Los gatos hidráulicos se utilizan en aplicaciones que requieren una gran capacidad de carga, o bien una máxima facilidad y velocidad de accionamiento (especialmente en las operaciones de plegado, que son inmediatas) para cargas medianas. Sus principales ventajas están relacionadas con su potencia y velocidad, con la posibilidad de controlarse mediante servomecanismos, y con la minimización de las pérdidas mecánicas asociadas con el rozamiento. Su principal inconveniente es que suelen ser equipos de una cierta complejidad de mantenimiento (especialmente en todos los aspectos relacionados con la ausencia absoluta de fugas del fluido que sirve para transmitir las cargas).

Los fluidos utilizados suelen ser aceites sintéticos de baja viscosidad debido a su capacidad de auto-lubricarse y a su estabilidad.

Los gatos más potentes utilizan bombas eléctricas, capaces de proporcionar la presión hidráulica necesaria para actuar a distancias considerables y con capacidad para desplazar grandes tonelajes de carga.

The operation of the hydraulic jack responds to Pascal's principle, which establishes that the pressure applied to a fluid contained in a closed container is transmitted uniformly at all points.

The device, in its simplest form, has two pistons arranged in a "U" shape, one with a very small section (in which pressure is applied to the fluid using a lever or a pump), and the other with a very large section (where the load to be lifted is placed). The key to operation is the one-way valves, which allow the flow of fluid in only one direction. Thus, when the small piston is actuated, a valve allows the flow of fluid to the larger piston, but not its return. Likewise, a second valve allows fluid to enter from a reservoir to the small plunger when the lever is raised, readying the device for a new drive cycle.

According to Pascal's principle, the pressure is the same in the two pistons, which means that between the small piston (with section and force) and the large piston (with section and force, corresponding to the weight to be lifted), the equation is fulfilled:

which is equivalent to:

the quotient being the multiplication coefficient of the applied force.

pneumatic jack

It is a special type of hydraulic jack, which uses compressed air - for example, air from a compressor - instead of a liquid to produce the lifting effect. Some models designed to replace scissor jacks in the automotive industry consist of a cylindrical plasticized canvas or rubber bag, with sufficient resistance to be inflated with a pressure similar to that of a tire (about 2 kiloponds per cm²) and with the size necessary to lift a car (a base of 50 cm² and a height of about 50 cm is enough to lift 1000 kg) to replace a wheel. From an energy point of view, they are not very efficient (a lot of heat is released in the air compression process), but they can be useful to avoid manual efforts when a mechanized source of compressed air is available.

Since ancient times there have been examples of simple machines used to multiply the human or animal force necessary to carry out certain tasks (such as the construction of large stone monuments), as simple as inclined planes, or as complex as hoists, whose operating principles were already known in the time of Archimedes.

However, we must wait until the Renaissance (when practical and theoretical knowledge of how gears and threaded parts work begin to develop) to find the first designs of mechanical mechanisms for lifting heavy loads (related to what are known today as mechanical jacks); as attested by some drawings of the century contained in Leonardo da Vinci's Codex Atlanticus.

The enormous current diffusion of this instrument is associated with the rise of the automobile industry, which has been including it since its first models as an essential tool for replacing flat tires (the first cars equipped with an inflated spare wheel were the Rambler in 1906.[4]​), although since the end of the century [5]​ the decision to replace the spare wheel (and consequently, the jack) with a foam spray, applied to a wheel, has gradually spread in some models. punctured, it allows you to drive a few kilometers to a workshop.

Regarding the hydraulic jack, although the principle on which it is based has been known since the 19th century, when it was formulated by the French physicist Blaise Pascal, it was necessary to wait until 1851 for the American inventor Richard Dudgeon to be granted a patent[6]​ for a portable hydraulic press, what is now known as a hydraulic jack, a tool that proved to be far superior to the screw jacks used at that time. Dudgeon also designed other types of hydraulic jacks, such as those used for lifting railway vehicles.

In addition to their best-known and most widespread use in the automotive industry, jacks have various applications in construction and industry, both for lifting or pushing heavy loads, and for tensioning metal parts.

