Patent Description:
Often when heavier machinery is used for applications such as construction, forestry, demolition or unbuilding and so on, various tools need to be connected to such machines for different purposes. In many cases tool holders are used for such applications, whereby tool holders act as intermediate devices that couple to the machine in a more permanent way, for example screwed and bolted, and to various tools in a releasable way for instance using a hydraulic or pneumatic system as described herein. Such tool holders are typically designed to be used with the hydraulic system and/or the electric system of the machine and in many cases these tools connect the hydraulic system and/or the electric system of the machine to the hydraulic components and/or electronic components of the tool. Since these tool holders also and in particular provide a mechanical coupling between the machine and the tool, safety is always a concern in particular the safety of the mechanical coupling, especially since these mechanical couplings usually are performed automatically from the cabin of the machine by the operator. This means that even though the operator can, at least from a distance/cabin, visually check the connection between the tool holder there is always a risk that the mechanical connection is not established in a safe manner. The mechanical connection of such tool holders is typically established by using a hydraulic system having a coupling mechanism, whereby the coupling mechanism is coupled to at least one hydraulic cylinder. In many cases the locking mechanism further comprises a hook shaped element and the hydraulic cylinder is connected to an arm. The tool typically comprises two brackets, for example in the form of rods, arranged at a distance to one another so that the hook shaped element of the locking mechanism can engage one bracket and the arm the other bracket by extending upon movement of the hydraulic cylinder. During the extension movement of the arm errors can occur, which errors can lead to unsafe connections between tool and tool holder and therewith may risk injury of personnel or damage of equipment. Attempts have been made to survey the mechanical couplings between tool holder and tools as disclosed in <CIT> and <CIT>.

<CIT> is built up as described above, whereby the tool holder comprises a hook shaped element or cut-out and an arm or locking plate that can be moved by a hydraulic cylinder (c. <FIG>) whereby a rod is connected to the cylinder. The rod comprises a metal ring that triggers an inductive sensor when the hydraulic cylinder and the locking element are in a closed position as shown in <FIG>. In order to detect that the second fastening pin is correctly engaged another inductive sensor is present that detects if the second fastening pin is snug embedded in a receiving portion. The solution disclosed in <CIT> requires a special setup with the rod comprising the metal ring, whereby the rod is also connected to the hydraulic cylinder. In addition, the situation where the cylinder is fully extended and fully retracted cannot be detected, in both positions none of the sensors will indicate contact.

<CIT> discloses another safety system for such a tool holder, which aims to determine a position of a piston of the hydraulic cylinder by measuring the amount of hydraulic fluid that is moved. The amount of hydraulic fluid moved is directly proportional to the stroke length of the piston. In order to measure the displaced hydraulic fluid a hydraulic supply line is provided with a restriction and a pressure sensor on either side of the restriction. Based on Bernoulli's equation the flow through the restriction can be determined and therewith the volume of the displaced hydraulic fluid and finally the stroke length. This restriction comes with certain challenges, one being that it increases the hydraulic pressure in the system and therewith the hydraulic system requires more energy.

A system for observing stroke length in hydraulic cylinders via pressure sensors is further shown in <CIT>, however the pressure cannot be detected on either side of the piston since the sensors are arranged in the hydraulic system and not directly at the hydraulic cylinder with channels into the pressure chamber. This also means that the seal in <CIT> does not move over the openings of the channels that are connected to pressure sensors. In addition, the <CIT> does not allow to detect four different states of the safety system but only two different states. <CIT> shows a safety system being able to detect a locked state.

In light of the above the present invention seeks to provide an improved safety system for a machine.

An object of the present invention is to provide a safety system for a machine that is robust, versatile, accurate and reliable.

