-16
Filing date: 1934-11-16
Publication date: 1937-12-14
Anticipated expiration: 1954-12-14

Description

Dec." 14, 1937.

J. HOFFMAN SAFETY MECHANISM Filed Nov. 16 1954 2 Sheets-Shet 2 Q Jacob Hoffmn,

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' fizz/672155 Patented Dec. 14, 1937 UNITED STATES PATENT OFFICE SAFETY MECHANISM Jacob Hofiman, Chicago, Ill., assignor of onehalf to Willy Dumke, Chicago, 111.

This invention relates to safety mechanism for punch presses or the like, and more particularly relates to mechanism of this character adapted to occupy both of the operators hands while the press is in operation.

Punch presses of the type to which the present invention is particularly applicable embody a movable part in the form of a reciprocating ram suitably supported for operating upon a work piece at rest upon a rigid platform or bolsterplate. The ram is usually power driven through the medium of a prime mover and is intermittently operated by suitable clutch mechanism controlled by a foot treadle. In general the work piece is placed under the ram by hand, and the finished piece is removed in the same manner. Should the operator engage the clutch too soon, or attempt to rearrange the position of the work piece during the interval between engagement of the clutch and the impact of the ram, his hand may be caught and severely injured if not amputated. Such accidents are, as a matter of fact, of all too frequent occurrence in the operation of punch presses and-result not only in injury or loss of limb to the operator but also in serious economic loss to the employer.

It is an object of thepresent invention, therefore, to provide safety mechanism for punch presses which will require the operator to employ both hands for operating the press and which will otherwise instantly act to halt movement of the ram whereby the operator cannot have either hand in such a position as to be caught under the ram at the impact thereof.

Another object is to provide mechanism for halting the movement of the impact member of the machine a predetermined distance from the impact point and embodying manually operable control means requiring the simultaneous use of both of the operators hands to release the impact member for further operation, the speed of the impact member being calculated to carry it from the halting point to the impact point before the operator can place his hands into the operative path of the impact member after releasing the same.

Another object is to provide a safety device of the foregoing character which may be installed easily and without rearranging the parts or changing the mode of operation of a press already set up for operation.

Another object is to provide a safety device operable as an auxiliary to the regular control means of the press to prevent operation of the ram until the operator manually releases a safety by the use of both his hands.

Another object of the invention is to provide a safety device of the foregoing character having a pair of spaced manual control means arranged to remain inoperative except when the operator uses both of his hands simultaneously to operate the same.

Another object is to provide a safety device of the foregoing character which is adjustable to vary the point at which the descending ram will be halted in spaced relation to the bolster plate.

Another object is to provide a safety device embodying shock absorbing means and adapted to lock the mechanism against further operation should the usual drag brake be improperly adjusted so that the apparatus is not conditioned properly to halt substantially instantaneously when the safety device is active.

Another object is to provide a safety device of the foregoing character embodying means operable to permit continuous operation of the press when desired.

Another object of the invention is to provide an apparatus of' this character which is simple 7 in design; economical to manufacture and maintain while being simple and positive in action; practical and efficient in operation, and in general to produce an economical and efficient apparatus of the character referred to.

Other objects and advantages will become apparent in the following description and from the accompanying drawings, in which: i

Figure 1 is a fragmentary side elevation of the head of a press embodying the principles of the invention.

Fig. 2- is a front elevation of the press;

Fig. 3 is a fragmentary sectional view on an enlarged scale showing details of the latch mechanism of the safety device.

Fig. 4 is a fragmentary sectional elevation taken on line 4-4 of Fig. 3.

Fig. 5 is a fragmentary sectional elevation taken substantially along line 5-5 of Fig. 2.

Fig. 6 is an enlarged perspective view of the latch forming part of the safety device.

Fig. 7 is an enlarged perspective View of the wheel 22.

"by rotation of the fly-wheel.

