HK1082462A - Pallet pressure monitor - Google Patents

Description

platen pressure monitor

Technical Field

The present invention relates to pressure monitors. More particularly, the present invention provides a pallet pressure monitor that can easily detect hydraulic pressure applied to a hydraulic system of a machine's pallet without physically connecting to the pallet.

Background

Hydraulic clamping devices are commonly used in manufacturing operations to clamp a workpiece to a fixture or platen so that the workpiece can be machined or otherwise processed. Machining can only be safely performed when secured by forcing pressurized hydraulic fluid into the clamp. Therefore, to protect operators, equipment, and materials from injury, it is important to detect fluid pressure to ensure that the clamps have been actuated.

Existing methods of monitoring such fluid pressure include wiring a pressure probe to a signaling device. However, the detector and the signal transmission device are usually installed at different positions. For example, the detector is typically mounted on a table, while the signaling device is typically mounted at the level of a human eye to signal the operator. This requires cabling between the detector and the signalling means. Unfortunately, such cabling often blocks the way of the operator, preventing the operator from viewing or moving. Furthermore, the cable system is often damaged because it must often be bent during machining, which can lead to fatigue and failure. Thus, cabling can be cumbersome and must be replaced frequently.

Accordingly, there is a need for an improved platen pressure monitor that overcomes the limitations of the prior art.

Disclosure of Invention

The present invention addresses the above-mentioned problems and provides a significant improvement in pressure monitor technology. More particularly, the present invention provides a pallet pressure monitor that can conveniently detect hydraulic pressure applied to a hydraulic system of a machine fixture or pallet without physically connecting to the pallet.

The monitor broadly includes: the hydraulic system includes a pressure sensor for sensing hydraulic pressure within the hydraulic system, a pallet transmitter for monitoring the sensor, and a base unit for receiving status signals from the pallet transmitter indicative of the status of the sensor. The machine preferably includes a platen designed to support the workpiece as it is being machined or otherwise processed. The workpiece is preferably secured to the platen by a plurality of hydraulic clamps that are actuated by forcing pressurized hydraulic fluid into the hydraulic system.

In the preferred embodiment, the detector includes an adjustable pressure switch in fluid communication with the hydraulic system. The switch is preferably adjustable by an adjustment screw to enable a technician to select a pressure setting, such as ten pounds Per Square Inch (PSI). For example, when pressure in the hydraulic system rises, the fluid presses against a diaphragm within the switch. When the pressure reaches a set point, the diaphragm closes a set of contacts within the switch. In this case, the switch operates as a normally open switch and the detector provides a discrete pressure signal representative of the state of the detector.

The pallet transmitter preferably includes a passive Integrated Circuit (IC) that receives power and monitors the detector through a wireless connection to the base unit. For example, the pallet transmitter may receive power in the form of electromagnetic energy that powers both the IC and the detector. The pallet transmitter transmits a status signal over the wireless connection in response to the pressure signal. The status signal may include a serial number that uniquely identifies the pallet transmitter and a status number that reflects the pressure signal. For example, the status number may be one when the contacts of the switch are closed and zero when the contacts of the switch are open.

The receiver unit preferably includes a power input, an Electromagnetic Energy Transmitter (EET) for providing power to the pallet transmitter, a signal receiver for receiving the status signal from the pallet transmitter, and at least one relay output actuated by the signal receiver in accordance with the status signal. The EET preferably converts the power received through the power input device into electromagnetic energy and transmits the electromagnetic energy to the pallet transmitter through the wireless connection. The relay output is preferably electrically connected to an alarm unit, or other signaling device, which alerts the machine operator when the pressure in the hydraulic system is below a set point.

