Slicer with staged dynamic braking system

A food slicer for automatic operation having a staged dynamic brake for bringing the slicer carriage to rest at a predetermined location in a smooth manner. A sensor or system of sensors are utilized to detect the slicer carriage location. The sensor output is fed through a microprocessor which controls a dynamic brake which in turn acts upon the slicer carriage. The brake acts upon the carriage in two or more stages, so as to bring the carriage to rest in a smooth manner. The invention can also operate to as to bring the carriage to rest in a predetermined location.

BACKGROUND OF THE INVENTION 
The present invention relates to a food slicer for automatic operation and, 
more particularly, to a food slicer with a staged dynamic brake for 
bringing the slicer carriage to rest in a predetermined location, such as 
the home location. 
Commercial food product slicers are widely utilized as rapid and effective 
means of slicing meat, cheese, vegetables and other food products. Food 
product slicers commonly include a motor driven circular slicing blade, 
and a carriage to pass the food product over the blade. A motor is 
normally used to drive both the blade and the carriage. The carriage 
includes a carriage platform and a carriage support arm, and the carriage 
is reciprocatingly mounted such that when the slicer is in operation the 
carriage reciprocates in a linear, horizontal path, passing the food 
product over the blade. Under the prior art, food slicers have no 
controlled braking system. When the operator wished to terminate the 
slicing process, the operator switched the power switch to the off 
position, thereby terminating the power to the slicer motor. Once the 
power was terminated, the carriage continued to coast along its reciprocal 
linear path until it came to rest in an arbitrary location. 
Because the carriages of prior art slicers comes to rest in a variable and 
arbitrary location, several complications arise. For example, food slicers 
are often used to slice meat, such as roast beef, and heat lamps may be 
utilized to keep the food product warm when the slicer is not in 
operation. However, if the final carriage resting position is 
undetermined, the most efficient location of where to aim the heat lamp 
also remains undetermined. This uncertainty reduces the utility and 
effectiveness of the heat lamp. 
Another drawback with the prior art slicers is due to the fact that the 
slicers may leave a piece of food dangling from the food loaf. When the 
carriage coasts to an arbitrary position, it can come to rest in a 
position where the blade is embedded in the food product such that it has 
made a partial cut of the food product, and the partial slice is left 
hanging from the food product loaf. This leaves the slicer and food 
product in a unattractive position for customers and consumers. The 
situation may additionally cause the partial slice to be wasted if it is 
left exposed to open air for too long. 
A further drawback with the prior art slicers is due to the fact that when 
the food slicer operator wishes to replace or replenish the food product 
on the carriage, it is most convenient to have the carriage located as 
close to the operator as possible (termed the "home" position). Under the 
prior art, the carriage is often located in an inconvenient position, and 
the operator will have to move the carriage to the home position under his 
or her own power. 
Accordingly, there exists the need for a food slicer that can return the 
carriage of a food slicer to a predetermined location. There also exists a 
need for a food slicer that can return the carriage to a predetermined 
location, where the predetermined location is the home position. 
The applicants have developed an invention that will return the carriage of 
a food slicer to any predetermined location along the carriage path, 
including the home position. In the course of this discovery, the 
applicants further determined that when the carriage of a food slicer is 
brought to a sudden stop, the force of the braking procedure places a 
severe strain upon the internal mechanical components of the slicer. It 
was discovered that sudden one-step braking causes wear on the system and 
creates an undesirable clatter when the brake is applied. Accordingly, 
there exists the need for a food slicer that can bring the carriage to 
rest in a predetermined location in a smooth manner so as to avoid 
excessive wear on the internal mechanical components. 
SUMMARY OF THE INVENTION 
The present invention is a food slicer with a dynamic brake for bringing 
the slicer carriage to rest at a predetermined location in a smooth 
manner. The slicer includes a base, a circular rotating blade, a brake 
activation switch, a braking system, a carriage. The carriage includes a 
carriage platform and a carriage support arm, and is mounted for lateral 
reciprocating motion along a linear path to bring the food product into 
contact with the blade. 
The braking system utilized in accordance with the present invention 
employs a sensor, or a network of sensors, to detect the location of the 
carriage. The sensor inputs are fed into a microprocessor or other logic 
device, which uses the sensor inputs to trigger the braking system such 
that the carriage is brought to rest in a predetermined location. 
