Feeding apparatus for stepwise feeding of continuous elongated material

Continuous, elongated material is fed lengthwise in steps by clamping devices of which one is stationary on supporting structure, the other is reciprocated. Each device includes clamping jaws backed by a fluid-operated jack and return springs in such a manner that the stationary jack is spring-biased toward the clamping position, and the reciprocating jack is spring-biased toward the material-releasing position, both jacks being operated intermittently, against the restraint of the return springs by the simultaneously supplied pressure fluid. The return spring in the reciprocating jack is weaker than that in the stationary jack. The springs may be replaced by equivalent pneumatic devices.

The invention relates to feeding apparatus for stepwise feeding of 
continuous, elongated material, and particularly to an improvement in the 
known basic type of feeding apparatus in which a continuous length of 
material is fed in a forward longitudinal direction during one stroke of a 
reciprocating clamping device and is prevented from moving backward during 
the other stroke by a stationary clamping device. 
It is known to equip the clamping devices of known feeding apparatus with 
return springs which bias the jaws of each device toward a 
material-releasing position, and to shift the jaws into the clamping 
position by means of suitably synchronized cams. While the known feeding 
apparatus functions well when newly built, the cam arrangements are 
subject to wear and relatively expensive to maintain and to replace. The 
cam pressure is transmitted to the guides of the movable clamping device 
resulting in further wear. 
The primary object of this invention is the provision of feeding apparatus 
which performs the functions of the afore-described known apparatus at 
least equally well when new, but is simpler in its structure and free from 
significant wear during extended operating periods. 
With this object and others in view, as will hereinafter become apparent, 
the invention provides two clamping devices spaced on a support in a 
predetermined direction in which a slide carrying one of the devices is 
reciprocated. Each clamping device includes a base portion and an 
operating portion movable relative to the base portion between two 
terminal positions. One portion includes a cylinder member enclosing a 
cavity therein while the other portion includes a piston member movable in 
the cavity and bounding a compartment of the cavity. Respective clamping 
jaws secured to the cylinder and piston members clamp the material to be 
fed in one terminal position of the operating portion, and they release 
the material in the other terminal position. A common pressure fluid 
supply device is connected to the two compartments for cyclically 
supplying pressure fluid to the compartments and for shifting the 
operating portion of one clamping device into its one terminal position 
while shifting the operating portion of the other clamping device into the 
other terminal position thereof by the pressure of the supplied fluid. 
When the fluid pressure decreases to a first value, the operating portion 
of the one clamping device is shifted by a return arrangement from its one 
to the other terminal position. When the fluid pressure decreases to a 
second value different from the afore-mentioned first value, the operating 
portion of the other clamping device is shifted by a second return 
arrangement from its other terminal position toward the one terminal 
position. The reciprocating movement of the slide and the cyclic variation 
in the pressure of the fluid supplied are actuated in timed sequence.

Referring now to the drawing in detail and initially to FIG. 1, there is 
shown only as much of a strip feeding apparatus as is needed for an 
understanding of the invention. As is conventional and not illustrated, 
metal strip 12 is to be unwound in continuous length from a storage reel 
and to be fed stepwise in a longitudinal direction to a stamping press of 
which only portions of a supporting frame 100 are shown. 
A slide 1 is guided on the supporting structure for reciprocating movement 
parallel to the path of the strip 12, and its stroke is limited in both 
directions by fixed abutments 2, 3 on the machine frame 100. The slide 1 
carries a clamping device 4 which is a single-acting hydraulic jack. 
Clamping jaws 5, 6 are mounted respectively on the cylinder 7 and the 
piston 16 of the jack 4, the jaw 6 being a rod axially guiding the piston 
16 in the cylinder 7. The jaw or piston rod 6 is biased away from the 
other, anvil-shaped jaw 5 by a helical compression spring 13 in one of the 
two compartments of the cylinder cavity which are separated by the piston 
16, the other compartment 17 being fluid-tight and connected with a piston 
pump 15 by a metal tube 18, a flexible hose 18', and other elements 
presently to be described. 
