FORM - 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TOUCH-BASED SAFETY SYSTEM FOR MACHINE-TOOLS
Applicant:
MAHINDRA & MAHINDRA LIMITED
An Indian Company,
GATEWAY BUILDING, APOLLO BUNDER, MUMBAI -400001,
MAHARASHTRA, INDIA.
Inventors:
A. M. JOSHI
S. K. TENDULKAR
M. M. GURAV
N. S. PATEL
P. YEWALE
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

Field of the Invention
The present invention relates to a safety-system for machine-tools, particularly a touch-based safety-system for machine-tools, more particularly a touch-based safety system for a hydraulic-press or the like, which rapidly disables and/or stops and/or reverses the machine-tool, whenever a machine-tool condition perceived to be dangerous to the operator or neighbouring / personnel is detected.
Background of the Invention
Generally, machine-tools have various cutting tools/surfaces/faces, which can pose extreme hazard on contacting the body or body part/s of the machine-tool operator or any other person in the vicinity of these cutting tools/surfaces/faces, if enough protective measures are not undertaken.
/Conventionally, suitable guards are provided in these machine-tools to physically isolate body or body parts of the persons working on these machine-tools or present in the vicinity thereof.
However, sometimes it may happen during the working of the machine-tools that the body or body part/s of the machine-tool operator or any other person present in the adjoining working area may inadvertently come in contact with the cutters of the machine-tool or rotating or pressing rams of the power presses on shop-floors, whereby serious injuries may be caused to them. / Several safety systems have been devised for machine-tools in order to prevent harms to persons working on shop floors in such situations, which will be briefly discussed below:

Prior Art
US 8336432 Bl discloses a safety system for a rotary saw or other dangerous machine-tools features a flesh-sensing circuit, located on a safety guard surrounding a dangerous machine part, which generates an electronic signal to trigger emergency stopping of the machine before the operator can contact the dangerous machine part. The stopping means preferably employs DC injection, winding current direction reversal and/or electromagnetic motor braking, in the event of detection of operator contact with the safety /guarding device. The system is adapted to be used both with newly-manufactured machine-tools and by retrofitting onto previously-manufactured machine-tools, by in-the-field modifications. However, this requires a safety guard surrounding a dangerous machine part for generating an electronic signal to trigger emergency stopping of the machine before the operator can contact the dangerous machine part.
US 2992420 A discloses a capacity type burglar alarm system for detecting an unauthorized entry, with a first DC source of potential changing from a
/ normal magnitude to another magnitude in response to a condition to be sensed; actuating means excitable by passing current therethrough for initiating an alarm by changing said first potential; a capacitor across said source for precluding operation of said actuating means for changing said potential below a predetermined value thereof regardless of its rate of change. It also includes a second DC source having a magnitude different from the normal magnitude of said first source and a rectifier element to control the current from said second DC source for exciting said actuating means only after said first potential source equals said second potential
/ source by a change in said first potential source in response to a condition to be sensed.

US 2704339 discloses a capacity operated electronic control circuit including a pair of interacting oscillators having a common ground, each
'' oscillator having a tank circuit in the oscillator grid circuit, said tank circuits having the same resonant frequency, each tank circuit comprising a sensing electrode connected to the corresponding oscillator grid and having capacity to ground, the capacity of each tank circuit said capacity to ground, one end of each tank inductor being connected to said ground and the other end being connected to the grid of the corresponding oscillator through a variable capacitor, whereby said electrodes provide a zone of detection for the presence of a foreign object through changes in the capacity of each to said ground whereby the level of oscillation of the corresponding oscillator is
/ lowered from normal in response to the presence of said foreign object in said zone of protection, said electrodes having capacity intercoupling therebetween which results in interaction between the oscillators essential to normal operation of each, and control means connected in the plate circuit of each of said oscillators and responsive to the level of output thereof.
US 2704339 discloses a capacity operated electronic control circuit having two companion loops arranged to detect changes in capacity to ground, such as by the approach of a foreign object, and each arranged to tune one of a /pair of interconnected oscillators, the outputs of which are separately amplified to operate separate relays having armatures arranged in series with each other in a controlled circuit which can be used for a wide variety of purposes, e.g. a safety device for a punch press with one loop placed on the platen around the sections of the die of the press and fastened securely in place and with the companion loop travelling with the ram of the press, both loops having insulator mountings and having a clearance of approximately two inches from the platen and ram respectively.

