JP3246283U - Pulse mechanism for power tools - Google Patents

Abstract

Disclosed herein is a hydraulic power tool for applying a torque pulse to a fastener to tighten the fastener, the hydraulic power tool comprising a hydraulic coupling mechanism (110, 10, 10') and a motor (108) having a motor shaft (132), the hydraulic coupling mechanism (110, 10, 10') comprising a first part (116, 16) having a passive space (120, 20) and a cylinder (130, 30) having at least one protrusion (124) configured to be driven by the motor shaft (132), an anvil configured to be coupled to the fastener to apply a torque pulse to the fastener, an active space (122, 22) and a cylinder (130, 30) having at least one protrusion (124) configured to be driven by the motor shaft (132), a second part (114, 14) having at least one hole (28) arranged on a periphery of the cylinder (130, 30) and at least one movable engagement element (126) for engaging with at least one protrusion (124) of the cylinder (130, 30), the engagement element (126) and the at least one protrusion (124) being arranged in the active space (122); and a gap (118, 18, 18') arranged between the first part (116, 16) and the second part (114, 14) and interconnecting the passive space (120, 20) and the active space (122, 22) via the at least one hole (28), the active space (122, 22) being filled with oil and the passive space (120, 20) being filled with oil and air. The hydraulic power tool may include a capillary mechanism (36, 36', 36'') disposed in the gap (118, 18, 18'), which holds oil in the gap (118, 18, 18') by means of capillary forces, such that the active space (122, 22) is filled with oil under all circumstances.

Description

The present invention relates to the field of power tools having a pulse mechanism, particularly a hydraulic pulse mechanism having a hydraulic coupling mechanism, for applying a torque pulse to an anvil coupled to an output shaft of the power tool, for example to transmit torque to a fastener via a bit adapter or a chuck.

Typically, tightening power tools are discontinuous devices that apply torque in small steps rather than in one continuous blow. When the fastener is moving freely, the power tool does not apply pulses and the drive or output shaft rotates continuously at high speed. As soon as the fastener or bolt starts to tighten the workpiece, and therefore the bolt meets resistance and requires torque to turn further, the tool starts pulsing, which means applying short bursts of torque lasting only a short time, so-called torque pulses.

The pulse source of the pulse tool is a hydraulic pulse mechanism consisting of two rotating cylindrical parts. The first part, driven by a motor, has an internal chamber filled with hydraulic fluid. The first part is connected to the motor of the power tool. The second part, usually called the anvil, fits inside the first part. The anvil is connected to the drive shaft of the tool and is bisected by two rolls or blades that are pushed outward by a spring. These rolls or blades separate the chamber into two halves. As the first part rotates, the blades of the anvil contact the inner wall of the internal chamber, which may have an engagement member on the inner wall for engaging with the anvil or may be formed asymmetrically. When the power tool is operating at free speed, the first part and the second part, the anvil, rotate in unison. At this point in the cycle, the rolls or blades are not engaging the inner wall or engagement member of the internal chamber and the hydraulic fluid is not under pressure. As the fastener resists rotation, the anvil begins to slow down, but the first part and the interior chamber continue to rotate at their original speed. The blade or roll is then forced inward toward the center of the anvil, either due to the asymmetric shape of the interior chamber or the engagement member, compressing the spring. This reduces the volume in the chamber and increases the pressure of the hydraulic fluid.

As the first part and the internal chamber continue to rotate, hydraulic pressure in the fluid builds up and the anvil begins to slow down slightly as it rotates. The hydraulic pressure rises and pushes against the roll or blade, forcing the anvil to rotate. When the hydraulic fluid reaches maximum pressure, the anvil stops rotating. At this point, the rotational force acting on the anvil is at its maximum.

As the anvil is pushed beyond this point and begins to move forward, the roll or blade is pushed outward again, the hydraulic pressure is reduced, the anvil accelerates, and another pulse cycle begins.

The advantage of this pulse tool construction is that the hydraulic fluid absorbs most of the vibration from the tightening process. Because the torque is applied intermittently in rapid short pulses, torque reactions are small and the operator's ergonomic environment is not compromised.

