Sheet material trolley

Abstract

A trolley 100 for carrying sheet material in a substantially upright position comprises a wheeled frame 102 with an inclined plate / base 104 on which material is placed, an upright / pillar 106 conne

Description

Field of the Invention The present invention relates to sheet material trolleys. Background of the Invention Sheet material trolleys are widely used for transporting sheets of raw materials, for example, around a construction site. A sheet material trolley typically includes a wheeled platform and a generally vertically extending element for supporting items of sheet material in an upright position. Some sheet material trolleys are operable to releasably secure sheet materials to the trolley to address issues of materials being damaged during transport, which may incur cost and time penalties during a construction project. Time pressures may be understood by users and operators of sheet material trolleys; motivating fast and efficient labour. However, an increased pace of work and repetition of familiar tasks can introduce risk. For example, if proper process is neglected in the name of expediency, a risk that materials may be damaged and / or workers injured may be increased. There is a need to mitigate of such risks while facilitating quick and efficient work. Summary of the Invention At its most general, the present invention provides a sheet material trolley comprising a height-adjustable clamp arm configured to aid retention of sheet materials on the trolley wherein uncontrolled retraction of the height-adjustable clamp under gravity is mitigated; a ‘safety stop’ is provided. Specifically, telescopic retraction of the height-adjustable clamp is arrested a predetermined height by a protrusion disposed on the clamp engaging with an upper surface of a component into which the height-adjustable clamp is configured to retract. In some embodiments, engagement of the protrusion and upper surface is ensured by an inclination of the clamp with respect to the vertical, in use, so that the protrusion is urged into engagement with the upper surface under gravity, until external intervention facilitates further, controlled, retraction of the clamp. According to a first aspect of the invention, there is provided a sheet material trolley configured to support sheet material in a substantially upright position, the sheet material trolley comprising: a wheeled frame comprising: a plate configured to support a first end of an item of sheet material; and a pillar arranged substantially normal to the plate, and configured to support a face of the item of sheet material; wherein the plate and the pillar are inclined such that an item of sheet material is urged by gravity into engagement with the pillar; and a height-adjustable clamp comprising: an arm comprising a proximal end configured to be telescopically received within the pillar and a distal end configured to protrude from the pillar; and a jaw arranged at the distal end of the arm and configured to secure the item of sheet material against the plate; wherein a position of the jaw with respect to the plate is adjustable by telescopic adjustment of the arm with respect to the pillar between a first position in which the jaw rests on a second end of the item of sheet material, the second end being opposite to the first end, and a second position in which the jaw is removed from the item of sheet material; and wherein the arm comprises a protrusion configured to engage with an upper surface of the pillar as the jaw moves from the second position towards the first position to arrest retraction of the arm into the pillar under gravity to mitigate collision of the jaw with the sheet material. A sheet material trolley may be a wheeled frame or platform configured to support materials in sheet or board form, e.g., plasterboard or plywood, in a substantially upright position for conveying relatively short distances, e.g., around a worksite. A sheet material trolley allows large sheets of material to be transported conveniently and in compliance with manual handling guidelines. In this way, use of a sheet material trolley may reduce a risk of damage to sheet materials and injury to those handling them. The sheet material trolley of the present invention comprises a wheeled frame comprising a plate and a pillar arranged to extend in a direction substantially normal to the plate. The plate is configured to support a first, i.e. lower, end of an item of sheet material and the pillar is configured to support a face of the item of sheet material. The plate and the pillar are inclined such that the item of sheet material is urged by gravity into engagement with the pillar. In this way, when disposed on the trolley, the sheet material is arranged substantially parallel to the pillar; inclined to the vertical. The sheet material trolley of the present invention comprises a height-adjustable clamp comprising an arm and a jaw arranged at the distal end of the arm. A proximal end of the arm is configured to be telescopically received within the pillar and a distal end of the arm is configured to protrude from the pillar. The jaw, arranged at the distal end of the arm, is configured to secure the item of sheet material against the plate by clamping the sheet material against the plate. In other words, the jaw is configured to protrude from the distal end of the arm and may extend in a direction substantially parallel to the plate of the trolley. A position of the jaw above the plate is adjustable by telescopic adjustment of the arm in the pillar between a first position in which the jaw rests on a second, i.e., upper, end of the item of sheet material, and a second position in which the jaw is removed from the item of sheet material. In this way, the jaw is adjustable between a clamping (first) position and a non-clamping (second) position. In the non-clamping position, the jaw may not interfere with removal and replacement of sheet materials on the trolley, i.e., on the plate and against the pillar. So, in some use cases, the clamp may be height-adjusted at the