In view of the above-mentioned challenges the inventors of the present invention have discovered that it is possible to detect different states of a hydraulic cylinder versus a coupling mechanism in a tool holder or the like by using at least one pressure sensor that is measuring the pressure in a pressure chamber of the hydraulic cylinder via a first channel into the pressure chamber. The inventors have discovered that this is possible, if a seal device is used that can withstand high pressures and that can move over or across openings that lead into the pressure chamber of the hydraulic cylinder. The seal device moves over the opening of the channel when the piston of the hydraulic cylinder is moved for locking and unlocking a tool or the like on the tool holder. For the described purpose, the inventors have discovered that it is possible to either use a second pressure sensor also directly coupled to the pressure chamber via a channel, whereby a first channel of the first pressure sensor and a second channel of the second pressure sensor and in particular openings of the first and second channels into the pressure chamber of the hydraulic cylinder are spaced apart as seen in a longitudinal direction of the hydraulic cylinder. Alternatively the inventors have discovered that a bypass channel in combination with the first pressure sensor may be used to detect various states of the coupling mechanism and the piston, respectively. The two openings of the bypass channel into the pressure chamber of the hydraulic cylinder are thereby also spaced apart longitudinally from one another and from the first channel. Finally, the inventors have discovered that it is possible to detected various states of the coupling mechanism in combination with a reader on a reversing valve arranged in a hydraulic system, in particular four states namely piston in locked position state, piston activated but blocked state, piston in fully retracted state and piston in fully extended state. As an alternative to the reader, the inventors have further discovered that a third pressure sensor arranged close to or at the hydraulic supply line of the a head side of the pressure chamber can be used to differentiate a piston fully extended state and a piston fully retracted state.

Disclosed herein is a safety system or tool holder for a machine comprising:.

The seal device is designed to move a plurality of times over openings of the first and second channels and wherein at least one different states of the safety system can be detected via the first and second pressure sensors, namely piston in locked position state.

Using this solution, no additional or extra system is required for determining a position of the coupling mechanism of a tool holder. Also, no restriction in the hydraulic system is needed to detect positions of a cylinder via volume of displaced hydraulic fluid, which means that a more efficient system is used and employed. Using the safety system directly on the hydraulic system as it is, further increases simplicity and therewith reliability of the safety system.

In an embodiment the first pressure sensor senses a pressure P1 and the second pressure sensor senses a pressure P2 and wherein a piston in locked position state is detected when: P1<P2.

During connection of a tool to the tool holder this may help an operator or electronic system of the machine to detect when a tool is successfully and safely coupled to the tool holder.

In a further embodiment the hydraulic fluid reservoir has a reservoir pressure Pres, which is lower than pressure generated by the pressurizing device, wherein the piston activated but blocked state is detected when: P1 = P2 = Pres.

This is one of the dangerous use cases, which needs to be detected. The operator may not spot this state and assume that the tool is correctly locked to the tool holder.

The detection of the above states is increasing safety of the tool holder and therewith the entire application. The differentiation and detection of further states are described referring to the figures.

The invention is now described in more detail referring to the figures.

The present invention will now be described, for exemplary purposes, in more detail by way of an embodiment(s) and with reference to the enclosed drawings, in which:.

<FIG> schematically illustrates a tool holder <NUM> and a tool <NUM> that can be connected to one another via a coupling system <NUM>. The tool holder <NUM> is typically coupled to a machine, for example an excavator or forestry machine or the like. The tool <NUM> or tool adapter <NUM> is typically arranged on a tool such as a shovel, forestry tool, cutter, compactor or the like. The tool <NUM> or tool adapter <NUM> is designed so that it can be coupled to the tool holder <NUM> automatically without manual interreference of an operator at the actual tool <NUM> or tool holder <NUM>. The coupling of the tool holder <NUM> to the tool <NUM> is established by a coupling mechanism <NUM> comprising at least one hydraulic or pneumatic cylinder <NUM> (c. <FIG> and <FIG>) connected to lock fingers <NUM> or lock protrusion and hook shaped cut outs <NUM> and at least partially hook shaped cut outs <NUM>' on the tool holder <NUM> and a pair of brackets <NUM> on the tool <NUM> or tool adapter <NUM>. In <FIG> the lock fingers <NUM> are shown in an at least partially extended state, thus with the hydraulic cylinder <NUM> at least partially extended. When the tool adapter <NUM> is connected to the tool holder <NUM> then the hook shaped cut outs <NUM> are engaged first in one of the brackets <NUM>. As soon as the hook shaped cut outs <NUM> have securely engaged the tool adapter <NUM> the tool adapter <NUM> or tool <NUM> can be lifted and tilted by the machine via the tool holder <NUM> so that the at least partially hook shaped cut outs <NUM>' can engage the other of the pair of brackets <NUM>, when the lock fingers <NUM> are retracted and typically with the help of gravity. Once the other of the pair of brackets <NUM> is engaged in the at least partially hook shaped cut outs <NUM>' the lock fingers <NUM> can be extended so that they lock both brackets <NUM> of the pair of brackets <NUM> securely and the tool can be used by the operator. The coupling does not necessarily need to be established by lifting the tool <NUM>, tilting it on the ground or just smoothly coupling while the tool is laying on the ground may be enough to connect both the pair of brackets <NUM> to the tool holder <NUM> via the coupling mechanism <NUM>.