In such power tools, the internal chamber in which the blade or roll is located must be 100% filled with oil to provide optimal functionality. The internal chamber is also called the active space or active chamber. When the power tool is used in an industrial environment, the oil in the internal or active chamber generally increases in temperature and therefore in volume, so that small holes are provided on the periphery of the internal chamber so that when the oil heats up and expands, it can escape through a small channel into the passive space, which contains air and a small amount of oil. In this way, the pressure in the internal chamber remains constant and the functionality of the tool remains the same even if the temperature of the oil in the active chamber increases or even decreases. The oil is pushed back from the passive space to the active space when the power tool is used again, and the centrifugal force provided by the motor shaft on the side where the passive space is located pushes the oil back into the active space through the gap and the small holes, using the centrifugal force from the motor shaft driving the first part. In known power tools, the width of the gap is constant at about 1 mm. This gap and width can cause air to enter the active space, as will be described later. Typically, the gap has a shape similar to or the same as the outer surface of a cone or truncated cone.

The drawback of the above mentioned solution is that in certain circumstances, therefore when the power tool is oriented upside down or at an angle or in particular when the drive shaft is oriented upwards with respect to gravity, air may be drawn back into the active space through small holes and gaps when the oil in the active space cools. If air or air bubbles enter the active space and thus the high pressure area of the power tool, the hydraulic coupling mechanism will not function properly and will not be able to perform its intended function. In particular, the first few rotations and therefore the first few tightenings after a rest period of the power tool are problematic. The reason is that the above mentioned centrifugal process requires several rotations and therefore the tightening of the fastener until the air is pushed out of the passive space and the oil enters the active space through the gaps and small holes. During this tightening, the power tool will not work correctly and properly. If the air bubbles themselves get into the wrong place in the power tool, the torque pulse will be interrupted at a stage where it is not completely completed and the torque pulse will be weak. This can affect the torque measurement and lead to a fastener or clamping force that does not have the correct target value.

Thus, a problem with prior art hydraulic power tools is that air can enter the active space through gaps and small holes.

The object of the present invention is to provide a reliable and robust hydraulic power tool for fastener tightening.

The inventors have realized that the key to a reliable and robust hydraulic power tool is to ensure that the gap between the hole leading to the active space containing oil and the passive space containing air and a small amount of oil is always saturated with oil regardless of the orientation of the hydraulic power tool. This can be achieved by utilizing a capillary mechanism or effect to interconnect the active space and the gap by reducing the gap towards small holes located at the periphery of the gap and the active space, or by providing a wick structure within the gap, or a combination thereof. The inventors have realized that either of these two solutions ensures that the gap is always filled with oil regardless of the orientation of the hydraulic power tool. The oil-filled gap prevents air from entering the active space, resulting in a very reliable and robust hydraulic power tool.

Disclosed herein is a hydraulic power tool for applying torque pulses to fasteners to tighten them, the hydraulic power tool comprising a hydraulic coupling mechanism and a motor having a motor shaft, the hydraulic coupling mechanism comprising: a first part having a passive space and a cylinder having at least one protrusion, the cylinder configured to be driven by the motor shaft; a second part having an anvil configured to be coupled to a fastener to apply a torque pulse to the fastener, an active space, at least one hole disposed on a periphery of the active space, and at least one movable engagement element for engaging with at least one protrusion of the cylinder, the engagement element and the at least one protrusion being disposed within the active space; and a gap disposed between the first part and the second part, interconnecting the passive space and the active space through at least one hole, the active space being filled with oil, and the passive space being filled with oil and air.

The hydraulic power tool may include a capillary mechanism disposed in the gap, which holds oil in the gap using capillary forces, such that the active space is filled with oil under all conditions, regardless of the orientation of the power tool, oil temperature, ambient and/or tool temperature, and/or other conditions such as vibration and/or shock.

The advantage of the above embodiment is that the gap is always saturated with oil, so air cannot enter the active space.

In one embodiment, the capillary mechanism is configured to use capillary forces to draw oil toward the hole and the active space, respectively.