Disadvantages with the prior art
However, all these safety systems include elaborate circuitry and are costly to manufacture. They also need a separate surface, e.g. safety guard and/or
oscillatory circuits, which cannot be adapted to different requirements.
/
Objects of the Invention
Therefore, there is a long-felt need for a cost-effective and dependable touch-based safety system for the machine-tool, the sensitivity of which can be easily adjusted to act as a sensor circuit as well as a proximity sensor.
Some of the objects of the present invention - satisfied by at least one embodiment of the present invention - are as follows:
I The object of the present invention is to provide a cost-effective touch-based safety system for machine-tools.
An object of the present invention is to provide a touch-based safety system for machine-tools, which can be suitably adjusted to act as a proximity
sensor.
A further object of the present invention is to provide a touch-based safety system for machine-tools working purely on capacitance principle.
/ Another object of the present invention is to provide a touch-based safety system for machine-tools, which uses the surface of the machine-tool itself as the sensing surface.
Yet another object of the present invention is a touch-based safety system for machine-tools, which requires no additional safety guard to protect machine-tool operator.

Still further object of the present invention is to provide a touch-based safety system for machine-tool, wherein the dangerous machine-tool area can be defined as per the machine-safety requirements.
Still another object of the present invention is to provide a touch-based safety system for machine-tools, which operates by detecting a capacitance-change by the touch of the operator and/or the neighbouring personnel.
/ ■ Yet another object of the present invention is to provide a touch-based safety
system for machine-tools, wherein the targeted zone can be defined
according to the type of machine-tool on the machine-tool surfaces itself.
Summary of the Invention
In accordance with the present invention, there is provided a touch-based safety system for machine-tools, in which the system comprises: at least one / human touch sensing circuit adapted for sensing the presence of the body part/s of an operator or personnel present in the vicinity of the portion/s of the machine-tool predefined as dangerous according to the desired safety requirements of the machine-tool and an electrical control safety station. The electrical control safety station and the sensing circuit configured to cooperate to offer electrical control and to display the machine-tool status and to actuate the means for emergency retraction or reversal of dangerous machine-tool portion for the safety of the machine-tool operator or the personnel present in the predefined area adjoining of the machine-tool.
/ Typically, the system comprises at least one sensing element configured on
the dangerous portion of the machine-tool, at least one sensing circuit
adapted to generate an electrical signal for triggering an emergency stopping

/ and/or reversal and/or retraction of the predefined dangerous portion of the machine-tool, at least one opto-driver circuit to provide isolation and to safely drive the load by means of a relay circuit.
Typically, the sensing circuit includes a resistance connected in series to the sensing element on one side and connected to an integrated circuit on the other side, a capacitor connected in parallel to the integrated circuit for adjusting the sensitivity of circuit, the integrated circuit connected to the terminals of an electrical direct current line, the output of the sensing circuit I connected to the input of the opto-driver circuit.
Typically, the opto-driver circuit is grounded to earth via a series resistance and the output of the integrated circuit is connected to the relay circuit.
Typically, the relay circuit includes an auxiliary contact adapted for retracting the dangerous machine-tool portion and a relay coil connected to one of the terminals of an electrical direct current line.
/ Typically, the dangerous portion of the machine-tool is predefined by setting-up the sensing circuit during the initializing phase thereof, based on the risk perception to the operator or personnel present in the vicinity of the machine-tool by coming in contact with the same.
Typically, the sensitivity of circuit can be varied by changing the capacitor.
Typically, the sensing circuit is configured to act as a proximity sensor.

Description of the Invention
Accordingly, a safety system for machine-tools or the like, which poses / substantial risk to the machine-tool operator or to the personnel present in
the neighbouring working areas, is described in accordance with the present
invention. For example, in an embodiment, a touch-based safety system for a
hydraulic press is described here, in which a human sensing circuit is
provided, which is located on the ram of the hydraulic press or in the vicinity
of a part dangerous to the operator or any other personnel present in the
neighbouring working area. This sensing circuit is adapted to generate an
electrical signal for triggering an emergency stopping of the machine-tool
(here, hydraulic press) as soon as the operator or any other personnel
/ inadvertently touches or comes in contact with the part or portion predefined
as dangerous to them. The emergency stopping operation preferably employs triggering a solenoid valve to retract or reverse the direction of motion of the ram or to initiate any other similar action in order to protect the operator or other personnel from any injury which may probably be caused thereby. The touch-based safety system for machine-tools in accordance with the present invention includes one or more of the following components: an auxiliary machine-tool operating control, an -electrical function as well as machine-tool status or condition indicators or displays. These components are / primarily intended for enhancing the safe operation of the machine-tool by
alerting both the machine-tool operator and other personnel present in close proximity who are also witness to machine-tool status.
The safety system is used to prevent improper and dangerous human interference during the machine-tool operation. Conventionally, safety measures like machine-tool safety guards or IR sensors are used to prevent such dangerous human interference. However, to further improve on the