beginning and end of a journey using the trolley, i.e., to clamp and release the sheet materials respectively. The arm is telescopically received within the pillar such that longitudinal axes of the arm and pillar are substantially collinear and the arm is slidably height-adjustable into and out of a volume defined by the pillar. It will be appreciated that the pillar may comprise any suitable shape into which the arm may be telescopically retracted, e.g., the pillar may have a circular, square, II-shaped or even L shaped cross-sectional shape. The arm of the trolley comprises a protrusion provided to arrest retraction of the arm into the pillar under gravity. In this way, uncontrolled retraction of the arm into the pillar may be halted before the jaw reaches the first position, i.e., before the jaw comes into contact with the sheet material or any item placed on the sheet material (e.g., a hand of a trolley user). The protrusion of the arm is configured to engage with an upper surface of the pillar as the jaw moves from the non-clamping position towards the clamping position. As such, uncontrolled collision of the jaw with the sheet material, or any intermediate item, is mitigated. The protrusion may be arranged at a predetermined height on the arm. The predetermined height may be selected so that retraction of the arm under gravity is halted by engagement of the protrusion with the upper surface before the jaw comes into contact with the sheet material. In some embodiments, the predetermined height is selected so that the protrusion engages with the upper surface of the pillar while a distance between the jaw and the plate that is greater than a standard dimension (e.g., length or width) of an item of sheet material. For example, where a standard width of an item of sheet material is 1200mm, the predetermined height may be selected so that the protrusion engages with the upper surface of the pillar while a distance between the jaw and the plate is between 1220mm and 1300mm, for example around 1280mmm. In this way, the trolley is configured to inhibit uncontrolled collision of the jaw with a standard width item of sheet material and / or a hand of the trolley user atop the item of sheet material. The upper surface of the pillar may be any upward-facing surface of the pillar arranged to engage with the protrusion. For example, the upper surface of the pillar may be an uppermost, e.g., top surface of the pillar. Alternatively, the upper surface may be an upward-facing surface of an aperture or channel in the pillar configured to engage with the protrusion. In some embodiments, the pillar may comprise more than one upper surface, that is, the arm may be arrested by engagement of the protrusion with a first upper surface at a first position and subsequently by engagement of the protrusion with a second upper surface at a second position. In this way, two arrest positions are provided and uncontrolled collision of the jaw with two standard sizes of sheet materials, or two orientations (e.g., lengthwise or width wise) of one standard size of sheet material, may be mitigated. By engaging with an upper surface, rather than a lower surface, the engagement is less susceptible to damages or interference from other parts of the trolley. Reliable engagement of the protrusion with the upper surface of the pillar may be ensured by the protrusion being disposed on a surface of the arm that, under gravity, is urged into engagement with a surface of the pillar. In other words, the protrusion may be disposed on a lower surface of the arm, that is, a surface opposite the surface of the pillar configured to support a face of the item of sheet material. In this way, gravity may assist engagement of the protrusion with the upper surface during uncontrolled retraction. Accordingly, the invention provides a simple and reliable mechanism for preventing uncontrolled collision of the jaw with items of sheet material on the trolley. In some embodiments, after the retraction of the arm into the pillar under gravity is arrested by the protrusion, the arm is adjustable to permit continued retraction of the arm into the pillar to dispose the jaw in the first position. In this way, after the protrusion has mitigated uncontrolled collision of the jaw with items of sheet material on the trolley, the jaw may be brought into contact with the sheet materials to secure them on the trolley in a controlled manner. The controlled manner may be manually, i.e., a user may push, pull or guide the jaw into engagement with the sheet materials to secure them to the trolley. Alternatively, the controlled manner may be under gravity but for a short distance such that the jaw does not collide with the sheet materials at speed. The controlled manner may involve moving the jaw relatively slowly relative to the uncontrolled motion under gravity. In some embodiments, a position of the arm within the pillar is adjustable in a plane perpendicular to a retraction direction to permit the protrusion to be received within the pillar thereby permitting continued retraction of the arm into the pillar to dispose the jaw in the first position. In this embodiment, the pillar is configured to accommodate the protrusion of the arm. The protrusion may engage with the upper surface of the pillar due to the protrusion being disposed on an outer surface of the arm that slides against an inner surface of the pillar during retraction, e.g., a back surface. Once retraction is halted by the protrusion, the arm may be adjusted, e.g., pushed, laterally so that the protrusion no longer engages with the upper surface and the arm may continue retracting into the pillar. In one example, the protrusion is a small plate arranged on a back side of the arm, inclined away from the vertical. The protrusion engages with the top of the pillar as the arm descends under gravity, halting the descent. Pushing on the protrusion to adjust a position of the longitudinal axis of the arm relative to the longitudinal axis of the pillar disengages the protrusion from the top surface of the pillar. The arm then continues