The direction of the force exerted by the capillary mechanism helps ensure that the oil does not leave the active space. This is ensured as the active space contains only oil and the passive space contains oil and air/gas as well. An increase in oil temperature due to operation of the hydraulic tool will lead to the oil being pushed out of the active space due to the expansion of the oil, and as the oil cools and reduces in volume, the capillary mechanism will pull the oil back into the active space due to capillary force or effect.

In one embodiment, the gap is at least partially shaped like the outer surface of a cone or a truncated cone.

The shape of the gap is typically determined by the respective shapes of the first and second parts.

The shape of the gap is rotationally symmetric about an axis defined by the motor shaft.

The fluid or oil pressure in the active space is greater than the pressure in the passive space.
This ensures accurate transmission of the torque pulses.

In one embodiment, the capillary mechanism can be a wick structure shaped to conform to the gap so that it can be closely positioned in the gap configured to draw oil toward the active space.

The wick structure is easy to implement and can be integrated into existing hydraulic power tools.

The wick structure may be shaped at least partially like the exterior surface of a cone.
Additionally, the wick structure can fit snugly within the gap.

In one embodiment, the wick structure may further comprise protrusions designed to reach the bottom of the passive space and also perform a wicking function, so that the wick structure is always saturated with oil.

In another embodiment, the wick structure can be made of metal, such as perforated metal, to generate capillary forces.
The metal may be aluminum.

This allows for a sturdy and durable wick structure.

In further embodiments, the wick structure can be made of a woven fabric such as cotton, fiberglass, or other suitable fibrous materials such as carbon fiber, or combinations thereof.

In another embodiment, the capillary mechanism may have a gap width that decreases continuously toward the hole.

This solution to the capillary mechanism can simplify the assembly of hydraulic power tools.

In another embodiment, the width of the gap can be selected to be 0.6 mm to 1 mm at a first end of the gap close to the passive space and 0.5 mm to 0.1 mm at a second end of the gap close to the active space, preferably 0.6 mm to 0.8 mm at the first end and 0.3 mm to 0.1 mm at the second end.

In this way, the capillary force increases towards the holes and active space, ensuring that there is always oil or liquid near the holes and active space.

Further disclosed herein is a wick structure suitable for use in the hydraulic power tool described above.

This wick structure can also be used in solutions where the gap has a continuously decreasing width towards the hole and towards the active space, respectively.

The following terms used in this specification are explained in more detail:

Wick Structure The term "wick structure" refers to a wick element that can draw liquid using capillary forces similar to the wick of an oil lamp. The wick structure can be made of a variety of materials, such as metal, fabric, carbon, or other potentially suitable materials. The shape of the wick structure is adapted to fit the shape of the gap between the first and second parts, which is typically a circularly symmetric geometric shape such as the outer surface of a cone or a truncated cone. In an embodiment, the wick structure can also be molded as a portion of a spherical outer surface.

Capillary Force The term "capillary force" as used herein refers to the phenomenon of capillary effect discovered by Leonardo da Vinci, which refers to the flow of liquids through narrow spaces without or against the force of gravity. Capillary force or effect is caused by intermolecular forces between the liquid and the surrounding solid surface. If the diameter of the tube is small enough, a combination of surface tension (which is caused by cohesive properties within the liquid) and adhesive forces between the liquid and the tube wall act to propel the liquid, causing it to flow along the tube or narrow space.

As used herein, the term "external surface of a cone or external surface of a truncated cone " refers to the external surface of a cone or a shape in which the top has been cut off, and thus corresponds to the external surface of a truncated cone. The wick structure and gaps may at least partially have this shape.

Capillary Mechanism The term "capillary mechanism" as used herein means any mechanism that utilizes the capillary effect to draw a liquid, here oil, towards a space such as the active space such that air cannot enter the active space. The capillary mechanism described herein provides a capillary force towards the active space. Due to the presence of air in the passive space, the capillary force is not strong enough to pull the liquid or oil out of the active space and create a vacuum therein, so the liquid or oil will always be drawn towards the active space.