In use, the operator preferably places the workpiece on the platen and actuates the hydraulic system. The pump preferably forces fluid into the hydraulic system, thereby actuating the clamp and the probe. The pallet transmitter monitors the detector substantially continuously and changes the status signal accordingly. The receiver unit substantially continuously receives the status signal and actuates the relay output accordingly. Thus, when the pressure in the hydraulic system reaches a set value, the contacts in the detector are preferably closed, thereby causing a change in the status signal. When the status signal changes, the relay output changes, causing the warning device to indicate that the workpiece is secured to the platen and that it is now safe to machine the workpiece.

Drawings

Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings, wherein:

FIG. 1 is a perspective view of a platen pressure monitor constructed in accordance with a preferred embodiment of the present invention and shown mounted on a machine; and

fig. 2 is a schematic of the combined hydraulic and electronic aspects of the monitor.

Detailed Description

Referring to fig. 1, a preferred platen pressure monitor 10 constructed in accordance with a preferred embodiment of the present invention is shown mounted on a machine 12. Referring also to fig. 2, the monitor 10 broadly includes: a pressure detector 14 for detecting hydraulic pressure within a hydraulic system 16 of the machine; a pallet transmitter 18 for monitoring the detector 14; and a receiver unit 20 for receiving a status signal from the pallet transmitter 18 indicative of the detector status. The machine 12 may be similar to that disclosed in U.S. patent No. 3,998,127, UNIVERSAL MILLING MACHINE (the contents of which are incorporated herein by reference), and preferably includes a platen 22 designed to support a workpiece as the machine 12 machines or otherwise processes the workpiece. The workpiece is preferably secured to the bedplate 22 by a plurality of HYDRAULIC clamps 24, such as those disclosed in U.S. patent No. 5,695,177, "HYDRAULIC SWING clamp HAVING SPEED CONTROL MECHNAISM," the contents of which are incorporated herein by reference.

The workpiece is typically secured to the platen 22 only when pressure is applied to the hydraulic system 16. For example, a pump 23 may be used to actuate the clamp 24 by forcing pressurized hydraulic fluid into the hydraulic system 16. Thus, for safety, the workpiece is preferably machined or otherwise processed by the machine 12 only when pressure is applied to the hydraulic system 16. Accordingly, the monitor 10 of the present invention preferably indicates when it is safe to machine a workpiece by indicating when pressure is applied to the hydraulic system 16.

In the preferred embodiment, the detector 14 includes an adjustable pressure switch in fluid communication with the hydraulic system 16. The switch is preferably adjustable by an adjustment screw and may be similar to those disclosed in U.S. Pat. No. 4,052,574, "PRESSURE SWITCH WITH SNAP-TOGGLE ADJUSTINGMEANS," the contents of which are incorporated herein by reference. The screw enables the technician to select a pressure setting, such as ten pounds Per Square Inch (PSI). For example, as pressure in the hydraulic system 16 increases, the fluid presses against a diaphragm 26 within the switch. When the pressure reaches the set point, the diaphragm 26 preferably closes a set of contacts 28 within the switch. In this case, the switch operates as a normally open switch. Alternatively, the switch may operate as a normally closed switch and open the contacts 28 when the pressure reaches a set point. In either case, the detector 14 provides a discrete pressure signal representative of the detector's status, or the pressure within the hydraulic system 16, as compared to a set point.

The pallet transmitter 18 preferably includes a passive Integrated Circuit (IC) that receives power through a wireless connection to the receiver unit 20. For example, the pallet transmitter 18 may receive power in the form of electromagnetic energy at approximately 126 kilohertz (KHz). The electromagnetic energy is preferably the only power provided to the pallet transmitter 18 and is used to power both the IC and the detector 14.

The IC preferably monitors the probe 14 and responds by transmitting a status signal of approximately 232 megahertz (MHz). The status signal may include a serial number that uniquely identifies the pallet transmitter 18 and a status number that reflects the pressure signal. For example, the status number may be one when the contacts of the switch are closed and zero when the contacts of the switch are open.