The pressure provided by the pressurizing device <NUM> is called system pressure Psyst. The pressure present in the tank <NUM> or reservoir is called reservoir pressure Pres. The system pressure Psyst is typically higher than the reservoir pressure Pres as it is used to power the system and move the cylinders in and out.

During the connection of the tool holder <NUM> to the tool adapter <NUM>, it is beneficial if the operator can actually see and observe the status of the coupling mechanism <NUM> so that it can be determined whether or not the tool <NUM> is securely coupled to the tool holder <NUM> or if there is a problem. The present invention is directed towards such issues and potential problems concerning the connection of the tool <NUM> to the tool holder <NUM>. In order to better survey and observe the connection between tool holder <NUM> and tool <NUM> embodiments of a safety system for a machine or a tool holder <NUM> is herewith described referring to <FIG>.

<FIG> illustrates, schematically, a hydraulic system <NUM> for a machine and shows the hydraulic cylinders <NUM> for the lock fingers <NUM> according to <FIG>. It consists of two hydraulic cylinders <NUM> each having a rod <NUM> and a head <NUM> which form the piston or plunger <NUM>. Each rod <NUM> is connected with a respective lock finger <NUM> (c. The hydraulic medium supply means comprises a tank <NUM>, a pressurizing device <NUM>, for example in the form of a pump or hydraulic pump, a supply line <NUM>, and a return line <NUM>. A reversing valve <NUM> connects the pressurizing device <NUM> with either the supply line <NUM> or the return line <NUM>. In the shown position of the reversing valve <NUM>, the pressurizing device <NUM> is connected with the supply line <NUM>.

From the supply line <NUM>, the hydraulic fluid, usually oil, is distributed to a respective branch line <NUM> via a respective non-return valve <NUM> to each of the pressure sides of the hydraulic cylinders <NUM>. Via a respective branch line <NUM>, the return line <NUM> is connected with each of the return sides of the hydraulic cylinders <NUM>. The branch lines <NUM>, <NUM> may also be denoted as first and second hydraulic lines <NUM>, <NUM>.

<FIG> further illustrates the safety system <NUM> comprising a first pressure sensor <NUM> and a second pressure sensor <NUM>. The first and second pressure sensors <NUM>, <NUM> are arranged so that they communicate with a pressure chamber <NUM> of the hydraulic cylinder <NUM> via a first channel <NUM> for the first pressure sensor <NUM> and a second channel <NUM> for the second pressure sensor <NUM>. The first and second pressure sensors <NUM>, <NUM> are designed to detect the pressure in the pressure chamber <NUM> on either side of the head <NUM> of the piston <NUM> depending on the position of the piston and the head <NUM>, respectively. By detecting the pressure in the pressure chamber <NUM> various states of the coupling mechanism <NUM> can be detected as further explained herein. In order to detect these various states, a first opening <NUM> (c. <FIG>) of the first channel <NUM> of the first pressure sensor <NUM> and the second opening <NUM> (c. <FIG>) of the second channel <NUM> of the second pressure sensor <NUM> need to be spaced apart longitudinally, as seen along the longitudinal axis defined by the hydraulic cylinder <NUM>. The safety system <NUM> allows to detect several states of the coupling mechanism <NUM> and these states will now be described referring to <FIG>. It is to be noted that the safety system <NUM> is illustrated to be arranged on one of the pairs of hydraulic cylinders <NUM> in <FIG>.

The safety system <NUM> may however also be installed on both cylinders <NUM> for redundancy and/or additional safety purposes. Further the coupling mechanism <NUM> may only comprise one hydraulic cylinder (not shown) or more than two hydraulic cylinders (not shown).

<FIG> further illustrates a processor <NUM> connected to the first pressure sensor <NUM>, the second pressure sensor <NUM> and the reader of the reversing valve <NUM> or the reversing valve <NUM> (dashed line in <FIG>) and/or the third pressure sensor (not shown in <FIG>).