The invention will now be described in more detail, by way of example only, by way of embodiments and with reference to the accompanying drawings, in which:

1 shows a schematic cross-sectional view of a hydraulic power tool according to the prior art; 2 shows a schematic cross-sectional view of a hydraulic coupling mechanism of the hydraulic power tool according to FIG. 1; 1 is a schematic cross-sectional view of a hydraulic coupling mechanism according to an embodiment of the present invention; 1A and 1B are schematic diagrams illustrating perspective views of a wick structure according to an embodiment of the present invention; 2 illustrates a cross-sectional view of a hydraulic coupling mechanism according to another embodiment of the present invention; 2A and 2B are schematic cross-sectional views of a wick structure according to another embodiment of the present invention;

The present invention will now be described in detail with reference to Figures 1 to 6, where Figures 1 and 2 disclose a hydraulic power tool 100 according to the prior art. The hydraulic power tool 100 comprises a housing 102, a handle 104, a motor unit 106 comprising a motor 108, and a hydraulic coupling mechanism 110 for coupling a motor shaft 112 to an anvil or second part 114. The motor 108 further comprises a motor shaft 132 coupled to a first part 116 (see Figure 2) of the hydraulic coupling mechanism 110. The hydraulic coupling mechanism 110 is configured to deliver torque pulses to a fastener (not shown) via the anvil or second part 114.

The hydraulic coupling mechanism 110 is shown in more detail in FIG. 2. It comprises a first part 116 and a second part 114, which are coupled to each other via a cylinder 130, which comprises two projections 124 extending into the active space 122 for engaging with an engagement element in the form of a blade or roll 126 of the anvil or second part 114. The engagement element 126 is mounted so as to be elastically movable towards a central axis A defined by the rotation axes of the motor 108 and the motor shaft 132, respectively. The first part 116 and the second part 114 are coupled to each other via a cylinder 130 which is coupled to or formed integrally with the first part 116. A gap 118 is arranged between the first part 116 and the second part 114. The gap 118 interconnects the active space 122 and the passive space 120 located in the first part 116 through holes (not shown in FIG. 2) provided on the periphery of the active space 122. The active space 122 or active chamber 122 is filled with oil only, and the passive space 120 is filled with oil and air. In this solution, the gap 118 can be filled with oil or air. The gap 118 has a constant width of about 1 mm.

When the hydraulic power tool 100 and the hydraulic coupling mechanism 110 are used, the cylinder 130 applies a torque pulse to the second part 114 or anvil on the engaging element 126 of the second part 114 via the protrusion 124. As long as the second part 114 and the fastener therewith are free to move, the engaging element 126 remains engaged on the protrusion 124 due to elastic loading, e.g., via a spring, and due to hydraulic pressure in the active space 122. When the second part 114 encounters a torque resistance, the engaging element is pushed inward toward the axis A, and the cylinder 130 is free to rotate approximately half a turn until the engaging element 126 again strikes the protrusion 124 and transmits the torque pulse. This process is repeated until the correct torque is applied to the fastener via the second part 114. During this process, many torque pulses are applied, which causes the oil in the active space 122 to be compressed and released several times, which causes the temperature to increase and leads to a volume expansion of the oil in the active space 122. Oil can spread through the holes (see FIG. 3) into the gap 118 and the passive space 120, as a large pressure change in the active space 122 would cause the hydraulic power tool 100 to not function properly.

When the hydraulic power tool 100 is no longer in use, the oil in the active space 122 cools, thereby contracting, at least in the ideal case, causing oil to be drawn back through the gap 118 and the passive space 120. Depending on the orientation of the hydraulic power tool 100, air or bubbles may be drawn back through the gap 118 and holes into the active space 120, causing the hydraulic power tool 100 to not operate properly. This can be avoided by the concept of the present invention, which will be described with reference to Figures 3 to 6.