The receiver unit 20 preferably includes a power input, an Electromagnetic Energy Transmitter (EET) to provide power to the pallet transmitter 18, a signal receiver to receive the status signal from the pallet transmitter 18, and at least one relay output 30 that is actuated by the signal receiver in accordance with the status signal. The power input device preferably accepts approximately twenty-four volts of power, which may be either direct current or alternating current. The EET preferably converts the power received through the power input device into electromagnetic energy and transmits the electromagnetic energy to the pallet transmitter 18.

Relay output 30 is preferably electrically connected to an alarm unit 32, or other signaling device, that alerts an operator of machine 12 when the pressure in hydraulic system 16 is below a set point. The relay output 30 is preferably capable of withstanding a signal current, such as five amperes dc, so that the relay output 30 can be used to drive almost any signaling device. For example, the alarm unit 32 may include a light, alarm, or other indicating device.

As described above, the receiver unit 20 preferably transmits electromagnetic energy to the pallet transmitter 18, which reacts by transmitting a status signal back to the receiver unit 20. Thus, the separation distance between the pallet transmitter 18 and the receiver unit 20 may be critical. To minimize power requirements and external disturbances, the separation distance is preferably no greater than approximately twelve inches. More specifically, to ensure reliable operation of the monitor 10, the separation distance is preferably between five and eight inches.

It is also important to note that the pallet transmitter 18 is preferably offset from the pallet 22 itself. The pallet 22 is typically made of metal and thus may interfere with the operation of the pallet transmitter 18. Thus, the pallet transmitter 18 is preferably offset from the pallet 22 by an indication of one quarter inch. Although there is theoretically no maximum offset distance, in practice the offset distance is generally limited to approximately eight inches. The offset distance is preferably embodied by an air gap, but may be embodied by any non-metallic material such as plastic.

As described above, the status signal may include a serial number in addition to the status number. Thus, the receiving unit 20 may identify the pallet transmitter 18. It follows that the receiver unit 20 may be used with more than one pallet transmitter 18 and may uniquely identify the pallet transmitters 18. For example, the receiver unit 20 may communicate with a first pallet transmitter monitoring a first detector set at five PSI and a second pallet transmitter monitoring a second detector set at fifty PSI. In this case, the receiver unit 20 may be used to indicate when the pressure within the hydraulic system 16 is below five PSI, between five and fifty PSI, and when fifty PSI is exceeded. In addition, the receiver unit 20 may also communicate with a number of pallet transmitters that monitor a plurality of probes in fluid communication with different hydraulic systems.

While the invention has been described above, it should be understood that various alternatives may be made. For example, the relay output 30 may actually be used to turn the machine 12 on and off to ensure that the workpiece is secured to the platen 22 before machining of the workpiece is permitted. Furthermore, the power input of the receiver unit 20 may accept power at other voltages, depending on the design. Further, if the pallet transmitter 18 and the receiver unit 20 are in communication and the pallet transmitter 18 receives power through a wireless connection, they may use different frequencies. These and other minor modifications are intended to be within the scope of the present invention.

Since the pallet transmitter 18 and receiver unit 20 transmit and receive status signals and electromagnetic energy, one of ordinary skill in the art will recognize that the pallet transmitter 18 and receiver unit 20 must employ some form of antenna. It is important to note that the separation distance and offset referred to above are only critical to the antenna. In the preferred embodiment, the antenna is integral with the pallet transmitter 18 and receiver unit 20. Thus, as described above, a separation distance and offset are applied to the pallet transmitter 18 and receiver unit 20. However, it is not required that the antenna be integral with the pallet transmitter 18 or receiver unit 20. Thus, the antennas may be mounted at the separation distances and offsets referred to above, and the remainder of the pallet transmitter 18 and receiver unit 20 may be mounted at other distances.