Referring to <FIG>, similar reference numbers are denoting the same or similar components as <FIG>, respectively, a coupling mechanism <NUM> and a safety system <NUM> is shown. In figure the coupling mechanism <NUM> and the piston <NUM>, respectively, is shown in a locked position. As can be seen in <FIG>, the lock fingers <NUM> lock and engage one of the brackets <NUM> of the tool adapter <NUM> or tool <NUM> and push it snug into the partial hook-shaped cut out <NUM>' while the other of the brackets <NUM> is fully engaged in the hook shaped cut out <NUM> for a secure coupling of the tool <NUM>.

The head <NUM> comprises a seal device <NUM> designed to divide the pressure chamber <NUM> into two compartments and also designed to be able to move over openings <NUM>, <NUM> of the first and second channels <NUM>, <NUM> that connect the first and second pressure sensors <NUM>, <NUM> with the pressure chamber <NUM>. In the state illustrated in <FIG>, namely the piston <NUM> in locked state, the piston <NUM> is extended but not fully extended and the lock fingers <NUM> engage the bracket <NUM> while the other bracket <NUM> is fully engaged in the hook-shaped cut out <NUM>. In the piston in the locked state, the hydraulics push the piston <NUM> towards a head side <NUM> of the pressure chamber <NUM>. The head side is the side of the pressure chamber <NUM> that is closest to the lock fingers <NUM>. The bracket <NUM> prohibits further movement of the piston <NUM> by blocking the lock fingers <NUM> from further extension due to a form fit between lock fingers <NUM> and bracket <NUM>. In this situation a first pressure P1 sensed at the first pressure sensor <NUM> is smaller than a second pressure P2 sensed at the second pressure sensor <NUM>.

In order for the pressure sensing to work smoothly it is of importance that the seal is designed to be able to slide over the openings <NUM>, <NUM> of the first and second channels <NUM>, <NUM>, respectively. The seal device <NUM> can handle up to <NUM> bar in pressure and comprises an O-ring and seal ring. The O-ring and the seal ring are thereby embedded in a groove in the head <NUM> so that the O-ring is arranged at the or close to the bottom of the groove and the seal ring on an outer side of the O-ring. During movement the O-ring can thereby move and provide space to the seal ring when the head <NUM> is sliding over one of the openings <NUM>, <NUM>. Typically the O-ring is made of a softer material than the seal ring. Any other type of seal device that is suitable to slide a plurality of times over an opening in the hydraulic cylinder when the plunger or piston of the hydraulic cylinder is moving can be employed and used in the invention present herein.

In view of <FIG>, the piston in locked state can therewith being detected by P1 < P2. It is to be noted that the reversing valve <NUM> is connected to a reader for determining a position of the reversing valve whereby the reversing valve can be moved between:.

Thus, in the situation according to <FIG>, the reversing valve <NUM> is in the first position connecting the head side with the supply line <NUM> (not shown in <FIG>) and the pressurizing device <NUM> (not shown in <FIG>) for locking the bracket <NUM> in the hook-shaped cut-out <NUM>. The first pressure P1 will correspond to the tank pressure Pres and the second pressure P2 to the system pressure Psyst. The reversing valve <NUM> is however not needed to determine the piston <NUM> in locked state.

Referring to <FIG> the other states or position of the piston <NUM> are herewith described. It can however be summarized that the other states basically all refer to an incorrect locking of the brackets <NUM> in the hook-shaped cut-outs <NUM> and at least partially hooked shaped cut-outs <NUM>'.

<FIG> illustrates the piston <NUM> in activated but blocked state in which the piston <NUM> is supposed to extended but the lock fingers <NUM> are blocked by the bracket <NUM> so that the first pressure P1 sensed at the first pressure sensor <NUM> is the same as the second pressure P2 sensed at the second pressure sensor <NUM> and whereby the first pressure P1 and the second pressure P2 correspond to the reservoir pressure Pres (c. <FIG>) provided by the pressurizing device <NUM>. This state, piston <NUM> activated but blocked state is dangerous and correspondingly signalled to the operated for example via a display and/or acoustically and/or haptically.