Los gatos hidráulicos se utilizan en aplicaciones que requieren una gran capacidad de carga, o bien una máxima facilidad y velocidad de accionamiento (especialmente en las operaciones de plegado, que son inmediatas) para cargas medianas. Sus principales ventajas están relacionadas con su potencia y velocidad, con la posibilidad de controlarse mediante servomecanismos, y con la minimización de las pérdidas mecánicas asociadas con el rozamiento. Su principal inconveniente es que suelen ser equipos de una cierta complejidad de mantenimiento (especialmente en todos los aspectos relacionados con la ausencia absoluta de fugas del fluido que sirve para transmitir las cargas).

Los fluidos utilizados suelen ser aceites sintéticos de baja viscosidad debido a su capacidad de auto-lubricarse y a su estabilidad.

Los gatos más potentes utilizan bombas eléctricas, capaces de proporcionar la presión hidráulica necesaria para actuar a distancias considerables y con capacidad para desplazar grandes tonelajes de carga.

The operation of the hydraulic jack responds to Pascal's principle, which establishes that the pressure applied to a fluid contained in a closed container is transmitted uniformly at all points.

The device, in its simplest form, has two pistons arranged in a "U" shape, one with a very small section (in which pressure is applied to the fluid using a lever or a pump), and the other with a very large section (where the load to be lifted is placed). The key to operation is the one-way valves, which allow the flow of fluid in only one direction. Thus, when the small piston is actuated, a valve allows the flow of fluid to the larger piston, but not its return. Likewise, a second valve allows fluid to enter from a reservoir to the small plunger when the lever is raised, readying the device for a new drive cycle.

According to Pascal's principle, the pressure is the same in the two pistons, which means that between the small piston (with section and force) and the large piston (with section and force, corresponding to the weight to be lifted), the equation is fulfilled:

which is equivalent to:

the quotient being the multiplication coefficient of the applied force.

pneumatic jack

It is a special type of hydraulic jack, which uses compressed air - for example, air from a compressor - instead of a liquid to produce the lifting effect. Some models designed to replace scissor jacks in the automotive industry consist of a cylindrical plasticized canvas or rubber bag, with sufficient resistance to be inflated with a pressure similar to that of a tire (about 2 kiloponds per cm²) and with the size necessary to lift a car (a base of 50 cm² and a height of about 50 cm is enough to lift 1000 kg) to replace a wheel. From an energy point of view, they are not very efficient (a lot of heat is released in the air compression process), but they can be useful to avoid manual efforts when a mechanized source of compressed air is available.

Since ancient times there have been examples of simple machines used to multiply the human or animal force necessary to carry out certain tasks (such as the construction of large stone monuments), as simple as inclined planes, or as complex as hoists, whose operating principles were already known in the time of Archimedes.

However, we must wait until the Renaissance (when practical and theoretical knowledge of how gears and threaded parts work begin to develop) to find the first designs of mechanical mechanisms for lifting heavy loads (related to what are known today as mechanical jacks); as attested by some drawings of the century contained in Leonardo da Vinci's Codex Atlanticus.

The enormous current diffusion of this instrument is associated with the rise of the automobile industry, which has been including it since its first models as an essential tool for replacing flat tires (the first cars equipped with an inflated spare wheel were the Rambler in 1906.[4]​), although since the end of the century [5]​ the decision to replace the spare wheel (and consequently, the jack) with a foam spray, applied to a wheel, has gradually spread in some models. punctured, it allows you to drive a few kilometers to a workshop.

Regarding the hydraulic jack, although the principle on which it is based has been known since the 19th century, when it was formulated by the French physicist Blaise Pascal, it was necessary to wait until 1851 for the American inventor Richard Dudgeon to be granted a patent[6]​ for a portable hydraulic press, what is now known as a hydraulic jack, a tool that proved to be far superior to the screw jacks used at that time. Dudgeon also designed other types of hydraulic jacks, such as those used for lifting railway vehicles.

In addition to their best-known and most widespread use in the automotive industry, jacks have various applications in construction and industry, both for lifting or pushing heavy loads, and for tensioning metal parts.