The present invention provides a food slicer for automatic operation food 
slicer for automatic operation, comprising a base; a circular blade 
mounted for rotation on the base; a carriage reciprocatingly mounted on 
the base, and being adapted to travel along a linear path crossing the 
blade, and having a surface adapted to support a food product and to bring 
the food product into contact with the blade; a motor drivingly connected 
to the carriage to produce the reciprocating motion of the carriage along 
the path, wherein the path of the carriage constitutes a linear segment 
with two end points, wherein the endpoint of the path further from the 
blade is designated the home position, and wherein the end point nearer to 
the blade is designated the knife position, and when the carriage is 
travelling from the home position to the knife position the carriage is 
termed to be travelling in the away direction, and when the carriage is 
travelling from the knife position to the home position the carriage is 
termed to be travelling in the toward direction; a sensor for detecting 
the position of the carriage along the path, with the sensor having a 
sensor output, wherein the sensor includes two positive feedback location 
sensors, wherein a first one of the positive feedback location sensors is 
located nearer to the knife position, and wherein a second one of the 
positive location feedback sensor is located nearer to the home position; 
a brake, responsive to the sensor output, for bringing the carriage to 
rest at or near a predetermined location along the path, wherein the brake 
is applied in a plurality of stages as the carriage travels along the 
path, the plurality of braking stages having a final brake stage, wherein 
the final brake stage is applied when the carriage is proximate to the 
predetermined location, the final brake stage operating so as to bring the 
carriage to rest at or near the predetermined location; a brake activation 
switch that can be activated, wherein the brake brings the carriage to 
rest after the brake activation switch is activated. 
The invention further provides a method for braking the carriage of a food 
slicer, the slicer having a base, a blade, a sensor for detecting the 
location of the carriage, wherein the sensor includes two positive 
feedback location sensors with a sensor output, wherein a first one of the 
positive feedback location sensors is located nearer to the knife 
position, and wherein a second one of the positive location feedback 
sensor is located nearer to the home position, and a brake, the carriage 
being reciprocatingly mounted on the base, the carriage being adapted to 
travel along a linear path and having a surface adapted to support a food 
product and bring the food product into contact with the blade, the slicer 
further having a motor drivingly connected to the carriage to produce the 
reciprocating motion of the carriage along the path, wherein the path of 
the carriage constitutes a linear segment with two end points, wherein the 
endpoint of the carriage path further from the blade is designated the 
home position, and wherein the end point of the carriage path nearer to 
the blade is designated the knife position, and when the carriage is 
travelling in a path from the home position to the knife position the 
carriage is termed to be travelling in the away direction, the method 
comprising the steps of: detecting the location of the carriage along the 
carriage path with the sensor; activating the brake in response to the 
sensor output, the brake acting on the carriage to bring the carriage to 
rest, wherein the brake is applied in a plurality of stages as the 
carriage travels along the linear path, the plurality of stages having a 
final stage, the final stage being applied when the carriage is proximate 
to the predetermined location whereby the final stage operates so as to 
bring the carriage to rest at or near the predetermined location. 
Other objects and advantages of the present invention will become apparent 
from the following description, the accompanying drawing and the appended 
claims.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 shows a food slicer 10 of the present invention. However, it should 
be here noted that the invention may be utilized in almost any 
configuration of food slicer, and the invention is not limited to the 
forms illustrated herein. The slicer 10 includes a base 12, a circular 
rotating blade 14, an on/off switch 15, a brake activation switch 16, and 
a carriage 17. The carriage 17 includes a carriage support arm 21 and a 
carriage platform 18 for supporting the food product. The carriage 17 is 
mounted for lateral reciprocating motion along a linear path to bring the 
food product into contact with the blade. The carriage support arm 21 is 
rigidly mounted to the carriage platform 18 and extends in the downward 
direction. The platform 18, carriage 17, and carriage support arm 21 
reciprocatingly travel in a path that constitutes a line segment, 
represented as line segment 23, with two end points 22, 24. The endpoint 
of the carriage path that is nearer to the operator (not shown), and 
further from the blade, is termed the home position 22. The endpoint that 
is closer to the blade is termed the knife position 24. 
The linear path along which the carriage reciprocates is resolved into two 
component paths 25, 26. When the carriage is travelling from the home 
position toward the knife position, it is termed to be travelling in the 
away path 25. On the other hand, when the carriage is travelling from the 
knife position toward the home position, it is termed to be travelling in 
the toward path 26. 