Additionally, the reversing valve <NUM> is in the first position connecting the head side with the pressurizing device <NUM> and the supply line <NUM>, respectively (c.

<FIG> illustrates the piston <NUM> in fully extended state, whereby the sensed first pressure P1 and the sensed second pressure P2 have the same value and also correspond to the system pressure Psyst and the reversing valve <NUM> is in the first position connecting the head side with the pressurizing device <NUM> and the supply line <NUM>, respectively.

Finally <FIG> illustrates the piston <NUM> in fully retracted state, whereby the first pressure P1 and the second pressure P2 are the same and correspond to the system pressure Psyst. The reversing valve <NUM> is in the second position connecting the rod side <NUM> with the pressurizing device <NUM> and the supply line <NUM>, respectively.

Referring back to <FIG>, Aalternatively, to the reader at the reversing valve <NUM>, a third pressure sensor <NUM> for sensing a third pressure P3 may be installed close to the head side or directly at the head side and not within the pressure chamber <NUM> of the hydraulic cylinder <NUM>. The third pressure sensor <NUM> may be installed on any of the shown embodiments but is only illustrated in <FIG> for simplicity reasons and to illustrate that it is not needed in all embodiments depending on the variant of piston state detection as described herein.

The third pressure <NUM> sensor may be used to differentiate the piston fully extended state and the piston fully retracted state, whereby the piston fully retracted state is detected when P1 equals P2 and the pressure P3 sensed at the third pressure sensor <NUM> is smaller than P1 and P2.

The piston fully extended state can be detected when P1 equals P2 and P2 equals P3.

In addition to the above the piston activated but blocked state can also be detected when P1 equals P2 but P3 is greater than P1 and P2.

The piston locked state can be detected when P1 is smaller than P2 and P2 equals P3.

The above examples are based on a certain distancing between the first pressure sensor <NUM> and the second pressure sensor <NUM> as illustrated. Depending on the chosen distance between the first opening <NUM> of the first channel <NUM> of the first pressure sensor <NUM> and the second opening <NUM> of the second channel <NUM> of the second pressure sensor <NUM> other conditions for the four different states may apply. The invention is based on the realization that channels and their openings can be used to connect a pressure chamber <NUM> of a hydraulic (or pneumatic) cylinder <NUM> to pressure sensors <NUM>, <NUM> using a seal device <NUM> at the head <NUM> of the piston, which seal device <NUM> is designed to glide over the openings of such channels.

The piston in fully extended state, the piston in fully retracted state and the piston activated but blocked state may be identified as a false and the piston in locked position state may be identified as true by the processor <NUM>. Corresponding visual, haptic and/or acoustic signals may be addressed to the operator of the machine.

Turning now to <FIG> another embodiment of the present invention is herewith described.

<FIG> illustrates a similar hydraulic system <NUM>' as <FIG> with similar or same components being denoted with the same reference numbers. The functionality and description and components referring to <FIG> apply also for the illustration of <FIG> with the difference in the safety system <NUM>'. The difference between the safety system <NUM>' according to <FIG> and the safety system <NUM> according to <FIG> is that the safety system <NUM>' illustrated in <FIG> comprises a bypass channel <NUM> instead of the second pressure sensor. The bypass channel <NUM> or bypass <NUM> is designed as a U-shaped bridge connection that has two openings <NUM>, <NUM>' into the pressure chamber <NUM> of the hydraulic cylinder <NUM>. The openings <NUM>, <NUM>' are spaced apart as seen in a longitudinal direction of the hydraulic cylinder <NUM> so that they can bridge the seal device <NUM> in a certain position of the piston <NUM>.

The bypass channel can be used to determine the states of the piston <NUM> as described in relation to <FIG>. Again in order for the bypass channel <NUM> to function properly a seal device <NUM> as previously described needs to be installed, which seal device <NUM> can move across the openings <NUM>, <NUM>' of the bypass channel <NUM> and the opening of the channel connecting the first pressure sensor <NUM> with the pressure chamber <NUM>.

