Metering device

An arrangement for metering a blast of air delivered to a driven machine, particularly a sheet separation device of a sheet feeder. A control slide is connected via an air intake opening to a pressure source, and the control slide has an air discharge opening connected to the driven machine and leading into the open. The latter opening is controlled or disconnected during upward movement or stoppage of the machine coupled to the driven machine by means of a control element actuated as a function of the machine speed. The air intake opening and the air discharge opening leading to the driven machine, face each other coaxially, and upon reaching a set final speed, these openings are connectable by means of a coaxial recess passing through the control element. A rotary valve plug with a through-bore is provided to form the control element. The air discharge opening leads to the outside and is located offset relative to the air intake opening in the valve plug direction of rotation corresponding to a speed reduction. The through-bore of the valve plug in this region has an oppositely-directed expansion corresponding to the amount of offset. The valve plug is connected by a crank arm mounted on a bearing trunnion, and this crank arm is connected to a servomotor operating as a function of the machine speed.

BACKGROUND OF THE INVENTION 
The present invention relates to a device for metering the blast air 
delivered to a driven machine, particularly the sheet separation device of 
a sheet feeder, with a control slide connected via an air intake opening 
to a pressure source; this control slide has an air discharge opening 
connected to the driven machine and leading into the open; the opening can 
be controlled or disconnected during the upward movement or stoppage of 
the machine coupled with the driven machine by means of a control element 
actuated as a function of the machine speed. 
An arrangement of this type during the starting process of, e.g., a sheet 
feeder makes possible adaptation to the requirement of the air blast 
delivered to the sheet separator. An immediate application to the sheet 
separator of the full amount of air adapted to the standard operating 
speed would have the result that the top sheets of the sheet stack during 
the start-up process would not only be loosened, but would be blown all 
over. 
An arrangement of the initially described type is already known. Compared 
to the previously known manually actuated adjustment device, this known 
device represents considerable progress. However, various disadvantages of 
the known devices are caused by the unfavorable air delivery in the region 
of the control slide, which is formed here by a cylinder provided with 
radial air connections and a double-piston which can move inside it and 
has a control groove. The air intake opening formed by a radial bore and 
the two air discharge openings are diametrally opposite and are offset in 
the axial direction in such a way that the control groove in the end 
positions of the double piston connects each time only one air discharge 
opening with the air intake opening and the other air discharge opening is 
cut off, except for a small advance air gap. Based on this axial offset, 
the air current undergoes a considerable deflection corresponding to the 
offset which may lead to considerable flow losses. The flow around the 
connection between the two piston portions suggests an additional increase 
of the flow losses. Such flow losses have a negative effect particularly 
during the normal operation which requires complete air delivery to the 
driven machine. This was accomplished in the past by enlarging the air 
pumps to compensate for the steady losses. However, this leads not only to 
a simultaneous increase of the power consumption, but also to increased 
space requirement and weight and thus not only an increase in operating 
costs, but also an increase in manufacturing costs. The disadvantages 
involved is seen in the evidently poor efficiency. 
There is already known another compressed air control device for sheet 
feeders where an air line is closed by means of a valve (slide) which is 
slid across the line cross-section as a function of the machine rpm. The 
flow in the air line with the slide pulled out does not experience 
deflection. In contrast to the initially discussed arrangement, the known 
arrangement in the lower speed range does not experience a division of the 
air into a partial flow leading to the driven machine and a remaining 
partial flow leading to the outside. Therefore, it is possible that during 
the starting process in the area of the throttle valve (slide) projecting 
into the line cross-section there results a considerable air excess and 
hence a corresponding air stagnation which affects the pump ahead of it 
and may lead to overloading the pump and the entire pump driven which 
again requires "beefing up" (overdimensioning) and may have a negative 
effect on the life and the efficiency. Aside from this, DL-PS- 85 367 
involves only schematic sketches. The practical execution of the 
afore-mentioned slide arrangement leads to arrangements which, as the 
initial arrangement, involve deflection and flow losses. 