retracting into the pillar, which is sized to accommodate the arm and the protrusion. As such, the invention provides a simple and reliable mechanism for temporarily halting uncontrolled retraction of the arm into the pillar. In this way, and risk of uncontrolled retraction of the arm causing damage to the sheet materials disposed on the trolley and injury to trolley users may be mitigated. In use, the trolley is loaded by telescopically extending the arm from the pillar such that the jaw is removed from a position to be occupied by sheet materials; the jaw is in the second position. Then, an item of sheet material is placed on the trolley such that an end of the item of sheet material is supported by the plate and a face of the item of sheet material is supported by the pillar. A plurality of items of sheet material may be loaded onto the trolley in this way. Next, the item(s) of sheet material are secured to the trolley by lowering the jaw from the second position towards the first position. If the arm is telescopically retracted under gravity to lower the jaw, an outer surface of the arm, comprising the protrusion, may slide along an inner surface of the pillar. During retraction, the protrusion engages with the upper surface of the pillar to arrest the retraction under gravity and mitigate collision of the jaw with the sheet materials on the trolley. Once arrested, the retraction may be continued by adjusting the arm to bring the jaw into the first position, into contact with the item(s) of sheet material, to clamp the material against the plate securely for onward transport. In some embodiments, once received within the pillar, the protrusion is configured to frictionally engage with an inner surface of the pillar to limit a rate of retraction of the arm into the pillar. In this way, the rate of retraction of the arm into the pillar after disengagement of the protrusion from the upper surface of the pillar is controlled by the protrusion to further mitigate the jaw causing damage to the sheet materials disposed on the trolley. In some embodiments, the protrusion is disposed on a surface of the arm that is urged into engagement with an upper surface of the pillar under gravity. Accordingly, the protrusion may reliably engage with the upper surface of the pillar. In some embodiments, the arm comprises a metal tube comprising a substantially square cross section. In some embodiments, the protrusion is formed of sheet metal. In some embodiments, the protrusion is connected to the arm via a welded joint. In this way, the trolley is cost-effective and simple to manufacture, robust and reliable. For example, by providing the arm with a square cross-section, the arm is inhibited from rotating within the pillar which may cause unreliable functioning. The welded joint may be suitable to withstand impact associated with arresting uncontrolled retraction of the arm into the pillar. In some embodiments, the sheet material trolley further comprises a bumper disposed on an underside surface of the jaw, the bumper being configured to provide a cushion between the second end of the item of sheet material and the jaw. In this way, damage to the sheet materials disposed on the trolley is further mitigated by providing the jaw with a cushion. In some embodiments, the bumper comprises an elastomeric material. For example, the bumper may comprise a compressible material, e.g., rubber. In some embodiments, the bumper comprises an elongate hollow tube. In this way, the bumper comprises an internal air cushion further configured to soften an impact of the jaw on items of sheet material disposed on the trolley. In some embodiments, the pillar comprises a fastener operable to engage with the arm and the pillar to releasably secure the jaw in the second position. Preferably the fastener may be fastened and unfastened without needing to use any tools. For example, the fastener may comprise a thumb screw, a wing bolt, a wing knob or a star knob. Any suitable fastener that is manually operable, i.e., without requiring a tool, may be used to secure the jaw in the second position. In some embodiments, the fastener is further operable to releasably secure the jaw in the first position, improving a security of the items of sheet material in transport. The fastener may also secure the jaw in any other suitable position, e.g., an intermediate third position. In other embodiments, the fastener may require tools to operate. In some embodiments, the upper surface of the pillar with which the protrusion is configured to engage as the jaw moves from the second position towards the first position under gravity is an upper surface of the fastener. In this way, the fastener provides the second surface as soon as it is loosened to cause retraction of the arm under gravity. In some cases, the inventors have found that the impact of the protrusion on the fastener during uncontrolled retraction damages the thread of the fastener. Surprisingly, this has been found to be beneficial as the thread damage inhibits complete removal (and subsequent misplacement) of the fastener from the trolley. In some embodiments, the fastener is operable to frictionally engage with the arm through the pillar to releasably secure the jaw in the second position. For example, the fastener may comprise a threaded stud configured to pass through a threaded hole in the pillar and a distal end of the stud may be configured to engage frictionally with an outer surface of the arm. In this way, the fastener may be simple, hand operable and retained with the trolley in use. In some embodiments, the sheet material trolley further comprises a plurality of wheeled frames connected along a spine. In this way, the trolley may accommodate long sheets of sheet material, be balanced and manoeuvrable. In some embodiments, the sheet material trolley further comprises a bar configured to extend from the jaw in a direction substantially normal to the jaw and towards the plate, the bar being slidable along the jaw into engagement with the item of sheet material to secure the item of sheet material against the