<FIG> illustrates the tool holder <NUM>' and the tool <NUM> or tool adapter <NUM> whereby the piston <NUM> is in the locked state in which the lock fingers <NUM> securely engage one of the brackets <NUM>. The bypass <NUM> channel or bypass <NUM> is arranged at a distance of the first pressure sensor <NUM> as seen along the longitudinal direction of the hydraulic cylinder <NUM>. The bypass channel <NUM> has two openings <NUM>, <NUM>' into the pressure chamber <NUM> of the hydraulic cylinder <NUM>. The bypass channel <NUM> is arranged closer to the rod side <NUM> of the hydraulic cylinder <NUM> while the first pressure sensor <NUM> is arranged closer to the head side <NUM> in the embodiment shown in <FIG>.

The bypass <NUM> is arranged so that it bridges the seal device <NUM> in the piston fully extended state (shown in <FIG>).

In order to detect the various states of the piston <NUM> a value for a limited pressure P1limit is defined, whereby P1limit is determined in relation to a diameter of the bypass channel and whereby the system pressure Psyst being provided by the pressurizing device <NUM> is always greater than P1limit and whereby a reservoir pressure Pres present in the hydraulic fluid reservoir or tank <NUM> is always lower than P1limit.

In <FIG> the piston <NUM> is in the locked state, which can be detected when the sensed pressure P1 sensed by the first pressure sensor <NUM> is higher than P1limit. In this state the reversing valve <NUM> is in the first position in which the head side <NUM> is connected with the pressurizing device <NUM> and the supply line <NUM>, respectively.

<FIG> illustrates the piston <NUM> in the activated but blocked state, thus when the lock fingers <NUM> try to extend due to the pressure from the piston <NUM> and the hydraulic system <NUM>', respectively, but are blocked by the bracket <NUM>. This piston <NUM> activated but blocked state can be detected when the sensed pressure P1 at the first pressure sensor <NUM> is lower than P1limit and wherein the sensed pressure P1 is equal to the reservoir pressure Pres. The reverse valve <NUM> is thereby in the first position connecting the head side <NUM> to the supply line <NUM>. Again, the reverse valve <NUM> position is not needed to detect piston <NUM> in the activated but blocked position.

<FIG> illustrates the piston <NUM> in the fully extended state, which can be detected when the sensed pressure P1 sensed by the first pressure sensor <NUM> is lower than P1limit but higher than the reservoir pressure Pres. In this state thus piston <NUM> fully extended state the reversing valve <NUM> is in the first position connecting the head side <NUM> with the supply line <NUM>. The reversing valve <NUM> position is not needed to determine the piston <NUM> fully extended state.

Finally, <FIG> shows the piston <NUM> in fully retracted state, which can be detected when the sensed pressure P1, sensed by the first pressure sensor <NUM>, is higher than P1limit and when the reversing valve <NUM> is in the second position connecting the rod side <NUM> with the supply line <NUM> (not shown).

Claim 1:
A safety system (<NUM>) for a machine comprising:
- a pressurizing device (<NUM>);
- at least one hydraulic cylinder (<NUM>) being coupled to a coupling mechanism (<NUM>) said at least one hydraulic cylinder (<NUM>) comprising a pressure chamber (<NUM>) and a piston (<NUM>) having a head (<NUM>) and a rod (<NUM>), the piston (<NUM>) being movable along a longitudinal direction of the hydraulic cylinder (<NUM>);
- a first pressure sensor (<NUM>) and a second pressure sensor (<NUM>), the first and second pressure sensors (<NUM>, <NUM>) being designed to measure the pressure within the pressure chamber (<NUM>) via a first channel (<NUM>) and a second channel (<NUM>) having first and second openings (<NUM>, <NUM>), which first and second channels (<NUM>, <NUM>) both extend into the pressure chamber (<NUM>), said first opening (<NUM>) and second channel (<NUM>) being spaced apart from one another as seen in the longitudinal direction of the at least one hydraulic cylinder (<NUM>);
- a seal device (<NUM>) arranged circumferentially around the head (<NUM>) of the piston (<NUM>);
- a hydraulic system (<NUM>) being fluidically connected to a head side (<NUM>) and a rod side (<NUM>) of the at least one hydraulic cylinder (<NUM>), the hydraulic system (<NUM>) being fluidically connected to a hydraulic fluid reservoir (<NUM>) and the pressurizing device (<NUM>);
characterised in that
the seal device (<NUM>) is designed to move a plurality of times over the first and second openings (<NUM>, <NUM>) and wherein at least one state of the safety system can be detected via the first and second pressure sensors (<NUM>, <NUM>), namely a piston in locked state.