In use, an operator preferably places a workpiece on the platen 22 and actuates the hydraulic system 16. The pump 23 preferably forces fluid into the hydraulic system 16 to actuate the clamp 24 and the detector 14. The pallet transmitter 18 substantially continuously monitors the detector 14 and changes the status signal accordingly. The receiver unit 20 receives the status signal substantially continuously and actuates the relay output accordingly. Thus, when the pressure in the hydraulic system 16 reaches a set point, the contacts in the probe 14 are preferably closed, thereby causing a change in the status signal. When the status signal changes, the relay output 30 also changes, thereby causing the warning device 32 to indicate that the workpiece is secured to the platen 22 and that it is now safe to machine the workpiece.

Having thus described the preferred embodiments of the present invention, what is claimed as novel and desired to be protected by letters patent is the following:

Claims (19)

1. A machine operable to process a workpiece, the machine comprising:

a platen operable to support a workpiece;

a plurality of clamps operable to secure a workpiece to the platen;

a hydraulic system operable to actuate the clamp;

a pressure sensor in fluid communication with the hydraulic system and operable to electrically respond to pressure within the hydraulic system;

a pallet transmitter mounted to the pallet, electrically connected to the detector, and operable to indicate the status of the detector; and

a receiver unit mounted at a spaced distance from the pallet transmitter and operable to resolve the status of the detector by wireless connection to the pallet transmitter.

2. The machine of claim 1 wherein the detector is a pressure switch operable to respond when the pressure in the hydraulic system reaches a set point.

3. The machine of claim 1 wherein the detector is an adjustable pressure switch operable to respond when the pressure within the hydraulic system reaches an adjustable set point.

4. The machine of claim 1, wherein the pallet transmitter is wired to the detector such that the detector changes the manner in which the pallet transmitter responds to the receiver unit.

5. The machine of claim 1, wherein the receiver unit transmits the electromagnetic energy substantially continuously.

6. The machine of claim 5 wherein the electromagnetic energy transmitted by the receiver unit powers the pallet transmitter.

7. The machine of claim 1, wherein the pallet transmitter transmits a status signal indicative of the detector's status using only power received from the receiver unit.

8. The machine of claim 1 wherein the separation distance is no greater than eight inches.

9. The machine of claim 1, wherein the receiver unit is stationary and the pallet transmitter moves with the pallet.

10. The machine of claim 1, wherein the receiver unit includes a relay output operable to actuate a signaling device based on the detector status as received by the pallet transmitter.

11. The machine of claim 1 wherein the pallet transmitter transmits a status signal indicative of the status of the detector via the wireless connection.

12. A pallet pressure monitor capable of detecting pressure applied to a hydraulic system of a pallet, the monitor comprising:

a pressure sensor in fluid communication with the hydraulic system and operable to electrically respond to pressure within the hydraulic system;

a pallet transmitter operatively mounted to the pallet, electrically connected to the detector, and indicating the status of the detector; and

a receiver unit operable to be mounted at a spaced distance from the pallet transmitter and to resolve the status of the detector by wireless connection to the pallet transmitter.

13. The monitor of claim 12, wherein the detector is an adjustable pressure switch operable to respond when the pressure within the hydraulic system reaches an adjustable set point.

14. The monitor of claim 12 wherein the pallet transmitter is wired to the detector such that the detector changes the manner in which the pallet transmitter responds to the receiver unit.

15. The monitor as set forth in claim 12, wherein the receiver unit substantially continuously transmits electromagnetic energy for powering the pallet transmitter.

16. The monitor of claim 12, wherein the pallet transmitter transmits a status signal indicative of the detector status using only power received from the receiver unit.

17. The monitor of claim 12 wherein the receiver unit is stationary and the pallet transmitter moves with the pallet.

18. The monitor of claim 12, wherein the receiver unit includes a relay output operable to actuate a signaling device based on the detector status as received by the pallet transmitter.

19. The monitor as set forth in claim 12, wherein the pallet transmitter transmits a status signal indicative of the detector's status via the wireless connection.