pillar. Where the jaw is provided to engage with an end of an item of sheet material, the bar may be provided to engage with a face of an item of sheet material. The bar may be provided to engage with a substantially opposite face of an item of sheet material to the face supported by the pillar. The bar may provide further securement to the item(s) of sheet material disposed on the trolley. Providing the bar protruding substantially normal to the jaw may require a second position of the jaw that is removed from the item of sheet material by at least a length of the bar. In this way, provision of the bar increases a need to arrest uncontrolled retraction of the arm into the pillar under gravity. In some embodiments, the bar comprises a jaw engaging element and the jaw comprises a bar retaining element, the jaw engaging element and the bar retaining element being configured to co-operate to limit translation of the bar along the jaw to retain the bar on the jaw in normal use. In this way, the bar may be translated along the jaw such that the position of the bar with respect to the pillar may be adjusted to accommodate a range of thicknesses of sheet material loads on the trolley. In addition, the translation of the bar along the jaw is limited such that the jaw engaging element and the bar retaining element inhibit removal of the bar from the jar. In this way, the bar is retained with the jaw of the trolley and not lost or misplaced. In some embodiments, the jaw engaging element comprises a pin and the bar retaining element comprises a slot extending parallel to a longitudinal axis of the jaw and having a closed end proximate a distal end of the jaw. In this way, the bar is operable to move freely along the jaw between limits, and effectively retained on the jaw. The jaw may comprise a fastener operable to engage with the bar and the jaw to releasably secure the bar in a desired position. The bar may be secured to the jaw via a bracket. In some embodiments, the pillar is rotatable to provide a storage configuration in which the pillar is configured to extend in a direction substantially parallel to the plate. For example, the pillars may pivot about their proximal ends respectively to fold towards the plate of the trolley. In this way, a compact configuration of the trolley is provided, e.g., for storage. According to a second aspect of the invention, there is provided a height-adjustable clamp configured to be used in the sheet material trolley of the first aspect of the invention. The height-adjustable clamp may comprise an arm and a jaw arranged at a distal end of the arm. The arm may be configured to be at least partially telescopically received within a pillar of a sheet material trolley. The jaw may be configured to secure an upper end of an item of sheet material disposed on the sheet material trolley. The arm may further comprise a protrusion configured to engage with the pillar of the sheet material trolley during telescopic retraction, as the jaw moves towards the sheet material disposed on the trolley, such that retraction under gravity is arrested before collision of the jaw with the sheet material. The arm of the second aspect may be retrofit to an existing sheet material trolley. The protrusion of the arm provides a ‘safety stop’ feature configured to mitigate damage to sheet materials and injury to trolley operators caused by collision of the jaw with sheet materials or operators during uncontrolled retraction of the arm into the pillar. Due to its simplicity and the nature of the protrusion as a protruding accessory, the arm may be compatible with a variety of existing sheet material trolleys comprising pillars configured to telescopically receive arms. Brief Description of the Drawings Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1 depicts an isometric view of a sheet material trolley according to an embodiment of the first aspect of the invention; Figure 2 depicts an isometric view of a further configuration of the sheet material trolley of Fig. 1; Figure 3 depicts a side partial cross-section view of a portion of the sheet material trolley of Fig. 1; Figure 4 depicts a schematic isometric view of the wheeled frame of the sheet material trolley of Fig. 1; Figure 5 depicts an isometric view of a height adjustable clamp according to an embodiment of the second aspect of the invention. Detailed Description With reference to Figure 1, there is illustrated a sheet material trolley 100 according to an embodiment of the first aspect of the invention. The sheet material trolley 100 of Fig. 1 is configured to support sheet material in a substantially upright position. The sheet material trolley 100 comprises a wheeled frame 102. The wheeled frame 102 comprises a plate 104 and a pillar 106. The plate 104 is configured to support a first end of an item of sheet material. The pillar 106 configured to support a face of the item of sheet material. The pillar 106 is arranged substantially normal to the plate 104. The plate 104 and the pillar 106 are inclined such that an item of sheet material is urged by gravity into engagement with the pillar 106. The sheet material trolley 100 of Fig. 1 further comprises a height-adjustable clamp 108. The height-adjustable clamp 108 comprises an arm 110 and a jaw 112. The arm 110 comprises a proximal end (not shown) configured to be telescopically received within the pillar 106 and a distal end 114 configured to protrude from the pillar 106. The jaw 112 is arranged at the distal end 114 of the arm 110. The jaw 112 is configured to secure the item of sheet material against the plate 104. In Fig. 1, a position of the jaw 112 with respect to the plate 104 is adjustable by telescopic adjustment of the arm 110 with respect to the pillar 106 between a first position and a second position. In the first position, the jaw 112 rests on a second end of the item of sheet material, the second end being opposite to the first end. In the second position, the jaw 112 is removed from the item of sheet material. In Fig. 1, a direction of adjustment, i.e., extension and retraction, between the first