It is, therefore, an object of the present invention to provide an 
arrangement of the initially described type where during normal operation 
line losses in the area of the control slides are avoided and which can be 
equipped with relatively light pumps whose manufacturing and operating 
costs are low and whose overloading is effectively prevented. 
Another object of the present invention is to provide an arrangement of the 
foregoing character which may be easily maintained in service and has a 
substantially long operating life. 
SUMMARY OF THE INVENTION 
The objects of the present invention are achieved by providing an 
arrangement of the initially-mentioned type with a control slide connected 
via an air intake opening connected to a pressure source which has an air 
discharge opening connected to the driven machine and an air discharge 
opening leading to the outside which during the raising or stopping of the 
machine coupled to the driven machine, so that it can be controlled or 
shut off by means of a control element actuated as a function of the 
machine rpm, in a surprisingly simple manner by having air intake opening 
and air discharge opening leading to the driven machine face each other 
coaxially. Upon reaching the set final rpm, they are connectable by means 
of a coaxial recess passing through the control element. As a result, the 
air at full speed and hence full air requirement encounters a straight 
unblocked flow path so that line losses are eliminated as much as 
possible. At the same time, the retention of the advantages inherent in an 
air split-up during starting are ensured. The design and manufacturing 
expense for the measures in accordance with the invention remains 
negligibly small. The measures in accordance with the present invention 
promise a particularly high efficiency and a long life. 
In accordance with a particularly simple and expedient embodiment of the 
present invention, to form the control element, a rotary stopcock (valve) 
plug is provided with a through-bore. The air discharge opening, leading 
to the outside, opposite the air intake opening may be offset in the 
direction of rotation of the plug, corresponding to a speed reduction, and 
the through-bore of the plug may in this area be provided with an 
oppositely-directed enlargement corresponding to the amount of offset. 
With an offset of the plug in the direction of speed reduction, i.e., an 
opening of the air discharge opening leading to the outside and a closing 
of the air discharge opening leading to the driven machine, there results 
an inclination of the axis of the through-bore of the valve. This 
inclination corresponds to the angle of rotation, relative to the common 
axis of the facing air intake opening and the air discharge opening 
leading to the driven machine. This oblique position in an advantageous 
manner causes a slight stagnation which brings about a quick and effective 
outflow of the excess air through the air discharge opening leading to the 
outside; a noticeable overload of the pump is avoided. The air discharge 
line leading to the outside, to reduce noise, may be provided with a 
damper without deterioration of the flow-off conditions. 
Another advantageous embodiment of the invention is that the plug during 
stoppage of the machine can be placed into a ready position which is 
adjustable to the amount of preliminary air required for starting. This 
ensures immediate readiness of the machine for a restart. 
In accordance with another embodiment of the invention, a shut-off slide 
may be provided in the air supply line ahead of the control slide, by 
means of which the air supply to the control slide can be shut off when 
the machine stops. These measures ensure an immediate interruption of the 
air flow in case of emergencies,--an emergency stop so that the sheet 
stack order is not jeopardized. This shut-off slide may be actuated by 
means of a solenoid. There may be simple coupling with diverse monitoring 
devices even over large distances, also ensuring short response times. 