The base portion of another clamping device 8, also a hydraulic jack, is a 
cylinder 11 in which a piston 19 is guided axially as the operating 
portion of the device by a piston rod 10. The piston rod functions as one 
jaw of the clamping device whose other jaw is constituted by an anvil 9 on 
the cylinder 11. The cylinder 11 is fixedly fastened on the machine frame 
100. The annular compartment 20 of the cylinder cavity may be filled with 
pressure fluid through a tube 21 to shift the rod 10 away from the anvil 9 
against the restraint of a helical compression spring 14 in the other 
cylinder compartment, the axial displacement of the piston 19 under the 
pressure of fluid in the compartment 20 being limited by abutment against 
an annular rib 38 on the inner cylinder wall before the several turns of 
the spring 14 axially engage each other. 
The two jacks 4, 8 are identical except for the location of their fluid 
connections 18, 21 and of their return springs 13, 14. Also, the spring 13 
is softer than the spring 14 and thus offers less resistance to the 
movement of the associated piston under equal force applied by pressure 
fluid. Additionally, the face of the piston 16 exposed to the pressure 
fluid in the compartment 17 is larger than the annular face of the piston 
19 exposed simultaneously to equal fluid pressure in the compartment 20 
during normal operation of the feeding apparatus. 
The piston rod 22 of the pump 15 carries a cam follower roller 23 on its 
free end outside the pump cylinder, and the piston 27 attached to the 
inner end of the rod 22 is reciprocated by a radial cam 25 mounted on a 
shaft 26 during each revolution of the shaft which is driven by an 
electric motor unit M. A return spring 24 in the pump cylinder maintains 
engagement between the cam follower 23 and the cam 25. The working 
compartment of the pump cylinder in which the compression spring 24 is 
mounted communicates with an open sump 29 through a one-way valve 28 which 
opens to admit hydraulic fluid to the pump 15 if subatmospheric pressure 
should occur in the pump due to leakage losses or the like. The maximum 
pressure maintained in the hydraulic system by the pump 15 is limited by a 
pressure-relief valve 35 in a line 30 connecting the working compartment 
to the sump 29. A pressure gage 36 at the end of a pipe 32 provides a 
visual indication of the fluid pressure in the pump 15. 
A two-way valve 33 is spring-biased toward the illustrated position in 
which it connects the output and intake conduit 31 of the pump 15 with the 
afore-mentioned tubes 18 and 21, the latter being provided with a shut-off 
valve 34. A float switch 37 deenergizes the motor unit M if the fluid 
level in the sump 29 drops below a desired minimum value. The motor unit M 
also turns a circular disc 42 about its axis once during each revolution 
of the cam 25. An eccentric, axial pin 43 hingedly fastens one end of a 
connecting rod 44 to the disc 42, the other end of the rod 44 being hinged 
to the slide 1 for reciprocating the same and the attached jack 7 as 
indicated by a double arrow. 
A source of electric current, conventionally represented in FIG. 1 by a 
battery 45, is series-connected with the switch 37 and the motor unit M 
for energizing the latter when the switch is closed. Another switch 46 and 
conductors 47, 48, 49, 50 connect the current source 45 with solenoid 
actuators of the valves 33, 34 for simultaneously shifting the valves into 
their non-illustrated positions when the switch 46 is closed. The shifted 
valve 34 seals the fluid in the cylinder compartment 20 of the jack 8 
regardless of the pressure prevailing in the pump 15, and the shifted 
valve 33 vents the cylinder compartment 17 of the jack 4 to the sump 29. 
The apparatus illustrated in FIG. 1 is operated in the following manner: 
While respective portions of the strip 12 are located between the jaws of 
the two clamping devices 4, 8, the switch 46 remains normally open and the 
switch 37 closed, and the valves 33, 34 remain in the illustrated 
positions. The springs 13, 14 initially hold the jaws 5, 6 in the 
strip-releasing position and the jaws 9, 10 in the strip-clamping 
position. No longitudinal forces are exerted on the strip 12 while the 
disk 42 starts turning clockwise from the illustrated position and the 
piston 27 drives liquid out of the pump 15 through the valve 33 into the 
compartments 17, 20. The spring 13 being weaker than the spring 14, and 
the exposed face of the piston 16 in the compartment 17 being larger than 
the face of the piston 19 in the compartment 11, the jaws 5, 6 grip the 
strip 12 for a brief instance before it is released by the jaws 9, 10 as 
the liquid pressure in the two clamping devices is built up by the pump 
15. The strip 12, released by the stationary jack 8, is fed forward by the 
jack 7 moving toward the left, as viewed in the drawing, with the slide 1. 