and second positions is indicated by an arrow 116. In Fig. 1, the arm 110 comprises a protrusion 118. The protrusion 118 is configured to engage with an upper surface 120 of the pillar 106 as the jaw 112 moves from the second position towards the first position to arrest retraction of the arm 110 into the pillar 106 under gravity to mitigate collision of the jaw 112 with the sheet material. The sheet material trolley 100 of Fig. 1 comprises a plurality of wheeled frames 102 connected along a spine 122. Each wheeled frame comprises a plate 104 and a pillar 106. In this way, a stable sheet material trolley 100 is provided. Each pillar 106 in Fig. 1 comprises a handle 124 to facilitate manoeuvring the trolley 100. In other embodiments, a pole projecting from the distal end 114 of the arm 110 may be provided by which the trolley 100 may be manoeuvred, e.g., steered, propelled along, brought to a stop. The pole may extend in a direction parallel to the arm 110, but preferably the pole may extend vertically, i.e., inclined to the arm, for compactness. The pole may be removable, e.g., unscrewable, from the arm 110 or retractable, e.g., telescopically into the arm 100, for storage. The wheeled frames 102 comprise two wheels 126 each. The wheels shown in Fig. 1 are castor wheels which may swivel to align with a direction of motion of the trolley 100 when the trolley 100 changes direction. The wheels 126 may each comprise a brake configured to inhibit rotation of the wheel. Alternatively, only two of the wheels 126 of the trolley 100 of Fig. 1 may comprise brakes. For example, one wheeled frame 102 may comprise wheels 126 with brakes, and the other wheeled frame 102 may comprise wheels 126 without brakes, such that the trolley 100 of Fig. 1 has two braked wheels and two non-braked wheels. In some cases, the non-braked wheels may comprise directional lock accessories configured to fixed the direction of those castor wheel, thereby enabling the user to control the manoeuvrability of the trolley. The wheeled frame 102 is formed largely from sheet metal. As such, the frame 102 is lightweight and easy to manoeuvre while providing a stable base for the trolley 100. The inclination of the plate 104 and pillar 106 is slight, e.g., between 5 and 15° and preferably 10°. In this way, the distal end 114 of the arm 110 does not extend laterally beyond a width of the wheeled frame 102. Therefore, a stability of the trolley 100 is ensured. In Fig. 1, the clamp 108 is extended from the pillar 106 such that the protrusion 118 is above and not engaged with the upper surface 120 of the pillar 106. So, the jaw 112 is in the second position, because, if there were any sheet material on the trolley 100, the jaw 112 would be removed from the item of sheet material. With reference to Figure 2, there is illustrated the sheet metal trolley 100 of Fig. 1 with the protrusion 118 of the arm 110 engaged with the upper surface 120 of the pillar 106. So in Fig. 2, the jaw 112 is closer to the first position than in Fig. 1, because the clamp 108 in Fig. 2 is partially retracted into the pillar 106. In Fig. 2 the jaw 112 is not disposed in the first position because, if there were any sheet material on the trolley 100, the jaw 112 would not be resting on the item of sheet material; retraction of the arm 110 has been arrested by the protrusion 118 engaging with the upper surface 120 to mitigate collision of the jaw 112 with the sheet material. Features of Fig. 2 that are discussed above in relation to Fig. 1 are indicated with like reference numerals and not discussed in detail again. Fig. 2 shows a configuration in which retraction of the arm 110 into the pillar 106 under gravity is arrested by the protrusion 118 engaging with the upper surface 120. After this configuration is reached, the arm 110 may be adjustable to permit continued retraction of the arm 110 into the pillar 106 to dispose the jaw 112 in the first position. For example, a position of the arm 110 within the pillar 106 may be adjustable in a plane perpendicular to a retraction direction 116 to permit the protrusion 118 to be received within the pillar 106. In this way, continued retraction of the arm 110 into the pillar 106 to dispose the jaw 112 in the first position is permitted. In Fig. 2, a direction of adjustment of the arm 110 to permit the protrusion 118 to be received within the pillar 106 is indicated by an arrow 202. As shown in Fig. 2, the protrusion 118 may be disposed on a surface 204 of the arm 110 that is urged into engagement with an upper surface 120 of the pillar 106 under gravity. That is, due to the inclination of the plate 104 and the pillar 106, surface 204 is urged into engagement with an inner surface of the pillar 106 by gravity, ensuring engagement of the protrusion 118 with the upper surface 120 during an uncontrolled retraction of the arm 110 into the pillar 106. With reference to Figure 3, there is illustrated the height-adjustable clamp 108 of the trolley 100 of Fig. 1 with the arm 110 of the clamp 108 substantially fully retracted into the pillar 106. In Fig. 3, the clamp 108 is retracted into the pillar 106 such that the protrusion 118 is below and not engaged with the upper surface 120 of the pillar 106. So, the jaw 112 is in the first position, because, if there were any sheet material on the trolley 100, the jaw 112 would be resting on the item of sheet material. Features of Fig. 3 that are discussed above in relation to Figs. 1 and 2 are indicated with like reference numerals and not discussed in detail again. In Fig. 3, the clamp 108 substantially fully retracted into the pillar 106 such that the protrusion 118 is disposed inside the pillar 106. Once received within the pillar 106, the protrusion 118 may be configured to frictionally engage with an inner surface of the pillar 106 to limit a rate of retraction of the arm 110 into the pillar 106. As shown in Fig. 3, the pillar 106 may comprise a fastener 302 operable to engage with the arm 110 and the pillar 106 to releasably secure the jaw 112 in the second (extended) position. The fastener 302 may also be operable