In a preferred embodiment of the invention, two positive location feedback 
sensors or switches 28, 29 are utilized in conjunction with the braking 
system. The sensors (also termed "switches" interchangeably herein) are 
located along the reciprocating path of the carriage support arm 21 so as 
to detect the linear position of the carriage support arm 21, and thus the 
carriage 17. 
When the carriage support arm passes by a particular sensor, that sensor is 
termed to be "activated" and it provides feedback to the microprocessor or 
other logic device (not shown). In accordance with the present invention, 
the home sensor, or home switch, 28 is located proximate to the home 
position, but slightly offset in the blade (or knife) direction from the 
home position. Correspondingly, the knife sensor, or knife switch, 29 is 
located proximate to the knife position, but slightly offset in the home 
direction from the knife position. 
The braking system is designed such that it commences the braking cycle 
only when the carriage is travelling in the away path 25, regardless of 
the carriage location when the operator signals the braking to begin. This 
is accomplished by programming the microprocessor or other logic device 
(not shown) to commence the braking cycle after the brake activation 
switch 16 has been activated by the operator; and 1) the home sensor 28 
has been activated, followed by 2) activation of the knife sensor 29. In 
other words, after the operator has activated the system, once when the 
knife sensor 29 is activated after the home sensor 28 has been activated, 
the braking cycle is commenced. In this manner, it is ensured the carriage 
16 is travelling in the away path 25 when the braking cycle is commenced. 
It should be noted that all of the steps described herein are controlled 
by a microprocessor or logic circuitry that receives sensor outputs and 
relays the outputs to the brake system. However, those skilled in the art 
will appreciate that any of a number of different logic processors may be 
used for the same purpose. 
After the carriage passes the knife sensor location in the away path, the 
power to the slicer motor is terminated. There is then a delay of a 
predetermined length of time, e.g., about 75 milliseconds, to allow A/C 
current in the motor to decay before the first dynamic braking stage is 
applied. 
The next step is the application of the first of two braking stages using a 
dynamic brake. Dynamic brakes are well known in the art, and utilize the 
motor that normally drives an item to operate as a brake on the same item 
when a direct current is applied across the motor. In the present 
invention, the dynamic brake is applied by passing a direct current across 
the A/C induction driving motor, which causes the motor to act as a 
dynamic brake to stop or slow down the carriage. 
After the predetermined delay (75 milliseconds in the present embodiment), 
the first dynamic braking stage is applied in what is termed the "soft" 
braking stage. In one embodiment of the present invention, about 1.6 amps 
of direct current is utilized during the soft braking stage. The level of 
applied current may be varied to account for various factors, such as 
differing slicer configurations (such as carriage weight), variations in 
the motor specifications, and differing pre-braking speeds of the 
carriage. 
Once the soft brake is activated, it is continuously applied as the 
carriage travels along its linear path until the carriage support arm 
reaches the home sensor 28. At this time the carriage will have reached 
the end of the away path, reversed direction, and will be travelling in 
the toward path all while the soft brake is applied. The soft brake stage 
normally slows down the carriage, but does not bring it to a stop. When 
the carriage reaches the home sensor 28, that sensor is activated, and it 
sends its output to the microprocessor. The microprocessor then actuates 
the "hard" brake, which is applied by increasing the level of current to 
the dynamic brake, thus increasing the applied braking force. In the 
current embodiment, the hard brake is applied at 2.5 amps of current. The 
hard brake is applied for a predetermined amount of time sufficient to 
ensure that the carriage is brought to rest. In the present embodiment, 
the hard brake is applied for roughly 1.5 seconds. 
In the current embodiment of the invention, when the carriage nears the 
home position 22, the home sensor 28 is activated and the hard brake is 
applied at that time. The distance between the home sensor 28 and the home 
position 22 is such that when the hard brake is applied, the carriage is 
brought to rest at or near the home position. Furthermore, the two-staged 
braking of the present invention allows for smooth braking, and the wear 
on the internal components of the slicer due to sudden one-step braking is 
substantially reduced. 
The flow chart diagram of FIG. 2 demonstrates the steps utilized in one 
embodiment of the current invention. At the first step, shown as step 30, 
the timer, ports, and systems are all initialized. At step 32, termed the 
"reset" step, the outputs are set up, as the carriage motor is enabled and 
the brake is switched to the OFF position. Step 34 is a decision step: if 
the carriage motor is on, the system progresses to step 36, and if the 
motor is not on, step 34 returns the system to the reset step 32. 