The novel features which are considered as characteristic for the invention 
are set forth in particular in the appended claims. The invention itself, 
however, both as to its construction and its method of operation, together 
with additional objects and advantages thereof, will be best understood 
from the following description of specific embodiments when read in 
connection with the accompany drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows a metering device intended for installation in a sheet feeder 
and is denoted by 1; by means of this metering device the start-up blast 
air supplied during the up-travel of the sheet feeder of a sheet separator 
60 can be metered dependent on the rpm. This avoids that in the lower 
speed ranges, the upper sheets of the sheet stack are blown away because 
of too much air. The metering device 1 comprises a control slide 2, which 
is integrated in the air line leading from a blower as pressure source to 
the sheet separator device as driven machine; the control element 3 of 
this slide is actuated depending on the rpm by means of a centrifugal 
governor indicated at 4. The control element 3 is formed in this case by a 
valve plug located rotatably in a housing block 5 having a suitable 
borehole; this plug is held in lateral housing covers 8, screw-fastened to 
housing block 5, with lateral bearing trunnions 6 and 7. The bearing 
trunnion 7 mounts a crank arm 9 which is provided with an axis-offset 
adjusting rod 10 engaging bushing 11 of the centrifugal governor 4. Thus 
the control element 3 formed by the valve plug can be rotated as a 
function of the rpm of the single-revolution shaft at 12 which operates in 
conjunction with the centrifugal governor 4. Metering devices of this type 
are located to advantage as close as possible to the suction head of the 
sheet feeder, for example, in the area of a side wall. 
During a revolution of shaft 12, bushing 11 is displaced by an amount 
depending on the speed of the shaft in the axial direction of the shaft. 
The crank arm 9, connected to the bearing trunnion 7 of valve plug 3 has 
an adjusting rod 10 offset from the bearing trunnion 7. This rod 10 
engages bushing 11, converting the axial displacement of bushing 11 by 
crank arm 9 into a rotary motion of bearing trunnion 7 and hence of valve 
plug 3. The mode of operation of a crank provided with axially offset 
trunnions is known. The rotary motion of bushing 11 has no influence on 
rod 10 since the rod 10, as shown in FIG. 1, engages a peripheral groove 
of bushing 11. 
The housing block 5, as seen in FIG. 2, has an air intake opening 21 to 
which an air line branch 22 leading to the blower (not shown) is 
connected. The air intake opening 21 diametrally opposite is a coaxial air 
discharge opening 23 of the same cross-section to which another air line 
branch 24 is connected; the latter leads to the sheet separating device 
(not shown). Also, the housing block 5 has another air discharge opening 
25 leading to the outside; it is offset relative to the air intake opening 
by 40.degree.. The air intake opening 21 and the air discharge openings 23 
and 25 can be formed by radial drill holes. In the embodiment shown, the 
air discharge opening 25 is formed by a pocket-like mill cut. To form a 
flow path from the air intake opening 21 to the two air discharge openings 
23 and 25, the valve plug forming control element 3 has a suitable recess 
which in this case is formed by a diametral through-bore 26 of the same 
diameter as the air intake opening 21 and the air discharge opening 23. An 
expansion 27 is present in the vicinity of the side facing the air intake 
opening 21 and the air discharge opening 25 leading to the outside. The 
expansion 27 can be produced by a milling cut inclined relative to the 
axis of the through-bore 26 and of the same diameter as the through-bore 
26 so that the boundary edge 28 of the expansion 27 and the facing edge 29 
of the through-bore 26 subtend the same angles as the outer edges, not 
facing each other, of the air intake opening 21 and the air discharge 
opening 25 leading to the outside. 
In the standard operating position corresponding to the full machine rpm, 
the valve plug 3 is to be held by the centrifugal governor 4 in the 
position indicated by solid lines in FIG. 2. In this operating position, 
the through-bore 26 is lined up with the drill holes forming the air 
intake opening 21 and the air discharge opening 23 leading to the driven 
machine. The expansion 27 is covered and blocked by the adjacent housing 
wall. The full air quantity furnished by the blower is delivered to the 
sheet separating device, without any deflection in the vicinity of the 
control slide 2 of the present invention, so that the line losses in this 
region are eliminated to a high degree. This advantage becomes manifest 
with the relatively low pressures of 1 atm gage since here relatively 
small losses have a relatively high percentage effect on the end result. 
Upon stoppage of the machine, the air supply is interrupted and the valve 
plug 3 is turned by the centrifugal governor 4 into the ready-position 
indicated by broken lines in FIG. 2; here a flow path, formed by expansion 
27 and the adjacent region of through-bore 26, is available from the air 
intake opening 21 to the air discharge opening 25 leading to the outside. 