Figs. 11 and 12 are front end side elevational views, respectively, of a modified form of the invention adapting the press for continuous operation.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawings and will herein describe in detail, the preferred embodiment, but it is to be understood that I do not thereby intend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

A safety mechanism according to the present invention may be built into the press during the course of its manufacture or it may be fashioned in the form of an auxiliary attachment to be incorporated in an existing machine. In either instance, the relationship of parts is such as to make the safety mechanism a part of the control mechanism of the press, and the nature of the mechanism is such that the operator will be required to employ both hands to effect operation of the machine.

As a matter of convenience, the invention is herein illustrated as being embodied in a conventional punch press including a stand or base It: supporting a standard [1. A work support such as a bolster plate [8 is disposed in the customary manner for receiving the stationary die and the work piece, while the usual movable impact member in the form of a reciprocable ram 13 is slidably mounted in the upper part of the standard for operating upon the work supported by the bolster plate. Actuation of the ram l9 through a predetermined cycle of operation is effected through a suitably journaled crank shaft 2t. Power from any suitable source continuously drives at the desired speed a prime mover such as a fly-wheel 22 which is freely rotatable on one end of the crank shaft.

Intermediary means such as a 'manipulable clutch mechanism 23 provides an operative connection of the crank shaft with the prime mover for actuating the ram.

The clutch mechanism 23 is herein shown as of a type embodying a clutch wheel 24 of substantial thickness suitably secured fast upon the shaft 26 coaxial with and in juxtaposition to the fly- Adjacent the periphery of the clutch wheel is a clutch bolt well herein shown as angular in form to receive a similarly shaped reciprocable pin or bolt 21. Near its hub, the flywheel 22 is provided with a plurality of shallow apertures 28 of substantially the same transverse dimensions as the well 25 and adapted tobe brought successively into alinement with the well A bore 29 is formed in the inner end of the bolt 21 to receive a coil spring. 3t which is seated at its outer end about a stud 32 in the inner wall of the well.25. This spring-is of a tension adapted normally to urge the bolt out of the well. It will thus be observed that the outer end of the bolt 21 will be forced by the spring against the adjacent face of the fly-wheel 22 and when one of the apertures 28 is brought into coincidence with the wheel 25, the

,bolt will instantly engage in the aperture. Thus,

the clutch wheel will be caused to follow the flywheel and thereby rotate the shaft 20, which in turn will cause the ram l9 to reciprocate.

In a usual arrangement, the means for controlling operation of the clutch takes the'form of a weighted or spring loaded foot treadle 33 operative upon being depressed to move a rod 34 which in turn is pivotally connected at its upper end to a latch lever 35. This lever is pivotally secured at one end as at 36, to the standard H, and its other end is formed as a wedge 31. In the periphery of the wheel 24 is a channel 39 within which the wedge 3'! is adapted to ride. The outer face of the bolt 21 extends substantially into the channel 39, and a transverse slot 42 in the bolt is adapted to be partially exposed within the channel 39 when the bolt is in clutching position within the aperture 28 in the fly-wheel. The exposed wall of the slot 42 is formed with a bevel is adapted to be engaged by the wedge 31 which forces the bolt inwardly against the force of the spring fail, to withdraw the bolt into the wheel 2%, as seen in Fig. 10, and thus disengage the driving connection.

The relationship of parts is such that whenever the driving connection is interrupted as aforesaid, the ram will be in the uppermost or open position. Thus, when the treadle 33 is depressed to withdraw the latch from the channel 39, the bolt 21 will be released and will engage in one of the apertures 28, causing actuation of the ram. Ordinarily in a single stroke machine the operator will release the treadle 33 immediately after the ram has begun to move, and the latch '35 will then automatically return to its position for engagement with the clutch bolt to halt operation of the machine upon completion of the ticn, and a period of short but perceptible duration will elapse between the moment when the clutch bolt 2'! is released and the moment when the ram strikes the work. This interval is sufficient to allow slight shifting of the Work on the bolster plate by a dextrous operator in order to prevent spoilation of a work piece that may have been carelessly or hurriedly put in position; or will allow an insertion by quick movement of a work piece under the ram before the same strikes should the treadle 33 be prematurely depressed. Such practice, however, eventually results in an accident whereby the operator is severely injured, and a salient feature of the present in- 'vention is the provision of safety mechanism for rneans requiring the use of both of the operators hands during the time when the ram is in movement toward the bolster plate.