presently available machine-tool safety systems, the inventors have conceived the present invention from the concept of touch screens used in today's smart phones, albeit using electrical principles by sensing the change in capacitance on human contact 'in a predefined area perceived to be dangerous to operator or personnel present in close proximity to a machine-tool.
This touch-based safety system for machine-tools primarily consist of two components, first an electrical control safety station and a human touch sensing circuit, which is adapted for sensing the presence of the body part, e.g. hand/s of an operator or other personnel present in close proximity to a dangerous portion of the machine-tool. This dangerous portion of the machine-tool can be predefined as per the desired safety requirements, by setting up the circuit during its initializing phase itself. These two / components of the touch-based safety system for machine-tools in accordance with the present invention work together to offer control, machine-tool status indicators and on sensing human contact, means for emergency retraction or reversal of the part of the machine-tool predefined to be dangerous for these personnel or taking a suitable alternative action for improving machine-tool safety in accordance with the invention.
It should be understood that the embodiment described herein is merely a preferred embodiment of the present invention. The person skilled in the art . may modify it electrically or electronically according to the requirements of various classes of machine-tools with regard to such parameters as size of the sensing element and its configuration as well as the layout, geometry, isolation thereof. All such modifications are to be considered within the spirit and ambit or scope of the present invention.

Brief Description of the Accompanying Drawings
The present invention will be briefly described with reference to the accompanying drawings, which include:
Figure 1 shows a block diagram, of the touch-based safety system for machine-tools in accordance with the present invention.
/■
Figure 2 shows a circuit diagram of the touch-based safety system for machine-tools in accordance with the present invention.
Detailed Description of the Accompanying Drawings
The touch-based safety system for machine-tools in accordance with the present invention will now be described in more details with reference to the accompanying drawings, without limiting the scope and ambit of the , disclosure in any way.
Figure 1 shows a block diagram of the touch-based safety system for machine-tools in accordance with the present invention, wherein a sensing element 10, a sensing circuit 20, an opto-driver (IC) circuit 30 and a load or electrical control 40 for safe operation of the machine-tool (e.g. hydraulic press, not shown here) are connected in this operational sequence.
Figure 2 shows a circuit diagram of the touch-based safety system for machine-tools in accordance with the present invention, in which the /electrical connections of the sensing element 10, sensing circuit 20, opto-driver circuit 30 and load or electrical control 40 are shown in more details. Initially, an electrical impulse (due to any change in capacitance) is detected by the sensing element 10 fixed on the surface/s of the machine-tool, which

/is predefined based on the risk perception to the operator or personnel present in the vicinity of the machine-tool by coming in contact with the same. This electrical signal is transmitted to the sensing circuit 20. The sensing circuit includes a resistance 22 connected in series to the sensing element 10 on one side and connected to an integrated circuit 26 on the other side. A capacitor 24 is connected in parallel to the integrated circuit 26 for adjusting the sensitivity of circuit. The first terminal of the integrated circuit 26 and thereby of the sensing circuit 20 is connected to one of the terminals of the 5 V DC line. The output of the sensing circuit 20 is connected to input
/of the opto-driver circuit 30, which is grounded to earth via a series resistance 32 selected as per the electrical current necessary to operate the IC internal transistor of the opto-driver IC 30. The isolated output contact of the IC 30 is connected to the relay coil 44 of the relay circuit 40 to be described further. The relay circuit 40 includes an auxiliary contact 42 for retracting the ram and a relay coil 44 connected to one of the terminals of a 24V DC connection. One of the terminals of opto-driver circuit 30 is connected to the other terminal of the 24V DC connection.
, Operation of the Touch-Based Safety System for Machine-tools
1. During initialization, the sensing area which is perceived to be dangerous for the operator or personnel present in close proximity can be predefined according to the safety desired during the machine-tool Initial start-up operation.
2. The sensing circuit is configured based of requirement and it works on the principle of change in capacitance, when any human touches the predefined area of the machine-tool. Here, one end of the sensing circuit where it is connected, acts as one of the plates of capacitor and on human touch, the body acts as the other plate of capacitor.