As the slide 1 reaches the abutment 3, the piston 27 starts drawing liquid 
from the compartments 17, 20, and the spring 14 clamps the stationary jaws 
9, 10 on the strip 12 a fraction of a second before the piston rod 6 is 
withdrawn from the strip inward of the cylinder 7, and the slide 1 
reverses its direction of movement. The flexible hose 18' which is secured 
between two relatively rigid sections of the pipe 18 by means of pipe 
clamps 40, 41 permits flow of liquid to and from the compartment 17 during 
movement of the slide 1. The hose 18' is soft enough to prevent the 
clamping stresses generated between the jaws 5, 6 from being transmitted 
to the slidably engaged surfaces of the slide 1 and the support 100. 
The several metallic elements of the illustrated feeding apparatus are 
sufficiently resilient to absorb stresses generated during each reversal 
of slide movement while both jacks 4, 8 simultaneously clamp the strip 12 
for a very brief moment. It is possible, though not normally necessary to 
construct the connecting rod 44 of two telescoping parts spring-biased 
toward a predetermined overall length, thus capable of expanding and 
contracting as needed when the slide 1 engages the abutments 2, 3 while 
the pin 43 still moves in a direction having a component parallel to the 
path of the slide. 
When the feeding apparatus is shut off, as at the end of a working day, the 
strip 12 is maintained in a precisely defined position by the spring 14, 
and operation may be resumed next day without any scrap loss from the 
leading end of the strip 12. For normal, continuous operation, the springs 
13, 14 may be dispensed with, and the piston 19 may be moved toward the 
illustrated position by the pressure of the atmosphere communicating with 
the cylinder cavity below the piston 19 when the suction of the pump 15 
generates a vacuum in the compartment 11. Correspondingly, the returning 
function of the spring 13 may be assumed by gravity acting on the piston 
16. The necessary dimensions and other parameters of the modified clamping 
devices will readily suggest themselves to those skilled in the art. 
When it is desired to switch from one type of strip material to another, 
the switch 46 is closed while the jaws 9, 10 are held apart by the 
pressure of liquid in the compartment 11. The energized solenoid of the 
valve 34 holds the jaws 9, 10 in the strip-releasing position, while the 
valve 33 permits the pressure fluid to be drained from the compartment 17 
to the sump 29, and the strip 12 to be released by the jaws 5, 6. The 
strip 12 may then be exchanged against other material, and production 
resumed with only minimal downtime due to the changeover. 
The feeding apparatus of the invention partly illustrated in FIG. 2 differs 
from that described above with reference to FIG. 1 in its structure only 
to the extent specifically shown and described, and it operates in 
practically the same manner. The springs 13, 14 are dispendsed with, and 
the compartments 58, 59, corresponding to those which receive the springs 
in the embodiment illustrated in FIG. 1, are made fluid tight. 
A resilient, fluid-tight membrane 52 is clamped between the two flanged 
halves of a spherical pressure tank 51. The cavity 53 of one half is 
filled with compressed air that may be replenished as needed through a 
valve 60. The cavity 54 of the other half is filled with oil or other 
hydraulic fluid and communicates with the compartments 58, 59 through a 
common throttling valve 55 and respective branch lines 56, 57, the air 
pressure in the tank portion 53 thus is transmitted to the smaller annular 
face of the piston 16 to exert a smaller force than that exerted by the 
same air pressure on the circular face of the piston 19 in the compartment 
59, the resulting mode of operation being closely analogous to that 
provided by the springs 13, 14 of different strengths described with 
reference to FIG. 1. 
Other modifications of the illustrated and described feeding apparatus of 
the invention will readily suggest themselves to those skilled in the art. 
It should be understood, therefore, that the foregoing disclosure relates 
only to preferred embodiments of the invention, and that it is intended to 
cover all changes and variations of the examples of the invention herein 
chosen for the purpose of the disclosure which do not constitute 
departures from the spirit and scope of the invention set forth in the 
appended claims.