As herein shown, the safety device is in the form of an attachment that may be secured to any press even after the same has been installed for operation. To this end, the mechanism of the device is supported principally upon a mounting plate 55 secured as by means of bolts M to the standard il adjacent the clutch wheel (Figs. 3 and 5).

Carried by the plate 55 is means adapted for operation with the clutch mechanism to withdraw the bolt 2'! from engagement the fly-wheel 22, this means being spaced only a partial revolution of the clutch wheel beyond the point where the latch 35 is adapted to engage theclutch bolt. As herein shown, a movable safety latch at is tangentially mounted relative to the clutch wheel to normally engage at its inner end within the channel 39, a concavity 49 being formed on that ,of a transverse lever arm 50. The inner end of I the latch 48 is substantially offset to provide an a in the groove 39 of the clutch Wheel, and with the :concave portion 49 snugly contacting :the .body' the collar 59 and thereby resiliently urges the rod' v or warrant, I have; shown a preferred practical angular shoulder and a nose portion 52having a beveled surface 53 adapted to engage with the bevel 43 in the wall of the slot 42 of the clutch bolt. 1 I

In the particular arrangement-here shown by way of example, the safety latch 48 is maintained normally in whatmaybe termed the active position, that is, with the beveledfinger 52 located of the wheel. To this end arod .54 is pivotally connected at one. end with the safety latch through a boss 55 forming'a part of or connected to the latch. This rod is slidably supported at its other end by means such as arreye bolt 5'! andis closely surrounded by a' coil spring58,.abutting at its forward end against av collar 59 rigid.

upon the rod. 'I'he'eye bolt 51 is secured to the supporting plate 45and forms an, abutment for the rear'endof the spring which bears against 54 against the latch. The spacing of the safety latch t8 from the treadle operated latch 35 in the direction of movement of the clutch Wheel is such that the ram will be halted a predetermined distance from the point of impact on the bolster plate.

Therefore, the operator cannot possibly be injured by having his hand in the operative path of the ram.

For releasing the safety latch to resume operation of the press, I providemeans which will necessitate the; simultaneous use of both of the operators hands. While this may take'a variety of forms as circumstances or conditions require releasing mechanism includinga pair of substantially spaced similar handles 60 conveniently disposed for simultaneous manipulationby the op- .erator and requiring him to use both hands removed a substantial distance from the operative a path ofthe ram l9.

Each handle is connected by'means such asa cable 62 with an opposite end of a transverse fulcrum lever bar 63, a stiff spring 64 being interposed between the end of the cable and the lever bar if desired to afford a resilient connection. At'its center, the lever bar is pivotally connected to a goose neck arm 65, having at one end a bifurcated'head 6'! for receiving the bar, a pin 68,

forming the pivotal connection. The other end 'of the arm 65.is rigid with the inner end of a transversely extending rod69 fast at its outer end with one end of alever 10. This lever is in loose engagement through the medium of a yoke H with the outer end of the rod 54 between the eye bolt 5'! and a rigidly secured collar 12. Intermediate its ends, as at 13, the lever is secured uponafixed pivotal fulcrum 13 on the'plate 45.

Thus, when the handlesare pulled, the cables 62' will draw the arm 65 and rod 69 forwardly, rocking the lever H! which. in turn draws the rod .54 to the right as seen in Figs. 3 and 5, against the pressure of the spring58. This movement of the rod 54 draws the latch 48 toward the inactive position as seen infdotted outline in Fig. 3, and

the clutch bolt will be released for operation. As soon as pressure is released. on the handles 60, the spring'58 again forces the safety :latch back toactive position.