The air discharge 23 leading to the driven machine in this case is 
entirely, or, as shown in FIG. 2, shut off except for a gap 30 required 
for start-up air. When the air supply is resumed upon starting the 
machine, not the entire air quantity, but only the set start-up air is 
applied to the sheet separating device, the remainder of the air quantity 
furnished by the blower escapes to the outside vai air discharge opening 
25. Because of the inclined position of the through-bore 26 relative to 
the air intake opening 21 there is a slight stagnation which favors escape 
of the remaining air through the air discharge opening 25 leading to the 
outside. Hence, constant delivery blowers can be used without the hazard 
of an overload to excessive backwash. To dampen the noise suitable damping 
elements 31 can be placed on the air discharge opening 25. With increased 
speed, the centrifugal governor 4 acts and turns the valve plug 3 back 
more and more till the position shown by solid lines in FIG. 2 is reached. 
In this position in which the air flowing through the control slide 2 
encounters a straight flow path, the valve plug 3 is held until the next 
machine stop. 
The above-mentioned start-up air depends on the type of paper to be 
handled. For setting gap 30, as shown in FIG. 3, a stop screw 40 may be 
provided where the crank arm 9 with pin 41 strikes, thus restricting the 
adjustment stretch of the valve plug 3. By turning the screw 40, any gap 
position desired can be set. In the embodiment shown, the adjustable stop 
screw 40 in turn is secured by a fixing screw 42. A spring 43 engaging the 
crank arm 9 makes sure that the pin is in contact with the stop screw 
while the machine is at rest. 
To interrupt the air supply upon machine stop, a shut-off slide suggested 
at 44 in FIG. 2 may be provided ahead of a control slide 2; this shut-off 
slide is actuated via a solenoid which in turn may act in conjunction with 
the sheet monitoring devices and can be automatically actuated by them. 
The solenoid 45 is preferably wired so that the unenergized position is 
the closed position of the shut-off slide 44. This makes sure that with an 
accidental current failure the air supply is interrupted in any case. The 
solenoid 45 is preferably arranged so that the solenoid core position 
corresponding to a free air passage for restarting the machine can be set 
by handle 45A. In the embodiment shown, the shut-off slide 44 has a rotary 
flap 46. As shown best by FIG. 4, the flap 46 may be of rectangular shape 
so that the line cross-section of branch 22 of the air line can be 
reliably shut off. Flap 46, as shown in FIG. 4, is fastened and mounted on 
a shaft 47 which rotates in the housing of the shut-off slide 44; this 
shaft 47 has a crank arm 48 which acts via a trunnion 49 with one arm of a 
valve rocker 51 rotating around 50 whose other lever arm has a fork groove 
52 holding a rod 53 connected to the solenoid. The valve rocker 51 permits 
bridging of a relatively long distance and simultaneously an enlargement 
or reduction of the motions of the armature of the solenoid 45. The 
solenoid 45 may, as indicated in FIG. 2, be mounted on the control slide 
2. As shown in FIG. 2, rod 53 can be provided with an engaging piece 54 
which maintains contact with the associate lever arm of the valve rocker 
51 via a spring 55 held by the housing. If the solenoid 45 could be 
accommodated in the narrow area of the shut-off slide 44, it might be 
conceivable to couple the armature directly with crank arm 48. To avoid a 
backwash affecting the blower upon actuation of the shut-off slide 44, 
relief pressure valves (not shown) may be provided in the present 
embodiment. 
The above describes a preferred embodiment of the invention, without 
constituting a restriction. There are a number of possibilities open to 
the expert to adapt the general idea of the invention to the conditions of 
an individual case. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of this invention, and 
therefore, such adaptations should and are intended to be comprehended 
within the meaning and range of equivalence of the following claims.