to engage with the arm 110 and the pillar 106 to releasably secure the jaw 112 in the first (retracted) position, and / or any intermediate position between the first and second positions. In Fig. 3 the fastener 302 comprises a threaded stud terminating in a star knob for easy tool-free operation. The fastener 302 operates as a star-handled grub screw. Other types of handle may be suitable, e.g., wings such on a wing bolt. The threaded stud is engaged through a tapped hole in the pillar 106 to connect with a surface of the arm 110, in this case, surface 204. The fastener 302 traps the arm 110 in frictional engagement between the end of the threaded stud and an inner surface of the pillar 106. As such, when the fastener is tightened up, i.e., wound in, telescopic motion of the arm 110 is inhibited. Alternative fastener types may be suitable, for example, a ball detect and / or index plunger mechanism may be used to inhibit telescopic motion. Alternatively, the fastener 302 may be configured to engage with a slot or hole in the surface 204 to secure the arm 110 with respect to the pillar 106. In some cases, the upper surface 120 of the pillar 106 with which the protrusion 118 is configured to engage as the jaw 112 moves from the second position towards the first position under gravity is an upper surface of the fastener 302. For example, retraction of the arm 110 may be arrested when the protrusion 118 meets a distal end of the threaded stud of fastener 302. In this way, the position of the upper surface 120 may be adjusted by moving the fastener 302 between predetermined tapped holes provided in the pillar 106 to adjust a height at which uncontrolled retraction of the arm 100 is arrested. In this way, the trolley 100 may be adapted for a variety of sizes of sheet material. Further, the inventors have found that collision of the protrusion 118 with the threaded stud of the fastener 302 may damage the threads of the stud such that the end of the stud can no longer easily be unscrewed from the pillar 106. This inhibits detachment of the fastener 302 from the pillar 106 such that the fastener is not easily misplaced or lost. As shown in Fig., 3, the trolley 100 may further comprise a bar 304. The bar 304 may be configured to extend from the jaw 112 in a direction substantially normal to the jaw 112 and towards the plate 104 (not shown in Fig. 3). The bar 304 may be slidable along the jaw 112 into engagement with an item of sheet material received on the trolley to secure the item of sheet material against the pillar 106. In Fig. 3, a direction in which the bar 304 may slide along the jaw 112 is indicated by an arrow 306. In the embodiment of Fig. 3, the bar 304 comprises a jaw engaging element 308 and the jaw 112 comprises a bar retaining element 310. The jaw engaging element 308 and the bar retaining element 110 are configured to co-operate to limit translation of the bar 304 along the jaw 112. In this way, the bar 304 may be retained on the jaw 112 in normal use. In one example, the jaw engaging element 308 comprises a pin 308 and the bar retaining element 310 comprises a slot 310. The slot 310 may extend parallel to a longitudinal axis of the jaw 112 and have a closed end (not shown) proximate a distal end of the jaw 112. The pin 308 may be disposed in the slot 310 and may therefore be limited by the extent of the slot 310, limiting the translation of the bar 304 along the jaw 112. The bar 304 may comprise a fastener 312. The fastener 312 may operate to inhibit motion of the bar 304 along the jaw 112. Specifically, in embodiments where the fastener 312 comprises a threaded stud terminating in a handle, e.g., star knob, the threaded stud is engaged through a tapped hole in the bar 304 (or bracket of the bar 304) and a distal end of the threaded stud connects with a surface of the jaw 112. Via threaded engagement, the fastener 302 is operable to urge the bar 304 in a direction of the axis of the fastener 312. When urged upwards, toward the star knob, the pin 308 of the bar 304 frictionally engages with an upper edge of the slot 310 of the jaw 112 and traps the bar 304 in frictional engagement with the jaw 112. As such, when the fastener is tightened up, i.e., wound in, lateral motion of the bar 304 along the jaw 112 is inhibited. With reference to Figure 4, there is illustrated the wheeled frame 102 of the sheet material trolley 100 of Fig. 1. The sheet material trolley 100 of the particular embodiment shown is collapsable into a storage configuration. In Fig. 4, the sheet material trolley 100 is shown in a partially collapsed position. Each pillar 106 is rotatable to provide the storage configuration. In Fig. 4, directions of rotation of each pillar 106 are indicated by arrows 402. In the storage configuration, each pillar 106 is configured to extend in a direction substantially parallel to the plate 104. Where the sheet material trolley comprises a spine 122, the pillars 106 are configured to extend in a direction substantially parallel to the spine 122 in the storage configuration. The pillars 106 are rotatable about their proximal ends, that is, the end of each pillar 106 connected to the respective plate 104. A rotatable joint between the pillar 106 and the plate 104 may be provided by any suitable type of joint. For example, each pillar 106 may comprise a pin disposed in a slot of the wheeled frame 102, e.g., a pillar bracket of the wheeled frame 102. The shape of the slot may describe and path along which the pillar 106 is moveable. When the pin is disposed at a lower end of the slot, the pillar 106 may be prevented from rotating into the storage configuration by a portion of the pillar bracket, or other part of the wheeled frame 102. When the pin is disposed at an upper end of the slot, the pillar 106 may be free to rotate around the pin into the storage configuration. With reference to Figure 5, there is illustrated a height-adjustable clamp 500 according to an embodiment of the second aspect of the invention. The height-adjustable clamp 500 is configured to be used in the sheet material trolley 100 of any of Figs. 