Due to the pivotal connection of the lever bar 63 with thearm 65, thebar'will simply pivot when only one of the handles 60 is pulled. Simultaneously uniform pressure on both handles is therefore required to operate the releasing mechanism, thereby insuring that both of the operators hands will be occupiedwhile the ram is in movement toward the impact point. Should the operator not uniformly and continuously depress the handles until the clutch :wheel has been rotated to carry the clutch bolt beyond the point where the safety latch will engage the bolt, the

ram will be halted. Moreover, the spacing of the ram from the bolsterplate in its thus halted position will shorten the space remaining through cables, suitable means being provided for engagement by the stops. In the present instance this means comprises rigid cable guide conduits 'l5 having their rear ends spaced a predetermined distance from the stops in the active position of the safety device. These conduits extenditoward the front of the press and are suitably secured thereto as by means of brackets 11. 'If desired, the handles 60 may be hollow as best seen in Fig. 5, to slidably embrace the forward ends of the conduits. Through this arrangement the handlesare always in a fixed position relative to other parts of the machine even when the press is tilted, and the operator must always uniformly pull both handles to effect a release of the safety device.

For halting the machine when declutched, and i for preventing back-lash, the usual band type brake 18 may be utilized. When the brake is tight enough relative to the speed at which the 7 press is being drivento halt the press substantially instantly, the apparatus is properly conditioned for operation. a In such event, the position .of the clutch bolt and safety latch will be as seen I in Fig. 4, with the outer end of the bolt practically flush with the face of the clutch wheel, While the cam surfaces 43 and 53 are in abutment, and the finger 52 of the bolt extends only partially through the slot 42. It will be observed that the shoulder is also substantially spaced from the side of the bolt. Such spaced relationship must normally be preserved in order to allow the inner edge of the-shoulder to move through an are as it is being moved to inactive position due to the tangential relation of the safety latch. In this relationship of parts'the latch 43 is instantly responsive to manipulation to release the bolt.

However, should the brake l8 be tooloose to exert sufficient force to stop the press substantially at once,,the apparatus is-not'properly conditioned and maybe dangerous. When this condition occurs the momentum-of the machine will be sufilcient to carry the clutch wheel beyond the V normal stopping point when the bolt 2'! is withdrawn, and the finger 52 of the safety latch will pass beyond the normal engagement point until the shoulder 5! abuts the side of the bolt as seen in Figs. 8 and 9. 1 Preferably the pitch and length of the coactingcam surfaces 43 and 42 and the thickness of the finger is such that when the finger 42 extends to its full extent into the slot 42 of the'clutch bolt, the bolt will be withdrawn farther than usual into the bolt well25. In this relationship of parts the inner edge of the shoulder 5| will be locked against the clutch bolt and thus prevent release of the safety latch until the clutch wheel has been reversed sufiiciently to provide the spacing necessary to permit the shoulder to move through the are it must descirbe in moving to release the bolt. The releasing force effected through manipulation of the handles 60 will be insufficient to overcome the weight of the ram and clutch wheel and cause the necessary reversal of the latter because the springs M will yield under the additional force necessary. Hence the operator will have to employ a suitable tool such as a crowbar sufiiciently to reverse the clutch wheel; and to prevent a repetition of the locking action he must properly ad-- just the brake.

To absorb the shock against the safety latch when the apparatus is not properly conditioned and the shoulder 5| comes forcibly into locking engagement with the bolt, the lever arm 59 is ivotally connected to the supporting plate ts as by means of a bolt F9 and cooperates with suitable shock absorbing means. In the present instance a shock absorber 88 provided with a strong spring 82 is connected to thesupporting plate in position to bear against the arm 5% Adjustment of the tension of the spring is possible through the medium 'ofa bolt 33. The normal position of the lever arm 59 under compression is maintained'by a stop pin 86. V

Under differing operative requirements it may be desirable to halt the ram is at varying dis tances from the bolster plate It. To this end, I provide a plurality of spaced bolt holes in the plate it so that the positionof the latch mechanism may be shifted by moving the pivotal bolt connection 19 as desired to provide the necessary adjustment. Thus, the safety latch may be moved to discontinue, movement of the ram at the desired distance above the bolster plate.