Steps 38 and 40 form a control loop where the system resides until either 
the brake activation switch is pressed (which the operator presses to 
activate the braking cycle), or until the carriage motor is turned off. 
The brake activation switch is termed the "Start/Slice Switch" in FIG. 2. 
The system resides in this loop while the actual slicing of the food 
product is executed. The system exits this loop when either the brake 
activation switch is pressed by the operator or when the power to the 
carriage motor is terminated. If the brake activation switch is pressed, 
the system progresses to the next step of the flow chart via step 38. If 
the carriage motor is off, the system returns to the reset step 32 via 
step 40. 
Steps 42 and 44 form another control loop, which operates so as to ensure 
that the home switch is activated before the system continues with the 
braking cycle. Ensuring that the home switch is activated is the first of 
the two steps carried out to ensure that the carriage is travelling in the 
away path before braking begins. The system exits this loop either when 
the home switch is activated, or when the carriage motor is turned off. If 
the home switch is activated, this means that the carriage arm has reach 
the home sensor and the system progresses to the next step via step 42. On 
the other hand, if the carriage motor is switched off while the system is 
in this loop, step 44 returns the system to the reset step 32. 
Steps 46 and 48 form a similar control loop to ensure that the knife switch 
is activated before the system advances. The system exit the loop via step 
46 when the knife switch is activated, or via step 48 when the carriage 
motor is switched off. The control loops of steps 42 and 44 and steps 46 
and 48 operate so as to ensure that the home switch is activated followed 
by the activation of the knife switch, before the brake is applied. In 
this manner, it is ensured that the carriage is travelling in the away 
path before the braking cycle is continued. 
After the system passes through step 46, the carriage motor is turned OFF 
at step 52. There is then delay (e.g. 75 milliseconds) at step 54 to allow 
the current in the carriage motor to decay before the dynamic brake is 
applied. 
Step 56 is the implementation of the soft brake, where the dynamic brake is 
activated and held at 1.6 amps in this particular embodiment. Step 58 
starts the timeout timer, which is used to switch the braking system OFF 
if the carriage support arm does not reach the home sensor within a 
predetermined amount of time after the application of the soft brake. The 
timeout timer is used to ensure that the system does not remain stuck in 
the soft brake stage if the carriage should not reach the home sensor for 
some reason. 
Steps 60 and 62 form a control loop which the system exits either when the 
home sensor is activated by the passing of the carriage support arm, or 
when the timeout timer signals the system at step 62 to return to the 
reset step 32. If the carriage support arm reaches the home sensor, step 
60 advances the system to step 64. Otherwise, if the timeout timer (set at 
6 second in the current embodiment) expires, the system is returned to the 
reset step 32. 
At step 64, the hard brake is applied in the form of a dynamic brake 
operated at 2.5 amps of current in the existing embodiment. At step 68, 
the brake timer, which controls the length of application of the hard 
brake, is started. Step 70 is a one-step loop in which the system resides 
until the brake timer reaches zero. The brake timer ensures that the hard 
brake is applied for a minimum length of time, which can vary, but in the 
present embodiment is about 1.5 seconds. At step 72, the brake is switched 
to the OFF position, followed by a delay (e.g. 20 milliseconds) to ensure 
that no braking force is being applied when the system progresses to the 
next step. At step 76, the carriage motor is enabled, and the system is 
then returned to the reset position at step 32. Once all of the above 
steps in the above-described embodiment have been carried out, the slicer 
carriage will have been brought to rest in the home position in a smooth 
manner, and the system is once again ready to begin slicing operations. 
In an alternative embodiment of the invention, the carriage may be brought 
to rest at any predetermined location along the carriage path. The 
microprocessor can be easily programmed and the braking system adjusted so 
as to bring the carriage to rest at any predetermined location along the 
carriage path. The braking cycles and applied braking forces may also be 
varied by providing a differing number of braking stages, or altering the 
force and/or length of application of each braking stage. Furthermore, a 
single or multiple brake stages may be applied in a "ramp" force profile, 
where the force of the applied brake begins at a low level and increases 
with time. This ramp force profile brake may be used to decelerate the 
carriage so that it is brought to rest in a smooth manner. 
While the forms of apparatus herein described constitute a preferred 
embodiment of the invention, it is to be understood that the present 
invention is not limited to these precise forms and that changes may be 
made therein without departing from the scope of the invention.