1-4. The height-adjustable clamp 500 comprises an arm 502 and a jaw 504. The arm 502 comprises a proximal end 506 configured to be telescopically received within a pillar of a sheet material trolley (e.g., pillar 106 of sheet material trolley 100) and a distal end 508. The jaw 504 is arranged at the distal end 508 of the arm 502. The jaw 504 is configured to secure an item of sheet material to a sheet material trolley, e.g., against a base of a sheet material trolley such as the plate 104 of sheet material trolley 100. The arm 502 comprises a protrusion 510 configured to engage with a surface to arrest retraction of the arm 502 under gravity to mitigate collision of the jaw 504 with an item of sheet material. In Fig. 5, the jaw 504 comprises a retaining element 512 comprising a slot 512. The retaining element 512 may be configured to retain a bar on the jaw 504. For example, a pin of a bar may be disposed in the slot 512 and therefore translation of the bar along the jaw 504 may be limited by the extent of the slot 512. The bar may be configured to engage with an item of sheet material to secure the item of sheet material to a sheet material trolley, e.g., against an upright portion of a sheet material trolley such as the pillar 106 of sheet material trolley 100. In Fig. 5, the clamp 500 is shown with a bar attached. It will be understood that the clamp 500 may be provided without the bar. In the embodiment of Fig. 5, the arm 502 comprises a metal tube comprising a substantially square cross section and the protrusion 510 is formed of sheet metal. The protrusion 510 is connected to the arm via a welded joint. In this way, the protrusion 510 is substantially permanently connected to the arm 502, and is not easily removed or adjusted. In this way, the advantage of the protrusion as a safety stop device, mitigating collision of the jaw 504 with the sheet material, is permanently provided. So, miscalculation or carelessness on behalf of a user or equipment provider may not disrupt the operation of the protrusion as a safety stop device. In other embodiments, the protrusion 510 may be formed of any suitable material and from any suitable stock by any suitable manufacturing method. The protrusion may be connected to the arm 502 in any suitable way, for example, by fasteners such as countersunk screws, or by an adhesive. In some embodiments, the protrusion 510 is itself a portion of a fastener, e.g., a head of a screw or bolt, the fastener being engaged with a tapped hole in the arm 502. In this way, the protrusion 510 is simply provided, may be adjustable (e.g., moveable between holes in the arm 502) and is cost effective to source and install. The clamp 500 further comprises a bumper 514 disposed on an underside surface of the jaw 504. The bumper 514 may be configured to provide a cushion between the item of sheet material and the jaw 504. The bumper 514 may comprise a compressible material configured to conform around a top edge of item of sheet materials disposed on a sheet material trolley. In this way, the bumper 514 may improve a security of items on a sheet material trolley. For example, the bumper 514 comprises an elastomeric material. In Fig. 5, the bumper 514 comprises an elongate hollow tube. An air pocket provided within the hollow tube may act as a cushion between the jaw 504 and any items of sheet material, or any other item the jaw comes into contact with, for example, a hand of an operator of the sheet material trolley. The bumper may comprise an elongate hollow tube having a substantially D-shaped cross-section. The present invention is not limited to the specific examples or structures illustrated. Further embodiments within the scope of the present invention may be envisaged that have not been described above, for example, the sheet material trolley and / or height-adjustable clamp may may comprise a greater or lesser number of components than are illustrated in the figures. The sheet material trolley may be any suitable size. The sheet material trolley may be formed of any suitable materials and using any suitable manufacturing methods. Various parts of the sheet material trolley may be integrally formed with one another or formed separately and assembled together to provide a sheet material trolley. The protrusion may have any suitable size or shape, be made of any suitable material(s) and be attached to the arm in any suitable manner. The bumper may have any suitable size or shape, be made of any suitable material(s) and be attached to the arm in any suitable manner. Height-adjustable clamps of different configurations may be used together on one sheet material trolley. To provide a simple and effective safety mechanism to a sheet material trolley, an innovative mechanism configured to mitigate collision of parts of the sheet material trolley with the sheet materials disposed thereupon is required. The device of the present invention provides an innovative solution involving engagement of a protrusion with a surface to arrest uncontrolled retraction of a height-adjustable clamp. By taking advantage of gravity, an elegant solution has been reached. The solution of the present invention is cost-effective, reliable and, in some cases, permanently provided. In sum, there has been herein described a sheet material trolley configured to support sheet material in a substantially upright position, the trolley comprising: a height-adjustable clamp comprising: an arm comprising a proximal end configured to be telescopically received within a pillar and a distal end configured to protrude from the pillar; and a jaw arranged at the distal end of the arm; wherein a position of the jaw with respect to the plate is telescopically adjustable between a first position in which the jaw rests on an end of the item of sheet material and a second position in which the jaw is removed from the item of sheet material; and wherein the arm comprises a protrusion configured to engage with an upper surface of the pillar to arrest retraction of the arm into the pillar under gravity to mitigate collision of the jaw with the sheet material.