Up to this point the machine has been described as being adapted for intermittent opcreation, that is, the ram being movable only at the will of the operator by releasing the safety mechanism. However, occasion may demand continuous operation of the ram as for blanking or die stamping, where the safety latch mechanism will not be necessary, but safety means to prevent the operator from placing his hand under the operating ram will nevertheless be desirable. To this end I have provided a removable cage guard Bl adapted to fit about a suitable die member. 8% on the bolster plate l3 and Ma height to prevent the operator from placing his hand under the ram regardless of the position of the latter. The ends of the guard are equipped with bayonet slots 39 adapting the guard ends to be removably received on bolts 96 suitably secured in the standard I'I. Clamps 92 are secured to the handles 60 and rods 93 connect the clamps to the sides of the cage guard 8! for retaining the handles in the latch releasing position. Thus, the safety latch will remain inactive throughout the die stamping operation but possible injury to the operator will be prevented by the cage guard.

In operation, the fly-wheel 22 will be continuously driven, but the ram l9 will remain in the inactive position, as seen in Fig. 2, until the treadle 33 is depressed to release the latch 35 whereupon the clutch bolt 21 will engage with the fly-wheel to begin rotation of the crank 26 for operating the ram. However, the safety latch 48 will act immediately to withdraw the clutch bolt from engagement with the fly-wheel, thus discontinuing further operation of the machine unless the operator has grasped and actuated both of the handles 60 to withdraw the safety latch to inactive position. Should the operator fail to actuate both handles 60 simultaneously, the ram will be instantly halted. Moreover, the point at which the ram will be halted by the safety mechanism and the speed of the ram when operating is such that it will reach the impact point before it would be possible for the operator to release his hold on.

either handle 60 and move his hand into the path of the ram should he be inclined to beat the ram for any purpose. As soon as either or both of the handles 60 are released, the safety latch returns to the position where it will again be active to halt movement of the ram after the treadle operated latch is released. Should the apparatus not be properly conditioned, the safety latch will lock with the clutch bolt and it will be necessary to reverse theclutch wheel to effect the release of the safety latch.

For continuous operation as in die stamping, the handles 6!! will be depressed to retain the safety latch in the inactive position, and means such'as thecage guard 81 will be utilized to prevent the operator from getting his hands under the ram.

Where the punch press is of such a character as to require the service of more than one operator, the safety apparatus may be provided with means requiring each operator to use both hands simultaneously to release the safety latch. Thus, a plurality of pairs of handles may be provided for operating the safety mechanism, so that each operator must utilize both of his hands simultaneously with every other operator in order to release the safety device and operate the machine.

punch presses that is simple and efiicient in operation, is sturdily and simply constructed, and is adapted for a variety of conditions.

I claim as my invention:

1. In a machine of the character described, a reciprocable impact element operable through a given working cycle including substantial movement from an initialposition to an impact position, a prime mover for driving said impact element at a predetermined speed, selectively operable connecting means including a driven member intermediate said prime mover and said impact element, means normally acting to effect a driving connection between said driven member and the prime mover, and control means requiring the simultaneous use of both of the operators hands for operating said connecting means and arranged normally to release said driving connection to halt operation of the machine if the operator removes either hand before said impact member has moved beyond a given intermediate position between said initial and impact positions whereafter the speed of the impact element will carry the latter from said intermediate position to impact position before the operator can move a hand from said control means into the path of the-element.

2. In a .punch press, the combination of a power driven impact element reciprocable through a working stroke of predetermined length, a prime mover for driving said ram at a predetermined speed, clutch mechanism for operatively connecting said prime mover, and impact element, control means adapted for intermittentlyoperating said clutch andincluding an actuator movable by the physical effort of an attendant operator, and additional manuallyi operable safety means requiring the simultaneous use of both of the operator's hands adapted to act with said clutch to'discontinue operation of said impact element after said control means has been operated if the operator releases either hand before said impact element has moved to Within a predetermined distance from the impact point, said distance being such that said impact elementwill reach the impact point before the operator can move a hand into its path.