In general, the hydraulic coupling mechanism 10 shown in FIG. 3 is constructed similarly to that shown in FIGS. 1 and 2, with the difference being that the gap 18 is designed differently. The embodiment shown in FIG. 3 is shown with certain components removed, such as the engagement element 126 and the protrusion 124, for simplicity. The hydraulic coupling mechanism 10 comprises a first part 16 and a second part 14 coupled to the first part 16 via a cylinder 30 rigidly and fixedly coupled to the first part 16. The cylinder 30 comprises a protrusion (not shown) that can engage with an engagement element (not shown), such as a roll or blade of the second part 16 or an anvil, to provide a torque pulse to the fastener coupled to the second part 14. The function of the hydraulic coupling mechanism shown in FIG. 3 is similar to that shown in FIGS. 1 and 2, and will not be described again here.

An active space 22 or active chamber is shown, which is disposed inside the cylinder 30 and is also surrounded by the second part 14. The active space 22 is connected to the passive space 20 of the first part 16 through a hole 28 and a gap 18. The hole 28 is formed at the periphery of the active space 22. Both the active space 22 and the passive space 20 are formed as rotationally symmetric spaces or chambers, whereby they are rotationally symmetric around an axis A defined by the motor shaft (not shown in FIG. 3). A capillary mechanism 36 is incorporated in or near the gap 18. In the illustration shown in FIG. 3, the capillary mechanism 36 is disposed in the gap 18 and is formed such that the width of the gap 18 decreases continuously towards the hole 28. The width of the gap 18 can decrease from 0.7 mm to 0.2 mm from point e towards point b, as shown in FIG. 3. Alternatively, the width of the gap 18 can be reduced from 1 mm, 0.9 mm, 0.8 mm, 0.7 mm, 0.6 mm at point e to 0.5 mm, 0.4 mm, 0.3 mm, 0.2 mm, or even 0.1 mm at point b. By designing the gap 18 in this way, the capillary effect on the oil becomes stronger the closer the liquid or oil moves to the hole 28. Thus, the capillary force acting on the liquid is always directed towards the hole 28. Thus, the liquid always remains in the gap 18, and as a result, air cannot enter the active space 22.

Now referring to FIG. 4, another solution of the capillary mechanism 36' in the form of a wick structure 38 is shown. The wick structure 38 is shaped to fit snugly into the gap 18 (see FIG. 3) and thereby as the outer surface of a truncated cone. The wick structure 38 can be made of perforated metals such as aluminum, steel, titanium, fabrics such as cotton, fiberglass, carbon fiber, other suitable materials, or combinations thereof. The wick structure 38 has the same effect of drawing the liquid towards the holes 28 by capillary action, so that the active chamber 22 is always filled with liquid and cannot admit air or bubbles. Due to the presence of air in the passive space 20, the capillary force will always act towards the holes 28 and the active space 22, respectively. Since the active space 22 is always filled with oil or liquid, the capillary force is not strong enough to act in the other direction.

The wick structure 38 is configured to be incorporated into the gap 118, 18 of a prior art hydraulic power tool 100 or into the gap 18 of a hydraulic power tool having a coupling mechanism 10 according to FIG. 3.

Figure 5 shows a coupling mechanism 10' in which a wick structure 38 is incorporated into the gap 18'. This results in the gap 18' having a shape similar to that shown in Figure 2, with a constant width between 0.5 mm and 1.5 mm. Again, the wick structure 38 can be incorporated into gaps 18 with a continuously decreasing width D, similar to the embodiment of Figure 3.

Figure 6 shows yet another capillary mechanism 36'', also in the form of a wick structure 38' with protrusions 42 or extensions configured to extend into the passive space 20 and all the way to the bottom 40 of the active space (see Figure 5) to ensure that the wick structure 38' is always saturated with liquid or oil.

Figures 3 and 5 show the hydraulic coupling mechanism 10, 10' in different orientations, angled in Figure 3 and upside down in Figure 5, to illustrate that the capillary mechanism 36, 36', 36'' described herein always supplies oil to the bore 28 and active space 22, respectively, regardless of the orientation of the hydraulic power tool.

When the wick structure 38, 38' is designed to be incorporated into the gap 18 according to FIG. 3, its thickness can be adapted accordingly to correspond to the decreasing width D of the gap 18 and to fit snugly into the gap 18.