3. On switching-on the supply to the circuit, any human touch brings
about a change in the capacitance of the circuit and this capacitance
change is detected by the Integrated circuit.
/
4. The circuit employs a burst of charge-transfer cycle to detect the signals. It has low power consumption in the micro-amperes, which dramatically reduces RF emission and thereby lowers its susceptibility to EMI. Internally, the signals are digitally processed to reject impulse noise.
5. Sensitivity of circuit can be varied by changing the capacitor 24.
6. Opto-driver circuit (IC) provides isolation and drives the load. Opto coupling circuit is used and the driver circuit is implemented for safe driving of the load.
7. In the above context, load is meant by any part/portion/component of
the machine-tool, e.g. ram of the hydraulic press in the embodiment
discussed in the above description, which is to be retracted and/or
reversed in order to avoid accident/s during the operation of the
machined-tool fitted with the safety system in accordance with the
invention. / ' Technical advantages and economic significance
a. Sensing area perceived to be dangerous for the operator or personnel
present in close proximity can be predefined during the machine-tool
initial start-up operation.
b. Circuit has low power-consumption in the micro-amperes, thus reducing
RF emission and lowering susceptibility to EMI.

c. Signals are digitally processed internally to reject impulse noise.
d. Sensitivity of circuit can be varied by changing the capacitor.
e. Circuit can selectively act as sensor circuit or as proximity sensor.
/ f. Circuit can be selectively activated or deactivated by the machine-tool operator.
Accordingly, the illustrative exemplary embodiment herein should not be construed as limiting the scope and ambit of the present invention. It is to be understood that the phraseology or terminology employed in this specification is merely for the purpose of description and not for limiting the scope thereof. The exemplary embodiment described in this specification is intended merely to provide an understanding of various manners in which I this embodiment may be used and to further enable the skilled person in the relevant art to practice this invention.
The description provided herein is purely by way of example and illustration. Various features and advantageous details are explained with reference to this non-limiting embodiment in the above description in accordance with the present invention. The descriptions of well-known components and manufacturing and processing techniques are consciously omitted in this specification, so .as not to unnecessarily obscure the
specification.
/
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but

not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
/Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the / values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed on the specific features of the preferred embodiment described here, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiments without departing from the principles of the invention. These and other changes in the preferred embodiment of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim:

1. A touch-based safety system for machine-tools, the system comprising: at least one human touch sensing circuit adapted for sensing the presence of the body part/s of an operator or personnel present in the vicinity of the portion/s of the machine-tool predefined as dangerous according to the desired safety requirements of the machine-tool and an electrical control safety station, wherein said sensing circuit and said electrical control safety station configured to cooperate to offer electrical control and to display the machine-tool status and to actuate the means for emergency retraction or reversal of dangerous machine-tool portion for the safety of the machine-tool operator or the personnel present in the predefined area adjoining of the machine-tool.
2. Touch-based safety system for machine-tools as claimed in claim 1, wherein said system comprises at least one sensing element configured on said dangerous portion of the machine-tool, at least one sensing circuit adapted to generate an electrical signal for triggering an emergency stopping and/or reversal and/or retraction of said predefined
/ dangerous portion of the machine-tool, at least one opto-driver circuit to provide isolation and to safely drive the load by means of a relay circuit.
3. Touch-based safety system for machine-tools as claimed in claim 2,
wherein said sensing circuit includes a resistance connected in series to
the sensing element on one side and connected to an integrated circuit on
the other side, a capacitor connected in parallel to said integrated circuit
for adjusting the sensitivity of circuit, said integrated circuit connected to
the terminals of an electrical direct current line, the output of said
/ sensing circuit connected to the input of said opto-driver circuit.

4. Touch-based safety system for machine-tools as claimed in any of the
preceding claims, wherein said opto-driver circuit is grounded to earth
via a series resistance and the output of said integrated circuit is
/ connected to said relay circuit.
5. Touch-based safety system for machine-tools as claimed in any of the preceding claims, wherein said relay circuit includes an auxiliary contact adapted for retracting said dangerous machine-tool portion and a relay coil connected to one of the terminals of an electrical direct current line.
6. Touch-based safety system for machine-tools as claimed in any of the preceding claims, wherein said dangerous portion of the machine-tool is predefined by setting-up said sensing circuit during the initializing phase thereof, based on the risk perception to the operator or personnel present in the vicinity of the machine-tool by coming in contact with the same.
7. Touch-based safety system for machine-tools as claimed in any of the preceding claims, wherein the sensitivity of circuit can be varied by
changing the capacitor.
8. Touch-based safety system for machine-tools as claimed in any of the
preceding claims, wherein said'sensing circuit is configured to act as a
/ proximity sensor.