3., A machine having a movable part, a prime mover for actuating said part through a predetermined movement cycle, intermediary means including. a clutch bolt acting with said prime mover for selectively engaging the same to actuate said movable part, control means including a control member normally active to discontinue engagement between said prime mover and clutch bolt, andmeans requiring the use-of both hands of the operator for moving said control member to inactive position placed at such a point relative to said movable part that said control means will operate to discontinue engagement between said prime mover and clutch bolt to halt movement of. said movable part more quickly than the operator can move his hand from said releasing means to a position in the path of said movable part.

.Eli?

4. In a machine of the class described,a movable part having a predetermined operative movement cycle, aprime mover for actuating said part, clutch means including a bolt for selectively engaging said prime mover to actuate said movable part, control means including, a latch adapted to discontinue engagement between said bolt and said prime mover, manual means operable only when manipulated by both hands of the operator for rendering said latch inactive, and means for adjusting the position of said latch for varying'the point-at which said latch becomes active. I

5. In a punch press including a power driven ram, operating means including an actuator movable at will conveniently disposed for actuation by the operator, clutch mechanism responsive to said operating means, safety mechanism auxiliary to said operating'means active to dis:

continue operation of said clutch mechanism after said operating means has been actuated by the operator, and manual means independent of said actuator including a pluralityof substantially separated members for rendering inactive said safety mechanism only when all of said members are actuated simultaneously.

6. In a machine of the character described, a movable part, a prime mover for actuating said part through a predetermined movement cycle, intermediary means acting with said prime mover for selectively engaging the same toactuate said movable part, controlmeans including a control member adapted to discontinue engagement between said prime mover and intermediary means, operatingmeans'for moving said control member to inactive position, adjustable means for properly conditioning said movable part to halt instantaneously when said intermediary means is disengaged by said control mem- V ber, and means operative with said control member adapted to lock said control member against movement by said operating means unless said movable part is properly conditioned.

V 7. In a machine of the character described, a movable part, a prime mover for actuating said part throughv a predetermined movementv cycle, intermediary means including a reciprocable element selectively engageable with said prime mover to actuate said movable part, control means including a control member adapted to discontinue engagement between said prime mover and reciprocable element, resiliently connected operating means for moving said control member to inactive position, an adjustable brake for properly conditioning the machine to halt movement of said'movable part substantially instantaneously when said reciprocable element is ciprocable element engageable with said prime mover for actuating said ram, control means including a control member adapted to discontinue engagement between said prime mover and said reciprocable element, manipulable means for releasing and moving said control member to inactive position, an adjustable friction brake tensioned to halt instantaneously movement of said ram when said reciprocable element is disengaged from said prime mover, and means on said control member engageable in active position with said reciprocable element for locking said control member against release by said manipulable means whensaid brake is out of adjustment and its tension is insufficient to instantaneously halt the ram. i

9. In apparatus of the character described, a movable part, a prime mover for actuating said part through a predetermined movement cycle, intermediary means acting with said prime mover for selectively engaging the same to actuate said releasing and rendering said control member inactive, and non-manual means cooperative with said manually operable means for holding the latter in releasing position for maintaining said control member continuously inactive toallow continuous operation of said movable part? 10. In apparatus of the character described, a movable part, a prime mover for actuating said part through a predetermined movement cycle, clutch mechanism between said prime mover and said movable part and including a member selectively engageable with said prime mover, control means including a principal latch adapted to discontinue engagement of said member with said prime mover, means operable to release said latch and allow engagement of said clutch member with said prime mover, an auxiliary latch spaced from said principal latch and arranged for engagement with said member to disengage the same from said prime mover immediately following release of said principal latch and before said movable part has traveled beyond a predetermined point, means for urging said auxiliary latch into active position, and manually operable means including a pair of spaced members operable to overcome said urging means for rendering said auxiliary latch inactive and arranged to require substantially equal and simultaneous manipulation for operation.