Claims

1. A sheet material trolley configured to support sheet material in a substantially upright position, the sheet material trolley comprising:a wheeled frame comprising:a plate configured to support a first end of an item of sheet material; anda pillar arranged substantially normal to the plate, and configured to support a face of the item of sheet material;wherein the plate and the pillar are inclined such that an item of sheet material is urged by gravity into engagement with the pillar; anda height-adjustable clamp comprising:an arm comprising a proximal end configured to be telescopically received within the pillar and a distal end configured to protrude from the pillar; anda jaw arranged at the distal end of the arm and configured to secure the item of sheet material against the plate;wherein a position of the jaw with respect to the plate is adjustable by telescopic adjustment of the arm with respect to the pillar between a first position in which the jaw rests on a second end of the item of sheet material, the second end being opposite to the first end, and a second position in which the jaw is removed from the item of sheet material; andwherein the arm comprises a protrusion configured to engage with an upper surface of the pillar as the jaw moves from the second position towards the first position to arrest retraction of the arm into the pillar under gravity to mitigate collision of the jaw with the sheet material.

2. The sheet material trolley of claim 1, wherein, after the retraction of the arm into the pillar under gravity is arrested by the protrusion, the arm is adjustable to permit continued retraction of the arm into the pillar to dispose the jaw in the first position.

3. The sheet material trolley of claim 2, wherein a position of the arm within the pillar is adjustable in a plane perpendicular to a retraction direction to permit the protrusion to be received within the pillar thereby permitting continued retraction of the arm into the pillar to dispose the jaw in the first position.

4. The sheet material trolley of claim 3, wherein, once received within the pillar, the protrusion is configured to frictionally engage with an inner surface of the pillar to limit a rate of retraction of the arm into the pillar.

5. The sheet material trolley of any preceding claim, wherein the protrusion is disposed on a surface of the arm that is urged into engagement with an upper surface of the pillar under gravity.

6. The sheet material trolley of any preceding claim, wherein the arm comprises a metal tube comprising a substantially square cross section.

7. The sheet material trolley of any preceding claim, wherein the protrusion is formed of sheet metal.

8. The sheet material trolley of any preceding claim, wherein the protrusion is connected to the arm via a welded joint.

9. The sheet material trolley of any preceding claim, further comprising a bumper disposed on an underside surface of the jaw, the bumper being configured to provide a cushion between the second end of the item of sheet material and the jaw.

10. The sheet material trolley of claim 9, wherein the bumper comprises an elastomeric material.

11. The sheet material trolley of claim 9 or claim 10, wherein the bumper comprises an elongate hollow tube.

12. The sheet material trolley of any preceding claim, wherein the pillar comprises a fastener operable to engage with the arm and the pillar to releasably secure the jaw in the second position.

13. The sheet material trolley of claim 12, wherein the upper surface of the pillar with which the protrusion is configured to engage as the jaw moves from the second position towards the first position under gravity is an upper surface of the fastener.

14. The sheet material trolley of claim 12 or claim 13, wherein the fastener is operable to frictionally engage with the arm through the pillar to releasably secure the jaw in the second position.

15. The sheet material trolley of any one of claims 12 to 14, wherein the fastener is further operable to releasably secure the jaw in the first position.

16. The sheet material trolley of any preceding claim, comprising a plurality of wheeled frames connected along a spine.

17. The sheet material trolley of any preceding claim, further comprising a bar configured to extend from the jaw in a direction substantially normal to the jaw and towards the plate, the bar being slidable along the jaw into engagement with the item of sheet material to secure the item of sheet material against the pillar.

18. The sheet material trolley of claim 17, wherein the bar comprises a jaw engaging element and the jaw comprises a bar retaining element, the jaw engaging element and the bar retaining element being configured to co-operate to limit translation of the bar along the jaw to retain the bar on the jaw in normal use.

19. The sheet material trolley of claim 18, wherein the jaw engaging element comprises a pin and the bar retaining element comprises a slot extending parallel to a longitudinal axis of the jaw and having a closed end proximate a distal end of the jaw.

20. The sheet material trolley of any preceding claim, wherein the pillar is rotatable to provide a storage configuration in which the pillar is configured to extend in a direction substantially parallel to the plate.

21. A height adjustable clamp configured to be used in the sheet material trolley of any preceding claim.s

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