The invention is described with reference to the attached drawings. Moreover, the invention includes various combinations. Different features from different embodiments can be combined to further improve the functionality and reliability of the hydraulic power tool. In an embodiment, the hydraulic power tool is a battery-operated power tool. However, the solution can also be considered to be applied to cable-operated or pneumatically-operated power tools.

Claims (13)

A hydraulic power tool for applying torque pulses to a fastener to tighten the fastener, the hydraulic power tool comprising a hydraulic coupling mechanism (110, 10, 10') and a motor (108) having a motor shaft (132), the hydraulic coupling mechanism (110, 10, 10') comprising:
a first part (116, 16) comprising a passive space (120, 20) and a cylinder (130, 30) having at least one protrusion (124), the cylinder (130, 30) being configured to be driven by the motor shaft (132);
a second part (114, 14) comprising an anvil configured to be coupled to the fastener for applying a torque pulse to the fastener, an active space (122, 22), at least one hole (28) arranged on a periphery of the active space (122, 22), and at least one movable engagement element (126) for engaging the at least one protrusion (124) of the cylinder (130, 30), the engagement element (126) and the at least one protrusion (124) being arranged within the active space (122);
a gap (118, 18, 18') disposed between the first part (116, 16) and the second part (114, 14) and interconnecting the passive space (120, 20) and the active space (122, 22) via the at least one hole (28), the active space (122, 22) being filled with oil and the passive space (120, 20) being filled with oil and air;
Equipped with
the hydraulic power tool comprises a capillary mechanism (36, 36', 36'') arranged in the gap (118, 18, 18'), the capillary mechanism (36, 36', 36'') retaining oil in the gap (118, 18, 18') by means of capillary forces, such that the active space (122, 22) is filled with oil under all circumstances;
A hydraulic power tool characterized by: the capillary mechanism (36, 36', 36'') is configured to draw oil towards the hole (28) and the active volume (122, 22), respectively, using capillary forces;
2. The hydraulic power tool of claim 1. the gap (118, 18, 18') is at least partially shaped like the outer surface of a cone or a truncated cone;
3. A hydraulic power tool according to claim 1 or 2. The pressure in the active space (122, 22) is higher than the pressure in the passive space (120, 20);
A hydraulic power tool according to any one of claims 1 to 3. the capillary mechanism (36', 36'') is a wick structure (38, 38') shaped to conform to the gap (118, 18, 18') so that it can be closely positioned in the gap (118, 18, 18') configured to draw oil towards the active volume (122, 22);
A hydraulic power tool according to any one of claims 1 to 4. The wick structure (38, 38') is at least partially shaped like the outer surface of a cone.
6. The hydraulic power tool of claim 5. The wick structure (38') further comprises a protrusion (42) that reaches to the bottom (40) of the passive space (20), so that the wick structure is always saturated with oil.
7. A hydraulic power tool according to claim 5 or 6. The wick structure (38, 38') is made of a metal such as a punched metal in order to generate a capillary force.
A hydraulic power tool according to any one of claims 5 to 7. The metal is aluminum.
9. The hydraulic power tool of claim 8. The wick structure (38, 38') is made of a woven material such as cotton, fiberglass, carbon fiber, other suitable fiber material, or a combination thereof;
A hydraulic power tool according to any one of claims 5 to 7. The capillary mechanism (36) is such that the width (D) of the gap (18) decreases continuously towards the hole (28);
A hydraulic power tool according to any one of claims 1 to 4. the width of said gap (18) is selected to be 0.6 mm to 1 mm at a first end (e) of said gap (18) close to said passive space (20) and 0.5 mm to 0.1 mm at a second end (b) of said gap close to said active space (22), preferably 0.6 mm to 0.8 mm at said first end (e) and 0.3 mm to 0.1 mm at said second end (b);
12. The hydraulic power tool of claim 11. A wick structure (38, 38') designed to be placed in a gap (118, 18, 18') of a hydraulic power tool according to any one of claims 1 to 12.

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