11. In apparatus of the character described, a movable part, a prime mover for actuating said part through a predetermined movement cycle, intermediary means acting with said prime mover for selectively engaging the same to actuate said movable part, control means including a control member adapted intermittently to discontinue engagement between said prime mover and intermediary means, handles hanging from the upper part of the apparatus and opcratively connected with said control member for releasing and rendering the same inactive, and means adapted to be connected to said handles for holding the latter in releasing position for maintaining said control member constantly inactive to allow continuous operation of said movable part.

12. In apparatus of the character described, a reciprocating ram, a prime mover for actuating said ram through a predetermined movement cycle, intermediary means acting with said prime mover for selectively engaging the same to actuate said ram, control means including a control member adapted intermittently to discontinue engagement between said prime mover and intermediary means, manually operable means for releasing and rendering said control member inactive, and safety means for entirely preventing lateral movement of the operators hands into the path of said ram including members extending into engagement with and connected to said manually operable means for holding the latter in releasing position for maintaining said control member constantly inactive to allow continuous operation of said ram.

13. In apparatus of the character described, a safety device comprising an auxiliary unit adapted for attachment to a power driven machine already installed for operation and having intermittently operable clutch mechanism for actuating the machine through a given working cycle, said device including a mounting member for attachment to the machine, aclutch actuator carried by said memberand normally operable promptly after the machine has been set into operation to render the clutch inactive and halt further movement of the machine, and manually operable means requiring the simultaneous use of both of the operators hands connected with said actuator for rendering said actuator inactive.

14. In a power driven punch press, in combination, a ram having a working stroke of predetermined length, a prime mover for driving said ram at a predetermined speed, connecting means including a part normally operable toeffeet a driving connection between said prime mover and said ram, and control mechanism having means normally active to coact with said part to maintain the latter against operation and embodying manually operable means requiring simultaneous use of both of the operators hands for rendering the normally active means inactive, said control mechanism being arranged to halt said ram at an intermediate position of its working stroke unless both hands of the operator are simultaneously occupied in operating said amass? mechanism, said intermediate position of the ram being in predetermined spaced relation to the end of its Working stroke whereby the speed at which said ram is driven will carry it. from said point to the end of its working stroke before the operator can move a hand from said manually operable means into the path of the ram.

15. In a power press or like machine embodying an impact element and driving means for moving said element through a given operating cycle including initial and impact positions,

a rotatable member including selectively movable means for connecting the same with said driving means and having a driving connection with said impact element, control means arranged to engage and to force said movable means to inoperative position when said element has reached initial position in'its operating cycle, and safety means supplemental to said control means requiring simultaneous use of both hands of the operator and having a part normally in a position spaced from said control means in the direction of movement of the driving means for engaging and rendering said movable means inoperative shortly after the latter has been reeased by said control means unless both hands of the operator are simultaneously in use to maintain said part inoperative.

16. In a power press or like machine including an impact element and driving means for moving said element through a given operating cycle, connecting means intermediate said element and said driving means for'effecting a driving connection therebetween and having selectively operable controlling means active at one point in said operating cycle to engage said connecting means to discontinue said driving connection, safety means requiring simultaneous use of both hands of theoperator effective after said element has commenced to move toward impact and at a point spaced from said controlling means in the dirction of movement of said driving means to engage said connecting means to discontinue the driving connection after it has been reestablished unless both hands of the operator are in use as required aforesaid, and means coactive with said safety means for absorbirg any shock thereon incident to the momentum of said element.

17. In combination in a machine having an element adapted for intermittent actuation through a predetermined movement cycle from an initial position to an operative position and return to initial position, continuously running driving means, means providing a driving connection between said element and said driving means and including a clutch biased for movement to effect said driving connection automatically, means for declutching said driving connection in said initial position of said element and being operable at will to permit resumed operation of the clutch, and auxiliary safety mechanism independent of said last mentioned means operable after said driving connection has been completedby the resumed operation of said clutch to declutch the same again and being arranged to maintain said element positively against movement toward said operative position.

JACOB HOFFMAN.